Mar 2024, Volume 7 Issue 3
    

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  • RESEARCH ARTICLE
    Ting Chen, Luchao Yue, Guoqiang Shu, Qing Yang, Dong Wang, Ruoyang Wang, Xianyan Qiao, Yan Sun, Benhe Zhong, Zhenguo Wu, Xiaodong Guo
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    Lithium metal battery has great development potential because of its lowest electrochemical potential and highest theoretical capacity. However, the uneven deposition of Li+ flux in the process of deposition and stripping induces the vigorous growth of lithium dendrites, which results in severely battery performance degradation and serious safety hazards. Here, the tetragonal BaTiO3 polarized by high voltage corona was used to build an artificial protective layer with uniform positive polarization direction, which enables uniform Li+ flux. In contrast to traditional strategies of using protective layer, which can guide the uniform deposition of lithium metal. The ferroelectric protective layer can accurately anchor the Li+ and achieve bottom deposition of lithium due to the automatic adjustment of the electric field. Simultaneously, the huge volume changes caused by Li+ migration change of the lithium metal anode during charging and discharging is functioned to excite the piezoelectric effect of the protective layer, and achieve seamless dynamic tuning of lithium deposition/stripping. This dynamic effect can accurately anchor and capture Li+. Finally, the layer-modified Li anode enables reversible Li plating/stripping over 1500 h at 1 mA cm−2 and 50 ℃ in symmetric cells. In addition, the assembled Li-S full cell exhibits over 300 cycles with N/P ≈ 1.35. This work provides a new perspective on the uniform Li+ flux at the Li-anode interface of the artificial protective layer.

  • RESEARCH ARTICLE
    Sajid Rauf, Muhammad Bilal Hanif, Faiz Wali, Zuhra Tayyab, Bin Zhu, Naveed Mushtaq, Yatao Yang, Kashif Khan, Peter D. Lund, Martin Motola, Wei Xu
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    Extending the ionic conductivity is the pre-requisite of electrolytes in fuel cell technology for high-electrochemical performance. In this regard, the introduction of semiconductor-oxide materials and the approach of heterostructure formation by modulating energy bands to enhance ionic conduction acting as an electrolyte in fuel cell-device. Semiconductor (n-type; SnO2) plays a key role by introducing into p-type SrFe0.2Ti0.8O3-δ (SFT) semiconductor perovskite materials to construct p-n heterojunction for high ionic conductivity. Therefore, two different composites of SFT and SnO2 are constructed by gluing p- and n-type SFT-SnO2, where the optimal composition of SFT-SnO2 (6:4) heterostructure electrolyte-based fuel cell achieved excellent ionic conductivity 0.24 S cm−1 with power-output of 1004 mW cm−2 and high OCV 1.12 V at a low operational temperature of 500 ℃. The high power-output and significant ionic conductivity with durable operation of 54 h are accredited to SFT-SnO2 heterojunction formation including interfacial conduction assisted by a built-in electric field in fuel cell device. Moreover, the fuel conversion efficiency and considerable Faradaic efficiency reveal the compatibility of SFT-SnO2 heterostructure electrolyte and ruled-out short-circuiting issue. Further, the first principle calculation provides sufficient information on structure optimization and energy-band structure modulation of SFT-SnO2. This strategy will provide new insight into semiconductor-based fuel cell technology to design novel electrolytes.

  • RESEARCH ARTICLE
    Jian Gao, Yiyu Feng, Wenyu Fang, Hui Wang, Jing Ge, Xiaoyu Yang, Huitao Yu, Mengmeng Qin, Wei Feng
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    Photoisomerization-induced phase change are important for co-harvesting the latent heat and isomerization energy of azobenzene molecules. Chemically optimizing heat output and energy delivery at alternating temperatures are challenging because of the differences in crystallizability and isomerization. This article reports two series of asymmetrically alkyl-grafted azobenzene (Azo-g), with and without a methyl group, that have an optically triggered phase change. Three exothermic modes were designed to utilize crystallization enthalpy (∆Hc) and photothermal (isomerization) energy (∆Hp) at different temperatures determined by the crystallization. Azo-g has high heat output (275–303 J g−1) by synchronously releasing ∆Hc and ∆Hp over a wide temperature range (−79 ℃ to 25 ℃). We fabricated a new distributed energy utilization and delivery system to realize a temperature increase of 6.6 ℃ at a temperature of −8 ℃. The findings offer insight into selective utilization of latent heat and isomerization energy by molecular optimization of crystallization and isomerization processes.

  • RESEARCH ARTICLE
    Chuanlin Li, Guangmeng Qu, Xixi Zhang, Chenggang Wang, Xijin Xu
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    Although Zn metal has been regarded as the most promising anode for aqueous batteries, its practical application is still restricted by side reactions and dendrite growth. Herein, an in-situ solid electrolyte interphase (SEI) film formed on the interface of electrode/electrolyte during the plating/stripping of zinc anodes by introducing trace amounts of multidentate ligand sodium diethyldithiocarbamate (DDTC) additive into 1 M ZnSO4. The synergistic effect of in-situ solid electrolyte interphase forming and chelate effect endows Zn2+ with uniform and rapid interface-diffusion kinetics against dendrite growth and surface side reactions. As a result, the Zn anode in 1 M ZnSO4 + DDTC electrolytes displays an ultra-high coulombic efficiency of 99.5% and cycling stability (more than 2000 h), especially at high current density (more than 600 cycles at 40 mA cm−2). Moreover, the Zn//MnO2 full cells in the ZnSO4 + DDTC electrolyte exhibit outstanding cyclic stability (with 98.6% capacity retention after 2000 cycles at 10 C). This electrode/electrolyte interfacial chemistry modulated strategy provides new insight into enhancing zinc anode stability for high-performance aqueous zinc batteries.

  • RESEARCH ARTICLE
    Linan Wang, Junle Zhang, Xi Zhang, Ge Shi, Yanjie He, Zhe Cui, Xiaomeng Zhang, Peng Fu, Minying Liu, Xiaoguang Qiao, Xinchang Pang
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    Liquid metal (LM) and liquid metal alloys (LMs) possess unique physicochemical features, which have become emerging and functionalized materials that are attractive applicants in various fields. Herein, uniform LM nanodroplets armored by carbon dots (LMD@CDs) were prepared and exhibited high colloidal stability in various solvents, as well as water. After optimization, LMD@CDs can be applied as functional additives for the 3D/4D printing of hydrogel and cross-linked resin through digital light processing (DLP). The light absorption of LMD@CDs not only improved the printing accuracy, but also led to the cross-linking density differential during the post-curing process. Base on the cross-linking density differential of soft hydrogel and photothermal performance of the LM, the 3D printed objects can exhibit stimulus responses to both water and laser irradiation. Additionally, the CDs shell and LM core of LMD@CDs provide the printed objects interesting photoluminescence and electric conductivity capabilities, respectively. We deduce this versatile 3D/4D printing system would provide a new platform for the preparation of multi-functional and stimuli-responsive advance materials.

  • RESEARCH ARTICLE
    Naifang Hu, Yuan Yang, Lin Li, Yuhan Zhang, Zhiwei Hu, Lan Zhang, Jun Ma, Guanglei Cui
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    Full concentration gradient lithium-rich layered oxides are catching lots of interest as the next generation cathode for lithium-ion batteries due to their high discharge voltage, reduced voltage decay and enhanced rate performance, whereas the high lithium residues on its surface impairs the structure stability and long-term cycle performance. Herein, a facile multifunctional surface modification method is implemented to eliminate surface lithium residues of full concentration gradient lithium-rich layered oxides by a wet chemistry reaction with tetrabutyl titanate and the post-annealing process. It realizes not only a stable Li2TiO3 coating layer with 3D diffusion channels for fast Li+ ions transfer, but also dopes partial Ti4+ ions into the sub-surface region of full concentration gradient lithium-rich layered oxides to further strengthen its crystal structure. Consequently, the modified full concentration gradient lithium-rich layered oxides exhibit improved structure stability, elevated thermal stability with decomposition temperature from 289.57 ℃ to 321.72 ℃, and enhanced cycle performance (205.1 mAh g−1 after 150 cycles) with slowed voltage drop (1.67 mV per cycle). This work proposes a facile and integrated modification method to enhance the comprehensive performance of full concentration gradient lithium-rich layered oxides, which can facilitate its practical application for developing higher energy density lithium-ion batteries.

  • RESEARCH ARTICLE
    Yanrong Li, Shuhu Yin, Long Chen, Xiaoyang Cheng, Chongtai Wang, Yanxia Jiang, Shigang Sun
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    Iron-nitrogen-carbon (Fe-N-C) catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) have seriously been hindered by their poor ORR performance of Fe-N-C due to the low active site density (SD) and site utilization. Herein, we reported a melamine-assisted vapor deposition approach to overcome these hindrances. The melamine not only compensates for the loss of nitrogen caused by high-temperature pyrolysis but also effectively etches the carbon substrate, increasing the external surface area and mesoporous porosity of the carbon substrate. These can provide more useful area for subsequent vapor deposition on active sites. The prepared 0.20Mela-FeNC catalyst shows a fourfold higher SD value and site utilization than the FeNC without the treatment of melamine. As a result, 0.20Mela-FeNC catalyst exhibits a high ORR activity with a half-wave potential (E1/2) of 0.861 V and 12-fold higher ORR mass activity than the FeNC in acidic media. As the cathode in a H2-O2 PEMFCs, 0.20Mela-FeNC catalyst demonstrates a high peak power density of 1.30 W cm−2, outstripping most of the reported Fe-N-C catalysts. The developed melamine-assisted vapor deposition approach for boosting the SD and utilization of Fe-N-C catalysts offers a new insight into high-performance ORR electrocatalysts.

  • RESEARCH ARTICLE
    Hiroki Yamada, Koji Ohara, Satoshi Hiroi, Atsushi Sakuda, Kazutaka Ikeda, Takahiro Ohkubo, Kengo Nakada, Hirofumi Tsukasaki, Hiroshi Nakajima, Laszlo Temleitner, Laszlo Pusztai, Shunsuke Ariga, Aoto Matsuo, Jiong Ding, Takumi Nakano, Takuya Kimura, Ryo Kobayashi, Takeshi Usuki, Shuta Tahara, Koji Amezawa, Yoshitaka Tateyama, Shigeo Mori, Akitoshi Hayashi
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    Controlling Li ion transport in glasses at atomic and molecular levels is key to realizing all-solid-state batteries, a promising technology for electric vehicles. In this context, Li3PS4 glass, a promising solid electrolyte candidate, exhibits dynamic coupling between the Li+ cation mobility and the PS43− anion libration, which is commonly referred to as the paddlewheel effect. In addition, it exhibits a concerted cation diffusion effect (i.e., a cation–cation interaction), which is regarded as the essence of high Li ion transport. However, the correlation between the Li+ ions within the glass structure can only be vaguely determined, due to the limited experimental information that can be obtained. Here, this study reports that the Li ions present in glasses can be classified by evaluating their valence oscillations via Bader analysis to topologically analyze the chemical bonds. It is found that three types of Li ions are present in Li3PS4 glass, and that the more mobile Li ions (i.e., the Li3-type ions) exhibit a characteristic correlation at relatively long distances of 4.0–5.0 Å. Furthermore, reverse Monte Carlo simulations combined with deep learning potentials that reproduce X-ray, neutron, and electron diffraction pair distribution functions showed an increase in the number of Li3-type ions for partially crystallized glass structures with improved Li ion transport properties. Our results show order within the disorder of the Li ion distribution in the glass by a topological analysis of their valences. Thus, considering the molecular vibrations in the glass during the evaluation of the Li ion valences is expected to lead to the development of new solid electrolytes.

  • RESEARCH ARTICLE
    Yeonguk Son, Hyungyeon Cha, Taeyong Lee, Yujin Kim, Adam Boies, Jaephil Cho, Michael De Volder
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    Small coin cell batteries are predominantly used for testing lithium-ion batteries (LIBs) in academia because they require small amounts of material and are easy to assemble. However, insufficient attention is given to difference in cell performance that arises from the differences in format between coin cells used by academic researchers and pouch or cylindrical cells which are used in industry. In this article, we compare coin cells and pouch cells of different size with exactly the same electrode materials, electrolyte, and electrochemical conditions. We show the battery impedance changes substantially depending on the cell format using techniques including Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic Intermittent Titration Technique (GITT). Using full cell NCA-graphite LIBs, we demonstrate that this difference in impedance has important knock-on effects on the battery rate performance due to ohmic polarization and the battery life time due to Li metal plating on the anode. We hope this work will help researchers getting a better idea of how small coin cell formats impact the cell performance and help predicting improvements that can be achieved by implementing larger cell formats.

  • RESEARCH ARTICLE
    Xin Wang, Jingzhe Zhang, Hui Wang, Mengjun Liang, Qiang Wang, Fuming Chen
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    Defect engineering can give birth to novel properties for adsorption and photocatalysis in the control of antibiotics and heavy metal combined pollution with photocatalytic composites. However, the role of defects and the process mechanism are complicated and indefinable. Herein, TiO2/CN/3DG was fabricated and defects were introduced into the tripartite structure with separate O2 plasma treatment for the single component. We find that defect engineering can improve the photocatalytic activity, attributing to the increase of the contribution from h+ and OH. In contrast to TiO2/CN/3DG with a photocatalytic tetracycline removal rate of 75.2%, the removal rate of TC with D-TiO2/CN/3DG has increased to 88.5%. Moreover, the reactive sites of tetracycline can be increased by adsorbing on the defective composites. The defect construction on TiO2 shows the advantages in tetracycline degradation and Cu2+ adsorption, but also suffers significant inhibition for the tetracycline degradation in a tetracycline/Cu2+ combined system. In contrast, the defect construction on graphene can achieve the cooperative removal of tetracycline and Cu2+. These findings can provide new insights into water treatment strategies with defect engineering.

  • RESEARCH ARTICLE
    Qingwen Li, Yulu Liu, Ziheng Zhang, Jinjie Chen, Zelong Yang, Qibo Deng, Alexander V. Mumyatov, Pavel A. Troshin, Guang He, Ning Hu
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    It is well accepted that a lithiophilic interface can effectively regulate Li deposition behaviors, but the influence of the lithiophilic interface is gradually diminished upon continuous Li deposition that completely isolates Li from the lithiophilic metals. Herein, we perform in-depth studies on the creation of dynamic alloy interfaces upon Li deposition, arising from the exceptionally high diffusion coefficient of Hg in the amalgam solid solution. As a comparison, other metals such as Au, Ag, and Zn have typical diffusion coefficients of 10–20 orders of magnitude lower than that of Hg in the similar solid solution phases. This difference induces compact Li deposition pattern with an amalgam substrate even with a high areal capacity of 55 mAh cm−2. This finding provides new insight into the rational design of Li anode substrate for the stable cycling of Li metal batteries.

  • RESEARCH ARTICLE
    Ai Lan, Yiqun Li, Huiwen Zhu, Jintao Zhu, Hong Lu, Hainam Do, Yifan Lv, Yonghua Chen, Zhikuan Chen, Fei Chen, Wei Huang
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    The interfacial contacts between the electron transporting layers (ETLs) and the photoactive layers are crucial to device performance and stability for OSCs with inverted architecture. Herein, atomic layer deposition (ALD) fabricated ultrathin Al2O3 layers are applied to modify the ETLs/active blends (PM6:BTP-BO-4F) interfaces of OSCs, thus improving device performance. The ALD-Al2O3 thin layers on ZnO significantly improved its surface morphology, which led to the decreased work function of ZnO and reduced recombination losses in devices. The simultaneous increase in open-circuit voltage (VOC), short-circuit current density (JSC) and fill factor (FF) were achieved for the OSCs incorporated with ALD-Al2O3 interlayers of a certain thickness, which produced a maximum PCE of 16.61%. Moreover, the ALD-Al2O3 interlayers had significantly enhanced device stability by suppressing degradation of the photoactive layers induced by the photocatalytic activity of ZnO and passivating surface defects of ZnO that may play the role of active sites for the adsorption of oxygen and moisture.

  • RESEARCH ARTICLE
    Xiaofeng Hao, Zhen Li, Min Xiao, Zhiheng Huang, Dongmei Han, Sheng Huang, Wei Liu, Shuanjin Wang, Yuezhong Meng
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    How to optimize and regulate the distribution of phosphoric acid in matrix, and pursuing the improved electrochemical performance and service lifetime of high temperature proton exchange membrane (HT-PEMs) fuel cell are significant challenges. Herein, bifunctional poly (p-terphenyl-co-isatin piperidinium) copolymer with tethered phosphonic acid (t-PA) and intrinsic tertiary amine base groups are firstly prepared and investigated as HT-PEMs. The distinctive architecture of the copolymer provides a well-designed platform for rapid proton transport. Protons not only transports through the hydrogen bond network formed by the adsorbed free phosphoric acid (f-PA) anchored by the tertiary amine base groups, but also rely upon the proton channel constructed by the ionic cluster formed by the t-PA aggregation. Thorough the design of the structure, the bifunctional copolymers with lower PA uptake level (<100%) display prominent proton conductivities and peak power densities (99 mS cm−1, 812 mW cm−2 at 160 ℃), along with lower PA leaching and higher voltage stability, which is a top leading result in disclosed literature. The results demonstrate that the design of intermolecular acid–base-pairs can improve the proton conductivity without sacrificing the intrinsic chemical stability or mechanical property of the thin membrane, realizing win-win demands between the mechanical robustness and electrochemical properties of HT-PEMs.

  • REVIEW
    Na-Yeong Kim, Ilgyu Kim, Behnoosh Bornamehr, Volker Presser, Hiroyuki Ueda, Ho-Jin Lee, Jun Young Cheong, Ji-Won Jung
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    A suitable interface between the electrode and electrolyte is crucial in achieving highly stable electrochemical performance for Li-ion batteries, as facile ionic transport is required. Intriguing research and development have recently been conducted to form a stable interface between the electrode and electrolyte. Therefore, it is essential to investigate emerging knowledge and contextualize it. The nanoengineering of the electrode-electrolyte interface has been actively researched at the electrode/electrolyte and interphase levels. This review presents and summarizes some recent advances aimed at nanoengineering approaches to build a more stable electrode-electrolyte interface and assess the impact of each approach adopted. Furthermore, future perspectives on the feasibility and practicality of each approach will also be reviewed in detail. Finally, this review aids in projecting a more sustainable research pathway for a nanoengineered interphase design between electrode and electrolyte, which is pivotal for high-performance, thermally stable Li-ion batteries.

  • RESEARCH ARTICLE
    Fengfeng Han, Liwen Fan, Xinzhi Ma, Huiqing Lu, Lu Li, Xitian Zhang, Lili Wu
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    Rechargeable Li–S batteries (LSBs) are emerging as an important alternative to lithium-ion batteries (LIBs), owing to their high energy densities and low cost; yet sluggish redox kinetics of LiPSs results in inferior cycle life. Herein, we prepared multifunctional self-supporting hyphae carbon nanobelt (HCNB) as hosts by carbonization of hyphae balls of Rhizopus, which could increase the S loading of the cathode without sacrificing reaction kinetics. Trace platinum (Pt) nanoparticles were introduced into HCNBs (PtHCNBs) by ion-beam sputtering deposition. Based on the X-ray photoelectron spectroscopy analyses, the introduced trace Pt regulated the local electronic states of heteroatoms in HCNBs. Electrochemical kinetics investigation combined with operando Raman measurements revealed the accelerated reaction mechanics of sulfur species. Benefiting from the synergistic catalytic effect and the unique structures, the as-prepared PtHCNB/MWNCT/S cathodes delivered a stable capacity retention of 77% for 400 cycles at 0.5 C with a sulfur loading of 4.6 mg cm−2. More importantly, remarkable cycling performance was achieved with an high areal S loading of 7.6 mg cm−2. This finding offers a new strategy to prolong the cycle life of LSBs.

  • RESEARCH ARTICLE
    Xun Li, Tian Tan, Wei Ji, Wanling Zhou, Yuwen Bao, Xiaohong Xia, Zhangfan Zeng, Yun Gao
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    Development of metal oxide semiconductors-based methane sensors with good response and low power consumption is one of the major challenges to realize the real-time monitoring of methane leakage. In this work, a self-assembled mulberry-like ZnO/SnO2 hierarchical structure is constructed by a two-step hydrothermal method. The resultant sensor works at room temperature with excellent response of ~56.1% to 2000 ppm CH4 at 55% relative humidity. It is found that the strain induced at the ZnO/SnO2 interface greatly enhances the piezoelectric polarization on the ZnO surface and that the band bending results in the accumulation of chemically adsorbed O2- ions close to the interface, leading to significant improvement in the sensing performance of the methane gas sensor at room temperature.

  • RESEARCH ARTICLE
    Changhyun Lee, Chanyong Lee, Kyungjin Chae, Taemin Kim, Seaeun Park, Yohan Ko, Yongseok Jun
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    Compared to organic–inorganic hybrid perovskites, the cesium-based all-inorganic lead halide perovskite (CsPbI3) is a promising light absorber for perovskite solar cells owing to its higher resistance to thermal stress. Nonetheless, additional research is required to reduce the nonradiative recombination to realize the full potential of CsPbI3. Here, the diffusion of Cs ions participating in ion exchange is proposed to be an important factor responsible for the bulk defects in γ-CsPbI3 perovskite. Calculations based on first-principles density functional theory reveal that the [PbI6]4− octahedral tilt modifies the perovskite crystallographic properties in γ-CsPbI3, leading to alterations in its bandgap and crystal strain. In addition, by substituting amorphous barium titanium oxide (a-BaTiO3) for TiO2 as the electron transport layer, interfacial defects caused by imperfect energy levels between the electron transport layer and perovskite are reduced. High-resolution transmission electron microscopy and electron energy loss spectroscopy demonstrate that a-BaTiO3 forms entirely as a single phase, as opposed to Ba-doped TiO2 hybrid nanoclusters or separate domains of TiO2 and BaTiO3 phases. Accordingly, inorganic perovskite solar cells based on the a-BaTiO3 electron transport layer achieved a power conversion efficiency of 19.96%.

  • RESEARCH ARTICLE
    Changfan Xu, Jiajia Qiu, Yulian Dong, Yueliang Li, Yonglong Shen, Huaping Zhao, Ute Kaiser, Guosheng Shao, Yong Lei
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    Sodium-carbon dioxide (Na-CO2) batteries are regarded as promising energy storage technologies because of their impressive theoretical energy density and CO2 reutilization, but their practical applications are restricted by uncontrollable sodium dendrite growth and poor electrochemical kinetics of CO2 cathode. Constructing suitable multifunctional electrodes for dendrite-free anodes and kinetics-enhanced CO2 cathodes is considered one of the most important ways to advance the practical application of Na-CO2 batteries. Herein, RuO2 nanoparticles encapsulated in carbon paper (RuCP) are rationally designed and employed as both Na anode host and CO2 cathode in Na-CO2 batteries. The outstanding sodiophilicity and high catalytic activity of RuCP electrodes can simultaneously contribute to homogenous Na+ distribution and dendrite-free sodium structure at the anode, as well as strengthen discharge and charge kinetics at the cathode. The morphological evolution confirmed the uniform deposition of Na on RuCP anode with dense and flat interfaces, delivering enhanced Coulombic efficiency of 99.5% and cycling stability near 1500 cycles. Meanwhile, Na-CO2 batteries with RuCP cathode demonstrated excellent cycling stability (>350 cycles). Significantly, implementation of a dendrite-free RuCP@Na anode and catalytic-site-rich RuCP cathode allowed for the construction of a symmetric Na-CO2 battery with long-duration cyclability, offering inspiration for extensive practical uses of Na-CO2 batteries.

  • RESEARCH ARTICLE
    Xingyun Luo, Yanlu Li, Xian Zhao
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    Due to ever-increasing concerns about safety issues in using Li ionic batteries, solid electrolytes have extensively explored. The Li-rich anti-perovskite Li3OBr has been considered as a promising solid electrolyte candidate, but it still suffers challenges to achieve a high ionic conductivity owing to the high intrinsic symmetry of the crystal lattice. Herein, we presented a design strategy that introduces various point defects and grain boundaries to break the high lattice symmetry of Li3OBr crystal, and their effect and microscopic mechanism of promoting the migration of Li-ion were explored theoretically. It has been found that Lii· are the dominant defects responsible for the fast Li-ion diffusion in bulk Li3OBr and its surface, but they are easily trapped by the grain boundaries, leading to the annihilating of the Frenkel defect pair V'Li + Lii· and thus limits the V'Li diffusion at the grain boundaries. The VBr· defect near the grain boundaries can effectively drive V'Li across the grain boundary, thereby converting the carrier of Li+ migration from Lii· in the bulk and surface to V'Li at the grain boundary, and thus improving the ionic conductivity in the whole Li3OBr crystal. This work provides a comprehensive insight into the Li+ transport and conduction mechanism in the Li3OBr electrolyte. It opens a new way of improving the conductivity for all-solid-state Li electrolyte material through the defect design.

  • RESEARCH ARTICLE
    Xiaojun Zeng, Qingqing Zhang, Chulong Jin, Hui Huang, Yanfeng Gao
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    Transition metal phosphides with metallic properties are a promising candidate for electrocatalytic water oxidation, and developing highly active and stable metal phosphide-based oxygen evolution reaction catalysts is still challenging. Herein, we present a facile ion exchange and phosphating processes to transform intestine-like CoNiPx@P,N-C into lotus pod-like CoNiFePx@P,N-C heterostructure in which numerous P,N-codoped carbon-coated CoNiFePx nanoparticles tightly anchors on the 2D carbon matrix. Meanwhile, the as-prepared CoNiFePx@P,N-C enables a core-shell structure, high specific surface area, and hierarchical pore structure, which present abundant heterointerfaces and fully exposed active sites. Notably, the incorporation of Fe can also induce electron transfer in CoNiPx@P,N-C, thereby promoting the oxygen evolution reaction. Consequently, CoNiFePx@P,N-C delivers a low overpotential of 278 mV (vs RHE) at a current density of 10 mA cm−1 and inherits excellent long-term stability with no observable current density decay after 30 h of chronoamperometry test. This work not only highlights heteroatom induction to tune the electronic structure but also provides a facile approach for developing advanced and stable oxygen evolution reaction electrocatalysts with abundant heterointerfaces.

  • RESEARCH ARTICLE
    Yanjiao Wei, Xinyu Wang, Mengjie Sun, Min Ma, Jian Tian, Minhua Shao
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    At present, the research on highly active and stable nitrogen reduction reaction catalysts is still challenging work for the electrosynthesis of ammonia (NH3). Herein, we synthesized atomically dispersed zinc active sites supported on N-doped carbon nanosheets (Zn/NC NSs) as an efficient nitrogen reduction reaction catalyst, which achieves a high ammonia yield of 46.62 μg h−1 mg−1cat. at −0.85 V (vs RHE) and Faradaic efficiency of 95.8% at −0.70 V (vs RHE). In addition, Zn/NC NSs present great stability and selectivity, and there is no significant change in NH3 rate and Faradaic efficiencies after multiple cycles. The structural characterization shows that the active center in the nitrogen reduction reaction process is the Zn–N4 sites in the catalyst. DFT calculation confirms that Zn/NC with Zn–N4 configuration has a lower energy barrier for the formation of *NNH intermediate compared with pure N-doped carbon nanosheets (N-C NSs), thus promoting the hydrogenation kinetics in the whole nitrogen reduction reaction process.

  • RESEARCH ARTICLE
    Sujeong Kim, Boseok Seo, Hyerim Park, Younghwan Im, Jeong Yeon Do, Byung Sub Kwak, Namgyu Son, Minkyu Kim, Misook Kang
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    CuS is an encouraging photoelectrode candidate that meets the essential requirements for efficient solar-to-hydrogen production, but it has not been thoroughly studied. A CuS light absorber layer is grown by the self-assembly of copper and sulfur precursors on a carbon paper (CP) electrode. Simultaneously, rGO is introduced as a buffer layer to control the optical and electrical properties of the absorber. The well-ordered microstructural arrangement suppresses the recombination loss of electrons and holes owing to enhanced charge-carrier generation, separation, and transport. The potential reaching 10 mA cm−2 in 1.0 M KOH solution is significantly lowered to 0.87 V, and the photocurrent density at 1.23 V is 94.7 mA cm−2. The computational result reveals that the potential-determining step is sensitive to O* stability; the lower stability of O* in the thin layer of CuS/rGO decreases the free-energy gap between the initial and final states of the potential-determining step, resulting in a lowering of the onset potential. The faradaic efficiency for the photoelectrochemical oxygen evolution reaction in the optimized 2CuS/1rGO/CP photoanode is 98.60%, and the applied bias photon-to-current and the solar-to-hydrogen efficiencies are 11.2% and 15.7%, respectively, and its ultra-high performance is maintained for 250 h. These record-breaking achievement indices may be a trigger for establishing a green hydrogen economy.

  • REVIEW
    Yuan Yuan, Si Wu, Xiaoxue Song, Jin Yong Lee, Baotao Kang
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    Aqueous zinc-ion batteries (ZIBs) have shown great potential in the fields of wearable devices, consumer electronics, and electric vehicles due to their high level of safety, low cost, and multiple electron transfer. The layered cathode materials of ZIBs hold a stable structure during charge and discharge reactions owing to the ultrafast and straightforward (de)intercalation-type storage mechanism of Zn2+ ions in their tunable interlayer spacing and their abilities to accommodate other guest ions or molecules. Nevertheless, the challenges of inadequate energy density, dissolution of active materials, uncontrollable byproducts, increased internal pressure, and a large de-solvation penalty have been deemed an obstacle to the development of ZIBs. In this review, recent strategies on the structure regulation of layered materials for aqueous zinc-ion energy storage devices are systematically summarized. Finally, critical science challenges and future outlooks are proposed to guide and promote the development of advanced cathode materials for ZIBs.

  • RESEARCH ARTICLE
    Sheng Liu, Chaozhu Shu, Yu Yan, Dayue Du, Longfei Ren, Ting Zeng, Xiaojuan Wen, Haoyang Xu, Xinxiang Wang, Guilei Tian, Ying Zeng
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    The interfacial chemistry of solid electrolyte interphases (SEI) on lithium (Li) electrode is directly determined by the structural chemistry of the electric double layer (EDL) at the interface. Herein, a strategy for regulating the structural chemistry of EDL via the introduction of intermolecular hydrogen bonds has been proposed (p-hydroxybenzoic acid (pHA) is selected as proof-of-concept). According to the molecular dynamics (MD) simulation and density functional theory (DFT) calculation results, the existence of hydrogen bonds realizes the anion structural rearrangement in the EDL, reduces the lowest unoccupied molecular orbital (LUMO) energy level of anions in the EDL, and the number of free solvent molecules, which promotes the formation of inorganic species-enriched SEI and eventually achieves the dendrite-free Li deposition. Based on this strategy, Li||Cu cells can stably run over 185 cycles with an accumulated active Li loss of only 2.27 mAh cm−2, and the long-term cycle stability of Li||Li cells is increased to 1200 h. In addition, the full cell pairing with the commercial LiFePO4 (LFP) cathodes exhibits stable cycling performance at 1C, with a capacity retention close to 90% after 200 cycles.

  • RESEARCH ARTICLE
    Yan Sun, Kaili Liang, Ren Tu, Xudong Fan, Charles Q. Jia, Zhiwen Jia, Yingnan Li, Hui Yang, Enchen Jiang, Hanwen Liu, Yonggang Yao, Xiwei Xu
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    The chemoselective hydrodeoxygenation of natural lignocellulosic materials plays a crucial role in converting biomass into value-added chemicals. Yet their complex molecular structures often require multiple active sites synergy for effective activation and achieving high chemoselectivity. Herein, it is reported that a high-entropy alloy (HEA) on high-entropy oxide (HEO) hetero-structured catalyst for highly active, chemoselective, and robust vanillin hydrodeoxygenation. The heterogenous HEA/HEO catalysts were prepared by thermal reduction of senary HEOs (NiZnCuFeAlZrOx), where exsolvable metals (e.g., Ni, Zn, Cu) in situ emerged and formed randomly dispersed HEA nanoparticles anchoring on the HEO matrix. This catalyst exhibits excellent catalytic performance: 100% conversion of vanillin and 95% selectivity toward high-value 2-methyl-4 methoxy phenol at low temperature of 120 ℃, which were attributed to the synergistic effect among HEO matrix (with abundant oxygen vacancies), anchored HEA nanoparticles (having excellent hydrogenolysis capability), and their intimate hetero-interfaces (showing strong electron transferring effect). Therefore, our work reported the successful construction of HEA/HEO heterogeneous catalysts and their superior multifunctionality in biomass conversion, which could shed light on catalyst design for many important reactions that are complex and require multifunctional active sites.

  • REVIEW
    Yong Wang, Yu Wang, Feng Gao, Deren Yang
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    Tunable bandgaps make halide perovskites promising candidates for developing tandem solar cells (TSCs), a strategy to break the radiative limit of 33.7% for single-junction solar cells. Combining perovskites with market-dominant crystalline silicon (c-Si) is particularly attractive; simple estimates based on the bandgap matching indicate that the efficiency limit in such tandem device is as high as 46%. However, state-of-the-art perovskite/c-Si TSCs only achieve an efficiency of ~32.5%, implying significant challenges and also rich opportunities. In this review, we start with the operating mechanism and efficiency limit of TSCs, followed by systematical discussions on wide-bandgap perovskite front cells, interface selective contacts, and electrical interconnection layer, as well as photon management for highly efficient perovskite/c-Si TSCs. We highlight the challenges in this field and provide our understanding of future research directions toward highly efficient and stable large-scale wide-bandgap perovskite front cells for the commercialization of perovskite/c-Si TSCs.

  • RESEARCH ARTICLE
    Nibagani Naresh, Suyoon Eom, Sang Jun Lee, Su Hwan Jeong, Ji-Won Jung, Young Hwa Jung, Joo-Hyung Kim
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    The layered δ-MnO2 (dMO) is an excellent cathode material for rechargeable aqueous zinc-ion batteries owing to its large interlayer distance (~0.7 nm), high capacity, and low cost; however, such cathodes suffer from structural degradation during the long-term cycling process, leading to capacity fading. In this study, a Co-doped dMO composite with reduced graphene oxide (GC-dMO) is developed using a simple cost-effective hydrothermal method. The degree of disorderness increases owing to the hetero-atom doping and graphene oxide composites. It is demonstrated that layered dMO and GC-dMO undergo a structural transition from K-birnessite to the Zn-buserite phase upon the first discharge, which enhances the intercalation of Zn2+ ions, H2O molecules in the layered structure. The GC-dMO cathode exhibits an excellent capacity of 302 mAh g−1 at a current density of 100 mA g−1 after 100 cycles as compared with the dMO cathode (159 mAh g−1). The excellent electrochemical performance of the GC-dMO cathode owing to Co-doping and graphene oxide sheets enhances the interlayer gap and disorderness, and maintains structural stability, which facilitates the easy reverse intercalation and de-intercalation of Zn2+ ions and H2O molecules. Therefore, GC-dMO is a promising cathode material for large-scale aqueous ZIBs.

  • RESEARCH ARTICLE
    Huachao Yang, Yiheng Qi, Zifan Wang, Qinghu Pan, Chuanzhi Zhang, Jianhua Yan, Kefa Cen, Zheng Bo, Kostya (Ken) Ostrikov
    PDF

    Safe operation of electrochemical capacitors (supercapacitors) is hindered by the flammability of commercial organic electrolytes. Non-flammable Water-in-Salt (WIS) electrolytes are promising alternatives; however, they are plagued by the limited operation voltage window (typically ≤2.3 V) and inherent corrosion of current collectors. Herein, a novel deep eutectic solvent (DES)-based electrolyte which uses formamide (FMD) as hydrogen-bond donor and sodium nitrate (NaNO3) as hydrogen-bond acceptor is demonstrated. The electrolyte exhibits the wide electrochemical stability window (3.14 V), high electrical conductivity (14.01 mS cm−1), good flame-retardance, anticorrosive property, and ultralow cost (7% of the commercial electrolyte and 2% of WIS). Raman spectroscopy and Density Functional Theory calculations reveal that the hydrogen bonds between the FMD molecules and NO3- ions are primarily responsible for the superior stability and conductivity. The developed NaNO3/FMD-based coin cell supercapacitor is among the best-performing state-of-art DES and WIS devices, evidenced by the high voltage window (2.6 V), outstanding energy and power densities (22.77 Wh kg−1 at 630 W kg−1 and 17.37 kW kg−1 at 12.55 Wh kg−1), ultralong cyclic stability (86% after 30 000 cycles), and negligible current collector corrosion. The NaNO3/FMD industry adoption potential is demonstrated by fabricating 100 F pouch cell supercapacitors using commercial aluminum current collectors.

  • RESEARCH ARTICLE
    Baolin Wu, Chunguang Chen, Dmitri L. Danilov, Zhiqiang Chen, Ming Jiang, Rüdiger-A. Eichel, Peter H. L. Notten
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    Anode-free Li-metal batteries are of significant interest to energy storage industries due to their intrinsically high energy. However, the accumulative Li dendrites and dead Li continuously consume active Li during cycling. That results in a short lifetime and low Coulombic efficiency of anode-free Li-metal batteries. Introducing effective electrolyte additives can improve the Li deposition homogeneity and solid electrolyte interphase (SEI) stability for anode-free Li-metal batteries. Herein, we reveal that introducing dual additives, composed of LiAsF6 and fluoroethylene carbonate, into a low-cost commercial carbonate electrolyte will boost the cycle life and average Coulombic efficiency of NMC||Cu anode-free Li-metal batteries. The NMC||Cu anode-free Li-metal batteries with the dual additives exhibit a capacity retention of about 75% after 50 cycles, much higher than those with bare electrolytes (35%). The average Coulombic efficiency of the NMC||Cu anode-free Li-metal batteries with additives can maintain 98.3% over 100 cycles. In contrast, the average Coulombic efficiency without additives rapidly decline to 97% after only 50 cycles. In situ Raman measurements reveal that the prepared dual additives facilitate denser and smoother Li morphology during Li deposition. The dual additives significantly suppress the Li dendrite growth, enabling stable SEI formation on anode and cathode surfaces. Our results provide a broad view of developing low-cost and high-effective functional electrolytes for high-energy and long-life anode-free Li-metal batteries.

  • RESEARCH ARTICLE
    Yuanpeng Dong, Peizhu Ji, Xinyue Xu, Rong Li, Yin Wang, Kevin Peter Homewood, Xiaohong Xia, Yun Gao, Xuxing Chen
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    Exploring high efficiency S-scheme heterojunction photocatalysts with strong redox ability for removing volatile organic compounds from the air is of great interest and importance. However, how to predict and regulate the transport of photogenerated carriers in heterojunctions is a great challenge. Here, density functional theory calculations were first used to successfully predict the formation of a CdS quantum dots/InVO4 atomic-layer (110)/(110) facet S-scheme heterojunction. Subsequently, a CdS quantum dots/InVO4 atomic-layer was synthesized by in-situ loading of CdS quantum dots with (110) facets onto the (110) facets of InVO4 atomic-layer. As a result of the deliberately constructed built-in electric field between the adjoining facets, we obtain a remarkably enhanced photocatalytic degradation rate for ethylene. This rate is 13.8 times that of pure CdS and 13.2 times that of pure InVO4. In-situ irradiated X-ray photoelectron spectroscopy, photoluminescence and time-resolved photoluminescence measurements were carried out. These experiments validate that the built-in electric field enhanced the dissociation of photoexcited excitons and the separation of free charge carriers, and results in the formation of S-scheme charge transfer pathways. The reaction mechanism of the photocatalytic C2H4 oxidation is investigated by in-situ electron paramagnetic resonance. This work provides a mechanistic insight into the construction and optimization of semiconductor heterojunction photocatalysts for application to environmental remediation.

  • RESEARCH ARTICLE
    Fan Liu, Xinghong Cai, Yang Tang, Wenqian Liu, Qianwei Chen, Peixin Dong, Maowen Xu, Yangyang Tan, Shujuan Bao
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    Electrocatalytic hydrogen evolution and sulfion (S2−) recycling are promising strategies for boosting H2 production and removing environmental pollutants. Here, a nano-Ni-functionalized molybdenum disulfide (MoS2) nanosheet was assembled on steel mesh (Ni-MoS2/SM) for use in sulfide oxidation reaction-assisted, energy-saving H2 production. Experimental and theoretical calculation results revealed that anchoring nano-Ni on high-surface-area slack MoS2 nanosheets not only optimized catalyst adsorption of polysulfides but also played an important role in promoting hydrogen evolution reaction kinetics by absorbing OHad, thereby greatly enhancing the catalytic performance toward sulfide oxidation reaction and hydrogen evolution reaction. Meanwhile, the Ni/MoS2-based hydrogen evolution reaction + sulfide oxidation reaction system achieved nearly 100% hydrogen production efficiency and only consumed 61% less power per kWh than the oxygen evolution reaction + hydrogen evolution reaction system, which suggested our proposed Ni-MoS2 and novel hydrogen production system are promising for sustainable energy production.

  • RESEARCH ARTICLE
    Wentao Qu, Yong Cai, Baohui Chen, Ming Zhang
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    Manganese-based material is a prospective cathode material for aqueous zinc ion batteries (ZIBs) by virtue of its high theoretical capacity, high operating voltage, and low price. However, the manganese dissolution during the electrochemical reaction causes its electrochemical cycling stability to be undesirable. In this work, heterointerface engineering-induced oxygen defects are introduced into heterostructure MnO2 (δa-MnO2) by in situ electrochemical activation to inhibit manganese dissolution for aqueous zinc ion batteries. Meanwhile, the heterointerface between the disordered amorphous and the crystalline MnO2 of δa-MnO2 is decisive for the formation of oxygen defects. And the experimental results indicate that the manganese dissolution of δa-MnO2 is considerably inhibited during the charge/discharge cycle. Theoretical analysis indicates that the oxygen defect regulates the electronic and band structure and the Mn-O bonding state of the electrode material, thereby promoting electron transport kinetics as well as inhibiting Mn dissolution. Consequently, the capacity of δa-MnO2 does not degrade after 100 cycles at a current density of 0.5 A g−1 and also 91% capacity retention after 500 cycles at 1 A g−1. This study provides a promising insight into the development of high-performance manganese-based cathode materials through a facile and low-cost strategy.

  • REVIEW
    Shuo Yang, Shruti Sarkar, Xing Xie, Dan Li, Jianmin Chen
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    The ever-increasing complexity of environmental pollutants urgently warrants the development of new detection technologies. Sensors based on the optical properties of hydrogels enabling fast and easy in situ detection are attracting increasing attention. In this paper, the data from 138 papers about different optical hydrogels (OHs) are extracted for statistical analysis. The detection performance and potential of various types of OHs in different environmental pollutant detection scenarios were evaluated and compared to those obtained using the standard detection method. Based on this analysis, the target recognition and sensing mechanisms of two main types of OHs are reviewed and discussed: photonic crystal hydrogels (PCHs) and fluorescent hydrogels (FHs). For PCHs, the environmental stimulus response, target receptors, inverse opal structures, and molecular imprinting techniques related to PCHs are reviewed and summarized. Furthermore, the different types of fluorophores (i.e., compound probes, biomacromolecules, quantum dots, and luminescent microbes) of FHs are discussed. Finally, the potential academic research directions to address the challenges of applying and developing OHs in environmental sensing are proposed, including the fusion of various OHs, introduction of the latest technologies in various fields to the construction of OHs, and development of multifunctional sensor arrays.

  • RESEARCH ARTICLE
    Sihang Cheng, Cuimei Liu, Yingqi Li, Huaqiao Tan, Yonghui Wang, Yangguang Li
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    Solar vapor generation (SVG) represents a promising technique for seawater desalination to alleviate the global water crisis and energy shortage. One of its main bottleneck problems is that the evaporation efficiency and stability are limited by salt crystallization under high-salinity brines. Herein, we demonstrate that the 3D porous melamine-foam (MF) wrapped by a type of self-assembling composite materials based on reduced polyoxometalates (i.e. heteropoly blue, HPB), oleic acid (OA), and polypyrrole (PPy) (labeled with MF@HPB-PPyn-OA) can serve as efficient and stable SVG material at high salinity. Structural characterizations of MF@HPB-PPyn-OA indicate that both hydrophilic region of HPBs and hydrophobic region of OA co-exist on the surface of composite materials, optimizing the hydrophilic and hydrophobic interfaces of the SVG materials, and fully exerting its functionality for ultrahigh water-evaporation and anti-salt fouling. The optimal MF@HPB-PPy10-OA operates continuously and stably for over 100 h in 10 wt% brine. Furthermore, MF@HPB-PPy10-OA accomplishes complete salt-water separation of 10 wt% brine with 3.3 kg m−2 h−1 under 1-sun irradiation, yielding salt harvesting efficiency of 96.5%, which belongs to the record high of high-salinity systems reported so far and is close to achieving zero liquid discharge. Moreover, the low cost of MF@HPB-PPy10-OA (2.56 $ m−2) suggests its potential application in the practical SVG technique.

  • RESEARCH ARTICLE
    Yanan Li, Shunchao Ma, Yuehua Zhao, Silin Chen, Tingting Xiao, Hongxing Yin, Huiyu Song, Xiumei Pan, Lina Cong, Haiming Xie
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    High Li+ transference number electrolytes have long been understood to provide attractive candidates for realizing uniform deposition of Li+. However, such electrolytes with immobilized anions would result in incomplete solid electrolyte interphase (SEI) formation on the Li anode because it suffers from the absence of appropriate inorganic components entirely derived from anions decomposition. Herein, a boron-rich hexagonal polymer structured all-solid-state polymer electrolyte (BSPE+10% LiBOB) with regulated intermolecular interaction is proposed to trade off a high Li+ transference number against stable SEI properties. The Li+ transference number of the as-prepared electrolyte is increased from 0.23 to 0.83 owing to the boron-rich cross-linker (BC) addition. More intriguingly, for the first time, the experiments combined with theoretical calculation results reveal that BOB anions have stronger interaction with B atoms in polymer chain than TFSI, which significantly induce the TFSI decomposition and consequently increase the amount of LiF and Li3N in the SEI layer. Eventually, a LiFePO4|BSPE+10% LiBOB|Li cell retains 96.7% after 400 cycles while the cell without BC-resisted electrolyte only retains 40.8%. BSPE+10% LiBOB also facilitates stable electrochemical cycling of solid-state Li-S cells. This study blazes a new trail in controlling the Li+ transport ability and SEI properties, synergistically.

  • RESEARCH ARTICLE
    Xuehao Zhu, Haoyu Cai, Cong Bai, Zhengzhe Wu, Wenjian Shen, Yiming Xiong, Juan Zhao, Fuzhi Huang, Yibing Cheng, Jie Zhong
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    In this work, a modified polyurethane adhesive (PUA) was prepared to realize a convenient encapsulation strategy for lead sedimentation and attachable perovskite solar cells (A-PSCs). The modified PUA can completely self-heal within 45 min at room temperature with an efficient lead ion-blocking rate of 99.3%. The PUA film can be coated on a metal electrode with slight efficiency improvement from 23.96% to 24.15%. The thermal stability at 65 ℃ and the humidity stability at 55% relative humidity (RH) are superior to the devices encapsulated with polyisobutylene. The PUA film has strong adhesion to the flexible substrate and the initial efficiency of the flexible perovskite module (17.2%) encapsulated by PUA remains 92.6% within 1825 h. These results suggest that PUA encapsulation is universal for rigid and flexible PSCs with enhanced stability and low lead hazards. Moreover, it was found that flexible PSCs can be well attached to various substrates with PUA, providing a facile route for the A-PSCs in various scenarios without additional encapsulation and installation.

  • RESEARCH ARTICLE
    Xuewen Wang, Yuzhe Feng, Kaili Sun, Nianyao Chai, Bo Mai, Sheng Li, Xiangyu Chen, Wenyu Zhao, Qingjie Zhang
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    Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is water processable, thermally stable, and highly conductive, PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials. However, the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity, thus cannot be directly utilized for TE applications. Here, a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated. Under optimal conditions, the electrical conductivity of the treated film is increased to 803.1 S cm−1 from 1.2 S cm−1 around three order of magnitude higher, and the power factor is improved to 19.0 μW m−1 K−2, which is enhanced more than 200 times. The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation, reduction of the interplanar stacking distance, and the removal of insulating PSS with increasing the oxidation level of PEDOT, facilitating the charge transportation. This work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.

  • REVIEW
    Chuanyin Xiong, Tianxu Wang, Jing Han, Zhao Zhang, Yonghao Ni
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    In recent years, paper-based functional materials have received extensive attention in the field of energy storage due to their advantages of rich and adjustable porous network structure and good flexibility. As an important energy storage device, paper-based supercapacitors have important application prospects in many fields and have also received extensive attention from researchers in recent years. At present, researchers have modified and regulated paper-based materials by different means such as structural design and material composition to enhance their electrochemical storage capacity. The development of paper-based supercapacitors provides an important direction for the development of green and sustainable energy. Therefore, it is of great significance to summarize the relevant work of paper-based supercapacitors for their rapid development and application. In this review, the recent research progress of paper-based supercapacitors based on cellulose was summarized in terms of various cellulose-based composites, preparation skills, and electrochemical performance. Finally, some opinions on the problems in the development of this field and the future development trend were proposed. It is hoped that this review can provide valuable references and ideas for the rapid development of paper-based energy storage devices.

  • RESEARCH ARTICLE
    Kejun Xu, Liuying Wang, Chaoqun Ge, Long Wang, Bin Wang, Zhuo Wang, Chuanwei Zhang, Gu Liu
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    NiO, an anodic electrochromic material, has applications in energy-saving windows, intelligent displays, and military camouflage. However, its electrochromic mechanism and reasons for its performance degradation in alkaline aqueous electrolytes are complex and poorly understood, making it challenging to improve NiO thin films. We studied the phases and electrochemical characteristics of NiO films in different states (initial, colored, bleached and after 8000 cycles) and identified three main reasons for performance degradation. First, Ni(OH)2 is generated during electrochromic cycling and deposited on the NiO film surface, gradually yielding a NiO@Ni(OH)2 core–shell structure, isolating the internal NiO film from the electrolyte, and preventing ion transfer. Second, the core–shell structure causes the mode of electrical conduction to change from first- to second-order conduction, reducing the efficiency of ion transfer to the surface Ni(OH)2 layer. Third, Ni(OH)2 and NiOOH, which have similar crystal structures but different b-axis lattice parameters, are formed during electrochromic cycling, and large volume changes in the unit cell reduce the structural stability of the thin film. Finally, we clarified the mechanism of electrochromic performance degradation of NiO films in alkaline aqueous electrolytes and provide a route to activation of NiO films, which will promote the development of electrochromic technology.

  • REVIEW
    Jiguo Tu, Cheng Chang, Jingxiu Wang, Haiping Lei, R. Vasant Kumar, Mingyong Wang, Shuqiang Jiao
    2024, 7(3): 12664-21. https://doi.org/10.1002/eem2.12664
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    Selenium (Se), as an important quasi-metal element, has attracted much attention in the fields of thin-film solar cells, electrocatalysts and energy storage applications, due to its unique physical and chemical properties. However, the electrochemical behavior of Se in different systems from electrolytic cell to battery are complex and not fully understood. In this article, we focus on the electrochemical processes of Se in aqueous solutions, molten salts and ionic liquid electrolytes, as well as the application of Se-containing materials in energy storage. Initially, the electrochemical behaviors of Se-containing species in different systems are comprehensively summarized to understand the complexity of the kinetic processes and guide the Se electrodeposition. Then, the relationship between the deposition conditions and resulting structure and morphology of electrodeposited Se is discussed, so as to regulate the morphology and composition of the products. Finally, the advanced energy storage applications of Se in thin-film solar cells and secondary batteries are reviewed, and the electrochemical reaction processes of Se are systematically comprehended in monovalent and multivalent metal-ion batteries. Based on understanding the fundamental electrochemistry mechanism, the future development directions of Se-containing materials are considered in view of the in-depth review of reaction kinetics and energy storage applications.