Rechargeable potassium-ion batteries (PIBs) have gained attention as sustainable, environmentally friendly, and cost-effective large-scale stationary energy storage technology. However, although this technology was assumed to perform in a manner similar to that of its monovalent counterparts, huge anode volume expansion and sluggish kinetics are posing challenges in up-scaling it. Apart from the efforts to develop and optimise electrode materials, recent research endeavours have also focussed on the essential role of sustainability. These attempts have often relied on bio-derived and bio-inspired materials to mimic the effectiveness of nature. Furthermore, the use of materials with self-healing properties can alleviate electrode degradation after cycling and augment its electrochemical performance. This review summarises the development of smart materials with self-healing properties that aid in overcoming the present issues of PIBs and highlights the relevance of the interphases. In addition, state-of-the-art design strategies for bio-derived and bio-inspired materials are presented and discussed. The incorporation of recycled and sustainable materials into the manufacturing of PIBs is expected to contribute towards the ultimate goal of achieving truly circular economy ecosystems. Finally, perspectives for further advancements are provided to kindle new ideas and open questions regarding the use of new-generation materials in the development of PIBs.
Despite extensive research efforts to develop non-aqueous sodium-ion batteries (SIBs) as alternatives to lithium-based energy storage battery systems, their performance is still hindered by electrode-electrolyte side reactions. As a feasible strategy, the engineering of electrolyte additives has been regarded as one of the effective ways to address these critical problems. In this review, we provide a comprehensive overview of recent progress in electrolyte additives for non-aqueous SIBs. We classify the additives based on their effects on specific electrode materials and discuss the functions and mechanisms of each additive category. Finally, we propose future directions for electrolyte additive research, including studies on additives for improving cell performance under extreme conditions, optimizing electrolyte additive combinations, understanding the effect of additives on cathode-anode interactions, and understanding the characteristics of electrolyte additives.
Ionic liquids (ILs) are a new group of novel solvents with great potential in design-synthesis. They are promising electrolyte candidates in energy storage applications, especially in rechargeable batteries. However, in practice, their usage remains limited due to the unfavorable high-viscosity (η) property at ambient conditions. To optimize the design synthesis of ILs, a systematic fundamental study of their structure-property relationship is deemed necessary. In this study, we employed a deep-learning (DL) model to predict the room-temperature viscosity of a wide range of ILs that consist of various cationic and anionic families. Based on this DL model, accurate prediction of IL viscosity can be realized, reaching an R2 score of 0.99 with a root mean square error of ~45 mPa·s. To further help identify low- and high-η ILs, a low/high-η binary classification model with an overall accuracy of 93% for test prediction is obtained based on the DL model. From the important structure-property relationship analysis governed by the top-rank molecular descriptors of this model, a list of very low-η ILs (i.e., η < 30 mPa·s) that could be potentially useful in battery electrolytes is identified. Based on the finding of the DL model, it suggests that in order to achieve low-η, grafting IL cations into smaller sizes (e.g., smaller head rings) and short alkyl chains and reducing ionization potentials/energies will help. Meanwhile, for the same cations, further reducing anions in sizes, chain lengths, and hydrogen bonds might be useful to further reduce the viscosity. Thus, with a fine selection and molecular grafting of anionic and cationic species in ILs, we believe fine-tuning IL viscosities can be achieved through the proper design synthesis of functional groups in ILs.
Conventional ether electrolytes are generally considered unsuitable for use with graphite anodes and high-voltage cathodes due to their co-intercalation with graphite and poor oxidation stability, respectively. In this work, a highly fluorinated ether molecule, 1,1,1-trifluoro-2-[(2,2,2-trifluoroethoxy) methoxy] ethane (TTME), is introduced as a co-solvent into the conventional ether system to construct a fluorinated ether electrolyte, which not only avoids the co-intercalation with graphite but also is compatible with high-voltage cathodes. Li||graphite half-cells using the fluorinated ether electrolyte deliver stable cycling with a capacity retention of 91.7% for 300 cycles. Moreover, LiNi0.8Co0.1Mn0.1O2 (NCM811)||graphite and LiCoO2 (LCO)||graphite full-cells (cathode loadings are ≈3 mAh/cm2) with the fluorinated ether electrolyte show capacity retentions of > 90% over 200 cycles with a charge cut-off voltage of 4.4 V and > 97% for 100 cycles with a charge cut-off voltage of 4.5 V, respectively. The dense and firm solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) formed by the fluorinated ether electrolyte on the anode and cathode, respectively, are key to excellent cell performance. These results have significance for the subsequent application of ether electrolytes for high-voltage lithium ion batteries (up to 4.5 V) with graphite anodes.
Stretchable energy-storage devices are required to power next-generation wearable electronics intimately integrated with the human body. The microbatteries and microsupercapacitors represent promising candidates featuring small footprints and facile system integration. This perspective reviews common strategies to convert conventional rigid devices into stretchable forms. Several prototype soft electronic systems are presented utilizing microbatteries and microsupercapacitors as power sources. We discuss the current challenges and perspectives of the stretchable microbattery and microsupercapacitor. Stretchable forms of miniaturized energy-storage devices often show a significant trade-off between mechanical deformability and electrochemical performances, which present attractive opportunities for the material and engineering community.
Potassium-ion batteries (PIBs) are considered as promising alternatives to lithium-ion batteries (LIBs) due to their abundant potassium resources, cost-effectiveness, and comparable electrochemical performance to LIBs. However, the practical application of PIBs is hindered by the slow dynamics and large volume expansion of anode materials. Owing to their unique morphology, rich pores, abundant active sites, and tunable composition, metal-organic framework (MOF)-derived carbon and its composites have been widely studied and developed as PIB anodes. In this review, the basic configuration, performance evaluation indicators, and energy storage mechanisms of PIBs were first introduced, followed by a comprehensive summary of the research progress in MOF-derived carbon and its composites, especially the design strategies and different types of composites. Moreover, the advances of in situ characterization techniques to understand the electrochemical mechanism during potassiation/depotassiation were also highlighted, which is crucial for the directional optimization of the electrochemical performance of PIBs. Finally, the challenges and development prospects of MOF-derived carbon and its composites for PIBs are prospected. It is envisioned that this review will guide and inspire more research efforts toward advanced MOF-derived PIB anode materials in the future.
The energy density of conventional graphite anode batteries is insufficient to meet the requirement for portable devices, electric cars, and smart grids. As a result, researchers have diverted to lithium metal anode batteries. Lithium metal has a theoretical specific capacity (3,860 mAh·g-1) significantly higher than that of graphite. Additionally, it has a lower redox potential of -3.04 V compared to standard hydrogen electrodes. These properties make high-energy lithium metal batteries a promising candidate for next-generation energy storage devices, which have garnered significant interest for several years. However, the high activity of lithium metal anodes poses safety risks (e.g., short circuits and thermal runaway) that hinder their commercial growth. Currently, modification of reversible lithium anodes is the primary focus of lithium metal batteries. This article presents conceptual models and numerical simulations that address failure processes and offer specific techniques to mitigate the challenges of lithium metal anodes, including electrolyte design, interface engineering, and electrode modification. It is expected that lithium metal batteries will recover and become a feasible energy storage solution.
The commercial lithium-ion batteries (LIBs) rely on lithium hexafluorophosphate (LiPF6), which is extremely sensitive to moisture and liable to thermal decomposition. Lithium bis (trifluoro methane sulfonyl) imide (LiTFSI), as a promising electrolyte salt, possesses high thermal stability and excellent moisture tolerance. However, LiTFSI is closely related to severe corrosion of the aluminum (Al) current collector at high voltage. Herein, phosphonate-functionalized imidazolium ionic liquid (PFIL) is developed and utilized as an electrolyte co-solvent to inhibit the oxidative dissolution of the Al current collector. PFIL can suppress Al corrosion by participating in the interface reaction and forming a stable and reliable protective film on the surface of Al foils, as confirmed by X-ray photoelectron spectroscopy. Thanks to the corrosion suppression of the Al current collector, the
The key R&D concern in the domain of new energy in recent years has been the large-scale development of electrochemical energy storage. However, the steep increase in pricing has constrained the further expansion of lithium-ion batteries, primarily due to the ongoing depletion of their scarce lithium supplies. A potential candidate material at the moment is the potassium-ion battery (KIB), which has an anode made of carbon and/or an alloy and rich reserves, offering an excellent theoretical capacity and ideal working voltage. More significant advancements are still required to achieve long life and high energy density, despite the fact that some significant breakthroughs have been reported. The most recent findings from research on carbon-based [graphite, hard carbon (HC), and nanoporous carbon] and alloy-based (mainly including Sb, Sn, P, and its compounds) anodes for KIBs are compiled in this document. Numerous simulations at the atomic level based on particular chemical interactions, phase transitions, ion/electron transport dynamics, and conduction band spin utilizing density functional theory (DFT) calculations have been conducted to thoroughly investigate the storage mechanism of K+ on various electrode materials. Moreover, this paper examined contemporary structural modification techniques used in carbon- and alloy-based anode electrode materials and applied DFT calculations to confirm the advancement of its thorough tests. To promote the manufacturing of rechargeable KIBs, the challenges and potential of KIBs were also explored in future research.