The primary challenges that impede the practical applications of lithium-sulfur batteries are the significant shuttle effect of polysulfides, huge volume expansion, and slow redox kinetics. In this work, three-dimensional nitrogen doping Ti₃C₂T_xMXenes (3D N-Ti₃C₂T_x) were successfully synthesized by spray drying and subsequent annealing, and hydrochloric acid-treated melamine effectively reduces the oxidation of MXenes in these processes. The formation of a unique nanoflower-shaped microsphere endows 3D N-Ti₃C₂T_x with a significant specific surface area and pore volume. The combination of nitrogen doping and the large specific surface area increased adsorption capacity and catalytic conversion ability for polysulfide intermediates. Consequently, the obtained 3D N-Ti₃C₂T_x/S cathode exhibited high-capacity retention (578.5 mAh g^-1 after 500 cycles at 0.5 C and 462.5 mAh g^-1 after 1,000 cycles at 1 C), superior rate performance (651.2 mAh g^-1 at 3 C), and excellent long-term cycling performance (capacity fading rate of 0.076% per cycle at 0.5 C and 0.046% per cycle at 1 C). This work expands the potential applications of MXenes for lithium-sulfur batteries.

Safety hazards associated with separators in lithium-ion batteries are more pronounced in light of the significant improvement of energy density of batteries, hindering their wide application. In this research, asymmetric poly (vinylidene fluoride) (PVDF)-coated polyimide separators with three-dimensionally homogeneous microporous (3DHM API/PVDF) structure are prepared, in which a PVDF layer with a thickness of 6 μm on one side of polyimide. Polyimide, as the base film, has a high heat-resistant temperature which ensures that as-prepared separators will not be shrunk and burned. The coated PVDF layer imparts 3DHM API/PVDF with thermal shutdown function at 175 °C due to the melting of PVDF. The temperature difference between the shutdown and meltdown temperature is over 100 °C, ensuring that the LIB assembled with 3DHM API/PVDF is safe for use. Moreover, the interconnected microporous structure of the separator facilitates the formation of 3D Li⁺ transport pathways and uniformity of lithium deposition, suppressing lithium dendrite growth. The coin cells assembled by 3DHM API/PVDF exhibit similar electrochemical performance to that of a commercial polypropylene separator at room temperature. Therefore, the novel 3DHM API/PVDF separator may be a promising candidate for a significantly safer LIB.

In order to satisfy the rapidly increasing demands for a large variety of applications, there has been a strong desire for low-cost and high-energy lithium-ion batteries and thus for next-generation cathode materials having low cost yet high capacity. In this regard, the research of cobalt (Co)-free and nickel (Ni)-rich (CFNR) layered oxide cathode materials, able to meet the low-cost and high-capacity requirements, has been extensively pursued but remains challenging largely due to the elimination of Co and high content of Ni in these materials. Herein, we systematically review the challenges and recent advances of CFNR cathode materials on these important aspects. Specifically, we first clarify the role of Co in Ni-rich layered oxides and the possibility of its elimination to fabricate CFNR cathode materials. We then discuss the methods developed to synthesize these cathode materials. This is followed by the elucidation about their degradation mechanisms and the research progress of modification strategies achieved in enhancing the properties for these materials. Finally, we discuss the current challenges and future prospects of CFNR cathode materials as the next-generation cathode materials for low-cost and high-energy lithium-ion batteries.

All-inorganic perovskites CsPbX₃ (X: halogen ions) have gained significant attention for application in next generation photovoltaic technologies due to their superior thermal stability and excellent optoelectronic properties. Compared with fabrication in N₂ glove boxes, ambient air processing could simplify the operation and reduce the fabrication cost, which is favorable for boosting the commercialization of perovskite solar cells (PSCs). However, the moisture in ambient air tends to cause the phase transformation of inorganic perovskite from the photoactive black phase to the photo-inactive yellow one, thus deteriorating the photovoltaic performance. Considering the obstacles from both the intrinsic structure instability and the external atmosphere, tremendous efforts have been made for pursuing high-efficiency and stable all-inorganic PSCs that can be processed in ambient air. In this review, we first analyze the challenges for fabricating CsPbX₃ in ambient air from both the intrinsic characters and external atmosphere and then overview the progress of the air-fabricated CsPbX₃ films for photovoltaic applications. The recently reported various modification strategies, including the compositional/precursor, solvent, additive, and interface engineering, for achieving high-quality and stable CsPbX₃ films are comprehensively summarized. Finally, a brief conclusion and outlook is given to inspire more research interest on air-fabricated CsPbX₃ photovoltaics. This review provides significant guidance for further optimizing the air-processible CsPbX₃ films to boost the large-scale commercialization of cost-effective PSCs in the future.

Covalent organic frameworks (COFs) that selectively enable lithium ions transport by their abundant sub-nano or nanosized pores and polar skeleton are considered as emerging coating materials for separators of lithium metal batteries. However, the COF-coated separators that combine high ionic conductivity with excellent lithium ions transference number ($ {t_{L i^{+}} } $) are still challenging, as the coating layer may increase the transport resistance of ions through the separator due to the elongated pathway. Different from conventional strategies that always focus on developing COFs with distinct structural motifs, this work proposes a crystallinity engineering tactic to improve the ion transport behaviors and thus battery performance. Amorphous (AM-CTF) and highly crystalline covalent triazine frameworks (HC-CTF) were successfully synthesized, and the effect of crystallinity of CTFs on the electrochemical properties of the separators and the battery performance are fully studied. Compared to amorphous covalent triazine framework, HC-CTF features a more regular structure and higher surface area, which further improves the $ {t_{L i^{+}} } $ (0.60) and ionic conductivity (0.67 mS cm^-1) of the coated separators. The LiFePO₄/Li cells assembled with the HC-CTF-coated separator exhibit an ultralong lifespan and extremely high-capacity retention (45.4% at 1 C for 1,000 cycles). This work opens up a new strategy for designing high-performance separators of lithium batteries.

Ammonia (NH₃) plays an irreplaceable role in traditional agriculture and emerging renewable energy. Its preparation in industry mainly relies on the energy-intensive Haber-Bosch process, which is associated with high energy consumption and large CO₂ emissions. Recently, the nitrate reduction reaction (NO₃^-RR) driven by renewable energy has received extensive attention. This reaction can efficiently synthesize NH₃ with water as a hydrogen source and NO₃^- as a nitrogen source under mild conditions, which is conducive to reducing energy consumption and promoting the carbon cycle. It is well known that the properties of electrocatalysts determine the performance of NO₃^-RR. As an emerging two-dimensional material, MXenes (transition metal carbides/nitrides/carbon nitrides) possess excellent electrical conductivity, large specific surface area and controllable surface functional groups, which shows great application potential in the field of NO₃^-RR. Herein, this review summarized the structure, properties and synthesis strategies of MXenes to elucidate the possibilities from foundation to application. Then, the latest research progress in applying MXene-based electrocatalysts to NO₃^-RR was summarized and the applicability of different NH₃ detection methods was analyzed. Finally, the present challenges and future prospects of NO₃^-RR were presented. This review aimed to provide thoughtful insights into the rational design of MXene-based electrocatalysts for sustainable NH₃ synthesis.

Metal halide perovskites (MHP) suffer from photo-structural-chemical instabilities whose intricacy requires state-of-the-art tools to investigate their properties under various conditions. This study addresses the damage caused by focused X-ray beams on MHP through a correlative multi-technique approach. The damage after high-dose irradiation is noticeable in many ways: the loss of iodine and organic components, whose relative amount is reduced; the formation of an excavated area modifying the sample morphology; and an altered optical reflectivity indicating an optically inactive layer. The damage mechanism combines radiolysis and sputtering processes. Interestingly, the bulk underneath the excavated area maintains the initial halide proportion demonstrated by a stable photoluminescence emission energy. We also show that controlling the beam dose and environment is an excellent strategy to mitigate the dose harm. Hence, we combined a controlled X-ray dose with an inert N₂ atmosphere to certify the conditions to probe MHP properties while mitigating damage efficiently. Finally, we applied optimized conditions in an X-ray ptychography experiment, reaching a 15-nm spatial resolution, an outcome that has never been attained in this class of materials.

One crucial problem hindering the commercial application of lithium-sulfur batteries with high theoretical specific energy is the ceaseless shuttle of soluble lithium polysulfides (LiPSs) between cathodes and anodes, which usually leads to rapid capacity fade and serious self-discharge issues. Herein, a unique bilayer coating strategy designed to modify the polypropylene separator was developed in this study, which consisted of a bottom zeolite (SSZ-13) layer serving as a LiPS movement barrier and a top ZnS layer used for accelerating redox processes of LiPSs. Benefiting from the synergetic effect, the bilayer-modified separator offers absolute block capability to LiPS diffusion, moreover, significant catalysis effect on sulfur species conversion, as well as outstanding lithium-ion (Li⁺) conductivity, excellent electrolyte wettability, and desirable mechanical properties. Consequently, the assembled lithium-sulfur cell with the SSZ-13/ZnS@polypropylene separator demonstrates excellent cycle stability and rate capability, showcasing a capacity decay rate of only 0.052% per cycle at 1 C over 500 cycles.

Ion migration is one of the prime reasons for the rapid degradation of metal halide perovskite solar cells (PSCs), and we report on a method for quantifying mobile ion concentration (N_o) using a transient dark current measurement. We perform both ex-situ and in-situ measurements on PSCs and study the evolution of N_o in films and devices under a range of temperatures. We also study the effect of device architecture, top electrode chemistry, and metal halide perovskite composition and dimensionality on N_o. Two-dimensional perovskites are shown to reduce the ion concentration along with inert C electrodes that do not react with halides by ~99% while also improving mechanical reliability by ~250%. We believe this work can provide design guidelines for the development of stable PSCs through the lens of minimizing mobile ions and their evolution over time under operational conditions.

The emergence of lithium metal batteries (LMBs) as a promising technology in energy storage devices is attributed to their high energy density. However, the inherent flammability and leakage of the internal liquid organic electrolyte pose serious safety risks when exposed to heat. In response to this challenge, gel polymer electrolytes (GPEs) have been developed to mitigate leakage and enhance nonflammability by incorporating flame-retardant groups, thereby improving the safety of LMBs. This review commences with a brief analysis of the thermal runaway mechanism specific to LMBs, emphasizing its distinctions from that of lithium-ion batteries. Following this, the various methods employed to assess the safety of LMBs are discussed, including flammability, thermal stability, and abuse assessment. The following section categorizes recent research on safe GPEs according to different flame retardancy levels providing a concise overview of each category. Finally, the review explores current advancements in developing safety-oriented GPEs and considers potential future research directions.

Most countries worldwide have committed to reaching carbon neutrality by the end of the century, with the aim to achieve Net Zero before 2060. To reduce the dependency of energy demands on fossil fuels, use of renewable energy and its gradual transition into the overall energy portfolio becomes increasingly critical. The solar and wind energy accounts for a major part of renewable energy. Considering unstable and noncontinuous production of electricity from these two sources, energy storage becomes essential. Lithium-ion batteries (LIBs) have become the most favorable choice of energy storage due to their good electrochemical performance (high capacity, low charge leakage and good cycle performance) and safety, in particular for portable (3C products, electric vehicles and drones) and stationary applications as well as for emergency electricity supply. However, the specific capacity of graphite, the most common commercial anode material, is reaching its theoretical limit, posing great challenges for improving the overall capacity of LIBs. It is therefore necessary to develop anode materials of higher capacity and better cycle performance. Biomass-derived carbon materials are ideal candidates for further enhancing the performance of LIBs due to their special microstructures, functional diversity and easy structure regulation. Most of these materials can reach capacities exceeding 500 mAh g^-1, even the best for more than 1,000 mAh g^-1 combined with other anode materials. This review provides an in-depth analysis of diverse carbon sources derived from biomass, categorized based on their distinct structural characteristics, with the focus on evaluating the current roles and bottlenecks of carbon as a component of the electrode materials used in LIBs. The failure mechanisms associated with biomass-derived carbon in LIBs are summarized, with potential solutions to these issues being proposed. The potential challenges and prospects for biomass-based LIBs are identified and thoroughly discussed. Overall, this review aims to serve as a resource for the strategic design and advancement of carbon-based materials, to achieve next-generation LIBs of superior performance.