Soft Carbon-Thiourea with Fast Bulk Diffusion Kinetics for Solid-State Lithium Metal Batteries

Preparation of N and S Codoped Ultramicroporous Carbon Materials with a High CO2 Adsorption Capacity

The environmental problems caused by excessive CO2 emissions have made the development of adsorbent materials for capturing CO2 an important topic. N-doped porous carbon materials are attractive for CO2 adsorption because of their large specific surface area, porous structure, and multiple active sites. S and N are known to work well together as codopants, but the effects of S on N and the synergistic effects of S and N on carbon materials need to be clarified. In this study, N and S codoped porous carbon samples with an ultramicroporous structure were prepared by using lignin as the carbon source and thiourea as the sulfur source. The prepared samples had a specific surface area of up to 1723 m2/g and N and S contents of up to 1.60 at % and 0.23 at %, respectively. In tests, the best-performing sample had a CO2 adsorption capacity of 3.58 mmol/g at 298 K and 1 bar, which can be attributed to ultramicropores (<1 nm) making up 67.8% of the pore volume. S doping had the synergistic effect of increasing the pyrrole N content on the sample surface, which increased the CO2 adsorption capacity. The present study provides insights into using N and S codoping to develop high-efficiency carbon-based adsorbents for CO2 capture.

Toward Practical All-Solid-State Batteries: Current Status of Functional Binders

All-solid-state batteries (ASSBs) are promising candidates for next-generation energy storage devices due to their high energy density and enhanced safety. Binder plays an irreplaceable role in stabilizing the electrode structure, enhancing carrier transport and modulating solid electrolyte interfaces by connecting each component of the electrode. The development of functional binders is seen as a key strategy to achieve higher energy densities of ASSBs. This review systematically examines recent progress in binder development, focusing on their roles, impacts, and failure mechanisms in ASSBs. It begins by outlining the specific functionalities required of binders in ASSBs and provides a comprehensive summary of their applications across different components, including the anode, cathode, and solid electrolyte. Furthermore, the review highlights innovative binder design principles while also summarizing key testing methods and advanced characterization techniques for evaluating binder performance. This review proposes future directions for binder design based on current developments and emerging technologies, with the aim of creating optimal binder systems for high-energy-density applications.

Ductile Inorganic Solid Electrolytes for All-Solid-State Lithium Batteries

Solid electrolytes, as the core of all-solid-state batteries (ASSBs), play a crucial role in determining the kinetics of ion transport and the interface compatibility with cathodes and anodes, which can be subdivided into catholytes, bulk electrolytes, and anolytes based on their functional characteristics. Among various inorganic solid electrolytes, ductile solid electrolytes, distinguished from rigid oxide electrolytes, exhibit excellent ion transport properties even under cold pressing, thus holding greater promise for industrialization. However, the challenge lies in finding a ductile solid electrolyte that can simultaneously serve as catholyte, bulk electrolyte, and anolyte. Fortunately, due to the immobility of solid electrolytes, combining multiple types of solid electrolytes allows for leveraging their respective advantages. In this review, we discuss five types of solid electrolytes, sulfides, halides, nitrides, antiperovskite-type, and complex hydrides, and the challenges and superiorities for these electrolytes are also addressed. The impact of pressure on ASSBs has been systematically discussed. Furthermore, the suitability of electrolytes as the catholyte, bulk electrolyte, and anolyte is discussed based on their functional characteristics and physicochemical properties. This discussion aims to deepen our understanding of solid electrolytes, enabling us to harness the advantages of various types of solid electrolytes and develop practical, high-performance ASSBs.

Emerging Nitrogen and Sulfur Co-doped Carbon Materials for Electrochemical Energy Storage and Conversion

The growing global energy demands, coupled with the imperative for sustainable environmental challenges, have sparked significant interest in electrochemical energy storage and conversion (EESC) technologies. Metal-free heteroatom-doped carbon materials, especially those codoped with nitrogen (N) and sulfur (S), have gained prominence due to their exceptional conductivity, large specific surface area, remarkable chemical stability, and enhanced electrochemical performance. The strategic incorporation of N and S atoms into the carbon framework plays a pivotal role in modulating electron distribution and creating catalytically active sites, thereby significantly enhancing the EESC performance. This review examines the key synthetic strategies for fabricating N, S codoped carbon materials (NSDCMs) and provides a comprehensive overview of recent advancements in NSDCMs for EESC applications. These encompass various electrochemical energy storage systems such as supercapacitors, alkali-ion batteries, and lithium-sulfur batteries. Energy conversion processes, including hydrogen evolution, oxygen reduction/evolution, and carbon dioxide reduction are also covered. Finally, future research directions for NSDCMs are discussed in the EESC field, aiming to highlight their promising potential and multifunctional capabilities in driving further advancements in electrochemical energy systems.

Direct Epitaxial Growth of Polycrystalline MOF Membranes on Cu Foils for Uniform Li Deposition in Long-life Anode-free Li Metal Batteries

Anode-free Li-metal battery (AFLMB) is being developed as the next generation of advanced energy storage devices. However, the low plating and stripping reversibility of Li on Cu foil prevents its widespread application. A promising avenue for further improvement is to enhance the lithophilicity of Cu foils and optimise their surfaces through a metal-organic framework (MOF) functional layer. However, excessive binder usage in the current approaches obscures the active plane of the MOF, severely limiting its performance. In response to this challenge, MOF polycrystalline membrane technology has been integrated into the field of AFLMB in this work. The dense and seamless HKUST-1 polycrystalline membrane was deposited on Cu foil (HKUST-1 M@Cu) via an epitaxial growth strategy. In contrast to traditional MOF functional layers, this binder-free polycrystalline membrane fully exposes lithophilic sites, effectively reducing the nucleation overpotential and optimising the deposition quality of Li. Consequently, the Li plating layer becomes denser, eliminating the effects of dendrites. When coupled with LiFePO4 cathodes, the battery based on the HKUST-1 membrane exhibits excellent rate performance and cycling stability, achieving a high reversible capacity of approximately 160 mAh g-1 and maintaining a capacity retention of 80.9 % after 1100 cycles.

Performance Degradation Mechanism of the Si@N, S-Doped Carbon Anode in Sulfide-Based All-Solid-State Batteries

Silicon (Si) anode is a promising anode material for all-solid-state lithium batteries with ultra-high theoretical specific capacity and low lithium dendrite risk. However, the inevitable vast volume expansion of Si anode during charge/discharge is recognized as a major limitation preventing its commercial application. Herein, an N, S self-doped amorphous carbon layer coated on porous micron-sized Si (p-mSi@C) is designed to construct an electron/ion conducting network while ensuring structural and interfacial stability. Uneven distribution of von mises stresses during p-mSi lithiation leads to irregular volume expansion and even fragmentation. Meanwhile, the growth of by-products at the interface between p-mSi and electrolyte contact leads to a rapid capacity decay. Compared to p-mSi anode, p-mSi@C reduces the risk of fragmentation thanks to the stress-absorbing effect of amorphous carbon, delivering excellent electrochemical performance (2679.65 mAh g-1 at 0.2 mA cm-2 with initial coulombic efficiency of 84%). More importantly, the chemical failure mechanisms of p-mSi and p-mSi@C composite anodes are revealed through structural characterization, chemical analysis, and simulation, which provides the necessary theoretical guidance for practicalization.

Hollow Core-Shelled Na4Fe2.4Ni0.6(PO4)2P2O7 with Tiny-Void Space Capable Fast-Charge and Low-Temperature Sodium Storage

Iron-based mixed polyanion phosphate Na4Fe3(PO4)2P2O7 (NFPP) is recognized as a promising cathode for Sodium-ion Batteries (SIBs) due to its low cost and environmental friendliness. However, its inherent low conductivity and sluggish Na+ diffusion limit fast charge and low-temperature sodium storage. This study pioneers a scalable synthesis of hollow core-shelled Na4Fe2.4Ni0.6(PO4)2P2O7 with tiny-void space (THoCS-0.6Ni) via a one-step spray-drying combined with calcination process due to the different viscosity, coordination ability, molar ratios, and shrinkage rates between citric acid and polyvinylpyrrolidone. This unique structure with interconnected carbon networks ensures rapid electron transport and fast Na+ diffusion, as well as efficient space utilization for relieving volume expansion. Incorporating regulation of lattice structure by doping Ni heteroatom to effectively improve intrinsic electron conductivity and optimize Na+ diffusion path and energy barrier, which achieves fast charge and low-temperature sodium storage. As a result, THoCS-0.6Ni exhibits superior rate capability (86.4 mAh g-1 at 25 C). Notably, THoCS-0.6Ni demonstrates exceptional cycling stability at -20 °C with a capacity of 43.6 mAh g-1 after 2500 cycles at 5 C. This work provides a universal strategy to design the hollow core-shelled structure with tiny-void space cathode materials for reversible batteries with fast-charge and low-temperature Na-storage features.

Dry-processed technology for flexible and high-performance FeS2-based all-solid-state lithium batteries at low stack pressure

All-solid-state lithium batteries (ASSLBs) are considered promising energy storage systems due to their high energy density and inherent safety. However, scalable fabrication of ASSLBs based on transition metal sulfide cathodes through the conventional powder cold-pressing method with ultrahigh stacking pressure remains challenging. This article elucidates a dry process methodology for preparing flexible and high-performance FeS2-based ASSLBs under low stack pressure by utilizing polytetrafluoroethylene (PTFE) binder. In this design, fibrous PTFE interweaves Li6PS5Cl particles and FeS2 cathode components, forming flexible electrolyte and composite cathode membranes. Beneficial to the robust adhesion, the composite cathode and Li6PS5Cl membranes are tightly compacted under a low stacking pressure of 100 MPa which is a fifth of the conventional pressure. Moreover, the electrode/electrolyte interface can sustain adequate contact throughout electrochemical cycling. As expected, the FeS2-based ASSLBs exhibit outstanding rate performance and cyclic stability, contributing a reversible discharged capacity of 370.7 mAh g-1 at 0.3C after 200 cycles. More importantly, the meticulous dQ/dV analysis reveals that the three-dimensional PTFE binder effectively binds the discharge products with sluggish kinetics (Li2S and Fe) to the ion-electron conductive network in the composite cathode, thereby preventing the electrochemical inactivation of products and enhancing electrochemical performance. Furthermore, FeS2-based pouch-type cells are fabricated, demonstrating the potential of PTFE-based dry-process technology to scale up ASSLBs from laboratory-scale mold cells to factory-scale pouch cells. This feasible dry-processed technology provides valuable insights to advance the practical applications of ASSLBs.

Fusion Bonding Technique for Solvent-Free Fabrication of All-Solid-State Battery with Ultrathin Sulfide Electrolyte

For preparing next-generation sulfide all-solid-state batteries (ASSBs), the solvent-free manufacturing process has huge potential for the advantages of economic, thick electrode, and avoidance of organic solvents. However, the dominating solvent-free process is based on the fibrillation of polytetrafluoroethylene, suffering from poor mechanical property and electrochemical instability. Herein, a continuously solvent-free paradigm of fusion bonding technique is developed. A percolation network of thermoplastic polyamide (TPA) binder with low viscosity in viscous state is constructed with Li6PS5Cl (LPSC) by thermocompression (≤5 MPa), facilitating the formation of ultrathin LPSC film (≤25 µm). This composite sulfide film (CSF) exhibits excellent mechanical properties, ionic conductivity (2.1 mS cm-1), and unique stress-dissipation to promote interface stabilization. Thick LiNi0.83Co0.11Mn0.06O2 cathode can be prepared by this solvent-free method and tightly adhered to CSF by interfacial fusion of TPA for integrated battery. This integrated ASSB shows high-energy-density feasibility (>2.5 mAh cm-2 after 1400 cycles of 9200 h and run for more than 10 000 h), and energy density of 390 Wh kg-1 and 1020 Wh L-1. More specially, high-voltage bipolar cell (≥8.5 V) and bulk-type pouch cell (326 Wh kg-1) are facilely assembled with good cycling performance. This work inspires commercialization of ASSBs by a solvent-free method and provides beneficial guiding for stable batteries.