Engineering Detrimental Functional Groups in Conductive Additives Toward High-Performance All-Solid-State Batteries.

Conductive additives are of great importance for the adequate utilization of active materials in all-solid-state lithium batteries by establishing conductive networks in the composite cathode. However, it usually causes severe interfacial side reactions with solid electrolytes, especially sulfide electrolytes, leading to sluggish ion transportation and accelerated performance degradation. Herein, a simple hydrogen thermal reduction process is proposed on a commonly used conductive additive Super P, which effectively removes the surface oxygen functional groups and weakens the interfacial side reactions with sulfide. With a small amount of 1 wt % reduced Super P, ASSLBs demonstrates a competitive capacity of 180.2 mAh g-1, which is much higher than the 130.8 mAh g-1 of untreated Super P. Impressively, reduced Super P based ASSLBs also exhibit a higher capacity retention of 81.8 % than 64.6 % of untreated Super P. The cathode interfacial chemical evolutions reveal that reduced Super P could effectively alleviate the side reactions of sulfide. Reduced Super P shows better reversible capacity compared to reduced carbon nanofiber with almost no loss of capacity retention, due to its more complete conductive network. Our results highlight the importance of oxygen-containing functional groups for conductive additives, lightening the prospect of low-cost 0D conductive additives for practical 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.

Advances and Prospects of Sulfide All-Solid-State Lithium Batteries via One-to-One Comparison with Conventional Liquid Lithium Ion Batteries.

Owing to the safety issue of lithium ion batteries (LIBs) under the harsh operating conditions of electric vehicles and mobile devices, all-solid-state lithium batteries (ASSLBs) that utilize inorganic solid electrolytes are regarded as a secure next-generation battery system. Significant efforts are devoted to developing each component of ASSLBs, such as the solid electrolyte and the active materials, which have led to considerable improvements in their electrochemical properties. Among the various solid electrolytes such as sulfide, polymer, and oxide, the sulfide solid electrolyte is considered as the most promising candidate for commercialization because of its high lithium ion conductivity and mechanical properties. However, the disparity in energy and power density between the current sulfide ASSLBs and conventional LIBs is still wide, owing to a lack of understanding of the battery electrode system. Representative developments of ASSLBs in terms of the sulfide solid electrolyte, active materials, and electrode engineering are presented with emphasis on the current status of their electrochemical performances, compared to those of LIBs. As a rational method to realizing high energy sulfide ASSLBs, the requirements for the sulfide solid electrolytes and active materials are provided along through simple experimental demonstrations. Potential future research directions in the development of commercially viable sulfide ASSLBs are suggested.