Hybrid Ionogel Electrolytes for Advanced Lithium Secondary Batteries: Developments and Challenges.

Incidents in the use of lithium-ion batteries are usually caused by the malfunction of flammable organic liquid electrolytes with poor thermal stability. Therefore, the development of noncombustible electrolytes is regarded as one of the most effective means to prevent the safety hazards of lithium-ion batteries. Ionic liquids have attracted much interest recently, mainly due to their high ionic conductivity, low volatility, and incombustibility. The application of ionic liquids to the preparation of quasi-solid-state gel electrolytes combines the advantages of ionic liquids and avoids the risks of organic liquid electrolytes. Therefore, the solid-state ionogels have been considered as a promising alternative electrolyte system, especially for the much-desired energy storage devices with higher energy density and flexibility. This review focuses on the recent progress of ionogel electrolytes for lithium-ion batteries. The preparation strategies for ionogel electrolytes based on different frameworks, namely inorganic matrix, organic matrix, and organic-inorganic hybrid matrix, are discussed. Subsequently, efforts to improve the properties of the ionogel electrolytes, including the ionic conductivity, mechanical properties, and lithium-ion transfer number, are summarized. Besides, the applications of ionogel electrolytes in high-voltage lithium-ion batteries and lithium metal batteries as well as the batteries under extreme environments are outlined. Finally, the perspectives on studying and improving the performances of ionogel electrolytes for advanced lithium-ion batteries are provided.

Interface Engineering to Boost Thermal Safety of Microsized Silicon Anodes in Lithium-Ion Batteries.

Battery safety is vital to the application of lithium-ion batteries (LIBs), especially for high energy density cells applied in electric vehicles. As an anode material with high theoretical capacity and natural abundance, Si has received extensive attention for LIBs. However, it suffers from severe electrode pulverization during cycling due to large volume changes and an unstable solid electrolyte interphase (SEI), resulting in accelerated capacity fading and even safety hazards. Therefore, safe and long-term cycling of Si-based anodes, especially under high-temperature cycling, is highly challenging for state-of-the-art high-energy LIBs. The thermal behavior of SEI is crucial for a high safety battery as the decomposition of SEI is the first step in thermal runaway. Here, highly reversible and thermotolerant microsized Si anodes for safe LIBs are demonstrated. Comprehensive electrochemical/mechanical/thermochemical behaviors of the SEI are systematically investigated. The rational design of robust SEI endows the Si-based cells with long-term durability at elevated temperatures and superior thermal safety. This work paves the way for designing industrial-scale, low-cost, microsized Si anodes with applications in next-generation LIBs with high energy densities and high safety.