Comprehensive Investigation of a Slight Overcharge on Degradation and Thermal Runaway Behavior of Lithium-Ion Batteries

High-Safety Lithium-Ion Batteries with Silicon-Based Anodes Enabled by Electrolyte Design

High-energy-density lithium-ion batteries (LIBs) with high safety have long been pursued for extending the cruise range of electric vehicles. Owing to the high gravimetric capacity, silicon is a promising alternative to the convention graphite anode for high-energy LIBs. However, it suffers from intrinsic poor interfacial stability with liquid electrolytes, inevitably increasing the risk of thermal runaway and posing serious safety challenges. In this review, we will focus on mitigating thermal runaway of silicon anodes-based LIBs from the perspective of electrolyte design. First, the thermal runaway mechanism of LIBs is briefly introduced, while the specific thermal failure reactions associated with silicon anodes and electrolytes are discussed in detail. We then summarize the safety countermeasures (e. g., thermally stable solid electrolyte interphase, nonflammable electrolytes, highly stable lithium salts, mitigating electrode crosstalk, and solid-state electrolytes) enabled by customized electrolyte design to address these triggers of thermal runaway. Finally, the remaining unanswered questions regarding the thermal runaway mechanism are presented, and future directions to achieve intrinsically safe electrolytes for silicon-based anodes are prospected. This review is expected to provide insightful knowledge for improving the safety of LIBs with silicon-based anodes.

All-temperature area battery application mechanism, performance, and strategies

Further applications of electric vehicles (EVs) and energy storage stations are limited because of the thermal sensitivity, volatility, and poor durability of lithium-ion batteries (LIBs), especially given the urgent requirements for all-climate utilization and fast charging. This study comprehensively reviews the thermal characteristics and management of LIBs in an all-temperature area based on the performance, mechanism, and thermal management strategy levels. At the performance level, the external features of the batteries were analyzed and compared in cold and hot environments. At the mechanism level, the heat generation principles and thermal features of LIBs under different temperature conditions were summarized from the perspectives of thermal and electrothermal mechanisms. At the strategy level, to maintain the temperature/thermal consistency and prevent poor subzero temperature performance and local/global overheating, conventional and novel battery thermal management systems (BTMSs) are discussed from the perspective of temperature control, thermal consistency, and power cost. Moreover, future countermeasures to enhance the performance of all-climate areas at the material, cell, and system levels are discussed. This study provides insights and methodologies to guarantee the performance and safety of LIBs used in EVs and energy storage stations.

Temperature-Shift-Induced Mechanical Property Evolution of Lithium-Ion Battery Separator Using Cyclic Nanoindentation

The evolution of mechanical properties of separators affected by temperature shifts is imperative for the performance of the lithium-ion battery. The flexible film characteristics hinder the evaluation of the micromechanical properties of separators. In the present study, considering the susceptibility of separators to temperature fluctuations, the temperature distribution of the battery during the discharging process at subzero temperature is obtained. Three sets of separator samples subjected to various temperature shifts are prepared. Through multicycle depth-sensitive nanoindentation, the temperature-dependent weakening of elastic modulus and hardness of separators is experimentally verified. Moreover, the variation trends of elastic modulus, hardness, and hysteresis response of the separator specimens in terms of temperature are investigated via extracting from the multicycle loading-unloading nanoindentation responses. The temperature-dependent variations in the elastic modulus of the separator were investigated by following heating, cooling, and thermostatic processes. Meanwhile, the indentation tests also verify that the effect of temperature shifts on the hardness exhibits an attenuation trend when heating or cooling is followed by a thermostatic process. The variation analysis of nanoindentation hardness as a function of temperature shifts shows typical size effects dependent on the nanoindentation depth. The temperature-induced residual stress and elemental distribution are also analyzed through characterization using X-ray diffraction and energy-dispersive X-ray spectroscopy, respectively. The obtained evolution law of temperature shift-induced mechanical properties of a separator could facilitate the optimal design of the separators and provide the supporting data to enhance the safety performance of lithium-ion batteries.