Constructing Robust Cathode/Electrolyte Interphase for Ultrastable 4.6 V LiCoO2 under -25 °C

Uniform Al Doping in LiCoO2 for 4.55 V Lithium-Ion Pouch Cells

As the classic cathode material, lithium cobalt oxide (LiCoO2, LCO) suffers from severe structural and interfacial degradation at voltage >4.5 V, which induces fast capacity decay of the cells. Herein, we adopt a simple and effective method, doping aluminum (Al) cations in precursors, to improve the structural stability of LCO and systematically investigate the effect of Al doping on the electrochemical performances. Doping in precursors rather than bulk particles is beneficial to realize uniform Al ions distribution. Even at 4.5 V charging voltage, the LCO/graphite pouch cells with high Al doping levels (8500 ppm) deliver initial and reversible discharge capacities of 386 and 369 mAh after 500 cycles, respectively. The capacity retention is as high as 95.5%. When the cutoff voltage reaches 4.55 V, the pouch cell maintains 79.0% of the first-cycle discharge capacity after 500 cycles. With optimized electrolyte, the pouch cell realizes 87.3% of the initial discharge capacity after 500 cycles at 45 °C. Moreover, the thermal safety performance of the pouch cells with Al doping is promising. Our work displays an excellent inspiration for developing high-voltage, long-cycle, and safe LCO cathode for commercial lithium-ion batteries.

Electronic Modulation and Structural Engineering of Carbon-Based Anodes for Low-Temperature Lithium-Ion Batteries: A Review

Lithium-ion batteries (LIBs) have become the preferred battery system for portable electronic devices and transportation equipment due to their high specific energy, good cycling performance, low self-discharge, and absence of memory effect. However, excessively low ambient temperatures will seriously affect the performance of LIBs, which are almost incapable of discharging at -40~-60 °C. There are many factors affecting the low-temperature performance of LIBs, and one of the most important is the electrode material. Therefore, there is an urgent need to develop electrode materials or modify existing materials in order to obtain excellent low-temperature LIB performance. A carbon-based anode is one candidate for use in LIBs. In recent years, it has been found that the diffusion coefficient of lithium ion in graphite anodes decreases more obviously at low temperatures, which is an important factor limiting its low-temperature performance. However, the structure of amorphous carbon materials is complex; they have good ionic diffusion properties, and their grain size, specific surface area, layer spacing, structural defects, surface functional groups, and doping elements may have a greater impact on their low-temperature performance. In this work, the low-temperature performance of LIBs was achieved by modifying the carbon-based material from the perspectives of electronic modulation and structural engineering.

Low-temperature lithium-ion batteries: challenges and progress of surface/interface modifications for advanced performance

Lithium-ion batteries are in increasing demand for operation under extreme temperature conditions due to the continuous expansion of their applications. A significant loss in energy and power densities at low temperatures is still one of the main obstacles limiting the operation of lithium-ion batteries at sub-zero temperatures. In addition to electrodes and electrolytes, more attention should be paid to the electrode-electrolyte interface, considering that the total internal resistance of batteries at low temperatures is dominated by interfacial charge transfer resistance. Here, we first review the main interfacial processes in lithium-ion batteries at low temperatures, including Li⁺ solvation or desolvation, Li⁺ diffusion through the solid electrolyte interphase and electron transport. Then, recent progress on the electrode surface/interface modifications in lithium-ion batteries for enhanced low-temperature performance is presented in detail. The lasting challenges and perspectives regarding electrode/electrolyte interface control in low-temperature lithium-ion batteries are finally discussed.