Despite increasing demands for higher energy density cathode materials, they can be bigger threats unless thermal stability is guaranteed. Herein, the thermal stability of Li_xNi_0.835Co_0.15Al_0.015O₂ (NCA83) and Li_xNi_0.8Co_0.15Al_0.05O₂ (NCA80) is compared by using in-situ transmission electron microscopy. Analysis demonstrates that NCA83 and NCA80 degrade thermally by distinct mechanisms. Al prevents the transition to CoO₂-type O1 phase by suppressing O-slab gliding by residual Li. At 67% SOC, in the sub-surface area, thermal degradation of NCA80 is mainly due to reduction of Ni, whereas thermal degradation of NCA83 is a result of concurrent reduction of Ni and Co. The difference indicates that NCA83 has both earlier transition to the rock-salt structure and poorer thermal stability than NCA80. This study presents a protocol to properly evaluate new high energy density cathode materials, and provides important insights into the thermal degradation mechanism of Ni-based layered oxides.

尽管对更高能量密度的阴极材料的需求不断增加，但除非保证热稳定性，否则它们可能是更大的威胁。在此，使用原位透射电子显微镜比较了Li _x Ni _0.835 Co _0.15 Al _0.015 O ₂（NCA83）和Li _x Ni _0.8 Co _0.15 Al _0.05 O ₂（NCA80）的热稳定性。分析表明，NCA83和NCA80通过不同的机理热降解。Al阻止过渡到CoO ₂通过抑制残留锂引起的O型平板滑动，使O1型O1相产生。在SOC为67％时，在次表面区域，NCA80的热降解主要是由于Ni的还原，而NCA83的热降解是同时还原Ni和Co的结果。岩石盐结构和热稳定性较NCA80差。这项研究提出了一个协议，以适当地评估新型高能量密度阴极材料，并提供了对镍基层状氧化物的热降解机理的重要见解。