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The cycling stability of a Ni-enriched compositionally graded LiNi 0.76 Co 0.09 Mn 0.15 O 2 cathode doped with Al (1 and 2 mol %) was explicitly demonstrated by cycling the cathodes in a full cell against a graphite anode up to 1000 cycles. Without Al doping, the pristine gradient cathode retained 88% of the initial discharge capacity, whereas the 2 mol % Al-doped gradient cathode retained 95% of its original capacity. Meanwhile, LiNi 0.82 Co 0.14 Al 0.04 O 2 (NCA), representing a typical cathode for commercialized electric vehicles, retained only 80% of the initial capacity. It was shown that Al doping together with the unique morphology of the compositionally graded cathode was able to suppress the microcracking and helped to preserve the mechanical integrity of the cathode particles, whereas the benchmark NCA cathode sustained continuous capacity loss during cycling and was completely pulverized. The remarkable long-term cyclability of the Al-doped gradient cathodes was attributed to the enhanced structural and the surface stabilization, which also improved the thermal stability.
Kim et al. (2017) studied this question.