Mitigated voltage decay and improved electrochemical properties of 0.5Li2MnO3•0.5LiNixCoyMn1-x-yO2 cathode via composition optimizing

As the most promising high-energy-density cathode material for lithium-ion batteries, the Li-rich layered oxide materials (LLOs) suffer from severe voltage decay, which hinders their practical application. In this work, a series of 0.5Li(2)MnO(3)center dot 0.5LiNi(x)Co(y)Mn(1-x-y)O(2) with different compositions are designed and prepared. It is found that as the Ni content increased, the electrochemical activation of the Li2MnO3 component is restrained, resulting in the reduced capacity of LLOs. Hence, 0.5Li(2)MnO(3)center dot 0.5LiNi(0.8)Co(0.1)Mn(0.1)O(2) delivers a low capacity of 228 mAh g(-1) compared to 251 mAh g(-1) of 0.5Li(2)MnO(3)center dot 0.5LiNi(1/3)Co(1/3)Mn(1/3)O(2). Furthermore, the increased Ni3+/Ni2+ ratio as well as the reduced electrochemical activation of Li2MnO3 restrains the Mn4+/Mn3+ redox and stabilizes the layered structure. As a result, the layered-to-spinel phase transformation is suppressed and 0.5Li(2)MnO(3) 0.5LiNi(0.8)Co(0.1)Mn(0.1)O(2) delivers a smaller voltage decay of 373 mV after 150 cycles at 1 C. Meanwhile, high-Ni-content LLOs exhibit lower charge transfer resistance and enhanced Li+ diffusion constant, which endows them improved rate performance. Especially, LL-523 delivers a combination of high capacity of 247 mAh g(-1), improved rate capability of 98 mAh g(-1) at 10 C, and mitigated voltage decay of 486 mV after 150 cycles at 1 C. Our results provide an effective way to design novel Li-rich layered cathode via composition optimization for the improved electrochemical performances.