Effects of gradient concentration on the microstructure and electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials

Abstract

Nickel(Ni)-rich layered materials have attracted considerable interests as promising cathode materials for lithium ion batteries (LIBs) owing to their higher capacities and lower cost. Nevertheless, Mn-rich cathode materials usually suffer from poor cyclability caused by the unavoidable side-reactions between Ni⁴⁺ ions on the surface and electrolytes. The design of gradient concentration (GC) particles with Ni-rich inside and Mn-rich outside is proved to be an efficient way to address the issue. Herein, a series of LiNi_0.6Co_0.2Mn_0.2O₂ (LNCM622) materials with different GCs (the atomic ratio of Ni/Mn decreasing from the core to the outer layer) have been successfully synthesized via rationally designed co-precipitation process. Experimental results demonstrate that the GC of LNCM622 materials plays an important role in their microstructure and electrochemical properties. The as-prepared GC3.5 cathode material with optimal GC can provide a shorter pathway for lithium-ion diffusion and stabilize the near-surface region, and finally achieve excellent electrochemical performances, delivering a discharge capacity over 176 mAh·g⁻¹ at 0.2 C rate and exhibiting capacity retention up to 94% after 100 cycles at 1 C. The rationally-designed co-precipitation process for fabricating the Ni-rich layered cathode materials with gradient composition lays a solid foundation for the preparation of high-performance cathode materials for LIBs.

Key words： gradient concentration; Ni-rich; LiNi_0.6Co_0.2-Mn_0.2O₂; electrochemical performance; lithium-ion battery

Acknowledgements

The authors are grateful to the financial support of the National Natural Science Foundation of China (Grant Nos. 91834301, 91534102 and 21271058). This work is also supported by Science and Technology Project of Anhui Province (Nos. 201903a05020021 and 17030901067).ƒ

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-020-1918-9 and is accessible for authorized users.

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