Thermal Expansion Neutralization Enhancing the Cycling Stability of Ni-Rich LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Material

As promising cathode candidates with advantageous capacityandprice superiority for lithium-ion batteries, Ni-rich materials areseverely impeded in the practical application due to their poor microstructuralstability induced by the intrinsic Li+/Ni2+ cationmixing and mechanical stress accumulation upon cycling. In this work,a synergetic approach is demonstrated to improve the microstructuraland thermal stabilities of Ni-rich LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode material through takingadvantage of the thermal expansion offset effect of the LiZr2(PO4)(3) (LZPO) modification layer. The optimizedNCM622@LZPO cathode exhibits a significantly enhanced cyclabilitywith a capacity retention of 67.7% after 500 cycles at 0.2 C and deliversa specific capacity of 115 mAh g(-1) with a capacityretention of 64.2% after 300 cycles under 55 & DEG;C. Exploiting thechemical environment analysis of the Ni element detected by the synchrotronradiation technique, it is found that the mixing degree of Li+/Ni2+ cations in the bulk Ni-rich material canbe effectively depressed through interfacial Zr4+ dopingduring the preparation of the LZPO-modified material. Additionally,time- and temperature-dependent powder diffraction spectra were collectedto monitor the structure evolutions of pristine NCM622 and NCM622@LZPOcathodes in the initial cycles and under various temperatures, revealingthe contribution of negative thermal expansion LZPO coating in promotingmicrostructural stability of the bulk NCM622 cathode. The introductionof NTE functional compounds might provide a universal strategy toaddress the stress accumulation and volume expansion issues of variouscathode materials for advanced secondary-ion batteries.