Suppressed Internal Intrinsic Stress Engineering in High-Performance Ni-Rich Cathode Via Multilayered In Situ Coating Structure

LiNixCoyAlzO2(NCA) cathode materials are drawing widespread attention, but the huge gap between the ideal and present cyclic stability still hinders their further commercial application, especially for the Ni-rich LiNixCoyAlzO2 (x > 0.8, x + y + z = 1) cathode material, which is owing to the structural degradation and particles' intrinsic fracture. To tackle the problems, Li0.5La2Al0.5O4 in situ coated and Mn compensating doped multilayer LiNi0.82Co0.14Al0.04O2 was prepared. XRD refinement indicates that La-Mn co-modifying could realize appropriate Li/Ni disorder degree. Calculated results and in situ XRD patterns reveal that the LLAO coating layer could effectively restrain crack in secondary particles benefited from the suppressed internal strain. AFM further improves as NCA-LM2 has superior mechanical property. The SEM, TEM, XPS tests indicate that the cycled cathode with LLAO-Mn modification displays a more complete morphology and less side reaction with electrolyte. DEMS was used to further investigate cathode-electrolyte interface which was reflected by gas evolution. NCA-LM2 releases less CO2 than NCA-P indexing on a more stable surface. The modified material presents outstanding capacity retention of 96.2% after 100 cycles in the voltage range of 3.0-4.4 V at 1C, 13% higher than that of the pristine and 80.8% at 1 C after 300 cycles. This excellent electrochemical performance could be attributed to the fact that the high chemically stable coating layer of Li0.5La2Al0.5O4 (LLAO) could enhance the interface and the Mn doping layer could suppress the influence of the lattice mismatch and distortion. We believe that it can be a useful strategy for the modification of Ni-rich cathode material and other advanced functional material.