Design of a hydrolysis-supported coating layer on the surface of Ni-rich cathodes in secondary batteries

The formation of Li₄SiO₄ (LSO) coating layer on LiNi_0.88Co_0.05Mn_0.07O₂ (LNCM) was achieved by incorporating a new tetraethyl orthosilicate (TEOS)-dropping coating method. This concept includes the hydrolysis reaction of TEOS on the surface of Ni_0.88Co_0.05Mn_0.07(OH)₂ and the subsequent calcination process with lithium source to obtain LSO-coated LNCM cathode materials successfully during the calcination process. This method provides the driving force for the formation of a more uniform and thin coating layer compared with the traditional wet-chemical coating method. The bare LNCM and LSO-coated LNCM showed similar capacity retention rates during room temperature (25°C) cycling, but the capacity retention of LSO-LNCM (81.6% after 100 cycles) for the cycling test at elevated temperature was significantly increased compared with bare LNCM (63.69% after 100 cycles). Additionally, the Li-ion accessibility of the coated LNCM electrode was improved by the existence of the Li-containing coating materials, and the results of analysis by the galvanostatic intermittent titration technique (GITT) confirmed the better Li-ion diffusivity of the coated sample. These results indicate the high possibility of this novel coating method for application in various materials for developing secondary batteries.