Enhancing the rate performance by in situ surface engineering to form amorphous fast ion conductor Li1.5La1.5TeO6 on Ni-rich cathodes

Layered Ni-rich cathodes LiNi _{1- x - y}Co _xMn _yO ₂ (1- x- y ≥ 0.6, NCM) struggle with thermal stability and capacity decline over time. Herein, we utilized the sol-gel method to in-situ coat a nanolayer of the amorphous fast ion conductor Li _1.5La _1.5TeO ₆ (LLTeO) on LiNi _0.83Co _0.12Mn _0.05O ₂ (NCM83). This coating reduces lithium residues and enhance the diffusion of Li ⁺ ion at the interface of the cathode materials, resulting in improved cycling stability and rate performance of NCM83. The Li ⁺ diffusion coefficient increased from 8.757 × 10 ^–12 cm ²·s ^-1 for pristine NCM83 to 2.967 × 10 ^–11 cm ²·s ^-1 for NCM83 modified with a 5 wt% LLTeO coating ( [email protected]). After 100 cycles at a discharge rate of 3 C, the discharge specific capacity of NCM-0.05LLTeO increased to 144.56 mAh·g ^-1 compared to the pristine NCM83 of 129.35 mAh·g ^-1, and the capacity retention for NCM-0.05LLTeO and the pristine NCM83 were 88.97 % and 83.22 %, respectively. This study manifests the efficacy of amorphous LLTeO coatings in surmounting the prevalent limitations of Ni-rich cathodes.