Stabilization of the surface and lattice structure for LiNi0.83Co0.12Mn0.05O2via B2O3 atomic layer deposition and post-annealing†

The Ni-rich LiNi_xCo_yMn_1−x−yO₂ cathode (x ≥ 0.6) shows weak rate capability due to its deleterious surface lithium impurities and lattice defects. Herein, uniform ultrathin B₂O₃ coatings built by atomic layer deposition (ALD) are utilized to construct a B³⁺ doped single-crystal LiNi_0.83Co_0.12Mn_0.05O₂ (SC83) via post-annealing. LiOH is consumed due to reacting with B₂O₃ during the B₂O₃ ALD process, and then B₂O₃ is transformed into B³⁺ doping accompanied by the reduction of Li₂CO₃ during the post-annealing. Surface and bulk characterization results show that B³⁺ tends to diffuse into the bulk of the SC83 during the post-annealing, which expands the a and c axes and reduces the Li⁺/Ni²⁺ mixing of the SC83. When the B³⁺ content exceeds 0.54 wt%, B³⁺ segregation occurs on the surface of the SC83, which decreases the electronic conductivity of the SC83. B³⁺ doping at the content of 0.54 wt% gives the highest capacity of 177.6 mA h g⁻¹ at 1C rate. The B₂O₃ ALD coupled with post-annealing builds a highly electronic and Li⁺ conductive surface and bulk for the SC83, which is the key to the improvement of the rate capability.