Stabilization of the surface and lattice structure for LiNiCoMnO BO atomic layer deposition and post-annealing

The Ni-rich LiNi x Co y Mn 1− x − y O 2 cathode ( x ≥ 0.6) shows weak rate capability due to its deleterious surface lithium impurities and lattice defects. Herein, uniform ultrathin B 2 O 3 coatings built by atomic layer deposition (ALD) are utilized to construct a B 3+ doped single-crystal LiNi 0.83 Co 0.12 Mn 0.05 O 2 (SC83) via post-annealing. LiOH is consumed due to reacting with B 2 O 3 during the B 2 O 3 ALD process, and then B 2 O 3 is transformed into B 3+ doping accompanied by the reduction of Li 2 CO 3 during the post-annealing. Surface and bulk characterization results show that B 3+ tends to diffuse into the bulk of the SC83 during the post-annealing, which expands the a and c axes and reduces the Li + /Ni 2+ mixing of the SC83. When the B 3+ content exceeds 0.54 wt%, B 3+ segregation occurs on the surface of the SC83, which decreases the electronic conductivity of the SC83. B 3+ doping at the content of 0.54 wt% gives the highest capacity of 177.6 mA h g −1 at 1C rate. The B 2 O 3 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. The effect of reactive B 2 O 3 coatings and B 3+ doping content on the electrochemical performance of a Ni-rich cathode is revealed.