Simultaneous Bulk Doping and Surface Coating of Sn to Boost the Electrochemical Performance of LiNiO2

Co-free, nickel-rich layered materials are crucial for the cost reduction of lithium ion batteries to meet the requirement of the electric vehicle market. However, the strategies to synthesize the practically applicable Co-free, nickel-rich materials are still challenging. Herein, we report a strategy for fabrication of the materials by Sn modification of LiNiO2. Under high temperature conditions, bulk doping of the Sn4+ ions and surface coating of Li2SnO3 can be simultaneously achieved. Due to the presence of the strong Sn-O bond and chemically inert property of the coating layer, the structure reversibility, integrity of the secondary particles, and interfacial stability of the Sn-modified materials during charge/discharge cycling can be greatly enhanced relative to those of the counterpart pristine LiNiO2. The optimized material, LiNi0.97Sn0.03O2, can deliver a discharge capacity of 216.76 mAh g-1 at 0.1 C with a capacity retention of 80.61% after 250 cycles at 0.5 C. In addition, the enlargement of the crystal lattice by Sn doping is also beneficial to the rate capability of the materials, providing a discharge capacity of 148.06 mAh g-1 at 5 C. Thus, the simultaneous dual functionalization of Sn to LiNiO2 could be a practicable approach to gaining the Co-free, nickel-rich materials.