Dual-phase structure design of Mn-site nickel doping Li2MnSiO4@C cathode material for improved electrochemical lithium storage performance

Summary The lithium transition metal orthosilicates (Li 2 MnSiO 4 ) compounds are considered key materials for the next-generation lithium-ion batteries (LIBs). However, they exhibit poor electronic conductivity and structural stability. Herein, the dual-phase ( Pmn2 1 , and Pn ) coexisting Li 2 Mn 1− x Ni x SiO 4 @C is prepared successfully via a two-step calcination process to address the aforementioned problems. The orthorhombic Pmn2 1 and Pn phase are expected to bring well solid-state Li diffusion properties (D Li + ) and structural stability for electrode material, respectively. Also, the Ni doping and carbon coating are expected to raise electronic conductivity. Then, the electrochemical performance of LIBs utilizing LiMn 0.995 Ni 0.005 SiO 4 @C, LiMn 0.985 Ni 0.015 SiO 4 @C, and LiMn 0.92 Ni 0.08 SiO 4 @C (ZNi-02 to ZNi-04) as cathode materials are investigated and compared with that of the LiB using Li 2 MnSiO 4 @C (ZNi-01). The ZNi-04 sample-based LiB shows well D Li + and a peak discharge capacity as high as 188.4 mAh g −1 . In addition, the ZNi-04 sample can still maintain a capacity of about 80 mAh g −1 at rate of 8 C. Such excellent electrochemical performance is ascribed to the synergistic effect of the dual-phase coexistence, the proper amount of Ni doping, and surface coating of carbon, which enhances the electrical conductivity and structural stability. Thus, Li 2 Mn 1− x Ni x SiO 4 @C has broad application chances as a high-performance LIBs electrode material.