Li+ and Cl- co-doped LiNi0.5Mn1.5O4 cathode material with truncated octahedral shape and enhanced electrochemical performance for Li-ion batteries

High-voltage spinel Li1+xNi0.5Mn1.5O4-xClx (0 <= x <= 0.04) cathode materials with different contents of Li+ and Cl co-doping were obtained through a solid-state process. Scanning electron microscopy and transmission electron microscopy images indicate that pure LiNi0.5Mn1.5O4 (LNMO, space group Fd-3 m) particles possess an octahedral morphology, predominantly exhibiting {111} crystallographic planes. While the specimens with Li+ and Cl co-doping display not only {111} crystal facets but also positive {100} and {110} facets (i.e. truncated octahedral shape) that could facilitate Li+ transport and stabilize the spinel structure. Compared to the pure LNMO, the Li+ and Cl- co-doped LNMO electrodes display superior electrochemical performances. For example, the Li1.03Ni0.5Mn1.5O3.97Cl0.03 exhibits the superior rate capability, with discharge capacities of 92.3 and 52.6 mA h g(-1) at 7C and 10C, respectively, which are much higher than those of pure LNMO (54.2 and 7.8 mA h g(-1) at 7C and 10C). An improved electrochemical properties of LNMO-Cl-0.03 is attributable to its relatively larger portion of {100} and {110} facets, lower charge-transfer resistance and electrode polarization, and higher Li+ diffusion coefficient.