Surface sulfidization of spinel LiNi0.5Mn1.5O4 cathode material for enhanced electrochemical performance in lithium-ion batteries

Abstract Stable interfacial structure is crucial for achieving superior electrochemical performances of high-voltage cathode materials for lithium-ion batteries. Herein, surface-sulfidized LiNi0.5Mn1.5O4 cathode materials are synthesized through electrostatic interactions between positively-charged LiNi0.5Mn1.5O4 and negatively-charged sulphur ion. A significant improvement in the rate capability, cycling stability and thermal stability has been achieved in surface-sulfidized LiNi0.5Mn1.5O4 electrode. A discharge capacity of 93.4 mAh g−1 can be still delivered at 2 C after 2500 cycles with a capacity retention of 74.9%, which is far beyond that of the pristine one (45.3% after 1800 cycles). 3D porous structure of sulfidized-layer helps to form a stable cathode electrolyte interphase (CEI) film on LiNi0.5Mn1.5O4 surface via accommodating interfacial strain between active materials and CEI film. Metal-sulfides on LiNi0.5Mn1.5O4 surface could facilitate electron transfer across the LiNi0.5Mn1.5O4/electrolyte interface, reduce charge transfer resistance and consequently enhance rate capability. The adsorption of SO42− on LiNi0.5Mn1.5O4 surface also helps to enhance LiNi0.5Mn1.5O4/electrolyte interfacial stability. Moreover, the reduced work function induced by surface-sulfidization is considered to suppress decomposition of the electrolyte, improve interfacial stability and improve cycling stability. In terms of the superior electrochemical performances, surface-sulfidized LiNi0.5Mn1.5O4 composites can be utilized as a promising cathode material for high-performance lithium ion batteries.