Improved electrochemical performance of high voltage spinel LiNi0.5Mn1.5O4 achieved by a dual electronic and ionic surface modification strategy

Spinel LiNi0.5Mn1.5O4 (LNMO) is considered as a promising cathode for lithium-ion batteries for its high operating voltage, energy density and low cost. However, it suffers from serious capacity fading due to the unstable surface structure. In this work, LNMO modified with ionic conductor Li1.4Al0.4Ti1.6(PO4)3 (LATP) and helical carbon nanotube (HCNT) was prepared. The effects of LATP and HCNT coating on the structure, morphology and electrochemical performance of LNMO were explored. It is found that the phase structure and morphology were little altered while the concentration of Mn3+ increased with LATP coating. The sample modified with both LATP and HCNT shows the best electrochemical performance. It kept the capacity of 109.2 mAh g−1 after 500 cycles at 2C with the capacity retention rate of 92.3%, much higher than those of pristine LNMO and the HCNT or LATP-only coated cathodes. The enhanced performance could be ascribed to the improved electronic and/or ionic conductivity of the interface between the cathode and electrolyte and the protective effect against the side reaction from the electrolyte.