Graphene-oxide-coated LiNi0.5Mn1.5O4 as high voltage cathode for lithium ion batteries with high energy density and long cycle life

Abstract

Lithium ion batteries are receiving enormous attention as power sources and energy storage devices in the renewable energy field. With the ever increasing demand for higher energy and power density, high voltage cathodes have emerged as an important option for new generation batteries. Here, we report graphene-oxide-coated LiNi_0.5Mn_1.5O₄ as a high voltage cathode and demonstrate that the batteries showed superior cycling performance for up to 1000 cycles. Mildly oxidized graphene oxide coating was found to improve the battery performance by enhancing the conductivity and protecting the cathode surface from undesired reactions with the electrolyte. As a result, the graphene-oxide-coated high voltage cathode LiNi_0.5Mn_1.5O₄ showed 61% capacity retention after 1000 cycles in the cycling test, which converts to only 0.039% capacity decay per cycle. At large current rates of 5 C, 7 C and 10 C, the batteries were able to deliver 77%, 66% and 56% of the 1 C capacity, respectively (1 C = 140 mA g⁻¹). In contrast, the LiNi_0.5Mn_1.5O₄ cathode without graphene oxide coating showed 88.7% capacity retention after only 100 cycles. The promising results demonstrated the potential of developing high energy density batteries with the high voltage cathode LiNi_0.5Mn_1.5O₄ and improving the battery performance by surface modification with mildly oxidized graphene oxide.