Lithium ion secondary batteries are one of the most important energy storage systems because of their higher energy density and power density. In particular, many different types of cathode materials are studied for increasing capacity and cell potential. Spinel-type LiNi_0.5Mn_1.5O₄ have been attracting significant attention due to higher redox potential, lower cost and low environmental load. The LNMO is possibly sorted into two type of spinel structure with different space group, ordered and disordered phase, which is typically identified due to formation of oxygen deficient, which cause reduction of Mn⁴⁺ to Mn³⁺ based on charge valance.     

Disordered spinel structures could also lead to improved rate capability due to higher electronic conductivity and Li-ion diffusive of Mn³⁺ ion, However, too much concentration of Mn³⁺ lead to structural distortion and disproportionation, and which can be reduce cyclability. Thus, suitable Mn cation adjustment as well as surface stabilization with thin layer for insulating the direct contact with liquid electrolyte is one of important factor for advanced LiNi_0.5Mn_1.5O₄ electrode.  

In this work, we performed two ways for the enhancement of high-voltage cyclability and rate capability in LiNi_0.5Mn_1.5O₄crystals through the substitution of F anion within oxygen deficient LiNi_0.5Mn_1.5O_4-d.crystals as well as surface modification with self-assembled monolayer of fluorocabon containing organosilane compound. We further calculational studies on the effect of fluorine substitution on their LIBs characteristics, including rate capability and cyclability by using first-principle calculation.