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 (LNMO) 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, Mn cation adjustment is one of important factor for advanced LNMO electrode.  

Therefore, in order to control efficiently Mn cation, fluorine was considered for substitution within LNMO. Because fluorine can easily control cation distribution due to charge valance and, which can adjust the degree of disorder. Besides, strong M-F bonding can be maintains spinel structure during long-term operation. In present work, we have demonstrated the flux growth of idiomorphic LiNi_0.5 Mn_1.5O_4-xF_x crystals and the effect of fluorine substitution on their LIBs characteristics, including rate capability and cyclability.