Synthesis And Modification Of LiNi_0.5Mn_1.5O₄as High Voltage Cathode Material For Lithium Ion Batteries

LiNio.5Mn1.5O4as high-voltage cathode material for lithium ion batteries could reversibly intercalate/deintercalate lithium ions at4.7V plateaus and with146.7mAh·g-1as its theoretical capacity. Compared to the traditional lithium ion cathode materials, LiNio.5Mn1.5O4presens much higher charge/discharge plateaus and energy density.In this paper, spinel cathode material LiNi0.5Mn1.5O4was successfully prepared through solid-state and co-preciptation methods and four important factors were investigated. The influence of the synthesis methods and sintering temperature as well as AIF3, BiPO4and FePO4as suface coating materials on the structure, morphology and electrochemical performance of LiNi0.5Mn1.5O4were investiagted. Additionally, the application of LiNi0.5Mn1.5O4in different electrolyte systems was also investigated.Measurement results demonstrated that cubic spinel structure particles were prepared via solid-state and (NH4)C2O4co-precipitation methods, spherical second particles were prepared via Na2CO3co-precipitation method, all the samples have Fd3m space group. The intial specific capacity of LiNi0.5Mn1.5O4synthesized via solid-state method and sintered at900℃is132.4mAh·g-1at0.1C and81.0%of the initial capacity retained after50cycles, LiNi0.5Mn1.5O4also presented excellent rate performance with specific capacity nearly110mAh·g-1at IOC Surface modifications also improved the performance and relieved the polarization of LiNi0.5Mn1.5O4after1wt.%AIF3-coated, the capacity retentions were improved form84.3%to91.8%at0.5C after50cycles and from80.6%to91.4%at IOC after100cycles. EC/EMC-based electrolyte systems could satisfy the application of high voltage cathode material in the traditional systems. In our study, the application LiNi0.5Mn1.5O4in0.95mol·L-1LiPF6+0.05mol·L-1LiB(C2O4)2-EC/EMC (3:7, v/v) presented best electrochemical performance with a capacity retention of87.8%at0.5C after150cycles and capacity100.4mAh·g-1at10C as well as83%capacity retained after220cycles at55℃.The capacity of LiNi0.5Mn1.5O4at0.5C was over120mAh·g-1and nearly no decline arter30cycles at0℃...