| Lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB) has good thermal stability, excellent film-forming properties, high capacity to maintain at high temperature. But the solubility and conductivity of LiBOB are low. The solid electrolyte interface (SEI) film formed in the electrolyte of LiBOB will gradually thicken with the recycling process. To improve the performance of LiBOB electrolyte, the performance of LiBOB mixed electrolyte and LiBOB additives were researched by cyclic voltammetry(CV), charge-discharge testing, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) methods.LiFePO4 and SCMG (shape controlled micrographite) were used as cathode and anode materials. The study indicated that the cyclic performance of cathode and anode materials in 0.8 mol·L-1 LiBOB/EC+PC+EMC (vol. 3:3:4) were worse than those of in 1.0mol·L-1 LiPF6/EC+EMC+DMC (vol. 3:3:4) electrolyte.When 5 mass% acetonitrile (ACN) was added to the LiBOB electrolyte, the conductivity of the electrolyte was increased, and the cyclic stability of LiFePO4 was improved. The initial capacity of SCMG was improved in the electrolyte of LiBOB contained 5 mass% ACN, but the cycle performance was depressed. When 2 mass% vinylene carbonate (VC) was added to the electrolyte of LiBOB, the cyclic performance of LiFePO4 were reduced, and the initial capacity of SCMG was improved, but the cycle performance was not affected.It was blended the electrolyte of 0.8 mol·L-1 LiBOB/EC+PC+EMC (vol. 3:3:4) and 1.0 mol·L-1 LiPF6/EC+PC+EMC (vol. 3:3:4) with the volume content of 1:0,3:1,1:1,1:3,0:1. The mixed electrolyte of 25% LiBOB and 75% LiPF6 behaved the best electrode material compatibility and excellent rate performance. BOB- polymerization was restrained effectively. The capacity of LiFePO4 in 0.1C, 0.5C, 1.0C rate mantained in 127 mAh·g-1, 120 mAh·g-1 and 115 mAh·g-1, and the reversible capacity of SCMG maintained in 314 mAh·g-1. Moreover the cyclic stability was excellent. It satisfied the requirement of application in hybrid electric vehicles (HEVs) and has the practical value. |
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