Guixian Li

Electrochemical performances of two kinds of ternary electrolyte mixtures with lithium bis(oxalate)borate

Conductivities (κ) of PC (propylene carbonate)/EMC (ethyl methyl carbon ate)/DMC (dimethyl carbonate) and EC (ethylene carbonate)/EMC/DMC solutions of lithium bis(oxalate)borate (LiBOB) were experimentally determined at a temperature (θ) range from −40.0 to 60.0°C. Under such experimental conditions, the effect factors on the κ, such as the salt molar concentrations (m), and the volume ratio of solvent compositions, were also investigated. The results showed that, in wide θ range, the higher κ were obtained with 0.7 mol L−1 LiBOB in PC/EMC/DMC and 0.6 mol L−1 LiBOB in EC/EMC/DMC and with a volume ratio of 1: 1: 1 and 1: 1: 2, respectively. When used in LiFePO4/Li cells, compared to the cell with the electrolyte system of 1.0 mol L−1 LiPF6-EC/EMC/DMC (1: 1: 1), LiBOB cells with PC/EMC/DMC and EC/EMC/DMC electrolyte systems with the same volume mixture solvent compositions exhibit several advantages, such as more stable cycle performance, higher mean voltage, excellent large current discharge capability, more capacity retention at high temperature, and more stable storage performance, etc. This study not only shows that LiBOB is a very promising alternative salt for lithium ion chemistry, but also provides appropriate solvent to improve LiBOB’s electrochemical performance.

Electrochemical performance of LiNi0.5Mn1.5O4 doped with la and its compatiblity with new electrolyte system

Cathode materials LiNi0.5Mn1.5O4 and LiNi0.5 − x/2LaxMn1.5 − x/2O4 (x = 0.04, 0.1, 0.14) were successfully prepared by the sol-gel self-combustion reaction (SCR) method. The X-ray diffraction (XRD) patterns indicated that, a few of doping La ions did not change the structure of LiNi0.5Mn1.5O4 material. The scanning electronic microscopy (SEM) showed that the sample heated at 800°C for 12 h and then annealed at 600°C for 10 h exhibited excellent geometry appearance. A novel electrolyte system, 0.7 mol L−1 lithium bis(oxalate)borate (LiBOB)-propylene carbonate (PC)/dimethyl carbonate (DMC) (1: 1, v/v), was used in the cycle performance test of the cell. The results showed that the cell with this novel electrolyte system performed better than the one with traditional electrolyte system, 1.0 mol L−1 LiPF6-ethylene carbonate (EC)/DMC (1: 1, v/v). And the electrochemical properties tests showed that LiNi0.45La0.1Mn1.45O4/Li cell performed better than LiNi0.5Mn1.5O4/Li cell at cycle performance, median voltage, and efficiency.