Conductivity and applications of Li-biphenyl-1,2-dimethoxyethane solution for lithium ion batteries

The total conductivity of Li-biphenyl-1,2-dimethoxyethane solution (Li_xBp(DME)_9.65, Bp=biphenyl, DME=1,2-dimethoxyethane, x=0.25, 0.50, 1.00, 1.50, 2.00) is measured by impedance spectroscopy at a temperature range from 0℃ to 40℃. The Li_1.50Bp(DME)_9.65 has the highest total conductivity 10.7 mS/cm. The conductivity obeys Arrhenius law with the activation energy (E_a(x=0.50)=0.014 eV, E_a(x=1.00)=0.046 eV). The ionic conductivity and electronic conductivity of Li_xBp(DME)_9.65 solutions are investigated at 20℃ using the isothermal transient ionic current (ITIC) technique with an ion-blocking stainless steal electrode. The ionic conductivity and electronic conductivity of Li_1.00Bp(DME)_9.65 are measured as 4.5 mS/cm and 6.6 mS/cm, respectively. The Li_1.00Bp(DME)_9.65 solution is tested as an anode material of half liquid lithium ion battery due to the coexistence of electronic conductivity and ionic conductivity. The lithium iron phosphate (LFP) and Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) are chosen to be the counter electrode and electrolyte, respectively. The assembled cell is cycled in the voltage range of 2.2 V–3.75 V at a current density of 50 mA/g. The potential of Li_1.00Bp(DME)_9.65 solution is about 0.3 V vs. Li⁺/Li, which indicates the solution has a strong reducibility. The Li_1.00Bp(DME)_9.65 solution is also used to prelithiate the anode material with low first efficiency, such as hard carbon, soft carbon and silicon.