Impact of Li(3)BO(3) Addition on Solid Electrode-Solid Electrolyte Interface in All-Solid-State Batteries

All-solid-state lithium-ion batteries raise the issue of high resistance at the interface between solid electrolyte and electrode materials that needs to be addressed. The article investigates the effect of a low-melting Li(3)BO(3) additive introduced into LiCoO(2)- and Li(4)Ti(5)O(12)-based composite electrodes on the interface resistance with a Li(7)La(3)Zr(2)O(12) solid electrolyte. According to DSC analysis, interaction in the studied mixtures with Li(3)BO(3) begins at 768 and 725 °C for LiCoO(2) and Li(4)Ti(5)O(12), respectively. The resistance of half-cells with different contents of Li(3)BO(3) additive after heating at 700 and 720 °C was studied by impedance spectroscopy in the temperature range of 25–340 °C. It was established that the introduction of 5 wt% Li(3)BO(3) into LiCoO(2) and heat treatment at 720 °C led to the greatest decrease in the interface resistance from 260 to 40 Ω cm(2) at 300 °C in comparison with pure LiCoO(2). An SEM study demonstrated that the addition of the low-melting component to electrode mass gave better contact with ceramics. It was shown that an increase in the annealing temperature of unmodified cells with Li(4)Ti(5)O(12) led to a decrease in the interface resistance. It was found that the interface resistance between composite anodes and solid electrolyte had lower values compared to Li(4)Ti(5)O(12)|Li(7)La(3)Zr(2)O(12) half-cells. It was established that the resistance of cells with the Li(4)Ti(5)O(12)/Li(3)BO(3) composite anode annealed at 720 °C decreased from 97.2 (x = 0) to 7.0 kΩ cm(2) (x = 5 wt% Li(3)BO(3)) at 150 °C.