The diaphragm of a lithium-ion battery has important functions, such as preventing a short circuit between the positive and negative electrodes of the battery and improving the movement channel for electrochemical reaction ions.
The zinc borate modified diaphragm was used as the structural-functional ceramic composite diaphragm, and the zinc borate and PVDF were prepared at a mass ratio of 90:10, and the ordinary diaphragm and the zinc oxide modified diaphragm were used as comparison samples. The battery electrolyte was 1 M LiPF6 in EC/DEC (1:1 vol ratio).
Therefore, the composite diaphragm can store more electrolytes under the same volume. Zinc borate has the synergistic effect of boric acid groups and polar metal bonds, which promotes the transmission of lithium ions in the electrode, thereby increasing the conductivity of lithium ions.
The LiFePO 4 /Li battery with composite diaphragm exhibits excellent rate and cycle performance. Due to the unique chemical structure of zinc borate, the Zn–O bond and -BO 3 group in the structure have a polar bond and Lewis acid action, respectively.
The lithium-ion migration numbers of ZnB modified diaphragm are 0.41, while the lithium-ion migration numbers of ZnO modified diaphragm and routine diaphragm are 0.3 and 0.21. When the battery is working, the charge transfer rate of lithium ions reflects the charging and discharging characteristics of the battery.
The BN diaphragm can achieve uniform nucleation of lithium, enhance the inhibition of lithium dendrite growth, and improve the overall electrochemical performance. In Li/Cu batteries, the Coulombic efficiency is as high as 92% after 90 cycles at one mA cm −2 .