A porous lithium silicate ceramic separator prepared from diatomite: Effect of LiOH on pore structure, composition and electrochemical properties of the separator

Diatomite is used as main raw material and calcined with LiOH to prepare a porous ceramic separator with lithium silicate as its main component. This diatomite ceramic separator has a developed three-dimensional pore structure and excellent thermal stability. With the increase of LiOH content, the pore size and porosity of the separator are improved, and the main components of the separator gradually change from Li2Si2O5 to Li2Si2O5–Li2SiO3 mixed phase. Lithium ions can migrate both in the separator channels and in the lithium silicate ceramic matrix, where lithium silicate acts as solid electrolyte. When the LiOH content is 30 wt%, the synergistic effect of the two ion migration modes enables the separator (DCS30 separator) to obtain maximum ionic conductivity (1.80 mS cm−1). The discharge specific capacity of the cell with DCS30 separator at the current density of 10 C is 45% higher than that of the cell with commercial polyolefin separator. And after 200 cycles, the cell with DCS30 separator still has a capacity retention rate of 99.9%. Therefore, the diatomite ceramic separator is very promising to be applied in the high-power lithium ion batteries.