Surface modification of LiCoO2 with Li3xLa2/3−xTiO3 for all-solid-state lithium ion batteries using Li2S–P2S5 glass–ceramic

To improve the electrochemical performance of all-solid-state cells using LiCoO2, a nano-sized lithium lanthanum titanate (Li3xLa2/3−xTiO3; LLTO) coating is employed to modify the surface of LiCoO2 via a sol–gel process. The crystalline structure of pristine LiCoO2 is not affected by the coating process, and nano-sized LLTO particles uniformly adhere to the surface of the LiCoO2 particle. All-solid-state cells with an In/78Li2S·22P2S5/LiCoO2 structure were constructed and tested by charge and discharge cycling at a current density of 0.06 mA cm−2 with a cut off voltage of 1.9–3.68 V (vs. Li–In). The all-solid-state cell using LiCoO2 modified with 0.05 wt% of Li0.75La0.42TiO3 shows the highest reversible capacity and capacity retention during all cycles. The Li3xLa2/3−xTiO3 coatings are effective in reducing the charge-transfer resistance and electrode polarization by control of the composition and coating amount of Li3xLa2/3−xTiO3 because a side reaction between the interface of LiCoO2 and 78Li2S·22P2S5 glass–ceramic solid electrolyte can be suppressed.