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

Abstract To improve the electrochemical performance of all-solid-state cells using LiCoO 2 , a nano-sized lithium lanthanum titanate (Li 3 x La 2/3− x TiO 3 ; LLTO) coating is employed to modify the surface of LiCoO 2 via a sol–gel process. The crystalline structure of pristine LiCoO 2 is not affected by the coating process, and nano-sized LLTO particles uniformly adhere to the surface of the LiCoO 2 particle. All-solid-state cells with an In/78Li 2 S·22P 2 S 5 /LiCoO 2 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 LiCoO 2 modified with 0.05 wt% of Li 0.75 La 0.42 TiO 3 shows the highest reversible capacity and capacity retention during all cycles. The Li 3 x La 2/3− x TiO 3 coatings are effective in reducing the charge-transfer resistance and electrode polarization by control of the composition and coating amount of Li 3 x La 2/3− x TiO 3 because a side reaction between the interface of LiCoO 2 and 78Li 2 S·22P 2 S 5 glass–ceramic solid electrolyte can be suppressed.