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 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/78Li(2)S center dot 22P(2)S(5)/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 78Li(2)S center dot 22P(2)S(5) glass ceramic solid electrolyte can be suppressed.