Surface modification of LiCoO_2 with Li_(3x)La_(2/3-x)TiO_3 for all-solid-state lithium ion batteries using Li_2S-P_2S_5 glass-ceramic

摘要

To improve the electrochemical performance of all-solid-state cells using LiCoO_2, a nano-sized lithium lanthanum titanate Li_(3x)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_2S ? 22P_2S_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_(3x)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 ofLi_(3x)La_(2/3-x)TiO_3 because a side reaction between the interface of LiCoO_2 and 78Li_2S ? 22P_2S_5 glass-ceramic solid electrolyte can be suppressed.