Electrochemical probings of Li1+xVS2

Re-investigation of Li insertion into the layers of Li1+xV1−yMyS2 (M = Cr, Ni and y = 0 and 0.1, x ≤ 0.8) reveals that the transformation of Li from octahedral to tetrahedral sites in Li1+xVS2 leads to a 1.0 V stabilization V(III)/V(II) plateau at 0.1C rate. Substitution of 10 mol% Ni for V to form Li1+xV0.9Ni0.1S2 increases the voltage on Li insertion by 0.1–0.2 V compared to nominal LiVS2, but it leads to an overall decrease in the capacity. An irreversible capacity loss on the initial charge/discharge cycle is the result of formation of an SEI layer at and below 1 V versus lithium. 10 mol% substitution of Cr for V (i.e. Li1+xV0.9Cr0.1S2) has no effect on the voltage, but it increases the capacity fade as the discharge/charge cycles progress.