Li(V(0.5)Ti(0.5))S(2) as a 1 V lithium intercalation electrode

Graphite, the dominant anode in rechargeable lithium batteries, operates at ∼0.1 V versus Li(+)/Li and can result in lithium plating on the graphite surface, raising safety concerns. Titanates, for example, Li(4)Ti(5)O(12), intercalate lithium at∼1.6 V versus Li(+)/Li, avoiding problematic lithium plating at the expense of reduced cell voltage. There is interest in 1 V anodes, as this voltage is sufficiently high to avoid lithium plating while not significantly reducing cell potential. The sulfides, LiVS(2) and LiTiS(2), have been investigated as possible 1 V intercalation electrodes but suffer from capacity fading, large 1st cycle irreversible capacity or polarization. Here we report that the 50/50 solid solution, Li(1+x)(V(0.5)Ti(0.5))S(2), delivers a reversible capacity to store charge of 220 mAhg(−1) (at 0.9 V), 99% of theoretical, at a rate of C/2, retaining 205 mAhg(−1) at C-rate (92% of theoretical). Rate capability is excellent with 200 mAhg(−1) at 3C. C-rate is discharge in 1 h. Polarization is low, 100 mV at C/2. To the best of our knowledge, the properties/performances of Li(V(0.5)Ti(0.5))S(2) exceed all previous 1 V electrodes.