New tin-containing spinel sulfide electrodes for ambient temperature rocking chair cells

Spinel compounds with Cu2CoSn2S8 and CuCoSn3S8 stoichiometries were evaluated as the active electrode materials in lithium anode and ‘rocking chair’-type cells. For lithium cells using CuCoSn3S8 cathodes, the current-composition curves obtained by step potential electrochemical spectroscopy revealed a first Co111/Co11 reduction peak during cell discharge at about 1 F mol−1, which is not observed for the Cu2CoSn3S8 composition. Lithium-ion diffusion coefficients were also larger in this interval. The galvanostatic cycling behaviour in the 2–2.5 V potential window leads to little capacity losses after the first cycle when using CuCoSn3S8 electrodes. Three electrodes sulfide/ LiClO4 (PC)/LiCoO2 rocking chair cells using lithium auxiliary electrode were examined by galvanostatic cycling experiments. When the cells are cycled in the 1.5–2.5 V interval, cell capacity (15 mAh g−1) remains basically unaffected between the second and tenth cycles. The presence of SnIV ions in these solids which are suitable for reduction at lower voltages may be of interest as overdischarge protection.