A novel Mg cathode material – CuCo2S4 – was identified as a conversion material where direct nano-synthesis was required to provide the best electrochemical performance and deliver 350 mAh·g-1 at 60 °C, a capacity nearly double that of ball-milled material with similar dimensions.
Significance and Impact
This work provides synthetic considerations which may be crucial in the discovery and design of multivalent cathode materials so that promising candidates are not overlooked when screening for new hosts.
- Nano-sized binary sulfides were directly prepared using wet synthesis, which significantly improved electrochemical performance (vs. micron-sized particles) in both intercalation (TiS2) and conversion (CuS) Mg cathode materials.
- Ternary CuTi2S4 could not be prepared through direct nano-synthesis, so bulk material was ball-milled (BM) to reduce particle size.
- BM-Ti2S4 exhibited better capacity retention than micron-sized material; however, the high energy milling process caused surface degradation which limited the initial discharge capacity.
- Nano-sized CuCo2S4 was directly prepared through a low temperature melt of xanthate salts (X).
- The electrochemical performance of bulk material was compared with nano-sized BM- and X-CuCo2S4 to directly assess the impact of synthetic methodology. X-CuCo2S4 exhibited significantly improved performance despite the apparent inactivity of micron-sized particles.