Direct Nano-Synthesis Methods Notably Benefit Mg-Battery Cathode Performance

(a) XRD patterns and (b) SEM images of micron-sized CuCo2S4 prepared through a solid state synthesis (red) and then ball-milled to reduce particle size (blue). (c) XRD pattern of nano-sized X-CuCo2S4 prepared directly through a low temperature melt of xanthate salts (black). Inset shows an SEM image, exhibiting a comparable particle size to ball-milled material. (d) Voltage profiles of X-, BM-, and micron-CuCo2S4 cycled at 10 mA·g-1 with a Mg anode. APC/THF electrolyte was used to collect 60 °C data and APC/G4 was used to collect 150 °C data.

Scientific Achievement

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.

Research Details

  • 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.

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DOI: 10.1002/smtd.202000029

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