Copper sulfide nanoparticles as high-performance cathode materials for Mg-ion batteries

Abstract

Rechargeable magnesium batteries are appealing as safe, low-cost systems with high-energy-density storage that employ predominantly dendrite-free magnesium metal as the anode. While significant progress has been achieved with magnesium electrolytes in recent years, the further development of Mg-ion batteries, however, is inherently limited by the lack of suitable cathode materials, mainly due to the slow diffusion of high-charge-density Mg-ions in the intercalation-type host structures and kinetic limitations of conversion-type cathodes that often causes poor cyclic stability. Nanostructuring the cathode materials offers an effective means of mitigating these challenges, due to the reduced diffusion length and higher surface areas. In this context, we present the highly reversible insertion of Mg-ions into nanostructured conversion-type CuS cathode, delivering high capacities of 300 mAh g −1 at room temperature and high cyclic stability over 200 cycles at a current density of 0.1 A g −1 with a high coulombic efficiency of 99.9%. These materials clearly outperform bulk CuS, which is electrochemically active only at an elevated temperature of 50 °C. Our results not only point to the important role of nanomaterials in the enhancement of the kinetics of conversion reactions but also suggest that nanostructuring should be used as an integral tool in the exploration of new cathodes for multivalent, i.e., (Mg, Ca, Al)-ion batteries.

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

“…[ 57,58 ] These results agree with other reports of nano‐CuS prepared through a variety of methods: enhanced Mg 2+ diffusion kinetics leads to improved electrochemical performance which can be obtained by using nanoparticles to prepare Mg electrodes. [ 59,60 ]…”

Cu2MoS4 Nanotubes as a Cathode Material for Rechargeable Magnesium‐ion Battery

“…A reduction of molybdenum center (Mo 6+ +3e − →Mo 3+ ) or a combination of reduction of molybdenum center (Mo 6+ +2e − →Mo 4+ ) and copper center (Cu + +1e − →Cu 0 ) could be responsible for the electrochemical reaction with Mg 2+ ion. Indeed, the reduction of Cu + center causing the intercalation of Mg 2+ has been reported for the case of CuS cathode …”

Electrophoretic Deposition of Aged and Charge Controlled Colloidal Copper Sulfide Nanoparticles

“…In addition, localized surface plasmon resonance (LSPR) effects are exhibited in Cu 2-x S NP due to the high free carrier density, depending on stoichiometry and size [ 19 , 20 ]. Hence, Cu 2-x S NPs are suitable for nanostructured applications such as battery electrodes [ 21 ], photocatalysts [ 22 ], sensors [ 23 ], biomedical devices [ 24 ], and photovoltaic cells [ 25 ], as they provide unique properties that cannot be achieved using the traditional bulk materials. For example, Otelaja et al (2014) [ 26 ] demonstrated that the EPD films obtained from Cu 2-x S NPs dispersed in hexane exhibit a higher conductivity than those prepared by spin-casting.…”