Micron-sized single-crystal cathodes for sodium-ion batteries.

Confining the particle-electrolyte interactions to the particle surface in electrode materials is vital to develop sustainable and safe batteries. Micron-sized single-crystal particles offer such opportunities. Owing to the reduced surface area and grain boundary-free core, particle-electrolyte interactions in micron-sized single-crystal particles will be confined to the particle surface. Here, we reveal the potential of such materials in sodium-ion batteries. We synthesized and investigated the chemical, electrochemical, and thermal properties of single-crystalline P2-type Na _0.7 Mn _0.9 Mg _0.1 O ₂ as a cathode material for sodium-ion batteries. Single-crystalline Na _0.7 Mn _0.9 Mg _0.1 O ₂ with a mean particle size of 8.1 μm exhibited high cycling and voltage stability. In addition, the exothermic heat released by the charged single-crystal Na _0.7 Mn _0.9 Mg _0.1 O ₂ cathodes was four times lower than that of the corresponding polycrystalline Na _0.7 Mn _0.9 Mg _0.1 O ₂ . This significantly enhances the thermal stability of electrode materials and possibly mitigates thermal runaways in batteries. Surprisingly, single crystals of Na _0.7 Mn _0.9 Mg _0.1 O ₂ were relatively stable in water and ambient atmosphere.
Competing Interests: The authors declare no competing interests.
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