Understanding the key role of {100} exposed crystal facets on the electrochemistry of the spinel LiMn2O4 cathode

Abstract

Tuning the exposed crystal facets of {111}, {110}, and {100} in the spinel LiMn₂O₄ cathode has been proposed to boost their structural stability for advanced lithium-ion batteries. Nevertheless, the role of these varied exposed crystal facets on the electrochemical properties is still controversial. Herein, we design octahedral LiMn₂O₄ with only exposed {111} facets and truncated octahedral LiMn₂O₄ (TO-LMO) with exposed {111} and {100} facets. The TO-LMO with different ratios of exposed {100}/{111} facets are prepared by employing the Li-deficient composite as an intermediate phase. It is demonstrated that the exposed {111} facets truncated by a portion of {100} facets reduce the Mn²⁺ content dissolving into the electrolytes and improve the cycling stability, especially at high operating temperatures. The improvement becomes remarkable with an increasing ratio of exposed {100}/{111} facets. The TO-LMO with a higher ratio of exposed {100}/{111} facets shows superior cycling stability with a capacity retention of 91.2% after 200 cycles at 50 °C and high-rate capability with a reversible capacity reaching 100 mA h g⁻¹ at 10C. These findings reveal the vital effect of {100} exposed crystal facets on the improvement of electrochemistry for spinel Mn-based cathodes.