Specific countermeasures to intrinsic capacity decline issues and future direction of LiMn2O4 cathode

Spinel LiMn2O4 cathodes are particularly attractive in lithium-ion batteries (LIBs) owing to the nontoxic Mn sources, abundant reserves, and high specific power. However, poor cycling stability due to the significant capacity decay becomes the key limitation for its application. With the continuous exploration, some deep-rooted causes of capacity decay are being challenged. To date, three intrinsic mechanisms have been shown to cause capacity loss, including the Jahn-Taller (J-T) effect, Mn disproportionation, and oxygen vacancy formation. Specifically, the capacity loss especially below 3 V caused by J–T distortion hinders the achievement of theoretical capacity. Besides, the irreversible phase transitions arising from Mn(III) disproportionation exacerbates Mn dissolution. Even worse, the Mn ions migration due to oxygen loss during the electrochemical cycling also leads to severe phase transition. Although some reviews have involved various strategies to overcome the related drawbacks, a summary of more comprehensive and specific coping strategies along with recent advances and future development direction is still lacking. Herein, we first introduce the comprehensive intrinsic capacity fading mechanisms of LiMn2O4. Then, recent progress in suppressing the J-T distortion, Mn disproportionation, and Mn migration is systematically reviewed, with a special focus on the advances in the up-to-date strategies such as cation disorder and epitaxial coating. We also put forward future research directions and opportunities for the development of longer-life LiMn2O4 cathode. This review aims to offer some guidance for the rational designing of sufficiently durable LiMn2O4 cathodes and the maximizing of their inherent capacity for meeting the high demands in LIBs.