Understanding and tackling lattice manganese exfoliation and deactivation of battery-type NiMn-LDH in fast electrochemical energy storage

Abstract

The suppression of irreversible phase change in battery-type materials during electrochemical process, leading to high-performance asymmetric supercapacitors (ASCs), remains one of the crucial challenges for the new generation of electrochemical energy storage devices. Herein, we propose a pre-activation strategy to address the corresponding problem based on an in-depth study of the failure mechanism of nickel–manganese layered double hydroxide (LDH), which is the inhibition of the exfoliation and deactivation of lattice Mn during the cycling process. The modified NiMn-LDH shows enhanced electrochemistry performance compared to pristine NiMn-LDH, with an increase in specific capacity from 855 to 1082 C g⁻¹ and a doubling of stability after 3000 cycles. Furthermore, the assembled ASC device achieves a high specific energy density of 48.9 W h kg⁻¹ at a power density of 810 W kg⁻¹. The anchored, activated lattice Mn provided by hydrogen peroxide in the pre-activation strategy is proved to play a vital role in achieving high-performance ASCs. This work paves a new avenue to solve the long-standing significant challenge of battery-type materials for asymmetric supercapacitors.