# Photochromic Molybdate for Advancing Anode Capacity of Lithium‐Ion Battery

## TL;DR

A new photochromic molybdate material is introduced to improve lithium-ion battery anode performance without complex equipment.

## Contribution

The first use of a photochromic polyoxomolybdate to enhance LIB anode capacity and rate performance is presented.

## Key findings

- The material MV[Mo9O28] forms a stable charge-separated state after UV irradiation, lasting up to 2 years.
- The anode capacity increases by 132 ± 14 mAh·g−1 after coloration and retains 7.6% more capacity at higher current densities.
- Theoretical calculations confirm the stable charge-separated state is responsible for improved performance.

## Abstract

Decoupling strategies can effectively enhance lithium‐ion battery (LIB) capacity, but suffer from the need for complex equipment, preventing widespread applicability. This work offers, for the first time, a decoupling strategy of electron‐transfer photochromism to improve LIB anode performance, without requiring complex equipment. The approach utilizes a new crystalline photochromic molybdate, MV[Mo9O28] (1, MV = methyl viologen cation) as the LIB anode. After UV irradiation, the initial 1 undergoes electron transfer from O to Mo, accompanied by a color change from colorless to blue and the generation of an ultra‐stable charge‐separated state with a lifetime of up to 2 years under ambient conditions. The observed capacity increases by 132 ± 14 mAh· g−1 across various current densities after coloration, along with superior rate performance—retaining 7.6% more capacity than the initial state even at a 100‐fold higher current density. Theoretical calculations confirm that the enhanced capacity and rate performance are attributable to the stable charge‐separated state. This unprecedented photochromic charge‐separated strategy contributes to the exploration of new outstanding anode materials for LIBs.

Photochromic polyoxomolybdate is first used to enhance the anode capacity and rate performance of Li‐ion batteries.