# Metastable Structure for Ultra‐Sustainable, High Capacity and Kinetics‐Enhanced Magnesium‐Ion Battery

## TL;DR

This paper introduces a new strategy for magnesium-ion batteries that improves performance by creating a metastable cathode structure, leading to better energy storage and longer battery life.

## Contribution

The paper introduces a metastable phase evolution strategy for magnesium-ion battery cathodes, enabling enhanced kinetics and stability.

## Key findings

- The T-VS4 cathode achieves a high specific capacity of 205.4 mAh g−1 at 50 mA g−1.
- The cathode exhibits excellent rate capability up to 1000 mA g−1 and long-term cycling stability over 3000 cycles.
- The metastable MgxT-VS4 structure facilitates Mg2+ migration and multi-electron redox reactions.

## Abstract

Cost‐effective magnesium ion batteries (MIBs) offer a promising new pathway for next‐generation large‐scale energy storage, and yet its development is largely hindered by the severe polarization, limited rate capability, and poor cycling stability, where the challenges are largely rooted in the sluggish kinetics of Mg2+ storage. Here, we report a metastable phase evolution strategy that enables high‐performance Mg2+ storage by leveraging Ti‐modulated VS4 (T‐VS4), demonstrating a structurally soft and yet dynamically adaptive lattice, which are among the preconditions for the metastable phase formation. Metastable MgxT‐VS4 is formed during the initial Mg2+ intercalation, significantly facilitating the subsequent Mg2+ migration, favoring multi‐electron redox reaction, and enhancing the charge transfer kinetics. Impressively, the T‐VS4 cathode demonstrates exceptional Mg2+ storage performance with a high specific capacity (205.4 mAh g−1 at 50 mA g−1), excellent rate capability (up to 1000 mA g−1), and long‐term cycling stability (over 3000 cycles). This work exemplifies a new metastable phase engineering approach as the design paradigm for breaking kinetic limitations in MIBs, offering a novel avenue toward next‐generation energy storage systems.

A metastable‐phase evolution strategy is proposed for magnesium‐ion batteries, enabling the in situ formation of a metastable MgxT‐VS4 cathode during cycling. The metastable state reshapes Mg2+ storage kinetics and enhances structural stability, offering a new design paradigm for multivalent ion battery cathodes.