Flexible and Scalable Magnesium Replenishment in NCM Cathode Enabled by Mobile Mg2+ Enriched MgV2O4

A small amount of Mg 2+ doping can show a significant effect on the surface protection and structural stability of the nickel-rich layered oxide cathode, but the traditional doping process involves completely changing the initial raw material proportions with subsequent trial and error adjustments. Herein, a concept of Mg 2+ release film is proposed, in which Mg 2+ can easily permeate into various layered oxide cathodes during cycling. Meanwhile, to realize this concept, MgV 2 O 4 with mobile Mg 2+ in the structures and then fabricated a self-supporting MgV 2 O 4 membrane are synthesized. As a protective layer for cathode, the MgV 2 O 4 membrane release Mg 2+ in situ during the electrochemical process, providing structural reinforcement to the cathode surface as a “pillar” within the lattice. Thanks to the MgV 2 O 4 membrane, the cycle life of LiNi o.8 Co 0.1 Mn 0.1 O 2 (NCM811) coupled with the MgV 2 O 4 interlayer at 1.0 C is increased by 1.9 times compared to bare NCM811. Furthermore, this novel Mg 2+ releasing film demonstrates excellent versatility, enabling other nickel-based layered oxide to achieve a high-capacity retention of 86.4% after 800 cycles at 1.0 C. This approach provides scalable cathode protection and repair strategies for commercially viable batteries.