Magneto-conversion anode design for unlocking high energy density and dendrite-free hybrid lithium–ion/lithium–metal batteries

Abstract

By coupling intercalation with controlled lithium (Li) metal plating, hybrid Li–ion/Li–metal anodes offer a promising route toward higher energy-density and dendrite-free Li batteries. However, conventional graphite-based electroactive hosts inherently suffer from limited capacity and sluggish Li plating kinetics, which constrain further advancement. Here, we introduce a novel magnetically tailored conversion strategy that integrates ferromagnetic transition metal oxides with an interfacial conductive carbon layer under an external magnetic field to significantly increase the energy-density and reversibility of the electrode. The converted ferromagnetic nanoparticles, embedded within a lithiophilic Li₂O matrix, regulate spatially uniform Li⁺ flux and homogenize nucleation barriers via magnetically modulated ionic pathways and interfacial Li kinetics. Concurrently, the intrinsic spin-polarized surface capacitance of the ferromagnetic conversion chemistry is exploited to enhance charge storage and reversibility. Operando X-ray micro-imaging and computational modelling reveal dynamic evolution of Li deposition, showing that micromagnetic fields from magnetized ferromagnetic nanoparticles induce Lorentz force-driven ionic redistribution, guiding compact and dendrite-free Li growth, even at high deposition rates. As a result, a superior reversible capacity of 1400 mAh g⁻¹ is achieved with outstanding cyclability, maintaining a Coulombic efficiency over 99% after 300 cycles and further validating its practical viability in stable full-cell configurations. These insights suggest a new paradigm in hybrid anode design by bridging conversion chemistry with magnetically modulated interfacial Li dynamics.