Unravelling the Secrets of Magnetic Field-Enhanced Li⁺ Ion Conduction in Solid-State Electrolytes

Solid-state lithium metal batteries (SSLMBs) promise high energy density but are limited by sluggish Li⁺ transport and dendrite formation in solid-state electrolytes (SSEs). Here, we introduce an operational, rather than materials-based, strategy to accelerate ion conduction by applying an external magnetic field during cell operation. The field induces a magnetohydrodynamic (MHD) effect, where the Lorentz force between the ionic current and the magnetic field promotes Li⁺ mobility and directs ion motion along favorable pathways. Under 240 mT, the ionic conductivity of an ion gel SSE rises from 7.44 × 10^-4 S cm^-1 to 1.64 × 10^-3 S cm^-1 and the Li⁺ transference number increases from 0.181 to 0.277 at 25 °C. Consequently, SSLMBs with a LiFePO₄ cathode achieve 157.2 mAh g^-1 after 250 cycles with 96.3% capacity retention. This work elucidates magnetic-field-enhanced Li⁺ conduction and offers a simple, scalable route to boost SSE performance toward practical, high-energy SSLMBs.