Researchers at Southeast University and HiNa Battery Technology in China have developed a sodium metal battery that can charge fully in four minutes and retain 90% of its capacity over 2,000 cycles, performance that, if scaled, could reshape the economics of electric vehicle batteries.
The key innovation, published in Nano-Micro Letters, is a tin-based quasi-solid gel electrolyte (Sn-FB QSE) fabricated through an in situ polymerization strategy. The electrolyte addresses the two fundamental challenges that have prevented sodium metal batteries from competing with lithium-ion: dendrite growth and limited cycle life.
How it works
The electrolyte uses a “dual interlocked mediator” design. Tin(II) ions (Sn²⁺) initiate the polymerization of 1,3-dioxolane into a uniform polymer network, while difluoro(oxalato)borate (DFOB⁻) anions act as a retarding agent that prevents runaway polymerization, resulting in a gel with high puncture strength (8.5 kPa) and low polydispersity.
The design achieves a sodium-ion transference number of 0.94, meaning sodium ions carry almost all the ionic current, eliminating concentration gradients that drive dendrite nucleation. For comparison, conventional quasi-solid electrolytes achieve transference numbers of 0.4 to 0.7.
During battery operation, the system builds protective layers on both electrodes simultaneously: Sn²⁺ is reduced at the anode to form a hybrid NaSn alloy and inorganic-rich solid-electrolyte interphase (SEI) that homogenizes the electric field, while DFOB⁻ oxidizes at the cathode to build a thin, robust cathode-electrolyte interphase (CEI). This bilateral engineering is what gives the battery its stability over thousands of cycles.
Performance
At a 15C charge rate, the battery reaches full charge in approximately four minutes, delivering 80.1 mAh g⁻¹ of specific capacity. At a more moderate 3C rate (20-minute charge), it retains 90% of its capacity over 2,000 cycles, matching the theoretical cycle-life limits of commercial lithium-ion batteries.
Sodium symmetric cells operated for 6,000 hours at 0.1 mA cm⁻² without any dendrite-related failure.
The economic case
Sodium is approximately 30 to 50 times cheaper than lithium and about 100 times more abundant in the Earth’s crust. Sodium-based batteries are projected to cost $40 to $60 per kilowatt-hour, compared to roughly $100 to $120/kWh for current lithium-ion packs. Combined with the safety advantages, sodium ions cannot cause thermal runaway, and the quasi-solid gel eliminates liquid electrolyte leakage, the technology offers a compelling package for applications where per-charge range is less critical than cost, safety, and rapid charging.
Urban commuter EVs, fleet vehicles, and public transport are the most natural early applications. For longer-range vehicles, the lower energy density of sodium chemistry (approximately 80 mAh g⁻¹ vs. 150–200 mAh g⁻¹ for lithium-ion) remains a limitation.
The work was supported by HiNa Battery Technology, one of the leading companies commercializing sodium-ion batteries, suggesting a clear path from laboratory demonstration to industrial scale.