Five Metals in One Spot: A Cathode for Sodium Batteries express
Sodium is lithium's neighbor on the periodic table, but it's hundreds of times more abundant in the Earth's crust and much cheaper. So sodium batteries could replace lithium ones in electric vehicles and energy storage. The problem is that sodium is larger than lithium, making it harder for it to navigate through the cathode's crystal lattice. The material quickly tires, and capacity drops.
Chemists in this study tried 'seasoning' the cathode with five different metals at once: chromium, molybdenum, aluminum, zirconium, and nickel. Each was added in tiny amounts — together they occupied only one-tenth of the vanadium sites in the crystal. But that was enough to make the lattice stronger and sodium ions more mobile.
The result: the cathode delivers 119 milliamp-hours per gram at slow charging, and at fast charging (10C) it retains 68% of its capacity after 1000 cycles. A full cell with hard carbon yields 326 watt-hours per kilogram of cathode — comparable to good lithium batteries. The authors measured how quickly sodium ions diffuse inside the cathode: the diffusion coefficient lies in the range of 10⁻¹¹–10⁻¹³ cm²/s. It's like a pedestrian's speed in a crowd — ions push between atoms, and the metal addition widens the passages.
This approach paves the way for cheap and durable sodium batteries. Instead of expensive lithium, ordinary table salt; instead of rare cobalt and nickel, common metals. If the technology reaches factories, electric vehicles and solar farms will get batteries that don't depend on the whims of global lithium prices.
Original abstract
as written by the authors arXiv:2602.04372
We designed a high-entropy doped NASICON cathode, Na$$_3$$V$$_{1.9}$$(CrMoAlZrNi)$$_{0.1}$$(PO$$_4$$)$$_3$$ and investigate its electrochemical performance for sodium-ion batteries (SIBs) to understand the diffusion mechanism including distribution of relaxation times analysis of interfacial kinetics. This trace doping induces high-entropy mixing at the vanadium site, tuning the lattice and enhancing specific capacity, activating V$$^{4+}$$/V$$^{5+}$$ redox couple 3.95~V. Interestingly, it delivers a reversible capacity of 119~mAh~g$$^{-1}$$ at 0.1~C, and demonstrate excellent stability of 68\% after 1000 cycles at 10~C. The calculated diffusion coefficient values are found within the range of \(10^{-11}\)--\(10^{-13}~\mathrm{cm^2\,s^{-1}}\). The systematic investigation of temperature and voltage-dependent impedance data using the distribution of relaxation times provides deeper insights into the underlying charge-transfer and transport processes. The full cells with hard carbon delivers 326~Wh~kg$$^{-1}$$ (with respect to cathode mass) at $$\approx$$3.2~V and retained $$\sim$$79\% capacity after 100 cycles at 2~C. Our study opens new avenues for developing high-entropy doped cathodes for enhanced structural stability, extended redox activity, and optimized electrochemical kinetics for practical implementation of SIBs.
Sodium is the sixth most abundant element in the Earth's crust. It can be extracted from seawater, while lithium can only be obtained from salt lakes and mines, of which there are few on the planet.
In John Scalzi's novel 'The Interdependency', ships fly on batteries charged by solar sails. Cheap sodium batteries would make such energy real.