|Electrochemical characteristics of Na2Ti3O7 and VOPO4 electrodes in the "half-cell format" vs. Na+/Na. Courtesy: G Yu|
Topics: Condensed Matter Physics, Nanotechnology, Semiconductor Technology, Solid State Physics
Researchers at the University of Texas at Austin in the US and Nanjing University of Aeronautics and Astronautics in China have developed a high-energy sodium-ion battery based on sodium titanate nanotubes and vanadyl phosphate layered nanosheet materials. The new device, which works over a wide temperature range of between –20 to +55°C, has a high operating voltage of close to 2.9 V and delivers a large reversible capacity of 114 mA h/g. It also boasts a high energy density of 220 Wh/kg, which makes it competitive with state-of-the-art lithium-ion batteries.
Sodium-ion batteries are similar to their lithium-ion cousins since they store energy in the same way. They consist of two electrodes – anode and cathode – separated by an electrolyte. When the battery is being charged with electrical energy, metal ions move from the cathode through the electrolyte to the anode, where they are absorbed into the bulk of the anode material. Sodium-based devices are in principle more attractive though since sodium is highly abundant on Earth (its Clarke’s number is 2.64) and is therefore much cheaper than lithium. Sodium is also more environmentally friendly than lithium.
However, the radius of the sodium ion is significantly larger than that of the lithium ion. This makes it difficult to find a host electrolyte material that allows ions to be rapidly absorbed and removed. What is more, sodium-ion batteries made thus far suffer from a relatively low working potential, large capacity decay during cycling (which leads to a limited battery life) and poor safety.
Nanotechweb: Sodium-ion device could compete with lithium-ion batteries, Belle Dumé