New anode material gives scope for EV sodium-ion battery future

In a boost to electric vehicle battery research, a team from the Korea Institute of Science and Technology’s (KIST) Center for Energy Storage Research has developed a high-performance, economical anode material for use in sodium-ion secondary batteries.

The novel material can store 1.5 times more electricity than the graphite anode used in commercial lithium-ion batteries, and its performance does not degrade even after 200 cycles at charging/discharging rates of 10 A/g.

With sodium being over 500 times more abundant in the Earth’s crust than lithium, sodium-ion batteries have drawn considerable attention as a next-generation secondary battery because they are reported to be 40% cheaper than lithium-ion batteries. However, compared with lithium ions, sodium ions are larger and cannot be stored as stably in graphite and silicon, which are widely used as anodes in such batteries.

Led by Dr Sang-Ok Kim, the KIST research team used molybdenum disulfide (MoS₂), a metal sulfide that has garnered interest as a candidate for large-capacity anode materials. MoS₂ can store a large amount of electricity, but has not been used historically because of its high electrical resistance and structural instability during battery operation.

The team overcame this problem by creating a ceramic nanocoating layer using silicone oil, a low-cost, eco-friendly material. Through the simple process of mixing the MoS₂ precursor with silicone oil and heat-treating the mixture, the researchers were able to produce a stable heterostructure with low resistance and enhanced stability. Their results are published in ACS Nano.

Schematic of the synthesis process of the nitrogen-doped MoS₂-based anode material. Image credit: Korea Institute of Science and Technology (KIST).

“We could successfully solve the high resistance and structural instability problems of MoS₂ through the nanocoating surface stabilisation technology,” Dr Kim said. “As a result, we could develop a sodium-ion battery that can stably store a large amount of electricity.

“Our method uses cost-effective, eco-friendly materials and, if adapted for the large-scale manufacturing of anode materials, can lower production costs and hence boost the commercialisation of sodium-ion batteries for large-capacity power storage devices.”

Top image credit: ©stock.adobe.com/au/artemegorov