South Korea's KERI research team has developed a new tin-iron negative electrode material to enhance the performance of all-solid-state batteries

On October 21, a research team led by Ha Yoon-cheol, director of the Next-generation Battery Research Center of the Korea Electric Research Institute (KERI), announced a breakthrough in battery technology. The research team has developed a new negative electrode material based on tin-based alloys, specifically tin-iron compounds (FeSn2), which is expected to significantly improve the performance and safety of all-solid-state batteries. The research results have been published in the journal Joule.

Image source: Joule

The newly developed negative electrode material FeSn2 has unique properties and is very suitable for use in all-solid-state batteries. Through mechanical property analysis, the research team found that FeSn2 particles become smaller with repeated charge and discharge cycles. This property enables the solid particles inside the battery to maintain close contact for a long time, thus forming a dense and uniform electrode. In addition, FeSn2 also exhibits high elasticity, high deformation energy and high electrochemical stability, and will not crack even when subjected to external stimuli.

All-solid-state batteries made using this negative electrode material have a capacity per unit area five times that of conventional lithium-ion batteries. These batteries have an energy density of up to 255 watt-hours (Wh) per kilogram, while lithium-ion batteries typically have an energy density of 200-300 Wh per kilogram. In addition, these batteries can still maintain a high capacity retention rate of 70-80% after more than 1,000 rapid charge and discharge cycles, which provides new possibilities for the commercialization of all-solid-state batteries.

Unlike lithium-ion batteries that use liquid electrolytes, all-solid-state batteries use solid electrolytes to transfer ions between the positive and negative electrodes of the battery. Liquid electrolytes turn into gas and explode when reacting at high temperatures, while solid electrolytes can greatly reduce this risk. However, its commercialization still faces challenges. The solid-state nature of the electrolyte requires advanced technology to ensure stability during charge and discharge cycles. In particular, the negative electrode has a significant impact on the charging speed and service life of the battery, so the choice of materials is crucial.

Currently, lithium metal is the most studied negative electrode material. However, lithium metal is prone to form dendrites on its surface during repeated charge and discharge cycles, causing internal short circuits and threatening the life and stability of the battery. Silicon negative electrodes can also be used as alternatives, but there are problems such as low electronic and ionic conductivity and cracking due to volume expansion.

The research team's results are significant because they have proposed a new anode material for the commercialization of all-solid-state batteries. The remaining challenge is to verify whether this material can maintain its performance in larger all-solid-state batteries. "We have demonstrated the great potential of tin-based alloy anode materials. To make larger batteries, other technological elements are needed in addition to new anode materials," said Ha Yoon-cheol.