A team at the Korea Institute of Science and Technology (KIST) used semiconductor manufacturing techniques to develop a new material design strategy for solid state battery technology.
The team, led by Dr. Sang-baek Park at the Centre for Energy Materials Research, in collaboration with the research team of Professor Hyun-jung Shin of Sungkyunkwan University, has developed a breakthrough material design strategy that can overcome the problem of high interfacial resistance between the solid electrolyte and the cathode, which is an obstacle to the commercialization of all-solid-state batteries.
Having a solid electrode-solid electrolyte interface creates a phenomenon that disturbs the atomic arrangement and limits charge transfer, increasing resistance and accelerating deterioration.
Methods of coating an appropriate material on the surface of the cathode and the electrolyte or inserting an intermediate layer are currently being studied to solve the above-mentioned problem. However, this further increases the costs and lowers the overall activity and energy density of the batteries.
To solve these problems, the joint KIST-Sungkyunkwan University team identified the crystal structure of the material that directly affects the solid interface. Using epitaxial film technology from semiconductor manufacturing to grow a thin film along the direction in which the crystals of the substrate were formed, cathode films having different exposed crystal planes were obtained under varying conditions.
The effect of the exposed crystal plane on the interface between the solid electrolyte and the cathode material was analyzed in detail, disregarding other factors such as particle size and contact area that could affect the result.
The results indicated that the leakage of the transition metal from the cathode material into the electrolyte was suppressed by the closely-packed structure of the exposed crystal plane, which improved the stability of the all-solid-state battery. In addition, when the interface of the crystals was arranged in parallel with the direction of movement of the electrons, the movement of ions and electrons along the crystals was not hindered, resulting in reduced resistance and improved output for a solid state battery.
“This means that improving the cathode material itself by increasing the density of the crystal plane and adjusting the direction of the interface between the crystals can ensure high performance and stability,” said Dr. Sang-baek Park at KIST. “We plan to accelerate the development of all-solid-state battery materials by overcoming the instability of the solid electrolyte and solid cathode interface and imparting improved ion-charge exchange characteristics through this study, which has investigated the mechanism of all-solid-state battery degradation.”
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