graphite active material without solid electrolyte
Successful design of lithium-ion electrode structure
Energy density increased 1.5 times compared to existing models


On the 15th, a joint research team from the Electronics and Telecommunications Research Institute (ETRI) and the Daegu Gyeongbuk Institute of Science and Technology (DGIST) announced that they have designed a new type of electrode structure for all-solid-state secondary batteries by identifying the characteristics of smooth lithium ion diffusion between active materials.
All-solid-state rechargeable batteries are next-generation batteries that utilize solids as the electrolyte to transfer ions at the battery electrodes. Unlike primary batteries, which cannot be reused after a single use, rechargeable batteries, such as smartphone batteries, can be recharged and used repeatedly even after being discharged. In addition, solid electrolytes are safer than liquid electrolytes, which can potentially cause a fire, and have the advantage of improving energy density by enabling the implementation of bipolar secondary batteries.

The electrode structure of commonly used all-solid-state secondary batteries consists of a solid electrolyte responsible for ion conduction, a conductive material responsible for electron conduction, an active material responsible for energy storage, and a binder that physically and chemically holds them together.

ETRI researchers confirmed through experiments that ions are transferred even between graphite active material particles and proposed a new type of electrode structure for all-solid-state secondary batteries composed of active material and binder, excluding solid electrolytes and conductive agents. This structure was theoretically verified through virtual electrochemical experiments using supercomputer-based modeling by collaborating research team member DGIST, and was successfully implemented experimentally.
Since a solid electrolyte is not required, more active material can be packed into the electrode in the same volume, maximizing the composition to the extent that the active material content in the electrode reaches 98 wt%. As a result, the energy density was increased by approximately 1.5 times compared to a conventional graphite composite electrode.

Changes were also sought in the manufacturing process. Sulfide-based solid electrolyte materials possess high ionic conductivity and excellent moldability, but their high chemical reactivity made the selection of solvents and binders challenging. In contrast, the research team fabricated electrodes by conducting various studies to improve the performance of all-solid-state secondary batteries, as the absence of a solid electrolyte allowed for greater freedom in the selection of solvents and binders.

Dr. Lee Young-ki of ETRI’s Intelligent Sensor Research Lab, the principal investigator of this research, stated, “We will strive to develop secondary batteries with even higher energy density using this technology, secure core source technologies, and achieve commercialization.”

Although this study focused on graphite anode active materials, ETRI plans to conduct applied research on various electrode materials and cathode active materials based on the same concept. In addition, the company plans to simultaneously carry out research to advance the technology by reducing interfacial issues between electrodes and making the electrodes thinner to increase efficiency.