KAIST identifies fast-charge degradation with 3D twin

The moment a fast charger is plugged in, a battery’s performance is not determined by charging speed alone. A KAIST research team reproduced the interior of a graphite anode with a 3D digital twin, narrowing down the cause of fast-charging degradation to the arrangement of the electrode’s internal structure.

The anode of a lithium-ion battery consists of graphite, which stores lithium; a binder, which holds the particles together; and void space through which lithium ions move. If charging is too fast, some lithium can accumulate on the graphite surface, causing lithium plating. The solid electrolyte interphase formed during charging can also reduce performance if it becomes excessively thick or uneven. Because these phenomena occur simultaneously inside the battery, it is difficult to observe the internal changes directly through experiments alone.

The research team, led by Professor Kang-Taek Lee of the Department of Mechanical Engineering and Professor Eun-Ae Cho of the Department of Materials Science and Engineering, calculated fast-charging conditions while varying the electrode thickness, the amount of void space and the binder’s position. Electrodes with similar overall charging capacities nevertheless showed different levels of damage depending on their internal structure. In particular, when the binder was concentrated on one side of the electrode, the void space available for lithium-ion transport decreased, causing lithium plating to increase by more than 10%. The difference grew as the electrode became thicker.

Void space is not only a pathway for lithium ions; it also helps distribute stress when graphite particles expand during charging. When void space is insufficient, there is less room for expansion and stress becomes concentrated in specific areas. The design approach proposed by the team goes beyond matching only the total amounts of binder and void space: it also adjusts where and how they are distributed.

The design approach proposed by this study takes into account not only the total amounts of electrode binder and void space, but also where and how they are distributed.