Analyzing of pore size distribution in carbon layers and its impact on the performance of anode-less all-solid-state batteries

Abstract

To develop batteries with high energy density, replacing graphite with lithium metal as the anode material is essential due to its higher specific capacity. Recently, anode-less all-solid-state batteries utilizing a carbon-based interlayer (c-layer) have gained attention for their ability to alter the Li growth direction and suppress Li dendritic growth. In the key mechanism of Li transport in the c- layer, coble creep, the pore in the c-layer are vital variables. However, existing research has primarily focused on the effect of pore size depending on the synthesized carbon particle size. This study aims to confirm the factors affecting pore size distribution (PSD) within the c-layer based on carbon black and analyze the influence of PSD on the performance of the c-layer, confirming the feasibility of applying coble creep to the c-layer based on carbon black and identifying an effective c-layer structure. In this study, the carbon material (ECP300J, super-p) and the amount of binder were set as variables to change the PSD of the c-layer. Using the BET method, we confirmed that the c-layer composed of ECP300J forms more micropore and mesopore than super-p, and that the total pore volume decreases as the amount of binder increases. The relation between PSD and coble creep suggests that smaller- sized pore (mesopore) can provide a faster coble creep diffusion rate than larger-sized pore. This was confirmed by three electrochemical tests, showing that c-layers with a high amount of mesopore exhibit fast coble creep diffusion and better performance. Additionally, Li morphology observations confirmed that the c-layer with a higher amount of mesopore has faster coble creep diffusion. Therefore, it was shown that the coble creep diffusion rate and the electrochemical performance of the c-layer are affected by PSD in the c-layer. This work confirms the feasibility of applying coble creep to the lithium transport mechanism in the c-layer, emphasizing the importance of choosing a carbon black material that forms a large amount of small-sized pore (mesopore) and optimizing the binder content to form an effective pore structure.