Multi-Scale tailoring of lithium ion diffusion from densification to coarsening

Abstract

The performance of lithium-ion batteries is highly dependent on the morphology of the grain and structure of the electrode, which can be optimized for either high power or high energy. Despite the progress in all-solid-state batteries, the behavior of densification and coarsening has not yet been investigated on cathode. Herein, we investigated the strategies how to manipulate Li-ion diffusion at the different dimensions of micro- to macro level, facilitating the diffusion as tailoring the multi-scale path from densification to coarsening. First, the influence of microstructure on tortuosity and diffusivity was studied to understand the effect of sintering. Increased sintering time was expected to deteriorate electrochemical properties owing to lower diffusivity, and higher tortuosity. Second, the grain growth and densification behavior were studied in conjunction with the critical temperature for multi-scale tailoring without significant thermal degradation. At longer sintering times, densification was sluggish and had a monotonous increment of 2.5 %/h. However, the grain sizes greatly increased to 8.37 μm, leading isolated pores breaking. Finally, the tailored diffusivity and tortuosity were compared with the calculated results to understand intra- and inter-diffusion. Our finding provides clues to facilitate the diffusion of Li-ion by controlled densification and coarsening behavior in highly densified electrode.