Electrochemical Performance of All-Solid-State Batteires Using Size Controlled Sulfide Based Solid Electrolyte
Authors: Noh Sungwoo , Choi Lak Young , Son Seung Hyeon , Park Chan Hwi , Shin Dongwook 
Published: February 2020

Since large-sized energy storage systems with high energy density such as electric vehicles and smart-grid systems has been intensive attention. Lithium ion batteries have been considered as one of realistic candidates. Nevertheless, the more energy demand the more focus on safety issues of because of ignite liquid electrolytes. To resolve this problem, all-solid-state batteries with solid electrolytes have been researched as next generation of lithium ion batteries. Even though all-solid-state batteries have better safety, main huddle of all-solid-state batteries is energy density of composite electrode in all-solid-state batteries which include solid electrolytes different from lithium ion batteries with liquid electrolyte. In spite of solid electrolytes act as important role for composite electrode in all-solid-state batteries due to create lithium ion path in the composite electrode, solid electrolyte don’t contribute to capacities of batteries. Therefore, Solid electrolyte in composite electrode for all-solid-state batteries are need to be minimized without sacrifice electrochemical performances. In order to find optimal composition of composite electrode for all-solid-state batteries, size of solid electrode powder were controlled to maximize the energy density of all-solid-state batteries.

In this research, size of sulfide based solid electrolytes were controlled via wet ball milling and ultra-sonication process with increasing milling time. Composite cathodes of all-solid-state batteries were produced with three different ratio of active materials and solid electrolyte for each sizes of solid electrolyte. To obtain composite cathode, the cathode materials, conductive additive and glass-ceramics solid electrolyte powders were mixed by dry mixing method using an agate mortar and pestle with hand. All-solid-state cells were constructed by uniaxial cold pressing method. Morphology of solid electrolyte were measured with FE-SEM. Size distribution of solid electrolyte were measured by Particle Size Analyzer. Microstructure and electrochemical properties of fabricated composite cathodes with different size of solid electrolyte were characterized.

Sizes of sulfide solid electrolyte showed drastically decrease and uniform distribution after wet ball milling process. Morphology of sulfide based solid electrolyte particle became irregularity and agglomeration shape to uniform and spherical shape. Therefore, electrochemical performance wet ball milled solid electrolyte showed better electrochemical performance at every cathode ratio of all-solid-state cells because of lithium ion paths are constructed by size controlled solid electrolyte particles. Improved electrochemical performances are indicating that size and morphology of solid electrolyte particle act as very important role in all-solid-state batteries. In addition, considerable electrochemical performance at cathode ratio over 90% can be achieved by more refined size and morphology of solid electrolyte particle in the future.

Figure 1