High-Packing-Density Electrodes by Self-forming Ion Conduction Pathway During Charge Process for All-Solid-State Lithium Ion Batteries

The Li2S-V2S3-LiIcathode materials doped with different LiI amounts developed in thisstudy presented a high charge/discharge capacity without solid electrolyteand carbon in the composite electrode. The reaction mechanism of thecathode materials was elucidated using a combination of analyticalmethods. Potential step measurements revealed that LiI doping amountsabove 10 mol % largely increased the ionic conductivity of the Li2S-V2S3-LiI cathodes duringcharging. The X-ray computed tomography and cross-sectional SEM-EDXmapping results demonstrated that the LiI-rich domain formed fromthe Li2S-V2S3-LiI cathodeduring charging because the lithium content of the cathode materialchanged. These results indicated that the self-forming LiI-rich domainserved as an ionic conduction pathway in the cathode matrix duringthe first charge cycle and improved the electrochemical performanceof the cathode materials. This material design strategy for compositeelectrodes with self-formed ionic conduction pathways is useful fordesigning high packing density electrodes for all-solid-state batteries,because the capacity per composite electrode is larger than that ofconventional composite electrodes consisting of solid electrolyteand electrode active material.