Highly safe quasi-solid-state lithium ion batteries with two kinds of nearly saturated and non-flammable electrolyte solutions

Charge/discharge performance of all-solid-state lithium ion batteries (LIBs) is not yet high, compared to those for conventional liquid-type LIBs, which is mainly due to the imperfect joining of solid electrolyte and electrodes. To promote the interfacial lithium ion transfer among the solids, in this study, the nearly saturated and non-flammable electrolyte solutions were incorporated into an interspace among the solids to obtain quasi-solid-state Si|LiNi0.8Co0.1Mn0.1O2 (NCM811) batteries. The Si negative- and NCM811 positive-electrodes were separated with a solid electrolyte sheet, and hence two different electrolyte solutions were used for each electrode. The nearly saturated electrolyte solutions suitable for each electrode and the solid electrolyte were designed, and 30 mAh-class quasi-solid-state pouch cells were fabricated using them. The improved safety and charge/discharge performance demonstrated the feasibility of quasi-solid-state batteries as a near-future technology. •A small amount of electrolyte solutions is incorporated into solid-state lithium-ion batteries.•High safety of batteries is achieved with the incorporated non-flammable solutions.•Charge/discharge performance improves with a use of two different types of electrolyte solutions.•The incorporated solutions facilitate Li+ transfer at a solid electrolyte/electrode interface.•A 30 mAh-class quasi-solid-state batteries of practical use successfully charge and discharge.