Slurry-Fabricable Li ⁺ -Conductive Polymeric Binders for Practical All-Solid-State Lithium-Ion Batteries Enabled by Solvate Ionic Liquids

For mass production of all-solid-state lithium-ion batteries (ASLBs) employing highly Li ⁺ conductive and mechanically sinterable sulfide solid electrolytes (SEs), the wet-slurry process is imperative. Unfortunately, the poor chemical stability of sulfide SEs severely restrict available candidates for solvents and in turn polymeric binders. Moreover, the binders interrupt Li ⁺ -ionic contacts at interfaces, resulting in the below par electrochemical performance. In this work, a new scalable slurry fabrication protocol for sheet-type ASLB electrodes made of Li ⁺ -conductive polymeric binders is reported. The use of intermediate-polarity solvent (e.g., dibromomethane) for the slurry allows for accommodating Li ₆ PS ₅ Cl and solvate-ionic-liquid-based polymeric binders (NBR-Li(G3)TFSI, NBR: nitrile−butadiene rubber, G3: triethylene glycol dimethyl ether, LiTFSI: lithium bis(trifluoromethanesulfonyl)imide) together without suffering from undesirable side reactions or phase separation. The LiNi _0.6 Co _0.2 Mn _0.2 O ₂ and Li ₄ Ti ₅ O ₁₂ electrodes employing NBR-Li(G3)TFSI show high capacities of 174 and 160 mA h g ⁻¹ at 30 °C, respectively, which are far superior to those using conventional NBR (144 and 76 mA h g ⁻¹ ). Moreover, high areal capacity of 7.4 mA h cm ⁻² is highlighted for the LiNi _0.7 Co _0.15 Mn _0.15 O ₂ electrodes with ultrahigh mass loading of 45 mg cm ⁻² . The facilitated Li ⁺ -ionic contacts at interfaces paved by NBR-Li(G3)TFSI are evidenced by the complementary analysis from electrochemical and ⁷ Li nuclear magnetic resonance measurements.