The biggest problem with solid-state batteries may finally be solved

A cellulose-derived polymer additive enables electro-chemo-mechanical regulation in all-solid-state batteries (ASSBs). The urethane-linked framework improves solid, solid interfacial contact, maintains continuous ion/electron pathways, and buffers mechanical stress in thick cathodes. The modified ASSBs deliver a high areal capacity of 6.4 mAh cm− 2, with 91.1% retention after 100 cycles and stable cycling over 620 cycles.

ABSTRACT

All-solid-state batteries (ASSBs) offer enhanced safety and energy density over conventional lithium-ion batteries. However, achieving high active material loading remains challenging due to poor interfacial contact from cold-pressing and the incompatibility of solvent-based processing with advanced solid-state electrolytes. Herein, we report a cellulose-derived polymer additive (CA-MDI) that establishes intimate solid, solid interfacial contact while ensuring continuous electron/ion transport in the composite cathodes. The efficacy of CA-MDI is ascribed to the urethane-linked cellulose framework, which is synthesized via the polymerization of cellulose acetate (CA) and methylene diphenyl diisocyanate (MDI). The as-constructed ASSBs incorporating a CA-MDI-modified LiNi0.89Co0.055Mn0.055O2 cathode achieve a high areal capacity of 6.4 mAh cm−2, delivering an initial discharge capacity of 136.6 mAh g−1 at 0.3C and retaining 91.1% of the capacity after 100 cycles, whereas additive-free cells show rapid degradation. At a lower areal capacity of 1.8 mAh cm−2, the CA-MDI-modified cell maintains 80% of its initial capacity for over 620 cycles at 1 C. The applicability of the CA-MDI additive is further demonstrated using LiCoO2 and Li-rich layered oxide cathodes. These results show that a mechanically adaptive polymer additive can improve the cycling stability of thick composite cathodes and provide a useful approach for developing high-energy-density ASSBs.