Nylon electrolyte chemistry in high-energy Li-metal batteries

Abstract

The practical options for polymer electrolytes (PEs) are predominantly confined to polyether matrices, which unfortunately falter at voltages exceeding 4 V. Herein, we introduce a pioneering approach using polyamide (PA, Nylon), a classical polymer with oxidation-resistant amide linkages, reengineered as high-voltage PEs compatible with Li-metal batteries (LMBs). Despite its resistance to most solvents, we observed that PA is susceptible to dissolution in dilute Li⁺ electrolytes. Upon dissolution, Li⁺ ions engage with the carbonyl moieties of PA, while anions establish H-bonds with their amido groups, thereby disrupting intrinsic H-bonds and fracturing the semi-crystalline framework of pure PA. These interactions facilitate Li⁺ transport and immobilize anions within the PA networks, resulting in (semi-)solid electrolytes with outstanding ionic conductivity (1.23 × 10⁻³ S cm⁻¹) and a high Li⁺ transference number (0.71). Notably, the nitrogen-rich nature of PA fosters the formation of a nitrided interphase on Li-metal, securing a completely dendrite-free Li chemistry. Consequently, the Li‖LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) battery exhibits a prolonged cycling life surpassing 800 cycles under practical conditions. Additionally, PA within the electrolyte can be easily regenerated using water-based solvents. This innovation not only establishes a high-voltage PE for high-energy LMBs but also introduces a sustainable new chemistry for utilizing and regenerating PA via benign Li⁺ solutions.