Developing inorganic-rich interphases through single-solvent siloxane electrolytes with weak solvation characteristics for high-voltage Ni-rich batteries

Enhancing the energy density of lithium-ion batteries through high-voltage cathodes holds great promise. However, traditional carbonate-based electrolytes face significant challenges due to limited oxidative stability and poor compatibility with high-nickel materials. This study introduces a novel electrolyte that combines bis(triethoxysilyl) methane (DMSP) as the sole solvent with lithium bis(fluorosulfonyl) imide (LiFSI) as the lithium salt. This formulation significantly improves the stability of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes and graphite anodes. The capacity retention of the NCM811 electrode increases from 5% to 95% after 1000 cycles at 1 C (3.0–4.5 V), while that of the graphite anode is improved from 22% to 92% after 400 cycles at 0.2 C (0.005–3.0 V). The NCM811//graphite pouch cell exhibits enhanced retention, rising from 12% to 66% at 25 °C and from 3% to 65% at 60 °C after 300 cycles at 0.2 C. Spectroscopic characterization and theoretical calculations reveal that the steric hindrance of the Si–O–CH₃ groups in DMSP creates a weakly solvating structure, promoting the formation of Li⁺-FSI⁻ ion pairs and aggregation clusters, which enriches the electrode interphase with LiF, Li₃N, and Li₂SO₃. Furthermore, DMSP with abundant Si–O effectively enhances the elasticity of the interphase layer, scavenging harmful substances such as HF and suppressing gas evolution and transition metal dissolution. The simplicity of the DMSP-based electrolyte formulation, coupled with its superior performance, ensures scalability for large-scale manufacturing and practical application in the high-voltage battery. This work provides critical insights into improving interfacial chemistry and addressing compatibility issues in high-voltage Ni-rich cathodes.