Design of a Dual-Electrolyte Battery System Based on a High-Energy NCM811-Si/C Full Battery Electrode-Compatible Electrolyte.

Rechargeable lithium-ion batteries using high-capacity anodes and high-voltage cathodes can deliver the highest possible energy densities among all electrochemical devices. However, there is no single electrolyte with a wide and stable electrochemical window that can accommodate both a high-voltage cathode and a low-voltage anode so far. Here, we propose that a strategy of using a hybrid electrolyte should be applied to realize the full potential of a Ni-rich LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811)-silicon/carbon (Si/C) full cell by simultaneously achieving optimal redox chemistry at both the NCM811 cathode and the Si/C anode. The hybrid-electrolyte design spatially separates the cathodic electrolytes from anodic electrolytes by a Nafion-based separator. The ionic liquid electrolyte (LiTFSI-Pyr ₁₃ TFSI) on the cathode side can stand high work potentials and form a stable cathodic electrolyte intermediate (CEI) on NCM811. Meanwhile, a stable solid electrolyte intermediate (SEI) and high cycling stability can also be achieved on the anode side, enabled by a localized high concentration of ether-based electrolytes (LiTFSI-DME/HFE). The decoupled NCM811-Si/C full cell exhibits excellent long-term cycling performance with ultrahigh capacity retention for over 1000 cycles, thanks to the synergy of the cathode-side and anode-side electrolytes. This hybrid-electrolyte strategy has been proven to be applicable for other high-performance battery systems such as dual-ion batteries (DIB).