Simultaneous Enhancement of Cathode and Anode Interfacial Stability in High-Voltage LiCoO₂–Si/C Batteries Through a Hydrogen-Free Multi-Cyano Ligand Inorganic Salt Electrolyte Additive

High-voltage layered oxide combined with silicon-base anode materials represents a promising candidate for the next-generation lithium-ion batteries. However, the strong catalytic nature of oxide surface renders severe electrolyte decomposition at the interface, accumulation of the acidic products (e.g. HF) and even damage to anode interphase. Here, we introduce the multiple-cyano-ligand salt as an electrolyte additive to regulate the harsh interphase of high-voltage LiCoO2. By tuning the non-metal centers bridged to cyano ligand, the tetracyanoborate (TCB) salt was identified with strong electrochemical stability and water tolerance. Strong adsorption of cyano groups efficiently deactivates the lattice oxygen, thereby inhibiting solvent dehydrogenation and subsequent decomposition. Moreover, the ligand exchange reaction between cyano and fluorine endows the TCB anion with acid-scavenging capability. With the addition of 1 wt% of potassium TCB salt as a multifunctional additive, a high-voltage LCO-Si/C pouch cell (4.5 V vs. Si/C) achieves excellent cycling stability, retaining 92.5 % of its initial capacity after 500 cycles. Furthermore, benefiting from the cyano- and LiF-rich interphases, the high-voltage LCO-Si/C full cell exhibits stable electrochemical performance even at elevated temperatures (45 degrees C). This work provides a new molecule design strategy for functional additives targeting high-voltage cathode materials.