Stable cycling of LiNi_0.9Co_0.05Mn_0.05O₂/lithium metal batteries enabled by synergistic tuning the surface stability of cathode/anode

Ni-rich layered oxides (LiNi_0.9Co_0.05Mn_0.05O₂) show great potential in long-range and low-cost lithium-ion batteries. However, due to the high surface sensitivity, their practical application is hindered by interfacial instability with electrolytes under high voltage for long cyclic life. Herein, by combining both first-principle calculations and time-of-flight secondary ion mass spectrometry (TOF-SIMS), a novel surface fluorinated reconstruction (SFR) mechanism is proposed to improve the interfacial stability under high voltage, which could effectively regulate the surface fluoride species to desensitize the LiNi_0.9Co_0.05Mn_0.05O₂ interface. We demonstrate here that by tuning the ratio of fluoride species, the LiNi_0.9Co_0.05Mn_0.05O₂/Li battery could achieve excellent long-term and high voltage performance (163.5 mA h g⁻¹ at 0.5 C for 300 cycles under 4.4 V), while the controlled sample decayed to 125.4 mA h g⁻¹ after 300 cycles. Moreover, the favorable cross-talk effect induced by SFR further facilitates the incorporation of suitable amounts of Ni ions into the construction of stable solid electrolyte interface (SEI) layer for anode surface. Therefore, the ultra-long cycling stability under high voltage can be achieved by the robust cathode/electrolyte and Li/electrolyte interfaces, which results in excellent interfacial stability after long cycling. This work provides new insights into the surface design of cathode materials and improves the stability of the electrode-electrode interface under high voltage.