High-voltage electrolyte design for a Ni-rich layered oxide cathode for lithium-ion batteries

LiNi0.8Co0.1Mn0.1O2 (NCM811) is one of the most promising cathode materials in high-energy-density Li-ion batteries (LIBs) because of its high capacity and low cost. However, it still suffers from irreversible capacity fading at high cut-off voltages. This is mainly because high voltage accelerates the hydrolysis reaction of lithium hexafluorophosphate with trace water to generate byproducts such as highly corrosive hydrogen fluoride (HF) resulting in an unstable cathode-electrolyte interface and continuous irreversible phase transitions. Here, we modify a conventional electrolyte by adding the dual additives of tetrabutyl titanate (TBT) and lithium difluoroxalate borate (LiDFOB) to form a stable Ti-, B-, and F-rich interfacial layer to eliminate the unfavorable cathode-electrolyte side reactions and suppress deleterious phase transitions. Additionally, TBT can stabilize the electrolyte by removing H2O/HF. With the synergistic effect of the dual additives, the cycling stability of NCM811 at high voltages is enhanced considerably. The Li divide NCM811 cell with dual additives exhibits a high capacity retention rate of 86% after 200 cycles at 1 C and a high cut-off voltage of 4.5 V. This strategy provides a reference for designing high-voltage electrolytes for LIBs.

Automated summary

LiNi0.8Co0.1Mn0.1O2 (NCM811) is a promising cathode material for high-energy-density Li-ion batteries (LIBs) due to its high capacity and low cost. However, it faces irreversible capacity fading at high cut-off voltages, mainly caused by hydrolysis reaction producing corrosive byproducts. By modifying the electrolyte with dual additives, a stable interfacial layer is formed to eliminate unfavorable reactions and suppress phase transitions. The dual additives also stabilize the electrolyte. With this strategy, the cycling stability of NCM811 at high voltages is significantly improved, providing a reference for high-voltage electrolyte design in LIBs.