Extending the Service Life of High-Ni Layered Oxides by Tuning the Electrode-Electrolyte Interphase

As a high-energy-density cathode for Li-ion batteries, high-Ni layered oxides, especially with ultrahigh Ni-content, suffer from short lifespans, due in part to their unstable electrode-electrolyte interphase (EEI). Herein, the cycle life of LiNi0.94Co0.06O2 is greatly extended by manipulating the EEI with a lithium bis(oxalate) (LiBOB) additive even when operated at a moderately high voltage (4.4 V vs Li/Li+). Impressively, the capacity retention can be increased from 61 to 80% after 500 cycles in a full cell paired with a graphite anode. Additionally, the presence of LiBOB enables a robust boron- and oxygen-enriched EEI that effectively inhibits continual electrolyte decomposition and offers a stable cathode surface. Moreover, the layered architecture of the cathode-electrolyte interphase (CEI) and the anode-electrolyte interphase (AEI) at the nanometer scale is revealed by time-of-flight secondary ion mass spectrometry. It is demonstrated that the cathode surface chemistry can significantly influence the AEI both chemically and physically, and AEI is modified from a thick "three-layer" to a thin "two-layer" architecture by tuning the cathode surface chemistry with LiBOB. This work presents a correlation between the EEI characteristics and battery performance and highlights the significance of manipulating surface chemistry in developing stable high-energy-density Li-ion batteries.