Insights into the defect-driven heterogeneous structural evolution of Ni-rich layered cathode in lithium-ion batteries

TL;DR

This study uses advanced imaging techniques to investigate how defects and heterogeneous structural evolution in Ni-rich cathodes affect lithium-ion battery performance, emphasizing the importance of electrode kinetics control.

Contribution

It provides new insights into the defect-driven structural evolution of Ni-rich cathodes and highlights the impact of anode choice on heterogeneity and battery longevity.

Findings

Heterogeneous evolution is less severe with graphite-silicon anode.

Defects like Li/Ni disorder and microcracks influence structure formation.

Inhomogeneity origins are linked to defect distribution and delithiation rates.

Abstract

Recently, considerable efforts have been made on research and improvement for Ni-rich lithium-ion batteries to meet the demand from vehicles and grid-level large-scale energy storage. Development of next-generation high-performance lithium-ion batteries requires a comprehensive understanding on the underlying electrochemical mechanisms associated with its structural evolution. In this work, advanced operando neutron diffraction and four-dimensional scanning transmission electron microscopy techniques are applied to clarify the structural evolution of electrodes in two distinct full cells with identical LiNi0.8Co0.1Mn0.1O2 cathode but different anode counterparts. It is found that both of cathodes in two cells exhibit non-intrinsic two-phase-like behavior at the early charge stage, indicating selective Li+ extraction from cathodes. But the heterogeneous evolution of cathode is less serious with graphite-silicon blended anode than that with graphite anode due to the different delithiation rate. Moreover, it is revealed that the formation of heterogeneous structure is led by the distribution of defects including Li/Ni disordering and microcracks, which should be inhibited by assembling appropriate anode to avoid potential threaten on cell performance. The present work unveils the origin of inhomogeneity in Ni-rich lithium-ion batteries and highlights the significance of kinetics control in electrodes for batteries with higher capacity and longer life.