In situ inorganic conductive network formation in high-voltage single-crystal Ni-rich cathodes

Xinming Fan,Yangzhong Li,Wengao Zhao,Corsin Battaglia,Lianfeng Zou,Bao Zhang,Xing Ou,Jiafeng Zhang,Guorong Hu,Yong Yang,Yun Liu,Lukas Seidl

doi:10.1038/s41467-021-25611-6

Abstract

High nickel content in LiNixCoyMnzO2 (NCM, x ≥ 0.8, x + y + z = 1) layered cathode material allows high specific energy density in lithium-ion batteries (LIBs). However, Ni-rich NCM cathodes suffer from performance degradation, mechanical and structural instability upon prolonged cell cycling. Although the use of single-crystal Ni-rich NCM can mitigate these drawbacks, the ion-diffusion in large single-crystal particles hamper its rate capability. Herein, we report a strategy to construct an in situ Li1.4Y0.4Ti1.6(PO4)3 (LYTP) ion/electron conductive network which interconnects single-crystal LiNi0.88Co0.09Mn0.03O2 (SC-NCM88) particles. The LYTP network facilitates the lithium-ion transport between SC-NCM88 particles, mitigates mechanical instability and prevents detrimental crystalline phase transformation. When used in combination with a Li metal anode, the LYTP-containing SC-NCM88-based cathode enables a coin cell capacity of 130 mAh g−1 after 500 cycles at 5 C rate in the 2.75-4.4 V range at 25 °C. Tests in Li-ion pouch cell configuration (i.e., graphite used as negative electrode active material) demonstrate capacity retention of 85% after 1000 cycles at 0.5 C in the 2.75-4.4 V range at 25 °C for the LYTP-containing SC-NCM88-based positive electrode.

Highlights

IntroductionNi-rich layered NCM undergoes large anisotropic volume variations during cycling, compromising the mechanical stability and generating intergranular cracks[6,7]
High nickel content in LiNixCoyMnzO2 (NCM, x ≥ 0.8, x + y + z = 1) layered cathode material allows high specific energy density in lithium-ion batteries (LIBs)
LYTP@SC-NCM88 precursor particles were transferred to a tube furnace for co-calcination to obtain LYTP-modified SC-NCM88 particles

Summary

Introduction

Ni-rich layered NCM undergoes large anisotropic volume variations during cycling, compromising the mechanical stability and generating intergranular cracks[6,7]. Such intergranular cracks propagate along particle grain boundaries causing spalling off the secondary microspheres and their subsequent pulverization, eventually resulting in fast capacity fading[8]. Quasi single-crystal layered NCM cathodes with primary particles of 2–5 μm diameter with a strong crystallographic texture were explored to minimize internal strain caused by the anisotropic volume variations during cycling[12,13], decreasing electrolyte-induced corrosion due to the absence of grain boundaries and intragranular cracks[14]. The introduction of quasi single-crystal particles can enhance the cycling stability by suppressing the formation of micro/nanocracks, it is still challenging to achieve long-term stability when cycling to high cut-off voltages (>4.3 V vs Li/Li+)

Methods

Results

Conclusion