A Simple Method for the Complete Performance Recovery of Degraded Ni-rich LiNi0.70Co0.15Mn0.15O2 Cathode via Surface Reconstruction

Binhua Huang; Dongqing Liu; Kun Qian; Lihan Zhang; Kai Zhou; Yuxiu Liu; Feiyu Kang; Baohua Li

doi:10.1021/acsami.8b22529

A Simple Method for the Complete Performance Recovery of Degraded Ni-rich LiNi_0.70Co_0.15Mn_0.15O₂ Cathode via Surface Reconstruction

ACS Appl Mater Interfaces. 2019 Apr 17;11(15):14076-14084. doi: 10.1021/acsami.8b22529. Epub 2019 Apr 4.

Authors

Binhua Huang^{1

2}, Dongqing Liu¹, Kun Qian^{3

2}, Lihan Zhang^{1

2}, Kai Zhou^{1

2}, Yuxiu Liu^{1

2}, Feiyu Kang^{1

3

4

2}, Baohua Li^{1

4}

Affiliations

¹ Engineering Laboratory for Next Generation Power and Energy Storage Batteries, and Engineering Laboratory for Functionalized Carbon Materials, Graduate School at Shenzhen , Tsinghua University , Shenzhen , 518055 , China.
² Laboratory of Advanced Materials, School of Materials Science and Engineering , Tsinghua University , Beijing , 100084 , China.
³ Shenzhen Environmental Science and New Energy Technology Engineering Laboratory , Tsinghua-Berkeley Shenzhen Institute , Shenzhen , 518055 , China.
⁴ Shenzhen Geim Graphene Center , Shenzhen , 518055 , China.

PMID: 30916929
DOI: 10.1021/acsami.8b22529

Abstract

The highly active surfaces of Ni-rich cathodes usually result in rapid surface degradation, which is manifested by poor cycle and rate capabilities. In this work, we propose a simple method to restore those degraded surfaces after storage. More importantly, the mechanism of surface degradation and recovery are investigated thoroughly. As storage in moist air, a lithium carbonate (Li₂CO₃) dominated impurity layer formed and tightly coated on the surface of the LiNi_0.70Co_0.15Mn_0.15O₂ particles. Except for the Li₂CO₃ layer, a NiO rock-salt structure was also found at near surface region by high-resolution transmission electron microscopy. These two inert species together impedance the transport of lithium ions and electrons, which result in no capacity at 4.3 V charge cutoff voltage of the stored material. We proposed a simple and effective method, i.e., three h calcination at 800 °C under oxygen flow. The restored LiNi_0.70Co_0.15Mn_0.15O₂ shows equivalent electrochemical performance compared to the pristine one. This is because the lithium ions in Li₂CO₃ layer return to the surface lattice of LiNi_0.70Co_0.15Mn_0.15O₂, and the NiO cubic phase transforms back to the layered structure with the oxidation of Ni²⁺. This method is not only insightful for cathode material design but also beneficial for practical application.

Keywords: lithium-ion batteries; nickel-rich cathode materials; performance recovery; storage failure; surface reconstruction.