Thermally-driven mesopore formation and oxygen release in delithiated NCA cathode particles

Münir M. Besli; Alpesh Khushalchand Shukla; Chenxi Wei; Michael Metzger; Judith Alvarado; Julian Boell; Dennis Nordlund; Gerhard Schneider; Sondra Hellstrom; Christina Johnston; Jake Christensen; Marca M. Doeff; Yijin Liu; Saravanan Kuppan

doi:10.1039/C9TA01720H

Thermally-driven mesopore formation and oxygen release in delithiated NCA cathode particles†

Münir M. Besli,

^ab Alpesh Khushalchand Shukla,

^c Chenxi Wei,^d Michael Metzger,

^a Judith Alvarado,^e Julian Boell,^a Dennis Nordlund,^d Gerhard Schneider,^bf Sondra Hellstrom,^a Christina Johnston,^a Jake Christensen,

^a Marca M. Doeff,

*^e Yijin Liu

*^d and Saravanan Kuppan

*^a

Author affiliations

* Corresponding authors

^a Robert Bosch LLC, Research and Technology Center, Sunnyvale, California 94085, USA
E-mail: saravanan.kuppan@us.bosch.com

^b Dept. of Mech. Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe 76131, Germany

^c National Center of Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

^d Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
E-mail: liuyijin@slac.stanford.edu

^e Lawrence Berkeley National Laboratory, Energy Storage and Distributed Resources Division, University of California, Berkeley, California 94720, USA
E-mail: mmdoeff@lbl.gov

^f Materials Research Institute, Aalen University, Aalen 73430, Germany

Abstract

The structural integrity of layered Ni-rich oxide cathode materials is one of the most essential factors that critically affect the performance and reliability of lithium-ion batteries. Prolonged battery operation often involves repeated phase transitions, buildup of mechanical stresses, and could provoke thermal spikes. Such sophisticated chemo-thermo-mechanical interplay can cause performance degradation through structural disintegration of the cathode active materials (CAMs). Herein, we systematically investigate the thermal decomposition, fracture, and oxygen evolution of chemically delithiated Li_0.3Ni_0.8Co_0.15Al_0.05O₂ (NCA) particles upon heating from 25 °C to 450 °C using a number of advanced X-ray and electron probes. We observed a continuous reduction of the Ni oxidation state upon heating, as well as the release of oxygen from the NCA lattice that undergoes the thermally induced phase transformations. The release of oxygen also created numerous mesopores throughout the analyzed particles, which could significantly affect the chemical and mechanical properties of the electrode. In addition, intergranular and intragranular fracturing at elevated temperatures also contribute to the degradation of the NCA cathode under these conditions. Our investigation of the mechanical integrity at elevated temperatures provides a fundamental understanding of the thermally driven chemomechanical breakdown of the NCA cathode active materials.

Journal of Materials Chemistry A

Thermally-driven mesopore formation and oxygen release in delithiated NCA cathode particles†

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Thermally-driven mesopore formation and oxygen release in delithiated NCA cathode particles

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