Onset Potential for Electrolyte Oxidation and Ni-Rich Cathode Degradation in Lithium-Ion Batteries

Wesley M Dose; Weiqun Li; Israel Temprano; Christopher A O'Keefe; B Layla Mehdi; Michael F L De Volder; Clare P Grey

doi:10.1021/acsenergylett.2c01722

Onset Potential for Electrolyte Oxidation and Ni-Rich Cathode Degradation in Lithium-Ion Batteries

ACS Energy Lett. 2022 Oct 14;7(10):3524-3530. doi: 10.1021/acsenergylett.2c01722. Epub 2022 Sep 22.

Authors

Wesley M Dose^{1

2

3}, Weiqun Li^{3

4}, Israel Temprano¹, Christopher A O'Keefe^{1

3}, B Layla Mehdi^{3

4}, Michael F L De Volder^{2

3}, Clare P Grey^{1

3}

Affiliations

¹ Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW Cambridge, U.K.
² Department of Engineering, University of Cambridge, 17 Charles Babbage Road, CB3 0FS Cambridge, U.K.
³ The Faraday Institution, Quad One, Harwell Science and Innovation Campus, Didcot OX11 0RA, U.K.
⁴ Department of Mechanical, Materials and Aerospace Engineering, University of Liverpool, Liverpool L69 3GH, U.K.

Abstract

High-capacity Ni-rich layered metal oxide cathodes are highly desirable to increase the energy density of lithium-ion batteries. However, these materials suffer from poor cycling performance, which is exacerbated by increased cell voltage. We demonstrate here the detrimental effect of ethylene carbonate (EC), a core component in conventional electrolytes, when NMC811 (LiNi_0.8Mn_0.1Co_0.1O₂) is charged above 4.4 V vs Li/Li⁺-the onset potential for lattice oxygen release. Oxygen loss is enhanced by EC-containing electrolytes-compared to EC-free-and correlates with more electrolyte oxidation/breakdown and cathode surface degradation, which increase concurrently above 4.4 V. In contrast, NMC111 (LiNi_0.33Mn_0.33Co_0.33O₂), which does not release oxygen up to 4.6 V, shows a similar extent of degradation irrespective of the electrolyte. This work highlights the incompatibility between conventional EC-based electrolytes and Ni-rich cathodes (more generally, cathodes that release lattice oxygen such as Li-/Mn-rich and disordered rocksalt cathodes) and motivates further work on wider classes of electrolytes and additives.