Understanding the limits of Li-NMC811 half-cells

McNulty, Rory C.; Hampson, Elizabeth; Cutler, Lewis N.; Grey, Clare P.; Dose, Wesley M.; Johnson, Lee R.

Abstract

As we push the boundaries of state-of-the-art lithium-ion intercalation materials, such as nickel-rich chemistries, the ability to isolate and understand specific degradation and performance limitations is becoming increasingly important. Half-cells, wherein lithium metal is employed as a dual counter and reference electrode, are commonly used in industry and academia for this purpose. However, the high reactivity of lithium metal drives premature electrolyte degradation and limits cell lifetime, bringing into question the reliability and validity of this cell configuration. Here we explore the limitations of half-cell studies of LiNi0.8Mn0.1Co0.1O2 (NMC811) electrodes with commercially relevant loading. We identify the failure mechanism of this cell configuration through a combination of electrochemical, chemical, and spectroscopic techniques and show that the Li has a direct detrimental impact on the NMC811 chemistry. Our measurements show that vinylene carbonate is critical for these half-cell studies and underpins the cycle limits. Furthermore, we demonstrate the use of Li4Ti5O12 (LTO) as an alternative counter electrode for understanding the performance of NMC positive electrode materials, due to its high coulombic efficiency and low reactivity with the organic carbonates routinely employed in lithium-ion battery cell chemistries. These data confirm that NMC811 electrodes can tolerate high voltages (stressed) conditions and that cell failure is mainly a result of crossover effects.

• Journal Article Type: Article
• Acceptance Date: Aug 2, 2023
• Online Publication Date: Aug 2, 2023
• Publication Date: Sep 14, 2023
• Deposit Date: Sep 11, 2023
• Publicly Available Date: Sep 11, 2023
• Journal: Journal of Materials Chemistry A
• Print ISSN: 2050-7488
• Electronic ISSN: 2050-7496
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Issue: 34
• Pages: 18302-18312
• DOI: https://doi.org/10.1039/d3ta00912b
• Keywords: General Materials Science, Renewable Energy, Sustainability and the Environment, General Chemistry
• Public URL: https://nottingham-repository.worktribe.com/output/24424205
• Publisher URL: https://pubs.rsc.org/en/content/articlelanding/2023/TA/D3TA00912B