On the Manganese Dissolution Process from LiMn2O4 Cathode Materials. Issue 8 (28th April 2021)

• Record Type: Journal Article
• Authors: Tesfamhret, Yonas; Liu, Haidong; Chai, Zhigang; Berg, Erik; Younesi, Reza
• Is Part Of: ChemElectroChem. Volume 8:Issue 8(2021)
• Page Start: 1516
• Page End: 1523
• Publication Date: 2021-04-28
• Subjects: ageing -- ALD -- hydrogen fluoride -- spinel -- transition metal; Electrochemistry -- Periodicals; 541.37
• DOI: 10.1002/celc.202001496
• Languages: English
• ISSNs: 2196-0216

Abstract

Abstract: Transition metal (TM) dissolution is a process experienced by most cathode materials based on lithium transition metal oxides. Spinel LiMn2 O4 (LMO) is the best‐known cathode material that suffers from TM dissolution. Therefore, LMO is selected here to understand the dissolution process and derive an inductively coupled plasma optical emission spectroscopy (ICP‐OES) method for quantifying dissolved metal ions. Furthermore, the LMO powder is coated with thin Al2 O3 films of different thicknesses using atomic layer deposition (ALD) in an attempt to suppress the dissolution of Mn. Two different types of counter electrodes, lithium iron phosphate (LFP) and Li‐metal, were used to investigate the role of the counter electrode on Mn dissolution. HF is identified as the lead cause of Mn dissolution, through comparisons of cells containing LiPF6 or LiClO4 based electrolytes. The results show that Li‐metal counter electrode effectively minimizes the dissolution process via likely consuming HF and H2 O impurity. In contradiction to the purpose of the protective Al2 O3 thin film coating, surface coated LMO showed higher dissolution of Mn compared to pristine LMO, both in LFP||LMO and Li||LMO configurations. Al2 O3 is proposed to generate H2 O when reacts with HF. H2 O could have the possibility to migrate back in the electrolyte and participate in the hydrolysis of LiPF6, resulting in more HF and thereby more Mn dissolution. Abstract : Hydrogen fluoride (HF) causes Mn‐ion dissolution from pristine LMO as well as from Al2 O3 coated LMO. The Al2 O3 coating, in the presence of HF, can lead to the formation of H2 O, and consequently to the hydrolysis of LiPF6 to produce more HF. The Li‐metal counter electrode consumes impurities, such as HF and H2 O, which leads to Mn dissolution in the electrolyte.