Abstract
Transition-metal dissolution from cathode materials, manganese in particular, has been held responsible for severe capacity fading in lithium-ion batteries, with the deposition of the transition-metal cations on anode surface, in elemental form or as chelated-complexes, as the main contributor for such degradations. In this work we demonstrate with diverse experiments and calculations that, besides interfacial manganese species on anode, manganese(II) in bulk electrolyte also significantly destabilizes electrolyte components with its unique solvation-sheath structure, where the decompositions of carbonate molecules and hexafluorophosphate anion are catalyzed via their interactions with manganese(II). The manganese(II)-species eventually deposited on anode surface resists reduction to its elemental form because of its lower electrophilicity than carbonate molecule or anion, whose destabilization leads to sustained consumption. The reveal understanding of the once-overlooked role of manganese-dissolution in electrolytes provides fresh insight into the failure mechanism of manganese-based cathode chemistries, which serves as better guideline to electrolyte design for future batteries.
Highlights
Transition-metal dissolution from cathode materials, manganese in particular, has been held responsible for severe capacity fading in lithium-ion batteries, with the deposition of the transition-metal cations on anode surface, in elemental form or as chelated-complexes, as the main contributor for such degradations
Differing from Li+ (Fig. 1a), the radial distribution function obtained from molecular dynamic (MD) simulation reveals that the first solvation shell of Mn2+ is dominated by carbonyl O in ethylene carbonate (EC), O in TFSI−, and to a much lesser extent by F in PF6− and carbonyl O in dimethyl carbonate (DMC) (Fig. 1b)
We demonstrated in this work that, besides interfacial Mn-species, the once overlooked Mn2+ in bulk electrolyte solution significantly contributes to destabilize the carbonate-based electrolytes
Summary
Transition-metal dissolution from cathode materials, manganese in particular, has been held responsible for severe capacity fading in lithium-ion batteries, with the deposition of the transition-metal cations on anode surface, in elemental form or as chelated-complexes, as the main contributor for such degradations. A disordered rocksalt material with reversible Mn2 +/Mn4+ redox-pairs was proposed, promising extremely high capacity of >300 mAh g−1 and energy density of ~1000 Wh kg−1 Such new materials created opportunities for the generation LIBs, but will inevitably encounter the decade-long challenge of Mn2+-dissolution in electrolytes, which has prevented the application of almost all Mn-rich materials[3]. In comparison with Li+, the bivalent Mn2+ forms larger solvation sheath containing both PF6− and carbonate molecules, wherein Mn2+ readily activates these solvation members either for side reactions in the bulk electrolyte or for electrochemical reductions at anode surface This destabilization becomes overwhelming at elevated temperatures, leading to significant change in both bulk electrolyte composition and interphasial chemistry. Such precise understanding of how soluble Mn-species affect battery performance constitutes critical knowledge to enable these Mn-rich cathode chemistries
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
