Lithium-Ion

Cycle Number

Counts

A Li3PO4 surface coating was applied to 0.7LiMn0.5Ni0.5O2 • 0.3Li2MnO3 to suppress Mn dissolution, a common degradation pathway for any Mn-containing cathode; the coating was applied via sol-gel and atomic layer deposition ALD) to determine the effect of processing technique. While both techniques provided some surface protection, ALD produced a more uniform Li3PO4 layer than sol-gel processing, underscoring the role of coating methodology. Surprisingly, this nano-scale coating led to substantially suppressed micro-scale particle cracking and pore/void formation over cycling. However, capacity fade after 450 cycles is still linked to Mn deposition (observed in EDS analysis of graphite anode), highlighting that residual Mn deposition still dominates long-term capacity fade and the need for additional mitigation strategies beyond surface coatings, such as cathode surface dopants and electrolyte modifications.

Discharge Capacity [mAh/g]

Measuring and Mitigating Transition Metal Dissolution from Mn-rich Cathodes

SEM images of cathode recovered after 120 cycles: (a) uncoated, (b) coating via sol-gel, and (c) coating via ALD

X-ray Energy KeV Top Discharge capacity at 1C, 24.8V, in full coin cells Bottom EDS analysis of graphite anode recovered after 120 and 450 cycles

A carefully processed layer of Li3PO4 to Mn-rich cathodes mitigates capacity fade, impedance rise, pore/void formation, and particle-scale damage; however, it does not mitigate voltage fade. It also does not solve the fundamental challenge of Mn-dissolution over long term cycling. Source: S. Mallick et al 2025.

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