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Instruments / Technical Area	Publication Details	Published
I09-Surface and Interface Structural Analysis	Cycle-induced interfacial degradation and transition-metal cross-over in LiNi0.8Mn0.1Co0.1O2–graphite cells Erik Bjorklund , Chao Xu , Wesley M. Dose , Christopher G. Sole , Pardeep K. Thakur , Tien-Lin Lee , Michael F. L. De Volder , Clare P. Grey , Robert S. Weatherup Chemistry Of Materials DOI: 10.1021/acs.chemmater.1c02722 Diamond Proposal Number(s): [21995, 26285] Show Abstract ▼ Abstract: Ni-rich lithium nickel manganese cobalt (NMC) oxide cathode materials promise Li-ion batteries with increased energy density and lower cost. However, higher Ni content is accompanied by accelerated degradation and thus poor cycle lifetime, with the underlying mechanisms and their relative contributions still poorly understood. Here, we combine electrochemical analysis with surface-sensitive X-ray photoelectron and absorption spectroscopies to observe the interfacial degradation occurring in LiNi0.8Mn0.1Co0.1O2–graphite full cells over hundreds of cycles between fixed cell voltages (2.5–4.2 V). Capacity losses during the first ∼200 cycles are primarily attributable to a loss of active lithium through electrolyte reduction on the graphite anode, seen as thickening of the solid-electrolyte interphase (SEI). As a result, the cathode reaches ever-higher potentials at the end of charge, and with further cycling, a regime is entered where losses in accessible NMC capacity begin to limit cycle life. This is accompanied by accelerated transition-metal reduction at the NMC surface, thickening of the cathode electrolyte interphase, decomposition of residual lithium carbonate, and increased cell impedance. Transition-metal dissolution is also detected through increased incorporation into and thickening of the SEI, with Mn found to be initially most prevalent, while the proportion of Ni increases with cycling. The observed evolution of anode and cathode surface layers improves our understanding of the interconnected nature of the degradation occurring at each electrode and the impact on capacity retention, informing efforts to achieve a longer cycle lifetime in Ni-rich NMCs.	Feb 2022
I11-High Resolution Powder Diffraction	Effect of anode slippage on cathode cutoff potential and degradation mechanisms in Ni-rich Li-ion batteries Wesley M. Dose , Chao Xu , Clare Grey , Michael F. L. De Volder Cell Reports Physical Science DOI: 10.1016/j.xcrp.2020.100253 Diamond Proposal Number(s): [25186] Open Access Show Abstract ▼ Abstract: Li-ion batteries based on Ni-rich layered cathodes are the state-of-the-art technology for electric vehicles; however, batteries using these advanced materials suffer from rapid performance fading. In this work, we report a critical turning point during the aging of graphite/LiNi0.8Mn0.1Co0.1O2 (NMC811) full cells, after which the degradation is significantly accelerated. This turning point was identified using differential voltage analysis (DVA) applied to standard two-electrode data, which shows that graphite becomes progressively less lithiated, as confirmed by operando long-duration X-ray diffraction, and therefore has a higher electrochemical potential at the end of charge. This increase leads to a proportional increase in the cathode potential, and an accelerated impedance increase is observed from this point. This mechanism is expected to be universal for the vast majority of Li-ion battery chemistries, particularly for Ni-rich cathodes, whose degradation is extremely sensitive to the upper cutoff voltage, and our work provides fundamental guidelines for developing effective countermeasures.	Nov 2020
I11-High Resolution Powder Diffraction	Strongly coloured thiocyanate frameworks with perovskite-analogue structures Matthew J. Cliffe , Evan N. Keyzer , Matthew T. Dunstan , Shahab Ahmad , Michael F. L. De Volder , Felix Deschler , Andrew J. Morris , Clare Grey Chemical Science 10, 793-801 DOI: 10.1039/C8SC04082F Diamond Proposal Number(s): [15118] Open Access Show Abstract ▼ Abstract: We report the first examples of thiocyanate-based analogues of the cyanide Prussian blue compounds, MIII[Bi(SCN)6], M = Fe, Cr, Sc. These compounds adopt the primitive cubic pcu topology and show strict cation order. Optical absorption measurements show these compounds have band gaps within the visible and near IR region, suggesting that they may be useful for applications where light harvesting is key, such as photocatalysis. We also show that Cr[Bi(SCN)6] can reversibly uptake water into its framework structure pointing towards the possibility of using these frameworks for host/guest chemistry.	Oct 2018

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