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Three-dimensional operando optical imaging of particle and electrolyte heterogeneities inside Li-ion batteries.

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Understanding (de)lithiation heterogeneities in battery materials is key to ensure optimal electrochemical performance. However, this remains challenging due to the three-dimensional morphology of electrode particles, the involvement of both solid- and liquid-phase reactants and a range of relevant timescales (seconds to hours). Here we overcome this problem and demonstrate the use of confocal microscopy for the simultaneous three-dimensional operando measurement of lithium-ion dynamics in individual agglomerate particles, and the electrolyte in batteries. We examine two technologically important cathode materials: LixCoO2 and LixNi0.8Mn0.1Co0.1O2. The surface-to-core transport velocity of Li-phase fronts and volume changes are captured as a function of cycling rate. Additionally, we visualize heterogeneities in the bulk and at agglomerate surfaces during cycling, and image microscopic liquid electrolyte concentration gradients. We discover that surface-limited reactions and intra-agglomerate competing rates control (de)lithiation and structural heterogeneities in agglomerate-based electrodes. Importantly, the conditions under which optical imaging can be performed inside the complex environments of battery electrodes are outlined.



40 Engineering, 4016 Materials Engineering, 34 Chemical Sciences, 3406 Physical Chemistry, 7 Affordable and Clean Energy

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Nat Nanotechnol

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Springer Science and Business Media LLC
Engineering and Physical Sciences Research Council (EP/L015978/1)
Swiss National Science Foundation (grant P400P2_199329). École Normale Supérieure Paris-Saclay ESPRC NanoDTC (EP/L015978/1). Faraday Institution (EP/S003053/1) LiSTAR project (FIRG014). UCL H. Walter Stern Scholarship. Clare College Cambridge, Junior Research Fellowship
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