Abstract
Lithium (Li) batteries comprising multivalent positive active materials such as copper vanadium oxide have high theoretical capacity. These batteries with a conventional liquid electrolyte exhibit limited cycle life because of copper dissolution into the electrolyte. We report here on the characterization of solid-state Li metal batteries with a positive electrode based on α-Cu6.9V6O18.9 (α-CuVO3). We replaced the liquid electrolyte by a nanostructured solid block copolymer electrolyte comprising of a mixture of polystyrene-b-poly(ethylene oxide) (SEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. In situ X-ray diffraction was used to follow the Li insertion/de-insertion mechanism into the α-CuVO3 host material and its reversibility. In situ X-ray scattering revealed that the multistep electrochemical reactions involved are similar in the presence of liquid or solid electrolyte. The capacity fade of the solid-state batteries is less rapid than that of α-CuVO3–Li metal batteries with a conventional liquid electrolyte. Hard X-ray microtomography revealed that upon cycling, voids and Cu-rich agglomerates were formed at the interface between the Li metal and the SEO electrolyte. The void volume and the volume occupied by the Cu-rich agglomerates were independent of C-rate and cycle number.
Highlights
There is considerable interest in copper vanadium oxide (CuVO) positive electrodes for rechargeable lithium (Li) batteries
Li metal batteries containing poly(ethylene oxide) (PEO)-based electrolytes are usually operated at temperature above the PEO melting temperature; the conductivity of crystalline PEO electrolyte is too low for practical applications
This study reports on the characterization of batteries comprising a Li metal negative electrode, a nanostructured block copolymer electrolyte film made by mixing polystyrene-b-poly(ethylene oxide) (SEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and α-Cu6.9V6O18.9 (α-CuVO3 for simplicity) as positive active material
Summary
There is considerable interest in copper vanadium oxide (CuVO) positive electrodes for rechargeable lithium (Li) batteries. This study reports on the characterization of batteries comprising a Li metal negative electrode, a nanostructured block copolymer electrolyte film made by mixing polystyrene-b-poly(ethylene oxide) (SEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and α-Cu6.9V6O18.9 (α-CuVO3 for simplicity) as positive active material.
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