Effect of carbon coating on elevated temperature performance of graphite as lithium-ion battery anode material

초록

The effect of carbon-coating on the elevated temperature performance of Li\graphite half-cells is investigated for 1 M LiPF6 in PC\EC\DEC (3:2:5) and 1 M LiBF4 in EC\DMC (2:1) electrolytes (PC = propylene carbonate; EC = ethylene carbonate; DEC = diethyl carbonate; DMC = dimethyl carbonate). Carbon-coated graphite is prepared by mixing synthetic graphite particles with polyvinyl chloride powders, followed by heating to 1000 degreesC under a flow of argon gas. For LiPF6-based cells, when pre-cycled cells are stored at 80 degreesC and then cycled at 30 degreesC, the loss of charge after storage at elevated temperature is much less with carbon-coated graphite than with untreated graphite electrode. When cycled at 80 degreesC without pre-cycling, the carbon-coated graphite electrode shows stable cycling behaviour, but untreated graphite results in premature cell failure. It appears that the carbon-coating preserves the graphite electrode even after storage at 60 degreesC in LiBF4-based electrolyte. From cycling and storage tests, it is concluded that surface modification through carbon-coating is very effective for the improvement of electrochemical performance and thermal stability of graphite electrodes at elevated temperatures. (C) 2003 Elsevier B.V. All rights reserved.

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