Li2CuO2 as an additive for capacity enhancement of lithium ion cells

The lithium-rich cuprate Li2CuO2 shows a high specific charge capacity of 320-340 mAh g-1 due to lithium extraction on oxidation up to 4.5 V versus Li. However, poor reversibility of this reaction limits the application of this material in lithium ion cells as the active material in the positive electrode. Nevertheless, this inexpensive, easily synthesized, air stable material may be useful as an additive to the positive electrode for reduction of capacity loss caused by poor reversibility of the negative electrode. Electrochemical testing of a composite Li2CuO2/LiMn2O4 electrode versus Li shows that no interference occurs between these two materials and that LiMn2O4 maintains its long cycle life in the voltage range 3.0-4.5 V versus Li. The calculated enhancement of effective specific capacity due to the additive increases with the fraction of charge lost at the negative, reaching 10% enhancement at 20% capacity loss.