Impact of the Electrode Potential of Negative Electrode on the Increase in Resistance of LiNi1/2Mn3/2O4 Positive Electrode

An increase in the resistance of electrode materials due to the formation of electrode/electrolyte interphases (EEI) induces capacity loss and power fading in lithium-ion batteries, and hence, is a significant problem that hinders the extension of battery lifetime. Previous studies have reported that the increase in the resistance of one electrode is affected by the other electrode, suggesting that the crosstalk reaction plays a crucial role in the increase in the resistance of the electrodes. In this study, to understand the resistance increase mechanism in relation to the crosstalk reaction, lithium-ion cells with a LiNi1/2Mn3/2O4 (LNMO) electrode with various materials (Li metal, graphite, Li[Li1/3Ti5/3]O4, and LiFePO4) as a negative electrode were examined via potentiostatic charge tests. The rate of increase in resistance of the LNMO electrodes against capacity due to side reactions depends on the electrode potential of the negative electrode: a lower electrode potential of the negative electrode slows down the rate of increase in resistance of the LNMO electrodes. Based on these results, an explanation for the resistance increase was provided by taking into consideration the crosstalk reaction. The crosstalk reaction reduces the amount of oxidative decomposition products generated at the LNMO electrode by consuming these products at the negative electrode; i.e., the resistance increase by EEI formation is minimized. A cell design based on the proposed mechanism, wherein the lower electrode potential of the negative electrode suppresses the increase in resistance of the positive electrodes, will open up the possibility of batteries with a long life.