Localized Electrochemical Analysis of Polyacrylate Binders on Graphite-Silicon Negative Electrodes in Lithium-Ion Batteries

Abstract

Graphite-silicon composite negative electrodes are expected to satisfy one of recent demands for creation of high performance lithium-ion batteries because of their high-capacity (above 1000 mAh/g). A major issue for their practical application is a control of large volume expansion/shrinkage of silicon materials, which is a key to realize their good reversible cyclability. Recently, Komaba et al. reported that polyacrylate binders improve their cyclability because of well-dispersion of graphite/silicon materials by coating them with polyacrylate homogeniously.1,2 Also, polyacrylate can suppress a formation of decomposition of organic electrolyte during lithiation process, which induces poor cyclability. For further investigation of existence of the decomposition, we have applied a scanning electrochemical cell microscopy with single barrel nano-pipette filled with organic electrolyte and a reference electrode, called nanoSECCM in Figure 1 a.3NanoSECCM can measure electrochemical properties (such by cyclic voltammetry, CV) with sub-micrometer scale locally. From localized CV results (scan rate at 100 mV/s) as shown in Figure 1 b, we have observed current response related to the formation of decomposition. This response was not observed by typical bulk CV measurement, suggesting that our technique is sensitive to investigate graphite-silicon composite negative electrodes for realization of high performance electrodes in lithium-ion batteries. [1] N. Yabuuchi et al., Adv. Energy Mater., 2011, 1, 759.[2] Z-J. Han et al., Phys. Chem. Chem. Phys., 2015, 17, 3783.[3] Y. Takahashi et al., Nat. Commun. 2014, 5, 6450. Figure 1