The Effect of Binder on Volume Variation in Electrodes of Lithium Ion Batteries

The reality of waste gas of automobiles being accounted for a large portion of air pollution

and the gradual depletion of fossil fuel has generated a huge demand of the new brand of energy

supply for electric vehicle (EV). Although the traditionally designed and manufactured lithium ion

battery has served well for devices that requires relatively lower energy and power density, such

as laptop and mobile phone, it is far less competitive compared to commonly-used fossil fuel as

energy storage and supply solutions in the emerging new technologies of hybrid and electric

vehicles. Most of past researchers focused on the thin graphite electrode that contains silicon,

while thicker electrode, which means more active material to provide a higher energy capacity,

was hardly paid attention on. One of the deep-rooted reasons is that the mechanical failure,

including delamination and cracking of electrode from current collector, caused by frequent and

large stress-induced volume variation.

In our current research, we report mechanical properties of silicon-contained graphite

electrodes with different kinds of binder, novel aqueous material CMC and commonly-used PVDF

respectively, in lithium battery via in-situ experimental method by white light interferometry, in

order to get a comprehensive understanding of the effect of different binder to maintaining the

mechanical integrity of batteries. The two layer cantilever are micro-fabricated by

photolithography and laser beam processing and composed of upper copper film acting as

current collector and bottom graphite/silicon film being active material. We characterized the

relative curvature change and deformation of cantilevers as electrochemical reaction is in

progress by using white light interferometry and electrochemical workstation simultaneously. In

addition, the scanning electron microscopy, energy-dispersive X-ray spectroscopy and coin cell

testing were also used in order to characterize the corresponding surface morphology, element

distribution and battery performance of such cantilever structures. The results would be of great

significance to quantify the effect of binders to mechanical deformation of electrodes and

propose an innovative method to mitigate the deteriorating phenomenon during cycles.