\”Pressure-sensitive\” type adhesive so that the expansion of the silicon nowhere to escape, to achieve stable long cycle

One because of the high theoretical specific capacity (3579 mAh g-1) is thought to be a lithium ion battery (LIBs) most promising negative electrode material silicon. However, silicon anode material in the process cycle will make a great volume expansion of the battery capacity fade quickly, hinder the further application of silicon anode material. Polymer binder Application can effectively improve the cycle stability of the lithium ion battery silicon anode material, polymer binder and therefore on the structure of design and synthesis become a hot topic in recent years. The pressure-sensitive adhesive plays an important role in daily life, widely used in adhesive tape, label paper.

Figure 1: chemical structure of the pressure-sensitive polymer as a binder and a schematic view of the effect of

Recently, Oak Ridge National Laboratory (Oak Ridge National Laboratory) of the Cao Pengfei researcher and Nankai University of Yang Bin researcher team will be an important component of Pressure sensitive adhesive – isooctyl acrylate polymer binder applied on a silicon negative electrode, proved the same can live with good adhesion particles, and a conductive network surrounding the silicon nano-based pressure-sensitive adhesive polymer, significantly enhance the cycle stability of the silicon negative electrode (Figure 1). The results published in the current \” ACS Applied Energy Materials \”, Oak Ridge National Laboratory Cao Pengfei and Nankai University of Yang Bin as a co-corresponding author.

Figure II: (A) a schematic diagram of the test mode atomic force microscope. (B) an atomic force microscope test results. (C) 180o peel test results

Such polymer-based pressure-sensitive adhesive by isooctyl acrylate (2-EHA) and acrylic acid (AA) copolymerized. AA may form hydrogen bonds with the silicon surface and the silicon surface thus enhancing effect of 2-EHA and can improve the viscoelastic polymer. 2-EHA and AA adjusting the ratio of AA can be a series of different densities and different viscoelastic polymer binder. By atom180o peel force microscope and characterization testing found that only when the binder has suitable viscoelasticity as well as AA group density (20 mol% of 2-EHA, PSA-20%), it is possible to set the silicon surface and a copper fluid strongest adhesion surface (Figure 2). Also teaches Konstantinos D. Vogiatzis U.S. theoretical calculations show that the 2-EHA relative to the polymer units of polyacrylic acid, a suitable content can significantly improve the binding energy with the silica surface.

FIG three: (A) in a pressure-sensitive adhesive is not the first week of the negative electrode binder a silicon charge and discharge curve. (B) corresponding to the first effective FIG. (C) corresponding to the cyclic performance
FIG four: (A) Si-PAA and Si-PSA-20% at a current density of 360 mA g 1-in cycle performance. (B) Si-PAA and Si-PSA-20% at a current density of 1.8 A cycling performance under g-1. (C) Si-PAA and Si-PSA-20% at a current density of 1.8 A g-1, a silicon loading of 1.2 mg cm-2 of the cycle performance. (D) in a binder PSA-20% silicon / graphite composite electrode material at a current density of 1.8 A g-1 of cycle performance.

First, their different ratio of 2-EHA and AA as polymer binder polymer silicon anode, the cycle performance is shown in Figure III, PSA-20% has the best electrochemical performance . To further explore the performance of PSA-20% as a binder, they are chosen as the control group of polyacrylic acid binder. Figure IV (A), as compared to polyacrylic acid as the binder of the negative electrode silicon (Si-PAA), Si-PSA-20% significantly improved stability. While a large current (1.8 A g-1) and at high loadings of silicon (1.2 mg cm-2) conditions, Si-PSA-20% also has a better electrochemical properties, four are shown in (B) and shown in Figure IV (C). PSA-20% used as the silicon / graphite composite electrode material binder also has good results, circulating at a current density of 1.8 A g-1 still holding 1000 weeks 606 mAh g-1 specific capacity as four (D) in FIG. Based on their research of such a pressure-sensitive adhesive polymer is applied in a silicon electrode for a polymer binder inexpensive and efficient design provides a new idea. References: Yiyang Pan et al Adhesive Polymers as Efficient Binders for High-Capacity Silicon Electrodes, DOI:. 10.1021 / acsem.9b02420