2,2-Dimethyl-1,3-dioxane-4,6?dione functionalized poly(ethylene oxide)-based polyurethanes as multi-functional binders for silicon anodes of lithium ion batteries

Chemically reactive groups (2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum's acid, MA) and poly(ethylene oxide) (PEO) segments are incorporated to polyurethanes as binders of silicon anode for lithium ion batteries, aiming to address the volume change issue of the silicon anode in lithiation/delithiation cycles. The polymeric binder builds up multiple interaction to silicon surfaces, including hydrogen bonding between the urethane linkages of the bonder and silanol groups of silicon surfaces and covalent linkages through the addition reaction between ketene groups (generated from MA thermolysis reaction) and silanol groups of silicon surfaces. Self-dimerization of ketene groups also results in crosslinked structure of the binder. Both of the above-mentioned interaction and crosslinked structure contribute to stabilize the silicon anode materials. Moreover, the PEO segments facilitate the transportation of lithium ions and increase the ion conductivity of the anode. Consequently, the corresponding silicon anode is workable at a high C rate (0.8C) to demonstrate a specific capacity of approximately 1,785 mAh g & minus; 1 and a capacity retention of 58% after a 600-cycle charge/discharge test. Morphological observation on the anode materials after a 300-cycle test indicates that the reactive PU binder could effectively depress cracks and interphase separation of the anode materials caused by the lithiation/delithiation-induced volume changes. The prepared binder also exhibits stabilization on the solid electrolyte interphase (SEI) layer and prevent anode material delamination. The results demonstrate a successful example of designs and preparation of multi-functional binders for silicon anodes. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Incorporating chemically reactive groups and PEO segments into polyurethanes as binders for silicon anodes in lithium ion batteries successfully addresses the volume change issue during lithiation/delithiation cycles. The multiple interactions and crosslinked structure contribute to stabilizing the anode materials, while PEO segments enhance ion conductivity. The designed multi-functional binders demonstrate high specific capacity, capacity retention, and improved morphological stability, showcasing a successful strategy for silicon anode design and preparation.