Abstract
A ureido-pyrimidinone (UPy)-functionalized poly(acrylic acid) grafted with poly(ethylene glycol)(PEG), designated PAU-g-PEG, was developed as a high performance polymer binder for Si anodes in lithium-ion batteries. By introducing both a ureido-pyrimidinone (UPy) unit, which is capable of self-healing through dynamic hydrogen bonding within molecules as well as with Si, and an ion-conducting PEG onto the side chain of the poly(acrylic acid), this water-based self-healable and conductive polymer binder can effectively accommodate the volume changes of Si, while maintaining electronic integrity, in an electrode during repeated charge/discharge cycles. The Si@PAU-g-PEG electrode retained a high capacity of 1,450.2 mAh g−1 and a Coulombic efficiency of 99.4% even after 350 cycles under a C-rate of 0.5 C. Under a high C-rate of 3 C, an outstanding capacity of 2,500 mAh g−1 was also achieved, thus demonstrating its potential for improving the electrochemical performance of Si anodes.
Highlights
A ureido-pyrimidinone (UPy)-functionalized poly(acrylic acid) grafted with poly(ethylene glycol)(PEG), designated PAU-g-Poly(ethylene glycol) (PEG), was developed as a high performance polymer binder for Si anodes in lithiumion batteries
Characterization of poly(acrylic acid‐co‐UPy acrylate)‐grafted‐PEG, PAU‐g‐PEG 1 and poly(acrylic acid)‐grafted‐PEG (PAA‐g‐PEG) 2. 1H-NMR and FT-IR spectroscopic analysis was employed for the structural analysis of PAU-g-PEG 1 and the control polymer PAA-g-PEG 2 (Figure S2 and S3)
The results showed that both electrodes fabricated from the PAA-g-PEG and PAA binders showed an increase in RSEI after cycles, but the size of the semi-circle was larger for the Si@PAA-g-PEG electrode, which had a higher RSEI after both 5 cycles and 50 cycles than the Si@PAA (Fig. 6e,f)
Summary
A ureido-pyrimidinone (UPy)-functionalized poly(acrylic acid) grafted with poly(ethylene glycol)(PEG), designated PAU-g-PEG, was developed as a high performance polymer binder for Si anodes in lithiumion batteries. 400%) volumetric expansion/ shrinking during repeated charge/discharge processes, which causes Si-based LIBs (cells) to have generally poor cycle lives These changes in volume tend to pulverize silicon particles, and lead to the repeated loss and formation of the solid electrolyte interphase (SEI) layer, and cause detachment from the current collector and structural collapse between electrodes. Since these issues are associated with the loss of active material (Si), low Coulombic efficiency, and loss of contact for ionic and electrical conduction, they result in the rapid decay of cell capacity. PVdF and other conventional polymeric binders require toxic and volatile organic solvents for electrode m anufacturing[22,23,24,25,26,27]
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