Fabrication Of Mussel-memetic Polymers With Self-healing And Electrochemical Properties

The emergence of lithium ion batteries shed lights on improving energy comsuption structure and environmental problems.Recently,lithium sulfur batteries and Si anode based lithium ion batteries have gained considerable interest from battery community due to their high theoretical capacity.However,adhesion failure of binders caused by swelling electrolyte and huge volume change of active particles would lead to the exfoliation of electrode materials.In addition,insulative active particles and electrolyte-soluble polysulfides further deteriorate the capcacity retention.Binders bridging the electrode materials and current collector play a vital role in maintaining electrode structural integrity and significantly influence the electrochemical performances.Herein,inspired by marine creature mussel,Fe3O4 nanoparticles doped elastomer and BN nanosheets doped adhesives were developed with excellent self-healing property and wet-adhesion performance.Three water-soluable binders were prepared to realize high performance lithium-sulfur batteries and Si/SiO anode based lithium ion batteries.Following are the main research works:A dual-crosslinked thermoset elastomer was prepared in situ by mixing P(GMA-r-PDMSPEMA),diethylenetriamine and dopamine modified Fe3O4 nanoparticles.The surface morphology,body structure,mechanical strength,glass-transition temperature,surface temperature under sunlight irradiation were investigated by varing the addition of Fe3O4 nanoparticles.The mechanical property of elastomer can be remarkably recovered,which was due to the synergistic interactions of magnetic nanoparticles'intrinsic photo-thermal effect,reversible catechol-Fe3+ coordination and hydrogen bond.This part provides practical guidance for the subsequent design and preparation of battery binders with well self-healing property.A dual pH-responsive adhesive was prepared in situ by mixing amino modified BN nanosheets and P(DMA-r-DMAEMA-r-FMPEG).The surface morphology,body structure,work of adhesion,mechanical strength were investigated by varing the addition of BN nanosheets.Interfacial adhesion,internal cohesion and surface tension of adhered materials were proved to heavily influence the adhesion strength.Moreover,DDF-BNNS5 showed pH-induced switchable adhesion capability(reversed between 0.30 and 1.44 MPa)due to the dynamic equilibrium of imine linkage and pH responsive PDMAEMA side chains' wettability.Based on the above reasearches,a water-soluble tricopolymer with catechols and sulfobetaines side chains was designed as binder of lithium-sulfur batteries.The reversible non-covalent interactions among side chains endowed superior volume change adaptability to prepared electrodes.SBMA side chains were also able to capture lithium polysulfides and promote lithium ion difusion.As a results,the cells with DSM binder exhibited outstanding cycle performance with high sulfur loading of 9.7 mg-cm-2,which delivered a high initial areal capacity of 10.2 mAh.cm-2 and maintained at 7.2 mAh·cm-2 after 70 cycles.To simplify the manufacturing process and lower the cost,a biomass-derived fluorinated corn starch emulsion was prepared by emulsifier-free polymerization and dopamine auto-polymerization.The three-dimensional crosslinked network formed in situ was beneficial to inhibit structure collapse of Si or Si-graphite/SiO-graphite composite anodes during charging and discharging process.Consequently,SSC4SA with suitable Tg and electrolyte uptake exhibited the best performance when applied in pure Si,Si-graphite and SiO-graphite composite electrode,which were far superior to commercial CMC-SBR binder based electrodes.Taking into account both the application in sulfur cathodes and Si anodes,binder with excellent comprehensive properties was prepared to realize high specific capacity and long cycle life.The tertiary amine side chains of copolymer were protonated and electrostatic complexed with phytic acid to generate a reversible crosslinking network in situ.Accompanying with polydopamine formed in situ,the prepared binder showed fast self-healing property,rapid lithium polysulfides adsorption and strong adhesion in electrolyte environment.As a results,initial diacharge capacity of S/A6D4-PA was 755 mAh·g-1 at 1 C,after 300 cycles the capacity retention maintained at 91.0%,The charge-discharge cycling of Si/A8D2-PA performed with Li insertion capacity limited to 1000 mAh·g-1 showed stable anode performance for more than 500 cycles.