Design And Application Of Low Temperature Tolerance Nanocellulose Composite Hydrogel

In recent years,portable,wearable and intelligent electronic devices have developed rapidly.However,due to high Young’s modulus,poor biocompatibility and poor responsiveness,the wide application of flexible electronic devices is still limited.Therefore,it is very necessary to overcome these defects and develop new flexible functional materials.Hydrogels are a class of polymer materials with three-dimensional cross-linked networks.Their excellent properties make them ideal candidates for next-generation flexible electronic devices.However,because the hydrogel will freeze under extreme conditions and reduce the mobility of water,the ion conductivity of the device will fail.Therefore,the research and development of low temperature tolerance hydrogels has important practical significance.This paper mainly studies and develops a variety of gel materials with good environmental adaptability and water retention performance in extreme environment,and develops their potential applications according to the unique properties of the materials.Specific research contents and main conclusions are as follows:1.A kind of temperature-resistant CNF-PVA-DMSO hydrogel electrolyte for flexible zinc ion capacitors was developed by using the cryo-physics crosslinking process with cellulose nanofibers（CNF）,polyvinyl alcohol（PVA）and dimethyl sulfoxide（DMSO）as nano-filler,polymer skeleton and antifreeze agent,respectively.CNF-PVA-DMSO organic hydrogel has excellent mechanical properties,water retention and good temperature resistance.At the same time,the CNF-PVA-DMSO gel electrolyte can effectively inhibit the growth of zinc dendrites and the occurrence of parasitic side reactions,and give the Zn/Zn symmetric battery a stable voltage distribution at the temperature of 60 to-20℃ and back to 30℃,indicating that it has good temperature adaptability.Zinc ion capacitors based on CNF-PVA-DMSO organic hydrogel electrolyte can maintain high specific capacity at-20 and 20℃,60.7 mAh g^-1 and 74.2 mAh g^-1 at1 A g^-1,respectively.And excellent cycle performance with high capacity retention rates of 87%and 99%,respectively,after 1500 cycles.2.Using cellulose nanofibers（CNF）,poly（ethylenimine）（PEI）,acrylamide（AAm）and trehalose（THL）as raw materials,a kind of hydrogel（CNF-PEI-PAAm-THL）with rapid polymerization and excellent water retention and frost resistance was prepared by one-pot method.Trehalose（THL）,as an environmentally friendly antifreeze component,is used to inhibit the formation of ice crystals.The results showed that the ionic conductivity of the gel was significantly increased with the increase of trehalose content at-30℃.In addition,the flexible Zn-air battery（ZAB）based on the CNF-PEI-PAAm-THL gel electrolyte has a high specific capacity of 764 mAh g^-1,long cycle performance and excellent mechanical flexibility.In addition,the flexible ZAB battery based on the CNF-PEI-PAAm-THL gel electrolyte can be used for practical applications even under the extreme operating conditions of-30℃.3.Using cellulose nanofibers（CNF）and acrylic acid（PAA）as the main network,water and glycerol as the antifreeze component,FeCl₃ and tannic acid（TA）were introduced,and the ultrafast polymerization of hydrogels was realized by using the REDOX reaction between Fe³⁺and TA in one pot method.A kind of CNF-TA-PAA hydrogel with self-healing and temperature resistance was prepared.The hydrogel can maintain good mechanical properties and sensitivity at-20℃.The hydrogel also has high sensitivity（GF=2.51）and can achieve fast response（0.3s）.When assembled into a flexible strain sensor,it can sensitively monitor some micro facial expressions.