Research On Energy Storage And Mechanical-Electrical Properties Of Hydroxyapatite Nanowire Composites

As a renewable biological material,nano-sized hydroxyapatite(HAP)has abundant oxygen-containing functional groups on the surface,and possesses good biocompatibility,outstanding adsorption and excellent mechanical properties.So far,researchers have carried out a lot of research on it,and synthesized HAP nanomaterials with various morphologies for specific uses,including nanoparticles,micro-nanospheres,nanosheets,nanowires,nanotubes,and nanorods.Among them,one-dimensional hydroxyapatite nanowires(HAP NWs)with large aspect ratios have the characteristics of flexibility,high strength,and thermal stability,and are easy to be constructed into a three-dimensional network.Therefore,HAP NWs have been widely used in cutting-edge fields such as biomedical devices,new energy sources,fire protection and heat insulation,air and water purification,surface hydrophobic coatings,and high-strength nanocomposites.On the other hand,it is a huge challenge to prepare hydroxyapatite nanowires with high crystallinity,high purity,ultra-length(>100?m),good dispersion and uniform size distribution.However,as far as high-temperature solid polymer electrolytes and ionic skin are concerned,there is no related research involving HAP NWs.Therefore,our research is focusing on preparing ultra-long HAP NWs with controllable morphology and further studying their surface modification to explore their potential application regarding the high-temperature solid polymer electrolytes and ionic skin.The specific research content is stated as follows:(1)Preparation and high temperature performance of hybrid solid polymer electrolyte1)The ultra-long HAP NWs suspension was synthesized by the hydrothermal reaction method,and the vacuum filtration device was used to construct a porous three-dimensional frame film for obtaining a thermally stable HAP NWs film with a self-supporting structure.Inspired by the traditional Chinese“Tai Chi”,the HAP NWs frame/polyethylene oxide(HAP-PEO)hybrid solid polymer electrolyte was then designed.2)In high temperature and open flame experiments,it is found that the HAP-PEO hybrid solid polymer electrolyte can maintain structural thermal stability at high temperatures,reducing the risk of high temperature short circuits of the battery.In the tensile experiment,the strength of the HAP-PEO hybrid solid polymer electrolyte is7200%higher than that of the pure PEO solid polymer electrolyte,which further provides a physical protection for inhibiting the growth of lithium dendrites.Through electrochemical analysis,it is found that HAP-PEO hybrid solid polymer electrolyte has high ion conductivity,wide voltage window,high ion mobility,and stable lithium symmetric battery cycleing performance at 160 ^oC,which proves the excellent electrochemical performance at high temperature.3)In the Li Fe PO₄/HAP-PEO/Li full battery charge and discharge experiment at a high rate of 4 C at 160 ^oC,77%of the discharge capacity is retained and the Coulombic efficiency keeps as high as 99%after 300 cycles.These results illustrate that the designed HAP-PEO hybrid solid polymer electrolyte can meet the needs of practical applications even at extreme high temperatures.(2)Research on the preparation and performance of multifunctional ion skin1)Using in-situ oxidation deposition method,tannic acid(TA)was grown in situ on the surface of HAP NWs to prepare TA-coated HAP NWs(TA@HAP NWs).A transparent and highly ionically conductive hydrogel that integrates multi-purpose sensing,UV-filtering,water-retaining and anti-freezing performances is achieved by the organic combination of TA@HAP NWs,polyvinyl alcohol(PVA),ethylene glycol(EG)and Al³⁺,which can be used to develop ionic skin.2)In the sensing performance test,it is found that the physical quantities of strain,pressure and temperature have a highly linear sensing response.Especially in the strain sensing test,it shows high sensitivity(GF=2.84)in a wide strain range(0?350%),high linearity(R²=0.99003),fast response(?50 ms),low sensing hysteresis(2.4%),strain sensing reversibility and excellent cycle stability.These results are at the leading level in the same research field.3)In mechanical and UV resistance tests,TA@HAP NWs as a nano-reinforced filler can improve the mechanical properties of the hydrogel system and endow it with UV shielding ability.The use of binary solvents(EG/W)guarantees water retention at high temperatures and frost resistance at low temperatures.These performances indicate that the ion skin can be applied in many fields.These studies are expected to promote the application of HAP NWs composite materials in the field of high-temperature solid polymer electrolytes and multifunctional ion skin with important scientific significance and practical value.