PVA-PAAM@MXene/AgNWs-supported Composite Phase Change Materials:Construction,Properties Characterization And Application In Thermal Management

Severe energy shortages and environmental pollution have led to an increased demand for renewable energy utilization and the development of new energy storage technologies.Among these,phase change materials（PCMs）play a crucial role in the advancement of thermal energy storage technologies and thermal management applications,as well as in balancing energy supply and demand and enhancing energy efficiency.However,the low thermal conductivity,potential volume fluctuations and liquid leakage during the phase change process of PCMs have significantly hindered the widespread adoption and application of phase change thermal storage technology.Therefore,in this paper,based on the structural design of polyvinyl alcohol（PVA）/polyacrylamide（PAAM）dual-network polymer-supported carriers,structurally tunable and performance-controlled composite PCMs containing MXene nanosheets and nanosilver wires（Ag NWs）were constructed by using disodium phosphate hydride dodecahydrate（Na₂HPO₄·12H₂O,DHPD）and poly（ethylene glycol）（PEG）as the phase-change medium.The research systematically investigates the thermal storage capacity,photothermal conversion capacity,and shape stability of PVA-PAAM polymer-based composite PCMs in different carrier forms and with different phase change media,reveals the encapsulation mechanism of PVA-PAAM matrix and the thermal conduction enhancement mechanism of nano-doped materials,explores the temperature-control effect of the composite PCMs in the thermal management of lithium-ion batteries and electronic devices,which provides experimental bases and ideas for solving the problems faced by the practical application of PCMs.Specific studies are as follows:（1）Preparation and performance study of PVA-PAAM hydrogel/DHPD composite PCMsDHPD was integrated into PVA-PAAM robust hydrogel modified with Ti₃C₂T_xMXene nanosheets and Ag NWs,thus,a kind of hydrated salt hydrogel with high enthalpy（150.6 J/g）,high thermal conductivity（1.25（W/m·K））and bloom heat transfer efficiency was prepared.Research indicates that the combination of MXene/Ag NWs three-dimensional thermal conductivity network and cross-linked dual network hydrogel provides a viable solution to overcoming the low thermal conductivity and rigidity of the PCM.The prepared hydrogel exhibits excellent shape stability as well as good flexibility and moldability.（2）Preparation and performance study of PVA-PAAM hydrogel/PEG composite PCMsThe preparation of tough organic hydrogel composite PCMs with excellent thermal performance was achieved by using an in-situ polymerization method with PVA-PAAM hydrogel as the supporting matrix,Ti₃C₂T_x MXene nanosheets and Ag NWs as thermal conductive additives,and PEG as the phase change material.The study shows that the excellent viscoelastic and mechanical properties of the PVA-PAAM hydrogel give the composite PCM better flexibility,while the effective combination of the hydrogel and PEG ensures the good energy storage capacity of the composite PCM（97.4 J/g）.The dispersed MXene nanosheets and Ag NWs in the hydrogel form a three-dimensional thermal conductive network,achieving the enhancement of the thermal conductivity（0.66（W/m·K））and the photothermal conversion efficiency of the composite PCM.In addition,the prepared composite PCM exhibits excellent thermal stability and outstanding shape stability.（3）Preparation and properties study of PVA-PAAM aerogel/PEG composite PCMsTi₃C₂T_x MXene nanosheets and Ag NWs modified PVA-PAAM hydrogels were used as precursors to obtain PVA-PAAM aerogels with high thermal conductivity and self-supporting structures through vacuum freeze-drying method.The aerogel was then utilized as a matrix for the incorporation of PEG as the phase change material using vacuum impregnation method,resulting in a high thermal conductivity shape-stabilized composite PCM.The research indicates that the unique three-dimensional network structure and abundant intermolecular forces of PVA-PAAM aerogel provide an efficient loading platform for PEG,leading to outstanding heat storage capacity with an enthalpy value reaching 124.8 J/g.Furthermore,the synergistic effect of MXene nanosheets and Ag NWs significantly enhances the thermal conductivity and photothermal conversion efficiency of the composite phase change material,reaching0.64（W/m·K）and 88.8%,respectively.（4）Research on the thermal management application of PVA-PAAM based composite PCMsTo verify the thermal management capability of the composite PCMs studied in this paper,different rate charge-discharge（1C,2C,and 3C）tests and 3C cycle charge-discharge tests were performed on lithium-ion power batteries.By comparing the temperature of the lithium-ion battery before and after installing the composite PCMs,it was found that the PVA-PAAM-based composite phase change material can effectively reduce the working temperature of the battery（12±0.5℃）.In terms of electronic devices,the working temperature of the electronic device at different output voltages before and after using the PVA-PAAM-based composite PCMs were compared to explore the thermal control ability of the composite phase change material.The research results show that the PVA-PAAM-based composite PCMs studied in this paper can reduce the temperature of the heating device by 18-29℃within 50s.Furthermore,the PVA-PAAM-based composite PCMs demonstrate excellent heating delay effects in electronic device testing,effectively avoiding transient temperature rise and providing strong protection for electronic devices.This article provides a new method and new ideas for the design and construction of high thermal conductivity shape-stable composite PCMs,opening up new directions for the application of PVA-PAAM polymers in the field of phase change energy storage and thermal management,and enriching the combination of PVA-PAAM polymers with different PCMs.The research results provide theoretical basis and experimental support for the development of efficient,functionalized,and highly reliable phase change thermal storage technology.