纤维素基柔性电致变色器件研究进展及展望

Progress and prospect of flexible electrochromic devices based on cellulose

电致变色技术是一门极具潜力的应用科学,正逐渐引起学术界和工业界的深度关注。主要从电致变色器件(Electrochromic Devices,ECD)的工作原理、器件结构、材料应用等方面进行介绍和总结。新兴的柔性ECD其具有质量轻、灵活、便携等优点在智能穿戴和柔性电子产品中的应用更为广泛。然而柔性ECD在生产应用中仍存在一些缺陷亟待解决:①常规的玻璃基底制备出的刚性电致变色器件柔性不足、原材料稀缺且不可再生;②传统的液态电解质在使用过程中易泄露、腐蚀、蒸发,严重影响器件的安全性及使用寿命;③电致变色层电化学稳定性较差,影响器件使用寿命。从结构和性质方面讨论了纤维素材料用作ECD柔性基底、电解质、电致变色层的应用和优势。纤维素材料具有优异的光学、力学性能,以其作为ECD器件的基底可规避常规玻璃基底柔性不足、原材料稀缺等缺陷;在电解质层中合理引入纤维素,其三维网络结构及主干上的官能团可通过形成离子键、氢键的方式提高电解质的机械性能与导电性能;在电致变色层中合理引入纤维素,纤维素的三维网状结构能为材料发生氧化还原反应提供更大的比表面积及缓解电子/离子嵌入、脱出过程引起的体积膨胀,有助于改善电致变色材料的电化学稳定性,延长器件的使用寿命。纤维素基柔性ECD在节能建筑、显示设备及储能设备等领域具有广阔的应用前景,在柔性电子器件引入纤维素对扩展其应用范围和提升利用价值具有重要意义。

Electrochromic technology is a potential applied science,which is gradually attracting the deep attention of academia and industry.In this paper,the working principle,device structure and material application of electrochromic devices(Electrochromic Devices,ECD)are introduced and summarized.The emerging flexible ECD has the advantages of light weight,flexibility and portability,which is more widely used in smart wear and flexible electronic products.However,there are still some defects to be solved in the production and application of flexible ECD:①The rigid electrochromic devices which prepared on conventional glass substrates are not flexible enough,the raw materials are scarce and non-renewable;② The traditional liquid electrolytes are easy to leak, corrode and evaporate, which seriously affect the safety and service life of the devices;③ The electrochemical stability of the electrochromic layer is poor, affecting the ser-vice life of the devices.The applications and advantages of cellulose as flexible substrate, electrolyte and electrochromic layer of ECD are discussed in terms of structure and properties. Cellulose material has excellent optical and mechanical properties, which can avoid the defects such as the insufficient flexibility of conventional glass substrate and the scarcity of raw materials when cellulose is used as the substrate of ECD devices, and the three-dimensional network structure and functional groups on the backbone of cellulose can improve the mechanical properties and electrical conductivity of elec-trolytes by forming ion bonds and hydrogen bonds. With the reasonable introduction of cellulose into the electrochromic layer, the three-dimensional reticular structure of cellulose can provide a larger specific surface area for redox reaction and alleviate the volume expansion caused by electron/ion intercalation and exfoliation process. It is helpful to improve the electrochemical stability of electrochromic materials and prolong the service life of the devices. Cellulose-based flexible ECD have a broad application prospect in the fields of energy-saving buildings, display equipment and energy storage devices. The introduction of cellulose into flexible electronic devices is of great significance to expand its scope of applic-ation and enhance its utilization value, and at the same time promote the development of green and environment-friendly intelligent flexible electronic devices.