Rarely negative-thermovoltage cellulose ionogel with simultaneously boosted mechanical strength and ionic conductivity via ion-molecular engineering

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2023-01, Vol.11 (5), p.2145-2154
• Main Authors: Chen, Qunfeng, Cheng, Binbin, Wang, Zequn, Sun, Xuhui, Liu, Yang, Sun, Haodong, Li, Jianwei, Chen, Lihui, Zhu, Xuhai, Huang, Liulian, Ni, Yonghao, An, Meng, Li, Jianguo
• Format: Article
• Language: English
• Subjects: Anions; Cations; Cellulose; Chemical bonds; Conductivity; Coupling (molecular); Dipole interactions; Doping; Engineering; Freezing; Hydrogen bonding; Ion currents; Mechanical properties; Modulus of elasticity; Thermoelectric materials; Zinc; Zinc chloride
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/D2TA09068F

Excellent mechanical strength and conductivity are essential and exigent features for advanced gel materials. The trade-off between them, however, remains a challenge. Here, we proposed an ion-molecular engineering strategy to develop a strong (4.46 MPa) yet high conductivity (67.43 mS cm −1 ), freezing tolerant (−103 °C), and transparent (94%) cellulose ionogel via ZnCl 2 doping (namely CZ ionogel). Doping Zn 2+ induces coordination interactions with cellulose molecules (Zn 2+ –COO − ) through coupling hydrogen bonding and ion–dipole interactions, resulting in a robust CZ ionogel with 15- and 10-times improvement in the elastic modulus and toughness, respectively. The Zn 2+ –cellulose engineering produces a confined nanostructure that supports the efficient transport of small-size Cl − anions, while limiting the movement of large-size cations, thereby allowing the CZ ionogel to function as a rare n-type ionic thermoelectric material to convert low-grade waste heat into useful electricity (∼110 mV at Δ T = 36 K). This ion-molecular engineering strategy offers unprecedented degrees of freedom for developing adaptable gel materials.