Double-fiber interlocked I@AC freestanding electrode: Ultrahigh mass-loading design for long-cycle zinc-iodine batteries.

Increasing the active material loading on electrodes provides an effective approach for improving the energy density of batteries. However, this approach is always hindered by intractable challenges such as poor structural stability, slow reaction kinetics, and low active material utilization. In this paper, a high-performance double-fiber interlocking binder system is developed to construct high-performance iodine cathodes, by leveraging a polyquaternium-10 (P10, a cationic cellulose) waterborne binder and a bacterial cellulose (BC) reinforcing fiber. The synergistic effect of mechanical interlocking and hydrogen bonding between BC and P10 forms a robust 3D network, enabling the construction of high-mass-loading freestanding I@AC cathodes. Furthermore, the highly hydrophilic BC-P10 network ensures rapid and uniform electrolyte infiltration, facilitating fast ion transport and full material utilization. At the same time, the network can firmly anchor the I@AC active material and the polyiodide intermediates, suppress the detrimental polyiodide shuttling and self-discharge, while retaining the mechanical strength and structural integrity. At routine iodine loading mass (2-3 mg cm), the BC-P10-bonded cathode delivers much higher capacity (182.6 vs.150.6 mA h g, 0.2 A g), better rate capability (137.6 vs.75.4 mA h g, 5.0 A g) and higher anti-self-discharge performance (capacity retention after 200 h: 76.0 vs. 68.4 %), compared with the conventional PVDF-bonded cathode. At an ultrahigh iodine loading mass of 32 mg cm, the BC-P10-bonded cathode delivers still an exceptional capacity of 150.3 mA h g at 0.2 A g (corresponding to an areal capacity of 4.8 mAh cm). The application viability of this binder system has also been demonstrated by constructing high-mass-loading rollable pouch batteries. This work opens a promising avenue for the development of high-performance iodine cathodes.