Nanocellulose is used to prepare flexible electrodes of lithium batteries

Electronic devices are rapidly developing towards lightweight, miniaturization, environmental protection and integration. To solve the practical application needs of smart communications, mobile medical care and other fields, an energy supply system that matches it is urgently needed. Therefore, it is particularly important for wearable and smart electronic devices to develop and utilize flexible multifunctional lithium-ion batteries. Nanocellulose can be combined with other lithium host components as a flexible substrate in anode/cathode composite. Table 2 summarizes and compares the electrochemical properties and strategies of various nanocellulose -based flexible lithium-ion battery electrode composites.

Li et al. prepared neatly arranged CNF/RGO composite microfibers by carbonization after wet spinning. Prepared fiber conductivity up to 649±60 S cm-1 lithium-ion battery anode. The stable discharge capacity of the anode is 312 mAh g-1. Wang et al. created an independent black phosphorus/nanocellulose nanowire composite anode through vacuum-assisted filtration. Black phosphorus/ nanocellulose nanowire composites provide a three-dimensional hybrid conductive network for the transmission of Li+ and electrons. Thanks to the versatility of nanocellulose, the black phosphorus/nanocellulose nanowire composite exhibits a high capacitance of 1020.1 mAh g-1 under the condition of 0.1 A g-1. Using TEMPO oxidized CNF as the fiber framework and bio-based adhesive, a flexible MoS2-based hybrid film with a layered structure was prepared. The flexible paper electrode assembled from carbonized CNF, CNT and ultrathin MoS2 nanosheets showed a high initial discharge specific capacity of 930 mAh g-1. In addition, nanocellulose-derived carbon materials can also be used as multifunctional conductive porous scaffolds to support the active anode material. Fe3O4 nanoparticles, SnO2 and Ge nanoparticles and MoS2 nanowaves were successfully synthesized on nanocellulose-derived carbon scaffolds by in situ growth method. A three-dimensional carbon aerogel flexible frame for supporting Fe2O3 was prepared using BC.

For LIB cathodes, the most common active materials on the commercial market are LiMn2O4, LiCoO2 and LiFePO4, but the cycle life and rate capabilities of these electrodes are still limited by severe structural degradation during repeated charge and discharge and slow transmission kinetics of electrons and Li+ . Therefore, nanocellulose can act as a flexible matrix to construct a cathode composite with a conductive material, thereby improving the ion and electron conductivity of the electrode and reducing stress/strain to maintain the integrity of the electrode. As shown in Figure 14d, the MXene@CNF film has higher mechanical strength and flexibility and shows interlaced topological microstructures. The assembled flexible LIB (MXene@CNF-Li membrane anode matches the flexible LiFePO4/cellulose nanofiber cathode) shows excellent stability and high specific capacity. Cao et al. used a pressure-controlled water extrusion process to demonstrate an independent lithium titanate (LTO)/CNT/CNF composite network film. The combination of CNF and CNT constructs a strongly conductive fiber network. In addition, the connection of CNT to LTO is designed to establish electronically conductive paths to help compensate for the inherent low electronic conductivity of LTO. The flexible anode used for LIB exhibits good high and low conductivity.

Overall, nanocellulose has high mechanical strength, network tangle structure and high aspect ratio, showing great potential in manufacturing flexible lithium-ion batteries. However, most of the lithium-ion battery electrode materials reported to date are simply synthesized by mixing nanocellulose with the active material, so the interface interaction is relatively weak. The interface structure and interaction of non-covalent or covalent chemical bonds should be considered to improve the interface interaction between nanocellulose and active materials, thereby achieving good electrochemical properties, strong mechanical strength, high flexibility and payload mass. electrode.