2.2 In-situ polymerization
Cellulose, as a natural 1D flexible material with high specific surface area, is only used as a binder of electrochemical active substances, which does not make full use of its surface space. Electroactive substances such as metals, metal oxides and conductive polymers are polymerized and deposited on the cellulose surface through in-situ polymerization. Compared with the paper-based electrode where cellulose is only used as the binder, this can effectively reduce the volume of electrode material and increase the utilization rate of cellulose. In the cellulose paper based electrode prepared by this method, cellulose not only provides mechanical properties, but also provides an electron transfer path for the cellulose composite fiber deposited with active substances, which can make outstanding contributions to electrochemical energy storage.
At present, the work of depositing active materials on cellulose surface can be roughly divided into two types. The first is by mixing the cellulose dispersion with the precursor of the active substance. Then the active substance is polymerized and deposited on the surface of the cellulose fiber to form 1D cellulose composite fiber. Finally, these 1D composite fibers were filtered through vacuum to obtain paper based electrodes. It should be clearly pointed out here that cellulose in the paper-based electrode summarized in the vacuum filtration section of this paper is only used as the binder. However, the paper based electrode obtained by in-situ polymerization of active substances polymerized and deposited on the cellulose surface, and then filtered by vacuum suction, is significantly different from the previous section. Therefore, it is necessary to classify 1D cellulose composite fibers into a single category. The second type is to directly put the prepared 2D cellulose paper into the precursor solution of the active substance, and directly polymerize and deposit the active substance on the 2D cellulose paper. This section summarizes and classifies the different loading modes of active substances in the preparation process, including the paper based electrode based on 1D cellulose composite fiber and the paper based composite electrode based on 2D cellulose paper. Table 2 summarizes the performance parameters of related work.
Table2 Performance parameters of cellulose paper based electrode prepared by in-situ polymerization