Nanocellulose is used to prepare flexible electrolyte membranes for lithium batteries

The diaphragm of the LIB is located between the anode and the cathode. It prevents short circuits from the anode and cathode from contact. The electrolyte acts as an electrolyte reservoir and forms a lithium ion transport channel during the charging/discharging process. Due to the excellent mechanical and thermal properties of . Recently, Sun et al. introduced ZIF8 into the CNF system through in-situ synthesis to improve the pore structure of the composite separator. The introduction of ZIF8 prevents the aggregation of CNF and makes the pore distribution more uniform. The ZIF8-CNF composite separator not only provides the advantages of an environmentally friendly CNF, but also exhibits excellent thermal stability (thermal stability up to 200 °C). These composite separators have faster wetting speed and good surface wetting, which can reduce the internal resistance of the battery and the electrolyte filling time. LIB assembled using ZIF8-CNF composite diaphragm showed better rate capacity, cycling performance, and discharge capacity retention. Huang et al. prepared TOBC membranes for LIB membranes. The TOBC membrane has sufficient porosity and ideal affinity with liquid electrolytes and lithium electrodes, thus having excellent electrolyte absorption capacity. Mainly focused on the development of safe separators with good electrolyte wetting properties. However, few studies have focused on chemically functionalized cellulose separators, which may also improve the performance of lithium batteries. Wang et al. have produced a flexible redox-active bilayer nanocellulose-based separator, which includes a redox-active PPy-containing support layer and a mesoporous insulated CNF layer. The PPy-containing layer adds additional capacity to the LIB and provides mechanical support for the CNF layer. The redox-active separator has high flexibility and no internal short circuit was found during the operation of these lithium batteries. Compared with liquid electrolytes, flexible colloidal solid electrolytes can provide greater portability and safety for lithium-ion batteries. To achieve this, the researchers used nanocellulose- based paper/film materials, they have been used in lithium batteries to improve power density, energy density, safety and cycle life by affecting battery dynamics, by influencing battery dynamics. nanocellulose as a candidate electrolyte to study the basic components of gel or solid electrolytes.

Xu et al. prepared an internal crosslinked BC network with high strength as gel polymer electrolytes. The lithium ion channels are formed through glycosidic bonds, ether groups and hydroxyl groups on the BC chain and the organic solvent is trapped, resulting in high ionic conductivity. BC nanofibers inhibit the vertical growth of lithium dendrites. Batteries assembled using gel polymer electrolytes have good rate and cycling properties. Du et al. prepared an environmentally friendly and mechanically strong cellulose gel film for electrolytes of LIB. Cellulose films containing 5% epoxychlorohydrin have not only wide electrochemical stability window, Li+ transfer number (0.82), high ionic conductivity (6.34 × 103 mS cm-1), and better interface compatibility with electrodes , also has good thermal stability and mechanical strength. Dong et al. prepared a BC-supported polymethylvinyl ether-salt-maleic anhydride (P(MVE-MA)) multifunctional polymer electrolyte for a 4.45 V grade LiCoO2 lithium metal battery (Fig. 15d,e). As shown in Figure 15f, the tensile strength of the obtained polymer electrolyte reaches 50 MPa, thanks to the hydrogen bonding between P(MVE-MA) and BC. Even at 60 °C, lithium cobalt oxide metal batteries made with polymer electrolytes exhibited high capacity retention (85% capacity retention after 700 cycles).

In short, to improve the electrochemical performance of lithium batteries, nanocellulose- based separators/electrolytes should have high pore structures to promote ion mobility in electrochemical reactions. In order to improve the mechanical flexibility of nanocellulose-based electrolytes, cross-linking networks have been introduced. For example, a dual crosslinked hydrogel with reversible bonds and strong covalent bonds such as dynamic borate bonds, ionic bonds and H bonds can support nanocellulose polymer composites with good elasticity and mechanical strength. To achieve multifunctional properties, such as anti-extreme environment and self-healing properties, it is also necessary to study the correlation between external stimuli and molecular interactions between components.