Fumed silica is a kind of tasteless white ultrafine powder material, which has the effects of thickening, anti-caking, rheology controlling, and thixotropy. In addition to traditional applications, fumed silica has been widely used in colloidal batteries ( gel batteries）.
The colloidal battery is a new type of battery developed based on traditional lead-acid battery. The colloidal battery has less acid fog when charging, can inhibit the fall off of active substances and plate sulfate, with low self-discharge rate and good discharge capacity of large current. It has the advantages of good reliability, high power density, strong charging acceptance ability, and so on, thus becoming the development direction of the future battery and being widely used in electric bicycles, military, communication, and other fields.
The core technology of colloidal battery is the glue-making process. Before the advent of fumed silica, in the process of the gel battery, the "silicon sol" is used, which has a weak gel effect due to its small specific surface area, and high impurity content high. After repeatedly charging and discharging, an obvious hydration layer appears in the electrolyte, which greatly reduces the performance of the battery and the hydration layer site used. Therefore, in a very long time, the research of the colloidal battery has been in a stagnant "wandering” state without any substantive progress.
Fumed silica (pyrogenic silica) thickens the colloidal electrolyte to form a stable network, which enables thixotropic properties, and makes gel battery elastic, thick but not sticky. It becomes thickened after charging and thinned after discharging. The thickening and thixotropic functions greatly improve the performance of the gel during the reaction. Also, the size of silica particles in the gas phase process has a great influence on its thickening effect. Thin particles often have good thickening effects and thick particles often have a bad thickening effect. The thickening effect of fumed silica is not obvious, thus forming an unstable network; the fumed silica with a too large specific surface area has a too significant thickening effect, which will shorten the gelation time and form too "dense" colloidal electrolyte network, which is not conducive to the diffusion and migration of electrolyte and gas. Therefore, it is suitable to use fumed silica with a specific surface area of 200㎡/g in the industry.
The hydrophilic fumed silica HL-200, produced by HUBEI HUIFU NANOMATERIAL CO.,LTD. （former company name : Yichang Huifu Silicon Material Co., Ltd.), has been widely used in colloidal batteries or gel batteries. As a professional manufacturer of hydrophilic and hydrophobic fumed silica. We led the stand-setting of ISO18473-3:20:18 Fumed Silica for Silicone Rubber and other domestic national standards of fumed silica.
The preparation of colloidal electrolytes requires the addition of some colloidal stabilizers, usually water-soluble polymer materials, including polyvinyl alcohol, dextrin, glycerin, polyethylene glycol, and polyacrylamide, etc. They have a synergistic effect with fumed silica, thus helping to change the surface charged state of colloidal particles, prevent colloidal aggregation, slow down gelation, and stabilize the colloidal electrolyte system.
With the development of the national new energy industry, the colloidal battery has great development space and contains great potential. With further development, the improvement of the technology level and the maturity of the production process, it is expected that the colloidal battery will be further developed. The further application of fumed silica in colloidal batteries will also promote the popularization of colloidal batteries.