The new technology will increase the power of friction nanogenerators by dozens of times

At present, China is striving to achieve high-quality economic and social development and the goal of carbon peak and carbon neutrality. In this context, friction nanogenerators have attracted much attention as a clean power generation method that can directly convert mechanical energy into electrical energy in the environment. Among them, the DC friction nanogenerator (DC-TENG) based on frictional starting and air breakdown has become the focus of global scholars due to its constant current output characteristics and high output power density.

Recently, Wang Jie, a researcher at the Beijing Institute of Nanoenergy and Systems, Chinese Academy of Sciences, found that DC-TENG has multiple discharge regions (multi-domain discharge), refreshing people’s knowledge and understanding of this field. Based on this discovery, the team proposed a comprehensive “barrel model” and used the model to increase the output power of a single device by dozens of times. On June 3, the study was published online in Nature Communications.

Schematic diagram of the working principle of DC friction nanogenerator. Photo courtesy of interviewee

Induces miniature lightning and makes efficient use of frictional charges

Triboelectric is the earliest electrical phenomenon discovered by human beings, and in recent years, in order to promote the realization of major strategies of carbon peaking and carbon neutrality, how to efficiently use friction nanogenerators has become one of the key research points. In the preliminary exploration, the research team found that a considerable part of the surface charge generated by friction will be released through the air, and cannot be effectively used because it cannot remain on the surface of the friction material.

So, is there a way to use this wasted charge? In 2019, the team proposed a DC friction nanogenerator based on triboelectric start-up and air breakdown. The working process of this micro-generator is mainly divided into two steps: one is to rub the electrode and the dielectric material to rub, so that the surface of the dielectric material carries a charge; Second, through a special structural design, the generation of miniature lightning is induced, and the charge on the surface of the dielectric material is released through air breakdown and captured by the charge collection electrode.

“In practical application scenarios, this generator has the characteristics of direct current or even constant current, and can directly drive electronic components.” Wang Jie told China Science News, “On scientific issues, the study of artificially induced miniature lightning can provide support for enhancing and inhibiting air breakdown at the same time, and provides a solid theoretical basis for the effective use of frictional charges.” ”

Schematic of multi-domain discharge characteristics. Photo courtesy of interviewee

Unravel the mystery of multi-domain discharge and open up new research perspectives

Over the past few years, the research team has insisted on optimizing the output performance of DC-TENG. With the deepening of theoretical research and experimental exploration, researchers gradually found that in the process of work, more than one area may produce miniature lightning.

“Through finite element simulation, we determined that there are three areas around DC-TENG that meet the criteria for generating micro-lightning, and there is a possibility that micro-lightning can be induced during operation.” Zhang Jiayue, the first author of the paper and a doctoral student at Tsinghua University, said, “Therefore, we captured the evidence of the existence of these miniature lightning bolts through long-exposure shooting, and further confirmed the existence of these three discharge domains through electrical measuring instruments.” ”

After rigorous analysis and verification, the research team systematically defined three possible discharge regions of DC-TENG during operation. Through the structural design, the regulation of the discharge amount in each region is realized, which provides a simple and feasible scheme for further improving the output performance.

Build a “barrel model” to significantly improve performance

Based on the new discovery, new ideas and new theories of multi-domain discharge, the research team established a comprehensive “barrel model”. That is, as the frictional charge increases, when the electric field strength on the surface of the dielectric layer reaches the threshold of air breakdown, miniature lightning in multiple regions is excited. Moreover, the charge participates in the discharge in different regions, and the effect of the output energy in the external circuit is also different. For example, a charge participating in a first-domain discharge can do work in an external circuit, while a charge participating in a second- and third-domain discharge cannot be used efficiently.

By suppressing the discharge in the second and third domains, the researchers enhanced the discharge in the first domain, which greatly improved the output performance of the generator. In addition, in order to make DC-TENG more practical, the research team has made relevant analysis and research in the ultra-large impedance range of 10M~3G external circuit load. Experimental results show that this method can enhance the output power by dozens of times in a large impedance range.

The review experts believe that the discovery of multi-domain discharge characteristics not only refreshes the understanding of DC friction nanogenerators, but also has an important impact on tribology, triboelectricity, and other electrostatic phenomena. (Source: Zhang Shuanghu, China Science News)

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