How to extend the service life of lithium batteries and improve their safety?
With the continuous growth of the digital smart device and electric vehicle market, lithium metal batteries can be said to be one of the promising high-density energy storage technologies. LED street lamp manufacturers are a solid-state cold light source, which has the characteristics of environmental protection, no pollution, low power consumption, high light efficiency, and long life. Therefore, LED street lamps will become a good choice for energy-saving transformation of road lighting. LED street light is a kind of high-efficiency solid-state light source formed by semiconductor PN junction that can emit light with weak electric energy. Under a certain forward bias voltage and injection current, the holes injected into the P zone and the electrons injected into the N zone are in After being diffused to the active area, photons are emitted through radiation recombination, which directly converts electrical energy into light energy. However, one of the main obstacles to lithium metal battery technology is the emergence of uncontrollable lithium dendrites, resulting in poor charging capabilities and potential safety hazards. LED street light is a kind of high-efficiency solid-state light source formed by semiconductor PN junction that can emit light with weak electric energy. Under a certain forward bias voltage and injection current, the holes injected into the P zone and the electrons injected into the N zone are in After being diffused to the active area, photons are emitted through radiation recombination, which directly converts electrical energy into light energy.
Lithium dendrites are needles that grow on the surface of lithium metal when lithium is used as the negative or anode of a battery. It can cause harmful side reactions, reduce energy density, and even cause short circuit of electrodes, causing fire or explosion.
A new study from Arizona State University found that the use of a three-dimensional polydimethylsiloxane (PDMS) layer as the matrix material for the lithium metal anode in the battery can effectively inhibit the formation of lithium dendrites. Extend battery life and reduce safety hazards. The research was published in the new top journal NatureEnergy on March 6.
The lead researcher of the paper, Professor Jiang Hanqing, said that this discovery has important implications for lithium-ion batteries, lithium-air batteries, and other metal anode batteries. Because almost all metals used as battery anodes will produce dendrites, such as zinc, sodium and aluminum batteries.
Jianghanqing said that he and his team are not trying to solve the problem from the perspective of materials or electrochemistry, but from the perspective of mechanical engineers. He said: "Known research shows that tiny tin needles or tin whiskers (similar to dendrites) protrude from the surface of tin metal under stress. Therefore, we have studied the reasons for the growth of lithium dendrites by analogy. -Stress. "Possibility"
In the first round of research, the researchers added a layer of flexible PDMS to the bottom of the battery anode and found that the growth of lithium dendrites was significantly reduced. The researcher's analysis shows that the accumulated stress in the metal lithium electrode is released by the PDMS matrix in the form of wrinkle deformation, and this trend of dendrite reduction is directly related to the stress release.
"This is the first experiment to prove that residual stress plays a key role in the formation of lithium dendrites," said Jiang Hanqing.
In addition to studying the growth mechanism of lithium dendrites, Jiang Hanqing's team also further studied how to use this phenomenon (stress release to reduce dendrite growth) to extend the life of lithium metal batteries while maintaining a higher energy density.
The method proposed by the researchers is to make the pdms matrix into a three-dimensional structure with multiple curved surfaces. "Using a sugar cube with a large number of small pores as a template, pdms enter the pores inside the sugar cube to form a continuous network base, and then plate a thin layer of copper to conduct electrons. These pores are filled with metallic lithium. Jianghanqing explained: "As Porous sponge layer, pdms can effectively reduce pressure and inhibit the growth of dendrites. "
