The Liquid Electrode Layer Can Improve The Charging Performance Of The Battery
2022-09-06
Anyone who pays attention to the development of solid-state lithium metal batteries knows that there will be many challenges in the charging process. The anode (negative electrode) in these batteries is composed of a thin lithium metal foil, which provides much more lithium ions than the graphite anode in use in lithium-ion batteries, thus generating higher energy display density. During charging, lithium needle dendrites cover the surface of lithium metal. The diffusion of the lithium dendrites of these needle like dendrites will lead to a short circuit of the battery and cause a fire.
Solid state battery
The solid part of the battery comes from solid polymer or ceramic electrolyte materials, which can inhibit the diffusion of lithium needle dendrites. This has achieved partial success, but the growth of dendrites still poses a long-term problem to the design. In the future, electric vehicles (EV) need fast DC charging. Unfortunately, the growth of dendrites grows rapidly with faster charging, and so far this problem has largely hindered the large-scale commercialization of practical solid-state lithium batteries.
Researchers are trying to solve problems in improving battery performance. Scientists in a group of research teams are composed of Massachusetts Institute of Technology (MIT), Texas A & M University (Tamu), Brown University and Carnegie Mellon University (CMU). Recently, they are studying the use of a layer of liquid metal electrode material film on the surface of lithium metal anode.
Liquid metal electrode
The research team was inspired to use melted metal electrodes in high-temperature battery experiments. These batteries work at a high temperature of several hundred degrees, so they are not applicable to portable battery driven devices or electric vehicles. However, these batteries can be charged at high current without forming harmful dendrites. MIT said in a press conference: "the motivation for developing electrodes is based on carefully selected alloy electrodes, which are used as self-healing components of metal electrodes in the introduction of liquid."
In order to provide a similar liquid-solid interface, the research team developed a semi-solid electrode, which is placed between the lithium metal anode and the solid electrolyte material. This semi-solid electrode provides a self-healing surface layer, and also helps to prevent micro cracks on the surface of brittle electrolyte, thus providing a site for dendritic growth. The material of the semi-solid electrode is composed of sodium and potassium, which is similar to the solid metal mixture used by dentists to fill cavities, but still can flow and shape.
According to the news, the research team can use a current 20 times larger than that of solid lithium metal when running the system on the liquid metal interface, without forming any dendritic lithium dendrites.
The research team believes that this new method can be adapted to different versions and structures of solid-state lithium batteries. One of the researchers, Professor of mechanical engineering at CMU, said: "we think we can apply this method to any solid-state lithium-ion battery. This method can be immediately used in battery development and expand the development of applications, from handheld devices to electric vehicles to electric aviation."
It is still too early to judge whether the liquid metal layer between the lithium metal anode and the solid electrolyte is a breakthrough or just another step towards the development of solid-state lithium batteries. By focusing on the characteristics of metal electrodes, rather than just the properties of solid electrolytes, this study may inspire further innovation.
Placing a layer of liquid metal between the lithium anode and the solid electrolyte shows an improvement in the charging of solid batteries.
Issued by Alex, R&D, Sep. 6, 2022.
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