According to news on September 7, this work was completed by Professor Wang Chunsheng, Dr. Yang Chongyin from the University of Maryland, and Xu Kang, a senior chemist at the US Army Research Laboratory. The paper was published in the journal "Joule" under the American Cell Press.
"This is the first time that a water-based electrolyte 4V battery has been implemented. It is a major fundamental breakthrough in principle." Yang Chongyin and others said in an email to reporters. They explained that traditional commercial lithium-ion batteries use extremely flammable organic electrolytes, which poses serious safety hazards. The problem with replacing organic electrolytes with non-flammable water-based electrolytes is that the electrochemical stability window of the former is generally less than 2 volts. Once the electrode voltage exceeds this number, the electrolyte will lose stability, so the energy density is limited.
They explained that the key to the latest research is to prevent the lithium metal or graphite electrode from directly contacting the water molecules in the water-based electrolyte to reduce hydrogen production. To this end, they developed a very hydrophobic colloidal protective layer material that evenly coats the electrode surface, effectively preventing the electrode failure caused by the side reaction of water decomposition.
More importantly, they found that during the initial charge-discharge cycle, specific components in the protective layer formed a denser hydrophobic solid electrolyte interface layer on the surface of the negative electrode in situ, further passivating the surface of the negative electrode, and this solid The interface layer can repair itself in the case of partial damage, ensuring the long-term stability of the battery.
Wang Chunsheng, Xu Kang and others pointed out that the research results provide new directions and ideas for the development of safe water-based lithium-ion batteries with high-voltage windows. From the perspective of basic science, "stable 4 volt water-based electrolyte can bring many new opportunities to various electrochemical devices." At the same time, the water-based lithium-ion battery can save the essential safety devices in the traditional lithium-ion battery, and further reduce the weight of the battery assembly.
They emphasized that the current research is only a proof-of-concept in the laboratory, and there is still a long way to go before commercialization. In the next step, they plan to further optimize and improve the chemical composition of the electrolyte protective layer material and battery structure, and increase the cycle life of the battery, from the current 70 to 100 cycles to the commercialization standard of more than 500 cycles.