New technology discovery is expected to solve the dilemma of cobalt material batteries

　　"We have opened up a new chemical space for battery technology," said senior author Gerbrand Ceder, a professor in the Department of Materials Science and Engineering at Berkeley.

　　"We have opened up a new chemical space for battery technology," said senior author Gerbrand Ceder, a professor in the Department of Materials Science and Engineering at Berkeley. "This is the first time we have a very cheap component that can carry out a lot of electronic exchange in the battery."

　　This research will be published in the April 12th issue of "Nature". This work is a collaboration between scientists from the University of California, Berkeley, Berkeley Laboratory, Argonne National Laboratory, Massachusetts Institute of Technology, and University of California Santa Cruz.

　　In today's lithium-based batteries, lithium ions are stored in the negative electrode (negatively charged electrode), which is a layered structure. Cobalt is essential for maintaining this layered structure. When the battery is charged, lithium ions are pulled from the negative electrode to the other side of the battery cell, the positive electrode. There is not much room for lithium ions in the negative electrode. Most metal ions will flood into this space, which will cause the negative electrode to lose its structure. But cobalt is one of the few elements that does not move, and it is very important to the battery industry.

　　In 2014, Ceder's laboratory discovered a way for the negative electrode to maintain high energy density without these layers. This concept is called disordered rock salt. This new study shows that manganese can play a role within this concept, which is a promising step away from cobalt dependence, because manganese is present in the soil, making it a cheap element.

　　"In order to solve the cobalt resource problem, you must get rid of this stratification of the negative electrode," Ceder said. "The disordered positive electrode allows us to play more of the periodic table."

　　In this new study, Ceder's laboratory demonstrated how to use new technology to obtain a large amount of capacity from the negative electrode. Scientists use a process called fluorine doping to incorporate large amounts of manganese into the negative electrode. More manganese ions with an appropriate charge allow the negative electrode to accommodate more lithium ions, thereby increasing the capacity of the battery.

　　Other research groups have tried to use fluorine doped anodes, but they have not been successful. Ceder said his laboratory's work on disordered structures is the key to their success.

　　The performance of the negative electrode is measured by the energy per unit weight, which is called watt-hour per kilogram. Disordered manganese anode is close to 1000 watt-hours per kilogram. A typical lithium ion negative electrode is 500-700 watt-hours per kilogram.

　　"In the field of batteries, this is a huge improvement over traditional negative electrodes," said lead author Jinhyuk Lee, who was a postdoctoral researcher in Ceder's laboratory during the research period and is now a postdoctoral fellow at the Massachusetts Institute of Technology.

　　The technology needs to be scaled up and more tested to determine whether it can be used in applications such as notebook computers or electric vehicles. But Ceder said that it doesn't matter whether this technology actually puts it inside the battery; the researchers opened up new possibilities for the negative electrode design, which is even more important.

　　"You can use almost any element in the periodic table, because we have shown that the negative electrode does not have to be stratified," Ceder said. "Suddenly we have more chemical freedom. I think this is the real excitement, because now we can explore new negative electrodes."