image: Polyhedral representation of the crystal structure of fluoride-phosphate of vanadium and potassium. The yellow denotes a three-dimensional channel system, which provides rapid transport of Li+ ions. view more
Credit: Stanislav Fedotov
Nowadays Li-ion batteries power a wide range of electronic devices: mobile phones, tablets, laptops. They became popular in 90s and subsequently ousted widespread nickel-metal hydride batteries.
However, Li-ion batteries suffer a number of disadvantages. For example, their capacity may drop when temperature falls below zero. The price is also discomforting, which is mostly caused by use of expensive lithium-containing materials. For instance, Li-ion batteries make about half a price of a popular electro car Tesla Model S. On the other hand, Li-ion batteries are compact, easy to use and highly capacious, which means that your device would live long having a relatively small battery.
A key element of the Li-ion batteries limiting its capacity is a material used for its cathode. For the majority of the materials their capacity limit has already been reached. Hence, scientists and engineers are actively searching for new cathode materials capable of recharging completely within minutes, operate under high current densities, and store more energy.
One of the most prospective classes of cathode materials for a new generation of Li-ion batteries are fluoride-phosphates of transition metals.
The work directed by Prof. Evgeny Antipov (correspondent member of the Russian Academy of Sciences and the head of the MSU Electrochemistry Department) was carried out by a team of MSU research scientists together with their Russian and Belgian colleagues. It was devoted to creation of a new high-power cathode material based on a fluoride-phosphate of vanadium and potassium for Li-ion batteries. The results were published in Chemistry of Materials (current IF -- 8.354)
'The work is based on a simple idea of geometric and crystal-chemical conformity of ionic sublattices,' -- says Stanislav Fedotov, one of the authors, junior research scientist at Electrochemistry Department, Faculty of Chemistry, MSU.
The scientists succeeded to stabilize a unique crystal structure, which provides a fast transport of lithium ions through spatial cavities and channels. Consequently, the suggested cathode material demonstrated high charge/discharge rates (down to 90 seconds) retaining more than 75% of an initial specific capacity. With its morphology and composition optimized, this material may become a serious contender to such well-known and commercialized high-power cathode materials as NaSICON.
According to the authors, the results of the presented work may not only open up ample opportunities in searching and further synthesis of new cathode materials for Li-ion batteries, but also promote the development of a new battery type where a role of a mobile ion (a charge carrier) would be performed by potassium ions instead of lithium.
'It is assumed that such batteries would not only deliver high energy density, but would also be economically attractive due to a replacement of expensive lithium-containing components with cheaper and hence affordable potassium-containing analogues' -- explains Stanislav Fedotov.
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Journal
Chemistry of Materials