LLTO anodes promise safe, long-lasting batteries
Electric vehicles, intelligent power grids, other mobile and stationary applications require batteries that can store as much energy as possible in the smallest possible space with the lowest possible weight. Lithium-ion batteries (LIB) still best meet these requirements, but there is always a need to further increase the energy density, power density, safety and lifetime of these batteries. The electrode materials play a key role in this. The active material used is predominantly graphite. However, negative electrodes made of graphite have a low charging rate. They also have safety problems. Among the alternative active materials, lithium titanate oxide (LTO) has already been commercialized. Negative electrodes with LTO offer a higher charging rate and are considered safer than those with graphite. However, LIB with LTO anodes tend to have a lower energy density.
The team around Professor Helmut Ehrenberg, head of the Institute of Applied Materials – Energy Storage Systems (IAM-ESS) of the Karlsruhe Institute of Technology (KIT), has now researched another promising anode material: lithium lanthanum titanate with perovskite crystal structure (LLTO). As the study, which was carried out together with scientists from Jilin University in Changchun, China, and other research institutes in China and Singapore, showed, LLTO anodes have a lower electrode potential compared to commercialized LTO anodes, which allows a higher cell voltage and a higher capacity to be achieved. “Cell voltage and storage capacity ultimately determine the energy density of a battery,” explains Ehrenberg. “In the future, LLTO anodes could enable particularly safe and long-lasting high-performance cells”. The study contributes to the work of CELEST (Center for Electrochemical Energy Storage Ulm & Karlsruhe), one of the largest battery research platforms worldwide.
In addition to energy density, power density, safety and service life, the charging rate also determines the suitability of a battery for demanding applications. In principle, maximum discharge current and minimum charging time depend on the transport of ions and electrons in the solid state and at the interfaces between electrode and electrolyte materials. To improve the charging rate, it is common practice to reduce the particle size of the electrode material from the micrometer to the nanometer scale. However, as the study published in the journal Nature Communications by KIT researchers and their cooperation partners shows, even particles of a few micrometers in size enable a higher power density and a better charging rate than LTO nanoparticles in perovskite-structured LLTO. The research team attributes this to so-called pseudo-capacitive properties of LLTO: Not only single electrons are attached to this anode material, but also charge-bearing ions that are bound by weak forces and can reversibly transfer charges to the anode. This property offers significant economic potential: thanks to the larger particles, LLTO enables simpler and more cost-effective production processes for electrode manufacture.
Original publication: https://www.nature.com/articles/s41467-020-17233-1
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