![]() ![]() They also hope that even more energy can be packed into the same volume through further experimentation with the particle size, combining smaller and larger spheres for even denser packing. Researchers say the new cathode material offers an increase in energy density by up to 25%. To alter the layered oxide morphology, Skoltech researchers tweaked the synthesis procedure, which relies on the so-called flux method. This should prolong the operating life of the cathode and battery on the whole. In addition to the denser packing, the spherical shape of the crystals reduces the area of contact with the electrolyte, minimizing unwanted interactions that, over time, cause cathode degradation due to crack formation in the particles of conventional NMCs. But on top of that, you can also pack more spherically shaped single crystals into the same limited volume than octahedron-shaped ones, so you get more density on that account, too,” study co-author Skoltech Research Scientist Aleksandra Savina said. Unlike polycrystals, the powder particles don’t have an internal structure, so there are no wasted spaces at grain boundaries. “Our material is a single-crystal NMC with spherical particles, combining the best of both worlds as far as maximizing density goes. These single crystals are usually octahedron-shaped. The single-crystal counterparts of polycrystalline NMCs are just what the name says – each powder particle is basically one large grain with no wasted spaces in it. The crystal structure within any given grain is nearly flawless, but since no two grains fit perfectly together, some empty spaces inevitably arise at grain boundaries. Credit: Ivan Moiseev et al./Energy AdvancesĬonventional NMCs are powered polycrystalline materials, meaning that each secondary particle is made up of randomly oriented grains. These scanning electron microscopy images at different magnifications reveal the spherelike morphology of the powder particles of NMC622. ![]() Without changing their chemical composition, Skoltech researchers improved NMC811 and its cousin NMC622 by tweaking the materials’ microstructural organization. These materials are known by technical names such as NMC811, where the numbers reflect the ratio between the three elements in the chemical formula. In currently used materials, some of the cobalt atoms are replaced by nickel and manganese. ![]() Scientists are hopeful that further experiments can boost the performance even further. Thanks to its ultra-high energy density, the new material will make the cathodes and the batteries themselves more compact, which means an electric car with a battery of the same size will be able to travel more kilometers on a single charge. ![]()
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