Cobalt-free lithium battery tops 800Wh/kg
Researchers in Japan have developed a high performance fast charging lithium ion battery cell that does not use cobalt or nickel.
The lithium ion battery cell developed at Yokohama University uses manganese as LiMnO2 as an electrode material to eliminate cobalt. This has been studied in the past but has always been limited by restrictive electrode performance. To address this, the cell design uses a ‘monoclinic’ nanostructure with a crystal that is a parallelogram. The Li/Mn arrangement with the monoclinic symmetry appears to be key in making LiMnO2 a feasible option for a positive electrode material.
The design reaches an energy density of 820Wh/kg, which is a target for existing nickel, manganese, cobalt (NMC) lithium-ion cells used in the majority of electric vehicles today as well as across the industry.
Many universities around the world are working on lithium ion battery cell designs without cobalt to avoid the use of the material, which can come from conflict zones. Battery startups Solid Power, TexPower and Nano One have all been working on cobalt free lithium battery cell technologies for next generation solid state battery cell designs.
After observing and testing variants, the structure developed at Yokohama can be synthesized directly from two components without having to use an intermediary step. The resulting material is competitive with nickel based layered materials and has excellent fast-charging abilities, which is key for electric vehicles.
The nanostructured LiMnO2 with the monoclinic layered domain is synthesized by a simple calcination process to yield a product with high-energy density, reaching 820Wh/kg, compared to about 750 Wh kg-1 for nickel-based layered materials and 500 Wh/kg for other low-cost lithium-based materials such as LFP.
There is also no reported voltage decay using nanostructured LiMnO2, which is common in manganese-based materials. Voltage decay is a phenomenon in which the voltage decreases gradually, over time reducing the performance and responsiveness of an electronic.
“Through the systematic study on different LiMnO2 polymorphs, it is found that the monoclinic layered domain effectively activates structural transition to the spinel-like phase. From this finding, nanostructured LiMnO2 with the monoclinic layered domain structures and high surface area has been directly synthesized by using a simple solid-state reaction,” said Naoaki Yabuuchi, author and researcher of the study at Yokohama.
However a practical issue can be observed with the dissolution of manganese. Over time, manganese can dissolve due to many factors, such as phase changes or reacting with acidic solutions. This can be curbed or completely mitigated by the use of a highly concentrated electrolyte solution and a lithium phosphate coating.
www.ynu.ac.jp; dx.doi.org/10.1021/acscentsci.4c00578
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