Existing lithium ion batteries use lithium transition-metal oxides as cathode materials; however, there is a growing interest in polyanion groups as cathode materials for their inherent stability against oxygen loss. Recent studies have made an example of LiFePO4 due to its low cost, high stability, low toxicity, and high rate capability as well as long cycle life. Using a borate group as the polyanion group has its benefits due to its low weight and high specific energy density. This technology relates to the hexagonal structure (P-6) and monoclinic crystal system (C12/c1) of LiMnB03 in their use in batteries and other electrochemical devices.
The demand for lightweight, high energy density batteries to power vehicles and portable electronic devices continues to rise. Although many compounds have been studied for use in batteries and other applications, it remains difficult to identify those with good thermal stability and high energy densities. Accordingly, improvements in compounds for use in batteries and other applications are still needed. LiMnBO3 forms a structure within a hexagonal setting with the space group of P-6. As a result, both polymorphs of LiMnBO3 exhibit very promising energy densities for future applications as strong cathode materials.
The presented technology relates to the synthesis of both polymorphs of lithium manganese borate by mixing amounts of Li2CO3, MnC2O4-2H2O, and H3BO3. These powders were then dispersed in acetone and milled for 24-72 hours and dried, fired at 350°C for 10 hours under argon atmosphere, and pressured into a pallet and sintered at 650°C for another 10 hours under argon atmosphere.
These polymorphs were then investigated by ab initio computations in the density functional theory framework using the generalized gradient approximation and a Hubbard U model. Even though the discharge capacities measured are rather small, the values illustrate a very substantial improvement compared to previous reports on LiMnBO3, which failed to extract any significant amount of Li from the material. In addition, further improvement of capacity is expected when a homogeneous monoclinic LiMnBO3 phase is formed. Forming a small particle size as well as particle surface coating by a conductive phase will also improve its elecrochemical performance, which would make Lithium Manganese Borate an even better cathode material for lithium-ion batteries.
- More promising theoretical energy densities (volumetric and gravimetric)
- Both polymorphs of LiMnB03 of are deemed safer than LiCoO2