Lithium ion batteries are currently the most used form of energy storage media for portable electronics and are also continually expanding to new application areas as demand increases. Major lithium ion battery manufacturers, as well as companies selling consumer electronics and hybrid electric vehicles, would benefit from this technology.
Lithium ion batteries dominate energy storage media for new areas such as hybrid and electric vehicles. Existing electrode materials suffer from limited capacity, limited safety, and high cost that prevent commercial production of lithium ion batteries for new, energy-intensive applications. Therefore, improved material components for lithium ion batteries are constantly being sought out as these new cathode materials have the potential to increase the capacity, rate capability, cyclability, and improve the safety of Lithium ion batteries.
The amount of charge that can be transferred in an electrode material depends on the amount of Li present. Since the weight and cost of the electrode material depend heavily on the metal content, the crystal structure created by this invention allows high amounts of Li to be transferred for a low amount of metal. Furthermore, this invention improves stability by retaining a sufficient amount of lithium after charging. The residual lithium is thought to form a bonding network that holds certain layers of the crystal structure together after removal of the active lithium, thus preventing decomposition of the electrode material.
The mixed diphosphate-phosphate cathode material was prepared via solid-state reactions using the precursors Li2CO3, NH4H2P04, V205 in stoichiometric amounts, ball milling the compound for 48 hours, heating under air for 6 hours at 300 C, regrinding, and heating once more for 24 hours at 800 C under a steady flow of reducing gas (97%Ar, 3% H2).
- Average voltage of ~3.9V for the V^(3/4) redox couple and ~4.4V for the V ^(4/5) redox couple
- Theoretical 725 Wh/kg and 1916 Wh/l energy density using both redox couples
- Fair stability with respect to oxygen release and comparable to MnO2 compounds which are currently in use