Intercalation cathode materials are mature and the main commercialized cathodes for lithium-ion batteries in the market. However, presently only one Li ion is involved in the electrochemical reaction, which limits the accessible capacity to < 200 Ah kg-1. This limits the application of lithium-ion batteries in a variety of applications, including electric vehicles. To get higher energy density, one way is using high-voltage cathode materials, but this generally requires a compatible stable high-voltage electrolyte to get the full capacity, which is very challenging. A feasible way to increase the capacity and energy density of Li-ion batteries is to find a material that can incorporate more than one lithium ion within the voltage window of current electrolyte systems. LixVOPO4 is a strong candidate, which can reversibly react two lithiums at about 4.0V and 2.5 V and has a theoretical capacity > 300 Ah kg-1 and energy density > 1000 Wh kg-1. Our group has conducted many studies on this material and already proved that good electrochemical performance can be obtained for different LiVOPO4 phases synthesized through various methods. However, these samples have large particles and high energy ball milling with carbon was required to decrease particle size and achieve good electrochemistry. Yet, the ball milling destroyed the crystallinity of the sample, creating highly sloped discharge curves which lowers the energy density. Consequently, direct nano-synthesis of LiVOPO4 is needed to produce good electrochemistry and high energy density.
Here, a novel polyol-mediated synthesis was first proposed by us to synthesize nanocrystalline triclinic LiVOPO4. This synthetic method is capable of producing particles smaller than 50nm in diameter without ball milling post treatment. Presently, a very good electrochemical performance was attained from our preliminary test: a reversible capacity above 300 Ah kg-1 was obtained at 0.04C, close to the theoretical capacity of 318 Ah kg-1; at 0.5C a capacity around 200 Ah kg-1 was still obtained. More characterizations and further optimization is in progress, and will be presented in the meeting. This work is supported by NECCES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0012583.