Nickel Hydride No. 5 battery

　　The Nickel Hydride No. 5 battery system constructed by pre-lithiation shows high power, long life and good low-temperature performance!

　　Recently, iChEM researchers, Professor Wang Yonggang of Fudan University and his research team used a simple prelithiation method to construct a Li2V2(PO4)3//LixC lithium-ion battery system, which exhibits high power, long life and good battery life. Low temperature performance.

　　In recent years, electric vehicles powered by lithium-ion batteries have been developing rapidly. However, it is known that the performance of lithium-ion batteries decreases rapidly as the temperature decreases. This will greatly limit the application of electric vehicles in winter or some alpine areas.

　　Previous studies have shown that in addition to the low ionic conductivity of the electrolyte at low temperatures, the low-temperature performance of conventional lithium-ion batteries based on graphite anodes is also limited by the desolvation/solvation of lithium ions in and out of graphite at low temperatures. To address this problem, the research group used a pre-lithiated hard carbon anode to replace the traditional graphite anode, and combined it with a lithium vanadium phosphate (Li2V2(PO4)3) cathode to form a new battery system.

　　In recent years, prelithiated hard carbon has been used in hybrid lithium-ion capacitors and has shown excellent electrochemical performance. However, the prelithiation process is complex and costly, and involves the use of pure lithium electrodes, which poses safety risks. In this study, the researchers cleverly used the multi-step delithiation process of Li3V2(PO4)3 cathode material to achieve prelithiation of hard carbon.

　　During the first charging process, lithium ions are extracted from the positive electrode to form Li2V2(PO4)3. At the same time, the extracted lithium ions are embedded in the hard carbon negative electrode and form a prelithiated hard carbon negative electrode (LixC). Subsequently, Li2V2(PO4)3 and LixC formed a lithium-ion battery system. When charged and discharged at 3.5 to 4.3V, the battery exhibits high power and long life similar to supercapacitors.

　　In addition, although conventional electrolyte LB303 was used, the battery showed excellent low-temperature performance. At minus 40 degrees Celsius, its capacity can maintain 67% of its normal temperature capacity, which is far superior to conventional lithium-ion batteries. This is mainly due to the good low-temperature performance of the nanocarbon-coated Li2V2(PO4)3 cathode material and the relatively fast kinetic process of the pre-lithiated hard carbon anode at low temperatures.

　　However, it is worth noting that this battery system only utilizes part of the capacity of Li3V2(PO4)3 and has limited energy density, making it more suitable for use as a start-stop battery. In addition, as the temperature decreases, the ionic conductivity of the electrolyte decreases rapidly, increasing the internal resistance of the battery. Therefore, the battery shows obvious polarization at low temperatures. In follow-up research, it is necessary to further develop high-performance low-temperature electrolytes to improve the electrochemical performance of such batteries at low temperatures.

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