Similar to the super capacitor, ultra-thin graphene nano materials excellent conductivity can form two-dimensional conductive contact with the particle electrode active material of lithium ion battery, constructing three-dimensional conductive network in the electrode, which can greatly improve the battery performance. The experimental results show that graphene conductive additives can greatly reduce the internal resistance of battery, improve the high rate charge and discharge performance of the battery, and prolong the battery cycle life; also can increase the capacity of active material g play, so as to improve the battery capacity; can also reduce the amount of conductive agent, is conducive to the design of high energy density batteries; in addition, containing graphene the conductive agent battery in high rate discharge in the process of heating is relatively small, the surface temperature of the battery is relatively lower, which is conducive to improving the safety of the battery.
Taking commercial lithium iron phosphate material as an example, low conductivity is the most important factor restricting its electrochemical performance. Based on the excellent conductivity of graphene, Liu Zhaoping proposed a new method for the modification of lithium iron phosphate by using graphene instead of conventional pyrolytic carbon. The synthesis of graphene / LiFePO4 composite cathode materials with spherical micro nano structure, including graphene uniformly coated lithium iron phosphate nanoparticles, and the formation of a three-dimensional conductive network in the two micron particles (Figure 3). Compared with carbon coating, graphene modification can significantly improve the rate performance and cycle stability of lithium iron phosphate. The work also provides useful guidance for the structural design and modification of other electrode materials.
In addition, graphene can also be coated on the foil collection fluid to form graphene functional coating aluminum foil. The coating using conductive graphene excellent and unique two-dimensional nanostructure, can significantly reduce the interfacial resistance between sheet and foil, and can improve the binding force between the active material and the current collector, and the collector can inhibit corrosion in a certain extent, so the new type collector can make the battery rate discharge capacity and cycle life has been further improved.
Graphene material has entered the stage of application and verification of downstream battery enterprises, but its cost problem still restricts its large-scale application. Although the cost of graphene has been greatly reduced in recent years, there is still a big gap compared with the traditional conductive carbon black and graphite. In the lithium industry severe downward pressure of the environment, the problem of graphene is still the development of low cost and high quality to be solved.