Lithium salt and graphene composite material as well as preparation method and application thereof

Abstract

The invention discloses a lithium salt and graphene composite material which is crystal formed by lithium salt and graphene, wherein the mass of the graphne accounts for 1-99% of the total mass of the composite material, and the mass of the lithium salt accounts for 1-99% of the total mass of the composite material. The invention also discloses a preparation method of the composite material, comprising the following process steps: preparation of a graphite oxide system, preparation of a mixing system of the lithium salt and the graphite oxide, formation of mixed powder of the lithium salt and the graphite oxide, reduction and crystallization. In the lithium salt and graphene composite material, the stability and the conductivity are high, and the composition of the graphene and the lithium salt is more uniform and more compact without generating falling. The composite material can be prepared only by mixing oxidized natural graphite with the lithium salt and then carrying out reduction and crystallization, so that the preparation method is simple in process, low in cost and suitable for entrepreneurial production.

Description

technical field [0001] The invention belongs to the technical field of electrode materials, and in particular relates to a lithium salt-graphene composite material, a preparation method thereof, and an application in electrode materials. Background technique [0002] Since Andre K. Geim (Andre K. Geim) of the University of Manchester in the United Kingdom prepared graphene materials in 2004. Due to its unique structure and optoelectronic properties, it has attracted extensive attention. Single-layer graphite is considered an ideal material due to its large specific surface area, excellent electrical and thermal conductivity, and low thermal expansion coefficient. Such as: 1, high strength, Young's molar weight, (~1,100GPa), breaking strength: (~125GPa); 2, high thermal conductivity, (~5,000W / mK); 3, high conductivity, carrier transport Rate, (200,000cm 2 / V*s); 4, high specific surface area, (theoretical calculation value: 2,630m 2 / g). In particular, its high conductiv...

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Problems solved by technology

[0004] But LiFePO 4 There is a fatal shortcoming: LiFePO 4 Low electrical conductivity, only about 10 at room temperature -8 S cm -1 , while LiCoO 2 about 10 -3 S cm -1 , LiMn 2 o 4 about 10 -5 S cm -1 , such a low conductivity leads to LiFePO 4 When used as a positive electrode material, its discharge capacity decreases sharply with the increase of discharge current. During the deintercalation process, LiFePO 4 Medium lithium ions span LiFePO 4 / FePO 4 The migration speed of the phase interface is small, and during the lithium intercalation process, LiFePO 4 The area of ​​the phase is continuously reduced, so when the high current density is discharged, the amount of lithium ions passing through the phase interface is not enough to maintain a large current, resulting in a decrease in the reversible capacity

But in general, the increase in conductivity is limited, or the increase in conductivity has brought about the reduction of other properties of the material, such as low stability of the material.

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