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Application of graphene materials in lithium-ion batteries

wallpapers Tech 2020-09-16
At present, lithium-ion batteries account for 66% of the scale of various energy storage technology devices. High energy density, sizeable reversible capacity, large open voltage, and long service life are the unique characteristics of lithium-ion batteries. It has an unparalleled advantage over other batteries. Lithium-ion batteries include four main components: positive and negative electrodes, electrolyte and separator. Traditional conductive additives for lithium-ion batteries are mainly composed of acetylene black and carbon black. Through a point-to-point method, the conductive additives and the positive and negative active material particles contact each other, bringing more excellent thermal resistance and high temperature for lithium batteries. The group carries unique security risks. Therefore, the need for new battery conductive additive materials to provide efficient conductive networks has become extremely urgent. New materials can not only reduce the amount of addition, but also significantly increase the conductivity of the positive and negative electrodes, reduce battery costs, and improve The rate and charge-discharge cycle performance of lithium-ion batteries.
Application of graphene in lithium-ion batteries

1 Application of graphene in cathode materials

For lithium-ion batteries, suitable cathode materials should meet the characteristics of sizeable reversible capacity, high and stable potential, non-toxicity, and low production cost. At present, the most common cathode materials for lithium-ion batteries are lithium iron phosphate (LiFePO4) materials, which have the characteristics of high specific capacity, non-toxicity, and low production cost. However, LiFePO4 has poor electrical conductivity and low lithium-ion mobility. If LiFePO4 material is compounded with graphene, theoretically, it can improve its conductivity and increase rate performance. Due to graphene materials' particularity, there is relatively little research on graphene materials in terms of positive electrodes. Studies have shown that the hydrothermal method directly covering graphene on the surface of LiFePO4 to make composite materials has an unsatisfactory performance improvement effect. The reason may be the stacking or destruction of the graphene material structure. Wei et al. found that the material formed after graphene half-wrapped LiFePO4 can improve LiFePO4 material's conductivity. Still, the ion transmission efficiency decreases after it is fully wrapped. It is speculated that it may be because lithium ions cannot pass through the six-membered ring structure of graphene. Some researchers have ultrasonically mixed LiFePO4 nanoparticles with graphite oxide to prepare LiFePO4/graphene composites with a more processed microstructure. After the material is further coated with conventional carbon, lithium insertion's specific capacity is much improved. It can still be maintained at about 70mAh/g under the condition of a high rate of 60C.

2 Application of graphene in anode materials

Graphene is directly used as the anode material of lithium-ion batteries. Its specific capacity is 540mAh/g; because graphene has a large specific surface area, scientists use graphene nanosheets as lithium battery anode materials to increase its reversible capacity at all times. The reversible capacity loss rate is lower afterward. Also, graphene can be used as a harmful electrode material for lithium-ion batteries after being composited with metal oxides and alloy materials, such as tin-based and silicon-based oxides. With more nanomaterials' characteristics, using the conductivity and structural attributes of graphene materials to transform it will increase the lithium-ion transmission rate and improve lithium-ion batteries' rate performance to compensate for the shortage of raw materials and many defects, and reduce costs.

3 Other applications of graphene in lithium-ion batteries

Given its excellent electrical conductivity, graphene materials can be used as conductive additives to optimize battery conductivity. Adding graphene materials to Si nanomaterials has better modification effects than general conductive additives such as natural graphite. Its first cycle reversible specific capacity is as high as 2347mAh/g. It can still reach 2041mAh/g after 20 cycles; graphene is added as a conductive additive to the graphite material to optimize the graphite material's conductivity. The mechanism is that graphene materials are built between graphite in a layered structure, similar to building a "bridge" through which electrons pass. This material has a large contact area with graphite to avoid performance degradation caused by the volume change of black acetylene particles and the reduction of the contact area with graphite material after multiple cycles. Graphene can also be used to improve the conductivity of LiFePO4 nanoparticles.

Also, graphene plays a unique role in preparing deformable lithium-ion batteries due to its excellent mechanical strength and toughness. The composite material formed by coating the surface of ethylene terephthalate with graphene film has considerable flexibility, reduces the density of the material, and optimizes its performance; vacuum filtration of the graphene material is attached to the surface of the filter paper to obtain Graphene/cellulose composites with superior mechanical properties and electrical conductivity. Those mentioned above and other flexible lithium-ion battery materials are mostly used in applications such as improving the environmental adaptability of lithium-ion batteries. With the development of research, such flexible electrode materials are also expected to be applied to wearable electronic devices.
 
Trunnano is a professional manufacturer of anode materials for lithium-ion batteries, silicon anode materials, graphite and graphene materials. If you have any requirements, please contact brad@ihpa.net.

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