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Advantages and disadvantages of graphene as anode material for lithium ion batteries

Advantages and disadvantages of graphene as anode material for lithium ion batteries

With the development of research, high performance lithium electrode materials emerge in an endless stream. The excellent properties of graphene, such as high electrical conductivity, high thermal conductivity, high specific surface area and so on, have very important theoretical and engineering value for solving this problem to some extent.

Advantages of graphene direct storage of lithium:
1)High specific capacity: Does lithium ion have non-stoichiometric embedding in graphene? The specific capacity can reach 700~2000 mAh/g;

2) High charge-discharge rate: the interlayer distance of multilayer graphene material is significantly larger than that of graphite, which is more conducive to the rapid embedding and deembedding of lithium ions. Most studies have also shown that the capacity of graphene negative electrode is about 540 mA·h/g, but due to the decomposition of a large number of oxygen-containing groups on its surface or the reaction with Li+ in the process of charging and discharging, resulting in the attenuation of battery capacity, its magnicity performance is also greatly affected.
Defects caused by doping of heteroatoms will change the surface morphology of graphene anode materials, thus improving the wettability between electrode and electrolyte, shortening the electron transfer distance inside the electrode, increasing the diffusion and transfer speed of Li+ in the electrode materials, and thus improving the conductivity and thermal stability of the electrode materials.

However, there are still some drawbacks to using graphene material directly as a negative electrode for batteries, including:
1)The prepared single-layer graphene is easy to accumulate, and the reduction of specific surface area makes it lose part of high lithium storage space;

2)The first coulomb efficiency is low, generally lower than 70%. Due to the large specific surface area and abundant functional groups, electrolyte decomposition occurs on the surface of graphene during the cycle, forming SEI film. At the same time, the residual oxygen-containing groups on the surface of carbon materials have irreversible side reactions with lithium ions, resulting in a further decline in reversible capacity.

3)Rapid initial capacity attenuation;

4)Voltage platform and voltage lag. Therefore, in order to solve this series of problems, graphene and other materials are combined to produce graphene based composite anode materials, which has become a hot spot of lithium battery research and a direction of lithium anode materials development.

For lithium cathode materials, transition metal oxides or promising Si based materials doped with graphene have shown excellent characteristics in terms of specific capacity, voltage characteristics, internal resistance, charge-discharge performance, cycling performance, rate performance and other electrochemical properties. The heteroatomic doping of graphene-based materials introduced more surface defects and improved the conductivity of graphene materials, resulting in better properties of composite materials.

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