Advantages and Disadvantages of Graphene as Anode Material

Advantages and Disadvantages of Graphene as Anode Material

With the development of research, high-performance lithium electrode materials emerge one after another. Graphene has many excellent characteristics, such as high electrical conductivity, high thermal conductivity, high specific surface area, etc., which has very important theoretical and engineering value to solve this problem to a certain extent.

Advantages of Graphene Lithium Storage:

1) High specific capacity: Lithium ion has non-stoichiometric embedding and deembedding in graphene, and the specific capacity can reach 700-2000 mAh/g;

2) High charge and discharge rate: the distance between layers of multilayer graphene materials is significantly larger than that of graphite, which is more conducive to rapid embedding and de-embedding of lithium ions. Most studies also show that the capacity of graphene anode is about 540 mA·h/g, but due to the degradation of battery capacity caused by decomposition or reaction with Li+ of a large number of oxygen-containing groups on its surface during charge and discharge, its rate performance is also greatly affected.

The defects caused by the doping of heteroatoms will change the surface morphology of the graphene anode material, thus improving the wettability between the electrode and the electrolyte, shortening the distance of electron transfer within the electrode, increasing the diffusion transfer speed of Li+ in the electrode material, thus improving the electrical conductivity and thermal stability of the electrode material.

Disadvantages of Graphene Materials as Battery Anode Include:

1) The prepared monolayer graphene sheets are easy to accumulate, and the reduction of specific surface area causes the loss of part of high lithium storage space;

2) The first Coulomb efficiency is low, generally less than 70%. Due to the large specific surface area and abundant functional groups, the electrolyte will decompose on the surface of graphene and form SEI film during circulation. At the same time, the residual oxygen-containing groups on the surface of carbon material react with lithium ion irreversibly, resulting in a further decrease of reversible capacity.

3) Fast attenuation of initial capacity

4) Voltage platform and voltage lag. Therefore, in order to solve these problems, graphene and other materials are compounded into graphene-based composite anode materials, which has become a hot spot in the research of lithium batteries and a direction of the development of lithium anode materials.

For lithium anode materials, transition metal oxides or promising Si based materials doped with graphene have shown excellent performance in specific capacity, voltage characteristics, internal resistance, charge-discharge performance, cycling performance, rate performance and other electrochemical properties. The impurity atom doping in the graphene base introduces more surface defects and improves the conductivity of the graphene material, resulting in better performance of the composite material.