Graphite Anode and Cathode Modifications for Lithium-Ion Batteries

Graphite is the material of choice for many anodes. It is cheap, has a long cycle life, and is compatible with the chemistry of lithium-ion batteries. But there are some safety issues associated with graphite anodes, including lithium dendrites and plating.

Increasing the coulombic efficiency of the graphite anode has been a major concern for researchers over the last two decades. Different approaches to reducing the first cycle irreversibility have been developed, leading to coulombic efficiencies of 90-96% for commercial graphite anodes.

One promising alternative to graphite is silicon. Silicon is relatively inexpensive, possesses high gravimetric and gravimetric capacitances, and can absorb more lithium than graphite. However, silicon has only a moderate intrinsic specific capacity. For this reason, it may be difficult to achieve the high energy densities required for energy-intense applications.

A potential solution to the problem is to enhance the solid electrolyte interphase (SEI) on the graphite electrode. This is done by modifying the surface of the anode in a way that prevents the dissolved Mn2+ from penetrating through the SEI layer.

An example of this is the use of ethylene carbonate as a co-solvent in the electrolyte of LIBs. This enables a stable, solid electrolyte interphase on the graphite electrode. The formation of this interphase inhibits the continuous electrolyte decomposition.

Another potential approach is to increase the reversible capacity of the anode. In LIBs, metallic lithium is plated on top of the graphite electrode. When this occurs, it reacts with the electrolyte. While this process reduces the dissolved Mn2+, it can also deposit Mn on the anode.

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