Li-Ion Battery Graphite Composites

Graphite is one of the most important active materials in Li ion batteries and is widely used as the negative electrode. It is highly versatile and offers a number of advantages, including excellent charging stability, suitable power density and high energy density.

Despite extensive research efforts to find suitable alternatives with enhanced power and/or energy densities, graphite remains a mainstay in presently available commercial Li ion batteries. Graphite also offers excellent cycleability as it is able to absorb and store lithium ions.

However, graphite is not the only active material in lithium-ion batteries, and the market for LiBs continues to grow at a fast rate. This is due to the emergence of electric vehicles, plug in vehicles and hybrid electric vehicles, which are rapidly becoming large markets.

For these new applications, graphite-containing composites have been developed. They can be either a pure graphite-based anode, or they can be a combination of a high-capacity compound (e.g., understoichiometric silicon oxide or a silicon-metal alloy) and graphite.

These combinations have been shown to provide a considerable increase in the first cycle coulombic efficiency compared to standard graphite-based electrodes. Moreover, the energy density is further increased when the composite electrode is pre-lithiated. This has been achieved, for instance, by preparing a pre-lithiated composite electrode consisting of SiOx/graphite and NCA with an areal capacity above 600 mA h cm-2, with an ICE of 86% after 150 cycles.

However, further improvement of the energy density is required for a successful commercial rollout. Besides the above-mentioned ex situ modifications of the graphite surface, a significant impact can be achieved by tailoring the electrolyte composition. Typically, this is done by adding additives to the EC.

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