Conductive Additives for Batteries

Jump to: Conductive Additive Properties | Types of Conductive Additive | High-Power vs High-Energy
Conductive additives play a significant role in enhancing the performance of electrodes in batteries by improving their electrical conductivity. Many electrode materials that play an active role in the electrochemical reactions involved in energy storage have relatively poor intrinsic electrical conductivity. By adding conductive additives to electrode mixtures, a conductive network forms throughout the electrode to ensure efficient electron movement. This network helps to distribute the current evenly throughout the electrode, minimizing localized overcharging. They also promote the full use of the active electrode materials and reduce the interfacial resistance between the electrode and the current collector.
Conductive Additive Properties
As well as electrical conductivity, conductive additives intrinsic properties are likely to influence other material characteristics such as mechanical strength, thermal behavior, and overall density.
The electrical conductivity of an electrode can be improved through the incorporation of conductive additives. At a critical volume fraction, the particles can form an interconnected network through the electrode, known as additive percolation. At this percolation threshold, a dramatic increase in electrical conductivity occurs. The percolation threshold depends on:
- Shape and size distribution of the conductive particles
- Electrode production method
- Homogeneity of the electrode mixture
- Surface interactions between the conductive particles and the other electrode components
Percolation must be balanced with other mechanical and physical properties. An excessive amount of additive may result in electrode failure through cracking, reduced mechanical integrity, or a drop in energy density, all of which may compromise performance for a given application. It is essential conductive additives either have no effect on the mechanical and thermal properties of the electrode or only improve them.
The mechanical properties of an electrode are also influenced by the ratio of electrode components. The conductive additive may be more robust that the active material and binder, providing added strength to the system. However, this may only be the case with thorough mixing and to avoid additive agglomeration. Or the conductive additive may reduce the strength of the electrode and therefore structural integrity, and conductivity must be balanced delicately.
Types of Conductive Additive
Conductive additives for batteries span a range of materials including carbon-based, nanomaterial-based and more. These materials possess high electrical conductivity which enhances the overall conductivity of the electrode in which they are added.
Carbon-based additives
Carbon-based conductive additives are most commonly used nanomaterial additives due to their excellent conductivity, high aspect ratio, and chemical stability. CNTs and graphene can reach conductivities close to that of metals (up to 106–107 S/m), making them ideal for enhancing charge transport in electrodes. Carbon black is less conductive (around 102–103 S/m) but is affordable and easy to disperse, so it's commonly used in commercial batteries. The actual performance depends on factors like dispersion, additive type, and network formation within the material.
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Nanomaterial Additives
Many conductive additives are both carbon-based and nanoscale. The nanoscale dimensions facilitate a lower percolation threshold which helps to maximise the ratio of active material, increasing overall energy density of the battery. Nanomaterials also have shorter electron tunnelling distances and higher surface contact areas which reduces internal resistance of the battery. They are also less likely to negatively impact the mechanical properties of the electrode system as a whole. Metallic nanomaterials are chosen for their superior conductivity, though often more expensive and less chemically stable than carbon materials.
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High-Power vs High-Energy
Batteries are typically designed for either high-power or high-energy applications. This involves a trade-off between delivering a large amount of power quickly versus releasing energy more gradually over a longer period.
This distinction influences whether you want to prioritize electrical conductivity or not. For high-power applications, conductive additives are highly attractive as they facilitate faster electron transport, enabling the battery to deliver current more rapidly.
In contrast, for high-energy applications the additives are viewed as a form of conductive dilution. The additive is taking up precious space where there could be active cathode or anode material. This drive for high energy capacity involves minimizing additive content.
High Energy Density | High Power Density |
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Low conductive additive content |
High conductive additive content |
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A ternary lithium battery is a type of lithium-ion battery (LIB) that has a cathode composed of three different metals. The metals are nickel (Ni), cobalt (Co), manganese (Mn) or aluminium (Al).
Read more...Power density vs energy density is an important consideration when it comes to battery science. Batteries that have high energy density, (can store a lot of energy) may not be able to deliver that energy quickly. Conversely batteries with high power density (can deliver a lot of power) may not be able to deliver that energy for a long period of time.
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