Carbon black is a fine, high-surface-area powder produced by the incomplete combustion or thermal decomposition of hydrocarbons like oil or gas. As a nearly pure form of elemental carbon, it is widely used as a reinforcing agent in rubber tires, a pigment in inks, coatings, and plastics, and as an conductive agent.
The conventional framing of carbon black in lithium-ion battery electrodes is electrochemical – an electrically conducting agent that enables the formation of the electrical wiring within an electrode. It has typically been specified by loading, surface area and subsequent powder or electrode resistivity. For wet slurry coating, this framing is broadly adequate. The solvent carries components into intimate contact and the carbon performs its conductivity function without much fanfare, or much else being asked of it.
The Structural Role of Carbon Black in Dry Electrode Processing
Dry electrode processing breaks this assumption. The evidence is accumulating that in the absence of a solvent carrier; carbon black does something considerably more structural, particularly during processing.
Specifications:
- Surface Area (BET): High surface area, typically ranging from 45 m²/g (e.g., C45) to 62 m²/g (C65) for standard applications, up to over 1000 m²/g for specialized high-surface products like Ketjen Black.
- Structure (DBP Absorption): High oil absorption (DBP) values, often >86 cc/100g, indicating a high-structure material that forms effective conductive networks.
- Purity: Very low impurity levels are critical to prevent cell failure. Ash content should be <0.025%
, and iron content should be <2ppm
.
- Particle Size: Nanopowder with an average particle size of approximately 30 nm.
- Moisture Content: Low moisture, typically
<0.5% to ensure slurry stability.
Based on IMERYS, Nouryon and Targray specifications for conductive carbon black materials.
Common Grades:
- Super C65 (Imerys) a standard conductive carbon with a BET surface area around 62 m²/g, often used for its balance of conductivity and dispersibility [1]
- Ketjen Black (EC-300J/600JD) high surface area (800-1400 m²/g) for applications requiring very high conductivity at low loading [2]
- C-NERGY C45 easy dispersibility and low viscosity in slurries [1]
References
- Specialty Carbons for the Negative Electrode of Lithium-ion Batteries, IMERYS
- Ketjenblack EC-300J, Nouryon
- Conductive Carbon Black, Targray