Percolation threshold is the minimum loading at which a conductive additive forms a continuous electronic network in a composite or electrode. Below this threshold, conductivity increases slowly; above it, conductivity rises sharply. For battery electrodes, a lower percolation threshold means higher energy density and lower inactive material content.
Carbon black relies on particle-to-particle contact to form conductive paths. Its low aspect ratio means a large amount is required to bridge gaps between active materials, leading to higher percolation thresholds and increased inactive mass.
Carbon nanotubes form long-range conductive networks due to their high aspect ratio. A small amount of CNT can span large distances within the electrode, dramatically reducing the percolation threshold compared with carbon black.