Meaning
Protective layer of disordered carbon material applied to the exterior of electrode particles to improve chemical stability and electronic conductivity. Use of a hard carbon coating limits the interaction between the electrolyte and the active core of the particle. This surface treatment ensures that the lithium ions can move freely into the electrode without destroying the underlying structure.
Surface Stabilization
The amorphous structure of the carbon acts as a barrier that prevents direct contact between the electrolyte and the highly reactive electrode surface. Applying a hard carbon coating reduces the initial capacity loss during the first charge cycle. This protection stops the continuous growth of the solid electrolyte interphase which would otherwise consume lithium.
Diffusion Rate
Unlike graphite, the disordered nature of this material provides many entry points for ions to pass through to the core. A hard carbon coating facilitates high rate charging by providing a low resistance path for ion migration. Enhanced movement of charge carriers allows the battery to deliver high power without measurable voltage drops.
Mechanical Resilience
Strong bonds within the carbon matrix help the particle resist the expansion and contraction associated with ion insertion. When a hard carbon coating is present, the active material is less likely to pulverize or detach from the current collector. This structural support is a primary factor in extending the total number of cycles a cell can perform.
