Chemistry & Cell Components

Chemistry & Cell Components

Silicon Anode | Technology

Silicon Anode | Technology

Silicon-based materials can provide a huge improvement in energy density since 1 silicon atom can hold 4 lithium atoms (compared to the incumbent graphite which takes 6 carbon atoms to hold 1 lithium atom. Silicon has a theoretical capacity of 3600 mAh/g compared to graphite which has 372 mAh/g. Downsides include large volumetric expansion (300-400%) in Li alloying/dealloying. This can cause solid electrolyte interphase (SEI) development through excess silicon exposure and can disintegrate the whole anode. As a result, it has been challenging to make silicon dominant anodes and only a sprinkle (3-8%) is generally used.

Silicon Anode Key Challenges

Silicon Oxide

Silicon composite

Metallic Silicon

Composition

Composed of silicon and oxygen

Common variants include: silicon monoxide (SiO) or silicon dioxide (SiO2)

Metallic silicon or Silicon oxide embedded in carbon matrix

Other form factors include silicon nanowires, carbon coatings on silicon particles, or 3D structures

Pure elemental silicon

Advantages

Higher theoretical capacities than graphite

Less volume expansion compared to pure silicon, addressing some of the mechanical stress concerns

Optimizes silicon/carbon matrix nanostructures to buffer the volume change of silicon

Composite carbon networks increase electrical conductivity, and add adhesion and higher chemical stability

Lowest manufacturing cost

Highest energy density of silicon materials

Challenges

Lower electrical conductivity compared to metallic silicon

Reversible capacity can be limited due to formation of SEI layers

Substantial volume expansion and contraction during lithiation and delithiation cycles

Mechanical stress and electrode pulverization

Higher production costs than metallic silicon and most SiO

Substantial volume expansion and contraction during lithiation and delithiation cycles

Mechanical stress and electrode pulverization

High capacity fade and reduced cycle life

Extracted from the PDF; charts and images may read imperfectly.