Chemistry: Anode

Silicon Basic Technology And Information Engineered silicon increases anode specific capacity as a blend with or replacement for graphite in Li-ion batteries LIBs Lithium is a metal that forms an alloy with silicon. Fully lithiated silicon Li15Si4) has a theoretical maximum capacity of 3,572 mAh/g—9.6 times that of graphite. However, silicon undergoes up to 400% volume expansion when lithium is inserted. Volume expansion and contraction during cycling can cause mechanical degradation and capacity fade. Materials engineering strategies aim to curb these issues, though often with a compromise in capacity compared to siliconʼs theoretical maximum. Production process: Vaporizing Si and SiO2 then condensing; and ball milling Si and SiO2 powders.

Silicon Monoxide

SiOx

Silicon in Carbon Si-C

Elemental Silicon Si

Established production methods and in widespread use for several years. Limited to < 10% in the anode for reasonable cycle life.

SUPPLIERS Leading suppliers of SiOx include Daejoo Electronic Materials Korea, BTR China, and Shin-Etsu Chemical Japan.

Production process: CVD of silane to form nano-silicon particles in engineered carbon structures.

Structures are designed to restrain volume expansion and degradation. Energy cost of thermal process required to produce the carbon micro-structures.

Production process: Grinding MGS (for μ Si); and CVD of silane on current collector or in graphite (for n Si).

No inactive anode material means higher specific capacity. Potential for volume changes and degradation.

Sources: Mazir Ashuri et al 2023 Silicon oxides for Li-ion battery anode... Journal of Power Sources, 559. Iwamura, S. et al 2015 Li-Rich Li-Si Alloy as a Lithium-Containing... Sci Rep, 5, 8085. Zhang et al 2023 Recent advances of SiOx-based anodes... Nano Research Energy, 23. Zuo, Xiuxia et al 2017 Silicon based lithium-ion battery anodes... Nano Energy, 311, 113143. P.U. Nzereogu et al 2022 Anode materials for lithium-ion batteries... Applied Surface Science Advances, 9.

ALTERNATIVES Silicon is considered to be the most promising anode material for LIBs due to its very high theoretical capacity. R&D to mitigate the capacity fade problem continues, e.g. with composites, micro-structures, nano-structuring, and coatings.

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