GRAPHITE

Lithium slips between the layers

Graphite is stacked sheets of carbon. On charge, lithium ions squeeze between the sheets until there is one lithium for every six carbons: LiC₆. That gives about 372 mAh/g at only about 0.1 V above lithium metal, with only about 10% swelling.

Graphite is cheap, stable and in almost every lithium-ion cell.

SILICON

Ten times the capacity, and the swelling

Silicon alloys with lithium instead of hosting it, storing roughly ten times more per gram. The catch is that it swells to three or four times its size.

Small blends of silicon boost energy without tearing the anode apart.

TAMING SILICON

Tricks that help

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🔬

Go nano

Tiny particles and wires crack less than big ones

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Leave room

Porous or silicon–carbon composite particles swell inward

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Better binders

Stretchy binders and additives like FEC keep things together

Most silicon anodes today are blends of a few percent up to a few tens of percent.

OTHER ANODES

Fast, safe, or ultimate

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LTO (Li₄Ti₅O₁₂) About 1.55 V vs lithium: no SEI and no plating, ultra-fast and 10,000+ cycles, but low cell voltage

Hard carbon Disordered carbon used in sodium-ion cells

Lithium metal About 3,860 mAh/g, the highest of all, but it grows dendrites

Every anode trades energy against life, speed or safety.

WHY CAREFUL CHARGING

Lithium plating

Graphite sits so close to lithium metal's potential that charging too fast or too cold can make lithium plate as metal on the surface instead of slipping inside. Plated lithium is lost capacity, and it can grow into needles that pierce the separator.

Fast-charging limits are mostly about keeping the anode from plating.

UNIT 7 STUDY COMPLETE

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Ready for the Fab Challenge?

You've seen why graphite rules, why silicon tempts, and why lithium metal is the ultimate prize.