WHY ON A CHIP?

Power where the circuit is

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Tiny

Micrometre-thin films on a chip or a flexible sheet

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All solid

No liquid to leak, so they can sit next to electronics

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Long-lived

Thin-film cells can cycle thousands of times

A battery that can be made with the same tools as the chip it powers.

THE STACK

A battery a few micrometres thick

Substrate Silicon, glass, ceramic or polymer

Current collector A thin metal film such as platinum or gold

Cathode Sputtered LiCoO₂, about 1–5 µm

Electrolyte LiPON glass, about 1–2 µm

Anode and seal Evaporated lithium metal, then a barrier against air

Every layer is a few micrometres, so the whole cell is thinner than a hair.

BUILD IT

Build a thin-film battery on a chip

Every step uses a standard microfabrication tool. Tap the steps in order.

Sputter, anneal, evaporate, seal.

LiPON

The glass that made it possible

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Lithium phosphorus oxynitride (LiPON) was developed at Oak Ridge National Laboratory in the early 1990s. It conducts lithium ions only modestly, but it is so thin and so stable against lithium metal that it made rechargeable thin-film cells practical.

A poor conductor works fine when it is only a micrometre thick.

USES AND LIMITS

Small cells, special jobs

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Medical

Implants and smart patches

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IoT

Sensor nodes that harvest energy and store it on-chip

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Limit

Capacity per area is small, often tens to a few hundred µAh/cm²

3D designs Coating films over etched pillars or trenches adds area, like the 3D electrodes in the Supercapacitors course

Thin-film cells trade capacity for size, safety and integration.

UNIT 20 STUDY COMPLETE

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Ready for the Fab Challenge?

You've built a battery the way a chip is built and seen where these tiny cells are used.