Silicon anode holds key to solid state batteries

Article By : R. Colin Johnson

A silicon anode eliminates the need for a liquid electrolyte and has less of a reaction to air and moisture even if partially exposed.

« Previously: Solid state batteries seek to overpower Li-ion
Once all the bugs have been worked out, rechargeable solid-state batteries using both solar and vibrational energy harvesting, plus charge-once-and-forget for the 10-year lifetime of the solid-state battery powered product, could become the rule rather than the exception.

Currently, Cymbet in Elk River, Minn., is offering development kits for its 250mm2 solid-state batteries, which may hit the market even earlier.

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Figure 1: *Rechargeable modules (right) can have backside integrated photovoltaic cells (middle, upright) constantly recharging solid-state batteries (left, upright) for indefinite lifetimes in the field, here a temperature sensor. (Source: Ilika) *

"Our solid-state batteries are based on lithium ion technology, but with solid-state safety, plus twice the energy density. Also, users can charge them in six-times faster than liquid Li-ion—15 minutes to recharge instead of 1-1/2 hours," Graeme Purdy, Ilika CEO, told EE Times.

"Regarding our relationship with Toyota, we jointly own the patents for the bulk batteries suitable for electric vehicles. But Ilika wholly owns the patents for small batteries," Purdy said. "Out patents covert three aspects: the combination of materials compared to conventional lithium ion, secondly the process (evaporation) is patented—instead of powder to ink-based printing on foil we heat to evaporate at 400°C—and thirdly we have patented the architecture and our way to combining the different ingredients."

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Figure 2: *A complete IoT device can be integrated with its solid-state battery, here on a daughter-board, or could even be integrated on the same SoC as runs a wearable with a 10-year lifetime. (Source: Ilika) *

The key, however, to solid-state batteries, according to Purdy, is the use of a silicon anode, which eliminates the need for a liquid electrolyte, is easier to encapsulate against the environment and even if partially exposed, has less of a reaction to air and moisture than liquid electrolyte Li-Ion batteries.

Purdy claims to already have licences on-hand for industrial IoT makers, using the extended temperature range IP, and from consumer product makers for the normal temperature range IP. In fact, Ilika's business model is never to compete with its licensees, but rather to prove-the-concept of its technology, offer design services and example applications, such as its Stereax M250 battery in a Perpetual Beacon Demonstration.

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Figure 3: *Wafers full of solid-state batteries make their manufacturing scalable and cheaper yet when ordered in high volumes. (Source: Ilika) *

Ilika has also qualified several foundries for its customers to build their chips using its licensed IP, including the Taiwan Semiconductor Manufacturing Co. (TSMC). However, the company claims that any foundry which routinely deals with compound semiconductors, such as GaAs, SiC, GaN or OLEDS, can also manufacture its solid-state batteries. For instance, Sharp Laboratories of Europe is developing an autonomous energy harvesting power source using Ilika IP.

First published by EE Times U.S.

« Previously: Solid state batteries seek to overpower Li-ion

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