Rather than zinc air hearing aid batteries - the one set of batteries you really can't afford to not last a whole day (even if that is a longer than usual day due to travel etc).

Put me down for two pairs, so that I can have a spare pair with me and switch them out when they run low.

Fully agree. Solid improvements in hearing aid batteries would improve quality of life for users far more than incremental improvements in mobile phone battery life.

My NHS hearing aids use rechargeable batteries, working fine for over a year so far, and thats with bluetooth enabled.

But the money is in the phones… If you look at many recent inventions and innovations you'll see that, aside from the ground breaking fundamental research, they're driven by the market. For example, it wasn't until it became fashionable for car manufacturers to want to reduce power for headlights, presumably to drive in-car entertainment, that money was spent developing LED lights. And we might never have got Li-Ion batteries if Sony hadn't been involved in the initial research.

A Panasonic CR2032 cell has about 225 mAh at 3 volts, or 775 mWh

Volume is about 1cm^3, implying 775 Wh/litre

Energiser's spec sheet gives 683 mWh/cc, so TDK's tech nis either much better than claimed or their current cells are rubbish...

So, it beats the non-rechargeable batteries by a reasonable margin then? 1000 Wh/litre vs 775/683? And it's rechargeable - presumably with a reasonable life span. Sounds like an improvement to me.

Good catch!

We can't rule out that a decimal point got shifted in-between the lab and and press release. Or maybe the marketing department read that it being good for 1,000 charge cycles makes it 1,000 more capacious.

In fact if you dig further through TDK's product pages and PDFs, they don't really boast of its capacity, and instead are selling the tech on its high operating temperature range, its inability to leak toxic liquids, and its fire resistance.

The first product to incorporate the tech was a Bluetooth cooking thermometer that you leave in the oven.

Depending on the internal volume, but Duracell lists between 433 and 699 Wh/l for its MicroLithium coin cells, 555 for the DL2032, so seems about right.

Still, a bit higher capacity *and* rechargeable is a nice upgrade, if not a game changer.

Because these solid ceramic cells don't require the robust shells that conventional cells do, they may in practice exhibit a superior energy density. This advantage is less pronounced at larger volumes such as that of laptop batteries.

Edit: Ninja'd by @Pete below!

The case around a button cell takes up a considerable part of its total volume.

I reckon that if only the active part of a button cell is considered, then the power per litre would be much greater. But just how the capacity of this solid-state battery was measured is am unknown variable.

Although once these go on sale on Aliexpress, I forecast a vast improvement in their capacity. Up to 9800mAh, easily!

A Rayovac 13 zinc air button cell is typically used in heading aids.

Its data sheet has 136 h at 2 mA and average 1.25 V giving 340 mWh. Volume is 0.26 cc implying 1300 Wh/L.

OK, it's not related to this TDK battery, but I'd dearly love to know how you can have an anode-free battery? Do they mean a distributed anode?

A quick Google suggests for a CR2032 from Panasonic:

Volume: 1cm³

Capacity: 0.675Wh

That works out at about 675Wh/l, so the TDK is about the same

If existing TDK batteries are only 10Wh/l, then that would explain why they are better known for the magnetic tapes than their batteries.

The Register couldn't easily find any watt-hour per litre specifications for button cells; we've asked TDK for clarification on this point.

The golden rule for any data sheet is what is left out is important - as it means it is rubbish and they don't want it mentioned. Same for any company that only provided a data sheet under NDA - almost certainly what they have has some crap aspect they don't want compared.

> The Register couldn't easily find any watt-hour per litre specifications for button cells; we've asked TDK for clarification on this point.

Translation: The Reg couldn't do the required calculations on easily obtainable data because their calculator's batteries have run flat.

My first thought after reading "high energy density" was: will that not lead to more fires after they suffer a short circuit or something ?

Is there some mitigation, or what ?

They're based on solid ceramic layers, and are sold on their robustness and high temperature operating range.

Since 2022 they've been used in Bluetooth cooking thermometers intended to be placed in ovens.

There is little direct correlation between energy density and fire risk: any hydrocarbon fuel has a much, much higher energy density than any battery, but they're nearly all less of a fire risk than, say Li-Ion batteries. The chemical properties, particularly between the various components, is more important: sodium is more reactive than lithium, but Na-Ion batteries pose much less of a fire risk than Li-Ion.

However, the underlying storage technology in a battery can have significant implications on the ability to scale because they essentially store electrical energy rather than the chemical sort: how and where the charge is stored is one of the main drivers behing solid state batteries.