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    A ‘Solid’ Future for Batteries?

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    I’m often skeptical of new technologies. It is not that I’m a Luddite. Innovation is a crucial part of the way the modern world has lifted so many people out of poverty, improved our quality of life and created many of the conveniences we enjoy on a daily basis. However, I’ve heard enough empty promises to be a jaded. I’m even more suspicious when such promises are accompanied by corporate representatives speaking “sales speak”. To an extent, my skepticism of carbon capture and on small modular reactors are informed by this instinct.

    As a result, I welcomed this week’s announcement that Japanese battery maker TDK (an Apple supplier) with cautious optimism. The company says it has successfully developed a material for solid-state batteries with 100-times higher energy density. Although it is not the first solid state battery nor the last, the announced density and safety improvements do seem to represent great steps forward. Of course, there is room for improvement, but solid state batteries, if and when they can successfully be commercialised, should go some way towards improving our ability to use electric products for longer and help us transition towards a more sustainable society. Could it be that, for once, I shall tuck away my critical brain and indulge in some warranted optimism?

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    How Do Batteries Work?

    A conventional battery is made of six parts. A positive electrode (“cathode”), a negative electrode (anode), a porous polymer separator that keeps the electrodes apart, two electric contacts (one at each electrode). Each electrode is made up of materials capable of storing energy via ions. The whole battery bathes in an electrolyte, a liquid that serves as a medium through which ions travel from one electrode of the battery to another. In a traditional lithium battery, the cathode exists in a stable structure that holds ions when the battery is in a discharged state.

    As the battery charges, the ions move from the cathode to the anode. This movement creates free electrons in the anode which creates a charge at the positive current collector. When a device is charged, the electrical current then flows from the current collector through a device being powered (cell phone, computer, etc.) to the negative current collector.

    Solid State Batteries and Their Risks

    A solid-state battery is an electrical battery uses a solid (ceramic) electrolyte to conduct ions between the electrodes, instead of the liquid or gel polymer electrolytes found in conventional batteries. This allows for higher “energy density”, a measure of the energy stored in the battery. In practice, it means that a solid state battery should be able to provide a higher charge than the traditional batteries currently used.

    Asides from this greater “energy density”, solid state batteries are also safer, as they don’t include the electrolyte liquid which is flammable and can cause the batteries in our phones and in EVs to catch fire. The main problem with solid state batteries is that the materials they contain are expensive which means their price is higher than conventional batteries. Another issue is their application. Although these batteries might work for consumer goods like smart devices and electric vehicles, practically speaking, “solid state batteries […] are unlikely to be a competitive choice for battery storage in the power sector, where energy density is a less important consideration,” the IEA notes.

    TDK’s Innovation

    According to the announcement, “TDK has managed to develop a material for the new solid-state battery with a significantly higher energy density than TDK’s conventional mass-produced solid-state batteries (Type: CeraCharge) due to the use of oxide-based solid electrolyte and lithium alloy anodes. The use of oxide-based solid electrolyte makes batteries extremely safe. It is intended for use in wearable and other devices that come in direct contact with the human body.”

    The solid state battery can be applied for replacing coin cell primary batteries in compliance with EU battery regulations, which require them to be replaced by rechargeable batteries, the battery maker says. This should contribute to the reduction of environmental impact.

    Still Some Way to Go

    It is important to note that this is still a research development rather than a commercial announcement. All the kinks have not yet been worked out. Thus, some caution should be applied.

    We should not expect this sort of product to hit the shelves next year. Estimates point towards the 2030s as a possible launch date. However, solid state batteries are a promising technology that should be able to contribute to the energy transition, for a wide enough range of applications at least. We should keep an eye out for it.

    Image courtesy of TDK
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