The future of EV? Honda begins pilot production of all-solid-state batteries in Japan

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A collection of unremarkable white factory buildings in Sakura, Japan, could house the key to Honda’s future – all-solid-state EV batteries.

In January 2025, it comes to life as a demonstration production line begins rolling, using equipment and methods developed to mass-manufacture the solid-state batteries intended to power a future generation of lighter, cheaper and longer-range electric motorbikes.

Honda electric concepts shown at EICMA 2024

Solid-state batteries are widely seen as the silver bullet for electric vehicles and promise huge strides to address all the shortcomings of today’s lithium-ion options.

They’re smaller, lighter, more resilient, faster-charging, use more easily sourced materials and pose less risk of fire, as well as promising reduced costs.

Inside Honda's new solid-state battery production facility

Honda’s initial design, due in production EVs in the second half of the 2020s, is expected to halve the size of batteries, cut their weight by 35% and reduce costs by 25%. By 2040, the company predicts they’ll be 60% smaller, 45% lighter and 40% cheaper.

That means EVs, including electric bikes, stand to either be substantially lighter than today or have twice the range of current models. Although the Honda plant is a demonstration facility at this stage, all the equipment inside is production-scale so the switch to full production should be straightforward once any bugs are ironed out.

Honda EV Fun concept front view

So, what’s the trick? Current lithium-ion batteries use a liquid electrolyte to pass ions between the electrodes (anode and cathode) via a permeable membrane – the separator – which prevents the two electrodes from coming into contact with each other and shorting out.

The problem is that the liquid electrolyte is made of lithium salts held in a flammable organic solvent, which helps the ions move but poses a fire risk. Sparks from an internal short circuit or thermal runaway from too much heat can lead to fires that are hard to extinguish because li-ion battery fires also release oxygen that feeds the flames.

Demonstration production line for solid-state batteries

Solid-state batteries have a solid electrolyte, eliminating the need for a separator because the electrodes can’t touch through it, helping make them more compact and lighter.

With no flammable liquid electrolyte they can safely withstand higher temperatures – allowing faster charging – and don’t need to be as heavily protected from damage, helping reduce the weight and size of battery cases.

Honda EV Fun concept at EICMA 2024

Keiji Otsu, President and Representative Director, Honda R&D, said: “Compared to liquid electrolyte, solid electrolyte is chemically more stable, allowing the selection of high-capacity materials such as lithium metal, which could not be used in liquid lithium-ion batteries, as well as electrode materials which will reduce geopolitical risks.

“The absence of a liquid electrolyte will lower the risk of vehicle fire due to minimum amount of flammable gas to be emitted. Also, all-solid-state batteries can be used stably in high temperature, such as 80°C, which will increase potential of fast charging.”

Outside Honda's solid-state battery production facility

Motorcycles stand to benefit from solid-state batteries even more than cars do because the batteries of electric bikes make up a larger proportion of the whole vehicle.

Halving their weight and slashing their cost could finally tip the balance to the point where an electric bike can genuinely compete with ICE, and Honda’s developments mean it’s due to happen before this decade is out.

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