The Science Behind Honda’s Solid-State Battery Breakthrough

By  James O'Neil  topspeed.com

Toyota launched the solid-state revolution, but Honda may finish it. The Japanese automaker shocked the automotive world when it announced that it would actually begin producing solid-state EV batteries in January 2025. Despite years of research and literal billions of dollars, no company has yet managed to set up a production line and bolt a solid-state battery into a test car. If Honda lives up to its own promises, it will be the most groundbreaking event in the history EVs since a medium-sized California startup called “Tesla” announced that it would start producing electric cars.

Solid-state batteries have started to look like a costly industry-wide folly, similar to the many years and dollars that Chrysler threw away on the Turbine car. However, Honda has made a daring announcement that it will have a factory up and running in a few short weeks. Toyota started the solid-state revolution over a decade ago, but its progress has been almost maddeningly slow. If Honda’s announcements are true, it may steal solid-state glory from Toyota.

In order to give you the most up-to-date and accurate information possible, the data used to compile this article was sourced from various manufacturer websites and other authoritative sources.

Revolutionizing Battery Production: Honda’s Demonstration Line

• Honda’s new factory is a demonstration line, not a full-scale production facility. Honda is finalizing its production methods.
• Honda expects to open its factory in January 2025.

Before everyone gets too excited about ASSB-powered Hondas (the abbreviation stands for All-Solid-State Battery), Honda’s factory is a demonstration line rather than a full-sized production factory. However, this marks a massive step in the development of car-sized SSBs. No other company has managed to get an SSB factory running regardless of size. A lot of major companies have claimed that they have factories under construction, but they have all claimed opening dates in the conveniently ambiguous future. Honda is the only automaker to claim that it will have a factory open in less than 2 months.

Setting The Stage For Mass Production

Honda officially calls this facility a “demonstration line.” This factory, located in Sakura City, Tochigi Prefecture, covers 27,400 m² (295,000 ft²). It was partially funded by Japan’s Green Innovation Fund, a government initiative that funds exactly what the name implies.

Honda has wasted no time in fitting it out with tooling. The buildings were completed in the spring of 2024. Even though the roof hasn't yet been nailed down for a full year, Honda has nearly finished installing the manufacturing equipment. Again, it cannot be emphasized enough that Honda is actually getting ready to crank out solid-state batteries instead of merely issuing press releases about them. This puts Honda ahead of everyone else in the industry.

Honda Is Producing The Batteries Of Tomorrow, Not The Batteries Of Next Year

The most stunning part of Honda’s announcement is the date. Production is set to begin in January 2025. Honda will focus on verifying mass production techniques and costs. Accordingly, the Sakura City facility incorporates technologies for use in weighing and mixing electrode materials, coating and roll pressing, and module assembly.

Mass production has been one of the biggest hurdles to ASSB development. Various companies have produced working battery prototypes, and a lot of them have also announced that they have factories under construction. However, Honda is the only company whose production date is in a few weeks instead of a couple of years.

From likable features to usable power, this Honda EV ticks all the right boxes for the masses

Roll-Pressing: The Key to Next-Gen Battery Efficiency

• Honda is pressing its batteries together, which makes them work better and also lowers production costs.
• Honda has developed a way to forestall dendrites, which are one of the main killers of solid-state batteries. It puts a plastic barrier over the area where the crystals would otherwise grow.

It should not be a surprise that Honda is ready to spin up a production line. While other automakers were issuing press releases about the range or predicted lifespan of their SSBs, Honda was already announcing various developments in production techniques. One of its biggest ones was roll-pressing its batteries together, which both streamlines production and also improves the batteries themselves.

Pressing Ahead with Solid-State Innovation

One of Honda’s biggest breakthroughs in solid-state batteries was its roll-pressing technique. This essentially means that the SSB cells are stamped together during assembly. Honda’s roll-pressing technique increases the density of solid electrolyte layers, improving energy efficiency.

“Density” and “electrode contact” have been two of the biggest problems preventing car-sized SSBs from hitting the road. Most battery types store their energy in a liquid or a paste, which naturally conforms to whatever space it’s in and makes near-perfect contact with the electrodes through which electricity flows. Solid-state batteries (as the name implies) store their energy in a solid electrolyte, which is usually a powder. As with any powder, solid-state electrolytes are full of tiny air gaps. And of course, electricity can’t travel through air unless it is arcing, which is not desirable inside of batteries. Pressing the batteries together (as opposed to any other method of assembly) literally squashes out the air and empty spaces. As a result, the solid electrolyte makes perfect contact with the battery’s electrodes (or as close to perfect as possible).

Also, pressing the batteries speeds up the production time. Welding and other methods take a lot longer than simply pushing the batteries through a press that mashes them together. Honda also aims to simplify the batteries’ cooling structures. Unlike lithium-ion batteries, ASSBs are fairly heat resistant. That is, heat doesn’t damage them very easily. Of course, SSBs still need to be kept cool. However, their inherent heat resistance allows Honda to simplify the batteries’ cooling systems.

Honda Is Extending Battery Life With A Simple Sheet Of Plastic

Honda has also developed a way to prevent dendrites, thus allowing its solid-state batteries to last longer. The solution is so simple it shouldn’t work: put a layer of plastic (which is thin enough to let electricity flow through) where the dendrites would otherwise grow.

Dendrites are small, spiky lithium crystals that form when the lithium separates out of the various compounds inside the battery. As they grow, they pierce their way through the battery’s internal structures and destroy it from the inside. Dendrites start growing out of small cracks in the battery’s electrodes (Every battery’s electrodes develop microfissures over time. It is the inevitable result of the metal repeatedly expanding and contracting with temperature changes). Honda’s polymer barrier prevents the lithium inside the battery from touching the electrode, which means there is nowhere for the dendrite crystals to take root.

Dendrites are one of the primary reasons that solid-state batteries age and die. Of course, it is unrealistic to claim that a thin polymer will last forever. Nevertheless, it can add years to the battery’s life.

Honda is also in the race for solid-state batteries, but will it get to the finish line first?

Scaling Up: From EVs to Aircraft

• Like its omnipresent crate engines, Honda aims to make its solid-state power systems viable for use over land, sea, air, and possibly even space.
• Honda aims to make its SSBs affordable by producing enough of them to attain economy of scale.

Honda has long been described as “an engine company that happens to make cars.” Indeed, Honda developed its motorcycle division long before it expanded to automobiles. And to this day, Honda has one of the most robust crate engine divisions in the entire automotive industry. Of course, every automaker produces crate engines. But Honda’s engines have been deep underground, up in space, in countless power tools, and everywhere in between. As the ICE gives way to EVs, Honda is already ensuring its future dominance in power systems.

Expanding Applications Across Mobility Sectors

Honda is already developing solid-state batteries for use on both land and air. If things go according to plan, Honda’s solid-state batteries will power cars, trucks, motorcycles, and aircraft. (Honda may also be planning to adapt SSBs to ships, but forgoing press releases about this initiative because ships rarely make headlines unless they wreck.) In other words, Honda is planning to put solid-state batteries everywhere its engines already go.

Lowering Cost Through Sheer Volume

Of course, another SSB hurdle (there are many) is cost. At present, every would-be battery manufacturer claims that SSBs are costly to produce and likely to remain so for quite some time. Indeed, Samsung neatly avoided all affordability problems when it announced that it would only sell its SSBs for use in luxury vehicles.

Honda’s answer to this comes right out of the Unit 1 from any economics textbook: economy of scale. This is an impressive gamble for a technology that, so far, has not been proven roadworthy. Honda is planning to invest the money to rapidly crank out solid-state batteries even though literally no one has ever bought a car that has one yet.

However, if solid-state batteries live up to their long-touted hype, they may prove easy to sell. TopSpeed’s own readers have confirmed that range is the biggest reason people haven't switched to EVs, with cost and charging time coming very close behind. Solid-state batteries can eliminate both of those problems. Estimates of range vary from one manufacturer to the next, but are always at least 500 miles. Most manufacturers claim ranges somewhere between 600 and 900 miles per charge, which is well ahead of any ICE vehicle with a full tank of fuel. Additionally, SSBs are far more resilient against fast-charging than lithium-ion batteries. An SSB-powered vehicle would barely require more charging time than an ICE car at a fuel pump.

A Vision for Carbon Neutrality by 2050

Honda aims to be carbon-neutral by 2050.

• Honda t plans to produce exclusively electrically-powered vehicles (both battery and hydrogen) by 2040.

Carbon neutrality has become one of the biggest trends in corporate press releases, and Honda is no exception. This is a natural progression for the company that won over American car buyers in the 1970s with vehicles that were both fuel-efficient and fun, two categories that American automakers never reconciled. (American automakers gave car buyers punitive econo-boxes like the Chevette, Honda offered zippy compacts like the Civic.)

Even in the 21st century, American automakers continue to fumble most vehicles that aren’t large enough to to accommodate an entire Little League team. It is therefore natural that Honda would aim for carbon neutrality without putting a deadline far away in the undefined future.

Driving the Future with Sustainable Energy Solutions

Honda’s history with EVs closely parallels that of its closest rival, Toyota. The latter company started making EVs several years ahead of Toyota, which had a few desultory and short-lived EVs before finally launching the competent yet forgettable bZ4X SUV. Instead, Toyota focused more on its lucrative hybrids and also on its sometimes quixotic hydrogen fuel-cell vehicles.

Honda’s history with EVs has been the same. Indeed, the two companies introduced their first FCEVs in the same year. However, Honda (like Toyota) is now expanding its EV lineup.

Honda May Produce Its Last ICE Car In Just 15 Years

It is currently becoming trendy for automakers to announce that they will end all internal combustion by some year in the near (but not too close) future, or at least reduce ICE to a small niche. Honda is no exception. The company officially aims to produce all battery-electric and fuel-cell vehicles by 2040. Solid-state batteries are a crucial part of Honda’s plan, because they eliminate a lot of the problems that keep EVs out of many people’s garages.

SSBs' high tolerance for heat simplifies the problem of battery cooling. All batteries get hot when either fast-charging or sending out large surges of power (such as when the driver mashes the accelerator). Additionally, it barely needs noting that EVs spend most of their lives outdoors, where the ambient heat can shorten a battery’s life even if it is not in use.

As Honda president Keiji Otsu stated: “All-solid-state batteries are a game changer in the EV era, driving Honda’s transformation into a leader in electrification.” It is truly impossible for any business executive to discuss solid-state batteries without saying “game changer” at least once. However, Honda may actually put the change into “game change.”