A solid-state battery is a type of battery that uses a solid electrolyte to generate an electrical current — unlike a conventional lithium-ion battery, in which the electrolyte is made out of liquid or gel. This design tweak creates an energy-dense power source that’s safer, compact and can last twice as long.
That’s good news, because, after three decades of being the go-to energy source for everyday electronics, the lithium-ion battery has peaked. This has left scientists and companies looking for a sustainable and renewable alternative.
Solid-State Battery Definition
A solid-state battery uses a solid electrolyte (typically made out of ceramic or a polymer mix) for conduction, instead of one made of liquid or gel, which is the case for traditional lithium-ion batteries.
“Across all electronics, we are not limited by technology,” explained Vikalp Raj, a battery scientist and postdoctoral researcher at the University of Texas. “We are limited by the batteries.”
What Is a Solid-State Battery?
A solid-state battery uses a solid electrolyte — as opposed to a liquid electrolyte, which is what a standard lithium-ion battery uses — to move ions from one electrode to another. It promises faster charging times and a longer overall lifespan, and has become an exciting development for electric vehicles in the transition from fossil fuels.
The idea is that solid-state batteries will “replace the highly flammable liquid electrolyte in a conventional lithium-ion battery with a safer, solid, ceramic electrolyte,” Reeja Jayan, an associate professor of mechanical engineering at Carnegie Mellon University, told Built In.
In electric vehicles, solid-state batteries charge faster, offer enhanced safety and solve “range-anxiety” by lasting longer over greater distances. Recently, a team of scientists at Harvard University developed a solid-state battery that can charge in the time it takes to fill up a petrol tank with a battery lifespan that lasts three-to-six times longer than the typical EV battery. Meanwhile, the world’s first anode-free, sodium-based solid-state battery introduces an environmentally friendly and more affordable alternative to popular lithium-based models.
While new innovations accumulate, solid-state batteries remain held up in research labs and on factory floors. They’re still too expensive to produce and challenging to manufacture at scale, making them commercially nonviable.
“If successful, solid state batteries provide us the best hope to get to safe, truly affordable, long-range electric cars that double in mileage,” Jayan said.
Solid-State Battery vs. Lithium-ion Battery: What’s the Difference?
Both solid-state batteries and lithium-ion batteries operate on the same principle. They take energy in, store it, then release it to whatever electronic device they’re inside of — from TV remotes to watches to cars.
What differentiates solid-state batteries from traditional lithium-ion batteries is the materials inside.
- Lithium-ion batteries use a liquid or gel electrolyte that’s essentially a lithium-salt solution dissolved in an organic solvent. While it allows for efficient ionic transfer, it carries notable risks. These materials are heavy, highly flammable and prone to leakage.
- Solid-state batteries use a solid electrolyte made of non-flammable, inorganic materials. This change also makes it possible to graduate from standard graphite-based anodes to those made of lithium metal, a sort of “holy grail” for battery tech, because of their exceptional energy capacity and low electrochemical potential. This makes for safe, long-lasting batteries in smaller, lighter packages.
“[Lithium-metal] is the lightest metal on the planet,” Tim Holme, the chief technology officer of solid-state battery startup QuantumScape, told Built In. “It’s nearly ten times more energy dense than the graphite that’s used in today’s batteries, enabling it to store more energy in the same volume.”
How Do Solid-State Batteries Work?
Inside of solid-state batteries, lithium ions generally move between two electrodes, the anode and cathode, to generate and store power. In this case, a solid electrolyte — often made of ceramic, polymer or glass materials — facilitates the transport from one pole to the other during charge and discharge cycles.
As a battery charges, lithium ions migrate from the cathode (made of a mix-metal oxides or phosphates) through the solid electrolyte to the anode (often composed of graphite, silicon or lithium metal), where they are stored. During discharge, the ions travel back to the cathode. This movement generates the electrical current that powers connected devices.
Different materials deliver different results. Toyota’s prototypes feature a sulfur-based electrolyte, while Samsung experiments with silver-carbon anodes. Other systems, like QuantumScape’s lithium-metal models, are built without an anode component entirely. Instead, it’s formed on the battery’s first charge, which “dramatically simplifies battery design,” Holme said.
The solid electrolyte’s role is crucial. It not only conducts lithium ions, it also acts as a separator that prevents direct contact between the anode and cathode — of positive and negative charges, respectively — thereby eliminating the risk of short circuits, providing a more stable and uniform ionic pathway.
Advantages of Solid State Batteries
The following list highlights why solid-state batteries are widely considered to be the next big thing in energy storage.
Enhanced Safety
Safety is the primary benefit ascribed to solid-state batteries. They are made out of thermally stable, inorganic materials, which virtually eliminates the risk of leaks, fires and explosions compared to their highly flammable, liquid-based counterparts. This allows them to withstand temperatures up to 1,000 degrees celsius, Raj estimates, making them a great asset in the production of electric vehicles, aerospace systems and industrial equipment where they may be exposed to extreme environments.
“Solid-state batteries have single-handedly eliminated safety risks [for electric vehicles]. There’s nothing inside that will burn,” Raj said, jokingly adding that “if you’re in a car accident, it’s ideal if that battery doesn’t react like a bomb.”
Higher Energy Density
Solid-state batteries are about 2.5 times more energy dense than lithium-ion batteries. That means solid-state batteries can store more energy in less space, maximizing energy capacity and prolonging battery life. Longer-lasting power enables electric vehicles to drive further distances on a single charge without increasing battery size or weight, and enhances the performance of portable electronics, with extended usage time and a reduced need for frequent recharging.
Lightweight, Compact Designs
Solid-state batteries use less materials — and lighter materials — than their liquid-based counterparts. This weight reduction means battery packs can be thin and sleek, increasing the mobility of a device or electric-powered vehicle. Without a liquid electrolyte, a solid-state battery simplifies sealing and eliminates the need for any additional cooling systems in large-scale equipment.
Faster Charge
By making it easier for lithium ions to oscillate from one side of the battery to the other, solid-state batteries can support rapid charging times compared to today’s standard. The lithium-metal batteries being developed for electric vehicles by QuantumScape, for example, can charge from 10 to 80 percent in less than 15 minutes, according to Holme, the company’s chief technology officer.
High Degree of Freedom in Shape
Solid-state batteries are not bound to the structural limitations of liquid-based batteries, which are designed to prevent leakage. They’re smaller and thinner, and can be bent, shaped, fit to overlap one another and even directly sintered into a part.
Disadvantages of Solid State Batteries
As a newer technology, solid-state batteries have some kinks to work out in the coming years. Below include a few hang-ups that scientists, researchers, startups and policymakers are working to solve as the technology develops.
High Cost
Solid-state batteries have not reached a level for mass production. The materials that they’re made out of are difficult to scale, with low-throughput manufacturing processes driving up the cost further. A recent study estimated the best-case scenario, where solid-state batteries reached mass production at $140 per kilowatt hour by 2028. But certain obstacles could inflate costs to $175 per kilowatt hour between 2032 and 2033, delaying commercial production by five years.
Materials Still Being Studied
Finding the right materials to actually build a solid-state battery proves to be tricky. Oxide-based electrolytes, for example, are porous enough to allow ions to pass through, but are often too brittle to break if bended. Those made out of sulfides are soft and perfectly deformable, but become chemically unstable when exposed to moisture. Switching a battery’s anode from graphite to lithium metal is the ultimate goal. The only thing is that the material “has the consistency of wet tissue paper,” which, as you can imagine, is difficult to work with on a mass scale. So even when promising materials are discovered, they still face challenges with scalability and manufacturing, hindering their practical use in commercial batteries.
Manufacturing Challenges
The cost of solid-state batteries is well beyond $100 per kilowatt hour, and it has everything to do with manufacturing hang-ups. Solid-state batteries require particular temperature and pressure conditions that are specific to each build and unique set of materials, complicating mass-scale production. But with each modification comes overall added costs, impeding their commercial viability.
Interface Issues
When a solid lies on top of another solid, the two surfaces rarely make full contact due to interfacial gaps and irregularities between them. Sometimes, this is only detectable under a microscope. Cracks and crevices between a solid electrolyte and an electrode result in sluggish ionic transfer — or no transfer at all — creating electrical resistance and poor conductivity. Over time, the lack of proper contact may degrade and even short circuit the battery.
Some solutions include coating these surfaces with an extremely thin interlayer of gel or glue that hardens post-application to maintain a “true” solid composition in a solid-state battery.
Frequently Asked Questions
What is a solid-state battery?
A solid-state battery uses a solid electrolyte instead of one made of a liquid or gel for conduction.
Do solid-state batteries exist yet?
Yes; Generally speaking, solid-state batteries are still in research and development stages, but some small devices like watches, hearing aids and pacemakers already feature the technology.
What is the problem with solid-state batteries?
Solid-state batteries are difficult to manufacture and scale. This drives up costs, and makes them commercially unviable. Researchers are also still studying which materials work best in order to optimize the device’s interface.
