Lab claims breakthrough as independent tests validate next-generation solid-state battery

The race to develop safer, lighter and more energy-dense batteries is one of the defining technology competitions of the modern era. From electric vehicles and drones to renewable energy storage and aerospace applications, battery performance remains a critical factor limiting how far electrification can advance.

Now Finnish technology company Donut Lab has announced independent test results that it says place its solid-state battery technology among the most promising emerging energy-storage systems currently under development. The company reports that testing conducted by VTT Technical Research Centre of Finland found that its Donut Battery achieved an energy density of 409 watt-hours per kilogram and 805 watt-hours per litre, performance levels that exceed those of many conventional lithium-ion batteries currently used in commercial applications.

The findings have attracted attention because battery energy density remains one of the most important metrics in evaluating next-generation energy storage technologies. Battery energy density determines how much energy can be stored for a given weight or volume. It is particularly important in applications where weight is a critical constraint, such as electric aircraft, drones, robotics and high-performance electric vehicles.

According to Donut Lab, VTT measured the battery cell by first determining its mass and dimensions before fully charging and discharging the cell under controlled laboratory conditions. The resulting energy output was then divided by the battery’s weight and volume to calculate gravimetric and volumetric energy density.

“These tests were fairly straightforward because energy density consists of two things: how much energy a battery cell holds and how much it weighs or how much space it occupies,” said Donut Lab chief technology officer Ville Piippo.

The company states that the tested cell used the same underlying chemistry as batteries assessed in earlier VTT evaluations but had undergone energy-optimisation improvements as part of ongoing development. If such performance can be replicated consistently at industrial scale, the implications could extend across multiple industries seeking lighter and more capable battery systems.

Canada takes an interest

Although Donut Lab is based in Finland, the findings could have particular relevance for Canada. Canada has emerged as a significant player in the global battery supply chain. The country possesses substantial reserves of critical battery minerals, including lithium, nickel, cobalt and graphite, while governments at both federal and provincial levels have invested heavily in attracting battery manufacturing and electric vehicle production.

Canadian battery-sector growth has accelerated alongside investments from major manufacturers and increasing demand for electric transportation. Higher-energy-density batteries could strengthen sectors that are particularly important to the Canadian economy, including electric transportation, mining equipment, aerospace systems, remote power applications and energy storage for renewable electricity generation. The country’s growing drone sector could also benefit. Long distances, difficult terrain and harsh weather often make Canada an attractive environment for testing and deploying advanced unmanned aerial systems. Improved battery performance directly translates into greater operational range and payload capacity.

As an example of the opportunities available, a key element of Donut Lab’s announcement concerns the architecture of its next-generation battery cells. The company recently engaged the international testing and certification organisation Intertek to independently examine the construction of its latest cells. According to Donut Lab, Intertek confirmed that the cells use what is known as a bipolar structure.

In conventional battery packs, individual cells are connected externally to increase voltage. In a bipolar architecture, multiple electrochemical layers are connected in series within a single cell, creating higher voltage internally rather than through external wiring.

According to Piippo, such designs are only feasible using solid electrolytes. “A bipolar cell structure is possible only with a solid electrolyte,” Piippo explained. “Any liquid would seep between the layers and allow ions to flow to the wrong places.”

The company argues that this provides independent confirmation that the batteries are genuinely solid-state devices rather than modified versions of conventional lithium-ion batteries.

Moving to the solid state

Solid-state batteries have long been viewed as one of the most promising successors to traditional lithium-ion technology. Unlike conventional cells, which use liquid electrolytes to transport ions between electrodes, solid-state batteries employ solid materials. The approach offers several theoretical advantages.

These include improved energy density, reduced fire risk, longer lifespan and the possibility of simpler battery pack designs. For years, however, commercialisation has proven elusive. Numerous battery developers have announced promising laboratory results, only to discover significant challenges when attempting large-scale manufacturing.

This explains why independent verification remains important. While performance claims frequently attract attention, third-party confirmation carries greater credibility among manufacturers, investors and regulators.

Beyond energy density and architecture, battery safety remains one of the industry’s most closely watched issues. Lithium-ion battery failures can result in thermal runaway, a chain reaction in which overheating spreads rapidly through a cell and can cause smoke, fire or explosion. To examine safety performance, Intertek conducted a nail penetration test on Donut Lab’s battery cells.

The test involved driving a steel nail through a fully charged battery and leaving it embedded inside the cell for an hour. Such tests are designed to simulate severe internal damage and create a worst-case short-circuit scenario.

According to Donut Lab, the cell remained stable throughout the test period. “The nail penetration test proves in its simplicity that our battery is very safe,” said Piippo. The company argues that safer cells could allow manufacturers to simplify battery-pack construction, reducing cost and weight while improving overall system efficiency.

Donut Lab is positioning its technology as a platform rather than a single battery product.bAccording to chief executive Marko Lehtimäki, the company is working on battery variants tailored to specific customer requirements rather than pursuing a one-size-fits-all design. Potential applications include electric vehicles, drones, robotics, battery energy storage systems, marine equipment and aerospace technologies. This approach mirrors a broader trend across the energy-storage industry, where developers increasingly optimise batteries for particular operating environments rather than relying on universal designs. For example, batteries intended for grid storage may prioritise durability and cycle life, while those used in aviation applications place greater emphasis on weight reduction and energy density.