Finnish startup Donut Lab has released the findings of its third independent test, a crucial evaluation aimed at settling questions about whether its claimed all-solid-state battery is, in fact, a supercapacitor.
Addressing Supercapacitor Doubts
The latest test, conducted by the VTT Technical Research Centre of Finland, specifically investigated the device’s self-discharge characteristics. This follows scrutiny after Donut Lab unveiled its battery in January, presenting specifications that significantly surprised industry observers.
Unpacking the Claims and Concerns
At the Consumer Electronics Show, Donut Lab asserted an energy density of 400 watt-hours per kilogram, a lifespan of 100,000 cycles, and a charging time of approximately five minutes. These claims positioned the startup as a potential leader in the highly competitive solid-state battery race.
However, concerns arose due to links between Donut Lab and Nordic Nano, a company that had previously developed a supercapacitor with an identical energy density figure for renewable energy applications. Although this information was reportedly removed from Nordic Nano’s website, it fueled skepticism within the industry.
The Fundamental Difference: Batteries vs. Supercapacitors
Understanding the distinction between batteries and supercapacitors is key to evaluating Donut Lab’s latest test. Both technologies store energy, but their mechanisms differ significantly.
Batteries store energy through chemical reactions within the cell. This process allows them to retain charge effectively over extended periods.
Supercapacitors, on the other hand, store energy in an electric field. This enables extremely rapid charging and discharging cycles but typically results in a much faster loss of stored energy when the device is idle.
Donut Lab’s Self-Discharge Test Results
To demonstrate its device’s behavior, Donut Lab subjected the cell to a rigorous self-discharge test. Researchers charged the cell to 50% of its capacity and then left it for 240 hours, simulating a period of inactivity.
Following this 240-hour idle period, the cell was re-examined. The results indicated a minimal voltage drop, with the cell retaining nearly 98% of the energy initially stored. This performance aligns with the characteristics of a battery, not a supercapacitor.
Expert Opinion and Lingering Questions
Professor Emeritus of Materials Chemistry at the Massachusetts Institute of Technology, Donald R. Sadoway, commented on the findings. He stated, “Super capacitors can give great power bursts but only for a short time duration.”
Sadoway’s assessment suggested that Donut Lab’s battery does not exhibit the typical traits of a supercapacitor based on this specific test. However, he also cautioned against fully endorsing the company’s broader claims.
He noted that the provided report was “too generic” and lacked the comprehensive detail required to substantiate Donut Lab’s extraordinary breakthrough assertions.
Previous Test Findings and Industry Skepticism
Donut Lab has been releasing test results incrementally each week. The previous tests focused on fast charging and high-temperature performance.
The first test aimed to prove the cell could charge fully in under ten minutes, a claim it reportedly met. The second test evaluated its performance at temperatures up to 100 degrees Celsius (212 degrees Fahrenheit), which the battery also passed in laboratory conditions for a limited number of cycles.
Despite these individual test successes, battery scientists have expressed ongoing skepticism. They emphasize that lab-scale results, particularly for a limited number of cycles, do not necessarily translate to real-world viability.
The consensus among many experts is that for a solid-state battery technology to be considered credible, it must demonstrate consistent performance at the pack level over thousands of cycles.
The Need for Robust Evidence
Professor Sadoway reiterated the need for more substantial proof, stating, “The report is too vague to be considered credible. Remarkable claims demand remarkable proof.”
The ongoing series of tests by Donut Lab aims to build confidence, but the industry awaits more comprehensive data that definitively proves the solid-state nature of the battery and its suitability for widespread adoption.