QuantumScape has not published cycle life, safety and energy density results from the same battery cell

Three results, three different cells

A solid state battery replaces the liquid chemical inside a normal lithium ion battery with a solid material, which can pack more energy into the same space and resist fire better. QuantumScape, a company building this kind of battery for electric cars, has published 3 separate test results since January 2024, a cycle life test, a safety test and an energy density measurement, how much energy a battery packs into its size and weight, and each one used a different cell design. None of the 5 sources for this article reports cycle life, safety and energy density from the same cell.

A cell matching the planned design completed 1,000 cycles

Charge cycles count how many times a battery can be charged and drained before it wears out. Volkswagen battery unit PowerCo tested a 24 layer QuantumScape cell at its laboratory in Salzgitter, Germany, and reported the cell completed more than 1,000 charge cycles while keeping 95% of its capacity. QuantumScape says this 24 layer design already matches its planned production cell. PowerCo states the industry standard for this stage is 700 cycles and a maximum capacity loss of 20%, so the tested cell beat both figures. PowerCo and QuantumScape say that cycle count matches more than half a million kilometres of driving for a car with a 500 to 600 kilometre range. Jagdeep Singh, founder and chief executive officer of QuantumScape, said this in the release.

These results from the Volkswagen Group's PowerCo testing make clear that QuantumScape's anodeless solid-state lithium-metal cells are capable of exceptional performance.

Jagdeep Singh, founder and chief executive officer of QuantumScape. Source 3.

A different cell passed safety tests

QuantumScape tested a second, separate 24 layer cell for safety, and states plainly that it is a prototype on the way to its QSE 5 design, not the final version. The results are graded on a hazard level scale that runs from Hazard Level 0, meaning no reaction, to Hazard Level 7, an explosion, and QuantumScape states that Hazard Level 4 or lower typically counts as a passing result for an electric vehicle cell. In a nail penetration test, the prototype scored Hazard Level 2. Heated to 300 degrees Celsius, it scored Hazard Level 3, meaning only minor gas venting. QuantumScape compares this with a conventional lithium ion cell, which it says reaches Hazard Level 6, a fire, at about 184 degrees Celsius.

The commercial cell was measured only for energy density

In October 2024, QuantumScape measured its QSE 5 B sample, the cell on its commercial product track, at 844 watt hours per litre and 301 watt hours per kilogram. The cell operates below 3.4 atmospheres of pressure applied by the pack around it. QuantumScape did not state a layer count or a cycle count for this cell. An independent, peer reviewed perspective on the industry names high pressure as a barrier for this kind of battery in general, without giving a number for QuantumScape specifically.

What it took to reach this point

Tim Holme, chief technology officer of QuantumScape, told a science writer that the company spent 5 years and 100 million dollars choosing the solid material for its battery, then another 5 years and 200 million dollars building prototypes to send to car companies for evaluation, running more than 2,000,000 tests.

Making a battery that's better than lithium-ion is really hard.

Tim Holme, chief technology officer of QuantumScape. Source 5.