QuantumScape’s new solid-state battery lasted 1000 charge cycles, but its biggest achievement lies elsewhere
US battery technology developer QuantumScape has unveiled its Osprey solid-state battery platform, with a test cell retaining approximately 80% of its original capacity after 1000 full charge-discharge cycles. More importantly, the battery operated under an external pressure of just one atmosphere. This could help solve one of the toughest problems facing solid-state batteries: the need for heavy, costly pressure-maintaining structures.
A solid-state battery with no liquid electrolyte
Osprey combines the company’s ceramic separator, an anode-free design and a cathode incorporating a sulphide-based solid electrolyte.
Unlike the earlier QSE platform, the new design does not use a liquid electrolyte in the cathode. This makes Osprey an all-solid-state battery cell.
The anode-free design means there is no separate lithium-metal anode when the battery is manufactured. During the first charge, metallic lithium deposits on the surface of the ceramic separator, forming the layer needed to store energy.
This approach allows material use to be reduced and energy density to be increased. However, uneven lithium deposition and maintaining contact between solid materials remain challenges.
Sulphide-based electrolytes conduct lithium ions well, but many existing designs require high external pressure. This makes the battery pack’s structure heavier and more complex.
1000 cycles without a substantial pressure-maintaining structure
QuantumScape tested a two-layer battery cell with a cathode measuring 50 × 65 mm.
At 30 °C and under an external pressure of one atmosphere, the cell completed 1000 full charge-discharge cycles. The charge and discharge rate was 1C, and the cathode’s areal capacity was 5.5 mAh/cm².
By the end of the test, the cell retained approximately 80% of its original capacity.
By comparison, some sulphide-based solid-state batteries require pressures of tens of atmospheres. In a large battery pack, this would mean significant additional weight.
Osprey’s result points to a way of overcoming this limitation.
However, the size of the test cell must be taken into account. Its capacity was approximately 0.3–0.4 Ah, whereas QuantumScape’s earlier QSE-5 cell has a capacity of around 5 Ah.
The company has therefore demonstrated that the technology works in a small laboratory cell, not yet in an electric vehicle battery suitable for mass production.
Five-minute charging required a temperature of 80 °C
QuantumScape also presented other impressive results.
According to the manufacturer, Osprey was able to increase the battery’s state of charge from 10% to 80% in five minutes. However, the test took place at 80 °C, above the normal operating temperature of a typical electric vehicle battery.
The company also demonstrated the battery operating at -20 °C. In this test, a small single-layer cell retained approximately 68% of the capacity measured at room temperature. The test used a relatively low discharge current.
QuantumScape projects an energy density of up to 1100 Wh/l for Osprey. However, this figure has not yet been achieved in a completed large-format cell.
By comparison, the company’s QSE-5 test cell has a volumetric energy density of approximately 844 Wh/l.
Assessing Osprey’s results therefore requires a distinction between three things: measured durability, charging speed achieved under special conditions and a projection of future energy density.
Volkswagen partnership gives QuantumScape an advantage
One of QuantumScape’s most important partners is PowerCo, the Volkswagen Group’s battery company.
The partnership aims to bring the company’s solid-state battery technology into large-scale production. QuantumScape is also developing the QSE-5 platform and preparing to license its technology to other battery manufacturers.
Osprey opens up an additional business opportunity. Partners can use QuantumScape’s ceramic separator with their own sulphide-based cathodes without having to redesign the entire battery chemistry.
This could give QuantumScape a greater role as a technology supplier, rather than solely a battery cell developer.
Competition is strong, however. Toyota, Samsung SDI, BYD and several other companies are also developing solid-state batteries. Their main challenge is no longer simply achieving high energy density, but ensuring stable, economically viable mass production.
Production readiness is decisive for electric vehicles
A solid-state battery requiring less pressure could offer significant advantages for the European automotive industry.
If a battery pack does not need a bulky pressure mechanism, its structural weight can be reduced and space freed up for additional cells. This could potentially improve both range and energy density.
However, 1000 charge cycles alone are not enough. Carmakers need evidence of large-format cells’ durability, safety, fast-charging performance and reliability at different temperatures.
QuantumScape has not yet announced when mass production of Osprey will begin.
Osprey’s greatest achievement is therefore not retaining 80% capacity after 1000 cycles, but achieving that result under low external pressure. If the company can maintain the same characteristic in larger battery cells, it could remove a significant obstacle to bringing solid-state batteries into electric vehicles.
For now, this is a promising laboratory result that will still require substantial development work to become a competitive industrial product.
