In its Q2 letter to shareholders, solid-state battery company QuantumScape reported successfully building and testing ts first prototype 24-layer cells. The 24-layer cells show similar early capacity retention behavior to the company’s earlier single-, four-, 10- and 16-layer cells.

This is an important result because, as we have previously indicated, 24-layer cells represent A-sample candidates for some automotive OEMs. While the precise definition of an A sample will vary by customer, delivering any such cell to an automotive customer is a high bar and remains one of our key goals for the year. Doing so requires that we make cells with sufficient performance and quality to meet our standards, and in sufficient quantities to complete our validation process and ship to a customer.

… Delivery of the A sample represents the beginning of the automotive qualification process, which involves several major delivery milestones—A, B and C samples—followed by the start of production. Each major sampling stage may consist of several generations of increasingly mature prototypes. We are currently targeting approximately 18 months between the A sample and prototype B-sample cells, which may use some low-volume processes. We anticipate a similar timeframe to go from B samples to C samples. Of course, these timelines involve uncertainty and will be influenced by a number of factors, including product and process development risks; the specification, ordering, and qualification of production tooling; other supply chain dynamics; and OEM validation timeframes.

—Letter to shareholders

Despite encountering challenges related to the quality and throughput of the production processes, the company said, it has made progress with the 24-layer cells.

The prototype cells were packaged in a variety of formats, including early variants of QuantumScape’s proprietary format under development which is designed to accommodate the expansion and contraction characteristic of Li-metal batteries during charge and dischage that results from plating and stripping of lithium metal.

The company also reported advances in separator manufacturing and the implementation of its second- generation catholyte.

• QuantumScape’s change to the separator manufacturing process results in higher uniformity, which is to result in better performance, reliability and scalability

• The second-generation catholyte has a set of properties that offers better low-pressure performance, improved low-temperature behavior, better high-rate support, and improved cell reliability compared to the first-generation catholyte. Cells made with this catholyte are also capable of discharging at ultralow temperatures of -30 °C with good capacity retention.