VTT Verifies Ultra-Fast Charging on Donut Lab Solid-State Cell, Notes Heat Constraints

Overview

• VTT measured the cell reaching 80% in about 4.5–5 minutes at 11C and 100% in just over seven minutes.
• At 5C, the cell reached 80% in roughly 9.5 minutes and 100% in 12–13.5 minutes with full usable energy recovered.
• Usable-capacity retention remained high, with 100% available after 5C charges and 98.4–99.6% after 11C charges in subsequent discharges.
• Thermal limits emerged under passive cooling, with one‑sided cooling hitting ~90 °C and forcing an interruption, while two‑sided cooling kept peaks lower (about 63 °C at 11C).
• The VTT document is a customer‑defined test on a single Donut‑provided cell released as part of a staged campaign, and it does not yet address cycle life, module or pack behavior, or manufacturability; industry skepticism and external design theories remain unconfirmed.