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VTT Test Finds Donut Lab Solid-State Cell Gains Capacity at 80 to 100°C, Raising Packaging Questions

Independent reports confirm select performance while core promises on energy density and cycle life remain unproven.

Overview

  • The VTT report shows a 26 Ah, 94 Wh pouch cell delivered 110.5% of its room‑temperature capacity at 80°C (1C) and 107.1% at 100°C (0.5C), then recharged normally.
  • After the 100°C run, VTT observed the pouch had lost its vacuum, highlighting unresolved durability and sealing questions even as the cell continued to function.
  • A prior VTT test validated rapid charging from 0 to 80% in roughly 4.5 minutes at 11C on the same cell, confirming ultra‑fast‑charge capability under controlled lab conditions.
  • Key claims remain unverified: the report omits cell weight needed to corroborate 400 Wh/kg, no independent data support a 100,000‑cycle life, and cold‑temperature and cost assertions are still untested.
  • Donut Lab is releasing third‑party results roughly weekly to address skepticism, and analysts note the strong high‑heat performance is consistent with expected solid‑state electrolyte behavior.