VoltStorage GmbH was a Munich-based developer of long-duration energy storage systems. The company was founded in 2016 by Jakob Bitner, Michael Peither and Felix Kiefl as a spin-off from the Technical University of Munich. It initially developed vanadium redox flow batteries, first as solar storage for private homes and later for commercial and agricultural customers. Its Iron Salt Battery was designed as a low-cost, non-flammable and long-lasting storage technology based on iron and salt, intended to provide base-load capacity for wind and solar farms.

VoltStorage received funding from SOSV, Korys, Bayern Kapital, EIT InnoEnergy, Energie360° and business angels, including a €6M round in 2020 and a €24M Series C led by Cummins in 2022. In 2023 the European Investment Bank provided a €30M venture debt loan, backed by the InnovFin Energy Demonstration Projects facility, to co-finance development and a new factory. In 2023 the company published a patent on its iron-salt battery health management system, and in 2024 it announced research into using industrial waste as an electrolyte component and a cooperation with ACWA Power on renewable energy for critical infrastructure in the Middle East and Africa. The company planned to bring the Iron Salt Battery to utility scale from 2025 onwards.

Volker Schulte was appointed CEO in September 2024, succeeding co-founder Jakob Bitner. VoltStorage ceased operations in August 2025 and entered insolvency administration. In February 2026 ESS Tech acquired the company's assets and intellectual property, combining two iron-based flow battery technologies.