Summary

Factorial Energy is a Cambridge, Massachusetts-based startup developing two solid-state battery platforms: FEST® (Factorial Electrolyte System Technology), a semi-solid/quasi-solid hybrid electrolyte platform validated at 375 Wh/kg with Stellantis; and Solstice™, a fully all-solid-state sulfide-based platform targeting up to 450 Wh/kg, developed in partnership with Mercedes-Benz using a dry cathode process. The company has JDAs with Stellantis, Mercedes-Benz, Hyundai, and Kia, and is expanding into drones and robotics. A SPAC merger with Cartesian Growth Corporation III is expected to close mid-2026, listing Factorial on Nasdaq (ticker: FAC) with ~$1.1B pre-money valuation.

Key Facts

  • Founded: 2019
  • HQ: Cambridge, MA, USA
  • Type: Private (SPAC merger filing in progress as of 2026)
  • Stage: Pre-IPO; $75M from Stellantis (2021); approximately $1.1B pre-money valuation at SPAC filing
  • Technology Platform 1: FEST® — semi-solid (quasi-solid/gel hybrid) electrolyte; 375 Wh/kg validated; Stellantis primary partner
  • Technology Platform 2: Solstice™ — fully all-solid-state (sulfide-based electrolyte, dry cathode process); up to 450 Wh/kg claimed; Mercedes-Benz primary partner; operation to 90°C
  • Cell format: Large-format (77 Ah validated for FEST®); designed for automotive pouch cells
  • Validated energy density (FEST®): 375 Wh/kg (77 Ah FEST® cells, Stellantis validation, 2025); 390+ Wh/kg in subsequent cells
  • Validated charge rate: 15% to 90% SoC in 18 minutes at room temperature (4C+)
  • Operating range (FEST®): −30°C to 45°C; Solstice™ rated to 90°C
  • Manufacturing compatibility: ~80% compatible with existing Li-ion production equipment (FEST®); Solstice™ uses dry cathode process with Philenergy equipment partner
  • Cycle life (validated): 600+ cycles in automotive qualification testing (2025); full automotive cycle target ongoing
  • Key partners: Stellantis (FEST®), Mercedes-Benz (Solstice™), Hyundai Motor Company, Kia, Karma Automotive, IQT, POSCO Future M, Philenergy (manufacturing equipment, Feb 2026 MOU)
  • IPO plan: SPAC merger with Cartesian Growth Corporation III; Nasdaq listing (ticker: FAC); ~$1.1B pre-money valuation; expected mid-2026

What It Is / How It Works

FEST® is a semi-solid or quasi-solid electrolyte — sometimes called a gel or hybrid electrolyte — positioned between conventional liquid electrolytes and fully solid ceramics. This design targets the core tradeoff in the solid-state space: fully solid electrolytes offer the best safety profile but are difficult to manufacture and exhibit high interface resistance; liquid electrolytes process easily but are flammable and limit the cell to graphite anodes.

Factorial’s approach uses the FEST® material to enable a lithium metal anode (which stores roughly 10× more energy per gram than graphite) while remaining processable enough to run on equipment already deployed in conventional lithium-ion factories. The company claims approximately 80% compatibility with existing Li-ion manufacturing tooling, which significantly reduces the capital expenditure and learning curve required for OEM partners to validate and eventually produce the cells.

In 2025, Stellantis validated the 77 Ah FEST® cell format in an automotive-relevant large-format pouch. Key confirmed specs: 375 Wh/kg energy density, 18-minute 15–90% charge at room temperature, operation across −30°C to 45°C, and more than 600 cycles of progress toward full automotive qualification (typically 1,000+ cycles). The cells are also rated for up to 4C discharge.

In early 2026, Factorial began pursuing adjacent markets beyond automotive, partnering with IQT (In-Q-Tel, the CIA’s strategic investment arm) and POSCO Future M (a major South Korean materials supplier) to adapt the FEST® platform for drone and robotics applications, where energy density and fast-charge are similarly high-value.

Solstice™ — Second Platform: Alongside FEST®, Factorial is developing Solstice™, a fully all-solid-state design using a sulfide-based electrolyte and a dry cathode manufacturing process. Announced in partnership with Mercedes-Benz, Solstice™ claims up to 450 Wh/kg energy density (approximately 80% higher than conventional Li-ion) and stable operation above 90°C. The use of a dry cathode process — eliminating the NMP solvent used in conventional wet cathode manufacturing — is a manufacturing efficiency and environmental advantage. In February 2026, Factorial signed an MOU with Philenergy, a South Korean battery equipment and manufacturing infrastructure provider, to evaluate integrating Philenergy’s automated precision assembly systems with Solstice™ cell designs.

A demo fleet of Stellantis Dodge Charger Daytona vehicles equipped with FEST® cells is planned for 2026. Karma Automotive validated the cells for its upcoming Kaveya EV (targeting late 2027 launch), which promises 250+ miles of range and 0–60 mph in under 3 seconds.

Notable Developments

  • 2026-03: Factorial announces partnerships with IQT and POSCO Future M to expand FEST® platform into drones and robotics. (BusinessWire)
  • 2026-03-02: Electrive reports Factorial is evaluating Philenergy production technology for solid-state manufacturing scale-up (Electrive)
  • 2026-02-26: Factorial and Philenergy sign MOU for strategic manufacturing collaboration on Solstice™ platform; Philenergy brings automated laser notching, precision stacking, and modular production infrastructure. (BusinessWire)
  • 2026-02: Karma Automotive independently validates FEST® cells for the Kaveya EV. (Electrive)
  • 2026: SPAC merger with Cartesian Growth Corporation III announced; Nasdaq listing (ticker: FAC) expected mid-2026; ~$1.1B pre-money valuation; $100M to fund growth.
  • 2026: Stellantis Dodge Charger Daytona demonstration fleet planned with FEST® cells.
  • 2025: Stellantis validates 77 Ah FEST® cell at 375 Wh/kg, 15–90% in 18 min; 600+ cycles in qualification testing. (Stellantis)
  • 2025: POSCO Future M partnership announced for cathode and anode materials development.
  • 2021: $75 million strategic investment from Stellantis; joint development agreements in place with Mercedes-Benz, Hyundai, and Kia.
  • 2019: Founded in Cambridge, MA by Siyu Huang and others.

Key People

Siyu Huang — CEO and Co-Founder

  • LinkedIn: linkedin.com/in/siyu-huang-6b126412
  • Role: CEO, leads technology strategy and OEM partnerships
  • Education: Uppsala University (chemistry) → Cornell University (PhD Chemistry, 2012; MBA)
  • Career (reverse-chronological):
    • Factorial Energy / Lionano (2013–present): co-founded Lionano as a Cornell spinout; rebranded to Factorial Energy in April 2021; CEO throughout
    • Johnson & Johnson (approx. 2012–2013): Marketing Leadership Development Program
  • Notes: Cornell connection shared with CTO Alex Yu (both PhD Cornell chemistry; both had Uppsala University affiliations before Cornell). The technology originated in Héctor Abruña’s Cornell electrochemistry lab.

Alex Yu — CTO and Co-Founder

  • LinkedIn: linkedin.com/in/alex-yu-96703719
  • Role: CTO; co-founded Lionano/Factorial; holds key battery technology patents
  • Education: Xiamen University (BS Chemistry) → Uppsala University (thesis, Photochemistry) → Cornell University (PhD Chemistry, 2014)
  • Career (reverse-chronological):
    • Factorial Energy (May 2022–present): CTO; also served as President 2020–2022
    • Lionano SE Inc. (2019–2020): CEO
    • Lionano Inc. (2013–2019): CEO / co-founder
  • Notes: ⚑ Shared background: Both Siyu Huang and Alex Yu completed work at Uppsala University and earned PhDs in chemistry from Cornell before co-founding the company together.

Note on Randall Fong: The existing entry listed “Randall Fong — CTO and co-founder.” Research does not confirm this attribution. The publicly documented CTO and co-founder is Alex Yu. The entry has been corrected.

People — Last Reviewed: 2026-03-24

Supply Chain Position

Factorial Energy operates at the Cell Manufacturing layer of the battery supply chain, producing FEST® semi-solid electrolyte cells in-house. Upstream, the company relies on POSCO Future M for cathode and anode materials (MOU December 2025) and on commodity lithium sourced through its materials partners. Downstream customers include Stellantis (validated partner, $75M investor), Mercedes-Benz, Hyundai, Kia, Karma Automotive, and IQT (defense/drones). ⚑ Shared supplier: POSCO Future M supplies or is negotiating to supply both Factorial Energy and Samsung SDI (which is the cell manufacturing partner for Solid Power), creating an indirect materials supply overlap between the two companies.

Claim Verification

Claim: 375 Wh/kg energy density (77 Ah FEST® cells)

Status: Verified (third-party automotive validation)

Supporting sources:

Refuting / questioning sources: None identified for the 375 Wh/kg figure specifically.

Summary: Energy density is the best-validated claim, confirmed by Stellantis in an automotive-grade large-format cell context.

Claim: 15–90% charge in 18 minutes at room temperature

Status: Verified (Stellantis validation)

Supporting sources:

Refuting / questioning sources: None identified.

Summary: Charging performance confirmed by an independent OEM partner.

Claim: ~80% compatibility with existing Li-ion manufacturing equipment

Status: Partially verified

Supporting sources:

Refuting / questioning sources:

  • No independent manufacturing audit has been published confirming the 80% figure at production scale; the claim is plausible given the gel/semi-solid approach but should be considered unverified until a production ramp is demonstrated.

Summary: Directionally credible given the semi-solid electrolyte approach; not independently verified at manufacturing scale.

Sources