---
schema_version: "secwatch.filing_event.v1"
accession: "0001628280-25-058583"
form_type: "8-K"
ticker: "EOSE"
cik: "0001805077"
company_name: "Eos Energy Enterprises, Inc."
filed_at: "2025-12-22T23:59:59+00:00"
generated_at: "2026-05-16T12:26:10.847505+00:00"
event_type: "leadership"
sentiment: "neutral"
materiality_score: 0.35
calibrated_materiality_score: 0.35
confidence: "high"
source: SEC EDGAR
---

# Eos Energy board chair Stidolph resigns; Joseph Nigro appointed successor

## Summary
- Russell Stidolph resigns from Board effective Dec 31, 2025, to focus on AltEnergy Acquisition Corp.
- Joseph Nigro to become non-executive Chair effective Jan 1, 2026.
- Nigro previously served as CFO of Exelon and CEO of Constellation; joined Eos Board in early 2025.
- Stidolph had been non-executive Chair since April 2018 and invested through AltEnergy for 11 years.

## SEC filing metadata
- accession: 0001628280-25-058583
- form_type: 8-K
- ticker: EOSE
- cik: 0001805077
- company_name: Eos Energy Enterprises, Inc.
- filed_at: 2025-12-22T23:59:59+00:00
- event_type: leadership
- sentiment: neutral
- materiality_score: 0.35
- calibrated_materiality_score: 0.35
- confidence: high
- sec_items: 5.02, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1805077/000162828025058583/0001628280-25-058583-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1805077/000162828025058583/eose-20251222.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001628280-25-058583
- JSON: https://secwatch.observer/filing/0001628280-25-058583.json
- Plain text: https://secwatch.observer/filing/0001628280-25-058583.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.