What is a Molten Salt Battery?
A molten salt battery (MSB) is a high-temperature energy storage system that uses molten (liquid) salts as the electrolyte. These salts become electrically conductive when heated above their melting point, typically between 200°C and 600°C depending on the chemistry. MSBs have a metal anode (like sodium or calcium), a salt-based electrolyte, and a metal or salt cathode (such as sulfur or antimony) separated by a solid ceramic electrolyte like beta-alumina.
What sets MSBs apart is their ability to do large scale, long duration energy storage with low material cost, high thermal stability and minimal fire risk. Originally developed for space and military applications, MSBs are now getting commercial traction as grid scale alternatives to lithium-ion batteries.
Why 2025-2030 is the Tipping Point
The push for decarbonization has increased the demand for energy storage systems that can go beyond lithium-ion limitations. Between 2025 and 2030 molten salt battery (MSB) technologies will be the backbone of long duration energy storage (LDES) as renewables like solar and wind expand across the globe.
Global LDES is forecast to grow at over 24% CAGR, molten salt solutions will offer the best 6-24 hour storage duration. Notably MIT published a prototype MSB with a cell cost of $9/kWh in 2024 vs $120/kWh for standard lithium-ion batteries. Market drivers include lithium supply constraints, increased wildfire related battery safety standards and national storage mandates in the US, EU, India and beyond.
From Sodium-Sulfur to Calcium-Antimony: A Quick Chemistry Primer
Molten salt batteries operate at high temperatures where their salt based electrolytes become conductive liquids. These batteries have metal anodes and solid or molten catholytes separated by beta-alumina solid electrolytes (BASE).
| Generation | Operating Temp (°C) | Anode | Cathode / Catholyte | Cycle Life | Commercial Status |
| Na-S (1st Gen) | 300-350 | Na | S | 2,500 | Deployed (Japan) |
| Na-NiCl₂ (ZEBRA) | 260-300 | Na | NiCl₂ + NaAlCl₄ | 4,000 | Bus fleets |
| Ca-Sb (Ambri) | 500 | Ca | Sb | >10,000 | Pilots (2025 launch) |
| Low-T hybrid salts | ≤200 | Na | Mixed halides | In lab | Experimental |
MSBs leverage BASE membranes to allow selective sodium-ion transport. Corrosion resistance, thermal management, and electrode stability remain ongoing challenges.
Molten Salt Battery vs Lithium-Ion: Which Energy Storage Tech Wins in 2025?
When comparing molten salt batteries (MSBs) with lithium-ion batteries (Li-ion), the key differences revolve around cost, safety, duration, and scalability.
| Feature | Molten Salt Battery | Lithium-Ion Battery |
| Operating Temperature | 200-600°C | 15-60°C |
| Energy Density | Lower (80-120 Wh/kg) | Higher (150-250 Wh/kg) |
| Safety | Non-flammable | Fire risk under stress |
| Duration | 6 to 24+ hours | 1 to 4 hours typical |
| Cost | $9-$50/kWh (projected) | $100-$200/kWh (current) |
| Scalability | Ideal for grid-scale | Ideal for mobile devices/EVs |
Winner? For grid-scale storage and long-duration power needs, MSBs outperform Li-ion on cost, fire safety, and thermal stability. However, Li-ion remains the best fit for portable and short-duration applications.
Market & Policy Tailwinds (2025-2030)
- U.S. Inflation Reduction Act (IRA) and EU Net-Zero Industry Act provide 30-50% capex subsidies.
- Curtailment of renewables is rising; in California alone, over 2 TWh of solar was curtailed in 2023.
- Storage mandates: U.S. targets 90 GW by 2035, India aims for 50 GW by 2030.
- Flammability concerns are steering utilities away from Li-ion toward thermally stable MSBs.
- Commercial buyers now demand 24/7 clean energy, requiring 10- to 12-hour storage systems.
Six Breakthrough Innovations to Watch
| Innovation | Details | Status |
| Low-Temp Molten Salts | Use of mixed metal halides to lower operating temps below 200°C, allowing cheaper containment materials. | Lab-stage |
| Ceramic BASE Membranes | Reinforced with yttria-stabilized zirconia to reduce Na+ crossover and increase lifetime. | Pilots |
| AI Thermal Monitoring | Predictive ML algorithms detect seal failures 2 hours in advance using thermal/impedance data. | 1 MW demo in test |
| Gigafactory-Scale Assembly | Ambri and BASF planning 1 GW/year lines with 18% learning curve cost declines. | FID expected 2026 |
| Heat + Power Modules | Danish pilot integrates 600°C thermal output for industrial use alongside electricity generation. | 100 MWh demo by 2025 |
| Self-Healing Gaskets | Alkali-resistant, nano-coated sealants reduce maintenance needs and extend stack life to 20 years. | In prototype stage |
Economics: Levelized Cost of Storage Outlook
- 2024: Li-ion LCOS = $0.14-$0.18/kWh-cycle; MSB demo = $0.03-$0.06/kWh-cycle
- 2030 projection: With a learning rate of 18% and scaling to 5 GWh, MSBs could reach $0.02/kWh-cycle
A typical MSB system also benefits from:
- High round-trip efficiency (75-85%)
- Non-flammable operation (lower insurance & safety costs)
- Modular design suitable for both grid and industrial co-gen applications
Deployments & Case Studies
- Ambri & Xcel Energy (Minnesota, USA): 1 MW / 4 MWh pilot focuses on multi-day thermal cycling and degradation studies.
- Reliance Industries (India): Building a 150 MWh solar-integrated salt battery plant near Gujarat.
- Nordic Heat Battery (Denmark): Using MSB-derived tech for 10-hour heat storage powering 100,000 homes via district heating.
Image source : sulzer.com
Denmark’s Gigawatt-Scale Molten Salt Battery: A Turning Point in Thermal Storage
In 2024, Denmark unveiled one of the world’s most ambitious molten salt battery (MSB) projects—a 1 GWh thermal energy storage system in the coastal city of Esbjerg. Developed by Danish startup Hyme Energy in partnership with Swiss engineering giant Sulzer, this facility demonstrates how high-temperature salt-based systems can scale up to meet both grid and industrial energy demands.
Key Highlights:
- Storage Capacity: 1 GWh, enough to power approximately 100,000 homes for 10 hours.
- Thermal Efficiency: 90% when used for industrial heat; 80–90% in combined heat and power (CHP) mode; ~40% efficiency for electricity-only use.
- Salt Type: The system uses recycled molten hydroxide salts, a byproduct of chlorine manufacturing, making it both cost-effective and sustainable.
- Operating Temperature: ~600 °C, allowing for direct heat delivery to industrial facilities.
Strategic Integration:
The Esbjerg MSB facility not only supports the local electricity grid but also supplies high-grade thermal energy to industrial clients, showcasing the dual-use capabilities of molten salt storage. This is particularly valuable for decarbonizing sectors like food processing, glass manufacturing, and district heating.
One of the first commercial clients is Arla Foods, a major dairy processor. A 200 MWh version of the system under construction in Holstebro will reduce Arla’s reliance on natural gas by 50% and cut energy costs by over €3 million annually.
Global Significance:
This Danish breakthrough underscores how MSBs can help solve two major challenges: long-duration energy storage and industrial heat decarbonization. The project’s use of recycled industrial salts and modular thermal containment also positions it as a replicable model for other high-renewables regions around the world.
With proven efficiency, scalable design, and rapid deployment potential, Denmark’s molten salt battery is more than a pilot—it’s a prototype for the clean-energy systems of the next decade.
Emerging Applications Beyond the Grid
- Industrial Heat: Cement kilns, metal foundries, and glass factories can utilize high-temperature steam (600°C) directly.
- CSP Retrofitting: Many Concentrated Solar Power (CSP) stations can integrate molten salt tanks for dispatchable energy.
- Off-Grid Microgrids: In island nations and remote mines, MSBs can replace diesel generators for reliable overnight storage.
- Space Applications: Radiation-resistant salt chemistries are under investigation for lunar and Martian surface missions.
Technical & Commercial Hurdles
| Challenge | Area | R&D Direction |
| Corrosion & Seal Degradation | Materials | High-entropy alloys & nano-barrier coatings |
| High Start-Up Energy | Operations | Thermal integration with solar waste heat |
| Upfront Capital Costs | Finance | Green bonds & government-backed guarantees |
| Regulatory Gaps | Safety & Policy | UL 1974-MS standard in draft phase (due 2026) |
R&D Pipeline & Funding Landscape
- DOE Storage Innovations 2030: Multi-million dollar grants for next-gen MSB chemistry development.
- Horizon Europe M-SALT 2.0: Funding public-private research consortia.
- Patent filings up 60% in 5 years, WIPO data shows US, China, Germany as hotspots.
Leading labs: MIT Energy Initiative, Helmholtz-Zentrum Berlin, Indian Institute of Science (IISc).
Strategic Recommendations
For Utilities:
- Co-locate MSBs with wind or solar to reduce curtailment and arbitrage prices <1¢/kWh.
For Developers:
- Focus on 8-12 hour storage systems to meet emerging 24/7 PPA demands.
For Policymakers:
- Include MSBs in clean energy tax credits and update safety standards.
Key Data & Glossary
| Term | Meaning |
| BASE | Beta-Alumina Solid Electrolyte |
| LCOS | Levelized Cost of Storage |
| TRL | Technology Readiness Level |
| Catholyte | Liquid or solid compound serving as the cathode in molten salt batteries |
| Round-Trip Efficiency | Ratio of energy output vs input in a charge-discharge cycle |
FAQs
Q1: How safe are molten salt batteries compared to lithium-ion?
A: Much safer due to non-flammable salt electrolytes and sealed metal casings.
Q2: What temperature do MSBs operate at?
A: Traditional ones at 250°C to 550°C. New ones at below 200°C.
Q3: Can MSBs be recycled?
A: Yes, metal components (Ca, Sb, Ni) and salts are easier to reclaim than Li-ion cathodes.
Q4: Who are the major players?
A: Ambri, BASF, Reliance Industries, EnergyNest.
Q5: What is the expected lifespan?
A: Up to 20 years or more with proper thermal cycling and seal maintenance.
Conclusion: Roadmap to 2030
By 2030, molten salt batteries could be a significant part of the global LDES market with:
- Sub-$50/kWh packs
- UL-certified safety standards
- 10 GW installed worldwideMSBs are no longer a niche solution; they are the new cornerstone for decarbonized, resilient energy systems globally. Their characteristics make them perfect for long-duration, high-temperature and heat-and-power applications – they stand out in the crowded storage space.
Meta :
