Smart electrolyte with inherent flame-retardancy for next generation fire-safe lithium-ion batteries.

Project Information

SMARTBATT

Grant agreement ID: 101066532

DOI

10.3030/101066532

Project closed

EC signature date 1 August 2022

Start date 1 June 2023

End date 31 August 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 181 152,96

Coordinated by

FUNDACION IMDEA MATERIALES
Spain

Periodic Reporting for period 1 - SMARTBATT (Smart electrolyte with inherent flame-retardancy for next generation fire-safe lithium-ion batteries.)

Reporting period: 2023-06-01 to 2025-08-31

Summary of the context and overall objectives of the project

(1) Context
As lithium-ion batteries (LIBs) underpin the transition to electrified transport and renewable energy storage, their safety remains a critical bottleneck. Despite technological advancements in energy density and lifecycle, the risk of thermal runaway, a self-accelerating exothermic reaction sequence leading to fire or explosion, still persists. Conventional safety measures such as shutdown separators (e.g. trilayer PP/PE/PP membranes) often fail in practice due to thermal shrinkage at high temperatures (~160 °C), which can cause internal short-circuits and system failure. Moreover, flame-retardant additives often compromise battery performance and increase manufacturing complexity.
This challenge becomes especially urgent in the context of Europe’s Green Deal, the Europe 2020 Strategy, and the BATTERY 2030+ initiative, which emphasize smart, safe, and sustainable battery technologies. The Horizon Europe framework identifies advanced battery safety as a key strategic priority in supporting the growth of electric mobility, grid resilience, and consumer electronics.

(2) Objectives
The SMARTBATT project aims to deliver a next-generation fire-safe lithium-ion battery by developing a smart electrolyte that undergoes a liquid-solid transition (TLST), coupled with inherent flame retardancy. The dual chemical foundation of this innovation lies in:
(i) Diels–Alder reaction chemistry – to trigger an in-situ, thermally activated liquid-to-solid transition and shutdown functionality
The proposed electrolyte remains fully functional under normal conditions but, at elevated temperatures (~100–120 °C), initiates a chemical transformation that:
- Reduces ionic conductivity
- Occludes separator micropores
- Initiates a two-step shutdown (warning phase and a complete shutdown)
(ii) Michael addition chemistry – to incorporate flame-retardant functional groups.

(3) Expected impacts
(i) Scientific and technological impact
- Breakthrough in intrinsic safety: The electrolyte autonomously triggers thermal shutdown without the need for external sensors or control systems.
- Exhibited prerequisite properties: High ionic conductivity (1.18 mS cm⁻¹) and lithium transference number (0.58) required for smooth operation of LIBs, are maintained at room temperature.
- Enhanced interfacial stability: Formation of poly(vinylene carbonate)-rich SEI stabilizes lithium cycling and reduces dendrite formation.
(ii) Economic and industrial impact
- Drop-in compatibility: The electrolyte is readily integrable into existing battery production lines, avoiding costly retooling.
- Low-cost and sustainable precursors: DMFu can be synthesized from biomass, and VC is already commercially used.
- Market-ready applications: EVs, grid storage, military, and consumer electronics will benefit from longer battery life, reduced recalls, and enhanced insurance and regulatory profiles.
(iii) Environmental and societal impact
- Reduced fire risk: Mitigates catastrophic battery failures and associated hazards.
- Green chemistry: Biomass-derived components support sustainability goals.
- Public trust: Promotes safer adoption of battery-powered technologies.

(4) Integration of social sciences and humanities
Although not explicitly framed in SSH terms, the project’s outcomes align with social priorities such as risk perception, public safety, climate responsibility, and sustainable innovation. Interdisciplinary engagement, particularly with regulatory studies and sustainability assessment, could further elucidate:
- Public acceptance of safer LIBs.
- Lifecycle and policy implications
- Socioeconomic analysis of safety-related adoption barriers

(5) Scale and significance
SMARTBATT addresses a pivotal challenge in the global energy transition: how to make LIBs fundamentally safer without sacrificing performance or scalability. Its impacts are projected to span across:
- European battery value chains (aligning with BATTERY 2030+ and Horizon Europe)
- Multinational industries (automotive, aerospace, electronics)
- Millions of end-users, whose safety and confidence in energy storage systems will be substantially improved.

In summary, SMARTBATT sets the foundation for a transformative shift in battery safety, replacing passive safety measures with chemically intelligent mechanisms designed for the next era of sustainable and secure energy technologies.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

(1) Overview of work performed
The SMARTBATT project successfully advanced a novel, thermoresponsive electrolyte system with integrated flame-retardant properties for lithium-ion batteries (LIBs). The scientific and technical activities were structured around a multidisciplinary approach, involving electrochemistry, polymer chemistry, thermal analysis, and materials characterization. The following key tasks were executed:

(2) Electrolyte design and synthesis
(i) A thermoreversible electrolyte formulation was developed using vinylene carbonate (VC) and 2,5-dimethylfuran (DMFu) as the base solvents.
(ii) The design exploited Diels–Alder cycloaddition reactions, triggered above 100 °C, to transform the liquid electrolyte into a high-viscosity, low-conductivity solid-like phase.
(iii) An optimized formulation, LiTFSI0.15DMFu0.8VC1.0,was identified, exhibiting both high room-temperature ionic conductivity and responsive thermal behavior.

(3) Thermal shutdown mechanisms
(i) Solid-state NMR, MALDI-TOF mass spectrometry, and DOSY NMR confirmed the in-situ formation of oligomers via Diels–Alder reactions at elevated temperatures.
(ii) These oligomers were shown to:
- Significantly increase the electrolyte viscosity at 120 °C,
- Occlude the micropores of Celgard PP/PE/PP separators,
- Reduce lithium-ion diffusion and electrolyte conductivity by nearly two orders of magnitude.
(iii) The dual-phase shutdown process was clearly demonstrated:
- Warning phase initiated at ~100 °C
- Complete shutdown occurred at ~120 °C

(4) Electrochemical performance evaluation
(i) Room-temperature ionic conductivity = 1.18 mS/cm
(ii) High Li⁺ transference number = 0.58
(iii) Long-term lithium plating/stripping was achieved in symmetric Li||Li cells.
(iv) Li||LiFePO4 cells showed high initial capacity (~169 mAh/g) with >99.7% Coulombic efficiency and capacity retention of 129 mAh/g after 200 cycles at 0.1C.
(v) A single-layer pouch cell demonstrated successful operation, delivering 0.87 mAh/cm2 capacity after 30 cycles.

(5) Thermal safety validation
(i) At 120 °C, a complete arrest of electrochemical activity was confirmed in both coin and pouch cells with the SMARTBATT electrolyte.
(ii) Electrochemical impedance spectroscopy (EIS) showed a dramatic increase in charge transfer resistance from 132 Ω to 3946 Ω, evidencing shutdown.
(iii) The Celgard separator retained dimensional stability post-shutdown due to protective Diels–Alder oligomer coating, as visualized via SEM.

(6) Benchmarking and control studies
(i) Compared to commercial LP30 electrolyte, the SMARTBATT electrolyte:
- Enabled thermal shutdown at ~120 °C,
- Prevented internal short circuits at elevated temperatures (160–170 °C),
- Offered early-warning functionality prior to complete shutdown

(7) Main scientific and technical achievements
(i) First demonstration of a thermoresponsive electrolyte featuring Diels–Alder-triggered shutdown.
(ii) Demonstrated a two-stage thermal safety mechanism based on reduced lithium-ion transport and blockage of separator pores.
(iii) Pioneered a smart electrolyte that:
- Works under normal conditions without performance compromise,
- Triggers autonomously at thermal thresholds,
- Requires no external sensors or control systems.
(iv) Room-temperature electrochemical performance across half- and full-cell configurations confirmed.
(v) Scalability demonstrated by successful fabrication and testing of practical a single-layered pouch cell.

The SMARTBATT project has delivered a chemically intelligent electrolyte technology capable of mitigating thermal runaway at the molecular level. The key outcomes including the design, proof-of-concept, mechanistic validation, and thermal-electrochemical benchmarking set the foundation for safer LIBs applicable to e-mobility, grid storage, and defense systems. These findings have been disseminated through peer-reviewed publication and form the basis for an upcoming patent filing.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

(1) Overview of results
The SMARTBATT project has delivered a paradigm-shifting innovation in the field of lithium-ion battery (LIB) safety through the design and validation of a chemically responsive electrolyte that autonomously prevents thermal runaway. The core breakthrough lies in a dual-function thermoresponsive electrolyte system that:
- Exhibits normal electrochemical performance at room temperature, and
- Undergoes a temperature-triggered Diels–Alder cycloaddition to initiate a two-step intelligent shutdown mechanism, a warning phase (100 °C) and a complete shutdown (120 °C)
This novel approach goes significantly beyond the current state of the art, which primarily relies on:
- Passive mechanical safety features (e.g. shutdown separators),
- External electronic controls (e.g. battery management systems),
- Flame-retardant additives that often impair performance.

(2) Results beyond the state of the art
(i) Smart electrolyte design with intrinsic safety function
- First-time integration of Diels–Alder reaction chemistry to achieve autonomous shutdown functionality in a liquid electrolyte.
- The electrolyte formulation (LiTFSI0.15DMFu0.8VC1.0) provides intrinsic fail-safe behavior without the need for external components or intervention.
- Unlike prior technologies that activate near or after the onset of thermal runaway, SMARTBATT intervenes at the SEI decomposition temperature, offering a preventive approach.
(ii) Dual Functionality without performance compromise
- Maintains high ionic conductivity (1.18 mS/cm) and high Li+ transference number (0.58) at room temperature.
- Long-term cycling, interfacial stability, and thermal resistance.
- Demonstrated successful operation in coin and pouch cell formats.
(iii) Mechanism-driven shutdown with polymer formation
- The in-situ formation of Diels–Alder oligomers blocks separator pores and impedes ion transport.
- Enhanced separator dimensional stability post-shutdown, proven by SEM imaging and thermal shrinkage tests.
- Verified via solid-state NMR, mass spectrometry, rheological and EIS studies, providing mechanistic insights.

(3) Potential impacts
(i) Scientific impact
- Opens a new research frontier in reactive electrolyte design, bridging synthetic organic chemistry with electrochemical safety.
- Provides a modular platform to explore other click-chemistries for tailored thermal responses.
- Offers a methodology to design temperature-responsive electrolytes for other battery chemistries.
(ii) Industrial and market impact
- Compatible with existing LIB manufacturing infrastructure; no need for retooling.
- Potential for licensing or integration into commercial supply chains for EVs, consumer electronics, and aerospace batteries.
- Biomass-derived DMFu provides a sustainability advantage in alignment with EU Green Deal.
(iii) IPR and commercialization readiness
- Patentable formulation and reaction-triggered shutdown mechanism have been disclosed and are under evaluation.
- The technology is at TRL 5, with lab-scale validation in pouch cells and reproducible shutdown behavior under thermal stress.

(4) Key needs to ensure further uptake and success
To ensure translation of this innovation into practical and commercial solutions, the following key areas must be addressed:
(i) Further research and development
- Scale-up synthesis of DMFu and optimization of reaction kinetics at manufacturing scale.
- Long-term thermal aging studies and compatibility with high-voltage cathodes (e.g. NMC, LCO).
- Development of multi-functional hybrid electrolytes with tailored reactivity and broadened voltage windows.
(ii) Demonstration and pilot testing
- Fabrication and validation of multi-layer pouch cells or battery packs using the SMARTBATT electrolyte.
- Accelerated safety testing under UL/IEC thermal abuse standards to demonstrate commercial viability.
(iii) Access to markets and finance
- Engagement with strategic battery manufacturers and OEMs (e.g. LG Energy, Northvolt, Tata Chemicals) for early-stage pilot deployment
- Pursuit of EIC Transition funding or national tech-transfer schemes for scaling and pre-commercial demonstration.
(iv) Standardization and regulation
- Advocacy for inclusion of chemical shutdown mechanisms in upcoming EU battery safety standards.
- Collaboration with certification bodies (e.g. TÜV, UL) to validate SMARTBATT’s prevention-first safety approach.
(v) Internationalization
- Strategic partnerships with Asian and European battery producers, facilitated by IP protection and joint research opportunities.

SMARTBATT’s scientific and technical achievements represent a quantum leap in intrinsic battery safety, enabled by the first-of-its-kind smart electrolyte design. The project delivers a low-cost, scalable, and sustainable solution that could redefine safety benchmarks in global LIB manufacturing. With targeted support in scale-up, market access, and regulatory recognition, the SMARTBATT technology is well-positioned for commercial translation and long-term impact across diverse battery-driven sectors.

SEM images proofs for thermal shutdown ability of the electrolyte

Li-LFP coin cell performance

Thermal stability of separators

Schematic of thermal shutdown mechanism of electrolyte

SEM images proofs of thermal shutdown feature of electrolyte

Experimental characterization of Diels-Alder reactions in electrolyte

Thermal shutdown characteristics of electrolyte in Graphite-LFP cells

Graphite-LFP pouch cell performance

Properties of electrolyte