ToNaBatt

What are the objectives of the project?

The work philosophy of ToNaBatt is to develop materials and processes free of toxic reagents and solvents and to lower the carbon footprint of battery production by using soft chemistry approaches. The proposed technology is expected to simplify the recycling processes and minimize the negative end-of-life impact. The overarching objective of ToNaBatt is to develop sustainable high energy density sodium batteries. To achieve this disruptive objective, ToNaBatt synergistically merges the unique expertise of the Project director and targets the following specific objectives:

• Establish the first research team in Romania on the development of Na batteries

• Deep fundamental knowledge for materials optimization – by studying the impact of Na sacrificial sources on the efficiency and stability of Na-anode-free cells Towards Gen.5 batteries: high-energy and long-cycle-life operation – by developing Na battery lab prototype cells with long-term cycling stability, targeted practical energy densities, and design electrolytes that attain >99% Coulombic efficiency

• Strengthened innovation excellence – ToNaBatt team will enable a critical mass to consolidate the leadership in this competitive field

Work plan

ToNaBatt brings together a team of researchers with interdisciplinary background. They complement each other with their research and practical expertise in the battery field. This interdisciplinary team will favor the know-how and knowledge transfer in order to boost ICSI’s scientific excellence and innovation capacity in developing new generation of viable high energy density and environmentally friendly Na based batteries. The project team has been built considering these specific requirements leading to a multidisciplinary partnership with widely acknowledged expertise in the respective domain. Such interdisciplinary, in a highly competitive and emerging field, is crucial to demonstrate to the public and to all value chain stakeholders the new breakthrough technology exploiting sustainable, CRM-free and environmentally friendly materials and processes towards transformative Na batteries.

Scientific Results and Impact!

Comprehensive assessment of sodium-ion battery technologies
A comprehensive state-of-the-art review on sodium-ion battery (SIB) technology was completed, covering recent scientific advances, market evolution, industrial development, cell architecture, operating principles, active materials, electrolytes, current technological challenges, and future research directions.
The study established the scientific framework for selecting materials, electrolyte systems, and electrode configurations investigated throughout the project.

Development and optimization of advanced sodium-based electrolytes
A wide range of ether-based electrolyte formulations was successfully developed using different sodium salts, including NaPF₆, NaBF₄, NaFSI, NaCF₃SO₃, NaTFSI, NaClO₄ and NaDFOB, as well as carbonate-based electrolyte systems and mixed-salt formulations. The influence of salt chemistry, concentration, co-solvents, and electrolyte additives on ionic conductivity, viscosity, electrochemical stability, and cell performance was systematically investigated. Comprehensive physicochemical characterization
demonstrated the expected dependence of electrolyte viscosity on salt concentration and temperature, while dielectric spectroscopy enabled detailed evaluation of ionic transport mechanisms over a broad temperature and frequency range.

Identification of optimized electrolyte formulations
Comparative electrochemical studies identified several optimized electrolyte systems capable of significantly improving cycling stability and Coulombic efficiency in sodium metal and anode-free cells.
Mixed-salt electrolyte formulations based on NaPF₆/NaDFOB and NaCF₃SO₃/NaDFOB exhibited enhanced interfacial stability, while low concentrations of fluorinated additives provided additional improvements in electrochemical performance. The optimized electrolyte formulations promoted stable solid electrolyte interphase (SEI) formation, reduced polarization, and improved sodium plating/stripping reversibility.

Development of solvent-free sodium cathodes
An environmentally friendly solvent-free electrode fabrication process was successfully developed for Na₃V₂(PO₄)₃ (NVP) cathodes using PTFE fibrillation technology. Different conductive carbon additives and electrode formulations were evaluated to optimize mechanical integrity and electrochemical performance.
Carbon nanofibers provided the best electrode flexibility and mechanical stability, while Super P conductive carbon delivered excellent electrochemical performance with specific capacities approaching 100 mAh g⁻¹ in optimized half-cell configurations.

Development of high-loading electrodes
High-mass-loading solvent-free NVP electrodes reaching approximately 83 mg cm⁻² were successfully manufactured and demonstrated excellent electrochemical stability, maintaining approximately 93% capacity retention after 60 charge-discharge cycles.

First anode-free sodium pouch cell prototype
The project achieved the successful fabrication of the first anode-free sodium pouch cell prototype based on solvent-free NVP cathodes. Optimized electrode processing, current collector selection, and pouch-cell assembly procedures demonstrated the technical feasibility of scaling laboratory electrode manufacturing toward practical sodium battery prototypes.

Optimization of current collectors
Several aluminum- and copper-based current collector configurations were evaluated, including chemically and thermally treated substrates as well as carbon- and graphite-coated aluminum foils. The study identified carbon-coated aluminum and untreated copper collectors as the most promising configurations for anode-free sodium cells, providing high Coulombic efficiency, stable cycling performance, and improved interfacial compatibility.

Development of organic sodium cathode materials
A multifunctional organic cathode material (Na₄-DOBDS) was successfully synthesized using both chemical and mechanochemical approaches and confirmed. The material delivered an initial specific capacity of approximately 125 mAh g⁻¹, corresponding to nearly 75% of its theoretical capacity, demonstrating its potential as a sustainable organic cathode for next-generation sodium-ion batteries.

Electrochemical protocol development
Dedicated electrochemical testing protocols were developed for half-cells, anode-free cells, symmetric sodium cells, and pouch-cell configurations. These procedures enabled reliable comparison of electrolyte formulations, electrode architectures, and substrate modifications while supporting reproducible evaluation of sodium plating/stripping behavior.

Advanced characterization of electrolyte–electrode interactions
Systematic studies demonstrated that optimized ether-based electrolyte systems improve Na⁺ transport, reduce voltage polarization, and enhance electrode wetting. The role of contact ion pairs (CIPs) in stabilizing the solid electrolyte interphase was experimentally confirmed, providing important insights into electrolyte design for sodium metal batteries.

Improvement of electrochemical performance
Optimization of electrolyte composition, conductive additives, separator selection, and electrode
architecture resulted in significant improvements in electrochemical performance, including:

− Coulombic efficiencies exceeding 99% in optimized half-cell configurations;
− Specific capacities approaching the theoretical value of 117 mAh g⁻¹ for NVP cathodes;
− Capacity retention up to 95% after prolonged cycling;
− Stable cycling over 200–300 cycles in optimized configurations;
− Reduced voltage polarization (<50 mV per cycle);
− Improved energy efficiency of approximately 90% in optimized anode-free cells.

Development of an actively controlled pouch-cell pressing system
A new generation pouch-cell clamping system was designed and optimized by integrating a high-precision force sensor capable of real-time pressure monitoring over a wide operating range (175 kPa–2 MPa). The upgraded system provides uniform pressure distribution, improved mechanical reproducibility, and establishes the basis for future electro-chemo-mechanical studies of sodium pouch cells.

Research infrastructure and knowledge transfer
The project strengthened the scientific capabilities of the ICSI Battery Development Laboratory through international collaboration with UCLouvain (Belgium), enabling advanced training in sodium battery development, electrode fabrication, and electrochemical testing methodologies. The acquired expertise has significantly enhanced the laboratory’s capacity to develop next-generation sodium-ion battery technologies.

Research Excellence and Project Impact
International Research Projects
The scientific expertise and research capacity developed through ToNaBatt significantly strengthened the participation of the ICSI Battery Development Group in highly competitive international funding programmes. During the implementation of the project, seven international collaborative research proposals were submitted under Horizon Europe and M-ERA.NET programmes. Of these, three projects were successfully funded, one proposal is currently under evaluation, and three proposals reached the evaluation stage but were not selected for funding.
The funded projects include:

− OLiMPUS – EurOpean, low-cost, safe and sustainable LiMFP//Gr battery cells at industrial scale (Horizon Europe, Grant Agreement preparation, 2026–2030);
− 4SIBAT – Sustainable Advanced Materials for Solid-State Sodium-Ion Batteries (M-ERA.NET, 2025–2028);
− COBRA – Calcium Organic Battery Alliance (M-ERA.NET, 2024–2027).

These successful applications demonstrate the competitiveness of the research team and its active integration into leading European battery research networks.

National Research Funding
The expertise developed within ToNaBatt also translated into success within the Romanian national research programmes.
During the project implementation, three national research proposals were submitted with ICSI acting as project coordinator. One project was successfully funded:

− SAFEBAT – Sustainable and Safe Batteries Based on New Sulfur Materials and Quasi-Solid Electrolytes (PED 2024 Programme, 2025–2026).

Two additional proposals (REPER and MIPEBAT) were successfully prepared and submitted, further strengthening the laboratory’s national research portfolio and expanding future research opportunities in advanced battery technologies.

Scientific Dissemination and International Visibility
ToNaBatt significantly increased the international visibility of the ICSI Battery Development Laboratory.
Project results were disseminated through participation in 13 international scientific conferences.
These contributions promoted the project’s scientific achievements while strengthening collaborations with leading European research institutions working in advanced battery technologies.

1. Preliminary Studies on Sodium-Based Battery Technology, Alexandru RIZOIU, Mihaela BUGA, Alexandru VLAD, Adnana SPÎNU-ZĂULEȚ, Danuț – Ionel VĂIREANU. EnergEN2023, 8–20 October2023, Băile Govora, Romania, poster presentation
2. Towards Long-Lasting Anode-Free Sodium Batteries: A Study on the Effect of Electrolytes on the Sodium Plating/Stripping Process, Sarah Aboubakr, Alexandru Rizoiu, Adnana Spînu-Zăuleț, Cosmin Ungureanu, Mihaela Buga, Alexandru Vlad. 23rd Romanian International Conference on Chemistry and Chemical Engineering (RICCCE 2024), held in Constanța–Mamaia, Romania, 4–7 September 2024, oral presentation.
3. Comparative Study of Different Electrolytes for Anode-Free Sodium Metal Cell Configurations, Alexandru Rizoiu, Sarah Aboubakr, Cosmin Ungureanu, Adnana Spînu-Zăuleț, Mihaela Buga, Alexandru Vlad, and Dănuț-Ionel Văireanu. 23rd Romanian International Conference on Chemistry and Chemical Engineering (RICCCE 2024), held in Constanța–Mamaia, Romania, 4–7 September 2024, poster presentation.
4. Simple Dry-Process for Solvent-Free Na₃V₂(PO₄)₃ Cathodes: An Approach Towards Enhanced Sustainability, Sarah Aboubakr, Alexandru Rizoiu, Adnana Spînu-Zăuleț, Cosmin Ungureanu, Mihaela Buga, and Alexandru Vlad. ElectROBatt 2024 – International Conference on Electrochemistry of Batteries and Energy Storage Technologies, held at the Radisson Blu Hotel, Bucharest, Romania, 31 October – 1 November 2024, poster presentation.
5. Characterization of In-Situ Sodium Deposition in Anode-Free Sodium Metal Systems, Sarah Aboubakr, Alexandru Rizoiu, Adnana Spînu-Zăuleț, Mihaela Buga, and Alexandru Vlad. 16th International Exergy, Energy and Environment Symposium (IEEES 2025), held in Craiova, Romania, from 14–18 December 2025, poster presentation.
6. Engineering a Catechol-Derived Sodium Salt for Stable High-Capacity Organic Sodium-Ion Battery Cathodes, Nagaraju Nakka, Rambabu Darsi, Adnana Spînu-Zăuleț, Anweshi Dewan, Alexandru Vlad, and Mihaela Buga. 16th International Exergy, Energy and Environment Symposium (IEEES 2025), held in Craiova, Romania, from 14–18 December 2025, poster presentation.
7. Solvent-Free NVP Cathodes for Next-Generation Sodium Metal Batteries: Enabling High Mass Loadings via Dry Electrode Processing, Sarah Aboubakr, Alexandru Rizoiu, Adnana Spînu-Zăuleț, Mihaela Buga, and Alexandru Vlad. 7th International Sodium Battery Symposium (SBS-7), to be held in Berlin, Germany, 13–17 September 2026, poster presentation.
8. Engineering Electrolytes and Interphases for Anode-Free Sodium Metal Batteries, Anweshi Dewan, Adina Melinte, Alexandru Rizoiu, Robert Răbuga, Sarah Aboubakr, Adnana Spînu-Zăuleț, Nagaraju Nakka, Mihaela Buga, and Alexandru Vlad. 7th International Sodium Battery Symposium (SBS-7), to be held in Berlin, Germany, 13–17 September 2026, poster presentation.
9. Synthesis of High Mass-Loading Na₃V₂(PO₄)₃ Cathodes via Dry Processing for Sustainable Anode-Free Sodium Metal Batteries, Sarah Aboubakr, Alexandru Rizoiu, Adnana Spînu-Zăuleț, Mihaela Buga, and Alexandru Vlad. ElectROBatt 2026 – International Conference on Electrochemistry ofCommentHighlight Batteries and Energy Storage Technologies, Bled, Slovenia, 4–6 November 2026, poster presentation.
10. Electrolyte Engineering and Stable Interfacial Chemistry for Anode-Free Sodium Metal Batteries, Anweshi Dewan, Adina Melinte, Alexandru Rizoiu, Robert Răbuga, Sarah Aboubakr, Adnana Spînu-Zăuleț, Nagaraju Nakka, Mihaela Buga, and Alexandru Vlad. ElectROBatt 2026 – International Conference on Electrochemistry of Batteries and Energy Storage Technologies, Bled, Slovenia, 4–6 November 2026, poster presentation.
11. Engineering and Electrochemical Evaluation of a Catechol-Derived Organic Cathode Material for Sodium-Ion Batteries, Nagaraju Nakka, Rambabu Darsi, Adnana Spînu-Zăuleț, Anweshi Dewan, Alexandru Vlad, and Mihaela Buga. ElectROBatt 2026 – International Conference on Electrochemistry of Batteries and Energy Storage Technologies, Bled, Slovenia, 4–6 November 2026, poster presentation.
12. Optimization of Stacking Pressure in Anode-Free Sodium-Metal Pouch Cells Through Uniform Pressure Distribution, Robert Răbuga, Alexandru Rizoiu, Sarah Aboubakr, Adnana Spînu-Zăuleț, Mihaela Buga, and Alexandru Vlad. ElectROBatt 2026 – International Conference on Electrochemistry of Batteries and Energy Storage Technologies, Bled, Slovenia, 4–6 November 2026, poster presentation.
13. Substrate Engineering for Anode-Free Sodium Cells: From Protocol Development to Performance Ranking, Alexandru Rizoiu, Robert Răbuga, Adina Melinte, Adnana Spînu-Zăuleț, Mihaela Buga, and Alexandru Vlad. ElectROBatt 2026 – International Conference on Electrochemistry of Batteries and Energy Storage Technologies, Bled, Slovenia, 4–6 November 2026, poster presentation.

Scientific Event Organization
ICSI successfully organized the first international conference on battery technologies, ElectROBatt 2024 – Electrochemistry of Batteries and Energy Storage Technologies, held in Bucharest between 30 October and 1 November 2024. The conference brought together internationally recognized experts from academia and industry, establishing ElectROBatt as an important European platform for battery research.
Building on this success, the second edition, ElectROBatt 2026, will be organized in Bled, Slovenia, in collaboration with the National Institute of Chemistry (NIC), Ljubljana, further expanding the project’s international impact.

Scientific Publications
The scientific excellence achieved within ToNaBatt has resulted in publications in leading international journals in the field of electrochemical energy storage.
Current scientific outputs include:

1. ACS Energy Letters (2024, Q1, IF = 18.2,), DOI: 10.1021/acsenergylett.4c01435
2. Journal of the American Chemical Society (JACS) (2026, Q1, IF 15.7), DOI: 10.1021/jacs.5c20277
3. ChemElectroChem (2026, Q2, IF = 5.2), DOI: 10.1002/celc.202500327
4. UPB Scientific Bulletin, Series B (2026), Indexed in Web of Science, Scopus, INSPEC, Cambridge Scientific Abstracts, and METADEX.CommentHighlight
5. Manuscript submitted to Energy & Environmental Science (Q1, IF 30.5), (submitted July 2026, Manuscript ID: EE-REV-07-2026-005092).

These publications reflect the project’s scientific impact and contribute to advancing the international knowledge base on next-generation sodium battery technologies.

Capacity Building and Human Resources
One of the major achievements of ToNaBatt has been the significant expansion of human research capacity within the ICSI Battery Development Group.

The project exceeded all initially planned recruitment targets by supporting:

− 5 full-time equivalent postdoctoral researchers:
   Dr. Adnana SPÎNU-ZĂULEȚ, Dr. Sarah ABOUBAKR, Dr. Anweshi DEWAN, Dr. Nagaraju NAKKA, Dr. Narvin NEEHALL
− 3 full-time equivalent PhD researchers:
   Phd Student Alexandru RIZOIU, PhD Student Robert RĂBUGA, PhD Student (Dr.) Cosmin UNGUREANU
   Project Director: Prof. Alexandru VLAD
   Project Responsible: PhD Mihaela BUGA
   Senior Researcher: PhD Mihai VARLAM
   Person responsible for the financial management of the project: ACS, Ec. Cristina TUDORA
   Person responsible for the financial management of the project: Ec. Ana-Maria PROTEASA

The recruitment of four international postdoctoral researchers, considerably strengthening the international and interdisciplinary character of the research team.

Training, Mobility and Knowledge Exchange
The ToNaBatt project actively promoted international scientific collaboration through research visits, professional training, and knowledge exchange with leading European research institutions.

– The first international mobility was carried out between 25–27 September 2023 at Université catholique de Louvain (UCLouvain), Institute of Condensed Matter and Nanosciences (IMCN), MOST Division, VLAD Energy Group, Louvain-la-Neuve, Belgium (Dr. Mihaela Buga, Dr. Adnana Spînu-Zăuleț, PhD student Alexandru Rizoiu, and Dr. Narvin Neehall).
– As part of the ToNaBatt project, a second international research and training visit was carried out between 12–22 May 2024, Postdoctoral Researcher Dr. Sarah Aboubakr and PhD Researcher Alexandru Rizoiu carried out a research and training visit at the Université catholique de Louvain (UCLouvain), Institute of Condensed Matter and Nanosciences (IMCN), MOST Division, Louvain-la-Neuve, Belgium.
– A third research visit was carried out between 16–26 March 2026 at Université catholique de Louvain (UCLouvain), Institute of Condensed Matter and Nanosciences (IMCN), MOST Division,CommentHighlight VLAD Energy Group, Louvain-la-Neuve, Belgium (Dr. Sarah Aboubakr, PhD student Robert Răbuga, and Dr. Anweshi Dewan).

This international collaboration strengthened the research capabilities of the ICSI Battery Development Laboratory, facilitated the transfer of advanced experimental methodologies, and established the foundation for long-term scientific cooperation with UCLouvain in the field of advanced battery technologies.

Doctoral Education and Research Training
A major milestone was the successful public defense of the PhD thesis entitled “Optimal Solutions for Electrical Energy Storage in Lithium-Ion Batteries”, completed by Dr. Eng. Cosmin Ungureanu within the Doctoral School of the Faculty of Energy Engineering, National University of Science and Technology POLITEHNICA Bucharest. In addition to this completed doctorate, the project currently supports two ongoing PhD research programmes focused on innovative sodium-ion battery technologies, further strengthening the long-term research capacity of the ICSI Battery Development Group and contributing to the development of highly qualified specialists in electrochemical energy storage.

Institutional Development and European Integration
Beyond its scientific achievements, ToNaBatt has significantly contributed to strengthening the institutional research capacity of ICSI Râmnicu Vâlcea.
The project supported the implementation of the Human Resources Strategy for Researchers (HRS4R), aligning the institute with the principles of the European Charter for Researchers and the Code of Conduct for the Recruitment of Researchers. Recruitment policies, research ethics procedures, gender equality strategies, and Open, Transparent and Merit-based Recruitment (OTM-R) practices have been updated as part of the ongoing evaluation process for the HR Excellence in Research award.

Overall, ToNaBatt has successfully fulfilled all contractual performance indicators while substantially increasing the international competitiveness, scientific visibility, and research excellence of the ICSI Battery Development Laboratory. The project has established a strong foundation for future European collaborations and positioned ICSI as an active contributor to the development of next-generation sodium-based energy storage technologies.