Preparing a stage-1 proposal in two months (HORIZON-CL5-2025-01-Two-Stage-D2-02)
7th July 2025 at 10:11 am
With the first-stage deadline set for 2 September 2025, the two-stage call HORIZON-CL5-2025-01-Two-Stage-D2-02 is looking for cost-effective, next-generation batteries for long-duration stationary storage. Funded under the Batt4EU Partnership, the topic has a strong industrial and strategic policy framing. If you are putting together a Stage 1 proposal, here is what evaluators will expect to see, even in just 10 pages.
The general must-haves for any Stage 1 proposal
As for any Horizon Europe application, it requires a convincing project idea that matches well with the call topic and a consortium of partners that bring together the necessary complementary expertise. And with the little page space available, our recommendation is to treat the Stage 1 proposal like a pitch: concise, jargon-free and with crystal-clear objectives, key performance indicators and a credible pathway to achieve the required impact.
Matching the call topic HORIZON-CL5-2025-01-Two-Stage-D2-02
In general, the expected outcome is clear: develop novel battery materials and systems that enable long-duration stationary storage, i.e., large-scale storage of electric energy from 10 hours to seasonal duration. But there are several additional requirements to be aware of.
- Focus on novel technologies at low technology readiness levels (TRL)
Technologies completely out of scope for this topic are lithium-ion, vanadium-based redox flow, sodium-ion using liquid electrolyte, molten sodium-sulphur and other already commercialised technologies. Instead, applicants are encouraged to implement computational models and/or AI methods for materials discovery and novel cell designs.
Pro tip: Check carefully whether your proposed battery chemistries or configurations are among the four that are given specific additional requirements in the call topic text and make sure these requirements are fulfilled.
- Minimise critical raw materials (CRMs) and aim for a European supply chain
The Critical Raw Materials Act is central to this topic. Proposals should demonstrate how they reduce reliance on CRMs through alternative chemistries or material recovery strategies. In addition, projects are expected to use materials, products and equipment produced in the EU or countries associated to Horizon Europe whenever possible.
Pro tip: Describe procurement strategies in the proposal, specifying the place of production of the materials used.
- Link clearly to Batt4EU objectives
This call is embedded in the European Partnership on Batteries (Batt4EU). That means your proposal must help achieve the Batt4EU KPIs.
Pro tip: Consult and refer to key documents such as the Strategic Research and Innovation Agenda published by Batt4EU’s members and have a look at their latest KPI benchmarking of early 2025.
- Plan for a competitive CAPEX benchmark
Your future system must aim for <50 €/kWh CAPEX, with credible technical and commercial scaling potential. Already at Stage 1, evaluators expect to see a trajectory toward that commercial target and the technical targets specified in the call topic.
Pro tip: Even if only in a brief paragraph, include early feasibility plans (pilot validation, cell compatibility with known processes, end-of-life pathway).
- Lump-sum budgeting with little time left
In general, it is advisable to already do the full work package planning and budgeting even for Stage 1, to avoid false expectations and potentially late surprises and discussions in Stage 2. However, the lump-sum budgeting foreseen for this call topic requires some careful planning and considerations of structuring the work plan. If there is time to do this for Stage 1 – great! But in case there is not enough time left, here is our final pro tip for today: Don’t waste time on budget planning details. Leave it at agreeing on a rough distribution of the five million euro funding foreseen for each project by the EU. For submission you only need to provide the total EU funding sought. Then sort out the details for the Stage 2 proposal for 31 March 2026.
How accelopment can support
We assist researchers, companies and institutions by reviewing proposals or offering full writing support. Our multi-disciplinary and highly qualified team has many years of experience, notably in projects in Energy, Materials, ICT and manufacturing and other areas. For example, we have successfully supported the PEPPERONI (perovskite/silicon tandem photovoltaics), SOLARX (concentrated solar power), CHEOPS (perovskite photovoltaics), macQsimal (quantum technology), SOSLeM (fuel cells) and Mat4Rail (materials) projects. We look forward to discussing with you your project idea and how we can support you best!
Dr. Johannes Ripperger
Research & Innovation Manager
Andreia Cruz
Research & Innovation Project Manager