Sustainable manufacturing and optimized materials and interfaces for lithium metal batteries with digital quality control

Project Information

SOLiD

Grant agreement ID: 101069505

DOI

10.3030/101069505

EC signature date 9 June 2022

Start date 1 September 2022

End date 30 April 2027

Funded under

• Climate, Energy and Mobility

Total cost

€ 7 026 000,75

EU contribution

€ 6 980 937,50

Coordinated by

TEKNOLOGIAN TUTKIMUSKESKUS VTT OY
Finland

Periodic Reporting for period 2 - SOLiD (Sustainable manufacturing and optimized materials and interfaces for lithium metal batteries with digital quality control)

Reporting period: 2024-03-01 to 2025-08-31

Summary of the context and overall objectives of the project

The SOLiD project aims to create a sustainable and cost-efficient pilot scale manufacturing process for a high energy density, safe and easily recyclable solid-state Li-metal battery. The project will develop a scalable process for each of the cell layers and interlayers and demonstrate the cell manufacturing and assembly in pilot and industrial scale, supported by inline inspection methods.
The high energy density will enable a longer driving range for electric vehicles and the protective layers on all interfaces enable high safety and increased charging rates. The cost-efficient processing methods (e.g. pulsed laser deposition, PLD) will help to gain reduced prices for the batteries while offering at the same time higher energy density, lifetime and safety. Being safe and long-lasting, the SOLiD batteries are well suitable e.g. as 2nd life batteries for stationary storage to enable integration of renewable energy production to households. The planned recycling-ready design approach of SOLiD, i.e. the polymeric interlayers to allow easy delamination and direct recycling, will help to accelerate the circular economy of batteries. The ultrahigh energy density and durability of the fully optimized SOLiD battery will enable their utilization in several applications, opening up new application areas to allow reduction of greenhouse gas emissions.

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

The first activities were dedicated to identifying initial specifications for the batteries that will be manufactured in the SOLiD project. Preliminary calculations of energy density and dimensions of the cells for the automotive application of the SOLiD technology were proposed. In details requirements for: i) the size, safety, and performance of the SOLiD battery prototypes, including pouch cell design; ii) the processing of the battery cell layers; iii) the materials and interface development; iv) the inline inspection and data handling; v) the cost and sustainability.
On the negative electrode side (metallic lithium), Pulsedeon has set up a process for producing Li-metal layers by PLD. Li layers of 3 and 10 µm in thickness have been produced on Cu substrates. In addition, Aalto university has screened and tested different protective layers on the Li metal to enhance its stability, processed by atomic layer deposition (ALD).
On the positive electrode side (NMC811), Aalto university has screened and tested different ALD coated protective layers on the cathode active material powder. The obtained coated electrodes were further exposed to galvanostatic charge-discharge cycling in Li half-cells (CR2016) filled with liquid electrolyte. In addition, Specific Polymers has provided a few different polymer electrolytes to VTT, and VTT has used those to optimise the dry extrusion process for the cathode composite layer in lab-scale. Armor Battery Films has provided current collectors coated with different primer layers for these tests. The extruded electrodes have been analysed by adhesion tests at Armor Battery Films and at VTT by electrochemical tests in half cells and liquid electrolyte.
Regarding the polymer electrolytes (to be used as the binder and the separator), Specific Polymers has synthetised and optimised the materials to match with the project objectives regarding e.g. the ionic conductivity and electrochemical stability window. CSEM and TBU have tested and optimised these electrolytes in test cells. Aalto university supported this activity by providing cross-section images of the extruded samples, containing NMC mixed with the electrolyte. In addition, CNRS has also worked to test and design polymeric interlayers to be used as a smart binder for maintaining a permanent electronic conductive path during volume expansions and contractions due to battery operation.
The inline inspection and quality control activities have been focused on developing sensors at BFH, VTT, CSEM and Coatema for the supervision of the SOLiD manufacturing process and for later use in a digital twin and feedback loops. Additionally, the work on the digital twin has been initiated a bit ahead of plan.

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)

The Li deposition process was transferred to an upscaled deposition tool, providing fourfold size in case of sheet samples, from ~40x60 mm2 to 100x100 mm2, in practically the same processing time. Moreover, both the quality and repeatability of the process were improved. Promising results regarding increase in lifetime have been achieved in test cells using different ALD coated barrier layers on Li and a liquid electrolyte.
The protecting layers on the cathode active material particles have shown increased lifetime in test cells with a liquid electrolyte. In addition, first successful dry extruded electrodes have been made in lab-scale with NMC811. The primer layer on the current collector has clearly improved both the adhesion and the electrochemical performance of the test cells.
The electrochemical stability window of the polymer electrolytes has been validated to be suitable for the high-voltage cathode materials. The ionic conductivity was also improved, and we are approaching the target of the SOLiD project, i.e. 0.5 mS/cm at 30°C for the binder electrolyte, and 0.1 mS/cm at 30°C for the separator electrolyte.
We have been able to detect 5 µm particles with laser speckle photometry and we have developed an optical method to create a 3D map from the electrode surface, based on a line camera and showing several different defects (holes, particles etc.). Optical methods were also used to monitor the coating process from the slot die head meniscus. In addition, we have installed an electrochemical impedance spectroscopy (EIS) inline monitoring system to a roll-based setup.

Picture from the SOLiD kick-off meeting at VTT