Periodic Reporting for period 2 - AM4BAT (Gen. 4b Solid State Li-ion battery by additive manufacturing)
Periodo di rendicontazione: 2024-01-01 al 2025-06-30
Batteries are a key technology for Europe’s transition to clean mobility and climate neutrality. However, conventional Li-ion batteries face limitations in energy density, charging speed, safety, and sustainability. AM4BAT (HORIZON-CL5-2021-D2-01-03, Grant Agreement No. 101069756) aims to address these challenges by developing a new generation of anode-less, all-solid-state batteries. The project integrates a UV-curable polymer electrolyte reinforced with LLZO ceramic fillers, high-energy cathodes, and thin anode-less current collectors. This unique configuration reduces inactive material, improves safety, and exploits scalable industrial processes such as photocuring. The objective is to deliver a battery concept with improved volumetric energy density, fast charging capability, and a more sustainable production route.
During the second reporting period, AM4BAT made substantial progress in all key battery components. In electrolyte development, a UV-curable hybrid solid electrolyte was formulated with 20 wt.% LLZO ceramic filler. The final composition achieved room-temperature ionic conductivities in the 10⁻⁴–10⁻³ S/cm range, an electrochemical stability window above 5 V vs. Li/Li⁺, and thermal stability beyond 300 °C. Comparative cycling tests in symmetric Li|HSE|Li cells confirmed stability for approximately 220 cycles before polarization while maintaining mechanical flexibility. The adoption of photocuring is particularly relevant from an industrial perspective, as it eliminates the need for energy-intensive thermal drying and enables compatibility with large-scale coating and printing processes.
Cathode development advanced on two parallel fronts. Zr-doped NMC811 was successfully synthesised using the ACTIM continuous mixing process, achieving a discharge capacity of 167 mAh g⁻¹ with 92% retention after 100 cycles at 0.1C while long-term testing at 1C demonstrated stable cycling over more than 500 cycles when MWCNTs were partially substituted for carbon black. Importantly, ACTIM demonstrated throughput of 0.52 kg h⁻¹, confirming its industrial scalability compared to conventional co-precipitation routes. Work on high-voltage LNMO cathodes confirmed stable operation in the 3.5–4.9 V window with rate capability up to 5C and cycling stability at 1C, broadening the cathode portfolio for integration into the AM4BAT cell concept. Benchmark tests confirmed that single-crystal NMC811 still provides superior rate and capacity retention, establishing a reliable baseline for integration.
On the anode side, the project focused on developing anode-less current collectors to maximize energy density. Silver-coated copper foils achieved excellent cycling stability exceeding 900 hours at 0.4 mA cm⁻², while tin-coated copper foils offered a more cost-effective solution, achieving areal capacities of 2.5 mAh cm⁻² although with higher sensitivity to deposition conditions. The design features a double-sided coating with a total thickness of only 40 microns, more than 50% thinner than conventional graphite anodes. This significant thickness reduction directly improves volumetric energy density and reduces inactive mass, which is critical for industrial applications where Wh L⁻¹ is a key metric.
Modelling and safety analysis supported the materials development by simulating ion transport in polymer and hybrid electrolytes, interface behavior, and the lithiation of current collectors. These models, validated against impedance spectroscopy and transference number experiments, helped interpret performance trends and guided optimization strategies, although further refinement of diffusion parameters is still needed. Life cycle assessment (LCA) was applied across all activities to ensure that sustainability criteria were integrated into technical decision-making. For example, the choice of the solid-state synthesis route for LLZO was made on the basis of lower energy and environmental impact compared with alternative processes.
Integration efforts are now moving towards prototype pouch cells. To manage material demand and reduce risk, 1 Ah cells are currently under assembly as intermediate demonstrators, with 3 Ah cells remaining the ultimate target. These prototypes will provide a crucial proof of concept for the AM4BAT design by bringing together thin anode-less collectors, high-energy cathodes, and UV-cured hybrid electrolytes.
Cathode development advanced on two parallel fronts. Zr-doped NMC811 was successfully synthesised using the ACTIM continuous mixing process, achieving a discharge capacity of 167 mAh g⁻¹ with 92% retention after 100 cycles at 0.1C while long-term testing at 1C demonstrated stable cycling over more than 500 cycles when MWCNTs were partially substituted for carbon black. Importantly, ACTIM demonstrated throughput of 0.52 kg h⁻¹, confirming its industrial scalability compared to conventional co-precipitation routes. Work on high-voltage LNMO cathodes confirmed stable operation in the 3.5–4.9 V window with rate capability up to 5C and cycling stability at 1C, broadening the cathode portfolio for integration into the AM4BAT cell concept. Benchmark tests confirmed that single-crystal NMC811 still provides superior rate and capacity retention, establishing a reliable baseline for integration.
On the anode side, the project focused on developing anode-less current collectors to maximize energy density. Silver-coated copper foils achieved excellent cycling stability exceeding 900 hours at 0.4 mA cm⁻², while tin-coated copper foils offered a more cost-effective solution, achieving areal capacities of 2.5 mAh cm⁻² although with higher sensitivity to deposition conditions. The design features a double-sided coating with a total thickness of only 40 microns, more than 50% thinner than conventional graphite anodes. This significant thickness reduction directly improves volumetric energy density and reduces inactive mass, which is critical for industrial applications where Wh L⁻¹ is a key metric.
Modelling and safety analysis supported the materials development by simulating ion transport in polymer and hybrid electrolytes, interface behavior, and the lithiation of current collectors. These models, validated against impedance spectroscopy and transference number experiments, helped interpret performance trends and guided optimization strategies, although further refinement of diffusion parameters is still needed. Life cycle assessment (LCA) was applied across all activities to ensure that sustainability criteria were integrated into technical decision-making. For example, the choice of the solid-state synthesis route for LLZO was made on the basis of lower energy and environmental impact compared with alternative processes.
Integration efforts are now moving towards prototype pouch cells. To manage material demand and reduce risk, 1 Ah cells are currently under assembly as intermediate demonstrators, with 3 Ah cells remaining the ultimate target. These prototypes will provide a crucial proof of concept for the AM4BAT design by bringing together thin anode-less collectors, high-energy cathodes, and UV-cured hybrid electrolytes.
The AM4BAT project demonstrates results that go well beyond the current state of the art in solid-state batteries. The hybrid solid electrolyte uniquely combines high conductivity at room temperature, a wide electrochemical stability window, and photocurable processability compatible with scalable manufacturing. The ACTIM cathode synthesis process has achieved industrially relevant throughput while delivering durable cycling performance over hundreds of cycles. The development of ultra-thin, stable anode-less collectors is another breakthrough. By removing the conventional graphite anode and instead relying on lithium plating and stripping at the current collector, the project enables a much higher volumetric energy density while reducing inactive mass. Achieving stable cycling for over 900 hours in this configuration is a major advance compared with previous reports, which typically struggled with rapid degradation. Importantly, the project integrates life cycle assessment into R&D from the outset, ensuring that all innovations are evaluated not only for performance but also for environmental and economic feasibility. Together, these achievements establish AM4BAT as a clear step beyond conventional Li-ion technology and a credible pathway toward industrial solid-state batteries.