Bedimensional S.p.A. and Politecnico of Turin are designing and developing reference electrodes for electrochemical sensing in Li-ion batteries in the framework of the SENSIBAT project. These reference electrodes will be positioned between the anode and cathode and will deliver accurate data for indications and understanding of degradation mechanisms that may happen at electrodes or electrolyte during cell operation. To achieve the optimal reference electrode, different materials have been screened for pastes formulation and printability. The pastes, containing Lithium iron phosphate (LFP) and few-layer graphene (FLG), were optimized by optimally balancing electrical, mechanical, and thermal performances, and deposited by doctor blading or screen printing on both rigid and flexible substrates (i.e., glass, plastics, and papers, see Figure 1).
Figure 1: LFP/SLG-based paste deposited on rigid (glass) and flexible (plastic, paper) substrate.
Finally, the optimized pastes were used to print the reference electrode directly on porous separator, achieving an electrical resistance up to 0.01 Ω·cm. The reference electrodes in a full pouch cell are currently evaluated in both three- and four-electrode configurations using the EC:DEC 1:1 LiPF6 1 M as electrolyte and NMC 622 and graphite as anode and cathode, respectively, see Figure 2. We are now working on the design and realization of 5 cm2 cell with the printed sensor.
Figure 2: Full pouch cell in three- (left) and four-electrode (right) configurations.