The low cost and abundance of sodium have lead some view rechargeable sodium-ion batteries (SIBs) as a promising solution for energy storage. Researchers from Manchester Metropolitan University looked at the use of additive manufacturing/3D printing to produce energy storage devices using Earth-abundant, low-cost transition metals especially Manganese and iron.
Specifically, they used the most common kind of 3D printing called fused deposition modeling (FDM). Fused deposition modeling uses a thermoplastic filament that is heated to its melting point. Then, it is extruded, layer by layer, to produce a three-dimensional structure. (See the diagrams and image of the 3D-printed battery and its components above courtesy of Advanced Energy Materials and the reference cited below).
They reported their findings in the online journal, Advanced Energy Materials. The researcher explained how they created the first freestanding sodium‐ion (full cell) battery formed entirely of components that were fabricated using AM/3D printing.
They had to find a highly active material that could be AM/3D printed that would work for energy storage. They searched the literature for potential materials that were made of elements that are both abundant and low cost as well as active.
For the cathode material, they integrating the active materials sodium manganese oxide (NaMnO2) and titanium oxide within what they describe as a highly novel, porous supporting material developed to maximize surface area.
From these unique materials they were able to AM/3D print a proof‐of‐concept model based upon the fundamental structures of a commercially available AA battery.
They used nuclear magnetic resonance spectroscopy to confirm the composition and conformaty of the fabricated sample of NaMnO2. They found that the NMR spectra exhibited stacking similar to that of nominally pure β‐NaMnO2 samples.
They found that the crystal structure of the NaMnO2 was not perfect and that the testing indicated a specific form of MnO2, often referred to as Ramsdellite.
The active battery materials had to be integrated into a porous polymer matrix so the electrolyte can penetrate the active components.
They integrated an immiscible water‐soluble polymer into an AM/3D printable polymer matrix.
PVA is the water soluable polymer that they mixed into the prinatable ABS polymer matrix along with the active materials, NaMnO2 for the cathode, and a TiO2 nanopowder for the anode. They also included
Super P nanocarbon to enhance the electrochemical conductivity.
The 3D printing extruded the resulting composites into filaments that were deposited via FDM.
The AM/3D printed electrodes are then sonicated in water for 4 hours to remove the micropockets of PVA (as PVA is easily dissolvable within water), leaving microporous electrochemically active AM/3D printed electrodes/energy storage architectures. The resulting electrode was dried at 60°C and stored under vacuum.
The cell’s design that they created allows for the insertion of the electrolyte without needing any kind of separator.
For a stable and safe electrolyte, they used NaBF4 in EMIBF4.
The freestanding and entirely AM/3D‐fabricated battery demonstrated a performance of 84.3 mAh g−1 with a current density of 8.43 mA g−1.
Down, M. P., Martínez‐Periñán, E., Foster, C. W., Lorenzo, E., Smith, G. C., Banks, C. E., Next‐Generation Additive Manufacturing of Complete Standalone Sodium‐Ion Energy Storage Architectures, Advanced Energy Materials, Feb 10, 2019. https://doi.org/10.1002/aenm.201803019