Graphite has a vital role to play in batteries which are used by many devices. The current method of making electrodes - coating a graphite paste onto a metal sheet - limits the amount of material that can be produced in one pass using a 3D printer. It also creates defects and gaps, which reduce electrode performance. Researchers developed an easy way to make graphite-based electrodes in perfect shape.
The team's new technique combines three separate steps. The team first makes pellets from a composite of graphite, polylactic acid and carbon black. They then add carbon nanotubes and carbon noir for added mechanical strength. While the 3D-printer's heated nozzle is guiding the melting material, it heats the graphite and forces the flake to face the desired direction. This orientation makes the pellets thicker, allowing the lithium ions to move quickly through the material. After that, they create a pattern in the layer of small holes for an entryway to liquid electrolyte. Finally, they print a second layer that acts as the separator. Researchers found that Hilbert curvatures are most efficient for lithium-ion battery liquid entry. Archimedean spirals and Octogram chords did not provide enough channels.
Researchers used 200um thick samples of 10%CSP-optimized 3D-printed materials as negative and positive electrodes to test their design. SEM was employed to examine the pore distribution and structure of both. The ionic conductivity, swelling and swellability were also evaluated to determine the effectiveness of the PLA/SiO2 homemade separator.
In comparison with the results from a previous experiment42, the reversible capability of 10%CSP electrodes 3D-printed increased dramatically during the initial cycle. At C/20 and C/10 it reached 162 and 165mAh g-1 active material, respectively. This was attributed both to improved conductive characteristics of CSP (upto 0.16 S cm-1 for C/20) as well as to good coherence among the redox-paired electrodes.
The ability to use 3D printing to fabricate complex, yet compact, electrode structures offers the promise of new battery designs such as cell-on-a-chip. For reproducible electrodes, the properties of ink that is used to print the graphite need to be improved. Further studies will be needed to see if the 3D printed electrodes' morphology can also be changed to improve performance.
English
Write a Message