Graphite can be used as a conductor. It has a high thermal resistance, excellent chemical stability and is a good material for batteries. It can deliver more than double the energy density of conventional batteries when combined with silicon. Although the graphite-electrode manufacturing process can be complicated and costly, it is a viable option. A new digital deposition method of graphite on a slurry can produce electrodes which have higher energy densities.
Multichannel graphite electrodes (MGrEs), consisting of 4 WEs, 1 pseudo-RE, and a reference electrode were made on an electrode platform. The electrode layout was created using a computer program and printed onto vinyl adhesive sheets to be used as stencil masks. The stencil is placed onto the PP surface and then carbon-graphite ink is spread over it with a squeegee. After the ink had dried, the PP was cured for 70 degC. This was done to evaporate the solvent. The squeegee removed, revealing graphite multichannel electrodes on PP.
Digitally printed electrodes exhibited good precision between the WE and the RE, with RSD values of less than 6%. They displayed better peak currents and peak to peak separation responses than the draw-down electrodes, and their capacity retained remained constant for longer cycles. The MGrEs showed better electrochemical performance in terms of exchange currents and electronic conductivities, as well as lower tortuosity.
A cross-sectional SEM study revealed that the electrodes deposited by syringes are trapezoidal, with a greater gap at the top of the collector than the bottom. The gap size was 0.05 mm. SEM images indicated that the particles of graphite were agglomerated. They also changed their alignment from parallel to oblique to the current collector.
All frequency ranges were studied and the syringe coated electrodes showed higher electronic conductivities. The reduced resistance to contact was due to the alignment and agglomeration graphite. This improved conductivity is also a result from the reduced SEI resistance due to the reduced tortuosity of the graphite and pore network.
The lithiation and the delithiation both of Si and graphite contributed to the overall capacity of the blended electrodes, with graphite contributing the most during lithiation. However, the contribution of each to the total capacitance depends on the mass ratio of the two materials. The greater the ratio of Si graphite in mass, the more graphite is able to contribute during lithiation. This results in higher specific capacities at higher SOCs. This suggests the use of mixed electrodes can help increase the battery's energy density without compromising the safety profile. This is very interesting and could lead to more investigations into the benefits associated with different blends.
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