(picture) Quiroga-Gonzales, E.,Carstensen Jurgen, Föll, Helmut, "Scalable processing and capacity of Si microwire arrays for Li ion battery anodes." Nanoscale Research Letters 2014.
Lasts Longer between Charges
Silicon has one of the highest lithium capacities of any other material. This feature allows for higher power and longer life between charging cycles. Unfortunately, because silicon can absorb so much Li, it expands 3 to 4 times its intial volume which leads to cracking and preventing the charge - discharge cycle. However, with pores, wires, or tubes etched into the Si anode, stress is reduced during exansion, and cracking is eliminated. This allows the high power, long life batteries to be cycled over and over without losing their initial properties.
Increased Lifetime
By controlling the balance between chemistry, current density, and silicon resistivity, porosity can be customized to achieve the desired capacity and cycling lifetime. During the charging or lithiation process phases of Li12Si5 and Li22Si5 can be found. The porosity or space between nano and /or microwires reduceds the strain during volume expansion at the same time allows room for full absorption of the Si at quicker lithiation and deliathion times due to more available surface area and better replentishment of the electrolyte around the wires.
Current Battery Trends.
<12V For consumer electronic and wearable electronic devices
48V For micro and mild hybridized vehicles
>300V For full electric drives.
48V For micro and mild hybridized vehicles
>300V For full electric drives.
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courtesy of Dr. Thierry Djenizian from the University of Aix en Marseille.
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courtesy of Dr. Biswal of Rice University.
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Possibilities for Si Anodes
Si can be etched in a multitude of different structures. Long needles can be created as well as sponge-like particles. Although the Silicon has a natural Doping or conductance Level, the anodes need to be conductively enhanced. This can be done by adding the Si particles to a conductive Matrix or coating the particles with carbon.
A chemically etched porous Silicon particle using the Vesta Process. Courtesy of Vesta Sciences, Inc.
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courtesy Dr. Thierry Djenizian from the University of Aix en Marseille.
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Making Batteries
By using the porous Silicon tape, the battery "sandwich" can be built up. (Cathode/Electrolyte/Membrane/Anode). PSi powders can be shaped into a flexible tape while preserving porosity and surface area using a Teflon defibrillation technique. Vesta Sciences, Inc.
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Battery Cell Composition
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Challenges and Opportunites for Batteries
1. High and low temperature stability:
2. Charge and discharge cycling:
3. Compactness (size,height weight):
4. Cost:
5. Liquid Lithium electrolyte stability:
2. Charge and discharge cycling:
3. Compactness (size,height weight):
4. Cost:
5. Liquid Lithium electrolyte stability:
Electromobility is here! (and tested)
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