Change Again, Lithium Ion-Silicon-Sulfur Ultra-capacitor/battery Hybrid

A project log for WRONG PROJECT 2


MECHANICUSMECHANICUS 08/19/2015 at 10:290 Comments

Since Super-capacitors can only hold a theoretical 400mWh per gram a change has been needed I do not see them as viable when placed in a race with a lithium sulfur battery with a theoretical 2200mWh per gram and a proven capacity of up to 1300mWh per gram.

A Lithium Ion, Sulfur-Cathode, Silicon Anode battery has not been tried yet. The question is why has this not been tried? Silicon-Lithium batteries are made with nano-silicon wires pre doped with lithium in the Anode. Sulfur Lithium batteries are made with a Solid Lithium Anode and a Sulfur Cathode. Combining the two should allow a greater increase in performance.

Lithium-Sulfur batteries have a theoretical energy density of 2200mAh per gram, Lithium-Silicon batteries also have a theoretical energy density of 4200mAh per gram. Super Capacitors have an theoretical energy density of 200-400mWh per gram.

The idea now is to combine all three and reduce the lithium required to make the Ultra-capacitor by half of that of a normal battery.

In order to create the Anode a very high loading of Urea will be required to fully reduce the Kieselguhr (amorphous Silicon Dioxide SiO2) GO, oxIMWCNT and lithium hydroxide. Kieselguhr should provide a benefit over SiO2 nanowires in that its total surface are should be much higher. The benefit should remove the need for a binder as the anode will be highly cross linked. MnO2 addition will increase the lithium ion storage capability of the small amount of Carbon needed to facilitate electron flow to and from the reduced SiO2[1}. This electrode will be spun cast onto a stainless electrode and reduced in-situ via microwave assisted urea reduction. I will harvest the lithium from an energizer battery and convert it to hydroxide by placing it in water.

A reduced Graphene Oxide, oxiMWCNT secondary Anode will protect the Primary Silicon Anode from sulfating significantly increasing the lifespan[2]. This should also provide a layer that will demonstrate Psuedo-capacitance with a phosphoric acid/lithium ion electrolyte. A dodecylbenzene sulfonic acid seperator will be applied to the interspacial area between the secondary anode and the cathode, this will allow the psuedocapacitive double layer to avoid leakage while remaining permable to ion flow under normal conditions this has also not been tried. Ideally the psuedocapacitive effect should have the least resistance and discharge/charge first allowing surge power and surge charging to happen almost instantaneously. A crosslinked solid PVA borax electrolyte should provide enough support to keep the secondary anode from degrading do to ion swell during charging. The amount of borax needed is a large variable and will require much experimentation. This electrode will be drop cast upon glass containing an aluminum mesh screen, then reduced in-situ via microwave assisted urea reduction.

The cathode will be constructed with a majority of Asphaltenes as the 7% sulfur and 3% nitrogen loading as well as vanadium and nickel hemes will allow a large amount of lithium to be adsorbed upon discharge of the cell and will facilitate faster charge/discharge rates{3,6}. A small amount of partially reduced N Ox MWCNT will allow higher conductivity on the Cathode. A binder in the form of Chitosan will be required due to the small amount of reduction and subsequent cross linking of the Cathode. The chitosan will also sufficiently retain the sulfur in the cathode reducing the significant wear rate from sulfur migration seen in as to date lithium-sulfur batteries. This electrode will be partially solvated and dispersed in household vinegar drop then drop cast onto a stainless steel charge carrier. It will then be reduced via urea microwave assisted reduction in-situ

Ideally the electrolyte should be an ionic liquid to allow higher super, constructed with quaternary ammonium salts. However I have tried unsuccessfully to create one with cheap readily available materials, as the urea used to form the deep eutectic solvent degrades upon charging releasing ammonia and reducing oxygen functional groups. Hence the desire to go back to a solid PVA phosphoric electrolyte. The proposed plan is to simply harvest lithium salts from a worn out lithium ion battery. Cutting one apart was scary but it did proved a large portion of lithium salts scraped from the semi-permeable membrane separator.

The question remains to whether the lithium ions will be motile in this electrolyte. Only time can tell as literature does not specifically cover PVA as an organic solvent that allows efficient transfer of lithium ions. It works for phosphoric acid so it should for the Li+ ion. Another issue is whether or not try and use a copper charge collector on the anode as is widely used in lithium ion batteries do to its electronegativity and excess electrons.

  1. Wu, Xiaomin; Li, Huan; Fei, Hailong; Zheng, Cheng; Wei, Mingdeng (2014). "Facile synthesis of Li2MnO3 nanowires for lithium-ion battery cathodes". New Journal of Chemistry 38: 584–587.
  2. "Li-S battery company OXIS Energy reports 300 Wh/kg and 25 Ah cell, predicting 33 Ah by mid-2015, 500 Wh/kg by end of 2018". Green Car Congress. November 12, 2014. Retrieved February 2015.
  3. Creative Commons Attribution-ShareAlike License.
  4.–sulfur_battery Creative Commons Attribution-ShareAlike License.
  5. Creative Commons Attribution-ShareAlike License.
  6. American Vanadium Corp. "Lithium Vanadium Phosphate Battery". Retrieved 2013-10-22.