Patent filing number: 613/KOL/2014
Technology title: Porous nanostructured tin-animony-copper intermetallic electrodes as anode material for lithium ion batteries
Technology title: Porous nanostructured tin-animony-copper intermetallic electrodes as anode material for lithium ion batteries
The
technology is capable of fabricating Tin-Antimony- Copper based open-pore three
dimensional nanostructure anodes for lithium ion batteries, which display high
discharge capacity as well as good cyclability. The fabrication was carried out
through electrodeposition route and devoid of any post-plating treatment except
vacuum drying. The developed anode did not contain any binder or additive which
take up lithium and add to capacity.
2.
Commercial aspects of the technology &
Industries benefiting from it
Electronics industries are heavily dependent
on high capacity batteries.Various automobile companies are looking forward to
launch electric vehicles to conserve fossil fuels. However they are stuck with performance
of the battery especially the specific capacity. This technology has come up
with a cheap fabrication process to increase battery capacity and will definitely
be in the eye of those companies.This methodology can also be implemented to
design and fabricate power sources for MEMS devices which are currently finding
its use in diverse fields like biomedical instrumentation.
3.
Advantages of this technology over the already
existing methods
Currently, most commercial lithium - ion batteries use
graphite as the anodic material and lithium mixed oxide (e.g. LiCoO2)
as the cathodic material. Graphite, though readily available at an economical
price, has a low theoretical gravimetric capacity (372mAh/g). This, in turn,
reduces the overall discharge capacity of the battery. Recently, tin has
emerged as one of the novel materials which have the potential to replace
carbonaceous anode materials as it has a very high theoretical capacity (993
mAh/g). It however suffers from the drawback of a very high volume change
during the lithiation/delithiation process (about 300%). This high volumetric
expansion can lead to the gradual detachment of the anodic material from the
current collector as well as its pulverization which ultimately results in a poor
cyclability performance of the battery.
Various efforts have been made in this direction to
overcome this particular shortcoming of tin based anodes. Alloying or forming
mixtures with other active metals, notably antimony, is one of the most tried
methods. While antimony is an active element, it reacts with lithium at a
potential different from tin and hence buffers the expansion of the latter when
it reacts with lithium.
Various efforts have been made in this direction to
overcome this particular shortcoming of tin based anodes. Alloying or forming
mixtures with other active metals, notably antimony, is one of the most tried
methods. While antimony is an active element, it reacts with lithium at a
potential different from tin and hence buffers the expansion of the latter when
it reacts with lithium.
4.
A summary of the technical details involved.
This method uses an aqueous solution of inorganic salts
of tin, antimony and copper and does not consist of any kind of surfactant or
detergent. Deposition was done at very high overvoltage to facilitate hydrogen
evolution in order to obtain a porous structure. The anode material shows a consistent
capacity over 1100mAh. This is possible because of the presence of
intermetallics in the material and open-pore morphology.
5.
Future prospects of
the technology.
To further increase the electronic conductivity of the
anode and hence improve the rate capability, we plan to incorporate carbon
nanotubes or graphene into our alloy system. This methodology is expected to
show a drastic increase in the power density of the anode. We further plan to
use this system as the anode for a battery along with the cathode which has
been developed by our collaborators and improve on the results which we will
obtain.
Inventors: Prof. Siddhartha Das, Prof. Karabi Das, Mr. Abhinav Kumar, Mr. Srijan Sengupta, Mr. Arijit
Mitra
The basic technology behind extrusion in this article was the assembly based on disposable syringes. This is depicted Fig. 1(a). A syringe of 230 microns diameter was bent at angle of 120 degree and inserted into an outer needle of diameter 700 microns. Both the syringes were commercially available, each costing Rs. 10 (USD 0.15). This assembly was sealed with adhesive to make it leak proof and also to maintain the concentric arrangement of the needles. The extrusion mechanism was carried out as depicted in Fig. 1(b) and 1(c). The polymer flow was facilitated by the pressure applied (140-200 kPa) by the nitrogen cylinder and the water was flown from an overhead tank due to gravity. The minimum height maintained for the spinning of fibers was 160 cm from the ground. The water flowing through the syringe forms the hollow core of the fiber which, after extrusion, was put into the gelation bath containing normal tap water. The fibers were then wound on the spool. In this whole arrangement, there was no need of electricity anywhere, except in the final step where the spool was rotated by a variable voltage variable frequency drive. Cost of syringe assembly was $0.3 (Rs.20) and the rest of the paraphernalia too were non-expensive making this technology to be ultra-low cost.