Nov 26 2015
Focus Graphite Inc. ("Focus" or the "Company") is pleased to announce excellent results from independent laboratory tests conducted to compare the long term cycling performance of Lac Knife surface coated spherical crystalline fine flake graphite with two commercial grades of coated crystalline flake graphite in the anodes of CR2016 coin cells.
The results presented are a follow up from data presented in Focus' February 26, 2015 news release where similar tests were run on "as-is" minus 200 mesh fines of Lac Knife graphite which also showed to have excellent long term cycling performance.
Testing was conducted at a globally recognized laboratory in Europe. The name of the laboratory is being withheld because of commercial and competitive confidentiality.
Highlights:
- Coin cell tests run on purified uncoated and coated standard grades of Lac Knife spherical graphite (SPG) showed that both grades exhibited essentially no loss in capacity up to the limit of the tests of 110 cycles
- Coin cell tests run under the same formulation and conditions showed that the two commercial grades of coated flake graphite exhibited capacity losses of 4.35% and 6.43% up to the limit of the tests of 110 cycles.
Focus Graphite is the sole owner of the high purity Lac Knife natural flake graphite project in the Côte-Nord region of northeastern Québec.
The Company's aim is to become one of the lowest cost producers of high-purity technology graphite. The purpose of its ongoing battery materials testing efforts is to validate the commercial viability of the high purity crystalline flake graphite recovered from its Lac Knife deposit, and to demonstrate that Lac Knife graphite holds the potential to improve the performance of anodes in Lithium Ion batteries. (See May 27th, 2014 and February 26th, 2015 News Releases).
The properties of the flake graphite recovered from the Lac Knife high quality and high carbon content graphite deposit, allow for the recovery of concentrate that grades 98% C even in the finer size fractions down to 200 mesh (75 microns) that are usually the most difficult products to sell. This holds the potential for Focus to create a high-margin business opportunity by providing customers with a finer grade, lower cost, value-added graphite product.
The Company's material testing program is supervised by Dr. Joseph E. Doninger, Focus' Director of Manufacturing and Technology, and a global expert in graphite processing and product development.
"Of particular note is that these new results showing that the Lac Knife graphite exhibits excellent long-term stability, adds to the results reported in our February 2015 news release," said Dr. Doninger.
"That previous data," he said, "presented Lac Knife's graphite as exhibiting very high reversible capacities and very low first cycle capacity losses.
"Combined, these improved properties would make Lac Knife graphite an excellent replacement for both the synthetic and natural flake graphites currently being used in the manufacture of Lithium-Ion batteries," said Dr. Doninger.
Battery manufacturers require a cost competitive alternative to current sources of synthetic and natural flake graphite. China produces the majority of the world's purified SPG, using methods generally regarded as environmentally unsustainable.
Presentation of Data:
All Lac Knife flake graphite materials tested were purified, spheronized and sized for application in the anodes (negative electrodes) of Lithium-Ion batteries. The anodes for all samples tested consisted of 90% graphite, 7% PVDF binder and 3% carbon black and a copper coil current collector with a thickness of 20 microns. All cells were assembled and tested in a CR2016 coin cell configuration prepared with 1M LiPF6/EC/DMC electrolyte and lithium foil counter electrodes. The coin cells were then cycled between 0.003 and 1.5 volts. Formation was carried out with C/10 current density and cycling was carried out with the same voltage limits at C/10. To evaluate the cycling performance, half cells made with the lithium metal counter electrode were charged and discharged at a relatively low current density and cycled galvanostatically at a C/10 rate until the limit of the test was reached.
Figure 1 below compares the long-term cycling performance of both the spheronized uncoated and surface coated standard grade of purified Lac Knife graphite. The standard sizing of the Focus Graphite's Lithium-Ion coated graphite has a d50 in the range of 23 to 29 micrometers. The surface area of the uncoated SPG was 5.25 m2/gram which actually is too high and not suitable for use directly in Lithium-Ion batteries.
The use of high surface area graphites have been known to contribute to thermal runaways and fires in Lithium-Ion batteries. It was this material that was coated with a passivating surface coating which reduced the surface area to less than 2.0 m2/gram to produce the standard grade of coated SPG and make it suitable for use in the anodes of Lithium-Ion batteries.
Figure 1. Long-term cycling performance of Lac Knife Purified Spheronized Standard Grade of natural crystalline flake graphite with and without surface coating (CR2016 cells, Li/Li+ counter electrode; C/10 cycling rate; reversible capacity only shown). http://file.marketwire.com/release/fms1125.jpg
As shown both the uncoated and coated standard Lithium-Ion grade of the Focus graphite exhibited essentially no capacity loss after 105 and 110 cycles, respectively which effectively was the end of both tests. What is important here is that, although the surface coating applied to the SPG is critical to the safety of Lithium-Ion batteries, it is the high quality of the Lac Knife graphite that provides the long term cycling stability to the Lithium-Ion battery. The data also show that the surface coating improves the reversible capacity of the Lac Knife SPG in the cell.
Figure 2 compares the long term cycling performance of the Lac Knife standard grade of coated SPG with two commercial Lithium-Ion grades of purified coated crystalline flake graphite. As noted previously both of these commercial Lithium-Ion grades were tested in CR2016 half cells under the same formulation and conditions of the Lac Knife cells.
Figure 2. Long-term cycling performance of Lac Knife Purified Spheronized Coated Standard Grade of natural crystalline flake graphite compared to two commercial grades of purified coated spheronized natural flake graphites (CR2016 cells, Li/Li+ counter electrode; C/10 cycling rate; reversible capacity only shown). http://file.marketwire.com/release/fms21125.jpg
The long term cycling performance of the standard grade of coated SPG is the same as that in Figure 1 which showed that there is essentially no capacity loss after 110 cycles. Although the cells made with all three graphites start out with a reversible capacity of around 350 mAh/g (Figure 2), only the cell made with the Lac Knife standard grade of coated SPG showed essentially no loss in capacity after 110 cycles and the conclusion of the test. The long term cycling tests of the first commercial grade of Lithium-Ion grade flake graphite ended up with a reversible capacity of 335.16 mAh/g after 110 cycles and a capacity loss of 4.35%. A similar loss in performance is observed with the second commercial Lithium-Ion grade of flake graphite ending up with a reversible capacity of 322.84 mAh/g and a 6.43% capacity loss after 110 cycles.
The fact that the Lithium-Ion half-cells made with the standard coated grade of Lac Knife SPG showed essentially no loss in capacity after long term cycling is critical to the performance of Lithium-Ion batteries for all applications in the field. For example, these data suggest that the excellent long-term stability achieved in half cells with the use of Lac Knife graphite in Lithium-Ion batteries should ultimately result in an increase in the range of electric vehicles before they have to be re-charged.
Qualified Person
Joseph E. Doninger, PhD., M.Sc., B.Sc. (Chemical Engineering) and Focus' Director of Manufacturing and Technology, a Qualified Person under National Instrument 43-101 - Standards of Disclosure for Mineral Projects, has reviewed and approved the technical content of this news release.
Source: http://www.focusgraphite.com/