HAWLEY George C. Hawley & Associates

Transcription

1 COMPARISON OF GRAPHITE ANODES WITH COMPETITORS GRAPHITE SUPPLY CHAIN NOVEMBER 2016 ISLAND HOTEL NEWPORT BEACH CALIFORNIA USA

2 GEORGE C. George Hawley was Research and Development Chemist at Morgan Crucible Company, one of the world s largest graphite product manufacturers. He worked on synthetic graphite, used for anodes, nuclear graphite, rocket nozzles, carbon brushes, clutch and brake pads, and trolley bus contacts He was R&D and Process Control Chemist at Pritchett & Gold, a division of Exide/Chloride, working on lead acid battery manufacture. This included all phases lead paste production, grids, pasting, formation, plastics separators, and battery cases In 2000, he returned to the graphite sector and has consulted for both North American graphite miners and multiple graphite juniors Main activities are environmentally acceptable process development of specialty graphite for lithium-ion battery electrodes and Generation 2 & 3 graphite-based electrodes Serves as Director of Technology for Alabama Graphite Corp.

3 COMPARISON OF GRAPHITE ANODES WITH COMPETITORS ABSTRACT Graphite, synthetic and natural, has been the standard lithium-ion anode active material since introduction by Sony in 1991 Graphite replaced lithium metal which had severe safety issues The electrochemical capacity of existing graphite anodes is not high. Natural graphite is up to 20% better than synthetic graphite Some metals and oxides have higher capacity than graphite. But all suffer from problems related to safety, cost and volume expansion Main competitors are nanolithium titanium oxide (LTO), silicon metal and lithium metal LTO is very stable, long lived and able to be charged rapidly, but has about one-quarter the energy of a graphite anode On charging, silicon metal expands by up to 370%. This causes fragmentation, loss of electrical contact and short cycle life Lithium metal is extremely reactive, gives off hydrogen when wetted, with resulting fires and explosions. On charging, it grows dendrites, fine metal filaments that penetrate the plastic separator and short out the battery Attempts to overcome these problems required exotic manufacturing processes that add cost Graphite remains the safest and most cost effective anode active material It is possible to increase the capacity of graphite by %.

4 SPECIFIC CAPACITY AND VOLUME CHANGE FOR SOME ANODE MATERIALS (GIVEN IN THEIR LITHIATED STATES) ANODE MATERIAL THEORETICAL SPECIFIC CAPACITY (mah/g) VOLUME CHANGE (%) LiC LTO Li 22 Si Li 3862 Depends on thickness Li 13 Sn Li 9 Al

5 COMPARISON OF ALABAMA GRAPHITE CORP. NATURAL COATED SPHERICAL PURIFIED GRAPHITE (CSPG) VS. SYNTHETIC GRAPHITE PROPERTY CPREME CPREME CPREME GELON MCMB GELON MCMB GELON MCMB GELON ALABAMA GRAPHITE CORP. G15 From coke G8 From coke G5 From coke High rate MCMB from pitch Standard MCMB High capacity MCMB GN 818 Natural purified spheronised ULTRA Natural purified spheronised coated D >=8 >= D D <=32 <= BET <=1.5<= TD >=1.2 >=1.28 >= Reversible capacity, mah/g >=300 >= Irreversible capacity loss % nd Initial Coulombic Efficiency % >=93 >=91 >=91 nd 94.9 Graphite % Price, US$/kg Source: ConocoPhillips CPreme literature; Linyi Gelon LIB Co., Ltd., (China) website; Alabama Graphite Corp. test results (January 19, 2016)

6 LITHIUM-ION INTERCALATION IN GRAPHITE IN C DIRECTION IN CROSS-SECTION RX (donor solvent) R (decomposed solvent) Li LiX

7 CROSS-SECTION OF A TYPICAL LITHIUM-ION CELL ANODE Anode Paste Cu Foil Anode Paste 90% Graphite 5% Binder 5% Carbon Black 45µ 10µ 45µ Electrolyte Separator Plastic, PP etc µ Electrolyte mah/g CATHODE Cathode Paste 84% LiNi 8 Co 0.8 Al 0.05 O 2 4% Graphite 4% Carbon Black 12-88%hi 8% Binder (PVDF or SBR) Aluminum Foil Cathode Paste 85-90µ 20µ 85-90µ

8 COMPARISON OF LTO WITH GRAPHITE ANODES PROPERTY COMMERCIAL LTO COMMERCIAL NATURAL GRAPHITE COMMERCIAL SYNTHETIC GRAPHITE Lithium doped anatase Crystalline carbon Crystalline carbon Purity Density, g./cc Particle size, d50, microns Surface area, BET, sqm./g. 100 crystals, 2-6 agglomerates Tap density, g./cc. < Cell voltage vs. LiFePO Reversible capacity, mah/g Irreversible capacity loss, % low Li+ diffusion rate, sq.cm/s 4.7 x x (30% SOC) 6.5 x (30% SOC) Expansion on charging, % e/ Cycle life 20,000 1,000-5,000 5,000

9 DISADVANTAGES OF LTO COMPARED TO GRAPHITE 56-65% of voltage 44-48% of specific capacity Swells on reaction with electrolyte to give off flammable/explosive gases 60% heavier than graphite Low electronic conductivity titanium dioxide is an insulator 20,000 cycles = 60 year life is claimed High cost $30/kg versus $10/kg for spherical coated graphite ADVANTAGES OF LTO COMPARED TO GRAPHITE Low expansion on charging 0.7% Faster Li+ diffusion coefficient Rapid charging 6 10 minutes Low irreversible capacity loss No dangerous heat build up is claimed Very large supply of titanium dioxide

10 USING SILICON ANODES INTRODUCES ANOTHER LEVEL OF COMPLEXITY BECAUSE WE RE APPLYING A NEW CONSTRAINT CHRISTIAN RUOFF CHARGED ELECTRIC VEHICLES MAGAZINE (2015)

11 EXPANSION OF SILICON UPON LITHIATION Silicon undergoes a large volume expansion as it soaks up lithium like a sponge Source: Rees Rankin, Argonne National Laboratory

12 GRAPHITE/SILICON ANODES-PANASONIC CELLS PROPERTY 3.4 AH (2012) 4.0 AH (2013) Cathode NCA NCA Anode Graphite Graphite + Silicon Capacity, Ah Voltage, discharge, V Mass, g Energy capacity, Wh (+11.5%) Specific capacity, Ah/g Volume Energy density, Wh/L Charging voltage, v Source: Green Car Congress

13 REACTIONS OF LITHIUM METAL Lithium metal reacts with water, oxygen, nitrogen, and carbon dioxide With water, each 6.94 grammes of lithium metal produces 11.2 litres of explosive and flammable hydrogen gas The Tesla S battery contains kg of lithium. But its anode contains graphite + silicon, NOT lithium metal It does not react with water and cannot form 13,233 16,461 litres of explosive hydrogen On charging, lithium metal anodes grow dendrites which penetrate the separator and short out the cell Lithium metal foil has limited supply and costs $105,000/tonne, 13 times the cost of anode graphite Good reasons not to use lithium metal anodes

14 ACTUAL EXPLOSIONS WITH LITHIUM METAL BATTERIES Avestor sold 17,000 lithium metal batteries to AT&T, in 2007, for use in broadband equipment cabinets, that were installed on customers lawns They started blowing up due to battery malfunction So all 17,000 were replaced by safer batteries, after Avestor went into bankrupcy 1 Bollore of France put lithium metal batteries in Blue cars, used by Autolib in Paris, France. They are the equivalent of Uber. So far, 25 of these cars have caught fire while parked

15 RULES FOR CARRY-ON OF LITHIUM-ION BATTERIES Both lithium metal and graphite battery types, including spare packs, are allowed as carry-on but cannot exceed the following lithium content: 2 grams for lithium metal or lithium alloy batteries 8 grams for lithium-ion batteries For a lithium-ion cell, this is calculated at 0.3 times the rated capacity (in ampere-hours) A 2Ah Li-ion cell has 0.6 grams of lithium content A typical 60 Wh laptop battery contains 4.8g lithium

16 ENERGY CONTENT OF A TESLA MODEL S BATTERY TESLA MODEL S BATTERY HAS 85 KILOWATTS OF ENERGY =

17 COMPARISON OF GRAPHITE ANODES WITH COMPETITORS CONCLUSIONS Substitutes for graphite as anode reactive material in lithium-ion batteries may be acceptable for use in small devices, like mobile phones and lap top computers Cost, volume and weight are not so critical in those applications, although safety remains an major issue In battery-driven electric vehicles of all types, safety is the primary concern, followed by cost, space and weight All competitors to graphite fall significantly short in one or more of these factors Natural graphite remains the safest, most cost-effective anode active material Natural graphite s one short-coming is its capacity, although research has demonstrated this can be improved by low-cost modification

18 NATURAL GRAPHITE REMAINS THE SAFEST, MOST COST-EFFECTIVE ANODE ACTIVE MATERIAL

19 THANK YOU