WO2020013718A1 - Method of manufacture of carbonaceous material for anode mass of lithium ion cell as well as material obtained using this method, and method of manufacture lithium ion cell anode using said material and anode obtained thereby - Google Patents

Method of manufacture of carbonaceous material for anode mass of lithium ion cell as well as material obtained using this method, and method of manufacture lithium ion cell anode using said material and anode obtained thereby Download PDF

Info

Publication number
WO2020013718A1
WO2020013718A1 PCT/PL2019/000053 PL2019000053W WO2020013718A1 WO 2020013718 A1 WO2020013718 A1 WO 2020013718A1 PL 2019000053 W PL2019000053 W PL 2019000053W WO 2020013718 A1 WO2020013718 A1 WO 2020013718A1
Authority
WO
WIPO (PCT)
Prior art keywords
anode
carbonaceous material
manufacture
graphite
mass
Prior art date
Application number
PCT/PL2019/000053
Other languages
French (fr)
Inventor
Maciej RATYŃSKI
Bartosz HAMANKIEWICZ
Andrzej CZERWIŃSKI
Original Assignee
Uniwersytet Warszawski
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Uniwersytet Warszawski filed Critical Uniwersytet Warszawski
Publication of WO2020013718A1 publication Critical patent/WO2020013718A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • a subject of the present invention is a method of manufacture of a carbonaceous material having increased intercalation capacity and electrochemical stability, which is a component of an anode mass of a lithium ion cell, and a carbonaceous material obtained using this method, and a method of manufacture of a lithium ion cell anode using said material and anode obtained thereby.
  • Li-ion cells are one of the most efficient electrochemical energy sources presently available on the market.
  • other types of cells are tested, for example sodium and calcium cells, however taking into account problems with reliability and safety of use, such cell has not found commercial use yet.
  • the lithium ion cells have energy density (per whole cell) up to 250 Wh/kg, substantially exceeding capacities obtained in commercially available cells of other types, for example in nickel hydrogen cells (55-90 Wh/kg) or acid lead cells (25-40 Wh/kg).
  • the average work voltage of the lithium ion cells is 3.2-3.8 V, exceeding values achieved by ceils of other types (the nickel hydrogen cells 1.2 V; the acid lead cells 2.0 V).
  • Li-ion cells are their relatively high price resulting partially from high price of metals being components of a positive electrode (like for example nickel and cobalt), and partially from expensive procedure of electrode materials preparation. Thus, there is unmet need for development of easier and cheaper procedure for preparation of such type materials.
  • the capacity of the negative electrode and its stability during many cycles of charge and discharge has direct impact on working parameters achieved by the cell.
  • the electrode materials presently used for design of negative electrodes of lithium ion cell can be divided into three groups: the materials forming metal alloys with lithium, the materials conversionally formed from metal oxides and intercalation materials.
  • the materials which form electrochemical alloys with lithium having a variable structure A y Li x are characterized by very high specific capacity (up to 3590 mAh/g for silicon), however their resistance on consecutive cycles of charge and discharge is weak taking into account significant changes of the material volume (up to 300%) during the uptake of lithium ions. This results in mechanical degradation of the electrode structure and considerable decrease in its capacity.
  • the conversional materials - forming a second group of materials for the construction of the negative electrodes of lithium ion cell, made of metal oxides, for example Sn0 2 , are characterized in that the reaction of forming of Li 2 0 together with the reduction of conversional material take place while the cell is working, resulting in separation of metal or its oxide at a lower oxidation degree. These materials achieve the capacity of approximately 1200 mAh/g, however taking into account incomplete reversibility of the electrode process their capacity drops fast in the subsequent cycles.
  • the intercalation materials have ability of uptaking lithium in their volume.
  • Most of the materials from this group are different types of carbon structural varieties or graphite. Typically, these materials achieve the specific capacity of approximately 300 mAh/g, and have low price and very high resistance on the consecutive cycles of charge and discharge.
  • the lithium ion cells are characterized by great work stability.
  • the cells having graphite electrodes have the highest resistance on the consecutive cycles of charge and discharge, in comparison to the cells which have electrodes made of carbonaceous materials of a lower level of alignment of the atom structure [Carbon 37 (1999) 165]
  • PVDF poly(vinylidene fluoride)
  • the polymer PVDF has a function as a binder and is added for mechanical stabilization of the electrode mass, which has positive impact on its performance during consecutive cycles of charge and discharge.
  • PVDF is usually added to the anode mass as 1-10% solution in N-methylpyridine (NMP) forming a paste, which is then layered on a base which forms a current collector for the electrodes [Electrochimica Acta, 56 (2011) 9700; Journal of Physics and Chemistry of Solids. 67 (2006) 1213]. NMP evaporates, and on the collector a uniform layer of the anode mass is formed.
  • a method of manufacture of a carbonaceous material for an anode mass of the lithium ion cell involving high energy milling of a graphite in the presence of a liquid medium, according to the present invention is characterized in that high energy milling is carried out in a non-metallic mill using energy of milling in the range of 10-34 Wh/g, preferably 22 Wh/g, wherein a mass ratio of the graphite to dispersing agent is maintained in the range of 10:15-10:35, preferably 10:24.
  • a graphite component there is used synthetic graphite with a high level of graphitization, and a diameter of the molecules of 100-1000 pm and a high initial purity, more than 95%, preferably more than 98%.
  • the milling is carried out in a planetary ball mill provided with ceramic milling elements.
  • the milling is carried out in an intermitted regime.
  • a dispersing medium being a mixture comprising no less than 90% of ethyl alcohol, no more than 5% of water and no more than 5% of diethyl ether.
  • a product is filtered on a filter, preferably on a cellulose filter, and then dried at 120°C for 12 h under the pressure below 10 mbar.
  • a carbonaceous material having an oxidation degree of a graphite surface of more than 5%, preferably more than 8% is obtained.
  • the carbonaceous material has much more developed specific surface area: 20-60 m 2 /g, preferably 40 m 2 /g.
  • the carbonaceous material for the anode mass of the lithium ion cell is characterized in that it is obtained (by the method presented above) from a synthetic graphite with a high level of graphitization and a high initial purity, more than 95%, preferably more than 98% and has an oxidation degree of the graphite surface of more than 5%, preferably more than 8%, and has much more developed specific surface area, around 20-60 m 2 /g, preferably 40 m 2 /g, which is preferably produced by a method described above.
  • the method of manufacture of a lithium ion cell anode which involves formation of an anode mass comprising a graphite carbonaceous material with the addition of a conductive carbon and with the addition of a polymer binding component, and then application of this mass on a conductive base, according to the present invention is characterized in that a described above carbonaceous material is used, preferably said material obtained by a method described above, wherein the amount of this graphite carbonaceous material in the anode mass is more than 70%, and preferably the anode mass comprises 80-90% of said graphite carbonaceous material, 5-10% of a conductive carbon and 5-10% of a polymer binding component.
  • a conductive carbon there is used a carbon black, an acetylene black or a commercially available conductive carbon.
  • a polymer binding component there is used poly(vinylidene fluoride), preferably in the form of 5% by weight solution in N-methylpyridine.
  • the anode mass is conditioned by mixing, and then put on the conductive base in a way providing uniform distribution of the mass, preferably by using an automatic applicator provided with a regulated aperture, wherein a thickness of a wet layer the anode mass is 50-400 pm, preferably 200 pm.
  • a conductive base there is used a non-metallic substrate or a metallic substrate, preferably a metallic substrate, particularly a substrate made of copper, steal or lead, the most preferably a substrate in the form of the copper foil having a thickness of 5-50 pm, preferably 10 pm.
  • the conductive base covered with anode mass is dried at elevated temperature under lowered pressure, preferably for more than 10 h, at above 110°C, under the pressure below 10 mbar.
  • the obtained electrodes have electrode packing of 1-5 mg/cm 2 , preferably 1.5 mg/cm 2 .
  • the electrodes have the intercalation capacity for lithium ions of more than 370 mAh/g in the initial work cycles and the capacity of more than 330 mAh/g in the 100-th work cycle, during work under the load no less than 370 mA/g.
  • the anode of the lithium ion cell based on the graphite carbonaceous material with the addition of the conductive carbon and with the addition of the polymer binding component, is characterized in that it consists of a conductive substrate, uniformly covered with the anode mass made of carbonaceous material, described above, obtained from synthetic graphite with a high level of graphitization and a high initial purity, more than 95%, preferably more than 98%, having the oxidation degree of the graphite surface at a level above 5%, preferably more than 8%, and greatly developed specific surface area of 20-60 m 2 /g, preferably 40 m 2 /g, preferably obtained by a method described above, wherein the electrode packing is 1-5 mg/cm 2 , preferably
  • Fig. 1 presents a relation between a specific surface area of the carbonaceous material obtained by the method according to the present invention and a milling energy
  • Fig. 2 presents the mass amount of the elements in the carbonaceous material obtained by the method according to the present invention using different milling energy
  • Fig. 3 presents the structure of the carbonaceous material obtained by the method according to the present invention, which was milled using energy 22 Wh/g (images were obtained by the scanning electron microscope, field A presents an image at high magnification, field B presents an overall image);
  • Fig. 4 presents a relation between the reversible capacity of the carbonaceous material obtained by the method according to the present invention and a milling energy of said material; the relations for 5-th and 100-th work cycle of the electrode made of said material are presented;
  • Fig. 5 presents curves of charge and discharge for the electrode made of the carbonaceous material obtained by the method according to the present invention, which was milled using energy 22 Wh/g; the curves for 1-st, 5-th and 100-th work cycles of this electrode are presented;
  • Fig. 6 presents the discharge capacity of the electrode made of the carbonaceous material obtained by the method according to the present invention, which was milled using energy 22 Wh/g; data obtained for cycles 1-100 are presented; Fig. 7 presents current efficiency of the cycle and cyclic resistances of charge and discharge for the electrodes made of the carbonaceous material obtained by the method according to the present invention, which was milled using energy 22 Wh/g;
  • Fig. 8 presents a relation between the irreversible capacity of the electrode made of the carbonaceous material obtained by the method according to the present invention and milling energy.
  • the present invention relates to the method of preparation the carbonaceous material used as the active component in the electrode mass of the negative electrode of the lithium ion cell (anodes), and the method of preparation of the lithium ion cell anodes using this carbonaceous material.
  • Said carbonaceous material and the anodes obtained using said material may be used in the most types of the lithium ion cells as a main component or an additive for the anode mass (the mass of the negative electrode).
  • the procedure is relatively cheap and the obtained material is characterized by higher electrochemical capacity than materials known from the state of the art, while maintaining high cyclic resistance and possibilities of discharging with a great intensity current (more than 1C).
  • the procedure may be easily adopted in facilities, wherein the carbonaceous materials are used as an active component of the negative electrode.
  • Method of manufacture of the carbonaceous material for the anode mass of lithium ion cell according to the invention involves mechanical modification of a graphite with the addition of dispersing agent. Then, the carbonaceous material is separated and dried in suitable conditions.
  • an initial carbonaceous material there is used graphite, preferably synthetic graphite with a high level of graphitization.
  • the optimal parameters are achieved by use of a material having initial diameter of the molecules in the range of 100-1000 pm.
  • the carbonaceous material of a high initial purity above 95%, preferably more than 98%.
  • a dispersing agent is a mixture comprising ethyl alcohol, water and diethyl ether, wherein the amount of ethyl alcohol exceeds 90% by weight, the amount of water does not exceed 5% by weight, and the amount of diethyl ether does not exceed 5% by weight - counted on total weight of the mixture acting as dispersing agent, which preferably is used in a liquid form.
  • a high energy milling is carried out in non-metallic high energy planetary, vibrational or rotational mill.
  • the milling elements can take the form of balls, discs or rings, applied alone or in combination.
  • ball mills are used.
  • the elements of the mill which are in contact with the milled electrode mass are made of non-metallic material, the most preferably of the ceramic material, for example zirconium dioxide.
  • a mass ratio of a graphite to a dispersing agent is maintained in the range of 10:15 to 10:35, wherein the optimal conditions are achieved preferably at weight ratio of 10:24.
  • the milling process is carried out using energy of milling (P) in the range of 10-34 Wh/g, preferably using energy of milling 22 Wh/g.
  • the total milling energy is dependent on the parameters such as: diameter of the mill (R p ), diameter of the milling vessel (R v ), number of the milling balls (N b ), weight of the milling balls (m), diameter of the milling balls (r), angular speed of the mill (W p ), angular speed of the milling vessel (WNase) , frequency of impacts of the milling balls (f b ), time of milling (t), weight of the milled material (PW) and degree of filling of the milling vessel (f).
  • Milling energy may be counted using a formula as below:
  • the milled mixture is gathered from the elements of the mill.
  • the carbonaceous material is filtered under the atmospheric pressure in the presence of air on a cellulose filter at room temperature. After filtering, the carbonaceous material is dried in vacuum, under the pressure below 10 mbar at 110-130°C for 12 hours.
  • obtained material is used for preparation of the anodes for the lithium ion cells.
  • Method of manufacture of a lithium ion cell anode comprises preparation of the anode mass through mixing the carbonaceous material made of graphite, conductive carbon and binding material, and then putting said mixture on the conductive substrate and fixation.
  • the electrochemical properties of the anode prepared by a method according to the present invention depend on the properties of the graphite modified according to the invention.
  • a carbonaceous material As a carbonaceous material, according to the invention, there is used material based on synthetic graphite described above. It is possible to use this carbonaceous material in any percentage amount, but preferably its amount is 80-90% by weight of the anode mass.
  • the carbonaceous material is mixed with the conductive carbon and binding material, the most preferably in a weight ratio of 9:1:1.
  • a conductive carbon preferably there is used carbon black, acetylene black or conductive carbon Vulcan XC-72R.
  • a binding material there is used polymer material, preferably PVDF (polyfvinylidene fluoride)) in the form of 5% by weight solution in N-methyipyridine.
  • the anode mass is conditioned by mixing.
  • conductive substrate as a current collector for the anode mass.
  • a metallic substrate particularly made of copper, steal, lead, the most preferably substrate is made of copper foil.
  • This foil cannot be too thin (below 5 pm), because it would be too delicate and susceptible to damage during workout.
  • too thick foil more than 50 miti
  • the optimal thickness of the copper foil is 10 pm.
  • the anode mass is preferably applied on the conductive substrate.
  • the mass is applied in a way providing its uniform distribution on the substrate surface, the most preferably by using automatic applicator provided with a regulated aperture.
  • a thickness of a wet layer of the anode mass is 50-400 pm, preferably 200 pm. Thin layers are excellent bound to the substrate and they are stable under the load of a substantial current. However, too small thickness of the mass results in reduction of the electrode capacity. In turn, whereas too thick layers tend to crack, however they provide greater electrochemical capacity.
  • the optimal thickness of the anode mass is 200 pm, because it provides at the same time great capacity and great stability of the electrode.
  • the electrode in the form of a conductive substrate covered with the layer of the anode mass is dried under the pressure below 10 mbar at 110-130°C for 12 hours.
  • the embodiments presented above are characterized by a simplicity and a low price in comparison to the methods of chemical modification of the carbonaceous materials known from the state of the art, as said known methods need purchasing suitable chemicals.
  • the main cost of the processes of the present invention is electric energy related to the milling, whereas the material costs are little. It should be noted that dispersing agent may be mostly recovered and used once again.
  • the used procedure may be easily scaled on the industrial scale, through suitable magnification of the milling device and selection of the suitable milling energy according to the formula relating to Milling energy (P) presented before.
  • the carbonaceous material for the anode mass of lithium ion cell, obtained by a method according to the present invention is characterized by a specific capacity exceeding theoretical maximum (372 mAh/g) in the initial work cycles (the theoretical maximum was obtained on the basis of the atomic mass of carbon in the structure UC 6 being a final product of intercalation).
  • the carbonaceous material obtains full specific capacity (388 mAh/g) in fifth work cycle, which is a value of approximately 10-30% higher in comparison to the materials known from the state of the art.
  • the specific surface area of the carbonaceous material increases as a result of the milling process used. On Fig.
  • the drawing presents selected relations imaging working parameters of the electrode produces by a method according to the present invention.
  • Fig. 4 a relation between the capacity in fifth and one hundredth work cycle of the electrode in function of the used milling energy is presented.
  • Fig. 5 the curves of charge and discharge for 5. and 100. work cycle of the electrode made of the carbonaceous material obtained by a method according to the present invention, by milling with energy of 22 Wh/g is presented.
  • Figs. 6 and 7 respectively, the discharge capacity, cyclic resistance of charge and discharge and current efficiency for 1-100 work cycles of electrode made of carbonaceous material obtained by a method according to the present invention, by milling with energy of 22 Wh/g are presented.
  • the carbonaceous material obtained by the method of the present invention is used according to the invention to the manufacture of the negative electrode of the lithium ion cell is characterized by a high resistance on consecutive cycles of charge and discharge carried out with a high intensity current (more than 1C).
  • the material maintains more than 86% of the initial capacity after 100 work cycles (the capacity more than 333 mAh/g), which is much better result in comparison to negative electrodes known from the state of the art. It should be underline that in the state of the art there are very few reports about tests of carbonaceous graphite materials using high intensity current during multiple cycles of charge and discharge. Available data are most often limited to a few initial cycles or the cycles are carried out with a small intensity current.
  • the anodes produced by a method according to the present invention may work under high current load (>1C, 372 mA/g), allowing to the use of lithium ion cells with these anodes in high power energy receivers.
  • the carbonaceous material obtained by a method according to the present invention by milling with energy of 22 Wh/g, in comparison to the materials milled with other energy, is characterized by a minimum irreversible capacity related to the electrolyte decomposition in the initial work cycles, what has a positive impact on the costs of production of the cells, improves safety of the work and reduces negative impact on the natural environment.
  • the electrolyte used in the lithium ion cells is typically flammable and dangerous for the natural environment. Its decomposition during work of the cell is related to the formation on surface of the electrodes a passive layer in the initial work cycles, below potential approximately of 0.8 V vs. Li/Li + .
  • Example 1 The carbonaceous material for the anode mass of the lithium ion cell was obtained by high energy milling of the synthetic graphite in a planetary ball mill. 10 g of the commercially available material - synthetic graphite was placed in the ball mill together with 273 porcelain balls with a diameter of 5 mm and average weight of 0,41 g. 24 g of dispersing agent comprising > 90% by weight of ethyl alcohol, ⁇ 5% by weight of water and ⁇ 5% by weight of diethyl ether was also added to the milling vessel. The milling vessel was filled in 65% of volume.
  • Milling was carried out at nominal rotation of the mill of 500 rpm, with 30 min brakes after one hour of milling, wherein total effective time of milling was 10 h, and total operation time 14.5 h. Milling energy (P) was 22 Wh/g.
  • the obtained product was gathered from the porcelain balls, and then separated from the dispersing agent by filtration on a cellulose filter.
  • the carbonaceous material was dried at 120°C for 12 h under the pressure below 10 mbar. In the process 9.33 g of the carbonaceous material was obtained. Yield was 93.3%.
  • a specific surface area of the obtained carbonaceous material was tested by a method of analysis nitrogen adsorption / desorption curve by a BET method.
  • the obtained carbonaceous material was characterized by a high specific surface area of around 40 m 2 /g ⁇ As a result of milling the specific surface area increased by more than 1300% in comparison to the specific surface area of the initial material of ⁇ 3,0 m 2 /g.
  • the morphology of the obtained carbonaceous material was also tested by using electron microscopy.
  • the obtained material was characterized by a high development of the surface and a partial exfoliation of the graphite in the surface part of the grains, while maintaining the inner layer structure of the graphite in their inner part.
  • Fig. 3 the microscopic images of the obtained carbonaceous material are presented.
  • the elemental composition of the obtained carbonaceous material was tested by a method of X-ray Energy Dispersive Spectrometry.
  • the obtained material was characterized by increased mass ration of oxygen to carbon.
  • the partial surface oxidation of the material was observed as a result of high energy milling in the presence of dispersing agent.
  • the obtained material milled using energy of 22 Wh/g, comprised 8% by weight of oxygen atoms, whereas the initial material has below 2% by weight of the oxygen atoms.
  • Fig. 2 the mass amount of the selected elements (carbon, oxygen, silicon, aluminium) in the sample of the carbonaceous material is presented.
  • Example 2 The negative electrode for the lithium ion cell was prepared by use of the carbonaceous material obtained in the example 1. 200 mg of the carbonaceous material (obtained in the example 1) was mixed with 25 mg conductive carbon Vulcan XC-72R from Cabot, and then said mixture was grinded manually in a porcelain mortar for 10 minutes. 25 mg of PVDF (poly(vinylidene fluoride)) in the form of 5% by weight solution in NMP (N-methylpyridine) was added to the grinded mixture, and then the whole mass was mixed for 4 hours with a magnetic stirrer with speed 400 rpm. The obtained mass was put on the copper foil by using automatic applicator provided with a regulated aperture, wherein a thickness of a wet layer was 200 pm.
  • PVDF poly(vinylidene fluoride)
  • NMP N-methylpyridine
  • the foil covered with a carbonaceous layer was dried for 12 h at 120°C under the pressure ⁇ 10 mbar.
  • the electrodes were formed by cutting out circles with a diameter of 9 mm from obtained foil by using a hand cutter. Finished electrodes were compacted for 60 s under the pressure of 200 bar by using hydraulic press. A packing of the electrode material on the electrode was 1,0-1.5 mg/cm 2 .
  • Example 3 The electrodes obtained in the example 2 were subjected to a standard assessment of the intercalation properties in relation to Li + ions.
  • the measurements of galvanostatic charge and discharge of the lithium ion cell were carried out, wherein the negative working electrode was electrode obtained in the example 2.
  • the auxiliary and reference electrode was a metallic lithium.
  • the electrolyte comprising 1M solution of LiPF 6 in the solvent mixture: ethylene carbonate/dimethyl carbonate in a weight ratio of 1:1 was used in the cell.
  • the polypropylene separator Celgard 2400 was used as a separator. Whole was placed in three- electrodes housing Swagelok ® .
  • the measurements were carried out on the apparatus provided with a digital recorder of charge and discharge curves. During test, the intensity of the current was 1C (372 mA/g).
  • the working cycle comprised galvanostatic charge and discharge between potential of 0,01V-3,00V in relation to a reference electrode made of metallic lithium.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

A method of manufacture of a carbonaceous material for an anode mass of a lithium ion cell involving high energy milling of a graphite in the presence of liquid medium, according to the present invention is characterized in that high energy milling is carried out in a non-metallic mill using energy of milling in the range of 10-34 Wh/g, preferably 22 Wh/g, wherein a mass ratio of a graphite to a dispersing agent is maintained in the range of 10:15-10:35, preferably 10:24. The obtained product has a developed specific surface area of 20-60 m2/g, and the oxidation degree of the graphite surface is more than 5%. A method of manufacture of a lithium ion cell anode, involving preparation of an anode mass comprising a graphite carbonaceous material with the addition of conductive carbon and polymer binding component, and then application of this mass on a conductive substrate, according to the present invention is characterized in that the amount of the graphite carbonaceous material in the anode mass is more than 70%, a preferably the anode mass comprises 80-90% of the graphite carbonaceous material, 5-10% of the conductive carbon and 5-10% of the polymer binding component. The obtained electrodes have packing of 1-5 mg/cm2, and the intercalation capacity in relation to lithium ions more than 372 mAh/g in the initial work cycles and a capacity more than 330 mAh/g in 100-th work cycle, during work under the load no less than 370 mA/g. The carbonaceous material obtained by a method according to the present invention and the anode made with this material, may be used in the most types of the lithium ion cells (Li-ion) as a main component or an additive for anode mass (of the mass of the negative electrode). This procedure is cheap and easy, and the obtained material is characterized by a greater electrochemical capacity than known materials. At the same time, the electrodes have high cyclic resistance and maintain more than 85% of the initial capacity in 100-th work cycle at charge and discharge with a high intensity current (more than 1C).

Description

Method of manufacture of carbonaceous material for anode mass of lithium ion cell as well as material obtained using this method, and method of manufacture lithium ion cell anode using said material and anode obtained thereby
A subject of the present invention is a method of manufacture of a carbonaceous material having increased intercalation capacity and electrochemical stability, which is a component of an anode mass of a lithium ion cell, and a carbonaceous material obtained using this method, and a method of manufacture of a lithium ion cell anode using said material and anode obtained thereby.
Considering capacity and power counted per mass unit, the lithium ion cells (Li-ion) are one of the most efficient electrochemical energy sources presently available on the market. Currently, other types of cells are tested, for example sodium and calcium cells, however taking into account problems with reliability and safety of use, such cell has not found commercial use yet.
The lithium ion cells have energy density (per whole cell) up to 250 Wh/kg, substantially exceeding capacities obtained in commercially available cells of other types, for example in nickel hydrogen cells (55-90 Wh/kg) or acid lead cells (25-40 Wh/kg). The average work voltage of the lithium ion cells is 3.2-3.8 V, exceeding values achieved by ceils of other types (the nickel hydrogen cells 1.2 V; the acid lead cells 2.0 V).
One disadvantage of the Li-ion cells is their relatively high price resulting partially from high price of metals being components of a positive electrode (like for example nickel and cobalt), and partially from expensive procedure of electrode materials preparation. Thus, there is unmet need for development of easier and cheaper procedure for preparation of such type materials.
The capacity of the negative electrode and its stability during many cycles of charge and discharge has direct impact on working parameters achieved by the cell.
The electrode materials presently used for design of negative electrodes of lithium ion cell can be divided into three groups: the materials forming metal alloys with lithium, the materials conversionally formed from metal oxides and intercalation materials.
The materials which form electrochemical alloys with lithium having a variable structure AyLix, for example aluminium, silicon, are characterized by very high specific capacity (up to 3590 mAh/g for silicon), however their resistance on consecutive cycles of charge and discharge is weak taking into account significant changes of the material volume (up to 300%) during the uptake of lithium ions. This results in mechanical degradation of the electrode structure and considerable decrease in its capacity. The conversional materials - forming a second group of materials for the construction of the negative electrodes of lithium ion cell, made of metal oxides, for example Sn02, are characterized in that the reaction of forming of Li20 together with the reduction of conversional material take place while the cell is working, resulting in separation of metal or its oxide at a lower oxidation degree. These materials achieve the capacity of approximately 1200 mAh/g, however taking into account incomplete reversibility of the electrode process their capacity drops fast in the subsequent cycles.
On the other hand, the intercalation materials have ability of uptaking lithium in their volume. Most of the materials from this group are different types of carbon structural varieties or graphite. Typically, these materials achieve the specific capacity of approximately 300 mAh/g, and have low price and very high resistance on the consecutive cycles of charge and discharge.
Considering advantages of the carbonaceous intercalation materials, the most of the commercially available lithium ion cells contain materials from this class as a main active component of the negative electrodes. Thus, the lithium ion cells are characterized by great work stability.
It has to be noted that the cells having graphite electrodes have the highest resistance on the consecutive cycles of charge and discharge, in comparison to the cells which have electrodes made of carbonaceous materials of a lower level of alignment of the atom structure [Carbon 37 (1999) 165]
There is a known impact of the morphology of the carbonaceous electrode material on its intercalation capacity. The capacity the cell electrodes depends on the size, shape and structure of the carbonaceous material grains [Journal of Power Sources 54 (1995) 383].
There is known a procedure of modification of a graphite involving its partial oxidation in the air at a temperature up to 550°C, resulting in an increase in the capacity of said material even up to 360 mAh/g in the initial work cycles of the lithium ion cell [Journal of the Electrochemical Society 143 (1996) L4]. A cyclical resistance of said material is slightly better in comparison to the graphite. However, it is difficult to obtain a precise evaluation of presented results, taking into account a small number (16) of the carried out cycles and different contents of water in the electrolyte during tests of the standard and modified electrodes.
There is also known a method of modification of a graphite through its partial oxidation in the chemical reaction with the oxidizing compounds (e.g. hot nitric acid or ammonium persulfate), which leads to an increase of the capacity of said material during work under small current load, lower than C/20 [Journal of the Electrochemical Society 144 (1997) 2968].
There is also known a method of modification of a graphite involving its jet milling, resulting in increase of the material capacity up to approximately 280 mAh/g under the load of a substantial current (1C), whereas non-milled graphite has much worse parameters [Journal of Power Sources 124 (2003) 555].
Additionally, there is known a method of modification of a graphite involving its milling in a ball mill in the atmosphere of a dry argon for 150 hours, which results in decreasing of the average size of the molecules to approximately 50 nm and increasing the initial capacity of the material up to 600 mAh/g however with a substantial decrease of its cyclic resistance (the capacity after 10 work cycles drops to 200 mAh/g (33% of the initial capacity)). With regard to a slight cyclic resistance, the use of said material in reversible cells designed to work in more than 100 cycles is not possible [Journal of Power Sources 76 (1998) 1].
There is known a method of modification of a graphite involving its milling in a ball mill in the atmosphere of a dry argon for 3-30 hours, which results in decreasing of the average size of the molecules to approximately 6-16 pm and increasing the initial capacity of the material to approximately 330 mAh/g, while maintaining a substantial cyclic resistance. The capacity of the material drops to 310 mAh/g after 100 work cycles at discharge current 1C and charge current C/2 (94% of the initial capacity) [Electrochimica Acta 56 (2011) 9700].
Moreover, there is known a method of modification of a graphite involving its milling in a ball mill in the presence of a liquid medium. An improvement of the material parameters was observed using dodecane as a medium. An increase of its capacity to 360 mAh/g was achieved. By contrast, the use of water as a liquid medium resulted in decrease of the intercalation capacity of the carbonaceous material, which is related to the presence of y-Fe203 resulting from oxidation of the mill elements. A cyclical resistance of the material was moderate and after 30 work cycles the capacity of the material dropped below 295 mAh/g (82% of the initial capacity) [Carbon 40 (2002) 2887]
There is known a method of modification of a graphite involving its milling in the atmosphere of the air in a stream mill and in a turbo mill, resulting in increase of the initial capacity of the material up to approximately 366 mAh/g under the current of 100 mA/g (approximately 0.3C) [Journal of Power Sources 83 (1999) 141]
There is known a method of modification of a graphite, which involves deposition on its surface a thin layer of a pyrolytic carbon in a high temperature incomplete combustion of a propane-butane gas, milling of the obtained material in a stream mill, and then covering once again the surface of the material with a layer of a pyrolytic carbon. This modification allows to increase of the initial capacity of the material from 310 mAh/g to 348 mAh/g [Russian Journal of Electrochemistry 49 (2013) 161] A cyclical resistance was not tested.
There is known a method of preparation of an anode mass for the lithium ion cells involving use of a conductive carbon as an additive, which improves electrical conductivity of said anode mass. The conductive carbon is added to the active material in order to increase the electrical conductivity on the boundary of the grains, resulting in an improvement of the parameters of work at increased current load. The electrical conductivity of the electrode mass may increase by 2-6 S/cm at 1% of a conductive carbon as an additive [Electrochimica Acta, 166 (2015) 367],
There is also known a method of preparation of an anode mass for the lithium ion cells involving use of a PVDF polymer (poiy(vinylidene fluoride) as an additive, which has positive impact on mechanical resistance of the produced electrodes. The polymer PVDF has a function as a binder and is added for mechanical stabilization of the electrode mass, which has positive impact on its performance during consecutive cycles of charge and discharge. PVDF is usually added to the anode mass as 1-10% solution in N-methylpyridine (NMP) forming a paste, which is then layered on a base which forms a current collector for the electrodes [Electrochimica Acta, 56 (2011) 9700; Journal of Physics and Chemistry of Solids. 67 (2006) 1213]. NMP evaporates, and on the collector a uniform layer of the anode mass is formed.
A phenomenon of the beneficial impact of the graphite surface oxidation on its intercalation capacity for Li+ ions was described in the publications mentioned above. Flowever, in the state of the art there is a lack of reports about a method, which would lead to an increase of the intercalation capacity of the material and being at the same time easy to be carried out.
Methods of graphite modification, known from the state of the art, do not allow to produce a carbonaceous material with a greater initial capacity than the theoretical maximum capacity of carbon (372 mAh/g), a material which at the same time would have great cyclic resistance and over 85% of the initial capacity after 100 work cycles of charge and discharge with a substantial current (more than 1C). Development of such material would allow the production of the lithium ion cells having better work parameters in comparison to the cells presently available on the market.
There is an unmet need for development of a method for increasing electrochemical capacity of the graphite material while maintaining its resistance on repeated cycles of charge and discharge.
Summary of the present invention.
A method of manufacture of a carbonaceous material for an anode mass of the lithium ion cell involving high energy milling of a graphite in the presence of a liquid medium, according to the present invention is characterized in that high energy milling is carried out in a non-metallic mill using energy of milling in the range of 10-34 Wh/g, preferably 22 Wh/g, wherein a mass ratio of the graphite to dispersing agent is maintained in the range of 10:15-10:35, preferably 10:24. As a graphite component there is used synthetic graphite with a high level of graphitization, and a diameter of the molecules of 100-1000 pm and a high initial purity, more than 95%, preferably more than 98%. The milling is carried out in a planetary ball mill provided with ceramic milling elements. The milling is carried out in an intermitted regime. There is used a dispersing medium being a mixture comprising no less than 90% of ethyl alcohol, no more than 5% of water and no more than 5% of diethyl ether. A product is filtered on a filter, preferably on a cellulose filter, and then dried at 120°C for 12 h under the pressure below 10 mbar. According to the invention, a carbonaceous material having an oxidation degree of a graphite surface of more than 5%, preferably more than 8% is obtained. The carbonaceous material has much more developed specific surface area: 20-60 m2/g, preferably 40 m2/g.
The carbonaceous material for the anode mass of the lithium ion cell is characterized in that it is obtained (by the method presented above) from a synthetic graphite with a high level of graphitization and a high initial purity, more than 95%, preferably more than 98% and has an oxidation degree of the graphite surface of more than 5%, preferably more than 8%, and has much more developed specific surface area, around 20-60 m2/g, preferably 40 m2/g, which is preferably produced by a method described above.
The method of manufacture of a lithium ion cell anode, which involves formation of an anode mass comprising a graphite carbonaceous material with the addition of a conductive carbon and with the addition of a polymer binding component, and then application of this mass on a conductive base, according to the present invention is characterized in that a described above carbonaceous material is used, preferably said material obtained by a method described above, wherein the amount of this graphite carbonaceous material in the anode mass is more than 70%, and preferably the anode mass comprises 80-90% of said graphite carbonaceous material, 5-10% of a conductive carbon and 5-10% of a polymer binding component. As a conductive carbon there is used a carbon black, an acetylene black or a commercially available conductive carbon. As a polymer binding component there is used poly(vinylidene fluoride), preferably in the form of 5% by weight solution in N-methylpyridine. The anode mass is conditioned by mixing, and then put on the conductive base in a way providing uniform distribution of the mass, preferably by using an automatic applicator provided with a regulated aperture, wherein a thickness of a wet layer the anode mass is 50-400 pm, preferably 200 pm. As a conductive base there is used a non-metallic substrate or a metallic substrate, preferably a metallic substrate, particularly a substrate made of copper, steal or lead, the most preferably a substrate in the form of the copper foil having a thickness of 5-50 pm, preferably 10 pm. The conductive base covered with anode mass is dried at elevated temperature under lowered pressure, preferably for more than 10 h, at above 110°C, under the pressure below 10 mbar. The obtained electrodes have electrode packing of 1-5 mg/cm2, preferably 1.5 mg/cm2. The electrodes have the intercalation capacity for lithium ions of more than 370 mAh/g in the initial work cycles and the capacity of more than 330 mAh/g in the 100-th work cycle, during work under the load no less than 370 mA/g. The anode of the lithium ion cell, based on the graphite carbonaceous material with the addition of the conductive carbon and with the addition of the polymer binding component, is characterized in that it consists of a conductive substrate, uniformly covered with the anode mass made of carbonaceous material, described above, obtained from synthetic graphite with a high level of graphitization and a high initial purity, more than 95%, preferably more than 98%, having the oxidation degree of the graphite surface at a level above 5%, preferably more than 8%, and greatly developed specific surface area of 20-60 m2/g, preferably 40 m2/g, preferably obtained by a method described above, wherein the electrode packing is 1-5 mg/cm2, preferably 1.5 mg/cm2, and the intercalation capacity in relation to lithium ions has a value of more than 372 mAh/g in the initial work cycles and the capacity above 330 mAh/g in 100-th work cycle, during work under the load no less than 370 mA/g. The conductive base is a metallic substrate, particularly made of copper, steal or lead, the most preferably substrate is in the form of the copper foil of a thickness of 5-50 pm, preferably 10 pm.
The method of manufacture of the carbonaceous material for the anode mass of the lithium ion cell and the method of manufacture of the lithium ion cell anode using said material is described in details below in the examples, with reference to the attached drawing, wherein:
Fig. 1 presents a relation between a specific surface area of the carbonaceous material obtained by the method according to the present invention and a milling energy;
Fig. 2 presents the mass amount of the elements in the carbonaceous material obtained by the method according to the present invention using different milling energy;
Fig. 3 presents the structure of the carbonaceous material obtained by the method according to the present invention, which was milled using energy 22 Wh/g (images were obtained by the scanning electron microscope, field A presents an image at high magnification, field B presents an overall image);
Fig. 4 presents a relation between the reversible capacity of the carbonaceous material obtained by the method according to the present invention and a milling energy of said material; the relations for 5-th and 100-th work cycle of the electrode made of said material are presented;
Fig. 5 presents curves of charge and discharge for the electrode made of the carbonaceous material obtained by the method according to the present invention, which was milled using energy 22 Wh/g; the curves for 1-st, 5-th and 100-th work cycles of this electrode are presented;
Fig. 6 presents the discharge capacity of the electrode made of the carbonaceous material obtained by the method according to the present invention, which was milled using energy 22 Wh/g; data obtained for cycles 1-100 are presented; Fig. 7 presents current efficiency of the cycle and cyclic resistances of charge and discharge for the electrodes made of the carbonaceous material obtained by the method according to the present invention, which was milled using energy 22 Wh/g;
Fig. 8 presents a relation between the irreversible capacity of the electrode made of the carbonaceous material obtained by the method according to the present invention and milling energy.
Detailed description of the present invention.
The present invention relates to the method of preparation the carbonaceous material used as the active component in the electrode mass of the negative electrode of the lithium ion cell (anodes), and the method of preparation of the lithium ion cell anodes using this carbonaceous material. Said carbonaceous material and the anodes obtained using said material may be used in the most types of the lithium ion cells as a main component or an additive for the anode mass (the mass of the negative electrode). The procedure is relatively cheap and the obtained material is characterized by higher electrochemical capacity than materials known from the state of the art, while maintaining high cyclic resistance and possibilities of discharging with a great intensity current (more than 1C). The procedure may be easily adopted in facilities, wherein the carbonaceous materials are used as an active component of the negative electrode.
Method of manufacture of the carbonaceous material for the anode mass of lithium ion cell according to the invention involves mechanical modification of a graphite with the addition of dispersing agent. Then, the carbonaceous material is separated and dried in suitable conditions.
According to the invention, as an initial carbonaceous material there is used graphite, preferably synthetic graphite with a high level of graphitization. The optimal parameters are achieved by use of a material having initial diameter of the molecules in the range of 100-1000 pm. There is used the carbonaceous material of a high initial purity above 95%, preferably more than 98%.
According to the invention, a dispersing agent is a mixture comprising ethyl alcohol, water and diethyl ether, wherein the amount of ethyl alcohol exceeds 90% by weight, the amount of water does not exceed 5% by weight, and the amount of diethyl ether does not exceed 5% by weight - counted on total weight of the mixture acting as dispersing agent, which preferably is used in a liquid form.
According to the invention, a high energy milling is carried out in non-metallic high energy planetary, vibrational or rotational mill. The milling elements can take the form of balls, discs or rings, applied alone or in combination. Preferably, ball mills are used. Preferably, the elements of the mill which are in contact with the milled electrode mass are made of non-metallic material, the most preferably of the ceramic material, for example zirconium dioxide.
According to the invention, during milling a mass ratio of a graphite to a dispersing agent is maintained in the range of 10:15 to 10:35, wherein the optimal conditions are achieved preferably at weight ratio of 10:24.
According to the invention, the milling process is carried out using energy of milling (P) in the range of 10-34 Wh/g, preferably using energy of milling 22 Wh/g. The total milling energy is dependent on the parameters such as: diameter of the mill (Rp), diameter of the milling vessel (Rv), number of the milling balls (Nb), weight of the milling balls (m), diameter of the milling balls (r), angular speed of the mill (Wp), angular speed of the milling vessel (W„), frequency of impacts of the milling balls (fb), time of milling (t), weight of the milled material (PW) and degree of filling of the milling vessel (f). Milling energy may be counted using a formula as below:
P = -f t Nb mb fb [Wv3(Rv - r)/Wp + WpWvRp](Rv-r)/ PW, [Wh/g].
According to the invention, when the milling is finished, the milled mixture is gathered from the elements of the mill. The carbonaceous material is filtered under the atmospheric pressure in the presence of air on a cellulose filter at room temperature. After filtering, the carbonaceous material is dried in vacuum, under the pressure below 10 mbar at 110-130°C for 12 hours. Thus obtained material is used for preparation of the anodes for the lithium ion cells.
Method of manufacture of a lithium ion cell anode, according to the invention, comprises preparation of the anode mass through mixing the carbonaceous material made of graphite, conductive carbon and binding material, and then putting said mixture on the conductive substrate and fixation. The electrochemical properties of the anode prepared by a method according to the present invention depend on the properties of the graphite modified according to the invention.
As a carbonaceous material, according to the invention, there is used material based on synthetic graphite described above. It is possible to use this carbonaceous material in any percentage amount, but preferably its amount is 80-90% by weight of the anode mass. The carbonaceous material is mixed with the conductive carbon and binding material, the most preferably in a weight ratio of 9:1:1. As a conductive carbon, preferably there is used carbon black, acetylene black or conductive carbon Vulcan XC-72R. As a binding material there is used polymer material, preferably PVDF (polyfvinylidene fluoride)) in the form of 5% by weight solution in N-methyipyridine. The anode mass is conditioned by mixing.
According to the invention, there is used conductive substrate as a current collector for the anode mass. Preferably, there is used a metallic substrate, particularly made of copper, steal, lead, the most preferably substrate is made of copper foil. This foil cannot be too thin (below 5 pm), because it would be too delicate and susceptible to damage during workout. On the other hand, too thick foil (more than 50 miti) would be dead mass, which would reduce needlessly energy density parameters of the cells. The optimal thickness of the copper foil is 10 pm.
According to the invention, the anode mass is preferably applied on the conductive substrate. Preferably, the mass is applied in a way providing its uniform distribution on the substrate surface, the most preferably by using automatic applicator provided with a regulated aperture. A thickness of a wet layer of the anode mass is 50-400 pm, preferably 200 pm. Thin layers are excellent bound to the substrate and they are stable under the load of a substantial current. However, too small thickness of the mass results in reduction of the electrode capacity. In turn, whereas too thick layers tend to crack, however they provide greater electrochemical capacity. The optimal thickness of the anode mass is 200 pm, because it provides at the same time great capacity and great stability of the electrode.
The electrode in the form of a conductive substrate covered with the layer of the anode mass is dried under the pressure below 10 mbar at 110-130°C for 12 hours.
The embodiments presented above (i.e. the method of a manufacture of the carbonaceous material for the anode mass of the lithium ion cell and the method of a manufacture of the lithium ion cell anode using said material) are characterized by a simplicity and a low price in comparison to the methods of chemical modification of the carbonaceous materials known from the state of the art, as said known methods need purchasing suitable chemicals. The main cost of the processes of the present invention is electric energy related to the milling, whereas the material costs are little. It should be noted that dispersing agent may be mostly recovered and used once again.
The used procedure may be easily scaled on the industrial scale, through suitable magnification of the milling device and selection of the suitable milling energy according to the formula relating to Milling energy (P) presented before.
The carbonaceous material for the anode mass of lithium ion cell, obtained by a method according to the present invention is characterized by a specific capacity exceeding theoretical maximum (372 mAh/g) in the initial work cycles (the theoretical maximum was obtained on the basis of the atomic mass of carbon in the structure UC6 being a final product of intercalation). The carbonaceous material obtains full specific capacity (388 mAh/g) in fifth work cycle, which is a value of approximately 10-30% higher in comparison to the materials known from the state of the art. The specific surface area of the carbonaceous material increases as a result of the milling process used. On Fig. 1 a relation between increase of the specific surface area of the carbonaceous materials milled by a method according to the present invention in function of the milling energy is presented. It is worth to note, that the carbonaceous material having the best electrochemical properties (milling energy 22 Wh/g) is characterized by a significantly larger specific surface area (approximately 40 m2/g) in comparison to the specific surface area of the initial synthetic graphite (below 1 m2/g).
The drawing presents selected relations imaging working parameters of the electrode produces by a method according to the present invention. On Fig. 4 a relation between the capacity in fifth and one hundredth work cycle of the electrode in function of the used milling energy is presented. On Fig. 5, the curves of charge and discharge for 5. and 100. work cycle of the electrode made of the carbonaceous material obtained by a method according to the present invention, by milling with energy of 22 Wh/g is presented. On Figs. 6 and 7 respectively, the discharge capacity, cyclic resistance of charge and discharge and current efficiency for 1-100 work cycles of electrode made of carbonaceous material obtained by a method according to the present invention, by milling with energy of 22 Wh/g are presented.
The carbonaceous material obtained by the method of the present invention is used according to the invention to the manufacture of the negative electrode of the lithium ion cell is characterized by a high resistance on consecutive cycles of charge and discharge carried out with a high intensity current (more than 1C). The material maintains more than 86% of the initial capacity after 100 work cycles (the capacity more than 333 mAh/g), which is much better result in comparison to negative electrodes known from the state of the art. It should be underline that in the state of the art there are very few reports about tests of carbonaceous graphite materials using high intensity current during multiple cycles of charge and discharge. Available data are most often limited to a few initial cycles or the cycles are carried out with a small intensity current.
The anodes produced by a method according to the present invention may work under high current load (>1C, 372 mA/g), allowing to the use of lithium ion cells with these anodes in high power energy receivers.
The carbonaceous material obtained by a method according to the present invention by milling with energy of 22 Wh/g, in comparison to the materials milled with other energy, is characterized by a minimum irreversible capacity related to the electrolyte decomposition in the initial work cycles, what has a positive impact on the costs of production of the cells, improves safety of the work and reduces negative impact on the natural environment. The electrolyte used in the lithium ion cells is typically flammable and dangerous for the natural environment. Its decomposition during work of the cell is related to the formation on surface of the electrodes a passive layer in the initial work cycles, below potential approximately of 0.8 V vs. Li/Li+. This decomposition takes place for all commonly used electrolytes and makes it necessary to use the excess of the electrolyte in the cell in order o balance this phenomenon. Reduction in the decomposition of the electrolyte in the cell results in less needed amount to proper work of the cell. On Fig. 8 a relation between irreversible capacities connected with the electrolyte decomposition for electrodes produced by a method according to the present invention with the carbonaceous material obtained according to the invention, with other milling energy is presented.
The method of a manufacture of the carbonaceous material for the anode mass of the lithium ion cell and the method of manufacture of the lithium ion cell anode using said material is described below in the examples.
Example 1. The carbonaceous material for the anode mass of the lithium ion cell was obtained by high energy milling of the synthetic graphite in a planetary ball mill. 10 g of the commercially available material - synthetic graphite was placed in the ball mill together with 273 porcelain balls with a diameter of 5 mm and average weight of 0,41 g. 24 g of dispersing agent comprising > 90% by weight of ethyl alcohol, < 5% by weight of water and < 5% by weight of diethyl ether was also added to the milling vessel. The milling vessel was filled in 65% of volume. Milling was carried out at nominal rotation of the mill of 500 rpm, with 30 min brakes after one hour of milling, wherein total effective time of milling was 10 h, and total operation time 14.5 h. Milling energy (P) was 22 Wh/g.
The obtained product was gathered from the porcelain balls, and then separated from the dispersing agent by filtration on a cellulose filter. The carbonaceous material was dried at 120°C for 12 h under the pressure below 10 mbar. In the process 9.33 g of the carbonaceous material was obtained. Yield was 93.3%.
A specific surface area of the obtained carbonaceous material was tested by a method of analysis nitrogen adsorption / desorption curve by a BET method. The obtained carbonaceous material was characterized by a high specific surface area of around 40 m2/g· As a result of milling the specific surface area increased by more than 1300% in comparison to the specific surface area of the initial material of <3,0 m2/g.
The morphology of the obtained carbonaceous material was also tested by using electron microscopy. The obtained material was characterized by a high development of the surface and a partial exfoliation of the graphite in the surface part of the grains, while maintaining the inner layer structure of the graphite in their inner part. On Fig. 3 the microscopic images of the obtained carbonaceous material are presented.
The elemental composition of the obtained carbonaceous material was tested by a method of X-ray Energy Dispersive Spectrometry. The obtained material was characterized by increased mass ration of oxygen to carbon. The partial surface oxidation of the material was observed as a result of high energy milling in the presence of dispersing agent. The obtained material, milled using energy of 22 Wh/g, comprised 8% by weight of oxygen atoms, whereas the initial material has below 2% by weight of the oxygen atoms. On Fig. 2 the mass amount of the selected elements (carbon, oxygen, silicon, aluminium) in the sample of the carbonaceous material is presented.
Example 2. The negative electrode for the lithium ion cell was prepared by use of the carbonaceous material obtained in the example 1. 200 mg of the carbonaceous material (obtained in the example 1) was mixed with 25 mg conductive carbon Vulcan XC-72R from Cabot, and then said mixture was grinded manually in a porcelain mortar for 10 minutes. 25 mg of PVDF (poly(vinylidene fluoride)) in the form of 5% by weight solution in NMP (N-methylpyridine) was added to the grinded mixture, and then the whole mass was mixed for 4 hours with a magnetic stirrer with speed 400 rpm. The obtained mass was put on the copper foil by using automatic applicator provided with a regulated aperture, wherein a thickness of a wet layer was 200 pm. The foil covered with a carbonaceous layer was dried for 12 h at 120°C under the pressure <10 mbar. The electrodes were formed by cutting out circles with a diameter of 9 mm from obtained foil by using a hand cutter. Finished electrodes were compacted for 60 s under the pressure of 200 bar by using hydraulic press. A packing of the electrode material on the electrode was 1,0-1.5 mg/cm2.
Example 3. The electrodes obtained in the example 2 were subjected to a standard assessment of the intercalation properties in relation to Li+ ions. The measurements of galvanostatic charge and discharge of the lithium ion cell were carried out, wherein the negative working electrode was electrode obtained in the example 2. The auxiliary and reference electrode was a metallic lithium. The electrolyte comprising 1M solution of LiPF6 in the solvent mixture: ethylene carbonate/dimethyl carbonate in a weight ratio of 1:1 was used in the cell. The polypropylene separator Celgard 2400 was used as a separator. Whole was placed in three- electrodes housing Swagelok®. The measurements were carried out on the apparatus provided with a digital recorder of charge and discharge curves. During test, the intensity of the current was 1C (372 mA/g). The working cycle comprised galvanostatic charge and discharge between potential of 0,01V-3,00V in relation to a reference electrode made of metallic lithium.

Claims

Claims
1. A method of a manufacture of a carbonaceous material for an anode mass of a lithium ion cell involving high energy milling of a graphite in the presence of a liquid medium,
characterized in that a high energy milling is carried out in a non-metallic mill using energy of milling in the range of 10-34 Wh/g, preferably 22 Wh/g, wherein a mass ratio of a graphite to a dispersing agent is maintained in the range of 10:15-10:35, preferably 10:24.
2. The method of manufacture of the carbonaceous material according to claim 1,
characterized in that a synthetic graphite with a high level of graphitization is used, with a diameter of the molecules is 100-1000 pm and a high initial purity, more than 95%, preferably more than 98%.
3. The method of manufacture of the carbonaceous material according to claim 1,
characterized in that a planetary ball mill provided with ceramic milling elements is used.
4. The method of manufacture of the carbonaceous material according to claim 1,
characterized in that milling is carried out in an intermitted regime.
5. The method of manufacture of the carbonaceous material according to claim 1,
characterized in that a dispersing medium being a mixture comprising no more than 90% ethyl alcohol, no less than 5% of water and no less than 5% of diethyl ether is used.
6. The method of manufacture of the carbonaceous material according to claim 1,
characterized in that a product is filtered on a filter, preferably on a cellulose filter, and then is dried at 120°C for 12 h under the pressure below 10 mbar.
7. The method of manufacture of the carbonaceous material according to claim 1,
characterized in that the carbonaceous material with an oxidation degree of the graphite surface more than 5%, preferably more than 8% is obtained.
8. The method of manufacture of the carbonaceous material according to claim 1,
characterized in that the carbonaceous material with a substantial development of the specific surface area of 20-60 m2/g, preferably 40 m2/g is obtained.
9. A carbonaceous material for an anode mass of a lithium ion cell characterized in that the carbonaceous material is obtained from synthetic graphite with a high level of graphitization and o high initial purity, more than 95%, preferably more than 98%, and has an oxidation degree of the graphite surface more than 5%, preferably more than 8% and has much more developed specific surface area of 20-60 m2/g, preferably 40 m2/g, which is preferably obtained by a method according to claim 1-8
10. The method of a manufacture of a lithium ion cell anode, involving formation of the anode mass comprising the graphite carbonaceous material with the addition of conductive carbon and addition of polymer binding component, and then application of this mass on a conductive substrate, characterized in that the carbonaceous material, described in claim 9 is used, preferably obtained by a method according to claim 1-8, wherein the amount of this graphite carbonaceous material in the anode mass is more than 70%, a preferably the anode mass comprises 80-90% of said graphite carbonaceous material, 5-10% of conductive carbon and 5-10% of polymer binding component.
11. The method of manufacture of the anode according to claim 10, characterized in that as a conductive carbon the black carbon, acetylene black or commercially available conductive carbon is used.
12. The method of manufacture of the anode according to claim 10, characterized in that as a polymer binding component poly(vinylidene fluoride) is used, preferably in the form of 5% by weight solution in N-methylpyridine.
13. The method of manufacture of the anode according to claim 10, characterized in that the anode mass is conditioned by mixing, and then is put on the conductive substrate in a way providing uniform distribution of the mass, preferably by using automatic applicator provided with a regulated aperture, wherein a thickness of a wet layer anode mass is 50-400 pm, preferably 200 pm.
14. The method of manufacture of the anode according to claim 10, characterized in that as a conductive substrate a non-metallic substrate or a metallic substrate is used, preferably a metallic substrate, particularly copper, steal or lead, the most preferably substrate in the form of the copper foil of a thickness 5-50 pm, preferably 10 pm.
15. The method of manufacture of the anode according to claim 10, characterized in that the conductive substrate covered with anode mass is optionally compacted and is dried at elevated temperature under lowered pressure, preferably for more than 10 h at more than 110°C under the pressure below 10 mbar.
16. The method of manufacture of the anode according to claim 10, characterized in that the electrode with electrode packing of 1-5 mg/cm2, preferably 1.5 mg/cm2 is obtained.
17. The method of manufacture of the anode according to claim 10, characterized in that the electrode with the intercalation capacity in relation to the lithium ions of more than 372 mAh/g in the initial work cycles and capacity more than 330 mAh/g in 100-th work cycle, during work under the load no less than 370 mA/g is obtained.
18. A lithium ion cell anode, based on a graphite carbonaceous material with the addition of a conductive carbon and with the addition of polymer binding component, characterized in that the anode consists of a conductive substrate, uniformly covered with an anode mass from carbonaceous material, described in claim 9, obtained from a synthetic graphite with a high level of graphitization and a high initial purity, more than 95%, preferably more than 98%, with the oxidation degree of the graphite surface more than 5%, preferably more than 8%, and a substantially developed specific surface area of 20-60 m2/g, preferably 40 m2/g, preferably obtained by a method according to claim 1-8, wherein the electrode packing is 1- 5 mg/cm2, preferably 1.5 mg/cm2, and the intercalation capacity in relation to lithium ions is more than 372 mAh/g in the initial work cycles and the capacity more than 330 mAh/g in 100-th work cycle, during work under the load no less than 370 mA/g.
19. The anode according to claim 18, characterized in that the conductive substrate is a metallic substrate, particularly copper, steal or lead, the most preferably substrate in the form of the copper foil of a thickness 5-50 pm, preferably 10 pm.
PCT/PL2019/000053 2018-07-13 2019-07-12 Method of manufacture of carbonaceous material for anode mass of lithium ion cell as well as material obtained using this method, and method of manufacture lithium ion cell anode using said material and anode obtained thereby WO2020013718A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
PLP.426330 2018-07-13
PL426330A PL240296B1 (en) 2018-07-13 2018-07-13 Method of obtaining carbon material for anode mass of a lithium-ion cell and material obtained by this method, and method of producing anode of a lithium-ion cell using this material and anode obtained by this method

Publications (1)

Publication Number Publication Date
WO2020013718A1 true WO2020013718A1 (en) 2020-01-16

Family

ID=67841127

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/PL2019/000053 WO2020013718A1 (en) 2018-07-13 2019-07-12 Method of manufacture of carbonaceous material for anode mass of lithium ion cell as well as material obtained using this method, and method of manufacture lithium ion cell anode using said material and anode obtained thereby

Country Status (2)

Country Link
PL (1) PL240296B1 (en)
WO (1) WO2020013718A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115881895A (en) * 2021-09-27 2023-03-31 天津理工大学 Amorphous carbon negative electrode material and preparation method and application thereof

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160211511A1 (en) * 2015-01-20 2016-07-21 Shenzhen Btr New Energy Materials Inc. Nano-silicon composite negative electrode material used for lithium ion battery, process for preparing the same and lithium ion battery
US20160351942A9 (en) * 2009-11-24 2016-12-01 Duracell U.S. Operations, Inc. Secondary electrochemical cells with separator and electrolyte combination
WO2017111542A1 (en) * 2015-12-23 2017-06-29 주식회사 엘지화학 Anode active material for lithium secondary battery and anode for lithium secondary battery including same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160351942A9 (en) * 2009-11-24 2016-12-01 Duracell U.S. Operations, Inc. Secondary electrochemical cells with separator and electrolyte combination
US20160211511A1 (en) * 2015-01-20 2016-07-21 Shenzhen Btr New Energy Materials Inc. Nano-silicon composite negative electrode material used for lithium ion battery, process for preparing the same and lithium ion battery
WO2017111542A1 (en) * 2015-12-23 2017-06-29 주식회사 엘지화학 Anode active material for lithium secondary battery and anode for lithium secondary battery including same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115881895A (en) * 2021-09-27 2023-03-31 天津理工大学 Amorphous carbon negative electrode material and preparation method and application thereof

Also Published As

Publication number Publication date
PL426330A1 (en) 2020-01-27
PL240296B1 (en) 2022-03-14

Similar Documents

Publication Publication Date Title
EP3780169A1 (en) Negative electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery
KR101805079B1 (en) Electrode material and use thereof in lithium ion batteries
KR101609406B1 (en) Negative electrode material for nonaqueous secondary battery
EP2892096B1 (en) Method for manufacturing a carbon material for nonaqueous electrolyte secondary battery
EP1720211B1 (en) Negative electrode for lithium secondary battery and lithium secondary battery
WO2018101072A1 (en) Negative electrode material and nonaqueous electrolyte secondary battery
EP3467911B1 (en) Negative electrode active material, mixed negative electrode active material, and method for producing negative electrode active material
KR20120128125A (en) High capacity anode materials for lithium ion batteries
KR101043010B1 (en) Anode material for lithium secondary battery and lithium secondary battery
Li et al. Structure and electrochemical properties of Sm-doped Li 4 Ti 5 O 12 as anode material for lithium-ion batteries
EP3179543B1 (en) Carbonaceous material for negative electrode of non-aqueous electrolyte secondary battery
EP3467912A1 (en) Negative electrode active material, mixed negative electrode active material, and method for producing negative electrode active material
CN115986067A (en) Positive electrode active material, preparation method thereof, positive electrode plate and lithium ion secondary battery
KR20110118790A (en) Carbon material for lithium ion secondary batteries
US10038188B2 (en) Cathode active material, process for its production, cathode and lithium ion secondary battery
WO2012169331A1 (en) Lithium titanate primary particles, lithium titanate aggregate, lithium ion secondary battery using lithium titanate primary particles or lithium titanate aggregate, and lithium ion capacitor using lithium titanate primary particles or lithium titanate aggregate
EP3467913B1 (en) Negative electrode active material, mixed negative electrode active material, and method for producing negative electrode active material
Hwang et al. A simple, one-pot synthesis of molybdenum oxide-reduced graphene oxide composites in supercritical methanol and their electrochemical performance
JP5528564B2 (en) Nonaqueous electrolyte secondary battery
JP4045438B2 (en) Double-layer carbon material for secondary battery and lithium secondary battery using the same
KR102522173B1 (en) Anode active material coated with nitrogen-doped carbon for sodium ion secondary battery and method of preparing the same
Chang et al. Sol–gel synthesis of low carbon content and low surface area Li 4 Ti 5 O 12/carbon black composites as high-rate anode materials for lithium ion batteries
WO2020013718A1 (en) Method of manufacture of carbonaceous material for anode mass of lithium ion cell as well as material obtained using this method, and method of manufacture lithium ion cell anode using said material and anode obtained thereby
KR102086589B1 (en) Electrode materials, electrochemical device comprising the same and method for manufacturing the same
JP2015230794A (en) Conductive material for lithium ion secondary battery, composition for forming lithium ion secondary battery negative electrode, composition for forming lithium ion secondary battery positive electrode, negative electrode for lithium ion secondary battery, positive electrode for lithium ion secondary battery, and lithium ion secondary battery

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 19762489

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 19762489

Country of ref document: EP

Kind code of ref document: A1