CN104916842A - Negative electrode active material for lithium ion secondary battery, negative electrode for lithium ion secondary battery using the same, and lithium ion secondary battery - Google Patents
Negative electrode active material for lithium ion secondary battery, negative electrode for lithium ion secondary battery using the same, and lithium ion secondary battery Download PDFInfo
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- CN104916842A CN104916842A CN201510109858.6A CN201510109858A CN104916842A CN 104916842 A CN104916842 A CN 104916842A CN 201510109858 A CN201510109858 A CN 201510109858A CN 104916842 A CN104916842 A CN 104916842A
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- secondary battery
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- 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
-
- 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
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- 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
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- 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
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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- 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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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- 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
Abstract
The invention provides a negative electrode active material for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery using the same, and a lithium ion secondary battery. The negative electrode active material possesses the practical features of realizing HEV and PHE vehicle purposes as the discharge capacity, initial efficiency, input characteristics and capacity retention of a lithium ion secondary battery, and the capacity of each unit volume (weight) s high. The negative electrode active material for a lithium ion secondary battery is prepared by carbon materials with the true specific gravity of 2.00-2.16 g/cm3; in the grain fineness distribution of grains based on a volume basis, D10 is in a range of 2-5 mum, D50 is in a range of 8-12 mum, D90 is in a range of 16-26 mum, and D50 is in a range of 5-10 mum, and a tap density is above 0.4g/cc; a BET specific area employing the nitrogen adsorption flowing method is 5.1-9.0 m2/g.
Description
Technical field
The present invention relates to a kind of lithium ion secondary battery cathode active material and use its lithium ion secondary battery negative pole and lithium rechargeable battery.
Background technology
From playing the large and excellent feature such as to have extended cycle life of high, the battery capacity of operating potential, and aspect low in the pollution of the environment is considered, lithium rechargeable battery replaces as the nickel-cadmium cell of main flow in the past, Ni-MH battery and using on a large scale.
In addition, in order to tackle energy problem, environmental problem, more be used as the power supply of electric motor car, the motor of combination Ni-MH battery driving and the mobile electronic device such as the hybrid electric vehicle (HEV:Hybrid ElectricAssistant) of gasoline engine and hand-held camera, its needs are also more and more higher from now in expection.
As the negative electrode active material of negative pole forming lithium rechargeable battery, from the viewpoint of fail safe and life-span, usually use material with carbon element.In material with carbon element, graphite material is the material with the excellence of high-energy-density that can more than about at least 2000 DEG C, usually obtain under the high temperature of about 2600 ~ 3000 DEG C, but there is problem in high input-output characteristic, cycle characteristics.Therefore, in the input-output characteristic purposes under the high input and output purposes, low temperature of such as electric power storage use, electric motor car etc., graphite material is not suitable for, and is studying the utilization of the material with carbon element of the structure had in addition.
In recent years, from the viewpoint of the further high performance of HEV, also require further high performance to lithium rechargeable battery, the raising of its performance becomes the task of top priority.Specifically, in order to supply the electric current of the energy source as HEV fully, the discharge capacity of lithium rechargeable battery is improved as important characteristic.In addition, as compared with charged electrical flow discharging current amount high fully, require that charging capacity is high relative to the ratio of discharge capacity, i.e. initial efficiency.And then in order to charge in the short time, lithium rechargeable battery also requires preferably to maintain charge capacity to high current density, and capacity dimension holdup is high.That is, require that balance improves the characteristic of such output characteristic, discharge capacity, initial efficiency, capacity dimension holdup well.
In order to provide such lithium rechargeable battery, more study the material with carbon element such as coke, graphite as negative electrode active material, although can increase above-mentioned discharge capacity, but initial efficiency is insufficient.In addition, actual cell voltage is insufficient and the high output characteristic that cannot meet in recent years, also cannot meet capacity dimension holdup important document.
Therefore, propose a kind of lithium ion secondary battery cathode active material and replace above-mentioned graphite material, it is characterized in that, by coal measures and/or petroleum (hereinafter referred to as " coal measures etc. ".) the calcined coke of green coke charcoal or coal measures etc. burn till separately or mix and burn till.
Such as, illustrated in patent documentation 1 and utilized by burning till at the temperature below 2000 DEG C, to active material surface carry out modification and and graphite-phase than have between wide crystal layer and the active material of micropore volume to manifest high input-output characteristic.In addition, propose in patent documentation 2 and use catalyst in order to expand between crystal layer when burning till, show by process under the firing temperature low when manufacturing than graphite can manufacture and graphite-phase than the active material had between wide crystal layer.
Although for the calcined cokes such as green coke charcoal and coal measures such as the coal measures of advantage can be enumerated as above, exist due to firing temperature compared with graphite material low and the crystallinity of carbon is low, make electrode time the capacity of per unit volume (weight) reduce such problem.That is, the capacity employing the electrode of common graphite material is 360mAh/g, bulk density is 1.4 ~ 1.8g/cm
3, on the other hand, in the electrode employing above-mentioned material, capacity is 240 ~ 340mAh/g, and bulk density is 1.0 ~ 1.2g/cm
3, therefore, the capacity as electrode reduces.Therefore, in the calcined cokes such as green coke charcoal and coal measures such as coal measures, the capacity including active material increase and electrode time the such problem of the increase of bulk density.
Such as, in patent documentation 3, show the high-energy-density in order to tackle lithium rechargeable battery, by different with specific area for breakdown strength 2 kinds of graphite materials, i.e. median particle diameter (D
50) be more than 13 μm and the approximate sphericity graphite particle and the median particle diameter (D that flakey Delanium have been carried out to almost spherical process of less than 15 μm
50) be more than 12 μm and after the mixing of the spherocrystal graphite compound of the mesophasespherule of less than 19 μm, even if obtain also can filling to high-density with little pressing pressure, and ensure that the negative electrode active material layer in the space of appropriateness.
In addition, as high electrode density and excellent, caused by discharge and recharge the capacitance loss of the permeability of electrolyte is few in patent documentation 4, and the negative electrode active material of the good lithium rechargeable battery of cycle performance, show and use average grain diameter (D
50) and D
90/ D
10the example of the different 3 kinds of powdered graphites of relation.
Prior art document
Patent documentation
Patent documentation 1 Japanese Unexamined Patent Publication 2009-224322 publication
Patent documentation 2 Japanese Unexamined Patent Publication 2011-9185 publication
Patent documentation 3 Japanese Unexamined Patent Publication 2009-164013 publication
Patent documentation 4 Japanese Unexamined Patent Publication 2007-324067 publication
Summary of the invention
Invent problem to be solved
The object of the invention is to, a kind of negative electrode active material is provided, it possesses the practical characteristic also can tackling the vehicle-mounted purposes such as HEV use, PHEV use of the discharge capacity, initial efficiency, input characteristics, capacity dimension holdup etc. of lithium rechargeable battery, can obtain the lithium rechargeable battery that the capacity of per unit volume (weight) is high.In addition, object of the present invention is also, provides a kind of lithium ion secondary battery negative pole and the lithium rechargeable battery that employ this lithium ion secondary battery cathode active material.
For solving the scheme of problem
The present inventor etc. concentrate on studies to solve above-mentioned problem, found that, by controlling as certain limit by the particle size distribution of the active material based on specified raw material, making the surface area of active material be the value specified simultaneously, above-mentioned problem can be solved, so that complete the present invention.
That is, the present invention is a kind of lithium ion secondary battery cathode active material, it is characterized in that, is 2.00 ~ 2.16g/cm by true specific gravity
3material with carbon element formed, in the D in the particle size distribution of the particle of volume reference
10the scope of 2 ~ 5 μm, D
50the scope of 8 ~ 12 μm, D
90the scope of 16 ~ 26 μm, and D
50-D
10the scope of 5 ~ 10 μm, tap density is more than 0.4g/cc, and the BET specific surface area (being designated as BET specific surface area below) adopting nitrogen adsorption flow through methods is 5.1 ~ 9.0m
2/ g.
As such active material, the calcined coke such as green coke charcoal, coal measures of coal measures and/or petroleum (coal measures etc.) preferably can be used to burn till separately or mix and to burn till and the active material obtained.
In addition, the present invention is a kind of lithium ion secondary battery negative pole, it is characterized in that, it has the composite layer above-mentioned lithium ion secondary battery cathode active material and adhesive mixing formed on the current collector, in the shape of the active material when observing the cross section of this negative pole, with regard to more than 80% of observed active material particle number, being equivalent to oval length ratio (be equivalent to oval minor axis length/be equivalent to oval long axis length) is 0.05 ~ 0.70, and the bulk density of described composite layer is 1.10 ~ 1.25g/cm
3.
And then the present invention is a kind of lithium rechargeable battery, it is characterized in that, above-mentioned lithium ion secondary battery negative pole and positive pole are formed via distance piece subtend.
Invention effect
According to the present invention, a kind of negative electrode active material can be provided, described active material can meet discharge capacity, initial efficiency, input characteristics, the capacity dimension holdups required by vehicle-mounted purposes such as such as HEV uses, PHEV uses, and improves bulk density when forming electrode (negative pole) simultaneously, can obtain the lithium rechargeable battery of performance balance excellence.
Embodiment
Below, embodiments of the present invention are described in detail.
The true specific gravity of lithium ion secondary battery cathode active material of the present invention is at 2.00 ~ 2.16g/cm
3scope.The calcined coke of the green coke charcoal or coal measures etc. of coal measures and/or petroleum (coal measures etc.) can be burnt till separately or mix and burnt till and obtain (in this manual by the lithium ion secondary battery cathode active material giving such true specific gravity, when being called " coal measures etc. ", refer to " coal measures and/or petroleum ", namely, can be coal measures, petroleum either party, also can be both mixed systems.)。If above-mentioned true specific gravity is less than 2.00g/cm
3, then, when being applied to lithium rechargeable battery, producing side reaction when discharge and recharge, causing the reduction of capacity, efficiency.In addition, if above-mentioned true specific gravity is more than 2.16g/cm
3, then, when being applied to battery, the characteristic of input-output characteristic, capacity dimension holdup reduces.Be explained, the green coke charcoals such as so-called coal measures, refer to petroleum and/or coal measures mink cell focus used the coked equipment such as such as delayed coking unit be up to Da Wendu be the temperature of 400 DEG C ~ about 700 DEG C under the material that obtains of carrying out pyrolysis polycondensation reaction 24 hours, the calcined cokes such as so-called coal measures, refer to the material green coke charcoals such as coal measures being implemented to calcination processing, refer to and be up to the coke of petroleum and/or the coal measures calcined under Da Wendu is 800 DEG C ~ about 1500 DEG C.
If describe in detail the method obtaining true specific gravity and give the lithium ion secondary battery cathode active material of above-mentioned scope, then to carry out pyrolytic polycondensation by the initial coked equipment such as such as delayed coking unit that the mink cell focuses such as coal measures are used under Da Wendu is the temperature of 400 DEG C ~ about 700 DEG C and react 24 hours and obtain the green coke charcoals such as coal measures being up to.Then, the block of the green coke charcoals such as the coal measures obtained is pulverized as required the size into regulation.Industrial used pulverizer can be used in pulverizing.Specifically, can enumerate: atomizer, thunder cover pulverizer, impeller mill, ball mill, shredding machine, jet mill, mixer (Ha イ Block リ ダ イ ザ ー), Orient mill (オ リ エ Application ト ミ Le) etc., but are not particularly limited to these.In addition, in the operation pulverized, the one kind or two or more of these devices can be used, also repeatedly can pulverize use with a kind of device.
The mink cell focuses such as coal measures used herein can be petroleum-derived heavy oil can be also coal measures mink cell focus, but coal measures mink cell focus is rich in fragrant attribute, and the impurity such as S, V, Fe are few, and volatile ingredient is also few, therefore, preferably use coal measures mink cell focus.
In addition, in order to manufacture the calcined cokes such as coal measures, be formed as the green coke charcoals such as the coal measures obtained as mentioned above to calcine to be up to Da Wendu 800 DEG C ~ 1500 DEG C under hypoxic atmosphere.Treatment temperature during calcining is preferably 1000 DEG C ~ 1500 DEG C, is more preferably the scope of 1200 DEG C ~ 1500 DEG C.The calcining of the green coke charcoals such as coal measures during manufacture calcined coke can use the equipment such as Rui Dehamu stove, shuttle-type stove, continuous tunnel furnace, rotary kiln, roller kilns or the microwaves that can carry out a large amount of process, but is not particularly limited to these.In addition, these calciners can be continous way or step any one.Then, the pulverizers such as the atomizer of industrial use are used by the block of the calcined cokes such as the coal measures obtained to be ground into the size of regulation in the same manner as the situation of green coke charcoal.In addition, the coke blacking after pulverizing cuts out micro mist by classification or utilizes sieve to wait removing meal, thus, and can the whole grain granularity that becomes to specify.
Green coke charcoal obtained above and calcined coke preferably can be carried out burning till process further.Firing temperature reaches thermometer can be set to more than 800 DEG C and less than 1500 DEG C to be up to.If firing temperature exceedes the upper limit, then excessively promote the crystal growth of coke material, be difficult to make true specific gravity be 2.16g/cm
3below.If true specific gravity is more than 2.16g/cm
3, then the crystal structure of coke orientation as graphite when burning till, crystal layer spacing narrows, and the characteristic that the structures such as input-output characteristic described above, capacity dimension holdup cause reduces.In addition, if firing temperature is lower than lower limit, then not only crystal structure is inflourishing, and true specific gravity is 2.00g/cm
3below, and the functional group's (OH base, COOH base etc.) being derived from raw material remains in coke surface, as mentioned above producing side reaction as during battery charging and discharging, causes capacity, efficiency to reduce.In addition, the retention time be up under Da Wendu of burning till process is not particularly limited, preferably more than 30 minutes.And then, about firing atmosphere, can be the inactive gas such as argon or nitrogen atmosphere.
In addition, burn till process and the green coke charcoals such as coal measures or calcined coke can be burnt till separately or mix and burn till, also can be set as burning till several times in this process to carry out.In addition, as long as meeting the scope of all conditions of active material of the present invention, then can as required containing shape controlling operations such as granulations or containing utilizing the modifying surface of organic and inorganic composition to active material or the operation of coating, and then, also can be set as at surface uniform or form metal ingredient dispersedly.
In addition, for the mensuration of the true specific gravity of negative electrode active material, Liquid displacement methods (another name bottle method) is utilized to measure.Specifically, in specific gravity bottle, put into powder (active material), add distilled water equal solvent liquid, by air and the solvent liquid of the method displacement sample surfaces such as vacuum degassing, obtain example weight and volume accurately, calculate true specific gravity value thus.
With regard to lithium ion secondary battery cathode active material of the present invention, need the D in the particle size distribution of this negative electrode active material
10be 2 ~ 5 μm, D
50be 8 ~ 12 μm, D
90be 16 ~ 26 μm, and D
50-D
10the scope of 5 ~ 10 μm.Preferred D
10be 2 ~ 4 μm, D
50be 8 ~ 12 μm, D
90be 18 ~ 24 μm, and D
50-D
10it is the scope of 6 ~ 10 μm.This refers to any one of the calcined cokes such as green coke charcoal, coal measures such as the coal measures as raw material to be burnt till separately or mix and to burn till and particle after the pulverizing of the material obtained has particle size distribution as above.In addition, the BET specific surface area of negative electrode active material is now made to be 5.1 ~ 9.0m
2/ g.The negative electrode active material of particle size distribution as above obtains by operation as follows: will according to circumstances carry out burning till the calcined cokes such as green coke charcoal, coal measures such as the coal measures of process separately or both mixedly utilized orient mill etc. to carry out coarse crushing, then, hammer-mill, jet mill etc. is utilized to carry out Crushing of Ultrafine, as required by removing micro mists such as air classifications.These breaking methods, stage division are not particularly limited, general method can be used.
For the particle size distribution of above-mentioned negative electrode active material, if D
10less than 2 μm, then specific area excessively increases and the initial efficiency of the secondary cell obtained is reduced.If D
90more than 26 μm, be then difficult to the electrode obtaining even and level and smooth surface texture when electrode fabrication because of the existence of coarse powder.If D
50-D
l0lower than 5 μm, then the having sharp grain size distribution of particle, the ratio of the micro mist that particle diameter is little becomes large, and when electrode fabrication, particle is difficult to form the closeest interstitital texture, result, and electrode density reduces.In addition, if D
50-D
10more than 10 μm, then there is D in result
90the possibility of the oversize grain such more than 26 μm uprises.The oversize grain such more than 26 μm makes the flatness of electrode surface reduce, likely cause reduce with the adaptation of collector body, the damage of distance piece side, the harmful effect such as the shed powder of oversize grain.In addition, if D
10be greater than 5 μm, then D
10be that the ratio of the micro mist of less than 2 μm diminishes, particle is difficult to form the closeest interstitital texture.From such reason, need above-mentioned particle size distribution in the present invention.In addition, D
50-D
l0represent the width (Wide Ga り) of the distribution shape in the particle size distribution of active material particle.Find by not using the D as central value in the past
50the width of designated size distribution and have the width of the distribution shown in the present invention, can make the electrode of fillibility excellence.In addition, any one of the calcined coke powdered carbons such as green coke powdered carbon, the coal measures such as above-mentioned coal measures can be used alone and obtain by raw material and the coke blacking with the negative electrode active material of above-mentioned particle size distribution, or also can by used in combination both it and obtain.
At this, for the particle size distribution of negative electrode active material (material with carbon element), in the present invention, use LMS-30 (society of seishin enterprise system) device, decentralized medium uses water+activating agent to measure.As the benchmark that there is ratio of particle, use laser diffraction and scattering method to measure volume distributed median, use and utilize the cumulative distribution of volume reference to carry out particle size distribution evaluation.That is, the particle size distribution of negative electrode active material utilizes laser diffraction and scattering method to measure, and the accumulation 10 volume % particle diameter in this particle size distribution is set to D
10.Equally, accumulation 50 volume % particle diameter is set to D
50, accumulation 90 volume % particle diameter is set to D
90.In addition, by D
50with D
10difference be set to D
50-D
10.
Negative electrode active material in the present invention is being pulverized and is becoming flat, lepidiod shape in the process of Control granularity distribution.As the shape of negative electrode active material, if observe the electrode sections made, then with regard to more than 80% of observed active material particle number, being equivalent to oval length ratio (be equivalent to oval minor axis length/be equivalent to oval long axis length) is 0.05 ~ 0.70.When being equivalent to oval length ratio more than 0.70, negative electrode active material becomes closer to spherical shape, even if the mode of fine and closely woven filling under identical particle size distribution, tap density also can change, electrode density, battery performance change.In addition, be equivalent to oval length than lower than 0.05 time, negative electrode active material becomes the shape closer to needle-like, and the mode of similarly not only filling, tap density change, and the surface area of negative electrode active material becomes excessive, produce the phenomenon that side reaction etc. reduces battery performance.Therefore, in the present invention, use from have on the current collector mix with adhesive and the cross-section of the electrode (negative pole) of composite layer that formed time negative electrode active material shape, more than 80% of observed negative electrode active material population counts 0.05 ~ 0.70 such negative electrode active material to be equivalent to oval length ratio (being equivalent to the long axis length of the minor axis length of ellipse/be equivalent to ellipse).
As the observational technique of above-mentioned electrode sections, the thickness making composite layer is the electrode of more than 50 μm, utilize the methods such as mechanical milling method, ultrathin sectioning, CP (Cross-section Polisher) method, focused ion beam (FIB) method to make electrode sections, utilize the methods such as SEM to observe the grain size of whole minimum grain size size more than 1 μm.Oval length ratio (be equivalent to oval minor axis length/be equivalent to oval long axis length) is equivalent to the particle measurement observed.Owing to observing the skewness etc. that there is particle in cross section, therefore, more than preferred view 20 visual field.For the mensuration of particle size, image analysis software (WinRooF: three paddy business Co., Ltd. systems) etc. can be used to analyze.
Lithium ion secondary battery cathode active material of the present invention is in order to improve initial stage density during electrode fabrication, and its tap density is more than 0.4g/cc, is preferably set to the scope of 0.4 ~ 0.8g/cc.If tap density is less than 0.4g/cc, the contact each other of negative electrode active material then during electrode fabrication becomes insufficient, and guiding path reduces, therefore, battery performance reduces, in addition, if raising density and increase pressing pressure, then it is large to be out of shape quantitative change, therefore, negative electrode active material ftractures, and because the increase of surface area, the adaptation reduction of electrode cause guiding path to reduce further, causes battery performance to reduce.Therefore, in order to improve the packed density before compacting, needing using tap density as index and making it be at least 0.4g/cc.In addition, in order to make it more than 0.8g/cc, such as, need to increase D
10lower than ratio or the increase D of the micro mist of 1 μm
90near the ratio of oversize grain, its result, the surface area of negative electrode active material becomes large or makes the uniformity of electrode, performance disorderly because of the impact of oversize grain, causes battery performance to reduce.Therefore, do not need to make tap density more than 0.8g/cc.
In the present invention, for the tap density of negative electrode active material, use the device of Tap DenserKYT-400 (society of Seishin enterprise system), use with the measured value of barrel volume 100cc, jolt ramming distance 38mm, number of taps 300 times.
The BET specific surface area of lithium ion secondary battery cathode active material of the present invention is 5.1 ~ 9.0m
2/ g.The shape during pulverizing of this BET specific surface area caused by the crystal state because of material with carbon element and the particle size distribution after pulverizing and determine.If BET specific surface area is less than 5.1m
2/ g, then the charge/discharge rates of lithium ion is slack-off, therefore undesirable, if be greater than 9.0m
2/ g, then tap density does not rise, and electrode density does not rise, therefore not preferred.BET specific surface area affects the speed of surface reaction during lithium ion turnover carbon structure, therefore, importantly controls as suitable value.
In the present invention, BET specific surface area utilizes nitrogen adsorption flow through methods to try to achieve, and uses BELSORP-miniII (Nippon-Bel Inc.) device.
The present invention is also for employing the lithium ion secondary battery negative pole of above-mentioned lithium ion secondary battery cathode active material, and negative pole comprises on the current collector (being generally Copper Foil) mixes the composite layer that above-mentioned lithium ion secondary battery cathode active material and adhesive formed.
In adhesive, the fluorine resin powder such as polyvinylidene fluoride (PVDF) or polyimides (PI) usually can be used to be the water-soluble binders such as resin, styrene butadiene ribber (SBR), carboxymethyl cellulose (CMC).
Composite layer formation on the current collector by using solvent to make slurry above-mentioned negative electrode active material and adhesive, can be applied on collector body and (being generally Copper Foil), dry, then, pressurizes and carry out under arbitrary condition.The solvent used is not particularly limited, but can use 1-METHYLPYRROLIDONE (NMP), dimethyl formamide or water, alcohol etc.
More specifically, such as can by with mass ratio range by negative electrode active material and adhesive mixing with the ratio of 93 ~ 97:7 ~ 3 (negative electrode active material: adhesive), this slurry is applied on the Copper Foil of specific thickness, dry solvent under the drying condition of 60 ~ 120 DEG C, then, negative electrode is made, by manufacturing condition being now set to above-mentioned scope to obtain bulk density for 1.10 ~ 1.25g/cm with linear pressure 100 ~ 600kg/cm pressurization
3the electrode of scope.At this, if linear pressure when too improving pressurization, then the bulk density of electrode improves, but active material is out of shape, destroys, and the contact in electrode is deteriorated, and causes the reduction of capacity, efficiency, therefore preferably sets the pressurized conditions of the bulk density becoming above-mentioned.
The negative pole manufactured as described above can be used to make lithium rechargeable battery of the present invention.Lithium rechargeable battery of the present invention configures in the mode that there is distance piece at above-mentioned negative pole and positive interpolar.Negative pole and positive pole, via distance piece subtend, as relative positive pole, can illustrate: lithium-containing transition metal oxide LiM (1) xO
2(in formula, x is the numerical value of the scope of 0≤x≤1, and in formula, M (1) represents transition metal, comprises at least a kind in Co, Ni, Mn, Ti, Cr, V, Fe, Zn, Al, Sn, In) or LiM (1) yM (2)
2-yO
4(in formula, y is the numerical value of the scope of 0≤y≤1, in formula, M (1), M (2) represent transition metal, comprise at least a kind in Co, Ni, Mn, Ti, Cr, V, Fe, Zn, Al, Sn, In, transient metal chalcogenide compound (Ti, S
2, NbSe, etc.), barium oxide (V
2o
5, V
6o
13, V
2o
4, V
3o
6deng) and lithium compound, formula M xMo
6ch
6-y is (in formula, the numerical value that x is 0≤x≤4, y is the scope of 0≤y≤1, in formula, M represents with transition metal to be the metal of representative, and Ch represents chalcogen metal) shown in thank freire phase (シ ェ Block レ Le phase) compound or the positive active material such as active carbon, activated carbon fiber.
In addition, as the electrolyte be full of between above-mentioned positive pole and negative pole, current known material all can use, such as, can enumerate: LiClO
4, LiBF
4, LiPF
6, LiAsF
6, LiB (C
6h
5), LiCl, LiBr, Li
3sO
3, Li (CF
3sO
2)
2n, Li (CF
3)
3sO
2)
3c, Li) CF
3cH
2oSO
2)
2n, Li (CF
3cF
2cH
2oSO
2)
2n, Li (HCF
2cF
2cH
2oSO
2)
2n, Li ((CF
3)
2cHOSO
2)
2n, LiB [C
6h
3(CF
3)
2]
4deng one kind or two or more mixture.
In addition, as non-water system electrolyte, such as propylene carbonate can be used, ethylene carbonate, butylene carbonate, chlorocarbonic acid ethyl, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1, 1-dimethoxy-ethane, 1, 2-dimethoxy-ethane, 1, 2-diethoxyethane, gamma-butyrolacton, oxolane, 2-methyltetrahydrofuran, 1, 3-dioxolanes, 4-methyl isophthalic acid, 3-dioxolanes, methyl phenyl ethers anisole, Anaesthetie Ether, sulfolane, methyl sulfolane, acetonitrile, chlorine nitrile, propionitrile, trimethylborate, quanmethyl silicate, nitromethane, dimethyl formamide, 1-METHYLPYRROLIDONE, ethyl acetate, trimethyl orthoformate, nitrobenzene, chlorobenzoyl chloride, benzoyl bromide, thiophane, dimethyl sulfoxide (DMSO), 3-methyl-2-oxazolidone, ethylene glycol, sulfite, the separate solvents such as dimethyl sulfite or mixed solvent of more than two kinds.
Embodiment
Below, based on embodiment, the present invention is described particularly.But content of the present invention does not limit by these embodiments.In addition, the mensuration of true specific gravity, particle size distribution, tap density and BET specific surface area is undertaken by said method.
(embodiment 1)
Use the refined bitumen eliminating quinoline non-soluble composition from coal measures mink cell focus, obtain at the temperature of 500 DEG C, carry out heat treatment in 24 hours by delayed coking process and the block coke (green coke charcoal) manufactured, carry out Crushing of Ultrafine with orient mill and jet mill, obtain average grain diameter (D
50) be the green coke carbon plate (Crushing of Ultrafine green coke charcoal) of 10.5 μm.
By rotary kiln by the green coke carbon plate that obtains as mentioned above under hypoxic atmosphere from temperature near entrance 700 DEG C to outlet near the temperature lower calcination more than 1 hour of temperature 1500 DEG C (being up to Da Wendu), obtain calcined coke.This calcined coke is utilized jet mill same as described above and suitably adjust time per unit treating capacity, process time gas flow rate and implement Crushing of Ultrafine, then, removed most of micro mist of less than 3 μm by air classification, obtaining true specific gravity is thus 2.15g/cm
3, D
10be 3.7 μm, D
50be 10.2 μm, D
90be 19.7 μm and D
50-D
10it is the lithium ion secondary battery cathode active material of 6.5 μm.The tap density of this negative electrode active material is 0.52g/cm
3, in addition, the BET specific surface area adopting nitrogen adsorption flow through methods is 6.7m
2/ g.
Then, relative to this lithium ion secondary battery cathode active material, to add as the styrene butadiene ribber (SBR, JSR Corp.'s system) of adhesive and carboxymethyl cellulose (CMC, Jujo Paper Co., Ltd's system) and mixing in the mode of the 5 quality % becoming slurry solids composition, make slurry.The slurry obtained is coated equably the surface of the Copper Foil of thickness 15 μm and dry at the temperature of 60 ~ 120 DEG C, then suppress with the line pressure of 300kg/cm, obtain the negative electrode of sheet thus.The bulk density of this electrode is 1.15g/cm
3.From this sheet material, cut out the circle of diameter 15mm φ, make the negative electrode of test thus.In order to evaluate the electrode characteristic of the negative electrode one pole of this test, use the lithium metal that cuts out about 15.5mm φ as to electrode.In addition, CP method is utilized to cut off at the electrode of making, utilize FE-SEM to observe (multiplying power 1500 times) its cross section, results verification to be equivalent to oval length than the active material particle of the scope 0.05 ~ 0.70 in the scope of the angle of visual field 75 μm × 30 μm in viewed active material particle be 88%.In addition, for field of view, in order to reduce inequality, use the mean value in 20 visuals field.
Be used in the mixed solvent (1:1 mixing by volume) of ethylene carbonate and diethyl carbonate and dissolve LiPF with the concentration of 1mol/l
6solution as electrolyte, use propylene perforated membrane as distance piece, use above-mentioned test negative electrode, make button battery and make lithium rechargeable battery.The capacity of the battery made is 1mA/cm
2.By the charging lower voltage limit with terminal voltage under the constant temperature of 25 DEG C be 0V, the upper voltage limit of electric discharge is 1.5V voltage range implements 1mA/cm
2constant current electric discharge and 20mA/cm
2constant current electric discharge time ratio calculate charging sustainment rate.Show the result in table 1.
In addition, use above-mentioned lithium rechargeable battery, 0V is charged to from 1.5V with the constant current of the current density 30mA/g of negative electrode active material Unit Weight, then constant voltage charging in 90 minutes is carried out, measure initial discharge capacity, stop being discharged to 1.5V with the constant current of current density 30mA/g from 0V after 30 minutes, measure primary charging capacity, calculate initial efficiency by the initial discharge capacity relative shown in following formula in the ratio of primary charging capacity.Show the result in table 1.
Initial efficiency (%)=100 × initial discharge capacity/primary charging capacity
In addition, the capacity of the unit volume of negative electrode active material, charging property rapidly and initial efficiency are evaluated in the judgement of table 1, are 1.10 ~ 1.25g/cm by bulk density
3, and initial efficiency more than 80% so that the charging situation of sustainment rate more than 40% be set to zero, be not such situation be set to ×.
(embodiment 2 ~ 3, comparative example 1 ~ 3)
Change the condition when jet mill after obtaining calcined coke is pulverized, in addition, carry out operation similarly to Example 1 respectively, obtain the lithium ion secondary battery cathode active material that particle size distribution such shown in table 1 is different.The characteristic of the negative electrode active material obtained is shown in table 1.In addition, observe the cross section of electrode made similarly to Example 1, results verification, with regard to be equivalent to oval length than 0.05 ~ 0.70 scope active material particle with regard to, sample is 85 ~ 89%.These particles are used to obtain negative electrode and lithium rechargeable battery similarly to Example 1, respectively investigation charging sustainment rate.Show the result in table 1.
(embodiment 4)
Pass through rotary kiln, by green coke carbon plate under hypoxic atmosphere from temperature near entrance 700 DEG C to outlet near temperature 1000 DEG C (being up to Da Wendu) temperature lower calcination more than 1 hour and obtain calcined coke, in addition, carry out operation similarly to Example 1, obtain lithium rechargeable battery.The characteristic of the negative electrode active material obtained is shown in table 1.In addition, observe the cross section of electrode made similarly to Example 1, it is 90% that results verification is equivalent to oval length than the active material particle of the scope 0.05 ~ 0.70.In addition, charging sustainment rate and initial efficiency is investigated similarly to Example 1.Show the result in table 1.
(comparative example 4)
Pass through rotary kiln, by green coke carbon plate under hypoxic atmosphere from temperature near entrance 700 DEG C to outlet near temperature 1800 DEG C (being up to Da Wendu) temperature carry out the heat treatment of more than 1 hour and obtain calcined coke, in addition, carry out operation similarly to Example 1, obtain lithium rechargeable battery.The characteristic of the negative electrode active material obtained is shown in table 1.In addition, observe the cross section of electrode made similarly to Example 1, it is 87% that results verification is equivalent to oval length than the active material particle of the scope 0.05 ~ 0.70.In addition, charging sustainment rate and initial efficiency is investigated similarly to Example 1.Show the result in table 1.
(embodiment 5)
Use the refined bitumen eliminating quinoline non-soluble composition from coal measures mink cell focus, pass through delayed coking process, obtain at the temperature of 500 DEG C, carry out heat treatment in 24 hours and the block coke (green coke charcoal) of the coal measures that manufactures, pass through rotary kiln, by block for the coal measures obtained coke (green coke charcoal) under hypoxic atmosphere from temperature near entrance 800 DEG C to outlet near temperature 1500 DEG C (being up to Da Wendu) temperature lower calcination more than 1 hour and obtain the calcined coke of coal measures bulk
Gas flow rate when block for the coal measures obtained as mentioned above calcined coke being utilized jet mill and suitably adjusts the treating capacity of time per unit, process and implement Crushing of Ultrafine, then, removed most of micro mist of less than 3 μm by air classification, obtain coal measures calcined coke.By rail kiln, the coal measures calcined coke obtained is burnt till more than 1 hour in a nitrogen atmosphere, being up at Da Wendu 1500 DEG C, and obtaining true specific gravity is thus 2.15g/cm
3, D
10be 3.0 μm, D
50be 10.2 μm, D
90be 20.0 μm and D
50-D
10it is the lithium ion secondary battery cathode active material of 7.2 μm.The tap density of this negative electrode active material is 0.55g/cm
3, in addition, the BET specific surface area adopting nitrogen adsorption flow through methods is 6.6m
2/ g.
In addition, observe the cross section of electrode made similarly to Example 1, it is 89% that results verification is equivalent to oval length than the active material particle of the scope 0.05 ~ 0.70.In addition, charging sustainment rate and initial efficiency is investigated similarly to Example 1.Show the result in table 1.
(embodiment 6 ~ 7)
The condition when jet mill changed after obtaining the block calcined coke of coal measures is pulverized, in addition, carries out operation similarly to Example 5 respectively, obtains the lithium ion secondary battery cathode active material that particle size distribution such shown in table 1 is different.The characteristic of the negative electrode active material obtained is shown in table 1.In addition, observe the cross section of electrode made similarly to Example 1, results verification, with regard to be equivalent to oval length than 0.05 ~ 0.70 scope active material particle with regard to, sample is 82 ~ 90%.These particles are used to obtain negative electrode and lithium rechargeable battery similarly to Example 1, investigation charging sustainment rate and initial efficiency.Show the result in table 1.
(embodiment 8)
By rail kiln, coal measures calcined coke is burnt till more than 1 hour in a nitrogen atmosphere, being up at Da Wendu 1000 DEG C, in addition, carries out operation similarly to Example 5, obtain lithium rechargeable battery.The characteristic of the negative electrode active material obtained is shown in table 1.In addition, observe the cross section of electrode made similarly to Example 1, it is 88% that results verification is equivalent to oval length than the active material particle of the scope 0.05 ~ 0.70.In addition, charging sustainment rate and initial efficiency is investigated similarly to Example 1.Show the result in table 1.
[table 1]
From table 1 clearly, employ the lithium rechargeable battery display high charge sustainment rate of the lithium ion secondary battery cathode active material meeting important document of the present invention, there is charge characteristic rapidly, and in this condition bulk density also more than 1.10g/cm
3, in addition, the initial efficiency worried because surface area increases also can keep high value.
In addition, if also the true specific gravity of known negative electrode active material is large, then charge characteristic is impaired rapidly.Think that one of its reason is, because firing temperature uprises, promote the crystallization of carbon, interfloor distance narrows as graphite.
Above, be illustrated in detail the present invention based on above-mentioned concrete example, the present invention is not limited to above-mentioned concrete example, only otherwise depart from the scope of the present invention, then can carry out all distortion, change.
Claims (4)
1. a lithium ion secondary battery cathode active material, is characterized in that, is 2.00 ~ 2.16g/cm by true specific gravity
3material with carbon element formed, in the D in the particle size distribution of the particle of volume reference
10the scope of 2 ~ 5 μm, D
50the scope of 8 ~ 12 μm, D
90the scope of 16 ~ 26 μm, and D
50-D
10the scope of 5 ~ 10 μm, tap density is more than 0.4g/cc, and the BET specific surface area adopting nitrogen adsorption flow through methods is 5.1 ~ 9.0m
2/ g.
2. lithium ion secondary battery cathode active material according to claim 1, wherein, active material is either party of coal measures and/or the green coke charcoal of petroleum or the calcined coke of coal measures and/or petroleum burnt till separately or both mixed and carry out burning till obtaining.
3. a lithium ion secondary battery negative pole, it is characterized in that, there is composite layer on the current collector that the lithium ion secondary battery cathode active material described in claim 1 or 2 and adhesive mixing are formed, in the shape of the active material when observing the cross section of this negative pole, with regard to more than 80% of observed active material particle number, being equivalent to oval length ratio (be equivalent to oval minor axis length/be equivalent to oval long axis length) is 0.05 ~ 0.70, and the bulk density of described composite layer is 1.10 ~ 1.25g/cm
3.
4. a lithium rechargeable battery, is characterized in that, is formed by lithium ion secondary battery negative pole according to claim 3 with positive pole via distance piece is relative.
Applications Claiming Priority (4)
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| JP2014-050666 | 2014-03-13 | ||
| JP2014050666 | 2014-03-13 | ||
| JP2015-027523 | 2015-02-16 | ||
| JP2015027523A JP2015187973A (en) | 2014-03-13 | 2015-02-16 | Negative electrode active material for lithium ion secondary battery, lithium ion secondary battery negative electrode using the same and lithium ion secondary battery |
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|---|---|
| CN104916842A true CN104916842A (en) | 2015-09-16 |
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|---|---|
| KR (1) | KR20150107656A (en) |
| CN (1) | CN104916842A (en) |
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2015
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