CN104508870B - Negative electrode for lithium secondary battery - Google Patents

Negative electrode for lithium secondary battery Download PDF

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Publication number
CN104508870B
CN104508870B CN201380039082.4A CN201380039082A CN104508870B CN 104508870 B CN104508870 B CN 104508870B CN 201380039082 A CN201380039082 A CN 201380039082A CN 104508870 B CN104508870 B CN 104508870B
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active material
silicon
material layer
discharge
particle
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CN104508870A (en
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八代仁
细田雅弘
繁田朗
山田宗纪
江口寿史朗
越后良彰
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Iwate University
Unitika Ltd
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Unitika Ltd
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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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Cell Electrode Carriers And Collectors (AREA)

Abstract

The present invention is provided with the negative electrode for lithium secondary battery of the active material layer of the silicon-based active material containing particle shape and adhesive, the content of silicon-based active material in active material layer is more than 50 mass %, under the conditions of the composition of following shown battery units and discharge and recharge, the discharge capacity of the 20th time during repeated charge 20 times is more than 1500mAh/g silicon-based active material.The composition ＞ batteries of ＜ battery units：Bipolar system pouch-type battery cell, to electrode：Lithium metal, electrolyte：LiPF6Mixed solvent (the volume ratio 1 of the ethylene carbonate, methyl ethyl carbonate and the dimethyl carbonate that are dissolved with 1mol/L concentration：1：1), ＜ discharge and recharges condition ＞ determines temperature：30 DEG C, voltage range：0.01~2V, charging current and discharge current：500mA/g silicon-based active materials.

Description

Negative electrode for lithium secondary battery
Technical field
Silicon systems particle be the present invention relates to the use of as the negative electrode for lithium secondary battery of active material.
Background technology
In the past, the negative pole of lithium rechargeable battery was used by the active carbon material containing particle shapes such as powdered graphites and absolutely The active material layer of the adhesive of edge is formed at the negative pole on the surface of the collector of the foil-like such as copper foil.Adhesive uses poly- inclined fluorine Ethene, polytetrafluoroethylene (PTFE) etc..
But, the use of the discharge capacity of the negative pole of active carbon material is at most 350mAh/g or so, it is therefore desirable to higher The active material of capacity.Therefore, it is proposed to using particle shape silicon-based active material instead active carbon material it is next The negative pole of the active material in generation.Known silicon shows the discharge capacities more than several times of graphite by the alloying reaction with lithium.
But, the silicon-based active material is big along with the Volume Changes of discharge and recharge, therefore along with repeated charge, silicon systems Active material is micronized, or is departed from from collector.Decline accordingly, there exist the electrical collector of negative pole and active matter quality, negative pole is put The problem of capacitance is significantly reduced.As under the cycle characteristics caused by Volume Changes when improving the repeated charge Proposed in the method for drop, patent document 1 by being 1~10 by average grain diameter is bonded using the excellent polyimides of mechanical characteristic Active material formed by the silicon particle of micron is arranged at the surface for the collector being made up of specific copper foil and negative pole is made Proposed in method, patent document 2 and use the compound being made up of silicon and carbon as active material, by the active material with polyamides The negative pole that imines is bonded.Polyamidoimide, polyacrylic acid are used as silicon in addition, being proposed respectively in non-patent literature 1,2 The negative pole of the adhesive of particle.
And then, proposed in patent document 3 and glue the electric conductivity of the adhesive of the high concentration in the surface engagement of collector Layer stackup is connect, and is provided with the outer surface of the electric conductivity adhesive linkage silicon active material layer containing adhesives such as polyimides Silicium cathode.
Prior art literature
Patent document
Patent document 1:No. 4471836 specification of patent
Patent document 2:International Publication No. 2011/056847
Patent document 3:No. 4212392 specification of patent
Non-patent literature
Non-patent literature 1：Journal of Power Sources 177(2008)590-594
Non-patent literature 2：ACS Appl.Mater.Interfaces,2010,2(11),3004-3010
The content of the invention
Even if however, using the negative pole described in above-mentioned prior art literature, it is also difficult to be adequately suppressed along with repeatedly The decline of the discharge capacity of discharge and recharge is, it is necessary to also maintain the negative pole of high discharge capacity after repeated charge.
It is therefore, a kind of when using silicon-based active material the purpose is to provide in order to solve above-mentioned problem in the present invention, After repeated charge, the lithium ion secondary battery cathode of high discharge capacity is also able to maintain that.
The present inventor furthers investigate repeatedly in order to solve above-mentioned problem, and its result completes the present invention.I.e., originally The purport of invention is as described below.
(1) a kind of negative electrode for lithium secondary battery, it is characterised in that be provided with the silicon-based active material containing particle shape and The content of silicon-based active material in the negative electrode for lithium secondary battery of the active material layer of adhesive, active material layer is more than 50 matter % is measured, under the conditions of the composition of following shown battery units and discharge and recharge, the electric discharge of the 20th time during repeated charge 20 times Capacity is more than 1500mAh/g- silicon-based active materials.
The composition ＞ of ＜ battery units
Battery：Bipolar system pouch-type battery cell
To electrode：Lithium metal
Electrolyte：LiPF6With the mixed of the ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate of 1mol/L concentration dissolving Bonding solvent (volume ratio 1：1：1)
＜ discharge and recharge conditions ＞
Determine temperature：30℃
Voltage range：0.01~2V
Charging current and discharge current：500mA/g- silicon-based active materials
(2) negative electrode for lithium secondary battery as described in (1), it is characterised in that the porosity of active material layer is 15~40 Volume %, and its electrolyte infiltration rate is less than 300 seconds.
(3) negative electrode for lithium secondary battery as described in (1) or (2), wherein, by the conduction formed on the collector of sheet Property adhesive linkage outer surface layer be laminated with active material layer layered product constitute.
(4) negative electrode for lithium secondary battery as any one of (1)~(3), it is characterised in that active material is by silicon The particle that monomer is constituted.
(5) negative electrode for lithium secondary battery as any one of (1)~(4), it is characterised in that silicon-based active material Average grain diameter is less than 1 μm.
The negative pole of the present invention also maintains high discharge capacity after repeated charge is carried out, therefore can use well Make negative electrode for lithium secondary battery.
Brief description of the drawings
Fig. 1 is the figure of charging and discharging curve when representing the negative pole using embodiments of the invention 1.
Embodiment
The negative electrode for lithium secondary battery of the present invention is provided with the activity of the silicon-based active material containing particle shape and adhesive The content of silicon-based active material in material layer, active material layer is more than 50 mass %.Also, with following shown batteries Under the conditions of the composition of unit and discharge and recharge, the discharge capacity of the 20th time during repeated charge 20 times is 1500mAh/g-silicon systems Characteristic more than active material.
The composition ＞ of ＜ battery units
Battery：Bipolar system pouch-type battery cell
To electrode：Lithium metal
Electrolyte：LiPF6With the mixed of the ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate of 1mol/L concentration dissolving Bonding solvent (volume ratio 1：1：1)
＜ discharge and recharge conditions ＞
Determine temperature：30℃
Voltage range：0.01~2V
Charging current and discharge current：500mA/g- silicon-based active materials
Here as the unit of discharge capacity and show " mAh/g- silicon-based active materials " and refer to based on active material Premised on the situation of the discharge and recharge of silicon-based active material coordinated in layer, the whole of the electricity (mAh) during the electric discharge of measurement is changed Calculate as the value of every gram of silicon-based active material.
Above-mentioned discharge capacity is more preferably more than 1700mAh/g, more preferably more than 2000mAh/g.In this way, can be with The negative electrode for lithium secondary battery of the excellent high discharge capacity of cycle characteristics is made.
The measure of discharge capacity is carried out using the battery unit of known pouch-type (laminate type).The battery unit with it is hard The differences such as the battery unit of coin type are the aluminium lamination press molds (stacked film of resin film and aluminium foil) for using softness as the electricity of exterior material Pool unit, when being discharge and recharge in the state of electrode does not apply pressure, determines the battery unit of discharge capacity.The battery of the pouch-type Unit for example can make in the following manner.
The negative pole of obtained sheet is cut out into the rectangle for 10mm × 40mm, 10mm × 10mm active material face is left Product, it is coated with deposition film.As to electrode, thickness 1mm lithium plate is cut out into the rectangle for 30mm × 40mm, to thickness 0.5mm Nickel down-lead (5mm × 50mm) doubling and crimp.Only negative pole is put into after bag-shaped distance piece (30mm × 20mm), and to electrode Face-to-face, electrode group is obtained.Distance piece uses the acrylic resin perforated membrane (25 μm of thickness) of rectangle.With two one group of square The aluminium lamination press mold (50mm × 40mm) of shape covers the electrode group, seals behind its three sides, injects 1mL's in bag-shaped aluminium lamination press mold Electrolyte.Electrolyte use by EC, DEC and EMC with volume ratio 1：1：The in the mixed solvent of 1 mixing is by LiPF6With 1 mole/L Concentration dissolving obtained from electrolyte.Thereafter, a remaining side is sealed, will be sealed in bag-shaped aluminium lamination press mold.This When outside, by being sealed in bag-shaped aluminium lamination press mold, one end of negative pole and nickel down-lead is extended into outside, terminal is used as.In this way, To test cell unit.These operations are all carried out in the control box of argon atmospher.
The content needs of the particle (being abbreviated as sometimes below " silicon systems particle ") of silicon-based active material in active material layer More than 50 mass %, preferably greater than 60 mass %.If below 50 mass %, even if then as the silicon systems active matter of active material The discharge capacity of every gram of matter is high, and discharge capacity when being converted into every gram of active material layer can also decline, and therefore, it is difficult to discharged The high negative pole of capacity.
As above-mentioned silicon systems particle, for example, the particles such as silicon monomer, silicon alloy, silicon silica complex can be enumerated, Its shape can be indefinite shape, spherical, any shape such as threadiness.In these silicon systems particles, the particle of silicon monomer (has below When be abbreviated as " silicon particle ") discharge capacity highest, therefore can preferably use.Here, silicon monomer refers to that purity is 95 matter Measure more than % crystalloid or amorphous silicon.
The average grain diameter of silicon systems particle is preferably less than 5 μm, more preferably less than 1 μm.Average grain diameter is smaller, the surface of particle Product is bigger, therefore can obtain high discharge capacity.Here, above-mentioned average grain diameter refers to such as laser diffraction formula particle size distribution dress Put the average grain diameter of the volume reference of measure.The average grain diameter can also use above-mentioned silicon systems particle to obtain after negative pole, by its table The SEM image in face confirms.
Above-mentioned silicon systems particle is bonded to one another by coordinating adhesive in above-mentioned silicon systems particle, membranaceous activity is formed Material layer.The species of the adhesive used is not limited, and preferably uses that mechanical characteristic is excellent, and excellent to the caking property of silicon systems particle Different polyimides system macromolecule.Here, polyimides system macromolecule refers to that main chain has the macromolecule of imide bond.It is used as tool Style, can enumerate polyimides, polyamidoimide, polyesterimide etc., and polyimides system macromolecule is not limited to them, As long as the resin that main chain has imide bond can then use any macromolecule.These resins are generally used alone, can also It is mixed with two or more.
In these polyimides system macromolecules, the excellent polyimides of especially mechanical characteristic, polyimides are preferably used In, further preferably using aromatic polyimide.Here aromatic polyimide refers to by following formulas (1) expression The polyimides of structure.
[changing 1]
In formula (1), R1 is the aromatic residue of 4 valencys, and R2 is the aromatic residue of divalent.
The aromatic polyimide can be thermoplasticity or non-thermal plasticity.As polyimides, can use by The polyimides of precursor type obtained from being dissolved in the polyimide precursor heat cure such as polyamic acid of solvent, solvent soluble type It is preferable to use precursor type polyimides for polyimides.In addition, precursor type polyimides for having used polyamic acid Detailed content, tells about later.
As above-mentioned polyimides system macromolecule, commercially available product can also be used.It is, for example, possible to use " U IMIDE AR ", " U IMIDE AH ", " U IMIDE CR ", " (space portion is emerging by U IMIDE CH " (being UNITIKA company systems) or U VARNISH A Production company system) etc. polyamide acid type varnish, make " RIKACOAT SN-20 " (new Japan Chemical company system) or " MATRIMID5218 " (Huntsman company systems) etc. is dissolved in solvent soluble type polyimide varnish, the VYLOMAX of solvent The polyamidoimide varnish such as HR-11NN (company system is spun by Japan).
From the viewpoint of discharge capacity and cycle characteristics, polyimides system in above-mentioned active material layer is high molecular to be contained Amount is preferably 5~30 mass %, more preferably 15~25 mass %.By setting by this way, work described later can be caused Property material layer the porosity be preferred scope, can be made the excellent high discharge capacity of cycle characteristics secondary lithium batteries bear Pole.
The porosity of above-mentioned active material layer is preferably 15~40 volume %, more preferably 25~35 volume %.By with This mode sets the porosity, can be by stomata absorption due to the Volume Changes of the discharge and recharge along with silicon active material The stress to active material layer produced, therefore good circulation can be obtained with not producing cracking in active material layer during discharge and recharge Characteristic.Therefore, when the porosity is outside the scope, the high discharge capacity after the repeated charge as purpose can not be obtained sometimes.
The porosity of above-mentioned active material layer be by active material layer apparent density, constitute each material of active material layer The value that the real density (proportion) and use level of (silicon systems particle, adhesive, electroconductive particle etc.) are calculated, is according to each material Use level, particle size and change.Specifically, silicon systems particle (real density A g/cm3) coordinating X mass %, adhesive is (true Density B g/cm3) coordinate Y mass %, electroconductive particle (real density C g/cm3) coordinate Z mass % active material layer to regard close Spend for Dg/cm3When the porosity (volume %) calculated by following calculating formula.Here, the real density of each material by based on JIS Z8807 are measured and obtained.
The porosity (volume %)=100-D (X/A+Y/B+Z/C)
In the present invention, in order to obtain high discharge capacity after charge and discharge cycles, the porosity is preferably set to 15~40 bodies Product %, and the electrolyte infiltration rate of active material layer is set to less than 300 seconds.Here, electrolyte infiltration rate is preferably Less than 200 seconds, more preferably less than 100 seconds.By the way that the electrolyte infiltration rate is set as into less than 300 seconds, electrolyte Can be during repeated charge, more effectively the surface with the silicon systems particle as active material is contacted, therefore reachable Into the high discharge capacity after repeated charge.Therefore, when electrolyte infiltration rate is outside the scope, conduct can not be obtained sometimes High discharge capacity after the repeated charge of purpose.In addition, for the detailed content of electrolyte infiltration rate, tell about later.
Here electrolyte infiltration rate can be determined by the following method.That is, by ethylene carbonate (EC), diethyl carbonate (DEC)), methyl ethyl carbonate (EMC) is with 1：1：20 DEG C of the μ L of electrolyte 5 that 1 volume ratio coordinates are added dropwise to active material layer Surface.Then, electrolyte is added dropwise to behind the surface of active material layer, the surface of electrolyte from the active material layer of dropwise addition is complete It is absorbed into entirely in the layer, visually to determine time of the drop untill the surface of active material layer disappears.By the measure when Between be set to electrolyte infiltration rate.
In the present invention, the thickness of above-mentioned active material layer is arbitrary, can be set to 10~300 μm or so of thickness.
In the present invention, in order to reduce the internal resistance of active material layer, conduction is contained preferably in above-mentioned active material layer Property particle.As electroconductive particle, for example, carbon material, the metal material of particle shape can be used.It is used as carbon material, preferably stone Ink, more preferably carbon black, graphite.As metal material, for example, silver, copper, nickel can be used.It is used as these carbon particles, metallic Particle diameter, preferably average grain diameter be less than 5 μm.
The content of electroconductive particle in above-mentioned active material layer is preferably 1~30 mass %, more preferably 5~25 matter Measure %.
The negative pole of the present invention is preferably that electric conductivity adhesive linkage is provided between above-mentioned active material layer and the collector of sheet Layered product.Thus, it is possible to relax expansion and contraction along with active material layer during discharge and recharge and active material layer with The stress that the interface of collector is produced, and inhibitory activity material layer peels off from collector.
Above-mentioned electric conductivity adhesive linkage is the layer for coordinating adhesive electroconductive particle.The species of adhesive used herein does not have Restricted, for example it is preferable to use above-mentioned polyimides system macromolecule.In polyimides system macromolecule, particularly preferably use Excellent polyamidoimide, the polyimides of solvent soluble type with the adhesion properties of the collector such as copper foil.Here polyamide acyl Imines refers to the polyamidoimide with the structure represented by following formulas (2).
[changing 2]
In formula (2), R3 is the aromatic residue of trivalent, and R4 is the aromatic residue of divalent.In conductive adhesive layer Adhesive can be that identical type can also be different from the adhesive in above-mentioned active material layer.
As the electroconductive particle used in above-mentioned electric conductivity adhesive linkage, for example, carbon material, the metal of particle shape can be used Material.It is used as carbon material, preferably graphite, carbon black, more preferably graphite.
As metal material, for example, silver, copper, nickel can be used.As these carbon particles, the particle diameter of metallic, preferably put down Equal particle diameter is less than 5 μm.The electroconductive particle that these electroconductive particles can coordinate with above-mentioned active material layer is identical type Can also be different.
It is preferred that the content of the adhesive in above-mentioned electric conductivity adhesive linkage is less than 30 mass %, i.e. the content of electroconductive particle is The content of adhesive in more than 70 mass %, more preferably above-mentioned electric conductivity adhesive linkage is less than 20 mass %, i.e. electroconductive particle Content be more than 80 mass %.
If being less than 70 mass % conduction for more than 30 mass %, the i.e. content of electroconductive particle using the content of adhesive Property adhesive linkage, then be difficult to make the porosity of active material layer be 15~40 volume % and make electrolyte infiltration rate be 300 seconds with Under.For example, being 80 mass %'s with regard to the polyimide content in the electric conductivity adhesive linkage described in the embodiment 1 of patent document 3 For negative pole, in the research of the present inventor etc., the electrolyte infiltration rate of active material layer is more than 1000 seconds.Its Reason is unclear, but can confirm unrelated with the adhesive species in adhesive linkage, is uprised with the content of adhesive, active material The infiltration rate of the electrolyte of layer is slack-off, it is taken as that the composition of electric conductivity adhesive linkage absorbs speed to the electrolyte of active material layer Degree is without any influence.
In addition, in the case of amount of binder in electric conductivity adhesive linkage is relatively little of, by will be almost swollen without volume The electroconductive particles such as the graphite of swollen contraction with adhesives of the active material layer with the content of degree, and use and copper foil There is the adhesive of high cementability Deng collector, the sufficient intensity as electric conductivity adhesive linkage can be also obtained.
From the viewpoint of electric conductivity and cementability between collector and active material layer, the thickness of electric conductivity adhesive linkage Preferably 1~15 μm, more preferably 2~5 μm.
As collector, for example, the metal foil such as copper foil, stainless steel foil, nickel foil can be used, preferably use as electrolytic copper foil, The copper foil of rolled copper foil etc.The thickness of metal foil is preferably 5~50 μm, more preferably 9~18 μm.In order to improve metal foil with The cementability of electric conductivity adhesive linkage, can implement roughened processing, antirust treatment to the surface of metal foil.
The negative electrode for lithium secondary battery of the present invention for example can simply be manufactured by following process.
1st process：Coordinate graphite particle in polyamideimide solution and obtain graphite dispersion (electric conductivity adhesive linkage Formation coating).
2nd process：After graphite dispersion is coated on copper foil, dries, obtain conductive coat.
3rd process：Coordinate silicon particle and graphite particle in polyimide precursor solution and obtain silicon dispersion (active matter Matter layer formation coating).
4th process：After silicon dispersion is coated on conductive coat, dry, obtain containing silicon coating film.
5th process：It is sub- by the way that polyimide precursor heat cure, to being heat-treated containing silicon coating film, to be transformed to polyamides Amine.
By the above method, it can easily manufacture and stack gradually collector, containing graphite particle and polyamidoimide Electric conductivity adhesive linkage and active material layer containing silicon particle, graphite particle and polyimides negative pole.
Drying temperature in 2nd process (conductive coat formation process) is preferably less than 200 DEG C, more preferably 150 DEG C with Under.From the viewpoint of drying efficiency, the drying temperature in the 2nd process (conductive coat formation process) is preferably more than 100 DEG C.
In 2nd process, the solvent for preferably using conductive coat drying into graphite dispersion remains 5 in conductive coat ~30 mass % or so degree.The solvent of the residual contributes to the good bonding strong of electric conductivity adhesive linkage and active material layer The embodiment of degree.
Drying temperature in 4th process (active material film formation process) is preferably less than 200 DEG C, and more preferably 150 Below DEG C.From the viewpoint of drying efficiency, the drying temperature in the 4th process (active material film formation process) is preferably More than 100 DEG C.
Fire damage is not produced to negative pole, polyimides will can be fully transformed to containing the polyimide precursor in silicon coating film From the aspect of, the heat treatment temperature of the 5th process is preferably 250~500 DEG C.Heat treatment is preferably in the non-active gas gas such as nitrogen Carried out under atmosphere, but it is also possible to carry out in atmosphere or under vacuum.In addition, can also be carried out as needed at hot pressurization after heat treatment Reason.
The coating of each dispersion of 2nd process and the 4th process can be carried out only 1 time, can also be divided into multiple progress.
Conduction is coated on as the method that conductive material dispersion is coated on to collector and by active substance dispersion The method of film, can be used in the method being continuously coated with by way of volume to volume, the method being coated with the way of piece Either method.As apparatus for coating, for example, die coating machine, multilayer die coating machine, gravure coater, comma coating machine, reverse can be used Roll-coater, knife type coater.
Polyamideimide solution can use commercially available product described above, but preferably use and will be used as the trimellitic acid of raw material Acid anhydride and diisocyanate about equimolar coordinate, and it is carried out solution obtained from polymerisation in a solvent.
As trimellitic anhydride, it can also use and one part is replaced into pyromellitic dianhydride, benzophenone tetracarboxylic The compound of acid anhydride, biphenyl tetracarboxylic acid anhydrides.
As diisocyanate, for example, m-benzene diisocyanate, PPDI, 4,4 '-diphenylmethyl can be used Alkane diisocyanate, 4,4 '-diphenyl ether diisocyanate, diphenyl sulphone (DPS) -4,4 '-diisocyanate, '-two of diphenyl -4,4 are different Cyanate, o-tolidine diisocyanate, 2,4 toluene diisocyanate, 2,6- toluene di-isocyanate(TDI)s, dimethylbenzene two are different Cyanate, naphthalene diisocyanate.They may be used singly or in combination of two or more.Among these, preferably 4, 4 '-methyl diphenylene diisocyanate.
The solid component concentration of polyamidoimide in polyamideimide solution is preferably 1~50 mass %, more excellent Elect 10~30 mass % as.
Viscosity in 30 DEG C of polyamideimide solution is preferably 1~150Pas, more preferably 5~100Pas.
Polyimide precursor solution can use commercially available product described above, it is also preferred that using will be used as the tetrabasic carboxylic acid two of raw material Acid anhydride and diamines about equimolar coordinate, and it is carried out polymerisation in a solvent and is obtained polyamic acid.
As tetracarboxylic dianhydride, for example, pyromellitic acid, 3,3 ', 4,4 '-bibenzene tetracarboxylic, 3,3 ', 4,4 '-two can be used Benzophenone tetracarboxylic acid, 3,3 ', 4,4 '-diphenyl sulfone tetraformic acid, 3,3 ', 4,4 '-diphenyl ether tetracarboxylic acid, 2,3,3 ', 4 '-hexichol first Ketone tetracarboxylic acid, 2,3,6,7- naphthalenetetracarbacidic acidics, 1,4,5,7- naphthalenetetracarbacidic acidics, 1,2,5,6- naphthalenetetracarbacidic acidics, 3,3 ', 4,4 '-diphenyl Double (3,4- dicarboxyphenyis) propane of methane tetracarboxylic acid, 2,2-, 2,2- double (3,4- dicarboxyphenyis) HFC-236fa, 3,4,9, Double [4- (3,4- di carboxyl phenyloxies) phenyl] propane of 10- tetra- Suo Ji perylenes, 2,2-, the double [4- (3,4- di carboxyl phenyloxies) of 2,2- Phenyl] HFC-236fa etc. dianhydride.They may be used singly or in combination of two or more.Among these, it is preferably Pyromellitic acid, 3,3 ', 4,4 '-bibenzene tetracarboxylic.
As diamines, for example, p-phenylenediamine, m-phenylene diamine (MPD), 3,4 '-diamino-diphenyl ether, 4,4 '-diaminourea can be used Double [4- (the 4- of diphenyl ether, 4,4 '-diaminodiphenyl-methane, 3,3 '-dimethyl -4,4 '-diaminodiphenyl-methane, 2,2- Amino-benzene oxygen) phenyl] propane, 1,2- double (anilino-) ethane, diaminodiphenylsulfone, diaminobenzene formailide, diaminourea Double (p-aminophenyl) HFC-236fas of double (p-aminophenyl) propane of benzoic ether, diamino diphenyl sulfide, 2,2-, 2,2-, Double (p-aminophenyl epoxide) benzene of the borontrifluoride benzene of 1,5- diaminonaphthalenes, diaminotoluene, diaminourea, 1,4-, 4,4 '-it is bis- (to amino Phenoxy group) biphenyl, diamino-anthraquinone, 4,4 '-bis- (3- aminophenoxy phenyls) diphenyl sulphone (DPS)s, double (anilino-) hexafluoros third of 1,3- Double (anilino-) octafluorobutanes of alkane, 1,4-, double (anilino-) Decafluoropentanes of 1,5-, double (anilino-) the ten tetrafluoro heptane of 1,7-.It May be used singly or in combination of two or more.Among these, preferably p-phenylenediamine, 4,4 '-diaminourea hexichol Double [4- (4- amino-benzene oxygens) phenyl] propane of base ether, 2,2-.
As the solid component concentration of the polyamic acid in polyimide precursor solution, preferably 1~50 mass % is more excellent Elect 5~25 mass % as.The polyamic acid contained in polyimide precursor solution can also partly imidizate.
Viscosity in 30 DEG C of polyimide precursor solution is preferably 1~150Pas, more preferably 10~100Pas.
As the solvent used in polyamideimide solution, polyimide precursor solution, as long as it can dissolve polyamide The solvent of acid imide, polyamic acid, there is no particular limitation, preferably uses acid amides series solvent.It is used as acid amides series solvent, example Such as, METHYLPYRROLIDONE (NMP), DMF (DMF), DMA can be enumerated (DMAc).They may be used singly or in combination of two or more.
Can be as needed before polyamideimide solution, polyimides in the range of the effect of the present invention is not damaged Addition such as various surfactants, the known additive of organo silane coupling agent in liquid solution.In addition, not damaging the present invention Effect in the range of can also as needed in polyamideimide solution, polyimide precursor solution addition remove polyamide Other polymer beyond acid imide, polyimide precursor.
Embodiment
Hereinafter, embodiments of the invention are explained, but the present invention is not limited to these embodiments.
The measure of various characteristic values in embodiment and comparative example and evaluation are as described below.
(I) porosity of active material layer and electrolyte infiltration rate
The porosity and electrolyte infiltration rate for active material layer, are determined by the above method.
(II) flash-over characteristic of silicon-based active material layer
First, the negative pole of the sheet obtained by use, makes bipolar system pouch-type battery cell (laminated cell by the following method Unit) it is used as the test cell unit of the discharge capacity for determining negative pole.
The negative pole of obtained sheet is cut out into the rectangle for 10mm × 40mm, 10mm × 10mm active material face is left Product, it is coated with deposition film.As to electrode, thickness 1mm lithium plate is cut out into the rectangle for 30mm × 40mm, to thickness 0.5mm Nickel down-lead (5mm × 50mm) doubling and crimp.Only negative pole is put into after bag-shaped distance piece (30mm × 20mm), and to electrode Face-to-face, electrode group is obtained.Distance piece uses the acrylic resin perforated membrane (25 μm of thickness) of rectangle.With two one group of square The aluminium lamination press mold (50mm × 40mm) of shape covers the electrode group, seals behind its three sides, injects 1mL's in bag-shaped aluminium lamination press mold Electrolyte.Electrolyte use by EC, DEC and EMC with volume ratio 1：1：The in the mixed solvent of 1 mixing is by LiPF6With 1 mole/L Concentration dissolving obtained from electrolyte.Thereafter, a remaining side is sealed, will be sealed in bag-shaped aluminium lamination press mold.This When outside, by being sealed in bag-shaped aluminium lamination press mold, one end of negative pole and nickel down-lead is extended into outside, terminal is used as.In this way, To test cell unit.These operations are all carried out in the control box of argon atmospher.
Then, using obtained test cell unit, according to above-mentioned ＜ discharge and recharges condition ＞ repeated charges, the 20th is obtained Secondary discharge capacity.
Binder solution, active material layer formation silicon dispersion and the electric conductivity used in embodiment and comparative example The preparation method of adhesive linkage formation graphite dispersion is as described below.
[preparation of polyimide precursor solution]
Make about equimolar 3,3 ', 4,4 '-bibenzene tetracarboxylic dianhydride (BPDA) and 4,4 '-oxygen diphenylamines (ODA) in NMP Middle reaction, obtains as the solid component concentration of polyimides being 20 mass % and being the uniform of 25Pas in 30 DEG C of viscosity Polyamic acid solution (P-1).
[preparation of polyamideimide solution]
Make about equimolar trimellitic anhydride (TMA) and 4,4 '-methyl diphenylene diisocyanate (DMI) in NMP Reaction, it is 18 mass % and molten in the uniform polyamidoimide that 30 DEG C of viscosity is 15Pas to obtain solid component concentration Liquid (P-2).
[preparation of active material layer formation silicon dispersion]
In solution obtained above (P-1), average grain diameter is added using the composition shown in table 1 (pure as 0.7 μm of silicon particle Degree：99 mass %) and average grain diameter be 3 μm of graphite particle, after being stirred in the way of being uniformly dispersed, add NMP.In this way, Obtain the silicon dispersion (the mass % of solid component concentration about 25) with the composition shown in table 1.
[table 1]
<The composition of active material layer formation silicon dispersion>
[preparation of electric conductivity adhesive linkage formation electroconductive particle dispersion]
In solution obtained above (P-1) or solution (P-2), average grain diameter is added as 3 μm using the composition shown in table 2 Graphite particle or carbon black (Ketjen black), after being stirred in the way of being uniformly dispersed, add NMP.In this way, obtaining with shown in table 2 Composition electroconductive particle dispersion a1~a10 (the mass % of solid component concentration about 30).
[table 2]
<The composition of electroconductive particle dispersion>
[table 3]
<Cathode property>
The ＞ of ＜ embodiments 1
Bar coater is used on the surface of the side of 18 μm of electrolytic copper foil (Furukawa Electric Industrial Co., Ltd system, F2-WS) of thickness In the way of piece equably after applying conductive particle dispersion a1, dried 10 minutes at 130 DEG C, obtain conductive coat.Graphite The coating weight of dispersion is to be prepared by the thickness of the conductive adhesion layer of gained in the way of 3~4 μm.Then, in conductive coat Surface is dried 10 minutes using bar coater equably silicon-coating dispersion A1 in the way of piece at 130 DEG C, obtains active material painting Film.The coating weight of silicon dispersion is to be prepared by the thickness of the active material layer of gained in the way of 40~50 μm.In this way, obtain according to The layered product of secondary stacking electrolytic copper foil, conductive coat and active material film.Then, by the layered product of gained in nitrogen It was warming up under gas atmosphere with 2 hours from 100 DEG C after 350 DEG C, the heat treatment of 1 hour is carried out at 350 DEG C., will by the heat treatment Polyamic acid in active material film is transformed to polyimides.In this way, obtaining stacking gradually electrolytic copper foil, electric conductivity bonding The negative pole A1a1 of layer and active material layer.The characteristic of the negative pole is shown in table 3.
In addition, the 1st time during the charge and discharge cycles of the negative pole, the 5th, the charging and discharging curve of the 10th time and the 20th time be shown in Fig. 1.As shown in Figure 1, it can obtain for only the 1st time after high discharge capacity, the 2nd time into the repeated charge of the 20th time, although Charging and discharging curve has a fluctuation, but because the decline of the discharge capacity of caused negative pole repeatedly is slight.
The ＞ of ＜ embodiments 2~5
In addition to electroconductive particle dispersion a1 is changed into electroconductive particle dispersion a2~a5, by with embodiment 1 same method obtains negative pole A1a2~A1a5.The characteristic of the negative pole is shown in table 3.In these negative poles, charging and discharging curve is also showed that The trend same with negative pole A1a1.
The ＞ of ＜ embodiments 6~7
In addition to silicon dispersion A1 is changed into silicon dispersion A2~A3, obtained by method similarly to Example 1 Negative pole A2a1~A3a1.The characteristic of the negative pole is shown in table 3.In these negative poles, charging and discharging curve also shows that same with negative pole A1a1 Trend.
The ＞ of ＜ comparative examples 1~5
In addition to electroconductive particle dispersion a1 is changed into electroconductive particle dispersion a6~a10, by with implementation The same method of example 1 obtains negative pole A1a6~A1a10.The characteristic of the negative pole is shown in table 3.In these negative poles, along with filling repeatedly Electric discharge, discharge capacity significantly declines, and the discharge capacity of the 20th time is as little as less than 1000mAh/g- silicon-based active materials.
The ＞ of ＜ comparative examples 6
In addition to silicon dispersion A1 is changed into silicon dispersion A4, negative pole is obtained by method similarly to Example 1 A4a1.The characteristic of the negative pole is shown in table 3.In the negative pole, the discharge capacity of the 20th time shows 1500mAh/g- silicon-based active materials Value, but content as little as 45 mass %, therefore low as the discharge capacity of negative pole of the silicon-based active material in active material layer.
As described above, the negative pole of embodiments of the invention has high discharge capacity, and excellent charge/discharge cycle characteristics, because This can function well as the negative pole of secondary lithium batteries.

Claims (3)

1. a kind of negative electrode for lithium secondary battery, it is characterised in that what the negative electrode for lithium secondary battery was formed on the current collector leads The outer surface layer of electrical adhesive linkage is laminated with active material layer, and meets following condition,
1) active material layer, electric conductivity adhesive linkage contain polyimides system macromolecule as adhesive,
2) content of the silicon particle in active material layer is more than 50 mass %, and the high molecular content of polyimides system is 5~30 matter Measure %,
3) porosity of active material layer is 15~40 volume %,
4) electrolyte infiltration rate is less than 300 seconds,
5) the high molecular content of polyimides system in electric conductivity adhesive linkage is below 30 mass %,
6) under the conditions of the composition of following shown battery units and discharge and recharge, the electric discharge of the 20th time during repeated charge 20 times Capacity be 1500mAh/g- silicon particles more than,
The composition ＞ of ＜ battery units
Battery：Bipolar system pouch-type battery cell,
To electrode：Lithium metal,
Electrolyte：LiPF6The mixing of the ethylene carbonate, methyl ethyl carbonate and the dimethyl carbonate that are dissolved with 1mol/L concentration is molten Agent, wherein, the volume ratio of three is 1：1：1,
＜ discharge and recharge conditions ＞
Determine temperature：30 DEG C,
Voltage range：0.01~2V,
Charging current and discharge current：500mA/g- silicon particles.
2. the manufacture method of the negative electrode for lithium secondary battery described in claim 1, it is characterised in that with following process,
1st process：Coordinate graphite particle in polyamideimide solution and obtain graphite dispersion,
2nd process：After graphite dispersion is coated on copper foil, dries, obtain conductive coat,
3rd process：Coordinate silicon particle and graphite particle in polyimide precursor solution and obtain silicon dispersion,
4th process：After silicon dispersion is coated on conductive coat, dry, obtain containing silicon coating film,
5th process：By the way that to being heat-treated containing silicon coating film, polyimide precursor heat cure is transformed into polyimides.
3. the manufacture method of negative electrode for lithium secondary battery as claimed in claim 2, wherein, in the 2nd process, solvent is being led 5~30 mass % are remained in electropaining film.
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