JP2018078063A - Manufacturing method of lithium ion battery, and lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode hard to cause agglomeration of a negative electrode mixture, and a lithium ion battery.SOLUTION: A method for manufacturing a lithium ion battery having a negative electrode mixture including amorphous carbon, a binding agent and an organic solvent comprises a process of producing the negative electrode mixture, which includes: a solid-kneading step (I) of mixing and kneading the amorphous carbon, the binding agent and the solvent together into a mixture; and a dilution step (II) of adding the organic solvent to the mixture obtained by the solid-kneading step to adjust a viscosity thereof. A solid content Z(%) of the mixture (Solid material weight (g)×100/Weight (g) of the mixture) in the solid-kneading step, and an NMP oil absorption Y(ml/100 g) of the amorphous carbon are in the relation given by the following expression (1): Z=-0.268Y+a (where 82.5≤a≤85.5) (1).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a lithium ion battery having a negative electrode using amorphous carbon as an active material, and a lithium ion battery.

  A carbonaceous material or the like is used for the negative electrode active material of the lithium ion battery, and the binder and the negative electrode active material are both dispersed in an organic solvent to form a slurry-like negative electrode mixture. A sheet-like negative electrode is produced by coating on top, drying the solvent, and rolling the negative electrode mixture. The slurry-like negative electrode mixture is a kneading step in which a negative electrode active material, a conductive agent, a binder, a solvent, and the like are mixed and kneaded, until the mixture obtained in the kneading step has a desired solid content ratio. It is manufactured through a dilution / dispersion step in which a solvent is added to dilute and the dispersibility of the mixture becomes uniform.

  If the amount of the organic solvent added in the solidifying step is excessive, sufficient shearing force is not applied to the charged electrode material, so the negative electrode active material, conductive agent, binder in the mixture obtained in the solidifying step The dispersion of the particles of the particles becomes uneven, and the particles of the negative electrode active material and the conductive agent are likely to aggregate in the negative electrode mixture even after the dilution / dispersion step. When the negative electrode mixture is applied to the current collector, the negative electrode mixture There is a possibility that the agent may be lumped or unevenly coated, causing a short circuit.

  In addition, when the particles aggregate in the negative electrode mixture, the battery capacity tends to vary due to the non-uniform film thickness distribution. When coating a negative electrode mixture on a current collector, it is applied continuously using a coating device, but the active material settles in the mixture over time, and the density distribution of the mixture Changes from the initial coating. As a result, the amount of active material applied to the current collector varies with the coating time. In particular, since the negative electrode active material has a larger charge / discharge capacity per unit weight than the positive electrode active material, variations in the amount of active material applied have a large effect on battery capacity and input / output characteristics.

  On the other hand, when the amount of the organic solvent to be added in the solidifying step is insufficient, an excessive shearing force is applied to the input electrode material, and the active material particles are likely to be cracked. When cracks occur in the active material, the surface area of the active material particles increases, leading to an increase in irreversible capacity and a decrease in life performance.

  As a method for preventing aggregation in the mixture, a method of defining the oil absorption amount of carbon black (for example, Patent Document 1), the oil absorption amount of the negative electrode active material, and the oil absorption amount at the maximum torque when measuring the oil absorption amount are 70%. Examples include a method (for example, Patent Document 2 and Patent Document 3) that defines the ratio of the amount of oil absorption during torque.

Japanese Patent No. 4310942 JP2015-32554A JP 2014-32922 A

  However, it has been found that, by these conventional techniques, excellent battery characteristics may not be obtained even if the material properties of the electrode are defined. The object of the present invention is made in view of the above circumstances, and is to provide a method for producing a lithium ion battery and a lithium ion battery in which the aggregation of the negative electrode mixture hardly occurs.

<1> In a method for producing a lithium ion battery having a negative electrode mixture containing amorphous carbon, a binder, and an organic solvent,
In the production process of the negative electrode mixture, the amorphous carbon and the binder are mixed and kneaded, and the organic solvent is added to the mixture kneaded by the kneading process and diluted. And a dilution step for adjusting the viscosity by
When the amount of NMP (N-methyl-2-pyrrolidone) oil absorption of the amorphous carbon is Y (ml / 100 g),
The solid content Z (%) of the mixture in the kneading step (solid weight (g) × 100 / weight of the mixture (g)) and the NMP oil absorption Y are:
Z = −0.268Y + a (where 82.5 ≦ a ≦ 85.5)
The manufacturing method of the lithium ion battery characterized by satisfy | filling the relationship of these.

  <2> The method for producing a lithium ion battery according to <1>, wherein the NMP oil absorption amount Y of the amorphous carbon is in a range of 70 ml / 100 g to 120 ml / 100 g.

<3> In the method of manufacturing a lithium ion battery including the negative electrode mixture containing amorphous carbon, a binder, an organic solvent, and a conductive agent, the negative electrode mixture production step includes the amorphous carbon and the binder. A kneading step of mixing and kneading the adhering agent and the conductive agent; and a dilution step of adjusting the viscosity by adding and diluting the organic solvent to the mixture kneaded by the kneading step, When the NMP (N-methyl-2-pyrrolidone) oil absorption amount of the mixed powder of the amorphous carbon and the conductive agent in the mixture is X (ml / 100 g), the solid state of the mixture in the solidification step Minute W (%) (weight of solid (g) × 100 / weight of mixture (g)) and the NMP oil absorption amount X are:
W = −0.28X + b (however, 83.5 ≦ b ≦ 87.0)
The manufacturing method of the lithium ion battery characterized by satisfy | filling the relationship of these.

  <4> The method for producing a lithium ion battery according to <3>, wherein the conductive agent is carbon black.

  <5> The method for producing a lithium ion battery according to <3> or <4>, wherein the NMP oil absorption amount X of the mixed powder of the amorphous carbon and the conductive agent is in a range of 70 ml / 100 g to 120 ml / 100 g.

<6> A lithium ion battery having a negative electrode in which a negative electrode mixture containing amorphous carbon, a binder, and an organic solvent is held in a current collector, the amorphous carbon and the binder And the solid content Z (%) of the mixture of the organic solvent and the NMP (N-methyl-2-pyrrolidone) oil absorption Y (ml / 100 g) of the amorphous carbon is Z = −0.268Y + a ( (82.5 ≦ a ≦ 85.5)
A lithium ion battery characterized by satisfying the following formula:

  <7> The lithium ion battery according to <6>, wherein the NMP oil absorption amount Y of the amorphous carbon is in a range of 70 ml / 100 g to 120 ml / 100 g.

<8> A lithium ion battery having a negative electrode in which a negative electrode mixture containing amorphous carbon, a conductive agent, a binder, and an organic solvent is held by a current collector,
Solid content W (%) of the mixture of the amorphous carbon, the conductive agent, the binder and the organic solvent, and the NMP oil absorption X (ml / 100 g) of the mixed powder of the amorphous carbon and the conductive agent. ) And W = −0.28X + b (where 83.5 ≦ b ≦ 87.0)
A lithium ion battery characterized by satisfying the following formula:

  <9> The lithium ion battery according to <8>, wherein the NMP oil absorption amount X of the mixed powder of the amorphous carbon and the conductive agent is in a range of 70 ml / 100 g to 120 ml / 100 g.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a lithium ion battery with little aggregation of negative electrode mixture and the lithium ion battery excellent in the battery characteristic can be provided.

It is a perspective view which shows the lithium ion battery of one embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various modifications by those skilled in the art are within the scope of the technical idea disclosed in this specification. Changes and modifications are possible.

(Lithium ion secondary battery)
The lithium secondary battery 20 includes a strip-shaped positive electrode current collector coated with a positive electrode active material and a strip-shaped negative electrode current collector coated with a negative electrode active material on a strip separator W5. An electrode group 6 is used, which is formed by winding a belt-shaped laminated body configured in the longitudinal direction. The electrode group 6 is accommodated in the battery container 5, and the electrolytic solution is also accommodated in the battery container 5. A positive electrode current collecting tab is connected to the positive electrode terminal, a negative electrode current collecting tab is connected to the negative electrode terminal, and a safety valve 10 is attached to the battery lid 4 that seals the battery container 5.

  The material of the battery container 5 is selected so that the material does not deteriorate due to corrosion by the electrolytic solution or alloying with lithium ions. It is selected from materials such as aluminum, stainless steel, and nickel-plated steel. The battery case 5 is placed in an electrically neutral state.

  As the shaft core 11, any known one can be used as long as it can support the electrode group 6. Even if the shaft core 11 is not provided, the shaft core 11 may not be used as long as the shape of the electrode group can be maintained.

  The electrode group 6 can be applied as long as it is a wound shape such as a flat shape in addition to the cylindrical shape shown in FIG. The shape of the battery case 5 may be selected from shapes such as a cylindrical shape, a flat oval shape, and a flat oval shape according to the shape of the electrode group 6.

  The lead pieces led out from the positive electrode were deformed, and all of them were collected near the bottom of the flange 7 on the positive electrode side and brought into contact with each other. The positive electrode side flange portion 7 is integrally formed so as to protrude from the periphery of the pole column (positive electrode external terminal 1) substantially on the extension line of the axis of the wound group 6, and has a bottom portion and a side portion. Thereafter, the lead piece was connected and fixed to the bottom of the flange 7 by ultrasonic welding. Similarly, the lead piece led out from the negative electrode and the bottom of the flange 7 on the negative electrode side were connected and fixed. The negative electrode side flange portion 7 is integrally formed so as to protrude from the periphery of the pole column (negative electrode external terminal 1 ′) substantially on the extension line of the axis of the wound group 6, and has a bottom portion and a side portion. . The thickness of the insulating coating (the number of turns of the adhesive tape) was adjusted so that the maximum diameter portion of the electrode group 6 was slightly smaller than the inner diameter of the stainless steel battery container 5, and the electrode group 6 was inserted into the battery container 5. . The battery container 5 had an outer diameter of 67 mm and an inner diameter of 66 mm.

  Next, as shown in FIG. 1, the ceramic washer 3 ′ is fitted into a pole column whose tip constitutes the positive electrode external terminal 1 and a pole column whose tip constitutes the negative electrode external terminal 1 ′.

  Then, the end surface around the battery lid 4 is fitted into the opening of the battery container 5, and the entire area of both contact portions is laser welded. At this time, the positive electrode external terminal 1 and the negative electrode external terminal 1 ′ protrude through the hole (hole) in the center of the battery cover 4 and protrude outside the battery cover 4. The battery lid 4 is provided with a cleavage valve 10 that cleaves in response to an increase in the internal pressure of the battery. Next, the metal nut 2 is screwed to the positive external terminal 1 and the negative external terminal 1 ′, and the battery cover 4 is tightened between the flange 7 and the nut 2 via the ceramic washer 3 and the ceramic washer 3 ′. Fix it. The tightening torque value at this time was 7 N · m. In this state, the power generation element inside the battery container 5 is shielded from the outside air by compression of a rubber (EPDM) O-ring interposed between the back surface of the battery lid 4 and the flange 7.

  Thereafter, an electrolytic solution was injected into the battery container 5 from the injection port 15 provided in the battery lid 4, and then the injection port 15 was sealed to complete the cylindrical lithium ion battery 20.

(Negative electrode)
The negative electrode (negative electrode plate) of the present embodiment is composed of a current collector and a negative electrode mixture formed on both surfaces thereof. Although the formation method in particular of a negative electrode compound material is not restrict | limited, It forms using a dry method and a wet method similarly to a positive electrode compound material. The negative electrode mixture contains a negative electrode active material capable of electrochemically occluding and releasing lithium ions.

  As the negative electrode active material, graphitizable carbon is used. Graphitizable carbon has graphitization properties that graphitize by heat treatment at 800 ° C. or higher. On the other hand, non-graphitizable carbon has non-graphitization property that hardly graphitizes even by heat treatment at 2800 ° C. or higher. This is because graphitizable carbon has an atomic arrangement structure that easily forms a layered structure, and has a property of easily changing to a graphite structure by heat treatment at a relatively low temperature as compared with non-graphitizable carbon.

  The amorphous carbon is preferably graphitizable carbon. The graphitizable carbon preferably has a C-axis direction plane d002 value of 0.34 nm or more and less than 0.36 nm obtained by the X-ray wide angle diffraction method, and is 0.341 nm or more and 0.355 nm or less. More preferably, it is 0.342 nm or more and 0.35 nm or less. The average particle diameter (d50) of graphitizable carbon is preferably 2 to 50 μm, more preferably 5 to 30 μm, and still more preferably 10 to 20 μm. For example, the particle size distribution can be measured with a laser diffraction particle size distribution measuring device (for example, SALD-3000J manufactured by Shimadzu Corporation) by dispersing a sample in purified water containing a surfactant, and the average particle size Is calculated as the median diameter (d50).

  The graphitizable carbon has a weight of 550 ° C. of 75% or more with respect to the weight of 25 ° C. in the air stream determined by thermogravimetry (TG), and the weight of 650 ° C. is 20% of the weight of 25 ° C. % Or less.

   From the viewpoint of battery performance, the weight of 550 ° C. in the air stream is 85% or more with respect to the weight of 25 ° C., and the weight of 650 ° C. is more preferably 10% or less with respect to the weight of 25 ° C. . Furthermore, it is preferable that the weight at 550 ° C. in the air stream is 95% or more with respect to the weight at 25 ° C., and the weight at 650 ° C. is less than 5% with respect to the weight at 25 ° C.

  When the weight at 550 ° C in the air stream is less than 75% with respect to the weight at 25 ° C, the input / output characteristics deteriorate, and when the weight at 650 ° C exceeds 20% with respect to the weight at 25 ° C, the life characteristics deteriorate. To do. Here, the thermogravimetric measurement device can be measured with a TG analyzer (for example, TG / DTA6200, manufactured by SII Nano Technology Co., Ltd.). The measurement condition is that a sample of 10 mg is taken and measurement can be performed at a heating rate of 1 ° C./min using alumina as a reference under a flow of dry air of 300 ml / min.

In this embodiment, when the amount of NMP (N-methyl-2-pyrrolidone) oil absorption of amorphous carbon is Y (ml / 100 g), the solid content Z (%) of the mixture in the solidification step (solid matter) Weight (g) × 100 / weight of the mixture (g)) and NMP oil absorption Y are
Z = −0.268Y + a (where 82.5 ≦ a ≦ 85.5) [Formula 1]
There is a relationship that satisfies. In particular, the NMP oil absorption Y of amorphous carbon is preferably in the range of 70 ml / 100 g to 120 ml / 100 g. The NMP (N-methyl-2-pyrrolidone) oil absorption amount of amorphous carbon is, for example, “oil absorption amount with respect to NMP measured by a method based on JIS K5101-13-1”.

  The solid content Z (%) (solid weight (g) × 100 / weight of the mixture (g)) of the mixture in the kneading step is the NMP oil absorption Y (ml / 100 g) of amorphous carbon (formula 1 ), A negative electrode mixture having a good dispersion state can be obtained.

When a conductive agent (carbon black in this embodiment) is added to the negative electrode mixture, amorphous carbon, a binder, and a conductive agent are mixed and kneaded in the production process of the negative electrode mixture. A solidifying step and a diluting step of adjusting the viscosity by adding an organic solvent to the mixture kneaded in the solidifying step and diluting are performed. Then, when the NMP (N-methyl-2-pyrrolidone) oil absorption of the mixed powder of amorphous carbon and conductive agent in the mixture is X (ml / 100 g), the solid content W ( %) (Weight of solid (g) × 100 / weight of mixture (g)) and NMP oil absorption X are
W = −0.28X + b (where 83.5 ≦ b ≦ 87.0) [Formula 2]
There is a relationship satisfying the following formula.

  The solid content W (%) of the mixture in the solidification step (solid weight (g) × 100 / weight of the mixture (g)) is obtained by combining the amorphous carbon and the conductive agent in the compounding ratio in the negative electrode mixture. By setting the mixed powder to have an NMP oil absorption amount X (ml / 100 g) of (Formula 2), a negative electrode mixture having a good dispersion state can be obtained. The conductive agent is preferably carbon black.

  Even in this case, the NMP oil absorption amount X of the mixed powder of amorphous carbon and conductive agent is preferably in the range of 70 ml / 100 g to 120 ml / 100 g.

(Positive electrode)
The positive electrode (positive electrode plate) of this embodiment consists of a current collector and a positive electrode mixture formed on the current collector. The positive electrode mixture is a layer including at least a positive electrode active material provided on the current collector. In the present embodiment, the positive electrode mixture includes a layered lithium-nickel-manganese-cobalt composite oxide. In addition to the positive electrode active material, the positive electrode mixture includes two or more kinds of conductive materials having different average particle diameters or DBP oil supply amounts. This positive electrode mixture may be formed (coated) on both surfaces of the current collector, for example.

In addition to the layered lithium-nickel-manganese-cobalt composite oxide (hereinafter referred to as NMC), the positive electrode active material includes lithium-containing composite metal oxides including spinel lithium-manganese oxide, olivine-type lithium oxide, chalcogen It may contain a compound, manganese dioxide and the like. The lithium-containing composite metal oxide is a metal oxide containing lithium and a transition metal or a metal oxide in which a part of the transition metal in the metal oxide is substituted with a different element. Here, examples of the different element include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B. Mn, Al, Co, Ni, Mg and the like are preferable. One kind or two or more kinds of different elements may be used. Among these, lithium-containing composite metal oxides are preferable. The lithium-containing composite metal oxide, for _{example, LixCoO 2, LixNiO 2, LixCoyNi} 1 -yO 2, LixCoyM 1 -yOz, LixNi 1 -yMyOz, LiMPO 4, Li 2 MPO 4 F ( in the respective formulas, M is Na , Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V, and B. x = 0 to 1. 2, y = 0 to 0.9, z = 2.0 to 2.3). Here, x value which shows the molar ratio of lithium increases / decreases by charging / discharging. Examples of the olivine type lithium oxide include LiFePO ₄ . Examples of the chalcogen compound include titanium disulfide and molybdenum disulfide. A positive electrode active material can be used individually by 1 type, or can use 2 or more types together.

(Electrolyte)
The electrolytic solution of the present embodiment includes a lithium salt (electrolyte) and a non-aqueous solvent that dissolves the lithium salt. You may add an additive as needed.

  The lithium salt is not particularly limited as long as it is a lithium salt that can be used as an electrolyte of an electrolyte solution for a lithium ion battery, and examples thereof include the following inorganic lithium salts, fluorine-containing organic lithium salts, and oxalatoborate salts. .

Examples of the inorganic lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiSbF inorganic fluoride salts and the like _6, LiClO _4, Libro _4, LiIO and perhalogenate such as _4, an inorganic chloride salts such as LiAlCl _4, etc. Is mentioned. A fluorine-containing organic lithium salt, a fluoroalkyl fluorophosphate, or the like may be used. Examples of the oxalatoborate salt include lithium bis (oxalato) borate and lithium difluorooxalatoborate.

These lithium salts may be used alone or in combination of two or more. Among them, lithium hexafluorophosphate (LiPF ₆ ) is preferable when comprehensively judging the solubility in a solvent, charge / discharge characteristics in the case of a battery, output characteristics, cycle characteristics, and the like.

  The concentration of the electrolyte in the electrolytic solution is not particularly limited, but the concentration range of the electrolyte is preferably 0.5 mol / L to 2 mol / L, more preferably 0.6 mol / L to 1.8 mol / L. Preferably, it is 0.7 mol / L-1.8 mol / L.

  When the concentration is 0.5 mol / L or more, sufficient electric conductivity of the electrolytic solution can be obtained. Moreover, since a viscosity does not become high too much that a density | concentration is 2 mol / L or less, the fall of electrical conductivity can be suppressed.

  The non-aqueous solvent is not particularly limited as long as it is a non-aqueous solvent that can be used as an electrolyte solvent for a lithium ion battery, but the following cyclic carbonate, chain carbonate, chain ester, cyclic ether, chain ether, etc. Is mentioned.

  For example, ethylene carbonate, propylene carbonate, butylene carbonate, dialkyl carbonate, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, methyl acetate, tetrahydrofuran, Examples include dimethoxyethane and dimethoxymethane.

(Separator)
The separator is a porous film of an olefin resin made of polypropylene or polyethylene, a porous film of a fluorine resin made of polytetrafluoroethylene, a porous film made of cellulose, or a porous film made of aramid. A structure in which the above porous films are laminated may be used, or a mixture of ceramic and binder, an acrylic adhesive, or the like may be applied to the surface of these porous films.

(Production of battery of example)
The negative electrode used the graphitizable carbon described above as amorphous carbon as the negative electrode active material. Polyvinylidene fluoride (PVDF) was used as the binder, and the weight ratio of amorphous carbon to the binder was 92: 8. NMP (N-methyl-2-pyrrolidone) was added as an organic solvent.

(Preparation of negative electrode)
A kneading step in which amorphous carbon and a binder are mixed and kneaded, and a diluting step in which the viscosity is adjusted by adding an organic solvent to the mixture kneaded in the kneading step and diluting the mixture. In the solidifying step, amorphous carbon as a negative electrode active material and polyvinylidene fluoride (PVDF) as a binder were blended in a weight ratio of 92: 8. In the dilution step, NMP (N-methyl-2-pyrrolidone) as an organic solvent was added thereto, and then kneaded with a planetary mixer to obtain a slurry-like negative electrode mixture. This negative electrode mixture was coated on both sides of a rolled copper foil having a thickness of 10 μm so that the solid content of the negative electrode mixture was 200 g / m ² or less, then dried, compressed, and cut. A negative electrode was obtained.

(Preparation of positive electrode)
Lithium manganate as a positive electrode active material, carbon black as a conductive agent, and polyvinylidene fluoride as a binder are mixed at a weight ratio of 90: 5: 5, and N-methylpyrrolidone is added as a solvent and kneaded. Thus, a slurry-like positive electrode mixture was obtained. This mixture was applied to both surfaces of an aluminum foil having a thickness of 20 μm, then dried, compressed, and cut to obtain a positive electrode.

(Separator)
As the separator, a polypropylene separator having a thickness of 30 μm was used. The electrolyte was 1.2 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) dissolved in a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). What added vinylene carbonate (VC) to the thing was used.

(Production of lithium ion secondary battery)
The produced positive electrode and negative electrode were wound through a polypropylene separator having a thickness of 30 μm and inserted into a cylindrical container. After injecting a predetermined amount of electrolyte from the injection port, a lid having a gas discharge valve for discharging the internal gas to the outside and the battery can were welded to obtain a cylindrical lithium ion battery.

  Hereinafter, the examples will be described in more detail. The present invention is not limited to the following examples.

(Example A1)
As shown in Table 1, in Example A1, graphitizable carbon (amorphous carbon) having an NMP oil absorption of 85 ml / 100 g was used as the negative electrode active material. The coating amount of the negative electrode mixture on both sides of the rolled copper foil was 160 g / m ² .

(Examples A2 to A5, Comparative Examples a1 to a2)
As shown in Table 1, in Examples A2 to A5 and Comparative Examples a1 to a2, batteries were produced in the same manner as in Example 1 except that the solidified solid content during the production of the negative electrode slurry was changed.

(Examples B1 to B3)
As shown in Table 2, in Examples B1 to B3, graphitizable carbon (amorphous carbon) having a different NMP oil absorption amount of the negative electrode active material was used, and the solidified solid content was changed according to the NMP oil absorption amount of the negative electrode active material. A battery was fabricated in the same manner as in Example 1 except that.

(Examples C1 to C4, Comparative Examples c1 to c4)
As shown in Table 3, in Examples C1 to C4 and Comparative Examples c1 to c4, the mixing ratio of the active material and carbon black and the solidified solid content were changed. A battery was fabricated in the same manner as in Example 1 except that the coating amount of the positive electrode was changed so as to be the same (negative electrode capacity / positive electrode capacity≈1.1).

(Evaluation test)
(Additional reverse capacity ratio)
For each of the batteries of Examples and Comparative Examples produced as described above, the total charge capacity when the first to fifth charge / discharge cycles are repeated and the irreversible capacity, which is the sum of the discharge capacities, are divided by the initial charge capacity, Was determined as a percentage.
Additional reverse capacity ratio (%) = (total discharge capacity for 5 times / total charge capacity for 5 times) × 100
(Coating standard deviation)
The variation in the coating amount was obtained by punching three points in the axial direction of the rolled copper foil with a diameter of 40 mm every 10 m in the length direction for the electrode 100 m produced under the conditions of the example and the comparative example. The weight was measured and evaluated from the measured value by the standard deviation of the coating amount of the solid content of the negative electrode mixture (hereinafter referred to as the coating amount standard deviation).

(Capacity maintenance rate)
As an evaluation of the life performance, the capacity maintenance rate at the 1000th cycle when charging / discharging is repeated at a current value of 1 ItA (current amount capable of discharging the rated capacity in one hour) in an environment of 25 ° C. is as follows: Asked.

  Capacity retention rate (%) = (discharge capacity at the 1000th cycle / discharge capacity at the first cycle) × 100

In Examples A1 to A5 in which an electrode mixture was prepared using amorphous carbon having an NMP oil absorption of 85.0 ml / 100 g, and in the range of solid solid content of 60.0% to 62.7%, the coating amount standard The deviation is within 2 g / m ² , the irreversible capacity ratio is about 18%, and the capacity retention ratio is about the same at around 90%, but in Comparative Example a1 where the solid content is smaller than the range of the invention, The quantity standard deviation is twice or more, and an increase in irreversible capacity and a decrease in capacity retention rate occur, suggesting that the finished state of the negative electrode mixture is not appropriate.

  Further, in Comparative Example a2 in which the solid content of the kneading is larger than the range of the present invention, the increase in the standard deviation of the coating amount is smaller than that in Comparative Example a1, but the decrease in the capacity retention rate is remarkable, and the negative electrode mixture There is a concern that the negative electrode active material particles are crushed during production.

  From Table 3, even when the blending ratio of carbon black as the conductive agent is changed, the appropriate range of the solidified solid content is slightly different from Examples A1 to A5 and B1 to B3 of the negative electrode active material (amorphous carbon) alone. However, by producing the negative electrode mixture with an appropriate kneaded solid content corresponding to the NMP oil absorption amount of the material, the coating amount standard deviation, the irreversible capacity, and the capacity retention rate can be maintained at a constant level.

  By producing a negative electrode by the method of the present invention, it is possible to produce a lithium ion battery with stable performance even if there are some fluctuations in the negative electrode active material and the conductive agent.

DESCRIPTION OF SYMBOLS 1 Positive external terminal 1 'Negative external terminal 2 Metal nut 3 Ceramic washer 3' Ceramic washer 4 Battery cover (a part of battery container)
5 Battery container 6 Winding group 7 External terminal collar 10 Cleavage valve 11 Shaft core 15 Injection port 20 Cylindrical lithium secondary battery W1 Positive electrode current collector (part of positive electrode)
W2 Positive electrode active material layer (part of positive electrode)
W3 Negative electrode current collector (part of negative electrode)
W4 Negative electrode active material layer (part of negative electrode)
W5 separator

Claims (9)

In a method for producing a lithium ion battery having a negative electrode mixture containing amorphous carbon, a binder, and an organic solvent,
In the production process of the negative electrode mixture, the amorphous carbon and the binder are mixed and kneaded, and the organic solvent is added to the mixture kneaded by the kneading process and diluted. And a dilution step for adjusting the viscosity by
When the amount of NMP (N-methyl-2-pyrrolidone) oil absorption of the amorphous carbon is Y (ml / 100 g),
The solid content Z (%) of the mixture in the kneading step (solid weight (g) × 100 / weight of the mixture (g)) and the NMP oil absorption Y are:
Z = −0.268Y + a (where 82.5 ≦ a ≦ 85.5)
The manufacturing method of the lithium ion battery characterized by satisfy | filling the relationship of these.   2. The method for producing a lithium ion battery according to claim 1, wherein the NMP oil absorption amount Y of the amorphous carbon is in a range of 70 ml / 100 g to 120 ml / 100 g. In the method of manufacturing a lithium ion battery including amorphous carbon, a binder, an organic solvent, and a conductive agent in the negative electrode mixture, the production process of the negative electrode mixture includes the amorphous carbon, the binder, and A kneading step for mixing and kneading the conductive agent, and a diluting step for adjusting the viscosity by adding and diluting the organic solvent to the mixture kneaded by the kneading step,
When the NMP (N-methyl-2-pyrrolidone) oil absorption of the mixed powder of the amorphous carbon and the conductive agent in the mixture is X (ml / 100 g),
The solid content W (%) of the mixture in the kneading step (solid weight (g) × 100 / weight of the mixture (g)) and the NMP oil absorption amount X are:
W = −0.28X + b (however, 83.5 ≦ b ≦ 87.0)
The manufacturing method of the lithium ion battery characterized by satisfy | filling the relationship of these.   The method for manufacturing a lithium ion battery according to claim 3, wherein the conductive agent is carbon black.   5. The method for producing a lithium ion battery according to claim 3, wherein the NMP oil absorption amount X of the mixed powder of the amorphous carbon and the conductive agent is in a range of 70 ml / 100 g to 120 ml / 100 g. A lithium ion battery having a negative electrode in which a negative electrode mixture containing amorphous carbon, a binder, and an organic solvent is held by a current collector,
Solid content Z (%) of a mixture of the amorphous carbon, the binder and the organic solvent, and an NMP (N-methyl-2-pyrrolidone) oil absorption Y (ml / 100 g) of the amorphous carbon Z = −0.268Y + a (where 82.5 ≦ a ≦ 85.5)
A lithium ion battery characterized by satisfying the following formula:   The lithium ion battery according to claim 6, wherein the NMP oil absorption Y of the amorphous carbon is in the range of 70 ml / 100 g to 120 ml / 100 g. A lithium ion battery having a negative electrode in which a negative electrode mixture containing amorphous carbon, a conductive agent, a binder, and an organic solvent is held by a current collector,
Solid content W (%) of the mixture of the amorphous carbon, the conductive agent, the binder and the organic solvent, and the NMP oil absorption X (ml / 100 g) of the mixed powder of the amorphous carbon and the conductive agent. ) And W = −0.28X + b (where 83.5 ≦ b ≦ 87.0)
A lithium ion battery characterized by satisfying the following formula:   9. The lithium ion battery according to claim 8, wherein the NMP oil absorption amount X of the mixed powder of the amorphous carbon and the conductive agent is in a range of 70 ml / 100 g to 120 ml / 100 g.