JP2015005373A - Method of manufacturing negative plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a negative plate, capable of reducing resistance of a negative electrode active material layer and forming a homogeneous negative electrode active material layer.SOLUTION: The method of manufacturing a negative plate 41 including a negative electrode plate 42 and a negative electrode active material layer 43 formed thereon comprises: a paste preparing step of preparing a negative electrode paste in which a thickener and negative electrode active material particles having, on their particle surfaces, a carboxyl group in an amount of 0.010-0.050 mmol/mper unit area of the particle surfaces are dispersed in a dispersion medium; and an active material layer forming step of applying the negative electrode paste onto the negative electrode plate 42 to form the negative electrode active material layer 43.

Description

  The present invention relates to a negative electrode plate and a method for manufacturing a negative electrode plate including a negative electrode active material layer formed thereon.

Conventionally, as the negative electrode active material particles constituting the negative electrode active material layer of the negative electrode plate, those having a surface functional group on the particle surface are known. For example, Patent Document 1 discloses that a negative electrode plate and a battery using the same are manufactured using negative electrode active material particles having such a surface functional group. Specifically, it is preferable to use “graphite having an acidic functional group amount of 5 meq / kg or less per mass and 0.3 μeq / m ² or more per specific surface area” as the negative electrode active material particles. (Refer to the claims of Patent Document 1).

JP 2005-108456 A

  However, as a result of studies by the present inventors, it has been found that the resistance of the negative electrode active material layer increases when the amount of surface functional groups on the particle surface, specifically, carboxyl groups (—COOH) is excessive. The reason is considered that the carboxyl group attached to the negative electrode active material particles inhibits the insertion of lithium ions. For example, when the negative electrode active material particles are graphite particles, the carboxyl group is considered to be easily attached to the edge surface of graphite. Since lithium ions are inserted between the graphite layers through the edge surface of graphite, it is presumed that the insertion of lithium ions between the graphite layers is hindered by the carboxyl groups when the amount of carboxyl groups increases to fill the edge surface.

On the other hand, if the amount of carboxyl groups on the particle surface is too small, a homogeneous negative electrode active material such as a streak-like dent (a portion where the negative electrode active material layer is thinned) or a pinhole is formed in the negative electrode active material layer. It has been found that it becomes difficult to form a material layer. The reason is considered as follows. If the amount of the carboxyl group of the negative electrode active material particles is too small, in the negative electrode paste containing the thickener, the thickener undissolved material (aggregates in which the thickener is not dissolved) or insoluble material ( Aggregates in which substances contained in the thickener and not dissolved or hardly dissolved in the dispersion medium are easily generated. Then, when the negative electrode paste is applied to the negative electrode plate, streaks are caused by the above-mentioned undissolved material or insoluble material, and as a result, streaky dents are formed in the negative electrode active material layer. In addition, when the negative electrode paste layer applied on the negative electrode plate is dried to form the negative electrode active material layer, the above-mentioned undissolved and insoluble materials in the negative electrode paste layer are greatly shrunk, It is thought that pinholes are formed.
Thus, in the conventional method for manufacturing a negative electrode plate, it has been difficult to achieve both a reduction in resistance of the negative electrode active material layer and formation of a homogeneous negative electrode active material layer.

  This invention is made | formed in view of this present condition, Comprising: While making resistance of a negative electrode active material layer low, it aims at providing the manufacturing method of the negative electrode plate which can form a homogeneous negative electrode active material layer.

One aspect of the present invention for solving the above problems is a method for producing a negative electrode plate and a negative electrode plate comprising a negative electrode active material layer formed thereon, on the particle surface of the negative electrode active material particles, A paste preparation step of preparing a negative electrode paste in which negative electrode active material particles having a carboxyl group of 0.010 to 0.050 mmol / m ² per unit area of the particle surface and a thickener are dispersed in a dispersion medium; An active material layer forming step of applying the negative electrode paste onto the negative electrode plate to form the negative electrode active material layer.

In this method for producing a negative electrode plate, a negative electrode active material particle is prepared using a negative electrode active material particle having a carboxyl group (—COOH) of 0.010 to 0.050 mmol / m ² per unit area of the particle surface, This is applied to the negative electrode plate to form a negative electrode active material layer. Since the amount of carboxyl groups on the particle surface is 0.050 mmol / m ² or less, it is possible to appropriately suppress an increase in resistance of the negative electrode active material layer. The reason is considered to be that the insertion of lithium ions is hardly inhibited by suppressing the amount of carboxyl groups on the particle surface.

On the other hand, since the amount of the carboxyl group on the particle surface is 0.010 mmol / m ² or more, it is possible to appropriately suppress the occurrence of undissolved or insoluble materials of the thickener in the negative electrode paste. The greater the amount of carboxyl groups in the negative electrode active material particles, the better the dispersibility of the negative electrode active material particles during kneading of the negative electrode paste and the greater the force applied to the negative electrode paste. It is believed that the product is crushed to reduce these amounts or to reduce their size sufficiently. Thereby, it is possible to suppress the generation of streak-like dents and pinholes in the negative electrode active material layer, thereby forming a homogeneous negative electrode active material layer.
Thus, according to this method for manufacturing a negative electrode plate, it is possible to achieve both reduction in resistance of the negative electrode active material layer and formation of a homogeneous negative electrode active material layer.

In addition, the amount (mmol / m ² ) of carboxyl groups attached to the particle surface of the negative electrode active material particles can be obtained by the following method.
(1) The sample (negative electrode active material particles) is subjected to XPS analysis, and the peak integrated area value of the carboxyl groups (287 to 289 eV) is used to determine the carboxyl group in the surface functional group attached to the particle surface of the negative electrode active material particles. Find the abundance ratio.
(2) A predetermined amount of the sample is subjected to pyrolysis gas chromatography, and the amount of surface functional groups attached to the surface of the negative electrode active material particles is determined from the amount of generated gas.
(3) Nitrogen BET is performed on a predetermined amount of sample to determine the specific surface area of the negative electrode active material particles.
(4) Using each numerical value obtained in (1) to (3), the amount of carboxyl groups per unit area on the particle surface of the negative electrode active material particles is obtained.

Moreover, the negative electrode active material particle which has a carboxyl group on the particle | grain surface can be obtained with the following methods, for example. That is, negative electrode active material particles having a carboxyl group can be prepared by mixing negative electrode active material particles and acetic acid (CH ₃ COOH) and performing heat treatment. In addition, a carboxyl group can be attached to the surface of the negative electrode active material particles using mechanofusion, a ball mill, a pin mill, or the like.

Moreover, the “negative electrode plate” produced by this production method can be used for, for example, a lithium ion secondary battery.
Examples of the “negative electrode active material particles” include particles made of a carbon material described later. Further, surface functional groups other than carboxyl groups (for example, lactone groups, carbonyl groups, methyl groups, hydroxy groups, etc.) may be attached to the particle surfaces of the “negative electrode active material particles”.
Examples of the “thickening agent” include cellulose derivatives such as carboxymethyl cellulose (CMC) and methyl cellulose (MC).
Examples of the “dispersion medium” include water.

  In addition to the negative electrode active material particles and the thickener, for example, a binder, a dispersant, a filler, an ionic conductive agent, and the like can be added to the “negative electrode paste”. Examples of the binder include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, and cellulose, rubbery polymers such as styrene / butadiene rubber, isoprene rubber, butadiene rubber, and ethylene / propylene rubber, and styrene.・ Butadiene / styrene block copolymer, hydrogenated product, styrene / ethylene / butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer, thermoplastic elastomeric polymer such as hydrogenated product, syndiotactic Soft resin-like polymers such as tic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (carbon number 2 to 12) copolymer, polyvinylidene fluoride, polytetrafluoroethylene, polytetrafluoro Ethylene Eth Emissions copolymer, and a fluorine-based polymer can be cited, and these can be used alone or in more mixed.

The “negative electrode paste” can be produced using a medialess disperser such as a homogenizer, a planetary mixer, a jet mill, an ultrasonic disperser, a disperser (stirring blade), or an extrusion kneader. Alternatively, the negative electrode paste may be produced by using a media dispersion method in which ceramic beads such as glass and zirconia are introduced into a dispersing machine such as a bead mill or a ball mill.
Examples of the material of the “negative electrode plate” include copper, nickel, and stainless steel.
In addition, examples of the application method for applying the negative electrode paste to the negative electrode plate in the active material forming step include die coating using a die coater and blade coating using a doctor blade.

  Furthermore, in the above method for producing a negative electrode plate, the thickener may be a method for producing a negative electrode plate that is carboxymethylcellulose.

  In this negative electrode plate manufacturing method, carboxymethyl cellulose (CMC) is used as a thickener. CMC is suitable as a thickener because it can be easily obtained and handled, and can easily produce a negative electrode paste having an appropriate viscosity by being dispersed in a dispersion medium such as water.

  The negative electrode plate manufacturing method according to any one of the above, wherein the negative electrode plate is a negative electrode plate used for a lithium ion secondary battery, and the negative electrode active material particles can insert and desorb lithium ions. A method for producing a negative electrode plate made of a carbon material is preferable.

In this negative electrode plate manufacturing method, the negative electrode plate is a negative electrode plate for a lithium ion secondary battery, and a carbon material capable of inserting and releasing lithium ions is used as the negative electrode active material particles. In this case, as described above, the increase in the resistance of the negative electrode active material layer can be effectively suppressed by setting the amount of the carboxyl group of the negative electrode active material particles to 0.050 mmol / m ² or less. On the other hand, by making the amount of the carboxyl group of the negative electrode active material particles 0.010 mmol / m ² or more, it is possible to effectively suppress the formation of streak-like dents and pinholes in the negative electrode active material layer. A negative electrode active material layer can be formed.
Examples of the “carbon material capable of inserting and removing lithium ions” include, for example, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, and the like. A plurality of types can be mixed and used.

It is a perspective view of the battery which concerns on embodiment. It is sectional drawing of the battery which concerns on embodiment. It is an expanded view of an electrode body which concerns on embodiment and shows the state which accumulated the positive electrode plate and the negative electrode plate through the separator. It is sectional drawing of the negative electrode plate which concerns on embodiment. It is a graph which shows the relationship between the quantity of the carboxyl group of negative electrode active material particle | grains, and the number of the stripe-shaped dent produced in the negative electrode active material layer. It is a graph which shows the relationship between the quantity of the carboxyl group of a negative electrode active material particle, and the force applied to a negative electrode paste at the time of paste kneading. It is a graph which shows the relationship between the quantity of the carboxyl group of negative electrode active material particle, and the resistance value of a negative electrode plate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a battery 10 using a negative electrode plate 41 according to this embodiment. FIG. 3 shows a state in which the flat wound electrode body 30 constituting the battery 10 is developed. FIG. 4 shows the negative electrode plate 41. Hereinafter, the battery thickness direction BH, the battery lateral direction CH, and the battery vertical direction DH of the battery 10 will be described as the directions shown in FIGS. 1 and 2.

  The battery 10 is a rectangular and sealed lithium ion secondary battery mounted on a vehicle such as a hybrid vehicle or an electric vehicle. The battery 10 includes a rectangular battery case 20, a flat wound electrode body 30 accommodated in the battery case 20, a positive terminal member 60 and a negative terminal member 70 supported by the battery case 20, and the like. It is composed of A non-aqueous electrolyte solution 27 is held in the battery case 20 (see FIGS. 1 and 2).

  Among these, the battery case 20 is made of metal (specifically, aluminum). The battery case 20 includes a bottomed rectangular tube-shaped case body 21 having a rectangular opening 21h only on the upper side, and a rectangular plate-shaped lid member 23 that seals the opening 21h of the case body 21. ing. In the lid member 23, a non-returnable safety valve 23v is provided near the center in the longitudinal direction (battery lateral direction CH). In addition, a liquid injection hole 23 h that is used when injecting the electrolyte solution 27 into the battery case 20 is provided in the vicinity of the safety valve 23 v and is hermetically sealed by the sealing member 25.

  Further, in the lid member 23, a positive electrode terminal member 60 and a negative electrode terminal member 70, which extend from the inside of the battery case 20 to the outside, are fixed in the vicinity of both ends in the longitudinal direction. Specifically, each of the positive electrode terminal member 60 and the negative electrode terminal member 70 is connected to the electrode body 30 in the battery case 20, and passes through the lid member 23 and extends to the outside of the battery case 20. The members 61 and 71 are composed of crank-shaped second terminal members 62 and 72 which are disposed on the lid member 23 and fixed to the first terminal members 61 and 71 by crimping. The positive electrode terminal member 60 and the negative electrode terminal member 70 are disposed inside the lid member 23 (inside the case) together with metal fastening members 65 and 75 for fastening connection terminals outside the battery, such as bus bars and crimp terminals. The first insulating members 67 and 77 made of resin and the second insulating members 68 and 78 made of resin disposed outside the case 23 (outside the case) are fixed to the cover member 23.

  Next, the electrode body 30 will be described (see FIGS. 2 and 3). The electrode body 30 is housed in the battery case 20 in a form in which the axial direction EH coincides with the battery lateral direction CH (see FIG. 2). The electrode body 30 is formed by laminating a belt-like positive electrode plate 31 and a belt-like negative electrode plate 41 with each other via a pair of separators 51 and 51 made of a porous resin (see FIG. 3) and winding around an axis. , Compressed flat. A part of the positive electrode plate 31 in the width direction protrudes from the separators 51 and 51 in a flat spiral shape toward one side EC (in FIG. 2, left, upper in FIG. 3) in the axial direction EH. The positive terminal member 60 is connected (welded) to the first terminal member 61. Further, a part of the negative electrode plate 41 in the width direction protrudes from the separators 51, 51 in a flat spiral shape toward the other side ED in the axial direction EH (in FIG. 2, right side, downward in FIG. 3). The first terminal member 71 of the negative electrode terminal member 70 is connected (welded).

  The positive electrode plate 31 has a strip-like positive electrode plate 32 made of aluminum foil as a core material. Bands are formed in the longitudinal direction (left and right direction in FIG. 3) on a part (lower part in FIG. 3) in the width direction (up and down direction in FIG. 3) of the front and back surfaces of the positive electrode plate 32, respectively. Porous positive electrode active material layers 33, 33 extending in the direction are formed. The positive electrode active material layer 33 is formed of positive electrode active material particles, a conductive material, and a binder. In this embodiment, lithium-cobalt-nickel-manganese composite oxide particles are used as positive electrode active material particles, acetylene black (AB) is used as a conductive material, and polyvinylidene fluoride (PVDF) is used as a binder.

  The negative electrode plate 41 has a strip-shaped negative electrode plate 42 made of copper foil as a core material (see FIGS. 3 and 4). Above part of the front and back surfaces of the negative electrode plate 42 in the width direction (vertical direction in FIG. 3, left and right direction in FIG. 4) (upward part in FIG. 3, left part in FIG. 4) Are formed with porous negative electrode active material layers 43, 43 extending in a strip shape in the longitudinal direction (the left-right direction in FIG. 3, the direction orthogonal to the paper surface in FIG. 4), respectively. The negative electrode active material layer 43 is formed of negative electrode active material particles, a binder, and a thickener.

In this embodiment, a carbon material capable of inserting and releasing lithium ions, specifically, natural graphite particles is used as the negative electrode active material particles. This negative electrode active material particle (natural graphite particle) has a surface functional group on the particle surface. This surface functional group is mainly a carboxyl group. Specifically, 80% of the surface functional groups are carboxyl groups (—COOH), 10% are methyl groups (—CH ₃ ), 5% are hydroxy groups (—OH), and the remaining 5 % Is other functional groups. Further, the anode active material particle (in the present embodiment 0.030 mmol / m ²⁾ per unit area 0.010~0.050mmol / m ² of particle surface having a carboxyl group.
In this embodiment, styrene butadiene rubber (SBR) is used as a binder, and carboxymethyl cellulose (CMC) is used as a thickener.

Next, a method for manufacturing the negative electrode plate 41 and a method for manufacturing the battery 10 using the negative electrode plate 41 will be described. First, a negative electrode paste is produced (paste preparation process). That is, negative electrode active material particles having a carboxyl group of 0.010 to 0.050 mmol / m ² per unit area of the particle surface, a thickener, and a binder are dispersed on the particle surface of the negative electrode active material particles. A negative electrode paste dispersed in a medium is prepared.

Specifically, natural graphite particles are prepared as negative electrode active material particles. Then, the surface of the particles of natural graphite particles, the (in this embodiment ^{0.030mmol / m 2) 0.010~0.050mmol / m} 2 per unit area of the grain surface is introducing a carboxyl group. First, 60 g (1 mol) of 100% acetic acid (CH ₃ COOH) is diluted with 1 liter of water (1 mol / L), and further diluted to prepare a 0.040 mmol / L acetic acid aqueous solution. Thereafter, the natural graphite particles are mixed with the acetic acid aqueous solution so as to be 0.040 mmol per unit area (m ² ) of the particle surface of the natural graphite particles, and heat treatment is performed. In this embodiment, it was dried at 120 ° C. Thereby, natural graphite particles having a carboxyl group of 0.030 mmol / m ² per unit area of the particle surface are obtained.

  Next, CMC is prepared as a thickener and SBR is prepared as a binder. Then, using a planetary mixer, natural graphite particles having a carboxyl group, CMC, and SBR are dispersed in a dispersion medium (specifically, water) to prepare a negative electrode paste. In this embodiment, natural graphite particles, CMC, and SBR are mixed at a weight ratio of 98: 1: 1.

  Next, this negative electrode paste is applied onto the negative electrode plate 42 to form a negative electrode active material layer 43 (active material layer forming step). Specifically, a negative electrode plate 42 made of copper foil is prepared. And the above-mentioned negative electrode paste is apply | coated to a part of width direction among one main surfaces of this negative electrode plate 42 using a die-coater. Thereafter, the negative electrode paste applied on the negative electrode plate 42 is dried with hot air to form the negative electrode active material layer 43. Similarly, a negative electrode paste is applied onto a main surface on the opposite side of the negative electrode plate 42 on a part in the width direction, and the negative electrode active material layer 43 is formed by drying the paste with hot air. Thereafter, the negative electrode active material layers 43 and 43 are compressed by a pressure roll to increase the density. Thus, the negative electrode plate 41 is formed (see FIG. 4).

  Next, the battery 10 is manufactured using the negative electrode plate 41. First, the positive electrode plate 110 is produced. That is, a belt-like positive electrode plate 32 is prepared. Then, a positive electrode paste containing positive electrode active material particles, a conductive material and a binder is applied onto a part of the width direction of one main surface of the positive electrode plate 32, and this is dried with hot air, A positive electrode active material layer 33 is formed. Similarly, a positive electrode paste is applied onto a main surface on the opposite side of the positive electrode plate 32 on a part in the width direction, and this is dried with hot air to form the positive electrode active material layer 33. Thereafter, the positive electrode active material layers 33 and 33 are compressed by a pressure roll to increase the density. Thus, the positive electrode plate 31 is formed.

Next, two strip-shaped separators 51 are prepared, and the above-described positive electrode plate 31 and negative electrode plate 41 are overlapped with each other through the separators 51 and 51 (see FIG. 3), and wound around the axis using a winding core. . Further, the electrode body 30 is formed by compressing it into a flat shape.
Separately, a lid member 23 for the battery case 20 is prepared, and a positive terminal member 60 and a negative terminal member 70 are fixed to the lid member 23, respectively. Furthermore, the positive electrode terminal member 60 and the negative electrode terminal member 70 are each welded to the electrode body 30. Then, after preparing the case main body 21 of the battery case 20 and accommodating the electrode body 30 in the case main body 21, the case main body 21 and the lid member 23 are welded to form the battery case 20. Thereafter, the electrolytic solution 27 is injected into the battery case 20 from the injection hole 23h, and the injection hole 23h is hermetically sealed with the sealing member 25. Thereafter, the battery is subjected to initial charging and various inspections. Thus, the battery 10 is completed.

(Test results)
Subsequently, the result of the test performed in order to verify the effect of the manufacturing method of the negative electrode plate 41 which concerns on embodiment is demonstrated. In the manufacturing method of the negative electrode plate 41 according to the embodiment, the concentration of the acetic acid aqueous solution to be mixed is changed, and the amount of the carboxyl group of the negative electrode active material particles is changed in the range of 0.005 to 0.062 mmol / m ² . Six types of negative electrode plates (area 1 m ² ) were manufactured in each of five. Then, for each type of negative electrode plate, the total number of streak-like dents generated in the negative electrode active material layer was examined visually. For example, when a plurality of (for example, three) streak-shaped dents are formed on one negative electrode plate, the total number of streaky dents is counted by adding the number (three). The results are shown in the graph of FIG.

As can be seen from the graph of FIG. 5, when the amount of the carboxyl group of the negative electrode active material particles is less than 0.010 mmol / m ² , the number of streak-like dents generated in the negative electrode active material layer increases rapidly. On the other hand, when the amount of the carboxyl group of the negative electrode active material particles is 0.010 mmol / m ² or more, the number of streak-like dents generated in the negative electrode active material layer is sufficiently reduced. In particular, it can be seen that when the amount of the carboxyl group is 0.015 mmol / m ² or more, the number of streak-like dents is reduced to such an extent that the streak-like dents cannot be further reduced.

The reason is considered as follows. When the amount of carboxyl groups in the negative electrode active material particles is less than 0.010 mmol / m ^2, undissolved and insoluble substances of the thickener are likely to be generated in the negative electrode paste containing the thickener. Then, when the negative electrode paste is applied to the negative electrode plate 42, streaks are generated due to the above-mentioned undissolved material or insoluble material, and a streak-like dent is formed in the negative electrode active material layer.

In contrast, when the carboxyl group content of the anode active material particles in the 0.010 mmol / m ² or more, further when the 0.015 mmol / m ² or more, undissolved or insoluble matters of the thickener in the negative electrode paste It is possible to appropriately suppress the occurrence.
Here, the relationship between the amount of carboxyl groups of the negative electrode active material particles and the force applied to the negative electrode paste during kneading of the negative electrode paste is shown in FIG. The force applied to the negative electrode paste during kneading is a value obtained by measuring the torque applied to rotation using a torque meter.

  As can be seen from the graph of FIG. 6, the force applied to the negative electrode paste during kneading increases as the amount of carboxyl groups of the negative electrode active material particles increases. This is presumably because the higher the amount of carboxyl groups, the better the dispersibility of the negative electrode active material particles. If the force applied to the negative electrode paste during kneading increases, the undissolved and insoluble materials of the thickener present in the negative electrode paste are easily pulverized, so that these amounts are reduced, or these sizes are sufficiently large It will be smaller. As a result, it is considered that streaking is less likely to occur when the negative electrode paste is applied to the negative electrode plate 42, and streak-like dents are less likely to be formed in the negative electrode active material layer.

Next, in the manufacturing method of the negative electrode plate 41 according to the embodiment, the amount of the carboxyl group of the negative electrode active material particles is changed in the range of 0.005 to 0.062 mmol / m ² to manufacture five types of negative electrode plates. did. Further, batteries were manufactured using each negative electrode plate. And about each battery, after adjusting to SOC60%, IV resistance was calculated | required in 50 A and 10 sec. The result is shown in the graph of FIG. In FIG. 7, the resistance value when the amount of the carboxyl group is 0.005 mmol / m ² is described as a reference (100%).

As can be seen from the graph of FIG. 7, it can be seen that when the amount of the carboxyl group of the negative electrode active material particles is made larger than 0.050 mmol / m ² , the resistance value of the negative electrode plate rapidly increases. The reason is that the carboxyl group is easily attached to the edge surface of the negative electrode active material particles (graphite particles). Since lithium ions are inserted between the graphite layers through the edge surfaces of graphite, when the carboxyl groups increase so as to fill the edge surfaces, the insertion of lithium ions between the graphite layers is inhibited by the carboxyl groups. As a result, the resistance value of the negative electrode plate is considered to increase.

On the other hand, the amount of the carboxyl groups of the anode active material particles when below 0.050 mmol / m ^2, and more when below 0.040 mmol / m ^2, the resistance value of the negative electrode plate is found to be sufficiently low. The amount of carboxyl groups 0.050 mmol / m ² or less, more by suppressing below 0.040 mmol / m ^2, carboxyl group is less stick to the edge face of the anode active material particles (graphite particles), lithium ions edge It becomes easy to be inserted between graphite layers through the surface. As a result, the resistance value of the negative electrode plate is considered to be low.

As described above, in the method of manufacturing the negative electrode plate 41, the negative electrode active material particles having a carboxyl group of 0.010 to 0.050 mmol / m ² per unit area of the particle surface are used. Then, this is applied to the negative electrode plate 42 to form the negative electrode active material layer 43. Since the amount of the carboxyl group on the particle surface is 0.050 mmol / m ² or less, it is possible to appropriately suppress the resistance of the negative electrode active material layer 43 from increasing. The reason is considered to be that the insertion of lithium ions is hardly inhibited by suppressing the amount of carboxyl groups on the particle surface.

On the other hand, since the amount of carboxyl groups on the particle surface is 0.010 mmol / m ² or more, it is possible to appropriately suppress the occurrence of undissolved or insoluble materials of the thickener in the negative electrode paste. The greater the amount of carboxyl groups in the negative electrode active material particles, the better the dispersibility of the negative electrode active material particles during kneading of the negative electrode paste and the greater the force applied to the negative electrode paste. Is crushed to reduce these amounts, or the size thereof is considered to be sufficiently small. Thereby, it is possible to suppress the generation of streak-like dents and pinholes in the negative electrode active material layer 43 and to form the homogeneous negative electrode active material layer 43.
As described above, according to the method for manufacturing the negative electrode plate 41, it is possible to achieve both the reduction of the resistance of the negative electrode active material layer 43 and the formation of the homogeneous negative electrode active material layer 43.

Furthermore, in the manufacturing method of the negative electrode plate 41, CMC is used as a thickener. CMC is suitable as a thickener because it can be easily obtained and handled, and can easily produce a negative electrode paste having an appropriate viscosity by being dispersed in a dispersion medium such as water.
The negative electrode plate 41 is a negative electrode plate for a lithium ion secondary battery, and a carbon material capable of inserting and releasing lithium ions is used as negative electrode active material particles. In this case, as described above, the increase in the resistance of the negative electrode active material layer 43 can be effectively suppressed by setting the amount of carboxyl groups of the negative electrode active material particles to 0.050 mmol / m ² or less. On the other hand, by making the amount of carboxyl groups of the negative electrode active material particles 0.010 mmol / m ² or more, the negative electrode active material layer 43 is effectively suppressed from causing streak-like dents and pinholes, and more homogeneous. The negative electrode active material layer 43 can be formed.

  In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

10 battery (lithium ion secondary battery)
30 Electrode body 31 Positive electrode plate 41 Negative electrode plate 42 Negative electrode plate 43 Negative electrode active material layer 51 Separator

Claims (3)

A negative electrode plate, and a method for producing a negative electrode plate comprising a negative electrode active material layer formed thereon,
On the particle surface of the negative electrode active material particles, negative electrode active material particles having a carboxyl group of 0.010 to 0.050 mmol / m ² per unit area of the particle surface and a thickener were dispersed in a dispersion medium. A paste preparation step for preparing a negative electrode paste;
An active material layer forming step of applying the negative electrode paste onto the negative electrode plate to form the negative electrode active material layer. It is a manufacturing method of the negative electrode plate according to claim 1,
The said thickener is a manufacturing method of the negative electrode plate which is carboxymethylcellulose. It is a manufacturing method of the negative electrode plate according to claim 1 or 2,
The negative electrode plate is a negative electrode plate used for a lithium ion secondary battery,
The negative electrode active material particle is a method for producing a negative electrode plate made of a carbon material capable of inserting and releasing lithium ions.

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