Carbon nanotube dispersion for electrode slurry, negative electrode slurry, non-aqueous electrolyte secondary battery, and method for producing carbon nanotube dispersion for electrode slurry

Abstract

Provided is an electrode slurry carbon nanotube liquid dispersion which improves charge / discharge cycle characteristics. An electrode slurry carbon nanotube liquid dispersion which is one aspect of the present disclosure and contains 0.1-1.5 mass% of carbon nanotubes, a dispersion medium, and carboxymethyl cellulose, the viscosity of which at 100s-1 in a 3% aqueous solution is 2-200mPa·s, wherein: the carboxymethyl cellulose content constitutes 50-250 parts by mass relative to 100 parts by mass of carbon nanotubes; the viscosity at 100s-1 is 50-200mPa·s in a state in which the carbon nanotubes are dispersed; and the particle distribution according to the laser diffraction method exhibits a D10 of 0.3-1.0μm, a D50 of 3-10μm and a D90 of 60μm or less in a state in which the carbon nanotubes are dispersed.

Description

[Technical Field]

[0001] This disclosure relates to a carbon nanotube dispersion for electrode slurry, a negative electrode slurry, a non-aqueous electrolyte secondary battery, and a method for producing a carbon nanotube dispersion for electrode slurry. [Background technology]

[0002] Carbon nanotubes are attracting attention as a conductive agent for electrodes in non-aqueous electrolyte secondary batteries. Compared to conventional conductive agents such as acetylene black, carbon nanotubes can significantly improve conductivity with a smaller content. However, carbon nanotubes tend to aggregate, posing a challenge in terms of dispersibility.

[0003] Patent Document 1 discloses a carbon nanotube dispersion for electrode slurry, which contains predetermined amounts of carbon nanotubes and partially hydrogenated nitrile rubber in a dispersion medium, and in which the dispersed particle size of the carbon nanotubes is specified. Furthermore, Patent Document 1 states that a secondary battery containing a positive electrode and a negative electrode made using this carbon nanotube dispersion for electrode slurry can have a reduced DCIR (direct current resistance). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6633654 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The inventors have found that viscosity is a very important factor in improving the dispersibility of carbon nanotubes in a carbon nanotube dispersion for electrode slurry. The technology described in Patent Document 1 does not take into consideration the viscosity of the carbon nanotube dispersion for electrode slurry, and there is still room for improvement. By improving the dispersibility of carbon nanotubes in a carbon nanotube dispersion for electrode slurry and producing an electrode with a uniform mixture layer, it is possible to suppress the decrease in battery capacity due to repeated charging and discharging in a secondary battery using such an electrode.

[0006] Therefore, the purpose of this disclosure is to provide a carbon nanotube dispersion for electrode slurries that improves charge-discharge cycle characteristics. [Means for solving the problem]

[0007] One aspect of the present disclosure of a carbon nanotube dispersion for electrode slurry comprises 0.1 to 1.5% by mass of carbon nanotubes, a dispersion medium, and a 3% aqueous solution of 100 s -1 It contains carboxymethylcellulose with a viscosity of 2 to 200 mPa·s, and the carboxymethylcellulose content is 50 to 250 parts by mass per 100 parts by mass of carbon nanotubes, and in a dispersed state of carbon nanotubes, 100 s -1 The viscosity is 50 to 200 mPa·s, and in a state where carbon nanotubes are dispersed, the particle size distribution measured by laser diffraction is characterized by D10 being 0.3 to 1.0 μm, D50 being 3 to 10 μm, and D90 being 60 μm or less.

[0008] One embodiment of the present disclosure, the negative electrode slurry, is characterized by comprising the above-mentioned carbon nanotube dispersion for electrode slurry, a carbon-based negative electrode active material, and a Si-containing negative electrode active material.

[0009] One embodiment of the present disclosure, a non-aqueous electrolyte secondary battery, is characterized by comprising a negative electrode prepared using the above-mentioned negative electrode slurry.

[0010] A method for producing a carbon nanotube dispersion for electrode slurry, as described in this disclosure, comprises 0.1 to 1.5% by mass of carbon nanotubes, a dispersion medium, and a 3% aqueous solution (100 s) -1 The method comprises a mixing step of preparing a mixture by mixing carboxymethylcellulose having a viscosity of 2 to 200 mPa·s with a dispersion step of dispersing carbon nanotubes contained in the mixture, characterized in that a high-pressure homogenizer is used in the dispersion step. [Effects of the Invention]

[0011] By using the carbon nanotube dispersion for electrode slurry according to this disclosure, the charge-discharge cycle characteristics of the battery can be improved. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of an electrode prepared using an electrode slurry containing a carbon nanotube dispersion for electrode slurry, which is an example of an embodiment. [Modes for carrying out the invention]

[0013] As a result of diligent research by the inventors, carbon nanotubes (CNTs) having a predetermined particle size distribution and a 3% aqueous solution are found to be in a 100s solution. -1 We found that using a carbon nanotube dispersion for electrode slurries containing carboxymethylcellulose (CMC) with a viscosity of 2-200 mPa·s in a certain proportion improves the capacity retention rate of batteries. It is presumed that forming a composite layer using a carbon nanotube dispersion for electrode slurries with improved carbon nanotube dispersibility increases the uniformity of the composite layer and improves the charge-discharge cycle characteristics of the battery. (3% aqueous solution, 100s) -1CMC with a viscosity of 2 to 200 mPa·s has a small molecular weight. This allows for a greater number of molecules in the dispersion compared to adding the same amount of CMC with a larger molecular weight to the carbon nanotube dispersion for electrode slurry, thus enabling effective dispersion of nanomaterials such as CNTs. Furthermore, the inventors have found that using a high-pressure homogenizer in the method for producing the carbon nanotube dispersion for electrode slurry allows for more efficient dispersion of CNTs compared to using other equipment.

[0014] The following describes in detail embodiments of the carbon nanotube dispersion for electrode slurry, the negative electrode slurry containing the carbon nanotube dispersion for electrode slurry, the non-aqueous electrolyte secondary battery equipped with a negative electrode prepared using the negative electrode slurry, and the method for producing the carbon nanotube dispersion for electrode slurry according to this disclosure. The embodiments described below are merely examples, and this disclosure is not limited to these embodiments. Furthermore, the drawings referenced in the description of the embodiments are schematic representations, and the dimensional ratios of the components depicted in the drawings should be determined by referring to the following description.

[0015] [Nonaqueous electrolyte secondary battery] The non-aqueous electrolyte secondary battery according to the present disclosure is, for example, a lithium-ion secondary battery. The battery case of the non-aqueous electrolyte secondary battery may be made of metal such as circular, rectangular, coin-shaped, etc., or may be made of a laminate sheet including a metal layer and a resin layer. The non-aqueous electrolyte secondary battery includes, for example, an electrode body and a non-aqueous electrolyte inside the battery case. The electrode body may be a wound type in which a positive electrode and a negative electrode are wound through a separator, or may be a stacked type in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked one by one through a separator. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, for example, esters, ethers, nitriles, amides, and a mixed solvent of two or more of these can be used. The non-aqueous solvent may contain a halogen-substituted product in which at least a part of the hydrogen of these solvents is substituted with a halogen atom such as fluorine. As the electrolyte salt, for example, a lithium salt such as LiPF6 is used.

[0016] FIG. 1 is a cross-sectional view of an electrode manufactured using an electrode slurry containing a carbon nanotube dispersion for an electrode slurry according to an example of an embodiment. The electrode 10 includes a core material 11 and an electrode mixture layer 12 laminated on the surface of the core material 11. As shown in FIG. 1, the electrode 10 may include electrode mixture layers 12 on both sides of the core material 11. The electrode 10 may be a long electrode constituting a wound electrode body, or may be a rectangular electrode constituting a stacked electrode body. Note that the electrode 10 can be applied to the positive electrode, negative electrode, or both of the non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery preferably includes a negative electrode manufactured using a negative electrode slurry containing a carbon nanotube dispersion for an electrode slurry described later. Hereinafter, a negative electrode manufactured using a negative electrode slurry containing a carbon nanotube dispersion for an electrode slurry will be described as an example, but a positive electrode may be manufactured using a positive electrode slurry containing a carbon nanotube dispersion for an electrode slurry.

[0017] For the core material 11, a metal foil, a film having a metal layer formed on its surface, or the like can be used. The thickness of the core material 11 is, for example, 5 to 20 μm. In the case of the positive electrode, a metal foil mainly composed of aluminum can be used for the core material 11. In the case of the negative electrode, a metal foil mainly composed of copper can be used. In this specification, the main component means the constituent component having the highest mass ratio. The core material 11 may be an aluminum foil substantially 100% aluminum or a copper foil substantially 100% copper.

[0018] The electrode binder layer 12 contains, for example, an active material, carbon nanotubes (CNT), carboxymethyl cellulose (CMC), a binder, and the like. The thickness of the electrode binder layer 12 is, for example, 30 to 200 μm, preferably 50 to 150 μm. Note that the electrode binder layer 12 may contain a carbon material such as carbon black (CB), acetylene black (AB), ketjen black, etc. as a conductive agent other than carbon nanotubes.

[0019] Examples of the positive electrode active material (positive electrode active material) contained in the electrode binder layer 12 include lithium transition metal composite oxides. Examples of the metal elements contained in the lithium transition metal composite oxides include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. Among them, it is preferable to contain at least one of Ni, Co, and Mn. Examples of the negative electrode active material (negative electrode active material) contained in the electrode binder layer 12 include carbon-based active materials such as natural graphite such as flaky graphite, massive graphite, and earthy graphite, artificial graphite such as massive artificial graphite (MAG), and mesophase carbon microbeads (MCMB) graphitized, and Si-based active materials that alloy with lithium. Examples of the Si-based active material include, for example, Si-containing compounds represented by SiO x (0.5 ≦ x ≦ 1.6) (hereinafter referred to as SiO), or Li 2y SiO (2+y)Examples of the Si-containing compound (hereinafter referred to as LSX) in which fine particles of Si are dispersed in a lithium silicate phase represented by (0 < y < 2). The active material is the main component of the electrode binder layer 12, and the content rate of the active material in the electrode binder layer 12 is preferably 85 to 99% by mass, more preferably 90 to 99% by mass.

[0020] Examples of the carbon nanotubes (CNT) contained in the electrode binder layer 12 include single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT). The CNT contained in the negative electrode binder layer is preferably SWCNT, and MWCNT may also be contained. The CNT contained in the positive electrode binder layer is preferably CNT synthesized by a catalyst containing Co, and among them, MWCNT is preferable. The positive electrode binder layer may contain SWCNT. The SWCNT has, for example, a diameter of 0.4 to 5.0 nm and a length of 5.0 to 20 μm. Here, the diameter of the SWCNT is calculated from the average value obtained by measuring the diameters of 10 CNTs using a transmission electron microscope (TEM). Also, the length of the CNT is calculated from the average value obtained by measuring the lengths of 10 CNTs using a scanning electron microscope (SEM). [[ID=​​​​​​​​​​The electrode 10 can be manufactured, for example, by applying an electrode slurry containing an active material, CNT, CMC, a binder, etc. onto the core material 11, drying to form the electrode mixture layer 12, and then rolling the electrode mixture layer 12.

[0024] The negative electrode slurry preferably contains a carbon nanotube dispersion liquid for electrode slurry, a carbon-based negative electrode active material, and a Si-based negative electrode active material described later. The negative electrode slurry may further contain SBR or a modified product thereof.

[0025] Next, a carbon nanotube dispersion liquid for electrode slurry and a manufacturing method thereof, which are an example of an embodiment, will be described.

[0026] [Carbon Nanotube Dispersion Liquid for Electrode Slurry] The carbon nanotube dispersion liquid for electrode slurry contains single-walled carbon nanotubes (SWCNT), a dispersion medium, and carboxymethyl cellulose (CMC). The carbon nanotube dispersion liquid for electrode slurry contains SWCNT having a predetermined particle size distribution and CMC having a predetermined viscosity at a certain ratio, as will be described later. Thereby, the uniformity of the mixture layer is enhanced, and the charge / discharge cycle characteristics of the battery are improved. The dispersion medium is, for example, water such as ion-exchanged water or distilled water.

[0027] The content rate of SWCNT in the carbon nanotube dispersion liquid for electrode slurry is 0.1 to 1.5 mass%, preferably 0.2 to 1.0 mass%, and more preferably 0.3 to 0.5 mass%. SWCNT has, for example, a diameter of 0.4 to 5.0 nm and a length of 5.0 to 20 μm.

[0028] CMC has a viscosity of 2 to 200 mPa·s at 100 s of a 3% aqueous solution -1 Dissolve CMC in water to prepare a 3% aqueous solution. For this aqueous solution, measure it at 25°C from 0.1 to 1000 s -1 using a rheometer. By performing the measurement up to -1The viscosity can be determined. For example, an Anton Paar MCR102 rheometer can be used. The viscosity of the carbon nanotube dispersion for electrode slurry, which will be described later, can be measured in the same way.

[0029] The CMC content in the carbon nanotube dispersion for electrode slurry is 50 to 250 parts by mass, preferably 100 to 200 parts by mass, and more preferably 120 to 180 parts by mass, per 100 parts by mass of SWCNT.

[0030] 100s carbon nanotube dispersion for electrode slurry -1 The viscosity in the dispersed SWCNTs is 50 to 200 mPa·s, preferably 60 to 180 mPa·s, and more preferably 70 to 150 mPa·s.

[0031] The particle size distribution of a carbon nanotube dispersion for electrode slurry, as determined by laser diffraction, shows that, in a state where single-walled carbon nanotubes (SWCNTs) are dispersed, D10 is 0.3 to 1.0 μm, D50 is 3 to 10 μm, and D90 is 60 μm or less. D90 is, for example, 20 μm or more. D10, D50, and D90 represent the particle sizes at which the cumulative frequency of the volume-based particle size distribution accounts for 10%, 50%, and 90% of the smallest particle size, respectively. The particle size distribution of a carbon nanotube dispersion for electrode slurry can be measured using a laser diffraction particle size distribution analyzer (e.g., Microtrac-Bell MT3000II).

[0032] [Method for producing a carbon nanotube dispersion for electrode slurry] A method for producing a carbon nanotube dispersion for electrode slurry involves using 0.1 to 1.5 mass% single-walled carbon nanotubes (SWCNTs), a dispersion medium, and a 3% aqueous solution for 100 seconds. -1The process includes a mixing step of preparing a mixture by mixing carboxymethylcellulose (CMC) having a viscosity of 2 to 200 mPa·s with the mixture, and a dispersion step of dispersing the SWCNTs contained in the mixture. The average length of the SWCNTs mixed in the mixing step is, for example, 0.1 to 200 μm.

[0033] In the mixing step, a mixture is prepared while adsorbing CMC onto SWCNTs using, for example, an in-line mixer. Adsorption of CMC onto SWCNTs suppresses the re-aggregation of SWCNTs. For example, an IKA magicLAB in-line mixer can be used.

[0034] In the dispersion step, a high-pressure homogenizer is used. This loosens and disperses the SWCNTs contained in the mixture, enabling the production of a carbon nanotube dispersion for electrode slurry. High-pressure homogenizers can loosen and disperse SWCNTs more efficiently than bead mills or ultrasonic dispersion devices. Both valve-type and nozzle-type high-pressure homogenizers can be used, as well as hybrid nozzle-type and valve-type homogenizers. Valve-type homogenizers are preferred because they are less prone to clogging than nozzle-type homogenizers. For example, the Equalizer Lab 02 manufactured by Sanmaru Machinery Industry Co., Ltd. can be used as a valve-type high-pressure homogenizer. In a high-pressure homogenizer, the dispersion state of SWCNTs can be changed by adjusting the flow rate, pressure, etc. Furthermore, the dispersibility of SWCNTs can be improved by passing the mixture through the high-pressure homogenizer multiple times. Here, improved dispersibility of SWCNTs means that the particle size distribution of single-walled carbon nanotubes (SWCNTs) satisfies the ranges of 0.3 to 1.0 μm for D10, 3 to 10 μm for D50, and 60 μm or less for D90. Note that if the mixture is passed through the high-pressure homogenizer too many times, the dispersibility of the SWCNTs will deteriorate, meaning that one or more of D10, D50, and D90 may fall outside the above ranges. [Examples]

[0035] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited to these examples.

[0036] <Example 1> [Preparation of carbon nanotube dispersions for electrode slurries] Single-walled carbon nanotubes (SWCNTs) with a diameter of 1.6 nm and an average length of 15 μm, and a 3% aqueous solution (100 s) -1 A mixture was prepared by mixing carboxymethylcellulose (CMC), which has a viscosity of 6.7 mPa·s, with water in a mass ratio of 0.4:0.6:99 using an in-line mixer (IKA magicLAB) (mixing step). Furthermore, this mixture was processed five times using a valve-type high-pressure homogenizer (Sanmaru Machinery Industry Econizer Lab 02) at a flow rate of 14 L / h and a pressure of 80 Pa to prepare a carbon nanotube dispersion for electrode slurry (dispersion step). In this state, with SWCNTs dispersed, the carbon nanotube dispersion for electrode slurry was subjected to 100 s -1 The viscosity was 114.5 mPa·s, and the particle size distribution determined by laser diffraction was 0.982 μm for D10, 8.78 μm for D50, and 54.93 μm for D90.

[0037] [Preparation of negative electrode slurry] A mixture of graphite, SiO₂, and LSX in a mass ratio of 95:3:2 was used as the negative electrode active material. The negative electrode slurry was prepared by mixing the negative electrode active material, carbon nanotube dispersion for electrode slurry, CMC, lithium polyacrylate, and styrene-butadiene rubber (SBR) in a solid mass ratio of 100:0.02:1:1:0.4.

[0038] [Fabrication of the negative electrode] A negative electrode slurry was applied to both sides of a negative electrode core made of copper foil using a die-coating method. After the coating film was dried, it was rolled using a rolling mill and cut to a predetermined electrode size to produce the negative electrode. The negative electrode was provided with an exposed portion of the negative electrode core material at one end in the width direction for connecting the negative electrode lead.

[0039] [Fabrication of the positive electrode] A lithium transition metal composite oxide of the NCA (Ni-Al-Co) type containing 88% by mass of Ni was used as the positive electrode active material. A carbon nanotube dispersion for positive electrode slurry was prepared, containing multi-walled carbon nanotubes (MWCNTs), polyvinylpyrrolidone (PVP), and N-methyl-2-pyrrolidone (NMP). The NMP was mixed with the carbon nanotube dispersion for positive electrode slurry and polyvinylidene fluoride (PVdF) in a solid mass ratio of 100:0.4:0.8 to prepare the positive electrode slurry. Next, the positive electrode slurry was applied to both sides of a positive electrode core made of aluminum foil by die coating, the coating was dried, and then rolled with a rolling mill and cut to a predetermined electrode size to produce the positive electrode. The positive electrode was provided with an exposed portion of the positive electrode core material for connecting a positive electrode lead at one end in the width direction.

[0040] [Preparation of non-aqueous electrolytes] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:3:4. Lithium hexafluoride phosphate (LiPF6) was dissolved in this mixed solvent at a concentration of 1.2 mol / liter to prepare a non-aqueous electrolyte.

[0041] [Preparation of test cells] A positive electrode lead was attached to the exposed portion of the positive electrode, and a negative electrode lead was attached to the exposed portion of the negative electrode. The positive and negative electrodes were then wound in a spiral shape via a polyolefin separator, and then press-molded radially to produce a flat, wound electrode body. This electrode body was housed in an outer casing made of aluminum laminate sheet, the non-aqueous electrolyte was injected, and the opening of the outer casing was sealed to obtain a test cell (battery capacity: 400mAh).

[0042] [Evaluation of capacity retention rate] The above test cell underwent the following cycle test. The discharge capacity after the first cycle and the discharge capacity after the 200th cycle were determined, and the capacity retention rate was calculated using the following formula. Capacity retention rate (%) = (Discharge capacity at 200 cycles ÷ Discharge capacity at 1 cycle) × 100 <Cycle Testing> The test cell was charged at a constant current of 0.5C under a temperature of 25°C until the battery voltage reached 4.2V. Then, it was charged at a constant voltage of 0.05C until the current value reached 4.2V, and finally discharged at a constant current of 0.7C until the battery voltage reached 2.5V. This constituted one cycle. A 10-minute break was taken between each cycle, and this was repeated 200 times.

[0043] <Example 2> In the preparation of the carbon nanotube dispersion for electrode slurry, the test cell was prepared in the same manner as in Example 1, except that the number of processing steps in the dispersion step was changed to 10. Measurement and evaluation were then performed.

[0044] <Example 3> In the preparation of the carbon nanotube dispersion for electrode slurry, the test cell was prepared in the same manner as in Example 1, except that the number of processing steps was changed to 40. Measurement and evaluation were then performed.

[0045] <Example 4> In the preparation of the carbon nanotube dispersion for electrode slurry, the test cell was prepared in the same manner as in Example 1, except that the number of processing steps was changed to 80. Measurement and evaluation were then performed.

[0046] <Example 5> In the preparation of a carbon nanotube dispersion for electrode slurry, CMC is used in a 3% aqueous solution for 100 seconds. -1 The test cell was prepared and measured / evaluated in the same manner as in Example 2, except that the viscosity of the sample was changed to 21.4 mPa·s.

[0047] <Comparative Example 1> In the preparation of a carbon nanotube dispersion for electrode slurry, CMC is used in a 3% aqueous solution for 100 seconds. -1 The test cell was prepared and measured / evaluated in the same manner as in Example 2, except that the viscosity was changed to 901 mPa·s.

[0048] <Comparative Example 2> In the preparation of a carbon nanotube dispersion for electrode slurry, CMC is used in a 3% aqueous solution for 100 seconds. -1 The test cell was prepared and measured / evaluated in the same manner as in Example 2, except that the viscosity of the sample was changed to 1615 mPa·s.

[0049] <Comparative Example 3> In the preparation of the carbon nanotube dispersion for electrode slurry, the test cell was prepared in the same manner as in Example 1, except that the number of processing steps was changed to 120. Measurement and evaluation were then performed.

[0050] <Comparative Example 4> In the preparation of the carbon nanotube dispersion for electrode slurry, the test cell was prepared in the same manner as in Example 1, except that the number of processing cycles in the dispersion step was changed to 150. Measurement and evaluation were then performed.

[0051] <Comparative Example 5> In the dispersion step for preparing the carbon nanotube dispersion for electrode slurry, a bead mill (DYNO MILL, manufactured by WAB) was used to process the dispersion using the same flow rate (14 L / h) and the same number of cycles (10 times) as in Example 2. Otherwise, a test cell was prepared and measured / evaluated in the same manner as in Example 2.

[0052] <Comparative Example 6> In the dispersion step for preparing the carbon nanotube dispersion for electrode slurry, the test cell was prepared in the same manner as in Example 2, except that the dispersion was processed using an ultrasonic dispersion device (GSD600RAT, manufactured by Sonic Technology Co., Ltd.) at an output setting of 600W, at the same flow rate (14L / h) and the same number of times (10 times) as in Example 2. Measurement and evaluation were then performed.

[0053] Table 1 shows the evaluation results of the volume retention rate in the examples and comparative examples. The volume retention rates of Examples 2-6 and Comparative Examples 1-6 are shown as relative values ​​with the volume retention rate of Example 1 set to 100. In addition, Table 1 also shows the viscosity and concentration of CMC and CNT contained in the carbon nanotube dispersion for electrode slurry, the equipment used in the dispersion step, the viscosity of the carbon nanotube dispersion for electrode slurry, and the particle size distribution of SWCNTs in the carbon nanotube dispersion for electrode slurry.

[0054] [Table 1]

[0055] The test cells in Examples 1 to 5 all have a negative electrode prepared using a carbon nanotube dispersion for electrode slurry that satisfies predetermined conditions. As a result, the test cells in Examples 1 to 5 are able to improve the charge-discharge cycle characteristics of the battery compared to the test cells in Comparative Examples 1 to 6. [Explanation of symbols]

[0056] 10 Electrode, 11 Core material, 12 Electrode mixture layer

Claims

1. 0.1 to 1.5 mass% of carbon nanotubes, Dispersion medium and 100 seconds of 3% aqueous solution at 25°C －１ It contains carboxymethylcellulose having a viscosity of 2 to 200 mPa·s, The carboxymethylcellulose content is 50 to 250 parts by mass per 100 parts by mass of carbon nanotubes in the carbon nanotube dispersion for electrode slurry at 25°C for 100 seconds. －１ The viscosity is 50 to 200 mPa·s. The carbon nanotube dispersion for electrode slurry, wherein the particle size distribution of carbon nanotubes in the dispersion, as determined by laser diffraction, is such that D10 is 0.3 to 1.0 μm, D50 is 3 to 10 μm, and D90 is 60 μm or less.

2. A negative electrode slurry comprising a carbon nanotube dispersion for electrode slurry according to claim 1, a carbon-based negative electrode active material, and a Si-based negative electrode active material.

3. A non-aqueous electrolyte secondary battery comprising a negative electrode prepared using the negative electrode slurry described in claim 2.

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