JP6981344B2 - Manufacturing method of non-aqueous electrolyte secondary battery - Google Patents

Description

The present disclosure relates to a method for manufacturing a non-aqueous electrolyte secondary battery.

Japanese Unexamined Patent Publication No. 2016-170945 (Patent Document 1) discloses a non-aqueous secondary battery containing a composite of a material containing Si and O as constituent elements and a carbon material as a negative electrode active material.

Japanese Unexamined Patent Publication No. 2016-170945

As a negative electrode active material of a non-aqueous electrolyte secondary battery (hereinafter, may be abbreviated as “battery” _{), a compound represented by the general formula SiO x} (where 0 <x ≦ 2) is added to a carbon material (for example, graphite). (Hereinafter, it may also be described as "silicon oxide") is being considered. When silicon oxide is used in addition to the carbon material as the negative electrode active material, an increase in battery capacity is expected.

However, a battery containing a carbon material and silicon oxide as a negative electrode active material tends to have a large capacity decrease due to a charge / discharge cycle. The cause is considered to be that silicon oxide expands and contracts significantly with charge and discharge.

For example, the shrinkage of silicon oxide may separate the silicon oxide from the carbon material and electrically isolate the silicon oxide. Electrically isolated silicon oxide is not considered to contribute to battery capacity. In addition, the expansion of silicon oxide may break the bonds between the carbon materials and disrupt the conductive network between the carbon materials. It is considered that the division of the conductive network between carbon materials causes carbon materials that do not contribute to the battery capacity. It is considered that this deteriorates the cycle characteristics and the high temperature storage characteristics.

The battery disclosed in Patent Document 1 contains a carbon material and silicon oxide as a negative electrode active material. Therefore, it is considered that there is room for improvement in suppressing the deterioration of the cycle characteristics and the deterioration of the high temperature storage characteristics.

An object of the present disclosure is to achieve both suppression of deterioration of cycle characteristics and suppression of deterioration of high temperature storage characteristics in a non-aqueous electrolyte secondary battery containing graphite and silicon oxide as negative electrode active materials.

Hereinafter, the technical configuration and the action and effect of the present disclosure will be described. However, the mechanism of action of the present disclosure includes estimation. The scope of claims should not be limited by the correctness of the mechanism of action.

[1] The method for producing a non-aqueous electrolyte secondary battery of the present disclosure includes at least the following (α) to (γ).
(Α) Silicon oxide and graphite are prepared as negative electrode active materials.
(Β) Negative electrode The active material, binder, and solvent are mixed to obtain a granulated product.
(Γ) The granulated body is transferred to the surface of the negative electrode current collector.
The average particle size A of silicon oxide is 11 μm or more and 21 μm or less. Graphite has an average particle size B of 10 μm or more and 20 μm or less. Silicon oxide and graphite have an average particle size ratio A / B of 0.7 or more and 1.3 or less.

Silicon oxide and graphite used as the negative electrode active material according to the present disclosure satisfy the above relationship. That is, the average particle size A of silicon oxide and the average particle size B of graphite have values close to each other while having an average particle size of at least 10 μm. In addition, the negative electrode is manufactured by transferring the granulated body containing the negative electrode active material to the surface of the negative electrode current collector as a negative electrode mixture layer. That is, the process of manufacturing the negative electrode mixture layer includes a granulation process for obtaining a granulated material.

FIG. 5 is a conceptual diagram showing the arrangement of silicon oxide and graphite in the negative electrode mixture layer of the first reference embodiment. For example, when the ratio A / B of the average particle size A of the silicon oxide 21 and the average particle size B of the graphite 22 is less than 0.7, the average particle size A of the silicon oxide 21 is compared with the average particle size B of the graphite 22. Means small. In such a case, as illustrated in FIG. 5, the particulate silicon oxide 21 may aggregate between the particulate graphite 22 and the graphite 22 in the negative electrode mixture layer, and the silicon oxide 21 may be isolated. .. As a result, it is considered that there is room for improvement in suppressing the deterioration of the cycle characteristics of the battery including the negative electrode.

FIG. 6 is a conceptual diagram showing the arrangement of silicon oxide and graphite in the negative electrode mixture layer of the second reference embodiment. For example, when the ratio A / B of the average particle size A of the silicon oxide 21 and the average particle size B of the graphite 22 exceeds 1.3, the average particle size B of the graphite 22 is compared with the average particle size A of the silicon oxide 21. Means small. In such cases, graphite 22 may have a large BET specific surface area. It is considered that this makes it easier for side reactions to proceed between the graphite 22 and the electrolytic solution. As a result, it is considered that there is room for improvement in suppressing the deterioration of the high temperature storage characteristics of the battery including the negative electrode.

FIG. 1 is a conceptual diagram showing the arrangement of silicon oxide and graphite in the negative electrode mixture layer of the present disclosure. In the present disclosure, since the average particle size A of the silicon oxide 21 and the average particle size B of the graphite 22 are close to each other, the particulate silicon oxide 21 is between the particulate graphite 22 and the graphite 22 in the negative electrode mixture layer. It is considered that the silicon oxide 21 is suppressed from being isolated. Further, it is considered that the increase in the BET specific surface area of the graphite 22 can be suppressed.

The process of obtaining the negative electrode mixture layer of the present disclosure includes a granulation process of obtaining a granulated material. The granulated material has a high solid content and is considered to be clay-like. Therefore, migration occurs when the sheet-shaped granules (that is, the negative electrode mixture layer) are dried, the binder distribution is biased in the negative electrode mixture layer, and the silicon oxide 21 is isolated in the negative electrode mixture layer. It is considered that the conversion is suppressed. By synergizing these characteristics, it is expected that a battery having both suppression of deterioration of cycle characteristics and suppression of deterioration of high temperature storage characteristics can be obtained.

It is a conceptual diagram which shows the arrangement of silicon oxide and graphite in the negative electrode mixture layer of this disclosure. FIG. 2 is a manufacturing flow of the negative electrode of the present embodiment. FIG. 3 is a flowchart showing an outline of a method for manufacturing a non-aqueous electrolyte secondary battery according to the present embodiment. FIG. 4 is a schematic view showing an example of the configuration of an electrode manufacturing apparatus used when manufacturing a negative electrode using the granulated body of the present embodiment. FIG. 5 is a conceptual diagram showing the arrangement of silicon oxide and graphite in the negative electrode mixture layer of the first reference embodiment. FIG. 6 is a conceptual diagram showing the arrangement of silicon oxide and graphite in the negative electrode mixture layer of the second reference embodiment.

Hereinafter, embodiments of the present disclosure (referred to as "the present embodiment" in the present specification) will be described. However, the following description does not limit the scope of claims.

<Manufacturing method of non-aqueous electrolyte secondary battery>
FIG. 3 is a flowchart showing an outline of a method for manufacturing a non-aqueous electrolyte secondary battery according to the present embodiment. The method for manufacturing a battery of the present embodiment includes "(A) manufacturing of a negative electrode", "(B) manufacturing of a positive electrode", and "(C) manufacturing of a battery". Which of "(A) manufacturing of the negative electrode" and "(B) manufacturing of the positive electrode" may be executed first.

<(A) Manufacture of negative electrode>
The method of manufacturing a battery of the present embodiment may include manufacturing a negative electrode.
FIG. 2 is a manufacturing flow of the negative electrode of the present embodiment. The method for producing a negative electrode of the present embodiment includes "preparation of (α) silicon oxide and graphite", "production of (β) granulation", and "transfer of (γ) granulation". Silicon oxide 21 and graphite 22 are negative electrode active materials. The production of granules involves mixing the negative electrode active material, the binder, and the solvent. The granulated body is transferred to the surface of the negative electrode current collector.

That is, in the method for manufacturing the battery of the present embodiment, silicon oxide and graphite are prepared as the negative electrode active material, the negative electrode active material, the binder, and the solvent are mixed to obtain a granulated body, and the granulated body is used as a negative electrode. Includes transferring to the surface of the current collector.

<< Preparation of (α) silicon oxide and graphite >>
The method for manufacturing a negative electrode of the present embodiment includes preparing silicon oxide 21 and graphite 22. The average particle size A of silicon oxide 21 is 11 μm or more and 21 μm or less. Graphite 22 has an average particle size B of 10 μm or more and 20 μm or less. Silicon oxide 21 and graphite 22 have an average particle size ratio A / B of 0.7 or more and 1.3 or less.

Here, the average particle size of the silicon oxide 21 and the graphite 22 can be measured using a scanning electron microscope (SEM). For example, the negative electrode mixture layer is observed using SEM, and an SEM image of the negative electrode mixture layer is obtained. The field of view of the image can be, for example, tens of μm square. Next, the particle sizes of the largest silicon oxide 21 and graphite 22 are measured on the obtained image. The work is performed in at least 10 fields of view. An arithmetic mean of the particle sizes of at least 10 silicon oxides 21 and graphite 22 can be employed as the average particle size.

<< Production of (β) granulated body >>
The method for producing a negative electrode of the present embodiment includes mixing a negative electrode active material, a binder, and a solvent to obtain a granulated product.

(Binder and solvent)
The binder should not be particularly limited. The binder may be, for example, carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyacrylic acid (PAA) or the like. The solvent may be, for example, water.

(Granulator)
The granulation body may contain 85-99% by mass of the negative electrode active material and 1-15% by mass of the binder with respect to the total solid content of the granulation body, and 4 to 15 with respect to the total solid content of the granulation body. It may contain mass% of silicon oxide 21. The granulated body may have, for example, a solid content of 70% by mass or more and 95% by mass or less, preferably 75% by mass or more and 90% by mass or less. Therefore, the granulated body becomes clay-like. Here, the "solid content ratio" indicates the ratio of the mass of the non-solvent component (nonvolatile component) to the total mass of all the raw materials including the solvent. If the solid content of the granulated product is less than 70% by mass, it may be difficult to produce a clay-like granulated product due to the large amount of solvent. When the solid content of the granules exceeds 95 mass, it may be difficult to prepare the granules because the amount of the solvent is small.

<< (γ) Granulation transfer >>
The method for manufacturing a negative electrode of the present embodiment includes transferring a granulated body to the surface of a negative electrode current collector. Thereby, the negative electrode can be manufactured.

(Electrode manufacturing equipment)
FIG. 4 is a schematic view showing an example of the configuration of an electrode manufacturing apparatus used when manufacturing a negative electrode. The electrode manufacturing apparatus 90 shown in FIG. 4 is an MPS apparatus. That is, the negative electrode can be manufactured by the MPS method. The electrode manufacturing apparatus 90 includes three rolls, that is, A roll 91, B roll 92, and C roll 93. Each roll is rotationally driven by a drive device (not shown). In FIG. 4, the curved arrow drawn on each roll indicates the rotation direction of each roll.

The granulated body 1a is supplied to the gap between the A roll 91 and the B roll 92. A load is applied to the A roll 91 in the direction from the A roll 91 toward the B roll 92. Therefore, in the gap between the A roll 91 and the B roll 92, the granulated body 1a is rolled and formed into a sheet shape, and the granulated body 1b is obtained.

The granulated body 1b (sheet body) is conveyed by the B roll 92 and supplied to the gap between the B roll 92 and the C roll 93. The negative electrode current collector 201 is conveyed by the C roll 93 and is supplied to the gap between the B roll 92 and the C roll 93. The negative electrode current collector 201 may be, for example, a copper (Cu) foil.

In the gap between the B roll 92 and the C roll 93, the granulation body 1b is rubbed against the negative electrode current collector 201. As a result, the granulation body 1b is crimped to the current collector 11 and the granulation body 1b is arranged on the surface of the negative electrode current collector 201. That is, the granulated body 1b is transferred from the surface of the B roll 92 to the surface of the negative electrode current collector 201.

By arranging the granulation body 1b on the surface of the negative electrode current collector 201, the granulation body 1b becomes the negative electrode mixture layer 202. After that, an operation of evaporating the solvent remaining in the granulated body 1b may be performed. The solvent evaporation operation can be performed in a drying oven (not shown). Further, a negative electrode for a non-aqueous electrolyte secondary battery can be manufactured by performing compression, cutting, or the like according to the specifications of the battery.

<(B) Manufacture of positive electrode>
The method of manufacturing a battery of the present embodiment may include manufacturing a positive electrode.
The method for manufacturing the positive electrode should not be particularly limited. The positive electrode can be manufactured by a conventionally known manufacturing method. For example, a positive electrode mixture paste can be prepared by mixing a positive electrode active material, a conductive material (for example, acetylene black, etc.), a binder (for example, PVdF, etc.) and a solvent (for example, N-methyl-2-pyrrolidone, etc.). The positive electrode mixture paste can be applied to the surface of the positive electrode current collector and dried to form a positive electrode mixture layer. After drying, the positive electrode mixture layer may be compressed. From the above, a positive electrode can be manufactured. The positive electrode can be used by being cut into a predetermined shape (for example, a band shape) according to the specifications of the battery.

The positive electrode active material electrochemically occludes and releases Li ions. The positive electrode active material should not be particularly limited. The positive electrode active material may be, for example, LiCoO ₂ , LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM), LiMnO ₂ , LiMn ₂ O ₄ , LiFePO _4, or the like. One kind of positive electrode active material may be used alone, or two or more kinds of positive electrode active materials may be used in combination. The positive electrode active material may have an average particle size of, for example, 1 to 30 μm.

<(C) Manufacture of batteries>
The method for manufacturing a battery of the present embodiment includes manufacturing a battery including at least a positive electrode, a negative electrode, and a non-aqueous electrolyte.

For example, a group of electrodes is prepared. The electrode group can be prepared by laminating the positive electrode, the separator and the negative electrode in this order and winding them in a spiral shape. The electrode group can also be prepared by alternately laminating the positive electrode and the negative electrode while sandwiching the separator between the positive electrode and the negative electrode. That is, the electrode group may be a wound type or a laminated type.

The separator is interposed between the positive electrode and the negative electrode. The separator is electrically insulating. The separator is porous. The separator may be, for example, a porous film made of polyethylene (PE), polypropylene (PP), or the like. The separator may have a thickness of, for example, 5 to 30 μm. The separator may include a heat-resistant layer on its surface. The refractory layer contains a refractory material (eg, alumina, etc.). The heat-resistant layer may have a thickness of, for example, 1 to 5 μm.

The exterior is prepared. The exterior body may be square or cylindrical. The exterior body may be, for example, a container made of pure Al, an Al alloy, a stainless alloy, or the like. The exterior body may be a pouch or the like made of an aluminum laminated film. That is, the battery may be a laminated battery.

Electrodes and non-aqueous electrolytes are housed in the exterior. The exterior is sealed. From the above, a battery can be manufactured.

The non-aqueous electrolyte can typically be a liquid electrolyte (electrolyte). However, the non-aqueous electrolyte of the present embodiment may be a gel electrolyte or a solid electrolyte. The electrolyte contains a solvent and a supporting salt. The solvent may be, for example, a mixture of cyclic carbonate and chain carbonate. The mixing ratio may be cyclic carbonate: chain carbonate = 1: 9 to 5: 5 (volume ratio). The cyclic carbonate may be, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or the like. The chain carbonate may be, for example, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) or the like. The cyclic carbonate and the chain carbonate may be used alone or in combination of two or more.

The electrolytic solution may contain, for example, 0.5 to 2 mL / l of a supporting salt. The supporting salt may be, for example, LiPF ₆ , LiBF ₄ , Li [N (FSO ₂ ) ₂ ], Li [N (CF ₃ SO ₂ ) ₂ ], or the like. One kind of supporting salt may be used alone, or two or more kinds of supporting salts may be mixed and used. The electrolytic solution may further contain various functional additives.

<Use, etc.>
It is considered that the battery of the present embodiment has both suppression of deterioration of cycle characteristics and suppression of deterioration of high temperature storage characteristics. Examples of applications in which these characteristics are utilized include driving power sources for hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), electric vehicles (EVs), and the like. However, the use of the battery of this embodiment should not be limited to the power source for driving an automobile. The battery of this embodiment can be applied to all uses.

Hereinafter, examples of the present disclosure will be described. However, the following description does not limit the scope of claims.

<Example 1>
<(A) Manufacture of negative electrode>
The negative electrode was manufactured according to the manufacturing flow shown in FIG.

<< Preparation of (α) silicon oxide and graphite >>
The following materials were prepared Graphite: Average particle size 16 μm
Silicon oxide: average particle size 16 μm
Thickener: CMC
Binder: SBR
Solvent: water

<< Production of (β) granulated body >>
95 parts by mass of graphite 22, 5 parts by mass of silicon oxide 21, 1 part by mass of CMC, 1 part by mass of SBR, and water were mixed by a high speed mixer. As a result, a granulated body 1a was obtained. The solid content of the granulated body 1a was 80% by mass, and the particle size of the granulated body 1a was 1 nm or more. The granulated body 1a was clay-like.

<< (γ) Granulation transfer >>
The electrode manufacturing apparatus 90 shown in FIG. 4 was prepared. As the negative electrode current collector 201, a Cu foil having a thickness of 10 μm was prepared. The granulated body 1a was supplied to the gap between the A roll 91 and the B roll 92. As a result, the granulated body 1b was transferred to the surface of the negative electrode current collector 201. By drying the transferred granulated body 1b, the negative electrode mixture layer 202 was formed on the surface of the negative electrode current collector 201. The negative electrode mixture layer 202 was compressed by the rolling mill. As a result, the negative electrode was manufactured. The negative electrode was cut into strips. In the negative electrode after cutting, the negative electrode mixture layer 202 has the following dimensions.

Width of negative electrode mixture layer: 122 mm
Negative electrode mixture layer length: 5835 mm
Negative electrode mixture layer thickness: 67 μm

<(B) Manufacture of positive electrode>
A positive electrode mixture paste was prepared by mixing 93 parts by mass of NCM, 4 parts by mass of acetylene black, 3 parts by mass of PVdF, and N-methyl-2-pyrrolidone.

As a positive electrode current collector, an Al foil having a thickness of 15 μm was prepared. The positive electrode mixture paste was applied to the surface (both front and back surfaces) of the positive electrode current collector by a coating machine and dried to form a positive electrode mixture layer. The positive electrode mixture layer was compressed by the rolling mill. This produced a positive electrode. The positive electrode was cut into strips. In the positive electrode after cutting, the positive electrode mixture layer has the following dimensions.

Width of positive electrode mixture layer: 117 mm
Length of positive electrode mixture layer: 5681 mm
Thickness of positive electrode mixture layer: 63.5 μm

<(C) Manufacture of batteries>
A strip-shaped porous film was prepared. The porous film has a thickness of 20 μm. The porous film is composed of a porous film made of PP, a porous film made of PE, and a porous film made of PP laminated in this order. A heat-resistant layer was formed on the surface of the porous film. The heat-resistant layer has a thickness of 4 μm. The heat resistant layer contains alumina and binder. From the above, a strip-shaped separator was prepared.

The positive electrode, the separator and the negative electrode were laminated in this order and wound in a spiral shape. As a result, a tubular electrode group was formed. The electrode group was formed into a flat shape by a flat plate press. The molding conditions were room temperature, 4 kN / cm ² , 2 minutes. An external terminal was attached to the electrode group.

The exterior was prepared. The exterior is a square container. The exterior body is made of Al alloy. The electrode group was housed in the exterior body. An electrolytic solution was prepared as a non-aqueous electrolyte. The electrolytic solution has the following composition.

Solvent: [EC: DMC: EMC = 3: 4: 3 (volume ratio)]
Supporting salt: LiPF ₆ (1 mol / l)

120 ml of electrolyte was injected into the exterior. The exterior was sealed. From the above, a non-aqueous electrolyte secondary battery (square lithium ion secondary battery) was manufactured. Batteries are designed to have a rated capacity of 35 Ah in the voltage range of 2.5 to 4.1 V.

<Example 2>
As shown in Table 1 below, except that the average particle size A of the silicon oxide 21 used for producing the granulated body 1a and the solid content ratio of the granulated body 1a were changed, the same as in Example 1. Batteries were manufactured in the same way.

<Example 3>
As shown in Table 1 below, the battery was manufactured in the same manner as in Example 1 except that the average particle size A of the silicon oxide 21 used for manufacturing the granulated body 1a was changed.

<Example 4 and Example 5>
As shown in Table 1 below, the batteries were manufactured in the same manner as in Example 1 except that the migration index was changed.

<Comparative Example 1>
As shown in Table 1 below, except that the average particle size A of the silicon oxide 21 used for producing the granulated body 1a and the solid content ratio of the granulated body 1a were changed, the same as in Example 1. Batteries were manufactured in the same way.

<Comparative Example 2>
As shown in Table 1 below, the battery was manufactured in the same manner as in Example 1 except that the average particle size A of the silicon oxide 21 used for manufacturing the granulated body 1a was changed.

<Comparative Example 3>
As shown in Table 1 below, the same as in Example 1 except that the average particle size B of the graphite 22 used for producing the granulated body 1a and the solid content ratio of the granulated body 1a are changed. Batteries were manufactured in.

<Comparative Example 4>
As shown in Table 1 below, the average particle size A of the silicon oxide 21 used in the production of the granulated body 1a, the average particle size B of the graphite 22, and the solid content ratio of the granulated body 1a have been changed. Except for this, the battery was manufactured in the same manner as in Example 1.

<Comparative Example 5 and Comparative Example 6>
As shown in Table 1 below, the solids content and migration index of the granulated body 1a were changed. In Comparative Example 5 and Comparative Example 6, the solid component of the granulated body 1a was low, and the granulated body 1a was not clay-like but paste-like. The paste-like granulated material 1a was applied to the surface (both front and back surfaces) of the negative electrode current collector 201 and dried to form the negative electrode mixture layer 202. Except for the above, the battery was manufactured in the same manner as in Example 1.

<Evaluation>
《Cycle test》
In each battery, 100 charge / discharge cycles were executed. One cycle shows a cycle of discharging with a constant current of 2C (3V cutoff) and charging with a constant current of 2C (4.1V cutoff). The discharge capacity at 100 cycles was measured. The results are shown in the "Cycle Characteristics" column of Table 1 below. The values shown in the “Cycle characteristics” column of Table 1 are relative values when the discharge capacity of Comparative Example 1 is “1”. The larger the value of the cycle characteristic, the larger the discharge capacity at 100 cycles. That is, it is shown that the deterioration of the cycle characteristics is suppressed.

<Initial capacity measurement test>
CCCV discharge was performed from 4.1 V to 2.5 V at a current value of 1 / 3C for the batteries according to the Examples and Comparative Examples in the initial state, and the initial capacity [Ah] was measured (termination current 0. 05C).

<High temperature storage test>
The batteries according to the Examples and Comparative Examples that had undergone the initial capacity measurement test were charged by CCCV charging to 4.2 V (SOC 100%) at a current value of 1 / 3C (termination current 0.05 C). Then, each battery was stored for 60 days in a constant temperature bath set at 60 ° C. After 60 days, each battery was taken out and the battery capacity after high temperature storage was measured in the same manner as the initial capacity. The capacity recovery rate was calculated by dividing the battery capacity after high temperature storage by the initial capacity. The results are shown in the "Preservation Properties" column of Table 1. The larger the value of the storage characteristic, the larger the capacity recovery rate after the high temperature storage test. That is, it is shown that the deterioration of the high temperature storage characteristic is suppressed.

<Migration index>
The distribution of the binder (SBR) in the negative electrode mixture layer 202 was evaluated using the migration index. The migration index was calculated by analyzing the cross section of the negative electrode mixture layer 202 by SEM-EDX (Energy Dispersive X-ray spectroscopy). The measurement procedure is as follows. First, a sample for cross-section observation was cut out from the negative electrode mixture layer 202, and the cross-section was cleaned using a cross-section polisher or the like. The SBR double bond was then modified with bromine (Br). After modifying the SBR, the cross section was surface-analyzed with SEM-EDX to perform Br mapping. At this time, the cross section was divided into two equal parts in the thickness direction, and the negative electrode current collector 201 side was designated as the first region and the surface side of the negative electrode mixture layer 202 was designated as the second region. The migration index was calculated by dividing the integrated value of the detected intensity of Br in the second region by the integrated value of the detected intensity of Br in the first region. The results are shown in the "Migration Index" column of Table 1. If the binder is uniformly distributed in the negative electrode mixture layer 202, the migration index will be close to 1.0. Further, if the binder segregates on the surface side (second region) of the negative electrode mixture layer 202, the migration index becomes a large value (for example, 1.5 or more).

<Result>
As shown in Table 1, the examples had good cycle and storage properties. That is, in the non-aqueous electrolyte secondary battery containing graphite 22 and silicon oxide 21 as the negative electrode active material, both suppression of deterioration of cycle characteristics and suppression of deterioration of high temperature storage characteristics were achieved. In the examples, the migration index was 0.7 or more and 1.2 or less. This result indicates that the binder is distributed substantially uniformly in the negative electrode mixture layer 202. It is considered that this prevented the silicon oxide 21 from being isolated.

Comparative Example 1 had lower cycle characteristics than Examples. Since the average particle size A of the silicon oxide 21 is as small as 6 μm and the A / B is as small as 0.4, aggregation of the silicon oxide 21 occurs as illustrated in FIG. 5, and in the negative electrode mixture layer 202. It is considered that the silicon oxide 21 is isolated. As a result, it is considered that the cycle characteristics have deteriorated.

Comparative Example 2 had lower cycle characteristics than Examples. The average particle size A of the silicon oxide 21 was as large as 24 μm, and the A / B was as large as 1.5. Therefore, it is considered that the volume change of the silicon oxide 21 due to charging and discharging becomes large, and the silicon oxide 21 is isolated in the negative electrode mixture layer 202. As a result, it is considered that the cycle characteristics have deteriorated.

Comparative Example 3 had lower cycle characteristics and storage characteristics than Examples. The A / B was a large value of 2.7, and the average particle size A of the silicon oxide 21 was larger than the average particle size B of the graphite 22. Therefore, it is considered that the silicon oxide 21 is isolated. Therefore, it is considered that the cycle characteristics have deteriorated. In addition, the average particle size B of graphite 22 was as small as 6 μm. Therefore, it is considered that graphite 22 had a large BET specific surface area. As a result, it is considered that a side reaction proceeded between the graphite 22 and the electrolytic solution, and the storage characteristics deteriorated.

Comparative Example 4 had lower storage characteristics than Examples. The average particle size B of graphite 22 was as small as 6 μm. Therefore, it is considered that graphite 22 had a large BET specific surface area. As a result, it is considered that a side reaction proceeded between the graphite 22 and the electrolytic solution, and the storage characteristics deteriorated.

Comparative Example 5 and Comparative Example 6 had lower cycle characteristics than the examples. These comparative examples had a high migration index. That is, the binder segregated on the surface side (second region) of the negative electrode mixture layer 202. It is probable that migration occurred when the paste-like granulated body 1a applied to the surface of the negative electrode current collector 201 was dried. It is probable that the silicon oxide 21 was isolated due to the uneven distribution of the binder in the negative electrode mixture layer 202, and the cycle characteristics were deteriorated.

The embodiments and examples disclosed this time are exemplary in all respects and are not restrictive. The technical scope defined by the scope of claims includes all changes within the meaning and scope equivalent to the scope of claims.

1a, 1b granulation, 21 silicon oxide, 22 graphite, 90 electrode manufacturing equipment, 91 A roll, 92 B roll, 93 C roll, 201 negative electrode current collector, 202 negative electrode mixture layer.

Claims (1)

Preparing silicon oxide and graphite as the negative electrode active material,
The negative electrode active material, the binder, and the solvent are mixed to obtain a granulated body, and
Including transferring the granulated material to the surface of a negative electrode current collector.
The silicon oxide has an average particle size A of 11 μm or more and 16 μm or less.
The graphite has an average particle size B of 10 μm or more and 16 μm or less.
The silicon oxide and the graphite have an average particle size ratio A / B of 0.7 or more and 1.3 or less.
The granulated body has a solid content of 75% by mass or more and 90% by mass or less.
A method for manufacturing a non-aqueous electrolyte secondary battery.

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