JP6207207B2 - Method for adjusting irreversible capacity of positive electrode for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a positive electrode for a non-aqueous electrolyte secondary battery capable of occluding and releasing lithium, a positive electrode composite, and a non-aqueous electrolyte secondary battery.

In recent years, non-aqueous electrolyte secondary batteries have become widespread for reasons such as having a high energy density. Such a nonaqueous electrolyte secondary battery utilizes the principle of charging and discharging by moving lithium ions between the positive electrode and the negative electrode.
As a positive electrode active material used for a non-aqueous electrolyte secondary battery, a compound having a layered rock salt structure such as lithium cobaltate (LiCoO ₂ ) and lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), etc. Lithium transition metal composite oxides such as compounds having a spinel structure are known. In addition, compounds in which part of the transition metal in these composite oxides is substituted with other metals have been proposed.

Further, carbon materials such as graphite and hard carbon are generally used as the negative electrode active material. Recently, in order to improve the energy density of batteries, metal materials having a high capacity such as silicon and tin have been studied.
A nonaqueous electrolyte secondary battery generally has a larger irreversible capacity of a negative electrode than a positive electrode. Therefore, lithium inserted into the negative electrode from the positive electrode in the first charge remains in the negative electrode without being discharged from the negative electrode during discharge, resulting in a decrease in the capacity of the positive electrode and a decrease in the capacity of the battery.
For example, techniques described in Patent Documents 1 to 4 have been proposed as techniques for increasing the irreversible capacity to increase the energy density.

In Patent Document 1, Li _y Ni _1-x Ti _x O ₂ (where 0 <x <0.7 and 1 ≦ y ≦ 1.1) is provided separately from the active material in the positive electrode layer. An irreversible capacity of the positive electrode is obtained by forming a positive electrode containing an appropriate amount of the represented compound as an additive and setting the cut-off potential of the non-aqueous electrolyte secondary battery equipped with the positive electrode to 4.2 to 5.0 V. Is described.

  Patent Document 2 describes that a lithium metal film is formed on the surface of the positive electrode facing the negative electrode, and lithium for the irreversible capacity of the negative electrode is filled in the negative electrode by the first charge. Patent Document 3 describes that metallic lithium is provided on the surface of a separator to supplement the negative electrode with lithium for the irreversible capacity of the negative electrode.

  In Patent Document 4, at least one cycle of charge and discharge is performed with a lithium supply source and a negative electrode using silicon or tin as an active material, thereby supplementing the negative electrode with lithium for the irreversible capacity of the negative electrode. Describes a method of constructing a lithium ion secondary battery with a negative electrode and a positive electrode supplemented with lithium.

JP 2010-129481 A Japanese Patent Laid-Open No. 2004-87251 JP 2007-220552 A JP 2008-4466 Gazette

However, as a result of intensive studies by the present inventors, the conventional prior art has the following problems.
Patent Document 1 describes that a compound represented by Li _y Ni _1-x Ti _x O ₂ is used as an additive. However, since it has not only an irreversible capacity but also a reversible capacity, the irreversible of the positive electrode. In order to increase the capacity, the amount of addition increases, leading to a decrease in the energy density of the battery. Furthermore, since it also has a function as an active material, deterioration may occur due to repeated charge and discharge.

  Patent Document 2 describes that the irreversible capacity of the negative electrode is compensated by the lithium metal film formed on the surface of the positive electrode, and Patent Document 3 describes that the irreversible capacity of the negative electrode is compensated by the lithium metal film formed on the surface of the separator. Then it is described. Vapor deposition is recommended as a method for forming these lithium metal films on the positive electrode and the separator, but deterioration may occur because a binder or polyolefin having low heat resistance is used for the positive electrode or the separator. Furthermore, an increase in manufacturing equipment for forming a lithium metal film and equipment for suppressing the reaction between the formed lithium metal and moisture are required.

  In Patent Document 4, a dedicated cell for filling the irreversible capacity of the negative electrode using silicon or tin as an active material is necessary, and at least one cycle of charge / discharge is performed to separate the negative electrode supplemented with the irreversible capacity from the dedicated cell. However, since silicon and tin have a very large volume change due to charge / discharge, the negative electrode active material may fall off even if charge / discharge is performed even in one cycle.

  The present invention has been made in view of the above-described circumstances, and a positive electrode for a non-aqueous electrolyte secondary battery that can be easily controlled to an irreversible capacity suitable for increasing the energy density of the secondary battery, and a non-aqueous electrolyte secondary An object of the present invention is to provide a positive electrode composite material and a non-aqueous electrolyte secondary battery.

To solve the problems described above, the present invention is a positive electrode containing an active material capable of at least lithium storage and release, is contained A l-Si alloy, the amount of the Al-Si alloy, the positive electrode and the combination by adjusting in response to the irreversible capacity of the negative electrode to be the irreversible capacity of the positive electrode, a comparable irreversible capacity of the negative electrode, and a nonaqueous electrolyte, characterized in der Rukoto more 3.1mAh / g Provided is a method for adjusting the irreversible capacity of a positive electrode for a secondary battery.

According to the construction of this, it is possible to suppress a decrease capacity of the battery by the irreversible capacity of the negative electrode, to obtain a positive electrode having a suitable irreversible capacity in the high energy density of the secondary battery easily.
In the above structure, the Al—Si alloy is heat-treated to promote the formation of an Al—Si eutectic structure.

  In the above structure, the Al content of the Al—Si alloy is 0.5% by mass or more. According to this configuration, a sufficient positive electrode irreversible capacity can be obtained.

  In the above structure, the positive electrode further includes a conductive material and a binder. According to this configuration, it is possible to ensure the conductivity of electrons and the adhesion of active materials, Al-Si alloys, and the like.

Further, the nonaqueous electrolyte secondary battery of the present invention includes at least a positive electrode including an active material capable of occluding and releasing lithium, a negative electrode capable of occluding and releasing lithium, a separator disposed between these positive and negative electrodes, The positive electrode contains an Al-Si alloy whose formation of an eutectic structure of Al-Si is promoted by heat treatment, and the added amount of the Al-Si alloy is combined with the positive electrode It is an amount for obtaining an irreversible capacity equivalent to the irreversible capacity of the negative electrode, and an amount for obtaining an irreversible capacity of 3.1 mAh / g or more . According to this configuration, a secondary battery having an irreversible capacity equivalent to the irreversible capacity of the negative electrode and having a high energy density can be obtained.

The present invention can suppress a decrease in battery capacity due to the irreversible capacity of the negative electrode, and easily obtain a positive electrode having an irreversible capacity suitable for increasing the energy density of the secondary battery.

It is the figure which showed typically the combination of the positive electrode and negative electrode from which irreversible capacity | capacitance differs. It is the figure which showed the charging / discharging curve of the positive electrode when the addition amount of an Al-Si alloy is changed. It is the figure which showed the charging / discharging curve of the positive electrode when Si content in an Al-Si alloy was changed.

  As a result of intensive studies on the problems of the prior art, the present inventors have found that a positive electrode active material layer and an alloy containing aluminum (Al) and silicon (Si) as additives separately from the active material. It has been found that the irreversible capacity of the positive electrode can be easily controlled by using an electrode containing a non-aqueous electrolyte secondary battery as a positive electrode (also referred to as a positive electrode plate).

A positive electrode for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention will be described. The positive electrode is produced by applying a positive electrode mixture containing a positive electrode active material, aluminum (Al), silicon (Si), etc. to a current collector, and then evaporating and scattering the solvent by drying.
Hereinafter, the case where an aluminum (Al) -silicon (Si) alloy is used will be described.
The positive electrode active material is not particularly limited as long as it can be used for a nonaqueous electrolyte secondary battery. For example, lithium metal oxides such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , and lithium iron phosphate (LiFePO ₄ ) Can be mentioned. In particular, LiFePO ₄ is preferable, and it is preferable that carbon of several nm is coated on the particle surface.

  In addition, an Al-Si alloy can be produced by, for example, gas atomization using a molten metal having a predetermined composition or mechanical alloying from a mixed powder composed of a predetermined proportion of aluminum powder and silicon powder. Commercially available Al—Si alloy powder can also be used. The composition is 0.5% by mass or more of silicon and the balance is aluminum. Magnesium, titanium, vanadium, chromium, manganese, iron, nickel, zinc, copper, etc., as long as the effects of the present invention are not affected. These elements may be included.

The active material layer contains an Al—Si alloy in addition to the positive electrode active material, and is used in a powder form. The particle diameter of the Al—Si alloy is preferably 0.1 μm to 50 μm. If it is less than 0.1 μm, it is difficult to handle, and if it exceeds 50 μm, it is difficult to apply uniformly.
The content of the Al—Si alloy in the positive electrode active material layer is appropriately adjusted depending on the irreversible capacity of the negative electrode (also referred to as negative electrode plate) combined with the positive electrode.

Here, FIG. 1 is a diagram schematically showing a combination of a positive electrode and a negative electrode having different irreversible capacities. In FIG. 1, the positive electrode A indicates a conventional general positive electrode, that is, a positive electrode having a remarkably small irreversible capacity compared to the negative electrode.
Moreover, in FIG. 1, the positive electrode B has shown the positive electrode used by this embodiment. FIG. 1 schematically shows the end positions of charge and discharge when the positive electrodes A and B are combined with the negative electrode in FIG.
As shown in FIG. 1, in this embodiment, the positive electrode B has an irreversible capacity equivalent to the irreversible capacity of the negative electrode. The battery capacity reduction due to the irreversible capacity can be suppressed, and the battery capacity that can be charged and discharged, that is, the capacity of the secondary battery can be increased. This makes it possible to obtain a non-aqueous electrolyte secondary battery with a high energy density.

The Si content of the Al—Si alloy (Si concentration in the Al—Si alloy) is preferably 0.5% by mass (hereinafter simply referred to as “%”) or more. When the Si content is less than 0.5%, the current response due to the oxidation reaction of the Al—Si alloy is small and a sufficient positive electrode irreversible capacity cannot be obtained, and the irreversible capacity of the negative electrode cannot be offset.
The Al—Si alloy is preferably heated to 200 ° C. or higher, which is the eutectic temperature of the Al—Si binary system. This is because the formation of an Al—Si eutectic structure can be promoted by heating at 200 ° C. or higher.

The positive electrode mixture preferably further contains a conductive material and a binder in addition to the above-described active material and Al—Si alloy. Moreover, the positive electrode mixture may further contain a thickener or a dispersant.
The conductive material is not particularly limited, and a known or commercially available material can be used. Examples thereof include carbon black such as acetylene black and ketjen black, carbon nanotubes, carbon fibers, activated carbon, and graphite.

  A binder is not specifically limited, A well-known or commercially available thing can be used. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), acrylic resin and the like.

  The solvent is not particularly limited, and known or commercially available solvents can be used. For example, N-methyl-2-pyrrolidone, water and the like can be mentioned. When using polyvinylidene fluoride as a binder, it is preferable to use N-methyl-2-pyrrolidone as a solvent. When using polyvinyl alcohol, carboxymethyl cellulose, or the like as a binder, water is preferably used as a solvent. preferable.

The negative electrode is not particularly limited as long as it can be used for a non-aqueous electrolyte secondary battery, and a graphite negative electrode capable of occluding and releasing lithium and a metal / oxide / alloy negative electrode are widely applicable.
The negative electrode active material is not particularly limited. For example, natural graphite, artificial graphite, mesocarbon microbeads (MCMB), carbon materials such as hard carbon and soft carbon, and lithium such as Al, Si, and Sn are occluded and released. Metal materials and alloy materials that can be used, oxide materials such as SiO, SiO ₂ , and lithium titanate (Li ₄ Ti ₅ 0 ₁₂ ) can be used.

  The binder is not particularly limited. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, styrene butadiene rubber, core shell binder, polyvinyl alcohol, carboxymethyl cellulose, polyimide, and polyamide. An imide resin such as imide can be used.

As the conductive additive, the same materials as those used for the positive electrode, for example, carbon black such as acetylene black and ketjen black, activated carbon, graphite and the like are used.
For the separator between the positive electrode and the negative electrode, generally used polymer films such as polyethylene (PE) and polypropylene (PP) are used. As the non-aqueous electrolyte, lithium hexafluorophosphate (LiPF ₆ ) or lithium perchlorate (LiClO ₄ ) dissolved in an organic solvent such as ethylene carbonate (EC) or diethyl carbonate (DEC) is used.

  The current collector is not particularly limited, and for example, a metal foil such as an aluminum foil or a copper foil, a porous metal such as porous aluminum, or the like can be used.

  Below, an Example and a comparative example are given and this invention is explained in full detail. The present invention is not limited to the following examples.

<Example 1>
(Preparation of Al-Si alloy)
The A1-12.6% Si alloy was heat-treated at 580 ° C. for 5 minutes in a vacuum. Then, it cooled to 25 degreeC.

(Preparation of positive electrode)
As the positive electrode active material, 100 parts by weight of carbon-coated lithium iron phosphate, 6.8 parts by weight of acetylene black as a conductive material, and a solid content concentration of 40 wt. % Acrylic copolymer 3 parts by weight (as solid content), as additive, A1-12.6% Si alloy is 0.5% by mass with respect to the positive electrode active material, and as a dispersant, Solid content concentration 2 wt. A positive electrode mixture containing 2 parts by weight of carboxymethyl cellulose (as solid content) was prepared, and the positive electrode mixture was dispersed in 20 g of ion-exchanged water as a solvent to prepare a slurry.
This slurry was applied to an aluminum foil having a thickness of 20 μm as a current collector (coating amount: 70 g / m ² ), dried at 70 ° C. for 10 minutes, and then adjusted to a predetermined electrode density (1.80 g / cc). Pressurization was performed by pressing until the positive electrode 1 was produced.

(Production of evaluation cell)
A tripolar evaluation cell using the positive electrode 1 as a working electrode was produced. Lithium metal was used for the counter electrode and the reference electrode. The electrolyte used was a non-aqueous electrolyte obtained by dissolving 1.3 mol / L of LiPF ₆ in a mixed solvent (volume ratio 2: 5: 3) with ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate. A microporous polyethylene membrane was used. A resin container in which a polypropylene block was processed was used for the exterior body, and the electrode group was housed and sealed so that the open ends of the terminals provided on the working electrode, the counter electrode, and the reference electrode were exposed to the outside.

(Battery test)
The charge / discharge characteristics were evaluated using the battery. In the charge / discharge test, the battery was charged at 0.1 C to 4.2 V and discharged at 0.1 C to 2.0 V. The charging capacity, the discharging capacity, the irreversible capacity that is the difference between the charging capacity and the discharging capacity, and the efficiency that is the ratio of the discharging capacity to the charging capacity were investigated.

<Example 2>
A positive electrode 2 was produced in the same manner as in Example 1 except that an A1-12.6% Si alloy as an additive was changed to 1.5 mass% with respect to the positive electrode active material. Next, an evaluation cell similar to that in Example 1 was prepared except that the positive electrode 2 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

<Example 3>
A positive electrode 3 was produced in the same manner as in Example 1 except that an A1-12.6% Si alloy as an additive was changed to 3.0% by mass with respect to the positive electrode active material. Next, an evaluation cell similar to that in Example 1 was prepared except that the positive electrode 3 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

<Example 4>
A positive electrode 4 was produced in the same manner as in Example 1 except that A1-12.6% Si alloy as an additive was changed to 10.0% by mass with respect to the positive electrode active material. Next, an evaluation cell similar to that in Example 1 was prepared except that the positive electrode 4 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

<Comparative Example 1>
100 parts by weight of carbon-coated lithium iron phosphate as a positive electrode active material, 6.8 parts by weight of acetylene black as a conductive material, and 3 parts by weight of an acrylic copolymer having a solid content concentration of 40% by mass as a binder. (As solid content), and as a dispersant, a positive electrode mixture containing 2 parts by weight (as solid content) of carboxymethyl cellulose having a solid content concentration of 2% by mass in an aqueous solution is prepared. The slurry was dispersed in 20 g of ion-exchanged water as a solvent.
This slurry was applied to an aluminum foil having a thickness of 20 μm as a current collector (coating amount: 70 g / m ² ), dried at 70 ° C. for 10 minutes, and then adjusted to a predetermined electrode density (1.80 g / cc). Pressurization was performed by press treatment until a positive electrode 5 was produced.
An evaluation cell similar to that in Example 1 was prepared except that the positive electrode 5 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

  Table 1 shows the initial charge / discharge capacity of the positive electrode 1 to the positive electrode 5, the irreversible capacity of the positive electrode, and the efficiency as the ratio of the discharge capacity to the charge capacity. Moreover, the charging / discharging curve of the positive electrode 1-the positive electrode 5 is shown in FIG. In FIG. 2, “Potential” indicates a potential, and “Capacity” indicates a capacity.

As is clear from the results shown in Table 1, the positive electrode 1 to the positive electrode 4 have a large charge capacity and irreversible capacity as compared with the positive electrode 5, and furthermore, the discharge capacity is equivalent, so that the low efficiency (53.4% to 92.0%). The reason why such performance is obtained is considered to be because an oxidation reaction derived from the A1-Si alloy occurs in the vicinity of 4 V (vs. Li) as shown in FIG.
Moreover, as shown in Table 1, the larger the amount of Al-Si alloy added, the larger the initial charge capacity and the irreversible capacity, and the lower the efficiency.

  Next, in order to confirm the effect of the Si content in the Al—Si alloy, the test was performed by changing the Si content (Si concentration).

<Example 5>
(Preparation of Al-Si alloy)
The A1-0.5% Si alloy was heat-treated at 350 ° C. for 1 hour in a vacuum. Then, it cooled to 25 degreeC.

As the positive electrode active material, 100 parts by weight of carbon-coated lithium iron phosphate, 6.8 parts by weight of acetylene black as a conductive material, and a solid content concentration of 40 wt. % Acrylic copolymer 3 parts by weight (as solids), A1-0.5% Si alloy 10% by weight as additive, and solids concentration 2wt. A positive electrode mixture containing 2 parts by weight of carboxymethyl cellulose (as solid content) was prepared, and the positive electrode mixture was dispersed in 20 g of ion-exchanged water as a solvent to prepare a slurry.
This slurry was applied to an aluminum foil having a thickness of 20 μm as a current collector (coating amount: 70 g / m ² ), dried at 70 ° C. for 10 minutes, and then adjusted to a predetermined electrode density (1.80 g / cc). The positive electrode 6 was manufactured by pressurizing until it became. Next, an evaluation cell similar to that in Example 1 was prepared except that the positive electrode 6 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

<Example 6>
A positive electrode 7 was produced in the same manner as in Example 1 except that the Si content in the Al—Si alloy was changed to Al-2.4% Si. Next, an evaluation cell similar to that in Example 1 was prepared except that the positive electrode 7 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

<Example 7>
A positive electrode 8 was produced in the same manner as in Example 1 except that the Si content in the Al—Si alloy was changed to Al-4.8% Si. Next, an evaluation cell similar to that in Example 1 was prepared except that the positive electrode 8 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

<Example 8>
A positive electrode 9 was produced in the same manner as in Example 1 except that the Si content in the Al—Si alloy was changed to Al-8.0% Si. Next, an evaluation cell similar to that in Example 1 was prepared except that the positive electrode 9 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

<Comparative example 2>
A positive electrode 10 was produced in the same manner as in Example 1 except that the Si content in the Al-Si alloy was changed to Al-0.4% Si. Next, an evaluation cell similar to that in Example 1 was prepared except that the positive electrode 10 was used as a test electrode, and a battery test similar to that in Example 1 was performed.

  Table 2 shows the charge / discharge capacity, positive electrode irreversible capacity, and efficiency of the positive electrode 4 and the positive electrodes 6 to 10. Moreover, the charge / discharge curves of the positive electrode 4 and the positive electrode 6 to the positive electrode 10 are shown in FIG. In FIG. 3, “Potential” indicates a potential, and “Capacity” indicates a capacity.

  As is clear from the results shown in Table 2, the positive electrode 4 and the positive electrodes 6 to 9 have a larger initial charge capacity and irreversible capacity than the positive electrode 10, and furthermore, the initial discharge capacity is the same. 53.4% to 98.1%). It is considered that the reason why such performance is obtained is that an irreversible reaction derived from the A1-Si alloy occurs in the vicinity of 4 V (vs. Li) as shown in FIG.

  Thus, the irreversible capacity of the positive electrode can be easily controlled by adjusting the addition amount of the Al—Si alloy and the Si content. For this reason, it is equivalent to the irreversible capacity of a negative electrode by using a positive electrode with an appropriate amount of A1-Si alloy added to a graphite negative electrode or a metal / oxide / alloy negative electrode with high capacity but low efficiency. A positive electrode having an irreversible capacity can be easily obtained. Therefore, it is possible to suppress a decrease in battery capacity due to the irreversible capacity of the negative electrode and obtain a non-aqueous electrolyte secondary battery with high energy density.

As described above, according to the present embodiment, the positive electrode including at least an active material capable of occluding and releasing lithium has at least aluminum (Al) and silicon (Si) such as an Al—Si alloy as additives. Therefore, the irreversible capacity of the positive electrode can be easily controlled, and as a result, a positive electrode having an irreversible capacity suitable for increasing the energy density of the nonaqueous electrolyte secondary battery can be easily obtained.
For example, when a 10 Ah non-aqueous electrolyte secondary battery is manufactured using a known method in which the positive electrode active material is lithium iron phosphate and the negative electrode active material is carbon, the irreversible capacity of the negative electrode is 1.5 Ah. On the other hand, when the positive electrode 7 of the present invention is used, the irreversible capacity of the negative electrode is about 1.5 Ah. That is, according to the present invention, the irreversible capacities of the positive electrode and the negative electrode are substantially the same, and a high-capacity nonaqueous electrolyte secondary battery can be obtained.
Since this configuration does not require high-voltage charging as compared with Patent Document 1 described above, it is possible to suppress decomposition of the electrolytic solution, gas generation, deterioration of the active material, and the like. Compared to the above, since it is not necessary to deposit a lithium metal film on the surface of the positive electrode, it is not necessary to deteriorate the metal film or add equipment for forming the metal film. Further, as compared with Patent Document 4, there is an effect that a dedicated cell is unnecessary.

Furthermore, in this configuration, since the Si content of the Al—Si alloy is 0.5 mass% or more, a sufficient positive electrode irreversible capacity can be obtained.
In addition, since the positive electrode active material layer includes a conductive material and a binder, it is possible to ensure electronic conductivity and adhesion of the active material, an Al—Si alloy, and the like.
In the present embodiment, an example in which an Al—Si alloy is added to the positive electrode active material separately from the positive electrode active material has been described, but the same may be true even when an alloy containing aluminum (Al) and silicon (Si) is added. It is possible to obtain the effect.
Although the positive electrode active material in the present embodiment shows an example using the carbon-coated lithium iron phosphate, lithium cobalt oxide (LiCoO _2), lithium nickelate (LiNiO _2), lithium manganate (LiMn ₂ O ₄₎ The same effect can be obtained even if a lithium metal compound is used.

Claims (5)

A positive electrode containing an active material capable of at least lithium storage and release, is contained A l-Si alloy,
The amount of the Al-Si alloy, wherein by adjusting according to the irreversible capacity of the negative electrode to be combined with the positive electrode, the irreversible capacity of the positive electrode, a comparable irreversible capacity of the negative electrode, and, 3.1MAh irreversible capacity adjustment method of a positive electrode for a non-aqueous electrolyte secondary battery according to / g or more der wherein Rukoto.   The method for adjusting the irreversible capacity of a positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the Al—Si alloy is subjected to a heat treatment that promotes formation of an eutectic structure of Al—Si.   The method for adjusting the irreversible capacity of a positive electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the Si content of the Al-Si alloy is 0.5 mass% or more.   The irreversible capacity adjustment method for a positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the positive electrode further contains a conductive material and a binder. A positive electrode including at least an active material capable of occluding and releasing lithium; a negative electrode capable of occluding and releasing lithium; a separator disposed between the positive and negative electrodes; and a non-aqueous electrolyte.
The positive electrode contains Al-Si alloy formation of the eutectic structure of Al-Si is promoted by applying a heat treatment,
Said amount of Al-Si alloy, an amount obtained irreversible capacity equivalent to the irreversible capacity of the negative electrode to be combined with the positive electrode, and an amount to obtain the irreversible capacity of more 3.1mAh / g nonaqueous electrolyte secondary batteries characterized.

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