JP2019046688A - Method for manufacturing lithium ion secondary battery - Google Patents

Abstract

To provide a method for manufacturing a lithium ion secondary battery in which an amount of aluminum depositing on a negative electrode is reduced.SOLUTION: A method for manufacturing a lithium ion secondary battery comprises the step of performing an initial charging operation from a positive electrode potential Vat time of starting to initially charge the lithium ion secondary battery through a positive electrode potential Vto a positive electrode final potential Vunder a particular condition, provided that the lithium ion secondary battery comprises: a positive electrode plate including positive electrode collector foil made of aluminum, and a positive electrode active material layer formed on a surface of the positive electrode collector foil; a negative electrode plate including negative electrode collector foil and a negative electrode active material layer formed on a surface of the negative electrode collector foil; a separator; and an electrolyte solution containing a lithium salt selected from lithium salts given by the general formula (1) and general formula (2). In the lithium ion secondary battery, a positive electrode uncoated part is present on the surface of the positive electrode collector foil, where the positive electrode active material layer is not formed; the positive and negative electrode plates are opposed to each other through the separator; and the positive electrode uncoated part is opposed to an end portion of the negative electrode active material layer.SELECTED DRAWING: None

Description

  The present invention relates to a method of manufacturing a lithium ion secondary battery.

In general, a lithium ion secondary battery comprises a positive electrode, a negative electrode and an electrolyte as main components. Then, an appropriate electrolyte is added to the electrolytic solution in an appropriate concentration range. For example, lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, etc. are added as electrolytes to the electrolyte of lithium ion secondary batteries. The concentration of the lithium salt in the electrolyte is generally about 1 mol / L.

  In addition, in order to dissolve the electrolyte suitably, an organic solvent having a high dielectric constant and high dipole moment, such as ethylene carbonate and propylene carbonate, is used as a mixture in an amount of about 30% by volume or more in the organic solvent used for the electrolytic solution. Is common.

  In addition, as reported in many documents, it is general to use a metal foil made of aluminum as a current collector in a positive electrode of a lithium ion secondary battery.

In fact, Patent Document 1 uses a mixed organic solvent containing 33% by volume of ethylene carbonate, and an electrolyte containing LiPF ₆ at a concentration of 1 mol / L, and a positive electrode using a positive electrode current collector foil made of aluminum. SUMMARY A lithium ion secondary battery is disclosed.

  Recently, Patent Document 2 reports an electrolytic solution containing a metal salt as an electrolyte at a high concentration and a lithium ion secondary battery equipped with the electrolytic solution, and the electrolytic solution is compared with a low concentration electrolytic solution. It has also been reported that the corrosion of aluminum can be suitably suppressed (see Example A, Comparative Example A, Evaluation Example A, etc.).

Further, a lithium ion secondary battery comprises a positive electrode plate comprising a positive electrode current collector foil and a positive electrode active material layer formed on the surface of the positive electrode current collector foil, a negative electrode current collector foil and the surface of the negative electrode current collector foil. A negative electrode plate comprising the formed negative electrode active material layer, and a separator, the positive electrode plate and the negative electrode plate generally face each other with the separator interposed therebetween, and further, the positive electrode current collector foil It is also common that the positive electrode uncoated portion where the positive electrode active material layer is not formed on the surface of the and the end portion of the negative electrode active material layer face each other.
The lithium ion tends to be concentrated at the end of the negative electrode active material layer, and there is a concern that metal lithium may precipitate due to the concentration of lithium ion, but the positive electrode uncoated portion does not have releasable lithium ion. By setting the end of the negative electrode active material layer to face with each other, the concentration of lithium ions on the end of the negative electrode active material layer can be suppressed, and the deposition of metal lithium can be suppressed. is there.

JP, 2013-149477, A International Publication No. 2016/063468

The present inventors actually manufactured a lithium ion secondary battery comprising a positive electrode having a positive electrode current collector foil made of aluminum and an electrolytic solution containing (FSO ₂ ) ₂ NLi at a concentration of 2.4 mol / L. When the charge and discharge test was performed, although the charge and discharge were performed at a potential assumed that aluminum corrosion did not occur, the aluminum was eluted from the positive electrode current collector foil of the lithium ion secondary battery and the negative electrode was The phenomenon of deposition on the top was confirmed. Therefore, the inventor recognized that there is room for improvement in terms of aluminum elution from the aluminum positive electrode current collector foil.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a lithium ion secondary battery in which the elution of aluminum from the positive electrode current collector foil made of aluminum is reduced, in other words, aluminum deposited on the negative electrode. An object of the present invention is to provide a reduced amount of lithium ion secondary battery.

  When the positive electrode current collector foil of the lithium ion secondary battery after the charge / discharge test described above by the present inventor is finely observed, the aluminum in the positive electrode uncoated portion facing the end of the negative electrode active material layer is corroded Found out the phenomena that From such findings, under charge and discharge conditions, the aluminum in the uncoated portion of the positive electrode facing the end of the negative electrode active material layer is dissolved in the electrolytic solution as aluminum ions, and the aluminum ions are reduced on the negative electrode It is believed to deposit as aluminum or an aluminum compound.

It is considered that this phenomenon is caused by the following mechanism.
At the interface between the aluminum in the uncoated portion of the positive electrode and the electrolyte, it is presumed that an equilibrium reaction occurs at the same time as the following equations (1) and (2). And since the reaction rate of Formula (2) is remarkably larger than the reaction rate of Formula (1) in the normal time, the aluminum ion concentration in electrolyte solution is a state which is remarkably low.
(1) Al → Al ³⁺ + 3e ⁻
(2) Al ³⁺ + 3e ⁻ → Al

Here, under the charge condition of the lithium ion secondary battery, electrons are supplied from the external circuit to the negative electrode active material layer through the negative electrode current collector foil. At this time, lithium ions corresponding to the number of electrons supplied are supplied from the positive electrode active material through the electrolytic solution to the negative electrode active material layer facing the positive electrode coating portion where the positive electrode active material layer is formed. The active material layer maintains electrical neutrality, and the potential of the negative electrode active material is lowered by absorbing lithium ions. On the other hand, electrons are similarly supplied to the end of the negative electrode active material layer, that is, the negative electrode active material layer of the portion facing the aluminum to which the positive electrode active material is not coated. Since the layer does not exist and lithium ions are not sufficiently supplied, the negative electrode active material at the end of the negative electrode active material layer can not occlude lithium ions, and the potential does not fall and electrons are accumulated and charged.
In this case, in the negative electrode active material layer, a potential difference occurs between the portion facing the positive electrode active material layer and the portion facing the positive electrode active material layer but not facing the positive electrode current collector foil made of aluminum, The next electrons to be supplied are easily supplied to the end of the high potential negative electrode active material layer, and it is considered that local charging progresses.
The end of the charged negative electrode active material layer is in a nucleophile state, and the equilibrium reaction of Formula (1) and Formula (2) occurs at the interface between aluminum and the electrolyte facing the end of the negative electrode active material layer. There is. Therefore, it is considered that aluminum ions, which are cations, are electrostatically attracted to the end portion side of the charged negative electrode active material layer through the electrolytic solution. Here, when aluminum ions combine with the electrons of the negative electrode active material layer to form zero-valent aluminum, the concentration of aluminum ions in the electrolytic solution decreases, so at the interface between the aluminum in the positive uncoated portion and the electrolytic solution The above-mentioned equilibrium reaction increases the reaction rate of the formula (1) as compared with that at normal times. As a result, it is considered that aluminum corrosion of the uncoated portion of the positive electrode proceeds.

Therefore, the present inventor recalled that the degree of the nucleophile state at the end of the negative electrode active material layer is reduced to suppress the phenomenon in which aluminum ions are attracted electrostatically to the end of the negative electrode active material layer. . In detail, at the time of initial charge of the lithium ion secondary battery, the negative electrode active material layer in which charging proceeded in the charge state before the positive electrode potential reached the corrosion potential of the aluminum current collector foil, and the positive electrode uncoated It was recalled to reduce the potential difference between the insufficiently charged end of the negative electrode active material layer facing the working part. As a means for this, the lithium introduced into the negative electrode active material layer is diffused inside the negative electrode active material layer before the positive electrode potential at the time of initial charge reaches the corrosion potential of the positive electrode current collector foil made of aluminum. It was recalled that lithium was introduced also to the end portion of the active material layer to equalize the potential in the negative electrode active material layer to some extent.
The method for producing a lithium ion secondary battery of the present invention embodies such means.

The method for producing a lithium ion secondary battery of the present invention is
A positive electrode plate comprising a positive electrode current collector foil made of aluminum and a positive electrode active material layer formed on the surface of the positive electrode current collector foil, a negative electrode current collector foil and a negative electrode active material formed on the surface of the negative electrode current collector foil A negative electrode plate having a layer, a separator, and an electrolytic solution containing a lithium salt selected from the following general formula (1) and general formula (2),
The positive electrode uncoated part in which the said positive electrode active material layer is not formed exists in the surface of the said positive electrode current collection foil,
The positive electrode plate and the negative electrode plate face each other with the separator interposed therebetween, and for a lithium ion secondary battery in which the positive electrode uncoated portion and the end of the negative electrode active material layer face each other,
From the positive electrode potential V _p-ocv (potential is based on lithium) at the start of the first charge, through the positive electrode potential V _P (potential is based on lithium: V _p-ocv <V _p <4.0 V), the positive electrode termination potential V _{P -Cutoff} (potential is based on lithium, 4.0 V ≦ VP _-cutoff ) The first charge is performed under any of the following conditions a) and b):
V _P charging step of charging up a) conditions the positive electrode potential V _P, aging step of aging the lithium ion secondary battery after V _P charging process, and the lithium ion secondary battery after aging step V _P-cutoff It includes a _VP-cutoff charging step to charge up to.
In _{V P} charging step of charging up b) conditions the positive electrode potential _{V P,} including charging at a rate of less than 0.1 C.

(R ¹ X ¹ ) (R ² SO ₂ ) NLi General formula (1)
(R ¹ is hydrogen, halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, an unsaturated alkyl group which may be substituted by a substituent, a substituent Or unsaturated cycloalkyl group which may be substituted, aromatic group which may be substituted by a substituent, heterocyclic group which may be substituted by a substituent, alkoxy group which may be substituted by a substituent An unsaturated alkoxy group which may be substituted by a substituent, a thioalkoxy group which may be substituted by a substituent, an unsaturated thioalkoxy group which may be substituted by a substituent, CN, SCN or OCN Be done.
R ² represents a hydrogen, a halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, an unsaturated alkyl group which may be substituted by a substituent, a substituent An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted by a substituent, a heterocyclic group which may be substituted by a substituent, an alkoxy group which may be substituted by a substituent, An unsaturated alkoxy group which may be substituted, a thioalkoxy group which may be substituted, an unsaturated thioalkoxy group which may be substituted, and a substituent selected from CN, SCN and OCN Ru.
Further, R ¹ and R ² may be bonded to each other to form a ring.
X ¹ is selected from SO ₂ , C = O, C = S, R ^a P = O, R ^b P = S, S = O, and SiOO.
R ^a and R ^b each independently represent hydrogen, a halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, or a substituent which may be substituted by a substituent A saturated alkyl group, an unsaturated cycloalkyl group which may be substituted by a substituent, an aromatic group which may be substituted by a substituent, a heterocyclic group which may be substituted by a substituent, a substituent Alkoxy group which may be substituted, unsaturated alkoxy group which may be substituted by a substituent, thioalkoxy group which may be substituted by a substituent, unsaturated thioalkoxy group which may be substituted by a substituent, OH , SH, CN, SCN, OCN.
In addition, R ^a and R ^b may combine with R ¹ or R ² to form a ring. )
R ³ SO ₃ Li General formula (2)
(R ³ is selected from an alkyl group or a halogen-substituted alkyl group.)

  In the method for producing a lithium ion secondary battery of the present invention, the terminus of the negative electrode active material layer is strong in the state of strong cation cation due to the initial charge under the conditions satisfying either a) or b). Suppress becoming. Therefore, the phenomenon in which aluminum ions are electrostatically attracted to the end portion side of the negative electrode active material layer is suppressed, so the amount of aluminum deposited on the negative electrode can be reduced.

  According to the method for producing a lithium ion secondary battery of the present invention, since the decrease in concentration of aluminum ions in the electrolytic solution is suppressed, the above-mentioned equilibrium reaction at the interface between the aluminum in the uncoated portion of the positive electrode and the electrolytic solution is usually As equation (2) remains advantageous. Therefore, it can be said that the a) conditions and the b) conditions in the method of manufacturing a lithium ion secondary battery of the present invention have an aluminum elution reduction effect.

FIG. 1 is a schematic view of a lithium ion secondary battery of Example 1;

  Below, the form for implementing this invention is demonstrated. In addition, unless otherwise indicated, the numerical range "ab" described in this specification includes the lower limit a and the upper limit b in the range. And a numerical range can be constituted by combining these arbitrarily including the upper limit and lower limit, and the numerical value listed in the example. Furthermore, numerical values arbitrarily selected from these numerical ranges can be used as new upper and lower numerical values.

The method for producing a lithium ion secondary battery of the present invention is
A positive electrode plate comprising a positive electrode current collector foil made of aluminum and a positive electrode active material layer formed on the surface of the positive electrode current collector foil, a negative electrode current collector foil and a negative electrode active material formed on the surface of the negative electrode current collector foil A negative electrode plate having a layer, a separator, and an electrolytic solution containing a lithium salt selected from the general formula (1) and the general formula (2),
The positive electrode uncoated part in which the said positive electrode active material layer is not formed exists in the surface of the said positive electrode current collection foil,
The positive electrode plate and the negative electrode plate face each other with the separator interposed therebetween, and the positive electrode uncoated portion and an end of the negative electrode active material layer (hereinafter, sometimes simply referred to as an “end”) face each other. Against the lithium ion secondary battery
From the positive electrode potential V _p-ocv (potential is based on lithium) at the start of the first charge, through the positive electrode potential V _P (potential is based on lithium: V _p-ocv <V _p <4.0 V), the positive electrode termination potential V _{P -Cutoff} (potential is based on lithium, 4.0 V ≦ VP _-cutoff ) The first charge is performed under any of the following conditions a) and b):
V _P charging step of charging up a) conditions the positive electrode potential V _P, aging step of aging the lithium ion secondary battery after V _P charging process, and the lithium ion secondary battery after aging step V _P-cutoff It includes a _VP-cutoff charging step to charge up to.
In _{V P} charging step of charging up b) conditions the positive electrode potential _{V P,} including charging at a rate of less than 0.1 C.

  Hereinafter, the lithium ion secondary battery manufactured by the method of manufacturing a lithium ion secondary battery of the present invention may be referred to as a lithium ion secondary battery of the present invention. The method for producing a lithium ion secondary battery of the present invention can be understood as the method for preparing a lithium ion secondary battery of the present invention and an initial charge method.

  The positive electrode plate used for the lithium ion secondary battery of the present invention comprises a positive electrode current collector foil made of aluminum and a positive electrode active material layer formed on the surface of the positive electrode current collector foil.

  The positive electrode current collector foil made of aluminum is made of aluminum or an aluminum alloy. Here, aluminum refers to pure aluminum, and aluminum having a purity of 99.0% or more is referred to as pure aluminum. An alloy obtained by adding various elements to pure aluminum is called an aluminum alloy. Examples of aluminum alloys include Al-Cu-based, Al-Mn-based, Al-Fe-based, Al-Si-based, Al-Mg-based, Al-Mg-Si-based and Al-Zn-Mg-based.

  As aluminum or aluminum alloy, specifically, for example, A1000 series alloys (pure aluminum series) such as JIS A1085, A1N30, A3000 series alloys such as JIS A3003, A3004 (Al-Mn series), JIS A8079, A8021 etc. A 8000 series alloy (Al-Fe series) is mentioned.

  The thickness of the positive electrode current collector foil is preferably in the range of 1 μm to 100 μm, more preferably in the range of 5 μm to 50 μm, and still more preferably in the range of 10 μm to 30 μm. The surface of the positive electrode current collector foil may be treated by a known method.

  The positive electrode active material layer contains a positive electrode active material, and, if necessary, a binder and / or a conductive aid. The thickness of the positive electrode active material layer is preferably in the range of 1 μm to 500 μm, more preferably in the range of 5 μm to 200 μm, and still more preferably in the range of 10 μm to 100 μm.

As a positive electrode active material, a general formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, La, Zr, Cu, Ca, Ir, Hf, Rh, Fe, Ge, Zn, Ru, At least one element selected from Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, lithium mixed metal oxide represented by 1.7 ≦ f ≦ 3), Li ₂ MnO ₃ can be mentioned. In addition, as a positive electrode active material, a metal oxide of spinel structure such as LiMn ₂ O ₄ , a solid solution composed of a mixture of a metal oxide of spinel structure and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ M is selected from at least one of Co, Ni, Mn, and Fe), and the like. Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as a positive electrode active material may have the above composition formula as a basic composition, and one obtained by replacing the metal element contained in the basic composition with another metal element can also be used. Further, as the positive electrode active material, one not containing charge carriers (for example, lithium ions contributing to charge and discharge) may be used. For example, elemental sulfur, compounds in which sulfur and carbon are complexed, metal sulfides such as TiS ₂ , oxides such as V ₂ O ₅ , MnO ₂ , polyaniline and anthraquinone, and compounds containing these aromatic groups in the chemical structure, conjugated Conjugated materials such as acetic acid-based organic materials and other known materials can also be used. Furthermore, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl or the like may be adopted as the positive electrode active material.
In the case of using a positive electrode active material containing no charge carrier such as lithium, the charge carrier needs to be previously added to the positive electrode and / or the negative electrode by a known method. The charge carrier may be added in the form of ions or may be added in the form of non ions such as metals. For example, when the charge carrier is lithium, a lithium foil may be attached to the positive electrode and / or the negative electrode to be integrated.

From the point of being excellent in high capacity and durability, etc., a general formula of layered rock salt structure as a positive electrode active material: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, At least one element selected from Rh, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, and represented by 1.7 ≦ f ≦ 3) It is preferable to use a lithium mixed metal oxide.

  In the above general formula, the values of b, c and d are not particularly limited as long as they satisfy the above conditions, but those with 0 <b <1, 0 <c <1, 0 <d <1 It is preferable that at least one of b, c and d be in the range of 10/100 <b <90/100, 10/100 <c <90/100, 5/100 <d <70/100. The range of 20/100 <b <80/100, 12/100 <c <70/100, and 10/100 <d <60/100 is more preferable, and 30/100 <b <70/100, The range of 15/100 <c <50/100 and 12/100 <d <50/100 is more preferable.

  The values of a, e and f may be numerical values within the range defined by the above general formula, preferably 0.5 ≦ a ≦ 1.5, 0 ≦ e <0.2, 1.8 ≦ f ≦ 2. And more preferably 0.8 ≦ a ≦ 1.3, 0 ≦ e <0.1, and 1.9 ≦ f ≦ 2.1, respectively.

Specific positive electrode active _{material, Li x A y Mn 2-} y O 4 (A spinel structure, Ca, Mg, S, Si , Na, K, Al, P, Ga, at least one selected from Ge The element and at least one metal element selected from transition metal elements, 0 <x ≦ 2.2, 0 ≦ y ≦ 1) can be exemplified. More specifically, LiMn ₂ O ₄ and LiNi _0.5 Mn _1.5 O ₄ can be exemplified.

Specific examples of the positive electrode active material include LiFePO ₄ , Li ₂ FeSiO ₄ , LiCoPO ₄ , Li ₂ CoPO ₄ , Li ₂ MnPO ₄ , Li ₂ MnSiO ₄ , and Li ₂ CoPO ₄ F. Li ₂ MnO ₃ -LiCoO ₂ can be exemplified as another specific positive electrode active material.

One type of positive electrode active material may be used, or a plurality of types may be used in combination. As a combined example of the positive electrode active material, a general formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Fe, Ge, Zn, At least one element selected from Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, and a lithium composite metal oxide represented by 1.7 ≦ f ≦ 3) A combined use with a polyanionic compound represented by LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (wherein M is selected from at least one of Co, Ni, Mn, and Fe) can be mentioned. In the combined use of the lithium composite metal oxide and the polyanion compound, the mass ratio of these is preferably in the range of lithium composite metal oxide: polyanion compound = 90: 10 to 50:50, and 80:20 to 60:40. Is more preferable. In addition, the positive electrode active material may be coated with carbon.

  60-100 mass% is preferable, as for mass% of the positive electrode active material in a positive electrode active material layer, 80-99 mass% is more preferable, and 85-96 mass% is more preferable.

  As the binder and the conductive auxiliary, those described in the negative electrode active material layer may be adopted as necessary. 0.1-10 mass% is preferable, as for mass% of the binder in a positive electrode active material layer, 0.5-7 mass% is more preferable, and 1-5 mass% is further more preferable. When the amount of the binder is too small, the formability is reduced. On the other hand, when the amount of the binder is too large, the energy density is reduced. 0.1-15 mass% is preferable, as for mass% of the conductive support agent in a positive electrode active material layer, 0.5-10 mass% is more preferable, and 1-10 mass% is further more preferable. If the amount of the conductive additive is too small, efficient conductive paths may not be formed. On the other hand, if the amount of the conductive additive is too large, the formability deteriorates and the energy density of the electrode decreases.

  In order to form the positive electrode active material layer on the surface of the positive electrode current collector foil, conventionally known methods such as roll coating method, die coating method, dip coating method, doctor blade method, spray coating method and curtain coating method are used. The positive electrode active material may be applied to the surface of the positive electrode current collector foil. Specifically, the positive electrode active material, the solvent, and, if necessary, the binder and the conductive auxiliary agent are mixed to form a slurry, and the slurry is applied to the surface of the positive electrode current collector foil and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone and water. The dried one may be compressed to increase the electrode density.

  The negative electrode plate used for the lithium ion secondary battery of the present invention comprises a negative electrode current collector foil and a negative electrode active material layer formed on the surface of the negative electrode current collector foil.

  As the negative electrode current collector foil, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, stainless steel, etc. Can be exemplified. The negative electrode current collector foil may be coated with a known protective layer. What processed the surface of the negative electrode current collector foil by a well-known method may be used as a negative electrode current collector foil.

  The thickness of the negative electrode current collector foil is preferably in the range of 1 μm to 100 μm, more preferably in the range of 5 μm to 50 μm, and still more preferably in the range of 8 μm to 30 μm.

  The negative electrode active material layer contains a negative electrode active material, and, if necessary, a binder and / or a conductive auxiliary. The thickness of the negative electrode active material layer is preferably in the range of 5 μm to 500 μm, more preferably in the range of 10 μm to 200 μm, and still more preferably in the range of 20 μm to 100 μm.

As the negative electrode active material, materials capable of inserting and extracting lithium ions can be used. Therefore, there is no particular limitation as long as it is a single body, an alloy or a compound capable of storing and releasing lithium ions. For example, Li as a negative electrode active material, a Group 14 element such as carbon, silicon, germanium, tin, a Group 13 element such as aluminum or indium, a Group 12 element such as zinc or cadmium, a Group 15 element such as antimony or bismuth, magnesium And alkaline earth metals such as calcium, and Group 11 elements such as silver and gold may be used alone. When silicon or the like is used as the negative electrode active material, one silicon atom reacts with a plurality of lithium, and thus a high-capacity active material is obtained. However, there is a problem that the volume expansion and contraction accompanying the lithium absorption and release become remarkable It is also preferable to use, as the negative electrode active material, an alloy or a compound in which another element such as a transition metal is combined with a single element such as silicon, since there is a possibility that such a risk may occur. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloys, Cu-Sn alloys, Co-Sn alloys, carbon-based materials such as various types of graphite, and SiO _x (disproportionate into silicon alone and silicon dioxide) Examples thereof include silicon-based materials such as 0.3 ≦ x ≦ 1.6), a simple substance of silicon, or a composite obtained by combining a silicon-based material and a carbon-based material. In addition, as the negative electrode active material, oxides such as Nb ₂ O ₅ , TiO ₂ , Li ₄ Ti ₅ O ₁₂ , WO ₂ , MoO ₂ , Fe ₂ O ₃ or Li _3-x M _x N (M = A nitride represented by Co, Ni, Cu) may be employed. One or more of these can be used as the negative electrode active material.

  As a more specific negative electrode active material, a material containing graphite or silicon can be exemplified. As a material containing silicon, any material containing Si and functioning as a negative electrode active material may be used. Specific examples of the Si-containing negative electrode active material include simple silicon, SiO x (0.3 ≦ x ≦ 1.6), alloys of Si and other metals, and silicon materials described in WO 2014/080608. it can. The Si-containing negative electrode active material may be coated with carbon. The Si-containing negative electrode active material coated with carbon is excellent in conductivity.

The silicon material described in WO 2014/080608 (hereinafter sometimes simply referred to as "silicon material") will be described in detail. For example, a silicon material may be reacted with CaSi ₂ and an acid to synthesize a layered silicon compound containing polysilane as a main component, and further, the layered silicon compound may be heated at 300 ° C. or higher to release hydrogen. It is manufactured.

The method for producing a silicon material described in WO 2014/080608 can be represented by the following ideal reaction formula when hydrogen chloride is used as an acid.
3CaSi ₂ +6 HCl → Si ₆ H ₆ +3 CaCl ₂
Si ₆ H ₆ → 6Si + 3H ₂ ↑

However, in the upper reaction for synthesizing Si ₆ H ₆ which is polysilane, water is generally used as a reaction solvent from the viewpoint of removal of by-products and impurities. And, since Si ₆ H ₆ can react with water, in the process of synthesizing the layered silicon compound including the reaction in the upper stage, the layered silicon compound is hardly produced as one containing only Si ₆ H ₆ , and the layered silicon compound is layered The silicon compound is represented by Si ₆ H _s (OH) _t X _u (X is an element or group derived from the anion of an acid, s + t + u = 6, 0 <s <6, 0 <t <6, 0 <u <6) Manufactured as In the above chemical formula, unavoidable impurities such as remaining Ca are not taken into consideration. And the silicon material obtained by heating the said layered silicon compound also contains the element derived from the anion of oxygen or an acid.

The silicon material has a structure in which a plurality of plate-like silicon bodies are stacked in the thickness direction. The plate-like silicon body preferably has a thickness in the range of 10 nm to 100 nm, and more preferably in the range of 20 nm to 50 nm, in order to efficiently insert and extract charge carriers such as lithium ions. The length in the longitudinal direction of the plate-like silicon body is preferably in the range of 0.1 μm to 50 μm. The plate-like silicon body preferably has a (longitudinal length) / (thickness) in the range of 2 to 1000. The layered structure of the plate-like silicon body can be confirmed by observation with a scanning electron microscope or the like. Moreover, this laminated structure is considered to be a remnant of the Si layer in the raw material CaSi ₂ .

  The silicon material preferably includes amorphous silicon and / or silicon crystallites. In particular, in the plate-like silicon body, it is preferable that amorphous silicon be a matrix and silicon crystallites be scattered in the matrix. The size of the silicon crystallite is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, still more preferably in the range of 1 nm to 50 nm, and particularly preferably in the range of 1 nm to 10 nm. The size of the silicon crystallite is calculated from the Scheller equation using the half width of the diffraction peak of the Si (111) plane of the obtained X-ray diffraction chart by performing X-ray diffraction measurement on the silicon material. .

  The amount and size of the plate-like silicon body, amorphous silicon and silicon crystallite contained in the silicon material mainly depend on the heating temperature and heating time. The heating temperature is preferably in the range of 350 ° C. to 950 ° C., and more preferably in the range of 400 ° C. to 900 ° C.

  In a lithium ion secondary battery including a negative electrode plate provided with a negative electrode active material containing graphite or Si, it is assumed that the positive electrode current collector foil is exposed to a high voltage during charging. Therefore, in the lithium ion secondary battery of the present invention provided with the negative electrode plate comprising the negative electrode active material containing graphite or Si, it can be said that the aluminum elution reduction effect under the conditions a) and b) is suitably exhibited.

  60-100 mass% is preferable, as for mass% of the negative electrode active material in a negative electrode active material layer, 80-99 mass% is more preferable, and 85-98 mass% is more preferable.

  The binder plays the role of anchoring the active material, the conductive additive and the like to the surface of the current collector foil.

  As the binder, fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resin, styrene butadiene A known material such as rubber may be employed.

  Moreover, you may employ | adopt the polymer which has a hydrophilic group as a binding agent. The lithium ion secondary battery of the present invention, which comprises a polymer having a hydrophilic group as a binder, can maintain its capacity more suitably. As a hydrophilic group of the polymer which has a hydrophilic group, carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, phosphate group, such as a phosphate group, etc. are illustrated. Among them, polymers containing a carboxyl group in the molecule such as polyacrylic acid, carboxymethylcellulose and polymethacrylic acid, or polymers containing a sulfo group such as poly (p-styrenesulfonic acid) are preferable.

  A polymer containing a large amount of carboxyl groups and / or sulfo groups, such as polyacrylic acid or a copolymer of acrylic acid and vinyl sulfonic acid, becomes water soluble. The polymer having a hydrophilic group is preferably a water-soluble polymer, and in the chemical structure, a polymer containing a plurality of carboxyl groups and / or sulfo groups in one molecule is preferable.

  The polymer containing a carboxyl group in the molecule can be produced, for example, by a method of polymerizing an acid monomer, a method of giving a carboxyl group to a polymer, or the like. Examples of acid monomers include acrylic acid, methacrylic acid, vinylbenzoic acid, crotonic acid, pentenoic acid, angelic acid, tiglic acid, etc. Acid monomers having one carboxyl group in the molecule, itaconic acid, mesaconic acid, citraconic acid, fumaric acid And maleic acid, 2-pentenedioic acid, methylene succinic acid, allyl malonic acid, isopropylidene succinic acid, 2,4-hexadiene diacid, acetylene dicarboxylic acid, and other acid monomers having two or more carboxyl groups in the molecule. Be done.

  A copolymer formed by polymerizing two or more kinds of acid monomers selected from the above-mentioned acid monomers may be used as a binder.

  Also, a polymer containing an acid anhydride group formed by condensation of carboxyl groups of a copolymer of acrylic acid and itaconic acid as described in, for example, JP-A 2013-065493 is contained in the molecule. It is also preferable to use a binder as a binder. If the binder has a structure derived from a highly acidic monomer having two or more carboxyl groups in one molecule in the binder, it is easy for the binder to trap lithium ions etc. before the electrolytic decomposition reaction occurs during charging. It is considered. Furthermore, although the polymer has more carboxyl groups per monomer than polyacrylic acid and polymethacrylic acid, the acidity is increased, but the acidity is increased because a predetermined amount of carboxyl groups is changed to an acid anhydride group. Is not too high. Therefore, in the secondary battery having the negative electrode using the polymer as a binder, the initial efficiency is improved, and the input / output characteristics are improved.

  In addition, a carboxyl group-containing polymer such as polyacrylic acid or polymethacrylic acid disclosed in WO 2016/063882 may be used as a binder a crosslinked polymer crosslinked with a diamine.

  Examples of the diamine used for the cross-linked polymer include alkylene diamines such as ethylene diamine, propylene diamine and hexamethylene diamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, isophorone diamine, bis (4-aminocyclohexyl) methane and the like. Saturated carbocyclic ring diamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, bis (4-aminophenyl) sulfone, benzidine, o-tolidine, 2,4- Aromatic diamines such as tolylene diamine, 2,6-tolylene diamine, xylylene diamine and naphthalene diamine can be mentioned.

  Further, a mixture or a reaction product of a carboxyl group-containing polymer such as polyacrylic acid or polymethacrylic acid and polyamideimide may be used as a binder.

  Polyamideimide means a compound having two or more amide bonds and two or more imide bonds in the molecule. Polyamideimide is produced by reacting an acid component which is to be a carbonyl moiety in an amide bond and an imide bond, and a diamine component or a diisocyanate component which is to be a nitrogen moiety in an amide bond and an imide bond. In order to obtain a polyamideimide, it may manufacture by the said method, and may purchase a commercially available polyamideimide.

  Examples of acid components used for producing polyamideimides include trimellitic acid, pyromellitic acid, biphenyl tetracarboxylic acid, diphenyl sulfone tetracarboxylic acid, benzophenone tetracarboxylic acid, diphenyl ether tetracarboxylic acid, oxalic acid, adipic acid, malonic acid, Sebacic acid, azelaic acid, dodecanedicarboxylic acid, dicarboxypolybutadiene, dicarboxypoly (acrylonitrile-butadiene), dicarboxypoly (styrene-butadiene), cyclohexane-1,4-dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, Dicyclohexylmethane-4,4'-dicarboxylic acid, terephthalic acid, isophthalic acid, bis (carboxyphenyl) sulfone, bis (carboxyphenyl) ether, naphthalene dicarboxylic acid, and These anhydrides, acid halides, mention may be made of derivatives. As the acid component, the above compounds may be employed singly or in a plurality, but from the viewpoint of forming an imide bond, an acid component or a carboxyl group is present at the adjacent carbon of the carbon to which the carboxyl group is bonded The equivalent is essential. As the acid component, trimellitic anhydride is preferable in terms of reactivity, heat resistance, and the like. In addition to trimellitic anhydride, in addition to trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic acid anhydride, biphenyltetramer as a part of the acid component from the viewpoint of tensile strength, tensile modulus of elasticity and electrolytic solution resistance of polyamideimide. It is preferred to employ a carboxylic acid anhydride.

  As a diamine component used for manufacture of polyamidoimide, what is necessary is just to employ | adopt the diamine used for the crosslinked polymer mentioned above. From the viewpoint of heat resistance and solubility, 4,4'-diaminodiphenylmethane, 2,4-tolylenediamine, o-tolidine, naphthalenediamine and isophoronediamine are preferable. From the viewpoint of tensile strength and tensile modulus of polyamideimide, o-tolidine and naphthalenediamine are preferred.

  As a diisocyanate component used for manufacture of polyamidoimide, what substituted the amine of the said diamine component by the isocyanate can be mentioned.

  0.1-20 mass% is preferable, as for mass% of the binder in a negative electrode active material layer, 0.5-15 mass% is more preferable, and 1-10 mass% is further more preferable. When the amount of the binder is too small, the formability is reduced. On the other hand, when the amount of the binder is too large, the energy density is reduced.

  A conductive aid is added to enhance the conductivity of the electrode. Therefore, the conductive additive may be optionally added when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent. The conductive support agent may be any chemically active high electron conductor, and carbon black fine particles such as carbon black, graphite, vapor grown carbon fiber, and various metal particles are exemplified. Ru. Examples of the carbon black include acetylene black, ketjen black (registered trademark), furnace black, channel black and the like. These conductive assistants can be added to the active material layer singly or in combination of two or more.

  0.1-30 mass% is preferable, as for mass% of the conductive support agent in a negative electrode active material layer, 0.5-20 mass% is more preferable, and 1-10 mass% is more preferable. If the amount of the conductive additive is too small, efficient conductive paths may not be formed. On the other hand, if the amount of the conductive additive is too large, the formability deteriorates and the energy density of the electrode decreases.

  In order to form the negative electrode active material layer on the surface of the negative electrode current collector foil, conventionally known methods such as roll coating method, die coating method, dip coating method, doctor blade method, spray coating method and curtain coating method are used. The negative electrode active material may be applied to the surface of the negative electrode current collector foil. Specifically, a negative electrode active material, a solvent, and, if necessary, a binder and a conductive additive are mixed to form a slurry, and the slurry is applied to the surface of a negative electrode current collector foil and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone and water. The dried one may be compressed to increase the electrode density.

  A separator is used in the lithium ion secondary battery of the present invention. The separator separates the positive electrode plate and the negative electrode plate, and allows lithium ions to pass while preventing a short circuit due to the contact of both electrodes. As the separator, a known one may be employed, and polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester, synthetic resin such as polyacrylonitrile, polysaccharide such as cellulose, amylose, fibroin Examples thereof include porous materials, non-woven fabrics, and woven fabrics using one or more kinds of natural polymers such as keratin, lignin and suberin, and electrically insulating materials such as ceramics. In addition, the separator may have a multilayer structure.

  The separator is positioned between the positive electrode plate and the negative electrode plate to prevent contact between the positive electrode plate and the negative electrode plate. The separator preferably has a surface larger than that of the facing positive and negative electrode active material layers. From the viewpoint of short circuit prevention and metal lithium deposition prevention, the order of separator> negative electrode active material layer> positive electrode active material layer is preferable as the size of the surface. In the facing state of the separator, the positive electrode active material layer, and the negative electrode active material layer, the negative electrode active material layer faces the positive electrode active material layer in a mode covering the entire surface of the positive electrode active material layer, and the positive electrode active material layer and the negative electrode active It is preferable that the separator faces the positive electrode active material layer and the negative electrode active material layer in such a manner that the entire surface of the material layer is covered.

  The lithium ion secondary battery of the present invention comprises an electrolytic solution containing a lithium salt selected from the following general formula (1) and general formula (2).

(R ¹ X ¹ ) (R ² SO ₂ ) NLi General formula (1)
(R ¹ is hydrogen, halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, an unsaturated alkyl group which may be substituted by a substituent, a substituent Or unsaturated cycloalkyl group which may be substituted, aromatic group which may be substituted by a substituent, heterocyclic group which may be substituted by a substituent, alkoxy group which may be substituted by a substituent An unsaturated alkoxy group which may be substituted by a substituent, a thioalkoxy group which may be substituted by a substituent, an unsaturated thioalkoxy group which may be substituted by a substituent, CN, SCN or OCN Be done.
R ² represents a hydrogen, a halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, an unsaturated alkyl group which may be substituted by a substituent, a substituent An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted by a substituent, a heterocyclic group which may be substituted by a substituent, an alkoxy group which may be substituted by a substituent, An unsaturated alkoxy group which may be substituted, a thioalkoxy group which may be substituted, an unsaturated thioalkoxy group which may be substituted, and a substituent selected from CN, SCN and OCN Ru.
Further, R ¹ and R ² may be bonded to each other to form a ring.
X ¹ is selected from SO ₂ , C = O, C = S, R ^a P = O, R ^b P = S, S = O, and SiOO.
R ^a and R ^b each independently represent hydrogen, a halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, or a substituent which may be substituted by a substituent A saturated alkyl group, an unsaturated cycloalkyl group which may be substituted by a substituent, an aromatic group which may be substituted by a substituent, a heterocyclic group which may be substituted by a substituent, a substituent Alkoxy group which may be substituted, unsaturated alkoxy group which may be substituted by a substituent, thioalkoxy group which may be substituted by a substituent, unsaturated thioalkoxy group which may be substituted by a substituent, OH , SH, CN, SCN, OCN.
In addition, R ^a and R ^b may combine with R ¹ or R ² to form a ring. )

R ³ SO ₃ Li General formula (2)
(R ³ is selected from an alkyl group or a halogen-substituted alkyl group.)

  The wording "may be substituted with a substituent" in the chemical structure represented by the above general formula (1) will be described. For example, "an alkyl group which may be substituted by a substituent" means an alkyl group in which one or more of the hydrogens of the alkyl group is substituted by a substituent, or an alkyl group having no substituent. Do.

  Examples of the substituent in the phrase "may be substituted with a substituent" include alkyl group, alkenyl group, alkynyl group, cycloalkyl group, unsaturated cycloalkyl group, aromatic group, heterocyclic group, halogen, OH , SH, CN, SCN, OCN, nitro group, alkoxy group, unsaturated alkoxy group, amino group, alkylamino group, dialkylamino group, dialkylamino group, aryloxy group, acyl group, alkoxycarbonyl group, acyloxy group, aryloxycarbonyl group, Acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, sulfo group, carboxyl group, Hydroxamic acid group, Rufino group, a hydrazino group, an imino group, and a silyl group. These substituents may be further substituted by a substituent. When two or more substituents are present, the substituents may be the same or different.

  The lithium salt is preferably one represented by the following general formula (1-1).

(R ²³ X ² ) (R ²⁴ SO ₂ ) NLi general formula (1-1)
(R ²³ and R ²⁴ are each independently C _n H _a F _b Cl _{c B r d} I _e (CN) _f (SCN) _g (OCN) _h .
n, a, b, c, d, e, f, g and h are each independently an integer of 0 or more and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
Further, R ²³ and R ²⁴ may be bonded to each other to form a ring, in which case 2n = a + b + c + d + e + f + g + h is satisfied.
X ² is selected from SO ₂ , C = O, C = S, R ^c P = O, R ^d P = S, S = O, Si = O.
R ^c and R ^d each independently represent hydrogen, a halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, or a group which may be substituted by a substituent A saturated alkyl group, an unsaturated cycloalkyl group which may be substituted by a substituent, an aromatic group which may be substituted by a substituent, a heterocyclic group which may be substituted by a substituent, a substituent Alkoxy group which may be substituted, unsaturated alkoxy group which may be substituted by a substituent, thioalkoxy group which may be substituted by a substituent, unsaturated thioalkoxy group which may be substituted by a substituent, OH , SH, CN, SCN, OCN.
R ^c and R ^d may combine with R ²³ or R ²⁴ to form a ring. )

  The meaning of the wording “in the substituent may be substituted” in the chemical structure represented by General Formula (1-1) is the same as that described in General Formula (1).

In the chemical structure represented by the above general formula (1-1), n is preferably an integer of 0 to 6, more preferably an integer of 0 to 4, and particularly preferably an integer of 0 to 2. When R ²³ and R ^{24 in the} chemical structure represented by the above general formula (1-1) are combined to form a ring, n is preferably an integer of 1 to 8, and 1 to 7 The integer of is more preferable, and the integer of 1 to 3 is particularly preferable.

  The lithium salt is more preferably one represented by the following general formula (1-2).

(R ²⁵ SO ₂ ) (R ²⁶ SO ₂ ) NLi general formula (1-2)
(R ²⁵ and R ²⁶ are each independently C _n H _a F _b Cl _c Br _d I _e .
n, a, b, c, d and e are each independently an integer of 0 or more and satisfy 2n + 1 = a + b + c + d + e.
R ²⁵ and R ²⁶ may be combined with each other to form a ring, in which case 2n = a + b + c + d + e is satisfied. )

In the chemical structure represented by the above general formula (1-2), n is preferably an integer of 0 to 6, more preferably an integer of 0 to 4, and particularly preferably an integer of 0 to 2. When R ²⁵ and R ^{26 in the} chemical structure represented by the above general formula (1-2) are bonded to form a ring, n is preferably an integer of 1 to 8, and 1 to 7 The integer of is more preferable, and the integer of 1 to 3 is particularly preferable.

  Moreover, in the chemical structure represented by the said General formula (1-2), that whose a, c, d, e is 0 is preferable.

In the general formula (2), the number of carbon atoms of ^{R 3} is preferably 1 to 6, more preferably 1 to 4, 1 to 2 is more preferred. As a halogen of the halogen substituted alkyl group, fluorine is preferable.

The lithium salt is (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) ₂ NLi, FSO ₂ (CF ₃ SO ₂ ) NLi, (SO ₂ CF ₂ CF ₂ SO ₂ ) NLi, (SO ₂ CF ₂ CF ₂ CF ₂ SO ₂ ) NLi, FSO ₂ (CH ₃ SO ₂ ) NLi, FSO ₂ (C ₂ F ₅ SO ₂ ) NLi, or FSO ₂ (C ₂ H ₅ SO ₂ ) NLi Particularly preferred is one selected from

  In the electrolytic solution, one type of lithium salt selected from General Formula (1) and General Formula (2) may be adopted, or plural types may be used in combination. Further, the electrolytic solution may contain an electrolyte other than the lithium salt selected from the general formula (1) and the general formula (2). The ratio of the lithium salt selected from the general formula (1) and the general formula (2) to the whole electrolyte in the electrolytic solution is preferably 30 to 100 mol%, more preferably 50 to 95 mol%, and 70 to 90 mol% Is more preferred. The concentration of the electrolyte containing a lithium salt selected from the general formula (1) and the general formula (2) in the electrolytic solution is 1.5 to 3 mol / L, 1.6 to 2.8 mol / L, 1.8 -2.6 mol / L and 2-2.5 mol / L can be illustrated.

The general formula (1) and electrolytes other than lithium salt selected from the general formula _{(2), LiPF 6, LiPF} 2 (OCOCOO) 2, LiBF 4, the LiAsF ₆ and _Li 2 SiF ₆ Specific exemplified. All these electrolytes have F which can be eliminated as F ⁻ . And, F ^- can react with aluminum to form a stable Al-F bond. Therefore, it can be expected that the surface of the positive electrode uncoated portion is protected by a passivation film containing Al-F bonds.

  The electrolytic solution contains an organic solvent for dissolving an electrolyte containing a lithium salt selected from General Formula (1) and General Formula (2). As the organic solvent, an organic solvent usable for the non-aqueous secondary battery may be adopted, and in particular, it is preferable to adopt a low polarity organic solvent which hardly dissolves aluminum.

  Examples of low polar organic solvents include linear carbonates represented by the following general formula (3).

R ¹⁰ OCOOR ¹¹ general formula (3)
^{(R 10, R 11} are each independently a linear alkyl _{C n H a F b Cl c} Br d I e, _{or, C m H f F g Cl} h Br i I contains a cyclic alkyl in the chemical structure .n selected from any of _j is an integer of 1 or more, m is an integer of 3 or more, a, b, c, d , e, f, g, h, i, j are each independently 0 or an integer And 2n + 1 = a + b + c + d + e, 2m-1 = f + g + h + i + j)

  In the linear carbonate represented by the above general formula (3), n is preferably an integer of 1 to 6, more preferably an integer of 1 to 4, and particularly preferably an integer of 1 to 2. m is preferably an integer of 3 to 8, more preferably an integer of 4 to 7, and particularly preferably an integer of 5 to 6.

  Among the linear carbonates represented by the above general formula (3), those represented by the following general formula (3-1) are particularly preferable.

R ¹² OCOOR ¹³ General Formula (3-1)
(R ¹² and R ¹³ are each independently selected from any of C _n H _a F _b which is a linear alkyl, or C _m H _f F _g which includes cyclic alkyl in its chemical structure. N is 1 The above integer, m is an integer of 3 or more, a, b, f and g are each independently an integer of 0 or more, and 2n + 1 = a + b and 2m-1 = f + g are satisfied.

  In the linear carbonate represented by the above general formula (3-1), n is preferably an integer of 1 to 6, more preferably an integer of 1 to 4, and particularly preferably an integer of 1 to 2. m is preferably an integer of 3 to 8, more preferably an integer of 4 to 7, and particularly preferably an integer of 5 to 6.

  Among the linear carbonates represented by the above general formula (3-1), dimethyl carbonate (hereinafter sometimes referred to as "DMC"), diethyl carbonate (hereinafter sometimes referred to as "DEC"), ethyl methyl Carbonate (hereinafter sometimes referred to as "EMC"), fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) Carbonate, fluoromethyl difluoromethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, pentafluoroethyl methyl carbonate, ethyl trifluoromethyl carbonate, bis (2,2,2-trifluoroethyl ether ) Carbonate is particularly preferred.

  As the linear carbonate, one type may be used for the electrolytic solution, or a plurality of types may be used in combination. By using a plurality of linear carbonates in combination, the low temperature fluidity of the electrolytic solution, the lithium ion transportability at low temperature, and the like can be suitably secured. As a combination example of a linear carbonate, two or three combinations selected from DMC, DEC and EMC can be mentioned. In the combined use of DMC and DEC or EMC, the molar ratio thereof is preferably in the range of DMC: DEC or EMC = 60: 40 to 95: 5, more preferably in the range of 70:30 to 95: 5, The range of 80:20 to 95: 5 is more preferable.

  In the electrolytic solution, in addition to the above-mentioned chain carbonate, other organic solvents (hereinafter, sometimes simply referred to as "other organic solvents") which can be used for electrolytic solution such as lithium ion secondary battery are contained. May be

  The above-mentioned linear carbonate is preferably contained in an amount of 70% by volume, 70% by mass or more, or 70% by mole or more based on the total organic solvent contained in the electrolytic solution, and 80% by volume or more and 80% by mass It is more preferably contained in% or more or 80 mol% or more, still more preferably contained in 90% by volume or more, 90% by mass or more or 90% by mol, 95% by volume or more, 95% by mass or more It is particularly preferred that the above be included. All organic solvents contained in the electrolytic solution may be the above-mentioned chain carbonate.

  Specific examples of other organic solvents include nitriles such as acetonitrile, propionitrile, acrylonitrile and malononitrile, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, 1, 3-dioxane, 1,4-dioxane, 2,2-dimethyl-1,3-dioxolane, 2-methyltetrahydropyran, 2-methyltetrahydrofuran, ethers such as crown ether, fluoroethylene carbonate, 4- (trifluoromethyl) Fluorine-containing cyclic carbonates such as 1,3-dioxolan-2-one, fluorine-free cyclic carbonates such as ethylene carbonate and propylene carbonate, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, N) -Methyl Amides such as lolidone, isocyanates such as isopropyl isocyanate, n-propyl isocyanate, chloromethyl isocyanate, methyl acetate, ethyl acetate, butyl acetate, propyl acetate, methyl propionate, methyl formate, ethyl formate, vinyl acetate, methyl acrylate, Esters such as methyl methacrylate, epoxys such as glycidyl methyl ether, epoxy butane, 2-ethyl oxirane, oxazoles, oxazoles such as 2-ethyl oxazole, oxazoline, 2-methyl-2-oxazoline, acetone, methyl ethyl ketone, methyl isobutyl Ketones such as ketones, acid anhydrides such as acetic anhydride and propionic acid anhydride, sulfones such as dimethyl sulfone and sulfolane, sulfoxides such as dimethyl sulfoxide, 1-nit Nitros such as propane and 2-nitropropane, furans such as furan and furfural, cyclic esters such as γ-butyrolactone, γ-valerolactone and δ-valerolactone, aromatic heterocycles such as thiophene and pyridine, tetrahydro Heterocycles such as -4-pyrone, 1-methyl pyrrolidine, and N-methyl morpholine; and phosphoric esters such as trimethyl phosphate and triethyl phosphate can be given.

  A known additive may be added to the electrolytic solution without departing from the scope of the present invention. Examples of known additives include cyclic carbonates having unsaturated bonds represented by vinylene carbonate (VC), vinyl ethylene carbonate (VEC), methyl vinylene carbonate (MVC), ethyl vinylene carbonate (EVC); phenyl ethylene carbonate and the like A carbonate compound represented by erythritan carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic acid anhydride, cyclopentane tetracarboxylic acid Dianhydrides, carboxylic acid anhydrides represented by phenylsuccinic anhydride; γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, ε-caprolactone Lactones; cyclic ethers represented by 1,4-dioxane; ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone, tetramethylthiuram Sulfur-containing compounds represented by monosulfide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, N-methyl succinimide Nitrogen-containing compounds represented by: monofluorophosphate, phosphate represented by difluorophosphate; saturated hydrocarbon compounds represented by heptane, octane and cycloheptane; biphenyl, alkylbiphenyl, terphenyl, ter Partially hydrogenated form of phenyl Shirubenzen, t- butyl benzene, t-amyl benzene, diphenyl ether, unsaturated hydrocarbon compounds and the like typified by dibenzofuran.

The method for manufacturing a lithium ion secondary battery of the present invention is directed to a lithium ion secondary battery assembled into a predetermined structure,
From the positive electrode potential V _p-ocv (potential is based on lithium) at the start of the first charge, through the positive electrode potential V _P (potential is based on lithium: V _p-ocv <V _p <4.0 V), the positive electrode termination potential V _{P -Cutoff} (potential is based on lithium, 4.0 V ≦ VP _-cutoff ) The first charge is performed under any of the following conditions a) and b):
V _P charging step of charging up a) conditions the positive electrode potential V _P, aging step of aging the lithium ion secondary battery after V _P charging process, and the lithium ion secondary battery after aging step V _P-cutoff It includes a _VP-cutoff charging step to charge up to.
In _{V P} charging step of charging up b) conditions the positive electrode potential _{V P,} including charging at a rate of less than 0.1 C.

Generally, under the charge condition of the lithium ion secondary battery, electrons are supplied from the external circuit to the negative electrode active material layer through the negative electrode current collector foil. At this time, lithium ions corresponding to the number of electrons supplied are supplied from the positive electrode active material through the electrolytic solution to the negative electrode active material layer facing the positive electrode coating portion where the positive electrode active material layer is formed. The layer maintains electrical neutrality, and the potential of the negative electrode active material is lowered by absorbing lithium ions. On the other hand, electrons are similarly supplied to the end of the negative electrode active material layer, that is, the negative electrode active material layer of the portion facing the aluminum to which the positive electrode active material is not coated. Since the layer does not exist and lithium ions are not sufficiently supplied, the negative electrode active material at the end of the negative electrode active material layer can not occlude lithium ions, and the potential does not fall and electrons are accumulated and charged.
In this case, in the negative electrode active material layer, a potential difference occurs between the portion facing the positive electrode active material layer and the portion facing the positive electrode active material layer but not facing the positive electrode current collector foil made of aluminum, The next electrons to be supplied are easily supplied to the end of the negative electrode active material layer having a high potential, local charging occurs, and the end of the negative electrode active material layer is in the nucleophile state.

  However, the initial charge in the method for producing a lithium ion secondary battery of the present invention is performed under conditions that satisfy either of a) conditions and b) conditions. Lithium is diffused in the negative electrode active material layer before the positive electrode potential reaches the corrosion potential of the positive electrode current collector foil made of aluminum by performing the initial charge under the conditions satisfying a) conditions and b) conditions. Lithium is also introduced to the end of the negative electrode active material layer. Therefore, it can be said that the potential inside the negative electrode active material layer is leveled to some extent. Then, it is considered that the degree to which the next electron supplied to the negative electrode is biased to the end of the negative electrode active material layer is alleviated. In other words, it can be said that the positivity state of the end of the negative electrode active material layer is alleviated. Therefore, it is thought that it can suppress that the aluminum ion which exists in the positive electrode uncoated part vicinity moves to the edge part side of a negative electrode active material layer through an electrolyte solution electrostatically.

  In addition, in the charge and discharge after the initial charge, the end of the negative electrode active material layer does not have the positive electrode active material layer facing each other, so lithium ions are not actively transferred at the end of the negative electrode active material layer. It is expected that lithium introduced to the end of the active material layer will stay at the end of the negative electrode active material layer. Then, it is presumed that the end of the negative electrode active material layer into which lithium has been introduced is prevented from becoming a cationic state even when charging, such as during normal use. Therefore, even if charge and discharge are repeated, in the lithium ion secondary battery of the present invention, the aluminum ions present in the vicinity of the uncoated portion of the positive electrode facing the end of the negative electrode active material layer It is considered that electrostatic movement to the end side of the material layer through the electrolytic solution can be suppressed for a certain period of time.

In Examples and Evaluation Examples described later, it was confirmed that the degree of aluminum corrosion of the positive electrode current collector foil significantly changed by changing the charge condition up to a positive electrode potential of 3.9 V based on lithium. Therefore, in the present invention, the positive electrode potential V _P of less than 4.0V _(potential relative to lithium.) And a key potential, and the invention is spending a lot of time from start of charging to more than key potential, the negative electrode active The technical idea is to relax the nucleophilic state at the end of the negative electrode active material layer by acquiring the diffusion time of lithium inside the material layer and leveling the potential inside the negative electrode active material layer as much as possible. In the present specification, the positive electrode potential and the negative electrode potential mean potentials based on lithium.

As the positive electrode potential _{V P} (potentials based on lithium _{.V p-ocv <V P <} 4.0V), specifically, the range of _{V P} ≦ 3.9V, the range of 3.2V ≦ _{V P} ≦ 3.9V For example, the range of 3.4 V ≦ V _p ≦ 3.9 V and the range of 3.6 V ≦ V _p ≦ 3.9 V can be exemplified. In addition, as the positive electrode end potential VP _-cutoff (potential is based on lithium: 4.0 V ≦ VP _-cutoff ), the range of 4.0 V ≦ VP _-cutoff ≦ 5.5 V, 4 V ≦ VP _-cutoff ≦ 5 V The range of 4 V ≦ VP _-cutoff ≦ 4.5 V can be exemplified.

The addition of the viewpoint potential of the negative electrode of V _P charging step of charging up positive potential V _P, the negative electrode potential V _n at which a positive potential V _P is said to lower the better. This is because an increase in the amount of lithium diffused to the end of the negative electrode active material layer can be expected when the negative electrode potential is lower, and the potential difference in the negative electrode generated in the _VP-cutoff process can be reduced.
When specifically expressed the above matters, V _P charging step, that _(the potential relative to lithium.) Negative electrode potential V _n-ocv upon first start of charging is performed until the negative electrode potential V _n which is 50% less It can be said that it is preferable. Relationship between V _n-ocv and _{V n} is, _{V n} ≦ 0.5 × _{V n-ocv} is preferred, other, Suitable _{relationships, 0.001 × V n-ocv ≦} V n ≦ 0.45 × V _n-ocv , 0.01 × V _n-ocv ≦ V _n ≦ 0.4 × V _n-ocv , 0.05 × V _n-ocv ≦ V _n ≦ 0.35 × V _n-ocv 0.1, V _n-ocv V V _n 0.3 0.3 x V _n-ocv can be exemplified.

a) The conditions will be described.
a) conditions, _{V P} charging step of charging up positive electrode potential _{V P,} aging step of aging the lithium ion secondary battery after _{V P} charge step, and, _{V P-cutoff} lithium ion secondary battery after the aging process It includes a _VP-cutoff charging step to charge up to.

Charging speed in V _P charging step may be a constant speed, it may be varied speed. If charging speed is fast it is possible to shorten the time of V _P charging process. On the other hand, even in it is V _P charging process the charging speed slow, it can be expected the diffusion of lithium in the anode active material layer. As the charging rate in the V _P charging step, 0.01 C above 15C or less, 0.5 C above 10C or less, 1C or 7C or less, can be exemplified 2C or 6C below.
Here, 1 C means a current value required to fully charge the lithium ion secondary battery (SOC 100%) in one hour at a constant current.

The _VP charging step is preferably performed under warm conditions. If the temperature is high, even in V _P charging process, it can be expected the diffusion of lithium in the anode active material layer. As heating conditions at V _P charging step, 30 ° C. or higher 120 ° C. or less, 40 ° C. or higher 110 ° C. or less, 50 ° C. or higher 100 ° C. or less, it can be exemplified 60 ° C. or higher 90 ° C. or less.

Aging process, V _P charging suspension process to pause charging the lithium ion secondary battery after the charging step, a voltage maintaining process for maintaining the V _P the lithium ion secondary battery after V _P charging step and, includes any step selected from heating step of heating the lithium ion secondary battery after V _P charging process. The voltage maintenance step is a step of performing so-called trickle charge.
Any of the steps, by going through the time without exceeding the positive electrode potential V _P, while preventing aluminum corrosion of the positive electrode current collector foil may promote diffusion of lithium in the negative electrode active material layer. The aging process may combine two processes among the three processes mentioned above, or may combine all three processes.

The time of the aging step should be long in order for lithium diffusion in the negative electrode active material layer to proceed sufficiently. As specific time for the entire aging step or for each step, 1 to 50 hours, 5 to 30 hours, and 10 to 25 hours can be exemplified.
If the temperature of the heating step is a temperature at which the components of the lithium ion secondary battery do not deteriorate, a higher temperature is preferable because it increases the lithium diffusion rate. As heating conditions in the heating step, 30 ° C. to 120 ° C., 40 ° C. to 110 ° C., 50 ° C. to 100 ° C., 60 ° C. to 90 ° C. can be exemplified.

The charging rate in the _VP-cutoff charging step may be a constant rate or may vary in rate. It is preferable that the charging speed is fast because the time for the _VP-cutoff charging step can be shortened. As a charge rate in a _VP-cutoff charge process, 1 C or more and 15 C or less, 2 C or more and 10 C or less, 3 C or more and 7 C or less, 4 C or more and 6 C or less can be exemplified.

Next, b) conditions will be described.
b) condition, the _{V P} charging step of charging up positive electrode potential _{V P,} is intended to include charging at a rate of less than 0.1 C. That, b) conditions are those that by charging at a relatively low rate earn time to reach the positive electrode potential V _P, prompt the lithium diffusion of the negative electrode active material layer.

  From the technical point of view, the charge rate under condition b) is preferably as low as possible, but from the viewpoint of production efficiency, it is not preferable if the charge rate under condition b) is too slow. The charge rate under the condition b) is preferably 0.005 C or more and less than 0.1 C, more preferably 0.01 C or more and 0.07 C or less, and still more preferably 0.03 C or more and 0.05 C or less.

From the technical point of view, under the condition b), if the charging at a low rate is partially performed in the range from the positive electrode potential V _p-ocv to the positive electrode potential V _P , the effect of lithium diffusion is exhibited. It can be said. Of course, charging at a low rate preferably occupies most of the range from the positive electrode potential V _p-ocv to the positive electrode potential V _P , for example, it is preferable to be carried out at 50% or more of the range, More preferably, it is carried out at 70% or more of the range, more preferably at 90% or more of the range, and most preferably carried out over all of the range.

In b) conditions, charging at a low rate may be carried out until the positive electrode cutoff potential _{V P-cutoff} beyond positive electrode potential _{V P.} The charging rate from exceeding the positive electrode potential _{V P} is, a) may be the same speed and _{V P-cutoff} charging process described in condition.

  b) The conditions are preferably carried out under heating conditions. As the temperature is higher, promotion of the diffusion of lithium in the negative electrode active material layer can be expected. As heating conditions, 30 ° C. to 120 ° C., 40 ° C. to 110 ° C., 50 ° C. to 100 ° C., 60 ° C. to 90 ° C. can be exemplified.

  The method for producing a lithium ion secondary battery of the present invention is characterized in that it is carried out under conditions satisfying either a) conditions or b) conditions, but under conditions satisfying both a) conditions and b) conditions. It is preferred to do.

  In the lithium ion secondary battery of the present invention, the laminate obtained by laminating the positive electrode plate, the separator and the negative electrode plate may be a wound type in which the laminate is wound, and the positive electrode plate, the separator and the negative electrode plate are in a planar state It may be of the laminated type as it is. From the viewpoint of controlling the facing relationship between the positive electrode uncoated portion and the end of the negative electrode active material layer, a laminated type is preferable.

  As a material of the battery container of the lithium ion secondary battery of this invention, the laminated body which laminated | stacked metal, such as aluminum, stainless steel, resin, and aluminum, and resin can be illustrated. The shape of the battery container of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as cylindrical, square, coin, and laminate types can be adopted.

  The lithium ion secondary battery of the present invention can be used under high voltage conditions because aluminum elution from the positive electrode current collector foil can be reduced by the manufacturing method under any of the conditions a) and b). Is possible. Specifically, as the high voltage condition, the potential at the positive electrode is 3.9 V or more, 4 V or more, 4 to 5.5 V, 4.1 to 5 V, 4.3 to 4.8 V, based on lithium. It can be illustrated. The lithium ion secondary battery of the present invention can also be recognized as a high voltage lithium ion secondary battery.

  The following charge control device can be grasped by the method of manufacturing a lithium ion secondary battery of the present invention.

  The charge control device includes a control unit that causes the lithium ion secondary battery to perform an initial charge under a condition that satisfies any of the above a) and b) conditions. The charge control device may be disposed in a manufacturing facility of a lithium ion secondary battery, or may be disposed in a charging system for charging the lithium ion secondary battery before or after shipment of the lithium ion secondary battery. It is preferable that the charge control device, the production facility, or the charge system include a temperature control unit that controls the temperature of the lithium ion secondary battery.

  The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle using electric energy from a lithium ion secondary battery for all or part of its power source, and may be, for example, an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form a battery pack. As an apparatus which mounts a lithium ion secondary battery, various household appliances driven by a battery, such as a personal computer and a mobile communication apparatus, as well as a vehicle, an office apparatus, an industrial apparatus and the like can be mentioned. Furthermore, the lithium ion secondary battery of the present invention can be used in wind power generation, solar power generation, hydroelectric power generation, storage devices and power smoothing devices for electric power systems, power sources for power and / or accessories of ships, etc., aircraft, Power supply source for power of spacecraft and / or accessories, auxiliary power supply for vehicles not using electricity as power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charge station etc. for electric vehicles.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. In the range which does not deviate from the summary of the present invention, it can carry out with various forms which gave change, improvement, etc. which a person skilled in the art can make. In the present specification, although a lithium ion secondary battery in which the charge carrier is lithium is specifically described as an embodiment of the present invention, in the technical matter disclosed in the present specification, the charge carrier is sodium The present invention is also applicable to a sodium ion secondary battery, a potassium ion secondary battery in which the charge carrier is potassium, a magnesium ion secondary battery in which the charge carrier is magnesium, and the like. When the technical matter disclosed in the present specification is applied to a sodium ion secondary battery or a potassium ion secondary battery, the descriptions of “lithium” and “Li” in the present specification are “sodium” and “lithium,” respectively. It may be read as Na "or" potassium "and" K ". When the technical matter disclosed in the present specification is applied to a magnesium ion secondary battery, the descriptions of “lithium” and “Li” in the present specification are appropriately matched in valence as necessary. Above, it should be read as “magnesium” and “Mg”.

  Hereinafter, the present invention will be specifically described by showing Examples and Comparative Examples. The present invention is not limited by these examples.

Example 1
The lithium ion secondary battery of Example 1 was manufactured under the following conditions a).

90 parts by mass of LiNi _50/100 Co _35/100 Mn _15/100 O ₂ which is a positive electrode active material, 5 parts by mass of acetylene black which is a conduction aid, 3 parts by mass of graphite which is a conduction aid, and a binder Two parts by mass of certain polyvinylidene fluoride were mixed. This mixture was dispersed in a suitable amount of N-methyl-2-pyrrolidone with some amount of dispersant to produce a slurry. As a current collector foil for positive electrodes, an aluminum foil corresponding to a 15 μm thick JIS A1000 series was prepared. The slurry was applied in the form of a film on the surface of the aluminum foil using a doctor blade. The N-methyl-2-pyrrolidone was removed by drying the slurry-coated aluminum foil at 80 ° C. for 20 minutes. Thereafter, this aluminum foil was pressed to obtain a bonded product. The obtained bonded product was dried by heating at 120 ° C. for 6 hours in a vacuum dryer to obtain an aluminum foil on which a positive electrode active material layer was formed. This was used as a positive electrode plate. The positive electrode coated portion on which the positive electrode active material layer is formed and the positive electrode uncoated portion on which the positive electrode active material layer is not formed are present on one surface of the aluminum foil of the positive electrode plate.

  As a negative electrode active material, 98 parts by mass of graphite, and 1 part by mass of styrene butadiene rubber as a binder and 1 part by mass of carboxymethyl cellulose were mixed. The mixture was dispersed in an appropriate amount of ion exchange water to prepare a slurry. A copper foil with a thickness of 10 μm was prepared as a current collector foil for the negative electrode. The slurry was applied in the form of a film on the surface of the copper foil using a doctor blade. The copper foil coated with the slurry was dried to remove water, and then the copper foil was pressed to obtain a joint. The obtained bonded product was dried by heating at 100 ° C. for 6 hours with a vacuum dryer to obtain a copper foil on which a negative electrode active material layer was formed. This was used as a negative electrode plate.

A mixed solvent was prepared by mixing dimethyl carbonate and ethyl methyl carbonate at a molar ratio of 9: 1. In the mixed solvent, (FSO ₂ ) ₂ NLi was dissolved at a concentration of 2.4 mol / L to prepare an electrolytic solution.

  As a separator, a polyethylene porous film having a thickness of 16 μm and a porosity of 47% was prepared.

  The separator was sandwiched between the positive electrode plate and the negative electrode plate to form an electrode plate group. The electrode plate group was covered with a pair of laminate films, the three sides were sealed, and then an electrolytic solution was injected into the bag-like laminate film. Thereafter, by sealing the other side, the four sides were airtightly sealed, and a lithium ion secondary battery in which the electrode plate group and the electrolytic solution were sealed was assembled. In the lithium ion secondary battery, the positive electrode plate and the negative electrode plate face each other with the separator interposed therebetween, and the positive electrode uncoated portion and the end of the negative electrode active material layer face each other.

a) Initial charge / _VP charge process according to conditions The assembled lithium ion secondary battery was charged to a voltage of 3.8 V at a constant current of 5C. Since a voltage of 3.8 V corresponds to a positive electrode potential of 3.9 V based on lithium, V _P = 3.9 V.
Aging Step A constant voltage charge was performed to maintain the voltage 3.8 V of the lithium ion secondary battery for 2 hours. Thereafter, charging of the lithium ion secondary battery was stopped, and the lithium ion secondary battery was placed in a 60 ° C. thermostat. Aging was performed by storing the lithium ion secondary battery in a constant temperature bath at 60 ° C. for 20 hours.
_-VP-cutoff charge step The lithium ion secondary battery after the aging step was charged to a voltage of 4.1 V at a constant current of 5 C, and the voltage was maintained for 2 hours. Since the voltage of 4.1 V corresponds to a positive electrode potential of 4.2 V based on lithium, V _{P -cutoff} = 4.2 V. The lithium ion secondary battery after the _VP-cutoff charging step was used as the lithium ion secondary battery of Example 1.

  The schematic diagram at the time of observing the lithium ion secondary battery of Example 1 from the thickness side of a positive electrode plate, a separator, and a negative electrode plate is shown in FIG. In the following description, the vertical means the vertical direction in FIG. 1 and the horizontal means the front side-back side direction in FIG.

The lithium ion secondary battery 1 of Example 1 is
A positive electrode plate 2 comprising a positive electrode current collector foil 20 made of aluminum and a positive electrode active material layer 21 formed on the surface of the positive electrode current collector foil 20, a negative electrode current collector foil 30 and a surface of the negative electrode current collector foil 30 A negative electrode plate 3 having the formed negative electrode active material layer 31, a separator 4, and an electrolytic solution 5 containing (FSO ₂ ) ₂ NLi as a lithium salt,
On the surface of the positive electrode current collector foil 20, a positive electrode uncoated portion 22 where the positive electrode active material layer 21 is not formed is present,
The positive electrode plate 2 and the negative electrode plate 3 face each other with the separator 4 interposed therebetween, and the positive electrode uncoated portion 22 and the end portion 32 of the negative electrode active material layer 31 face each other.

The positive electrode current collector foil 20 is a pure aluminum of JIS A1000 series, and is a foil having a thickness of 15 μm, a length of 40 mm, and a width of 30 mm. On one surface of the positive electrode current collector foil 20, a positive electrode active material layer 21 is formed with a width of 30 mm and a thickness of 22 μm from the lower end in the vertical direction of the positive electrode current collector foil 20 to 25 mm in the upper end direction. In the positive electrode active material layer 21, 90 parts by mass of LiNi _50/100 Co _35/100 Mn _15/100 O ₂ which is a positive electrode active material, 5 parts by mass of acetylene black which is a conductive agent, and graphite which is a conductive agent 3 parts by mass, and 2 parts by mass of polyvinylidene fluoride as a binder.

Furthermore, the positive electrode uncoated portion 22 where the positive electrode active material layer 21 is not formed on the surface of the positive electrode current collector foil 20 is a portion where the positive electrode active material layer 21 is formed, that is, from the end of the positive electrode coating portion , Over the upper end of the positive electrode current collector foil 20. The positive electrode uncoated portion 22 is in a facing relationship with the end portion 32 of the negative electrode active material layer 31 via the separator 4.
The upper end of the positive electrode current collector foil 20 is connected to the external power supply 15 via the positive electrode conductor 24.

The negative electrode current collector foil 30 is a copper foil having a thickness of 10 μm, a length of 40 mm, and a width of 32 mm. On one surface of the negative electrode current collector foil 30, a negative electrode active material layer 31 is formed with a width of 32 mm, extending from the upper end in the vertical direction of the negative electrode current collector foil 30 to the lower end direction for 30 mm. The negative electrode active material layer 31 contains 98 parts by mass of graphite as a negative electrode active material, 1 part by mass of carboxymethylcellulose as a binder, and 1 part by mass of styrene butadiene rubber as a binder. Is doped with lithium.
The lower end of the negative electrode current collector foil 30 is connected to the external power supply 15 via the negative electrode conductor 34.

  The separator 4 is a polyethylene porous membrane with a thickness of 16 μm. The separator 4 has a surface larger than the surfaces of the positive electrode active material layer 21 and the negative electrode active material layer 31 facing the separator 4. The separator 4 is positioned between the positive electrode plate 2 and the negative electrode plate 3 so as to prevent the positive electrode plate 2 from contacting the negative electrode plate 3.

The positive electrode plate 2, the negative electrode plate 3 and the separator 4 are sealed inside the battery container 10 in a stacked state maintaining a flat surface. The battery case 10 is made of an aluminum laminate film. The electrolytic solution 5 is injected into the inside of the battery case 10. The electrolytic solution 5 contains (FSO ₂ ) ₂ NLi as a lithium salt, and contains, as an organic solvent, a mixed solvent in which dimethyl carbonate and ethyl methyl carbonate are mixed at a molar ratio of 9: 1. The concentration of (FSO ₂ ) ₂ NLi in the electrolyte solution 5 is 2.4 mol / L.

(Example 2)
A lithium ion secondary battery of Example 2 was manufactured in the same manner as Example 1, except that the initial charge was performed under the following conditions b).

b) Initial charge according to conditions The assembled lithium ion secondary battery was charged to a voltage of 4.1 V at a constant current of 0.05 C under room temperature conditions, and the voltage was maintained for 2 hours. The resultant was used as a lithium ion secondary battery of Example 2.

(Comparative example 1)
A lithium ion secondary battery of Comparative Example 1 was manufactured in the same manner as Example 1, except that the initial charge was performed as follows.

Initial Charge The assembled lithium ion secondary battery was charged to a voltage of 4.1 V at a constant current of 5 C under room temperature conditions, and the voltage was maintained for 2 hours. The resultant was used as a lithium ion secondary battery of Comparative Example 1.

(Evaluation example 1)
For the lithium ion secondary battery of Example 1, the charge and discharge cycle of discharging to 3.3 V with a constant current of 2 C and charging to 4.1 V at 60 ° C. was repeated 30 times. Further, the battery was discharged to 3.0 V at a constant current of 1 C rate under the condition of 25 ° C., and then the voltage was maintained for 2 hours.
Disassembling the lithium ion secondary battery of Example 1 in which the above charge and discharge were performed, and leaving the negative electrode plate in the solution of dimethyl carbonate for 10 minutes while repeating the solution three times to replace the remaining electrolyte The liquid components were washed and then the negative plate was subjected to analysis. The amount of aluminum attached to the negative electrode plate was measured by ICP emission analysis. The same evaluation was performed on the lithium ion secondary batteries of Example 2 and Comparative Example 1. The results are shown in Table 1.

  From the results in Table 1, it can be seen that the aluminum deposition on the negative electrode plate is remarkably suppressed by performing the initial charge under the conditions satisfying either a) conditions or b) conditions. It can be said that the technical significance of the present invention is supported.

DESCRIPTION OF SYMBOLS 1 lithium ion secondary battery 2 positive electrode plate 3 negative electrode plate 4 separator 5 electrolyte solution 10 battery container 15 external power supply 20 positive electrode current collector foil 21 positive electrode active material layer 22 positive electrode uncoated portion 24 positive electrode lead 30 negative electrode current collector foil 31 negative electrode active Material layer 32 end 34 negative lead

Claims (6)

A positive electrode plate comprising a positive electrode current collector foil made of aluminum and a positive electrode active material layer formed on the surface of the positive electrode current collector foil, a negative electrode current collector foil and a negative electrode active material formed on the surface of the negative electrode current collector foil A negative electrode plate having a layer, a separator, and an electrolytic solution containing a lithium salt selected from the following general formula (1) and general formula (2),
The positive electrode uncoated part in which the said positive electrode active material layer is not formed exists in the surface of the said positive electrode current collection foil,
The positive electrode plate and the negative electrode plate face each other with the separator interposed therebetween, and for a lithium ion secondary battery in which the positive electrode uncoated portion and the end of the negative electrode active material layer face each other,
From the positive electrode potential V _p-ocv (potential is based on lithium) at the start of the first charge, through the positive electrode potential V _P (potential is based on lithium: V _p-ocv <V _p <4.0 V), the positive electrode termination potential V _{P -cutoff} lithium ion secondary (potential of lithium reference .4.0V ≦ _{V P-cutoff)} and performing under conditions satisfying either the first charge to charge up, the following a) conditions and b) conditions Method of manufacturing secondary battery.
V _P charging step of charging up a) conditions the positive electrode potential V _P, aging step of aging the lithium ion secondary battery after V _P charging process, and the lithium ion secondary battery after aging step V _P-cutoff It includes a _VP-cutoff charging step to charge up to.
In _{V P} charging step of charging up b) conditions the positive electrode potential _{V P,} including charging at a rate of less than 0.1 C.
(R ¹ X ¹ ) (R ² SO ₂ ) NLi General formula (1)
(R ¹ is hydrogen, halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, an unsaturated alkyl group which may be substituted by a substituent, a substituent Or unsaturated cycloalkyl group which may be substituted, aromatic group which may be substituted by a substituent, heterocyclic group which may be substituted by a substituent, alkoxy group which may be substituted by a substituent An unsaturated alkoxy group which may be substituted by a substituent, a thioalkoxy group which may be substituted by a substituent, an unsaturated thioalkoxy group which may be substituted by a substituent, CN, SCN or OCN Be done.
R ² represents a hydrogen, a halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, an unsaturated alkyl group which may be substituted by a substituent, a substituent An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted by a substituent, a heterocyclic group which may be substituted by a substituent, an alkoxy group which may be substituted by a substituent, An unsaturated alkoxy group which may be substituted, a thioalkoxy group which may be substituted, an unsaturated thioalkoxy group which may be substituted, and a substituent selected from CN, SCN and OCN Ru.
Further, R ¹ and R ² may be bonded to each other to form a ring.
X ¹ is selected from SO ₂ , C = O, C = S, R ^a P = O, R ^b P = S, S = O, and SiOO.
R ^a and R ^b each independently represent hydrogen, a halogen, an alkyl group which may be substituted by a substituent, a cycloalkyl group which may be substituted by a substituent, or a substituent which may be substituted by a substituent A saturated alkyl group, an unsaturated cycloalkyl group which may be substituted by a substituent, an aromatic group which may be substituted by a substituent, a heterocyclic group which may be substituted by a substituent, a substituent Alkoxy group which may be substituted, unsaturated alkoxy group which may be substituted by a substituent, thioalkoxy group which may be substituted by a substituent, unsaturated thioalkoxy group which may be substituted by a substituent, OH , SH, CN, SCN, OCN.
In addition, R ^a and R ^b may combine with R ¹ or R ² to form a ring. )
R ³ SO ₃ Li General formula (2)
(R ³ is selected from an alkyl group or a halogen-substituted alkyl group.)   The method for producing a lithium ion secondary battery according to claim 1, wherein the concentration of the electrolyte containing the lithium salt in the electrolytic solution is 1.5 to 3 mol / L. Wherein _{V P} is method for producing a lithium ion secondary battery according to claim 1 or 2 in the range of 3.2V ≦ _{V P} ≦ 3.9V. Said _{V P} charging step, the anode potential _{V n-ocv} upon first start of charging (potential relative to lithium.) Is performed until the anode potential _{V n} which is 50% or less, in any one of claims 1 to 3 The manufacturing method of the lithium ion secondary battery as described. The aging process is the charging suspension process to pause charging the lithium ion secondary battery after the V _P charging process, the voltage maintenance to maintain the V _P the lithium ion secondary battery after the V _P charging step step, and a lithium ion secondary according to claim 1, comprising any of the steps selected from the heating step of the V _P warming a lithium ion secondary battery after charging step How to make a battery.   The method for producing a lithium ion secondary battery according to any one of claims 1 to 5, wherein the initial charge is performed under conditions satisfying both the a) conditions and the b) conditions.

Images