JP2019021394A - Lithium ion secondary battery - Google Patents

Abstract

To provide a lithium ion secondary battery in which an amount of aluminum deposited on a negative electrode is reduced.SOLUTION: A lithium ion secondary battery 1 comprises: a positive electrode plate 2 including positive electrode current collector foil 20 made of aluminum and a positive electrode active material layer 21 formed on a surface of the positive electrode current collector foil 20; a negative electrode plate 3 including negative electrode current collector foil 30 and a negative electrode active material layer 31 formed on a surface of the negative electrode current collector foil 30; a separator 4; and an electrolyte solution 5. In the surface of the positive electrode current collector foil 20, there is a positive electrode uncoated part 22 where the positive electrode active material layer 21 is not formed. The positive electrode plate 2 and the negative electrode plate 3 are opposed to each other through the separator 4, and the positive electrode uncoated part 22 is opposed to an end portion 32 of the negative electrode active material layer 31. In the lithium ion secondary battery 1, the separator 4 includes: a first separator part 41 between the positive electrode active material layer 21 and the negative electrode active material layer 31; and a second separator part 42 between the positive electrode uncoated part 22 and the end portion of the negative electrode active material layer 31. The second separator part 42 is lower, in gas permeability, than the first separator part 41.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lithium ion secondary battery.

Generally, a lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution as main components. An appropriate electrolyte is added to the electrolytic solution in an appropriate concentration range. For example, a lithium salt such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , CF ₃ SO ₃ Li, or (CF ₃ SO ₂ ) ₂ NLi is added as an electrolyte to the electrolyte solution of a lithium ion secondary battery. Here, the concentration of the lithium salt in the electrolytic solution is generally about 1 mol / L.

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

  Moreover, as reported in many literatures, it is common to use the metal foil made from aluminum for the collector in the positive electrode of a lithium ion secondary battery.

Actually, in Patent Document 1, a mixed organic solvent containing 33% by volume of ethylene carbonate and an electrolytic solution containing LiPF ₆ at a concentration of 1 mol / L, a positive electrode using a positive electrode current collector foil made of aluminum, and There is disclosed a lithium ion secondary battery comprising:

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

In addition, the lithium ion secondary battery includes a positive electrode plate having a positive electrode current collector foil and a positive electrode active material layer formed on the surface of the positive electrode current collector foil, and a negative electrode current collector foil and a surface of the negative electrode current collector foil. A negative electrode plate having a formed negative electrode active material layer; and a separator, the positive electrode plate and the negative electrode plate are generally facing each other with the separator interposed therebetween, and the positive electrode current collector foil In general, the positive electrode uncoated portion where the positive electrode active material layer is not formed on the surface of the negative electrode active material layer and the end portion of the negative electrode active material layer face each other.
Although there is a tendency for lithium ions to concentrate at the end of the negative electrode active material layer, and there is a concern that metallic lithium may precipitate due to the concentration of lithium ions, the positive electrode uncoated part that does not have releasable lithium ions And the end of the negative electrode active material layer facing each other, so that concentration of lithium ions at the end of the negative electrode active material layer can be suppressed, and precipitation of metallic lithium can be suppressed. is there.

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

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

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

  When the present inventors have closely observed the positive electrode current collector foil of the lithium ion secondary battery after the charge / discharge test described above, the aluminum in the uncoated positive electrode portion facing the end of the negative electrode active material layer was corroded. I found out the phenomenon. From this knowledge, under charge / discharge conditions, aluminum in the positive electrode uncoated portion facing the end of the negative electrode active material layer was dissolved in the electrolyte as aluminum ions, and the aluminum ions were reduced on the negative electrode. It is thought to deposit as aluminum or aluminum compounds.

This phenomenon is considered to have occurred by the following mechanism.
It is presumed that an equilibrium reaction in which the following equations (1) and (2) occur simultaneously occurs at the interface between the aluminum and the electrolytic solution in the positive electrode uncoated portion. In normal times, the reaction rate of the formula (2) is significantly higher than the reaction rate of the formula (1), so that the aluminum ion concentration in the electrolytic solution is extremely low.
(1) Al → Al ³⁺ + 3e ⁻
(2) Al ³⁺ + 3e ⁻ → Al

  However, electrons are supplied to the negative electrode active material layer under the charging conditions of the lithium ion secondary battery. At this time, Li ions corresponding to the number of supplied electrons 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 on which the positive electrode active material layer is formed. The material layer remains electrically neutral. On the other hand, electrons are also supplied to the negative electrode active material layer at the end of the negative electrode active material layer, that is, the portion of the negative electrode active material layer facing the aluminum that is not coated with the positive electrode active material. Therefore, Li ions are not supplied and electrons accumulate and are charged. The end of the charged negative electrode active material layer is in a cationic state, and an equilibrium reaction of formula (1) and formula (2) occurs at the interface between the aluminum and the electrolyte facing the end of the negative electrode active material layer. . Therefore, it is considered that aluminum ions that are cations are electrostatically attracted to the end of the charged negative electrode active material layer via the electrolytic solution. Here, when aluminum ions are combined with electrons in the negative electrode active material layer to become zero-valent aluminum, the concentration of aluminum ions in the electrolytic solution decreases, and therefore, at the interface between the positive electrode uncoated portion aluminum and the electrolytic solution. In the above-described equilibrium reaction, the reaction rate of the formula (1) is increased as compared with the normal time. As a result, it is considered that aluminum corrosion of the positive electrode uncoated portion proceeds.

  Then, this inventor recalled inhibiting aluminum ion moving to the edge part side of a negative electrode active material layer. As a specific means, since the aluminum ions generated from the positive electrode current collector foil of the positive electrode uncoated portion pass through the holes of the separator and reach the end of the negative electrode active material layer, the positive electrode uncoated portion and the end Recalling that the separator sandwiched between the parts is in a state where it is difficult for aluminum ions to pass through.

The lithium ion secondary battery of the present invention is
A positive electrode plate comprising an aluminum 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 a negative electrode active material formed on the surface of the negative electrode current collector foil A negative electrode plate comprising a layer, a separator, and an electrolyte solution,
On the surface of the positive electrode current collector foil, there is a positive electrode uncoated portion where the positive electrode active material layer is not formed,
The positive electrode plate and the negative electrode plate face each other with the separator interposed therebetween, and the positive electrode uncoated part and the end of the negative electrode active material layer face each other,
The separator includes a first separator portion sandwiched between the positive electrode active material layer and the negative electrode active material layer, and a second separator portion sandwiched between end portions of the positive electrode uncoated portion and the negative electrode active material layer, The air permeability of the second separator is lower than the air permeability of the first separator.

  In the lithium ion secondary battery of the present invention, the amount of aluminum deposited on the negative electrode is reduced because the second separator portion sandwiched between the positive electrode uncoated portion and the end portion of the negative electrode active material layer suppresses the passage of aluminum ions. it can.

  According to the lithium ion secondary battery of the present invention, since the decrease in the concentration of aluminum ions in the electrolytic solution is suppressed, the above-described equilibrium reaction at the interface between the positive electrode uncoated portion aluminum and the electrolytic solution is as usual, Equation (2) remains advantageous. Therefore, it can be said that the separator including the first separator portion and the second separator portion has an aluminum elution reduction effect.

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

  Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from these numerical ranges can be used as new upper and lower numerical values.

The lithium ion secondary battery of the present invention is
A positive electrode plate comprising an aluminum 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 a negative electrode active material formed on the surface of the negative electrode current collector foil A negative electrode plate comprising a layer, a separator, and an electrolyte solution,
On the surface of the positive electrode current collector foil, there is a positive electrode uncoated portion where the positive electrode active material layer is not formed,
The positive electrode plate and the negative electrode plate face each other with the separator interposed therebetween, and the positive electrode uncoated part and the end part of the negative electrode active material layer (hereinafter, simply referred to as “end part”) face each other. A lithium ion secondary battery,
The separator includes a first separator portion sandwiched between the positive electrode active material layer and the negative electrode active material layer, and a second separator portion sandwiched between end portions of the positive electrode uncoated portion and the negative electrode active material layer, The air permeability of the second separator is lower than the air permeability of the first separator.

  The positive electrode plate used for the lithium ion secondary battery of the present invention comprises an aluminum positive electrode current collector foil 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 referred to as an aluminum alloy. Examples of the aluminum alloy include Al—Cu, Al—Mn, Al—Fe, Al—Si, Al—Mg, Al—Mg—Si, and Al—Zn—Mg.

  Specific examples of aluminum or aluminum alloy include A1000 series alloys (pure aluminum series) such as JIS A1085 and A1N30, A3000 series alloys (Al-Mn series) such as JIS A3003 and A3004, JIS A8079, A8021, etc. A8000-based alloy (Al-Fe-based).

  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. As the positive electrode current collector foil, the surface thereof may be used after being treated by a known method.

  The positive electrode active material layer includes 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 the positive electrode active material, the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e 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, Ru, At least one element selected from Sc, Sn, In, Y, Bi, S, Si, Na, K, P, and V, 1.7 ≦ f ≦ 3), a lithium mixed metal oxide represented by Li ₂ MnO ₃ can be mentioned. Further, as a positive electrode active material, a spinel structure metal oxide such as LiMn ₂ O ₄ , a solid solution composed of a mixture of a spinel structure metal oxide and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (wherein M is selected from at least one of Co, Ni, Mn, and Fe). 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 the positive electrode active material may have the above composition formula as a basic composition, and a metal element contained in the basic composition may be substituted with another metal element. Moreover, you may use as a positive electrode active material the thing which does not contain a charge carrier (for example, lithium ion which contributes to charging / discharging). For example, sulfur alone, compounds in which sulfur and carbon are compounded, metal sulfides such as TiS ₂ , oxides such as V ₂ O ₅ and MnO ₂ , compounds containing polyaniline and anthraquinone, and aromatics in their chemical structures, conjugated two Conjugated materials such as acetic acid organic materials and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl, etc. may be adopted as the positive electrode active material.
When using a positive electrode active material that does not contain a charge carrier such as lithium, it is necessary to add a charge carrier to the positive electrode and / or the negative electrode in advance by a known method. The charge carrier may be added in an ionic state or in a non-ionic state such as a metal. For example, when the charge carrier is lithium, it may be integrated by attaching a lithium foil to the positive electrode and / or the negative electrode.

From the viewpoint of excellent and high capacity, and durability, as the positive electrode active material, the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e 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, 1.7 ≦ f ≦ 3) It is preferable to employ a lithium composite metal oxide.

  In the above general formula, the values of b, c, and d are not particularly limited as long as the above conditions are satisfied, but those in which 0 <b <1, 0 <c <1, 0 <d <1 are satisfied. And at least one of b, c, and d is in the range of 10/100 <b <90/100, 10/100 <c <90/100, 5/100 <d <70/100. More preferably, the ranges are 20/100 <b <80/100, 12/100 <c <70/100, 10/100 <d <60/100, 30/100 <b <70/100, More preferably, the ranges are 15/100 <c <50/100 and 12/100 <d <50/100.

  About a, e, and f, what is necessary is just a numerical value within the range prescribed | regulated by the said general formula, Preferably 0.5 <= a <= 1.5, 0 <= e <0.2, 1.8 <= f <= 2 0.5, more preferably 0.8 ≦ a ≦ 1.3, 0 ≦ e <0.1, 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 Examples include at least one metal element selected from an element and a transition metal element, 0 <x ≦ 2.2, 0 ≦ y ≦ 1). 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. As another specific positive electrode active material, Li ₂ MnO ₃ —LiCoO ₂ can be exemplified.

One type of positive electrode active material may be used, or a plurality of types may be used in combination. As a combination example of the positive electrode active material, the general formula of the 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 given. In the combined use of the lithium composite metal oxide and the polyanion compound, these mass ratios are preferably in the range of lithium composite metal oxide: polyanion compound = 90: 10 to 50:50, and 80:20 to 60:40. The range of is more preferable. The positive electrode active material may be coated with carbon.

  60-100 mass% is preferable, as for the 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 further more preferable.

  What is necessary is just to employ | adopt what is demonstrated with a negative electrode active material layer as a binder and a conductive support agent as needed. 0.1-10 mass% is preferable, as for the 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. This is because if the amount of the binder is too small, the moldability is lowered, whereas if the amount of the binder is too large, the energy density is lowered. 0.1-15 mass% is preferable, as for the 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 auxiliary is too small, an efficient conductive path may not be formed. On the other hand, if the amount of the conductive auxiliary is excessive, the moldability is deteriorated and the energy density of the electrode is lowered.

  In order to form the positive electrode active material layer on the surface of the positive electrode current collector foil, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used. A positive electrode active material may be applied to the surface of the positive electrode current collector foil. Specifically, a positive 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 the positive electrode current collector foil and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.

  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, and stainless steel, etc. The metal material can be exemplified. The negative electrode current collector foil may be coated with a known protective layer. You may use what processed the surface of the negative electrode current collector foil by the well-known method as 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 includes a negative electrode active material and, if necessary, a binder and / or a conductive aid. The thickness of the negative electrode active material layer is preferably within the range of 5 μm to 500 μm, more preferably within the range of 10 μm to 200 μm, and even more preferably within the range of 20 μm to 100 μm.

As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Accordingly, there is no particular limitation as long as it is a simple substance, alloy, or compound that can occlude and release lithium ions. For example, as a negative electrode active material, Li, group 14 elements such as carbon, silicon, germanium and tin, group 13 elements such as aluminum and indium, group 12 elements such as zinc and cadmium, group 15 elements such as antimony and bismuth, magnesium , Alkaline earth metals such as calcium, and group 11 elements such as silver and gold may be employed alone. When silicon or the like is used for the negative electrode active material, a silicon atom reacts with a plurality of lithiums, so that it becomes a high-capacity active material. However, there is a problem that volume expansion and contraction due to insertion and extraction of lithium becomes significant. In order to reduce the fear, it is also preferable to employ an alloy or compound in which another element such as a transition metal is combined with a simple substance such as silicon as the negative electrode active material. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloy, Cu-Sn alloy, Co-Sn alloy, carbon-based materials such as various graphites, SiO _x (disproportionated to silicon simple substance and silicon dioxide). Examples thereof include silicon-based materials such as 0.3 ≦ x ≦ 1.6), silicon alone, or composites obtained by combining silicon-based materials and carbon-based materials. 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 materials 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. Any material containing silicon may be used as long as it contains Si and functions as a negative electrode active material. Specific examples of the Si-containing negative electrode active material include silicon alone, SiOx (0.3 ≦ x ≦ 1.6), alloys of Si and other metals, and silicon materials described in International Publication No. 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 International Publication No. 2014/080608 (hereinafter sometimes simply referred to as “silicon material”) will be described in detail. For example, the silicon material is subjected to a process of synthesizing a layered silicon compound containing polysilane as a main component by reacting CaSi ₂ with an acid, and further a process of heating the layered silicon compound at 300 ° C. or higher to desorb hydrogen. It is manufactured.

The method for producing a silicon material described in International Publication No. 2014/080608 is shown as an ideal reaction formula when hydrogen chloride is used as an acid.
3CaSi ₂ + 6HCl → Si ₆ H ₆ + 3CaCl ₂
Si ₆ H ₆ → 6Si + 3H ₂ ↑

However, in the upper reaction for synthesizing Si ₆ H ₆ which is polysilane, water is usually used as a reaction solvent from the viewpoint of removing by-products and impurities. Since Si ₆ H ₆ can react with water, in the step of synthesizing the layered silicon compound including the upper reaction, the layered silicon compound is hardly manufactured as containing only Si ₆ H ₆ , and the layered The silicon compound is represented by Si ₆ H _s (OH) _t X _u (X is an element or group derived from an acid anion, s + t + u = 6, 0 <s <6, 0 <t <6, 0 <u <6). Manufactured as a product. In the above chemical formula, inevitable impurities such as Ca that can remain are not taken into consideration. A silicon material obtained by heating the layered silicon compound also contains an element derived from an anion of oxygen or acid.

The silicon material has a structure in which a plurality of plate-like silicon bodies are laminated in the thickness direction. In order for charge carriers such as lithium ions to efficiently occlude and release, the plate-like silicon body preferably has a thickness in the range of 10 nm to 100 nm, more preferably in the range of 20 nm to 50 nm. The length in the longitudinal direction of the plate-like silicon body is preferably within a range of 0.1 μm to 50 μm. The plate-like silicon body preferably has (length in the longitudinal direction) / (thickness) in the range of 2 to 1000. The laminated structure of the plate-like silicon body can be confirmed by observation with a scanning electron microscope or the like. 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, the above plate-like silicon body is preferably in a state where amorphous silicon is used as a matrix and silicon crystallites are 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 Scherrer equation using X-ray diffraction measurement on the silicon material and using the half-value width of the diffraction peak of the Si (111) plane of the obtained X-ray diffraction chart. .

  The abundance 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 the heating time. The heating temperature is preferably in the range of 350 ° C to 950 ° C, more preferably in the range of 400 ° C to 900 ° C.

  In a lithium ion secondary battery comprising a negative electrode plate comprising graphite or a Si-containing negative electrode active material, 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 including the negative electrode plate having graphite or Si-containing negative electrode active material, the aluminum elution reduction effect by the separator including the first separator part and the second separator part is suitably exhibited. It can be said.

  60-100 mass% is preferable, as for the 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 further more preferable.

  The binder plays a role of connecting an active material, a conductive auxiliary agent, and the like to the surface of the current collector foil.

  Binders include 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 resins, and styrene butadiene. What is necessary is just to employ | adopt well-known things, such as rubber | gum.

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

  A polymer containing many 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 terms of 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 by, for example, a method of polymerizing an acid monomer or a method of imparting a carboxyl group to the polymer. Acid monomers include acrylic acid, methacrylic acid, vinyl benzoic 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 , Maleic acid, 2-pentenedioic acid, methylene succinic acid, allyl malonic acid, isopropylidene succinic acid, 2,4-hexadiene diacid, acetylenedicarboxylic acid, etc., acid monomers having two or more carboxyl groups in the molecule Is done.

  A copolymer obtained by polymerizing two or more acid monomers selected from the above acid monomers may be used as a binder.

  Further, for example, 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 JP 2013-065493 A, in the molecule It is also preferable to use as a binder. When the binder has a structure derived from a highly acidic monomer having two or more carboxyl groups in one molecule, it becomes easier for the binder to trap lithium ions etc. before the electrolyte decomposition reaction occurs during charging. It is considered. Furthermore, since the polymer has more carboxyl groups per monomer than polyacrylic acid or polymethacrylic acid, the acidity is increased, but since the predetermined amount of carboxyl groups is changed to acid anhydride groups, the acidity is increased. Is not too high. Therefore, a secondary battery having a negative electrode using the polymer as a binder has improved initial efficiency and improved input / output characteristics.

  In addition, a crosslinked polymer obtained by crosslinking a carboxyl group-containing polymer such as polyacrylic acid or polymethacrylic acid disclosed in International Publication No. 2016/063882 with a diamine may be used as a binder.

  Examples of the diamine used in the crosslinked polymer include alkylene diamines such as ethylene diamine, propylene diamine, and hexamethylene diamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, isophorone diamine, and bis (4-aminocyclohexyl) methane. Saturated carbocyclic diamine, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, bis (4-aminophenyl) sulfone, benzidine, o-tolidine, 2,4- Aromatic diamines such as tolylenediamine, 2,6-tolylenediamine, xylylenediamine, and naphthalenediamine are exemplified.

  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 imide bonds in the molecule. Polyamideimide is produced by reacting an acid component that becomes a carbonyl moiety in an amide bond and an imide bond with a diamine component or diisocyanate component that becomes a nitrogen moiety in the amide bond and imide bond. In order to obtain a polyamideimide, it may be produced by the method, or a commercially available polyamideimide may be purchased.

  Acid components used for the production of polyamideimide include trimellitic acid, pyromellitic acid, biphenyltetracarboxylic acid, diphenylsulfonetetracarboxylic acid, benzophenonetetracarboxylic acid, diphenylethertetracarboxylic 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, naphthalenedicarboxylic 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 combination, but from the point of forming an imide bond, an acid component in which a carboxyl group is present on the carbon adjacent to the carbon to which the carboxyl group is bonded or Its equivalent is essential. As the acid component, trimellitic anhydride is preferable from the viewpoints of reactivity and heat resistance. In addition to trimellitic acid anhydride, pyromellitic acid anhydride, benzophenonetetracarboxylic acid anhydride, biphenyltetra, as part of the acid component in addition to trimellitic acid anhydride, from the viewpoint of tensile strength, tensile modulus, and electrolyte resistance of polyamideimide It is preferable to employ a carboxylic acid anhydride.

  What is necessary is just to employ | adopt the diamine used for the crosslinked polymer mentioned above as a diamine component used for manufacture of a polyamideimide. 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 preferable.

  Examples of the diisocyanate component used for producing the polyamideimide include those obtained by replacing the amine of the diamine component with an isocyanate.

  0.1-20 mass% is preferable, as for the 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. This is because if the amount of the binder is too small, the moldability is lowered, whereas if the amount of the binder is too large, the energy density is lowered.

  The conductive assistant is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be any chemically inert electronic high conductor, and examples thereof include carbon black, graphite, Vapor Grown Carbon Fiber, and various metal particles. The Examples of carbon black include acetylene black, ketjen black (registered trademark), furnace black, and channel black. These conductive assistants can be added to the active material layer alone or in combination of two or more.

  0.1-30 mass% is preferable, as for the 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 further more preferable. If the amount of the conductive auxiliary is too small, an efficient conductive path may not be formed. On the other hand, if the amount of the conductive auxiliary is excessive, the moldability is deteriorated and the energy density of the electrode is lowered.

  In order to form a negative electrode active material layer on the surface of the negative electrode current collector foil, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used. A 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 the negative electrode current collector foil and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.

  The separator separates the positive electrode plate and the negative electrode plate and allows lithium ions to pass through while preventing a short circuit due to contact between the two electrodes. The lithium ion secondary battery of the present invention includes a first separator portion sandwiched between the positive electrode active material layer and the negative electrode active material layer, and a second separator portion sandwiched between end portions of the positive electrode uncoated portion and the negative electrode active material layer. In addition, a separator characterized in that the air permeability of the second separator part is lower than the air permeability of the first separator part is used.

  The air permeability of the second separator portion being lower than the air permeability of the first separator portion means that the fluid is less likely to pass through the second separator portion than the first separator portion. Since the aluminum ions contained in the electrolyte around the positive electrode uncoated portion are also difficult to pass through the second separator portion, the negative electrode active material layer is not an aluminum ion at the end of the negative electrode active material layer in a cation-philic state. Lithium ions that are abundant in the vicinity of the end of the substrate are preferentially supplied. In the second separator part, it is considered that lithium ions having an ion radius smaller than aluminum ions may pass preferentially.

The air permeability of the first separator part and the second separator part is preferably confirmed by the Gurley method in the air permeability of the JIS L 1913 general nonwoven fabric test method. The air permeability value (Gurley value) calculated by the Gurley method is the time (seconds) through which 100 mL of air passes. The larger the Gurley value, the lower the air permeability. Relationship Gurley G ₁ and the Gurley value G ₂ of the second separator portion of the first separator unit is G _{1 <G 2.} To illustrate the relationship between G ₁ and G ₂ , G ₁ <G ₂ <100 × G ₁ , 1.1 × G ₁ <G ₂ <80 × G ₁ , 1.5 × G ₁ <G ₂ <50 × G ₁ , 2 × G ₁ <G ₂ <10 × G ₁ , 3 × G ₁ <G ₂ <5 × G ₁ can be mentioned.

Specific Gurley _{G 1} of the first separator _{unit, 10s / 100mL <G 1 <} 500s / 100mL, 50s / 100mL <G 1 <400s / 100mL, the _{100s / 100mL <G 1 <300s} / 100mL exemplified . Specific Gurley value _{G 2} of the second separator _{section, 100s / 100mL <G 2 <} 5000s / 100mL, 200s / 100mL <G 2 <3000s / 100mL, 300s / 100mL <G 2 <2000s / 100mL, 600s / 100 mL <G ₂ <1000 s / 100 mL can be exemplified.

  When the relationship between the first separator part and the second separator part is described in terms of the structure, there may be a state in which the through-hole diameter of the second separator part is smaller than the through-hole diameter of the first separator part. There may be a state in which the number of through holes is smaller than the number of through holes in the first separator portion. Furthermore, it can be said that there may be a state in which the two states described above are combined.

The second separator portion may be non-breathable. In this case, the Gurley value G ₂ of the second separator unit to the infinite, the second separator section it can be said that the air through-hole is not present can pass.

  As a material of the first separator part and the second separator part, a known material used as a separator may be adopted. As materials of the first separator part and the second separator part, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester, polyacrylonitrile and other synthetic resins, cellulose, amylose and other polysaccharides, Examples thereof include porous materials, nonwoven fabrics, woven fabrics, and the like using one or more electrical insulating materials such as natural polymers such as fibroin, keratin, lignin, and suberin and ceramics. The first separator part and the second separator part may have a multilayer structure.

  The same material may be employ | adopted for a 1st separator part and a 2nd separator part on condition that the air permeability relationship is satisfied, and a different material may be employ | adopted. A first separator part and a second separator part may be formed by partially subjecting a general separator to heat treatment or chemical treatment. Further, a general separator may be partially laminated to form the first separator part and the second separator part.

  The separator including the first separator portion and the second separator portion is positioned between the positive electrode plate and the negative electrode plate so as to prevent contact between the positive electrode plate and the negative electrode plate. There is no particular limitation on the size of the first separator part on the premise that it is sandwiched between the positive electrode active material layer and the negative electrode active material layer. However, from the viewpoint of lithium ion permeability, it is preferable that the first separator portion face the entire surface of the positive electrode active material layer.

  There is no particular limitation on the size of the second separator part on the assumption that it is sandwiched between the positive electrode uncoated part and the end part of the negative electrode active material layer. However, the state in which the second separator portion faces the entire portion of the positive electrode uncoated portion that faces the negative electrode active material layer is preferable. Moreover, a 2nd separator part may also face the location which is not facing the negative electrode active material layer among positive electrode uncoated parts. In this case, it is possible to more suitably reduce the passage of aluminum ions through the separator.

  The separator including the first separator part and the second separator part preferably has a surface larger than the surfaces of the positive electrode active material layer and the negative electrode active material layer facing each other. From the viewpoint of short circuit prevention and prevention of metallic lithium precipitation, the size of the surface is preferably in the order of separator> negative electrode active material layer> positive electrode active material layer. As 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 manner covering the entire surface of the positive electrode active material layer, and the positive electrode active material layer and the negative electrode active material layer are covered. A state in which the separator faces the positive electrode active material layer and the negative electrode active material layer in a manner covering the entire surface of the material layer is preferable.

  The thickness of the first separator part and the second separator part is preferably within the range of 1 μm to 100 μm, more preferably within the range of 3 μm to 50 μm, further preferably within the range of 5 μm to 30 μm, and further within the range of 10 μm to 25 μm. preferable. The thickness of the first separator part and the second separator part may be the same or different.

  Although there is no limitation in particular as electrolyte solution of the lithium ion secondary battery of this invention, The electrolyte solution containing the lithium salt selected from following General formula (1) and General formula (2) is preferable. A book including a separator including a first separator portion and a second separator portion, even if the electrolyte solution contains a lithium salt selected from the following general formula (1) and general formula (2), which may cause aluminum elution. The lithium ion secondary battery of the invention can preferably suppress aluminum elution.

(R ¹ X ¹ ) (R ² SO ₂ ) NLi General formula (1)
(R ¹ is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R ² represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
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, Si = O.
R ^a and R ^b are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
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 term “may be substituted with a substituent” in the chemical structure represented by the general formula (1) will be described. For example, “an alkyl group which may be substituted with a substituent” means an alkyl group in which one or more of the hydrogens of the alkyl group are substituted with a substituent, or an alkyl group having no substituent To do.

  Examples of the substituent in the phrase “may be substituted with a substituent” include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an unsaturated cycloalkyl group, an aromatic group, a heterocyclic group, a halogen, and OH. SH, CN, SCN, OCN, nitro group, alkoxy group, unsaturated alkoxy group, amino group, alkylamino 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 with a substituent. When there are two or more substituents, the substituents may be the same or different.

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

(R ²³ X ² ) (R ²⁴ SO ₂ ) NLi Formula (1-1)
(R ²³ and R ²⁴ are each independently C _n H _a F _b Cl _c Br _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.
R ²³ and R ²⁴ may combine with each other to form a ring, in which case 2n = a + b + c + d + e + f + g + h is satisfied.
X ^{2 _{is, SO 2, C = O,}} C = S, R c P = O, R d P = S, S = O, is selected from Si = O.
R ^c and R ^d are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R ^c and R ^d may combine with R ²³ or R ²⁴ to form a ring. )

  The meaning of the phrase “may be substituted with a substituent” in the chemical structure represented by the general formula (1-1) is the same as described in the general formula (1).

In the chemical structure represented by the 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. In addition, when R < ²³ > and R < ²⁴ > of the chemical structure represented by the general formula (1-1) are combined to form a ring, n is preferably an integer of 1 to 8, and 1 to 7 Is more preferable, and an 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 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 combine 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 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. In addition, when R < ²⁵ > and R < ²⁶ > of the chemical structure represented by the general formula (1-2) are combined to form a ring, n is preferably an integer of 1 to 8, and 1 to 7 Is more preferable, and an integer of 1 to 3 is particularly preferable.

  In the chemical structure represented by the general formula (1-2), those in which a, c, d, and e are 0 are 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 the halogen of the halogen-substituted alkyl group, fluorine is preferable.

Lithium salts are (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 Those selected from are particularly preferred.

  In the electrolytic solution, one type of lithium salt selected from the general formula (1) and the general formula (2) may be adopted, or a plurality of types may be used in combination. Further, the electrolyte solution may contain an electrolyte other than the lithium salt selected from the general formula (1) and the general formula (2). The proportion of the lithium salt selected from the general formula (1) and the general formula (2) with respect to the entire electrolyte in the electrolytic solution is preferably 30 to 100 mol%, more preferably 50 to 95 mol%, and 70 to 90 mol%. Is more preferable. The concentration of the electrolyte containing the 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, 2-2.5 mol / L can be illustrated.

Specific examples of the electrolyte other than the lithium salt selected from the general formula (1) and the general formula (2) include LiPF ₆ , LiPF ₂ (OCOCOO) ₂ , LiBF ₄ , LiAsF _6, and Li ₂ SiF ₆ . All of these electrolytes have F that can be desorbed as F ⁻ . F ⁻ can react with aluminum to generate a stable Al—F bond. Therefore, it can be expected that the surface of the positive electrode uncoated portion is protected with a passive film containing an Al—F bond.

  The electrolytic solution contains an organic solvent for dissolving an electrolyte containing a lithium salt selected from the general formula (1) and the general formula (2). As the organic solvent, an organic solvent that can be used for a non-aqueous secondary battery may be employed, and it is particularly preferable to employ a low-polar organic solvent that hardly dissolves aluminum.

  Examples of the low polarity organic solvent include chain carbonates represented by the following general formula (3).

R ¹⁰ OCOOR ¹¹ general formula (3)
(R ¹⁰ and R ¹¹ are each independently C _n H _a F _b Cl _c Br _d I _e which is a chain alkyl, or C _m H _f F _g Cl _h Br _i I containing a cyclic alkyl in the chemical structure. selected from _j , n 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 an integer of 0 or more 2n + 1 = a + b + c + d + e, 2m-1 = f + g + h + i + j is satisfied.)

  In the chain carbonate represented by the 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.

  Of the chain carbonates represented by the general formula (3), those represented by the following general formula (3-1) are particularly preferred.

R ¹² OCOOR ¹³ general formula (3-1)
(R ¹² and R ¹³ are each independently selected from either C _n H _a F _b which is a chain alkyl or C _m H _f F _g containing a cyclic alkyl in the chemical structure. (The above integers, m is an integer of 3 or more, a, b, f, and g are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b and 2m-1 = f + g.)

  In the chain carbonate represented by the 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 chain carbonates represented by the general formula (3-1), dimethyl carbonate (hereinafter sometimes referred to as “DMC”), diethyl carbonate (hereinafter sometimes referred to as “DEC”), ethylmethyl 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, fluoromethyldifluoromethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, pentafluoroethyl methyl carbonate, ethyl trifluoromethyl carbonate, bis (2,2,2-trifluoroethyl) ) Carbonate is particularly preferred.

  One type of chain carbonate may be used for the electrolytic solution, or a plurality of types may be used in combination. By using a plurality of chain carbonates in combination, it is possible to suitably ensure the low temperature fluidity of the electrolyte and the lithium ion transportability at low temperatures. As a combination example of the chain carbonate, two or three types selected from DMC, DEC and EMC can be used. In the combined use of DMC and DEC or EMC, these molar ratios are 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, More preferably within the range of 80:20 to 95: 5.

  In the electrolytic solution, in addition to the chain carbonate, other organic solvents that can be used in an electrolytic solution such as a lithium ion secondary battery (hereinafter sometimes simply referred to as “other organic solvents”) are included. May be.

  In the electrolytic solution, the chain carbonate is preferably contained in an amount of 70% by volume, 70% by mass or more, or 70% by mol or more, based on the total organic solvent contained in the electrolytic solution, and 80% by volume, 80% by mass or more. Or more preferably 80 mol% or more, more preferably 90 vol%, 90 mass% or more, or 90 mol% or more, and more preferably 95 vol%, 95 mass% or more, or 95 mol% or more. Is particularly preferred. All the organic solvents contained in the electrolytic solution may be the chain carbonate.

  Specific examples of other organic solvents include nitriles such as acetonitrile, propionitrile, acrylonitrile, malononitrile, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, 1, Ethers such as 3-dioxane, 1,4-dioxane, 2,2-dimethyl-1,3-dioxolane, 2-methyltetrahydropyran, 2-methyltetrahydrofuran, 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 loridone, 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, glycidyl methyl ether, epoxy butane, epoxy such as 2-ethyloxirane, oxazole such as oxazole, 2-ethyloxazole, oxazoline, 2-methyl-2-oxazoline, acetone, methyl ethyl ketone, methyl isobutyl Ketones such as ketones, acid anhydrides such as acetic anhydride and propionic anhydride, sulfones such as dimethyl sulfone and sulfolane, sulfoxides such as dimethyl sulfoxide, 1-nitrate 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 Mention may be made of heterocyclic rings such as -4-pyrone, 1-methylpyrrolidine and N-methylmorpholine, and phosphoric esters such as trimethyl phosphate and triethyl phosphate.

  A known additive may be added to the electrolytic solution without departing from the spirit of the present invention. Examples of known additives include cyclic carbonates having unsaturated bonds typified by vinylene carbonate (VC), vinyl ethylene carbonate (VEC), methyl vinylene carbonate (MVC), and ethyl vinylene carbonate (EVC); Carbonate compounds typified by erythritan carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic acid Carboxylic anhydrides represented by dianhydrides and phenylsuccinic anhydrides; in place of γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone Lactones; cyclic ethers typified 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-methylsuccinimide Nitrogen-containing compounds represented by: phosphates represented by monofluorophosphates and difluorophosphates; saturated hydrocarbon compounds represented by heptane, octane and cycloheptane; biphenyls, alkylbiphenyls, terphenyls, terphenyls Partially hydrogenated phenyl, cyclohexane Shirubenzen, t- butyl benzene, t-amyl benzene, diphenyl ether, unsaturated hydrocarbon compounds and the like typified by dibenzofuran.

  In the lithium ion secondary battery of the present invention, the laminate in which the positive electrode plate, the separator, and the negative electrode plate are laminated may be a wound type with the laminated body interposed therebetween, or the positive electrode plate, the separator, and the negative electrode plate are in a planar state. It may be a laminated type that is still laminated. From the viewpoint of controlling the positional relationship between the positive electrode uncoated portion, the end portion of the negative electrode active material layer, and the second separator portion, the laminated type is preferable.

  Examples of the material of the battery container of the lithium ion secondary battery of the present invention include a laminate in which a metal such as aluminum, stainless steel, resin, and aluminum and a resin are laminated. 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 a cylindrical shape, a square shape, a coin shape, and a laminate shape can be adopted.

  The lithium ion secondary battery of the present invention can be used under high voltage conditions because the presence of the separator including the first separator portion and the second separator portion can reduce aluminum elution from the positive electrode current collector foil. . Specific examples of the high voltage condition include a condition where the potential on the basis of lithium to which the positive electrode is exposed is 4 V or more, 4 to 5.5 V, 4.1 to 5 V, 4.3 to 4.8 V. It can also be recognized that the lithium ion secondary battery of the present invention is a high voltage 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 that uses electric energy generated by a lithium ion secondary battery for all or a part of its power source. For example, the vehicle may be 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 an assembled battery. Examples of devices equipped with lithium ion secondary batteries include various home appliances driven by batteries such as personal computers and portable communication devices, office devices, and industrial devices in addition to vehicles. Furthermore, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power supplies for ships and / or auxiliary power supply sources, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a 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 charging station for electric vehicles.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art. In the present specification, a lithium ion secondary battery in which the charge carrier is lithium is specifically described as an embodiment of the present invention. However, the technical matter disclosed in this specification is that the charge carrier is sodium. The present invention can also be applied to sodium ion secondary batteries, potassium ion secondary batteries in which the charge carrier is potassium, magnesium ion secondary batteries in which the charge carrier is magnesium, and the like. When the technical matter disclosed in this specification is applied to a sodium ion secondary battery or a potassium ion secondary battery, the description of “lithium” and “Li” in this specification is referred to as “sodium” and “ What is necessary is just to read as "Na" or "potassium" and "K". When the technical matters disclosed in this specification are applied to a magnesium ion secondary battery, the descriptions of “lithium” and “Li” in this specification are appropriately matched in valence as necessary. In the above, it should be read as “magnesium” and “Mg”.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, this invention is not limited by these Examples.

(Production Example 1)
A polyethylene porous membrane having a thickness of 16 μm and a porosity of 47% was prepared. A part of the polyethylene porous membrane was heat-treated using a heat sealing machine to obtain the separator of Production Example 1. Of the separator of Production Example 1, the unheated part corresponds to the first separator part, and the heat-treated part corresponds to the second separator part.

(Production Example 2)
A separator of Production Example 2 was produced in the same manner as in Production Example 1 except that the heat treatment conditions of the heat sealing machine were strengthened.

(Production Example 3)
A separator of Production Example 3 was produced in the same manner as Production Example 2, except that the heat treatment conditions of the heat sealer were further strengthened.

(Comparative Production Example 1)
A polyethylene porous membrane having a thickness of 16 μm and a porosity of 47% was used as the separator of Comparative Production Example 1.

(Evaluation example 1)
Using a Gurley type air permeability tester, the second separator part of the separator of Production Example 1, the second separator part of the separator of Production Example 2, the second separator part of the separator of Production Example 3, and the Comparative Production Example 1 The separator was tested for air permeability. The air permeability of the separator of Comparative Production Example 1 corresponds to the air permeability of the first separator portion in the separators of Production Examples 1 to 3. The results are shown in Table 1.

Example 1
FIG. 1 shows a schematic diagram when the lithium ion secondary battery of Example 1 using the separator of Production Example 1 is observed from the thickness side of the positive electrode plate, the separator, and the negative electrode plate. In the following description, “vertical” means the vertical direction in FIG. 1, and “horizontal” means the front side-back side direction in FIG.

The lithium ion secondary battery 1 of Example 1 is
On the surface of the positive electrode plate 2 comprising the positive electrode current collector foil 20 made of aluminum and the positive electrode active material layer 21 formed on the surface of the positive electrode current collector foil 20, the negative electrode current collector foil 30 and the surface of the negative electrode current collector foil 30 A negative electrode plate 3 including 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, there is a positive electrode uncoated portion 22 where the positive electrode active material layer 21 is not formed,
The positive electrode plate 2 and the negative electrode plate 3 face each other with the separator 4 in between, and the positive electrode uncoated portion 22 and the end portion 32 of the negative electrode active material layer 31 face each other. 1 and
The separator 4 includes a first separator portion 41 sandwiched between the positive electrode active material layer 21 and the negative electrode active material layer 31, and a second separator portion 42 sandwiched between the positive electrode uncoated portion 22 and the end portion 32. The air permeability of the second separator portion 42 is lower than the air permeability of the first separator portion 41.

The positive electrode current collector foil 20 is JIS A1000 series pure aluminum, 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 lateral width of 30 mm and a thickness of 22 μm extending from the lower end in the vertical direction of the positive electrode current collector foil 20 to the upper end direction by 25 mm. The positive electrode active material layer 21 includes 90 parts by mass of LiNi _50/100 Co _35/100 Mn _15/100 O _{2 as} a positive electrode active material, 5 parts by mass of acetylene black as a conductive auxiliary agent, and graphite as a conductive auxiliary agent. 3 parts by mass, and 2 parts by mass of polyvinylidene fluoride as a binder.

Further, 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 formed from a portion where the positive electrode active material layer 21 is formed, that is, from the end of the positive electrode coated portion. And over the upper end of the positive electrode current collector foil 20. The positive electrode uncoated portion 22 is in a face-to-face relationship with the end portion 32 of the negative electrode active material layer 31 through the separator 4.
The upper end of the positive electrode current collector foil 20 is connected to the external power source 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 lateral width of 32 mm and a thickness of 40 μm extending from the upper end in the vertical direction of the negative electrode current collector foil 30 to the lower end direction by 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 carboxymethyl cellulose as a binder, and 1 part by mass of styrene butadiene rubber as a binder.
The lower end of the negative electrode current collector foil 30 is connected to the external power source 15 via the negative electrode conducting wire 34.

  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 contact between the positive electrode plate 2 and the negative electrode plate 3.

  The separator 4 includes a first separator portion 41 and a second separator portion 42. The first separator portion 41 is disposed between the positive electrode active material layer 21 and the negative electrode active material layer 31, and the second separator portion 42 is disposed between the positive electrode uncoated portion 22 and the end portion 32 of the negative electrode active material layer 31. Is arranged. Since the air permeability of the second separator portion 42 is lower than the air permeability of the first separator portion 41, liquid passage and movement of aluminum ions through the second separator portion 42 are suppressed.

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 in which a flat surface is maintained. The battery container 10 is made of an aluminum laminate film. An electrolytic solution 5 is injected into the battery container 10. The electrolytic solution 5 contains (FSO ₂ ) ₂ NLi as a lithium salt and contains a mixed solvent in which dimethyl carbonate and ethyl methyl carbonate are mixed at a molar ratio of 9: 1 as an organic solvent. The concentration of (FSO ₂ ) ₂ NLi in the electrolytic solution 5 is 2.4 mol / L.

(Example 2)
The lithium ion secondary battery of Example 2 has the same configuration as the lithium ion secondary battery of Example 1 except that the separator is the separator of Production Example 2.

(Example 3)
The lithium ion secondary battery of Example 3 has the same configuration as the lithium ion secondary battery of Example 1 except that the separator is the separator of Production Example 3.

(Comparative Example 1)
The lithium ion secondary battery of Comparative Example 1 has the same configuration as the lithium ion secondary battery of Example 1 except that the separator is the separator of Comparative Production Example 1.

(Evaluation example 2)
About the lithium ion secondary battery of Example 1, it charged to 4.1V by the constant current of 5C rate on 25 degreeC conditions, and charging for maintaining the same voltage was performed for 2 hours after that. Next, a charge / discharge cycle of discharging to 3.3 V at a constant current of 2C rate and charging to 4.1 V under a condition of 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 same voltage was maintained for 2 hours.
The lithium ion secondary battery of Example 1 that was charged and discharged as described above was disassembled, and the negative electrode plate was left in the dimethyl carbonate solution for 10 minutes. The liquid component was washed, and then the negative electrode 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 for the lithium ion secondary batteries of Example 2, Example 3, and Comparative Example 1. The results are shown in Table 2.

  From the results in Table 2, it can be seen that the amount of aluminum deposited on the negative electrode plate decreases as the Gurley value of the second separator portion in the separator increases, that is, as the air permeability of the second separator portion decreases. It was proved that aluminum precipitation on the negative electrode plate can be suppressed by the second separator portion suppressing the movement of aluminum ions to the negative electrode.

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Positive electrode plate 3 Negative electrode plate 4 Separator 41 1st separator part 42 2nd separator part 5 Electrolytic solution 10 Battery container 15 External power supply 20 Positive electrode current collection foil 21 Positive electrode active material layer 22 Positive electrode uncoated part 24 Positive electrode lead wire 30 Negative electrode current collector foil 31 Negative electrode active material layer 32 End portion 34 Negative electrode lead wire

Claims (4)

A positive electrode plate comprising an aluminum 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 a negative electrode active material formed on the surface of the negative electrode current collector foil A negative electrode plate comprising a layer, a separator, and an electrolyte solution,
On the surface of the positive electrode current collector foil, there is a positive electrode uncoated portion where the positive electrode active material layer is not formed,
The positive electrode plate and the negative electrode plate face each other with the separator interposed therebetween, and the positive electrode uncoated part and the end of the negative electrode active material layer face each other,
The separator includes a first separator portion sandwiched between the positive electrode active material layer and the negative electrode active material layer, and a second separator portion sandwiched between end portions of the positive electrode uncoated portion and the negative electrode active material layer, A lithium ion secondary battery, wherein the air permeability of the second separator portion is lower than the air permeability of the first separator portion. The lithium ion secondary battery according to claim 1, wherein the electrolytic solution contains 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 with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R ² represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
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, Si = O.
R ^a and R ^b are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
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 lithium ion secondary battery according to claim 2, wherein the electrolyte contains a lithium salt having a concentration of 1.5 to 3 mol / L.   The lithium ion secondary battery according to claim 1, wherein the positive electrode plate, the negative electrode plate, and the separator are stacked in a planar state.

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