JP2008305662A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having further superior cycle characteristics in respective charge voltages in the nonaqueous electrolyte secondary battery in which the charge voltage is set 4.25 V or more. <P>SOLUTION: The nonaqueous electrolyte secondary battery is equipped with a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator. An open circuit voltage in a completely charged state per a pair of the positive electrode and the negative electrode is 4.25 to 6.00 V. This has a porous insulating layer containing an insulating metal oxide at least at one position between the positive electrode and the negative electrode, and the separator contains polyethylene and other materials, and has a trilaminar-structure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery having an open circuit voltage of 4.25 V or more in a fully charged state per pair of positive electrode and negative electrode.

  With the remarkable development of portable electronic technology in recent years, electronic devices such as mobile phones and notebook computers have begun to be recognized as fundamental technologies that support an advanced information society. In addition, research and development related to the enhancement of the functions of these electronic devices have been energetically advanced, and the power consumption of these electronic devices has been increasing proportionally. On the other hand, these electronic devices are required to be driven for a long time, and a high energy density of a secondary battery as a driving power source has been inevitably desired. In addition, it has been desired to extend the cycle life for environmental reasons.

  From the standpoint of the occupied volume and mass of the battery built in the electronic device, the higher the energy density of the battery, the better. At present, since lithium ion secondary batteries have an excellent energy density, they have been built into most devices.

  Usually, in lithium ion secondary batteries, lithium cobaltate is used for the positive electrode and a carbon material is used for the negative electrode, and the operating voltage is used in the range of 4.2V to 2.5V. In the unit cell, the terminal voltage can be increased to 4.2 V largely due to excellent electrochemical stability such as a non-aqueous electrolyte material and a separator.

On the other hand, in a conventional lithium ion secondary battery operating at a maximum of 4.2 V, the positive electrode active material such as lithium cobaltate used for the positive electrode only uses about 60% of its theoretical capacity. Absent. For this reason, it is possible in principle to utilize the remaining capacity by further increasing the charging pressure. In fact, it is known that high energy density is manifested by setting the voltage during charging to 4.25 V or more (see Patent Document 1).
International Publication No. 03/019713 Pamphlet

  However, in the lithium ion secondary battery in which the charging voltage is set to 4.25 V or more, there is a problem that the separator is oxidatively decomposed and the cycle characteristics are deteriorated as a result of the oxidizing atmosphere particularly in the vicinity of the positive electrode surface.

Therefore, in a lithium ion secondary battery in which the charging voltage is set to 4.25 V or more, by including materials such as polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, aramid, polyimide, polyacrylonitrile in addition to polyethylene as a separator. It has been proposed to suppress oxidative decomposition of the separator (see Patent Document 2).
JP 2006-286531 A

  However, in the lithium ion secondary battery to which the separator described in Patent Document 2 is applied, an internal short circuit due to oxidation can be prevented by the separator, but there is a problem that thermal contraction during a short circuit and a large current short circuit cannot be prevented.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to provide each charging voltage even in a nonaqueous electrolyte secondary battery in which the charging voltage is set to 4.25 V or more. Is to provide a non-aqueous electrolyte secondary battery having more excellent cycle characteristics.

  The inventors of the present invention have made extensive studies in order to achieve the above object, and in a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator, a fully charged state per pair of positive electrode and negative electrode. An open circuit voltage in the region is 4.25 to 6.00 V, a porous insulating layer containing an insulating metal oxide is provided in at least one position between the positive electrode and the negative electrode, and the separator is made of polyethylene and other materials. It has been found that the above-mentioned object can be achieved by, for example, having a three-layer structure, and the present invention has been completed.

  That is, the non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, in a fully charged state per pair of positive electrode and negative electrode. An open circuit voltage is 4.25 to 6.00 V, and has a porous insulating layer containing an insulating metal oxide in at least one position between the positive electrode and the negative electrode; It has a three-layer structure while containing polyethylene and other materials.

  According to the present invention, in the nonaqueous electrolyte secondary battery including the positive electrode, the negative electrode, the nonaqueous electrolyte, and the separator, the open circuit voltage in a fully charged state per pair of the positive electrode and the negative electrode is 4.25 to 6.00 V. A porous insulating layer containing an insulating metal oxide is provided in at least one position between the positive electrode and the negative electrode, and the separator contains polyethylene and other materials and has a three-layer structure. Therefore, even in the non-aqueous electrolyte secondary battery in which the charging voltage is set to 4.25 V or more, it is possible to provide a non-aqueous electrolyte secondary battery having more excellent cycle characteristics at each charging voltage.

  Hereinafter, the nonaqueous electrolyte secondary battery of the present invention will be described. In the present specification and claims, “%” for content, concentration, etc. represents a mass percentage unless otherwise specified.

As described above, the nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator, and is fully charged per pair of positive electrode and negative electrode. The open circuit voltage in the state is 4.25 to 6.00 V, and has a porous insulating layer containing an insulating metal oxide in at least one position between the positive electrode and the negative electrode. And other materials and a three-layer structure.
By adopting such a configuration, more excellent cycle characteristics are obtained.
In addition, when the non-aqueous electrolyte secondary battery generates heat due to a micro short circuit or the like, there is a case where a preferable effect that a large current chute that may occur due to the thermal contraction of the separator can be suppressed may be obtained.

Moreover, the 1st suitable form of the nonaqueous electrolyte secondary battery of this invention has a porous insulating layer containing an insulating metal oxide between a negative electrode and a separator.
By adopting such a configuration, more excellent cycle characteristics are obtained. Furthermore, even in a nonaqueous electrolyte secondary battery in which the charging voltage is set to 4.25 V or more, safety at the time of a strong impact can be ensured.

Further, according to a second preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, the porous insulating layer containing an insulating metal oxide is formed of alumina, silica, magnesia, titania or zirconia, and any combination thereof. It contains such an insulating metal oxide.
By adopting such a configuration, further excellent cycle characteristics are obtained.

According to a third preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, the porous insulating layer containing an insulating metal oxide is made of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, styrene butadiene rubber or carboxy It contains methyl cellulose and those related to any combination thereof.
By adopting such a configuration, further excellent cycle characteristics are obtained.

Furthermore, as for the 4th suitable form of the nonaqueous electrolyte secondary battery of this invention, a negative electrode contains the graphite whose average particle diameter is 10-30 micrometers.
By adopting such a configuration, it is possible to suppress that the interface with the non-aqueous electrolyte cannot be sufficiently formed due to the graphite particle size being too large, or excessive decomposition reaction of the non-aqueous electrolyte due to being too small can be suppressed. Since it can prevent, it has the further excellent cycling characteristics.

In a fifth preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, the negative electrode contains graphite and one or both of silicon and tin as constituent elements.
By adopting such a configuration, further excellent cycle characteristics are obtained. In addition, the energy density can be further improved.

Further, in a sixth preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, the negative electrode contains a synthetic rubber having a copolymer structure of 1,3-butadiene.
By adopting such a configuration, it is possible to improve the binding property with the negative electrode active material and the conductive agent added as necessary, and it is possible to suppress peeling even when the negative electrode expands. Furthermore, it has excellent cycle characteristics.

In a seventh preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, the negative electrode contains carbon fiber.
By adopting such a configuration, even when the negative electrode expands, the electron conductivity in the negative electrode can be secured, and further excellent cycle characteristics can be obtained.

Furthermore, an eighth preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention is a lithium transition metal composite oxide in which the positive electrode contains cobalt and nickel, manganese, iron, or any combination thereof. It contains.
By setting it as such a structure, since the oxidative decomposition between a positive electrode and a nonaqueous electrolyte can be suppressed, it has the further outstanding cycling characteristics.

The ninth preferred embodiment of the non-aqueous electrolyte secondary battery of the present invention is such that the above-mentioned other materials are polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, aramid, polyimide or polyacrylonitrile, and any combination thereof. Including those related to
By adopting such a configuration, it is possible to suppress the oxidative decomposition of the separator that is in physical contact with the positive electrode, and thus has further excellent cycle characteristics.

Furthermore, in a tenth preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, the nonaqueous electrolyte contains a cyclic carbonate derivative having a halogen atom.
By adopting such a configuration, these are decomposed at the active part of the negative electrode to form a film and suppress the decomposition of the non-aqueous electrolyte, so that further excellent cycle characteristics are obtained.

Hereinafter, some embodiments of the nonaqueous electrolyte secondary battery of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a cylindrical secondary battery according to the first embodiment of the non-aqueous electrolyte secondary battery of the present invention.
As shown in the figure, this secondary battery has a battery element 20 inside a battery can 31 that is a part of an exterior member and has a substantially hollow cylindrical shape. In the battery element 20, the positive electrode 21 and the negative electrode 22 are positioned to face each other via a three-layer separator 24 having a three-layer structure, and contain a non-aqueous electrolyte (not shown).
Further, as will be described in detail later, the battery element 20 has a porous insulating layer (not shown) at at least one position between the positive electrode 21 and the negative electrode 22.
The battery element 20 excluding the non-aqueous electrolyte is referred to as a wound electrode body 20A.

The battery can 31 is made of, for example, steel plated with nickel, and has one end closed and the other end open. Inside the battery can 31, the insulating plate 11 is disposed so as to sandwich the battery element 20 from above and below.
In addition, at the open end of the battery can 31, a battery lid 32 constituting a part of the exterior member, a safety valve mechanism 12 provided inside the battery lid 32, and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) ) 13 is attached by caulking through the gasket 14, and the inside of the battery can 31 is sealed.

  The battery lid 32 is made of, for example, the same material as the battery can 31. The safety valve mechanism 12 is electrically connected to the battery lid 32 via the heat sensitive resistance element 13, and when the internal pressure of the battery exceeds a certain level due to internal short circuit or external heating, the disc plate 12A Is reversed to disconnect the electrical connection between the battery lid 32 and the battery element 20. When the temperature rises, the heat-sensitive resistor element 13 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current, and is made of, for example, a barium titanate semiconductor ceramic. The gasket 14 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The battery element 20 is wound around, for example, the center pin 15. A positive electrode lead 16 made of aluminum or the like is connected to the positive electrode 21 of the battery element 20, and a negative electrode lead 17 made of copper, nickel, stainless steel or the like is connected to the negative electrode 22. The positive electrode lead 16 is electrically connected to the battery lid 32 by welding to the safety valve mechanism 12, and the negative electrode lead 17 is welded and electrically connected to the battery can 31.

FIG. 2 is an enlarged cross-sectional view showing a part of a wound electrode body in the cylindrical secondary battery shown in FIG.
As shown in the figure, the wound electrode body 20 </ b> A has a positive electrode 21, a negative electrode 22, a three-layer separator 24, and a porous insulating layer 25.
Here, the positive electrode 21 has a structure in which a positive electrode active material layer 21B is coated on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. The positive electrode current collector 21A is made of a metal foil such as an aluminum foil. Although not shown in the figure, the positive electrode current collector has a portion exposed without being covered with the positive electrode active material layer at one end in the longitudinal direction, and the positive electrode lead described above is attached to this exposed portion. Yes.
Similarly to the positive electrode 21, the negative electrode 22 has a structure in which a negative electrode active material layer 22B is coated on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. The anode current collector 22A is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The negative electrode current collector has a portion that is exposed without being coated with the negative electrode active material layer at one end in the longitudinal direction, and the negative electrode lead described above is attached to the exposed portion.
Further, the porous insulating layer 25 is located between the negative electrode 22 and the three-layer separator 24 which is an example of at least one position between the positive electrode 21 and the negative electrode 22.
Although not shown, the positive electrode and the negative electrode have a structure in which a positive electrode active material layer and a negative electrode active material layer are respectively coated on one side of a positive electrode current collector and a negative electrode current collector having a pair of opposed surfaces. It may be. Although not shown, the porous insulating layer may be positioned between the positive electrode and the three-layer separator, which is another example between the positive electrode and the negative electrode, and the positive electrode, the three-layer separator, the negative electrode, and the three-layer separator. It may be located on both sides of the separator. Further, although not shown, the porous insulating layer may be located on one side of the positive electrode and the negative electrode.

[Positive electrode]
The positive electrode active material layer 21B includes, for example, a positive electrode material that can occlude and release lithium ions as a positive electrode active material, and may include a conductive agent and a binder as necessary.
Here, the positive electrode active material, the conductive agent, and the binder need only be uniformly dispersed, and the mixing ratio is not limited.

As a positive electrode material capable of occluding and releasing lithium used as a positive electrode active material, for example, lithium oxide, lithium phosphorous oxide, lithium sulfide, or an intercalation compound containing lithium is used depending on the type of the target battery. Lithium-containing compounds are suitable, and two or more of these may be mixed and used. In order to increase the energy density, a lithium-containing compound containing lithium, a transition metal element, and oxygen (O) is preferable. Among them, as the transition metal element, cobalt (Co), nickel (Ni), manganese (Mn), and iron It is more preferable if it contains at least one of the group consisting of (Fe). Examples of such a lithium-containing compound include a lithium composite oxide having a layered rock salt structure represented by the average composition shown in (1) to (3), and the average composition shown in (4). A lithium composite oxide having a spinel structure, or a lithium composite phosphate having an olivine structure represented by the average composition shown in (5). Specifically, LiNi _0.50 Co _0.20 Mn _0.30 O ₂ , Li _a CoO ₂ (a≈1), Li _b NiO ₂ (b≈1), Li _c1 Ni _c2 Co _1-c2 O ₂ (c1≈1,0, <c2 < _{1), Li d Mn 2 O} 4 (d ≒ 1) or _{Li e F e PO 4 (e} ≒ 1) and the like.

Moreover, it is preferable to contain lithium transition metal complex oxide shown in (1) as a positive electrode active material from a viewpoint that a high energy density is obtained. Furthermore, lithium-containing compounds shown in (2) to (5) can be further mixed and used as the positive electrode active material.
Furthermore, from the viewpoint that higher electrode filling properties and cycle characteristics can be obtained, the surface of the core particle made of any one of the lithium-containing compounds shown in (1) to (5) is made more than any of the other lithium-containing compounds. The composite particles may be coated with fine particles.

Li _f Co _(1-g) M1 _g O _(2-h) F _j (1)
(In the formula, M1 is nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). g, h, and j are values within the ranges of 0.8 ≦ f ≦ 1.2, 0 ≦ g <0.5, −0.1 ≦ h ≦ 0.2, and 0 ≦ j ≦ 0.1. (Note that the composition of lithium varies depending on the state of charge and discharge, and the value of f represents the value in a fully discharged state.)

Li _k Mn _(1-mn) Ni _m M2 _n O _(2-p) F _q (2)
(In the formula, M2 is cobalt (Co), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu ), Zinc (Zn), zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). m, n, p and q are 0.8 ≦ k ≦ 1.2, 0 <m <0.5, 0 ≦ n ≦ 0.5, m + n <1, −0.1 ≦ p ≦ 0.2, (It is a value within the range of 0 ≦ q ≦ 0.1. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of k represents the value in the fully discharged state.)

Li _r Ni _(1-s) M3 _s O _{(2-t) Fu} (3)
(In the formula, M3 is cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). s, t, and u are values within the range of 0.8 ≦ r ≦ 1.2, 0.005 ≦ s ≦ 0.5, −0.1 ≦ t ≦ 0.2, and 0 ≦ u ≦ 0.1. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of r represents the value in a fully discharged state.)

_{Li v Mn 2-w M4 w} O x F y ... (4)
(In the formula, M4 is cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). w, x, and y are values within the range of 0.9 ≦ v ≦ 1.1, 0 ≦ w ≦ 0.6, 3.7 ≦ x ≦ 4.1, and 0 ≦ y ≦ 0.1. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of v represents the value in a fully discharged state.)

Li _z M5PO ₄ (5)
(Wherein M5 is cobalt (Co), manganese (Mn), iron (Fe), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V ), Niobium (Nb), copper (Cu), zinc (Zn), molybdenum (Mo), calcium (Ca), strontium (Sr), tungsten (W), and zirconium (Zr). Z is a value in a range of 0.9 ≦ z ≦ 1.1, wherein the composition of lithium varies depending on the state of charge and discharge, and the value of z represents a value in a complete discharge state. )

  As the conductive agent, for example, a carbon material such as carbon black or graphite is used. Furthermore, as the binder, for example, polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene trifluoride, or the like is used.

[Negative electrode]
The negative electrode active material layer 22B includes one or more negative electrode materials capable of occluding and releasing lithium ions as the negative electrode active material, and, as necessary, the negative electrode active material layer. In addition, a conductive agent and a binder may be included. Furthermore, other materials that do not contribute to charging, such as a viscosity modifier, may be included. Here, for example, the negative electrode active material, the conductive agent, and the binder need only be uniformly dispersed, and the mixing ratio is not limited.

Examples of negative electrode materials capable of inserting and extracting lithium include non-graphitizable carbon, graphitizable carbon, natural or artificial graphite, pyrolytic carbons, cokes, glassy carbons, and organic polymers. Carbon materials, such as a compound baking body, carbon fiber, or activated carbon, are mentioned. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body is a carbonized material obtained by firing a polymer material such as a phenol resin or a furan resin at an appropriate temperature, and partially non-graphitizable carbon or graphitizable carbon. Some are classified as: These carbon materials are preferable because the change in crystal structure that occurs during charge and discharge is very small, a high charge and discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Further, non-graphitizable carbon is preferable because excellent characteristics can be obtained. Furthermore, those having a low charge / discharge potential, specifically, those having a charge / discharge potential close to that of lithium metal are preferable because a high energy density of the battery can be easily realized.
For example, the average particle diameter of graphite is preferably 10 to 30 μm. When the thickness exceeds 30 μm, the interface of the nonaqueous electrolyte may not be sufficiently formed. When the thickness is less than 10 μm, the excessive decomposition reaction of the nonaqueous electrolyte may not be prevented.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and including at least one of a metal element and a metalloid element as a constituent element. . This is because a high energy density can be obtained by using such a material. In particular, the use with a carbon material is more preferable because a high energy density can be obtained and excellent cycle characteristics can be obtained. This negative electrode material may be a single element or an alloy or a compound of a metal element or a metalloid element, or may have at least a part of one or more of these phases. Note that in this specification, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of metal elements or metalloid elements constituting the negative electrode material include magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), and germanium (Ge). ), Tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd) ) Or platinum (Pt). These may be crystalline or amorphous.

  Among these, as the negative electrode material, a material containing a 4B group metal element or metalloid element as a constituent element in the short-period type periodic table is preferable, and at least one of silicon (Si) and tin (Sn) is particularly preferable. It is included as an element. This is because silicon (Si) and tin (Sn) have a large ability to occlude and release lithium (Li), and a high energy density can be obtained.

  As an alloy of tin (Sn), for example, as a second constituent element other than tin (Sn), silicon (Si), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), magnesium (Mg), vanadium (V), gallium At least of the group consisting of (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), cerium (Ce), hafnium (Hf), tantalum (Ta), tungsten (W) and chromium (Cr) The thing containing 1 type is mentioned. As an alloy of silicon (Si), for example, as a second constituent element other than silicon (Si), tin (Sn), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb) and chromium (Cr) at least The thing containing 1 type is mentioned.

  Examples of the tin (Sn) compound or silicon (Si) compound include those containing oxygen (O), carbon (C), boron (B), aluminum (Al), or phosphorus (P), and tin. In addition to (Sn) or silicon (Si), the second constituent element described above may be included.

  Among these, as the negative electrode material, a CoSnC-containing material containing tin, cobalt, and carbon as constituent elements, the carbon content is 9.9 to 29.7% or less, and tin and cobalt are included. A CoSnC-containing material having a cobalt content of 30 to 70 parts by weight with respect to the total content of 100 parts by weight is preferable. This is because a high energy density can be obtained in such a composition range, and excellent cycle characteristics can be obtained.

  This CoSnC-containing material may further contain other constituent elements as necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus (P), gallium (Ga) or bismuth is preferable, and two or more kinds are included. Also good. This is because the negative electrode discharge capacity or cycle characteristics can be further improved.

  The CoSnC-containing material has a phase containing tin, cobalt, and carbon, and this phase preferably has a low crystallinity or an amorphous structure. Further, in this CoSnC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a metalloid element as another constituent element. The decrease in cycle characteristics is thought to be due to the aggregation or crystallization of tin or the like, but this is because such aggregation or crystallization can be suppressed by combining carbon with other elements. .

  As a measuring method for examining the bonding state of elements, for example, X-ray photoelectron spectroscopy (XPS) can be cited. In XPS, the peak of the carbon 1s orbital (C1s) appears at 284.5 eV in an energy calibrated apparatus so that the peak of the gold atom 4f orbital (Au4f) is obtained at 84.0 eV if it is graphite. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. On the other hand, when the charge density of the carbon element is high, for example, when carbon is bonded to a metal element or a metalloid element, the C1s peak appears in a region lower than 284.5 eV. That is, when the peak of the synthetic wave of C1s obtained for the CoSnC-containing material appears in a region lower than 284.5 eV, at least a part of the carbon contained in the CoSnC-containing material is a metal element or a half of other constituent elements. Combined with metal elements.

  In XPS measurement, for example, the C1s peak is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, which is used as an energy standard. In the XPS measurement, the waveform of the C1s peak is obtained as a shape including the surface contamination carbon peak and the carbon peak in the CoSnC-containing material. For example, by analyzing using a commercially available software, the surface contamination The carbon peak and the carbon peak in the CoSnC-containing material are separated. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  Examples of the conductive agent include carbon fiber, graphite fiber, metal fiber, and metal powder. Further, examples of the binder include fluorine-based polymer compounds such as polyvinylidene fluoride, and synthetic rubbers such as styrene butadiene rubber and ethylene propylene diene rubber. In particular, a synthetic rubber having a 1,3-butadiene copolymer structure is preferable because it has excellent binding properties as described above. Furthermore, examples of the viscosity modifier include carboxymethyl cellulose.

[Three-layer separator]
The three-layer separator 24 separates the positive electrode 21 and the negative electrode 22 from each other and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The three-layer separator 24 contains polyethylene and other materials and has three layers. It needs to have a structure.
Examples of the other materials include polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, aramid, polyimide, polyacrylonitrile and the like. One of these may be used alone, or two or more of these may be mixed or polymerized. Furthermore, at least one kind of ceramics typified by metal oxides such as alumina and silica may be contained. For example, when a metal oxide is included, the metal oxide particles may be contained almost uniformly throughout the separator. For example, the separator may be unevenly distributed in a part of the separator, for example, in a multilayer shape. It may be. Polyolefin porous membranes are preferable because they are excellent in short-circuit prevention effects and can improve battery safety due to shutdown effects.
Further, although not particularly limited, it is typically preferable to use a polyethylene layer as an intermediate layer, and to provide layers having the same composition on both sides of the other materials.

[Porous insulation layer]
The porous insulating layer 25 needs to contain an insulating metal oxide. Examples of such metal oxides include alumina, silica, magnesia, titania, zirconia and the like. Further, when forming a porous insulating layer containing these, for example, a binder may be used as long as porosity and insulating properties can be secured. As such a binder, for example, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, styrene butadiene rubber, carboxymethyl cellulose, or the like can be used.
These may be used alone or in combination or polymerized.
Note that the porosity of the porous insulating layer is not particularly limited as long as it allows lithium ions to pass therethrough, and the porous insulating layer only needs to have the same degree of porosity as the separator. Further, the insulating property of the porous insulating layer is preferably about the same as that of the separator. Furthermore, it is preferable that the porous insulating layer has better heat shrinkage resistance than the separator. Unlike the three-layer separator, the porous insulating layer contains a metal oxide that can improve the heat resistance inside, so that the heat-shrinkability of the porous insulating layer may be superior to that of the separator. it can.

[Nonaqueous electrolyte]
The nonaqueous electrolyte is contained in, for example, all or part of the three-layer separator 24, the porous insulating layer 25, the positive electrode active material layer 21B, and the negative electrode active material layer 22B described above. As such a non-aqueous electrolyte, for example, a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent can be used.

As the electrolyte salt, it is preferable to use, for example, one containing lithium hexafluorophosphate (LiPF ₆ ) from the viewpoint of obtaining high ionic conductivity of the electrolytic solution.

The concentration of lithium hexafluorophosphate (LiPF ₆ ) is preferably in the range of 0.1 to 2.0 mol / kg in the electrolytic solution. This is because the ion conductivity can be further increased within this range.

As the electrolyte salt, another electrolyte salt may be further mixed and used. Other electrolyte salts include, for example, LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO _{2 C 2 F 5) 2, LiN} (SO 2 CF 3) (SO 2 C 2 F 5), LiN (SO 2 CF 3) (SO 2 C 3 F 7), LiN (SO 2 CF 3) (SO 2 C _{4 F 9), LiC (SO} 2 CF 3) 3, LiAlCl 4, LiSiF 6, LiCl, LiSiF 6, difluoro [oxalato--O, O '] lithium borate, lithium bis (oxalato) borate, and the like LiBr. Other electrolyte salts may be used alone or in combination of two or more.

  As the non-aqueous solvent, for example, cyclic carbonates such as ethylene carbonate and propylene carbonate can be used, and it is preferable to use one of ethylene carbonate and propylene carbonate, particularly a mixture of both. This is because the cycle characteristics can be improved.

  As the non-aqueous solvent, in addition to these cyclic carbonates, it is preferable to use a mixture of chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate. This is because high ionic conductivity can be obtained.

In addition to these, non-aqueous solvents include 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one, 4-trifluoromethyl-1,3- Dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one, butylene carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 4-methyl-1,3-dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropironitrile, N, N-dimethylformamide, N-methyl Pyrrolidinone, N-methyloxazolidinone, N, N-dimethylimidazolidino Nitromethane, nitroethane, sulfolane, fluorobenzene, dimethyl sulfoxide, trimethyl phosphate and the like.
In addition, a non-aqueous solvent may be used individually by 1 type, and multiple types may be mixed and used for it.

Among them, it is preferable to use a mixture of a high dielectric constant solvent having a relative dielectric constant of 30 or more and a low viscosity solvent having a viscosity of 1 mPa · s or less. This is because high ion conductivity can be obtained. Examples of the high dielectric constant solvent include cyclic compounds such as cyclic carbonates such as ethylene carbonate and propylene carbonate, 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolane. Cyclic carbonate derivatives having a halogen atom such as 2-one, 4-trifluoromethyl-1,3-dioxolan-2-one, and 4,5-difluoro-1,3-dioxolan-2-one are preferred, 4-Fluoro-1,3-dioxolan-2-one and 4-chloro-1,3-dioxolan-2-one are more preferred, and 4-fluoro-1,3-dioxolan-2-one is particularly desirable. This is because it has high oxidation resistance and is difficult to be decomposed.
Examples of the low-viscosity solvent include chain compounds, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable. As for the high dielectric constant solvent and the low viscosity solvent, one kind may be used alone, or two or more kinds may be mixed and used.

The non-aqueous electrolyte may be liquid, but may be gel. The gel-like nonaqueous electrolyte is formed by gelling a nonaqueous electrolyte with a matrix polymer.
The gel-like nonaqueous electrolyte is configured such that a nonaqueous electrolyte is impregnated or held in a matrix polymer. By such swelling, gelation or non-fluidization of the matrix polymer, it is possible to effectively suppress leakage of the nonaqueous electrolyte in the obtained battery.
As the non-aqueous electrolyte described above, those generally used for lithium ion secondary batteries can be used.

As the gel-like nonaqueous electrolyte, the above-mentioned nonaqueous electrolyte solution is gelled with a matrix polymer. The matrix polymer is not particularly limited as long as it is compatible with a nonaqueous electrolytic solution obtained by dissolving the electrolyte salt in the nonaqueous solvent and can be gelled. Examples of such a matrix polymer include fluorine polymer compounds such as polyvinylidene fluoride or a copolymer with vinylidene fluoride, ether polymer compounds such as polyethylene oxide or a crosslinked product containing polyethylene oxide, and polymethacrylate. Examples thereof include polymers containing an ester polymer compound, an acrylate polymer compound, polypropylene oxide, polyacrylonitrile, or polymethacrylonitrile in a repeating unit.
Specifically, a copolymer of polyvinylidene fluoride and hexafluoropropylene, a copolymer of polyvinylidene fluoride, hexafluoropropylene, and monochlorotrifluoroethylene, polyvinylidene fluoride, hexafluoropropylene, and monomethylmaleic acid ester And the like.
In particular, from the viewpoint of redox stability, it is desirable to use a fluorine-based polymer compound such as a vinylidene fluoride polymer.
Such a polymer may be used individually by 1 type, and may mix and use 2 or more types.

Next, an example of a method for manufacturing the secondary battery described above will be described.
The cylindrical secondary battery described above can be manufactured as follows.
First, the positive electrode 21 is produced. For example, when a particulate positive electrode active material is used, a positive electrode mixture is prepared by mixing the positive electrode active material and, if necessary, a conductive agent and a binder, and a dispersion medium such as N-methyl-2-pyrrolidone. To produce a positive electrode mixture slurry.
Next, the positive electrode mixture slurry is applied to the positive electrode current collector 21A, dried, and compression molded to form the positive electrode active material layer 21B.

  Moreover, the negative electrode 22 is produced. For example, when using a particulate negative electrode active material, a negative electrode active material is mixed with a conductive agent and a binder as necessary to prepare a negative electrode mixture, and N-methyl-2-pyrrolidone, water, etc. A negative electrode mixture slurry is prepared by dispersing in a dispersion medium. Thereafter, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, dried, and compression molded to form the negative electrode active material layer 22B.

  Furthermore, the porous insulating layer 25 is produced. For example, an insulating metal oxide and a binder are mixed and dispersed in a dispersion medium such as N-methyl-2-pyrrolidone to prepare a mixed solution. Next, a porous insulating layer 25 is formed on the negative electrode 22 obtained above with a gravure roller.

  Next, the positive electrode lead 16 is led out from the positive electrode current collector 21A, and the negative electrode lead 17 is led out from the negative electrode current collector 22A. Thereafter, for example, the positive electrode 21 and the negative electrode 22 are wound through a three-layer separator 24 to form a wound electrode body 20A, and the tip of the positive electrode lead 16 is welded to the safety valve mechanism 12 and the tip of the negative electrode lead 17 The part is welded to the battery can 31, and the wound positive electrode 21 and negative electrode 22 are sandwiched between the pair of insulating plates 11 and stored in the battery can 31. After the positive electrode 21 and the negative electrode 22 are housed in the battery can 31, a non-aqueous electrolyte (not shown) is injected into the battery can 31 and impregnated in the three-layer separator 24, the porous insulating layer 25, and the like. Thereafter, the battery lid 32, the safety valve mechanism 12, and the heat sensitive resistance element 13 are fixed to the opening end of the battery can 31 by caulking through the gasket 14. Thereby, the cylindrical secondary battery shown in FIGS. 1 and 2 is completed.

In addition, such a secondary battery can also be produced as follows.
As described above, the wound electrode body 20A is accommodated in the battery can 31, and the nonaqueous electrolyte is not finally poured into the battery can, but a gel-like nonaqueous electrolyte is formed on the positive electrode 21 and the negative electrode 22, Alternatively, the battery element 20 may be formed by winding the anode 21 and the anode 22 via the three-layer separator 24 and accommodate the battery element 31 in the battery can 31.

FIG. 3 is an exploded perspective view showing an example of a laminated secondary battery according to the second embodiment of the nonaqueous electrolyte secondary battery of the present invention.
As shown in the figure, the secondary battery is configured by enclosing a battery element 20 to which a positive electrode lead 16 and a negative electrode lead 17 are attached in a film-like exterior member 30. The positive electrode lead 16 and the negative electrode lead 17 are led out from the inside of the exterior member 30 to the outside, for example, in the same direction. The positive electrode lead 16 and the negative electrode lead 17 are each composed of a metal material such as aluminum (Al), copper (Cu), nickel (Ni), or stainless steel.

The exterior member 30 is configured by a rectangular laminate film 33 in which, for example, a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. The exterior member 30 is arrange | positioned so that the polyethylene film side and the battery element 20 may oppose, for example, and each outer edge part is mutually joined by melt | fusion or the adhesive agent.
An adhesion film 34 is inserted between the exterior member 30 and the positive electrode lead 16 and the negative electrode lead 17 to prevent intrusion of outside air. The adhesion film 34 is made of a material having adhesion to the positive electrode lead 16 and the negative electrode lead 17. For example, when the positive electrode lead 16 and the negative electrode lead 17 are made of the metal materials described above, polyethylene, polypropylene, modified It is preferably composed of a polyolefin resin such as polyethylene or modified polypropylene.

In addition, the exterior member 30 may be configured by another structure, for example, a laminate film having no metal material, a polymer film such as polypropylene, or a metal film, instead of the above-described laminate film.
Here, the general structure of a laminate film can be represented by the laminated structure of exterior layer / metal foil / sealant layer (however, the exterior layer and sealant layer may be composed of a plurality of layers), and the above. In this example, the nylon film corresponds to the exterior layer, the aluminum foil corresponds to the metal foil, and the polyethylene film corresponds to the sealant layer.
In addition, as metal foil, it is sufficient if it functions as a moisture-permeable barrier film, and not only aluminum foil but also stainless steel foil, nickel foil and plated iron foil can be used, but it is thin and lightweight. Thus, an aluminum foil excellent in workability can be suitably used.

  As the exterior member, usable configurations are listed in the form of (exterior layer / metal foil / sealant layer): Ny (nylon) / Al (aluminum) / CPP (unstretched polypropylene), PET (polyethylene terephthalate) / Al / CPP, PET / Al / PET / CPP, PET / Ny / Al / CPP, PET / Ny / Al / Ny / CPP, PET / Ny / Al / Ny / PE (polyethylene), Ny / PE / Al / LLDPE (direct) Chain low density polyethylene), PET / PE / Al / PET / LDPE (low density polyethylene), and PET / Ny / Al / LDPE / CPP.

FIG. 4 is a schematic cross-sectional view taken along line IV-IV of the battery element 20 shown in FIG. As shown in the figure, the battery element 20 is positioned so as to face each other with a positive electrode 21, a negative electrode 22, a non-aqueous electrolyte layer 23 made of a non-aqueous electrolyte, and a three-layer separator 24. The outermost peripheral part is protected by a protective tape 26. The negative electrode 22 has a porous insulating layer 25 on one side or both sides thereof.
Note that the details of each configuration are the same as those in the first embodiment, and a description thereof will be omitted.

The laminated secondary battery described above can be manufactured as follows.
First, the positive electrode 21 is produced. For example, when a particulate positive electrode active material is used, a positive electrode mixture is prepared by mixing the positive electrode active material and, if necessary, a conductive agent and a binder, and a dispersion medium such as N-methyl-2-pyrrolidone. To produce a positive electrode mixture slurry.
Next, the positive electrode mixture slurry is applied to the positive electrode current collector 21A, dried, and compression molded to form the positive electrode active material layer 21B.

  Moreover, the negative electrode 22 is produced. For example, when using a particulate negative electrode active material, a negative electrode active material is mixed with a conductive agent and a binder as necessary to prepare a negative electrode mixture, and N-methyl-2-pyrrolidone, water, etc. A negative electrode mixture slurry is prepared by dispersing in a dispersion medium. Thereafter, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, dried, and compression molded to form the negative electrode active material layer 22B.

  Furthermore, the porous insulating layer 25 is produced. For example, an insulating metal oxide and a binder are mixed and dispersed in a dispersion medium such as N-methyl-2-pyrrolidone to prepare a mixed solution. Next, a porous insulating layer 25 is formed on the negative electrode 22 obtained above with a gravure roller.

  Next, the positive electrode lead 16 is attached to the positive electrode 21 and the negative electrode lead 17 is attached to the negative electrode 22, and then the three-layer separator 24, the positive electrode 21, the three-layer separator 24, and the negative electrode 22 are sequentially stacked and wound. The protective tape 26 is adhered to form the wound electrode body 20A. Further, the wound electrode body 20A is sandwiched between laminate films 33, and the outer peripheral edge except one side is heat-sealed to form a bag.

  Thereafter, an electrolyte salt such as lithium hexafluorophosphate and a nonaqueous electrolyte containing a nonaqueous solvent such as ethylene carbonate are prepared, and injected into the wound electrode body 20A from the opening of the laminate film 33, The opening of the laminate film 33 is heat-sealed and sealed. Thereby, the nonaqueous electrolyte composition layer 23 is formed, and the laminate type secondary battery shown in FIGS. 3 and 4 is completed.

In addition, you may manufacture this secondary battery as follows.
Instead of injecting the nonaqueous electrolyte after producing the wound electrode body 20A as described above, an electrolyte salt such as lithium hexafluorophosphate and the like on the positive electrode 21 and the negative electrode 22 or the three-layer separator 24 and A nonaqueous electrolyte layer 23 containing a nonaqueous electrolyte solution containing a nonaqueous solvent such as ethylene carbonate and a monomer or polymer of a polymer matrix may be formed and then wound and sealed in the laminate film 33. .

  In the secondary battery described above, when charged, lithium ions are released from the positive electrode active material layer 21B and inserted into the negative electrode active material layer 22B through a non-aqueous electrolyte and a non-aqueous electrolyte layer 23 (not shown). When the discharge is performed, lithium ions are released from the negative electrode active material layer 22B and inserted into the positive electrode active material layer 21B through the nonaqueous electrolyte.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Specifically, the operations described in the following examples were performed to produce a cylindrical secondary battery as shown in FIGS. 1 and 2, and its performance was evaluated.

(Example 1-1 to Example 1-4)
<Preparation of positive electrode>
First, 0.5 mol of lithium carbonate and 1 mol of cobalt carbonate were mixed, and then this mixture was fired at 890 ° C. for 5 hours in an air atmosphere to synthesize lithium cobalt composite oxide (LiCoO ₂ ). This was made into a powder having an average particle size of 10 μm.
As a result of X-ray diffraction measurement of the obtained lithium cobalt composite oxide, it was in good agreement with the spectrum of lithium cobalt composite oxide (LiCoO ₂ ) registered in the JCPDS file.
The obtained powder was used as a core particle, and the surface thereof was coated with LiMn _0.5 Ni _0.5 O ₂ fine particles in a high-speed air stream by an impact method to produce composite particles of LiCoO ₂ as a positive electrode active material.

Next, 94 parts by weight of the LiCoO ₂ composite particles, 3 parts by weight of ketjen black (amorphous carbon powder) as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder were mixed, and N-methyl- A positive electrode mixture slurry was obtained by dispersing in 2-pyrrolidone. Next, the obtained positive electrode mixture slurry was uniformly applied to both surfaces of a positive electrode current collector made of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and compression molded to form a positive electrode active material layer. Produced. Thereafter, an aluminum positive electrode lead was attached to one end of the positive electrode current collector.

<Production of negative electrode>
Also, 96 parts by weight of a granular natural graphite powder (Mitsubishi Chemical 10-17G) having an average particle size of 20 μm as a negative electrode active material, 1 part by weight of carbon fiber (SDG-H made by Showa Denko) as a conductive agent, and Mix 1.5 parts by weight of acrylic acid modified styrene-butadiene copolymer (manufactured by Nippon Zeon Co., Ltd., BM-400B, solid content 40%) and 1.5 parts by weight of carboxymethyl cellulose as a viscosity modifier. The mixture was dispersed in an appropriate amount of water to obtain a negative electrode mixture slurry. Next, the obtained negative electrode mixture slurry was uniformly applied to both surfaces of a negative electrode current collector made of a strip-shaped copper foil having a thickness of 15 μm, dried, and compression molded to form a negative electrode active material layer. Produced. At that time, the amount of the positive electrode active material and the amount of the negative electrode active material were adjusted, and the open circuit voltage (that is, the battery voltage) at the time of full charge was designed to be the value shown in Table 1 below.

<Preparation of porous insulating layer>
80 parts by weight of alumina particle powder as an insulating metal oxide and 20 parts by weight of polyvinylidene fluoride as a binder were mixed and dispersed in N-methyl-2-pyrrolidone to obtain a mixed solution. Next, apply to the negative electrode obtained above with a coater, control the film thickness with a gravure roller, then remove the solvent through the negative electrode through a dryer at 120 ° C. atmosphere to form a 5 μm thick porous insulating layer on the negative electrode did. Thereafter, a nickel negative electrode lead was attached to one end of the negative electrode current collector.

<Preparation of nonaqueous electrolyte>
As the non-aqueous electrolyte, ethylene carbonate: propylene carbonate: dimethyl carbonate: ethyl methyl carbonate: 4-fluoro-1,3-dioxolan-2-one (FEC) = 25: 5: 60: 5: 5 (weight ratio) A non-aqueous electrolyte solution in which LiPF ₆ was dissolved in a non-aqueous solvent mixed at a ratio to a concentration of 1.2 mol / kg was used.

<Battery assembly>
The obtained positive electrode and negative electrode are laminated via a microporous separator having a three-layer structure (thickness: 15 μm, configuration: polypropylene (PP) / polyethylene (PE) / polypropylene (PP)) and wound up many times. A wound electrode body (outer diameter: 17.5 mm) was produced. The wound electrode body was sandwiched between a pair of insulating plates and the negative electrode lead was welded to the bottom of a nickel-plated steel battery can, and the positive electrode lead was welded to the protrusion of the safety valve mechanism and placed in the battery can. Then, after injecting the non-aqueous electrolyte obtained in this battery can by a decompression method, the battery lid is caulked to the steel battery can through an insulating sealing gasket, and the safety valve mechanism, the heat sensitive resistance element and the battery lid are fixed. The cylindrical secondary battery (diameter: 18 mm, height: 65 mm) of each example was obtained.

(Example 2-1 to Example 2-4)
In producing the porous insulating layer, the same procedure as in Example 1-1 to Example 1-4 was repeated except that the positive electrode was used instead of the negative electrode and the positive electrode was formed. The next battery was obtained.

(Comparative Example 1-1 to Comparative Example 1-4)
When the battery is assembled without producing a porous insulating layer, a microporous separator having a three-layer structure is used instead of a microporous separator having a three-layer structure (thickness: 15 μm, configuration: PP / PE / PP). Except for using a separator (thickness: 20 μm, configuration; PP / PE / PP), the same operations as in Examples 1-1 to 1-4 were repeated, respectively. Got.

(Comparative Example 2-1 to Comparative Example 2-4)
In assembling the battery, instead of the microporous separator having a three-layer structure (thickness: 15 μm, configuration; PP / PE / PP), the microporous separator having a single-layer structure (thickness: 15 μm, configuration: PE) ) Was used, and the same operations as in Example 1-1 to Example 1-4 were repeated to obtain cylindrical secondary batteries of the respective examples.

(Comparative Example 3-1 to Comparative Example 3-4)
In the production of the porous insulating layer, the positive electrode is used instead of the negative electrode, the positive electrode is formed on the positive electrode, and the microporous separator (thickness: 15 μm, configuration: PP / PE / PP) having a three-layer structure is assembled in assembling the battery. Instead, except that a microporous separator having a single layer structure (thickness: 15 μm, configuration: PE) was used, the same operations as in Example 1-1 to Example 1-4 were repeated, respectively. An example cylindrical secondary battery was obtained.

(Comparative Example 4-1 to Comparative Example 4-5)
In preparation of the positive electrode and the negative electrode, the amount of the positive electrode active material and the amount of the negative electrode active material were adjusted, and the open circuit voltage (that is, the battery voltage) at the time of full charge was designed to be the value shown in Table 1 below. Except for the above, the same operations as in Example 1-1, Example 2-1, Comparative Example 1-1, Comparative Example 2-1 and Comparative Example 3-1 were repeated, and the cylindrical secondary batteries of the respective examples. Got. Table 1 shows the specifications of each example.

[Performance evaluation]
With respect to the cylindrical secondary battery of each of the above examples, the cycle characteristic value (%) and the through-short safety were evaluated as follows.

<Cycle characteristic evaluation>
In an environment of 25 ° C., constant current and constant voltage charging was performed at a predetermined voltage of 2000 mA, and then constant current discharging was performed at a constant current of 1500 mA until the battery voltage reached 3 V, and this charging and discharging was repeated. From the discharge capacity at the first cycle and the discharge capacity at the 100th cycle, the discharge capacity retention rate was calculated by the following equation [1], and this was defined as the cycle characteristic value (%). The obtained results are also shown in Table 1.
Cycle characteristic value (%) = (discharge capacity at the 100th cycle) / (discharge capacity at the first cycle) × 100 (%)... [1]

<Through short safety>
A fully charged cylindrical secondary battery was completely penetrated through the center with a 5φ nail perpendicular to the longitudinal axis of the battery at a speed of 30 mm / second or more. The state of the battery was confirmed. If spark, smoke, or ignition was confirmed, “NG” was indicated. If not confirmed, “OK” was indicated. The obtained results are also shown in Table 1.

From Table 1, Examples 1-1 to 1-4 and Examples 2-1 to 2-4 belonging to the scope of the present invention are Comparative Examples 1-1 to 1-4 outside the present invention. Compared with Comparative Example 2-1 to Comparative Example 2-4 and Comparative Example 3-1 to Comparative Example 3-4, it can be seen that each charging voltage has excellent cycle characteristics.
Further, in Example 1-1 to Example 1-4 and Example 2-1 to Example 2-4 and Comparative Example 2-1 to Comparative Example 2-4, the separator after the cycle was examined. In the separators of Comparative Example 2-1 to Comparative Example 2-4, it was found that the separator was oxidized and a micro short circuit occurred, and thus it was found that the cycle characteristics were deteriorated.
Furthermore, it can be seen that the cycle characteristics do not change much when the porous insulating layer is provided on either the positive electrode side or the negative electrode side. However, from the result of the through-short safety, the porous insulating layer is provided on the negative electrode side. It can be seen that the through-short safety is improved. This is presumably because the negative electrode active material has better electrical conductivity than the positive electrode active material, and therefore generates a large amount of heat when short-circuited, and is more effective when protected than the positive electrode.

(Example 3-1 to Example 3-4)
In producing the porous insulating layer, the thickness of the porous insulating layer was changed as shown in Table 2, and in assembling the battery, separators having different thicknesses were used as shown in Table 2 except for using the separator of Example 1- The same operation as 2 was repeated to obtain cylindrical secondary batteries of the respective examples.

(Example 3-5 and Example 3-6)
In producing the porous insulating layer, the same operation as in Example 1-2 was repeated except that the type of the metal oxide contained in the porous insulating layer was changed as shown in Table 2, and the cylinder of each example A type secondary battery was obtained. The specifications of each example are shown in Table 2 together with the specifications of Example 1-2. In addition, cycle characteristic values were measured and calculated in the same manner as described above. The obtained results are also shown in Table 2.

From Table 2, it was found that the thickness of the porous insulating layer is preferably 1 to 8 μm. When the thickness of the porous insulating layer is large, the reason why the cycle characteristics are lowered is that the thickness of the three-layer separator of PP / PE / PP is thinned, so that the oxidation resistance on the positive electrode side is lowered. Conceivable.
On the other hand, when the thickness of the porous insulating layer is thin, the cycle characteristics are deteriorated because the air permeability of the insulating layer is lower than that of the separator, and sufficient diffusion of lithium ions is achieved when the insulating layer is thick. This is probably because it is not enough.
Moreover, when Example 1-2 was compared with Example 3-5 and Example 3-6, the difference in a cycle characteristic was not seen. It is considered that the same use is possible as long as it is a metal oxide having an appropriate particle size that is insulative, stable in the battery, and can secure the binding property with the binder.

(Example 4-1 to Example 4-4)
In producing the negative electrode, the same operations as in Example 1-2 were repeated except that granular natural graphite powders having different average particle diameters were used as shown in Table 3 to obtain cylindrical secondary batteries of the respective examples. It was. The specifications of each example are shown in Table 3 together with the specifications of Example 1-2. In addition, cycle characteristic values were measured and calculated in the same manner as described above. The results obtained are also shown in Table 3.

  From Table 3, it was found that the average particle size of graphite is preferably 10 to 30 μm. If it exceeds 30 μm, the interface of the nonaqueous electrolyte may not be sufficiently formed, and if it is less than 10 μm, excessive decomposition reaction of the nonaqueous electrolyte may not be prevented.

(Example 5-1 to Example 5-4)
In producing the negative electrode, the carbon fiber content was changed as shown in Table 4 (in addition, when the carbon fiber content was increased or decreased, the content of the natural graphite powder was decreased or increased, respectively. A cylindrical secondary battery of each example was obtained by repeating the same operation as in Example 1-2 except that the ratio of the substances was constant.
When 10% of carbon fiber was added, the electrode could not be produced successfully. The specifications of each example are shown in Table 4 together with the specifications of Example 1-2. In addition, cycle characteristic values were measured and calculated in the same manner as described above. The obtained results are also shown in Table 4.

From Table 4, it was found that the content of carbon fiber in the negative electrode mixture was preferably 1 to 5%. There is an optimum value for the amount of carbon fiber added because it makes it possible to ensure the electron conductivity in the electrode during expansion, and if it is added in a large amount during electrode preparation, the electrode properties before coating deteriorate. It is thought that.
When the carbon fiber content was 10%, in this example, the electrode could not be produced in a desired shape.

(Example 6-1 to Example 6-3)
The negative electrode active material was synthesized using a mechanochemical reaction, and its composition was changed as shown in Table 5. Specifically, the second constituent element is cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, silver, indium, cerium, hafnium, tantalum, tungsten. , Silicon or bismuth, and the third constituent element was carbon.

  The negative electrode comprises 80 parts by weight of the obtained negative electrode active material powder, 14 parts by weight of artificial graphite (KS-15 made by Lonza) and 1 part by weight of acetylene black as a conductive agent, and 5 parts by weight of polyvinylidene fluoride as a binder. It mixed and disperse | distributed to N-methyl-2-pyrrolidone which is a solvent, and it apply | coated to the negative electrode collector, and produced by forming a negative electrode active material layer. Otherwise, the same operation as in Example 1-2 was repeated to obtain a cylindrical secondary battery of each example.

As mentioned above, although this invention was demonstrated with some embodiment and an Example, this invention is not limited to these, A various deformation | transformation is possible within the range of the summary of this invention.
For example, in the above embodiment, the case where a battery element in which a negative electrode and a positive electrode are stacked and wound is described, but the present invention is a flat plate having a structure in which a pair of positive and negative electrodes are folded or stacked. The present invention can also be applied to a case where a battery element or a stacked battery element in which a plurality of positive electrodes and negative electrodes are stacked is provided.
In the above embodiment, the case where a battery can or a film-shaped exterior member is used has been described. However, the present invention is similarly applied to a battery having another shape such as a so-called square shape, coin shape, or button shape. be able to.

  Further, in the above embodiments and examples, a so-called lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium has been described. However, the present invention relates to lithium metal as the negative electrode active material. The capacity of the negative electrode used is a so-called lithium metal secondary battery represented by a capacity component due to precipitation and dissolution of lithium, or the charge capacity of the negative electrode material capable of inserting and extracting lithium is higher than the charge capacity of the positive electrode. The same applies to a secondary battery in which the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is expressed by the sum thereof, by reducing the capacity. be able to.

  Furthermore, as described above, the present invention relates to a battery using lithium as an electrode reactant, but the technical idea of the present invention is that other alkali metals such as sodium (Na) or potassium (K), magnesium The present invention can also be applied to the case of using an alkaline earth metal such as (Mg) or calcium (Ca), or another light metal such as aluminum.

1 is a cross-sectional view illustrating an example of a cylindrical secondary battery according to a first embodiment of a nonaqueous electrolyte secondary battery of the present invention. It is sectional drawing which expands and shows a part of winding electrode body in the cylindrical secondary battery shown in FIG. It is 2nd Embodiment of the nonaqueous electrolyte secondary battery of this invention, Comprising: It is a disassembled perspective view which shows an example of a laminate type secondary battery. It is typical sectional drawing along the IV-IV line of the battery element shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Insulation board, 12 ... Safety valve mechanism, 12A ... Disk board, 13 ... Heat sensitive resistance element, 14 ... Gasket, 15 ... Center pin, 16 ... Positive electrode lead, 17 ... Negative electrode lead, 20 ... Battery element, 20A ... Winding Electrode body 21... Positive electrode 21 A. Positive electrode current collector 21 B. Positive electrode active material layer 22. Negative electrode 22 A. Negative electrode current collector 22 B. Negative electrode active material layer 23 23 Non-aqueous electrolyte layer 24. Separator, 25 ... porous insulating layer, 26 ... protective tape, 30 ... exterior member, 31 ... battery can, 32 ... battery lid, 33 ... laminate film, 34 ... adhesive film

Claims (14)

A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator,
The open circuit voltage in a fully charged state per pair of positive and negative electrodes is 4.25 to 6.00 V,
At least one position between the positive electrode and the negative electrode has a porous insulating layer containing an insulating metal oxide,
The separator contains polyethylene and other materials and has a three-layer structure.
A non-aqueous electrolyte secondary battery.   The nonaqueous electrolyte secondary battery according to claim 1, further comprising a porous insulating layer containing an insulating metal oxide between the negative electrode and the separator.   The porous insulating layer containing the insulating metal oxide contains at least one selected from the group consisting of alumina, silica, magnesia, titania and zirconia. Non-aqueous electrolyte secondary battery.   The porous insulating layer containing the insulating metal oxide contains at least one selected from the group consisting of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, styrene butadiene rubber and carboxymethyl cellulose. The nonaqueous electrolyte secondary battery according to claim 1.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode contains graphite.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the negative electrode contains graphite having an average particle diameter of 10 to 30 μm.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the negative electrode contains graphite and silicon and / or tin as constituent elements. The negative electrode contains a first constituent element, a second constituent element, and a third constituent element,
The first constituent element is tin,
The second constituent element is cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, silver, indium, cerium, hafnium, tantalum, tungsten, bismuth and At least one selected from the group consisting of silicon,
The third constituent element is at least one selected from the group consisting of boron, carbon, aluminum, and phosphorus.
The non-aqueous electrolyte secondary battery according to claim 1, wherein:   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode contains a synthetic rubber having a copolymer structure of 1,3-butadiene.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the negative electrode contains carbon fiber.   2. The non-aqueous solution according to claim 1, wherein the positive electrode contains a lithium transition metal composite oxide containing cobalt and at least one selected from the group consisting of nickel, manganese, and iron. Electrolyte secondary battery.   2. The non-material according to claim 1, wherein the other material includes at least one selected from the group consisting of polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, aramid, polyimide, and polyacrylonitrile. Water electrolyte secondary battery.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous electrolyte contains a cyclic carbonate derivative having a halogen atom.   The cyclic carbonate derivative having a halogen atom is 4-fluoro-1,3-dioxolan-2-one and / or 4,5-difluoro-1,3-dioxolan-2-one, The nonaqueous electrolyte secondary battery according to claim 13.

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