JP2008066020A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a high energy density and superior storage characteristics in a nonaqueous electrolyte secondary battery of which open circuit voltage in a full charge state is 4.25 V or more and 6.00 V or less. <P>SOLUTION: The nonaqueous electrolyte secondary battery having an open circuit voltage of 4.25 V or more and 6.00 V or less in full charge state includes a positive electrode 21 having a positive electrode active material layer 21B and a negative electrode 22 having a negative electrode active material layer 22B, and a non-aqueous electrolyte. The positive electrode 21 and the negative electrode 22 are installed oppositely so that the most end part position L<SB>1</SB>of the positive electrode active material layer 21B may be inside the most end part position L<SB>2</SB>of the negative electrode active material layer 22B. Since the end part distance ΔL from the end part position L<SB>1</SB>of the positive electrode active material layer 21B to the end part position L<SB>2</SB>of the negative electrode active material layer 22B satisfies the relations 0 mm<ΔL=L<SB>2</SB>-L<SB>1</SB><6 mm, excessive rise of a positive electrode potential can be suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery. Specifically, the present invention relates to a nonaqueous electrolyte secondary battery having an open circuit voltage of 4.25 V or more in a fully charged state.

  Due to the remarkable development of portable electronic technology in recent years, mobile phones and notebook computers are recognized as basic technologies that support an advanced information society. Research and development related to the enhancement of functions of these devices has been energetically advanced, and it has been a problem that the increase in power consumption due to the enhancement of functions shortens the driving time. In order to ensure a driving time of a certain level or higher, it is essential to increase the energy density of a secondary battery used as a drive power supply. For example, a high-functional secondary battery represented by a lithium ion secondary battery or the like Higher energy density at is expected.

  In a conventional lithium ion secondary battery, a lithium cobaltate is used for the positive electrode and a carbon material is used for the negative electrode, and the operating voltage has been 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.

  By the way, the positive electrode active material such as lithium cobaltate used in the conventional lithium ion secondary battery operating at a maximum of 4.2 V only uses a capacity of about 60% of its theoretical capacity. In principle, it is possible to utilize the remaining capacity by increasing the charging pressure. In fact, for example, as disclosed in Patent Document 1, it is known that high energy density can be realized by setting the voltage during charging to 4.25 V or more.

  On the other hand, it has been reported that when the charging voltage is increased, the battery characteristics are significantly deteriorated. For example, as described in Non-Patent Document 1, when a lithium ion secondary battery in which a charging voltage is set to about 4.4 V is evaluated, the basic characteristic deterioration of the battery is remarkable particularly in a temperature region higher than room temperature. .

  Conventionally, with regard to such a deterioration phenomenon, for example, as described in Patent Document 2, deterioration due to strain or fatigue generated in the crystal structure due to an increase in the amount of insertion / extraction of lithium ions, or the positive electrode itself Chemical changes in electrolyte materials due to increased oxidizability have been reported.

Therefore, in order to suppress such a deterioration phenomenon, for example, as disclosed in Non-Patent Documents 2 and 3, for example, a lithium-containing composite oxide having a layered structure is converted into an oxide such as ZnO or Al ₂ O ₃ . Improvement methods centering mainly on improvement of the positive electrode active material have been reported, such as a compound coated with bismuth.

International Publication No. 03/019713 Pamphlet JP 2004-55539 A J.R.Dahn et al., Electrochimica Acta, 49, 1079-1090, (2004). J. Prakash et al., Journal of the Electrochemical Society, 150 (7), A970-A972 (2003). B. Park et al., Journal of the Electrochemical Society, 149 (2), A127-A132 (2002).

  However, in the conventional improvement method centering on improvement of the positive electrode active material, a certain level of effect can be obtained, but further improvement in storage characteristics particularly at high temperatures is required. Moreover, the energy density improvement in normal use conditions was also required by improving the charge / discharge efficiency at the beginning of the charge / discharge cycle.

  Accordingly, an object of the present invention is to realize a high energy density and excellent storage characteristics in a non-aqueous electrolyte secondary battery whose open circuit voltage in a fully charged state is in the range of 4.25 V to 6.00 V. The object is to provide a water electrolyte secondary battery.

  The present inventor has intensively studied to solve the above-described problems of the prior art. The outline will be described below.

  As a result of intensive studies to improve the storage characteristics particularly at high temperatures, the present inventors have come to know that an increase in the potential of the positive electrode end causes deterioration of the storage characteristics. Then, in order to elucidate the cause of the potential increase at the positive electrode end, the present inventors have conducted further intensive studies and have found that the cause is as follows. That is, when the positive electrode and the negative electrode are opposed so that the extreme end position of the positive electrode active material layer is inside the extreme end position of the negative electrode active material layer, the end of the negative electrode active material layer becomes the positive electrode active material layer. Will not be opposed. When a battery having such a positional relationship is charged to a fully charged state, it will be affected by the charging conditions, but the lithium ions desorbed from the end of the positive electrode active material layer are not connected to the end of the positive electrode active material layer. After being occluded in the portion of the negative electrode active material layer facing the portion, it diffuses toward the end of the negative electrode active material layer not facing the positive electrode active material layer. Due to this diffusion phenomenon, the amount of lithium ions extracted at the end of the positive electrode active material layer increases, and as a result, the potential at the end of the positive electrode active material layer increases as compared with the potential at the center.

  As a result of further intensive studies on the phenomenon of the potential increase at the positive electrode end by the present inventors, the conventional non-aqueous electrolyte secondary battery having an upper limit voltage of 4.2 V is caused by the potential increase at the positive electrode end. While the capacity deterioration phenomenon is almost negligible, in the case of a new battery assuming a charging voltage of 4.25 V or more as in the present invention, the capacity deterioration due to the potential increase at the positive electrode end is so large that it cannot be ignored. It came to know that. That is, it has been found that the capacity deterioration due to the potential increase at the positive electrode end portion becomes apparent in a new battery assuming a charging voltage of 4.25 V or more.

Accordingly, the present inventors have made extensive studies through experiments in order to minimize deterioration of storage characteristics based on the knowledge obtained as described above. As a result, the present inventors have found that there is a certain correlation between the edge positions of the facing positive electrode active material layer and negative electrode active material layer and the deterioration phenomenon of storage characteristics. That is, the end portion distance ΔL from the extreme end position L ₁ of the positive electrode active material layer to the extreme end position L ₂ of the negative electrode active material layer satisfies 0 mm <ΔL = L ₂ −L ₁ <6 mm. In particular, the inventors have found that the storage characteristics particularly at high temperatures are remarkably improved.

Furthermore, according to the result of earnest study by the present inventors, it has been found that the charge / discharge efficiency at the initial stage of the charge / discharge cycle can be improved by satisfying the end portion distance ΔL. That is, it has been found that the end portion distance ΔL has a synergistic effect not only on improvement of storage characteristics at high temperatures but also on improvement of energy density under normal use conditions.
The present invention has been devised based on the above studies.

  In addition, as described above, in the nonaqueous electrolyte secondary battery in which the open circuit voltage in the fully charged state is 4.25 V or more and 6.00 V or less, the extreme end positions of the positive electrode active material layer and the negative electrode active material layer, and the capacity Knowledge about the relationship with the deterioration behavior is not publicly known. Therefore, it is considered that the present invention is useful and novel in realizing a high energy density battery with higher practicality.

The present invention provides a non-aqueous electrolyte secondary battery in which an open circuit voltage in a fully charged state is in a range of 4.25 V or more and 6.00 V or less,
A positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer, and a nonaqueous electrolyte,
The positive electrode and the negative electrode are provided to face each other so that the extreme end position L ₁ of the positive electrode active material layer is inside the extreme end position L ₂ of the negative electrode active material layer,
The nonaqueous electrolyte secondary battery is characterized in that an end portion distance ΔL from the extreme end position L ₁ of the positive electrode active material layer to the extreme end position L ₂ of the negative electrode active material layer satisfies the following formula 1. .
0 mm <ΔL = L ₂ −L ₁ <6 mm (Formula 1)

  In the present invention, the negative electrode active material layer preferably contains a carbonaceous material, a material that forms an intermetallic compound with lithium metal, silicon, or lithium metal.

In the present invention, since the end distance ΔL is in the range of 0 mm <ΔL <6 mm, the lithium ions that are desorbed from the end of the positive electrode active material layer and occluded in the negative electrode active material layer are absorbed in the negative electrode active material layer. It is possible to limit the distance of diffusion toward the extreme end. Therefore, an excessive increase in the positive electrode potential can be suppressed. Further, since the positive electrode and the negative electrode are provided so as to face each other so that the extreme end position L ₁ of the positive electrode active material layer is inside the extreme end position L ₂ of the negative electrode active material, the end of the negative electrode active material layer Precipitation of lithium ions in the vicinity can be suppressed.

  As described above, according to the present invention, in a non-aqueous electrolyte secondary battery whose open circuit voltage in a fully charged state is in the range of 4.25V to 6.00V, high energy density and excellent storage characteristics are obtained. Can be realized.

(1) First Embodiment (1-1) Configuration of Nonaqueous Electrolyte Secondary Battery FIG. 1 is a cross-sectional view showing an example of the configuration of a nonaqueous electrolyte secondary battery according to the first embodiment of the present invention. . This non-aqueous electrolyte secondary battery is a so-called cylindrical type, and a strip-shaped positive electrode 21 and a strip-shaped negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. A wound electrode body 20 is provided. The separator 23 is impregnated with an electrolytic solution. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 and a thermal resistance element (PTC element) 16 provided inside the battery lid 14 are provided via a sealing gasket 17. The battery can 11 is attached by being caulked, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The sealing gasket 17 is made of, for example, an insulating material, and the surface thereof is coated with asphalt.

  The wound electrode body 20 is wound around a center pin 24, for example. A positive electrode lead 25 made of aluminum or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 is a cross-sectional view showing an example of the configuration of the positive electrode 21 and the negative electrode 22. The positive electrode 21 includes, for example, a positive electrode current collector 21A having a pair of opposed surfaces and a positive electrode active material layer 21B provided on both surfaces or one surface of the positive electrode current collector 21A. The negative electrode 22 includes, for example, a negative electrode current collector 22A having a pair of opposed surfaces, and a negative electrode active material layer 22B provided on both surfaces or one surface of the negative electrode current collector 22A.

  FIG. 3 is a plan view showing the positional relationship between the extreme ends of the positive electrode active material layer 21B and the negative electrode active material layer 22B. FIG. 4 is a cross-sectional view showing the positional relationship between the extreme ends of the positive electrode active material layer 21B and the negative electrode active material layer 22B. In FIG. 3, the positive electrode current collector 21A, the negative electrode current collector 22A, and the separator 23 are not shown in order to facilitate understanding of the positional relationship between the positive electrode active material layer 21B and the negative electrode active material layer 22B. Yes.

  As shown in FIG. 3, the area of the negative electrode active material layer 22B is larger than the area of the positive electrode active material layer 21B, and in the state where the positive electrode active material layer 21B and the negative electrode active material layer 22B face each other, The end portion 21 </ b> C is positioned inside the negative electrode active material layer endmost portion 22 </ b> C. This is because when the positive electrode active material layer endmost portion 21C is positioned outside the negative electrode active material layer endmost portion 22C, lithium is deposited in the vicinity of the end portion of the negative electrode active material layer 22B.

Here, as shown in FIG. 4, and the distance from the outermost end position L ₁ of the positive electrode active material layer 21B outermost to the end position L ₂ of the anode active material layer 22B is defined as a end distance [Delta] L, the positive electrode active material For example, when the layer 21B and the negative electrode active material layer 22B are formed in a rectangular shape on the positive electrode current collector 21A and the negative electrode current collector 22A, respectively, as shown in FIG. There will be a distance ΔL.

  The end distance ΔL is in the range of 0 mm <ΔL <6 mm, preferably 3 mm <ΔL <6 mm. When the end distance ΔL is greater than 0 mm, the non-aqueous electrolyte secondary battery having an open circuit voltage in the range of 4.25V to 6.00V can suppress the deterioration of the initial charge / discharge efficiency, thereby increasing the energy density. When the end distance ΔL is less than 6 mm, the non-aqueous electrolyte secondary battery having an open circuit voltage in the range of 4.25 V to 6.00 V can suppress significant deterioration of the capacity recovery rate. This is because excellent storage characteristics can be realized.

Here, the reason for limiting the above-described end portion distance ΔL will be specifically described with reference to FIG. The positive electrode 21 and the negative electrode 22 are made to face each other so that the extreme end position L ₁ of the positive electrode active material layer 21B is inside the extreme end position L ₂ of the negative electrode active material layer 22B. Assume that the battery is charged. When charged, at the central part of the positive electrode 21 and the negative electrode 22, lithium ions are desorbed from the positive electrode active material layer 21B and inserted into the negative electrode active material layer 22B through the electrolytic solution impregnated in the separator 23. On the other hand, at the end portions of the positive electrode 21 and the negative electrode 22, lithium ions are desorbed from the positive electrode active material layer 21 </ b> B and occluded by the negative electrode active material layer 22 </ b> B, and then toward the end 22 </ b> C of the negative electrode active material layer. Spread.

  As described above, when the end portion distance ΔL is in the range of 0 mm <ΔL <6 mm, the diffusion distance in which lithium ions diffuse toward the end 22C of the negative electrode active material layer is limited. It is possible to suppress the potential of the portion from rising compared to the potential of the central portion, and to significantly improve the storage characteristics at high temperatures. On the other hand, when the end portion distance ΔL is 6 mm ≦ ΔL, the diffusion distance for diffusing toward the end 22C of the negative electrode active material layer becomes longer after lithium ions are occluded in the negative electrode active material layer 22B. The potential at the end of the positive electrode 21 is higher than the potential at the center, and storage characteristics at high temperatures are significantly deteriorated. Such a correlation between the end distance ΔL and the significant deterioration of the storage characteristics at high temperature is hardly recognized in the conventional battery system in which the open circuit voltage in the fully charged state is 4.2 V or less, This is manifested in the battery system of the present application in which the open circuit voltage in the fully charged state is 4.25 V or more.

The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum (Al) foil. The positive electrode active material layer 21B includes, for example, a positive electrode active material, and may include a conductive agent such as graphite and a binder such as polyvinylidene fluoride as necessary. As the positive electrode active material, a lithium-containing compound, for example, lithium oxide, lithium sulfide, or an intercalation compound containing lithium is suitable, and two or more of these may be used in combination. In particular, in order to increase the energy density, it is preferable to include a lithium composite oxide mainly composed of Li _x MO ₂ as a positive electrode active material. Note that M is preferably one or more transition metals, specifically, from cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), aluminum, vanadium (V), and titanium (Ti). At least one of the group is preferred. In addition, x varies depending on the charge / discharge state of the battery, and is usually a value in the range of 0.05 ≦ x ≦ 1.10. Specific examples of such lithium composite oxide include, for example, Li _a CoO ₂ (a≈1), Li _b NiO ₂ (b≈1), or Li _c Ni _d Co _1-d O ₂ (c≈1, 0 <d <1). Examples of the lithium composite oxide include Li _e Mn ₂ O ₄ (e≈1) having a spinel structure or Li _f FePO ₄ (f≈1) having an olivine structure.

More specifically, the general formula _{Li [Li x Mn (1-} xyz) Ni y M 'z] O (2-a) F b ( wherein M' is cobalt (Co), manganese (Mg), aluminum ( Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), zirconium (Zr), molybdenum (Mo), tin ( At least one element selected from Sn), calcium (Ca), strontium (Sr), and tungsten (W), where x is 0 <x ≦ 0.2, y is 0.3 ≦ y ≦ 0.8, 0 ≦ z ≦ 0.5, −0.1 ≦ a ≦ 0.2, 0 ≦ b ≦ 0.1), or a general formula Li _c Ni _(1-d) M ′ _d O _(2-e) F _f (wherein M ′ is cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron Element (B), Titanium (Ti), Vanadium (V), Chromium (Cr), Iron (Fe), Copper (Cu), Zinc (Zn), Mo (Molybdenum), Tin (Sn), Calcium (Ca), At least one element selected from strontium (Sr) and tungsten (W), c is −0.1 ≦ c ≦ 0.1, d is 0.005 ≦ d ≦ 0.5, and −0.1 ≦ e. Lithium transition metal composite oxide having a composition of ≦ 0.2, 0 ≦ f ≦ 0.1), general formula Li _c Co _(1-d) M ′ _d O _(2-e) F _f (wherein M ′ 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 (S ), At least one element selected from tungsten (W), c is −0.1 ≦ c ≦ 0.1, d is 0 ≦ d ≦ 0.5, −0.1 ≦ e ≦ 0.2, In addition to the lithium transition metal composite oxide having a composition of 0 ≦ f ≦ 0.1), the general formula Li _s Mn _2−t M ″ _t O _u F _v (where M ″ 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), at least one element selected from tungsten (W), s is s ≧ 0.9, t is 0.005 ≦ t ≦ 0 .6, u is 3.7 ≦ u ≦ 4.1, v is 0 ≦ v ≦ 0.1) It is possible to use a metal composite oxide. In addition, the general formula LiM ′ ″ PO ₄ (wherein M ′ ″ 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), zirconium ( A lithium transition metal composite phosphate having a composition of at least one element selected from Zr) and zinc (Zn) can also be used.

To achieve the positive electrode material to withstand use at high charging voltage, the positive electrode surface made of LiCoO ₂ or LiNiO _2, more voltage resistance high _{Li (Co x Ni y Mn z} ) O 2 (x, y , Z is a small number of 1 or less) and Li (Ni _y Mn _z ) O ₂ (y, z is a small number of 1 or less) or other thin oxides are particularly effective. Such a surface modification method is not particularly limited. For example, by attaching Ni, Mn-based oxide or hydroxide to the surface of LiCoO ₂ by an appropriate method, firing at a high temperature of 900 ° C. or higher, relatively uniform Li on the surface of _{LiCoO 2 (Co x Ni y Mn} z) O 2 (x, y, z few 1 below) _{and, Li (Ni y Mn z)} O 2 (y, z is 1 or less Positive electrode material to which a small number of (A) is attached can be obtained.

The anode current collector 22A is made of a metal foil such as a copper (Cu) foil. The negative electrode active material layer 22B includes, for example, a negative electrode active material, and may include a binder such as polyvinylidene fluoride as necessary. The negative electrode active material includes a negative electrode material capable of inserting and extracting lithium (hereinafter referred to as a negative electrode material capable of inserting and extracting lithium). Examples of negative electrode materials capable of inserting and extracting lithium include carbon materials, metal compounds, oxides, sulfides, lithium nitrides such as LiN ₃ , lithium metals, metals that form alloys with lithium, or polymer materials. Is mentioned.

  Examples of the carbon material include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, carbon fibers, and activated carbon. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body refers to a carbonized material obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as: In addition, examples of the polymer material include polyacetylene and polypyrrole.

  Among such negative electrode materials capable of inserting and extracting lithium, those having a charge / discharge potential relatively close to lithium metal are preferable. This is because the lower the charge / discharge potential of the negative electrode 22, the easier it is to increase the energy density of the battery. Among these, a carbon material is preferable because a change in crystal structure that occurs during charge / discharge is very small, a high charge / 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. Moreover, non-graphitizable carbon is preferable because excellent cycle characteristics can be obtained.

  Examples of the negative electrode material capable of inserting and extracting lithium include lithium metal alone, a metal element or a metalloid element capable of forming an alloy with lithium, an alloy, or a compound. These are preferable because a high energy density can be obtained, and in particular, when used together with a carbon material, a high energy density can be obtained and excellent cycle characteristics can be obtained, and therefore, it is more preferable. Note that in this specification, alloys include those composed of one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. The structures include solid solutions, eutectics (eutectic mixtures), intermetallic compounds, or those in which two or more of them coexist.

Examples of such metal elements or metalloid elements include tin (Sn), lead (Pb), aluminum (Al), indium (In), silicon (Si), zinc (Zn), antimony (Sb), and bismuth. (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf). These alloys or compounds, for example, those represented by the chemical formula Ma _s Mb _t Li _u or a chemical formula Ma _p Mc _q Md _r,. In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, Mb represents at least one of a metal element and a metalloid element other than lithium and Ma, Mc represents at least one of nonmetallic elements, and Md represents at least one of metallic elements and metalloid elements other than Ma. The values of s, t, u, p, q, and r are s> 0, t ≧ 0, u ≧ 0, p> 0, q> 0, and r ≧ 0, respectively.

  Among these, a simple substance, alloy or compound of Group 4B metal element or semimetal element in the short-period type periodic table is preferable, and silicon (Si) or tin (Sn), or an alloy or compound thereof is particularly preferable. These may be crystalline or amorphous.

In addition, inorganic compounds that do not contain lithium, such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , NiS, and MoS, can also be used for either the positive or negative electrode.

  The nonaqueous solvent preferably contains at least one of ethylene carbonate and propylene carbonate, for example. This is because the cycle characteristics can be improved. In particular, it is preferable to mix and contain ethylene carbonate and propylene carbonate because cycle characteristics can be further improved. The non-aqueous solvent preferably contains at least one of chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate. This is because the cycle characteristics can be further improved.

  The non-aqueous solvent preferably further contains at least one of 2,4-difluoroanisole and vinylene carbonate. This is because 2,4-difluoroanisole can improve discharge capacity, and vinylene carbonate can further improve cycle characteristics. In particular, it is more preferable that they are mixed and contained because both the discharge capacity and the cycle characteristics can be improved.

  Nonaqueous solvents further include butylene carbonate, γ-butyrolactone, γ-valerolactone, those in which some or all of the hydrogen groups of these compounds are substituted with fluorine groups, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl Tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropironitrile, N, N-dimethylformamide N-methylpyrrolidinone, N-methyloxazolidinone, N, N-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide, or trimethyl phosphate may be included. .

  Depending on the electrode to be combined, the reversibility of the electrode reaction may be improved by using an electrode in which part or all of the hydrogen atoms of the substances contained in the above non-aqueous solvent group are substituted with fluorine atoms. Therefore, these substances can be used as appropriate.

Examples of the lithium salt include LiPF ₆ , 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 , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, LiBF ₂ (ox), LiBOB, or LiBr are suitable, and any one or more of these may be used in combination. Among these, LiPF ₆ is preferable because it can obtain high ion conductivity and can improve cycle characteristics.

  The separator material that can be used in the present invention will be described below. As a separator material, it is possible to use those used in conventional batteries. Among these, it is particularly preferable to use a polyolefin microporous film that is excellent in short-circuit prevention effect and can improve battery safety by a shutdown effect. For example, a microporous film made of polyethylene or polypropylene resin is preferable. More preferably, it is preferable to use a laminate or mixture of polyethylene having a lower shutdown temperature and polypropylene having excellent oxidation resistance because both shutdown performance and float characteristics can be achieved.

  It is further preferable to provide a structure that suppresses the oxidative decomposition of the battery, which is characterized by a high charging voltage. For example, a method of interposing an insulating layer such as a fluororesin layer, a metal oxide, or a metal ion salt at the interface between the positive electrode 21 and the separator 23 can be used. Particularly in the case of a fluororesin, a material having a basic skeleton of polytetrafluoroethylene, polyvinylidene fluoride, or polyhexafluoropropylene can be used. Furthermore, those copolymers can also be utilized. In addition, it is possible to use perfluoroalkoxyalkane (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin), ethylene-tetrafluoroethylene copolymer, perfluoroethylene-propene copolymer, ethylene-chlorotrifluoroethylene copolymer, and the like. . Examples of the metal oxide and metal ion salt include alumina, zirconia, aluminum phosphate, and aluminum nitrate.

These layers must be carefully arranged so as not to hinder the movement of ions serving as electrode reactive species. As a method of actually interposing, for example, a method of supporting in advance on the positive electrode surface or the separator surface can be mentioned. Furthermore, in a system employing a wound electrode element, for example, it is possible to spray directly on the interface between the positive electrode and the separator during winding. The amount of the intervening fluororesin layer is defined by the weight per unit area. It is preferable to intervene so that it becomes 0.1 mg / cm ² or more and 10 mg / cm ² or less. When it is less than 0.1 mg / cm ² , it is difficult to exert a protective effect against the oxidative decomposition reaction. On the other hand, if it exceeds 10 mg / cm ² , the decrease in energy density becomes remarkable due to the redundancy of the ion conduction path length due to the increase in the distance between the electrodes.

  As a method of providing a fluororesin layer, a metal oxide, or a metal ion salt layer on the electrode surface or the separator surface, a method of drying after spraying a fluororesin suspension on the deposition surface, or a dispersion or solution of these As a representative example, a method of drying after coating with a bar coater or the like can be given. Although the method of providing such a layer is not limited, the above-described spraying method of the suspension easily forms a porous structure in which the fluororesin layer, the metal oxide, and the metal ion salt layer are rich. This is a more preferable method because it can ensure the permeability of the electrolytic solution.

  In the non-aqueous electrolyte secondary battery having the above-described configuration, the open circuit voltage in the fully charged state is, for example, in the range of 4.25 V to 6.00 V, preferably 4.25 V to 4.5 V. If it is 4.25V or more, the utilization factor of the positive electrode active material can be increased, and more energy can be taken out. If it is 4.5V or less, oxidation of the separator 23 and chemical change of the electrolytic solution are suppressed. Because you can.

(1-1) Nonaqueous electrolyte secondary battery manufacturing method The nonaqueous electrolyte secondary battery having the above-described configuration can be manufactured, for example, as follows. For example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as 1-methyl-2-pyrrolidone to form a positive electrode mixture slurry. To do. Next, after applying this positive electrode mixture slurry to the positive electrode current collector 21A and drying the solvent, the positive electrode active material layer 21B is formed by compression molding using a roll press or the like, and the positive electrode 21 is produced. Further, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as 1-methyl-2-pyrrolidone to obtain a negative electrode mixture slurry. Next, after applying this negative electrode mixture slurry to the negative electrode current collector 22A and drying the solvent, the negative electrode active material layer 22B is formed by compression molding using a roll press or the like, and the negative electrode 22 is produced. Next, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. Thereafter, the positive electrode 21 and the negative electrode 22 were wound through the separator 23, and the tip portion of the positive electrode lead 25 was welded to the safety valve mechanism 15, and the tip portion of the negative electrode lead 26 was welded to the battery can 11 and wound. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are housed in the battery can 11, an electrolyte is injected into the battery can 11 and impregnated in the separator 23. Thereafter, the battery lid 14, the safety valve mechanism 15 and the heat sensitive resistance element 16 are caulked and fixed to the opening end portion of the battery can 11 via the sealing gasket 17, whereby the nonaqueous electrolyte secondary battery shown in FIG. 1 is obtained. Complete.

The non-aqueous electrolyte secondary battery having the above-described configuration, the end portion a distance [Delta] L from the outermost end position L ₁ of the positive electrode active material layer 21B outermost to the end position L ₂ of the anode active material layer 22B, 0 mm <[Delta] L < Since the 6 mm relationship is satisfied, the diffusion distance in which lithium ions occluded in the negative electrode active material layer 22B from the end of the positive electrode active material layer 21B diffuse toward the negative electrode active material layer 22C is limited. . Therefore, since the potential increase at the positive electrode end can be suppressed, the storage characteristics at high temperatures can be improved. Further, by making the end portion distance ΔL satisfy the relationship of 0 mm <ΔL <6 mm, not only the storage characteristics at high temperature but also the energy density under normal use conditions can be realized.

  Moreover, in the nonaqueous electrolyte secondary battery having the above-described configuration, when charged, for example, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and are inserted in the positive electrode 21 through the electrolytic solution. When conductive fibers are added to the negative electrode 22, capacity deterioration is suppressed particularly under high temperature storage, and as a result, high reliability is ensured.

(2) Second Embodiment (2-1) Configuration of Nonaqueous Electrolyte Secondary Battery FIG. 6 is a perspective view showing an example of the configuration of the nonaqueous electrolyte secondary battery according to the second embodiment of the present invention. . In this nonaqueous electrolyte secondary battery, the wound electrode body 30 to which the positive electrode lead 31 and the negative electrode lead 32 are attached is housed in a film-like exterior member 40, and is reduced in size, weight and thickness. It is possible.

  The positive electrode lead 31 and the negative electrode lead 32 are led out from the inside of the exterior member 40 to the outside, for example, in the same direction. The positive electrode lead 31 and the negative electrode lead 32 are each made of a metal material such as aluminum (Al), copper (Cu), nickel (Ni), or stainless steel, and each have a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 40 is disposed so that the polyethylene film side and the wound electrode body 30 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 40 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 7 is a cross section taken along line VII-VII of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is obtained by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween, and the outermost peripheral portion is protected by a protective tape 37.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on one or both surfaces of a positive electrode current collector 33A. The negative electrode 34 has a structure in which a negative electrode active material layer 34B is provided on one surface or both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B and the positive electrode active material layer 33B are arranged to face each other. Yes. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are the positive electrode current collector 21A and the positive electrode active material layer described in the first embodiment, respectively. This is the same as 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23. Further, the positional relationship between the extreme ends of the positive electrode active material layer 33B and the negative electrode active material layer 34B is the positional relationship between the extreme ends of the positive electrode active material layer 21B and the negative electrode active material layer 22B described in the first embodiment. It is the same.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte layer 36 is preferable because high ion conductivity can be obtained and battery leakage can be prevented. The configuration of the electrolytic solution (that is, the solvent, the electrolyte salt, and the like) is the same as that of the nonaqueous electrolyte secondary battery according to the first embodiment described above. Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and polyhexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, poly Examples include siloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, and polycarbonate. In particular, in consideration of electrochemical stability, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, polyethylene oxide, and the like are preferable.

(2-2) Manufacturing Method of Nonaqueous Electrolyte Secondary Battery The nonaqueous electrolyte secondary battery having the above-described configuration can be manufactured, for example, as follows. First, a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent is applied to each of the positive electrode 33 and the negative electrode 34, and the mixed solvent is volatilized to form the electrolyte layer 36. After that, the positive electrode lead 31 is attached to the end of the positive electrode current collector 33A by welding or the like, and the negative electrode lead 32 is attached to the end of the negative electrode current collector 34A by welding or the like. Next, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are laminated via a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and a protective tape 37 is attached to the outermost peripheral portion. The wound electrode body 30 is formed by bonding. Finally, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edges of the exterior members 40 are sealed and sealed by heat fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the nonaqueous electrolyte secondary battery shown in FIG. 6 is obtained.

  In addition, this nonaqueous electrolyte secondary battery may be manufactured as follows. First, the positive electrode 33 and the negative electrode 34 are prepared as described above, and after the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode 33 and the negative electrode 34, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 and wound. Rotate and adhere the protective tape 37 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 30. Next, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge except for one side is heat-sealed to form a bag shape, which is then stored inside the exterior member 40. Next, an electrolyte composition including a solvent, an electrolyte salt, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared, and the exterior member Inject into 40.

  After injecting the electrolyte composition, the opening of the exterior member 40 is heat-sealed and sealed in a vacuum atmosphere. Next, the gelled electrolyte layer 36 is formed by applying heat to polymerize the monomer to obtain a polymer compound. As a result, the nonaqueous electrolyte secondary battery shown in FIG. 6 is obtained.

  The operation and effect of the second embodiment are the same as those of the first embodiment described above.

  Hereinafter, specific examples of the present invention will be described in detail with reference to FIGS. 1 to 4, but the present invention is not limited to the examples.

(Example 1)
The positive electrode 21 was produced as follows. A positive electrode mixture was prepared by mixing lithium cobaltate, amorphous carbon powder (Ketjen Black), and polyvinylidene fluoride in a ratio of 94% by mass, 3% by mass, and 3% by mass, respectively. After this positive electrode mixture was dispersed in 1-methyl-2-pyrrolidone to produce a positive electrode mixture slurry, this positive electrode mixture slurry was uniformly applied to both surfaces of a positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 15 μm. did. The obtained coated material was dried with hot air and then compression molded with a roll press to form the positive electrode active material layer 21B. The total thickness of the positive electrode 21 was set to 160 μm.

The negative electrode 22 was produced as follows. 90% by mass and 8% by mass of spherical graphite powder having an average particle size of 15 μm and a specific surface area of 0.8 g / cm ³ , polyvinylidene fluoride, and carbon fiber (fiber average diameter of 0.1 μm, aspect ratio of 5), respectively. A negative electrode mixture was prepared by mixing at a ratio of 2% by mass. After this negative electrode mixture was dispersed in 1-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry, the negative electrode mixture slurry was uniformly applied to both surfaces of a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 12 μm. Further, the negative electrode active material layer 22B was formed by hot press molding. The total thickness of the negative electrode 22 was set to 160 μm.

  After producing the positive electrode 21 and the negative electrode 22, a microporous film mainly composed of polyethylene is used as the separator 23, and the separator 23, the positive electrode 21, and the negative electrode 22 are connected in this order: A jelly roll type wound electrode body 20 having an outer diameter of 17.0 mm was manufactured by stacking and winding a number of times in a spiral shape.

In the above steps, after molding the cathode 21 and the anode 22 to the strip as shown in FIG. 3, the outermost end position of the anode active material layer 22B from the top end position L ₁ of the positive electrode active material layer 21B after endmost distance ΔL to _{L 2 (= L 2 -L 1} ) is arranged precisely cathode 21 and the anode 22 so that 0.5 mm, thereby the spirally wound electrode body 20 by winding it did.

  After producing the wound electrode body 20, a pair of insulating plates 12 and 13 are arranged perpendicular to the peripheral surface of the wound electrode body 20 so as to sandwich the wound electrode body 20, and the current collector of the positive electrode 21 is collected. Therefore, one end of the aluminum positive electrode lead 25 was led out from the positive electrode current collector 21A, and the other end was electrically connected to the battery lid 14 via the disk plate 15A. Further, in order to collect the current of the negative electrode 22, one end of the nickel negative electrode lead 26 was led out from the negative electrode current collector 22 </ b> A, and the other end was welded to the battery can 11. In addition, the wound electrode body 20 was housed inside the battery can 11, and 4.0 g of the electrolyte solution was injected into the battery can 11 by a reduced pressure method.

In the electrolytic solution, after adjusting a mixed solvent in which 35% by mass of ethylene carbonate, 63% by mass of dimethyl carbonate and 2% by mass of vinylene carbonate were mixed, LiPF ₆ was added in a molar ratio of 1.5 mol to this mixed solvent. What was dissolved so that it might become / kg was used. Finally, the battery can 11 is caulked through a sealing gasket 17 coated with asphalt to seal the safety valve mechanism 15, the heat sensitive resistance element 16, and the battery lid 14 in a stacked state, and has a diameter of 18 mm and a height of 50 mm. This was a cylindrical nonaqueous electrolyte secondary battery.

(I) Evaluation of initial charge / discharge efficiency Initial charge / discharge efficiency was evaluated by the following method. First, after charging a non-aqueous electrolyte secondary battery that has never been charged with a charging current of 500 mA under constant current conditions, charging control is performed under constant voltage conditions when the closed circuit voltage reaches 4.35V. Switched to. The charging operation was terminated when 8 hours had elapsed from the start of charging, and immediately after that, a 500 mA discharging current was applied under a constant current condition, and when the closed circuit voltage reached 3.00 V, the discharging operation was terminated. The initial charge / discharge efficiency was calculated by substituting the discharge capacity and the charge capacity obtained during the main charging operation and the discharging operation into Equation 2 below. The results are shown in Table 1 and FIG. For the convenience of explanation, the above-described control condition for the initial charge / discharge operation is referred to as “condition A”.
[First charge / discharge efficiency] = [Discharge capacity] / [Charge capacity] × 100 (Formula 2)

(Ii) Evaluation of capacity recovery rate The capacity recovery rate (capacity deterioration during high-temperature storage) was evaluated by the following method. First, the non-aqueous electrolyte secondary battery whose initial charge / discharge efficiency was evaluated was charged and discharged only once under the condition A at room temperature, and the obtained discharge capacity A was recorded. Next, the non-aqueous electrolyte secondary battery was charged again at the same temperature and conditions, and then stored in a 45 ° C. thermostat. After 3 weeks from the start of storage, the non-aqueous electrolyte secondary battery is taken out of the thermostat, allowed to cool at room temperature for 24 hours, and then a 500 mA discharge current is applied under constant current conditions, and the closed circuit voltage is 3 When the voltage reached 0.000 V, the discharge operation was terminated. This non-aqueous electrolyte secondary battery was again charged and discharged only once under the condition A at room temperature, and the resulting discharge capacity B was recorded. The capacity recovery rate was calculated by substituting the discharge capacities A and B thus obtained into the following Equation 3. The results are shown in Table 1 and FIG.
[Capacity recovery rate] = [Discharge capacity B] / [Discharge capacity A] × 100 (Formula 3)

(Examples 2 to 6)
As shown in Table 1, after the nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the end distance ΔL was changed within the range of 1 mm to 7 mm, each initial charge / discharge efficiency and capacity were The recovery rate was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIGS.

(Comparative Examples 1 and 2)
As shown in Table 1, the end distance ΔL was changed to 0 mm or less, that is, the end position L ₂ of the negative electrode active material layer 22B was changed to the end position L of the positive electrode active material layer 21B as shown in FIG. _After the non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1 except that the position was changed to the same position as that in FIG. Evaluation was performed in the same manner. The results are shown in Table 1 and FIGS.

(Comparative Examples 3 to 7)
As shown in Table 1, after the nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the end distance ΔL was changed within the range of 8 mm to 12 mm, each initial charge / discharge efficiency and capacity were The recovery rate was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIGS.

(Evaluation results)
It can be seen from Table 1 and FIGS. 9 and 10 that there is a correlation between the initial charge / discharge efficiency and capacity recovery rate and the end portion distance ΔL. Specifically, it can be seen that the initial charge / discharge efficiency tends to deteriorate significantly when the end portion distance ΔL is less than 0.5 mm. On the other hand, it can be seen that the capacity recovery rate tends to deteriorate significantly when the end portion distance ΔL is less than 0 mm or more than 7 mm.
Considering the above points, in a non-aqueous electrolyte secondary battery having a maximum charge voltage of 4.35 V, the deterioration of the initial charge and discharge efficiency and the capacity recovery rate is suppressed, and a high energy density and excellent storage characteristics are realized. It is understood that the end portion distance ΔL is preferably in the range of 0.5 mm ≦ ΔL ≦ 7 mm.

(Examples 7 to 12)
As shown in Table 2, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the end distance ΔL was changed within the range of 0.5 mm to 7 mm. Thereafter, the initial charge / discharge efficiency and the capacity recovery rate were evaluated in the same manner as in Example 1 except that the maximum charge voltage in Condition A was changed to 4.25V. The results are shown in Table 2 and FIGS.

(Comparative Examples 8 and 9)
As shown in Table 2, the end distance ΔL was changed to 0 mm or less, that is, the end position L ₂ of the anode active material layer 22B was changed to the end position L of the cathode active material layer 21B as shown in FIG. _A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 7 except that the position was changed to the same position as that in ₁ or a position inside thereof, and then the initial charge / discharge efficiency and capacity recovery rate were the same as in Example 7. And evaluated. The results are shown in Table 2 and FIGS.

(Comparative Examples 10-14)
As shown in Table 2, after the nonaqueous electrolyte secondary battery was produced in the same manner as in Example 7 except that the end distance ΔL was changed within the range of 8 mm to 12 mm, each initial charge / discharge efficiency and capacity were The recovery rate was evaluated in the same manner as in Example 7. The results are shown in Table 2 and FIGS.

(Evaluation results)
From Table 2 and FIGS. 11 and 12, the initial charge / discharge efficiency and capacity recovery rate and the end portion distance ΔL have the same correlation as in Examples 1 to 6 and Comparative Examples 1 to 7 described above. I understand that. Therefore, in a non-aqueous electrolyte secondary battery having a maximum charging voltage of 4.25 V, in order to suppress deterioration of initial charge / discharge efficiency and capacity recovery rate, and to realize high energy density and excellent storage characteristics, end portions It can be seen that the distance ΔL is preferably in the range of 0.5 mm ≦ ΔL ≦ 7 mm.

(Examples 13 to 17)
The nonaqueous electrolyte secondary was the same as in Example 1 except that the thickness of the negative electrode 22 was changed to 175 μm and the end distance ΔL was changed within the range of 0.5 mm to 6 mm as shown in Table 3. A battery was produced. Thereafter, the initial charge / discharge efficiency and the capacity recovery rate were evaluated in the same manner as in Example 1 except that the maximum charge voltage in Condition A was changed to 4.50V. The results are shown in Table 3 and FIGS.

(Comparative Examples 15 and 16)
As shown in Table 3, the end distance ΔL was changed to 0 mm or less, that is, the end position L ₂ of the negative electrode active material layer 22B was changed to the end position L ₁ of the positive electrode active material layer 21B as shown in FIG. After the non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 13 except that the position was changed to the same position or inside thereof, the initial charge / discharge efficiency and capacity recovery rate were evaluated in the same manner as in Example 13. did. The results are shown in Table 3 and FIGS.

(Comparative Examples 17-22)
As shown in Table 3, after the non-aqueous electrolyte secondary battery was produced in the same manner as in Example 13 except that the end distance ΔL was changed within the range of 7 mm to 12 mm, each initial charge / discharge efficiency and capacity recovery were obtained. The rate was evaluated as in Example 13. The results are shown in Table 3 and FIGS.

(Evaluation results)
It can be seen from Table 3 and FIGS. 13 and 14 that there is a correlation between the initial charge / discharge efficiency and capacity recovery rate and the end portion distance ΔL. Specifically, it can be seen that the initial charge / discharge efficiency tends to deteriorate significantly when the end portion distance ΔL is less than 1 mm. On the other hand, it can be seen that the capacity recovery rate tends to deteriorate significantly when the end portion distance ΔL is less than 1 mm or more than 6 mm.
In consideration of the above points, in a non-aqueous electrolyte secondary battery with a maximum charge voltage of 4.5 V, the deterioration of the initial charge / discharge efficiency and the capacity recovery rate is suppressed, and a high energy density and excellent storage characteristics are realized. It is understood that the end portion distance ΔL is preferably in the range of 1 mm ≦ ΔL ≦ 6 mm.

(Examples 18 to 22)
Using a mixture of carbon (C), tin (Sn) and cobalt (Co) alloys as the negative electrode active material, the carbon (C) and metal mixing ratios were 20 wt% and 80 wt%, respectively, and the total negative electrode thickness Was changed to 100 μm, and as shown in Table 4, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the end distance ΔL was changed within the range of 0.5 mm to 6 mm. Then, each initial charge-discharge efficiency and capacity | capacitance recovery rate were evaluated like Example 1 except having changed the maximum charging voltage in the conditions A into 4.30V. The results are shown in Table 4 and FIGS.

(Comparative Examples 23 and 24)
As shown in Table 4, the end distance ΔL was changed to 0 mm or less, that is, the end position L ₂ of the negative electrode active material layer 22B was changed to the end position L of the positive electrode active material layer 21B as shown in FIG. _After the non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 18 except that the position was changed to the same position as or inward of FIG. ₁ , the initial charge / discharge efficiency and capacity recovery rate were the same as in Example 18. And evaluated. The results are shown in Table 4 and FIGS.

(Comparative Examples 25-30)
As shown in Table 4, after the nonaqueous electrolyte secondary battery was produced in the same manner as in Example 18 except that the end distance ΔL was changed within the range of 7 mm to 12 mm, each initial charge / discharge efficiency and capacity were The recovery rate was evaluated in the same manner as in Example 18. The results are shown in Table 4 and FIGS.

(Evaluation results)
From Table 4 and FIGS. 15 and 16, it can be seen that there is a correlation between the initial charge / discharge efficiency and capacity recovery rate and the end portion distance ΔL. Specifically, it can be seen that the initial charge / discharge efficiency tends to deteriorate significantly when the end portion distance ΔL is less than 1 mm. On the other hand, it can be seen that the capacity recovery rate tends to deteriorate significantly when the end portion distance ΔL is less than 1 mm or more than 6 mm.
Considering the above points, in the nonaqueous electrolyte secondary battery using a mixture of carbon (C), tin (Sn) and cobalt (Co) as the negative electrode active material, the initial charge and discharge efficiency and capacity recovery rate are It can be seen that the end distance ΔL is preferably in the range of 1 mm ≦ ΔL ≦ 6 mm in order to suppress deterioration and achieve a high energy density and excellent storage characteristics.

(Examples 23 to 27)
Except for using a negative electrode in which a silicon layer was formed on a copper foil by vacuum deposition under a condition of a thickness of 50 μm, and changing the edge distance ΔL within a range of 0.5 mm to 6 mm as shown in Table 5, A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1. Thereafter, the initial charge / discharge efficiency and the capacity recovery rate were evaluated in the same manner as in Example 1 except that the maximum charge voltage in Condition A was changed to 4.3V. The results are shown in Table 5 and FIGS.

(Comparative Examples 31, 32)
As shown in Table 5, the end distance ΔL was changed to 0 mm or less, that is, the end position L ₂ of the negative electrode active material layer 22B was changed to the end position L of the positive electrode active material layer 21B as shown in FIG. _After the non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 23, except that the position was changed to the same position as that in FIG. ₁ or inside thereof, the initial charge / discharge efficiency and capacity recovery rate were the same as in Example 23. And evaluated. The results are shown in Table 5 and FIGS.

(Comparative Examples 33-38)
As shown in Table 4, after the non-aqueous electrolyte secondary battery was produced in the same manner as in Example 23 except that the end distance ΔL was changed within the range of 7 mm to 12 mm, each initial charge / discharge efficiency and capacity were The recovery rate was evaluated in the same manner as in Example 23. The results are shown in Table 5 and FIGS.

(Evaluation results)
From Table 5 and FIGS. 17 and 18, it can be seen that there is a correlation between the initial charge / discharge efficiency and capacity recovery rate and the end portion distance ΔL. Specifically, it can be seen that the initial charge / discharge efficiency tends to deteriorate significantly when the end portion distance ΔL is less than 1 mm. On the other hand, it can be seen that the capacity recovery rate tends to deteriorate significantly when the end portion distance ΔL is less than 1 mm or more than 6 mm.
Considering the above points, in the non-aqueous electrolyte secondary battery using silicon (Si) as the negative electrode active material, the deterioration of the initial charge and discharge efficiency and the capacity recovery rate is suppressed, and the high energy density and the excellent storage characteristics In order to realize the above, it is understood that the end portion distance ΔL is preferably in the range of 1 mm ≦ ΔL ≦ 6 mm.

(Comparative Examples 39-51)
As shown in Table 6, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the end distance ΔL was changed within the range of −1 mm to 12 mm. Thereafter, as shown in Table 6, the initial charge / discharge efficiency and the capacity recovery rate were evaluated in the same manner as in Example 1 except that the maximum charge voltage in Condition A was changed to 4.2V. The results are shown in Table 6 and FIGS.

(Evaluation results)
From Table 6 and FIGS. 19 and 20, the initial charge / discharge efficiency and the end portion distance ΔL have the same correlation as in the above-described examples and comparative examples, whereas the capacity recovery rate and the end distance ΔL. It can be seen that there is no correlation with the part distance ΔL as in the above-described examples and comparative examples. That is, in a non-aqueous electrolyte secondary battery having a maximum charge voltage of 4.25 V or more, the capacity recovery rate tends to decrease remarkably as the end portion distance ΔL increases, whereas the non-aqueous electrolyte secondary battery having a maximum charge voltage of 4.2 V. In the electrolyte secondary battery, it can be seen that the capacity retention rate is substantially constant even when the end portion distance ΔL is large, and tends to hardly deteriorate.
Considering the above points, it can be seen that the significant reduction in the capacity recovery rate when the end portion distance ΔL is increased is a deterioration mode unique to the nonaqueous electrolyte secondary battery having a maximum charge voltage of 4.25 V or more.

(Comprehensive evaluation results)
Summarizing the above evaluation results, high energy density and excellent storage characteristics are realized in a non-aqueous electrolyte secondary battery whose open circuit voltage in the fully charged state is in the range of 4.25V to 6.00V. Therefore, it can be seen that it is preferable to set the end portion distance ΔL in the range of 1 mm ≦ ΔL ≦ 6 mm. This numerical range does not change even when an alloy of carbon (C), tin (Sn) and cobalt (Co), silicon (Si), graphite, or the like is used as the negative electrode active material. It turns out that it is not dependent.
In addition, it is understood that it is preferable to set the end portion distance ΔL in the range of 0 <ΔL ≦ 6 mm, considering that the performance value tends to improve when the value of ΔL shifts from negative to positive.

  Table 1 shows the initial charge / discharge efficiency and capacity recovery rate of Examples 1 to 6 and Comparative Examples 1 to 7. Table 2 shows the initial charge / discharge efficiency and capacity recovery rate of Examples 7 to 12 and Comparative Examples 8 to 14. Table 3 shows the initial charge / discharge efficiency and capacity recovery rate of Examples 13 to 17 and Comparative Examples 15 to 22. Table 4 shows the initial charge / discharge efficiency and the capacity recovery rate of Examples 18 to 22 and Comparative Examples 23 to 30. Table 5 shows the initial charge / discharge efficiency and capacity recovery rate of Examples 23 to 27 and Comparative Examples 31 to 38. Table 6 shows the initial charge / discharge efficiency and capacity recovery rate of Comparative Examples 39 to 51.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible.

  For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as necessary.

  In the above-described embodiment, the case where the present invention is applied to a wound type nonaqueous electrolyte secondary battery has been described as an example. However, the present invention can also be applied to a stack type nonaqueous electrolyte secondary battery. It is.

  Moreover, although the above-mentioned embodiment demonstrated as an example the case where an electrode has a collector and an active material layer, it is good also as a structure from which an electrode consists only of an active material layer.

  In the above-described embodiment, the case where the electrolyte is an electrolytic solution or a gel electrolyte has been described as an example. However, instead of these electrolytes, other electrolytes may be used. Other electrolytes include, for example, a polymer solid electrolyte using an ion conductive polymer or an inorganic solid electrolyte using an ion conductive inorganic material. These can be used alone or in combination with other electrolytes. Also good. Examples of the polymer compound that can be used for the polymer solid electrolyte include polyether, polyester, polyphosphazene, and polysiloxane. Examples of the inorganic solid electrolyte include ion conductive ceramics, ion conductive crystals, and ion conductive glass.

It is sectional drawing which shows an example of a structure of the nonaqueous electrolyte secondary battery by the 1st Embodiment of this invention. It is sectional drawing which shows an example of a structure of a positive electrode and a negative electrode. It is a top view which shows the positional relationship of the extreme end part of a positive electrode active material layer and a negative electrode active material layer. It is sectional drawing which shows the positional relationship of the extreme end part of a positive electrode active material layer and a negative electrode active material layer. It is a schematic diagram for demonstrating the limitation reason of edge part distance (DELTA) L of the nonaqueous electrolyte secondary battery by the 1st Embodiment of this invention. It is a perspective view which shows an example of a structure of the nonaqueous electrolyte secondary battery by the 2nd Embodiment of this invention. 7 is a cross section taken along line VII-VII of the spirally wound electrode body illustrated in FIG. 6. It is a top view which shows the positional relationship of the extreme end part of a positive electrode active material layer and a negative electrode active material layer. It is a graph which shows the first time charge / discharge efficiency of Examples 1-6 and Comparative Examples 1-7. It is a graph which shows the capacity | capacitance recovery rate of Examples 1-6 and Comparative Examples 1-7. It is a graph which shows the first time charge / discharge efficiency of Examples 7-12 and Comparative Examples 8-14. It is a graph which shows the capacity | capacitance recovery rate of Examples 7-12 and Comparative Examples 8-14. It is a graph which shows the first time charge / discharge efficiency of Examples 13-17 and Comparative Examples 15-22. It is a graph which shows the capacity | capacitance recovery rate of Examples 13-17 and Comparative Examples 15-22. It is a graph which shows the first time charge / discharge efficiency of Examples 18-22 and Comparative Examples 23-30. It is a graph which shows the capacity | capacitance recovery rate of Examples 18-22 and Comparative Examples 23-30. It is a graph which shows the first time charge / discharge efficiency of Examples 23-27 and Comparative Examples 31-38. It is a graph which shows the capacity | capacitance recovery rate of Examples 23-27 and Comparative Examples 31-38. It is a graph which shows the first time charge / discharge efficiency of Comparative Examples 39-51. It is a graph which shows the capacity | capacitance recovery rate of Comparative Examples 39-51.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulating plate, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Sealing gasket, 20 ... wound electrode body, 21 ... positive electrode, 21A ... positive electrode current collector, 21B ... positive electrode active material layer, 21C ... extreme end of positive electrode active material layer, 22. .. Negative electrode, 22A ... Negative electrode current collector, 22B ... Negative electrode active material layer, 22C ... Negative electrode active material layer endmost part, 23 ... Separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... negative electrode lead, 30 ... wound electrode body, 31 ... positive electrode lead, 32 ... negative electrode lead, 33 ... positive electrode, 33A ... positive electrode current collector, 33B ... Positive electrode active material layer, 34 ... Negative electrode, 34A ... Negative electrode current collector, 34B ... Negative electrode active material layer, 35 ... separator, 36 ... electrolyte layer, 37 ... protective tape, 40 ... outer member, 41 ... adhesive film

Claims (5)

In the non-aqueous electrolyte secondary battery in which the open circuit voltage in the fully charged state is in the range of 4.25V to 6.00V,
A positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer, and a nonaqueous electrolyte,
The positive electrode and the negative electrode are provided to face each other so that the extreme end position L ₁ of the positive electrode active material layer is inside the extreme end position L ₂ of the negative electrode active material layer,
The nonaqueous electrolyte secondary battery, wherein an end distance ΔL from the extreme end position L ₁ of the positive electrode active material layer to the extreme end position L ₂ of the negative electrode active material layer satisfies the following formula 1. .
0 mm <ΔL = L ₂ −L ₁ <6 mm (Formula 1)   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material layer includes a carbonaceous material.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material layer includes a material that forms an intermetallic compound with lithium metal.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material layer contains silicon.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material layer contains lithium metal.

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