JP2010080407A - Positive electrode active material, positive electrode, and non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a positive electrode active material having a high capacity, with superior charge and discharge cycle characteristics, and capable of suppressing the occurrence of gas; a positive electrode using this; and a non-aqueous electrolyte secondary battery. <P>SOLUTION: The positive electrode 21 has a positive electrode active material. The positive electrode active material has: lithium transition metal compound oxide particles containing lithium and a transition metal as a constituent element; and a covering layer provided at least on part of the surface of the lithium transition metal compound oxide particles. Manganese (Mn) is included at least in the covering layer, and in the absolute value of a radius vector structure function obtained by Fourier transforming an extensive X-ray absorption fine structure (EXAFS) multiplying cube of the cycle of a photoelectron at MnK absorption end, the ratio of a second proximity peak intensity near 5.2 Å to the first proximity peak intensity near 1.5 Å is 0.3 or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a positive electrode active material, a positive electrode, and a nonaqueous electrolyte secondary battery. More specifically, the present invention relates to a positive electrode active material capable of suppressing gas generation inside the battery, and a positive electrode and a non-aqueous electrolyte secondary battery using the same.

  In recent years, the technology of portable electronic devices has been remarkably developed, and electronic devices such as mobile phones and notebook computers have begun to be recognized as basic 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 is 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, lithium ion secondary batteries have a high voltage and an excellent energy density as compared with other battery systems, and thus have been built into most devices.

Usually, in lithium ion secondary batteries, lithium transition metal composite oxides such as lithium cobaltate (LiCoO ₂ ) and lithium nickelate (LiNiO ₂ ) are used for the positive electrode, and a carbon material is used for the negative electrode. It 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.

  Many studies have been conducted for the purpose of further enhancing the performance and expanding the applications of such lithium ion secondary batteries. As one of them, for example, it has been studied to increase the energy density of a positive electrode active material such as lithium cobaltate by increasing the charging voltage to increase the capacity of the lithium ion secondary battery.

  However, when charging / discharging is repeated at a high capacity, there is a problem that the capacity is deteriorated and the battery life is shortened. Further, when used in a high temperature environment, gas is generated inside the battery, causing problems such as leakage and battery deformation.

  Thus, for example, Patent Document 1 below discloses a method of improving battery characteristics such as charge / discharge cycle characteristics by coating a surface of a positive electrode with a metal oxide. Patent Document 2 listed below describes a method for improving the structural stability and thermal stability by coating the surface of a positive electrode active material with a metal oxide.

Japanese Patent No. 3172388 Japanese Patent No. 3691279

  In addition, in the surface coating of the positive electrode active material, the effect of improving the cycle characteristics and the thermal stability due to the coating form has been studied. For example, the following Patent Literature 3, Patent Literature 4, Patent Literature 5, Patent Literature 6, Patent Literature 7, and Patent Literature 8 describe a method of uniformly coating a lithium transition metal composite oxide. Patent Document 9 below describes a positive electrode active material in which a lump of metal oxide is attached on a metal oxide layer.

JP 7-235292 A JP 2000-149950 A JP 2000-156227 A JP 2000-164214 A JP 2000-195517 A JP 2002-231227 A Japanese Patent Laid-Open No. 2001-256969

  Further, elements used for surface coating have also been studied. For example, Patent Document 10 below discloses a positive electrode active material in which one or more surface treatment layers containing two or more coating elements are formed on the surface of a lithium compound serving as a core. Are listed.

JP 2002-164053 A

  The following Patent Document 11 discloses a battery having excellent charge / discharge characteristics by using a material whose particle surface is coated with phosphorus (P). Patent Document 12 below discloses a battery having excellent charge / discharge cycle characteristics and large current charge / discharge characteristics by using a positive electrode to which phosphorus (P) is added. Patent Document 13 below discloses a method for forming a layer containing boron (B), phosphorus (P), or nitrogen (N). Furthermore, the following patent document 14, the following patent document 15, and the following patent document 16 disclose a method of containing a phosphate compound or the like in the positive electrode.

Japanese Patent No. 3054829 JP 05-36411 A Japanese Patent No. 3192855 JP-A-10-154532 Japanese Patent Laid-Open No. 10-241681 JP-A-11-204145

Patent Document 17 discloses a method for improving thermal stability by disposing a surface treatment layer containing a compound represented by MXO _k on the particle surface. Patent Document 18 discloses a technique for forming a surface layer represented by MIPmOn. In a state in which the presence of the layer on the particle surface, such as MXO _k in the same way that these coating treatment, was also insufficient like the effect of suppressing gas generation with cause deterioration in charge and discharge efficiency.

JP 2003-7299 A JP 2006-127932 A

  However, in the covering element, the covering method, and the covering form disclosed in Patent Document 1 and Patent Document 2, since lithium ion diffusion is inhibited, a sufficient capacity cannot be obtained with a charge / discharge current value in a practical range. There is.

  According to the methods disclosed in Patent Literature 3, Patent Literature 4, Patent Literature 5, Patent Literature 6, Patent Literature 7, and Patent Literature 8, although high capacity can be maintained, the cycle characteristics are improved to a high degree and further gas generation is achieved. It is not enough to suppress this. In addition, when a positive electrode active material having a structure in which a lump of metal oxide was adhered on a metal oxide layer by the method disclosed in Patent Document 9, sufficient charge / discharge efficiency was not obtained, and the capacity was large. The result decreased.

  The effect of Patent Document 10 is limited to the improvement of thermal stability. Moreover, when a positive electrode active material was produced by the manufacturing method disclosed in Patent Document 10, a uniform multilayer was formed, and not only an effect was not recognized particularly for suppressing gas generation, but gas generation increased on the contrary. As a result.

  In Patent Document 11, Patent Document 12, and Patent Document 13, the cycle characteristics are improved by adding or coating phosphorus to the positive electrode active material, but these techniques using only light elements that are inert to lithium. Then, sufficient reversible capacity cannot be obtained.

  Patent Document 14 is a technology related to safety during overcharge. In addition, simply mixing a phosphate compound or the like in the positive electrode does not actually provide a sufficient effect. Similarly, in Patent Document 15 and Patent Document 16 described above, since a phosphate compound or the like is simply mixed in the positive electrode, the effect is insufficient.

In the state where the layer such as MXO _k used in the coating treatment of Patent Document 17 and Patent Document 18 was present on the particle surface, the charge / discharge efficiency was deteriorated and the effect of suppressing gas generation was insufficient.

  Accordingly, an object of the present invention is to provide a positive electrode active material that has a high capacity, is excellent in charge / discharge cycle characteristics, and can further suppress gas generation, and a positive electrode and a nonaqueous electrolyte secondary battery using the same. is there.

Using an active material mainly composed of lithium-containing transition metal oxides such as LiCoO ₂ and LiNiO ₂ , the maximum charge voltage is 4.20 V or more, preferably 4.35 V or more in a state where the ratio of positive and negative electrodes is appropriately designed. It is possible to improve the energy density of the battery by charging the battery so that it is more preferably 4.40 V or higher.

  However, as the charging voltage is increased, the reactivity at the interface between the positive electrode active material and the electrolyte increases, so that the transition metal component is eluted from the positive electrode, the active material is degraded, and the eluted metal is deposited on the negative electrode side. This is thought to cause the deterioration of battery characteristics, such as inhibiting Li occlusion and release by accelerating, accelerating the decomposition reaction of the electrolyte solution at the interface, generating a film on the surface, and causing gas generation. When charging / discharging is repeated in a high charge voltage state of 4.25 V or more, the cause of deterioration of charge / discharge cycle life and high temperature characteristics is caused by an increase in the amount of Li extraction at the interface between the active material and the electrolyte. It is conceivable that the reactivity of the active material increases and the active material and the electrolytic solution deteriorate during charging.

  As a result of intensive studies in view of such problems, the inventors of the present application include Mn in at least a part of the surface of the lithium-containing transition metal oxide, and the coating treatment is performed so that Mn is in a specific state. By using the applied lithium transition metal composite oxide, a positive electrode active material, a positive electrode, and a non-aqueous electrolyte battery that achieve both high capacity and battery characteristics with less cycle characteristics and gas generation than before are invented. It was.

In order to solve the above-mentioned problems,
The first invention is
Lithium transition metal composite oxide particles containing lithium and a transition metal as constituent elements;
A coating layer provided on at least a part of the surface of the lithium transition metal composite oxide particles,
At least the coating layer contains manganese (Mn),
In the absolute value of the radial structure function obtained by Fourier transform of the wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the wavenumber of the photoelectron at the MnK absorption edge, the first proximity peak intensity near 1.5Å It is a positive electrode active material in which the ratio of the second proximity peak intensity in the vicinity of 5.2% is 0.3 or more.

The second invention is
Lithium transition metal composite oxide particles containing lithium and a transition metal as constituent elements;
A coating layer provided on at least a part of the surface of the lithium transition metal composite oxide particles,
At least the coating layer contains manganese (Mn),
In the absolute value of the radial structure function obtained by Fourier transform of the wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the wavenumber of the photoelectron at the MnK absorption edge, the first proximity peak intensity near 1.5Å It is a positive electrode including a positive electrode active material in which the ratio of the second adjacent peak intensity in the vicinity of 5.2% is 0.3 or more.

The third invention is
A positive electrode having a positive electrode active material, a negative electrode, and an electrolyte;
The positive electrode active material is
Lithium transition metal composite oxide particles containing lithium and a transition metal as constituent elements;
And a coating layer provided on at least a part of the surface of the lithium transition metal composite oxide particles,
At least the coating layer contains manganese (Mn),
In the absolute value of the radial structure function obtained by Fourier transform of the wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the wavenumber of the photoelectron at the MnK absorption edge, the first proximity peak intensity near 1.5Å It is a nonaqueous electrolyte secondary battery in which the ratio of the second proximity peak intensity in the vicinity of 5.2% is 0.3 or more.

  In the first to third aspects of the invention, the positive electrode active material is provided on at least part of the surfaces of the lithium transition metal composite oxide particles containing lithium and transition metal as constituent elements and the lithium transition metal composite oxide particles. And having a coating layer, at least the coating layer contains manganese (Mn), and is obtained by Fourier transform of a wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the photoelectron wavenumber at the MnK absorption edge. In the absolute value of the radial structure function, since the ratio of the second adjacent peak intensity near 5.2 に 対 す る to the first adjacent peak intensity near 1.5 で あ is 0.3 or more, the cycle characteristics are better than before. Therefore, gas generation is small, and both high capacity and battery characteristics can be achieved.

  According to the present invention, it is possible to achieve both high capacity, suppression of deterioration of charge / discharge cycle characteristics, and suppression of gas generation.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless stated to the effect, the present invention is not limited to the embodiment. The description will be given in the following order.
1. First embodiment (positive electrode active material)
2. Second embodiment (an example of a non-aqueous electrolyte secondary battery)
3. Third embodiment (another example of a nonaqueous electrolyte secondary battery)
4). Embodiment 5 FIG. Other embodiment (modification)

1. First Embodiment First, a positive electrode active material according to a first embodiment of the present invention will be described.
[Composition of cathode active material]
The positive electrode active material according to the first embodiment of the present invention includes a lithium transition metal composite oxide particle containing lithium as a mother particle and a transition metal as constituent elements, and at least a part of the surface of the lithium transition metal composite particle And a coating layer containing manganese (Mn), and Mn (manganese) has the following characteristics (1) to (3).

(1) In the absolute value of the radial structure function around Mn obtained by Fourier transform of the wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the wavenumber of photoelectrons at the MnK absorption edge, The ratio of the peak intensity near 5.2 to the peak intensity is 0.3 or more.
(2) In the absolute value of the radial structure function around Mn obtained by Fourier transform of the wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the wavenumber of the photoelectron at the MnK absorption edge, The first adjacent peak intensity is lower than the second adjacent peak intensity near 2.4 mm.
(3) A straight line approximating the area before the MnK absorption edge was subtracted, and the intensity of the curve approximating the EXAFS vibration center in the area after the absorption edge was normalized to be 1 in the energy area of the measurement range. In the X-ray absorption fine structure (XAFS) spectrum at the MnK absorption edge, the absorption edge energy giving an intensity of 0.5 is 6552 eV or more.

  In the positive electrode active material according to the first embodiment of the present invention having the characteristics of (1) to (3), the Mn-containing layer suppresses the reaction between the positive electrode active material and the electrolytic solution, so that deterioration of cycle characteristics and gas It is presumed to have an effect of suppressing the occurrence. However, this mechanism is only a guess, and even if the effect of the present invention is obtained by a mechanism other than the above mechanism, the technical scope of the present invention has no influence.

[XAFS method]
Here, an X-ray absorption fine structure (XAFS) method capable of clarifying the characteristics (1) to (3) will be described.

  While irradiating the sample with X-rays and changing the energy of the X-rays irradiated before and after the desired absorption edge energy, the intensity of the X-rays before irradiating the sample and the intensity of the X-rays transmitted through the sample are measured. . At this time, when evaluating the overall state of the sample, it is preferable to measure the intensity of the transmitted X-ray, but when evaluating the vicinity of the surface of the sample, in order to increase the surface sensitivity, the absorbing atoms It is desirable to measure the intensity of conversion electrons from In some cases, this is replaced by measuring the intensity of fluorescent X-rays from the absorbing atoms.

  When the transmitted X-ray is measured, the natural logarithm of the intensity of the X-ray irradiated to the sample divided by the intensity of the transmitted X-ray, or the intensity of the converted electron or fluorescent X-ray is measured. X-ray absorption spectrum is obtained by plotting the X-ray intensity divided by the intensity of X-rays or the intensity of fluorescent X-rays against the energy of the irradiated X-rays.

  The analysis of the X-ray absorption spectrum is performed according to a normal procedure as follows. First, from the original X-ray absorption spectrum, the background estimated linearly on the low energy side of the absorption edge is subtracted, and then a quadratic function fitted to the spectrum in the region on the high energy side of the absorption edge. The spectrum is normalized so that the intensity of 1 becomes 1 in all energy regions. At this time, the function form may be appropriately changed depending on the spectrum shape. The position of the absorption edge of the X-ray absorption spectrum reflects the redox state of the absorbing atoms in addition to the local structure of the sample.

Estimate the vibration center of the EXAFS (extended X-ray absorption fine structure) vibration component generated on the higher energy side of the absorption spectrum with respect to the normalized spectrum using an appropriate function such as a cubic spline function, The EXAFS vibration component χ (k) is extracted by subtracting the estimated vibration center from the spectrum and dividing by the spectrum increment (jump amount) at the absorption edge. Here, χ (k) is usually plotted against the wavenumber k of photoelectrons excited from the absorbing atoms, converted from the energy of the irradiated X-rays. A radial structure function representing the scattering intensity according to the distance from the absorbing atom is obtained by Fourier transforming χ (k) in an appropriate wavenumber range. At the time of Fourier transform, the high wave number side is usually emphasized by multiplying χ (k) by a power of wave number k (such as k ³ ).

  In the radial structure function, depending on the distance from the absorbing atom such as the first proximity and the second proximity, a peak of the scattering intensity due to the adjacent coordination atom appears. Since the position of this peak reflects the position of coordination atoms around the absorbing atom, it depends on the local structure (crystal structure, etc.) of the sample. In addition, the intensity of the peak changes depending on the number of coordination atoms around the absorbing atom and the disorder of the position, so it reflects the structural integrity (strain, etc.) in addition to the differences in the local structure itself. To do.

[Lithium transition metal composite oxide]
The lithium-transition metal acid composite oxide of the mother particle is not particularly limited as long as it is a lithium-transition metal composite oxide that can occlude and release lithium. For example, lithium transition metal composite acid oxides having a layered structure such as lithium cobaltate, lithium nickelate, and nickel cobalt manganese composite lithium oxide are preferable from the viewpoint of high capacity.

  Among these, lithium transition metal composite oxides mainly composed of lithium cobaltate are preferable because they have high fillability and high discharge voltage. The lithium transition metal composite oxide mainly composed of lithium cobaltate may be substituted with at least one element selected from Group 2 to Group 15, and has been subjected to fluorination treatment or the like. May be.

[Coating layer]
The coating layer is provided on at least a part of the composite oxide particles and contains at least manganese (Mn). Here, the coating layer is a layer having a composition element or composition ratio different from that of the composite oxide particles and covering at least a part of the surface of the composite oxide particles.

  It is preferable that the coating layer does not contain nickel (Ni). This is because when nickel (Ni) is contained, gas generation increases, and the swelling suppression effect by manganese (Mn) cannot be sufficiently exhibited. In this case, when an X-ray absorption fine structure (XAFS) spectrum is measured, there is no X-ray absorption edge between 8300 and 8350 eV.

The coating layer of the lithium transition metal composite oxide preferably contains magnesium (Mg). This is because the presence of magnesium (Mg) makes it easier for manganese (Mn) to form a layered rock salt structure. At least a part of manganese (Mn) is an element constituting a layered rock salt structure. When a compound containing manganese (Mn) constitutes a layered rock salt structure, occlusion and release of lithium become smooth. For example, manganese (Mn) _{is, Li p Mn q M1 r O} (2-y) X z (M1 is at least one kind of element selected from Groups 2 to 15, except for Mn, X represents an F. p, q, r, y, z are 0 ≦ p ≦ 1.5, 0 ≦ q ≦ 1.0, 0 ≦ r ≦ 1.0, −0.20 ≦ y ≦ 0.20, 0 ≦ z ≦ 0 It is a value in the range of .2).

[Method for producing positive electrode active material]
A method for producing a positive electrode active material according to the first embodiment of the present invention will be described. In the method for producing a positive electrode active material according to the first embodiment, the lithium transition metal composite oxide particles that serve as a base material can be used as starting materials that are usually available as a positive electrode active material. In the method for producing a positive electrode active material according to the first embodiment, a lithium transition metal composite oxide particle as a base material and a compound that covers the base material particle as a coating material are pulverized, mixed, and deposited. can do. As this means, a ball mill, a jet mill, a grinder, a fine grinder, or the like can be used. In this case, it is also effective to add a small amount of liquid which can be exemplified by water. Further, the metal compound can be deposited by mechanochemical treatment or by a vapor phase method such as sputtering or CVD (Chemical Vapor Deposition). Furthermore, a coating layer containing manganese (Mn) can be formed on lithium transition metal composite oxide particles by mixing raw materials in a solvent such as water or ethanol, or by neutralization titration. Further, the surface of the metal composite oxide particles coated with manganese (Mn) may be fired at 300 ° C. to 1000 ° C. Further, after firing, the particle size may be adjusted by light pulverization or classification operation, if necessary. Further, different coating layers may be formed by performing the coating treatment twice or more.

2. Second Embodiment A nonaqueous electrolyte secondary battery according to a second embodiment of the present invention will be described.
[Configuration example of non-aqueous electrolyte secondary battery]
FIG. 1 shows a cross-sectional structure of a non-aqueous electrolyte secondary battery according to a second embodiment of the present invention. This battery is, for example, a non-aqueous electrolyte secondary battery, using lithium (Li) as an electrode reactant, and 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 (Li). Next battery.

  This battery is called a so-called cylindrical type, and is a wound electrode in which a pair of strip-like positive electrode 21 and strip-like negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. It has a body 20. 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 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, 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 gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum (Al) 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 (Ni) 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.

[Positive electrode]
FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. As shown in FIG. 2, the positive electrode 2 includes, for example, a positive electrode current collector 2A having a pair of opposed surfaces, and a positive electrode mixture layer 2B provided on both surfaces of the positive electrode current collector 2A. In addition, you may make it have the area | region where the positive mix layer 2B was provided only in the single side | surface of 2 A of positive electrode collectors. The positive electrode current collector 2A is made of, for example, a metal foil such as an aluminum (Al) foil. The positive electrode mixture layer 2B contains a positive electrode active material, and may contain a conductive agent such as graphite and a binder such as polyvinylidene fluoride as necessary. As the positive electrode active material, the positive electrode active material according to the first embodiment described above is used.

[Negative electrode]
As shown in FIG. 2, 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. Yes. In addition, you may make it have the area | region in which the negative electrode active material layer 22B was provided only in the single side | surface of 22 A of negative electrode collectors. 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 other materials that do not contribute to charging, such as a conductive agent, a binder, or a viscosity modifier, as necessary. Examples of the conductive agent include graphite fiber, metal fiber, and metal powder. Examples of the binder include a fluorine-based polymer compound such as polyvinylidene fluoride, or a synthetic rubber such as styrene butadiene rubber or ethylene propylene diene rubber. Examples of the viscosity modifier include carboxymethylcellulose.

  The negative electrode active material includes one or more negative electrode materials capable of electrochemically inserting and extracting lithium (Li) at a potential of lithium metal of 2.0 V or less. Yes.

Examples of negative electrode materials capable of inserting and extracting lithium (Li) include carbonaceous materials, metal compounds, oxides, sulfides, lithium nitrides such as LiN ₃ , lithium metals, and alloys with lithium. Examples thereof include metals and polymer materials.

  Examples of carbonaceous materials include non-graphitizable carbon, graphitizable carbon, artificial graphite, natural graphite, pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon Blacks, carbon fibers or activated carbon can be used. 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 (Li), 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.

  As a negative electrode material capable of inserting and extracting lithium (Li), a single element, alloy, or compound of a metal element or a metalloid element capable of forming an alloy with lithium (Li) can be given. 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.

Examples of the negative electrode material capable of inserting and extracting lithium further include oxides, sulfides, and other metal compounds such as lithium nitrides such as LiN ₃ . Examples of the oxide include MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , NiS, and MoS. In addition, examples of oxides that have a relatively low potential and can occlude and release lithium include iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, and tin oxide. Examples of the sulfide include NiS and MoS.

[Separator]
The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes.

  The separator 23 is made of, for example, a synthetic resin porous film made of polytetrafluoroethylene (PTFE), polypropylene (PP), polyethylene (PE), or the like, or a ceramic porous film. Two or more kinds of porous films may have a laminated structure. Among them, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve battery safety by a shutdown effect. In particular, polyethylene can obtain a shutdown effect within a range of 100 ° C. or more and 160 ° C. or less, and is a resin having electrochemical stability, and is copolymerized with polyethylene or polypropylene, You may hit with a blend. Alternatively, a separator in which a porous resin layer such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE) is formed on a polyolefin porous film may be used.

  The separator 23 is impregnated with an electrolytic solution as a liquid electrolyte.

[Electrolytes]
As the electrolyte, for example, a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent can be used. These can utilize what has been used for the conventional nonaqueous electrolyte secondary battery.

  Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3- Examples include dioxolane, 4 methyl 1,3 dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate ester, butyrate ester, propionate ester and the like. These may be used alone or in admixture of two or more. Among them, for example, it is preferable that at least one kind is selected from cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as diethyl carbonate and dimethyl carbonate. This is because the cycle characteristics can be improved. In this case, it is particularly preferable to contain a mixture of a high viscosity (high dielectric constant solvent) such as propylene carbonate and ethylene carbonate and a low viscosity solvent such as diethyl carbonate and dimethyl carbonate. This is because the dissociation property of the electrolyte salt and the ion mobility are improved, so that a higher effect can be obtained.

  As an electrolyte salt, for example, a lithium salt can be cited as one that generates ions by dissolving or dispersing in the above non-aqueous solvent.

Examples of the lithium salt include lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiCl, LiBr and the like can be mentioned, and these can be used alone or in combination of two or more. Among these, lithium hexafluorophosphate (LiPF ₆ ) is preferable because high ion conductivity can be obtained and cycle characteristics can be improved.

  In addition, the content of such an electrolyte salt is preferably within a range of 0.1 mol to 3.0 mol, for example, with respect to 1 liter (l) of the solvent, and more preferably within a range of 0.5 mol to 2.0 mol. preferable. This is because higher ion conductivity can be obtained within this range.

  In the non-aqueous electrolyte secondary battery, when charged, for example, lithium ions are released from the positive electrode active material layer 21B and inserted in the negative electrode active material layer 22B through the electrolytic solution. Further, when discharging is performed, for example, lithium ions are released from the negative electrode active material layer 22B and inserted into the positive electrode active material layer 21B through the electrolytic solution.

  In this non-aqueous electrolyte secondary battery, by adjusting the amount between the positive electrode active material and the negative electrode active material capable of occluding and releasing lithium, the negative electrode active material described above is more than the charge capacity of the positive electrode active material. Therefore, the lithium metal does not deposit on the negative electrode 22 even during full charge.

  The upper limit charging voltage of the nonaqueous electrolyte secondary battery may be, for example, 4.20V, but is preferably designed to be higher than 4.20V and within a range of 4.25V to 4.80V, More preferably, it is designed to be in the range of 4.35V to 4.65V. Moreover, it is preferable that a minimum discharge voltage shall be 2.00V or more and 3.30V or less. For example, when the battery voltage is set to 4.25 V or higher, the amount of lithium released per unit mass is increased even with the same positive electrode active material as compared with a 4.2 V battery. The amount of the active material and the negative electrode active material is adjusted, and a high energy density is obtained.

  In the nonaqueous electrolyte secondary battery according to the first embodiment of the present invention, by using the positive electrode active material according to the first embodiment as the positive electrode active material, high capacity, suppression of battery characteristic deterioration, and suppression of gas generation are achieved. Can be achieved.

[Method for producing non-aqueous electrolyte secondary battery]
Next explained is a method for manufacturing a nonaqueous electrolyte secondary battery according to the first embodiment of the invention.

  The positive electrode 21 is, for example, a method in which a known binder or conductive agent is added to the positive electrode active material, and a solvent is added to apply on the positive electrode current collector 21A. A known binder or conductive agent is added to the positive electrode active material. And the like, and a method of coating the positive electrode current collector 21A by heating, a positive electrode active material alone or mixed with a conductive agent or a binder, and performing a treatment such as molding to form a molded body on the positive electrode current collector 21A. Although it can produce by the method of producing an electrode, it is not limited to them. More specifically, for example, a positive electrode active material 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. A slurry is prepared, this positive electrode mixture slurry is applied to the positive electrode current collector 21A, and the solvent is dried. Then, 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 obtained. Alternatively, regardless of the presence or absence of the binder, the positive electrode 21 having strength can be produced by pressure molding while applying heat to the positive electrode active material.

  The negative electrode 22 is, for example, a method in which a known binder or conductive agent is added to the negative electrode active material, a solvent is added, and the negative electrode current material 22A is applied onto the negative electrode current collector 22A. Etc., and a method of coating the negative electrode current collector 22A by heating, a negative electrode active material alone or mixed with a conductive agent or a binder, and performing a treatment such as molding to form a molded body on the negative electrode current collector 22A. Although it can produce by the method of producing an electrode, it is not limited to them. More specifically, 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 form a negative electrode mixture. A slurry is prepared, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, and the solvent is dried. Then, 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 obtained. Alternatively, regardless of the presence or absence of the binder, it is also possible to produce a strong negative electrode by pressure molding while applying heat to the negative electrode active material.

  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 accommodated 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 fixed to the opening end of the battery can 11 by caulking through the gasket 17. Thus, the secondary battery shown in FIG. 2 is manufactured.

3. Third Embodiment Next, a nonaqueous electrolyte secondary battery according to a third embodiment of the present invention will be described.
[Configuration of non-aqueous electrolyte secondary battery]
FIG. 3 shows the configuration of the nonaqueous electrolyte secondary battery according to the third embodiment. This non-aqueous electrolyte secondary battery is a so-called laminate film type, in which a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is accommodated inside a film-like exterior member 40. .

  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 made of, for example, a metal material such as aluminum, copper, nickel, or stainless steel, and each have a thin plate shape or a mesh shape.

[Exterior material]
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.

[Wound electrode body]
FIG. 4 shows a cross-sectional structure taken along line II 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 same as the positive electrode current collector 21A and the positive electrode active material layer 21B in the second embodiment described above. This is the same as the anode current collector 22A, the anode active material layer 22B, and the separator 23.

  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. A gel electrolyte 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 and the electrolyte salt) is the same as that of the secondary battery according to the second embodiment.

  As the polymer material, various polymers that can be gelled by absorbing the above-described electrolyte can be used. Specifically, for example, a fluorine-based polymer such as poly (vinylidene fluoride) or poly (vinylidene fluoride-co-hexafluoropropylene), an ether-based polymer such as poly (ethylene oxide) or a crosslinked product thereof, or Poly (acrylonitrile) can be used. In particular, in view of redox stability, it is desirable to use a fluorine-based polymer such as a polymer of vinylidene fluoride.

  The operation and effects of the nonaqueous electrolyte secondary battery according to the third embodiment of the present invention are the same as those of the above-described nonaqueous electrolyte secondary battery according to the second embodiment of the present invention. In addition, according to the third embodiment of the present invention, since gas generation inside the battery is suppressed, the expansion and deformation of the nonaqueous electrolyte secondary battery can be suppressed.

[Method for producing non-aqueous electrolyte secondary battery]
The nonaqueous electrolyte secondary battery according to the third embodiment of the present invention can be manufactured, for example, by the following three types of manufacturing methods.

  In the first production method, first, a precursor solution containing an electrolytic solution, 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. . Thereafter, the positive electrode lead 31 is attached to the end portion of the positive electrode current collector 33A by welding, and the negative electrode lead 32 is attached to the end portion of the negative electrode current collector 34A by welding. 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 FIGS. 3 and 4 is completed.

  In the second manufacturing method, 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 connected to the separator 35. Are laminated and wound, and a protective tape 37 is adhered to the outermost peripheral portion 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. Subsequently, an electrolyte composition including an electrolytic solution, 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 interior of the exterior member 40 Inject.

  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 described above, the nonaqueous electrolyte secondary battery shown in FIGS. 3 and 4 is obtained.

  In the third manufacturing method, a wound body is formed to form the inside of the bag-shaped exterior member 40 in the same manner as in the first manufacturing method described above, except that the separator 35 coated with the polymer compound on both sides is used. Store in. Examples of the polymer compound applied to the separator 35 include a polymer containing vinylidene fluoride as a component, that is, a homopolymer, a copolymer, or a multi-component copolymer. Specifically, polyvinylidene fluoride, binary copolymers containing vinylidene fluoride and hexafluoropropylene as components, and ternary copolymers containing vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Etc. In addition, the high molecular compound may contain the other 1 type, or 2 or more types of high molecular compound with the polymer which uses the above-mentioned vinylidene fluoride as a component.

  Then, after preparing electrolyte solution etc. and inject | pouring into the exterior member 40, the opening part of the exterior member 40 is sealed by heat sealing | fusion etc. As shown in FIG. Finally, the exterior member 40 is heated while applying a load, and the separator 35 is brought into close contact with the positive electrode 33 and the negative electrode 34 through the polymer compound. As a result, the electrolytic solution is impregnated into the polymer compound, and the polymer compound is gelled to form the electrolyte layer 36. Thus, the nonaqueous electrolyte secondary battery is completed.

  In the third manufacturing method, the swollenness characteristics are improved as compared with the second manufacturing method. Further, in the third manufacturing method, compared to the second manufacturing method, the monomer or solvent that is a raw material of the polymer compound hardly remains in the electrolyte layer 36, and the polymer compound forming process is excellent. Therefore, sufficient adhesion can be obtained between the positive electrode 33, the negative electrode 34, and the separator 35 and the electrolyte layer 36.

  The nonaqueous electrolyte secondary batteries according to the second to third embodiments of the present invention have characteristics of light weight, high capacity, and high energy density, such as video cameras, notebook personal computers, word processors, radio cassette recorders, mobile phones. It can be widely used for portable small electronic devices such as telephones.

4). EXAMPLES Hereinafter, the present invention will be described using examples and comparative examples, but the present invention is not limited to the examples.

<Example 1>
MgCO ₃ , MnCO ₃ and (NH ₄ ) ₂ HPO ₄ have a ratio of MgCO ₃ : MnCO ₃ : (NH ₄ ) ₂ HPO ₄ = 2: 2: 1 (Mg: Mn: P molar ratio). Weighing and mixing gave powder as a coating material. This powder was weighed so that the value of Mn / (Co + Mn) was 1.5 mol% with respect to lithium cobalt oxide having an average particle diameter of 13 μm (measured by laser scattering method), treated with a mechanochemical apparatus for 1 hour, and then lithium cobalt oxide. MgCO ₃ , MnCO ₃ and (NH ₄ ) H ₂ PO ₄ were deposited on the surface. The calcined precursor was heated at a rate of 3 ° C. per minute, held at 900 ° C. for 3 hours and then gradually cooled to obtain the positive electrode active material of Example 1.

Using this positive electrode active material, measurements described below were performed.
(A) XAFS analysis [preparation of positive electrode]
A positive electrode mixture was prepared by mixing 98 wt% of the positive electrode active material, 0.8 wt% of amorphous carbon powder (Ketjen black), and 1.2 wt% of polyvinylidene fluoride (PVdF). After this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone (NMP) to produce a positive electrode mixture slurry, this positive electrode mixture slurry was uniformly applied to both surfaces of a positive electrode current collector made of a strip-shaped aluminum foil. . The obtained coated product was dried with hot air, and then compression molded with a roll press to form a positive electrode mixture layer.

[Production of negative electrode]
A negative electrode mixture was prepared by mixing 90 wt% of graphite powder and 10 wt% of polyvinylidene fluoride (PVdF). After this negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry, the negative electrode mixture slurry was uniformly applied to both sides of a negative electrode current collector made of a strip-shaped copper foil. A negative electrode mixture layer was formed by hot press molding.

[Preparation of separator]
The separator was produced as follows. First, N-methyl-2pyrrolidone was added to a polyvinylidene fluoride (PVdF) resin (average molecular weight 150,000) at a mass ratio of 10:90 and sufficiently dissolved, and N-methyl-2pyrrolidone of polyvinylidene fluoride (PVdF) was 10 wt%. A solution was made. Next, the prepared slurry was applied on a microporous membrane which is a mixture of polyethylene (PE) and polypropylene having a thickness of 7 μm as a base material layer using a tabletop coater, and then phase-separated in a water bath. It was dried with hot air to obtain a microporous membrane having a polyvinylidene fluoride microporous layer having a thickness of 4 μm.

[Preparation of electrolyte]
A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a mixed solvent having a volume mixing ratio of ethylene carbonate and diethyl carbonate of 1: 1 so as to have a concentration of 1 mol / dm ³ .

  A coin cell was manufactured using the positive electrode, the negative electrode, the separator, and the electrolytic solution. The coin cell is charged with a constant current and a constant voltage up to a predetermined charging voltage of 4.4 V with a charging current of 0.2 C, and then is discharged with a discharge current of 0.2 C and a final voltage of 3.0 V. The battery was charged with constant current and constant voltage up to 4.4V at 2C.

  Thereafter, the coin cell was disassembled and the positive electrode was taken out. This positive electrode was washed with dimethyl carbonate to wash away salts and solvents adhering to the surface. The X-ray absorption spectrum at the MnK absorption edge was measured by the method of measuring the conversion electron intensity among the XAFS measurement methods described in the embodiment for the obtained positive electrode.

  In the measurement, the dismantling operation was performed in an inert gas atmosphere such as argon (Ar) or the like in a dry room having a dew point of −50 ° C. or lower in order to suppress the sample from being deteriorated by moisture. In addition, introduction of the sample into the measuring device should be performed in an inert gas atmosphere such as argon (Ar) so as not to be exposed to the atmosphere, or the surface alteration should be suppressed as much as possible even if it is exposed to the atmosphere. I tried to do it in a very short time (1, 2 minutes).

  As described in the embodiment, the obtained X-ray absorption spectrum is obtained by subtracting a straight line approximating the region before the MnK absorption edge, and the intensity of the curve approximating the EXAFS vibration center of the region after the MnK absorption edge is It was standardized to be 1 in the energy range of the measurement range.

Furthermore, the vibration center of the EXAFS (extended X-ray absorption fine structure) vibration component generated at the higher energy side than the absorption edge is estimated by a cubic spline function for the normalized spectrum, and the estimation is performed. The EXAFS vibration component χ (k) was extracted by subtracting the generated vibration center from the spectrum and dividing by the spectrum increment (jump amount) at the absorption edge. Then, k ³ χ (k) obtained by multiplying the EXAFS vibration component χ (k) by the cube of the photoelectron wave number (k) is Fourier-transformed in the photoelectron wave number range of ³ to 12Å ⁻¹ to obtain a radial radius around Mn. The structure function is obtained.

  In the absolute value of the radial structure function around Mn, the ratio of the peak intensity near 5.2 に 対 す る to the first adjacent peak intensity near 1.5 お よ び and the vicinity of 1.5 に 対 す る with respect to the second adjacent peak intensity near 2.4 、 The ratio of peak intensities was determined. Further, in the X-ray absorption fine structure (XAFS) spectrum at the MnK absorption edge, the absorption edge energy giving an intensity of 0.5 was determined.

(B) Measurement of initial capacity The positive electrode and the negative electrode prepared in (a) were laminated in the order of the negative electrode, the separator, the positive electrode, and the separator, and wound many times to prepare a power generation element. After this power generation element and the above electrolyte solution are put in a 180 μm thick moisture-proof aluminum laminate film, vacuum sealing and thermocompression bonding are performed to obtain a flat laminate battery having dimensions of approximately 34 mm × 50 mm × 3.8 mm. Produced.

  About the produced laminated battery, after performing constant current and constant voltage charging under conditions of an environmental temperature of 45 ° C., a charging voltage of 4.40 V, a charging current of 800 mA, and a charging time of 5 hours, discharging was performed at a discharging current of 400 mA and a final voltage of 3.0 V. The initial capacity was measured.

(C) Charging / discharging cycle characteristics Charging / discharging was repeated under the same conditions as when the initial capacity was determined, and the discharge capacity at the 200th cycle was measured to determine the capacity retention ratio relative to the initial capacity.

(D) Measurement of rate of increase in thickness The laminate battery whose initial capacity was determined was charged at a constant current and a constant voltage under the conditions of a charging voltage of 4.40 V, a charging current of 800 mA, and a charging time of 2.5 hours, After time storage, the increase rate of the cell thickness before and after storage was determined by {(cell thickness after storage−cell thickness before storage) / cell thickness before storage} × 100.

<Example 2>
A positive electrode active material of Example 2 was obtained in the same manner as Example 1 except that LiCo _0.98 Al _0.01 Mg _0.01 O ₂ was used instead of lithium cobalt oxide (LiCoO ₂ ). Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Example 3>
A positive electrode active material of Example 3 was obtained in the same manner as Example 1 except that LiCo _0.98 Zr _0.02 O ₂ was used instead of lithium cobaltate (LiCoO ₂ ). Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Example 4>
In the same manner as in Example 2, the positive electrode active material of Example 4 was obtained. Using this positive electrode active material, the above measurements (a) to (d) were performed. In the measurements of (a) to (d), the charging voltage in each measurement was 4.20V.

<Example 5>
In the same manner as in Example 2, the positive electrode active material of Example 5 was obtained. Using this positive electrode active material, the above measurements (a) to (d) were performed. In the measurement of (a) to (d), the charging voltage in each measurement was 4.35V.

<Example 6>
In the same manner as in Example 2, the positive electrode active material of Example 6 was obtained. Using this positive electrode active material, the above measurements (a) to (d) were performed. In the measurement of (a) to (d), the charging voltage in each measurement was 4.45V.

<Example 7>
MgCO ₃ , MnCO ₃ and (NH ₄ ) ₂ HPO ₄ have a ratio of MgCO ₃ : MnCO ₃ : (NH ₄ ) ₂ HPO ₄ = 2: 2: 1 (Mg: Mn: P molar ratio). And weighed and mixed to obtain a powder as a coating material. This powder was weighed so that the value of Mn / (Co + Mn) was 0.5 mol% with respect to LiCo _0.98 Al _0.01 Mg _0.01 O ₂ . Others were the same as in Example 2, and the positive electrode active material of Example 7 was obtained. Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Example 8>
Mg (NO ₃ ) ₂ and Mn (NO ₃ ) ₂ aqueous solution is added dropwise to an aqueous solution in which lithium cobaltate and (NH ₄ ) ₂ HPO ₄ are mixed, and then filtered and dried at 120 ° C. A compound of Mn and P was deposited on the surface. The ratio of Mg, Mn and P is Mg: Mn: P = 3: 3: 4 (mol ratio), and the value of Mn / (Co + Mn) is 1.0 mol% with respect to LiCo _0.98 Al _0.01 Mg _0.01 O ₂ . It was. Further, ammonia water was appropriately added for pH adjustment. The calcined precursor was heated at a rate of 3 ° C. per minute, held at 900 ° C. for 3 hours, and then gradually cooled to obtain a positive electrode active material of Example 8. Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Example 9>
Mg (NO ₃ ) ₂ and Mn (NO ₃ ) ₂ aqueous solution was added dropwise to an aqueous solution in which lithium cobalt oxide and NH ₄ F were mixed with stirring, followed by filtration and drying at 120 ° C. Mn and F compounds were deposited. The ratio of Mg, Mn and F is Mg: Mn: F = 1: 1: 4 (mol ratio), and the value of Mn / (Co + Mn) is 1.0 mol% with respect to LiCo _0.98 Al _0.01 Mg _0.01 O ₂ . did. The calcined precursor was heated at a rate of 3 ° C. per minute, held at 900 ° C. for 3 hours and then gradually cooled to obtain a positive electrode active material of Example 9. Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Comparative Example 1>
The lithium cobalt oxide that was not subjected to the coating treatment of Example 1 was used as the positive electrode active material of Comparative Example 1. Using this positive electrode active material, the above measurements (a) to (d) were performed. In the measurements of (a) to (d), the charging voltage in each measurement was 4.20V.

<Comparative example 2>
The lithium cobalt oxide that was not subjected to the coating treatment of Example 1 was used as the positive electrode active material of Comparative Example 2. Using this positive electrode active material, the above measurements (a) to (d) were performed. In the measurement of (a) to (d), the charging voltage in each measurement was 4.35V.

<Comparative Example 3>
The lithium cobalt oxide that was not subjected to the coating treatment of Example 1 was used as the positive electrode active material of Comparative Example 3. Using this positive electrode active material, the above measurements (a) to (d) were performed. In the measurements of (a) to (d), the charging voltage in each measurement was 4.40V.

<Comparative example 4>
The lithium cobalt oxide that was not subjected to the coating treatment of Example 1 was used as the positive electrode active material of Comparative Example 4. Using this positive electrode active material, the above measurements (a) to (d) were performed. In the measurement of (a) to (d), the charging voltage in each measurement was 4.45V.

<Comparative Example 5>
The same treatment as in Example 1 was performed except that the coating material was LiMn ₂ O ₄ and the baking treatment was not performed, and the positive electrode active material of Comparative Example 5 was obtained. Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Comparative Example 6>
Li ₂ CO ₃ and MnCO ₃ were weighed and mixed so as to have a ratio of Li ₂ CO ₃ : MnCO ₃ = 1: 1 (Li: Mn mol ratio) to obtain a powder as a coating material. Otherwise, the same treatment as in Example 1 was performed to obtain a positive electrode active material of Comparative Example 6. Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Comparative Example 7>
Li ₂ CO ₃ , MnCO ₃ , (NH ₄ ) ₂ HPO ₄ , Li ₂ CO ₃ : MnCO ₃ : (NH ₄ ) ₂ HPO ₄ = 9: 3: 2 (Li: Mn: P molar ratio) Weighed and mixed so as to obtain powder as a coating material. Otherwise, the same treatment as in Example 2 was performed to obtain a positive electrode active material of Comparative Example 7. Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Comparative Example 8>
A positive electrode active material of Comparative Example 8 was obtained in the same manner as in Example 2 except that the amount of coating material added was Mn / (Co + Mn) = 5.0 mol%. Using this positive electrode active material, the above measurements (a) to (d) were performed.

<Comparative Example 9>
Li ₂ CO ₃ , Ni (OH) ₂ and MnCO ₃ are weighed so that Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = 4: 3: 1 (Li: Ni: Mn molar ratio) And mixed to obtain a powder as a coating material. Otherwise, the same treatment as in Example 2 was performed to obtain a positive electrode active material of Comparative Example 9. Using this positive electrode active material, the above measurements (a) to (d) were performed.

  The measurement results are shown in Table 1. Moreover, the XANES (X-ray Absorption Near Edge Structure) spectrum of the MnK absorption edge calculated | required in Example 2 is shown in FIG. The radial structure function around Mn obtained in Example 2 is shown in FIG. The XANES spectrum of the MnK absorption edge obtained in Comparative Example 7 is shown in FIG. The radial structure function around Mn obtained in Comparative Example 8 is shown in FIG. 6 and 8, the horizontal axis represents the distance r from the absorbing atom Mn, and the vertical axis represents the absolute value intensity | F (r) | of the radial structure function around Mn.

  As shown in Table 1, in Examples 1 to 9, the positive electrode active material having the characteristics (1) to (3) described in the first embodiment is used, and charge / discharge cycle characteristics, swelling The characteristics were good. In Comparative Example 5 to Comparative Example 9, in the radial structure function around Mn, a positive electrode active material in which the ratio of the peak intensity near 5.2% to the peak intensity near 1.5% is smaller than 0.3, Good characteristics could not be obtained.

5). Other Embodiments The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, the shape of the battery is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, a button shape, and a laminate seal shape can be used. Further, for example, the electrode body may be manufactured by a lamination method in which a positive electrode, a negative electrode, and a separator are sequentially laminated.

  Furthermore, for example, the method for manufacturing the positive electrode and the negative electrode is not limited to the above-described example. For example, a method in which a known binder or the like is added to the material and heated to apply, the material alone or a conductive material, and further mixed with the binder and subjected to a treatment such as molding, and then on the current collector However, the present invention is not limited to this method. More specifically, it can be prepared by forming a slurry mixed with a binder, an organic solvent, and the like, and then applying and drying on a current collector. Alternatively, regardless of the presence or absence of the binder, it is possible to produce an electrode having a high degree by performing pressure molding while applying heat to the active material.

  Furthermore, for example, as a battery manufacturing method, a manufacturing method of winding around a core via a separator between a positive electrode and a negative electrode, a stacking method of sequentially stacking an electrode and a separator, or the like is taken. This is also effective when a winding method is adopted when a rectangular battery is produced.

  In the second embodiment, a non-aqueous electrolyte secondary battery having an electrolyte as an electrolyte has been described. In the third embodiment, a non-aqueous electrolyte secondary battery having a gel electrolyte as an electrolyte has been described. It is not limited to. For example, a solid electrolyte containing an electrolyte salt can be used as the electrolyte. As the solid electrolyte, any inorganic solid electrolyte or polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. The polymer compound is an ether polymer such as poly (ethylene oxide) or a crosslinked product thereof, poly (methacrylate) ester, or acrylate. Etc. can be used singly or in a molecule or in a mixture.

It is a schematic sectional drawing of the nonaqueous electrolyte secondary battery by 2nd Embodiment of this invention. FIG. 2 is an enlarged sectional view of a part of a wound electrode body shown in FIG. 1. It is the schematic which shows the structure of the nonaqueous electrolyte secondary battery by embodiment of 3b of this invention. FIG. 4 is an enlarged cross-sectional view of a part of the battery element shown in FIG. 3. 6 is a diagram illustrating an XANES spectrum of an MnK absorption edge obtained in Example 2. FIG. 6 is a diagram illustrating a radial structure function around Mn obtained in Example 2. FIG. 10 is a diagram illustrating an XANES spectrum of an MnK absorption edge obtained in Comparative Example 7. FIG. 10 is a diagram illustrating a radial structure function around Mn obtained in Comparative Example 8. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Battery can 12 ... Insulating plate 14 ... Battery cover 15A ... Disk board 15 ... Safety valve mechanism 16 ... Heat sensitive resistance element 17 ... Gasket 20 ... Winding electrode Body 21 ... Positive electrode 21A ... Positive electrode current collector 21B ... Positive electrode active material layer 22 ... Negative electrode 22A ... Negative electrode current collector 22B ... Negative electrode active material layer 23 ... Separator 24 ..Center pin 25... Positive electrode lead 26... Negative electrode lead 30... Winding electrode body 31... Positive electrode lead 32. ... 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 ... Exterior Member 41 ... adhesion film

Claims (10)

Lithium transition metal composite oxide particles containing lithium and a transition metal as constituent elements;
A coating layer provided on at least a part of the surface of the lithium transition metal composite oxide particles,
At least the coating layer contains manganese (Mn),
In the absolute value of the radial structure function around Mn obtained by Fourier transform of the wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the wavenumber of photoelectrons at the MnK absorption edge, the first proximity near 1.5Å A positive electrode active material in which the ratio of the peak intensity near 5.2 to the peak intensity is 0.3 or more. The lithium transition metal composite oxide has a layered rock salt structure,
2. The positive electrode active material according to claim 1, wherein the coating layer has no X-ray absorption edge between 8300 eV and 8350 eV when an X-ray absorption fine structure (XAFS) spectrum is measured. 2. The positive electrode active material according to claim 1, wherein in the absolute value of the radial structure function around Mn, the first adjacent peak intensity near 1.5% is lower than the second adjacent peak intensity near 2.4%. MnK absorption normalized so that the straight line approximating the region before the MnK absorption edge is subtracted and the intensity of the curve approximating the EXAFS vibration center in the region after the MnK absorption edge is 1 in the energy region of the measurement range 2. The positive electrode active material according to claim 1, wherein, in an X-ray absorption fine structure (XAFS) spectrum at an edge, an absorption edge energy giving an intensity of 0.5 is 6552 eV or more. The positive electrode active material according to claim 1, wherein at least a part of the manganese (Mn) is an element constituting a layered rock salt structure. The positive electrode active material according to claim 1, wherein the coating layer contains magnesium (Mg). The positive electrode active material according to claim 1, wherein the lithium transition metal composite oxide contains cobalt (Co) as a main element. Lithium transition metal composite oxide particles containing lithium and a transition metal as constituent elements;
A coating layer provided on at least a part of the surface of the lithium transition metal composite oxide particles,
At least the coating layer contains manganese (Mn),
In the absolute value of the radial structure function around Mn obtained by Fourier transform of the wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the wavenumber of photoelectrons at the MnK absorption edge, the first proximity near 1.5Å A positive electrode containing a positive electrode active material having a ratio of a peak intensity near 5.2 to a peak intensity of 0.3 or more. A positive electrode having a positive electrode active material, a negative electrode, and an electrolyte;
The positive electrode active material is
Lithium transition metal composite oxide particles containing lithium and a transition metal as constituent elements;
A coating layer provided on at least a part of the surface of the lithium transition metal composite particles,
At least the coating layer contains manganese (Mn),
In the absolute value of the radial structure function around Mn obtained by Fourier transform of the wide-area X-ray absorption fine structure (EXAFS) multiplied by the cube of the wavenumber of photoelectrons at the MnK absorption edge, the first proximity near 1.5Å A non-aqueous electrolyte secondary battery in which the ratio of the peak intensity near 5.2 to the peak intensity is 0.3 or more.   The non-aqueous electrolyte secondary battery according to claim 9, wherein the upper limit charging voltage is 4.25 V or more and 4.80 V or less, and the lower limit discharging voltage is 2.00 V or more and 3.30 V or less.

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