JP6353310B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  In recent years, non-aqueous electrolyte secondary batteries mounted on portable electronic devices such as mobile phones and notebook computers are required to have a higher capacity by charging at a higher voltage and to improve their safety.

For example, (Patent Document 1) includes a general composition formula Li _{1 + t} Co _1-x-yz Al _x Mg _y M _z O ₂ (where M is Zr, Ti, Cr, Fe, Ge, Sn, Ce, It represents at least one element selected from the group consisting of Hf, Y, Yb, Er, Nb, Mo, Mn, Ni, B, and P, -0.05 ≦ t ≦ 0.1, 0.001 ≦ x ≦ 0.015, 0 ≦ y ≦ 1.5x, 0.15y ≦ z) is used for the positive electrode, so that safety at high temperature and high voltage is high and high. It is described that a non-aqueous electrolyte secondary battery having a capacity is provided.

JP 2009-212021 A

  When the lithium-containing cobalt oxide described in (Patent Document 1) is used at a temperature of, for example, about 40 ° C. to 60 ° C., the lithium-containing cobalt oxide has excellent charge / discharge cycle life at high voltage, high safety, and high A capacitive electrochemical element may be constructed. However, a lithium ion secondary battery is constructed using the lithium-containing cobalt oxide described in (Patent Document 1) as a positive electrode active material, and the battery is stored at a high voltage of 4.4 V or higher at a high temperature of 60 ° C. or higher. As a result, it was found that the battery characteristics were significantly deteriorated. This is presumably because Co elution is promoted by storage at a high voltage, structural destruction of the positive electrode active material occurs, or resistance increases due to Co deposition on the negative electrode surface.

  In addition, conventional electrochemical devices using lithium-containing cobalt oxide have been used at a charge end voltage of about 4.2V. At about 4.2 V, capacity is obtained by using about 60% of Li in the lithium-containing cobalt oxide. By raising this to 4.4 V, about 70% of Li is used, and a capacity of about 10% can be increased. However, if the voltage is further increased, the crystal structure is destroyed by the structural phase transition, so that it is difficult to further increase the capacity.

  The present invention has been made in view of the above-mentioned problems, and its object is to provide a non-aqueous electrolyte secondary battery that has a final voltage exceeding 4.3 V, high capacity, and excellent high-temperature storage characteristics. There is to do.

In order to achieve the above object, the non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, and the positive electrode includes a positive electrode active material, a binder, and a conductive material. A positive electrode mixture layer containing an auxiliary agent is laminated on one or both sides of a current collector, the positive electrode active material includes a positive electrode active material A and a positive electrode active material B, and the positive electrode active material A is Li _{1 + x} M1O. ₂ (wherein, −0.15 ≦ x ≦ 0.15, M1 is Ni or two or more elements including Ni, and the Ni content in M1 is 30 mol% or more), and the positive electrode The active material B is Li _α-x Na _x Co _1-yz Ni _y M2 _z O _2-δ (where 1.011 ≦ α ≦ 1.13, 0 ≦ x ≦ 0.03, 0.01 ≦ y ≦ 0.05, 0.0005 ≦ z ≦ 0.03, 0 ≦ δ ≦ 0.002, and M2 (It is one or more elements including at least one selected from the group consisting of Al, Mg, Zr, Mn, V, W, Mo, Cr, Bi, Ti, Si, Fe, P, F, S and Cl) It is characterized by being.

  According to the present invention, in a non-aqueous electrolyte secondary battery in which constant current-constant voltage charging is performed at a final voltage exceeding 4.3 V, the non-aqueous electrolyte secondary battery having high capacity and excellent high-temperature storage characteristics is provided. Can be provided. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is a schematic diagram which shows one Embodiment of the nonaqueous electrolyte secondary battery of this invention, (a) is a top view, (b) is a fragmentary sectional view. It is a perspective view which shows one Embodiment of the nonaqueous electrolyte secondary battery of this invention.

  Hereinafter, the nonaqueous electrolyte secondary battery of the present invention will be described in detail with reference to the drawings.

(Non-aqueous electrolyte secondary battery)
FIG. 1 is a schematic view showing an embodiment of the nonaqueous electrolyte secondary battery of the present invention, in which (a) is a plan view and (b) is a partial sectional view. As shown in FIG. 1 (b), after the positive electrode 1 and the negative electrode 2 are spirally wound through the separator 3, they are pressed so as to be flat, thereby forming a flat wound electrode body 6. It is accommodated together with a non-aqueous electrolyte in a rectangular (rectangular cylindrical) outer can 4. However, in FIG. 1B, in order to avoid complication, a metal foil, a non-aqueous electrolyte, or the like as a current collector used in manufacturing the positive electrode 1 and the negative electrode 2 is not illustrated.

  The outer can 4 is made of, for example, an aluminum alloy and constitutes an outer body of the battery, and the outer can 4 also serves as a positive electrode terminal. And the insulator 5 which consists of PE sheets is arrange | positioned at the bottom part of the armored can 4, From the flat wound electrode body 6 which consists of the positive electrode 1, the negative electrode 2, and the separator 3, it is in each one end of the positive electrode 1 and the negative electrode 2 The connected positive electrode lead body 7 and negative electrode lead body 8 are drawn out. Further, a stainless steel terminal 11 is attached to an aluminum alloy lid (sealing lid plate) 9 for sealing the opening of the outer can 4 through a PP insulating packing. A stainless steel lead plate 13 is attached via 12.

  And the lid | cover 9 is inserted in the opening part of the armored can 4, and the opening part of the armored can 4 is sealed by welding the junction part of both, and the inside of a battery is sealed. Further, in the nonaqueous electrolyte secondary battery shown in FIG. 1, an electrolyte solution inlet 14 is provided in the lid 9, and a sealing member is inserted into the electrolyte solution inlet 14, for example, laser welding or the like. As a result, the battery is hermetically sealed. Therefore, in the non-aqueous electrolyte secondary battery shown in FIG. 1 and FIG. 2, the electrolyte inlet 14 is actually composed of an electrolyte inlet and a sealing member. An electrolyte inlet 14 is shown. Further, the lid 9 is provided with a cleavage vent 15 as a mechanism for discharging the internal gas to the outside when the battery temperature rises.

  In this non-aqueous electrolyte secondary battery, the outer can 4 and the lid 9 function as a positive electrode terminal by directly welding the positive electrode lead body 7 to the lid 9, and the negative electrode lead body 8 is welded to the lead plate 13. The terminal 11 functions as a negative electrode terminal by conducting the negative electrode lead body 8 and the terminal 11 through the plate 13. However, depending on the material of the outer can 4, the sign may be reversed. is there.

  FIG. 2 is a perspective view showing the appearance of the nonaqueous electrolyte secondary battery shown in FIG. FIG. 2 is a diagram illustrating that the nonaqueous electrolyte secondary battery according to this embodiment is a prismatic battery, schematically showing the battery, and identifying the components of the battery. Only those are shown. Also in FIG. 1B, the cross section of the inner peripheral side portion of the wound electrode body 6 is not shown, and the hatching showing the cross section of the separator 3 is omitted.

  Although details will be described later, the positive electrode 1 of the non-aqueous electrolyte secondary battery can be generally manufactured by the following procedure. First, a positive electrode active material for a non-aqueous electrolyte secondary battery is mixed with a binder, a conductive auxiliary agent, and the like, and dispersed in, for example, N-methyl-2-pyrrolidone (hereinafter referred to as NMP) and kneaded into a slurry. Then, the slurry containing a positive electrode active material is apply | coated to the surface of the positive electrode electrical power collector which consists of metal foil, and a positive mix layer is formed on this electrical power collector.

  The nonaqueous electrolyte secondary battery according to the present invention is characterized in that the positive electrode mixture layer laminated on the surface of the current collector of the positive electrode 1 includes a positive electrode active material A and a positive electrode active material B described later. There are no particular restrictions on the configuration and structure other than the positive electrode 1. By using the positive electrode active material A and the positive electrode active material B that satisfy the general composition formula described later for the positive electrode 1, a non-aqueous electrolyte secondary battery having a large charge / discharge capacity and excellent high-temperature storage characteristics can be obtained. Hereinafter, the components contained in the positive electrode mixture layer of the positive electrode 1 of the nonaqueous electrolyte secondary battery of the present invention will be described in detail.

(Positive electrode active material A)
As the positive electrode active material A contained in the positive electrode 1 of the nonaqueous electrolyte secondary battery according to the present invention, a lithium-containing composite oxide represented by the following general composition formula (A) is used.
Li _{1 + x} M1O ₂ (A)
In the general composition formula (A), M1 is Ni or two or more elements including Ni. When M1 is two or more elements including Ni, examples of elements other than Ni included in M1 include, for example, Co, Mn, Ti, Cr, Fe, Cu, Zn, Al, Ge, Sn, Mg , Ag, Ta, Nb, B, P, Zr, Ca, Sr, Ga, Ba and the like. In the case where M1 is two or more elements including Ni, the element other than Ni included in M1 may be only one of the above examples, or may be two or more.

  The surface of the positive electrode active material A made of the lithium-containing composite oxide is an oxide or fluoride containing at least one element selected from the group consisting of Li, Zr, Ti, Al, Ni, Mn, Zn, and P Can be coated. In this case, the effect of suppressing deterioration due to the charge / discharge cycle is improved. However, if the amount of oxide or fluoride to be coated is too large, the resistance increases and the battery capacity decreases. Therefore, the number of atoms of the element contained in the oxide or fluoride is preferably 10 mol% or less of the number of molecules of the positive electrode active material A represented by the general composition formula (A) to be coated.

  In the lithium-containing composite oxide represented by the general composition formula (A), Ni is a component that contributes to an increase in capacity of the lithium-containing composite oxide. Therefore, in the general composition formula (A), when the total number of elements constituting M1 is 100 mol%, the proportion of Ni is 30 mol% or more from the viewpoint of improving the capacity of the lithium-containing composite oxide, and 50 mol % Or more is more preferable. Further, since M1 may be only Ni, the ratio of Ni may be 100 mol% or less. However, when M1 is two or more elements including Ni, the action of elements other than Ni is caused. From the viewpoint of achieving good performance, the Ni content in M1 is preferably 90 mol% or less, and more preferably 70 mol% or less.

  The lithium-containing composite oxide represented by the general composition formula (A) particularly preferably contains Co and Mn together with Ni as M1.

  When the lithium-containing composite oxide contains Co, Co contributes to the capacity of the lithium-containing composite oxide, and also contributes to an improvement in packing density in the positive electrode mixture layer. From the viewpoint of favorably ensuring the above-described action by Co, in the general composition formula (A), when the total number of elements constituting M1 is 100 mol%, the ratio of Co is preferably 5 mol% or more. . If the amount of Co in the lithium-containing composite oxide is too large, there is a risk of increasing costs and reducing safety. Therefore, in the general composition formula (A), when the total number of elements constituting M1 is 100 mol%, the ratio of Co is preferably 35 mol% or less.

  When the lithium-containing composite oxide contains Mn, Mn is present in the crystal lattice of the lithium-containing composite oxide, thereby improving the thermal stability of the lithium-containing composite oxide. Therefore, by using such a lithium-containing composite oxide as the positive electrode active material, it is possible to configure a battery with higher safety. From the viewpoint of ensuring the above-described effect of Mn satisfactorily, in the general composition formula (A), when the total number of elements constituting M1 is 100 mol%, the ratio of Mn is preferably 5 mol% or more. Moreover, it is preferable to set it as 35 mol% or less.

  Further, when the lithium-containing composite oxide represented by the general composition formula (A) contains Co and Mn as M1, Mn associated with insertion and release of Li during battery charging / discharging by the action of Co. The average valence of Mn can be stabilized at a value close to tetravalent, and the reversibility of charge / discharge can be further improved. Therefore, by using such a lithium-containing composite oxide, it becomes possible to configure a battery with more excellent charge / discharge cycle characteristics. Therefore, the lithium-containing composite oxide represented by the general composition formula (A) more preferably contains Co and Mn as M1.

  As described above, the lithium-containing composite oxide represented by the general composition formula (A) includes M1, Ti, Cr, Fe, Cu, Zn, Al, Ge, Sn, Mg, Ag, Ta, and Nb. , B, P, Zr, Ca, Sr, Ga and Ba may be contained. However, in the general composition formula (A), when the total number of elements constituting M1 is 100 mol%, the total ratio of these elements (elements other than Ni, Co, Mn, Li and O) is 15 mol%. Or less, more preferably 3 mol% or less.

  For example, in the lithium-containing composite oxide, if Al is present in the crystal lattice, the crystal structure of the lithium-containing composite oxide can be stabilized, and the thermal stability thereof can be improved. High non-aqueous electrolyte secondary battery can be configured. In addition, since Al is present at the grain boundaries and surfaces of the lithium-containing composite oxide particles, the stability over time and side reactions with the electrolytic solution can be suppressed, and a longer-life nonaqueous electrolyte secondary battery can be obtained. It can be configured.

  However, since Al cannot participate in the charge / discharge capacity, increasing the content in the lithium-containing composite oxide may cause a decrease in capacity. Therefore, in the general composition formula (A), when the total number of elements constituting M1 is 100 mol%, the Al ratio is preferably 10 mol% or less. In addition, in order to ensure the above-mentioned effect by containing Al more satisfactorily, when the total number of elements constituting M1 is 100 mol% in the general composition formula (A) representing the lithium-containing composite oxide. In addition, the Al ratio is preferably 0.02 mol% or more.

  In the lithium-containing composite oxide, when Mg is present in the crystal lattice, the crystal structure of the lithium-containing composite oxide can be stabilized and the thermal stability thereof can be improved, so that the safety is higher. A non-aqueous electrolyte secondary battery can be configured. In addition, when the phase transition of the lithium-containing composite oxide occurs due to Li insertion and desorption during charging and discharging of the nonaqueous electrolyte secondary battery, Mg is rearranged to relax the irreversible reaction, and the lithium-containing Since the reversibility of the crystal structure of the composite oxide can be increased, a non-aqueous electrolyte secondary battery having a longer charge / discharge cycle life can be configured. In particular, in the general composition formula (A) representing the lithium-containing composite oxide, when x <0 and the lithium-containing composite oxide has a Li-deficient crystal structure, Mg instead of Li becomes a Li site. A lithium-containing composite oxide can be formed in a form that enters, and a stable compound can be obtained.

  However, since Mg has little influence on the charge / discharge capacity, if the content in the lithium-containing composite oxide is increased, the capacity may be reduced. Therefore, in the said general compositional formula (A) showing the said lithium containing complex oxide, when the total number of elements which comprise M1 is 100 mol%, it is preferable that the ratio of Mg shall be 10 mol% or less. In addition, in order to ensure the above-mentioned effect by containing Mg more satisfactorily, when the total number of elements constituting M1 is 100 mol% in the general composition formula (A) representing the lithium-containing composite oxide. Furthermore, it is preferable that the Mg ratio is 0.02 mol% or more.

In the lithium-containing composite oxide, when Ti is contained as M1, in the LiNiO ₂ type crystal structure, Ti is arranged in a defect portion of the crystal such as an oxygen vacancy to stabilize the crystal structure. The reversibility of the reaction of the oxide is increased, and a nonaqueous electrolyte secondary battery having more excellent charge / discharge cycle characteristics can be configured. In order to ensure the above-mentioned effect satisfactorily, in the general composition formula (A) representing the lithium-containing composite oxide, when the total number of elements constituting M1 is 100 mol%, the ratio of Ti is set to 0 It is preferable to set it as 0.01 mol% or more, and it is more preferable to set it as 0.1 mol% or more. However, when the Ti content is increased, Ti does not participate in charging / discharging, so that the capacity is reduced, and it is easy to form a heterogeneous phase such as Li ₂ TiO ₃ , which may cause deterioration of characteristics. Therefore, in the general composition formula (A) representing the lithium-containing composite oxide, when the total number of elements constituting M1 is 100 mol%, the proportion of Ti is preferably 10 mol% or less, preferably 5 mol% More preferably, it is more preferably 2 mol% or less.

  The lithium-containing composite oxide contains at least one element M ′ selected from Ge, Ca, Sr, Ba, B, Zr and Ga as M1 in the general composition formula (A). Is preferable in that each of the following effects can be secured.

  When the lithium-containing composite oxide contains Ge, the crystal structure of the composite oxide after Li is destabilized can improve the reversibility of the charge / discharge reaction, It is possible to configure a non-aqueous electrolyte secondary battery with higher safety and more excellent charge / discharge cycle characteristics. In particular, when Ge is present on the particle surface or grain boundary of the lithium-containing composite oxide, disorder of the crystal structure due to Li desorption / insertion at the interface is suppressed, greatly contributing to improvement of charge / discharge cycle characteristics. be able to.

In addition, when the lithium-containing composite oxide contains an alkaline earth metal such as Ca, Sr, or Ba, the growth of primary particles is promoted, and the crystallinity of the lithium-containing composite oxide is improved. The non-aqueous electrolyte secondary battery has a non-aqueous electrolyte, and the non-aqueous electrolyte secondary battery has improved stability over time when a positive electrode mixture layer-forming composition for forming a positive electrode mixture layer can be prepared. Irreversible reaction with the electrolyte can be suppressed. Further, since these elements are present on the particle surface and grain boundary of the lithium-containing composite oxide, the CO ₂ gas in the battery can be trapped, so that the non-aqueous electrolyte secondary battery has better storage characteristics and longer life. Can be configured. In particular, when the lithium-containing composite oxide contains Mn, the primary particles tend to be difficult to grow. Therefore, the addition of alkaline earth metals such as Ca, Sr, and Ba is more effective.

  Even when B is contained in the lithium-containing composite oxide, the growth of primary particles is promoted and the crystallinity of the lithium-containing composite oxide is improved. Therefore, active sites can be reduced, Irreversible reactions with moisture, the binder used for forming the positive electrode mixture layer, and the nonaqueous electrolyte of the battery can be suppressed. For this reason, the stability over time when the composition for forming a positive electrode mixture layer is improved, gas generation in the battery can be suppressed, and the non-aqueous electrolyte secondary battery having better storage characteristics and longer life Can be configured. In particular, in lithium-containing composite oxides containing Mn, the addition of B is more effective because primary particles tend to be difficult to grow.

  When Zr is contained in the lithium-containing composite oxide, the electrochemical properties of the lithium-containing composite oxide are impaired due to the presence of Zr at the grain boundaries and surfaces of the particles of the lithium-containing composite oxide. Therefore, since the surface activity is suppressed, it is possible to constitute a non-aqueous electrolyte secondary battery having better storage characteristics and a longer life.

  When Ga is contained in the lithium-containing composite oxide, the growth of primary particles is promoted and the crystallinity of the lithium-containing composite oxide is improved, so that the active sites can be reduced, and the positive electrode mixture The stability over time when the layer forming composition is prepared can be improved, and the irreversible reaction with the nonaqueous electrolyte can be suppressed. Further, by dissolving Ga in the crystal structure of the lithium-containing composite oxide, the layer interval of the crystal lattice can be expanded, and the rate of expansion and contraction of the lattice due to insertion and desorption of Li can be reduced. For this reason, the reversibility of a crystal structure can be improved and it becomes possible to comprise the nonaqueous electrolyte secondary battery with a longer charge-discharge cycle life. In particular, when the lithium-containing composite oxide contains Mn, the addition of Ga is more effective because primary particles tend to be difficult to grow.

  In order to easily obtain the effect of the element M ′ selected from Ge, Ca, Sr, Ba, B, Zr and Ga, the ratio is 0 when the total number of elements constituting M1 is 100 mol%. It is preferable that it is 1 mol% or more. Further, when the total number of elements constituting M1 is 100 mol%, the ratio of the element M ′ is preferably 10 mol% or less.

  Elements other than Ni, Co, and Mn in M1 may be uniformly distributed in the lithium-containing composite oxide, or may be segregated on the particle surface of the lithium-containing composite oxide.

The lithium-containing composite oxide having the above composition has a large true density of 4.55 g / cm ^{3 to} 4.95 g / cm ³ , and becomes a material having a high volume energy density. Note that the true density of the lithium-containing composite oxide containing Mn in a certain range varies greatly depending on the composition, but the structure is stabilized and the uniformity can be improved in the narrow composition range as described above. It is considered to be a large value close to the true density of LiCoO ₂ . Moreover, the capacity | capacitance per mass of lithium containing complex oxide can be enlarged, and it can be set as the material excellent in reversibility.

When the lithium-containing composite oxide has a composition close to the stoichiometric ratio, the true density increases. Specifically, in the general composition formula (A), −0.15 ≦ x ≦ 0.15 is preferable, and the true density and reversibility are improved by adjusting the value of x in this way. Can do. x is more preferably −0.05 or more and 0.05 or less. In this case, the true density of the lithium-containing composite oxide can be set to a higher value of 4.6 g / cm ³ or more. .

  The composition analysis of the lithium-containing composite oxide used as the positive electrode active material can be performed as follows using an ICP (Inductive Coupled Plasma) method. First, 0.2 g of a lithium-containing composite oxide to be measured is collected and placed in a 100 mL container. Thereafter, 5 mL of pure water, 2 mL of aqua regia, and 10 mL of pure water are sequentially added and dissolved by heating. After cooling, the mixture is further diluted 25 times and analyzed by ICP (calibration curve method). The composition formula of the lithium-containing composite oxide can be derived from the results obtained by this analysis.

(Method for producing positive electrode active material A)
The lithium-containing composite oxide represented by the general composition formula (A) is included in Li-containing compounds (lithium hydroxide, monohydrate, etc.), Ni-containing compounds (nickel sulfate, etc.), and M1 as necessary. Compound containing elements other than Ni (Co compounds such as cobalt sulfate, Mn containing compounds such as manganese sulfate, Al containing compounds such as aluminum sulfate, Mg containing compounds such as magnesium sulfate, etc.) are mixed and fired, etc. Can be manufactured. Moreover, in order to synthesize the lithium-containing composite oxide with higher purity, a composite compound (hydroxide, oxide, etc.) containing a plurality of elements contained in M1 and a Li-containing compound are mixed and fired. Is preferred.

  The firing conditions can be, for example, 800 ° C. to 1050 ° C. for 1 hour to 24 hours, but once heated to a temperature lower than the firing temperature (for example, 250 ° C. to 850 ° C.), the temperature is maintained. It is preferable to carry out preliminary heating by heating and then raise the temperature to the firing temperature to advance the reaction. The preheating time is not particularly limited, but is usually about 0.5 to 30 hours. The atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (argon, helium, nitrogen, etc.) and oxygen gas, an oxygen gas atmosphere, etc. The oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.

  When coating Zr, Ti, Al, Ni, Mn, and Zn oxide, in a sodium hydroxide or lithium hydroxide aqueous solution adjusted to a pH value of 9 to 11 and a temperature of 60 ° C. to 80 ° C. The positive electrode active material A powder is charged, stirred and dispersed, and then nitrate or sulfate of the covering element is dropped. At this time, a coprecipitate is produced by simultaneously dropping ammonia water so that the pH value does not change. Thereafter, the coprecipitate and the positive electrode active material A powder are continuously stirred for 5 hours or more and adjusted so that the pH value does not fluctuate with sodium hydroxide or lithium hydroxide as needed. In particular, when obtaining a coprecipitate such as Ni and Mn, it is more preferable to replace the dissolved oxygen in the aqueous solution with nitrogen. Next, the powder of the positive electrode active material A to which the coprecipitate is adhered and the aqueous solution are separated by suction filtration, and the separated positive electrode active material A is washed with ultrapure water and dried. The positive electrode active material A for a non-aqueous electrolyte secondary battery in which a coating layer of Zr, Ti, Al, Ni, Mn, and Zn oxide is formed by firing the powder of the positive electrode active material A to which the coprecipitate is adhered. Is obtained.

  As another method for coating Zr, Ti, Al, Ni, Mn, and Zn oxide, an alkoxide of a desired element is dissolved in an alcohol solvent, and stirred and dried at a temperature of 60 ° C. to 80 ° C. There is also a method of adhering to the positive electrode active material A and baking.

In the case of coating Zr, Ti, Al, Ni, Mn, Zn, and P oxide containing Li, after the precursor of the coating element is attached to the surface of the positive electrode active material A by any of the above methods Then, LiOH or Li ₂ CO ₃ may be mixed and fired.

  For example, when a fluoride such as AlF is coated, the positive electrode active material A is placed in an aqueous solution of sodium hydroxide or lithium hydroxide adjusted to a pH value of 9 to 11 and a temperature of 60 ° C. to 80 ° C. After the powder is added and stirred and dispersed, aluminum nitride hydrate is added. Ammonium fluoride aqueous solution is dripped little by little, and after stirring for 5 hours or more, it may be filtered, dried, and fired in an inert gas atmosphere.

  The firing temperature at the time of coating is preferably 400 ° C. or more and 600 ° C. or less, and the firing time is preferably 5 hours or more and 24 hours or less. The firing atmosphere is preferably an oxidizing atmosphere such as air or oxygen when obtaining an oxide, and an inert atmosphere such as nitrogen when obtaining a fluoride.

(Positive electrode active material B)
In addition to the positive electrode active material A, the positive electrode 1 of the nonaqueous electrolyte secondary battery according to the present invention includes a lithium-containing cobalt oxide represented by the following general composition formula (B) as the positive electrode active material B.
Li _α-x Na _x Co _1-yz Ni _y M2 _z O _2-δ (B)
In the general composition formula (B), M2 is a group consisting of Al, Mg, Zr, Mn, V, W, Mo, Cr, Bi, Ti, Si, Fe, P, F, S, and Cl as described above. One or more elements including at least one selected from That is, in addition to at least one selected from the group consisting of Al, Mg, Zr, Mn, V, W, Mo, Cr, Bi, Ti, Si, Fe, P, F, S, and Cl as M2, it is necessary Depending on, any other element can be included. In that case, the Al, Mg, Zr, Mn, V, W, Mo, Cr, Bi, Ti, Si, Fe, and P in M2 are obtained so that the effect of improving the battery characteristics by adding the positive electrode active material B can be obtained. The ratio of at least one element selected from the group consisting of F, S, and Cl is preferably 60 mol% or more, and M2 is Al, Mg, Zr, Mn, V, W, Mo, Cr, Bi, Ti. It is particularly preferable that it is composed of only at least one element selected from the group consisting of Si, Fe, P, F, S and Cl.

  In the present embodiment, the lithium-containing cobalt oxide is in the form of particles, and is composed of secondary particles in which primary particles are aggregated or primary particles, and each particle has a substantially spherical shape. The shape of the particles can be confirmed by observing the particles present in a predetermined region with an SEM (Scanning Electron Microscope). The diameter of the particles is preferably in the range of 5 μm to 50 μm, and more preferably distributed so as to have peaks in the range of 5 μm to 15 μm and in the range of 18 μm to 50 μm. The particle size distribution described above can be measured by a laser diffraction / scattering particle size distribution measuring apparatus.

  With the particle size distribution as described above, the positive electrode mixture layer provided in the positive electrode 1 of the nonaqueous electrolyte secondary battery can be densified, and thus the battery characteristics of the nonaqueous electrolyte secondary battery can be further improved.

  The lithium-containing cobalt oxide needs to have a small interface with the nonaqueous electrolyte from the viewpoint of suppressing Co elution. Therefore, it is advantageous that the BET specific surface area is small. However, if the BET specific surface area of the particles is too small, the density when the particles are stacked decreases, and the non-aqueous electrolyte 2 using the lithium-containing cobalt oxide as the positive electrode is reduced. In the secondary battery, the battery capacity may be reduced, or the discharge characteristics at a high load may be deteriorated.

Therefore, the BET specific surface area of the lithium-containing cobalt oxide is preferably 0.01 m ² / g or more and 1.0 m ² / g or less. The BET specific surface area can be determined by measuring the surface area using the BET formula, which is a theoretical formula for multimolecular layer adsorption. In the present embodiment, the BET specific surface area is obtained by using a specific surface area measuring device by a nitrogen adsorption method.

  The surface of the positive electrode active material B made of the lithium-containing cobalt oxide is an oxide or fluoride containing at least one element selected from the group consisting of Li, Zr, Ti, Al, Ni, Mn, Zn, and P Can be coated. In this case, in addition to improving the deterioration suppressing effect due to the charge / discharge cycle, the Co elution suppressing effect is also improved. However, if the amount of oxide or fluoride to be coated is too large, the resistance increases and the battery capacity decreases. Therefore, the number of atoms of the element contained in the oxide or fluoride to be coated is preferably 10 mol% or less of the number of molecules of the positive electrode active material B represented by the general composition formula (B).

  In the general composition formula (B), α relating to Li is 1.011 ≦ α ≦ 1.13, and 0 ≦ x ≦ 0.03, and particularly preferably 0.001 ≦ x ≦ 0.03. . When α is less than 1.011, a spinel structure is partially formed, so that a sufficient battery capacity cannot be obtained. Also, Co elution is likely to occur. On the other hand, when α exceeds 1.13, oxygen deficiency occurs. For this reason, the potential in the low charge state is lowered, and the output is lowered in the low charge state. In addition, since the oxygen is deficient, the structure is easily collapsed and the cycle life is shortened. Furthermore, since there is a lot of lithium on the surface of the positive electrode active material particles, the positive electrode mixture slurry prepared using such a positive electrode active material becomes a gel, and the resistance of the formed positive electrode mixture layer increases, In some cases, gas is generated.

  In the general composition formula (B), α in the range of 1.011 ≦ α ≦ 1.13 means that Li is in an excess state than the stoichiometric composition. That is, Li is present between part of Co and between lattices. In such a state, a phase transition phenomenon accompanied by structural collapse at a high voltage of 4.5 V or higher is suppressed, and deterioration due to Co elution is prevented. The valence of Co is preferably 2.8 or more and 3.3 or less. The valence of Co is calculated from ICP and iodometric titration, and is obtained by quantifying the atomic ratio of Li and Co and the amount of oxygen.

  In the general composition formula (B), in the range of 0.001 ≦ x ≦ 0.03 related to Na, it is possible to replace Na at the Li site and promote grain growth without reducing the capacity and cycle life. It becomes possible. In such a state, not only the effect of suppressing the number of reaction sites from which Li is desorbed even at a high voltage, but also the phase transition accompanied by structural collapse at a high voltage of 4.5 V or more by mixing Na into the Li site. The phenomenon is suppressed and Co elution is prevented. From the viewpoint of maintaining good cycle characteristics, it is particularly preferable to satisfy 0.001 ≦ x ≦ 0.01.

  In the general composition formula (B), y related to Ni is preferably 0.01 ≦ y ≦ 0.05. The addition of Ni has a great effect of suppressing Co elution. When other elements are substituted to stabilize the structure and suppress Co elution, other characteristics such as capacity are deteriorated. However, with respect to Ni, if it is within the scope of the present invention, the change in the battery capacity due to the increase or decrease of the Ni addition amount is very small, so it is preferable as an additive element that suppresses Co elution while maintaining the battery at a high capacity. When y is less than 0.01, the effect of suppressing Co elution is not sufficient. On the other hand, when y exceeds 0.05, a problem arises in that the potential in a low charge state decreases. From the viewpoint of cycle characteristics and safety, it is more preferable that 0.01 ≦ y ≦ 0.03.

  At least selected from the group consisting of Al, Mg, Zr, Mn, V, W, Mo, Cr, Bi, Ti, Si, Fe, P, F, S and Cl as M2 in the general composition formula (B) Z relating to one or more elements including one kind is preferably 0.0005 ≦ z ≦ 0.03, and more preferably 0.001 ≦ z ≦ 0.03. Regarding Al, Mg, Zr, Mn, V, W, Mo, Cr, Bi, and Ti, various battery characteristics can be improved by replacing part of Co. In addition, Si, Fe, P, F, S, Cl, and the like are inevitably contained as impurities.

  The addition of Al and Mg as M2 in the general composition formula (B) has the effect of stabilizing the structure of the lithium-containing cobalt oxide and improving the heat resistance in addition to the effect of suppressing the elution of Co. When z is less than 0.0005, these effects are not sufficient. On the other hand, when z exceeds 0.03, the crystal lattice of the lithium-containing cobalt oxide is distorted and the capacity of the battery is reduced. It causes a decrease in load characteristics due to a decrease in mobility. In addition, when Mg is excessively contained, there is a problem that Mg is eluted with a charge / discharge cycle and causes a decrease in battery life. Therefore, the amount of Mg added is the Co atom contained in the positive electrode active material B. The number of Mg atoms relative to the number is more preferably 0.02 or less, and preferably 0.01 or more from the viewpoint of improving thermal stability.

  The addition of Zr as M2 in the general composition formula (B) has the effect of improving the high voltage charge / discharge cycle life at 4.3 V or higher in addition to the effect of increasing the potential in the low charge state and improving the output. . The amount of Zr is particularly preferably 0.0005 or more and 0.005 or less, and if it exceeds 0.005, the growth of the positive electrode active material particles may be suppressed and may be reduced. When the layer of the positive electrode active material is formed using such small particles, the density is small, and thus a sufficient battery capacity may not be obtained. Further, since the surface area becomes large, Co elution may easily occur. Mn, V, W, Mo, Cr, Ti, and the like can exhibit the same effect as Zr.

  The addition of Bi as M2 in the general composition formula (B) has the same effect as Na, promotes grain growth, and has the effect of suppressing the Co elution reaction even at a high voltage. The amount of Bi added is particularly preferably 0.0005 or more and 0.005 or less, and if it exceeds 0.005, a heterogeneous phase may appear and electrochemical characteristics may deteriorate.

  In the general composition formula (B), δ relating to oxygen is preferably 0 ≦ δ ≦ 0.002. The collapse of the crystal structure due to the desorption of oxygen is considered to be one cause of Co elution. If δ is 0.002 or less, oxygen deficiency is sufficiently small.

(Method for producing positive electrode active material B)
Next, the manufacturing method of the positive electrode active material B which consists of a lithium containing cobalt oxide represented with the said general composition formula (B) is demonstrated. The positive electrode active material B made of a lithium-containing cobalt oxide represented by the general composition formula (B) is manufactured through a firing step. For example, the positive electrode active material B can be obtained by solidifying and baking a mixed powder obtained by mixing Li compound, Na compound, Co compound, Ni compound, M2 compound and the like in an appropriate ratio into a pellet. In addition, the manufacturing method of the positive electrode active material B is not limited to this, For example, it manufactures by mixing the precursor hydroxide except Li and Na with a Li compound and Na compound by a coprecipitation method etc., and baking. It is also possible.

The Li compound is preferably LiOH, Li ₂ CO ₃ , or LiCl, and the Na compound is preferably NaOH, Na ₂ CO ₃ , or NaCl. Further, as the Co compound, Ni compound, and M2 compound, hydroxides, oxides, chlorides, and the like of these elements are preferable.

  The firing temperature in the firing step is preferably 650 ° C. or higher and 1200 ° C. or lower. When the firing temperature is lower than 650 ° C., it becomes difficult to obtain a layered rock salt structure in the lithium-containing cobalt oxide. In addition, it is difficult to realize a firing temperature exceeding 1200 ° C. due to restrictions such as equipment and oxygen concentration. The firing time here is preferably about 5 hours to 48 hours, for example.

  In the manufacturing method of this embodiment, what is necessary is just to have the said baking process once or more. That is, the number of firings may be one time or two or more times. However, the final firing step is preferably performed at 900 ° C. or more and 1200 ° C. or less, and the firing time is preferably 0.5 hours or more and 48 hours or less, more preferably 10 hours or more and 48 hours or less. preferable.

  At least selected from the group consisting of Li, Zr, Ti, Al, Ni, Mn, Zn and P with respect to the surface of the positive electrode active material B made of a lithium-containing cobalt oxide represented by the general composition formula (B) The step of coating an oxide or fluoride containing one element can be performed, for example, by the following procedure.

  When coating with Zr, Ti, Al, Ni, Mn, and Zn oxide, in an aqueous solution of sodium hydroxide or lithium hydroxide adjusted to a pH value of 9 to 11 and a temperature of 60 ° C. to 80 ° C. The powder of the positive electrode active material B is added, and after stirring and dispersing, nitrate or sulfate of the covering element is dropped. At this time, a coprecipitate is produced by simultaneously dropping ammonia water so that the pH value does not change. Thereafter, the coprecipitate and the positive electrode active material B powder are continuously stirred for 5 hours or more and adjusted so that the pH value does not fluctuate with sodium hydroxide or lithium hydroxide as needed. In particular, when obtaining a coprecipitate such as Ni and Mn, it is more preferable to replace the dissolved oxygen in the aqueous solution with nitrogen. Next, the powder of the positive electrode active material B to which the coprecipitate is adhered and the aqueous solution are separated by suction filtration, and the separated positive electrode active material B is washed with ultrapure water and dried. The positive electrode active material B for a non-aqueous electrolyte secondary battery in which a coating layer of Zr, Ti, Al, Ni, Mn, and Zn oxide is formed by firing the powder of the positive electrode active material B to which the coprecipitate is adhered. Is obtained.

  As another method for coating Zr, Ti, Al, Ni, Mn, and Zn oxide, an alkoxide of a desired element is dissolved in an alcohol solvent, and stirred and dried at a temperature of 60 ° C. to 80 ° C. There is also a method of attaching to the positive electrode active material B and baking.

In the case of coating Zr, Ti, Al, Ni, Mn, Zn, and P oxide containing Li, after the precursor of the coating element is attached to the surface of the positive electrode active material B by any of the above methods Then, LiOH or Li ₂ CO ₃ may be mixed and fired.

  In the case of coating a fluoride such as AlF, for example, the positive electrode active material B is placed in a sodium hydroxide or lithium hydroxide aqueous solution adjusted to a pH value of 9 to 11 and a temperature of 60 ° C. to 80 ° C. After the powder is added and stirred and dispersed, aluminum nitride hydrate is added. Ammonium fluoride aqueous solution is dripped little by little, and after stirring for 5 hours or more, it may be filtered, dried, and fired in an inert gas atmosphere.

  The firing temperature at the time of coating is preferably 400 ° C. or more and 600 ° C. or less, and the firing time is preferably 5 hours or more and 24 hours or less. The firing atmosphere is preferably an oxidizing atmosphere such as air or oxygen when obtaining an oxide, and an inert atmosphere such as nitrogen when obtaining a fluoride.

(Production method of positive electrode)
Next, the manufacturing method of the positive electrode 1 using the positive electrode active material A and the positive electrode active material B is demonstrated. The ratio A / B (mass ratio) between the positive electrode active material A and the positive electrode active material B is preferably set to 0.1 or more and 0.7 or less from the viewpoint of better ensuring the effect of increasing the capacity. From the viewpoint of characteristics and safety, it is more preferable to contain it in a mass ratio of 0.3 to 0.5.

  In order to produce the positive electrode 1 containing the positive electrode active material A and the positive electrode active material B, as described above, first, the positive electrode active material is mixed with a binder, a conductive auxiliary agent, etc., and dispersed in a solvent to obtain a positive electrode mixture slurry. Next, this positive electrode mixture slurry is applied to the surface of the positive electrode current collector to form a positive electrode mixture layer.

  As the binder related to the positive electrode mixture layer, conventionally known various binders can be applied. Among them, polyvinylidene fluoride (PVdF) and vinylidene fluoride (1,1-difluoroethylene, etc.)-Chloro A trifluoroethylene copolymer (a copolymer of vinylidene fluoride and chlorotrifluoroethylene, VDF-CTFE) is preferably used in combination.

The positive electrode active material A represented by the general composition formula (A) has a larger capacity than, for example, LiCoO ₂ which is widely used for the positive electrode active material of the nonaqueous electrolyte secondary battery, but is mixed and remaining in the synthesis process. The amount of the alkali component thus produced is large, and this reacts with PVdF in the positive electrode mixture slurry to cause thickening of the positive electrode mixture slurry. When a positive electrode manufactured using a thickened positive electrode mixture slurry is used, the charge / discharge capacity of the nonaqueous electrolyte secondary battery may be reduced due to the increase in resistance.

  However, when VDF-CTFE is used together with PVdF, the viscosity increase of the positive electrode mixture slurry is suppressed because VDF-CTFE acts as a terminator for the reaction between PVdF molecular chains due to alkali components. Therefore, since the positive electrode in the present invention can ensure good characteristics while containing a high capacity positive electrode active material, the nonaqueous electrolyte secondary battery of the present invention having such a positive electrode has a high capacity, and It has good charge / discharge cycle characteristics.

  Moreover, when only VDF-CTFE is used for the binder of the positive electrode mixture layer, the thickening of the positive electrode mixture slurry by the alkaline component contained in the positive electrode active material B represented by the general composition formula (B) is suppressed. On the other hand, the viscosity of the positive electrode mixture slurry tends to be very low, making it difficult to adjust the viscosity to be suitable for application to the current collector, and positive electrode productivity, and in turn, production of non-aqueous electrolyte secondary batteries. May deteriorate. On the other hand, when PVdF is used together with VDF-CTFE for the binder of the positive electrode mixture layer, the positive electrode mixture slurry can be easily adjusted to a viscosity suitable for application to the current collector. The productivity of the secondary battery is also improved.

  The composition of VDF-CTFE used for the positive electrode mixture layer is such that the unit derived from vinylidene fluoride is used in order to better ensure the effect of improving the charge / discharge cycle characteristics of the nonaqueous electrolyte secondary battery by using VDF-CTFE. When the total with the unit derived from chlorotrifluoroethylene is 100 mol%, the ratio of the unit derived from chlorotrifluoroethylene is preferably 0.5 mol% or more, and more preferably 1 mol% or more. However, if the proportion of units derived from chlorotrifluoroethylene in VDF-CTFE becomes too high, the nonaqueous electrolyte (nonaqueous electrolyte) is easily absorbed and swelled, and the characteristics of the positive electrode may be deteriorated. Therefore, in VDF-CTFE used for the positive electrode mixture layer, when the total of the units derived from vinylidene fluoride and the units derived from chlorotrifluoroethylene is 100 mol%, the ratio of the units derived from chlorotrifluoroethylene is 15 mol% or less is preferable.

  In the positive electrode mixture layer, the total of PVdF and VDF-CTFE was set to 100% by mass from the viewpoint of better ensuring the effect of improving the charge / discharge cycle characteristics of the nonaqueous electrolyte secondary battery by using VDF-CTFE. When the ratio of VDF-CTFE is preferably 25% by mass or more, more preferably 40% by mass or more. However, if the proportion of VDF-CTFE in the total of PVdF and VDF-CTFE becomes too large, for example, the positive electrode mixture layer is more easily swollen by the non-aqueous electrolyte (non-aqueous electrolyte), and the characteristics of the positive electrode May decrease. Therefore, when the total of PVdF and VDF-CTFE in the positive electrode mixture layer is 100% by mass, the proportion of VDF-CTFE is preferably 80% by mass or less, and more preferably 75% by mass or less. .

  The conductive additive used for the positive electrode mixture layer may be either an inorganic material or an organic material as long as it is chemically stable in the nonaqueous electrolyte secondary battery. For example, carbon such as graphite such as natural graphite and artificial graphite, single- or multi-walled carbon nanotubes, graphene, fullerene, VGCF, acetylene black, ketjen black (registered trademark), channel black, furnace black, lamp black, thermal black, etc. Conductive fiber such as black, carbon fiber, metal fiber, metal powder such as aluminum powder, conductive whisker made of carbon fluoride, zinc oxide, potassium titanate, conductive metal oxide such as titanium oxide, polyphenylene derivative, etc. The organic conductive material or the like can be used. These may be used alone or in combination of two or more. Among these, graphite having high conductivity and carbon black excellent in liquid absorption are preferable.

  As the form of the conductive auxiliary agent, for example, when the conductive auxiliary agent is in the form of particles, the conductive auxiliary agent is not limited to only primary particles, and those having an aggregate form such as secondary particles or chain structures can also be used. . In the case of a conductive additive having such an aggregate form, it is easier to handle and the productivity of the positive electrode can be increased.

  The proportion of the positive electrode active material in the positive electrode mixture layer is preferably 85% by mass or more and 99% by mass or less. When the content ratio of the positive electrode active material is less than 85%, the battery capacity is decreased. Conversely, when the content ratio is greater than 99%, the amount of the conductive auxiliary agent is relatively decreased, and the resistance of the positive electrode is increased.

  The amount of the binder in the positive electrode mixture layer is preferably 0.2% by mass or more and 5% by mass or less. Moreover, it is preferable that the quantity of the conductive support agent which occupies for a positive mix layer shall be 0.5 mass% or more and 8 mass% or less. For example, the positive electrode mixture layer can contain graphite and carbon black in a proportion of 0.5 mass% to 8 mass%.

  A slurry mixture composition is prepared by dispersing a cathode mixture containing a cathode active material for a non-aqueous electrolyte secondary battery, a binder, a conductive additive and the like in NMP or the like. After this mixture composition is applied to one or both sides of the positive electrode current collector, NMP is evaporated, and a press treatment is performed to form a positive electrode mixture layer on the current collector surface. The press treatment is for adjusting the thickness and density of the positive electrode mixture layer, and can be performed using, for example, a roll press machine or a hydraulic press machine.

The density of the positive electrode mixture layer thus produced is preferably 3.5 g / cm ³ or more and 4.0 g / cm ³ or less. The method for manufacturing the positive electrode is not limited to the above, and other manufacturing methods may be used.

  The material of the positive electrode current collector is not particularly limited as long as it is a chemically stable electron conductor in the nonaqueous electrolyte secondary battery. For example, in addition to aluminum, aluminum alloy, stainless steel, nickel, titanium, carbon, conductive resin, etc., aluminum, aluminum alloy, a composite material in which a carbon layer or a titanium layer is formed on the surface of stainless steel, or the like can be used. . Among these materials, aluminum or aluminum alloy is preferable because it is lightweight and has high conductivity. As the positive electrode current collector, for example, a foil, a film, a sheet, a net, a punching sheet, a glass body, a porous body, a foamed body, a molded body of a fiber group, or the like made of the above materials can be used. Further, the surface of the positive electrode current collector can be roughened by surface treatment. The thickness of the positive electrode current collector is not particularly limited, but is preferably about 1 μm or more and 500 μm or less, for example.

  Various methods such as spin coating, dipping, and screen printing can be used as a method of applying the slurry containing the positive electrode active material on the current collector surface, that is, the positive electrode mixture slurry.

  The non-aqueous electrolyte secondary battery of the present invention has a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. The positive electrode may be the positive electrode described above, and there are no particular restrictions on other configurations and structures. Various configurations and structures adopted in the used non-aqueous electrolyte secondary battery can be applied.

(Method for producing negative electrode)
As the negative electrode 2, a structure having a negative electrode mixture layer containing a negative electrode active material, a binder and the like on one side or both sides of a current collector can be used.

  Examples of the negative electrode active material include graphite materials such as natural graphite (flaky graphite), artificial graphite, and expanded graphite; graphitizable carbonaceous materials such as coke obtained by calcining pitch; furfuryl alcohol resin ( Carbon materials such as non-graphitizable carbonaceous materials such as amorphous carbon obtained by low-temperature firing of PFA), polyparaphenylene (PPP), and phenol resins. In addition to the carbon material, lithium or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include lithium alloys such as Li—Al, and alloys containing elements that can be alloyed with lithium such as Si and Sn. Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used.

When using the graphite material in the negative electrode active material. As the graphite material, R value is the peak intensity ratio of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the argon ion laser Raman spectrum _(I 1360 _/ I ₁₅₈₀₎ is 0 1 or more and 0.5 or less, and the surface spacing d002 of the 002 plane is preferably 0.338 nm or less. This type of graphite material has excellent load characteristics, and in particular, has characteristics of excellent charging characteristics at a low temperature of 0 ° C. or lower. By using this as a negative electrode active material, a non-aqueous electrolyte secondary battery can be obtained. It is possible to improve the load characteristics and charging characteristics at low temperatures.

  The R value is obtained from a Raman spectrum obtained using an argon laser having a wavelength of 514.5 nm (for example, “T-5400” (Laser power: 1 mW) manufactured by Ramanaor).

  The graphite material satisfying the R value and d002 satisfies the above values, for example, natural graphite having d002 of 0.338 nm or less or graphite obtained by spherically shaping artificial graphite, and the surface thereof is coated with an organic compound. After baking at 800 ° C. to 1500 ° C., it can be obtained by crushing and sizing through a sieve. The organic compound covering the base material includes aromatic hydrocarbons; tars or pitches obtained by polycondensation of aromatic hydrocarbons under heat and pressure; tars mainly composed of a mixture of aromatic hydrocarbons. , Pitch or asphalt; In order to coat the base material with the organic compound, a method of impregnating and kneading the base material into the organic compound can be employed. Also, the R value and d002 satisfy the above-mentioned values by a vapor phase method in which a hydrocarbon gas such as propane or acetylene is carbonized by pyrolysis and deposited on the surface of graphite having d002 of 0.338 nm or less. A material can be made.

  For example, PVDF, polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), or the like is suitably used for the binder related to the negative electrode mixture layer.

  Moreover, you may make the negative mix layer contain conductive assistants, such as various carbon blacks, such as acetylene black, and a carbon nanotube, as needed.

  The negative electrode is prepared, for example, by preparing a negative electrode mixture slurry in which a negative electrode active material and a binder, and further, if necessary, a conductive additive dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) or water (however, The binder may be dissolved in a solvent), and this is applied to one or both sides of the current collector, dried, and then subjected to a press treatment such as calender treatment as necessary. The negative electrode is not limited to those manufactured by the above method, and may be manufactured by other manufacturing methods.

  The thickness of the negative electrode mixture layer is preferably 10 μm to 100 μm per side of the current collector. Moreover, as a composition of a negative mix layer, it is preferable that the quantity of a negative electrode active material is 80 mass%-95 mass%, for example, it is preferable that the quantity of a binder is 1 mass%-20 mass%, and electroconductivity. When using an auxiliary agent, it is preferable that the quantity is 1 mass%-10 mass%.

  As the current collector for the negative electrode, a foil made of copper or nickel, a punching metal, a net, an expanded metal or the like can be used, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is preferably 5 μm.

(Separator)
As the separator 3 in the nonaqueous electrolyte secondary battery of the present invention, a separator used in a normal nonaqueous electrolyte secondary battery, for example, a microporous membrane made of polyolefin such as polyethylene (PE) or polypropylene (PP) is used. Can be used. The microporous membrane constituting the separator may be, for example, one using only PE or one using only PP, or a laminate of a microporous membrane made of PE and a microporous membrane made of PP. There may be.

  Further, a laminated separator in which a heat-resistant porous layer containing a heat-resistant inorganic filler is formed on the surface of the microporous film may be used. When such a stacked separator is used, the shrinkage of the separator is suppressed even when the temperature in the battery rises, and a short circuit due to contact between the positive electrode and the negative electrode can be suppressed. A high nonaqueous electrolyte secondary battery can be obtained.

  As the inorganic filler to be contained in the heat-resistant porous layer, boehmite, alumina, silica and the like are preferable, and one or more of them can be used. The heat-resistant porous layer preferably contains a binder for binding the inorganic fillers or bonding the heat-resistant porous layer and the microporous film. The binder includes ethylene-vinyl acetate copolymer (EVA, structural unit derived from vinyl acetate of 20 mol% to 35 mol%), ethylene-acrylic acid copolymer such as ethylene-ethyl acrylate copolymer, fluorine rubber, etc. Styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), cross-linked acrylic resin, polyurethane, epoxy resin, etc. Of these, one or more of them can be used.

  The thickness of the separator (a separator made of a microporous membrane made of polyolefin, or the laminated separator) is preferably 10 μm to 30 μm, for example. In the case of the laminated separator, the heat-resistant porous layer preferably has a thickness of 3 μm to 8 μm, for example.

(Nonaqueous electrolyte)
As the non-aqueous electrolyte in the non-aqueous electrolyte secondary battery of the present invention, for example, a solution (non-aqueous electrolyte) in which a lithium salt is dissolved in an organic solvent can be used. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li ⁺ ions and hardly causes a side reaction such as decomposition in a voltage range used as a battery. For example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF _{6 and} other inorganic lithium salts, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiCnF _{2n + 1} SO ₃ (n ≧ 2), LiN (RfO _{2 S 2} O ₂ ) ₂ (where Rf is a fluoroalkyl group), etc. Can do.

  The organic solvent used for the non-aqueous electrolyte is not particularly limited as long as it dissolves the lithium salt and does not cause a side reaction such as decomposition in the voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; dimethoxyethane, Chain ethers such as diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile; ethylene Sulfites such as glycol sulfite; and the like. These may be used in combination of two or more. In order to obtain a battery having better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate. Further, for the purpose of improving charge / discharge cycle characteristics, high-temperature storage characteristics, safety of overcharge, etc., to these nonaqueous electrolytes, acid anhydrides, sulfonate esters, dinitriles, vinylene carbonates, 1,3- Additives (including these derivatives) such as propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, and t-butylbenzene can also be added as appropriate.

  The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.5 mol / l to 1.5 mol / l, and more preferably 0.9 mol / l to 1.25 mol / l. Moreover, you may use for the nonaqueous electrolyte secondary battery of this invention what added gelatinizers, such as a well-known polymer, to the said nonaqueous electrolyte solution, and was made into the gel form (gel electrolyte).

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further in detail, this invention is not limited to these Examples.

Example 1
<Preparation of positive electrode>
Lithium-containing composite oxide represented by Li _1.00 Ni _0.89 Co _0.06 Mn _0.02 Mg _0.02 Al _0.01 O _{2 as the} positive electrode active material A: 95 parts by mass, and a conductive additive Ketjen black: 3 parts by mass, VDF-CTFE as a binder: 2 parts by mass, and dehydrated NMP were mixed with a planetary mixer to prepare slurry (a). Further, Li _1.01 Na _0.002 Co _0.97 Ni _0.02 Mg _0.01 O ₂ as the positive electrode active material B: 95 parts by mass, Ketjen black as a conductive auxiliary agent: 3 parts by mass, 2 parts by mass of PVdF as a binder and dehydrated NMP were mixed with a planetary mixer to prepare slurry (b). And the said slurry (a) and slurry (b) were mixed by the mass ratio from which (a) / (b) was set to 0.25, and the positive mix slurry was prepared.

  This positive electrode mixture slurry is intermittently applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm, and after drying, a press treatment is performed to form a positive electrode mixture layer having a thickness of 72.5 μm per side of the current collector. Formed on both sides. Thereafter, this was cut into a width of 54 mm to obtain a strip-shaped positive electrode. Further, a tab was welded to the exposed portion of the positive electrode current collector to form a lead portion.

<Production of negative electrode>
Graphite A having an average particle size D50% of 16 μm, d002 of 0.3360 nm and an R value of 0.05, and graphite B coated with pitch coating on the surface of the graphite A (average particle size D50%: 18 μm, d002: 0. 3380 nm, R value of 0.18, specific surface area of 3.2 m ² / g) mixed at a mass ratio of 30:70: 98 parts by mass, viscosity adjusted to the range of 1500 mPa · s to 5000 mPa · s 1% by mass CMC aqueous solution: 1.0 part by mass and SBR: 1.0 part by mass using ion-exchanged water having a specific conductivity of 2.0 × 10 ⁵ Ω / cm or more as a solvent. An aqueous negative electrode mixture layer forming paste was prepared.

  The negative electrode mixture layer forming paste is intermittently applied to both surfaces of a current collector made of copper foil and having a thickness of 10 μm, dried, and then subjected to press treatment so that the total thickness is 142 μm. The negative electrode was fabricated by adjusting the thickness of the material and cutting it to a width of 55 mm. Further, a tab was welded to the exposed portion of the negative electrode current collector to form a lead portion.

<Battery assembly>
The positive electrode and the negative electrode are overlapped via a separator (thickness 18 μm, porosity 50%) made of a PE microporous film, wound into a roll, and then welded to the positive and negative electrodes. It was inserted into an aluminum alloy outer can having a thickness of 49 mm, a width of 42 mm, and a height of 61 mm (494261 type), and a lid was welded to the open end of the outer can. Thereafter, LiPF ₆ was added at a concentration of 1 mol to a non-aqueous electrolyte (a solution in which vinylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7 at a concentration of 3% by mass from the electrolyte inlet of the lid). / L): 3.6 g is injected into the outer can, and the electrolyte injection port is sealed, and the rectangular nonaqueous electrolyte secondary battery having the structure shown in FIG. 1 and the appearance shown in FIG. Got.

(Example 2)
In the same procedure as in Example 1, the slurry (a) and the slurry (b) were mixed at a mass ratio where (a) / (b) was 0.1 to prepare a positive electrode mixture slurry. A positive electrode was produced. Using this positive electrode, a nonaqueous electrolyte secondary battery according to Example 2 was produced in the same procedure as in Example 1.

(Example 3)
In the same procedure as in Example 1, the slurry (a) and the slurry (b) are mixed at a mass ratio where (a) / (b) is 0.3 to prepare a positive electrode mixture slurry. A positive electrode was produced. Using this positive electrode, a nonaqueous electrolyte secondary battery according to Example 3 was produced in the same procedure as in Example 1.

Example 4
In the same procedure as in Example 1, the slurry (a) and the slurry (b) were mixed at a mass ratio (a) / (b) of 0.67 to prepare a positive electrode mixture slurry. A positive electrode was produced. Using this positive electrode, a nonaqueous electrolyte secondary battery according to Example 4 was produced in the same procedure as in Example 1.

(Example 5)
As the positive electrode active material B, a lithium-containing cobalt oxide represented by a general composition formula Li _1.01 Na _0.002 Co _0.945 Ni _0.05 Mg _0.005 O ₂ was used. pH value of 9 to 11, after the temperature was charged with powder of the positive active material B in aqueous solution of lithium hydroxide adjusted to 80 ° C. below 60 ° C. or more and stirred to disperse, Al (NO ₃₎ the ₃ · 9H ₂ O was dropped. At this time, Al (OH) ₃ coprecipitate was produced by simultaneously dropping ammonia water so that the pH value would not change. Thereafter, stirring was continued for 5 hours or more, and the pH value was adjusted with lithium hydroxide so as not to fluctuate as needed. Next, the powder of the positive electrode active material B to which Al (OH) ₃ was adhered and the aqueous solution were separated by suction filtration, washed with ultrapure water, and vacuum-dried at 80 ° C. for 24 hours. This powder was fired at 400 ° C. for 10 hours in an air atmosphere (oxygen concentration: 21%). In the oxide film formed on the surface of the positive electrode active material B by such a process, a material containing 1 mol% of Al in a molar ratio with respect to the positive electrode active material B was prepared. Using this positive electrode active material B, a nonaqueous electrolyte secondary battery according to Example 5 was produced in the same procedure as in Example 3.

(Example 6)
As the positive electrode active material B, a lithium-containing cobalt oxide represented by a general composition formula Li _1.01 Na _0.002 Co _0.945 Ni _0.05 Mg _0.005 O ₂ was used. Zirconium isopropoxide was dissolved in an isopropyl alcohol solvent, stirred with the positive electrode active material B powder at a temperature of 60 ° C. for 10 hours, and dried at 80 ° C. This powder was fired at 400 ° C. in an air atmosphere for 10 hours. In the oxide film formed on the surface of the positive electrode active material B by such a process, a material containing 1 mol% of Zr in a molar ratio with respect to the positive electrode active material B was prepared. Using this positive electrode active material B, a nonaqueous electrolyte secondary battery according to Example 6 was produced in the same procedure as in Example 3.

(Example 7)
As the positive electrode active material B, a lithium-containing cobalt oxide represented by a general composition formula Li _1.01 Na _0.002 Co _0.945 Ni _0.05 Mg _0.005 O ₂ was used. The positive electrode active material B powder was put into a lithium hydroxide aqueous solution adjusted to a pH value of 9 or more and 11 or less and a temperature of 60 ° C., stirred and dispersed, and then aluminum nitride hydrate was added. Ammonium fluoride aqueous solution was dripped little by little, and after stirring for 10 hours or more, suction filtration was performed, followed by washing with ultrapure water, followed by vacuum drying at 80 ° C. for 24 hours. This powder was fired in a nitrogen gas atmosphere for 10 hours. A product containing 1 mol% of AlF formed on the surface of the positive electrode active material B by such a process in a molar ratio with respect to the positive electrode active material B was produced. Using this positive electrode active material B, a nonaqueous electrolyte secondary battery according to Example 7 was produced in the same procedure as in Example 3.

(Example 8)
As the positive electrode active material B, a lithium-containing cobalt oxide represented by the general composition formula Li _1.01 Na _0.002 Co _0.97 Ni _0.02 Al _0.01 O ₂ was used, and the same as in Example 3 above. A nonaqueous electrolyte secondary battery according to Example 8 was produced according to the procedure.

Example 9
Using lithium-containing cobalt oxide represented by the general composition formula Li _1.01 Na _0.002 Co _0.97 Ni _0.02 Mn _0.01 O ₂ as the positive electrode active material B, the same procedure as in Example 3 Thus, a nonaqueous electrolyte secondary battery according to Example 9 was produced.

(Example 10)
Using lithium-containing cobalt oxide represented by the general composition formula Li _1.01 Na _0.002 Co _0.97 Ni _0.02 Mo _0.01 O ₂ as the positive electrode active material B, the same procedure as in Example 3 Thus, a nonaqueous electrolyte secondary battery according to Example 10 was produced.

(Example 11)
The same procedure as in Example 3 was performed using a lithium-containing cobalt oxide represented by the general composition formula Li _1.01 Na _0.002 Co _0.97 Ni _0.02 V _0.01 O ₂ as the positive electrode active material B. A non-aqueous electrolyte secondary battery according to Example 11 was produced.

(Example 12)
The same procedure as in Example 3 was performed using a lithium-containing cobalt oxide represented by the general composition formula Li _1.01 Na _0.002 Co _0.97 Ni _0.02 W _0.01 O ₂ as the positive electrode active material B. Thus, a nonaqueous electrolyte secondary battery according to Example 12 was produced.

(Example 13)
The same procedure as in Example 3 was performed using a lithium-containing cobalt oxide represented by the general composition formula Li _1.01 Na _0.002 Co _0.978 Ni _0.02 Bi _0.002 O ₂ as the positive electrode active material B. Thus, a non-aqueous electrolyte secondary battery according to Example 13 was produced.

(Example 14)
Example 3 Using a lithium-containing composite oxide represented by the general composition formula Li _1.00 Ni _0.89 Co _0.06 Mn _0.02 Mg _0.02 Ba _0.01 O ₂ as the positive electrode active material A, A nonaqueous electrolyte secondary battery according to Example 14 was produced in the same procedure as described above.

(Example 15)
Example 3 using a lithium-containing composite oxide represented by the general composition formula Li _1.00 Ni _0.89 Co _0.06 Mn _0.02 Mg _0.02 Sr _0.01 O ₂ as the positive electrode active material A A non-aqueous electrolyte secondary battery according to Example 15 was produced in the same procedure as described above.

(Example 16)
Example 3 using a lithium-containing composite oxide represented by the general composition formula Li _1.00 Ni _0.89 Co _0.06 Mn _0.02 Mg _0.02 Ti _0.01 O ₂ as the positive electrode active material A A nonaqueous electrolyte secondary battery according to Example 16 was produced in the same procedure as described above.

(Example 17)
Example 3 Using a lithium-containing composite oxide represented by the general composition formula Li _1.00 Ni _0.89 Co _0.06 Mn _0.02 Mg _0.02 Zr _0.01 O ₂ as the positive electrode active material A, A non-aqueous electrolyte secondary battery according to Example 17 was produced in the same procedure as described above.

(Example 18)
Example 5 Using a lithium-containing composite oxide represented by the general composition formula Li _1.00 Ni _0.89 Co _0.06 Mn _0.02 Mg _0.02 Al _0.01 O ₂ as the positive electrode active material A, In the same procedure as described above, an Al oxide coating containing 1 mol% of Al in a molar ratio with respect to the positive electrode active material A on the surface of the positive electrode active material A was produced. Using this positive electrode active material A, a nonaqueous electrolyte secondary battery according to Example 18 was fabricated in the same procedure as in Example 5.

(Example 19)
Using lithium-containing cobalt oxide represented by the general composition formula Li _1.01 Co _0.965 Ni _0.02 Mg _0.01 Zr _0.005 O ₂ as the positive electrode active material B, the same procedure as in Example 5 Thus, an Al oxide coating containing 1 mol% of Al on the surface of the positive electrode active material B in a molar ratio with respect to the positive electrode active material B was prepared. Using this positive electrode active material B, a nonaqueous electrolyte secondary battery according to Example 19 was produced in the same procedure as in Example 3.

(Example 20)
Example 5 Using a lithium-containing cobalt oxide represented by the general composition formula Li _1.01 Na _0.002 Co _0.97 Ni _0.02 Mg _0.01 Zr _0.005 O ₂ as the positive electrode active material B, In the same procedure, an Al oxide coating containing 1 mol% of Al on the surface of the positive electrode active material B in a molar ratio with respect to the positive electrode active material B was produced. Using this positive electrode active material B, a nonaqueous electrolyte secondary battery according to Example 20 was produced in the same procedure as in Example 3.

(Example 21)
The same procedure as in Example 19 was used, and the positive electrode active material B coated with Al oxide and the positive electrode active material A coated with Al oxide in the same procedure as in Example 18 were used. A nonaqueous electrolyte secondary battery according to Example 21 was produced in the same procedure.

(Example 22)
In the same procedure as in Example 20, the positive electrode active material B coated with Al oxide and the positive electrode active material A coated with Al oxide in the same procedure as in Example 18 were used. A nonaqueous electrolyte secondary battery according to Example 22 was fabricated in the same procedure.

(Example 23)
Lithium-containing composite oxide represented by Li _1.00 Ni _0.89 Co _0.06 Mn _0.02 Mg _0.02 Al _0.01 O _{2 as the} positive electrode active material A: 95 parts by mass, and a conductive additive Ketjen Black: 3 parts by mass, PVdF: 2 parts by mass of binder, and dehydrated NMP were mixed in a planetary mixer to prepare a slurry (a), and the same procedure as in Example 1 was performed. A non-aqueous electrolyte secondary battery was produced.

(Comparative Example 1)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that only the lithium-containing cobalt oxide LiCoO ₂ was used as the positive electrode active material.

(Comparative Example 2)
Other than using only the lithium-containing composite oxide represented by Li _1.00 Ni _0.89 Co _0.06 Mn _0.02 Mg _0.02 Al _0.01 O _{2 as the} positive electrode active material A as the positive electrode active material A Produced a non-aqueous electrolyte secondary battery in the same manner as in Example 1.

(Comparative Example 3)
Instead of the positive electrode active material B, Li _1.14 Na _0.01 Co _0.97 Ni _0.02 Mg _0.01 O _1.97 : 95 parts by mass and Ketjen black as a conductive auxiliary agent: 3 parts by mass A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that 2 parts by mass of PVdF as a binder and dehydrated NMP were mixed with a planetary mixer to prepare slurry (b). .

The compositions of the positive electrode active material and the elements covering the surface of the positive electrode active material in Examples 1 to 23 and Comparative Examples 1 to 3 are shown in Table 1 and Table 2 below. Examples 19 and 21 are reference examples.

(Battery evaluation)
For each of the nonaqueous electrolyte secondary batteries of Examples 1 to 23 and Comparative Examples 1 to 3, the standard capacity, storage characteristics, and continuous charge storage characteristics were evaluated in the following manner.
<Standard capacity>
After each battery of Examples and Comparative Examples was stored at 60 ° C. for 7 hours, it was charged at 20 ° C. with a current value of 850 mA for 3 hours, and discharged at a current value of 850 mA until the battery voltage was reduced to 2.5V. The charge / discharge cycle was repeated until the discharge capacity became constant. Next, constant current-constant voltage charging (constant current: 850 mA, constant voltage: 4.35 V, total charging time: 3 hours) is performed, and after discharging for 1 hour, discharging is performed until the battery voltage reaches 2.5 V at a current value of 340 mA. The standard capacity was determined. The standard capacity was measured for 100 batteries for each battery, and the average value was used as the standard capacity for each example and comparative example.

<Storage characteristics>
The batteries of Examples and Comparative Examples were charged with constant current-constant voltage (constant current: 850 mA, constant voltage: 4.40 V, total charging time: 3 hours), then placed in a constant temperature bath at 60 ° C. and left for 7 days. Thereafter, the battery is taken out from the thermostat and discharged until the battery voltage is reduced to 2.5 V at a current value of 340 mA, and constant current-constant voltage charging (constant current: 850 mA, constant voltage: 4.35 V, total charging time: 3) The battery was discharged at a current value of 340 mA at a current value of 340 mA until the battery voltage reached 2.5 V, and the recovery capacity was determined. The battery whose recovery capacity with respect to the standard capacity at this time was 85% or more was evaluated as a, the battery exceeding 80% was evaluated as b, and the battery lower than 80% was evaluated as c.

<Continuous charge storage characteristics>
Each battery of Examples and Comparative Examples was charged with constant current-constant voltage (constant current: 850 mA, constant voltage: 4.40 V, total charge time: 3 hours), and then placed in a constant temperature bath at 60 ° C. The time until the current value increased to 850 mA was obtained by constant voltage charging. The battery in which the time was 500 hours or more was evaluated as a, the battery exceeding 400 hours as b, and the battery having less than 400 hours as c. The evaluation results are shown in Table 3 below.

  From the results shown in Table 3, the following can be understood. In the nonaqueous electrolyte secondary batteries according to Examples 1 to 23, the standard capacity exceeded 1670 mAh, and the storage characteristics and the continuous charge storage characteristics were also good. In particular, it was found that the highest standard capacity was obtained in Example 4 in which the ratio of the positive electrode active material A was increased, and the cycle characteristics were also good. Examples 10 to 13 use Mo, V, W, or Bi as the M2 element of the positive electrode active material B. These tend to have a slightly lower standard capacity, and the evaluation of the continuous charge storage characteristics is b. It became. In particular, these elements are unlikely to be solid-solved in the lithium-containing cobalt oxide represented by the general composition formula (B), so that it is considered that the continuous charge storage characteristics are reduced as a result of the suppression of crystal growth. Since the nonaqueous electrolyte secondary battery of Example 23 has a large amount of alkali component mixed and remaining in the synthesis process of the general composition formula (A), this reacts with PVdF in the positive electrode mixture slurry, and the positive electrode mixture It is thought that the viscosity of the slurry was increased and the charge / discharge capacity was lowered.

  On the other hand, in the nonaqueous electrolyte secondary batteries according to Comparative Examples 1 to 3, the standard capacity tends to be as low as 1640 mAh or less. In Comparative Example 1, the storage characteristics and the continuous charge storage characteristics are evaluated as c. Comparative Example 2 The storage characteristic was evaluated as c, and Comparative Example 3 was evaluated as b for both the storage characteristic and the continuous charge storage characteristic. In the non-aqueous electrolyte secondary battery of Comparative Example 1, side reaction with the electrolyte becomes significant due to high voltage charging of 4.40 V, and Co elution and crystal structure collapse occur, resulting in a decrease in standard capacity, storage, Not only the continuous charge storage characteristics but also the cycle characteristics deteriorated. Since the non-aqueous electrolyte secondary battery of Comparative Example 2 contains a large amount of Ni of the above general composition formula (A), the irreversible capacity is probably increased due to the influence of the transition of Ni to the Li site, and the standard capacity is decreased. It is thought that. Since the non-aqueous electrolyte secondary battery of Comparative Example 3 has a large amount of alkali component mixed and remaining in the synthesis process of the general composition formula (B), this reacts with PVdF in the positive electrode mixture slurry, and the positive electrode mixture It is thought that the viscosity of the slurry was increased and the charge / discharge capacity was lowered. In addition, it is considered that the crystallinity is lowered due to the introduction of oxygen deficiency due to the large amount of Li, which causes the deterioration of the storage characteristics and the continuous charge storage characteristics.

  As described above, according to the nonaqueous electrolyte secondary battery of the present invention, a nonaqueous electrolyte secondary battery having a large capacity and excellent in continuous charge storage characteristics at a high voltage at a high temperature can be provided. In particular, the non-aqueous electrolyte secondary battery according to the present invention is excellent in charge capacity when charged until the positive electrode potential becomes 4.30 V or higher on the basis of lithium, storage characteristics in a high temperature environment, and continuous charge storage characteristics.

  The embodiment of the present invention has been described in detail above, but the specific configuration is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention, It is included in the present invention.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Outer can 5 Insulator 6 Winding electrode body 7 Positive electrode lead body 8 Negative electrode lead body 9 Lid 11 Terminal 12 Insulator 13 Lead plate 14 Electrolyte injection port 15 Cleavage vent

Claims (6)

A non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode mixture layer containing a positive electrode active material, a binder and a conductive auxiliary agent on one or both sides of the current collector And the positive electrode active material includes a positive electrode active material A and a positive electrode active material B,
The positive electrode active material A is Li _{1 + x} M1O ₂ (wherein, −0.15 ≦ x ≦ 0.15, M1 is Ni or two or more elements including Ni, and the Ni content in M1 is 30 mol) % Or more)
The positive electrode active material B is Li _α-x Na _x Co _1-yz Ni _y M2 _z O _2-δ (where 1.011 ≦ α ≦ 1.13, 0.001 ≦ x ≦ 0.03). 0.01 ≦ y ≦ 0.05, 0.0005 ≦ z ≦ 0.03, 0 ≦ δ ≦ 0.002, and M2 is Al, Mg, Zr, Mn, V, W, Mo, Cr, Bi , Ti, Si, Fe, P, F, S and Cl, which is one or more elements including at least one selected from the group consisting of Ti and Si).   The nonaqueous electrolyte secondary battery according to claim 1, wherein a ratio A / B (mass ratio) of the positive electrode active material A and the positive electrode active material B is 0.1 or more and 0.7 or less.   Oxide or fluoride containing at least one element selected from the group consisting of Li, Zr, Ti, Al, Ni, Mn, Zn, and P, at least one surface of positive electrode active material A and positive electrode active material B The nonaqueous electrolyte secondary battery according to claim 1, wherein the number of atoms of the element is 10 mol% or less of the number of molecules of at least one of the positive electrode active material A and the positive electrode active material B to be coated.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the binder includes polyvinylidene fluoride and a vinylidene fluoride-chlorotrifluoroethylene copolymer.   The non-aqueous solution according to claim 4, wherein the ratio of the vinylidene fluoride-chlorotrifluoroethylene copolymer to the total of the polyvinylidene fluoride and the vinylidene fluoride-chlorotrifluoroethylene copolymer is 25% by mass or more and 75% by mass or less. Electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 4, wherein the proportion of units derived from chlorotrifluoroethylene in the vinylidene fluoride-chlorotrifluoroethylene copolymer is 0.5 mol% or more and 15 mol% or less.