JP2009218112A - Nonaqueous electrolyte secondary battery and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure that a nonaqueous electrolyte secondary battery that employs a transition metal oxide containing low-cost lithium for a positive electrode active material has superior electrical discharge properties. <P>SOLUTION: The nonaqueous electrolyte secondary battery, comprising a positive electrode containing a transition metal oxide which contains lithium, expressed by a general expression Li<SB>1+x</SB>Ni<SB>a</SB>Mn<SB>b</SB>M<SB>c</SB>O<SB>2+d</SB>as a positive electrode active material; a negative electrode, containing a negative electrode active material other than metal lithium; and a nonaqueous electrolyte, having lithium ion conductivity is activated, by performing charging, such that the potential of the positive electrode will be in the range of 4.4 to 4.6 V (vs. Li/Li<SP>+</SP>) relative to metallic lithium. In the expression, M is at least one kind of element selected from among a group of Na, K, B, F, Mg, Al, Ti, Cr, V, Fe, Cu, Zn, Nb, Mo, Zr, Sn and W, and satisfies the condition of x+a+b+c=1, 0<x≤0.1, 0.7≤a/b≤1.3, 0≤c≤0.05, -0.1≤d≤0.1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a nonaqueous electrolyte secondary battery comprising a positive electrode including a lithium-containing transition metal oxide as a positive electrode active material, a negative electrode including a negative electrode active material other than metallic lithium, and a nonaqueous electrolyte having lithium ion conductivity. In particular, the lithium-containing transition metal oxide in which the main component of the transition metal is composed of two elements of nickel and manganese is used as the positive electrode active material, and the cost of the positive electrode active material is reduced. Even when a positive electrode active material is used, it is characterized in that a non-aqueous electrolyte secondary battery excellent in high rate discharge characteristics can be obtained.

  In recent years, mobile information terminals such as mobile phones, camcorders, notebook personal computers and the like have been rapidly reduced in size and weight, and there is a demand for higher capacity of batteries used as a driving power source.

  In order to meet such demands, in recent years, as a new secondary battery with high output and high energy density, a non-aqueous electrolyte is used, and lithium ions are moved between the positive electrode and the negative electrode to charge and discharge. Non-aqueous electrolyte secondary batteries designed to perform the above have come to be widely used.

  In recent years, the use of non-aqueous electrolyte secondary batteries as high-output power supplies such as power supplies for tools and hybrid automobiles has been studied. Discharge during high-rate discharge of non-aqueous electrolyte secondary batteries. There is a need to increase capacity.

Here, in the non-aqueous electrolyte secondary battery as described above, a lithium-containing transition metal oxide mainly composed of cobalt such as lithium cobaltate LiCoO ₂ is mainly used as the positive electrode active material of the positive electrode. .

  However, cobalt used in the above positive electrode active material is a scarce resource, and there are problems such as high cost and difficulty in stable supply, especially when used as a power source for electric vehicles. However, since a large amount of cobalt is required, there is a problem that the cost of the power source becomes very high.

  For this reason, in recent years, as a positive electrode active material that can be supplied inexpensively and stably, a positive electrode active material using nickel or manganese as a main material instead of cobalt has been studied.

For example, lithium nickelate LiNiO ₂ having a layered structure is expected as a material capable of obtaining a large discharge capacity, but has the drawbacks of poor thermal stability and poor safety and a large overvoltage.

Further, lithium manganate LiMn ₂ O ₄ having a spinel structure has the advantage of being rich in resources and inexpensive, but has a low energy density and that manganese elutes in a non-aqueous electrolyte under a high temperature environment. There were drawbacks.

  Therefore, in recent years, lithium-containing transition metal oxides having a layered structure in which the main component of the transition metal is composed of two elements of nickel and manganese have attracted attention from the viewpoint of low cost and excellent thermal stability. Has been.

  For example, in Patent Document 1, the energy density is almost the same as that of lithium cobaltate, and safety is lowered like lithium nickelate, or manganese is a non-aqueous electrolyte in a high temperature environment like lithium manganate. Lithium composite oxide having a rhombohedral structure that contains nickel and manganese as a positive electrode active material that does not elute in, and has an atomic ratio error of nickel and manganese within 10 atomic% Things have been proposed.

  However, in the case of the lithium-containing transition metal oxide shown in Patent Document 1, the high rate charge / discharge characteristics are remarkably inferior to lithium cobaltate, and it is used as a power source that requires high output such as an electric vehicle. There was a problem that it was difficult.

  Patent Document 2 proposes a single-phase cathode material in which a part of the nickel and manganese is replaced with cobalt in a lithium-containing transition metal oxide having a layered structure containing at least nickel and manganese.

  However, in the case of the single-phase cathode material disclosed in Patent Document 2, when the amount of cobalt that substitutes a part of nickel and manganese increases, there arises a problem that the cost increases as described above, while the cobalt that is substituted. When the amount is reduced, there is a problem that the high rate charge / discharge characteristics are greatly deteriorated.

  Moreover, in patent document 3, in order to reduce the internal resistance of a nonaqueous electrolyte secondary battery and to improve a high rate charge / discharge characteristic, it has a layered structure which consists of a transition metal containing lithium, nickel, and manganese. A positive electrode active material has been proposed in which a metal compound (metal stearate) such as Al, Mg, Sn, Ti, Zn, and Zr is surface-modified on a composite oxide.

However, even when the positive electrode active material disclosed in Patent Document 3 is used, there is still a problem that the high rate charge / discharge characteristics cannot be sufficiently improved.
JP 2007-12629 A Japanese Patent No. 3571671 JP-A-2005-346955

  The present invention relates to a nonaqueous electrolyte secondary battery comprising a positive electrode including a lithium-containing transition metal oxide as a positive electrode active material, a negative electrode including a negative electrode active material other than metallic lithium, and a nonaqueous electrolyte having lithium ion conductivity. In particular, the above-described positive electrode active material contains lithium having a layered structure in which the main component of the transition metal is composed of two elements of nickel and manganese. Using a transition metal oxide, the cost of the positive electrode active material is reduced, and even when the cost of the positive electrode active material is reduced in this way, a nonaqueous electrolyte secondary battery excellent in high rate discharge characteristics can be obtained. Doing so is a challenge.

In the present invention, in order to solve the above-described problems, the general formula Li _{1 + x} Ni _a Mn _b M _c O _{2 + d} (where M is Na, K, B, F, Mg, Al, Ti). , Cr, V, Fe, Cu, Zn, Nb, Mo, Zr, Sn, and W, x + a + b + c = 1, 0 <x ≦ 0.1, 0.7 ≦ a /B≦1.3, 0 ≦ c ≦ 0.05, −0.1 ≦ d ≦ 0.1.), And a positive electrode containing a lithium-containing transition metal oxide represented by A non-aqueous electrolyte secondary battery including a negative electrode containing a negative electrode active material other than metallic lithium and a non-aqueous electrolyte having lithium ion conductivity is used. The positive electrode has a potential of 4.4 to 4.6 V based on metallic lithium. The battery was activated by being charged so as to be in the range of (vs. Li ^/ Li ⁺ ).

  Here, in the above lithium-containing transition metal oxide, the one in which the composition ratio a of nickel Ni and the composition ratio b of manganese Mn satisfy the condition of 0.7 ≦ a / b ≦ 1.3 is used. When the value of a / b exceeds 1.3, the proportion of Ni increases and the thermal stability decreases. On the other hand, when the value of a / b becomes less than 0.7, the proportion of Mn increases. This is because the impurity layer is generated and the capacity is reduced. Particularly, in order to improve the thermal stability and suppress the capacity reduction, a material satisfying the condition of 0.9 ≦ a / b ≦ 1.1 is used. It is more preferable.

  In addition, in the above lithium-containing transition metal oxide, a material in which x in the composition ratio (1 + x) of lithium Li satisfies the condition of 0 <x ≦ 0.1 is used when the output characteristic is 0 <x. On the other hand, when x> 0.1, the alkali remaining on the surface of the lithium-containing transition metal oxide increases, and gelation occurs in the slurry and a redox reaction occurs in the process of manufacturing the battery. This is because the amount of transition metal decreases and the capacity decreases, and more preferably, a metal that satisfies the condition of 0.05 ≦ x ≦ 0.1 is used.

  In the above lithium-containing transition metal oxide, d in the composition ratio (2 + d) of oxygen O satisfies the condition of −0.1 ≦ d ≦ 0.1. This is to prevent the metal oxide from being in an oxygen deficient state or an oxygen-excess state and damaging its crystal structure.

In addition, when the non-aqueous electrolyte secondary battery is activated as described above, the positive electrode is charged in the range of 4.4 to 4.6 V (vs. Li / Li ⁺ ) with respect to metal lithium. When the positive electrode is charged so that the potential of the positive electrode is 4.4 V or higher with respect to the metal lithium, not only nickel but also manganese in the lithium-containing transition metal oxide is oxidized, and the positive electrode active material is improved. It is thought that the characteristics are improved. On the other hand, if charging is performed until the potential of the positive electrode exceeds 4.6 V on the basis of metallic lithium, the above-described oxidative decomposition reaction of the nonaqueous electrolyte becomes remarkable, and the performance of the battery deteriorates.

In addition, when charging and discharging the nonaqueous electrolyte secondary battery of the present invention, charging and discharging are generally performed in a range where the charging potential of the positive electrode is 4.2 to 4.3 V (vs. Li / Li ⁺ ) based on metallic lithium. However, in activating the non-aqueous electrolyte secondary battery, as described above, the positive electrode was charged to a high potential that was 4.4 to 4.6 V (vs. Li / Li ⁺ ) with respect to the metallic lithium. In such a case, even if a negative electrode active material other than metallic lithium is used, metallic lithium may be deposited on the negative electrode and the battery may be deteriorated.

For this reason, in the non-aqueous electrolyte secondary battery of the present invention, the ratio of the positive electrode active material in the positive electrode to the negative electrode active material in the negative electrode is such that the potential of the positive electrode is 4.4 V (vs. Li / Li ⁺ ) based on metallic lithium. Charging until the ratio of the negative electrode charging capacity to the positive electrode charging capacity in the range of 1 to 1.35 in the range of 1 to 1.35 and the positive electrode potential is 4.5 V (vs. Li / Li ⁺ ) with respect to metallic lithium. The ratio of the charge capacity of the negative electrode to the charge capacity of the positive electrode in the range of 1-1.20, and the positive electrode when charged until the potential of the positive electrode is 4.6 V (vs. Li / Li ⁺ ) with respect to metallic lithium The ratio of the negative electrode charge capacity to the charge capacity is preferably in the range of 1 to 1.10. Note that the negative electrode charge capacity is the maximum charge capacity that can be accepted without destroying the structure of the negative electrode active material.

  In the present invention, when the particle size of the lithium-containing transition metal oxide used for the positive electrode active material is too large, the discharge performance is deteriorated. On the other hand, when the particle size is too small, the reaction with the non-aqueous electrolyte is performed. Therefore, it is preferable to use a primary particle having an average particle size of 0.5 μm or more and 2 μm or less, and a secondary particle having an average particle size of 5 μm or more and 15 μm or less. .

  In addition, the positive electrode active material of the nonaqueous electrolyte secondary battery according to the present invention is not particularly limited as long as the above-described lithium-containing transition metal oxide is a main component. It is also possible to use a material in which other oxide particles are attached or coated on the surface. Furthermore, the above lithium-containing transition metal oxide and other positive electrode active materials can be mixed and used. As the other positive electrode active material to be mixed, lithium can be reversibly inserted and desorbed. It is not particularly limited as long as it is a compound. For example, it is preferable to use a layered structure capable of inserting and extracting lithium while maintaining a stable crystal structure, a spinel structure, or an olivine structure.

  Further, in the nonaqueous electrolyte secondary battery of the present invention, the negative electrode active material used for the negative electrode is not particularly limited as long as it is capable of reversibly occluding and releasing lithium other than metallic lithium. A material, a metal alloyed with lithium, an alloy material, a metal oxide, or the like can be used. From the viewpoint of material cost, it is preferable to use a carbon material for the negative electrode active material. For example, natural graphite, artificial graphite, mesophase pitch-based carbon fiber (MCF), mesocarbon microbeads (MCMB), coke, hard carbon Fullerenes, carbon nanotubes, and the like can be used. In particular, from the viewpoint of improving the high rate charge / discharge characteristics, it is preferable to use a carbon material obtained by coating a graphite material with low crystalline carbon.

  In the non-aqueous electrolyte secondary battery of the present invention, as the non-aqueous solvent used for the non-aqueous electrolyte, a known non-aqueous solvent that has been conventionally used in non-aqueous electrolyte secondary batteries can be used, for example, In addition, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, and chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate can be used. In particular, it is preferable to use a mixed solvent of a cyclic carbonate and a chain carbonate as a non-aqueous solvent having a low viscosity, a low melting point and a high lithium ion conductivity, and the volume ratio of the cyclic carbonate and the chain carbonate in the mixed solvent is A range of 2/8 to 5/5 is preferable.

  An ionic liquid can also be used as the non-aqueous solvent of the non-aqueous electrolyte. In this case, the cation species and the anion species are not particularly limited, but low viscosity, electrochemical stability, hydrophobic properties are not limited. From the viewpoint, a combination using a pyridinium cation, an imidazolium cation, or a quaternary ammonium cation as the cation and a fluorine-containing imide anion as the anion is particularly preferable.

Moreover, as a solute used for the non-aqueous electrolyte, a known lithium salt that is conventionally used in a non-aqueous electrolyte secondary battery can be used. As such a lithium salt, a lithium salt containing one or more elements among P, B, F, O, S, N, and Cl can be used. Specifically, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (C ₂ F ₅ SO ₂ ) Lithium salts such as ₃ , LiAsF ₆ , LiClO ₄ and mixtures thereof can be used. In particular, LiPF ₆ is preferably used in order to enhance the high rate charge / discharge characteristics and durability of the nonaqueous electrolyte secondary battery.

  Further, in the non-aqueous electrolyte secondary battery of the present invention, the separator interposed between the positive electrode and the negative electrode prevents a short circuit due to contact between the positive electrode and the negative electrode and impregnates the non-aqueous electrolyte, The material is not particularly limited as long as the material can obtain ion conductivity. For example, a polypropylene or polyethylene separator, a polypropylene-polyethylene multilayer separator, or the like can be used.

In the present invention, the positive electrode active material in the positive electrode includes a lithium-containing transition metal in which the main component of the transition metal represented by the general formula Li _{1 + x} Ni _a Mn _b M _c O _{2 + d} is composed of nickel and manganese. Since this non-aqueous electrolyte secondary battery is activated by charging the non-aqueous electrolyte secondary battery with a positive electrode potential in the range of 4.4 to 4.6 V based on metallic lithium, the above lithium-containing transition metal is activated by this charging. Not only nickel in the oxide but also manganese was oxidized to improve the positive electrode active material, and the high rate discharge characteristics in the nonaqueous electrolyte secondary battery were improved.

  Hereinafter, the non-aqueous electrolyte secondary battery according to the present invention will be specifically described with reference to examples. In the non-aqueous electrolyte secondary battery according to this example, the main component of the transition metal is nickel and the positive electrode active material. By using a comparative example, it will be clarified that high-rate discharge characteristics are improved when a lithium-containing transition metal oxide composed of two elements with manganese is used. The nonaqueous electrolyte secondary battery of the present invention is not limited to those shown in the following examples, and can be implemented with appropriate modifications within the scope not changing the gist thereof.

Example 1
In Example 1, in preparing the positive electrode active material, Li ₂ CO ₃ and Ni _0.50 Mn _0.50 (OH) ₂ obtained by the coprecipitation method were mixed at a predetermined ratio, and these were mixed at 1000 ° C. in the air. As a lithium-containing transition metal oxide represented by the above general formula, Li _0.6 Ni _0.47 Mn _0.47 O ₂ having a layered structure in which the transition metal element is composed of Ni and Mn was obtained. The average particle size of the primary particles of Li _1.06 Ni _0.47 Mn _0.47 O ₂ thus obtained was about 1 μm, and the average particle size of the secondary particles was about 7 μm.

Then, the positive electrode active material and a vapor grown carbon fiber as a conductive agent (VGCF), N-methyl-2-pyrrolidone solution of polyvinylidene fluoride as a binder consisting of the above Li _1.06 Ni _0.47 Mn _0.47 O ₂ Are adjusted so that the mass ratio of the positive electrode active material, the conductive agent and the binder is 92: 5: 3, and these are kneaded to prepare a positive electrode mixture slurry, which is made of an aluminum foil. It was applied onto a positive electrode current collector, dried, and then rolled with a rolling roller, and an aluminum current collecting tab was attached thereto to produce a positive electrode.

As shown in FIG. 2, the positive electrode produced as described above is used as the working electrode 11, while metallic lithium is used for the counter electrode 12 and the reference electrode 13 serving as the negative electrode, and ethylene is used as the non-aqueous electrolyte 14. LiPF ₆ was dissolved to a concentration of 1 mol / l in a mixed solvent in which carbonate, methyl ethyl carbonate, and dimethyl carbonate were mixed at a volume ratio of 3: 3: 4, and 1% by mass of vinylene carbonate was further dissolved. A three-electrode test cell was prepared using the above.

In Example 1, the above-described three-electrode test cell was subjected to a current density of 0.2 mA / cm ² , and the potential of the positive electrode serving as the working electrode was 4.4 V with respect to the reference electrode using metallic lithium. The battery was charged until it became (vs. Li ^/ Li ⁺ ), and further activated by charging at a constant voltage of 0.04 mA at a constant voltage of 4.4 V.

(Example 2)
In Example 2, a three-electrode test cell produced in the same manner as in Example 1 above was used, and the above-mentioned three-electrode test cell became a working electrode at a current density of 0.2 mA / cm ^2. The battery is charged until the potential of the positive electrode becomes 4.5 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium, and further constant at this constant voltage of 4.5 V until the current value becomes 0.04 mA. It was activated by voltage charging.

(Example 3)
In Example 3, a three-electrode test cell produced in the same manner as in Example 1 above was used, and the above-mentioned three-electrode test cell became a working electrode at a current density of 0.2 mA / cm ^2. The battery is charged until the potential of the positive electrode becomes 4.6 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium, and further, this constant voltage of 4.6 V is constant until the current value becomes 0.04 mA. It was activated by voltage charging.

(Comparative Example 1)
In Comparative Example 1, a three-electrode test cell produced in the same manner as in Example 1 was used, and the above-mentioned three-electrode test cell became a working electrode at a current density of 0.2 mA / cm ^2. The battery is charged until the potential of the positive electrode becomes 4.3 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium, and the current value is constant until the current value becomes 0.04 mA at the constant voltage of 4.3 V. It was activated by voltage charging.

Next, in each of the three-electrode test cells activated in Examples 1 to 3 and Comparative Example 1 activated as described above, the potential of the positive electrode serving as the working electrode is 0.2 mA / cm ^2. The battery was discharged to 2.5 V (vs. Li ^/ Li ⁺ ) with respect to a reference electrode using metallic lithium.

Then, after activating and discharging each of the three-electrode test cells of Examples 1 to 3 and Comparative Example 1 as described above, the positive electrode serving as a working electrode at a current density of 0.2 mA / cm ^2. Is charged until the potential becomes 4.3 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium, and the constant voltage until the current value becomes 0.04 mA at the constant voltage of 4.3 V. After charging, the battery is discharged at a low current density of 0.2 mA / cm ² until the potential of the positive electrode serving as the working electrode becomes 2.5 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium. Thus, the discharge capacity Q _L at a low rate was obtained.

Next, in each of the three-electrode test cells, the potential of the positive electrode serving as the working electrode is 4.3 V (vs. vs. current) with a current density of 0.2 mA / cm ² with respect to the reference electrode using metallic lithium. Li / Li ⁺ ), and further at a constant voltage of 4.3 V until the current value reaches 0.04 mA, and then at a high current density of 100.04 mA / cm ² , the working electrode Then, discharge was performed until the potential of the positive electrode becomes 2.5 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium, and the discharge capacity Q _H at a high rate was obtained.

Then, from the discharge capacity Q _L at the low rate and the discharge capacity Q _H at the high rate obtained as described above, the three-electrode test cells of Examples 1 to 3 and Comparative Example 1 are obtained by the following formula. The discharge load factor (%) was determined and the results are shown in Table 1 below.

Discharge load factor (%) = (Q _H / Q _L ) × 100

As a result, Li _1.06 Ni _0.47 Mn _0.47 O ₂ , which is a lithium-containing transition metal oxide that satisfies the conditions represented by the above general formula, was used as the positive electrode active material, and the positive electrode potential used as the working electrode was metal lithium. In Examples 1 to 3, which were activated by charging in a range of 4.4 to 4.6 V (vs. Li / Li ⁺ ) with respect to the reference electrode, the potential of the positive electrode serving as the working electrode was Compared to that of Comparative Example 1 which was activated by charging to 4.3 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium, the discharge load factor was improved and the high rate Discharge characteristics were improved.

(Comparative Examples 2 and 3)
In Comparative Examples 2 and 3, the lithium-containing transition metal oxide of the positive electrode active material contains Co as a transition metal element in addition to Ni and Mn, and the conditions of the lithium-containing transition metal oxide represented by the above general formula are as follows. A three-electrode test cell was prepared in the same manner as in Example 1 except that Li _1.05 Ni _0.46 Mn _0.46 Co _0.03 O ₂ was used.

Then, in activating the above three-electrode test cell, in Comparative Example 2, the potential of the positive electrode serving as the working electrode at a current density of 0.20.04 mA / cm ² is applied to the reference electrode using metallic lithium. On the other hand, the battery is charged until it reaches 4.6 V (vs. Li ^/ Li ⁺ ), and further activated at a constant voltage of 4.6 V until the current value reaches 0.04 mA. The battery was charged until it reached 4.3 V (vs. Li ^/ Li ⁺ ), and was further activated by constant voltage charging at a constant voltage of 4.3 V until the current value reached 0.04 mA.

(Comparative Examples 4 and 5)
In Comparative Examples 4 and 5, the lithium-containing transition metal oxide of the positive electrode active material contains Co as a transition metal element in addition to Ni and Mn, and the conditions of the lithium-containing transition metal oxide represented by the above general formula are as follows. A three-electrode test cell was prepared in the same manner as in Example 1 except that _unfilled Li _1.05 Ni _0.38 Mn _0.38 Co _0.19 O ₂ was used.

Then, in activating the above-described three-electrode test cell, in Comparative Example 4, the potential of the positive electrode serving as the working electrode at a current density of 0.20.04 mA / cm ² becomes a reference electrode using metallic lithium. On the other hand, the battery was charged until it reached 4.6 V (vs. Li ^/ Li ⁺ ), and further activated at a constant voltage of 4.6 V until the current value reached 0.04 mA. The battery was charged until it reached 4.3 V (vs. Li ^/ Li ⁺ ), and was further activated by constant voltage charging at a constant voltage of 4.3 V until the current value reached 0.04 mA.

(Comparative Examples 6 and 7)
In Comparative Examples 6 and 7, the lithium-containing transition metal oxide of the positive electrode active material contains Co as a transition metal element in addition to Ni and Mn, and the conditions for the lithium-containing transition metal oxide represented by the above general formula are as follows: A three-electrode test cell was produced in the same manner as in Example 1 except that _unfilled Li _1.06 Ni _0.33 Mn _0.28 Co _0.33 O ₂ was used.

Then, in activating the above three-electrode test cell, in Comparative Example 6, the potential of the positive electrode serving as the working electrode at a current density of 0.20.04 mA / cm ² is applied to the reference electrode using metallic lithium. On the other hand, the battery was charged until it reached 4.6 V (vs. Li ^/ Li ⁺ ), and further activated at a constant voltage of 4.6 V until the current value reached 0.04 mA. The battery was charged until it reached 4.3 V (vs. Li ^/ Li ⁺ ), and was further activated by constant voltage charging at a constant voltage of 4.3 V until the current value reached 0.04 mA.

(Comparative Examples 8 and 9)
In Comparative Examples 8 and 9, as the lithium-containing transition metal oxide of the positive electrode active material, the lithium-containing transition metal represented by the above general formula, which contains Ni, Co, and Al as transition metal elements and does not contain Mn A three-electrode test cell was prepared in the same manner as in Example 1 except that Li _1.02 Ni _0.81 Co _0.13 Al _0.04 O ₂ not satisfying the oxide conditions was used.

Then, in activating the above-described three-electrode test cell, in Comparative Example 8, the potential of the positive electrode serving as the working electrode at a current density of 0.20.04 mA / cm ² becomes the reference electrode using metallic lithium. On the other hand, the battery was charged until it reached 4.6 V (vs. Li ^/ Li ⁺ ), and further activated at a constant voltage of 4.6 V until the current value reached 0.04 mA. The battery was charged until it reached 4.3 V (vs. Li ^/ Li ⁺ ), and was further activated by constant voltage charging at a constant voltage of 4.3 V until the current value reached 0.04 mA.

Next, in each of the three-electrode test cells of Comparative Examples 2 to 9 activated as described above, the potential of the positive electrode serving as the working electrode is metal lithium at a current density of 0.2 mA / cm ² . After being discharged to 2.5 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode, the discharge capacity Q _L at the low rate and the discharge capacity Q _H at the high rate are the same as in the above case. The discharge load factor (%) in each of the three-electrode test cells of Comparative Examples 2 to 9 was determined by the above formula, and the results are shown in Table 2 below.

As a result, the positive electrode active material contains Co as a transition metal element in addition to Ni and Mn, and also contains Ni, Co and Al, and does not contain Mn, but does not satisfy the conditions shown in the above general formula. When the contained transition metal oxide was used, it was activated by being charged so that the potential of the positive electrode serving as the working electrode was 4.6 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium. In Comparative Examples 2, 4, 6, and 8, the positive electrode serving as the working electrode is charged and charged so that the potential of the positive electrode is 4.3 V (vs. Li ^/ Li ⁺ ) with respect to the reference electrode using metallic lithium. Compared to those of Comparative Examples 3, 5, 7, and 9, the discharge load factor was reduced and the high rate discharge characteristics were reduced, and the conditions shown in the above general formula for the positive electrode active material Examples 1-3 using a lithium-containing transition metal oxide satisfying The case of Comparative Examples 1 was supposed to reverse the result.

For this reason, when the positive electrode is charged and activated so that the potential of the positive electrode is in the range of 4.4 to 4.6 V (vs. Li / Li ⁺ ) with respect to metallic lithium, the discharge load factor is improved and increased. It has been found that the improvement in rate discharge characteristics is a characteristic effect when a lithium-containing transition metal oxide satisfying the condition represented by the above general formula is used for the positive electrode active material.

  Moreover, in any of the above Comparative Examples 2 to 9, since Co is contained in the positive electrode active material, compared with the positive electrode active material used in the above Examples 1 to 3, the positive electrode active material There was a problem that the cost was high.

  In the three-electrode test cells in Examples 1 to 3, metallic lithium was used for the counter electrode serving as the negative electrode. However, when an actual nonaqueous electrolyte secondary battery was manufactured, metallic lithium was used for the negative electrode. In order to prevent precipitation, a material other than metallic lithium is used as the negative electrode active material.

Further, in producing a non-aqueous electrolyte secondary battery using a negative electrode active material other than metallic lithium as described above, the ratio of the positive electrode active material in the positive electrode to the negative electrode active material in the negative electrode is determined as follows. The ratio of the charge capacity of the negative electrode to the charge capacity of the positive electrode when charged to 4.4 V (vs. Li / Li ⁺ ) based on the metal lithium is in the range of 1-1.35, and the potential of the positive electrode is based on the metal lithium The ratio of the charge capacity of the negative electrode to the charge capacity of the positive electrode when charged to 4.5 V (vs. Li ^/ Li ⁺ ) is in the range of 1 to 1.20, and the potential of the positive electrode is 4.6 V (based on metallic lithium). vs. Li ^/ Li ⁺ ) When the ratio of the charge capacity of the negative electrode to the charge capacity of the positive electrode when charged to be in the range of 1 to 1.10. 4.4 to 4.6 (Vs.Li/Li ⁺⁾ to a high potential to be allowed to charge even when activated, without that the battery is deteriorated by metal lithium is precipitated on the anode, also to contain extra negative electrode active material Therefore, the battery capacity is not reduced.

It is a schematic explanatory drawing of the three-electrode type test cell which used the positive electrode produced in Examples 1-3 and Comparative Examples 1-9 of this invention for the working electrode.

Explanation of symbols

11 Working electrode (positive electrode)
12 Counter electrode (negative electrode)
13 Reference electrode 14 Non-aqueous electrolyte

Claims (8)

Formula _{Li 1 + x Ni a Mn b} M c O 2 + d ( wherein, M is Na, K, B, F, Mg, Al, Ti, Cr, V, Fe, Cu, Zn, Nb, Mo, At least one element selected from the group consisting of Zr, Sn, and W, x + a + b + c = 1, 0 <x ≦ 0.1, 0.7 ≦ a / b ≦ 1.3, 0 ≦ c ≦ 0.05, A positive electrode containing a lithium-containing transition metal oxide represented by -0.1 ≦ d ≦ 0.1 as a positive electrode active material, a negative electrode containing a negative electrode active material other than metallic lithium, and lithium ion conduction A positive non-aqueous electrolyte, and activated by being charged so that the potential of the positive electrode is in a range of 4.4 to 4.6 V (vs. Li / Li ⁺ ) with respect to metallic lithium. Non-aqueous electrolyte secondary battery characterized.   2. The nonaqueous electrolyte secondary battery according to claim 1, wherein a lithium-containing nickel / manganese composite oxide in which c in the general formula is 0 is used as the positive electrode active material. 3. Secondary battery. 3. The nonaqueous electrolyte secondary battery according to claim 1, wherein the ratio of the positive electrode active material in the positive electrode to the negative electrode active material in the negative electrode is such that the potential of the positive electrode is 4.4 V (vs. Li / Li ⁺ ratio ranges of charge capacity 1 to 1.35 of the negative electrode to the charge capacity of the positive electrode when the charged until), 4.5V at a potential of the positive electrode metallic lithium reference (vs.Li/Li ⁺ ) Until the ratio of the negative electrode charge capacity to the positive electrode charge capacity in the range of 1 to 1.20 when charged until the positive electrode potential is 4.6 V (vs. Li / Li ⁺ ) on the basis of metallic lithium. A nonaqueous electrolyte secondary battery characterized in that a ratio of a negative electrode charge capacity to a positive electrode charge capacity when charged is in a range of 1 to 1.10.   4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material is a carbon material. 5.   5. The nonaqueous electrolyte secondary battery according to claim 1, wherein an average particle size of primary particles of the lithium-containing transition metal oxide used for the positive electrode active material is 0.5 μm or more and 2 μm. A nonaqueous electrolyte secondary battery having a secondary particle average particle size of 5 μm or more and 15 μm or less.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein vinylene carbonate is contained in the nonaqueous electrolyte at a ratio of 2.0% by mass or less. A non-aqueous electrolyte secondary battery.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the nonaqueous solvent in the nonaqueous electrolyte includes 2/8 to 5/5 of a cyclic carbonate and a chain carbonate. A non-aqueous electrolyte secondary battery using a volume ratio. Formula _{Li 1 + x Ni a Mn b} M c O 2 + d ( wherein, M is Na, K, B, F, Mg, Al, Ti, Cr, V, Fe, Cu, Zn, Nb, Mo, At least one element selected from the group consisting of Zr, Sn, and W, x + a + b + c = 1, 0 <x ≦ 0.1, 0.7 ≦ a / b ≦ 1.3, 0 ≦ c ≦ 0.05, A positive electrode containing a lithium-containing transition metal oxide represented by -0.1 ≦ d ≦ 0.1 as a positive electrode active material, a negative electrode containing a negative electrode active material other than metallic lithium, and lithium ion conduction A non-aqueous electrolyte secondary battery equipped with a non-aqueous electrolyte having such a property that the potential of the positive electrode is in the range of 4.4 to 4.6 V (vs. Li / Li ⁺ ) with respect to metallic lithium. And a method for producing a non-aqueous electrolyte secondary battery.

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