JP5732122B2 - Positive electrode active material, positive electrode, and lithium ion secondary battery - Google Patents

Description

  The present invention relates to a positive electrode active material and a positive electrode of a lithium ion secondary battery, and a lithium ion secondary battery.

  Lithium-ion secondary batteries, especially when used in plug-in hybrid vehicle batteries, are low in cost, low in volume, and lightweight, while maintaining high safety that does not cause battery ignition or rupture due to exothermic reactions. And higher output are desired. For this reason, a lithium ion secondary battery is required to have a high capacity and high safety, and a positive electrode material is required to satisfy such a requirement.

  Patent Document 1 describes a lithium transition metal oxide as a positive electrode active material of a lithium battery. In this lithium transition metal oxide, the ratio of Li to the transition metal is 1.00 to 1.08.

The battery described in Patent Document 2, the composition formula _{Li f Co g Ni h Mn j} M1 k O (2-m) X1 n (X1 is, F, at least one selected from the group consisting of Cl and Br .f, g, h, j, k, m and n are 0.8 ≦ f ≦ 1.2, 0 ≦ g <1, 0 <h ≦ 1, 0 ≦ j <1, 0 ≦ k ≦ 0.1, g + h + j + k = 1, −0.1 ≦ m ≦ 0.2, 0 ≦ n ≦ 0.1) and the like, and a cyclic carbonate derivative having a halogen atom High temperature characteristics are improved by using a separator impregnated with an electrolyte solution containing.

In the lithium secondary battery described in Patent Document 3, the composition formula Li _a Ni _1- bc M ¹ _b M ² _c O ₂ (0.95 ≦ a ≦ 1.05, 0.01 ≦ b ≦ 0.10). 0.10 ≦ c ≦ 0.20, M ¹ is at least ^one element selected from Al, B, Y, Ce, Ti, Sn, V, Ta, Nb, W, and Mo. M ² is Co, Mn , One or more elements selected from Fe). The Li content of this positive electrode active material is represented by a, and 0.95 ≦ a ≦ 1.05.

JP 2010-47466 A JP 2006-332020 A JP 2000-323143 A

  Conventional positive electrode active materials for lithium ion secondary batteries have not achieved the characteristics required for batteries for plug-in hybrid vehicles, that is, high capacity and high safety.

  For example, when the ratio of Li to the transition metal is 1.00 to 1.08 as in the positive electrode active material described in Patent Document 1, capacity reduction due to element substitution cannot be sufficiently compensated. Further, for example, in the case of the positive electrode active material described in Patent Document 2, in the case of a large battery used for a plug-in hybrid vehicle, the Ni content in the transition metal layer must be increased, but heat generation is reduced and safety is increased. The ratio of elements such as Mo that improve the ratio is reduced. For this reason, an increase in heat generation is a concern. Moreover, in the positive electrode active material described in Patent Document 3, since the Li content is small, the capacity reduction due to element substitution cannot be sufficiently compensated.

  An object of the present invention is to provide a positive electrode active material and a positive electrode that can achieve a high-capacity and high-safety lithium ion secondary battery, and to provide a high-capacity and high-safety lithium-ion secondary battery.

The positive electrode active material according to the present invention has a composition formula Li _{1.1 + x} Ni _a M1 _b M2 _c O ₂ (M1 represents Co or Co and Mn, M2 represents Mo, W, or Nb; −0.07 ≦ x ≦ 0.1, 0.6 ≦ a ≦ 0.9, 0.05 ≦ b ≦ 0.38, 0.02 ≦ c ≦ 0.06). Features.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material and positive electrode which can achieve a high capacity | capacitance and a highly safe lithium ion secondary battery can be provided. Furthermore, a high capacity and high safety lithium ion secondary battery can be provided.

The graph which shows the result of the differential scanning calorimetry of the prototype battery in Example 1 and Comparative Example 1. Sectional drawing of a lithium ion secondary battery.

Lithium ion secondary batteries are required to have high capacity and high safety in order to be used in batteries for plug-in hybrid vehicles. In the lithium ion secondary battery, this characteristic is closely related to the properties of the positive electrode material, particularly the positive electrode active material. In the layered positive electrode active material represented by the composition formula LiMO ₂ (M is a transition metal), it is necessary to increase the Ni content in the transition metal layer in order to obtain a high capacity.

  However, a positive electrode active material with a high Ni content has low structural stability in a charged state. Therefore, when the temperature of the battery rises due to an internal short circuit or the like, oxygen released from the positive electrode reacts with the electrolytic solution at a relatively low temperature, and a large exothermic reaction occurs. This exothermic reaction may cause the battery to ignite or rupture.

The positive electrode active material according to the present invention solves such a problem, and the composition formula Li _{1.1 + x} Ni _a M1 _b M2 _c O ₂ (M1 represents Co or Co and Mn, M2 Represents Mo, W, or Nb, −0.07 ≦ x ≦ 0.1, 0.6 ≦ a ≦ 0.9, 0.05 ≦ b ≦ 0.38, 0.02 ≦ c ≦ 0. 06)).

  The Ni content in the transition metal layer is preferably 70 to 80% (0.7 ≦ a ≦ 0.8), and the M2 content is preferably 3 to 5% (0.03 ≦ c ≦ 0.05). .

  The positive electrode according to the present invention uses a positive electrode active material represented by the above composition formula. The lithium ion secondary battery according to the present invention includes a positive electrode capable of inserting and extracting lithium, a negative electrode capable of inserting and extracting lithium, and a separator, and the positive electrode according to the present invention is used as the positive electrode.

  A positive electrode active material having a high Ni content can provide a high capacity, but has a drawback of low thermal stability in a charged state. Therefore, Mo, W, or Nb was added to the positive electrode active material having a high Ni content to improve the thermal stability in the charged state. Mo, W, and Nb are elements that can reduce the maximum heat generation value and improve the thermal stability of the charged state.

  Since the positive electrode active material according to the present invention has a large Ni content and does not contain an additive element (Mo, W, or Nb), the calorific value when the temperature is raised together with the electrolytic solution is greatly reduced. The possibility of ignition and rupture when the battery is heated can be reduced, and safety can be improved.

  By using this positive electrode active material, it is possible to provide a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery that are less likely to ignite or rupture when heated and have improved safety.

  Here, the Li content of the positive electrode active material, that is, the ratio of Li to the transition metal (1.1 + x in the above composition formula) is 1.03 or more and 1.2 or less (−0.07 ≦ x ≦ 0.1). ). If it is less than 1.03 (x <−0.07), the amount of Li present in the Li layer is small and the capacity is lowered. When the ratio is larger than 1.2 (x> 0.1), the amount of transition metal in the composite oxide decreases, and the capacity decreases. A preferable Li content is 1.05 or more and 1.15 or less (−0.05 ≦ x ≦ 0.05).

  The Ni content of the positive electrode active material is represented by a in the above composition formula, and 0.6 ≦ a ≦ 0.9. When a <0.6, the content of Ni that mainly contributes to the charge / discharge reaction decreases, and the capacity decreases. When a> 0.9, the content of other elements (especially M2) decreases, and the thermal stability decreases. Preferably, 0.7 ≦ a ≦ 0.8.

  The content of M1 in the positive electrode active material is represented by b in the above composition formula, and 0.05 ≦ b ≦ 0.38. When b <0.05, the Coulomb efficiency is lowered. When b> 0.38, the content of Ni mainly contributing to the charge / discharge reaction is decreased, and the capacity is decreased.

  The content of M2 in the positive electrode active material is represented by c in the above composition formula, and 0.02 ≦ c ≦ 0.06. If c <0.02, the low thermal stability of the charged state cannot be improved. When c> 0.06, the crystal structure becomes unstable and the capacity decreases. Preferably, 0.03 ≦ c ≦ 0.05.

(Preparation of positive electrode active material)
A method for producing a positive electrode active material used in Examples and Comparative Examples described later will be described. In Examples and Comparative Examples, 29 types of positive electrode active materials were produced as described in Table 1 shown later.

  Nickel oxide and cobalt oxide were used as raw materials. Furthermore, one or two of manganese dioxide, molybdenum oxide, tungsten oxide, niobium oxide, magnesium oxide, zirconium oxide, and titanium oxide were selected and used in accordance with the composition described in Table 1. These oxides were weighed so as to have a predetermined atomic ratio, and pure water was added to form a slurry.

  The slurry was pulverized with a zirconia bead mill until the average particle size became 0.2 μm. In this slurry, a polyvinyl alcohol (PVA) solution was converted to a solid content ratio of 1 wt. %, And further mixed for 1 hour, and then granulated and dried by a spray dryer.

  Lithium hydroxide and lithium carbonate were added to the granulated particles so that the ratio of Li to transition metal was 1.1: 1.

  Next, the powder obtained by adding lithium hydroxide and lithium carbonate to the granulated particles was fired at 750 ° C. for 10 hours to form crystals having a layered structure. Thereafter, this crystal was crushed to obtain a positive electrode active material. After removing coarse particles having a particle size of 30 μm or more by classification, a positive electrode was produced using this positive electrode active material.

  The method for producing the positive electrode active material according to the present invention is not limited to the above method, and other methods such as a coprecipitation method may be used.

(Preparation of positive electrode)
A method for manufacturing the positive electrode used in Examples and Comparative Examples will be described. In Examples and Comparative Examples, 29 types of positive electrodes were produced using 29 types of positive electrode active materials produced as described above.

  The positive electrode active material and the carbon-based conductive agent were weighed to a mass ratio of 85: 10.7 and mixed using a mortar. A mixed material of a positive electrode active material and a conductive agent and a binder dissolved in N-methyl-2-pyrrolidone (NMP) were mixed at a mass ratio of 95.7: 4.3 to obtain a slurry.

The uniformly mixed slurry was applied onto an aluminum current collector foil having a thickness of 20 μm, dried at 120 ° C., and compression-molded with a press so that the electrode density was 2.7 g / cm ^3. Got.

  Thereafter, the electrode plate was punched into a disk shape having a diameter of 15 mm to produce a positive electrode.

(Production of prototype battery)
In Examples and Comparative Examples, 29 types of prototype batteries were manufactured using 29 types of positive electrodes manufactured as described above.

The negative electrode was produced using metallic lithium. As the non-aqueous electrolyte, 1.0 mol / liter of LiPF ₆ was dissolved in a mixed solvent of EC (ethylene carbonate) and DMC (dimethyl carbonate) at a volume ratio of 1: 2.

  Table 1 shows the metal composition ratio of the positive electrode active materials synthesized in Examples and Comparative Examples. Table 1 shows the Li content and the various transition metal contents when the total content of transition metals in the positive electrode active material is 100. In Examples and Comparative Examples, 29 types of positive electrode active materials from positive electrode active materials 1 to 29 were produced.

  In Examples 1 to 17 and Comparative Examples 1 to 12, positive electrode active materials 1 to 29 shown in Table 1 were used as positive electrode active materials one by one in order to prepare a positive electrode and a prototype battery, and charging / discharging the prototype battery Tests and differential scanning calorimetry were performed.

(Charge / discharge test)
The prototype battery was initialized by repeating charging and discharging three times at 0.1 C with an upper limit voltage of 4.3 V and a lower limit voltage of 2.7 V. Furthermore, at 0.1 C, charging / discharging with an upper limit voltage of 4.3 V and a lower limit voltage of 2.7 V was performed, and the discharge capacity was measured.

(Differential scanning calorimetry)
The prototype battery was charged to 4.3 V at a constant current / constant voltage, and then the taken out positive electrode was washed with DMC. Thereafter, the positive electrode was punched into a disk shape having a diameter of 3.5 mm, put into a sample pan, 1 μl (liter) of an electrolyte was added, and the sample was sealed.

  The heat generation behavior when this sample was heated from room temperature to 400 ° C. at 5 ° C./min was examined.

  In Tables 2-6, as a result of the charging / discharging test and differential scanning calorimetry in Examples 1-17 and Comparative Examples 1-12, a capacity ratio and a maximum exothermic value ratio are shown. Moreover, the used positive electrode active material and its composition are also shown.

  As a result of the charge / discharge test, for Examples 1-7, 10-17 and Comparative Examples 1, 3, 4, 6-12, the capacity ratio is obtained by dividing the obtained discharge capacity by the discharge capacity of Comparative Example 1. As shown in Table 2, Table 4, Table 5, and Table 6. For Examples 8 and 9 and Comparative Examples 2 and 5, Table 3 shows the capacity ratio obtained by dividing the obtained discharge capacity by the discharge capacity of Comparative Example 2.

  As for the results of differential scanning calorimetry, in Examples 1 to 7, 10 to 17 and Comparative Examples 1, 3, 4, and 6 to 12, the maximum value of heat generation (maximum heat generation value) obtained was the maximum heat generation of Comparative Example 1. The value divided by the value is shown in Table 2, Table 4, Table 5, and Table 6 as the maximum exothermic value ratio. For Examples 8 and 9 and Comparative Examples 2 and 5, Table 3 shows a value obtained by dividing the obtained maximum heat generation value by the maximum heat generation value of Comparative Example 2 as a maximum heat generation value ratio.

  Table 2 will be described. Table 2 is a table comparing Examples 1 to 7 with Comparative Examples 1, 3, 4, 6, and 7. In Examples 1 to 7, the Li content in the positive electrode active material was changed from 103 to 120, and Co was used as M1 and Mo was used as M2 in the composition formula representing the positive electrode active material. Of the transition metals, the Ni content is 80%, the Co content is 16%, and the Mo content is 4%. In the positive electrode active materials of Comparative Examples 1, 3, and 4, the transition metal has a Ni content of 60% and does not contain M2 (Mo, W, or Nb) in the composition formula. In the positive electrode active materials of Comparative Examples 6 and 7, the Ni content is 80%, and Mo is 4% as M2 in the composition formula. The Li contents are 100 and 125, respectively.

  From Table 2, the results that Examples 1-7 had a large discharge capacity and a small maximum heat generation value compared with Comparative Example 1 were obtained. The reason why the discharge capacity shows a large value is considered that the positive electrode active material used in Examples 1 to 7 has a high Ni content of 80% in the transition metal layer. Moreover, it is thought that the maximum exothermic value is small because 4% of the element (Mo) that can improve the thermal stability of the charged state is present in the transition metal layer.

  On the other hand, in Comparative Examples 3, 4, 6, and 7, it was impossible to achieve both improvement of the discharge capacity and reduction of the maximum heat generation value. In Comparative Example 3, since the Li content was as low as 100, the discharge capacity was reduced. In Comparative Example 4, the Li content was 110 and M2 was not included, and the discharge capacity was reduced. The reason for this is considered to be that Li is not taken into the crystal and does not participate in charge / discharge because the Li content is large. On the other hand, in Example 1, although Li content is 110, discharge capacity is large. From this, it can be seen that when M2 is contained, it is better that the Li content is larger. In Comparative Example 6, since the Li content was as low as 100, the discharge capacity was reduced. Comparative Example 7 had a high Li content of 125 and contained 4% Mo as M2, but the discharge capacity was reduced. From this, it can be seen that, even if M2 is contained, if the Li content is too large, Li is not taken into the crystal and the discharge capacity is reduced.

  From the above, when the Li content in the positive electrode active material is 103 to 120 and Mo is used as M2 in the composition formula and 4% of the transition metal is contained, both improvement of the discharge capacity and reduction of the maximum heat generation value can be achieved. all right.

  Table 3 will be described. Table 3 is a table comparing Examples 8 and 9 with Comparative Examples 2 and 5. In Examples 8 and 9, the Li content in the positive electrode active material is 110, Co is used as M1 in the composition formula representing the positive electrode active material, and Mo is used as M2. Of the transition metals, the Ni content is 70% in Example 8 and 60% in Example 9, the Co content is 26% in Example 8, and 36% in Example 9, and the Mo content Both amounts are 4%. In the positive electrode active material of Comparative Example 2, the content of Ni in the transition metal is 50% and does not contain M2 (Mo, W, or Nb) in the composition formula. In the positive electrode active material of Comparative Example 5, the Ni content is 50%, and Mo is 4% as M2 in the composition formula.

  From Table 3, the results that Examples 8 and 9 had a larger discharge capacity and a smaller maximum heat generation value than those of Comparative Example 2 were obtained. The reason why the discharge capacity shows a large value is considered that the positive electrode active materials used in Examples 8 and 9 have a high Ni content of 70% and 60%, respectively, in the transition metal layer. Moreover, it is thought that the maximum exothermic value is small because 4% of Mo that can improve the thermal stability of the charged state was present in the transition metal layer.

  On the other hand, in Comparative Example 5, it was impossible to achieve both an improvement in discharge capacity and a reduction in the maximum heat generation value. In Comparative Example 5, the maximum heat generation value was reduced because 4% of Mo was contained as M2, but the discharge capacity was lowered because the Ni content was as low as 50%.

  From the above, when Mo is used as M2 in the composition formula and 4% of the transition metal is contained, if the Ni content in the transition metal layer in the positive electrode active material is 60% or more, the discharge capacity It has been found that both improvement of the value and reduction of the maximum heat generation value can be achieved.

  Table 4 will be described. Table 4 is a table comparing Examples 10 and 11 with Comparative Examples 8 to 10. In Examples 10 and 11, the Li content in the positive electrode active material is 110, and Co is used as M1 in the composition formula representing the positive electrode active material. Of the transition metals, the Ni content is 80% and the Co content is 16%. Further, as M2 of the composition formula representing the positive electrode active material, W is used in Example 10 and Nb is used in Example 11. The contents of W and Nb in the transition metal are both 4%. In the positive electrode active materials of Comparative Examples 8 to 10, the contents of Li, Ni, and Co are the same as those in Examples 10 and 11. However, as M2, Mg is compared in Comparative Example 8, Zr is compared in Comparative Example 9, and In Example 10, Ti is used.

  Table 4 shows that Examples 10 and 11 have a larger discharge capacity and a smaller maximum heat generation value than Comparative Example 1. The reason why the discharge capacity shows a large value is considered that the positive electrode active material used in Examples 10 and 11 has a high Ni content of 80% in the transition metal layer. Further, the reason why the maximum heat generation value is small is considered to be that 4% of elements (W, Nb) that can reduce the maximum heat generation value and improve the thermal stability of the charged state were present in the transition metal layer.

  On the other hand, in Comparative Examples 8 to 10, it was impossible to achieve both improvement of the discharge capacity and reduction of the maximum heat generation value. Compared to Comparative Example 1, Comparative Examples 8 to 10 have a maximum heat generation value reduced by only a few percent. Although the positive electrode active material in Comparative Examples 8 to 10 contains Mg, Zr, or Ti, since it does not contain Mo, W, or Nb that can reduce the maximum heat generation value, the maximum heat generation value should be reduced. I can't. Since the positive electrode active materials in Examples 10 and 11 and Examples 1 to 7 contain Mo, W, or Nb, the maximum heat generation value is reduced by 50% or more.

  From the above, it was found that when the positive electrode active material contains Mo, W, or Nb, the maximum heat generation value can be reduced and the discharge capacity can be improved. Therefore, even if W or Nb is contained as M2 in the composition formula, the maximum heat generation value can be reduced and the discharge capacity can be improved as in the case where Mo is contained as M2.

  Table 5 will be described. Table 5 is a table comparing Examples 12 and 13 with Comparative Examples 11 and 12. In any example, the Li content in the positive electrode active material is 110, Co is used as M1 in the composition formula representing the positive electrode active material, and the Ni content of the transition metal is 80%. In Examples 12 and 13 and Comparative Example 12, Mo was used as M2 in the composition formula representing the positive electrode active material, but Comparative Example 11 does not contain M2. The Mo content of the transition metal is 2% in Example 12, 6% in Example 13, and 8% in Comparative Example 12.

  From Table 5, the results that Examples 12 and 13 had a larger discharge capacity and a smaller maximum heat generation value than those of Comparative Example 1 were obtained. The reason why the discharge capacity shows a large value is considered that the positive electrode active material used in Examples 12 and 13 has a high Ni content of 80% in the transition metal layer. Moreover, it is considered that the maximum exothermic value is small because Mo that can improve the thermal stability of the charged state is present in the transition metal layer at 2% or 6%.

  On the other hand, in Comparative Examples 11 and 12, it was impossible to achieve both improvement of the discharge capacity and reduction of the maximum heat generation value. Since the positive electrode active material in Comparative Example 11 does not contain Mo that can reduce the maximum heat generation value, the maximum heat generation value cannot be reduced. Since the positive electrode active material in Comparative Example 12 contains a large amount of Mo that is not involved in charge / discharge at 8%, the discharge capacity was reduced.

  From the above, it was found that the content of Mo used for reducing the maximum heat generation value is preferably 2 to 6% of the transition metal in consideration of the results of Examples 1 to 9. As can be seen from the results of Examples 10 and 11, W or Nb may be used instead of Mo. Therefore, the content of M2 (Mo, W, or Nb) in the composition formula of the positive electrode active material is a transition metal. It can be seen that 2 to 6% is good.

  Table 6 will be described. Table 6 is a table comparing Examples 14-17. In Examples 14 to 17, the Li content in the positive electrode active material is 110, the Ni content of the transition metal is 80%, and Mn and Co are used as M1 in the composition formula representing the positive electrode active material. Mo was used as M2. In Examples 1 to 13, only Co was used as M1, but in Examples 14 to 17, a part of Co was replaced with Mn. In Examples 14 to 17, the Mn content is 2%, 4%, 6%, and 8%, respectively, and the Co content is 14%, 12%, 10%, and 8%, respectively. The Mo content is 4% in any of Examples 14-17.

  From Table 6, the results that Examples 14-17 had a large discharge capacity and a small maximum heat generation value were obtained as compared with Comparative Example 1. The reason why the discharge capacity shows a large value is considered that the positive electrode active materials used in Examples 14 to 17 have a high Ni content of 80% in the transition metal layer. Moreover, it is thought that the maximum exothermic value is small because 4% of Mo that can improve the thermal stability of the charged state was present in the transition metal layer.

  From the above, it has been found that even when Mn and Co are used as M1 in the composition formula representing the positive electrode active material and Mo is used as M2, it is possible to achieve both improvement of the discharge capacity and reduction of the maximum heat generation value. As can be seen from the results of Examples 10 and 11, W or Nb may be used as M2 instead of Mo.

  From the results shown in Tables 2 to 6, the Li content in the positive electrode active material was 103 to 120, the Ni content in the transition metal layer was 60 to 80%, and M1 in the composition formula representing the positive electrode active material Co is used, or Mn and Co are used, the content of M1 in the transition metal layer is 16 to 36%, Mo, W, or Nb is used as M2 in the composition formula, and the content of M2 in the transition metal layer It has been found that when the amount is 2 to 6%, it is possible to achieve both improvement of the discharge capacity and reduction of the maximum heat generation value.

  The preferable content of Li is 105 to 115. The content of Ni can be increased within a range where the thermal stability does not decrease, and can be set to 60 to 90%. A preferable content of Ni is 70 to 80%. The content of M1 can be reduced within a range where the crystal structure does not become unstable, and can be increased within a range where the content of Ni does not decrease and the capacity does not decrease. For this reason, content of M1 can be 5 to 38%. A preferable content of M2 is 3 to 5%.

  FIG. 1 is a graph showing the results of differential scanning calorimetry of prototype batteries in Example 1 and Comparative Example 1. The horizontal axis represents temperature, and the vertical axis represents heat flow. The result of Example 1 is denoted by reference numeral 1, and the result of Comparative Example 1 is denoted by numeral 2. As can be seen from FIG. 1, the prototype battery according to Example 1 generally generates less heat than the prototype battery according to Comparative Example 1. From this, it can be seen that the positive electrode active material 1 used in Example 1 has a smaller maximum exothermic value due to an exothermic reaction than the positive electrode active material 18 used in Comparative Example 1, and exhibits high safety.

  FIG. 2 is a cross-sectional view of a lithium ion secondary battery according to an embodiment of the present invention. The lithium ion secondary battery 12 shown in FIG. 2 includes an electrode having a positive electrode plate 3 coated with a positive electrode material on both sides of a current collector, a negative electrode plate 4 coated with a negative electrode material on both sides of the current collector, and a separator 5. Provide a group. In this embodiment, the positive electrode plate 3 and the negative electrode plate 4 are wound through a separator 5 to form a wound electrode group. This wound body is inserted into the battery can 9.

  The negative electrode plate 4 is electrically connected to the battery can 9 via the negative electrode lead piece 7. A sealing lid 8 is attached to the battery can 9 via a packing 10. The positive electrode plate 3 is electrically connected to the sealing lid portion 8 via the positive electrode lead piece 6. The wound body is insulated by the insulating plate 11.

  The electrode group may not be a wound body as shown in FIG. 2, but may be a laminated body in which the positive electrode plate 3 and the negative electrode plate 4 are laminated via the separator 5.

  By using a positive electrode produced by applying a positive electrode material containing the positive electrode active material shown in the present embodiment as the positive electrode plate 3 of the lithium ion secondary battery 12, a high capacity and high safety lithium ion secondary battery is obtained. be able to. Therefore, according to the present invention, it is possible to provide a positive electrode active material, a positive electrode, and a lithium ion secondary battery that can achieve high capacity, high output, and high safety required for a battery for a plug-in hybrid vehicle.

  The present invention can be used for a positive electrode active material and a positive electrode of a lithium ion secondary battery, and a lithium ion secondary battery, and in particular, can be used for a lithium ion secondary battery for a plug-in hybrid vehicle.

  DESCRIPTION OF SYMBOLS 1 ... As a result of differential scanning calorimetry of the prototype battery by Example 1, 2 ... As a result of differential scanning calorimetry of the prototype battery by the comparative example 1, 3 ... Positive electrode plate, 4 ... Negative electrode plate, 5 ... Separator, 6 ... Positive electrode lead Pieces: 7 ... Negative electrode lead piece, 8 ... Sealing lid, 9 ... Battery can, 10 ... Packing, 11 ... Insulating plate, 12 ... Lithium ion secondary battery.

Claims (5)

Compositional formula Li _{1.1 + x} Ni _a M1 _b M2 _c O ₂
(M1 represents Co or Co and Mn, M2 represents at least one selected from the group consisting of Mo, W, and Nb, and 0 <x <0.1, 0.6 ≦ (a ≦ 0.9, 0.05 ≦ b ≦ 0.38, 0.02 ≦ c ≦ 0.06)
In the represented, the positive electrode active material, characterized in Rukoto used in the positive electrode for a lithium ion secondary battery.   The positive electrode active material according to claim 1, wherein 0.7 ≦ a ≦ 0.8.   The positive electrode active material according to claim 1, wherein 0.03 ≦ c ≦ 0.05. Using the positive electrode active material of claim 1, wherein a positive electrode, characterized in Rukoto used a lithium ion secondary battery. In a lithium ion secondary battery comprising a positive electrode capable of occluding and releasing lithium, a negative electrode capable of occluding and releasing lithium, and a separator,
The said positive electrode is a positive electrode of Claim 4, The lithium ion secondary battery characterized by the above-mentioned.

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