JP5447576B2 - Non-aqueous electrolyte secondary battery positive electrode active material, non-aqueous electrolyte secondary battery positive electrode active material manufacturing method, non-aqueous electrolyte secondary battery positive electrode, and non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery used for a positive electrode of a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery using the positive electrode active material for a non-aqueous electrolyte secondary battery. The present invention relates to a secondary battery positive electrode and a non-aqueous electrolyte secondary battery. In particular, the positive electrode active material used for the positive electrode of the nonaqueous electrolyte secondary battery is improved.

  In recent years, mobile information terminals such as mobile phones, notebook computers, and PDAs have been rapidly reduced in size and weight, and a battery used as a driving power source has been required to have a higher capacity. In order to meet such demands, a non-aqueous electrolyte secondary battery that performs charge / discharge by moving lithium ions between a positive electrode and a negative electrode as a new secondary battery with high output and high energy density is used. Secondary batteries are widely used.

In such a non-aqueous electrolyte secondary battery, as the positive electrode active material in the positive electrode, lithium cobaltate LiCoO ₂ , spinel type lithium manganate LiMn ₂ O ₄ , cobalt-nickel-manganese lithium composite oxide, aluminum-nickel-manganese Lithium composite oxide, aluminum-nickel-cobalt lithium composite oxide, etc. are generally used. In addition, as the negative electrode active material in the negative electrode, a carbon material such as graphite or a material alloyed with lithium such as Si or Sn is used.

  However, in recent years, enhancement of entertainment functions such as video playback and game functions in mobile information terminals has progressed, and power consumption tends to further increase, and further higher capacity and higher performance are required. Therefore, in order to increase the capacity of the nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary battery is charged to a high voltage, and the positive electrode active material and the negative electrode active material filled in the nonaqueous electrolyte secondary battery are reduced. It is conceivable to increase the packing density.

  When the nonaqueous electrolyte secondary battery is charged to a high voltage, the positive electrode active material has strong oxidizing power. Further, the positive electrode active material has a catalytic transition metal (for example, Co, Fe, Ni, Mn, etc.). For this reason, the nonaqueous electrolytic solution reacts and decomposes on the surface of the positive electrode active material. As a result, the cycle characteristics, storage characteristics, and characteristics after continuous charging in the non-aqueous electrolyte secondary battery are greatly reduced, and gas is generated inside the battery and the battery expands. In particular, there is a problem that the deterioration of the non-aqueous electrolyte secondary battery is further increased under a high temperature environment.

  In addition, when the packing density of the positive electrode active material and the negative electrode active material filled in the non-aqueous electrolyte secondary battery is increased, the penetration of the non-aqueous electrolyte in the positive electrode and the negative electrode is deteriorated, and the charge / discharge reaction is appropriately performed. It is not performed, and charge / discharge characteristics are deteriorated. In addition, since the charge / discharge reaction becomes non-uniform, a portion that is locally charged to a high voltage is generated, and the same problem as in the case where the nonaqueous electrolyte secondary battery is charged to a high voltage occurs.

In Patent Document 1, in order to suppress the reaction between the positive electrode active material and the non-aqueous electrolyte during overcharge, a positive electrode in which a rare earth oxide such as La ₂ O ₃ is contained in a composite oxide containing Li or Ni. It has been proposed to use a positive electrode active material in which rare earth oxide particles such as La ₂ O ₃ are attached to the surface of an active material or composite oxide particles containing Li, Ni, or the like.

However, even when the positive electrode active material disclosed in Patent Document 1 is used, when the non-aqueous electrolyte secondary battery is charged to a high voltage and used, the positive electrode active material and the non-aqueous electrolyte still react. In particular, in a high temperature environment, the cycle characteristics, storage characteristics, and characteristics after continuous charging of the nonaqueous electrolyte secondary battery are greatly reduced, and there is a problem that gas is generated inside the battery and the battery expands.

In Patent Document 2, as a positive electrode active _material, Li x CoO ₂ and _{Li y Ni s Co t M u} O 2 contained and the amount of _{Li y Ni s Co t M u} O 2 to the total amount of both 10 It has been proposed to use 45% by weight. _Further, as the M in the _{Li y Ni s Co t M u} O 2, B, Mg, there is shown the case where in addition to Al or the like is included lanthanide elements.

In Patent Document 2, and a solid solution of the element M in the _{Li y Ni s Co t M u} O 2 of the positive electrode active material. However, in such a case, when the nonaqueous electrolyte secondary battery is charged to a high voltage, it is difficult to sufficiently suppress the oxidative decomposition of the nonaqueous electrolyte. For this reason, even when the non-aqueous electrolyte secondary battery is charged to a high voltage even in the one disclosed in Patent Document 2, the cycle characteristics, storage characteristics, and characteristics after continuous charging in the non-aqueous electrolyte secondary battery are still large. There is a problem that gas is generated inside the battery and the battery expands.

  Patent Document 3 discloses oxides, hydroxides, oxyhydroxides, oxycarbonates, and hydroxycarbonates containing various coating elements such as Mg, Al, and Co on a core made of a lithium compound having a predetermined particle size. Those having a surface treatment layer such as the above have been proposed.

However, even the one disclosed in Patent Document 3 still reacts with the positive electrode active material and the non-aqueous electrolyte when the non-aqueous electrolyte secondary battery is charged to a high voltage and used. In particular, in a high temperature environment, the cycle characteristics, storage characteristics, and characteristics after continuous charging of the nonaqueous electrolyte secondary battery are greatly deteriorated, and there is a problem that gas is generated inside the battery and the battery expands.
JP 2005-196992 A Japanese Patent No. 3712251 JP 2002-158011 A

  An object of the present invention is to improve the positive electrode active material used for the positive electrode of the nonaqueous electrolyte secondary battery and suppress the reaction between the positive electrode active material and the nonaqueous electrolyte even when the charging voltage is increased.

  And charge / discharge cycle characteristics at high voltage in non-aqueous electrolyte secondary batteries, storage characteristics and charge / discharge characteristics after storage in a charged state in a high temperature environment, storage characteristics after continuous charging in a high temperature environment, Improve charge / discharge characteristics. It is another object of the present invention to suppress expansion of the battery due to gas generation inside the battery.

In the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, particles of at least one erbium compound selected from erbium hydroxide and erbium oxyhydroxide are formed on the surface of the positive electrode active material particles containing lithium, and water. Particles of at least one ytterbium compound selected from ytterbium oxide and ytterbium oxyhydroxide, particles of at least one terbium compound selected from terbium hydroxide and terbium oxyhydroxide, dysprosium hydroxide and oxyhydroxide At least one dysprosium compound particle selected from dysprosium, at least one holmium compound particle selected from holmium hydroxide and holmium oxyhydroxide, and thulium hydroxide and thulium oxyhydroxide At least And particles of one thulium compound was deposited particles of at least one particle size 100nm following compounds selected from the particles of at least one of lutetium compound selected from lutetium hydroxide oxyhydroxide lutetium.

  By using the positive electrode active material for a non-aqueous electrolyte secondary battery as described above for a non-aqueous electrolyte secondary battery, the positive electrode active material and the non-aqueous electrolysis are caused by deposits on the surface of the positive electrode active material particles when the charging voltage is increased. Reaction with the liquid can be suppressed.

  Here, in order to disperse and adhere the erbium compound particles to the surface of the positive electrode active material particles containing lithium, the erbium compound is preferably erbium oxyhydroxide. Thereby, reaction with a positive electrode active material and a nonaqueous electrolyte can be suppressed further.

  In order to disperse and adhere the ytterbium compound particles to the surface of the positive electrode active material particles containing lithium, it is preferable that the ytterbium compound is ytterbium oxyhydroxide. Thereby, reaction with a positive electrode active material and a non-aqueous electrolyte can be suppressed further.

Here, a positive electrode active material for a non-aqueous electrolyte secondary battery in which particles of at least one erbium compound selected from erbium hydroxide and erbium oxyhydroxide are attached to the surface of lithium-containing positive electrode active material particles. In order to manufacture, a step of adding an erbium salt solution to a solution in which positive electrode active material particles are dispersed to deposit erbium hydroxide on the surface of the positive electrode active material particles, and positive electrode active material particles on which erbium hydroxide is deposited The process of heat-treating is performed. In this case, the pH of the solution in which the positive electrode active material is dispersed in the step of depositing erbium hydroxide on the surface of the positive electrode active material particles is preferably 6 or more.

  This is because the erbium salt does not change to erbium hydroxide when the pH of the solution in which the positive electrode active material is dispersed in the step of depositing erbium hydroxide on the surface of the positive electrode active material particles is less than 6. In particular, in order to appropriately disperse and deposit fine erbium hydroxide on the surface of the positive electrode active material particles, the pH of the solution in which the positive electrode active material is dispersed is preferably in the range of 7-10.

  Here, the temperature at which erbium hydroxide is decomposed to change to erbium oxyhydroxide is about 230 ° C., and the temperature at which this erbium oxyhydroxide is further decomposed to change to erbium oxide is about 440 ° C. When the heat treatment temperature of the positive electrode active material particles on which erbium hydroxide is deposited is set to 440 ° C. or higher, erbium hydroxide changes to erbium oxide and erbium is diffused into the positive electrode active material particles. In this case, it becomes difficult to sufficiently suppress the reaction between the positive electrode active material and the non-aqueous electrolyte, and the charge / discharge characteristics of the positive electrode active material are greatly deteriorated.

  Accordingly, it is preferable that the heat treatment temperature of the positive electrode active material particles on which erbium hydroxide is deposited be less than 440 ° C. Furthermore, in order to further suppress the reaction between the positive electrode active material and the non-aqueous electrolyte by changing erbium hydroxide deposited on the surface of the positive electrode active material particles to erbium oxyhydroxide, the heat treatment temperature is set to 230 ° C. or higher. It is more preferable.

In addition, a positive electrode active material for a non-aqueous electrolyte secondary battery in which particles of at least one ytterbium compound selected from ytterbium hydroxide and ytterbium oxyhydroxide are attached to the surface of lithium-containing positive electrode active material particles is manufactured. In order to achieve this, a step of adding a ytterbium salt solution to a solution in which positive electrode active material particles are dispersed to deposit ytterbium hydroxide on the surface of the positive electrode active material particles; and positive electrode active material particles on which ytterbium hydroxide is deposited The process of heat-treating is performed. In this case, the pH of the solution in which the positive electrode active material is dispersed in the step of depositing ytterbium hydroxide on the surface of the positive electrode active material particles is preferably 6 or more.

When the pH of the solution in which the positive electrode active material is dispersed in the step of depositing ytterbium hydroxide on the surface of the positive electrode active material particles is less than 6, the ytterbium salt does not change to ytterbium hydroxide. In particular, in order to appropriately disperse and deposit fine ytterbium hydroxide on the surface of the positive electrode active material particles, the pH of the solution in which the positive electrode active material is dispersed is preferably in the range of 7 to 10.

  Here, with regard to ytterbium hydroxide, the thermogravimetric analysis was performed by increasing the heat treatment temperature by 5 ° C. per minute. As a result, inflection points of weight change were observed at about 230 ° C. and about 400 ° C. The change became smaller and stable. This is because ytterbium hydroxide starts to be decomposed into ytterbium oxyhydroxide at a temperature of about 230 ° C., and further at a temperature of about 400 ° C., the ytterbium oxyhydroxide starts to be further decomposed and converted into ytterbium oxide. This is probably because ytterbium oxyhydroxide was changed to ytterbium oxide at a temperature of 500 ° C.

  Therefore, when the heat treatment temperature of the positive electrode active material particles on which ytterbium hydroxide is deposited is 400 ° C. or higher, ytterbium hydroxide starts to change to ytterbium oxide, and when 500 ° C. or higher, ytterbium hydroxide changes to ytterbium oxide. The ytterbium is diffused inside the positive electrode active material particles. In this case, it becomes difficult to sufficiently suppress the reaction between the positive electrode active material and the non-aqueous electrolyte, and the charge / discharge characteristics of the positive electrode active material are greatly deteriorated.

  For this reason, the temperature which heat-processes the positive electrode active material particle in which the ytterbium hydroxide was deposited shall be less than 500 degreeC, Preferably it will be less than 400 degreeC. Furthermore, in order to change the ytterbium hydroxide deposited on the surface of the positive electrode active material particles to ytterbium oxyhydroxide and further suppress the reaction between the positive electrode active material and the non-aqueous electrolyte, the heat treatment temperature is 230 ° C. or higher. More preferably.

In addition, a positive electrode active material for a non-aqueous electrolyte secondary battery in which particles of at least one terbium compound selected from terbium hydroxide and terbium oxyhydroxide are attached to the surface of positive electrode active material particles containing lithium is manufactured. In order to achieve this, a step of adding a terbium salt solution to a solution in which the positive electrode active material particles are dispersed to deposit terbium hydroxide on the surface of the positive electrode active material particles; and a positive electrode active material particle on which terbium hydroxide is precipitated are provided. A heat treatment step. In this case, the pH of the solution in which the positive electrode active material is dispersed in the step of depositing terbium hydroxide on the surface of the positive electrode active material particles is preferably 6 or more.

  When the pH of the solution in which the positive electrode active material is dispersed in the step of depositing terbium hydroxide on the surface of the positive electrode active material particles is less than 6, the terbium salt does not change to terbium hydroxide. In particular, in order to appropriately disperse and deposit fine terbium hydroxide on the surface of the positive electrode active material particles, the pH of the solution in which the positive electrode active material is dispersed is preferably in the range of 7 to 10.

  Here, as for terbium hydroxide, the temperature at which terbium hydroxide is decomposed to terbium oxyhydroxide is about 295 ° C., and the temperature at which this terbium oxyhydroxide is further decomposed to change to terbium oxide is about 395. ° C. When the heat treatment temperature of the positive electrode active material particles on which terbium hydroxide is deposited is set to 395 ° C. or higher, terbium hydroxide changes to terbium oxide and terbium is diffused into the positive electrode active material particles. In this case, it becomes difficult to sufficiently suppress the reaction between the positive electrode active material and the non-aqueous electrolyte, and the charge / discharge characteristics of the positive electrode active material are greatly reduced. For this reason, it is preferable that the temperature which heat-processes the positive electrode active material particle in which terbium hydroxide was deposited shall be less than 395 degreeC.

In addition, a positive electrode active material for a non-aqueous electrolyte secondary battery in which particles of at least one dysprosium compound selected from dysprosium hydroxide and dysprosium oxyhydroxide are attached to the surface of the positive electrode active material particles containing lithium is manufactured. In order to achieve this, a step of adding a dysprosium salt solution to a solution in which positive electrode active material particles are dispersed to deposit dysprosium hydroxide on the surface of the positive electrode active material particles, and positive electrode active material particles on which dysprosium hydroxide is precipitated are provided. A heat treatment step. In this case, it is preferable that the pH of the solution in which the positive electrode active material is dispersed in the step of depositing dysprosium hydroxide on the surface of the positive electrode active material particles is 6 or more.

  When the pH of the solution in which the positive electrode active material is dispersed in the step of depositing dysprosium hydroxide on the surface of the positive electrode active material particles is less than 6, the dysprosium salt does not change to dysprosium hydroxide. In particular, in order to appropriately disperse and deposit fine dysprosium hydroxide on the surface of the positive electrode active material particles, the pH of the solution in which the positive electrode active material is dispersed is preferably in the range of 7-10.

  Here, as for dysprosium hydroxide, the temperature at which dysprosium hydroxide is decomposed to change to dysprosium oxyhydroxide is about 275 ° C., and the temperature at which dysprosium oxyhydroxide is further decomposed to change to dysprosium oxide is about 450 ° C. It is. When the heat treatment temperature of the positive electrode active material particles on which dysprosium hydroxide is deposited is set to 450 ° C. or higher, dysprosium hydroxide changes to dysprosium oxide and dysprosium is diffused into the positive electrode active material particles. In this case, it becomes difficult to sufficiently suppress the reaction between the positive electrode active material and the non-aqueous electrolyte, and the charge / discharge characteristics of the positive electrode active material are greatly deteriorated. For this reason, it is preferable that the temperature which heat-processes the positive electrode active material particle in which dysprosium hydroxide was deposited is less than 450 degreeC.

In addition, a positive electrode active material for a non-aqueous electrolyte secondary battery in which particles of at least one holmium compound selected from holmium hydroxide and holmium oxyhydroxide are attached to the surface of positive electrode active material particles containing lithium is manufactured. In order to achieve this, a step of adding a holmium salt solution to a solution in which the positive electrode active material particles are dispersed to deposit holmium hydroxide on the surface of the positive electrode active material particles, and a positive electrode active material particle on which the holmium hydroxide is precipitated are provided. A heat treatment step. In this case, the pH of the solution in which the positive electrode active material is dispersed in the step of depositing holmium hydroxide on the surface of the positive electrode active material particles is preferably 6 or more.

  When the pH of the solution in which the positive electrode active material is dispersed in the step of depositing holmium hydroxide on the surface of the positive electrode active material particles is less than 6, the holmium salt does not change to holmium hydroxide. In particular, in order to appropriately disperse and deposit fine holmium hydroxide on the surface of the positive electrode active material particles, the pH of the solution in which the positive electrode active material is dispersed is preferably in the range of 7-10.

  Here, as for holmium hydroxide, the temperature at which holmium hydroxide is decomposed to change to holmium oxyhydroxide is about 265 ° C., and the temperature at which this holmium oxyhydroxide is further decomposed to change to holmium oxide is about 445 ° C. ° C. When the heat treatment temperature of the positive electrode active material particles on which holmium hydroxide is deposited is set to 445 ° C. or higher, the holmium hydroxide changes to holmium oxide and holmium is diffused into the positive electrode active material particles. In this case, it becomes difficult to sufficiently suppress the reaction between the positive electrode active material and the non-aqueous electrolyte, and the charge / discharge characteristics of the positive electrode active material are greatly deteriorated. For this reason, it is preferable that the temperature which heat-processes the positive electrode active material particle in which holmium hydroxide was deposited shall be less than 445 degreeC.

In addition, a positive electrode active material for a non-aqueous electrolyte secondary battery in which at least one type of thulium compound particle selected from thulium hydroxide and thulium oxyhydroxide is attached to the surface of lithium-containing positive electrode active material particles is manufactured. In the process, a step of adding a thulium salt solution to a solution in which the positive electrode active material particles are dispersed to deposit thulium hydroxide on the surface of the positive electrode active material particles, and heat treating the positive electrode active material particles on which the thulium hydroxide is deposited And performing the process. In this case, the pH of the solution in which the positive electrode active material is dispersed in the step of depositing thulium hydroxide on the surface of the positive electrode active material particles is preferably 6 or more.

When the pH of the solution in which the positive electrode active material is dispersed in the step of depositing thulium hydroxide on the surface of the positive electrode active material particles is less than 6, the thulium salt is not changed to thulium hydroxide. In particular, in order to appropriately disperse and deposit fine thulium hydroxide on the surface of the positive electrode active material particles, the pH of the solution in which the positive electrode active material is dispersed is preferably in the range of 7 to 10.

  Here, regarding thulium hydroxide, the temperature at which thulium hydroxide is decomposed to change to thulium oxyhydroxide is about 250 ° C., and the temperature at which this thulium oxyhydroxide is further decomposed to change to thulium oxide is about 405. ° C. When the heat treatment temperature of the positive electrode active material particles on which thulium hydroxide is deposited is set to 405 ° C. or higher, thulium hydroxide changes to thulium oxide and thulium is diffused into the positive electrode active material particles. In this case, it becomes difficult to sufficiently suppress the reaction between the positive electrode active material and the non-aqueous electrolyte, and the charge / discharge characteristics of the positive electrode active material are greatly deteriorated. For this reason, it is preferable that the temperature which heat-processes the positive electrode active material particle in which thulium hydroxide was deposited shall be less than 405 degreeC.

In addition, a positive electrode active material for a non-aqueous electrolyte secondary battery in which particles of at least one lutetium compound selected from lutetium hydroxide and lutetium oxyhydroxide are attached to the surface of lithium-containing positive electrode active material particles is manufactured. In order to achieve this, a step of adding a lutetium salt solution to a solution in which the positive electrode active material particles are dispersed to deposit lutetium hydroxide on the surface of the positive electrode active material particles, and a positive electrode active material particle on which lutetium hydroxide is precipitated are provided. A heat treatment step. In this case, the pH of the solution in which the positive electrode active material is dispersed in the step of depositing lutetium hydroxide on the surface of the positive electrode active material particles is preferably 6 or more.

  When the pH of the solution in which the positive electrode active material is dispersed in the step of depositing lutetium hydroxide on the surface of the positive electrode active material particles is less than 6, the lutetium salt does not change to lutetium hydroxide.

  Here, as a result of thermogravimetric analysis of lutetium hydroxide, the temperature at which lutetium hydroxide is decomposed into lutetium oxyhydroxide is about 280 ° C., and this lutetium oxyhydroxide is further decomposed into lutetium oxide. The changing temperature was about 405 ° C. When the heat treatment temperature of the positive electrode active material particles on which lutetium hydroxide is deposited is set to 405 ° C. or higher, lutetium hydroxide changes to lutetium oxide and lutetium is diffused into the positive electrode active material particles. In this case, it becomes difficult to sufficiently suppress the reaction between the positive electrode active material and the non-aqueous electrolyte, and the charge / discharge characteristics of the positive electrode active material are greatly deteriorated. For this reason, it is preferable that the temperature which heat-processes the positive electrode active material particle in which lutetium hydroxide was deposited shall be less than 405 degreeC.

  The positive electrode for a nonaqueous electrolyte secondary battery in the present invention uses the positive electrode active material for a nonaqueous electrolyte secondary battery as described above in the present invention.

  In the nonaqueous electrolyte secondary battery according to the present invention, the positive electrode for a nonaqueous electrolyte secondary battery using the positive electrode active material for a nonaqueous electrolyte secondary battery is used as the positive electrode.

  Here, in the non-aqueous electrolyte secondary battery in the present invention, the type of the positive electrode active material containing lithium, the type of the negative electrode active material in the negative electrode, and the type of the non-aqueous electrolyte are not particularly limited and are generally used. Can be used.

Examples of the positive electrode active material include lithium cobalt oxide LiCoO ₂ , spinel type lithium manganate LiMn ₂ O ₄ , cobalt-nickel-manganese lithium composite oxide, aluminum-nickel-manganese lithium composite oxide, aluminum-nickel- Various lithium oxides generally used such as cobalt lithium composite oxide can be used.

  As the negative electrode active material in the negative electrode, for example, a carbon material such as graphite or a material alloyed with lithium such as Si or Sn can be used. In particular, in order to increase the battery capacity, it is preferable to use a material that is alloyed with lithium such as Si having a high capacity.

  As the non-aqueous electrolyte, a solution obtained by dissolving a solute in a non-aqueous solvent can be used. As the non-aqueous solvent in the non-aqueous electrolyte, for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, 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.

Examples of the solute include 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 (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiAsF ₆ , LiClO ₄ , Li ₂ B ₁₀ Cl ₁₀ , Li ₂ B ₁₂ Cl ₁₂ , mixtures thereof, etc. Can be used. In addition to these lithium salts, it is preferable to include a lithium salt having an oxalato complex as an anion. And lithium-bis (oxalato) borate etc. can be used as a lithium salt which uses such an oxalato complex as an anion.

  According to the present invention, the positive electrode active material for a non-aqueous electrolyte secondary battery can be used even when the charge voltage is increased to increase the capacity of the non-aqueous electrolyte secondary battery and used at a high temperature. The reaction between the active material and the non-aqueous electrolyte is prevented.

Moreover, according to the nonaqueous electrolyte secondary battery in the present invention, even when the charge voltage is increased to increase the capacity of the nonaqueous electrolyte secondary battery, the charge / discharge cycle characteristics do not deteriorate.
In addition, according to the nonaqueous electrolyte secondary battery of the present invention, the storage characteristics and charge / discharge characteristics after the nonaqueous electrolyte secondary battery is stored in a charged state in a high temperature environment or after being continuously charged in a high temperature environment are improved. Is done. Furthermore, the expansion of the battery due to gas generation inside the nonaqueous electrolyte secondary battery is suppressed.

  Furthermore, when the erbium compound attached to the surface of the positive electrode active material particles is erbium oxyhydroxide and the ytterbium compound attached to the surface of the positive electrode active material particles is ytterbium oxyhydroxide, a non-aqueous electrolyte solution due to a reaction with the positive electrode active material Can be further prevented, and the above effect is improved.

It is the partial cross section explanatory drawing and schematic perspective view of the flat electrode body produced in the Example and comparative example of this invention. It is a schematic plan view of the nonaqueous electrolyte secondary battery produced in the Example and the comparative example. It is the figure which showed the relationship between the calorie | heat amount and temperature which made the positive electrode in Example A1 and comparative example a1 into the charge condition, and was thermally analyzed with the differential scanning calorimeter (DSC).

Examples of positive electrode active material for nonaqueous electrolyte secondary battery according to the present invention, method for producing positive electrode active material for nonaqueous electrolyte secondary battery, positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery Specific explanation will be given. Further, in the nonaqueous electrolyte secondary battery according to the embodiment of the present invention, the characteristics when the charge voltage is increased to increase the capacity of the nonaqueous electrolyte secondary battery, in particular, stored in a charged state in a high temperature environment. It will be clarified by a comparative example that the storage characteristics, charge / discharge characteristics, etc. are improved after charging or after continuous charging in a high temperature environment. The positive electrode active material for a nonaqueous electrolyte secondary battery, the method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery, the positive electrode for a nonaqueous electrolyte secondary battery, and the nonaqueous electrolyte secondary battery of the present invention are as follows. It is not limited to what was shown in the example, It can implement by changing suitably in the range which does not change the summary.

(Example A1)
In Example A1, a positive electrode, a negative electrode, and a nonaqueous electrolytic solution prepared as described below were used.

[Production of positive electrode]
As the positive electrode active material particles, lithium cobalt oxide in which 0.5 mol% of Mg and Al were dissolved was used. Then, 1000 g of the positive electrode active material particles were put into 3 liters of pure water, and while stirring this, an aqueous erbium nitrate solution in which 5.79 g of erbium nitrate pentahydrate was dissolved in 200 ml of pure water was added. . At this time, a 10% by mass sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and erbium hydroxide was adhered to the surface of the positive electrode active material particles. And this was suction-filtered, the processed material was collected by filtration, and this processed material was dried at 120 degreeC, and the positive electrode active material particle by which erbium hydroxide was disperse | distributed and adhered to the surface was obtained.

  Next, the positive electrode active material particles having erbium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 300 ° C. for 5 hours. As a result, a positive electrode active material in which particles of an erbium compound composed of erbium hydroxide and erbium oxyhydroxide were dispersed and adhered to the surface of the positive electrode active material particles was obtained.

  Here, in this positive electrode active material, the ratio of the erbium element (Er) in the erbium compound adhering to the surface with respect to the positive electrode active material particle which consists of lithium cobaltate was 0.22 mass%. Further, most of the erbium hydroxide adhered to the surface of the positive electrode active material particles was changed to erbium oxyhydroxide.

  Moreover, as a result of observing the positive electrode active material of Example A1 by SEM, most of the particle diameters of the erbium compound particles attached to the surfaces of the positive electrode active material particles were 100 nm or less. In addition, erbium compound particles were dispersed and adhered to the surface of the positive electrode active material particles.

Next, this positive electrode active material, a conductive agent acetylene black, and an N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride as a binder is dissolved are mixed and stirred by a special stirring device (made by Tokushu Kika Co., Ltd .: Combimix). ) To prepare a positive electrode mixture slurry. At this time, the positive electrode active material, the conductive agent, and the binder were in a mass ratio of 95: 2.5: 2.5. And after apply | coating this positive mix slurry uniformly on both surfaces of the positive electrode collector which consists of aluminum foil, this is dried and rolled with a rolling roller, and a positive mix layer is formed on both surfaces of a positive electrode collector A positive electrode was obtained. In addition, the packing density of the positive electrode active material in this positive electrode was 3.60 g / cm ³ .

[Production of negative electrode]
Artificial graphite of negative electrode active material, CMC (carboxymethylcellulose sodium) and SBR (styrene-butadiene rubber) of binder are mixed in an aqueous solution at a mass ratio of 98: 1: 1 to prepare a negative electrode mixture slurry. did. Then, the negative electrode mixture slurry is uniformly applied to both surfaces of the negative electrode current collector made of copper foil, dried, and rolled by a rolling roller, so that a negative electrode mixture layer is formed on both surfaces of the negative electrode current collector. A negative electrode was obtained. The packing density of the negative electrode active material in this negative electrode was 1.75 g / cm ³ .

[Preparation of non-aqueous electrolyte]
In a mixed solvent in which ethylene carbonate and diethyl carbonate, which are nonaqueous solvents, are mixed at a volume ratio of 3: 7, solute LiPF ₆ is dissolved to a concentration of 1.0 mol / liter, and a nonaqueous electrolytic solution is prepared. Produced.

[Production of battery]
As shown in FIGS. 1 (A) and 1 (B), a separator 13 made of a polyethylene microporous membrane permeable to lithium ions is interposed between a positive electrode 11 and a negative electrode 12, and this is pressed. A flat electrode body 10 was produced. Next, as shown in FIG. 2, the flat electrode body 10 was accommodated in a battery container 20 made of an aluminum laminate film, and a non-aqueous electrolyte was added to the battery container 20. And the positive electrode current collection tab 11a provided in the positive electrode 11 and the negative electrode current collection tab 12a provided in the negative electrode 12 were taken out outside, and the opening part of the battery container 20 was sealed. As a result, a flat-type nonaqueous electrolyte secondary battery having a design capacity of 780 mAh when charged to 4.40 V was produced.

(Example A2)
In Example A2, in the production of the positive electrode in Example A1, the positive electrode active material particles having erbium hydroxide dispersed and adhered to the surface were heat-treated at 200 ° C. for 5 hours in an air atmosphere. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material of Example A2, most of the erbium hydroxide attached to the surface of the positive electrode active material particles was not changed to erbium oxyhydroxide, but remained in the state of erbium hydroxide.

(Example A3)
In Example A3, in the production of the positive electrode in Example A1, the positive electrode active material particles having erbium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 400 ° C. for 5 hours. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material of Example A3, most of the erbium hydroxide attached to the surface of the positive electrode active material particles was changed to erbium oxyhydroxide.

(Example A4)
In Example A4, in the production of the positive electrode in Example A1, the positive electrode active material particles in which erbium hydroxide was dispersed and adhered to the surface were terminated by a heat treatment only by drying at 120 ° C. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material of Example A4, erbium hydroxide attached to the surface of the positive electrode active material particles did not change to erbium oxyhydroxide.

(Example A5)
In Example A5, in the production of the positive electrode in Example A1, the amount of erbium nitrate pentahydrate dissolved in 200 ml of pure water was changed to 2.76 g for attaching erbium hydroxide to the surface of the positive electrode active material particles. did. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  Here, in Example A5, the ratio of the erbium element (Er) in the erbium compound adhered to the surface of the positive electrode active material particles made of lithium cobaltate was 0.11% by mass.

(Example A6)
In Example A6, in the production of the positive electrode in Example A1, the amount of erbium nitrate pentahydrate dissolved in 200 ml of pure water was changed to 1.78 g when attaching erbium hydroxide to the surface of the positive electrode active material particles. did. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  Here, in Example A6, the ratio of the erbium element (Er) in the erbium compound adhering to the surface with respect to the positive electrode active material particle which consists of lithium cobaltate was 0.067 mass%.

(Example A7)
In Example A7, in the production of the positive electrode in Example A1, the amount of erbium nitrate pentahydrate dissolved in 200 ml of pure water was changed to 0.93 g when attaching erbium hydroxide to the surface of the positive electrode active material particles. did. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  Here, in Example A7, the ratio of the erbium element (Er) in the erbium compound adhered to the surface of the positive electrode active material particles made of lithium cobalt oxide was 0.035% by mass.

(Comparative Example a1)
In Comparative Example a1, no erbium compound was attached to the surface of the positive electrode active material particles made of lithium cobaltate in the production of the positive electrode in Example A1. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

(Comparative Example a2)
In Comparative Example a2, in preparation of the positive electrode in Example A1, positive electrode active material particles 500 g made of lithium cobaltate and 1.25 g of erbium oxide obtained by pulverizing an erbium oxide reagent until the primary particle diameter becomes 300 nm, A positive electrode active material was prepared by mixing using a mixing processor (manufactured by Hosokawa Micron Corporation: Nobilta) and mechanically attaching erbium oxide to the surface of the positive electrode active material particles made of lithium cobaltate. And the nonaqueous electrolyte secondary battery was produced like the case of Example A1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example a2, the ratio of the erbium element (Er) in the erbium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.22% by mass. It was.

  Moreover, as a result of observing the positive electrode active material of Comparative Example a2 by SEM, erbium oxide was aggregated and adhered to the recessed portion of the positive electrode active material particles, and was not dispersed and adhered to the surface of the positive electrode active material particles. .

(Comparative Example a3)
In Comparative Example a3, a positive electrode active material was produced by changing the amount of erbium oxide having a primary particle diameter of 300 nm in Comparative Example a2 to 5 g. And the nonaqueous electrolyte secondary battery was produced like the case of Example 1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example a3, the proportion of the erbium element (Er) in the erbium compound attached to the surface of the positive electrode active material particles made of lithium cobaltate is 0.87% by mass. there were.

  Further, as a result of observing the positive electrode active material of Comparative Example a3 by SEM, as in Comparative Example a2, erbium oxide is aggregated and attached to the recessed portions of the positive electrode active material particles. It was not dispersed and adhered to the surface.

(Comparative Example a4)
In Comparative Example a4, in the production of the positive electrode in Example A1, the positive electrode active material particles having erbium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 500 ° C. for 5 hours. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Comparative Example a4, erbium hydroxide attached to the surface of the positive electrode active material particles changes to erbium oxide, and part of the erbium is the positive electrode active material particles. It was diffused inside.

(Comparative Example x1)
In Comparative Example x1, in the production of the positive electrode active material in Example A1, 1000 g of the positive electrode active material particles were put into 3 liters of pure water, and 30.9 g of aluminum nitrate nonahydrate was added to pure water while stirring this. An aqueous solution of aluminum nitrate dissolved in was added. At this time, a 10 mass% sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and aluminum hydroxide was adhered to the surface of the positive electrode active material particles.

  Then, this was suction-filtered, the processed material was collected by filtration, and this processed material was dried at 120 ° C. to obtain a positive electrode active material in which an aluminum compound was adhered to the surface of the positive electrode active material particles. And the nonaqueous electrolyte secondary battery was produced like the case of Example A1 except using the positive electrode active material of the comparative example x1.

  Here, in the positive electrode active material of Comparative Example x1, the ratio of the aluminum element (Al) in the aluminum compound attached to the surface of the positive electrode active material particles was 0.22% by mass. The aluminum compound adhered to the surface of the positive electrode active material particles was aluminum hydroxide.

(Comparative Example x2)
In Comparative Example x2, the positive electrode active material obtained as shown in Comparative Example x1 was further heat-treated in an air atmosphere at a temperature of 500 ° C. for 5 hours to obtain a positive electrode active material. And the nonaqueous electrolyte secondary battery was produced like the case of Example A1 except using the positive electrode active material of the comparative example x2.

  Here, in the positive electrode active material in Comparative Example x2, the ratio of the aluminum element (Al) in the aluminum compound attached to the surface of the positive electrode active material particles was 0.22% by mass. Further, the aluminum compound attached to the surface of the positive electrode active material particles was changed to aluminum oxide.

(Comparative Example x3)
In Comparative Example x3, in the production of the positive electrode active material in Comparative Example x1, an aqueous aluminum nitrate solution in which 9.27 g of aluminum nitrate nonahydrate was dissolved in pure water was added, and the heat treatment was only dried at 120 ° C. Other than that was carried out similarly to the comparative example x1, and obtained the positive electrode active material. And the nonaqueous electrolyte secondary battery was produced like the case of Example A1 except using the positive electrode active material of the comparative example x3.

  Here, in the positive electrode active material of Comparative Example x3, the ratio of the aluminum element (Al) in the aluminum compound attached to the surface of the positive electrode active material particles was 0.067% by mass. Moreover, the aluminum compound adhered to the surface of the positive electrode active material particles was in the state of aluminum hydroxide as in Comparative Example x1.

(Comparative Example y1)
In Comparative Example y1, in the production of the positive electrode active material in Example A1, 1000 g of the positive electrode active material particles were put into 3 liters of pure water, and 19.4 g of zinc sulfate heptahydrate was added to the pure water while stirring this. An aqueous solution of zinc sulfate dissolved in was added. At this time, a 10% by mass sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and zinc hydroxide was adhered to the surfaces of the positive electrode active material particles. Then, this was suction-filtered, the processed material was collected by filtration, and this processed material was dried at 120 ° C. to obtain a positive electrode active material in which a zinc compound was adhered to the surface of the positive electrode active material particles. And the nonaqueous electrolyte secondary battery was produced like the case of Example A1 except using the positive electrode active material of the comparative example y1.

  Here, in the positive electrode active material of Comparative Example y1, the ratio of zinc element (Zn) in the zinc compound attached to the surface of the positive electrode active material particles was 0.22% by mass. Further, the zinc compound attached to the surface of the positive electrode active material particles was in the state of zinc oxide.

(Comparative Example z1)
In Comparative Example z1, 6.84 g of cerium nitrate hexahydrate was used in place of 5.79 g of erbium nitrate pentahydrate in the production of the positive electrode active material in Example A1, and otherwise, Example A1 and A positive electrode active material was produced in the same manner. And the nonaqueous electrolyte secondary battery was produced like the case of Example A1 except using the positive electrode active material of the comparative example z1.

  Here, in the positive electrode active material in Comparative Example z1, the ratio of the cerium element (Ce) in the cerium compound attached to the surface of the positive electrode active material particles was 0.22% by mass.

Cerium hydroxide is represented by the chemical formula of CeO ₂ · 2H ₂ O, and as a result of measuring by thermal mass spectrometry at a heating rate of 5 ° C./min, it is up to 110 ° C. to CeO ₂ · 0.5H ₂ O. It decomposed and could not exist stably as cerium hydroxide, and decomposed to CeO ₂ at 280 ° C. For this reason, it is considered that the cerium compound dispersed and adhered to the surface of the positive electrode active material is not in the state of cerium hydroxide or cerium oxyhydroxide.

  Next, the nonaqueous electrolyte secondary batteries of Examples A1 to A7 and Comparative Examples a1 to a4 were charged at a constant current up to 4.40 V, and then charged at a constant voltage of 4.40 V to be initially charged. Here, in the constant current charging, each nonaqueous electrolyte secondary battery was charged to 4.40 V (lithium metal reference 4.50 V) at a constant current of 750 mA at room temperature. In constant voltage charging, charging was performed at a constant voltage of 4.40 V until the current value reached 37.5 mA.

  Each nonaqueous electrolyte secondary battery initially charged in this manner was paused for 10 minutes, and then initially discharged at a constant current of 750 mA until it reached 2.75V. The discharge capacity Qo at this time was measured.

  And the initial charging / discharging efficiency was calculated | required about each nonaqueous electrolyte secondary battery of Example A1-A7 and Comparative Example a4. As a result, in each of the nonaqueous electrolyte secondary batteries of Examples A1 to A7, the initial charge / discharge efficiency was 89%, whereas in the nonaqueous electrolyte secondary battery of Comparative Example a4, the initial charge / discharge efficiency was The efficiency was 86%. This is because, in the case of the non-aqueous electrolyte secondary battery of Comparative Example a4, erbium hydroxide attached to the surface of the positive electrode active material particles changes to erbium oxide, and part of erbium diffuses inside the positive electrode active material particles. It is thought that it was because it was done.

Next, after the initial charge / discharge of each of the nonaqueous electrolyte secondary batteries of Examples A1 to A7 and Comparative Examples a1 to a4 was charged at a constant current to 4.40 V in the room temperature state as in the case of the initial charge. After charging at a constant voltage of 4.40 V, each nonaqueous electrolyte secondary battery was stored in an atmosphere of 60 ° C. for 5 days. Thereafter, each non-aqueous electrolyte secondary battery is cooled to room temperature and 750 m as in the case of the initial discharge.
It discharged until it became 2.75V with the constant current of A, and discharge capacity Q1 after high temperature preservation | save was calculated | required.

  Then, the remaining capacity ratio (%) after high-temperature storage was determined by the following formula (1), and the results are shown in Table 1 below.

Remaining capacity ratio (%) = (Q1 / Qo) × 100 (1)

  Next, each non-aqueous electrolyte secondary battery for which the discharge capacity Q1 after storage at high temperature was obtained was charged at a constant current to 4.40 V at room temperature in the same manner as in the initial charging, and then at a constant voltage of 4.40 V. Charged. And after resting for 10 minutes, it discharged until it became 2.75V with a 750 mA constant current. The charge capacity Qa and the discharge capacity Q2 at this time were determined. And while calculating | requiring the return capacity rate (%) after high temperature preservation | save by following formula (2), charging / discharging efficiency (%) after high temperature preservation | save is calculated | required by following formula (3), The result is shown in following Table 1 It was shown to.

Return capacity ratio (%) = (Q2 / Qo) × 100 (2)
Charging / discharging efficiency (%) = (Q2 / Qa) × 100 (3)

  Moreover, about each nonaqueous electrolyte secondary battery of Example A1-A7 and Comparative Examples a1-a4, the thickness increase amount of each nonaqueous electrolyte secondary battery before and behind preserve | saving for 5 days in 60 degreeC atmosphere as mentioned above The results are shown in Table 1 below.

From Table 1, Examples A1 to A7 using positive electrode active materials in which particles of erbium compound composed of erbium hydroxide and erbium oxyhydroxide were dispersed and adhered to the surface of positive electrode active material particles composed of lithium cobaltate. Each non-aqueous electrolyte secondary battery showed a high value for the remaining capacity ratio, the restored capacity ratio, and the charge / discharge efficiency after high-temperature storage when charged to a high voltage of 4.40V. On the other hand, the non-aqueous electrolyte secondary batteries of Comparative Examples a1 to a4 have a remaining capacity after high-temperature storage when charged to a high voltage of 4.40 V compared to the non-aqueous electrolyte secondary batteries of Examples A1 to A7. The rate, the return capacity rate, and the charge / discharge efficiency all decreased.

  Moreover, regarding the thickness increase amount of the nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary batteries of Comparative Examples a1 and a2 are compared with the nonaqueous electrolyte secondary batteries of Examples A1 to A7 and Comparative Examples a3 and a4. The increase in thickness was small. This is considered to be because in the case of the nonaqueous electrolyte secondary batteries of Comparative Examples a1 and a2, the potential of the positive electrode decreased due to self-discharge in these positive electrodes, and the reaction between the positive electrode active material and the nonaqueous electrolyte solution decreased. .

  Next, each nonaqueous electrolyte secondary battery of Examples A1 to A7 and Comparative Examples a1 to a4, x1 to x3, y1 and z1 was initially charged and discharged, and the initial discharge capacity Qo was measured. The water electrolyte secondary battery was charged in a constant current until it reached 4.40 V at a constant current of 750 mA while being held in a constant temperature bath at 60 ° C., respectively. Then, the high temperature continuous charge test which charges for 3 days in the state which maintained the voltage of 4.40V was done. And the thickness increase amount of each nonaqueous electrolyte secondary battery after the high temperature continuous charge test with respect to the test was calculated | required, and the result was shown in following Table 2.

  In addition, each non-aqueous electrolyte secondary battery after the high-temperature continuous charge test is brought to room temperature and discharged at a constant current of 750 mA until it reaches 2.75 V to obtain the discharge capacity Q3 after the high-temperature continuous charge test for 10 minutes. Paused. And the remaining capacity rate (%) after a high-temperature continuous charge test was calculated | required by following formula (4), and the result was shown in following Table 2.

Remaining capacity ratio (%) = (Q3 / Qo) × 100 (4)

  Furthermore, each non-aqueous electrolyte secondary battery after resting for 10 minutes was charged at a constant current to 4.40 V in the room temperature state as in the case of initial charging, and then charged at a constant voltage at 4.40 V. And after resting for 10 minutes, it discharged until it became 2.75V with a 750 mA constant current. The charge capacity Qb and the discharge capacity Q4 at this time were determined. And while calculating | requiring the return capacity rate (%) after a high-temperature continuous charge test by following formula (5), calculating | requiring the charge / discharge efficiency (%) after a high-temperature continuous charge test by following formula (6), The results are shown in Table 2 below.

Return capacity ratio (%) = (Q4 / Qo) × 100 (5)
Charging / discharging efficiency (%) = (Q4 / Qb) × 100 (6)

  From Table 2, each nonaqueous electrolyte secondary battery of Examples A1 to A7 has a small increase in thickness of the battery after the high-temperature continuous charge test as compared with the nonaqueous electrolyte secondary batteries of Comparative Examples a1 to a4. The residual capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the continuous charge test were greatly improved.

Moreover, each non-aqueous electrolyte secondary battery of Examples A1-A7 is the amount of increase in battery thickness after the high-temperature continuous charge test as compared with the non-aqueous electrolyte secondary batteries of Comparative Examples x1-x3, y1, z1. The residual capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the high-temperature continuous charge test were greatly improved.
This is because the contact between the non-aqueous electrolyte and the positive electrode active material particles is suppressed by adhering particles of an aluminum compound or a zinc compound not involved in charge / discharge to the surface of the positive electrode active material particles. It is considered that the decomposition of the non-aqueous electrolyte on the surface of the positive electrode active material could not be sufficiently suppressed by the contained transition metal having catalytic properties.

  In addition, each nonaqueous electrolyte secondary battery of Example A1 and Comparative Example a1 was charged with a constant current up to 4.40 V in the same manner as in the initial charging, and then charged with a constant voltage at 4.40 V. Then, each of these nonaqueous electrolyte secondary batteries was disassembled and the positive electrode was taken out. Each positive electrode taken out is put in a closed cell made of SUS together with a non-aqueous electrolyte, sealed, heated to 350 ° C. at a rate of 5 ° C./min, and heated by a differential scanning calorimeter (DSC). Analysis was performed to determine the relationship between the amount of heat and temperature, and the results are shown in FIG.

  According to FIG. 3, in the positive electrode in Example A1 and Comparative Example a1, there was almost no difference in the relationship between the amount of heat and the temperature, and the change in thermal stability as shown in Patent Document 3 did not occur.

(Example A8)
In Example A8, in the production of the positive electrode in Example A1, lithium cobalt oxide in which 0.5 mol% of Mg, Al, and Zr were dissolved as positive electrode active material particles was used. Otherwise, in the same manner as in Example A1, a positive electrode was prepared by attaching erbium compound particles to the surface of the positive electrode active material particles, and a nonaqueous electrolyte secondary battery was prepared using this positive electrode. .

(Comparative Example a5)
In Comparative Example a5, in producing the positive electrode in Example A1, the same positive electrode active material particles as in Example A8 were used, and no erbium compound was attached to the surfaces of the positive electrode active material particles. Other than that was carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  And also about each nonaqueous electrolyte secondary battery of Example A8 and Comparative Example a5, it is the same as that of Example A1-A7 and Comparative Examples a1-a4, and the remaining capacity ratio (%) after high temperature storage, high temperature The return capacity ratio after storage (%), the charge / discharge efficiency after high temperature storage (%), and the increase in thickness of the nonaqueous electrolyte secondary battery after high temperature storage were determined. These results are shown in Table 3 below together with the results of the nonaqueous electrolyte secondary batteries of Example A1 and Comparative Example a1.

  Moreover, also about each nonaqueous electrolyte secondary battery of Example A8 and Comparative Example a5, it is the same as that of Example A1-A7 and Comparative Examples a1-a4, and the remaining capacity rate (%) after a high-temperature continuous charge test Then, the return capacity ratio (%) after the high-temperature continuous charge test, the charge / discharge efficiency (%) after the high-temperature continuous charge test, and the thickness increase amount of the nonaqueous electrolyte secondary battery after the high-temperature continuous charge test were determined. These results are shown in Table 4 below together with the results of the nonaqueous electrolyte secondary batteries of Example A1 and Comparative Example a1.

  As a result, similarly to the nonaqueous electrolyte secondary batteries of Examples A1 to A7, the nonaqueous electrolyte secondary battery of Example A8 is stored at a higher temperature than the nonaqueous electrolyte secondary batteries of Comparative Examples a1 and a5. The remaining capacity rate, the return capacity rate, and the charge / discharge efficiency were all improved.

  Further, the non-aqueous electrolyte secondary battery of Example A8 has a much smaller increase in battery thickness after the high-temperature continuous charge test than the non-aqueous electrolyte secondary batteries of Comparative Examples a1 and a5. The remaining capacity ratio, the return capacity ratio, and the charge / discharge efficiency were significantly improved.

  Further, the non-aqueous electrolyte secondary battery of Example A8 has a smaller increase in battery thickness after high-temperature storage than the non-aqueous electrolyte secondary battery of Example A1, and the remaining capacity ratio after high-temperature storage and recovery The capacity ratio and charge / discharge efficiency are further improved, and the remaining capacity ratio and the return capacity ratio after the high-temperature continuous charge test are further improved. In particular, the increase in the thickness of the battery after the high-temperature continuous charge test is very small. It was.

  This is because, as shown in Example A8, a positive electrode active material in which an erbium compound is dispersed and adhered to the surface of positive electrode active material particles made of lithium cobaltate in which Zr is dissolved in addition to Mg and Al. When used, the crystal structure of the positive electrode active material is stabilized by the dissolved Zr. Further, the reaction between the positive electrode active material and the non-aqueous electrolyte is prevented by the erbium compound dispersed and adhered to the surface. And it is thought by these synergistic effects that the thickness increase amount of the battery after a high-temperature continuous charge test greatly decreased.

  In contrast, in the nonaqueous electrolyte secondary battery of Comparative Example a5, the increase in thickness of the battery after the high-temperature continuous charge test did not become smaller than that of the nonaqueous electrolyte secondary battery of Comparative Example a1. As shown in Comparative Example a5, even if positive electrode active material particles made of lithium cobaltate in which Zr is dissolved in addition to Mg and Al are used, the erbium compound is dispersed on the surface of the positive electrode active material particles. In addition, since the positive electrode active material and the nonaqueous electrolytic solution react with each other, the effect of stabilizing the crystal structure of the positive electrode active material due to the solid solution of Zr was not obtained.

(Example B1)
In Example B1, a positive electrode produced as follows was used.

[Production of positive electrode]
As the positive electrode active material particles, lithium cobalt oxide in which 0.5 mol% of Mg and Al were dissolved was used. Then, 1000 g of the positive electrode active material particles were put into 3 liters of pure water, and while stirring this, an aqueous ytterbium nitrate solution in which 5.24 g of ytterbium nitrate trihydrate was dissolved in 200 ml of pure water was added. . At this time, a 10% by mass sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and ytterbium hydroxide was adhered to the surfaces of the positive electrode active material particles.

  And this was suction-filtered, the processed material was collected by filtration, and this processed material was dried at 120 degreeC, and the positive electrode active material particle by which the ytterbium hydroxide was disperse | distributed and adhered to the surface was obtained.

  Next, the positive electrode active material particles having ytterbium hydroxide dispersed and adhered to the surface were heat-treated at a temperature of 300 ° C. for 5 hours in an air atmosphere. As a result, a positive electrode active material in which particles of ytterbium compound composed of ytterbium hydroxide and ytterbium oxyhydroxide were dispersed and adhered to the surface of the positive electrode active material particles was obtained.

  Here, in the positive electrode active material, the ratio of the ytterbium element (Yb) in the ytterbium compound attached to the surface of the positive electrode active material particles made of lithium cobalt oxide was 0.22% by mass. Further, most of the ytterbium hydroxide attached to the surface of the positive electrode active material particles was changed to ytterbium oxyhydroxide.

  Moreover, as a result of observing the positive electrode active material of Example B1 with SEM, most of the ytterbium compound particles adhered to the surface of the positive electrode active material particles had a particle size of 100 nm or less. The ytterbium compound particles were dispersed and attached to the surfaces of the positive electrode active material particles.

Next, a positive electrode active material, a conductive agent acetylene black, and a N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride as a binder is dissolved are mixed and agitated by a special stirrer (made by Tokushu Kika Co., Ltd .: Combimix). Were mixed and stirred to prepare a positive electrode mixture slurry. At this time, the positive electrode active material, the conductive agent, and the binder were in a mass ratio of 95: 2.5: 2.5. And after apply | coating this positive mix slurry uniformly on both surfaces of the positive electrode collector which consists of aluminum foil, this is dried and rolled with a rolling roller, and a positive mix layer is formed on both surfaces of a positive electrode collector A positive electrode was obtained. In addition, the packing density of the positive electrode active material in this positive electrode was 3.60 g / cm ³ .

  A flat nonaqueous electrolyte secondary battery having a design capacity of 780 mAh when charged to 4.40 V was produced in the same manner as in Example A1 except that the above positive electrode was used.

(Example B2)
In Example B2, in the production of the positive electrode in Example B1, the positive electrode active material particles having ytterbium hydroxide dispersed and adhered to the surface were heat-treated at a temperature of 200 ° C. for 5 hours in an air atmosphere. Other than that was carried out similarly to the case of Example B1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Example B1, most of the ytterbium hydroxide attached to the surface of the positive electrode active material particles was not changed to ytterbium oxyhydroxide, but in the ytterbium hydroxide state. It remained.

(Example B3)
In Example B3, in the production of the positive electrode in Example B1, the positive electrode active material particles in which ytterbium hydroxide was dispersed and adhered to the surface were finished by a heat treatment only by drying at 120 ° C. Other than that was carried out similarly to the case of Example B1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the heat treatment of only drying at 120 ° C. as in Example B3, ytterbium hydroxide attached to the surface of the positive electrode active material particles did not change to ytterbium oxyhydroxide.

(Example B4)
In Example B4, in the production of the positive electrode in Example B1, the amount of ytterbium nitrate trihydrate dissolved in 200 ml of pure water was changed to 1.59 g when attaching ytterbium hydroxide to the surface of the positive electrode active material particles. did. Other than that was carried out similarly to the case of Example B1, and produced the nonaqueous electrolyte secondary battery.

  Here, in Example B4, the ratio of the ytterbium element (Yb) in the ytterbium compound attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.067% by mass. Further, most of the ytterbium hydroxide attached to the surface of the positive electrode active material particles was changed to ytterbium oxyhydroxide.

(Comparative Example b1)
In Comparative Example b1, the ytterbium compound was not adhered to the surface of the positive electrode active material particles made of lithium cobaltate in the production of the positive electrode in Example B1. Other than that was carried out similarly to the case of Example B1, and produced the nonaqueous electrolyte secondary battery.

(Comparative Example b2)
In Comparative Example b2, in the production of the positive electrode in Example B1, 500 g of positive electrode active material particles made of lithium cobaltate and 1.25 g of ytterbium oxide obtained by pulverizing ytterbium oxide reagent until the particle diameter of primary particles was 300 nm, Mixing was performed using a mixing processor (manufactured by Hosokawa Micron Corporation: Nobilta). In this way, ytterbium oxide was mechanically attached to the surface of the positive electrode active material particles made of lithium cobaltate to produce a positive electrode active material.

  And the nonaqueous electrolyte secondary battery was produced like the case of Example B1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example b2, the ratio of the ytterbium element (Yb) in the ytterbium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate is 0.22% by mass. there were.

  Moreover, as a result of observing the positive electrode active material of Comparative Example b2 by SEM, ytterbium oxide was aggregated and adhered to the recessed portion of the positive electrode active material particles, and was not dispersed and adhered to the surface of the positive electrode active material particles.

(Comparative Example b3)
In Comparative Example b3, a positive electrode active material was prepared by changing the amount of ytterbium oxide having a primary particle diameter of 300 nm in Comparative Example b2 to 5 g. And the nonaqueous electrolyte secondary battery was produced like the case of Example B1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example b3, the ratio of the ytterbium element (Yb) in the ytterbium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate is 0.87% by mass. there were.

  Further, as a result of observing the positive electrode active material of Comparative Example b3 by SEM, as in Comparative Example b2, ytterbium oxide is aggregated and attached to the recessed portions of the positive electrode active material particles. It was not dispersed and adhered to the surface.

(Comparative Example b4)
In Comparative Example b4, in the production of the positive electrode in Example B1, the positive electrode active material particles in which ytterbium hydroxide was dispersed and adhered to the surface were heat-treated at a temperature of 500 ° C. for 5 hours in an air atmosphere. Other than that was carried out similarly to the case of Example B1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Comparative Example b4, ytterbium hydroxide attached to the surface of the positive electrode active material particles is changed to ytterbium oxide, and part of the ytterbium is positive electrode active material particles. Was diffused inside.

  Next, the nonaqueous electrolyte secondary batteries of Examples B1 to B4 and Comparative Examples b1 to b4 were charged with a constant current up to 4.40 V in the same manner as in the case of the nonaqueous electrolyte secondary batteries of Example A1 and the like. After that, the battery was charged at a constant voltage of 4.40 V and initially charged. Thereafter, each of the initially charged nonaqueous electrolyte secondary batteries was paused for 10 minutes, and then initially discharged at a constant current of 750 mA until it reached 2.75V. The discharge capacity Qo at this time was measured.

  And the initial charging / discharging efficiency was calculated | required about each nonaqueous electrolyte secondary battery of Examples B1-B4 and Comparative Example b4.

  As a result, in each of the nonaqueous electrolyte secondary batteries of Examples B1 to B4, the initial charge / discharge efficiency was 89%, whereas in the nonaqueous electrolyte secondary battery of Comparative Example b4, the initial charge / discharge efficiency was The efficiency was 87%. This is because, in the case of the non-aqueous electrolyte secondary battery of Comparative Example b4, the ytterbium hydroxide attached to the surface of the positive electrode active material particles changes to ytterbium oxide, and part of the ytterbium diffuses inside the positive electrode active material particles. It is thought that it was because it was done.

  Next, the non-aqueous electrolyte secondary batteries of Examples B1 and B2 and Comparative Examples b1 to b4 after the initial charge / discharge were set to 4.40 V in the same manner as the non-aqueous electrolyte secondary batteries of Example A1 and the like. Then, the battery was charged at a constant current up to 4.40V. Each nonaqueous electrolyte secondary battery was stored in an atmosphere at 60 ° C. for 5 days. Thereafter, each non-aqueous electrolyte secondary battery is cooled to room temperature in the same manner as in the case of the non-aqueous electrolyte secondary battery such as Example A1, and discharged to 2.75 V at a constant current of 750 mA. The discharge capacity Q1 after storage was determined. And the residual capacity ratio (%) after high temperature preservation | save was calculated | required by Formula (1), and the result was shown in following Table 5.

  Next, each non-aqueous electrolyte secondary battery whose discharge capacity Q1 after storage at high temperature was determined was charged with a constant current to 4.40 V in the same manner as in the case of the non-aqueous electrolyte secondary battery of Example A1, etc. A constant voltage was charged at 40V. Then, after resting for 10 minutes, the battery was discharged at a constant current of 750 mA until it reached 2.75 V, and the charge capacity Qa and the discharge capacity Q2 at this time were determined. And while calculating | requiring the return capacity rate (%) after high temperature preservation | save by Formula (3), charging / discharging efficiency (%) after high temperature preservation | save was calculated | required by Formula (4), The result was shown in following Table 5.

  Moreover, each nonaqueous electrolyte secondary battery of Examples B1, B2 and Comparative Examples b1 to b4 was increased in thickness before and after being stored for 5 days in an atmosphere at 60 ° C. as described above. The amount was determined and the results are shown in Table 1 below.

  From Table 5, Examples B1 and B2 using positive electrode active materials in which particles of ytterbium hydroxide and ytterbium oxyhydroxide particles were dispersed and adhered to the surface of the positive electrode active material particles made of lithium cobaltate. Each non-aqueous electrolyte secondary battery showed a high value for the remaining capacity ratio, the restored capacity ratio, and the charge / discharge efficiency after high-temperature storage when charged to a high voltage of 4.40V. On the other hand, the non-aqueous electrolyte secondary batteries of Comparative Examples b1 to b4 have a remaining capacity after high-temperature storage when charged to a high voltage of 4.40 V compared to the non-aqueous electrolyte secondary batteries of Examples B1 and B2. The rate, the return capacity rate, and the charge / discharge efficiency all decreased.

  Moreover, regarding the thickness increase amount of the nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary batteries of Comparative Examples b1 and b2 are compared with the nonaqueous electrolyte secondary batteries of Examples B1 and B2 and Comparative Examples b3 and b4. The increase in thickness was small. This is considered to be because in the case of the non-aqueous electrolyte secondary batteries of Comparative Examples b1 and b2, the potential of the positive electrode decreased due to self-discharge in these positive electrodes, and the reaction between the positive electrode active material and the non-aqueous electrolyte decreased. .

  Next, the nonaqueous electrolyte secondary batteries of Examples B1 to B4 and Comparative Examples b1 to b4 were initially charged and discharged, and the initial discharge capacity Qo was measured. Thereafter, a high-temperature continuous charge test was performed on each non-aqueous electrolyte secondary battery in the same manner as in the case of the non-aqueous electrolyte secondary battery such as Example A1. And the thickness increase amount in each nonaqueous electrolyte secondary battery after the high temperature continuous charge test with respect to the high temperature continuous charge test was calculated | required. The results are shown in Table 6 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  In addition, each non-aqueous electrolyte secondary battery after the high-temperature continuous charge test is discharged at room temperature to a constant current of 750 mA until it reaches 2.75 V, and the discharge capacity Q3 after the high-temperature continuous charge test is obtained to rest for 10 minutes. did. And the remaining capacity rate (%) after a high-temperature continuous charge test was calculated | required by Formula (4). The results are shown in Table 6 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

Further, after each non-aqueous electrolyte secondary battery after 10 minutes of rest is charged at a constant current of 750 mA to 4.40 V at room temperature, the current value becomes 37.5 mA at a constant voltage of 4.40 V. The charge capacity Qb was obtained by charging at a constant voltage. Then, each nonaqueous electrolyte secondary battery was paused for 10 minutes. Then, it discharged until it became 2.75V with a constant current of 750 mA, and discharge capacity Q4 was calculated | required. And while calculating | requiring the return capacity rate (%) after a high temperature continuous charge test by Formula (5), the charging / discharging efficiency (%) after a high temperature continuous charge test was calculated | required by Formula (6). The results are shown in Table 6 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  From Table 6, each nonaqueous electrolyte secondary battery in Examples B1 to B4 has a small increase in battery thickness after the high-temperature continuous charge test, compared with the nonaqueous electrolyte secondary batteries in Comparative Examples b1 to b4. The remaining capacity rate, the return capacity rate, and the charge / discharge efficiency after the continuous charge test were also greatly improved.

  Moreover, each nonaqueous electrolyte secondary battery of Example B1-B4 is also compared with the nonaqueous electrolyte secondary battery of Comparative Examples x1-x3, y1 similarly to each nonaqueous electrolyte secondary battery of Examples A1-A7. Thus, the increase in the thickness of the battery after the high-temperature continuous charge test was small, and the remaining capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the high-temperature continuous charge test were also greatly improved.

(Example C1)
In Example C1, a positive electrode produced as follows was used.

[Production of positive electrode]
As the positive electrode active material particles, lithium cobalt oxide in which 0.5 mol% of Mg and Al were dissolved was used. Then, 1000 g of the positive electrode active material particles were put into 3 liters of pure water, and an aqueous terbium nitrate solution in which 6.19 g of terbium nitrate hexahydrate was dissolved in 200 ml of pure water was added while stirring the particles. . At this time, a 10% by mass sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and terbium hydroxide was adhered to the surfaces of the positive electrode active material particles. And this was suction-filtered, the processed material was collected by filtration, and this processed material was dried at 120 degreeC, and the positive electrode active material particle by which terbium hydroxide was disperse | distributed and adhered to the surface was obtained.

Next, the positive electrode active material particles having terbium hydroxide dispersed and adhered to the surface thereof were heat-treated in an air atmosphere at a temperature of 300 ° C. for 5 hours. As a result, a positive electrode active material in which terbium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained.

  In the positive electrode active material of Example C1, the ratio of the terbium element (Tb) in the terbium compound attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.22% by mass. In the terbium compound attached to the surface of the positive electrode active material particles, most of the terbium hydroxide was changed to terbium oxyhydroxide.

  Moreover, as a result of observing the positive electrode active material of Example C1 by SEM, most of the particle diameters of the terbium compound particles attached to the surfaces of the positive electrode active material particles were 100 nm or less. Further, the particles of the terbium compound were dispersed and attached to the surfaces of the positive electrode active material particles.

Next, a positive electrode active material, a conductive agent acetylene black, and a N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride as a binder is dissolved are mixed and agitated by a special stirrer (made by Tokushu Kika Co., Ltd .: Combimix). Were mixed and stirred to prepare a positive electrode mixture slurry. At this time, the positive electrode active material, the conductive agent, and the binder were in a mass ratio of 95: 2.5: 2.5. And after apply | coating this positive mix slurry uniformly on both surfaces of the positive electrode collector which consists of aluminum foil, this is dried and rolled with a rolling roller, and a positive mix layer is formed on both surfaces of a positive electrode collector A positive electrode was obtained. In addition, the packing density of the positive electrode active material in this positive electrode was 3.60 g / cm ³ .

  A flat nonaqueous electrolyte secondary battery having a design capacity of 780 mAh when charged to 4.40 V was produced in the same manner as in Example A1 except that the above positive electrode was used.

(Example C2)
In Example C2, in the production of the positive electrode in Example C1, the positive electrode active material particles having terbium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 200 ° C. for 5 hours. Other than that was carried out similarly to the case of Example C1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Example C2, most of the terbium hydroxide attached to the surface of the positive electrode active material particles was not changed to terbium oxyhydroxide, but in the terbium hydroxide state. It remained.

(Example C3)
In Example C3, in the production of the positive electrode in Example C1, the positive electrode active material particles in which erbium hydroxide was dispersed and adhered to the surface were terminated by a heat treatment only by drying at 120 ° C. Other than that was carried out similarly to the case of Example C1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the heat treatment of only drying at 120 ° C. as in Example C3, the terbium hydroxide attached to the surface of the positive electrode active material particles did not change to terbium oxyhydroxide.

(Example C4)
In Example C4, in making the positive electrode in Example C1, the amount of terbium nitrate hexahydrate dissolved in 200 ml of pure water was changed to 1.91 g for attaching terbium hydroxide to the surface of the positive electrode active material particles. did. Other than that was carried out similarly to the case of Example C1, and produced the nonaqueous electrolyte secondary battery.

  Here, in Example C4, the ratio of the terbium element (Tb) in the terbium compound attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.067% by mass. Further, most of the terbium hydroxide attached to the surface of the positive electrode active material particles was changed to terbium oxyhydroxide.

(Comparative Example c1)
In Comparative Example c1, the terbium compound was not attached to the surface of the positive electrode active material particles made of lithium cobaltate in the production of the positive electrode in Example C1. Other than that was carried out similarly to the case of Example C1, and produced the nonaqueous electrolyte secondary battery.

(Comparative Example c2)
In Comparative Example c2, in the production of the positive electrode in Example C1, 500 g of positive electrode active material particles made of lithium cobaltate and 1.25 g of terbium oxide obtained by pulverizing a terbium oxide reagent until the particle diameter of the primary particles becomes 300 nm, Mixing was performed using a mixing processor (manufactured by Hosokawa Micron Corporation: Nobilta). Thus, terbium oxide was mechanically attached to the surface of the positive electrode active material particles made of lithium cobalt oxide to produce a positive electrode active material.

  And the nonaqueous electrolyte secondary battery was produced like the case of Example C1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example c2, the ratio of the terbium element (Tb) in the terbium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.22% by mass. It was.

  In addition, as a result of observing the positive electrode active material of Comparative Example c2 by SEM, terbium oxide was aggregated and adhered to the recessed portions of the positive electrode active material particles, and was not dispersed and adhered to the surface of the positive electrode active material particles.

(Comparative Example c3)
In Comparative Example c3, a positive electrode active material was prepared by changing the amount of terbium oxide having a primary particle diameter of 300 nm in Comparative Example c2 to 5 g. And the nonaqueous electrolyte secondary battery was produced like the case of Example C1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example c3, the ratio of the terbium element (Tb) in the terbium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.87% by mass. It was.

  Further, as a result of observing the positive electrode active material of Comparative Example c3 by SEM, as in Comparative Example c2, terbium oxide was aggregated and adhered to the dents of the positive electrode active material particles. It was not dispersed and adhered to the surface.

(Comparative Example c4)
In Comparative Example c4, in the production of the positive electrode in Example C1, the positive electrode active material particles having terbium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 500 ° C. for 5 hours. Other than that was carried out similarly to the case of Example C1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Comparative Example c4, terbium hydroxide attached to the surface of the positive electrode active material particles is changed to terbium oxide, and part of the terbium is the positive electrode active material particles. It was diffused inside.

Next, after each of the nonaqueous electrolyte secondary batteries of Examples C1 to C4 and Comparative Examples c1 to c4 was charged with a constant current to 4.40 V as in the case of the nonaqueous electrolyte secondary batteries of Example A1 and the like. The battery was charged at a constant voltage of 4.40 V and initially charged. Thereafter, each of the initially charged nonaqueous electrolyte secondary batteries was paused for 10 minutes, and then initially discharged at a constant current of 750 mA until it reached 2.75V. The discharge capacity Qo at this time was measured. And the initial charge-discharge efficiency was calculated | required about each nonaqueous electrolyte secondary battery of Examples C1-C4 and Comparative Example c4.

  As a result, in each of the nonaqueous electrolyte secondary batteries of Examples C1 to C4, the initial charge / discharge efficiency was 89%, whereas in the nonaqueous electrolyte secondary battery of Comparative Example c4, the initial charge / discharge efficiency was The efficiency was reduced to 86%. This is because, in the case of the nonaqueous electrolyte secondary battery of Comparative Example c4, terbium hydroxide attached to the surface of the positive electrode active material particles changes to terbium oxide, and part of terbium diffuses into the positive electrode active material particles. It is thought that it was because it was done.

  In addition, after the initial charge / discharge, a high-temperature continuous charge test was performed on each non-aqueous electrolyte secondary battery in the same manner as in the case of the non-aqueous electrolyte secondary battery such as Example A1. And the thickness increase amount in each nonaqueous electrolyte secondary battery after the high temperature continuous charge test with respect to the high temperature continuous charge test was calculated | required. The results are shown in Table 7 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  In addition, each non-aqueous electrolyte secondary battery after the high-temperature continuous charge test is discharged at room temperature to a constant current of 750 mA until it reaches 2.75 V, and the discharge capacity Q3 after the high-temperature continuous charge test is obtained to rest for 10 minutes. did. And the remaining capacity rate (%) after a high-temperature continuous charge test was calculated | required by Formula (4). The results are shown in Table 7 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  Further, after each non-aqueous electrolyte secondary battery after 10 minutes of rest is charged at a constant current of 750 mA to 4.40 V at room temperature, the current value becomes 37.5 mA at a constant voltage of 4.40 V. The charge capacity Qb was obtained by charging at a constant voltage. Then, each nonaqueous electrolyte secondary battery was paused for 10 minutes. Then, it discharged until it became 2.75V with a constant current of 750 mA, and discharge capacity Q4 was calculated | required. And while calculating | requiring the return capacity rate (%) after a high temperature continuous charge test by Formula (5), the charging / discharging efficiency (%) after a high temperature continuous charge test was calculated | required by Formula (6). The results are shown in Table 7 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  From Table 7, Examples C1 to C4 using positive electrode active materials in which particles of a terbium compound composed of terbium hydroxide and terbium oxyhydroxide were dispersed and adhered to the surface of the positive electrode active material particles composed of lithium cobaltate. Each non-aqueous electrolyte secondary battery had a small increase in battery thickness after the high-temperature continuous charge test, and also exhibited high values for the remaining capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the high-temperature continuous charge test. On the other hand, the non-aqueous electrolyte secondary batteries of Comparative Examples c1 to c4 have a large increase in battery thickness after the high-temperature continuous charge test, compared to the non-aqueous electrolyte secondary batteries of Examples C1 to C4. The residual capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the test also decreased.

  In addition, the nonaqueous electrolyte secondary batteries of Examples C1 to C4 are also nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1, and z1, similarly to the nonaqueous electrolyte secondary batteries of Examples A1 to A7. In comparison with, the increase in the thickness of the battery after the high-temperature continuous charge test was small, and the remaining capacity ratio, the return capacity ratio and the charge / discharge efficiency after the high-temperature continuous charge test were also greatly improved.

(Example D1)
In Example D1, a positive electrode produced as follows was used.

[Production of positive electrode]
As the positive electrode active material particles, lithium cobalt oxide in which 0.5 mol% of Mg and Al were dissolved was used. Then, 1000 g of the positive electrode active material particles were put into 3 liters of pure water, and an aqueous dysprosium nitrate solution in which 5.89 g of dysprosium nitrate pentahydrate was dissolved in 200 ml of pure water was added while stirring the particles. . At this time, a 10% by mass sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and dysprosium hydroxide was adhered to the surface of the positive electrode active material particles. And this was suction-filtered, the processed material was collected by filtration, and this processed material was dried at 120 degreeC, and the positive electrode active material particle by which the dysprosium hydroxide was disperse | distributed and adhered to the surface was obtained.

  Next, the positive electrode active material particles having dysprosium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 300 ° C. for 5 hours. As a result, a positive electrode active material in which dysprosium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained.

  Here, in this positive electrode active material, the ratio of the dysprosium element (Dy) in the dysprosium compound adhering to the surface with respect to the positive electrode active material particle which consists of lithium cobaltate was 0.22 mass%. Further, in the dysprosium compound attached to the surface of the positive electrode active material particles, most of the dysprosium hydroxide was changed to dysprosium oxyhydroxide.

  Moreover, as a result of observing the positive electrode active material of Example D1 by SEM, most of the particle diameters of the dysprosium compound particles attached to the surfaces of the positive electrode active material particles were 100 nm or less. Further, the dysprosium compound particles were dispersed and adhered to the surface of the positive electrode active material particles.

Next, a positive electrode active material, a conductive agent acetylene black, and a N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride as a binder is dissolved are mixed and agitated by a special stirrer (made by Tokushu Kika Co., Ltd .: Combimix). Were mixed and stirred to prepare a positive electrode mixture slurry. At this time, the positive electrode active material, the conductive agent, and the binder were in a mass ratio of 95: 2.5: 2.5. And after apply | coating this positive mix slurry uniformly on both surfaces of the positive electrode collector which consists of aluminum foil, this is dried and rolled with a rolling roller, and a positive mix layer is formed on both surfaces of a positive electrode collector A positive electrode was obtained. In addition, the packing density of the positive electrode active material in this positive electrode was 3.60 g / cm ³ .

  A flat nonaqueous electrolyte secondary battery having a design capacity of 780 mAh when charged to 4.40 V was produced in the same manner as in Example A1 except that the above positive electrode was used.

(Example D2)
In Example D2, in the production of the positive electrode in Example D1, the positive electrode active material particles having dysprosium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 200 ° C. for 5 hours. Other than that was carried out similarly to the case of Example D1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Example D2, most of the dysprosium hydroxide attached to the surface of the positive electrode active material particles was not changed to dysprosium oxyhydroxide, but in the state of dysprosium hydroxide. It remained.

(Example D3)
In Example D3, in the production of the positive electrode in Example D1, the positive electrode active material particles in which erbium hydroxide was dispersed and adhered to the surface were terminated by a heat treatment only by drying at 120 ° C. Other than that was carried out similarly to the case of Example D1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the heat treatment of only drying at 120 ° C. as in Example D3, dysprosium hydroxide attached to the surface of the positive electrode active material particles did not change to dysprosium oxyhydroxide.

(Example D4)
In Example D4, in the production of the positive electrode in Example D1, the amount of dysprosium nitrate pentahydrate dissolved in 200 ml of pure water was changed to 1.81 g when adhering dysprosium hydroxide to the surface of the positive electrode active material particles. did. Other than that was carried out similarly to the case of Example D1, and produced the nonaqueous electrolyte secondary battery.

  Here, in Example D4, the proportion of the dysprosium element (Dy) in the dysprosium compound attached to the surface of the positive electrode active material particles made of lithium cobalt oxide was 0.067% by mass. Moreover, most of the dysprosium hydroxide adhered to the surface of the positive electrode active material particles was changed to dysprosium oxyhydroxide.

(Comparative Example d1)
In Comparative Example d1, the dysprosium compound was not attached to the surface of the positive electrode active material particles made of lithium cobaltate in the production of the positive electrode in Example D1. Other than that was carried out similarly to the case of Example D1, and produced the nonaqueous electrolyte secondary battery.

(Comparative Example d2)
In Comparative Example d2, in preparation of the positive electrode in Example D1, 500 g of positive electrode active material particles made of lithium cobaltate and 1.25 g of dysprosium oxide obtained by pulverizing a dysprosium oxide reagent until the particle diameter of primary particles becomes 300 nm, Mixing was performed using a mixing processor (manufactured by Hosokawa Micron Corporation: Nobilta). Thereby, the positive electrode active material was produced by mechanically attaching dysprosium oxide to the surface of the positive electrode active material particles made of lithium cobalt oxide.

  And the nonaqueous electrolyte secondary battery was produced like the case of Example D1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example d2, the ratio of the dysprosium element (Dy) in the dysprosium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.22% by mass. It was.

  Moreover, as a result of observing the positive electrode active material of Comparative Example d2 by SEM, dysprosium oxide was aggregated and adhered to the dents of the positive electrode active material particles, and was not dispersed and adhered to the surface of the positive electrode active material particles.

(Comparative Example d3)
In Comparative Example d3, a positive electrode active material was prepared by changing the amount of dysprosium oxide having a primary particle diameter of 300 nm in Comparative Example d2 to 5 g. And the nonaqueous electrolyte secondary battery was produced like the case of Example D1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example d3, the ratio of the dysprosium element (Dy) in the dysprosium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.87% by mass. It was.

  Further, as a result of observing the positive electrode active material of Comparative Example d3 by SEM, as in Comparative Example d2, dysprosium oxide is aggregated and attached to the recessed portions of the positive electrode active material particles. It was not dispersed and adhered to the surface.

(Comparative Example d4)
In Comparative Example d4, in the production of the positive electrode in Example D1, the positive electrode active material particles having dysprosium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 500 ° C. for 5 hours. Other than that was carried out similarly to the case of Example D1, and produced the nonaqueous electrolyte secondary battery.

Here, in the positive electrode active material obtained by heat treatment as in Comparative Example d4, dysprosium hydroxide attached to the surface of the positive electrode active material particles is changed to dysprosium oxide, and part of the dysprosium is the positive electrode active material particles. It was diffused inside.

  Next, after each nonaqueous electrolyte secondary battery of Examples D1 to D4 and Comparative Examples d1 to d4 was charged with a constant current to 4.40 V, as in the case of the nonaqueous electrolyte secondary battery of Example A1, etc. The battery was charged at a constant voltage of 4.40 V and initially charged. Thereafter, each of the initially charged nonaqueous electrolyte secondary batteries was paused for 10 minutes, and then initially discharged at a constant current of 750 mA until it reached 2.75V. The discharge capacity Qo at this time was measured. And the initial charging / discharging efficiency was calculated | required about each nonaqueous electrolyte secondary battery of Examples D1-D4 and Comparative Example d4.

  As a result, in each of the nonaqueous electrolyte secondary batteries of Examples D1 to D4, the initial charge / discharge efficiency was 89%, whereas in the nonaqueous electrolyte secondary battery of Comparative Example d4, the initial charge / discharge efficiency was Efficiency dropped to 86%. This is because, in the case of the nonaqueous electrolyte secondary battery of Comparative Example d4, dysprosium hydroxide attached to the surface of the positive electrode active material particles changes to dysprosium oxide, and part of the dysprosium diffuses inside the positive electrode active material particles. It is thought that it was because it was done.

  In addition, after the initial charge / discharge, a high-temperature continuous charge test was performed on each non-aqueous electrolyte secondary battery in the same manner as in the case of the non-aqueous electrolyte secondary battery such as Example A1. And the thickness increase amount in each nonaqueous electrolyte secondary battery after the high temperature continuous charge test with respect to the high temperature continuous charge test was calculated | required. The results are shown in Table 8 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  In addition, each non-aqueous electrolyte secondary battery after the high-temperature continuous charge test is discharged at room temperature to a constant current of 750 mA until it reaches 2.75 V, and the discharge capacity Q3 after the high-temperature continuous charge test is obtained to rest for 10 minutes. did. And the remaining capacity rate (%) after a high-temperature continuous charge test was calculated | required by Formula (4). The results are shown in Table 8 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  Further, after each non-aqueous electrolyte secondary battery after 10 minutes of rest is charged at a constant current of 750 mA to 4.40 V at room temperature, the current value becomes 37.5 mA at a constant voltage of 4.40 V. The charge capacity Qb was obtained by charging at a constant voltage. Then, each nonaqueous electrolyte secondary battery was paused for 10 minutes. Then, it discharged until it became 2.75V with a constant current of 750 mA, and discharge capacity Q4 was calculated | required. And while calculating | requiring the return capacity rate (%) after a high temperature continuous charge test by Formula (5), the charging / discharging efficiency (%) after a high temperature continuous charge test was calculated | required by Formula (6). The results are shown in Table 8 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  From Table 8, each nonaqueous electrolyte secondary battery of Examples D1 to D4 using a positive electrode active material in which particles of dysprosium compound composed of dysprosium hydroxide and dysprosium oxyhydroxide are dispersed and adhered is a high-temperature continuous charge test. The amount of increase in the thickness of the battery later was small, and the remaining capacity ratio, return capacity ratio, and charge / discharge efficiency after the high-temperature continuous charge test also showed high values. On the other hand, the non-aqueous electrolyte secondary batteries of Comparative Examples d1 to d4 have a larger battery thickness increase amount after the high-temperature continuous charge test than the non-aqueous electrolyte secondary batteries of Examples D1 to D4, and the high-temperature continuous charge. The residual capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the test also decreased.

  Further, the nonaqueous electrolyte secondary batteries of Examples D1 to D4 are also nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1, and z1, similarly to the nonaqueous electrolyte secondary batteries of Examples A1 to A7. In comparison with, the increase in the thickness of the battery after the high-temperature continuous charge test was small, and the remaining capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the high-temperature continuous charge test were greatly improved.

(Example E1)
In Example E1, the positive electrode produced as follows was used.

[Production of positive electrode]
As the positive electrode active material particles, lithium cobalt oxide in which 0.5 mol% of Mg and Al were dissolved was used. Then, 1000 g of the positive electrode active material particles were put into 3 liters of pure water, and an aqueous holmium nitrate solution in which 5.84 g of holmium nitrate pentahydrate was dissolved in 200 ml of pure water was added while stirring the particles. . At this time, a 10% by mass sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and holmium hydroxide was adhered to the surface of the positive electrode active material particles. And this was suction-filtered, the processed material was filtered, and this processed material was dried at 120 degreeC, and the positive electrode active material particle by which holmium hydroxide was disperse | distributed and adhered to the surface was obtained.

  Next, the positive electrode active material particles on which holmium hydroxide was dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 300 ° C. for 5 hours. As a result, a positive electrode active material was obtained in which holmium compound particles were dispersed and adhered to the surface of the positive electrode active material particles.

  Here, in the positive electrode active material of Example E1, the ratio of the holmium element (Ho) in the holmium compound attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.22% by mass. It was. Further, most of the holmium compound attached to the surface of the positive electrode active material particles was changed to holmium oxyhydroxide.

  Moreover, as a result of observing the positive electrode active material of Example E1 by SEM, most of the particle diameters of the holmium compound particles adhered to the surface of the positive electrode active material particles were 100 nm or less. The holmium compound particles were dispersed and adhered to the surfaces of the positive electrode active material particles.

Next, a positive electrode active material, a conductive agent acetylene black, and a N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride as a binder is dissolved are mixed and agitated by a special stirrer (made by Tokushu Kika Co., Ltd .: Combimix). Were mixed and stirred to prepare a positive electrode mixture slurry. At this time, the positive electrode active material, the conductive agent, and the binder were in a mass ratio of 95: 2.5: 2.5. And after apply | coating this positive mix slurry uniformly on both surfaces of the positive electrode collector which consists of aluminum foil, this is dried and rolled with a rolling roller, and a positive mix layer is formed on both surfaces of a positive electrode collector A positive electrode was obtained. In addition, the packing density of the positive electrode active material in this positive electrode was 3.60 g / cm ³ .

  A flat nonaqueous electrolyte secondary battery having a design capacity of 780 mAh when charged to 4.40 V was produced in the same manner as in Example A1 except that the above positive electrode was used.

(Example E2)
In Example E2, in the production of the positive electrode in Example E1, the positive electrode active material particles having holmium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 200 ° C. for 5 hours. Other than that was carried out similarly to the case of Example E1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Example E2, most of the holmium hydroxide adhering to the surface of the positive electrode active material particles was not changed to holmium oxyhydroxide, but in the state of holmium hydroxide. It remained.

(Example E3)
In Example E3, in the production of the positive electrode in Example E1, the positive electrode active material particles in which erbium hydroxide was dispersed and adhered to the surface were terminated by heat treatment only by drying at 120 ° C. as described above. Other than that was carried out similarly to the case of Example E1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the heat treatment of only drying at 120 ° C. as in Example E3, holmium hydroxide attached to the surface of the positive electrode active material particles did not change to holmium oxyhydroxide.

(Example E4)
In Example E4, in the production of the positive electrode in Example E1, the amount of holmium nitrate pentahydrate dissolved in 200 ml of pure water was changed to 1.80 g when adhering holmium hydroxide to the surface of the positive electrode active material particles. did. Other than that was carried out similarly to the case of Example E1, and produced the nonaqueous electrolyte secondary battery.

Here, in Example E4, the ratio of the holmium element (Ho) in the holmium compound attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.067% by mass. Further, most of the holmium hydroxide adhered to the surface of the positive electrode active material particles was changed to holmium oxyhydroxide.

(Comparative Example e1)
In Comparative Example e1, in the production of the positive electrode in Example E1, the holmium compound was not attached to the surface of the positive electrode active material particles made of lithium cobaltate. Other than that was carried out similarly to the case of Example E1, and produced the nonaqueous electrolyte secondary battery.

(Comparative Example e2)
In Comparative Example e2, in preparation of the positive electrode in Example E1, 500 g of positive electrode active material particles made of lithium cobaltate and 1.25 g of holmium oxide obtained by pulverizing a holmium oxide reagent until the particle diameter of primary particles becomes 300 nm, Mixing was performed using a mixing processor (manufactured by Hosokawa Micron Corporation: Nobilta). Thus, holmium oxide was mechanically attached to the surface of the positive electrode active material particles made of lithium cobaltate to produce a positive electrode active material.

  And the nonaqueous electrolyte secondary battery was produced like the case of Example E1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example e2, the ratio of the holmium element (Ho) in the holmium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.22% by mass. It was.

  Moreover, as a result of observing the positive electrode active material of Comparative Example e2 by SEM, holmium oxide was aggregated and adhered to the recessed portion of the positive electrode active material particles, and was not dispersed and adhered to the surface of the positive electrode active material particles.

(Comparative Example e3)
In Comparative Example e3, a positive electrode active material was produced by changing the amount of holmium oxide having a primary particle diameter of 300 nm in Comparative Example e2 to 5 g. And the nonaqueous electrolyte secondary battery was produced like the case of Example E1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example e3, the ratio of the holmium element (Ho) in the holmium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.87% by mass. It was.

  Further, as a result of observing the positive electrode active material of Comparative Example e3 by SEM, as in Comparative Example e2, the holmium oxide is aggregated and attached to the recessed portions of the positive electrode active material particles. It was not dispersed and adhered to the surface.

(Comparative Example e4)
In Comparative Example e4, in the production of the positive electrode in Example E1, the positive electrode active material particles in which holmium hydroxide was dispersed and attached to the surface were heat-treated in an air atmosphere at a temperature of 500 ° C. for 5 hours. Other than that was carried out similarly to the case of Example E1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Comparative Example e4, holmium hydroxide attached to the surface of the positive electrode active material particles is changed to holmium oxide, and a part of the holmium is made up of the positive electrode active material particles. It was diffused inside.

Next, after the nonaqueous electrolyte secondary batteries of Examples E1 to E4 and Comparative Examples e1 to e4 were charged with a constant current to 4.40 V, as in the case of the nonaqueous electrolyte secondary batteries of Example A1 and the like. The battery was charged at a constant voltage of 4.40 V and initially charged. Thereafter, each of the initially charged nonaqueous electrolyte secondary batteries was paused for 10 minutes, and then initially discharged at a constant current of 750 mA until it reached 2.75V. The discharge capacity Qo at this time was measured. And the initial charging / discharging efficiency was calculated | required about each nonaqueous electrolyte secondary battery of Examples E1-E4 and Comparative Example e4.

  As a result, in each of the nonaqueous electrolyte secondary batteries of Examples E1 to E4, the initial charge / discharge efficiency was 89%, whereas in the nonaqueous electrolyte secondary battery of Comparative Example e4, the initial charge / discharge efficiency was Efficiency dropped to 86%. This is because, in the case of the non-aqueous electrolyte secondary battery of Comparative Example e4, holmium hydroxide attached to the surface of the positive electrode active material particles is changed to holmium oxide, and part of the holmium is diffused inside the positive electrode active material particles. It is thought that it was because it was done.

  In addition, after the initial charge / discharge, a high-temperature continuous charge test was performed on each non-aqueous electrolyte secondary battery in the same manner as in the case of the non-aqueous electrolyte secondary battery such as Example A1. And the thickness increase amount in each nonaqueous electrolyte secondary battery after the high temperature continuous charge test with respect to the high temperature continuous charge test was calculated | required. The results are shown in Table 9 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  In addition, each nonaqueous electrolyte secondary battery after the high-temperature continuous charge test was discharged at room temperature to 2.75 V at a constant current of 750 mA, and the discharge capacity Q3 after the high-temperature continuous charge test was obtained for 10 minutes. Paused. And the remaining capacity rate (%) after a high-temperature continuous charge test was calculated | required by Formula (4). The results are shown in Table 9 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  Further, after each non-aqueous electrolyte secondary battery after 10 minutes of rest is charged at a constant current of 750 mA to 4.40 V at room temperature, the current value becomes 37.5 mA at a constant voltage of 4.40 V. The charge capacity Qb was obtained by charging at a constant voltage. Then, each nonaqueous electrolyte secondary battery was paused for 10 minutes. Then, it discharged until it became 2.75V with a constant current of 750 mA, and discharge capacity Q4 was calculated | required. And while calculating | requiring the return capacity rate (%) after a high temperature continuous charge test by Formula (5), the charging / discharging efficiency (%) after a high temperature continuous charge test was calculated | required by Formula (6). The results are shown in Table 9 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  From Table 9, Examples E1 to E4 using positive electrode active materials in which particles of holmium compound composed of holmium hydroxide and holmium oxyhydroxide were dispersed and adhered to the surface of the positive electrode active material particles composed of lithium cobaltate. Each non-aqueous electrolyte secondary battery had a small increase in battery thickness after the high-temperature continuous charge test, and also exhibited high values for the remaining capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the high-temperature continuous charge test. On the other hand, the nonaqueous electrolyte secondary batteries of Comparative Examples e1 to e4 have a large increase in the thickness of the battery after the high temperature continuous charge test, compared with the nonaqueous electrolyte secondary batteries of Examples E1 to E4, and the high temperature continuous charge. The residual capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the test also decreased.

  In addition, the nonaqueous electrolyte secondary batteries of Examples E1 to E4 are also nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1, similarly to the nonaqueous electrolyte secondary batteries of Examples A1 to A7. In comparison with, the increase in the thickness of the battery after the high-temperature continuous charge test was small, and the remaining capacity ratio, the return capacity ratio and the charge / discharge efficiency after the high-temperature continuous charge test were greatly improved.

(Example F1)
In Example F1, a positive electrode produced as follows was used.

[Production of positive electrode]
As the positive electrode active material particles, lithium cobalt oxide in which 0.5 mol% of Mg and Al were dissolved was used. Then, 1000 g of this positive electrode active material particle was put into 3 liters of pure water, and while stirring this, an aqueous solution of thulium nitrate in which 5.53 g of thulium nitrate tetrahydrate was dissolved in 200 ml of pure water was added. . At this time, a 10 mass% sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and thulium hydroxide was adhered to the surface of the positive electrode active material particles. And this was suction-filtered, the processed material was filtered, and this processed material was dried at 120 degreeC, and the positive electrode active material particle by which thulium hydroxide was disperse | distributed and adhered to the surface was obtained.

  Next, the positive electrode active material particles having thulium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 300 ° C. for 5 hours. Thus, a positive electrode active material in which thulium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained.

  Here, in this positive electrode active material, the ratio of thulium element (Tm) in the thulium compound attached to the surface of the positive electrode active material particles made of lithium cobalt oxide was 0.22% by mass. Further, in the thulium compound attached to the surface of the positive electrode active material particles, most of thulium hydroxide was changed to thulium oxyhydroxide.

  Moreover, as a result of observing the positive electrode active material of Example F1 with SEM, most of the particle diameters of the thulium compound particles attached to the surfaces of the positive electrode active material particles were 100 nm or less. Further, the thulium compound particles were dispersed and adhered to the surface of the positive electrode active material particles.

Next, a positive electrode active material, a conductive agent acetylene black, and a N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride as a binder is dissolved are mixed and agitated by a special stirrer (made by Tokushu Kika Co., Ltd .: Combimix). Were mixed and stirred to prepare a positive electrode mixture slurry. At this time, the positive electrode active material, the conductive agent, and the binder were in a mass ratio of 95: 2.5: 2.5. And after apply | coating this positive mix slurry uniformly on both surfaces of the positive electrode collector which consists of aluminum foil, this is dried and rolled with a rolling roller, and a positive mix layer is formed on both surfaces of a positive electrode collector A positive electrode was obtained. In addition, the packing density of the positive electrode active material in this positive electrode was 3.60 g / cm ³ . A flat nonaqueous electrolyte secondary battery having a design capacity of 780 mAh when charged to 4.40 V was produced in the same manner as in Example A1 except that the above positive electrode was used.

(Example F2)
In Example F2, in the production of the positive electrode in Example F1, the positive electrode active material particles in which thulium hydroxide was dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 200 ° C. for 5 hours. Other than that was carried out similarly to the case of Example F1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Example F2, most of the thulium hydroxide attached to the surface of the positive electrode active material particles was not changed to thulium oxyhydroxide, and in the thulium hydroxide state. It remained.

(Example F3)
In Example F3, in the production of the positive electrode in Example F1, the positive electrode active material particles in which erbium hydroxide was dispersed and adhered to the surface were terminated by a heat treatment only by drying at 120 ° C. Other than that was carried out similarly to the case of Example F1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the heat treatment of only drying at 120 ° C. as in Example F3, thulium hydroxide attached to the surface of the positive electrode active material particles did not change to thulium oxyhydroxide.

(Example F4)
In Example F4, in the production of the positive electrode in Example F1, the amount of thulium nitrate tetrahydrate dissolved in 200 ml of pure water was changed to 1.70 g when attaching thulium hydroxide to the surface of the positive electrode active material particles. did. Other than that was carried out similarly to the case of Example F1, and produced the nonaqueous electrolyte secondary battery.

Here, in Example F4, the ratio of the thulium element (Tm) in the thulium compound attached to the surface of the positive electrode active material particles made of lithium cobaltate was 0.067% by mass. In addition, most of the thulium hydroxide adhered to the surface of the positive electrode active material particles was changed to thulium oxyhydroxide.

(Comparative Example f1)
In Comparative Example f1, in the production of the positive electrode in Example F1, no thulium compound was attached to the surface of the positive electrode active material particles made of lithium cobaltate. Other than that was carried out similarly to the case of Example F1, and produced the nonaqueous electrolyte secondary battery.

(Comparative Example f2)
In Comparative Example f2, in preparation of the positive electrode in Example F1, 500 g of positive electrode active material particles made of lithium cobaltate and 1.25 g of thulium oxide obtained by pulverizing a thulium oxide reagent until the particle diameter of the primary particles was 300 nm, Mixing was performed using a mixing processor (manufactured by Hosokawa Micron Corporation: Nobilta). Thereby, the positive electrode active material was produced by mechanically attaching thulium oxide to the surface of the positive electrode active material particles made of lithium cobalt oxide. And the nonaqueous electrolyte secondary battery was produced like the case of Example F1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example f2, the ratio of thulium element (Tm) in thulium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate is 0.22% by mass. there were.

  In addition, as a result of observing the positive electrode active material of Comparative Example f2 by SEM, thulium oxide was aggregated and adhered to the recessed portions of the positive electrode active material particles, and was not dispersed and adhered to the surface of the positive electrode active material particles.

(Comparative Example f3)
In Comparative Example f3, a positive electrode active material was produced by changing the amount of thulium oxide having a primary particle diameter of 300 nm in Comparative Example f2 to 4.97 g. And the nonaqueous electrolyte secondary battery was produced like the case of Example F1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example f3, the ratio of thulium element (Tm) in thulium oxide attached to the surface of the positive electrode active material particles made of lithium cobaltate is 0.87% by mass. there were.

  Further, as a result of observing the positive electrode active material of Comparative Example f3 by SEM, as in Comparative Example f2, thulium oxide is aggregated and attached to the dents of the positive electrode active material particles. It was not dispersed and adhered to the surface.

(Comparative Example f4)
In Comparative Example f4, in producing the positive electrode in Example F1, the positive electrode active material particles having thulium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 500 ° C. for 5 hours. Other than that was carried out similarly to the case of Example F1, and produced the nonaqueous electrolyte secondary battery.

  Here, in the positive electrode active material obtained by heat treatment as in Comparative Example f4, thulium hydroxide attached to the surface of the positive electrode active material particles is changed to thulium oxide, and a part of thulium is made up of the positive electrode active material particles. It was diffused inside.

Next, after the nonaqueous electrolyte secondary batteries of Examples F1 to F4 and Comparative Examples f1 to f4 were charged with a constant current up to 4.40 V as in the case of the nonaqueous electrolyte secondary batteries of Example A1 and the like. The battery was charged at a constant voltage of 4.40 V and initially charged. Thereafter, each of the initially charged nonaqueous electrolyte secondary batteries was paused for 10 minutes, and then initially discharged at a constant current of 750 mA until it reached 2.75V. The discharge capacity Qo at this time was measured. And the initial charging / discharging efficiency was calculated | required about each nonaqueous electrolyte secondary battery of Examples F1-F4 and Comparative Example f4.

  As a result, in each of the nonaqueous electrolyte secondary batteries of Examples F1 to F4, the initial charge / discharge efficiency was 89%, whereas in the nonaqueous electrolyte secondary battery of Comparative Example f4, the initial charge / discharge efficiency was Efficiency dropped to 86%. This is because, in the case of the non-aqueous electrolyte secondary battery of Comparative Example f4, thulium hydroxide attached to the surface of the positive electrode active material particles changes to thulium oxide, and part of thulium diffuses inside the positive electrode active material particles. It is thought that it was because it was done.

  In addition, after the initial charge / discharge, a high-temperature continuous charge test was performed on each non-aqueous electrolyte secondary battery in the same manner as in the case of the non-aqueous electrolyte secondary battery such as Example A1. And the thickness increase amount in each nonaqueous electrolyte secondary battery after the high temperature continuous charge test with respect to the high temperature continuous charge test was calculated | required. The results are shown in Table 10 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  In addition, each non-aqueous electrolyte secondary battery after the high-temperature continuous charge test is discharged at room temperature to a constant current of 750 mA until it reaches 2.75 V, and the discharge capacity Q3 after the high-temperature continuous charge test is obtained to rest for 10 minutes. did. And the remaining capacity rate (%) after a high-temperature continuous charge test was calculated | required by Formula (4). The results are shown in Table 10 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  Further, after each non-aqueous electrolyte secondary battery after 10 minutes of rest is charged at a constant current of 750 mA to 4.40 V at room temperature, the current value becomes 37.5 mA at a constant voltage of 4.40 V. The charge capacity Qb was obtained by charging at a constant voltage. Then, each nonaqueous electrolyte secondary battery was paused for 10 minutes. Then, it discharged until it became 2.75V with a constant current of 750 mA, and discharge capacity Q4 was calculated | required. And while calculating | requiring the return capacity rate (%) after a high temperature continuous charge test by Formula (5), the charging / discharging efficiency (%) after a high temperature continuous charge test was calculated | required by Formula (6). The results are shown in Table 10 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  From Table 10, Examples F1 to F4 using positive electrode active materials in which particles of thulium compound composed of thulium hydroxide and thulium oxyhydroxide were dispersed and adhered to the surface of the positive electrode active material particles composed of lithium cobaltate. Each non-aqueous electrolyte secondary battery had a small increase in battery thickness after the high-temperature continuous charge test, and also exhibited high values for the remaining capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the high-temperature continuous charge test. On the other hand, the non-aqueous electrolyte secondary batteries of Comparative Examples f1 to f4 have a larger amount of increase in battery thickness after the high-temperature continuous charge test than the non-aqueous electrolyte secondary batteries of Examples F1 to F4. The residual capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the test also decreased.

  In addition, the nonaqueous electrolyte secondary batteries of Examples F1 to F4 are also nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1, and z1, similarly to the nonaqueous electrolyte secondary batteries of Examples A1 to A7. In comparison with, the increase in the thickness of the battery after the high-temperature continuous charge test was small, and the remaining capacity ratio, the return capacity ratio and the charge / discharge efficiency after the high-temperature continuous charge test were also greatly improved.

(Example G1)
In Example G1, a positive electrode produced as follows was used.

[Production of positive electrode]
As the positive electrode active material particles, lithium cobalt oxide in which 0.5 mol% of Mg and Al were dissolved was used. Then, 1000 g of the positive electrode active material particles were put into 3 liters of pure water, and while stirring this, an aqueous solution of lutetium nitrate in which 5.21 g of lutetium nitrate trihydrate was dissolved in 200 ml of pure water was added. . At this time, a 10% by mass sodium hydroxide aqueous solution was appropriately added so that the pH of this solution was 9, and lutetium hydroxide was adhered to the surfaces of the positive electrode active material particles. And this was suction-filtered, the processed material was filtered, and this processed material was dried at 120 degreeC, and the positive electrode active material particle by which the lutetium hydroxide was disperse | distributed and adhered to the surface was obtained.

  Next, the positive electrode active material particles having lutetium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 300 ° C. for 5 hours. As a result, a positive electrode active material in which lutetium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained.

  Here, in this positive electrode active material, the ratio of the lutetium element (Lu) in the lutetium compound adhered to the surface of the positive electrode active material particles made of lithium cobaltate was 0.22% by mass. Further, in the lutetium compound attached to the surface of the positive electrode active material particles, most of the lutetium hydroxide was changed to lutetium oxyhydroxide.

  Moreover, as a result of observing the positive electrode active material of Example G1 with SEM, most of the particle diameters of the particles of the lutetium compound attached to the surfaces of the positive electrode active material particles were 100 nm or less. Further, the lutetium compound particles were dispersed and adhered to the surface of the positive electrode active material particles.

Next, a positive electrode active material, a conductive agent acetylene black, and a N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride as a binder is dissolved are mixed and agitated by a special stirrer (made by Tokushu Kika Co., Ltd .: Combimix). Were mixed and stirred to prepare a positive electrode mixture slurry. At this time, the positive electrode active material, the conductive agent, and the binder were in a mass ratio of 95: 2.5: 2.5. And after apply | coating this positive mix slurry uniformly on both surfaces of the positive electrode collector which consists of aluminum foil, this is dried and rolled with a rolling roller, and a positive mix layer is formed on both surfaces of a positive electrode collector A positive electrode was obtained. In addition, the packing density of the positive electrode active material in this positive electrode was 3.60 g / cm ³ .

  A flat nonaqueous electrolyte secondary battery having a design capacity of 780 mAh when charged to 4.40 V was produced in the same manner as in Example A1 except that the above positive electrode was used.

(Example G2)
In Example G2, in the production of the positive electrode in Example G1, the positive electrode active material particles having lutetium hydroxide dispersed and adhered to the surface were heat-treated in an air atmosphere at a temperature of 200 ° C. for 5 hours. Otherwise, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example G1.

  Here, in the positive electrode active material obtained by heat treatment as in Example G2, most of the lutetium hydroxide attached to the surface of the positive electrode active material particles was not changed to lutetium oxyhydroxide, but in the state of lutetium hydroxide. It remained.

(Example G3)
In Example G3, in the production of the positive electrode in Example G1, the positive electrode active material particles having lutetium hydroxide dispersed and adhered to the surface were finished by a heat treatment only by drying at 120 ° C. Otherwise, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example G1.

  Here, in the heat treatment of only drying at 120 ° C. as in Example G3, lutetium hydroxide attached to the surface of the positive electrode active material particles did not change to lutetium oxyhydroxide.

(Example G4)
In Example G4, the amount of lutetium nitrate trihydrate dissolved in 200 ml of pure water was changed to 1.59 g when attaching lutetium hydroxide to the surface of the positive electrode active material particles in the production of the positive electrode in Example G1. did. Otherwise, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example G1.

Here, in Example G4, the ratio of the lutetium element (Lu) in the lutetium compound attached to the surface of the positive electrode active material particles made of lithium cobaltate is 0.06.
It was 7 mass%. Further, most of the lutetium hydroxide adhered to the surface of the positive electrode active material particles was changed to lutetium oxyhydroxide.

(Comparative Example g1)
In Comparative Example g1, the lutetium compound was not attached to the surface of the positive electrode active material particles made of lithium cobaltate in the production of the positive electrode in Example G1. Otherwise, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example G1.

(Comparative Example g2)
In Comparative Example g2, in preparation of the positive electrode in Example G1, 500 g of positive electrode active material particles made of lithium cobaltate and 1.25 g of lutetium oxide obtained by pulverizing a lutetium oxide reagent until the particle diameter of primary particles is 300 nm, Mixing was performed using a mixing processor (manufactured by Hosokawa Micron Corporation: Nobilta). Thereby, the positive electrode active material was produced by mechanically attaching lutetium oxide to the surface of the positive electrode active material particles made of lithium cobalt oxide. And the nonaqueous electrolyte secondary battery was produced like the case of Example G1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example g2, the ratio of the lutetium element (Lu) in the lutetium oxide adhered to the surface of the positive electrode active material particles made of lithium cobaltate was 0.22% by mass. It was.

  In addition, as a result of observing the positive electrode active material of Comparative Example g2 by SEM, lutetium oxide was aggregated and adhered to the recessed portions of the positive electrode active material particles, and was not dispersed and adhered to the surface of the positive electrode active material particles.

(Comparative Example g3)
In Comparative Example g3, a positive electrode active material was produced by changing the amount of lutetium oxide having a primary particle diameter of 300 nm in Comparative Example g2 to 4.97 g. And the nonaqueous electrolyte secondary battery was produced like the case of Example G1 except using the positive electrode active material produced in this way.

  Here, in the positive electrode active material of Comparative Example g3, the ratio of the lutetium element (Lu) in the lutetium oxide adhered to the surface of the positive electrode active material particles made of lithium cobaltate was 0.87% by mass. It was.

  Further, as a result of observing the positive electrode active material of Comparative Example g3 by SEM, as in Comparative Example g2, the lutetium oxide was aggregated and adhered to the recessed portions of the positive electrode active material particles. It was not dispersed and adhered to the surface.

(Comparative Example g4)
In Comparative Example g4, in the production of the positive electrode in Example G1, the positive electrode active material particles having lutetium hydroxide dispersed and adhered to the surface were heat-treated at a temperature of 500 ° C. for 5 hours in an air atmosphere. Otherwise, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example G1.

  Here, in the positive electrode active material obtained by heat treatment as in Comparative Example g4, lutetium hydroxide attached to the surface of the positive electrode active material particles changes to lutetium oxide, and part of the lutetium is the positive electrode active material particles. It was diffused inside.

Next, after each of the nonaqueous electrolyte secondary batteries of Examples G1 to G4 and Comparative Examples g1 to g4 was charged with a constant current to 4.40 V in the same manner as the nonaqueous electrolyte secondary batteries of Example A1 and the like. The battery was charged at a constant voltage of 4.40 V and initially charged. Thereafter, each of the initially charged nonaqueous electrolyte secondary batteries was paused for 10 minutes, and then initially discharged at a constant current of 750 mA until it reached 2.75V. The discharge capacity Qo at this time was measured. And the initial charging / discharging efficiency was calculated | required about each nonaqueous electrolyte secondary battery of Examples G1-G4 and Comparative Example g4.

  As a result, in each of the nonaqueous electrolyte secondary batteries of Examples G1 to G4, the initial charge / discharge efficiency was 89%, whereas in the nonaqueous electrolyte secondary battery of Comparative Example g4, the initial charge / discharge efficiency was Efficiency dropped to 86%. This is because, in the case of the nonaqueous electrolyte secondary battery of Comparative Example g4, lutetium hydroxide attached to the surface of the positive electrode active material particles changes to lutetium oxide, and part of the lutetium diffuses into the positive electrode active material particles. It is thought that it was because it was done.

  In addition, after the initial charge / discharge, a high-temperature continuous charge test was performed on each non-aqueous electrolyte secondary battery in the same manner as in the case of the non-aqueous electrolyte secondary battery such as Example A1. And the thickness increase amount in each nonaqueous electrolyte secondary battery after the high temperature continuous charge test with respect to the high temperature continuous charge test was calculated | required. The results are shown in Table 11 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  In addition, each non-aqueous electrolyte secondary battery after the high-temperature continuous charge test is discharged at room temperature to a constant current of 750 mA until it reaches 2.75 V, and the discharge capacity Q3 after the high-temperature continuous charge test is obtained to rest for 10 minutes. did. And the remaining capacity rate (%) after a high-temperature continuous charge test was calculated | required by Formula (4). The results are shown in Table 10 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  Further, after each non-aqueous electrolyte secondary battery after 10 minutes of rest is charged at a constant current of 750 mA to 4.40 V at room temperature, the current value becomes 37.5 mA at a constant voltage of 4.40 V. The charge capacity Qb was obtained by charging at a constant voltage. Then, each nonaqueous electrolyte secondary battery was paused for 10 minutes. Then, it discharged until it became 2.75V with a constant current of 750 mA, and discharge capacity Q4 was calculated | required. And while calculating | requiring the return capacity rate (%) after a high temperature continuous charge test by Formula (5), the charging / discharging efficiency (%) after a high temperature continuous charge test was calculated | required by Formula (6). The results are shown in Table 11 below together with the results of the nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1 and z1.

  From Table 11, Examples G1 to G4 using positive electrode active materials in which particles of lutetium hydroxide and lutetium oxyhydroxide particles were dispersed and adhered to the surfaces of the positive electrode active material particles made of lithium cobaltate. Each non-aqueous electrolyte secondary battery had a small increase in battery thickness after the high-temperature continuous charge test, and also exhibited high values for the remaining capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the high-temperature continuous charge test. On the other hand, the non-aqueous electrolyte secondary batteries of Comparative Examples g1 to g4 have a large increase in battery thickness after the high-temperature continuous charge test compared to the non-aqueous electrolyte secondary batteries of Examples G1 to G4, and the high-temperature continuous charge. The residual capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the test also decreased.

  In addition, the nonaqueous electrolyte secondary batteries of Examples G1 to G4 are also nonaqueous electrolyte secondary batteries of Comparative Examples x1 to x3, y1, and z1, similarly to the nonaqueous electrolyte secondary batteries of Examples A1 to A7. In comparison with, the increase in the thickness of the battery after the high-temperature continuous charge test was small, and the remaining capacity ratio, the return capacity ratio and the charge / discharge efficiency after the high-temperature continuous charge test were also greatly improved.

(Example H1)
In Example H1, spinel-type lithium manganate LiMn ₂ O _{4 in} which 1 mol% of Mg and Al were each dissolved as a positive electrode active material particle not containing Co or Ni was used in producing the positive electrode. A positive electrode active material in which erbium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained in the same manner as in Example A1 except that the positive electrode active material particles were used.

  Here, in the positive electrode active material of Example H1, the ratio of the erbium element (Er) in the erbium compound adhered to the surface of the positive electrode active material particles was 0.22% by mass. Further, most of the erbium hydroxide adhered to the surface of the positive electrode active material particles was changed to erbium oxyhydroxide.

  In addition, most of the particles of the erbium compound particles adhered to the surfaces of the positive electrode active material particles were 100 nm or less. The erbium compound particles were dispersed and adhered to the surface of the positive electrode active material particles.

  A non-aqueous electrolyte secondary battery was produced in the same manner as in Example A1, using a positive electrode active material in which erbium compound particles were dispersed and adhered to the surface of positive electrode active material particles made of spinel type lithium manganate. .

(Example H2)
In Example H2, similarly to Example H1, spinel type lithium manganate LiMn ₂ O _{4 in} which 1 mol% of Mg and Al were dissolved as positive electrode active material particles was used. Then, a positive electrode active material in which ytterbium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained in the same manner as in Example B1 except that the positive electrode active material particles were used.

  Here, in the positive electrode active material of Example H2, the ratio of the ytterbium element (Yb) in the ytterbium compound attached to the surface of the positive electrode active material particles was 0.22% by mass. Further, most of the ytterbium hydroxide attached to the surface of the positive electrode active material particles was changed to ytterbium oxyhydroxide. Moreover, most of the ytterbium compound particles adhered to the surfaces of the positive electrode active material particles had a particle size of 100 nm or less. The ytterbium compound particles were dispersed and attached to the surfaces of the positive electrode active material particles.

  Then, using the positive electrode active material in which the particles of the ytterbium compound are dispersed and adhered to the surface of the positive electrode active material particles made of spinel type lithium manganate as described above, a nonaqueous electrolyte secondary battery is obtained in the same manner as in Example A1. Was made.

(Example H3)
Also in Example H3, similarly to Example H1, spinel type lithium manganate LiMn ₂ O _{4 in} which 1 mol% of Mg and Al were dissolved as positive electrode active material particles was used.

  Then, a positive electrode active material in which terbium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained in the same manner as in Example C1 except that the positive electrode active material particles were used.

  Here, in the positive electrode active material of Example H3, the ratio of the terbium element (Tb) in the terbium compound attached to the surface of the positive electrode active material particles was 0.22% by mass. Further, most of the terbium hydroxide adhered to the surface of the positive electrode active material particles was changed to terbium oxyhydroxide. Further, most of the particles of the terbium compound particles adhered to the surfaces of the positive electrode active material particles were 100 nm or less. The terbium compound particles were dispersed and attached to the surfaces of the positive electrode active material particles.

  A non-aqueous electrolyte secondary battery was produced in the same manner as in Example A1, using a positive electrode active material in which particles of a terbium compound were dispersed and adhered to the surface of positive electrode active material particles made of spinel type lithium manganate. .

(Example H4)
Also in Example H4, similarly to Example H1, spinel type lithium manganate LiMn ₂ O _{4 in} which 1 mol% of Mg and Al were dissolved as positive electrode active material particles was used.

A positive electrode active material in which particles of a dysprosium compound were dispersed and adhered to the surface of the positive electrode active material particles was obtained in the same manner as in Example D1 except that the positive electrode active material particles were used.

  Here, in the positive electrode active material of Example H4, the ratio of the dysprosium element (Dy) in the dysprosium compound adhered to the surface of the positive electrode active material particles was 0.22% by mass. Further, most of the dysprosium hydroxide attached to the surface of the positive electrode active material particles was changed to dysprosium oxyhydroxide. Moreover, most of the particle diameters of the dysprosium compound particles attached to the surfaces of the positive electrode active material particles were 100 nm or less. Further, dysprosium compound particles were dispersed and adhered to the surface of the positive electrode active material particles.

  A nonaqueous electrolyte secondary battery was produced in the same manner as in Example A1, using a positive electrode active material in which particles of a dysprosium compound were dispersed and adhered to the surface of positive electrode active material particles made of spinel type lithium manganate. .

(Example H5)
Also in Example H5, similarly to Example H1, spinel type lithium manganate LiMn ₂ O _{4 in} which 1 mol% of Mg and Al were dissolved as positive electrode active material particles was used.

  Then, a positive electrode active material in which holmium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained in the same manner as in Example E1 except that the positive electrode active material particles were used.

  Here, in the positive electrode active material of Example H5, the ratio of the holmium element (Ho) in the holmium compound attached to the surface of the positive electrode active material particles was 0.22% by mass. Further, most of the holmium hydroxide adhered to the surface of the positive electrode active material particles was changed to holmium oxyhydroxide. Moreover, most of the particle diameters of the holmium compound particles adhered to the surfaces of the positive electrode active material particles were 100 nm or less. The holmium compound particles were dispersed and adhered to the surface of the positive electrode active material particles.

  A non-aqueous electrolyte secondary battery was produced in the same manner as in Example A1, using a positive electrode active material in which holmium compound particles were dispersed and adhered to the surface of positive electrode active material particles made of spinel type lithium manganate. .

(Example H6)
Also in Example H6, as in Example H1, spinel type lithium manganate LiMn ₂ O _{4 in} which 1 mol% of Mg and Al were dissolved as positive electrode active material particles was used.

  A positive electrode active material in which thulium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained in the same manner as in Example F1 except that the positive electrode active material particles were used.

  Here, in the positive electrode active material of Example H6, the ratio of thulium element (Tm) in the thulium compound attached to the surface of the positive electrode active material particles was 0.22% by mass. Further, most of the thulium hydroxide attached to the surface of the positive electrode active material particles was changed to thulium oxyhydroxide. Most of the thulium compound particles adhered to the surface of the positive electrode active material particles had a particle size of 100 nm or less. The thulium compound particles were dispersed and attached to the surfaces of the positive electrode active material particles.

  A non-aqueous electrolyte secondary battery was produced in the same manner as in Example A1, using a positive electrode active material in which thulium compound particles were dispersed and adhered to the surface of positive electrode active material particles made of spinel type lithium manganate. .

(Example H7)
In Example H7, similarly to Example H1, spinel type lithium manganate LiMn ₂ O _{4 in} which 1 mol% of Mg and Al were dissolved as positive electrode active material particles was used.

  Then, a positive electrode active material in which lutetium compound particles were dispersed and adhered to the surface of the positive electrode active material particles was obtained in the same manner as in Example G1, except that the positive electrode active material particles were used.

  Here, in the positive electrode active material of Example H7, the ratio of the lutetium element (Lu) in the lutetium compound attached to the surface of the positive electrode active material particles was 0.22% by mass. Further, most of the lutetium hydroxide adhered to the surface of the positive electrode active material particles was changed to lutetium oxyhydroxide. Moreover, most of the particles of the lutetium compound particles adhered to the surfaces of the positive electrode active material particles were 100 nm or less. Moreover, the particles of the lutetium compound were dispersed and adhered to the surfaces of the positive electrode active material particles.

  Then, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example A1, using a positive electrode active material in which particles of a lutetium compound were dispersed and adhered on the surface of positive electrode active material particles made of spinel type lithium manganate. .

(Comparative Example h)
In Comparative Example h, as the positive electrode active material particles, spinel type lithium manganate LiMn ₂ O _{4 in} which 1 mol% each of Mg and Al as in Example H1 was solid-dissolved was used. Also did not adhere.

  And using this positive electrode active material particle, it carried out similarly to the case of Example A1, and produced the nonaqueous electrolyte secondary battery.

  Next, each of the nonaqueous electrolyte secondary batteries of Examples H1 to H7 and Comparative Example h was charged to 4.20 V at a constant current of 750 mA at room temperature, and the current value was 37 at a constant voltage of 4.20 V. The battery was charged at a constant voltage until it reached 0.5 mA, paused for 10 minutes, and then charged and discharged at a constant current of 750 mA until it reached 2.75 V. The discharge capacity Qo at this time was measured.

  Next, each non-aqueous electrolyte secondary battery that was initially charged / discharged was released into a thermostat at 60 ° C. for 1 hour, and then charged to 4.20 V at a constant current of 750 mA in the thermostat at 60 ° C. In addition, a high temperature continuous charge test is performed in which the battery is charged for 3 days while maintaining a voltage of 4.20 V, and the increase in thickness in each nonaqueous electrolyte secondary battery after the high temperature continuous charge test before the test is obtained. Is shown in Table 12 below.

  In addition, each non-aqueous electrolyte secondary battery after the high-temperature continuous charge test is discharged at room temperature to a constant current of 750 mA until it reaches 2.75 V, and the discharge capacity Q3 after the high-temperature continuous charge test is obtained to rest for 10 minutes. did. And the residual capacity rate (%) after a high-temperature continuous charge test was calculated | required by Formula (4), and the result was shown in following Table 12.

Further, after each non-aqueous electrolyte secondary battery after 10 minutes of rest is charged at a constant current of 750 mA to 4.40 V at room temperature, the current value becomes 37.5 mA at a constant voltage of 4.40 V. The charge capacity Qb was obtained by charging at a constant voltage. Then, each nonaqueous electrolyte secondary battery was paused for 10 minutes. Then, it discharged until it became 2.75V with a constant current of 750 mA, and discharge capacity Q4 was calculated | required. And while calculating | requiring the return capacity rate (%) after a high-temperature continuous charge test by Formula (5), calculating | requiring the charge / discharge efficiency (%) after a high-temperature continuous charge test by Formula (6), the result is shown in the following table | surface. This is shown in FIG.

  From the results of Table 12, even when spinel-type lithium manganate containing no Co or Ni is used for the positive electrode active material particles, the surface of the positive electrode active material particles is erbium compound, ytterbium compound, terbium compound or dysprosium compound. Each of the nonaqueous electrolyte secondary batteries of Examples H1 to H7 using the positive electrode active material in which particles of holmium compound, thulium compound, thulium compound, and lutetium compound are dispersed and adhered is dispersed and adhered. Compared with the nonaqueous electrolyte secondary battery of Comparative Example h using a positive electrode active material that was not, the remaining capacity ratio, the return capacity ratio, and the charge / discharge efficiency after the high-temperature continuous charge test were improved.

  However, regarding the increase in thickness of the battery after the high-temperature continuous charge test, there was almost no difference between the nonaqueous electrolyte secondary batteries of Examples H1 to H7 and the nonaqueous electrolyte secondary battery of Comparative Example h. This is because spinel type lithium manganate that does not contain Co or Ni has a lower catalytic property than a positive electrode active material such as lithium cobaltate, so the decomposition reaction of the non-aqueous electrolyte even during high-temperature continuous charging This is thought to be because it is difficult to accelerate. For this reason, from the viewpoint of suppressing the increase in the thickness of the battery after the high-temperature continuous charge test, particularly for positive electrode active material particles containing Co and Ni, erbium compound, ytterbium compound, terbium compound and dysprosium compound It was found effective when particles of holmium compound, thulium compound or lutetium compound were dispersed and adhered.

DESCRIPTION OF SYMBOLS 10 Flat electrode body 11 Positive electrode 11a Positive electrode current collection tab 12 Negative electrode 12a Negative electrode current collection tab 13 Separator 20 Battery container

Claims (21)

At least one kind of erbium compound particles selected from erbium hydroxide and erbium oxyhydroxide and at least one kind selected from ytterbium hydroxide and ytterbium oxyhydroxide on the surface of the positive electrode active material particles containing lithium Particles of ytterbium compound, particles of at least one terbium compound selected from terbium hydroxide and terbium oxyhydroxide, particles of at least one dysprosium compound selected from dysprosium hydroxide and dysprosium oxyhydroxide, and particles of at least one of holmium compound selected from the holmium hydroxide oxyhydroxide holmium, and particles of at least one thulium compound selected from hydroxide thulium oxyhydroxide, thulium and lutetium hydroxide Alkoxy at least one of at least one of the positive electrode active material for a nonaqueous electrolyte secondary battery, wherein the particles having a particle diameter of 100nm or less of the compounds are attached are selected from particles of lutetium compound selected from lutetium hydroxide . 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the compound particles attached to the surface of the positive electrode active material particles containing lithium are erbium oxyhydroxide. Positive electrode active material for electrolyte secondary battery. 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the compound particles attached to the surface of the positive electrode active material particles containing lithium are ytterbium oxyhydroxide. Positive electrode active material for electrolyte secondary battery.   The positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the positive electrode active material particles containing lithium contain nickel and / or cobalt. A positive electrode active material for a non-aqueous electrolyte secondary battery.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein zirconium is solid-solved in the positive electrode active material particles containing lithium. Positive electrode active material for non-aqueous electrolyte secondary battery.   In manufacturing the positive electrode active material for non-aqueous electrolyte secondary batteries according to claim 1 or 2, the positive electrode active material particles are obtained by adding an erbium salt solution to a solution in which the positive electrode active material particles are dispersed. The positive electrode in the step of depositing erbium hydroxide on the surface of the positive electrode active material particles, and the step of heat treating the positive electrode active material particles on which the erbium hydroxide is deposited. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the pH of the solution in which the active material particles are dispersed is set to 6 or more.   7. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 6, wherein the heat treatment temperature of the positive electrode active material particles on which erbium hydroxide is deposited is less than 440 ° C. A method for producing a positive electrode active material for a secondary battery.   In manufacturing the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 3, the positive electrode active material particles are obtained by adding a solution of ytterbium salt to a solution in which the positive electrode active material particles are dispersed. The positive electrode in the step of depositing ytterbium hydroxide on the surface of the positive electrode active material particles, and the step of heat treating the positive electrode active material particles on which the ytterbium hydroxide is deposited. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the pH of the solution in which the active material particles are dispersed is set to 6 or more. 9. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 8, wherein the heat treatment temperature of the positive electrode active material particles on which ytterbium hydroxide is deposited is less than 400 ° C. A method for producing a positive electrode active material for a secondary battery.   In manufacturing the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, a terbium salt solution is added to a solution in which the positive electrode active material particles are dispersed, and water is added to the surface of the positive electrode active material particles. A step of precipitating terbium oxide; and a step of heat-treating the positive electrode active material particles on which terbium hydroxide is precipitated, and the positive electrode active material particles in the step of precipitating terbium hydroxide on the surface of the positive electrode active material particles. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the pH of the dispersed solution is 6 or more.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 10, wherein the heat treatment temperature of the positive electrode active material particles on which terbium hydroxide is deposited is less than 395 ° C. A method for producing a positive electrode active material for a secondary battery.   In manufacturing the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, a dysprosium salt solution is added to a solution in which the positive electrode active material particles are dispersed, and water is added to the surface of the positive electrode active material particles. The positive electrode active material particles in the step of depositing dysprosium hydroxide on the surface of the positive electrode active material particles, comprising the step of precipitating dysprosium oxide and the step of heat treating the positive electrode active material particles on which the dysprosium hydroxide is deposited. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the pH of the dispersed solution is 6 or more.   13. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 12, wherein the heat treatment temperature of the positive electrode active material particles on which dysprosium hydroxide is deposited is less than 450 ° C. A method for producing a positive electrode active material for a secondary battery.   In manufacturing the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, a holmium salt solution is added to a solution in which the positive electrode active material particles are dispersed, and water is added to the surface of the positive electrode active material particles. The positive electrode active material particles in the step of depositing holmium hydroxide on the surface of the positive electrode active material particles, comprising a step of precipitating holmium oxide and a step of heat treating the positive electrode active material particles on which the holmium hydroxide is precipitated. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the pH of the dispersed solution is 6 or more.   15. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 14, wherein the heat treatment temperature of the positive electrode active material particles on which holmium hydroxide is deposited is less than 445 ° C. A method for producing a positive electrode active material for a secondary battery.   In manufacturing the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, a thulium salt solution is added to a solution in which the positive electrode active material particles are dispersed, and water is added to the surface of the positive electrode active material particles. The positive electrode active material particles in the step of depositing thulium hydroxide on the surface of the positive electrode active material particles, the method comprising the step of precipitating thulium oxide and the step of heat treating the positive electrode active material particles on which the thulium hydroxide is deposited. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the pH of the dispersed solution is 6 or more.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 16, wherein the heat treatment temperature of the positive electrode active material particles on which thulium hydroxide is deposited is less than 405 ° C. A method for producing a positive electrode active material for a secondary battery. In producing a positive electrode active material for a non-aqueous electrolyte secondary battery of claim 1, water was added a solution of lutetium salt to a solution dispersing the positive electrode active material particles of the above on the surface of the positive electrode active material of the It has a step of precipitating lutetium oxide and a step of heat-treating the positive electrode active material on which lutetium hydroxide is deposited, and the pH in the step of precipitating lutetium hydroxide on the surface of the positive electrode active material is 6 or more. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 18, wherein the heat treatment temperature of the positive electrode active material particles on which lutetium hydroxide is deposited is less than 405 ° C. A method for producing a positive electrode active material for a secondary battery.   A positive electrode for a nonaqueous electrolyte secondary battery, wherein the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 5 is used.   A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode for a non-aqueous electrolyte secondary battery according to claim 20 is used as the positive electrode. Electrolyte secondary battery.