JP6135980B2 - Positive electrode active material and storage element - Google Patents

Description

  The present invention relates to a positive electrode active material and a power storage element.

  Conventionally, as an example of a battery mounted on a hybrid electric vehicle (HEV) or the like, a non-aqueous electrolyte secondary battery such as a lithium ion battery is known. As such a battery, generally, a form in which a power generation element (element) including at least a positive electrode plate and a negative electrode plate is accommodated in a container is known. Specifically, the positive electrode plate includes a positive electrode current collector and a positive electrode active material supported on the positive electrode current collector, and the negative electrode plate includes a negative electrode current collector and the negative current collector. And a negative electrode active material supported on the body. The power generation element is configured by laminating the positive electrode plate, the negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. An electrolytic solution is injected into the container.

  As this type of non-aqueous electrolyte secondary battery, a battery in which the positive electrode active material is a compound containing iron such as a lithium iron phosphate compound is known. A nonaqueous electrolyte secondary battery equipped in an automobile may be used in a high temperature environment. In such a case, iron (Fe) present in the positive electrode active material may be eluted into the electrolytic solution. And the elution thing precipitates on the surface of a negative electrode member, and there exists a problem that the fall of charging / discharging capacity is accelerated | stimulated because a deposit coat | covers this surface (high temperature durability is low).

  On the other hand, a material containing a lithium iron phosphate compound and a manganese (Mn) component has been proposed as the positive electrode active material (see Patent Documents 1 to 3). Thus, since the lithium iron phosphate compound contains the manganese component, the ionic conductivity of the positive electrode active material is improved, so that the discharge capacity of the non-aqueous electrolyte secondary battery is increased.

JP 2010-528410 A JP 2009-104983 A JP 2005-047751 A

  However, even in a battery having an active material as shown in Patent Documents 1 to 3, when used in a high temperature environment, the charge / discharge capacity may be reduced, and it is difficult to say that the high temperature durability is sufficient.

  In view of the above problems, an object of the present invention is to provide a positive electrode active material and a power storage element that are excellent in high-temperature durability.

  As a result of diligent research, the present inventors have found that in a positive electrode active material containing a lithium iron phosphate compound, when the manganese component is not contained, the iron component is eluted and the high-temperature durability is lowered, whereas the above-mentioned It has been found that even when the manganese component is contained as in the prior art, when the manganese component is too much, the manganese component is eluted and the high temperature durability is lowered. And it discovered that the positive electrode active material by which the fall of high temperature durability was suppressed was set by setting the manganese content in the said active material to a predetermined range, and came to complete this invention.

The positive electrode active material according to the present invention is
A positive electrode active material used for a storage element,
It contains lithium iron phosphate to which 811 mass ppm or more and 1088 mass ppm or less of manganese is added as an additive element.

  Here, in such a configuration, the content of manganese means the content of manganese with respect to the whole positive electrode active material.

According to such a configuration, a battery using the positive electrode active material, even when or used are left at a high temperature, and that reduction of the charge and discharge capacity is suppressed.
Therefore, according to the said structure, the positive electrode active material excellent in high temperature durability is obtained.
In the case where manganese is contained as an impurity in the positive active material, the content of manganese as the impurity is usually at 100ppm or less with respect to the entire positive electrode active material, the manganese content of more than 300ppm is This can be achieved by intentionally adding manganese into the active material.

Moreover, the electricity storage device according to the present invention is:
A positive electrode containing the positive electrode active material;
A negative electrode,
A separator;
An electrolyte solution.

  According to this configuration, since the positive electrode active material is provided, a power storage element having excellent high-temperature durability can be obtained.

  As described above, according to the present invention, a positive electrode active material and a power storage device excellent in high temperature durability are provided.

1 is a schematic perspective view showing a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. The schematic perspective view which shows the electric power generation element with which the nonaqueous electrolyte secondary battery of this embodiment was equipped. Schematic plan view schematically showing the positive electrode plate, separator and negative electrode plate of FIG.

  Hereinafter, a power storage device including the positive electrode active material according to the present invention will be described with reference to the drawings, taking as an example a case where the power storage device is a non-aqueous electrolyte secondary battery.

As shown in FIGS. 1 and 2, the non-aqueous electrolyte secondary battery 1 of the present embodiment includes a container 2, a power generation element (element) 10 accommodated in the container 2, and the container 2. The electrolyte solution 20 is provided. The power generating element 10 includes a positive electrode plate 11 as a positive electrode, a negative electrode plate 13 as a negative electrode having a polarity opposite to that of the positive electrode plate 11, and a separator 15 disposed between the two electrode plates. These are laminated.
It has.

  The container 2 includes a container body 3 that can accommodate the power generation element 10 and a lid member 4 that covers the container body 3. The container body 3 and the lid member 4 are made of, for example, a stainless steel plate and are welded to each other.

  An outer gasket 5 made of an insulating material is disposed on the outer surface of the lid member 4. The lid member 4 and the external gasket 5 each have an opening, and the opening of the lid member 4 and the opening of the external gasket 5 are continuous. An external terminal 21 is accommodated in the external gasket 5.

  The external terminal 21 passes through the opening of the external gasket 5 and the opening of the lid member 4 and protrudes into the container body 3, and the protruding portions of the external terminal 21 are the positive and negative electrodes 11 of the power generation element 10. , 13 is connected to a current collector (not shown). The shape of the current collector is not particularly limited, but is, for example, a plate shape. The current collector is formed of the same type of metal member as the electrode member to be connected. The external terminal 21 is made of, for example, an aluminum alloy material such as aluminum or an aluminum alloy.

  The external gasket 5 and the external terminal 21 are provided for a positive electrode and a negative electrode. The external gasket 5 and the external terminal 21 for the positive electrode are arranged on one end side in the longitudinal direction of the lid member 4, and the external gasket 5 and the external terminal 21 for the negative electrode are arranged on the other end side in the longitudinal direction.

  The lid member 4 has an injection port (not shown) for injecting the electrolytic solution 20 into the container body 3, and this injection port is sealed after the injection of the electrolytic solution 20. .

  A power generation element 10 is accommodated in the container body 3. One power generation element 10 may be accommodated in the container body 3, or a plurality of power generation elements 10 may be accommodated. In the latter case, the plurality of power generation elements 10 are electrically connected in parallel.

  The positive electrode plate 11 is formed by arranging a positive electrode mixture 11b containing a positive electrode active material on both surfaces of a positive electrode current collector 11a such as an aluminum foil. Specifically, the positive electrode plate 11 includes a positive electrode current collector 11a and a layered positive electrode mixture 11b having a positive electrode active material, and the positive electrode mixture 11b is laminated on the positive electrode current collector 11a. Is formed.

  The details of the positive electrode mixture 11b and the positive electrode active material will be described later. In the present embodiment, the positive electrode mixture 11b is arranged in a layer on the positive electrode current collector 11a. However, the positive electrode mixture 11b arranged on the positive electrode current collector 11a has such a layered shape. It is not specifically limited to.

  The thickness of the positive electrode mixture 11b layer is not particularly limited, but is usually about 20 μm to 200 μm per side.

  The negative electrode plate 13 is formed by disposing a negative electrode mixture 13b on a negative electrode current collector 13a such as a copper foil. Specifically, the negative electrode plate 13 includes a negative electrode current collector 13a and a layered negative electrode mixture 13b containing a negative electrode active material, and the negative electrode mixture 13b is laminated on the negative electrode current collector 13a. Is formed.

Examples of the negative electrode active material contained in the negative electrode mixture 13b include carbon-based materials such as amorphous carbon, non-graphitizable carbon, graphitizable carbon, and graphite.
The negative electrode mixture 13b may have a binder such as polyvinylidene fluoride (PVDF), a conductive auxiliary agent such as acetylene black, and the like in addition to the negative electrode active material.

  The layer thickness of the negative electrode mixture 11b is not particularly limited, but is usually about 20 μm to 200 μm per one side.

  The separator 15 allows passage of the electrolyte solution 20 while blocking electrical connection with the positive and negative electrode plates 11 and 13. Examples of the separator 15 include a porous film formed from a polyolefin resin such as polyethylene. Such a porous film may contain additives such as a plasticizer, an antioxidant, and a flame retardant.

The electrolytic solution 20 is configured by dissolving an electrolyte in an organic solvent. There is no restriction | limiting in particular as an organic solvent used for the said electrolyte solution 20, For example, ethers, ketones, lactones, nitriles, amines, amides, a sulfur compound, halogenated hydrocarbons, ester, carbonates , Nitro compounds, phosphate ester compounds, sulfolane hydrocarbons and the like. Among these, ethers, ketones, esters, lactones, halogenated hydrocarbons, carbonates, and sulfolane compounds are preferable. Examples of these are tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, anisole, monoglyme, 4-methyl-2-pentanone, ethyl acetate, methyl acetate, methyl propionate, ethyl propionate, 1,2-dichloroethane. Γ-butyrolactone, dimethoxyethane, methyl formate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethylformamide, dimethyl sulfoxide, dimethylthioformamide, sulfolane, 3-methyl-sulfolane, phosphorus And trimethyl phosphate, triethyl phosphate, and mixed solvents thereof. Cyclic carbonates and cyclic esters are preferred. Most preferably, the organic solvent is a mixture of one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate.
As the electrolyte salt used in the electrolytic solution 20 is not particularly _{limited, LiClO 4, LiBF 4, LiAsF} 6, CF 3 SO 3 Li, LiPF 6, LiN (CF 3 SO 2) 2, LiN (C 2 F ₅ SO ₂ ) ₂ , LiI, LiAlCl _{4 and the} like and mixtures thereof. Among these, a lithium salt obtained by mixing one or more of LiBF ₄ and LiPF ₆ is preferable.
In addition, the electrolyte solution 20 is not specifically limited to the electrolyte solution containing said organic solvent and electrolyte salt.
In addition to the above, a membrane (solid electrolyte membrane) that is supplementarily formed from a solid ion conductive material may be further used as the electrolyte. In this case, the non-aqueous electrolyte secondary battery 1 can be formed by the positive electrode plate 11, the negative electrode plate 13, the separator 15 disposed between them, the solid electrolyte membrane, and the electrolyte solution 20. Further, the non-aqueous electrolyte secondary battery 1 can be formed by the positive electrode plate 11, the negative electrode plate 13, the solid electrolyte membrane disposed therebetween, and the electrolyte solution 20.
In addition, the solid electrolyte membrane is an organic solid electrolyte formed from polyethylene oxide, polyacrylonitrile or polyethylene glycol, and modified products thereof, and the like. It is advantageous. Furthermore, in addition to the above, the solid electrolyte membrane may be formed using an inorganic solid electrolyte or a mixed material of an organic solid electrolyte and an inorganic solid electrolyte.

  And in this embodiment, the said positive mix 11b contains the said positive electrode active material, a binder, and a conductive support agent.

  The positive electrode active material contains a lithium phosphate compound (lithium iron phosphate) and a manganese component (manganese) as an additive in an amount of 300 to 1500 ppm by mass with respect to the entire positive electrode active material. In addition, content of the said manganese component means content of the manganese component with respect to the said whole mixture.

The lithium iron phosphate compound is a compound represented by LiFePO ₄ .

  As described above, since the positive electrode active material contains a lithium iron phosphate compound and a manganese component of 300 to 1500 mass ppm, the nonaqueous electrolyte secondary battery 1 using the positive electrode active material is used. Even when is left at high temperature or used, elution of the iron component and the manganese component is suppressed. Thereby, as for this nonaqueous electrolyte secondary battery 1, the fall of charging / discharging capacity | capacitance will be suppressed. Therefore, a positive electrode active material excellent in high temperature durability can be obtained.

  Moreover, it is preferable that content of the said manganese component is 500-1080 mass ppm with respect to the whole this positive electrode active material from a viewpoint that high temperature durability is exhibited more reliably. Content of this manganese component is measured by the method described in the Example mentioned later.

  In the usual general range, the positive electrode active material is contained in an amount of 80 to 96% by mass with respect to the entire positive electrode mixture 11b. The content of the positive electrode active material is preferably 85 to 95% by mass with respect to the entire positive electrode mixture 11b.

  The positive electrode active material is preferably configured to include carbon on the surface of the primary particles. Thereby, since the favorable electroconductive network which spreads between primary particles is formed with carbon, the electroconductivity of the said positive electrode active material is improved.

  Examples of the binder include polyvinylidene fluoride (PVDF). Such a binder is contained in an amount of 2 to 10% by mass with respect to the entire positive electrode mixture 11b in a normal general range. As for content of this binder, 3-7 mass% is preferable with respect to the whole positive electrode mixture 11b.

  Examples of the conductive assistant include carbon black and acetylene black. Such a binder is contained in an amount of 2 to 10% by mass with respect to the whole positive electrode mixture 11b in a normal general range. The content of the conductive auxiliary is preferably 3 to 7% by mass with respect to the whole positive electrode mixture 11b.

  The positive electrode mixture 11b may contain other components other than the positive electrode active material, the binder, and the conductive additive.

  The positive electrode mixture 11b contains a lithium iron phosphate compound, a manganese component of 270 to 1350 mass ppm relative to the whole of the positive electrode mixture 11b, a binder, and a conductive additive. .

  Thus, when the positive electrode mixture 11b contains a lithium iron phosphate compound and a manganese component of 270 to 1350 mass ppm, non-water using the positive electrode plate 11 containing the positive electrode plate 11b is used. Even when the electrolyte secondary battery 1 is left at a high temperature or used, elution of the iron component and the manganese component is suppressed. Thereby, as for this nonaqueous electrolyte secondary battery 1, the fall of charging / discharging capacity | capacitance will be suppressed. Therefore, the positive electrode plate 11 excellent in high temperature durability can be obtained.

  Further, from the viewpoint that high-temperature durability is more reliably exhibited, the content of the manganese component is preferably 450 to 975 mass ppm with respect to the entire positive electrode mixture 11b. In addition, content of this manganese component is measured by the method described in the Example mentioned later.

  Then, the manufacturing method of the positive electrode active material of this embodiment, the positive electrode mixture 11b, and the nonaqueous electrolyte secondary battery 1 is demonstrated.

  First, the manufacturing method of the positive electrode active material of this embodiment is demonstrated.

For example, first, lithium hydroxide monohydrate (LiOH.H ₂ O) and diammonium hydrogen phosphate ((NH 4) ₂ HPO ₄ ) are weighed to a predetermined amount and dissolved in ion-exchanged water. After that, both solutions are mixed with stirring to prepare a first mixed solution. Nitrogen gas bubbling can be performed on the obtained first mixed solution, whereby iron oxidation is suppressed and deterioration is prevented.
Subsequently, manganese sulfate pentahydrate (MnSO ₄ .5H ₂ O) as a manganese component is weighed out into ion-exchanged water in which ascorbic acid is dissolved, and further, iron sulfate heptahydrate ( FeSO ₄ .7H ₂ O) is weighed out to a predetermined amount, and dissolved to prepare a second mixed solution. Similarly to the above, nitrogen gas bubbling can also be performed on the obtained second mixed solution. In addition, manganese content in a positive electrode active material is adjusted by changing the addition amount of manganese sulfate added as a manganese component.

  The second mixed solution is added to the first mixed solution while stirring and mixed to prepare a precursor solution.

  After the precursor solution obtained above is introduced into a hydrothermal reaction vessel and sufficiently substituted with nitrogen gas, hydrothermal synthesis is performed at 160 to 200 ° C. The hydrothermal synthesis time (time for maintaining the hydrothermal synthesis temperature) can be set, for example, to 6 to 24 hours, but is not limited to this range as long as the reaction proceeds well. It is preferable to stir by the stirring blade attached to the hydrothermal reaction vessel from the temperature rise to the removal.

  And after the product obtained by this hydrothermal reaction is fully washed by using ion-exchanged water and acetone, etc., vacuum drying is performed at 80 to 150 ° C. for 5 hours or more, thereby A powder of lithium iron phosphate containing manganese is produced as a positive electrode active material.

  Further, a small amount of polyvinyl alcohol and water heated to 50 ° C. are added to this powder and mixed to form a gum-like paste, and then an atmosphere substitution type firing furnace is used, and 600 to 800 under a nitrogen gas flow. By performing heating at ° C., a positive electrode active material having carbon on the surface can be produced.

  Next, the manufacturing method of the positive electrode plate 11 and the nonaqueous electrolyte secondary battery of the present embodiment will be described.

  For example, first, the positive electrode active material, the binder, the conductive auxiliary agent, and an organic solvent such as N-methylpyrrolidone are mixed to prepare a paste-like mixture (positive electrode mixture paste). The After this mixture is applied onto the positive electrode current collector 11a and dried, the obtained laminate is compressed by a roll press or the like, and the positive electrode plate 11 is produced. At this time, the amount of the manganese component in the positive electrode mixture 11b is adjusted by adjusting the blending amount between the positive electrode active material having the manganese component in the content, the binder, and the conductive additive. Content is adjusted.

  Similarly, the negative electrode active material, the binder, the conductive auxiliary agent, and the organic solvent are mixed to obtain a paste-like mixture (negative electrode mixture paste). After this mixture is applied onto the negative electrode current collector 13a and dried, the obtained laminate is compressed by a roll press or the like, and the negative electrode plate 13 is produced.

  Next, the positive electrode plate 11, the separator 15, the negative electrode plate 13, and the separator 15 are laminated in this order, and then wound to form the power generation element 10. The power generation element 10 is inserted into the container body 3, the current collector is connected to the positive and negative plates 11 and 13, and the container body 3 is covered with the lid member 4 to which the external gasket 5 and the external terminal 21 are attached. Thus, the current collector and the external terminal 21 are connected, and in this state, the container body 3 and the lid member 4 are welded, the electrolyte solution 20 is injected through an inlet (not shown), and the inlet is closed. Thus, a non-aqueous electrolyte secondary battery is produced.

  In addition, the manufacturing method of the non-aqueous-electrolyte secondary battery 1 of this embodiment is not specifically limited to the said manufacturing method.

As described above, the positive electrode active material of the present embodiment is a positive electrode active material used for a power storage element,
It contains lithium iron phosphate and 300-1500 mass ppm manganese as an additive element. According to this configuration, the positive electrode active material contains a lithium iron phosphate compound and a manganese component of 300 to 1500 mass ppm, so that the nonaqueous electrolyte secondary battery 1 using the positive electrode active material is used. Even if it is left at high temperature or used, the decrease in charge / discharge capacity is suppressed. Therefore, according to the said structure, the positive electrode active material excellent in high temperature durability is obtained.

  The positive electrode plate 11 of the present embodiment includes a positive electrode current collector 11a and a positive electrode mixture 11b disposed on the positive electrode current collector 11a. The positive electrode mixture 11a includes a lithium iron phosphate compound and 270 to 1350 ppm by mass of manganese component. According to this configuration, the positive electrode mixture 11b contains a lithium iron phosphate compound and a manganese component of 270 to 1350 mass ppm, whereby the nonaqueous electrolyte secondary battery 1 using the positive electrode plate 11 is used. Even if it is left at high temperature or used, the decrease in charge / discharge capacity is suppressed. Therefore, according to the said structure, the positive electrode plate 11 excellent in high temperature durability is obtained.

  Further, the non-aqueous electrolyte secondary battery 1 of the present embodiment includes a positive electrode plate 11 containing the positive electrode active material, a negative electrode plate 13 having a polarity opposite to that of the positive electrode plate 11, a separator 15, and an electrolytic solution 20. And. According to such a configuration, by providing the positive electrode plate 11, the nonaqueous electrolyte battery 1 excellent in high temperature durability can be obtained.

  The positive electrode active material and the electricity storage device of the present invention are as described above, but the present invention is not limited to the above-described embodiment, and can be appropriately modified within the intended scope of the present invention. The battery of the present invention is preferably a non-aqueous electrolyte secondary battery, particularly preferably a lithium ion secondary battery, and a lithium ion secondary battery for a hybrid electric vehicle (HEV). The secondary battery is particularly suitable, but is not particularly limited thereto. Moreover, the effect of this invention is not limited to the said embodiment.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

<Preparation of Lithium Iron Phosphate (LiFePO ₄ ) Containing Manganese Component>
First, 90.6 g of lithium hydroxide monohydrate (LiOH · H ₂ O) (Nacalai Tesque, Inc., the same shall apply hereinafter) and diammonium hydrogen phosphate ((NH 4) ₂ HPO ₄ ) (Nacalai Tesque, Inc., hereinafter) 142.5 g of the same was weighed and dissolved in 540 mL of ion-exchanged water, and then both solutions were mixed with stirring to prepare a first mixed solution. Nitrogen gas bubbling (flow rate 0.5 L / min) was performed on this first mixed solution for about 30 minutes.
Next, manganese sulfate pentahydrate (MnSO ₄ .5H ₂ O) (Nacalai Tesque Co., Ltd.) as a manganese component was added to 1200 mL of ion-exchanged water in which 21.0 g of ascorbic acid (Nacalai Tesque Co., Ltd., hereinafter the same) was dissolved. However, the same applies to the following, so that the content of the manganese component relative to the whole positive electrode active material is as shown in Table 1, 0.150 g, 0.225 g, 0.375 g, 0.600 g, 0.810 g, respectively. 0.900 g, 1.120 g, 1.270 g. Further, 300.0 g of iron sulfate heptahydrate (FeSO ₄ · 7H ₂ O) (Nacalai Tesque, Inc., the same shall apply hereinafter) is weighed and dissolved in each solution to prepare a second mixed solution. It was done. Also for this second mixed solution, nitrogen gas bubbling (flow rate 0.5 L / min) was performed for about 30 minutes. Each of these second mixed solutions was added to the first solution obtained above with stirring and mixed to obtain a precursor solution.
After each precursor solution was introduced into a hydrothermal reaction vessel and sufficiently replaced with nitrogen gas, hydrothermal synthesis was performed at 170 ° C. The hydrothermal synthesis time (time for maintaining the hydrothermal synthesis temperature) was 15 hours. The rate of temperature increase was 100 ° C./h, and the temperature was naturally allowed to cool. Between the temperature rise and removal, the liquid in the container was stirred at 100 rpm by the stirring blade attached to the hydrothermal reaction container. The obtained product is thoroughly washed with ion-exchanged water and acetone, and then dried under reduced pressure at 120 ° C. for 6 hours to contain the manganese component having the content shown in Table 1. Each of the powders of lithium iron phosphate (positive electrode active material) was obtained.
The content of manganese component in each obtained powder (manganese content and Mn content with respect to the whole of each powder) is determined after the powder is dissolved using commercially available concentrated hydrochloric acid (special grade). It was measured by ICP analysis of a solution diluted to an appropriate concentration with exchange water. The results are shown in Table 1.

<Preparation of positive electrode plate>
The positive electrode active material produced as described above was used, and 90% by mass of each positive electrode active material, 5% by mass of acetylene black as a conductive auxiliary agent, and 5% by mass of PVDF were mixed, and N- Methylpyrrolidone was added to form a positive electrode mixture paste. This paste was applied to both surfaces of an aluminum foil as a positive electrode current collector. At this time, the mixture was applied so that the weight of the mixture per side after drying was 1.6 g / 100 cm ² . Moreover, after drying this, a 500 kgf / cm load was applied with the roll press and it compression-molded. Thereby, a strip-like positive electrode plate was produced. The size of each positive electrode member was 210 cm in length and 13 cm in width, and the total thickness of the positive electrode current collector and the positive electrode mixture on both sides was 190 μm.
Moreover, 0.2g of positive electrode compound materials were extract | collected by peeling a compound material part from aluminum foil using the front-end | tip of sharp metal pieces, such as an office cutter, from a positive electrode plate. And the content of the manganese component in the collected positive electrode mixture (manganese content and Mn content with respect to the whole of each powder) was dissolved using the commercially available concentrated hydrochloric acid (special grade). It was measured by ICP analysis of a solution diluted to an appropriate concentration with ion-exchanged water. The results are shown in Table 1.

<Preparation of negative electrode plate>
90% by weight of graphite as a negative electrode active material and 10% by weight of polyvinylidene fluoride (PVDF) as a binder are mixed, and N-methylpyrrolidone as a solvent is added to this mixture to form a negative electrode mixture paste. It was done. This paste was applied to both sides of a copper foil as a negative electrode current collector. At this time, the mixture was applied so that the weight of the mixture on one side after drying was 0.74 g / 100 cm ² . After this was dried, a load of 100 kgf / cm was applied by a roll press and compression molded. Thereby, a strip-shaped negative electrode member was produced. The size of the negative electrode plate was 220 cm in length, 13 cm in width, and the total thickness of the negative electrode current collector and the negative electrode mixture on both sides was 120 μm.

<Production of test battery>
A positive electrode tab and a negative electrode tab were attached to each of the positive electrode member and the negative electrode member manufactured as described above.
A polyolefin microporous membrane having a width of 12 cm and a thickness of 25 μm was prepared as a separator.

  Next, each positive electrode member, separator, negative electrode member, and separator were stacked in this order and wound into a long cylindrical shape. Thereby, the power generation element was produced. Such a power generation element was accommodated in a container, the container was covered, and an electrolytic solution was injected to manufacture each test battery.

<Capacity retention test>
Each test battery was used and a capacity retention test was performed.
Specifically, a constant current and constant voltage charge (CV charge) is performed for 3 hours in total at a current of 1 CA to a voltage of 3.6 V, and then a constant current discharge (CC discharge) is performed to a voltage of 2.0 V at a current of 1 CA. The discharge capacity when measured was measured (hereinafter, this discharge capacity is described as 1 CA discharge capacity).
Next, this test battery was charged at a constant current to a voltage of 3.6 V at a current of 2 CA, and then charged and discharged at 1000 cycles under a charge / discharge condition of a constant current to a voltage of 2.0 V at a current of 2 CA Then, the 1CA discharge capacity was calculated, and the discharge capacity retention rate (%) was calculated. Here, the “discharge capacity retention ratio (%)” is a value obtained by multiplying the value obtained by dividing the discharge capacity after 1000 cycles by the initial discharge capacity by 100. The results are shown in Table 1.

  As shown in Table 1, when the content of the manganese component in the positive electrode active material is 300 mass ppm or more and 1500 ppm or less, the capacity retention is remarkable as compared with the case where it is less than 300 mass ppm and the case where it exceeds 1500 ppm. It was expensive. Moreover, when the content of the manganese component in the positive electrode mixture was 270 mass ppm or more and 1350 ppm or less, the capacity retention was remarkably high compared to the case of less than 270 mass ppm and the case of exceeding 1350 ppm.

1: nonaqueous electrolyte secondary battery, 3: container, 10: element, 11: positive electrode plate, 11a: positive electrode current collector, 11b: positive electrode mixture, 13: negative electrode plate, 13a: negative electrode current collector, 13b: Negative electrode mixture, 15: separator, 20: electrolyte

Claims (2)

A positive electrode active material used for a storage element,
811 ppm by weight or 1088 ppm by weight of manganese containing lithium iron phosphate was added as an additive element, the positive electrode active material. A positive electrode comprising the positive electrode active material according to claim 1;
A negative electrode,
A separator;
An electricity storage device comprising an electrolytic solution.

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