JP6959028B2 - Manufacturing method of non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery such as a lithium ion battery and a method for manufacturing a non-aqueous electrolyte secondary battery.

Lithium-ion secondary batteries, which are one of the non-aqueous electrolyte secondary batteries, have high energy density and high capacity, and are therefore used as power sources for driving electric vehicles (EVs) and hybrid vehicles (HEVs). Has been done. If the lithium ion secondary battery is a lithium ion secondary battery having an electrode body in which a positive electrode plate and a negative electrode plate having active material layers provided on both sides of the electrode core are wound or laminated via a separator, the positive electrode plate and the negative electrode plate and the negative electrode plate are used. The facing area of the negative electrode plate becomes large, and it becomes easy to take out a large current.

On the other hand, lithium ion secondary batteries are required to ensure safety during overcharging.
The lithium ion secondary battery described in Patent Document 1 contains a wound electrode body in which a positive electrode and a negative electrode are wound with a separator sandwiched between them, a non-aqueous electrolytic solution containing a gas generating agent, and a wound electrode body. It is provided with a battery case provided in.

The positive electrode contains a LiNiComnO ₂ system positive electrode active material. The calcium content in the positive electrode active material provided at the axial end of the wound electrode body is higher than the calcium content in the positive electrode active material provided inside the wound electrode body in the axial direction. Since the positive electrode active material becomes hard when the calcium content is high, it is possible to prevent a decrease in the pore volume of the positive electrode mixture layer due to rolling at the axial end of the wound electrode body, and thus non-aqueous electrolysis. The liquid holding capacity can be maintained high. That is, when the non-aqueous electrolyte secondary battery is in an overcharged state, a gas generation reaction is likely to occur at the axial end of the wound electrode body in which the holding capacity of the non-aqueous electrolyte solution is maintained high. Therefore, the safety of the non-aqueous electrolyte secondary battery can be maintained high.

Japanese Unexamined Patent Publication No. 2015-153695

By the way, it is also known that the shape of the positive electrode active material can be easily maintained by adding calcium even if the positive electrode active material does not contain calcium, and the safety of the non-aqueous electrolyte secondary battery is maintained high. There is. However, it is unavoidable that a part of the calcium added to the positive electrode active material is eluted and moved to the negative electrode plate to become metallic calcium. That is, the metallic calcium generated on the negative electrode plate may increase the concentration of lithium ions and reduce the lithium precipitation resistance (performance that makes it difficult for metallic lithium to precipitate) on the negative electrode plate.

The present invention has been made in view of such circumstances, and an object of the present invention is a non-aqueous electrolyte secondary battery capable of suppressing a decrease in lithium precipitation resistance while maintaining safety during overcharging. Another object of the present invention is to provide a method for manufacturing a non-aqueous electrolyte secondary battery.

The non-aqueous electrolyte secondary battery for solving the above problems includes a battery case, an electrode body and a non-aqueous electrolyte housed in the battery case, a positive electrode plate and a negative electrode plate constituting the electrode body, and the positive electrode plate. A nitrogen oxide (CaNOx) comprising a positive electrode active material and calcium mixed with the positive electrode active material, and containing calcium atoms in the negative electrode plate with respect to the molecular weight of all calcium atoms in the negative electrode plate. ) Has a molecular weight ratio of the calcium atom of "0.5" or more.

According to such a configuration, in a non-aqueous electrolyte secondary battery in which the positive electrode plate contains calcium that maintains safety during overcharging, even if the negative electrode plate contains calcium, Li precipitation occurs. The probability that it exists as CaNOx that does not affect resistance is increased. In other words, the probability that it exists as metallic calcium that reduces Li precipitation resistance is suppressed. As a result, the non-aqueous electrolyte secondary battery contains calcium necessary for ensuring the safety of overcharging, and the decrease in Li precipitation resistance can be suppressed.

As a preferable configuration, the mass of calcium atoms contained in the positive electrode plate is 0.2 [mass%] or more with respect to the mass of the positive electrode active material.
According to such a configuration, the Li precipitation resistance is maintained even if 0.2 [mass%] or more of calcium is added to the positive electrode plate.

As a preferred configuration, the positive electrode plate contains an amine.
According to such a configuration, a larger amount of CaNOx can be produced by containing an amine in the positive electrode plate. As the amine, at least one of methylamine, dimethylamine and trimethylamine can be used. As a result, the amount of calcium transferred from the positive electrode plate to the negative electrode plate is relatively reduced, so that the generation of metallic calcium from Ca in the negative electrode plate is suppressed, and the decrease in Li precipitation resistance is suppressed.

A method for manufacturing a non-aqueous electrolyte secondary battery that solves the above problems is a battery case, an electrode body and a non-aqueous electrolyte housed in the battery case, a positive electrode plate and a negative electrode plate constituting the electrode body, and the positive electrode body. A method for producing a non-aqueous electrolyte secondary battery comprising a positive electrode mixture constituting a plate and containing a positive electrode active material to which calcium is added, wherein the positive electrode mixture is used. At the time of production, a stirring step of increasing nitrogen oxides (CaNOx) containing calcium atoms in the positive electrode mixture by adding amine and stirring, and the electrode body and the non-aqueous electrolyte are housed in the battery case. The present invention comprises a charging step of increasing the proportion of CaNOx by charging the non-aqueous electrolyte secondary battery produced in the process.

According to such a method, in a non-aqueous electrolyte secondary battery containing calcium that can ensure the safety of overcharging, the ratio of calcium to CaNOx increases, which adversely affects the Li precipitation resistance in the negative electrode plate. The proportion of metallic calcium that gives is suppressed. Therefore, the safety of overcharging can be ensured, and the decrease in Li precipitation resistance can be suppressed.

As a preferred method, in the charging step, the charging is performed with a current of 3C or more in the non-aqueous electrolyte secondary battery.
According to such a method, the ratio of CaNOx in the negative electrode plate is increased by setting the charging current to 3C or more, which is 2 to 3 times or more that of the conventional one, in the charging step.

As a preferred method, in the stirring step, at least one of a heat treatment for heating the positive electrode mixture and a pressure treatment for pressurizing the positive electrode mixture is performed in combination.
According to such a method, since the positive electrode mixture is agitated together with at least one of the heat treatment and the pressure treatment, the ratio of CaNOx produced in the positive electrode mixture is increased.

As a preferred method, the heat treatment is a treatment for adjusting the positive electrode mixture to 45 ° C. or higher and 60 ° C. or lower, and the pressurization treatment is a treatment for increasing the positive electrode mixture from 1 atm to pressurize the mixture. be.

According to such a method, the ratio of CaNOx produced in the stirring step is appropriately increased.

According to the present invention, it is possible to suppress a decrease in lithium precipitation resistance while maintaining safety during overcharging.

The front view which shows the internal front structure about one Embodiment of the lithium ion secondary battery which embodies the non-aqueous electrolyte secondary battery. The schematic diagram which shows typically the cross-sectional structure of the electrode plate group in the same embodiment. The graph which shows the relationship between the amount of calcium in a positive electrode plate and Li precipitation resistance in the same embodiment. The graph which shows the condition about manufacturing of the electrode plate group in the same embodiment. The flowchart which shows the procedure of the manufacturing process of the lithium ion secondary battery in the same embodiment. The graph which shows the relationship between the manufacturing condition and Li precipitation resistance in the same embodiment. The figure explaining the charging process in the same embodiment.

An embodiment of a secondary battery 10 embodying a lithium ion secondary battery, which is an example of a non-aqueous electrolyte secondary battery, will be described with reference to FIGS. 1 to 7. A plurality of the secondary batteries 10 of the present embodiment are connected by a bus bar to form an assembled battery. The assembled battery is mounted on an electric vehicle or a hybrid vehicle to supply electric power to an electric motor or the like. The secondary battery 10 is a sealed battery having a rectangular parallelepiped outer shape.

As shown in FIG. 1, the secondary battery 10 includes a rectangular battery case 11 having an opening on the upper side, a lid 12 for sealing the battery case 11, and an electrode body housed inside the battery case 11. 20 as a non-aqueous electrolyte solution 27 as a non-aqueous electrolyte injected into the battery case 11. The battery case 11 and the lid 12 are made of a metal such as an aluminum alloy. The secondary battery 10 is formed by attaching a lid 12 to the battery case 11 to form a sealed battery case. Further, the secondary battery 10 is provided with two external terminals 13 used for charging and discharging electric power on the lid body 12.

The electrode plate group 20 is formed by flatly winding a positive electrode plate 21, a negative electrode plate 22, and a separator 23 arranged between them. The electrode plate group 20 is laminated in multiple layers by being folded back at both ends 26 in the winding direction (winding direction). The electrode plate group 20 has a positive electrode portion 21A having a positive electrode plate 21 protruding from one end side in a direction orthogonal to the winding direction (winding axis direction) and a negative electrode portion 22 having a negative electrode plate 22 protruding from the other end side in the same orthogonal direction. It has 22A and. A part of the positive electrode portion 21A and the negative electrode portion 22A is compressed, and the electrode terminals 14 connected to the external terminals 13 are welded to the compressed portions of the positive electrode portion 21A and the negative electrode portion 22A, respectively. There is.

The separator 23 is a non-woven fabric made of polypropylene or the like for holding the non-aqueous electrolytic solution 27 between the positive electrode plate 21 and the negative electrode plate 22. Further, as the separator 23, a porous polymer film such as a porous polyethylene film, a porous polyolefin film, and a porous polyvinyl chloride film, or a lithium ion or ionic conductive polymer electrolyte film is used alone or in combination. You can also do it.

The non-aqueous electrolyte solution 27 is a composition in which a supporting salt is contained in a non-aqueous solvent. Here, as the non-aqueous solvent, one or two selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like. More than seed materials can be used. As supporting salts, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiI One or more lithium compounds (lithium salts) selected from the above can be used.

(Positive plate)
The configuration of the electrode plate group 20 will be described with reference to FIG.
First, the positive electrode will be described in detail. The positive electrode plate 21 is coated with the positive electrode mixture 212 on the surface of the positive electrode base material 211. As the base material of the positive electrode plate 21, the same components as those of the conventional secondary battery can be used. For example, as the material of the base material, a conductive material made of a metal having good conductivity is preferably used. For example, as the conductive material, a material containing aluminum and a material containing an aluminum alloy can be used.

The positive electrode mixture 212 has a positive electrode active material. The positive electrode active material may additionally contain one or more elements in addition to the transition metal element (ie, at least one of Ni, Co and Mn). Additional elements include Group 1 (alkali metals such as sodium), Group 2 (alkaline earth metals such as magnesium and calcium), Group 4 (transition metals such as titanium and zirconium), and Group 6 (chromium) in the periodic table. , A transition metal such as tungsten), and any element belonging to Group 8 (transition metal such as iron) can be contained. Further, the additional element may include any element belonging to Group 13 (metalloid element such as boron or aluminum) and Group 17 (halogen such as fluorine) in the periodic table. can. Preferably, the positive electrode active material is "LiNiComnO _2- based positive electrode active material". The "LiNiCoMnO _2- based positive electrode active material" means a composite oxide containing Li, Ni, Co, and Mn, and may further contain a metal element different from Li, Ni, Co, and Mn.

For example, the positive electrode active material is represented by the general formula _{Li (1 + s) Ni x} Co y Mn z M v O 2, it consists of hexagonal lithium-containing composite oxide having a layered structure. In the above general formula, “−0.05 ≦ s ≦ 0.20”, “x + y + z + v = 1”, “0.3 ≦ x ≦ 0.7”, “0.1 ≦ y ≦ 0.4”, “ 0.1 ≦ z ≦ 0.4 ”,“ 0.0002 ≦ v ≦ 0.02 ”, where M is Na, Mg, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W. Represents at least one element.

By the way, it is known that the positive electrode active material is improved in overcharge resistance by being mixed with calcium (Ca). It is considered that one of the reasons for the improvement in overcharge resistance is that the structure is strengthened by mixing Ca and the collapse of the structure of the positive electrode active material is suppressed.

Therefore, in the present embodiment, the positive electrode mixture 212 further contains Ca. For example, the positive electrode mixture 212 is _{contained in the positive electrode mixture 212 by adding calcium sulfate (CaSO 4} ) or calcium chloride (CaCl ₂ ) to the positive electrode active material and mixing it with the positive electrode active material.

Graph L3 of FIG. 3 shows the relationship between the “positive electrode calcium amount”, which is the amount of Ca contained in the positive electrode plate 21, and the overcharge resistance. Graph L3 shows that the overcharge resistance of the electrode group 20 improves as the amount of positive electrode calcium increases. Therefore, in order to improve the overcharge resistance of the electrode plate group 20, it is desirable to increase the amount of Ca contained in the positive electrode plate 21. Although Ca is incorporated into the structure of the positive electrode active material to improve the overcharge resistance, a part of Ca is not incorporated into the structure of the positive electrode active material or is separated from the structure to be charged. Sometimes it is inevitable to move to the negative electrode. The "positive electrode calcium amount" is [mass%] based on the total mass of calcium atoms contained in the positive electrode plate 21 with respect to the mass of the positive electrode mixture 212 of the positive electrode plate 21. That is, the total mass of calcium atoms includes elemental Ca, calcium atoms constituting compounds such as nitrogen oxides (CaNOx), and the like.

Further, the positive electrode mixture 212 may contain a conductive material. As the conductive material, for example, carbon black such as acetylene black (AB) and Ketjen black, and graphite (graphite) can be used.

In the positive electrode plate 21, for example, a positive electrode active material, Ca, a conductive material, an amine, a solvent, and a binder are kneaded, and the kneaded positive electrode mixture 212 is applied to the positive electrode base material 211. It is produced by drying. Here, as the solvent, for example, an NMP (N-methyl-2-pyrrolidone) solution can be used. Further, as the binder, for example, polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC) and the like can be used. Further, as the positive electrode base material 211, a thin film made of aluminum or an alloy containing aluminum as a main component can be used.

Examples of amines include primary amines such as methylamine (CH ₃ NH ₂ ), secondary amines such as dimethylamine ((CH ₃ ) ₂ NH), and primary amines such as trimethylamine ((CH ₃ ) ₃ N). At least one of the tertiary amines can be used. In the present embodiment, regardless of whether it is a primary to tertiary amine, amine is contained in an amount of 0.02% by mass or more and 0.1% by mass or less based on the total mass of the positive electrode active material. ing.

(Negative electrode plate)
Next, in the negative electrode plate 22, the negative electrode mixture 222 is applied to the surface of the negative electrode base material 221. In the present embodiment, the surface of the negative electrode base material 221 constitutes the surface of the negative electrode.

The negative electrode mixture 222 has a negative electrode active material. The negative electrode active material is a material capable of occluding and releasing lithium, and for example, a powdered carbon material made of graphite or the like can be used. Then, the negative electrode plate 22 is manufactured by kneading the negative electrode active material, the solvent, and the binder, applying the kneaded negative electrode mixture 222 to the negative electrode base material 221 and drying it, similarly to the positive electrode plate 21. NS. In this embodiment, the binder comprises carboxymethyl cellulose (CMC) having a sodium salt. Here, as the negative electrode base material 221, for example, a thin film made of copper, nickel, or an alloy thereof can be used.

Example 1 of Table L4 of FIG. 4 shows an example of the secondary battery 10 of the present embodiment. FIG. 4 shows the relationship between the amount of Ca in the positive electrode plate 21 and the amount of nitrogen oxides (hereinafter, CaNOx) containing calcium atoms in the negative electrode plate 22. Specifically, the detection result of "the ratio of CaNOx" (= "Ca in CaNOx" / "total Ca") in the negative electrode plate 22 is shown. In addition, "x" in "CaNOx" is an arbitrary integer, and is preferably an integer of 1 or 2, for example. In the present embodiment, the "ratio of CaNOx" is the ratio of the molecular weight of calcium atoms contained in all CaNOx in the negative electrode plate to the molecular weight of all calcium atoms in the negative electrode plate 22. This detection is performed by X-ray photoelectron spectroscopy. X-ray Photoelectron Spectroscopy (XPS) is a method of analyzing the constituent elements of the sample surface and their electronic states by irradiating the sample surface with X-rays and measuring the energy of the emitted photoelectrons. Is. XPS is carried out by a method according to the "JIS K 0167: 2011" standard.

(Action)
The secondary battery 10 of the present embodiment contains Ca in the positive electrode plate 21 for improving the overcharge resistance. On the other hand, if the amount of Ca contained in the positive electrode plate 21 is large, the positive electrode plate 21 may not be incorporated into the structure of the positive electrode active material, the amount of Ca separated from the positive electrode active material may increase, and the positive electrode plate 21 may be charged. The amount of Ca that moves from the negative electrode plate 22 to the negative electrode plate 22 also increases. When Ca moves to the negative electrode plate 22, it precipitates as metallic calcium and lowers the Li precipitation resistance of the negative electrode plate 22, so that the overcharge resistance of the secondary battery 10 may decrease. Therefore, in the present embodiment, by suppressing the amount of Ca that moves from the positive electrode plate 21 to the negative electrode plate 22, the precipitation of metallic calcium on the negative electrode plate 22 is suppressed. As a result, the Li precipitation resistance of the secondary battery 10 is maintained.

More specifically, in the secondary battery 10 of the present embodiment, amine is added to the positive electrode plate 21.
Amine is Ca that does not contribute to the overcharge resistance of the positive electrode plate 21, and acts on Ca that is not incorporated into the structure of the positive electrode active material or is separated from the positive electrode active material, and is a nitrogen oxide of Ca. Promotes the production of CaNOx). Therefore, in the positive electrode plate 21, nitrogen oxides (CaNOx) are generated from a part of Ca in the positive electrode plate 21. A part of Ca and CaNOx existing in the positive electrode plate 21 moves from the positive electrode plate 21 to the negative electrode plate 22 when the secondary battery 10 is charged.

In the positive electrode plate 21, the amount of Ca decreases in inverse proportion to the generation and increase of CaNOx. Therefore, as CaNOx is generated on the positive electrode plate 21, Ca moving to the negative electrode plate 22 decreases, and the amount of metallic calcium precipitated on the negative electrode plate 22 also decreases. Since CaNOx does not have conductivity, neither the positive electrode plate 21 nor the negative electrode plate 22 affects the movement of lithium ions, and the Li precipitation resistance of the secondary battery 10 is preferable assuming that a large amount of CaNOx is generated. Be maintained.

In the negative electrode plate 22, CaNOx that has moved from the positive electrode plate 21 is present in an ionic state, and Ca that has also moved is precipitated as metallic calcium. Ca and CaNOx move from the positive electrode plate 21 to the negative electrode plate 22 in an ionic state during charging, particularly when charging the secondary battery 10 immediately after production.

CaNOx of the negative electrode plate 22 has no effect on the movement of lithium ions during charging. On the other hand, since the metallic calcium precipitated on the negative electrode plate 22 has conductivity, there is a possibility that the movement of lithium ions during charging may be affected by the concentration of lithium ions and the like. For example, lithium ions are likely to be concentrated on metallic calcium protruding in the direction of the positive electrode, and when lithium ions are concentrated, lithium is likely to be deposited. In addition, the precipitation of lithium ions may lead to the precipitation of further lithium ions on the portion.

That is, the negative electrode plate 22 has a performance that makes it difficult for metallic lithium to precipitate, that is, so-called lithium precipitation resistance (Li precipitation resistance), due to the precipitation of metallic calcium. Generally, if the Li precipitation resistance is high, a large amount of lithium ions can be transferred in a short time, that is, a large current can be charged and discharged, and the battery performance is high. On the contrary, if the Li precipitation resistance is low, there are few lithium ions that can be moved in a short time, that is, only charging and discharging with a small current can be performed. That is, charging with a current exceeding the permissible value has a high possibility of precipitating lithium, so that the charging current is suppressed to a small value and the battery performance is lowered. Further, since the negative electrode plate 22 grows in the direction of the positive electrode plate 21 in which lithium ions move, the electrical distance from the positive electrode plate 21 becomes short, and the negative electrode plate 22 reaches the positive electrode plate 21 via lithium. There is a possibility that the insulation property in the battery may be deteriorated or a minute short circuit may occur, such as a short circuit, and the battery performance may be further deteriorated. From these facts, in this embodiment, the precipitation of metallic calcium is suppressed, and the decrease in the precipitation resistance of lithium due to the precipitation of metallic calcium is suppressed.

(Manufacturing method of secondary battery)
The procedure for manufacturing the secondary battery 10 will be described with reference to FIGS. 5 to 7.
As shown in FIG. 5, the manufacturing process of the secondary battery 10 includes a positive electrode mixture kneading step (step S10) as a stirring step, a positive electrode mixture coating step (step S11), and a electrode plate group manufacturing step (step). S12), a battery assembly step (step S13), and a battery activation step (step S14) as a charging step are provided.

In the positive electrode mixture kneading step (step S10), the positive electrode active material containing Ca and the positive electrode active material are mixed with amine, so that the positive electrode active material containing Ca to which amine is added can be applied to the base material as a positive electrode mixture. To create. In the present embodiment, the mixture of the positive electrode active material containing Ca and amine is heated and stirred in a closed container. As a result, the mixture of the positive electrode active material, Ca and amine is added with the action of stirring, the action of heating and the action of pressurization, and the positive electrode active material is mixed with the positive electrode active material, Ca and amine. For Ca that has not been incorporated into the structure of, the reaction that causes it to become CaNOx can be promoted (for example, Example 1). Conventionally, it is known that a positive electrode mixture is produced by stirring in a vacuum environment, that is, under reduced pressure for defoaming (for example, Reference Example 1).

In the positive electrode mixture kneading step with reference to FIG. 6, a range of stirring temperature and stirring pressure is set as the manufacturing condition 1, and a slurry of the positive electrode active material is generated based on the manufacturing condition 1. For example, in the positive electrode mixture kneading step, the heat treatment set to the stirring temperature under the manufacturing condition 1 is performed, and the pressurizing treatment set to the stirring pressure under the manufacturing condition 1 is performed.

With reference to FIG. 5, in the positive electrode mixture coating step (step S11), the positive electrode plate 21 is manufactured by applying the slurry of the positive electrode active material to the positive electrode base material 211 by a die coating method or the like.
The electrode plate group manufacturing step (step S12) is a step of manufacturing the electrode plate group 20 which is a laminated body. In the electrode plate group manufacturing process, the electrode plate group 20 is generated by winding the positive electrode plate 21 and the negative electrode plate 22 in the winding direction so that the separator 23 is interposed between them. For example, the laminated body before winding is laminated in the order of the positive electrode plate 21, the separator 23, the negative electrode plate 22, and the separator 23, and the overlap between the positive electrode plate 21 and the negative electrode plate 22 is slightly shifted in the winding axis direction. There is. Therefore, the electrode plate group 20 in which the positive electrode portion 21A protrudes from one end in the winding axis direction and the negative electrode portion 22A protrudes from the other end is manufactured.

In the battery assembly step (step S13), the electrode plate group 20 is inserted into the battery case 11 through the opening. After the electrode plate group 20 is inserted, the battery case 11 accommodates the electrode plate group 20 inside by welding the lid body 12 to the opening thereof. After that, after the inside of the battery case is dried, the non-aqueous electrolyte solution 27 is injected into the battery case, the injection port of the non-aqueous electrolyte solution 27 opened in the lid 12 is sealed, and the battery case 11 is sealed. Will be done. As a result, the secondary battery 10 is manufactured.

In the battery activation step (step S14), the manufactured secondary battery 10 is fully charged with a predetermined amount of electricity and fully discharged with a predetermined amount of electricity to adjust the secondary battery to a usable state. ..

As shown in FIG. 6, in the battery activation step, a charging rate is set as the manufacturing condition 2, and the secondary battery 10 manufactured by charging or the like based on the manufacturing condition 2 is activated. At this time, by setting the charging rate to a current of a predetermined magnitude or more, CaNOx is applied to Ca that has not been incorporated into the positive electrode active material in the positive electrode plate 21 in which the positive electrode active material containing Ca and amine are mixed. The reaction to cause calcium can be further promoted (for example, Example 1). Conventionally, a process of activating a secondary battery by charging at a charging rate that does not promote the reaction of CaNOx is known (for example, Reference Example 1).

With the above, the manufacturing process of the secondary battery 10 is completed.
(Li precipitation resistance of secondary batteries)
As shown in Table L4 of FIG. 4, three secondary batteries 10 of Reference Example 1, Reference Example 2, and Example 1 were prepared in order to compare the Li precipitation resistance of the secondary battery 10.

Here, the “positive electrode calcium amount (after activation)” shown in FIG. 4 is an index of a large amount of Ca moving to the negative electrode plate 22. More specifically, a part of Ca of the positive electrode plate 21 moves to the negative electrode plate 22 during charging. The more Ca contained in the positive electrode plate 21, the more Ca moves from the positive electrode plate 21 to the negative electrode plate 22. In other words, there is a positive correlation between the amount of Ca that moves to the negative electrode plate 22 by charging and the amount of Ca contained in the positive electrode plate 21 after charging.

Further, "amount of amine added to the positive electrode" indicates the amount of amine added to the positive electrode plate 21 of Reference Example 2 and Example 1. The amount of amine is increased according to the amount of Ca contained in the positive electrode plate 21. On the other hand, in Reference Example 1, amine was not added to the positive electrode plate 21.

Under such conditions, the "percentage of CaNOx" in the negative electrode of the activated secondary battery 10 is compared. The larger the value of "CaNOx ratio", the higher the Li precipitation resistance is maintained.

In Reference Example 1, Ca is not generated in the positive electrode plate 21 because Ca is contained in the positive electrode plate 21, but amine is not contained, and the current in the activation step is low (1C to 1.5C). Therefore, the “percentage of CaNOx” does not exist in the negative electrode plate 22 at a significant value (≈0).

In Example 1 and Reference Example 2, the "percentage of CaNOx" is present in the negative electrode plate 22 at a significant value. Roughly speaking, as the "positive electrode calcium amount (after activation)" increases, the "CaNOx ratio" in the negative electrode plate 22 decreases. Further, if the "positive electrode calcium amount (after activation)" is the same, the higher the "CaNOx ratio", the more the risk of metallic calcium precipitation on the negative electrode plate 22 is suppressed.

For example, in the "ratio of CaNOx" of Example 1, the "positive electrode calcium amount (after activation)" is "0.13 [mass%]" and the "amine addition amount to the positive electrode" is "0.02 [". When it is "% by mass", it is "1 (= 0.3 / 0.3)". Further, when the "positive electrode calcium amount (after activation)" is "0.15 [mass%]" and the "amine addition amount to the positive electrode" is "0.03 [mass%]", "0. 68 (= 0.27 / 0.4) ”. Further, when the "positive electrode calcium amount (after activation)" is "0.2 [mass%]" and the "amine addition amount to the positive electrode" is "0.05 [mass%]", "0. 58 (= 0.29 / 0.5) ”. Further, when the "positive electrode calcium amount (after activation)" is "0.4 [mass%]" and the "amine addition amount to the positive electrode" is "0.1 [mass%]", "0. 5 (= 0.3 / 0.6) ”.

On the other hand, for example, in the "ratio of CaNOx" of Reference Example 2, the "positive calcium amount (after activation)" is "0.13 [mass%]", and the "amine addition amount to the positive electrode" is. When it is "0.02 [mass%]", it is "0.8 (= 0.24 / 0.3)". Further, when the "positive electrode calcium amount (after activation)" is "0.15 [mass%]" and the "amine addition amount to the positive electrode" is "0.03 [mass%]", "0. 6 (= 0.24 / 0.4) ”. Further, when the "positive positive calcium amount (after activation)" is "0.2 [mass%]" and "0.05 [mass%]", "0.3 (= 0.15 / 0.)". When "5)" and "amount of positive electrode calcium (after activation)" are "0.4 [mass%]" and "amount of amine added to the positive electrode" is "0.1 [mass%]", " 0.15 (= 0.09 / 0.6) ”.

That is, when the "positive electrode calcium amount (after activation)" and the "amine addition amount to the positive electrode" are the same, the "CaNOx ratio" in Example 1 is larger than the "CaNOx ratio" in Reference Example 2. It gets higher. Specifically, the "percentage of CaNOx" between Example 1 and Reference Example 2 is "1" and "0.8", "0.68" and "0.6", and "0.58", respectively. It becomes "0.3", "0.5" and "0.15". In Example 1, the ratio of "CaNOx ratio" is higher than that in Reference Example 2 (see FIG. 4), and the Li precipitation resistance is maintained high (see FIG. 6).

(Example 1)
The secondary battery 10 corresponding to the first embodiment was manufactured under the conditions shown in Table L6 of FIG.
That is, in the positive electrode mixture kneading step, it is prepared as a slurry that can be applied to the positive electrode base material 211. As the production condition 1, the stirring temperature was set to "45 ° C. to 60 ° C." and the stirring pressure was increased from 1 atm. By setting the stirring temperature to "45 ° C. to 60 ° C." and stirring in a closed container, the pressure inside the container rises due to evaporation of the dispersion medium or the like. That is, it is agitated under a pressure of 1 atm or more. The stirring temperature is preferably "45 ° C." or higher and "60 ° C." or lower, and more preferably "50 ° C." or higher and "60 ° C." or lower. The stirring pressure is preferably higher than 1 atm, more preferably 1.5 atm or higher.

Further, as shown in the graph L7 of FIG. 7, the charging rate was set to “3C” or higher as the manufacturing condition 2 in the battery activation step. The secondary battery 10 of the first embodiment is charged with a small current L71 and then charged with a large current, here, a current L72 of "3C" or more, until it is fully charged. After the secondary battery 10 is fully charged, it is discharged with the current L73. Here, "C" indicates that the battery is charged with a current corresponding to the battery capacity for 1 hour.

As shown in FIG. 7, the charging current L71 between the elapsed time t71 and the elapsed time t72 is smaller than the current L72. Specifically, the current L71 is 1/3 or less of the current L72. The period from the elapsed time t71 to the elapsed time t72 is not particularly limited, but is preferably, for example, between 30 seconds and 10 minutes.

The charging current L72 between the elapsed time t73 and the elapsed time t74 is "3C". The period from the elapsed time t73 to the elapsed time t74 is about one hour. Then, the electric current is discharged from the elapsed time t74 to the elapsed time t75 with the current L73. Conventionally, charging with a current of "2.5 C" or more in the activation step has been avoided because it gives an unnecessary load to the secondary battery and has only a demerit. Therefore, in consideration of reducing the load, the maximum charging current is limited to "1.5C".

However, the present inventors promote the change of Ca contained in the positive electrode plate 21 to CaNO by charging with a current of "3C" or more in the activation step, and move from the positive electrode plate 21 to the negative electrode plate 22. It was found that the ratio of CaNOx to Ca increased. Therefore, the predetermined current used for charging in the activation step is set to a "3C" current larger than the conventional one. Then, a secondary battery 10 corresponding to Example 1 having the “CaNOx ratio” shown in FIG. 4 and having the Li precipitation resistance shown in FIG. 6 was obtained.

That is, as shown in FIG. 6, in the secondary battery 10 of Example 1, the "positive electrode calcium amount (after activation)" is "0.13 [mass%]", "0.15 [mass%]", and so on. Regardless of whether it is "0.2 [mass%]" or "0.4 [mass%]", the Li precipitation resistance to charging at the rated current is well maintained. That is, the precipitation of lithium on the negative electrode plate 22 was suppressed.

(Reference example 1)
The secondary battery 10 corresponding to Reference Example 1 was manufactured under the conditions shown in Table L6 of FIG.
That is, in the positive electrode mixture kneading step, Ca is mixed with the positive electrode active material but amine is not mixed, and the positive electrode active material to which Ca is added but amine is not added is applied to the positive electrode base material 211. Create as a possible slurry. Further, as the production condition 1 in the positive electrode mixture kneading step, the stirring temperature was set to "30 ° C. or higher and lower than 45 ° C." and the stirring pressure was set to "1 atm". Further, as the manufacturing condition 2 in the battery activation step, the charging rate was set to "1C to 1.5C".

Then, the Li precipitation resistance of the secondary battery 10 of Reference Example 1 was measured. The secondary battery 10 of Reference Example 1 had good Li precipitation resistance to charging at a rated current when the “positive electrode calcium amount (after activation)” was “0.13 [mass%]”. On the other hand, when the "positive electrode calcium amount (after activation)" is "0.15 [mass%]", "0.2 [mass%]" or "0.4 [mass%]", the rated current is used. The Li precipitation resistance to charging was poor.

(Reference example 2)
The secondary battery 10 corresponding to Reference Example 2 was manufactured under the conditions shown in Table L6 of FIG.
That is, in the positive electrode mixture kneading step, the positive electrode active material, Ca and amine are mixed, and the positive electrode active material to which Ca and amine are added is prepared as a slurry that can be applied to the positive electrode base material 211. Further, the production condition 1 in the positive electrode mixture kneading step was set to the same conditions as in Reference Example 1. Specifically, the stirring temperature was set to "30 ° C. or higher and lower than 45 ° C.", and the stirring pressure was set to "1 atm". Further, the manufacturing condition 2 in the battery activation step was set to the same condition as that of the reference example 1. Specifically, the charging rate was set to "1C to 1.5C".

Then, the Li precipitation resistance of the secondary battery 10 of Reference Example 2 was measured. The secondary battery 10 of Reference Example 2 is charged with a rated current when the “positive electrode calcium amount (after activation)” is “0.13 [mass%]” and “0.15 [mass%]”. The Li precipitation resistance was good. On the other hand, when the "positive electrode calcium amount (after activation)" is either "0.2 [mass%]" or "0.4 [mass%]", the Li precipitation resistance to charging at the rated current is high. It was bad.

(Action effect)
As shown in FIG. 6, if the "positive electrode calcium amount (after activation)" is as small as "0.13 [mass%]", Li is in any of Reference Examples 1 and 2 and Example 1. Although the precipitation resistance is good, the overcharge resistance is low because the amount of Ca added is small (see FIG. 3).

When the "positive electrode calcium amount (after activation)" becomes "0.15 [mass%]", the Li precipitation resistance of Reference Example 1 becomes poor, but both Reference Example 2 and Example 1 have Li precipitation resistance. Well maintained. The reason why the Li precipitation resistance is poor in Reference Example 1 is that the overcharge resistance is improved by increasing the amount of Ca added, but the Ca of the positive electrode plate 21 moves to the negative electrode plate 22 and precipitates. It is believed that there is. In Reference Example 2, the Li precipitation resistance is maintained well because the amine added to the positive electrode plate 21 changes a part of Ca in the positive electrode plate 21 to CaNOx, so that Ca that precipitates metallic calcium is the negative electrode. This is because the rate of movement to the plate 22 decreases. At this time, the “CaNOx ratio” of the negative electrode plate 22 of Reference Example 2 is “0.6”, and the Li precipitation resistance is well maintained theoretically or empirically.

When the "positive electrode calcium amount (after activation)" becomes "0.2 [mass%]", the Li precipitation resistance of Reference Example 2 also becomes poor, but in Example 1, the Li precipitation resistance is maintained well. .. The reason why the Li precipitation resistance is poor in Reference Example 2 is that, as in Reference Example 1, the overcharge resistance was improved by increasing the amount of Ca added, but the Ca of the positive electrode plate 21 moved to the negative electrode plate 22. Precipitation is considered to be one of the causes. Further, although amine was added to the positive electrode plate 21 of Reference Example 2, the "percentage of CaNOx" of the negative electrode plate 22 was "0.3", which was reduced to about half of the above-mentioned "0.6". Theoretically or empirically, the Li precipitation resistance is not well maintained. On the other hand, in Example 1, the overcharge resistance is improved by increasing the amount of Ca added, and the Li precipitation resistance is well maintained. This is because the amine added to the positive electrode plate 21 of Example 1 promotes the conversion of Ca of the positive electrode plate 21 to CaNOx according to the production conditions 1 and 2. Therefore, the "percentage of CaNOx" of the negative electrode plate 22 is maintained at "0.58", which is close to "0.6", so that the Li precipitation resistance is satisfactorily maintained.

When the "positive electrode calcium amount (after activation)" becomes "0.4 [mass%]", the Li precipitation resistance is poor in Reference Example 1 and Reference Example 2, but the Li precipitation resistance is good in Example 1. Be maintained. In Example 1, the overcharge resistance is further improved by increasing the amount of Ca added, and the Li precipitation resistance is well maintained. The positive electrode plate 21 of Example 1 is a positive electrode plate due to the addition of amine, production conditions 1 and 2 in the positive electrode mixture kneading step, and charging with a large current “3C” in the battery activation step. The conversion of 21 Ca to CaNOx is promoted. Therefore, the "percentage of CaNOx" of the negative electrode plate 22 is maintained at "0.5", which is close to "0.6", so that the Li precipitation resistance is satisfactorily maintained.

As described above, according to the method for manufacturing the lithium ion secondary battery and the lithium ion secondary battery of the present embodiment, the effects described below can be obtained.
(1) In the secondary battery 10 in which the positive electrode plate 21 contains Ca that maintains safety during overcharging, even if the negative electrode plate 22 contains Ca, it affects the Li precipitation resistance. The probability that it exists as absent CaNOx is increased. In other words, the probability that it exists as metallic calcium that reduces Li precipitation resistance is suppressed. Therefore, it contains Ca necessary for ensuring the safety of overcharging, and the decrease in Li precipitation resistance is suppressed.

(2) Even if 0.2 [mass%] or more of Ca is added to the positive electrode plate 21, Li precipitation resistance is maintained.
(3) By containing amine in the positive electrode plate 21, more CaNOx can be produced. As the amine, at least one of methylamine, dimethylamine and trimethylamine can be used. Further, since Ca moving from the positive electrode plate 21 to the negative electrode plate 22 is relatively reduced, the generation of metallic calcium from Ca in the negative electrode plate 22 is suppressed, and the decrease in Li precipitation resistance is suppressed.

(4) In the secondary battery 10 containing Ca that can ensure the safety of overcharging, the ratio of Ca becoming CaNOx increases, so that the ratio of metallic calcium that adversely affects the Li precipitation resistance in the negative electrode plate 22 Is suppressed. Therefore, the safety of overcharging can be ensured, and the decrease in Li precipitation resistance can be suppressed.

(5) Since the positive electrode mixture is agitated together with the heat treatment and the pressure treatment in the positive electrode mixture kneading step, the ratio of CaNOx produced in the positive electrode mixture is increased.
(6) In the heat treatment, the positive electrode mixture is kept at 45 ° C. or higher and 60 ° C. or lower, and in the pressurization treatment, the positive electrode mixture is raised from 1 atm and pressurized to appropriately increase the proportion of CaNOx produced. Be done.

(7) In the battery activation step, the ratio of CaNOx in the negative electrode plate 22 is increased by charging with a current of "3C" or more.
(Other embodiments)
The above embodiment can also be implemented in the following embodiments.

-In the above embodiment, the case where the ratio of CaNOx in the negative electrode plate 22 is detected by XPS has been illustrated, but the ratio of CaNOx is detected by other detectors such as XAFS (X-ray absorption fine structure) or a detection method. May be good.

-In the above embodiment, the case where the electrode plate group 20 is wound with the positive electrode plate and the negative electrode plate sandwiching the separator is illustrated, but the present invention is not limited to this, and if the electrode plate group 20 has a flat shape, a plurality of electrodes are used. A positive electrode plate and a plurality of negative electrode plates may be laminated with a separator interposed therebetween.

-In the above embodiment, in the positive electrode mixture kneading step, a case where the positive electrode mixture is heated to a temperature of "45 ° C." or higher and "60 ° C." or lower is illustrated. However, the present invention is not limited to this, and the heating temperature may be lower than "45 ° C." or higher than "60 ° C." as long as the change of Ca to CaNOx can be promoted.

-In the above embodiment, in the positive electrode mixture kneading step, the case where the positive electrode mixture is increased from 1 atm and pressurized is illustrated. However, the present invention is not limited to this, and if the reaction with CaNOx can be promoted, the positive electrode mixture may be kneaded after being pressurized to a predetermined pressure higher than 1 atm, or the pressurized predetermined pressure may be kneaded. The pressure may be further increased from the pressure. On the contrary, the pressure may be lowered from the pressurized predetermined pressure within a range not less than 1 atm.

-In the above embodiment, the case where both the heat treatment and the pressure treatment are performed in the positive electrode mixture kneading step is illustrated. However, the present invention is not limited to this, and in the positive electrode mixture kneading step, only one of the heat treatment and the pressure treatment may be performed. Even with only one treatment, the change of Ca to CaNOx is promoted in the positive electrode mixture.

-In the above embodiment, the case where the period from the elapsed time t73 to the elapsed time t74 is about one hour is illustrated. However, the present invention is not limited to this, and the period from the elapsed time t73 to the elapsed time t74 may be less than one hour. For example, it may be 1 minute or more and 20 minutes or less. This is because the movement of CaNOx becomes predominant especially in the initial period when charging of 3C or more is started.

-In the above embodiment, the case of charging with a current of "3C" or more in the battery activation step has been illustrated, but the present invention is not limited to this, and the charging current is less than "3C" if the change of Ca to CaNOx is promoted. It may be.

-In the above embodiment, a case where heat treatment in the positive electrode mixture kneading step, pressurization treatment in the same step, and charging with a large current in the battery activation step are performed has been exemplified. However, the present invention is not limited to this, and at least one of heat treatment in the positive electrode mixture kneading step, pressurization treatment in the same step, and charging with a large current in the battery activation step may be performed. For example, only one of the positive electrode mixture kneading step and the battery activation step may be performed. Since the change of Ca to CaNOx is promoted in each step in any of the steps, the Li precipitation resistance can be maintained by performing at least one step.

-In the above embodiment, the case where the amine is any one of methylamine, dimethylamine and trimethylamine has been illustrated. However, the present invention is not limited to this, and the amine may be composed of at least two or more of methylamine, dimethylamine and trimethylamine.

-In the above embodiment, the case where the Li precipitation resistance is maintained even when Ca of 0.4 [mass%] or less is added to the positive electrode plate is illustrated. However, not limited to this, if the Li precipitation resistance is maintained at the charging current in the range of use, even if it is judged that the Li precipitation resistance is maintained when 0.4 [mass%] or more of Ca is added. good. On the contrary, it may be determined that the Li precipitation resistance is not maintained unless the added Ca is a predetermined value of less than 0.4 [mass%]. Thereby, the amount of Ca added and the resistance to Li precipitation can be set according to the use of the secondary battery 10 and the charge / discharge current.

-In the above embodiment, the case where the Li precipitation resistance is good when the "Percentage of CaNOx" in the negative electrode plate 22 is "0.5" has been illustrated. However, the present invention is not limited to this, and the "percentage of CaNOx" may be smaller than "0.5" as long as the Li precipitation resistance is maintained during charging under the condition of using a secondary battery. On the contrary, if it is not larger than "0.5", the Li precipitation resistance may not be maintained.

-In the above embodiment, the case where the secondary battery 10 is a lithium ion secondary battery has been illustrated. However, the present invention is not limited to this, and the secondary battery may be a battery that uses an electrolytic solution made of a non-aqueous electrolyte.

-In the above embodiment, the case where the secondary battery 10 is used as a power source for an automobile has been illustrated. However, the present invention is not limited to this, and the secondary battery may be used as a power source other than the automobile such as various mobile bodies and fixed bodies as long as it is used as a power source.

10 ... Secondary battery, 11 ... Battery case, 12 ... Lid, 13 ... External terminal, 14 ... Electrode terminal, 20 ... Electrode plate group, 21 ... Positive electrode plate, 21A ... Positive electrode part, 22 ... Negative electrode plate, 22A ... Negative electrode Part, 23 ... Separator, 26 ... Edge, 27 ... Non-aqueous electrolyte solution, 211 ... Positive electrode base material, 212 ... Positive electrode mixture, 221 ... Negative electrode base material, 222 ... Negative electrode mixture.

Claims (5)

Battery case and
The electrode body and the non-aqueous electrolyte housed in the battery case,
The positive electrode plate and the negative electrode plate constituting the electrode body, and the positive electrode mixture constituting the positive electrode plate,
The amine contained in the positive electrode plate, the positive electrode active material, and
Calcium mixed with the positive electrode active material and
Wherein the calcium is in the mass of the calcium atoms in the mass of the positive electrode mixture material to said positive electrode plate is 0.2 [wt%] or more,
In the negative electrode plate, the ratio of the molecular weight of calcium atoms contained in the nitrogen oxide (CaNOx) containing calcium atoms in the negative electrode plate to the molecular weight of all calcium atoms in the negative electrode plate is "0.5" or more. Water electrolyte secondary battery. The positive electrode mixture comprises a battery case, an electrode body and a non-aqueous electrolyte housed in the battery case, a positive electrode plate and a negative electrode plate constituting the electrode body, and a positive electrode mixture constituting the positive electrode plate. the positive electrode plate in the calcium mass 0.2 [wt%] or more calcium is added, the non-aqueous electrolyte secondary battery where the positive electrode active material is contained in the atoms contained with respect to the mass of the positive electrode mixture material to It ’s a manufacturing method,
When the positive electrode mixture is produced, an amine is added and stirred to increase nitrogen oxides (CaNOx) containing calcium atoms in the positive electrode mixture, and a stirring step.
Manufacture of a non-aqueous electrolyte secondary battery comprising a charging step of increasing the proportion of CaNOx by charging the non-aqueous electrolyte secondary battery produced by accommodating the electrode body and the non-aqueous electrolyte in the battery case. Method. In the charging step, the charging is performed with a current of 3C or more in the non-aqueous electrolyte secondary battery.
The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 2. In the stirring step, at least one of a heat treatment for heating the positive electrode mixture and a pressure treatment for pressurizing the positive electrode mixture is performed in combination.
The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 2 or 3. The heat treatment is a treatment for adjusting the positive electrode mixture to 45 ° C. or higher and 60 ° C. or lower.
The pressurization treatment is a treatment of increasing the positive electrode mixture from 1 atm to pressurize the mixture.
The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 4.

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