JP2017069020A - Method for manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a nonaqueous electrolyte secondary battery, by which a nonaqueous electrolyte secondary battery low in internal resistance can be manufactured.SOLUTION: A method for manufacturing a nonaqueous electrolyte secondary battery according to the present invention comprises: a positive electrode active material-processing step; a positive electrode plate-fabricating step; an assembling step; and an initial charging step. The positive electrode active material-processing step includes: performing the pretreatment of immersing, in aqueous solvent, a positive electrode active material arranged by substituting a transition metal for part of manganese of a lithium manganate having a spinel type crystalline structure; and drying the positive electrode active material after the pretreatment.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery using trilithium phosphate (Li ₃ PO ₄ ) as one of positive electrode materials for forming a positive electrode active material layer.

  In lithium ion secondary batteries, oxidative decomposition of the electrolyte may occur with charge and discharge. In addition, in a lithium ion secondary battery in which an acid is generated by oxidative decomposition of the electrolytic solution, the transition metal of the positive electrode active material may be eluted by the acid. And when the transition metal of a positive electrode active material elutes, there exists a possibility that the capacity | capacitance maintenance factor of a lithium ion secondary battery may fall.

  For example, Patent Document 1 describes a nonaqueous electrolyte secondary battery in which a positive electrode active material layer contains trilithium phosphate as an additive together with a positive electrode active material. And it is supposed that the elution of the transition metal of the positive electrode active material accompanying charging / discharging of a non-aqueous electrolyte secondary battery can be prevented by containing trilithium phosphate in the positive electrode active material layer. Specifically, it is said that trilithium phosphate can function as an acid consuming material by reacting with hydrofluoric acid (HF) produced in the electrolyte. As a result, elution of the transition metal of the positive electrode active material can be suppressed, and the durability of the nonaqueous electrolyte secondary battery can be enhanced.

JP 2014-103098 A

  Here, when trilithium phosphate as an additive is contained in the positive electrode active material layer, in the initial charging step of the lithium ion secondary battery, trilithium phosphate and hydrofluoric acid react to react with each other. A film is formed on the surface of the active material. Since the coating film is formed on the surface of the positive electrode active material, when the coating film has low conductivity, the internal resistance may be increased in the lithium ion secondary battery.

  The present invention has been made for the purpose of solving the problems of the prior art described above. That is, the subject is providing the manufacturing method of the non-aqueous electrolyte secondary battery which can manufacture the non-aqueous electrolyte secondary battery with low internal resistance.

  The method for producing a non-aqueous electrolyte secondary battery of the present invention made for the purpose of solving this problem includes a positive electrode plate, a negative electrode plate, a non-aqueous electrolyte containing an ion compound having fluorine, a positive electrode plate, and a negative electrode. A non-aqueous electrolytic solution having a battery case that houses the plate together with an electrolytic solution, the positive electrode plate having a positive electrode current collector foil and a positive electrode active material layer formed on a surface of the positive electrode current collector foil A method of manufacturing a secondary battery, in which a positive electrode active material obtained by substituting a part of manganese of lithium manganate having a spinel crystal structure with a transition metal is pretreated by immersing it in an aqueous solvent. The positive electrode active material layer is formed on the surface of the positive electrode current collector foil by a positive electrode active material treatment step for drying the treated positive electrode active material, a binder, trilithium phosphate, and a positive electrode active material after the positive electrode active material treatment step. Form and manufacture positive plate A positive electrode plate manufacturing process, an assembling process for assembling a nonaqueous electrolyte secondary battery by containing a nonaqueous electrolyte, a positive electrode plate and a negative electrode plate in a battery case, and a nonaqueous electrolyte solution after the assembling process. It has an initial charge process which performs initial charge with respect to a secondary battery, It is a manufacturing method of a nonaqueous electrolyte secondary battery characterized by the above-mentioned.

In the method for producing a non-aqueous electrolyte secondary battery according to the present invention, first, the positive electrode active material can be formed with a sufficiently thick Mn ³⁺ layer on the surface by the positive electrode active material treatment step. . In the initial charging in the initial charging step, a protective film is formed on the surface of the positive electrode active material. The protective film on the surface of the positive electrode active material formed in the initial charging step can be made thin by using a positive electrode active material having a sufficiently thick Mn ³⁺ layer on the surface. Thereby, the internal resistance of the manufactured non-aqueous electrolyte secondary battery can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the nonaqueous electrolyte secondary battery which can manufacture a nonaqueous electrolyte secondary battery with low internal resistance is provided.

It is sectional drawing of the battery which concerns on embodiment. It is sectional drawing for demonstrating the positive electrode plate etc. which are used for the battery which concerns on embodiment. It is a figure for demonstrating the manufacturing procedure of the battery which concerns on embodiment. It is a figure which shows the initial stage internal resistance value of the battery of an Example and a comparative example.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the drawings.

  First, the battery 100 (refer FIG. 1) which concerns on this form is demonstrated. FIG. 1 shows a cross-sectional view of a battery 100 according to this embodiment. As shown in FIG. 1, the battery 100 is a lithium ion secondary battery in which an electrode body 110 and an electrolytic solution 120 are accommodated in a battery case 130. The battery case 130 includes a case body 131 and a sealing plate 132. The sealing plate 132 includes an insulating member 133.

The electrolyte 120 of this embodiment is a non-aqueous electrolyte made of an organic solvent in which a lithium salt is dissolved. Specifically, in the electrolytic solution 120 of this embodiment, a mixed organic solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) is used as the organic solvent that is a nonaqueous solvent. In addition, dimethyl carbonate (DMC) etc. which are other nonaqueous solvents can also be used for the electrolyte solution 120. FIG. Below, the volume ratio in the mixed organic solvent of the electrolyte solution 120 of this form is shown.
EC: 3
EMC: 7

Further, the electrolyte solution 120 of this embodiment uses lithium hexafluorophosphate (LiPF ₆ ), which is a fluorine-containing compound, as the lithium salt. That is, the electrolytic solution 120 is a non-aqueous electrolytic solution containing an ionic compound having fluorine. As the lithium salt, other _{LiPF 6, LiBF 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 the like You can also. Further, a plurality of the above lithium salts may be used in combination. In addition, the electrolytic solution 120 of this embodiment is obtained by adding LiPF ₆ to the above mixed organic solvent to make the concentration of Li ions 1.0 mol / l.

  FIG. 2 is a cross-sectional view of the positive electrode plate 160, the negative electrode plate 170, and the separator 180 that constitute the electrode body 110. Each of the positive electrode plate 160, the negative electrode plate 170, and the separator 180 is in the form of a sheet that is long in the depth direction in FIG. The electrode body 110 is obtained by winding a positive electrode plate 160, a negative electrode plate 170, and a separator 180 in a flat shape with the left-right direction in FIG. 2 as the direction of the winding axis, as shown in FIG.

As shown in FIG. 2, the positive electrode plate 160 is formed by forming a positive electrode active material layer 162 on both surfaces of a positive electrode current collector foil 161. An aluminum foil can be used as the positive electrode current collector foil 161. 2 includes a positive electrode active material 165, a conductive auxiliary material 166, a binder 167, and trilithium phosphate (Li ₃ PO ₄ ) 168.

The positive electrode active material 165 is a component that contributes to charging and discharging in the battery 100 and can occlude and release lithium ions. In this embodiment, as the positive electrode active material 165, a material obtained by substituting a part of manganese (Mn) of lithium manganate (LiMn ₂ O ₄ ) having a spinel crystal structure with a transition metal is used. In this embodiment, specifically, LiNi _1/2 Mn _3/2 O ₄ is used as the positive electrode active material 165. In this LiNi _1/2 Mn _3/2 O ₄ , the upper limit of the operating potential when the metallic lithium (Li) is used as a reference is 4.75V.

  The conductive auxiliary material 166 can increase the conductivity of the positive electrode active material layer 162. As the conductive additive 166, for example, acetylene black (AB) can be used. The binder 167 forms the positive electrode active material layer 162 by binding the materials contained in the positive electrode active material layer 162 to each other, and binds the positive electrode active material layer 162 to the surface of the positive electrode current collector foil 161. Is something that can be done. As the binder 167, for example, polyvinylidene fluoride (PVdF) can be used. Trilithium phosphate 168 is an additive capable of forming a protective film on the surface of the positive electrode active material 165. This point will be described later.

  Further, as shown in FIG. 2, the negative electrode plate 170 is formed by forming a negative electrode active material layer 172 on both surfaces of a negative electrode current collector foil 171. A copper foil can be used as the negative electrode current collector foil 171. Further, the negative electrode active material layer 172 according to this embodiment includes a negative electrode active material 175 and a binder 176.

  The negative electrode active material 175 is a component that contributes to charging and discharging in the battery 100 and can occlude and release lithium ions. The binder 176 forms the negative electrode active material layer 172 by binding materials contained in the negative electrode active material layer 172 to each other, and binds the negative electrode active material layer 172 to the surface of the negative electrode current collector foil 171. Is something that can be done. As the negative electrode active material 175, for example, natural graphite can be used. As the binder 176, for example, styrene butadiene rubber (SBR) can be used.

  Further, as shown in FIG. 2, the positive electrode plate 160 has a portion where the positive electrode active material layer 162 is not formed and the positive electrode current collector foil 161 is exposed. The negative electrode plate 170 also has a portion where the negative electrode active material layer 172 is not formed and the negative electrode current collector foil 171 is exposed.

  In the electrode body 110 after winding shown in FIG. 1, the right end is a portion formed only of the exposed portion of the positive electrode current collector foil 161 on the positive electrode plate 160. Further, the left end portion of the electrode body 110 shown in FIG. 1 is a portion consisting only of an exposed portion of the negative electrode current collector foil 171 in the negative electrode plate 170.

  Further, as shown in FIG. 1, a positive electrode terminal 140 is connected to the right end made of the positive electrode current collector foil 161 of the electrode body 110. A negative electrode terminal 150 is connected to the left end portion of the negative electrode current collector foil 171 of the electrode body 110. The positive electrode terminal 140 and the negative electrode terminal 150 have their ends that are not connected to the electrode body 110 protruding outside the battery case 130 via the insulating member 133.

  On the other hand, in the central portion of the electrode body 110 in FIG. 1, as shown in FIG. 2, a portion where the positive electrode active material layer 162 of the positive electrode plate 160 is formed and a negative electrode active material layer 172 of the negative electrode plate 170 are formed. The part which has overlapped via the separator 180 is. The battery 100 is charged and discharged at the central portion of the electrode body 110 via the positive electrode terminal 140 and the negative electrode terminal 150.

  Next, a method for manufacturing the battery 100 of this embodiment will be described. The manufacturing procedure of the battery 100 of this embodiment is shown in FIG. As shown in FIG. 3, in this embodiment, the battery 100 includes a positive electrode active material processing step (S101), a positive electrode paste manufacturing step (S102), a positive electrode plate manufacturing step (S103), an assembly step (S104), and an initial charging step ( S105).

First, the positive electrode active material processing step (S101) will be described. In this step, the positive electrode active material 165 is pretreated while being immersed in an aqueous solvent and is dried. Specifically, first, LiNi _1/2 Mn _3/2 O ₄ which is the positive electrode active material 165 is put into water and kneaded. The underwater kneading can be performed, for example, for 15 minutes. In addition, the underwater kneading may also serve as a crushing treatment for the positive electrode active material 165. Then, this underwater kneading causes an exchange reaction between Li ⁺ ions of LiNi _1/2 Mn _3/2 O ₄ and H ⁺ ions of water.

Subsequently, in the positive electrode active material treatment step, the positive electrode active material 165 after being kneaded in water is dried at, for example, a temperature of 150 ° C. for 3 hours. Due to this high temperature drying, oxygen is partially released from the positive electrode active material 165. The desorption of oxygen is more likely to occur on the surface of the positive electrode active material 165. Then, the composition of the positive electrode active material 165 is changed by high-temperature drying, and the positive electrode active material 165 can have a sufficiently thick Mn ³⁺ layer formed on the surface.

Next, a positive electrode paste manufacturing step (S102) is performed. In the positive electrode paste manufacturing process, a positive electrode paste used for forming the positive electrode active material layer 162 of the positive electrode plate 160 is manufactured. For the production of the positive electrode paste, the positive electrode active material 165, the conductive additive 166, the binder 167, and the trilithium phosphate 168, which are the components included in the positive electrode active material layer 162 described above, are used. As the positive electrode active material 165, a material having a Mn ³⁺ surface layer obtained by the positive electrode active material treatment step is used.

  Then, the positive electrode active material 165, the conductive additive 166, the binder 167, and the trilithium phosphate 168 are dispersed in a solvent to produce a positive electrode paste. As the solvent, N-methylpyrrolidone (NMP) can be used. Specifically, the positive electrode paste manufacturing process can be performed by using, for example, a high-speed disperser homodisper. Moreover, what is necessary is just to adjust the viscosity of a positive electrode paste to 2500 cp or more.

Moreover, an example of the mass ratio of each material used for the positive electrode paste is shown below.
LiNi _1/2 Mn _3/2 O ₄ : 92.1
AB: 0.9
PVdF: 4
Li ₃ PO ₄ : 3

  Next, a positive electrode plate manufacturing step (S103) is performed. In the positive electrode plate manufacturing process, the positive electrode active material layer 162 is formed from the positive electrode paste manufactured in the positive electrode paste manufacturing process. That is, the positive electrode plate 160 is manufactured by forming the positive electrode active material layer 162 on the surface of the positive electrode current collector foil 161.

  Specifically, first, a positive electrode paste is applied to a region of the surface of the positive electrode current collector foil 161 where the positive electrode active material layer 162 is to be formed. Next, the applied positive electrode paste is dried, and the solvent component in the positive electrode paste is removed. The positive electrode paste can be dried at a temperature of 140 ° C. to 190 ° C., for example. Thereby, the positive electrode active material layer 162 can be formed on the surface of the positive electrode current collector foil 161.

  That is, by drying the positive electrode paste, the materials such as the positive electrode active material 165 included in the positive electrode paste are bound to each other by the binder 167, whereby the positive electrode active material layer 162 is formed. Further, the positive electrode active material layer 162 is bound to the surface of the positive electrode current collector foil 161 by the binder 167. Thereby, the positive electrode plate 160 is manufactured.

Furthermore, in the positive electrode plate manufacturing process of this embodiment, pressing is performed to pressurize the positive electrode active material layer 162 formed on the surface of the positive electrode current collector foil 161 in the thickness direction. A small roll press can be used for this press. Then, the density of the positive electrode active material layer 162 can be adjusted by pressing. In this embodiment, the density of the positive electrode active material layer 162 is set to 2.2 to 2.4 g / cm ³ by pressing.

  Subsequently, an assembly process (S104) is performed. In the assembly process, first, the electrode body 110 is manufactured. Specifically, the positive electrode plate 160 manufactured in the positive electrode plate manufacturing process is manufactured by winding it together with the negative electrode plate 170 into a flat shape while sandwiching the separator 180 therebetween. As the separator 180, polypropylene (PP), polyethylene (PE), or the like can be used alone, or a composite material in which a plurality of these are laminated.

  The negative electrode plate 170 can be manufactured using a negative electrode paste made of a material different from that of the positive electrode plate 160. That is, the negative electrode paste can be produced by dispersing the negative electrode active material 175 and the binder 176 in a solvent. Then, the negative electrode active material layer 172 can be formed by applying the negative electrode paste to the negative electrode current collector foil 171 and drying the applied negative electrode paste. Thereby, the negative electrode plate 170 having the negative electrode active material layer 172 on the surface of the negative electrode current collector foil 171 can be manufactured.

  Next, the electrode body 110 is housed inside the case body 131 through the opening. Further, the opening of the case body 131 is closed by the sealing plate 132 and these are joined. The positive electrode terminal 140 and the negative electrode terminal 150 may be connected to the electrode body 110 before the electrode body 110 is accommodated in the case body 131. The joining of the battery case 130 and the joining of the positive terminal 140 and the negative terminal 150 and the electrode body 110 can be performed by welding or the like.

  Further, in the assembly process, the electrolytic solution 120 is also accommodated in the battery case 130. The electrolyte 120 can be accommodated in the inside of the opening of the case body 131 before the battery case 130 is joined, for example. Alternatively, a liquid injection port communicating with the inside and the outside of the battery case 130 may be provided, and liquid may be injected into the battery case 130 from the liquid injection port. The injection port may be closed after the electrolyte 120 is injected. Therefore, the battery 100 can be assembled by the assembly process.

  Next, an initial charging step (S105) is performed. This process is a process of performing initial charging, which is the initial charging of the battery 100 configured by the assembly process. In the initial charging process of this embodiment, CC (Constant Current) charging is performed until the charging capacity of the battery 100 reaches the full charging capacity, and SOC (State Of Charge) is set to 100%. In this embodiment, the battery 100 can be manufactured by performing this initial charging step.

Here, in this embodiment, LiNi _1/2 Mn _3/2 O ₄ whose upper limit of the operating potential is 4.3 V or higher with respect to metallic lithium is used as the positive electrode active material 165. Specifically, LiNi _1/2 Mn _3/2 O ₄ used in the present embodiment has an upper limit of the working potential of 4.75 V based on metallic lithium as described above. For this reason, in the initial charging step, the battery voltage of the battery 100 is 4.75 V, which is 4.3 V or more.

  Then, on the surface of the positive electrode active material 165 in the positive electrode active material layer 162 whose potential has increased to 4.3 V or higher, the solvent component in the electrolytic solution 120 tends to be oxidatively decomposed to generate hydrogen ions. Furthermore, hydrofluoric acid (HF) is generated by the generated hydrogen ions reacting with fluorine ions in the electrolyte 120.

  In addition, hydrofluoric acid generated in the initial charging step reacts with trilithium phosphate 168 contained in the positive electrode active material layer 162. That is, trilithium phosphate 168 is dissolved by reacting with hydrofluoric acid. Further, the dissolved trilithium phosphate 168 reacts with the metal ion species present on the surface of the positive electrode active material 165. A film is formed on the surface of the positive electrode active material 165 by the reaction between the trilithium phosphate 168 dissolved by hydrofluoric acid and the metal ion species present on the surface of the positive electrode active material 165.

  The film formed on the surface of the positive electrode active material 165 can function as a protective film for the positive electrode active material 165. That is, on the surface of the positive electrode active material 165 on which the protective film is formed, the solvent component in the electrolytic solution 120 is suppressed from being oxidatively decomposed thereafter. Therefore, the transition metal of the positive electrode active material 165 is prevented from being eluted by hydrofluoric acid, and the battery 100 can be prevented from deteriorating.

  As described above, the protective film of the positive electrode active material 165 is formed by a reaction between trilithium phosphate 168 dissolved by hydrofluoric acid and metal ion species present on the surface of the positive electrode active material 165. For this reason, when there are few metal ion species which exist on the surface of the positive electrode active material 165, it exists in the tendency for the reaction rate concerning formation of the protective film of the positive electrode active material 165 to become slow. Therefore, when the metal ion species present on the surface of the positive electrode active material 165 is small, the amount of hydrofluoric acid generated during the initial charge tends to increase.

  Furthermore, as the amount of hydrofluoric acid generated during initial charging increases, the protective film of the positive electrode active material 165 formed tends to be thicker. This is because the amount of metal ion species present on the surfaces of the trilithium phosphate 168 and the positive electrode active material 165 that react with hydrofluoric acid during initial charging increases. The protective film of the positive electrode active material 165 tends to have a higher resistance value as the thickness increases. That is, when the number of metal ion species present on the surface of the positive electrode active material 165 is small, there is a problem that the internal resistance value of the battery 100 increases.

Therefore, in this embodiment, the positive electrode active material treatment process is performed in advance for the positive electrode active material 165. In the positive electrode active material treatment step, as described above, the positive electrode active material 165 has a sufficiently thick Mn ³⁺ layer formed on the surface. For this reason, in the positive electrode active material 165 in contact with the electrolytic solution 120, a disproportionation reaction occurs in the Mn ³⁺ layer on the surface, thereby generating Mn ions. The disproportionation reaction occurring in the Mn ³⁺ layer is a reaction represented by the following formula (1).
2Mn ³⁺ → Mn ²⁺ + Mn ⁴⁺ (1)

In other words, in this embodiment, Mn ²⁺ is eluted by the disproportionation reaction generated in the Mn ³⁺ layer on the surface of the positive electrode active material 165, so that the metal ion species Mn ²⁺ is sufficiently present in the vicinity of the positive electrode active material 165. It can be in the state that exists. Therefore, in this embodiment, the reaction rate related to the formation of the protective film of the positive electrode active material 165 is high, and the protective film can be formed on the surface of the positive electrode active material 165 early in the initial charge. Therefore, the amount of hydrofluoric acid generated during initial charging can be reduced, and the protective film formed on the positive electrode active material 165 can be made thin. Thereby, in this embodiment, the internal resistance of the battery 100 can be reduced.

  In addition, the amount of hydrofluoric acid generated during initial charging tends to increase as the C rate during initial charging increases. However, in this embodiment, since the reaction rate related to the formation of the protective film of the positive electrode active material 165 is high, the amount of hydrofluoric acid generated is suppressed even if the initial charge is performed at a high C rate. This is because a protective film can be formed on the surface of the positive electrode active material 165 early in the initial charging. That is, in this embodiment, the protective film formed on the positive electrode active material 165 can be thin even if the initial charging is performed at a high C rate. In addition, by performing the initial charging at a high C rate, the initial charging process can be performed in a short time and at a low cost. That is, in this embodiment, the battery 100 with low internal resistance can be manufactured in a short time and at a low cost.

  Moreover, the present inventors confirmed the effect of this invention by the experiment demonstrated below. In this experiment, the batteries of Examples 1 and 2 according to the present invention and the batteries of Comparative Examples 1 and 2 for comparison with the batteries were produced and used.

  The difference between the example and the comparative example is whether or not the positive electrode active material processing step (S101) described with reference to FIG. 3 was performed. That is, in the example, a battery was manufactured by the method described with reference to FIG. On the other hand, in the comparative example, a battery was manufactured without performing the positive electrode active material treatment step in the procedure shown in FIG. That is, in the comparative example, a battery was manufactured by the procedure after the positive electrode paste manufacturing step (S102) described with reference to FIG.

  In the comparative example, each material used for manufacturing the battery is the same as in the example. For this reason, the positive electrode active material used in the positive electrode paste manufacturing process of the comparative example is the same as the positive electrode active material used in the positive electrode active material process of the example and before the positive electrode active material process. Table 1 below shows the different conditions in the battery fabrication process for the examples and comparative examples.

  As shown in Table 1, in Examples 1 and 2, the positive electrode active material treatment step was performed using water having different pHs. Specifically, in Example 1, the positive electrode active material treatment step was performed using pH 7 water. In Example 2, the positive electrode active material treatment step was performed using water having a pH of 5.

Table 1 shows the thickness of the Mn ³⁺ layer on the surface of the positive electrode active material used in the positive electrode paste manufacturing process for each of Examples 1 and 2 and Comparative Examples 1 and 2. The thickness of the Mn ³⁺ layer on the surface of the positive electrode active material is determined according to STEM-EELS (Electron Energy Loss Spectroscopy) for the positive electrode active material after mixing in the positive electrode paste in the positive electrode paste manufacturing process after the positive electrode active material treatment process. It is a value obtained from the measurement used.

As shown in Table 1, since both of Comparative Examples 1 and 2 were not subjected to the positive electrode active material treatment step, the thickness of the Mn ³⁺ layer on the surface of the positive electrode active material was as thin as 5 nm. On the other hand, in both Examples 1 and 2, the thickness of the Mn ³⁺ layer on the surface of the positive electrode active material is greater than 5 nm by the positive electrode active material treatment step. Specifically, in Example 1, the thickness of the Mn ³⁺ layer on the surface of the positive electrode active material was 20 nm. In Example 2, the thickness of the Mn ³⁺ layer on the surface of the positive electrode active material was 200 nm.

  Further, as shown in Table 1, in Examples 1 and 2 and Comparative Example 2, the initial charging step was performed by one charge at a current value of 5C. On the other hand, about the comparative example 1, the initial charge process was performed by 3 times charge with the electric current value of 0.3C.

  In this experiment, the initial internal resistance after the initial charging was measured for each of the batteries of Examples and Comparative Examples manufactured as described above, and the measured values were compared. The initial internal resistance was measured by discharging the battery of the example and the comparative example from a state where the SOC was 60% for a certain period of time in an environment at a temperature of 25 ° C., and changing the voltage during that time. FIG. 4 shows the initial internal resistance values measured for the batteries of the examples and comparative examples.

  As shown in FIG. 4, Comparative Example 2 has a higher initial internal resistance value than Comparative Example 1. This is probably because the initial internal resistance value was higher in Comparative Example 2 than in Comparative Example 1 because the initial charging was performed at a higher C rate. That is, in Comparative Example 2, the C rate related to the initial charge is higher than that in Comparative Example 1, so that the amount of hydrofluoric acid generated during the initial charge is large, and the protective coating formed on the surface of the positive electrode active material has a large thickness. It is thought that it became thick. Further, in Comparative Example 2, it is considered that the initial internal resistance value was higher than that in Comparative Example 1 due to the thickness of the protective film on the surface of the positive electrode active material.

On the other hand, as shown in FIG. 4, both Examples 1 and 2 have lower initial internal resistance values than Comparative Example 1. This is because in both Examples 1 and 2, the positive electrode active material in which the thickness of the Mn ³⁺ layer on the surface was increased by the positive electrode active material treatment step was used. That is, in Examples 1 and 2, as described above, since the metal ion species Mn ²⁺ was sufficiently present in the vicinity of the positive electrode active material, the surface of the positive electrode active material was protected early in the initial charge. It is thought that a film was formed and the amount of hydrofluoric acid generated was reduced. Therefore, in both Examples 1 and 2, it is considered that the initial internal resistance value was lower than that of Comparative Example 1 because the protective coating on the surface of the positive electrode active material was thin.

  Further, both Examples 1 and 2 have a higher C rate for initial charging than Comparative Example 1. That is, in both Examples 1 and 2, the time required for the initial charging process is shorter than that in Comparative Example 1. Therefore, it was confirmed by this experiment that in Examples 1 and 2 according to this embodiment, a battery having a low internal resistance can be manufactured in a short time and at a low cost.

As described above in detail, the method for manufacturing battery 100 according to the present embodiment includes a positive electrode active material treatment process, a positive electrode plate manufacturing process, an assembly process, and an initial charging process. In the positive electrode active material treatment step, LiNi _1/2 Mn _3/2 O ₄ , which is a positive electrode active material obtained by substituting a part of manganese of lithium manganate having a spinel crystal structure with a transition metal, is immersed in water. While pre-kneading while kneading, then dry. By this positive electrode active material step, the positive electrode active material can have a sufficiently thick Mn ³⁺ layer formed on the surface. In the positive electrode plate manufacturing process, a positive electrode active material layer is formed on the surface of the positive electrode current collector foil using a positive electrode paste manufactured from a binder, trilithium phosphate, and a positive electrode active material after the positive electrode active material treatment process. Manufacturing. In the assembly process, the positive electrode plate and the negative electrode plate are wound while sandwiching a separator between them to form an electrode body, which is housed in the battery case together with the electrolyte. After that, a protective film is formed on the surface of the positive electrode active material in the initial charging in the initial charging step. The protective film on the surface of the positive electrode active material formed in the initial charging step is thin by using a positive electrode active material having a sufficiently thick Mn ³⁺ layer on the surface. Thereby, the manufacturing method of the nonaqueous electrolyte secondary battery which can manufacture a nonaqueous electrolyte secondary battery with low internal resistance is implement | achieved.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, not only the flat wound electrode body 110 but also a cylindrical wound electrode body can be used. Further, for example, the present invention can be applied not only to a wound type but also to a laminated type electrode body.

DESCRIPTION OF SYMBOLS 100 Battery 110 Electrode body 120 Electrolyte 130 Battery case 160 Positive electrode plate 161 Positive electrode current collection foil 162 Positive electrode active material layer 165 Positive electrode active material 167 Binder 168 Trilithium phosphate 170 Negative electrode plate

Claims (1)

A positive electrode plate, a negative electrode plate, a nonaqueous electrolytic solution containing an ionic compound having fluorine, and a battery case containing the positive electrode plate and the negative electrode plate together with the electrolytic solution,
In the method for producing a non-aqueous electrolyte secondary battery, wherein the positive electrode plate has a positive electrode current collector foil and a positive electrode active material layer formed on the surface of the positive electrode current collector foil,
The cathode active material obtained by substituting a part of manganese of lithium manganate having a spinel type crystal structure with a transition metal is subjected to a pretreatment soaking in an aqueous solvent, and the cathode active material after the pretreatment is A positive electrode active material treatment step to be dried;
A positive electrode plate manufacturing the positive electrode plate by forming the positive electrode active material layer on the surface of the positive electrode current collector foil with a binder, trilithium phosphate, and the positive electrode active material after the positive electrode active material treatment step. Process,
An assembly step of assembling the non-aqueous electrolyte secondary battery by accommodating the non-aqueous electrolyte, the positive electrode plate and the negative electrode plate in the battery case;
A non-aqueous electrolyte secondary battery manufacturing method comprising: an initial charging step of performing initial charging on the non-aqueous electrolyte secondary battery after the assembly step.

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