KR101895670B1 - Nonaqueous electrolyte secondary battery and method of manufacturing the same - Google Patents

Abstract

The nonaqueous electrolyte secondary battery manufacturing method has a positive electrode paste manufacturing step, a positive electrode plate manufacturing step, an assembling step, and an initial charging step. In the positive electrode paste manufacturing process, the positive electrode active material 165, the binder 167, and the metal phosphate 168 are dispersed in a solvent to prepare a positive electrode paste. As the metal phosphate, the first metal phosphate 168a and the second metal phosphate 168b having an average particle diameter larger than the average particle diameter of the first metal phosphate by 1.3 占 퐉 or more are used.

Description

TECHNICAL FIELD [0001] The present invention relates to a nonaqueous electrolyte secondary battery and a method of manufacturing the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a nonaqueous electrolyte secondary battery and a manufacturing method thereof. More particularly, the present invention relates to a nonaqueous electrolyte secondary battery including a positive electrode active material having a high potential in a positive electrode active material layer and a method for manufacturing the same.

BACKGROUND ART [0002] Lithium ion secondary batteries are required to have improved performance such as high output and high capacity. In addition, in order to produce a high-performance lithium ion secondary battery, a high potential such as a NiMn spinel system has attracted attention as a positive electrode active material. This is because the operating voltage of the lithium ion secondary battery can be increased by using the high-potential positive electrode active material.

However, in a lithium ion secondary battery manufactured using a positive electrode active material having a high potential, an electrolytic solution may be decomposed with charging and discharging due to an increase in the operating voltage. In addition, in a lithium ion secondary battery in which an acid is generated by decomposition of an electrolytic solution, the transition metal of the positive electrode active material may be eluted by the acid. When the transition metal of the positive electrode active material is eluted, the capacity retention rate of the lithium ion secondary battery may be lowered.

For example, Japanese Laid-Open Patent Application No. 2014-103098 discloses a non-aqueous electrolyte secondary battery containing trisodium phosphate (Li ₃ PO ₄ ) as an additive together with a positive electrode active material having a high potential in the positive electrode active material layer. The presence of trisodium phosphate in the positive electrode active material layer can prevent elution of the transition metal in the positive electrode active material accompanied by charge and discharge of the nonaqueous electrolyte secondary battery. Specifically, it is said that trisodium phosphate can react with hydrofluoric acid (HF) produced in an electrolytic solution to function as an acid consumer material. In this way, the elution of the transition metal in the positive electrode active material is suppressed, and the durability of the nonaqueous electrolyte secondary battery can be enhanced.

Here, in the case where tritium phosphate as an additive is contained in the positive electrode active material layer, a film is formed on the surface of the positive electrode active material by reacting trisodium phosphate with hydrofluoric acid in the initial charging step of the lithium ion secondary battery. Since the coating film is formed on the surface of the positive electrode active material, if the coating film has low conductivity, the internal resistance of the lithium ion secondary battery may be increased. Further, additives such as trisodium phosphate are preferably inexpensive ones. This is because the manufacturing cost of the positive electrode plate can be reduced and the manufacturing cost of the battery using the positive electrode plate can be reduced.

The present invention provides a nonaqueous electrolyte secondary battery having low manufacturing cost and low internal resistance, and a method of manufacturing the same.

A first aspect of the present invention is a positive electrode comprising a positive electrode plate, a negative electrode plate, a nonaqueous electrolyte solution containing an ionic compound having fluorine, and a battery case containing therein a positive electrode plate and a negative electrode together with an electrolytic solution, And a positive electrode active material layer formed on a surface of the positive electrode current collector foil. A positive electrode paste is produced by dispersing a positive electrode active material, a binder and a metal phosphate in a solvent. The positive electrode paste is applied to the surface of a current collector foil and the applied positive electrode paste is dried to form a positive electrode active material layer. A positive electrode plate manufacturing process for manufacturing a positive electrode plate, a positive electrode plate manufacturing process for manufacturing a plate, a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte, a positive electrode plate and a negative electrode plate in the battery case, And has an initial charging process. The metal phosphate includes a first metal phosphate group of a first metal phosphate particle having a first average particle diameter and a second metal phosphate group having a second average particle diameter larger than the first average particle diameter by at least 1.3 탆 do.

In this manufacturing method, a protective film is formed on the surface of the positive electrode active material by reacting metal phosphate with hydrofluoric acid in the initial charging step. The protective coating tends to have a higher conductivity when the metal phosphate is used as a small particle. The smaller the amount of the metal phosphate is, the higher the dispersibility in the positive electrode paste is, so that the metal phosphate can be uniformly distributed in the positive electrode active material layer. This is because by increasing the frequency of reaction of the metal phosphate with hydrofluoric acid, the reaction can be performed in a short time, and the protective film formed on the surface of the positive electrode active material can be made thin. That is, the protective coating formed on the surface of the positive electrode active material by the first metal phosphate can have high conductivity. Thereby, the internal resistance of the produced nonaqueous electrolyte secondary battery can be reduced.

In the non-aqueous electrolyte secondary battery, hydrofluoric acid also occurs during normal use after production. Further, the metal phosphate functions as an acid consuming agent for hydrofluoric acid generated during normal use, so that the charge capacity of the nonaqueous electrolyte secondary battery can be suppressed from lowering. The function of the metal phosphate as an acid consuming agent is exhibited without depending on the size of the metal phosphate particles. Further, metal phosphates tend to be expensive as the particles are smaller. That is, even a cheap second metal phosphate having a large particle size can function properly as an acid consuming agent. Therefore, by using the first metal phosphate and the second metal phosphate together, a non-aqueous electrolyte secondary battery having a low internal resistance can be produced at low cost.

In the positive electrode paste production step, the ratio of the mass of the second metal phosphate to the total mass of the metal phosphate combined with the mass of the first metal phosphate and the mass of the second metal phosphate may be 1/3 or more. This is because the nonaqueous electrolyte secondary battery having a low internal resistance can be manufactured at a lower cost.

In the positive electrode paste manufacturing step, the ratio of the mass of the first metal phosphate to the total mass of the metal phosphate combined with the mass of the first metal phosphate and the mass of the second metal phosphate may be 1/6 or more. This is because the internal resistance of the non-aqueous electrolyte secondary battery can be surely lowered.

In the positive electrode paste production step, the metal phosphate having a particle size at an integrated value of 10% from the fine particle side in the synthetic particle size distribution of the particle size distribution of the first metal phosphate and the particle size distribution of the second metal phosphate is 0.4 탆 or less May be used. In the metal phosphate, the battery can be manufactured at low cost by making the particles small as necessary for forming the protective coating having high conductivity in the positive electrode active material.

A second aspect of the present invention is a positive electrode current collector comprising a positive electrode current collector foil, a positive electrode plate formed on the surface of the positive electrode current collector foil and having a positive electrode active material layer containing a metal phosphate having at least two peaks in a particle size distribution, A non-aqueous electrolyte containing an ionic compound having fluorine, and a battery case accommodating therein the positive electrode plate and the negative electrode plate together with the electrolyte solution.

According to the present invention, there is provided a manufacturing method of a non-aqueous electrolyte secondary battery capable of manufacturing a non-aqueous electrolyte secondary battery having a reduced manufacturing cost and a low internal resistance.

The features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like elements are represented by like numerals.

1 is a cross-sectional view of a battery according to an embodiment;
2 is a sectional view for explaining a positive electrode plate or the like used in a battery according to the embodiment;
3 is a view for explaining a battery manufacturing procedure according to the embodiment;
4 is a view for explaining a positive electrode paste production step according to the embodiment;
5 is a view showing the relationship between the average particle diameter of trisodium phosphate and the initial internal resistance ratio;
6 is a graph showing the relationship between the average particle diameter of trisodium phosphate and the capacity retention rate;
7 is a view showing initial internal resistance ratios of batteries of Examples and Comparative Examples in the first experiment.
8 is a view showing an example of a synthetic particle size distribution in which the particle size distribution of trisodium phosphate of small particle size and the particle size distribution of trisodium phosphate of large particle size are combined.
9 is a view showing initial internal resistance ratios of batteries of Examples and Comparative Examples in the second experiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the drawings.

First, the battery 100 (see Fig. 1) according to this embodiment will be described. 1 is a cross-sectional view of a battery 100 according to this embodiment. The battery 100 is a lithium ion secondary battery in which an electrode body 110 and an electrolyte solution 120 are accommodated in a battery case 130 as shown in Fig. The battery case 130 includes a case body 131 and a sealing plate 132. The sealing plate 132 is provided with an insulating member 133.

The electrolytic solution 120 of this embodiment is a nonaqueous electrolytic solution comprising an organic solvent in which a lithium salt is dissolved. Specifically, in the electrolytic solution 120 of this embodiment, fluoroethylene carbonate (FEC) and methyl 2,2,2-trifluoroethyl carbonate (MTFEC) are mixed at a ratio of 1: 1 is used as a mixed organic solvent. Other non-aqueous solvents such as ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) may be used for the electrolyte solution 120. The non-aqueous solvent may be used in combination.

In the electrolyte solution 120 of this embodiment, lithium hexafluorophosphate (LiPF ₆ ), which is a fluorine-containing compound, is used as a lithium salt. That is, the electrolyte solution 120 is a non-aqueous electrolyte containing an ionic compound having fluorine. In addition to 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 and the like may be used as the lithium salt . Further, a plurality of lithium salts described above may be used in combination. Alternatively, in addition to the lithium salt described above, LiClO ₄ and LiI may be used. In the electrolyte 120 of this embodiment, LiPF ₆ is added to the above-mentioned mixed organic solvent, and the concentration of Li ion is 1.0 mol / l.

2 is a sectional view of the positive electrode plate 160, the negative electrode plate 170, and the separator 180 constituting the electrode body 110. As shown in Fig. The positive electrode plate 160, the negative electrode plate 170 and the separator 180 all have a long sheet shape in the depth direction of the paper in Fig. The electrode assembly 110 has a structure in which the positive electrode plate 160, the negative electrode plate 170 and the separator 180 are overlapped as shown in Fig. 2, It is a turning point.

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. As shown in Fig. As the positive electrode current collector foil 161, an aluminum foil can be used. The positive electrode active material layer 162 according to this embodiment includes a positive electrode active material 165, a conductive material 166, a binder 167, and trisodium phosphate 168.

The positive electrode active material 165 is a component contributing to charging and discharging of the battery 100 and capable of storing and releasing lithium ions. In this embodiment, as the positive electrode active material 165, the upper limit of the operating potential when the metal lithium (Li) is used is 4.3 V or more. Examples of the positive electrode active material 165 include those having a spinel structure including nickel (Ni) and manganese (Mn). In this embodiment, specifically, LiNi _0.5 Mn _1.5 O ₄ is used as the positive electrode active material 165.

The conductive material 166 can increase the conductivity of the positive electrode active material layer 162. The binder 167 binds the materials contained in the positive electrode active material layer 162 to each other to form a positive electrode active material layer 162 and binds the positive electrode active material layer 162 to the surface of the positive electrode collector foil 161 It can be done. As the conductive material 166, for example, acetylene black (AB) can be used. As the binder 167, for example, polyvinylidene fluoride (PVDF) can be used.

The trisodium phosphate 168 can form a protective coating on the surface of the positive electrode active material 165 and can function as an acid consuming agent in normal use in which normal charging and discharging of the battery 100 is performed It is an additive. This point will be described later.

2, the negative electrode plate 170 is formed by forming a negative electrode active material layer 172 on both surfaces of the negative electrode collector foil 171. [ As the negative electrode current collector foil 171, a copper foil can be used. 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 contributing to charging and discharging of the battery 100 and capable of absorbing and desorbing lithium ions. The binder 176 bonds the materials contained in the negative electrode active material layer 172 to each other to form a negative electrode active material layer 172 and binds the negative electrode active material layer 172 to the surface of the negative electrode collector foil 171 It can be done. As the negative electrode active material 175, for example, natural graphite and the like can be used. As the binder 176, for example, styrene butadiene rubber (SBR) or the like can be used.

2, the positive electrode plate 160 is not provided with the positive electrode active material layer 162 but has a portion where the positive electrode collector foil 161 is exposed. Also in the negative electrode plate 170, there is a portion where the negative electrode active material layer 172 is not formed and the negative electrode current collector foil 171 is exposed.

1, the right end is a portion formed only of the exposed portion of the positive electrode current collecting foil 161 in the positive electrode plate 160. In the electrode body 110 shown in Fig. The left end of the electrode body 110 shown in FIG. 1 is a portion formed only of the exposed portion of the negative electrode current collecting foil 171 in the negative electrode plate 170.

1, the positive electrode terminal 140 is connected to the right end of the positive electrode current collector foil 161 of the electrode assembly 110. [ A negative terminal 150 is connected to the left end of the electrode assembly 110, which is formed by the negative electrode collector foil 171. The positive electrode terminal 140 and the negative electrode terminal 150 project the end of the side not connected to the electrode body 110 to the outside of the battery case 130 through the insulating member 133.

2, a portion of the positive electrode plate 160 where the positive electrode active material layer 162 is formed and a portion of the positive electrode active material layer 162 of the negative electrode plate 170, The portion where the negative electrode active material layer 172 is formed is a portion overlapping with the separator 180 interposed therebetween. The battery 100 is charged and discharged in the central portion of the electrode body 110 through the positive electrode terminal 140 and the negative electrode terminal 150.

Next, a method of manufacturing the battery 100 of the present embodiment will be described. A manufacturing procedure of the battery 100 of this embodiment is shown in Fig. As shown in Fig. 3, in this embodiment, the battery 100 is manufactured by a positive electrode paste manufacturing step (S101), a positive electrode plate manufacturing step (S102), a assembling step (S103), and an initial charging step (S104).

First, the positive electrode paste production process (S101) will be described. In the positive electrode paste production process, a positive electrode paste for use in forming the positive electrode active material layer 162 of the positive electrode plate 160 is produced. The positive electrode active material 165, the conductive material 166, the binder 167, and the trisodium phosphate 168, which are components contained in the above-described positive electrode active material layer 162, are used for the production of the positive electrode paste. Then, these are dispersed in a solvent to prepare a positive electrode paste. Details of the positive electrode paste production process will be described later.

Next, a positive electrode plate manufacturing step (S102) is performed. In the positive electrode plate manufacturing step, the positive electrode active material layer 162 is formed by the positive electrode paste produced in the positive electrode paste manufacturing step. That is, the positive electrode active material layer 162 is formed on the surface of the positive electrode collector foil 161 to manufacture the positive electrode plate 160.

Specifically, first, a positive electrode paste is applied to a region of the surface of the positive electrode collector foil 161 where the positive electrode active material layer 162 is to be formed. Next, the applied positive electrode paste is dried to remove the solvent component in the positive electrode paste. 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 respective materials such as the positive electrode active material 165 contained in the positive electrode paste are bound to each other by the binder 167, whereby the positive electrode active material layer 162 is formed. The positive electrode active material layer 162 is bonded to the surface of the positive electrode collector foil 161 by the binder 167. [ Thereby, the positive electrode plate 160 is produced.

Subsequently, the assembling step (S103) is performed. In the assembling step, first, the electrode body 110 is manufactured. Specifically, the positive electrode plate 160 manufactured in the positive electrode plate manufacturing step is manufactured by winding the negative electrode plate 170 together with the separator 180 therebetween while being flatly wound. As the separator 180, polypropylene (PP), polyethylene (PE) or the like can be used singly or a composite material in which a plurality of these are laminated can be used.

The negative electrode plate 170 can be manufactured by the same method using a material different from that of the positive electrode plate 160. That is, the negative electrode paste is prepared by dispersing the negative electrode active material 175 and the binder 176 in a solvent, and the negative electrode paste is applied to the negative electrode collector foil 171.

Then, the negative electrode active material layer 172 can be formed by drying the coated negative electrode paste. Thus, the negative electrode plate 170 having the negative electrode active material layer 172 on the surface of the negative electrode collector foil 171 can be manufactured.

Next, the electrode body 110 is housed inside the case body 131 from the opening thereof. 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. [ Bonding of the battery case 130 and bonding of the positive electrode terminal 140 and the negative electrode terminal 150 to the electrode body 110 can be performed by welding or the like.

In the assembling step, the electrolyte solution 120 is accommodated in the battery case 130 as well. The electrolyte solution 120 can be received from the opening of the case main body 131, for example, before the battery case 130 is joined. Alternatively, a main liquid port communicating with the inside and the outside of the battery case 130 may be formed, and the liquid may be poured into the battery case 130 from the liquid inflow port. The main liquid may be blocked after the electrolyte solution 120 is poured. Therefore, the battery 100 can be assembled by the assembling process.

Subsequently, an initial charging step (S104) is performed. This step is a step of performing initial charging, which is the initial charging of the battery 100 constituted by the assembling process. By performing this initial charging step, the battery 100 is manufactured.

Here, the positive electrode paste manufacturing step (step S101 in Fig. 3) in this embodiment will be further described. Fig. 4 shows details of the positive electrode paste production process. 4, the positive electrode active material 165, the conductive material 166, the binder 167, the trisodium phosphate 168, and the solvent 169 used for the positive electrode paste are first prepared in the positive electrode paste production step . As the solvent 169, N-methylpyrrolidone (NMP) can be used.

Then, the respective materials of the positive electrode active material 165, the conductive material 166, the binder 167, and the trisodium phosphate 168 are put into the solvent 169 and kneaded. By this kneading, the respective materials of the positive electrode active material 165, the conductive material 166, the binder 167, and the trisodium phosphate 168 are dispersed in the solvent 169 to produce a positive electrode paste.

In the positive electrode paste manufacturing process of this embodiment, as shown in Fig. 4, tris (triflate) 168a and tris (dibutyl phosphate) 168b are used as trisodium phosphate 168. The trisphosphate trisodium phosphate 168a and the second trisphosphate trisilicate 168b are identical in their components. However, the first trisodium phosphate 168a and the second trisodium phosphate 168b are groups of particles having different average particle diameters.

Specifically, the primary trisodium phosphate 168a has an average particle diameter of 0.2 占 퐉. On the other hand, the second trisodium phosphate 168b has an average particle diameter of 1.5 占 퐉. In other words, the second trisodium phosphate 168b has an average particle diameter larger than that of the first trisodium phosphate 168a by 1.3 占 퐉 or more. In the present embodiment, the average particle diameter is based on the median diameter, which is the particle diameter at the integrated value of 50% in the particle size-based particle size distribution obtained by the laser diffraction / scattering method.

As shown in Fig. 4, the first tris (tri-trithiophyllithium) phosphate 168a of this embodiment was subjected to small-particle diameter treatment to a powder of trisodium phosphate having an average particle size of 1.5 占 퐉 to reduce the average particle size to 0.2 占 퐉 will be. In this embodiment, the same trisodium phosphate trisodium phosphate 168a powder as that used for the second trisodium phosphate 168b can be used as the trisodium phosphate powder having an average particle size of 1.5 mu m before the small particle size treatment.

The small particle diameter treatment can be performed by using a wet atomizing apparatus. Specifically, in this embodiment, first trisphosphate trisodium phosphate 168a having an average particle diameter of 0.2 占 퐉 was produced by treatment with a small-diameter particle using a wet-type bead mill. Further, in the small particle diameter treatment of this embodiment performed by wet, NMP was used as a solvent in the same manner as the solvent 169 used for producing the positive electrode paste.

When the positive electrode paste was kneaded, the primary trisodium phosphate 168a was mixed in the state of being dispersed in the NMP by small particle size treatment. On the other hand, when the positive electrode paste was kneaded, the second trisphosphate lithium 168b was mixed into the powder state. The positive electrode active material 165, the conductive material 166, and the binder 167 were also mixed in the state of powder when the positive electrode paste was kneaded.

The positive electrode active material 165, the conductive material 166, the binder 167 and the trisodium phosphate 168 are all dispersed in NMP to produce a positive electrode paste by kneading. Further, in kneading in the positive electrode paste production step, it is not always necessary to mix the above-mentioned respective materials at the same time, and the above-mentioned materials may be mixed in the solvent 169 in order. That is, after the mixed material is appropriately dispersed in the solvent 169 by kneading, the kneading may be performed while sequentially mixing the following materials. For kneading in the positive electrode paste production process, a high speed disperser homodisperser can be used.

In the positive electrode plate manufacturing process of the present embodiment, the positive electrode active material layer 162 is formed by using the positive electrode paste produced in the positive electrode paste manufacturing step shown in Fig. As a result, the positive electrode active material layer 162 of the positive electrode plate 160 produced in the positive electrode plate manufacturing step contains both the first trisodium phosphate 168a and the second trisodium phosphate 168b.

Herein, the function of the trisodium phosphate 168 in the produced battery 100 will be described. As the function of the trisodium phosphate 168, first, a protective coating is formed on the surface of the positive electrode active material 165. Secondly, the function as an acid consuming agent when the battery 100 is used normally can be mentioned. Hereinafter, the functions of these trisodium phosphate 168 will be described in order.

First, the formation of the protective coating on the surface of the positive electrode active material 165, which is the first function of the trisodium phosphate 168, will be described. In this embodiment, as described above, LiNi _0.5 Mn _1.5 O ₄ having an operating potential upper limit of 4.3 V or higher based on metal lithium is used as the positive electrode active material 165. Therefore, in the initial charging step, the working potential when the metal lithium of the positive electrode active material 165 is used 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 rises to 4.3 V or more, the solvent component in the electrolyte solution 120 is oxidized and decomposed to generate hydrogen ions. In addition, the generated hydrogen ions react with the fluorine ions in the electrolytic solution 120 to generate hydrofluoric acid (HF).

The hydrofluoric acid generated in the initial charging step reacts with the trisodium phosphate 168 contained in the positive electrode active material layer 162. A film is formed on the surface of the positive electrode active material 165 by reacting phloric acid trisodium 168 with hydrofluoric acid. The coating of the surface of the positive electrode active material 165 contains a fluorine element F and a phosphorus element P. [ Specifically, a compound having a fluorine element (more specifically, a fluorine compound such as LiF) and a compound having a phosphorus element (more specifically, a compound having a phosphate ion such as Li ₃ PO ₄ , Li ₂ HPO ₄ , LiH ₂ PO ₄ , H ₃ PO _4, and the like).

This coating film can function as a protective coating for the positive electrode active material 165. [ That is, the positive electrode active material 165 having the protective coating formed thereon is inhibited from being eluted from the transition metal by hydrofluoric acid thereafter.

The present inventors have also found that the smaller the particle diameter of tris (Phosphorus trioxide) 168 is used for the protective coating of the positive electrode active material 165 formed by the reaction of trisodium phosphate 168 and hydrofluoric acid, And the like. 5 is a graph showing the relationship between the initial internal resistance ratio of the battery and the average particle diameter of trisodium phosphate.

Fig. 5 shows the results of measurement of the initial internal resistance of a test battery, which is a lithium ion secondary battery, using trisodium phosphate with different average particle diameters. In the graph of FIG. 5, a lithium ion secondary battery having the same configuration as the battery 100 of the present embodiment is used. However, for the test cell used for obtaining the graph of Fig. 5, two types of trisodium phosphate having different average particle diameters are not used as in this embodiment.

That is, the graph of FIG. 5 is obtained by measuring the initial internal resistance, which is the internal resistance after the initial charging process, for each test battery manufactured by using only one type of trisodium phosphate having different average particle diameters. Specifically, as shown in Fig. 5, each test cell was a lithium trisodium phosphate having an average particle diameter of 0.2 占 퐉, an average particle diameter of 1.0 占 퐉, an average particle diameter of 1.5 占 퐉, an average particle diameter of 3.0 占 퐉 . ≪ / RTI > The initial internal resistance ratio of each test cell shown in the vertical axis of FIG. 5 was calculated by multiplying the initial internal resistance value of each test battery by the initial internal resistance value of the test battery manufactured using trisodium phosphate having an average particle diameter of 3.0 mu m As shown in Fig.

As shown in FIG. 5, the initial internal resistance is lower for a test battery using a small-average-particle-size lithium trisodium phosphate. It is considered that this is because the protective film formed on the surface of the positive electrode active material 165 can have higher conductivity when the tris (tri) phosphate is used.

That is, since tris (tri-trityl phosphate) particles having a smaller particle size have a higher dispersibility, they can be uniformly dispersed in the positive electrode paste. Further, the more the positive electrode paste in which trisodium phosphate is uniformly dispersed, the more uniform the positive active material layer in which trisodium phosphate is distributed. In addition, the more frequently the positive electrode active material layer in which trisodium phosphate is uniformly distributed, the higher the frequency of reaction of trisodium phosphate and hydrofluoric acid. This is because the occurrence frequency of trisodium phosphate is high at the occurrence site of hydrofluoric acid.

In addition, since the reaction frequency of trisodium phosphate and hydrofluoric acid is high, a protective coating can be formed on the surface of the positive electrode active material 165 in a short time. Further, it is considered that by forming the protective coating of the positive electrode active material 165 in a short time, the protective coating can be made thin and high in conductivity. Therefore, it is believed that the use of trisodium phosphate having a small particle diameter makes it possible to produce a lithium ion secondary battery having a low internal resistance.

Next, a function as an acid consuming agent in a normal use, which is the second function of the trisodium phosphate 168, will be described. As described above, in the initial charging process of the battery 100, the working potential when the metal lithium of the positive electrode active material 165 is used is 4.3 V or higher, thereby generating hydrofluoric acid. The generation of the hydrofluoric acid may occur not only in the initial charging step but also in a subsequent charging process. This is because the working potential when the metal lithium of the positive electrode active material 165 is used as a reference may be 4.3 V or more even when the battery is charged during normal use.

In addition, the hydrofluoric acid generated by the normal use may elute the transition metal even in the case of the positive electrode active material 165 after the protective coating is formed. That is, in a state in which a great amount of hydrofluoric acid is generated, the transition metal may be eluted from the positive electrode active material 165. Then, the transition metal is eluted from the positive electrode active material 165, so that there is a possibility that the charging capacity of the battery 100 is lowered.

However, in the battery 100 of this embodiment, since the lithium trisodium phosphate 168 is contained in the positive electrode active material layer 162, it can function as an acid consuming agent. That is, the trisodium phosphate 168 which is not consumed at the time of forming the protective coating of the positive electrode active material 165 in the initial charging step remains in the positive electrode active material layer 162 thereafter. In addition, since the remaining trisodium phosphate 168 functions as an acid consuming agent which reacts with hydrofluoric acid, it is possible to inhibit the transition metal from eluting from the positive electrode active material 165. By suppressing the dissolution of the transition metal from the positive electrode active material 165, a decrease in the charging capacity of the battery 100 can be suppressed.

The inventors of the present invention have found that trisodium phosphate 168 which functions as an acid consuming agent in this normal use is different from the trisodium phosphate 168 which contributes to the formation of the protective coating of the positive electrode active material 165, I found that this need not be small. 6 is a graph showing the relationship between the capacity retention rate of the battery and the average particle diameter of trisodium phosphate.

Fig. 6 shows the results of measurement of the capacity retention rate of a test battery, which is a lithium ion secondary battery, using trisodium phosphate having different average particle diameters. 6, a lithium ion secondary battery having the same structure as the battery 100 of the present embodiment is used. However, as in the case of Fig. 5, the test cell used for obtaining the graph of Fig. 6 does not use two kinds of trisodium phosphate having different average particle diameters as in this embodiment. Specifically, as shown in Fig. 6, each test cell was made of trisodium phosphate, having an average particle diameter of 0.2 mu m, an average particle diameter of 1.5 mu m, and an average particle diameter of 3.0 mu m .

6 is obtained by measuring the capacity retention rate of each test battery. The capacity retention rate is represented by the ratio of the charging capacity after the cycle test to the initial charging capacity before the cycle test. The cycle test was carried out by charging and discharging the test cells a plurality of times.

As shown in FIG. 6, the capacity retention rate of the lithium ion secondary battery is also about the same, even when trisodium phosphate having a different average particle diameter is used. That is, the function as an acid consuming agent of trisodium phosphate can be demonstrated without depending on the particle size of trisodium phosphate.

Therefore, in the positive electrode paste manufacturing process of this embodiment, as described above, the tritium phosphate 168a having an average particle diameter of 0.2 占 퐉 and the secondary phosphate tree 168a having an average particle diameter of 1.5 占 퐉, Lithium (168b) is used.

In the battery 100 according to this embodiment, the first tris (tri-trithio) phosphate 168a contained in the positive electrode active material layer 162 of the positive electrode plate 160 is reacted with hydrofluoric acid in the initial charging step, A protective film can be formed on the surface of the protective film 165. The primary trisodium phosphate 168a has an average particle diameter of 0.2 占 퐉 and a small particle size. Therefore, the protective coating formed on the surface of the positive electrode active material 165 in the initial charging step of the battery 100 of this embodiment can be of high quality with high conductivity. The battery 100 can be made to have a low internal resistance.

On the other hand, the dibasic trisodium phosphate 168b can function as an acid consuming agent for hydrofluoric acid generated by the normal use of the battery 100. The second lithium trisodium phosphate 168b has an average particle diameter of 1.5 占 퐉 and a large particle size. However, since the function as an acid consuming agent is independent of the particle size, even the second trisodium phosphate 168b having a large particle size can appropriately function as an acid consuming agent and suppress the decrease in the charging capacity of the battery 100 have.

Further, the second tribary Phosphorus trioxide 168b having a larger particle size is cheaper than the first tribary Phosphorus trioxide 168a having a smaller particle size. As described above, the second tris (tri) phosphate (168b) does not need to be subjected to small-particle diameter treatment like the first tris (tri) phosphate (168a).

Therefore, the battery 100 of the present embodiment has a low internal resistance and appropriately suppresses a reduction in the charging capacity accompanying use. In addition, the battery 100 has a lower manufacturing cost than the case where only the first trisodium phosphate 168a is used.

The inventors of the present invention confirmed the effect of the present invention by the first experiment and the second experiment described below. First, the first experiment will be described. In the first experiment, the batteries of Examples 1, 2, and 3 according to the present invention, and Comparative Examples 1 and 2 for comparison with this battery were produced and used.

The battery of the example in the first experiment and the battery of the comparative example are different from the tritium phosphate used in the positive electrode paste production step. With respect to the other conditions, the batteries of the examples and the batteries of the comparative examples were produced under the same conditions. The conditions of the positive electrode paste production step common to the examples and the comparative examples are shown below.

[Material used for positive electrode paste]

Positive electrode active material: LiNi _{0 . 5} Mn _{1 . 5} O ₄

Conductive material: acetylene black (AB)

Binder: Polyvinylidene fluoride (PVDF)

Additive: acid tree lithium (Li ₃ PO ₄₎

Solvent: N-methylpyrrolidone (NMP)

[Weight ratio in positive electrode paste (weight percentage)] [

Positive electrode active material: Conductive material: Binder: Additive = 92.1: 0.9: 4.0: 3.0

[Condition for kneading]

Paste making device: High speed disperser homodisperse

Rotation speed: 2000 to 4000 rpm

That is, in the first experiment, the amount of the trisodium phosphate used as the additive in the positive electrode paste was set to 3.0 wt% in both of the examples and the comparative examples. Table 1 below shows the details of the amount of trisodium phosphate used in the positive electrode paste production process in each of Examples and Comparative Examples in the first experiment.

As shown in Table 1, all of the examples used trisodium phosphate having an average particle diameter of 0.2 占 퐉 and trisodium phosphate having an average particle diameter of 1.5 占 퐉 both as described in the above embodiment. In Table 1, trisodium phosphate having an average particle diameter of 0.2 mu m is referred to as " small particle size ", and trisodium phosphate having an average particle diameter of 1.5 mu m is referred to as " large particle size ". On the other hand, in Comparative Example 1, only "triplet phosphor" with an average particle diameter of 1.5 μm was used. In Comparative Example 2, only "small particle diameter" trisodium phosphate having an average particle diameter of 0.2 μm was used.

Table 1 shows the small particle size ratios for Examples and Comparative Examples. The small particle size ratio is a ratio of the mass of trisodium phosphate having an average particle size of 0.2 占 퐉 to the total mass of the mass of tri-lithium phosphate having an average particle diameter of 0.2 占 퐉 and the mass of tri-lithium phosphate having an average particle diameter of 1.5 占 퐉.

The positive electrode plates of Examples and Comparative Examples were produced by forming a positive electrode active material layer on an aluminum foil as a positive electrode collector foil by using a positive electrode paste obtained by a positive electrode paste manufacturing process under the above-described conditions. In the production of the positive electrode plates of Examples and Comparative Examples, the conditions for application of the positive electrode paste and the conditions for drying the positive electrode paste were the same. In addition, the batteries of Examples and Comparative Examples were produced using the above-described positive electrode plate. Regarding the negative electrode plate and the electrolyte other than the positive electrode plate, the same batteries as those of the battery 100 were used in all of the examples and the comparative examples.

In the first experiment, the initial internal resistance measured after the initial charging of the batteries of the above-described Examples and Comparative Examples was compared. The measurement of the initial internal resistance was carried out for a certain period of time from the state in which the SOC was 60% in the environment of the temperature of 25 캜 for the batteries of the examples and the comparative examples, Fig. 7 shows the relationship between the initial internal resistance ratio and the small particle size ratio for the cells of the examples and the comparative examples, respectively.

The initial internal resistance ratios of the batteries shown in the vertical and vertical axes of FIG. 7 are shown by the ratios of the initial internal resistance values of the batteries of Examples and Comparative Examples to the initial internal resistance value of the battery of Comparative Example 1 will be. As can be seen from Fig. 7, all of the batteries of the Examples had lower initial internal resistance values than the batteries of Comparative Example 1. [ The initial internal resistance value of the battery of Comparative Example 2 is lower than that of the battery of Comparative Example 1.

This is because, in Comparative Example 1, a battery having a positive electrode plate produced using only trisodium phosphate having an average particle diameter of 1.5 m was used, in the battery of Example and the battery of Comparative Example 2, the positive electrode plate was replaced with a phosphate tree This is because they are made using lithium. That is, in the battery of the example and the battery of the comparative example 2, the protective coating of the positive electrode active material has high conductivity, so that the internal resistance of the battery is lower than that of the battery of the comparative example 1.

The positive electrode plate of the battery of Comparative Example 2 was produced using only trisodium phosphate with an average particle diameter of 0.2 mu m. As a result, the battery of Comparative Example 2 has a low internal resistance but a high manufacturing cost. This is because trisodium phosphate having an average particle diameter of 0.2 占 퐉 is produced by small particle size treatment and is higher in price than trisodium phosphate having an average particle size of 1.5 占 퐉.

On the other hand, all of the positive electrode plates of the batteries of the Examples use trisodium phosphate having an average particle diameter of 0.2 占 퐉 and also use trisodium phosphate having an average particle diameter of 1.5 占 퐉. As a result, all of the batteries of the Examples are lower in manufacturing cost than the batteries of Comparative Example 2.

7, it was confirmed that the internal resistance of the battery of Example 3 was about the same as the internal resistance of the battery of Comparative Example 2 in the first experiment. Thus, in the positive electrode paste production process, the ratio of the mass of trisodium phosphate having an average particle diameter of 1.5 mu m to the total mass of the trisodium phosphate having an average particle diameter of 0.2 mu m and the mass of trisodium phosphate having an average particle diameter of 1.5 mu m, It is preferable that the thickness is 1/3 or more.

When the ratio of the mass of trisodium phosphate having an average particle size of 1.5 mu m to the total mass of trisodium phosphate is less than 1/3, the effect of reducing the internal resistance of the battery can not be expected much compared with the case of 1/3 . On the other hand, the smaller the ratio of the mass of the trisodium phosphate having the average particle diameter of 1.5 탆, the higher the production cost of the battery. That is, by setting the ratio of the mass of tri-lithium phosphate having an average particle diameter of 1.5 μm to the total mass of trisodium phosphate to 1/3 or more, a battery having a low internal resistance can be manufactured at a lower cost.

In the first experiment, in the positive electrode paste production step, the ratio of the mass of trisodium phosphate having an average particle diameter of 0.2 mu m to the total mass of trisodium phosphate is preferably 1/6 or more as in Example 1 . This is because the ratio of the mass of trisodium phosphate having an average particle size of 0.2 mu m to the mass ratio of 1/6 or more as in Example 1 can reliably exert the effect of lowering the internal resistance of the battery.

Next, the second experiment will be described. In the second experiment, the batteries of Example 4, Example 5, and Example 6 according to the present invention, and Comparative Examples 3 and 4 for comparison with this battery were produced and used.

Also in the second experiment, the battery of the example and the battery of the comparative example are different from the trisodium phosphate used in the positive electrode paste production step. In the second experiment, under the other conditions, both the batteries of the examples and the batteries of the comparative examples were produced under the same conditions. Also in the second experiment, the conditions of the positive electrode paste production step common to the examples and the comparative examples were the same as those of the first experiment described above. The manufacturing conditions of the battery using the produced positive electrode paste were the same as those of the first experiment described above.

Also in the second experiment, the amount of trisodium phosphate in the positive electrode paste was set to 3.0 wt% for both the examples and the comparative examples, as in the first experiment. Table 2 below shows details of the amount of trisodium phosphate used in the positive electrode paste production process for the examples and the comparative examples in the second experiment.

As shown in Table 2, the tritium phosphate used in Examples of the second experiment is one having a " small particle size " and a " large particle size ". Specifically, in Examples 4, 5, and 6, trisodium phosphate of small particle size was used, and average particle diameters of 0.2 탆, 0.4 탆, and 0.6 탆 were used, respectively. Further, in any of Examples 4, 5, and 6, as the trisodium phosphate of "large particle diameter", an average particle diameter of 3.0 μm is used. In other words, also in the embodiment of the second experiment, as the trisodium phosphate of the "large particle size", the one having an average particle diameter of 1.3 μm or more is used as compared with the "small particle size" trisodium phosphate. Also in the second experiment, trisodium phosphate of "small particle size" was produced by performing small particle size treatment on the same material as that of trisodium phosphate of "large particle size".

On the other hand, in Comparative Example 3, only tri-lithium phosphate of the "large particle size" is used. In Comparative Example 4, only "small particle size" tri-trisodium phosphate was used. Specifically, in Comparative Example 3, only trisodium phosphate having an average particle diameter of 3.0 占 퐉 is used. In Comparative Example 4, only trisodium phosphate having an average particle diameter of 0.4 mu m is used. Table 2 also shows the small particle size ratios for the examples and the comparative examples.

In Table 2 concerning the second experiment, " D10 particle size " is shown for each of the examples. The " D10 particle size " is the particle size at an integrated value of 10% from the particle side in the synthetic particle size distribution of particle size distribution of trisodium phosphate of "small particle size" and particle size distribution of trisodium phosphate of "large particle size". The synthetic particle size distribution in the second experiment was obtained by separately obtaining particle size distributions from particle groups of "small particle size" trisodium phosphate and "large particle size" trisodium phosphate, and combining them. Fig. 8 shows Example 5 as an example of the composite particle size distribution of trisodium phosphate in "small particle size" and "large particle size".

The particle size distribution of trisodium phosphate used for obtaining the " D10 particle size " in the second experiment is also based on the volume obtained by the laser diffraction / scattering method. The synthetic particle size distribution of trisodium phosphate in "small particle size" and "large particle size" can also be obtained from a mixed particle group obtained by mixing "tiny particle size" and "large particle size" trisodium phosphate. The surface of the positive electrode plate taken out of the nonaqueous electrolyte secondary battery can be photographed by an electron microscope to measure the number and particle size of trisodium phosphate to examine the particle size distribution of trisodium phosphate in the nonaqueous electrolyte secondary battery after the production.

Also in the second experiment, the initial internal resistances of the batteries of the above-described Examples and Comparative Examples were compared after initial charging. The initial internal resistance was measured in the same manner as in the first experiment described above. Fig. 9 shows the relationship between the initial internal resistance ratio and the small particle size ratio for the batteries of Examples and Comparative Examples, respectively. The initial internal resistance ratios of the batteries shown in the vertical axis and the comparative example shown in Fig. 9 are shown by the ratios of the initial internal resistance values of the batteries of the examples and the comparative example to the initial internal resistance value of the battery of the comparative example 3 will be.

As can be seen from Fig. 9, in the second experiment, all of the batteries of the Examples are lower in the initial internal resistance value than the batteries of Comparative Example 3. [ Also, the battery of Comparative Example 4 had lower initial internal resistance than the battery of Comparative Example 3.

This is because, in Comparative Example 3, the battery having the positive electrode plate produced using only the "large-particle-size" lithium triphosphate having a large average particle diameter was used, whereas in the battery of Example and the battery of Comparative Example 4, Quot; small particle size " of 1.3 占 퐉 or more than that of the " small particle size " That is, also in the second experiment, in the battery produced by using the "small particle diameter" trisodium phosphate having an average particle diameter of 1.3 μm or more larger than the "large particle size", the protective coating of the positive electrode active material has high conductivity, The resistance is reduced.

In the second experiment, the positive electrode plate of the battery of Comparative Example 4 was produced using only "small particle size" tri-lithium phosphate. On the other hand, all of the positive electrode plates of the batteries of the Examples use trisodium phosphate of "small particle diameter" and also use trisodium phosphate of "large diameter". As a result, all of the batteries of the Examples are lower in manufacturing cost than the batteries of Comparative Example 4.

9, it was confirmed that the internal resistance of the batteries of Examples 4 and 5 was about the same as the internal resistance of the battery of Comparative Example 4 in the second experiment. Therefore, in the positive electrode paste production process, it is preferable to set the " D10 particle size " at the integrated value of 10% from the fine particle side in the synthetic particle size distribution of trisodium phosphate of " small particle size " Which is preferable. This is because the internal resistance of the battery can be made as low as that in the case of using only "small particle size" trisodium phosphate while using an inexpensive "large-particle-size" lithium trisodium phosphate. This is because it is thought that the tribasic phosphoric acid tritium particles having a particle size of " D10 " of 0.4 占 퐉 or less contain a sufficient amount of trisodium phosphate particles having a small particle diameter that can make the protective coating of the positive electrode active material highly conductive do. Since the particles of lithium triphosphate to be used are as small as necessary for forming the protective coating having high conductivity in the positive electrode active material, the battery can be manufactured at low cost.

In the battery 100 described above, an example of using trisodium phosphate 168 as an additive for the positive electrode active material layer 162 is shown, but other metal phosphates may be used in place of trisilicate phosphate 168. That is, as the metal phosphate which is the additive of the positive electrode active material layer 162, a phosphate or pyrophosphate containing at least one of an alkali metal and a Group 2 element as a metal and containing a phosphate ion (PO ₄ ^3- ) can be used . That is, examples of additives for the positive electrode active material layer 162 include sodium phosphate (Na ₃ PO ₄ ), potassium phosphate (K ₃ PO ₄ ), magnesium phosphate (Mg ₃ (PO ₄ ) ₂ ) Calcium phosphate (Ca ₃ (PO ₄ ) ₂ ) and the like can be used.

This is because such a metal phosphate can exert both the first function of forming a protective coating on the above-mentioned positive electrode active material and the second function of an acid consuming agent in normal use. In addition, since the battery has a high withstand voltage against a high voltage, it is possible to appropriately exert the above two functions even in a cell having a high open-circuit voltage such as the battery 100 of the present embodiment. Further, a plurality of metal phosphates as described above may be used in combination. In the above embodiment, two metal phosphates (trisodium phosphate) having different average particle diameters are mixed, but three or more metal phosphates having different average particle diameters may be mixed.

As described in detail above, the method of manufacturing the battery of the present embodiment has a positive electrode paste manufacturing step, a positive electrode plate manufacturing step, a assembling step, and an initial charging step. In the positive electrode paste production step, trisodium phosphate trisodium phosphate group and a second group of trisodium phosphate trisodium phosphate group having an average particle diameter of 1.3 m or more larger than the first trisodium phosphate group are used as trisodium phosphate. The tribasic lithium trisodium phosphate group can form a protective coating having a high conductivity on the surface of the positive electrode active material to reduce the internal resistance of the battery. In addition, the inexpensive dibasic trisodium phosphate particles can function as an acidic consumption agent of hydrofluoric acid generated during normal use of the battery. Thereby, a manufacturing method of a non-aqueous electrolyte secondary battery capable of manufacturing a non-aqueous electrolyte secondary battery having a reduced manufacturing cost and a low internal resistance is realized.

It should be noted that the present embodiment is merely an example and does not limit the present invention at all. Accordingly, the present invention can be variously modified and modified within the scope not departing from the gist of the present invention. For example, not limited to a rolled electrode body 110 having a flat shape, a rolled electrode body having a cylindrical shape may be used. For example, the present invention is not limited to the winding type, but can be applied to a laminate type electrode body.

Claims (8)

A nonaqueous electrolytic solution comprising 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 electrolyte solution, And a positive electrode active material layer formed on a surface of the positive electrode current collector foil,
A positive electrode paste production process for producing a positive electrode paste by dispersing a positive electrode active material, a binder, and a metal phosphate in a solvent,
Forming a positive electrode active material layer by coating the positive electrode paste on the surface of the current collector foil and drying the applied positive electrode paste to produce the positive electrode plate;
An assembling step of assembling the nonaqueous electrolyte secondary battery by receiving the nonaqueous electrolyte, the positive electrode plate and the negative electrode in the battery case,
And an initial charging step of performing initial charging of the non-aqueous electrolyte secondary battery after the assembling step,
The metal phosphate includes a first metal phosphate group of a first metal phosphate particle having a first average particle diameter and a second metal phosphate group having a second average particle diameter larger than the first average particle diameter by at least 1.3 탆 Lt; / RTI > The method according to claim 1,
Wherein the ratio of the mass of the second metal phosphate to the total mass of the metal phosphate combined with the mass of the first metal phosphate and the mass of the second metal phosphate is 1/3 or more, Gt; 3. The method according to claim 1 or 2,
Wherein the ratio of the mass of the first metal phosphate to the total mass of the metal phosphate combined with the mass of the first metal phosphate and the mass of the second metal phosphate is 1/6 or more, Gt; 3. The method according to claim 1 or 2,
In the positive electrode paste production step, the metal phosphate has a particle size at an integrated value of 10% from the fine particle side in a synthetic particle size distribution of the particle size distribution of the first metal phosphate and the particle size distribution of the second metal phosphate as 0.4 Mu m or less. A non-aqueous electrolyte secondary battery comprising:
A positive electrode current collector foil; a positive electrode plate formed on the surface of the positive electrode current collector foil and having a positive electrode active material layer including a metal phosphate and a positive electrode active material having at least two peaks in a particle size distribution;
A negative electrode plate,
A nonaqueous electrolytic solution containing an ionic compound having fluorine,
And a battery case for accommodating the positive electrode plate and the negative electrode plate together with the electrolyte solution,
Wherein a coating film is formed on the surface of the positive electrode active material by the metal phosphate in the charging step of the nonaqueous electrolyte secondary battery. 6. The method of claim 5,
Wherein a peak of the smallest particle diameter among the at least two peaks is located at a particle diameter of 0.4 占 퐉 or less. The method according to claim 5 or 6,
Wherein an interval between two peaks of said at least two peaks is 1.3 占 퐉 or more. The method of claim 3,
In the positive electrode paste production step, the metal phosphate has a particle size at an integrated value of 10% from the fine particle side in a synthetic particle size distribution of the particle size distribution of the first metal phosphate and the particle size distribution of the second metal phosphate as 0.4 Mu m or less.

Images