Lithium ion secondary battery and manufacturing method thereof

Abstract

To suppress the deposition of metallic lithium Li on a negative electrode plate.SOLUTION: In a lithium ion secondary battery, a coating material containing a lithium salt is added to a non-aqueous electrolyte, and when a negative electrode composite layer of a negative electrode plate contains Na, a plurality of band-shaped coating layers 41 extending along a winding direction are provided on a separator 4, and a resistance RS [Ω] at each position in a width direction of the coating layer 41 is adjusted according to resistance distribution of a resistance RN [Ω] of the negative electrode composite layer 22, such that the resistance RS [Ω] of the separator 4 becomes high according to a portion where the resistance RN [Ω] of the negative electrode composite layer is high, and the resistance RS [Ω] of the separator 4 becomes low according to a portion where the resistance RN [Ω] of the negative electrode composite layer 22 is low, thereby providing resistance distribution of the coating layer resistance RC [Ω] for each position.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a lithium ion secondary battery and a manufacturing method thereof, and more particularly to a lithium ion secondary battery that suppresses deposition of metallic lithium Li on a negative electrode plate and a manufacturing method thereof. [Background technology]

[0002] Lithium ion secondary batteries are lightweight, have high energy density, and are capable of inputting and outputting large currents, and therefore are preferably used as high-output power sources for vehicles and stationary power storage facilities.

[0003] FIG. 1 is a perspective view showing an outline of the external configuration of a lithium-ion secondary battery 10 of the present embodiment. FIG. 2 is a schematic diagram showing the configuration of a wound electrode body 12. FIG. 12 is a schematic diagram showing the lithium ions Li + FIG.

[0004] In one example of such a lithium ion secondary battery 10, a positive electrode plate 3 and a negative electrode plate 2 are insulated by a separator 4 and stacked, and an electrode body 12 wound into an elliptical cylinder is housed in a single battery case 11. In such a lithium ion secondary battery 10, lithium ions Li are generated from the positive electrode active material 34 of the positive electrode mixture layer 32 of the positive electrode plate 3 during charging. + moves to negative plate 2.

[0005] The lithium ion secondary battery 10 has a separator 4 holding a non-aqueous electrolyte 13 between a positive electrode plate 3 and a negative electrode plate 2, which are then laminated and wound to form an electrode assembly 12. Conventional separators are basically designed to keep resistance low and evenly distribute lithium ions (Li) so as not to increase unnecessary internal resistance. + It was formed homogeneously so that it could be penetrated.

[0006] Incidentally, in the lithium ion secondary battery 10, when the battery is initially charged after manufacture, a film of SEI (Solid Electrolyte Interface) is formed on the surface of the negative electrode active material 24 of the negative electrode mixture layer 22. The SEI film is present between the negative electrode active material 24 and the non-aqueous electrolyte solution 13, and the lithium ions Li + The SEI film facilitates the absorption and release of oxygen into and from the negative electrode, and also suppresses the decomposition of the non-aqueous electrolyte solution 13. For this reason, the SEI film is essential for maintaining good battery characteristics.

[0007] On the other hand, in the conventional lithium-ion secondary battery 10, the SEI film grows due to charging and discharging after production, and the resistance [Ω] increases. + and consumes the nonaqueous electrolyte 13. For this reason, an additive such as lithium bis(oxalato)borate (LiBOB) is sometimes added to suppress the growth of the SEI film.

[0008] However, when the negative electrode mixture layer 22 contains Na, there is a problem that the resistance [Ω] of the central portion 22a in the width direction W of the negative electrode mixture layer 22 increases. + will be less receptive.

[0009] When charging is performed in this state, current flows through the widthwise center 22a of the negative electrode mixture layer 22, which has a high resistance [Ω], in the negative electrode plate 2, in the same manner as through the end 22b of the negative electrode mixture layer 22, which has a low resistance. Then, lithium ions Li + This exceeds the allowable range of acceptance, causing local overcharging in the widthwise central portion 22a. This causes a potential [V] at which metallic lithium Li precipitates in the negative electrode active material of the negative electrode mixture layer 22, which causes a problem that metallic lithium Li is more likely to precipitate. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2016-201327 A Summary of the Invention [Problem to be solved by the invention]

[0011] In addition, the invention disclosed in Patent Document 1 discloses a separator that is not homogeneous. However, the purpose of this is to increase the peel strength of the heat-resistant layer by disposing a heat-resistant layer with a large amount of binder at the end of the separator in the width direction, thereby suppressing the thermal shrinkage of the separator. In other words, no consideration is given to the increase in resistance caused by disposing a heat-resistant layer with a large amount of binder, and the suppression of the precipitation of metallic lithium Li that increases in the center of the width direction due to this, and no knowledge of this kind is disclosed. For this reason, the problem of precipitation of metallic lithium Li as described above has not been solved. The present inventors have found a new configuration for the separator configuration to solve such problems.

[0012] The problem to be solved by the lithium ion secondary battery and the method for producing the same of the present invention is to suppress deterioration of the electrode body of the lithium ion secondary battery. [Means for solving the problem]

[0013] In order to solve the above problems, the lithium ion secondary battery of the present invention is a lithium ion secondary battery having an electrode assembly in which a positive electrode plate and a negative electrode plate are laminated and wound with a separator interposed therebetween and filled with a nonaqueous electrolyte, the nonaqueous electrolyte being added with a coating material containing a lithium salt, When the negative electrode mixture layer of the negative electrode plate contains Na, a plurality of strip-shaped coating layers extending along the winding direction L are provided on the separator, and the resistance R at each position in the width direction W perpendicular to the winding direction L of the coating layer is S [Ω] is the resistance R of the negative electrode mixture layer N According to the resistance distribution of the negative electrode mixture layer, the resistance RS [Ω] of the separator is made high in a portion where the resistance RN [Ω] of the negative electrode mixture layer is high, and the resistance R N The resistance R of the separator is SThe resistance R of the coating layer at each position is set to be low [Ω]. C It is characterized by having a resistance distribution of [Ω].

[0014] In addition, the resistance R of the plurality of coating layers C The resistance value [Ω] may be set according to the thickness T [μm]. The separator has a non-coated portion in the gap between the plurality of coating layers, and the resistance R of the separator is adjusted by adjusting the area ratio between the coating layer and the non-coated portion according to the position in the width direction W. S A resistance distribution of [Ω] may be set.

[0015] The coating layer may be formed in a central portion in the width direction W of the separator, excluding the ends in the width direction W. The coating layer may be formed on the surface of the positive electrode plate.

[0016] The coating layer may be configured to include insulating particles and a binder. The resistance [Ω] per unit area of ​​the multiple coating layers may be adjusted by adjusting the content of the insulating particles or the binder.

[0017] The insulating particles may be made of boehmite or alumina. The film-forming material having a lithium salt added to the non-aqueous electrolyte may be lithium bis(oxalato)borate (LiBOB, LiB(C2O4)2).

[0018] In the method for producing a lithium ion secondary battery of the present invention, a positive electrode plate and a negative electrode plate are laminated and wound with a separator therebetween, and a lithium ion secondary battery is provided with an electrode body filled with a non-aqueous electrolyte. In the method for producing a lithium ion secondary battery of the present invention, a coating material containing a lithium salt is added to the non-aqueous electrolyte, and when the negative electrode mixture layer of the negative electrode plate contains Na, a plurality of band-shaped coating layers extending along a winding direction L are provided on the separator, and a resistance R at each position in a width direction W perpendicular to the winding direction L of the coating layer is calculated. S [Ω] is the resistance R of the negative electrode mixture layer NAccording to the resistance distribution [Ω], the resistance R N The resistance R of the separator is S The resistance R of the negative electrode mixture layer is increased. N The resistance R of the separator is S [Ω] is reduced so that the resistance R of the coating layer at each position is C A resistance distribution of [Ω] may be set.

[0019] The method may include a coating step in which the coating layers are formed by coating a coating layer paste in which insulating particles and a binder are made into a paste state by a solvent. In the coating step, a plurality of the coating layers may be simultaneously or successively coated.

[0020] Resistance R of the plurality of coating layers C The resistance value [Ω] may be set according to the thickness T [μm]. The separator has a non-coated portion formed between a plurality of the coated layers, and the resistance R of the separator is controlled by adjusting the area ratio between the coated layer and the non-coated portion according to the position in the width direction W. S A resistance distribution of [Ω] may be set.

[0021] The coating layer may be formed in the center portion in the width direction W of the separator, excluding the ends in the width direction W. Effect of the Invention

[0022] The lithium ion secondary battery and the method for producing the same of the present invention have the effect of suppressing the deposition of metallic lithium Li on the negative electrode plate. [Brief description of the drawings]

[0023] [Figure 1] 1 is a perspective view showing the outline of the external configuration of a lithium-ion secondary battery according to an embodiment of the present invention; [Diagram 2] 2 is a schematic diagram showing the configuration of a wound electrode body 12. FIG. [Diagram 3] FIG. 2 is a schematic diagram showing the state of movement of lithium ions Li+ during charging of the lithium ion secondary battery according to the first embodiment of the present invention. [Figure 4] 4 is a graph showing the relationship between the position in the width direction W of the negative electrode mixture layer and the resistance RN [Ω] in the present embodiment. [Diagram 5] 4 is a graph showing the relationship between the position in the width direction W of the separator and the resistance RS [Ω] of the present embodiment. [Figure 6] 13 is a table showing the relationship between the resistance ratio [%] and the resistance RN [Ω] of the other end at a distance [mm] from one end of a negative electrode composite layer, taken as 100 [%]. [Figure 7] The relationships in the table of FIG. 6 are shown in a graph. [Figure 8] 1 is a graph showing the thickness T [μm] of the coating layer and the resistance ratio [%] of the resistance RC [Ω] of the coating layer when the thickness T [μm] of the coating layer is set to 0 [μm]. [Figure 9] 1 is a table showing the thickness T [μm] of the coating layer at the distance [mm] from one end of the separator. [Figure 10] FIG. 4 is a schematic diagram showing a second embodiment of a coating layer. [Figure 11] FIG. 4 is a schematic diagram showing a third embodiment of a coating layer. [Figure 12] FIG. 11 is a schematic diagram showing a coating process according to a third embodiment. [Figure 13] FIG. 1 is a schematic diagram showing the movement of lithium ions Li+ during charging of a conventional lithium ion secondary battery. [Figure 14] 1 is a graph showing the relationship between the position in the width direction W of a conventional negative electrode mixture layer and resistance RN [Ω]. [Figure 15] 1 is a graph showing the relationship between the position in the width direction W and the resistance RS [Ω] of a conventional separator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, regarding the lithium-ion secondary battery of the present invention and its manufacturing method, taking an embodiment of the manufacturing method of the lithium-ion secondary battery 10 as an example, it will be described with reference to FIGS. 1 to 15. <Principle of this embodiment> First, the principle of suppressing the precipitation of metallic lithium Li in the negative electrode plate 2 of the lithium-ion secondary battery 10 of this embodiment will be described.

[0025] As described in the background art, in the lithium-ion secondary battery 10, unevenness may occur in the resistance distribution in the width direction W of the negative electrode composite material layer 22 for some reason. In this embodiment, it is characterized in that the composite resistance with the negative electrode composite material layer 22 is made uniform in the width direction W by the coating layer 41 of the separator 4 with respect to such unevenness in the resistance distribution in the width direction W of the negative electrode composite material layer 22. Note that the unevenness in the resistance distribution in the width direction W of the negative electrode composite material layer 22 may occur for various reasons. In particular, when an additive such as lithium bisoxalate borate (LiBOB) is added to the negative electrode composite material layer 22 as a film inhibitor in the non-aqueous electrolyte 13 and the negative electrode composite material layer 22 contains Na, it is remarkable. Therefore, in this embodiment, such a case will be described as an example.

[0026] <Relationship between LiBOB and Na> The SEI film is formed by the first charge immediately after the manufacture of the lithium-ion secondary battery 10. The SEI exists between the negative electrode active material 24 and the non-aqueous electrolyte 13, and smooths the occlusion and release of lithium ions Li + into and from the negative electrode, and suppresses the decomposition of the non-aqueous electrolyte 13. Therefore, the SEI film is essential for maintaining good battery characteristics.

[0027] However, the SEI film is formed by decomposition products of the non-aqueous electrolyte 13 and additives, and the decomposition products take in lithium ions Li + during the formation process. Then, by repeatedly charging and discharging or storing the battery for a long time, the SEI film becomes thicker. Then, not only does the internal resistance increase, but it may also cause a decrease in battery capacity due to the consumption of lithium ions Li + and the decomposition of the non-aqueous electrolyte 13.

[0028] To solve this problem, it has been proposed to add a film-forming material to the non-aqueous electrolyte 13 in advance. The film-forming material is a compound having a lithium salt, such as lithium bis(oxalato)borate (LiBOB, LiB(C2O4)2). According to this method, bis(oxalato)borate ions (BOB - ,BOB ion,B(C2O4)2 - ) is decomposed and polymerized, and a stable coating derived from BOB ions can be formed on the surface of the particles of the negative electrode active material 24. This makes it possible to suppress the growth of the SEI coating.

[0029] Incidentally, the material constituting the electrode body 12 used in the lithium ion secondary battery 10 may contain sodium salt. For example, the negative electrode mixture layer 22 is composed of a binder, a thickener, an additive, a solvent, and the like in addition to the negative electrode active material 24. Some of these use SBR (styrene butadiene copolymer) as the binder and CMC (carboxymethyl cellulose) as the thickener. SBR and CMC contain sodium salt. For this reason, the BOB ions BOB ionized from LiBOB may be dissolved in water. + is the sodium ion Na ionized from sodium salt + It also reacts with the negative electrode mixture layer 22 to form a NaBOB coating. The NaBOB coating becomes a part of the coating on the negative electrode mixture layer 22. This NaBOB coating has a relatively high resistance.

[0030] When the non-aqueous electrolyte 13 is poured into the battery case 11, the non-aqueous electrolyte 13 permeates the wound electrode assembly 12 from the end of the negative electrode plate 2. Sodium ions Na + The ion diffusion rate of NaBOB ions is faster than that of BOB ions. Therefore, a larger amount of the NaBOB coating is likely to be formed in the center portion 22a in the width direction W of the negative electrode mixture layer 22.

[0031] FIG. 14 shows the relationship between the position in the width direction W and the resistance R of a conventional negative electrode mixture layer 22. N 1 is a graph showing the relationship between the resistance R [Ω] and the surface area [Ω] of the negative electrode composite layer 22. The central portion 22a of the negative electrode composite layer 22, in which the amount of the coating of NaBOB is excessively large, has a higher resistance R [Ω] than the surrounding area.N The resistance [Ω] becomes high, and resistance unevenness is formed in negative electrode mixture layer 22.

[0032] That is, for the above reasons, central portion 22a of negative electrode mixture layer 22 in this embodiment has a resistance R N [Ω] is getting larger. <Conventional separator 4> FIG. 15 shows the relationship between the position in the width direction W and the resistance R of the conventional separator 4. S Here, a conventional separator 4 will be described. As the separator 4, for example, a porous film made of a resin such as PP (polypropylene) or PE (polyethylene) is used. The separator 4 is a material that can absorb lithium ions Li + The separator 4 is required to have the functions of electrically insulating the positive electrode plate 3 and the negative electrode plate 2 while allowing the electrolyte 13 to pass therethrough, retaining the nonaqueous electrolyte 13, a shutdown function, and a short-circuit prevention function. In particular, the lithium-ion secondary battery 10 has a problem of the formation of dendrites due to the precipitation of metallic lithium Li caused by overcharging or the like in the negative electrode plate 2. If such dendrites break through the separator 4, a short circuit will occur.

[0033] In the conventional separator 4, the separator 4 is designed not to increase the internal resistance and to uniformly distribute the lithium ions Li + As shown in Figure 15, the resistance R is uniform across the width W. S It was common technical knowledge to write it as [Ω].

[0034] <Deposition of metallic lithium Li on the negative electrode plate 2> The deposition of metallic lithium Li in the negative electrode plate 2 is caused by a positional resistance R N This is caused by unevenness in the distribution of resistance [Ω]. Typically, this is the case where the resistance of the central portion 22a of the negative electrode mixture layer 22 is greater than that of the end portion 22b in the width direction W of the negative electrode plate 2 as described above. In this state, the resistance R N The central portion 22a of the negative electrode mixture layer 22, in which the resistance [Ω] is large, is filled with lithium ions Li +In this state, when a separator 4 having a homogeneous structure as shown in FIG. 15 is used, current does not flow easily in the central portion 22a of the negative electrode mixture layer 22, and local overcharging occurs on the surface of a part of the negative electrode active material 24. As a result, the potential [V] of the surface of the negative electrode active material 24 becomes the potential [V] at which metallic lithium Li is deposited. Once metallic lithium Li is deposited, current flows more easily in that portion, and metallic lithium Li grows as branched dendrites extending in the direction of the separator 4.

[0035] Therefore, measures against the formation of such dendrites have been considered. One approach would be to simply increase the mechanical strength of the separator 4. However, the approach in this embodiment aims to suppress the precipitation of metallic lithium Li itself, which is the essential cause of dendrites.

[0036] <Separator 4 of this embodiment> FIG. 3 shows the lithium ion Li when the lithium ion secondary battery 10 of this embodiment is being charged. + In the lithium ion secondary battery 10 of this embodiment, a coating layer 41 is provided in the center portion 4a in the width direction W of the surface of the separator 4 on the positive electrode plate 3 side. The coating layer 41 is a portion in which insulating particles are fixed in a layer shape on the surface of the separator 4 with a binder. The insulating particles are S The change is proportional to the thickness T [μm] of the coating layer 41.

[0037] FIG. 4 shows the relationship between the position in the width direction W of the negative electrode mixture layer 22 and the resistance R N As described above, the negative electrode mixture layer 22 of the present embodiment has a higher resistance R in the central portion 22a than in the end portion 22b. N [Ω] is large. Therefore, in FIG. 4, the graph at the center portion 22a is convex upward.

[0038] FIG. 5 shows the relationship between the position in the width direction W of the separator 4 and the resistance R S5 is a graph showing the relationship between the resistance R [Ω] of the negative electrode mixture layer 22 shown in FIG. N In order to match the resistance R S [Ω] is relatively small, but the resistance R S [Ω] is getting larger.

[0039] <Main Effects of This Embodiment> In this embodiment, the separator 4 is provided with such a coating layer 41, and the resistance R S [Ω] and the resistance R of the negative electrode mixture layer 22 N As a result, the amount of lithium ions Li ions in the central portion 22a of the negative electrode mixture layer 22 during charging is reduced. + The flow of lithium ions Li is suppressed, and the lithium ions Li that can be received in the central portion 22a of the negative electrode mixture layer 22 are prevented from flowing. + As a result, lithium-ion Li + becomes overcharged on the surface of the negative electrode active material 24, pushing up the potential [V] and suppressing it from becoming a deposition potential [V] of metallic lithium Li. By the above-mentioned mechanism, it is possible to suppress the deposition of metallic lithium Li in the negative electrode active material 24. By suppressing the deposition of metallic lithium Li, it is possible to suppress the generation and growth of dendrites.

[0040] As a result, the so-called lithium precipitation resistance is increased, so that the limit of the current [A] allowed for the lithium ion secondary battery 10 is increased, and high-rate charging is possible, making it possible to safely and fully utilize the capabilities of the lithium ion secondary battery 10. In addition, the life of the lithium ion secondary battery 10 can be extended.

[0041] (First embodiment) The lithium ion secondary battery 10 of this embodiment, which is provided with the separator 4 having the coating layer 41 as described above, will be described in detail below.

[0042] <Configuration of lithium-ion secondary battery 10> 1 is a perspective view showing the outline of the external configuration of a lithium-ion secondary battery 10 according to the present embodiment. First, the configuration of the lithium-ion secondary battery 10 according to the present embodiment, which is one example of the present invention, will be described.

[0043] As shown in FIG. 1, the lithium ion secondary battery 10 illustrated in this embodiment is configured as a cell battery constituting a battery module housed in a battery pack that is a driving source for an automobile. The lithium ion secondary battery 10 includes a plate-shaped rectangular parallelepiped battery case 11 having an opening on the upper side. An electrode body 12 is housed inside the battery case 11. A nonaqueous electrolyte 13 is filled into the battery case 11 through a liquid filling hole. The battery case 11 is made of a metal such as an aluminum alloy, and forms a battery container sealed by a lid. The lithium ion secondary battery 10 also includes a positive electrode external terminal 14 and a negative electrode external terminal 15 used for charging and discharging power. The positive electrode external terminal 14 is electrically connected to a positive electrode current collector terminal 16 inside the battery case 11 via the lid. The negative electrode external terminal 15 is electrically connected to a negative electrode current collector terminal 17 inside the battery case 11 via the lid. The positive electrode current collector terminal 16 is electrically connected to a positive electrode current collector part 33 (see FIG. 2) of the electrode body 12. Moreover, the negative electrode current collector terminal 17 is electrically connected to the negative electrode current collector portion 23 of the electrode body 12 (see FIG. 2).

[0044] <Electrode body 12> 2 is a schematic diagram showing the configuration of the wound electrode body 12. The electrode body 12 is formed by stacking a negative electrode plate 2, a positive electrode plate 3, and a separator 4 arranged therebetween. The stacked negative electrode plate 2, positive electrode plate 3, and separator 4 are wound to form a flat shape. The negative electrode plate 2 has a negative electrode composite layer 22 formed on a negative electrode current collector 21 made of copper foil as a base material. A negative electrode current collector 23 is provided on one end side of a width direction W (winding axis direction) perpendicular to the winding direction (winding direction L). The negative electrode current collector 23 is configured such that the negative electrode composite layer 22 is not formed and the negative electrode current collector 21 is exposed.

[0045] In the positive electrode plate 3, a positive electrode composite layer 32 is formed on a positive electrode collector 31 made of aluminum foil as a base material. As shown in Fig. 2, a positive electrode collector 33 is provided on the other end side (opposite to the negative electrode collector 23) in a direction (width direction W) perpendicular to the direction in which the positive electrode collector 31 is wound (winding direction L). The positive electrode collector 33 does not have the positive electrode composite layer 32 formed thereon, and the metal of the positive electrode collector 31 is exposed.

[0046] <Layer structure of electrode body 12> As shown in FIG. 2, the basic configuration of an electrode assembly 12 of a lithium ion secondary battery 10 includes a negative electrode plate 2, a positive electrode plate 3, and a separator 4.

[0047] The negative electrode plate 2 includes a negative electrode mixture layer 22 on both sides of a negative electrode current collector 21 serving as a negative electrode base material. One end of the negative electrode current collector 21 serves as a negative electrode current collecting portion 23 where the metal is exposed. The positive electrode plate 3 includes a positive electrode mixture layer 32 on both sides of a positive electrode current collector 31 serving as a positive electrode base material. The other end of the positive electrode current collector 31 serves as a positive electrode current collecting portion 33 where the metal is exposed.

[0048] The negative electrode plate 2 and the positive electrode plate 3 are stacked with a separator 4 interposed therebetween to form a laminate. As shown in Fig. 2, this laminate is wound in the longitudinal direction around the winding axis to form a wound-type electrode body 12 that is shaped flat as shown in Fig. 1.

[0049] <Nonaqueous electrolyte 13> The electrode body 12 of the lithium ion secondary battery 10 of this embodiment shown in FIG. 1 is impregnated with a nonaqueous electrolyte 13. The nonaqueous electrolyte 13 is a composition in which a lithium salt is dissolved in an organic solvent. As the lithium salt, LiClO4, LiPF6, LiAsF6, LiBF4, LiSO3CF3, etc. can be used. As the organic solvent, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran, and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, and phosphorus compounds such as triethyl phosphate and trioctyl phosphate can be used. As the nonaqueous electrolyte 13, one or more of these can be mixed and used. The composition of the nonaqueous electrolyte 13 is not limited to this.

[0050] As described above, the nonaqueous electrolyte 13 of this embodiment is previously added with a film-forming material containing Li. The film-forming material is, for example, lithium bis(oxalato)borate (LiBOB, LiB(C2O4)2). According to this method, bis(oxalato)borate ions (BOB - ,BOB ion,B(C2O4)2 - ) can be decomposed and polymerized to form a stable coating derived from BOB ions on the surface of the negative electrode active material particles.

[0051] <Components of electrode body 12> Next, the negative electrode plate 2, the positive electrode plate 3, and the separator 4, which are the components that make up the electrode assembly 12, will be described.

[0052] <Negative electrode plate 2> 2, negative electrode mixture layers 22 are formed on both sides of negative electrode current collector 21, which is a negative electrode base material, to form negative electrode plate 2. Negative electrode mixture layer 22 is formed by applying a negative electrode mixture paste to negative electrode current collector 21. After that, negative electrode plate 2 is completed through a drying process, a pressing process, and a cutting process.

[0053] <Negative electrode current collector 21> In this embodiment, the negative electrode current collector 21 is made of Cu foil. The negative electrode current collector 21 serves as a base for the aggregate of the negative electrode mixture layer 22, and also functions as a current collecting member that collects electricity from the negative electrode mixture layer 22. One end of the negative electrode current collector 21 serves as a negative electrode current collecting part 23 where the negative electrode mixture layer 22 is not formed and the metal surface is exposed. In other words, the negative electrode active material particles are electrically connected to the negative electrode external terminal 15 via the negative electrode current collector 21, the negative electrode current collecting part 23, and the negative electrode current collecting terminal 17.

[0054] <Negative electrode composite layer 22> In this embodiment, the negative electrode active material 24 shown in FIG. 3 is a powdered carbon material made of graphite or the like having a layered structure, and is used to charge and discharge lithium ions Li + It is a material that can absorb and release energy.

[0055] <Positive electrode plate 3> 2, the positive electrode plate 3 is composed of a positive electrode current collector 31, which is a positive electrode base material, and a positive electrode mixture layer 32 applied thereto. The positive electrode mixture layer 32 is formed by applying a positive electrode mixture paste to the positive electrode current collector 31. The positive electrode plate 3 is then completed through a drying process, a pressing process, and a cutting process.

[0056] <Positive electrode current collector 31> A positive electrode mixture layer 32 is formed on both sides of a positive electrode current collector 31, which is a positive electrode base material, to form a positive electrode plate 3. In this embodiment, the positive electrode current collector 31 is made of an Al foil. The positive electrode current collector 31 serves as a base for the aggregate of the positive electrode mixture layer 32, and also functions as a current collecting member that collects electricity from the positive electrode mixture layer 32.

[0057] First, the positive electrode base material constituting the positive electrode current collector 31 is exemplified as an Al foil, but may be made of a conductive material made of a metal having good conductivity. As a material having good conductivity, for example, in addition to Al foil, a material containing an Al alloy may be used. The configuration of the positive electrode current collector 31 is not limited to this.

[0058] <Positive electrode mixture layer 32> Positive electrode mixture layer 32 is formed by applying a positive electrode mixture paste to positive electrode current collector 31 and drying it. Positive electrode mixture layer 32 contains additives such as a conductive assistant, a binder, and a dispersant in addition to particles of a positive electrode active material as shown in FIG.

[0059] <Composition of positive electrode active material> The particles of the positive electrode active material contain a lithium transition metal oxide having a layered crystal structure. The lithium transition metal oxide contains one or more predetermined transition metal elements in addition to Li. The transition metal element contained in the lithium transition metal oxide is preferably at least one of Ni, Co, and Mn. The positive electrode active material of this embodiment is exemplified by a ternary system called NCM, which has a lithium transition metal oxide containing all of Ni, Co, and Mn.

[0060] The positive electrode active material of this embodiment is not limited to those having lithium transition metal oxides containing all of Ni, Co, and Mn. In addition, other than these, for example, compositions containing Al may be used. In addition, the positive electrode active material may be LiMnO4, LiFePO4, etc. Furthermore, it is not limited to these.

[0061] <Separator 4> The separator 4 is a highly insulating nonwoven fabric made of polypropylene or the like, which is a porous resin for holding the nonaqueous electrolyte 13 between the negative electrode plate 2 and the positive electrode plate 3. As the separator 4, a porous polymer membrane such as a porous polyethylene membrane, a porous polyolefin membrane, and a porous polyvinyl chloride membrane, or a lithium ion or ion conductive polymer electrolyte membrane can be used alone or in combination.

[0062] The separator 4 of this embodiment is provided with the coating layer 41 as described above. Next, the coating layer 41 of this embodiment will be described in detail using examples. <Configuration of Coating Layer 41> FIG. 3 shows the lithium ion Li when the lithium ion secondary battery 10 of this embodiment is discharged. +The coating layer 41 is a plurality of strip-shaped portions extending along the winding direction L of the separator 4. The coating layer 41 is a resistance R of the separator 4 at each position in the width direction W perpendicular to the winding direction L of the separator 4. S In other words, the resistance R [Ω] of the negative electrode mixture layer 22 is adjusted. N According to the resistance distribution [Ω], the resistance R of the negative electrode mixture layer 22 N [Ω] depending on the part with high resistance R of separator 4 S On the other hand, the resistance R N [Ω] depending on the low part of the separator 4 resistance R S The resistance R of the coating layer 41 at each position is set to be low. C Specifically, the resistance R of the central portion 4a of the separator 4 is S [Ω] is set to be high.

[0063] The coating layer 41 contains insulating particles. Examples of insulating particles include ceramics obtained by sintering metal oxides, which have high insulating properties, high heat resistance, high mechanical strength, and high corrosion resistance. Specifically, particles of boehmite or alumina are used. Of course, any insulating material may be used, and particles of heat-resistant resin or the like may also be used. In this embodiment, as an example, boehmite is used as the insulating particles.

[0064] A binder is also mixed in order to form a layer of insulating particles that adhere to the surface of the separator 4. A solvent is added and kneaded to disperse these mixtures homogeneously, but the solvent evaporates in the drying process and does not generally remain in the product.

[0065] <Boehmite> Boehmite is an aluminum hydroxide (γ-AlO(OH)) mineral and a component of the aluminum ore bauxite. It exhibits a vitreous to pearlescent luster, a Mohs hardness of 3-3.5, and a specific gravity of 3.00-3.07. It has high insulating, heat-resistant, and hardness properties, and industrially it can be used as an inexpensive flame-retardant additive for fire-resistant polymers.

[0066] Boehmite has the chemical composition AlO(OH) or Al2O3·H2O, and is generally a chemically stable alumina monohydrate produced by heating or hydrothermally treating alumina trihydrate in air. Boehmite has a high dehydration temperature of 450-530°C, and by adjusting the production conditions, it can be controlled into various shapes such as plate-like boehmite, needle-like boehmite, and hexagonal plate-like boehmite. In addition, the aspect ratio and particle size can be controlled by adjusting the production conditions.

[0067] In this embodiment, in order to avoid clogging of the separator 4, the average particle diameter (d 50 ) is 3 to 5 μm. The measurements are the average values ​​measured by laser diffraction. <Binding material> The binder may be, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyacrylic acid, polyacrylate, or the like.

[0068] <Separator 4 Configuration> The separator 4 can be a porous resin sheet made of a resin such as polyethylene (PE) or polypropylene (PP) to hold the non-aqueous electrolyte 13 while insulating the positive electrode plate 3 and the negative electrode plate 2 from each other. Such a porous resin sheet can have a single-layer structure using various materials alone, or a multi-layer structure combining various materials. For example, the porous resin sheet can be made of a surface layer made of PP with high heat resistance and an intermediate layer made of PE that shuts down when heated. In addition, PP with high mechanical strength is used for the surface layer, and the average diameter (d 50 The average diameter (d 50 ) [μm] is the average diameter measured by mercury intrusion. 50 ) [μm], an appropriate particle size is selected.

[0069] In this embodiment, the separator 4 has a width of 100 mm and a thickness of 15 to 19 μm. <Method of forming coating layer 41> The coating layer 41 is produced by adding a solvent to the insulating particles and the binder and kneading them in a kneader to produce a coating layer paste in a paste form. At this time, the composition (80 [wt%] in this embodiment), solid content rate NV (28 [wt%] in this embodiment), viscosity (3000 [Pa s] in this embodiment), etc. are adjusted.

[0070] While conveying a long uncut separator 4 in the length direction, the coating layer paste is applied using a die nozzle 5 (see FIG. 12). The die nozzle 5 stores the coating layer paste in an internal die 51, and discharges it from a nozzle 52 under pressure.

[0071] In the case shown in Fig. 3, a nozzle 52 is provided corresponding to the coating layer 41a to be formed on the central portion 4a of the separator 4. In addition, nozzles 52 corresponding to the coating layers 41b to be formed on both end portions 4b of the separator 4 are provided adjacent to each other. The adjacent nozzles 52, 52 may be located at the same position in the conveyance direction of the separator 4, or may be shifted forward and backward in the conveyance direction. Coating is performed using these three nozzles 52.

[0072] In this embodiment, the resistance R of the coating layer 41a applied by the nozzle 52 corresponding to the coating layer 41a is C [Ω] is the resistance R of the coating layer 41b applied by the nozzle 52 corresponding to the coating layer 41b. C It is set so that the resistance value [Ω] is higher than [Ω].

[0073] <Resistance R of coating layer 41 C [Ω]> As described above, in this embodiment, the resistance R of the separator 4 shown in FIG. S The resistance distribution in the width direction W [Ω] is shown in FIG. N As a result, the negative electrode active material 24 of the negative electrode mixture layer 22 is charged to the lithium ion Li +In this case, the resistance distribution in the width direction W of the separator 4 itself, excluding the coating layer 41, is flat. C [Ω] represents the resistance R of the separator 4 including the coating layer 41 S Correct [Ω].

[0074] Resistance R C Methods for changing [Ω] include changing the components of the coating layer paste itself and changing the thickness T of the coating layer 41. Here, first, a method for changing the thickness T of the coating layer 41 will be described.

[0075] FIG. 6 shows the resistance R N 7 is a table showing the relationship between the resistance ratio [%] and the resistance [Ω] taken as 100 [%]. FIG. 7 is a graph showing the relationship in the table of FIG. 6. As can be seen from FIG. 7, the resistance R N The resistance R [Ω] is approximately 50 [mm], that is, the resistance R N It can be seen that the resistance R N [Ω] is the resistance R of the end 22b N The resistance R of the central portion 4a of the separator 4 is set to approximately 124% of the resistance R of the central portion 4a of the separator 4. S [Ω] needs to be adjusted to approach 124[%] of end 4b.

[0076] FIG. 8 is a graph showing the relationship between the thickness T [μm] of the coating layer 41 and the resistance R of the separator 4 when the thickness T [μm] of the coating layer 41 is set to 0 [μm]. S 8 is a table showing the resistance ratio [%] of the separator 4 when the thickness T [μm] of the coating layer 41 is 0 [μm]. S The increase in [Ω] is proportional to the thickness T [μm] of the coating layer 41.

[0077] As described above, in the embodiment, the resistance ratio of the central portion 22a of the negative electrode mixture layer 22 was approximately 124[%] as shown in FIG. 8. S In order to make the resistance ratio of the separator 4 to 124%, if the thickness T of the coating layer 41 is approximately 2.3 μm, the resistance R S The resistance ratio of [Ω] can be approximately 124[%].

[0078] FIG. 9 is a table showing the thickness T [μm] of the coating layer 41 at a distance [mm] from one end of the separator 4. In this embodiment, as shown in FIG. 9, the thickness T [μm] of the coating layer 41 is set to 2.3 [μm] at the center of the separator 4, i.e., at a distance of 50 [mm]. Also, the thickness T [μm] of the coating layer 41 is made thinner toward the end. Since the coating layer paste of this embodiment has fluidity, the coating layer paste discharged from the nozzle 52 corresponding to the center portion 4a moves to the portion coated by the end portion 4b. For this reason, it is dispersed as shown in FIG. 9, and as a result, the resistance R of the separator 4 is increased. S The resistance distribution [Ω] is the resistance R N This is close to the resistance distribution of [Ω].

[0079] The nozzles 52 are disposed at predetermined positions in the width direction W of the separator 4 (in this embodiment, positions of 30 to 70 mm corresponding to the separator center portion 4a, and positions of 0 to 30 mm and 70 to 100 mm corresponding to the adjacent end portion 4b).

[0080] The material is discharged from the nozzle at a predetermined gap (50 [μm] in this embodiment). At this time, the conveying speed of the separator 4 (1 [m / s] in this embodiment), the discharge amount (0.5 [g / s] in this embodiment), etc. are adjusted, and the basis weight (0.5 [mg / cm 2[μm]), the thickness T of the coating layer 41 (0.17 to 4.48 [μm] in this embodiment), etc. are adjusted. After coating, the coating layer paste coated on both end portions 4b of the separator 4 flows toward the center portion 4a of the separator 4 due to the fluidity of the coating layer paste. As a result, a gradient of the thickness T [μm] of the coating layer 41 is formed, where the coating layer 41 is thick on the center portion 4a side of the separator 4 and thin on both end portions 4b of the separator 4.

[0081] After the coating layer paste is applied, the solvent is volatilized by hot air or infrared rays, and the paste is fixed onto the separator 4 . Thereafter, the long separator 4 on which the coating layer 41 is formed is cut to fit the product.

[0082] <Manufacture of lithium ion secondary battery 10> The manufacturing process of the lithium ion secondary battery 10 of this embodiment will be briefly described below. First, in the source process, the elements of each battery are prepared. Specifically, the positive electrode plate 3, the negative electrode plate 2, and the separator 4 are prepared. Next, as shown in FIG. 2, the positive electrode plate 3, the negative electrode plate 2, and the separator 4 are stacked and wound. This wound body is pressed to a predetermined thickness by a press machine to be shaped. A positive electrode collector terminal 16 and a negative electrode collector terminal 17 are attached to the electrode body 12 thus prepared. The electrode body 12 to which the positive electrode collector terminal 16 and the negative electrode collector terminal 17 are attached is housed in a battery case 11 to which an insulating film is attached. The upper opening of the battery case 11 is closed with a lid body and welded and sealed. Next, the inside of the battery case is dried by overheating, and moisture is removed. After drying, the nonaqueous electrolyte 13 is poured into the battery case and the pouring port is sealed. At this stage, the assembly of the lithium ion secondary battery 10 as shown in FIG. 1 is completed. After that, once conditioning and aging are complete, they are inspected and the cell battery is completed as a product. After that, several battery cells are combined to create a battery module. Furthermore, several battery modules are combined and housed in a case to become an on-board battery pack.

[0083] (Action of this embodiment) In this embodiment, the separator 4 is provided with such a coating layer 41, and the resistance R S [Ω] and the resistance R of the negative electrode mixture layer 22N As a result, the amount of lithium ions Li ions in the central portion 22a of the negative electrode mixture layer 22 during charging is reduced. + The flow of lithium ions Li is suppressed, and the lithium ions Li that can be received in the central portion 22a of the negative electrode mixture layer 22 are prevented from flowing. + As a result, lithium-ion Li + By suppressing overcharging on the surface of the negative electrode active material 24, it is possible to suppress the deposition potential [V] of metallic lithium Li. By the above-mentioned mechanism, it is possible to suppress the deposition of metallic lithium Li in the negative electrode active material 24. By suppressing the deposition of metallic lithium Li, it is possible to suppress the generation and growth of dendrites.

[0084] As a result, the so-called lithium precipitation resistance is increased, so that the limit of the current [A] allowed for the lithium ion secondary battery 10 is increased, and high-rate charging is possible, making it possible to safely and fully utilize the capabilities of the lithium ion secondary battery 10. In addition, the life of the lithium ion secondary battery 10 can be extended.

[0085] (Effects of the First Embodiment) (1-1) The lithium ion secondary battery 10 and the manufacturing method thereof according to this embodiment have the advantage that deposition of metallic lithium Li on the negative electrode plate 2 can be suppressed.

[0086] (1-2) In particular, even when a coating material containing a lithium salt is added to the nonaqueous electrolyte solution 13 and the negative electrode mixture layer 22 of the negative electrode plate 2 contains Na, the precipitation of metallic lithium Li can be effectively suppressed.

[0087] (1-3) A plurality of strip-shaped coating layers 41 extending along the winding direction L are provided on the separator 4. The resistance R at each position in the width direction W of the coating layer 41 is S [Ω] is the resistance R of the negative electrode mixture layer 22 N In this case, the resistance R of the negative electrode mixture layer 22 is adjusted according to the resistance distribution [Ω]. N [Ω] depending on the part with high resistance R of separator 4 SIn addition, the resistance R N [Ω] depending on the low part of the separator 4 resistance R S In other words, the resistance R [Ω] of the coating layer 41 at each position in the width direction W is made low. C The resistance distribution [Ω] is the resistance R N As a result, the resistance R of the negative electrode mixture layer 22 during charging N Lithium ions Li move to areas with large [Ω] + This has the effect of suppressing the amount of lithium ions in the negative electrode active material 24, thereby suppressing local overcharging on the surface of the negative electrode active material 24, and suppressing the deposition of metallic lithium Li.

[0088] (1-4) Resistance R of the multiple coating layers 41 C The resistance value of each of the coating layers 41 is set according to its thickness T [μm]. C This has the effect of allowing you to set [Ω].

[0089] (1-5) The coating layer 41 is formed on the surface of the positive electrode plate 3. Therefore, the lithium ions Li + Before moving to the separator 4, the lithium ions Li + This has the effect of suppressing the movement of the

[0090] (1-6) The coating layer 41 is configured to contain insulating particles and a binder, which has the effect of allowing the coating layer 41 to be formed in a stable state. (1-7) In particular, since the insulating particles are made of boehmite or alumina, it is possible to obtain the coating layer 41 having excellent heat resistance and durability.

[0091] (1-8) The film-forming material having a lithium salt added to the nonaqueous electrolyte 13 is lithium bis(oxalato)borate (LiBOB, LiB(C2O4)2). This has the effect of effectively suppressing the formation of a film of the SEI while suppressing the precipitation of metallic lithium Li, thereby solving the problems of such film-forming materials.

[0092] Second embodiment 10 is a schematic diagram showing a second embodiment of the coating layer 41. The second embodiment differs from the first embodiment in that the end portion 4b of the separator 4 is provided with a non-coated portion 42 without the coating layer 41. Therefore, the resistance R S [Ω] can be made smaller.

[0093] In the first embodiment, the same coating layer paste is used, and the thickness T is adjusted to set the resistance RC [Ω] of the coating layer 41. In contrast, in the second embodiment, the resistance R of the coating layer 41 is set by adjusting, for example, the content of the insulating particles in the coating layer paste. C For example, the same discharge amount and thickness T are used, and the resistance R C [Ω] can be differentiated.

[0094] Furthermore, in the second embodiment, the central coating layer 41a is further provided with an intermediate portion 41a′ adjacent to the center portion, and the resistance R S The resistance distribution of [Ω] is N The resistance distribution can be close to Ω.

[0095] (Effects of the second embodiment) (2-1) The coating layer 41 is formed in the central portion 4a in the width direction W of the separator 4, except for the end portion 4b in the width direction W. This has the effect of preventing the resistance at the end portion 4b in the width direction W from being unnecessarily increased.

[0096] (2-2) The multiple coating layers 41 have a resistance R per unit area depending on the content of insulating particles and binder.C [Ω] is adjusted. Therefore, with the same discharge amount and the same thickness T, the resistance R C This has the effect of creating a difference in [Ω].

[0097] (Third embodiment) Fig. 11 is a schematic diagram showing a third embodiment of the coating layer. Fig. 12 is a schematic diagram showing a coating process of the third embodiment. As shown in Fig. 12, a plurality of nozzles 52 of a die nozzle 5 are arranged at a predetermined interval to coat the coating layer paste. Therefore, in the third embodiment, a non-coated portion 42 where no coating layer 41 is present is formed between adjacent coating layers 41. As a result, the separator 4 has non-coated portions 42 in the gaps between the plurality of coating layers 41. The non-coated portions 42 have a resistance R higher than that of the coating layers 41. C Therefore, if the area of ​​the non-coated portion 42 is made larger than that of the coated layer 41, the average resistance R S Conversely, if the area of ​​the non-coated portion 42 is made smaller than that of the coated layer 41, the average resistance R S In this way, the resistance R of the separator can be increased by adjusting the area ratio of the coating layer 41 and the non-coated portion 42 according to the position in the width direction W. S A resistance distribution of [Ω] is set.

[0098] By configuring it in this way, the coating layer paste of the same composition, the same thickness T [mm], and the same width W C [mm], the resistance R S In this case, the width W of the non-coated portion 42 can be set to a resistance distribution of [Ω]. A The size of the separator 4 in that area, R S For example, in FIG. 12, the width W of the coating layer 41 in the central portion 4a of the separator 4 can be changed. C2 [mm] and the width W of the coating layer 41 at the end 4b C1 In this case, the width W [mm] of the non-coated portion 42 of the central portion 4a is the same. A2[mm] is the width W of the non-coated portion 42 of the end 4b A1 [mm], the average resistance R S [Ω] is the average resistance R of the end 4b S [Ω] or greater.

[0099] Furthermore, the composition of the coating layer paste of the multiple coating layers 41, the coating thickness T, and the width W of the coating layer 41 are C By adopting the combination of the above, a larger resistance R S Difference in [Ω] and fine resistance R S You can also adjust [Ω].

[0100] In this way, by providing the non-coated portion 42 between the coating layers 41, the resistance R S The resistance distribution of [Ω] is N The resistance distribution can be close to Ω.

[0101] (Effects of the third embodiment) (3-1) The separator 4 has non-coated portions 42 in the gaps between the multiple coated layers 41, and the resistance R of the separator 4 is adjusted by adjusting the area ratio of the coated layers 41 to the non-coated portions 42 according to the position in the width direction W. S The resistance distribution of [Ω] is set. Therefore, the resistance R S The resistance distribution of [Ω] is N This has the effect of making it possible to obtain a resistance distribution close to that of [Ω].

[0102] (Another example) The first to third embodiments can be combined as long as no contradiction occurs. ○ Thickness T and width W of the multiple coating layers 41 C A combination of the above may also be employed.

[0103] In this embodiment, the coating layer 41 is provided on the positive electrode plate 3 side. However, it may be provided on the negative electrode plate 2 side or on both sides of the separator 4. In this embodiment, the cell battery of the lithium ion secondary battery 10 for vehicle use is illustrated, but the present invention is not limited to this. In addition, the present invention is not limited to a flat electrode body 12, and may be implemented in a cylindrical electrode body 12.

[0104] The configuration of the present invention is not limited to the lithium ion secondary battery 10 illustrated in the embodiment, and the positive electrode plate 3, the negative electrode plate 2, the separator 4, the non-aqueous electrolyte 13, and additives added thereto can be appropriately selected by a person skilled in the art.

[0105] The exemplified values ​​and numerical limitations can be optimized by those skilled in the art. It goes without saying that those skilled in the art may add, delete or modify the components of the present invention without departing from the scope of the claims. [Explanation of symbols]

[0106] 10...Lithium-ion secondary battery 11…Battery case 12...Electrode body 13...Nonaqueous electrolyte 14…Positive external terminal 15...Negative external terminal 16…Positive current collecting terminal 17...Negative current collecting terminal 2...Negative electrode plate 21...Negative electrode current collector 22...Negative electrode composite material layer 23...Negative electrode current collector 24...Negative electrode active material 3…Positive electrode plate 31...Positive electrode current collector 32...Positive electrode mixture layer 33…Positive electrode current collector 34...Cathode active material 4…Separator 41…Coat layer W C1 , W C2 [mm]…Coat layer width T [μm]…(coat layer) thickness 42…Non-coated area W A1, W A2 [mm]…Uncoated section width 5…Die nozzle 51…Die 52…Nozzle

Claims

1. A lithium ion secondary battery having an electrode assembly in which a positive electrode plate and a negative electrode plate are stacked and wound with a separator interposed therebetween and filled with a nonaqueous electrolyte, A film-forming material having a lithium salt is added to the non-aqueous electrolyte solution, When the negative electrode mixture layer of the negative electrode plate contains Na, A plurality of strip-shaped coating layers extending along a winding direction L are provided on the separator, and a resistance R at each position in a width direction W perpendicular to the winding direction L of the coating layers is calculated. Ｓ [Ω] is the resistance R of the negative electrode mixture layer Ｎ According to the resistance distribution [Ω], the resistance R Ｎ The resistance R of the separator is determined according to the portion where [Ω] is high. Ｓ The resistance R of the negative electrode mixture layer is increased. Ｎ The resistance R of the separator is determined according to the portion where [Ω] is low. Ｓ The resistance R of the coating layer at each position is reduced so that [Ω] is Ｃ It has a resistance distribution of [Ω] A lithium ion secondary battery comprising:

2. Resistance R of the plurality of coating layers Ｃ [Ω] is the resistance value set by its thickness T [μm] 2. The lithium ion secondary battery according to claim 1 .

3. The separator has a non-coated portion in the gap between the plurality of coating layers, and the resistance R of the separator is adjusted by adjusting the area ratio between the coating layer and the non-coated portion according to the position in the width direction W. Ｓ The resistance distribution of [Ω] is set.

2. The lithium ion secondary battery according to claim 1 .

4. The coating layer is formed in the center of the separator in the width direction W, except for the ends in the width direction W.

4. The lithium ion secondary battery according to claim 3 .

5. The coating layer is formed on the surface of the positive electrode plate.

2. The lithium ion secondary battery according to claim 1 .

6. The coating layer is configured to include insulating particles and a binder.

2. The lithium ion secondary battery according to claim 1 .

7. The resistance [Ω] per unit area of ​​the multiple coating layers is adjusted by the content of the insulating particles or the binder.

7. The lithium ion secondary battery according to claim 6 .

8. 7. The lithium ion secondary battery according to claim 6, wherein the insulating particles are made of boehmite or alumina.

9. The film-forming material having a lithium salt added to the non-aqueous electrolyte is lithium bis(oxalato)borate (LiBOB, LiB(C ２ O ４ ) ２ 2. The lithium ion secondary battery according to claim 1, wherein

10. A method for manufacturing a lithium ion secondary battery including an electrode assembly in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween and wound, and filled with a nonaqueous electrolyte, comprising the steps of: A film-forming material having a lithium salt is added to the non-aqueous electrolyte solution, When the negative electrode mixture layer of the negative electrode plate contains Na, A plurality of strip-shaped coating layers extending along a winding direction L are provided on the separator, and a resistance R at each position in a width direction W perpendicular to the winding direction L of the coating layers is calculated. Ｓ [Ω] is the resistance R of the negative electrode mixture layer Ｎ According to the resistance distribution [Ω], the resistance R Ｎ The resistance R of the separator is determined according to the portion where [Ω] is high. Ｓ The resistance R of the negative electrode mixture layer is increased. Ｎ The resistance R of the separator is determined according to the portion where [Ω] is low. Ｓ The resistance R of the coating layer at each position is reduced so that [Ω] is Ｃ Set the resistance distribution in [Ω] A method for producing a lithium ion secondary battery comprising the steps of:

11. The coating process includes a step of coating a coating layer paste in which insulating particles and a binder are made into a paste by a solvent, and the coating layer paste is applied to the coating layer. The method for producing a lithium ion secondary battery according to claim 10 .

12. In the coating step, a plurality of the coating layers are simultaneously or successively coated. The method for producing a lithium ion secondary battery according to claim 11 .

13. Resistance R of the plurality of coating layers Ｃ [Ω] sets the resistance value according to the thickness T [μm] The method for producing a lithium ion secondary battery according to claim 10 .

14. The separator has a non-coated portion formed between a plurality of the coating layers, and the resistance R of the separator is controlled by adjusting the area ratio between the coating layer and the non-coated portion according to the position in the width direction W. Ｓ Set the resistance distribution in [Ω] The method for producing a lithium ion secondary battery according to claim 10 .

15. The coating layer is formed in the center of the separator in the width direction W, except for the ends in the width direction W. The method for producing a lithium ion secondary battery according to claim 10 .

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