JP2012234822A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery excellent in safety and capable of preventing abnormal heat generation due to a short circuit when burr or powder breaks through a separator.SOLUTION: The nonaqueous secondary battery of the invention includes: a positive electrode 11 which is a wound electrode body and includes a collector 12 made of metal foil with a metal foil portion exposed therefrom, and an active material mixture layer 14 provided on both surfaces of the collector 12; a negative electrode 17; a separator 23 through which the positive electrode 11 counters to the negative electrode 17 together with the exposed metal foil portion; and a protective layer 16 made of non-insulation material with electronic conductivity lower than that of the metal foil and formed on a position in the exposed metal foil portion countering to the negative electrode 17 through the separator 23.

Description

  The present invention relates to a non-aqueous secondary battery, and more particularly to a non-aqueous secondary battery excellent in safety that can prevent abnormal heat generation due to a short circuit when burrs, powders, or the like break through a separator.

  With the rapid spread of portable electronic devices, electric vehicles (EV), hybrid electric vehicles (HEV), etc., the required specifications for the batteries used for them are becoming stricter year by year.・ High output, excellent cycle characteristics, and stable performance are required. In the field of secondary batteries, non-aqueous secondary batteries represented by lithium-ion batteries, which have a higher energy density than other batteries, are attracting attention. The proportion of lithium non-aqueous secondary batteries accounts for the secondary battery market. It shows great growth.

  This lithium non-aqueous secondary battery is, for example, a lithium non-aqueous secondary battery having a wound electrode group, and an active material for negative electrode is formed on both sides of a negative electrode core (current collector) made of an elongated sheet-like copper foil. A microporous polyethylene film between a negative electrode coated with a coating agent and a positive electrode coated with a positive electrode active material mixture on both sides of a positive electrode core made of an elongated sheet-like aluminum foil, etc. After placing a separator made of polypropylene film or laminated film of them, winding the negative electrode and the positive electrode in a cylindrical or elliptical shape with the separators insulated from each other, and in the case of a square battery, press the wound electrode body further. It has a configuration in which it is crushed and formed into a flat shape, and a negative electrode tab and a positive electrode tab are connected to predetermined portions of the negative electrode and the positive electrode, respectively, and accommodated in an exterior of a predetermined shape.

  Further, in a lithium non-aqueous secondary battery having a laminated electrode group, a negative electrode in which a negative electrode active material mixture is applied in a film form on one or both sides of a negative electrode core made of a sheet-like copper foil, and a sheet-like A separator made of a microporous polyethylene film, a polypropylene film, or a laminated film thereof is disposed between the positive electrode core body made of aluminum foil and the like and coated with a positive electrode active material mixture in a film form. In addition, a large number of negative electrodes and positive electrodes are laminated in a state of being insulated from each other by a separator to form a laminated electrode group, and positive electrode tabs and negative electrode tabs formed at respective predetermined portions of the respective negative electrodes and positive electrodes are connected in parallel. It has the structure accommodated in the exterior of a predetermined shape.

  By the way, in a non-aqueous secondary battery represented by a lithium ion battery, the negative electrode mixture layer must be coated with a positive electrode mixture in order to smoothly store lithium ions released from the positive electrode active material during charging into the negative electrode active material. It must face each other across the separator via a separator. Therefore, there are not a few structures in the non-aqueous secondary battery in which the active material uncoated part of the positive electrode, that is, the part where the current collector made of metal foil is exposed faces the negative electrode through the separator. To do.

  When a part of the current collector made of the metal foil of one of the electrodes has a structure in which the other electrode is opposed to the other electrode through the separator, a part of the electrode or the electrode may be dropped or vibrated. When the powder peeled off from the metal penetrates the separator and is short-circuited, a large current flows, which may cause heat generation. Further, in the production of the wound electrode group or the laminated electrode group as described above, a predetermined negative electrode and positive electrode are cut out from the negative electrode material and the positive electrode material, and at that time, from the cut ends of the negative electrode and the positive electrode, that is, from the metal foil A burr may occur at the cut end of the current collector, and the burr breaks an adjacent separator, and the negative electrode and the positive electrode are electrically connected through the burr to form a short circuit. Sometimes. Even in this case, the battery generates abnormal heat during use due to the short circuit, leading to a decrease in capacity and a cause of shortening the battery life.

  Therefore, for example, in Patent Documents 1 and 2 below, an electrode winding formed in a state in which a positive electrode and a negative electrode are stacked with a separator interposed between at least a portion of a positive electrode, a separator, and a negative electrode facing a positive electrode lead. Predetermined insulating tape that is thicker than the height of burrs generated on the positive electrode side and / or the negative electrode side, which causes a short circuit with the positive electrode when the electrode winding body is formed when the electrode winding body is formed during the production of the rotating body Is affixed at a position where a short circuit with the positive electrode is assumed on at least one surface of the positioned negative electrode.

  Further, in Patent Document 3 below, for example, an insulating layer made of an insulating resin is formed on both surfaces of the base portion of the protruding portion where the positive and negative electrodes of the wound electrode body are exposed, thereby causing the winding displacement in the axial direction of the separator. Even if the non-projecting ends of the positive and negative electrodes are exposed due to the presence of the insulating layer, the short circuit between the positive and negative electrodes and the base part of the projecting parts of the positive and negative electrodes is prevented. A non-aqueous secondary battery is disclosed in which a short circuit is prevented.

  Here, an example of the nonaqueous secondary battery provided with the wound electrode group disclosed in Patent Document 3 will be described with reference to FIGS. 12 is a cross-sectional perspective view of the entire non-aqueous secondary battery including the wound electrode group disclosed in Patent Document 3 below, and FIG. 13 is a cross-sectional view schematically showing the wound electrode group of FIG. It is a schematic diagram.

  As shown in FIG. 12, the non-aqueous secondary battery 50 provided with the wound electrode group includes a core rod 53 having a positive electrode terminal 51 and a negative electrode terminal 52 at both ends, a positive electrode plate 54, a negative electrode plate 55, and a second electrode. A wound electrode body 57 composed of a single separator 56 and a case 58 are included. The core rod 53 is a winding shaft core of the winding electrode body 57, and a pair of positive and negative positive electrode terminals 51 for supplying electric power to the outside by projecting from the case 58 so as to face each other at both ends in the longitudinal direction of the winding axis. It has a negative electrode terminal 52. That is, the core rod 53 includes a positive electrode terminal 51, a negative electrode terminal 52, and an insulating connection pin 59 that is interposed between the electrode terminals 51 and 52 and insulates and connects the electrode terminals 51 and 52. The connecting pin 59 is fitted into the electrode terminals 51 and 52 to connect the electrode terminals 51 and 52 together.

  The wound electrode body 57 includes a belt-like positive electrode plate 54 and a negative electrode plate 55, and two belt-like separators 56 interposed between the electrode terminals 51 and 52 and wound together with the electrode plates 54 and 55, respectively. Consists of. The positive electrode plate 54 includes a current collector plate 61 made of a strip-shaped aluminum foil that forms the protrusion 60, and a positive electrode active material layer 62 such as lithium manganese oxide applied to rectangular regions on both sides of the current collector plate 61. Consists of. Similarly, the negative electrode plate 55 includes a current collector plate 64 made of a strip-shaped copper foil that forms the protrusion 63, and a negative electrode active material layer 65 such as carbon applied to rectangular regions on both sides of the current collector plate 64. Become.

  The protruding portion 60 of the positive electrode plate 54 and the protruding portion 63 of the negative electrode plate 55 are formed so as to protrude on the opposite sides with respect to the winding axis length direction. The active materials 62 and 65 are not applied to the projecting portions 60 and 63, and the metal foil portions of the current collector plates 61 and 64 are exposed. That is, the active materials 62 and 65 are applied only to the rectangular regions separated by the separator 56 of the current collector plates 61 and 64 of the positive electrode plate 54 and the negative electrode plate 55. Both protrusions 60 and 63 have insulating layers 66 and 67 which are short-circuit prevention layers disposed with a predetermined width at the root portions of the inner and outer peripheral surfaces, respectively. The insulating layers 66 and 67 are formed by thinly applying polyethylene, which is a resin insoluble in the electrolytic solution, by a hot melt method.

  Therefore, as shown in FIG. 13, the separators 56 are sandwiched between the projecting portions 60 and 63 of the positive and negative bipolar plates 54 and 55, respectively, and the non-projecting portions 68 and 69 of the other pole, so The portions 60 and 63 and the non-projecting portions 68 and 69 of the other pole are insulated by the separator 56, but they are also insulated by the insulating layers 66 and 67. Therefore, even when winding deviation occurs in the winding process, and the separator 56 is separated from between the protruding portions 60 and 63 of one pole and the non-projecting portions 68 and 69 of the other pole, the insulating layer 66, The presence of 67 prevents a short circuit between the electrode plates 54 and 55, and further prevents a short circuit between the positive and negative bipolar plates 54 and 55 even if a burr due to punching occurs at the side edge of the positive electrode plate. It is said that.

JP-A-10-241737 (paragraphs [0018] to [0027], [0040] to [0050], FIG. 1, FIG. 5, FIG. 7) JP 2002-028881 (right column on page 3 to left column on page 4, FIG. 8) JP 2001-093583 A (claims, paragraphs [0154] to [0173], [0275] to [0276], FIGS. 1 to 3)

  According to the conventional example as described above, the problem caused by burrs generated during the production of the positive electrode and the negative electrode can be sufficiently solved. However, if an insulating layer is used as a short-circuit prevention layer, charging / discharging is possible even if the separator is broken through, as described above. As a starting point, the separator broke, causing a large short circuit, and there was a problem that the battery generated abnormal heat.

  The inventors of the present application are concerned with a configuration that can ensure the safety of a non-aqueous secondary battery that is not short-circuited, although the above-described burrs and powders peeled off from the electrode have broken through the separator. As a result of various experiments, if such a state can cause a gentle discharge rather than maintaining insulation, the battery voltage on the device side is reduced due to a decrease in battery voltage while avoiding abnormal heat generation. It has been found that the abnormality of the non-aqueous secondary battery can be ensured because the battery can be completely discharged and eventually the battery is completely discharged. As a configuration that can cause a gentle discharge when such burrs or powder breaks through the separator but is not short-circuited, the above-described conventional non-aqueous secondary battery It has been found that the problem can be solved by using a non-insulating material as the protective layer, although the electronic conductivity is lower than that of the current collector, instead of the insulating layer which is the short-circuit preventing layer.

  On the other hand, in non-aqueous secondary batteries for EV and HEV applications, in order to improve the large current load characteristics, the active material mixture coating amount per unit area is reduced to reduce the thickness, and the layers are laminated or long. It is practiced to use an electrode group in which these electrodes are wound in several layers. In order to automatically detect such misalignment or winding misalignment of the electrode group, the amount of X-ray transmission is small even if it is detected by a conventionally used X-ray transmission image, and the misalignment of the electrode group is small. It is difficult to detect winding deviation. In addition, it is necessary to detect each boundary between the active material mixture layer, the protective layer, and the current collector for detecting the stacking deviation or winding deviation of the electrode group in which the protective layer as described above is formed. For this reason, it is more difficult to identify by the conventional detection method using an X-ray transmission image.

  The inventors of the present application not only ensure the safety of the non-aqueous secondary battery by forming such a protective layer, but also each of the active material mixture layer, the protective layer, and the current collector. As a result of further studies on the constituent material and detection means of the protective layer, the conductivity added to the protective layer can be detected so that the boundary between the electrodes can be detected and the stacking deviation or winding deviation of the electrode group can be detected. By changing the particle size (specific surface area) of the carbon material as the material, image processing is easily performed using an optical sensor, and each boundary between the active material mixture layer, the protective layer, and the current collector is easily achieved. Found that can be detected.

  That is, according to the present invention, in a non-aqueous secondary battery, abnormal heat generation due to a short circuit can be prevented by causing a gentle discharge when burrs or powder breaks through the separator. A non-aqueous secondary battery with excellent safety that can detect battery abnormalities and can eventually discharge the battery completely so that the equipment that uses the battery does not operate The purpose is to supply.

  Furthermore, the present invention can prevent abnormal heat generation due to a short circuit by causing a gentle discharge when a burr or the like breaks through a separator in a non-aqueous secondary battery. Abnormality can be detected, and finally the battery can be completely discharged to prevent the device using the battery from operating, and the electrode group stacking deviation can be automatically detected during manufacturing. Another object of the present invention is to provide a non-aqueous secondary battery that can detect winding deviation and is excellent in productivity and safety.

In order to achieve the above object of the present invention, the non-aqueous secondary battery according to claim 1 comprises:
It has a wound electrode group in which a long positive electrode and a long negative electrode are wound through a separator,
The positive electrode is a non-aqueous secondary material in which active material mixture layers are disposed on both surfaces of a current collector made of metal foil, and the metal foil is exposed at at least one end along the longitudinal direction. A battery,
Of the exposed portion of the metal foil, a portion facing the negative electrode through the separator has a protective layer made of a non-insulating material having a lower electronic conductivity than the metal foil. It is characterized by being formed along the longitudinal direction.

  In the present invention, the non-aqueous secondary battery has a wound electrode group in which a long positive electrode and a long negative electrode are wound through a separator, and the positive electrode is a collection of metal foils. The active material mixture layer is disposed on both surfaces of the electric body, and at least one end along the longitudinal direction has a portion where the metal foil is exposed. The protective layer is more than the metal foil. However, it is essential that the material is made of a non-insulating material with low electronic conductivity. When the electronic conductivity of the protective layer is the same as or better than that of the metal foil, a large current flows substantially as in the case where the positive electrode and the negative electrode are directly short-circuited. As a result, the battery will generate abnormal heat, and the desired effect will not be achieved.

  In the present invention, carbonates, lactones, ethers, esters and the like can be used as the non-aqueous solvent (organic solvent) constituting the non-aqueous solvent-based electrolyte, and two or more of these solvents can be used. Can also be used in combination. Among these, carbonates, lactones, ethers, ketones, esters and the like are preferable, and carbonates are more preferably used.

  Specific examples include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), cyclopentanone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, 3-methyl. -1,3-oxazolidine-2-one, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), methyl propyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, dipropyl carbonate, γ -Butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, 1,4-dio Xanthan can be mentioned.

Similarly, electrolytes include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethylsulfonate ( Examples thereof include lithium salts such as LiCF ₃ SO ₃ ) and bistrifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₂ ) ₂ ]. Of these, LiPF ₆ and LiBF ₄ are preferably used, and the amount dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / L.

  The invention according to claim 2 is the nonaqueous secondary battery according to claim 1, wherein the protective layer is along a boundary between the active material mixture layer forming portion and the non-forming portion of the positive electrode. It is characterized by being formed.

  The invention described in claim 3 is the non-aqueous secondary battery according to claim 1 or 2, wherein the negative electrode has a portion where the metal foil is exposed at at least one end along the longitudinal direction. The portion where the metal foil of the positive electrode is exposed is located at one end of the wound electrode group, and the portion where the metal foil of the negative electrode is exposed is located at the other end of the wound electrode group. It is characterized by.

  The invention according to claim 4 is the nonaqueous secondary battery according to any one of claims 1 to 3, wherein the current collector made of the metal foil of the positive electrode is made of aluminum or an alloy mainly composed of aluminum. It is characterized by that.

  The invention according to claim 5 is the nonaqueous secondary battery according to any one of claims 1 to 4, wherein the active material mixture layer of the positive electrode contains a metal oxide.

As this metal oxide, a lithium transition metal composite oxide represented by LixMO ₂ (wherein M is at least one of Co, Ni, and Mn) capable of reversibly occluding and releasing lithium ions. , _{i.e., LiCoO 2, LiNiO 2, LiNiyCo} 1-y O 2 (y = 0.01~0.99), Li 0.5 MnO 2, LiMnO 2, LiCo x Mn y Ni z O 2 (x + y + z = 1) May be used singly or in combination.

  The invention described in claim 6 is the nonaqueous secondary battery according to any one of claims 1 to 5, wherein the negative electrode includes an active material mixture layer mainly composed of carbon. To do. In this case, as the active material mainly composed of carbon, natural graphite, artificial graphite, carbon black, coke, glassy carbon, carbon fiber, or a mixture of one or more of these fired bodies can be used.

  The invention according to claim 7 is the nonaqueous secondary battery according to claim 6, wherein the carbon-based active material mixture layer is disposed on at least one surface of a current collector made of metal foil. It is characterized by.

  The invention according to claim 8 is the non-aqueous secondary battery according to claim 5, wherein the current collector made of the metal foil of the negative electrode is made of copper or an alloy mainly composed of copper. To do.

  The invention according to claim 9 is the non-aqueous secondary battery according to claim 5, wherein the current collector made of the metal foil of the negative electrode is made of Ni or an alloy mainly composed of Ni. To do.

  According to a tenth aspect of the present invention, in the nonaqueous secondary battery according to the fifth aspect, the current collector made of the metal foil of the negative electrode is made of stainless steel.

  The invention according to claim 11 is the non-aqueous secondary battery according to any one of claims 1 to 10, wherein the protective layer includes an insulating polymer substance, electronically conductive carbon, a semiconductor material, It is characterized in that a powder of at least one material selected from the group consisting of conductive oxides is dispersed.

  The invention according to claim 12 is the nonaqueous secondary battery according to claim 11, wherein the insulating polymer material is at least one selected from the group consisting of polyimide, polyamideimide, and polyvinylidene fluoride. It is characterized by being.

  The invention according to claim 13 is the non-aqueous secondary battery according to any one of claims 1 to 10, wherein the protective layer includes an insulating polymer substance, electronically conductive carbon, a semiconductor material, It is characterized in that at least one material selected from the group consisting of conductive oxides and a filler are dispersed.

  The invention according to claim 14 is the non-aqueous secondary battery according to claim 13, wherein the filler is at least one selected from the group consisting of polyimide powder and alumina powder. .

The invention according to claim 15 is the non-aqueous secondary battery according to claim 14, wherein the carbon powder has a specific surface area of 40 m ² / g or less.

  By providing the above configuration, the present invention has the following excellent effects. That is, according to the first to third aspects of the present invention, even if the burr formed at the end of the negative electrode or the powder released from the electrode may break through the separator and come into contact with the positive electrode, Since it contacts the protective layer provided on the positive electrode, it is possible to avoid abnormal heat generation of the battery by gently discharging the battery and to detect an abnormality of the battery on the device side due to a decrease in battery voltage. In particular, in a non-aqueous secondary battery including a wound electrode group, a current path can be obtained from many portions on the end face of the current collector, which is suitable for a high output battery. On the other hand, in this configuration, the metal is exposed in a long range along the winding direction, and since there is a high possibility that a short circuit due to burrs or the like occurs, the protective layer of the present invention may be included. Is particularly effective.

  According to the invention of claim 4, aluminum or an alloy mainly composed of aluminum has been conventionally used as a current collector for a positive electrode of a non-aqueous secondary battery such as a lithium ion battery. Thus, a positive electrode having stable characteristics similar to that of the conventional non-aqueous secondary battery can be obtained.

  Further, according to the invention of claim 5, the metal oxide has been conventionally used as a positive electrode active material of a non-aqueous secondary battery such as a lithium ion battery, and has a high charge potential. A secondary battery is obtained.

  Further, according to the invention of claim 6, the carbonaceous material as the negative electrode active material has a discharge potential comparable to that of lithium metal or lithium alloy, but has high safety because dendrite does not grow. In addition, a non-aqueous secondary battery having excellent effects of excellent initial efficiency, good potential flatness, and high energy density can be obtained.

  Further, according to the invention of claim 7, as the negative electrode, not only the active material mixture layer mainly composed of carbon provided on both surfaces of the metal foil but also one provided on one surface can be arbitrarily selected and used. Therefore, the degree of freedom in battery design increases.

  Further, according to the inventions of claims 8 to 10, copper or an alloy mainly composed of copper (invention 8), Ni or an alloy mainly composed of Ni (invention 9), a metal of stainless steel (invention 10) The negative electrode current collector made of foil has been used for a wide range of current collectors for negative electrode active materials mainly composed of carbon in non-aqueous secondary batteries such as lithium ion batteries, and is stable. A non-aqueous secondary battery having the negative electrode characteristics obtained can be obtained.

  In addition, according to the inventions of claims 11 to 12, since the insulating polymer material is made by dispersing the powder of an inorganic material such as electronically conductive carbon, semiconductor material, conductive oxide, etc. A protective layer made of a non-insulating material having a lower electronic conductivity than the metal constituting the current collector can be formed. In particular, when the insulating polymer substance is at least one selected from the group consisting of polyimide, polyamideimide, and polyvinylidene fluoride, a protective layer made of a non-insulating material can be formed particularly effectively.

  Furthermore, according to the inventions of claims 13 to 14, since the protective layer uses an insulating polymer substance, a carbon material that imparts conductivity to the insulating polymer substance, and a filler, the protective layer after drying. Since there is a color difference between the active material mixture layer and the current collector, the optical sensor clearly defines the boundary between the active material mixture layer and the current collector and between the protective layer and the active material mixture. The non-aqueous secondary battery can be automatically detected when the non-aqueous secondary battery is manufactured by using the optical sensor and the image processing apparatus to detect the stacking deviation or winding deviation of the electrode plate group. The production efficiency is improved. In particular, by using at least one selected from the group consisting of polyimide powder and alumina powder as a filler, it becomes possible to effectively color the protective layer, and between the active material mixture layer and the current collector and The boundary between the protective layer and the active material mixture can be detected more clearly.

According to the invention of claim 15, by setting the specific surface area of the carbon material to 40 m ² / g or less, the boundary between the protective layer and the active material mixture can be reliably detected by the optical sensor. This is because if the specific surface area of the carbon material exceeds 40 m ² / g, the color of the protective layer and the color of the active material mixture will be the same black, so even if an optical sensor is used, the boundary between the two is detected. This is because it becomes difficult. Moreover, since the particle size of a carbon material will become large and the coating property of a protective layer will worsen when the specific surface area of a carbon material will be less than 1.5 m < ² > / g, 1.5 m < ² > / g is preferable for a minimum.

4 is a plan view showing an electrode size of a non-aqueous secondary battery of Reference Example 1. FIG. FIG. 3 is a plan view seen through an exterior showing a schematic configuration of a non-aqueous secondary battery of Reference Example 1. It is the sectional view on the AA line of FIG. 4 is a graph showing a change over time in battery behavior of the non-aqueous secondary battery of Reference Example 1. 6 is a graph showing a change in battery behavior over time of a non-aqueous secondary battery in Comparative Example 1. 6 is a graph showing a change over time in battery behavior of a non-aqueous secondary battery in Comparative Example 2. 6 is a graph showing a time change of another battery behavior of the non-aqueous secondary battery of Reference Example 1. 10 is a graph showing a time change of another battery behavior of the non-aqueous secondary battery of Comparative Example 2. 10 is a cross-sectional view of a non-aqueous secondary battery in Reference Example 6. FIG. 2 is a partial enlarged cross-sectional view of an electrode portion of the nonaqueous secondary battery of Example 1. FIG. It is a perspective view which cut | disconnects and shows the non-aqueous secondary battery of Example 1 to the vertical direction. It is a cross-sectional perspective view of the whole non-aqueous secondary battery provided with the conventional winding electrode group. It is a cross-sectional schematic diagram which shows schematically the wound electrode group of FIG.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to reference examples, examples and comparative examples. However, the following examples illustrate non-aqueous secondary batteries for embodying the technical idea of the present invention, and are not intended to specify the present invention to these examples. The present invention can be equally applied to various changes made without departing from the technical idea shown in the claims.

[Reference Example 1]
First, a method for manufacturing the non-aqueous secondary battery used in Reference Example 1 will be described with reference to FIGS. FIG. 1 is a plan view showing the electrode size of the non-aqueous secondary battery of Reference Example 1, and FIG. 2 is a plan view of the exterior showing the schematic configuration of the non-aqueous secondary battery of Reference Example 1, 3 is a cross-sectional view taken along line AA in FIG.

[Production of positive electrode]
The positive electrode 11 was produced as follows. First, 94% by mass of a positive electrode active material composed of a composite oxide composed of lithium, nickel, cobalt, and manganese, 3% by mass of carbon powder such as acetylene black and graphite, and 3% of a binder composed of polyvinylidene fluoride (PVdF). %, And N-methylpyrrolidone (NMP) was added to the resulting mixture and kneaded to prepare an active material mixture slurry. These active material mixture slurries were uniformly applied to one side of a positive electrode current collector 12 made of an aluminum foil having a thickness of 20 μm so that an exposed portion 13 of the aluminum foil was formed at the end of the electrode. A positive electrode plate coated with the active material layer 14 was formed. Thereafter, the positive electrode plate coated with the active material layer 14 was passed through a drier to remove the organic solvent necessary for the preparation of the slurry and dry it. After drying, this dried positive electrode plate was rolled by a roll press to obtain a positive electrode plate having a thickness of 0.06 mm.

Next, a masking tape is applied on the aluminum foil exposed portion 13 with a distance of 5.5 mm from the boundary 15 between the active material applied portion and the exposed portion, and N-methylpyrrolidone is placed between the active material applied portion and the masking tape. As a solvent, a slurry mixed so that the mass ratio of polyimide and carbon powder having a specific surface area of 70 m ² / g was 1: 1 was applied and dried to provide the protective layer 16. The electrode thus produced was cut into a size of 55.5 mm × 70 mm to obtain a positive electrode 11 provided with a strip-shaped aluminum foil exposed portion 13 having a width of 9 mm and a strip-shaped protective layer 16 having a width of 5.5 mm. This protective layer 16 was confirmed to have a resistance higher than that of the aluminum foil by a surface resistance meter.

(Production of negative electrode)
The negative electrode 17 was produced as follows. First, 98% by mass of graphite powder, 1% by mass of carboxymethyl cellulose and styrene butadiene rubber were mixed, and water was added to knead to prepare a slurry. A negative electrode in which the slurry is uniformly applied to one side of a negative electrode current collector 18 made of a copper foil having a thickness of 12 μm so that an exposed portion 19 of the copper foil is formed at an end of the electrode, and a negative electrode active material layer 20 is applied. I got a plate. Thereafter, the negative electrode plate coated with the active material layer 20 was passed through a dryer to remove the organic solvent that was necessary when the slurry was prepared, and dried. After drying, the dried negative electrode plate was rolled by a roll press to obtain a negative electrode plate having a thickness of 0.05 mm. Next, the obtained electrode was cut into a size of 55.5 mm × 70 mm, and a negative electrode 17 provided with a strip-shaped copper foil exposed portion 19 having a width of 9 mm as shown in FIG. 1 was obtained.

(Preparation of electrolyte)
LiPF ₆ was dissolved at 1 mol / L in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7 to obtain an electrolytic solution.

[Production of battery]
An aluminum collector tab 21 is connected to the aluminum foil exposed portion 13 of the positive electrode, and a nickel current collector tab 22 is connected to the copper foil exposed portion 19 of the negative electrode, respectively, and the positive electrode, the negative electrode, and a polyethylene porous separator 23 having a thickness of 0.022 mm are stacked. Inserted into the laminate film outer body 24 and sealed to the lead-out portions of the aluminum current collecting tab 21 and the nickel current collecting tab 22 through the thin sealing material 25, and the other two directions are sealed, and the remaining one direction A pre-injection battery was prepared using the injection port. After the pre-injection battery is dried in a vacuum, the electrolyte solution is injected in a dry box in an argon atmosphere, pressure reduction is performed to remove bubbles and permeate the electrolyte solution, and then the injection port Was sealed. The structure of the completed battery 10 is as shown in FIGS.

  The obtained battery 10 was charged at a constant current of 50 mA at 25 ° C. until the battery voltage reached 4.2V. After the battery voltage reached 4.2V, the battery 10 was charged at a constant voltage of 4.2V. Charged for hours. Then, a part of the laminated case of the charged battery is cut off, and a separator in a region where the negative electrode 17 and the protective layer 16 of the positive electrode 11 overlap (a portion indicated by a broken line indicated by a reference numeral 26 in FIG. 2) is cut out by 3 mmφ. The protective layer 16 and the negative electrode 17 were brought into contact with each other with a 1 mmφ alumina rod from the back side. The battery surface temperature and voltage at that time were measured to confirm the battery behavior. The time change of the battery behavior is shown in FIG. 4, and the battery voltage and the temperature increase result after 5 minutes from the start of the test are shown in Table 1 below.

[Comparative Example 1]
The non-aqueous secondary battery of Comparative Example 1 was produced in the same procedure as in Reference Example 1 except that the part where the protective layer was provided in Reference Example 1 was left as aluminum foil in the positive electrode production procedure. Then, the obtained battery was charged at a constant current of 50 mA at 25 ° C. until the battery voltage reached 4.2V, and after the battery voltage reached 4.2V, the battery was charged at a constant voltage of 4.2V. Charged for hours. Then, a part of the laminated case of the charged battery is cut open, and the separator in the region where the negative electrode and the positive electrode aluminum foil exposed portion overlap (the portion corresponding to the dotted circle shown by reference numeral 26 in FIG. 2) is cut out by 3 mmφ, The aluminum foil exposed portion and the negative electrode were brought into contact with each other by protruding from the back surface of the negative electrode with a 1 mmφ alumina rod. The battery surface temperature and voltage at that time were measured to confirm the battery behavior. The time change of the battery behavior is shown in FIG. 5, and the battery voltage and the temperature increase result 5 minutes after the start of the test are shown together with the result of Reference Example 1 in Table 1 below.

[Comparative Example 2]
The non-aqueous secondary battery of Comparative Example 2 was produced in the same procedure as in Reference Example 1 except that the configuration of the protective layer in Reference Example 1 was changed in the procedure for producing the positive electrode. The protective layer was changed to the protective layer produced in Reference Example 1, and an insulating layer was provided by applying a slurry in which only polyimide was mixed using N-methylpyrrolidone as a solvent. This insulating layer is substantially the same as the insulating layer disclosed in Patent Document 3.

  The obtained battery is charged at a constant current of 50 mA at 25 ° C. until the battery voltage reaches 4.2 V. After the battery voltage reaches 4.2 V, the battery is charged at a constant voltage of 4.2 V for 2 hours. Went. Then, a part of the laminated case of the charged battery is cut open, and the separator in the region where the negative electrode and the positive electrode protective layer overlap (the part corresponding to the broken circle shown by reference numeral 26 in FIG. 2) is cut out by 3 mmφ, The protective layer and the negative electrode were brought into contact with each other with a 1 mmφ alumina rod from the side. The battery surface temperature and voltage at that time were measured to confirm the battery behavior. The time change of the battery behavior is shown in FIG. 6, and the battery voltage and temperature increase result 5 minutes after the start of the test are shown together with the result of Reference Example 1 in Table 1 below.

  The following can be understood from the results shown in Table 1 and FIGS. That is, while the non-aqueous secondary battery of Reference Example 1 shows a gentle voltage drop with time at the time of short circuit, the non-aqueous secondary battery of Comparative Example 1 suddenly drops to 0.1 V at the time of short circuit. Also, the temperature of the battery surface increased by 4 ° C. Therefore, when the protective layer according to the present invention was provided, the battery could be discharged gently while suppressing a rapid temperature increase due to a short circuit.

  On the other hand, in the case of the nonaqueous secondary battery of Comparative Example 2, since the protective layer was an insulating layer, no change was observed even if the insulating layer of the negative electrode and the positive electrode contacted each other and the insulating layer was damaged. As shown in FIG. 6, the measurement was stopped in 5 minutes (300 seconds). The non-aqueous secondary battery of Comparative Example 2 is in a state where the battery can be charged / discharged even if the separator is damaged or broken.

  In this state, when the positive electrode current collector and the negative electrode are short-circuited due to progress of breakage of the separator and deformation of the electrode due to dropping, vibration, etc., or dropping of the insulating layer facing the broken separator, as in Comparative Example 1 Can cause a large short circuit. Therefore, for the non-aqueous secondary batteries of Reference Example 1 and Comparative Example 2 immediately after performing the above test, assuming the above situation, the area around the location where the 3 mmφ hole was drilled 1 hour after the test was started. The protective layer (Reference Example 1) or the insulating layer (Comparative Example 2) was peeled off by 5 mmφ, and the positive electrode current collector and the negative electrode were brought into contact with the 1 mmφ alumina rod from the back side of the negative electrode to short-circuit the battery. The battery surface temperature and voltage at that time were measured to confirm the battery behavior. FIG. 7 (Reference Example 1) and FIG. 8 (Comparative Example 2) show the changes in battery behavior over time. The results of battery voltage and temperature rise after 5 minutes from the start of the test are shown in Table 2 below.

  The following can be understood from the results shown in Table 2. That is, in the non-aqueous secondary battery of Reference Example 1, no battery temperature increase was observed even when short-circuited, but in the non-aqueous secondary battery of Comparative Example 2, a temperature increase of 4 ° C. was observed after the short-circuit. This is because the electronic conductivity of the protective layer used in the non-aqueous secondary battery of Reference Example 1 is smaller than the electronic conductivity of the aluminum foil as the positive electrode current collector. When scratches occur, the non-aqueous secondary battery of Reference Example 1 continues to discharge gently, and the battery voltage gradually decreases (see Table 1 and FIG. 4). Even if the positive electrode current collector and the negative electrode are directly contacted and short-circuited due to the progress of rupture and deformation of the electrode, or the protective layer falling off the ruptured separator, a large current no longer flows. It means no rise was seen. Since this decrease in battery voltage can be easily detected, the abnormality of the battery can be easily detected on the device side using the non-aqueous secondary battery of Reference Example 1.

  In contrast, in the battery of Comparative Example 2, even when a hole or a flaw occurs once in the separator due to burrs or the like, the battery can be charged and discharged as shown in FIG. Works normally. However, if the positive electrode current collector and the negative electrode are directly contacted and short-circuited due to the progress of the breakage of the separator and the deformation of the electrode due to the fall, vibration, etc. in this state, or the protective layer facing the broken separator, the large current is generated. Since it flows, the surface temperature of a battery will rise. Therefore, in the non-aqueous secondary battery of Comparative Example 2 using an insulating layer, it is not possible to detect that a hole or a scratch has occurred in the separator until the positive electrode and the negative electrode of the battery are short-circuited. In the non-aqueous secondary battery of Reference Example 1 using a non-insulating protective layer with low conductivity, a hole or a scratch was generated in the separator before the positive electrode and the negative electrode of the battery were short-circuited due to a decrease in battery voltage. Therefore, a non-aqueous secondary battery excellent in safety can be obtained.

In Reference Example 1 described above, an example in which a carbon material made of acetylene black having a large specific surface area of 70 m ² / g was used as the conductive particles among the non-insulating protective layer forming material was described. Even if the non-insulating protective layer has a good effect in terms of ensuring safety, the color of the dried protective layer and the active material mixture layer becomes substantially the same black, so that the optical sensor However, it is difficult to detect the boundary between the protective layer and the active material mixture layer. Therefore, in Reference Examples 2 to 5 below, the state of detection of the boundary between the protective layer and the active material mixture layer by the optical sensor and the protective layer and the current collector are changed by variously changing the physical properties of the protective layer forming material. The state of detection of the boundary with the body was confirmed.

[Reference Example 2]
94% by mass of a positive electrode active material composed of a composite oxide of lithium, nickel, cobalt, and manganese was obtained by mixing 3% by mass of carbon powder such as acetylene black and graphite and 3% by mass of a binder composed of PVdF. NMP was added to the mixture and kneaded to prepare an active material mixture slurry. These active material mixture slurries were uniformly applied to one side of a positive electrode current collector 12 made of an aluminum foil having a thickness of 20 μm so that an exposed portion 13 of the aluminum foil was formed at the end of the electrode. A positive electrode plate coated with the active material layer 14 was formed. Thereafter, the positive electrode plate coated with the active material layer 14 was passed through a drier to remove the organic solvent necessary for the preparation of the slurry and dry it. After drying, this dried positive electrode plate was rolled by a roll press to obtain a positive electrode plate 11 having a thickness of 0.06 mm.

Next, 0.1 g of carbon powder having a specific surface area of 40 m ² / g as a conductive material is mixed with 5.0 g of a polyimide varnish containing 20% by mass of polyimide using NMP as a solvent, and NMP is added so that the total amount becomes 25.1 g. Mixed. This mixture was uniformly applied to an aluminum foil having a thickness of 20 μm with a doctor blade having a gap of 50 μm and dried to prepare a protective layer. The positive electrode and protective layer of Reference Example 2 produced in this way were cut into a predetermined width, and it was investigated whether or not the boundary of the aluminum foil, the positive electrode active material layer, and the protective layer could be determined using an optical sensor. The results are shown in Table 3 together with the results of other reference examples.

[Reference Example 3]
In Reference Example 3, a protective layer was produced in the same procedure as Reference Example 2 except for the preparation of the protective material. That is, 20 g of a binder solution containing 5% by mass of PVdF in an NMP solvent is mixed with 1 g of polyimide powder and 0.1 g of carbon powder having a specific surface area of 40 m ² / g, and NMP is added to make 25.1 g as a whole. Mixed. Similarly, the results using the optical sensor are shown in Table 3 together with the results of other reference examples.

[Reference Example 4]
In Reference Example 4, a protective layer was produced in the same procedure as Reference Example 2 except for the preparation of the protective material. That is, 1 g of polyimide powder and 0.1 g of carbon powder having a specific surface area of 40 m ² / g were mixed in a binder solution containing 21.1% by mass of polyamideimide in an NMP solvent, and NMP was further added to obtain 25. It mixed so that it might become 1g. Similarly, the results using the optical sensor are shown in Table 3 together with the results of other reference examples.

[Reference Example 5]
In Reference Example 5, a protective layer was prepared in the same procedure as Reference Example 2 except for the preparation of the protective material. That is, 1 g of alumina powder and 0.1 g of carbon powder having a specific surface area of 40 m ² / g were mixed in a binder solution containing 21.1% by mass of polyamideimide in an NMP solvent, and NMP was added to a total of 25.1 g. It mixed so that it might become. Similarly, the results using the optical sensor are shown in Table 3 together with the results of other reference examples.

  From the results of Table 3, in Reference Examples 2 to 5 using a carbon material having a small specific surface area (large particle size), the color of the protective layer after drying can be clearly distinguished from the color of the active material mixture layer. It was confirmed that the boundary between the protective layer and the current collector and the boundary between the protective layer and the active material mixture can be easily detected by image processing using an optical sensor.

In Reference Example 1, since the specific surface area of the carbon material is as large as 70 m ² / g (particle size is small), the color after drying is the same black as the color of the protective layer, and an optical sensor is used. However, it was difficult to automatically identify the boundary between the protective layer and the active material mixture. When the specific surface area of the carbon material is gradually smaller than 70 m ² / g (gradually increasing the particle size), the color tone changes from black to green to gray, and when the specific surface area is 40 m ² / g or less, the optical material is substantially optical. The sensor can now identify the boundary between the protective layer and the active material mixture without error.

Further, although the color tone of the protective layer varies depending not only on the carbon material but also on the physical properties of the filler, it has been found that at least the specific surface area of the carbon material in the protective layer is preferably 40 m ² / g or less. Therefore, by using a carbon material in the specific surface area range as the carbon material in the protective layer, in addition to the effect of improving the safety of the non-aqueous secondary battery by providing the protective layer, the non-aqueous secondary battery Since it becomes possible to automatically detect stacking deviations or winding deviations of the electrode plate group using an optical sensor and an image processing device at the time of manufacturing the battery, an effect of improving the manufacturing efficiency of the nonaqueous secondary battery may also be produced. become.

[Reference Example 6]
In Reference Example 1, an example was shown in which a laminated battery having a single layer for each of the positive electrode and the negative electrode was shown. However, the present invention is not particularly limited to the shape and configuration of the battery, and a stack type in which a plurality of electrodes are laminated. The present invention can also be applied to a battery or a cylindrical battery provided with a wound electrode group. As Reference Example 6, a non-aqueous secondary battery 10A having a stack structure was manufactured. A cross-sectional view of the non-aqueous secondary battery 10A of Reference Example 6 will be described with reference to FIG. 9, but the same components as those of the non-aqueous secondary battery 10 of Reference Example 1 shown in FIGS. Are given the same reference numerals and their detailed description is omitted. 9 is a longitudinal sectional view of a non-aqueous secondary battery having the stack structure of Reference Example 6.

  The positive electrode 11A of the non-aqueous secondary battery 10A of Reference Example 6 is provided with the positive electrode active material layer 14 on both surfaces of the positive electrode current collector 12, and has lower electronic conductivity and non-insulating properties than the metal of the positive electrode current collector 12. The protective layer 16 was prepared in the same manner as the positive electrode of Reference Example 1 except that the protective layer 16 was provided on both sides. Similarly, the negative electrode 17A was produced in the same manner as the negative electrode of Reference Example 1 except that the negative electrode active material layer 20 was provided on both surfaces of the negative electrode current collector 18. Then, the nonaqueous secondary battery 10A of Reference Example 6 uses four sets of the positive electrode 11A and the negative electrode 17A, and is laminated while being insulated from each other by the separator 23 so that current collectors of the same electrode extend in the same direction. Then, the current collectors on the positive electrode side and the current collectors on the negative electrode side are connected to each other by the current collector plates 26 to 27, and the injection of the electrolyte solution and the same as in the case of the non-aqueous secondary battery 10 of Reference Example 1 The laminate film outer body 24 was sealed, and the positive electrode terminal 28 and the negative electrode terminal 29 were derived.

  In the non-aqueous secondary battery 10A of Reference Example 6 as well, the metal of the positive electrode current collector 12 is disposed on the portion of the current collector 12 of the positive electrode 11A exposed to the negative electrode 17 through the separator 23. Since the protective layer 16 made of a non-insulating material having a lower electronic conductivity than the non-aqueous secondary battery of Reference Example 1 has the same effect as the non-aqueous secondary battery of Reference Example 1. A secondary battery is obtained.

[Example 1]
As Example 1, a non-aqueous secondary battery 10B including a wound electrode group was produced. A cross-sectional view of the battery of Example 1 will be described with reference to FIGS. 10 and 11, but the same components as those of the non-aqueous secondary battery 10 of Reference Example 1 shown in FIGS. 1 to 3 are the same. A detailed description thereof will be omitted. 10 is a partial enlarged cross-sectional view of the electrode portion of the non-aqueous secondary battery 10B of Example 1, and FIG. 11 is a longitudinal cross-sectional view of the cylindrical non-aqueous secondary battery 10B according to Example 1. It is a perspective view shown.

  The positive electrode 11B of the non-aqueous secondary battery 10B of Example 1 has a positive electrode active material layer 14 on both sides of a strip-shaped positive electrode current collector 12, and has a lower electronic conductivity than the metal of the positive electrode current collector 12 and A non-insulating protective layer 16 was also produced in the same manner as the positive electrode of Reference Example 1 except that it was provided on both sides. Similarly, the negative electrode 17B was produced in the same manner as the negative electrode of Reference Example 1 except that the negative electrode active material layer 20 was provided on both surfaces of the strip-shaped negative electrode current collector 18.

  After that, the spiral electrode body 30 is produced by winding it through the positive electrode 11B, the negative electrode 17B, and the separator 23. The current collector plates 26 and 27 are disposed above and below the spiral electrode body 30, respectively, and also serve as the negative electrode terminal. It is housed inside a steel cylindrical battery outer can 33, and the exposed metal portion 19 of the negative electrode 17B is welded to the current collecting plate 27, and the current collecting plate 27 is welded to the inner bottom portion of the battery outer can 33, thereby positive electrode 11B. The metal exposed portion 13 is welded to the current collector plate 26, and the current collector plate 26 is welded to the bottom plate portion of the sealing body 34. After injecting a predetermined non-aqueous electrolyte from the opening of the battery outer can 33, It was manufactured by sealing the battery outer can 33 with the sealing body 34.

  Such a non-aqueous secondary battery originally has an excellent effect of high battery performance and high battery reliability. However, in the non-aqueous secondary battery 10B of the first embodiment, the metal of the positive electrode 11B is exposed. Among these parts, a protective layer 16 made of a non-insulating material having a lower electronic conductivity than the metal of the positive electrode current collector 12 is provided in a part facing the negative electrode 17B through the separator 23. Therefore, a non-aqueous secondary battery that is more safe than the non-aqueous secondary battery of Reference Example 1 can be obtained.

10, 10A, 10B Non-aqueous secondary batteries 11, 11A, 11B Positive electrode 12 Positive electrode current collector 13 Metal exposed portion 14 of positive electrode 14 Positive electrode active material layer 15 Boundary 16 between active material application portion and exposed portion 16 Protective layers 17, 17A, 17B Negative electrode 18 Negative electrode current collector 19 Negative metal exposed portion 20 Negative electrode active material layer 21 Positive electrode current collecting tab 22 Negative electrode current collecting tab 23 Separator 26, 27 Current collecting plate 28 Positive electrode terminal 29 Negative electrode terminal

Claims (15)

It has a wound electrode group in which a long positive electrode and a long negative electrode are wound through a separator,
The positive electrode is a non-aqueous secondary material in which active material mixture layers are disposed on both surfaces of a current collector made of metal foil, and the metal foil is exposed at at least one end along the longitudinal direction. A battery,
Of the exposed portion of the metal foil, a portion facing the negative electrode through the separator has a protective layer made of a non-insulating material having a lower electronic conductivity than the metal foil. A non-aqueous secondary battery characterized in that it is formed along the longitudinal direction.   2. The non-aqueous secondary battery according to claim 1, wherein the protective layer is formed along a boundary portion between the forming portion and the non-forming portion of the active material mixture layer in the positive electrode. The negative electrode has a portion where the metal foil is exposed at at least one end along the longitudinal direction,
The portion where the positive electrode metal foil is exposed is located at one end of the wound electrode group, and the portion where the negative electrode metal foil is exposed is located at the other end of the wound electrode group. The non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery is provided.   The non-aqueous secondary battery according to claim 1, wherein the current collector made of the metal foil of the positive electrode is made of aluminum or an alloy mainly composed of aluminum.   The non-aqueous secondary battery according to claim 1, wherein the positive electrode active material mixture layer includes a metal oxide.   The non-aqueous secondary battery according to claim 1, wherein the negative electrode includes an active material mixture layer mainly composed of carbon.   The non-aqueous secondary battery according to claim 6, wherein the carbon-based active material mixture layer is disposed on at least one side of a current collector made of a metal foil.   The non-aqueous secondary battery according to claim 7, wherein the current collector made of the metal foil of the negative electrode is made of copper or an alloy mainly composed of copper.   The non-aqueous secondary battery according to claim 7, wherein the current collector made of the metal foil of the negative electrode is made of Ni or an alloy mainly containing Ni.   The non-aqueous secondary battery according to claim 7, wherein the current collector made of the metal foil of the negative electrode is made of stainless steel.   The protective layer is obtained by dispersing a powder of an insulating polymer substance and at least one material selected from the group consisting of an electron conductive carbon, a semiconductor material, and a conductive oxide. The non-aqueous secondary battery according to claim 1.   The non-aqueous secondary battery according to claim 11, wherein the insulating polymer material is at least one selected from the group consisting of polyimide, polyamideimide, and polyvinylidene fluoride.   The protective layer is obtained by dispersing an insulating polymer substance, at least one material selected from the group consisting of an electron conductive carbon, a semiconductor material, and a conductive oxide, and a filler. The non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery is a non-aqueous secondary battery.   The non-aqueous secondary battery according to claim 13, wherein the filler is at least one selected from the group consisting of polyimide powder and alumina powder. The non-aqueous secondary battery according to claim 13, wherein the carbon powder has a specific surface area of 40 m ² / g or less.

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