JP4088757B2 - Non-aqueous secondary battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous secondary battery, and more particularly to a non-aqueous secondary battery for a power storage system.
[0002]
[Prior art]
In recent years, from the viewpoint of effective use of energy aiming at resource saving and global environmental problems, attention has been focused on home-use distributed storage systems for the storage of late-night power storage and solar power generation, storage systems for electric vehicles, etc. Collecting. For example, Japanese Patent Laid-Open No. 6-86463 proposes a total system that combines electricity, gas cogeneration, fuel cells, storage batteries, and the like supplied from a power plant as a system that can supply energy to energy consumers under optimum conditions. ing. A secondary battery used in such a power storage system requires a large battery having a large capacity, unlike a small secondary battery for portable equipment having an energy capacity of 10 Wh or less. For this reason, in the above power storage system, a plurality of secondary batteries are usually stacked in series and used as an assembled battery having a voltage of 50 to 400 V, for example, and in most cases, lead batteries are used.
[0003]
On the other hand, in the field of small secondary batteries for portable devices, the development of nickel-metal hydride batteries and lithium secondary batteries as new batteries has progressed to meet the needs for small size and high capacity, and has a volumetric energy density of 180 Wh / l or more. Batteries are commercially available. In particular, a lithium ion battery has a possibility of a volume energy density exceeding 350 Wh / l, and reliability such as safety and cycle characteristics is superior to a lithium secondary battery using metallic lithium as a negative electrode. , Has dramatically expanded its market.
[0004]
In response, in the field of large-scale batteries for power storage systems, lithium-ion batteries are targeted as candidates for high-energy density batteries, and development is actively underway by the Lithium Battery Power Storage Technology Research Association (LIBES) and others. .
[0005]
The energy capacity of these large-sized lithium ion batteries is about 100 Wh to 400 Wh, and the volume energy density is 200 to 300 Wh / l, the same level as a small secondary battery for portable devices. The shape is typically a cylindrical shape having a diameter of 50 mm to 70 mm, a length of 250 mm to 450 mm, and a flat prismatic shape such as a square or oblong square having a thickness of 35 mm to 50 mm.
[0006]
However, although such a large lithium ion battery can obtain a high energy density, since its battery design is generally an extension of the small battery for portable devices, the diameter or thickness of the small battery for portable devices is small. The battery shape is three times or more, such as a cylindrical shape and a rectangular shape. In this case, heat is likely to be accumulated inside the battery due to Joule heat generation due to the internal resistance of the battery during charging and discharging, or internal heat generation of the battery due to change in entropy of the active material due to the entry and exit of lithium ions. For this reason, the temperature difference between the temperature inside the battery and the vicinity of the battery surface is large, and accordingly, the internal resistance is unevenly distributed, and as a result, the charge amount and the voltage are likely to vary. In addition, since this type of battery is used as a plurality of assembled batteries, the ease of heat storage differs depending on the installation position of the batteries in the system, resulting in variations among the batteries, and accurate control of the entire assembled battery is possible. It becomes difficult. In addition, because of insufficient heat dissipation during high-rate charging / discharging, etc., the battery temperature rises, leaving the battery unfavorable, resulting in a decrease in life due to decomposition of the electrolyte, and thermal runaway of the battery. Problems such as induction of reliability, particularly safety, remained.
[0007]
In order to solve the above problem, WO99 / 60652 discloses a flat nonaqueous secondary battery in which a nonaqueous electrolyte containing a positive electrode, a negative electrode, a separator, and a lithium salt is contained in a battery container, An aqueous secondary battery has a flat shape with a thickness of less than 12 mm, a non-aqueous secondary battery having an energy capacity of 30 Wh or more and a volume energy density of 180 Wh / l or more is disclosed. It has been proposed that the battery has a unique battery shape (flat shape) to solve the problems of reliability and safety caused by the heat storage that becomes a barrier to practical use.
[0008]
By the way, in general, a battery container can withstand a shock from the outside such as an object colliding, and has a function of holding an electrode stored in the battery container and pressing it when gas is generated. The material, shape, etc. are selected according to the size, battery shape, battery usage environment, and the like. In particular, in the case of a large battery, unlike a small battery, in order to ensure the reliability and safety of the battery, it is particularly important to determine the design of the battery container, that is, the material, shape, and the like. For example, when the battery shape is rectangular, stainless steel or iron is generally used as the material of the battery container because a high-strength material is required because the pressure resistance of the flat plate portion is lower than that of a cylindrical battery. It has been.
[0009]
However, a large-sized battery having a large capacity (30 Wh or more) and a flat shape having a thickness of less than 12 mm as described above has a flat plate member having a large area, and battery container material for the whole battery as compared with a square or cylindrical battery. The proportion of the volume of increases. Therefore, in such a thin and flat battery, when stainless steel or iron is used for the battery container, there is a problem that a ratio of closing the battery container weight is high with respect to the total battery weight. In other words, the conventional flat battery has a problem that the weight energy density is extremely lowered although a high volume energy density can be realized.
[0010]
Therefore, if an aluminum-based material is used for the battery container, the container weight can be reduced to about one third, and the decrease in the weight energy density can be suppressed. However, when high-purity aluminum is used for both the bottom container and the upper lid, there are problems such as a decrease in laser weldability and a tendency to deform due to external stress. In addition, when aluminum alloy with high laser weldability is used for both the bottom container and the top lid, the material hardness is high, drawing with a small R (curvature radius) becomes difficult, and the internal effective volume of the entire battery is difficult to increase. There was a problem.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to provide a nonaqueous secondary battery having a high capacity, a high volume energy density, and a high weight energy density in a flat nonaqueous battery having a thickness of less than 12 mm. .
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides the following nonaqueous secondary battery.
[0013]
Item 1. A nonaqueous electrolyte containing a positive electrode, a negative electrode, a separator, and a lithium salt is accommodated in a battery container, has a flat shape with a thickness of less than 12 mm, an energy capacity of 30 Wh or more, and a volume energy density of 180 Wh / l or more. In a non-aqueous secondary battery, the battery container is composed of a flat top lid and a bottom container that has been subjected to drawing processing, and the top lid includes a portion made of an aluminum alloy as a main member, and the bottom container is made of high-purity aluminum. A non-aqueous secondary battery comprising a metal part as a main member.
[0014]
Item 2. Item 2. The nonaqueous secondary battery according to Item 1, wherein the bottom container of the battery container is composed of high-purity aluminum containing 99% by weight or more of an Al component.
[0015]
Item 3. Item 3. The nonaqueous secondary battery according to Item 2, wherein the upper lid of the battery container is composed of an aluminum alloy containing 0.5 wt% to 2.0 wt% of a Mn component.
[0016]
Item 4. The non-aqueous secondary battery according to claim 3, wherein the upper lid of the battery container is made of an aluminum alloy containing 0.02 wt% to 0.8 wt% Mg component.
[0017]
Item 5. Item 5. The nonaqueous secondary battery according to any one of Items 1 to 4, wherein the pressure in the battery container is less than atmospheric pressure.
[0018]
Item 6. Item 6. The nonaqueous system according to Item 5, wherein the pressure in the battery container is reduced to less than atmospheric pressure by being finally sealed in a state where the pressure in the battery container is less than atmospheric pressure after being charged at least once. Next battery.
[0019]
Item 7. The pressure in the battery container is 8.66 × 10 ^Four Item 7. The nonaqueous secondary battery according to any one of Items 1 to 6, which is Pa or less.
[0020]
Item 8. Item 8. The nonaqueous secondary battery according to any one of Items 1 to 7, wherein the negative electrode contains a material capable of doping and dedoping lithium.
[0021]
Item 9. Item 9. The nonaqueous secondary battery according to any one of Items 1 to 8, wherein the positive electrode contains a manganese oxide.
[0022]
Item 10. Item 10. The nonaqueous secondary battery according to any one of Items 1 to 9, wherein the flat front and back surfaces are rectangular.
[0023]
Item 11. Item 11. The nonaqueous secondary battery according to any one of Items 1 to 10, wherein the battery container has a plate thickness of 0.2 mm to 1 mm.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a non-aqueous secondary battery according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a plan view and a side view of a flat rectangular (note type) non-aqueous secondary battery for a power storage system as an example of the present embodiment, and FIG. 2 shows the inside of the battery shown in FIG. It is a side view which shows the electrode laminated body accommodated in.
[0025]
As shown in FIGS. 1 and 2, the non-aqueous secondary battery according to the present embodiment includes a battery container composed of an upper lid 1 and a bottom container 2, a plurality of positive electrodes 101a and negative electrodes housed in the battery container. 101b, 101c, and an electrode laminate including the separator 104. In the case of a flat type non-aqueous secondary battery as in the present embodiment, the positive electrode 101a and the negative electrode 101b (or the negative electrode 101c disposed on both outer sides of the laminate) are provided via a separator 104 as shown in FIG. However, the present invention is not particularly limited to this arrangement, and the number of stacked layers can be variously changed depending on the required capacity. The shape of the nonaqueous secondary battery shown in FIGS. 1 and 2 is, for example, 300 mm long × 210 mm wide × 6 mm thick, and LiMn is formed on the positive electrode 101a. ₂ O _Four In the case of a lithium secondary battery using a carbon material for the negative electrodes 101b and 101c, for example, it can be used in a power storage system.
[0026]
Moreover, as shown in FIG. 1, the positive electrode terminal 3 and the negative electrode terminal 4 are attached to the upper lid 1 of the battery container in a state insulated from the upper lid 1, and each positive electrode 101a shown in FIG. The positive electrode current collector 105 a is electrically connected, and the negative electrode current collector 105 b of each of the negative electrodes 101 b and 101 c is electrically connected to the negative electrode terminal 4.
[0027]
The top lid 1 and the bottom container 2 constitute a battery container by melting the point A shown in the enlarged view in FIG. 1, that is, the peripheral edge of the top lid 1 and welding it to the bottom container 2. Examples of the welding method include laser welding, arc welding, resistance welding, and the like. Among them, laser welding is preferable because the welding area is small and energy can be concentrated, so that deformation deformation of the container and thermal influence on the periphery are small. The upper lid 1 is provided with an electrolytic solution injection port 5, and after the electrolytic solution injection, is sealed using, for example, a sealing film 6 made of an aluminum-modified polypropylene laminate film.
[0028]
The positive electrode active material used for the positive electrode 101a is not particularly limited as long as it is a lithium-based positive electrode material, and lithium composite cobalt oxide, lithium composite nickel oxide, lithium composite manganese oxide, or a mixture thereof, A system in which one or more different metal elements are added to these composite oxides can be used, and a high voltage and high capacity battery can be obtained, which is preferable. In addition, in the case of emphasizing safety, which is the most important issue in the practical application of a large-sized lithium secondary battery, it is preferable to use a positive electrode mainly composed of manganese oxide having a high thermal decomposition temperature. As this manganese oxide, LiMn ₂ O _Four Lithium composite manganese oxide, a system in which one or more different metal elements are added to these composite oxides, and Li in which lithium is made in excess of the stoichiometric ratio _{1 + x} Mn _2-y O _Four Is mentioned.
[0029]
The negative electrode active material used for the negative electrodes 101b and 101c is not particularly limited as long as it is a lithium-based negative electrode material, and is a material capable of doping and dedoping lithium, such as safety and reliability such as cycle life. Is preferable. Examples of materials that can be doped and dedoped with lithium include graphite-based materials, carbon-based materials, tin oxide-based, silicon oxide-based metal oxides, and polyacene, which are used as negative electrode materials for known lithium ion batteries. Examples thereof include conductive polymers represented by organic organic semiconductors. In particular, from the viewpoint of safety, a polyacene-based substance having a small heat generation at around 150 ° C. and a material containing the same are preferable.
[0030]
Although the structure of the separator 104 is not particularly limited, a single-layer or multi-layer separator can be used, and at least one sheet is preferably a nonwoven fabric. In this case, cycle characteristics are improved. The material of the separator 104 is not particularly limited, and examples thereof include polyolefins such as polyethylene and polypropylene, polyamides, kraft paper, glass, cellulosic materials, and the like, depending on the heat resistance and safety design of the battery. It is determined appropriately. Among these, polyethylene, polypropylene, and the like are preferable from the viewpoints of cost, water content, and the like. Further, when polyethylene or polypropylene is used as the separator 104, the basis weight of the separator is preferably 5 to 30 g / m. ² More preferably 5-20 g / m ² More preferably 5 to 20 g / m ² Degree. Separator weight is 30g / m ² In the case where it exceeds 1, the separator becomes too thick, the porosity is lowered, and the internal resistance of the battery is increased, which is not preferable. In contrast, the basis weight of the separator is 5 g / m ² If the ratio is less than 1, practical strength cannot be obtained, which is not preferable.
[0031]
As the electrolyte of the secondary battery of the present invention, a known non-aqueous electrolyte containing a lithium salt can be used, which is appropriately determined according to the use conditions such as the positive electrode material, the negative electrode material, the charging voltage, and more specifically, LiPF. ₆ , LiBF _Four LiClO _Four Lithium salts such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, γ-butyrolactone, methyl acetate, methyl formate, or a mixed solvent of two or more of these are dissolved. The thing etc. are illustrated. Further, the concentration of the electrolytic solution is not particularly limited, but generally 0.5 mol / l to 2 mol / l is practical, and this electrolytic solution naturally has a water content of 100 ppm or less. It is preferable to use it. In addition, the non-aqueous electrolyte used in this specification means a concept including a non-aqueous electrolyte solution and an organic electrolyte solution, and also refers to a concept including a gel-like or solid electrolyte.
[0032]
The non-aqueous secondary battery configured as described above can be used for a household power storage system (night power storage, cogeneration, solar power generation, etc.), a power storage system such as an electric vehicle, and the like. It can have an energy density. In this case, the energy capacity is preferably 30 Wh or more, more preferably 50 Wh or more, and the energy density is preferably 180 Wh / l or more, more preferably 200 Wh / l. When the energy capacity is less than 30 Wh or when the volumetric energy density is less than 180 Wh / l, the capacity is small for use in the power storage system, and it is necessary to increase the number of series-parallel batteries to obtain sufficient system capacity. In addition, it is not preferable for a power storage system because a compact design becomes difficult.
[0033]
The non-aqueous secondary battery of this embodiment has a flat shape, and its thickness is less than 12 mm, more preferably less than 10 mm. As for the lower limit of the thickness, 2 mm or more is practical in consideration of the filling factor of the electrode and the battery size (the area becomes larger in order to obtain the same capacity as the thickness is reduced). When the thickness of the battery is 12 mm or more, it becomes difficult to sufficiently dissipate the heat generated inside the battery to the outside, or the temperature difference between the inside of the battery and the vicinity of the battery surface increases, resulting in different internal resistances. Variation in the amount of charge and voltage in the battery becomes large. The specific thickness is appropriately determined according to the battery capacity and the energy density, but it is preferable to design with the maximum thickness that provides the expected heat dissipation characteristics.
[0034]
Moreover, the non-aqueous secondary battery of this embodiment can be made into various shapes, such as a square shape, circular shape, and oval shape, for example, the flat front and back surfaces of a battery container. However, it may be a polygon such as a triangle or a hexagon. Furthermore, it can also be made into cylindrical shapes, such as a thin cylinder. In the case of a cylinder, the thickness of the cylinder is the thickness referred to here. Further, from the viewpoint of ease of manufacture, the flat front and back surfaces of the battery are rectangular, and a notebook shape as shown in FIG. 1 is preferable.
[0035]
In this embodiment, the battery container is composed of a flat-shaped upper lid and a bottom container that has been subjected to drawing processing, the upper lid 1 includes a portion made of an aluminum alloy as a main member, and the bottom container 2 is made of high-purity aluminum metal. This part is provided as a main member. The entire battery container is not necessarily made of an aluminum-based material, and a portion made of an aluminum-based material may be provided as a main constituent member. However, in order to sufficiently achieve the effects of the present invention described later, it is preferable that 80% or more of the entire battery container is made of an aluminum-based material, and more preferably 90% or more.
[0036]
The bottom container material of the battery container is preferably composed of high-purity aluminum having an Al component content of 99% by weight or more, and more preferably 99.5% or more. If the Al component content is as low as less than 99% and the ratio of Mn, Cu component, etc. is high, the mechanical strength increases, but the elongation decreases. In that case, cutting occurs in the drawing process, and it is difficult to draw deeply. In addition, when the R of each corner portion is designed to be small in order to increase the energy density as a battery, there is a high possibility that a material that is not easily stretched will be cut or cracked by drawing. From this point of view, it is desirable that the material of the battery bottom container to be drawn is made of high-purity aluminum having a high elongation ratio with an Al component content of 99% by weight or more as a main member.
[0037]
The aluminum alloy material used for the upper lid of the battery container is, for example, an alloy of one or more metals selected from Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and the like with aluminum. Can be used. In the component of the Al-Mn alloy, the content of the Mn component is preferably 0.5 wt% to 2.0 wt%. When the Mn component is less than 0.5% by weight, mechanical strength and rigidity at a large size are lowered. In addition, formability and laser welding characteristics are degraded. On the other hand, even if it exceeds 2.0% by weight, the effect of improving the strength does not increase so much, and the possibility of cracking due to the expression of a rough intermetallic compound increases. Moreover, it is preferable that content of Mg component in Mg-Al type alloy shall be 0.02 weight%-0.8 weight%. When the Mg component is 0.8% by weight or more, welding defects such as cracks and holes are likely to occur when laser welding a battery container.
[0038]
As described above, in a battery container, by combining an upper lid made of an aluminum alloy and a bottom container made of high-purity aluminum, the battery can have both mechanical strength, laser weldability, and high energy density. .
[0039]
The thicknesses of the top cover 1 and the bottom container 2 constituting the battery container are appropriately determined depending on the use of the battery, the material of the battery case, etc., and are not particularly limited, but preferably 80% or more of the battery surface area. The thickness of the portion (thickness of the portion having the largest area constituting the battery container) is 0.2 mm or more. If the thickness is less than 0.2 mm, there is a problem that the strength required for battery production cannot be obtained. From this viewpoint, the thickness is more preferably 0.3 mm or more, and further preferably 0.4 mm or more. It is. The thickness of the same part is desirably 1 mm or less. If this thickness exceeds 1 mm, the force to hold down the electrode surface increases, but it is not desirable because the internal volume of the battery is reduced and sufficient capacity cannot be obtained, or the weight is increased. Preferably it is 0.7 mm or less.
[0040]
As described above, the battery container is made of aluminum or an alloy mainly composed of aluminum, and the thickness of the nonaqueous secondary battery is designed to be less than 12 mm, so that the battery has a large capacity of 30 Wh or more and 180 Wh / l. Even when high rate charge / discharge is performed in the case of a high energy density, excellent heat dissipation characteristics can be realized, and an increase in battery temperature can be suppressed. Accordingly, the heat storage of the battery due to internal heat generation can be reduced, and as a result, the thermal runaway of the battery can be suppressed, and a non-aqueous secondary battery excellent in reliability and safety can be provided. In particular, in the present embodiment, since the battery container is made of an aluminum-based material, the battery container can be reduced in weight as compared with the conventional battery container made of stainless steel or the like. Can be reduced in weight. As a result, although depending on the battery thickness and the battery surface area, the weight energy density can be improved by about 1.2 to 1.5 times compared to the case of using stainless steel.
[0041]
On the other hand, when the battery container is changed from, for example, a stainless steel to an aluminum-based material in a large-sized rectangular battery or a cylindrical battery having a general shape, the ratio of the volume of the battery container material to the entire battery is Since it is smaller than a flat battery, the improvement in weight energy density is at most about 1.2 times.
[0042]
As described above, in a non-aqueous secondary battery having a flat shape with a thickness of less than 12 mm, a large capacity of 30 Wh or more and a high energy density of 180 Wh / l or more, aluminum or an alloy mainly composed of aluminum is applied to the battery container. The effect to do is extremely great.
[0043]
By the way, compared to stainless steel and iron generally used for battery containers, when aluminum or an alloy mainly composed of aluminum is used, the force to pinch and press the electrode surface is weakened, so that the internal resistance increases, or , The cycle life may be reduced and battery performance may be affected. In particular, in order to obtain a high volume energy density in a battery having a thickness of 8 mm or less, it is necessary to reduce the thickness of the material that constitutes the battery container. Become. To solve these problems, the thickness of the battery container can be reduced even if aluminum or an alloy mainly composed of aluminum is used for the battery container by sealing the inside of the battery so as to be less than atmospheric pressure as described below. It has been found that the same characteristics as stainless steel and iron can be obtained without increasing.
[0044]
In order to reduce the internal pressure of the battery after completion to less than atmospheric pressure, the positive electrode 101a, the negative electrodes 101b and 101c, the separator 104, and the nonaqueous electrolyte are accommodated in the battery container, and the pressure in the battery container is set to atmospheric pressure. The final sealing step of the battery container is performed in a state of less than. This final sealing step is preferably performed after at least one charging operation. In this case, gas may be generated inside due to the decomposition of the electrolytic solution at the initial stage of the first charge. In this case, if the final sealing step is performed at less than atmospheric pressure without performing the charging operation, the subsequent first time This is because there is a case where the inside of the battery is pressurized (atmospheric pressure or more) by the charging operation, the thickness of the battery increases, the internal resistance and capacity of the battery vary, and stable cycle characteristics cannot be obtained. In particular, when a liquid electrolyte using graphite for the negative electrode and a lithium composite oxide for the positive electrode is used, gas is likely to be generated.
[0045]
This charging operation may employ various conditions depending on the types of positive electrode material, negative electrode material, separator, electrolyte, etc. used in the battery, the moisture content and impurities of these materials, the voltage at which the battery is used, etc. However, for example, the battery may be charged at a rate of about 4 to 8 hours to the working voltage of the battery, a constant voltage may be applied as necessary, and the battery may be discharged at a rate of about 8 hours to the normal lower limit voltage. The final sealing step is performed after this charging operation. In addition, sealing may be performed after performing only the charging operation below the capacity of the battery, or various charging operations such as sealing after repeating charging and discharging twice or more are possible. It is important to maintain the internal pressure of the battery below atmospheric pressure.
[0046]
As described above, in this embodiment, after performing the charging operation to generate gas, degassing is performed and the final sealing step is performed at less than atmospheric pressure, so that aluminum or an alloy mainly composed of aluminum is used for the battery container. It is possible to solve the problem that the container that is likely to swell in a case is swollen. In this case, when the first charging operation is performed, the internal pressure of the battery is not particularly limited, but it is preferable that the internal pressure of the battery is lower than atmospheric pressure.
[0047]
Moreover, the method of making the inside of the battery less than atmospheric pressure is not particularly limited, but specifically, it can be performed as follows.
[0048]
First, as shown in FIG. 2, after the electrode laminate obtained by laminating the positive electrode 101 a, the negative electrode 101 b, 101 c and the separator 104 is accommodated in the upper lid 1 and the bottom container 2, the upper lid 1 and the bottom container 2 Weld the outer periphery. Next, an electrolytic solution is injected into the battery container from the injection port 5 shown in FIG. Subsequently, for the temporary sealing, the liquid injection port 5 is once sealed by using the heat-sealing type sealing film 6 represented by the aforementioned aluminum-modified polypropylene laminate film and aluminum-modified polyethylene laminate film and having a low water permeability. Then, after charging at least once as described above, the sealing film 6 is removed. In addition, the method of temporary sealing is not limited to the above-mentioned example, For example, you may seal the injection port 5 temporarily using a screw etc., and the state which removed the water | moisture content, for example, air | blocking air In a dry environment with a dew point of −40 ° C. or lower, the above charging operation may be performed without sealing.
[0049]
Next, the sealing film 6 is heat-sealed as a final sealing step. The method used in the final sealing step is not limited to heat sealing of the sealing film, but a metal plate or a foil is welded, or a cock is attached to the battery container and a predetermined pressure ( After reducing the pressure to less than atmospheric pressure, the cock may be closed.
[0050]
In the final sealing step, the pressure in the battery is set to less than atmospheric pressure, but 8.66 × 10 ^Four It is preferable to set it to Pa (650 Torr) or less, and 7.33 × 10 ^Four It is more preferable to set it to Pa (550 Torr) or less. This pressure is determined according to the internal pressure required for the finally completed battery. The portion for forming the injection port 5 is preferably located on either the front or back surface excluding the outer peripheral portion of 5 mm of the battery. In the case of the flat shape shown in FIG. 1, it is more preferable to provide in a dead space between the positive electrode terminal 3 and the negative electrode terminal 4 disposed in the upper lid 1 from the viewpoint of securing energy density by effective use of the space. Moreover, after the final sealing step, in the metal battery container, it is preferable to cover portions other than the positive and negative external terminals with an insulating film or the like. This is because it is possible to prevent an external short circuit due to contact between the bipolar external terminals and the metal container in the case of assuming a module or the like in which batteries are arranged in a stack or in normal handling.
[0051]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0052]
Example
(1) LiMn ₂ O _Four 100 parts by weight, 8 parts by weight of acetylene black and 3 parts by weight of polyvinylidene fluoride (PVDF) were mixed with 100 parts by weight of N-methylpyrrolidone (NMP) to obtain a positive electrode mixture slurry. The slurry was applied to both sides of a 20 μm thick aluminum foil serving as a current collector, dried, and then pressed to obtain a positive electrode. FIG. 3A is an explanatory diagram of the positive electrode. In this embodiment, the application area (W1 × W2) of the positive electrode 101a is 262.5 × 192 mm. ² It is applied to both sides of a 20 μm current collector with a thickness of 110 μm. As a result, the electrode thickness t is 240 μm. Moreover, the positive electrode current collection piece 106a in which the electrode material is not apply | coated is provided in the short side of an electrode, and the hole of diameter 3mm is formed in the center.
[0053]
(2) 100 parts by weight of graphitized mesocarbon microbeads (MCMB, manufactured by Osaka Gas Chemical Co., No. 6-28) and 10 parts by weight of PVDF were mixed with 90 parts by weight of NMP to obtain a negative electrode mixture slurry. The slurry was applied to both sides of a 14 μm thick copper foil serving as a current collector, dried, and then pressed to obtain a negative electrode. FIG. 3B is an explanatory diagram of the negative electrode. The coating area (W1 × W2) of the negative electrode 101b is 267 × 195 mm. ² It is applied to both sides of a 14 μm current collector with a thickness of 90 μm. As a result, the electrode thickness t is 194 μm. Further, a negative electrode current collecting piece 106b to which no electrode material is applied is provided on the short side of the electrode, and a hole having a diameter of 3 mm is formed at the center thereof. Further, a single-sided electrode having a thickness of 104 μm was prepared by the same method except that the coating was applied to only one side. Single-sided electrodes are arranged on both outer sides of the electrode laminate of item (3) (101c in FIG. 2).
[0054]
(3) As shown in FIG. 2, 8 positive electrodes and 9 negative electrodes (2 inner surfaces) obtained in the above item (1) were used as separators A104a (rayon system, basis weight 12.6 g / m). ² ) And separator B104b (polyethylene microporous membrane; basis weight 13.3 g / m) ² ) And the separator 104 combined with each other, and further, the separator B104a is arranged on the outer side of the outer negative electrode 101c for insulation from the battery container, thereby preparing an electrode laminate. The separator 104 was arranged so that the separator A104a was on the positive electrode side and the separator B104b was on the negative electrode side.
[0055]
(4) As shown in FIG. 4, the bottom container 2 constituting the battery container is a thin plate made of high-purity aluminum 1050 (symbol according to JIS H 4000) having a thickness of 0.5 mm (Al purity 99.50% or more), It was made into a tray shape at a depth of 5 mm and four corners R3 by drawing. The upper lid 1 was made by punching a thin plate made of Mn-Al alloy 3003 having a thickness of 0.5 mm from a flat plate. Further, as shown in FIG. 4, a positive electrode terminal 3 made of aluminum and a negative electrode terminal 4 made of copper (head portion 6 mmφ, screw portion of tip M <b> 3) were attached to the upper lid 1. The positive electrode terminal 3 and the negative electrode terminal 4 were insulated from the upper lid 1 by a Teflon (registered trademark) gasket.
[0056]
(5) The screw portion of the positive electrode terminal 3 is inserted into the hole of each positive electrode current collecting piece 106a of the electrode laminate prepared in the above item (3), and the screw portion of the negative electrode terminal 4 is inserted into the hole of each negative electrode current collector piece 106b. After the nuts made of aluminum and copper were fastened, the electrode laminate was fixed to the upper lid 1 with insulating tape, and the overlapping portion A of the upper lid 1 and the bottom container 2 flange portion shown in FIG. Laser welding was performed from the upper lid over the circumference. Thereafter, LiPF was added to the solvent at a concentration of 1 mol / l from an injection port 5 (6 mmφ) into a solvent in which ethylene carbonate and diethyl carbonate were mixed at a 1: 1 weight ratio as an electrolyte. ₆ The solution in which was dissolved was injected. Subsequently, the liquid injection port 5 was once sealed using a temporary fixing bolt under atmospheric pressure.
[0057]
(6) After charging this battery to 4.2 V with a current of 5 A, constant current and constant voltage charging for applying a constant voltage of 4.2 V is performed for 8 hours, and subsequently discharging to 3.0 V with a constant current of 5 A did.
[0058]
(7) Remove the temporary fixing bolt attached to the battery, 4.00 × 10 ^Four Under a reduced pressure of Pa (300 Torr), a sealing film 6 made of an aluminum foil-modified polypropylene laminate film having a thickness of 0.08 mm punched to 12 mmφ was subjected to a temperature of 250 to 350 ° C., a pressure of 98.1 to 294 kPa (1 to 3 kg / cm ² The liquid injection port 5 was finally sealed by heat-sealing under conditions of a pressurization time of 5 to 10 seconds, and a flat battery having a thickness of 6 mm was obtained. A total of 10 cells were prototyped, but no liquid leakage occurred.
[0059]
Subsequently, the battery is charged to 4.2 V with a current of 5 A, and then a constant current and constant voltage charge for applying a constant voltage of 4.2 V is performed for 8 hours. Subsequently, the battery is discharged to 3.0 V with a constant current of 5 A. And confirmed the capacity. The discharge capacity calculated thereby was 27 Ah. This battery had an energy capacity of 100 Wh, a volume energy density of 265 Wh / l, and a weight energy density of 140 Wh / Kg. When discharged at a constant current of 10 A, the discharge capacity was 24.9 Ah.
[0060]
Comparative Example 1
The batteries were assembled in the same manner as in the above example except that both the bottom container 2 and the top lid 1 were made of a high-purity aluminum 1050 thin plate having a thickness of 0.5 mm, but small cracks occurred in some cells during laser welding. In addition, a small amount of liquid leakage was confirmed in the column liquid process in 2 out of 10 prototype cells. In addition, when a drop test on a concrete surface was performed from a height of 1.9 m using the same battery, the flange corners of some batteries were greatly deformed, and the state was just before opening. From the above, when the aluminum 1050 thin plate material having a thickness of 0.5 mm is used for both the bottom container 2 and the upper lid 1, there is a problem in airtightness during laser welding and mechanical strength during use.
[0061]
Comparative Example 2
In order to assemble the battery in the same manner as in the above example except that both the bottom container 2 and the top lid 1 are made of aluminum alloy 3003 thin plate having a thickness of 0.5 mm, the bottom container is 5 mm deep and has a corner portion R2 as in the example. A total of 10 cells were drawn. However, a small hole was found in the vicinity of the corner in one of ten containers. Therefore, when the above alloy is used, it is necessary to make R a little larger. However, when R is designed to be large, there is a problem that the internal effective volume of the whole battery is reduced and the energy density of the battery is lowered.
[0062]
【The invention's effect】
As is apparent from the above, according to the present invention, in a flat non-aqueous secondary battery having a flat shape with a thickness of less than 12 mm, a large capacity of 30 Wh or more and a volume energy density of 180 Wh / l or more, In addition, the upper cover is made of aluminum alloy and the bottom container is made of high-purity aluminum as a main component, making it possible to reduce the weight of the battery container. A non-aqueous secondary battery that realizes energy density can be provided. In addition, the combination of the above aluminum-based materials allows the upper lid to have mechanical strength and laser weldability, and the bottom container can be deeply processed with a small R, so that a battery design with a higher volumetric energy density can be achieved.
[Brief description of the drawings]
1A and 1B are a plan view and a side view of a nonaqueous secondary battery for a power storage system according to an embodiment of the present invention.
2 is a side view showing a configuration of an electrode laminate housed in the battery shown in FIG. 1. FIG.
FIG. 3 is a plan view of a positive electrode, a negative electrode, and a separator constituting the laminate shown in FIG.
4 is a cross-sectional view showing a state in which an upper lid and a bottom container of the battery shown in FIG. 1 are separated.
[Explanation of symbols]
1 Upper lid
2 Bottom container
3 Positive terminal
4 Negative terminal
5 Injection port
6 Sealing film
101a Positive electrode (both sides)
101b Negative electrode (both sides)
101c Negative electrode (single side)
104 separator
105a Positive electrode current collector
105b Negative electrode current collector
106a Positive electrode current collector
106b Negative electrode current collector

Claims (11)

A nonaqueous electrolyte containing a positive electrode, a negative electrode, a separator, and a lithium salt is accommodated in a battery container, has a flat shape with a thickness of less than 12 mm, an energy capacity of 30 Wh or more, and a volume energy density of 180 Wh / l or more. In the non-aqueous secondary battery, the battery container is composed of a flat top lid and a bottom container subjected to a drawing process, and the top lid includes a portion made of an aluminum alloy as a main member, and the bottom container is 99% by weight or more. A non-aqueous secondary battery comprising, as a main member, a portion made of high-purity aluminum containing the Al component . Bottom container in the battery container, 99. The non-aqueous secondary battery according to claim 1, comprising high-purity aluminum containing 5 % by weight or more of an Al component. The non-aqueous secondary battery according to claim 1 , wherein an upper lid of the battery container is made of an aluminum alloy containing 0.5 wt% to 2.0 wt% of a Mn component.   The non-aqueous secondary battery according to claim 3, wherein the upper lid of the battery container is made of an aluminum alloy containing 0.02 wt% to 0.8 wt% Mg component.   The nonaqueous secondary battery according to any one of claims 1 to 4, wherein the pressure in the battery container is less than atmospheric pressure.   The non-aqueous system according to claim 5, wherein the pressure in the battery container is reduced to less than atmospheric pressure by being finally sealed in a state where the pressure in the battery container is less than atmospheric pressure after being charged at least once. Secondary battery. The nonaqueous secondary battery according to any one of claims 1 to 6, wherein the pressure in the battery container is 8.66 x 10 ⁴ Pa or less.   The non-aqueous secondary battery according to claim 1, wherein the negative electrode includes a material capable of doping and dedoping lithium.   The non-aqueous secondary battery according to claim 1, wherein the positive electrode contains a manganese oxide.   The non-aqueous secondary battery according to claim 1, wherein the shape of the flat front and back surfaces is a rectangle.   The nonaqueous secondary battery according to any one of claims 1 to 10, wherein a thickness of the battery container is 0.2 mm or more and 1 mm or less.

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