JP2013012448A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly safe nonaqueous electrolyte secondary battery in which thermal runaway is prevented.SOLUTION: According to an embodiment, a nonaqueous electrolyte secondary battery 1 is provided including an exterior member, an electrode group 3 including a cathode and an anode, a nonaqueous electrolyte, and a gas generating member 10. The gas generating member 10 includes a gas generating agent 10b and a sealing container 10a having the gas generating agent 10b sealed therein and releases a gas in a range of 100-250°C. The gas generating agent 10b contains an alkanolamine solution which has absorbed a gas.

Description

  Embodiments described herein relate generally to a non-aqueous electrolyte secondary battery.

  In recent years, non-aqueous electrolyte secondary batteries have attracted attention as power sources for hybrid electric vehicles and as power storage devices for generators using natural energy such as sunlight and wind power. A non-aqueous electrolyte battery using a lithium-titanium composite oxide as a negative electrode is capable of stable rapid charge / discharge and has a longer life than a battery using a carbon-based negative electrode. However, such a non-aqueous electrolyte secondary battery may generate abnormal heat due to factors inside or outside the battery. If the battery temperature becomes abnormally high, thermal runaway occurs, resulting in the risk of the battery igniting or exploding. Therefore, a method for preventing thermal runaway of the battery is required.

JP 2008-226807 A

  Provided is a highly safe non-aqueous electrolyte secondary battery in which thermal runaway is prevented.

  According to the embodiment, a nonaqueous electrolyte secondary battery including an exterior member, an electrode group including a positive electrode and a negative electrode, a nonaqueous electrolyte, and a gas generating member is provided. The gas generating member includes a gas generating agent and an enclosing container that encloses the gas generating agent, and releases gas in the range of 100 to 250 ° C. The gas generating agent includes an alkanolamine solution in which gas is absorbed.

The cross-sectional schematic diagram which shows an example of the nonaqueous electrolyte secondary battery of 1st Embodiment. The expanded sectional view of the A section of FIG. The cross-sectional schematic diagram which shows the modification of the nonaqueous electrolyte secondary battery of 1st Embodiment. The partial notch perspective view of the nonaqueous electrolyte secondary battery of 2nd Embodiment. The external view of the nonaqueous electrolyte secondary battery of 3rd Embodiment. The expansion | deployment perspective view of the battery of FIG. The expansion | deployment perspective view of the electrode group used for the battery of FIG. The expansion | deployment perspective view which shows the 1st modification of the battery of 3rd Embodiment. The expansion | deployment perspective view which shows the 2nd modification of the battery of 3rd Embodiment. The expansion | deployment perspective view which shows the 3rd modification of the battery of 3rd Embodiment. The expansion | deployment perspective view which shows the 4th modification of the battery of 3rd Embodiment. The expansion | deployment perspective view which shows the 5th modification of the battery of 3rd Embodiment.

  Hereinafter, the nonaqueous electrolyte secondary battery of each embodiment will be described with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment, and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram for promoting the explanation of the embodiment and understanding thereof, and its shape, dimensions, ratio, and the like are different from those of an actual apparatus. However, these are considered in the following explanation and known techniques. Thus, the design can be changed as appropriate.

(First embodiment)
FIG. 1 is a cross-sectional view of a flat type nonaqueous electrolyte battery. FIG. 2 is an enlarged cross-sectional view of a part A in FIG. The battery 1 includes an outer bag 2, a flat wound electrode group 3, and a gas generating member 10.

  The exterior bag 2 is a bag-shaped exterior member made of a laminate film. As the laminate film, a multilayer film in which a metal layer is interposed between resin films is used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for weight reduction. For the resin film, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used. The laminate film can be formed into the shape of an exterior member by sealing by heat sealing. The laminate film preferably has a thickness of 0.2 mm or less.

  The wound electrode group 3 is housed in the laminated film-made outer bag 2. As shown in FIG. 2, the wound electrode group 3 is formed by winding a laminate in which the negative electrode 5, the separator 6, the positive electrode 4, and the separator 6 are laminated in this order from the outside in a spiral shape and press-molding.

  The positive electrode 4 includes a positive electrode current collector 4a and a positive electrode layer 4b. The positive electrode layer 4b contains a positive electrode active material. The positive electrode layer 4b is formed on both surfaces of the positive electrode current collector 4a.

  The negative electrode 5 includes a negative electrode current collector 5a and a negative electrode layer 5b. The negative electrode layer 5b contains a negative electrode active material. As shown in FIG. 2, the outermost negative electrode 5 has a configuration in which a negative electrode layer 5b is formed on one surface on the inner surface side of the negative electrode current collector 5a. In the other negative electrode 5, negative electrode layers 5b are formed on both surfaces of the negative electrode current collector 5a.

  As shown in FIG. 2, the positive electrode terminal 7 is connected to the positive electrode current collector 4 a of the positive electrode 4 in the vicinity of the outer peripheral end of the wound electrode group 3. Further, in the vicinity of the outer peripheral end of the wound electrode group 3, the negative electrode terminal 8 is connected to the negative electrode current collector 5 a of the negative electrode 5 of the outermost layer. The positive electrode terminal 7 and the negative electrode terminal 8 are extended to the outside through the opening of the outer bag 2. A non-aqueous electrolyte is further injected into the exterior bag 2. By heat-sealing the opening of the outer bag 2 with the positive electrode terminal 7 and the negative electrode terminal 8 sandwiched therebetween, the wound electrode group 3 and the nonaqueous electrolyte are completely sealed.

  The positive electrode terminal 7 is formed of, for example, a material having electrical stability and conductivity in a range where the potential with respect to the lithium ion metal is 3 V or more and 5 V or less, preferably 3.0 V or more and 4.25 V or less. It is preferably formed from aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu and Si. The positive electrode terminal 7 is preferably formed of the same material as that of the positive electrode current collector 4a in order to reduce the contact resistance with the positive electrode current collector 4a.

  The negative electrode terminal 8 is formed of, for example, a material that is electrochemically stable and has conductivity at the Li occlusion / release potential of the negative electrode active material. It is preferably formed from copper, nickel, stainless steel or aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu and Si. The negative electrode terminal 8 is preferably formed of the same material as the negative electrode current collector 5a in order to reduce the contact resistance with the negative electrode current collector 5a.

  The battery 1 further includes a gas generating member 10 that releases gas at a battery temperature of 100 ° C. or higher and 250 ° C. or lower. The gas generating member 10 includes a sealed container 10a and a gas generating agent 10b sealed in the sealed container 10b. The enclosure 10a is formed of a resin film. The gas generating agent 10b includes an alkanolamine solution that has absorbed gas.

  The gas generating member 10 is disposed in the gap between the outer bag 2 and the wound electrode group 3. The gas released from the gas generating member 10 is preferably carbon dioxide.

  In FIG. 1, the gas generating member 10 has a cylindrical shape, and is installed between the curved portions on both sides of the wound electrode group 3 and the outer bag 2.

  When the battery temperature rises abnormally due to the influence of overcharge or the like and reaches 100 ° C. or higher, gas is released from the gas generating agent 10b. As a result, the sealed container 10 is ruptured, or the fused portion of the sealed container 1 is melted, and the gas is released to the outside of the sealed container 1. Thereby, the pressure inside a battery rises, the fusion | melting of the seal | sticker part of a laminate film peels, and nonaqueous electrolyte solution discharge | releases outside with the gas inside a battery. Thereby, the function of the battery is lost, and thermal runaway can be prevented.

  The gas generating agent 10b includes an alkanolamine solution that has absorbed gas. The gas absorbed in the alkanolamine solution is preferably carbon dioxide. As a method of absorbing gas in the alkanolamine solution, for example, bubbling can be used.

  The gas generating member 10 can contain water together with the alkanolamine solution. By adding water to the alkanolamine solution, absorption of gases such as carbon dioxide can be made easier.

  Examples of alkanolamines include monoethanolamine (MEA) and primary alkanolamines such as 2-amino-2-methyl-1-propanol (AMP), 2-methylaminoethanol (MAE), 2-ethyl Secondary alkanolamines such as aminoethanol (EAE), diethanolamine (DEA), 2- (propylamino) ethanol (PAE), and diisopropanolamine (DIPA), N-methyldiethanolamine (MEDA), N-ethyldiethanolamine Tertiary alkanolamines such as (EDEA), 2-dimethylaminoethanol (DMAE), and 2-diethylaminoethanol (DEAE) are included. These alkanolamines can be used alone or in combination of two or more.

  The alkanolamine is preferably selected from monoethanolamine, 2-ethylaminoethanol, and 2-dimethylaminoethanol.

  By using an alkanolamine solution in which gas is absorbed as the gas generating agent 10b, the gas can be released at a temperature of 100 ° C. or higher and 250 ° C. or lower. That is, since gas is not generated below 100 ° C., there is no influence during normal use of the battery. Further, since the gas can be generated at a desired temperature of 250 ° C. or lower, it is possible to prevent the battery temperature from rising excessively. The temperature at which the gas is released can be adjusted by changing the type and combination of alkanolamines. Here, the temperature at which the gas is released refers to the battery temperature, and may be the temperature at the center of the surface of the battery outer can. The temperature can be measured using, for example, a thermocouple.

The temperature at which the gas generating member 10 releases the gas is preferably 120 to 200 ° C.

  The resin forming the enclosure 10a preferably has a melting point higher than the temperature at which the gas generating agent 10b releases the gas. Examples of such resins include polyimide, polyamide, epoxy, acrylic, urethane, phenol. The resin forming the enclosure 10a is preferably insulating. When the resin is not insulative, it is arranged so as not to contact the battery terminals.

  Note that when the gas is released from the gas generating member 10, the fusion of the seal portion of the outer bag 2 is peeled off, and when the nonaqueous electrolyte is released to the outside, even if the internal resistance of the battery increases, It is possible that the battery function is not completely lost. In this case, the battery temperature further increases, and thermal runaway may occur. However, since alkanolamine degrades aluminum, it can degrade the current collector and increase battery resistance. Thereby, an electric current can be interrupted | blocked and a battery can be deactivated. Therefore, further temperature rise of the battery can be suppressed and thermal runaway can be prevented.

  Since tertiary alkanolamine has a high carbon dioxide release property and has a strong tendency to deteriorate aluminum, it is more preferable to use tertiary alkanolamine as a gas generating agent.

  According to the present embodiment, the gas generating agent 10b is enclosed in the enclosure 10a, thereby preventing factors other than temperature from affecting the gas generating agent 10b. Further, since the resin forming the sealed container 10a has a melting point higher than the temperature at which the gas generating agent 10b releases the gas, the gas generating agent 10b is sealed before the gas is released from the gas generating agent 10b. Can be prevented from leaking out.

  FIG. 3 shows a modification of the battery according to the first embodiment. This modification has the same configuration as the battery 1 shown in FIG. 1 except that the shape and installation position of the gas generating member 10 are different.

  In this modification, the gas generating member 10 has a sheet shape and is disposed between the flat surface of the wound electrode group 3 and the flat surface of the outer bag 2. According to such a configuration, the gas generating member 10 can be easily installed. Further, the gas discharge area is wide, and gas can be released quickly. Moreover, since the surface area is large, it is possible to make the reaction to the temperature rise sensitive.

  In FIG. 3, the sheet-like gas generating member 10 is installed only on one of the flat surfaces of the wound electrode group 3, but another gas generating member 10 may be installed on the other flat surface.

  According to this embodiment, by providing the gas generating member 10 that releases gas in the range of 100 to 250 ° C., no gas is generated below 100 ° C., and there is no influence during normal use of the battery. Further, gas can be generated at a desired temperature of 250 ° C. or lower. Furthermore, since the function of the battery can be deactivated and the temperature rise can be suppressed, thermal runaway can be prevented. Therefore, according to the present embodiment, it is possible to provide a nonaqueous electrolyte secondary battery excellent in safety.

  Since the nonaqueous electrolyte secondary battery of this embodiment is excellent in safety, it is particularly suitably used as a vehicle battery.

  Note that the electrode group provided in the battery is not limited to the wound electrode group, and a stacked electrode group in which the separator is folded into ninety nines and the positive electrode and the negative electrode are alternately arranged at the folded portion may be used.

(Second Embodiment)
The nonaqueous electrolyte secondary battery of the second embodiment is shown in FIG. The battery 20 of this embodiment includes an outer can 21, a flat wound electrode group 22, a positive electrode lead 23, a negative electrode lead 24, a lid body 25, a positive electrode terminal 26, a negative electrode terminal 27, a rupture 28, and a gas generating member 29. Prepare.

  The outer can 21 is a bottomed rectangular cylinder made of metal. The outer can 21 is preferably formed from a metal plate having a thickness of 0.5 mm or less, and more preferably formed from a metal plate having a thickness of 0.2 mm or less.

  The outer can 21 is made of aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc and silicon. Aluminum or an aluminum alloy preferably has a transition metal content such as iron, copper, nickel and chromium of 100 ppm or less in order to dramatically improve long-term reliability and heat dissipation in a high temperature environment. .

  The average grain size of aluminum or aluminum alloy forming the outer can 21 is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 5 μm or less. When the average crystal grain size is 50 μm or less, the strength increases dramatically, and the outer can 21 can be made thinner. As a result, a non-aqueous electrolyte battery that is lightweight, has high output, and has excellent long-term reliability can be realized. Such a nonaqueous electrolyte battery is particularly suitably used for in-vehicle use.

  The wound electrode group 22 is accommodated in the outer can 21. The wound electrode group 22 may have the same configuration as the wound electrode group used in the first embodiment. A positive electrode lead 23 is connected to the positive electrode current collector. A negative electrode lead 24 is connected to the negative electrode current collector.

  A metal rectangular lid 25 is attached to the opening of the outer can 21. For example, a plate-like positive electrode terminal 26 is inserted into the lid 25. In the vicinity of the end portion of the positive electrode terminal 26 located in the outer can 21, a positive electrode lead 23 is joined by welding, for example. For example, the plate-like negative electrode terminal 27 is inserted into the lid 25 by a hermetic seal with a glass material 30 interposed, for example. Near the end of the negative terminal 27 located in the outer can 21, a negative lead 24 is joined by welding, for example.

  The lid 25 is provided with a rupture 28 for releasing the pressure inside the battery. The rupture 28 is a rectangular recess. A cross-shaped groove is provided on the bottom surface of the recess. The groove is thin. The shape of the safety valve is not limited to this, and may be any shape as long as it can be broken by the pressure increase in the container to release the gas to the outside.

  A nonaqueous electrolyte is further accommodated in the outer can 21.

  Further, the battery 20 includes a gas generating member 29. The gas generating member 29 is the same as the gas generating member of the first embodiment except that the shape is different.

  In the present embodiment, the gas generating member 29 has a rectangular parallelepiped shape and is disposed between the wound electrode group 22 and the lid body 25.

  When the battery temperature is in the range of 100 to 250 ° C., the gas is released from the gas generating member 10 to increase the pressure inside the battery. As a result, the rupture 28 is opened, and the non-aqueous electrolyte is discharged to the outside together with the gas inside the battery. This deactivates the battery function.

  According to this embodiment, by providing the gas generating member 29 that releases gas in the range of 100 to 250 ° C., no gas is generated below 100 ° C., and there is no influence during normal use of the battery. Further, gas can be generated at a desired temperature of 250 ° C. or lower. Furthermore, since the function of the battery can be deactivated and the temperature rise can be suppressed, thermal runaway can be prevented. Therefore, according to the present embodiment, it is possible to provide a nonaqueous electrolyte secondary battery excellent in safety. Since the nonaqueous electrolyte secondary battery of this embodiment is excellent in safety, it is particularly suitably used as a vehicle battery.

  The outer can is not limited to the above example, and may be any shape such as a flat type, a square type, a cylindrical type, a coin type, a button type, a sheet type, and a laminated type.

(Third embodiment)
The nonaqueous electrolyte secondary battery of 3rd Embodiment is demonstrated with reference to FIGS.

  The battery 31 of the present embodiment is a sealed square nonaqueous electrolyte secondary battery. The battery 31 includes an outer can 32, a flat wound electrode group 33, a positive electrode lead 34, a negative electrode lead 35, a lid body 36, a rupture 45, and a gas generating member 47.

  The outer can 32 has a bottomed rectangular tube shape, and is formed of a metal such as aluminum, an aluminum alloy, iron, or stainless steel, for example. The wound electrode group 33 is accommodated in the outer can 32 so as to be directed in a direction perpendicular to the winding axis.

  The wound electrode group 33 includes a positive electrode 39 and a negative electrode 40. The wound electrode group 33 has a positive current collecting tab 39a at one end and a negative current collecting tab 40a at the other end. FIG. 7 shows a development view of the wound electrode group 33. The positive electrode 39 includes a strip-shaped positive electrode current collector 39c made of, for example, metal foil, and a positive electrode active material layer 39b formed on one or both surfaces thereof. The positive electrode active material layer 39b is formed such that a region having a constant width (non-coated portion) remains on one end side along the longitudinal direction of the belt-shaped positive electrode current collector 39c. This uncoated portion is a portion where the positive electrode current collector 39c is exposed, and becomes a positive electrode current collecting tab 39a. Similarly, the negative electrode 40 includes a strip-shaped negative electrode current collector 40c made of, for example, a metal foil, and a negative electrode active material layer 40b formed on one or both surfaces thereof. The negative electrode active material layer 40b is formed in the strip-shaped negative electrode current collector 40c so that a region having a constant width (uncoated portion) remains on the other end side (the opposite side to one end of the positive electrode 39) along the longitudinal direction. . This uncoated portion is a portion where the negative electrode current collector 40c is exposed, and becomes a negative electrode current collecting tab 40a.

  The positive electrode 39 and the negative electrode 40 are alternately stacked with strip-shaped separators 41a and 41b. At this time, the positive electrode current collecting tab 39a is disposed on one end side in the winding axis direction, and the negative electrode current collecting tab 40a is disposed on the other end side. The separator 41 a stacked under the positive electrode 39 is arranged so that one end along the longitudinal direction is located inside the end of the positive electrode 39 on the positive electrode current collecting tab side. Thereby, the positive electrode current collection tab 39a protrudes from the positive electrode active material layer 39b, the negative electrode active material layer 40b, and the separator 41a which constitute the wound electrode group 33. In addition, the separator 41 a is arranged so that the other end along the longitudinal direction is located outside the other end of the positive electrode 39. The separator 41b sandwiched between the positive electrode 39 and the negative electrode 40 is disposed such that one end along the longitudinal direction is located inside the end of the negative electrode 40 on the negative electrode current collecting tab side. Thereby, the negative electrode current collection tab 40a protrudes from the positive electrode active material layer 39b, the negative electrode active material layer 40b, and the separator 41b which constitute the wound electrode group 33. In addition, the separator 41 b is arranged so that the other end along the longitudinal direction is located outside the other end of the negative electrode 40.

  By winding the stacked separator 41a, positive electrode 39, separator 41b, and negative electrode 40, and then pressing, the flat wound electrode group 33 is formed.

  The wound electrode group 33 is wound with an insulating tape 44. The insulating tape 44 covers a region other than the outermost current collecting tab of the wound electrode group 33 and makes the region insulating. The number of turns of the insulating tape 44 may be one or more.

  A metal lid 36 is secured to the opening of the outer can 32 by welding, for example. The positive terminal 37 and the negative terminal 38 are caulked and fixed to the lid body 36 via insulating gaskets 42 and 43, respectively. The positive terminal 37 and the negative terminal 38 protrude from the back surface of the lid 36 toward the inside of the outer can 32. The fixing method of the positive electrode terminal 37 and the negative electrode terminal 38 may be a hermetic seal using glass in addition to caulking and fixing with the insulating gaskets 42 and 43.

  The positive lead 34 has a plate-like connection plate which is a connection portion connected to the positive terminal 37, a through hole opened in the connection plate, and a bifurcated branch from the connection plate. The first and second sandwiching strips are sandwiching portions extending in a direction perpendicular to the first and second sandwiching strips. The connection plate is brought into contact with the back surface of the lid body 36 through an insulating sheet (not shown) at the location of the positive electrode terminal 37. A positive terminal 37 protruding from the back surface of the lid 36 caulks and fixes the through hole.

  The first and second sandwiching strips of the positive electrode lead 34 sandwich the positive current collecting tab 39a from a direction perpendicular to the winding axis, and the first and second sandwiching strips and the positive current collecting tab 39a are, for example, welded. Be joined.

  Similarly, the negative electrode lead 35 is branched into a plate-shaped connection plate which is a connection part connected to the negative electrode terminal 38, a through hole opened in the connection plate, and the connection plate. It has the 1st, 2nd clamping strip which is a clamping part extended toward the orthogonal | vertical direction with respect to the winding axis | shaft. The connection plate is brought into contact with the back surface of the lid body 36 through an insulating sheet (not shown) at the position of the negative electrode terminal 38. A negative terminal 38 protruding from the back surface of the lid 36 caulks and fixes the through hole.

  The first and second sandwiching strips of the negative electrode lead 35 sandwich the negative current collecting tab 40a from a direction perpendicular to the winding axis, and the first and second sandwiching strips and the negative current collecting tab 40a are welded, for example, by welding. Be joined.

  In addition, said welding may be implemented by methods, such as resistance welding and ultrasonic welding.

  The lid body 36 is made of, for example, a metal such as aluminum, an aluminum alloy, iron, or stainless steel. The lid 36 and the outer can 32 are preferably formed from the same type of metal.

  After the lid 36 is fixed to the outer can 32, an electrolytic solution (not shown) is injected from an inlet 46 provided in the lid 36. After the injection, the flat electrode group 33 is impregnated with the electrolytic solution.

  The battery 31 includes two gas generation members 47 having a rectangular parallelepiped shape. The gas generating member 47 is the same as the gas generating member of the first embodiment except that the shape and size are different.

  In the present embodiment, one of the gas generating members 47 is disposed in a gap surrounded by the upper end of the positive electrode current collecting tab 39a, the lid body 36, and the first and second sandwich strips of the positive electrode lead 34. The other gas generating member 47 is disposed in the gap surrounded by the upper end of the negative electrode current collecting tab 40 a, the lid 36, and the first and second sandwich strips of the negative electrode lead 35.

  The gas release member 47 is not limited to the above example, and can be installed in any gap in the outer can 32. Further, the gas generating member 47 may have an arbitrary shape such as a rectangular parallelepiped shape, a columnar shape, a rod shape, a spherical shape, or a sheet shape. The shape and size can be appropriately selected according to the shape of the gap between the exterior member and the electrode group. Further, the number of gas generating members 47 may be one or two or more.

  Below, the battery of the some modification which changed the shape and installation position of the gas generation member 47 is shown. The batteries of these modified examples have the same configuration as the battery 31 shown in FIGS. 5 and 6 except that the shape, size, and installation position of the gas generating member 47 are different.

  In the first modified example shown in FIG. 8, two gas generating members 47 are used. The gas generating member 47 has a rectangular parallelepiped shape, and includes a gap between the lower end of the positive electrode current collecting tab 39a and the bottom surface of the outer can 32, and a space between the lower end of the negative electrode current collecting tab 40a and the lower surface of the outer can 32. Are disposed in the gaps.

  In the second modified example shown in FIG. 9, one gas generating member 47 is used. The gas generating member 47 is thin and has an elongated rectangular parallelepiped shape, and is disposed in the gap between the lower end of the wound electrode group 33 and the bottom surface of the outer can 32.

  In the third modification shown in FIG. 10, one gas generating member 47 is used. The gas generating member 47 is thin and has a relatively short rectangular parallelepiped shape, and is disposed in the gap between the upper end of the wound electrode group 33 and the lid 36. The gas generating member 47 may be disposed immediately below the rupture 45. Note that the gas generating member 47 is not disposed immediately below the inlet 46 in order not to block the inlet 46.

  In the fourth modified example shown in FIG. 11, two gas generating members 47 are used. The gas generating member 47 is thin and has an elongated rectangular parallelepiped shape.

  Since the positive electrode current collecting tab 39a is wound, the positive electrode current collecting tab 39a forms a hollow elliptical bundle in which a plurality of current collecting tabs are overlapped, and has a gap at the center of the ellipse. Similarly, the negative electrode current collecting tab 40a also forms a hollow elliptical bundle in which a plurality of current collecting tabs are overlapped, and has a gap at the center of the ellipse.

  One of the gas generating members 47 is disposed in the central gap of the hollow oblong bundle of the positive electrode current collecting tab 39a. The other gas generating member 47 is disposed in the center gap of the hollow oblong bundle of the negative electrode current collecting tab 40a.

  In the fifth modified example shown in FIG. 12, four gas generating members 47 are used. The gas generating member 47 is thin and has an elongated rectangular parallelepiped shape. The four gas generating members 47 are sandwiched in the gaps between the first and second sandwich strips of the positive electrode lead 34 and the first and second sandwich strips of the negative electrode lead 35 and the outer can 32, respectively. It arrange | positions so that it may contact | abut to a strip. In FIG. 12, only two gas generating members 47 on the front side of the battery are shown, and the two gas generating members arranged on the opposite side are not shown.

  As described above, the gas generating member 47 can be disposed in any gap inside the outer can 32. According to this embodiment, by providing the gas generating member 47 that releases gas in the range of 100 to 250 ° C., no gas is generated below 100 ° C., and there is no influence during normal use of the battery. Further, gas can be generated at a desired temperature of 250 ° C. or lower. Furthermore, since the function of the battery can be deactivated and the temperature rise can be suppressed, thermal runaway can be prevented. Therefore, according to the present embodiment, it is possible to provide a nonaqueous electrolyte secondary battery excellent in safety. Since the nonaqueous electrolyte secondary battery of this embodiment is excellent in safety, it is particularly suitably used as a vehicle battery.

(Positive electrode)
The positive electrode used for the batteries of the first to third embodiments will be described.
The positive electrode includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material layer is formed on one side or both sides of the positive electrode current collector.

  An aluminum foil or an aluminum alloy foil is preferably used for the positive electrode current collector. The average crystal grain size is preferably 50 μm or less, more preferably 30 μm or less, and still more preferably 5 μm or less. A current collector made of an aluminum foil or aluminum alloy foil having such an average crystal grain size has dramatically increased strength. Therefore, it is possible to increase the density of the positive electrode using a high press pressure. As a result, the battery capacity can be increased. The average crystal grain size (diameter) of an aluminum foil or aluminum alloy foil is influenced by many factors in the manufacturing process, such as material composition, impurities, processing conditions, heat treatment history, and annealing heating conditions. By adjusting these factors, an aluminum foil or an aluminum alloy foil having a desired diameter is obtained.

  The thickness of the aluminum foil and the aluminum alloy foil is preferably 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% or more. The aluminum alloy preferably contains elements such as magnesium, zinc and silicon. On the other hand, the content of transition metals such as iron, copper, nickel and chromium is preferably 1% or less.

Various oxides, sulfides and polymers can be used as the positive electrode active material. Examples of oxides include manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (eg Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide (eg Li _x NiO _2), lithium cobalt composite oxide _(Li x _CoO 2), lithium nickel cobalt composite oxide (e.g., _{LiNi 1-y Co y O 2} ), lithium manganese cobalt composite oxides (e.g. LiMn _y Co _1-y O ₂ ), spinel type lithium manganese nickel composite oxide (Li _x Mn _{2 -y} Ni _y O ₄ ), lithium phosphorus oxide having an olivine structure (Li _x FePO ₄ , Li _x Fe _1-y Mn _y PO ₄ , Li such _x CoPO _4), iron sulfate _{(Fe 2 (SO 4) 3} ), vanadium oxide (e.g. ₂ O ₅₎ is included. In addition, it is preferable that x and y in the above formula are in the range of 0-1. Further, the composition is Li _a Ni _b Co _c Mn _d O ₂ (however, the molar ratios a, b, c and d are 0 ≦ a ≦ 1.1, 0.1 ≦ b ≦ 0.5, 0 ≦ c ≦ It is also possible to use a lithium nickel cobalt manganese composite oxide represented by 0.9 and 0.1 ≦ d ≦ 0.5.

  In addition, conductive polymer materials such as polyaniline and polypyrrole, disulfide polymer materials, organic materials such as sulfur (S) and carbon fluoride, and inorganic materials can also be used as the positive electrode active material.

  As the positive electrode active material, the above compounds can be used alone or in combination.

Lithium manganese composite oxide (Li _x Mn ₂ O ₄ ), lithium nickel composite oxide (Li _x NiO ₂ ), lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel cobalt composite oxide (Li _x Ni _{1− y} Co _y O _2), spinel type lithium-manganese-nickel composite oxide _{(Li x Mn 2-y Ni} y O 4), lithium manganese cobalt composite oxide _{(Li x Mn y Co 1-} y O 2) and lithium phosphate An oxide capable of obtaining a high battery voltage, such as iron (Li _x FePO ₄ ), is more preferably used. In addition, it is preferable that x and y in the above formula are in the range of 0-1.

  In addition, a battery in which nickel is contained in the positive electrode active material has a high temperature rise rate and tends to run out of heat. Therefore, in the battery in which nickel is included in the positive electrode active material, the effect of the present embodiment can be obtained more remarkably.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide, and polyamide.

  Examples of the conductive agent include acetylene black, carbon black, graphite, carbon fiber, carbon nanotube, and fullerene.

  The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 18% by weight of the conductive agent, and 2 to 17% by weight of the binder.

  The positive electrode can be produced, for example, by the following method. First, a positive electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of the positive electrode current collector and dried to produce a positive electrode active material layer. Then press. Alternatively, the positive electrode active material, the conductive agent, and the binder can be formed in a pellet shape and used as the positive electrode active material layer. The density of the positive electrode active material layer is preferably 3 g / cc or more.

(Negative electrode)
The negative electrode used for the batteries of the first to third embodiments will be described.
The negative electrode includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material layer is formed on one side or both sides of the negative electrode current collector.

  For the negative electrode current collector, an aluminum foil or an aluminum alloy foil that is electrochemically stable in a potential range nobler than 1.0 V is preferably used.

  The negative electrode active material preferably has a Li storage potential of 0.4 V (vs. Li / Li +) or more. This is because a negative electrode active material (eg, graphite, lithium metal, etc.) that occludes lithium at a potential lower than 0.4 V (vs. Li / Li +) This is because metallic lithium is deposited and grows in the form of dendrites.

  Negative electrode active materials capable of occluding lithium at 0.4 to 3 V (vs. Li / Li +) include metal oxides, metal sulfides, metal nitrides, and alloys.

Examples of metal oxides include titanium-containing metal composite oxides, tin-based oxides such as SnB _0.4 P _0.6 O _3.1 and SnSiO ₃ , silicon-based oxides such as SiO, and WO ₃ is included. Among these, titanium-containing metal composite oxides are preferably used.

  Examples of the titanium-containing metal composite oxide include lithium titanium oxide and lithium titanium composite oxide in which a part of constituent elements of the lithium titanium oxide is replaced with a different element. In addition, a titanium-based oxide that does not contain lithium and can be stored by charging a battery can be used during oxide synthesis.

Examples of the lithium titanium oxide include lithium titanate having a spinel structure (for example, Li _{4 + x} Ti ₅ O ₁₂ ) and ramsteride type lithium titanate (for example, Li _{2 + y} Ti ₃ O ₇ ). In the above equation, x changes in the range of 0 ≦ x ≦ 3 due to charge / discharge, and y changes in the range of 0 ≦ y ≦ 3 due to charge / discharge. On the other hand, the molar ratio of oxygen is formal, and its value changes due to the influence of oxygen non-stoichiometry and the like.

Examples of titanium-based oxides include TiO ₂ and metal composite oxides containing at least one element selected from the group consisting of Ti and P, V, Sn, Cu, Ni, Co, and Fe. .

TiO ₂ is preferably anatase type. Moreover, it is preferable that it is a low crystalline thing heat-processed at the temperature of 300-500 degreeC.

Examples of the metal composite oxide containing at least one element selected from the group consisting of Ti and P, V, Sn, Cu, Ni, Co, and Fe include TiO ₂ —P ₂ O ₅ , TiO ₂ —V. ₂ O ₅ , TiO ₂ —P ₂ O ₅ —SnO ₂ , and TiO ₂ —P ₂ O ₅ —MeO (Me is at least one element selected from the group consisting of Cu, Ni, Co and Fe). It is. This metal composite oxide preferably has a microstructure in which a crystalline phase and an amorphous phase coexist, or has a microstructure in which an amorphous phase is present alone. By using the metal composite oxide having a microstructure, the cycle performance of the battery can be greatly improved.

  As the negative electrode active material, it is more preferable to use lithium titanium oxide or a metal composite oxide containing at least one element selected from the group consisting of Ti and P, V, Sn, Cu, Ni, Co and Fe, It is particularly preferable to use lithium titanium oxide having a spinel structure.

Examples of metal sulfides include titanium sulfides such as TiS ₂ , molybdenum sulfides such as MoS ₂ , and irons such as FeS, FeS ₂ and Li _x FeS ₂ (0 ≦ x ≦ 4). System sulfide is included.

Examples of the metal nitride include lithium-based nitride (for example, (Li, Me) ₃ N, where Me represents a transition metal element).

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide, and polyamide.

  Examples of the conductive agent include acetylene black, carbon black, graphite, carbon fiber, carbon nanotube, and fullerene.

  The mixing ratio of the negative electrode active material, the conductive agent, and the binder is preferably 70 to 96% by weight of the negative electrode active material, 2 to 28% by weight of the conductive agent, and 2 to 28% by weight of the binder. By blending the conductive agent at a ratio of 2% by weight or more, excellent large current characteristics due to high current collecting performance can be obtained. By blending the binder at a ratio of 2% by weight or more, the binding property between the negative electrode layer and the negative electrode current collector can be secured, and the cycle characteristics can be improved. On the other hand, from the viewpoint of increasing the capacity, the negative electrode conductive agent and the binder are each preferably 28% by weight or less.

  The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a negative electrode conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of the negative electrode current collector and dried to produce a negative electrode active material layer. Then press. Alternatively, the negative electrode active material, the negative electrode conductive agent, and the binder may be formed in a pellet shape and used as the negative electrode active material layer. The density of the negative electrode active material layer is preferably 2 g / cc or more.

(Nonaqueous electrolyte)
The nonaqueous electrolyte used for the batteries of the first to third embodiments will be described.
As the non-aqueous electrolyte, a liquid non-aqueous electrolyte or a gel non-aqueous electrolyte can be used. The liquid non-aqueous electrolyte can be prepared by dissolving the electrolyte in a non-aqueous solvent. The gel-like nonaqueous electrolyte can be prepared by combining a liquid electrolyte and a polymer material.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), trifluorometa Lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ) and bistrifluoromethylsulfonylimitolithium [LiN (CF ₃ SO ₂ ) ₂ ] are included. These electrolytes can be used alone or in combination of two or more.

  The electrolyte is preferably dissolved in a concentration range of 0.5 to 2.5 mol / L with respect to the organic solvent.

  Examples of non-aqueous solvents are ethylene carbonate (EC), propylene carbonate (PC), cyclic carbonates such as vinylene carbonate (VC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC). Chain carbonates, cyclic ethers such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), chain ethers such as dimethoxyethane (DME), γ-butyrolactone (BL) acetonitrile (AN), and sulfolane (SL) ) Is included. These organic solvents can be used alone or in combination of two or more.

  Examples of the polymer material used for the gel-like nonaqueous electrolyte include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

(Separator)
The separator used for the batteries of the first to third embodiments will be described.
As the separator, a porous film, a woven fabric, a non-woven fabric, and a combination thereof can be used. Examples of materials that form the separator include polyethylene, polypropylene, cellulose, and polyvinylidene fluoride (PVdF). A porous film made of polyethylene or polypropylene is more preferable because it melts at a constant temperature and can block the current. By using such a film, the safety of the battery can be improved.

  Embodiments will be described below using examples, but the present invention is not limited to these examples.

Example 1
<Preparation of positive electrode>
As the positive electrode active material, 80% by weight of lithium nickel manganese cobalt oxide (LiNi ₅ Co ₂ Mn ₃ O ₂ ) powder and 20% by weight of lithium cobalt oxide (LiCoO 2) powder were used. 93% by weight of the positive electrode active material, 3.33% by weight of acetylene black, 1.67% by weight of graphite, and 2% by weight of polyvinylidene fluoride (PVdF) were mixed, and this was mixed with N-methylpyrrolidone (NMP). Were added and mixed to prepare a slurry. This slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm and an average crystal particle diameter of 30 μm, and then dried and pressed. This produced the positive electrode whose electrode density is 3.15 g / cm < ³ >.

<Production of negative electrode>
As the negative electrode active material, lithium titanate (Li ₄ Ti ₅ O ₁₂ ) having a Li storage potential of 1.55 V (vs. Li / Li ⁺ ) and having a spinel structure was used. The negative electrode active material is 96% by weight, the conductive material is graphite by 4% by weight, and polyvinylidene fluoride (PVdF) is mixed by 2% by weight, and N-methylpyrrolidone (NMP) is added and mixed to the slurry. Prepared. This slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm and an average crystal particle diameter of 30 μm, and then dried and pressed. This produced the negative electrode with an electrode density of 2.2 g / cm < ³ >.

<Production of electrode group>
A positive electrode, a separator made of a polyethylene porous film having a thickness of 12 μm, a negative electrode, and a separator were laminated in this order, and then wound in a spiral shape. This was heated and pressed at about 90 ° C. to produce an electrode group. The obtained electrode group was housed in a rectangular metal can of the type shown in FIG. 4 and dried in a vacuum at about 80 ° C. for 24 hours.

<Production of gas generating member>
A film made of polyimide was formed into a bag shape to produce a gas generating agent-sealed container. As a gas generating agent, monoethanolamine (MEA) in which carbon dioxide was absorbed was used. 10 cc of a gas generating agent was injected into the sealed container and sealed by heat sealing to obtain a gas generating member.

<Preparation of liquid nonaqueous electrolyte>
To a mixed solvent of propylene carbonate (PC) and diethyl carbonate (DEC) (volume ratio 30:70), 1.0 mol / L of lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte, lithium tetrafluoroborate ( LiBF ₄ ) was dissolved at a concentration of 0.5 mol / L. Thereby, a liquid non-aqueous electrolyte was obtained.

<Preparation of nonaqueous electrolyte secondary battery>
The space in the square metal can containing the electrode group was about 50 cc. A gas generating member was placed on the electrode group housed in the rectangular metal can, and the gas generating member was disposed in the gap between the electrode group and the lid. Next, a liquid non-aqueous electrolyte was poured into a metal can and then completely sealed. Thereby, a non-aqueous electrolyte secondary battery was produced.

(Example 2)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that 5 cc of MEA having absorbed carbon dioxide was used as the gas generating agent.

(Example 3)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 8 cc of MEA and 2 cc of water and used as a gas generating agent.

Example 4
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of MEA 6.7 cc and 1.7 cc of water and used as a gas generating agent.

(Example 5)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 5 cc of MEA and 5 cc of water and used as a gas generating agent.

(Example 6)
A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1 except that 10 cc of 2-ethylaminoethanol (DEA) having absorbed carbon dioxide was used as the gas generating agent.

(Example 7)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that 5 cc of DEA having absorbed carbon dioxide was used as a gas generating agent.

(Example 8)
A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 8 cc of DEA and 2 cc of water and used as a gas generating agent.

Example 9
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 6.7 cc of DEA and 1.7 cc of water and used as a gas generating agent.

(Example 10)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 5 cc of DEA and 5 cc of water and used as a gas generating agent.

(Example 11)
A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1 except that 10 cc of 2-dimethylaminoethanol (DMAE) having absorbed carbon dioxide was used as the gas generating agent.

(Example 12)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that 5 cc of DMAE having absorbed carbon dioxide was used as the gas generating agent.

(Example 13)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 8 cc of DMAE and 2 cc of water and used as a gas generating agent.

(Example 14)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of DMAE 6.7 cc and 1.7 cc of water and used as a gas generating agent.

(Example 15)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 5 cc of DMAE and 5 cc of water and used as a gas generating agent.

(Example 16)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 5 cc of MEA and 5 cc of DEA and used as a gas generating agent.

(Example 17)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 5 cc of MEA and 5 cc of DMAE and used as a gas generating agent.

(Example 18)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that carbon dioxide was absorbed into a mixture of 5 cc DEA and 5 cc DMAE and used as a gas generating agent.

(Comparative example)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the gas generating member was not used.

(Overcharge test)
An overcharge test was performed using the batteries of Examples 1 to 18 and the comparative example. The overcharge test was conducted by constant current charging at a 1C rate. The temperature at which the rupture was released and the maximum battery temperature were measured. The battery temperature was measured with a thermocouple at the center position on the surface of the metal can. The results are shown in Table 1.

  As shown in Table 1, in each of the batteries of Examples 1 to 18, the rupture was released at a lower temperature than the battery of the comparative example that did not use the gas generating member. Moreover, the maximum temperature of the battery was significantly lower than that of the comparative example. From this, it was shown that a highly safe battery can be provided by using a gas generating member.

  Moreover, it was shown that the opening temperature of the rupture can be adjusted by changing the type and composition of the gas generating agent. Moreover, it was shown that even if water is contained in the gas generating agent, it does not affect the opening temperature of the rupture.

  In addition, when the battery characteristics (discharge capacity, cycle characteristics, etc.) of the batteries of Examples 1 to 18 and the comparative example were confirmed, no significant difference was observed. Therefore, it was confirmed that the battery characteristics were not affected even when the gas generating member was installed.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1,20,31 ... Non-aqueous electrolyte secondary battery, 2 ... Exterior bag, 3, 22, 33 ... Winding electrode group 10, 29, 47 ... Gas generating member, 10a, 29a, 47a ... Enclosed container, 10b, 29b, 47b ... gas generating agent, 7 ... positive electrode terminal, 8 ... negative electrode terminal, 21, 32 ... outer can, 23, 34 ... positive electrode lead, 24, 35 ... negative electrode lead, 28, 45 ... rupture.

Claims (5)

An exterior member;
An electrode group including a positive electrode and a negative electrode;
A non-aqueous electrolyte,
A gas generating member that includes a gas generating agent and an enclosure that encloses the gas generating agent, and that releases gas in a range of 100 to 250 ° C;
With
The non-aqueous electrolyte secondary battery, wherein the gas generating agent includes an alkanolamine solution in which gas is absorbed.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the gas generating member is disposed in a gap between the exterior member and the electrode group.   The non-aqueous electrolyte secondary battery according to claim 2, wherein the alkanolamine is at least one selected from monoethanolamine, 2-ethylaminoethanol, and 2-dimethylaminoethanol.   The nonaqueous electrolyte secondary battery according to claim 2 or 3, wherein the gas released from the gas generating member is carbon dioxide.   The non-aqueous electrolyte secondary battery according to any one of claims 2 to 3, wherein the positive electrode includes a lithium nickel-containing oxide.

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