JP5224336B2 - Film exterior electrochemical device - Google Patents

Description

  The present invention relates to a film-clad electrochemical device in which an electrochemical device element is thermally fused and sealed by a film-clad body.

  Today, as an electrochemical device such as a secondary battery or an electric double layer capacitor, a battery element in which a positive electrode plate and a negative electrode plate are alternately stacked or wound via a separator is surrounded by an outer casing together with an electrolyte. An electrolyte secondary battery is used as a power source for portable devices and electric vehicles. A nonaqueous electrolyte secondary battery is a nonaqueous electrolyte battery in which a separator is interposed between a positive electrode containing an active material such as lithium cobalt oxide or lithium manganese oxide and a negative electrode containing a carbon-based material such as graphite. The thing of the structure accommodated in the metal can with the electrolyte solution is known. Here, an electrolyte solution containing a non-aqueous solvent having a low viscosity and a low boiling point is known as a non-aqueous electrolyte solution (for example, Patent Document 1).

  In the above example, a box-shaped exterior body is used. However, the exterior body used as a power source for portable devices, electric vehicles, and the like is strongly required to be lightweight and thin.

  Therefore, the exterior body can be further reduced in weight and thickness in place of conventional metal cans that are limited in weight and thickness, and can have a free shape compared to metal cans. As described above, a metal thin film or a laminate film obtained by laminating a metal thin film and a heat-fusible resin film has come to be used.

  A typical example of the laminate film is a three-layer laminate film in which resin films such as polypropylene and nylon are laminated on both surfaces of an aluminum thin film that is a metal thin film.

  In a film exterior body using a laminate film as the exterior body, an electrochemical device element in which a positive electrode and a negative electrode are laminated via a separator is surrounded by the film exterior body, and a peripheral portion of the film exterior body is heat-sealed hermetically. Has been. Furthermore, in order to pull out the positive electrode and the negative electrode of the electrochemical device element to the outside of the film outer package, one end is connected to the positive electrode or the negative electrode, and the other end is pulled out of the film outer package and the negative electrode lead terminal and the negative electrode lead Terminals are provided. As the separator, a porous film formed using a thermoplastic resin such as polyolefin is generally used (for example, Patent Document 2).

  However, a film-clad battery using a non-aqueous solvent electrolyte solution having a low viscosity and a low boiling point consumes the electrolyte solution due to the action of electrochemical or volatilization as the charge / discharge cycle progresses, and the cell exterior cell is caused by gas generation. There is a problem that swelling and deterioration of battery capacity occur.

  In addition, in the electrode group formed by winding the strip-shaped positive electrode, the negative electrode, and the separator, the width of the strip-shaped positive electrode, the negative electrode, and the separator is set such that the positive electrode width <the negative electrode width <the separator width, thereby preventing the discharge capacity against vibration and dropping. There is a flat non-aqueous electrolyte secondary battery that prevents deterioration, leakage, breakage, etc., and is disclosed in Patent Document 3, for example.

  Further, in a wound electrode body formed by winding a belt-like positive electrode, a negative electrode, and a separator, each width of the belt-like positive electrode, the negative electrode, and the separator is set such that positive electrode width <negative electrode width <separator width, There is a wound type non-aqueous electrolyte secondary battery in which a gap is provided in the center, which is disclosed in Patent Document 4, for example.

JP-A-4-14769 JP 2002-110233 A JP 2004-342478 A JP 2001-229980 A

  When the above means is used as a battery container, the electrolytic solution is consumed by the action of electrochemical or volatilization as the charge / discharge cycle proceeds, and a trace amount of gas continues to be generated inside the battery. The battery container swells and deforms. In particular, in the case of a laminate film shape, there is a problem that if the container is deformed, the battery may not fit in the electronic device or the battery characteristics may be deteriorated.

  In this type of external battery, the positive electrode width, the negative electrode width, and the separator width of the battery element need to satisfy the positive electrode width <the negative electrode width <the separator width in order to prevent a small amount of stacking deviation in the electrode group manufacturing process. However, extreme battery containers due to charge / discharge cycles may swell and improve electrolyte retention in order to prevent deformation. Therefore, if the separator is made too wide, the separator may shrink during the heat fusion process in the battery assembly process. And the area occupied by the separator also increases, so the energy density decreases.

  In the case of a wound battery, it is possible to provide a gap in the center of the wound electrode body as a means for improving the electrolyte retention without reducing the energy density. Only the vicinity of the central portion has the effect of retaining the electrolyte, and the effect does not reach the vicinity of the outer peripheral portion of the wound electrode body. Although it is possible to increase the retention of the electrolytic solution by increasing the thickness of the separator, in this case, the thickness of the cell itself increases.

  Further, this type of external battery is often provided with a safety valve that automatically opens when the internal pressure rises above a predetermined pressure and exhausts gas or the like to the outside. Therefore, the laminate film is opened by the safety valve, thereby preventing the battery from bursting or unintentional gas ejection.

  One of the great advantages of the film-clad battery having the above structure is that it is thin. Therefore, when providing a structure for preventing the safety valve and the cycle characteristics from deteriorating, it is necessary to avoid an increase in thickness so that the above advantages are not impaired.

  That is, the technical problem of the present invention is based on the feature that the film-clad electrochemical device has a safety valve that automatically opens and exhausts gas and the like when the internal pressure rises, and An object of the present invention is to provide a film-covered electrochemical device that ensures reliability over a long period of time without impairing the advantage of the thin chemical device.

The present invention is formed on a part of a film-clad electrochemical device so as to protrude to the outside of the electrochemical device element in succession to a portion for accommodating the electrochemical device element and a portion for accommodating the electrochemical device element. In addition, a separator storage portion in which the protruding portion of the separator is stored is provided. The electrochemical device element has a plurality of positive and negative electrode plates stacked via separators, and a positive electrode extended portion and a negative electrode extended portion that are drawn from the negative electrode plate are bonded together to the positive electrode lead terminal or the negative electrode lead terminal, respectively. The film-covered electrochemical device is sealed by thermal fusion.

The film-clad electrochemical device of the present invention is a film in which an electrochemical device element consisting of a positive electrode and a negative electrode laminated with a separator and an electrolytic solution are housed in a film-clad body, and the outer peripheral part is thermally fused to seal It is an exterior electrochemical device, a heat-sealed narrow part is provided in a part of the outer peripheral part of the film exterior body, and a protruding part that protrudes to the outside of the electrochemical device element is provided in a part of the separator , The projecting portion is housed in a separator housing portion formed inside the heat-sealed narrow portion.

  Moreover, it is preferable that the said heat fusion narrow width part is open | released when an internal pressure rises. When the internal pressure due to the gas is increased, the separator housing portion in which the separator is housed acts as a safety valve because the pressure is concentrated on the heat-sealed narrow portion, and the film exterior electrochemical device bursts. In addition, gas ejection in an unintended direction is prevented.

  According to the present invention, it is possible to provide a film-clad electrochemical device that ensures reliability over a long period of time without impairing the advantage that the film-clad body is thin.

  According to the present invention, since the electrolytic solution is held in the separator formed so as to be drawn out of the electrochemical device element, a film-covered battery having good cycle characteristics over a long period of time can be obtained.

  According to the present invention, when the electrochemical device element extreme due to the charge / discharge cycle is provided with a structure for preventing swelling and deformation, the separator formed so as to be drawn out of the electrochemical device element is provided. Since a part of the heat-sealed narrow portion of the separator housing portion installed also serves as a safety valve that releases the internal pressure, the advantage of the thin film-covered electrochemical device can be obtained.

  According to the present invention, even if a separator formed so as to be drawn out of the electrochemical device element can be used, it can be formed by an assembly process equivalent to the conventional one, so that high working efficiency can be obtained.

  Next, an embodiment of the present invention will be described with reference to the drawings for a film-clad battery as an example of a film-clad electrochemical device.

  FIG. 1 is a plan view showing a heat-sealed portion of a film-clad battery of the present invention by hatching, and FIG. 2 is an exploded perspective view of an electric device element of the film-clad battery of the present invention. As shown in FIG. 1, a film-clad battery 1 includes a film-clad body 2 containing an electrochemical device element 7, a positive electrode lead terminal 3 and a negative electrode that are connected to the electrochemical device element 7 and project outside the film-clad body 2. And lead terminals 4. The film outer package 2 is heat-sealed around the electrochemical device element 7 as shown by hatching in FIG.

  The separator housing portion 6 in which the separator formed so as to be drawn out of the electrochemical device element 7 is installed is a non-thermal fusion portion, and is thermally fused at the time of sealing around the film outer package 2. Since it can form simultaneously with the part 5, it can provide without requiring a special man-hour.

In the present embodiment, an extreme film due to a charge / discharge cycle is provided by providing a separator storage portion in which a separator formed so as to be drawn out of the electrochemical device element is provided, and an electrolyte is held in the separator. Swelling and deformation of the external electrical device can be suppressed, and good cycle characteristics can be maintained over a long period of time.
In addition, a safety valve that functions by utilizing internal pressure pressure is provided in a part of the heat-sealed part of the separator housing part to ensure safety, so that the film-clad battery bursts or gas is ejected in an unintended direction. Is prevented.

  Furthermore, even when the separator formed so as to be pulled out of the electrochemical device element can be formed by an assembly process equivalent to the conventional one, it is a feature of the film-clad battery without reducing work efficiency. The advantage of being thin is not lost.

  The film outer package of the present invention is composed of a three-layer laminate film in which resin films such as polypropylene and nylon are laminated on both surfaces of an aluminum thin film.

  The film-clad electrochemical device surrounds the electrochemical device element, and the outer periphery of the film-clad electrochemical device is heat-sealed secretly. In the film-covered electrochemical device, it is preferable in terms of safety to provide a heat-sealed narrow portion on the outer peripheral portion.

  The separator accommodating portion may have any shape such as a square, a circle, and a triangle, and the number of the separator accommodating portions is not necessarily one, and may be two or more. Furthermore, the thickness of the film-covered electrochemical device in the separator housing portion need not be the same as the thickness of the film-covered electrochemical device other than the separator housing portion. It may be thinner than the thickness of the chemical device.

  In addition, as a safety valve, it is also possible to provide a protruding portion heat fusion and gas discharge portion in the separator housing portion. When the film-covered electrochemical device in the separator housing portion expands, stress in the peeling direction concentrates on a part of the heat-sealed narrow portion, and the heat-sealed portion is selectively peeled off. When the peeling reaches the outer peripheral portion of the film-clad electrochemical device, the inside of the film-clad electrochemical device communicates with the outside air, and the gas inside is reliably discharged to the outside. Any method may be used to prevent rupture of the film-clad electrochemical device and ejection of gas in an unintended direction.

  Examples of the present invention are described in detail below.

Example 1
As Example 1 of the present invention, a film-clad battery will be described with reference to FIG. As shown in FIG. 1, the film-clad battery 1 includes an electrochemical device element 7, a film exterior body 2 that houses the electrochemical device element 7, and an electrochemical device element 7 that is connected to the exterior of the film exterior body 2. The positive electrode lead terminal 3 and the negative electrode lead terminal 4 are provided. The film outer package 2 is a periphery of the electrochemical device element 7 and is heat-sealed to form a heat-sealed portion 5 as shown by hatching, and is sealed.

  The separator housing portion 6 in which a separator formed so as to be drawn out of the electrochemical device element 7 is a non-thermal fusion portion, and is thermally fused at the time of sealing around the film outer package 2 to be thermally fused. It can be formed simultaneously with the landing portion 5.

  For the production of the positive electrode, lithium manganate powder having a spinel structure, a carbonaceous conductivity imparting material, and polyvinylidene fluoride are mixed and dispersed in NMP (N-methyl-2-pyrrolidone) at a weight ratio of 90: 5: 5 and stirred. To give a slurry.

  This slurry was uniformly applied to one side of an aluminum foil having a thickness of 20 μm serving as a positive electrode plate using a doctor blade. At the time of application, the unapplied part (part where the positive electrode plate was exposed) was made to be slightly streaked. Next, this was vacuum-dried at 100 ° C. for 2 hours.

  Similarly, the slurry was applied to the other surface and vacuum-dried. At this time, the uncoated portions on the front and back sides were made to coincide. Thus, the sheet | seat (not shown) which apply | coated the slurry on both surfaces was roll-pressed. This was cut out into a rectangle including an uncoated portion to obtain a positive electrode 9. The slurry uncoated part was cut out except for a part of one side left in a rectangle, and the remaining part was used as the positive electrode lead terminal 3.

  The negative electrode was manufactured by mixing amorphous carbon powder and polyvinylidene fluoride in NMP at a weight ratio of 91: 9, dispersing and stirring to form a slurry.

  This slurry was applied to one side of a 10 μm thick copper foil serving as a negative electrode plate using a doctor blade. At the time of application, the non-applied part (part where the negative electrode plate was exposed) was made to be slightly streaked. Next, this was vacuum-dried at 100 ° C. for 2 hours. At this time, the film thickness of the slurry was adjusted so that the theoretical capacity per unit area of the negative electrode layer and the theoretical capacity per unit area of the positive electrode layer were 1: 1.

  Similarly, the slurry was applied to the other surface and vacuum-dried. Thus, the sheet | seat (not shown) which apply | coated the slurry on both surfaces was roll-pressed. The negative electrode 10 was obtained by adding the negative electrode lead terminal 4 to a copper foil coated with a slurry having a size that is 2 mm longer and wider than the size of the positive electrode lead terminal 3 removed from the positive electrode 9. The slurry non-applied part was cut out except for a part of one side left in a rectangle, and the remaining part was used as the negative electrode lead terminal 4.

  As shown in FIG. 2, the positive electrode 9 and the negative electrode 10 manufactured as described above, and the size obtained by adding the size of the separator housing 6 to the size larger by 2 mm in length and width than the size obtained by removing the negative electrode lead terminal 4 from the negative electrode 10. Microporous separators (hereinafter also referred to as separators) having a three-layer structure of polypropylene / polyethylene / polypropylene were alternately laminated. A part of the separator 11 was formed so as to be drawn out of the electrochemical device element. The outermost electrode was the negative electrode 10, and a separator 11 was placed on the outer side of the negative electrode (separator 11 / negative electrode 10 / separator 11 / positive electrode 9 / separator 11 /.../ separator 11 / positive electrode. 9 / Separator 11 / Negative electrode 10 / Separator 11). The positive electrode lead terminal 3 of the laminated positive electrode and an aluminum plate (not shown) as the positive electrode lead portion were ultrasonically welded together. Similarly, an electrochemical device element 7 was manufactured by ultrasonically welding together a negative electrode lead terminal 4 of a laminated negative electrode and a nickel plate (not shown) as a negative electrode lead part.

  As shown in FIG. 1, the film-clad battery 1 includes a positive electrode lead terminal 3 and a negative electrode lead terminal 4 that protrude to the outside of a film outer package 2 that houses an electrochemical device element 7. The film outer package 2 is heat-sealed around the electrochemical device element 7 as shown by hatching in FIG. The separator housing 6 is not heat-sealed.

Of the heat-sealed portions of the film outer package 2 containing the electrochemical device elements 7, three sides excluding one side including the separator housing portion 6 were heat-sealed. An electrolyte solution was injected into the separator housing portion 6 from one side that was not thermally fused. The electrolyte was 1 mol / L LiPF ₆ as a supporting salt, and a mixed solvent of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate (weight ratio 30:50:20) was used as a solvent. After injecting the electrolytic solution, the film outer package 2 was sealed in a vacuum to obtain a film outer battery 1.

  In the film-clad battery 1, when the film-clad body 2 expands, the heat-sealed portion is selectively peeled off from the heat-sealed narrow portion 8 where the width of the heat-sealing is narrowed in the separator housing portion 6. As a result, the film exterior electrochemical device communicates with the outside air, and the gas generated inside the battery is discharged to the outside. The width of the heat-sealing narrow portion 8 is 2.5 mm, the width of the separator housing portion 6 is 7.5 mm, and the width of the heat-sealing portion is 10 mm. Moreover, the length of the separator accommodating part 6 is 50 mm.

(Comparative Example 1)
A film-sheathed battery having a film-sheathed electrochemical device was produced in the same manner as in Example 1 except that a separator housing portion in which a separator formed so as to be pulled out of the electrical device element was not provided.

(Example 2)
A film-clad battery having a film-clad electrochemical device was produced in the same manner as in Example 1 except that the electrolyte was a 1 mol / L ethylene carbonate / diethyl carbonate mixed solvent (weight ratio 30:70).

(Comparative Example 2)
A film-sheathed battery having a film-sheathed electrochemical device was produced in the same manner as in Example 2 except that a separator housing portion in which a separator formed so as to be drawn out of the electrical device element was not provided.

(Example 3)
The separator (microporous separator having a three-layer structure of polypropylene / polyethylene / polypropylene) is a microporous separator having a single-layer structure of polyethylene formed so as to be partially drawn out of the electric device element. In the same manner as in Example 1, a film-clad battery having a film-clad electrochemical device was produced.

(Comparative Example 3)
A film-clad battery having a film-clad electrochemical device was produced in the same manner as in Example 3 except that a separator housing portion in which a separator formed so as to be drawn out of the electrical device element was not provided.

  Table 1 shows the relationship between the capacity retention ratios of Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3. The capacity retention rate of the lithium ion secondary battery having the film outer package 2 obtained by the example and the comparative example is the discharge capacity (1.0C) of the 1000th cycle with respect to the discharge capacity (1.0C) of the first cycle. Shown as a percentage. The cycle conditions were an upper limit voltage of 4.2 V and a current of 1.0 C for 2.5 hours for charging, and a lower limit voltage of 2.5 V and a current of 1.0 C for discharging, both at 20 ° C. Is.

  It was found that the capacity retention ratio 85% of Example 1 was larger than 70% of Comparative Example 1. By providing a separator housing portion 6 for installing a separator formed so as to be drawn out of the electrochemical device element 7 and holding the electrolytic solution in the separator, It can be seen that the deformation can be suppressed and good cycle characteristics can be maintained over a long period of time, and the desired effect can be obtained.

  It was found that the capacity retention rate of 90% in Example 2 was greater than 75% in Comparative Example 2. By providing a separator housing portion 6 for installing a separator formed so as to be drawn out of the electrochemical device element 7 and holding the electrolytic solution in the separator, It can be seen that the deformation can be suppressed and good cycle characteristics can be maintained over a long period of time, and the desired effect can be obtained.

  It was found that the capacity retention rate of 80% in Example 3 was larger than 65% in Comparative Example 3. By providing a separator housing portion 6 for installing a separator formed so as to be drawn out of the electrochemical device element 7 and holding the electrolytic solution in the separator, It can be seen that the deformation can be suppressed and good cycle characteristics can be maintained over a long period of time, and the desired effect can be obtained.

  Considering the data in Table 1 as a result of the above Examples 1 to 3 in total, a separator storage portion for installing a separator formed so as to be pulled out of the electrochemical device element is provided. It can be seen that the electrolyte solution is retained to suppress the swelling and deformation of the extreme film-clad electrochemical device due to the charge / discharge cycle, and maintain good cycle characteristics over a long period of time.

  The embodiments of the present invention have been described above using the embodiments. However, the present invention is not limited to these embodiments, and the present invention is not limited to the scope of the present invention. Included in the invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

The top view of the film-clad battery of this invention. The disassembled perspective view of the electric device element of the film-clad battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film exterior battery 2 Film exterior body 3 Positive electrode lead terminal 4 Negative electrode lead terminal 5 Thermal fusion part 6 Separator storage part 7 Electrochemical device element 8 Thermal fusion narrow part 9 Positive electrode 10 Negative electrode 11 Separator

Claims (2)

Electrochemical device element and electrolyte solution consisting of a positive electrode and a negative electrode laminated via a separator are housed in a film exterior body, and a film exterior electrochemical device that is sealed by thermal fusion of the outer peripheral portion,
A heat-sealed narrow portion is provided in a part of the outer peripheral portion of the film exterior body,
A part of the separator is provided with a protruding part that protrudes to the outside of the electrochemical device element, and the protruding part is accommodated in a separator accommodating part that is formed inside the narrow part of the thermal fusion width. Film exterior electrochemical device characterized by.   The film-covered electrochemical device according to claim 1, wherein the heat-sealed narrow portion is opened when the internal pressure is increased.

Images