JP2014220109A - Method of manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a nonaqueous electrolyte secondary battery in which a coat of good quality, derived from an additive added to an electrolyte, can be formed on the surface of an electrode plate.SOLUTION: A method of manufacturing a nonaqueous electrolyte secondary battery where an electrolyte containing an additive, and a flat electrode body formed by winding positive and negative electrode plates, while sandwiching a separator, are housed in a battery case, and a coat derived from the additive is formed on at least one surface of the positive and negative electrode plates is provided. A hot press process for heating the battery case housing the electrode body, while restraining by applying a load in the thickness direction of the electrode body, is performed after housing the electrode body in the battery case and before injecting the electrolyte, added with the additive, into the battery case.

Description

  The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery having a flat wound electrode body.

  In recent years, the demand for lithium ion secondary batteries as a power source for vehicles such as hybrid vehicles and electric vehicles has increased. The lithium ion secondary battery has an electrode body and an electrolytic solution therein. The electrolytic solution is obtained by dissolving a lithium salt in an organic solvent. The electrode body is composed of positive and negative electrode plates and a separator, and contributes to charge / discharge in the lithium ion secondary battery.

  For example, Patent Document 1 is known as a conventional technique related to the manufacture of an electrode body. In Patent Document 1, a flat electrode body is manufactured by winding a positive and negative electrode plate into a cylindrical shape with a separator interposed therebetween, and thermally compressing the wound body in the diameter direction. . In addition, after the step of processing the electrode body into a flat shape, a process of cooling the electrode body and a step of welding a current collecting terminal for connecting the external terminal and the electrode body in the battery to the electrode body are performed. Is housed in a battery case. Furthermore, a lithium ion secondary battery is manufactured by injecting an electrolyte into a battery case containing an electrode body.

JP 2011-258493 A

  Here, an electrolytic solution to which an additive such as lithium bisoxalate borate (hereinafter, LiBOB) is added may be used. This is because a film derived from an additive is formed on the surface of the electrode plate in the electrode body to improve battery performance. For that purpose, it is preferable that the film derived from the additive is formed with a uniform thickness on the surface of the electrode plate.

  However, in the above prior art, a plurality of steps are performed after the step of forming the electrode body into a flat shape and before the step of injecting the electrolytic solution. For this reason, the electrode plate of the electrode body or the like in the electrolyte injection process may be bent. Thereby, when using what added LiBOB as electrolyte solution, there existed the following problems.

  That is, the electrode plates and separators that are stacked are in close contact with the electrode body portion where no deflection occurs in the electrode plates. On the other hand, in the portion of the electrode body in which the electrode plate or the like is bent, the stacked electrode plates and separators do not adhere to each other, and a gap is formed between them. Then, the portion of the electrode body having a larger gap is in a state containing more injected electrolyte.

  In addition, the thickness of the LiBOB coating formed on the surface of the electrode plate is different between the portion of the electrode body that contains a large amount of the electrolyte solution to which LiBOB is added and the portion that contains a small amount. Therefore, the deflection of the electrode plate or the like of the electrode body when injecting the electrolytic solution makes it impossible to manufacture a lithium ion secondary battery in which a LiBOB film having a uniform thickness is formed on the surface of the electrode plate. There was a problem.

  The present invention has been made for the purpose of solving the problems of the prior art described above. That is, the problem is to provide a method for producing a non-aqueous electrolyte secondary battery capable of forming a high-quality coating film due to the additive added to the electrolyte solution on the surface of the electrode plate.

  In order to solve this problem, the non-aqueous electrolyte secondary battery manufacturing method of the present invention includes an electrolyte containing an additive and a positive and negative electrode plate sandwiched between a separator and a battery case. A method of manufacturing a non-aqueous electrolyte secondary battery having a flat electrode body that is wound while having a coating derived from an additive formed on at least one surface of a positive and negative electrode plate. After the electrode body is accommodated in the battery case, the battery case containing the electrode body is restrained by applying a load in the thickness direction of the electrode body before injecting the electrolyte with the additive into the battery case. A non-aqueous electrolyte secondary battery manufacturing method is characterized in that a heating press step of heating is performed.

  In order to form a coating having a uniform thickness on the surface of the electrode plate derived from the additive contained in the electrolytic solution, it is important that the electrolytic solution is uniformly present inside the electrode body. In the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention, a heating press step of a battery case containing an electrode body is performed before the electrolyte is injected. By the heat pressing step, the deflection of the flat portion of the electrode body having a flat outer shape is removed by receiving a load from the heat pressing. In addition, the curved surface portion of the electrode body having a curved outer surface is tightened by the contraction force of the separator that contracts by heating, and the deflection is removed. Then, the electrolytic solution injected after the hot pressing step is impregnated in the inside of the electrode body, so that the electrode body is uniformly present. Thereby, the film derived from the additive contained in the electrolytic solution is formed with a uniform thickness on the electrode plate constituting the electrode body.

  In the method for producing a non-aqueous electrolyte secondary battery described above, in the heat press step, the load in the thickness direction of the electrode body applied to the battery case is within the range of 0.15 MPa to 4.40 MPa as the pressure. It is preferable to heat the electrode body so that the temperature of the electrode body is within a range from 80 ° C. to 110 ° C. This is because the deflection of the electrode plate and the like in the electrode body can be appropriately removed by setting the pressure and temperature in the heating press step within the above ranges, respectively. When the pressure received by the electrode body is lower than the lower limit value within the above range, the contracting force of the separator that contracts due to heating cannot be suppressed appropriately. That is, the electrode body may be greatly deformed. On the other hand, when the pressure received by the electrode body is higher than the upper limit within the above range, the pores of the separator, which is a porous member, are crushed, increasing the internal resistance of the non-aqueous electrolyte secondary battery after completion. There is a risk of it. Further, when the temperature of the electrode body is lower than the lower limit value within the above range, the contraction force of the separator may be too weak. In this case, the deflection of the curved surface portion of the electrode body is not sufficiently removed due to the shrinkage of the separator. On the other hand, when the temperature of the electrode body is higher than the upper limit within the above range, the contraction force of the separator is too strong, and the contraction force may increase the deflection of the curved surface portion of the electrode body.

  In the method for manufacturing a non-aqueous electrolyte secondary battery described above, the additive is LiBOB, and the electrolyte is injected into the battery case by setting the temperature of the electrolyte within a range from 20 ° C to 30 ° C. , It is preferable to carry out in a state where the temperature of the electrode body is in the range from 35 ° C. to 50 ° C. If the temperature of the electrolytic solution during impregnation of the electrode body is too low, the viscosity of the electrolytic solution increases, and this may not be satisfactorily impregnated into the electrode body. That is, the state of the electrolyte in the electrode body becomes non-uniform, and a LiBOB-derived film cannot be formed on the electrode plate with a uniform thickness. On the other hand, at high temperatures, the LiBOB coating formed on the surface of the electrode plate is unlikely to be high quality and stable. In addition, when the temperature of the electrolytic solution is too high, an unnecessary product is generated in the battery, and this may be mixed in the LiBOB coating or may cover the surface, thereby reducing the battery performance. Then, by setting the temperature of the electrolytic solution and the dry battery within the above range, a good LiBOB film can be formed on the surface of the electrode plate.

  Further, in the method for manufacturing a non-aqueous electrolyte secondary battery described above, the electrolyte is injected into the battery case, and the ratio of the heat capacity of the battery before the electrolyte is injected to the heat capacity of the electrolyte is expressed as follows: It is preferable to carry out in a state in the range of 0.9 to 1.5. This is because the temperature of the electrolyte during impregnation of the electrode body can be maintained within a suitable range.

  Further, in the method for manufacturing a non-aqueous electrolyte secondary battery described above, the heating press step may also serve as a dehydration step for removing moisture in the battery case before pouring the electrolyte into the battery case. Good. Generally, a dehydration process is performed immediately before the electrolyte injection process in order to remove moisture in the dry battery. However, the moisture in the dry battery is sufficiently removed by the hot press process.

  According to the present invention, there is provided a method for manufacturing a non-aqueous electrolyte secondary battery capable of forming a high-quality film resulting from an additive added to an electrolyte solution on the surface of an electrode plate.

It is sectional drawing which shows the secondary battery which concerns on this form. It is a perspective view of the electrode body which concerns on this form. It is a figure which shows the positive electrode plate, negative electrode plate, and separator which comprise the same electrode body. It is a figure which shows the apparatus used for a heating press.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the drawings. In this embodiment, the present invention is applied to a lithium ion secondary battery.

  First, the secondary battery 10 (refer FIG. 1) manufactured by the manufacturing method of the lithium ion secondary battery of this form is demonstrated. FIG. 1 is a cross-sectional view of a secondary battery 10 according to this embodiment. The secondary battery 10 is a lithium ion secondary battery in which an electrode body 20 and an electrolytic solution 30 are accommodated in a battery case 40 as shown in a sectional view in FIG. The electrolytic solution 30 of this embodiment is a nonaqueous electrolytic solution obtained by adding LiBOB to a solution obtained by dissolving a lithium salt in an organic solvent.

  The battery case 40 includes a battery case main body 41 and a sealing plate 42. The sealing plate 42 includes an insulating member 43. In addition, a liquid injection port 44 is formed in the sealing plate 42. The liquid injection port 44 is for injecting the electrolytic solution 30 into the battery case 40. Further, the liquid injection port 44 is sealed with a liquid injection stopper 45.

  FIG. 2 is a perspective view of the electrode body 20. As shown in FIG. 2, the electrode body 20 is a flat wound electrode body. FIG. 3 is a cross-sectional view of the positive electrode plate 50, the negative electrode plate 60, and the separator 70 constituting the electrode body 20 before winding. The positive electrode plate 50, the negative electrode plate 60, and the separator 70 are all in the form of strips that are long in the depth direction of the paper in FIG.

  As shown in FIG. 3, the positive electrode plate 50 is formed by forming a positive electrode active material layer 52 on both surfaces of an aluminum foil 51 that is a positive electrode current collector foil. The negative electrode plate 60 is formed by forming a negative electrode active material layer 62 on both surfaces of a copper foil 61 that is a negative electrode current collector foil. Both the positive electrode active material layer 52 and the negative electrode active material layer 62 contain an active material capable of inserting and extracting lithium ions. In addition, the positive electrode active material layer 52 and the negative electrode active material layer 62 are suitably used for forming an active material layer by fixing a conductive auxiliary material and an active material on the current collector foil for enhancing the conductivity in the active material layer. Contains binders.

  The separator 70 is a porous member that can transmit lithium ions while preventing a short circuit between the positive electrode plate 50 and the negative electrode plate 60. As this porous member, a porous film made of polypropylene (PP), polyethylene (PE) or the like can be used alone. It is also possible to use a composite material in which a plurality of these are laminated in the thickness direction. The width of the separator 70 (the length in the left-right direction in FIG. 3) is narrower than the width of the positive electrode plate 50 and the negative electrode plate 60.

  Here, as shown in FIG. 3, the range in which the positive electrode active material layer 52 and the negative electrode active material layer 62 are respectively formed in the positive electrode plate 50 and the negative electrode plate 60 is about the same width as the separator 70. . However, in practice, the width of the separator 70 is slightly wider. This is for reliably preventing a short circuit between the positive electrode plate 50 and the negative electrode plate 60.

  Also, as shown in FIG. 3, the positive electrode plate 50 and the negative electrode plate 60 have portions where the positive electrode active material layer 52 and the negative electrode active material layer 62 are not formed, respectively. The aluminum foil 51 is exposed at a portion of the positive electrode plate 50 where the positive electrode active material layer 52 is not formed. The portion where the aluminum foil 51 is exposed protrudes to the right in FIG. 3 from the negative electrode plate 60 and the separator 70. On the other hand, the copper foil 61 is exposed at a portion of the negative electrode plate 60 where the negative electrode active material layer 62 is not formed. The portion where the copper foil 61 is exposed protrudes to the left in FIG. 3 from the positive electrode plate 50 and the separator 70.

  The electrode body 20 has a flat shape as shown in FIG. 2 while the positive electrode plate 50, the negative electrode plate 60, and the separator 70 are overlapped as shown in FIG. The flat electrode body 20 includes a curved surface portion 20R in which outer peripheral surfaces at both ends in the vertical direction in FIG. 2 are curved, and a flat portion 20F in which an outer peripheral surface sandwiched between the curved surface portions 20R is flat. The direction in which the electrode plates and the like in the flat portion 20F are laminated is the thickness direction of the electrode body 20.

  Further, as shown in FIG. 2, the electrode body 20 includes a power storage unit 21, a positive electrode end 22, and a negative electrode end 23. The positive electrode end portion 22 and the negative electrode end portion 23 are both end portions of the electrode body 20 in the width direction (left-right direction in FIG. 2). The power storage unit 21 is a central portion in the width direction of the electrode body 20 sandwiched between the positive electrode end 22 and the negative electrode end 23.

  The power storage unit 21 is a portion in which the positive electrode plate 50, the negative electrode plate 60, and the separator 70 in the center in the width direction are alternately overlapped in the superposition illustrated in FIG. In the power storage unit 21 of the electrode body 20 shown in FIG. 2, the positive electrode plate 50 and the negative electrode plate 60 are in close contact with the separator 70 sandwiched therebetween. And the electrical storage part 21 is a part which can contribute to charging / discharging. On the other hand, the positive electrode end portion 22 is a portion made of an aluminum foil 51 protruding to the right end in FIG. Further, the negative electrode end portion 23 is a portion made of the copper foil 61 protruding to the left end in FIG.

  In the secondary battery 10 shown in FIG. 1, a positive electrode terminal 80 is connected to the positive electrode end 22. A negative electrode terminal 90 is connected to the negative electrode end portion 23. In the positive electrode terminal 80 and the negative electrode terminal 90, ends 81 and 91 on the side not connected to the electrode body 20 are protruded to the outside of the battery case 40 through an insulating member 43 provided on the sealing plate 42. The secondary battery 10 performs charging and discharging in the power storage unit 21 of the electrode body 20 via the positive electrode terminal 80 and the negative electrode terminal 90.

  In the secondary battery 10 having the above-described configuration, a LiBOB-derived film (LiBOB film) added to the electrolytic solution 30 is formed on the surface of the negative electrode plate 60 constituting the electrode body 20. In detail, the LiBOB film is formed on the surface of the negative electrode active material layer 62 of the negative electrode plate 60. Since the LiBOB film is formed on the negative electrode plate 60, the secondary battery 10 has high battery performance. Further, in order to satisfactorily exert the effect of forming the LiBOB coating on the negative electrode plate 60, in the secondary battery 10 of this embodiment, a high-quality LiBOB coating is formed on the surface of the negative electrode plate 60 by a method described in detail later. Is formed.

Next, the manufacturing process of the secondary battery 10 will be described. In this embodiment, the secondary battery 10 is manufactured by the following five processes. Hereinafter, each process is demonstrated in order.
1. 1. Production of electrode body 20 2. Storage of the electrode body 20 in the battery case 40 3. Heating press 4. Injection of electrolytic solution 30 Activation processing, etc.

(1. Production of electrode body 20)
In this step, first, the positive electrode plate 50 and the negative electrode plate 60 constituting the electrode body 20 are manufactured. Each of these positive and negative electrode plates can be obtained by manufacturing a paste containing an electrode active material and a binder, applying the paste to a current collector foil, and then drying to form an electrode active material layer. Further, while the manufactured positive electrode plate 50, negative electrode plate 60, and separator 70 are overlapped as shown in FIG. 3, they are wound into a cylindrical shape. Furthermore, the cylindrical wound body is formed into a flat shape by being pressed while being sandwiched from both sides in the diameter direction, and the electrode body 20 is manufactured. Or the electrode body 20 can also be manufactured by winding the positive electrode plate 50, the negative electrode plate 60, and the separator 70 so that it may become flat shape.

(2. Accommodation of the electrode body 20 in the battery case 40)
Next, the positive electrode terminal 80 and the negative electrode terminal 90 are connected to the positive electrode end portion 22 and the negative electrode end portion 23 of the manufactured electrode body 20, respectively. The connection can be made, for example, by resistance welding. Further, the electrode body 20 to which the positive electrode terminal 80 and the negative electrode terminal 90 are connected is sealed in the battery case 40. The battery case body 41 and the sealing plate 42 of the battery case 40 can be joined by welding, for example. Note that the secondary battery 10 at this time is still in a state where the electrolyte solution 30 is not injected into the battery case 40. For this reason, the liquid injection port 44 is not yet sealed by the liquid injection stopper 45.

(3. Heating press)
Subsequently, the secondary battery 10 after the electrode body 20 is accommodated is subjected to a heat press. This step is performed for the purpose of removing the deflection in the electrode body 20 as will be described in detail later. In this embodiment, the secondary battery 10 in a state before the electrolytic solution 30 is injected is heated while being pressed in the thickness direction (the depth direction in FIG. 1) of the electrode body 20 accommodated therein. Do. Therefore, for example, a hot press apparatus 100 as shown in FIG. 4 can be used.

  The hot press apparatus 100 includes a fixed part 110 and a movable part 120. The fixed part 110 and the movable part 120 have pressing surfaces 111 and 121 for pressing the secondary battery 10, respectively. The movable part 120 can move in the vertical direction in FIG. 4 toward the fixed part 110.

  In the state of FIG. 4, the secondary battery 10 is disposed on the compression surface 111 of the fixing unit 110. When the movable part 120 is lowered in this state, the secondary battery 10 is sandwiched between the compression surface 111 of the fixed part 110 and the compression surface 121 of the movable part 120 in the thickness direction (vertical direction in FIG. 4). It is pressed. Here, the thickness direction of the secondary battery 10 is the same direction as the thickness direction of the electrode body 20.

  Furthermore, the fixed part 110 and the movable part 120 have a heater for heating the secondary battery 10 therein. Thereby, the heat press apparatus 100 can perform the heat processing which raises the temperature of the secondary battery 10, pressing the secondary battery 10 in the thickness direction and making it a restraint state. And the movable part 120 of the heating press apparatus 100 rises after completing the heating press of the secondary battery 10.

  In general, immediately before the electrolytic solution 30 is injected, a dehydration process of the secondary battery 10 is performed. This is because moisture is removed from the secondary battery 10 before the electrolyte solution 30 is injected, and the electrolyte solution 30 is injected in a state where the secondary battery 10 is sufficiently dried. However, in this embodiment, the secondary battery 10 is sufficiently dried by performing this heating press. Therefore, since this process can also serve as a dehydration process, it is not necessary to perform a special dehydration process before the electrolyte solution 30 is injected thereafter.

(4. Injection of electrolyte 30)
Then, the electrolytic solution 30 is injected into the battery case 40 after the heating press step. The electrolyte 30 to be injected is in a state where a lithium salt is dissolved in an organic solvent and LiBOB is added. The electrolytic solution 30 is injected from a liquid injection port 44 formed in the sealing plate 42 of the battery case 40.

  Moreover, in this embodiment, the electrolytic solution 30 adjusted to a temperature in the range of 20 to 30 ° C. is injected into the secondary battery 10 in which the temperature of the electrode body 20 is adjusted in the range of 35 to 50 ° C. For this reason, before performing injection | pouring of the electrolyte solution 30 to the secondary battery 10, temperature adjustment is performed beforehand so that the temperature of the secondary battery 10 and the electrolyte solution 30 may become in said range. In this embodiment, the temperature adjustment of the electrode body 20 is performed by leaving the secondary battery 10 in a temperature environment within the above range for a sufficient time. For this reason, both the temperature of the battery case 40 and the electrode body 20 located in the battery case 40 is adjusted within the above range. Therefore, confirmation that the temperature of the electrode body 20 has been adjusted within the above range can be performed by measuring the temperature of the battery case 40. Alternatively, in the case where the electrolytic solution 30 is injected before the heat conduction from the battery case 40 to the electrode body 20 is sufficiently performed, by obtaining these temperature relationships in advance, the measured temperature of the battery case 40 can be obtained. It is also possible to confirm that the temperature of the electrode body 20 is within the above range. Moreover, the secondary battery 10 is heated in the heating press which is a pre-process. Therefore, what is necessary is just to adjust the temperature of the secondary battery 10 within the range of 35-50 degreeC, without once returning to normal temperature.

  Here, in order to form a LiBOB coating having a uniform thickness on the surface of the negative electrode plate 60 constituting the electrode body 20, the electrolyte solution 30 to which LiBOB is added is present uniformly in the electrode body 20. It is important that However, the viscosity increases as the temperature of the electrolytic solution 30 decreases. Further, the higher the viscosity of the electrolytic solution 30, the slower the impregnation rate into the electrode body 20 when injected into the battery case 40.

  For this reason, when the temperature of the injected electrolyte 30 is too low, it takes a long time for the injected electrolyte 30 to impregnate the entire interior of the electrode body 20. In the meantime, the ratio of the electrolyte solution 30 in the electrode body 20 is not uniform. Therefore, when the temperature of the injected electrolytic solution 30 is too low, unevenness occurs in the thickness of the LiBOB film formed on the surface of the negative electrode plate 60.

  On the other hand, even when the temperature of the electrolytic solution 30 is too high, a good LiBOB film cannot be formed on the surface of the negative electrode plate 60 of the electrode body 20. The higher the temperature of the electrolytic solution 30, the faster the LiBOB film is formed. That is, when the temperature of the electrolytic solution 30 is too high, unevenness in the thickness of the LiBOB film formed on the surface of the negative electrode plate 60 is likely to occur. In addition, the LiBOB film formed at a high temperature is unlikely to be high quality and stable. Furthermore, the electrolytic solution 30 whose temperature is too high may promote the dissolution of the components of the members constituting the secondary battery 10. And the product produced | generated by the component which melt | dissolved may cause the fall of battery performance by mixing in the LiBOB film formed in the surface of the negative electrode plate 60, or coat | covering the surface.

  Therefore, by injecting the electrolytic solution 30 while keeping the temperature of the secondary battery 10 and the electrolytic solution 30 within the above range, a high-quality coating derived from LiBOB added to the electrolytic solution 30 is formed on the surface of the negative electrode plate 60. Can be formed.

  Furthermore, in this embodiment, the value of the heat capacity ratio Cb / Ce of the heat capacity Cb of the secondary battery 10 to the heat capacity Ce of the electrolyte 30 when the electrolyte 30 is injected into the secondary battery 10 is 0.9 to 1.. It is preferable to be within the range of 5. That is, when the temperature of the secondary battery 10 is higher than the temperature of the electrolyte 30 to be injected, the injected electrolyte 30 is heated. In this case, if the value of the heat capacity ratio Cb / Ce is too high, the electrolytic solution 30 may be heated too much.

  In addition, when the electrolyte solution 30 is injected while the temperature of the secondary battery 10 is close to the lower limit within the above range and the value of the heat capacity ratio Cb / Ce is too low, the temperature of the injected electrolyte solution 30 is , It may decrease while impregnating the inside of the electrode body 20. For this reason, the temperature of the electrolytic solution 30 may be excessively lowered before the electrolytic solution 30 is completely impregnated in the electrode body 20. That is, the viscosity of the electrolytic solution 30 may increase so that the electrolytic solution 30 is not sufficiently impregnated in the electrode body 20.

  Therefore, the temperature of the secondary battery 10 and the electrolytic solution 30 is set within the above range, and the heat capacity ratio Cb / Ce is adjusted to be within the range of 0.9 to 1.5. Thus, a high-quality LiBOB film can be formed more reliably. The heat capacity Cb can be obtained from the respective heat capacities of the electrode body 20, the battery case 40, etc., for the secondary battery 10 having a configuration before injection of the electrolytic solution 30.

  In addition, after the electrolyte solution 30 is injected, the injection port 44 is sealed with an injection plug 45. The sealing is performed, for example, by laser welding the periphery of the liquid injection port 44 in a state where the liquid injection port 44 is closed by the liquid injection stopper 45.

(5. Activation processing, etc.)
After injecting the electrolytic solution 30 and sealing the injection port 44, conditioning or aging treatment is performed. Conditioning is a process of charging and discharging the secondary battery 10 for the first time. The aging process is performed by leaving the secondary battery 10 in a predetermined temperature environment. Through these steps, the secondary battery 10 is activated, and the battery performance can be sufficiently exhibited. In addition, a battery inspection process for removing defective batteries in the manufacturing process is also performed.

  Here, in the manufacturing process of the secondary battery 10 according to the above-described embodiment, a process of heating the secondary battery 10 in a restrained state is performed in “3. Heating press” in the previous process of injecting the electrolytic solution 30. The effect will be described.

  The positive electrode plate 50, the negative electrode plate 60, and the separator 70 in the electrode body 20 may be bent by connecting the positive electrode end 22 and the negative electrode end 23, accommodating in the battery case 40, etc. after the electrode body 20 is manufactured. May occur. When the deflection occurs, the positive electrode plate 50, the negative electrode plate 60, and the separator 70 are not in close contact with each other in the bent portion, and a gap is formed between them. On the other hand, in a portion where there is no deflection, the positive electrode plate 50, the negative electrode plate 60, and the separator 70 are in close contact with each other.

  For this reason, the injected electrolyte solution 30 is present in an amount that is impregnated in the separator 70 in a portion where there is no deflection in the electrode body 20. On the other hand, in the bent portion, in addition to the portion impregnated in the separator 70, there is also a portion that enters the gap formed by the deflection. That is, the existence ratio of the electrolytic solution 30 is different between the portion where the deflection in the electrode body 20 occurs and the portion where the deflection does not occur. In addition, the larger the deflection, the larger the gap formed, and the greater the amount of electrolyte 30 present there.

  However, as described above, in order to form a LiBOB film having a uniform thickness on the surface of the negative electrode plate 60, the electrolyte solution 30 to which LiBOB is added must be uniformly present in the electrode body 20. is important. Therefore, it is preferable that the positive electrode plate 50, the negative electrode plate 60, and the separator 70 of the electrode body 20 accommodated in the secondary battery 10 are in a state in which there is no deflection when the electrolytic solution 30 is injected.

  Therefore, in this embodiment, the deflection of the electrode body 20 is removed by performing a process of heating the secondary battery 10 in a restrained state in a heating press step that is a step before the step of injecting the electrolytic solution 30. That is, the deflection in the flat portion 20F of the electrode body 20 is removed by placing the secondary battery 10 in a restrained state. This is because the flat portion 20F of the electrode body 20 accommodated in the secondary battery 10 receives in the thickness direction thereof.

  The material used as the separator 70 generally has a property of shrinking at 80 ° C. or higher. That is, the separator 70 contracts by heating the secondary battery 10. The electrode body 20 is tightened by the contraction. Therefore, by appropriately heating the secondary battery 10 in a restrained state, the electrode body 20 can be tightened without excessive deformation due to the contraction of the separator 70, and in particular, the bending at the curved surface portion 20R can be removed.

  When the restraining load of the secondary battery 10 is too low, the contracting force of the separator 70 due to heating cannot be suppressed by the restraining force due to the restraining load. That is, the electrode body 20 may be greatly deformed by the contraction of the separator 70, and the deflection of the electrode body 20 may be increased. On the other hand, when the restraint load is too high, the pores of the separator 70 are crushed by the restraint load, causing clogging, and the internal resistance in the secondary battery 10 after completion increases.

  Moreover, when the temperature which heats the secondary battery 10 is too low, the clamping | tightening of the electrode body 20 by shrinkage | contraction of the separator 70 will become weak. In this case, only the effect of only the restraint load can be obtained, and in particular, it cannot be expected to remove the deflection at the curved surface portion 20R of the electrode body 20. On the other hand, when the heating temperature is too high, the separator 70 contracts too much at the position of the curved surface portion 20R of the electrode body 20 where no restraint load is applied by the press. That is, there is a possibility that the deflection of the curved surface portion 20R of the electrode body 20 may be increased.

  Therefore, in consideration of these points, in the “3. Heating press” step, the load that the secondary battery 10 receives in the thickness direction is set to a pressure within a range of 0.15 to 4.40 MPa. It is preferable to restrain the secondary battery 10. Furthermore, it is preferable to perform a heating process so that the temperature of the electrode body 20 inside the secondary battery 10 is in the range of 80 to 110 ° C.

  In addition, the hot press apparatus 100 shown in FIG. 4 is a thing of the structure which presses the secondary battery 10 uniformly in the thickness direction. However, any configuration may be used as long as it hatches at least the portion indicated by A in FIG. The portion indicated by A in FIG. 4 is a portion expressed on the surface of the battery case 40 by projecting a portion located in the flat portion 20F of the power storage unit 21 of the electrode body 20 in the thickness direction of the secondary battery 10. is there. In other words, at least the restraint load may be applied to the flat portion 20F of the power storage unit 21 of the electrode body 20. This is because the portion of the negative electrode plate 60 located in the power storage unit 21 is a portion where the negative electrode active material layer 62 on which the LiBOB coating is formed is formed. In addition, the restraining load is applied when the secondary battery 10 is pressed in the thickness direction because the flat portion 20F of the electrode body 20 is applied. In addition, as a configuration of such a heating press apparatus 100, for example, it is conceivable that the pressing surface 111 of the fixed portion 110 and the pressing surface 121 of the movable portion 120 have a size indicated by A in FIG. Moreover, what is necessary is just to perform about heating so that the temperature of the electrical storage part 21 of the electrode body 20 may become in said range.

  In addition, the present inventor confirmed the effect of the present invention by the following experiment. In this experiment, secondary batteries of a plurality of examples and comparative examples were manufactured under different conditions. The manufacturing conditions are shown in Table 1 below.

  The secondary batteries of the examples and comparative examples are basically the same in structure as the secondary battery 10 described above. However, the manufacturing process was made under different conditions. Specifically, among the steps described in the above manufacturing process, the conditions in the two steps “3. Heating press” and “4. Injection of electrolyte solution 30” are different.

  With respect to these steps, each of the secondary batteries of the examples was prepared by a method satisfying all the above-described conditions by using an electrolyte added with LiBOB. In this experiment, the pressure received by the secondary battery in the heating press is in the range of 0.15 to 4.40 MPa when the binding load in Table 1 is in the range of 0.75 to 20 kN. Has been.

  On the other hand, the secondary battery of the comparative example was manufactured by a method that did not satisfy at least one of the above conditions. In Table 1, the different conditions from the above-described embodiment are shown in italics for each comparative example.

  Table 1 shows the output values measured after the endurance test for the secondary batteries of the examples and comparative examples after the manufacture. The durability test was performed by repeatedly charging and discharging the secondary batteries of the examples and comparative examples under the same conditions.

  As shown in Table 1, all the secondary batteries of the examples had high output measured after the durability test. This is because all of the secondary batteries of the examples were manufactured according to “3. Heating press” and “4. Injection of electrolytic solution 30” in the above-described embodiment. That is, in the electrode body according to the example, there is no deflection in the electrode plate or the like when the electrolytic solution is injected, and the injected electrolytic solution can be satisfactorily impregnated in the electrode body without the deflection. This is because a good LiBOB film is formed on the surface of the negative electrode plate.

  On the other hand, for the secondary battery of the comparative example, the output measured after the endurance test was lower than that of the example. That is, as shown in Table 1, in Comparative Example 1, the secondary battery is heated without being constrained in the step before the electrolyte injection. That is, it is considered that the electrode body is deflected by contraction of the separator in an unconstrained state, and the thickness of the LiBOB film formed on the surface of the negative electrode plate is uneven.

  Moreover, in the comparative example 2, it does not heat in the process before injection | pouring of electrolyte solution. That is, it is considered that the deflection of the curved surface portion of the electrode body cannot be removed because the separator does not contract, and the thickness of the LiBOB film formed on the surface of the negative electrode plate is uneven. In Comparative Example 3, the process for removing the deflection in the electrode body is not performed, and the electrolytic solution is injected while the deflection is generated in the electrode body. Therefore, it is considered that the thickness of the LiBOB coating formed on the surface of the negative electrode plate has become uneven.

  In Comparative Example 4, the heating press is not performed before the electrolyte is injected, and the secondary battery is heated without being constrained after the electrolyte is injected. That is, it is considered that the deflection of the electrode body was not removed, and the thickness of the LiBOB film formed on the surface of the negative electrode plate was uneven. In Comparative Example 5, the heat press is not performed before the electrolyte is injected, and the heat press is performed after the electrolyte is injected. For this reason, it is considered that the impregnation of the electrolytic solution into the electrode body was hindered by the restraint during the hot pressing, and the thickness of the LiBOB film formed on the surface of the negative electrode plate was uneven.

  In Comparative Examples 6 and 7, an electrolytic solution to which no LiBOB is added is injected. Therefore, the LiBOB coating is not formed on the surface of the negative electrode plate, and the effect does not occur, so the output after the durability test is reduced.

  In Comparative Example 8, the temperature in the heating press before the electrolyte injection is low. For this reason, it is thought that the effect | action which removes the deflection | deviation of the electrode body by shrinkage | contraction of a separator is small, and the nonuniformity has arisen in the thickness of the LiBOB film formed in the surface of a negative electrode plate. About the comparative example 9, the temperature in the heating press before injection | pouring of electrolyte solution is high. For this reason, it is considered that the deflection in the curved surface portion of the electrode body that is not subjected to the restraining load is increased, and the thickness of the LiBOB film formed on the surface of the negative electrode plate is uneven.

  In Comparative Example 10, the restraining load in the heating press before the electrolyte injection is small. For this reason, it is considered that the electrode body is greatly deflected by the contraction force of the separator, and the thickness of the LiBOB film formed on the surface of the negative electrode plate is uneven. About the comparative example 11, the restraint load in the heating press before injection | pouring of electrolyte solution is large. For this reason, it is thought that the pores of the separator were crushed by the restraining load, causing clogging, and the output decreased.

  In Comparative Example 12, the temperature of the secondary battery into which the electrolytic solution is injected is too low. In Comparative Example 14, the temperature of the injected electrolyte is too low. Further, in Comparative Example 16, the temperature of the secondary battery is the lower limit within the above preferable range, and the value of the heat capacity ratio Cb / Ce of the heat capacity Cb of the secondary battery to the heat capacity Ce of the electrolytic solution is too low. For this reason, in Comparative Examples 12 and 16, the temperature of the injected electrolyte solution becomes too low before the electrode body is completely impregnated. That is, in all of Comparative Examples 12, 14, and 16, the viscosity of the electrolyte when impregnating the electrode body after injection is too high. Therefore, it is considered that the electrolyte solution was not satisfactorily impregnated in the electrode body, and the thickness of the LiBOB coating formed on the surface of the negative electrode plate was uneven.

  In Comparative Example 13, the temperature of the secondary battery into which the electrolytic solution is injected is too high. In Comparative Example 15, the temperature of the injected electrolyte is too high. In Comparative Example 17, the temperature of the secondary battery is the upper limit within the above preferable range, and the value of the heat capacity ratio Cb / Ce of the heat capacity Cb of the secondary battery to the heat capacity Ce of the electrolytic solution is too high. That is, in Comparative Examples 13 and 17, the injected electrolyte solution is heated by the secondary battery having a high temperature, so that the temperature becomes too high. For this reason, it is considered that in all of Comparative Examples 13, 15, and 17, a good LiBOB film was not formed on the surface of the negative electrode plate. The reason for this is that, particularly in Comparative Examples 13 and 17, the LiBOB coating is a mixture of products generated from components dissolved from the constituent members of the secondary battery, or the surface is covered with the products. It is thought that. Further, the LiBOB coating in Comparative Example 15 had no problem with respect to the uniformity of thickness, but it was not good quality and stable.

  As described above in detail, in the method for manufacturing the secondary battery 10 according to this embodiment, in the previous step of injecting the electrolytic solution, a heating press for heating the secondary battery 10 in a restrained state in the thickness direction is performed. . By this heating press, the deflection of the positive electrode plate 50, the negative electrode plate 60, and the separator 70 in the electrode body 20 is removed. After removing the deflection, an LiBOB-coated film having a uniform thickness can be formed on the surface of the negative electrode plate 60 by injecting an electrolytic solution to which LiBOB is added. Therefore, a method for manufacturing a non-aqueous electrolyte secondary battery capable of forming a high-quality film resulting from the additive added to the electrolyte on the surface of the electrode plate has been realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Accordingly, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. That is, for example, with respect to the heating press of the secondary battery 10 in the previous step of injecting the electrolyte solution 30, the method of using the heating press device 100 having the fixed portion 110 and the movable portion 120 has been described in the above embodiment. It is not limited to. For example, the secondary battery 10 can also be constrained by sandwiching the secondary battery 10 in the thickness direction between two plates and tightening the two plates with bolts. In addition, for example, the heating of the secondary battery 10 in the heating press is not limited to the heaters inside the fixed part 110 and the movable part 120, and for example, the environmental temperature of the secondary battery 10 is in the range of 80 ° C. to 110 ° C. Can also be done.

DESCRIPTION OF SYMBOLS 10 Secondary battery 20 Electrode body 30 Electrolytic solution 40 Battery case 44 Injection port 50 Positive electrode plate 60 Negative electrode plate 70 Separator 100 Heating press apparatus 110 Fixed part 120 Movable part

Claims (5)

Inside the battery case, it has an electrolyte solution containing an additive, and a flat electrode body formed by winding a positive and negative electrode plate with a separator sandwiched between them,
In the method of manufacturing a non-aqueous electrolyte secondary battery in which a film derived from the additive is formed on at least one surface of the positive and negative electrode plates,
After containing the electrode body in the battery case, before injecting the electrolyte solution with the additive added into the battery case,
A method for producing a non-aqueous electrolyte secondary battery, wherein a heating press step is performed in which the battery case containing the electrode body is heated while being restrained by applying a load in a thickness direction of the electrode body. In the manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1,
In the heating press process,
While restraining the load in the thickness direction of the electrode body on the battery case to be within the range from 0.15 MPa to 4.40 MPa as the pressure,
A method for producing a non-aqueous electrolyte secondary battery, wherein the electrode body is heated so that the temperature is within a range from 80 ° C to 110 ° C. In the manufacturing method of the nonaqueous electrolyte secondary battery according to claim 1 or 2,
The additive is LiBOB;
Injecting the electrolyte into the battery case,
The temperature of the electrolyte is in the range of 20 ° C. to 30 ° C .;
The method for producing a non-aqueous electrolyte secondary battery is performed in a state where the temperature of the electrode body is in a range from 35 ° C to 50 ° C. In the manufacturing method of the nonaqueous electrolyte secondary battery according to claim 3,
Injecting the electrolyte into the battery case,
The non-aqueous electrolyte is characterized in that the heat capacity ratio of the battery of the configuration before the electrolyte injection to the heat capacity of the electrolyte is within a range of 0.9 to 1.5. A method for manufacturing a secondary battery. In the manufacturing method of the non-aqueous-electrolyte secondary battery in any one of Claims 1-4,
The heating press process includes:
A method for producing a non-aqueous electrolyte secondary battery, which also serves as a dehydration step for removing moisture in the battery case before injection of the electrolyte into the battery case.

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