JP2015230761A - Method for manufacturing secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a secondary battery which enables the suppression of the precipitation of charged carriers.SOLUTION: A method for manufacturing a secondary battery 100 having of an electrolyte, an excessive electrolyte 70 remaining in a battery case 10 without being impregnated into an electrode body 20, which the present invention offers, comprises the steps of: encasing the electrode body 20 having a positive electrode 30 and a negative electrode 40, and an electrolyte absorber 60 in the battery case 10, provided that the electrolyte absorber 60 is disposed so as not to be in contact with the electrode body 20; injecting the electrolyte into the battery case 10; using the electrolyte absorber 60 to absorb, of the injected electrolyte, the excessive electrolyte 70 remaining without being impregnated into the electrode body 20; and initially charging the electrode body 20.

Description

  The present invention relates to a method for manufacturing a secondary battery including an electrode body and an electrolytic solution.

  A secondary battery such as a lithium ion secondary battery (for example, Patent Document 1) is used in, for example, a power source mounted on a vehicle that uses electricity as a drive source, a personal computer, a portable terminal, or other electrical products. In particular, a lithium ion secondary battery that is lightweight and has a high energy density is preferably used as a high-output power source for mounting on a vehicle.

  In a secondary battery such as this type of lithium ion secondary battery, a part of the electrolytic solution is decomposed during initial charging, and a coating made of the decomposition product on the surface of the active material (eg, negative electrode active material such as graphite particles). That is, a SEI (Solid Electrolyte Interface) film can be formed. The SEI film protects the active material and prevents charge carriers (for example, Li ions in the case of a lithium ion secondary battery) from being directly exposed to the deposition potential. It is required that the potential and temperature conditions to be exposed to are in place.

JP2013-084483A

  By the way, in a secondary battery such as a lithium ion secondary battery, even when the electrolyte is properly distributed to each part of the electrode body at the time of manufacturing (typically, the electrode body has sufficiently penetrated the entire electrode body) There may be a portion where the electrolyte is partially insufficient (so-called “liquid withdrawing” phenomenon) due to a period or use at a high rate. As a method for preventing liquid withering, for example, it is conceivable to store an excessive amount of electrolytic solution (excess electrolytic solution) in the battery in advance at the time of manufacturing the battery so as not to cause shortage of the electrolytic solution.

  However, according to the study of the present inventor, in the secondary battery in which the surplus electrolyte is previously stored in the battery so as not to cause the electrolyte shortage, the surplus electrolysis of the electrode body is started at the start of the initial charge (initial stage). When the temperature of a part already in contact with the liquid (for example, a part of the lower side of the electrode body immersed in excess electrolyte solution) is smaller than that of the other part and thus does not reach the SEI film formation temperature. There is. For this reason, the SEI film is not sufficiently formed on the surface of the active material at the place where it is in contact with the surplus electrolyte, and charge carriers (for example, Li ions) are directly exposed to the deposition potential, resulting in the deposition of charge carriers. was there. The present invention solves the above problems.

  The manufacturing method proposed here is a method for manufacturing a secondary battery in which a surplus electrolytic solution remaining without being impregnated in an electrode body is contained in a battery case. This manufacturing method includes accommodating an electrode body having a positive electrode and a negative electrode and an electrolyte solution absorber in a battery case (accommodating step). Here, the electrolyte solution absorber is disposed so as not to contact the electrode body. Further, the method includes pouring an electrolytic solution into the battery case (a pouring step). Furthermore, the electrolyte solution absorber is made to absorb the excess electrolyte solution which was not impregnated in the electrode body among the injected electrolyte solution (absorption process). And it includes performing initial charge with respect to the said electrode body after the said absorption process (initial charge process).

  According to this manufacturing method, since the surplus electrolyte is absorbed by the electrolyte absorber at the start (initial stage) of the initial charge, the surplus electrolyte is not in contact with the electrode body. Therefore, it is possible to eliminate or alleviate an event in which charge carriers (for example, Li ions) are precipitated due to the surplus electrolyte solution contacting the electrode body at the start of initial charging.

It is a cross-sectional schematic diagram which shows the secondary battery which concerns on one Embodiment of this invention. It is a figure which shows the manufacturing process of the secondary battery which concerns on one Embodiment of this invention. It is a figure which shows the manufacturing process of the secondary battery which concerns on one Embodiment of this invention. It is a figure which shows the manufacturing process of the secondary battery which concerns on one Embodiment of this invention. It is a figure which shows the manufacturing process of the secondary battery which concerns on one Embodiment of this invention. It is a figure which shows the presence or absence of Li precipitation of a comparative example. It is a figure which shows the presence or absence of Li precipitation of an Example. It is a graph which shows the excess electrolyte solution amount of an Example and a comparative example.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a so-called storage battery such as a lithium ion secondary battery and a power storage element such as an electric double layer capacitor. The “lithium ion secondary battery” refers to a secondary battery that uses lithium ions as electrolyte ions and is charged and discharged by the movement of lithium ions between positive and negative electrodes. As a preferred embodiment of a method for producing a secondary battery disclosed herein, a method for producing a lithium ion secondary battery will be described in detail as an example. It is not intended to be limited to secondary batteries.

  FIG. 1 is a cross-sectional view schematically showing a lithium ion secondary battery (secondary battery) 100 according to the present embodiment. As shown in FIG. 1, the lithium ion secondary battery 100 includes a battery case 10 made of metal (for example, made of aluminum, and also preferably made of resin or laminate film). A battery case (outer container) 10 includes a case body (exterior case) 12 having a flat bottomed box shape (typically a rectangular parallelepiped shape) with an open upper end, and a lid for closing the opening of the case body 12. And a body 14. On the upper surface (that is, the lid body 14) of the battery case 10, a positive electrode terminal 50 electrically connected to the positive electrode sheet (positive electrode) 30 of the wound electrode body (electrode body) 20 and a negative electrode sheet 40 of the wound electrode body 20. A negative electrode terminal 52 is provided to be electrically connected to.

  An electrolytic solution is injected into the battery case 10. From the viewpoint of preventing liquid drainage, the amount of the electrolyte injected into the battery case 10 realizes a state in which the electrolyte has spread (permeated) the entire electrode body 20, and some electrolyte is excessive. The amount should be enough to remain as minutes. That is, the electrolyte injected into the battery case 10 includes an electrode internal electrolyte (not shown) impregnated in the electrode body 20 and an excess electrolyte 70 remaining without being impregnated in the electrode body 20. It is out. The excess electrolyte solution 70 and the electrolyte solution in the electrode may be in a state in which they can circulate with each other. In this embodiment, the excess electrolyte solution 70 stays in the lower part of the battery case 10 due to gravity. It is preferable that the amount of electrolyte used is such that the excess electrolyte 70 accumulated below can soak a part of the lower side of the electrode body 20. In addition, a liquid injection port (not shown) for injecting an electrolyte solution into the electrode body 20 is formed in the lid body 14 of the battery case 10. The liquid injection port is sealed with a sealing stopper (not shown).

As said electrolyte solution, the thing similar to the electrolyte solution conventionally used for a lithium ion secondary battery can be used without limitation. Such an electrolytic solution typically has a composition in which a supporting salt is contained in a suitable nonaqueous solvent (organic solvent). Examples of the non-aqueous solvent include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and the like. Can be used. Further, as the supporting salt (supporting electrolyte), for _example, it can be used lithium salts such as LiPF 6, LiBF _4. Further, difluorophosphate (LiPO ₂ F ₂ ) or lithium bisoxalate borate (LiBOB) may be dissolved in the non-aqueous electrolyte.

  An electrolytic solution absorber 60 is accommodated in the battery case 10. The electrolyte solution absorber 60 is a member for absorbing the excess electrolyte solution 70 remaining in the electrolyte solution without being impregnated in the electrolyte solution before and after the initial charging described later. The electrolyte solution absorber 60 may be disposed at a distance from the electrode body 20 so as not to contact the electrode body 20. In this embodiment, the electrolytic solution absorber 60 is fixed to the inner surface of the lid body 14.

  The electrolytic solution absorber 60 used in the present embodiment is preferably one that can sufficiently absorb the excess electrolytic solution 70 that remains without being impregnated in the electrode body 20. Moreover, it is preferable to use the electrolytic solution absorber 60 which is electrochemically stable without reacting with the electrolytic solution. Furthermore, it is preferable that the electrolyte solution absorber 60 be capable of releasing the surplus electrolyte solution 70 as the battery internal pressure during initial charging described later increases. The electrolytic solution absorber 60 satisfying such conditions can be used without particular limitation. As the electrolytic solution absorber 60, a porous body made of a polymer material or the like can be used. Specifically, urethane processed into a sponge shape can be used as appropriate. In this embodiment, the electrolytic solution absorber 60 is made of urethane sponge.

  The amount of the electrolytic solution absorber 60 accommodated in the battery case 10 is substantially the same as the excess electrolytic solution 70 remaining without being impregnated in the electrode body 20 out of the electrolytic solution injected into the battery case 10. Any amount that can be absorbed is acceptable.

Next, a preferred embodiment of a method for producing the lithium ion secondary battery (secondary battery) 100 will be described with reference to FIGS.
The method for manufacturing a secondary battery disclosed herein includes housing the electrode body 20 having the positive electrode 30 and the negative electrode 40 and the electrolyte solution absorber 60 in the battery case 10 (accommodating step); Injecting the liquid (injection step); causing the electrolyte solution absorber 60 to absorb the surplus electrolyte 70 remaining without being impregnated in the electrode body 20 among the injected electrolyte (absorption step); Performing initial charging of the body 20 (initial charging step). Hereinafter, each process is explained in full detail.

  In the housing step, as shown in FIG. 2, the electrode body 20 having the positive electrode 30 and the negative electrode 40 and the electrolytic solution absorber 60 are housed in the battery case 10. At this time, the electrolytic solution absorber 60 is disposed so as not to contact the electrode body 20. Here, the electrolytic solution absorber 60 is fixed to the inner surface of the lid body 14 so as not to contact the electrode body 20. For example, the electrode body 20 may be accommodated in the case body 12, the opening of the case body 12 may be closed with the lid body 14, and sealed by welding or the like.

  In the liquid injection process, an electrolyte solution is injected into the battery case 10 as shown in FIG. In this embodiment, an electrolytic solution is injected into the battery case 10 from a liquid injection port (not shown) formed in the lid body 14. At this time, the injection amount of the electrolytic solution may be set to an amount that allows the electrolytic solution to reach the entire electrode body 20 and that some electrolytic solution remains as a surplus. Then, a liquid injection port (not shown) of the battery case 10 into which a predetermined amount of electrolytic solution has been injected is sealed with a sealing plug by welding or the like. At this time, in the case main body 12, there can be an excess electrolytic solution 70 that remains without being impregnated in the electrode body 20 among the injected electrolytic solution.

  In the absorption step, the electrolyte solution absorber 60 absorbs the excess electrolyte solution 70 remaining without being impregnated in the electrode body 20 among the injected electrolyte solution. Here, as shown in FIG. 4A, the excess electrolyte solution 70 is moved to the inner surface of the lid body 14 by rotating the battery case 10 180 degrees so that the lid body 14 is at the bottom (upside down). . Then, as shown in FIG. 4B, the excess electrolyte solution 70 is absorbed by the electrolyte solution absorber 60 fixed to the inner surface of the lid body 14. The time required for the excess electrolyte solution 70 to be absorbed by the electrolyte absorber 60 may be about 15 to 20 seconds.

  In the initial charging step, the electrode body 20 is initially charged after the absorption step. Here, as shown in FIG. 5 (a), the battery case 10 is again rotated 180 ° (inverted vertically), so that the electrolytic solution absorber 60 that has absorbed the excess electrolytic solution 70 is disposed above the electrode body 20. . Then, the electrode body 20 is charged to a predetermined voltage value in the normal temperature range. Typically, an external power source is connected between the positive electrode 30 (positive electrode terminal 50) and the negative electrode 40 (negative electrode terminal 52), and charging to a predetermined voltage (typically constant current and constant voltage charging) is performed. Here, the normal temperature region in the initial charging step refers to a temperature region that is typically normal temperature, and refers to 20 ° C. ± 15 ° C. In addition, the voltage between the positive and negative terminals (typically the highest voltage reached) in the initial charging process may vary depending on the active material used, the type of non-aqueous solvent, and the like, but the SOC (State of Charge) of the battery ) May be a voltage range that can be shown when it is in the range of about 80% or more (typically 90 to 105%) of the fully charged state (typically the rated capacity of the battery). The charging rate in the initial charging process may be the same as a conventionally known charging rate that can be generally adopted when initially charging a conventional battery, and may be about 0.1 to 10 C, for example.

  At the start of the initial charging, as shown in FIG. 5A, the excess electrolyte 70 remaining without being impregnated in the electrode body 20 of the electrolyte is absorbed by the electrolyte absorber 60. 70 is not in contact with the electrode body 20. Therefore, at the start of initial charging, initial charging is performed in a state where the excess electrolyte solution 70 is not in contact with the electrode body 20. Further, when the initial charging proceeds, gas is generated in the battery case 10 due to decomposition of the electrolytic solution and the pressure in the battery (internal pressure) increases. Due to the increase in the internal pressure, the electrolytic solution absorber 60 made of urethane sponge is compressed, and the excess electrolytic solution 70 is released from the electrolytic solution absorber 60 (see FIG. 5B). The discharged excess electrolytic solution 70 stays in the lower part of the battery case 10 and comes into contact with the electrode body 20 (see FIG. 5C). In this way, a secondary battery having the excess electrolyte solution 70 remaining in the electrolyte solution without being impregnated in the electrode body 20 in the battery case 10 can be manufactured. Then, you may perform processes, such as degassing and a quality inspection, as needed.

  According to this manufacturing method, after the excess electrolytic solution 70 remaining without being impregnated in the electrode body 20 is absorbed by the electrolytic solution absorber 60, the electrode body 20 is initially charged. In the initial stage, the excess electrolyte solution 70 is not in contact with the electrode body 20. Therefore, it is possible to prevent an event in which charge carriers (Li ions in this case) are deposited due to the surplus electrolyte 70 being in contact with the electrode body 20 at the start of initial charging.

  Moreover, in the said embodiment, since the electrolyte solution absorber 60 is comprised so that the excess electrolyte solution 70 can be discharge | released with the raise of the internal pressure at the time of initial charge, after the initial charge, the excess electrolyte solution 70 is electrode. It comes into contact with the body 20 again. By bringing the excess electrolyte solution 70 into contact with the electrode body 20 in this manner, it is possible to prevent the electrode body 20 from being drained due to long-term use or use at a high rate.

  In addition, the material and member itself which comprise the winding electrode body (electrode body) 20 may be the same as the electrode body with which the conventional lithium ion secondary battery is equipped, and there is no restriction | limiting in particular. For example, the wound electrode body 20 has a long (strip-shaped) sheet structure in a stage before assembling the wound electrode body 20.

  As shown in FIG. 1, the positive electrode sheet 30 has a structure in which a positive electrode active material layer containing a positive electrode active material is held on both surfaces of a long sheet-like foil-shaped positive electrode current collector 32. However, the positive electrode active material layer is not attached to one side edge of the positive electrode sheet 30 in the width direction, and the positive electrode active material layer non-forming portion 33 is formed in which the positive electrode current collector is exposed with a certain width. . Similarly to the positive electrode sheet 30, the negative electrode sheet 40 has a structure in which a negative electrode active material layer containing a negative electrode active material is held on both surfaces of a long sheet-like foil-shaped negative electrode current collector 42. However, the negative electrode active material layer is not attached to one side edge in the width direction of the negative electrode sheet 40, and the negative electrode active material layer non-forming portion 43 is formed in which the negative electrode current collector is exposed with a certain width. .

  In producing the wound electrode body 20, the positive electrode sheet 30 and the negative electrode sheet 40 are laminated via a separator sheet (not shown). At this time, the positive electrode sheet 30 and the negative electrode sheet 40 are so formed that the positive electrode active material layer non-formation part 33 of the positive electrode sheet 30 and the negative electrode active material layer non-formation part 43 of the negative electrode sheet 40 protrude from both sides in the width direction of the separator sheet. Are overlapped with a slight shift in the width direction. The laminated body thus stacked is wound, and then the obtained wound body is crushed from the side surface direction and ablated to produce the flat wound electrode body 20.

  In the central portion of the wound electrode body 20 in the winding axis direction, a wound core portion (that is, a portion where the positive electrode active material layer of the positive electrode sheet 30, the negative electrode active material layer of the negative electrode sheet 40, and the separator sheet are densely laminated) ) Is formed. Moreover, the electrode active material layer non-formation portions 33 and 43 of the positive electrode sheet 30 and the negative electrode sheet 40 protrude outward from the wound core portion at both ends of the wound electrode body 20 in the winding axis direction. A positive electrode lead terminal 54 and a negative electrode lead terminal 56 are respectively attached to the positive electrode side protruding portion (namely, the positive electrode active material layer non-forming portion) 33 and the negative electrode side protruding portion (namely, the negative electrode active material layer forming portion) 43. The positive electrode terminal 50 and the negative electrode terminal 52 are electrically connected to each other.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Example>
Weighing so that the mass ratio of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material, PVDF as the binder, and acetylene black as the conductive material is 89: 8: 3, These materials were dispersed in NMP to prepare a paste-like composition for forming a positive electrode active material layer. The composition was applied to both sides of a positive electrode current collector (aluminum foil) having a thickness of 15 μm and dried to prepare a positive electrode sheet having a positive electrode active material layer on the positive electrode current collector.

  On the other hand, the graphite particles as the negative electrode active material, the SBR as the binder, and the CMC as the thickener are weighed so that the mass ratio is 98: 1: 1, and these materials are dispersed in water. A paste-like composition for forming a negative electrode active material layer was prepared. The composition was applied to both surfaces of a negative electrode current collector (copper foil) having a thickness of 10 μm and dried to prepare a negative electrode sheet having a negative electrode active material layer on the negative electrode current collector.

  The produced positive electrode sheet and negative electrode sheet were wound into a flat shape via two separator sheets (polypropylene / polyethylene / polypropylene three-layer structure) to produce a wound electrode body. Then, as shown in FIG. 2, the electrode body 20 was accommodated in the rectangular case body 12 together with the electrolyte absorber 60, and the opening of the case body 12 was sealed with the lid body 14. The electrolyte solution absorber 60 (urethane sponge was used here) was fixed to the back surface of the lid body 14 so as not to contact the electrode body 20 (accommodating step). Next, as shown in FIG. 3, an electrolyte solution was injected into the battery case. The amount of electrolyte solution injected was such that the excess electrolyte solution 70 accumulated below could immerse a part of the lower R portion of the wound electrode body 20. Then, it was left for 24 hours (injection process). Next, as shown in FIGS. 4A and 4B, the battery case is turned upside down so that the lid body 14 is at the bottom, and the excess electrolyte solution 70 is absorbed into the electrolyte solution absorber 60 for 15 seconds (absorption). Process). And as shown to Fig.5 (a)-(c), the battery case was turned upside down again and the electrode body 20 was initially charged. Initial charging was performed by constant current constant voltage charging to 4.1 V at a charging rate of 1 C (initial charging step). Then, the lithium ion secondary battery which concerns on an Example was produced through the predetermined conditioning process.

<Comparative example>
In this example, the electrolytic solution absorber 60 is not disposed in the battery case in the housing step, and the absorption step is omitted. Other than that produced the lithium ion secondary battery which concerns on a comparative example in the same procedure as an Example.

<Presence or absence of Li precipitation>
About each battery of an Example and a comparative example, the battery was disassembled after initial charge, and the presence or absence of Li precipitation in the lower side R part (part where the excess electrolyte solution 70 was immersed) of the wound electrode body 20 was confirmed visually. . Here, the presence or absence of Li precipitation was confirmed in the outermost periphery R part of the negative electrode sheet. The results are shown in FIG. 6 (Comparative Example) and FIG. 7 (Example). As shown in FIGS. 6 and 7, Li precipitation was observed in the comparative example, but no Li precipitation was observed in the examples. From this result, it was confirmed that precipitation of Li can be suppressed by using this production method.

<Measurement of excess electrolyte amount>
The batteries of the examples and comparative examples were disassembled, and the amount of excess electrolyte solution 70 that did not soak into the wound electrode body 20 was measured. The results are shown in FIG. The surplus electrolyte amount was 23 cm ³ in the comparative example and 18 cm ^{3 in the} example, and it was possible to secure the surplus electrolyte amount to such an extent that the liquid did not dry out (approximately 8 cm ³ or more).

  Although the secondary battery according to one embodiment of the present invention has been described above, the secondary battery according to the present invention is not limited to any of the above-described embodiments, and various modifications can be made.

  As described above, the present invention can contribute to improving the performance of secondary batteries (for example, lithium ion secondary batteries). The present invention is suitable for a lithium ion secondary battery for a vehicle driving power source such as a driving battery for a hybrid vehicle or an electric vehicle. That is, for example, the lithium ion secondary battery can be suitably used as a vehicle driving power source for driving a motor (electric motor) of a vehicle such as an automobile. The power source for driving the vehicle may be an assembled battery in which a plurality of secondary batteries are combined.

DESCRIPTION OF SYMBOLS 10 Battery case 12 Case main body 14 Cover body 20 Winding electrode body 30 Positive electrode 40 Negative electrode 50 Positive electrode terminal 52 Negative electrode terminal 60 Electrolyte absorber 70 Excess electrolyte 100 Secondary battery

Claims (1)

A method for manufacturing a secondary battery having, in a battery case, a surplus electrolyte that remains without being impregnated in an electrode body among electrolytes,
A housing step of housing an electrode body having a positive electrode and a negative electrode and an electrolytic solution absorber in a battery case, wherein the electrolytic solution absorber is disposed so as not to contact the electrode body;
A liquid injection step of injecting an electrolyte into the battery case;
An absorption step of causing the electrolyte absorber to absorb excess electrolyte remaining without being impregnated in the electrode body among the injected electrolyte; and
An initial charging step of performing initial charging on the electrode body after the absorption step;
A method for manufacturing a secondary battery.