Secondary battery

Abstract

To provide a secondary battery capable of suppressing the deterioration of battery performance.SOLUTION: The secondary battery includes: a wound body 12; an electrolyte 13; a case 11 accommodating the wound body 12 and the electrolyte 13; and a support part 14 placed on the bottom of the case 11 for supporting a curved portion 12a of the wound body 12. The support part 14 is formed of a material that allows the electrolyte 13 to pass through. With this, the lower R part of the wound body can be supported by the support part that allows the electrolyte to pass through, and the deterioration of battery performance can be suppressed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to secondary batteries. [Background technology]

[0002] In recent years, secondary batteries that are configured by housing a wound body and an electrolyte in a case have been used. Patent Document 1 describes a method in which a support is provided so as to come into contact with a curved portion of the wound body, thereby preventing the wound body from being damaged by contact with the support. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-168283 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, resistance to lithium precipitation is one of the properties that affect the battery performance and safety of secondary batteries. In secondary batteries, lithium is easily precipitated due to loosening or deterioration of the wound body, and the battery performance is reduced due to the lithium precipitation. Therefore, there is a demand to suppress the deterioration of the battery performance of secondary batteries by making it difficult for lithium to precipitate.

[0005] On the other hand, in the secondary battery disclosed in Patent Document 1, since the support part is provided so as to abut against the curved part of the wound body, the electrolyte contained in the case may have difficulty in contacting the wound body. Also, if the electrolyte cannot sufficiently contact the wound body, the battery performance may be deteriorated.

[0006] The present disclosure provides a secondary battery in which deterioration of battery performance is suppressed. [Means for solving the problem]

[0007] The secondary battery according to the present disclosure comprises a wound body, an electrolyte, a case that contains the wound body and the electrolyte, and a support portion arranged on the underside of the case and supporting a curved portion of the wound body, the support portion being formed from a material that allows the electrolyte to pass through. This allows the R portion at the bottom of the wound body to be supported by the support portion that allows the electrolyte to pass through. Effect of the Invention

[0008] According to the present disclosure, a secondary battery in which deterioration of battery performance is suppressed can be provided. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view showing an example of the outer shape of a secondary battery according to a first embodiment. [Diagram 2] 1 is a cross-sectional view showing the inside of a secondary battery according to a first embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of a process in which lithium is deposited in the secondary battery according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First embodiment Hereinafter, a secondary battery according to the present embodiment will be described with reference to the drawings. Fig. 1 is a diagram showing an example of the external appearance of a secondary battery. Fig. 2(a) is a diagram showing an example of a cross section taken along the dashed line in Fig. 1.

[0011] As shown in FIGS. 1 and 2, the secondary battery 1 includes a case 11, a wound body 12 housed in the case 11, an electrolyte 13, and a support portion .

[0012] As shown in FIG. 1, the case 11 has a substantially rectangular parallelepiped shape, and has a space therein capable of accommodating the wound body 12, the electrolyte 13, and the support portion .

[0013] As shown in Fig. 2(a), the wound body 12 is an electrode body in which the upper and lower parts are formed in an R-shape. The R-shaped curved parts formed in the upper and lower parts are referred to as R-parts 12a. Fig. 2(b) is a cross-sectional view similar to Fig. 2(a), specifically showing the state in which the wound body 12 is formed of multiple electrodes 21 in the inner and outer directions, and also showing the state in which the R-parts 12a are supported by a support part 14. Note that in Fig. 2(b), the case 11 and the electrolyte 13 are omitted for ease of understanding.

[0014] Here, there may be a case where the gap between the electrodes 21 of the R portion 12a of the wound body 12 becomes loose. Specifically, the gap between the electrodes 21 may be caused by loose winding in the early stage after the winding body 12 is formed, and the gap may be caused by gas accumulation or the like after that.

[0015] The electrolyte 13 is a liquid that is contained in the case 11 in a state where it is in contact with the wound body 12. In the secondary battery 1, the electrolyte 13 is in sufficient contact with the wound body 12, so that the secondary battery 1 can function as a battery.

[0016] The support portion 14 is disposed inside the case 11 and on the lower surface 11a. More specifically, the support portion 14 is disposed between the lower surface 11a of the case 11 and the R portion 12a of the wound body 12, and abuts against both. The support portion 14 is a resin mesh sheet, and it is desirable to use polypropylene (PP) or polyphenylene sulfide (PPS) that is resistant to the electrolyte 13, but the material is not limited to these and may be any material that allows the electrolyte 13 to pass through.

[0017] Here, in order to explain the effect of supporting R portion 12a of wound body 12 using a resin mesh sheet as support portion 14, an example of a state in which electrodes 21 in R portion 12a of wound body 12 are loosened, i.e., a process in which lithium (Li) is precipitated in R portion 12a of wound body 12, will be described with reference to Figures 3(a) to 3(e).

[0018] As shown in FIG. 3(a), in the initial stage after the winding body 12 is formed, a certain degree of uneven distribution occurs in the distance between the electrodes 21, particularly in the R portion 12a.

[0019] 3(b), when the wound body 12 is placed in the electrolyte 13, gas accumulates in pockets where there is a difference in distance between the electrodes 21 of the wound body 12. In other words, bubbles remain in some of the spaces between the electrodes 21 that form the wound body 12.

[0020] When current is applied from the state shown in FIG. 3(b), Li precipitates at the outlines of the bubbles remaining in the wound body 12, as shown in FIG. 3(c).

[0021] 3(d), even if the bubbles are removed from between the electrodes 21 of the wound body 12, the distance distribution between the electrodes 21 is changed in the pockets where the bubbles had been retained. That is, in the wound body 12, there are places where the distance between the electrodes 21 is short, and power tends to concentrate in these places where the distance between the electrodes 21 is short.

[0022] After that, as shown in FIG. 3(e), new Li precipitates between the Li precipitates that have precipitated at the bubble outlines in FIG. 3(c).

[0023] In order to suppress the deposition of Li in the secondary battery 1 that occurs in this way, the following is effective.

[0024] 3(a), pockets are generated and become gas pockets due to uneven distribution between the electrodes 21, particularly in the R portion 12a of the wound body 12. Therefore, it is effective to support the R portion 12a of the wound body 12 to reduce the uneven distribution.

[0025] 3(a), the support portion 14 supports the R portion 12a of the wound body 12 from below in a state where it is sandwiched between the lower surface 11a of the case 11 and the R portion 12a of the wound body 12. As a result, the electrodes 21 of the R portion 12a of the wound body 12 are held by an external force, and the occurrence of gaps between the electrodes 21 is suppressed.

[0026] 3(e), the support portion 14 is used to support the R portion 12a of the wound body 12 by an external force, thereby suppressing the gap between the electrodes 21 caused by gas generation. Therefore, the deposition of Li caused by the difference in the distance between the electrodes 21 of the wound body 12 can be suppressed.

[0027] Furthermore, by using a resin mesh sheet that is easily permeable to the electrolyte for the support 14, the R portion 12a of the wound body 12 is easily in contact with the electrolyte 13. Therefore, in the secondary battery 1, a decrease in battery performance caused by providing the support 14 can be suppressed.

[0028] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention. In other words, the above description has been omitted or simplified as appropriate for the purpose of clarity, and a person skilled in the art can easily modify, add, or convert each element of the embodiment within the scope of the present invention. [Explanation of symbols]

[0029] 1 Secondary battery 11 Cases 11a Bottom side 12 Wound body 12a R section 13 Electrolyte 14 Support part 21 electrodes

Claims

[Claim 1] A wound body; An electrolyte; a case that contains the wound body and the electrolyte; a support portion disposed in a lower portion of the case and supporting a curved portion of the winding body; The support portion is formed of a material that allows the electrolyte to pass through. Secondary battery.

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