JP2022074288A - Secondary battery - Google Patents

Abstract

To propose a secondary battery capable of promoting a heat radiation of an electrode body in charging in a temperature region where a temperature is equal to or larger than a normal temperature region, and suppressing the heat radiation of the electrode body in charging in a low temperature region.SOLUTION: A secondary battery 100 comprises: an electrode body 20; a battery case 10 in which the electrode body 20 is housed; and a heat radiator 40 formed of an elastic body. The heat radiator 40 is arranged between a side face 20a of the electrode body 20 and an inner side face 11c of the battery case 10 opposite to the side face 20a of the electrode body 20. The heat radiator 40 comprises: a first contact part 41 that is contacted to the side face 20a of the electrode body 20; and a second contact part 42 that is contacted to the inner side face 11c of the battery case 10 so as to be connected to the first contact part 41. In at least one of the first contact part 41 and the second contact part 42, at least tip end 42a1 is contacted to the side face 20a of the electrode body 20 or the inner side face 11c of the battery case 10, and includes a projection 42a in which a cross sectional area is progressively reduced toward the tip end 42a1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a secondary battery.

A secondary battery that can be charged and discharged has been conventionally known. In a secondary battery, the electrode body generates heat due to a chemical reaction during charging and discharging. Therefore, some secondary batteries have a configuration in which this heat is released to the outside. Patent Document 1 discloses a cylindrical lithium ion secondary battery housed in an outer tube having concave portions and convex portions formed in the circumferential direction. According to Patent Document 1, when a plurality of batteries are stored in a tray, a heat flow path can be formed by the recesses of the outer tube.

Further, Patent Document 2 discloses a secondary battery in which a metal gap filling material is arranged in a gap between an electrode winding body and a case member. According to Patent Document 2, the heat of the electrode winding body can be efficiently released to the outside of the case member through the gap filler made of a metal having high thermal conductivity.

Japanese Unexamined Patent Publication No. 2009-211908 Japanese Unexamined Patent Publication No. 2012-138211

If the secondary battery is provided with a configuration in which the heat generated by the electrode body is released to the outside of the battery, the heat of the electrode body is dissipated even during charging in a low temperature range. In the secondary battery, the electrical conductivity of cations decreases and the charging rate decreases in the low temperature range. Therefore, in charging in a low temperature range, it is desirable to keep the electrode body warm rather than dissipating the heat of the electrode body of the secondary battery.

Therefore, here, we propose a secondary battery that can promote heat dissipation of the electrode body when charging in a temperature range higher than the normal temperature range, and suppress heat dissipation of the electrode body when charging in a low temperature range.

The secondary battery proposed here includes an electrode body, a battery case in which the electrode body is housed, and a radiator body made of an elastic body. The radiator is arranged between the side surface of the electrode body and the inner surface of the battery case facing the side surface of the electrode body. The radiator includes a first contact portion that is in contact with the side surface of the electrode body, and a second contact portion that is connected to the first contact portion and is in contact with the inner surface surface of the battery case. At least one of the first contact portion and the second contact portion has a protrusion whose tip is in contact with the side surface of the electrode body or the inner side surface of the battery case and whose cross-sectional area gradually decreases toward the tip. ..

According to the above secondary battery, the contact area between the protrusion of the elastic body whose cross-sectional area gradually decreases toward the tip and the side surface of the electrode body or the inner surface of the battery case is elastic when the electrode body expands due to charging. It increases as the crushing increases. When the contact area between the protrusion and the side surface of the electrode body or the inner surface of the battery case is increased, heat conduction between the electrode body and the battery case is improved, and heat dissipation of the electrode body is promoted. On the other hand, when charging in the low temperature range, charging does not proceed as compared with the case where the temperature is above the normal temperature range, so that the contact area between the protrusion and the side surface of the electrode body or the inner surface of the battery case does not increase so much. Therefore, the heat dissipation of the electrode body is suppressed.

The secondary battery may be configured such that the first contact portion is in surface contact with the side surface of the electrode body and the second contact portion has protrusions. Alternatively, the secondary battery may be configured such that the second contact portion is in surface contact with the inner surface of the battery case and the first contact portion has a protrusion. The radiator can function even if one of the first contact portion and the second contact portion does not have a protrusion, and from the viewpoint of heat dissipation efficiency, the contact portion having no protrusion and the electrode body It is desirable that the contact area between the side surface of the battery case and the inner surface surface of the battery case is large. According to the secondary battery, the first contact portion or the second contact portion makes surface contact with the side surface of the electrode body or the inner surface surface of the battery case. Therefore, the contact area between the first contact portion and the side surface of the electrode body or the contact area between the second contact portion and the inner surface surface of the battery case becomes large. As a result, it is possible to improve the heat dissipation efficiency during charging in the normal temperature range.

The electrode body of the secondary battery may be formed in a substantially rectangular shape by stacking a sheet-shaped positive electrode and a sheet-shaped negative electrode via a separator, and the side surface of the electrode body is a stack of a positive electrode and a negative electrode. It may be the outer surface of the electrode body facing in the direction. The expansion and contraction of the electrode body is large in the stacking direction of the positive electrode and the negative electrode. Therefore, according to such a configuration, the function of the radiator is more effectively exhibited.

In the above secondary battery, the radiator may be formed of a resin mixed with ceramic powder. The radiator needs to have elasticity and preferably has high thermal conductivity. When viewed as a material for a radiator, resin has elasticity but low thermal conductivity. On the other hand, ceramic has a higher thermal conductivity than resin but does not have elasticity. Therefore, if the radiator is formed of a resin mixed with ceramic powder, it is possible to obtain a radiator having elasticity and higher thermal conductivity than the resin.

It is sectional drawing of the secondary battery. It is sectional drawing of the radiator on the front side. It is sectional drawing of the radiator during high-rate charging of a secondary battery. It is a graph which shows the relationship between the charge | charge in a normal temperature range, and the temperature of an electrode body. It is a graph which shows the relationship between the charge | charge in a low temperature region, and the temperature of an electrode body. It is sectional drawing of the secondary battery which concerns on other aspects.

Hereinafter, an embodiment of the secondary battery will be described. It should be noted that the embodiments described here are, of course, not intended to specifically limit the present invention. In addition, each figure is a schematic view and does not necessarily faithfully reflect the actual product. In the following, members and parts having the same function are designated by the same reference numerals, and overlapping description will be omitted or simplified as appropriate. Here, in the figure, front, back, top, and bottom are represented by F, Rr, U, and D, respectively. However, the front, back, top, and bottom are merely directions for convenience of explanation, and do not limit the installation mode of the secondary battery.

[Secondary battery configuration]
FIG. 1 is a cross-sectional view of the secondary battery 100. As shown in FIG. 1, the secondary battery 100 includes a battery case 10, an electrode body 20, an electrode terminal 30, and a radiator body 40. The battery case 10 houses the electrode body 20, the electrolytic solution, and the radiator body 40. As shown in FIG. 1, the battery case 10 includes a case main body 11 and a lid body 12. The case body 11 is a substantially rectangular parallelepiped flat square container. FIG. 1 is a vertical cross-sectional view of a flat-angle secondary battery 100 from the narrow surface side. Here, the normal direction of the pair of wide surfaces 11a of the case body 11 is the front-back direction of the secondary battery 100. The lid 12 is welded to the peripheral edge of the opening 11b opened on the upper surface of the case body 11. The case body 11 and the lid 12 are formed of, for example, aluminum or an aluminum alloy.

The electrode body 20 is formed by stacking a sheet-shaped positive electrode sheet 21 and a sheet-shaped negative electrode sheet 22 via separator sheets 23 and 24 to form a substantially rectangular parallelepiped shape. The electrode body 20 is housed in the case body 11. The first separator sheet 23, the positive electrode sheet 21, the second separator sheet 24, and the negative electrode sheet 22 are stacked and wound in this order, and are housed in the case body 11. Here, the stacking direction of the positive electrode sheet 21 and the negative electrode sheet 22 substantially coincides with the normal direction of the wide surface 11a of the battery case 10.

The positive electrode sheet 21 is a member in which a positive electrode active material layer containing a positive electrode active material is formed on both surfaces of a metal foil (for example, an aluminum foil) having a predetermined width and thickness. The positive electrode active material is, for example, a material that can release lithium ions during charging and absorb lithium ions during discharging, such as a lithium transition metal composite material in a lithium ion secondary battery. Various positive electrode active materials have been generally proposed in addition to the lithium transition metal composite material, and are not particularly limited.

The negative electrode sheet 22 is a member in which a negative electrode active material layer containing a negative electrode active material is formed on both surfaces of a metal foil (for example, a copper foil) having a predetermined width and thickness. The negative electrode active material is, for example, in a lithium ion secondary battery, a material that can absorb lithium ions during charging and release the stored lithium ions during charging, such as natural graphite. Various negative electrode active materials have been generally proposed in addition to natural graphite, and are not particularly limited. The positive electrode sheet 21 and the negative electrode sheet 22 are each connected to an electrode terminal 30 provided outside the battery case 10.

The heat radiating body 40 is arranged between the side surface of the electrode body 20 and the inner side surface of the battery case 10 facing the side surface of the electrode body 20. The side surface of the electrode body 20 with which the heat radiating body 40 comes into contact is not particularly limited, but here, it is the outer surfaces 20a and 20b of the electrode body 20 facing the stacking direction of the positive electrode sheet 21 and the negative electrode sheet 22. Therefore, the inner side surface of the battery case 10 facing the side surfaces 20a and 20b of the electrode body 20 is the inner side surfaces 11c and 11d of the pair of wall portions constituting the wide surface 11a. Here, a pair of front and rear radiators 40 are provided. The pair of radiators 40 are configured here symmetrically. Therefore, in the following, the front radiator 40 will be described in detail, and the rear radiator 40 will be omitted.

The radiator 40 is made of an elastic body. The radiator 40 is formed here by a resin mixed with ceramic powder. The resin is, for example, polyethylene. The ceramic powder is, for example, an alumina or silicon carbide-based ceramic powder. The material constituting the radiator 40 is preferably an insulating material, and preferably has solvent resistance that can withstand the solvent of the electrolytic solution and the electrolyte. Further, it is preferable that the radiator 40 has heat resistance that can withstand the maximum temperature or the maximum environmental temperature of the secondary battery 100 at the time of charging / discharging. Further, the radiator 40 preferably has a high thermal conductivity. Polyethylene has a relatively high thermal conductivity (about 0.3 to 0.5 W / m · K) and high solvent resistance among the resins, but its thermal conductivity is lower than that of alumina, for example (heat of alumina). The conductivity is 30-40 W / m · K). Ceramic has a high thermal conductivity, but does not have the elasticity required for the radiator 40. Therefore, in the present embodiment, the ceramic powder is mixed with the resin to form the radiator 40 having elasticity and higher thermal conductivity than the resin alone. However, the material of the radiator 40 is not particularly limited except that it is an elastic body.

FIG. 2 is a cross-sectional view of the radiator 40. As shown in FIG. 2, the radiator 40 includes a first contact portion 41 in contact with the side surface 20a of the electrode body 20, and a second contact portion 42 in contact with the inner side surface 11c of the battery case 10. The second contact portion 42 is connected to the first contact portion 41. The radiator 40 is one molded product here, and the first contact portion 41 and the second contact portion 42 are continuous. Note that FIG. 2 shows the radiator 40 in a state where the secondary battery 100 is not charged or discharged.

As shown in FIG. 2, the first contact portion 41 is in surface contact with the side surface 20a of the electrode body 20. The first contact portion 41 is configured to be flat. As shown in FIG. 1, the vertical length of the first contact portion 41 is longer than the vertical length of the electrode body 20. Although not shown, the first contact portion 41 extends in the left-right direction (the depth direction of the paper surface in FIG. 1). The length of the first contact portion 41 in the left-right direction is longer than the length of the electrode body 20 in the left-right direction. The first contact portion 41 is in contact with the entire surface of the side surface 20a of the electrode body 20.

As shown in FIG. 2, the second contact portion 42 includes a plurality of protrusions 42a that come into contact with the inner side surface 11c of the battery case 10. The plurality of protrusions 42a are provided side by side in the vertical direction. Each protrusion 42a projects from the first contact portion 41 toward the inner side surface 11c of the battery case 10. Each protrusion 42a is configured such that at least the tip 42a1 is in contact with the inner surface 11c of the battery case 10. As shown in FIG. 2, the cross-sectional area of each protrusion 42a gradually decreases toward the tip 42a1. Here, each protrusion 42a has a substantially triangular shape that narrows toward the inner side surface 11c of the battery case 10 in the left-right direction view. Although not shown, each protrusion 42a extends in the left-right direction while maintaining a substantially triangular cross-sectional shape.

The radiator 40 is sandwiched between the side surface 20a of the electrode body 20 and the inner surface 11c of the battery case 10. Therefore, as shown in FIG. 2, the tip 42a1 of the protrusion 42a is elastically crushed by the inner side surface 11c of the battery case 10. In the state shown in FIG. 2 (the state in which the secondary battery 100 is not charged or discharged), the contact area between the radiator 40 and the inner side surface 11c of the battery case 10 is the length L1 of FIG. 2 in the left-right direction of the electrode body 20. It is the area multiplied by the length of. The length L1 is the length in the vertical direction of the contact surface between the protrusion 42a and the inner side surface 11c of the battery case 10.

[When charging in the normal temperature range]
Next, the state of the radiator 40 when the secondary battery 100 is charged in a normal temperature range, particularly high-rate charging with a large current will be described. When the secondary battery 100 is charged, cations such as lithium ions are stored in the negative electrode sheet 22, and the negative electrode sheet 22 expands. FIG. 3 is a cross-sectional view of the radiator 40 during high-rate charging of the secondary battery 100. As shown in FIG. 3, during charging (particularly during high-rate charging in a normal temperature range), the electrode body 20 expands and a gap between the side surface 20a of the electrode body 20 and the inner side surface 11c of the battery case 10 Is getting narrower.

Further, the electrode body 20 generates heat when the secondary battery 100 is charged. When the temperature of the secondary battery 100 becomes high due to the heat generated by the electrode body 20, there is a high possibility that the deterioration of the secondary battery 100 will progress due to the generation of gas from the electrolytic solution or the like. Therefore, it becomes necessary to release the heat generated by the electrode body 20 to the outside of the secondary battery 100.

As shown in FIG. 3, when the electrode body 20 expands due to charging, the protrusion 42a of the heat radiating body 40 is further crushed as compared with the state of FIG. Therefore, the vertical length L2 of the contact surface between the protrusion 42a and the inner side surface 11c of the battery case 10 is longer than the same length L1 (see FIG. 2) when charging and discharging are not performed. In other words, the contact area between the radiator 40 and the inner surface 11c of the battery case 10 increases during charging as compared with when charging and discharging. In the secondary battery 100, the expansion of the electrode body 20 increases as the charging rate increases, so that the contact area between the radiator 40 and the inner surface 11c of the battery case 10 also increases as the charging rate increases.

When the contact area between the heat radiating body 40 and the inner side surface 11c of the battery case 10 increases, the heat conduction between the electrode body 20 and the battery case 10 is improved, and the heat dissipation of the electrode body 20 is promoted. In particular, as the charging rate increases, the contact area between the radiator 40 and the inner surface 11c of the battery case 10 increases, so that the radiator capacity of the radiator 40 also increases. The heat generated by the electrode body 20 increases as the charging rate increases. Therefore, as a result, as the calorific value of the electrode body 20 increases, the heat dissipation capacity of the radiator body 40 also increases.

[When charging in a low temperature range]
Next, the state of the radiator 40 when the secondary battery 100 is being charged in a low temperature range will be described. The electrolytic solution of the secondary battery 100 has a high viscosity in a low temperature range, and the ability to move cations (electrical conductivity of cations) decreases. Therefore, the charge rate is unlikely to increase in the low temperature range. In the low temperature range, it is preferable to raise the temperature of the secondary battery 100 rather than lower it in order to raise the charging rate.

In the low temperature range, charging does not proceed so much, so that the electrode body 20 does not expand much. Therefore, the contact area between the radiator 40 and the inner side surface 11c of the battery case 10 does not increase so much. Along with this, the heat dissipation capacity of the radiator body 40 does not increase so much. As a result, heat dissipation of the electrode body 20 is suppressed.

Some conventional secondary batteries are equipped with a radiator having a high heat dissipation capacity, but such a radiator dissipates heat from the electrode body even when charging in a low temperature range, so that the heat dissipation body is released in a low temperature range. Then, it was difficult for the temperature of the secondary battery to rise. On the other hand, according to the secondary battery 100 according to the present embodiment, it is possible to suppress heat dissipation of the electrode body 20 in charging in a low temperature range. As a result, the charging rate in the low temperature range can be improved.

FIG. 4 is a graph showing the relationship between charging in the normal temperature range and the temperature of the electrode body 20. FIG. 5 is a graph showing the relationship between charging in a low temperature range and the temperature of the electrode body 20. The horizontal axis of FIGS. 4 and 5 is time. The vertical axis of FIGS. 4 and 5 represents the temperature of the electrode body 20 and ON / OFF of charging. The graph G1A of FIG. 4 and the graph G2A of FIG. 5 show the temperature of the electrode body 20 when the radiator is not provided. The graph G1B of FIG. 4 and the graph G2B of FIG. 5 show the temperature of the electrode body 20 when the conventional radiator is provided. The graph G1C of FIG. 4 and the graph G2C of FIG. 5 show the temperature of the electrode body 20 when the radiator body 40 according to the present embodiment is provided.

As shown in the graph G1A of FIG. 4, when the secondary battery is not provided with the radiator, the temperature of the electrode body 20 rises with the start of charging in the normal temperature range. However, as shown in the graphs G1B and G1C of FIG. 4, when the secondary battery is provided with the conventional radiator and when the radiator 40 according to the present embodiment is provided, the temperature rise of the electrode body 20 is caused by the radiator. It can be suppressed as compared with the case where is not provided. The radiator 40 according to the present embodiment efficiently releases the heat of the electrode body 20 in the normal temperature range. Note that FIG. 4 is only an example of the heat dissipation capacity of the radiator body 40 according to the present embodiment in the normal temperature range. In other cases, the heat dissipation capacity of the radiator 40 according to the present embodiment in the normal temperature range may be smaller or larger than that in FIG. The same applies to FIG.

Next, FIG. 5 in the case of a low temperature range will be described. As shown in the graph G2B of FIG. 5, when the secondary battery is provided with the conventional radiator, the temperature rise of the electrode body 20 is suppressed to be low in the low temperature region. The heat of the electrode body 20 is dissipated by the conventional radiator body. On the other hand, as shown in the graphs G2A and G2C of FIG. 5, when the secondary battery is not provided with the radiator and when the radiator 40 according to the present embodiment is provided, the temperature of the electrode body 20 is conventionally set. It rises as compared with the case where the radiator is provided. The heat radiating body 40 according to the present embodiment suppresses heat dissipation of the electrode body 20 in a low temperature range. As a result, the temperature of the secondary battery 100 rises, and the charging rate also improves.

[Action and effect of this embodiment]
As described above, according to the secondary battery 100 according to the present embodiment, between the radiator 40 and the inner side surfaces 11c and 11d of the battery case 10 due to the protrusion 42a of the elastic body whose cross-sectional area gradually decreases toward the tip. The thermal conductivity of the battery increases and decreases as the charging rate increases and decreases. Therefore, it is possible to promote heat dissipation of the electrode body 20 when charging in a temperature range higher than the normal temperature range where the charging rate is high, and suppress heat dissipation of the electrode body 20 when charging in a low temperature range where the charging rate is low.

Further, according to the secondary battery 100 according to the present embodiment, since the first contact portion 41 of the radiator body 40 is in surface contact with the electrode body 20, the heat radiation efficiency of the electrode body 20 in a temperature range higher than the normal temperature range. Can be enhanced.

According to the secondary battery 100 according to the present embodiment, the radiator 40 is the outer surfaces 20a and 20b of the electrode body 20 facing the stacking direction of the positive electrode sheet 21 and the negative electrode sheet 22, and the inner side surface 11c of the battery case 10. , 11d and between. The electrode body 20 has a large expansion and contraction in the stacking direction between the positive electrode sheet 21 and the negative electrode sheet 22. Therefore, the function of the heat radiating body 40 that links the expansion and contraction of the electrode body 20 and the heat radiating capacity can be effectively exerted. Further, since the positive electrode sheet 21 and the negative electrode sheet 22 are configured in a sheet shape, the stacking direction thereof substantially coincides with the normal direction of the positive electrode sheet 21 and the negative electrode sheet 22. Therefore, the radiator body 40 can efficiently dissipate heat from the electrode body 20.

In the present embodiment, the radiator 40 is formed of a resin mixed with ceramic powder. Therefore, the radiator 40 can be made to have elasticity and high thermal conductivity.

[Other embodiments]
The embodiment of the secondary battery proposed here has been described above. However, the above embodiment is only an example, and can be implemented in other embodiments. For example, the shape of the radiator is not limited to the above. FIG. 6 is a cross-sectional view of the secondary battery 100 according to another aspect. As shown in FIG. 6, the second contact portion 46 of the radiator 45 may include only one protrusion 46a. Here, the protrusion 46a is formed in an arc shape in the longitudinal direction of the secondary battery 100. The protrusion 46a is configured such that at least the tip 46a1 is in contact with the inner side surface 11c of the battery case 10 and the cross-sectional area gradually decreases toward the tip 46a1. Even with this shape, the contact area between the radiator 45 and the inner side surface 11c of the battery case 10 increases or decreases depending on how the protrusion 46a is crushed. The shape of the protrusions of the radiator is not limited as long as the cross-sectional area gradually decreases toward the tip, and the number of protrusions is not limited.

Further, the protrusion may be provided on the first contact portion that comes into contact with the side surface of the electrode body. In that case, the second contact portion that contacts the inner surface of the battery case may or may not be provided with a protrusion. In other words, in the radiator, it is sufficient that at least one of the first contact portion and the second contact portion has a protrusion.

The “between the side surface of the electrode body and the inner surface of the battery case” in which the radiator is arranged is not limited to the wide surface of the electrode body and the inner surface of the battery case facing the wide surface of the electrode body. Further, the number of radiators is not limited to one pair. The radiator may be arranged, for example, below the electrode body 20 in FIG. 1, on the left side (front side of the paper surface), on the right side (back side of the paper surface), and the like. In addition, unless otherwise specified, the embodiments of the secondary battery mentioned here do not limit the present invention.

10 Battery case 11 Case body 11a Wide surface 11b Opening 11c Inner side surface of battery case 11d Inner side surface of battery case 12 Lid body 20 Electrode body 20a Side surface (outer surface) of electrode body
20b Side surface (outer surface) of the electrode body
21 Positive electrode sheet (positive electrode)
22 Negative electrode sheet (negative electrode)
23 First separator sheet (separator)
24 Second separator sheet (separator)
30 Electrode terminal 40 Radiator 41 First contact portion 42 Second contact portion 42a Protrusion 42a1 Protrusion tip 45 Dissipator (other embodiment)
46 Second contact portion (other embodiment)
46a protrusions (other embodiments)
46a1 Tip of protrusion (other embodiment)
100 secondary battery

Claims (5)

With the electrode body,
The battery case in which the electrode body is housed and
A radiator body made of an elastic body, which is arranged between a side surface of the electrode body and an inner side surface of the battery case facing the side surface of the electrode body, is provided.
The radiator is
The first contact portion in contact with the side surface of the electrode body and
A second contact portion connected to the first contact portion and in contact with the inner side surface of the battery case is provided.
At least one of the first contact portion and the second contact portion has at least a tip in contact with the side surface of the electrode body or the inner side surface of the battery case, and the cross-sectional area gradually decreases toward the tip. Has protrusions,
Secondary battery. The first contact portion is in surface contact with the side surface of the electrode body.
The second contact portion has the protrusion.
The secondary battery according to claim 1. The second contact portion is in surface contact with the inner side surface of the battery case.
The first contact portion has the protrusion.
The secondary battery according to claim 1. The electrode body is formed in a substantially rectangular parallelepiped shape by stacking a sheet-shaped positive electrode and a sheet-shaped negative electrode via a separator.
The side surface of the electrode body is an outer surface of the electrode body facing the stacking direction of the positive electrode and the negative electrode.
The secondary battery according to any one of claims 1 to 3. The radiator is formed of a resin mixed with ceramic powder.
The secondary battery according to any one of claims 1 to 4.

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