WO2013069622A1

WO2013069622A1 - Secondary cell

Info

Publication number: WO2013069622A1
Application number: PCT/JP2012/078693
Authority: WO
Inventors: 晃一谷山; 拓也宮下; 耕嗣北田; 恭平下山; 健治酒井
Original assignee: 三菱自動車工業株式会社; 三菱自動車エンジニアリング株式会社
Priority date: 2011-11-10
Filing date: 2012-11-06
Publication date: 2013-05-16
Also published as: KR20140105454A; CN103931041B; JP5800146B2; CN103931041A; JP2013105544A; KR101571988B1

Abstract

A secondary cell (1) provided with a cell case (11), an electrode body (13) accommodated inside the cell case, and an electrolytic solution (14) containing an initial additive and filling the interior of the cell case, the electrode body being provided with adding means (a capsule (3)) for adding to the electrolytic solution a restoring additive for restoring a deteriorated state of a coating film formed by the initial additive, and the additive being added in response to the deteriorated state.

Description

Secondary battery

The present invention relates to a secondary battery.

In recent years, a large number of electrically powered vehicles such as electric vehicles and plug-in hybrid vehicles have been put to practical use. A rechargeable lithium ion secondary battery is used as a drive battery mounted on such an electric vehicle.

In lithium ion secondary batteries, lithium ions and an electrolytic solution (electrolyte) react with each other to form a solid electrolyte interface (SEI) on the surface of an electrode. If the formation of this SEI is insufficient, there is a problem that the electrolyte and the electrode react excessively and the operation of the secondary battery becomes unstable. However, if the formation of SEI proceeds too much, between the positive electrode and the negative electrode in the battery There is a problem that the moving lithium ion decreases and the battery is deteriorated.

Conventionally, in order to solve such a problem, it is known to add, for example, vinylene carbonate (VC) as an additive to an electrolytic solution (see, for example, Patent Document 1). In patent document 1, VC is added and the film (henceforth a VC film) by VC is formed in an electrode surface, it has suppressed that SEI is formed too much. However, the VC film is gradually peeled off by the expansion and contraction of the electrode body.

Therefore, in the invention described in Patent Document 1, this VC is put into a capsule so that VC can be gradually added to the electrolyte with the passage of time, and the VC film peeled off by expansion and contraction is continuously regenerated. Control the formation of As a result, deterioration of the battery is suppressed.

JP, 2009-501419, A (claim 1 grade)

In Patent Document 1, since the capsule is a sustained release capsule and VC is gradually released with the passage of time, it is possible to recover the deterioration in the use state where the battery is deteriorated with the passage of time, which is effective. There is also.

However, if the additive is continuously added by means of a sustained release capsule, it is conceivable that the additive is released even when the battery has not deteriorated with the passage of time. In such a case, there is a problem that even if the additive is released too much, the VC film becomes too thick and the internal resistance becomes high. Such a problem occurs not only in the case of VC but also in the case of adding other additives for recovering the deteriorated state.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a secondary battery capable of effectively suppressing the deterioration of the battery without adding an additive excessively.

The secondary battery of the present invention is a secondary battery comprising a battery case, an electrode body housed inside the battery case, and an electrolytic solution filled in the battery case, containing an initial additive. The electrode body is characterized in that an adding means for adding a recovery additive for recovering the deteriorated state according to the deteriorated state of the film formed by the initial additive is provided to the electrolytic solution. By adding a recovery additive for recovering the deteriorated state according to the deteriorated state, the deterioration of the battery can be effectively suppressed. In addition, recovery of the degradation state as used herein refers to recovery of the degradation state of the battery due to peeling off of the film from the electrode due to expansion and contraction.

It is preferable that the addition means adds the additive to the electrolytic solution when the internal pressure in the battery case due to the deterioration of the secondary battery rises to a predetermined value or more. That is, the deterioration of the battery can be more effectively suppressed by detecting the deterioration of the battery by the increase in internal pressure and adding the additive to the electrolytic solution.

In a preferred embodiment of the present invention, the predetermined value is larger than the internal pressure change due to expansion and contraction during charge and discharge of the electrode body.

It is preferable that the addition means has a separation means for separating the additive from the electrolytic solution, and the separation means releases the additive to the electrolytic solution by being deformed according to the internal pressure. Thus, it is possible to add an additive more simply by comprising from the member which deform | transforms by an internal pressure directly, without having a measurement means which measures an internal pressure especially.

The addition means is a capsule as the separation means containing the additive, and the wall surface of the capsule is broken when the internal pressure reaches a predetermined value or more, and the additive is added to the electrolytic solution. Is preferred. By using such an addition means, an additive for recovering the deteriorated state can be easily added according to the deteriorated state.

The addition means is fitted in a tubular member whose one end side is sealed and the other end side is opened, and a hollow portion of the tubular member, and the hollow portion is moved to the one end side by the increase of the internal pressure And a storage unit in communication with the opening provided at one end side of the initial installation position of the moving unit of the cylindrical member, the storage unit containing the additive, It is preferable that the moving part move by the rising to add the additive to the electrolytic solution. By using such an addition means, an additive for recovering the deteriorated state can be easily added according to the deteriorated state.

It is preferable that an air reservoir part is formed in the said one end side of the said cylindrical member as the said addition means. By being comprised in this way, the internal pressure change by the expansion-contraction at the time of charge / discharge of the said electrode body can be absorbed.

According to the secondary battery of the present invention, the additive can be added according to the deterioration state, and the excellent effect that the deterioration of the battery can be effectively suppressed can be exhibited.

FIG. 1 is a perspective view of a secondary battery according to a first embodiment. FIG. 1 is a cross-sectional view of a secondary battery according to Embodiment 1. FIG. 6 is a cross-sectional view of a secondary battery according to a second embodiment. FIG. 7 is a schematic view of an addition device according to Embodiment 3. It is a schematic diagram of the addition apparatus concerning another embodiment.

(Embodiment 1)
A first embodiment of the present invention will be described using FIGS. FIG. 1 is a perspective view showing a secondary battery according to the present embodiment, FIG. 2 (1) is a cross-sectional view taken along the line AA 'of FIG. 1, and FIG. 2 (2) is B of FIG. It is sectional drawing in-B 'line.

The secondary battery 1 includes a substantially rectangular case 11 and a lid 12 disposed at the opening of the case 11 to seal the case 11. As shown in FIG. 2, the electrode body 13 is housed in the case 11. Further, the inside of the case 11 is filled with the electrolytic solution 14, and the electrode body 13 is immersed in the electrolytic solution 14. The electrode body 13 is formed by winding a laminate of a positive electrode plate and a negative electrode plate with a separator interposed therebetween, and the lamination direction is the lateral direction in the drawing.

The lid 12 is provided with a positive electrode terminal 15 and a negative electrode terminal 16. The positive electrode current collector 17 is connected to the positive electrode terminal 15. Further, a negative electrode current collector 18 is connected to the negative electrode terminal 16. The positive electrode current collecting unit 17 and the negative electrode current collecting unit 18 are connected to the positive electrode plate and the negative electrode plate of the electrode body 13 respectively. That is, the positive electrode plate, the positive electrode current collecting portion 17 and the positive electrode terminal 15 are electrically connected to each other. Further, the negative electrode plate, the negative electrode current collector portion 18 and the negative electrode terminal 16 are electrically connected to each other.

The positive electrode plate is made of a commonly used positive electrode material. Commonly used positive electrode materials include, for example, metal oxides capable of absorbing and desorbing lithium, such as metal oxides of layered structure type, spinel type metal oxides and metal compounds, metal salts of oxide salt type, etc. Be The layered structure type metal oxide may, for example, be a lithium nickel composite oxide, a lithium cobalt composite oxide, or a ternary composite oxide (LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ ). Preferably, lithium nickel oxide (LiNiO ₂ ) is mentioned as the lithium nickel composite oxide. The lithium cobalt-based composite oxide preferably includes lithium cobaltate (LiCoO ₂ ). The spinel-type metal oxides, lithium-manganese-based composite oxide such as lithium manganate (LiMn 2 _O ₄₎ can be mentioned. Examples of the oxide salt type metal oxide include lithium iron phosphate (LiFePO ₄ ), lithium manganese phosphate (LiMnPO ₄ ), lithium silicon phosphate and the like.

The negative electrode plate is made of a commonly used negative electrode active material. Examples of the negative electrode active material include commonly used active materials such as metal lithium, lithium alloy, metal oxide, metal sulfide, metal nitride, and carbon materials such as graphite. Examples of the metal oxide include those having irreversible capacity such as tin oxide and silicon oxide. The graphite as the carbon-based material may be artificial graphite or natural graphite, and in the present embodiment, graphite is used as the active material of the negative electrode.

Each of the positive electrode plate and the negative electrode plate may further contain a binder, and for example, polyvinylidene fluoride can be used. The active material layer may contain a conductivity improver such as acetylene black, an electrolyte (for example, a lithium salt (supporting electrolyte), an ion conductive polymer, etc.). In addition, when an ion conductive polymer is included, a polymerization initiator for polymerizing the polymer may be included.

The electrolyte solution 14 is a mixed solution of a commonly used electrolyte, for example, ethylene carbonate and propylene carbonate which are cyclic carbonates, and linear carbonates, and 1 mol of LiPF _{6 in} a mixed solution of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate. The organic electrolyte solution melt | dissolved to a density | concentration extent is mentioned. Further, vinylene carbonate (VC) is added to the electrolytic solution 14 as an initial additive.

Further, in the present embodiment, the electrolyte solution 14 contains

capsules

3 and 3A in which a recovery additive (hereinafter, also simply referred to as an additive) for recovering the film on the surface of the electrode is enclosed. In the present embodiment, when the internal pressure is equal to or higher than the predetermined internal pressure from the

capsules

3 and 3A, the additive sealed therein is released, so that the deterioration of the battery can be suppressed.

The

capsules

3 and 3A are made of a resin insoluble in the electrolyte, and their thicknesses are set so as to break when a predetermined pressure is applied. In the present embodiment, the capsule 3A is thicker than the capsule 3 and is hard to break. When the secondary battery is deteriorated by use, the internal pressure of the case 11 is increased. Therefore, the internal pressure of the case 11 is broken to release the encapsulated additive and the required amount according to the deterioration state. Additives can be added to the electrolyte, thereby suppressing the deterioration.

Hereinafter, the relationship between the internal pressure and the deterioration state will be specifically described. The secondary battery is used, and when lithium ions intercalate in the carbon electrode, lithium ions react with the electrolyte to generate a gas, whereby a solid electrolyte interface layer (SEI) is formed on the surface of the electrode. It is formed. SEI is necessary to stably charge and discharge at the time of initial operation of the secondary battery, but it is a lithium ion that can move between the positive electrode and the negative electrode in a state where SEI continues to be formed thereafter. And the battery capacity is likely to be reduced (deteriorated state). That is, in the state where SEI is formed, deterioration of the secondary battery is easily caused by reduction of battery capacity due to decrease of lithium ions which can move between the positive electrode and the negative electrode due to SEI formation. The problem is that the battery's external shape changes due to the rise in internal pressure due to the release of

On the other hand, vinylene carbonate (VC) is usually added in advance to the electrolyte as an initial additive for suppressing the formation of SEI in the secondary battery. As a result, a VC film is formed on the electrode surface to suppress the formation of SEI, and as a result, a decrease in battery capacity is suppressed, and at the same time, an increase in internal pressure is suppressed. However, the use of a secondary battery causes the VC film to peel off from the electrode surface due to expansion and contraction of the electrode. Then, SEI is likely to be formed at the peeled portion, and as a result, lithium ions which can move between the positive electrode and the negative electrode may be reduced to reduce the battery capacity. In this case, if VC is excessively added in advance in the secondary battery, the VC film may become too thick and internal resistance may increase.

Therefore, in the present embodiment, the

capsules

3 and 3A as an addition means for adding an additive according to the deterioration state of the secondary battery 1, that is, according to the increase in internal pressure, are contained in the electrolyte solution 14 in the secondary battery 1. It is contained. The state in which the internal pressure is rising corresponds to the deterioration state in which the VC film is peeled off and SEI is easily formed due to use as described above. Therefore, if the additive is released according to the increase in internal pressure, Thus, the coating on the electrode surface can be recovered.

By breaking the capsule 3 and releasing the additive, the VC film can be formed again in the area where the VC film on the electrode surface is peeled off (that is, the VC film can be recovered), and the formation of SEI Thus, it is possible to suppress the deterioration of the battery, that is, the capacity decrease due to the reduction of lithium ions which can move between the positive electrode and the negative electrode. Furthermore, since the additive is added in a deteriorated state, that is, in a state in which there is a region where the VC film on the electrode surface is peeled off, it is possible to suppress the VC film itself from being thickened and the battery resistance rising. For example, if the capsule is formed so as to dissolve after a certain period of time, the additive may be released from the capsule even in a state where the number of times of use is low and no deterioration occurs, and this causes the VC film to be thickened. It is not preferable because it is conceivable. Therefore, it is preferable to be able to add an additive in the state which degraded like this embodiment, and, thereby, deterioration of a battery can be effectively suppressed without adding an additive excessively.

The internal pressure also changes due to the expansion and contraction of the electrode during charge and discharge, but the internal pressure change due to the expansion and contraction of the electrode is smaller than the internal pressure change due to deterioration. Therefore, the capsule 3 is broken due to the expansion and contraction of the electrode during charge and discharge by setting the predetermined internal pressure value to break the capsule 3 larger than the amount of change in internal pressure due to the expansion and contraction of the electrode during charge and discharge. There is no.

The addition of the additive in this way is considered to prevent the internal pressure from turning to decrease, but the formation of the VC film can suppress the increase in internal pressure for a certain period of time. This simultaneously suppresses the deterioration of the battery. Then, when the VC film on the surface of the electrode is peeled off again by the expansion and contraction of the electrode again, the internal pressure gradually increases again. Then, another capsule 3A other than the torn capsule 3 is broken at a low internal pressure to release the additive. Thus, by containing a plurality of capsules having different thicknesses (in the present embodiment, two capsules having different thicknesses are contained, but the invention is not limited thereto), each is broken at a predetermined internal pressure to form a VC film. can do.

In addition, you may be made to contain two or more capsules according to the addition amount of an additive. That is, a plurality of

capsules

3 and 3A may be contained, or different numbers may be contained according to the addition amount. Of course, three or more capsules having different thicknesses may be contained.

Examples of the resin insoluble in the electrolyte constituting the

capsules

3 and 3A include polyolefins such as polyethylene and polypropylene, polystyrene, nylon, polycaprolactone, polyamide, and cellulose.

In the present embodiment, an additive capable of forming a VC film again is added, but the additive is not limited to the above-described VC. The additive may be any one as long as it can recover the film which has fallen off due to expansion and contraction of the electrode as described above, and examples thereof include vinylene ethylene carbonate, fluoro-ethylene carbonate, succinic anhydride, lactide, caprolactam, Ethylene sulfite, propane sultone (PS), propene sultone, vinyl sulfone, and derivatives thereof and halogen-substituted compounds can be mentioned. Furthermore, as an additive, for example, ethylenediaminetetraacetic acid, tetramethylethylenediamine, pyridine, dipyridyl, ethylenebis (diphenylphosphine), butyronitrile, succinonitrile, iodine and ammonium halide, such as hexamethyldisiloxane, hexamethoxycyclotriphosphazene , Hexamethylphosphoramide, cyclohexylbenzene, biphenyl, dimethylpyrrole, and their derivatives. One or more of these additives may be selected and contained in the

capsules

3 and 3A. The initial additive may also be the same as the additive described above.

The total amount of additives released in one addition may be about 0.5 to 1.0% by weight based on the amount of the electrolyte.

The initial additive and the recovery additive may be the same as in the present embodiment or may be different. Even if the initial additive and the recovery additive are different, it is sufficient if the reduction of lithium ions which can move between the positive electrode and the negative electrode can be suppressed by protecting the electrode and suppressing the formation of SEI.

Second Embodiment
The present embodiment differs from the first embodiment in that an addition device 4 shown in FIG. 3 is used instead of a capsule as an addition means.

The adding device 4 is installed, for example, on the back surface side of the lid 12 of the secondary battery 1 and adds an additive to the electrolyte solution 14 according to a change in internal pressure. The addition device 4 has a cylindrical portion 41 and a large diameter portion 42 provided on one end side of the cylindrical portion 41 and having a diameter larger than that of the cylindrical portion 41. The other end side of the cylindrical portion 41 is open. The cylindrical portion 41 is provided with a plurality of openings 43 along the longitudinal direction. Reservoir parts 44 communicate with the respective openings 43 respectively. The storage unit 44 is cylindrical with a bottom, and the additive 45 is stored therein. In addition, the cylindrical portion 41 is provided with a plug portion 46 which is fitted to the inner wall substantially in agreement with the inner diameter of the cylindrical portion 41. The plug portion 46 is made of, for example, a substance such as rubber. The plug portion 46 is configured to be movable in the tubular portion 41. The plug portion 46 is installed on the other end side of the cylindrical portion 41 as an initial state. The plug 46 is installed and fitted to the other end of the cylindrical portion 41 so that the pressure is the same as the external pressure in a state in which the large diameter portion 42 side of the plug 46 in the addition device 4 receives air. Is configured.

In the addition device 4, when the battery is deteriorated, that is, the internal pressure rises, the plug 46 is pressed by the internal pressure and gradually moves in the longitudinal direction of the cylindrical portion 41 toward one end, that is, the large diameter portion 42 side. Then, as shown in FIG. 3 (2), when the plug portion 46 moves and passes the storage portion 44 closest to the opening side of the cylindrical portion 41, the additive 45 stored in the storage portion 44 is opened. It passes through 43 and is released into the electrolyte 14. Therefore, as the internal pressure rises, the plug portion 46 moves in the cylindrical portion 41, whereby the additive 45 in each storage portion 44 is released into the electrolytic solution 14.

That is, also in the present embodiment, the additive 45 is discharged into the electrolyte solution 14 when the secondary battery 1 is deteriorated, that is, the VC film is removed and the increase in internal pressure exceeds a predetermined value. Thus, since VC is added when the VC film at the electrode is in a peeled state, the VC film can be formed again in the region where the VC film of the electrode is peeled, and the secondary battery is recovered. It is possible.

In this case, since the large diameter portion 42 is provided, the internal pressure change at the time of charge and discharge can be absorbed. That is, even if there is an internal pressure change at the time of charge and discharge, the detection pressure can be lowered by the air contained in the large diameter portion 42 being pressed outward. As a result, the plug 46 moves due to the change in internal pressure due to deterioration rather than the change in internal pressure due to normal charge and discharge. Since the addition device 4 is provided on the back surface side of the lid 12, the addition device 4 is unlikely to be affected by the expansion and contraction of the electrode body 13. This is because the electrode body 13 expands and contracts in the stacking direction.

(Embodiment 3)
The present embodiment differs from the second embodiment in that the plug portion 46 of the addition device 5 shown in FIG. 4 is pressed to the outside by an elastic body.

The addition device 5 according to the present embodiment is also provided, for example, on the back surface side of the lid 12 in the same manner as the addition device 4 (see FIG. 3), and adds an additive to the electrolyte according to the change in internal pressure. The addition device 5 is provided with a spring 51, one end of which is connected to a spring seat 52 provided on the large diameter portion 42, and the other end side is connected to the plug portion 46. The plug portion 46 installed near the inlet of the cylindrical portion 41 is pressed outward by the spring 51. However, as the internal pressure in the secondary battery 1 increases due to deterioration, the internal pressure is higher than the elastic force of the spring 51. As it becomes larger, the plug 46 moves inward. With such a configuration, the plug 46 can be more precisely controlled according to the internal pressure.

That is, also in the present embodiment, the additive 45 is discharged into the electrolyte solution 14 when the capacity of the secondary battery 1 is decreased, that is, the VC film is peeled off and the increase in internal pressure exceeds a predetermined value. Thus, since VC is added when the VC film at the electrode is in a peeled state, the VC film can be formed again in the area where the VC film of the electrode is peeled, and the secondary battery 1 is recovered. It is possible to

The addition means is not limited to the

capsules

3 and 3A and the

addition devices

4 and 5 described above. The additive 45 may be added according to the deterioration state. If the separator 45 has separation means for separating the additive 45 from the electrolytic solution and the separation means is configured to be deformed according to the internal pressure, the addition is easily performed according to the change in the internal pressure without providing any measurement means etc. The agent 45 can be effectively added.

The shapes of the

addition devices

4 and 5 are not limited to the above-described embodiments. For example, as shown in FIG. 5, it may be a shape having no large diameter portion. Furthermore, as shown in FIG. 5, the thickness of the cylindrical portion 41 is not constant, and the thickness gradually decreases from the other end side (open side) to the one end side (bottom side). May be In this case, as the plug portion 46 moves to one end side, the plug portion 46 is fitted into the inner wall of the cylindrical portion 41.

In each embodiment, the addition means is disposed in the electrolyte, but is not limited thereto. For example, as long as the plug 46 can be pressed by a change in internal pressure, it is not limited to being disposed in the electrolytic solution.

1

Secondary battery

3,

3A capsule

4, 5 Addition device (addition means)
DESCRIPTION OF SYMBOLS 5 Addition means 11 Case 12 Lid 13 Electrode body 14 Electrolyte 15 Positive electrode terminal 16 Negative electrode terminal 17 Positive electrode current collection part 18 Negative electrode current collection part 41 Tubular part 42 Large diameter part 43 Opening 44 Reservoir part 45 Additive 46 Plug part

Claims

A secondary battery comprising: a battery case; an electrode body housed inside the battery case; and an electrolyte solution containing an initial additive and filled in the battery case,
A secondary battery comprising an addition means for adding to the electrolytic solution a recovery additive for recovering the deteriorated state according to the deteriorated state of the film formed by the initial additive on the electrode body.
The said addition means adds the said additive to the said electrolyte solution, when the internal pressure in the said battery case by deterioration of the said secondary battery rises and it becomes more than predetermined value. Secondary battery.
The secondary battery according to claim 2, wherein the predetermined value is larger than a change in internal pressure due to expansion and contraction at the time of charge and discharge of the electrode body.
The addition means includes separation means for separating the additive from the electrolyte, and the separation means is deformed according to the internal pressure to release the additive to the electrolyte. Item 4. A secondary battery according to item 2 or 3.
The addition means is a capsule as the separation means containing the additive, and the wall surface of the capsule is broken when the internal pressure reaches a predetermined value or more, and the additive is added to the electrolytic solution. The secondary battery according to claim 4, characterized in that:
The addition means is fitted in a tubular member whose one end side is sealed and the other end side is opened, and a hollow portion of the tubular member, and the hollow portion is moved to the one end side by the increase of the internal pressure And a storage unit in communication with the opening provided at one end side of the initial installation position of the moving unit of the cylindrical member, the storage unit containing the additive, The secondary battery according to claim 4, wherein the moving part is moved by the rising to add the additive to the electrolytic solution.
The secondary battery according to claim 6, wherein the addition means has an air reservoir formed on the one end side of the cylindrical member.