JP2022086615A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a non-aqueous electrolyte secondary battery that can appropriately reduce oxygen gas concentration inside a battery case when abnormal heat generation occurs.SOLUTION: A non-aqueous electrolyte secondary battery disclosed herein includes: an electrode body 20 having a positive electrode 50 and a negative electrode 60; a non-water electrolyte; and a battery case 30 capable of hermetically accommodating the electrode body and the non-aqueous electrolyte. The battery case 30 is provided with an outgassing valve 36 that releases internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. Inside the battery case 30, an oxygen scavenger 92, and sodium hydrogen carbonate, 94, and a water adsorbent are housed. Further, in the vertical direction as of when the above non-aqueous electrolyte secondary battery is used, the oxygen scavenger 92 is arranged on a relatively lower side, and the sodium hydrogen carbonate 94 is arranged on a relatively upper side, and the water adsorbent is arranged in the vicinity of sodium hydrogen carbonate 94.SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte secondary battery including an oxygen scavenger, sodium hydrogen carbonate, and a water adsorbent.

In recent years, secondary batteries such as lithium-ion secondary batteries have been used as portable power supplies for personal computers, mobile terminals, etc., and vehicle drive power supplies for electric vehicles (EV), hybrid vehicles (HV), plug-in hybrid vehicles (PHV), etc. It is suitably used for.

When an abnormal heat generation occurs in a secondary battery, oxygen gas may be generated from a positive electrode or the like. Therefore, conventional measures have been taken to improve safety when an abnormal heat generation occurs. For example, Patent Document 1 describes a gas generating agent that generates a nonflammable gas in order to reduce the oxygen gas concentration that can be generated inside the battery case when the non-aqueous electrolyte secondary battery generates abnormal heat. It is disclosed that it is placed inside. Further, Patent Document 2 describes a battery accommodating container for accommodating a plurality of batteries in order to reduce the concentration of oxygen gas released to the outside of the secondary battery when the non-aqueous electrolyte secondary battery generates abnormal heat. It is disclosed that a gas generating agent that generates a nonflammable gas is arranged therein, and Patent Document 3 discloses that an oxygen deoxidizing agent is arranged in a housing accommodating a plurality of secondary batteries.

Japanese Unexamined Patent Publication No. 2002-319436 Japanese Unexamined Patent Publication No. 2001-332237 Japanese Unexamined Patent Publication No. 2020-78727

By the way, in Patent Document 3, although it is possible to maintain the inside of the housing in a low oxygen state, there is a problem that the oxygen gas concentration inside each of the secondary batteries housed in the housing increases when abnormal heat generation occurs. In order to obtain a safer secondary battery, it is desirable to suppress an increase in oxygen gas concentration inside each secondary battery.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of reducing the oxygen gas concentration inside the battery case when abnormal heat generation occurs. ..

In order to solve the above problems, the non-aqueous electrolyte secondary battery disclosed here includes an electrode body having a positive electrode and a negative electrode, a non-aqueous electrolyte, and a battery case capable of hermetically accommodating the electrode body and the non-aqueous electrolyte. The battery case is provided with a gas release valve that releases the internal pressure when the internal pressure of the battery case rises above a predetermined level, and the inside of the battery case is provided with a deoxidizing agent. , Sodium hydrogen carbonate and a water adsorbent are contained. Further, in the vertical direction when the non-aqueous electrolyte secondary battery is used, the oxygen scavenger is relatively arranged on the lower side, and the sodium hydrogen carbonate is arranged on the relatively upper side. , The water adsorbent is arranged in the vicinity of the sodium hydrogen carbonate.
According to this configuration, when abnormal heat generation occurs in the non-aqueous electrolyte secondary battery, the increase in oxygen gas concentration inside the battery case can be suppressed by the deoxidizing agent and the carbon dioxide gas generated from sodium hydrogen carbonate. It is possible to release the internal pressure of the battery case more safely. Further, at the time of abnormal heat generation, the internal pressure of the battery case can be increased by the carbon dioxide generated from sodium hydrogen carbonate, and the gas release valve can be opened earlier.

Further, in a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the gas release valve is provided on the upper surface of the battery case in the vertical direction when the non-aqueous electrolyte secondary battery is used. ..
According to such a configuration, it is possible to release the gas in a state where the oxygen gas concentration is lowered by the carbon dioxide gas from the inside of the battery case at the time of abnormal heat generation.

Further, in a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the sodium hydrogen carbonate is arranged in the vicinity of the outgassing valve.
According to such a configuration, the oxygen concentration of the gas released from the gas release valve can be further reduced by the carbon dioxide gas generated from the sodium hydrogen carbonate at the time of abnormal heat generation.

Further, in a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the moisture adsorbent is arranged in a state of being contained in an insulating sheet.
According to such a configuration, the insulating property of the water adsorbent can be more reliably ensured.

Further, in a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the sodium hydrogen carbonate is sandwiched and held by an insulating sheet containing the water adsorbent.
With such a configuration, it is possible to prevent sodium hydrogencarbonate from dissolving in water and prevent sodium hydrogencarbonate from decomposing except during abnormal heat generation.

Further, in a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the oxygen scavenger is arranged on the lower surface of the battery case in the vertical direction when the non-aqueous electrolyte secondary battery is used. There is.
According to such a configuration, the oxygen scavenger is held more stably, and the oxygen gas inside the battery case can be absorbed more efficiently.

Further, in a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, an iron-based oxygen scavenger is included as the oxygen scavenger.
According to such a configuration, oxygen gas inside the battery case can be absorbed more quickly.

It is sectional drawing which shows typically the structure of the lithium ion secondary battery which concerns on one Embodiment. It is a schematic exploded view which shows the structure of the winding electrode body of the lithium ion secondary battery which concerns on one Embodiment.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Matters other than those specifically mentioned in the present specification and necessary for implementation can be grasped as design matters of those skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art. Further, in the following drawings, members / parts having the same function are designated by the same reference numerals, and duplicate explanations may be omitted or simplified. Further, the dimensional relations (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relations.
In addition, when the numerical range is described as A to B (where A and B are arbitrary numerical values) in this specification, it is the same as the general interpretation and means A or more and B or less. ..

As used herein, the term "secondary battery" refers to a general storage device that can be repeatedly charged and discharged, and includes so-called storage batteries (that is, chemical batteries) such as lithium ion secondary batteries, nickel hydrogen batteries, and nickel cadmium batteries, as well as electricity. Includes capacitors (ie, physical batteries) such as double layer capacitors. Further, in the present specification, the "lithium ion secondary battery" is a non-aqueous electrolyte secondary battery that uses lithium ions as a charge carrier and realizes charge / discharge by the transfer of charges accompanying the lithium ions between the positive and negative electrodes. Say. Hereinafter, a lithium ion secondary battery 100 will be described in detail as an example of the non-aqueous electrolyte secondary battery disclosed here.
In the following description, the reference numerals X and Y in the drawings represent the width direction and the height direction of the lithium ion secondary battery 100, respectively. Further, in the present specification, the vertical direction when the lithium ion secondary battery 100 is used is the above-mentioned height direction (reference numeral Y direction), and more specifically, the upward direction is the reference numeral U and the downward direction (the gravity direction) is the reference numeral D. show. However, the upward direction and the downward direction are merely directions for convenience of explanation, and do not limit the installation form when the lithium ion secondary battery 100 is used.

The lithium ion secondary battery 100 shown in FIG. 1 is constructed by accommodating a flat electrode body (wound electrode body) 20 and a non-aqueous electrolyte (not shown) inside the battery case 30. It is a square sealed battery. Further, the oxygen scavenger 92, the sodium hydrogen carbonate 94, and the water adsorbent (for example, the water adsorbent sheet 96) are housed inside the battery case 30. The oxygen scavenger 92 is arranged relatively downward in the vertical direction when the lithium ion secondary battery 100 is used, and the sodium hydrogen carbonate 94 is arranged relatively upward in the vertical direction. The water adsorbent (for example, the water adsorbent sheet 96) is arranged in the vicinity of the sodium hydrogen carbonate 94. With such an arrangement, the oxygen scavenger 92 can efficiently absorb oxygen gas that may be generated from the positive electrode 50 or the like at the time of abnormal heat generation. Further, the sodium hydrogen carbonate 94 decomposes at the time of abnormal heat generation to generate carbon dioxide gas, and the carbon dioxide gas moves downward due to gravity, so that the oxygen gas concentration inside the battery case 30 is lowered more uniformly. Can be done. As a result, it is possible to suppress an increase in the oxygen gas concentration inside the battery case 30 at the time of abnormal heat generation, so that a safer non-aqueous electrolyte secondary battery (here, a lithium ion secondary battery 100) is provided. Can be done. The "relatively lower side" typically refers to a region of the lower half of the height of the battery case 30 in the vertical direction when the non-aqueous electrolyte secondary battery is used. Further, the above-mentioned "relatively upper side" typically indicates a region of the upper half of the height of the battery case 30 in the vertical direction when the non-aqueous electrolyte secondary battery is used.

The battery case 30 has a six-sided box shape, and may include a case body 32 having an opening and a lid 34 for closing the opening. The case body 32 includes a rectangular bottom wall and four rectangular side walls. Further, when the internal pressure rises to a predetermined level (generally 0.1 MPa to 1.0 MPa, for example 0.3 MPa to 0.5 MPa), the battery case 30 releases a thin gas set to release the internal pressure. A valve 36 is provided. Further, the battery case 30 is provided with a liquid injection port (not shown) for injecting a non-water electrolytic solution (non-water electrolyte). Further, the battery case 30 is provided with a positive electrode terminal 42 and a negative electrode terminal 44 for external connection. The material of the battery case 30 is preferably a metal material having high strength, light weight, and good thermal conductivity, and examples of such a metal material include aluminum and steel.
The position of the gas release valve 36 is not particularly limited, but the upper surface of the battery case 30 (here, the lid 34) is placed in the vertical direction (Y direction in FIG. 1) when the lithium ion secondary battery 100 is used. ) Is preferable. With such a configuration, it is possible to release the gas inside the battery case 30 to the outside after the carbon dioxide gas generated from the sodium hydrogen carbonate 94 reduces the oxygen gas concentration by gravity at the time of abnormal heat generation.

As shown in FIGS. 1 and 2, the electrode body (rolled electrode body) 20 has a long sheet-shaped positive electrode 50 and a long sheet-shaped negative electrode 60 composed of two long sheet-shaped separators. It is laminated via 70 and is wound around a winding axis. The positive electrode 50 includes a positive electrode current collector 52 and a positive electrode active material layer 54 formed in the longitudinal direction on one or both sides of the positive electrode current collector 52. On one edge of the positive electrode current collector 52 in the winding axis direction (that is, the sheet width direction orthogonal to the longitudinal direction), the positive electrode active material layer 54 is not formed in a band shape along the edge. A portion where the positive electrode current collector 52 is exposed (that is, a positive electrode current collector exposed portion 52a) is provided. Further, the negative electrode 60 includes a negative electrode current collector 62 and a negative electrode active material layer 64 formed in the longitudinal direction of one side or both sides of the negative electrode current collector 62. At the edge of the negative electrode current collector 62 on one side opposite to the winding axis direction, the negative electrode active material layer 64 is not formed in a band shape along the edge, and the negative electrode current collector 62 is exposed ( That is, the negative electrode current collector exposed portion 62a) is provided. A positive electrode current collector plate 42a and a negative electrode current collector plate 44a are bonded to the positive electrode current collector exposed portion 52a and the negative electrode current collector exposed portion 62a, respectively. The positive electrode current collector plate 42a is electrically connected to the positive electrode terminal 42 for external connection, and realizes conduction between the inside and the outside of the battery case 30. Similarly, the negative electrode current collector plate 44a is electrically connected to the negative electrode terminal 44 for external connection, and realizes conduction between the inside and the outside of the battery case 30.

Examples of the positive electrode current collector 52 constituting the positive electrode 50 include aluminum foil. Examples of the positive electrode active material included in the positive electrode active material layer 54 include lithium composite metal oxides such as a layered structure and a spinel structure (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , etc. LiFeO ₂ , LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiCrMnO ₄ , LiFePO ₄ , etc.). Further, the positive electrode active material layer 54 may contain a conductive material, a binder, or the like. As the conductive material, for example, carbon black such as acetylene black (AB) or other carbon material (graphite or the like) can be preferably used. As the binder, for example, polyvinylidene fluoride (PVDF) or the like can be used.
In the positive electrode active material layer 54, the positive electrode active material and a material (conductive material, binder, etc.) used as needed are dispersed in an appropriate solvent (for example, N-methyl-2-pyrrolidone: NMP) to form a paste (or It can be formed by preparing a composition (in the form of a slurry), applying an appropriate amount of the composition to the surface of the positive electrode current collector 52, and drying the composition.

Examples of the negative electrode current collector 62 constituting the negative electrode 60 include copper foil and the like. The negative electrode active material layer 64 includes a negative electrode active material, and for example, a carbon material such as graphite, hard carbon, or soft carbon can be used. Further, the negative electrode active material layer 64 may further contain a binder, a thickener and the like. As the binder, for example, styrene butadiene rubber (SBR) or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) or the like can be used.
In the negative electrode active material layer 64, a negative electrode active material and a material (binder or the like) used as needed are dispersed in an appropriate solvent (for example, ion-exchanged water) to prepare a paste-like (or slurry-like) composition. , An appropriate amount of the composition can be applied to the surface of the negative electrode current collector 62 and dried.

As the separator 70, various microporous sheets similar to those conventionally used for lithium ion secondary batteries can be used, and for example, a microporous resin made of a resin such as polyethylene (PE) or polypropylene (PP). The sheet is mentioned. The microporous resin sheet may have a single-layer structure or a multi-layer structure having two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). Further, the surface of the separator 70 may be provided with a heat-resistant layer (HRL).

As the non-aqueous electrolyte, the same as the conventional lithium ion secondary battery can be used, and typically, a non-aqueous solvent containing a supporting salt can be used. As the non-aqueous solvent, an aprotic solvent such as carbonates, esters, ethers and the like can be used. Among them, carbonates, for example, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like can be preferably adopted. Alternatively, a fluorinated solvent such as a fluorinated carbonate such as monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyldifluoromethyl carbonate (F-DMC) and trifluorodimethylcarbonate (TFDMC) is preferably used. be able to. As such a non-aqueous solvent, one kind may be used alone, or two or more kinds may be used in combination as appropriate. As the supporting salt, for example, lithium salts such as LiPF ₆ , LiBF ₄ , and LiClO ₄ can be preferably used. The concentration of the supporting salt is not particularly limited, but is preferably about 0.7 mol / L or more and 1.3 mol / L or less.
The non-aqueous electrolyte may contain components other than the above-mentioned non-aqueous solvent and supporting salt as long as the effects of the present invention are not significantly impaired. It may contain various additives such as thickeners.

Further, in the lithium ion secondary battery 100, the insulating film 80 may be arranged between the inner wall of the battery case 30 and the electrode body 20 so as to separate the battery case 30 and the electrode body 20. The insulating film 80 can secure the insulation between the battery case 30 and the electrode body 20. The shape of the insulating film 80 is not particularly limited as long as such insulation can be realized, and may be, for example, a bottomed bag having an opening, and the electrode body 20 may be formed from the opening. Can be housed inside.
The insulating film 80 is made of a material that can function as an insulating member, and for example, various thermoplastic resins, typically polypropylene (PP), polyethylene (PE), and the like can be used. Further, the insulating film 80 may have a single-layer structure or a laminated structure having two or more layers.

The oxygen scavenger 92 can absorb oxygen gas that may exist inside the battery case 30. Inside the battery case 30, there are oxygen gas that can be contained when the battery case 30 is sealed, oxygen gas that can enter from the outside due to long-term use, oxygen gas that can be generated from the positive electrode 50 or the like during abnormal heat generation, and the like. obtain. Since the oxygen gas has a higher specific gravity than the nitrogen gas which can be the main gas inside the battery case 30, the oxygen gas is in the lower part inside the battery case 30 in the vertical direction when the lithium ion secondary battery 100 is used. It becomes easy to accumulate in. Therefore, the oxygen scavenger 92 is preferably arranged in a relatively lower portion inside the battery case 30, and is preferably arranged on, for example, the lower surface of the battery case 30. With such an arrangement, the oxygen scavenger 92 can be arranged in a more stable state, and oxygen gas that may exist inside the battery case 30 can be removed more efficiently.

The type of the deoxidizing agent 92 is not particularly limited, and for example, an iron-based deoxidizing agent (for example, iron powder), an organic-based deoxidizing agent (for example, sodium ascorbate) and the like can be used. Above all, it is preferable to use an iron-based oxygen scavenger. The iron-based oxygen scavenger quickly forms a compound with oxygen gas by an oxidation reaction, and can remove oxygen gas with high efficiency. The iron-based oxygen scavenger refers to an oxygen-based oxygen scavenger that has iron and utilizes the property of absorbing oxygen gas required for oxidation of the iron from the surrounding atmosphere. The oxygen scavenger has an organic substance that undergoes oxidative decomposition, and refers to an oxygen scavenger that utilizes the property of absorbing oxygen gas when the organic substance undergoes oxidative decomposition.

The amount of the oxygen scavenger 92 is not particularly limited, but for example, it is preferable to use an amount having the following formula (1).
S> B + E ... Equation (1)
(In the above formula (1), S is the oxygen absorption amount (mL) of the oxygen scavenger 92, B is the amount of oxygen gas existing when the battery case 30 is sealed [mL], and E is the battery case over time. The amount of oxygen gas [mL] that can enter the inside from the outside of 30 is shown.)
As the above S, the nominal oxygen absorption amount of the oxygen scavenger 92 to be used may be used. In B, the amount of oxygen gas may be roughly calculated from the volume inside the battery case 30 to be used, the electric power when the battery case 30 is sealed, and the composition of the gas sealed inside the pond case 30. The above E calculates the amount of oxygen gas that invades in a predetermined period (for example, one month) by a preliminary experiment, and based on the calculated value, the oxygen gas that can invade in the predicted battery usage period (for example, 20 years or more). You just need to find the approximate amount of. From the viewpoint of safety, the above S is preferably larger than the value on the right side in the equation (1), and is preferably 1.1 times or more, for example. By arranging the oxygen scavenger 92 so as to have such an amount, oxygen that may be generated at the time of abnormal heat generation can be absorbed more efficiently.

Sodium hydrogen carbonate 94 can undergo thermal decomposition at the time of abnormal heat generation to generate carbon dioxide gas. As a result, it is possible to promote an increase in the internal pressure of the battery case 30, so that the gas release valve 36 can be opened earlier when abnormal heat generation occurs. Further, the carbon dioxide gas generated can reduce the oxygen gas concentration inside the battery case 30. As a result, the oxygen concentration of the gas released from the gas discharge valve 36 decreases, so that higher safety can be ensured.

The sodium hydrogen carbonate 94 is preferably arranged relatively upward in the vertical direction when the lithium ion secondary battery 100 is used. Carbon dioxide gas has a higher specific density than nitrogen gas, which can be the main gas inside the battery case 30. Therefore, in such an arrangement, the carbon dioxide gas generated from the sodium hydrogen carbonate 94 at the time of abnormal heat generation moves from the upper side to the lower side inside the battery case 30 inside the battery case 30, so that the inside of the battery case 30 is used. The overall oxygen gas concentration can be efficiently reduced.

It is more preferable that the sodium hydrogen carbonate 94 is arranged in the vicinity of the gas discharge valve 36 included in the battery case 30. With such an arrangement, when the gas release valve 36 is opened, the carbon dioxide gas concentration of the gas released to the outside of the battery case 30 can be increased, so that the oxygen gas concentration can be further lowered, so that higher safety is achieved. Can be secured.

The amount of sodium hydrogen carbonate 94 is not particularly limited and can be appropriately changed depending on the internal volume of the battery case 30 and the opening conditions of the gas release valve 36, but from the viewpoint of safety, the sodium hydrogen carbonate 94 is used. Depending on the volume of carbon dioxide gas generated, an amount that can suppress the ratio of oxygen gas inside the battery case 30 at the time of abnormal heat generation to, for example, A volume% or less (typically, 15% by volume or less) is arranged. Is preferable. When the opening condition of the outgassing valve 36 is when the volume inside the battery case 30 expands x times, the amount of carbon dioxide gas y (mL) that can be generated from the sodium hydrogen carbonate 94 is the following formula (2). It is preferable to provide.
y> V ・ x－VV ・ x ・ (A / 100) ・ ・ ・ Equation (2)
(V in the above formula (2) indicates the initial volume [mL] inside the battery case 30 (that is, the state in which the battery case 30 is not deformed). The oxygen inside the battery case 30 before the abnormal heat generation is generated. It is assumed that the proportion of gas is 0% by volume.)
In other words, equation (2)
(Volume of carbon dioxide gas generated from sodium hydrogen carbonate 94 [mL])> (Volume inside the battery case 30 when the gas release valve 36 is open [mL])-(Initial volume inside the battery case 30 [mL]) ])-(Volume of A volume% inside the battery case 30 when the gas release valve 36 is open [mL])
Is shown. By providing the above formula (2), it is possible to open the gas release valve 36 while suppressing the proportion of oxygen gas in the entire inside of the battery case 30 from becoming higher than A volume% at the time of abnormal heat generation. This makes it possible to provide a lithium ion secondary battery with higher safety.

The sodium hydrogen carbonate 94 is preferably arranged in a powder state. When sodium hydrogencarbonate 94 is dissolved in water (or contains water), it has a property that the temperature for thermal decomposition becomes low, so that the decomposition can proceed gradually even at normal temperature and pressure. As a result, even when abnormal heat generation does not occur, the gas release valve 36 may be opened due to the increase in the internal pressure of the battery case 30 due to the carbon dioxide generated from the sodium hydrogen carbonate 94. Therefore, by using sodium hydrogen carbonate 94 in a powder state, carbon dioxide gas can be appropriately generated at the time of abnormal heat generation.

The water adsorbent can absorb the water that may exist inside the battery case 30. By absorbing such water, it is possible to prevent the sodium hydrogen carbonate 94 from being dissolved (or containing water) in water. Therefore, it is preferable that the water adsorbent is arranged in the vicinity of the sodium hydrogen carbonate 94. The water adsorbent is not particularly limited, but for example, silica gel, zeolite, porous glass and the like can be used.

It is preferable that the moisture adsorbent is arranged in a state of being contained in the insulating sheet (moisture adsorbent sheet 96). This makes it possible to more reliably insulate the water adsorbent that has absorbed water. The insulating sheet may be made of a material that can function as an insulating member, and for example, polypropylene (PP), polyethylene (PE), or the like can be used. Although not particularly limited, the moisture adsorbent sheet 96 may be fixed to, for example, the inner wall of the battery case 30 by a known method (for example, an adhesive, an adhesive, etc.).

As shown in FIG. 1, for example, the water adsorbent sheet 96 can be arranged with the sodium hydrogen carbonate 94 sandwiched therein. With such a configuration, since the sodium hydrogen carbonate 94 and the water adsorbent sheet 96 are arranged closer to each other, it is possible to more efficiently prevent the sodium hydrogen carbonate 94 from dissolving in water (or containing water). obtain. Further, with such a configuration, the sodium hydrogen carbonate 94 can be arranged more stably.
The shape of the water adsorbent sheet 96 is not particularly limited. For example, a bag-shaped product may be prepared in advance and sodium hydrogencarbonate 94 may be contained therein, or two moisture adsorbent sheets may be bonded (or welded) to each other in a state of facing each other. , Sodium hydrogen carbonate 94 may be sandwiched and held between the moisture adsorbent sheets. When the sodium hydrogen carbonate 94 is sealed in the water adsorbent sheet 96, the carbon dioxide gas generated from the sodium hydrogen carbonate 94 is sealed in the water adsorbent sheet 96 even when abnormal heat generation occurs, and the inside of the battery case 30 is sealed. It is preferable that at least a part of the water adsorbent sheet 96 sandwiching the sodium hydrogen carbonate 94 is open because there is a possibility that the gas does not diffuse into the water adsorbent.

The amount of the water adsorbent is not particularly limited, but for example, it is preferable to have the following formula (3).
W> (RA ・_A・ t ・ (h1 _－h2 ) K1) _/ (( _{C2 -} C1) ・^10-2 ) _＋ K2 ・ D ・ ・ ・ Equation (3)
(In the above formula (3), W: amount of moisture adsorbent [g], R: moisture permeability [g / m ² years], A: outer surface surface surface of the battery case 30 [m ² ], t: used. Period [year], h ₁ : Average humidity [%] outside the battery case 30, h ₂ : Average humidity [%] inside the battery case 30, K ₁ : Factors depending on the period of use and the outer material of the battery, C ₂ : Moisture absorption rate of moisture adsorbent at the start of use [%], C ₁ : Equilibrium moisture absorption rate of moisture adsorbent [%], K ₂ : Factor determined by the moisture absorption rate of the material inside the battery case 30, D: Inside the battery case 30 Indicates the mass [g] of the hygroscopic material.)
By providing the formula (3), the humidity inside the battery case 30 can be sufficiently lowered, so that the decomposition of sodium hydrogencarbonate 94 can be suppressed except when abnormal heat generation occurs.

The lithium ion secondary battery 100 can be used for various purposes. For example, it can be suitably used as a high-output power source (driving power source) for a motor mounted on a vehicle. The type of vehicle is not particularly limited, but typically examples thereof include automobiles, for example, plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), electric vehicles (EVs), and the like. The lithium ion secondary battery 100 can also be used in the form of an assembled battery in which a plurality of lithium ion secondary batteries 100 are electrically connected.

As described above, the lithium ion secondary battery provided with the wound electrode body has been described in detail as an example, but this is merely an example and does not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the above-described embodiments. For example, instead of the wound electrode body, a secondary battery having a laminated electrode body in which a sheet-shaped positive electrode and a sheet-shaped negative electrode are laminated via a sheet-shaped separator may be used. Further, the battery case 30 may have a shape other than a square shape (for example, a cylindrical shape). Further, the lithium ion secondary battery 100 may be an all-solid-state battery that uses a solid electrolyte as an electrolyte, or a polymer battery that uses a polymer electrolyte.

20 Electrode body 30 Battery case 32 Case body 34 Lid body 36 Gas discharge valve 42 Positive electrode terminal 42a Positive electrode current collector plate 44 Negative electrode terminal 44a Negative electrode current collector plate 50 Positive electrode 52 Positive electrode current collector 52a Positive electrode current collector exposed part 54 Positive electrode active material Layer 60 Negative electrode 62 Negative electrode current collector 62a Negative electrode current collector Exposed part 64 Negative electrode active material layer 70 Separator 80 Insulation film 92 Deoxidizer 94 Sodium hydrogen carbonate 96 Moisture adsorbent sheet 100 Lithium ion secondary battery

Claims (7)

An electrode body having a positive electrode and a negative electrode, a non-aqueous electrolyte, and a battery case capable of hermetically accommodating the electrode body and the non-aqueous electrolyte.
A non-aqueous electrolyte secondary battery equipped with
The battery case is provided with an outgassing valve that releases the internal pressure when the internal pressure of the battery case rises above a predetermined level.
An oxygen scavenger, sodium hydrogen carbonate, and a water adsorbent are housed inside the battery case.
Here, in the vertical direction when the secondary battery is used,
The oxygen scavenger is relatively lower and is located on the lower side.
The sodium hydrogen carbonate is arranged relatively on the upper side, and is arranged on the relatively upper side.
The water adsorbent is arranged in the vicinity of the sodium hydrogen carbonate,
Non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 1, wherein the gas release valve is provided on the upper surface of the battery case in the vertical direction when the secondary battery is used. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the sodium hydrogen carbonate is arranged in the vicinity of the outgassing valve. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the water adsorbent is arranged in a state of being contained in an insulating sheet. The non-aqueous electrolyte secondary battery according to claim 4, wherein the sodium hydrogen carbonate is sandwiched and held by an insulating sheet containing the water adsorbent. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the oxygen scavenger is arranged on the lower surface of the battery case in the vertical direction when the secondary battery is used. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, which contains an iron-based oxygen scavenger as the oxygen scavenger.

Images