WO2016035309A1 - Power storage element - Google Patents

Abstract

　The purpose of the present invention is to provide a power storage element in which impurity contamination of the interior of a packaging body, when a reference electrode part is provided within the packaging body, is minimized. The power storage element (1) is provided with a power storage element (3), the packaging body (2) comprising a conductor which is electrically insulated from the power storage element (3), and the reference electrode part (42), the reference electrode part (42) being configured such that a reference electrode mixture is directly formed on the inner surface of the packaging body (2). This makes it possible to minimize generation of packaging body (2) fragments and prevent generation of fragments from the reference electrode part (42) when the reference electrode part (42) is formed within the packaging body (2). As a result, it is possible to minimize impurity contamination in the interior of the packaging body (2).

Description

Electricity storage element

The technology disclosed in this specification relates to a power storage element having a reference electrode portion.

Conventionally, an electrochemical cell including a conductor case and a power generation element accommodated in the case is known (see Patent Document 1). The electrochemical cell includes a reference electrode that is housed in a case and is electrically connected to the case. This reference electrode is affixed to the bottom surface of the case.

According to the above electrochemical cell, since the potential of the positive electrode terminal with respect to the reference electrode and the potential of the negative electrode terminal with respect to the reference electrode can be measured, the state of the power generation element can be clearly detected.

JP 2013-30302 A

According to the above configuration, when the reference electrode having the reference electrode mixture layer formed on the surface of the current collector foil (metal foil) is attached in the case, the case and the current collector foil of the reference electrode can be welded. Conceivable. However, when the case and the reference electrode are welded, there is a possibility that case debris generated by welding or current collector foil debris of the reference electrode may be mixed into the case as impurities.

This specification discloses a technology related to a storage element in which impurities are prevented from being mixed into the exterior body when the reference electrode portion is provided in the exterior body.

The power storage element described in the present specification includes a power storage element, an exterior body made of a conductor that is electrically insulated from the power storage element, and a reference electrode part, and the reference electrode part includes a reference electrode mixture. It is formed in contact with the inner surface of the exterior body.

According to the technique disclosed in the present specification, it is possible to prevent impurities from being mixed into the exterior body when the reference electrode portion is provided in the exterior body.

The perspective view which shows the electrical storage element which concerns on this Embodiment 1 of this invention. The exploded perspective view which shows the electrical storage element of this invention Sectional drawing which shows the electrical storage element of this invention The block diagram which shows the electrical storage element system of this invention The side view which shows the several electrical storage element of this invention Schematic which shows the electrical storage apparatus provided with the electrical storage element of this invention Schematic which shows the motor vehicle provided with the electrical storage apparatus provided with the electrical storage element of this invention.

(Outline of the embodiment)
The power storage element described in the present specification includes a power storage element, an outer package made of a conductor that is electrically insulated from the power storage element, and a reference electrode part, and the reference electrode part includes a reference electrode mixture. It is formed in contact with the inner surface of the exterior body.

According to the above configuration, when the reference electrode portion is provided in the exterior body, it is possible to prevent impurities from being mixed into the exterior body. This is considered to be due to the following reasons.

To provide a reference electrode having a reference electrode mixture layer formed on the surface of the current collector foil in the outer package, and to fix the reference electrode in a state of being electrically connected to the outer package, for example, the outer package and the reference electrode It is conceivable to weld the current collector foil.

However, when the exterior body and the current collector foil of the reference electrode are welded, the current collector foil of the reference electrode or the fragments of the exterior body are generated by welding, and there is a possibility that they are mixed as impurities into the exterior body.

In view of the above points, according to the technique described in the present specification, the reference electrode mixture containing the reference electrode active material that absorbs or desorbs lithium ions is formed in contact with the inner surface of the exterior body. The reference electrode portion is formed. Thereby, when forming a reference pole part in an exterior body, while generating a fragment from an exterior body, it can also suppress that a fragment generate | occur | produces from a reference electrode part. As a result, it is possible to prevent impurities from being mixed into the exterior body when the reference electrode portion is provided in the exterior body.

A part of the outer surface of the exterior body may be cooled by a cooling medium, and the reference electrode portion may be formed in a region opposite to a part of the outer surface via the exterior body.

According to the above configuration, the temperature of the reference electrode part can be maintained in a relatively low state as compared with the case where the reference electrode part is provided in a region of the exterior body that is not cooled by the cooling medium. Thereby, since it is possible to suppress the self-discharge of the reference electrode part, the potential of the reference electrode part can be stabilized.

An insulating sheet through which lithium ions pass may be disposed between the electricity storage element and the reference electrode portion.

According to the above configuration, even if the reference electrode part is dropped from the case, the reference electrode part dropped from the case is in contact with the power storage element by the protective sheet disposed between the reference electrode part and the power storage element. Can be suppressed.

The reference electrode portion may contain a compound having a two-phase coexistence region.

According to the above configuration, the compound having a two-phase coexistence region has a constant potential in the two-phase coexistence region, so that the potential of the reference electrode portion can be stabilized.

The compound having the two-phase coexistence region may be a lithium phosphate transition metal compound.

According to the above configuration, in the lithium phosphate transition metal compound, the oxidation-reduction reaction in which lithium ions are deinserted proceeds by a two-phase coexistence reaction and has a flat potential region, so that the potential of the reference electrode portion is stabilized. be able to.

The area of the inner surface of the exterior body where the reference electrode part is formed may be rougher than the area of the inner surface of the exterior body where the reference electrode part is not formed.

According to the above configuration, since the area of the inner surface of the exterior body where the reference electrode portion is formed is rough, it is possible to make it difficult for the reference electrode portion to be detached from the inner surface of the exterior body.

A plurality of the power storage elements may be used to form a power storage device.

The power storage device may be used as an automobile.

<Embodiment 1>
A power storage device 1 according to Embodiment 1 will be described with reference to FIGS. In the following description, in FIG. 1, the lower right side of the sheet with the symbol F is the front side of the electricity storage element 1, the upper right side of the page with the symbol R is the right side of the electricity storage element 1, and the symbol U is attached. The upper side of the drawing is the upper side of the storage element 1.

(Storage element 1)
1 is a rechargeable secondary battery, more specifically a nonaqueous electrolyte secondary battery, and more specifically a lithium ion battery. The power storage element 1 is mounted on a vehicle such as an electric vehicle or a hybrid vehicle as an automobile, and supplies power to a power source that operates with electric energy.

As shown in FIG. 2, the power storage element 1 has a configuration in which a power storage element 3 is accommodated in an exterior body 2 together with an electrolyte (not shown). The electrolyte may be an electrolytic solution or a solid electrolyte.

(Exterior body 2)
The exterior body 2 includes a case main body 4 and a lid body 5. The case main body 4 has a substantially rectangular parallelepiped shape as a whole, and an opening 4A is formed on one end surface side, that is, the upper end surface side. The case body 4 is made of a conductive material, and is made of metal such as aluminum or aluminum alloy. The case body 4 may be made of an iron-based material such as iron or stainless steel.

The opening 4A has a rectangular shape in which the width dimension in the left-right direction is longer than the width dimension in the direction orthogonal to the left-right direction, that is, the front-rear direction. The case body 4 contains the electricity storage element 3 and is filled with an electrolyte. The power storage element 3 is accommodated inside the case body 4 in a posture in which the longitudinal direction of the case body 4 coincides with the longitudinal direction of the power storage element 3.

The lid 5 is provided with a positive electrode terminal 6, a negative electrode terminal 7, a positive electrode current collector 8, and a negative electrode current collector 9. The lid body 5 has a substantially rectangular shape as a whole, and has substantially the same shape as the opening 4A. The lid 5 is joined to the case body 4 so as to close the opening 4 </ b> A of the case body 4. The lid 5 is made of a conductive material, and is made of metal such as aluminum or aluminum alloy. The lid 5 may be formed of an iron-based material such as iron or stainless steel.

A positive electrode terminal 6 and a negative electrode terminal 7 are arranged on the outer surface, ie, the upper surface of the lid 5. Specifically, the positive electrode terminal 6 is disposed on one end side in the longitudinal direction of the lid 5, that is, the left side, and the negative electrode terminal 7 is disposed on the other end side in the longitudinal direction, that is, the right side.

Two positive electrode current collectors 8 extending downward from the lower surface of the lid 5 are disposed near the left end of the lid 5. Although not shown in detail, the upper end portion of the positive electrode current collector 8 is electrically connected to the positive electrode terminal 6.

The positive electrode current collector 8 has an elongated shape along the portion where the positive electrode current collector foil 33 is exposed in the electricity storage element 3 to be described later. The two positive electrode current collectors 8 are arranged so that their plate surfaces face each other. The positive electrode current collector 8 is made of a metal plate having a sufficient thickness so as to obtain a large current capacity, such as an aluminum alloy plate.

Two negative electrode current collectors 9 extending downward from the lower surface of the lid 5 are disposed at a position from the right end of the lid 5. Although not shown in detail, the upper end portion of the negative electrode current collector 9 is electrically connected to the negative electrode terminal 7.

The negative electrode current collector 9 has an elongated shape along the portion where the negative electrode current collector foil 34 is exposed in the electricity storage element 3 to be described later. The two negative electrode current collectors 9 are arranged so that their plate surfaces face each other. The negative electrode current collector 9 is made of a metal plate having a sufficient thickness so as to obtain a large current capacity, such as a copper alloy plate.

(Storage element 3)
The power storage element 3 is formed by, for example, winding a positive electrode 31 and a negative electrode 32 through a separator 37 with the long side of a polyethylene core having a substantially rectangular plate shape being the center of the winding axis. This is a winding type electric storage element.

Thereby, the electrical storage element 3 corresponds to the core, and is long in the direction along the winding axis of the core, short in the direction perpendicular to the winding axis of the core, and perpendicular to the plate surface of the core. It is configured in a cylindrical shape wound in a short flat shape. The electricity storage element 3 has a shape in which the area of the region formed by the direction along the short side direction of the core and the direction along the long side direction of the core is larger than the areas of the other regions. And the electrical storage element 3 is accommodated in the case main body 4 by making the long side direction of a winding core into the left-right direction.

The cross-sectional shape of the electricity storage element 3 in the direction orthogonal to the winding axis is substantially oval. The substantially oval shape includes an oval shape and also includes a shape that can be regarded as an oval shape even if it is not an oval shape. Further, the substantially oval shape includes an elliptical shape.

(Positive electrode 31)
The positive electrode 31 is obtained by forming a positive electrode mixture layer on the surface of an aluminum foil having a strip shape in which the winding direction is the longitudinal direction. The positive electrode 31 has a portion where the positive electrode current collector foil 33 is exposed without forming the positive electrode mixture layer on one edge extending in the longitudinal direction. The positive electrode mixture layer includes a positive electrode active material, and may include a conductive additive, a binder, and the like in addition to the positive electrode active material.

The positive electrode active material is not particularly limited as long as it can occlude and release lithium ions, and may be an inorganic compound or an organic compound. For example, as an inorganic compound, transition metal oxides such as manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, vanadium oxide (for example, V ₂ O ₅ ); spinel type represented by LiMn ₂ O ₄ or the like Lithium manganese oxide, lithium transition metal oxide having a spinel type crystal structure represented by spinel type lithium nickel manganese oxide represented by LiNi _1.5 Mn _0.5 O ₄ or the like; LiCoO ₂ , LiNiO ₂ , LiMeO ₂ type having an α-NaFeO ₂ structure represented by LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , Li _1.1 Co _2/3 Ni _1/6 Mn _1/6 O _{2 and the} like (Me transition metal) lithium transition metal composite _{oxide; Li x FePO 4, Li x} Fe 1-y Mn y PO 4, olivine such as Li x CoPO ₄ Lithium transition metal phosphate compound or the like having a concrete and the like. Examples of the organic compound include conductive polymer materials such as polyaniline and polypyrrole; disulfide polymer materials; sulfides such as sulfur (S); iron sulfate (Fe ₂ (SO ₄ ) ₃ ), and the like.

As the positive electrode active material, a so-called lithium-excess type lithium transition metal composite oxide that can be expressed as Li _{1 + α} Me _1-α O ₂ (α> 0) can also be used. These positive electrode active materials may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of conductive assistants include carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, conductive ceramic material, etc. Materials. These conductive assistants may be used alone or in combination of two or more.

The type of the binder is not particularly limited as long as it is a material that is stable with respect to a solvent and an electrolytic solution used at the time of electrode production and is stable with respect to an oxidation-reduction reaction at the time of charge and discharge. Examples of the binder include thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, and polypropylene; ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, and styrene butadiene rubber (SBR). ), Polymers having rubber elasticity such as fluororubber. These binders may be used individually by 1 type, and may be used in combination of 2 or more type.

Further, if necessary, the positive electrode mixture may contain a viscosity modifier and the like. As the viscosity modifier, any compound such as carboxymethylcellulose (CMC) and N-methylpyrrolidone (NMP) can be appropriately selected as necessary.

The positive electrode 31 is overlapped so that the portion where the positive electrode current collector foil 33 is exposed is arranged on one end side, that is, on the positive electrode 31 side (left side) from the separator 37 and the positive electrode mixture layer. Moreover, the negative electrode 32 is overlaid so that the portion where the negative electrode current collector foil 34 is exposed is arranged on the other end side of the separator 37 and the negative electrode mixture layer, that is, on the negative electrode 32 side (right side).

Thereby, only the part which the positive electrode current collector foil 33 exposes is laminated | stacked and provided in the one end side of the electrical storage element 3, ie, the positive electrode 31 side (left side), and the other end side, ie, the negative electrode 32 side (right side). Only the portion where the negative electrode current collector foil 34 is exposed is laminated.

(Negative electrode 32)
The negative electrode 32 is obtained by forming a negative electrode mixture layer on the surface of a copper foil having a strip shape in which the winding direction is the longitudinal direction. The negative electrode 32 has a portion where the negative electrode current collector foil 34 is exposed without forming the negative electrode mixture layer at one edge extending in the longitudinal direction. The negative electrode mixture layer includes a negative electrode active material, and may include a conductive additive, a binder, and the like in addition to the negative electrode active material.

As the conductive additive, binder, viscosity modifier and the like used for the negative electrode 32, the same ones as those used for the positive electrode 31 can be appropriately selected and used.

The negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions. Specific examples of the negative electrode active material include amorphous carbon such as non-graphitizable carbon (hard carbon) and graphitizable carbon (soft carbon); graphite; Al, Si, Pb, Sn, Zn, Cd, etc. Alloys of these metals and lithium; tungsten oxide; molybdenum oxide; iron sulfide; titanium sulfide; lithium titanate and the like. These negative electrode active materials may be used individually by 1 type, and may be used in combination of 2 or more type. Among these negative electrode active materials, amorphous carbon and graphite are preferable.

(Separator 37)
The separator 37 is not particularly limited as long as it has insulating properties. As the separator 37, for example, a polyolefin microporous film; a synthetic resin woven or non-woven fabric; a natural fiber, glass fiber, or ceramic fiber woven or non-woven fabric; paper or the like can be used. The polyolefin microporous membrane can be selected from polyethylene, polypropylene, and composite membranes thereof. The synthetic resin fiber can be selected from polyolefins such as polyacrylonitrile (PAN), polyamide (PA), polyester, polyethylene terephthalate (PET), polypropylene (PP) or polyethylene (PE), and mixtures thereof.

(Electrolytes)
As the electrolyte, an electrolytic solution or a solid electrolyte can be used. As the electrolytic solution, a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent can be used. In the exterior body 2, the electrolyte solution is impregnated in the positive electrode mixture layer, the negative electrode mixture layer, and the separator 37. The electrolytic solution is not limited, and those generally proposed for use in lithium ion batteries and the like can be used. Nonaqueous solvents include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate and other cyclic carbonates; γ-butyrolactone, γ-valerolactone and other cyclic esters; dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and other chains Examples of the carbonates include chain esters such as methyl formate, methyl acetate, and methyl butyrate alone or a mixture of two or more thereof, but are not limited thereto. In addition, you may add a well-known additive to electrolyte solution.

Examples of the electrolyte salt include inorganic ion salts containing one kind of lithium (Li), sodium (Na), or potassium (K) such as LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , and LiSCN; LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F _And organic ion salts such as ₅ SO ₂ ) ₃ and (CH ₃ ) ₄ NBF ₄ . These ionic compounds can be used alone or in admixture of two or more. The content of the supporting salt in the electrolyte is not particularly limited, and may be set as appropriate according to the type of the supporting salt used, the solvent, etc., for example, 0.1 to 5.0 mol / L, preferably 0. 8 to 2.0 mol / L can be mentioned.

Furthermore, by mixing and using a lithium salt having a perfluoroalkyl group such as LiN (C ₂ F ₅ SO ₂ ) ₂ , it is possible to reduce the viscosity of the electrolyte and to suppress self-discharge of the storage element. It is possible and preferable.

Also, a room temperature molten salt or ionic liquid may be used as the electrolytic solution.

When a solid electrolyte is used as the electrolyte, a polymer solid electrolyte can be used as the solid electrolyte, and a porous polymer solid electrolyte membrane can be used as the polymer solid electrolyte. The polymer solid electrolyte can further contain an electrolytic solution. Further, when a gel polymer solid electrolyte is used as the electrolyte, the electrolyte solution constituting the gel may be different from the electrolyte solution contained in the pores.

(Connection structure between current collector and power storage element 3)
The positive electrode current collector 8 and the positive electrode current collector foil 33 are connected by ultrasonic welding while being sandwiched between the clips 35. The negative electrode current collector 9 and the negative electrode current collector foil 34 are connected by ultrasonic welding while being sandwiched between the clips 36.

The clip 35 is made of a material having a resistance value substantially equal to the material of the positive electrode current collector 8 and the positive electrode current collector foil 33 to be connected. In the present embodiment, the clip 35 on the positive electrode 31 side is made of, for example, an aluminum alloy.

The clip 36 is made of a material having a resistance value substantially equal to the material of the negative electrode current collector 9 and the negative electrode current collector foil 34 to be connected. In the present embodiment, the clip 36 on the negative electrode 32 side is made of, for example, a copper alloy.

(Reference pole part 42)
As shown in FIGS. 2 and 3, the case body 4 of the exterior body 2 includes a bottom wall 40 at a position opposite to the opening 4 </ b> A. From the four side edges of the bottom wall 40, side walls 50 are formed to rise upward.

In addition, the bottom wall 40 does not mean a wall arranged on the lower side with respect to gravity, but means a wall arranged on the side opposite to the opening 4A of the case body 4. For this reason, when the electrical storage element 1 is used, for example, the bottom wall 40 may be in a posture positioned on the upper side with respect to gravity. The electrical storage element 1 can be arrange | positioned with arbitrary attitude | positions as needed.

As shown in FIG. 3, the reference electrode portion 42 is formed so that the reference electrode mixture is in contact with the inner surface 41 of the bottom wall 40. In the configuration in which the reference electrode portion 42 is formed by the reference electrode mixture contacting the inner surface 41 of the bottom wall 40, for example, the reference electrode having the reference electrode mixture layer formed on the surface of the current collector foil is the bottom. A configuration in which the reference electrode portion 42 is formed by being attached to the inner surface 41 of the wall 40 is not included.

The reference electrode portion 42 includes a substance capable of inserting and extracting lithium ions, and may include a conductive aid, a binder and the like in addition to the substance capable of inserting and extracting lithium ions.

As the substance capable of inserting and extracting lithium ions, known materials can be used as appropriate. When the exterior body 2 (the case body 4 and the lid body 5) is made of aluminum or an aluminum alloy, a compound having a so-called two-phase coexistence region can be used for the reference electrode portion 42. Examples of the compound having two phase coexisting region, the general formula _{LiMn 1-x-y Fe x} Co y PO 4 (0.1 ≦ x ≦ 0.2,0 <y ≦ 0.2) or the general formula _Li x FePO ₄ A lithium phosphate transition metal compound represented by (0 ≦ x ≦ 1.0) or the like can be used.

Further, when the exterior body 2 (the case body 4 and the lid body 5) is formed of an iron-based material such as iron or stainless steel, the reference electrode portion 42 is Li [Li _1/3 Ti _5/3 ]. One selected from the group consisting of titanium-based materials such as lithium titanate having a spinel crystal structure typified by O ₄ and carbon materials (eg, graphite, hard carbon, low-temperature fired carbon, amorphous carbon, etc.) Or it is good also as a structure containing a some substance.

The material capable of inserting and extracting lithium ions contained in the reference electrode portion 42 and the positive electrode active material contained in the positive electrode mixture layer may be the same material or different materials. .

The capacity of the reference electrode part 42 is not particularly limited, but is preferably 0.05% or more and 3% or less, and more preferably 0.05% or more and 1% or less with respect to the discharge capacity of the positive electrode.

The type of the conductive auxiliary agent is not particularly limited. For example, carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, conductive ceramics A conductive material such as a material can be used. The conductive auxiliary agent used for the lithium ion supply layer 42 and the conductive auxiliary agent used for the positive electrode 31 may be the same substance or different substances.

The type of the binder is not particularly limited as long as it is stable with respect to the solvent and electrolyte used during electrode production. Examples of the binder include thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, and polypropylene; ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, and styrene butadiene rubber (SBR). ), Polymers having rubber elasticity such as fluororubber. These binders may be used individually by 1 type, and may be used in combination of 2 or more type. The binder used for the lithium ion supply layer 42 and the binder used for the positive electrode 31 may be the same material or different materials.

The composition of the reference electrode mixture in the reference electrode part 42 is not particularly limited to the upper limit that the substance capable of occluding and releasing lithium ions is included in the reference electrode mixture, but the substance capable of occluding and releasing lithium ions is 50 parts by mass. It is 96 parts by mass or less, the conductive additive is 2 parts by mass or more and 30 parts by mass or less, and the binder is 2 parts by mass or more and 30 parts by mass or less. The reference electrode mixture may contain components other than those described above.

The reference electrode portion 42 and the case body 4 are electrically connected. Further, since the case body 4 and the lid 5 are also electrically connected, the reference electrode portion 42 is also electrically connected to the lid 5.

The reference electrode portion 42 is formed by applying a mixture containing a substance capable of occluding and releasing lithium ions, a conductive aid, and a binder to the inner surface 41 of the bottom wall 40 of the case body 4 and drying. can do. Moreover, the reference electrode part 42 can also be formed by applying so-called overcoating repeatedly by applying a mixture and drying it, and further applying and drying the mixture. The reference electrode portion 42 can also be formed by applying a mixture to the inner surface 41 of the bottom wall 40 of the case body 4 and then sintering the mixture. For example, the reference electrode can be obtained by hanging a mixture containing a substance capable of inserting and extracting lithium ions, a conductive additive, and a binder on the inner surface 41 of the bottom wall 40 of the case body 4 and then drying the mixture. The part 42 can be formed.

Further, the reference electrode portion 42 may be formed by spraying a material capable of occluding and releasing lithium ions on the inner surface 41 of the bottom wall 40. Further, the reference electrode portion 42 may be formed by vapor-depositing a material capable of inserting and extracting lithium ions on the inner surface 41 of the bottom wall 40. Thus, the reference electrode part 42 can be directly formed on the inner surface of the exterior body by an arbitrary method as necessary. However, the structure which affixes the reference electrode in which the reference electrode layer was formed on the surface of current collection foil to the inner surface 41 of the bottom wall 40 is remove | excluded.

Since the oxidation-reduction reaction in which lithium ions are electrochemically desorbed into the lithium phosphate transition metal compound proceeds by a two-phase coexistence reaction, a flat potential region is generated. By setting the potential of the reference electrode portion 42 in this flat potential region, the potential of the positive electrode 31 or the negative electrode 32 can be measured stably and accurately. Examples of the lithium phosphate transition metal compound include lithium iron phosphate (LiFePO ₄ ).

The inner surface 41 of the bottom wall 40 of the case body 4 may be configured such that a roughened region in which the inner surface 41 of the bottom wall 40 is roughened is formed in a region where the reference electrode portion 42 is formed.

The roughened region is roughened from the region of the inner surface 41 of the bottom wall 40 of the case body 4 that is different from the region where the reference electrode portion 42 is formed. That is, the roughened region is a region that is rougher than the region of the inner surface of the exterior body in which the reference electrode portion is not formed. The roughened region can be formed by a known method such as embossing, brushing with a metal brush, sand blasting, laser irradiation, etching, or the like.

(Sheet 61)
The surface of the reference electrode portion 42 is covered with an insulating sheet 61 that allows lithium ions to pass therethrough. By being covered with the sheet 61, the reference electrode portion 42 is suppressed from falling off from the inner surface 41 of the bottom wall 40 of the case body 4.

As the sheet 61, a polyolefin microporous film, a synthetic resin woven or non-woven fabric; a natural fiber, glass fiber, or ceramic fiber woven or non-woven fabric; paper or the like can be used. As the polyolefin microporous membrane, polyethylene, polypropylene, or a composite membrane thereof can be used. The synthetic resin fiber can be selected from polyolefins such as polyacrylonitrile (PAN), polyamide (PA), polyester, polyethylene terephthalate (PET), polypropylene (PP) or polyethylene (PE), and mixtures thereof.

(Cooling structure)
A part of the outer surface of the outer package 2 is cooled by a cooling medium (not shown). In the present embodiment, the outer surface 43 of the bottom wall 40 of the case body 4 is cooled by the cooling medium. The cooling medium may be air or a liquid such as water or an organic solvent. The cooling medium may be in direct contact with the outer surface 43 of the bottom wall 40 of the case body 4, and the path through which the cooling medium flows and the outer surface 43 of the bottom wall 40 of the case body 4 transfer heat. It is good also as a structure which touches automatically. The term “heat transfer contact” includes a configuration in which the outer surface of the path through which the cooling medium flows and the outer surface 43 of the bottom wall 40 of the case body 4 are in direct contact with each other. The outer surface 43 of the bottom wall 40 of 4 includes the structure which contacts indirectly through a heat-transfer sheet | seat etc., for example.

(Storage element system 70)
In FIG. 4, an example of the electrical storage element system 70 which concerns on this embodiment is shown. In addition, the electrical storage element system 70 is not limited to the following description. The positive electrode terminal 6 of the electricity storage element 1 is connected to a load 71.

The probe 72 is in contact with the outer surface of the outer package 2 of the storage element 1. The probe 72 and the exterior body 2 are electrically connected. The probe 72 detects the potential of the exterior body 2 and transmits a signal related to the potential of the exterior body 2 to the determination unit 73. Since the exterior body 2 and the reference electrode portion 42 are electrically connected, the potential of the exterior body 2 is the same as the potential of the reference electrode portion 42.

In addition, as shown in FIG. 5, when a plurality of power storage elements 1 are included in the power storage element system 70, a probe 72 can be connected to each power storage element 1.

The negative electrode side control part 74 is electrically connected to the negative electrode terminal 7 of the electrical storage element 1. In addition, a positive electrode side control unit 75 is electrically connected to the positive electrode terminal 6 of the electric storage element 1. The negative electrode side control unit 74 and the positive electrode side control unit 75 are each electrically connected to the determination unit 73. The determination unit 73 detects the potential of the negative electrode terminal 7 through the negative electrode side control unit 74 and detects the potential of the positive electrode terminal 6 through the positive electrode side control unit 75.

The determination unit 73 includes a nonvolatile storage unit (not shown) and a volatile storage unit (not shown).

(Discharge control)
The determination unit 73 determines the potential of the negative electrode terminal 7 from the potential of the exterior body 2 (the potential of the reference electrode unit 42) acquired from the probe 72 and the potential of the negative electrode terminal 7 acquired through the negative electrode side control unit 74. vs. Li ⁺ / Li). In addition, the determination unit 73 determines the potential (vs. Li ⁺ / Li) of the positive electrode terminal 6 from the potential of the exterior body 2 acquired from the probe 72 and the potential of the positive electrode terminal 6 acquired via the positive electrode side control unit 75. ) Is calculated.

The determination unit 73 reads a predetermined threshold value from the nonvolatile storage unit, and determines whether the potential (vs. Li ⁺ / Li) of the negative electrode terminal 7 is lower than this threshold value. When it is determined that the potential (vs. Li ⁺ / Li) of the negative electrode terminal 7 is lower than the threshold value, the determination unit 73 causes the negative electrode side control unit 74 to reduce the current flowing through the power storage element 1. . Further, when the storage element 1 is an SC cell, the determination unit 73 may be configured to restrict the use of the storage element 1 to the negative electrode side control unit 74.

More specifically, the determination unit 73 acquires the current that flows through the power storage element 1, the temperature of the power storage element 1, and the SOC factor of the power storage element 1. The determination unit 73 reads a block (data) recorded in advance in the nonvolatile storage unit. The determination unit 73 compares the current flowing through the power storage element 1, the temperature of the power storage element 1, and the SOC factor of the power storage element 1 with the block read from the non-volatile storage unit. Determine the current to flow. Determination unit 73 causes negative electrode side control unit 74 to flow the determined current to power storage element 1.

In addition, the determination unit 73 detects the end of discharge of the electricity storage device 1 from the potential of the negative electrode terminal 7 acquired via the negative electrode side control unit 74. The determination unit 73 acquires the potential of the negative electrode terminal 7, acquires the potential of the exterior body 2, and calculates the potential (vs. Li ⁺ / Li) of the negative electrode terminal 7. Similarly, the determination unit 73 acquires the potential of the positive electrode terminal 6, acquires the potential of the outer package 2, and calculates the potential of the positive electrode terminal 6 (vs. Li ⁺ / Li).

Next, the determination unit 73 reads the life prediction block of the power storage device 1 recorded in advance in the nonvolatile storage unit. Thereafter, the determination unit 73 compares the potential (vs. Li ⁺ / Li) of the negative electrode terminal 7 with the life prediction block. The determination unit 73 calculates the positive / negative balance based on the potential (vs. Li ⁺ / Li) of the negative electrode terminal 7 and the life prediction block, and calculates the remaining life of the electricity storage device 1. Determination unit 73 records the remaining life of power storage element 1 in a volatile storage unit.

As described above, the determination unit 73 can manage the occurrence of electrodeposition on the negative electrode 32 by monitoring the potential (vs. Li ⁺ / Li) of the negative electrode terminal 7. Thereby, while improving the safety of the negative electrode 32, the lifetime of the negative electrode 32 can be estimated accurately.

(Supplementary charging)
The determination unit 73 integrates the time when the power storage element 1 is energized and records it in the volatile storage unit.

The determination unit 73 reads the accumulated time that the power storage element 1 is energized from the volatile storage unit. In addition, the determination unit 73 reads a predetermined supplementary charging period from the nonvolatile storage unit.

The predetermined supplementary charging period is set so as to prevent the potential of the exterior body 2 from entering the fluctuation region due to self-discharge of the reference electrode portion 42. The length of the auxiliary charging period depends on the temperature of the electricity storage device 1 when the electricity storage device 1 is used or the environmental temperature of the electricity storage device 1. The supplementary charging period can be set as appropriate depending on the usage status of the power storage device 1 from a period of one month to three years, for example.

判断 Determining unit 73 compares the accumulated time during which power storage element 1 is energized with a predetermined supplementary charging period. If the determination unit 73 determines that the accumulated time during which the power storage element 1 is energized has exceeded a predetermined auxiliary charging period, the determination unit 73 sets the negative terminal 7 to a negative voltage and sets the probe 72 to a positive voltage. The charging current for the reference electrode portion 42 is caused to flow through the negative electrode side control portion 74.

The determination unit 73 acquires the potential of the reference electrode unit 42 via the probe 72. The determination unit 73 acquires a predetermined threshold value from the non-volatile storage unit, and compares the threshold value with the potential of the reference electrode unit 42. When the determination unit 73 determines that the potential of the reference electrode unit 42 exceeds a predetermined threshold, the negative electrode side control unit 74 stops the charging current for the reference electrode unit 42.

(Manufacturing process of embodiment)
Then, an example of the manufacturing process of the electrical storage element 1 which concerns on this embodiment is demonstrated. In addition, the manufacturing process of the electrical storage element 1 is not limited to the following description.

The positive electrode 31 is manufactured as follows. A positive electrode active material (for example, lithium transition metal oxide), a binder (for example, polyvinylidene fluoride), and a conductive additive (for example, acetylene black) are mixed. A positive electrode mixture is prepared by appropriately adding N-methylpyrrolidone (NMP) to this to prepare a paste. This positive electrode mixture is applied to both surfaces of a positive electrode substrate made of an aluminum foil. This is dried, and the positive electrode 31 is produced by pressurizing with a roll press.

The negative electrode 32 is produced as follows. A negative electrode active material (for example, hard carbon) and a binder (for example, polyvinylidene fluoride) are mixed. N-methylpyrrolidone is appropriately added thereto to prepare a paste, thereby preparing a negative electrode mixture. This negative electrode mixture is applied to both surfaces of a negative electrode substrate made of copper foil. This is dried and the negative electrode 32 is produced by pressurizing with a roll press.

As the separator 37, for example, a polyolefin microporous film is used.

The winding type power storage element 3 is manufactured by winding the positive electrode 31 and the negative electrode 32 obtained as described above through the separator 37.

A case body 4 having an opening 4A and a lid 5 are prepared using a metal plate. A positive terminal 6 and a negative terminal 7 are attached to the lid 5. A positive electrode current collector 8 is connected to the positive electrode terminal 6, and a negative electrode current collector 9 is connected to the negative electrode terminal 7.

In a state where the positive electrode current collector foil 33 and the positive electrode current collector 8 are sandwiched between the clips 35, the clip 35 is ultrasonically welded to the positive electrode current collector foil 33 and the positive electrode current collector 8. Further, the clip 36 is ultrasonically welded to the negative electrode current collector foil 34 and the negative electrode current collector 9 in a state where the negative electrode current collector foil 34 and the negative electrode current collector 9 are sandwiched between the clips 36. Thereby, the electrical storage element 3 is connected to the lid 5.

The case body 4 is formed into a predetermined shape using a metal plate. A reference pole portion 42 is formed on the inner surface 41 of the bottom wall 40 of the case body 4. The sheet 61 is overlapped and covered on the surface of the reference electrode portion 42.

Subsequently, the power storage element 3 connected to the lid 5 is inserted into the case body 4 from the opening 4 </ b> A of the case body 4. The hole edge of the opening 4A of the case body 4 and the side edge of the lid 5 are welded by a known method. An electrolyte is injected from an injection port (not shown) provided on the side wall 50 of the case body 4, and the injection port is sealed.

Then, the SOC (State 参照 Of Charge) of the reference electrode active material included in the reference electrode portion 42 is adjusted. The method for adjusting the SOC of the reference electrode active material is not particularly limited. For example, after sealing the power storage element 1, between the outer package 2 and the positive electrode terminal 6, or between the outer package 2 and the negative electrode terminal 7. The SOC of the reference electrode active material can be adjusted by applying a voltage to the reference electrode active material.

The current flowing between the exterior body 2 and the negative electrode terminal 7 (or the positive electrode terminal 6) can be equal to or less than the current (A) having the same numerical value as the capacity of the reference electrode portion 42. The voltage applied between the outer package 2 and the negative electrode terminal 7 (or the positive electrode terminal 6) varies depending on the type of the reference electrode active material included in the reference electrode part 42, but can be 3.3V to 4V. . By appropriately adopting these, the SOC of the reference electrode active material contained in the reference electrode portion 42 can be set appropriately, and the potential of the reference electrode portion 42 can be set in a flat potential region for a long time.

For example, when LiFePO ₄ (lithium iron phosphate), which is a polyanion type compound, is used as the reference electrode active material as the compound having a two-phase coexistence region, the SOC of LiFePO ₄ is set in the range of 20% to 90%. Therefore, the potential is 3.43 Vvs. Since it takes a constant value of Li ⁺ / Li, it is preferable.

(Operation and effect of the embodiment)
Then, the effect | action and effect of this embodiment are demonstrated. The power storage device 1 according to the present embodiment includes a power storage element 3, an exterior body 2 made of a conductor that is electrically insulated from the power storage element 3, and a reference electrode portion 42. The agent is formed in contact with the inner surface of the outer package 2.

According to the above configuration, it is possible to prevent impurities from being mixed into the exterior body 2 when the reference electrode portion 42 is provided in the exterior body 2. This is considered to be due to the following reasons.

In order to fix the reference electrode with the reference electrode having a reference electrode mixture layer formed on the surface of the current collector foil in the outer package, and electrically connecting the reference electrode to the outer package, for example, the outer package and the reference electrode It is conceivable to weld the current collector foil. When the outer package and the current collector foil of the reference electrode are welded, the current collector foil of the reference electrode or the fragments of the outer package generated by welding may be mixed as impurities into the outer package.

In view of the above points, according to the present embodiment, the reference electrode mixture containing the reference electrode active material that occludes or desorbs lithium ions is formed in contact with the inner surface of the exterior body 2, whereby the reference electrode portion 42 is formed. Thereby, when forming the reference pole part 42 in the exterior body 2, generation | occurrence | production of the fragment of the exterior body 2 is suppressed, and it can also suppress that a fragment generate | occur | produces from a reference electrode part. As a result, when the reference electrode portion 42 is provided in the exterior body 2, it can be suppressed that impurities are mixed in the exterior body 2.

Further, according to the present embodiment, a part of the outer surface 43 of the bottom wall 40 of the case body 4 is cooled by the cooling medium, and the reference pole portion 42 is the inner surface of the inner surface 42 of the bottom wall 40 of the case body 4. You may form in the area | region corresponding to a part of outer surface 43 of the bottom wall 40 of the case main body 4 cooled by the cooling medium.

With the above configuration, the temperature of the reference electrode portion 42 can be kept relatively low as compared with the case where the reference electrode portion 42 is provided in the region of the case body 4 that is not cooled by the cooling medium. Thereby, since it is possible to suppress the self-discharge of the reference electrode part 42, the potential of the reference electrode part 42 can be stabilized.

Further, according to the present embodiment, an insulating sheet 61 through which lithium ions pass may be disposed between the electricity storage element 3 and the reference electrode portion 42. Thereby, even if the reference electrode part 42 falls off from the inner surface 41 of the bottom wall 40 of the case body 4, the bottom wall of the case body 4 is provided by the sheet 61 disposed between the reference electrode part 42 and the power storage element 3. It is possible to prevent the reference electrode portion 42 that has dropped from the inner surface 41 of the 40 from coming into contact with the power storage element 3.

Moreover, according to the present embodiment, the reference electrode portion 42 may include a compound having a two-phase coexistence region. Thereby, since the potential of the compound having the two-phase coexistence region becomes constant in the two-phase coexistence region, the potential of the reference electrode portion 42 can be stabilized.

<Other embodiments>
The technology disclosed in the present specification is not limited to the embodiments described with reference to the above description and drawings, and includes, for example, the following various aspects.

In the above embodiment, an example in which the electricity storage element 1 is a lithium ion battery which is a kind of nonaqueous electrolyte secondary battery has been described. However, the present invention is not limited thereto, and the storage element 1 may be another secondary battery such as a lead storage battery or a nickel hydride battery, or may be a primary battery. Moreover, a capacitor etc. may be sufficient.

In the above embodiment, the power storage element 3 of the power storage element 1 is the wound power storage element 3 formed in a flat shape by winding the positive electrode 31 and the negative electrode 32 via the separator 37, but is not limited thereto. For example, the power storage element may be a stacked power storage element formed by stacking the positive electrode 31 and the negative electrode 32 with the separator 37 interposed therebetween.

The power storage element 1 according to the above embodiment is configured to include one power storage element 3, but is not limited thereto, and the power storage element 1 may be configured to include two or more power storage elements 3.

In the above embodiment, the outer surface 44 of the bottom wall 40 of the case body 4 is cooled by the cooling medium. However, the present invention is not limited to this, and the outer surface of the side wall 50 of the case body 4 is cooled by the cooling medium. The outer surface of the lid 5 may be cooled with a cooling medium. Moreover, it is good also as a structure where the outer surface of the exterior body 2 is not cooled with a cooling medium.

When the exterior body 2 (the case body 4 and the lid body 5) is formed of an iron-based material such as iron or stainless steel, the reference electrode portion 42 may include lithium titanate. In this case, the determination unit 73 applies a base potential to the positive electrode side control unit 75 and applies a noble potential to the positive electrode terminal 6 to charge the reference electrode unit 42. Also good.

In the above-described embodiment, the positive electrode side control unit 75 and the negative electrode side control unit 74 are connected to the power storage element 1. However, the configuration is not limited thereto, and only the positive electrode side control unit 75 is connected to the power storage element 1. May be connected, or only the negative electrode side control unit 74 may be connected to the power storage element 1.

In the above embodiment, the reference electrode unit 42 is charged using the probe 72. However, the configuration is not limited thereto, and the reference electrode unit 42 is charged using a voltage detection line that detects the voltage of the storage element 1. It is good also as a structure.

A power storage device can be configured by combining a plurality of power storage elements according to the above embodiment, and one embodiment thereof is shown in FIG. The power storage device 101 includes a plurality of power storage units 100. Each power storage unit 100 includes a plurality of power storage elements 1. The power storage device 101 can be mounted as a power source for vehicles such as an electric vehicle (EV), a hybrid vehicle (HEV), and a plug-in hybrid vehicle (PHEV), and one embodiment thereof is shown in FIG.

Since the electricity storage device according to the present invention can suppress the entry of impurities into the exterior body when the reference electrode portion is provided in the exterior body, the electric vehicle (EV), the hybrid vehicle (HEV), and the plug-in hybrid It can be effectively used as a power source for automobiles such as automobiles (PHEV), a power source for electronic devices and a power storage power source.

1: Power storage element 2: Exterior body 3: Power storage element 30: Exterior body 31: Positive electrode 32: Negative electrode 37: Separator 40: Bottom wall 41: Inner surface 42: Reference electrode portion 43: Outer surface 61: Sheet 100: Power storage unit 101: Power storage Device 102: Car body 103: Automobile

Claims (8)

A storage element;
An exterior body made of a conductor electrically insulated from the electricity storage element;
With a reference pole,
The reference electrode part is a power storage element in which a reference electrode mixture is formed in contact with an inner surface of the exterior body. A part of the outer surface of the exterior body is cooled by a cooling medium,
The electric storage element according to claim 1, wherein the reference electrode portion is formed in a region on the opposite side of a part of the outer surface through the exterior body. The electrical storage element according to claim 1 or 2, wherein an insulating sheet through which lithium ions pass is disposed between the electrical storage element and the reference electrode portion. The electric storage element according to any one of claims 1 to 3, wherein the reference electrode portion includes a compound having a two-phase coexistence region. The electricity storage device according to claim 4, wherein the compound having the two-phase coexistence region is a lithium phosphate transition metal compound. 6. The region of the inner surface of the outer package in which the reference electrode portion is formed is rougher than the region of the inner surface of the outer package in which the reference electrode portion is not formed. 6. The electrical storage element as described in. A power storage device comprising a plurality of power storage elements according to any one of claims 1 to 6. An automobile provided with the power storage device according to claim 7.

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