JP2018142429A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery in which short circuit between electrodes can be prevented and furthermore an energy density can be improved.SOLUTION: A secondary battery comprises an electrode 110, a first organic fiber layer 2 and a second organic fiber layer 3. The electrode 110 comprises: a collector 111 having an edge portion; an active material-containing layer 112 carried by at least one surface of the collector 111; and a tab that extends from the active material-containing layer 112 and the edge portion of the collector 111 and includes a first surface 113a and a second surface 113b, the active material-containing layer 112 including an end carried by the edge portion of the collector 111. The first organic fiber layer 2 includes an organic fiber layer and is connected to at least an end surface of the active material-containing layer 112. The second organic fiber layer 3 includes the organic fiber layer 2 and is connected to a part where at least the first organic fiber layer 2 is not connected from among the surface of the active material-containing layer 112.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a secondary battery.

In a secondary battery such as a lithium secondary battery, a porous separator is used in order to avoid contact between the positive electrode and the negative electrode. Usually, the separator is prepared as a self-supporting film separate from the positive electrode and the negative electrode. For example, a separator is sandwiched between a positive electrode and a negative electrode to form a unit structure (electrode cell), which is wound or laminated to form a battery group.

A general separator includes a microporous membrane made of polyolefin resin film. Such a separator is manufactured, for example, by extruding a melt containing a polyolefin resin composition into a sheet, extracting and removing substances other than the polyolefin resin, and then stretching the sheet.

Since the separator made of a resin film needs to have mechanical strength so as not to be broken at the time of producing a battery, it is difficult to make it thinner to some extent. Therefore, particularly in a battery of a type in which a large number of electrode cells are stacked or wound, the amount of unit electrode cells that can be stored per unit volume of the battery is limited by the thickness of the separator. This leads to a decrease in battery capacity. In addition, the separator made of a resin film has poor durability, and when used for a secondary battery, there is a disadvantage that the separator deteriorates during repeated charging and discharging and the cycle performance of the battery is lowered.

JP 2010-182922 A

Problem to be solved by the invention is providing the secondary battery which can improve an energy density, preventing the short circuit between electrodes.

In order to solve the above problems, the secondary battery of the present embodiment includes a current collector having an edge, an active material-containing layer supported on at least one surface of the current collector, and the current collector. A tab extending from the edge and having a first surface and a second surface, the active material-containing layer comprising an electrode including an end carried on the edge of the current collector, and an organic fiber A first organic fiber layer bonded to at least an end face of the active material layer, and an organic fiber layer, and at least the first organic fiber layer of the surface of the active material layer. And a second organic fiber layer bonded to the unbonded portion.

FIG. 1 is a schematic diagram illustrating an example of a positional relationship between an electrode and an organic fiber layer included in the secondary battery according to the first embodiment. FIG. 2 is a schematic diagram illustrating an example method for forming a layer of organic fibers. FIG. 3 is a schematic partially cutaway perspective view of the secondary battery according to the embodiment. FIG. 4 is a schematic exploded perspective view of the secondary battery according to the embodiment. FIG. 5 is a schematic view of a tear strength test according to the embodiment.

(First embodiment)
Hereinafter, embodiments will be described with reference to the drawings.

According to the embodiment, a secondary battery is provided. The secondary battery includes an electrode and an organic fiber layer. The electrode includes a current collector, an active material-containing layer, and a tab. The current collector has an edge. The active material-containing layer is supported on at least one surface of the current collector. The tab extends from the edge of the current collector. The tab has a first surface and a second surface. The organic fiber layer includes at least a first organic fiber layer and a second organic fiber layer.

In the secondary battery according to the embodiment, the current collector may have a plurality of edges, and a tab may extend from one of them. The current collector can also carry an active material-containing layer on both sides thereof. The electrode can also include an end surface that includes one edge of the current collector that is different from the edge from which the tab extends. The tab is more preferably formed of at least one conductive material selected from the group consisting of aluminum, an aluminum alloy, and copper.

  Hereinafter, the secondary battery according to the embodiment will be described in more detail.

The secondary battery according to the embodiment can be, for example, a nonaqueous electrolyte secondary battery. Alternatively, the secondary battery according to the embodiment may be a secondary battery using an aqueous solution as an electrolyte.

The secondary battery which concerns on embodiment can also comprise the additional electrodes other than the electrode demonstrated previously.

The secondary battery according to the embodiment typically includes one or more negative electrodes and one or more positive electrodes. The electrode described above is preferably a negative electrode.

The negative electrode can include a negative electrode current collector, a negative electrode active material-containing layer carried on at least one surface of the negative electrode current collector, and a negative electrode current collector tab extending from the negative electrode current collector. The negative electrode current collector and the negative electrode current collector tab may be integrated or separate.

As the negative electrode current collector, for example, a metal foil such as aluminum or copper can be used. As the material of the negative electrode current collector tab, the same material as that of the negative electrode current collector can be used.

The negative electrode active material-containing layer can include a negative electrode active material, an optional negative electrode conductive agent, and an optional negative electrode binder.

When the electrode demonstrated previously is a negative electrode, it is preferable that the negative electrode active material content layer contains lithium titanate.

Lithium titanate can act as a negative electrode active material. Examples of lithium titanate include Li4 + xTi5O12 (0≤x≤3) having a spinel structure and Li2 + yTi3O7 (0≤y≤3) having a ramsteride structure.

Such lithium titanate can occlude and release lithium ions at a potential of, for example, 1.55 V (vs. Li / Li +) or higher, so the surface of the negative electrode active material-containing layer containing lithium titanate In principle, lithium dendrite is not deposited even after repeated charge and discharge. Moreover, lithium titanate has almost no volume change accompanying charging / discharging reaction. Thanks to these, the organic fiber layer bonded to the surface of the negative electrode active material-containing layer of the negative electrode can be thinned and the porosity can be increased, and as a result, higher energy density can be achieved. it can.

The lithium titanate preferably has an average primary particle size in the range of 0.001 to 1 μm. Such a negative electrode active material-containing layer containing lithium titanate can exhibit high flatness on the surface and high adhesion to the organic fiber layer. Thanks to this, peeling of the organic fiber layer from the surface of the negative electrode active material-containing layer can be prevented.

Examples of other active materials that can be included in the negative electrode active material-containing layer include carbonaceous materials such as graphite, tin-silicon alloy materials, and the like.

The particle shape of the negative electrode active material may be either granular or fibrous. In the case of a fiber, the fiber diameter is preferably 0.1 μm or less.

Examples of the negative electrode conductive agent include acetylene black, carbon black, and graphite. Examples of the binder for binding the negative electrode active material and the negative electrode conductive agent include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber, and the like.

The positive electrode can include a positive electrode current collector, a positive electrode active material-containing layer supported on at least one surface of the positive electrode current collector, and a positive electrode current collector tab extending from the positive electrode current collector. The positive electrode current collector and the positive electrode current collector tab may be integrated or separate.

As the positive electrode current collector, for example, a metal foil such as aluminum or copper can be used. As a material for the positive electrode current collector tab, the same material as that for the positive electrode current collector can be used.

The positive electrode active material-containing layer can contain a positive electrode active material, an optional positive electrode conductive agent, and an optional positive electrode binder.

As the positive electrode active material, for example, a general lithium transition metal composite oxide can be used. For example, LiCoO2, LiNi1-xCoxO2 (0 <x <0.3), LiMnxNiy
CozO2 (0 <x <0.5, 0 <y <0.5, 0 ≦ z <0.5), LiMn2-xMxO4 (
M is Li, Mg, Co, Al, Ni, 0 <x <0.2), LiMPO4 (M is Fe, Co
, Ni).

Examples of the positive electrode conductive agent include carbonaceous materials such as acetylene black, carbon black, and graphite. As the binder, for example, polytetrafluoroethylene (PT
FE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

The organic fiber included in the organic fiber layer is selected from the group consisting of, for example, polyamideimide, polyamide, polyolefin, polyether, polyimide, polyamideimide, polyketone, polysulfone, cellulose, polyvinyl alcohol (PVA), and polyvinylidene fluoride (PVdF). Can be included. Examples of the polyolefin include polypropylene (PP) and polyethylene (PE). The organic fiber layer preferably contains an organic fiber containing polyimide. Since polyimide is insoluble and infusible even at 250 to 400 ° C. and does not decompose, an organic fiber layer having excellent heat resistance can be obtained when polyimide is used.

The organic fiber preferably has a length of 1 mm or more and a thickness of 1 μm or less. The organic fiber layer containing such organic fibers has sufficient strength, porosity, air permeability, pore diameter, electrolyte resistance,
Since it can have oxidation-reduction resistance and the like, it can function as a good separator. The thickness of the organic fiber is observed with an electron microscope (SEM) and a scanning probe microscope (SPM).
It can be measured by a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM) or the like. Further, the length of the organic fiber is obtained based on the length measurement by SEM observation.

When the secondary battery according to the embodiment is a non-aqueous electrolyte secondary battery in which lithium ions are involved in charging and discharging, it is necessary to ensure ion permeability and electrolyte content, so that an organic fiber layer is formed. It is preferable that 30% or more of the total volume of the fibers is an organic fiber having a thickness of 1 μm or less. A more preferable range of the thickness is 350 nm or less, and a more preferable range is 50 nm.
nm or less. The volume of the organic fiber having a thickness of 1 μm or less, more preferably 350 nm or less, and even more preferably 50 nm or less, more preferably occupies 80% or more of the total volume of the fibers forming the organic fiber layer. . More preferably, the organic fibers having a thickness of 40 nm or less occupy 40% or more of the total volume of the fibers forming the organic fiber layer. When the diameter of the organic fiber is small, it is possible to reduce the influence of obstructing the movement of lithium ions. Such a state can be confirmed by SEM observation of the organic fiber layer.

  The organic fiber layer preferably has pores, and the pores have an average pore diameter of 5 nm to 10 μm.

The porosity is preferably 10 to 90%. When the secondary battery according to the embodiment is a battery in which lithium ions are involved in charging / discharging, the organic fiber layer having such pores is:
Since the influence of obstructing the movement of lithium ions can be reduced, excellent permeability of lithium ions can be exhibited and good impregnation of the electrolyte can be exhibited. Further, the porosity is more preferably 70% or more. The average pore diameter and porosity of the pores in the organic fiber layer can be confirmed by, for example, mercury porosimetry, calculation from volume and density, SEM observation, and gas desorption method.

The length of the portion of the first surface of the tab where the organic fiber layers are bonded is preferably 1 mm or more and 5 mm or less. The length of the portion of the first surface of the tab where the organic fiber layers are bonded is 1
When the thickness is within the range of 5 mm to 5 mm, peeling of the organic fiber layer from the electrode can be sufficiently suppressed, and when the tab is connected to another member, for example, when the tab is welded, Interference can be ignored. Here, the length is the length in the direction in which the tab extends.

The electrode described above can form an electrode group together with the opposite electrode. The structure of the electrode group that the secondary battery according to the embodiment can have is not particularly limited. For example, the electrode group can have a stack structure. The stack structure has a structure in which the positive electrode and the negative electrode are laminated so that the positive electrode active material-containing layer and the negative electrode active material-containing layer are spaced apart from each other. Alternatively, the electrode group may have a wound structure. The wound structure is a structure in which the laminated body obtained by laminating as described above is wound in a spiral shape. An example of the secondary battery according to the embodiment including the electrode group having the stack structure and an example of the secondary battery according to the embodiment including the electrode group having the wound structure will be described later.

The secondary battery according to the embodiment may further include an electrolyte. The electrolyte may be impregnated in the electrode group.

In the case of a nonaqueous electrolyte battery, a nonaqueous electrolyte is used as the electrolyte. Examples of the non-aqueous electrolyte include a liquid non-aqueous electrolyte prepared by dissolving an electrolyte in an organic solvent, and a gel non-aqueous electrolyte obtained by combining a liquid electrolyte and a polymer material. The liquid non-aqueous electrolyte can be prepared, for example, by dissolving the electrolyte in an organic solvent at a concentration of 0.5 mol / l or more and 2.5 mol / l or less.
Examples of the electrolyte include lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium arsenic hexafluoride (Li
Examples thereof include lithium salts such as AsF6), lithium trifluorometasulfonate (LiCF3SO3), bistrifluoromethylsulfonylimitolithium [LiN (CF3SO2) 2], and mixtures thereof. It is preferable that it is difficult to oxidize even at a high potential, and LiPF6 is most preferable.

Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate, and diethyl carbonate (DE).
C), chain carbonates such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2Me
THF), dioxolane (DOX) and other cyclic ethers, dimethoxyethane (DME),
Examples include chain ethers such as dietoethane (DEE), γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents may be used alone or as a mixture of two or more.

Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), and the like.

As the nonaqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, or the like may be used.

The secondary battery according to the embodiment may further include a battery container that houses the electrode group and the electrolyte.

As a battery container, the metal can formed from aluminum, aluminum alloy, iron, stainless steel etc. can be used, for example. The plate thickness of the battery container is preferably 0.5 mm or less, and more preferably 0.2 mm or less.

Alternatively, as the battery container, a container formed from a laminate film can be used instead of the metal can. As the laminate film, it is preferable to use a multilayer film composed of a metal foil and a resin film covering the metal foil. Polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) as resin
) And the like can be used. The thickness of the laminate film is desirably 0.2 mm or less.

Various shapes such as a square shape, a cylindrical shape, a thin shape, and a coin shape can be adopted as the shape of the battery container depending on the application.

In addition, the secondary battery according to the embodiment may further include a lead electrically connected to the electrode group. For example, the secondary battery according to the embodiment may include two leads. One lead can be electrically connected to the negative electrode current collecting tab. The other lead can be electrically connected to the positive current collecting tab.

The lead material is not particularly limited, and for example, the same material as the positive electrode current collector and the negative electrode current collector can be used.

The secondary battery according to the embodiment may further include a terminal electrically connected to the lead and drawn out from the battery container. For example, the secondary battery according to the embodiment can include two terminals. One terminal can be connected to a lead electrically connected to the negative current collector tab. The other terminal can be connected to a lead electrically connected to the positive current collecting tab.

Although the material of a terminal is not specifically limited, For example, the same material as a positive electrode collector and a negative electrode collector can be used.

Next, an example of the positional relationship between the electrode and the organic fiber layer included in the secondary battery according to the embodiment will be described in detail with reference to FIG.

FIG. 1 is a schematic cross-sectional view illustrating an example of a positional relationship between an electrode and an organic fiber layer included in the secondary battery according to the embodiment.

The electrode group assembly 200 shown in FIG. 1 includes an electrode pair 100 and a first organic fiber layer 2 and a second organic fiber layer 3 bonded to a part of the surface of the electrode pair 100. In the present embodiment, the first organic fiber layer 2 is preferably made of, for example, polyamideimide having relatively high mechanical strength in the organic fiber group, and the second organic fiber layer 3 is made of other organic fibers. Fiber is preferred.

The electrode pair 100 includes a first electrode 110 shown in the lower part of FIG. 1 and a second electrode 120 shown in the upper part of FIG.

The first electrode 110 illustrated in FIG. 1 is a negative electrode. The negative electrode 110 includes a negative electrode current collector 111, a negative electrode active material-containing layer 112, and a negative electrode current collector tab 113.

The negative electrode current collecting tab 113 has a first surface 113a and a second surface 113b. The negative electrode current collector 111 and the negative electrode current collector tab 113 are integrated, and a negative electrode active material containing layer 112 is supported on both surfaces of the negative electrode current collector 111.

The second electrode 120 shown in FIG. 1 is a positive electrode. As shown in FIG. 1, the positive electrode 120 includes a positive electrode current collector 121, a positive electrode active material-containing layer 122, and a positive electrode current collector tab 123.

The positive electrode current collecting tab 123 has a first surface 123a and a second surface 123b. The positive electrode current collector 121 and the positive electrode current collector tab 123 are integrated, and a positive electrode active material-containing layer 122 is supported on both surfaces of the positive electrode current collector 121.

In the electrode pair 100 shown in FIG. 1, the negative electrode 110 and the positive electrode 120 have one negative electrode active material-containing layer 1.
12 and one positive electrode active material-containing layer 122 are opposed to each other, and a positive electrode current collecting tab 123 is arranged so as to extend in a direction opposite to the negative electrode current collecting tab 113.

As shown in FIG. 1, the first organic fiber layer 2 is at least the negative electrode 110 shown on the left side of FIG.
Of the negative electrode active material-containing layer 112, and a portion 112 b adjacent to the end surface 110 e of the negative electrode 110. The second organic fiber layer 3 is bonded to at least a portion of the negative electrode active material-containing layer 112 where the first organic fiber layer 2 and the negative electrode current collector 111 are not bonded.

A portion 11 adjacent to the end face 110e of the negative electrode 110, to which the first organic fiber layer 2 is bonded.
The length of the portion bonded to 2b is preferably 1 mm or more and 10 mm or less. In this case, it is possible to sufficiently suppress a short circuit between the electrodes while suppressing excessive material use. Here, the length is the length in the direction in which the tab extends.

Further, the second organic fiber layer 3 has an end face 112e at the end of one negative electrode active material-containing layer 112.
And a portion 2a bonded to a portion 113a-1 of the first surface of the negative electrode current collecting tab 113 as a part. Moreover, the part 2b couple | bonded with part 113b-1 of the 2nd upper surface of the negative electrode current collection tab 113 is included as a part.

Further, it is more preferable that the second organic fiber layer 3 is bonded so as to overlap the first organic fiber layer 2.

In addition, the positional relationship between the electrode and the first organic fiber layer 2 and the second organic fiber layer 3 is not limited to the above-described relationship. When it is realized, it may be either of the case where it is realized in both the negative electrode 110 and the positive electrode 120.

Next, an example method for forming the organic fiber layer will be described.
The organic fiber layer described above can be easily formed in a state of being bonded to the electrode described above, for example, by an electrospinning method.

In the electrospinning method, a layer of organic fibers can be formed by discharging a raw material solution from the spinning nozzle over the surface of a predetermined electrode while applying a voltage to the spinning nozzle using a high-pressure generator. The applied voltage is appropriately determined according to the solvent / solute species, the boiling point / vapor pressure curve of the solvent, the solution concentration, temperature, nozzle shape, sample-nozzle distance, etc. It can be set to 100 kV. The feed rate of the raw material solution is also appropriately determined according to the solution concentration, solution viscosity, temperature, pressure, applied voltage, nozzle shape, and the like. In the case of a syringe type, for example, it can be about 0.1 to 500 μl / min per nozzle. In the case of multiple nozzles or slits, the supply speed may be determined according to the opening area.

According to the electrospinning method, it is possible to form an organic fiber layer that can exhibit a high peel strength with respect to the electrode, specifically, a peel strength of 0.4 N or more, for the following reasons. The peel strength with respect to the electrode is more preferably 0.06 N or more. Peel strength is
For example, the measurement can be performed using a measuring device manufactured by Rheotech Co., Ltd. whose model number is RT-2020D-D-CW or a device having an equivalent function.

In the electrospinning method, the raw material solution is charged by the voltage applied to the spinning nozzle, and the amount of charge per unit volume of the raw material solution increases due to volatilization of the solvent from the raw material solution. Since the volatilization of the solvent and the accompanying increase in the charge amount per unit volume occur continuously, the raw material solution discharged from the spinning nozzle extends in the longitudinal direction and is deposited on the electrode as nano-sized organic fibers. A Coulomb force is generated between the organic fiber and the electrode due to a potential difference between the nozzle and the electrode. Therefore, the contact area with the electrode can be increased by the nano-sized organic fiber, and the organic fiber can be deposited on the electrode by Coulomb force, so that the peel strength of the organic fiber layer to the electrode can be increased. It becomes possible. In addition, as described above, an organic fiber layer that can exhibit higher peel strength can be formed by bonding an organic fiber layer to a tab having a small surface roughness. The peel strength can be controlled, for example, by adjusting the solution concentration, the sample-nozzle distance, and the like.

In the electrospinning method, for example, as shown in FIG.
In the state where the mask M is placed on the portion A ′ where the organic fiber is not desired to be deposited, the spinning nozzle B
As described above, the organic fiber layer C can be formed only at a desired location of the substrate A by discharging the raw material solution.

According to such an electrospinning method, in principle, a single continuous fiber can be formed. Therefore, the organic fiber layer can be given resistance to breakage due to bending and film cracking. The single organic fiber contained in the organic fiber layer has a low probability of fraying or partial loss of the organic fiber layer, which is advantageous in terms of suppressing self-discharge.

Further, according to the electrospinning method, since the organic fiber layer is directly formed on the electrode surface in a dry state, it is substantially avoided that the solvent penetrates into the electrode. The residual amount of the solvent inside the electrode is extremely low at a ppm level or less. The residual solvent inside the electrode causes an oxidation-reduction reaction to cause battery loss, leading to deterioration of battery performance. According to the electrospinning method, the risk of such inconveniences being reduced as much as possible, so that the performance of the battery can be improved.

The raw material solution used in the electrospinning method can be prepared by dissolving an organic material in a solvent at a concentration of, for example, about 5 to 60% by mass.

As the organic material, those mentioned above as the organic fiber material that can be included in the organic fiber layer can be used. In particular, polyimide and polyvinylidene fluoride (PVdF) have been considered to be materials that are generally difficult to be fibrous. However, it has been found that fibers containing these materials can be formed as a layer according to the electrospinning method.

The solvent for dissolving the organic material is not particularly limited. Any solvent such as dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), N, N′dimethylformamide (DMF), N-methylpyrrolidone (NMP), water, alcohols, etc. A solvent can be used. Also,
For an organic material having low solubility, electrospinning is performed while melting the sheet-like organic material with a laser or the like. In addition, mixing of a high boiling point organic solvent and a low melting point solvent is allowed.

Or the layer of an organic fiber can be formed in the state couple | bonded with the electrode by the inkjet method, the jet dispenser method, or the spray coating method.

Further, in this embodiment, a layer can be formed by selecting an organic fiber that can exhibit a high tear strength with respect to the electrode, specifically, a tear strength of 0.06 N or more. As shown in FIG. 5, the tear strength of the negative electrode 110 having the first organic fiber layer 2 and the second organic fiber layer 3 does not extend from the edge where the tab extends. When tearing in the direction of the arrow together with the organic fiber toward the edge, the strength when the first organic fiber layer 2 or the second organic fiber layer 3 breaks at the edge where the tab does not extend. Say that. The tear strength can be measured using a tear measurement mode having a model number of AGX300kNX manufactured by Shimadzu Corporation or a device having the same function.

Thus, according to the embodiment, by providing a fiber having high mechanical strength at the edge where the tab does not extend, it is possible to provide a secondary battery that can improve energy density while sufficiently preventing a short circuit between the electrodes. it can.

Furthermore, the organic fiber layer is preferably bonded to the surface and end surface of the end portion of the active material-containing layer. Such organic fiber layers can exhibit higher peel strength to the electrode.

The organic fiber layer does not need to be a self-supporting film because it is bonded to the edge of the active material-containing layer and the portion of the first surface of the tab adjacent to the edge of the current collector. The organic fiber layer is 10 μm.
It can have a thickness of less than m. The organic fiber layer having a small thickness can increase the energy density of the secondary battery. On the other hand, a thickness of 10 μm or more is required to form a separator with a self-supporting film. That is, the organic fiber layer can perform a separator function superior to the separator of the self-supporting film in terms of energy density.

The organic fiber layer can serve as a separator between the active material-containing layer of the electrode and the active material-containing layer of the opposite electrode.

In the organic fiber layer, the porosity can be increased if the organic fiber contained in the organic fiber layer is in a sparse state. For example, it is not difficult to obtain a layer having a porosity of about 90%. For example, when the secondary battery according to the embodiment is a non-aqueous electrolyte secondary battery in which lithium ions are involved in charge and discharge, by increasing the porosity, the lithium ion has excellent permeability and good non-aqueous electrolyte impregnation Can be achieved.

Such an organic fiber layer can exhibit higher peel strength to the electrode. Also,
Such a layer of organic fibers can prevent a short circuit between the electrodes through the end face of the electrode and a portion adjacent thereto.

  Next, an example of the secondary battery according to the embodiment will be described in detail with reference to the drawings.

  First, a first example of the secondary battery according to the embodiment will be described with reference to FIG.

  FIG. 3 is a schematic partially cutaway perspective view of the secondary battery of the first example according to the embodiment.

As illustrated in FIG. 3, the secondary battery 1 of the first example includes an electrode group 200, a container 300, a negative electrode terminal 400, a positive electrode terminal 500, and a nonaqueous electrolyte (not shown). . That is, the secondary battery 1 of the first example is a nonaqueous electrolyte battery.

As shown in FIG. 3, the electrode group 200 includes three negative electrodes 110 and three positive electrodes 120. The three negative electrodes 110 and the three positive electrodes 120 are alternately stacked to form an electrode group 200.
Is forming. That is, the electrode group 200 shown in FIG. 3 has a stack type structure.

One negative electrode 110 and one positive electrode 120 facing each other constitute the electrode group assembly 200 described with reference to FIG. The electrode group 200 shown in FIG. 3 includes three assemblies 200 shown in FIG.

Although not shown, the negative electrode current collecting tabs 113 of the three negative electrodes 110 are combined into one,
It is connected to the negative terminal 400 shown in FIG. Similarly, the positive electrode current collecting tabs 123 of the three positive electrodes 120 are combined into one and connected to the positive electrode terminal 500 shown in FIG. Thereby, the assembly 200 composed of the negative electrode 110 and the positive electrode 120 shown in FIG. 1 and two further assemblies having the same structure are connected in parallel to each other to form the electrode group 200.

Such an electrode group 200 is accommodated in the container 300. As shown in FIG. 3, a part of the negative electrode terminal 400 and the positive electrode terminal 500 connected to the electrode group 200 is drawn to the outside of the container 300.

  The secondary battery 1 of the 1st example shown in FIG. 3 can prevent the short circuit between electrodes.

The container 300 further contains a non-aqueous electrolyte (not shown). Non-aqueous electrolyte is the container 3
In 00, the electrode group 200 is impregnated.

Since the organic fiber layer 2 can exhibit a high porosity, the secondary battery 1 of the first example can exhibit a high energy density.

That is, the secondary battery 1 of the first example can improve the energy density while sufficiently preventing a short circuit between the electrodes.

  Next, a secondary battery of a second example will be described with reference to FIG.

  FIG. 4 is a schematic exploded perspective view of the secondary battery of the second example according to the embodiment.

As shown in FIG. 4, the secondary battery 1 of the second example includes an electrode group 200, a container 300, a negative electrode terminal 400, a positive electrode terminal 500, and a nonaqueous electrolyte (not shown). . That is, the secondary battery 1 of the second example is a nonaqueous electrolyte battery.

As shown in FIG. 4, the electrode group 200 includes one negative electrode 110 and one positive electrode 120. The negative electrode 110 and the positive electrode 120 are the electrode group assembly 20 described with reference to FIG.
0 is configured.

As shown in FIG. 4, one negative electrode 110 and one positive electrode 120 are wound so that the positive electrode 120 has the outermost periphery in a stacked state. That is, the electrode group 200 shown in FIG.
It has a wound structure. In the wound electrode group 200, as shown in FIG. 4, the negative electrode current collecting tab 113 and the positive electrode current collecting tab 123 extend in opposite directions.

As shown in FIG. 4, the negative electrode current collector tab 113 is sandwiched between two negative electrode current collector plates 410.
Similarly, the positive electrode current collecting tab 123 is sandwiched between two positive electrode current collecting plates 510.

As shown in FIG. 4, the electrode group 200 is housed in a container 300 having an opening 310. Although the exploded view is shown in FIG. 4, the opening 310 is sealed with a sealing plate 320. The sealing plate 320 includes a negative electrode terminal 400 and a positive electrode terminal 500. Negative terminal 40
0 is electrically connected to the negative electrode current collector plate 410. Similarly, the positive electrode terminal 500 is electrically connected to the positive electrode current collector plate 500.

The secondary battery 1 of the second example can prevent a short circuit between the electrodes for the same reason as described with reference to FIG. In particular, in the formation of the wound electrode group, a large stress is applied in the vicinity of the ridge that may exist at the end of the active material-containing layer, and there is a possibility that a short circuit between the electrodes occurs. However, in the secondary battery 1 of the second example, a part 2b of the organic fiber layer 2 is one positive electrode active material-containing layer 12.
2 can serve as a further cushion for the bulge of the end 122a of the second layer, and a portion 2b ′ of the organic fiber layer 2 ′ can be further bulged for the bulge of the end 122a of the negative electrode active material-containing layer 112. Therefore, it is possible to further prevent a short circuit between the electrodes in forming the wound electrode group 200.

And since the layers 2 and 2 'of organic fiber can show a high porosity, the secondary battery 1 of a 1st example can show a high energy density.

That is, the secondary battery 1 of the first example can improve the energy density while sufficiently preventing a short circuit between the electrodes.

In the secondary battery according to the embodiment described above, the organic fiber layer is bonded to the portion having the maximum thickness of the active material-containing layer and the portion adjacent to the surface of the tab. Short circuit can be prevented. Moreover, energy density can be improved thanks to the organic fiber layer.

The secondary battery according to the embodiment may further include an electrolyte. The electrolyte may be impregnated in the electrode group.

The first organic fiber layer 2 and the second organic fiber layer 3 can serve as a cushion between the negative electrode active material layer and the positive electrode active material layer.

In the electrode assembly 200 shown in FIG. 1, a short circuit between the negative electrode 110 and the positive electrode 120 can be prevented.

Further, the organic fiber layer 2 is bonded to the first surface portion 113 a-1 of the negative electrode current collecting tab 113 and is formed on the portion 112 b of the negative electrode active material containing layer 112 facing the positive electrode 120. Since they are bonded, the fiber layer 2 can exhibit high peel strength with respect to the negative electrode 110.
Similarly, the organic fiber layer 2 ′ is bonded to the first surface portion 123 a-1 of the positive electrode current collecting tab 123 and a portion of the positive electrode active material-containing layer 122 not facing the negative electrode 110. Since it is bonded to 122 b, the organic fiber layer 2 ′ can exhibit high peel strength with respect to the positive electrode 120.

Further, in the electrode assembly 200 shown in FIG. 1, the organic fiber layer 2 is formed on the end face 1 of the negative electrode 110.
The short circuit through 10e can be prevented, and the organic fiber layer 2 ′ can prevent the short circuit through the end face 120e of the positive electrode 120.

(Second embodiment)
In 2nd embodiment, there exists a part from which the position of the 1st organic fiber 2 differs. Therefore, the first
The same portions as those in the embodiment are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

The second electrode 120 illustrated in FIG. 5 is a positive electrode. As shown in FIG. 1, the positive electrode 120 includes a positive electrode current collector 121, a positive electrode active material-containing layer 122, and a positive electrode current collector tab 123.

The positive electrode current collecting tab 123 has a first surface 123a and a second surface 123b. The positive electrode current collector 121 and the positive electrode current collector tab 123 are integrated, and a positive electrode active material-containing layer 122 is supported on both surfaces of the positive electrode current collector 121.

In the electrode pair 100 shown in FIG. 1, the negative electrode 110 and the positive electrode 120 have one negative electrode active material-containing layer 1.
12 and one positive electrode active material-containing layer 122 are opposed to each other, and a positive electrode current collecting tab 123 is arranged so as to extend in a direction opposite to the negative electrode current collecting tab 113.

As shown in FIG. 1, the first organic fiber layer 2 has an end face 110 of the negative electrode 110 shown on the left side of FIG.
e, negative electrode active material-containing layer 112, end face 110e of negative electrode 110, one negative electrode active material-containing layer 11
The second end surface 112e of the negative electrode current collector tab 113 and the second surface portion 113b-1 of the negative electrode current collecting tab 113 are coupled to the second surface portion 113b-1. 2b as a part. The second organic fiber layer 3 is bonded so as to cover the first organic fiber layer 2.

According to the present embodiment, an insulating effect similar to or higher than that of the first embodiment can be obtained.

  Examples will be described below.

Example 1
Aluminum foil was used for the negative electrode current collector foil, lithium titanate was used for the negative electrode active material, and lithium cobaltate was used for the positive electrode active material. The first organic fiber layer 2 is composed of polyamideimide on the entire surface of the negative electrode by electrospinning, and the second organic fiber layer 3 is composed of polyimide on the structure of the negative electrode and polyamideimide by electrospinning. .

The constituent conditions of the first organic fiber layer 2 by electrospinning will be described. Polyamideimide was mixed with N-methylpipolydon at a solid content ratio of 30 wt%, and dissolved in a constant temperature layer at 95 ° C. with stirring.

The obtained solution was set in an electrospinning apparatus, set to a voltage of 40 kV and a liquid supply amount of 1 mL / h, and formed on the negative electrode with a film thickness of 5 μm.

The constituent conditions of the second organic fiber layer 3 by electrospinning will be described. Polyimide was mixed with N-methylpipolydon at a solid content ratio of 30 wt% and dissolved in a constant temperature layer at 95 ° C. with stirring.

The obtained solution was placed in an electrospinning apparatus, set to a voltage of 40 kV and a liquid supply amount of 1 mL / h, and formed on a polyamideimide / negative electrode structure with a film thickness of 10 μm.

(Example 2)
Aluminum foil was used for the negative electrode current collector foil, lithium titanate was used for the negative electrode active material, and lithium cobaltate was used for the positive electrode active material. Also, as the first organic fiber layer 2, polyamideimide is formed by electrospinning from the slit end of the negative electrode coating part to 10 mm in the coating width direction, and from the slit end part of the coating part to 2 mm in the direction opposite to the coating width. Then, as the second organic fiber layer 3, polyimide was formed on the negative electrode and polyamideimide structure by electrospinning.

The constitution conditions of the first organic fiber layer 2 and the second organic fiber layer 3 by the electrospinning method are the same as in Example 1.

(Comparative example)
Aluminum foil was used for the negative electrode current collector foil, lithium titanate was used for the negative electrode active material, and lithium cobaltate was used for the positive electrode active material. Moreover, the polyimide was comprised on the negative electrode by the electrospinning method as a layer of an organic fiber.

The constitution conditions of the organic fiber layer by the electrospinning method are the same as those of the second organic fiber layer 3 of Example 1.

Using the configurations of the example and the comparative example, a wound structure was formed, and a square cell was manufactured. The square cell was set to a discharge capacity of 20 Ah.

The resistance value was measured using an ammeter after the wound structure was fabricated. After that, the square cell is assembled and the SOC
(State Of Charge) The battery was charged to 100% and the self-discharge amount at 25 ° C. for 2 days was measured. The results are shown below.
Insulation resistance after winding Self-discharge [% / 2day]
Example 1 98 MΩ 0.5
Example 2 103 MΩ 0.5
Comparative Example 1 300mΩ 100

As can be seen from the above, the insulation resistance in the wound structure of Example 1 and Example 2 using two types of organic fibers has a resistance value on the order of MΩ, while in Comparative Example 1, the resistance value is on the order of mΩ. It can be seen that a short-circuit phenomenon occurs. As the self-discharge data shows,
If the resistance value is on the order of mΩ, the battery cannot function sufficiently.

According to the embodiments and examples described above, the energy density can be improved while sufficiently preventing a short circuit between the electrodes.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions can be made without departing from the spirit of the invention.
Can be replaced or changed. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Secondary battery, 2 ... First organic fiber layer, 3 ... Second organic fiber layer, 100 ... Electrode pair, 1
10 ... 1st electrode, 120 ... 2nd electrode

Claims (11)

A current collector having an edge, an active material-containing layer carried on at least one surface of the current collector, and a tab extending from the edge of the current collector and having a first surface and a second surface The active material-containing layer includes an electrode including an end portion carried on the edge portion of the current collector,
A first organic fiber layer including an organic fiber layer and bonded to at least an end face of the active material layer;
A second organic fiber layer that includes an organic fiber layer and is bonded to at least a portion of the surface of the active material layer to which the first organic fiber layer is not bonded;
A secondary battery comprising: The layer of the second organic fiber is further bonded to the surface of the layer of the first organic fiber bonded to the surface of the active material layer. Secondary battery. The secondary battery according to claim 1, wherein the first organic fiber layer has a thickness of less than 40 μm. 4. The secondary battery according to claim 1, wherein the second organic fiber layer has a thickness of less than 40 μm. 5. The first organic fiber layer or the second organic fiber layer has pores having an average pore diameter of 5 nm or more and 10 nm or less, and a porosity of 5% or more and 90% or less. The secondary battery according to any one of claims 1 to 4. The secondary battery according to any one of claims 1 to 5, wherein the first organic fiber layer or the second organic fiber layer has a porosity of 80% or less. . The secondary strength according to any one of claims 1 to 6, wherein the mechanical strength of the first organic fiber layer and the mechanical strength of the second organic fiber layer are different from each other. battery.   The secondary battery according to claim 7, wherein the mechanical strength is a tensile property. 9. The tear load of the first organic fiber layer and the second organic fiber layer covering the end surface is 0.06 N or more, 9. Secondary battery described in 1. The material of the first organic fiber layer and the second organic fiber layer is polyimide, polyamideimide, polyvinylidene fluoride, cellulose, polyolefin, polyether, polyetherimide, polyketone, polysulfone, polyethersulfone, The secondary battery according to any one of claims 1 to 9, wherein the secondary battery is selected from the group consisting of polyvinyl alcohol, polyvinyl acetal, and a copolymer of isobutylene and maleic anhydride. 11. The active material-containing layer contains lithium titanate.
The secondary battery as described in any one of.

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