JP6702903B2 - Secondary battery - Google Patents

Description

Embodiments of the present invention relate to a secondary battery.

In a secondary battery such as a lithium secondary battery, a porous separator is used 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.

As a general separator, a microporous membrane made of a polyolefin resin film can be mentioned. Such a separator is produced, 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.

The separator made of a resin film needs to have mechanical strength so as not to break during the production of a battery, and thus it is difficult to make it thinner than a certain extent. Therefore, particularly in a battery of a type in which a large number of electrode cells are stacked or wound, the thickness of the separator limits the amount of unit electrode cells that can be stored per unit volume of the battery. This leads to a decrease in battery capacity. In addition, the separator made of a resin film has poor durability, and when used in a secondary battery, there is a disadvantage that the separator deteriorates during repeated charging and discharging and the cycleability of the battery deteriorates.

JP, 2010-182922, A

The problem to be solved by the present invention is to provide a secondary battery capable of improving the energy density while preventing a short circuit between electrodes.

In order to solve the above problems, the assembled battery of the present embodiment has a current collector having an edge portion, an active material-containing layer carried on at least one surface of the current collector, and the edge of the current collector. A secondary battery comprising a tab extending from a portion, wherein the active material-containing layer includes an electrode including an end supported on the edge of the current collector as a positive electrode and a negative electrode, and an organic fiber Surface of the active material layer of the electrode that includes a layer of an organic fiber that is bonded to at least the main surface of the active material layer of the positive electrode or the negative electrode, and that does not include a layer of the organic fiber that includes an inorganic material. And an inorganic film bonded to at least a portion adjacent to the edge portion of the tab.

FIG. 1 is a schematic diagram showing an example of a positional relationship among electrodes, a layer of organic fibers, and an inorganic film included in the secondary battery according to the first embodiment. FIG. 2 is a schematic diagram showing an example method of 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 diagram showing an example of the positional relationship between the electrodes and the organic fiber layers included in the secondary battery according to the second embodiment. It is a table|surface which shows the result concerning an Example.

(First embodiment)
Embodiments will be described below with reference to the drawings.

According to the embodiment, a secondary battery is provided. This secondary battery has an electrode, an organic fiber layer,
An inorganic film and a separator are provided. 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 carried 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.

In the secondary battery according to the embodiment, the current collector may have a plurality of edges, and the tab may extend from one of the edges. Further, 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. Further, it is more preferable that the tab is formed of at least one kind of conductive material selected from the group consisting of aluminum, 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 may be, for example, a non-aqueous 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 according to the embodiment may include further electrodes other than the electrodes described above.

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 may 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 may be separate bodies.

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 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 above-described electrode is a negative electrode, the negative electrode active material-containing layer preferably contains lithium titanate.

Lithium titanate can act as a negative electrode active material. Examples of lithium titanate include Li _4+x Ti ₅ O ₁₂ (0≦x≦3) having a spinel structure and Li _2+y Ti ₃ O ₇ (0≦y≦3) having a ramsteride structure. Can be mentioned.

Since such lithium titanate can occlude and release lithium ions at a potential of 1.55 V (vs. Li/Li+) or higher, for example, the surface of the negative electrode active material-containing layer containing lithium titanate In principle, lithium dendrite does not deposit even after repeated charging and discharging. In addition, lithium titanate hardly changes in volume due to charge/discharge reaction. Thanks to these, the layer of the organic fiber 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 diameter 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 can exhibit high adhesion with the organic fiber layer. By virtue of 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 contained in the negative electrode active material-containing layer include carbonaceous materials such as graphite and tin-silicon alloy materials.

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

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

The positive electrode may include a positive electrode current collector, a positive electrode active material-containing layer carried 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 may be separate bodies.

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

The positive electrode active material-containing layer can include 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, LiCoO ₂ , LiNi1-xCoxO ₂ (0<x<0.3), LiMnxNiy
CozO ₂ (0<x<0.5, 0<y<0.5, 0≦z<0.5), LiMn ₂ -xMxO ₄ (
M is Li, Mg, Co, Al, Ni, 0<x<0.2), LiMPO ₄ (M is Fe, Co
, Ni) and the like.

Examples of the positive electrode conductive agent include carbonaceous materials such as acetylene black, carbon black and graphite. Examples of the binder include polytetrafluoroethylene (PT
FE), polyvinylidene fluoride (PVdF), and fluororubber.

The organic fiber contained in the organic fiber layer is selected from the group consisting of polyamideimide, polyamide, polyolefin, polyether, polyimide, polyamideimide, polyketone, polysulfone, cellulose, polyvinyl alcohol (PVA), and polyvinylidene fluoride (PVdF). At least one of the above can be included. Examples of the polyolefin include polypropylene (PP) and polyethylene (PE). The layer of organic fibers preferably comprises organic fibers including polyimide. Since polyimide is insoluble and infusible even at 250 to 400° C. and does not decompose, the use of polyimide makes it possible to obtain an organic fiber layer having excellent heat resistance.

The organic fiber preferably has a length of 1 mm or more and a thickness of 1 μm or less. A layer of organic fibers containing such organic fibers has sufficient strength, porosity, air permeability, pore diameter, electrolytic solution 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 by an electron microscope (SEM) and a scanning probe microscope (SPM).
, A transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), and the like. Moreover, 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 secure ion permeability and electrolytic solution-containing property, and thus an organic fiber layer is formed. It is preferable that 30% or more of the volume of the entire fiber is an organic fiber having a thickness of 1 μm or less. A more preferable range of thickness is 350 nm or less, and a further preferable range is 50 nm.
nm or less. Further, the volume of the organic fiber having a thickness of 1 μm or less, more preferably 350 nm or less, and further preferably 50 nm or less, more preferably accounts for 80% or more of the volume of the entire fiber forming the organic fiber layer. .. Further, it is more preferable that the organic fibers having a thickness of 40 nm or less occupy 40% or more of the volume of the entire fibers forming the organic fiber layer. When the diameter of the organic fiber is small, the influence of obstructing the movement of lithium ions can be reduced. Such a state can be confirmed by SEM observation of the organic fiber layer.

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

Further, 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 and discharging, the organic fiber layer having such holes is:
Since the effect of hindering the movement of lithium ions can be reduced, excellent permeability of lithium ions can be exhibited, and good impregnation property of the electrolyte can be exhibited. The porosity is more preferably 70% or more. The average pore diameter and the porosity of the pores in the organic fiber layer can be confirmed by, for example, a mercury intrusion method, 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 layer is 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 layer is bonded is 1
When the thickness is in the range of 5 mm or more and 5 mm or less, peeling of the organic fiber layer from the electrode can be sufficiently suppressed, and at the time of connecting the tab to another member, for example, when welding, the organic fiber layer Interference can be ignored. The length here is the length in the direction in which the tab extends.

The inorganic material included in the inorganic film can include at least one selected from the group consisting of alumina, titanium, silica, mica, zirconium silicate, barium sulfate, barium oxide, and calcium silicate.

The inorganic film is preferably made of an inorganic material having an average particle diameter of 20 μm or less. The thickness of the inorganic film is preferably 40 μm or less.

The electrodes described above can form an electrode group together with the opposite electrodes. The structure of the electrode group that can be included in the secondary battery according to the embodiment is not particularly limited. For example, the electrode group can have a stack structure. The stack structure has a structure in which a positive electrode and a negative electrode are stacked so that the positive electrode active material-containing layer and the negative electrode active material-containing layer face each other with a space therebetween. Alternatively, the electrode group can have a wound structure. The wound structure is a structure in which a laminated body obtained by laminating as described above is spirally wound. 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 winding structure will be described later.

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

In the case of a non-aqueous electrolyte battery, a non-aqueous electrolyte is used as the electrolyte. Examples of the non-aqueous electrolyte include a liquid non-aqueous electrolyte prepared by dissolving the electrolyte in an organic solvent, and a gel non-aqueous electrolyte obtained by combining the 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 (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenide (Li).
AsF _6), lithium trifluoro meth sulfonate (LiCF ₃ SO _3), and bis trifluoromethylsulfonyl Imi tritium _{[LiN (CF 3 SO 2)} 2] Lithium salt such as or mixtures thereof. It is preferable that it is difficult to oxidize even at a high potential, and LiPF ₆ is most preferable.

Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate, and diethyl carbonate (DE).
C), dimethyl carbonate (DMC), chain carbonate such as methyl ethyl carbonate (MEC), tetrahydrofuran (THF), 2 methyl tetrahydrofuran (2Me
THF), cyclic ethers such as dioxolane (DOX), dimethoxyethane (DME),
Examples thereof 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 kinds.

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

As the non-aqueous 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 accommodating the electrode group and the electrolyte.

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

Alternatively, as the battery container, a container formed of a laminated film can be used instead of the metal can. For 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 other polymers can be used. The thickness of the laminate film is preferably 0.2 mm or less.

The shape of the battery container may be square, cylindrical, thin, coin-shaped, or the like, 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 collector tab. The other lead can be electrically connected to the positive electrode current collector tab.

The material of the lead is not particularly limited, but 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 from the battery container. For example, the secondary battery according to the embodiment may include two terminals. One terminal can be connected to a lead electrically connected to the negative electrode current collector tab. The other terminal can be connected to a lead electrically connected to the positive electrode current collector tab.

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

Next, with reference to FIG. 1, an example of the positional relationship among the electrode, the organic fiber layer, and the inorganic film included in the secondary battery according to the embodiment will be described in detail.

FIG. 1 is a schematic cross-sectional view showing an example of a positional relationship among electrodes, an organic fiber layer, and an inorganic film included in the secondary battery according to the embodiment.

The electrode group assembly 200 shown in FIG. 1 includes an electrode pair 100, a layer 2 of organic fibers bonded to a part of the surface of the electrode pair 100, and an inorganic film 3.

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 shown 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 the negative electrode active material-containing layers 112 are respectively carried 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 collector 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 the positive electrode active material-containing layers 122 are respectively carried 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 are one negative electrode active material-containing layer 1.
12 and one positive electrode active material-containing layer 122 face each other, and the positive electrode current collecting tab 123 is arranged so as to extend in the direction opposite to the negative electrode current collecting tab 113.

As shown in FIG. 1, the organic fiber layer 2 is bonded to at least all the main surfaces of the negative electrode active material-containing layer 112 of the negative electrode 110. In addition, the inorganic film 3 has a positive electrode 12
0, the end face 122f of the positive electrode 120 shown at least on the left side of FIG.
3 is connected to a part 123a-1 of the first surface and a part 123b-1 of the second surface.

Next, an example method for forming the layer of the organic fiber layer will be described. The layer of the organic fiber 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, the temperature, the nozzle shape, the sample-nozzle distance, and the like. It can be 100 kV. The supply 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 a layer of an organic fiber capable of exhibiting a high peel strength with respect to an 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 with a model number of RT-2020D-D-CW manufactured by Rheotech Co., Ltd. or a device having a function equivalent to this.

In the electrospinning method, the raw material solution is charged by the voltage applied to the spinning nozzle, and the volatilization of the solvent from the raw material solution increases the charge amount per unit volume of the raw material solution. As the solvent volatilizes and the amount of charge per unit volume increases accordingly, the raw material solution discharged from the spinning nozzle extends in the longitudinal direction and is deposited on the electrode as nanosized organic fibers. A Coulomb force is generated between the organic fiber and the electrode due to the 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 the Coulomb force, so that the peel strength of the organic fiber layer from the electrode can be increased. It will be possible. In addition, as described above, by bonding the organic fiber layer to the tab having a small surface roughness, the organic fiber layer capable of exhibiting higher peel strength can be formed. The peel strength can be controlled by adjusting the solution concentration, the sample-nozzle distance, and the like.

In the electrospinning method, for example, as shown in FIG.
Of the spinning nozzle B with the mask M placed on the portion A'of which organic fibers are not desired to be deposited.
By discharging the raw material solution as described above, the layer C of the organic fiber can be formed only at a desired position on the base material A.

According to such an electrospinning method, since one continuous fiber can be formed in principle, the organic fiber layer can be provided with resistance to breakage due to bending and film cracking. Having only one organic fiber in the organic fiber layer has a low probability of fraying or partial loss of the organic fiber layer, and is advantageous in suppressing self-discharge.

Further, according to the electrospinning method, the organic fiber layer is directly formed on the electrode surface in a dry state, so that the solvent is substantially prevented from penetrating into the electrode. The residual amount of solvent inside the electrode is extremely low, below the ppm level. The residual solvent inside the electrode causes a redox reaction to cause a loss of the battery, which leads to deterioration of battery performance. According to the electrospinning method, the possibility of causing such an inconvenience is 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 material of the organic fiber that can be contained in the layer of the organic fiber can be used. In particular, polyimide and polyvinylidene fluoride (PVdF) have been generally regarded as materials that are difficult to form into fibers. However, it has been found that electrospinning techniques can be used to form fibers containing these materials as layers.

The solvent that dissolves the organic material is not particularly limited, and may be any solvent such as dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), N,N′ dimethylformamide (DMF), N-methylpyrrolidone (NMP), water, alcohols, and the like. A solvent can be used. Also,
For an organic material having low solubility, electrospinning is performed while melting the sheet-shaped organic material with a laser or the like. In addition, it is acceptable to mix a high boiling point organic solvent with a low melting point solvent.

Alternatively, the organic fiber layer can be formed in a state of being bonded to the electrode by an inkjet method, a jet dispenser method, or a spray coating method.

Next, an example method of forming the inorganic film 3 will be described. The inorganic film 3 described above can be easily formed in a state of being bonded to the electrode described above by a coating device such as a die coater or a gravure coater.

As described above, according to the embodiment, by providing the organic fiber on one electrode and providing the inorganic film on the portion including the tab of the electrode facing the organic fiber, it is possible to sufficiently prevent the short circuit between the electrodes and improve the energy density. A secondary battery can be provided.

Further, the organic fiber layer is preferably bonded to the surface and the end surface of the end portion of the active material containing layer. Layers of such organic fibers can exhibit higher peel strength to the electrodes.

The organic fiber layer and the inorganic film do not have to be self-supporting films because they are bonded to the active material-containing layer and a part of the tab. The layer of organic fibers and the inorganic membrane can have a thickness of less than 10 μm. The organic fiber layer having a small thickness can increase the energy density of the secondary battery.
On the other hand, to form a separator with a self-supporting film, a thickness of 10 μm or more is required. That is, the organic fiber layer and the inorganic film can perform a separator function superior to the separator of the self-supporting film in terms of energy density.

The layer of organic fibers and the inorganic film 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 by making the contained organic fibers sparse, so that it is not difficult to obtain a layer having a porosity of about 90%, for example. 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, excellent permeability of lithium ions and good non-aqueous electrolyte impregnability Can be achieved.

Such an organic fiber layer and an inorganic film can exhibit even higher peel strength with respect to the electrode. Moreover, such a layer of organic fibers and an inorganic film can prevent a short circuit between the electrodes via the end faces of the electrodes and the portions 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 shown 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 non-aqueous 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 the electrode group 200.
Is formed. 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 form the electrode assembly 200 described with reference to FIG. 1. The electrode group 200 shown in FIG. 3 includes three assemblies 200 shown in FIG.

Although not shown, the negative electrode current collector tabs 113 of the three negative electrodes 110 are combined into one,
It is connected to the negative electrode terminal 400 shown in FIG. Similarly, the positive electrode collector tabs 123 of the three positive electrodes 120 are combined into one and connected to the positive electrode terminal 500 shown in FIG. As a result, the assembly 200 including the negative electrode 110 and the positive electrode 120 shown in FIG. 1 and two additional assemblies having a similar structure are connected in parallel to each other to form the electrode group 200.

Such an electrode group 200 is housed in the container 300. As shown in FIG. 3, the negative electrode terminal 400 and the positive electrode terminal 500 connected to the electrode group 200 are partially pulled out to the outside of the container 300.

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

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

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

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

Next, the secondary battery of the 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 non-aqueous 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 correspond to the electrode group assembly 20 described with reference to FIG.
Configures 0.

As shown in FIG. 4, one negative electrode 110 and one positive electrode 120 are wound so that the positive electrode 120 is 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 collector tab 113 and the positive electrode current collector tab 123 extend in directions opposite to each other.

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 collector tab 123 is sandwiched between two positive electrode current collector 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 by the sealing plate 320. The sealing plate 320 includes a negative electrode terminal 400 and a positive electrode terminal 500. Negative electrode 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.

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

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

Further, the end surface of the electrode is more likely to receive an impact from the outside than the other part of the electrode. Therefore, the strength of the insulator that insulates the end face of the electrode from the tab portion of the electrode facing the electrode is required. In the present embodiment, since the inorganic film 3 is provided on at least a part of the tab of the electrode not provided with the organic fiber layer 2, the end face of the electrode provided with the organic fiber layer 2 and the tab of the other electrode are provided. The parts come into contact with each other and a short circuit can be sufficiently prevented.

The secondary battery of the embodiment described above can improve the energy density because it has the organic fiber layer 2 and the inorganic film 3.

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

Even when the inorganic film 3 and the active material-containing layer are adjacent to each other without a gap, the components of the inorganic film 3 and the active material-containing layer are mixed at the boundary between the inorganic film 3 and the active material-containing layer. However, even if there is a small gap between the inorganic film 3 and the active material-containing layer, for example, 10 mm or less, a short circuit can be prevented.

(Second embodiment)
In the second embodiment, there is a portion where the position of the inorganic film 3 is different. Therefore, the same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be appropriately omitted.

As shown in FIG. 5, the organic fiber layer 2 is bonded to at least the entire main surface of the negative electrode active material-containing layer 112 of the negative electrode 110. In addition, the inorganic film 3 includes the negative electrode 11
Of 0, it is bonded to at least the end surface 110e of the negative electrode 110 shown on the left side of FIG.

The end face of the electrode is more likely to receive an impact from the outside than the other part of the electrode. Therefore, the strength of the insulator that insulates the end face of the electrode from the tab portion of the electrode facing the electrode is required. According to this embodiment, in addition to the insulation by the organic fiber layer 2, the end face of the negative electrode 110 and the positive electrode 12 are
Since the tabs of No. 0 are insulated from each other by the inorganic film, the secondary battery according to the present embodiment can both improve the energy density and the insulation between the electrodes.

Examples will be described below.

(Example 1)
An aluminum foil was used as the negative electrode current collector foil, lithium titanate was used as the negative electrode active material, and lithium cobalt oxide was used as the positive electrode active material. In addition, polyamide imide was formed on the negative electrode as the organic fiber layer 2 by the electrospinning method, and alumina was formed on the positive electrode tab as the inorganic film 3.

The constitutional conditions of the organic fiber layer 2 by the electrospinning method will be described. Polyamideimide was mixed with N-methylpipolidone so as to have a solid content ratio of 30 wt %, and dissolved while stirring in a constant temperature layer at 95°C.

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

The constituent conditions of alumina on the positive electrode tab will be described. Alumina particles and PVdF were mixed with polyamide-imide in N-methylpipolidone so that the solid content ratio was 60 wt %, and dispersed with stirring.

The resulting dispersion was placed in a slot die device, and a film having a thickness of 10 μm and a width of 5 mm was formed on the tab of the positive electrode.

(Comparative example)
An aluminum foil was used as the negative electrode current collector foil, lithium titanate was used as the negative electrode active material, and lithium cobalt oxide was used as the positive electrode active material. As the organic fiber layer 2, polyamideimide was formed by electrospinning from the slit end of the coated portion of the negative electrode to 10 mm in the coating width direction and from the slit end of the coated portion to 2 mm in the direction opposite to the coating width.

The conditions for forming the organic fiber layer 2 by the electrospinning method are the same as in Example 1.

(result)
A prismatic cell was produced by using the structures of Examples and Comparative Examples to form a wound structure. The rectangular cell was set to a discharge capacity of 20 Ah.

The resistance value was measured using an ammeter after the winding structure was manufactured. After that, assemble the rectangular cells and
(State Of Charge) The battery was charged to 100% and the self-discharge amount at 25°C for 2 days was measured. The result is shown in FIG.

As can be seen from FIG. 6, the insulation resistance in the wound structure of Examples and Examples using two kinds of organic fibers has a resistance value of MΩ order, while the comparative example has a resistance value of mΩ order. It can be seen that a short circuit phenomenon has occurred. As shown by the self-discharge amount data, when the resistance value is in the order of mΩ, the battery cannot sufficiently function.

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

Although some embodiments of the present invention have been described, these embodiments are presented as examples 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 scope of the invention.
It can be replaced and changed. For example, the same effect can be obtained by replacing the positive electrode and the negative electrode. The embodiments and their modifications are included in the scope of the invention and the scope thereof, and are included in the invention described in the claims and the scope of equivalents thereof.

DESCRIPTION OF SYMBOLS 1... Secondary battery, 2... Layer of organic fiber, 3... Inorganic film, 100... Electrode pair, 110... 1st electrode,
120...second electrode

Claims (8)

A current collector having an edge portion, an active material-containing layer carried on at least one surface of the current collector, and a tab extending from the edge portion of the current collector, wherein the active material-containing layer is the current collector. A secondary battery comprising an electrode including an end portion supported on the edge portion of an electric body as a positive electrode and a negative electrode,
A layer of an organic fiber including a layer of an organic fiber, which is bonded to at least the main surface of the active material layer of the positive electrode or the negative electrode,
An inorganic film containing an inorganic substance, which is bonded to at least a portion of the surface of the active material layer of the electrode not provided with the organic fiber layer, which is adjacent to the edge portion of the tab,
A secondary battery comprising: A current collector having an edge portion, an active material-containing layer carried on at least one surface of the current collector, and a tab extending from the edge portion of the current collector, wherein the active material-containing layer is the current collector. A secondary battery comprising an electrode including an end portion carried on the edge of an electric body, as an electrode of at least one of a positive electrode and a negative electrode,
A layer of an organic fiber including a layer of an organic fiber, which is bonded to at least the main surface of the active material layer of the positive electrode or the negative electrode,
An inorganic film containing an inorganic material, which is bonded to at least a portion of the surface of the active material layer of the electrode adjacent to the edge portion of the tab,
A secondary battery comprising: Wherein the layer of organic fibers, the secondary battery according to claim 1 or claim 2 characterized in that it has a thickness of less than 40 [mu] m. 4. The 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, according to any one of claims 1 to 3. The secondary battery described. The secondary battery according to any one of claims 1 to 4 , wherein the organic fiber layer has a porosity of 80% or less. The material of the layer of the organic fiber is polyimide, polyamideimide, polyvinylidene fluoride, cellulose, polyolefin, polyether, polyetherimide, polyketone, polysulfone, polyether sulfone, polyvinyl alcohol, polyvinyl acetal and isobutylene and maleic anhydride. the secondary battery according to any one of claims 1 to 5, characterized in that it is selected from the group consisting of a copolymer. 7. The material of the inorganic film is selected from the group consisting of alumina, titanium, silica, mica, zirconium silicate, barium sulfate, barium oxide, and calcium silicate, according to any one of claims 1 to 6 . The secondary battery according to item 1. The secondary battery according to any one of claims 1 to 7 wherein the active material-containing layer is characterized by containing a lithium titanate.

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