Patent Application
20220393250
The present disclosure relates to an electrode plate, non-aqueous electrolyte secondary battery, and a method for producing an electrode plate.
An electrode plate of a positive electrode or a negative electrode that configures a non-aqueous electrolyte secondary battery has a mixture layer on a surface of each electrode core body. If the active material included in the mixture layer falls off inside of the battery, an internal short circuit may occur, and the reliability of the battery can be improved by suppressing falling-off of the active material. The active material especially tends to fall off at the end portion of the electrode plate, and therefore, for example. Patent Literature 1 discloses a secondary battery in which the mixture layer is removed from the end portion of the electrode plate.
In the method disclosed in Patent Literature 1, there is the possibility that the active material falls off in the interface between the part where the electrode core body is exposed and the part where the mixture layer is formed on the surface of the electrode core body, and there is still room for improvement.
An electrode plate that is one aspect of the present disclosure is an electrode plate included in a wound type or stacked type electrode assembly, and comprises a band-shaped electrode core body, a mixture layer formed on both surfaces of the electrode core body, and a tab extended from one end portion of the electrode core body in a short side direction of the electrode core body, in which a tip end portion of the electrode core body is covered with the mixture layer in the end portion on a side where the tab extends.
A non-aqueous electrolyte secondary battery that is one aspect of the present disclosure is a non-aqueous electrolyte secondary battery comprising a wound type or stacked type electrode assembly including the above described electrode plate, an exterior body having an opening that houses the electrode assembly, and a sealing plate that seals the opening and is connected with the tab, in which as for a width, in the short side direction of the electrode core body, of the tip end portion of the electrode core body, a width “a” in one surface is larger than a width “b” in the other surface, and a root of the tab tilts, and an angle formed by a surface of the tab on a side where the width of the tip end portion is “a” and a top surface of the electrode assembly is an obtuse angle.
A method for producing an electrode plate that is one aspect of the present disclosure is a method for producing an electrode plate included in a wound type or stacked type electrode assembly, and includes a mixture layer forming step of forming a band-shaped mixture layer on both surfaces of a base material for a band-shaped electrode core body along a longitudinal direction of the base material for the band-shaped electrode core body, and a cutting step of cutting out an electrode plate having the band-shaped electrode core body with the mixture layer formed on the both surfaces, and a tab extended from one end portion of the electrode core body in a short side direction of the electrode core body, by irradiating one surface of the base material for the electrode core body with laser light, in which in the electrode plate that is cut out in the cutting step, a tip end portion of the electrode core body is covered with the mixture layer in the end portion on a side where the tab extends.
According to one aspect of the present disclosure, it is possible to suppress falling-off of an active material from the electrode plate.
Hereinafter, one example of an embodiment will be described in detail. In the present description, the vertical direction of the paper in
A configuration of a non-aqueous electrolyte secondary battery 100 that is one example of the embodiment will be described with reference to
The sealing plate 2 has an electrolyte solution injection hole 13. The electrolyte solution injection hole 13 is sealed by a sealing plug 14 after an electrolyte solution described later is injected. Further, the sealing plate 2 has a gas exhaust vent 15. The gas exhaust vent 15 operates when pressure inside the battery has a predetermined value or more, and discharges gas inside of the battery to outside of the battery.
A positive electrode terminal 4 is mounted to the sealing plate 2 to protrude to outside of the battery case 16. Specifically, the positive electrode terminal 4 is inserted in a positive electrode terminal mounting hole formed in the sealing plate 2, and is mounted to the sealing plate 2 in a state electrically insulated from the sealing plate 2 by an outer side insulating member 9 disposed outside of the battery in the positive electrode terminal mounting hole, and an inner side insulating member 8 disposed inside of the battery. The positive electrode terminal 4 is electrically connected to a positive electrode current collector 5 in the battery case 16. The positive electrode current collector 5 is provided at the sealing plate 2 with the inner side insulating member 8 between the positive electrode current collector 5 and the sealing plate 2. The inner side insulating member 8 and the outer side insulating member 9 are each preferably made of a resin.
Further, a negative electrode terminal 6 is mounted to the sealing plate 2 to protrude to outside of the battery case 16. Specifically, the negative electrode terminal 6 is inserted in a negative electrode terminal mounting hole formed in the sealing plate 2, and is mounted to the sealing plate 2 in a state electrically insulated from the sealing plate 2 by an outer side insulating member 11 disposed outside of the battery in the negative electrode terminal mounting hole, and an inner side insulating member 10 disposed inside of the battery. The negative electrode terminal 6 is electrically connected to a negative electrode current collector 7 in the battery case 16. The negative electrode current collector 7 is provided at the sealing plate 2 with the inner side insulating member 10 between the negative electrode current collector 7 and the sealing plate 2. The inner side insulating member 10 and the outer side insulating member 11 are each preferably made of a resin.
The non-aqueous electrolyte secondary battery 100 comprises an electrode group 3 and an electrolyte solution, and the exterior body 1 houses the wound type electrode group 3 and the electrolyte solution. As described later, the electrode group 3 includes two electrode assemblies each having a wound structure in which a positive electrode plate 20 and a negative electrode plate 30 are wound via separators 40. At an upper part of the electrode group 3, positive electrode tabs 28 and negative electrode tabs 38 protrude respectively from the positive electrode plate 20 and the negative electrode plate 30. The positive electrode tab 28 and the negative electrode tab 38 are bent in a depth direction, and are respectively connected to the positive electrode current collector 5 and the negative electrode current collector 7 by welding or the like. The electrode assembly is not limited to the wound type and may be of a stacked type.
As shown in
The electrolyte solution includes a solvent, and electrolyte salt dissolved in the solvent. As the solvent, a non-aqueous solvent can be used. As the non-aqueous solvent, for example, carbonates, esters, ethers, nitriles, amides, a mixed solvent of two or more of these, and the like may be used. As carbonates, there are cited cyclic carbonates such as an ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, and vinylene carbonate, and chain carbonates such as a dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate. The non-aqueous solvent may contain a halogen substituent in which at least a part of hydrogen in the above solvent is replaced with a halogen atom such as fluorine. The electrolyte solution is not limited to a liquid electrolyte and may be a solid electrolyte using a gel polymer or the like. The electrolyte salt includes a lithium salt. As the lithium salt, it is possible to use LiPF6 or the like that is generally used as a supporting electrolyte in the conventional non-aqueous electrolyte secondary battery 100. Further, an additive such as vinylene carbonate (VC) can be properly added.
For the separator 40, a porous sheet having ion permeability and insulation is used. Specific examples of the porous sheet include microporous membranes, woven fabrics, nonwoven fabrics and the like. As a material of the separator 40, olefin resins such as polyethylene and polypropylene, cellulose and the like are preferable. The separator 40 may be a stack having a cellulose fiber layer and a thermoplastic resin fiber layer of olefin resin or the like. Further, the separator 40 may be a multilayer separator including a polyethylene layer and a polypropylene layer, and it is possible to use the separator 40 with a surface thereof coated with a resin such as an aramid resin, or inorganic fine particles of alumina, titania or the like.
Hereinafter, the positive electrode plate 20 and the negative electrode plate 30 that configure the electrode group 3 will be described in detail with reference to
First, the positive electrode plate 20 will be described. As shown in
For the positive electrode core body 22, a foil of a metal that is stable within a potential range of the positive electrode plate 20 such as aluminum is used. The thickness of the positive electrode core body 22 is, for example, 10 to 20 μm.
The positive electrode mixture layer 24 is formed into a band shape on at least a part of the surface of the positive electrode core body 22, along a longitudinal direction of the positive electrode core body 22. The positive electrode mixture layer 24 is preferably provided at corresponding positions on both the surfaces of the positive electrode core body 22. The positive electrode mixture layer 24 includes a positive electrode active material, a binder, and a conductive agent, and can be produced by coating both the surfaces of the positive electrode core body 22 with a positive electrode active material slurry including the positive electrode active material, binder, conductive agent and the like, drying a coating film, and thereafter compressing the coating film by a roller or the like.
As the positive electrode active material, a lithium metal composite oxide expressed by a general formula Li1+xMaO2+b (in the formula, x, a, and b satisfy the conditions of x+a=1, −0.2<x≤0.2, and −0.1≤b≤0.1, M includes Ni and Co, and includes at least one element selected from the group consisting of Mn and Al). As the positive electrode active material, a small amount of other lithium metal composite oxides or the like may be included, but the lithium metal composite oxide expressed by the above described general formula is preferably used as a main component.
The lithium metal composite oxide may include the other elements than Ni, Co, Mn, and Al. As the other elements, there are cited alkali metal elements other than Li, transition metal elements other than Ni, Co, and Mn, alkaline earth metal elements, group 12 elements, group 13 elements other than Al, and group 14 elements. Specifically, Zr, B, Mg, Ti, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, Ca, W, Mo, Nb, Si and the like can be illustrated. Particles of an inorganic compound such as a zirconium oxide, tungsten oxide, aluminum oxide, and lanthanoid-containing compounds may adhere to the particle surface of the lithium metal composite oxide.
A particle size of the lithium metal composite oxide is not particularly limited, and an average particle size is preferably 2 μm or more to less than 30 μm, for example. When the average particle size is less than 2 μm, conduction by the conductive agent in the positive electrode mixture layer 24 may be inhibited to increase resistance. On the other hand, when the average particle size is 30 μm or more, load characteristics may decrease due to decrease in reaction area. The average particle size means a volume average particle size measured by a laser diffraction method, and a median diameter at which a volume integrated value is 50% in a particle size distribution. The average particle size can be measured by using the laser diffraction/scattering type particle size distribution measuring device (made by HORIBA, Ltd.).
As the binder included in the positive electrode mixture layer 24, there are cited fluorine resin such as polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, polyolefin resin and the like. One of these binders may be used alone, or a plurality of types may be mixed and used.
As the conductive agent included in the positive electrode mixture layer 24, there are cited carbon materials such as carbon black (CB), acetylene black (AB), Ketjen black and graphite, and the like. One of these conductive agents may be used alone, or a plurality of types may be mixed and used.
A filling density of the positive electrode mixture layer 24 may be 2.0 g/cm to 4.0 g/cm3. The higher the filling density of the positive electrode mixture layer 24, the larger the capacity of the battery.
As shown in
The positive electrode tab 28 extends from one end portion of the positive electrode core body 22 in the short side direction. The positive electrode plate 20 has a plurality of positive electrode tabs 28 in the longitudinal direction of the positive electrode core body 22, and distances among the positive electrode tabs 28 in the longitudinal direction of the positive electrode core body 22 are adjusted such that the positive electrode tabs 28 are aligned when the positive electrode core body 22 is wound.
A protection layer having higher electric resistance than the positive electrode core body 22 may be provided to cover a part or whole of the positive electrode mixture layer uncoated portion 26 including roots of the positive electrode tabs 28. The protection layer is provided to suppress occurrence of conduction in an unintended portion of the positive electrode mixture layer uncoated portion 26. The thickness of the protection layer is, for example, 20 μm to 120 μm, and may be 50 μm to 100 μm. The protection layer may include ceramic particles such as alumina, zirconia, titania and silica, and a binder such as polyvinylidene fluoride (PVdF).
A shape of the positive electrode tab 28 is not particularly limited, and may be a lateral symmetrical shape, for example. Further, the respective shapes of the positive electrode tabs 28 may be different, but are preferably same shapes in order to bundle the positive electrode tabs 28.
Next, the negative electrode plate 30 will be described. As shown in
For the negative electrode core body 32, it is possible to use a foil of a metal that is stable within a potential range of the negative electrode plate 30 such as copper is used. The thickness of the negative electrode core body 32 is, for example, 5 to 15 prn.
The negative electrode mixture layer 34 is formed in a band shape on a surface of the negative electrode core body 32, along a longitudinal direction of the negative electrode core body 32 and may be formed on the entire surface of the negative electrode core body 32. Further, the negative electrode mixture layer 34 is preferably provided at corresponding positions on both the surfaces of the negative electrode core body 32. The negative electrode plate 30 includes a negative electrode active material and a binder. The negative electrode plate 30 can be produced by coating a negative electrode active material slurry including the negative electrode active material, binder, and the like on the negative electrode core body 32, drying a coating film, and thereafter compressing the coating film by a roller or the like to form the negative electrode mixture layer 34 on both the surfaces of the negative electrode core body 32.
As the negative electrode active material, there is cited a low crystalline carbon coated graphite made by forming a coating film of low crystalline carbon on a surface of graphite, for example. The low crystalline carbon is a carbon material in a state of amorphous or microcrystals with a disordered layer structure in which a graphite crystal structure does not develop, or a carbon material with a very fine particle size rather than a spherical or scaly shape. For example, carbon materials with a d(002) plane spacing larger than 0.340 nm by X-ray diffraction are low crystalline carbons. Further, carbon materials with an average particle size of primary particles observed and measured by a scanning electron microscope (SEM) or the like of 1 am or less are also low crystalline carbons. Specific examples of the low crystallin carbon include, for example, carbon black such as hard carbon (non-graphitizable carbon), soft carbon (graphitizable carbon), acetylene black, Ketjen black, thermal black, and furnace black, carbon fibers, activated carbon and the like. As the negative electrode active material is not particularly limited as long as it can reversely store and release lithium ions, and it is possible to use a carbon material such as natural graphite, or artificial graphite, a metal that alloys with Li such as silicon (Si) or tin (Sn), an oxide including a metal element such as Si or Sn or the like. Further, the negative electrode mixture layer 34 may include a lithium-titanium composite oxide.
As the binder included in the negative electrode mixture layer 34, it is possible to use a well-known binder, and as in the case of the positive electrode mixture layer 24, it is possible to use fluorine resin such as PTFE, and PVdF, PAN, polyimide resin, acrylic resin, polyolefin resin and the like. Further, as the binder that is used when the negative electrode active material slurry is prepared by using an aqueous solvent, it is possible to illustrate CMC or salt thereof styrene butadiene rubber (SBR), polyacrylic acid (PAA) or salt thereof, polyvinyl alcohol (PVA) and the like.
A filling density of the negative electrode mixture layer 34 may be 1.0 g/cm3 to 2.0 g/cm3. The higher the filling density of the negative electrode mixture layer 34, the larger the capacity of the battery.
Next, the negative electrode plate 30 will be described with reference to
A shape of the negative electrode tab 38 is not particularly limited, and may be a lateral symmetrical shape, for example. Further, the respective shapes of the negative electrode tabs 38 may be different, but are preferably same shapes in order to bundle the negative electrode tabs 38.
As shown in
The thickness of the negative electrode mixture layer 34 that covers the tip end portion 36 may be thinner than the thickness of one surface of the negative electrode mixture layer 34 formed on an inner side from the tip end portion 36 of the negative electrode core body 32.
Further, as for a width, in the short side direction of the negative electrode core body 32, of the tip end portion 36 of the negative electrode core body 32, a width “a” in one surface may be larger than a width “b” in the other surface. In
The width “a” of the tip end portion 36 in one surface is, for example, 30 μm to 100 μm. The width “b” of the tip end portion 36 in the other surface is, for example, 5 μm to 50 μm.
As shown in
Next, the negative electrode tab 38 inside of the non-aqueous electrolyte secondary battery 100 will be described with reference to
Further, as shown in
Next, a method for producing the negative electrode plate 30 will be described. The method for producing the negative electrode plate 30 includes a mixture layer forming step and a cutting step. In the mixture layer forming step, the band-shaped negative electrode mixture layers 34 are formed on both surfaces of a base material for the band-shaped negative electrode core body 32 along the longitudinal direction of the base material for the band-shaped negative electrode core body 32. The negative electrode mixture layer 34 can be produced by coating the surface of the base material for the negative electrode core body 32 with a negative electrode active material slurry including a negative electrode active material, a binder and the like, drying the coated film, and thereafter compressing the coated film by a roller or the like to form the negative electrode mixture layer 34 on both the surfaces of the negative electrode core body 32. In the cutting step, one surface of the base material for the negative electrode core body 32 is irradiated with laser light, and thereby the negative electrode plate 30 is cut out, which has the band-shaped negative electrode core body 32 with the negative electrode mixture layer 34 formed on both the surfaces, and the negative electrode tabs 38 extended from one end portion of the negative electrode core body 32 in the short side direction. In the negative electrode plate 30 cut out in the cutting step, the tip end portion 36 of the negative electrode core body 32 is covered with the negative electrode mixture layer 34 in the end portion on the side where the tab extends.
Hereinafter, a method for cutting the negative electrode plate 30 will be described, and the positive electrode plate 20 may also be cut similarly.
Characteristics of the laser light and a laser irradiation optical system are not particularly limited, and it is possible to produce the desired negative electrode plate 30 by properly adjusting them according to thicknesses, compositions and the like of the negative electrode core body 32 and the negative electrode mixture layer 34 in a range of conditions in Table 1, for example.
When a repetition frequency is low, pulse energy becomes large and an electrode plate cut surface becomes rough, and therefore the repetition frequency is preferably 10 kHz or more, whereas when the repetition frequency is high, pulse energy decreases to worsen workability to decrease a line speed, and therefore the repetition frequency is preferably 150 kHz or less.
When the energy per electrode plate thickness is small, the mixture agent peels from the core body surface, and therefore the energy per electrode plate thickness is preferably 0.33 mJ/mm·μm or more, whereas when the energy per electrode plate thickness is large, the width “a” of the tip end portion 36 becomes too large, and therefore the energy per electrode plate thickness is preferably 4.13 mmJ/mm·μm or less.
The pulse width is preferably 10 to 300 ns, and more preferably 50 to 200 ns.
In order to scan the laser light, the base material for the negative electrode core body 32 may be moved, or the laser light may be moved by using a galvano scanner system, for example. Further, an end portion on an opposite side to the side where the negative electrode tab 38 extends, a winding start end, and a winding termination end may be cut by using the laser light as described above or may be cut by using a slit blade.
As described above, according to the electrode plate of the present embodiment, it is possible to suppress falling-off of the active material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-199732 | Nov 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/039214 | 10/19/2020 | WO |
