阅读说明：本技术 一种混合电容器的正极及其制备方法和用途 (Positive electrode of hybrid capacitor and preparation method and application thereof ) 是由 罗垂意 卜芳 祝媛 袁中直 刘建华 刘金成 于 2020-10-16 设计创作，主要内容包括：本发明涉及一种混合电容器的正极及其制备方法和用途,所述正极包括集流体,以及依次位于集流体表面的粘结层和正极材料层,所述粘结层包括第一粘结剂,所述正极材料层中包括第二粘结剂、导电剂、正极活性物质和富锂化合物,所述导电剂中包括第一导电剂和第二导电剂,所述第一导电剂包括石墨粉、导电碳黑或乙炔黑中的至少一种,所述第二导电剂包括石墨烯类材料以及一维碳材料中的至少一种。本发明提供的正极中,粘结层提高集流体与正极材料层的结合能力,降低极片内阻,正极材料层中的导电剂、富锂化合物和正极活性物质等物质相互配合,提升了正极的能量密度和倍率性能,同时在充电过程中提供锂离子进入负极,实现负极的免预锂化。(The invention relates to a positive electrode of a hybrid capacitor, a preparation method and application thereof, wherein the positive electrode comprises a current collector, and a bonding layer and a positive electrode material layer which are sequentially arranged on the surface of the current collector, the bonding layer comprises a first bonding agent, the positive electrode material layer comprises a second bonding agent, a conductive agent, a positive electrode active substance and a lithium-rich compound, the conductive agent comprises a first conductive agent and a second conductive agent, the first conductive agent comprises at least one of graphite powder, conductive carbon black or acetylene black, and the second conductive agent comprises at least one of a graphene material and a one-dimensional carbon material. In the positive electrode provided by the invention, the bonding layer improves the bonding capacity of the current collector and the positive electrode material layer, reduces the internal resistance of the pole piece, and substances such as a conductive agent, a lithium-rich compound, a positive electrode active substance and the like in the positive electrode material layer are matched with each other, so that the energy density and the rate capability of the positive electrode are improved, and lithium ions are provided to enter the negative electrode in the charging process, so that the pre-lithiation-free negative electrode is realized.)

1. The positive electrode of the hybrid capacitor is characterized by comprising a current collector, and a bonding layer and a positive electrode material layer which are sequentially positioned on the surface of the current collector;

the bonding layer comprises a first bonding agent, and the positive electrode material layer comprises a second bonding agent, a conductive agent, a positive electrode active substance and a lithium-rich compound.

2. The positive electrode according to claim 1, wherein the binder layer has a thickness of 0.5-10 μm, preferably 1-5 μm;

preferably, the conductive agent comprises a first conductive agent and a second conductive agent, the first conductive agent comprises at least one of graphite powder, conductive carbon black or acetylene black, and the second conductive agent comprises at least one of a graphene-based material and a one-dimensional carbon material;

preferably, the positive electrode active material includes a lithium-containing positive electrode active material and a carbon-based positive electrode active material;

preferably, the lithium-containing positive active material comprises any one or a combination of at least two of lithium cobaltate, lithium nickelate, lithium manganate, lithium iron phosphate, a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material or a nickel-cobalt-manganese-aluminum quaternary material, preferably any one or a combination of at least two of lithium nickelate, a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material or a nickel-cobalt-manganese-aluminum quaternary material;

preferably, the carbon-based cathode active material includes any one of activated carbon, graphene, doped graphene, or porous biomass carbon, or a combination of at least two of the foregoing.

3. The positive electrode according to claim 1 or 2, wherein the conductive carbon black comprises a small particle conductive carbon black having a particle diameter of 10 to 200nm and/or a large particle conductive carbon black having a particle diameter of 1 to 30 μm;

preferably, the graphene-based material comprises any one of graphene, graphene oxide or doped graphene or a combination of at least two of the graphene and the doped graphene;

preferably, the one-dimensional carbon material comprises carbon nanotubes and/or carbon fibers;

preferably, in the positive electrode material layer, the mass ratio of the graphene-based material to the one-dimensional carbon material is (1-2) to (3-6);

preferably, the first and second binders are meltable fluorocarbon resins;

preferably, the first binder and the second binder are independently selected from any one or a combination of at least two of PVDF, PTFE or PFA;

preferably, the lithium-rich compound comprises Li₂NiO₂、Li₅FeO₄、Li₃N、Li₂O、Li₂O₂Or any one or the combination of at least two of M/lithium fluoride, wherein M comprises any one or the combination of at least two of Co, Ni or Fe, and is preferably Li₂NiO₂、Li₃N or M/lithium fluoride or a combination of at least two thereof.

4. The positive electrode according to claim 2, wherein a third conductive agent is further included in the adhesive layer, and the third conductive agent is preferably conductive carbon black.

5. The positive electrode according to any one of claims 1 to 4, wherein the total mass fraction of the first binder and the second binder is 2 to 10% based on 100% of the total mass of the binder layer and the positive electrode material layer;

preferably, the mass fraction of the first conductive agent is 1-6% based on 100% of the total mass of the adhesive layer and the positive electrode material layer;

preferably, the total mass fraction of the graphene-based material and the one-dimensional carbon material is 0.5 to 3% based on 100% of the total mass of the bonding layer and the positive electrode material layer;

preferably, the mass ratio of the third conductive agent to the first binder is (1-5):1, preferably (2-4): 1;

preferably, the mass fraction of the lithium-containing positive electrode active material is 5-80% based on 100% of the total mass of the bonding layer and the positive electrode material layer;

preferably, the mass fraction of the carbon-based positive electrode active material is 10 to 90% based on 100% of the total mass of the adhesive layer and the positive electrode material layer;

preferably, the mass fraction of the positive electrode active material is 85-95% based on 100% of the total mass of the binder and the positive electrode material layer;

preferably, the mass ratio of the lithium-containing positive electrode active material to the carbon-based positive electrode active material is 1 (0.5-1.5), preferably 1 (1-1.2);

preferably, the mass fraction of the lithium-rich compound is 2-30% based on 100% of the total mass of the bonding layer and the positive electrode material layer.

6. The method for producing a positive electrode according to any one of claims 1 to 5, comprising the steps of:

(1) mixing a second binder, a conductive agent, a positive electrode active substance and a lithium-rich compound to obtain positive electrode slurry, wherein the conductive agent comprises a first conductive agent and a second conductive agent, the first conductive agent comprises at least one of graphite powder, conductive carbon black or acetylene black, and the second conductive agent comprises at least one of a graphene material and a one-dimensional carbon material;

(2) coating dispersion liquid containing a first binder on the surface of a current collector, baking for the first time to prepare a bonding layer, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking for the second time to obtain an intermediate product;

(3) and (3) rolling the intermediate product obtained in the step (2), and baking for the third time to obtain the anode.

7. The method according to claim 6, wherein the current collector of the step (2) comprises any one of an etched current collector, a coated current collector, a pure current collector or a through-hole current collector;

preferably, in the dispersion liquid in the step (2), the mass fraction of the binder is 1-10%, preferably 2-8%;

preferably, the dispersion liquid in the step (2) further comprises a third conductive agent;

preferably, the temperature of the first baking in the step (2) is 60-180 ℃, preferably 80-150 ℃;

preferably, the thickness of the bonding layer in the step (2) is 0.5-10 μm, preferably 1-5 μm;

preferably, the temperature of the second baking in the step (2) is 80-150 ℃, preferably 100-130 ℃.

8. The method according to claim 6 or 7, wherein the ambient temperature is controlled to be 20-30 ℃ and the humidity is controlled to be 3-40% during the steps (1) and (2).

9. The method for preparing a composite material according to any one of claims 6 to 8, wherein the rolling of step (3) is performed at a rate of 2 to 50 m/min;

preferably, the rolling way of the step (3) is cold pressing and/or hot pressing;

preferably, the temperature of the cold pressing is 0-45 ℃;

preferably, the temperature of the hot pressing is 60-270 ℃, preferably 80-250 ℃;

preferably, the third baking in step (3) comprises vacuum baking;

preferably, the vacuum degree of the vacuum baking is 5-200 Pa;

preferably, the temperature of the third baking in the step (3) is 80-150 ℃;

preferably, the time of the third baking in the step (3) is 10-60 min.

10. The method for preparing according to any one of claims 6 to 9, comprising the steps of:

(1) the method comprises the steps of dry-mixing a first conductive agent, a second binder, a positive active material and a lithium-rich compound for 1-3 hours, adding the second conductive agent, stirring and mixing for 1-2 hours, adding an organic solvent, and stirring for 4-6 hours to obtain positive slurry;

(2) coating dispersion liquid of a first binder on the surface of a current collector, baking at 60-180 ℃ to prepare a bonding layer, controlling the thickness of the bonding layer to be 0.5-10 mu m, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking at 80-150 ℃ to obtain an intermediate product;

(3) controlling the rolling speed of the intermediate product obtained in the step (2) to be 2-50m/s, carrying out hot pressing at the temperature of 60-270 ℃, and baking for 10-60min under the conditions of 80-150 ℃ and the vacuum degree of 5-200Pa to obtain the anode;

wherein, the step (1) and the step (2) are both carried out in the environment with the temperature of 20-30 ℃ and the humidity of 3-40%.

11. A hybrid capacitor, characterized in that it comprises a positive electrode according to any one of claims 1 to 4.

Technical Field

The invention relates to the technical field of hybrid capacitors, in particular to a positive electrode of a hybrid capacitor and a preparation method and application thereof.

Background

With the increasing prominence of energy and environmental problems, clean energy and renewable energy are widely researched and utilized. Super capacitors have been attracting attention and studied as a new type of high efficiency energy storage element between conventional capacitors and secondary batteries. Among them, carbon-based super capacitor uses carbon material as main electrode material, is widely used, activated carbon is one of the commonly used carbon materials, but the specific capacitance of the activated carbon is generally between 25 and 35F/g, and the compaction density is only 0.5 to 0.6g/m²The energy density of the capacitor using pure activated carbon as an electrode is only 2-10Wh/kg, which is severely limited. In addition, the active carbon electrode is mainly obtained by preparing water system slurry to coat the surface of the foil for drying and rolling, and because the active carbon has strong adsorption capacity, the residual moisture is difficult to dry, and the voltage and the discharge performance of the device are further influenced. Therefore, research focus is shifted to hybrid capacitors, and lithium ion capacitors have the advantages of high energy density and power density, high electrostatic capacity and longer cycle life than lithium ion batteries, and are expected to be widely applied to the fields of new energy automobiles, wind energy, internet of things and the like.

Currently, in order to obtain high energy density and increase the negative electrode potential, the negative electrode of the lithium ion capacitor generally needs to be subjected to a pre-lithium intercalation process. CN104538194A discloses a lithium ion adopting a pre-lithiated hard carbon cathodePreparation method of container (LIC) with commercial activated carbon as positive electrode, hard carbon as negative electrode, and 1M LiPF₆And the/EC + DEC is electrolyte to assemble the lithium ion capacitor. LIC with the lithium embedding capacity of 400mAh/g, the highest energy density and the highest power density are 76.5Wh/kg and 5.1kW/kg respectively, and after 1000 cycles, the energy retention rate is still as high as 92.0%. The energy density of the lithium ion capacitor subjected to pre-lithiation for 15 hours can reach 97.2Wh/kg, and the lithium ion capacitor has the minimum impedance and good cycle performance (after the lithium ion capacitor is cycled for 1000 times under the current density of 1A/g, the energy conservation rate is 91.2%). When the mass ratio of the positive electrode to the negative electrode is 2.2, the energy conservation rate is 57.0 percent. At the same time, the capacitor had very small internal resistance to charge transfer (10.4), with maximum energy and power densities of 88.7Wh/kg and 12kW/kg, respectively. However, the preparation method provided by the invention has the advantages of complex process, long time and high cost, and cannot meet the requirements of an Internet of things power supply on the rate capability and the energy density.

CN104617335A discloses a low-temperature chemical power source and a manufacturing method thereof, the manufacturing method comprises the following steps: 1) preparing a battery cell, welding a tab, packaging the battery cell in a shell, and drying; 2) drying the battery cell after the battery cell is packaged in the shell, and completing primary liquid injection; 3) carrying out formation treatment on the lithium ion capacitor or the lithium ion battery; 4) carrying out secondary liquid injection on the monomer after the formation is finished; 5) and shaping the monomer and carrying out subsequent treatment. The invention takes two times of liquid injection, the first time of liquid injection mainly aims at forming a film, and the second time of liquid injection aims at improving the conductivity and the low-temperature characteristic of a device. Although the invention improves the low-temperature performance of the chemical power supply, the requirement of the Internet of things power supply for the working temperature of-40 ℃ to 125 ℃ cannot be met.

Based on the research of the documents, how to develop a hybrid capacitor which meets the requirements of power supply application of the internet of things, has high energy density, good rate capability, no lithium pre-preparation for a negative electrode and low cost becomes a problem to be solved urgently.

Disclosure of Invention

In view of the problems in the prior art, the invention provides a positive electrode of a hybrid capacitor, and a preparation method and application thereof. The anode of the hybrid capacitor solves the problems that the energy density of a carbon-based capacitor is low and the cathode needs pre-lithium-embedding treatment by improving the conventional anode formula and process, improves the energy density and rate capability of a device, and can meet the requirement of high-rate pulse discharge at the temperature of-40-125 ℃. The method is particularly suitable for improving the rate capability at room temperature and the rate capability at low temperature, and simultaneously realizes that the negative electrode is free from pre-lithium and reduces the production cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a positive electrode for a hybrid capacitor, which comprises a current collector, and an adhesive layer and a positive electrode material layer which are sequentially arranged on the surface of the current collector, wherein the adhesive layer comprises a first adhesive, and the positive electrode material layer comprises a second adhesive, a conductive agent, a positive electrode active substance and a lithium-rich compound.

According to the positive electrode provided by the invention, the bonding layer is arranged between the current collector and the positive electrode material layer, so that the bonding capability of the positive electrode material and the current collector is improved, and the internal resistance of the pole piece is reduced; the lithium-rich compound and the positive active material provide lithium ions to enter the negative electrode in the charging process to carry out lithium intercalation action, so that the negative electrode can be free from the pre-lithiation step; the substances interact with each other, so that the rate capability of the anode is improved, and the requirement of high-rate charge and discharge can be met.

Preferably, the thickness of the adhesive layer is 0.5 to 10 μm, and may be, for example, 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 9 μm, 10 μm, or the like, preferably 1 to 5 μm. The thickness is less than 0.5 mu m, the adhesive force of the conductive adhesive layer to the powder is small, and the resistance of the pole piece cannot be effectively reduced and the powder cannot be prevented from falling off; if the thickness is larger than 10 μm, the thickness of the pole piece is too large, which is not beneficial to improving the energy density of the device.

Preferably, the conductive agent includes a first conductive agent and a second conductive agent, the first conductive agent includes at least one of graphite powder, conductive carbon black or acetylene black, and the second conductive agent includes at least one of a graphene-based material and a one-dimensional carbon material. In the anode material layer, a graphene material and/or a one-dimensional carbon material construct a three-dimensional conductive network, and at least one particle of graphite powder, conductive carbon black or acetylene black is dispersed in and/or on the surface of the conductive network to form a perfect conductive system and improve the conductivity of the material.

Preferably, the positive electrode active material includes a lithium-containing positive electrode active material and a carbon-based positive electrode active material.

Preferably, the lithium-containing positive active material includes any one or a combination of at least two of lithium cobaltate, lithium nickelate, lithium manganate, lithium iron phosphate, a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material, or a nickel-cobalt-manganese-aluminum quaternary material, preferably any one or a combination of at least two of lithium nickelate, a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material, or a nickel-cobalt-manganese-aluminum quaternary material. Typical but non-limiting combinations thereof: lithium cobaltate and lithium manganate, lithium manganate and lithium iron phosphate, lithium iron phosphate and lithium cobaltate, nickel cobalt manganese ternary material and nickel cobalt aluminum ternary material, nickel cobalt aluminum ternary material and nickel cobalt manganese aluminum quaternary material, preferably any one or the combination of at least two of lithium nickelate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material or nickel cobalt manganese aluminum quaternary material.

Preferably, the carbon-based cathode active material includes any one of activated carbon, graphene, doped graphene, or porous biomass carbon, or a combination of at least two of the foregoing.

In the present invention, the carbon-based positive electrode active material has a large specific surface area, generally 1500m²More than g (e.g. 1500 m)²/g、1600m²/g、1700m²/g、1800m²/g、2000m²(ii)/g or 2100m²And/g, etc.), can achieve an increase in the energy density of the capacitor when mixed with a lithium-containing positive electrode active material.

Preferably, the conductive carbon black includes a small particle conductive carbon black having a particle size of 10 to 200nm and/or a large particle conductive carbon black having a particle size of 1 to 30 μm, for example, the small particle conductive carbon black may have a particle size of 10nm, 15nm, 20nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 190nm, 200nm, or the like; the particle diameter of the large-particle conductive carbon black may be 1 μm, 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 28 μm, 30 μm, or the like.

In the present invention, the kind of the small particle conductive carbon black or the large particle conductive carbon black is not particularly limited, and may be SP, and any substance commonly used by those skilled in the art is suitable for the present invention.

In the invention, the graphene material comprises any one of graphene, graphene oxide and doped graphene or a combination of at least two of the graphene, the graphene oxide and the doped graphene.

Preferably, the one-dimensional carbon material comprises carbon nanotubes and/or carbon fibers.

Preferably, the second conductive agent includes at least one of graphene-based materials and at least one of one-dimensional carbon materials.

Preferably, in the positive electrode material layer, the mass ratio of the graphene-based material to the one-dimensional carbon material is (1-2): (3-6), and a super conductive network is formed in the positive electrode material layer at the preferred ratio, so that excellent conductivity is obtained, wherein the mass ratio can be 1:3, 1:4, 1:5, 1:6, 2:3, 2:5, 2:6 or the like, and if the mass fraction is less than 1:6, the positive electrode is difficult to construct a three-dimensional conductive network; the mass fraction is more than 2:3, the dispersion of the graphene materials is difficult, and the internal resistance of the device is increased. It is to be understood that the graphene-based material may be a component of the second conductive agent, or may be a component of the carbon-based positive electrode active material, and is included in the above-described content range as long as it is located in the positive electrode material layer.

Preferably, the first and second binders are meltable fluorocarbon resins.

Preferably, the first and second binders are independently selected from any one of PVDF, PTFE or PFA or a combination of at least two thereof, with a typical but non-limiting combination: PVDF and PFA, PFA and PTFE.

Preferably, the lithium-rich compound comprises Li₂NiO₂、Li₅FeO₄、Li₃N、Li₂O、Li₂O₂Or any one or the combination of at least two of M/lithium fluoride, wherein M comprises any one or the combination of at least two of Co, Ni or Fe, and is preferably Li₂NiO₂、Li₃N or M/lithium fluoride or a combination of at least two thereof. Typical but non-limiting combinations thereof: li₂NiO₂And Li₅FeO₄，Li₃N and Li₂O，Li₂O and Li₂O₂，Li₃N、Li₂O and Li₂O₂，Li₂NiO₂And Ni/lithium fluoride, Li₂NiO₂、Li₃N or M/lithium fluoride or a combination of at least two thereof.

The "M/lithium fluoride" is a complex of a metal M and lithium fluoride.

In a preferred embodiment of the positive electrode of the present invention, the binder further includes a third conductive agent, and the third conductive agent is preferably conductive carbon black.

Preferably, the total mass fraction of the first binder and the second binder is 2-10%, for example, 2%, 3%, 5%, 6%, 8%, 10%, or the like, based on 100% of the total mass of the adhesive layer and the positive electrode material layer.

The ratio of the first binder and the second binder is not particularly limited, and may be selected by those skilled in the art as needed.

Preferably, the mass fraction of the first conductive agent is 1 to 6%, for example, 1%, 2%, 3%, 4%, 5%, 6%, or the like, based on 100% by mass of the total of the adhesive layer and the positive electrode material layer.

Preferably, the total mass fraction of the graphene-based material and the one-dimensional carbon material is 0.5 to 3%, for example, 0.5%, 1%, 2%, 2.5%, 3%, or the like, based on 100% by mass of the total of the binder layer and the positive electrode material layer. If the mass is less than 0.5%, the low-temperature rate performance of the device is affected; the quality is higher than 3%, the internal resistance of the device is increased, and the electrical property is influenced. It is to be understood that the graphene-based material may be a component of the second conductive agent, or may be a component of the carbon-based positive electrode active material, and is included in the above-described content range as long as it is located in the positive electrode material layer.

Preferably, the mass ratio of the third conductive agent to the first binder is (1-5):1, and may be, for example, 1:1, 2:1, 3:1, 4:1, or 5:1, and preferably (2-4): 1.

Preferably, the mass fraction of the lithium-containing positive electrode active material is 5 to 80% based on 100% of the total mass of the binder layer and the positive electrode material layer, and may be, for example, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or the like.

Preferably, the mass fraction of the carbon-based positive electrode active material is 10 to 90%, for example, may be 10%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% or the like, based on 100% by mass of the total of the adhesive layer and the positive electrode material layer.

Preferably, the mass fraction of the positive electrode active material is 85% to 95%, for example, 85%, 88%, 90%, 92%, 93%, or 95%, etc., based on 100% by mass of the total mass of the binder and the positive electrode material layer.

The mass ratio of the lithium-containing positive electrode active material to the carbon-based positive electrode active material is preferably 1 (0.5 to 1.5), for example, 1:0.5, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.3, or 1:1.5, and preferably 1 (1 to 1.2).

Preferably, the mass fraction of the lithium-rich compound is 2 to 30%, for example, 2%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, or the like, based on 100% by mass of the total of the binder layer and the positive electrode material layer. If the mass is less than 2%, the capacity and the discharge median voltage of the device are lower; quality is higher than 30%, and device raw material cost is increased.

In a second aspect, the present invention provides a method for preparing a positive electrode as described in the first aspect above, comprising the steps of:

(1) mixing a second binder, a conductive agent, a positive electrode active substance and a lithium-rich compound to obtain positive electrode slurry, wherein the conductive agent comprises a first conductive agent and a second conductive agent, the first conductive agent comprises at least one of graphite powder, conductive carbon black or acetylene black, and the second conductive agent comprises at least one of a graphene material and a one-dimensional carbon material;

(2) coating dispersion liquid containing a first binder on the surface of a current collector, baking for the first time to prepare a bonding layer, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking for the second time to obtain an intermediate product;

(3) and (3) rolling the intermediate product obtained in the step (2), and baking for the third time to obtain the anode.

According to the preparation method provided by the invention, the surface of the positive current collector is coated with the dispersion liquid containing the first binder, and then rolling and baking are carried out, so that all substances of the positive electrode are combined with the current collector more tightly, the internal resistance of a pole piece is reduced, and the high-power charge and discharge performance is improved; the first conductive agent and the second conductive agent can construct a three-dimensional conductive network; the lithium-rich oxide and the positive active material provide lithium ions to enter the negative electrode in the charging process to perform lithium intercalation, so that the negative electrode can be free from a pre-lithiation step, the process is simplified, the production cost is reduced, and the lithium-rich oxide and the positive active material have higher application value.

The mixing method of the positive electrode slurry in the step (1) is not particularly limited, and the positive electrode slurry may be mixed in one step or mixed in steps, for example, the mixing method may be divided into two steps, three steps, four steps, and the like, and one skilled in the art may prepare the positive electrode slurry as required.

Preferably, gas substances except the graphene material are dry-mixed to obtain mixed powder, then the graphene material is mixed with the mixed powder, and finally, an organic solvent is added to the mixed powder to be uniformly mixed to obtain the anode slurry.

In the present invention, the kind of the organic solvent is not particularly limited, and any organic solvent commonly used by those skilled in the art can be suitably used in the present invention.

Preferably, the current collector of step (2) comprises any one of an etched current collector, a coated current collector, a pure current collector or a through-hole current collector.

Preferably, in the dispersion liquid in the step (2), the mass fraction of the binder is 1-10%, such as 1%, 3%, 5%, 8%, 9%, 10%, etc., preferably 2-8%.

Preferably, the dispersion liquid in the step (2) further comprises a third conductive agent.

Preferably, the temperature of the first baking in step (2) is 60-180 ℃, for example, 60 ℃, 70 ℃, 75, 80 ℃, 85 ℃, 90 ℃, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 170 ℃ or 180 ℃, preferably 80-150 ℃; the temperature is lower than 60 ℃, and the organic solvent cannot be dried; above 180 ℃, the pole piece may crack.

Preferably, the thickness of the adhesive layer in step (2) is 0.5-10 μm, such as 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 9 μm, or 10 μm, and preferably 1-5 μm; the thickness is less than 0.5 mu m, the adhesive force of the conductive adhesive layer to the powder is small, and the resistance of the pole piece cannot be effectively reduced and the powder cannot be prevented from falling off; if the thickness is larger than 10 μm, the thickness of the pole piece is too large, which is not beneficial to improving the energy density of the device.

Preferably, the temperature of the second baking in step (2) is 80-150 ℃, such as 80 ℃, 85 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃ or 150 ℃, preferably 100-; the temperature is lower than 80 ℃, and residual solvent and water of the pole piece cannot be taken away; when the temperature is higher than 150 ℃, the pole piece is baked excessively and can fall off.

Preferably, the temperature of the environment during steps (1) and (2) is controlled to be 20-30 ℃ and the humidity is controlled to be 3-40%, for example, the temperature can be 20 ℃, 22 ℃, 25 ℃, 26 ℃, 28 ℃ or 30 ℃ and the like, and the humidity can be 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35% or 40% and the like.

Preferably, the rolling speed in step (3) is 2-50m/min, such as 2m/min, 5m/min, 10m/min, 20m/min, 25m/min, 30m/min, 35m/min, 40m/min, 45m/min, 48m/min or 50m/min, and if the speed is less than 2m/min, the pole piece production efficiency is low; the speed is more than 50m/min, and the bonding layer and the slurry cannot be well bonded.

Preferably, the rolling manner in the step (3) is cold pressing and/or hot pressing.

Preferably, the cold pressing temperature is 0-45 deg.C, such as 0 deg.C, 5 deg.C, 10 deg.C, 15 deg.C, 20 deg.C, 30 deg.C, 40 deg.C or 45 deg.C.

Preferably, the hot pressing temperature is 60-270 ℃, for example, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 160 ℃, 180 ℃, 190 ℃, 200 ℃, 230 ℃, 250 ℃ or 270 ℃, preferably 80-250 ℃; the temperature is lower than 60 ℃, the adhesive in the adhesive layer can not be melted, and the adhesive force is not generated; above 270 c, the structure of the adhesive may be destroyed.

Preferably, the third baking in step (3) comprises vacuum baking.

Preferably, the vacuum degree of the vacuum baking is 5-200Pa, and for example, the vacuum degree can be 5Pa, 10Pa, 15Pa, 20Pa, 50Pa, 80Pa, 100Pa, 150Pa, 180Pa or 200 Pa.

Preferably, the temperature of the third baking in step (3) is 80-150 deg.C, such as 80 deg.C, 90 deg.C, 100 deg.C, 110 deg.C, 120 deg.C, 130 deg.C, 135 deg.C, 140 deg.C, 145 deg.C or 150 deg.C.

Preferably, the time of the third baking in step (3) is 10-60min, such as 10min, 20min, 30min, 40min, 50min or 60 min.

Preferably, the preparation method comprises the following steps:

(1) the method comprises the steps of dry-mixing a first conductive agent, a second binder, a second conductive agent, a positive active material and a lithium-rich compound for 1-3 hours, adding 0.5-3 wt% of a third conductive agent, stirring and mixing for 1-2 hours, adding an organic solvent, and stirring for 4-6 hours to obtain positive slurry;

(2) coating dispersion liquid of a first binder on the surface of a current collector, baking at 60-180 ℃ to prepare a bonding layer, controlling the thickness of the bonding layer to be 0.5-10 mu m, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking at 80-150 ℃ to obtain an intermediate product;

(3) controlling the rolling speed of the intermediate product obtained in the step (2) to be 2-50m/s, carrying out hot pressing at the temperature of 60-270 ℃, and baking for 10-60min under the conditions of 80-150 ℃ and the vacuum degree of 5-200Pa to obtain the anode;

wherein, the step (1) and the step (2) are both carried out in the environment with the temperature of 20-30 ℃ and the humidity of 3-40%.

In a third aspect, the present invention also provides a hybrid capacitor comprising a positive electrode as described in the first aspect above.

According to the hybrid capacitor provided by the invention, the positive electrode is adopted, the positive electrode comprises the current collector, and the bonding layer and the positive electrode material layer which are sequentially positioned on the surface of the current collector, and the lithium-rich compound and the positive electrode active substance in the positive electrode material layer can be extracted from lithium ions and enter the negative electrode in the charging process, so that the negative electrode is free from pre-lithium intercalation, the manufacturing process of the hybrid capacitor is simple, and the cost is low; meanwhile, the energy density and the rate capability are improved, and the requirement of the power supply of the Internet of things can be met.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides a positive electrode, which comprises a current collector, and an adhesive layer and a positive electrode material layer which are sequentially arranged on the surface of the current collector, wherein the adhesive layer improves the binding capacity of the current collector and the positive electrode material layer, reduces the internal resistance of a pole piece, and substances such as a conductive agent, a lithium-rich compound, a positive electrode active substance and the like in the positive electrode material layer are matched with each other, so that the energy density and the rate capability of the positive electrode are improved, and meanwhile, lithium ions are provided to enter a negative electrode in the charging process, so that the pre-lithiation of the;

(2) according to the preparation method of the positive electrode, the surface of the positive electrode current collector is coated with the dispersion liquid containing the first binder, and then rolling and baking are carried out, so that all substances of the positive electrode are combined with the current collector more tightly, the internal resistance of a pole piece is reduced, and the high-power charge and discharge performance is improved; the first conductive agent and the second conductive agent construct a three-dimensional conductive network; lithium-rich compound and positive active material provide lithium ion to enter the negative electrode in the charging process to carry out lithium intercalation, so that the negative electrode can be free from pre-lithiation, the process is simplified, the production cost is reduced, and the industrialization is easy;

(3) according to the hybrid capacitor provided by the invention, the anode comprises the current collector, the bonding layer and the anode material layer which are sequentially positioned on the surface of the current collector, so that the energy density of the capacitor is improved, the rate capability is improved, the lithium pre-preparation of the cathode is avoided, and the requirement of an internet of things power supply is met.

Detailed Description

The technical means adopted by the present invention to achieve the intended technical effects will be further described below by way of specific embodiments, which are described in detail below.

The embodiment of the invention does not limit the types of the current collectors, and the current collectors can be corrosion current collectors, coating current collectors, pure current collectors or through hole current collectors, and the like, wherein the corrosion current collectors are corrosion aluminum foils, can be commercially available, and can also be prepared by corroding the aluminum foils, the specific method for corroding the aluminum foils is the prior art, and the technical personnel in the field can prepare the aluminum foils by referring to the method disclosed by the prior art; the coating current collector is a carbon-coated aluminum foil.

Example 1

The embodiment provides a positive electrode of a hybrid capacitor, which comprises a current collector, and an adhesive layer and a positive electrode material layer which are sequentially arranged on the surface of the current collector; the bonding layer is composed of a first bonding agent (specifically composed of PTFE and 1 μm thick), the positive electrode material layer comprises a second bonding agent (specifically composed of PVDF), a conductive agent, a positive electrode active substance and a lithium-rich compound, the conductive agent comprises a first conductive agent and a second conductive agent, the first conductive agent is graphite powder, and the second conductive agent is a mixture of graphene and carbon nanotubes in a mass ratio of 1: 4; the positive active substance is a mixture of active carbon and lithium cobaltate; the lithium-rich compound being Li₂NiO₂；

Wherein the total mass fraction of the first binder layer and the second binder layer is 5 wt% based on 100% of the total mass of the binder layer and the positive electrode material layer; the mass fraction of the first conductive agent is 4%, and the mass fraction of the second conductive agent is 1%; the mass fraction of lithium cobaltate is 45 wt%, the mass fraction of activated carbon is 40 wt%, and the mass fraction of the lithium-rich compound is 5%.

The embodiment provides a preparation method of the positive electrode of the hybrid capacitor, which comprises the following steps:

(1) graphite powder, PVDF, active carbon, lithium cobaltate and Li₂NiO₂After dry mixing for 3h, adding a mixture of graphene and carbon nanotubes, stirring and mixing for 2h, then adding NMP, and stirring for 4h to obtain anode slurry;

(2) coating PTFE dispersion liquid with the mass fraction of 3% on the surface of a current collector, baking at 90 ℃ to prepare a conductive bonding layer, controlling the thickness of the bonding layer to be 1 mu m, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking at 85 ℃ to obtain an intermediate product;

(3) controlling the rolling speed of the intermediate product obtained in the step (2) to be 2m/min, carrying out hot pressing at the temperature of 140 ℃, and baking for 30min at the temperature of 140 ℃ under the condition that the vacuum degree is 5Pa to obtain the anode;

wherein, the step (1) and the step (2) are both carried out at the ambient temperature of 25 ℃ and the humidity of 5 percent.

Example 2

The embodiment provides a positive electrode of a hybrid capacitor, which comprises a current collector, and an adhesive layer and a positive electrode material layer which are sequentially arranged on the surface of the current collector; the positive electrode material layer comprises a first binder (specifically composed of PVDF and 0.5 μm in thickness), the positive electrode material layer comprises a second binder (specifically composed of PTFE), a conductive agent, a positive electrode active substance and a lithium-rich compound, the conductive agent comprises a first conductive agent and a second conductive agent, the first conductive agent is acetylene black, and the second conductive agent is a mixture of graphene oxide and carbon nanotubes in a mass ratio of 2: 3; the positive active substance is a mixture of graphene and lithium manganate; the lithium-rich compound being Li₃N；

Wherein the total mass fraction of the first binder layer and the second binder layer is 2 wt% based on 100% of the total mass of the binder layer and the positive electrode material layer; the mass fraction of the first conductive agent is 1 percent, and the mass fraction of the second conductive agent is 0.5 percent; the mass fraction of the lithium manganate is 84.5 wt%, and the mass fraction of the graphene is 10 wt%; the mass fraction of the lithium-rich compound is 2%.

The embodiment provides a preparation method of a hybrid capacitor anode, which comprises the following steps:

(1) mixing acetylene black, PTFE, graphene oxide, lithium manganate and Li₃After N is dry-mixed for 1h, adding a mixture of graphene and carbon nanotubes, stirring and mixing for 2h, then adding NMP, and stirring for 5h to obtain anode slurry;

(2) coating 8 mass percent of PVDF dispersion liquid on the surface of a current collector, baking at 60 ℃ to prepare a bonding layer, controlling the thickness of the bonding layer to be 0.5 mu m, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking at 80 ℃ to obtain an intermediate product;

(3) controlling the rolling speed of the positive plate obtained in the step (2) to be 2m/min, carrying out hot pressing at the temperature of 90 ℃, and baking for 30min at the temperature of 80 ℃ under the condition that the vacuum degree is 200Pa to obtain the positive electrode;

wherein, the step (1) and the step (2) are both carried out at the ambient temperature of 20 ℃ and the humidity of 3 percent.

Example 3

The embodiment provides a positive electrode of a hybrid capacitor, which comprises a current collector, and an adhesive layer and a positive electrode material layer which are sequentially arranged on the surface of the current collector; the bonding layer is composed of a first bonding agent (specifically composed of PFA and 5 μm thick), the positive electrode material layer comprises a second bonding agent (specifically composed of PFA), a conductive agent, a positive electrode active substance and a lithium-rich compound, the conductive agent comprises a first conductive agent and a second conductive agent, the first conductive agent is SP, and the second conductive agent is a mixture of graphene and carbon nanotubes in a mass ratio of 2: 4; the positive active material is a mixture of active carbon and NCM 811; the lithium-rich compound being Li₂O；

Wherein the total mass fraction of the first binder layer and the second binder layer is 5 wt% based on 100% of the total mass of the binder layer and the positive electrode material layer; the mass fraction of the first conductive agent is 3 percent, and the mass fraction of the second conductive agent is 1.5 percent; the mass fraction of NCM811 is 35 wt%, the mass fraction of activated carbon is 45 wt%, and the mass fraction of the lithium-rich compound is 10.5%.

The embodiment provides a preparation method of the positive electrode of the hybrid capacitor, which comprises the following steps:

(1) mixing SP, PFA, carbon fiber, NCM811 and Li₂After O is dry-mixed for 2 hours, adding a mixture of graphene and carbon nanotubes, stirring and mixing for 3 hours, then adding NMP, and stirring for 5 hours to obtain anode slurry;

(2) coating PFA dispersion liquid with the mass fraction of 4% on the surface of a current collector, baking at 120 ℃ to prepare a bonding layer, controlling the thickness of the bonding layer to be 5 mu m, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking at 120 ℃ to obtain an intermediate product;

(3) controlling the rolling speed of the positive plate obtained in the step (2) to be 25m/min, carrying out hot pressing at the temperature of 150 ℃, and baking for 20min at the temperature of 120 ℃ under the condition that the vacuum degree is 100Pa to obtain the positive electrode;

wherein, the step (1) and the step (2) are both carried out at the ambient temperature of 25 ℃ and the humidity of 5 percent.

Example 4

The embodiment provides a positive electrode of a hybrid capacitor, which comprises a current collector, and an adhesive layer and a positive electrode material layer which are sequentially arranged on the surface of the current collector; the bonding layer comprises a first bonding agent and a third conductive agent (specifically, the first bonding agent is PTFE, the third conductive agent is SP, the thickness is 3 mu m), the positive electrode material layer comprises a second bonding agent (specifically, PVDF), a conductive agent, a positive electrode active substance and a lithium-rich compound, the conductive agent comprises a first conductive agent and a second conductive agent, the first conductive agent is acetylene black, and the second conductive agent is a mixture of graphene and carbon nanotubes in a mass ratio of 1: 6; the positive active substance is porous biomass carbon and LiNi_0.85Al_0.075Mn_0.075O₂A mixture of (a); the lithium-rich compound is Co/lithium fluoride;

wherein the total mass fraction of the first binder layer and the second binder layer is 5 wt% based on 100% of the total mass of the binder layer and the positive electrode material layer; the mass fraction of the first conductive agent is 2%, the mass fraction of the second conductive agent is 2%, and the mass fraction of the third conductive agent is 6%; LiNi_0.85Al_0.075Mn_0.075O₂The mass fraction of (2) is 50 wt%, the mass fraction of the porous biomass carbon is 10 wt%, and the mass fraction of the lithium-rich compound is 25%. The embodiment provides a preparation method of the positive electrode of the hybrid capacitor, which comprises the following steps:

(1) acetylene black, PVDF, porous biomass carbon and LiNi_0.85Al_0.075Mn_0.075O₂After the mixture and Co/lithium fluoride are dry-mixed for 2 hours, adding a mixture of graphene and carbon nano tubes, stirring and mixing for 3 hours, then adding NMP, and stirring for 6 hours to obtain anode slurry;

(2) coating dispersion liquid of PTFE and acetylene black with the mass fraction of 3% on the surface of a current collector, baking at 180 ℃ to prepare a bonding layer, controlling the thickness of the bonding layer to be 3 mu m, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking at 150 ℃ to obtain an intermediate product;

(3) controlling the rolling speed of the positive plate obtained in the step (2) to be 50m/min, carrying out hot pressing at the temperature of 200 ℃, and baking for 10min at the temperature of 150 ℃ under the condition that the vacuum degree is 60Pa to obtain the positive electrode;

wherein, the step (1) and the step (2) are both carried out at the ambient temperature of 30 ℃ and the humidity of 40 percent.

Example 5

The embodiment provides a positive electrode of a hybrid capacitor, which comprises a current collector, and an adhesive layer and a positive electrode material layer which are sequentially arranged on the surface of the current collector; the bonding layer comprises a first bonding agent and a third conductive agent (specifically, the first bonding agent is PTFE, the third conductive agent is SP, the thickness is 4 mu m), the positive electrode material layer comprises a second bonding agent (specifically, PVDF), a conductive agent, a positive electrode active substance and a lithium-rich compound, the conductive agent comprises the first conductive agent and the second conductive agent, the first conductive agent is SP, the second conductive agent is a mixture of graphene and carbon nanotubes according to a mass ratio of 2:5, and the third conductive agent is SP; the positive active substance is porous biomass carbon and LiNi_0.85Al_0.075Mn_0.075O₂A mixture of (a); the lithium-rich compound is Ni/lithium fluoride;

wherein the total mass fraction of the first binder layer and the second binder layer is 3 wt% based on 100% of the total mass of the binder layer and the positive electrode material layer; the mass fraction of the first conductive agent is 1%, the mass fraction of the second conductive agent is 1%, and the mass fraction of the third conductive agent is 5%; LiNi_0.85Al_0.075Mn_0.075O₂The mass fraction of (2) is 5 wt%, the mass fraction of the porous biomass carbon is 87 wt%, and the mass fraction of the lithium-rich compound is 3%.

The embodiment provides a preparation method of the positive electrode of the hybrid capacitor, which comprises the following steps:

(1) mixing SP, PVDF, porous biomass carbon and LiNi_0.85Al_0.075Mn_0.075O₂After the mixture and Ni/lithium fluoride are dry-mixed for 2 hours, adding a mixture of graphene and carbon nanotubes, stirring and mixing for 3 hours, then adding NMP, and stirring for 6 hours to obtain anode slurry;

(2) coating dispersion liquid of PTFE and SP with the mass fraction of 1% on the surface of a current collector, baking at 180 ℃ to prepare a bonding layer, controlling the thickness of the bonding layer to be 10 mu m, coating the positive electrode slurry obtained in the step (1) on the surface of the bonding layer, and baking at 150 ℃ to obtain an intermediate product;

(3) controlling the rolling speed of the positive plate obtained in the step (2) to be 50m/min, carrying out hot pressing at the temperature of 270 ℃, and baking for 10min at the temperature of 150 ℃ under the condition that the vacuum degree is 180Pa to obtain the positive electrode;

wherein, the step (1) and the step (2) are both carried out at the ambient temperature of 30 ℃ and the humidity of 40 percent.

Example 6

The only difference compared to example 1 is that the hot pressing in step (3) was replaced by a cold pressing at 5 ℃.

Example 7

The only difference compared to example 1 is that the hot pressing in step (3) was replaced by a cold pressing at 40 ℃.

Example 8

The only difference compared with example 1 is that the total mass ratio of lithium cobaltate and activated carbon is the same as example 1, both 85%, and the mass ratio of lithium cobaltate to activated carbon is 2.5: 1.

Example 9

The only difference compared with example 1 was that the ratio of the total mass of lithium cobaltate and activated carbon was 85% as in example 1, and the ratio of the mass of lithium cobaltate to the mass of activated carbon was 2: 8.

Comparative example 1

Compared with the embodiment 1, the difference is only that the positive electrode provided by the comparative example is prepared by the method without adding the lithium-rich compound Li₂NiO₂While keeping the mass ratio between the remaining substances in the positive electrode material layer unchanged.

Comparative example 2

The difference from example 1 is only that the positive electrode provided in this comparative example was prepared without adding activated carbon and was replaced with an equal amount of lithium cobaltate.

Comparative example 3

Compared with example 1, the difference is only that the positive electrode provided by the present comparative example is prepared without adding a mixture of graphene and carbon nanotubes, and is replaced with an equal amount of graphite powder.

Comparative example 4

The difference from example 1 is that no binder layer was provided, and the content of the binder in the positive electrode material layer was kept the same as the total amount of the first binder and the second binder in example 1.

Evaluation of hybrid capacitor performance:

the positive electrode of the hybrid capacitor prepared by the above examples and comparative examples and the graphite negative electrode are assembled into a capacitor, and the capacity, room temperature multiplying power and low temperature test at-40 ℃ are carried out, wherein the test method is as follows:

and (3) capacity testing: placing the mixed capacitor in an environment of 25 ℃, standing for 5min, charging to 3.9V at constant current and constant voltage of 5mA, and stopping current to be 0.5 mA; standing for 5min, discharging with constant current of 5mA to 2.2V, and finishing.

And (3) rate testing: placing the mixed capacitor in an environment with the temperature of 25 ℃, charging the Xinwei 5V5A precision discharge cabinet with 5mA constant current and constant voltage to 3.68V, and stopping the current to 0.5 mA; and (5) standing for 5min, multiplying power by 500C, discharging for 1s in a pulse mode, recording the lowest voltage, and ending.

-40 ℃ low temperature test: placing the mixed capacitor in an environment with the temperature of 25 ℃, charging the 5V5A precision discharge cabinet with 5mA constant current and constant voltage to 3.68V, and cutting off the current to 0.5 mA; and (4) transferring the mixed capacitor to a high-low temperature box to stand for 6h in a-40 ℃ environment, carrying out 150C multiplying power pulse for 0.1s, recording the lowest voltage, and ending.

The batteries prepared in the examples and comparative examples of the present invention were of the same size (15500), and the higher the capacity, the higher the energy density.

The test results are shown in table 1.

TABLE 1

Note: in the table, the voltage of 25 ℃ and 500 ℃ represents the lowest voltage tested under the condition that the current is 500 ℃ and the temperature is 25 ℃; the voltage of-40 ℃ and 150C represents the lowest voltage tested under the condition of-40 ℃ and the current of 150C.

The higher the voltage at 25 ℃ and 500 ℃ and the higher the voltage at-40 ℃ and 150 ℃, the better the rate capability of the material is.

The following points can be seen from table 1:

(1) by combining example 1 and comparative example 1, it can be seen that the positive electrode of comparative example 1 does not contain Li₂NiO₂The capacity and rate capability were decreased, indicating that the positive electrode contained Li₂NiO₂The energy density, the room temperature rate capability and the low temperature rate capability of the hybrid capacitor are improved.

(2) It can be seen from the combination of example 1 and comparative example 2 that the positive electrode active material of comparative example 2 is lithium cobaltate, and although the capacity is high, the rate capability is poor, so that the positive electrode contains active carbon and lithium cobaltate, which is helpful for the hybrid capacitor to have good energy density, room temperature rate capability and low temperature rate capability;

(3) it can be seen from a combination of example 1 and comparative example 3 that the positive electrode of comparative example 3, which does not contain a mixture of graphene and carbon nanotubes and is replaced with graphite powder, causes a decrease in capacity and rate capability, thus demonstrating that the positive electrode containing a mixture of graphene and carbon nanotubes contributes to an increase in energy density, room temperature rate capability and low temperature rate capability of a hybrid capacitor.

(4) It can be seen from a combination of example 1 and comparative example 4 that comparative example 4 is not provided with a binder layer, resulting in a decrease in rate performance, thus illustrating that the binder layer provided between the positive electrode material layer and the current collector contributes to an improvement in the room-temperature rate performance and the low-temperature rate performance of the hybrid capacitor.

(5) It can be seen from the combination of examples 1, 8 and 9 that the amounts of the lithium-containing positive electrode active material and the carbon-based positive electrode active material added have an important influence on the capacity and rate capability of the material, and that the mass ratio of the lithium-containing positive electrode active material to the carbon-based positive electrode active material is in the preferable range of 1 (0.5-1.5) to achieve both of the above effects.

The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.