KR20210010103A - Method of preparing secondary battery and secondary battery thereby - Google Patents

Abstract

The present invention relates to a production method of a secondary battery having excellent electrochemical properties and, more specifically, to a production method of a secondary battery, comprising the steps of: producing a composite electrolyte precursor by mixing solid electrolyte powder represented by chemical formula 1, Li_1+xAl_xM_2-x(PO_4)_3 and a polymer electrolyte solution; producing a composite electrolyte membrane using the composite electrolyte precursor; and thermosetting after bringing the composite electrolyte membrane in contact with a negative electrode.

Description

Method of manufacturing secondary battery and secondary battery manufactured accordingly BACKGROUND [Method of preparing secondary battery and secondary battery thereby}

It relates to a method of manufacturing a secondary battery and a secondary battery manufactured accordingly.

Lithium secondary batteries are a leading energy storage device with high energy density and long cycle life. Recently, lithium secondary batteries are used as a representative energy source for IT devices that require portability and mobility such as mobile phones, notebook computers, and electric vehicles. In addition to the basic physical properties that require high-speed charging and large capacity, a battery that is free to deform, such as a wearable device, and stability that eliminates the risk of fire or explosion are emphasized. In order to satisfy this, the liquid electrolyte used in the existing lithium-ion battery is not suitable because of safety problems, and all solid-state batteries in which a solid-state electrolyte exhibiting high ionic conductivity of lithium ions is grafted are being studied.

Currently, the development direction of lithium secondary battery technology is in the direction of improving physical properties related to high energy density and high-speed charging and discharging, or providing additional functionality such as all-solid-state or flexible batteries. . The former are mainly issues related to the improvement of the physical properties of electrode materials such as anodes and anodes, and the latter are related to research and development of high ion conductivity electrolytes.

The liquid electrolyte currently in use has the best lithium ion activation and electrochemical properties, but it is vulnerable to physical external shocks, so stability problems such as explosion and water leakage have been pointed out. There are limitations. In order to replace this, a solid (or solid) electrolyte that can withstand external impacts is required, and is typically a polymer (or ceramic) based electrolyte.

However, since a typical polymer electrolyte has ionic conductivity through an oxygen ion-based hopping mechanism generated in an amorphous amorphous step, it has relatively low ionic conductivity at room temperature.

In addition, ceramic electrolytes such as phosphate, oxide and sulfide have high ionic conductivity and chemically and mechanically stable physical properties of a maximum level of 10 ^-2 S/cm, but require a high pressurization/heating process and a relatively brittle solid phase ( solid state) and lack of flexibility, the interface contact is inferior and the interface resistance with the electrode material of the cell is high, so interface control is essential.

In order to solve these physical properties, studies on composite electrolytes through the composite of two different materials are being conducted. Among the methods of applying the solidified solid polymer electrolyte to a battery, a method of injecting a solid polymer electrolyte solution and then assembling a solid polymer electrolyte solution during cell assembly to solidify it through thermal curing is known. However, in this case, a separator must be provided to prevent a short circuit between both electrodes before thermal curing, and it is difficult to confirm complete solidification after thermal curing.

In addition, in the case of a polymer solid electrolyte in which heterogeneous materials are composited, the current biggest problem is that the cell has low ionic conductivity due to high interfacial resistance with both electrodes, and thus the expression capacity is low or it is difficult to drive itself. In order to reduce the interfacial resistance, various methods have been attempted, such as assembling a polymer solid electrolyte by impregnating a liquid electrolyte in order to activate the interfacial contact with both electrodes, or injecting a liquid component between the electrode and the electrolyte. However, these ancillary methods do not contain liquid components, so they cannot be regarded as all-solid-state batteries that are safe from fire or explosion accidents due to external shock or electrolyte leakage.

Therefore, it is possible to solidify before assembling the cell, and by making a free-standing electrolyte that does not require a separator, the interfacial contact method with both electrodes is changed to maintain the stability of the interface state while maintaining the stability of the interface state, for all solid state batteries that have flexible and mechanical strength. The development of electrolytes is important.

In this regard, Korean Patent Registration No. 10-1915558 discloses a composite electrolyte including a phosphate-based solid electrolyte.

An object of the present invention is a method of manufacturing a secondary battery that has excellent electrochemical properties and is easy to process or mold by controlling an unstable interface state between a solid electrolyte and both electrodes, and a composite electrolyte prepared therethrough. It is to provide a secondary battery.

In order to achieve the above object, in one aspect of the present invention

Preparing a composite electrolyte precursor by mixing a solid electrolyte powder and a polymer electrolyte solution represented by the following Formula 1;

Preparing a composite electrolyte membrane using the composite electrolyte precursor; And

There is provided a method of manufacturing a secondary battery comprising a step of thermosetting after contacting the composite electrolyte membrane with a negative electrode.

[Formula 1]

Li _{1 + x} Al _x M _{2 -x} (PO ₄ ) ₃

(In Formula 1, M is Ti or Ge, and 0 <x <2).

In addition, in another aspect of the present invention

A secondary battery manufactured by the above manufacturing method is provided.

Furthermore, in another aspect of the present invention

A device including the secondary battery is provided.

In one aspect of the present invention, a secondary battery including a composite electrolyte for a secondary battery composed of a phosphate-based solid electrolyte and a conductive polymer electrolyte component first contacts a negative electrode with the composite electrolyte and thermally cures it, thereby establishing an interface state between the negative electrode and the composite electrolyte. By stabilizing it, the interface resistance is reduced, so that the electrochemical properties such as discharge capacity and polarization characteristics of the secondary battery are excellent. In addition, as the content of the phosphate-based solid electrolyte is high, stability is maximized, it is possible to manufacture a secondary battery including a complete solid-state composite electrolyte, and there is an advantage in that processing or molding is free while having flexibility.

1 is a flow chart showing a manufacturing process of a secondary battery provided in one aspect of the present invention;
2 and 3 are photographs of observing the shape of a composite electrolyte for a secondary battery;
4 is a photograph showing a shape of a positive electrode attached by thermosetting a composite electrolyte for a secondary battery;
5 is a photograph showing a shape of a negative electrode attached by thermosetting a composite electrolyte for a secondary battery;
6 is a graph measuring ionic conductivity of a composite electrolyte for a secondary battery;
7 is a graph measuring charging and discharging of the secondary battery prepared in Comparative Example 1;
8 is a graph measuring charging and discharging of the secondary battery prepared in Comparative Example 2;
9 is a graph measuring charging and discharging of the secondary battery prepared in Example 1.

In one aspect of the present invention

Preparing a composite electrolyte precursor by mixing a solid electrolyte powder and a polymer electrolyte solution represented by the following Formula 1;

Preparing a composite electrolyte membrane using the composite electrolyte precursor; And

There is provided a method of manufacturing a secondary battery comprising a step of thermosetting after contacting the composite electrolyte membrane with a negative electrode.

[Formula 1]

Li _{1 + x} Al _x M _{2 -x} (PO ₄ ) ₃

(In Formula 1, M is Ti or Ge, and 0 <x <2.)

At this time, Fig. 1 shows a method of manufacturing a secondary battery provided in one aspect of the present invention through a flow chart,

Hereinafter, a method of manufacturing a secondary battery provided in one aspect of the present invention will be described in detail for each step with reference to the flow chart of FIG. 1.

First, a method of manufacturing a secondary battery provided in an aspect of the present invention includes preparing a composite electrolyte precursor by mixing a solid electrolyte powder represented by Chemical Formula 1 and a polymer electrolyte solution.

The secondary battery provided in one aspect of the present invention is a composite electrolyte formed by mixing a solid electrolyte powder and a polymer electrolyte solution, thereby securing more stability and improving the capacity retention rate due to excellent rate control characteristics. .

Thus, in the above step, a composite electrolyte precursor is prepared by mixing a solid electrolyte powder and a polymer electrolyte solution.

At this time, the solid electrolyte powder is a phosphate-based solid electrolyte, and may be represented by Formula 1. In addition, the solid electrolyte powder represented by Chemical Formula 1 may be a spherical small particle phosphate-based solid electrolyte.

The spherical small particle phosphate-based solid electrolyte may be prepared by the following method.

First, a method of preparing a spherical small particle phosphate-based solid electrolyte may include a step of obtaining a solid electrolyte precursor by stirring and reacting a lithium salt, a Ti and Al precursor, and a phosphoric acid.

At this time, the lithium salt is LiCH ₃ COO, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₄ , LiAlCl- ₄ , LiCl, LiI, LiB(C ₂ O ₄ ) ₂ , and may include a lithium salt selected from the group consisting of combinations thereof, but limited thereto It is not.

Further, the reaction may be performed at about 150° C. to about 300° C., but is not limited thereto. For example, the reaction is about 150°C to about 300°C, about 170°C to about 300°C, about 190°C to about 300°C, about 200°C to about 300°C, about 220°C to about 300°C, about 240°C To about 300°C, about 260°C to about 300°C, about 280°C to about 300°C, about 150°C to about 280°C, about 150°C to about 260°C, about 150°C to about 240°C, about 150°C to about It may be performed at 220° C., about 150° C. to about 200° C., about 150° C. to about 190° C., or about 150° C. to about 170° C., but is not limited thereto. When the reaction is performed below the temperature range, the reaction may not be performed smoothly and thus it may be difficult to form a solid electrolyte precursor phase. When the reaction is performed above the temperature range, an impurity phase may be included in addition to the precursor.

The reaction may be performed through a solvent heat synthesis method, and in this case, a solvent may be added, but is not limited thereto. The solvent is preferably a dispersant, for example, an alcoholic organic solvent in which polyethylene glycol is dissolved in a certain concentration, the lithium salt such as 2-methoxyethanol, a Ti and Al precursor, and an alcohol-based solvent in which phosphoric acid can be dissolved. Accordingly, the lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid may be self-polymerized in a solution in which the lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid are dissolved.

Next, a method of manufacturing a spherical small particle phosphate-based solid electrolyte includes a step of heat-treating the solid electrolyte precursor to obtain a solid electrolyte represented by Formula 1 above.

In this case, the heat treatment may be performed at about 400°C to about 600°C, but is not limited thereto. For example, the heat treatment is about 400°C to about 600°C, about 420°C to about 600°C, about 440°C to about 600°C, about 460°C to about 600°C, about 480°C to about 600°C, about 500°C To about 600°C, about 520°C to about 600°C, about 540°C to about 600°C, about 560°C to about 600°C, about 580°C to about 600°C, about 400°C to about 580°C, about 400°C to about 560°C, about 400°C to about 540°C, about 400°C to about 520°C, about 400°C to about 500°C, about 400°C to about 480°C, about 400°C to about 460°C, about 400°C to about 440°C , Or may be performed at about 400 ℃ to about 420 ℃, but is not limited thereto. When the heat treatment is performed below the temperature range, the solid electrolyte represented by Formula 1 may not be obtained because the combination of lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid may not be performed smoothly, and the temperature range may be exceeded. When carried out in, it may induce formation of a secondary phase other than a phosphate-based electrolyte having a desired crystal structure or induce excessive grain growth.

In addition, the heat treatment may be performed for about 3 hours to about 7 hours, and preferably may be performed for about 4 hours to about 6 hours, but is not limited thereto. When the heat treatment is performed for less than the above range, the solid electrolyte represented by Formula 1 may not be obtained because the combination of lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid may not be performed smoothly. When performed, it may induce formation of a secondary phase other than a phosphate-based electrolyte having a desired crystal structure or induce excessive grain growth.

Next, the method of manufacturing a spherical small particle phosphate-based solid electrolyte includes the step of milling the heat-treated solid electrolyte to obtain a spherical small particle solid electrolyte.

The milling process is a bead mill, a ball-mill, a high energy ball mill, a planetary mill, a stirred ball mill, or a vibration mill. mill) can be used.

In addition, the milling process may be performed at a rotation speed of 50 rpm to 150 rpm, but is not limited thereto. For example, it may be performed at 60 rpm to 140 rpm, 70 rpm to 130 rpm, 80 rpm to 120 rpm, and 90 rpm to 110 rpm, but is not limited thereto.

In addition, the milling process may be performed for 2 to 4 hours, but is not limited thereto. For example, it may be performed for 2.5 to 3.5 hours, but is not limited thereto.

When the rotational speed of the milling process exceeds 150 rpm and the execution time of 4 hours, there may be a problem that the granular shape of the spherical small particles is crushed and a solid electrolyte is not produced, and the rotational speed of the milling process is 50 rpm and execution time 2 If it is carried out in less than time, there may be a problem in that the agglomeration is less released and thus the spherical small particle shape cannot be produced.

In one embodiment of the present invention, the milling process was performed for 3 hours at a rotation speed of 100 rpm by ball milling, but this is only an example, and is not limited thereto, and the spherical small particle phosphate-based solid electrolyte of the present invention, specifically, spherical In the form of small particle Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ solid electrolyte by performing a milling process, the aggregated solid electrolyte in which individual particles are agglomerated is dispersed to exist as individual particles, and the size of the particles is constant.

The particle diameter of the spherical small particle phosphate-based solid electrolyte of the present invention prepared through the milling step may be 50 nm to 250 nm, but is not limited thereto. For example, 60 nm to 240 nm, 70 nm to 230 nm, 80 nm to 220 nm, 90 nm to 210 nm, 100 nm to 200 nm, 110 nm to 190 nm, 120 nm to 180 nm, 130 nm to 170 nm, 140 nm to 160 nm, but is not limited thereto.

When the particle diameter of the spherical small-particle phosphate-based solid electrolyte of the present invention exceeds 250 nm, there is a problem that it is difficult to uniformly disperse the spherical small-particle solid electrolyte in the composite electrolyte, and if it is less than 50 nm, the possibility of re-aggregation due to high specific surface area I have this high problem.

The particle diameter of the spherical small-particle phosphate-based solid electrolyte prepared in an embodiment of the present invention may be about 150 nm, which is smaller than that of a commercial phosphate-based electrolyte.

The polymer electrolyte solution may include one or more polymers selected from the group consisting of a polyethylene glycol polymer, a polypropylene glycol polymer, and a polyvinylidene fluoride polymer, but is not limited thereto.

In addition, the polymer electrolyte solution may further include a non-aqueous solvent, and the non-aqueous solvent is ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butyrene carbonate, methylpropyl carbonate, ethylpropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrroly It may be one or more solvents selected from the group consisting of don (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone, titrahydrofuran (THF), and sulfolane.

Furthermore, the polymer electrolyte solution may further include a lithium salt, a crosslinking agent, an initiator, a plasticizer, and a binder in the polymer.

The lithium salt is LiCH ₃ COO, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₄ , LiAlCl- ₄ , LiCl, LiI, LiB(C ₂ O ₄ ) ₂ , and may include a lithium salt selected from the group consisting of combinations thereof, but is not limited thereto. .

The crosslinking agent may be added to promote crosslinking of the solid electrolyte and the polymer electrolyte, and the crosslinking agent is polyethyleneglycol diacrylate, triethyleneglycol diacrylate, trimethylolpropane ethoxylate It may be one or more selected from the group consisting of trimethylolpropaneethoxylate triacrylate and bisphenol A ethoxylate dimethacrylate.

The initiators are Tert-Butyl peroxyneodecanoate, Naphtha (petroleum), Hydrotreated heavy, Hydroperoxide, 1,1- Dimethylethyl (1,1-dimethylethyl), neodekenoyl chloride (Neodecanoyl chloride), and the like may be used.

As the binder, a thermoplastic resin or a thermosetting resin may be used. More specifically, as the binder, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, Vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer , Propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinylether-tetrafluoro To use a material selected from the group consisting of ethylene copolymer, ethylene-acrylic acid copolymer, poly(vinylidene fluoride-co-hexafluoropropylene) and combinations thereof However, the present invention is not limited thereto, and any one that can be used as a binder in the art may be used.

The composite electrolyte precursor may contain a solid electrolyte in an amount of 0.001 to 0.4 parts by weight, 0.01 to 0.4 parts by weight, 0.1 to 0.4 parts by weight, and 0.2 based on 1 part by weight of the polymer electrolyte component. It may be included in parts by weight to 0.4 parts by weight.

Next, a method of manufacturing a secondary battery provided in an aspect of the present invention includes manufacturing a composite electrolyte membrane using the composite electrolyte precursor.

In the above step, a composite electrolyte membrane in the form of a membrane is prepared by using a composite electrolyte precursor including a solid electrolyte and a polymer electrolyte, and may be performed through heat treatment or thermal curing.

As a specific example, the composite electrolyte membrane may be manufactured by heat treatment while applying pressure to the composite electrolyte precursor. The liquid component in the composite electrolyte precursor may be vaporized to form a solid composite electrolyte membrane having ion conductivity while curing. The heat treatment may be performed at about 50°C to about 150°C, but is not limited thereto. For example, the heat treatment is about 50°C to about 150°C, about 80°C to about 150°C, about 100°C to about 150°C, about 120°C to about 150°C, about 140°C to about 150°C, about 50°C It may be performed at about 140° C., about 50° C. to about 120° C., about 50° C. to about 100° C., or about 50° C. to about 80° C., but is not limited thereto. When the heat treatment is performed below the temperature range, the curing of the polymer electrolyte may be insufficient, so that the formation of the molded body may be incomplete. When the heat treatment is performed above the temperature range, electrical properties may be unstable due to thermal decomposition of the polymers.

In addition, the heat treatment may be performed for 1 to 5 hours, and preferably may be performed for 2 to 4 hours, but is not limited thereto. When the heat treatment is performed for less than the above range, the curing of the polymer electrolyte may be insufficient and the film formation may be incomplete. When the heat treatment is performed above the temperature range, electrical properties may be unstable due to thermal decomposition of the polymers.

Further, the pressure applied to the composite electrolyte precursor may be about 100 MPa to about 400 MPa, but is not limited thereto. [0090]

For example, the pressure is about 100 MPa to about 400 MPa, about 150 MPa to about 400 MPa, about 200 MPa to about 400 MPa, about 250 MPa to about 400 MPa, about 300 MPa to about 400 MPa, about 350 MPa To about 400 MPa, about 100 MPa to about 350 MPa, about 100 MPa to about 300 MPa, about 100 MPa to about 250 MPa, about 100 MPa to about 200 MPa, or about 100 MPa to about 150 MPa, It is not limited. When the pressure is less than the above range, the bonding between the solid electrolyte and the polymer electrolyte may be weakened, and when the pressure exceeds the above range, the membrane having a desired size and shape may not be maintained.

Next, a method of manufacturing a secondary battery provided in one aspect of the present invention includes the step of thermosetting after contacting the composite electrolyte membrane with a negative electrode.

In the present invention, in order to improve a composite electrolyte including a solid electrolyte and a polymer electrolyte, which is more stable but has poor battery characteristics due to an unstable interface with an electrode, thermal curing is performed by changing contact conditions when assembling the composite electrolyte membrane and the electrode.

Specifically, in forming the negative electrode of the secondary battery, the composite electrolyte membrane is brought into contact with the negative electrode and then thermally cured. The negative electrode may include a negative electrode active material capable of storing and releasing lithium. The negative electrode active material may include lithium metal. Since lithium metal has a low density and a low standard reduction potential, it is useful as a negative electrode of a lithium secondary battery having high energy density and excellent discharge capacity retention characteristics.

The thermal curing may be performed at a temperature of 80°C to 120°C, for example, the curing step is about 80°C to about 110°C, about 80°C to about 100°C, about 80°C to about 90°C, It may be performed at about 90°C to about 120°C, about 100°C to about 120°C, about 90°C to about 110°C, and about 95°C to about 105°C, but is not limited thereto. In this case, the thermosetting temperature range may be higher than the heat treatment temperature performed when forming the composite electrolyte membrane.

In addition, the thermal curing is performed by applying pressure, and the pressure may be greater than the pressure applied when manufacturing the composite electrolyte membrane. The thermal curing is finally curing the composite electrolyte membrane and bonding it to the negative electrode, and may be performed while applying pressure. The pressure is about 100 MPa to about 400 MPa, about 150 MPa to about 400 MPa, about 200 MPa to about 400 MPa, about 250 MPa to about 400 MPa, about 300 MPa to about 400 MPa, about 350 MPa to about 400 MPa , About 100 MPa to about 350 MPa, about 100 MPa to about 300 MPa, about 100 MPa to about 250 MPa, about 100 MPa to about 200 MPa, or about 100 MPa to about 150 MPa, but is not limited thereto. . However, the pressure may be higher than the pressure applied when forming the composite electrolyte membrane.

The method of manufacturing the secondary battery may further include forming a negative electrode by performing a step of thermosetting after contacting the composite electrolyte membrane with a negative electrode, and then forming a positive electrode. By performing the above steps, an electrolyte and a negative electrode may be prepared, and a positive electrode may be finally formed.

The positive electrode is formed on the positive electrode current collector, and may include lithium transition metal oxide as a positive electrode active material, but is not limited thereto. As the positive electrode current collector, a porous body such as a mesh or a mesh may be used, and a porous metal plate such as stainless steel, nickel, or aluminum may be used, but is not limited thereto, and any material that can be used as a current collector in the art. It is possible. In addition, the positive electrode current collector may be coated with an oxidation-resistant metal or alloy film to prevent oxidation.

In addition, in the positive electrode, a compound capable of reversible intercalation and deintercalation of lithium (retiated intercalation compound) may be used as the positive electrode active material. Specifically, a lithium-containing transition metal oxide may be used, and more specifically, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li(NiaCobMnc)O ₂ (0<a<1, 0<b<1, 0<c<1, a+b+c=1), LiNi _{1 - y} Co _y O ₂ , LiCo _{1 - y} Mn _y O ₂ , LiNi _{1 - y} Mn _y O ₂ (O≤y<1), Li _{(Ni a Co b Mn c)} O 4 (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn 2 - z Ni z O 4, LiMn 2 - _z Co _z O ₄ (0<z<2), LiCoPO ₄ , LiFePO ₄ , and may include a material selected from the group consisting of combinations thereof, but is not limited thereto. In addition, in addition to the oxide as described above, sulfide, selenide, and halide may be used, but the present invention is not limited thereto. In addition, an initial Li-free type of positive electrode active material without lithium is also possible, and may include, for example, TiS ₂ , FeS ₂ or V ₂ O ₅ , but is not limited thereto.

In addition, the anode may include a conductive material, but is not limited thereto. In this case, the conductive material may be porous. Accordingly, the conductive material may be used without limitation as long as it has porosity and conductivity, and for example, a carbon-based material having porosity may be used.

Such a carbon-based material may include a material selected from the group consisting of carbon black, graphite, graphene, activated carbon, carbon fiber, and combinations thereof, but is not limited thereto. Further, examples of the conductive material include metallic conductive materials such as metal fibers and metal meshes; Metallic powders such as copper, silver, nickel, and aluminum; Alternatively, an organic conductive material such as a polyphenylene derivative can also be used. The conductive materials may be used alone or in combination.

In addition, the positive electrode may optionally further include a binder, but is not limited thereto. As the binder, a thermoplastic resin or a thermosetting resin may be used. More specifically, as the binder, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, fluorinated Vinylidene-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, Propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene It may be to use a material selected from the group consisting of a copolymer, an ethylene-acrylic acid copolymer, and combinations thereof, but is not limited thereto, and any material that can be used as a binder in the art may be used.

The positive electrode as described above may be prepared by mixing a positive electrode active material, a conductive material, and optionally a binder to prepare a composition for forming a positive electrode active material layer, and then coating it on at least one surface of the positive electrode current collector, drying, and rolling. As another method, the composition for forming a positive active material layer may be cast on a separate support, and then a film obtained by peeling from the support may be laminated on a positive electrode current collector.

In addition, in another aspect of the present invention

A secondary battery manufactured by the above manufacturing method is provided.

The secondary battery may be a lithium secondary battery, a nickel cadmium battery, a nickel hydride battery, or a lead storage battery, but is not limited thereto.

When the secondary battery is a lithium secondary battery, the lithium secondary battery may include a positive electrode; A negative electrode disposed spaced apart from the positive electrode and including a lithium metal; And a composite electrolyte for a lithium secondary battery interposed between the positive electrode and the negative electrode, wherein the composite electrolyte for a lithium secondary battery includes a solid electrolyte and a polymer electrolyte, and the solid electrolyte is represented by Formula 1 below, and the composite The electrolyte is characterized in that it is thermosetted in contact with the negative electrode.

[Formula 1]

Li _{1 + x} Al _x M _{2 -x} (PO ₄ ) ₃

(In Formula 1, M is Ti or Ge, and 0 <x <2.)

In the secondary battery provided in another aspect of the present invention, a secondary battery including a composite electrolyte for a secondary battery composed of a phosphate-based solid electrolyte and a conductive polymer electrolyte component first contacts the negative electrode to the composite electrolyte and thermally cures it between the negative electrode and the composite electrolyte. By stabilizing the interface state, the interface resistance is reduced, so that the electrochemical characteristics such as discharge capacity and polarization characteristics of the secondary battery are excellent. In addition, as the content of the phosphate-based solid electrolyte is high, stability is maximized, it is possible to manufacture a secondary battery including a complete solid-state composite electrolyte, and there is an advantage in that processing or molding is free while having flexibility.

Furthermore, in another aspect of the present invention

A device including the secondary battery is provided.

The device may be any one of a mobile phone, a portable computer, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device.

Hereinafter, the present invention will be described in detail through examples and experimental examples.

However, the following examples and experimental examples are only for explaining the present invention, and the contents of the present invention are not limited by the following examples and experimental examples.

< Example 1> Manufacture of a secondary battery in which a negative electrode is attached to a composite electrolyte membrane containing spherical small particle phosphate solid electrolyte and conductive polymer electrolyte components

A secondary battery was prepared by thermally curing a composite electrolyte and a negative electrode including a spherical small particle phosphate-based solid electrolyte and a conductive polymer electrolyte component by the following method.

Step 1: spherical small particle phosphate solid electrolyte ( Li _{One . 3} Al _{0 . 3} Ti _{One . 7} (PO ₄ ) ₃ )of Produce

The spherical small particle phosphate-based solid electrolyte was prepared in the following manner.

Step 1-1: Solvent heat synthesis method

Spherical small particle phosphate solid electrolyte was prepared through a solvent heat synthesis method.

Specifically, to 150 mL of 2-methoxyethanol, 0.85235 g of lithium acetate, 0.45665 g of aluminum chloride hexahydrate, 3.75692 mL of titanium butoxide, 2.58568 mL of phosphoric acid, and 15 mL of polyethylene glycol as a dispersant were added and stirred for 0.5 hours, and then distilled water 300 After adding µl and stirring for 1 hour, the solution was transferred to a Teflon container for a microwave reactor in order to proceed with the solvent heat synthesis method, and a crystallization reaction was performed by setting the microwave scanning condition to 200°C for 10 minutes. Thereafter, the solution was centrifuged and the solvent was removed using a vacuum oven, put in an alumina boat, and heat treated for 5 hours in an atmosphere of 525°C and 5% hydrogen/95% nitrogen at a heating rate of 5°C per minute using an electric furnace. I did.

Step 1-2: Ball milling

After performing the solvent heat synthesis method, a ball milling treatment step was performed.

After the heat treatment in step 1, the sample was ball-milled in ethanol at 100 rpm for 3 hours, and then dried in an oven at 120° C. Li _{1 in the} form of spherical small particles _{. 3} Al _{0 . 3} Ti _{1 .7} (PO _{4) 3} were prepared solid electrolyte.

Li _{1 in the} form of spherical small particles prepared through step 1 _{. 3} Al _{0 . 3} Ti _{1 .7} (PO ₄₎ was observed the shape of the solid electrolyte ₃ by a scanning electron microscope (SEM).

Li _{1 in the} form of spherical small particles, which is a spherical small particle phosphate-based solid electrolyte prepared in the present invention _{. 3} Al _{0 . It can be seen that the 3} Ti _{1 .7} (PO ₄ ) ₃ solid electrolyte has a constant particle size and a particle diameter of about 150 nm.

This is Li _{1 . 3} Al _{0 . 3} Ti _{1 .7} (PO ₄ ) _{3 It} is believed that the agglomeration of solid electrolyte particles was dispersed into individual particles through the ball milling process.

Step 2: Crosslinking agent Preparation of included polymer electrolyte solution

Ethylene of a specific molar ratio (poly(ethylene glycol) dimethyl ether and bisphenol A ethoxylate diacrylate to 0.6 g of a polymer poly(ethylene glycol) dimethyl ether) (number average molecular weight 500) When the lithium salt is completely dissolved at a temperature of 60℃ by adding bis (trifluoromethanae) sulfonamide lithium salt (Bis (trifluoromethanae) sulfonamide lithium salt) so that the number of moles of oxide: the number of moles of lithium ions = 20: 1) Until sufficiently dissolved and stirred.

When the temperature of the solution dropped to room temperature, 0.4 g of Bisphenol A ethoxylate diacrylate (number average molecular weight 688) and 0.04 g of an initiator were added, followed by sufficiently stirring to prepare a polymer electrolyte solution. At this time, the initiators are Tert-Butyl peroxyneodecanoate (74-76%), Naphtha (petroleum)), hydrotreated heavy (20-26%) , Hydroperoxide (Hydroperoxide), 1,1-dimethylethyl (1,1-dimethylethyl), neodekenoyl chloride (Neodecanoyl chloride) contains. All of the above solutions were prepared in a dry room.

Step 3: Complex electrolyte containing spherical small particle phosphate solid electrolyte and conductive polymer electrolyte component Paste Produce

In the polymer electrolyte solution of Step 2, 1 part by weight of the spherical small particle phosphate-based solid electrolyte of Step 1 of the conductive polymer electrolyte (poly(ethylene glycol) dimethyl ether): bisphenol A detoxylate diacrylic Rate (Bisphenol A ethoxylate diacrylate) = 6:4 (weight ratio) mixed component 1 part by weight), mixed so as to be included in 0.4 parts by weight to prepare a composite electrolyte paste. All the preparation of the paste was carried out in a glove box.

Step 4: Forming a negative electrode by contacting a lithium metal electrode with a composite electrolyte membrane containing a spherical elementary particle phosphate solid electrolyte and a conductive polymer electrolyte component

The curing of the composite electrolyte paste was performed on a hot plate. A composite electrolyte paste was placed on a Teflon dish, and pressure was applied using a Teflon plate as a cover to form a membrane and cured at a temperature of 80° C. for 3 hours to prepare a free-standing solid composite electrolyte membrane.

After that, remove the Teflon plate cover and attach a lithium metal electrode to improve the interfacial contact on the composite electrolyte. After raising the Teflon plate cover again, cure at 100℃ for 2 hours by applying higher pressure to the lithium metal electrode on the composite electrolyte membrane. Formed. At this time, when the Teflon plate was removed after curing for 2 hours, the sus was attached to the lithium metal electrode and cured to remove the adhesion to the lithium metal electrode. All of the preparation of the composite electrolyte membrane was carried out in a glove box. Fig. 5 shows a photographic image of a solid-state composite electrolyte of a composite electrolyte membrane with a lithium metal electrode formed on a Teflon dish.

Step 5: anode formation

A secondary battery was finally manufactured using a positive electrode which is a lithium iron phosphate composite electrode to which polyethylene glycol dimethyl ether was added.

< Manufacturing example 1>

A composite electrolyte membrane was prepared by performing steps 1-4 of Example 1, but in step 4, a composite electrolyte paste was put on a Teflon dish and pressure was applied using a Teflon plate as a cover to form the membrane and cured at 80° C. for 3 hours. Then, a freestanding composite electrolyte membrane was prepared, and then cured at 100° C. for 2 hours by applying a higher pressure to cure without attaching any electrodes to the composite electrolyte membrane, thereby preparing a freestanding composite electrolyte membrane. Images of the solid composite electrolyte formed in the Teflon dish are shown in FIGS. 2 and 3.

< Comparative example 1>

A secondary battery was manufactured by performing steps 1-5 of Example 1, but in step 4, a composite electrolyte paste was put on a Teflon dish, and pressure was applied using a Teflon plate as a cover to form a membrane and cured at 80° C. for 3 hours. To prepare a free-standing composite electrolyte membrane, and then cured at 100° C. for 2 hours under higher pressure to cure without attaching any electrodes to the composite electrolyte membrane to prepare a free-standing composite electrolyte membrane. A secondary battery was manufactured by using and assembling.

< Comparative example 2> Composite containing spherical small particle phosphate solid electrolyte and conductive polymer electrolyte component On the electrolyte membrane Manufacturing of secondary battery with positive electrode attached

A secondary battery was manufactured by performing steps 1-5 of Example 1, but in step 4, a composite electrolyte paste was put on a Teflon dish, and pressure was applied using a Teflon plate as a cover to form a membrane and cured at 80° C. for 3 hours. To prepare a free-standing solid composite electrolyte membrane, remove the Teflon plate cover, attach a positive electrode, which is a lithium iron phosphate composite electrode to which polyethylene glycol dimethyl ether is added, on the composite electrolyte, raise the Teflon plate cover again, and apply a higher pressure. Then, it was cured at a temperature of 100° C. for 2 hours to form a positive electrode on the composite electrolyte membrane. At this time, when the Teflon plate was removed after curing for 2 hours, a suspension was attached to the positive electrode and cured in order to remove the adhesion to the positive electrode. All of the preparation of the composite electrolyte membrane was carried out in a glove box. Fig. 4 shows an image of a solid-state composite electrolyte of a composite electrolyte membrane formed on a Teflon dish and a composite electrolyte membrane attached thereto.

Thereafter, in step 5, a secondary battery was finally manufactured using a negative electrode as a lithium metal electrode.

< Experimental example 1> compound Of the electrolyte membrane Ion conductivity measurement

In order to evaluate the electrochemical properties of the composite electrolyte membrane according to the present invention, the composite electrolyte membrane prepared in Comparative Example 1 was sandwiched between the suspension and the suspension, and the ionic conductivity was measured after assembling a cell, and the results are shown in FIG. 6 and the table below. It is shown in 1.

Temperature (℃) Ion conductivity (S/cm) 15 2.51×10 ^-5 30 5.60×10 ^-5 45 1.10×10 ^-4 60 2.07×10 ^-4 75 3.59×10 ^-4

As shown in Table 1, it can be seen that the composite electrolyte provided in one aspect of the present invention exhibits excellent ionic conductivity.

< Experimental example 2> Measurement of discharge capacity according to the interface contact method between composite electrolyte and electrode

In order to evaluate the electrochemical properties of the composite electrolyte according to the present invention, the discharge capacity according to the interfacial contact method between the composite electrolyte, the positive electrode and the negative electrode in the secondary curing of the composite electrolyte was measured through cell characteristics. Specifically, charging and discharging of the secondary batteries prepared in Example 1, Comparative Example 1 and Comparative Example 2 were measured, and the results are shown in FIGS. 7 to 9 and Table 2 below.

Discharge capacity (mAhg ^-1 ) Polarization (△V) Comparative Example 1 119 0.87 Comparative Example 2 - 1.16 Example 1 117 0.57

In Example 1, an electrolyte with a lithium metal electrode attached to the composite electrolyte membrane during secondary curing was completed, and charging and discharging were measured after assembling the cell using a lithium iron phosphate composite electrode to which polyethylene glycol dimethyl ether was added. I did.

Comparative Example 1 is not curing the interfacial contact between the composite electrolyte and the positive electrode (lithium iron phosphate composite electrode, lithium metal electrode added with polyethylene glycol dimethyl ether) during the preparation of the composite electrolyte, but when assembling the cell polyethyl Charge and discharge were measured after cell assembly using a lithium iron phosphate composite electrode and a lithium metal electrode to which tenglycol dimethyl ether was added.

In Comparative Example 2, an electrolyte with a lithium iron phosphate composite electrode to which polyethylene glycol dimethyl ether was added during secondary curing on the composite electrolyte membrane was completed, and charging and discharging were measured after cell assembly using a lithium metal electrode. I did.

As a result, it was confirmed that the secondary battery of Example 1 had excellent electrochemical properties.

Accordingly, the secondary battery including the composite electrolyte for a secondary battery composed of a phosphate-based solid electrolyte and a conductive polymer electrolyte component provided in one aspect of the present invention is thermally cured by first contacting the negative electrode with the composite electrolyte to provide an interface between the negative electrode and the composite electrolyte. By stabilizing the state, it can be seen that the electrochemical properties such as discharge capacity and polarization characteristics of the secondary battery are excellent by reducing the interface resistance.

Claims (12)

Preparing a composite electrolyte precursor by mixing a solid electrolyte powder and a polymer electrolyte solution represented by the following Formula 1;
Preparing a composite electrolyte membrane using the composite electrolyte precursor; And
The method of manufacturing a secondary battery comprising a step of thermosetting after contacting the composite electrolyte membrane with a negative electrode:
[Formula 1]
Li _{1 + x} Al _x M _{2 -x} (PO ₄ ) ₃
(In Formula 1, M is Ti or Ge, and 0 <x <2).
The method of claim 1,
The polymer electrolyte solution is a method of manufacturing a secondary battery comprising at least one polymer selected from the group consisting of a polyethylene glycol polymer, a polypropylene glycol polymer, and a polyvinylidene fluoride polymer.
The method of claim 1,
The polymer electrolyte solution further comprises at least one selected from the group consisting of a lithium salt, a crosslinking agent, an initiator, a plasticizer, and a binder in the polymer.
The method of claim 4,
The crosslinking agent is polyethyleneglycol diacrylate, triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, and bisphenol aethoxylate dimethacrylate (Bisphenol A ethoxylate dimethacrylate) at least one selected from the group consisting of secondary battery manufacturing method.
The method of claim 1,
The composite electrolyte precursor is a method of manufacturing a secondary battery comprising 0.001 to 0.4 parts by weight of a solid electrolyte based on 1 part by weight of a polymer electrolyte component.
The method of claim 1,
The composite electrolyte membrane is a method of manufacturing a secondary battery manufactured by heat treatment while applying pressure to a composite electrolyte precursor.
The method of claim 1,
The negative electrode is a method of manufacturing a secondary battery comprising a negative electrode active material capable of storing and releasing lithium.
The method of claim 1,
The thermal curing is a method of manufacturing a secondary battery performed at a temperature of 80 ℃ to 120 ℃.
The method of claim 6,
The thermal curing is performed while applying pressure,
The method of manufacturing a secondary battery, characterized in that the pressure is greater than the pressure applied when manufacturing the composite electrolyte membrane.
A secondary battery manufactured by the manufacturing method of claim 1.
A device comprising the secondary battery of claim 11.
The method of claim 11,
The device is a device selected from the group consisting of a mobile phone, a portable computer, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device.

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