KR20190118811A - Binder for all-solid-state lithium secondary battery, electrode slurry comprising the same, and the all-solid-state lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a binder for an all-solid-state lithium secondary battery, electrode slurry including the same, and a lithium secondary battery manufactured using the electrode slurry. The binder for an all-solid-state lithium secondary battery according to the present invention can enhance interfacial adhesion with an electrode active material and form a stable surface protective layer on a surface of the electrode active material.

Description

Binder for all-solid-state lithium secondary battery, electrode and all-solid-state lithium secondary battery comprising same

The present invention relates to a binder for an all-solid-state lithium secondary battery, an electrode slurry including the same, and an all-solid-state lithium secondary battery manufactured using the electrode slurry.

Recently, as the spread of portable electronic devices such as smart phones and laptops has been expanded, high energy density of batteries has been required to meet the trend of light weight and miniaturization of these electronic devices. In addition, the field of application of energy storage technology from the power source for vehicles such as electric vehicles to energy storage systems is expanding and medium-large and large, the situation is required to increase the high energy density of secondary batteries that can store a larger amount of electrical energy.

While the commercialization of lithium secondary batteries as secondary batteries is expanding, problems regarding their large capacity and safety have emerged. Although the lithium secondary battery basically has excellent battery characteristics, the performance of safety, especially overcharging and life characteristics is not sufficient. In terms of safety, a liquid electrolyte-based lithium secondary battery using a nonaqueous electrolyte in which a lithium salt is dissolved in an organic solvent as an electrolyte has a risk of explosion and ignition of the liquid electrolyte, which makes it difficult to secure safety. Accordingly, all-solid-state lithium secondary batteries are attracting attention for the purpose of solving the instability problem.

All-solid-state lithium secondary batteries use solid electrolytes instead of liquid electrolytes used in conventional lithium secondary batteries to overcome the limitations of existing liquid electrolytes due to high capacity and high voltage of electrodes and to increase safety in accordance with high performance. Has

An all-solid-state lithium secondary battery using a solid electrolyte has an electrolyte layer including a solid electrolyte, a cathode and an anode are formed on both sides thereof, and a current collector is coupled to each electrode. The all-solid-state lithium secondary battery has an electrode structure in which an ion conductor solid electrolyte and an electrode active material are combined with pores existing in an existing lithium ion battery electrode, so that physical contact between these components becomes an important factor for battery performance. Therefore, various methods for minimizing the resistance of the resistance increase due to inefficient contact in the electrode when manufacturing the all-solid-state lithium secondary battery, but the performance improvement effect was not sufficient.

On the other hand, the binder applied to the all-solid-state lithium secondary battery serves to fix the electrode active material and the conductive material to the current collector, if the content is low may be peeled off with the current collector, if the content is high in the electrode Increasing resistance may reduce electrode characteristics. In particular, the all-solid-state lithium secondary battery uses a solid electrolyte, so the resistance due to inefficient contact in the electrode is high, and thus the importance of the binder in performance improvement cannot be neglected.

Therefore, in providing an all-solid-state lithium secondary battery that can ensure safety, even if the use of a small amount of binder to increase the binding capacity between the active material particles and the current collector to achieve excellent performance even at high energy density and high voltage There is a need for research and development on a binder applied to a solid state lithium secondary battery.

Korea Patent Publication No. 10-1422908 (2014.07.23.)

The present invention is excellent in interfacial adhesion with the electrode active material, by forming a protective layer on the surface of the electrode active material can accommodate the volume expansion of the active material generated during repeated charging and discharging can ensure safety even at high energy density and high voltage It is an object of the present invention to provide a binder for an all-solid-state lithium secondary battery capable of improving durability.

In addition, the present invention is a solid-state lithium secondary battery binder, an electrode slurry comprising the same, which can improve battery performance including not only safety of the electrode structure but also excellent cycle characteristics, long-term stability and high energy density, despite a small content. An object of the present invention is to provide an all-solid lithium secondary battery manufactured therefrom.

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

The present invention relates to a binder for an all-solid-state lithium secondary battery including a polyimide copolymer containing a repeating unit represented by Formula 1 and a repeating unit represented by Formula 2.

[Formula 1]

[Formula 2]

(In Formula 1 and Formula 2, R ₁ to R ₆ are each independently a functional group selected from -CH _3-x F _x and -F, R ₇ is a carboxyl group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group and At least one functional group selected from the group consisting of acid anhydride groups, wherein x is an integer of 1 to 3, and a and b are each independently an integer of 2 to 200.

In the binder for an all-solid-state lithium secondary battery according to an embodiment of the present invention, the polyimide copolymer has a molar ratio (a / b) of a repeating unit represented by Formula 1 and a repeating unit represented by Formula 2 to 1 to 10. It may be.

In the binder for an all-solid-state lithium secondary battery according to an embodiment of the present invention, the polyimide copolymer may include a repeating unit represented by Formula 3 and a repeating unit represented by Formula 4.

[Formula 3]

[Formula 4]

(In Formulas 3 and 4, a and b are each independently an integer of 2 to 200.)

In the binder for an all-solid-state lithium secondary battery according to an embodiment of the present invention, the polyimide copolymer may have a weight average molecular weight of 10,000 to 200,000 g / mol.

In addition, another aspect of the present invention relates to an electrode slurry comprising the above-mentioned binder for all-solid-state lithium secondary batteries, an electrode active material, a conductive material and a solvent.

In the electrode slurry according to an embodiment of the present invention, the binder may be included in the range of 1 to 50% by weight based on the total weight of the binder, the electrode active material and the conductive material.

In the positive electrode for an all-solid-state lithium secondary battery of the present invention, the positive electrode active material is Li _a Ni _1-xy Co _x Mn _y M _b O ₂ (0.98 ≦ a ≦ 1.1, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, 0 ≤ b ≤ 0.1, M is a transition metal or lanthanide selected from the group consisting of Al, Cr, Fe, Mg, Ti, V, Cu, Zn, Ca, La, Ce, Sr, Sn, Si and combinations thereof Element)., LiCoO ₂ , x Li ₂ MnO _3. (1- x) LiMn _1-yz Ni _y Co _z O ₂ (0.05 ≦ x ≦ 0.95, 0.01 ≦ _y ≦ 0.98, 0 ≦ _z ≦ 0.98) and Li _a Mn _2-x M _x N _b O ₄ (0.98 ≦ a ≦ 1.1, 0 ≦ x ≦ 1, 0 ≦ b ≦ 0.1, and M consists of Ni, Cr, Fe, V, Cu, Zn and combinations thereof It may be any one selected from the group, N is any one selected from the group consisting of Ni, Cr, Fe, V, Cu, Zn, Mg, Ca, La, Ce, Sr, Sn, Si and combinations thereof It may be any one or more selected from).

In the positive electrode for an all-solid-state lithium secondary battery of the present invention, the positive electrode active material is an oxide, fluoride, phosphide or any one or more of the metals selected from the group consisting of Al, Zr, Sn, Si, Zn, Nb, Ni and Co. And may be coated with sulfides.

In addition, another aspect of the present invention relates to an all-solid-state lithium secondary battery comprising a current collector, a positive electrode formed by coating the electrode slurry on one surface of the current collector, and a solid electrolyte layer formed on one surface of the positive electrode.

In the all-solid-state lithium secondary battery according to an embodiment of the present invention, the solid electrolyte layer includes any one or more inorganic compounds selected from the group consisting of polymer, oxide, phosphate, sulfide, and boron compounds. It may be.

In the all-solid-state lithium secondary battery according to an embodiment of the present invention, the charge cutoff voltage may be 4.2V to 6.0V.

The all-solid-state lithium secondary battery according to one embodiment of the present invention may have an operating temperature of -40 ° C to 450 ° C.

The binder for an all-solid-state lithium secondary battery according to the present invention can improve interfacial adhesion with an electrode active material and form a stable surface protective layer on the surface of the electrode active material, as well as increase thermal stability, and can provide an electrode structure even at high energy density and high voltage. It can secure stability and has the advantage of improving the durability of the all-solid-state lithium secondary battery in the long term.

In addition, the electrode including the binder according to the present invention and the all-solid-state lithium secondary battery prepared by using the electrode has a high capacity and high rate of battery characteristics, further excellent capacity retention characteristics, cycle characteristics and improved life characteristics of repeated charging and discharging Has the advantage of implementing

1 schematically shows particle change according to Comparative Example 1. FIG.
2 schematically illustrates particle change according to Example 1. FIG.
Figure 3 shows the NMR analysis of the polyimide copolymer prepared in Preparation Example 1.
Figure 4 shows the cycle characteristics of the lithium secondary battery according to Example 1 and Comparative Example 1.

Hereinafter, a binder for an all-solid-state lithium secondary battery of the present invention, an electrode slurry including the same, and an all-solid-state lithium secondary battery manufactured using the electrode slurry will be described in detail. The invention can be better understood by the following examples. The following examples are for illustrative purposes of the invention and are not intended to limit the scope of protection defined by the appended claims. In this case, unless otherwise defined, the technical and scientific terms used have the meanings that are commonly understood by those of ordinary skill in the art.

The inventors of the present invention, while deepening the research on all-solid-state lithium secondary battery that can increase the energy density and ensure safety at high voltage in the all-solid-state lithium secondary battery having a non-ignition characteristics including a solid electrolyte, fluorine functional group It is possible to form a stable surface protective layer on the surface of the electrode active material by providing a binder comprising a polyimide having a combination of specific functional groups, and providing the binder as a component of the electrode composition, thereby It can accommodate the volume expansion of the electrode active material, further reduce the electrode resistance by inducing improved adhesion to the solid electrolyte layer can ensure electrode stability, particularly thermal stability and high voltage stability, and can significantly increase the electrode capacity Excellent capacity retention characteristics, cycle characteristics and long lifespan characteristics To find that to implement thereby completing the present invention.

According to one aspect of the invention, the all-solid-state lithium secondary battery binder is characterized in that it comprises a polyimide copolymer having an acid group and a fluorine group at the same time. Specifically, the polyimide copolymer according to the present invention includes a repeating unit represented by Formula 1 and a repeating unit represented by Formula 2.

[Formula 1]

[Formula 2]

In the repeating unit compound according to Formula 1 and Formula 2, R ₁ to R ₆ are each independently fluorine or fluoroalkyl having 1 to 3 carbon atoms, and specifically, R ₁ to R ₆ are each independently − Fluorine group selected from CH _3-x F _x and -F. In this case, x is an integer of 1 to 3.

In addition, the R ₇ may be any one or more acid groups selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group and an acid anhydride group, but is not limited thereto. Specifically, R ₇ may be a carboxyl group or a hydroxyl group.

In addition, a and b are each independently an integer of 2 to 200, specifically 10 to 100, more specifically 30 to 80. When the above range is satisfied, it is advantageous to form a surface protective layer on the surface of the electrode active material and may have a characteristic of minimizing performance deterioration and ensuring safety even in repeated charging and discharging, but this is only one non-limiting example. It is not limited to the above numerical range.

The polyimide copolymer is a polymer including a repeating unit represented by Chemical Formula 1 and a repeating unit represented by Chemical Formula 2, but the form of the copolymer is not particularly limited, but an alternating copolymer or a random copolymer The copolymer may be any one or more copolymers selected from random copolymers, block copolymers, and graft copolymers.

According to one aspect of the present invention, the binder for an all-solid-state lithium secondary battery including the polyimide copolymer may increase adhesion between the conductive material and the electrode active material, and at the same time, improve adhesion between the electrode and the current collector. Has the property. In particular, the binder may have a composite performance by forming a surface protective layer on the surface of the electrode active material. That is, it is more effective in accommodating the volume expansion of the electrode active material that may occur during repeated charging and discharging to improve the stability, thermal stability and battery characteristics of the electrode electrode structure, specifically high rate, high capacity and cycle characteristics.

The polyimide copolymer may have a molar ratio (a / b) of the repeating unit represented by Formula 1 and the repeating unit represented by Formula 2. Specifically, in the polyimide copolymer, the molar ratio (a / b) of the repeating unit represented by Formula 1 and the repeating unit represented by Formula 2 may be 1 to 10, specifically 2 to 7, more specifically 3 to 5 days. have. More specifically, the polyimide copolymer may have a molar ratio of the repeating unit represented by Formula 1: molar ratio of the repeating unit represented by Formula 2 may be 3: 1 to 5: 1. When the above range is satisfied, it is more effective in terms of improving battery performance including high rate, high capacity, and cycle life characteristics, as well as securing thermal stability and stability at high voltage.

The polyimide copolymer is not particularly limited in weight average molecular weight, specifically, 10,000 to 200,000, specifically, 19,000 to 186,000 g / mol, more specifically, may be 25,000 to 85,000 g / mol. If the above range is satisfied, it is effective in terms of improving adhesion between the electrode active material and the conductive material and stability of the electrode structure, but this is merely an example and is not limited to the above numerical range. At this time, the weight average molecular weight is measured by dissolving the sample in tetrahydrofuran (THF) using gel osmosis chromatography (GPC) (analysis column: Styragel HR, WATERS, standard: polystyrene (PS)).

According to an aspect of the present invention, the polyimide copolymer may include a repeating unit represented by Formula 3 and a repeating unit represented by Formula 4.

[Formula 3]

[Formula 4]

In this case, in Formulas 3 and 4, a and b are integers of 2 to 200.

According to an aspect of the present invention, the binder for an all-solid-state lithium secondary battery including the polyimide copolymer is more effective to be applied to a positive electrode. In general, in terms of structural stability of the electrode, there is a large change in characteristics due to the combination of the conductive material and the electrode active material, and the binder contained in the electrode slurry is important for the adhesion between the electrode active material or the conductive material, and the uniformity or dispersibility of the electrode slurry containing them. The binder may be used as the all-solid-state lithium secondary battery positive electrode in terms of preventing a decrease in capacity such as dissolution of lithium or deterioration of cycle characteristics, but is not limited thereto.

According to one aspect of the present invention, the binder has a binding property through coordination with respect to the positive electrode material of the dislocation metal oxide component including a carboxyl group, and has an effect of providing excellent adhesion with the electrode active material. Furthermore, it has a property of controlling the binding property on the surface of the transition metal oxide anode by adjusting the ratio of carboxyl groups. In one non-limiting example, the -CF ₃ group increases the polarity and thus increases the solubility of the binder, thereby having an effect of forming a uniform surface layer on the anode surface (FIG. 2). In addition, the binder can significantly improve the electrochemical oxidation stability and thermal stability as compared to the conventional commercially available PVdF binder, the binder forms a uniform protective layer on the surface of the anode at a charge cutoff voltage of 4.2V or more It has a property to prevent the electrochemical oxidation of the electrolyte at the interface generated.

Another aspect of the present invention is to provide an electrode slurry comprising the above-described binder for all-solid-state lithium secondary batteries, an electrode active material, a conductive material and a solvent.

The electrode slurry may be dried after casting on one surface of the current collector to form an electrode, which may provide an all-solid secondary battery together with a solid electrolyte.

Electrode slurry according to an aspect of the present invention by including the above-mentioned binder for all-solid-state lithium secondary battery not only facilitates the formation of a surface protective layer that can increase the structural stability on the surface of the electrode active material in spite of a small amount of binder It is possible to reduce the resistance by improving the electrode structure stability and adhesion with the solid electrolyte, which is excellent in the capacity characteristics and charge and discharge characteristics of the secondary battery, and furthermore, it is possible to stably output even at high voltage and to improve the energy density. Is more effective.

According to an aspect of the present invention, the binder for the all-solid-state lithium secondary battery may include 1 to 50% by weight, specifically 3 to 30% by weight, and more specifically 5 to 20% by weight, based on the total weight of the binder, the electrode active material, and the conductive material. Can be. It is possible to implement the desired physical properties of the present invention within the above range, in particular, even if it contains a small amount compared to the commonly used binder has an advantageous characteristic in that it can achieve the desired purpose, but this is just one non-limiting example, the numerical range Not restricted to

According to one aspect of the present invention, the electrode slurry may be used in addition to a binder for an all-solid-state lithium secondary battery by mixing with a known one other than the binder in a range not departing from the desired effect of the present invention.

The binder may include polyvinylidene fluoride (PVdF), hexafluoro propylene (HFP), polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene Fluoride-trichloroethylene (polyvinylidene fluorideco-trichloroethylene), polyacrylic acid, sodium polyacrylate, sodium alginate, polymethylmethacrylate, polybutylacrylate ), Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butylate (cellulose acetate butyrate), cellulose acetate Cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, pullulan, cyanoethylsucrose, Carboxylic methyl cellulose (CMC), polyimide, polyamide, polyamideimide, polystyrene, styrene-butadiene rubber (SBR), styrene ethylene butyl Styrene-styrene-butylene-styrene (SEBS), polyvinyl alcohol (PVA), and ethylene vinyl acetate copolymer (ethylene-vinyl acetate copolymer); EVA) may be any one or more selected from the group consisting of, but is not limited thereto.

According to one aspect of the present invention, the electrode slurry may be for forming a positive electrode in terms of preventing elution of lithium and increasing capacity and improving cycle characteristics, and the binder for an all-solid-state lithium secondary battery contained in the slurry may be combined with an electrode active material. It can provide excellent adhesion, form a uniform protective layer on the surface of the positive electrode active material, and further increase the adhesion at the interface with the solid electrolyte in combination with other components including the binder for the all-solid-state lithium secondary battery. The resistance can be reduced, and by manufacturing a positive electrode having an appropriate porosity and a high loading level, it is possible to improve the diffusion and charge / discharge performance of lithium ions and thus has excellent cycle life characteristics.

According to an aspect of the present invention, as the electrode active material, a cathode active material may use a conventional cathode active material used in the art, and specifically, lithium cobalt composite oxide (LiCoO ₂ ) and spinel crystalline lithium manganate composite oxide. (LiMn ₂ O ₄ ), lithium manganate complex (LiMnO ₂ ), lithium nickelate complex oxide (LiNiO ₂ ), lithium iron phosphate (LiFePO ₄ ), lithium manganese phosphate (LiMnPO ₄ ), lithium cobalt phosphate (LiCoPO ₄ ), iron pyrophosphate (Li ₂ FeP ₂ O ₇ ), lithium niobate composite oxide (LiNbO ₂ ), lithium ferric oxide composite oxide (LiFeO ₂ ), lithium magnesium oxide composite oxide (LiMgO ₂ ), calcium lithium compound oxide (LiCaO _2), copper lithium compound oxide (LiCuO _2), zincate lithium composite oxide (LiZnO _2), molybdate and lithium compound oxide (LiMoO _2), lithium tantalate complex oxide (LiTaO _2), tungsten lithium compound oxide (LiWO _2), lithium-nickel-cobalt Aluminum composite oxide _{(LiNi 0.8 Co 0.15 Al 0.05 O} 2), lithium-nickel-cobalt-manganese composite oxide _{(LiNi 1-xy Co x Mn} y O 2), and lithium permanganate between the compound oxide (xLi ₂ MnO ₃ · (1 x) LiMn _1-yz Ni _y Co _z O ₂ ), manganese oxide-nickel (LiNi _0.5 Mn _1.5 O ₄ ), and the like, but are not limited thereto.

More specifically, the cathode active material is Li _a Ni _1-xy Co _x Mn _y M _b O ₂ (0.98 ≤ a ≤ 1.1, 0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5, 0 ≤ b ≤ 0.1, M is Al, Cr, Fe, Mg, Ti, V, Cu, Zn, Ca, La, Ce, Sr, Sn, Si, and a combination thereof, or a lanthanide element selected from the group consisting of a combination thereof), LiCoO ₂ , xLi ₂ MnO _3. (1- x) LiMn _1-yz Ni _y Co _z O ₂ (0.05 ≦ x ≦ 0.95, 0.01 ≦ _y ≦ 0.98, 0 ≦ _z ≦ 0.98) and Li _a Mn _2-x M _x N _b O ₄ (0.98 ≦ a ≦ 1.1, 0 ≦ x ≦ 1, 0 ≦ b ≦ 0.1, and M may be any one selected from the group consisting of Ni, Cr, Fe, V, Cu, Zn, and combinations thereof , N may be any one selected from the group consisting of Ni, Cr, Fe, V, Cu, Zn, Mg, Ca, La, Ce, Sr, Sn, Si, and combinations thereof.) It may be abnormal. In the case of using the positive electrode active material, the combination of the above-described polyimide copolymer improves capacity retention characteristics and cycle life characteristics even after repeated charging and discharging at high voltage charge cut-off voltage of 4.2 V or higher, and electrode structure stability even at thermal and high voltage. It is more effective in terms of securing it.

The electrode active material may be included in an amount of 2 to 95 wt%, specifically 20 to 85 wt%, and more specifically 50 to 75 wt%, based on the total mass of the binder, the electrode active material, and the conductive material. The present invention is effective in that the desired effect can be achieved, but this is only one non-limiting example and is not limited to the above numerical range.

The conductive material is not particularly limited as long as it has conductivity, and specifically, carbon powder may be used. For example, carbon black, Super-P carbon black, acetylene black, ketjen black, graphite, carbon fiber, carbon tube, carbon nanofiber, carbon One or more selected from the group consisting of nanotubes, carbon nanowires and graphene, but is not limited thereto.

The content of the conductive material may include 1 to 50% by weight, specifically 3 to 30% by weight, more specifically 5 to 20% by weight, based on the total mass of the binder, the electrode active material and the conductive material. It is effective in terms of being able to move electrons effectively to impart high rate and high capacity characteristics, but this is only a non-limiting example and is not limited to the numerical range.

The solvent is not limited in kind, but specifically, methanol, butanol, pentanol, hexanol, toluene, xylene, hexadecane, N-methyl-2-pyrrolidone (NMP), 1,4-dioxane , N, N-dimethylacetamide, triethyl phosphate, dimethyl sulfoxide and tetrahydrofuran may be any one or more selected from the group consisting of.

The current collector may have any electrical conductivity and may be used without particular limitation as long as it is a material capable of energizing the electrode material. For example, any one or more selected from the group consisting of C, Ti, Cr, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Au, and Al may be used. Specifically, as a current collector, C, Al, stainless steel, etc. are mentioned, More specifically, Al is preferable at cost and efficiency. The shape of the current collector is not particularly limited, but may be a thin film substrate or a three-dimensional substrate such as a foamed metal, a mesh, a woven fabric, a nonwoven fabric, a foam, or the like. Even if the content is low, an electrode of high capacity density can be obtained, which is effective in high rate and charge / discharge characteristics.

Another aspect of the present invention is to provide an all-solid-state lithium secondary battery comprising a positive electrode formed by applying and drying the above-described electrode slurry on one surface of a current collector and a solid electrolyte layer formed on one surface of the positive electrode.

In addition to the positive electrode, a mixture prepared by applying a mixture including a negative electrode active material, a conductive material, and a binder on a negative electrode current collector as a negative electrode may be used.

The negative electrode active material is selected from lithium metal foil, lithium metal powder, graphite, hard carbon, soft carbon, glass carbon, graphene, silicon, silicon oxide, tin, tin oxide, lithium titanium oxide, titanium oxide and combinations thereof Any one or more may be used, but is not limited thereto.

According to an aspect of the present invention, the all-solid-state secondary battery may be manufactured by laminating and pressing materials of the positive electrode, the solid electrolyte layer, and the negative electrode described above, but is not limited thereto.

The solid electrolyte layer may be a conventional ion conductive solid, and specifically, a solid lithium ion conductor made of any one or more compounds selected from the group consisting of polymer, oxide, phosphate, sulfide and boron compounds It may be included as an electrolyte, but may be in the form of a molded body, a sintered body or a film thereof, but is not necessarily limited thereto. The molded body may be in the form of pellets, may have sufficient strength to support the electrodes, and may include pores. In addition, the pores in the solid electrolyte layer may be to form an open channel (open channel). The polymer compound may be any one or more components selected from the group consisting of polyethylene oxide (PEO), polyacrylate (polyacrylate) and polysiloxane (polysiloxane). In addition, the oxide-based compound is Li _3x La ₂ / _(3-x) TiO ₃ (0 <X ≤ 2) and Li _7-y La _3-x A _x Zr _2-y M _y O ₁₂ (A is Y , Nd, Sm, or Gd, M may be Nb or Ta, and 0 ≦ x <3, 0 ≦ y <2), and any one or more components selected from the group consisting of Li _7-y La _3-x A _x Zr _2-y M _y O _{12 It} may be composed of Li ₇ La ₃ Zr ₂ O ₁₂ corresponding to the case of x = 0 and y = 0. In addition, the phosphate compound is represented by Li _{1 + x + y} (Al, Ga) _x (Ti, Ge) _2-x Si _y P _3-y O ₁₂ (0 ≦ x ≦ 1, 0 ≦ _y ≦ l) It may be composed of a single component or two or more components, the sulfide-based compound is Li ₁₀ GeP ₂ S ₁₂ , Li ₁₀ SiP ₂ S ₁₂ , Li _{10 + δ} (Sn _y Si _1-y ) _{1 + δ} P _{2- δ} S ₁₂ , Li _3.25 Ge _0.25 P _0.75 S ₄ , Li ₂ S, Li ₂ SP ₂ S ₅ , Li ₂ S-SiS ₂ , Li ₂ S-GeS ₂ , Li ₂ SB ₂ S ₅ , Li ₂ SB ₂ S _{Any of 3} -LiI, Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ SP ₂ S ₅ , Li ₂ S-Al ₂ S ₅ and Li ₂ PS ₄ -Li ₄ SnS ₄ -Li ₄ SiS ₄ It may be composed of one or more components, but is not limited thereto.

The all-solid-state lithium secondary battery according to an aspect of the present invention is excellent in thermal characteristics, stability at high voltage, and cycle life characteristics, and may implement high rate and high capacity characteristics.

Specifically, the present invention provides an all-solid-state lithium secondary battery for high capacity and high voltage, wherein the lithium secondary battery has a charge cut off voltage of 4.2 V to 6.0 V, specifically 4.3 V to 5.5 V, more specifically. It may be 4.3 to 5.0V. It is possible to ensure stability even at high temperature and high voltage within the above range, and has a cycle life characteristic with high rate, high capacity characteristics.

In addition, the all-solid-state lithium secondary battery may be an operating temperature of -40 ℃ to 450 ℃, specifically 20 ℃ to 100 ℃. Due to the structural stability even at low or high temperature as in the above range has excellent battery characteristics including charge and discharge performance without cracking or damage during operation.

The all-solid-state lithium secondary battery requires high capacity, high output, and high safety, and may be used as a unit battery in a medium-large battery module including a plurality of battery cells used as a power source for a small device or a power source for a medium-large device. Examples of such devices include mobile devices, wearable devices, power tools powered by an electric motor; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; Electric motorcycles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf carts; Smart grid-connected power storage device (Energy Storage System) and the like, but is not limited thereto.

Hereinafter, the binder for the all-solid-state lithium secondary battery and the lithium secondary battery manufactured using the same according to the present invention will be described in more detail. However, the following examples are only one reference for describing the present invention in detail, and the present invention is not limited thereto and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing particular embodiments only and is not intended to be limiting of the invention.

Also, the singular forms used in the specification and the appended claims may be intended to include the plural forms as well, unless the context clearly indicates otherwise.

(Manufacture example 1)

Polyimide copolymers were prepared in which the 6-FDA / TFDB / DABA monomers were each combined in a 5: 4: 1 molar ratio. TFDB (19.1 g, 59.6 mmol, Aldrich) and 6-FDA (33.1 g, 74.5 mmol, Aldrich) were dissolved in 90 ml of DMF (N, N'-dimethylformamide) and DABA (2.30 g, 14.9 mmol, Aldrich) What was dissolved in 50 ml of DMF was placed in a round flask under nitrogen atmosphere and mixed at 0 ° C. for 5 hours. The temperature was raised to room temperature (25 ° C.) and stirred for 17 hours. Thereafter, 40 ml of acetic anhydride and 29 ml of pyridine were added thereto, followed by stirring to make a polyamic acid solution. The mixture was stirred at 80 ° C. for 24 hours. After cooling to room temperature and dropwise to precipitate in a beaker containing distilled water. This was filtered and washed and dried at 120 ° C. to prepare a polyimide copolymer (a / b = 4, weight average molecular weight = 55,000 g / mol) comprising a unit represented by Formula 3 and a unit represented by Formula 4 It was. As a result of NMR analysis of the prepared polyimide copolymer, as shown in FIG. 3, it was confirmed that the copolymer of Formula 3 and Formula 4 was produced.

[Formula 3]

[Formula 4]

(Example 1)

70 wt% of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (diameter: about 10 μm) as a positive electrode active material, a polyimide copolymer comprising a unit represented by the following formula (3) and a unit represented by the formula (4) as a binder (a / b = 4, weight average molecular weight = 55,000 g / mol) 6% by weight, 8% by weight carbon black (super-P) as a conductive material, 3% by weight of lithium salt Bis (trifluoromethane) sulfonamide (LiTFSI), lithium ion conductor PEGDME (Polyethylene) glycol dimethyl ether, M _W = 250) 13% by weight was mixed. At this time, the weight percent was based on these total weights. The above components were put in methylpyrrolidone (NMP) and then mixed uniformly to prepare a positive electrode active material slurry. The prepared slurry was applied onto an aluminum foil as a current collector, and then dried at 110 ° C. for 120 minutes to prepare a cathode for an all-solid lithium secondary battery including a cathode active material layer. In addition, a lithium metal foil anode is used as a counter electrode, and the polymer electrolyte is a crosslinking agent (Bisphenol-A ethoxylatediacrylate), lithium trifluoromethanesulfonimide (LiTFSI) salt, PEGDME (M _W = 250), and an initiator ( t-Butyl peroxypivalate (t-BPP) was used to prepare a solid lithium coin cell.

(Comparative Example 1)

Instead of the binder used in Example 1, it was carried out in the same manner as in Example 1 except for using a commercially available PVdF (Kynar ™ 761, Arkema).

Battery Characteristic Evaluation

Initial charge-discharge characteristics were evaluated using the all-solid lithium cells prepared in Example 1 and Comparative Example 1. Specifically, charging and discharging the manufactured lithium coin cell under the condition of 0.1C / 0.1C in the drive voltage range of 3.0 to 4.4V at 45 ℃ and the results are shown in FIG.

As can be seen in Figure 4, despite the high-temperature high-voltage charging voltage conditions, in Example 1 using the polyimide copolymer according to the present invention as a binder, the capacity value of the positive electrode is 207 mAh / It was confirmed that excellent high voltage stability was achieved by showing 190 mAh / g and 92% capacity retention rate when the battery was charged and discharged five times from g. On the other hand, in Comparative Example 1 using a conventional commercial PVdF binder, as shown in FIGS. 1 and 4, the binder binding force and the electrode active material retention due to high temperature and high voltage charging are reduced, and the capacity value of the positive electrode is charged and discharged once. 5 times charging and discharging from 205 mAh / g showed 183 mAh / g, and showed 89% capacity retention rate, it is expected that a faster capacity decrease compared to Example 1 as the number of cycles increases. This is to confirm that the binder according to an embodiment of the present invention has the effect of further improving the retention characteristics and capacity retention rate of the electrode active material in spite of the high voltage charging.

As described above in the present invention has been described by a limited embodiment, but this is only provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments, the present invention is not limited to the common knowledge Those having a variety of modifications and variations are possible from these descriptions.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all of the equivalents or equivalents of the claims as well as the claims to be described later belong to the scope of the present invention. .

Claims (11)

A binder for an all-solid-state lithium secondary battery comprising a polyimide copolymer containing a repeating unit represented by Formula 1 and a repeating unit represented by Formula 2.
[Formula 1]

[Formula 2]

(In Formula 1 and Formula 2, R ₁ to R ₆ are each independently a functional group selected from -CH _3-x F _x and -F, R ₇ is a carboxyl group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group and And at least one functional group selected from the group consisting of acid anhydride groups, wherein x is an integer of 1 to 3, and a and b are each independently an integer of 2 to 200. The method of claim 1,
The polyimide copolymer is a binder for an all-solid-state lithium secondary battery, wherein the molar ratio (a / b) of the repeating unit represented by Formula 1 and the repeating unit represented by Formula 2 is 1 to 10.
The method of claim 2,
The polyimide copolymer is a binder for an all-solid-state lithium secondary battery comprising a repeating unit represented by Formula 3 and a repeating unit represented by Formula 4.
[Formula 3]

[Formula 4]

(In Formulas 3 and 4, a and b are each independently an integer of 2 to 200.) The method of claim 1,
The polyimide copolymer has a weight average molecular weight of 10,000 to 200,000 g / mol binder for all solid lithium secondary batteries. An electrode slurry comprising the binder for an all-solid-state lithium secondary battery selected from claims 1 to 4, an electrode active material, a conductive material, and a solvent. The method of claim 5,
The all-solid-state lithium secondary battery binder is an electrode slurry containing 1 to 50% by weight based on the total weight of the binder, electrode active material and conductive material. The method of claim 5,
The electrode active material is Li _a Ni _1-xy Co _x Mn _y M _b O ₂ (0.98 ≦ a ≦ 1.1, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, 0 ≦ b ≦ 0.1, and M is Al, Cr, Is a transition metal or lanthanide element selected from the group consisting of Fe, Mg, Ti, V, Cu, Zn, Ca, La, Ce, Sr, Sn, Si, and combinations thereof), LiCoO ₂ , xLi ₂ MnO ₃ (1- x) LiMn _1-yz Ni _y Co _z O ₂ (0.05 ≦ x ≦ 0.95, 0.01 ≦ _y ≦ 0.98, 0 ≦ _z ≦ 0.98) and Li _a Mn _2-x M _x N _b O ₄ (0.98 ≤ a ≤ 1.1, 0 ≤ x ≤ 1, 0 ≤ b ≤ 0.1, M may be any one selected from the group consisting of Ni, Cr, Fe, V, Cu, Zn and combinations thereof, N is Ni And Cr, Fe, V, Cu, Zn, Mg, Ca, La, Ce, Sr, Sn, Si, and combinations thereof. The collector, the positive electrode formed by applying the electrode slurry according to claim 5 on one surface of the current collector and the all-solid-state lithium secondary battery comprising a solid electrolyte in the positive electrode. The method of claim 8,
The solid electrolyte layer is an all-solid-state lithium secondary battery comprising any one or more compounds selected from the group consisting of polymers, oxides, phosphates, sulfides and boron compounds. The method of claim 8,
The all-solid-state lithium secondary battery is an all-solid-state lithium secondary battery having a charge cutoff voltage of 4.2V to 6.0V. The method of claim 8,
The lithium ion battery is an all-solid-state lithium secondary battery of the operating temperature is -40 ℃ to 450 ℃.

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