KR101561678B1 - Electrode material for rechargeable battery and method of fabricating the same - Google Patents

Abstract

The present invention relates to an electrode composition for a secondary battery and a method for producing the same. The electrode composition according to one embodiment of the present invention includes polymer chains each having at least one anion group and a binder complex comprising a divalent or more metal cations ionically bonded to the at least one anion group to fix the polymer chains to each other ; And active material particles fixed by the binder composite.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrode composition for a secondary battery,

The present invention relates to a secondary battery technology, and more particularly, to an electrode composition for a secondary battery and a manufacturing method thereof.

The secondary battery is a battery capable of charging and discharging using an electrode material having excellent reversibility, and a lithium secondary battery has been typically used. The lithium secondary battery can be used not only as a small power source for small IT devices such as a smart phone, a portable computer, and an electronic paper, but also as a medium and large power source used in a power source such as a smart grid, Application is expected.

When a lithium metal is used as a cathode material of a lithium secondary battery, there is a danger of explosion or short-circuiting of the battery due to the formation of dendrites. Therefore, graphite, which can intercalate and deintercalate lithium instead of the lithium metal, And crystalline carbon or soft carbon such as artificial graphite, and hard carbon and carbon-based active material. However, as the application of the secondary battery extends not only to a small power source but also to a medium and large-sized power source, there is a continuing demand for high capacity and high output of the lithium secondary battery. In response to these demands, metals and semi-metal cathode materials which can be alloyed with lithium such as silicon (Si), tin (Sn) or aluminum (Al) having a theoretical capacity 8 times or more higher than the carbon- A non-carbon-based negative electrode material containing a metal oxide such as lithium-titanium oxide (LTO) of lithium metal is attracting attention.

However, the non-carbon anode material has problems such as breakdown of electrical connection between active materials due to volume change during charging and discharging of the cell, separation of active material from the current collector and erosion of active material by electrolyte. There is a barrier. Therefore, in order to apply the non-carbon anode material, it is required to improve the irreversibility of the battery in accordance with the change in volume during charging and discharging.

In addition, it is necessary to bond the active material particles and maintain the adhesion between the particles and the current collector for high-speed charging and discharging. In this case, a large amount of binder is required. The binder acts as an electrical resistance element of the electrode, thereby ultimately lowering the total energy density of the battery and reducing the charge / discharge efficiency.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a secondary battery capable of minimizing the amount of binder by securing an electrode adhesive force without deteriorating charge / discharge characteristics of the secondary battery, Which can improve the lifetime of the battery.

Another object of the present invention is to provide a method for manufacturing an electrode composition for a secondary battery having the above-described advantages economically and rapidly in a large amount.

According to an aspect of the present invention, there is provided an electrode composition for a secondary battery, comprising a binder composite and active material particles fixed by the binder composite. Wherein the binder complex comprises polymer chains each having at least one anion group; And divalent metal cations which are ionically bonded to the at least one anion group to fix the polymer chains to each other.

The average molecular weight of the polymer chains is in the range of 40,000 g / mol to 3,000,000 g / mol. In one embodiment, the polymer chains are selected from the group consisting of polysaccharides, styrene butadiene, acrylates, ethylene vinyl acetate, polyacrylonitrile, acrylonitrile-butadiene-styrene, poly (vinyl chloride), poly (vinylidene chloride) But are not limited to, vinyl pyrrolidone, carboxylated styrene-butadiene, alginic acid, sodium alginate, carboxymethyl cellulose, carboxymethyl starch, carboxymethyl guar gum, carboxymethyl xanthane gum, carboxymethyl tara gum, low methoxyl pectin, carrageenan, polyacrylic acid, polyprolylene, for example, polypropylene, polystyrene, poly (methylmethacrylate), nylon, polyethylene, LOS may comprise (cellulose), amylose (amylose), chitosan, glucose, sucrose, maltose, lactose, starch, glycogen, a natural rubber or a mixture thereof.

Preferably, the polymer chains may have a linear structure. For example, the polymer chains may be selected from the group consisting of polyacrylic acid, polypropylene, polystyrene, poly (methylmethacrylate), nylon, polyethylene, cellulose cellulose, amylose, natural rubber (a polymer of isoprene), or mixtures thereof.

The anionic group is _{^{-CO 2 -, -SO 2 -,}} -SO 3 -, -OSO 3 -, -PO 3 2-, -OPO 3 2-, -OP (OH) O -, -CS 2 - or -OCO ₂ ^- . ≪ / RTI > The metal cations are cations of alkaline earth metals, transition metals, or alloys thereof. Wherein the alkaline earth metal comprises beryllium, magnesium, calcium, strontium, or barium; and the transition metal is selected from the group consisting of titanium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel or copper; Yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, or cadmium; Or hafnium, tantalum, tungsten, or iridium.

In one embodiment, the ratio of the polymer chains and the metal cations can satisfy the following formula (1). The value of the ratio may be selected in consideration of the average diameter of the secondary particles as the electrode composition.

[Formula 1]

0 <Amount of positive charge per weight of metal cation / Amount of charge per weight of polymer chain ≤ 1

The active material particles may be selected from active materials having a volume change rate of 100% to 400% at the time of charge / discharge of the battery. The active material particles may be any one of Sn, Si, Sb, Zn, Ge, Al, Cu, Bi, Cd, Mg, As, Ga, Pb and Fe; Intermetallic compounds thereof; Oxides thereof; Or an active material core formed of a nitride thereof. Further, in some embodiments, the active material particles may include an active material core and a conductive layer coated on the active material core.

According to another aspect of the present invention, there is provided a method of manufacturing an electrode composition for a secondary battery, comprising: providing active material particles for a battery in a polar solvent; Providing polymer chains having anionic groups in the polar solvent; Providing two or more metal cations in the polar solvent; Forming a binder complex including the polymer chains and the metal cations on the active material particles by inducing ionic bonding between the anion groups of the polymer chains and the metal cations; And obtaining the active material particles.

In some embodiments, the polar solvent is selected from the group consisting of water, alcohols, acetic acid, acetone, N, N-dimethylformamide, N, N-dimethylacetamide or N-methylpyrrolidone (NMP), octylether, butylether, But are not limited to, benzyl ether, phenyl ether, decyl ether, ethyl methyl ether, dimethyl ether, diethyl ether, diphenyl ether, tetrahydrofuran, 1,4-dioxane, polyethylene glycol (PEG), polypropylene glycol (PTMG), polyoxymethylene (POM), polytetrahydrofuran, polyethylene terephthalate, acrylate ester, cellulose acetate, isobutyl acetate, isopropyl acetate, allyl hexanoate, benzyl acetate ), Bornyl acetate, butyl acetate or lactone, preferably the polar solvent is water.

According to the embodiment of the present invention, by fixing the active material particles with the binder composite having polymer chains having strong polymer chains bonded to each other by ionic bonding, the volume change ratio accompanying the charge and discharge of the active material particles is reduced, The lifetime and reliability of the lithium ion secondary battery can be improved and the metal ions do not deteriorate the charging and discharging characteristics of the battery in the case of the lithium secondary battery but rather contribute to the improvement of the life span and the reliability. In addition, since the active material particles are fixed between the active material particles or between the active material particles and the active material particles regardless of the size of the active material particles by strong ionic bonding, the amount of binder used can be minimized, And the binder complex segregates the surface of the active material particles and the electrolyte to prevent the undifferentiated particles of the active material, thereby improving the life and reliability.

In addition, according to the embodiments of the present invention, since the active material particles and the binder complex can be simultaneously formed in the polar solvent by using a polar solvent, preferably water, the binder complex is uniformly wetted to the active material particles And can provide a production method capable of forming an electrode composition for a battery economically and rapidly in a large amount while minimizing the environmental load when water is used.

1 shows a structure of a binder composite according to an embodiment of the present invention.
2A and 2B are cross-sectional views illustrating structures of active material particles according to various embodiments of the present invention.
3 is a flowchart showing a method of manufacturing a battery active material composition according to an embodiment of the present invention.
4A to 4C are transmission electron microscope images showing the active material particles prepared according to Examples 1 to 3 of the present invention, respectively.
FIGS. 5A and 5B are graphs showing the capacity and the capacity retention rate for the number of charge / discharge cycles of the half-cells manufactured using the electrode compositions according to Examples 1 to 3 and Comparative Examples, respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified in various other forms, The present invention is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

In the following drawings, thickness and size of each layer are exaggerated for convenience and clarity of description, and the same reference numerals denote the same elements in the drawings. As used herein, the term "and / or" includes any and all combinations of any of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a,""an," and "the" include singular forms unless the context clearly dictates otherwise. Also, &quot; comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

1 shows the structure of a binder composite 10 according to an embodiment of the present invention.

1, the binder composite 10 is ionically bonded to the polymer chains 10_2 each having at least one anion group 10_1 and the anion group 10_1 of each polymer chain 10_2, And a divalent or more metal cation 10_3 that fixes the metal ions 10_2 to each other.

The polymer chains 10_2 may be linear polymers, branched polymers, or crosslinked polymers having a three-dimensional structure. Preferably, the polymer chains 10-2 may be linear polymers. Even when the active material particles to be described below are miniaturized to have a nano-sized diameter, the linear polymer is in point contact with the active material particles, thereby securing sufficient pores to prevent reduction of lithium migration by the binder composite 10, In the slurry production process of the present invention, it is possible to maintain the appropriate viscosity by plasticity, thereby facilitating the application to the current collector.

The polymer chains 10-2 may be a homopolymer or a copolymer. The average molecular weight of the polymer chains (10_2) is in the range of 40,000 g / mol to 3,000,000 g / mol. When the average molecular weight of the polymer chains (10_2) is less than 40,000 g / mol, the molecular size of the active material particles having an average diameter of several tens of nanometers to several hundreds of micrometers is small, Sufficient binding force can not be obtained. When it exceeds 3,000,000 g / mol, uniform mixing between the metal cation and the polymer chain becomes difficult, which makes it difficult to produce a slurry and a sufficient bonding force can not be obtained between the active material particles.

In one embodiment, the polymer chains 10_2 may be selected from the group consisting of polysaccharides, styrene butadiene, acrylates, ethylene vinyl acetate, polyacrylonitrile, acrylonitrile-butadiene-styrene, poly (vinyl chloride) ), Polyvinyl pyrrolidone, carboxylated styrene-butadiene, alginic acid, sodium alginate, carboxymethyl cellulose, carboxymethyl starch, carboxymethyl guar gum carboxymethyl guar gum, carboxymethyl xanthane gum, carboxymethyl tara gum, low methoxyl pectin, carrageenan, polyacrylic acid, But are not limited to, polypropylene, polystyrene, poly (methylmethacrylate), nylon, polyethylene, (Polymer of isoprene), or a mixture thereof. Preferably, the polymer chains 10_2 are selected from the group consisting of cellulose, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, It is also possible to use linear polymers such as polyacrylic acid, polypropylene, polystyrene, poly (methylmethacrylate), nylon, polyethylene, cellulose, amylose amylose, natural rubber (a polymer of isoprene), or mixtures thereof.

Anion exchanger (10_1) is _{^{-CO 2 -, -SO 2 -,}} -SO 3 -, -OSO 3 -, -PO 3 2-, -OPO 3 2-, -OP (OH) O -, -CS 2 - Or -OCO ₂ ^- . The anion group 10_1 may be bonded to the main chain and / or side chains of the polymer chains 10_2. 1 illustrates that the anion group 10_1 is bonded to the main chain of the polymer chains 10_2. The anion groups 10_1 allow the polymer chains 10_2 to be locally electrically negatively charged in a solvent, for example, a polar solvent or slurry state.

The metal cation 10_3, which is ionically bonded to the anion group 10_1 and fixes the polymer chains 10_2, is electrically charged positively in the solvent. Therefore, in the solvent, the anion groups 10_1 and the metal cations 10_3 of the polymer chains 10_2 are locally ion-bonded as indicated by dotted ellipses IB. As a result, the polymer chains 10_2 have a mechanically strong and pore network structure.

The metal cation 10_3 may be divalent or more since it is required to fix the different polymer chains 10_2 by ionic bonding with the anion groups 10_1 of the polymer chains 10_2. The ratio K of the addition amount of the metal cation (10_3) considering the valence of the metal cation (10_3) and the charge amount depending on the addition amount of the polymer chains can be determined so as to satisfy the following formula (1). The amount of charge of the metal cation (10_3) is the number of cations × the number of ions, and the charge amount of the polymer chains (10_2) is the number of anion groups (10_1) × number of ions.

 [Formula 1]

0 <Amount of positive charge per weight of metal cation / Amount of charge per weight of polymer chain ≤ 1

When K is more than 0 and less than 1, the intermolecular chain linkage bonds between the polymer chains mediated by the metal cations. When the K is more than 1, the metal cations can be exposed in a free state in the electrolyte, It may adversely affect the reduction reaction. When K is more than 0 and less than 1, the intermolecular chain linkage bonds between the polymer chains mediated by the metal cations. When the K is more than 1, the metal cations can be exposed in a free state in the electrolyte, It may adversely affect the reduction reaction. Preferably, the K value can be determined according to the kind of the metal cation to be added. This will be described later.

The bivalent or higher metal cation (10_3) may include a cation of an alkaline earth metal, a transition metal, or an alloy thereof. The alkaline earth metal may include beryllium, magnesium, calcium, strontium, or barium. The transition metal may be, for example, titanium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel or copper; Yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, or cadmium; Or hafnium, tantalum, tungsten, or iridium.

2A and 2B are sectional views showing the structure of the active material particles 20A and 20B according to various embodiments of the present invention.

Referring to FIG. 2A, the active material particle 20A may include a binder composite 10 surrounding at least a part of the active material core 20_1 and the active material core 20_1. For the binder composite 10, reference can be had to that disclosed in Fig.

In one embodiment, the active material core 20_1 may be an energy storage material capable of charging and discharging the battery. For example, the active material core 20_1 may be made of a metal, a metalloid or a metal, which accompanies the oxidation and reduction reaction of lithium ions by a reversible reaction mechanism such as alloying and arming with lithium ions, occlusion and release, or adsorption / And a mixture of these materials. In one embodiment, the metal or metalloid is selected from Sn, Si, Sb, Zn, Ge, Al, Cu, Bi, Cd, Mg, As, Ga, Pb and Fe, or SnSb, SnAg, and Sn ₂ Fe. &Lt; / RTI &gt;

However, the above-described metal or metalloid active material core 20_1 is illustrative, and the present invention is not limited thereto. For example, the active material core 20_1 may include other materials capable of obtaining a high capacity since the stress due to the rate of change in volume accompanying the charging and discharging of the battery can be alleviated by the binder composite 10. For example, the active material core (20_1) may be a volume change rate is within a range of materials of 100% to 400% caused by the charge and discharge of the battery, and other high capacity of silicon oxide rather than a metal or metalloid (SiO ₂₎ or An oxide such as tin oxide (SnO ₂ ), or a nitride such as Li _x M _y N ₂ (where M is a metal). Alternatively, it may have a mixed structure of the above-mentioned materials or a composite structure such as a core-shell.

In another embodiment, the active material core 20_1 may include a positive electrode active material. For example, the positive electrode active material may include lithium salts such as lithium manganese oxide, lithium cobalt oxide, or lithium ion phosphorous.

The active material core 20_1 may be primary particles of the above-described materials or secondary particles formed by aggregating these primary particles together. The average particle diameter of the active material core 20_1 may be within the range of 20 nm to 2 mu m and may be appropriately selected depending on the application of the battery and the electrode structure.

In some embodiments, the active material core 20_1 may have voids (not shown) therein. The void may be a cavity in which a plurality of separated cavities or cavities are communicated with each other within the active material core 20_1 and extends to the surface of the active material core 20_1 to form a passage connecting the inside of the active material core 20_1 with the surface . Through the voids, lithium ions can perform an electrochemical reaction with the active material core 20_1 such as alloying and dialing, occlusion and release, or adsorption / desorption, and the reaction surface area between the active material core 20_1 and lithium And can function as a buffer for the volume expansion of the active material core 20_1 upon charging.

The active material cores 20_1 which are in contact with each other via the binder composite 10 can be fixed to each other by the binder composite 10 coating each of the active material cores 20_1 with each other. The binder between the binder complex 10 and the anion group 10_1 of the polymer chains 10_2 itself and the polymer chains 10_2 by ionic bonds between the anions 10_1 and 10_3 of the polymer chains 10_2, ). &Lt; / RTI &gt;

Since the ionic bonds more strongly bind the polymer chains 10_2 than the covalent bonds, the ionic bonds can increase the tensile strength of the polymer chains 10_2 and increase the elastic modulus of the entire binder complex 10. As a result, according to the embodiment of the present invention, it is possible to reduce the rate of change in volume accompanying the charging / discharging between the active material particles 20A including the active material core 20_1 so that the volume change rate becomes 100% to 400% In addition, it is possible not only to improve the initial charging efficiency with a large volume expansion, but also to prevent cracking due to volume change and to improve the service life. In addition, strong ionic bonding can improve the energy density of the battery by minimizing the amount of the binder that reduces the energy density of the battery, as compared with the conventional binder that fixes the active material particles only by the covalent bond.

Referring to FIG. 2B, the active material particle 20B may further include a conductive layer 20_2 on the active material core 20_1. Accordingly, the active material core 20_1 and the conductive layer 20_2 may have a core-shell structure. The conductive layer 20_2 is for electrical connection between the active material cores 20_1 that contact each other and reduces the internal resistance of the electron path between the active material core 20_1 and the current collector (not shown).

In some embodiments, the conductive layer 20_2 may comprise a crystalline or amorphous carbon-based conductive layer, such as graphite, soft carbon, carbon nanotubes, or graphene. The carbon-based conductive layer may have a conductive SP ₂ graphite structure and an insulating SP ₃ diamond structure. In order for the carbon-based conductive layer to have conductivity, the SP ₂ has a larger mole fraction than SP ₃ Which can be controlled and secured through the heat treatment process described below. In another embodiment, the conductive layer 20_2 may be a nanostructured particle of a conductive metal oxide, such as antimony zinc oxide or antimony tin oxide, or a layer containing it. The materials for the conductive layer 20_2 are illustrative, and the present invention should not be limited thereto.

The thickness of the conductive layer 20_2 may be 2 nm to 5 [mu] m, and the present invention is not limited thereto. The conductive layer 20_2 functions as a physical barrier that isolates the active material core 20_1 in the entire electrode from other active material cores. As a result, agglomeration between the active material cores 20_1 can be prevented.

2B illustrates the structure of one active material particle 20B. However, as described with reference to FIG. 2A, a plurality of active material particles 20B are firmly fixed by the binder complex 10 surrounding the active material particles 20B to form an electrode layer can do. The binder complex 10 functions as a resilient matrix as a buffer for volume expansion due to charging and discharging of the battery. In particular, when the binder composite 10 has a linear structure, sufficient pores are secured in the network structure, Can freely pass between the active material particles 20B and the electrolyte (not shown) without lowering the mobility.

3 is a flowchart showing a method of manufacturing a battery active material composition according to an embodiment of the present invention.

Referring to FIG. 3, active material particles are dispersed in a polar solvent (S10). The active material particles are materials having a particle structure including the above-described active material core 20_1, and optionally the conductive film 20_2 with reference to Figs. 2A and 2B. The polar solvent may be selected from a liquid solvent capable of inducing dispersion of the active material particles and capable of easily dissolving and dispersing a polymer chain having an anion group described below. For example, the polar solvent may be selected from the group consisting of water, alcohol (including, but not limited to, methanol, ethanol, isobutyl alcohol, octanol, polyvinyl alcohol ethyl alcohol, methyl alcohol, isopropyl alcohol, isobutyl alcohol, Cyclohexanol, octyl alcohol, decanol, hexatecanol, glycerol, propylene glycol, ethylene glycol, propylene glycol, pinacol, 1,2-octanediol, 1,2-dodecanediol and 1,2- Or a mixture thereof, and other primary alcohol, secondary alcohol and tertiary alcohol may be used), acetic acid, acetone, N, N-dimethylformamide, N, N- Methylpyrrolidone (NMP).

In another embodiment, the polar solvent is selected from the group consisting of octyl ether, butyl ether, hexyl ether, benzyl ether, phenyl ether, decyl ether, ethyl methyl ether, dimethyl ether, diethyl ether, diphenyl ether, tetrahydrofuran, And cyclic ethers such as dioxane or polyethers such as polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), polyoxymethylene (POM) and polytetrahydrofuran. Alternatively, the polar solvent may be selected from the group consisting of polyethylene terephthalate, acrylate esters and cellulose acetate, isobutyl acetate, isopropyl acetate, allyl hexanoate, benzyl acetate, bornyl acetate, Or cyclic ester-based daily such as lactone. Preferably, however, the liquid solvent is water capable of minimizing the environmental load.

Polymer chains having anionic groups in the polar solvent are provided (S20). The polymer chains may be dissolved and / or dispersed in the polar solvent. In one embodiment, the polymer chains may be added to the polar solvent in a monomorphic form having an anion group, and then polymerized into the polymer chains by injecting energy such as light, initiator, and heat. In another embodiment, the polymer chains may be provided in the polar solvent in solid or liquid form, with the polymer chains previously polymerized externally.

Thereby providing two or more metal cations in the polar solvent (S30). The metal cations may be provided in the polar solvent in the form of a metal salt. The metal salt may be ionized in the polar solvent. The metal salts may be oxides, carbonates, nitrides, nitrates, sulfides, sulfides, hydroxides or halides of alkaline earth metals and transition metals, but the present invention is not limited thereto. For example, the calcium ion may be provided in the polar solvent as a halide chloride (CaCl ₂ ) or hydroxide (Ca (OH) ₂ ). In addition, magnesium may be provided as a sulfur oxide (MgSO ₄ .7H ₂ O). These salts can be applied to any compound that can be easily ionized in a polar solvent among commercially available compounds, and thus the present invention is not limited thereto. Alternatively, the metal cations may be provided by dissociable organic or inorganic metal polymer precursors in the polar solvent, such as polyaluminum chloride.

In one embodiment, the metal salt or metal polymer precursor can be provided such that the ratio K of the polymer chains and the metal cations can satisfy Equation 1 below. If K is greater than 0, the bonds between the polymer chains can be achieved. If it exceeds 1, metal cations can be exposed in the electrolyte in a free state, which can adversely affect the oxidation and reduction of lithium.

[Formula 1]

0 <Amount of positive charge per weight of metal cation / Amount of charge per weight of polymer chain ≤ 1

Also, the ratio K can be selected in consideration of the average diameter of the secondary particles, which is the electrode composition synthesized. For example, from experiments, Ca (OH) 2, the precursor of Ca, forms a suitable secondary particle size at 0.5 ≤ K ≤ 1. When the K value is less than 0.5, aggregation between the active material particles does not occur well, and secondary particles of active material particles having an appropriate size can be obtained when the K value is 0.5 or more. As another example, in the case of polychlorinated aluminum, it has a suitable secondary particle size at 0 < K? 0.3. When K is more than 0.3, the size of the secondary particles becomes large, and an additional process such as a pulverization process is required for use, which is not suitable for application as an active material composition.

The active material particles may be selected from an active material having a theoretical value of volume change rate during charge / discharge of the battery within a range of 100% to 400%. In this case, the K value is preferably set to 0 (zero) so as to have a suitable secondary particle size and a strength capable of suppressing the rate of volume change for ensuring the capacity retention rate and lifetime for the active material having a volume change rate during the charging / discharging of 100% And may be selected within a range of 1 or less.

The active material particles may be any one of Sn, Si, Sb, Zn, Ge, Al, Cu, Bi, Cd, Mg, As, Ga, Pb and Fe; Intermetallic compounds thereof; Oxides thereof; Or an active material core formed of a nitride thereof. Further, in some embodiments, the active material particles may include an active material core and a conductive layer coated on the active material core.

In some embodiments, a surfactant may be added to the polar solvent to improve dispersion stability of the metal cations and / or active material particles. The surfactant may be selected from, for example, octylamine, trioctylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, olefins, C24 to C24 amine surfactants selected from the group consisting of oleylamine, octadecylamine, tribenzylamine, triphenylamine, or mixtures thereof.

The above-described steps S10-S30 may be performed sequentially or any one of the steps may be reversed. For example, polymer chains may be first provided in a polar solvent (S20), and then active materials and metal ions may be added to the polar solvent (S10, S30). At this time, the stirring process can be performed, and further, additional operations such as temperature control and ultrasonic dispersion can be performed.

In some embodiments, a conductive material may be added together in the polar solvent. The conductive material may be carbon black, ultrafine graphite particles, fine carbon such as acetylene black, nano metal particle paste, or ITO (indium tin oxide) paste, but the present invention is not limited thereto.

According to the steps S10-S30, the polymer chains are coated on the active material particles, and the polymer chains coating the active material particles with the metal cations are strengthened to form a layer composed of the binder complex (S40). In addition, the active material particles coated with the binder composite are in contact with each other, and the binder composites that are in contact with each other are bonded to each other via metal cations, so that the active material particles are agglomerated. When the conductive material is added in the polar solvent, the conductive material together with the active material particles will be fixed to the outside of the active material particle by the binder composite.

After the agglomerated active material particles are obtained, they are dried and disintegrated using a suitable milling or classifier to obtain active material particles coated with the binder composite. Thereafter, the active material particles are prepared in dry or slurry form and coated or impregnated into the current collector in a wet manner to form an electrode. The binder composite that coats the active material particles can be used as a binder for fixing between the current collector and the active material particles.

Example

The negative electrode composition was synthesized according to the embodiments of the present invention described above. Table 1 shows the results of Examples 1 to 3 as shown in Table 1, in which the active material particles of the negative electrode composition, the precursor of the binder complex, and the combination of the polar solvent are distinguished. In addition, as a comparative example to the embodiments of the present invention, a negative electrode composition in which a binder was composed of only polymer chains was synthesized without applying a metal salt.

About 10 g of nanosilicon or nanosilicon-carbon composite is added to 100 ml of a polar solvent in which about 0.5 g of polymer chains including anion groups are dissolved and dispersed for 24 hours using a ball mill. Thereafter, Ca (OH) ₂ or poly (aluminum chloride), which is a metal salt, is added to the mixed solution to induce ionic bonding between the binder having the anion group and the metal cation Ca ²⁺ or Al ³⁺ , A negative electrode composition for a secondary battery, which is an agglomerated body containing shell composite particles, was synthesized.

Example Active material particle Binder complex precursor Polar solvent /
volume Polymer chains /
Average molecular weight Metal salt /
Average weight Example 1 silicon
Core particle PAA (polyacrylamide) /
Mw 450,000 g / mol Ca (OH) ₂ /
0.25 g Methanol /
100 ml Example 2 Silicon core /
Carbon shell composite particle PAA (polyacrylamide) /
450,000 g / mol Polychlorinated aluminum /
0.1 mg Methanol /
100 ml Example 3 Silicon core /
Carbon shell composite particle PVP (polyvinyl pyrolidone) /
1,250,000 g / mol Ca (OH) ₂ /
0.4 g Distilled water/
100 ml Comparative Example Silicon particles PAA
450,000 g / mol - Methanol /
100 ml

Examples 1 to 3 are illustrative and the present invention is not limited thereto. It is also possible to disperse the active material particles first in the polar solvent, followed by adding the precursor of the polymer chains.

4A to 4C are transmission electron microscope images showing the active material particles prepared according to Examples 1 to 3 of the present invention, respectively. Referring to these drawings, the active material particles are primary particles including a carbon layer 20_2 which is a conductive layer coated on a silicon core 20_1 or a silicon core 20_1, and a binder composite on the active material particles It can be confirmed that the coating layer 10 is formed with a uniform thickness.

Table 2 shows the results of measuring the tensile strength of the binder complex constituting the negative electrode composition for a secondary battery according to each of Examples 1 to 3 of the present invention. The tensile strength of only the PAA according to the comparative example was 90 MPa, and the tensile strength of the binder complexes of Examples 1 to 3 was remarkably improved to 55 to 65% as compared with the comparative example.

Example Binder complex The tensile strength Example 1 PAA / Ca About 150 MPa Example 2 PAA / Al About 150 MPa Example 3 PVP / Ca 140 MPa Comparative Example PAA About 90 MPa

FIGS. 5A and 5B are graphs showing the capacity and the capacity retention rate for the number of charge / discharge cycles of the half-cells manufactured using the electrode compositions according to Examples 1 to 3 and Comparative Examples, respectively. In these graphs, the curves EX_1, EX_2 and EX_3 are the measurement results of the half-cells according to the first to third embodiments, respectively, and RE is the measurement result of the half-cell according to the comparative example. The rate of charge / discharge rate is 0.5C.

Referring to Figs. 5A and 5B, in the case of Examples 1 to 3 and Comparative Example, the initial capacity shows a capacity larger than 2,500 mAh / g. However, the capacity is maintained at 90% or more in the case of the 50 cycles, while the capacity is reduced to 75% in the case of the comparative example. Table 3 shows the average electrode expansion rate of the cathode according to Experimental Examples 1 to 3 and the thickness variation of the average electrode expansion rate of the cathode according to the comparative example. Referring to Table 3, in the case of Examples 1 to 3, the change in thickness during charging was suppressed to less than 150% based on the initial thickness, and the change in thickness during charging and discharging was suppressed to 30% or less based on the charging time .

However, the electrode according to the comparative example showed a change in the thickness at the time of charging at about 220% based on the initial thickness, and the change in thickness during charging and discharging showed a thickness change of more than 50% .

Average electrode inflation rate Example 1 Example 2 Example 3 Comparative Example A * 133% 142% 139% 220% B ** 32% 28% 29% 52%

* A = (Thickness at charging - Initial thickness) / Thickness at charging x 100 (%)

** B = (Thickness at charging - Thickness at discharging) / Thickness at charging x 100 (%)

Therefore, by fixing the active material particles with the binder composite having polymer chains in which the lifetime and the capacity retention rate of Examples 1 to 3 are improved more strongly than those of the Comparative Examples by ionic bonds, It is considered that the expansion ratio is effectively suppressed. According to the embodiment of the present invention, it can be seen that even in the case of the non-carbon anode material having a large volume change rate, stable lifetime and reliability can be secured. In addition, since the active material particles are fixed between the active material particles or between the active material particles and the active material particles regardless of the size of the active material particles by strong ionic bonding, the amount of binder used can be minimized, Can be improved.

Although the above-described embodiments relate to negative electrode active material particles, the same applies to the case of the positive electrode as described above. In addition, the electrode composition described above may be prepared by dispersing active material particles into primary particles or secondary particles and dispersing them in a solvent as a slurry to be applied to the current collector, or further adding a binder to the current collector have.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be clear to those who have knowledge.

Claims (20)

Polymer chains each having at least one anion group; And a binder complex comprising divalent or more metal cations ionically bonded to the at least one anion group to fix the polymer chains to each other; And
And active material particles fixed by the binder composite,
The polymer chains may be selected from the group consisting of polysaccharide, styrene butadiene, acrylate, ethylene vinyl acetate, polyacrylonitrile, acrylonitrile-butadiene-styrene, poly (vinyl chloride), poly (vinylidene chloride), polyvinylpyrrolidone, Alginic acid, sodium alginate, carboxymethyl cellulose, carboxymethyl starch, carboxymethyl guar gum, carboxymethyl cellulose, carboxymethyl cellulose, carboxymethyl cellulose, But are not limited to, carboxymethyl xanthane gum, carboxymethyl tara gum, low methoxyl pectin, carrageenan, polyacrylic acid, polypropylene, polystyrene polystyrene, poly (methylmethacrylate), nylon, polyethylene, cellulose, Milos (amylose), chitosan, glucose, and include sucrose, maltose, lactose, starch, glycogen, natural rubber (a polymer of isoprene) or mixtures thereof,
The anionic group is _{^{-CO 2 -, -SO 2 -,}} -SO 3 -, -OSO 3 -, -PO 3 2-, -OPO 3 2-, -OP (OH) O -, -CS 2 - or -OCO ₂ ^- , &lt; / RTI &gt;
Wherein the metal cations include cations of an alkaline earth metal, a transition metal, or an alloy thereof, wherein the alkaline earth metal includes beryllium, magnesium, calcium, strontium, or barium, and the transition metal is selected from the group consisting of titanium, scandium, titanium, vanadium , Chromium, manganese, iron, cobalt, nickel or copper; Yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, or cadmium; Or an electrode composition for a secondary cell comprising hafnium, tantalum, tungsten, or iridium. The method according to claim 1,
Wherein the average molecular weight of the polymer chains is in the range of 40,000 g / mol to 3,000,000 g / mol. delete The method according to claim 1,
Wherein the polymer chains have a linear structure. 5. The method of claim 4,
The polymer chains may be selected from the group consisting of polyacrylic acid, polypropylene, polystyrene, poly (methylmethacrylate), nylon, polyethylene, cellulose, amylose, amylose, natural rubber (polymer of isoprene), or a mixture thereof. delete delete delete The method according to claim 1,
Wherein the ratio of the polymer chains to the metal cations satisfies the following formula:
[expression]
0 <Amount of positive charge per weight of metal cation / Amount of charge per weight of polymer chain ≤ 1. The method according to claim 1,
Wherein the active material particles are selected from an active material having a volume change rate of 100% to 400% at the time of charge / discharge of the battery. The method according to claim 1,
The active material particles may be any one of Sn, Si, Sb, Zn, Ge, Al, Cu, Bi, Cd, Mg, As, Ga, Pb and Fe; Intermetallic compounds thereof; Oxides thereof; Or an active material core formed of a nitride thereof. The method according to claim 1,
Wherein the active material particles further comprise an active material core and a conductive layer coated on the active material core. Providing active material particles for a secondary battery in a polar solvent;
Providing polymer chains having anionic groups in the polar solvent;
Providing two or more metal cations in the polar solvent;
Forming a binder complex including the polymer chains and the metal cations on the active material particles by inducing ionic bonding between the anion groups of the polymer chains and the metal cations; And
And obtaining the active material particles,
The polymer chains may be selected from the group consisting of polysaccharide, styrene butadiene, acrylate, ethylene vinyl acetate, polyacrylonitrile, acrylonitrile-butadiene-styrene, poly (vinyl chloride), poly (vinylidene chloride), polyvinylpyrrolidone, But are not limited to, carboxylated styrene-butadiene, alginic acid, sodium alginate, carboxymethyl cellulose, carboxymethyl starch, carboxymethyl guar gum, But are not limited to, carboxymethyl xanthane gum, carboxymethyl tara gum, low methoxyl pectin, carrageenan, polyacrylic acid, polypropylene, polystyrene polystyrene, poly (methylmethacrylate), nylon, polyethylene, cellulose, Milos (amylose), chitosan, glucose, and include sucrose, maltose, lactose, starch, glycogen, natural rubber (a polymer of isoprene) or mixtures thereof,
The anionic group is _{^{-CO 2 -, -SO 2 -,}} -SO 3 -, -OSO 3 -, -PO 3 2-, -OPO 3 2-, -OP (OH) O -, -CS 2 - or -OCO ₂ ^- , &lt; / RTI &gt;
Wherein the metal cations include cations of an alkaline earth metal, a transition metal, or an alloy thereof, wherein the alkaline earth metal includes beryllium, magnesium, calcium, strontium, or barium, and the transition metal is selected from the group consisting of titanium, scandium, titanium, vanadium , Chromium, manganese, iron, cobalt, nickel or copper; Yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, or cadmium; Or an electrode composition for a secondary battery comprising hafnium, tantalum, tungsten, or iridium. 14. The method of claim 13,
Wherein the average molecular weight of the polymer chains is in the range of 40,000 g / mol to 3,000,000 g / mol. delete 14. The method of claim 13,
Wherein the polymer chains have a linear structure. 17. The method of claim 16,
The polymer chains may be selected from the group consisting of polyacrylic acid, polypropylene, polystyrene, poly (methylmethacrylate), nylon, polyethylene, cellulose, amylose, (amylose), natural rubber (polymer of isoprene), or a mixture thereof. delete delete 14. The method of claim 13,
The polar solvent may be selected from the group consisting of water, alcohol, acetic acid, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone (NMP), octylether, butylether, hexylether, (PEG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), polytetramethyleneglycol (PTMG), polyethyleneglycol Polyoxyethylene (POM), polytetrahydrofuran, polyethylene terephthalate, acrylate ester, cellulose acetate, isobutyl acetate, isopropyl acetate, allyl hexanoate, benzyl acetate, bornyl acetate, butyl acetate or a lactone.

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