WO2015126227A1

WO2015126227A1 - Electrode composition for secondary battery and preparation method therefor

Info

Publication number: WO2015126227A1
Application number: PCT/KR2015/001781
Authority: WO
Inventors: 조영태; 최용길; 박승철; 서희영; 이용의; 홍영진
Original assignee: (주)오렌지파워
Priority date: 2014-02-24
Filing date: 2015-02-24
Publication date: 2015-08-27
Also published as: KR101561678B1; KR20150100028A

Abstract

The present invention relates to an electrode composition for a secondary battery and a preparation method therefor. The electrode composition according to one embodiment of the present invention comprises a binder composite and active material particles fixed by the binder composite, wherein the binder composite comprises: polymer chains each having at least one anion radical; and at least divalent metal cations which are ionically bonded to the at least one anion radical, thereby fixing the polymer chains to each other.

Description

Electrode composition for secondary battery and method for producing same

TECHNICAL FIELD The present invention relates to secondary battery technology, and more particularly, to an electrode composition for a secondary battery and a method of manufacturing the same.

The secondary battery is a battery which can be charged and discharged using an electrode material having excellent reversibility, and typically a lithium secondary battery has been commercialized. The lithium secondary battery is not only a small power source of small IT devices such as smart phones, portable computers, and electronic paper, but also a medium-large power source that is mounted on a vehicle such as an automobile or used for power storage of a power supply network such as a smart grid. Applications are expected.

When lithium metal is used as a negative electrode material of a lithium secondary battery, graphite may be intercalated and deintercalated in place of the lithium metal, because there is a risk of battery short circuit or explosion due to the formation of dendrites. And crystalline carbon or soft carbon such as artificial graphite, and hard carbon and carbon-based active materials. However, as the application of the secondary battery is expanded to not only a small power source but also a medium-large power source, there is a continuous demand for high capacity and high output of the lithium secondary battery. In response to these demands recently, metal and metalloid negative electrode materials or spinel structures capable of alloying with lithium such as silicon (Si), tin (Sn), or aluminum (Al) having a theoretical capacity of 8 times higher than carbon-based materials. Attention has been paid to non-carbon-based negative electrode materials containing metal oxides such as lithium titanium oxide (LTO).

However, the non-carbon-based negative electrode material has problems such as breakdown of the electrical connection between the active materials due to volume change in the process of charging and discharging the battery, separation of the active material from the current collector, and erosion of the active material by the electrolyte. There is a barrier. Therefore, in order to apply a non-carbon negative electrode material, it is required to improve the irreversibility of a battery according to the volume change at the time of charge and discharge.

In addition, for fast charging and discharging, bonding between active material particles and maintaining adhesion between the particles and the current collector are required, in which case a large amount of binder is required. The binder acts as an electrical resistance element of the electrode, ultimately lowering the overall energy density of the battery and reducing the charge and discharge efficiency.

Accordingly, the technical problem to be solved by the present invention is to minimize the amount of the binder by securing the electrode adhesion without deteriorating the charge and discharge characteristics of the secondary battery, and also to reduce the volume change accompanying the charge and discharge of the battery. It is providing the secondary battery electrode composition which can suppress and improve the lifetime of a battery.

In addition, another technical problem to be solved by the present invention is to provide a manufacturing method capable of economically and quickly forming a large amount of the electrode composition for secondary batteries having the above-described advantages.

An electrode composition for a secondary battery according to an embodiment of the present invention for solving the above technical problem includes a binder composite and active material particles fixed by the binder composite. The binder composite includes polymer chains each having at least one anionic group; And divalent or more metal cations ion-bonded with the at least one anionic group to fix the polymer chains together.

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 polysaccharide, styrene butadiene, acrylate, ethylene vinyl acetate, polyacrylonitrile, acrylonitrile-butadiene-styrene, poly (vinyl chloride), poly (vinylidene chloride), poly Vinylpyrrolidone, carboxylated styrene-butadiene, alginic acid, sodium alginate, carboxymethyl cellulose, carboxymethyl starch, carboxymethyl guar gum gum, carboxymethyl xanthane gum, carboxymethyl tara gum, low methoxyl pectin, carrageenan, polyacrylic acid, polyproylene (polypropylene), polystyrene, poly (methylmethacrylate), nylon (nylon), polyethylene (polyethylen), cell 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 include polyacrylic acid, polypropylene, polystyrene, poly (methylmethacrylate), nylon (nylon), polyethylene (polyethylen), and cellulose (polyacrylic acid). cellulose, amylose, natural rubber (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 ^- may be included. The metal cations are cations of alkaline earth metals, transition metals or alloys thereof. The alkaline earth metal may include beryllium, magnesium, calcium, strontium, or barium, and the transition metal may include 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 may satisfy the following Equation 1. The value of the ratio may be selected in consideration of the average diameter of the secondary particles which are the synthesized electrode composition.

[Equation 1]

0 <positive charge per weight of metal cations / negative charge per weight of polymer chains ≤ 1

The active material particles may be selected from active materials having a volume change rate of 100% to 400% during charging and discharging of a battery. The active material particles are any one of Sn, Si, Sb, Zn, Ge, Al, Cu, Bi, Cd, Mg, As, Ga, Pb and Fe; Intermetallic compounds thereof; Oxides thereof; Or it may include an active material core formed of a nitride thereof. In addition, 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, the method comprising: providing active material particles for a battery in a polar solvent; Providing polymer chains having anionic groups in the polar solvent; Providing divalent or more metal cations in the polar solvent; Inducing an ionic bond between the anionic groups of the polymer chains and the metal cations to form a binder composite including the polymer chains and the metal cations on the active material particles; And obtaining the active material particles.

In some embodiments, the polar solvent is water, alcohol, acetic acid, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, or N-Methylpyrrolidone (NMP), octyl ether, butyl ether, hexyl ether, Benzyl ether, phenyl ether, decyl ether, ethyl methyl ether, dimethyl ether, diethyl ether, diphenyl ether, tetrahydrofuran, 1,4-dioxane, polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene Glycol (PTMG), polyoxymethylene (POM), polytetrahydrofuran, polyethylene terephthalate, acrylate esters, cellulose acetate, isobutyl acetate, isopropyl acetate, aryl hexanoate, benzyl acetate ), Bornyl acetate, butyl acetate or lactone, preferably the polar solvent is water.

According to an embodiment of the present invention, by fixing the active material particles by a binder composite having polymer chains strongly bonded to each other by ion bonding, the rate of change in volume accompanying charge and discharge of the active material particles is reduced, thereby using a non-carbon negative electrode material. In addition, the lifespan and reliability can be improved, and the metal ions do not deteriorate the charge / discharge characteristics of the battery in the case of a lithium secondary battery. In addition, since the strong ionic bonds fix the particles between the active material particles or the current collector and the active material particles regardless of the size of the active material particles, the amount of the binder is minimized compared to the conventional binder which fixes the active material particles only by covalent bonding. To improve the energy density of the binder composite is to isolate the surface of the active material particles and the electrolyte solution to prevent the differentiation of the active material particles to improve the life and reliability.

In addition, according to embodiments of the present invention, since the active material particles and the binder composite can be simultaneously formed in the polar solvent using a polar solvent, preferably water, the binder composite may be uniformly wetted on the active material particles. In addition, when using water, a manufacturing method capable of economically and rapidly forming a large amount of electrode composition for a battery while minimizing environmental load may be provided.

1 illustrates 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 disclosure.

3 is a flowchart illustrating 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 active material particles prepared according to Examples 1 to 3, respectively, of the present invention.

5A and 5B are graphs showing capacity and capacity retention with respect to the number of charge / discharge cycles of half batteries manufactured using the electrode compositions according to Examples 1 to 3 and Comparative Examples, respectively.

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

The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art, and the following examples can be modified in various other forms, and the scope of the present invention is It is not limited to an Example. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art.

In addition, in the following drawings, the thickness or size of each layer is exaggerated for convenience and clarity of description, the same reference numerals in the drawings refer to the same elements. As used herein, the term “and / or” includes any and all combinations of one or more 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" may include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, "comprise" and / or "comprising" specifies the presence of the mentioned shapes, numbers, steps, actions, members, elements and / or groups of these. It is not intended to exclude the presence or the addition of one or more other shapes, numbers, acts, members, elements and / or groups.

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

Referring to FIG. 1, the binder composite 10 is ion-bonded with the polymer chains 10_2 having at least one anion group 10_1, and the anion group 10_1 of each of the polymer chains 10_2. And a divalent or higher metal cation 10_3 that fixes the ones 10_2 to each other.

The polymer chains 10_2 may be linear polymers, or may be branched polymers or three-dimensional crosslinked polymers. Preferably, the polymer chains 10_2 may be linear polymers. Even when the active material particles described later are micronized to have a nano-sized diameter, the linear polymer is in point contact with the active material particles, thereby securing sufficient pores to prevent the mobility of lithium from being reduced by the binder composite 10, and It is also easy to apply it to the current collector by maintaining a suitable viscosity by plasticity in the slurry production process of.

The polymer chains 10_2 may be homopolymers or copolymers. The average molecular weight of the polymer chains 10_1 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_1) is less than 40,000 g / mol, the molecular size is small compared to the size of the active material particles having an average diameter of several tens of nanometers to several hundred micrometers between the polymer chains for fixing between the active material particles If sufficient binding force cannot be obtained, and in excess of 3,000,000 g / mol, uniform mixing between the metal cations and the polymer chains becomes difficult, making slurry not only difficult, but also sufficient binding force cannot be obtained between the active material particles.

In one embodiment, the polymer chains 10_2 are polysaccharide, styrene butadiene, acrylate, ethylene vinyl acetate, polyacrylonitrile, acrylonitrile-butadiene-styrene, poly (vinyl chloride), poly (vinylidene chloride ), Polyvinylpyrrolidone, carboxylated styrene-butadiene, alginic acid, sodium alginate, carboxymethyl cellulose, carboxymethyl starch, carboxymethyl guar gum (carboxymethyl guar gum), carbomethylmethyl xanthane gum, carboxymethyl tara gum, low methoxyl pectin, carrageenan, polyacrylic acid, Polypropylene, polystyrene, poly (methylmethacrylate), nylon (nylon), polyethylene (polyethylen), cellulite Cellulose, amylose, chitosan, glucose, sucrose, maltose, lactose, starch, glycogen, natural rubber (polymer of isoprene) or mixtures thereof. Polyacrylic acid, polypropylene, polystyrene, poly (methylmethacrylate), nylon (nylon), polyethylene (polyethylen), cellulose, amylose (polyacrylic acid) amylose), natural rubber (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 ^- can be. Anionic group 10_1 may be bonded to the main chain and / or side chain 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 polymer chains 10_2 may be locally electrically negatively charged in a solvent such as a polar solvent or a slurry by the anion group 10_1.

The metal cation 10_3 that is ionically bonded to the anionic group 10_1 to fix the polymer chains 10_2 is electrically positively charged in the solvent. Therefore, the anion group 10_1 and the metal cation 10_3 of the polymer chains 10_2 in the solvent are locally ionically bonded as indicated by the dotted ellipse IB. As a result, the polymer chains 10_2 have a network structure that is mechanically strong and has pores.

The metal cation 10_3 may be more than bivalent because the metal cations 10_3 must be ionically bonded to the anion group 10_1 of each of the polymer chains 10_2 to fix different polymer chains 10_2. The ratio K between the addition amount of the metal cation 10_3 and the charge amount according to the addition amount of the polymer chains in consideration of the valence of the metal cation 10_3 may be determined to satisfy Equation 1 below. The charge amount of the metal cation 10_3 is the number of cations x ion valence, and the charge amount of the polymer chains 10_2 is the number x ion valence of the anion group 10_1.

[Equation 1]

When K is greater than 0 and less than or equal to 1, the interchain linkage between the polymer chains is mediated by the metal cations. When the K exceeds 1, the metal cations may be exposed freely in the electrolyte to oxidize lithium and It can adversely affect the reduction reaction. When K is greater than 0 and less than or equal to 1, the interchain linkage between the polymer chains is mediated by the metal cations. When the K exceeds 1, the metal cations may be exposed freely in the electrolyte to oxidize lithium and It can adversely affect the reduction reaction. Preferably, the K value may be determined according to the type of metal cation added. This will be described later.

The divalent 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 cross-sectional views illustrating structures of

active material particles

20A and 20B according to various embodiments of the present disclosure.

Referring to FIG. 2A, the active material particles 20A may include an active material core 20_1 and a binder composite 10 surrounding at least a portion of the active material core 20_1. Regarding the binder composite 10, reference may be made to the matter disclosed in FIG. 1.

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 a metal, metalloid, or metal that involves oxidation and reduction of lithium ions by reversible reaction mechanisms such as alloying and de-alloying, occluding and releasing, or adsorption / desorption with lithium ions. It may be an active material for a negative electrode including a mixture thereof. In one embodiment, the metal or metalloid is Sn, Si, Sb, Zn, Ge, Al, Cu, Bi, Cd, Mg, As, Ga, Pb and Fe, or SnSb, SnAg, and Sn _It may be an intermetallic compound such as ₂ Fe.

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

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

The active material core 20_1 may be primary particles of the aforementioned materials or secondary particles formed by agglomeration of the primary particles with each other. The average particle diameter of the active material core 20_1 may be in the range of 20 nm to 2 μm, and may be appropriately selected according to 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 communicate with each other in the active material core 20_1, and extend to the surface of the active material core 20_1 to connect the inside and the surface of the active material core 20_1. It may be formed. Through the voids, lithium ions may be subjected to electrochemical reactions such as alloying and de-alloying, occlusion and release, or adsorption / desorption with the active material core 20_1, and a reaction surface area of the active material core 20_1 with lithium Increase and act as a buffer for volume expansion of the active material core 20_1 upon filling.

The active material cores 20_1, which are in contact with each other through the binder composite 10, may be fixed to each other by the binder composite 10 coating at least a portion of the respective active material cores 20_1. The fixation between the binder composite 10 is the polymer chains 10_2 by covalent bonds of the polymer chains 10_2 itself and ionic bonds between the anion group 10_1 and the cation 10_3 of each of the polymer chains 10_2. Is achieved by a combination of

Since the ionic bonds bind the polymer chains 10_1 more strongly than the covalent bonds, the ionic bonds may increase the tensile strength of the polymer chains 10_1 and increase the elastic modulus of the entire binder composite 10. As a result, according to the embodiment of the present invention, the volume change rate accompanying charge and discharge between the active material particles 20A including the active material core 20_1 is reduced, so that the volume change rate is in the range of 100% to 400% In addition, it is also possible to improve the initial filling efficiency with large volume expansion, as well as to prevent cracking due to the volume change to improve the life. In addition, the strong ionic bond can improve the energy density of the battery by minimizing the amount of the binder to reduce the energy density of the battery compared to the conventional binder for fixing the active material particles only by covalent bonds.

Referring to FIG. 2B, the active material particles 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 silicon cores 10_1 in contact with each other and reduces the internal resistance of the electron path between the silicon cores 10_1 and the current collector (not shown).

In some embodiments, the conductive layer 20_2 may include a crystalline or amorphous carbon based conductive layer such as graphite, soft carbon, carbon nanotubes, or graphene. The carbon-based conductive layer may include a conductive SP ₂ graphite structure and a diamond structure of SP ₃ having an insulating property, and in order for the carbon-based conductive layer to have conductivity, the molar fraction of SP ₂ is larger than that of SP _3. It may be to have, which can be adjusted and secured through the heat treatment process described later. In another embodiment, the conductive layer 20_2 may be a nanoscale particles of a conductive metal oxide such as antimony zinc oxide or antimony tin oxide or a layer including the same. Materials relating to the conductive layer 20_2 are exemplary, and the present invention is not limited thereto.

The thickness of the conductive layer 20_2 may be 2 nm to 5 μm, which is illustrative only 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 from other active material cores in the entire electrode. As a result, aggregation between the active material cores 20_1 can be prevented.

Although the structure of one active material particle 20B is illustrated in FIG. 2B, as described with reference to FIG. 2A, the plurality of active material particles 20B are strongly fixed by the binder composite 10 surrounding the electrode layer to form an electrode layer. can do. The binder composite 10 functions as a resilient matrix as a buffer for volume expansion caused by charging and discharging of a battery, and in particular, when the binder composite 10 has a linear structure, sufficient pores are secured in the network structure to obtain lithium. Metal ions such as these can freely pass between the active material particles 20B and the electrolyte (not shown) without reducing the mobility.

Referring to FIG. 3, active material particles are dispersed in a polar solvent (S10). The active material particles are a material having a particle structure including the active material core 20_1 described above with reference to FIGS. 2A and 2B, and optionally the conductive film 20_2. The polar solvent may be selected from a liquid solvent which induces dispersion of the active material particles and in which a polymer chain having an anionic group described later can be easily dissolved and dispersed. For example, the polar solvent may be water, alcohol (including but not limited to methanol, ethanol, isobutyl alcohol, octanol, polyvinyl alcohol ethyl alcohol, methyl alcohol, isopropyl alcohol, isobutyl alcohol, polyvinyl alcohol, Cyclohexanol, octyl alcohol, decanol, hexatecanol, glycerol, propylene glycol, ethylene glycol, propylene glycol, pinacol, 1.2-octanediol, 1,2-dodecanediol and 1,2-hexadecanediol Any one or a mixture thereof and other primary, secondary and tertiary alcohols may be used), acetic acid, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, or N- Methylpyrrolidone (NMP) may be included.

In another embodiment, the polar solvent is octyl ether, butyl ether, hexyl ether, benzyl ether, phenyl ether, decyl ether, ethyl methyl ether, dimethyl ether, diethyl ether, diphenyl ether, tetrahydrofuran, 1,4- Cycle ethers such as dioxane, or polyether solvents such as polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), polyoxymethylene (POM), polytetrahydrofuran. Alternatively, the polar solvent may be polyethylene terephthalate, acrylate ester and cellulose acetate, isobutyl acetate, isopropyl acetate, aryl hexanoate, benzyl acetate, bornyl acetate, butyl acetate Or a cyclic ester solvent such as lactone. However, preferably, the liquid solvent is water capable of minimizing environmental load.

Polymer chains having an anionic group 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 in the polar solvent in the form of a monomo having an anionic 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, previously polymerized externally.

It provides divalent 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 salt may be an oxide, a carbonate, a nitride, a nitride, a sulfide, a sulfur oxide, a hydroxide, or a halide of an alkaline earth metal and a transition metal, but the present invention is not limited thereto. For example, calcium ions may be provided in the polar solvent as chloride (CaCl ₂ ) or hydroxide (Ca (OH) ₂ ) as a halide. Magnesium may also be provided as sulfur oxides (MgSO ₄ .7H ₂ O). These salts are applicable as long as they can be easily ionized in polar solvents among the commercialized compounds, and the present invention is not limited thereto. Alternatively, the metal cations may be provided by an organic or inorganic metal polymer precursor that is dissociable in the polar solvent, such as polyaluminum chloride.

In one embodiment, the metal salt or metal polymer precursor may be provided such that the ratio K of the polymer chains and the metal cations satisfies Equation 1 below. When K is greater than 0, it is possible to bond between polymer chains, and when it is greater than 1, metal cations may be exposed freely in the electrolyte, which may adversely affect the oxidation and reduction reaction of lithium.

[Equation 1]

In addition, the ratio K may be selected in consideration of the average diameter of the secondary particles of the synthesized electrode composition. For example, from experiments, Ca (OH) 2, a 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 the active material particles having a suitable size may be obtained from 0.5 or more. As another example, in the case of polyaluminum chloride, it has a suitable secondary particle size at 0 <K ≦ 0.3. When K exceeds 0.3, the size of the secondary particles is coarse and additional processes such as a grinding process are required for use, so they are not suitable for application as an active material composition.

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

The active material particles are any one of Sn, Si, Sb, Zn, Ge, Al, Cu, Bi, Cd, Mg, As, Ga, Pb and Fe; Intermetallic compounds thereof; Oxides thereof; Or it may include an active material core formed of a nitride thereof. In addition, 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 in the polar solvent to improve the dispersion stability of the metal cations and / or active material particles. The surfactant may be, for example, octylamine, trioctylamine, decylamine, decylamine, dodecylamine, tetratradecylamine, hexadecylamine, hexadecylamine, or oleate. C8 to C24 amine surfactants selected from oleylamine, octadecylamine, tribenzylamine, triphenylamine, or mixtures thereof.

The above-described steps S10-S30 may be performed sequentially or one of the steps may be reversed. For example, polymer chains may be first provided in the polar solvent (S20), and then active materials and metal ions may be added to the polar solvent (S10 and S30). At this time, the stirring process may be performed, and optionally, additional operations such as temperature control and ultrasonic dispersion may 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, and fine carbon such as acetylene black, nano metal particle paste, or indium tin oxide (ITO) paste, but the present invention is not limited thereto.

By the steps S10-S30, the polymer chains are coated on the active material particles, and the polymer chains coating the active material particles by the metal cation may be strengthened to form a layer made of a binder composite (S40). In addition, the active material particles coated with the binder composite are in contact with each other, the contacting binder composites are bonded to each other through a metal cation to aggregate the active material particles. When a 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 particles by the binder composite.

Aggregated active material particles can be obtained, then dried and disintegrated using a suitable milling or classification apparatus to obtain active material particles coated with a binder composite. Thereafter, the active material particles are prepared in a dry or slurry form to be coated or impregnated on the current collector in a wet manner to form an electrode. The binder composite coating the active material particles can be used as a binder for fixing between the current collector and the active material particles.

Example

A negative electrode composition was synthesized according to the embodiments of the present invention described above. Table 1 distinguishes the combination of the active material particles, the precursor of the binder composite and the polar solvent of the prepared negative electrode composition as shown in Examples 1 to 3 as shown in Table 1. In addition, as a comparative example for the embodiments of the present invention, a negative electrode composition having a binder composed of only polymer chains without applying a metal salt was also synthesized.

To 100 ml of polar solvent in which about 0.5 g of polymer chains containing an anionic group are dissolved, about 10 g of nano silicon or nano silicon-carbon composite is added and dispersed for 24 hours using a ball-mill. Subsequently, Ca (OH) ₂ or polyaluminum chloride, which is a metal salt, is added to the mixed solution to induce an ionic bond between the binder having the anionic group and the metal cation Ca ²⁺ or Al ³⁺ to form a silicon particle or a silicon core / carbon. The negative electrode composition for secondary batteries which is an aggregate containing the composite particle of a shell was synthesize | combined.

Table 1

Example	Active material particles	Binder composite precursor		Polar solvent / volume
Example	Active material particles	Polymer chains / average molecular weight	Metal salt / average weight	Polar solvent / volume
Example 1	Silicon core particles	PAA (poly acrylamide) / Mw 450,000 g / mol	Ca (OH) ₂ / 0.25 g	Methanol / 100 ml
Example 2	Silicon Core / Carbon Shell Composite Particles	PAA (poly acrylamide) / 450,000 g / mol	Poly Aluminum Chloride / 0.1 mg	Methanol / 100 ml
Example 3	Silicon Core / Carbon Shell Composite Particles	Polyvinyl pyrolidone (PVP) / 1,250,000 g / mol	Ca (OH) ₂ /0.4 g	Distilled water / 100 ml
Comparative example	Silicon particles	PAA450,000 g / mol	-	Methanol / 100 ml

Examples 1 to 3 are exemplary and the present invention is not limited thereto. In addition, the active material particles may first be dispersed in a polar solvent, and then precursors of the polymer chains may be added.

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

Table 2 is a result of measuring the tensile strength (tensile strength) of the binder composite constituting the negative electrode composition for secondary batteries prepared according to Examples 1 to 3 of the present invention. The tensile strength of PAA alone according to the comparative example is 90 MPa, and the tensile strength of the binder composites of Examples 1 to 3 is significantly improved to 55 to 65% compared to the comparative example.

TABLE 2

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

5A and 5B are graphs showing capacity and capacity retention with respect to the number of charge / discharge cycles of half batteries manufactured using the electrode compositions according to Examples 1 to 3 and Comparative Examples, respectively. In these graphs, curves EX_1, EX_2 and EX_3 are the measurement results of the half cells according to Examples 1 to 3, respectively, and RE is the measurement result of the half cells according to the comparative example. Charge and discharge rate is 0.5 C.

Referring to FIGS. 5A and 5B, in Examples 1 to 3 and Comparative Examples, the initial capacity is larger than 2,500 mAh / g. However, it can be seen that the capacity is maintained at 90% or more in the case of 50 cycles, but deterioration occurs while the capacity is drastically reduced to 75% in the comparative example. Table 3 shows the thickness change of the average electrode expansion rate of the negative electrode according to Experimental Examples 1 to 3 and the average electrode expansion rate of the negative electrode according to Comparative Example. Referring to Table 3, in Examples 1 to 3, the thickness change during charging is suppressed to less than 150% based on the initial thickness, and the thickness change during charging and discharging is suppressed to 30% or less based on the charging. .

However, the electrode according to the comparative example showed a thickness change of about 220% based on the initial thickness, and the thickness change during charging and discharging reached 52% based on the charging time, indicating a thickness change of 50% or more. It was.

TABLE 3

Average electrode expansion 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 × 100 (%)

** B = (thickness at charging-thickness at the time of discharge) / thickness at the charge × 100 (%)

Therefore, the electrodes involved in charging and discharging of the active material particles by fixing the active material particles by a binder composite having polymer chains strongly bonded to each other by ionic bonds in which the lifespan and capacity retention rate of Examples 1 to 3 are improved compared to the comparative example It is considered that the expansion ratio is effectively suppressed, and according to the embodiment of the present invention, it can be seen that even in the case of the non-carbon-based negative electrode material having a large volume change rate, stable life and reliability can be ensured. In addition, since the strong ionic bonds fix the particles between the active material particles or the current collector and the active material particles regardless of the size of the active material particles, the amount of the binder is minimized compared to the conventional binder which fixes the active material particles only by covalent bonding. Can improve the energy density.

Although the above embodiments relate to the 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 is a material in which the active material particles are primary particles or secondary particles, and are dispersed in a solvent and applied to the current collector in the form of a slurry, or additionally, a binder may be applied to the current collector in the form of a slurry by further adding a binder. have.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and alterations are possible within the scope without departing from the technical spirit of the present invention, which are common in the art. It will be apparent to those who have knowledge.

According to an embodiment of the present invention, the battery binder composite minimizes the amount of binder used compared to the conventional binder to improve the energy density of the battery, isolate the surface of the active material particles and the electrolyte solution to prevent the differentiation of the active material particles life and reliability To improve.

Claims

Polymer chains each having at least one anionic group; And a bivalent or higher metal cation ion-bonded with the at least one anionic group to fix the polymer chains to each other. And

Electrode composition for a secondary battery comprising active material particles fixed by the binder composite.
The method of claim 1,

The average molecular weight of the polymer chain is in the range of 40,000 g / mol to 3,000,000 g / mol electrode composition for secondary batteries.
The method of claim 1,

The polymer chains are polysaccharide, styrene butadiene, acrylate, ethylene vinyl acetate, polyacrylonitrile, acrylonitrile-butadiene-styrene, poly (vinyl chloride), poly (vinylidene chloride), polyvinylpyrrolidone, Carboxylated styrene-butadiene, alginic acid, sodium alginate, carboxymethyl cellulose, carboxymethyl starch, carboxymethyl guar gum, carbosi Carboxymethyl xanthane gum, carboxymethyl tara gum, low methoxyl pectin, carrageenan, polyacrylic acid, polypropylene, polypropylene, polystyrene (polystyrene), poly (methylmethacrylate), nylon (nylon), polyethylene (polyethylen), cellulose, Milos (amylose), chitosan, glucose, sucrose, maltose, lactose, starch, glycogen, natural rubber (a polymer of isoprene) or secondary cell electrode composition containing a mixture thereof.
The method of claim 1,

The polymer chains have a linear structure electrode composition for a secondary battery.
The method of claim 4, wherein

The polymer chains are polyacrylic acid, polypropylene, polystyrene, polymethacrylate, poly (methylmethacrylate), nylon (nylon), polyethylene (polyethylen), cellulose, amylose (amylose), natural rubber (polymer of isoprene), or a mixture thereof.
The method of claim 1,

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 a secondary battery electrode composition containing a-2.
The method of claim 1,

The metal cations include a cation of an alkaline earth metal, a transition metal or an alloy thereof.
The method of claim 7, wherein

The alkaline earth metal includes beryllium, magnesium, calcium, strontium, or barium,

The transition metal may be 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 secondary batteries containing hafnium, tantalum, tungsten, or iridium.
The method of claim 1,

The ratio of the polymer chains and the metal cations satisfies the following formula:

[expression]

0 <positive charge per weight of metal cations / negative charge per weight of polymer chains ≤ 1.
The method of claim 1,

The active material particles are the active material composition for a secondary battery is selected from active materials having a volume change rate in the range of 100% to 400% during charging and discharging of a battery.
The method of claim 1,

The active material particles are 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 electrode composition for a secondary battery comprising an active material core formed of a nitride thereof.
The method of claim 1,

The active material particles further comprises an active material core and a conductive layer coated on the active material core electrode composition for a secondary battery.
Providing active material particles for a secondary battery in a polar solvent;

Providing polymer chains having anionic groups in the polar solvent;

Providing divalent or more metal cations in the polar solvent;

Inducing an ionic bond between the anionic groups of the polymer chains and the metal cations to form a binder composite including the polymer chains and the metal cations on the active material particles; And

Method of producing an electrode composition for a secondary battery comprising the step of obtaining the active material particles.
The method of claim 13,

The average molecular weight of the polymer chain is a method for producing an electrode composition for secondary batteries in the range of 40,000 g / mol to 3,000,000 g / mol.
The method of claim 13,

The polymer chains are polysaccharide, styrene butadiene, acrylate, ethylene vinyl acetate, polyacrylonitrile, acrylonitrile-butadiene-styrene, poly (vinyl chloride), poly (vinylidene chloride), polyvinylpyrrolidone, Carboxylated styrene-butadiene, alginic acid, sodium alginate, carboxymethyl cellulose, carboxymethyl starch, carboxymethyl guar gum, carbosi Carboxymethyl xanthane gum, carboxymethyl tara gum, low methoxyl pectin, carrageenan, polyacrylic acid, polypropylene, polypropylene, polystyrene (polystyrene), poly (methylmethacrylate), nylon (nylon), polyethylene (polyethylen), cellulose, Milos (amylose), chitosan, glucose, sucrose, maltose, lactose, starch, glycogen, natural rubber (a polymer of isoprene) or a method of producing a secondary battery electrode composition containing a mixture thereof.
The method of claim 13,

The polymer chain is a method of manufacturing an electrode composition for a secondary battery having a linear structure.
The method of claim 16,

The polymer chains are polyacrylic acid, polypropylene, polystyrene, polymethacrylate, poly (methylmethacrylate), nylon (nylon), polyethylene (polyethylen), cellulose, amylose (Amylose), natural rubber (polymer of isoprene) or a mixture thereof, a method for producing an electrode composition for a secondary battery.
The method of claim 13,

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 - the method of the secondary battery electrode composition comprising a.
The method of claim 13,

The metal cations include a cation of an alkaline earth metal, a transition metal or an alloy thereof.
The method of claim 13,

The polar solvent is water, alcohol, acetic acid, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, or N-Methylpyrrolidone (NMP), octyl ether, butyl ether, hexyl ether, benzyl ether, phenyl ether , Decyl ether, ethyl methyl ether, dimethyl ether, diethyl ether, diphenyl ether, tetrahydrofuran, 1,4-dioxane, polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), Polyoxymethylene (POM), polytetrahydrofuran, polyethylene terephthalate, acrylate esters, cellulose acetate, isobutyl acetate, isopropyl acetate, aryl hexanoate, benzyl acetate, carbonyl acetate ( bornyl acetate), a butyl acetate or a method for producing an electrode composition for a secondary battery comprising lactone.