KR20230071054A - Method for preparing anode slurry, anode and secondary battery - Google Patents

Abstract

The present invention relates to a method for manufacturing negative electrode slurry, a method for manufacturing a negative electrode using the slurry manufactured according to the method, and a secondary battery including the negative electrode. Provided is a method for manufacturing negative electrode slurry, including the steps of: manufacturing first slurry including a first negative electrode active material, a conductive agent, and a conductive polymer; and adding a second negative electrode active material and a thickener to the first slurry and mixing the same to manufacture second slurry.

Description

Anode slurry manufacturing method, cathode manufacturing method and secondary battery {METHOD FOR PREPARING ANODE SLURRY, ANODE AND SECONDARY BATTERY}

The present invention relates to a method for preparing a negative electrode slurry, a method for preparing a negative electrode using the slurry prepared according to the above method, and a secondary battery including the negative electrode.

Secondary batteries are commonly applied to portable devices as well as electric vehicles or hybrid vehicles driven by an electrical driving source, power storage devices, etc. These secondary batteries not only have the primary advantage of dramatically reducing the use of fossil fuels, but also are environmentally friendly in that no by-products are generated due to the use of energy, so they are a new energy source for improving energy efficiency. is getting attention as

Accordingly, technology development for secondary batteries is continuously expanding. In particular, it is known that a negative electrode using a silicon-based negative electrode active material has a theoretical capacity of 3580 mAh/g, which is several times larger than the theoretical capacity of 372 mAh/g of a negative electrode using a graphite-based negative electrode active material. For this reason, silicon-based negative electrode active materials are in the limelight as negative electrodes for lithium secondary batteries to be used in next-generation mobile devices, EVs, and ESSs.

However, silicon-based anode active materials have low conductivity, and when they react with lithium, that is, during charging and discharging of the battery, they are accompanied by a significant volume change (~400%), which may cause separation between the anode active material and the current collector or the anode active material. There are downsides to that. The problem of volume expansion of the silicon negative electrode active material can cause a loss of reversible capacity of the lithium secondary battery as a long-term charge/discharge cycle progresses, thereby deteriorating the lifespan characteristics and greatly degrading the performance of the lithium secondary battery.

In addition, since the degree of volume change of the battery due to volume expansion due to insertion and detachment of lithium during charging and discharging must be considered in designing the cell, the energy density per unit volume can be greatly reduced.

Therefore, due to these problems, despite the advantage of having a high capacity, a lithium secondary battery including a silicon-based negative electrode has difficulties in practical use.

Therefore, it is necessary to develop a lithium secondary battery having high capacity and excellent lifespan characteristics by improving conductivity and improving performance degradation due to volume expansion of the silicon-based negative electrode active material during charging and discharging while using an anode including a silicon-based negative electrode active material. do.

The present invention is to solve the above problems, a method for producing a negative electrode slurry capable of improving conductivity and improving the deterioration problem due to volume expansion of a silicon-based negative electrode active material during charging and discharging, and the negative electrode slurry prepared according to the method It is intended to provide a negative electrode and a secondary battery including the negative electrode.

The present invention is to provide a method for producing a negative electrode slurry, the method comprising the steps of preparing a first slurry containing a silicon-based first negative electrode active material, a conductive agent and a binder; and preparing a second slurry by mixing the first slurry with a second carbon-based negative electrode active material and a thickener.

The conductive agent may be at least one selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

The binder is styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, ethylene-propylene copolymer, polyepichlorohydrin, polyphosphazene, polyacrylonitrile , polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol resin, acrylate resin, polyaniline (PANI) ), polythiophene (PT), polyacetylene, polypyrrole (PPy), and poly(3,4-ethylene dioxythiophene) (PEDOT).

The thickener is carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxy It may be at least one selected from the group consisting of ethyl cellulose (ethyl hydroxyethyl cellulose, EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC), and cellulose gum.

The first slurry may further include a thickening agent.

The first slurry may be prepared in an inline mixer.

The second slurry may be prepared in a PD mixer.

According to another aspect of the present invention, applying the negative electrode slurry prepared according to the manufacturing method to at least one surface of the negative electrode current collector; and drying the negative electrode current collector coated with the negative electrode slurry.

According to another aspect of the present invention, a negative electrode prepared according to the method; anode; and a separator interposed between the negative electrode and the positive electrode.

According to the present invention, by preparing a slurry by first mixing a silicon-based negative electrode active material and a conductive agent, a large amount of conductive agent can be disposed around the silicon-based negative electrode active material, and then, even if the carbon-based negative electrode active material is mixed into the slurry, the silicon-based negative electrode active material It is possible to maintain the distribution of the conductive agent around the silicon negative electrode active material to improve the conductivity.

1 is a photograph showing an example of an in-line mixer used for preparing a first slurry.
2 is a photograph showing an example of a PD mixer used for preparing the second slurry.
3 is a graph showing changes in capacity and resistance according to the number of cycles for the electrodes of Example 1 and Comparative Example 1.

Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, the embodiments of the present invention may be modified in various forms, and the scope of the present invention is not limited to the embodiments described below.

The silicon-based negative electrode active material has a characteristic of low conductivity. In order to compensate for such low conductivity, the particle size of the silicon-based negative electrode active material is reduced or the surface is coated with carbon. In addition, since the silicon-based negative electrode active material has a higher expansion rate than the graphite-based material when reacting with lithium according to charging and discharging of the battery, various conductive agents are used to compensate for this.

On the other hand, in preparing a negative electrode slurry containing a silicon-based negative electrode active material, blending of the silicon-based negative electrode active material and the carbon-based negative electrode active material is performed by simultaneously introducing the silicon-based negative electrode active material and the carbon-based negative electrode active material, and then adding a conductive agent, a thickener, and a solvent to proceed with mixing at a solid content level of 60 to 70%, and then additionally add a thickener and lower the solids content by adding a solvent to proceed with additional mixing, for example, after finally adding a binder It is finished by mixing.

However, since the conductive agent introduced in a small amount is evenly distributed throughout the silicon-based negative electrode active material and the carbon-based negative electrode active material, the effect of improving the conductivity and reducing the expansion rate of the silicon-based negative electrode active material is insignificant because the content of the conductive agent connected to the silicon-based negative electrode active material is small. In this case, due to the low conductivity of the silicon-based negative electrode active material, a large load is applied to the carbon-based negative electrode active material as the charging rate increases, and a problem occurs in that particles that are not charged are generated among the particles of the silicon-based negative electrode active material.

Accordingly, the present invention is intended to solve the above problems, and provides an improved method for preparing a negative electrode slurry containing a silicon-based negative electrode active material.

According to one aspect of the present invention, preparing a first slurry containing a first negative electrode active material, a conductive agent and a binder; and preparing a second slurry by adding and mixing a second negative electrode active material and a thickener into the first slurry.

First, a step of preparing a first slurry including a first negative electrode active material, a conductive agent, and a binder is performed.

The first anode active material is a silicon-based anode active material containing silicon, but is not particularly limited, and may be SiOx (0<x<2) particles such as Si or SiO, Si—C composites, or Si—Q alloys. In the Si—Q alloy, Q may be an element selected from the group consisting of alkali metals other than Si, alkaline earth metals, transition metals, group 13 elements, group 14 elements, rare earth elements, and combinations thereof, and specifically, Mg , Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os , Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po , And may be selected from the group consisting of combinations thereof.

The conductive agent is a material used to impart conductivity to the silicon-based negative electrode active material, and carbon nanotubes may be used, but is not particularly limited. At least one selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes may be used.

As described above, the present invention prepares a negative electrode slurry by preparing a first slurry by mixing a silicon-based first negative electrode active material and a conductive agent in advance, and then adding a second carbon-based negative electrode active material such as graphite to prepare a second slurry do.

When the first slurry is prepared by mixing the silicon-based first negative electrode active material and the conductive agent first, the conductive agent is distributed in a large amount around the silicon-based first negative electrode active material to improve the contact between the silicon-based first negative electrode active material and the conductive agent. can In this way, by distributing the conductive agent around the silicon-based first negative electrode active material, it may contribute to improving the low conductivity of the silicon-based first negative electrode active material. Furthermore, even if the conductive agent distributed around the silicon-based first negative electrode active material is subsequently added to the second negative electrode active material, the carbon-based negative electrode active material to prepare the second slurry, the content of the conductive agent present around the silicon-based first negative electrode active material can be maintained high. there is.

In this way, since a large amount of the conductive agent is present on the surface of the silicon-based first negative electrode active material, an effect of improving insufficient conductivity of the silicon-based first negative electrode active material may be secured. Furthermore, when the volume expansion of the silicon-based first negative electrode active material occurs during charging and discharging, the conductive agent can prevent separation between the negative electrode active materials or between the negative electrode active material and the negative electrode current collector due to the volume expansion, and the negative electrode active material due to the volume expansion. It is possible to maintain contact between the two layers, thereby reducing internal resistance.

In preparing the first slurry, a binder may be included. The binder may include binders commonly used in preparing negative electrodes, but are not limited thereto, and examples thereof include styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylic rubber. , butyl rubber, ethylene-propylene copolymer, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, Acrylic resins, phenol resins, epoxy resins, polyvinyl alcohol resins, and acrylate-based resins are exemplified.

In general, the anode active material has a particle shape, and the anode active material is fixed to a current collector by the binder as described above, and particles of the anode active material come into contact with each other. At this time, since the negative electrode active material particles fixed by the binder are electrically connected between the negative electrode active material particles and between the negative electrode active material and the current collector by point contact, the contact between the negative electrode active material particles or between the negative electrode active material and the negative electrode current collector When the degree is low or the contact area is small, the internal resistance of the battery has a large value. In addition, isolated negative electrode active material particles that are not connected by contact do not contribute to battery capacity. Therefore, maintaining a large contact area between negative electrode active material particles can contribute to improving battery characteristics.

On the other hand, during charging and discharging of the battery, a battery reaction occurs between the negative electrode and the positive electrode inside the battery. When this battery reaction occurs, lithium ions are inserted or released into the particle structure of the negative electrode active material, and lithium ions are intercalated and released from the negative electrode active material. The particle expands and contracts. Therefore, as charging and discharging progresses, an electrical connection state due to point contact between active material particles may become unstable.

Therefore, the above-described commonly used binders may be used as the binder, and a conductive polymer may be used as the binder together with or instead of the conventional binders.

When the conductive polymer is used as a binder, contact defects can be improved by the conductive polymer even if point contact between negative electrode active material particles occurs due to contraction and expansion of the silicon-based negative electrode active material, and furthermore, problems such as increased internal resistance can be improved. can contribute to

The conductive polymer is not limited thereto, but, for example, polyaniline (PANI), polythiophene (PT), polyacetylene, polypyrrole (PPy) and PEDOT (poly(3,4 -ethylene dioxythiophene)), and any one of these may be used alone or in combination of two or more. More specifically, the conductive polymer may be polyaniline.

The first slurry may also include a thickening agent. The thickener is added to impart viscosity to the slurry, and although not particularly limited, cellulose-based compounds may be used. The cellulose compound is not limited thereto, but methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxyethyl cellulose ( It may be at least one selected from the group consisting of ethyl hydroxyethyl cellulose (EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC), carboxy methyl cellulose (CMC), and cellulose gum. And, for example, carboxymethyl cellulose can be used.

A mixer may be used to prepare the first slurry by mixing the first negative electrode active material, the conductive agent, and the binder. The mixer used for mixing the first slurry is generally used for mixing two or more components, and any equipment that can be used for mixing a small amount of slurry may be used without particular limitation.

For example, the first slurry can be prepared using an in-line mixer as the mixer, and the in-line mixer is illustrated in FIG. 1 and includes a rotator, a stator, and a rotor rotating at high speed A small-capacity mixer including a blade shaft can be suitably used in preparing the first slurry.

In addition, a PD mixer (Planetary Disperser Mixer), which is usually used for producing electrode slurry, may be used. The PD mixer is commonly used for mixing large-capacity slurries, as illustrated in FIG. 2, and may be used for mixing the first slurry.

In the present invention, the silicon-based first negative electrode active material, the conductive agent, and the binder are included in relatively small amounts with respect to the total weight of the negative electrode slurry. It may be more efficient to use a small-capacity in-line mixer to mix the components included in such a small amount.

and preparing a second slurry by mixing the first slurry with a second negative electrode active material after preparing the first slurry.

The second anode active material may be a carbon-based anode active material. The carbon-based negative electrode active material is not particularly limited, but may include graphite, for example, artificial graphite, natural graphite, and graphitized mesocarbon microbeads. These graphites can be used alone or in combination of two or more. More specifically, artificial graphite or a mixture of artificial graphite and natural graphite may be used.

By including the silicon-based first negative electrode active material and the carbon-based second negative electrode active material at the same time, the capacity of the battery using the silicon-based first negative electrode active material is improved while suppressing side effects due to volume change of the negative electrode active material that may occur during the charging and discharging process of the negative electrode. Thus, the lifetime of the cathode can be improved.

If necessary, additional anode active materials may be further mixed in addition to the carbon-based second anode active material. For example, the additional anode active material may include a tin (Sn)-based anode active material or a lithium vanadium oxide anode active material. .

The Sn-based negative electrode active material may be Sn, SnO ₂ , or a Sn-R alloy. In the Sn-R alloy, R is composed of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof other than Sn and Si. It may be an element selected from the group, specifically, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Tl, Ge, P, As, It may be selected from the group consisting of Sb, Bi, S, Se, Te, Po, and combinations thereof.

In preparing the second slurry, a thickener may also be added to the first slurry together with the carbon-based second negative electrode active material.

The thickener is added to impart viscosity to the slurry, and although not particularly limited, cellulose-based compounds may be used. The cellulose compound is not limited thereto, but methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose (MHPC), ethyl hydroxyethyl cellulose ( It may be at least one selected from the group consisting of ethyl hydroxyethyl cellulose (EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC), carboxy methyl cellulose (CMC), and cellulose gum. And, for example, carboxymethyl cellulose can be used.

In manufacturing the said 2nd slurry, the said in-line mixer can be used, Moreover, a PD mixer can be used. More specifically, a PD mixer can be used. The PD mixer is a series of mixers for mixing powder and solvent, and can provide a mixing effect by planetary motion of blades and an action of crushing agglomerates (aggregates) by dispersing effect of high-speed shear blades, and can be used for large-capacity mixing. more suitable for application.

For example, in the present invention, an in-line mixer may be used to prepare a first slurry having a relatively small capacity, and a PD mixer may be used to prepare a second slurry having a large capacity. In this way, by preparing the first slurry using the in-line mixer, the slurry can be prepared only by adding an in-line mixer without the need to replace the equipment of the PD mixer previously used for the production of the electrode slurry, thereby improving fairness and Economic efficiency can be further improved.

As a result, an anode slurry including a negative electrode active material including a silicon-based first negative electrode active material and a carbon-based second negative electrode active material, a conductive agent, a conductive polymer, and a thickener can be prepared.

Although not limited thereto, based on the total weight of solids contained in the negative electrode slurry, the negative electrode active material may be included in an amount of 93 to 98% by weight. Furthermore, the silicon-based first negative electrode active material and the carbon-based second negative active material may have a weight ratio of 1% to 30%: 99% to 70% with respect to the total weight of the negative electrode active material.

The conductive agent included in the negative electrode slurry may be included in an amount of 0.1 to 3% by weight based on the total weight of the solid content of the negative electrode slurry. If the content of the conductive agent is less than 0.1% by weight, it may be insufficient to improve the conductivity of the silicon-based first negative electrode active material and to improve problems such as detachment due to volume expansion of the silicon-based first negative electrode active material, and exceed 3% by weight In this case, a large amount of binder may be required, resulting in a decrease in capacity.

The conductive polymer may be included in an amount of 1 to 3% by weight based on the total weight of the solid content of the negative electrode slurry. The conductive polymer is provided as a binder, and when the content thereof is less than 1% by weight, it is difficult to sufficiently provide binding force between the negative electrode active materials or between the negative electrode active material and the negative electrode current collector, and furthermore, the effect of improving the low conductivity of the first silicon-based negative electrode active material is small. can On the other hand, when the amount of the conductive polymer exceeds 3% by weight, the content of the negative electrode active material may be relatively decreased, resulting in a decrease in electrode capacity.

The thickener may be included in an amount of 0.1 to 3% by weight based on the total weight of the solid content of the negative electrode slurry. The thickener contributes to improving workability in applying the negative electrode slurry to the surface of the negative electrode current collector by adjusting the viscosity of the slurry. On the other hand, when the content of the thickener exceeds 3% by weight, the viscosity of the slurry is too high, which may rather inhibit the coating property of the slurry on the surface of the electrode current collector.

The cathode slurry includes a solvent. As the solvent, an aqueous solvent such as water may be used. The amount of the solvent included in the anode slurry is not particularly limited, but, for example, the content of the solvent in the entire anode slurry may be 30 to 80% by weight. If the content of the solvent is less than 30% by weight, a high load may be caused during the slurry mixing process, resulting in a decrease in the yield of the mixing process, and if it exceeds 80% by weight, the yield of the coating process may be reduced due to low viscosity.

According to another aspect of the present invention, applying the negative electrode slurry prepared as described above to at least one surface of the negative electrode current collector; and drying the negative electrode current collector coated with the negative electrode slurry.

The anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, aluminum-cadmium alloy, etc. can be heard In addition, copper or stainless steel, the surface of which is treated with carbon, nickel, titanium, silver, or the like, may be used as the negative current collector.

The shape of the negative current collector is not particularly limited, and may be in various forms such as a film, sheet, foil, net, porous material, foam, or non-woven fabric.

In addition, the negative electrode current collector may form fine irregularities on the surface to enhance bonding strength between the negative electrode active material and the negative electrode current collector.

The coating and drying of the negative electrode slurry on the negative electrode current collector may be performed by a method commonly performed in the art, and is not particularly limited. For example, a coating method using a slot die may be used for application, and in addition, a Mayer bar coating method, a gravure coating method, a dip coating method, a spray coating method, and the like may be used.

The above drying can be performed, for example, in a "drying" atmosphere at room temperature or the like, or can be dried under a predetermined temperature in an oven.

The negative electrode mixture layer formed on the negative electrode current collector by the coating and drying may be passed through a metal rolling roll of a calendering equipment to perform rolling, thereby manufacturing a negative electrode having a predetermined density.

According to another aspect according to the present invention, the prepared negative electrode; anode; and a separator interposed between the negative electrode and the positive electrode. Anodes and separators commonly used in the art may be used without limitation, and a detailed description thereof will be omitted herein.

As described above, since the negative electrode using the negative electrode slurry prepared according to the present invention has a large amount of the conductive agent connected to the surface of the silicon-based negative electrode active material, the conductivity is improved, and the contact problem due to the expansion of the silicon-based negative electrode active material is improved, thereby increasing the capacity of the battery. In addition, the lifespan of the negative electrode may be improved by suppressing volume change of the negative electrode active material that may occur during charging and discharging of the negative electrode.

Example

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are intended to show specific examples of carrying out the present invention, and are not intended to limit the present invention thereby.

Example 1

Based on the solid content of the final anode slurry, 3 wt% of SiOx as a first anode active material, 0.3 wt% of SWCNT as a conductive agent, 0.5 wt% of SBR as a binder, and 0.5 wt% of CMC as a thickener were mixed, and water was used as a solvent. After adding so that it became 66% by weight, it was mixed using an in-line mixer to prepare a first slurry.

Based on the solid content of the final negative electrode slurry, 94.7% by weight of artificial graphite as the second negative electrode active material and 1% by weight of CMC as a thickener were added to the prepared first slurry along with water as a solvent in a PD mixer, and mixed to obtain a second slurry was manufactured. At this time, the amount of water introduced was used so that the solid content contained in the entire composition was 45% by weight.

The prepared negative electrode slurry was coated on a copper foil having a thickness of 8 μm, dried, and then rolled to prepare a negative electrode having a negative electrode mixture layer having a thickness of 105 μm.

A positive electrode slurry was prepared by mixing 98% by weight of NCM with a Ni content of 88% as a cathode active material, 1% by weight of PVDF as a binder, and 1% by weight of CNT as a conductive agent with an NMP solvent (solid content: 77% by weight).

After the positive electrode slurry was applied to both sides of an aluminum foil having a thickness of 12 μm, it was dried and rolled to prepare a positive electrode having a thickness of 95 μm as a positive electrode mixture layer.

A battery was manufactured by alternately stacking the prepared cathode and anode with a separator as a boundary.

Comparative Example 1

Based on the solid content of the final anode slurry, 3% by weight of SiOx and 94.7% by weight of artificial graphite as anode active materials, 0.3% by weight of SWCNT as a conductive agent, 0.5% by weight of SBR as a binder and 1.5% by weight of CMC as a thickener were mixed with water as a solvent and PD. It was added to a mixer and mixed to prepare a negative electrode slurry. At this time, the amount of water introduced was used so that the solid content contained in the entire composition was 45% by weight.

A battery was manufactured in the same manner as in Example 1, except that a negative electrode was prepared in the same manner as in Example 1 using the prepared negative electrode slurry.

Battery property evaluation

For each battery obtained in Example 1 and Comparative Example 1, the following battery characteristics were evaluated.

[electrode resistance]

Using Hioki's electrode resistance measurement system, the resistance is measured by the potential difference of the electrodes when minute currents of at least 10 μA to 10 mA flow from the four probes for 30 seconds.

[Electrode Adhesion]

The adhesion between the electrode layer and the foil is measured using a 90-degree peel tester from Hi-Test, and the strength measured when one side of the double-sided rolled electrode is attached to the tape on the floor and pulled 10 cm in the 90° direction at a constant speed of 30 mm/min am.

[electrode swelling]

The change in thickness of the negative electrode of the battery before the conversion process and the negative electrode of the fully charged battery after the conversion process is represented by the following equation, and the thickness is measured with a micrometer.

[Volume]

The battery that has undergone the chemical conversion process is loaded into a charger/discharger, charged up to 4.2V at 1/3C current, up to 1/20C at constant current and constant voltage, and discharged at 2.5V at 1/3C at constant current.

[resistance]

After setting the SOC 50% at 1/3C in a 25℃ environment by installing the battery that has undergone the conversion process into a charger/discharger, check the OCV after 30 seconds with a 1C current and calculate it as resistance (V2-V1/I).

[Capacity Change]

Rapid charging of batteries that have completed the conversion process Max. After charging at 5C rate, repeat discharging at 1/3C rate and observe the degree of deterioration of capacity.

[Resistance change amount]

Observe the degree of increase in resistance during the rapid charging cycle of the battery that has completed the conversion process.

The evaluation results of the physical properties of each battery are shown in Table 1 below. In addition, the change in capacity and resistance according to the number of cycles of the battery is shown in FIG. 3 .

unit Example 1 Comparative Example 1 electrode characteristics electrode resistance Ω cm 0.0396 0.0467 electrode adhesion N 0.47 0.48 electrode swelling % 27.1 27.2 Cell
BOL Capacity (1/3C, 2.5V-4.2V, 25℃) Ah 60.8 61.0 Resistance (1C, SOC50%, 25℃) mohm 1.518 1.550 Cell EOL
(@ 500 times) change in capacity % 90.0 89.0 resistance change % 127.7 138

As can be seen from Table 1, Example 1 and Comparative Example 1 were evaluated as having the same properties for electrode adhesion and electrode swelling, but in terms of electrode resistance, the negative electrode of Example 1 showed a significantly reduced result. On the other hand, the battery using the negative electrode of Example 1 had the same capacity and capacity change compared to the battery using the negative electrode of Comparative Example 1, but the battery resistance was significantly reduced and the resistance change was improved. showed up

In addition, it can be seen from FIG. 3 that the increase in resistance according to the number of cycles is significantly reduced compared to Comparative Example 1.

From these results, as in the present invention, a large amount of conductive agent can be present on the surface of the silicon-based negative electrode active material by first contacting the silicon-based negative electrode active material with CNT by applying a mixing process twice in the negative electrode including the silicon-based negative electrode active material, resulting in electrode resistance can be improved, and it can be seen that the change in resistance during cycling is small. At this time, the small increase in resistance is evaluated as a result of improved contact with the CNT when the silicon-based negative electrode active material contracts and expands.

Claims (9)

preparing a first slurry containing a silicon-based first anode active material, a conductive agent, and a binder; and
A method for producing a negative electrode slurry comprising the step of preparing a second slurry by mixing a carbon-based second negative electrode active material and a thickener with the first slurry. The method of claim 1, wherein the conductive agent is at least one selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. The method of claim 1, wherein the binder is styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, ethylene-propylene copolymer, polyepichlorohydrin, polyphos Pazen, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol resin, acrylate resin A method for producing a negative electrode slurry comprising at least one conductive binder selected from the group consisting of polyaniline, polythiophene, polyacetylene, polypyrrole, and PEDOT. The method of claim 1, wherein the thickener is at least one selected from the group consisting of carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, methyl hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, methyl ethyl hydroxyethyl cellulose, and cellulose gum. A method for producing a negative electrode slurry comprising a species. The method of claim 1, wherein the first slurry further comprises a thickener. The method of claim 1, wherein the first slurry is prepared in an in-line mixer. The method of claim 1, wherein the second slurry is prepared in a PD mixer. Applying the negative electrode slurry prepared according to any one of claims 1 to 7 on at least one surface of the negative electrode current collector; and
A method of manufacturing a negative electrode comprising the step of drying the negative electrode current collector to which the negative electrode slurry is applied. a negative electrode prepared according to claim 8; anode; and a separator interposed between the negative electrode and the positive electrode.

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