KR20140087770A - Negative electrode for secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention provides a negative electrode for a secondary battery including an electrode collector; a first coating layer that is applied onto the electrode collector and contains a negative electrode active material, a first non-aqueous binder, and a conductive material; and a second coating layer that is applied onto the first coating layer and contains a second non-aqueous binder. The negative electrode of the present invention is highly capable of buffering change in the volume of the negative electrode active material. Accordingly, cycle characteristics of a lithium battery can be improved in a case where the negative electrode of the present invention is adopted.

Description

TECHNICAL FIELD [0001] The present invention relates to a negative electrode for a secondary battery, and a lithium secondary battery including the same. BACKGROUND OF THE INVENTION < RTI ID = 0.0 >

The present invention relates to a negative electrode for a secondary battery and a lithium secondary battery comprising the negative electrode. More particularly, the present invention relates to a negative electrode for a secondary battery capable of effectively improving degradation of a silicon-based negative electrode having a large volume change during charging and discharging, To a lithium secondary battery.

Recent developments in cell phones, camcorders, notebook PCs, and electric vehicles are increasing interest in energy storage technology. Among them, electrochemical devices have attracted the most attention, and rechargeable batteries that can be charged and discharged are of particular interest.

In particular, a lithium secondary battery using lithium and an electrolyte has been actively developed because of its high possibility of realizing a compact, lightweight, and high energy density.

Conventional lithium secondary batteries mainly use carbon-based compounds capable of reversible intercalation and elimination of lithium ions while maintaining structural and electrical properties as negative electrode active materials. Recently, it has been known that silicon, tin or an alloy thereof that causes a chemical reaction with lithium can reversibly store and release a large amount of lithium, and so much research is underway.

The silicon is promising as a high capacity anode material because its theoretical maximum capacity is about 4020 mAh / g (9800 mAh / cc, specific gravity 2.23) which is very large compared to graphite materials. However, the above-mentioned silicon or its alloy has a disadvantage in that the cycle deteriorates due to degeneration of the negative electrode while repeatedly expanding and contracting during charging and discharging. That is, when lithium ions enter the anode active material (silicon) at the time of charging, the volume of the entire anode active material expands, resulting in a denser structure. Thereafter, at the time of discharging, the lithium ions are again discharged into the ionic state, and the volume of the negative electrode active material is reduced. At this time, since the components mixed together with the negative electrode active material have different expansion ratios, a space is created, and even the spatially separated portions are electrically disconnected and electrons are not smoothly moved. Further, when the elasticity of the binder mixed together with the negative electrode active material is lowered and cracks are generated, the electrical contact is blocked and the resistance is increased. This results in deterioration of the cathode and deteriorates the cycle characteristics of the secondary battery. This phenomenon is further exacerbated as the content of silicon, which is a high-capacity negative electrode active material, is increased in order to manufacture a cell having a high energy density.

In order to improve the above disadvantages, an attempt has been made to increase the binder content in order to increase the adhesive strength between the negative electrode active materials in manufacturing the negative electrode. However, this method has a disadvantage in that the content of the conductive material or the negative electrode active material is relatively lowered, the resistance characteristic of the battery is lowered, the conductivity is lowered, and the battery capacity and output are lowered.

Thus, there is a great need for a technology that improves the adhesion between the lithium metal oxide and the current collector while improving the electrical conductivity and performance of the secondary battery, such as capacity and output characteristics, while using an appropriate amount of binder.

An object of the present invention is to provide a negative electrode for a secondary battery, which further comprises a coating layer made of a non-aqueous binder in order to effectively deteriorate degradation of a silicon-based negative electrode having a large volume change during charging and discharging.

It is another object of the present invention to provide a lithium battery having improved cycle characteristics by including the negative electrode for a secondary battery.

Hereinafter, the present invention will be described in more detail.

The present invention provides a negative electrode for a secondary battery further comprising a second coating layer made of a non-aqueous binder on the entire surface or entire surface of the first coating layer, which is the negative active material layer, in order to effectively improve degradation of the silicon- to provide.

Specifically, in the present invention,

Electrode collector;

A first coating layer coated on the electrode current collector, the first coating layer including a negative active material, a first non-aqueous binder, and a conductive material; And

And a second coating layer coated on the first coating layer, the second coating layer including a second non-aqueous binder.

In the negative electrode of the present invention, the electrode collector may be a surface treated with stainless steel, nickel, copper, titanium or an alloy thereof, copper or stainless steel with carbon, nickel, titanium or silver, Of these, copper or a copper alloy is preferable.

In the negative electrode of the present invention, the negative electrode active material which is the main component of the first coating layer which is the negative electrode active material layer may be natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, Carbon and graphite materials; A metal such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt or Ti capable of forming an alloy with lithium and a compound including these elements; Complexes of metals and their compounds and carbon and graphite materials; Lithium-containing nitride, and the like. However, the present invention is not limited to these. More specifically, examples of the negative electrode active material include a combination of one or more materials selected from the group consisting of crystalline carbon, amorphous carbon, a silicon-based active material, a tin-based active material, and a silicon-carbon based active material.

Further, in the negative electrode of the present invention, the first non-aqueous binder included in the first coating layer is excellent in wetting and permeability in the depth direction of the electrode, so that the bonding force between the negative electrode active material and the current collector is further improved Polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), acrylonitrile-containing binder (X-linking agent), polyvinyl alcohol, polyvinyl chloride, poly A non-aqueous binder mixed with at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl pyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene.

The first non-aqueous binder is a component that assists in bonding to the negative electrode active material, the conductive material, and the current collector, and may include 1 to 50% by weight based on the total weight of the first coating layer. If the content of the first non-aqueous binder exceeds 50% by weight, the area of the binder binding the negative electrode active material increases, thereby increasing the resistance.

The conductive material may further include 1 to 20% by weight based on the total weight of the first coating layer as a component for further improving the conductivity of the electrode active material. Such a conductive material is not particularly limited as long as it can impart conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And conductive materials such as polyphenylene derivatives.

The first coating layer may further contain other additives in addition to the above-mentioned components, if necessary, and the specific content and amount of the first coating layer may be generally sufficient.

The first coating layer is a negative electrode active material layer formed by mixing a negative electrode active material, a first non-aqueous binder, a conductive material, and a solvent to prepare a first slurry, coating the current collector on the current collector, and drying the first slurry.

As the solvent, various solvents such as alcohols and ketones capable of dissolving N-methylpyrrolidone (NMP) or non-aqueous binder may be used.

In addition, the thickness of the first coating layer may be suitably changed according to the capacity design of a desired battery cell, and may have a thickness of several tens to several hundreds of microns.

At this time, the first binder may be coated on the entire surface of the negative electrode active material particles, or may be coated only on the contact area between the negative electrode active material particles, specifically, .

In the negative electrode of the present invention, the second non-aqueous binder contained in the second coating layer may be the same as or different from the second non-aqueous binder included in the first coating layer. For example, the second non-aqueous binder can be selected from the group consisting of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), an acrylonitrile containing X-linking agent, polyvinyl alcohol, polyvinyl chloride, poly A non-aqueous binder mixed with at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl pyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene.

The second coating layer is formed by mixing a second binder and a solvent to prepare a second slurry, applying the first slurry to a part or whole surface of the electrode coated with the dried first coating layer, and drying the second slurry.

As the solvent, various solvents such as alcohols and ketones capable of dissolving N-methylpyrrolidone (NMP) or non-aqueous binder may be used.

The second coating layer is formed using a general coating method, and the forming method thereof is not particularly limited, and can be applied using a conventional dip coating method, spray coating method or the like.

The second coating layer including the second binder 15 may be applied to the entire surface of the electrode on which the first coating layer is formed or may be coated on the first binder 13 bonded to the point contact portion of the adjacent anode active material 11 Can be selectively coated (see Fig. 1).

Specifically, the second coating layer may be formed in an amount of about 100 wt% or less, specifically about 1 to 50 wt%, more specifically about 1 to 10 wt%, based on the total weight of the electrode on which the first coating layer is formed By weight, more specifically about 1 to 5% by weight.

The second coating layer may further include a conductive material and other additives to improve conductivity.

In addition, the present invention provides a lithium secondary battery including the negative electrode, the positive electrode, the electrolyte, and the separator of the present invention and having improved charge / discharge characteristics and cycle characteristics.

The positive electrode may be prepared by applying a slurry containing a positive electrode active material, a conductive material and a binder on a positive electrode current collector by the same method as the negative electrode and drying the slurry. If necessary, the positive electrode slurry may further contain a filler.

The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel Surface-treated with carbon, nickel, titanium, silver, or the like may be used. The positive electrode current collector may form fine irregularities on the surface to increase the adhesive force with the positive electrode active material. The positive electrode current collector can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; _{LiNi 1 - xy Co x (Al} ) y O 2 ( where, x = 0.15, Y = 0.05 ) oxide, or the general formula _{Li 1 + x Mn 2 -x O} 4 ( here, x is from 0 to 0.33), LiMnO ₃ , Lithium manganese oxides such as LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _{1 - x} M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); Formula _{LiMn 2 - x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 to 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like can be used, but it is preferable to use LiNi _x Mn _{2 - x} O ₄ (x = 0.01 to 0.6), more preferably LiNi _{0 .5} Mn _{1 .5} O ₄ or LiNi _{0 .4} may be a Mn ₁ O _{4 .6.} That is, in the present invention, it is preferable to use a spinel lithium manganese composite oxide of LiNi _x Mn _{2 - x} O ₄ (x = 0.01 to 0.6) having a relatively high potential due to a high potential of the negative electrode active material as a cathode active material .

The conductive material may be added in an amount of 1 to 10% by weight based on the total weight of the slurry for the positive electrode, and is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery. For example, Graphite and other graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

Further, the binder is added as an ingredient for improving the bonding to the active material, the conductive material and the current collector, and usually 1 to 50% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include PVDF, which is a non-aqueous binder.

The filler is optionally used as a component for suppressing expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin-based polymerizers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

As the electrolyte solution, a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, or the like is used as the electrolyte solution containing a lithium salt, but the present invention is not limited thereto.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenyl lithium borate, and imide.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate , Gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, But are not limited to, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, Derivatives, tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

Further, the separator is interposed between the positive electrode and the negative electrode, and an insulating thin film having high ion permeability and mechanical strength is used. Examples of such a separation membrane include an olefin-based polymer such as polypropylene, which is resistant to chemicals and hydrophobicity; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

 Also, the present invention provides a battery module including the secondary battery as a unit battery, a battery pack including the battery module, and a device including the battery pack.

As described above, in the conventional negative electrode, the elasticity of the binder mixed together with the negative active material at the time of charging and discharging is lowered and the ability to buffer the change of the volume of the negative active material is insufficient. However, the negative electrode of the present invention contains the first non- By further applying a coating layer including the second non-aqueous binder on the active material layer, it is possible not only to maintain a proper bonding force between the active material layer and the collector, but also to buffer the volume change of the negative electrode active material during charging and discharging of the electrode, It is possible to manufacture a lithium secondary battery with improved cycle life and charge / discharge characteristics without increasing the resistance of the electrode.

According to the present invention, by further forming a second coating layer made of a non-aqueous binder on the first coating layer, which is a negative active material layer, degeneration of a silicon-based negative electrode having a large volume change during charging and discharging can be effectively prevented, Charge and discharge characteristics and cycle characteristics can be improved.

1 is a schematic view of a negative electrode active material structure of the present invention.
2 is a graph showing the results of cycle retention measurement according to an embodiment of the present invention.
FIGS. 3A and 3B are graphs showing the results of measurement of the capacity retention rate of the lithium secondary battery of the present invention obtained from Experimental Example 4. FIG.
4A and 4B are graphs showing the results of resistance characteristics tests of the lithium secondary battery of the present invention obtained from Experimental Example 4. FIG.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

I. The present invention For coating layer Slurry  Produce

(Production Example 1)

Polyacrylonitrile (PAN) (2 g) was dissolved in 100 mL of N-methylpyrrolidone (NMP) and stirred for 1 hour to prepare a second coating layer slurry.

(Production Example 2)

A slurry for a second coating layer was prepared in the same manner as in Preparation Example 1, except that polyvinylidene fluoride (PVDF) was used in place of the polyacrylonitrile (PAN).

(Production Example 3)

A slurry for the second coating layer was prepared in the same manner as in Preparation Example 1, except that an acrylonitrile-containing binder (X-linking agent) was used in place of the polyacrylonitrile (PAN).

II . Cathode manufacture

(Example 1)

(10 wt%) of a polyvinylidene fluoride (PVDF) solution and 12 g (5 wt%) of a carbon nanotube solution used as a conductive material were uniformly mixed using a mechanical stirrer. To the mixed solution, a high-capacity negative electrode active material SiO _x and graphite having stable charge / discharge behavior were added at a ratio of about 1: 2, and the slurry for the first coating layer was prepared by dispersing the active material using a mechanical stirrer.

Next, the slurry was coated on a copper (Cu) current collector with a thickness of about 100 탆 using a comma coater, and then dried again under vacuum and at a temperature of 110 캜 to form a first coating layer Thereby preparing a negative electrode plate.

Subsequently, the slurry for the second coating layer prepared in Preparation Example 1 was applied to the negative electrode plate (first coating layer) using the dip coating method and dried to form a second coating layer containing the second coating layer Thereby preparing a negative electrode plate.

Next, 45 wt% of LiNi _{1 - xy} Co _x (Al) _y O ₂ (where x = 0.15, Y = 0.05) (NCA, Todasa), 2.5 wt% of carbon black (Super- 2.5% by weight of vinylidene fluoride / hexafluoropropylene copolymer (Solef 6020, Solvey) and 50% by weight of N-methylpyrrolidone were mixed to prepare a cathode active material composition, which was coated on the aluminum current collector in a thickness of 200 탆 And then dried to prepare a positive electrode plate.

Next, LiPF ₆ was added to a solvent in which ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate were mixed in a volume ratio of 3: 4: 3 to prepare an organic electrolyte solution having a lithium salt concentration of 1.2M.

Thereafter, polyethylene as a separator was disposed between the negative electrode plate and the positive electrode plate to form an electrode assembly, which was then placed in a battery case, and the electrolyte solution was injected to prepare a lithium secondary battery.

(Example 2)

A negative electrode plate and a secondary battery including the negative electrode plate were prepared in the same manner as in Example 1, except that the slurry for the second coating layer of Production Example 2 was applied instead of the slurry for the second coating layer of Production Example 1.

(Example 3)

A negative electrode plate and a secondary battery including the negative electrode plate were prepared in the same manner as in Example 1 except that the slurry for the second coating layer of Production Example 3 was used instead of the slurry for the second coating layer of Production Example 1

(Comparative Example 1)

(10 wt%) of a polyvinylidene fluoride (PVDF) solution and 12 g (5 wt%) of a carbon nanotube solution used as a conductive material were uniformly mixed using a mechanical stirrer. To the mixed solution, a high-capacity negative electrode active material SiO _x and graphite having stable charge / discharge behavior were added at a ratio of about 1: 2, and the slurry for the first coating layer was prepared by dispersing the active material using a mechanical stirrer.

Next, the slurry was coated on a copper (Cu) current collector with a thickness of about 100 탆 using a comma coater, and then dried again under vacuum and at a temperature of 110 캜 to form a first coating layer Thereby preparing a negative electrode plate.

Subsequently, 45 wt% of LiNi _{1 - xy} Co _x (Al) _y O ₂ (where x = 0.15, Y = 0.05) (NCA, Toda), 2.5 wt% of carbon black (Super- 2.5% by weight of fluoride / hexafluoropropylene copolymer (Solef 6020, Solvey) and 50% by weight of N-methylpyrrolidone were mixed to prepare a cathode active material composition, which was coated on the aluminum current collector to a thickness of 200 탆 And dried to prepare a positive electrode plate.

Next, LiPF ₆ was added to a solvent in which ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate were mixed in a volume ratio of 3: 4: 3 to prepare an organic electrolyte solution having a lithium salt concentration of 1.2M.

Thereafter, polyethylene as a separator was disposed between the negative electrode plate and the positive electrode plate to form an electrode assembly, which was then placed in a battery case, and the electrolyte solution was injected to prepare a lithium secondary battery.

III . Adhesion and power experiment

(Experimental Example 1)

The anode plate prepared in Example 1 was cut at intervals of 10 mm and subjected to 180 ^o peel test to measure the adhesion force of the electrode coated with the second coating layer and the first coating layer, The results are shown in Table 1 and FIG.

(Experimental Example 2)

The adhesive force was measured in the same manner as in Experimental Example 1, except that the negative electrode plate of Example 2 was used in place of the negative electrode plate of Example 1, and the results are shown in Table 1 and FIG.

(Experimental Example 3)

The adhesive force was measured in the same manner as in Experimental Example 1, except that the negative electrode plate of Example 3 was used in place of the negative electrode plate of Example 1, and the results are shown in Table 1 and FIG.

(Comparative Experimental Example 1)

The adhesive force was measured in the same manner as in Experimental Example 1, except that the negative electrode plate of Comparative Example 1 was used instead of the negative electrode plate of Example 1, and the results are shown in Table 1 and FIG.

Cathode plate (% By weight) of the second coating layer, Adhesion (gf / 10mm) Example 1 2.0 218.2 Example 2 3.9 223.5 Example 3 3.9 265.4 Comparative Example 1 - 101.1

As shown in Table 1 and FIG. 2, in the case of the negative electrode plate in which the second coating layer of Examples 1 to 3 was formed, the adhesive force between the electrodes formed with the second coating layer and the first coating layer was improved, There is no significant difference in the cycle retention value thereafter. On the other hand, in the case of the negative electrode plate in which only the first coating layer of Comparative Example 1 is formed singly, the adhesive force is as low as about 100, and the cycle retention value decreases after a long cycle Respectively. Comparing the remaining capacity according to the cycle shown in FIG. 2, the capacity retention rate after 300 cycles in the case of Comparative Example 1 was as low as 80%, but in the case of Examples 1 to 3, It can be seen that the lifetime is improved to a level of 825 or more.

(Experimental Example 4)

The output and resistance of the secondary batteries manufactured in Examples 1 to 3 and Comparative Example 1 were measured using a hybrid pulse power characterization (HPPC) method.

The battery was charged from SOC 10 to a full charge (SOC = 100) up to 4.3 V at 0.1 C (4 mA), and the battery was stabilized for 1 hour. Then, the output and resistance of the lithium secondary battery were measured according to the HPPC test method. In addition, the battery was discharged SOC 10 to SOC 100 to SOC 10, and each battery was stabilized for 1 hour, and the output and resistance of the lithium secondary battery were measured by the HPPC test method for each SOC step.

Capacity retention rates after initial charge-discharge and 300 charge-discharge cycles are shown in Figs. 3A and 3B, and capacitances (resistance characteristic results) after initial charge-discharge and 300 charge-discharge cycles are shown in Figs. 4A and 4B.

That is, as shown in FIGS. 3A and 3B, in the case of the comparative example 1, the output value after 300 cycles is lower than the initial value in the entire SOC region, but in the case of the embodiment 1, The output reduction width is improved. As shown in FIGS. 4A and 4B, in the case of Comparative Example 1, the resistance value after 300 cycles fell in the entire SOC region compared with the initial value. In Example 1, however, Is improved.

This result shows that even if the second coating layer is repeatedly charged and discharged by the second coating layer, the second coating layer keeps bonding with the electrode having the first coating layer as the negative active material layer, and the volume change of the negative active material can be alleviated, It is possible to prevent the battery from being electrically disconnected and to reversibly store / release lithium ions, thereby improving the cycle characteristics of the secondary battery.

11: anode active material
13: first binder
15: Second binder

Claims (12)

Electrode collector;
A first coating layer coated on the electrode current collector, the first coating layer including a negative active material, a first non-aqueous binder, and a conductive material; And
And a second coating layer coated on the first coating layer and including a second non-aqueous binder. The method according to claim 1,
The first non-aqueous binder may be at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), an acrylonitrile containing X-linking agent, polyvinyl alcohol, polyvinyl chloride, polyvinylpyrrolidone , Polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene. The negative electrode according to claim 1, wherein the negative electrode is a non-aqueous binder selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene. The method according to claim 1,
Wherein the first non-aqueous binder is present at a point-contact portion of adjacent anode active material particles, and binds the anode active material particles to each other. The method according to claim 1,
And the second non-aqueous binder is a binder of the same kind as the first non-aqueous binder or a binder of another kind. The method of claim 4,
The second non-aqueous binder is selected from the group consisting of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), an acrylonitrile-containing binder (X-linking agent), polyvinyl alcohol, polyvinyl chloride, polyvinylpyrrolidone , Polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene. The negative electrode according to claim 1, wherein the negative electrode is a non-aqueous binder selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene. The method according to claim 1,
Wherein the second coating layer is coated on the entire surface of the electrode on which the first coating layer is formed or selectively coated on the first binder formed on the point contact portion of the adjacent anode active material particles. The method according to claim 1,
Wherein the second coating layer is coated in an amount of 100% by weight or less based on the total weight of the electrode on which the first coating layer is formed. The method of claim 7,
Wherein the second coating layer is coated in an amount of 1 to 50 wt% based on the total weight of the electrode having the first coating layer formed thereon. The method of claim 8,
Wherein the second coating layer is coated in an amount of 1 to 10 wt% based on the total weight of the electrode having the first coating layer formed thereon. The method of claim 9,
Wherein the second coating layer is coated in an amount of 1 to 5 wt% based on the total weight of the electrode on which the first coating layer is formed. The method according to claim 1,
Lt; RTI ID = 0.0 > 1, < / RTI > wherein the second coating layer further comprises a conductive material. A lithium secondary battery comprising the negative electrode, the positive electrode, the electrolytic solution and the separator according to claim 1.

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