KR20200122212A - an anode active material, anode comprising the same, and lithium secondary battery comprising the anode - Google Patents

Abstract

The present invention relates to a negative electrode active material comprising: a core including a carbon-based material; and a polycyclic ionic group-containing compound bonded to a surface of the carbon-based material, and capable of reducing the content of a binder, to a negative electrode comprising the same, and to a lithium secondary battery comprising the negative electrode.

Description

An anode active material, anode comprising the same, and lithium secondary battery comprising the anode}

It relates to a negative electrode active material, a negative electrode including the same, and a lithium secondary battery including the negative electrode.

Lithium batteries are used as power sources for portable electronic devices such as video cameras, mobile phones, and notebook computers. The rechargeable lithium secondary battery has more than three times the energy density per unit weight and can be charged at a high speed compared to conventional lead storage batteries, nickel-cadmium batteries, nickel hydrogen batteries, and nickel zinc batteries.

In general, a lithium secondary battery uses a material capable of reversible intercalation and deintercalation of lithium ions as a positive electrode active material and a negative electrode active material, and an electrolyte between the positive electrode including the positive electrode active material and the negative electrode including the negative electrode active material It is prepared by filling.

At this time, as the negative electrode active material used for the negative electrode of the lithium secondary battery, a carbon-based material whose stability has been verified is mainly used, and an appropriate amount of a binder is used together to strengthen contact between the negative electrode active material and other materials included in the negative electrode.

On the other hand, the negative electrode that has been used in the past has a problem that the negative electrode active material is deteriorated due to a decrease in conductivity or a side reaction with the electrolyte due to the generation of spaces between the materials included in the negative electrode according to the volume change due to repeated charging and discharging. Has been raised.

In order to solve this problem, there have been attempts to modify the surface of the active material by acid treatment or heat treatment on the surface of a negative electrode active material, for example, a carbon-based material, but the carbon-based material is an organic material, such as acid and heat. It is vulnerable to, and there is a problem in that some of the covalent bonds on the carbon surface are decomposed and the conductivity is lowered.

Accordingly, there is still a demand for a negative electrode active material that allows the negative electrode active material, a binder, and a conductive material included in the negative electrode to be firmly bound and maintained.

According to one aspect, an anode active material included in a cathode, an anode active material having improved binding strength of a binder, etc., an anode including the same, and a lithium secondary battery including the anode are provided.

According to one aspect,

A core containing a carbon-based material;

A polycyclic compound represented by the following formula 1 provided on the core surface;

A negative electrode active material comprising a is provided.

<Formula 1>

L is a single bond, a substituted or unsubstituted C ₁ -C ₂₀ alkylene group, a substituted or unsubstituted C ₂ -C ₂₀ alkenylene group, a substituted or unsubstituted C ₂ -C ₂₀ alkynylene group, and a substituted or unsubstituted It is selected from a cyclic C ₆ -C ₂₀ aryl group,

R is a polar group or an ionic group,

m≥2, n≥1,

When n is 2 or more, 2 or more -L-Rs may be the same as or different from each other.

According to another aspect, a negative electrode comprising a substrate and a negative electrode active material layer formed on the substrate, wherein the negative electrode active material layer includes the aforementioned negative electrode active material and a binder, and the negative electrode active material is present in a non-covalent bond state with the binder Is provided.

According to another aspect, a negative electrode including the negative electrode active material; anode; And there is provided a lithium secondary battery including an electrolyte.

In the negative electrode active material according to an aspect, by non-covalent bonding between a core containing a carbon-based material and a polycyclic compound containing a polar group and/or an ionic group, deterioration of the negative electrode active material is prevented, as well as a polar group and a polar group among the polycyclic compounds. /Or the non-covalent bonding strength with other materials, such as a binder and a conductive material, is improved by the ionic group, so that the content of the binder can be reduced.

1 is a schematic diagram showing the structure of a lithium secondary battery according to an embodiment.
2 is a graph showing the results of the binding strength test in Example 1 and Comparative Examples 1 and 2.
3 is a graph showing the thickness increase rate of the negative electrode after one charge of the half cells of Example 5 and Comparative Examples 8 and 9;
4 is a graph showing the results of the binding force test in Example 2 and Comparative Examples 3 and 4;
5 is a graph showing the thickness increase rate of the negative electrode after one charge of the half cells of Example 6 and Comparative Examples 10 and 11.
6 is a graph showing the results of the binding force test in Example 3 and Comparative Examples 5 and 6.
7 is a graph showing the thickness increase rate of the negative electrode after one charge of the half cells of Example 7, and Comparative Examples 12 and 13.
8 is a graph showing the results of the bonding strength test in Example 4 and Comparative Examples 3 and 7.
9 is a graph showing the thickness increase rate of the negative electrode after one charge of the half cells of Example 8 and Comparative Examples 10 and 14.
<Explanation of symbols for major parts of drawings>
1: lithium battery 2: negative electrode
3: anode 4: separator
5: battery case 6: cap assembly

The present inventive concept described below may apply various transformations and may have various embodiments. Specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present creative idea to a specific embodiment, it is to be understood as including all transformations, equivalents or substitutes included in the technical scope of the present creative idea.

The terms used below are only used to describe specific embodiments, and are not intended to limit the present inventive idea. Singular expressions include plural expressions unless the context clearly indicates otherwise. Hereinafter, terms such as "comprises" or "have" are intended to indicate the existence of features, numbers, steps, actions, components, parts, components, materials, or a combination thereof described in the specification. It is to be understood that the above other features, or the possibility of the presence or addition of numbers, steps, actions, components, parts, components, materials, or combinations thereof, are not excluded in advance. "/" used below may be interpreted as "and" or "or" depending on the situation.

In the drawings, the diameter, length, and thickness are enlarged or reduced in order to clearly express various elements, layers, and regions. The same reference numerals are assigned to similar parts throughout the specification. Throughout the specification, when a part such as a layer, film, region, plate, etc. is said to be "on" or "on" another part, this includes not only the case directly above the other part, but also the case where there is another part in the middle. . Throughout the specification, terms such as first and second may be used to describe various components, but the components should not be limited by terms. The terms are used only for the purpose of distinguishing one component from another. In the drawings, some of the components may be omitted, but this is to help understanding the features of the invention and is not intended to exclude the omitted components.

In the present specification, the term "C ₁ -C ₁₀ alkyl group" refers to a linear or branched chain hydrocarbon monovalent group consisting of 1 to 10 carbon atoms, for example methyl group, ethyl group, isopropyl group, propyl group, butyl group And the like.

In the present specification, the term "C ₁ -C ₂₀ alkylene group" refers to a divalent group having the same structure as a C ₁ -C ₂₀ alkyl group.

In the present specification, the term "C ₂ -C ₂₀ alkenylene group" refers to a hydrocarbon divalent group including one or more carbon-carbon double bonds among C ₂ -C ₂₀ alkyl groups.

In the present specification, the term "C ₂ -C ₂₀ alkynylene group" refers to a hydrocarbon divalent group including one or more carbon-carbon triple bonds among C ₂ -C ₂₀ alkyl groups.

In the present specification, the term "C ₆ -C ₂₀ arylene group" refers to an aromatic hydrocarbon ring divalent group consisting of 6 to 20 carbon atoms. In this case, when two or more hydrocarbon rings are included, the two or more hydrocarbon rings may be condensed with each other.

In the present specification, a substituted C ₁ -C ₁₀ alkyl group, a substituted C ₁ -C ₂₀ alkylene group, a substituted C ₂ -C ₂₀ alkenylene group, a substituted C ₂ -C ₂₀ alkynylene group, and a substituted C ₆ At least one of the substituents of the -C ₂₀ arylene group,

Halogen, C ₁ -C ₁₀ alkyl group, C ₂ -C ₁₀ alkenyl group, C ₂ -C ₁₀ alkynyl group;

C ₆ -C ₂₀ arylene group; And

A C ₆ -C ₂₀ arylene group substituted with at least one of a C ₁ -C ₁₀ alkyl group, a C ₂ -C ₁₀ alkenyl group, and a C ₂ -C ₁₀ alkynyl group;

Can be selected from.

Hereinafter, a negative electrode active material according to exemplary embodiments, a negative electrode including the same, and a lithium secondary battery including the negative electrode will be described in more detail.

A negative electrode active material according to an aspect includes a core including a carbon-based material; Includes; polycyclic compound represented by the following formula 1 provided on the core surface:

<Formula 1>

L is a single bond, a substituted or unsubstituted C ₁ -C ₂₀ alkylene group, a substituted or unsubstituted C ₂ -C ₂₀ alkenylene group, a substituted or unsubstituted C ₂ -C ₂₀ alkynylene group, and a substituted or unsubstituted It is selected from a ringed C ₆ -C ₂₀ arylene group,

R is a polar group or an ionic group,

m≥2, n≥1,

When n is 2 or more, 2 or more -L-Rs may be the same as or different from each other.

The anode active material is formed by disposing a polycyclic compound having a polar group and/or an ionic group on the surface of the core, so that the polar group and/or the ionic group are adjacent to other anode active material slurry materials, for example, a binder, a conductive material, In addition to improving the bonding strength with the anode active materials, the bonding strength with the anode current collector is also improved. Accordingly, as the materials included in the negative electrode are firmly bonded, volume expansion of the negative electrode active material during charging is effectively suppressed, thereby having an advantageous effect of decreasing the rate of increase in the thickness of the electrode. The decrease in the rate of increase in the electrode thickness decreases the size of the gap between the active materials according to the volume change of the anode active material, and as a result, deterioration of the active material due to a side reaction between the active material and the electrolyte is prevented.

The polycyclic compound may be bonded to the core surface by a non-covalent bond. Here, "non-covalent bond" is a bond by an interaction other than a covalent bond in which an atom or molecule bonds in a way that shares electrons, and includes electrostatic interaction, hydrogen bonding, van der Waals interaction, hydrophobic interaction, etc. do.

The polycyclic moiety of the polycyclic compound and the surface of the core including the carbon-based material may be bonded to each other by a π-π interaction. Here, "π-π interaction" is one of the non-covalent interactions that occur when the π electron cloud in one molecule is adjacent to the π electron cloud in another molecule, and is a partial positive/negative charge formed by the distribution of the electron cloud. It refers to the interaction that occurs through miraculous attraction. The polycyclic moiety of the polycyclic polar group-containing compound and the surface of the core including the carbon-based material are bonded by π-π interactions, thereby forming a hydrophobic carbon-based material or a core having a carbon-based material on the outer surface thereof. The surface is modified with the ionic moiety of the polycyclic compound. By such surface modification, the surface of the core having the carbon-based material or the carbon-based material on the outer surface becomes hydrophilic, and the binding strength is improved through enhanced non-covalent interaction with a general binder including a hydrophilic group.

The polycyclic compound may be included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the negative active material.

For example, the polycyclic compound is 0.01 to 4.5 parts by weight, 0.01 to 4.0 parts by weight, 0.01 to 3.5 parts by weight, 0.01 to 3.0 parts by weight, 0.01 to 2.5 parts by weight, 0.01 to 2.0 parts by weight based on the total 100 parts by weight of the negative active material. Parts by weight, 0.01 to 1.5 parts by weight, 0.01 to 1.0 parts by weight, 0.01 to 0.5 parts by weight, 0.01 to 0.45 parts by weight, 0.01 to 0.40 parts by weight, 0.01 to 0.35 parts by weight, 0.01 to 0.30 parts by weight, 0.01 to 0.25 parts by weight , 0.01 to 0.20 parts by weight, 0.01 to 0.15 parts by weight, or 0.01 to 0.10 parts by weight may be included, but the present invention is not limited thereto, and an amount sufficient to obtain a desired binding force of the negative electrode active material may be selected.

The core may further include a metal alloyable with lithium and/or an oxide of a metal alloyable with lithium. When the core further includes a metal alloyable with lithium and/or an oxide of a metal alloyable with lithium, a negative electrode active material having a higher capacity than an active material composed of only carbon-based materials may be obtained.

For example, the metal alloyable with lithium is Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y ₁ alloy (the Y ₁ is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal , Rare earth elements and any one or more elements selected from a combination thereof, but not including Si), Sn-Y ₂ alloy (the Y ₂ is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal , Rare earth elements, and any one or more elements selected from a combination thereof, but not including Sn), and the like. The elements Y ₁ and Y ₂ are independently of each other 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, Ti, Ge, P, As , Sb, Bi, S, Se, or Te.

For example, the oxide of a metal that can be alloyed with lithium may include a silicon oxide represented by Formula 2 below, but is not limited thereto:

<Formula 2>

SiOx (0<x≤2)

According to one embodiment, the core may include a carbon-based material and/or an oxide of a metal alloyable with lithium, and the carbon-based material may be disposed on a surface of an oxide of a metal alloyable with lithium.

According to one embodiment, the core may include a metal alloyable with lithium whose surface is coated with a carbon-based material. For example, the core may include silicon particles or silicon-carbon composite particles in which the surfaces of silicon secondary particles formed by aggregation of silicon particles are coated with a carbon-based material.

According to another embodiment, the core may include an oxide of a metal alloyable with lithium whose surface is coated with a carbon-based material. For example, the core may include silicon oxide-carbon composite particles in which a surface of silicon oxide is coated with a carbon-based material.

According to another embodiment, the core may include a metal alloyable with lithium and an oxide of a metal alloyable with lithium coated with a carbon-based material. For example, the core may include carbon-coated silicon-based composite particles in which the surfaces of silicon secondary particles in which silicon particles and silicon oxide are mixed are coated with a carbon-based material.

According to another embodiment, the core may include a carbon-based material including a cavity in the center. For example, the core may include a carbon-based material including a cavity such as carbon nanotubes and fullerenes.

According to another embodiment, the core may be made of only a carbon-based material. For example, the core may include natural graphite or artificial graphite.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as amorphous, plate-shaped, flake, spherical or fibrous natural graphite or artificial graphite, and the amorphous carbon is soft carbon (low temperature calcined carbon) or hard carbon (hard carbon). carbon), mesophase pitch carbide, calcined coke, or the like.

According to one embodiment, the carbon-based material may include crystalline carbon. For example, the carbon-based material may be plate-shaped natural graphite or artificial graphite formed by condensation of benzene rings on the same plane. As a result, a negative electrode active material having a structure in which a polycyclic ionic group-containing compound is stacked on a carbon-based material by π-π interaction between a benzene ring in the carbon-based material and a polycyclic moiety in the polycyclic ionic group-containing compound can be obtained. have. Therefore, despite the introduction of the polycyclic ionic group-containing compound, a decrease in the conductivity of the carbon-based material is not caused, and insertion and desorption of lithium ions are not disturbed.

는 하기 화학식 2-1 내지 2-23으로부터 선택된 그룹일 수 있으나, 이에 한정되는 것은 아니며, 벤젠 고리가 m개 축합된 다양한 구조의 다환 방향족 고리가 선택될 수 있다.In Formula 1

May be a group selected from Formulas 2-1 to 2-23 below, but is not limited thereto, and polycyclic aromatic rings having various structures in which m benzene rings are condensed may be selected.

.

.

In Formula 1, L is

Single bond;

Methylene group, ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, and decylene group; And

A methylene group substituted with one or more of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups, ethylene, propylene, butylene, pentylene, hexylene Group, heptylene group, octylene group, nonylene group and decylene group;

It may be selected from, but is not limited thereto.

According to an embodiment, in Formula 1, L is

Methylene group, ethylene group, propylene group, butylene group, and pentylene group; And

A methylene group, an ethylene group, a propylene group, and a butylene group substituted with one or more of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group;

It may be selected from, but is not limited thereto.

In Formula 1, R may be a polar group or an ionic group.

According to one embodiment, the ionic group may include a cationic group, an anionic group, or a combination thereof.

For example, the ionic groups are _{^{-COO -, -SO 3 -, -SO}} 4 2- or -PO ₄ ^2-; And NH ₃ ⁺ , NH ₂ R _a ⁺ , NHR _a R _b ⁺ , NR _a R _b R _c ⁺ , or PR _a R _b R _c ⁺ (R _a , R _b , R _c are independently substituted or unsubstituted It may be selected from the C ₁ -C ₁₀ alkyl group), but is not limited thereto.

For example, the polar group -OH, -CHO -COOH, -SO ₃ H, -SO ₄ H, -PO ₄ H, -NH ₂ , -NHR _a or -NR _a R _b (R _a , R _b is It may be independently selected from a substituted or unsubstituted C ₁ -C ₁₀ alkyl group), but is not limited thereto.

Here, the substituent of the substituted C ₁ -C ₁₀ alkyl group is, for example, a group consisting of methyl group, ethyl group, propyl group, iso-propyl group, butyl group, sec-butyl group, iso-butyl group, and tert-butyl group Can be selected from

In Formula 1, wherein R is a polar group or an ionic group, by a non-covalent interaction between the surface of the negative electrode active material modified with the polycyclic compound through a π-π interaction and a binder including a hydrophilic group, between the negative electrode active material, the current collector The bonding strength between the and the negative active material was improved.

In Formula 1, m≥4 and n may be 1 or 2. For example, when m is 4, n may be 1 or 2.

According to one embodiment, m is 4x, and n may be an integer selected from x to 2x (an integer equal to or greater than x=1). For example, when m is 8, n may be 2 to 4. When m and n satisfy the above ratio, the negative electrode active material and other materials constituting the negative electrode, such as a binder, a conductive material, and a negative electrode current collector have improved binding strength, and the negative electrode including the same has a reduced electrode expansion rate Has.

The negative electrode according to one aspect includes the negative electrode active material described above.

The negative electrode according to an aspect includes a substrate and a negative electrode active material layer formed on the substrate, the negative electrode active material layer includes the negative electrode active material and a binder, and the negative electrode active material may exist in a non-covalent bond state with the binder. have.

For example, the non-covalent bonds may include electrostatic interactions, hydrogen bonding, van der Waals interactions, hydrophobic interactions, and combinations thereof.

The substrate may be a negative electrode current collector. The negative electrode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof.

According to one embodiment, the binding force between the anode active material layer and the substrate may be 0.5 gf/mm or more.

A lithium secondary battery according to an aspect includes a negative electrode including the negative electrode active material described above; anode; Contains electrolyte.

The lithium secondary battery may have a thickness increase rate of 50% or less after charging once. For example, the lithium secondary battery has a thickness increase rate of less than 50%, 49% or less, 48% or less, 47% or less, 46% or less, 45% or less, 44% or less, 43% or less after a single charge, It may be 42% or less, 41% or less, 40% or less, 39% or less, 38% or less, 37% or less, 36% or less, or 35% or less.

For example, the lithium secondary battery may be manufactured by the following method.

First, the anode is prepared.

For example, a positive electrode active material composition in which a positive electrode active material, a conductive material, a binder, and a solvent are mixed is prepared. The positive electrode active material composition is directly coated on a metal current collector to prepare a positive electrode plate. Alternatively, the positive electrode active material composition may be cast on a separate support, and then a film peeled from the support may be laminated on a metal current collector to prepare a positive electrode plate. The anode is not limited to the shapes listed above, but may be in a shape other than the above shape.

The positive electrode active material is a lithium-containing metal oxide and may be used without limitation as long as it is commonly used in the art. For example, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used. In another example, Li _a A _1-b B ¹ _b D ¹ ₂ (where 0.90≦a≦1.8, and 0≦b≦0.5); Li _a E _1-b B ¹ _b O _2-c D ¹ _c (in the above formula, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05); LiE _2-b B ¹ _b O _4-c D ¹ _c (where 0≦b≦0.5, 0≦c≦0.05); Li _a Ni _1-bc Co _b B ¹ _c D ¹ _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Co _b B ¹ _c O _2-α F ¹ _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Co _b B ¹ _c O _2-α F ¹ ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B ¹ _c D ¹ _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Mn _b B ¹ _c O _2-α F1 _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B ¹ _c O _2-α F ¹ ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1); Li _a NiG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a CoG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a MnG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90≦a≦1.8 and 0.001≦b≦0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiI ¹ O ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≦f≦2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≦f≦2); A compound represented by any one of the formulas of LiFePO ₄ can be used:

In the above formula, A is Ni, Co, Mn, or a combination thereof; B ¹ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or combinations thereof; D ¹ is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F ¹ is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

For example, LiCoO ₂ , LiMn _x O _2x (x=1, 2), LiNi _1-x Mn _x O _2x (0<x<1), LiNi _1-xy Co _x Mn _y O ₂ (0≤x≤ 0.5, 0≤y≤0.5), LiFePO ₄ and the like.

Of course, one having a coating layer on the surface of the compound may be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may contain a coating element compound of oxide, hydroxide, oxyhydroxide of coating element, oxycarbonate of coating element, or hydroxycarbonate of coating element. The compound constituting these coating layers may be amorphous or crystalline. As a coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. The coating layer formation process may be any coating method as long as the compound can be coated by a method that does not adversely affect the physical properties of the positive electrode active material by using these elements (e.g. spray coating, dipping method, etc.). Since the content can be well understood by those engaged in the relevant field, detailed description will be omitted.

Carbon black, graphite fine particles, etc. may be used as the conductive material, but are not limited thereto, and any material that can be used as a conductive material in the art may be used.

As the binder, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, or styrene butadiene rubber-based polymer, etc. Although may be used, it is not limited thereto, and any one that can be used as a binder in the art may be used.

As the solvent, N-methylpyrrolidone, acetone, or water may be used, but are not limited thereto, and any solvent that can be used in the art may be used.

The contents of the positive electrode active material, the conductive material, the binder, and the solvent are generally used in lithium batteries. One or more of the conductive material, the binder, and the solvent may be omitted depending on the use and configuration of the lithium battery.

Next, the cathode is prepared.

For example, an anode active material composition is prepared by mixing the aforementioned anode active material, conductive material, binder, and solvent. The negative electrode active material composition is directly coated and dried on a metal current collector to prepare a negative electrode plate. Alternatively, after the negative active material composition is cast on a separate support, a film peeled from the support may be laminated on a metal current collector to prepare a negative electrode plate.

The content of the binder may be 1.0 to 10 parts by weight based on 100 parts by weight of the total negative active material layer. As the negative electrode active material layer improves the binding force to the current collector, the content of the binder may decrease. In addition, as the content of the binder in the negative electrode active material layer decreases, the resistance of the electrode decreases and the capacity density increases, thereby improving battery performance.

The content of the conductive material and the solvent is the level commonly used in lithium batteries. One or more of the conductive material, the binder, and the solvent may be omitted depending on the use and configuration of the lithium battery.

Next, a separator to be inserted between the positive and negative electrodes is prepared.

Any of the separators can be used as long as they are commonly used in lithium batteries. Those having low resistance to ion migration of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, as selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, it may be a non-woven fabric or a woven fabric. For example, a woundable separator such as polyethylene or polypropylene may be used for a lithium ion battery, and a separator having excellent organic electrolyte impregnation ability may be used for a lithium ion polymer battery. For example, the separator may be manufactured according to the following method.

A polymer resin, a filler, and a solvent are mixed to prepare a separator composition. The separator composition may be directly coated and dried on an electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled off from the support may be laminated on an electrode to form a separator.

The polymer resin used for manufacturing the separator is not particularly limited, and all materials used for the bonding material of the electrode plate may be used. For example, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof may be used.

Next, the electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte. In addition, the electrolyte may be a solid. For example, boron oxide, lithium oxynitride, etc. may be used, but the present invention is not limited thereto, and any solid electrolyte may be used as long as it can be used as a solid electrolyte in the art. The solid electrolyte may be formed on the negative electrode by a method such as sputtering.

For example, the organic electrolyte may be prepared by dissolving a lithium salt in an organic solvent.

The organic solvent may be used as long as it can be used as an organic solvent in the art. For example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate , Benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethylsulfoxide , Dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

The lithium salt may also be used as long as it can be used as a lithium salt in the art. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x,y are natural numbers), LiCl, LiI, or a mixture thereof.

As shown in FIG. 1, the lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2 and the separator 4 described above are wound or folded to be accommodated in the battery case 5. Subsequently, an organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium battery 1. The battery case 5 may be cylindrical, rectangular, thin-film, or the like. For example, the lithium battery 1 may be a thin film type battery. The lithium battery 1 may be a lithium ion battery.

A separator may be disposed between the positive electrode and the negative electrode to form a battery structure. After the battery structure is stacked in a bi-cell structure, it is impregnated with an organic electrolyte, and the resulting product is accommodated in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of battery structures are stacked to form a battery pack, and the battery pack can be used in all devices requiring high capacity and high output. For example, it can be used for laptop computers, smart phones, electric vehicles, and the like.

In addition, since the lithium battery has excellent life characteristics and high rate characteristics, it can be used in an electric vehicle (EV). For example, it can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in a field requiring a large amount of power storage. For example, it can be used for electric bicycles, power tools, and the like.

The present invention will be described in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Preparation Example 1 (-NH ₃ ⁺ Preparation of a pyrene derivative containing)

After mixing 0.05 g of 1-Pyrenemethylamine hydrochloride and 15 mL of distilled water, the mixture was heated to 40° C. and stirred for a day to obtain a surface modification solution containing a pyrene derivative represented by the following formula. .

Preparation Example 2 (-COO ^- Preparation of a pyrene derivative containing)

After mixing 0.1 g of 1-Pyrene butyric acid and 10 mL of distilled water, lithium hydroxide monohydrate equivalent to 1 equivalent of 1-pyrene butyric acid was added, and at 40°C. The mixture was heated and stirred for one day to obtain a surface modification solution containing a pyrene derivative represented by the following formula.

Preparation Example 3 (Preparation of monocyclic ionic group-containing compound)

After mixing 0.1 g of 4-phenyl butyric acid0 and 10 mL of distilled water, lithium hydroxide monohydrate equivalent to 1 equivalent of 4-phenylbutyric acid was added and heated at 40℃ for a day. During stirring, a surface modification solution containing a monocyclic ionic group-containing compound represented by the following formula was obtained.

Preparation Example 4 (Preparation of a pyrene derivative containing -OH)

0.1M 1-pyrene methanol (sigma-Aldrich) was dissolved in DMSO to obtain a surface modification solution containing a polycyclic polar group-containing compound represented by the following formula.

Preparation Example 5 (Preparation of monocyclic compound containing -OH)

0.1M phenylmethanol was dissolved in DMSO to obtain a surface modification solution containing a monocyclic polar group-containing compound represented by the following formula.

(Manufacture of cathode)

Examples 1 and 2, and Comparative Examples 2 and 4

In order to prepare the negative electrode, 1 g of the core material and 0.1 mL of the surface modifier prepared in Preparation Example 2 or 3 were added to the Sinki mixer and mixed as described in Table 1 below. Subsequently, a binder obtained by mixing styrene butadiene rubber (SBR) and carboxymethylcellulose (CMC) in a weight ratio of 1:1 was added to the negative electrode active material slurry in the weight% shown in Table 1, and distilled water was added to the Sinki mixer. It was added and mixed to obtain a negative electrode active material slurry. The slurry was cast on a copper current collector and dried at 110° C. for 10 minutes at atmospheric pressure to prepare a negative electrode.

Examples 3 to 4 and Comparative Examples 6 to 7

As shown in Table 1 below, 1 g of the core material and 10 mL of the surface modifier prepared in Preparation Example 4 or 5 were mixed and stirred at room temperature for two days. Thereafter, the obtained mixture was filtered, and the obtained active material was dried for two days at 70° C. under normal pressure conditions to obtain a negative electrode active material.

A binder obtained by mixing 1 g of the obtained negative electrode active material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) at a weight ratio of 1:1 was added to a Syncy mixer, followed by mixing to obtain a negative electrode active material slurry. The slurry was cast on a copper current collector and dried at 110° C. for 10 minutes at atmospheric pressure to prepare a negative electrode.

Comparative Examples 1, 3 and 5

In order to prepare a negative electrode, a binder obtained by mixing 1 g of the core material shown in Table 1 below, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a weight ratio of 1: 1 was prepared in the weight% shown in Table 1 below. Then, a negative electrode active material slurry was obtained. The slurry was cast on a copper current collector and dried at 110° C. for 10 minutes at atmospheric pressure to prepare a negative electrode.

core Surface modifier Binder content ratio
(weight%) Example 1 black smoke Manufacturing Example 2 5 Example 2 Carbon coated SiO Manufacturing Example 2 10 Example 3 black smoke Manufacturing Example 4 2 Example 4 Carbon coated SiO Manufacturing Example 4 10 Comparative Example 1 black smoke - 5 Comparative Example 2 black smoke Manufacturing Example 3 5 Comparative Example 3 Carbon coated SiO - 10 Comparative Example 4 Carbon coated SiO Manufacturing Example 3 10 Comparative Example 5 black smoke - 2 Comparative Example 6 black smoke Manufacturing Example 5 2 Comparative Example 7 Carbon coated SiO Manufacturing Example 5 10

(Creation of Coin Cell)

Examples 5 to 8 and Comparative Examples 8 to 13

A lithium foil was used as the negative electrode and counter electrode prepared in Examples 1 to 4 and Comparative Examples 1 to 7, and a porous polyethylene film was disposed as a separator between the negative electrode and the counter electrode, and an organic electrolyte (1M LiPF ₆ EC/DEC = 1/ 1 (v/v) FEC 10 wt%) was injected to prepare a negative half cell.

Evaluation Example 1: Evaluation of binding force

The negative electrodes prepared in Examples 1 to 4 and Comparative Examples 1 to 7 were cut into 30 mm in width and 60 mm in length. The negative electrode sample was attached to a glass substrate with a double-sided tape having a width of 25 mm and a length of 30 mm, and one end of the glass substrate and one end of the negative electrode sample were fixed to a universal testing machine at 180 degrees. The displacement was specified as 0 ~ 30 mm, and the strength of the force applied when the negative electrode sample adhered from the glass substrate fell off was quantitatively measured. The results are shown in Figures 2, 4, 6, and 8.

Referring to FIG. 2, a negative electrode including a carbon-based negative electrode active material surface-modified by a charged pyrene derivative (Example 1) includes a negative electrode including a carbon-based negative electrode active material that is not surface-modified (Comparative Example 1), and Compared to the negative electrode (Comparative Example 2) including the carbon-based negative electrode active material surface-modified by the phenyl derivative, the maximum binding force was increased by about 50% or more. The strength of the binding force generally refers to the force while the graph remains relatively stable after a distance of 5 mm.

Referring to FIG. 4, a negative electrode including a silicon-based negative electrode active material surface-modified by a charged pyrene derivative (Example 2) is a negative electrode (Comparative Example 3) and a phenyl derivative containing a silicon-based negative electrode active material that is not surface-modified. The maximum binding force was increased by about 15% or more compared to the negative electrode (Comparative Example 4) including the silicon-based negative electrode active material surface-modified by.

Referring to FIG. 6, a negative electrode including a carbon-based negative electrode active material surface-modified by a pyrene derivative having a polar group (Example 3) includes a negative electrode containing a carbon-based negative electrode active material that is not surface-modified (Comparative Example 5) and phenyl. The maximum binding force was increased by about 30% or more compared to the negative electrode (Comparative Example 6) including the carbon-based negative electrode active material surface-modified by the derivative.

Referring to FIG. 8, a negative electrode (Example 4) including a silicon-based negative electrode active material surface-modified by a pyrene derivative having a polar group was applied to a negative electrode (Comparative Example 3) and a phenyl derivative including a silicon-based negative electrode active material that was not surface-modified. Compared to the negative electrode (Comparative Example 7) including the silicon-based negative active material surface-modified by the above, the maximum binding force was increased by about 30% or more.

Evaluation Example 2: Evaluation of electrode expansion rate

Examples 5 to 8 and Comparative Examples 8 and 14 were charged once at a current density of 0.2 C, and then the negative electrode was separated, and the change in thickness before and after charging was measured. The rate of increase in electrode thickness is shown in FIGS. 3, 5, 7 and 9.

Referring to FIG. 3, the negative electrode (Example 5) including the carbon-based negative electrode active material surface-modified by the charged pyrene derivative was about as compared to the negative electrode (Comparative Example 8) including the carbon-based negative electrode active material that was not surface-modified. The electrode thickness change rate was reduced by 5%, and the electrode thickness change rate was decreased by about 10% compared to the negative electrode (Comparative Example 9) including the anode active material surface-modified by phCOO-.

Referring to FIG. 5, a negative electrode including a silicon-based negative electrode active material surface-modified by a charged pyrene derivative (Example 6) was about 15% compared to a negative electrode (Comparative Example 10) including a silicon-based negative electrode active material that was not surface-modified. It showed a reduced rate of change of electrode thickness, and showed a rate of change of electrode thickness reduced by about 17% compared to the negative electrode (Comparative Example 11) including a silicon-based negative electrode active material surface-modified by phCOO-.

Referring to FIG. 7, a negative electrode including a carbon-based negative active material surface-modified by a pyrene derivative having a polar group (Example 7) is about 5 compared to a negative electrode (Comparative Example 12) including a carbon-based negative active material that is not surface-modified. A% decreased electrode thickness change rate was shown, and an electrode thickness change rate decreased by about 4% compared to the negative electrode (Comparative Example 13) including a carbon-based negative electrode active material surface-modified with phenyl methanol.

Referring to FIG. 9, a negative electrode including a silicon-based negative electrode active material surface-modified by a charged pyrene derivative (Example 8) was about 17% compared to a negative electrode (Comparative Example 10) containing a silicon-based negative electrode active material that was not surface-modified. A reduced electrode thickness change rate was shown, and an electrode thickness change rate decreased by about 15% compared to the negative electrode (Comparative Example 14) including the negative electrode active material surface-modified with phenyl methanol.

As described above, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto are It should be construed as being included in the scope of the present invention.

Claims (18)

A core containing a carbon-based material;
A polycyclic compound represented by the following formula 1 provided on the core surface;
Anode active material comprising:
<Formula 1>

L is a single bond, a substituted or unsubstituted C ₁ -C ₂₀ alkylene group, a substituted or unsubstituted C ₂ -C ₂₀ alkenylene group, a substituted or unsubstituted C ₂ -C ₂₀ alkynylene group, and a substituted or unsubstituted It is selected from a cyclic C ₆ -C ₂₀ aryl group,
R is a polar group or an ionic group,
m≥2, n≥1,
When n is 2 or more, 2 or more -LR may be the same as or different from each other. The method of claim 1,
The polycyclic compound is bonded to the surface of the core by a non-covalent bond, the negative electrode active material. The method of claim 1,
The polycyclic moiety of the polycyclic compound and the surface of the core are bonded by a π-π interaction, the negative electrode active material. The method of claim 1,
The polycyclic compound is included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the negative active material. The method of claim 1,
The core further comprises an oxide of a metal alloyable with lithium and/or a metal alloyable with lithium. The method of claim 5
The metal alloyable with lithium is selected from Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y ₁ alloy, and Sn-Y 2 alloy,
In this case, Y ₁ is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, and any one or more elements selected from a combination thereof, but does not include Si, and Y ₂ is an alkali Any one or more elements selected from a metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth element, and combinations thereof, and does not contain Sn. The method of claim 5,
The oxide of the metal alloyable with lithium is a silicon oxide represented by the following formula (2), a negative electrode active material:
<Formula 2>
SiOx (0<x≤2) The method of claim 7,
The core includes a carbon-based material and/or an oxide of a metal alloyable with lithium, and the carbon-based material is disposed on a surface of an oxide of a metal alloyable with lithium. The method of claim 1,
The carbon-based material is crystalline carbon, amorphous carbon, or a mixture thereof, the negative electrode active material. The method of claim 1,
In Formula 1

Is a group selected from the following formulas 2-1 to 2-23, the negative electrode active material:

. The method of claim 1,
L is
Single bond;
Methylene group, ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, and decylene group; And
A methylene group substituted with one or more of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups, ethylene, propylene, butylene, pentylene, hexylene Group, heptylene group, octylene group, nonylene group and decylene group;
A negative active material selected from. The method of claim 1,
The ionic group comprises a cationic group, an anionic group, or a combination thereof. The method of claim 1,
R is
-OH, -CHO, -COOH, -SO ₃ H, -SO ₄ H, -PO ₄ H, -NH ₂ , -NHR _a , -NR _a R _b ;
^{_{-COO -, -SO 3 -, -SO}} 4 2- or -PO ₄ ^2-; And
-NH ₃ ⁺ , -NH ₂ R _a ⁺ , -NHR _a R _b ⁺ , -NR _a R _b R _c ⁺ , -PR _a R _b R _c ⁺ ;
Is selected from,
Here, R _a , R _b , R _c are each independently selected from a substituted or unsubstituted C ₁ -C ₁₀ alkyl group, an anode active material. The method of claim 1,
m≥4, and n is 1 or 2, the negative electrode active material. A substrate, and a negative electrode active material layer formed on the substrate,
The negative active material layer includes the negative active material according to any one of claims 1 to 14, and a binder,
The negative electrode active material is a negative electrode present in a non-covalent bond state with the binder. The method of claim 15,
The negative electrode has a binding force of 0.5 gf/mm or more between the negative active material layer and the substrate. A negative electrode comprising the negative active material according to any one of claims 1 to 14;
anode; And
Electrolyte;
Lithium secondary battery comprising a. The method of claim 17,
After one charge of the lithium secondary battery, a thickness increase rate of the negative electrode is 40% or less compared to before charging.

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