KR20190077782A - Negative electrode active material for rechargeable lithium battery, and rechargeable lithium battery including the same - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, which comprises: a porous silicon-carbon composite; hard carbon; and a coal-based pitch. The hard carbon and the coal-based pitch are dispersed in pores of the porous silicon-carbon composite. The hard carbon originates from an aqueous binder. The porosity of the negative electrode active material is 26 vol% or less based on the total volume of the negative electrode active material. The present invention can provide a negative electrode active material for a lithium secondary battery with a remarkably enhanced high rate characteristics and cycle life characteristics.

Description

[0001] The present invention relates to a negative electrode active material for a lithium secondary battery, and a lithium secondary battery comprising the negative active material, and a lithium secondary battery comprising the lithium secondary battery. BACKGROUND OF THE INVENTION < RTI ID =

Embodiments of the present invention relate to a negative electrode active material for a lithium secondary battery and a lithium secondary battery comprising the same. More specifically, the present invention relates to a negative active material for a lithium secondary battery having improved structural stability and excellent high- A lithium secondary battery can be provided.

BACKGROUND ART Lithium secondary batteries are the most widely used secondary battery systems, ranging from small-sized devices such as portable electronic communication devices to large-sized devices such as electric vehicles and energy storage devices.

Such a lithium secondary battery has advantages such as high energy density and operating voltage, relatively low self-discharge rate, and the like, compared with a commercially available water-based secondary battery (Ni-Cd, Ni-MH, etc.).

However, in order to increase the operating time (i.e., lifetime characteristics) in a small-sized apparatus and to improve energy characteristics in a large-sized apparatus, the electrochemical characteristics of the lithium secondary battery still need to be improved. As a result, many researches and developments have been actively conducted on the four raw materials such as the anode, the cathode, the electrolyte, and the separator of the lithium secondary battery.

Among these raw materials, graphite based materials exhibiting excellent capacity preservation characteristics and efficiency have been commercialized in the case of a negative electrode. However, graphite materials have relatively low theoretical capacity values (e.g., LiC ₆ And about 372 mAh / g in the case of the negative electrode), and since it has a low discharge capacity ratio, it is somewhat inadequate to meet the characteristics of the high energy and high output density of the battery required in the related market.

Therefore, many researchers are interested in the Group IV elements (Si, Ge, Sn, etc.) on the periodic table. Among them, silicon (Si) exhibits a higher theoretical capacity (for example, 3600 mAh / g in the case of a Li ₁₅ Si ₄ cathode) than a graphite based material and has a low operating voltage (~ 0.1 V vs. Li / Li +) It is the material which is spotlighted by.

However, in the case of a general silicon-based anode material, as the charge / discharge cycle of the battery is repeated, the battery has a volume change of up to 300% and exhibits a low discharge capacity ratio characteristic.

The present embodiments provide a negative electrode active material for a lithium secondary battery in which a high rate characteristic and a cycle life characteristic are remarkably improved.

The anode active material for a lithium secondary battery according to an embodiment of the present invention includes a porous silicon-carbon composite material, a hard carbon, and a coal-based pitch, and the non-graphitizable carbon and the coal- The non-graphitizable carbon is derived from an aqueous binder, and the porosity of the negative electrode active material may be 26 vol% or less based on the total volume of the negative electrode active material.

The lithium secondary battery according to an embodiment includes a cathode, a cathode, and an electrolyte, and the cathode may include a cathode active material for a lithium secondary battery according to an embodiment of the present disclosure.

According to the embodiments, it is possible to provide a negative electrode active material for a lithium secondary battery in which structural stability is improved and an excellent conductive path is provided, whereby the high rate characteristic and the cycle life characteristic are remarkably improved.

1 is a cross-sectional SEM photograph of a negative electrode active material prepared according to Example 1. Fig.
2 is a cross-sectional SEM photograph of the negative electrode active material prepared according to Example 2. Fig.
3 is a cross-sectional SEM photograph of the negative electrode active material prepared according to Comparative Example 1. Fig.
FIG. 4 shows the results of measurement of C-rate characteristics of the lithium secondary batteries produced according to Examples 1 and 2 and Comparative Example 1. FIG.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In addition, since the sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, the present invention is not necessarily limited to those shown in the drawings.

Also, throughout the specification, when an element is referred to as "including" an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. It will be understood that when an element such as a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the element directly over another element, Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

Hereinafter, a negative electrode active material for a lithium secondary battery according to an embodiment of the present invention will be described in detail.

The anode active material for a lithium secondary battery according to one embodiment may include a porous silicon-carbon composite, a hard carbon, and a coal based pitch.

First, the porous silicon-carbon composite material may be a form in which a plurality of nanosilicon particles are embedded between a plurality of graphite particles and a plurality of pores are included. .

Even if the volume of the plurality of nanosilicon particles expands or shrinks, the nanosilicon particles are buried by the plurality of graphite particles, so that electrical contact with the internal constituent material can be maintained.

In addition, the silicon particles included in the composite having a stable porous structure and having a size of nano unit contribute not only to volume expansion but also to ensure high capacity of the negative electrode active material.

In this embodiment, the content of the nanosilicon may be 25 wt% to 40 wt%, more specifically 25 wt% to 35 wt%, based on 100 wt% of the porous silicon-carbon composite. When the content of the nano-silicon satisfies the above range, excellent capacity characteristics can be ensured and the volume expansion of the electrode due to the progress of charging / discharging can be suppressed with respect to the battery using the negative electrode active material of this embodiment.

The average particle diameter of the nanosilicon particles may be 1 to 9.99 nm.

As described above, the silicon particles having an average particle size finer in the nano size can minimize the volume expansion due to charging / discharging of the battery.

The aqueous binder material used for forming the porous silicon-carbon composite becomes carbonized graphitized carbon. Such non-graphitized carbon may deteriorate the characteristics of the silicon-carbon composite. To prevent this, a coal-based pitch may be included together.

Therefore, the non-graphitizable carbon is derived from an aqueous binder, and the non-graphitized carbon and the coal-based pitch are dispersed and positioned between the pores of the porous silicon-carbon composite.

The coal-based pitch can also function as a viscous binder for stably supporting the porous structure. Since the non-graphitized carbon and the coal-based pitch are dispersed and located between the pores of the porous silicon-carbon composite, When the active material is applied to a battery, it is possible to prevent the porous structure of the silicon-carbon composite from being collapsed even when the charge / discharge cycle is repeated.

On the other hand, in this embodiment, the fixed carbon value of the coal-based pitch may be, for example, 50 or more, and more specifically, in the range of 60 to 80.

As the fixed carbon value of the coal-based pitch increases, the Si and the conductive path having low self-conductivity can be generated to increase the capacity and the efficiency. When the fixed carbon value satisfies the above range, the internal pores of the negative electrode active material of the present embodiment can be reduced. Accordingly, the side reaction with the electrolyte can be reduced, which can contribute to the initial efficiency increase of the battery.

The β-resin value of the coal-based pitch may be in the range of, for example, 22 or more, and more specifically, in the range of 25 to 40 or 25 to 35.

Specifically, the β-resin value refers to a value obtained by removing the benzene-insoluble amount from benzene-insoluble. These beta-resin values are proportional to the integrity. In this embodiment, the porous structure of the porous silicon-carbon composites can be more stably maintained because the beta-resin value includes coal-based pitches satisfying the above range. Accordingly, when the negative electrode active material according to this embodiment is employed, a lithium secondary battery having excellent lifetime characteristics and electrode plate expansion characteristics can be realized.

On the other hand, the water-based binder can be used in a group including, for example, polyacrylic acid (PAA), gum arabic, polyvinyl alcohol (PVA), and cellulose And may include at least one selected.

In the negative electrode active material for a lithium secondary battery of this embodiment, the content of each constitution is as follows. That is, the porous silicon-carbon composite includes 25 to 40% by weight of the nanosilicone particles and 20 to 45% by weight of the coal pitch based on the total weight of the negative electrode active material (100% by weight) The non-graphitized carbon may be included as the remainder.

In the negative electrode active material for a lithium secondary battery, when the content of each constituent is in the above range, a spherical negative active material having a dense structure that can stably maintain the porous structure of the composite and prevent deterioration due to the expansion of silicon can be realized .

Next, the porosity of the negative electrode active material is 26 vol% or less, more specifically 15 vol% to 26 vol%, or 15 vol% or more and less than 20 vol%, based on the total volume (100 vol%) of the negative electrode active material . When the porosity of the negative electrode active material satisfies the above range, the volume expansion of the silicon can be effectively mitigated.

The D90 particle size of the negative electrode active material is preferably, for example, less than 50 mu m, more specifically, in the range of 10 mu m to 48 mu m. If the D90 particle size of the negative electrode active material exceeds the above range, particle damage may occur due to rolling rolls during electrode rolling after coating, which may lead to deterioration of overall performance such as efficiency, lifetime and electrode expansion rate of the battery.

In this embodiment, since it includes the coal-based pitch having specific physical properties, it is possible to provide a negative electrode active material for a lithium secondary battery having improved structural stability and an excellent conductive path. In addition, since such an anode active material is applied, a lithium secondary battery having remarkably improved high-rate characteristics and cycle life characteristics can be realized.

The above-mentioned negative electrode active material can be usefully used for a negative electrode of a lithium secondary battery. That is, the lithium secondary battery according to one embodiment includes a cathode and an electrolyte including the above-described anode active material together with a cathode.

The lithium secondary battery according to an embodiment may include an electrode assembly including an anode, a cathode, and a separator disposed between the anode and the cathode. Such an electrode assembly is wound or folded and accommodated in a case to constitute a lithium secondary battery.

At this time, the case may have a cylindrical shape, a square shape, a thin film shape, or the like, and may be appropriately modified according to the type of apparatus to be applied.

The negative electrode may be prepared by mixing a negative electrode active material, a binder and optionally a conductive material to prepare a composition for forming a negative electrode active material layer, and then applying the composition to an anode current collector.

The negative electrode collector may be, for example, a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The negative electrode active material may include porous silicon-carbon composites, hard carbon, and coal-based pitches, as described in one embodiment. The details of each configuration are the same as those described above, and will not be described here.

Examples of the binder include polyvinyl alcohol, carboxymethylcellulose / styrene-butadiene rubber, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene Polypropylene and the like can be used, but the present invention is not limited thereto. The binder may be mixed in an amount of 1% by weight to 30% by weight based on the total amount of the composition for forming the anode active material layer.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and specifically includes graphite such as natural graphite and artificial graphite; Carbon black such as 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; Conductive materials such as polyphenylene derivatives and the like can be used. The conductive material may be mixed in an amount of 0.1% by weight to 30% by weight based on the total amount of the composition for forming the negative electrode active material layer.

Next, the positive electrode may be prepared by mixing a positive electrode active material, a binder and optionally a conductive material to prepare a composition for forming a positive electrode active material layer, and then applying the composition to a positive electrode current collector. At this time, the binder and the conductive material are used in the same manner as in the case of the above-mentioned negative electrode.

The positive electrode current collector may be, for example, stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel coated with carbon, nickel, titanium or silver.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used.

The cathode active material may be at least one compound selected from the group consisting of cobalt, manganese, nickel, or a combination of metals and lithium, and specific examples thereof include compounds represented by any one of the following formulas. Li _a A _{1 - b} R _b D ₂ wherein, in the formula, 0.90? A? 1.8 and 0? B? 0.5; Li _a E _{1 - b} R _b O _{2 - c} D _c , wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05; LiE _{2 - b} R _b O _{4 - c} D _{c where} 0? B? 0.5, 0? C? 0.05; Li _a Ni _{1 -b- c} Co _b R _c D _{α where} 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2; Li _a Ni _{1 -b- c} Co _b R _c O _{2 - ?} Z _{? Where} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Co _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z _{? Where} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _1-bc Mn _b R _c O _2-α Z ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 <α <2; Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 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, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a MnG _b O ₂ wherein, in the above formula, 0.90? A? 1.8 and 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 ; LiTO 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); And LiFePO _4.

In the above formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z 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; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

As the electrolyte to be filled in the lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte may be used, and a lithium salt dissolved therein may be used.

The lithium salt may be, 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 , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCl, and LiI may be used.

Examples of the solvent of the non-aqueous electrolyte include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and? -Butyrolactone; Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran; Nitriles such as acetonitrile; Amides such as dimethylformamide, and the like can be used, but the present invention is not limited thereto. These may be used singly or in combination. Particularly, a mixed solvent of cyclic carbonate and chain carbonate can be preferably used.

As the electrolyte, a gelated polymer electrolyte in which an electrolyte solution is impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li ₃ N can be used.

The separator may be an olefin-based polymer such as polypropylene, which is chemically resistant and hydrophobic; A sheet or a nonwoven fabric made of glass fiber, polyethylene or the like can be used. When a solid electrolyte such as a polymer is used as the electrolytic solution, the solid electrolytic solution may also serve as a separation membrane.

Hereinafter, preferred embodiments of the present invention and experimental examples therefor will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example  One

(1) Preparation of negative electrode active material

The nanocrystalline silicon powder and graphite powder were milled to form a porous silicon-carbon mixture (Si: C = 30: 70 weight ratio) containing a plurality of nanosilicon particles between a plurality of graphite particles.

Polyvinyl alcohol (PVA) and coal pitch (trade name: U2, manufacturer: OCI) were added to the porous silicon-carbon mixture as an aqueous binder to prepare a mixed powder. At this time, the detailed physical properties of the coal-based pitch are as shown in Table 1 below.

The mixed powder includes 7 parts by weight of an aqueous binder and 15 parts by weight of a coal-based pitch based on 100 parts by weight of the porous silicon-carbon mixture.

Then, 150 parts by weight of distilled water as a solvent was added to 100 parts by weight of the mixed powder to prepare a mixed solution. The mixed solution was stirred at room temperature, spray dried using a spray drier, and heat treated to prepare a negative active material having a D90 of about 35 탆.

(2) Production of lithium secondary battery

The negative electrode active material, the binder (SBR-CMC), and the conductive material (Super P) were prepared so that the weight ratio of the negative electrode active material: binder: conductive material was 85: 5: 10 and then mixed in distilled water. .

The slurry was uniformly applied to a copper (Cu) current collector, compressed by a roll press, and dried to prepare a negative electrode.

Lithium metal (Li-metal) was used as a counter electrode, and a mixed solvent of ethylene carbonate (EC: Ethylene Carbonate): dimethyl carbonate (DMC, Dimethyl Carbonate) ₆ solution was used.

A CR 2032 half-coin cell was fabricated according to a conventional manufacturing method using the negative electrode, lithium metal, and electrolyte.

Example  2

(1) Preparation of negative electrode active material

An anode active material was prepared in the same manner as in (1) of Example 1, except that the anode active material having the physical properties shown in Table 1 below was used as the coal-based pitch.

(2) Production of lithium secondary battery

A lithium secondary battery was produced in the same manner as in (2) of Example 1, using the negative active material of (1).

Comparative Example  One

(1) Preparation of negative electrode active material

An anode active material was prepared in the same manner as in (1) of Example 1, except that the anode active material having the physical properties shown in Table 1 below was used as the coal-based pitch.

(2) Production of lithium secondary battery

A lithium secondary battery was produced in the same manner as in (2) of Example 1, using the negative active material of the above (1).

Physical properties of coal-based pitch Example 1 Example 2 Comparative Example 1 Fixed carbon 77.7 62.8 54.4 β-resin 28.05 27.16 20.51

Experimental Example  One

SEM analysis was performed on the negative electrode active material prepared in Examples 1 and 2 and Comparative Example 1 to confirm the pore distribution image of the cross section, and the negative electrode active material was measured using a mercury porosimeter (AUTOPORE V model manufactured by Micromeritics Co., Ltd.) Was measured.

FIG. 1 is a cross-sectional SEM image of the negative electrode active material prepared according to Example 1, FIG. 2 is a SEM photograph of a negative electrode active material prepared according to Example 2, and FIG. 3 is a cross- SEM picture. The results of the porosity measurement are shown in Table 2 below.

division Example 1 Example 2 Comparative Example 1 Porosity of active material particles (%) 25.14 19.35 34.51

Referring to FIGS. 1 and 2, it can be seen that the negative electrode active material prepared according to Examples 1 and 2 is uniformly formed with small pores. On the other hand, referring to FIG. 3, it can be seen that a very large pore is formed in the case of the negative electrode active material produced according to Comparative Example 3.

Also, referring to Table 2, it can be seen that the porosity of the negative electrode active material prepared according to Examples 1 and 2 is 26% or less, but the porosity of Comparative Example 1 is at least 13% or more. When the porosity of the negative electrode active material is large, the structure of the negative electrode active material in the rolling process may be damaged, and the electrolyte may be impregnated unevenly in the pores. As a result, even in the case of a battery employing such an anode active material, there is a problem that the performance and the life characteristics are deteriorated due to deterioration of performance, lack of conductivity of nanosilicon particles, and the like.

Accordingly, by including the coal-based pitch that satisfies specific physical property values as in the present embodiment, it is possible to provide a negative electrode active material for a lithium secondary battery having improved structural stability of the negative electrode active material and having an excellent conductive path. In addition, since such an anode active material is applied, a lithium secondary battery having remarkably improved high-rate characteristics and cycle life characteristics can be realized.

Experimental Example  2 - Initial Charging and discharging  Efficiency and C-rate measurement

The initial charge-discharge efficiency of the lithium secondary batteries produced in Examples 1 to 2 and Comparative Example 1 was measured.

Specifically, each battery was charged and discharged once at 0.1 C, and the charging capacity and the discharging capacity were measured. The results are shown in Table 3 below.

Next, for each cell, the cell was charged at a constant current of 0.1 C (1 C = 3.9 mAh / cm 2) per 1 g of the negative electrode active material at room temperature (25) until the voltage reached 0.005 V (vs. Li) And charged at a constant voltage until the current became 0.005C. Then, the battery was discharged at a rate of 0.1 C up to 1.5 V, and the charge current density was changed based on the capacity value at this time to perform the charged C-rate test. The discharging capacity measurement after charging at each rate was fixed to 0.2 V and 1.0 V, and the current density at the time of charging was sequentially increased while repeating the charging / discharging cycle three times for each charging rate. The current densities at charging were 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 3 C, and 0.1 C rate, respectively.

Thereafter, the discharge capacity ratio of the angular rate to the 0.1C discharge capacity was determined, and the capacity maintenance ratio (%) was shown in Fig. The efficiency according to the angular rate is also shown in FIG.

division Example 1 Example 2 Comparative Example 1 Initial efficiency (%) 83.44 87.88 81.23

As shown in Table 3, the higher the carbonization yield of carbonaceous pitch after carbonization, the higher the initial efficiency. This is because nanosilicon particles and the conductive path were increased as the fixed carbon value of the coal-based pitch increased .

Also, referring to FIG. 4, it can be seen that the capacity retention rate and the capacity according to the cycle progress of each of the charge ratios of Examples 1 and 2 are also superior to those of Comparative Example 1.

Therefore, it can be confirmed that when the negative electrode active material according to the embodiments of the present disclosure is employed, a battery having excellent initial capacity and life characteristics can be realized.

Experimental Example  3 - Measurement of electrode expansion rate

The lithium secondary batteries produced according to Examples 1 and 2 and Comparative Example 1 were measured for the rate of electrode expansion.

Specifically, the electrode expansion ratio is calculated by calculating the thickness ratio between the electrode before the lithium secondary battery and the electrode of the lithium secondary battery after the C-rate measurement.

At this time, the lithium secondary battery after the C-rate measurement was subjected to a constant current charging of 0.1 C and 0.005 V and a constant voltage charging of 0.005 V and 0.005 C cut-off. The lithium secondary battery was disassembled in a glove box in an argon (Ar) atmosphere, And the electrode expansion rate was measured using a dried electrode.

The thickness of each electrode was measured using a micrometer in which the significant digit was the third decimal place. The results are shown in Table 4 below.

division Example 1 Example 2 Comparative Example 1 Electrode Expansion Ratio (%) 94 72 154

Referring to Table 4, it can be confirmed that the lithium secondary battery of Comparative Example 1 expanded at least 1.6 times more than the electrodes of Examples 1 and 2.

Accordingly, it can be confirmed that the electrode expansion rate of the battery employing the negative electrode active material having the same characteristics as those of this embodiment can be remarkably improved.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (8)

Porous silicon-carbon composites;
Hard carbon; And
Including coal pitch,
The non-graphitized carbon and the coal-based pitch are dispersed between the pores of the porous silicon-carbon composite,
The non-graphitized carbon is derived from an aqueous binder,
The porosity of the negative electrode active material is 26 vol% or less based on the total volume of the negative electrode active material. The method according to claim 1,
Wherein the fixed carbon value of the coal based pitch is 50 or more. The method according to claim 1,
Wherein the fixed carbon value of the coal based pitch ranges from 60 to 80. The negative electrode active material for a lithium secondary battery according to claim 1, The method according to claim 1,
Wherein the beta resin value of the coal-based pitch is 22 or more. The method according to claim 1,
And the beta resin value of the coal-based pitch is in the range of 25 to 40. The negative electrode active material for a lithium secondary battery according to claim 1, The method according to claim 1,
The porous silicon-
A plurality of graphite particles and a plurality of nanosilicon particles embedded between the plurality of graphite particles,
Wherein the content of the nanosilicon is 25 wt% to 40 wt% with respect to 100 wt% of the porous silicon-carbon composite. The method according to claim 1,
The water-
A negative electrode active material for a lithium secondary battery, comprising at least one of polyacrylic acid (PAA), gum arabic, polyvinyl alcohol (PVA), and a cellulose compound. anode;
cathode; And
Comprising an electrolyte,
The lithium secondary battery according to any one of claims 1 to 7, wherein the negative electrode comprises the negative electrode active material for a lithium secondary battery.

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