KR101772114B1 - Anode active material, anode and lithium battery containing the same, and preparation method thereof - Google Patents

Abstract

Wherein the core is a crystalline carbon-based material having an interplanar spacing d ₀₀₂ of 0.35 nm or more; Titanium oxide particles; And a metal capable of forming an alloy with lithium.

Description

[0001] The present invention relates to an anode active material, an anode and a lithium battery employing the same, and an anode active material, an anode and a lithium battery containing the same, and a preparation method thereof,

A negative electrode employing the same, a lithium battery, and a method of manufacturing the same.

Lithium batteries are used for a variety of applications by having high voltage and high energy density. For example, the fields of electric automobiles (HEV, PHEV) and the like can operate at high temperatures, require a large amount of electricity to be charged or discharged, and must be used for a long time. Therefore, a lithium battery having excellent heat stability, high rate characteristics, do.

The carbon-based material is porous and stable in terms of volume change during charging and discharging. However, in general, the carbon-based material has a low cell capacity due to the porous structure of carbon. For example, the theoretical capacity of high crystalline graphite is 372 mAh / g in the LiC ₆ composition. In addition, the high-rate characteristics are low.

A metal capable of alloying with lithium may be used as a negative electrode active material having a higher electric capacity than the carbon-based material. For example, metals capable of alloying with lithium are Si, Sn, Al, and the like. However, the metals capable of alloying with lithium are liable to be deteriorated, so that the life characteristics are low. For example, as Sn is repeatedly charged and discharged, aggregation and disintegration of Sn particles are repeated, and Sn particles are electrically disconnected.

In addition, the lithium battery may cause thermal runaway due to short circuit or the like.

Therefore, there is a demand for a lithium battery having improved discharge capacity, life characteristics, and thermal stability.

One aspect is to provide a novel negative active material comprising an increased crystalline carbon-based material, a metal capable of forming an alloy with lithium, and a titanium-based oxide.

Another aspect is to provide a negative electrode comprising the negative active material.

Another aspect is to provide a lithium battery employing the negative electrode.

Another aspect provides a method for producing the negative electrode active material.

According to one aspect,

The core comprising:

A crystalline carbon-based material having an interplanar spacing d ₀₀₂ of 0.35 nm or more;

Titanium oxide particles; And

There is provided a negative electrode active material comprising a metal capable of forming an alloy with lithium.

According to another aspect,

A negative electrode comprising the negative active material is provided.

According to another aspect,

A lithium battery employing the negative electrode is provided.

According to another aspect,

Preparing a crystalline carbon-based material having an interplanar spacing d ₀₀₂ of 0.35 nm or more; And

Preparing a core comprising the crystalline carbon-based material, titanium-based oxide particles, and a metal capable of forming an alloy with lithium; and a method of manufacturing the anode active material.

According to one aspect, the discharge capacity, lifetime characteristics, and thermal stability of a lithium battery can be improved by including a crystalline carbon-based material, a titanium-based oxide particle, and a new negative active material including a metal capable of forming an alloy with lithium.

FIG. 1A is an SEM image of the negative electrode active material powder prepared in Example 1. FIG.
1B is an SEM image of the negative electrode active material particles prepared in Example 1. Fig.
2A is an SEM image of the crystalline carbon-based material produced in Production Example 1. FIG.
2B is a TEM image of the crystalline carbon-based material produced in Production Example 1. FIG.
3 is an XRD spectrum of the anode active material powder prepared in Example 1. Fig.
4 is a DSC (dynamic scanning calorimeter) measurement result of the negative electrode active material powder used in Examples 19 and 31 and Comparative Example 2. FIG.
5 is a schematic diagram of a lithium battery according to an exemplary embodiment.
Description of the Related Art
1: Lithium battery 2: cathode
3: anode 4: separator
5: Battery case 6: Cap assembly

Hereinafter, a negative electrode active material according to exemplary embodiments, a negative electrode including the same, a lithium battery employing the negative electrode, and a method for manufacturing the negative active material will be described in detail.

In one embodiment, the negative electrode active material comprises a core, the core is a crystalline carbon-based material having an interplanar spacing d ₀₀₂ of 0.35 nm or greater; Titanium oxide particles; And a negative active material containing a metal capable of forming an alloy with lithium. For example, the interplanar spacing d ₀₀₂ of the crystalline carbon-based material may be 0.35 nm to 0.4 nm. For example, the interplanar spacing d ₀₀₂ of the crystalline carbon-based material may be 0.35 nm to 0.37 nm.

The negative electrode active material can obtain improved discharge capacity, lifetime characteristics, and thermal stability by simultaneously including a crystalline carbon-based material, titanium oxide particles, and a metal capable of forming an alloy with lithium.

The core comprising the crystalline carbon-based material, the titanium-based oxide particles, and the metal capable of forming an alloy with lithium may have various configurations. For example, in the core, the titanium-based oxide particles and a metal capable of forming an alloy with lithium are clustered in the core, and the metal capable of forming the alloy with the titanium- Based material may be coated. According to the above configuration, the titanium-based oxide particles and the metal capable of forming an alloy with lithium can be prevented from being exposed to the outside of the core. Alternatively, the metal capable of forming an alloy with lithium other than the titanium-based oxide particles may be entirely dispersed in the core. That is, the titanium-based oxide particles and the metal capable of forming an alloy with lithium may be mixed with the crystalline carbon-based material. With the above-described configurations, it is possible to prevent the deterioration of the metal that can form an alloy with lithium.

On the other hand, in the core, the titanium-based oxide particles and a metal capable of forming an alloy with lithium may form a composite with the crystalline carbon-based material. By forming the composite of the crystalline carbon-based material and the titanium-based oxide particles and the metal capable of forming an alloy with lithium, the electrical connection can be maintained despite the volume change of the metal particles upon charging and discharging.

The content of the titanium oxide particles in the negative electrode active material may be more than 0 to 10% by weight based on the total weight of the core. For example, the content may be more than 0 to 6% by weight. If the content of the titanium oxide is too high, the initial capacity may be lowered.

The particle size of the titanium oxide particles in the negative electrode active material may be 10 nm to 990 nm. For example, the particle size may be 100 to 900 nm. For example, the particle size may be 200 to 500 nm. If the particle size of the titanium oxide particles is too small, there is a problem of moisture absorption. If the particle diameter of the titanium oxide particles is too large, it may be difficult to exist in the core.

In the negative electrode active material, the titanium-based oxide may be at least one selected from the group consisting of Li ₄ Ti ₅ O ₁₂ , TiO ₂ , LiTiO ₃ , and Li ₂ Ti ₃ O ₇ .

The content of the metal capable of forming an alloy with lithium in the negative electrode active material may be more than 0 to 20% by weight based on the total weight of the core. For example, the content may be from greater than 0 to 10% by weight. If the content of the metal capable of forming an alloy with lithium is excessively high, cracking of the active material may occur due to a change in volume of the metal during charging and discharging.

In the negative electrode active material, a metal capable of forming an alloy with lithium may be particles having a particle diameter of 10 nm to 990 nm. For example, the particle size of the particles may be between 100 and 900 nm. For example, the particle size of the particles may be 200 to 500 nm. If the particle diameter of the metal particles capable of forming an alloy with lithium is too small, the surface may be easily oxidized. If the particle diameter of the metal particles capable of forming an alloy with lithium is excessively large, Cracks may occur in the active material.

In the negative electrode active material, the metal capable of forming an alloy with lithium may be at least one selected from the group consisting of Si, Sn, Pb, Ge, Al, and oxides of the metals.

In the negative electrode active material, a metal capable of forming an alloy with lithium may form a coating layer on one surface of the crystalline carbon-based material. The coating layer can be obtained by reducing a precursor of a metal capable of forming an alloy with lithium. The coating layer may be coated to a thickness of 1 to 100 nm on the surface of the crystalline carbon-based material.

The metal capable of forming an alloy with lithium forms a coating layer on the surface of the crystalline carbon-based material, thereby preventing deterioration of a metal capable of forming an alloy with lithium during charging and discharging. For example, even if cracks are generated on the surface of the coating layer, the coating layer may remain electrically connected to the crystalline carbon-based material until the coating layer is completely separated.

In the negative electrode active material, the crystalline carbon-based material has n polycyclic nano-sheets in which six carbon atoms are connected in a hexagonal shape and the rings are condensed to form a single plane, Wherein n is an integer of 2 to 250, and a first one of the carbons of the n polycyclic nanosheets and a second one of the carbons of the n polycyclic nanosheets are L1 ≪ / RTI > L2 where L2 represents the distance between the first carbon and the second carbon, and L2 represents the distance between the first carbon and the second carbon of the n polycyclic nanosheets, The distance between any third carbon and any fourth carbon except for the first carbon, the second carbon and the third carbon among the carbons of the n polycyclic nanosheets) With axis and z axis Wherein the second carbon has a coordinate B (p, q, r), the p and q are independently 10 mu m or less, and the second carbon has a coordinate A (0, 0, 0) r may be 100 nm or less.

Specifically, the crystalline carbon-based material may have an irregular shape, but basically has a "plate-like" shape. The shape of the crystalline carbon-based material is based on a "plate-like shape ", but may have various deformed shapes such as warped or curled ends. The shape of the crystalline carbon-based material is basically "plate-like ", which can be easily understood from the photograph of the crystalline carbon-based material of Fig.

The crystalline carbon-based material has a structure in which n rings of polycyclic nano-sheets arranged on one plane are condensed with rings of six carbon atoms connected in a hexagonal shape to form a direction perpendicular to the one plane And has a laminated structure.

In the present specification, the term "ring formed by connecting six carbon atoms in a hexagonal shape" is a hexagonal ring, which indicates a ring in which carbon is located at each vertex of the hexagonal shape. Hereinafter, the abbreviation is also referred to as a "6-membered carbon ring ". The polycyclic nanosheet has a plurality of six-membered carbon rings, wherein the plurality of six-membered carbon rings are fused to each other to form a honeycomb and are arranged on one plane. Here, the term "arranged on one plane " indicates that a plurality of six-membered carbon rings are condensed to the right and left to be arranged and extended, and that condensed vertically and arranged and extended are excluded.

Adjacent carbons among the carbons of the polycyclic nanosheet may be connected to each other by sp2 bonding. Thereby, a resonance structure in the six-membered carbon ring can be formed, so that the movement of electrons can be facilitated.

The polycyclic nanosheets may have a structure in which a plurality of six-membered carbon rings are condensed with each other and arranged on one plane. For example, the thickness of the polycyclic nanosheets may be in the range of carbon atom diameter 0.1 nm. Here, the fact that the thickness of the polycyclic nanosheet has a carbon atom diameter of " 0.1 nm "reflects that the polycyclic nanosheet may have a warped shape, a terminal shape may have a dried form, and may be partially defective.

The crystalline carbon-based material has a structure in which n polycyclic nanosheets as described above are laminated. Here, the n polycyclic nanosheets are stacked in a direction perpendicular to one plane in which a plurality of six-membered carbon rings of the polycyclic nanosheets are condensed and arranged.

N is an integer of 2 to 100, for example, an integer of 2 to 80, for example an integer of 2 to 70, for example an integer of 2 to 40, particularly an integer of 2 to 20, May be an integer of 2 to 10.

In the crystalline carbon-based material, the first carbon of the n polycyclic nanosheets and the second carbon of the n polycyclic nanosheets are selected to be Ll > L2 so that the first carbon is divided into x- , the second carbon has a coordinate B (p, q, r), and p and q are independent from each other when they are positioned at the origin A (0, 0, 0) of the three- , 10 mu m or less, and r may be 100 nm or less. Here, L1 represents a distance between the first carbon and the second carbon, L2 represents any third carbon other than the first carbon and the second carbon among the carbons of the n polycyclic nanosheets, represents the distance between any four carbons of the n polycyclic nanosheets excluding the first carbon, the second carbon and the third carbon. That is, it can be understood that the first carbon and the second carbon are two carbon selected so that the distance between the carbon among the carbons contained in the n polycyclic nanosheets is the longest.

The p and q may independently be 10 탆 or less, for example, 0.1 탆 to 10 탆. For example, from 1 탆 to 10 탆. The p and q may be transverse and longitudinal in the direction perpendicular to the thickness direction of the crystalline carbon-based material.

The r may be 100 nm or less, for example, 0.5 nm to 100 nm, specifically 0.5 nm to 90 nm, more specifically 0.5 nm to 50 nm. For example, r may be from 0.5 nm to 20 nm, but is not limited thereto. The r may be a length in the thickness direction of the crystalline carbon-based material. For example, the crystalline carbon-based material may be a nanoparticle powder having a plate-like shape.

By satisfying the above-described ranges of p, q and r of the crystalline carbon-based material, it is not intended to be limited to a specific theory, but it is easy to transfer electrons and the like, and excellent conductivity can be obtained.

A carbon-based coating layer may be additionally formed on the core in the negative electrode active material. The carbon-based coating layer may include amorphous carbon. By forming the carbon-based coating layer on the core, SEI is formed, and it is possible to prevent the crystalline carbon-based material from contacting with the electrolyte or the like due to the selective passage of Li + ions.

The negative electrode active material may be spherical particles having an aspect ratio of less than 2. For example, spherical particles having an aspect ratio of from 2 to 1, for example, from 1.5 to 1. The negative electrode active material has a spherical shape, which is advantageous for slurry dispersion and can increase the strength of the electrode plate.

The spherical particles may have an average particle diameter (d50) of 1 탆 to 100 탆. For example, the average particle diameter may be 3 to 60 mu m. If the average particle size of the spherical particles is too small, it may be difficult to prepare an active material slurry and coat the coating on the electrode plate. If the average particle size of the spherical particles is too large, the coating layer may be uneven or the high-rate characteristics may be deteriorated.

The negative electrode according to another embodiment includes the negative electrode active material. The negative electrode may be manufactured, for example, by forming the negative electrode active material composition containing the negative electrode active material and the binder in a predetermined shape or by applying the negative electrode active material composition to a current collector such as copper foil.

Specifically, an anode active material composition in which the anode active material, the conductive material, the binder, and the solvent are mixed is prepared. The negative electrode active material composition is directly coated on the metal current collector to produce a negative electrode plate. Alternatively, the negative electrode active material composition may be cast on a separate support, and then the film peeled off from the support may be laminated on the metal current collector to produce a negative electrode plate. The negative electrode is not limited to the above-described form, but may be in a form other than the above-described form.

As the conductive material, metal powders such as acetylene black, Ketjen black, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, copper, nickel, aluminum and silver, metal fibers, In addition, one or more conductive materials such as polyphenylene derivatives may be used in combination, but the present invention is not limited thereto, and any conductive material may be used as long as it can be used as a conductive material in the related art. In addition, the above-described crystalline carbon-based material can be added as a conductive material.

Examples of the binder include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, styrene butadiene rubber-based polymers, etc. May be used, but are not limited thereto and can be used as long as they can be used as bonding agents in the art.

As the solvent, N-methylpyrrolidone, acetone, water or the like may be used, but not limited thereto, and any solvent which can be used in the technical field can be used.

The content of the negative electrode active material, the conductive material, the binder, and the solvent is a level commonly used in a lithium battery. At least one of the conductive material, the binder and the solvent may be omitted depending on the use and configuration of the lithium battery.

A lithium battery according to another embodiment employs a negative electrode comprising the above negative electrode active material. The lithium battery can be produced by the following method.

First, a negative electrode is prepared according to the negative electrode manufacturing method.

Next, a cathode active material composition in which a cathode active material, a conductive material, a binder, and a solvent are mixed is prepared. The positive electrode active material composition is directly coated on the metal current collector and dried to produce a positive electrode plate. Alternatively, the cathode active material composition may be cast on a separate support, and then the film peeled from the support may be laminated on the metal current collector to produce a cathode plate.

The positive electrode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide. However, May be used.

For example, Li _a A _1-b B _b D ₂ , wherein 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5; Li _a E _1-b B _b O _{2 -c} D _c wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05; LiE (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05) 2-b B b O 4-c D c; Li _a Ni _{1 -bc} Co _b B _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1- b c} Co _b B _c O _{2 -?} F _? Wherein? 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1- b c} Co _b B _c O _2-α F ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2; Li _a Ni _1-bc Mn _b B _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _1-bc Mn _b B _c O _2-α F _α wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2; Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ wherein 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 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 wherein, in the above formula, 0.90? A? 1.8, and 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 wherein, 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 ; LiIO 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); In the formula of LiFePO ₄ may be used a compound represented by any one:

In the above formula, A is Ni, Co, Mn, or a combination thereof; B 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; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or combinations 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.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise an oxide, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a coating element compound of the hydroxycarbonate of the coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be any coating method as long as it can coat the above compound by a method that does not adversely affect physical properties of the cathode active material (for example, spray coating, dipping, etc.) by using these elements, It will be understood by those skilled in the art that a detailed description will be omitted.

For example, LiNiO ₂ , LiCoO ₂ , LiMn _x O ₂ x (x = 1, 2), LiNi _1-x Mn _x O ₂ (0 <x <1), LiNi _1-xy Co _x Mn _y O ₂ ? 0.5, 0? Y? 0.5), LiFeO ₂ , V ₂ O ₅ , TiS, MoS and the like can be used.

As the conductive material, binder and solvent in the positive electrode active material composition, the same materials as those of the negative electrode active material composition may be used. It is also possible to add a plasticizer to the cathode active material composition and / or the anode active material composition to form pores inside the electrode plate.

The content of the cathode active material, the conductive material, the binder, and the solvent is a level commonly used in a lithium battery. Depending on the application and configuration of the lithium battery, one or more of the conductive material, the binder, and the solvent may be omitted.

Next, a separator to be inserted between the positive electrode and the negative electrode is prepared. The separator can be used as long as it is commonly used in a lithium battery. A material having low resistance against the ion movement of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric. For example, a rewindable separator such as polyethylene, polypropylene, or the like is used for the lithium ion battery, and a separator having excellent organic electrolyte impregnation capability can be used for the lithium ion polymer battery. For example, the separator may be produced 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 coated directly on the electrode and dried to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled from the support may be laminated on the electrode to form a separator.

The polymer resin used in the production of the separator is not particularly limited, and any material used for the binder 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, and the like, but not limited thereto, and any of them can be used as long as they can be used as solid electrolytes in the art. The solid electrolyte may be formed on the cathode by a method such as sputtering.

For example, an organic electrolytic solution can be prepared. The organic electrolytic solution can be prepared by dissolving a lithium salt in an organic solvent.

The organic solvent may be any organic solvent which can be used in the art. Examples of the solvent include 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 N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, gamma -butyrolactone, dioxolane, , 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 in the art as a lithium salt. 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 , _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl, LiI, or a mixture thereof.

As shown in FIG. 5, the lithium battery 1 includes an anode 3, a cathode 2, and a separator 4. The anode 3, the cathode 2 and the separator 4 described above are wound or folded and housed in the battery case 5. Then, an organic electrolytic solution is injected into the battery case 5 and is sealed with a cap assembly 6 to complete the lithium battery 1. The battery case may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. For example, the lithium battery may be a thin film battery. The lithium battery may be a lithium ion battery.

A separator may be disposed between the anode and the cathode to form a battery structure. The cell structure is laminated in a bi-cell structure, then impregnated with an organic electrolyte solution, and the obtained result is received in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of battery assemblies may be stacked to form a battery pack, and such battery pack may be used for all devices requiring high capacity and high output. For example, a notebook, a smart phone, an electric vehicle, and the like.

Particularly, the lithium battery is suitable for an electric vehicle (EV) because it has a high rate characteristic and a good life characteristic. For example, it is suitable for a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV).

According to another embodiment of the present invention, there is provided a method for manufacturing a negative active material, comprising: preparing a crystalline carbon-based material having an interplanar spacing d ₀₀₂ of 0.35 nm or more; And preparing a core comprising the crystalline carbon-based material, titanium-based oxide particles, and a metal capable of forming an alloy with lithium.

The step of preparing the crystalline carbon-based material may include heat-treating the expandable graphite at 300 ° C to 700 ° C for 0.1 to 5 hours. The heat treatment temperature may be, for example, 400 ° C to 600 ° C, for example, 450 ° C to 550 ° C. The heat treatment time may be, for example, 0.5 to 3 hours, for example, 0.5 to 2 hours.

The expanded graphite can be obtained by immersing natural graphite, artificial graphite, carbon fiber, constituent graphite and the like in a strong acid solution such as sulfuric acid or hydrochloric acid for 1 to 24 hours. However, the expansion graphite is not necessarily limited to this method, Anything you can do is possible.

Preparing the core comprises: preparing the mixture by mixing the crystalline carbon-based material, titanium-based oxide particles, and metal particles capable of forming an alloy with lithium in a solution; And drying and spheronizing the mixture. For example, the titanium-based oxide particles may be nanoparticles or microparticles.

Alternatively, the step of preparing the core may include preparing a heat treatment result by mixing, drying and heat-treating the crystalline carbon-based material and a metal precursor solution capable of forming an alloy with lithium; Mixing the resultant of the heat treatment with titanium oxide particles in a solution to prepare a mixture; And drying and spheronizing the mixture. The precursor is reduced by mixing, drying and heat-treating the crystalline carbon-based material and a metal precursor solution capable of forming an alloy with lithium to form an alloy with lithium on the surface of the crystalline carbon-based material A coating layer containing a metal can be formed.

Wherein in the method for producing the precursor of the metal is _{SiCl 4, SiH 2 Cl 2,} SnCl 4, PbCl 4 and GeCl ₄ be at least one selected from a group but containing, not necessarily limited to, a lithium alloy in the art Any material that can be used as a precursor of a metal that can be formed is possible.

The method for manufacturing an anode active material may further include forming a carbon-based coating layer by coating and firing a carbon precursor on the core.

The thickness of the carbon-based coating layer may be 10 nm to 100 nm. If the thickness of the coating layer is excessively thin, there may be a portion that is not coated, and the core may be exposed to the electrolyte. If the thickness of the coating layer is too thick, the lithium ion is not easily transferred, have.

The carbon precursor may be at least one selected from the group consisting of polymers, coal tar pitch, petroleum pitch, meso-phase pitch, coke, low molecular weight oil, coal pitch and derivatives thereof. The calcination of the carbon precursor may be performed at 800 to 1200 ° C for 0.1 to 10 hours.

The present invention will be described in more detail by way of the following examples and comparative examples. However, the examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

(Production of a forming carbon-based material)

Preparation Example 1:

After expanding 100 g of expanded graphite by heating at 500 DEG C for 1 hour, The resulting gas is exhausted through an exhaust port of an oven, and the resulting product Dispersed in ethanol, and pulverized at 10,000 rpm for 10 minutes using a homogenizer. The resulting mixture was further pulverized using a micro fluidizer, followed by filtration using a filtering equipment, followed by washing with ethanol and drying in an oven at 120 ° C. to obtain a crystalline carbon-based material powder &Lt; / RTI &gt;

A photograph of the crystalline carbon-based material powder observed with an SEM (electron scanning microscope) is shown in Fig. According to FIG. 2A, it can be confirmed that the individual crystalline carbon-based material nanoparticles included in the nanoparticle powder of the crystalline carbon-based material basically have a "plate-like" shape.

A photograph of the nanoparticles of the crystalline carbon-based material nanoparticle powder observed with a TEM (transmission electron microscope) is shown in FIG. 2B. In FIG. 2B, the portion indicated by the dotted circle corresponds to, for example, the side surface of the plate-like crystalline carbon-based material nano-particles in FIG. 2A, and it can be confirmed that the thickness is about 10 nm. Therefore, it can be seen from Fig. 2b that the crystalline carbon-based material nanoparticles prepared as described above have a r of about 10 nm (the definition of "r" above is related to the detailed description of the invention).

Meanwhile, the size dispersion of the nanoparticles contained in the crystalline carbon-based material nanoparticle powder was evaluated using Melvern, Hydro 2000. The component in the direction corresponding to p or q of the crystalline carbon-based material nano-particle powder (see the relevant part of the description of the present invention for the definitions of "p" and "q") is d ₁₀ is 2.1 micrometer, d ₅₀ Is 4.11 micrometer, and d ₉₀ is 7.16 micrometer.

Production Example 2

A crystalline carbon-based material nano-particle powder was prepared in the same manner as in Production Example 1, except that the calcination temperature was changed to 400 캜.

Production Example 3

A crystalline carbon-based material nano-particle powder was prepared in the same manner as in Production Example 1, except that the calcination temperature was changed to 300 캜.

Production Example 4

A crystalline carbon-based material nano-particle powder was prepared in the same manner as in Production Example 1, except that the calcination temperature was changed to 200 ° C.

Production Example 5

A crystalline carbon-based material nano-particle powder was prepared in the same manner as in Production Example 1, except that the calcination temperature was changed to 150 캜.

Production Example 6

A crystalline carbon-based material nano-particle powder was prepared in the same manner as in Production Example 1, except that heat shock was applied at a sintering temperature of 1000 占 폚 for 30 seconds.

(Preparation of negative electrode active material)

Example 1

80 parts by weight of the crystalline carbon-based material nanoparticles prepared in Preparation Example 1, 5 parts by weight of LTO (Li ₄ Ti ₁₂ O ₅ ) nanoparticles having an average particle diameter of 300 nm and 15 parts by weight of Si nanoparticles having an average particle diameter of 300 nm were dissolved in an ethanol solvent 200 , And the mixture was stirred to prepare a mixed solution. After the mixed solution was dried, the dried material was sphered with a sphering apparatus (hybridization system) to prepare a core powder. The granulation and sphering were carried out at a speed of 100 to 150 m / s for 5 to 10 minutes.

10 parts by weight of mesophase pitch was mixed with 100 parts by weight of the core powder, mechanically milled and heat-treated at 900 ° C for 1 hour to form a carbon-based coating layer on the core to prepare an anode active material powder.

Scanning micrographs of the anode active material powder prepared in Example 1 are shown in FIGS. 1A and 1B. The aspect ratio of the negative electrode active material powder was 1 to 1.5, and the average particle diameter (d50) was 20 占 퐉.

Examples 2-6

An anode active material was prepared in the same manner as in Example 1, except that the crystalline carbon-based material nanoparticles prepared in Preparation Example 2-6 were used.

Example 7

After the crystalline carbon-based material nanoparticle powder prepared in Preparation Example 1 was immersed in a 1.5M aqueous solution of SiCl ₄ , drying and annealing at 300 ° C were repeated at least twice, followed by drying at 600 ° C for 2 And the phase was stabilized. After three washing and drying processes, the crystalline carbon-based material nanoparticle powder was coated with Si to a thickness of about 1 to 10 nm.

95 parts by weight of the Si-coated crystalline carbon-based material nano-particles powder and 5 parts by weight of LTO (Li ₄ Ti ₅ O ₁₂ ) nanoparticles having an average particle size (d50) of 300 nm were added to 200 parts by weight of an ethanol solvent, . After the mixed solution was dried, the dried material was granulated and spheronized by a sieving machine to prepare a core powder. The assembly and sphering were carried out at a speed of 100 to 150 m / s for 5 to 10 minutes.

10 parts by weight of mesophase pitch was mixed with 100 parts by weight of the core powder, mechanically milled and heat-treated at 900 ° C for 1 hour to form a carbon-based coating layer on the core to prepare an anode active material powder.

The negative electrode active material powder had an aspect ratio of 1 to 1.5 and an average particle diameter (d50) of 20 占 퐉.

Examples 8-12

An anode active material was prepared in the same manner as in Example 7, except that the crystalline carbon-based material nanoparticles prepared in Preparation Example 2-6 were used.

Example 13

65 parts by weight of the crystalline carbon-based material nanoparticles prepared in Preparation Example 1, 5 parts by weight of LTO (Li ₄ Ti ₁₂ O ₅ ) nanoparticles having an average particle diameter of 300 nm and SiO _x (0 <x <2) 30 parts by weight of the nanoparticles were added to 200 parts by weight of an ethanol solvent and stirred to prepare a mixed solution.

After the mixed solution was dried, the dried material was sphered with a sphering apparatus (hybridization system) to prepare a core powder. The granulation and sphering were carried out at a speed of 100 to 150 m / s for 5 to 10 minutes. 10 parts by weight of mesophase pitch was mixed with 100 parts by weight of the core powder, mechanically milled and heat-treated at 900 ° C for 1 hour to form a carbon-based coating layer on the core to prepare an anode active material powder.

The aspect ratio of the negative electrode active material powder was 1 to 1.5, and the average particle diameter (d50) was 20 占 퐉.

Examples 14-18

An anode active material was prepared in the same manner as in Example 13, except that the crystalline carbon-based material nanoparticles prepared in Preparation Example 2-6 were used.

Comparative Example 1

85 parts by weight of the crystalline carbon-based material nanoparticle powder prepared in Preparation Example 1 and 15 parts by weight of Si nanoparticles having an average particle diameter (d50) of 300 nm were added to 200 parts by weight of an ethanol solvent and stirred to prepare a mixed solution. After the mixed solution was dried, the dried material was granulated and spheronized by a hybridization system to prepare a core powder. The granulation and sphering conditions were carried out at a speed of 100 to 150 m / s for 5 to 10 minutes.

10 parts by weight of mesophase pitch was mixed with 100 parts by weight of the core powder, mechanically milled and heat-treated at 900 ° C for 1 hour to form a carbon-based coating layer on the core to prepare an anode active material powder.

(Preparation of positive electrode and lithium battery)

Example 19

The anode active material powder and PI (polyimide) binder solution synthesized in Example 1 were added to prepare a slurry having a weight ratio of active material: binder = 94: 6.

The active material slurry was coated on the Cu foil having a thickness of 10 탆 and dried to form a negative electrode plate, followed by further vacuum drying to prepare a coin cell (CR2016 type) having a diameter of 32 mm.

Cells produced during the counter electrode (counter electrode) roneun was used as a metal lithium, a polypropylene separator to separator (separator, Cellgard ^ⓡ 3510), its use, and is the electrolyte EC (ethylene carbonate): DEC (diethyl carbonate) (3: 7 Volume ratio) mixed solvent containing 1.3 M LiPF ₆ dissolved therein.

Examples 20-36

A lithium battery was prepared in the same manner as in Example 19 except that the anode active material powder synthesized in Example 2-18 was used.

Comparative Example 2

A lithium battery was produced in the same manner as in Example 19, except that the anode active material powder synthesized in Comparative Example 1 was used.

Evaluation example 1: XRD experiment

XRD experiments were performed on the anode active material powders prepared in Example 1-18 and Comparative Example 1. [ The experimental conditions were CuK-alpha characteristic X-ray wavelength of 1.541 Å.

As shown in FIG. 3, the negative electrode active material particles of Example 1 exhibited characteristic peaks for crystalline carbon in (1), characteristic peaks for Si in (2), and characteristic peaks for LTO in (3), respectively.

The interplanar spacings calculated from the peaks for the crystalline carbon contained in the negative electrode active material of Example 1-6 are shown in Table 1 below.

The inter-crystal distance (d002)
[nm] Example 1 0.38 Example 2 0.37 Example 3 0.37 Example 4 0.36 Example 5 0.35 Example 6 0.38

As shown in Table 1, the intergranular distance of the crystalline carbon-based material contained in Example 1-6 was 0.35 nm to 0.38 nm, which was different from that of conventional graphite.

Evaluation Example 2: Evaluation of high rate characteristics

The coin cells prepared in Examples 19-36 and Comparative Example 2 were charged at a constant current of 0.1 C rate in a voltage range of 2.5 to 4.1 V with respect to lithium metal at room temperature and the discharging capacity And the charge / discharge efficiency was calculated from this ratio. The current densities at discharge were 0.1 C, 0.2 C, 0.5 C, 1 C and 2 C rates, respectively. The charging / discharging efficiency at 2C is calculated by the following equation (1), and a part of the results are shown in Table 2.

&Quot; (1) &quot;

Charge / discharge efficiency [%] = [2C discharge capacity / 0.1C charge capacity] × 100

Charging / discharging efficiency at 2C
[%] Example 19 98.1% Example 20 96.6% Example 21 95.2% Example 22 92.3% Example 23 91.8% Example 24 93.1% Example 25 97.4% Example 26 94.2% Example 27 92.1% Example 28 90.7% Example 29 89.2% Example 31 97.2% Comparative Example 2 85.3%

As shown in the following Table 2, the lithium batteries of Examples 19-29 and 31 had remarkably improved high-rate characteristics as compared with the lithium batteries of Comparative Example 2.

Evaluation Example 3: Life characteristic evaluation

The coin cells prepared in Examples 19-29 and 31 and Comparative Example 2 were charged and discharged at a constant current of 1 C rate in a voltage range of 2.5 to 4.1 V relative to lithium metal at room temperature, Respectively. The capacity retention ratio at room temperature is expressed by the following equation (1). The discharge capacity in the 50th cycle is also shown.

&Quot; (1) &quot;

Capacity retention rate [%] = [Discharge capacity in 50 ^th cycle / Discharge capacity in 1 ^st cycle] × 100

Capacity retention rate [%] Discharge capacity [mAh / g] in 50 ^th cycle Example 19 88.3 715.2 Example 20 85.2 690.1 Example 21 83.5 676.3 Example 22 81.5 660.1 Example 23 79.4 643.1 Comparative Example 24 82.3 666.6 Example 25 90.1 729.8 Example 26 87.3 707.1 Example 27 84.2 682.0 Example 28 82.5 668.2 Example 29 80.2 649.6 Example 31 94% 690.0 Comparative Example 2 69.2 560.5

As shown in Table 3, the lithium batteries of Examples 19-29 and 31 exhibited remarkably improved life characteristics and discharge capacities as compared with the lithium battery of Comparative Example 2 at a high rate.

Evaluation Example 4: Evaluation of thermal stability

The coin cells prepared in Examples 19 to 36 and Comparative Example 2 were charged and discharged once at a constant current of 8.5 mA / g (0.05 C rate) at a voltage range of 2.5 to 4.1 V relative to lithium metal at 25 캜, The battery was charged and discharged twice at a constant current of 17 mA / g (0.1 C rate) in a voltage range of 2.5 to 4.1 V as compared with the metal.

Subsequently, the coin cell was charged once at a constant current of 8.5 mA / g (0.05 C rate) to a voltage of 4.1 V relative to lithium metal at 25 캜.

Subsequently, after the charged coil cell was broken, the negative electrode active material was extracted and subjected to DSC (Dynamic Scanning Calorimeter) analysis. Part of the analysis results are shown in Table 4 and FIG. In Table 4, the calorific value is calculated as the integral value of the exothermic curve of FIG.

Calorific value [J / g] Example 19 5200 Example 31 5520 Comparative Example 2 9050

As shown in Table 4 and FIG. 4, the cathode active materials prepared in Examples 1 and 13 used in the lithium batteries of Examples 19 and 31, respectively, are superior to the cathode active material of Comparative Example 1 used in the lithium battery of Comparative Example 2 The size of the exothermic peak was reduced, and the temperature at which the exothermic peak appeared increased, thereby improving the thermal stability.

Claims (26)

The core comprising:
A crystalline carbon-based material having an interplanar spacing d ₀₀₂ of 0.35 nm or more;
Titanium oxide particles; And
And a metal capable of forming an alloy with lithium,
Wherein the content of the titanium oxide particles is more than 0 to 10% by weight based on the total weight of the core,
Further comprising a carbon-based coating layer formed on the core,
Wherein the carbon-based coating layer comprises amorphous carbon. The negative active material according to claim 1, wherein the crystalline carbon-based material has an interplanar spacing d ₀₀₂ of 0.35 nm to 0.4 nm. The negative electrode active material according to claim 1, wherein the titanium-based oxide particles and a metal capable of forming an alloy with lithium are coated with the crystalline carbon-based material. The negative electrode active material according to claim 1, wherein the titanium-based oxide particles and a metal capable of forming an alloy with lithium are dispersed in the core. delete The negative electrode active material according to claim 1, wherein the titanium oxide particles have a particle diameter of 10 to 990 nm. The negative electrode active material according to claim 1, wherein the titanium oxide is at least one selected from the group consisting of Li ₄ Ti ₅ O ₁₂ , TiO ₂ , LiTiO ₃ and Li ₂ Ti ₃ O ₇ . The negative electrode active material according to claim 1, wherein the content of the metal capable of forming an alloy with lithium is from more than 0 to 10% by weight based on the total weight of the core. The negative electrode active material according to claim 1, wherein the metal capable of forming an alloy with lithium is particles having a particle diameter of 10 to 990 nm. The negative electrode active material according to claim 1, wherein the metal capable of forming an alloy with lithium is at least one selected from the group consisting of Si, Sn, Pb, Ge, Al and oxides thereof. The negative electrode active material according to claim 1, wherein the metal capable of forming an alloy with lithium forms a coating layer on one surface of the crystalline carbon-based material. 12. The negative electrode active material according to claim 11, wherein the coating layer is obtained by reducing a precursor of a metal capable of forming an alloy with lithium. The method of claim 1, wherein the crystalline carbon-based material has n rings of polycyclic nano-sheets arranged on one plane, wherein rings formed by connecting six carbon atoms in a hexagonal shape are condensed with each other, Wherein n is an integer of 2 to 250, and the first carbon of the n polycyclic nanosheets and the second carbon of the n polycyclic nanosheets, L2 is a distance between the first carbon and the second carbon, and L2 is a distance between the first carbon and the second carbon of the n polycyclic nanosheets, And the fourth carbon other than the first carbon, the second carbon and the third carbon among the carbons of the n polycyclic nanosheets except the third carbon and the nth polycyclic nanosheet. , the y axis and the z axis The second carbon has a coordinate B (p, q, r), the p and q are independently 10 mu m or less, and the r Is an anode active material having a thickness of 100 nm or less. delete delete The negative electrode active material according to claim 1, wherein the negative electrode active material is spherical particles having an aspect ratio of less than 2. 17. The negative electrode active material according to claim 16, wherein the particles have an average particle diameter of 1 to 100 mu m. An anode comprising the anode active material according to any one of claims 1 to 4 and 6 to 13, 16 and 17. A lithium battery employing the negative electrode according to claim 18. delete delete delete delete delete delete delete

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