KR20060036588A - Electrode active material comprising zinc-tin compound and lithium secondary battery using the same - Google Patents

Abstract

The present invention a) an electrode active material capable of occluding and releasing lithium; And b) provides a lithium secondary battery electrode active material and a manufacturing method thereof comprising a zinc-tin-based compound coating layer of the general formula (I) formed on part or all of the surface of the electrode active material particles. In addition, the present invention is added to the electrode prepared from the electrode slurry prepared by including the electrode active material or containing a zinc-tin compound of the general formula (I), the zinc-tin compound of the general formula (I) It provides an electrolytic solution and / or separator and a lithium secondary battery having the same.

Zn _x Sn _y A _z (I)

(In the above, A is an oxygen or hydroxy group, and 0 <x <10, 0 <y <10, 0 <z <15)

The electrode active material including the zinc-tin-based coating layer represented by the general formula (I) of the present invention is stored at high temperature by suppressing the exothermic reaction inside the electrode due to the endothermic decomposition reaction of the zinc-tin-based compound occurring at a high temperature. A lithium secondary battery having improved characteristics and safety can be provided.

Zinc, Tin, Electrode Active Material, Additive, Safety Lithium Secondary Battery

Description

Electrode active material containing a zinc-tin compound and a lithium secondary battery using the same TECHNICAL FIELD

The present invention is to suppress the exothermic reaction in the electrode high temperature storage characteristics and safety, in particular, the electrode active material with improved thermal safety, the electrode prepared from the electrode slurry containing the electrode active material or zinc-tin compound, zinc- The present invention relates to an electrolyte and / or separator prepared by adding a tin compound and a lithium secondary battery having the same.

In recent years, with the trend of miniaturization and weight reduction of electronic devices, miniaturization and weight reduction of batteries acting as power sources are also required. BACKGROUND ART Lithium-based secondary batteries have been put to practical use as small, light weight, high capacity rechargeable batteries, and are used in portable electronic and communication devices such as small video cameras, mobile phones, and notebook computers.

The lithium secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte, and transfers energy while reciprocating both electrodes such that lithium ions from the positive electrode active material are inserted into a negative electrode active material, such as carbon particles, and are detached again when discharged. Since it is possible to charge and discharge.

The lithium secondary battery has an advantage that the operating voltage is higher and the energy density is larger than that of the conventional Ni-MH conventional battery using an aqueous solution electrolyte, but more important than this is a safety characteristic of the lithium secondary battery. For this purpose, the ignition and smoke in the battery are strictly regulated.

Currently, as an electrode active material of a lithium secondary battery, a cathode active material uses a lithium-containing composite oxide, and a cathode active material uses a kind of carbon material. However, the electrode manufactured using the electrode active material may be a decomposition of the anode due to the exothermic reaction with the charged electrode and the electrolyte under abnormal conditions such as overcharge or high temperature storage of the battery, oxidation reaction and explosion of the electrolyte, etc. The problem of lack of thermal safety of the same cell arises. In particular, when the temperature of the positive electrode active material is continuously increased in a charged state, when the binding force between metal ions and oxygen in the metal oxide structure, which is an electrode active material, drops sharply above a certain temperature, the generation of oxygen rapidly increases. Eventually a thermal runaway occurs in the cell. When this phenomenon occurs, the battery's surface temperature is usually above 400 ° C, leading to explosions with flames.

In order to solve the above problems, many efforts have been made so far, but most of them have been used to reduce the reactivity of the electrode and the battery by using an additive having the characteristic of being oxidized or reduced under abnormal conditions such as overcharge or high temperature storage. . However, the additives only improve safety in a certain region of temperature or voltage, and ultimately cannot prevent safety degradation such as ignition and explosion of the battery. Therefore, there is an urgent need for the development of an electrode active material or an electrode having excellent thermal safety that can secure safety and reliability of a battery system under abnormal conditions such as heat exposure, combustion, or overcharging.

The inventors have found that when a zinc-tin (Zn-Sn) -based compound that decomposes in a high temperature region of 200 to 400 ° C. beyond the normal operating temperature range of a battery and absorbs ambient heat is added to the electrode active material particles or added to an electrode slurry, It has been found that the safety of a lithium secondary battery can be improved by suppressing the exothermic reaction occurring within.

Accordingly, an object of the present invention is to provide an electrode active material for a lithium secondary battery in which part or all of the surface of an electrode active material particle is coated with the zinc-tin compound.

In addition, the present invention includes the electrode prepared by the electrode active material or prepared by the addition of the zinc-tin-based compound, the electrolyte and / or separator prepared by the addition of the zinc-tin-based compound at the time of electrode slurry production Another object is to provide one lithium secondary battery.

The present invention a) an electrode active material capable of occluding and releasing lithium; And b) provides a lithium secondary battery electrode active material and a manufacturing method thereof comprising a zinc-tin-based compound coating layer represented by the following formula (1) formed on part or all of the surface of the electrode active material particles.

Zn _x Sn _y A _z (I)

In the above,

A is an oxygen or hydroxy group, and 0 <x <10, 0 <y <10, 0 <z <15.

In addition, the present invention includes the electrode prepared by the addition of the electrode active material or prepared by adding a zinc-tin compound represented by the formula (1) to the electrode active material when the electrode slurry is prepared, the zinc-tin compound of the formula (1) It provides an electrolytic solution and / or separator and a lithium secondary battery having the same.

Hereinafter, the present invention will be described in detail.

Among the electrode active materials of the present invention, the cathode active material may be a lithium transition metal composite oxide capable of occluding and releasing lithium, and non-limiting examples thereof include lithium manganese oxide (lithiated magnesium oxide) and lithium cobalt oxide (lithiated cobalt oxide). And lithium intercalation materials such as composite oxide formed by lithium nickel oxide, lithium iron phosphate, or a combination thereof.

The negative electrode active material of the electrode active material of the present invention is a lithium alloy, carbon, petroleum coke, activated carbon, graphite, or other carbons that can occlude and release lithium Lithium adsorption materials can be used, and other metal oxides such as TiO ₂ , SnO ₂ or Li ₄ Ti ₅ O ₁₂ , which can occlude and release lithium and have a potential for lithium of less than 2V, can also be used.

The electrode manufactured by using the electrode active material is a cathode (egg) due to the exothermic reaction with the charged electrode and the electrolyte under abnormal conditions such as overcharging or high temperature storage of the battery, generation of oxygen and thereby the surface of the battery The thermal runaway phenomenon in which the temperature is higher than 400 ° C. occurred in series, causing a problem of a lack of thermal safety of the battery such as fuming and explosion.

Accordingly, the present invention is coated by coating the surface of the electrode active material or the zinc-tin-based compound of the formula (1), which is decomposed to cause an endothermic reaction when outside the normal temperature range of the battery (100 ~ 200 ℃ or less) or by adding during the production of electrode slurry More fundamentally, it is to improve the safety and high temperature storage characteristics of the battery.

The coating layer component formed on part or all of the surface of the electrode active material according to the present invention is preferably a zinc-tin compound represented by the formula (1). Specific examples of the zinc-tin compound include Zn ₂ SnO ₄ , ZnSnO ₃ (zinc stannate, ZS), ZnSn (OH) ₆ (zinc hydroxy stannate, ZHS), and the like. Do.

The zinc-tin compound of Formula 1 coated on the surface of the electrode active material undergoes an endothermic reaction while decomposition reaction occurs at about 200 ° C., and exothermic reaction forming char at 400 ° C. When the zinc-tin compound undergoes an endothermic reaction, abnormal heat in the battery is absorbed and consumed, thereby suppressing the progress of the series exothermic reaction of the battery. In addition, since the gas and char generated during the exothermic reaction of the zinc-tin compound have excellent flame retardant properties, the combustion reaction is suppressed so that thermal runaway generated inside the battery no longer proceeds to ignition and explosion. It plays a role.

The coating layer of the present invention composed of the above-described zinc-tin-based compound may be present in amorphous, crystalline or mixed form thereof. In addition, the thickness of the zinc-tin coating layer is not particularly limited and is the same as the thickness of the coating layer formed by a conventional method.

The content of the zinc-tin coating layer compound represented by Formula 1 of the present invention is preferably in the range of 0.01 to 10% by weight per 100% by weight of the electrode active material. If it is less than 0.01% by weight, it is not possible to effectively improve the safety of the electrode active material, in particular, the thermal safety, and if it exceeds 10% by weight, the amount of the electrode active material is relatively lowered, resulting in a problem of lowering the charge / discharge capacity of the battery.

Method for producing an electrode active material comprising a zinc-tin-based coating layer of the formula 1 according to the present invention can be prepared using a conventional coating method known in the art, for example, a) represented by the formula (1) Preparing a coating solution by dissolving the zinc-tin compound in a solvent; And b) adding the electrode active material to the coating solution prepared in step a), stirring, and coating the same, followed by drying.

First, 1) The zinc-tin compound of formula 1 is dissolved in a solvent.

The electrode active material and the zinc-tin compound are the same as described above, and an organic solvent such as water or alcohol may be used as the solvent.

2) After adding and stirring the electrode active material particles capable of occluding and releasing lithium in the prepared coating solution, it is dried.                     

In this case, the coating process may use a general coating method commonly used in the art, for example, solvent evaporation, co-precipitation, precipitation, sol-gel method, post-sorption filter method, sputtering, CVD, etc. .

The electrode active material coated with a zinc-tin compound as described above is completed by drying. At this time the drying temperature and time is not particularly limited, and proceeds according to conventional methods known in the art.

The dried electrode active material may then optionally be subjected to a heat treatment step, the heat treatment temperature range and heat treatment time is not particularly limited, 100 to 1000 ℃ and 1 to 20 hours are appropriate, respectively.

According to the present invention, the zinc-tin compound represented by Chemical Formula 1 may be used as an electrode additive when preparing an electrode slurry, in addition to the coating material of the electrode active material described above, and may also be added when preparing an electrolyte or separator of a battery. At this time, the amount of the zinc-tin compound is not particularly limited and may be adjusted to improve battery safety.

The present invention provides a lithium secondary electrode comprising a zinc-tin compound represented by the formula (1).

The electrode for a lithium secondary battery may be prepared according to conventional methods known in the art, and is not particularly limited. As an embodiment of the electrode manufacturing method for the lithium secondary battery, an electrode active material including a zinc-tin-based coating layer prepared as described above is mixed with a binder to prepare an electrode slurry, and the electrode slurry is coated on a current collector to prepare an electrode slurry. Can be prepared. As another embodiment, an electrode slurry is prepared by mixing an electrode active material, that is, a cathode active material and / or a cathode active material, and a zinc-tin electrode additive represented by Chemical Formula 1, and applying the prepared electrode slurry to each current collector. Can be prepared.

As the conductive agent, any electronically conductive material which does not cause chemical change in the battery constructed can be used. For example, carbon black, such as acetylene black, Ketjen black, Farnes black, and thermal black; Natural graphite, artificial graphite, conductive fibers and the like can be used. Carbon black, graphite powder and carbon fiber are particularly preferable.

As the binder, any one of a thermoplastic resin and a thermosetting resin may be used, or a combination thereof may be used. Among these, polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE) is preferable, and PVdF is particularly preferable.

The current collector is not particularly limited as long as it is made of a conductive material, but a foil made of aluminum, nickel or a combination thereof is preferable for the positive electrode, and copper, gold, nickel, a copper alloy, or a combination thereof for the negative electrode. Preferred foils are preferred.

In addition, the present invention provides a lithium secondary electrolyte and / or separator comprising a zinc-tin compound represented by the formula (1).

The electrolyte solution for a lithium secondary battery according to the present invention is obtained by adding a zinc-tin compound represented by Chemical Formula 1 to a conventional electrolyte solution consisting of an electrolyte solvent and a lithium salt.

The lithium salt may be at least one selected from the group consisting of LiClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiBF ₄ , LiAsF ₆ and LiN (CF ₃ SO ₂ ) ₂ .

The electrolyte solvent is ethylene co (carbonate), propylene carbonate, butylene carbonate, vinylene carbonate, sulfolane, γ-butylo lactone, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxy ethane, tetrahydrofuran And one or more selected from the group consisting of a mixture thereof.

The lithium secondary battery separator according to the present invention may be prepared by adding a zinc-tin compound represented by Chemical Formula 1 to a conventional separator, that is, a porous separator having pores according to a conventional method known in the art.

Examples of the separator may include a polypropylene-based, polyethylene-based, and polyolefin-based porous separator, but are not limited thereto.

For example, a method of manufacturing a separator for a lithium secondary battery may be performed using a mixture of a zinc-tin compound and a polymer of Formula 1, and a separator may be formed alone. It can be formed by coating on a separator substrate.

In addition, the present invention is a lithium secondary battery comprising a separator and an electrolyte interposed between a positive electrode, a negative electrode, both electrodes, the positive electrode, the negative electrode or both electrodes are coated with a zinc-tin compound of formula (1) An electrode prepared by including the prepared electrode active material or the zinc-tin-based compound represented by Chemical Formula 1 when preparing an electrode slurry; Or it provides a lithium secondary battery characterized in that the separator and / or the electrolyte is prepared by adding the zinc-tin compound of the formula (1).

In this case, the lithium secondary battery includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

Lithium secondary battery according to the present invention can be prepared by putting a porous separator between the positive electrode and the negative electrode in a conventional manner known in the art.

Although the external shape of the lithium secondary battery manufactured by the above method is not limited, it is possible to have a cylindrical, coin-shaped, square or pouch type of cans.

The invention is explained in more detail based on the following examples and experimental examples. However, Examples and Experimental Examples are for illustrating the present invention and are not limited to these.

[Examples 1-3. Electrode, Electrolyte and Lithium Secondary Battery Manufacturing]

Example 1

(Anode manufacturing)

ZnSnO ₃ After dissolving in methanol, 100 g of LiCoO ₂ (Nippon Chem) powder having a particle size of 10 µm was added thereto, followed by stirring for 10 minutes. The solvent was evaporated with stirring, the solvent was completely removed and the powder obtained was dried in a vacuum oven at 100 ° C. for 5 hours, then heat treated at 600 ° C. for 5 hours and slowly cooled. 92% by weight of the obtained positive electrode active material, 4% by weight of carbon black (carbon black) as a conductive agent, 4% by weight of PVdF as a binder is added to the solvent N-methyl-2 pyrrolidone (NMP) to prepare a positive electrode mixture slurry. The positive electrode is prepared by applying and drying the positive electrode mixture slurry on a thin film of aluminum (Al) of a positive electrode current collector having a thickness of 20 μm.

(Cathode production)

N-methyl-2 pyrrolidone as a solvent by using carbon powder as a negative electrode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon black as a conductive agent at 96% by weight, 3% by weight, and 1% by weight, respectively. After adding to (NMP) to prepare a negative electrode mixture slurry, the negative electrode mixture slurry is applied to a thin copper (Cu) thin film, which is a negative electrode current collector having a thickness of 10 μm, to prepare a negative electrode.

(Battery assembly)

After assembling the battery using the separator prepared as described above, the cathode, the anode, and the polypropylene / polyethylene / polypropylene (PP / PE / PP), 1 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in EC. The electrolyte is injected as a / EMC solution to finally complete the battery.

Example 2

An electrode and a lithium secondary battery were manufactured by the same method as Example 1, except that ZnSn (OH) ₆ (ZHS) was used instead of ZnSnO ₃ as a zinc-tin compound.

Example 3 Preparation of Electrolyte for Lithium Secondary Battery

An electrolyte solution and a lithium secondary battery were prepared in the same manner as in Example 1, except that 3M by weight of Zn ₂ SnO ₄ was added to an EC / EMC solution in 1M LiPF ₆ .

Experimental Example 1. Evaluation of safety of lithium secondary battery

In order to evaluate the safety of a lithium secondary battery having an electrode prepared using an electrode active material coated with a zinc-tin compound according to the present invention, a hot box experiment known in the art was carried out, and then Observe the condition.

Lithium secondary battery according to the present invention is produced by coating a zinc-tin compound that absorbs the surrounding heat during high-temperature decomposition on the surface of the electrode active material or added during the production of electrode slurry, thereby generating abnormal heat such as overcharge or high temperature storage By suppressing the exothermic reaction inside the battery can improve the safety and high temperature storage characteristics.

Claims (7)

a) an electrode active material capable of occluding and releasing lithium; And b) a zinc-tin compound coating layer of the following general formula (I) formed on part or all of the surface of the electrode active material particles; Electrode active material for a lithium secondary battery comprising a. Zn _x Sn _y A _z (I) (In the above, A is an oxygen or hydroxy group, and 0 <x <10, 0 <y <10, 0 <z <15) The electrode active material according to claim 1, wherein the zinc-tin compound represented by the general formula (I) is one or more selected from the group consisting of Zn ₂ SnO ₄ , ZnSnO _3, and ZnSn (OH) ₆ . The electrode active material according to claim 1, wherein the amount of the zinc-tin compound represented by the general formula (I) is 0.01 to 10% by weight based on 100% by weight of the electrode active material. An electrode for a lithium secondary battery, comprising the electrode active material of claim 1 or prepared from an electrode slurry comprising an electrode active material and a zinc-tin compound represented by the following general formula (I). Zn _x Sn _y A _z (I) (In the above, A is an oxygen or hydroxy group, and 0 <x <10, 0 <y <10, 0 <z <15) A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between both electrodes, and an electrolyte, the positive electrode, the negative electrode or both electrodes of claim 4; Or the electrolyte and / or separator is prepared by adding a zinc-tin compound represented by the following general formula (I). Zn _x Sn _y A _z (I) (In the above, A is an oxygen or hydroxy group, and 0 <x <10, 0 <y <10, 0 <z <15) a) dissolving a zinc-tin compound in a solvent to prepare a coating solution; And b) adding the electrode active material particles to the coating solution prepared in step a) and stirring the coating, and then drying them; And Method for producing an electrode active material for a lithium secondary battery coated with a zinc-tin compound represented by the following general formula (I), including. Zn _x Sn _y A _z (I) (In the above, A is an oxygen or hydroxy group, and 0 <x <10, 0 <y <10, 0 <z <15) The method of claim 6, further comprising the step of further heat treatment after step b).