KR20080057817A - Electrode comprising reducing agent of halogen acid and secondary battery comprising the same - Google Patents

Abstract

An electrode is provided to improve high-temperature storage characteristics and high-temperature performances of a battery. An electrode includes inorganic particles selected from the group comprising NiO, CoO, MnO, MnO2, Co2O3, CaCO3, and talc. The inorganic particles reduce a concentration of halogen acid in a battery through a neutralization reaction with the halogen acid present in the battery. The inorganic particles are used as an element of an electrode material or as a coating component of the prefabricated electrode. A secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode, negative electrode, or both electrodes is the fabricated electrode.

Description

Electrode including a halogen acid reducing agent and a secondary battery comprising the electrode TECHNICAL FIELD

1 is a graph of the concentration of HF over time measured in Experimental Example 1.

2 is (a) the concentration of water measured in Experimental Example 2; And (b) HF concentration graph.

3 is a graph of remaining capacity of a battery according to cycle life measured in Experimental Example 3. FIG.

The present invention relates to a secondary battery having an electrode including a halogen acid reducing agent and having improved high temperature storage characteristics thereof.

Recently, as miniaturization and light weight of electronic equipment have been realized and the use of portable electronic devices has become common, research on lithium secondary batteries having high energy density has been actively conducted.

The lithium secondary battery is manufactured by using a material capable of inserting and detaching lithium ions as a negative electrode and a positive electrode, and filling an electrolyte solution between the positive electrode and the negative electrode, oxidizing when lithium ions are inserted and desorbed from the positive electrode and the negative electrode, Electrical energy is generated by the reduction reaction. However, much research is still required in improving the performance of a secondary battery, and the high temperature storage characteristics of the battery are very important.

In secondary batteries, lithium salts containing halogen anions such as LiBF ₄ , LiPF ₆ , and LiClO ₄ are generally used as electrolyte salts. The lithium salts react with moisture present in electrodes or electrolytes to form a strong acid, halogen acid (HX: X may form F, Cl, Br, I), which may cause undesirable side reactions in the cell. That is, the HF produced above not only degenerates by dissolution of the positive electrode material, in particular the positive electrode active material, but also forms lithium fluoride (LiF) on the surface of the positive electrode, resulting in an increase in electrical resistance. . In particular, the rate of halogen acid formation and the rate of dissolution of the electrode by the halogen acid rises under high temperature, which causes a great problem in the high temperature storage characteristics of the battery.

In order to solve the above problems, a method of using a compound capable of neutralizing reaction with a halogen acid as a component of an electrolyte, a separator, or an electrode of a battery has been proposed, but the water produced as a result of the neutralization reaction is again an electrolyte salt. The amount of use tended to be very limited in order to prevent the formation of halogen acid by reaction with.

In order to solve the above-mentioned problems, the inventors of the present invention, as inorganic particles capable of neutralizing reaction with halogen acid (HX: X = F, Cl, Br, I), the water produced as a result of the reaction is no longer reused in the reaction of forming a halogen acid. High temperature storage of the battery when using electrodes containing inorganic particles, more particularly NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , talc, or mixtures thereof, that prevents recycling It has been found that the properties and high temperature performance can be improved.

Accordingly, an object of the present invention is to provide an electrode including the inorganic particles and a secondary battery including the electrode.

The present invention provides an electrode comprising an inorganic particle selected from the group consisting of NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ and talc; And it provides an electrochemical device comprising the electrode.

In another aspect, the present invention provides a halogen acid reducing agent for a secondary battery composed of inorganic particles selected from the group consisting of NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ and talc (talc).

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention is an inorganic particle capable of neutralization reaction with halogen acid (HX: X = F, Cl, Br, I), NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , talc or these An electrode comprising a mixture of is characterized in that the concentration of halogen acid in the cell is reduced while the water produced as a result of the neutralization reaction is no longer recycled to the halogen acid formation reaction.

The reaction of lithium fluoride salts such as LiPF ₆ with moisture, which is mainly used as the electrolyte salt, generally follows the mechanism of the following reaction formulas (1) and (2), where the reaction of the following reaction formula (1) can be neglected at room temperature. It is known.

[Reaction Mechanism]

LiPF ₆ → LiF + PF ₅ ‥‥‥‥‥‥‥‥‥‥‥‥ (1)

PF ₅ + H ₂ O → POF ₃ + 2HF ‥‥‥‥‥‥‥‥‥ (2)

On the other hand, in Journal of Fluorine Chemistry 126 (2005) 27-31, it was reported that HF, which is the result of Scheme (2), acts as a cocatalyst for the reaction of Scheme (1).

In the present invention, the reaction of Scheme (1) is negligible at room temperature, but the instability of LiPF ₆ increases at high temperatures, so that the reaction rate of Scheme (1) may affect the overall reaction rate between LiPF ₆ and water. point; And the reaction rate of Scheme (1) is influenced by the concentration of HF acting as a catalyst.

That is, 1) the present invention is inorganic particles capable of neutralization reaction with halogen acid (HX: X = F, Cl, Br, I), NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , talc ( talc) or mixtures thereof may be introduced into the electrode to reduce the concentration of halogen acid in the cell. Therefore, elution and degeneration of the positive electrode material, in particular the positive electrode active material, by the halogen acid can be prevented, and the lifespan performance of the battery can also be improved.

2) In addition, since the reaction of the reaction formula (1) is affected by the concentration of the halide acid as a cocatalyst, in the present invention, the concentration of the halogen acid in the battery is reduced by the inorganic particles, so that the reaction rate of the reaction formula (1) is reduced. Is very slow. Therefore, the amount of lithium fluoride (LiF) produced can be reduced, and an increase in electrical resistance due to lithium fluoride (LiF) can be prevented.

In addition, since the reaction rate of Reaction Scheme (1) is very slow, and the reaction of Reaction Scheme (2), which is a subsequent reaction, is difficult to proceed, in the present invention, there is a concern that halogen acid is continuously generated by the water produced by the neutralization reaction. In addition, since NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , and talc introduced in the present invention are inorganic particles having excellent water adsorption capacity, they adsorb water in a battery, The reaction with the electrolyte salt can be prevented. In addition, the reaction of the reaction formula (1) under high temperature contributes greatly to the overall reaction rate, the present invention can improve the high temperature storage characteristics of the battery.

The inorganic particles introduced to the electrode of the present invention are NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , or talc, which may be used alone or in combination. Among these, talc is a compound of the formula Mg ₃ (OH) ₂ Si ₄ O ₁₀ , in addition to neutralization with the halogen acid, it can adsorb the halogen acid in the battery to reduce the concentration of the halogen acid in the battery. This is because talc has excellent pores due to the well developed pores, and the adsorption power is excellent, and acid molecules having a higher polarity such as halogen acids can be more easily adsorbed.

In the present invention, the concentration of HX decreases due to the neutralization reaction or adsorption of the inorganic particles introduced to the electrode, wherein the residual concentration of HX (X = F, Cl, Br, I) in the battery is preferably 50 ppm or less. However, the present invention is not limited thereto.

The size of the inorganic particles used in the present invention is not limited but is preferably 10nm to 100μm. If it is less than 10nm, not only manufacturing is difficult, but also the size of pores formed in the electrode by the inorganic particles is too small may inhibit the performance of the electrode sufficient. On the other hand, if it exceeds 100㎛ it is difficult to introduce a uniform thickness to the electrode, the thickness of the final electrode is increased may increase the size of the device or may lead to a reduction in the electrical capacity due to the reduced amount of the electrode active material.

The content of the inorganic particles can be adjusted according to the goal to improve the overall performance of the electrochemical device, in particular 0.01 to 30 parts by weight relative to 100 parts by weight of the electrode active material. If it is less than 0.01 part by weight, the effect of improving the high temperature storage characteristics of the battery is insignificant, and if it exceeds 30 parts by weight, it is because the electric capacity and performance may be deteriorated.

The electrode of the present invention may be made by using the above-described inorganic particles in combination with an electrode material, or may be formed by coating a surface of a prepared electrode.

The method for manufacturing the electrode according to the present invention is not particularly limited, but is prepared by applying and drying a conventional method known in the art as an example, that is, an electrode slurry including a positive electrode active material or a negative electrode active material on a current collector. . In this case, a small amount of a conductive agent and / or a binder may be optionally added.

The positive electrode active material may be a conventional positive electrode active material that can be used for the positive electrode of a conventional secondary battery, non-limiting examples of lithium such as LiM _x O _y (M = Co, Ni, Mn, Co _a Ni _b Mn _c ) Transition metal composite oxides (for example, lithium manganese composite oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , lithium cobalt oxides such as LiCoO ₂ , and some of the manganese, nickel and cobalt oxides of these oxides And the like, or a vanadium oxide containing lithium) or a chalcogen compound (for example, manganese dioxide, titanium disulfide, molybdenum disulfide, and the like). Preferably LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _1-Y Co _Y O ₂ , LiCo _1-Y Mn _Y O ₂ , LiNi _1-Y Mn _Y O ₂ (where 0 ≦ Y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2-z Ni _z O ₄ , LiMn _2-z Co _z O ₄ ( Here, 0 <Z <2), LiCoPO ₄ , LiFePO _4, or a mixture thereof is mentioned.

The negative electrode active material may be a conventional negative electrode active material that can be used for the negative electrode of a conventional secondary battery, non-limiting examples of lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite lithium adsorbents such as graphite or other carbons. Non-limiting examples of the positive electrode current collector is a foil made by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

Conventional binders may be used, and non-limiting examples thereof include polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR).

The present invention also provides a secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode, the negative electrode, or the positive electrode is an electrode containing the inorganic particles of the present invention.

The secondary battery is preferably a lithium secondary battery, and non-limiting examples thereof include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The secondary battery of the present invention can be prepared according to conventional methods known in the art. For example, after the assembly between the negative electrode and the positive electrode prepared according to the present invention by interposing a separator (介 在), it can be prepared by injecting an electrolyte solution.

The electrolyte includes conventional electrolyte components known in the art, such as electrolyte salts and electrolyte solvents. At this time, the electrolyte salt is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, and comprising an alkali metal cation or an ion composed of a combination thereof, such as K ^+, B ^- is PF ₆ ^{-, _{BF 4 -, Cl -, Br}} -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) Salts containing ions consisting of anions such as ₃ ⁻ or combinations thereof.

The electrolyte solvent may be a conventional organic solvent known in the art, such as cyclic or linear carbonates, esters, ethers, ketone organic solvents. Non-limiting examples of the solvent solvent is propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), dimethyl sulfoxide Said, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC), butyrolactone, gamma butyrolactone (GBL), valerian Rolactone, caprolactone, fluoroethylene carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate or halogen derivatives thereof Etc. These electrolyte solvents can be used individually or in mixture of 2 or more types.

The separator that can be used in the present invention is not particularly limited, but a porous separator may be used, for example, a polypropylene-based, polyethylene-based, or polyolefin-based porous separator. Alternatively, a porous separator into which inorganic particles are introduced may also be used.

The shape of the secondary battery manufactured by the above method is not limited, but may be cylindrical, square, pouch type or coin type using a can.

Furthermore, the present invention is a halogen acid for a secondary battery (HX: X = F, Cl, Br consisting of inorganic particles selected from the group consisting of NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , and talc) , I) provide a reducing agent. The inorganic particles may reduce the concentration of halogen acid in the battery through neutralization reaction or adsorption. The said inorganic particle can be used individually or in mixture.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1

1-1. Preparation of the anode.

89 wt% of LiCoO ₂ as positive electrode active material, NiO as halogen acid reducing agent A positive electrode mixture slurry was prepared by adding 3% by weight, 4% by weight of carbon black as a conductive agent and 4% by weight of PVDF as a binder to a solvent, N-methyl-2 pyrrolidone (NMP). The positive electrode mixture slurry was coated on a thin film of aluminum (Al) of a positive electrode current collector having a thickness of 20 μm and manufactured to produce a positive electrode, followed by roll press.

1-2. Preparation of the negative electrode.

N-methyl-2 pyrroli 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 material at 96% by weight, 3% by weight, and 1% by weight, respectively. A negative electrode mixture slurry was prepared by adding to NMP. The negative electrode mixture slurry was coated on a copper (Cu) thin film, which is a negative electrode current collector having a thickness of 10 μm, to prepare a negative electrode through drying, and then roll press was performed.

1-3. Fabrication of Lithium Secondary Battery

A separator consisting of the positive electrode, the negative electrode, and polypropylene / polyethylene / polypropylene (PP / PE / PP) prepared above was assembled using a stacking method, and 1M lithium hexafluorophosphate ( A lithium secondary battery was prepared by injecting an ethylene carbonate / propylene carbonate / diethyl carbonate (EC: PC: DEC = 30: 20: 50 wt%) electrolyte solution in which LiPF ₆ ) was dissolved.

Example 2

A lithium secondary battery was manufactured in the same manner as in Example 1, except that CoO was used instead of NiO in preparing the cathode.

Example 3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that MnO was used instead of NiO in preparing the cathode.

Example 4

A lithium secondary battery was manufactured in the same manner as in Example 1, except that MnO ₂ was used instead of NiO in preparing the cathode.

Example 5

A lithium secondary battery was manufactured in the same manner as in Example 1, except that Co ₂ O ₃ was used instead of NiO in preparing the cathode.

Example 6

A lithium secondary battery was manufactured in the same manner as in Example 1, except that CaCO ₃ was used instead of NiO in preparing the cathode.

Example 7

A lithium secondary battery was manufactured in the same manner as in Example 1, except that talc was used instead of NiO when preparing the cathode.

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as in Example 1, except that NiO was not used to prepare the cathode.

Experimental Example  One

In order to evaluate the effect of reducing the halogen acid of the inorganic particles used in the present invention under conditions similar to those in the battery environment in which the halogen acid is present, the following experiment was conducted.

HF was dissolved in 50 g of propylene carbonate at a concentration of 2000 ppm, and NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ and talc were added to each other. Measured. The results are shown in FIG.

As a result of the experiment, when the inorganic particles of the present invention is used, the concentration of HF was found to be remarkably reduced. From this, it was found that the concentration of HF in the battery can be significantly reduced by neutralization reaction with HF and / or adsorption of HF.

Experimental Example 2 Comparative Evaluation of HF Concentration and Water Content

In order to evaluate the effect of reducing the halogen acid of the inorganic particles used in the present invention and HF regeneration of water in the battery under conditions similar to those in the battery environment, the following experiment was conducted.

Ethylene carbonate (EC): ₃ g of NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , and talc were added to 1M LiPF ₆ solution having a volume ratio of ethylmethyl carbonate (EMC) = 1: 2. As a control thereof, a solution without using the inorganic particles; And a solution using MgO, Al ₂ O ₃ , zeolite instead of the inorganic particles. After 1 hour at 25 ° C., the concentration of water in the solution was measured, and after 15 days at 65 ° C., the concentration of water and HF concentration were measured. The results are shown in (a) and (b) of FIG. 2.

As a result, in the control solution containing MgO, Al ₂ O ₃ After leaving for 15 days at 65 ℃, the concentration of HF in the solution was very high, the MgO, Al ₂ O ₃ has little effect of reducing the halogen acid in the battery And it was found.

In addition, in the control solution containing zeolite, the HF concentration in the solution was lower after 15 days at 65 ° C., but the concentration of water after 15 days at 65 ° C. was much higher than that of the initial water. This is presumably because the water molecules trapped in the zeolite lattice are eluted into the electrolyte solution over time under high temperature. Therefore, when the electrode containing zeolite is used in the battery, it can be expected that the amount of moisture in the electrolyte is increased at high temperatures. In this case, gas may be generated due to the electrolysis of the water, thereby increasing the internal pressure of the battery, or reacting the water with the electrolyte salt to form hydrofluoric acid, thereby eluting the electrode.

When the inorganic particles of the present invention were used, the initial water concentration and the water concentration after 15 days of standing at 65 ° C. appeared to be at similar levels, and the HF concentration in the solution after standing for 15 days at 65 ° C. showed a very low level. From this, it was found that when the inorganic particles of the present invention were used, water in the battery was no longer recycled to the HF formation reaction during the high temperature storage of the battery, but existed in the form of water in the battery. In addition, when the inorganic particles according to the present invention are used, it was predicted that the formation of HF at high temperature and the dissolution of the electrode active material or other side reactions thereof were suppressed, thereby improving the high temperature storage characteristics of the battery.

Experimental Example 3. High Temperature Performance Evaluation of Lithium Secondary Battery

Using the batteries prepared in Example 1, Comparative Examples 1 to 4, the residual discharge capacity according to the cycle life at 45 ℃ was measured, the results are shown in FIG.

Each battery was charged to 4.2 V at 1 C, and then charged at a voltage up to a current of 5% battery capacity. Discharge discharged each battery to 3V at 1 C, and this charge / discharge was called once.

As a result of the experiment, the battery of Examples 1 to 7 using the electrode containing the inorganic particles according to the present invention showed a higher capacity than the battery of Comparative Example 1 using the conventional electrode, the longer the cycle life. From this, it was confirmed that the high temperature performance of the battery can be improved when using the electrode containing the inorganic particles according to the present invention.

The present invention is an inorganic particle capable of neutralizing a reaction with halogen acid (HX: X = F, Cl, Br, I), and the inorganic particle which prevents the water produced as a result of the reaction from being recycled to the halogen acid formation reaction anymore. In more detail, by using an electrode including NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , talc, or a mixture thereof, high temperature storage characteristics and high temperature performance of the battery can be improved. .

Claims (6)

An electrode comprising inorganic particles selected from the group consisting of NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , and talc. The electrode of claim 1, wherein the inorganic particles reduce the concentration of halogen acid in the battery through a neutralization reaction with the halogen acid present in the battery. The electrode according to claim 1, wherein the inorganic particles are prepared by using the inorganic particles as a constituent of an electrode material or as a coating component of a prepared electrode. In a secondary battery comprising a positive electrode, a negative electrode, an electrolyte and a separator, The secondary battery, wherein the positive electrode, the negative electrode, or the positive electrode is the electrode according to any one of claims 1 to 3. The battery of claim 4, wherein the secondary battery is a lithium secondary battery. A halogen acid reducing agent for a secondary battery composed of inorganic particles selected from the group consisting of NiO, CoO, MnO, MnO ₂ , Co ₂ O ₃ , CaCO ₃ , and talc.

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