KR20110078307A - Metal based zn negative active material and lithium secondary battery comprising thereof - Google Patents

Abstract

PURPOSE: A metal-based zinc negative active material is provided to improve physical and electrochemical characteristics, specific capacity of negative electrodes, and capacitance density due to high density. CONSTITUTION: A metal-based zinc negative active material comprises a zinc material. The zinc material is obtained by applying carbons to the surface of the zinc material through the mixing with a carbon precursor and the carbonization of the carbon precursor. The zinc material is pure zinc or materials including alloy and a mixture of different elements with zinc. The zinc material is an zinc-graphite composite.

Description

Metal-based zinc anode active material and lithium secondary battery using same {Metal based Zn Negative Active Material and Lithium Secondary Battery Comprising}

The present invention relates to a metal-based zinc negative electrode active material and a lithium secondary battery using the same, wherein zinc may be used as a negative electrode active material of a lithium secondary battery, and a metal-based zinc negative electrode active material and a lithium secondary battery using the same to implement a high performance lithium secondary battery. It is about.

Recently, the development of the electronic and information communication industry is showing rapid growth through the portable, miniaturized, lightweight, and high-performance electronic devices. In addition, today's battery development is accelerating fierce competition between countries and companies as the demand for hybrid and electric vehicles increases.

Accordingly, a high capacity lithium secondary battery capable of responding to these demands and having a high output is being employed as a power supply device for various electronic devices, and its range of use is further expanded.

In particular, since their product performance depends on batteries, which are the key components, the demand for high performance batteries is very large. The characteristics required for the rechargeable battery that can be reused after charging are various aspects such as charge and discharge characteristics, lifespan, high rate characteristics, and stability at high temperature, and lithium secondary batteries are most commonly used [1].

The lithium secondary battery has a high voltage and a high energy density, and thus is a battery that is attracting the most attention and is mainly composed of a positive electrode, a negative electrode, an electrolyte, a separator, and an exterior material. The positive electrode is formed by binding a mixture of a positive electrode active material, a conductive agent, and a binder to a current collector. As the positive electrode active material, a lithium transition metal compound having a high electrochemical reaction potential such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , or LiMnO ₂ is mainly used.

Here, lithium metal, carbon, or graphite is mainly used as the negative electrode active material of the lithium secondary battery and has a low electrochemical reaction potential as opposed to the positive electrode active material. Typically, the standard reduction potential of lithium metal is -3.05 V.

Lithium secondary batteries have been increasing in capacity due to the improvement of negative electrode active materials from 18300 cylindrical battery to 1600mAh in 1993 to 2600mAh in 2008. Initially, the negative electrode active material showed 160mAh / g of carbon material after low temperature heat treatment, but artificial graphite currently used shows 300mAh / g level and natural graphite shows a specific capacity of 360mAh / g level. With the development of this technology, there is a need to develop a new high capacity anode material that can replace the graphite cathode active material of 372 mAh / g of theoretical capacity.

In order to improve the performance of the lithium secondary battery, it is important to improve the characteristics of the positive electrode and the negative electrode, and development of a high-performance negative electrode material is an important problem. In order to develop a new high performance anode material that can replace the existing graphite, the research of the metal-based anode material is in progress. As a high-capacity negative electrode material, metal-based materials such as silicon and tin, and alloy-based materials of lithium and metal-based materials have been studied, but these materials can be said to be of limited use due to rapid volume expansion when reacted with lithium. This volume expansion causes a crack in the inside and the surface of the electrode, which causes the active material to drop into the electrolyte, causing the cycle capacity to rapidly deteriorate due to a decrease in electrical contact. Many studies have been conducted to solve the problem of volume change of the electrode. [1].

The zinc material is a negative active material for lithium secondary batteries and has a theoretical specific capacity of 412 mAh per gram. The maximum filling composition of zinc is Li ₁ Zn ₁ . A thermodynamic modeling study of the temperature range up to 833K of lithium-zinc alloy was reported in 2008, and the high temperature state diagram of the lithium-zinc alloy was analyzed [2]. The characteristics of half-cells with lithium on graphite-zinc composites prepared using zinc chloride and potassium-graphite were reported, and the 10th discharge specificity was reported to be 355mAh / g. A study of alloying materials mainly containing zinc and containing nickel and indium was published in 2007, with specific capacities of 350-490 mAh / g [4].

<References>

1. G.-A. Nazri, G. Pistoia, Lithium Batteries; Science and Technology, KLUWEN, Academic publishers, Boston, 2004.

2.Y. Liang, Z. Du, C. Guo, C. Li, J. Alloys and Compounds, 455 (2008) 236-242.

3. A. Dailly, J. Ghanbaja, P. Willmann, D. Billaud, J. Appl. Electrochem., 34 (2004) 885-890.

4.N. Jayaprakash, K. Sathiyanarayanan, N. Kalaiselvi, Electrochimica Acta, 52 (2007) 2453-2460.

In the case of known anode materials of silicon and tin, the chemical compositions of the maximum lithium charge are Li _4.4 Si and Li _4.4 Sn and the theoretical specific capacities are high values of 993 mAh / g and 4199 mAh / g, respectively. Accordingly, the volume expansion has values of 420% and 380% with respect to the initial volume, and thus the cycle characteristics are not good. The zinc material is a negative active material for lithium secondary batteries and has a theoretical specific capacity of 412 mAh per gram. As the maximum filling composition of zinc is Li ₁ Zn ₁ , the amount of lithium that can be charged is lower than that of silicon or tin, so that the volume expansion is small and the cycle characteristics can be improved.

In addition, metallic zinc has excellent electron conduction characteristics and exhibits higher output characteristics than silicon of semiconductors, and the density of zinc is 7.14 g / ml, which makes it possible to manufacture high-density electrodes compared to 2.33 g / ml of silicon. . The theoretical capacity density of zinc is 2940 mAh / ml, somewhat lower than 9784 mAh / ml of silicon, but 3.5 times higher than that of 818 mAh / ml of conventional graphite.

Therefore, the present invention can use zinc as a negative electrode active material of a lithium secondary battery, and to provide a metal-based zinc negative electrode active material and a lithium secondary battery using the same for the implementation of a high-performance lithium secondary battery.

The present invention for achieving the above object, in the negative electrode active material of the components of the lithium secondary battery, comprising a zinc material, the zinc material is mixed with a carbon precursor and carbonized the carbon precursor on the surface of the zinc material Metal-based zinc anode active material, characterized in that the coating of carbon and a lithium secondary battery using the same as the technical gist.

In addition, the zinc material is preferably using a material containing a mixture of zinc or a mixture of hetero elements in zinc or zinc, in particular, the zinc material is to use a zinc-graphite composite in which graphite is mixed with zinc. More preferred.

In addition, the zinc-graphite composite preferably further includes a conductive material such as a polymer binder and carbon black.

In addition, the carbon precursor, the carbon precursor is a material that can provide carbon so that carbon can be applied to the zinc material by carbonization, vinyl-based such as polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC) It is preferable to use a conductive polymer or a doped conductive polymer of any one of resin, polyaniline (PAn), polyacetylene, polypyrrole and polythiophene, and the weight ratio of the zinc material and carbon precursor Is preferably used in the range from 2: 8 to 5: 5.

As a result of analyzing the physical and electrochemical characteristics of the negative electrode active material and the lithium secondary battery according to the present invention, it was confirmed that the lithium storage characteristics are shown, and the applicability of the lithium secondary battery as a negative electrode active material was confirmed. By adopting a zinc-based electrode material, the specific capacity of the negative electrode can be improved, and the capacity density can be improved by the high density characteristic, so that a high energy lithium secondary battery can be developed.

Hereinafter, the present invention will be described in more detail.

First, the metal-based zinc anode active material according to the present invention will be described.

The negative electrode active material according to the present invention includes zinc ash, wherein the zinc material is carbonized by mixing the carbon precursor and carbonizing the carbon precursor. In addition, the zinc material may be a pure zinc or a material containing an alloy and a mixture of hetero elements in combination with zinc, in particular, a zinc-graphite composite in which graphite is mixed with zinc. In addition, the zinc-graphite composite may further include carbon black as a polymer material and a conductive material as a binder.

In addition, the zinc-graphite composite may be mixed with the carbon precursor and carbonized on the carbon precursor to apply carbon to the surface. In addition, a negative electrode active material used in the technical field of the present invention may be mixed and used, which is also included in the present invention.

The mixing weight ratio of the carbon material such as zinc and graphite is not limited, but is good in the range of 9: 1 to 1: 9, and particularly preferably having a mixing weight ratio of 1: 1. The mixed weight ratio of 1: 1 also includes a mixed weight ratio within a range that can be seen as an error range and an equivalent range.

The carbon precursor is not limited as long as it is a material capable of providing carbon so that carbon can be applied to the composite by carbonization, and is particularly preferably a high molecular material. Vinyl-based resins such as polyvinylidene fluoride (PVDF) and polyvinyl chloride (PVC), and conductive polymers such as polyaniline (PAn), polyacetylene, polypyrrole, polythiophene, and the like are selected The conductive polymer may be a conductive polymer doped with hydrochloric acid or the like. Carbon precursors are particularly preferred polyvinylchloride (PVC). The mixing weight ratio of zinc and carbon precursor mixed with zinc and graphite is not limited, but is preferably in the range of 2: 8 to 5: 5.

Hereinafter will be described a method of manufacturing a negative electrode active material according to the present invention. Description of the following manufacturing method also includes a description of the negative electrode active material. In the method of manufacturing the negative electrode active material according to the present invention, it is preferable to prepare a zinc-graphite composite by mixing zinc and graphite. In the composition of the negative electrode according to the present invention, there is provided a configuration in which the above-described zinc-graphite composite, a polymer material as a binder and a carbon material as a conductive material are added.

In order to achieve the above another technical problem, the present invention provides a lithium secondary battery including the zinc-graphite composite according to the present invention as an electrode material. The present invention also provides a lithium secondary battery including the metal zinc anode active material as a negative electrode material and a lithium electrode using a positive electrode material made of a metal oxide.

The negative electrode active material according to the present invention is not limited as long as it is a battery using alloying / dealloying or injection / desorption of lithium ions, and may be applied as a negative electrode active material.

Lithium secondary batteries employing a negative electrode having a zinc-graphite composite as an active material according to the present invention have an increase in the discharge cost on a weight basis and a discharge capacity density on a volume basis due to the high density of zinc. It is possible to configure a high capacity lithium secondary battery, and employing a metallic active material is excellent in electronic conductivity and exhibits high output characteristics.

Physical and electrochemical properties of the zinc-graphite composite electrode according to the embodiment of the present invention manufactured by the above process were measured, and the measurement results will be described in more detail with reference to the following examples.

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

&Lt; Example 1 >

In the present invention, in order to prepare a zinc-graphite composite anode active material, zinc and graphite powder were mixed at a weight ratio of 1: 1 to prepare a thin mixture for 1 hour or more with a thinky mixer (Kurabo AR-250).

In order to manufacture a negative electrode for a lithium secondary battery using the prepared zinc-graphite composite, 10 wt% of polyvinylidene fluoride (PVDF) as an electrode binder was used and 90 wt% of the zinc-graphite composite as an electrode active material was used. N-methyl-2-pyrrolidone (NMP) was used as the dispersion solvent for dispersion. Dispersion was performed using a syncki mixer. The prepared slurry was applied to a thin copper film, dried and pressed to prepare an electrode. The density of the prepared electrode was 2.5g / ml level.

1 is a scanning electron micrograph of the surface shape of zinc and graphite as a raw material for producing a zinc-graphite composite.

Figure 2 is a diagram showing the XRD tendency of zinc and graphite as a raw material for producing a zinc-graphite composite.

3 is a particle size distribution diagram of the zinc material used. Referring to Figure 3, the average particle size distribution of the zinc powder used in the present invention is 80㎛ level. Zinc material having an average particle size of 80 μm is used as an example for the present invention, and performance may be improved through optimization of the particle size.

4 is a scanning electron micrograph of the surface shape of the zinc-graphite composite anode as a negative electrode active material for a lithium secondary battery.

5 is a graph showing XRD tendency of a zinc-graphite composite anode as a negative electrode active material for a lithium secondary battery.

In order to investigate the characteristics of the battery by applying the prepared zinc-graphite composite anode to a lithium secondary battery, a 2025 disc-shaped battery was constructed using the prepared electrode, a lithium metal foil, a separator, and an electrolyte. The electrode composite had a weight of 14 mg, and the electrolyte contained EC / EMC = 1/1 (v / v) +2 wt% VC (EC: ethylene carbonate, EMC: ethyl methyl carbonate, and VC: vinylene carbonate) containing 1.0 M LiPF ₆ . ) Was used. The batteries manufactured as described above were subjected to capacity tests and cycle tests at a constant current density at room temperature. Charge and discharge potential control was performed at 0.01V and 1.5V, respectively. The current density of charge and discharge was 37.2 mA / g, which is 0.1 C, based on the theoretical capacity of 372 mAh / g, which is the theoretical specific capacity of graphite.

Figure 6 is a diagram showing a constant current charge and discharge test results of the zinc-graphite composite anode lithium battery at room temperature. The charge and discharge characteristics were not good at room temperature.

<Example 2>

7 and 8 show voltage and cycle results of charging and discharging a battery manufactured as in Example 1 under the same conditions as in Example 1 at 60 ° C.

Figure 7 shows the results of the constant current charge and discharge test of the zinc-graphite composite anode lithium battery at a temperature of 60 ℃. The primary charge specific capacity of the zinc-graphite composite anode lithium battery was about 399 mAh / g, and the discharge specific capacity was about 268 mAh / g.

Figure 8 shows the life characteristics at a temperature of 60 ℃ of the zinc-graphite composite anode lithium battery. As the cycle progressed, the capacity gradually decreased.

The characteristics of the lithium secondary battery using zinc of the present invention are not optimized, and in theory, it shows a specific capacity of 412 mAh / g and a capacity density of 2940 mAh / ml, which shows a specific capacity of 372 mAh / g and 818 mAh / of the existing graphite electrode. It can be used as a negative electrode material for lithium secondary batteries with high energy storage characteristics exceeding the capacity density of ml.

<Example 3>

The battery manufactured as in Example 1 was charged and discharged under the same conditions as in Example 1, and the first charge and discharge was performed at 60 ° C., and after the second, charge and discharge were performed at room temperature. 9 and 10 show the voltage change and the capacity change according to the cycle with respect to the time of charge and discharge.

Figure 9 shows the result of the first charge-discharge test of the zinc-graphite composite anode lithium battery at a temperature of 60, and then from the second charge-discharge discharge at room temperature constant current charge-discharge test.

The primary charge specific amount at 60 ° C. was 391 mAh / g, and the discharge specific amount was 258 mAh / g. The charge and discharge after the second at room temperature showed a low specific capacity.

Figure 10 shows the life characteristics at room temperature from the secondary charge and discharge after the first charge and discharge of the zinc-graphite composite anode lithium battery at a temperature of 60 ℃. The cycle temperature characteristics after the first charge and discharge at 60 ° C. were not good.

1 is a SEM photograph of the raw material of the present invention,

2 is an XRD diffraction analysis of the raw material of the present invention,

3 is a distribution chart relating to particle size analysis of raw materials of the present invention;

Figure 4 is a SEM photograph of the zinc-graphite composite electrode according to an embodiment of the present invention,

5 is a XRD diffraction analysis of the zinc-graphite composite electrode according to an embodiment of the present invention,

6 is a constant current charge and discharge test results at room temperature of the zinc-graphite composite anode lithium battery according to an embodiment of the present invention,

7 is a result of the constant current charge and discharge test at 60 ℃ of the zinc-graphite composite anode lithium battery according to an embodiment of the present invention,

8 is a life characteristics test results at 60 ℃ of the zinc-graphite composite anode lithium battery according to an embodiment of the present invention,

9 is a result of a constant current charge and discharge test at room temperature from the second charge and discharge after the first charge and discharge at 60 ° C. of the zinc-graphite composite anode lithium battery according to one embodiment of the present invention.

10 is a result of life characteristics test at room temperature from the second charge and discharge after the first charge and discharge at 60 ° C. of the zinc-graphite composite anode lithium battery according to one embodiment of the present invention.

Claims (8)

In the negative electrode active material of the components of the lithium secondary battery, It comprises a zinc material, the zinc material is a metal-based zinc anode active material characterized in that the carbon precursor is mixed with the carbon precursor and carbonized on the surface of the zinc material. The metal-based zinc anode active material according to claim 1, wherein the zinc material is a material containing pure zinc or a mixture and an alloy in which hetero elements are combined with zinc. 3. The metal-based zinc anode active material according to claim 2, wherein the zinc material is a zinc-graphite composite in which graphite is mixed with zinc. The metal-based zinc anode active material of claim 3, wherein the zinc-graphite composite further comprises a binder and a conductive material. The method of claim 1, wherein the carbon precursor, The carbon precursor is a material capable of providing carbon so that carbon can be applied to the zinc material by carbonization. The carbon precursor may be a vinyl resin such as polyvinylidene fluoride (PVDF) or polyvinyl chloride (PVC), polyaniline (PAn), A metal-based zinc anode active material using a conductive polymer or a doped conductive polymer of polyacetylene, polypyrrole and polythiophene. The metal-based zinc anode active material according to claim 1, wherein the weight ratio of the zinc material and the carbon precursor is in the range of 2: 8 to 5: 5. A lithium secondary battery using the metal-based zinc negative electrode active material according to any one of claims 1 to 6 as a negative electrode material. 8. The lithium secondary battery according to claim 7, wherein the metal-based zinc anode active material is made of a negative electrode material, and the lithium electrode is made of a positive electrode material made of a metal oxide.

Images