Composition for an electrode active material, an electrode containing the same, and a secondary battery

Abstract

The present invention relates to an electrode active material composition containing an electrode active material, a binder, and a conductive material, wherein the binder contains polyhydroxyalkanoate (PHA), and an electrode and a secondary battery containing the same. By containing polyhydroxyalkanoate (PHA) as a binder, the electrode active material composition can further improve the adhesion between the active materials and between the active material and the electrode current collector, is excellent in oxidation resistance, electrochemically stable, and even when a small amount of binder is used, high life characteristics, high capacity, and high output of the secondary battery can be achieved. Therefore, it can be used not only in battery cells used as power sources for small devices, but also usefully in unit cells of medium and large-sized battery modules containing a large number of cells.

Description

Detailed Description of the Invention

[0001] [Technical Field] The present invention relates to an electrode active material composition, an electrode containing the same, and a secondary battery.

[0002] [Background Art] As technology development and demand for various means of transportation such as electric vehicles, electric motorcycles, electric kick scooters, electric scooters, electric wheelchairs, and electric bicycles, as well as mobile devices, increase, the demand for secondary batteries as energy sources has been rapidly increasing. Among such secondary batteries, lithium secondary batteries have been commercialized and widely used because they exhibit high energy density, operating potential, long cycle life, and low self-discharge rate.

[0003] The electrodes of lithium secondary batteries are produced by mixing an electrode active material, a binder, and a conductive material to prepare an active material composition, applying the composition to the surface of an electrode current collector, and drying it to form a composite layer.

[0004] In the above electrode, the binder is used to ensure the adhesion strength or bonding strength between the active materials or between the active material and the electrode current collector. However, an excessive amount of binder is required to improve the adhesion strength between the electrode current collector and the active material.

[0005] However, an excessive amount of binder may cause problems such as reducing the capacity and conductivity of the electrode. On the other hand, a small amount of binder reduces the adhesion strength, and insufficient adhesion strength may cause electrode peeling during processes such as electrode drying and pressing, increasing the electrode defect rate. Also, electrodes with low adhesion strength may peel off due to external shock. Such electrode peeling may increase the contact resistance between the electrode material and the current collector, causing a decrease in the electrode output performance.

[0006] On the one hand, currently commercially available binders include polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC), etc. However, it is necessary to develop a binder that can replace the above binders, is easily available, environmentally friendly, and can achieve an effect equivalent to or better than that of the secondary battery in terms of life characteristics, output characteristics, and capacity characteristics.

[0007] [Prior Art Documents] [Patent Documents] [Patent Document 1] Korean Registered Patent No. 10-2071585

[0008] [Summary of the Invention] [Problems to be Solved by the Invention] The object of the present invention is to provide an electrode active material composition that contains polyhydroxyalkanoate (PHA) as a binder, is environmentally friendly, provides excellent adhesion strength between the active materials and between the active material and the electrode current collector, improves oxidation resistance and electrochemical stability, and can simultaneously achieve high capacity and high output as well as the life characteristics of the secondary battery even when using a small amount of binder, and has a flame-retardant property in which combustion does not spread and no harmful substances are generated during the incineration of polyhydroxyalkanoate (PHA).

[0009] Another object of the present invention is to provide an electrode and a secondary battery including the electrode active material composition having the above characteristics.

[0010] [Means for Solving the Problems] According to one embodiment of the present invention, there is provided an electrode active material composition including an electrode active material, a binder, and a conductive material, wherein the binder contains polyhydroxyalkanoate (PHA).

[0011] According to another embodiment, the polyhydroxyalkanoate (PHA) may have a glass transition temperature (Tg) of -45°C to 80°C and a melt index (MI) measured at a temperature of 165°C and a load of 5.0 kg in accordance with ASTM D1238 of 0.1 g / 10 min to 500 g / 10 min.

[0012] According to another embodiment, the polyhydroxyalkanoate (PHA) may include one or more monomers selected from the group consisting of 4-hydroxybutyrate (4-HB), 3-hydroxybutyrate (3-HB), 3-hydroxypropionate (3-HP), 3-hydroxyvalerate (3-HV), 3-hydroxyhexanoate (3-HH), 4-hydroxyvalerate (4-HV), 5-hydroxyvalerate (5-HV), and 6-hydroxyhexanoate (6-HH).

[0013] According to another embodiment, the polyhydroxyalkanoate (PHA) may include a PHA homopolymer composed of 4-hydroxybutyrate (4-HB) monomers.

[0014] According to another embodiment, the polyhydroxyalkanoate (PHA) includes a PHA copolymer containing 4-hydroxybutyrate (4-HB) monomers, and the 4-hydroxybutyrate (4-HB) monomers may be contained in an amount of 1 mol% to 99 mol% based on the total moles of the monomers contained in the PHA copolymer.

[0015] According to another embodiment, the binder may be contained in an amount of 0.1 wt% to 20 wt% based on the total weight of the electrode active material composition.

[0016] According to another embodiment, the weight ratio of the electrode active material, the binder, and the conductive material may be (4.0 to 9.8):(0.1 to 3.0):(0.1 to 3.0).

[0017] According to another embodiment, the electrode active material may be a negative electrode active material.

[0018] According to another embodiment, the negative electrode active material contains one or more selected from the group consisting of a carbon-based negative electrode active material, a silicon-based negative electrode active material, lithium metal, and a lithium alloy, and the conductive material may contain one or more selected from the group consisting of graphite, carbon black, a conductive fiber, a conductive tube, a metal powder, a conductive whisker, and a conductive metal oxide.

[0019] According to another embodiment of the present invention, there is provided an electrode including an electrode active material, a binder, and a conductive material, wherein the binder contains polyhydroxyalkanoate (PHA).

[0020] According to another embodiment of the present invention, there is provided a secondary battery including a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolytic solution, wherein one or more of the negative electrode and the positive electrode contain a binder containing polyhydroxyalkanoate (PHA).

[0021] According to another embodiment, when the secondary battery is charged at a constant current of 0.05C until the voltage reaches 3V and discharged at a constant current of 0.05C until the voltage reaches 0.01V, the Coulomb efficiency represented by the following formula 1 is 93% or more, and the specific capacity measured after repeating the charging and discharging twice is 280 mAhg -1 or more. [Formula 1] Coulomb efficiency (%) = discharge capacity / charge capacity × 100

[0022] [Advantages of the Invention] The electrode active material composition according to an embodiment of the present invention contains polyhydroxyalkanoate (PHA) as a binder, so that the adhesion strength between the active materials and between the active material and the electrode current collector can be further improved, and it has excellent oxidation resistance and electrochemical stability. Even with a small amount of binder, high life characteristics, high capacity, and high output of the secondary battery can be achieved.

[0023] Furthermore, the secondary battery according to an embodiment of the present invention includes the electrode active material composition having the above characteristics, thereby further improving the electrochemical performance such as Coulomb efficiency and capacity characteristics. It can be used not only for battery cells used as power sources for small devices, but also usefully for unit cells of medium and large-sized battery modules including a large number of battery cells.

[0024] In particular, the present invention can replace conventional binders such as polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC). It is easily available, can achieve effects equivalent to or better than those of conventional binders with respect to the physical properties of secondary batteries, and since PHA is used, it has flame retardant properties in which combustion does not spread and no harmful substances are generated during incineration. Therefore, including polyhydroxyalkanoate (PHA) as a binder has great technical significance.

Brief Description of the Drawings

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[0026] [Mode for Carrying Out the Invention] Hereinafter, the invention will be described in detail through embodiments. The embodiments are not limited to the content disclosed below, and can be modified into various forms as long as the gist of the invention is not changed.

[0027] In this specification, when a certain part "includes" a certain component, this means that, unless otherwise stated to the contrary, it can further include other components rather than excluding other components.

[0028] When it is described in this specification that one component is formed "above" or "below" another component, this includes that one component is formed directly "above" or "below" another component, or indirectly via another component.

[0029] In this specification, terms such as first and second are used to describe various components, and the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. It should be understood that all numerical values indicating physical property values, dimensions, etc. of the components described in this specification are modified by the term "about" in all cases unless otherwise stated.

[0030] [Electrode Active Material Composition] The electrode active material composition according to an embodiment of the present invention includes an electrode active material, a binder, and a conductive material, and the binder includes polyhydroxyalkanoate (PHA).

[0031] Generally, in a secondary battery, a binder is a substance that physically stabilizes the electrodes of the secondary battery. It not only serves as a kind of adhesive to fix the electrode active material and the conductive material to the current collector, but also plays a role in preventing the bond between the electrode active material and the conductive material from loosening when the charge and discharge of the secondary battery are repeated. Therefore, the adhesive properties, solubility in solvents, structural stability, oxidation resistance, etc. of the binder may have an important impact on the performance of the secondary battery.

[0032] In the present invention, by including polyhydroxyalkanoate (PHA) as a binder, the adhesive strength between the active materials and between the active material and the electrode current collector can be further improved. It has excellent oxidation resistance and electrochemical stability, and even with a small amount of binder, high life characteristics, high capacity, and high output of the secondary battery can be achieved. There is a great advantage in that when polyhydroxyalkanoate (PHA) is incinerated, combustion does not spread and no harmful substances are generated, having flame-retardant properties.

[0033] Hereinafter, each component of the electrode active material composition of the present invention will be described in detail.

[0034] (Binder) The electrode active material composition according to an embodiment of the present invention includes a binder, which is a polymer additive capable of physically stabilizing the electrodes, and the binder may include polyhydroxyalkanoate (hereinafter referred to as PHA).

[0035] The PHA is a substance that can replace conventional binders. It is easily available and can achieve effects equivalent to or better than those of conventional binders with respect to the performance of secondary batteries, so it can be usefully utilized in secondary batteries.

[0036] Specifically, the PHA has excellent adhesion strength, is electrochemically stable, has excellent oxidation resistance, and is extremely suitable as a binder for secondary batteries. Also, when the binder is used in a secondary battery, it can maintain structural stability even after a long period of cycling, thereby achieving high capacity and lifespan characteristics. Since the resistance is low even when the charge-discharge cycle is repeated, high-capacity cycling can be maintained for a long time, and the performance of the secondary battery can be improved.

[0037] The PHA has physical properties similar to those of synthetic polymers such as conventionally petroleum-derived polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate terephthalate (PBST), and polybutylene succinate adipate (PBSA), while showing complete biodegradability and excellent biocompatibility.

[0038] Specifically, the PHA is a thermoplastic natural polyester polymer accumulated in microbial cells, is a biodegradable material that can be composted, generates no toxic waste, and can ultimately be decomposed into carbon dioxide, water, and organic waste. In particular, since the PHA resin can be biodegraded in soil and the ocean, it has environmentally friendly characteristics.

[0039] The PHA may be a PHA homopolymer composed of one monomer or a PHA copolymer containing two or more different monomers. Alternatively, the PHA may contain the PHA homopolymer and the PHA copolymer.

[0040] When the PHA is a copolymer, for example, it may be a copolymerized PHA containing two or more different repeating units in which different monomers are irregularly distributed in the polymer chain.

[0041] Examples of monomers that may be included in the PHA include 2-hydroxybutyrate, lactic acid, glycolic acid, 3-hydroxybutyrate (hereinafter referred to as 3-HB), 3-hydroxypropionate (hereinafter referred to as 3-HP), 3-hydroxyvalerate (hereinafter referred to as 3-HV), 3-hydroxyhexanoate (hereinafter referred to as 3-HH), 3-hydroxyheptanoate (hereinafter referred to as 3-HHep), 3-hydroxyoctanoate (hereinafter referred to as 3-HO), 3-hydroxynonanoate (hereinafter referred to as 3-HN), 3-hydroxydecanoate (hereinafter referred to as 3-HD), 3-hydroxydodecanoate (hereinafter referred to as 3-HDd), 4-hydroxybutyrate (hereinafter referred to as 4-HB), 4-hydroxyvalerate (hereinafter referred to as 4-HV), 5-hydroxyvalerate (hereinafter referred to as 5-HV), and 6-hydroxyhexanoate (hereinafter referred to as 6-HH). The PHA can include one or more monomers selected therefrom.

[0042] Specifically, the polyhydroxyalkanoate (PHA) can include one or more monomers selected from the group consisting of 4-hydroxybutyrate (4-HB), 3-hydroxybutyrate (3-HB), 3-hydroxypropionate (3-HP), 3-hydroxyvalerate (3-HV), 3-hydroxyhexanoate (3-HH), 4-hydroxyvalerate (4-HV), 5-hydroxyvalerate (5-HV), and 6-hydroxyhexanoate (6-HH).

[0043] More specifically, the PHA can include a PHA homopolymer composed of monomers selected from the group consisting of 4-HB, 3-HB, 3-HP, 3-HV, 3-HH, 4-HV, 5-HV, and 6-HH, or a PHA copolymer containing one or more monomers selected from the group consisting of 4-HB, 3-HB, 3-HP, 3-HV, 3-HH, 4-HV, 5-HV, and 6-HH.

[0044] Specifically, the PHA may be a PHA homopolymer composed of monomers selected from the group consisting of 4-HB and 3-HB, or a PHA copolymer containing one or more monomers selected from the group consisting of 4-HB and 3-HB.

[0045] More specifically, the PHA can contain 4-HB monomers.

[0046] The PHA can include a PHA homopolymer composed of 4-HB monomers.

[0047] Furthermore, the PHA may be a PHA copolymer containing 4-HB monomers.

[0048] For example, the PHA may be a PHA copolymer that contains 4-HB monomers and further contains one monomer different from the 4-HB monomers, or further contains two, three, four, five, six, or more monomers different from each other.

[0049] According to one embodiment of the present invention, the PHA can contain 4-HB monomers; and one or more monomers selected from the group consisting of 3-HB, 3-HP, 3-HV, 3-HH, 4-HV, 5-HV, and 6-HH. More specifically, the PHA can include a PHA copolymer containing 3-HB monomers and 4-HB monomers.

[0050] For example, the PHA may be poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (hereinafter referred to as 3HB-co-4HB).

[0051] Furthermore, the PHA can contain isomers. For example, the PHA can contain structural isomers, enantiomers, or geometric isomers. Specifically, the PHA can contain structural isomers.

[0052] According to an embodiment of the present invention, it can be preferably used as a binder for a secondary battery, and in order to achieve the performance of the electrode and the secondary battery targeted by the present invention, in particular, a PHA containing the 4-HB monomer can be used. In this case, it may be important to adjust the content ratio of the 4-HB monomer.

[0053] For example, the polyhydroxyalkanoate (PHA) includes a PHA copolymer containing a 4-hydroxybutyrate (4-HB) monomer, and the 4-hydroxybutyrate (4-HB) monomer may be contained in an amount of 1 mol% to 99 mol% based on the total moles of the monomers contained in the PHA copolymer.

[0054] Specifically, the PHA can include a PHA copolymer containing the 3-HB monomer and the 4-HB monomer, and the PHA copolymer can contain the 4-hydroxybutyrate (4-HB) monomer in an amount of 1 mol% to 99 mol% based on the total moles of the 3-hydroxybutyrate (3-HB) monomer and the 4-hydroxybutyrate (4-HB) monomer. For example, the PHA copolymer can contain the 4-hydroxybutyrate (4-HB) monomer in an amount of 1 mol% or more, 2 mol% or more, 3 mol% or more, 5 mol% or more, or 10 mol% or more, and 99 mol% or less, 95 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, or 60 mol% or less based on the total moles of the 3-hydroxybutyrate (3-HB) monomer and the 4-hydroxybutyrate (4-HB) monomer. Specifically, the PHA copolymer contains the 4-hydroxybutyrate (4-HB) monomer in an amount of 1 mol% to 99 mol%, 1 mol% to 95 mol%, 1 mol% to 90 mol%, 1 mol% to 89 mol%, 1 mol% to 85 mol%, 1 mol% to 80 mol%, 1 mol% to 79 mol%, 1 mol% to 75 mol%, 1 mol% to 70 mol%, 1 mol% to 65 mol%, 1 mol% to 60 mol%, 1 mol% to 55 mol%, 1 mol% to 50 mol%, 2 mol% to 55 mol%, 3 mol% to 55 mol%, 3 mol% to 50 mol%, 5 mol% to 55 mol%, 5 mol% to 50 mol%, 10 mol% to 55 mol%, 10 mol% to 50 mol%, 15 mol% to 60 mol%, 15 mol% to 55 mol%, 15 mol% to 50 mol%, 20 mol% to 60 mol%, 20 mol% to 55 mol%, 20 mol% to 50 mol%, 25 mol% to 60 mol%, 25 mol% to 55 mol%, 25 mol% to 50 mol%, 25 mol% to 45 mol%, 25 mol% to 40 mol%, 30 mol% to 60 mol%, 30 mol% to 55 mol%, 30 mol% to 50 mol%, 30 mol% to 45 mol%, 30 mol% to 40 mol%, 35 mol% to 60 mol%, 35 mol% to 55 mol%, 35 mol% to 50 mol%, 40 mol% to 60 mol%, 40 mol% to 55 mol%, or 45 mol% to 55 mol% based on the total moles of the 3-hydroxybutyrate (3-HB) monomer and the 4-hydroxybutyrate (4-HB) monomer.

[0055] As another embodiment, the PHA copolymer may contain 4-HB monomer in an amount of 1 mol% to 99 mol% based on the total moles of monomers contained in the PHA copolymer. For example, the content of the PHA monomer may be 1 mol% or more, 2 mol% or more, 3 mol% or more, 5 mol% or more, or 10 mol% or more, and 99 mol% or less, 95 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, or 60 mol% or less based on the total moles of monomers contained in the PHA copolymer. For example, the content of the PHA monomer may be 1 mol% to 99 mol%, 1 mol% to 95 mol%, 1 mol% to 90 mol%, 1 mol% to 89 mol%, 1 mol% to 85 mol%, 1 mol% to 80 mol%, 1 mol% to 79 mol%, 1 mol% to 75 mol%, 1 mol% to 70 mol%, 1 mol% to 65 mol%, 1 mol% to 60 mol%, 0.1 to 55 mol%, 0.5 to 60 mol%, 0.5 to 55 mol%, 1 mol% to 60 mol%, 1 mol% to 55 mol%, 1 mol% to 50 mol%, 2 mol% to 55 mol%, 3 mol% to 55 mol%, 3 mol% to 50 mol%, 5 mol% to 55 mol%, 5 mol% to 50 mol%, 10 mol% to 55 mol%, 10 mol% to 50 mol%, 15 mol% to 60 mol%, 15 mol% to 55 mol%, 15 mol% to 50 mol%, 20 mol% to 60 mol%, 20 mol% to 55 mol%, 20 mol% to 50 mol%, 25 mol% to 60 mol%, 25 mol% to 55 mol%, 25 mol% to 50 mol%, 25 mol% to 45 mol%, 25 mol% to 40 mol%, 30 mol% to 60 mol%, 30 mol% to 55 mol%, 30 mol% to 50 mol%, 30 mol% to 45 mol%, 30 mol% to 40 mol%, 35 mol% to 60 mol%, 35 mol% to 55 mol%, 35 mol% to 50 mol%, 40 mol% to 60 mol%, 40 mol% to 55 mol%, or 45 mol% to 55 mol%.

[0056] In addition, the PHA contains at least one or more of the 4-HB monomers, and the crystallinity of the PHA can be adjusted by controlling the content of the 4-HB monomers. That is, the PHA can be a PHA copolymer with adjusted crystallinity.

[0057] The PHA with adjusted crystallinity may be one in which crystallinity and amorphousness are adjusted by increasing the irregularity in the molecular structure. Specifically, it may be one in which the type of monomer, the ratio of monomers, or the type and / or content of isomers are adjusted.

[0058] On the other hand, the PHA may have a glass transition temperature (Tg) of, for example, -45°C to 80°C, -35°C to 80°C, -30°C to 80°C, -25°C to 75°C, -20°C to 70°C, -35°C to 5°C, -25°C to 5°C, -35°C to 0°C, -25°C to 0°C, -30°C to -10°C, -35°C to -15°C, -35°C to -20°C, -30°C to -20°C, -20°C to 0°C, -15°C to 0°C, or -15°C to -5°C.

[0059] The PHA may have a crystallization temperature (Tc) of, for example, not measurable in some cases, or for example, 60°C to 120°C, 70°C to 120°C, 75°C to 120°C, 75°C to 115°C, 75°C to 110°C, or 90°C to 110°C in some cases.

[0060] The PHA may have a melting temperature (Tm) of, for example, not measurable in some cases, or for example, 100°C to 170°C, for example, 110°C to 150°C, or for example, 120°C to 140°C in some cases.

[0061] The PHA may have a weight-average molecular weight (Mw) of, for example, 10,000 g / mol to 1,200,000 g / mol. For example, the weight-average molecular weight of the PHA may be 50,000 g / mol to 1,200,000 g / mol, 100,000 g / mol to 1,200,000 g / mol, 50,000 g / mol to 1,000,000 g / mol, 100,000 g / mol to 1,000,000 g / mol, 200,000 g / mol to 1,200,000 g / mol, 250,000 g / mol to 1,150,000 g / mol, 300,000 g / mol to 1,100,000 g / mol, 350,000 g / mol to 1,000,000 g / mol, 350,000 g / mol to 950,000 g / mol, 100,000 g / mol to 900,000 g / mol, 200,000 g / mol to 800,000 g / mol, 200,000 g / mol to 700,000 g / mol, 250,000 g / mol to 650,000 g / mol, 200,000 g / mol to 400,000 g / mol, 300,000 g / mol to 800,000 g / mol, 300,000 g / mol to 600,000 g / mol, 500,000 g / mol to 1,200,000 g / mol, 500,000 g / mol to 1,000,000 g / mol, 550,000 g / mol to 1,050,000 g / mol, 550,000 g / mol to 900,000 g / mol, or 600,000 g / mol to 900,000 g / mol.

[0062] The PHA may have a melt index (MI) measured at a temperature of 165 °C and a load of 5.0 kg in accordance with ASTM D1238 of 0.1 g / 10 min or more, 0.5 g / 10 min or more, 1 g / 10 min or more, or 2 g / 10 min or more, and may also be 500 g / 10 min or less, 450 g / 10 min or less, 400 g / 10 min or less, 350 g / 10 min or less, 300 g / 10 min or less, 200 g / 10 min or less, 100 g / 10 min or less, 80 g / 10 min or less, 50 g / 10 min or less, 30 g / 10 min or less, 20 g / 10 min or less, 10 g / 10 min or less, or 5 g / 10 min or less. Specifically, it may be 0.1 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 400 g / 10 min, 1 g / 10 min to 500 g / 10 min, 10 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 300 g / 10 min, 300 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 100 g / 10 min, 100 g / 10 min to 200 g / 10 min, 200 g / 10 min to 300 g / 10 min, 300 g / 10 min to 400 g / 10 min, 400 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 80 g / 10 min, 0.1 g / 10 min to 50 g / 10 min, 0.1 g / 10 min to 30 g / 10 min, 0.1 g / 10 min to 20 g / 10 min, 0.1 g / 10 min to 10 g / 10 min, 1 g / 10 min to 30 g / 10 min, 1 g / 10 min to 20 g / 10 min, 1 g / 10 min to 10 g / 10 min, 0.1 g / 10 min to 2 g / 10 min, 2 g / 10 min to 5 g / 10 min, 5 g / 10 min to 8 g / 10 min, 8 g / 10 min to 12 g / 10 min, 12 g / 10 min to 16 g / 10 min, 16 g / 10 min to 20 g / 10 min, or 20 g / 10 min to 30 g / 10 min.

[0063] For example, the polyhydroxyalkanoate (PHA) may have a glass transition temperature (Tg) of -45 °C to 80 °C and a melt index (MI) measured at a temperature of 165 °C and a load of 5.0 kg in accordance with ASTM D1238 of 0.1 g / 10 min to 500 g / 10 min.

[0064] On the one hand, the PHA may include a combination of two or more PHAs with different crystallinities. That is, the PHA may be adjusted by mixing two or more PHAs with different crystallinities so as to have the content of 4-HB monomer within the specific range.

[0065] Specifically, the PHA may include a first PHA resin, a second PHA resin, or a mixed resin of the first PHA resin and the second PHA resin.

[0066] The first PHA resin and the second PHA resin may have different contents of 4-HB monomer, glass transition temperatures (Tg), crystallization temperatures (Tc), and melting temperatures (Tm).

[0067] Specifically, the first PHA resin may contain the 4-HB monomer in an amount of, for example, 15 mol% to 60 mol%, 15 mol% to 55 mol%, 20 mol% to 55 mol%, 25 mol% to 55 mol%, 30 mol% to 55 mol%, 35 mol% to 55 mol%, 20 mol% to 50 mol%, 25 mol% to 50 mol%, 30 mol% to 50 mol%, 35 mol% to 50 mol%, or 20 mol% to 40 mol% based on the total moles of monomers contained in the first PHA resin.

[0068] The first PHA resin may have a glass transition temperature (Tg) of, for example, -45°C to -10°C, -35°C to -10°C, -35°C to -15°C, -35°C to -20°C, or -30°C to -20°C.

[0069] The first PHA resin may have a crystallization temperature (Tc) that, for example, may not be measurable or may be, for example, 60°C to 120°C, 60°C to 110°C, 70°C to 120°C, or 75°C to 115°C.

[0070] The first PHA resin may have a melting temperature (Tm) that, for example, may not be measurable or may be, for example, 100°C to 170°C, 100°C to 160°C, 110°C to 160°C, or 120°C to 150°C.

[0071] The first PHA resin may have a weight average molecular weight (Mw) of, for example, 10,000 g / mol to 1,200,000 g / mol, 10,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 1,000,000 g / mol, 50,000 g / mol to 1,200,000 g / mol, 200,000 g / mol to 1,200,000 g / mol, 300,000 g / mol to 1,000,000 g / mol, 100,000 g / mol to 900,000 g / mol, 500,000 g / mol to 900,000 g / mol, 200,000 g / mol to 800,000 g / mol, or 200,000 g / mol to 400,000 g / mol.

[0072] The first PHA resin may have a melt index (MI) measured at a temperature of 165°C and a load of 5.0 kg in accordance with ASTM D1238 of 0.1 g / 10 min or more, 0.5 g / 10 min or more, 1 g / 10 min or more, or 2 g / 10 min or more, and may also be 500 g / 10 min or less, 450 g / 10 min or less, 400 g / 10 min or less, 350 g / 10 min or less, 300 g / 10 min or less, 200 g / 10 min or less, 100 g / 10 min or less, 80 g / 10 min or less, 50 g / 10 min or less, 30 g / 10 min or less, 20 g / 10 min or less, 10 g / 10 min or less, or 5 g / 10 min or less. Specifically, it may be 0.1 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 400 g / 10 min, 1 g / 10 min to 500 g / 10 min, 10 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 300 g / 10 min, 300 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 100 g / 10 min, 100 g / 10 min to 200 g / 10 min, 200 g / 10 min to 300 g / 10 min, 300 g / 10 min to 400 g / 10 min, 400 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 80 g / 10 min, 0.1 g / 10 min to 50 g / 10 min, 0.1 g / 10 min to 30 g / 10 min, 0.1 g / 10 min to 20 g / 10 min, 0.1 g / 10 min to 10 g / 10 min, 1 g / 10 min to 30 g / 10 min, 1 g / 10 min to 20 g / 10 min, 1 g / 10 min to 10 g / 10 min, 0.1 g / 10 min to 2 g / 10 min, 2 g / 10 min to 5 g / 10 min, 5 g / 10 min to 8 g / 10 min, 8 g / 10 min to 12 g / 10 min, 12 g / 10 min to 16 g / 10 min, 16 g / 10 min to 20 g / 10 min, or 20 g / 10 min to 30 g / 10 min.

[0073] On the one hand, the second PHA resin may contain the 4-HB monomer in an amount of 0.1 mol% to 30 mol% based on the total moles of the monomers contained in the second PHA resin. For example, the second PHA may contain the 4-HB monomer in an amount of 0.1 mol% to 30 mol%, 0.5 mol% to 30 mol%, 1 mol% to 30 mol%, 3 mol% to 30 mol%, 1 mol% to 28 mol%, 1 mol% to 25 mol%, 1 mol% to 24 mol%, 1 mol% to 20 mol%, 1 mol% to 15 mol%, 2 mol% to 25 mol%, 3 mol% to 25 mol%, 3 mol% to 24 mol%, 5 mol% to 24 mol%, 5 mol% to 20 mol%, more than 5 mol% to less than 20 mol%, 7 mol% to 20 mol%, 10 mol% to 20 mol%, 15 mol% to 25 mol%, or 15 mol% to 24 mol% based on the total moles of the monomers contained in the second PHA resin.

[0074] The first PHA resin and the second PHA resin may have different contents of the 4-HB monomer.

[0075] The second PHA resin may have a glass transition temperature (Tg) of, for example, -30°C to 80°C, for example, -30°C to 10°C, for example, -25°C to 5°C, for example, -25°C to 0°C, for example, -20°C to 0°C, or for example, -15°C to 0°C.

[0076] The glass transition temperature (Tg) of the first PHA resin and the glass transition temperature (Tg) of the second PHA resin may be different from each other.

[0077] The second PHA resin may have a crystallization temperature (Tc) of, for example, 70°C to 120°C, for example, 75°C to 115°C, or 80°C to 110°C, or may not be measured, for example.

[0078] The second PHA resin may have a melting temperature (Tm) of, for example, 100°C to 170°C, for example, 105°C to 165°C, for example, 110°C to 160°C, for example, 100°C to 150°C, for example, 115°C to 155°C, for example, 120°C to 160°C, or for example, 120°C to 150°C.

[0079] The second PHA resin may have a weight average molecular weight (Mw) of 10,000 g / mol to 1,200,000 g / mol, 50,000 g / mol to 1,100,000 g / mol, 100,000 g / mol to 1,000,000 g / mol, 300,000 g / mol to 1,000,000 g / mol, 100,000 g / mol to 900,000 g / mol, 200,000 g / mol to 800,000 g / mol, 200,000 g / mol to 600,000 g / mol, 200,000 g / mol to 400,000 g / mol, or 400,000 g / mol to 700,000 g / mol.

[0080] Specifically, the first PHA resin has a glass transition temperature (Tg) of -35°C to -15°C, and the second PHA resin satisfies at least one property selected from a glass transition temperature (Tg) of -15°C to 0°C, a crystallization temperature (Tc) of 80°C to 110°C, and a melting temperature (Tm) of 120°C to 160°C. The glass transition temperature (Tg) of the first PHA resin and the glass transition temperature (Tg) of the second PHA resin may be different from each other. Also, the crystallization temperature (Tc) and the melting temperature (Tm) of the first PHA resin may not be measured.

[0081] The melt index (MI) of the second PHA resin, measured at a temperature of 165°C and a load of 5.0 kg in accordance with ASTM D1238, may be 0.1 g / 10 min or more, 0.5 g / 10 min or more, 1 g / 10 min or more, or 2 g / 10 min or more, and may also be 500 g / 10 min or less, 450 g / 10 min or less, 400 g / 10 min or less, 350 g / 10 min or less, 300 g / 10 min or less, 200 g / 10 min or less, 100 g / 10 min or less, 80 g / 10 min or less, 50 g / 10 min or less, 30 g / 10 min or less, 20 g / 10 min or less, 10 g / 10 min or less, or 5 g / 10 min or less. Specifically, it may be 0.1 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 400 g / 10 min, 1 g / 10 min to 500 g / 10 min, 10 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 300 g / 10 min, 300 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 100 g / 10 min, 100 g / 10 min to 200 g / 10 min, 200 g / 10 min to 300 g / 10 min, 300 g / 10 min to 400 g / 10 min, 400 g / 10 min to 500 g / 10 min, 0.1 g / 10 min to 80 g / 10 min, 0.1 g / 10 min to 50 g / 10 min, 0.1 g / 10 min to 30 g / 10 min, 0.1 g / 10 min to 20 g / 10 min, 0.1 g / 10 min to 10 g / 10 min, 1 g / 10 min to 30 g / 10 min, 1 g / 10 min to 20 g / 10 min, 1 g / 10 min to 10 g / 10 min, 0.1 g / 10 min to 2 g / 10 min, 2 g / 10 min to 5 g / 10 min, 5 g / 10 min to 8 g / 10 min, 8 g / 10 min to 12 g / 10 min, 12 g / 10 min to 16 g / 10 min, 16 g / 10 min to 20 g / 10 min, or 20 g / 10 min to 30 g / 10 min.

[0082] The melt index (MI) of the first PHA resin and the melt index (MI) of the second PHA resin may be different from each other.

[0083] When the first PHA resin and the second PHA resin each satisfy at least one of the content of 4-HB monomer, glass transition temperature (Tg), crystallization temperature (Tc), melting temperature (Tm), and melt index (MI) within the above ranges, it may be more advantageous for achieving the effects targeted in the present invention.

[0084] Also, the first PHA resin and the second PHA resin may each be a PHA with adjusted crystallinity.

[0085] For example, the first PHA resin may contain an amorphous PHA resin (hereinafter referred to as an aPHA resin), and the second PHA resin may contain a semi-crystalline PHA resin (hereinafter referred to as an scPHA resin).

[0086] Specifically, the first PHA resin may be an aPHA resin or a mixed resin of an aPHA resin and an scPHA resin.

[0087] Specifically, the second PHA resin may be an scPHA resin or a mixed resin of an aPHA resin and an scPHA resin.

[0088] The aPHA resin and the scPHA resin can be distinguished by the content of 4-HB monomer, glass transition temperature (Tg), crystallization temperature (Tc), melting temperature (Tm), and melt index (MI), etc.

[0089] The aPHA resin may contain 4-HB monomer in an amount of, for example, 25 mol% to 50 mol% based on the total moles of monomers contained in the PHA resin.

[0090] The glass transition temperature (Tg) of the aPHA resin may be, for example, -35°C to -20°C.

[0091] The crystallization temperature (Tc) of the aPHA resin may not be measurable.

[0092] The melting temperature (Tm) of the aPHA resin may not be measurable.

[0093] The scPHA resin may contain 4-HB monomer in an amount of, for example, 1 mol% to less than 25 mol% based on the total moles of monomers contained in the PHA resin.

[0094] The glass transition temperature (Tg) of the scPHA resin may be -20°C to 0°C.

[0095] The crystallization temperature (Tc) of the scPHA resin may be 75°C to 115°C.

[0096] The melting temperature (Tm) of the scPHA resin may be, for example, 110°C to 160°C.

[0097] According to one embodiment of the present invention, the binder may be contained in an amount of 0.1% by weight or more, 0.2% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 1% by weight or more, 2% by weight or more, 3% by weight or more, or 5% by weight or more, and 20% by weight or less, 18% by weight or less, 17% by weight or less, 16% by weight or less, 15% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, or 5% by weight or less, based on the total weight of the electrode active material composition.

[0098] Specifically, the electrode active material composition may contain the binder in an amount of 0.1% by weight to 20% by weight, 0.2% by weight to 18% by weight, 0.5% by weight to 15% by weight, 1% by weight to 15% by weight, 3% by weight to 15% by weight, 5% by weight to 15% by weight, or 5% by weight to 10% by weight, based on the total weight of the electrode active material composition.

[0099] When the content of the binder is less than the above range, the effect of using the binder may be reduced. When it exceeds the above range, the capacity of the secondary battery per unit volume may decrease due to the relative decrease in the content of the electrode active material caused by the increase in the content of the binder.

[0100] According to another embodiment of the present invention, when the PHA contains a mixed resin of a first PHA resin and a second PHA resin, the weight ratio of the first PHA resin: the second PHA resin may be, for example, 1:0.5 to 3, for example, 1:0.5 to 2.5, or for example, 1:0.5 to 2.

[0101] According to another embodiment of the present invention, the weight ratio of the electrode active material, binder, and conductive material may be (4.0 to 9.8):(0.1 to 3.0):(0.1 to 3.0), (6.0 to 9.6):(0.2 to 2.0):(0.2 to 2.0), (6.0 to 9.0):(0.5 to 2.0):(0.5 to 2.0), or (7.0 to 9.0):(0.5 to 1.5):(0.5 to 1.5).

[0102] In the electrode active material composition, when the content of the binder and the weight ratio of the electrode active material, binder, and conductive material satisfy the above range, while reducing the use of the binder, the adhesion strength and the performance of the secondary battery can be efficiently improved.

[0103] Further, the electrode active material composition may further include various commonly used binders such as poly(vinylidene fluoride - hexafluoropropylene) (PVdF - co - HFP), polyvinylidene fluoride (PVdF), polyacrylonitrile, polymethyl methacrylate, styrene - butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), and polyvinyl acetate.

[0104] When the PHA is mixed with the various commonly used binders, as long as the effects intended in the present invention are not impaired, the mixing ratio thereof is not particularly limited.

[0105] Furthermore, the binder may be included in the negative electrode active material composition applied to the negative electrode, the positive electrode active material composition applied to the positive electrode, or both of them. For example, when the binder is included in the negative electrode active material composition, the effects intended in the present invention can be efficiently achieved.

[0106] (Electrode active material) The electrode active material composition according to an embodiment of the present invention may include an electrode active material.

[0107] The electrode active material may include a negative electrode active material, a positive electrode active material, or both. Specifically, the electrode active material may be a negative electrode active material.

[0108] The negative electrode active material is not particularly limited as long as it can reversibly occlude or release lithium (Li + ).

[0109] The negative electrode active material may include one or more selected from the group consisting of, for example, a carbon-based negative electrode active material, a silicon-based negative electrode active material, lithium metal, and a lithium alloy.

[0110] The carbon-based negative electrode active material can include low-crystalline carbon, highly crystalline carbon, or a mixture thereof. The low-crystalline carbon can include soft carbon, hard carbon, or a mixture thereof. The highly crystalline carbon can include one or more high-temperature calcined carbons selected from the group consisting of natural graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesocarbon microbeads, mesophase pitch, and coke derived from petroleum or coal tar pitch.

[0111] The silicon-based negative electrode active material can include, for example, one or more selected from the group consisting of Si, silicon oxide particles (SiO x , 0 < x ≤ 2), Si-metal alloys, and alloys of Si and silicon oxide particles (SiO x , 0 < x ≤ 2). The silicon oxide particles (SiO x , 0 < x ≤ 2) may be a composite composed of crystalline SiO2 and amorphous Si.

[0112] The lithium metal may be in the form of a lithium metal thin film or lithium metal powder.

[0113] The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0114] On the other hand, examples of the positive electrode active material include lithium cobalt oxide (LiCoO2); lithium nickel oxide (LiNiO2); Li[Ni a Co b Mn c M 1 d O2 (in the above formula, M 1 is any one or two or more of the elements selected from the group consisting of Al, Ga, and In, 0.3 ≦ a < 1.0, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.5, 0 ≦ d ≦ 0.1, and a + b + c + d = 1); Li(Li e M 2 f-e-f’ M 3 f’ )O 2-g A g (in the above formula, 0 ≦ e ≦ 0.2, 0.6 ≦ f ≦ 1, 0 ≦ f’ ≦ 0.2, 0 ≦ g ≦ 0.2, M 2 includes Mn and one or more selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti, M 3 is one or more selected from the group consisting of Al, Mg, and B, and A is one or more selected from the group consisting of P, F, S, and N); Li 1+h Mn 2-h O4 (in the above formula 0 ≦ h ≦ 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; the formula LiNi 1-i M 4 i O2 (in the above formula, M 4is Co, Mn, Al, Cu, Fe, Mg, B or Ga, and is a Ni-site type lithium nickel oxide represented by 0.01 ≦ i ≦ 0.3); the formula LiMn 2-j M 5 j O2 (in the above formula, M 5 is Co, Ni, Fe, Cr, Zn or Ta, 0.01 ≦ j ≦ 0.1), or Li2Mn3M 6 O8 (in the above formula, M 6 is Fe, Co, Ni, Cu or Zn) represented lithium manganese composite oxide; LiMn2O4 in which part of Li in the formula is substituted with alkaline earth metal ions; disulfide compounds; LiFe3O4; and layered compounds such as Fe2(MoO4)3 or compounds substituted with one or more transition metals, but is not limited thereto only.

[0115] The electrode active material may be contained in an amount of 40% by weight or more, 50% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, or 80% by weight or more, and 98% by weight or less, 95% by weight or less, 90% by weight or less, 88% by weight or less, or 85% by weight or less based on the total weight of the electrode active material composition.

[0116] (Conductive material) The electrode active material composition according to an embodiment of the present invention may contain a conductive material.

[0117] The conductive material is for improving electrical conductivity and is not particularly limited as long as it is an electron conductive substance that does not cause a chemical change in the secondary battery.

[0118] The conductive material can be, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, Super P, etc.; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbons, aluminum, nickel powder, etc.; conductive whiskers such as zinc oxide, potassium titanate, etc.; or conductive metal oxides such as titanium oxide. Specifically, the conductive material can include carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, Super P, etc.

[0119] The conductive material may be contained in an amount of 1% by weight or more, 2% by weight or more, 3% by weight or more, 5% by weight or more, or 10% by weight or more, and 30% by weight or less, 25% by weight or less, or 20% by weight or less based on the total weight of the electrode active material composition.

[0120] (Additive) The electrode active material composition according to an embodiment of the present invention may contain an additive in addition to the electrode active material, the binder, and the conductive material.

[0121] The additive may include, for example, a viscosity modifier, a filler, a dispersant, or a combination thereof.

[0122] The viscosity modifier may be carboxymethyl cellulose, polyacrylic acid, or the like. The viscosity can be adjusted by adding the viscosity modifier so that the coating process on the electrode current collector becomes easy.

[0123] The filler is an auxiliary component for suppressing the expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not induce a chemical change in the secondary battery, and may be, for example, an olefin-based polymer such as polyethylene or polypropylene, or a fibrous substance such as glass fiber or carbon fiber.

[0124] The dispersant may include an aqueous dispersant or an organic dispersant such as N-methyl-2-pyrrolidone.

[0125] [Electrode] According to an embodiment of the present invention, an electrode including the electrode active material composition is provided.

[0126] Specifically, the electrode includes the electrode active material, the binder, and the conductive material, and the binder may include polyhydroxyalkanoate (PHA).

[0127] For example, the electrode can be manufactured by mixing the electrode active material composition in a solvent to produce an electrode slurry (negative electrode slurry or positive electrode slurry), applying this on an electrode (negative electrode or positive electrode) current collector, drying, and then pressing.

[0128] The solvent contained in the electrode slurry can be an organic solvent such as N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), acetone, dimethylacetamide, or water. These solvents can be used alone or in combination of two or more. The amount of the solvent used is an amount sufficient to dissolve and disperse the electrode active material, binder, and conductive material in consideration of the coating thickness of the slurry and the manufacturing yield.

[0129] The electrode may include a negative electrode, a positive electrode, or both of them.

[0130] The negative electrode can be manufactured by a conventional method known in the art. For example, a negative electrode slurry including the electrode active material composition (negative electrode active material composition) and a solvent is manufactured, applied on a negative electrode current collector, dried, and then pressed.

[0131] The current collector for the negative electrode may have a thickness of 3 μm to 500 μm. The current collector for the negative electrode is not particularly limited as long as it has conductivity without inducing a chemical change in the secondary battery. For example, copper, gold, stainless steel, aluminum, nickel, titanium, fired carbon, or copper or stainless steel surface-treated with carbon, nickel, titanium, or silver, or an aluminum-cadmium alloy can be used. Further, fine irregularities can be formed on the surface to strengthen the binding force of the negative electrode active material, and it can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0132] The positive electrode can be manufactured by a conventional method known in the art. For example, a positive electrode slurry containing the electrode active material composition (positive electrode active material composition) and a solvent is manufactured, applied (coated) to a current collector of a metal material, pressed, and then dried to manufacture the positive electrode.

[0133] The current collector of the metal material is a metal with high conductivity, a metal to which the positive electrode slurry can easily adhere, and is not particularly limited as long as it has high conductivity without inducing a chemical change in the secondary battery within the voltage range of the secondary battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver can be used. Further, fine irregularities can be formed on the surface of the current collector to increase the bonding strength of the positive electrode active material. The current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc., and may have a thickness of 3 to 500 μm.

[0134] [Secondary battery] According to an embodiment of the present invention, a secondary battery is provided that includes a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolytic solution, wherein one or more of the negative electrode and the positive electrode include a binder containing polyhydroxyalkanoate (PHA).

[0135] The separation membrane is used to physically separate the two electrodes in the secondary battery of the present invention, and generally, any separation membrane commonly used in lithium secondary batteries can be used without particular limitation. Particularly, those with low resistance to ion movement of the electrolyte and excellent electrolyte wetting ability are preferred.

[0136] The separation membrane may be made of a porous substrate. As the porous substrate, any porous substrate commonly used in electrochemical elements can generally be used. For example, a polyolefin-based porous membrane or non-woven fabric can be used, but it is not particularly limited thereto.

[0137] Examples of the polyolefin-based porous membrane include membranes formed by using polyethylene such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polypropylene, polybutylene, polypentene, and other polyolefin-based polymers alone or as mixtures thereof.

[0138] Examples of the non-woven fabric include non-woven fabrics formed from polymers such as polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate, in addition to polyolefin-based non-woven fabrics. The structure of the non-woven fabric may be a spunbond non-woven fabric or a meltblown non-woven fabric composed of long fibers.

[0139] The thickness of the porous substrate is not particularly limited, but it may be 1 to 100 μm, or 5 to 50 μm.

[0140] The size and porosity of the pores present in the porous substrate are also not particularly limited. For example, the size of the pores present in the porous substrate may be 0.001 to 50 μm, and the porosity may be 10 to 95%.

[0141] On the one hand, the electrolytic solution may contain a lithium salt.

[0142] The lithium salt can serve as a passage through which lithium ions (Li + ) can move.

[0143] The lithium salt is not particularly limited in the present invention, and those commonly used in electrolytic solutions for secondary batteries can be used without limitation.

[0144] Specifically, the lithium salt may include one or more selected from the group consisting of LiPF6, LiAsF6, LiFSI, LiTFSI, LiCF3SO3, LiN(CF3SO2)2, LiBF4, LiBF6, LiSbF6, LiN(C2F5SO2)2, and LiSO3CF3. More specifically, the lithium salt may include one or more selected from the group consisting of LiPF6, LiAsF6, LiFSI, LiTFSI, and LiBF4.

[0145] Furthermore, the electrolytic solution may contain an organic solvent.

[0146] The organic solvent can be used without limitation those commonly used in electrolytic solutions for secondary batteries. Typically, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ-butyrolactone, propylene sulfite, and tetrahydrofuran, any one selected from the group consisting of these or a mixture of two or more thereof can be usually used.

[0147] Specifically, the organic solvent may include one or more selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC).

[0148] In addition, the electrolytic solution may further contain additives such as overcharge preventives contained in ordinary electrolytic solutions.

[0149] The secondary battery according to the present invention can be manufactured by laminating (stacking) and folding a separator and an electrode in addition to a general winding process.

[0150] The shape of the secondary battery is not particularly limited, and various shapes such as cylindrical, laminated, and coin-shaped are possible.

[0151] When the secondary battery according to an embodiment of the present invention is charged at a constant current of 0.05C until the voltage reaches 3V and discharged at a constant current of 0.05C until the voltage reaches 0.01V, the Coulomb efficiency represented by the following formula 1 may be, for example, 90% or more, for example, 92% or more, for example, 93% or more, for example, 94% or more, or for example, 95% or more. [Formula 1] Coulomb efficiency (%) = discharge capacity / charge capacity × 100

[0152] Note that for the secondary battery according to an embodiment of the present invention, the specific capacity measured after repeating the charging and discharging twice is 250 mAhg -1 or more, 270 mAhg -1 or more, 280 mAhg -1 or more, 285 mAhg -1 or more, 290 mAhg -1 or more, 295 mAhg -1 or more, 300 mAhg -1 or more, 310 mAhg -1 or more, 320 mAhg -1 or more, or 330 mAhg -1 or more.

[0153] The secondary battery according to an embodiment of the present invention has a low resistance even during repeated cycling of the secondary battery due to the strong adhesive force of the binder, and can maintain a high-capacity cycle for a long time even when the amount of the binder is reduced, and can maintain excellent structural stability even after a long-term cycle.

[0154] Furthermore, by using polyhydroxyalkanoate (PHA) as the binder in the secondary battery according to an embodiment of the present invention, it is possible to have flame-retardant properties in which combustion does not spread and no harmful substances are generated during incineration.

[0155] Therefore, the secondary battery according to the present invention can be used not only for battery cells used as power sources for small devices, but also advantageously for unit cells of medium and large-sized battery modules including a large number of battery cells.

[0156] The battery module can be used as a power source for medium and large-sized devices that require high-temperature stability, long cycle characteristics, and high capacity characteristics.

[0157] Examples of the medium and large-sized devices include power tools powered by electric motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheel vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; power storage systems, etc., but are not limited thereto.

[0158] [Mode for Carrying Out the Invention] Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are intended to illustrate the present invention, and the scope of the present invention is not limited only to these.

[0159] Example 1 [Manufacture of Negative Electrode] [Manufacture of Negative Electrode Active Material Composition and Negative Electrode Slurry] As the negative electrode active material, graphite, as the binder, PHA (3-HB-co-4-HB, aPHA) (manufacturer: CJ), and as the conductive material, Super P were mixed at a weight ratio of 8:1:1 to produce a negative electrode active material composition.

[0160] 80 mg of the negative electrode active material composition was added to 0.5 mL of N-methyl-2-pyrrolidone (NMP) as a solvent to produce a negative electrode slurry.

[0161] Manufacture of the negative electrode After coating the negative electrode slurry on a 20-μm copper foil with a thickness of 15 μm, it was dried in a vacuum oven at 100 °C for 12 hours and then rolled to manufacture the negative electrode.

[0162] <Manufacture of the positive electrode> Manufacture of the positive electrode active material composition and the positive electrode slurry As the positive electrode active material, LiCoO2, as the binder, polyvinylidene fluoride (PVdF), and as the conductive material, carbon black were mixed at a weight ratio of 8:1:1 to manufacture the positive electrode active material composition.

[0163] 80 mg of the positive electrode active material composition was added to 0.5 mL of N-methyl-2-pyrrolidone (NMP) as a solvent to manufacture the positive electrode slurry.

[0164] Manufacture of the positive electrode After coating the positive electrode slurry on an 18-μm aluminum (Al) foil with a thickness of 15 μm, it was dried in a vacuum oven at 100 °C for 12 hours and then rolled to manufacture the positive electrode.

[0165] <Manufacture of the lithium secondary battery> The negative electrode manufactured above was punched out to have a surface area of 1.2 cm 2 and the positive electrode manufactured above was punched out to have a surface area of 1.2 cm 2 to fabricate a coin cell.

[0166] LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC):dimethyl carbonate (DMC) = 1:1 (volume ratio) at a concentration of 1 M to manufacture the electrolyte.

[0167] Thereafter, the coin cell was sealed using a crimper and then charged at a constant current of about 0.05C following a constant voltage charging procedure in which the voltage was maintained until it reached about 1 / 6 of the current.

[0168] Example 2 A negative electrode active material composition, a negative electrode, a positive electrode, and a lithium secondary battery were produced in the same manner as in Example 1, except that graphite was used as the negative electrode active material, PHA (3-HB-co-4-HB, aPHA) (manufacturer: CJ) was used as the binder, and Super P was used as the conductive material and mixed at a weight ratio of 8.5:0.5:1.

[0169] Comparative Example 1 A negative electrode active material composition, a negative electrode, a positive electrode, and a lithium secondary battery were produced in the same manner as in Example 1, except that polyvinylidene fluoride (PVdF) was used as the binder during the production of the negative electrode active material composition.

[0170] Evaluation Example Evaluation Example 1: Solubility Evaluation 10 mg of PVdF (powder), which is the binder used in Comparative Example 1 and Example 1, and 10 mg of aPHA (pellet) were each added to a mixed solvent of ethylene carbonate (EC):dimethyl carbonate (DMC) = 1:1 (volume ratio) and left for 1 day. The solubility of each binder at the initial stage and 1 day after addition was observed. The results are shown in Figure 1.

[0171] As can be seen from Figure 1, for PVdF used in Comparative Example 1, the PVdF (powder) was initially mixed with the mixed solvent and separated from the mixed solvent to form a layer after 1 day. For aPHA (pellet) used in Example 1, it remained undissolved in the mixed solvent both initially and 1 day after addition, and remained as aPHA (pellet).

[0172] Evaluation Example 2: Oxidation Resistance Evaluation Using cyclic voltammetry (WBCS3000, Wonatech, Korea), the oxidation resistance was evaluated under the conditions of a half cell. The results are shown in Figure 2.

[0173] Specifically, (a) in Figure 2 shows the voltage-current curves of the electrodes of Comparative Example 1 and Example 1. (b) in Figure 2 shows the voltage-current curves of the polyvinylidene fluoride (PVdF) binder used in Comparative Example 1 and the PHA (3-HB-co-4-HB, aPHA) binder used in Example 1.

[0174] As can be seen from Figure 2, the electrode of Example 1 using aPHA as a binder was excellent in oxidation resistance and electrochemically stable at the same level as the electrode of Comparative Example 1 using PVdF as a binder.

[0175] Evaluation Example 3: Evaluation of Electrochemical Characteristics The electrochemical characteristics of the secondary batteries of Example 1 and 2 and Comparative Example 1 were evaluated respectively.

[0176] (1) Specific Capacity The secondary batteries manufactured in the examples and comparative examples were charged at a constant current of 0.05C until the voltage reached 3V, and discharged at a constant current of 0.05C until the voltage reached 0.01V to measure the specific capacity of constant current charge and discharge.

[0177] (2) Coulombic Efficiency The secondary batteries manufactured in the examples and comparative examples were charged at a constant current of 0.05C until the voltage reached 3V, and discharged at a constant current of 0.05C until the voltage reached 0.01V to calculate the coulombic efficiency represented by the following formula 1. [Formula 1] Coulombic efficiency (%) = discharge capacity / charge capacity × 100

[0178] Figures 3 to 5 are graphs showing the results of measuring the specific capacity and coulombic efficiency of the secondary batteries of Example 1, Example 2, and Comparative Example 1. The results are summarized in Table 1 below.

[0179]

Table 1

[0180] As shown in Figures 3 to 5 and Table 1, in the secondary batteries of Example 1 and 2 using aPHA as a binder, both the specific capacity and the coulombic efficiency were improved compared to the secondary battery of Comparative Example 1 using PVdF as a binder.

[0181] Also, when comparing the specific capacity and Coulomb efficiency of the secondary batteries of Examples 1 and 2 in which the binder content was adjusted, in the secondary battery of Example 2 where the weight ratio of negative electrode active material: binder: conductive material was 8.5:0.5:1 and the binder content was decreased, despite using a small amount of binder, a Coulomb efficiency at the same level as that of the secondary battery of Example 1 where the weight ratio of negative electrode active material: binder: conductive material was 8:1:1 was maintained, and the specific capacity was further improved.

[0182] On the other hand, FIGS. 6 and 7 are graphs showing the results of measuring the impedance of the secondary batteries of Example 1 and Comparative Example 1 at the first cycle and the tenth cycle.

[0183] The impedance was measured under the conditions of 0.01 V and 0.02 Ag -1 and.

[0184] As can be seen from FIGS. 6 and 7, the secondary battery of Example 1 using aPHA as the binder had a lower resistance even during cycle repetition due to excellent adhesion strength compared to the secondary battery of Comparative Example 1 using PVdF as the binder.

[0185] Also, FIG. 8 is a graph showing the results of measuring the specific capacity and Coulomb efficiency according to the number of cycles (0 to 70) of the secondary battery of Example 2.

[0186] As can be seen from FIG. 8, in the secondary battery of Example 2, the specific capacity and Coulomb efficiency did not decrease even when the number of cycles increased.

Claims

1. It comprises an electrode active material, a binder, and a conductive material, The binder comprises polyhydroxyalkanoate (PHA), The electrode active material composition comprises a polyhydroxyalkanoate (PHA) comprising a PHA copolymer containing a 4-hydroxybutyrate (4-HB) monomer, wherein the PHA copolymer contains the 4-hydroxybutyrate (4-HB) monomer in an amount of 25 mol% to 50 mol% based on the total moles of monomers contained in the PHA copolymer.

2. The aforementioned polyhydroxyalkanoate (PHA) is The glass transition temperature (Tg) is -45°C to 80°C. The electrode active material composition according to claim 1, wherein the melting index (MI), measured in accordance with ASTM D1238 at a temperature of 165°C and a load of 5.0 kg, is 0.1 g / 10 min to 500 g / 10 min.

3. The electrode active material composition according to claim 1, wherein the binder is contained in an amount of 0.1% to 20% by weight based on the total weight of the electrode active material composition.

4. The electrode active material composition according to claim 1, wherein the weight ratio of the electrode active material, the binder, and the conductive material is (4.0 to 9.8):(0.1 to 3.0):(0.1 to 3.0).

5. The electrode active material composition according to claim 1, wherein the electrode active material is a negative electrode active material.

6. The anode active material comprises one or more selected from the group consisting of carbon-based anode active materials, silicon-based anode active materials, lithium metals, and lithium alloys. The electrode active material composition according to claim 5, wherein the conductive material comprises one or more selected from the group consisting of graphite, carbon black, conductive fibers, conductive tubes, metal powders, conductive whiskers, and conductive metal oxides.

7. It comprises an electrode active material, a binder, and a conductive material, The binder comprises polyhydroxyalkanoate (PHA), The electrode comprises a polyhydroxyalkanoate (PHA) including a PHA copolymer containing a 4-hydroxybutyrate (4-HB) monomer, wherein the PHA copolymer contains the 4-hydroxybutyrate (4-HB) monomer in an amount of 25 mol% to 50 mol%, based on the total moles of monomers contained in the PHA copolymer.

8. The system includes a negative electrode, a positive electrode, a separation membrane interposed between the negative electrode and the positive electrode, and an electrolyte. One or more of the negative and positive electrodes contain a binder containing polyhydroxyalkanoate (PHA), The polyhydroxyalkanoate (PHA) comprises a PHA copolymer containing a 4-hydroxybutyrate (4-HB) monomer, and the PHA copolymer contains the 4-hydroxybutyrate (4-HB) monomer in an amount of 25 mol% to 50 mol%, based on the total moles of monomers contained in the PHA copolymer, in a secondary battery.

9. When the aforementioned secondary battery is charged with a constant current of 0.05C until the voltage reaches 3V, and then discharged with a constant current of 0.05C until the voltage reaches 0.01V, The Coulomb efficiency expressed in the following formula 1 is 93% or higher, The specific capacity measured after repeating the aforementioned charging and discharging cycle twice was 280 mAhg. －１ The secondary battery according to claim 8, wherein the above is true. [Formula 1] Coulomb efficiency (%) = Discharge capacity / Charge capacity × 100

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