Lithium secondary battery

Abstract

Lithium secondary battery, comprising: a positive electrode, a separator and a negative electrode, wherein the positive electrode comprises a lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co); The negative electrode comprises a silicon-based active material and a carbon-based active material: where a and b are the efficiency constants of the silicon-based active material and the carbon-based active material, respectively; c is the efficiency constant of the lithium composite transition metal compound; a* represents the parts by weight of the silicon-based active material based on 100 parts by weight of the total amount of the silicon-based active material and the carbon-based active material, and where a, a*, b and c satisfy the following equation 1: [ ( a × a* ) + { b × ( 100-a* )} ] / c > 103 .5 and whereby The efficiency constant a is defined as the percentage ratio of the discharge capacity to the charge capacity, measured using a silicon-based active material as the active material of the negative electrode, that is, [ discharge capacity a ¨ t ( carbon-based ) / charge capacity a ¨ t ( carbon-based ) * 100 ] . the efficiency constant b is defined as the percentage ratio of the discharge capacity and the charge capacity, measured using a carbon-based active material as the active material of the negative electrode, that is, [discharge capacity (carbon-based) / charge capacity (carbon-based)* 100]; and the efficiency constant c is defined as the percentage ratio of the discharge capacity to the charge capacity, measured using an active material of the positive electrode as the active material, that is, [discharge capacity (nickel-kobalt-basiert) / charging capacity (nickel-kobalt-basiert) *100], wherein the discharge capacity and the charge capacity are determined according to the procedure as defined in the description, and where the constant of action a is 70 to 85, the constant of action b is 85 to 98, and the constant of action c is 85 to 90.

Description

TECHNICAL AREA

[0001] The present invention relates to a lithium secondary battery. STATE OF THE ART

[0002] Secondary batteries are used not only universally for portable devices, but also for electric vehicles (EVs) and hybrid electric vehicles (HEVs) powered by electric drive sources.

[0003] Since such a secondary battery not only offers the main advantage of drastically reducing the use of fossil fuels, but also the advantage of producing no byproducts through energy use, the secondary battery is attracting attention as a new energy source because it is environmentally friendly and improves energy efficiency.

[0004] In general, a secondary battery contains a positive electrode, a negative electrode, a separator inserted between the positive and negative electrodes, an electrolyte, and the like. Furthermore, an electrode such as a positive electrode and a negative electrode may have an active material layer provided on a current collector.

[0005] With the increasing use of secondary batteries, different battery performance characteristics are required. Although attempts have been made to modify the active material layer of the electrode to improve battery performance or durability, depending on the choice or combination of materials, one type of battery performance may be improved, while another type may be negatively affected. Therefore, further research is needed regarding the selection or combination of materials suitable for maintaining or improving the performance of a secondary battery while also preserving or improving its durability. BRIEF DESCRIPTION OF THE INVENTION

[0006] The present invention was developed to provide a lithium secondary battery that has a high energy density and excellent lifetime characteristics, thus providing a secondary battery that includes more sustainable product features.

[0007] One embodiment of the present invention provides a lithium secondary battery comprising: a positive electrode, a separator, and a negative electrode. wherein the positive electrode comprises a lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co); The negative electrode comprises a silicon-based active material and a carbon-based active material; where a and b are the efficiency constants of the silicon-based active material and the carbon-based active material, respectively; c is the efficiency constant of the lithium composite transition metal compound; a* represents the parts by weight of the silicon-based active material based on 100 parts by weight of the total amount of the silicon-based active material and the carbon-based active material; and where a, a*, b, and c satisfy the following equation 1: [(a×a*)+{b×(100-a*)}] / c>103.5

[0008] According to the embodiments described in this specification, a high-energy-density secondary battery can be provided by selecting materials that exhibit excellent charge and discharge efficiency as active materials for a positive and a negative electrode, and at the same time, an improved efficiency balance between the positive and negative electrodes can be achieved by adjusting the efficiency constants and the content of the active materials contained in the positive and negative electrodes so that the efficiency constants and the content correspond to a specific equation, thereby improving the battery's lifespan and fast-charging performance, and consequently the sustainability of the secondary battery provided. DETAILED DESCRIPTION

[0009] The present invention is described in more detail below to facilitate understanding. The present invention can be implemented in various forms and is not limited to the embodiments described herein. In this case, terms or words used in the specification and claims should not be interpreted as being limited to typical or dictionary meanings, but rather with a meaning and concept that adequately defines the term and is consistent with the technical spirit of the present invention based on the principle, so that an inventor can adequately define a concept of a term to best describe their own invention.

[0010] In the present invention, the term “comprise”, “contain” or “have” is intended to indicate the presence of the feature, number, step, component or any implemented combination thereof and is to be understood as not excluding the presence or possibility of adding one or more other features or numbers, steps, components or any combination thereof.

[0011] When the term "approximately" is used, it can refer to a value that may vary by, for example, ±10% of the defined value, ±5% of the defined value, ±1% of the defined value, or ±0.1% of the defined value.

[0012] A case in which a part exists as a layer "above" or "on top" of another part includes a case in which the part is "immediately above" another part, but also a case in which yet another part is in between. Conversely, the case in which a part is "immediately above" means that no other part is in between. Furthermore, "above" or "on" a reference part means that something is above or below the reference part, and not necessarily that it is "above" or "on" it in the direction opposite to gravity.

[0013] In this specification, the term “primary particles” means particles that do not exhibit grain boundaries in appearance when viewed with a scanning electron microscope at 5,000 to 20,000 times magnification.

[0014] In the present specification, the “secondary particles” are particles that are formed by the aggregation of primary particles.

[0015] In this specification, "single particle" is a term used to distinguish single particles from particles of the positive electrode's active material in the form of secondary particles. Secondary particles are formed by the aggregation of a large number (for example, more than 50 or hundreds) of primary particles, generally as described herein. On the other hand, the term "single particle" refers to a particle composed of a single primary particle or of an aggregate of 50 or fewer primary particles, for example, 20 or fewer primary particles, or 10 or fewer primary particles.

[0016] In this specification, the term "particle" may be interpreted to include one or all of the individual particles, secondary particles, and primary particles.

[0017] A lithium secondary battery according to an embodiment of the present invention comprises a positive electrode, a separator, and a negative electrode, wherein the positive electrode comprises a lithium composite transition metal compound containing nickel (Ni) and cobalt (Co); the negative electrode comprises a silicon-based active material and a carbon-based active material; wherein a and b are the efficiency constants of the silicon-based active material and the carbon-based active material, respectively; c is the efficiency constant of the lithium composite transition metal compound; a* represents the weight parts of the silicon-based active material based on 100 weight parts of the total amount of the silicon-based active material and the carbon-based active material; and wherein a, a*, b, and c satisfy the following equation 1. [(a×a*)+{b×(100-a*)}] / c>103.5

[0018] The value of equation 1 can be calculated as a value to one decimal place.

[0019] The inventors recognized that highly efficient positive and negative materials with good charge / discharge efficiency must be used to achieve a high energy density in a battery. However, the use of a silicon-based active material with a high capacity-to-weight ratio as the material for the negative electrode can lead to degradation of the negative electrode, which can also impair the long-term service life.The inventors have discovered that the long lifespan can be influenced by adjusting the efficiency balance between the positive and negative electrodes by simultaneously using a highly efficient silicon-based active material as the active material of the negative electrode and a lithium-nickel-cobalt-based compound as the active material of the positive electrode, while simultaneously meeting a specific efficiency parameter.In particular, if the components described above, which are contained in the positive electrode and the negative electrode, satisfy equation 1, a battery with high energy density can be provided, and at the same time the efficiency balance between the positive electrode and the negative electrode can be improved, thereby preventing deterioration of the initial negative electrode and significantly improving its lifetime characteristics.

[0020] According to one embodiment, the silicon-based active material can be a silicon-carbon composite or silicon oxide and can optionally include crystalline silicon, while the carbon-based active material can be graphite. The lithium composite transition metal compound, including nickel (Ni) and cobalt (Co), can be a single particle.

[0021] According to one embodiment, the lithium composite transition metal compound containing nickel (Ni) and cobalt (Co) can contain 80 mol% or more, for example, 80 mol% or more and less than 100 mol% nickel, based on the total mole count of nickel, cobalt, and an additional metal M of the lithium composite transition metal compound, excluding lithium. If the nickel content is high, as described above, the efficiency of the positive electrode can be increased to achieve the high energy density of a battery.

[0022] According to the present invention, the lithium composite transition metal compound comprises the metals lithium (Li), nickel (Ni), and cobalt (Co) and may optionally also include one or more additional metals M. For example, the one or more additional metals are selected from the group consisting of Mn, Al, Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo.

[0023] If the lithium composite transition metal compound does not include any metal M besides lithium (Li), nickel (Ni) and cobalt (Co), the lithium composite transition metal compound including nickel (Ni) and cobalt (Co) may contain 80 mol% or more, for example 80 mol% or more and less than 100 mol% nickel (Ni), where the percentage refers to the sum of the molar content of nickel (Ni) and cobalt (Co).However, if the lithium composite transition metal compound includes one or more metals M in addition to lithium (Li), nickel (Ni) and cobalt (Co), the lithium composite transition metal compound including nickel (Ni) and cobalt (Co) may contain 80 mol% or more, for example 80 mol% or more and less than 100 mol% nickel (Ni), where the percentage refers to the sum of the molar content of nickel (Ni), cobalt (Co) and the one or more metals M present in addition to lithium (Li), nickel (Ni) and cobalt (Co).

[0024] According to one embodiment, the lithium composite transition metal compound containing nickel (Ni) and cobalt (Co) can further contain at least one metal M1 selected from the group consisting of manganese and aluminum. In particular, the lithium composite transition metal compound containing nickel (Ni) and cobalt (Co) can be represented by the following chemical formula 1. Li a Ni (1-x-y) Co x M1 y M2 w O2 [Chemical Formula 1] where in the chemical formula 1 1.0≤a≤1.50≤x≤0.2,0≤y≤0.2,0≤w≤0.1,0≤x+y≤0.2, M1 is at least one metal selected from the group consisting of Mn and Al, and M2 is one or more metallic elements selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb and Mo.

[0025] The average particle diameter (D50) of the lithium composite transition metal compound can range from 12 µm to 30 µm, for example, from 13 µm to 28 µm, from 15 µm to 25 µm, or from 17 µm to 23 µm. The specific BET surface area of ​​the lithium composite transition metal compound can range from 0.5 m² 2 / g and 1.1 m 2 / g lie, for example between 0.6 m 2 / g and 1 m 2 / g or between 0.7 m 2 / g and 0.9 m 2 / g. The composition ratio, the average particle diameter (D50), the BET surface area, etc. of the lithium composite transition metal compound influence the efficiency constant c of the lithium composite transition metal compound.

[0026] According to one embodiment, the positive electrode can contain 90 parts by weight to 100 parts by weight of the lithium composite transition metal compound including nickel (Ni) and cobalt (Co), for example more than 92 parts by weight, more than 94 parts by weight, more than 96 parts by weight, more than 98 parts by weight or between 98 parts by weight and 100 parts by weight, based on 100 parts by weight of the active material of the positive electrode.

[0027] In this specification, the silicon-carbon composite is a composite material of Si and C, can also be represented by a Si / C-based active material, and differs from silicon carbide, which is represented by SiC. The silicon-carbon composite can be a composite material of silicon and graphite and can also form a structure in which a core of a silicon-graphite composite or the like is surrounded by graphene and amorphous carbon. In the silicon-carbon composite, the silicon can be nanosilicon, which is a nanoscale silicon particle dispersed within the silicon-carbon composite.

[0028] The silicon dioxide, SiO x (0≤x<2) contains a silicon-based composite particle including SiO x (0 <x<2) und Poren sein.

[0029] According to the present disclosure, when referring to particles of a silicon-based active material, the term composite particle refers to particles comprising a silicon-based active material, optionally other elements or compounds and pores.

[0030] According to the present disclosure, a composite material refers to two or more materials that are physically aggregated but not chemically bonded.

[0031] The silicon-based composite particle comprises a SiO₂ x (0 <x<2)-Matrix einschließlich Si und SiO2, wobei das Si auch eine separate Phase bilden kann und kristallines Si sein kann. D. h., das x entspricht dem Zahlenverhältnis von O zu Si, das in dem SiO x is included (0 <x<2).

[0032] The silicon-based active material can achieve an average particle diameter (D 50The particle size should range from 2 µm to 15 µm, particularly from 3 µm to 13 µm, and more precisely from 4 µm to 12 µm. If the above range is met, side reactions between the silicon-based composite particles and an electrolyte solution can be controlled, and the discharge capacity and initial efficiency of the battery can be effectively achieved. Additionally, the size of the Si crystal grains (i.e., crystalline Si) contained in the silicon-based active material can range from 10 nm to 30 nm, for example, from 15 nm to 25 nm.

[0033] The composition ratio of the elements that make up the silicon-based active material, the presence or type of a coating layer on the particle surface, the average particle diameter (D50), the size of the Si crystal grains, etc., influence the efficiency constant a of the silicon-based active material.

[0034] In the present specification, an average particle diameter (D) can be defined. 50 ) is defined as a particle diameter that corresponds to 50% of a cumulative volume in a particle diameter distribution curve of the particles. The average particle diameter (D 50 The particle size can be measured, for example, using a laser diffraction method. This method can typically measure particle diameters of approximately several millimeters in the submicrometer range, yielding results with high reproducibility and high resolution.

[0035] In the present specification, the “crystal grain size” can be quantitatively analyzed using X-ray diffraction analysis (XRD) with Cu-Kα X-rays.

[0036] In this specification, the “specific surface area” is measured according to the BET method; in particular, it can be determined by degassing for 2 hours at 130 °C with a BET measuring device (BEL-SORP-mini, Nippon Bell) for a measured object and by N2 absorption / desorption at 77 K.

[0037] According to one embodiment, the silicon-based active material has a discharge efficiency of 85% to 95%, for example 87% to 93%, 89% to 91%, or for example 85% to 90%, or 90% to 95%.

[0038] The charging capacity and discharging capacity of the active materials of the negative electrode and the positive electrode can be measured as follows.

[0039] First, the active material, a conductive Super-C™ material: a carboxymethylcellulose (CMC) thickener: a styrene-butadiene rubber (SBR) binder polymer, is added to water in a weight ratio of 95:1:1:3 to prepare a paste, and a copper foil is coated with the paste, punched and rolled so that it covers an area of ​​1.4875 cm². 2The material is then dried to produce an electrode. An electrode assembly is fabricated by using lithium metal as a counter electrode along with the electrode and inserting a polypropylene separator between them. After adding 1 M LiPF6 to an organic solvent to achieve a concentration of 1 wt% by mixing ethylene carbonate and ethyl methyl carbonate in a 3:7 volume ratio and adding vinylene carbonate to prepare a non-aqueous electrolyte solution, a coin cell (CHC) is fabricated by injecting the non-aqueous electrolyte solution into the electrode assembly.

[0040] After the coin-operated half-cell (CHC) manufactured above has been charged, a constant current of 0.005 V is applied at a rate of 0.2 C using a constant current-constant voltage (CC-CV) method, and then the current is controlled by a constant voltage of 0.005 V. During discharge, the discharge efficiency can be measured by switching off at 1.5 V using a constant current-constant voltage method at a rate of 0.2 C.

[0041] The efficiency constant a of a silicon-based active material can be defined as the percentage ratio of the discharge capacity to the charge capacity, measured using a silicon-based active material as the active material of the negative electrode, that is, [discharge capacity (siliziumbasiert) / charging capacity (siliziumbasiert) *100].

[0042] The efficiency constant b of a carbon-based active material can be defined as the percentage ratio of the discharge capacity and the charge capacity measured using a carbon-based active material as the active material of the negative electrode, that is, [discharge capacity (kohlenstoffbasiert) / charging capacity (kohlenstoffbasiert) *100].

[0043] The efficiency constant c of the lithium composite transition metal compound containing nickel (Ni) and cobalt (Co) can be defined as the percentage ratio of the discharge capacity to the charge capacity, measured using an active material of the positive electrode as the active material, that is, [discharge capacity (nickel-kobalt-basiert) / charging capacity (nickel-kobalt-basiert) *100].

[0044] For example, a can be 70 to 85, like 75 to 80, b can be 85 to 98, like 90 to 95, and c can be 85 to 90, like 86 to 89.

[0045] According to one embodiment, the silicon-based active material can be present in an amount of 1 part by weight to 20 parts by weight, such as 2 parts by weight to 18 parts by weight, 3 parts by weight to 15 parts by weight, 4 parts by weight to 10 parts by weight, 5 parts by weight to 7 parts by weight, based on 100 parts by weight of the active material of the negative electrode. Furthermore, the silicon-based active material can be present in an amount of 1 part by weight to 20 parts by weight, for example, 2 parts by weight to 18 parts by weight, 5 parts by weight to 15 parts by weight, based on 100 parts by weight of the total amount of silicon-based active material and the carbon-based active material. Maintaining a silicon-based active material content of 1 part by weight...-% or more can make it possible to achieve a capacity gain of at least a certain level, and it can be an advantage to use the materials, and if the content is 20 wt% or less, excessive swelling is prevented, which can be advantageous in terms of lifespan and battery characteristics and competitive in terms of cost.

[0046] According to one embodiment, the graphite contained in the negative electrode can be natural graphite, synthetic graphite, or a mixture thereof. The graphite may be present in amounts of 80 parts by weight or more and 99 parts by weight or less, for example, 85 parts by weight to 98 parts by weight, 87 parts by weight to 97 parts by weight, or 92 parts by weight to 96 parts by weight, based on 100 parts by weight of the active material contained in the negative electrode. If the graphite contains both synthetic and natural graphite, the ratio of synthetic to natural graphite may be 5:5 to 9:1, for example, 6:4 to 8:2 or 7:3.The average particle diameter (D50) of synthetic graphite can be 5 µm to 20 µm, for example 6 µm to 18 µm or 7 µm to 15 µm or 8 µm to 12 µm, and the average particle diameter (D50) of natural graphite can be 5 µm to 30 µm, for example 7 µm to 28 µm or 10 µm to 27 µm or 12 µm to 26 µm or 15 µm to 25 µm.

[0047] According to one embodiment, the negative electrode can include a current collector and an active material layer for the negative electrode, which is provided on the current collector.

[0048] The active material of the negative electrode, based on 100 parts by weight of the active material layer of the negative electrode, can be contained in a quantity of 80 parts by weight or more and 99.9 parts by weight or less, for example from 88 parts by weight to 98 parts by weight, from 92 parts by weight to 97 parts by weight.

[0049] In some embodiments, the active material layer of the negative electrode may comprise, in addition to the negative active materials, further ingredients or compounds, such as a binder or a conductive material. According to one embodiment of the present specification, the active material layer of the negative electrode may also contain a binder for the negative electrode, in addition to the silicon-based active material and the carbon-based active material.

[0050] The binder for the negative electrode can serve to improve the bond between the particles of the active material of the negative electrode and the adhesion between the particles of the active material of the negative electrode and the current collector of the negative electrode.Binders for the negative electrode may be those known in the field, and non-exhaustive examples thereof may include at least one selected from the group consisting of a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, an ethylene propylene diene monomer (EPDM), a sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid and a material in which the hydrogen of these is replaced by Li, Na, Ca or the like, and may also include various copolymers thereof.

[0051] The binder for the negative electrode may be contained in an amount of 0.1 parts by weight or more and 20 parts by weight or less, 0.2 parts by weight or more or 18 parts by weight or less, 0.3 parts by weight or more or 16 parts by weight or less, 0.4 parts by weight or more or 14 parts by weight or less, 0.5 parts by weight or more or 12 parts by weight or less, 0.6 parts by weight or more or 10 parts by weight or less, for example preferably 0.3 parts by weight or more and 20 parts by weight or less, and preferably 0.5 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the active material layer of the negative electrode.

[0052] The active material layer of the negative electrode must not contain any conductive material, but may contain a conductive material if necessary. The conductive material contained in the active material layer of the negative electrode is not particularly limited, as long as the conductive material exhibits electrical conductivity without causing a chemical change to the battery. Examples of permissible conductive materials include graphite, such as natural or synthetic graphite; carbon black, such as acetylene carbon black, Ketjen carbon black, sewer carbon black, furnace carbon black, flame carbon black, and thermal carbon black; a conductive fiber, such as carbon fiber or metal fiber; a conductive tube, such as a carbon nanotube; a metal powder, such as fluorocarbon powder, aluminum powder, and nickel powder; a conductive whisker, such as zinc oxide and potassium titanate; a conductive metal oxide, such as titanium oxide; a conductive material, such as polyphenylene derivatives; and the like.The content of conductive material in the active material layer of the negative electrode can be 0.01 parts by weight to 20 parts by weight, 0.05 parts by weight to 18 parts by weight, 0.10 parts by weight to 16 parts by weight, 0.50 parts by weight to 14 parts by weight, 1.50 parts by weight to 12 parts by weight, 3 parts by weight to 10 parts by weight, 5 parts by weight to 8 parts by weight, preferably 0.03 parts by weight to 18 parts by weight, based on 100 parts by weight of the active material layer of the negative electrode.

[0053] For the purposes of this disclosure, if the carbon-based active material is graphite, such as natural or synthetic graphite, the weight fractions of the graphite used as the carbon-based active material are not to be considered when defining the total weight fractions of conductive material. Similarly, when selecting graphite as the conductive material for the negative electrode, the described weight fractions of the conductive material are not to be included when defining the total weight fractions of the active material of the carbon-based negative electrode.When graphite is selected both as a carbon-based active material for negative electrodes and as a conductive material for negative electrodes, the total weight fractions of graphite correspond to the addition of the weight fractions of graphite used as a carbon-based active material for negative electrodes and the weight fractions of graphite used as a conductive material for negative electrodes.

[0054] The conductive material contained in the active material layer of the negative electrode is, for example, carbon black such as acetylene carbon black, ketjen carbon black, kanal carbon black, furnace carbon black, flame carbon black and thermal carbon black; a conductive fiber such as carbon fiber or metal fiber; a conductive tube such as a carbon nanotube.

[0055] In one embodiment of the present specification, the active material layer of the negative electrode may have a thickness of 5 µm or more and 500 µm or less, 20 µm or more and 400 µm or less, 50 µm or more and 300 µm or less, 100 µm or more and 200 µm or less.

[0056] In one embodiment of the present application, the current collector with a negative electrode is sufficient as long as it exhibits electrical conductivity without causing a chemical change to the battery, and is not particularly restricted. For example, copper, stainless steel, aluminum, nickel, titanium, burnt carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, and the like can be used as the current collector. In particular, a transition metal, such as copper or nickel, which readily adsorbs carbon, can be used as the current collector. Although the current collector may have a thickness of 1 µm to 50 µm, for example, 2 µm to 40 µm, 5 µm to 30 µm, or 10 µm to 20 µm, the thickness of the current collector is not limited to these values.

[0057] In one embodiment of the present specification, the positive electrode comprises a positive electrode current collector and an active material layer of the positive electrode formed on the positive electrode current collector, which includes the lithium-derived transition metal compound containing nickel (Ni) and cobalt (Co). The active material layer of the positive electrode can have a thickness of 20 µm or more and 500 µm or less, 30 µm or more and 400 µm or less, 50 µm or more and 300 µm or less, or 100 µm or more and 200 µm or less.

[0058] The positive electrode current collector is not particularly limited in its applications, as long as it exhibits electrical conductivity without causing a chemical change in the battery. Suitable materials include, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, silver, and the like. Furthermore, the positive electrode current collector can typically have a thickness of 1 to 50 µm, for example, 2 µm to 40 µm, 5 µm to 30 µm, or 10 µm to 20 µm. The adhesion of the active material of the positive electrode can also be improved by the formation of fine irregularities on the surface of the current collector. For example, the positive electrode current collector can be used in various forms, such as film, sheet, foil, mesh, porous body, foam body, and non-woven body.

[0059] In one embodiment, the active material of the positive electrode can be contained in 100 parts by weight of each of the active material layer of the positive electrodes in an amount of 80 parts by weight or more and 99.9 parts by weight or less, for example from 80 parts by weight to 98 parts by weight, from 85 parts by weight to 95 parts by weight, preferably 90 parts by weight or more and 99.9 parts by weight or less, more preferably 95 parts by weight or more and 99.9 parts by weight or less.

[0060] According to a further embodiment of the present specification, the active material layer of the positive electrode according to the embodiment described above may further contain a binder for the positive electrode and a conductive material.

[0061] The binder for the positive electrode can serve to improve the bonding between the particles of the active material of the positive electrode and the adhesion between the particles of the active material of the positive electrode and the current collector of the negative electrode. Binders known in the field can be used for the positive electrode; these include, among others, polyvinylidene fluoride (PVDF), a vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, an ethylene propylene diene monomer (EPDM), a sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof; one of these or a mixture of two or more of them can be used.

[0062] The binder for the positive electrode can be contained in an amount of 0.1 parts by weight or more and 20 parts by weight or less, for example preferably 0.3 parts by weight or more and 35 parts by weight or less, and more preferably 0.5 parts by weight or more and 20 parts by weight or less, based on 100 parts by weight of the active material layer of the positive electrode.

[0063] The conductive material contained in the active material layer of the positive electrode is used to impart electrical conductivity to the electrode and can be used without particular restriction as long as the conductive material exhibits electronic conductivity without causing a chemical change in a battery. Specific examples include graphite, such as natural or synthetic graphite; a carbon-based material such as carbon black, acetylene carbon black, ketine carbon black, sewer carbon black, furnace carbon black, flame carbon black, thermal carbon black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; a conductive whisker such as zinc oxide and potassium titanate; a conductive metal oxide such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, and any of these, or a mixture of two or more, can be used.

[0064] In particular, the conductive material can comprise one or more single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The conductive material can be present in an amount of 0.1 parts by weight or more and 2 parts by weight or less, for example, preferably 0.3 parts by weight or more and 1.5 parts by weight or less, and more preferably 0.5 parts by weight or more and 1.2 parts by weight or less, based on 100 parts by weight of the composition for an active material layer of the positive electrode.

[0065] The positive electrode and the negative electrode can be produced according to a prior art method for producing a positive electrode and a negative electrode, with the exception that the aforementioned active materials are used for the positive electrode and the negative electrode. In particular, according to a composition for forming an active material layer enclosing the aforementioned active material and optionally applying a binder and a conductive material to current collectors, the positive electrode and the negative electrode can be produced by drying and rolling the current collectors.

[0066] One embodiment relates to a method for manufacturing a secondary battery according to the present specification, wherein the method comprises: Applying an active material layer of the positive electrode, comprising a lithium composite transition metal compound including nickel (Ni) and cobalt (Co), to a positive electrode current collector to obtain a positive electrode; Applying an active material layer of the negative electrode, comprising a silicon-based active material and a carbon-based active material, to a current collector of the negative electrode to obtain a negative electrode; Drying and rolling of the positive and negative electrodes; Stacking the positive electrode and the negative electrode with a separator in between; where a and b are the efficiency constants of the silicon-based active material and the carbon-based active material, respectively; c is the efficiency constant of the lithium composite transition metal compound; a* represents the parts by weight of the silicon-based active material based on 100 parts by weight of the total amount of the silicon-based active material and the carbon-based active material, and where a, a*, b and c satisfy the following equation 1: [(a×a*)+{b×(100-a*)}] / c>103.5

[0067] The types and amounts of the positive and negative active materials, binders, and conductive materials are as described above. The solvent may be a commonly used solvent in the field; examples include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or similar solvents; and any one of these, or a mixture of two or more, may be used. The amount of solvent used is sufficient as long as it dissolves or disperses the active material, the conductive material, and the binder, taking into account the application thickness and the preparation yield of the paste, and has a viscosity that provides excellent thickness uniformity in subsequent application for the fabrication of the positive and negative electrodes.Alternatively, the positive electrode and the negative electrode can be produced by another method, by casting the composition to form an active material layer onto a separate support and then laminating a film obtained by peeling it off the support onto a current collector.

[0068] The separator separates the negative electrode from the positive electrode and provides a passage for the movement of lithium ions. It can be used without particular restrictions as long as it is typically used as a separator in a secondary battery. In particular, a separator with excellent moisture retention capacity in an electrolyte solution and low resistance to ion movement within the electrolyte is preferable. Specifically, it is possible to use a porous polymer film, for example, a porous polymer film formed from a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof.Furthermore, a typical porous nonwoven fabric, such as one made of high-melting-point glass fiber, polyethylene terephthalate fiber, or similar materials, can be used. Additionally, a coated separator containing a ceramic component or polymer material can be employed to ensure heat resistance or mechanical strength, and can be selectively used as a single-layer or multi-layer structure.

[0069] Examples of electrolytes include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten-type inorganic electrolytes, and the like, which can be used to manufacture a lithium secondary battery.

[0070] In particular, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0071] For example, a non-aqueous organic solvent such as N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfrance, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triesters, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, ethyl propionate, or the like may be used.

[0072] Particularly among carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate can be preferably used, since, as high-viscosity organic solvents, cyclic carbonates have a high permittivity and thus dissociate a lithium salt well, and such cyclic carbonates can be used preferentially because the cyclic carbonate can be mixed with a linear carbonate with low viscosity and low permittivity, such as dimethyl carbonate and diethyl carbonate, in a suitable ratio and used to prepare an electrolyte with high electrical conductivity.

[0073] A lithium salt can be used as the metal salt, wherein the lithium salt is a material that dissolves readily in the non-aqueous electrolyte solution, and, for example, it is possible to use one or more of the following anions as the lithium salt: F-, Cl-, I-, NO3-, N(CN)2-, BF4-, ClO4-, PF6-, (CF3)2PF4-, (CF3)3PF3-, (CF3)4PF2-, (CF3)5PF-, (CF3)6P-, CF3SO3-, CF3CF2SO3-, (CF3SO2)2N-, (F SO2)2N-, CF3CF2(CF3)2CO-, (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-, CF3(CF2)7SO3-, CF3CO2-, CH3 CO2-, SCN-, and (CF3CF2SO2)2N-.

[0074] To improve the lifespan characteristics of a battery, to suppress capacity degradation, and to improve the battery's discharge capacity, and thus to improve the battery's sustainability, one or more additives may be included in addition to the electrolyte components mentioned above, such as a halogenated carbonate-based compound like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphotriamide, a nitrobenzene derivative, sulfur, a quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, an ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride.

[0075] A lithium secondary battery according to an embodiment of the present invention comprises an assembly containing a positive electrode, a negative electrode, a separator and an electrolyte.

[0076] An additional embodiment of the present invention provides a paste for the positive electrode of a lithium secondary battery according to the embodiments of the present invention, wherein the paste comprises at least 90 parts by weight of a lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co), for example more than 92 parts by weight, more than 94 parts by weight, more than 96 parts by weight, more than 98 parts by weight or between 98 parts by weight and 100 parts by weight, based on 100 parts by weight of the active material of the positive electrode. wherein the lithium composite transition metal compound containing nickel (Ni) and cobalt (Co) has an average particle diameter (D 50 ) from 12 µm to 30 µm, for example from 13 µm to 28 µm, 15 µm to 25 µm, 17 µm to 23 µm, and a BET surface area of ​​0.5 m 2 / g up to 1.1 m 2 / g, such as about 0.6 m 2 / g to 1 m 2 / g or 0.7 m 2 / g up to 0.9 m 2 / g, as well as an efficiency constant c of 85 to 90, such as 86 to 89.

[0077] An additional embodiment of the present invention provides a paste for the negative electrode of a lithium secondary battery according to the embodiments of the present invention, wherein the paste comprises at least 1 part by weight of a silicon-based active material and at least 80 parts by weight of a carbon-based active material, based on 100 parts by weight of the active material negative electrode active material; wherein the silicon-based active material is a silicon-carbon composite or silicon oxide with an efficiency constant a of 70 to 85, for example 75 to 80, and the carbon-based active material is graphite with an efficiency constant b of 85 to 98, for example 90 to 95; wherein the graphite comprises both synthetic and natural graphite in a synthetic to natural graphite ratio of 5:5 to 9:1, for example 6:4 to 8:2 or 7:3; and wherein the average particle diameter (D 50 ) of artificial graphite 5 µm to 20 µm, for example 6 µm to 18 µm, or 7 µm to 15 µm, or 8 µm to 12 µm, and the average particle diameter (D 50 ) of natural graphite 5 µm to 30 µm, for example 7 µm to 28 µm or 10 µm to 27 µm or 12 µm to 26 µm or 15 µm to 25 µm.

[0078] According to one embodiment of the present invention, the pastes disclosed herein for the positive or negative electrode further comprise one or more of a binder and a conductive material according to the embodiments of the present invention.

[0079] An additional embodiment of the present invention provides a battery module that includes the lithium secondary battery described above as a unit cell, as well as a battery pack that includes this. The battery module and the battery pack contain the secondary battery, which has a high capacity, high rate characteristics, and high cycle characteristics, and can therefore be used as an energy source for a medium-sized and large device selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and an energy storage system.

[0080] Since the lithium secondary battery according to embodiments of the present invention exhibits excellent discharge capacity, performance characteristics, and cycle life, it can be used as a power source for portable devices such as mobile phones, notebooks, and digital cameras, as well as medium-sized and large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems. For example, the battery module or battery pack can be used as a power source for one or more medium-sized and large power tools; an electric vehicle, including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); and an energy storage system.

[0081] Preferred embodiments are suggested below to facilitate understanding of the present invention, but these embodiments are provided only to illustrate the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present invention, and it is natural that such changes and modifications also fall within the accompanying claims. Example 1.

[0082] A copper foil with a thickness of 10 µm was coated with a composition for forming an active material layer of the negative electrode, including a negative electrode active material containing SiO₂ and graphite (the weight ratio of SiO₂ and graphite is a* and (100-a*, respectively), a conductive material (carbon black, CNT), a binder (SBR), and a thickener (CMC) in a weight ratio of 95.6:1.0:2.3:1.1, resulting in a dry thickness of 140 µm, and then dried to produce a negative electrode. Here, the SiO₂ had a particle diameter (D50) of 10 µm, and the size of the Si crystal was 20 nm. The graphite mentioned above consists of synthetic and natural graphite in a weight ratio of 7:3, and the average particle diameter (D50) of both synthetic and natural graphite was 10 µm. or 20 µm.

[0083] An aluminum foil with a thickness of 15 µm was coated with a composition to form an active material layer of the positive electrode, including a lithium-nickel-based oxide of Li 1,0 Ni 0,86 Co 0,06 Mn 0,08 The material was coated with O2, a binder (PVDF), and a conductive material (CNT) in a weight ratio of 97:1:2, resulting in a dry thickness of 130 µm, and then dried to produce a positive electrode. Here, the particle size (D50) of the lithium-nickel-based oxide was 20 µm, and the BET surface area was 0.8 m². 2 / G.

[0084] The positive and negative electrodes were stacked with an intermediate separator, and an electrolyte solution was injected to fabricate a battery. A 12 µm thick separator was used, coated with a layer of Al₂O₃ and a PVDF binder on a PE / PP / PE three-layer base film. The electrolyte solution consisted of 1 M LiPF₆, ethylene carbonate (EC) / ethyl methyl carbonate (EMC) (volume ratio 3 / 7), and vinylene carbonate (VC) / propanesultone (PS) (each in amounts of 3 parts by weight and 1.5 parts by weight, respectively, based on 100 parts by weight of the electrolyte).

[0085] The values ​​of Equation 1 described above for the manufactured batteries are shown in Table 1. To measure the room temperature and high-temperature lifetime of the manufactured battery, the capacity retention rate during 200 charge and discharge cycles under the following conditions is shown in Table 2. * Lifespan at room temperature: The cycle was performed by charging with constant current / constant voltage (CC / CV) (0.0.5 C cutoff) and discharging with constant current (CC) 0.5 C (2.5 V cutoff) the manufactured cell to 4.2 V at 0.33 CC at room temperature (2.5 °C). * High temperature lifespan: The cycle was performed by charging the manufactured cell with constant current / constant voltage (CC / CV) (0.05 C cutoff) and discharging it with constant current (CC) from 0.33 C (2.5 V cutoff) to 4.2 V at 0.33 C at high temperature (45 °C). * Battery life during fast charging: Cycles with a 25-minute charge from SOC (state of charge) 0% to 80% and discharge at 0.33C constant current (CC) (2.5V cutoff). Example 2

[0086] An experiment was conducted in the same manner as in Example 1, except that a silicon-carbon composite (Si / C) was used instead of SiO₂ in the active material of the negative electrode. Here, the silicon-carbon composite had a particle diameter (D50) of 10 µm, and the size of the crystalline Si was 20 nm. Comparative example 1

[0087] An experiment was conducted in the same manner as in Example 1, with the difference that a lithium nickel-based oxide of Li was used. 1,0 Ni 0,84 Co 0,08 Mn 0,08 O2 instead of a lithium nickel-based oxide of Li 1,0 Ni 0,86 Co 0,06 Mn 0,08O2 was used. Here, the particle size (D50) of the lithium-nickel-based oxide was 10 µm and the BET surface area was 1.2 m². 2 / G. Comparative example 2

[0088] An experiment was conducted in the same way as in Example 1, with the difference that a lithium nickel-based oxide of Li was used. 1,0 Ni 0,84 Co 0,08 Mn 0,08 O2 instead of a lithium nickel-based oxide of Li 1,0 Ni 0,86 Co 0,06 Mn 0,08 O2 was used, and a silicon-carbon composite (Si / C) was used instead of SiO in the active material of the negative electrode. Here, the particle size (D50) of the lithium-nickel-based oxide was 10 µm, and the BET surface area was 1.2 m². 2 / G. Comparative example 3

[0089] An experiment was conducted in the same way as in Example 1, with the difference that a lithium nickel-based oxide of Li was used.1,0 Ni 0,84 Co 0,08 Mn 0,08 O2 instead of a lithium nickel-based oxide of Li 1,0 Ni 0,86 Co 0,06 Mn 0,08 O2 was used and the weight ratio a* of SiO in the active material of the negative electrode 3 was [value missing]. Here, the particle size (D50) of the lithium-nickel-based oxide was 10 µm and the BET surface area was 1.2 m². 2 / G. [Table 1] a a* b c Value of equation 1[(axa*)+{bx (100-a*)}] / c Example 1 75 6 93 88 104,5 Example 2 80 6 93 88 104,8 Comparative example 1 75 6 93 90 102,1 Comparative example 2 80 6 93 90 102,5 Comparative example 3 75 3 93 90 102,7 [Table 2] Test temperature (°C) Number of cycles Capacity maintenance rate (%) at room temperature and high temperature Fast charging cycle Fast charging capacity maintenance rate Example 1 25 200 95 50 97 45 200 94 - - Example 2 25 200 96 50 97 45 200 94 - - Comparative example 1 25 200 80 50 85 45 200 90 - - Comparative example 2 25 200 82 50 88 45 200 92 - - Comparative example 3 25 200 85 50 88 45 200 94 - -

[0090] As shown in Table 2, it was confirmed that the capacity retention rates after 200 cycles at room temperature and high temperature, and after 50 fast-charge cycles, were excellent in Examples 1 and 2 compared to those in the comparison examples. The results demonstrate that the batteries according to the invention are more sustainable due to their higher capacity retention rates after 200 cycles and 50 cycles, respectively.

Claims

[1] Lithium secondary battery, comprising: a positive electrode, a separator and a negative electrode, wherein the positive electrode comprises a lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co); The negative electrode comprises a silicon-based active material and a carbon-based active material: where a and b are the efficiency constants of the silicon-based active material and the carbon-based active material, respectively; c is the efficiency constant of the lithium composite transition metal compound; a* represents the parts by weight of the silicon-based active material based on 100 parts by weight of the total amount of the silicon-based active material and the carbon-based active material, and where a, a*, b and c satisfy the following equation 1: [(a×a*)+{b×(100-a*)}] / c>103.5 and whereby The efficiency constant a is defined as the percentage ratio of the discharge capacity to the charge capacity, measured using a silicon-based active material as the active material of the negative electrode, that is, [Discharge capacity (carbon-based) / Charge capacity (carbon-based)*100]. the efficiency constant b is defined as the percentage ratio of the discharge capacity and the charge capacity, measured using a carbon-based active material as the active material of the negative electrode, that is, [discharge capacity (carbon-based) / charge capacity (carbon-based)* 100]; and the efficiency constant c is defined as the percentage ratio of the discharge capacity to the charge capacity, measured using an active material of the positive electrode as the active material, that is, [discharge capacity (nickel-kobalt-basiert) / charging capacity (nickel-kobalt-basiert)*100], wherein the discharge capacity and the charge capacity are determined according to the procedure as defined in the description, and where the constant of action a is 70 to 85, the constant of action b is 85 to 98, and the constant of action c is 85 to 90. [2] Lithium secondary battery according to claim 1, wherein the silicon-based active material is a silicon-carbon composite or silicon oxide and the carbon-based active material is graphite. [3] Lithium secondary battery according to claim 2, wherein the silicon-carbon composite material has a discharge efficiency of 85% to 95% as defined in the description using a constant current (CC) method at a rate of 0.2 C. [4] Lithium secondary battery according to one of claims 2 or 3, wherein the average particle diameter (D 50) of the silicon-based composite particle is 2 µm to 15 µm, where the average particle diameter (D 50 ) is measured using a laser diffraction method. [5] Lithium secondary battery according to any one of claims 2 to 4, wherein the graphite contains both artificial graphite and natural graphite and the ratio of artificial graphite to natural graphite is 5:5 to 9:

1. [6] Lithium secondary battery according to claim 5, wherein the average particle diameter (D 50 ) of artificial graphite lies between 5 µm and 20 µm and the average particle diameter (D 50 ) of natural graphite lies between 5 µm and 30 µm, where the average particle diameter (D 50 ) is measured using a laser diffraction method. [7] Lithium secondary battery according to any one of claims 1 to 6, wherein the positive electrode comprises 90 parts by weight to 100 parts by weight of the lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co), based on 100 parts by weight of the active material of the positive electrode. [8] Lithium secondary battery according to any one of claims 1 to 7, wherein the lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co) is represented by the following chemical formula 1: Li a Ni (1-x-y) Co x M1 y M2 w O2 [Chemical Formula 1] where in the chemical formula 1 1.0≤a≤1.50≤x≤0.2,0≤y≤0.2,0≤w≤0.1,0≤x+y≤0.2, M1 is at least a metal made of Mn or Al, and M2 is one or more metallic elements selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb and Mo. [9] Lithium secondary battery according to any one of claims 1 to 8, wherein the lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co) comprises 80 mol% or more of nickel, based on the total mole number of nickel, cobalt and any additional metal M of the lithium composite transition metal compound, excluding lithium. [10] Lithium secondary battery according to any one of claims 1 to 9, wherein the average particle diameter (D 50 ) of the lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co), is between 12 µm and 30 µm, with the average particle diameter (D 50 ) is measured using a laser diffraction method. [11] Lithium secondary battery according to any one of claims 1 to 10, wherein the BET surface area of ​​the lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co) is 0.5 m² / g to 1.1 m²2 / g. [12] Battery module, including a lithium secondary battery according to any one of claims 1 to 11. [13] Paste for the positive electrode of a lithium secondary battery according to any one of claims 1 to 11, wherein the paste comprises at least 90 parts by weight of a lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co), based on 100 parts by weight of the active material of the positive electrode, wherein the lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co) comprises a particle with an average particle diameter (D 50 ) from 12 µm to 30 µm and a BET surface area of ​​0.5 m² 2 / g up to 1.1 m 2 / g is and has an efficiency constant c of 85 to 90, where the average particle diameter (D 50 ) is measured using a laser diffraction method; where The efficiency constant c is defined as the percentage ratio of the discharge capacity to the charge capacity, measured using an active material of the positive electrode as the active material, that is, [discharge capacity (nickel-kobalt-basiert) / charging capacity (nickel-kobalt-basiert) *100]. [14] Paste for the negative electrode of a lithium secondary battery according to any one of claims 1 to 11, wherein the paste comprises at least 1 part by weight of a silicon-based active material and at least 80 parts by weight of a carbon-based active material, based on 100 parts by weight of the active material of the negative electrode; where the silicon-based active material is a silicon-carbon composite or silicon oxide with an efficiency constant a of 70 to 85, and the carbon-based active material is a graphite with an efficiency constant b of 85 to 98; wherein the graphite contains both synthetic and natural graphite in a synthetic to natural graphite ratio of 5:5 to 9:1; and wherein the average particle diameter (D 50 ) of the artificial graphite is 5 µm to 20 µm and the average particle diameter (D 50 ) of natural graphite is 5 µm to 30 µm, where the average particle diameter (D 50 ) is measured using a laser diffraction method; and whereby the efficiency constant a is defined as the percentage ratio of the discharge capacity to the charge capacity, measured using a silicon-based active material as the active material of the negative electrode, that is, [discharge capacity (silicon-based) / charge capacity (silicon-based)* 100]; and the efficiency constant b is defined as the percentage ratio of the discharge capacity and the charge capacity, measured using a carbon-based active material as the active material of the negative electrode, that is, [Discharge capacity (carbon-based) / Charge capacity (carbon-based)*100].