Electrochemical apparatus and electronic apparatus including the same

Abstract

The present invention relates to an electrochemical device and an electronic device including the same. The electrochemical device according to the present invention includes a negative electrode, a positive electrode, and an electrolyte. The positive electrode includes a current collector and a positive electrode active material layer located on the current collector, the positive electrode active material layer including a positive electrode active material. The electrolyte includes an additive A, and the additive A is LiPO 2 F 2 The active specific surface area of ​​the positive electrode is X m 2 / g, and the weight of the LiPO 2 F 2 When the weight percentage of is Y%, the above X and Y satisfy 0.005≦X / Y≦2. The electrochemical device according to the present invention has improved cycle characteristics, storage characteristics, and overcharge characteristics, and has reduced impedance.

Description

[Technical Field]

[0001] The present invention relates to the field of energy storage, and more specifically to electrochemical devices and electronic devices including them, in particular to lithium-ion batteries. [Background technology]

[0002] Currently, lithium-ion batteries are widely used in fields such as electric vehicles, home appliances, and energy storage devices. Due to their advantages, including high energy density and lack of memory effect, they are gradually becoming the dominant battery in these sectors. In particular, the electric vehicle, micropower, and energy storage industries are rapidly developing, providing a broad market for lithium-ion battery applications. Due to the properties of lithium iron phosphate, the cathode material itself, batteries composed of it are highly safe, have a long service life, excellent high-temperature performance, low cost, and are environmentally friendly. Therefore, these batteries have significant advantages and promising application prospects compared to other types of lithium-ion batteries. Although these batteries have a relatively long lifespan, the demand for longer battery life in the power battery and energy storage sectors is increasing, making the challenge of further improving the storage characteristics, cycle characteristics, safety characteristics, and kinetic characteristics of lithium-ion batteries at low cost still of significant value.

[0003] Improving the lifespan and safety characteristics of lithium iron phosphate batteries through electrolyte optimization offers high cost-effectiveness. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Embodiments of the present invention provide an electrochemical apparatus to solve, to at least some extent, one of the problems present in the related field. Embodiments of the present invention further provide an electronic apparatus including the electrochemical apparatus. [Means for solving the problem]

[0005] In one embodiment, the present invention provides an electrochemical apparatus comprising a negative electrode, a positive electrode, and an electrolyte. The positive electrode comprises a current collector and a positive electrode active material layer located on the current collector, and the positive electrode active material layer comprises a positive electrode active material. The electrolyte comprises additive A, and additive A comprises LiPO2F2. The active specific surface area of ​​the positive electrode is X m 2 When the weight of LiPO2F2 is given as / g and Y% is the weight percentage of the electrolyte, then X and Y satisfy 0.005 ≤ X / Y ≤ 2.

[0006] In one embodiment, X and Y are, (i) X satisfies 0.01 ≤ X ≤ 0.1, (ii) Y satisfies 0.01 ≤ Y ≤ 2, (iii) X and Y satisfy 0.005 ≤ X / Y ≤ 1, It satisfies at least one of the following conditions.

[0007] In one embodiment, the electrolyte further contains vinylene carbonate, and when Z is the weight percentage of the vinylene carbonate relative to the weight of the electrolyte, Z is between 0.01 and 6.

[0008] In some examples, Z / Y is between 0.5 and 600.

[0009] In some examples, the electrolyte further contains fluoroethylene carbonate, which is present in an amount of 0.01% to 5% by weight relative to the weight of the electrolyte.

[0010] In some embodiments, the electrolyte further contains additive B, The above additive B is at least one selected from the group consisting of lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, B4Li2O7, Li3BO3, CF3LiO3S, lithium hexafluorophosphate, and lithium perchlorate, and / or The additive B described above is present in an amount of 0.01% to 16% by weight relative to the weight of the electrolyte.

[0011] In some embodiments, the positive electrode active material contains an M element, and the M element is at least one selected from the group consisting of Fe, Mn, Al, Ca, K, Na, Mg, Ti, and Zn.

[0012] In some examples, when the weight of the vinylene carbonate is W1g and the weight of the negative electrode is W2g, the ratio of W1 / W2 is 0.001 to 0.031.

[0013] In some examples, the electrolyte further comprises an S=O functional group-containing compound. The above S=O functional group-containing compound is at least one selected from the group consisting of 1,3-propanesultone, ethylene sulfate, methylene methane disulfonate, propensultone, 4-methyl-1,3,2-dioxathiolan-2,2-dioxide, 1,4-butanesultone, and 1,2,6-oxadithian-2,2,6,6-tetraoxide, and / or The above S=O functional group-containing compound is present in an amount of 0.01% to 5% by weight relative to the weight of the electrolyte.

[0014] In another embodiment, the present invention provides an electronic apparatus including an electrochemical apparatus described in an embodiment of the present invention.

[0015] The electrochemical apparatus provided by the present invention offers improved cycle characteristics, high-temperature storage characteristics, and excellent charging characteristics and energy efficiency.

[0016] Other aspects and advantages of the embodiments of the present invention will be partially described and shown in the following description, or can be described through the implementation of the embodiments of the present invention.

Mode for Carrying Out the Invention

[0017] The embodiments of the present invention will be described in detail below. The embodiments of the present invention should not be construed as limiting the present application.

[0018] In this specification, amounts, ratios, and other numerical values may be presented in a range format. It should be understood that such a range format is used for convenience and brevity. This range format should be flexibly understood to include not only the numerical values explicitly specified as range limitations, but also all individual numerical values or sub-ranges included within that range, as if each numerical value and sub-range were explicitly specified.

[0019] In the mode for carrying out the invention and the claims, a list of items connected by terms such as "one of", "one of", "one type of", or other similar terms can mean any one of the listed items. For example, when listing items A and B, the phrase "one of A and B" means only A or only B. In another example, when listing items A, B, and C, the phrase "one of A, B, and C" means only A, only B, or only C. Item A may include one element or a plurality of elements. Item B may include one element or a plurality of elements. Item C may include one element or a plurality of elements.

[0020] In the embodiments for carrying out the invention and the claims, a list of items connected by terms such as "at least one of", "at least one of", "at least one kind of" or other similar terms can mean any combination of the listed items. For example, when listing items A and B, the phrase "at least one of A and B" means only A, only B, or A and B. In another embodiment, when listing items A, B, and C, the phrase "at least one of A, B, and C" means only A, only B, only C, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may include one element or a plurality of elements. Item B may include one element or a plurality of elements. Item C may include one element or a plurality of elements.

[0021] I. Electrochemical device In some embodiments, the present invention provides an electrochemical device, and the electrochemical device includes a negative electrode, a positive electrode, and an electrolyte.

[0022] In some embodiments, the positive electrode includes a current collector and a positive electrode active material layer located on the current collector. The positive electrode active material layer includes a positive electrode active material. The electrolyte includes additive A, and additive A includes LiPO2F2. When the specific surface area of the positive electrode is X m 2 / g, and the weight percentage of LiPO2F2 with respect to the weight of the electrolyte is Y%, X and Y satisfy 0.005 ≦ X / Y ≦ 2.

[0023] In some embodiments, X and Y satisfy 0.005 ≦ X / Y ≦ 1 or 0.015 ≦ X / Y ≦ 1. In some embodiments, X / Y is 0.005, 0.0075, 0.01, 0.02, 0.05, 0.08, 0.10, 0.15, 0.3, 0.5, 0.8, 1, 1.5, 2 or a range consisting of any two of these numerical values.

[0024] In some embodiments, X is between 0.01 and 0.1. In some embodiments, X is a range consisting of 0.01, 0.015, 0.02, 0.05, 0.08, 0.1, or any two of these values.

[0025] In some embodiments, Y is between 0.01 and 2. In some embodiments, Y is within the range of 0.01, 0.03, 0.05, 0.06, 0.1, 0.14, 0.16, 0.2, 0.4, 0.6, 0.8, 1.0, 1.1, 1.2, 1.4, 1.6, 1.8, 2, or any two of these values.

[0026] In some embodiments, the electrolyte further contains vinylene carbonate, and when Z is the weight percentage of the vinylene carbonate relative to the weight of the electrolyte, Z is between 0.01 and 6.

[0027] In some embodiments, Z is a range consisting of 0.01, 0.05, 0.08, 0.1, 0.2, 0.5, 0.8, 0.01, 1, 1.5, 2, 2.5, 2.8, 3, 3.5, 3.8, 4, 4.5, 4.8, 5, 5.5, 5.8, 6, or any two of these values.

[0028] In some embodiments, Z / Y is between 0.5 and 600. In some embodiments, Z / Y is between 0.5 and 50. In some embodiments, Z / Y is in the range of 0.5, 1, 1.5, 2, 3, 4, 5, 6, 10, 20, 40, 50, 100, 150, 200, 300, 350, 400, 450, 500, 550, 600, or any two of these values.

[0029] In some examples, the electrolyte further comprises fluoroethylene carbonate. In some examples, the amount of fluoroethylene carbonate is 0.01% to 5% by weight relative to the weight of the electrolyte. In some examples, the amount of fluoroethylene carbonate is in the range of 0.01%, 0.05%, 0.07%, 0.1%, 0.15%, 0.3%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 4.8%, 5%, or any two of these values, relative to the weight of the electrolyte.

[0030] In some examples, the electrolyte and additive B are further comprising the above electrolyte, and additive B is at least one selected from the group consisting of lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, B4Li2O7, Li3BO3, CF3LiO3S, lithium hexafluorophosphate, and lithium perchlorate.

[0031] In some embodiments, the amount of additive B is 0.01% to 16% by weight relative to the weight of the electrolyte. In some embodiments, the amount of additive B is in the range of 0.01%, 0.04%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16% or any two of these values ​​by weight relative to the weight of the electrolyte.

[0032] In some examples, when the weight of the vinylene carbonate is W1g and the weight of the negative electrode is W2g, the ratio of W1 / W2 is 0.001 to 0.031.

[0033] In some embodiments, W1 / W2 is a range consisting of 0.001, 0.006, 0.008, 0.01, 0.02, 0.025, 0.031, or any two of these values.

[0034] In some examples, the electrolyte further comprises an S=O functional group-containing compound, the S=O functional group-containing compound being at least one selected from the group consisting of 1,3-propanesultone, ethylene sulfate, methylene methane disulfonate, propensultone, 4-methyl-1,3,2-dioxathiolane-2,2-dioxide, 1,4-butanesultone, and 1,2,6-oxadithiane-2,2,6,6-tetraoxide.

[0035] In some examples, the S=O functional group-containing compound is present in an amount of 0.01% to 5% by weight relative to the weight of the electrolyte. In some examples, the S=O functional group-containing compound is present in an amount of 0.01%, 0.03%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 1.8%, 2.0%, 2.5%, 2.8%, 3%, 5%, or any two of these values ​​relative to the weight of the electrolyte.

[0036] In some embodiments, the positive electrode active material contains an M element, and the M element is at least one selected from the group consisting of Fe, Mn, Al, Ca, K, Na, Mg, Ti, and Zn.

[0037] In some embodiments, the positive electrode active material is at least one selected from the group consisting of lithium iron phosphate and lithium iron manganese phosphate.

[0038] In some embodiments, the positive electrode active material layer further comprises a conductive agent. In some embodiments, the conductive agent comprises at least one of carbon nanotubes, carbon fibers, acetylene black, graphene, Ketjenblack, and carbon black.

[0039] In some examples, the positive electrode active material layer further comprises a binder. In some examples, the binder comprises at least one of polyvinylidene fluoride, carboxymethylcellulose, styrene-butadiene rubber, polyvinyl alcohol, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly(1,1-difluoroethylene), polyethylene, polypropylene, acrylic acid (esterified) styrene-butadiene rubber, epoxy resin, and nylon.

[0040] In some embodiments, the current collector includes at least one of copper foil and aluminum foil.

[0041] In some embodiments, the positive electrode can be prepared by known preparation methods in the art. For example, the positive electrode can be obtained by preparing an active material composition by mixing a positive electrode active material, a conductive agent, and an adhesive in a solvent, and then applying the active material composition to a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone.

[0042] In some embodiments, the electrochemical apparatus includes any apparatus for initiating an electrochemical reaction.

[0043] In some embodiments, the electrochemical apparatus further includes a separator located between the positive electrode and the negative electrode.

[0044] In some embodiments, the electrochemical apparatus described above is a lithium secondary battery.

[0045] In some embodiments, the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery, or an all-solid-state secondary lithium battery.

[0046] negative electrode In some embodiments, the materials, configuration, and manufacturing methods of the negative electrode used in the electrochemical apparatus according to the present invention may include any techniques disclosed in the prior art. In some embodiments, the negative electrode is the negative electrode described in US Patent Application US9812739B, and all of its contents are incorporated into the present invention by reference.

[0047] In some embodiments, the negative electrode comprises a current collector and a negative electrode active material layer located on the current collector. In some embodiments, the negative electrode active material layer comprises a negative electrode active material. In some embodiments, the negative electrode active material is lithium metal, structured lithium metal, structured lithium metal, natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen material (e.g., SiO, SiO2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium TiO2-Li4Ti5O having a spinel structure 12 This includes, but is not limited to, Li-Al alloys or any combination thereof.

[0048] In some examples, the negative electrode active material layer includes an adhesive. In some examples, the adhesive includes, but is not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly(1,1-difluoroethylene), polyethylene, polypropylene, styrene-butadiene rubber, acrylic acid (esterified) styrene-butadiene rubber, epoxy resin, or nylon.

[0049] In some embodiments, the negative electrode active material layer includes a conductive material. In some embodiments, the conductive material includes, but is not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, metal fiber, copper, nickel, aluminum, silver, or polyphenylene derivatives.

[0050] In some embodiments, the current collector includes, but is not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal.

[0051] In some embodiments, the negative electrode can be obtained by preparing an active material composition by mixing an active material, a conductive material, and an adhesive in a solvent, and then applying the active material composition to a current collector.

[0052] In some examples, the solvent may include, but is not limited to, deionized water and N-methylpyrrolidone.

[0053] In some embodiments, the negative electrode in an all-solid-state secondary lithium battery is a metallic lithium foil.

[0054] Separator In some embodiments, the material and shape of the separator used in the electrochemical apparatus according to the present invention are not particularly limited and may be any prior art disclosed. In some embodiments, the separator includes a polymer or inorganic material formed from a material stable in the electrolyte of the present invention.

[0055] For example, the separator may include a base layer and a surface treatment layer. The base layer is a nonwoven fabric, film, or composite film having a porous structure, and the material of the base layer is at least one selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used.

[0056] A surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material.

[0057] The inorganic layer comprises inorganic particles and a binder. The inorganic particles consist of at least one or a combination of several particles selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder consists of one or a combination of several particles selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, and the polymer material includes at least one of the following: polyamide, polyacrylonitrile, polymer of acrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0058] electrolyte In some embodiments, the electrolyte used in the electrolyte of the embodiment of the present invention may be an electrolyte known in the prior art, such as inorganic lithium salts such as LiClO4, LiPF6, LiBF4, LiSbF6, LiSO3F, LiN(FSO2)2, for example LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,3-hexafluoropropanedisulfonimidolithium, cyclic 1,2-tetrafluoroethanedisulfonimidolithium, LiN(CF3SO2)(C4F9SO2), LiC(CF3SO2) 3. This includes, but is not limited to, fluorine-containing organolithium salts such as LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2, as well as lithium salts containing dicarboxylic acid complexes such as lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tris(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate. The electrolytes described above may be used individually, or two or more may be used simultaneously. For example, in some examples, the electrolyte includes a combination of LiPF6 and LiBF4. In some examples, the electrolyte includes a combination of an inorganic lithium salt such as LiPF6 or LiBF4 and a fluorine-containing organic lithium salt such as LiCF3SO3, LiN(CF3SO2)2, or LiN(C2F5SO2)2. In some examples, the electrolyte concentration is in the range of 0.8 to 3 mol / L, for example, in the range of 0.8 to 2.5 mol / L, in the range of 0.8 to 2 mol / L, in the range of 1 to 2 mol / L, in the range of 0.5 to 1.5 mol / L, in the range of 0.8 to 1.3 mol / L, in the range of 0.5 to 1.2 mol / L, or for example, 1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L.

[0059] 2.Electronic equipment The electronic device according to the present invention may be any device using the electrochemical apparatus according to the embodiment of the present invention.

[0060] In some embodiments, electronic devices include, but are not limited to, laptop computers, pen-input computers, mobile computers, e-book players, mobile phones, portable facsimile machines, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric-assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashes, cameras, large household storage batteries, or lithium-ion capacitors.

[0061] The preparation of lithium-ion batteries will be described below, using lithium-ion batteries as an example and referring to specific embodiments. Those skilled in the art should understand that the preparation method described in this invention is merely an example, and any other suitable preparation method falls within the scope of this invention.

[0062] Examples The following describes the characterization of examples and comparative examples of lithium-ion batteries according to the present invention.

[0063] 1. Preparation of Lithium-ion Batteries (1) Preparation of the electrolyte In a glove box under an argon atmosphere with a water content of less than 10 ppm, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC:EMC:DEC = 35:40:25. After adding additives and stirring thoroughly, LiPF6 was added and mixed uniformly to obtain the electrolyte. Here, LiPF6 was 12.5% ​​by weight relative to the weight of the electrolyte. The specific types and contents of the additives used in the electrolyte are shown in the table below. The content of each substance in the electrolyte described in this invention was calculated relative to the weight of the electrolyte.

[0064] (2) Preparation of the positive electrode A positive electrode slurry was obtained by mixing lithium iron phosphate (LFP), the positive electrode active material, conductive carbon black (Super P), the conductive agent, and polyvinylidene fluoride, the binder, in a weight ratio of 96.3:1.5:2.2, adding N-methylpyrrolidone (NMP), and uniformly stirring with a vacuum stirrer. The solid content of the positive electrode slurry was 72 wt%. Subsequently, the positive electrode slurry was uniformly applied to aluminum foil, which served as the positive electrode current collector. The aluminum foil was dried at 85°C, cold-pressed, cut, and slit, and then dried under vacuum conditions at 85°C for 4 hours to obtain the positive electrode.

[0065] (3) Preparation of the negative electrode A negative electrode slurry was obtained by mixing artificial graphite, a conductive agent Super P, a thickener sodium carboxymethylcellulose (CMC), and a binder styrene-butadiene rubber (SBR) in a weight ratio of 96.4:1.5:0.5:1.6, adding deionized water, and stirring with a vacuum stirrer. The solid content of the negative electrode slurry was 54 wt%. Subsequently, the negative electrode slurry was uniformly applied to a copper foil, which was the negative electrode current collector. The copper foil was dried at 85°C, cold-pressed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to obtain the negative electrode.

[0066] (4) Preparation of separators A polyethylene (PE) separator with a thickness of 7 μm was used.

[0067] (5) Preparation of lithium-ion batteries A bare cell was obtained by stacking the positive electrode, separator, and negative electrode in order, winding them together, and having the separator interposed between the positive and negative electrodes to act as an isolation. After welding the tabs, the bare cell was placed on an aluminum plastic film that served as the outer casing, and the prepared electrolyte was injected into the dried bare cell. After processes such as vacuum packaging, standing, formation (charging with a constant current of 0.02C until 3.3V, then charging with a constant current of 0.1C until 3.6V), shaping, and capacity measurement, a soft pack lithium-ion battery (thickness 3.3mm, width 39mm, length 96mm) was obtained.

[0068] II. Test Method 1. Cycle performance testing of lithium-ion batteries: 25°C Cycle Performance Test A lithium-ion battery was placed in a 25°C incubator and left undisturbed for 30 minutes to bring it to a constant temperature. The lithium-ion battery, now at a constant temperature, was charged with a constant current of 1C until the voltage reached 3.65V, then charged again with a constant voltage of 3.65V until the current reached 0.05C, and finally discharged with a constant current of 1C until the voltage reached 2.5V. This constituted one charge-discharge cycle. The initial discharge capacity was set to 100%, and the charge-discharge cycle was repeated until the discharge capacity decreased to 70%. The test was then stopped, and the number of cycles was recorded as an evaluation index for the cycle characteristics of the lithium-ion battery.

[0069] 45°C Cycle Performance Test The test method for the battery's cycle characteristics at 45°C was largely the same as the 25°C cycle characteristics test described above, except that the test temperature was 45°C.

[0070] 2. High-temperature storage test of lithium-ion batteries in a highly charged state (100% SOC): The lithium-ion batteries were placed in a 25°C incubator and left undisturbed for 30 minutes to allow them to reach a constant temperature. After charging with a constant current of 1C until the voltage reached 3.65V, they were charged again with a constant voltage of 3.65V until the current reached 0.05C, and then discharged with a constant current of 1C until the voltage reached 2.5V. The discharge capacity was recorded as the initial capacity of the lithium-ion battery. Then, after charging with a constant current of 0.5C until the voltage reached 3.65V, they were charged again with a constant voltage of 3.65V until the current reached 0.05C, and the thickness of the battery was measured and recorded using a micrometer. The tested lithium-ion batteries were transferred to a 60°C incubator and stored for 90 days. During this period, the thickness of the battery was measured and recorded every 30 days.

[0071] The batteries were transferred to a 25°C incubator and left standing for 60 minutes. They were then discharged at a constant current of 1C until the voltage reached 2.5V, and the discharge capacity was recorded as the remaining capacity of the lithium-ion battery. After charging at a constant current of 1C until the voltage reached 3.65V, the batteries were charged at a constant voltage of 3.65V until the current reached 0.05C, and then discharged at a constant current of 1C until the voltage reached 2.5V. The discharge capacity was recorded as the recoverable capacity of the lithium-ion battery. The battery thickness (THK), open-circuit voltage (OCV), and impedance (IMP) were measured. The batteries were discharged at a constant current of 1C until the voltage reached 2.5V, and the recovery discharge capacity was recorded. The storage remaining capacity retention rate and recoverable capacity retention rate of the lithium-ion battery were calculated and used as indicators to evaluate the high-temperature storage characteristics of the lithium-ion battery. Remaining capacity retention rate = (Remaining capacity after 90 days of storage - Initial battery capacity) / Initial battery capacity * 100% Recovery capacity retention rate = (Recoverable capacity after 90 days of storage - Initial battery capacity) / Initial battery capacity * 100%

[0072] 3. High-temperature storage test of lithium-ion batteries in a low charge state (0% SOC): The lithium-ion batteries were placed in a 25°C incubator and left to stand for 30 minutes to allow them to reach a constant temperature. They were then charged with a constant current of 1C until the voltage reached 3.65V, then charged again with a constant voltage of 3.65V until the current reached 0.05C, and then discharged with a constant current of 1C until the voltage reached 2.5V. The discharge capacity was recorded as the initial capacity of the lithium-ion battery. The battery thickness was then measured and recorded using a micrometer. The tested lithium-ion batteries were transferred to a 60°C incubator and stored for 90 days. During this period, the battery thickness was measured and recorded every 30 days. The batteries were then transferred to a 25°C incubator and left to stand for 60 minutes. They were then charged with a constant current of 1C until the voltage reached 3.65V, then charged again with a constant voltage until the current reached 0.05C, and then discharged with a constant current of 1C until the voltage reached 2.5V. The discharge capacity was recorded as the recoverable capacity of the lithium-ion battery. The battery thickness (THK), open-circuit voltage (OCV), and impedance (IMP) were measured. The lithium-ion battery was discharged at a constant current of 1C until the voltage reached 2.5V. The expansion rate of the battery's thickness during storage was calculated and recorded, and this was used as an index to evaluate the high-temperature storage characteristics of the lithium-ion battery at 0% SOC. Storage thickness expansion rate at 0% SOC = (Thickness after 90 days of storage - Initial battery thickness) / Initial battery thickness * 100%

[0073] 4. DC Resistance (DCR) Test of Lithium-ion Batteries (-10°C): The lithium-ion battery was placed in a high / low temperature box at -10°C and left undisturbed for 4 hours to allow it to reach a constant temperature. It was then charged with a constant current of 0.1C until it reached 3.65V, then charged with a constant voltage of 3.65V until the current was 0.05C, and left undisturbed for 10 minutes. Next, it was discharged with a constant current of 0.1C until it reached 2.5V, and the capacity at this step was recorded as the actual discharge capacity D0. Then, it was left undisturbed for 5 minutes, charged with a constant current of 0.1C until it reached 3.65V, and then charged with a constant voltage of 3.65V until the current was 0.05C (the current was calculated using the capacity corresponding to D0). After leaving it undisturbed for 10 minutes, it was discharged with a constant current of 0.1C for 7 hours (the current was calculated using the capacity corresponding to D0), and the voltage V1 at this time was recorded. Next, the cell was discharged for 1 second at a constant current of 1C (sampling was performed at 100ms, with the current calculated according to the nominal capacity of the cell), and the voltage V2 at this time was recorded. Then, the DC resistance (DCR) corresponding to the 30% charge state (SOC) of the cell was calculated, and the calculation formula was as follows. 30%SOC DCR=(V2-V1) / 1C

[0074] 5. Energy conversion efficiency (RTE) test (25°C) of lithium-ion batteries: The lithium-ion battery was placed in a 25°C incubator and left undisturbed for 30 minutes to allow it to reach a constant temperature. It was then discharged at a constant current of 0.5C until the voltage reached 2.5V, and left undisturbed for 15 minutes. It was then charged at a constant current of 0.5C until the voltage reached 3.65V, and then charged again at a constant voltage of 3.65V until the current reached 0.05C. After leaving it undisturbed for 60 minutes, it was discharged at a constant current of 0.5C until the voltage reached 2.5V. Three consecutive charge-discharge cycles were performed using the above current values, and the charge and discharge energies were recorded. The charge energy E of the final cycle was then recorded. c and discharge energy E d The energy conversion efficiency was calculated using [the specified method / equation]. Energy conversion efficiency = Discharge energy E d / Charging energy E c *100%

[0075] 6. Overcharge test of lithium-ion batteries: At 25°C, the battery was discharged at 0.5C until it reached 2.5V, then charged at a constant current of 1C until it reached 6.5V, and charged at a constant voltage of 6.5V for 3 hours, while monitoring the temperature change on the surface of the battery. (The pass criterion for the overcharge test is that the battery does not catch fire, burn, or explode.) In each example or comparative example, 10 batteries were tested and the number of batteries passing the test was recorded.

[0076] 7. Active specific surface area test of the positive electrode of the lithium-ion battery: Button-type batteries (LFP / / Li) were assembled using the positive electrodes of lithium-ion batteries. Then, a step potential of 10 mV was applied to the button-type batteries coated with the positive electrode active material, maintained for 30 seconds, and the charge quantity Q of the active electrode was obtained based on the integration of the current-time curve, and the capacitance C was obtained by Q / 10 mV.

[0077] The active specific surface area was calculated by the capacitance method (for details, refer to "Electrochemical Research Methods" by Mr. Tian Zhaowu). S1 = C / (20uf) cm 2 S=(S1×10 -4 [[ID=十七]]) / M m 2 / g

[0078] Here, S is the active specific surface area of the positive electrode, with the unit of m 2 / g, and is denoted as X m 2 / g. S1 is the active surface area of the positive electrode, with the unit of cm 2 . C is the capacitance of the measurement sample, and uf is the capacitance unit of microfarad. M is the coating mass after subtracting the mass of the current collector from the mass of the electrode (one side), with the unit of g. 20uf is the electric double layer capacitance per square centimeter of a smooth electrode.

[0079] Hereinafter, X represents the numerical value of the active specific surface area of the positive electrode.

[0080] A. Table 1 shows the types and contents of additives in the relevant examples and comparative examples, and the relevant characteristic parameters of the lithium-ion battery.

[0081] [Table 1]

[0082] As can be seen from the comparison between Examples 1-1 to 1-12 and Comparative Example 1-1, by adding the additive LiPO2F2 to the electrolyte, the cycle characteristics and storage characteristics of lithium-ion batteries can be significantly improved, and the impedance of lithium-ion batteries can be reduced.

[0083] As can be seen from the comparison between Examples 1-1 to 1-12 and Comparative Example 1-2, if the value of X / Y is too large (for example, 10), the cycle characteristics and storage characteristics of the lithium-ion battery deteriorate significantly. By controlling X / Y within an appropriate range, excellent storage characteristics, cycle characteristics, and reaction kinetic characteristics can be ensured. In the present invention, the range of X / Y may be 0.005 to 2.

[0084] Table 2 shows the types and contents of additives in the relevant examples and comparative examples, and the relevant characteristic parameters of the lithium-ion battery. Here, the electrolytes in Examples 2-1 to 2-12 were obtained by adding vinylene carbonate (VC) to the electrolyte of Example 1-4. The active specific surface area of ​​the positive electrode in Examples 2-1 to 2-12 is the same as the active specific surface area of ​​the positive electrode in Example 1-4.

[0085] [Table 2]

[0086] As can be seen from the results of the above characteristic tests, by adding vinylene carbonate (VC) to an electrolyte satisfying 0.005 ≤ X / Y ≤ 2, the cycle characteristics and storage characteristics of lithium-ion batteries can be significantly improved without a significant change in impedance. In particular, when Z / Y is within the range of 0.5 to 300, the cycle characteristics and storage characteristics of lithium-ion batteries can be significantly improved.

[0087] Vinylen carbonate can form a solid electrolyte interface (SEI) film on the graphite surface that exhibits excellent thermal and chemical stability. This effectively suppresses side reactions of the solvent on the graphite surface and inhibits the deposition of transition metals. However, because vinylene carbonate has a high impedance for film formation, excessively high content can easily lead to lithium deposition during battery charging and deterioration of discharge characteristics. By simultaneously introducing LiPO2F2 into an electrolyte containing vinylene carbonate, the decomposition of vinylene carbonate can be suppressed, and a synergistic film can be formed. By controlling the ratio of vinylene carbonate to LiPO2F2, a stable SEI film with low impedance can be formed, thereby ensuring excellent storage characteristics, cycle characteristics, and reaction kinetic characteristics. Therefore, in this invention, the preferred range for Z / Y is 0.5 to 300.

[0088] Table 3 shows the types and contents of additives in the relevant examples and comparative examples, and the relevant characteristic parameters of the lithium-ion battery. The electrolytes in Examples 3-1 to 3-8 were obtained by adding fluoroethylene carbonate (FEC) to the electrolyte of Example 2-3. The active specific surface area of ​​the positive electrode and the concentration of LiPO2F2 in the electrolyte in Examples 3-1 to 3-8 are the same as in Example 2-3.

[0089] [Table 3]

[0090] As can be seen from the results of the above characteristic tests, by satisfying 0.005 ≤ X / Y ≤ 2 and further adding fluoroethylene carbonate (FEC) to an electrolyte containing vinylene carbonate (VC), the cycle characteristics, storage characteristics, and energy conversion efficiency of lithium-ion batteries can be significantly improved without a significant change in impedance.

[0091] Fluoroethylene carbonate can form a SEI film on the graphite surface that has excellent thermal and chemical stability and low impedance. This effectively suppresses side reactions of the solvent on the graphite surface, inhibits the deposition of transition metals, effectively reduces the loss of active lithium in the graphite anode, and significantly improves the capacity retention rate during the cycle and storage process. However, if the content is too high, the viscosity of the electrolyte increases, and the reaction kinetic properties deteriorate. Also, if the content is too high, it decomposes at high temperatures, generating a large amount of HF and creating a risk of gas generation during storage. Therefore, in this invention, the preferred content of fluoroethylene carbonate is 0.01% to 5%.

[0092] Table 4 shows the types and contents of additives in the relevant examples and comparative examples, and the relevant characteristic parameters of the lithium-ion battery. Here, the electrolytes in Examples 4-1 to 4-19 were obtained by adding the additives shown in Table 4 to the electrolyte of Example 1-4. The active specific surface area of ​​the positive electrode and the concentration of LiPO2F2 in the electrolyte in Examples 4-1 to 4-19 are the same as in Example 1-4.

[0093] [Table 4]

[0094] Table 5 shows the relevant characteristic parameters of the lithium-ion batteries in the above examples and comparative examples.

[0095] [Table 5]

[0096] Lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium tetrafluoroborate (LiBF4), B4Li2O7, Li3BO3, CF3LiO3S, and lithium hexafluorophosphate (LiPF6) can all form protective films with good thermal and chemical stability on the surfaces of the positive and negative electrodes. This suppresses side reactions between the electrodes and the electrolyte, enabling excellent cycle stability, storage stability, reaction kinetic properties, and safety characteristics. Furthermore, LiFSI and LiTFSI have high thermal stability, low anion-cation association, and high solubility and dissociation in carbonate ester systems. By using LiFSI and LiTFSI as electrolytes in place of some or all of LiPF6, better cycle characteristics, storage characteristics, reaction kinetic properties, and safety characteristics can be obtained.

[0097] Table 6 shows the composition and performance test results of lithium-ion batteries in the relevant examples. The electrolyte composition in Examples 5-1 and 5-2 is the same as in Example 1-4. The types of positive electrode active materials in Examples 5-1 and 5-2 are shown in Table 6. LFP represents lithium iron phosphate, and LMFP represents lithium manganese iron phosphate.

[0098] [Table 6]

[0099] As can be seen from the results of the above characteristic tests, the cycle characteristics and storage characteristics of the lithium-ion battery do not change significantly when LMFP or a mixture of LMFP and LFP is used as the positive electrode active material compared to when LFP is used as the positive electrode active material. Therefore, the electrolyte in the above example is also applicable to positive electrodes using LMFP or a mixture of LFP and LMFP as the active material.

[0100] Table 7 shows the composition and performance test results of lithium-ion batteries in the relevant examples. The electrolytes in Examples 6-1 to 6-11 were obtained by adding VC to the electrolyte of Example 1-3. The active specific surface area of ​​the positive electrode and the concentration of LiPO2F2 in the electrolyte in Examples 6-1 to 6-11 are the same as in Example 1-3. The weight of vinylene carbonate in the electrolyte is W1g, the weight of the negative electrode is W2g, and W1 / W2 represents the VC content in the negative electrode per unit mass.

[0101] [Table 7]

[0102] As can be seen from the results of the above characteristic tests, by adding VC to an electrolyte that satisfies 0.005 ≤ X / Y ≤ 2, the cycle characteristics and storage characteristics of lithium-ion batteries can be significantly improved, but the impedance does not change significantly. In particular, when W1 / W2 is between 0.001 and 0.031, the cycle characteristics and storage characteristics of lithium-ion batteries are significantly improved, and the impedance also decreases.

[0103] Vinylene carbonate can form a SEI film on the graphite surface that has excellent thermal and chemical stability. This effectively suppresses side reactions of the solvent on the graphite surface and inhibits the deposition of transition metals. If the amount of VC is sufficient, it is possible to ensure the formation of a dense protective film on the graphite surface, but because the impedance of this film formation is large, if the content is too high, it tends to lead to lithium deposition during battery charging and deterioration of discharge characteristics. Therefore, in the present invention, the VC content in the negative electrode per unit mass is preferably 0.001 to 0.031.

[0104] Table 8 shows the composition and performance test results of lithium-ion batteries in the relevant examples. The electrolytes in Examples 7-1 to 7-12 were obtained by adding the following S=O functional group-containing compound to the electrolyte of Example 6-7. The active specific surface area of ​​the positive electrode and the concentration of LiPO2F2 in the electrolyte in Examples 7-1 to 7-12 are the same as in Example 6-7. The weight of vinylene carbonate in the electrolyte is W1g, and the weight of the negative electrode is W2g, where W1 / W2 represents the VC content in the negative electrode per unit mass.

[0105] The general terms for the English abbreviations in Table 8 are as follows: DTD: Ethylene sulfate MMDS: Methylene methane disulfonate PS: 1,3-propanethultone

[0106] [Table 8]

[0107] Table 9 shows the results of the characteristic tests of the above-described embodiment.

[0108] [Table 9]

[0109] As can be seen from the results of the above characteristic tests, by adding an S=O functional group-containing compound to an electrolyte that satisfies 0.005 ≤ X / Y ≤ 2 and / or W1 / W2 is 0.001 to 0.031, the cycle characteristics, storage characteristics, and overcharge test characteristics of lithium-ion batteries can be significantly improved, and the resistance can also be reduced.

[0110] The S=O functional group-containing compound forms a protective film with good thermal and chemical stability on the surfaces of the positive and negative electrodes, suppressing side reactions between the electrodes and the electrolyte, and achieving excellent cycle stability, storage stability (suppression of gas generation and improvement of capacity retention), reaction kinetic properties, and safety properties. If the content of the S=O functional group-containing compound is too low, the protection by film formation will be insufficient, and the improvement in properties will not be significant. If the content of the S=O functional group-containing compound is too high, the impedance of film formation on the positive and negative electrodes will be high, so the properties will not be improved and the reaction kinetics will deteriorate. Therefore, in the present invention, the content of the S=O functional group-containing compound is preferably 0.01% to 5%.

[0111] Throughout the specification, any reference by “several examples,” “some examples,” “one example,” “another example,” “example,” “specific example,” or “some examples” means that at least one example or instance of the present invention includes the specific features, structures, materials, or properties described in that example or instance. Therefore, any reference by “in some examples,” “in an example,” “in one example,” “in another example,” “in one example,” “specific example,” or “example” found anywhere in the specification does not necessarily refer to the same example or instance in the present invention. Furthermore, any specific features, structures, materials, or properties described herein can be incorporated in any suitable manner into one or more examples or instances.

[0112] Although exemplary embodiments have been provided for the explanation, those skilled in the art should understand that the embodiments described above should not be construed as limiting the present application, and that embodiments can be modified, substituted, or altered without departing from the spirit, principles, and scope of the invention.

Claims

1. An electrochemical apparatus comprising a negative electrode, a positive electrode, and an electrolyte, The positive electrode comprises a current collector and a positive electrode active material layer located on the current collector, and the positive electrode active material layer comprises a positive electrode active material. The electrolyte contains additive A, and additive A is LiPO ２ F ２ Includes, The active specific surface area of ​​the positive electrode is X m ２ Let / g be used, and the LiPO is used relative to the weight of the electrolyte. ２ F ２ When the weight percentage of is Y%, then X and Y satisfy 0.005 ≤ X / Y ≤ 2. The electrolyte further contains additive B, The additive B is at least one selected from the group consisting of lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, B4Li2O7, Li3BO3, CF3LiO3S, lithium hexafluorophosphate, and lithium perchlorate. The additive B is present in an amount of 0.01% to 16% by weight relative to the weight of the electrolyte. An electrochemical apparatus in which the positive electrode active material is at least one selected from the group consisting of lithium iron phosphate and lithium iron manganese phosphate.

2. (i) The above X satisfies 0.01 ≤ X ≤ 0.1, (ii) The above Y satisfies 0.01 ≤ Y ≤ 2, (iii) The above X and Y satisfy 0.005 ≤ X / Y ≤ 1, The electrochemical apparatus according to claim 1, satisfying at least one of the following conditions.

3. The electrolyte further comprises vinylene carbonate, The electrochemical apparatus according to claim 1, wherein when the weight percentage of vinylene carbonate relative to the weight of the electrolyte is Z%, Z is 0.01 to 6.

4. The electrochemical apparatus according to claim 3, wherein Z / Y is 0.01 to 600.

5. The electrolyte further contains fluoroethylene carbonate, The electrochemical apparatus according to claim 1, wherein the fluoroethylene carbonate is present in an amount of 0.01% to 5% by weight relative to the weight of the electrolyte.

6. The positive electrode active material contains element M, The electrochemical apparatus according to claim 1, wherein the aforementioned M element is at least one selected from the group consisting of Fe, Mn, Al, Ca, K, Na, Mg, Ti, and Zn.

7. The electrochemical apparatus according to claim 3, wherein when the weight of the vinylene carbonate is W1 g and the weight of the negative electrode is W2 g, W1 / W2 is 0.001 to 0.

031.

8. The electrolyte further comprises an S=O functional group-containing compound, The S=O functional group-containing compound is at least one selected from the group consisting of 1,3-propanesultone, ethylene sulfate, methylenemethane disulfonate, propensultone, 4-methyl-1,3,2-dioxathiolan-2,2-dioxide, 1,4-butanesultone, and 1,2,6-oxadithian-2,2,6,6-tetraoxide, and / or The electrochemical apparatus according to claim 1, wherein the S=O functional group-containing compound is present in an amount of 0.01% to 5% by weight relative to the weight of the electrolyte.

9. An electronic apparatus comprising an electrochemical apparatus as described in any one of claims 1 to 8.

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