Electrochemical device and electronic device including the electrochemical device

Abstract

The present invention relates to an electrochemical device, the electrochemical device includes a positive electrode sheet, a negative electrode sheet, and an electrolytic solution, the negative electrode sheet includes a negative electrode active material layer, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material layer includes an aluminum element, and the content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m 2 ) satisfy 3 ≤ A / B ≤ 25, and the positive electrode active material includes lithium manganate and a manganese-containing compound.

Description

Technical Field

[0001] The present invention relates to the field of energy storage, and more specifically, to an electrochemical device and an electronic device including the electrochemical device.

Background Art

[0002] Electrochemical devices such as lithium-ion batteries have advantages such as being lightweight and having a high energy density, so their market share has been increasing year by year. With the rapid development of new energy vehicles and the energy storage field, higher charge and discharge capacities are required for cathode active materials such as lithium manganate, and better cycle characteristics and storage characteristics are also required for electrochemical devices.

Summary of the Invention

[0003] According to one aspect of the present invention, the present invention relates to an electrochemical device, the electrochemical device includes a positive electrode sheet, a negative electrode sheet, and an electrolytic solution, the negative electrode sheet includes a negative electrode active material layer, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material layer includes an aluminum element, and the content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m 2 ) satisfy 3 ≦ A / B ≦ 25, and the positive electrode active material includes lithium manganate and a manganese-containing compound. The aluminum element can stabilize the crystal structure, improve the stability of the unit cell during the insertion or desorption of lithium ions, make the structure of the positive electrode active material more stable, and improve the cycle characteristics of the electrochemical device. The manganese-containing compound has a relatively low voltage plateau, can replenish the lithium ions consumed by the CEI film during the first charge of lithium manganate, provides a diffusion path for lithium ions, facilitates the insertion and rapid desorption of lithium ions, and is advantageous for the slow reinsertion of lithium ions during cycling and storage, and can increase the charge and discharge capacity of the positive electrode active material. The content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m 2) When the above relational expression is satisfied, the structures of lithium manganate and the manganese-containing compound can be made more stable, the synergistic effect between lithium manganate and the manganese-containing compound can be exerted, and the cycle characteristics and high-temperature storage characteristics of the electrochemical device can be significantly improved.

[0004] In some embodiments, the content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m 2 ) of the negative electrode active material layer satisfy 8 ≤ A / B ≤ 23.

[0005] In some embodiments, the mass fraction of the manganese-containing compound is 3% - 20% based on the mass of the positive electrode active material.

[0006] In some embodiments, A is in the range of 0.005 - 0.04.

[0007] In some embodiments, A is in the range of 0.01 - 0.035.

[0008] In some embodiments, when the average particle diameter of the lithium manganate is C μm and the average particle diameter of the manganese-containing compound is D μm, C and D satisfy 1 ≤ D / C ≤ 15.

[0009] In some embodiments, the manganese-containing compound satisfies at least one of the following conditions. (1) The Dv50 of the manganese-containing compound is 5 μm - 40 μm. (2) The surface of the manganese-containing compound has steps with a width of 1 nm - 1000 nm.

[0010] In some embodiments, the tap density of the positive electrode active material is 1.5 g / cm 3 ~2.5 g / cm 3 .

[0011] In some embodiments, the positive electrode active material layer contains Nb, Mg, Ti, Ce, W, Ga, Zr 、YIt further contains at least one of V, Na, Sr, Mo, Cr, Sn, and La.

[0012] In some embodiments, the Nb, Mg, Ti, Ce, W, Ga, Zr 、Y The mass fraction M of V, Na, Sr, Mo, Cr, Sn, or La is 0.01% to 3.5% with respect to the mass of the positive electrode active material layer.

[0013] In some embodiments, the negative electrode active material layer contains a negative electrode active material, the negative electrode active material contains graphite, and the d(002) of the graphite is 3.363 ± 0.004 Å.

[0014] In some embodiments, at least one of the following conditions is satisfied. (1) The OI value of the graphite is 4 ± 1. (2) The porosity of the negative electrode active material layer is 25 ± 5%. (3) The compression density of the negative electrode sheet is 1.3 g / cm 3 ~1.8 g / cm 3 is.

[0015] In some embodiments, the compression density of the positive electrode sheet is 2.2 g / cm 3 ~2.8 g / cm 3 is.

[0016] According to another aspect of the present invention, the present invention relates to an electronic device including the electrochemical device described in any of the foregoing embodiments.

[0017] In the present invention, the positive electrode active material layer contains aluminum element, and the content A (mmol) of aluminum element in the positive electrode active material layer and the total area B (m 2) satisfies 3 ≦ A / B ≦ 25, and the positive electrode active material contains lithium manganate and manganese-containing compounds. The aluminum element can make the structure of the positive electrode active material more stable. The manganese-containing compound can supplement the lithium ions consumed by lithium manganate to form the CEI film during the first charge, provide a diffusion path for lithium ions, and increase the charge-discharge capacity of the positive electrode active material. The content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m 2 ) When the above relational expression is satisfied, the structures of lithium manganate and the manganese-containing compound can be made more stable, the synergistic effect of lithium manganate and the manganese-containing compound can be exerted, and the cycle characteristics and high-temperature storage characteristics of the electrochemical device can be significantly improved. Therefore, the electrochemical device of the present invention and the electronic device including the same can simultaneously have significantly improved cycle characteristics and high-temperature storage characteristics. Significantly improve the cycle characteristics and high-temperature storage characteristics of the electrochemical device.

Brief Description of the Drawings

[0018]

Figure 1(a)

Figure 1(b)

Embodiments for Carrying out the Invention

[0019] Hereinafter, the present invention will be described in detail. The terms used in the specification and the appended claims are not limited to the general meaning and the dictionary meaning, but should be understood to be interpreted based on the meaning and concept corresponding to the technical aspects of the present invention according to the principle that the inventor is permitted to appropriately define the terms for the optimal interpretation. Therefore, the description shown in the embodiments described in the specification is merely a specific example for the purpose of explanation and is not intended to show all the technical aspects of the present invention. Also, it should be understood that when submitting the present invention, equivalents and variants of multiple options can be completed.

[0020] In specific embodiments and claims, a list of items connected by the terms "one of", "one of", "one type of", or other similar terms means any one of the listed items. For example, if item A and item B are listed, the phrase "one of A and B" means only A or only B. In other examples, if item A, item B, and item C are listed, the phrase "one of A, B, and C" means only A, only B, or only C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0021] In specific embodiments and claims, a list of items connected by the terms "at least one of", "at least one of", "at least one type of", or other similar terms means any combination of the listed items. For example, if item A and item B are listed, the phrase "at least one of A and B" means only A, only B, or A and B. In other examples, if item A, item B, and item C are listed, 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, C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0022] In addition, 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. It should also be understood that it is to be read flexibly so as to include not only the numerical values explicitly specified as range limitations, but also all individual numerical values or sub-ranges included within the range that explicitly specify each numerical value and sub-range. I. Electrochemical device

[0023] According to one aspect of the present invention, the present invention relates to an electrochemical device, the electrochemical device including a positive electrode sheet, a negative electrode sheet, and an electrolytic solution, the negative electrode sheet including a negative electrode active material layer, the positive electrode sheet including a positive electrode active material layer, the positive electrode active material layer including a positive electrode active material, the positive electrode active material layer including an aluminum element, and the content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m 2 ) satisfy 3 ≦ A / B ≦ 25, and the positive electrode active material includes lithium manganate and manganese-containing compounds. Manganese-containing compounds can replenish lithium ions consumed when lithium manganate forms a positive electrode-electrolyte interface (CEI) during the first charge, are advantageous for improving the cycle characteristics and high-temperature storage characteristics of the electrochemical device, can provide a diffusion path for lithium ions, facilitate the insertion and rapid desorption of lithium ions, and have a relatively low voltage plateau (for example, a plateau of 3.9 V). They are advantageous for the slow reinsertion of lithium ions during the charge and discharge of the positive electrode active material, can increase the charge and discharge capacity of the positive electrode active material, and can significantly improve the cycle characteristics and high-temperature storage characteristics of the electrochemical device. At the same time, the aluminum element can improve the stability of the unit cell during the insertion or desorption of lithium ions, make the crystal structure more stable, enhance the structural stability of the positive electrode active material, and improve the cycle characteristics of the electrochemical device. However, if the content of the aluminum element is too high, the amount of desorbed lithium decreases and the reversible capacity decreases. Therefore, the content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m 2) is limited to satisfy 3 ≦ A / B ≦ 25. The manganese-containing compound can replenish the lithium ions consumed by lithium manganate to form the CEI film during the first charge, provide a diffusion path for lithium ions, and increase the charge-discharge capacity of the positive electrode active material. The content A (mmol) of aluminum element in the positive electrode active material layer and the total area B (m 2 ) When the above relational expression is satisfied, the structures of lithium manganate and the manganese-containing compound can be made more stable, the synergistic effect of lithium manganate and the manganese-containing compound can be exerted, and the cycle characteristics and high-temperature storage characteristics of the electrochemical device can be significantly improved. In some embodiments, the content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m 2 ) satisfies 8 ≦ A / B ≦ 23. In this case, the aluminum element can more effectively stabilize the structures of lithium manganate and the manganese-containing compound, and further improve the cycle characteristics and high-temperature storage characteristics of the electrochemical device.

[0024] In some embodiments, the A is in the range of 0.005 to 0.04. The aluminum element can improve the stability of the unit cell during the insertion or desorption of lithium ions, make the crystal structure more stable, enhance the structural stability of the positive electrode active material, and improve the cycle characteristics of the electrochemical device. However, if the content of the aluminum element is too low, the improvement effect is limited. If the content of the aluminum element is too high, the amount of desorbed lithium decreases and the reversible capacity decreases. Therefore, it is limited that the content of the aluminum element in the positive electrode active material layer is in the range of 0.005 mmol to 0.04 mmol, and the cycle characteristics of the electrochemical device can be further improved. In some embodiments, the A is in the range of 0.01 to 0.035. When the aluminum element content is within this range, the positive electrode active material has a more stable crystal structure and can endow the electrochemical device with better cycle characteristics.

[0025] In some embodiments, the mass fraction of the manganese-containing compound is 3% to 20% based on the mass of the positive electrode active material. In some embodiments, the mass fraction of the manganese-containing compound is 3%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, or 20% based on the mass of the positive electrode active material, or within the range consisting of any two of the above numerical values.

[0026] If the content of the manganese-containing compound is too low, the capacity per gram of the first charge of the electrochemical device manufactured therefrom will decrease. If the content of the manganese-containing compound is too high, the first Coulomb efficiency of the electrochemical device manufactured therefrom will decrease. This is mainly because the manganese-containing compound has a relatively high capacity per gram of the first charge, and lithium manganese oxide can supplement the Li+ consumed for forming the CEI film during the first charge, but during the first discharge, only a part of Li can be reinserted into the manganese-containing compound. According to research, when the content of the manganese-containing compound is limited within the above range, both the capacity per gram of the first charge and the first Coulomb efficiency of the electrochemical device are significantly improved.

[0027] In some embodiments, the manganese-containing compound has a layered structure. In some embodiments, the manganese-containing compound contains one or more of LiMn2O3, Li2MnO3, and LiNi 0.5 Mn 0.5 O2.

[0028] In some embodiments, when the average particle size of the lithium manganese oxide is C μm and the average particle size of the manganese-containing compound is D μm, C and D satisfy 1 ≦ D / C ≦ 15. In some embodiments, C and D satisfy 5 ≦ D / C ≦ 10.

[0029] In some embodiments, the manganese-containing compound satisfies at least one of the following conditions: (1) The Dv50 of the manganese-containing compound is 5 μm to 40 μm. (2) The surface of the manganese-containing compound has steps with a width of 1 nm to 1000 nm. In some embodiments, the compression density of the positive electrode sheet is 2.2 g / cm 3 ~2.8 g / cm 3 . In some embodiments, the tap density of the positive electrode active material is 1.5 g / cm 3 ~2.5 g / cm 3 .

[0030] Referring to FIGS. 1(a) and 1(b). The large particles are particles of the manganese-containing compound, which has a layered structure and has step-by-step steps on the surface, where the width of the steps is 1 nm to 1000 nm. By adding the layered manganese-containing compound to the positive electrode active material, the capacity, rate characteristics, high-temperature storage, and cycle characteristics of the electrochemical device were all significantly improved. This is mainly because the layered manganese-containing compound can replenish the lithium ions consumed in forming the CEI during the first charge of the electrochemical device, is advantageous for improving the cycle and storage characteristics of the electrochemical device, and at the same time can provide a diffusion path for lithium ions, facilitating the insertion and rapid desorption of lithium ions. Moreover, it has a relatively low voltage plateau (for example, a plateau of 3.9 V), which is advantageous for the slow reinsertion of lithium ions during cycling and storage, and can increase the charge and discharge capacity of the positive electrode active material.

[0031] On one hand, between the particles of the manganese-containing compound and the particles of lithium manganate, they match each other, increasing the compression density, improving the contact between particles, increasing the diffusion path of active ions, enhancing the cycle characteristics of the electrochemical device, and enhancing the infiltration of the electrolyte. The smaller the average particle diameter of the lithium manganate particles, the larger the specific surface area of the material, the more serious the elution of manganese, thereby destroying the cathode structure and deteriorating the cycle characteristics of the electrochemical device. The smaller the particle diameter of the manganese-containing compound, the larger the active surface area exposed with the same usage amount, and the more remarkable the effect of improving the initial charge capacity. Moreover, the smaller the particle diameter of the manganese-containing compound, the shorter the diffusion path of lithium ions, which is beneficial to the insertion and desorption of lithium ions and is beneficial to the improvement of the capacity and cycle of the material. By limiting D / C within the above range, ideal device performance can be obtained.

[0032] In some embodiments, the positive electrode active material layer further contains at least one of Nb, Mg, Ti, Ce, W, Ga, Zr 、Y and at least one of V, Na, Sr, Mo, Cr, Sn, and La. In some embodiments, the mass fraction M of Nb, Mg, Ti, Ce, W, Ga, Zr 、 Y, V, Na, Sr, Mo, Cr, Sn, or La is 0.01% to 3.5% with respect to the mass of the positive electrode active material layer. In some embodiments, the mass fraction M is 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, or 3.5% with respect to the mass of the positive electrode active material, or within the range composed of any two of the above numerical values. When the mass fraction M is within the above range, the above elements can stabilize the structure of the positive electrode active material, facilitate the diffusion of lithium ions, reduce the phase transition of the material, suppress the elution of transition metals, and improve the cycle characteristics and high-temperature storage characteristics of the electrochemical device. However, if the content of the above elements is too high, the lattice inside the positive electrode active material will expand, the structural stability of the material will be destroyed, and the cycle characteristics of the electrochemical device will be affected.

[0033] In some embodiments, the negative electrode active material layer contains a negative electrode active material, the negative electrode active material contains graphite, and the d(002) of the graphite is 3.363 ± 0.004 Å. Graphite that satisfies this condition has a good degree of graphitization. The better the degree of graphitization, the higher the crystallinity of the graphite, the denser the internal structure, the higher the initial Coulomb efficiency of the graphite, and when combined with the positive electrode active material having a higher charge capacity, the electrochemical device is provided with a high discharge capacity.

[0034] In some embodiments, the OI value of the graphite is 4 ± 1. The smaller the OI value, the better the isotropy of the graphite, which is advantageous for improving the solid-phase diffusion of Li+, thereby reducing the charge transfer resistance of the electrochemical device, improving the kinetics of the graphite, and thereby enhancing the cycle characteristics of the electrochemical device. In some embodiments, the OI value of the graphite is 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, or 11.5, or within the range consisting of any two of the above numerical values.

[0035] The graphite described in the present invention has a higher surface crystallinity, fewer surface defects, is advantageous for the diffusion of lithium ions, and at the same time, the graphite has a single-particle structure and relatively good kinetics. Due to the synergistic effect of the two, the charge transfer resistance (Rct) of the negative electrode sheet is significantly reduced.

[0036] In some embodiments, the porosity of the negative electrode active material layer is 25 ± 5%. When the porosity of the negative electrode active material layer exceeds the above range, a large amount of electrolyte is consumed during the formation of the SEI film, the initial Coulomb efficiency of the electrochemical device decreases, and the cycle characteristics of the electrochemical device are affected due to the consumption of the electrolyte.

[0037] In some embodiments, the compression density of the negative electrode sheet is 1.3 g / cm 3 ~1.8 g / cm 3That is. When the compression density is within this range, the particles have an appropriate effective active area, there is no breakage on the particle surface, which is advantageous for improving the initial Coulomb efficiency of graphite and the discharge capacity of the battery. At the same time, an appropriate compression density is advantageous for better infiltration of the electrolyte and improvement of kinetics, thereby improving the cycle characteristics of the electrochemical device.

[0038] According to another aspect of the present invention, the present invention relates to an electronic device including the electrochemical device described in any of the foregoing embodiments. II. Preparation method of the electrochemical device

[0039] Hereinafter, taking a lithium-ion battery as an example, the preparation method of the electrochemical device of the present invention will be described in detail.

[0040] Preparation of the negative electrode: The negative electrode active material, conductive agent, binder, and thickener are dispersed in a solvent system at a certain mass ratio, stirred sufficiently, and uniformly mixed, and then coated on the negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0041] For example, the negative electrode active material may be one or more of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate Li4Ti5O with a spinel structure 12 , Li-Al alloy, and metallic lithium. The conductive agent may be one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber. The binder may be one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethyl cellulose (CMC). The thickener may be carboxymethyl cellulose (CMC).

[0042] The negative electrode current collector may be made of materials such as metal foil or porous metal plate. For example, it may be made of foil materials or porous plates of metals such as copper, nickel, titanium, or iron, or their alloys. For example, copper foil may be used.

[0043] Preparation of the positive electrode: Preparation of the manganese-containing compound in the positive electrode active material: a) MnOOH Put it into a corundum crucible, heat it up to 500 °C at a heating rate of 5 °C / min under an air atmosphere, maintain the constant temperature for 1 h to obtain anhydrous Mn3O4.

[0044] b) Weigh anhydrous Mn3O4 and LiOH in a molar ratio of Li:Mn of 1.05:1, mix them for 8 h using a mixing device, and add nano-Al2O3 in a molar ratio of Al:Mn of 0.08:1 to obtain a mixture precursor.

[0045] c) Put the mixture precursor into a corundum crucible, pass nitrogen gas through it at a rate of 2 m 3 / h, heat it up to 940 °C at a heating rate of 5 °C / min, maintain the constant temperature for 10 h, and let it cool naturally to room temperature to obtain the manganese-containing compound.

[0046] Mix the positive electrode active material (lithium manganese oxide (LiMn2O4)), the above manganese-containing compound, a conductive agent, and a binder in a certain weight ratio, add them to a solvent, stir evenly to obtain a slurry. Coat the slurry evenly on an aluminum foil which is the positive electrode current collector, and dry it under the condition of 90 °C to obtain an initial positive electrode sheet. The initial positive electrode sheet goes through processes such as cold pressing and cutting to obtain the positive electrode sheet.

[0047] In some embodiments, the conductive agent improves the conductivity of the positive electrode active material layer by providing a conductive path to the active material. The conductive agent can include at least one of acetylene black, ketjen black, natural graphite, carbon black, carbon fiber, metal powder, and metal fiber (such as copper, nickel, aluminum or silver), but the examples of the conductive agent are not limited thereto. In some embodiments, the amount of the conductive agent can be appropriately adjusted. The range of the amount of the conductive agent is 1 to 30 parts by weight based on 100 parts by weight in total of the positive electrode active material, the conductive agent, and the positive electrode binder.

[0048] In some embodiments, examples of the solvent include, but are not limited to, N-methylpyrrolidone, acetone, or water. In some embodiments, the amount of the solvent can be appropriately adjusted.

[0049] In some embodiments, the binder improves the adhesion characteristics between the positive electrode active material particles and the adhesion characteristics between the positive electrode active material particles and the current collector. Examples of the positive electrode binder may be one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), and polyvinyl alcohol (PVA), but are not limited thereto. The range of the amount of the positive electrode binder is 1 to 30 parts by weight based on 100 parts by weight in total of the active material, the conductive agent, and the positive electrode binder.

[0050] In some embodiments, the current collector has a thickness in the range of 3 μm to 20 μm, but the present invention is not limited thereto. The current collector is conductive and does not cause chemical changes that are disadvantageous to the manufactured battery. Examples of the current collector include, but are not limited to, copper, stainless steel, aluminum, nickel, titanium, or alloys (e.g., copper-nickel alloy). In some embodiments, the surface of the current collector may include fine irregularities (e.g., surface roughness) for enhancing the adhesion of the active material on the surface of the current collector. In some embodiments, the current collector can be used in various forms, and examples thereof include films, sheets, foils, meshes, porous structures, foams, or non-woven fabrics, but the present invention is not limited thereto.

[0051] Separator: The embodiments of the present invention have no particular limitation on the separator, and the separator includes a polyolefin microporous membrane and a coating (applied to the surface of the polyethylene microporous membrane). The separator is a single-layer or multi-layer polyolefin microporous membrane composed of one or more selected from polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-methyl methacrylate copolymer. The coating contains inorganic ceramic particles, and the inorganic ceramic particles are one or more selected from SiO2, Al2O3, CaO, TiO2, ZnO2, MgO, ZrO2, and SnO2.

[0052] Electrolyte: According to an embodiment of the present invention, the electrolyte contains a non-aqueous organic solvent and a lithium salt. The non-aqueous organic solvent may include a carbonate ester, a carboxylic acid ester, an ether compound, a sulfone compound, or other aprotic solvents. Examples of the carbonate ester solvent include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, di(2,2,2-trifluoroethyl) carbonate, and the like. Examples of the ether compound solvent include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, bis(2,2,2-trifluoroethyl) ether, 1,3-dioxane, 1,4-dioxane, and the like. Examples of the sulfone compound solvent include ethyl vinyl sulfone, methyl isopropyl sulfone, isopropyl-sec-butyl sulfone, sulfolane, and the like.

[0053] According to an embodiment of the present invention, the non-aqueous organic solvent in the electrolyte may be a single non-aqueous organic solvent, or a plurality of non-aqueous organic solvents may be mixed. When a mixed solvent is used, the mixing ratio can be controlled according to the desired performance of the electrochemical device.

[0054] According to an embodiment of the present invention, the lithium salt in the electrolyte contains at least one of an organic lithium salt and an inorganic lithium salt, or is at least one selected from an organic lithium salt and an inorganic lithium salt. The lithium salt is lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB), lithium difluoro(oxalate)borate (LiBF2(C2O4), LiDFOB), lithium hexafluoroantimonate (LiSbF6), lithium hexafluoroarsenate (LiAsF6), lithium perfluorobutanesulfonate (LiC4F9SO3), lithium perchlorate (LiClO4), lithium aluminate (LiAlO2), lithium tetrachloroaluminate (LiAlCl4), lithium bis( fluoro sulfonyl)imide (LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), where x and y are natural numbers), lithium chloride (LiCl), lithium fluoride (LiF), or at least one selected from the above substances.

[0055] Preparation of electrolyte: In a glove box with an argon atmosphere having a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), and propyl propionate (PP) are uniformly mixed at a mass ratio of 1:1:1:1:1, and then a sufficiently dried lithium salt LiPF 6 is dissolved in the above non-aqueous solvent to obtain a base electrolyte. Here, LiPF the mass fraction of 6 is 12.5%.

[0056] The positive electrode, separator, and negative electrode are stacked in order, with the separator positioned between the positive electrode and the negative electrode to play a role in isolation, and then wound to obtain a bare cell. The obtained bare cell is placed in an outer package, injected with the electrolyte and encapsulated, and then subjected to processes such as formation, degassing, and insulation cutting to obtain a lithium-ion battery.

[0057] III. Electronic Device The present invention provides an electronic device including the electrochemical device described in the above content.

[0058] According to some embodiments of the present invention, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an e-book player, a mobile phone, a portable facsimile, a portable copier, a portable printer, a stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disk, a transceiver, an electronic organizer, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an assist bicycle, a bicycle, a lighting fixture, a toy, a game machine, a clock, a power tool, a strobe, a camera, a large household battery, etc.

[0059] IV. Specific Embodiments Hereinafter, the present invention will be described in more detail by taking a lithium-ion battery as an example. However, it should be understood that the following examples are merely examples and the embodiments of the present invention are not limited thereto.

[0060] Performance Measurement Method Measurement Method for Particle Morphology and Particle Size Particle Morphology: Using a scanning electron microscope (JSM-6360LV type manufactured by JEOL), an SEM photograph of the positive electrode sheet obtained by disassembling the lithium-ion battery was taken, and the morphology of the positive electrode active material particles was observed.

[0061] Measurement of Average Particle Size of Particles: An SEM photograph of the positive electrode sheet obtained by disassembling the lithium-ion battery was taken using a scanning electron microscope, the positive electrode active material particles were observed, and then 30 particles were randomly selected from the SEM photograph using image analysis software. The area of each of these particles was determined. Next, assuming that the particles are spherical, the particle diameter D (diameter) of each particle was determined by the following formula. D = 2×(S1 / π) 1 / 2 . Here, S1 is the area of the particle, and the particle diameters of the obtained 30 particles were arithmetically averaged to obtain the average particle size of the particles.

[0062] Method for measuring compression density The lithium-ion battery was disassembled to obtain a positive electrode sheet (double-sided coating). A small circular piece with an area of 1540.25 mm 2 was cut from the region of the positive electrode active material layer of the positive electrode sheet, and its weight m1 and thickness d1 were measured. A small circular piece with an area of 1540.25 mm 2 was also cut from the blank region of the current collector of the positive electrode sheet, and its weight m0 and thickness d0 were measured. Compression density = (m1 - m0) / 2 / 1540.25 / ((d1 - d0) / 2).

[0063] Method for measuring element content The lithium-ion battery was disassembled to obtain a positive electrode sheet. The positive electrode sheet was washed with DMC. The positive electrode active material layer of the washed positive electrode sheet was scraped off with a doctor blade and dissolved in a mixed solvent (for example, for 0.4 g of the positive electrode active material layer, a mixed solvent of 10 mL of aqua regia (a mixture of nitric acid and hydrochloric acid in a ratio of 1:1) and 2 mL of HF was used), and after volume was fixed to 100 mL, the mass fraction of Nb, Mg, Ti, Ce, W, Ga, Zr 、Y , V, Na, Sr, Mo, Cr, Sn or La in the solution was measured using an ICP (Inductively coupled plasma) analyzer.

[0064] Method for measuring interplanar spacing and OI value of crystal X-ray diffraction analysis was performed on graphite powder.

[0065] Instrument model number: Bruker D8 ADVANCE, Target: Cu Kα, Scanning angle: 5 - 80°.

[0066] Measurement of the capacity of the lithium-ion battery. The capacity per gram (mAh g -1 ) of the first charge and discharge under the conditions of 25°C and 0.2C Four lithium-ion batteries prepared using the cathode materials shown in the Examples and Comparative Examples were taken as a set, and under the constant temperature condition of 25°C, first, constant current charging was performed at a current of 0.5C (i.e., the current value when the theoretical capacity is completely discharged within 2 h). After charging to 4.2V, constant voltage charging was performed. Then, constant current discharging was performed at a current of 0.2C until discharging to 2.8V, and the initial discharge capacity at 0.2C was calculated as the capacity of the battery. Initial Coulomb efficiency = Initial discharge capacity / Initial charge capacity

[0067] Measurement of cycle characteristics of lithium-ion batteries Four lithium-ion batteries prepared using the cathode materials shown in the Examples and Comparative Examples were taken as a set, and charging and discharging were repeatedly performed on the four lithium-ion batteries respectively according to the following procedure, and the discharge capacity retention rate of the battery was calculated.

[0068] First, the first charge and discharge were performed in an environment of 25 / 45°C respectively. First, constant current charging was performed at a current of 0.5C. After charging to 4.2V, constant voltage charging was performed. Then, constant current discharging was performed at a current of 1C until discharging to 2.8V, and the discharge capacity of the first cycle was recorded. Then, 1500 / 400 cycles of charge and discharge were performed, and the discharge capacity of the 500 / 400 nth cycle was recorded.

[0069] 25°C cycle capacity retention rate = (Discharge capacity of the 1500th cycle / Discharge capacity of the first cycle) × 100%.

[0070] 45°C cycle capacity retention rate = (Discharge capacity of the 400th cycle / Discharge capacity of the first cycle) × 100%.

[0071] Measurement of high-temperature storage of lithium-ion batteries Four lithium-ion batteries prepared using the cathode materials shown in the examples and comparative examples were taken as a set, four at a time, and in an environment of 60°C, first, constant current charging was performed at a current of 0.5C until charging reached 4.2V, then constant voltage charging was performed. After that, constant current discharging was performed at a current of 1C until discharging reached 2.8V, and the discharge capacity was recorded as the capacity before storage. Charging was performed at a constant current of 0.5C until 3.99V, and then constant voltage charging was performed until the current was less than 0.05C. After storing the battery in an oven at 60°C for 14D, constant current discharging was performed at a discharge current of 1C until discharging reached 2.8V. Then, constant current charging and constant voltage charging were performed at a charging current of 0.5C until the upper limit voltage reached 4.2V. After that, constant current discharging was performed at a discharge current of 1C until discharging reached 2.8V, and the discharge capacity was recorded as the capacity after storage.

[0072] Retention rate of capacity after high-temperature storage at 60°C = Capacity after storage / Capacity before storage × 100%.

[0073] A. Examples 1-1 to 1-5 and Comparative Examples 1 to 2 Preparation method of Example 1-1: Cathode: Step (1) - Preparation of manganese-containing compound: a) MnOOH was placed in a corundum crucible and heated to 500°C at a heating rate of 5°C / min under an air atmosphere, and the constant temperature was maintained for 1 h to obtain anhydrous Mn3O4.

[0074] b) Anhydrous Mn3O4 and LiOH were weighed at a molar ratio of Li:Mn of 1.05:1, and nano-Al2O3 was added at a molar content of aluminum element of 0.014 mmol, and nano-Cr2O3 was added at an elemental mass ratio of Cr:Mn of 0.213:1. The above substances were uniformly mixed using a sand mill equipment and mixed for 8 h using a mixing equipment to obtain a mixture precursor.

[0075] c) The mixture precursor was placed in a corundum crucible at a speed of 2m 3Nitrogen gas was passed through at a flow rate of / h, the temperature was raised to 940 °C at a rate of 5 °C / min, held at a constant temperature for 10 h, and then naturally cooled to room temperature to obtain a manganese-containing compound. Here, the surface of the manganese-containing compound particles had a step with a width of 600 nm to 700 nm, and its Dv50 was 19.3 μm.

[0076] Step (2): The manganese-containing compound prepared in step (1), lithium manganate, conductive carbon black (Super P), carbon nanotubes (CNT), and polyvinylidene fluoride (PVDF) were mixed at a weight ratio of 90:5:1.8:1.2:2, N-methylpyrrolidone (NMP) was added as a solvent, and formulated into a slurry with a solid content of 0.75, and uniformly stirred to obtain a slurry. The slurry was uniformly coated on both sides of an aluminum foil which is a positive electrode current collector, and dried under the condition of 90 °C to obtain an initial positive electrode sheet. The initial positive electrode sheet was subjected to processes such as cold pressing and cutting to obtain a positive electrode sheet.

[0077] Negative electrode: Graphite as the negative electrode active material, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed at a weight ratio of 97:1.0:2.0, N-methylpyrrolidone (NMP) was added as a solvent, and formulated into a slurry with a solid content of 0.8, and uniformly stirred. The slurry was uniformly coated on a copper foil which is a negative electrode current collector, and dried under the condition of 80 °C to obtain an initial negative electrode sheet. The initial negative electrode sheet was subjected to processes such as cold pressing and cutting to obtain a negative electrode sheet.

[0078] Electrolyte: In a glove box with an argon atmosphere having a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), and propyl propionate (PP) were uniformly mixed at a mass ratio of 1:1:1:1:1, and a further sufficiently dried lithium salt LiPF 6 was dissolved in the above non-aqueous solvent to obtain a base electrolyte. Here, LiPF The mass fraction of 6 was 12.5 wt%.

[0079] Separator: A PE porous polymer film was used as the separator.

[0080] The positive electrode, separator, and negative electrode were stacked in order, with the separator positioned between the positive electrode and the negative electrode to play a role of isolation, wound, placed in an outer package, and encapsulated by injecting the formulated electrolyte, and a lithium battery was obtained through processes such as formation, degassing, and insulation cutting.

[0081] The differences between Examples 1-2 to 1-5 and Example 1-1 are only the differences in the content of the manganese-containing compound (here, the adjustment of the content of the manganese-containing compound was carried out based on the total weight fraction of the manganese-containing compound and lithium manganate being 95%). The difference between Example 1-6 and Example 1-1 is the difference in the content of the manganese-containing compound and the difference in the graphite used for the negative electrode. The graphite in Example 1-6 is graphite with a low initial Coulombic efficiency (its d (0 02) = 3.3710, OI value = 12.3). The difference between Comparative Example 1 and Example 1-1 is that the positive electrode active material in Comparative Example 1 has only lithium manganate and does not have a manganese-containing compound, and the aluminum element content in the positive electrode active material layer of Comparative Example 1 is 0.008 mmol. Here, in Table 1, the average particle size of the manganese-containing compound is 18.9 μm, and the average particle size of lithium manganate is 2.7 μm. Examples 1-1 to 1-6 are different from the aluminum element content in the positive electrode active material layer in Comparative Examples 1 and 2. With the increase in the content of the manganese-containing compound, the aluminum element content in the active material layer per unit area increased. Specifically, referring to the following Table 1, Table 1 shows the differences in the composition and performance of the lithium-ion batteries of Examples 1-1 to 1-5 and Comparative Examples 1 and 2.

[0082]

Table 1

[0083] Referring to Table 1, compared with Comparative Example 1 in which the positive electrode active material contains only lithium manganate, the lithium-ion batteries of Examples 1-1 to 1-6 in which the positive electrode active material contains lithium manganate and a manganese-containing compound have an initial chargeThe capacity per gram of discharge and the capacity retention rate after 1500 cycles at 25°C were both significantly improved, and it was found that the battery still had a relatively high initial Coulomb efficiency. The manganese-containing compound can replenish the lithium ions consumed by lithium manganate to form the cathode-electrolyte interface (CEI) during the first charge, which is advantageous for improving the cycle characteristics and high-temperature storage characteristics of the lithium-ion battery. It can provide a diffusion path for lithium ions, facilitate the insertion and rapid desorption of lithium ions, and has a relatively low voltage plateau (a plateau at 3.9 V). During the cycle and storage of the lithium-ion battery, it is advantageous for the slow reinsertion of lithium ions, can increase the charge-discharge capacity of the cathode active material, and can significantly improve the cycle characteristics and high-temperature storage characteristics of the lithium-ion battery. However, during the first discharge, only a part of the Li can be reinserted in the manganese-containing compound, which affects the Coulomb efficiency of the lithium-ion battery. The aluminum element stabilizes the crystal structure, improves the stability of the unit cell during the insertion or desorption of lithium ions, makes the structure of the cathode active material more stable, improves the cycle characteristics of the electrochemical device, and when the content A (mmol) of the aluminum element in the cathode active material layer and the total area B (m 2 ) satisfy 3 ≦ A / B ≦ 25, the lithium-ion battery can obtain better cycle characteristics and high-temperature storage characteristics.

[0084] B. Example 1-1 and Examples 2-1 to 2-8 The difference between Examples 2-1 to 2-8 and Example 1-1 is only the difference in the graphite used in the negative electrodes of Examples 2-1 to 2-8. Table 2 below shows the compositional differences and performance of the lithium-ion batteries of Example 1-1 and Examples 2-1 to 2-8.

[0085]

Table 2

[0086] Referring to Table 2, it was found that as the graphitization temperature increases, d(002) decreases, and the higher the graphitization degree, the higher the initial Coulomb efficiency and the initial discharge capacity of the lithium-ion battery prepared thereby. However, if the temperature is too high, the cost increases and the increase in performance is limited. According to research, when the d(002) of graphite is 3.363 ± 0.004 Å, the graphitization degree of graphite is good, the crystallinity of graphite is high, the internal structure is dense, and the initial Coulomb efficiency of graphite is high. When combined with the positive electrode active material having a higher charge capacity, the lithium-ion battery has a higher discharge capacity.

[0087] C. Example 1-1 and Examples 3-1 to 3-4 The difference between Examples 3-1 to 3-4 and Example 1-1 is only the difference in the OI value of graphite.

[0088] Table 3 below shows the differences in the composition and performance of the lithium-ion batteries of Example 1-1 and Examples 3-1 to 3-4.

[0089]

Table 3

[0090] According to the examples in Table 3, when the OI value of the graphite is between 3 and 12, the lithium-ion battery prepared thereby has relatively excellent cycle characteristics. In this case, the isotropy of the graphite is relatively good, which is advantageous for improving the solid-phase diffusion of Li+, thereby reducing the charge transfer resistance of the lithium-ion battery, improving the kinetics of the graphite, and thereby enhancing the cycle characteristics of the lithium-ion battery.

[0091] D. Example 1-1 and Examples 4-1 to 4-3 The difference between Examples 4-1 to 4-3 and Example 1-1 is only the difference in the ratio (D / C) of the average particle size C (μm) of lithium manganate and the average particle size D (μm) of the manganese-containing compound, and the resulting difference in the compression density of the electrode sheet. Here, the difference in D / C is mainly realized by changing the particle size of the raw materials.

[0092] Table 4 below shows the differences in composition and performance between Lithium-ion battery of Example 1-1 and Examples 4-1 to 4-3.

[0093]

Table 4

[0094] Referring to Table 4, it was found that the average particle size C (μm) of lithium manganate and the average particle size D (μm) of the manganese-containing compound satisfy 1 ≤ D / C ≤ 15.

[0095] The particles of the manganese-containing compound and the particles of lithium manganate match each other, the contact between particles becomes better, the diffusion path of lithium ions can be shortened, which is advantageous for the insertion and desorption of lithium ions, can increase the capacity of the material, increase the compression density of the positive electrode sheet, and improve the cycle characteristics and high-temperature storage characteristics of the lithium-ion battery. By limiting D / C within the above range, ideal device performance can be obtained.

[0096] E. Example 1-1 and Examples 5-1 to 5-5 The difference between Examples 5-1 to 5-5 and Example 1-1 is only the compression density of the negative electrode sheet. Table 5 below shows the differences in composition and performance between Lithium-ion battery of Example 1-1 and Examples 5-1 to 5-5.

[0097]

Table 5

[0098] Referring to Table 5, the compression density of the negative electrode sheet is 1.3 g / cm 3 ~1.8 g / cm 3If so, the negative electrode active material particles have an appropriate effective active area, there is no breakage on the particle surface, the lithium-ion battery has a higher initial Coulomb efficiency, the discharge capacity of the lithium-ion battery is increased, and an appropriate compression density is found to be advantageous for better infiltration of the electrolyte, improvement of the dynamics inside the battery, and improvement of the cycle characteristics of the lithium-ion battery.

[0099] Throughout the specification, references by "some embodiments", "a part of an embodiment", "one embodiment", "another example", "example", "specific example", or "a part of an example" mean that at least one embodiment or example of the present invention includes the specific features, structures, materials, or characteristics described in the said embodiment or example. Therefore, references described at various places throughout the specification, such as "in some embodiments", "in an embodiment", "in one embodiment", "in another example", "in one example", "in a specific example", or "example", do not necessarily refer to the same embodiment or example in the present invention. Also, the specific features, structures, materials, or characteristics of this specification can be combined in any suitable way in one or more embodiments or examples.

[0100] Exemplary embodiments have been described and explained, but those skilled in the art should understand that the above-described embodiments should not be construed as limiting the present invention, and modifications, substitutions, and changes to the embodiments are possible without departing from the technical idea, principle, and scope of the present invention.

Claims

1. An electrochemical device, wherein the electrochemical device includes a positive electrode sheet, a negative electrode sheet, and an electrolytic solution, the negative electrode sheet includes a negative electrode active material layer, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material layer includes aluminum element, The content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m ２ 2) of the negative electrode active material layer satisfy 3 ≤ A / B ≤ 25, and the positive electrode active material includes lithium manganate and a manganese-containing compound, an electrochemical device.

2. The electrochemical device, (1) The content A (mmol) of the aluminum element in the positive electrode active material layer and the total area B (m ２ ) of the negative electrode active material layer satisfy 8 ≦ A / B ≦ 23, and wherein (2) A is in the range of 0.005 to 0.04, and / or (3) A is in the range of 0.01 to 0.035, satisfies at least one of the above, the electrochemical device according to Claim 1.

3. When the average particle diameter of the lithium manganate is Cum and the average particle diameter of the manganese-containing compound is Dum, D / C satisfies 1 ≤ D / C ≤ 15, the electrochemical device according to Claim 1.

4. D / C satisfies 5 ≤ D / C ≤ 10, the electrochemical device according to Claim 3.

5. The manganese-containing compound, wherein (1) Dv50 of the manganese-containing compound is 5 μm to 40 μm, and / or (2) the surface of the manganese-containing compound has steps with a width of 1 nm to 1000 nm, satisfies at least one of the above, the electrochemical device according to Claim 1.

6. The positive electrode active material layer further includes at least one of Nb, Mg, Ti, Ce, W, Ga, Zr, W, Y, V, Na, Sr, Mo, Cr, Sn, and La, and the mass fraction M of Nb, Mg, Ti, Ce, W, Ga, Zr, W, Y, V, Na, Sr, Mo, Cr, Sn, or La is 0.01% to 3.5% with respect to the mass of the positive electrode active material layer, the electrochemical device according to Claim 1.

7. The negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes graphite, and d(002) of the graphite is 3.363 ± 0.004 Å, the electrochemical device according to Claim 1.

8. The electrochemical device, wherein (1) the OI value of the graphite is 4 ± 1, and / or (2) the porosity of the negative electrode active material layer is 25 ± 5%, (3) The compression density of the negative electrode sheet is 1.3 g / cm ３ ~1.8 g / cm ３ and satisfies at least one of the above, the electrochemical device according to Claim 7.

9. The compression density of the positive electrode sheet is 2.2 g / cm ３ to 2.8 g / cm ３ The electrochemical device according to claim 1, wherein the compression density is as described above.

10. An electronic device including the electrochemical device according to any one of Claims 1 to 9.

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