Anode, and electrochemical device and electronic device using same

Abstract

To provide an electrochemical device that has reduced impedance and improved rate and cycle characteristics.SOLUTION: The present invention provides a negative electrode, and an electrochemical device and an electronic device using the same. The negative electrode according to the present invention includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes graphite and hard carbon, and based on a total mass of the hard carbon, a content ratio of hydrogen element to carbon element in the hard carbon is W1, and based on a total mass of the graphite, a content ratio of hydrogen element to carbon element in the hard carbon is W2, W1 / W2 is in a range of 5 to 19.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of energy storage, and in particular to anodes and electrochemical and electronic devices using the same. [Background technology]

[0002] Electrochemical devices (e.g., lithium-ion batteries) have advantages such as high volumetric and mass energy density, environmental friendliness, high operating voltage, small volume, light weight, and long cycle life, and are widely used in the field of portable household appliances. With the rapid development of electric vehicles and mobile electronic devices in recent years, the requirements for battery energy density, safety, cycle performance, etc. are increasing, and the emergence of new electrochemical devices with comprehensive improvements in performance is expected. Among these, rapid charge / discharge performance and cycle performance have already become important technical issues that need to be resolved urgently, and improving the active materials in electrodes is one research direction to solve these issues. Graphite is currently the most widely used negative electrode material and has advantages such as high efficiency and a stable charge / discharge platform. However, the performance of currently available graphite has been almost fully developed, and one of the major challenges is how to further improve its fast charge / discharge characteristics, rate characteristics, and cycle characteristics. Therefore, it is necessary to provide an improved negative electrode to further improve and resolve the fast charge characteristics, rate characteristics, and cycle characteristics of current graphite negative electrodes. Summary of the Invention

[0003] To solve at least one problem in the related art to some extent, embodiments of the present invention provide a negative electrode and a method for manufacturing the same, and further provide electrochemical and electronic devices that use the negative electrode.

[0004] In one embodiment, the present invention provides a negative electrode comprising a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, the negative electrode active material including graphite and hard carbon, wherein W1 is a ratio of the hydrogen content to the carbon content in the hard carbon relative to the total mass of the hard carbon, and W2 is a ratio of the hydrogen content to the carbon content in the graphite relative to the total mass of the graphite, and W1 / W2 is in the range of 5 to 19.

[0005] In some embodiments, the compressed density of the hard carbon is d1g / cm 3 The compressed density of graphite is d2g / cm 3 When this is the case, d1 / d2 is in the range of 0.38 to 0.55.

[0006] In some embodiments, d1 is between 0.7 and 1.2, and / or d2 is between 1.8 and 2.0.

[0007] In some embodiments, W1 / W2 is in the range of 8 to 18.6.

[0008] In some embodiments, W1 / W2 is in the range of 12-18.

[0009] In some embodiments, the negative electrode active material has a 1300 cm -1 ~1400cm -1 The peak intensity at ID is 1530 cm -1 ~1630cm -1 When the peak intensity at this point is IG, the value of ID / IG is in the range of 0.2 to 0.5.

[0010] In some embodiments, the graphite and hard carbon are (1) Hard carbon D1v 50 is 0.1 μm to 3 μm, (2) Graphite D2v 50 is 7 μm to 20 μm, (3) Graphite D2v 50and hard carbon D1v 50 is D2v 50 / D1v 50 ≧4.5 and (4) D1v of the hard carbon 50 and hard carbon D1v 90 is 1.5 <D1v 90 / D1v 50 ≦6 and (5) Graphite D2v 50 and graphite D2v 90 is D2v 90 / D2v 50 >1.5 and Satisfy at least one of the following:

[0011] In some embodiments, the particle size measurement of the negative electrode active material has a peak intensity A in the range of 0.5 μm to 2 μm and a peak intensity B in the range of 8 μm to 17 μm, and B / A is 15 or greater.

[0012] In some embodiments, the specific surface area of ​​the hard carbon is 5 m 2 / g~30m 2 / g range.

[0013] In some embodiments, the mass percentage of the hard carbon is 1% to 10% based on the total mass of the negative electrode active material.

[0014] In another embodiment, the present invention provides a method for preparing a negative electrode according to the present invention, the method comprising: (1) preparing hard carbon, the hard carbon preparation process comprising: (a) using at least one of glucose or a resin as a precursor and heating the precursor to obtain a product; (b) calcining the product of step (a) at a temperature of 600°C-1500°C to obtain a calcined product; (c) using an alkane gas to coat the fired product in step (b) to obtain the hard carbon; (2) preparing graphite, the graphite preparation process comprising: The method includes heating artificial graphite to 500°C-1000°C with C2H2 gas, maintaining the temperature for 1-5 hours, and then cooling the graphite under an inert atmosphere, and obtaining the graphite; (3) Hard carbon and graphite are used as the negative electrode active material to prepare a negative electrode.

[0015] In another embodiment, the present invention provides an electrochemical device comprising a negative electrode according to the present invention.

[0016] In another embodiment, the present invention provides an electronic device including an electrochemical device according to an embodiment of the present invention.

[0017] The present invention improves the current distribution of the negative electrode by controlling the addition of hard carbon to the negative electrode active material, which is graphite, and by controlling the ratio of the ratio W1 of the hydrogen content to the carbon content in the hard carbon to the ratio W2 of the hydrogen content to the carbon content in the graphite, thereby improving the rate performance and cycle performance of the electrochemical device and reducing the impedance of the electrochemical device.

[0018] Other aspects and advantages of embodiments of the invention will be described in part in the description that follows, or will be illustrated by, or may be learned by, the practice of embodiments of the invention. [Brief explanation of the drawings]

[0019] In the following, in order to explain the embodiments of the present invention, the drawings necessary for explaining the embodiments of the present invention or the prior art will be briefly described. Obviously, the drawings described below are only a part of the embodiments of the present invention. Those skilled in the art can still obtain drawings of other embodiments based on the structures illustrated in these drawings without requiring creative work. [Figure 1] FIG. 1 shows a scanning electron microscope (SEM) photograph of a cross section of the negative electrode in Example 6 of the present invention. [Figure 2]FIG. 2 shows the particle size distribution curve of the negative electrode active material in Example 6 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Examples of the present invention will be described in detail below, but the examples of the present invention should not be construed as limiting the present invention.

[0021] As used herein, the term "about" is intended to describe and account for small variations. When the term "about" is used in conjunction with an example or situation, the term can refer to an instance in which the example or situation occurs exactly, as well as an instance in which the example or situation occurs very approximately. For example, when the term "about" is used in conjunction with a numerical value, the term can refer to a range of variation of ±10% or less of the numerical value, such as ±5% or less, ±4% or less, ±3% or less, ±2% or less, ±1% or less, ±0.5% or less, ±0.1% or less, or ±0.05% or less.

[0022] It should be noted that amounts, ratios, and other numerical values ​​are presented in range format herein. Such range format is used for convenience and brevity and should be interpreted flexibly; such ranges include not only the values ​​expressly specified as range limits, but also all values ​​and subranges subsumed within the range, as if each value and subrange were expressly specified.

[0023] In specific embodiments and in the claims, a list of terms connected by the terms "one of," "one of," "a type of," or other similar terms, refers to any of the listed terms. For example, if terms A and B are listed, the short phrase "one of A and B" refers to A only or B only. In another example, if terms A, B, and C are listed, the short phrase "one of A, B, and C" refers to A only, B only, or C only. Term A may include a single element or multiple elements. Term B may include a single element or multiple elements. Term C may include a single element or multiple elements.

[0024] In specific embodiments and in the claims, a list of terms connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms refers to any combination of the listed terms. For example, if terms A and B are listed, the phrase "at least one of A and B" means A only; B only; or A and B. In another example, if terms A, B, and C are listed, "at least one of A, B, and C" means A only, or B only, or C only, or A and B (excluding C), or A and C (excluding B), or B and C (excluding A), or all of A, B, and C. Term A may include a single element or multiple elements. Term B may include a single element or multiple elements. Term C may include a single element or multiple elements.

[0025] 1. Electrochemical equipment In some embodiments, the present invention provides an electrochemical device, the electrochemical device including a positive electrode, a negative electrode, and an electrolyte.

[0026] 1, negative electrode An embodiment of the present invention provides a negative electrode comprising a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, the negative electrode active material including graphite and hard carbon, wherein W1 is a ratio of the hydrogen content to the carbon content in the hard carbon relative to the total mass of the hard carbon, and W2 is a ratio of the hydrogen content to the carbon content in the graphite relative to the total mass of the graphite, and W1 / W2 is in the range of 5 to 19.

[0027] Because hard carbon can contain hydrogen both internally and on its surface, the ratio W1 (the ratio of hydrogen to carbon) of the hard carbon can be relatively high. Because graphite has a perfect internal crystalline structure and a small amount of hydrogen on its surface, the ratio W2 (the ratio of hydrogen to carbon) of the graphite can be relatively low. The ratio W1 to W2 reflects the composition of the anode active material, which is related to factors such as the particle size and specific surface area of ​​the hard carbon in the anode active material, and can therefore be used as a parameter to characterize the anode active material. The larger the W1 / W2 value, the smaller the particle size and specific surface area of ​​the hard carbon, which allows for uniform mixing with graphite, resulting in uniform anode porosity and improved anode current distribution, thereby improving the rate and cycle performance of the electrochemical device. At the same time, the smaller the particle size of the hard carbon, the shorter the transport distance of active ions, contributing to improved rate performance of the electrochemical device. The improved current distribution in the negative electrode piece and the shortened transport distance of the active ions also contribute to the improvement of the electrochemical impedance and diffusion impedance on the negative electrode side, and the improvement of the rate capability of the electrochemical device.

[0028] In some embodiments, the value of W1 / W2 is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19, or a range consisting of any two of these values. In some embodiments, W1 / W2 is in the range of 8 to 18.6. In some embodiments, W1 / W2 is in the range of 12 to 18. When W1 / W2 is in the above range, the rate performance of the electrochemical device can be further improved.

[0029] In some embodiments, W1 is in the range of 0.05 to 0.2. In some embodiments, W1 is 0.05, 0.07, 0.09, 0.1, 0.12, 0.14, 0.16, 0.18, or 0.2, or a range consisting of any two of these values. When W1 is in the above range, transport of active ions is further promoted, improving the rate characteristics of the electrochemical device.

[0030] In some embodiments, W2 is in the range of 0.005 to 0.02. 、 In some embodiments, the hard carbon of the present invention has a molecular weight of 0.005, 0.007, 0.009, 0.01, 0.012, 0.014, 0.016, 0.018, or 0.02, or a range consisting of any two of these values. (1) providing at least one of a glucose solution or a resin as a precursor and heating the precursor; (2) carbonizing the product of step (1) at a temperature of 600°C-1500°C; (3) a step of gas-phase coating the carbonized product of step (2) using an alkane gas.

[0031] In some embodiments, the graphite of the present invention is prepared by the following preparation method.

[0032] Commercially available artificial graphite is heated to 500-1000°C in a rotary furnace with 10% C2H2 gas, maintained at this temperature for 1-5 hours, then the gas is switched to N2 gas and the material is allowed to cool naturally to obtain the final graphite material. Those skilled in the art will understand that the ratio of hydrogen to carbon in hard carbon and graphite can be controlled by adjusting the preparation conditions (for example, reaction time, temperature, etc.).

[0033] In some embodiments, the compressed density of the hard carbon is d1g / cm 3 The compressed density of graphite is d2g / cm 3 When this is the case, d1 / d2 is in the range of 0.38 to 0.55.

[0034] In some embodiments, the value of d1 / d2 is 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, or 0.55, or a range consisting of any two of these values. The pressed density of the hard carbon or graphite can reflect the particle size of the material. When the pressed densities of the hard carbon and graphite satisfy the above conditions, the hard carbon and graphite have appropriate particle sizes and are uniformly dispersed in the gaps between the graphite, thereby further improving the rate characteristics and cycle characteristics of the electrochemical device and reducing the impedance of the electrochemical device.

[0035] In some embodiments, d1 is 0.7 to 1.2. In some embodiments, d1 is 0.7, 0.8, 0.9, 1.0, or 1.2, or a range consisting of any two of these values. When the compressed density of the hard carbon satisfies the above conditions, the rate performance and cycle performance of the electrochemical device can be further improved.

[0036] In some embodiments, d2 is 1.8 to 2.0. In some embodiments, d2 is 1.8, 1.85, 1.9, 1.95, or 2.0, or a range consisting of any two of these values. When the packed density of graphite satisfies the above conditions, the rate performance and cycle performance of the electrochemical device can be further improved.

[0037] In some embodiments, the negative electrode active material has a 1300 cm -1 ~1400cm -1 The first characteristic peak intensity at 1530 cm is designated as ID. -1 ~1630cm -1 When the intensity of the second characteristic peak in the graphite is IG, the value of ID / IG ranges from 0.2 to 0.5. In some embodiments, the value of ID / IG is 0.2, 0.3, 0.4, or 0.5, or a range consisting of any two of these values. ID / IG can reflect the degree of defects in the negative electrode active material. The first characteristic peak is mainly due to more disordered hard carbon, and therefore, the addition of hard carbon can increase the D / IG value of the negative electrode pieces. The smaller the particle size of the hard carbon, the more uniformly it is distributed in the graphite. When the ID / IG value is within the above range, a better synergistic effect between the hard carbon and graphite can be achieved, for example, increasing the surface current density of the electrode pieces during uniform charge / discharge and improving the rate characteristics of the electrochemical device.

[0038] In some embodiments, the hard carbon D1v 50 In some embodiments, D1v is between 0.1 μm and 3 μm. 50 is 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm, or in a range consisting of any two of these values.

[0039] In some embodiments, graphite D2v 50 In some embodiments, D2v is between 7 μm and 20 μm. 50is 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, or 20 μm, or in a range consisting of any two of these values.

[0040] In some embodiments, graphite D2v 50 and hard carbon D1v 50 is D2v 50 / D1v 50 ≧4.5. In some embodiments, D 50 / D1v 50 In some embodiments, D2v is 4.5-15. 50 / D1v 50 is 4.5, 5, 7, 9, 11, 13, or 15, or in a range consisting of any two of these values.

[0041] In some embodiments, the hard carbon D1v 50 and hard carbon D1v 90 is 1.5 <D1v 90 / D1v 50 In some embodiments, D1v 90 / D1v 50 is 1.6, 2, 3, 4, 5, or 6, or a range consisting of any two of these values.

[0042] In some embodiments, graphite D2v 50 and graphite D2v 90 is D2v 90 / D2v 50 >1.5. In some embodiments, D2v 90 / D2v 50 In some embodiments, D2v is 1.6-10. 90 / D2v 50 is 1.6, 2, 3, 4, 5, 6, 7, 8, 9, or 10, or in a range consisting of any two of these values. When the particle sizes of the hard carbon and graphite satisfy the above conditions, the combination of the particle sizes of the hard carbon and graphite is appropriate, and the hard carbon can be uniformly dispersed in the gaps in the graphite, thereby further improving the rate characteristics and cycle characteristics of the electrochemical device and reducing the impedance of the electrochemical device.

[0043] In some embodiments, the particle size measurement of the negative electrode active material has a peak intensity A in the range of 0.5 μm to 2 μm and a peak intensity B in the range of 8 μm to 17 μm, and B / A is 15 or greater.

[0044] In some embodiments, the value of B / A is 15 to 100. In some embodiments, the value of B / A is 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 100, or a range consisting of any two of these values. In some embodiments, the value of peak intensity A is 0.4 to 0.8. In some embodiments, the value of peak intensity A is 0.4, 0.5, 0.6, 0.7, 0.8, or a range consisting of any two of these values.

[0045] In some embodiments, the value of peak intensity B is between 6 and 12. In some embodiments, the value of peak intensity B is 6, 7, 8, 9, 10, 11, or 12, or a range consisting of any two of these values. When the peak intensities A and B of the negative electrode active material satisfy the above conditions, it contributes to improving the rate characteristics and cycle characteristics of the electrochemical device, and can reduce the impedance of the electrochemical device.

[0046] In some embodiments, the specific surface area of ​​the hard carbon is 5 m 2 / g~30m 2 In some embodiments, the specific surface area of ​​the hard carbon is in the range of 5 m 2 / g, 8m 2 / g, 10m 2 / g, 12m2 / g, 15m 2 / g, 18m 2 / g, 20m 2 / g, 23m 2 / g, 25m 2 / g, 28m 2 / g, or 30m 2 / g, or in a range consisting of any two of these values.

[0047] In some embodiments, the specific surface area of ​​the graphite is 0.5 m 2 / g~2m 2 In some embodiments, the specific surface area of ​​the graphite is in the range of 0.5 m / g. 2 / g, 0.8m 2 / g, 1m 2 / g, 1.2m 2 / g, 1.5m 2 / g, 1.8m 2 / g, or 2m 2 / g, or in a range consisting of any two of these values. When the specific surface area of ​​the hard carbon and graphite is within the above range, it contributes to improving the rate characteristics and cycle characteristics of the electrochemical device, and can reduce the impedance of the electrochemical device.

[0048] In some embodiments, the mass percentage of the hard carbon is 1% to 10% relative to the total mass of the negative electrode active material, or 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, or a range consisting of any two of these values, relative to the total mass of the negative electrode active material.

[0049] In some embodiments, the mass percentage of graphite is 90% to 99% based on the total mass of the negative electrode active material, or 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, or a range consisting of any two of these values ​​based on the total mass of the negative electrode active material. When the content of hard carbon and graphite in the negative electrode active material is within the above range, it contributes to improving the rate characteristics and cycle characteristics of the electrochemical device and reducing the impedance of the electrochemical device.

[0050] In some embodiments, the present invention provides a method for producing a pharmaceutical composition comprising: (1) using at least one of glucose or a resin as a precursor and heating the precursor to obtain a product; (2) calcining the product of step (1) at a temperature of 600°C-1500°C to obtain a calcined product; (3) coating the fired product of step (2) with an alkane gas.

[0051] In some embodiments, the heating temperature in step (1) is 150° C.-500° C. In some embodiments, the heating temperature in step (1) is 150° C., 200° C., 250° C., 300° C., 350° C., 400° C., 450° C., or 500° C., or a range consisting of any two of these values.

[0052] In some embodiments, the heating time in step (1) is 3 hours to 30 hours, hi some embodiments, the heating time in step (1) is 3 hours, 4 hours, 6 hours, 10 hours, 15 hours, 20 hours, 23 hours, 25 hours, or 30 hours, or a range consisting of any two of these values.

[0053] In some embodiments, the firing temperature in step (2) is 600°C, 680°C, 1000°C, 1200°C, 1300°C, 1400°C, or 1500°C, or a range consisting of any two of these values.

[0054] In some embodiments, the baking time in step (2) is 1 hour to 5 hours, hi some embodiments, the baking time in step (2) is 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours, or a range consisting of any two of these values.

[0055] In certain embodiments, the alkane gas comprises C2H2.

[0056] In some embodiments, the coating in step (3) is performed at 500° C.-1000° C. In some embodiments, the coating temperature in step (3) is 500° C., 600° C., 700° C., 800° C., 900° C., or 1000° C., or a range consisting of any two of the foregoing values.

[0057] In some embodiments, the coating time in step (3) is 2 hours to 10 hours, hi some embodiments, the coating time in step (3) is 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, or a range consisting of any two of these values.

[0058] In some embodiments, the present invention provides a method for preparing graphite, comprising: The method comprises heating artificial graphite to 500-1000°C with C2H2 gas, maintaining the temperature for 1-5 hours, and then cooling it down under an inert atmosphere to obtain the graphite.

[0059] In certain embodiments, the heating temperature is 500°C, 600°C, 700°C, 800°C, 900°C, or 1000°C, or a range consisting of any two of these values.

[0060] In some embodiments, the heating time is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or a range consisting of any two of the foregoing values.

[0061] In some embodiments, the present invention provides a method for preparing a negative electrode. The method includes preparing a negative electrode using the hard carbon and graphite prepared by the above-described method as a negative electrode active material. In some embodiments, the negative electrode active material layer includes an adhesive. In some embodiments, the adhesive includes, but is not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0062] In some embodiments, the negative electrode active material layer includes a conductive material, including, but not limited to, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder, metal fiber, copper, nickel, aluminum, silver, or a polyphenylene derivative.

[0063] 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 conductive metal coated polymer substrate.

[0064] In some embodiments, the negative electrode pieces can be obtained by mixing an active material, a conductive material, and an adhesive in a solvent to prepare an active material composition, and then applying the active material composition to a current collector.

[0065] In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone.

[0066] 2, positive electrode The materials, constructions, and methods of manufacturing the positive electrode in embodiments of the present invention include any of those disclosed in the prior art. In some embodiments, the positive electrode is the positive electrode described in U.S. Patent Application No. US9812739B, the entire contents of which are incorporated herein by reference.

[0067] In some embodiments, the positive electrode includes a current collector and a positive electrode active material layer disposed on the current collector.

[0068] In some embodiments, the positive electrode active material includes, but is not limited to, lithium cobalt oxide (LiCoO), lithium nickel cobalt manganese (NCM) ternary material, lithium ferrous phosphate (LiFePO), or lithium manganese oxide (LiMnO).

[0069] In some embodiments, the positive electrode active material layer further comprises an adhesive and, optionally, a conductive material, which improves adhesion between the positive electrode active material particles and between the positive electrode active material and the current collector.

[0070] In some embodiments, the adhesive may include, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, or nylon.

[0071] In some embodiments, the conductive material includes, but is not limited to, a carbon-based material, a metal-based material, a conductive polymer, and a mixture thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, and any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, and silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0072] In some embodiments, the current collector includes, but is not limited to, aluminum.

[0073] The positive electrode may be prepared by a preparation method known in the art. For example, the positive electrode may be obtained by mixing an active material, a conductive material, and an adhesive in a solvent to prepare an active material composition, and then coating the active material composition on a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone.

[0074] 3, Electrolyte The electrolyte used in the embodiments of the present invention may be any electrolyte known in the prior art.

[0075] In some embodiments, the electrolyte solution includes an organic solvent, a lithium salt, and an additive. The organic solvent of the electrolyte solution according to the present invention may be any organic solvent known in the prior art to be used as a solvent for electrolyte solutions. The electrolyte used in the electrolyte solution according to the present invention is not particularly limited and may be any electrolyte known in the prior art. The additive of the electrolyte solution according to the present invention may be any additive known in the prior art to be used as an additive for electrolyte solutions.

[0076] In some embodiments, the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, or ethyl propionate. In some embodiments, the lithium salt comprises at least one of an organic lithium salt and an inorganic lithium salt.

[0077] In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium difluorophosphate (LiPOF), lithium bis(trifluoromethanesulfonyl)imide LiN(CFSO) (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SOF)) (LiFSI), lithium bis(oxalato)borate LiB(CO) (LiBOB), or lithium difluoro(oxalato)borate LiBF(CO) (LiDFOB).

[0078] In some embodiments, the concentration of the lithium salt in the electrolyte is about 0.5 to 3 mol / L, about 0.5 to 2 mol / L, or about 0.8 to 1.5 mol / L.

[0079] 4. Separator In some embodiments, a separator is provided between the positive and negative electrode pieces to prevent short circuits. The material and shape of the separator used in embodiments of the present invention are not particularly limited and may be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic material formed from a material stable with the electrolyte of the present invention.

[0080] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, film, or composite film having a porous structure, and the material of the substrate layer is at least one selected from 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 membrane can be selected and used.

[0081] A surface treatment layer is provided on at least one surface of the base material layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic material.

[0082] The inorganic layer includes inorganic particles and a binder, the inorganic particles being one or more selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, 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, and the binder being one or more selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0083] The polymer layer includes a polymer, and the polymer material is at least one selected from polyamide, polyacrylonitrile, acrylic ester polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0084] 5. Electrochemical equipment The present invention provides an electrochemical device comprising a negative electrode according to the present invention. In some embodiments, V1 / V2 is in the range of 0.985 to 1, where V1 is the capacity of the electrochemical device at 25°C and V2 is the capacity of the electrochemical device at 45°C.

[0085] In some embodiments, V1 / V2 is 0.985, 0.986, 0.987, 0.988, 0.989, 0.992, 0.994, 0.996, 0.998, or 1, or a range consisting of any two of these values.

[0086] In some embodiments, the electrochemical device of the present invention includes, but is not limited to, any type of primary battery, secondary battery, fuel cell, solar cell, or capacitor.

[0087] In some embodiments, the electrochemical device is a lithium secondary battery.

[0088] 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.

[0089] 6, electronic equipment The present invention provides an electronic device including an electrochemical device according to an embodiment of the present invention.

[0090] In some embodiments, the electronic device includes, but is not limited to, a notebook computer, a pen-based computer, a mobile computer, an electronic book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headset, a video recorder, an LCD television, a portable vacuum cleaner, a portable CD player, a minidisc, a walkie-talkie, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electric bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household storage battery, and a lithium ion capacitor.

[0091] Hereinafter, the preparation of a lithium ion battery will be described with reference to specific examples, taking a lithium ion battery as an example. Those skilled in the art should understand that the manufacturing method described in the present invention is merely exemplary, and any other suitable manufacturing method is within the scope of the present invention.

[0092] Example In the following description, characteristics of the lithium ion battery of the present invention will be evaluated using examples and comparative examples. 1. Preparation of lithium-ion batteries 1. Preparation of the negative electrode A. Hard carbon materials were prepared by the following method. (1) A glucose solution of a certain concentration was prepared, and 700 mL of the glucose solution was added to a 1 L reactor, which was then sealed and subjected to a hydrothermal reaction. The hydrothermal reaction conditions were to heat the solution to 180-330°C, hold it for 5 hours, and then let it cool naturally to 25°C. (2) The material obtained in step (1) was filtered and dried to obtain a black-brown powder, which was then carbonized in a rotary furnace protected with N2 gas at a temperature of 1000°C for 2 hours. (3) If necessary, the temperature of the carbonized powder was lowered from 1000°C to 700°C, the gas was switched to 10% C2H2 gas, and the temperature was maintained for 5 hours. The gas was then switched to N2 gas, and the temperature was allowed to naturally decrease to obtain the final hard carbon material. The parameters involved in the above preparation steps are given in Table 1.

[0093] [Table 1]

[0094] B. The graphite material was prepared by the following method. Commercially available artificial graphite was heated to 700°C in a rotary furnace with 10% C2H2 gas, held for a certain period of time, then switched to N2 gas and allowed to cool naturally to obtain the final graphite material. The specific preparation parameters are shown in Table 2.

[0095] [Table 2]

[0096] C. Anode active material (graphite material or graphite material and hard carbon material), styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 97:2:1 with an appropriate amount of deionized water and thoroughly stirred to form a uniform anode slurry. The solid content of the anode slurry was 40 wt%. This slurry was applied to an anode current collector (copper foil), dried at 85°C, cold pressed, cut, slit, and then dried in a vacuum at 120°C for 12 hours to obtain the anode. The contents of hard carbon and graphite in the negative electrode active material are shown in Tables 3 and 5. Here, "3% hard carbon 1 + graphite 1" in Example 1 in Table 3 indicates that the mass percentage of hard carbon 1 is 3% with respect to the total mass of the negative electrode active material, and the remaining 97% is graphite 1. Tables 3 and 5 also show the contents of hard carbon and graphite in other Examples and Comparative Examples.

[0097] 2. Preparation of the positive electrode The positive electrode active material, lithium cobalt oxide (LiCoO2), the conductive agent, Super P, and the binder, polyvinylidene fluoride (PVDF), were mixed in a weight ratio of 97:1.4:1.6 with an appropriate amount of solvent, N-methylpyrrolidone (NMP), and stirred thoroughly to form a uniform positive electrode slurry. The solid content of the positive electrode slurry was 72 wt%. This slurry was applied to an aluminum foil positive electrode current collector, dried at 85°C, then cold pressed, cut, slit, and dried in a vacuum at 85°C for 4 hours to obtain the positive electrode.

[0098] 3. Preparation of electrolyte In a glove box with a dry argon gas atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed uniformly in a mass ratio of EC:EMC:DEC = 30:50:20, and LiPF6, a lithium salt, was added and mixed uniformly to obtain an electrolyte solution, the mass percentage of LiPF6 being 12.5% ​​of the mass of the electrolyte solution.

[0099] 4. Preparation of separator A 7 μm thick polyethylene (PE) porous polymer film was used as the separator.

[0100] 5. Preparation of Lithium-ion Battery The positive electrode, separator, and negative electrode are stacked in this order, with the separator positioned between the positive and negative electrodes to act as an insulator. The resulting structure is then wound and a tab is welded onto it. The resulting structure is then placed in an aluminum plastic film exterior foil, and the electrolyte is injected. The resulting soft-pack lithium-ion battery is then vacuum packaged, left to stand, formed, shaped, and measured for capacity.

[0101] 2. Lithium-ion battery characteristic measurement method 1. Method for measuring the H / C value of negative electrode active material Definition of H / C value: The molar ratio of H to C in hard carbon or graphite materials. H and C elements were measured using an elemental analyzer, a UNICUBE elemental analyzer. The H / C value was obtained by thoroughly combusting the hard carbon or graphite material in a high-purity oxygen atmosphere and then measuring the molar contents of H2O and CO2. The ratio H / C of the hydrogen content to the carbon content in the hard carbon material was defined as W1, and the ratio H / C of the hydrogen content to the carbon content in the graphite material was defined as W2.

[0102] 2. Method for measuring ID / IG values ​​of negative electrode active material A cross section was cut out of the negative electrode piece using ion polishing, and the cross section was placed on a Raman spectrometer and measured after focusing. A 200 μm × 500 μm area was selected for the measurement, and more than 200 equally spaced points were measured within this area, with the measurement range of each point being 1000–2000 cm. -1 Between 1320-1370cm -1 The peak appearing between 1570 and 1620 cm is the D peak, and its peak intensity is the ID peak. -1 The peak appearing between these points was designated G, and the peak intensity was designated IG. The intensity ratios of ID / IG at each point were counted and average values ​​were calculated to measure the ID / IG value of the negative electrode active material.

[0103] 3. Measurement of specific surface area (BET) of graphite and hard carbon materials: The specific surface area was measured according to GB / T 19587-2017. The specific surface area was calculated based on the Brunauer-Emmett-Teller adsorption theory (BET) and its equation. A 1-8 g sample of hard carbon or graphite material (the sample should cover at least 1 / 3 of the ball volume) was weighed and placed in a 1 / 2-inch tube with a ball (the diameter of the tube at the ball is 12 mm). The sample was pre-treated at 200°C for 2 hours, and then placed in a TriStar 3030 (Micromeritics, USA) measuring device. The adsorption gas used was N2 (purity: 99.999%). The measurement was performed at 77 K, and the specific surface area was calculated based on the Brunauer-Emmett-Teller adsorption theory and its equation (BET).

[0104] 4. Particle size measurement: Approximately 0.02 g of the negative electrode active material sample was added to a clean 50 ml beaker, and approximately 20 ml of deionized water was added. Two to three drops of a 1% surfactant were then added to completely disperse the sample in water. The dispersion was then ultrasonicated for 5 minutes in a 120 W ultrasonic cleaner, and the particle size distribution was measured using a MasterSizer 2000.

[0105] 5. Measurement method of peak intensity A and peak intensity B The fully discharged negative electrode pieces were washed with DMC solution and dried. The negative electrode active material was lightly scraped off from the current collector, washed five times with ethanol, centrifuged, and dried. Particle size measurements were then performed using the particle size measurement method described above, and a distribution curve of peak intensity and particle size was obtained. The peak between 0.1 and 5 μm was designated Peak A, and the peak between 5 and 25 μm was designated Peak B. The intensities of Peak B and Peak A were read, and their intensity ratio was calculated.

[0106] 6. Method for measuring compressed density The compressed density was measured in accordance with the Chinese national standard GB / T 24533-2009, "Graphite-based negative electrode materials for lithium-ion batteries." The measurement device was a Sansi UTM7305 measuring device. Approximately 1 g of graphite or hard carbon material sample was placed in the mold of the device, and a constant pressure (1 to 5 tons) was set. The device recorded the thickness of the sample at different pressures, and the volume of the sample at different pressures was obtained. The compressed density of the sample was then calculated using the formula ρ = m / V. Here, the compressed density of the hard carbon was defined as d1, and the compressed density of the graphite was defined as d2, both of which were compressed densities at a pressure of 3 tons.

[0107] 7. Impedance measurement method: After discharging the lithium ion battery (electrochemical device) to 3.0 V, that is, in a 0% SOC state, the DC impedance was measured and defined as the 0% SOC impedance.

[0108] 8. Rate characteristic measurement method The lithium-ion battery was subjected to rate charging at a constant temperature. First, a fully discharged lithium-ion battery was charged to 4.48V at a constant current of 1C, then charged to 0.05C at a constant voltage, and then discharged to 3.0V at a constant current of 1C. The resulting discharge capacity was designated as capacity A. The battery was then further charged to 4.48V at a constant current of 5C, then charged to 0.05C at a constant voltage, and then discharged to 3.0V at a constant current of 1C. The resulting discharge capacity was designated as capacity B, and B / A was the 5C / 1C rate characteristic.

[0109] 9. Measurement method for low temperature -20℃ / 25℃ maintenance rate characteristics Charge-discharge measurements were performed on a lithium-ion battery at different temperatures. First, a fully discharged lithium-ion battery was charged at room temperature (25°C) at a constant current of 1C to 4.48V, then charged at a constant voltage of 0.05C, and then discharged at a constant current of 1C to 3.0V. The resulting discharge capacity was defined as capacity C. The lithium-ion battery was then charged again at a constant current of 1C to 4.48V and at a constant voltage of 0.05C. The lithium-ion battery was then transferred to a -20°C incubator, left for 8 hours, and then discharged at a constant current of 1C to 3.0V. The resulting discharge capacity was defined as capacity D. D / C was the maintenance ratio of the low temperature (-20°C / 25°C).

[0110] 10. Measurement method for room temperature cycle characteristics In an atmosphere of 25°C, a fully discharged lithium-ion battery was charged at a constant current of 3C to a voltage of 4.48V, then charged at a constant voltage of 0.05C, and discharged at a constant current of 1C to 3V (one cycle), and the discharge capacity E of the first cycle was recorded. After 800 cycles, the discharge capacity F of the 800th cycle was recorded. The ratio of F / E was taken as the cycle retention rate at 25°C.

[0111] 11. Measurement method for high-temperature cycle characteristics In an atmosphere of 45°C, a fully discharged lithium-ion battery was charged at a constant current of 3C to a voltage of 4.48V, then charged at a constant voltage of 0.05C, and discharged at a constant current of 1C to 3V (one cycle), and the discharge capacity G of the first cycle was recorded. After 800 cycles, the discharge capacity H of the 800th cycle was recorded. The ratio H / G was taken as the cycle retention rate at 45°C.

[0112] 12. How to measure V1 and V2 Charge and discharge measurements were performed on a lithium-ion battery at different temperatures. First, a fully discharged lithium-ion battery was charged at room temperature (25°C) at a constant current of 1C to 4.48V, then charged at a constant voltage to 0.05C, and then discharged at a constant current of 1C to 3.0V. The resulting discharge capacity was designated as V1. The lithium-ion battery was then transferred to an incubator at 45°C and left for 8 hours. After that, it was charged at a constant current of 1C to 4.48V, charged at a constant voltage to 0.05C, and then discharged at a constant current of 1C to 3.0V. The resulting discharge capacity was designated as V2, and the ratio of V2 / V1 was calculated.

[0113] 3. Measurement results of lithium-ion battery characteristics Tables 3 and 4 show parameters related to the hard carbon, graphite, and lithium-ion batteries of each example and comparative example. Table 5 shows the characteristics of the lithium-ion batteries of each example and comparative example.

[0114] [Table 3]

[0115] [Table 4]

[0116] [Table 5]

[0117] As can be seen from the comparison between the above Comparative Examples and Examples, compared to a negative electrode active material that does not contain a hard carbon material, a negative electrode that uses hard carbon and graphite as a negative electrode active material can significantly reduce the impedance of a lithium-ion battery and significantly improve the rate and cycle characteristics. Furthermore, when the ratio (W1 / W2) of the ratio W1 of the hydrogen content to the carbon content in the hard carbon to the ratio W2 of the hydrogen content to the carbon content in the graphite is within the range of 5 to 19, the impedance of the lithium-ion battery can be significantly reduced and the rate and cycle characteristics can be significantly improved.

[0118] Figure 1 shows a scanning electron microscope (SEM) photograph of the cross section of the negative electrode in Example 6. As can be seen from the photograph, the negative electrode contains flake graphite and spherical hard carbon, with the hard carbon uniformly distributed in the gaps between the graphite. Figure 2 shows the particle size distribution curve of the negative electrode active material in Example 6 of the present invention. As can be seen from the photograph, the particle size distribution curve has two peaks, of which the peak with the smaller particle size corresponds to the hard carbon and the peak with the larger particle size corresponds to the graphite.

[0119] And W1 / W2, d1, d2, ID / IG, D1v 50 , D2v 50 , D1v 90 , D2v 90 When parameters such as B / A and B / A satisfy certain relationships or are within certain ranges, the lithium ion battery has lower impedance and better rate and cycle capabilities.

[0120] Throughout the specification, references to "some embodiments," "some embodiments," "one embodiment," "another embodiment," "an embodiment," "an example," "particular example," or "some examples" mean that at least one embodiment or example of the present invention includes a particular feature, structure, material, or characteristic described in that embodiment or example. Thus, the appearances of, for example, "in some embodiments," "in an embodiment," "in one embodiment," "in other embodiments," "in one example," "in a particular example," or "an example" in various places throughout the specification do not necessarily refer to the same embodiment or example of the present invention. Furthermore, particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

[0121] While illustrative embodiments have been disclosed and described, those skilled in the art should understand that the above-described embodiments cannot be construed as limiting the present invention, and that modifications, substitutions, and alterations can be made to the embodiments without departing from the spirit, principle, and scope of the present invention.

Claims

1. 1. An electrochemical device comprising: a positive electrode, a negative electrode, and an electrolyte; the electrochemical device is a lithium ion battery; the negative electrode has a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material, the negative electrode active material includes graphite and hard carbon, The ratio of the hydrogen content to the carbon content in the hard carbon with respect to the total mass of the hard carbon is W １ year, The ratio of the hydrogen content to the carbon content in the graphite relative to the total mass of the graphite is W ２ When W １ / W ２ is in the range of 5 to 19, electrochemical device.

2. The compressed density of the hard carbon is d １ g / cm ３ year, The compressed density of the graphite is d ２ g / cm ３ When d １ / d ２ 2. The electrochemical device of claim 1, wherein is in the range of 0.38 to 0.

55.

3. Said d １ is 0.7 to 1.2, and / or ２ The electrochemical device according to claim 2, wherein is 1.8 to 2.

0.

4. The W １ / W ２ The electrochemical device of claim 1 , wherein is in the range of 8 to 18.

6.

5. 1300 cm of the negative electrode active material －１ ~1400cm －１ The peak intensity at is ID, and 1530 cm －１ ~1630cm －１ When the peak intensity at is IG, 2. The electrochemical device of claim 1, wherein the value of ID / IG is in the range of 0.2 to 0.

5.

6. The graphite and the hard carbon are (1) D of the hard carbon １ v ５０ is 0.1 μm to 3 μm; (2) D of the graphite ２ v ５０ is 7 μm to 20 μm; (3) D of the graphite ２ v ５０ and the hard carbon D １ v ５０ is D ２ v ５０ / D １ v ５０ ≧4.5; (4) D of the hard carbon １ v ５０ and the hard carbon D １ v ９０ is 1.5<D １ v ９０ / D １ v ５０ ≦6 is satisfied, (5) D of the graphite ２ v ５０ and the graphite D ２ v ９０ is D ２ v ９０ / D ２ v ５０ > 1.5 and (6) The specific surface area of ​​the hard carbon is 5 m ２ / g to 30m ２ / g, and (7) The mass percentage of the hard carbon is 1% to 10% with respect to the total mass of the negative electrode active material; (8) The W １ / W ２ is in the range of 12 to 18, The electrochemical device according to claim 1 , wherein at least one of the following is satisfied:

7. 2. The electrochemical device according to claim 1, wherein, by particle size measurement, the negative electrode active material has a peak intensity A in the range of 0.5 μm to 2 μm and a peak intensity B in the range of 8 μm to 17 μm, and B / A is 15 or greater.

8. An electronic device comprising an electrochemical device according to any one of claims 1 to 7.

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