Negative electrode active materials and electrochemical and electronic devices using them

Abstract

This application relates to a negative electrode active material and electrochemical and electronic devices using the same. Specifically, this application provides a negative electrode active material wherein the interplanar spacing of the negative electrode active material is 0.35 nm to 0.45 nm, and the negative electrode active material contains a metal element, which includes at least one selected from gold, silver, platinum, zirconium, zinc, magnesium, calcium, barium, vanadium, iron, or aluminum, and the content of the metal element is from 20 ppm to 400 ppm based on the total weight of the negative electrode active material. The negative electrode active material of this application helps to improve the energy density, cycle performance, and safety performance of electrochemical devices.

Description

Technical Field

[0001] This application relates to the field of energy storage, specifically to a negative electrode active material and an electrochemical and electronic device using the same. Background Technology

[0002] Electrochemical devices (e.g., lithium-ion batteries) are widely used due to their advantages such as environmental friendliness, high operating voltage, large specific capacity, and long cycle life, making them one of the most promising new green chemical power sources in the world today. Small-sized lithium-ion batteries are commonly used as power sources for portable electronic communication devices (e.g., portable cameras, mobile phones, or laptops), especially high-performance portable devices. In recent years, medium-sized and large-sized lithium-ion batteries with high output characteristics have been developed for use in electric vehicles (EVs) and large-scale energy storage systems (ESS). As the application of lithium-ion batteries expands from consumer electronics to hybrid and pure electric vehicles, their energy density, cycle performance, and safety have become key technical issues that urgently need to be addressed. Improving the active materials in the electrodes is one research direction for solving these problems.

[0003] In view of this, it is indeed necessary to provide an improved negative electrode active material and an electrochemical and electronic device using it. Summary of the Invention

[0004] This application attempts to solve at least one problem existing in the relevant field by providing a negative electrode active material and an electrochemical and electronic device using the same.

[0005] According to one aspect of this application, a negative electrode active material is provided, wherein the interplanar spacing of the negative electrode active material is 0.35 nm to 0.45 nm, and the negative electrode active material comprises a metal element, wherein the metal element comprises at least one selected from gold, silver, platinum, zirconium, zinc, magnesium, calcium, barium, vanadium, iron, or aluminum, and the content of the metal element is 20 ppm to 400 ppm based on the total weight of the negative electrode active material. In some embodiments, the interplanar spacing of the negative electrode active material is 0.35 nm to 0.40 nm. In some embodiments, the content of the metal element is 50 ppm to 300 ppm based on the total weight of the negative electrode active material. In some embodiments, the content of the metal element is 100 ppm to 200 ppm based on the total weight of the negative electrode active material. In some embodiments, the content of the metal element is 20 ppm, 50 ppm, 80 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, or 400 ppm based on the total weight of the negative electrode active material.

[0006] According to embodiments of this application, the negative electrode active material further comprises a non-metallic element, including at least one selected from phosphorus, boron, silicon, arsenic, or selenium. Based on the total weight of the negative electrode active material, the content of the non-metallic element is from 50 ppm to 300 ppm. In some embodiments, based on the total weight of the negative electrode active material, the content of the non-metallic element is from 100 ppm to 150 ppm. In some embodiments, based on the total weight of the negative electrode active material, the content of the non-metallic element is 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm, 120 ppm, 130 ppm, 140 ppm, 150 ppm, 160 ppm, 170 ppm, 180 ppm, 190 ppm, 200 ppm, 210 ppm, 230 ppm, 260 ppm, 280 ppm, or 300 ppm.

[0007] According to an embodiment of this application, the negative electrode active material, as measured by Raman spectroscopy, has a wavelength of 1345 cm⁻¹. -1 Up to 1355cm -1 The half-peak width Id of the peak that appears at 1595cm is similar to that at 1595cm. -1 Up to 1605cm -1 The ratio of the full width at half maximum (FWHM) Ig of the peak appearing at a given location, Id / Ig, is 0.7 to 1.5. In some embodiments, the Id / Ig of the negative electrode active material, as measured by Raman spectroscopy, is 1.0 to 1.2. In some embodiments, the Id / Ig of the negative electrode active material, as measured by Raman spectroscopy, is 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5.

[0008] According to an embodiment of this application, the negative electrode active material includes channels, which are located on the surface of the negative electrode active material, inside the negative electrode active material, through the negative electrode active material, or any combination thereof. Based on the total volume of the negative electrode active material, the amount of the channels is no more than 50% by volume, and the inner wall of the channels contains the metallic material.

[0009] According to an embodiment of this application, the negative electrode active material includes channels, which are located on the surface of the negative electrode active material, inside the negative electrode active material, through the negative electrode active material, or any combination thereof. Based on the total volume of the negative electrode active material, the amount of the channels is no more than 50% by volume, and the inner wall of the channels contains the non-metallic material.

[0010] In some embodiments, the amount of pores is no more than 40% by volume, based on the total volume of the negative electrode active material. In some embodiments, the amount of pores is no more than 30% by volume, based on the total volume of the negative electrode active material. In some embodiments, the amount of pores is no more than 20% by volume, based on the total volume of the negative electrode active material. In some embodiments, the amount of pores is 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40% by volume, based on the total volume of the negative electrode active material.

[0011] According to an embodiment of this application, the specific surface area of ​​the negative electrode active material is 2m². 2 / g to 50m 2 / g. In some embodiments, the specific surface area of ​​the negative electrode active material is 5m². 2 / g to 40m 2 / g. In some embodiments, the specific surface area of ​​the negative electrode active material is 8m². 2 / g to 40m 2 / g. In some embodiments, the specific surface area of ​​the negative electrode active material is 10m². 2 / g to 35m 2 / g. In some embodiments, the specific surface area of ​​the negative electrode active material is 30m². 2 / g to 40m 2 / g. In some embodiments, the specific surface area of ​​the negative electrode active material is 2m². 2 / g、5m 2 / g、8m 2 / g, 10m 2 / g、12m 2 / g, 16m 2 / g、18m 2 / g、20m 2 / g、22m 2 / g、24m 2 / g、28m 2 / g、35m 2 / g、45m 2 / g or 50m 2 / g.

[0012] According to another aspect of this application, an electrochemical device is provided, comprising a positive electrode, an electrolyte, and a negative electrode, wherein the positive electrode comprises a positive electrode active material layer and a positive electrode current collector, and the negative electrode comprises a negative electrode active material layer and a negative electrode current collector, wherein the negative electrode active material layer comprises the negative electrode active material according to this application.

[0013] According to embodiments of this application, the porosity of the negative electrode active material layer is 15% to 45%. In some embodiments, the porosity of the negative electrode active material layer is 20% to 40%. In some embodiments, the porosity of the negative electrode active material layer is 25% to 30%. In some embodiments, the porosity of the negative electrode active material layer is 15%, 20%, 25%, 30%, 35%, 40%, or 45%.

[0014] According to embodiments of this application, the cohesive strength of the negative electrode active material is from 5 N / m to 100 N / m. In some embodiments, the cohesive strength of the negative electrode active material is from 10 N / m to 80 N / m. In some embodiments, the cohesive strength of the negative electrode active material is from 20 N / m to 60 N / m. In some embodiments, the cohesive strength of the negative electrode active material is from 30 N / m to 50 N / m. In some embodiments, the cohesive strength of the negative electrode active material is 10 N / m, 15 N / m, 20 N / m, 25 N / m, 30 N / m, 35 N / m, 40 N / m, 45 N / m, 50 N / m, 55 N / m, 60 N / m, 65 N / m, 70 N / m, 75 N / m, or 80 N / m.

[0015] According to embodiments of this application, the peel strength between the negative electrode active material layer and the negative electrode current collector is 3 N / m to 40 N / m. In some embodiments, the peel strength between the negative electrode active material layer and the negative electrode current collector is 5 N / m to 30 N / m. In some embodiments, the peel strength between the negative electrode active material layer and the negative electrode current collector is 10 N / m to 20 N / m. In some embodiments, the peel strength between the negative electrode active material layer and the negative electrode current collector is 3 N / m, 5 N / m, 10 N / m, 15 N / m, 20 N / m, 25 N / m, 30 N / m, 35 N / m, or 40 N / m.

[0016] According to embodiments of this application, the weight of the positive electrode active material layer is 1.5 to 15 times the weight of the negative electrode active material layer. In some embodiments, the weight of the positive electrode active material layer is 3 to 10 times the weight of the negative electrode active material layer. In some embodiments, the weight of the positive electrode active material layer is 5 to 8 times the weight of the negative electrode active material layer. In some embodiments, the weight of the positive electrode active material layer is 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 times the weight of the negative electrode active material layer.

[0017] According to embodiments of this application, the capacity of the negative electrode active material is from 300 mAh / g to 1200 mAh / g. In some embodiments, the capacity of the negative electrode active material is from 500 mAh / g to 1000 mAh / g. In some embodiments, the capacity of the negative electrode active material is from 600 mAh / g to 800 mAh / g. In some embodiments, the capacity of the negative electrode active material is 300 mAh / g, 400 mAh / g, 500 mAh / g, 600 mAh / g, 700 mAh / g, 800 mAh / g, 900 mAh / g, 1000 mAh / g, 1100 mAh / g, or 1200 mAh / g.

[0018] According to another aspect of this application, this application provides an electronic device that includes the electrochemical device described in this application.

[0019] Additional aspects and advantages of this application will be described, shown, or illustrated in part by way of implementation of embodiments thereof in the following description. Attached Figure Description

[0020] The accompanying drawings, necessary for describing embodiments of this application or the prior art, will be briefly described below to facilitate the depiction of embodiments of this application. It is obvious that the drawings described below represent only a portion of the embodiments in this application. Those skilled in the art will be able to derive other embodiments from the structures illustrated in these drawings without requiring inventive effort.

[0021] Figure 1 This is a scanning electron microscope (SEM) image of a negative electrode active material with through-holes.

[0022] Figure 2 This is a scanning electron microscope (SEM) image of a negative electrode active material with internal pores.

[0023] Figure 3 This is a scanning electron microscope (SEM) image of a negative electrode active material with pores on its surface. Detailed Implementation

[0024] Embodiments of this application will be described in detail below. In this specification, identical or similar components and components having identical or similar functions are indicated by similar reference numerals. The embodiments described herein with reference to the accompanying drawings are illustrative and diagrammatic in nature and are intended to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting the application.

[0025] In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0026] As used in this article, "pore" refers to the pore or void structure in a single negative electrode active material particle.

[0027] As used in this article, "pores" refers to the gaps between multiple particles of the negative electrode active material.

[0028] To improve the energy density, cycle performance, and safety of electrochemical devices (e.g., lithium-ion batteries), improving the active materials of the electrodes is one of the research directions. The theoretical upper limit of the electrochemical capacity of graphitized anode active materials is 372 mAh / g, and the electrochemical capacity of previously known graphitized anode active materials is difficult to exceed this limit. Silicon anode active materials have high electrochemical capacity, and the energy density of electrochemical devices can be significantly improved by increasing the dopant content in silicon anode active materials. However, the anode active materials undergo significant volume expansion, which can significantly reduce the performance of electrochemical devices, especially the capacity retention rate during long cycles.

[0029] To address these issues, this application provides a negative electrode active material, wherein the interplanar spacing of the negative electrode active material is 0.35 nm to 0.45 nm, and the negative electrode active material contains a metal element, which includes at least one selected from gold, silver, platinum, zirconium, zinc, magnesium, calcium, barium, vanadium, iron, or aluminum. Based on the total weight of the negative electrode active material, the content of the metal element is 20 ppm to 400 ppm. The pores can be formed by washing the metal element in the negative electrode active material with aqua regia. By controlling the ratio of aqua regia to the metal element and the mixing reaction time, some of the metal element can be retained in the negative electrode active material. When the content of the metal element in the negative electrode active material is within the above range, it helps to improve the cycle performance and safety of the electrochemical device.

[0030] The interplanar spacing of the negative electrode active material can be obtained by X-ray diffraction spectroscopy: using an X-ray diffractometer (e.g., X'Pert PRO), the test is performed according to the standard "GB / T 24533-2009 Graphite Anode Materials for Lithium-ion Batteries". The interplanar spacing d is calculated using the Bragg formula: 2dsinθ=nλ, where λ represents the wavelength of the X-ray and θ represents the diffraction half-angle.

[0031] In some embodiments, the interplanar spacing of the negative electrode active material is 0.35 nm to 0.40 nm.

[0032] In some embodiments, the content of the metal element is from 50 ppm to 300 ppm based on the total weight of the negative electrode active material. In some embodiments, the content of the metal element is from 100 ppm to 200 ppm based on the total weight of the negative electrode active material. In some embodiments, the content of the metal element is 20 ppm, 50 ppm, 80 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, or 400 ppm.

[0033] According to embodiments of this application, the negative electrode active material further comprises a non-metallic element, including at least one selected from phosphorus, boron, silicon, arsenic, or selenium. Based on the total weight of the negative electrode active material, the content of the non-metallic element is from 50 ppm to 200 ppm. In some embodiments, based on the total weight of the negative electrode active material, the content of the non-metallic element is from 100 ppm to 150 ppm. In some embodiments, based on the total weight of the negative electrode active material, the content of the non-metallic element is 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm, 120 ppm, 130 ppm, 140 ppm, 150 ppm, 160 ppm, 170 ppm, 180 ppm, 190 ppm, or 200 ppm.

[0034] According to an embodiment of this application, the negative electrode active material, as measured by Raman spectroscopy, has a wavelength of 1345 cm⁻¹. -1 Up to 1355cm -1 The half-peak width Id of the peak that appears at 1595cm is similar to that at 1595cm. -1 Up to 1605cm -1The ratio of the full width at half maximum (FWHM) Ig of the peak appearing at a given location, Id / Ig, is between 0.7 and 1.5. In some embodiments, the Id / Ig of the negative electrode active material, as measured by Raman spectroscopy, is between 1.0 and 1.2. In some embodiments, the Id / Ig of the negative electrode active material, as measured by Raman spectroscopy, is 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5. When the Id / Ig of the negative electrode active material is within the above-mentioned range, there are more crystal defects on the surface of the negative electrode active material, and the disorder of the negative electrode active material is higher.

[0035] According to an embodiment of this application, the negative electrode active material comprises channels, and the inner wall of the channels contains the metallic material. When the inner wall of the channels contains metallic elements, the metallic elements are close to the lithium ion insertion sites and readily form alloy compounds with lithium, thereby improving the electrochemical activity of lithium without forming lithium dendrites.

[0036] According to an embodiment of this application, the negative electrode active material includes channels, and the inner wall of the channels contains the non-metallic material.

[0037] According to embodiments of this application, the channels are located on the surface of the negative electrode active material (e.g., Figure 3 As shown), inside the negative electrode active material (e.g. Figure 2 As shown), penetrating the negative electrode active material (such as... Figure 1 (as shown) or any combination thereof. Different forms of pores (e.g., on the surface of the negative electrode active material, inside the negative electrode active material, and / or through the negative electrode active material) have little effect on the electrochemical capacity of the negative electrode active material. Porous negative electrode active materials have a larger specific surface area, and the inner walls of the pores can effectively adsorb lithium, which helps to improve the electrochemical capacity of the negative electrode active material.

[0038] According to embodiments of this application, the amount of pores is no more than 50% by volume based on the total volume of the negative electrode active material. In some embodiments, the amount of pores is no more than 40% by volume based on the total volume of the negative electrode active material. In some embodiments, the amount of pores is no more than 30% by volume based on the total volume of the negative electrode active material. In some embodiments, the amount of pores is no more than 20% by volume based on the total volume of the negative electrode active material. In some embodiments, the amount of pores is 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40% by volume based on the total volume of the negative electrode active material. The amount of pores in the negative electrode active material can be achieved by controlling the reaction time, reaction temperature, amount of raw material added, pH value of the first solution, and molar ratio of aqua regia to metal oxide.

[0039] According to an embodiment of this application, the specific surface area of ​​the negative electrode active material is 20 m².2 / g to 50m 2 / g. In some embodiments, the specific surface area of ​​the negative electrode active material is 30m². 2 / g to 40m 2 / g. In some embodiments, the specific surface area of ​​the negative electrode active material is 20m². 2 / g、25m 2 / g、30m 2 / g、35m 2 / g、40m 2 / g、45m 2 / g or 50m 2 / g. The presence of pores can significantly increase the specific surface area of ​​the negative electrode active material, thereby increasing the contact sites between the negative electrode active material and the electrolyte. The specific surface area of ​​the negative electrode active material can be obtained by nitrogen adsorption testing: according to GB / T19587-2017 standard, the test is conducted using a Tristar II 3020M instrument: a helium-nitrogen mixture (helium:nitrogen = 4:1, helium as the carrier gas, nitrogen as the adsorbate gas) is flowed through the sample, and the ratio change before and after nitrogen adsorption is accurately measured by utilizing the adsorption of nitrogen at liquid nitrogen temperature and the desorption under liquid nitrogen conditions. The specific surface area of ​​the sample is calculated using the solid standard reference method as the analysis model of the test software.

[0040] According to embodiments of this application, the cohesive strength of the negative electrode active material is from 5 N / m to 100 N / m. In some embodiments, the cohesive strength of the negative electrode active material is from 10 N / m to 80 N / m. In some embodiments, the cohesive strength of the negative electrode active material is from 20 N / m to 60 N / m. In some embodiments, the cohesive strength of the negative electrode active material is from 30 N / m to 50 N / m. In some embodiments, the cohesive strength of the negative electrode active material is 10 N / m, 15 N / m, 20 N / m, 25 N / m, 30 N / m, 35 N / m, 40 N / m, 45 N / m, 50 N / m, 55 N / m, 60 N / m, 65 N / m, 70 N / m, 75 N / m, or 80 N / m. The presence of pores reduces the contact sites between the active material and the binder, thereby reducing the cohesive strength of the negative electrode active material. When the cohesive strength of the negative electrode active material is within the above range, the particles of the negative electrode active material have appropriate adhesion, which can avoid powder shedding during the rolling and winding process, avoid the formation of micro short circuit sites inside the cell, and thus avoid safety hazards; it can also prevent the negative electrode active material from expanding in volume during the charging and discharging process, avoid incomplete lithium intercalation, and thus ensure the capacity of the electrochemical device.

[0041] The cohesive strength of the negative electrode active material can be tested using an Instron (model 33652) tester: Take an electrode sheet (30mm wide and 100-160mm long), fix it to a steel plate with double-sided adhesive tape (model: 3M9448A, 20mm wide and 90-150mm long), attach the tape to the surface of the negative electrode active material layer, and connect one side of the tape to a paper strip of the same width. Adjust the limit block of the tensile testing machine to a suitable position, fold the paper strip upward and slide it 40mm at a sliding speed of 50mm / min, and test the polymerization strength between particles inside the negative electrode active material layer at 180° (i.e., reverse stretching).

[0042] According to embodiments of this application, the capacity of the negative electrode active material is from 300 mAh / g to 1200 mAh / g. In some embodiments, the capacity of the negative electrode active material is from 500 mAh / g to 1000 mAh / g. In some embodiments, the capacity of the negative electrode active material is from 600 mAh / g to 800 mAh / g. In some embodiments, the capacity of the negative electrode active material is 300 mAh / g, 400 mAh / g, 500 mAh / g, 600 mAh / g, 700 mAh / g, 800 mAh / g, 900 mAh / g, 1000 mAh / g, 1100 mAh / g, or 1200 mAh / g.

[0043] In some implementations, the negative electrode active material may include, but is not limited to, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Or LI-1 alloys. Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon, and mixtures thereof. Crystalline carbon can be amorphous or flake-shaped, small flake-shaped, spherical, or fibrous natural or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbides, calcined coke, etc.

[0044] negative electrode

[0045] The negative electrode includes a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is disposed on the negative electrode current collector. The negative electrode active material layer includes the negative electrode active material according to this application.

[0046] The negative current collector used in this application may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0047] According to embodiments of this application, the porosity of the negative electrode active material layer is 15% to 45%. In some embodiments, the porosity of the negative electrode active material layer is 20% to 40%. In some embodiments, the porosity of the negative electrode active material layer is 25% to 30%. In some embodiments, the porosity of the negative electrode active material layer is 15%, 20%, 25%, 30%, 35%, 40%, or 45%. The porosity of the negative electrode active material layer can be achieved by controlling the rolling pressure during the negative electrode preparation process. By controlling the rolling pressure, the thickness of the negative electrode active material layer can be continuously varied, thereby controlling the porosity of the negative electrode active material layer. Specifically, the porosity of the negative electrode active material layer can be calculated by the mass-volume method using the AccuPyc II 1340 testing instrument, according to the standard GB / T24586-2009 "Determination of Apparent Density, True Density and Porosity of Iron Ore". When the porosity of the negative electrode active material layer is within the above range, it helps to improve the energy density of the electrochemical device.

[0048] According to embodiments of this application, the peel strength between the negative electrode active material layer and the negative electrode current collector is 3 N / m to 40 N / m. In some embodiments, the peel strength between the negative electrode active material layer and the negative electrode current collector is 5 N / m to 30 N / m. In some embodiments, the peel strength between the negative electrode active material layer and the negative electrode current collector is 10 N / m to 20 N / m. In some embodiments, the peel strength between the negative electrode active material layer and the negative electrode current collector is 3 N / m, 5 N / m, 10 N / m, 15 N / m, 20 N / m, 25 N / m, 30 N / m, 35 N / m, or 40 N / m. When the peel strength between the negative electrode active material layer and the negative electrode current collector is within the above range, there is appropriate adhesion between the negative electrode active material layer and the negative electrode current collector, which can prevent delamination or burr generation during rolling or slitting processes, thereby avoiding safety hazards. Simultaneously, it can ensure that the internal resistance of the battery cell is within an acceptable range, guaranteeing the kinetic and cycle performance of the electrochemical device.

[0049] The peel strength between the negative electrode active material layer and the negative electrode current collector can be achieved by controlling the rolling process during the negative electrode preparation. Specifically, the peel strength between the negative electrode active material layer and the negative electrode current collector can be tested using an Instron (model 33652) tester: Take an electrode sheet (30mm wide, 100-160mm long), fix it to a steel plate with double-sided adhesive tape (model: 3M9448A, 20mm wide, 90-150mm long), attach the adhesive tape to the surface of the negative electrode active material layer, with one side of the adhesive tape connected to a paper strip of equal width, adjust the tensile testing machine limit block to a suitable position, fold the paper strip upwards and slide it 40mm at a sliding speed of 50mm / min, and test the peel strength between the negative electrode active material layer and the negative electrode current collector at 180° (i.e., reverse stretching).

[0050] According to embodiments of this application, the negative electrode further includes a conductive layer. In some embodiments, the conductive material of the conductive layer may include any conductive material, as long as it does not cause a chemical change. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, graphene, etc.), metal-based materials (e.g., metal powders, metal fibers, such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0051] According to embodiments of this application, the negative electrode further includes an adhesive selected from at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0052] positive electrode

[0053] The positive electrode includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector. The specific type of positive electrode active material is not limited and can be selected according to requirements.

[0054] In some implementations, the positive electrode active material includes a positive electrode material capable of absorbing and releasing lithium (Li). Examples of positive electrode materials capable of absorbing / releasing lithium (Li) may include lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.

[0055] Specifically, the chemical formula of lithium cobalt oxide can be as shown in Chemical Formula 1:

[0056] Li x Co a M1 b O 2-c Chemical Formula 1

[0057] Where M1 represents at least one of nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), zirconium (Zr), and silicon (Si), and the values ​​of x, a, b, and c are respectively within the following ranges: 0.8≤x≤1.2, 0.8≤a≤1, 0≤b≤0.2, and -0.1≤c≤0.2.

[0058] The chemical formulas of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide can be as shown in Chemical Formula 2:

[0059] Li y Ni d M2 e O 2-f Chemical formula 2

[0060] Where M2 represents at least one selected from cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr), and silicon (Si), and the values ​​of y, d, e, and f are respectively within the following ranges: 0.8≤y≤1.2, 0.3≤d≤0.98, 0.02≤e≤0.7, and -0.1≤f≤0.2.

[0061] The chemical formula of lithium manganese oxide can be as shown in chemical formula 3:

[0062] Li z Mn 2-g M3 g O 4-h Chemical formula 3

[0063] Where M3 represents at least one selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W), and the values ​​of z, g, and h are in the following ranges: 0.8≤z≤1.2, 0≤g<1.0, and -0.2≤h≤0.2, respectively.

[0064] In some embodiments, the weight of the positive electrode active material layer is 1.5 to 15 times the weight of the negative electrode active material layer. In some embodiments, the weight of the positive electrode active material layer is 1.9 to 10 times the weight of the negative electrode active material layer. In some embodiments, the weight of the positive electrode active material layer is 5 to 8 times the weight of the negative electrode active material layer. In some embodiments, the weight of the positive electrode active material layer is 1.5, 1.8, 1.9, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 times the weight of the negative electrode active material layer.

[0065] In some embodiments, the positive electrode active material layer may have a coating on its surface, or may be mixed with another compound having a coating. The coating may include at least one coating element compound selected from oxides, hydroxides, hydroxyoxides, oxycarbonates, and hydroxycarbonates of the coating element. The compound used for the coating may be amorphous or crystalline. The coating element contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, or mixtures thereof. The coating may be applied by any method, as long as the method does not adversely affect the performance of the positive electrode active material. For example, the method may include any coating method well known to those skilled in the art, such as spraying, dipping, etc.

[0066] In some embodiments, the positive electrode active material layer also includes an adhesive, and optionally also includes a positive electrode conductive material.

[0067] Adhesives can improve the bonding between positive electrode active material particles and also improve the bonding between the positive electrode active material and the current collector. Non-limiting examples of adhesives include 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, nylon, etc.

[0068] The positive electrode active material layer includes a positive electrode conductive material, thereby imparting conductivity to the electrode. The positive electrode conductive material may include any conductive material, as long as it does not cause a chemical change. Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0069] The positive electrode current collector used in the electrochemical device according to this application may be aluminum (Al), but is not limited thereto.

[0070] electrolyte

[0071] The electrolyte that can be used in the embodiments of this application can be an electrolyte known in the prior art.

[0072] Electrolytes that can be used in the electrolytes of this application embodiment include, but are not limited to: inorganic lithium salts, such as LiClO4, LiAsF6, LiPF6, LiBF4, LiSbF6, LiSO3F, LiN(FSO2)2, etc.; fluorinated organic lithium salts, such as LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,3-hexafluoropropanedisulfonylimide lithium, cyclic 1,2-tetrafluoroethanedisulfonylimide lithium, LiN(CF3SO2)(C4F9S The electrolytes include LiC(CF3SO2)3, LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2; and lithium salts containing dicarboxylic acid complexes, such as lithium bis(oxalate)borate, lithium difluorooxalate borate, lithium tri(oxalate)phosphate, lithium difluorobis(oxalate)phosphate, and lithium tetrafluoro(oxalate)phosphate. Furthermore, one of the above electrolytes can be used alone, or two or more can be used simultaneously. In some embodiments, the electrolyte includes a combination of LiPF6 and LiBF4. In some embodiments, the electrolyte comprises a combination of an inorganic lithium salt such as LiPF6 or LiBF4 and a fluorinated organic lithium salt such as LiCF3SO3, LiN(CF3SO2)2, or LiN(C2F5SO2)2. In some embodiments, the electrolyte comprises LiPF6.

[0073] In some embodiments, the concentration of the electrolyte is in the range of 0.8-3 mol / L, for example, in the range of 0.8-2.5 mol / L, 0.8-2 mol / L, 1-2 mol / L, or for example, 1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L.

[0074] Solvents that can be used in the electrolytes of this application include, but are not limited to: carbonate compounds, ester-based compounds, ether-based compounds, ketone-based compounds, alcohol-based compounds, aprotic solvents, or combinations thereof.

[0075] Examples of carbonate compounds include, but are not limited to, chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.

[0076] Examples of chain carbonate compounds include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof. Examples of fluorinated carbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.

[0077] Examples of ester-based compounds include, but are not limited to, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valproic acid lactone, caprolactone, methyl formate, and combinations thereof.

[0078] Examples of ether-based compounds include, but are not limited to, dibutyl ether, tetraethylene dimethyl ether, diethylene dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0079] Examples of ketone-based compounds include, but are not limited to, cyclohexanone.

[0080] Examples of alcohol-based compounds include, but are not limited to, ethanol and isopropanol.

[0081] Examples of aprotic solvents include, but are not limited to, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, nitromethane, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.

[0082] Separating membrane

[0083] In some embodiments, a separator is provided between the positive and negative electrodes to prevent short circuits. The material and shape of the separator used in the embodiments of this application are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic material formed from a material stable to the electrolyte of this application.

[0084] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected. The porous structure can improve the heat resistance, oxidation resistance, and electrolyte wetting properties of the separator, and enhance the adhesion between the separator and the electrode.

[0085] A surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances.

[0086] The inorganic layer comprises inorganic particles and a binder. The inorganic particles are selected from one or more of the following: alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from one or more of the following: polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0087] The polymer layer contains a polymer, the polymer material of which is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0088] Electrochemical device

[0089] This application also provides an electrochemical device comprising a positive electrode, an electrolyte, and a negative electrode. The positive electrode comprises a positive electrode active material layer and a positive electrode current collector, and the negative electrode comprises a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer comprises the negative electrode active material according to this application.

[0090] The electrochemical device of this application includes any device in which an electrochemical reaction occurs, and specific examples include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0091] Electronic devices

[0092] This application also provides an electronic device that includes an electrochemical device according to this application.

[0093] The application of the electrochemical device described in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the electrochemical device described in this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0094] The following uses a lithium-ion battery as an example and combines specific embodiments to illustrate the preparation of a lithium-ion battery. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0095] Example

[0096] The following describes the performance evaluation based on the embodiments and comparative examples of the lithium-ion battery of this application.

[0097] I. Preparation of Lithium-ion Batteries

[0098] 1. Preparation of negative electrode active materials

[0099] 2 kg of artificial graphite was dispersed in ethanol to obtain the first solution. 0.05 mol of citric acid was dissolved in 1 mL of isopropanol. After complete dissolution, 1.5 mol of magnesium nitrate hexahydrate was added, and the mixture was stirred at 1000 rpm for at least 30 minutes. After filtration through an aqueous filter membrane, a magnesium oxide sol-gel solution was obtained. Nanoparticles (gold nanoparticles, silver nanoparticles, or gold-silver alloy nanoparticles) were rapidly injected into the magnesium oxide sol-gel solution, yielding the second solution. 1000 mL of the second solution was added to the first solution, and the mixture was stirred continuously at 50 °C for 90 minutes to obtain the third solution. Aqua regia was then dispersed in the third solution to elute the nanoparticles (gold nanoparticles, silver nanoparticles, or gold-silver alloy nanoparticles), releasing the space they occupied to form pores (containing some residual gold or silver). The solvent was removed by drying at 70 °C for 10 hours, followed by heat treatment at 1000 °C under an argon atmosphere to remove impurities, yielding the negative electrode active material.

[0100] 2. Preparation of the negative electrode

[0101] The negative electrode active material, styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) were thoroughly mixed in an appropriate amount of deionized water at a weight ratio of 97:2:1 to form a uniform negative electrode slurry with a solid content of 54 wt%. This slurry was coated onto a negative electrode current collector (copper foil), dried at 85°C, and then cold-pressed, cut, and slit before being dried under vacuum at 120°C for 12 hours to obtain the negative electrode.

[0102] 3. Preparation of the positive electrode

[0103] Lithium cobalt oxide (LiCoO2), a positive electrode active material, Super P, and polyvinylidene fluoride (PVDF), a binder, were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 97:1.4:1.6 to form a uniform positive electrode slurry with a solid content of 72 wt%. This slurry was coated onto aluminum foil for the positive electrode current collector, dried at 85°C, and then cold-pressed, cut, and slit before being dried under vacuum at 85°C for 4 hours to obtain the positive electrode.

[0104] 4. Preparation of electrolyte

[0105] In a dry argon atmosphere glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC:EMC:DEC = 30:50:20. Then, 1.5% of 1,3-propanesulfonyl lactone and 2% of fluoroethylene carbonate were added, dissolved, and stirred thoroughly. Lithium salt LiPF6 was then added and mixed evenly to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0106] 5. Preparation of the separating membrane

[0107] A 7μm thick porous polyethylene (PE) polymer film was used as the separator.

[0108] 6. Preparation of lithium-ion batteries

[0109] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. Then, the electrodes are wound, the tabs are welded, and the battery is placed in an outer packaging foil aluminum-plastic film. Electrolyte is injected, and the battery undergoes vacuum sealing, settling, formation, shaping, and capacity testing to obtain a soft-pack lithium-ion battery.

[0110] II. Testing Methods

[0111] 1. Test method for cycle capacity retention of lithium-ion batteries

[0112] In an environment of 25℃, the lithium-ion battery was charged at a constant current of 0.7C to a voltage of 4.4V, and then charged at a constant voltage; it was then discharged at a constant current of 1C to a voltage of 3V. This is recorded as one cycle, and the discharge capacity of the first cycle is recorded. 200 cycles were performed, and the discharge capacity of the 200th cycle is recorded. The cycle capacity retention rate of the lithium-ion battery is calculated using the following formula:

[0113] Cycle capacity retention = (Discharge capacity of the 200th cycle / Discharge capacity of the first cycle) × 100%.

[0114] Five samples were tested for each embodiment or comparative example, and the average value was taken.

[0115] 2. Test method for thermal shock withstand time of lithium-ion batteries

[0116] The lithium-ion battery was fully charged and placed in a high-temperature chamber at 150°C. The time when the lithium-ion battery began to show signs of flame was recorded as the thermal shock withstand time. Five samples were tested for each embodiment or comparative example, and the average value was taken.

[0117] 3. Overcharge test method for lithium-ion batteries

[0118] The surface temperature of the lithium-ion battery was tested by overcharging it at a 1C rate current density under 10V. Five samples were tested for each example or comparative example, and the average value was taken.

[0119] 4. Penetration test method for lithium-ion batteries

[0120] The lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 0.5C to a voltage of 4.4V, followed by constant voltage charging at 4.4V to a current of 0.025C. The fully charged battery was transferred to a nail-piercing tester. Maintaining an ambient temperature of 25°C ± 2°C, a 4mm diameter steel nail was driven through the center of the battery at a constant speed of 30mm / s for 300 seconds. The surface temperature of the battery was then measured. Five samples were tested for each example or comparative example, and the average value was taken.

[0121] 5. Impact Test Methods for Lithium-ion Batteries

[0122] At 25°C, the lithium-ion battery was charged at a constant current of 0.5C to a voltage of 4.3V, and then charged at a constant voltage of 4.3V to a current of 0.05C. The UL1642 test standard was used, in which a 9.8kg, 15.8mm diameter weight was used to drop the lithium-ion battery from a height of 61±2.5cm for impact testing. The surface temperature of the lithium-ion battery was also measured. Five samples were tested for each example or comparative example, and the average value was taken.

[0123] 6. Test method for cohesive strength of negative electrode active materials

[0124] Tests were conducted using an Instron (model 33652) tester: An electrode sheet (30mm wide, 100-160mm long) was taken and fixed to a steel plate with double-sided adhesive tape (model: 3M9448A, 20mm wide, 90-150mm long). The tape was then attached to the surface of the negative electrode active material layer, with one side of the tape connected to a paper strip of equal width. The tensile testing machine limit block was adjusted to a suitable position, and the paper strip was folded upwards and slid 40mm at a sliding rate of 50mm / min. The polymerization strength between particles inside the negative electrode active material layer was tested at 180° (i.e., reverse stretching).

[0125] 7. Test method for specific surface area of ​​negative electrode active material

[0126] According to GB / T 19587-2017 standard, the Tristar II 3020M instrument was used for testing: a helium-nitrogen mixture (helium:nitrogen = 4:1, helium as the carrier gas, nitrogen as the adsorbate) was flowed through the sample, and the ratio change before and after nitrogen was accurately measured by utilizing the adsorption of nitrogen at liquid nitrogen temperature and the desorption under liquid nitrogen conditions. The specific surface area of ​​the sample was calculated using the solid standard reference method as the analysis model of the testing software.

[0127] 8. Test method for peel strength between negative electrode active material layer and negative electrode current collector

[0128] The test was conducted using an Instron (model 33652) tester: An electrode sheet (30mm wide and 100-160mm long) was taken and fixed to a steel plate with double-sided adhesive tape (model: 3M9448A, 20mm wide and 90-150mm long). The tape was then attached to the surface of the negative electrode active material layer, with one side of the tape connected to a paper strip of equal width. The tensile testing machine limit block was adjusted to a suitable position, and the paper strip was folded upwards and slid 40mm at a sliding rate of 50mm / min. The peel strength between the negative electrode active material layer and the negative electrode current collector was tested at 180° (i.e., in the opposite direction of tension).

[0129] 9. Test method for porosity of negative electrode active material layer

[0130] According to the standard GB / T 24586-2009 "Determination of Apparent Density, True Density and Porosity of Iron Ore", the apparent density, true density and porosity of iron ore were determined using the AccuPyc II 1340 testing instrument and the porosity was calculated by the mass-volume method. The volume of each sample was measured at least three different locations, and the average value was taken. The mass of the samples was measured using an electronic balance, with each sample measured at least three times and the average value taken. The porosity of the negative electrode active material layer was calculated using the following formula:

[0131] Porosity = m / V × Ps × 100%

[0132] Where: m is the average mass obtained from the test (g), and V is the average volume obtained from the test (cm³). 3 Ps is the true density of the sample (g / cm³). 3 ).

[0133] III. Test Results

[0134] Tables 1-3 illustrate the characteristics of the negative electrode active materials used in the lithium-ion batteries of the embodiments and comparative examples according to this application, and their impact on the energy density, cycle performance, and safety of the lithium-ion batteries. In Table 2, except for the parameters listed, Examples 24-40 are subject to the same conditions as Example 15, and Example 41 is subject to the same conditions as Example 3. In Table 3, except for the parameters listed, Examples 42-67 are subject to the same conditions as Example 15.

[0135] As shown in Table 1, the negative electrode active material used in Comparative Example 1 has a crystal plane spacing of less than 0.35 nm and contains no metal elements. The lithium-ion battery exhibits extremely low cycle capacity retention, a very short thermal shock withstand time, and very high surface temperatures in overcharge, nail penetration, and impact tests, making it prone to high-temperature safety hazards and exhibiting poor safety performance. The negative electrode active material used in Comparative Example 2 has a crystal plane spacing in the range of 0.35 nm to 0.45 nm but does not contain metal elements. The lithium-ion battery shows slightly improved cycle capacity retention but remains low, a very short thermal shock withstand time, and very high surface temperatures in overcharge, nail penetration, and impact tests (i.e., poor safety). As shown in Comparative Examples 3 and 4, when the metal element content in the negative electrode active material is less than 20 ppm or greater than 400 ppm, the lithium-ion battery exhibits low cycle capacity retention, a very short thermal shock withstand time, and very high surface temperatures in overcharge, nail penetration, and impact tests (i.e., poor safety).

[0136] As shown in Examples 1-20, when the interplanar spacing of the negative electrode active material is in the range of 0.35 nm to 0.45 nm and contains 20 ppm to 400 ppm of metal elements, the cycle capacity retention rate of the lithium-ion battery is significantly increased, the thermal shock withstand time is significantly reduced, and the surface temperature in overcharge tests, nail penetration tests, and impact tests is significantly reduced. In other words, the lithium-ion battery exhibits significantly improved cycle performance and safety performance. When the negative electrode active material contains channels and the inner walls of the channels contain metal elements, the cycle capacity retention rate of the lithium-ion battery can be further improved, and the thermal shock withstand time and surface temperature in overcharge tests, nail penetration tests, and impact tests can be reduced. Different types of metal elements can achieve essentially equivalent effects.

[0137] Furthermore, when the negative electrode active material further incorporates 50 ppm to 200 ppm of non-metallic elements, the cycle capacity retention, thermal shock withstand time, and surface temperature in overcharge, nail penetration, and impact tests of lithium-ion batteries can be further improved. When the negative electrode active material contains pores and the inner walls of these pores contain non-metallic elements, it helps to further improve the cycle performance and safety performance of lithium-ion batteries. Different types of non-metallic elements can achieve essentially equivalent effects.

[0138] As shown in Table 2, when the Id / Ig ratio of the negative electrode active material, as measured by Raman spectroscopy, is in the range of 0.7 to 1.5, it can further improve the cycle capacity retention of lithium-ion batteries and reduce the thermal shock withstand time and surface temperature in overcharge, nail penetration, and impact tests. When the volume content of pores in the negative electrode active material is no more than 50%, it helps to further improve the cycle performance and safety performance of lithium-ion batteries. When the specific surface area of ​​the negative electrode active material is 2m²... 2 / g to 50m 2When the value is within the range of / g, it helps to further improve the cycle performance and safety performance of lithium-ion batteries.

[0139] As shown in Table 3, when the porosity of the negative electrode active material layer is in the range of 15% to 45%, the cohesive strength of the negative electrode active material is in the range of 5 N / m to 100 N / m, the peel strength between the negative electrode active material layer and the negative electrode current collector is in the range of 3 N / m to 40 N / m, the weight ratio of the positive electrode active material layer to the negative electrode active material layer is in the range of 1.5 to 15, and the capacity of the negative electrode active material is in the range of 300 mAh / g to 1200 mAh / g, it helps to further improve the cycle performance and safety performance of lithium-ion batteries.

[0140] Improving the cycle performance of lithium-ion batteries while ensuring their safety helps expand their application areas and provides broad space for their development.

[0141]

[0142]

[0143]

[0144]

[0145] Throughout this specification, references to "embodiment," "partial embodiment," "one embodiment," "another example," "example," "specific example," or "partial example" mean that at least one embodiment or example in this application includes a specific feature, structure, material, or characteristic described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics described herein can be combined in any suitable manner in one or more embodiments or examples.

[0146] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A negative electrode active material, wherein, The negative electrode active material includes a carbon material, which includes crystalline carbon, amorphous carbon, and mixtures thereof. The interplanar spacing of the negative electrode active material is 0.35 nm to 0.45 nm, and the negative electrode active material contains a metal element, which includes at least one of gold, silver, platinum, zirconium, zinc, magnesium, calcium, barium, vanadium, iron, or aluminum. Based on the total weight of the negative electrode active material, the content of the metal element is 20 ppm to 400 ppm. The negative electrode active material further comprises a non-metallic element, which includes at least one of boron, arsenic or selenium, and the content of the non-metallic element is from 50 ppm to 300 ppm based on the total weight of the negative electrode active material. The negative electrode active material includes channels, which are located on the surface of the negative electrode active material, inside the negative electrode active material, through the negative electrode active material, or any combination thereof. Based on the total volume of the negative electrode active material, the amount of the channels is no more than 50% by volume, and the inner wall of the channels contains the metallic element and the non-metallic element.

2. The negative electrode active material according to claim 1, wherein the negative electrode active material, as determined by Raman spectroscopy, exhibits a polarity at 1345 cm⁻¹. -1 Up to 1355cm -1 The half-peak width Id of the peak that appears at 1595cm is similar to that at 1595cm. -1 Up to 1605cm -1 The ratio of the half-peak width Ig of the peak appearing at a certain point, Id / Ig, is 0.7 to 1.

5.

3. The negative electrode active material according to claim 1, wherein the specific surface area of ​​the negative electrode active material is 2m². 2 / g to 50m 2 / g.

4. An electrochemical device comprising a positive electrode, an electrolyte, and a negative electrode, wherein the positive electrode comprises a positive electrode active material layer and a positive electrode current collector, and the negative electrode comprises a negative electrode active material layer and a negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material according to any one of claims 1 to 3.

5. The electrochemical device according to claim 4, wherein the porosity of the negative electrode active material layer is 15% to 45%.

6. The electrochemical device according to claim 4, wherein the cohesive strength of the negative electrode active material is from 5 N / m to 100 N / m.

7. The electrochemical device according to claim 4, wherein the peel strength between the negative electrode active material layer and the negative electrode current collector is 3 N / m to 40 N / m.

8. The electrochemical device according to claim 4, wherein the weight of the positive electrode active material layer is 1.5 to 15 times the weight of the negative electrode active material layer.

9. The electrochemical device according to claim 4, wherein the capacity of the negative electrode active material is from 300 mAh / g to 1200 mAh / g.

10. An electronic device comprising an electrochemical device according to any one of claims 4 to 9.

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