Electrochemical devices and electronic devices

Abstract

The present application relates to an electrochemical device and an electronic device. Specifically, the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material, the negative electrode active material contains broken particles, and the particle breakage rate of the negative electrode active material is 20% to 80%. The electrochemical device of the present application has improved cycle performance and safety performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of energy storage, and in particular, to an electrochemical device and an electronic device. BACKGROUND

[0002] Electrochemical devices (e.g., lithium ion batteries) have been widely used due to their environmental friendliness, high operating voltage, large specific capacity, and long cycle life, and have become the most promising new green chemical power source in the world today. Small-sized lithium ion batteries are usually used as power sources for driving portable electronic communication devices (e.g., camcorders, mobile phones, or notebook computers, etc.), especially for high-performance portable devices. In recent years, medium- and large-sized lithium ion batteries with high output characteristics have been developed for application in electric vehicles (EVs) and large-scale energy storage systems (ESSs). As the application field of lithium ion batteries is expanded from consumer electronics to hybrid and pure power fields, the cycle performance and safety of lithium ion batteries have become key technical problems to be solved. Improving the active material in the electrode is one of the research directions to solve the above problems.

[0003] In view of this, it is necessary to provide an improved electrochemical device and an electronic device. SUMMARY

[0004] The present application attempts to solve at least one problem existing in the related art, at least to some extent, by providing an electrochemical device and an electronic device.

[0005] According to an aspect of the present application, the present application provides an electrochemical device, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises broken particles, and the particle breakage rate of the negative electrode active material is 20% to 80%. In some embodiments, the particle breakage rate of the negative electrode active material is 30% to 60%. In some embodiments, the particle breakage rate of the negative electrode active material is 40% to 50%. In some embodiments, the particle breakage rate of the negative electrode active material is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%.

[0006] According to an embodiment of the present application, the broken particles have cracks or fissures with a width of no more than 4 μm. In some embodiments, the broken particles have cracks or fissures with a width of no more than 3.5 μm. In some embodiments, the broken particles have cracks or fissures with a width of no more than 2.5 μm. In some embodiments, the broken particles have cracks or fissures with a width of no more than 2 μm.

[0007] According to embodiments of the present application, the roughness of the negative electrode active material layer is not greater than 6 pm. In some embodiments, the roughness of the negative electrode active material layer is not greater than 5 pm. In some embodiments, the roughness of the negative electrode active material layer is not greater than 3 pm. In some embodiments, the roughness of the negative electrode active material layer is not greater than 1 pm. In some embodiments, the roughness of the negative electrode active material layer is 0.5 pm, 1 pm, 2 pm, 3 pm, 4 pm, 5 pm, or 6 pm.

[0008] According to embodiments of the present application, the cohesion strength of the negative electrode active material is 5 N / m to 30 N / m. In some embodiments, the cohesion strength of the negative electrode active material is 8 N / m to 25 N / m. In some embodiments, the cohesion strength of the negative electrode active material is 5 N / m, 10 N / m, 15 N / m, 20 N / m, 25 N / m, or 30 N / m.

[0009] According to embodiments of the present application, the adhesion between the negative electrode active material layer and the negative electrode current collector is 5 N / m to 20 N / m. In some embodiments, the adhesion between the negative electrode active material layer and the negative electrode current collector is 10 N / m to 15 N / m. In some embodiments, the adhesion between the negative electrode active material layer and the negative electrode current collector is 5 N / m, 8 N / m, 10 N / m, 12 N / m, 14 N / m, 16 N / m, 18 N / m, or 20 N / m.

[0010] According to embodiments of the present application, the negative electrode active material has a peak appearing at 1345 cm -1 to 1355 cm -1 -1, and a half-peak width of the peak appearing at 1595 cm -1 to 1605 cm -1 -1 is 0.7 to 1.5. In some embodiments, the negative electrode active material has an Id / Ig of 1.0 to 1.2. In some embodiments, the negative electrode active material has an Id / Ig of 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5.

[0011] According to embodiments of the present application, the Id is 200 cm -1 to 1100 cm -1 -1. In some embodiments, the Id is 2200 cm -1 to 1000 cm -1 -1. In some embodiments, the Id is 2500 cm -1 to 900 cm -1 -1. In some embodiments, the Id is 200 cm-11 , 300 cm -1 , 400 cm -1 , 500 cm -1 , 550 cm -1 , 600 cm -1 , 700 cm -1 , 850 cm -1 , 900 cm -1 , 1000 cm -1 , 1100 cm -1 .

[0012] According to embodiments of the present application, the negative electrode active material contains at least one of a metal element or a non-metal element, the metal element contains at least one of 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; the non-metal element includes at least one of phosphorus, boron, silicon, arsenic or selenium, and the content of the non-metal element is 50 ppm to 400 ppm based on the total weight of the negative electrode active material.

[0013] 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.

[0014] In some embodiments, the content of the non-metal element is 100 ppm to 350 ppm based on the total weight of the negative electrode active material. In some embodiments, the content of the non-metal 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, 210 ppm, 240 ppm, 280 ppm, 310 ppm, 380 ppm or 400 ppm based on the total weight of the negative electrode active material.

[0015] According to embodiments of the present application, the negative electrode active material has pores, the pore size of the pores is not greater than 3 μm, and the inner wall of the pores has the metal element.

[0016] According to embodiments of the present application, the negative active material has pores having a pore size of no more than 3 pm, and inner walls of the pores have the non-metallic element.

[0017] According to embodiments of the present application, the pores have a pore size of no more than 2.5 pm. In some embodiments, the pores have a pore size of no more than 2 pm. In some embodiments, the pores have a pore size of no more than 1.5 pm. In some embodiments, the pores have a pore size of 0.5 pm, 1 pm, 1.5 pm, 2 pm, 2.5 pm, or 3 pm.

[0018] According to embodiments of the present application, the negative current collector includes a region where the negative active material layer is not disposed, and the region where the negative active material layer is not disposed is no more than 10% based on a total area of the negative current collector. In some embodiments, the region where the negative active material layer is not disposed is no more than 8% based on the total area of the negative current collector. In some embodiments, the region where the negative active material layer is not disposed is no more than 5% based on the total area of the negative current collector. In some embodiments, the region where the negative active material layer is not disposed is no more than 3% based on the total area of the negative current collector. In some embodiments, the region where the negative active material layer is not disposed is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% based on the total area of the negative current collector.

[0019] According to yet another aspect of the present application, the present application provides an electronic device including the electrochemical device according to the present application.

[0020] Additional layers and advantages of the application will be described in part, be apparent, or be learned from the descriptions that follow, by reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings that are described below will be briefly explained in order to describe embodiments of the present application, which are necessary for describing embodiments of the present application or the prior art. It is obvious that the drawings described in the following description are only some of the embodiments in the present application. Other drawings of embodiments can be obtained from the structures illustrated in the drawings by those skilled in the art without requiring inventive labor.

[0022] Figure 1 is a scanning electron microscope (SEM) image of a negative active material having broken particles according to embodiments of the present application. DETAILED DESCRIPTION

[0023] Embodiments of the present application will be described in detail below. In the present application, the same or similar components and components having the same or similar functions are denoted by like reference numerals. The embodiments described herein with reference to the accompanying drawings are illustrative in nature, diagrammatic and serve to provide a basic understanding of the present application. Embodiments of the present application should not be construed as limiting the present application.

[0024] In the detailed description and in the claims, a list of items connected by the term "at least one of' can mean any combination of the items in the list. For example, if the items enumerated are A and B, the phrase "at least one of A and B" can mean A alone; B alone; or A and B. In another example, if the items enumerated are A, B, and C, the phrase "at least one of A, B, and C" can mean A alone; B alone; C alone; A and B (excluding C); A and C (excluding B); B and C (excluding A); or A, B, and C. Item A can include a single element or multiple elements. Item B can include a single element or multiple elements. Item C can include a single element or multiple elements.

[0025] As used herein, "pore" refers to a pore or hole structure in a single particle of negative active material.

[0026] As used herein, "pore" refers to a pore or hole structure in a single particle of negative active material.

[0027] As used herein, "particle breakage rate" refers to the percentage of the total number of particles of negative active material that are broken particles.

[0028] To improve the energy density, cycle performance and safety performance of electrochemical devices (e.g., lithium ion batteries), improving the active material of the electrode is one of the research and development directions. The upper limit of the theoretical electrochemical capacity of graphitized negative active material is 372 mAh / g, and the electrochemical capacity of previously known graphitized negative active material is difficult to break through this upper limit. Silicon negative active material has high electrochemical capacity, and as the content of doping material in the silicon negative active material increases, the energy density of the electrochemical device can be significantly improved, but the negative active material will undergo significant volume expansion, which will significantly reduce the performance of the electrochemical device, especially the capacity retention rate in long cycle.

[0029] To solve these problems, the present application provides an electrochemical device, which comprises a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative active material layer disposed on the negative electrode current collector, the negative active material layer comprises a negative active material, and the negative active material comprises a certain amount of broken particles.

[0030] Negative electrode

[0031] In the electrochemical device of the present application, the particle breakage rate of the negative electrode active material is 20% to 80%. In some embodiments, the particle breakage rate of the negative electrode active material is 30% to 60%. In some embodiments, the particle breakage rate of the negative electrode active material is 40% to 50%. In some embodiments, the particle breakage rate of the negative electrode active material is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%. The broken particles can increase the specific surface area of the negative electrode active material, increase the contact sites between the negative electrode active material and the electrolyte, and thus improve the cycle performance and energy density of the electrochemical device. The particle breakage rate of the negative electrode active material can be obtained by counting the negative electrode active particles in the scanning electron microscope (SEM) image. Specifically, at least 4 regions (5 μm x 5 μm) are selected in the scanning electron microscope (SEM) image of the negative electrode active material, the number of broken particles and the total number of negative electrode active material particles in the 4 regions are counted, and the particle breakage rate of the negative electrode active material is calculated by the following formula: particle breakage rate = number of broken particles / total number of negative electrode active material particles x 100%.

[0032] According to embodiments of the present application, the broken particles have cracks or fissures with a width of no more than 4 μm. In some embodiments, the broken particles have cracks or fissures with a width of no more than 3.5 μm. In some embodiments, the broken particles have cracks or fissures with a width of no more than 2.5 μm. In some embodiments, the broken particles have cracks or fissures with a width of no more than 2 μm. Figure 1 A scanning electron microscope (SEM) image of the negative electrode active material with broken particles is shown, in which the particles circled by solid lines are broken particles with fissures, and the particles circled by dashed lines are broken particles with cracks.

[0033] According to embodiments of the present application, the roughness of the negative electrode active material layer is no more than 6 μm. In some embodiments, the roughness of the negative electrode active material layer is no more than 5 μm. In some embodiments, the roughness of the negative electrode active material layer is no more than 3 μm. In some embodiments, the roughness of the negative electrode active material layer is no more than 1 μm. In some embodiments, the roughness of the negative electrode active material layer is 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or 6 μm. The negative electrode active material layer is formed by random arrangement of negative electrode active material particles, and the surface roughness depends on the unevenness of the particles with small spacing and tiny peaks and valleys on the surface. The roughness of the negative electrode active material layer can be obtained by the following method: within the sampling length, the arithmetic average of the absolute values of the distances of the points on the particle profile to the reference line, i.e. the profile arithmetic average deviation Ra, is calculated. The smaller the Ra, the smaller the roughness of the negative electrode active material layer, and the smoother the negative electrode active material layer.

[0034] According to embodiments of the present application, the cohesion strength of the negative active material is 5 N / m to 30 N / m. In some embodiments, the cohesion strength of the negative active material is 8 N / m to 25 N / m. In some embodiments, the cohesion strength of the negative active material is 5 N / m, 10 N / m, 15 N / m, 20 N / m, 25 N / m or 30 N / m. The presence of broken particles invalidates the contact sites between part of the active material and the binder, thereby reducing the cohesion strength of the negative active material. When the cohesion strength of the negative active material is within the above range, the negative active material particles have proper adhesion, which can avoid the phenomenon of powder falling during the rolling and winding processes, avoid the formation of micro-short circuit sites inside the lithium ion battery, thereby avoiding safety hazards; also can avoid the volume expansion of the negative active material during the charging and discharging process, avoid incomplete intercalation of lithium, thereby ensuring the capacity of the electrochemical device. The cohesion strength of the negative active material can be tested using an Instron (model 33652) tester: take a negative electrode sheet (width of 30 mm, length of 100-160 mm), fix it on a steel plate with double-sided adhesive tape (model: 3M9448A, width of 20 mm, length of 90-150 mm), the adhesive tape is attached to the surface of the negative active material layer, one side of the adhesive tape is connected with a paper tape of the same width, adjust the position of the tension machine limit block to the appropriate position, fold and slide the paper tape upward by 40 mm, the sliding rate is 50 mm / min, test the cohesion strength between the particles inside the negative active material layer at 180° (i.e., reverse direction stretching).

[0035] According to embodiments of the present application, the adhesion between the negative active material layer and the negative current collector is 5 N / m to 20 N / m. In some embodiments, the adhesion between the negative active material layer and the negative current collector is 10 N / m to 15 N / m. In some embodiments, the adhesion between the negative active material layer and the negative current collector is 5 N / m, 8 N / m, 10 N / m, 12 N / m, 14 N / m, 16 N / m, 18 N / m, or 20 N / m. When the adhesion between the negative active material layer and the negative current collector is within the above range, the negative active material layer can be prevented from being detached or generating burrs during the rolling or slitting process, thereby avoiding safety hazards, while also ensuring that the internal resistance of the battery cell is within an acceptable range, ensuring the kinetic performance and cycle performance of the electrochemical device. The peel strength between the negative active material layer and the negative current collector can be achieved by controlling the rolling process during the preparation of the negative electrode. Specifically, the adhesion between the negative active material layer and the negative current collector can be tested using an Instron (model 33652) tester: take a negative electrode (30 mm wide, 100-160 mm long), fix it to a steel plate with double-sided tape (model 3M9448A, 20 mm wide, 90-150 mm long), and attach the tape to the surface of the negative active material layer. The tape is connected to a paper tape of the same width on one side, the limit block of the tensile testing machine is adjusted to the appropriate position, the paper tape is folded upward and shifted by 40 mm at a rate of 50 mm / min, and the adhesion between the negative active material layer and the negative current collector is tested at 180° (i.e., reverse direction stretching).

[0036] According to embodiments of the present application, the ratio Id / Ig of the half-peak width Id of the peak appearing at 1345 cm -1 to 1355 cm -1 and the half-peak width Ig of the peak appearing at 1595 cm -1 to 1605 cm -1 is 0.7 to 1.5. In some embodiments, the Id / Ig of the negative active material obtained by Raman spectroscopy is 1.0 to 1.2. In some embodiments, the Id / Ig of the negative active material obtained 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 active material is within the above range, the degree of crystalline defects and disorder on the surface of the negative active material is within an appropriate range, which helps to increase the specific capacity of the negative active material.

[0037] According to embodiments of the present application, Id is 200 cm -1 to 1100 cm -1 . In some embodiments, Id is 2200 cm -1to 1000 cm -1 In some embodiments, Id is 2500 cm -1 to 900 cm -1 In some embodiments, Id is 200 cm -1 , 300 cm -1 , 400 cm -1 , 500 cm -1 , 550 cm -1 , 600 cm -1 , 700 cm -1 , 850 cm -1 , 900 cm -1 , 1000 cm -1 , 1100 cm -1 .

[0038] According to embodiments of the present application, the negative electrode active material comprises at least one of a metal element or a non-metal element, the metal element comprises at least one of gold, silver, platinum, zirconium, zinc, magnesium, calcium, barium, vanadium, iron or aluminum, the content of the metal element is 20 ppm to 400 ppm based on the total weight of the negative electrode active material; the non-metal element comprises at least one of phosphorus, boron, silicon, arsenic or selenium, the content of the non-metal element is 50 ppm to 400 ppm based on the total weight of the negative electrode active material.

[0039] 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.

[0040] In some embodiments, the content of the non-metal element is 100 ppm to 350 ppm based on the total weight of the negative electrode active material. In some embodiments, the content of the non-metal 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, 210 ppm, 240 ppm, 280 ppm, 310 ppm, 380 ppm or 400 ppm based on the total weight of the negative electrode active material.

[0041] According to embodiments of the present application, the negative active material has pores with a pore size no greater than 3 pm, and the inner wall of the pores has the metal element.

[0042] According to embodiments of the present application, the negative active material has pores with a pore size no greater than 3 pm, and the inner wall of the pores has the non-metal element.

[0043] According to embodiments of the present application, the pore size of the pores is no greater than 2 pm. In some embodiments, the pore size of the pores is no greater than 1 pm. In some embodiments, the pore size of the pores is no greater than 0.5 pm. In some embodiments, the pore size of the pores is 0.5 pm, 1 pm, 1.5 pm, 2 pm, 2.5 pm, or 3 pm. The specific surface area of the negative active material with pores is large, and the inner wall of the pores can effectively adsorb lithium, which helps to improve the electrochemical capacity of the negative active material. When the pore size of the pores is within the above range, the electrolyte can effectively infiltrate the negative active material to form a solid-liquid interface.

[0044] According to embodiments of the present application, the negative current collector includes a region where the negative active material layer is not disposed, and the region where the negative active material layer is not disposed is no more than 10% based on the total area of the negative current collector. In some embodiments, the region where the negative active material layer is not disposed is no more than 8% based on the total area of the negative current collector. In some embodiments, the region where the negative active material layer is not disposed is no more than 5% based on the total area of the negative current collector. In some embodiments, the region where the negative active material layer is not disposed is no more than 3% based on the total area of the negative current collector. In some embodiments, the region where the negative active material layer is not disposed is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% based on the total area of the negative current collector.

[0045] In some embodiments, the negative active material can include, but is not limited to, natural graphite, artificial graphite, meso-carbon microbeads (MCMB for short), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, Sn02, spinel-structured lithiated Ti02-Li4Ti50 12 or LI-l alloy. Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon, and mixtures thereof. The crystalline carbon can be amorphous or flaky, small flaky, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonizate, calcined coke, etc.

[0046] According to embodiments of the present application, the negative electrode further includes a conductive layer. In some embodiments, the conductive material of the conductive layer can include any conductive material as long as it does not cause chemical changes. Non-limiting examples of the conductive material include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, graphene, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0047] According to embodiments of the present application, the negative electrode further includes a binder selected from at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, or nylon, etc.

[0048] The negative electrode current collector for use in the negative electrode described herein can be selected from a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0049] Positive electrode

[0050] The positive electrode includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector. The specific kind of the positive electrode active material is not particularly limited and can be selected as desired.

[0051] In some embodiments, the positive electrode active material includes a positive electrode material capable of absorbing and releasing lithium (Li). Examples of the positive electrode material capable of absorbing / releasing lithium (Li) can include lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium manganate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.

[0052] Specifically, the chemical formula of the lithium cobaltate can be as Chemical Formula 1:

[0053] Li x Co a M1 b O 2-c Chemical Formula 1

[0054] wherein M1 represents at least one selected from 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 x, a, b, and c values are respectively in the following ranges: 0.8≤x≤1.2, 0.8≤a≤1, 0≤b≤0.2, -0.1≤c≤0.2.

[0055] The chemical formula of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide can be as Chemical Formula 2:

[0056] Li y Ni d M2 e O 2-f Chemical Formula 2

[0057] wherein 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 y, d, e, and f values are respectively in the following ranges: 0.8≤y≤1.2, 0.3≤d≤0.98, 0.02≤e≤0.7, -0.1≤f≤0.2.

[0058] The chemical formula of lithium manganese oxide can be as Chemical Formula 3:

[0059] Li z Mn 2-g M3 g O 4-h Chemical Formula 3

[0060] wherein 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 z, g, and h values are respectively in the following ranges: 0.8≤z≤1.2, 0≤g<1.0, and -0.2≤h≤0.2.

[0061] 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 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 times, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, 11 times, 12 times, 13 times, 14 times, or 15 times the weight of the negative electrode active material layer.

[0062] In some embodiments, the positive electrode active material layer can have a coating on the surface, or can be mixed with another compound having a coating. The coating can include at least one coating element compound selected from oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compound used for the coating can be amorphous or crystalline. The coating elements contained in the coating can include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, or mixtures thereof. The coating can 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 can include any coating method well known to one of ordinary skill in the art, such as spraying, dipping, etc.

[0063] In some embodiments, the positive electrode active material layer further includes a binder, and optionally further includes a positive electrode conductive material.

[0064] The binder can improve the binding between the positive electrode active material particles, and also improve the binding between the positive electrode active material and the current collector. Non-limiting examples of the binder include polyvinyl alcohol, 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, nylon, etc.

[0065] The positive active material layer includes a positive electrode conductive material, thereby imparting conductivity to the electrode. The positive electrode conductive material can include any conductive material, so long as it does not cause chemical changes. 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 fibers, etc.), metal-based materials (e.g., metal powders, metal fibers, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0066] The positive current collector for the electrochemical device according to the present application can be aluminum (Al), but is not limited thereto.

[0067] Electrolyte

[0068] The electrolyte solution that can be used in embodiments of the present application can be an electrolyte solution known in the art.

[0069] The electrolyte in the electrolyte solution that can be used in embodiments of the present application includes, but is not limited to, inorganic lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiSbF6, LiSO3F, LiN(FSO2)2, etc.; fluorine-containing organic lithium salts such as LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,3-hexafluoropropanedisulfonimide lithium, cyclic 1,2-tetrafluoroethane disulfonimide lithium, LiN(CF3SO2)(C4F9SO2), LiC(CF3SO2)3, LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2; dicarboxylic acid complex-containing lithium salts such as lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tris(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, etc. In addition, the above electrolytes can be used singly, or two or more kinds can be used simultaneously. In some embodiments, the electrolyte includes a combination of LiPF6and LiBF4. In some embodiments, the electrolyte includes a combination of an inorganic lithium salt such as LiPF6or LiBF4with a fluorine-containing organic lithium salt such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, etc. In some embodiments, the electrolyte includes LiPF6.

[0070] In some embodiments, the electrolyte has a concentration in the range of 0.8-3 mol / L, such as in the range of 0.8-2.5 mol / L, in the range of 0.8-2 mol / L, in the range of 1-2 mol / L, and 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.

[0071] Solvents that can be used in the electrolyte of embodiments of the present 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.

[0072] Examples of carbonate compounds include, but are not limited to, chain carbonate compounds, cyclic carbonate compounds, fluorinated carbonate compounds, or combinations thereof.

[0073] 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 the cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof. Examples of the 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-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate, trifluoromethyl ethylene carbonate, and combinations thereof.

[0074] Examples of ester-based compounds include, but are not limited to, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decalactone, valerolactone, methylvaleronolactone, caprolactone, methyl formate, and combinations thereof.

[0075] Examples of ether-based compounds include, but are not limited to, dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0076] Examples of ketone-based compounds include, but are not limited to, cyclohexanone.

[0077] Examples of alcohol-based compounds include, but are not limited to, ethanol and isopropanol.

[0078] Examples of the aprotic solvent include, but are not limited to, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, formamide, dimethylformamide, acetonitrile, nitromethane, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphates, and combinations thereof.

[0079] Separator

[0080] In some embodiments, a separator film is provided between the positive electrode and the negative electrode to prevent short circuiting. The material and shape of the separator film that can be used in the embodiments of the present application are not particularly limited and can be any of the techniques disclosed in the prior art. In some embodiments, the separator film includes a polymer or inorganic substance formed of a material stable to the electrolyte of the present application, or the like.

[0081] For example, the separator film can include a base layer and a surface treatment layer. The base layer is a nonwoven fabric, a film, or a composite film having a porous structure, and the material of the base layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used. The porous structure can improve the heat resistance, oxidation resistance, and electrolyte impregnation properties of the separator film, and enhance the adhesion between the separator film and the electrode sheet.

[0082] A surface treatment layer is provided on at least one surface of the base layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed of a mixture of a polymer and an inorganic substance.

[0083] The inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from one or a combination of several of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from one or a combination of several of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0084] The polymer layer includes a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0085] Electrochemical device

[0086] The present application also provides an electrochemical device comprising a positive electrode, an electrolyte, and a negative electrode, the positive electrode comprising a positive electrode active material layer and a positive electrode current collector, the negative electrode comprising a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer comprising the negative electrode active material according to the present application.

[0087] The electrochemical device of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include primary batteries, secondary batteries, fuel cells, solar cells, or capacitors of all kinds. In particular, the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0088] Electronic device

[0089] The present application also provides an electronic device comprising the electrochemical device according to the present application.

[0090] The use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the art. In some embodiments, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable telephones, portable facsimile machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini-disc players, transceivers, electronic organizers, calculators, memory cards, portable audio recorders, radios, backup power supplies, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting appliances, toys, game machines, timepieces, power tools, flashlights, cameras, home-use large storage batteries, and lithium ion capacitors, etc.

[0091] The preparation of lithium ion batteries is described below using lithium ion batteries as an example and in conjunction with specific examples, and those skilled in the art will understand that the preparation methods described in the present application are merely examples, and any other suitable preparation method is within the scope of the present application.

[0092] Examples

[0093] The following describes the performance evaluation of examples and comparative examples of lithium ion batteries according to the present application.

[0094] I. Preparation of lithium ion batteries

[0095] 1. Preparation of negative electrode active material

[0096] 2 kg of artificial graphite was dispersed in ethanol to obtain a first solution. 0.05 mol of triammonium citrate was dissolved in 1 mL of isopropyl alcohol, after complete dissolution, 1.5 mol of zinc acetate was added, stirred at 1000 rpm for at least 30 minutes, filtered through a water-based filter membrane to obtain a zinc oxide sol-gel solution. The same amount of hydrochloric acid as zinc acetate was added to the zinc oxide sol-gel solution to obtain a second solution. 1000 mL of the second solution was added to the first solution, continuously stirred at 50°C for 90 minutes to obtain a third solution. Then, the obtained third solution was left to stand for 180 minutes, dried at 70°C for 10 hours to remove the solvent, and then impurities were removed by heat treatment at 1000°C under argon atmosphere to obtain a negative electrode active material.

[0097] The negative electrode active material obtained from this step was made into a negative electrode sheet, and the negative electrode active material with a desired particle breakage rate could be formed by controlling the rolling pressure and / or rolling time. The content of the second solution in the third solution was also controlled to achieve the control of the particle breakage rate.

[0098] 2. Preparation of a negative electrode

[0099] The negative electrode active material prepared above, a binder styrene butadiene rubber (SBR), and a thickener sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 97:1:2 in a proper amount of deionized water to form a uniform negative electrode slurry, and the solid content of the negative electrode slurry was 54 wt%. The slurry was coated on a negative electrode current collector (copper foil), dried at 85°C, and then cold-pressed, cut, and slit, and dried at 120°C under vacuum conditions for 12 hours to obtain a negative electrode.

[0100] 3. Preparation of a positive electrode

[0101] Lithium cobalt oxide (LiCoO2), Super P, and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97:1.4:1.6 in a proper amount of N-methyl pyrrolidone (NMP) solvent to form a uniform positive electrode slurry, and the solid content of the positive electrode slurry was 72 wt%. The slurry was coated on a positive electrode current collector aluminum foil, dried at 85°C, and then cold-pressed, cut, and slit, and dried at 85°C under vacuum conditions for 4 hours to obtain a positive electrode.

[0102] 4. Preparation of an electrolyte

[0103] In a dry argon atmosphere glove box, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC: EMC: DEC = 30:50:20, then 3% of fluoroethylene carbonate and 1.5% of 1,3 propane sultone were added, dissolved and stirred thoroughly, then lithium salt LiPF6 was added, and the electrolyte was obtained after mixing uniformly, wherein the concentration of LiPF6 was 1 mol / L.

[0104] 5. Preparation of separator film

[0105] A 7 μm thick porous polyethylene (PE) film was used as the separator film.

[0106] 6. Preparation of lithium ion battery

[0107] The positive electrode, the separator film, and the negative electrode were stacked in order with the separator film between the positive electrode and the negative electrode to function as a separator, and then wound, after which the tab was welded and placed in an outer packaging foil aluminum plastic film. The above-prepared electrolyte was injected, and the lithium ion battery was obtained after vacuum packaging, standing, formation, shaping, capacity testing, and the like.

[0108] II. Test methods

[0109] 1. Test method for cycle capacity retention rate of lithium ion battery

[0110] The lithium ion battery was charged at 0.7 C to a voltage of 4.4 V and then charged at a constant voltage in an environment at 25°C. The battery was discharged at 1 C to a voltage of 3 V, which was recorded as one cycle, and the discharge capacity of the first cycle was recorded. The battery was cycled 200 times, and the discharge capacity of the 200th cycle was recorded. The cycle capacity retention rate of the lithium ion battery was calculated by the following formula:

[0111] Cycle capacity retention rate = (discharge capacity of the 200th cycle / discharge capacity of the first cycle) x 100%.

[0112] Five samples were tested for each example or comparative example, and the average value was taken.

[0113] 2. Test method for thermal shock endurance time of lithium ion battery

[0114] The lithium ion battery was brought to a full charge state and placed in a high-temperature oven at 150°C. The time at which the lithium ion battery began to show flames was recorded as the thermal shock endurance time. Five samples were tested for each example or comparative example, and the average value was taken.

[0115] 3. Test method for overcharge of lithium ion battery

[0116] The lithium ion battery was overcharged at a current density of 1 C at 10 V, and the surface temperature of the lithium ion battery was tested. Five samples were tested for each example or comparative example, and the average value was taken.

[0117] 4. Test method for nail penetration of lithium ion battery

[0118] The lithium ion battery was placed in a 25°C constant temperature oven and allowed to stand for 30 minutes to allow the lithium ion battery to reach a constant temperature. The lithium ion battery that reached a constant temperature was charged at a constant current of 0.5C to a voltage of 4.4V, and then charged at a constant voltage of 4.4V to a current of 0.025C. The fully charged lithium ion battery was transferred to a nail penetration tester, the test environment temperature was maintained at 25°C±2°C, a steel nail with a diameter of 4mm was used to penetrate the center of the lithium ion battery at a speed of 30mm / s, and the lithium ion battery was retained for 300 seconds. The surface temperature of the lithium ion battery was tested. Five samples were tested for each example or comparative example, and the average value was taken.

[0119] 5. Impact test method of lithium ion battery

[0120] The lithium ion battery was charged at a constant current of 0.5C to a voltage of 4.3V at 25°C, and then charged at a constant voltage of 4.3V to a current of 0.05C, and the lithium ion battery was subjected to an impact test using the UL1642 test standard, wherein the weight of the weight was 9.8kg, the diameter was 15.8mm, and the drop height was 61±2.5cm. The surface temperature of the lithium ion battery was tested. Five samples were tested for each example or comparative example, and the average value was taken.

[0121] 6. Test method of cohesion strength of negative electrode active material

[0122] An Instron (model 33652) tester was used for testing: a pole piece (width 30mm, length 100-160mm) was fixed on a steel plate with double-sided adhesive tape (model 3M9448A, width 20mm, length 90-150mm), the adhesive tape was attached to the surface of the negative electrode active material layer, one side of the adhesive tape was connected to a paper tape of the same width, the stopper of the tensile machine was adjusted to the appropriate position, the paper tape was folded upward and shifted by 40mm at a speed of 50mm / min, and the cohesion strength between the particles inside the negative electrode active material layer was tested at 180° (i.e., reverse direction stretching).

[0123] 7. Test method of adhesion between negative electrode active material layer and negative electrode current collector

[0124] An Instron (model 33652) tester was used for testing: a pole piece (width 30mm, length 100-160mm) was fixed on a steel plate with double-sided adhesive tape (model 3M9448A, width 20mm, length 90-150mm), the adhesive tape was attached to the surface of the negative electrode active material layer, one side of the adhesive tape was connected to a paper tape of the same width, the stopper of the tensile machine was adjusted to the appropriate position, the paper tape was folded upward and shifted by 40mm at a speed of 50mm / min, and the adhesion between the negative electrode active material layer and the negative electrode current collector was tested at 180° (i.e., reverse direction stretching).

[0125] 8. Method for testing particle breakage rate of negative electrode active material

[0126] In the scanning electron microscope (SEM) image of the disassembled negative electrode active material, at least 4 regions (5 μm x 5 μm) were selected to observe the negative electrode active material particles, and the particles without binder at the particle interface were broken particles. The number of broken particles and the total number of negative electrode active material particles in the 4 regions were counted, and the particle breakage rate of the negative electrode active material was calculated by the following formula: particle breakage rate = number of broken particles / total number of negative electrode active material particles x 100%. Five samples were tested for each example or comparative example.

[0127] III. Test results

[0128] Table 1 shows the effect of the particle breakage rate of the negative electrode active material and Id / Ig on the cycle performance and safety of the lithium ion battery, and the width of the crack or crack of the broken particle in Table 1 is not more than 4 μm.

[0129] Table 1

[0130]

[0131]

[0132] The results show that, compared with the comparative example, when the negative electrode active material contains broken particles and the particle breakage rate is 20% to 80%, the cycle capacity retention rate of the lithium ion battery is significantly increased, the heat shock resistance time is significantly prolonged, and the surface temperature in the overcharge test, the nail penetration test and the impact test is significantly reduced, that is, the cycle performance and safety of the lithium ion battery are significantly improved. On this basis, controlling the Id / Ig of the negative electrode active material in the range of 0.7 to 1.5 can further improve the cycle capacity retention rate of the lithium ion battery, prolong the heat shock resistance time, and reduce the surface temperature in the overcharge test, the nail penetration test and the impact test. On the basis of Id / Ig being 0.7 to 1.5, controlling Id to be 200 cm -1 to 1100 cm -1 , which helps to further improve the cycle performance and safety of the lithium ion battery.

[0133] Table 2 shows the effect of metal elements, non-metal elements and pores in the negative electrode active material on the cycle performance and safety of the lithium ion battery. In addition to the parameters listed in Table 2, the other settings of Examples 13-40 are consistent with those of Example 3, and the other settings of Example 41 are consistent with those of Example 2.

[0134] Table 2

[0135]

[0136]

[0137] The results show that when the negative active material contains 20 ppm to 400 ppm of metal elements and / or 50 ppm to 400 ppm of non-metal elements, it helps to further improve the cycle performance and safety of the lithium ion battery. When the negative active material has pores and the inner wall of the pores has metal elements and / or non-metal elements, it helps to further improve the cycle performance and safety of the lithium ion battery.

[0138] Table 3 shows the effect of the properties of the negative active material on the cycle performance and safety of the lithium ion battery. In addition to the parameters listed in Table 3, Examples 42-54 are consistent with the other settings of Example 3.

[0139] Table 3

[0140]

[0141] The results show that when the roughness of the negative active material layer is not more than 6 μm, the cohesion strength of the negative active material is in the range of 5 N / m to 30 N / m, and / or the adhesion between the negative active material layer and the negative current collector is in the range of 5 N / m to 20 N / m, it helps to further improve the cycle performance and safety of the lithium ion battery.

[0142] Table 4 shows the effect of the proportion of the area of the negative current collector without the negative active material layer on the cycle performance and safety of the lithium ion battery. In addition to the parameters listed in Table 4, Examples 55-58 are consistent with the other settings of Example 3.

[0143] Table 4

[0144]

[0145] The results show that when the area without the negative active material layer is not more than 10%, it helps to further improve the cycle performance and safety of the lithium ion battery.

[0146] Improving the cycle performance of the lithium ion battery while ensuring its safety helps to expand the application field of the lithium ion battery, providing a broad space for its development.

[0147] References throughout this specification to "an embodiment", "particular embodiments", "one embodiment", "another embodiment", "certain embodiments", "some embodiments", "some examples", "one example", "particular examples" or "examples" mean that a particular feature, structure, material or characteristic is included in at least one embodiment or example of the present application. Thus, appearances of the phrases such as "in some embodiments", "in an embodiment", "in one embodiment", "in another embodiment", "in one example", "in particular embodiments" or "in some examples" in various places throughout this specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0148] While the illustrative embodiments have been described and illustrated, it will be understood by those skilled in the art that the above-described embodiments are not the only ways in which the present application can be practiced. Changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims

1. An electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material comprising broken particles, the particle breakage rate of the negative electrode active material being 20% ​​to 80%; and the cohesive strength of the negative electrode active material being 5 N / m to 30 N / m; The negative electrode active material has pores, and the inner wall of the pores has metallic and / or non-metallic elements; The metallic element includes at least one of gold, silver, platinum, zirconium, zinc, magnesium, calcium, barium, vanadium, iron, or aluminum, and the content of the metallic element is from 50 ppm to 300 ppm based on the total weight of the negative electrode active material; the non-metallic element includes at least one of phosphorus, boron, silicon, arsenic, or selenium, and the content of the non-metallic element is from 50 ppm to 400 ppm based on the total weight of the negative electrode active material.

2. The electrochemical device according to claim 1, wherein the broken particles have cracks or fissures with a width of no more than 4 μm.

3. The electrochemical device according to claim 1, wherein the roughness of the negative electrode active material layer is not greater than 6 μm.

4. The electrochemical device according to claim 1, wherein the adhesion force between the negative electrode active material layer and the negative electrode current collector is 5 N / m to 20 N / m.

5. The electrochemical device according to claim 1, wherein the negative electrode active material, as determined by Raman spectroscopy, is 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.

6. The electrochemical device according to claim 5, wherein Id is 200cm -1 Up to 1100cm -1 .

7. The electrochemical device according to claim 1, wherein the negative electrode active material has pores, and the pore diameter is not greater than 3 μm.

8. The electrochemical device according to claim 1, wherein the negative electrode current collector includes a region where the negative electrode active material layer is not disposed, and based on the total area of ​​the negative electrode current collector, the region where the negative electrode active material layer is not disposed does not exceed 10%.

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

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