Electrochemical device and electronic device including the electrochemical device

Abstract

To provide an electrochemical device and an electronic device including the electrochemical device, which can effectively reduce impedance of a negative electrode, control the temperature rise of a cell, and further reduce a cycle expansion rate of an electrochemical device, and improve its cycle performance.SOLUTION: An electrochemical device includes a positive electrode, a separator, and a negative electrode, the negative electrode includes a negative electrode current collector 201, a negative electrode active material layer 202, and a negative electrode tab 203, and the negative electrode tab is installed on a long axis side of the negative electrode current collector and is in contact with a negative electrode material layer. The negative electrode active material layer includes a silicon-based material, a distance from a center position of the negative electrode tab to one end of the negative electrode active material layer in a long axis direction is a first length 204, a length of a long axis of the negative electrode active material layer is a second length 205, and the negative electrode satisfies 0.5≥D≥0.6×G, and D is a value of a ratio between the first length and the second length, G is a weight ratio of the silicon-based material, and the weight ratio of the silicon-based material is 70% or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present application relates to the technical field of energy storage, and in particular to a negative electrode structure and a battery comprising the negative electrode structure. It relates to gas and chemical devices, as well as electronic devices. [Background technology]

[0002] With the rapid development of mobile electronic technology, people are increasingly using mobile phones, tablets and laptops. As the frequency of use of mobile electronic devices such as drones and the demands for user experience increase, Therefore, electrochemical devices (lithium ion batteries) that provide energy to electronic devices batteries) have higher energy density, higher rate, greater safety, and It should exhibit less capacity fade after cycling.

[0003] The energy density and cycling performance of electrochemical devices are closely related to their anode materials. Currently, at least one silicon-based material, silicon alloy, or silicon compound has a high Because of its theoretical capacity per gram, silicon-based materials are used instead of existing graphite materials. However, silicon-based materials have too low electrical conductivity and are difficult to withstand high temperatures. Because of the problem of too high expansion coefficient, the negative electrode structure of the negative electrode material further contains silicon-based material. Improvements and optimization of the structure are required. Summary of the Invention

[0004] This application seeks to solve, at least to some extent, at least one problem that exists in the related art. To this end, an electrochemical device and an electronic device including the electrochemical device are provided.

[0005] According to one aspect of the present application, the present application provides an electrochemical device comprising a positive electrode, a separator, and a negative electrode. wherein the negative electrode comprises a negative electrode current collector, a negative electrode active material layer, and a negative electrode tab. The negative electrode active material layer includes a silicon-based material, and the negative electrode tab is attached to the long axis side of the negative electrode current collector. The negative electrode tab is disposed on the long axis side of the negative electrode current collector and contacts the negative electrode active material layer. the negative electrode active material layer in the longitudinal direction from the center position of the negative electrode tab. a distance to either end is defined as a first length, and a length of the major axis of the negative electrode active material layer is defined as a second length; The negative electrode satisfies the following relational formula (I):

number

[0006] The electrochemical device of the present application uses a negative electrode tab that satisfies the above-mentioned requirements, thereby reducing the impedance of the negative electrode. It can effectively reduce the impedance and control the temperature rise of the cell, and further, Reduce the cycle expansion rate and improve its cycle performance.

[0007] According to another aspect of the present application, the present application further provides an electronic device comprising the electrochemical device described above. do.

[0008] Other aspects and advantages of the present embodiments are described, illustrated, or otherwise discussed in part in the following description. will be explained by implementing the embodiments of the present application. [Brief explanation of the drawings]

[0009] In the following, in order to easily explain the present embodiment or the prior art, The drawings necessary for explaining the present invention will be briefly described below. The drawings described below are some examples of the present invention. and a person skilled in the art would be able to easily implement the structures illustrated in these drawings without making any inventive effort. It is clear that other embodiments can be obtained based on the drawings.

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of a prior art negative electrode structure. [Figure 2] FIG. 2 is a schematic top view of a prior art negative electrode structure. [Figure 3] FIG. 3 is a schematic diagram of the structure of a wound cell according to the prior art. [Figure 4] FIG. 4 is a schematic cross-sectional view of a negative electrode structure according to an embodiment of the present application. [Figure 5] FIG. 5 is a schematic top view of a negative electrode structure according to an embodiment of the present application. [Figure 6] FIG. 6 is a schematic diagram of a wound cell structure according to an embodiment of the present application. [Figure 7] FIG. 7 is a schematic diagram of the current distribution when the negative electrode tabs are placed on both ends of the negative electrode longitudinal axis. [Figure 8] FIG. 8 is a schematic diagram of the current distribution when the negative electrode tab is placed at the center of the negative electrode long axis. [Figure 9] FIG. 9 is a three-dimensional graph showing the installation position of the negative electrode tab, the silicon-based material content of the negative electrode active material, and the temperature rise of the cell according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following examples of the present application are described in detail. Components and components having the same or similar functions are designated by like reference numerals. The embodiments described with reference to the drawings are illustrative and schematic and are not intended to be limiting for a basic understanding of the present application. The examples of the present application should not be construed as limiting the present application. There is no.

[0012] As used herein, the terms "approximately," "roughly," "substantially," and "about" mean Used to describe and explain small changes. Used in conjunction with an event or situation. When used, the term refers to the exact instance in which the event or circumstance occurs, and For example, it can be used in conjunction with numbers. When used, the term can refer to a range of variation of up to ±10% of the numerical value. For example, ±5 % or less, ±4% or less, ±3% or less, ±2% or less, ±1% or less, ±0.5% or less, ±0.1 % or less, ±0.05% or less. For example, if the difference between two values ​​is ±10% of the average value of the values, % or less (e.g., ±5% or less, ±4% or less, ±3% or less, ±2% or less, ±1% or less, ±0 ±0.5%, ±0.1%, ±0.05%), the two figures are "approximately" It is considered to be the same.

[0013] In this specification, unless otherwise specified or limited, terms such as "center", "longitudinal", "Lateral," "Front," "Rear," "Right," "Left," "Inner," "Outer" "," "low," "high," "horizontal," "vertical," "higher than," "lower than," Relative terms such as "above," "below," "top," and "bottom" and their derivatives Terms (e.g., "horizontally," "downward," "upward," etc.) are used in discussions or drawings. These relative terms should be interpreted as referring to the directions shown on the face of the device. It is used for convenience and does not require the present application to be constructed or operated in a particular direction.

[0014] Also, amounts, percentages, and other numerical values ​​may be described herein in a range format. The range format is for convenience and brevity of the description and is not intended to be a clearly defined A range includes not only the values ​​defined by the range, but also all individual values ​​subsumed within that range. It should be understood flexibly to include any range or subrange.

[0015] In specific embodiments and in the claims, the term "at least one of" "at least one of," "at least one kind of," or other similar terms A list of items connected by means of any combination of the listed items. For example, if items A and B are listed, "at least one of A and B" The phrase means A only, B only, or A and B. Another example is the item If the methods A, B, and C are listed, it is written as "at least one of A, B, and C." The phrases are A only, B only, C only, A and B (excluding C), A and C (excluding B), B and Item A means a single element or multiple elements. Item B can contain a single element or multiple elements. Item C can contain a single element or multiple elements.

[0016] Silicon-based materials themselves have semiconductor properties, and the powder conductivity of silicon-based materials is higher than that of conventional black powders. For anode materials containing silicon-based materials, the powder conductivity is much lower than that of lead materials. During the charge-discharge cycle, the impedance of both electrons and ions is high, especially at high levels. Under standard charging and discharging conditions, the internal impedance of cells containing silicon-based materials is high, This heat generation increases energy consumption and the temperature of the cells rises significantly. This leads to poor electrochemical performance, such as accelerated cycling capacity fade and reduced discharge rate. This can pose a potential safety issue due to thermal runaway in electrochemical devices.

[0017] 1 and 2 are schematic top views of a commonly used negative electrode structure in the prior art. Figure 3 is a schematic diagram of a cell having a wound structure in the prior art.

[0018] As shown in FIGS. 1 and 2, in the prior art, the negative electrode active material layer 102 is formed on the negative electrode current collector 10 The negative electrode current collector 101 is provided on the surface of the negative electrode active material layer 102 at both ends in the longitudinal direction. The negative electrode tab 103 is set in the uncoated area at one end of the negative electrode current collector. The negative electrode, the positive electrode, and the separator 107 are wound together to form a cell. The structure is shown in FIG. 3. In the prior art, the negative electrode tab 106 is attached to the blank foil area at one end of the negative electrode current collector 101. The positive electrode tab 106 was attached to the blank foil without the positive electrode active material layer 105 at one end of the positive electrode current collector 104. By placing the negative electrode tab 103 and the positive electrode tab 106 in the region, the negative electrode tab 103 and the positive electrode tab 106 are positioned at the top of the cell during the winding process. This design ensures that the electrochemical device is installed in the center. This effectively improves processability and reduces manufacturing costs. Therefore, when using a negative electrode active material with a high capacity per gram (for example, a silicon-based material), The higher the content of silicon-based material in the negative electrode active material, the lower the conductivity of the negative electrode material layer. This causes an increase in the internal impedance of the negative electrode and an increase in the heat generation power, and further increases the This can lead to a decrease in cycle performance and the risk of thermal runaway, which is a safety issue. The placement of empty foil areas in the electrodes reduces the energy density of the electrochemical device.

[0019] According to one aspect of the present application, the present application provides a method for limiting the position of the negative electrode tab and the content of the silicon-based material. This reduces the impedance of the negative electrode active material layer and also reduces the current in each part of the negative electrode. Improved density and reduced heat generation power due to the internal resistance of the negative electrode during charge / discharge cycles. This improves the cycle performance and safety performance of the electrochemical device.

[0020] 4 and 5 are schematic cross-sectional and top views of negative electrode structures according to some embodiments of the present application. do.

[0021] As shown in FIGS. 4 and 5, the present invention provides a negative electrode current collector 201, a negative electrode active material layer 202, and a negative electrode including a negative electrode tab 203, the negative electrode tab 203 being attached to the long axis side of the negative electrode current collector 201; The negative electrode active material layer 202 is made of a silicon-based material. In this case, the negative electrode active material layer 202 is The distance to either end is defined as a first length 204, and the length of the major axis of the negative electrode active material layer is defined as a second length 205. 05. The above negative electrode satisfies the following relational formula (I):

number

[0022] An electrochemical device having a negative electrode that satisfies the above relationship (I) is The temperature rise during the charge / discharge cycle is less than 15°C. In the negative electrode of the present invention, a part of the current in the negative electrode active material layer flows through the negative electrode active material layer. The distance can be effectively reduced, thereby reducing the internal impedance of the negative electrode itself and the negative This is advantageous in reducing the current density in the electrode sheet area around the electrode tabs, reducing cell polarization. In another embodiment, when the weight ratio G of the silicon-based material is more than 70%, the negative electrode tab The center position of 203 is the center of the negative electrode active material layer 202 (i.e., the first length 204 and the second length 205 When the ratio D is 0.5, the charging and discharging of the electrochemical device during operation can be The temperature rise caused by the power cycle process can be reduced.

[0023] In some embodiments, as shown in FIG. 4, the negative electrode satisfies the following relationship (II): Add.

number

[0024] In some embodiments, as shown in FIG. 5, the negative electrode active material layer 202 has a groove 2 06, the groove being defined by the negative electrode active material layer 202, and the negative electrode current collector 20 1, where the negative electrode tab 203 is placed in the recess. In this embodiment, in order to avoid short circuits due to contact between the negative electrode tab and the positive electrode active material layer or the positive electrode tab, An insulating material and / or an adhesive material is placed in the groove to secure the negative electrode tab 203. The insulating material and the adhesive material may be any suitable material common in the art. It is understood that the material may be any material.

[0025] 7 and 8 show the current when the negative electrode tabs are installed at both ends and the center of the negative electrode longitudinal axis, respectively. FIG. 1 is a schematic diagram of the flow distribution.

[0026] For each part of the negative electrode current collector, the ohmic heat Q of the current flowing through the current collector is calculated using the following formula: The corresponding resistance value R can be calculated.

number

[0027] As shown in Figure 8, when the negative electrode tab is installed at the center of the negative electrode current collector, X at the farthest end from n / 2 A part of the current flowing out from part X1 flows from part X n / 2 Only the part flows Well, the other end is X n / 2 A part of the current flowing out from part X1 flows from part X n / 2 'Club The negative electrode structure of the present application allows the negative electrode current collector to flow during discharge at the same discharge current intensity. It can effectively reduce the current intensity, and further reduce the internal impedance of the negative electrode; Reduces overheating and temperature rise of the anode, and also reduces the thermal expansion of the silicon-based material in the anode. can be avoided.

[0028] In some embodiments, the negative electrode current collector 201 is a copper foil or a nickel foil. However, other negative electrode current collectors commonly used in the art may also be employed. is not limited to.

[0029] In some embodiments, the thickness of the negative electrode current collector 201 is from about 4 μm to about 30 μm. In another embodiment, the thickness of the negative electrode current collector 201 is, for example, about 4.0 μm, about 5.0μm, approx. 10.0μm, approx. 15.0μm, approx. 20.0μm, approx. 25.0μm, approx. 3 0.0 μm, or a range consisting of any two of these values.

[0030] The negative electrode active material layer 202 absorbs and deposits lithium (Li) in addition to silicon-based materials. anode material that can absorb / deposit lithium (hereinafter referred to as "anode material that can absorb / deposit lithium (Li)" Examples of negative electrode materials that can absorb / deposit lithium (Li) include carbon materials, metals, etc. Lithium compounds, oxides, sulfides, lithium nitrides such as LiN3, lithium metal, lithium alloys In some embodiments, the silicon-based polymeric material is a metal that forms a gold layer. Silicon-based materials include silicon, silicon compounds, silicon alloys, and silicon-oxygen materials. In some embodiments, the silicon-oxygen material comprises at least one of S iO x where x is about 0.5 to about 1.5, The silicon-oxygen material may be in a crystalline state, an amorphous state, or a combination of the two.

[0031] In some embodiments, the silicon-based material comprises at least one silicon-based material at a surface thereof. The material layer may further include a material layer disposed on at least a portion of the surface of the substrate, the material layer including a polymer, inorganic particles, The material contains at least one of amorphous carbon and carbon nanotubes.

[0032] In some embodiments, the inorganic particles include lithium cobalt oxide, lithium iron phosphate, Lithium nickel cobalt manganese oxide, Lithium nickel cobalt aluminate, Silicon At least one of silicon, silicon compounds, silicon alloys, and silicon-oxygen materials The polymer may be selected from the group consisting of polyvinylidene fluoride, polyacrylic acid, polyvinyl chloride, Carboxymethyl cellulose, polyethylene, polypropylene, polyethylene terephthalate The material includes at least one of acrylate, polyamide, and aramid.

[0033] In some embodiments, the negative electrode active material layer The weight ratio G of the silicon-based material in the composition is greater than about 0% and not more than 70%. In the negative electrode active material layer, the weight ratio G of the silicon-based material is, for example, about 0%, about 1% 0%, approximately 20%, approximately 30%, approximately 50%, approximately 70%, or any two of these values It is within the range.

[0034] In some embodiments, the length of the major axis of the negative electrode active material layer and the length of the major axis of the negative electrode current collector are In some embodiments, the ratio of the length of the negative electrode to the length of the negative electrode is about 0.8 to about 1.0. The ratio of the length of the major axis of the active material layer to the length of the major axis of the negative electrode current collector is about 0.9 to about 0.95 The area of ​​the region where the negative electrode active material layer is not provided on both ends of the negative electrode current collector and the area of ​​the negative electrode tab By eliminating the area of ​​empty foil, the utilization rate of the negative electrode current collector is increased, and the energy density of the electrochemical device is improved. can be further increased.

[0035] According to another aspect of the present application, there is provided an electrochemical device comprising the negative electrode of the present application. In some embodiments, the electrochemical device is a lithium ion battery. The ON battery includes a positive electrode, a separator, and the negative electrode according to the above embodiment, and the separator is It is provided between the positive electrode and the negative electrode.

[0036] FIG. 6 is a schematic diagram of a cell having a wound structure of an electrochemical device according to some embodiments of the present application. be.

[0037] As shown in FIG. 6, in some embodiments, the electrochemical device includes a positive electrode, a negative electrode, and a and a separator are sequentially stacked or wound together. The negative electrode is a negative electrode current collector 20 1, a negative electrode active material layer 202, and a layer disposed at a position three layers or more away from the center of the wound structure. and a negative electrode tab 203.

[0038] In some embodiments, the positive electrode tab 209 of the positive electrode is located in the same position as the negative electrode tab 203. The winding structure is placed at a position one layer away from the center of the winding structure. The positive electrode tab 209 and the negative electrode tab 203 are spaced apart by just one layer to the outside. This can reduce the risk of short-circuiting between the negative electrode tab 209 and the negative electrode tab 203.

[0039] In some embodiments, placing a negative electrode tab on the negative electrode current collector in the present application This is done by welding the negative electrode tab to the installation portion on the negative electrode current collector. The negative electrode active material layer is formed by ultrasonic cleaning, so the positive and negative electrode active material layers are When used in commercial electrochemical devices, the positive and negative electrodes do not have watermark problems. In addition, the distance between the negative electrode tab and the installation location of the negative electrode current collector to be welded can be shortened. This is advantageous to further reduce the impedance of the tab.

[0040] In some embodiments, as shown in FIG. 6, the negative electrode active material layer 202 and the positive electrode active material layer 203 may be The electrode active material layer 208 is disposed around the negative electrode tab 203 or the positive electrode tab 209. The groove 206 is formed in the negative electrode active material layer 202 or the positive electrode active material layer 203. 208, and a part of the negative electrode current collector 201 or the positive electrode current collector 207 In another embodiment, the recessed groove 206 is further exposed to the negative electrode tab 203 or The positive electrode tab 209 is placed in the region 206' of the positive electrode material layer or the negative electrode material layer corresponding to the positive electrode tab 209. In another embodiment, insulating material and / or adhesive material may be provided in the groove 206. The insulating material and the adhesive material can be formed by a method known in the art. It is understood that the material may be any suitable material common in the field. By providing an adhesive material, the risk of short circuits in the cell structure can be further reduced.

[0041] In some embodiments, the positive electrode comprises a positive electrode current collector 207 and a positive electrode active material layer 208 Further includes:

[0042] In some embodiments, the positive electrode current collector 207 is made of aluminum foil or nickel. The positive electrode current collector may be a foil, but other materials commonly used in the art may also be employed. It may be, and is not limited thereto.

[0043] The positive electrode active material layer 208 is made of a positive electrode material (hereinafter referred to as "Li") that absorbs and deposits lithium (Li). Some examples include cathode materials capable of absorbing / depositing lithium (Li). In the embodiment, the positive electrode material capable of absorbing / depositing lithium Li is lithium cobalt oxide, nickel Lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium manganese vanadium phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, Lithium manganese oxide, lithium iron phosphate, lithium titanate, and lithium manganese-based materials It may contain one or more of them.

[0044] In the above positive electrode material, the chemical formula of lithium cobalt oxide is Li y Co a M1 b O 2-c where M1 is 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 (S n), calcium (Ca), strontium (Sr), tungsten (W), yttrium At least one of the following: Y, Lanthanum (La), Zirconium (Zr), and Silicon (Si) The values ​​of y, a, b, and c are 0.8≦y≦1.2, The ranges are 0.8≦a≦1, 0≦b≦0.2, and −0.1≦c≦0.2.

[0045] In the positive electrode material, lithium nickel cobalt manganese oxide or nickel cobalt manganese oxide is used. The chemical formula for lithium aluminate is Li z Ni d M2 e O 2-f Here, M2 are 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), silicon (Si ) and the values ​​of z, d, e, and f are 0. 8≦z≦1.2, 0.3≦d≦0.98, 0.02≦e≦0.7, -0.1≦f≦0.2 is in the range.

[0046] In the above positive electrode material, the chemical formula of lithium manganese oxide is Li u Mn 2-g M3 g O 4- h where M3 is 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) The values ​​of z, g, and h are 0.8≦u≦1.2, respectively. The ranges are 0≦g<1.0 and −0.2≦h≦0.2.

[0047] In some embodiments, the positive electrode comprises at least one of an adhesive and a conductive agent. Those skilled in the art will be able to select the appropriate one according to their actual needs without being limited thereto. It is understood that conventional adhesives and conductive agents in the art may be selected for this purpose.

[0048] In some embodiments, the separator is made of polyethylene, polypropylene, polyethylene At least one selected from the group consisting of polyethylene terephthalate, polyamide and aramid As an example, the polyethylene may be, but is not limited to, high density polyethylene. At least one component selected from the group consisting of polyethylene, low density polyethylene, and ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene are excellent at preventing short circuits and have a good turn-off effect. This can improve the stability of lithium-ion batteries.

[0049] The electrochemical device of the present application further includes an electrolyte, which may be a gel electrolyte, a solid electrolyte, or and an electrolyte solution, the electrolyte solution containing a lithium salt and a non-aqueous solvent. .

[0050] In some embodiments, the lithium salt is LiPF6, LiBF4, LiAs F6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, L iN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and One or more selected from lithium difluoroborate. The lithium salt is selected as LiPF6 because it can provide high conductivity and improve cycle characteristics.

[0051] The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, It may be other organic solvents, or a combination thereof.

[0052] The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a full carbonate compound, or a cyclic carbonate compound. The compound may be a benzophenone, a benzophenone, a benzophenone-3, a benzophenone-4, a benzophenone-5, a benzophenone-6, a benzophenone-7, a benzophenone-8, a benzophenone-9, a benzophenone-10, a benzophenone-11, a benzophenone-12, a benzophenone-13, a benzophenone-14, a benzophenone-15, a

[0053] Examples of the other organic solvents include dimethyl sulfoxide, 1,2-dioxolane, sulfonyl alcohol, and the like. Lan, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2- Pyrrolidone, formamide, dimethylmethanamide, acetonitrile, trimethylphosphine phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.

[0054] In some embodiments, the non-aqueous solvent is ethylene carbonate, propylene carbonate, carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, Propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonates, and combinations thereof.

[0055] Positive electrode, negative electrode, separator, and method for preparing lithium-ion battery according to embodiments of the present application may be prepared by any suitable conventional method in the art according to the particular needs without departing from the spirit of the present application. It should be understood that the selection can be made arbitrarily, but is not limited to this. In one embodiment of the method for preparing the lithium ion battery, the method for preparing the lithium ion battery comprises In the embodiment, the positive electrode, separator, and negative electrode are wound in this order to form a cell, and the cell is then wound with aluminum. The battery is placed in a plastic film, and the electrolyte is injected. After that, the battery is vacuum sealed, left to stand, and then chemically treated. By carrying out processes such as molding, a lithium ion battery is obtained.

[0056] The cells of the electrochemical device of the present application not only have a wound structure, but also in some embodiments It also has a stacked structure and a folded structure.

[0057] Although the lithium ion battery has been described as an example above, those skilled in the art will understand that, according to the present application, It is contemplated that the present negative electrodes may be used in other suitable electrochemical devices. Suitable electrochemical devices include any device that produces an electrochemical reaction, and examples include primary batteries, This includes any type of secondary battery, fuel cell, solar cell, or capacitor. Chemical equipment includes lithium metal secondary batteries, lithium ion secondary batteries, and lithium polymer secondary batteries. and lithium secondary batteries, including lithium ion polymer secondary batteries.

[0058] Some embodiments of the present application relate to an electronic device including an electrochemical device according to an embodiment of the present application. Further provide.

[0059] The electronic device according to the embodiment of the present application is not particularly limited, and may be any existing electronic device according to the prior art. In some embodiments, the electronic device is a laptop computer. , pen-input computers, mobile computers, e-book players, mobile phones , portable fax machines, portable copiers, portable printers, stereo headphones Phones, video recorders, LCD TVs, portable cleaners, portable CD players yers, minidiscs, transceivers, electronic notepads, calculators, memory cards, portable Recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric assist Bicycles, bicycles, lighting equipment, toys, game consoles, watches, power tools, flashes, cameras , large household batteries, and lithium-ion capacitors. do not have. Example

[0060] In order to more clearly explain the technical solution of the present application, several examples are given below. DC resistance test, discharge rate test for electrochemical devices (lithium ion batteries), Tests are conducted on cycle performance and cell surface temperature rise.

[0061] 1. Testing Method 1.1 DC Resistance Test: DC resistance is R=(U 0.1C -U 1C ) / (I 1C -I 0.1C ) where , R is the DC resistance, and I 1C is the current of a lithium-ion battery with a discharge rate of 1C. Ri, I 0·1C is the current of a lithium-ion battery with a discharge rate of 0.1C, and U 1C is the terminal voltage of the lithium-ion battery after discharging for 1 second at a discharge rate of 1C, and U 0·1C is the terminal voltage of a lithium-ion battery after discharging at a discharge rate of 0.1C for 1 second. The procedure for the resistance test is as follows: After fully charging the lithium ion battery in the following example, Discharge at a constant current of C for 10 seconds, and the current I 0·1C and terminal voltage U 0·1C Record the Discharge at a constant current of 1C for 1 second, and the current I 1C and terminal voltage U 1C Record the results for each group. Using four lithium-ion batteries as test batteries, the DC resistance of the lithium-ion batteries was measured. The average resistance is calculated.

[0062] 1.2 Discharge Rate Test: The lithium ion battery of the following example was left in a thermostatic chamber at 25°C ± 2°C for 2 hours, and then heated at 0.5C. Charge at a constant current to 4.35V, then charge at a constant voltage of 4.35V at 0.05C for 15 minutes. Leave the battery to stand for 1 minute, then discharge it at a constant current of 0.2 C until the voltage reaches 3.0 V. Charge at a constant current of 0.5C to 4.35V, then reduce to 0.05C at a constant voltage of 4.35V. Charge and discharge at a constant current of 1.0C to 3.0V. Discharge at a constant current of 0.2C. The discharge capacity of the lithium ion battery when discharged at a constant current of 1.0 C is recorded.

[0063] Four lithium-ion batteries were used as test batteries for each group. Calculate the average discharge rate of the battery. Discharge rate = Discharge capacity at a constant current of 1.0 C ( mAh) / Discharge capacity (mAh) at a constant current of 0.2C.

[0064] 1.3 Cycling performance test: The lithium ion battery of the following example was left in a thermostatic chamber at 25°C ± 2°C for 2 hours, and then heated at 0.5C. Charge at a constant current to 4.35V, then charge at a constant voltage of 4.35V at 0.05C for 15 minutes. Letting it stand for 1 minute and then discharging it to 3.0V at a constant current of 0.5C is equivalent to one charge / discharge cycle. The discharge capacity of the lithium-ion battery on the first cycle is recorded, and The above method was repeated to perform multiple charge-discharge cycles, and the discharge capacity after 100 cycles was Record the following.

[0065] Four lithium-ion batteries were used as test batteries for each group. Calculate the average capacity retention rate of a lithium-ion battery. Retention rate = Discharge capacity after 100 cycles (mAh) / Discharge capacity after the first cycle (mAh) ×100%.

[0066] 1.4 Cell surface temperature rise test: The lithium ion battery of the following example was placed in a sealed incubator at 25°C ± 2°C. The temperature of four different positions on the surface of a lithium-ion battery cell is monitored. The process is as follows: Charge a lithium-ion battery to 2.8V at a constant current of 1.0C. After discharging and leaving it for 30 minutes, charge it to 4.35V at a constant current of 1.0C and leave it for 5 minutes. Furthermore, discharging to 2.8V at a constant current of 1.0C is considered as one charge / discharge cycle. The charge / discharge cycle is repeated three times. The average temperature rise on the surface of the lithium-ion battery cell is calculated. do.

[0067] 2. Preparation method 2.1 Preparation of the positive electrode Lithium cobalt oxide, acetylene black, polyvinylidene fluoride in a ratio of 94:3:3 The aluminum alloy was dissolved in an N-methylpyrrolidone (NMP) solution to form a positive electrode slurry. The positive electrode slurry is applied to the positive electrode current collector using aluminum foil as the positive electrode current collector, then dried, cold pressed, and After cutting and other processes, a positive electrode was obtained.

[0068] 2.2 Preparation of separator Polyvinylidene fluoride is dissolved in water and mechanically stirred to form a uniform slurry. The surfaces of both sides of a porous substrate (polyethylene) with a ceramic coating applied on both sides The slurry was applied to the separator and dried to form a separator.

[0069] 2.3 Preparation of electrolyte In an environment with a water content of less than 10 ppm, lithium hexafluorophosphate and a non-aqueous organic solvent (heavy The ratio by weight is ethylene carbonate (EC): diethyl carbonate (DEC): propylene Carbonate (PC): Propyl propionate (PP): Vinylene carbonate (VC) =20:30:20:28:2) were mixed in a weight ratio of 8:92 to form an electrolyte solution.

[0070] Example 1-1 Artificial graphite and elemental silicon are uniformly dispersed in deionized water at a certain weight ratio to form a negative electrode slurry. The negative electrode slurry was applied to a negative electrode current collector having a thickness of 8 μm using copper foil as the negative electrode current collector. The coating mass is 105 mg, and after drying, cold pressing, cutting, etc., the thickness is A negative electrode tab having a diameter of 80 μm was attached to one end of the negative electrode current collector in the longitudinal direction to obtain a negative electrode. The weight ratio of the silicon to the negative electrode active material layer is 20%. The positive electrode, separator, and negative electrode are stacked in this order and wound into a cell to provide isolation between the The cell has seven layers (one layer of positive and negative electrodes on both sides). The cells were then placed in a plastic film and the moisture was removed at 80°C to obtain dry cells. The liquid is injected into the dry cell, and the lithium ion is stored through processes such as vacuum mounting, standing, chemical conversion, and molding. Got a battery.

[0071] Example 1-2 In Example 1-2, artificial graphite and silicon carbon were mixed and dissolved in deionized water to prepare a negative electrode. The weight ratio of elemental silicon to the negative electrode active material layer is 40%. The preparation method is the same as that in Example 1-1.

[0072] Examples 1-3 In Examples 1-3, artificial graphite and silicon carbon were mixed and dissolved in deionized water to prepare anode sinters. The weight ratio of elemental silicon to the negative electrode active material layer is 50%. The preparation method is the same as that in Example 1-1.

[0073] Examples 1-4 In Examples 1-4, artificial graphite and silicon carbon were mixed and dissolved in deionized water to prepare anode sinters. The weight ratio of elemental silicon to the negative electrode active material layer is 70%. The preparation method is the same as that in Example 1-1.

[0074] Examples 1-5 In Examples 1-5, artificial graphite and silicon carbon were mixed and dissolved in deionized water to prepare anode sinters. The weight ratio of elemental silicon to the negative electrode active material layer is 90%. The preparation method is the same as that in Example 1-1.

[0075] Examples 2-1 to 2-5 In Examples 2-1 to 2-5, the negative electrode active material layer was The distance to the nearest end is 0.125 times the length of the long axis of the negative electrode active material layer, and The positive electrode tab is located one layer away from the center of the above wound structure toward the outside of the negative electrode tab. In addition, the preparation method is the same as that of Example 1-1. The negative electrode active material in the present invention contains artificial graphite and silicon carbon, and the silicon carbon in the negative electrode active material layer The weight ratios are 20%, 40%, 50%, 70%, and 90%, respectively.

[0076] Examples 3-1 to 3-5 In Examples 3-1 to 3-5, the negative electrode active material layer was The distance to the nearest end is 0.25 times the length of the long axis of the negative electrode active material layer, and The electrode tab is placed one layer away from the center of the wound structure relative to the negative electrode tab. In addition, the preparation method is the same as that of Example 1-1. The negative electrode active material in the negative electrode active material layer contains artificial graphite and silicon carbon. The weight ratios are 20%, 40%, 50%, 70%, and 90%, respectively.

[0077] Examples 4-1 to 4-5 In Examples 4-1 to 4-5, the negative electrode active material layer was The distance to the nearest end is 0.5 times the length of the long axis of the negative electrode active material layer, and the positive electrode The tab is placed one layer away from the center of the winding structure relative to the negative electrode tab. In addition, the preparation method is the same as that of Example 1-1. The negative electrode active material contains artificial graphite and silicon carbon, and the weight of the silicon carbon in the negative electrode active material layer is The quantity ratios are 20%, 40%, 50%, 70%, and 90%, respectively.

[0078] Examples 5-1 to 5-2 In Examples 5-1 and 5-2, the negative electrode active material layer was The distances to the nearest ends are 0.1 and 0.15 times the length of the long axis of the negative electrode active material layer, respectively. The thickness of the negative electrode active material coating layer applied to the negative electrode current collector is 35 μm and 4 μm, respectively. 5 μm, and the positive electrode tab is one layer from the center of the wound structure to the outside of the negative electrode tab. In addition to being installed at a distance, the preparation method is the same as that of Example 1-1. The negative electrode active material in Examples 5-1 and 5-2 includes artificial graphite and silicon carbon. The weight ratio of silicon carbon in the porous layer is 20%.

[0079] Examples 5-3 to 5-4 In Examples 5-3 and 5-4, the negative electrode active material layer was The distance to the nearest end is 0.125 times the length of the long axis of the negative electrode active material layer, and The positive electrode tab is located one layer away from the center of the wound structure relative to the negative electrode tab. In addition to the above, the preparation method is the same as that of Example 1-1. The thicknesses of the negative electrode current collectors in Examples 5-3 and 5-4 were 4 μm and 30 μm, respectively. The weight ratio of silicon carbon in the negative electrode active material layer in -4 is 20%.

[0080] The lithium ion batteries in the above examples were subjected to DC resistance tests and discharge rate tests. Tests were conducted on the cell surface temperature rise and cycle performance, and the test results were recorded. did.

[0081] DC resistance test and discharge rate test of lithium ion batteries in all examples; The results of the cycle performance test and cell surface temperature rise test are shown in Tables 1-5 below.

[0082] [Table 1]

[0083] [Table 2]

[0084] [Table 3]

[0085] [Table 4]

[0086] [Table 5]

[0087] FIG. 9 shows the placement position of the negative electrode tab and the silicon-based negative electrode active material according to the examples of Tables 1 to 4 of the present application. 9 is a three-dimensional graph showing the material content and the temperature rise of the cell. So, how does the installation position of the negative electrode tab and the silicon content affect the cycle performance and safety of the electrochemical device? According to the results in Table 1, Examples 1-1, 2-1, 2-2, From the center of the negative electrode tabs of 3-1, 3-2, 3-3, 4-1, 4-2, 4-3, and 4-4, the distance to either end of the negative electrode active material layer in the direction of the arrow A and the length of the major axis of the negative electrode active material layer The ratio D and the weight ratio G of silicon in the negative electrode active material layer satisfy the relation D≧0.6×G. As can be seen from the above examples, the electrochemical device according to the present invention has a high rechargeability in the charge-discharge cycle. During the process, the temperature rise of the cell can be effectively reduced to less than 15°C.

[0088] According to Examples 5-1 to 5-4, when the thickness of the negative electrode tab was 80 μm, The thickness S1, the thickness S2 of the negative electrode tab, and the thickness S3 of the negative electrode active material layer are expressed by the relation 0.9 × (S1 + 2 The temperature rise of the cell is proportional to the thickness of the negative electrode current collector. Since the strength of the current collector decreases with increasing thickness, it is necessary to comprehensively evaluate the strength of the current collector and the energy density of the cell. Therefore, in the present embodiment, a current collector with a thickness of 8 μm is preferred. By controlling the relationship, when the negative electrode material has the same silicon content, Such electrochemical devices have lower DC resistance and better discharge rates, and In addition, the negative electrode tab installation position in the present example The embodiment that meets the range of the relationship with the silicon content effectively reduces the average temperature rise of the cell surface. This allows for control and ensures the safety performance of the electrochemical device.

[0089] By comparing the above examples, the electrochemical device of the present invention has the following advantages: By limiting the weight ratio of silicon in the negative electrode active material layer, the size of the electrochemical device can be controlled. Driving and safety performance can be significantly improved.

[0090] Throughout this specification, the terms "some embodiments," "some embodiments," "one embodiment," "an embodiment," "an "," "as another example," "for example," "as a specific example," or "as some examples." Reference herein to at least one embodiment or example means that the invention is in accordance with the principles of the present invention. It means that the particular features, structures, materials or characteristics described are included. The description throughout the specification may include, for example, "in some embodiments," "in an embodiment," or "in one embodiment." "in one embodiment," "in another example," "in one example," "in a particular example" Or "in an example" does not necessarily refer to an example or example in the present application. A particular feature, structure, material, or characteristic described herein may be used in one or more embodiments or examples. The components can be combined in any suitable manner.

[0091] Although exemplary embodiments have been shown and described, those skilled in the art will recognize that the above embodiments are not intended to be limiting of the present application. It is not to be construed that the embodiments may be modified, substituted, and / or altered without departing from the spirit, principles, and scope of the present application. It is understood that this can be modified.

Claims

1. 1. An electrochemical device comprising: A positive electrode and A separator; a negative electrode, The negative electrode is a negative electrode current collector; a negative electrode active material layer containing a silicon-based material; a negative electrode tab disposed on a side of the negative electrode current collector along a major axis thereof and disposed in a region of the negative electrode current collector between both ends of the negative electrode active material layer, wherein a distance from a center position of the negative electrode tab to either end of the negative electrode active material layer in the major axis direction is defined as a first length, and a length of the major axis of the negative electrode active material layer is defined as a second length, and the negative electrode satisfies the following relational formula (I): [Equation 1] wherein D is a ratio of the first length to the second length, G is a weight ratio of the silicon-based material to the negative electrode active material layer, and the weight ratio of the silicon-based material to the negative electrode active material layer is 0.7 or less, The negative electrode satisfies the following relational formula (II): [Equation 2] Here, the thickness of the negative electrode current collector is S 1 , the thickness of the negative electrode tab is S 2 , and the thickness of the negative electrode active material layer is S 3 . Electrochemical equipment.

2. The silicon-based material includes at least one of silicon element, silicon compound, silicon alloy, and silicon-oxygen material. The electrochemical device of claim 1 .

3. The ratio of the length of the major axis of the negative electrode active material layer to the length of the major axis of the negative electrode current collector is 0.8 to 1.

0. The electrochemical device of claim 1 .

4. the electrochemical device has a wound structure, and the negative electrode tab is disposed at a position three layers or more away from the center of the wound structure; The electrochemical device of claim 1 .

5. a positive electrode tab of the positive electrode is disposed at a position one layer away from the center of the wound structure and outward from the position of the negative electrode tab; 5. The electrochemical device of claim 4.

6. The silicon-based material further includes a material layer disposed on at least a portion of a surface of the silicon-based material, the material layer including at least one of a polymer, an inorganic particle, amorphous carbon, and a carbon nanotube. The electrochemical device of claim 1 .

7. The inorganic particles include at least one of lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, silicon element, silicon compound, silicon alloy, and silicon oxygen material, and the polymer includes at least one of polyvinylidene fluoride, polyacrylic acid, polyvinyl chloride, carboxymethyl cellulose, polyethylene, polypropylene, polyethylene terephthalate, polyamide, and aramid.

7. The electrochemical device of claim 6.

8. A groove is formed in the negative electrode, and the negative electrode tab is installed in the groove. The electrochemical device of claim 1 .

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

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