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 having the negative electrode structure. It relates to chemical and pneumatic 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 a result, the frequency of use of mobile electronic devices such as drones and the demands on user experience are increasing. Therefore, the electrochemical devices that provide energy to electronic devices (lithium ion Batteries) have higher energy density, higher rate, greater safety, and improved charge / discharge 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-based alloy, or silicon-based 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. The negative electrode structure of the negative electrode material further contains silicon-based materials because of the problem of the expansion coefficient being too high. 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 existing 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. a negative electrode tab extending from the center of the negative electrode tab to the negative electrode active material layer a distance to either one 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, In addition, the negative electrode satisfies the following relational formula (I).

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[0006] The electrochemical device of the present application uses a negative electrode tab that satisfies the above requirements, thereby improving 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 the 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 embodiments of the present application are described, illustrated, or in part described in the following description. is illustrated by the implementation of an embodiment of the present application. [Brief description 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. The drawings described below are some examples of the present application. 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 apparent that other embodiments may be derived based on the drawings.

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of a prior art negative electrode structure. [Diagram 2] FIG. 2 is a schematic top view of a prior art negative electrode structure. [Diagram 3] FIG. 3 is a schematic diagram of a wound cell structure 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. [Diagram 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 long 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 PREFERRED EMBODIMENTS

[0011] The following examples of the present application are described in detail. Components and components having the same or similar functions are designated with like reference numerals. The embodiments described with reference to the drawings are illustrative and schematic and are not intended to provide a basic understanding of the present application. The examples of the present application should not be construed as limiting the present application. There is none.

[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 to refer to instances in which When used in a numerical range, 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, the difference between two values ​​is ±10% of the average 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 numbers are "approximately" It is considered to be the same.

[0013] In this specification, unless otherwise specified or limited, the terms "center", "longitudinal", "vertical ... "Side", "Front", "Rear", "Right", "Left", "Inner", "Outer" "," "low," "high," "horizontal," "vertical," "higher than," "lower than," Relative terms such as "upper," "lower," "top," and "bottom" and their derivatives Words (e.g., "horizontally," "downward," "upward," etc.) may be written or illustrated in the discussion. These relative terms should be interpreted as referring to the orientation shown on the surface of the It is used for convenience and does not require that the present application be constructed or operated in a particular orientation.

[0014] Also, amounts, percentages, and other numerical values ​​may be described herein in a range format. The format of the range is for convenience and brevity of the description and is not intended to be a clearly defined Not only is a range inclusive, but it also includes every individual value subsumed within that range. or subranges.

[0015] In specific embodiments and in the claims, the term "at least one of ... "at least one of," "at least one type of," or other similar terminology A list of items connected by means of any combination of the enumerated 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 three groups A, B, and C are listed, it is written "at least one of A, B, and C." The phrases are A only, B only, C only, A and B (except C), A and C (except B), B and Item A means either a single element or multiple elements. Item B may 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. In the charge-discharge cycle, the impedance of both electrons and ions is large, 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 causes the temperature of the cells to rise significantly. This leads to poor electrochemical performance, such as accelerated cycling capacity fade and reduced discharge rate. Furthermore, this could pose a potential safety issue due to thermal runaway in electrochemical devices.

[0017] 1 and 2 are schematic top views of a typical commercially available anode 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 1, and anode active material layers 102 are formed on both ends of the anode current collector 101 in the longitudinal direction. The negative electrode tab 103 is installed 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 winding process, This design ensures that the electrochemical device is installed in the center. It is possible to effectively improve the processability and reduce the manufacturing cost. Therefore, when using a negative electrode active material with a high capacity per gram (e.g., silicon-based material), The higher the content of silicon-based material in the negative electrode active material, the lower the electrical 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, which in turn causes a deterioration in the electrochemical device. This can lead to a decrease in cycle performance and a safety issue called thermal runaway. 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 location 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 reduces the current in each part of the negative electrode. Improved density and reduced heat generation caused by 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 anode structures according to some embodiments of the present application. do.

[0021] As shown in FIGS. 4 and 5, the present application relates to a negative electrode current collector 201, a negative electrode active material layer 202, and 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).

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[0022] An electrochemical device having a negative electrode conforming to the above formula (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 tab, 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 increased 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.

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[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 the embodiment, in order to avoid a short circuit 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 hold the negative electrode tab 203. The insulating material and the adhesive material may be any suitable material commonly known in the art. It is understood that the material may be any material.

[0025] 7 and 8 show the current distribution when the negative electrode tabs are installed at both ends and at the center of the negative electrode long 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 then be calculated.

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[0027] As shown in Figure 8, when the negative tab is installed at the center of the negative 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 of X n / 2 A part of the current flowing out of part X1 flows from part X n / 2 ' The negative electrode structure of the present application allows the negative electrode current collector to be charged with the same discharge current intensity during discharge. 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 improves the thermal expansion state 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 be employed. The present invention is not limited to the above.

[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 materials capable of absorbing / depositing lithium (hereinafter referred to as "anode materials capable of absorbing / depositing lithium (Li)") Examples of anode materials capable of absorbing / depositing lithium (Li) include carbon materials, metals, etc. Lithium compounds, oxides, sulfides, lithium nitrides such as LiN3, lithium metal, lithium and In some embodiments, the silicon-containing polymer material is a metal that forms the silicon-containing polymer. Silicon-based materials include silicon, silicon compounds, silicon alloys, and silicon-oxygen materials. In some embodiments, the silicon-oxygen material includes 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 substrate, the material layer including a polymer, an inorganic particle, 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 polymers include polyvinylidene fluoride, polyacrylic acid, polyvinyl chloride, Carboxymethylcellulose, polyethylene, polypropylene, polyethylene terephthalate The material includes at least one of a cellulose, a polyamide, and an 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%, about 20%, about 30%, about 50%, about 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 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 major axis length of the active material layer to the major axis length 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 empty foil area, 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, The negative electrode has a wound structure in which a negative electrode current collector 20 and a separator are laminated or wound in this order. 1, a negative electrode active material layer 202, and a negative electrode active material layer 203 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 in the same position as the negative electrode tab 203. The coil is placed at a position one layer away from the center of the coil structure on the inside or outside. The positive electrode tab 209 and the negative electrode tab 203 are spaced apart from each other by one layer. 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 The negative electrode tab is welded to the mounting portion on the negative electrode current collector. The position is formed by cleaning the negative electrode active material layer with ultrasonic waves, so the positive and negative electrode active material layers are coated 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 portion 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 are 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 collector 201 or the positive electrode collector 207 is In another embodiment, the recess 206 is further exposed to the negative electrode tab 203 or The positive electrode tab 209 is disposed in a region 206' of the positive electrode material layer or the negative electrode material layer corresponding to the positive electrode tab 209. In another embodiment, an insulating material and / or an adhesive material may be provided in the groove 206. The insulating material and the adhesive material can be provided by a method according to the present invention. It is understood that the material may be any suitable material commonly used in the field. By providing a sealing material, the risk of short-circuiting 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 be employed. and is not limited thereto.

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

[0044] In the above positive electrode material, the chemical formula of lithium cobalt oxide is Li y Co a M1 b O 2-c Here, M1 may be 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 elements: Y, La, Zr, and 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 above positive electrode material, lithium nickel cobalt manganese oxide or nickel cobalt a 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 ) is selected, 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 Here, M3 may be 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, 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 can easily determine the method according to the 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 ethylene 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 in preventing short circuits and have a 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, the electrolyte including 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 since it can provide high thermal 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. orocarbonate compounds, or combinations thereof.

[0053] Examples of the other organic solvents include dimethyl sulfoxide, 1,2-dioxolane, sulfo Lan, Methylsulfolane, 1,3-Dimethyl-2-imidazolidinone, N-Methyl-2- Pyrrolidone, formamide, dimethylmethanamide, acetonitrile, trimethylphosphine phosphate, triethyl phosphate, trioctyl phosphate, and phosphate ester 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] Methods for preparing positive electrodes, negative electrodes, separators, and lithium-ion batteries according to embodiments of the present application However, the present invention is not limited to the above, and may be modified in various ways according to the present invention without departing from the spirit of the present invention. It should be understood that the selection may be arbitrary, but is not limited thereto. In one embodiment of the method for preparing a lithium ion battery, the method for preparing a lithium ion battery comprises the steps of: In the embodiment, the positive electrode, the separator, and the negative electrode are wound in sequence to form a cell, and the cell is then sealed in an aluminum alloy. The battery is placed in a plastic film, the electrolyte is injected, and then the battery is vacuum sealed, left to stand, chemically converted, and then cooled. A lithium ion battery is obtained by carrying out a process such as molding.

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

[0057] Although the above description is given taking a lithium ion battery as an example, those skilled in the art will understand that It is contemplated that the negative electrodes of the present application may be used in other suitable electrochemical devices. Electrochemical devices include any device that produces an electrochemical reaction, and specific examples include primary batteries, This includes any type of secondary battery, fuel cell, solar cell, or capacitor. The chemical equipment is used for 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. , pen-based computers, mobile computers, e-book players, mobile phones , portable fax machines, portable copiers, portable printers, stereo headsets Phones, video recorders, LCD TVs, portable cleaners, portable CD players , mini disks, transceivers, electronic notepads, calculators, memory cards, portable Recorders, radios, backup power sources, motors, automobiles, motorcycles, electric assist Bicycles, bicycles, lighting equipment, toys, game consoles, watches, power tools, flashes, cameras , large household batteries, lithium ion capacitors, but are not limited to do not have. Working 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), Cycle performance tests and cell surface temperature rise tests are carried out.

[0061] 1. Test 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. 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 a 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 embodiment, Discharge at a constant current of C for 10 seconds, current I 0·1C and terminal voltage U 0·1C Record the following and then 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. Four lithium-ion batteries were used as test batteries to measure the DC resistance of the lithium-ion batteries. The average resistance is calculated.

[0062] 1.2 Discharge rate test: The lithium-ion battery of the following example was placed in a thermostat at 25°C ± 2°C for 2 hours and then heated at 0.5C. Charge at constant current to 4.35V, then charge at constant voltage of 4.35V at 0.05C for 15 minutes. Leave the battery for 10 minutes, then discharge it at a constant current of 0.2C until the voltage reaches 3.0V. Charge at a constant current of 0.5C to 4.35V, then charge at a constant voltage of 4.35V down to 0.05C. Charge and discharge at a constant current of 1.0C until the voltage drops to 3.0V. Discharge at a constant current of 0.2C. The discharge capacity of the lithium ion battery is recorded when it is discharged at a constant current of 1.0 C and 1.0 C.

[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 ( Discharge capacity (mAh) / 0.2C constant current.

[0064] 1.3 Cycling performance test: The lithium-ion battery of the following example was placed in a thermostat at 25°C ± 2°C for 2 hours and then heated at 0.5C. Charge at constant current to 4.35V, then charge at constant voltage of 4.35V at 0.05C for 15 minutes. 3.0V at a constant current of 0.5C. The discharge capacity of the lithium-ion battery on the first cycle is recorded, and The above method was repeated for 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 lithium-ion batteries. Retention rate = Discharge capacity after 100 cycles (mAh) / Discharge capacity after first cycle (mAh) ×100%.

[0066] 1.4 Cell surface heating test: The lithium ion battery of the following example is 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 flow of the test is as follows: A lithium-ion battery is charged 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 cell surface temperature rise of the lithium-ion battery 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 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. Both surfaces of a porous substrate (polyethylene) with a ceramic coating on both sides The slurry was applied to the substrate 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 of 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 Synthetic 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 the thickness is reduced through processes such as drying, cold pressing, and cutting. 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 elemental silicon to the negative electrode active material layer is 20%. The positive electrode, separator, and negative electrode are stacked in order and wound into a cell so that the positive electrode acts as an insulator between the positive electrode and the negative electrode. The number of layers in the cell is 7 (one layer for 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 cells are then vacuum mounted, left to stand, chemically formed, and molded to produce lithium ion 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. A slurry was formed, and the weight ratio of elemental silicon to the negative electrode active material layer was 40%. The preparation method is the same as that of Example 1-1.

[0072] Examples 1-3 In Example 1-3, artificial graphite and silicon carbon were mixed and dissolved in deionized water to prepare a negative electrode. A slurry was formed, and the weight ratio of elemental silicon to the negative electrode active material layer was 50%. The preparation method is the same as that of 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 slag. A slurry was formed, and the weight ratio of elemental silicon to the negative electrode active material layer was 70%. The preparation method is the same as that of 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 slag. The weight ratio of elemental silicon to the negative electrode active material layer is 90%. The preparation method is the same as that of 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 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 present invention includes 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 The electrode tab is placed one layer away from the center of the 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 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 The 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 contains artificial graphite and silicon carbon, and the weight ratio of silicon carbon in the negative electrode active material layer is The quantitative 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 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 major axis of the negative electrode active material layer, and The positive electrode tab is set at a position one layer away from the center of the above-mentioned wound structure toward the outside with respect to the negative electrode tab. In addition, 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 battery in the above embodiment was subjected to a DC resistance test and a discharge rate test. Tests were performed on the cell surface and the cycle performance, and the cell surface temperature rise was recorded. did.

[0081] Testing the DC resistance and discharge rate of the lithium-ion batteries in all the examples; The results of the cycle performance tests and cell surface temperature rise tests 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 negative electrode tab installation position 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 temperature rise of the cell. So, how does the negative electrode tab installation position and 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 along the long axis The distance from the negative electrode active material layer to one end in the negative electrode active material layer in the direction of the negative electrode active material layer is 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 is 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 following formula: 0.9 × (S1 + 2 S1+S2 ≦ 1.1 × (S1+2S3) is satisfied. The temperature rise of the cell is Since the strength of the current collector decreases with increasing thickness, it is necessary to evaluate the strength of the current collector and the energy density of the cell comprehensively. In this embodiment, a current collector having a thickness of 8 μm is preferable. By controlling the relationship, when the negative electrode material has the same silicon content, the present embodiment Such electrochemical devices have lower DC resistance and better discharge rates, and In addition, the negative electrode tab in the present embodiment is located at a good position. The embodiment that meets the range of the relationship with the silicon content effectively reduces the average temperature rise of the cell surface. Therefore, the electrochemical device can be controlled and the safety performance of the electrochemical device can be ensured.

[0089] By comparing the above examples, the electrochemical device of the present application has a negative electrode tab installation position and By limiting the weight ratio of silicon in the negative electrode active material layer, the size of the electrochemical device can be reduced. This can significantly improve driving performance and safety.

[0090] Throughout this specification, the terms "some embodiments," "some examples," "one embodiment," "an ", "as another example," "for example," "as a specific example," or "as some examples" Reference herein to at least one embodiment or example includes the following: It is meant 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," "one embodiment," "an "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 described in one or more embodiments or examples. The components may 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. No changes, substitutions, or modifications of the embodiments are permitted 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 including a silicon-based material; a negative electrode tab disposed on a major axis side of the negative electrode current collector; The distance from the center position to one end of the negative electrode active material layer in the major axis direction is defined as a first length. The 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): death, [0010] Here, D is the ratio of the first length to the second length, and G is the silicon-based material and the weight ratio of the silicon-based material is 70% or less. Electrochemical equipment.

2. The thickness of the negative electrode current collector is 4 μm to 30 μm, and the negative electrode is ) is satisfied, [0025] Here, the thickness of the negative electrode current collector is S １ and the thickness of the negative electrode tab is S ２ and The thickness of the negative electrode active material layer is S ３ is 2. The electrochemical device of claim 1.

3. The silicon-based material includes silicon alone, silicon compounds, silicon alloys, and silicon At least one of the oxygen materials 2. The electrochemical device of claim 1.

4. 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 It is 1.0 2. The electrochemical device of claim 1.

5. The electrochemical device is a wound structure, and the negative electrode tab is disposed in the wound structure. It is located at least three floors away from the center 2. The electrochemical device of claim 1.

6. The positive electrode tab of the positive electrode is positioned outwardly from the center of the wound structure relative to the location of the negative electrode tab. Located one floor away 6. The electrochemical device of claim 5.

7. The silicon-based material is disposed on at least a portion of a surface of the silicon-based material. The method further includes the step of forming a layer of a material, the layer of material being made of a polymer, inorganic particles, amorphous carbon, and Contains at least one of carbon nanotubes 2. The electrochemical device of claim 1.

8. The inorganic particles include lithium cobalt oxide, lithium iron phosphate, nickel cobalt manganese, etc. Lithium aluminate, lithium nickel cobalt aluminate, silicon, silicon compounds, silicon and at least one of a silicon alloy and a silicon-oxygen material, and the polymer is a poly Vinylidene fluoride, polyacrylic acid, polyvinyl chloride, carboxymethyl cellulose, Polyethylene, polypropylene, polyethylene terephthalate, polyamide, and aramide Contains at least one of the following:

8. The electrochemical device of claim 7.

9. The negative electrode has a groove, and the negative electrode tab is placed in the groove.

2. The electrochemical device of claim 1.

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

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