CN113437251B

CN113437251B - Negative electrode active material, electrochemical device, and electronic device

Info

Publication number: CN113437251B
Application number: CN202110685952.1A
Authority: CN
Inventors: 刘茜; 郑席; 杜鹏; 谢远森
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2021-06-21
Filing date: 2021-06-21
Publication date: 2022-10-25
Anticipated expiration: 2041-06-21
Also published as: CN113437251A; CN115663181A

Abstract

The invention relates to a negative electrode active material, an electrochemical device, and an electronic device. The negative active material comprises a second material and a first material covering at least one part of the surface of the second material, wherein the first material has a sheet interval d1, the second material has a sheet interval d2, and the following conditions are satisfied: d1/d2 is more than or equal to 0.85 and less than or equal to 1.05. The negative active material can improve the cycle performance and improve the cycle expansion when being used as the negative material of the lithium ion battery.

Description

Negative electrode active material, electrochemical device, and electronic device

Technical Field

The present application relates to the field of lithium ion batteries. Specifically, the present application relates to a negative active material and a method of preparing the same. The present application also relates to an anode, an electrochemical device, and an electronic device including the anode active material.

Background

For the negative electrode material of the lithium ion battery, the most material applied in the market at present is graphite, but the microstructure of the graphite is compact, the surface has no buffer structure, lithium ions are easy to form and accumulate on the surface in the rapid charging process, lithium dendrites are further formed, and the electrical property and the safety performance of the battery are influenced. Meanwhile, the specific surface area of graphite is small, and lithium ions are not enough to enter and exit channels, so that the capacity is easily and rapidly reduced in the rapid charging and discharging process. In order to improve the rapid charge and discharge performance of graphite, a material having rapid charge and discharge capability, such as hard carbon, soft carbon, carbon nanotube, etc., is generally used as a buffer layer. And because the cladding is thinner, the lifting space brought about is relatively small, and a new way still needs to be found to meet the higher and higher requirements.

Disclosure of Invention

To the deficiencies of the prior art, the present application provides a negative active material that can promote cycle performance and improve cycle expansion as a negative material for lithium ion batteries.

In a first aspect, the present application provides a negative active material comprising a second material and a first material covering at least a portion of a surface of the second material, wherein the first material has a sheet spacing of d1, and the second material has a sheet spacing of d2, and satisfies: d1/d2 is more than or equal to 0.85 and less than or equal to 1.05.

According to some embodiments of the present application, the anode active material satisfies at least one of the following conditions (a) to (f): (a) The average coverage of the first material on the surface of the second material is more than 50 percent; (b) The thickness of the first material is 3nm to 500nm, preferably 20nm to 300nm; (c) The included angle theta between the length direction of the first material and the surface of the second material is 45-135 degrees; (d) The first material has a size of 3nm to 500nm, preferably 20nm to 300nm; (e) d1 ranges from 0.33nm to 0.34nm, d2 ranges from 0.34nm to 0.40nm; (f) The included angle theta between the length direction of at least 50% of the first materials in the first materials and the surface of the second materials is 70-120 degrees; (g) d2 ranges from 0.34nm to 0.40nm.

According to some embodiments of the present application, I of the negative active material _G /I _2D Is 0.3 to 5,I _G /I _D Is 0.3 to 1.5, wherein I _2D Is located at 2500cm in Raman spectrum ^-1 To 2800cm ^-1 Peak intensity of the range of (1), I _D Is located at 1300cm in Raman spectrum ^-1 To 1400cm ^-1 Peak intensity of the range of (1), I _G Is located at 1550cm in Raman spectrum ^-1 To 1650cm ^-1 Peak intensity of the range of (a).

According to some embodiments of the present application, the first material comprises graphite and the second material comprises hard carbon; preferably, the first material is a graphite sheet and the second material is hard carbon.

According to some embodiments of the present application, the anode active material has a specific surface area of 2m ² G to 10m ² /g。

According to some embodiments of the present application, the anode active material of the present application has an X-ray diffraction pattern in which a first peak and a second peak exist between 18 ° and 30 °, wherein the first peak is located between 22 ° and 26 °, the second peak is located between 26.3 ° and 26.6 °, and a ratio R of an intensity of the second peak to an intensity of the first peak is 0.9 to 20.

In a second aspect, the present application provides an electrochemical device comprising a positive electrode, a negative electrode, an electrolyte, and a separator, the negative electrode comprising a current collector and a negative electrode active material layer on a surface of the current collector, the negative electrode active material layer comprising the negative electrode active material according to the first aspect.

According to some embodiments of the present application, the electrolyte includes at least one of fluoroether, fluoroethylene carbonate or ether nitrile.

According to some embodiments of the present application, the electrolyte includes a lithium salt including lithium bis (fluorosulfonyl) imide and lithium hexafluorophosphate, wherein the lithium salt concentration is 1 to 2mol/L, and the mass ratio of lithium bis (fluorosulfonyl) imide to lithium hexafluorophosphate is 0.06 to 5.

In a third aspect, the present application provides an electronic device comprising the electrochemical device of the second aspect.

According to the negative electrode active material provided by the application, the first material with a specific lamellar structure is constructed on the surface of the second material, and the polarization of a lithium ion intercalation process is reduced through the first material structure, so that the intercalation of lithium ions is accelerated. Meanwhile, the lithium ion intercalation and deintercalation path is increased, so that the intercalation and deintercalation performance of the material is improved.

Drawings

Fig. 1 is a schematic structural view of an anode active material according to an embodiment of the present application.

Fig. 2 is a schematic structural view of an anode active material according to another embodiment of the present application.

Fig. 3 is a schematic diagram of a lithium ion transport pathway according to an embodiment of the present application.

Fig. 4 is a TEM image of an anode active material according to an embodiment of the present application.

Fig. 5 is an SEM image of the negative electrode active material according to an embodiment of the present application.

Fig. 6 is a schematic view of the angle θ between the graphite sheet and the hard carbon surface according to one embodiment of the present application.

Detailed Description

For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and similarly any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each separately disclosed point or individual value may itself, as a lower or upper limit, be combined with any other point or individual value or with other lower or upper limits to form ranges not explicitly recited.

In the description herein, "above" and "below" include the present numbers unless otherwise specified.

Unless otherwise indicated, terms used in the present application have well-known meanings that are commonly understood by those skilled in the art. Unless otherwise indicated, the numerical values of the parameters mentioned in the present application can be measured by various measurement methods commonly used in the art (for example, the test can be performed according to the methods given in the examples of the present application).

A list of items to which the term "at least one of," "at least one of," or other similar term is connected may imply any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and all of C. Item A may comprise a single component or multiple components. Item B can comprise a single component or multiple components. Item C may comprise a single component or multiple components.

1. Negative electrode active material

The negative active material provided by the application comprises a second material and a first material covering at least one part of the surface of the second material, wherein the lamella interval of the first material is d1, the lamella interval of the second material is d2, and the following conditions are met: d1/d2 is more than or equal to 0.85 and less than or equal to 1.05.

According to some embodiments of the application, d1/d2 is 0.86, 0.88, 0.90, 0.92, 0.94, 0.95, 0.97, 0.99, 1.00, or any value in between. When the ratio of d1/d2 is between 0.85 and 1.05, the interplanar spacing of the second material is wider than that of the first material, so that a channel for rapidly extracting lithium ions can be provided, and the resistance of lithium ions in the first material is reduced. Meanwhile, the first material layer with relatively small crystal face spacing can increase material conductance, reduce polarization and maintain higher multiplying power and circulation level of the material. When d1/d2 is larger than 1.05, the second material has small crystal face distance, lithium ion intercalation internal resistance is increased, rate performance is poor under large rate, and meanwhile, the problem of large expansion caused by small crystal face distance is solved, and the cyclic expansion rate of the electrochemical device is large.

According to some embodiments of the present application, the lamella spacing d1 of the first material is 0.33nm to 0.34nm. According to some embodiments of the present application, the lamella spacing d1 of the first material is 0.33nm, 0.333nm, 0.336nm, or 0.337nm.

According to some embodiments of the present application, the second material has a lamella spacing d2 of 0.34nm to 0.40nm. According to some embodiments of the present application, the second material has a lamella spacing d2 of 0.35nm, 0.36nm, 0.37nm, 0.38nm, or 0.39nm. In some embodiments of the present application, the inter-sheet distance d2 of the second material is 0.36nm to 0.40nm. The second material has smaller interlayer spacing, which causes larger lithium intercalation resistance and slows down the diffusion of lithium ions, so that the overall rate capability of the material is reduced, and the capacity loss of high-rate charge-discharge cycle is larger. At the same time, the smaller spacing of the second material results in lithium intercalation expansion and greater expansion of the overall electrochemical device.

According to some embodiments of the present application, the average coverage of the first material on the surface of the second material is 50% or more. In some embodiments of the present application, the average coverage of the first material on the surface of the second material is 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%. According to some embodiments, the average coverage of the first material on the surface of the second material is 70% or more. In some embodiments, the average coverage of the first material on the surface of the second material is 90% or more.

In the present application, the average coverage of the first material on the surface of the second material means the coverage of the surface of the second material by the first material, which is determined by the following method: randomly selecting 20 TEM (equipment model is Talos F200X) samples, observing the surface area of the second material under the condition of magnifying a ruler to 10nm, wherein the frequency of the occurrence of the first material layer is N, and the coverage of the first material on the surface of the second material is as follows: (N/20). Times.100%.

According to some embodiments of the application, the first material has a thickness of 3nm to 500nm, such as 5nm, 10nm, 30nm, 50nm, 70m, 90nm, 100nm, 110nm, 130nm, 150nm, 180nm, 200nm, 220nm, 250nm, 270nm, 290nm, 310nm, 350nm, 370nm, 400nm or 450nm. In some embodiments of the present application, the first material has a thickness of 20nm to 300nm. The first material is too thick, so that a part of lithium embedding channels are difficult to enter rapidly by lithium ions, the integral rate capability of the material is reduced, the components of the first material in the material are increased along with the increase of the thickness of the first material, and the expansion degree of the pole piece is increased.

According to some embodiments of the present application, the angle θ between the length direction of the first material and the surface of the second material is 45 ° to 135 °, for example 50 °, 55 °, 60 °, 65 °, 70 °, 75 °, 80 °, 85 °, 90 °, 95 °, 100 °, 105 °, 110 °, 115 °, 120 °, 125 °, or 130 °. In the present application, the included angle θ between the length direction of the first material and the surface of the second material is determined by: taking an SEM (scanning Electron microscope) picture of a CP (Cross Section Polisher) sample of an ion beam Cross Section of an active material layer by using a scanning electron microscope, wherein the visible surface of a particle on the outermost layer in an SEM picture has a structure approximately vertical to the surface of the particle, making a tangent line (straight line 1) at the contact point of the particle surface and a first material by using an image processing system, forming a straight line (straight line 2) between the contact point of the first material and the particle surface and two points of the other end point of the first material farthest from the particle surface, wherein the included angle of the two straight lines is theta 1, randomly selecting 5 theta 1 in each SEM picture, then selecting 10 SEM pictures, and calculating the average value of 10 multiplied by 5 positions theta 1, namely the included angle theta of the first material and the second material surface. According to some embodiments of the present application, at least 50% of the first material is at an angle θ of 70 ° to 120 ° to the surface of the second material, for example at least 60%, at least 70%, at least 80% or at least 90% of the first material is at an angle θ of 70 ° to 120 ° to the surface of the second material. In some embodiments of the present application, at least 50% of the first material in the first material layer is at an angle θ of 70 ° to 120 ° with respect to the surface of the second material, i.e., 10 × 5 positions θ 1 are randomly counted, and at least 50% (25 positions) of the first material is at an angle θ of 70 ° to 120 ° with respect to the surface of the second material.

According to some embodiments of the application, the first material has a size of 3nm to 500nm, such as 5nm, 10nm, 30nm, 50nm, 70m, 90nm, 100nm, 110nm, 130nm, 150nm, 180nm, 200nm, 220nm, 250nm, 270nm, 290nm, 310nm, 350nm, 370nm, 400nm or 450nm. According to some embodiments of the present application, the first material has a size of 20nm to 300nm. When the first material is oversized, lithium ion channels are reduced, resulting in loss of rate capability.

According to some embodiments of the application, the first material is a graphite sheet. According to some embodiments of the present application, the second material is hard carbon.

According to the negative active material, at least part of the surface of a second material, such as hard carbon, is coated with a first material, such as a graphite sheet, so that the specific surface area of the material is reduced due to the covering effect of the first material, and the rate capability of the material is improved. Meanwhile, the conductivity of the material is increased, so that the integral polarization of the material is reduced, and the polarization resistance can be reduced in the charging process, thereby improving the lithium embedding capacity of the material to a certain extent, accelerating the electronic conductance and obtaining better rapid charge and discharge performance. However, only the first material is simply coated on the surface of the second material in an amorphous form, and the thickness of the first material needs to be ensured to be thinner so as to reduce the degree of coating on the surface of the second material, and further avoid affecting the lithium release and insertion path of the material. Therefore, the first material covers the surface of the second material at a certain angle, so that a direct extraction channel is provided for partial lithium ions, the extraction path of the lithium ions is shortened, the extraction speed of the lithium ions is accelerated, and the cycle and rate performance of the whole material are further optimized.

As shown in fig. 3, since the extraction of lithium ions needs to be performed by the microcrystalline layer of hard carbon, which is irregularly arranged, the transmission path of lithium ions is lengthened (fig. 3-1), which affects the extraction rate. The graphite sheet layer vertical to the surface of the hard carbon is synthesized on the surface of the hard carbon, and the sheet layer not only has a certain surface covering effect, reduces the specific surface area and enhances the electronic conductance. Meanwhile, as a direct extraction channel is provided for partial lithium ions, the extraction path of the lithium ions is shortened, and the extraction rate of the lithium ions is accelerated (figure 3-2), so that the cycle and rate performance of the whole material are optimized.

According to some embodiments of the present application, I of the negative active material _G /I _2D Is 0.3 to 5, such as 0.5, 1.0, 2.0, 3.0 or 4.0, wherein I _2D Is at 2500cm in Raman spectrum ^-1 To 2800cm ^-1 Peak intensity of the range of (1), I _G Is located at 1580cm in Raman spectrum ^-1 To 1620cm ^-1 Peak intensity of the range of (a).

According to some embodiments of the present application, I of the negative active material _G /I _D Is 0.3 to 1.5, such as 0.5, 0.7, 0.9, 1.0 or 1.3, wherein I _D Is located at 1300cm in Raman spectrum ^-1 To 1400cm ^-1 Peak intensity of the range of (1), I _G Is located at 1580cm in Raman spectrum ^-1 To 1620cm ^-1 Peak intensity of the range of (a). The testing equipment adopted is a laser micro-confocal Raman spectrometer (Raman, HR Evolution, HORIBA scientific instruments and institutions).

In this application, the Raman spectrum shows a 2D peak, indicating the presence of the coated graphite sheet (fewer graphite layers), while the mere mixing of graphite and hard carbon does not show a distinct 2D peak. Meanwhile, because the proportion of the amorphous carbon part of the material is still the main part, the proportion of the graphite part is smaller, and the ratio of the amorphous carbon part of the material is I _G /I _D Between 0.3 and 1.5.

According to some embodiments of the present application, the anode active material has a specific surface area of 2m ² G to 10m ² (ii) in terms of/g. According to some embodiments of the present application, the specific surface area of the anode active material is 3m ² /g、4m ² /g、5m ² /g、6m ² /g、7m ² /g、8m ² /g、9m ² G or any value in between.

According to some embodiments of the present application, the anode active material has an X-ray diffraction pattern in which a first peak and a second peak exist between 18 ° and 30 °, wherein the first peak is located between 22 ° and 26 °, the second peak is located between 26.3 ° and 26.6 °, and a ratio R of an intensity of the second peak to an intensity of the first peak is 0.9 to 20. According to some embodiments of the application, R is 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19. In some embodiments of the present application, R is 3 to 15.

According to some embodiments of the application, the first peak has a half-width of 4 ° to 10 °. According to some embodiments of the application, the second peak has a half-width of 0.1 ° to 2 °.

In the application, a first peak between 22 and 26 degrees represents a diffraction peak of a (002) crystal face of a hard carbon microchip layer, a second peak between 26.3 and 26.6 degrees represents a diffraction peak of a (002) crystal face of a graphite microchip layer, and the ratio R of the intensity of the second peak to the intensity of the first peak can reflect the coating amount of the graphite sheet layer, so that the number of the graphite sheet layers is more, and the R value is larger. An excessively small R value means that the coating amount of the graphite sheet is excessively low, and the improvement effect on the material is not obvious. The R value is too large, so that partial lithium storage sites are easily covered, and the capacity of the material per se is influenced.

According to some embodiments of the present application, the XPS spectrum of the anode active material second material has peaks in at least one of the following ranges: 398eV to 404eV, 102eV to 104eV, and 130eV to 132eV. According to some embodiments of the present application, the XPS spectrum of the anode active material second material has at least one peak in a range of 285eV to 289 eV. In the XPS spectrum of this application, the peak in the range of 398eV to 404eV represents a nitrogen-containing group, the peak in the range of 102eV to 104eV represents a siloxy group, the peak in the range of 130eV to 132eV represents a phosphorus oxy group, and the peak in the range of 285eV to 289eV represents a carbon oxy group.

According to some embodiments of the present application, the anode active material second material comprises at least one of N, P, S, si or B element. According to some embodiments of the present application, the negative electrode is activeThe powder conductivity of the material was 1X 10 ⁷ S/cm to 9X 10 ⁸ S/cm。

2. Method for preparing negative active material

The preparation method of the negative active material comprises the step of coating the first material on the second material through a Physical Vapor Deposition (PVD) method. According to some embodiments of the present application, the method for preparing the negative active material includes sputtering the target material on a substrate with the first material as the target material and the second material as the substrate. In some embodiments of the present application, the method for preparing the negative active material includes the following specific steps:

step A, placing a second material as a substrate on a support;

b, taking the first material as a target material, and depositing the first material on the base material in the step A in a sputtering mode;

and step C, annealing the base material on which the target is deposited.

According to some embodiments of the application, the support comprises a slide. In some implementations of the present application, the distance between the target and the substrate is 5cm to 20cm. According to some embodiments of the present application, the sputtering gas is high purity argon with a purity >99.99%, the sputtering power is 100W to 500W, and the sputtering time is 30min to 120min. According to some embodiments of the present application, the deposition temperature is 200 ℃ to 1000 ℃. According to some embodiments of the present application, the annealing temperature is 300 ℃ to 600 ℃ and the annealing time is 15min to 60min.

3. Electrochemical device

An electrochemical device includes a negative electrode, a positive electrode, an electrolyte, and a separator.

Negative electrode

The negative electrode in the electrochemical device of the present application includes a current collector and a negative electrode active material layer on a surface of the current collector, the negative electrode active material layer including the negative electrode active material according to the first aspect.

In some embodiments, the current collector comprises: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, or any combination thereof.

In some embodiments, the negative active material layer further includes a binder including, but not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, or the like.

In some embodiments, the negative electrode active material layer further includes a conductive agent including, but not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fibers, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

The negative electrode of the present application can be prepared by a method known in the art. Generally, a negative electrode active material, an optional conductive agent (such as carbon materials such as carbon black and metal particles), a binder (such as SBR), other optional additives (such as PTC thermistor materials) and the like are mixed together and dispersed in a solvent (such as deionized water), uniformly stirred and then uniformly coated on a negative electrode current collector, and dried to obtain a negative electrode containing a negative electrode membrane. As the negative electrode current collector, a material such as a metal foil or a porous metal plate may be used.

Positive electrode

Materials, compositions, and methods of making positive electrodes useful in embodiments of the present application include any of the techniques disclosed in the prior art.

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

In some embodiments, the positive active material comprises a positive material capable of absorbing and releasing lithium, including but not limited to lithium cobaltate, lithium nickel cobalt manganese, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium iron phosphate, lithium titanate, and lithium rich manganese-based materials. In particular, the amount of the solvent to be used,

specifically, the chemical formula of lithium cobaltate may be as shown in chemical formula 1:

Li _x Co _a M1 _b O _2-c chemical formula 1

Wherein M1 represents at least one selected from the group consisting of nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), zirconium (Zr), and silicon (Si), and x, a, B, and c values are respectively in the following ranges: x is more than or equal to 0.6 and less than or equal to 1.2, a is more than or equal to 0.8 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 0.2, and c is more than or equal to-0.1 and less than or equal to 0.2.

The chemical formula of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminate can be as shown in chemical formula 2:

Li _y Ni _d M2 _e O _2-f chemical formula 2

Wherein M2 represents at least one selected from the group consisting of cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr), and silicon (Si), and y, d, e, and f values are respectively in the following ranges: y is more than or equal to 0.8 and less than or equal to 1.2, d is more than or equal to 0.3 and less than or equal to 0.98, e is more than or equal to 0.02 and less than or equal to 0.7, and f is more than or equal to 0.1 and less than or equal to 0.2;

the chemical formula of lithium manganate can be as chemical formula 3:

Li _z Mn _2-g M3 _g O _4-h chemical formula 3

Wherein M3 represents at least one selected from the group consisting of cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W), and z, g, and h values are respectively in the following ranges: z is more than or equal to 0.8 and less than or equal to 1.2, g is more than or equal to 0 and less than or equal to 1.0, and h is more than or equal to-0.2 and less than or equal to 0.2.

In some embodiments, the positive active material layer further includes a binder, and optionally a conductive material. The binder improves the binding of the positive electrode active material particles to each other, and also improves the binding of the positive electrode active material to the current collector.

In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, or the like.

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

In some embodiments, the current collector may include, but is not limited to: aluminum.

The positive electrode may be prepared by a preparation method well known in the art. For example, the positive electrode can be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector. In some embodiments, the solvent may include, but is not limited to: n-methyl pyrrolidone.

Electrolyte solution

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In some embodiments, examples of ethernitriles are ethylene glycol bis (propionitrile) ether, 1,4-bis (cyanoethoxy) butane, ethylene glycol di (2-cyanoethyl) ether, diethylene glycol di (2-cyanoethyl) ether, triethylene glycol di (2-cyanoethyl) ether, tetraethylene glycol di (2-cyanoethyl) ether, 3,6,9,12,15,18-hexaoxaeicosanoic acid dinitrile, 1,3-bis (2-cyanoethoxy) propane, 1,4-bis (2-cyanoethoxy) butane, 1,5-bis (2-cyanoethoxy) pentane and ethylene glycol di (4-cyanobutyl) ether, 3,3' - [ [2- [ (2-cyanoethoxy) methyl ] -2-ethyl-1,3-propanediyl ] di (oxy) ] di-propionitrile, and combinations thereof.

In some embodiments, the electrolyte comprises an organic solvent including, but not limited to: ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate.

In some embodiments, the electrolyte comprises a lithium salt, wherein the lithium salt comprises lithium bis (fluorosulfonyl) imide (LiFSI) and lithium hexafluorophosphate (LiPF) ₆ ). In some embodiments, the lithium salt concentration is 1 to 2mol/L and the mass ratio of lithium bis (fluorosulfonyl) imide to lithium hexafluorophosphate is 0.06 to 5.

Isolation film

In some embodiments, a separator is provided between the positive and negative electrodes to prevent short circuits. The material and shape of the separation film usable for the embodiments of the present application are not particularly limited, and may be any of those disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance or the like formed of a material stable to the electrolyte of the present application.

In some embodiments, the separator includes at least one selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid. For example, the polyethylene includes at least one component selected from the group consisting of high density polyethylene, low density polyethylene, and ultra high molecular weight polyethylene. Particularly polyethylene and polypropylene, which have a good effect on preventing short circuits and can improve the stability of the battery through a shutdown effect.

The surface of the separator may further include a porous layer disposed on at least one surface of the separator, the porous layer including inorganic particles selected from alumina (Al) and a binder ₂ O ₃ ) Silicon oxide (SiO) ₂ ) Magnesium oxide (MgO), titanium oxide (TiO) ₂ ) Hafnium oxide (HfO) ₂ ) Tin oxide (SnO) ₂ ) Cerium oxide (CeO) ₂ ) Nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO) ₂ ) Yttrium oxide (Y) ₂ O ₃ ) One or a combination of more of silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from one or a combination of more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

The porous layer on the surface of the isolating membrane can improve the heat resistance, the oxidation resistance and the electrolyte infiltration performance of the isolating membrane and enhance the adhesion between the isolating membrane and the pole piece.

In some embodiments, the electrochemical devices of the present application include, but are not limited to: all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors.

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

In some embodiments, the lithium secondary battery includes, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

4. Electronic device

The electronic device of the present application may be any device using the electrochemical device according to the third aspect of the present application.

In some embodiments, the electronic devices include, but are not limited to: a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting apparatus, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery or a lithium ion capacitor, and the like.

The test method comprises the following steps:

first material sheet spacing, second material sheet spacing, thickness of first material:

method 1. Fully grinding the material, grinding the sample as far as possible by using a mortar so that the size of the sample is between 50nm and 70nm, then dissolving the powder sample in absolute ethyl alcohol, dispersing the sample as far as possible by using an ultrasonic dispersion method, and then fishing up the sample by using a supporting net to prepare the sample.

And 2, embedding and curing the epoxy resin on the material, and then cutting the material into the size of 50nm to 70nm by using an ultrathin section method to prepare a sample.

Selecting the particle surface by using a high-power transmission electron microscope for observation, selecting 3-10 lamellar regions from long-range regularly arranged line (first material lamellar) regions on the surface, randomly selecting 20 regions, measuring the width by using a system, obtaining the average distance between lamellar layers by using the width/number of layers, then calculating the average value of the average distance between lamellar layers of 3-10 lamellar layers in 20 regions, and taking the average value of the average distance between 3-10 lamellar layers in 20 regions as the first material lamellar interval;

selecting a granular amorphous area (without long-range regular lamellae and disordered lamella arrangement) by using a high-power transmission electron microscope for observation, selecting 3-5 lamellae in an area of an internally appearing microcrystalline lamella area, randomly selecting 20 areas, measuring the width of the area by using a system, obtaining the average distance between lamellae by using the width/number of layers, then calculating the average value of the average distance between lamellae of 3-5 lamellae in 20 areas, and taking the average value of the average distance between 3-5 lamellae in the 20 areas as the second material lamella interval;

the particle surfaces are selected by a high-power transmission electron microscope (TEM, the equipment model is Talos F200X) for observation, the width (the distance from the surface of the second material to the outermost side of the first material) of an arrangement line (the first material layer) of Cheng Guize with the length appearing on the test surface of 5 positions is selected on each TEM, the average value of 5 measurements is calculated to be a1, 10 TEM images are selected, and then the average value of 10 multiplied by 5 positions is calculated to be the thickness of the first material.

XRD test:

testing the cathode active material by an X-ray powder diffractometer (XRD, instrument model: bruker D8 ADVANCE), wherein the target material is Cu Ka; the voltage current is 40KV/40mA, the scanning angle range is 5-80 degrees, the scanning step size is 0.00836 degrees, and the time of each step size is 0.3s.

Included angle theta between the length direction of the first material and the surface of the second material is as follows:

preparation of negative ion milled (CP) samples: the negative electrode active material layer was cut to a size of 0.5cm × 1cm, the cut negative electrode active material layer was pasted on a silicon wafer carrier of a size of 1cm × 1.5cm using a conductive paste, and then one end of the negative electrode was treated using argon ion polishing (parameter: acceleration voltage of 8KV, 4 hours per sample) to obtain an active material layer CP sample. The argon ion polishing is to ionize argon by using a high-voltage electric field to generate an ionic state, and the generated argon ions bombard the surface of the negative electrode at a high speed under the action of accelerating voltage to degrade the negative electrode layer by layer so as to achieve the polishing effect.

After the active material layer CP is manufactured, taking an SEM picture of an ion beam Cross Section grinding (CP) sample of the active material layer by using a scanning electron microscope, wherein the visible surface of the most superficial particle in the SEM picture has a structure approximately vertical to the particle surface, making a tangent (a straight line 1) at the contact point of the particle surface and a first material by using an image processing system, forming a straight line (a straight line 2) between the contact point of the first material and the particle surface and two points of the other end point of the first material farthest from the particle surface, wherein the included angle of the two straight lines is theta 1, randomly selecting 5 theta 1 from each SEM picture, then selecting 10 SEM pictures, and calculating the average value of 10 multiplied by 5 positions theta 1, namely the included angle theta between the first material and the second material surface.

Size of the first material:

similar to the process of testing the included angle θ, after preparing the CP sample, the SEM system measures the distance from the bottom of the first material sheet (the contact point with the surface) to the top of the first material sheet (i.e., the position where the first sheet is farthest from the contact point with the surface), selects 3 first material sheets from each SEM image, randomly selects 10 SEM images, and calculates the average size of 10 × 3 first material sheets as the size of the first material.

Average coverage of the first material on the surface of the second material:

randomly selecting 20 TEM (equipment model is Talos F200X) samples, observing the surface of the second material of each TEM pattern in a state of magnifying a ruler to 10nm, counting 1 (counting at most once for each TEM pattern) when a crystalline graphite layer (first material layer) appears, observing 20 TEM samples, and defining the coverage of the material as follows when the cumulative number of the occurrences is N: (N/20). Times.100%.

Specific surface area test:

referring to GB/T19587-2017, the specific process is that 1g to 8g of samples (the samples are weighed to be at least 1/3 of the volume of a sphere) are weighed and placed in a 1/2inch long pipe with a bulb (the pipe diameter of the sphere part is 12 mm), the samples are placed in a testing device TriStar3030 (American Mac corporation) after being pretreated for 2h at 200 DEG CThe adsorbed gas used is N ₂ (purity: 99.999%) was measured under 77K and the specific surface area was measured by the BET calculation method.

The anode active materials of examples 1 to 30 and comparative examples 1 to 5 were prepared as follows:

taking a graphite base block as a target material, and taking hard carbon as a base material to be placed on a glass slide, wherein the distance between the target material and the base material is controlled to be 5 cm-20 cm, and the purity of sputtering gas is>99.99% high purity argon, background vacuum between 2X 10 ^-4 pa to 4 x 10 ^-4 pa, the deposition temperature is 200 ℃ to 1000 ℃, the sputtering power is 100W to 500W, the sputtering time is controlled to be 30min to 120min, the annealing temperature is 300 ℃ to 600 ℃, and the annealing time is 15min to 60min.

The negative electrode of comparative example 6 was prepared as follows:

preparation of a negative electrode: mixing graphite, hard carbon, and conductive agent (conductive carbon black, super)

) And binder PAA in a ratio of about 92:5:0.5:2.5, adding an appropriate amount of water, and kneading at a solid content of about 55 to 70% by weight. Adding a proper amount of water, and adjusting the viscosity of the slurry to be about 4000 Pa.s to 6000 Pa.s to prepare the cathode slurry. And coating the prepared negative electrode slurry on a negative electrode current collector copper foil, drying and cold pressing to obtain a negative electrode.

Full battery evaluation

(1) Preparation of lithium ion battery

Preparation of the positive electrode: subjecting LiCoO to condensation ₂ The conductive carbon black and polyvinylidene fluoride (PVDF) were thoroughly stirred and mixed in an N-methylpyrrolidone solvent system in a weight ratio of about 95. And coating the prepared anode slurry on an anode current collector aluminum foil, drying and cold pressing to obtain the anode.

Preparing a negative electrode: negative active materials, conductive agents (conductive carbon black, super) prepared according to examples and comparative examples

) And binder PAA in a weight ratio of about 96. Adding a proper amount of water, and adjusting the viscosity of the slurry to be about 4000 Pa.s to 6000 Pa.s to prepare the cathode slurry. And coating the prepared negative electrode slurry on a negative electrode current collector copper foil, drying and cold pressing to obtain a negative electrode.

Preparing an electrolyte: in a dry argon atmosphere, liPF ₆ Mixing uniformly, wherein LiPF ₆ Was added with about 12.5wt% of fluoroethylene carbonate (FEC) to a concentration of about 1mol/L, and mixed uniformly to obtain an electrolyte solution.

Preparing an isolating membrane: the PE porous polymer film is used as a separation film.

Preparing a lithium ion battery: the anode, the isolating film and the cathode are sequentially stacked, and the isolating film is positioned between the anode and the cathode to play a role in isolation. And winding to obtain the naked electric core. And arranging the bare cell in an external package, injecting electrolyte and packaging. The lithium ion battery is obtained through the technological processes of formation, degassing, edge cutting and the like.

(2) Rate capability test

The lithium ion battery is stood for 5 minutes at 25 ℃, then charged to 4.45V by a current constant current of 0.7C, then charged to 0.05C by a constant voltage of 4.45V, stood for 5 minutes, and then discharged to 3.0V by a constant current of 0.5C, and stood for 5 minutes. And repeating the charge and discharge processes, discharging at 0.1C, recording the 0.1C discharge capacity of the lithium ion battery, and then discharging at 10C and 15C respectively, and recording the 10C discharge capacity and 15C discharge capacity of the lithium ion battery. Retention of 10C and 15C discharge capacity of lithium ion batteries by the formula:

a discharge capacity retention rate (D1) = (10C discharge capacity/0.1C discharge capacity) × 100% at 10C

Discharge capacity retention rate (D2) = (15C discharge capacity/0.1C discharge capacity) × 100% at 15C

(3) Cycle performance test

The average value of 5 lithium ion batteries prepared in all comparative examples and examples was obtained.

The lithium ion battery is stood for 5 minutes at 25 ℃, then is charged to 4.45V by a constant current of 0.7C, is charged to 0.05C by a constant voltage of 4.45V, and is stood for 5 minutes. Testing the thicknesses of three position points of the lithium ion battery by an MMC test method, and taking an average value to record as the MMC ₀ . The lithium ion battery was then discharged to 3.0V at a constant current of 0.5C, left for 5 minutes, and the discharge capacity of the first cycle was recorded. Repeating the charge-discharge cycle for 400 circles, recording the discharge capacity of the 400 th circle, testing the thickness of three position points of the lithium ion battery, and taking an average MMC ₄₀₀ ，

400 cycles capacity retention ratio = (discharge capacity at 400 cycles/discharge capacity at first cycle) × 100%,

400-cycle battery expansion rate = (MMC) ₄₀₀ /MMC ₀ )×100％。

Table 1 shows the effect of the inter-lamellar spacing of the first material (graphite platelets), the inter-lamellar spacing of the second material (hard carbon), the thickness of the first material on the cell performance. Wherein, the XRD peak intensity ratio R is the ratio of the diffraction peak intensity of the (002) crystal face of the hard carbon microchip layer to the diffraction peak intensity of the (002) crystal face of the graphite flake microchip layer. The anode active materials of examples 1 to 10 and comparative examples 1 to 5 were of a coated type as shown in fig. 1.

TABLE 1

By comparing examples 1 to 10 with comparative examples 1 to 5, the ratio d1/d2 is between 0.85 and 1.05, i.e. when the interplanar spacing of the second material is wide relative to the interplanar spacing of the first material, the material has excellent rate performance at super-high rates and can keep the cyclic expansion at a small level. The resistance of lithium ion insertion into the interior is reduced mainly because the material can provide a path for rapid lithium ion extraction. Meanwhile, the first material with relatively small interplanar spacing can increase the material conductance and reduce polarization. When d1/d2 is more than 1.05, the interplanar spacing of the second material is small, the lithium ion intercalation internal resistance is increased, the rate performance is poor under a large rate, and the battery cyclic expansion rate is large due to the small interplanar spacing.

As can be seen from the comparison between examples 1 and 6, examples 2 and 7, examples 3 and 8, examples 4 and 9, and examples 5 and 10, respectively, when the microcrystalline interlayer spacing of the second material is small, the resistance to lithium intercalation is relatively large, the diffusion of lithium ions is slowed down, so that the overall rate capability of the material is relatively reduced, and at the same time, the second material spacing is relatively small, so that the expansion of the overall battery is large.

As can be seen from comparison between examples 1 and 5, the coated first material is too thick to allow the lithium intercalation channels to be reduced and to be difficult to rapidly enter by lithium ions, so that the rate capability of the whole material is reduced, and as the thickness of the coated first material is increased, the composition of graphite sheets in the material is increased, and the degree of battery expansion is increased to different extents.

Comparative example 6 parameters: comparative example 6 is a blending system of graphite and hard carbon, in which the Dv99 of graphite particles is between 17 μm and 25 μm, and the negative electrode is made after mixing with hard carbon in the slurry stage, the R value of XRD test is 80, and the battery of comparative example 6 negative electrode, using the same test procedure as example 1, gives D1:12%, D3:5%, 400-cycle capacity retention ratio: 62.4%, 400-cycle cell expansion: 13.5 percent

As can be seen from comparison between example 1 and comparative example 6, although the rate performance of the battery in comparative example 6 is improved to a certain extent, the rate performance is still lower than that of example 1, and the material performance is damaged under the condition of high-rate charge and discharge. Meanwhile, the negative active material obtained by simply doping graphite and hard carbon in the comparative example 6 has no way of inhibiting the expansion in the circulation process, and the expansion degree of the material is larger, so that the circulation performance is reduced.

The difference from the coating conditions in table 1 is that in table 2, a very small amount of silicon is preferentially deposited on the surface of the hard carbon substrate during the experimental treatment process, the target is guided to form vertical growth, and the hard carbon substrate in the coating material is not subjected to deposition treatment after being removed by acid washing.

Table 2 shows the influence of the inter-lamellar spacing of the first material (graphite sheet), the inter-lamellar spacing of the second material (hard carbon), R (the ratio of the intensity of the diffraction peak of the crystal face of the hard carbon microchip layer (002) to the intensity of the diffraction peak of the crystal face of the graphite sheet microchip layer (002)), the negative electrode active material specific surface area BET, the first material (graphite sheet) size, and the like on the battery performance. In examples 11 to 30, the negative active material was a vertical sheet type as shown in fig. 2, and the angle θ between the length direction of at least 50% of the first material in the first material and the surface of the second material was 70 ° to 120 °.

TABLE 2

From a comparison of example 11 to example 30, it can be seen that: the second material structure of examples 11 to 20 has a lattice spacing of 0.36nm, and has a relatively large resistance in the lithium insertion process, a relatively slightly lower rate capability and a relatively larger expansion compared with the material with a lattice structure of 0.38nm to a certain extent. The second material structure of examples 21 to 30 has a relatively large crystal plane spacing, the overall rate capability of the material is relatively good, and the battery expansion is relatively small.

Examples 21 to 23 show the influence of the size of graphite sheets, wherein the size of the sheets is preferably 20nm to 50nm, and when the size of the sheets reaches 200nm, the sheets on the surface of the material grow into large sheets with certain coverage effect, lithium ion channels of the relatively small sheets are reduced, and the multiplying power and the like are partially lost.

Examples 24 to 27 were conducted by comparing the influence of the parameter R representing the number of graphite sheets, the parameter being larger the more the graphite sheets are. When R is 0.97, the clad sheet content is small, contributing relatively little to the performance. When R is 3-10, the comprehensive performance of capacity retention rate and multiplying power is better, a certain number of coating layers increase electron conductance, and meanwhile, enough channels are provided, so that lithium ions can be conveniently extracted. However, when R reaches 20, the number of cladding layers is dense, the lithium intercalation channels are partially blocked, and the expansion of the laminated layer after lithium intercalation is larger, so that the expansion of the battery is larger indirectly, the specific surface area of the material is increased, and the performances of material circulation and the like are influenced. (wherein the average coverage varies with R and is 50%)

Examples 28 to 29 mainly examine the relationship between the specific surface area BET and the cell performance, and the BET is 2m in comparison with example 30 ² G to 5m ² In/g, the better cycle performance is at comparable rate performance, probably due to BET of greater than 10m ² At the time of/g, an SEI film is easy to decompose and reconstruct continuously in the circulation process, a large amount of electrolyte is consumed, adverse effects are generated on circulation, and the capacity retention rate is reduced quickly.

Table 3 shows the effect on performance of a change in the number fraction of graphite flakes with theta of 70 ° to 120 °, where examples 31 and 32 differ from example 22 by the number fraction (%) of graphite flakes with theta of 70 ° to 120 °.

TABLE 3

Examples 31 and 32 compared to example 22, the angle θ between the length direction of at least 50% of the first material in the first material and the surface of the second material was 70 ° to 120 °, and the rate and capacity retention performance was better improved.

Tables 4 and 5 show the role of LiFSI in the electrochemical device.

TABLE 4

TABLE 5

Note: liFSI 187.07g/mol, liPF ₆ The molar mass was 151.91g/mol.

In Table 4, examples 33 to 35 differ from example 7 only by LiFSI and LiPF in the electrolyte ₆ The compositions (see table 4) of examples 33 to 35 were improved in both capacity retention and battery swelling properties; in Table 5, examples 36 to 38 differ from example 22 only in LiFSI and LiPF in the electrolyte ₆ The compositions (see Table 5) of examples 36 to 38 were improved in both capacity retention and battery swelling properties. The possible reason is that since LiFSI has high conductivity, it interacts with the anode material to improve the capacity retention rate and the battery swelling property.

While certain exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. Rather, one of ordinary skill in the art will recognize that certain modifications and changes can be made to the described embodiments without departing from the spirit and scope of the present application, as described in the appended claims.

Claims

1. An anode active material comprising a second material and a first material covering at least a portion of a surface of the second material, wherein the first material has a sheet spacing d1 and the second material has a sheet spacing d2, such that: d1/d2 is more than or equal to 0.85 and less than or equal to 0.99,

wherein the first material comprises graphite and the second material comprises hard carbon.

2. The anode active material according to claim 1, wherein the anode active material satisfies at least one of the following conditions (a) to (g):

(a) The average coverage of the first material on the surface of the second material is more than 50 percent;

(b) The thickness of the first material is 3nm to 500nm;

(c) The included angle theta between the length direction of the first material and the surface of the second material is 45-135 degrees;

(d) The first material has a size of 3nm to 500nm;

(e) The value range of d1 is 0.33nm to 0.34nm;

(f) The included angle theta between the length direction of at least 50% of the first materials in the first materials and the surface of the second materials is 70-120 degrees;

(g) The value range of d2 is 0.34nm to 0.40nm.

3. The negative electrode active material according to claim 1, wherein I of the negative electrode active material _G /I _2D Is 0.3 to 5,I _G /I _D Is in the range of 0.3 to 1.5,

in which I _2D Is located at 2500cm in Raman spectrum ^-1 To 2800cm ^-1 Peak intensity of the range of (1), I _D Is located at 1300cm in Raman spectrum ^-1 To 1400cm ^-1 Peak intensity of the range of (1), I _G Is located at 1550cm in Raman spectrum ^-1 To 1650cm ^-1 Peak intensity of the range of (a).

4. The negative electrode active material according to claim 1, having a specific surface area of 2m ² G to 10m ² /g。

5. The negative electrode active material according to claim 1,

in an X-ray diffraction pattern of the negative electrode active material, a first peak and a second peak exist between 18 degrees and 30 degrees,

wherein the first peak is positioned between 22 DEG and 26 DEG, the second peak is positioned between 26.3 DEG and 26.6 DEG, and the ratio R of the intensity of the second peak to the intensity of the first peak is 0.9 to 20.

6. An electrochemical device comprising a positive electrode, a negative electrode, an electrolyte, and a separator, the negative electrode comprising a current collector and a negative electrode active material layer on a surface of the current collector, the negative electrode active material layer comprising the negative electrode active material according to any one of claims 1 to 5.

7. The electrochemical device of claim 6, the electrolyte comprising at least one of fluoroether, fluoroethylene carbonate, or ether nitrile.

8. The electrochemical device according to claim 6, the electrolyte includes a lithium salt including lithium bis (fluorosulfonyl) imide and lithium hexafluorophosphate, the lithium salt having a concentration of 1 to 2mol/L, and a mass ratio of lithium bis (fluorosulfonyl) imide to lithium hexafluorophosphate being 0.06 to 5.

9. An electronic device comprising the electrochemical device of any one of claims 6 to 8.