Electrochemical devices and electronic devices

Abstract

The present application relates to an electrochemical device and an electronic device. Specifically, the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, and an electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material and a low-density binder, wherein the positive electrode active material has a first element, the first element includes at least one of aluminum, magnesium, titanium, zirconium, or tungsten. The electrochemical device of the present application has improved high-temperature cycle performance and safety.

Description

Technical Field

[0001] This application relates to the field of energy storage, specifically to an electrochemical device and an electronic device, particularly a lithium-ion battery. Background Technology

[0002] In recent years, with the rapid development of electronic products such as smartphones, tablets, and wearable devices, consumers have increasingly higher demands for the energy density of lithium-ion batteries, considering the varying usage time and operating environments of these products. Currently, the energy density of lithium-ion batteries is mainly improved by using high-voltage (4.4V and above) lithium cobalt oxide positive electrode active material and high-capacitance, high-density graphite negative electrode material. However, as temperature and voltage increase, the cycle performance and safety of these lithium-ion batteries deteriorate significantly. Simultaneously, the intensifying effects of global warming (such as in specific usage regions like India and Africa) place even higher demands on the high-temperature performance of batteries.

[0003] In view of this, it is indeed necessary to provide an electrochemical device and an electronic device with improved high-temperature performance. Summary of the Invention

[0004] This application provides an electrochemical and electronic device with improved high-temperature cycling performance and safety to address, to some extent, the problems existing in the prior art.

[0005] In one aspect of this application, an electrochemical device is provided, comprising: a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and a binder, wherein: the positive electrode active material has a first element, the first element including at least one of aluminum, magnesium, titanium, zirconium, or tungsten, and the binder has a density of ag / cm³. 3 The value of a ranges from 0.6 to 1.5.

[0006] According to the embodiments of this application, the value of a ranges from 0.6 to 1.2, 0.7 to 1.0, or 0.7 to 0.9.

[0007] According to an embodiment of this application, the porosity of the adhesive is b%, where b ranges from 20 to 50, and a and b satisfy: 17 ≤ a × b ≤ 60.

[0008] According to embodiments of this application, the adhesive comprises a fluoropolymer, preferably polyvinylidene fluoride.

[0009] According to embodiments of this application, the electrochemical device satisfies at least one of the following:

[0010] a. The first element includes aluminum and at least one of magnesium, titanium, zirconium, or tungsten;

[0011] b. The first element includes tungsten and at least one of magnesium, titanium, zirconium or aluminum;

[0012] c. The first element comprises aluminum and tungsten, and based on the weight of the positive electrode active material, the contents of aluminum and tungsten are x% and y%, respectively, where x and y satisfy: 1≤x / y≤5;

[0013] d. Based on the weight of the positive electrode active material, the content of the first element is 0.01% to 2%.

[0014] According to an embodiment of this application, the first element includes aluminum, and the aluminum content is x% based on the weight of the positive electrode active material, and x and a satisfy 0.2≤x / a≤1.

[0015] According to an embodiment of this application, the electrolyte includes a compound having a sulfur-oxygen double bond, and the content of the compound having a sulfur-oxygen double bond is c% based on the weight of the electrolyte, where c ranges from 0.01 to 5.

[0016] According to an embodiment of this application, c and a satisfy: 0.5 ≤ c / a ≤ 3.

[0017] According to an embodiment of this application, the electrolyte includes a trinitrile compound, and the content of the trinitrile compound is d% based on the weight of the electrolyte, where d ranges from 0.01 to 5.

[0018] According to an embodiment of this application, d and a satisfy: 0.2≤d / a≤4.

[0019] According to embodiments of this application, the electrolyte includes at least one of succinic acid, adiponitrile, ethylene glycol di(2-cyanoethyl) ether, fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic phosphate anhydride.

[0020] In another aspect of this application, an electronic device is provided that includes an electrochemical device according to this application.

[0021] The combination of doped positive electrode active material and low-density binder used in this application effectively improves the interfacial stability of the positive electrode, thereby significantly improving the high-temperature cycling performance and safety of the electrochemical device.

[0022] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Detailed Implementation

[0023] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0024] Unless otherwise expressly stated, the terms used herein have the meanings indicated below.

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

[0026] I. Positive electrode

[0027] Common methods for improving the energy density of electrochemical devices (e.g., lithium-ion batteries) include using high-voltage (4.4V and above) lithium cobalt oxide positive electrode active material and high-capacity, high-density graphite negative electrode material. However, with increasing temperature and voltage, the structural stability of lithium cobalt oxide deteriorates, and metal ions easily dissolve from the positive electrode and are reduced and deposited on the negative electrode surface, thereby damaging the structure of the solid electrolyte interphase (SEI) film. This leads to a continuous increase in negative electrode impedance and battery thickness, resulting in capacity loss and deterioration of the lithium-ion battery's cycle performance. Furthermore, under high temperature and high pressure, the electrolyte is prone to oxidative decomposition on the positive electrode surface, generating a large amount of gas, which causes the lithium-ion battery to swell and the electrode interface to be damaged, thus worsening the lithium-ion battery's performance. Simultaneously, under high temperature and high voltage, due to the high oxidative activity of lithium cobalt oxide, the side reactions between it and the electrolyte are intensified, causing the electrolyte decomposition products to continuously deposit on the positive electrode surface. This further increases the internal resistance of the lithium-ion battery, thus negatively impacting its high-temperature cycle performance. These factors also pose significant safety hazards to lithium-ion batteries.

[0028] The industry typically uses aluminum, magnesium, titanium, zirconium, or tungsten doping in positive electrode active materials (such as lithium cobalt oxide or ternary materials). Aluminum and magnesium are more easily incorporated into the crystal structure of the material, while titanium and zirconium tend to accumulate on the particle surface. Tungsten is used to improve conductivity. However, there are no reports of these elements being used to improve the safety of electrochemical devices. Furthermore, the binder density currently used in positive electrode slurries is mostly around 1.7 g / cm³. 3Based on existing knowledge, it is unforeseen that the simultaneous use of a positive electrode active material, including at least one of aluminum, magnesium, titanium, zirconium, or tungsten, and a low-density binder would play a significant role in improving the high-temperature cycling and safety performance of electrochemical devices.

[0029] This application unexpectedly solves the problems related to high-temperature cycling and safety performance of electrochemical devices by using a positive electrode active material containing at least one of aluminum, magnesium, titanium, zirconium, or tungsten, and a low-density binder. Doping the positive electrode active material with at least one of aluminum, magnesium, titanium, zirconium, or tungsten effectively improves lattice stability, thereby suppressing particle volume changes during charge-discharge cycles under high or low temperature conditions, reducing particle cracking and breakage, and also improving the interfacial stability of the positive electrode. The low-density binder achieves good bonding and is less affected by compaction density during positive electrode preparation, contributing to improved surface properties of the positive electrode. The specific combination of the positive electrode active material and binder in this application not only effectively improves the high-temperature cycling performance of electrochemical devices but also significantly enhances the safety of electrochemical devices (e.g., short-circuit safety and thermal abuse safety).

[0030] The positive electrode includes a positive current collector and a layer of positive active material formed on the positive current collector. The positive active material layer can be one or more layers. The positive active material layer includes positive active material, and each layer of the multilayer positive active material can contain the same or different positive active material.

[0031] The main feature of the electrochemical device of this application is that: the positive electrode active material layer comprises a positive electrode active material and a binder, the positive electrode active material has a first element, the first element comprising at least one of aluminum, magnesium, titanium, zirconium or tungsten, and the density of the binder is ag / cm³. 3 The value of 'a' ranges from 0.6 to 1.5. In some embodiments, the value of 'a' ranges from 0.6 to 1.2. In some embodiments, the value of 'a' ranges from 0.7 to 1.0. In some embodiments, the value of 'a' ranges from 0.7 to 0.9.

[0032] The density of commonly used positive electrode binders in the battery industry is typically greater than 1.7 g / cm³. 3 This is to ensure sufficient adhesion. However, the inventors of this application unexpectedly discovered that when the density of the positive electrode binder is greater than 1.5 g / cm³, [the adhesion is compromised]. 3 When the density of the positive electrode binder is less than 0.6 g / cm³, it will affect the flexibility of the positive electrode to some extent, making it prone to breakage during winding; 3At times, insufficient adhesion of the binder negatively impacts the electrochemical stability of the electrochemical device. Furthermore, the positive electrode binder possesses a highly porous structure, which is beneficial for improving electrode strength and accelerating electrolyte wetting. Controlling the density of the positive electrode binder within the aforementioned range not only achieves good adhesion but also significantly enhances the high-temperature cycling performance and safety of the electrochemical device.

[0033] In some embodiments, the porosity of the binder is b%, where b ranges from 20 to 50. In some embodiments, b ranges from 25 to 45. In some embodiments, b is 20, 22, 25, 30, 35, 40, 45, 50, or within a range consisting of any two of the above values. When the porosity of the binder is within the above range, it helps to further improve the high-temperature cycling performance and safety of the electrochemical device.

[0034] In some embodiments, a and b satisfy the condition: 17 ≤ a × b ≤ 60. In some embodiments, a and b satisfy the condition: 20 ≤ a × b ≤ 50. In some embodiments, a × b is 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, or within a range consisting of any two of the above values. When the density and porosity of the binder satisfy the above relationships, it helps to further improve the high-temperature cycling performance and safety of the electrochemical device.

[0035] In some embodiments, the adhesive comprises a fluoropolymer. In some embodiments, the fluoropolymer comprises polyvinylidene fluoride.

[0036] In some embodiments, the content of the first element is 0.01 to 2% based on the weight of the positive electrode active material. In some embodiments, the content of the first element is 0.05 to 1% based on the weight of the positive electrode active material. In some embodiments, the content of the first element is 0.1 to 0.5% based on the weight of the positive electrode active material. In some embodiments, the content of the first element is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2% or within a range of any two of the above values, based on the weight of the positive electrode active material. When the content of the first element in the positive electrode active material satisfies the above relationship, surface defects in the crystal structure of the positive electrode active material can be reduced, effectively suppressing the continuous damage to the passivation layer on the positive electrode surface during the charge-discharge cycle of the electrochemical device, reducing the number of repairs, and fully improving the interfacial stability of the positive electrode active material layer, thereby further improving the high-temperature cycle performance and safety of the electrochemical device.

[0037] In some embodiments, the first element comprises at least two of aluminum, magnesium, titanium, zirconium, or tungsten. In this case, the positive electrode active material exhibits higher stability under high temperature and high pressure, and its combination with a low-density binder can further enhance the high-temperature cycling performance and safety of the electrochemical device.

[0038] In some embodiments, the first element further includes aluminum and at least one of magnesium, titanium, zirconium, or tungsten.

[0039] In some embodiments, the first element further includes tungsten and at least one of magnesium, titanium, zirconium or aluminum.

[0040] In some embodiments, the first element comprises aluminum and tungsten, with the contents of aluminum and tungsten being x% and y% respectively, based on the weight of the positive electrode active material. x and y satisfy the condition: 1 ≤ x / y ≤ 5. In some embodiments, x and y satisfy the following relationship: 1.5 ≤ x / y ≤ 4.5. In some embodiments, x / y is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or within a range consisting of any two of the above values. When the contents of aluminum and tungsten in the positive electrode active material satisfy the above relationship, the decomposition and regeneration of the passivation layer on the positive electrode surface during the cycling process of the electrochemical device can be reduced, significantly improving the interfacial stability of the positive electrode active material layer and contributing to further enhancing the high-temperature cycling performance and safety of the electrochemical device.

[0041] In some embodiments, the first element includes aluminum, with the aluminum content being x% based on the weight of the positive electrode active material, and x and a satisfying 0.2 ≤ x / a ≤ 1. In some embodiments, x / a is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or within a range of any two of the above values. When the aluminum content and binder density in the positive electrode active material satisfy the above relationship, the decomposition and regeneration of the passivation layer on the positive electrode surface during the cycling process of the electrochemical device can be reduced, the interfacial stability of the positive electrode active material layer can be significantly improved, and the high-temperature cycling performance and safety of the electrochemical device can be further enhanced.

[0042] In some embodiments, the value of x ranges from 0.01 to 1. In some embodiments, the value of x ranges from 0.05 to 0.5. In some embodiments, the value of x ranges from 0.1 to 0.3. In some embodiments, x is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range consisting of any two of the above values.

[0043] In some embodiments, the value of y ranges from 0.01 to 1. In some embodiments, the value of y ranges from 0.05 to 0.5. In some embodiments, the value of y ranges from 0.1 to 0.3. In some embodiments, y is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range consisting of any two of the above values.

[0044] There are no particular limitations on the type of positive electrode active material, as long as it can electrochemically adsorb and release metal ions (e.g., lithium ions). In some embodiments, the positive electrode active material is a substance containing lithium and at least one transition metal. Examples of positive electrode active materials may include, but are not limited to, lithium transition metal composite oxides and lithium transition metal phosphate compounds.

[0045] In some embodiments, a substance with a different composition may be attached to the surface of the aforementioned positive electrode active material. Examples of such surface-attached substances may include, but are not limited to: oxides such as aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; and carbon. By attaching a substance to the surface of the positive electrode active material, the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, thereby improving the lifespan of the electrochemical device. When the amount of surface-attached substance is too small, its effect cannot be fully realized; when the amount of surface-attached substance is too large, it will hinder the entry and exit of lithium ions, and thus the resistance may sometimes increase. In this application, the positive electrode active material to which a substance with a different composition is attached to the surface of the positive electrode active material is also referred to as "positive electrode active material".

[0046] In some embodiments, the positive electrode active material includes at least one of lithium cobalt oxide or lithium nickel cobalt manganese oxide.

[0047] In some embodiments, the shape of the positive electrode active material particles includes, but is not limited to, blocky, polyhedral, spherical, ellipsoidal, plate-like, needle-like, and columnar shapes. In some embodiments, the positive electrode active material particles include primary particles, secondary particles, or combinations thereof. In some embodiments, primary particles may aggregate to form secondary particles.

[0048] There are no restrictions on the type of positive electrode conductive material; any known conductive material can be used. Examples of positive electrode conductive materials include, but are not limited to, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; carbon materials such as amorphous carbon such as needle coke; carbon nanotubes; graphene, etc. The above-mentioned positive electrode conductive materials can be used alone or in any combination.

[0049] There are no restrictions on the type of solvent used to form the positive electrode slurry, as long as it can dissolve or disperse the positive electrode active material, conductive material, positive electrode binder, and thickener used as needed. Examples of solvents used to form the positive electrode slurry can include any of aqueous solvents and organic solvents. Examples of aqueous media can include, but are not limited to, water and mixtures of alcohol and water. Examples of organic media can include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide.

[0050] Thickeners are typically used to adjust the viscosity of slurries. In the case of aqueous media, thickeners and styrene-butadiene rubber (SBR) latex can be used for slurry preparation. There are no particular limitations on the types of thickeners; examples include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts. The above-mentioned thickeners can be used alone or in any combination.

[0051] There are no particular limitations on the type of positive electrode current collector; it can be any material known to be suitable for use as a positive electrode current collector. Examples of positive electrode current collectors may include, but are not limited to, metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metallic material. In some embodiments, the positive electrode current collector is aluminum.

[0052] To reduce the electronic contact resistance between the positive current collector and the positive active material layer, the surface of the positive current collector may include a conductive additive. Examples of conductive additives may include, but are not limited to, carbon and precious metals such as gold, platinum, and silver.

[0053] The positive electrode can be manufactured by forming a layer of positive electrode active material containing positive electrode active material and binder on a current collector. The manufacture of a positive electrode using positive electrode active material can be carried out by conventional methods, namely, dry mixing the positive electrode active material, binder, and conductive material and thickener as needed, forming a sheet, and pressing the resulting sheet onto the positive electrode current collector; or dissolving or dispersing these materials in a liquid medium to form a slurry, coating the slurry onto the positive electrode current collector and drying it, thereby forming a layer of positive electrode active material on the current collector, thus obtaining the positive electrode.

[0054] In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 95%, preferably 96%, and more preferably 97%. In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 98%. In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 99%. When the mass fraction of the positive electrode active material in the positive electrode active material layer is within the above ranges, the energy density of the electrochemical device can be significantly improved.

[0055] When the positive electrode active material consists of primary particles, the average particle size refers to the primary particle size. When the primary particles of the positive electrode active material agglomerate to form secondary particles, the average particle size refers to the secondary particle size.

[0056] In some embodiments, the average particle size of the positive electrode active material is D μm, where D ranges from 5 to 30. In some embodiments, D ranges from 10 to 25. In some embodiments, D ranges from 12 to 20. In some embodiments, D is 5, 7, 9, 10, 12, 15, 18, 20, 25, 30, or within a range consisting of any two of the above values.

[0057] When the average particle size of the positive electrode active material is within the above-mentioned range, a positive electrode active material with high tap density can be obtained, which can suppress the degradation of the performance of the electrochemical device and prevent problems such as streaking during the preparation of the positive electrode of the electrochemical device (i.e., when the positive electrode active material, conductive material, and binder are slurried with solvent and coated in a thin film). Mixing two or more positive electrode active materials with different average particle sizes can further improve the filling properties during positive electrode preparation.

[0058] The average particle size of the positive electrode active material can be determined using a laser diffraction / scattering particle size analyzer: Using a HORIBA LA-920 particle size analyzer, a 0.1% sodium hexametaphosphate aqueous solution was used as the dispersion medium. After ultrasonic dispersion for 5 minutes, the refractive index was set to 1.24 for measurement. The average particle size of the positive electrode active material can also be measured using a laser diffraction particle size analyzer (Shimadzu SALD-2300) and a scanning electron microscope (ZEISS EVO18, with at least 100 samples).

[0059] II. Electrolyte

[0060] The electrolyte used in the electrochemical device of this application includes an electrolyte and a solvent for dissolving the electrolyte.

[0061] In some embodiments, the electrolyte further includes a compound having a sulfur-oxygen double bond.

[0062] In some embodiments, the compound having a sulfur-oxygen double bond includes at least one of the following compounds: cyclic sulfate, chain sulfate, chain sulfonate, cyclic sulfonate, chain sulfite, or cyclic sulfite.

[0063] In some embodiments, the cyclic sulfate esters include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate, 1,2-butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1,4-pentanediol sulfate, and 1,5-pentanediol sulfate, etc.

[0064] In some embodiments, the chain sulfate ester includes, but is not limited to, one or more of the following: dimethyl sulfate, methyl ethyl sulfate, and diethyl sulfate, etc.

[0065] In some embodiments, the chain sulfonate includes, but is not limited to, one or more of the following: fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, butyl dimethanesulfonate, methyl 2-(methanesulfonyloxy)propionate and ethyl 2-(methanesulfonyloxy)propionate, etc.

[0066] In some embodiments, the cyclic sulfonate ester includes, but is not limited to, one or more of the following: 1,3-propanesulfonate lactone, 1-fluoro-1,3-propanesulfonate lactone, 2-fluoro-1,3-propanesulfonate lactone, 3-fluoro-1,3-propanesulfonate lactone, 1-methyl-1,3-propanesulfonate lactone, 2-methyl-1,3-propanesulfonate lactone, 3-methyl-1,3-propanesulfonate lactone, 1-propene-1,3-sulfonate lactone, 2-propene-1,3-sulfonate lactone, 1-fluoro-1-propene-1,3-sulfonate lactone, 2-fluoro-1-propene-1,3-sulfonate lactone, 3-fluoro-1-propene-1,3-sulfonate lactone Esters, 1-fluoro-2-propene-1,3-sulfonate lactone, 2-fluoro-2-propene-1,3-sulfonate lactone, 3-fluoro-2-propene-1,3-sulfonate lactone, 1-methyl-1-propene-1,3-sulfonate lactone, 2-methyl-1-propene-1,3-sulfonate lactone, 3-methyl-1-propene-1,3-sulfonate lactone, 1-methyl-2-propene-1,3-sulfonate lactone, 2-methyl-2-propene-1,3-sulfonate lactone, 3-methyl-2-propene-1,3-sulfonate lactone, 1,4-butanesulfonate lactone, 1,5-pentanesulfonate lactone, methylene disulfonate, and ethylene disulfonate, etc.

[0067] In some embodiments, the chain sulfite includes, but is not limited to, one or more of the following: dimethyl sulfite, methyl ethyl sulfite, and diethyl sulfite, etc.

[0068] In some embodiments, the cyclic sulfites include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfite, 1,2-propanediol sulfite, 1,3-propanediol sulfite, 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3-pentanediol sulfite, 1,4-pentanediol sulfite, and 1,5-pentanediol sulfite, etc.

[0069] In some embodiments, the compound containing a sulfur-oxygen double bond includes compounds of formula I:

[0070]

[0071] in:

[0072] W selected

[0073] L are each independently selected from single bonds or methylene groups;

[0074] m can be 1, 2, 3, or 4;

[0075] n is 0, 1, or 2; and

[0076] p can be 0, 1, 2, 3, 4, 5, or 6.

[0077] In some embodiments, the compound of formula I includes at least one of the following:

[0078]

[0079] In some embodiments, the bicyclic sulfonyl lactone comprises a compound of formula II:

[0080]

[0081] A1, A2, A3 and A4 are each independently selected from substituted or unsubstituted C1-3 alkylene groups. When substituted, the substituents are selected from C1-5 alkyl, halogen or halo-C1-5 alkyl groups.

[0082] In some embodiments, the compound of formula II comprises at least one of the following:

[0083]

[0084]

[0085] In some embodiments, the content of the compound having a sulfur-oxygen double bond is c%, based on the weight of the electrolyte, with c ranging from 0.01 to 5. In some embodiments, c is in the range of 0.01 to 3. In some embodiments, c is in the range of 0.1 to 2. In some embodiments, c is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or within a range consisting of any two of the above values. When the content of the compound having a sulfur-oxygen double bond in the electrolyte is within the above range, it helps to further improve the high-temperature cycling performance and safety of the electrochemical device.

[0086] In some embodiments, c and a satisfy: 0.5 ≤ c / a ≤ 3. In some embodiments, c and a satisfy: 0.8 ≤ c / a ≤ 2. In some embodiments, c and a satisfy: 1 ​​≤ c / a ≤ 2.5. In some embodiments, c / a is 0.5, 0.6, 0.7, 0.8, 1, 1.2, 1.5, 2, 2.5, 3, or within a range consisting of any two of the above values. When the content of compounds with sulfur-oxygen double bonds in the electrolyte and the density of the binder satisfy the above relationships, it helps to further improve the high-temperature cycling performance and safety of the electrochemical device.

[0087] In some embodiments, the electrolyte further includes a trinitrile compound.

[0088] In some embodiments, the trinitrile compound includes at least one selected from 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, or 1,2,5-tris(cyanoethoxy)pentane.

[0089] In some embodiments, the content of the trinitrile compound is d% based on the weight of the electrolyte, where d ranges from 0.01 to 5. In some embodiments, d is in the range of 0.01 to 3. In some embodiments, d is in the range of 0.1 to 2. In some embodiments, d is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or within a range consisting of any two of the above values. When the content of the trinitrile compound in the electrolyte is within the above range, it helps to further improve the high-temperature cycling performance and safety of the electrochemical device.

[0090] In some embodiments, d and a satisfy: 0.2 ≤ d / a ≤ 4. In some embodiments, d and a satisfy: 0.5 ≤ d / a ≤ 3.5. In some embodiments, d and a satisfy: 1 ​​≤ c / a ≤ 3.5. In some embodiments, d / a is 0.2, 0.3, 0.5, 0.6, 0.7, 0.8, 1, 1.2, 1.5, 2, 2.5, 3, 3.5, 4, or within a range consisting of any two of the above values. When the content of trinitrile compounds in the electrolyte and the density of the binder satisfy the above relationships, it helps to further improve the high-temperature cycling performance and safety of the electrochemical device.

[0091] In some embodiments, the electrolyte further includes at least one selected from succinic anhydride, adiponitrile, ethylene glycol di(2-cyanoethyl) ether, fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic phosphate anhydride. In some embodiments, the content of the above compounds is 0.1%-6% based on the mass of the electrolyte. In some embodiments, the content of the above compounds is 0.5%-5% based on the mass of the electrolyte. In some embodiments, the content of the above compounds is 1%-3% based on the mass of the electrolyte. These compounds help stabilize the interface between the positive electrode and the electrolyte, thereby further improving the cycle performance and safety of the electrochemical device under high temperature and high pressure.

[0092] In some embodiments, the electrolyte further comprises any non-aqueous solvent known in the art that can be used as a solvent for an electrolyte.

[0093] In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonates, chain carbonates, cyclic carboxylic esters, chain carboxylic esters, cyclic ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.

[0094] In some embodiments, examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate. In some embodiments, the cyclic carbonate has 3-6 carbon atoms.

[0095] In some embodiments, examples of the chain carbonate may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl n-propyl carbonate, ethyl n-propyl carbonate, di n-propyl carbonate, and other chain carbonates. Examples of fluorine-substituted chain carbonates may include, but are not limited to, one or more of the following: bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethylmethyl carbonate, 2,2-difluoroethylmethyl carbonate, and 2,2,2-trifluoroethylmethyl carbonate, etc.

[0096] In some embodiments, examples of the cyclic carboxylic acid ester may include, but are not limited to, one or more of the following: γ-butyrolactone and γ-valerolactone. In some embodiments, some hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.

[0097] In some embodiments, examples of the chain carboxylic acid ester may include, but are not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate. In some embodiments, some hydrogen atoms of the chain carboxylic acid ester may be substituted with fluorine. In some embodiments, examples of fluorinated chain carboxylic acid esters may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetate.

[0098] In some embodiments, examples of the cyclic ether may include, but are not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.

[0099] In some embodiments, examples of the chain ether may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane, etc.

[0100] In some embodiments, examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene phosphate, ethylene phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tri(2,2,2-trifluoroethyl) phosphate, and tri(2,2,3,3,3-pentafluoropropyl) phosphate, etc.

[0101] In some embodiments, examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of the following: sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methylpropyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. In some embodiments, some hydrogen atoms of the sulfur-containing organic solvent may be substituted with fluorine.

[0102] In some embodiments, the aromatic fluorinated solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.

[0103] In some embodiments, the solvent used in the electrolyte of this application includes cyclic carbonates, linear carbonates, cyclic carboxylic acid esters, linear carboxylic acid esters, and combinations thereof. In some embodiments, the solvent used in the electrolyte of this application comprises an organic solvent selected from the group consisting of: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, ethyl acetate, and combinations thereof. In some embodiments, the solvent used in the electrolyte of this application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, γ-butyrolactone, and combinations thereof.

[0104] In some embodiments, the electrolyte is not particularly limited, and any substance known as an electrolyte can be used. In the case of lithium secondary batteries, lithium salts are typically used. Examples of electrolytes may include, but are not limited to, inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, and LiWF7; lithium tungstates such as LiWOF5; lithium carboxylate salts such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, and CF3CF2CF2CF2CO2Li; and lithium carboxylate salts such as FSO3Li and CH3SO3Li. Lithium sulfonate salts such as CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, and CF3CF2CF2CF2SO3Li; lithium sulfonate salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane disulfonylimide lithium, and cyclic 1,3-perfluoropropane disulfonylimide. Lithium, imide lithium salts such as LiN(CF3SO2)(C4F9SO2); methylated lithium salts such as LiC(FSO2)3, LiC(CF3SO2)3, and LiC(C2F5SO2)3; lithium malonate lithium salts such as bis(malonate)borate and difluoro(malonate)borate; lithium tri(malonate)phosphate, lithium difluorobis(malonate)phosphate, and lithium tetrafluoro(malonate)phosphate; and lithium malonate phosphates such as LiPF4(CF3)2 and LiPF4(C2F5)2. Fluorine-containing organic lithium salts such as LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2; lithium oxalate borate salts such as lithium difluorooxalate borate and lithium bis(oxalate) borate; and lithium oxalate phosphate salts such as lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, and lithium tri(oxalate) phosphate.

[0105] In some embodiments, the electrolyte is selected from LiPF6, LiSbF6, FSO3Li, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane disulfonylimide lithium, cyclic 1,3-perfluoropropane disulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, lithium difluorooxalateborate, lithium bis(oxalate)borate, or lithium difluorobis(oxalate)phosphate, which helps to improve the output power characteristics, high-rate charge-discharge characteristics, high-temperature storage characteristics, and cycle characteristics of the electrochemical device.

[0106] There are no particular limitations on the content of the electrolyte, as long as it does not impair the effectiveness of this application. In some embodiments, the total molar concentration of lithium in the electrolyte is greater than 0.3 mol / L, greater than 0.4 mol / L, or greater than 0.5 mol / L. In some embodiments, the total molar concentration of lithium in the electrolyte is less than 3 mol / L, less than 2.5 mol / L, or less than 2.0 mol / L. In some embodiments, the total molar concentration of lithium in the electrolyte is within the range of any two of the above values. When the electrolyte concentration is within the above range, the amount of lithium as charged particles will not be too low, and the viscosity can be kept within an appropriate range, thus easily ensuring good conductivity.

[0107] When using two or more electrolytes, the electrolyte comprises at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte comprises a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte comprises a lithium salt. In some embodiments, the content of a salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is greater than 0.01% or greater than 0.1% based on the weight of the electrolyte. In some embodiments, the content of a salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is less than 20% or less than 10% based on the weight of the electrolyte. In some embodiments, the content of a salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is within the range of any two of the above values.

[0108] In some embodiments, the electrolyte comprises one or more substances selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, and one or more other salts. Examples of other salts include lithium salts exemplified above, and in some embodiments, LiPF6, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane disulfonylimide lithium, cyclic 1,3-perfluoropropane disulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, and LiPF3(C2F5)3. In some embodiments, the other salt is LiPF6.

[0109] In some embodiments, the content of other salts, based on the weight of the electrolyte, is greater than 0.01% or greater than 0.1%. In some embodiments, the content of other salts, based on the weight of the electrolyte, is less than 20%, less than 15%, or less than 10%. In some embodiments, the content of other salts is within the range of any two of the above values. The presence of other salts at the above-mentioned levels helps to balance the conductivity and viscosity of the electrolyte.

[0110] III. Negative electrode

[0111] The negative electrode includes a negative electrode current collector and a layer of negative electrode active material disposed on one or both surfaces of the negative electrode current collector, the negative electrode active material layer containing negative electrode active material. The negative electrode active material layer can be one or more layers, and each layer in multiple layers can contain the same or different negative electrode active materials. The negative electrode active material is any material capable of reversibly inserting and deintercalating metal ions such as lithium ions. In some embodiments, the rechargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional deposition of lithium metal on the negative electrode during charging.

[0112] As the current collector for retaining the active material of the negative electrode, any known current collector can be used. Examples of negative electrode current collectors include, but are not limited to, metallic materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.

[0113] When the negative electrode current collector is a metallic material, its form may include, but is not limited to, metal foil, metal cylinder, metal strip roll, metal plate, metal film, metal mesh, stamped metal, foamed metal, etc. In some embodiments, the negative electrode current collector is a metal film. In some embodiments, the negative electrode current collector is copper foil. In some embodiments, the negative electrode current collector is rolled copper foil based on rolling or electrolytic copper foil based on electrolysis.

[0114] In some embodiments, the thickness of the negative electrode current collector is greater than 1 μm or greater than 5 μm. In some embodiments, the thickness of the negative electrode current collector is less than 100 μm or less than 50 μm. In some embodiments, the thickness of the negative electrode current collector is within the range of any two of the above values.

[0115] There are no particular restrictions on the negative electrode active material, as long as it can reversibly absorb and release lithium ions. Examples of negative electrode active materials may include, but are not limited to, carbon materials such as natural graphite and artificial graphite; metals such as silicon (Si) and tin (Sn); or oxides of metal elements such as Si and Sn. Negative electrode active materials can be used alone or in combination.

[0116] The negative electrode active material layer may also include a negative electrode binder. The negative electrode binder improves the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector. There are no particular limitations on the type of negative electrode binder, as long as it is a material stable to the electrolyte or the solvent used in electrode manufacturing. In some embodiments, the negative electrode binder includes a resin binder. Examples of resin binders include, but are not limited to, fluoropolymers, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, etc. When a negative electrode slurry is prepared using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salts, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salts, polyvinyl alcohol, etc.

[0117] The negative electrode can be prepared by coating a negative electrode slurry containing negative electrode active material, resin binder, etc. onto a negative electrode current collector, drying it, and then calendering it to form a negative electrode active material layer on both sides of the negative electrode current collector, thereby obtaining the negative electrode.

[0118] IV. Separating membrane

[0119] To prevent short circuits, a separator is typically placed between the positive and negative electrodes. In this case, the electrolyte of this application is typically used after penetrating into the separator.

[0120] There are no particular limitations on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application. The separator may be a resin, glass fiber, inorganic material, or other material formed from a material stable to the electrolyte of this application. In some embodiments, the separator includes a porous sheet or non-woven fabric-like material with excellent liquid retention properties. Examples of materials for resin or glass fiber separators may include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above-mentioned separator materials can be used alone or in any combination.

[0121] The separator can also be a material formed by laminating the above-mentioned materials, examples of which include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in that order.

[0122] Examples of inorganic materials may include, but are not limited to, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). Inorganic materials may be in, but are not limited to, particulate or fibrous forms.

[0123] The separator can be in the form of a thin film, examples of which include, but are not limited to, nonwoven fabrics, woven fabrics, microporous membranes, etc. In the form of a thin film, the pore size of the separator is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the above-mentioned independent thin film separator, the following separator can also be used: a separator formed by using a resin-based adhesive to form a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and / or negative electrode, for example, a separator formed by using fluororesin as an adhesive to form a porous layer of alumina particles with a particle size of less than 1 μm on both sides of the positive electrode.

[0124] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. In some embodiments, the thickness of the separator is within the range of any two of the above values. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and the rate capability and energy density of the electrochemical device can be ensured.

[0125] When using porous materials such as porous sheets or nonwoven fabrics as the separator, the porosity of the separator is arbitrary. In some embodiments, the porosity of the separator is greater than 10%, greater than 15%, or greater than 20%. In some embodiments, the porosity of the separator is less than 60%, less than 50%, or less than 45%. In some embodiments, the porosity of the separator is within the range of any two of the above values. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, and membrane resistance can be suppressed, giving the electrochemical device good safety characteristics.

[0126] The average pore size of the separator is also arbitrary. In some embodiments, the average pore size of the separator is less than 0.5 μm or less than 0.2 μm. In some embodiments, the average pore size of the separator is greater than 0.05 μm. In some embodiments, the average pore size of the separator is within the range of any two of the above values. If the average pore size of the separator exceeds the above range, a short circuit is likely to occur. When the average pore size of the separator is within the above range, the electrochemical device has good safety characteristics.

[0127] V. Electrochemical Device Components

[0128] Electrochemical device components include electrode arrays, current collectors, housings, and protective elements.

[0129] The electrode assembly can be either a laminated structure formed by stacking the positive and negative electrodes with the separator membrane in between, or a structure formed by spirally winding the positive and negative electrodes with the separator membrane in between. In some embodiments, the proportion of the electrode assembly's mass in the battery's internal volume (electrode assembly occupancy) is greater than 40% or greater than 50%. In some embodiments, the electrode assembly occupancy is less than 90% or less than 80%. In some embodiments, the electrode assembly occupancy falls within the range of any two of the above values. When the electrode assembly occupancy is within the above range, the capacity of the electrochemical device can be ensured, while suppressing the degradation of characteristics such as repeated charge-discharge performance and high-temperature storage associated with increased internal pressure.

[0130] There are no particular limitations on the current collector structure. In some embodiments, the current collector structure is one that reduces the resistance of the wiring portion and the joint portion. When the electrode group has the above-described laminated structure, it is suitable to use a structure formed by bundling the metal core portions of each electrode layer together and soldering them to the terminals. As the area of ​​an electrode increases, the internal resistance increases; therefore, it is also suitable to provide two or more terminals within the electrode to reduce the resistance. When the electrode group has the above-described wound structure, the internal resistance can be reduced by providing two or more lead structures on the positive and negative electrodes respectively and bundling them together on the terminals.

[0131] There are no particular restrictions on the material of the outer casing, as long as it is a substance stable to the electrolyte used. The outer casing can be, but is not limited to, nickel-plated steel, stainless steel, aluminum or aluminum alloy, magnesium alloy, or a laminated film of resin and aluminum foil. In some embodiments, the outer casing is an aluminum or aluminum alloy metal or a laminated film.

[0132] Metal casings include, but are not limited to, encapsulated and hermetically sealed structures formed by fusing metals together using laser welding, resistance welding, or ultrasonic welding; or riveted structures formed using the aforementioned metals with a resin gasket in between. Casings using the aforementioned laminated films include, but are not limited to, encapsulated and hermetically sealed structures formed by thermally bonding resin layers together. To improve sealing, a resin different from the resin used in the laminated film can be sandwiched between the resin layers. When forming a hermetically sealed structure by thermally bonding resin layers using current collectors, a resin with polar groups or a modified resin with introduced polar groups can be used as the sandwiched resin due to the bonding between the metal and the resin. Furthermore, the shape of the casing is arbitrary, and can be, for example, any of the following: cylindrical, square, laminated, button-shaped, or large.

[0133] Protective components can include positive temperature coefficient (PTC) devices that increase resistance when abnormal heat generation or excessive current flows, temperature fuses, thermistors, and valves (current cut-off valves) that cut off current flowing through the circuit by causing a rapid increase in internal battery pressure or temperature during abnormal heat generation. These protective components can be selected to avoid operation under normal high-current conditions, or they can be designed to prevent abnormal heat generation or thermal runaway even without the protective components.

[0134] The electrochemical device of this application includes any device in which an electrochemical reaction occurs, and specific examples include lithium metal secondary batteries or lithium-ion secondary batteries.

[0135] This application also provides an electronic device that includes the electrochemical device described in this application.

[0136] The application of the electrochemical device in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the electrochemical device of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0137] The following uses a lithium-ion battery as an example and combines specific embodiments to illustrate the preparation of a lithium-ion battery. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0138] Example

[0139] I. Preparation of Lithium-ion Batteries

[0140] 1. Preparation of the negative electrode

[0141] Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose were mixed with deionized water in a mass ratio of 96%:2%:2% and stirred until homogeneous to obtain a negative electrode slurry. This negative electrode slurry was coated onto a 9μm copper foil, dried, cold-pressed, and then cut and welded with tabs to obtain the negative electrode.

[0142] 2. Preparation of the positive electrode

[0143] A certain amount of Co3O4 and LiOH powder were weighed, thoroughly mixed and ground in an agate mortar, and then calcined at 900℃ for 10 hours. A specific stoichiometric ratio of oxide, sulfate or nitrate containing the first element was added to the calcined mixture, and alcohol was used as a solvent. After ball milling for 10 hours, the mixture was calcined at 800℃ for 10 hours to obtain lithium cobalt oxide containing the first element.

[0144] The positive electrode active material (lithium cobalt oxide with / without the first element), carbon nanotubes, and polyvinylidene fluoride were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 97:1:2 and stirred until homogeneous to obtain a positive electrode slurry. This positive electrode slurry was coated onto a 12 μm aluminum foil, dried, cold-pressed, and then cut and welded to obtain the positive electrode.

[0145] 3. Preparation of electrolyte

[0146] EC, PC, and DEC (weight ratio 1:1:1) were mixed under a dry argon atmosphere, and LiPF6 was added and mixed thoroughly to form a basic electrolyte with a LiPF6 concentration of 12.5%. Electrolytes of different embodiments and comparative examples were obtained by adding different amounts of additives to the basic electrolyte.

[0147] The abbreviations and names of the components in the electrolyte are shown in the table below:

[0148] Material Name abbreviation Material Name abbreviation Ethylene carbonate EC Ethylene carbonate PC diethyl carbonate DEC Fluoroethylene carbonate FEC Succinic acid SN adiponitrile ADN Ethylene glycol di(2-cyanoethyl) ether EDN 1,3,6-Hexanetrionitrile HTCN 1,2,3-Tris(2-cyanoethoxy)propane TCEP 1,3-Propanesulfonate lactone PS Compound I-1 Formula I-1 Compounds of Formulas 1-3 Formula I-3 Compound I-4 Formula I-4 Compound II-1 Formula II-1 Compound II-4 Formula II-4 Compound II-5 Formula II-5 1-Propylphosphate cyclic anhydride T3P vinyl sulfate DTD Ethylene carbonate VC

[0149] 4. Preparation of the separating membrane

[0150] Polyethylene porous polymer film is used as the separator.

[0151] 5. Preparation of lithium-ion batteries

[0152] The obtained positive electrode, separator, and negative electrode are wound in sequence and placed in an outer packaging foil, leaving an injection port. Electrolyte is poured in through the injection port, the battery is sealed, and then processed through formation, capacity testing, and other procedures to produce a lithium-ion battery.

[0153] II. Testing Methods

[0154] 1. Test method for high-temperature cycle capacity retention of lithium-ion batteries

[0155] At 65°C, the lithium-ion battery is charged at a constant current of 1C to 4.7V, then charged at a constant voltage of 4.7V to a current of 0.05C, and finally discharged at a constant current of 1C to 3.0V. This constitutes the first cycle. The lithium-ion battery is subjected to 500 cycles under these conditions. "1C" refers to the current value at which the battery capacity is completely discharged within one hour.

[0156] The capacity retention rate of a lithium-ion battery after cycling is calculated using the following formula:

[0157] Post-cycle capacity retention = (Post-cycle discharge capacity / Post-cycle discharge capacity) × 100%.

[0158] 2. Test method for high-temperature short-circuit deformation rate of lithium-ion batteries

[0159] At 25°C, the lithium-ion battery was left to stand for 30 minutes, then charged at a constant current rate of 0.5C to 4.7V, and then charged at a constant voltage rate of 4.7V to 0.05C. After standing for 60 minutes, the thickness T1 of the lithium-ion battery was measured. Then, the lithium-ion battery was short-circuited with 100mΩ for 10 seconds, and the thickness T2 of the lithium-ion battery was measured again. The high-temperature short-circuit deformation rate of the lithium-ion battery was calculated using the following formula:

[0160] Short-circuit deformation rate = [(T2-T1) / T1]×100%.

[0161] III. Test Results

[0162] Table 1 illustrates the impact of the positive electrode active material and binder on the high-temperature cycle performance and safety of lithium-ion batteries. In the various examples and comparative examples, the positive electrode active material is lithium cobalt oxide containing / not containing the first element.

[0163] Table 1

[0164]

[0165]

[0166] As shown in Comparative Example 1-1, when the positive electrode active material is undoped, even with the low-density positive electrode binder of this application, the lithium-ion battery exhibits a lower high-temperature cycle capacity retention rate and a higher short-circuit deformation rate. As shown in Comparative Examples 1-2 and 1-3, when the positive electrode active material includes at least one doping element selected from aluminum, magnesium, titanium, zirconium, or tungsten, but the density of the positive electrode binder is too high (greater than 1.5 g / cm³), the battery exhibits a lower high-temperature cycle capacity retention rate and a higher short-circuit deformation rate. 3 ) or too low (less than 0.6 g / cm³) 3Even at high temperatures, lithium-ion batteries still exhibit low high-temperature cycle capacity retention and high short-circuit deformation rate.

[0167] As shown in Examples 1-1 to 1-24, when the positive electrode active material includes at least one doping element selected from aluminum, magnesium, titanium, zirconium, or tungsten, and the positive electrode binder has a concentration of 0.6-1.5 g / cm³, 3 At a density of [specific value], the high-temperature cycle capacity retention rate of lithium-ion batteries can be significantly improved and their short-circuit deformation rate can be significantly reduced.

[0168] Table 2 illustrates the impact of binder porosity and its relationship with density on the high-temperature cycling performance and safety of lithium-ion batteries. Except for the parameters listed in Table 2, Examples 2-1 to 2-16 were identical to those in Example 1-1.

[0169] Table 2

[0170]

[0171]

[0172] The results show that when the porosity of the adhesive is 20%-50% and the porosity b% of the adhesive is related to the density ag / cm³, 3 When 17≤a×b≤60 is satisfied, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and their short-circuit deformation rate can be reduced.

[0173] Table 3 shows the effect of aluminum and tungsten content in the positive electrode active material on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 3, the settings of Examples 3-1 to 3-9 are the same as those of Example 1-1.

[0174] Table 3

[0175]

[0176] The results show that when the positive electrode active material includes aluminum and tungsten elements and the aluminum content x% and tungsten content y% satisfy 1≤x / y≤5, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and their short-circuit deformation rate can be reduced.

[0177] Table 4 shows the effect of the relationship between aluminum content and binder density in the positive electrode active material on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 4, the settings of Examples 4-1 to 4-10 are the same as those of Example 1-1.

[0178] Table 4

[0179]

[0180] The results show that when the positive electrode active material includes aluminum and the aluminum content is x%, the binder density is ag / cm³. 3 When 0.2≤x / a≤1 is satisfied, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and their short-circuit deformation rate can be reduced.

[0181] Table 5 illustrates the impact of compounds with sulfur-oxygen double bonds in the electrolyte and their relationship with binder density on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 5, Examples 5-1 to 5-14 were set up identically to Example 1-1.

[0182] Table 5

[0183]

[0184]

[0185] The results show that when the electrolyte also contains 0.01%-5% of compounds with sulfur-oxygen double bonds, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and their short-circuit deformation rate can be reduced.

[0186] When the content (c%) of compounds with sulfur-oxygen double bonds in the electrolyte is related to the density (ag / cm³) of the positive electrode binder... 3 When 0.5≤c / a≤3 is met, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and their short-circuit deformation rate can be reduced.

[0187] Table 6 illustrates the impact of trinitrile compounds in the electrolyte and their relationship with binder density on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 6, Examples 6-1 to 6-14 were set up identically to Example 1-1.

[0188] Table 6

[0189]

[0190] The results show that when the electrolyte also contains 0.01%-5% trinitrile compounds, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and their short-circuit deformation rate can be reduced.

[0191] When the content (d%) of compounds with sulfur-oxygen double bonds in the electrolyte is related to the density (ag / cm³) of the positive electrode binder... 3 When 0.2≤d / a≤4 is satisfied, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and their short-circuit deformation rate can be reduced.

[0192] Table 7 illustrates the effects of additives in the electrolyte on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 7, Examples 7-1 to 7-10 are identical to those in Example 1-1.

[0193] Table 7

[0194]

[0195] The results show that when the electrolyte contains at least one of succinic anionibacterium, adiponitrile, ethylene glycol di(2-cyanoethyl) ether, fluoroethylene carbonate, vinylene carbonate, or 1-propyl phosphate cycloanhydride, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and their short-circuit deformation rate can be reduced.

[0196] Throughout this specification, references to "embodiment," "partial embodiment," "one embodiment," "another example," "example," "specific example," or "partial example" mean that at least one embodiment or example in this application includes a specific feature, structure, material, or characteristic described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics described herein can be combined in any suitable manner in one or more embodiments or examples.

[0197] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. An electrochemical device comprising: A positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer including a positive electrode active material and a binder, wherein: The positive electrode active material has a first element, which includes aluminum, or the first element includes aluminum and also includes at least one of magnesium, titanium, zirconium or tungsten. Based on the weight of the positive electrode active material, the aluminum content is x%, and x and a satisfy 0.2≤x / a≤1; The density of the adhesive is ag / cm³. 3 The value of a ranges from 0.6 to 1.

5.

2. The electrochemical device according to claim 1, wherein the value of a ranges from 0.6 to 1.

2.

3. The electrochemical device according to claim 1, wherein the value of a ranges from 0.7 to 1.

0.

4. The electrochemical device according to claim 1, wherein the value of a ranges from 0.7 to 0.

9.

5. The electrochemical device according to claim 1, wherein the binder comprises a fluoropolymer.

6. The electrochemical device according to claim 5, wherein the fluoropolymer is polyvinylidene fluoride.

7. The electrochemical device according to claim 1, wherein the electrochemical device satisfies at least one of the following: a. The first element also includes tungsten; b. The first element includes aluminum and tungsten, and based on the weight of the positive electrode active material, the contents of aluminum and tungsten are x% and y%, respectively, where x and y satisfy: 1≤x / y≤5; c. Based on the weight of the positive electrode active material, the content of the first element is 0.01 to 2%.

8. The electrochemical device according to claim 1, wherein the electrolyte comprises a compound having a sulfur-oxygen double bond, and the content of the compound having a sulfur-oxygen double bond is c% based on the weight of the electrolyte, where c ranges from 0.01 to 5.

9. The electrochemical device according to claim 8, wherein c and a satisfy: 0.5 ≤ c / a ≤ 3.

10. The electrochemical device according to claim 1, wherein the electrolyte comprises a trinitrile compound, and the content of the trinitrile compound is d% based on the weight of the electrolyte, where d ranges from 0.01 to 5.

11. The electrochemical device according to claim 10, wherein d and a satisfy: 0.2 ≤ d / a ≤ 4.

12. The electrochemical device according to claim 1, wherein the electrolyte comprises at least one selected from succinic anhydride, adiponitrile, ethylene glycol di(2-cyanoethyl) ether, fluoroethylene carbonate, vinylene carbonate, or 1-propyl cyclic phosphate anhydride.

13. An electronic device comprising an electrochemical device according to any one of claims 1-12.

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