Electrolyte, battery and electric equipment

Abstract

The invention provides an electrolyte, a battery and electric equipment, the electrolyte comprises an electrolyte salt, a solvent and an additive, and the additive comprises a cerium oxide material. The electrolyte provided by the invention can improve the high-temperature storage performance and the safety performance of the battery.

Description

Technical Field

[0001] The present invention relates to an electrolyte, in particular to an electrolyte, a battery and an electrical device, belonging to the technical field of secondary ion batteries. Background Art

[0002] With the rapid development and widespread application of various portable electronic devices, new energy electric vehicles, and energy storage systems, the market demand for secondary ion batteries with high energy density, long cycle life, safe operation, and excellent rate characteristics is becoming increasingly urgent. However, due to factors such as side reactions between the electrode materials and the electrolyte in the battery, existing batteries generally suffer from severe gassing (especially at high temperatures) and poor high-temperature cycling and storage performance, which urgently need to be addressed.

[0003] For example, ternary cell systems have attracted widespread attention due to their high energy density, long cycle life, and good safety performance. However, under high temperature conditions, the cycle performance and storage performance of ternary cell systems deteriorate severely. In addition, the amount of gas generated during aging, storage, and cycling at high temperatures seriously affects the safety performance of the battery, ultimately severely limiting the application of ternary cell systems.

[0004] Based on the above problems, those skilled in the art are in urgent need of developing an electrolyte that can improve the high-temperature storage performance and safety performance of batteries. Summary of the Invention

[0005] The present invention provides an electrolyte, which can improve the high-temperature storage performance and safety performance of a battery.

[0006] The present invention provides a battery having excellent high-temperature storage performance and safety performance.

[0007] The present invention provides an electrical device having excellent high-temperature storage performance and safety performance.

[0008] The present invention provides an electrolyte, which comprises an additive, wherein the additive comprises a cerium oxide material.

[0009] The electrolyte as described above, wherein the cerium element in the cerium oxide material includes trivalent cerium element and tetravalent cerium element.

[0010] In the electrolyte as described above, in the cerium oxide material, the content of trivalent cerium accounts for greater than or equal to 10% of the total cerium content; and / or the content of tetravalent cerium accounts for less than or equal to 90% of the total cerium content.

[0011] In the electrolyte as described above, the content of trivalent cerium accounts for 10% to 60% of the total cerium content, preferably 10% to 40%; and / or the content of tetravalent cerium accounts for 40% to 90% of the total cerium content, preferably 60% to 90%.

[0012] The electrolyte as described above, wherein the cerium oxide material comprises a cerium oxide material with a nanosheet structure.

[0013] In the electrolyte as described above, the cerium oxide material includes at least one of ceria and cerium trioxide.

[0014] In the electrolyte as described above, the average thickness of the nanosheet-structured cerium oxide material is less than or equal to 10 nm, preferably 1 nm to 10 nm.

[0015] In the electrolyte as described above, the Dn50 particle size of the cerium oxide material is less than or equal to 60 nm, preferably 20 nm to 60 nm.

[0016] The electrolyte as described above, wherein the mass percentage a of the cerium oxide material in the electrolyte satisfies 0<a≤1%, preferably 0.2%≤a≤1%.

[0017] The electrolyte as described above, wherein the electrolyte further comprises an electrolyte salt, the electrolyte salt comprises a lithium salt, and the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

[0018] The electrolyte as described above, wherein the electrolyte further comprises a solvent, the solvent comprises an organic solvent, and the organic solvent comprises one or more of carbonate, fluorocarbonate, carboxylate and ether.

[0019] The present invention provides a battery comprising the electrolyte described above.

[0020] The battery as described above, wherein the battery further comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises a positive electrode ternary material.

[0021] The present invention provides an electric device comprising the battery as described above.

[0022] The present invention provides an electrolyte, a battery, and electrical equipment. The electrolyte includes a cerium oxide material. The cerium element in the cerium oxide material has a unique outer electron structure - 4f15d16s2. The special 4f layer can effectively store and release electrons, so that the cerium oxide material contains a large number of oxygen vacancies. Therefore, the cerium oxide material can serve as an oxygen storage material to remove oxygen free radicals formed during the phase change of positive electrode materials such as ternary positive electrode materials, thereby avoiding oxidation of the electrolyte and reducing oxidation gas production of the electrolyte. In addition, the cerium oxide material has high stability and can improve the high-temperature storage performance and safety performance of the battery. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0024] The present invention provides an electrolyte. The electrolyte comprises an additive, and the additive comprises a cerium oxide material.

[0025] The additive in the embodiment of the present invention includes a cerium oxide material, which refers to an oxide material formed by the cerium element.

[0026] During phase transitions, lattice oxygen is released from the cathode material (such as the ternary cathode material in a ternary battery system), forming oxygen free radicals. These oxygen free radicals attack the electrolyte solvent components, oxidizing the electrolyte and leading to a series of uncontrollable side reactions such as proton hydrogen production and gas production, ultimately degrading the battery's storage performance and safety at high temperatures. According to the above solution provided by the present invention, the cerium oxide material is applied to the electrolyte, which can provide the battery with excellent storage performance and safety performance at high temperatures. The inventors analyzed this principle and believed that the reason may be that the cerium element in the cerium oxide material has a unique outer electron structure - 4f15d16s2. Among them, the special 4f layer can effectively store and release electrons, so that there are more oxygen vacancies in the cerium oxide material. Therefore, the cerium oxide material can be used as an oxygen storage material to remove oxygen free radicals formed during the phase change of the positive electrode material, thereby avoiding oxidation of the electrolyte and reducing electrolyte oxidation gas production. In addition, the cerium oxide material has high stability, thereby improving the high-temperature storage performance and safety performance of the battery. Specifically, it can improve the high-temperature storage capacity recovery rate of the battery, reduce the high-temperature storage gas production volume, and significantly reduce the proportion of high-temperature storage hydrogen.

[0027] In a specific embodiment, the cerium element in the cerium oxide material includes trivalent cerium element (i.e., cerium element with a valence of 3) and tetravalent cerium element (i.e., cerium element with a valence of 4). The trivalent cerium element in the embodiment of the present invention refers to a cerium ion with a positive trivalent valence state, i.e., Ce 3+ The tetravalent cerium element in the embodiment of the present invention refers to a cerium ion with a positive tetravalent valence state, namely Ce 4 + The cerium oxide material of the present invention includes trivalent cerium ions and tetravalent cerium ions. The conversion between trivalent cerium ions and tetravalent cerium ions can reversibly combine with oxygen, so that the cerium oxide material exhibits the activity of scavenging oxygen free radicals, thereby reducing the probability of oxidation of the electrolyte and improving the cycle performance, storage performance and safety performance of the battery at high temperature.

[0028] In a specific embodiment, in the cerium oxide material, the content of trivalent cerium element accounts for greater than or equal to 10% of the total content of cerium element.

[0029] In a specific embodiment, in the cerium oxide material, the content of tetravalent cerium element accounts for less than or equal to 90% of the total content of cerium element.

[0030] It should be clarified that the cerium element in the present invention is essentially trivalent cerium and tetravalent cerium, that is, the total content of trivalent cerium and tetravalent cerium is substantially equal to 100% cerium. When the proportions of trivalent cerium and tetravalent cerium to the total cerium content are within the above ranges, the cerium oxide material contains more oxygen vacancies, which can provide active sites for oxygen free radical scavenging, thereby significantly improving the oxygen free radical scavenging efficiency, and further enhancing the battery's high-temperature cycling performance, storage performance, and safety performance.

[0031] In a specific embodiment, in the cerium oxide material, the content of trivalent cerium element accounts for 10% to 60% of the total cerium element content, for example, 10%, 20%, 30%, 40%, 50% or 60%, and the content of trivalent cerium element accounts for the total cerium element content can further be 10% to 40%.

[0032] In a specific embodiment, in the cerium oxide material, the content of tetravalent cerium element accounts for 40% to 90% of the total cerium element content, the content of tetravalent cerium element accounts for the total cerium element content, including but not limited to 40%, 50%, 60%, 70%, 80%, 90% or a range consisting of any two of them, and the content of tetravalent cerium element accounts for the total cerium element content can further be 60% to 90%.

[0033] The present invention further limits the ratio of the content of trivalent cerium to the total content of cerium and the ratio of the content of tetravalent cerium to the total content of cerium, which is beneficial to further improve the efficiency of scavenging oxygen free radicals in the above-mentioned electrolyte.

[0034] Specifically, in the embodiment of the present invention, the ratio of the content of trivalent cerium element to the total content of cerium element and the ratio of the content of tetravalent cerium element to the total content of cerium element are both atomic ratios. The cerium oxide material can be analyzed by XPS (X-ray photoelectron spectroscopy) to measure the content of trivalent cerium element and the content of tetravalent cerium element, as well as the ratio of each of them to the total content of cerium element. For example, the Ce 3d signal data can be subjected to peak separation processing, and Ce 3+ The characteristic peaks can be divided into V0, U0, V ’ 、U ’ , Ce 4+ The characteristic peaks can be divided into V, U, V", U", V"', U"', and Ce 3+ The peak area of ​​the total Ce 3d peak area is expressed as Ce 3+ The ratio of cerium ion concentration is the ratio of the content of trivalent cerium to the total content of cerium.

[0035] In a specific embodiment, the cerium oxide material includes a cerium oxide material with a nanosheet structure. The nanosheet structured cerium oxide material of the embodiment of the present invention refers to a cerium oxide material with a nanometer-sized sheet. When the cerium oxide material has a nanosheet structure, the content of the trivalent cerium element in the cerium oxide material is higher, the cubic structure symmetry is destroyed by tetragonal distortion, the structure of the cerium oxide material becomes (200) crystal plane orientation, and the covalency of the Ce-O bond is enhanced, thereby making the total antioxidant activity of the (200) crystal plane orientation stronger, thereby being able to avoid electrolyte oxidation to a greater extent, further improving the cycle performance, storage performance and safety performance of the battery at high temperature.

[0036] In addition, the above-mentioned cerium oxide material includes at least one of cerium dioxide (cerium element is tetravalent) and cerium trioxide (cerium element is trivalent). The present invention uses the above-mentioned cerium oxide material as an additive to further enhance the ability of the electrolyte to scavenge oxygen free radicals.

[0037] In a specific embodiment, the thickness of the nanosheet-structured cerium oxide material is less than or equal to 10 nm. When the thickness of the cerium oxide material is within the above range, the specific surface area of ​​the cerium oxide material is higher, more active sites are exposed, and the oxygen free radicals in the electrolyte can be removed to a greater extent, thereby better improving the high-temperature cycle performance, high-temperature storage performance and safety performance of the battery. Preferably, the average thickness of the nanosheet-structured cerium oxide material is 1 nm to 10 nm, for example, 2 nm, 4 nm, 6 nm, 8 nm or 10 nm. When the thickness of the cerium oxide material is within the above range, while improving the ability of the cerium oxide material to remove oxygen free radicals formed during the phase change process of the positive electrode material, it is more conducive to the synthesis of the cerium oxide material, for example, it can avoid the problem that the size of the cerium oxide material is too small and not easy to synthesize.

[0038] In one specific embodiment, the Dn50 particle size (diameter) of the cerium oxide material is less than or equal to 60 nm. When the Dn50 particle size (or particle size Dn50) of the cerium oxide material is within the above range, the specific surface area of ​​the cerium oxide material is further increased, and the free sites for binding with oxygen free radicals can be more exposed, thereby further improving the efficiency of scavenging oxygen free radicals, thereby improving the high-temperature cycle performance, high-temperature storage performance, and safety performance of the battery. Preferably, the Dn50 particle size of the cerium oxide material is 20 nm to 60 nm, for example, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, or 60 nm.

[0039] Specifically, in the embodiment of the present application, the thickness and particle size of the cerium oxide material can be regulated by controlling the oxygen content of the environment, the heating temperature, the reaction time, etc. during the preparation process of the cerium oxide material.

[0040] Specifically, the particle size and thickness of the cerium oxide material in the embodiment of the present application can be tested by the following steps: first, the electrolyte including the cerium oxide material is centrifuged, and the precipitate obtained by centrifugation is washed and dried with an organic solvent such as DMC to obtain the cerium oxide material, and the cerium oxide material is tested using a transmission electron microscope (TEM).

[0041] When using TEM to test the average thickness of cerium oxide materials, the thickness of at least 20 particles is tested, and then the average value is taken as the final measurement result; in specific implementation, the thickness of 60 particles can be tested, and the average value is calculated as the final test result.

[0042] In addition, when using TEM to test the Dn50 particle size of cerium oxide materials, the particle sizes of at least 20 particles are tested and the Dn50 value (median particle size) is statistically obtained. In specific implementation, the particle sizes of 60 particles can be tested and the Dn50 value is statistically obtained as the final measurement result.

[0043] In one embodiment, the cerium oxide material is prepared by a preparation method comprising the following steps:

[0044] 1) mixing a cerium source and oleate in a mixed system of a polarity regulator, water, and a saturated hydrocarbon solvent, and performing a first heating reaction to obtain a cerium oleate complex;

[0045] The heating temperature of the first heating reaction is 50°C to 100°C, and the heating time is 2h to 6h;

[0046] 2) mixing the cerium oleate complex, oleic acid, oleylamine, and a long-chain unsaturated hydrocarbon in an atmosphere containing an inert gas, and performing a second heating reaction to obtain a cerium oxide material;

[0047] The second heating reaction comprises the following steps: heating at 100°C to 200°C for 10 minutes to 30 minutes, and then heating to 300°C to 350°C and maintaining for 45 minutes to 75 minutes.

[0048] In a specific implementation, in step 2), after mixing the cerium oleate complex, oleic acid, oleylamine, and long-chain unsaturated hydrocarbon, an inert gas (e.g., argon) is introduced to provide an inert gas atmosphere, and then the system is first heated to temperature T and stirred uniformly at temperature T, and then heated to a second heating reaction temperature, and a second heating reaction is carried out at the second heating reaction temperature. The temperature T can be 120°C to 200°C, for example, 120°C, 125°C, 135°C, 150°C, 165°C, 180°C, or 200°C, and the stirring time at temperature T can be 15 min to 25 min, for example, 15 min, 18 min, 20 min, 23 min, or 25 min, etc.

[0049] For example, the temperature of the first heating reaction can be 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, etc., and the heating time of the first heating reaction can be 2h, 3h, 4h, 5h or 6h, etc.

[0050] Illustratively, the temperature of the second heating reaction can be 300°C, 310°C, 320°C, 330°C, 340°C or 350°C, and the heating time of the first heating reaction can be 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, etc.

[0051] In the above preparation process, the present invention does not impose any particular limitation on the cerium source of the cerium oxide material. For example, the cerium source of the cerium oxide material includes at least one of cerium acetate, cerium nitrate, cerium sulfate, and cerium chloride.

[0052] The present invention does not impose any particular limitation on the oleate, as long as it can form a cerium oleate complex with a cerium source. For example, the oleate includes at least one of sodium oleate and potassium oleate.

[0053] The present invention does not specifically limit the type of polarity modifier. For example, the polarity modifier includes alcohol compounds and ether compounds, such as at least one of methanol, ethanol, propanol, isopropanol, isobutanol, diethyl ether, dipropyl ether, and tetrahydrofuran.

[0054] Specifically, in the above-described preparation process, the present invention can adjust the ratio of trivalent cerium ions to tetravalent cerium ions in the cerium oxide material by adjusting the temperature of the second heating reaction in step 2). For example, when the second heating reaction in step 2) is maintained at a temperature of 300°C to 350°C, the ratio of trivalent cerium ions to the cerium element can be 20% to 40%.

[0055] In addition, the saturated hydrocarbon solvent includes at least one of hexane, heptane, and octane.

[0056] The long-chain unsaturated hydrocarbons include at least one of 1-hexadecene, 1-heptadecene, 1-octadecene and 1-nonadecene.

[0057] In one specific embodiment, the mass percentage a of the cerium oxide material in the electrolyte satisfies 0 < a ≤ 1%, for example, a is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1%. When the mass percentage of the cerium oxide material is within this range, the cerium oxide material can effectively scavenge oxygen free radicals in the electrolyte, effectively preventing the effects of electrolyte oxides on the battery. It can also mitigate the increase in battery impedance caused by excessive cerium oxide material, reduce precipitation of cerium oxide material, and reduce precipitation on the electrode surface, thereby further improving the battery's high-temperature cycling performance, high-temperature storage performance, and safety performance. Preferably, 0.2% ≤ a ≤ 1%.

[0058] In a specific embodiment, the electrolyte further comprises an electrolyte salt, and the electrolyte salt comprises a lithium salt or a sodium salt. The electrolyte comprising the lithium salt or the sodium salt can be applied to a lithium ion battery or a sodium ion battery, respectively. The lithium salt of the embodiment of the present invention comprises one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide. When the lithium salt is selected from the above compounds, the lithium salt can fully exert its effect and prepare an electrolyte with high ionic conductivity and high stability, thereby enabling the battery to fully exert its electrochemical properties.

[0059] In one embodiment, the concentration of the lithium salt in the electrolyte is 0.5M to 2.0M (mol / L). When the concentration of the lithium salt in the electrolyte is within this range, the lithium salt in the electrolyte is more effectively exerted, the ionic conductivity of the electrolyte is higher, and the high-temperature cycling performance, high-temperature storage performance, and safety performance of the battery are improved.

[0060] In one specific embodiment, the electrolyte further comprises a solvent, and the solvent comprises an organic solvent, and the organic solvent comprises one or more of carbonates, fluorocarbonates, carboxylates, and ethers. When the organic solvent is selected from the above organic solvents, the lithium salt and additives can be fully dissolved, resulting in an electrolyte with high stability and high conductivity. At the same time, the electrolyte has an appropriate viscosity, thereby allowing the lithium salt and additives to better exert their functions, thereby enabling the battery to exhibit higher high-temperature cycle performance, high-temperature storage performance, and safety performance.

[0061] Exemplarily, the organic solvent in the electrolyte may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), etc.

[0062] The embodiment of the present invention does not limit the preparation method of the electrolyte. In a specific implementation, it is sufficient to mix the lithium salt, the organic solvent, and the additive in a prescribed ratio.

[0063] The present invention provides a battery comprising the above electrolyte. Based on the electrolyte provided by the present invention, the battery exhibits excellent high-temperature cycle performance, high-temperature storage performance and safety performance.

[0064] In a specific embodiment, the battery further comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises a positive electrode ternary material (LiNi x Co y Mn zO2, x+y+z=1), such as at least one of NCM111, NCM523, NCM622, and NCM811. When the positive electrode active material is a positive electrode ternary material, it is beneficial to improve the discharge specific capacity of the battery.

[0065] The positive electrode sheet of the embodiment of the present invention includes a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder. The positive electrode current collector is generally aluminum foil.

[0066] The lithium-ion battery of an embodiment of the present invention includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent and a binder. Among them, the negative electrode current collector is generally copper foil, and the negative electrode active material is selected from one or more of graphite, hard carbon, soft carbon, mesophase carbon microbeads, silicon-based negative electrode materials and lithium-containing metal composite oxide materials.

[0067] The conductive agent and the binder in the positive electrode active material layer and the negative electrode active material layer of the embodiment of the present invention can be conventional materials in the art.

[0068] The lithium-ion battery of the embodiment of the present invention also includes a diaphragm, which is a diaphragm known in the art that can be used in batteries and is stable to the electrolyte used. It can include one or more of polyolefins, aromatic polyamides, polytetrafluoroethylene, and polyethersulfone, and can be specifically configured as needed.

[0069] The present invention also provides an electrical device including the above-mentioned battery. The electrical device has the same advantages as the above-mentioned electrolyte, which will not be described in detail.

[0070] The electrical equipment in the embodiments of the present invention can be conventional electrical equipment in this field, such as power equipment (such as electric vehicles, electric cars), electronic equipment (such as mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.), energy storage power stations, etc., without special restrictions.

[0071] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0072] The present invention is further described below by way of specific examples and comparative examples. Unless otherwise specified, the reagents, materials, and instruments used below are all conventional reagents, materials, and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthesis methods.

[0073] Example 1

[0074] The preparation method of the electrolyte of this embodiment comprises the following steps:

[0075] 1. Preparation of cerium oxide material: ethanol, deionized water and hexane were mixed in a mass ratio of 1:1:2, 1.4 wt% cerium acetate hydrate and 5.5 wt% sodium oleate were added, and the mixture was reacted at 75°C for 3 hours. After cooling to room temperature, the upper organic phase was washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene were mixed in a mass ratio of 1:2:5:8, argon was introduced, and the mixture was heated to 125°C and stirred continuously for 18 minutes, and then heated to 330°C and maintained for 55 minutes (i.e., the second heating reaction temperature was 330°C and the time was 55 minutes). After cooling, ethanol was added and centrifuged to obtain a cerium oxide material;

[0076] XPS testing of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 35.2% of the total cerium content, and the remainder was basically tetravalent cerium (i.e., the content of tetravalent cerium in the cerium oxide material accounted for 64.8% of the total cerium content).

[0077] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 50 nm and the average thickness was 4 nm.

[0078] 2. Preparation of the electrolyte: The electrolyte was prepared in a glove box filled with 99.999% pure argon, with the moisture content in the glove box controlled at ≤0.1ppm and the temperature controlled at room temperature. EC, DMC, and EMC were mixed in a volume ratio of 1:1:1, and LiPF6 was added thereto to prepare an electrolyte base solution. The cerium oxide material was then added to the electrolyte base solution and ultrasonically dispersed to obtain an electrolyte solution.

[0079] The concentration of LiPF6 in the electrolyte is 1M, and the mass percentage a of the cerium oxide material is 0.2%.

[0080] Example 2

[0081] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the preparation method of the cerium oxide material is different, and includes the following steps:

[0082] Preparation of cerium oxide material: ethanol, deionized water and hexane were mixed in a mass ratio of 1:1:2, 1.4wt% cerium acetate hydrate and 5.5wt% sodium oleate were added, and the mixture was reacted at 80°C for 2.5h. After cooling to room temperature, the upper organic phase was washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene were mixed in a mass ratio of 1:2:5:8, argon was introduced, and the mixture was heated to 150°C and stirred continuously for 15min, then heated to 330°C and maintained for 55min. After cooling, ethanol was added and the mixture was centrifuged to obtain a cerium oxide material;

[0083] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 27.5% of the total cerium content.

[0084] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 35 nm and the average thickness was 4 nm.

[0085] Example 3

[0086] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the preparation method of the cerium oxide material is different, and includes the following steps:

[0087] Preparation of cerium oxide material: ethanol, deionized water and hexane were mixed in a mass ratio of 1:1:2, 1.4wt% cerium nitrate hydrate and 5.5wt% sodium oleate were added, and the mixture was reacted at 75°C for 3h. After cooling to room temperature, the upper organic phase was washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene were mixed in a mass ratio of 1:2:5:8, argon was introduced, and the mixture was heated to 125°C and stirred continuously for 18min, then heated to 330°C and maintained for 55min. After cooling, ethanol was added and the mixture was centrifuged to obtain a cerium oxide material;

[0088] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 26.5% of the total cerium content.

[0089] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 25 nm and the average thickness was 8 nm.

[0090] Example 4

[0091] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the preparation method of the cerium oxide material is different, and includes the following steps:

[0092] Preparation of cerium oxide material: ethanol, deionized water and hexane are mixed in a mass ratio of 1:1:2, 1.4wt% cerium acetate hydrate and 5.5wt% sodium oleate are added, and the mixture is reacted at 80°C for 2.5h. After cooling to room temperature, the upper organic phase is washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene are mixed in a mass ratio of 1:2:5:8, argon is introduced, and the mixture is heated to 150°C and stirred continuously for 15min, then heated to 250°C and maintained for 75min. After cooling, ethanol is added and centrifuged to obtain a cerium oxide material;

[0093] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 39.5% of the total cerium content.

[0094] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 30 nm and the average thickness was 6 nm.

[0095] Example 5

[0096] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the preparation method of the cerium oxide material is different, and includes the following steps:

[0097] Preparation of cerium oxide material: ethanol, deionized water and hexane were mixed in a mass ratio of 1:1:2, 1.4wt% cerium acetate hydrate and 5.5wt% sodium oleate were added, and the mixture was reacted at 80°C for 2.5h. After cooling to room temperature, the upper organic phase was washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene were mixed in a mass ratio of 1:2:5:8, argon was introduced, and the mixture was heated to 150°C and stirred continuously for 15min, then heated to 350°C and maintained for 45min. After cooling, ethanol was added and centrifuged to obtain a cerium oxide material;

[0098] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 20.5% of the total cerium content.

[0099] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 45 nm and the average thickness was 4 nm.

[0100] Example 6

[0101] Preparation of cerium oxide material: ethanol, deionized water and hexane are mixed in a mass ratio of 1:1:2, 1.4wt% cerium acetate hydrate and 5.5wt% sodium oleate are added, and the mixture is reacted at 80°C for 2.5h. After cooling to room temperature, the upper organic phase is washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene are mixed in a mass ratio of 1:2:5:8, argon is introduced, and the mixture is heated to 150°C and stirred continuously for 15min, then heated to 350°C and maintained for 75min. After cooling, ethanol is added and centrifuged to obtain a cerium oxide material;

[0102] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 9.7% of the total cerium content.

[0103] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 30 nm and the average thickness was 6 nm.

[0104] Example 7

[0105] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the preparation method of the cerium oxide material is different, and includes the following steps:

[0106] Preparation of cerium oxide material: ethanol, deionized water and hexane were mixed in a mass ratio of 1:1:2, 1.4wt% cerium acetate hydrate and 5.5wt% sodium oleate were added, and the mixture was reacted at 75°C for 3h. After cooling to room temperature, the upper organic phase was washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene were mixed in a mass ratio of 1:2:5:8, argon was introduced, and the mixture was heated to 200°C and stirred continuously for 35min, then heated to 400°C and maintained for 75min. After cooling, ethanol was added and the mixture was centrifuged to obtain a cerium oxide material;

[0107] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 8.7% of the total cerium content.

[0108] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 80 nm and the average thickness was 15 nm.

[0109] Example 8

[0110] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the preparation method of the cerium oxide material is different, and includes the following steps:

[0111] Preparation of cerium oxide material: ethanol, deionized water and hexane are mixed in a mass ratio of 1:1:2, 1.4wt% cerium acetate hydrate and 5.5wt% sodium oleate are added, and the mixture is reacted at 80°C for 2.5h. After cooling to room temperature, the upper organic phase is washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene are mixed in a mass ratio of 1:2:5:8, argon is introduced, and the mixture is heated to 100°C and stirred continuously for 10 minutes, then heated to 250°C and maintained for 45 minutes. After cooling, ethanol is added and centrifuged to obtain a cerium oxide material;

[0112] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 25.6% of the total cerium content.

[0113] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 20 nm and the average thickness was 2 nm.

[0114] Example 9

[0115] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the preparation method of the cerium oxide material is different, and includes the following steps:

[0116] Preparation of cerium oxide material: ethanol, deionized water and hexane were mixed in a mass ratio of 1:1:2, 1.4wt% cerium acetate hydrate and 5.5wt% sodium oleate were added, and the mixture was reacted at 80°C for 2.5h. After cooling to room temperature, the upper organic phase was washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene were mixed in a mass ratio of 1:2:5:8, argon was introduced, and the mixture was heated to 180°C and stirred continuously for 25min, then heated to 340°C and maintained for 75min. After cooling, ethanol was added and the mixture was centrifuged to obtain a cerium oxide material;

[0117] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 10.3% of the total cerium content.

[0118] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 60 nm and the average thickness was 10 nm.

[0119] Example 10

[0120] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the preparation method of the cerium oxide material is different, and includes the following steps:

[0121] Preparation of cerium oxide material: ethanol, deionized water and hexane are mixed in a mass ratio of 1:1:2, 1.4wt% cerium acetate hydrate and 5.5wt% sodium oleate are added, and the mixture is reacted at 80°C for 2.5h. After cooling to room temperature, the upper organic phase is washed to obtain a cerium oleate complex, and then the cerium oleate complex, oleic acid, oleylamine and 1-octadecene are mixed in a mass ratio of 1:2:5:8, argon is introduced, and the mixture is heated to 200°C and stirred continuously for 25min, then heated to 350°C and maintained for 75min. After cooling, ethanol is added and centrifuged to obtain a cerium oxide material;

[0122] XPS analysis of the cerium oxide material revealed that the content of trivalent cerium in the cerium oxide material accounted for 10.1% of the total cerium content.

[0123] TEM testing of the cerium oxide material revealed that the Dn50 particle size of the cerium oxide material was 65 nm and the average thickness was 12 nm.

[0124] Example 11

[0125] The preparation method of the electrolyte of this embodiment is substantially the same as that of embodiment 1, except that a is 0.5%.

[0126] Example 12

[0127] The preparation method of the electrolyte of this embodiment is substantially the same as that of embodiment 1, except that a is 1%.

[0128] Example 13

[0129] The preparation method of the electrolyte of this embodiment is substantially the same as that of embodiment 1, except that a is 0.1%.

[0130] Example 14

[0131] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that a is 1.1%.

[0132] Example 15

[0133] The preparation method of the electrolyte of this embodiment is substantially the same as that of Example 1, except that the cerium oxide material is replaced by nano-cerium dioxide powder (the cerium dioxide particles are spherical). The nano-cerium dioxide powder is purchased from Sigma-Aldrich Company with the product number 522841.

[0134] Comparative Example 1

[0135] The preparation method of the electrolyte in this comparative example is substantially the same as that in Example 1, except that no cerium oxide material is added to the electrolyte.

[0136] Test example

[0137] A lithium-ion battery was prepared by combining the electrolytes of the embodiment and the comparative example with a positive electrode sheet, a negative electrode sheet and a separator. Specifically, the positive electrode active material ternary NCM811, the conductive material CNT, the conductive carbon black and the binder (polyvinylidene fluoride) PVDF were dispersed in the solvent NMP in a mass ratio of 94:2:2:2 to obtain a positive electrode active material layer slurry; the positive electrode active material layer slurry was evenly coated on the surface of the positive electrode current collector aluminum foil, and the positive electrode sheet was obtained after drying, rolling, baking, slitting and spot welding the electrode ears.

[0138] The negative electrode active material artificial graphite, conductive agent conductive carbon black, CNT, sodium carboxymethyl cellulose and binder SBR are dispersed in deionized water in a mass ratio of 95:1.25:1.25:1.25:1.25, and stirred evenly to obtain a negative electrode active material layer slurry; the negative electrode active material layer slurry is evenly coated on the surface of the negative electrode current collector copper foil, and the negative electrode sheet is obtained after drying, rolling, baking, slitting and spot welding of the electrode ears.

[0139] The prepared positive electrode sheet, negative electrode sheet, and separator are stacked in order. Celgard 2400 polypropylene film is used as the separator and placed between the positive and negative electrode sheets. After winding, the battery cell is placed in an aluminum-plastic film package, dried, and sealed with electrolyte. After standing, forming, secondary sealing, and capacity separation, a lithium-ion battery is obtained. In the lithium-ion battery, the ratio of the negative electrode sheet capacity to the positive electrode sheet capacity (i.e., the positive / negative electrode sheet N / P ratio) is 1.1.

[0140] The following battery performance tests were performed on lithium batteries containing the electrolytes of the embodiments and comparative examples. The test method was as follows:

[0141] High temperature (60°C) storage performance test: The lithium-ion battery was charged at 25°C with a constant current to constant voltage of 1C to 3.8V, cut off at 0.05C, and allowed to stand for 0.5h, and then discharged at a constant current of 1C to 2.2V. This discharge capacity was recorded as the initial capacity C0. The battery was charged at 25°C with a constant current to constant voltage of 1C to 3.8V, cut off at 0.05C, and the fully charged battery was transferred to a high temperature test cabinet and stored at 60°C for 60 days (60D). After storage, the test battery was taken out and placed at room temperature for 8h, and then discharged at a constant current of 1C to 2.2V, placed for 0.5h, and charged at a constant current to constant voltage of 1C to 3.8V, cut off at 0.05C, and then placed for 0.5h and discharged at a constant current of 1C to 2.2V. The discharge capacity C1 was recorded. High temperature (60°C) storage capacity recovery rate (60D high temperature storage capacity recovery rate) = (C1 / C0)*100%. The results are shown in Table 1.

[0142] High-temperature storage gas production test: According to the above method, the fully charged battery was transferred to a high-temperature test cabinet and stored at 60°C for 60 days. The gas in the battery was then extracted using a syringe. The volume of the extracted gas (i.e., the high-temperature storage gas production volume) is shown in Table 1 (the gas extracted from the battery using a syringe is the gas produced by the battery during high-temperature storage). The gas composition of the extracted gas was tested by gas chromatography-mass spectrometry (GC-MS), and the proportion of hydrogen in the extracted gas (i.e., the proportion of hydrogen in high-temperature storage) was measured and shown in Table 1.

[0143] Table 1

[0144]

[0145] As can be seen from Table 1, compared with Comparative Example 1, Examples 1 to 15 improve the high-temperature storage capacity recovery rate of the battery, reduce the reduction in high-temperature storage gas production volume, and significantly reduce the proportion of high-temperature stored hydrogen by introducing cerium oxide materials into the electrolyte, so that the battery exhibits good high-temperature storage performance and safety performance.

[0146] It can be further seen from Examples 1 to 10 that, relative to Examples 6, 7 and 10, Examples 1 to 5, 8 and 9 can further take into account both improving the high-temperature storage capacity recovery rate of the battery and reducing the high-temperature storage gas production volume and the proportion of high-temperature stored hydrogen by further controlling at least one of the following conditions: the content of trivalent cerium in the cerium oxide material accounts for 10% to 60% of the total cerium element content, the Dn50 particle size of the cerium oxide material is in the range of 20nm to 60nm, and the average thickness of the cerium oxide material is in the range of 1nm to 10nm, so that the battery exhibits better high-temperature storage performance and safety performance.

[0147] It can be further seen from Example 1 and Examples 11 to 14 that, relative to Example 14, Example 1 and Examples 11 to 13 can further balance improving the high-temperature storage capacity recovery rate of the battery and reducing the high-temperature storage gas production volume and high-temperature storage hydrogen ratio of the battery by further controlling the mass percentage a of the cerium oxide material in the electrolyte within the range of 0<a≤1%, so that the battery exhibits better high-temperature storage performance and safety performance. In particular, Example 1, Example 11 and Example 12 can more significantly improve the high-temperature storage performance and safety performance of the battery by further controlling 0.2%≤a≤1%.

[0148] In addition, compared with Example 15, Examples 1 to 14 use cerium oxide materials containing trivalent cerium and tetravalent cerium, and the content of trivalent cerium accounts for more than or equal to 10% of the total cerium content, which can further improve the high-temperature storage performance and safety performance of the battery. The reason for this is that, based on the Ce in the cerium oxide material, 3+ and Ce 4+ As well as the structural characteristics of oxygen vacancies, they can be used to remove oxygen free radicals. In Examples 1 to 14, the cerium oxide materials containing trivalent cerium and tetravalent cerium, wherein the content of trivalent cerium accounts for more than or equal to 10% of the total cerium content, on the one hand, Ce 3+ The ion ratio is high. On the other hand, its special morphology of nanosheet structure makes the cerium oxide material have high active oxygen scavenging efficiency, which can inhibit the damage of oxygen free radicals released by the ternary battery cell under working conditions to the electrolyte and improve the stability of the battery system.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that: An additive is included, the additive comprising a cerium oxide material.

2. The electrolyte according to claim 1, characterized in that The cerium element in the cerium oxide material includes trivalent cerium element and tetravalent cerium element.

3. The electrolyte according to claim 2, characterized in that In the cerium oxide material, the content of trivalent cerium element accounts for greater than or equal to 10% of the total content of cerium element; And / or, the content of tetravalent cerium element accounts for less than or equal to 90% of the total content of cerium element.

4. The electrolyte according to claim 3, characterized in that The content of the trivalent cerium element accounts for 10% to 60% of the total cerium content, preferably 10% to 40%; And / or, the content of the tetravalent cerium element accounts for 40% to 90% of the total cerium content, preferably 60% to 90%.

5. The electrolyte according to claim 1, characterized in that The cerium oxide material includes a cerium oxide material with a nanosheet structure.

6. The electrolyte according to any one of claims 1 to 5, characterized in that The cerium oxide material includes at least one of ceria and cerium trioxide.

7. The electrolyte according to claim 5, characterized in that The average thickness of the nanosheet-structured cerium oxide material is less than or equal to 10 nm, preferably 1 nm to 10 nm.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The Dn50 particle size of the cerium oxide material is less than or equal to 60 nm, preferably 20 nm to 60 nm.

9. The electrolyte according to any one of claims 1 to 8, characterized in that In the electrolyte, the mass percentage a of the cerium oxide material satisfies 0<a≤1%, preferably 0.2%≤a≤1%.

10. The electrolyte according to any one of claims 1 to 9, characterized in that The electrolyte solution further includes an electrolyte salt, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

11. The electrolyte according to any one of claims 1 to 10, characterized in that The electrolyte further includes a solvent, wherein the solvent includes an organic solvent, and the organic solvent includes one or more of carbonate, fluorocarbonate, carboxylate and ether.

12. A battery, characterized in that: The electrolyte comprising the electrolyte according to any one of claims 1 to 11.

13. The battery according to claim 12, characterized in that The battery further comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises a positive electrode ternary material.

14. An electrical device, characterized in that: A battery comprising the battery according to claim 12 or 13.

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