Positive electrode material and electrochemical device and electronic device using the same

Abstract

This application relates to a cathode material and electrochemical and electronic devices using the same. Specifically, the application provides a cathode material having a layered structure including a strip-like structure containing atomic clusters. The cathode material of the application helps improve the cycling performance and storage performance of electrochemical devices under high voltage operating conditions.

Description

[0001] This application is a divisional application of an application filed on March 11, 2020, with application number 202010163888.6, and invention name “Positive electrode material and electrochemical device and electronic device using the same”. Technical Field

[0002] The present application relates to the field of energy storage, and in particular to a positive electrode material and an electrochemical device and an electronic device using the same. Background Art

[0003] Electrochemical devices (e.g., lithium-ion batteries) are widely used in wearable devices, smartphones, drones, electric vehicles, large-scale energy storage devices, and other fields due to their advantages such as high energy density, long cycle life, and no memory effect. They have become the most promising new green chemical power source in the world today.

[0004] Under high voltage operating conditions, the cathode surface of lithium-ion batteries is prone to producing byproducts, which can affect the cycling performance of lithium-ion batteries. Using traditional oxide or fluoride coatings on the cathode surface reduces the contact between the electrolyte and the cathode material and hinders the passage of lithium ions, thus adversely affecting the performance of lithium-ion batteries.

[0005] In view of this, it is indeed necessary to provide an improved positive electrode material. Summary of the Invention

[0006] The present application attempts to solve at least one problem existing in the related art to at least some extent by providing a positive electrode material having a layered structure.

[0007] According to one aspect of the present application, the present application provides a positive electrode material, wherein the positive electrode material has a layered structure, and the layered structure includes a strip-shaped structure containing atomic clusters.

[0008] According to an embodiment of the present application, the layered structure contains an element M1 between two adjacent layers, and the element M1 is selected from at least one of Y and Ca, and the layered structure contains an element M2, and the element M2 is selected from at least two of La, Ho, Zr, Sc, W, Ce, Mo, Nb, Hf, Zn or Ti.

[0009] According to an embodiment of the present application, the element M1 is contained between two adjacent layers in the strip-shaped structure.

[0010] According to an embodiment of the present application, the atomic cluster includes the element M2.

[0011] According to an embodiment of the present application, the distance between two adjacent strip-shaped structures is 0.5 nm to 0.75 nm, and the sum of the total thickness of the strip-shaped structures and the distance between the strip-shaped structures is no more than 10 nm.

[0012] In some embodiments, the spacing between two adjacent layers of stripe-shaped structures is 0.55 nm to 0.7 nm. In some embodiments, the spacing between two adjacent layers of stripe-shaped structures is about 0.55 nm, about 0.60 nm, about 0.65 nm, about 0.70 nm, or a range consisting of any two of these values.

[0013] In some embodiments, the sum of the total thickness of the strip-like structures and the spacing between each strip-like structure is no greater than 8 nm. In some embodiments, the sum of the total thickness of the strip-like structures and the spacing between each strip-like structure is no greater than 5 nm. In some embodiments, the sum of the total thickness of the strip-like structures and the spacing between each strip-like structure is about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, or a range consisting of any two of these values.

[0014] According to an embodiment of the present application, based on the total weight of the positive electrode material, the content of the element M1 is in the range of 0.08 wt % to 0.5 wt %, and the content of the element M2 is in the range of 0.04 wt % to 0.5 wt %.

[0015] In some embodiments, the content of the element M1 is in a range of about 0.1 wt % to about 0.5 wt % based on the total weight of the positive electrode material. In some embodiments, the content of the element M1 is about 0.08 wt %, about 0.10 wt %, about 0.12 wt %, about 0.15 wt %, about 0.18 wt %, about 0.2 wt %, about 0.25 wt %, about 0.3 wt %, about 0.35 wt %, about 0.4 wt %, or a range consisting of any two of these values, based on the total weight of the positive electrode material.

[0016] In some embodiments, based on the total weight of the positive electrode material, the content of each of the elements M2 is in the range of 0.05 wt % to 0.10 wt %. In some embodiments, based on the total weight of the positive electrode material, the content of each of the elements M2 is in the range of 0.06 wt % to 0.08 wt %. In some embodiments, based on the total weight of the positive electrode material, the content of the element M2 is about 0.04 wt %, about 0.05 wt %, about 0.08 wt %, about 0.10 wt %, about 0.12 wt %, about 0.14 wt %, about 0.2 wt %, about 0.25 wt %, about 0.3 wt %, about 0.35 wt %, or a range consisting of any two of these values.

[0017] According to an embodiment of the present application, the layered structure includes an oxide of element M1 and an oxide of element M2. In some implementations, the oxide of element M1 includes at least one of Y2O3 or CaO. In some implementations, the oxide of element M2 includes at least two of La2O3, Ho2O3, ZrO2, Sc2O3, WO3, CeO2, MoO3, Nb2O5, HfO2, ZnO, or TiO2.

[0018] According to an embodiment of the present application, the positive electrode material includes lithium cobalt oxide, and the Dv99:Dv50 of the lithium cobalt oxide is in the range of 2.2 to 2.8. In some embodiments, the lithium cobalt oxide includes lithium cobaltate (LiCoO2). In some embodiments, the Dv99:Dv50 of the lithium cobalt oxide is about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, or about 2.8.

[0019] According to an embodiment of the present application, the positive electrode material includes a ternary material, and the ternary material is selected from LiNi a Co b Mn c O2 or LiNi d Co e Al f O2, wherein a+b+c≤1, 0<a<1, 0<b<1, 0<c<1; d+e+f≤1, wherein 0<d<1, 0<e<1, 0<f<1; the Dv99:Dv50 of the ternary material is in the range of 2.2 to 2.8. In some embodiments, the ternary material includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.6 Co 0. 2Mn 0.2 O2、LiNi 0.8 Co 0.15 Al 0.05 O2、LiNi 0.88 Co 0.11 Mn 0.11 In some embodiments, the Dv99:Dv50 of the ternary material is about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, or about 2.8.

[0020] According to another aspect of the present application, the present application provides an electrochemical device comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises the positive electrode material according to an embodiment of the present application.

[0021] According to yet another aspect of the present application, the present application provides an electronic device comprising the electrochemical device according to the embodiment of the present application.

[0022] Additional aspects and advantages of the present application will be described, shown, or explained in part in the following description through implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A transmission electron microscope (TEM) image of lithium cobalt oxide (LiCoO2) is shown.

[0024] Figure 2 A schematic diagram of the microstructure of the positive electrode material according to an embodiment of the present application is shown.

[0025] Figure 3 TEM images of the positive electrode materials according to the embodiments of the present application are shown. DETAILED DESCRIPTION

[0026] The embodiments of the present application will be described in detail below. The embodiments of the present application should not be interpreted as limiting the present application.

[0027] As used herein, the term "about" is used to describe and illustrate small variations. When used in conjunction with an event or situation, the term may refer to an example in which the event or situation occurs precisely as well as an example in which the event or situation occurs very approximately. For example, when used in conjunction with a numerical value, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. In addition, amounts, ratios, and other numerical values ​​are sometimes presented in this article in a range format. It should be understood that such range formats are for convenience and brevity and should be flexibly understood to include not only the numerical values ​​explicitly designated as range limits, but also all individual numerical values ​​or subranges encompassed within the range, as if each numerical value and subrange were explicitly designated.

[0028] In the detailed description and claims, a list of items linked by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means 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 can contain a single element or multiple elements. Item B can contain a single element or multiple elements. Item C can contain a single element or multiple elements.

[0029] positive electrode

[0030] The positive electrode includes a positive electrode current collector and a positive electrode material disposed on the positive electrode current collector, wherein the positive electrode material includes a positive electrode active material. The positive electrode current collector used in the electrochemical device according to the present application may be aluminum (Al), but is not limited thereto.

[0031] The cathode material of the present application is characterized by having a layered structure, wherein the layered structure includes a striped structure containing atomic clusters. "Atomic cluster" refers to a clustered structure formed by at least three atoms gathered together. In some embodiments, the layered structure is formed on the surface of the cathode active material.

[0032] Lithium cobalt oxide, lithium manganese oxide, ternary materials, lithium iron phosphate and spinel lithium nickel manganese oxide are commonly used positive electrode materials, among which lithium cobalt oxide is widely used because of its high voltage platform and high volume energy density. Taking lithium cobalt oxide (LiCoO2) as an example, Figure 1 A transmission electron microscope (TEM) photograph of lithium cobalt oxide is shown, in which the crystal structure of lithium cobalt oxide has a layered structure with regular atomic arrangement. When lithium cobalt oxide is used as the positive electrode material, over-lithiation is prone to occur near the surface of the positive electrode material during lithium insertion and removal, resulting in excessive layer spacing in the surface area, making the Co-O bonds in the surface layer more easily destroyed, which is extremely detrimental to the cycle and storage performance of lithium-ion batteries. To solve this problem, the positive electrode material of the present application includes a strip-like structure containing atomic clusters. Figure 2 A schematic diagram of the microstructure of the positive electrode material according to an embodiment of the present application is shown, which includes a lithium cobalt oxide (LiCoO2) crystal structure A and a layered structure B, wherein the layered structure B includes strip structures C1, C2 and C3, and the strip structures contain atomic clusters a, b and c, etc. Figure 3Transmission electron microscope (TEM) photos of the positive electrode material according to the embodiment of the present application are shown, which confirm that a strip-like structure and a layered structure are formed on the surface of the lithium cobalt oxide. The strip-like structure can improve the aggregation density of the atomic clusters and increase the structural stability of the positive electrode material. It can not only effectively suppress the adverse effects caused by the excessive layer spacing during the lithium ion deintercalation process, but also stabilize the (003) crystal plane. The (003) crystal plane is a crystal plane composed of Co-O bonds in LiCoO2. In lithium cobalt oxide particles, the (003) crystal plane is usually exposed to the outside and is an unstable crystal plane. It is easily corroded by the electrolyte, and the Co-O bond is easily broken during the charge and discharge process, resulting in an unstable material structure and performance degradation. Stabilizing the (003) crystal plane can reduce side reactions such as cobalt dissolution caused by crystal plane peeling in a high delithiation state. In addition, the positive electrode material with a strip-like structure of the present application has fewer side reactions with the electrolyte at high voltage, and the oxygen release phenomenon and cobalt dissolution phenomenon are significantly improved, thereby broadening the selectivity of the electrolyte. Therefore, the positive electrode material with a strip-shaped structure of the present application has improved cycle performance and storage performance under high voltage working conditions (for example, at a voltage above 4.5 V).

[0033] In some embodiments, the layered structure contains an element M1 between two adjacent layers, and the element M1 is selected from at least one of Y or Ca, and the layered structure contains an element M2, and the element M2 is selected from at least two of La, Ho, Zr, Sc, W, Ce, Mo, Nb, Hf, Zn or Ti.

[0034] In some embodiments, the strip-shaped structure includes elements M1 between two adjacent layers.

[0035] In some embodiments, the atomic cluster includes the element M2.

[0036] like Figure 2 As shown, the cathode material of the present application has a layered structure B with a mixed arrangement of multiple elements, wherein the element M2 forms atomic clusters a, b, and c, etc., which in turn form a strip-like structure, and the element M1 is formed between two adjacent layers of the strip-like structure. This arrangement effectively increases the density of atomic aggregation, enabling it to better protect the cathode surface. In addition, different elements can form different types of complexes with oxygen, and their mutual matching can play a synergistic role, increasing the oxygen binding energy, thereby improving the cycle performance and storage performance of lithium-ion batteries.

[0037] In some embodiments, the spacing between two adjacent layers of strip-like structures is 0.5 nm to 0.75 nm. In some embodiments, the spacing between two adjacent layers of strip-like structures is 0.55 nm to 0.7 nm. In some embodiments, the spacing between two adjacent layers of strip-like structures is about 0.55 nm, about 0.60 nm, about 0.65 nm, or about 0.70 nm.

[0038] In some embodiments, the sum of the total thickness of the strip-like structure and the spacing between each strip-like structure is no more than 8 nm. In some embodiments, the sum of the total thickness of the strip-like structure and the spacing between each strip-like structure is no more than 5 nm. In some embodiments, the sum of the total thickness of the strip-like structure and the spacing between each strip-like structure is about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm or a range consisting of any two of these values. "The total thickness of the strip-like structure" refers to the sum of the thicknesses of each strip-like structure itself. "The spacing between each strip-like structure" refers to the spacing between any two adjacent strip-like structures. Figure 2 As shown, the total thickness of the strip-like structure is the sum of the thicknesses of the strip-like structures C1, C2 and C3; the spacing between the strip-like structures is the sum of the spacing between the strip-like structures C1 and C2 and the spacing between the strip-like structures C2 and C3; the sum of the total thickness of the strip-like structure and the spacing between the strip-like structures is the thickness of the layered structure B.

[0039] In some embodiments, based on the total weight of the positive electrode material, the content of the element M1 is in the range of 0.08 wt % to 0.5 wt %. In some embodiments, based on the total weight of the positive electrode material, the content of the element M1 is in the range of 0.1 wt % to 0.15 wt %. In some embodiments, based on the total weight of the positive electrode material, the content of the element M1 is about 0.08 wt %, about 0.10 wt %, about 0.12 wt %, about 0.15 wt %, about 0.18 wt %, about 0.2 wt %, about 0.25 wt %, about 0.3 wt %, about 0.4 wt %, about 0.5 wt % or a range consisting of any two of these values.

[0040] In some embodiments, based on the total weight of the positive electrode material, the content of the element M2 is in the range of 0.04wt% to 0.5wt%. In some embodiments, based on the total weight of the positive electrode material, the content of the element M2 is in the range of 0.05wt% to 0.4wt%. In some embodiments, based on the total weight of the positive electrode material, the content of the element M2 is in the range of 0.06wt% to 0.3wt%. In some embodiments, based on the total weight of the positive electrode material, the content of the element M2 is about 0.04wt%, about 0.05wt%, about 0.08wt%, about 0.10wt%, about 0.12wt%, about 0.14wt%, about 0.2wt%, about 0.25wt%, about 0.3wt%, about 0.35wt% or a range consisting of any two of these values.

[0041] In some embodiments, the layered structure includes an oxide of element M1. In some implementations, the oxide of element M1 includes at least one of Y2O3 or CaO.

[0042] In some embodiments, the layered structure includes an oxide of element M2. In some implementations, the oxide of element M2 includes at least two of La2O3, Ho2O3, ZrO2, Sc2O3, WO3, CeO2, MoO3, Nb2O5, HfO2, ZnO, or TiO2.

[0043] In some embodiments, the cathode material comprises lithium cobalt oxide. In some embodiments, the lithium cobalt oxide comprises lithium cobaltate (LiCoO2).

[0044] In some embodiments, the Dv99:Dv50 of the lithium cobalt oxide is in the range of about 2.2 to about 2.8. In some embodiments, the Dv99:Dv50 of the lithium cobalt oxide is about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, or a range consisting of any two of these values.

[0045] In some embodiments, the cathode material comprises a ternary material. In some embodiments, the ternary material is selected from LiNi a Co b Mn c O2 or LiNi d Co e Al f O2, wherein a+b+c≤1, 0<a<1, 0<b<1, 0<c<1; d+e+f≤1, wherein 0<d<1, 0<e<1, 0<f<1. In some embodiments, the ternary material includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.15 Al 0.05 O2 or LiNi 0.88 Co 0.11 Mn 0.11 At least one of O2.

[0046] In some embodiments, the Dv99:Dv50 of the ternary material is in the range of 2.2 to 2.8. In some embodiments, the Dv99:Dv50 of the ternary material is about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, or a range consisting of any two of these values.

[0047] In some embodiments, the positive electrode material further comprises a binder and optionally a positive electrode conductive material.

[0048] The binder improves the bonding between the positive electrode active material particles and also improves the bonding between the positive electrode active material and the current collector. Non-limiting examples of binders include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0049] In some embodiments, the positive electrode material further includes a positive electrode conductive material, thereby imparting electrode conductivity. The positive electrode conductive material may include any conductive material as long as it does not cause chemical changes. Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives) and mixtures thereof.

[0050] In some embodiments, the positive electrode material is prepared by a solid phase mixing sintering method.

[0051] In some embodiments, the positive electrode material is prepared by combining and sintering an oxide of the M1 element, an oxide of the M2 element, and a precursor material.

[0052] In some embodiments, the cathode material is prepared by the following method:

[0053] (1) taking a certain amount of an oxide of the element M1, an oxide of the element M2, and a lithium salt, wherein the mass ratio of the oxide of the element M1 to the lithium salt is 0.02% to 0.16%, and the mass ratio of the oxide of the element M2 to the lithium salt is 0.01% to 0.12%, and mixing the above materials;

[0054] (2) mixing the precursor material with the mixture in step (1) and stirring for about 2-4 hours;

[0055] (3) Sintering the mixture obtained in step (2) for 6-8 hours and then cooling it naturally to obtain the positive electrode material.

[0056] In some embodiments, the method for preparing the positive electrode material further comprises:

[0057] (4) The positive electrode material obtained in step (3) is flow-crushed, passed through a 500-mesh sieve, and vacuum-packed.

[0058] In some embodiments, in step (2), the stirring rate is 35 r / min to 60 r / min.

[0059] In some embodiments, in step (3), the sintering heating rate is about 10°C / min, the sintering temperature is 1000°C to 1150°C, and the sintering atmosphere is an oxygen atmosphere.

[0060] In some embodiments, the precursor is Co3O4, and the lithium salt is Li2CO3.

[0061] When Co3O4 is used as a precursor and Li2CO3 is used as a lithium salt, the positive electrode material can also be prepared by the following method:

[0062] (a) mixing Co3O4 and Li2CO3 so that the molar ratio of Li atoms to Co atoms is 1.05 to 1.06;

[0063] (b) adding an oxide of element M1 and an oxide of element M2 to the mixture of step (a) so that the content of the oxide of element M1 accounts for 0.08% to 0.2% of the total weight, and the content of the oxide of element M2 accounts for 0.04% to 0.14% of the total weight;

[0064] (c) sintering the mixture obtained in step (b) to obtain a positive electrode material.

[0065] In some embodiments, the method for preparing the positive electrode material further comprises:

[0066] (d) The cathode material obtained in step (c) was crushed, passed through a 500-mesh sieve, and vacuum packaged.

[0067] In some embodiments, in step (c), the sintering temperature is increased at a rate of about 10° C. / min, the sintering temperature is about 1010° C. to about 1160° C., and the sintering atmosphere is an oxygen atmosphere.

[0068] negative electrode

[0069] The negative electrode includes a current collector and a negative electrode active material layer disposed on the current collector. The specific types of negative electrode active materials are not subject to specific restrictions and can be selected according to needs.

[0070] In some embodiments, the negative electrode active material is selected from natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithiated TiO2-Li4Ti5O 12 , one or more of Li-Al alloys.

[0071] Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon and mixtures thereof. Crystalline carbon can be amorphous or flake-shaped, platelet-shaped, spherical or fibrous natural graphite or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, etc.

[0072] In some embodiments, the negative active material layer may include a binder and, optionally, a conductive material.

[0073] The binder improves the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector. Non-limiting examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0074] The negative electrode active material layer includes a conductive material to impart conductivity to the electrode. The conductive material may include any conductive material as long as it does not cause chemical changes. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0075] The current collector for the negative electrode described herein may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0076] electrolyte

[0077] The lithium salts that can be used in the electrolyte of the embodiment of the present application include, but are not limited to: inorganic lithium salts, such as LiClO4, LiAsF6, LiPF6, LiBF4, LiSbF6, LiSO3F, LiN(FSO2)2, etc.; fluorine-containing organic lithium salts, such as LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,3-hexafluoropropane disulfonyl imide lithium, cyclic 1,2-tetrafluoroethane disulfonyl imide lithium, LiN(CF3SO2)(C4F9S O2), LiC(CF3SO2)3, LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2; lithium salts containing dicarboxylic acid complexes, such as lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium tris(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, etc. In addition, the above lithium salts can be used alone or in combination of two or more. In some embodiments, the lithium salt comprises a combination of LiPF6 and LiBF4. In some embodiments, the lithium salt comprises an inorganic lithium salt such as LiPF6 or LiBF4 and a fluorine-containing organic lithium salt such as LiCF3SO3, LiN(CF3SO2)2, or LiN(C2F5SO2)2. In some embodiments, the concentration of the lithium salt is in the range of 0.8 mol / L to 3 mol / L, 0.8 mol / L to 2.5 mol / L, 0.8 mol / L to 2 mol / L, or 1 mol / L to 2 mol / L. In some embodiments, the concentration of the lithium salt is about 1 mol / L, about 1.15 mol / L, about 1.2 mol / L, about 1.5 mol / L, about 2 mol / L, or about 2.5 mol / L.

[0078] The solvents that can be used in the electrolyte of the embodiments of the present application include, but are not limited to, cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, cyclic ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.

[0079] In some embodiments, the cyclic carbonate includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some embodiments, the cyclic carbonate has 3-6 carbon atoms.

[0080] In some embodiments, the linear carbonates include, but are not limited to, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate and the like; and fluorine-substituted linear carbonates include, for example, 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-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate.

[0081] In some embodiments, the cyclic carboxylic acid ester includes, but is not limited to, γ-butyrolactone and γ-valerolactone. In some embodiments, some of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.

[0082] In some embodiments, the chain carboxylic acid esters include, but are not limited to: 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 of the hydrogen atoms of the chain carboxylic acid esters may be substituted with fluorine. In some embodiments, fluorine-substituted chain carboxylic acid esters include, but are not limited to: methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate and 2,2,2-trifluoroethyl trifluoroacetate.

[0083] In some embodiments, cyclic ethers include, but are not limited to, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.

[0084] In some embodiments, chain ethers include, but are not limited to, dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane.

[0085] In some embodiments, the phosphorus-containing organic solvent includes, but is not limited to, trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, diethyl methyl phosphate, ethylidene methyl phosphate, ethylidene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(2,2,3,3,3-pentafluoropropyl) phosphate.

[0086] In some embodiments, the sulfur-containing organic solvent includes, but is not limited to: 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 of the hydrogen atoms of the sulfur-containing organic solvent may be substituted with fluorine.

[0087] In some embodiments, the aromatic fluorine-containing solvent includes, but is not limited to, fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.

[0088] In some embodiments, the solvent used in the electrolyte of the present application includes one or more of the above. In some embodiments, the solvent used in the electrolyte of the present application includes cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present application includes an organic solvent selected from the group consisting of the following substances: 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 the present application includes: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, γ-butyrolactone, or a combination thereof.

[0089] Additives that can be used in the electrolyte of the embodiment of the present application include, but are not limited to: compounds having 2-3 cyano groups, cyclic carbonates containing carbon-carbon double bonds, compounds containing sulfur-oxygen double bonds, and lithium difluorophosphate.

[0090] In some embodiments, the compound having 2-3 cyano groups may include at least one selected from succinonitrile (SN), adiponitrile (ADN), ethylene glycol bis(propionitrile) ether (EDN), 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile (HTCN), 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane (TCEP) or 1,2,4-tris(2-cyanoethoxy)butane; based on the total weight of the electrolyte, the content of the compound having 2-3 cyano groups is 0.1%-10%.

[0091] In some embodiments, the cyclic carbonate having a carbon-carbon double bond specifically includes, but is not limited to, at least one of vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, vinyl vinyl ethylene carbonate, or 1,2-dimethylvinylene carbonate.

[0092] In some embodiments, the compound containing a sulfur-oxygen double bond includes, but is not limited to, at least one of vinyl sulfate, 1,2-propylene glycol sulfate, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, or 3-fluoro-1,3-propane sultone.

[0093] Isolation film

[0094] A separator may be provided between the positive and negative electrodes to prevent short circuits. The material and shape of the separator used in the embodiments of this application are not particularly limited and may be any known prior art material. In some embodiments, the separator comprises a polymer or inorganic material, for example, formed from a material that is stable to the electrolyte of this application.

[0095] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, film, or composite film having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, polypropylene porous film, polyethylene porous film, polypropylene non-woven fabric, polyethylene non-woven fabric, or polypropylene-polyethylene-polypropylene porous composite film can be used.

[0096] A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.

[0097] The inorganic layer includes inorganic particles and a binder, wherein the inorganic particles are selected from one or a combination of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from one or a combination of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0098] The polymer layer contains polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0099] electrochemical devices

[0100] The electrochemical device of the present application includes any device that generates an electrochemical reaction, and its specific examples include all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors. In particular, the electrochemical device is a lithium secondary battery, a sodium secondary battery and a zinc secondary battery. The lithium secondary battery may include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

[0101] electronic devices

[0102] The present application further provides an electronic device comprising an electrochemical device according to the present application. The use of the electrochemical device of the present application is not particularly limited, and it can be used for any electronic device known in the prior art. In some embodiments, the electrochemical device of the present application can be used for, but not limited to, laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0103] The preparation of lithium-ion batteries is described below using lithium-ion batteries as an example and in combination with specific embodiments. 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.

[0104] Example

[0105] The following describes the performance evaluation of the lithium-ion battery according to the embodiments and comparative examples of the present application.

[0106] 1. Preparation of lithium-ion batteries

[0107] 1. Preparation of positive electrode

[0108] When LiCoO2 is used as the positive electrode active material, the positive electrode is prepared by the following steps: a certain amount of Co3O4 is mixed with a lithium salt (Li2CO3) according to a molar ratio of Li atoms to Co atoms of about 1.05 to about 1.06, and an oxide of element M1 and / or a mixture of element M2 are added to the above mixture according to the settings of each embodiment and comparative example, stirred, sintered, and then crushed and sieved to obtain a lithium cobalt oxide positive electrode material.

[0109] When LiNi 1 / 3 Co 1 / 3 Mn 1 / 3When O2 ternary material is used as the positive electrode active material, the positive electrode is prepared by the following steps: under inert gas conditions, NiSO4, CoSO4 and MnSO4 are mixed in a molar ratio of 1:1:1, ammonia water is added to control the pH between 10 and 12, and stirred at a rate of 20r / min to 35r / min to make the above materials react uniformly and co-precipitate. The co-precipitate is filtered and washed with deionized water to obtain a precursor. The precursor is then dry-mixed with LiOH and sintered at 750°C for 18 hours to obtain LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 ternary material.

[0110] The positive electrode active material, acetylene black, and polyvinylidene fluoride (PVDF) were dissolved in N-methylpyrrolidone (NMP) at a weight ratio of 97:1.5:1.5 and thoroughly stirred to obtain a positive electrode slurry. The positive electrode slurry was coated onto the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode active material layer. The positive electrode was then cut into pieces and the tabs were welded to obtain the positive electrode.

[0111] 2. Preparation of negative electrode

[0112] Graphite, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are thoroughly mixed in a suitable amount of deionized water at a weight ratio of 97.5:1.5:1 to form a uniform negative electrode slurry. This slurry is then applied to the negative electrode current collector copper foil and dried at 85°C. The slurry is then trimmed, cut, slit, and dried to form the negative electrode active material layer. The negative electrode is then cut and the tabs welded to the negative electrode.

[0113] 3. Preparation of electrolyte

[0114] In a dry argon environment, LiPF6 was added to a solvent mixed with propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (weight ratio 1:1:1) and mixed evenly, wherein the concentration of LiPF6 was 1.15 mol / L to obtain a basic electrolyte.

[0115] The electrolyte used in Examples 1-18 and 21-40 and Comparative Example 1-5 was as follows: 4 wt % of fluoroethylene carbonate (FEC), 3 wt % of adiponitrile and 1 wt % of 1,3,6-hexanetricarbonitrile were added to the base electrolyte and mixed uniformly to obtain an electrolyte.

[0116] The electrolyte used in Example 19: 4 wt % of fluoroethylene carbonate (FEC) and 4 wt % of adiponitrile were added to the basic electrolyte and mixed evenly to obtain an electrolyte.

[0117] The electrolyte used in Example 20: 4 wt % of fluoroethylene carbonate (FEC), 3 wt % of adiponitrile, and 0.6 wt % of 1,3,6-hexanetricarboxylic acid nitrile were added to the basic electrolyte and mixed evenly to obtain an electrolyte.

[0118] 4. Preparation of isolation membrane

[0119] The PE porous polymer film was used as the separator.

[0120] 5. Preparation of lithium-ion batteries

[0121] The positive electrode, separator, and negative electrode are stacked in order, wound, placed in an outer package, injected with electrolyte, and sealed. After the formation, degassing, and trimming processes, a lithium-ion battery is obtained.

[0122] 2. Test Method

[0123] 1. Test method for cycle performance of lithium-ion batteries

[0124] (1) Test method at 4.55V voltage:

[0125] At room temperature (25°C), charge the lithium-ion battery at a constant current rate of 0.7C to a cutoff voltage of 4.55V. Then, charge at a constant voltage of 4.55V until the current drops below 0.05C, bringing the lithium-ion battery to a fully charged state at 4.55V. Next, discharge the fully charged lithium-ion battery at a rate of 1C to 3V. This constitutes one charge-discharge cycle, and the discharge capacity D0 is recorded at this point. Repeat the charge-discharge cycle until the discharge capacity decays to 80%. Stop the test, record the number of cycles, and record the discharge capacity D1.

[0126] The capacity retention rate of lithium-ion batteries at 25°C and 4.55V is calculated using the following formula:

[0127] Capacity retention rate (25°C, 4.55V) = D1 / D0×100%.

[0128] The cycle number and capacity retention rate of lithium-ion batteries at 45°C and 4.55V were tested using basically the same method, except that the test temperature was 45°C.

[0129] (2) Test method at 4.3V voltage:

[0130] The thickness expansion rate of the lithium-ion battery at 4.3V is tested using a method that is substantially the same as the test method at 4.55V, with the only difference being that the full charge voltage of the lithium-ion battery is 4.3V.

[0131] 2. Test method for high temperature storage performance of lithium-ion batteries

[0132] (1) Test method at 4.55V voltage:

[0133] At room temperature (25°C), the thickness of the lithium-ion battery to be tested is tested and recorded as T0. The lithium-ion battery is charged at a constant current of 0.5C rate to a voltage higher than 4.55V, and then charged at a constant voltage of 4.55V to a current lower than 0.05C, so that it is in a fully charged state of 4.55V. The fully charged battery is placed in a 60°C oven for 30 days. During this period, the test thickness is taken out every 3 days and recorded. After the test, the average value of the measured thickness is recorded as T1. The thickness expansion rate of the lithium-ion battery stored at 60°C for 30 days is calculated by the following formula:

[0134] Thickness expansion ratio (60°C, 30 days, 4.55V) = (T1-T0) / T0×100%.

[0135] At room temperature (25°C), the thickness of the lithium-ion battery to be tested is measured and recorded as T0'. The lithium-ion battery is charged at a constant current of 0.5C to a voltage higher than 4.55V, and then charged at a constant voltage of 4.55V to a current lower than 0.05C, so that it is in a fully charged state of 4.55V. The fully charged battery is placed in an 80°C oven for 24 hours. After the lithium-ion battery is taken out, its thickness is immediately measured and recorded as T1'. The thickness expansion rate of the lithium-ion battery stored at 80°C for 24 hours is calculated by the following formula:

[0136] Thickness expansion ratio (80°C, 24 hours, 4.55V) = (T1′ - T0′) / T0′ × 100%.

[0137] (2) Test method at 4.3V voltage:

[0138] The thickness expansion rate of the lithium-ion battery at 4.3V is tested using a method that is substantially the same as the test method at 4.55V, with the only difference being that the full charge voltage of the lithium-ion battery is 4.3V.

[0139] 3. Test Results

[0140] Tables 1 and 2 show the compositions of the cathode materials for lithium-ion batteries of various examples and comparative examples, as well as their cycling and storage performance. The results demonstrate that the layered structure and the cluster-containing ribbon-like structure within the layered structure can be applied to different types of cathode active materials, improving the cycling and storage performance of corresponding lithium-ion batteries at high voltages.

[0141] LiCoO2 is used as the positive electrode active material in each embodiment and comparative example in Table 1. A full charge voltage of 4.55V is a high voltage operating condition for LiCoO2.

[0142] As shown in Comparative Example 1, when the positive electrode material of the lithium-ion battery does not have an interlayer structure composed of the strip-like structure, the number of cycles of the lithium-ion battery at high voltage (4.55V) is small, and the high-temperature storage thickness expansion rate is high. As shown in Comparative Example 2, the positive electrode material includes element M1 but M1 is not present between two adjacent layers in the strip-like structure, and it is unable to form an interlayer structure composed of a strip-like structure. The number of cycles of the lithium-ion battery at high voltage (4.55V) is small, and the high-temperature storage thickness expansion rate is high. As shown in Comparative Example 3, the positive electrode material contains only one element M2, which is unable to form an interlayer structure composed of a strip-like structure. The number of cycles of the lithium-ion battery at high voltage (4.55V) is small, and the high-temperature storage thickness expansion rate is high. The number of cycles of the lithium-ion battery at high voltage (4.55V) and the high-temperature storage thickness expansion rate are slightly improved, but the effect is still not good.

[0143] As shown in Examples 1-23, when the positive electrode material of a lithium-ion battery has a layered structure and the layered structure contains a strip-shaped structure of atomic clusters, the lithium-ion battery has a significantly increased number of cycles and a significantly reduced high-temperature storage thickness expansion rate at a high voltage (4.55V).

[0144] When the content of element M1 in the positive electrode material is in the range of 0.08wt% to 0.5wt% and the content of element M2 in the positive electrode material is in the range of 0.04wt% to 0.5wt%, it helps to further improve the number of cycles and high-temperature storage thickness expansion rate of the lithium-ion battery at high voltage (4.55V). When the total thickness of the layered structure is not more than 10nm, it helps to further improve the number of cycles and high-temperature storage thickness expansion rate of the lithium-ion battery at high voltage (4.55V). When the Dv99:Dv50 of lithium cobalt oxide is in the range of 2.2 to 2.8, it helps to further improve the number of cycles and high-temperature storage thickness expansion rate of the lithium-ion battery at high voltage (4.55V).

[0145] In Table 2, each embodiment and comparative example adopts LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 ternary material is used as positive electrode active material. The full charge voltage of 4.3V has a great influence on the performance of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 ternary material is suitable for high voltage working conditions.

[0146] As shown in Comparative Example 4, when the positive electrode material of a lithium-ion battery does not have an interlayer structure composed of a strip-like structure, the lithium-ion battery has a low number of cycles at a high voltage (4.3V) and a high thickness expansion rate during high-temperature storage. As shown in Comparative Example 5, when the positive electrode material contains only the element M2, which cannot form an interlayer structure composed of a strip-like structure, the number of cycles at a high voltage (4.3V) and the thickness expansion rate during high-temperature storage of the lithium-ion battery are slightly improved, but the results are still not good.

[0147] As shown in Examples 24-40, when the positive electrode material of a lithium-ion battery has a layered structure and the layered structure contains a strip-like structure of atomic clusters, the lithium-ion battery has a significantly increased number of cycles and a significantly reduced high-temperature storage thickness expansion rate at a high voltage (4.3V). When the content of element M1 in the positive electrode material is in the range of 0.08wt% to 0.5wt% and the content of element M2 in the positive electrode material is in the range of 0.04wt% to 0.5wt%, it helps to further improve the number of cycles and high-temperature storage thickness expansion rate of the lithium-ion battery at a high voltage (4.3V).

[0148] When the total thickness of the layered structure is no more than 10nm, it helps to further improve the number of cycles of lithium-ion batteries at high voltage (4.3V) and the thickness expansion rate of high-temperature storage. When the Dv99:Dv50 ratio of the ternary material is in the range of 2.2 to 2.8, it helps to further improve the number of cycles of lithium-ion batteries at high voltage (4.3V) and the thickness expansion rate of high-temperature storage.

[0149]

[0150]

[0151]

[0152] References throughout this specification to "an embodiment," "part of an embodiment," "one embodiment," "another example," "an example," "a specific example," or "a part of an example" mean that at least one embodiment or example in this application includes the specific features, structures, materials, or characteristics 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 "an example," are not necessarily references to the same embodiment or example in this application. In addition, the specific features, structures, materials, or characteristics described herein may be combined in any suitable manner in one or more embodiments or examples.

[0153] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A positive electrode material for a lithium-ion battery, wherein the positive electrode material comprises a positive electrode active material and a layered structure formed on the surface of the positive electrode active material, the layered structure comprising a stripe-like structure containing atomic clusters, and the sum of the total thickness of the stripe-like structure and the spacing between the stripe-like structures is no more than 10 nm; The layered structure contains an element M1 between two adjacent band structures, and the element M1 is selected from at least one of Y and Ca, and the layered structure contains an element M2, and the element M2 is selected from at least two of La, Ho, Zr, Sc, W, Ce, Mo, Nb, Hf, Zn or Ti. 2 . The positive electrode material according to claim 1 , wherein the atomic cluster comprises the element M2. 3 . The cathode material according to claim 1 , wherein the distance between two adjacent strip-shaped structures is 0.5 nm to 0.75 nm. 4 . The cathode material according to claim 1 , wherein the content of the element M1 is in the range of 0.08 wt % to 0.5 wt %, and the content of the element M2 is in the range of 0.04 wt % to 0.5 wt %, based on the total weight of the cathode material. The cathode material according to claim 1 , wherein the layered structure comprises an oxide of element M1 and an oxide of element M2. 6 . The cathode material according to claim 1 , comprising lithium cobalt oxide, wherein the lithium cobalt oxide has a Dv99:Dv50 in the range of 2.2 to 2.

8.

7. The positive electrode material according to claim 1, comprising a ternary material comprising LiNi a Co b Mn c O2 or LiNi d Co e Al f At least one of O2, wherein a+b+c≤1, 0<a<1, 0<b<1, 0<c<1; d+e+f<1, wherein 0<d<1, 0<e<1, 0<f<1; Dv99:Dv50 of the ternary material is in the range of 2.2 to 2.

8.

8. An electrochemical device, which is a lithium-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises the positive electrode material according to any one of claims 1 to 7.

9. An electronic device comprising the electrochemical device according to claim 8.

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