Battery positive electrode and preparation method thereof, lithium ion battery

Abstract

The present invention relates to a battery positive electrode, a preparation method thereof, and a lithium-ion battery. The battery positive electrode comprises a current collector, a substrate material layer, and an epitaxial growth material layer. The substrate material layer is arranged on the current collector, and the epitaxial growth material layer is arranged on the side of the substrate material layer away from the current collector. The substrate material layer comprises a positive electrode material having an olivine structure, and the epitaxial growth material layer comprises a layered lithium cobalt oxide. The positive electrode material with an olivine structure can maintain structural stability at high voltages, and has a small lattice constant difference with the lithium cobalt oxide positive electrode material. The layered lithium cobalt oxide can be deposited on the surface of the substrate material layer by epitaxial growth, and the layered lithium cobalt oxide has excellent gram-to-gram capacity at high voltages. The positive electrode material with an olivine structure suppresses the lattice change of the lithium cobalt oxide through the lattice matching effect, thereby improving the high-voltage stability of the lithium cobalt oxide. The battery positive electrode has a high capacity and can improve the battery cycle performance.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical energy storage, and in particular to a battery positive electrode and a preparation method thereof, and a lithium ion battery. Background Art

[0002] With the development of social and economic life, people's demand for high-energy-density batteries is increasing. By charging the positive electrode material to a higher voltage, more capacity can be released and a higher charge and discharge platform can be achieved, thereby improving the battery's energy density. Generally speaking, batteries with voltages higher than the common standard are considered high-voltage batteries. High-voltage batteries have advantages such as high energy output and long battery life.

[0003] Lithium-ion batteries are widely used due to their advantages, including high voltage, long life, no memory effect, and high energy density. Layered lithium cobalt oxide (LiCoO2) was the first commercialized cathode material and has been widely used in 3C batteries. However, under high voltage, LiCoO2 experiences severe lattice distortion, accompanied by the release of lattice oxygen and the dissolution of transition metal elements, causing material failure and reducing battery cycle performance. Summary of the Invention

[0004] Based on this, it is necessary to provide a battery positive electrode and a preparation method thereof, and a lithium-ion battery to improve the battery cycle performance.

[0005] The first aspect of the present invention is to provide a battery positive electrode, the scheme is as follows:

[0006] A battery positive electrode includes a current collector, a substrate material layer, and an epitaxial growth material layer. The substrate material layer is arranged on the current collector, and the epitaxial growth material layer is arranged on a side of the substrate material layer away from the current collector. The material of the substrate material layer includes a positive electrode material with an olivine structure, and the material of the epitaxial growth material layer includes lithium cobalt oxide (LiCoO2) with a layered structure.

[0007] In one embodiment, the material of the current collector includes metal Al.

[0008] In one embodiment, the positive electrode material having an olivine structure is selected from LiMnPO4, LiCoPO4, LiMn 0.6 Fe 0.4 PO4、LiFe 0.5 Co 0.5 PO4、LiMn 0.6 Co 0.4 One or more of PO4.

[0009] In one embodiment, the in-plane lattice constant of the positive electrode material having an olivine structure is 9.5~14.5 Å, and the in-plane lattice constant of the layered structure LiCoO2 is 11.1~14.2 Å.

[0010] In one embodiment, the lattice mismatch between the positive electrode material having an olivine structure and the layered structure LiCoO2 is less than 8%.

[0011] In one embodiment, the battery positive electrode further includes a surface protection layer, which is arranged on a side of the epitaxial growth material layer away from the substrate material layer, and the material of the surface protection layer includes LiF, LiBr, Li3N, Li2O, LiLaCl4, Li 0.7 Zr 0.3 La 0.7 Cl4、Li5CrZrCl 12 、Li2ZrCl6、Li 2.5 ZrCl5F 0.5 O 0.5 、Li 2.375 Sc 0.375 Zr 0.625 Cl6, Li3YCl6, Li3YBr6, Li3YBr 5.7 F 0.3 、Li 2.75 Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl6、Li 2.6 In 0.8 Ta 0.2 Cl6、Li3InCl6、Li 3.25 InCl 5.75 O 0.25 and at least one of LiTaCl6.

[0012] In one embodiment, the thickness of the substrate material layer is 2µm to 8µm.

[0013] In one embodiment, the thickness of the epitaxial growth material layer is 1µm to 4µm.

[0014] In one embodiment, the thickness of the surface protection layer is 5 nm to 20 nm.

[0015] The second aspect of the present invention is to provide a method for preparing a positive electrode of a battery, the scheme is as follows:

[0016] A method for preparing a battery positive electrode comprises the following steps:

[0017] providing a current collector;

[0018] Preparing a substrate material layer on the current collector, wherein the material of the substrate material layer includes a positive electrode material having an olivine structure;

[0019] An epitaxial growth material layer is obtained by epitaxial growth on a side of the substrate material layer away from the current collector, and the material of the epitaxial growth material layer includes LiCoO2 with a layered structure.

[0020] In one embodiment, the step of preparing the epitaxial growth material layer includes:

[0021] A working gas with a flow rate of 10 sccm to 100 sccm is introduced, wherein the working gas includes argon and oxygen in a volume ratio of 7-9:1-3, the gas pressure is controlled to be 0.2 Pa to 1 Pa, the power is 100 W to 200 W, and the epitaxial growth material layer is grown on the substrate material layer using a radio frequency mode.

[0022] In one embodiment, the preparation method further comprises the following steps:

[0023] A surface protection layer is prepared on the side of the epitaxial growth material layer away from the substrate material layer, and the material of the surface protection layer includes LiF, LiBr, Li3N, Li2O, LiLaCl4, Li 0.7 Zr 0.3 La 0.7 Cl4、Li5CrZrCl 12 、Li2ZrCl6、Li 2.5 ZrCl5F 0.5 O 0.5 、Li 2.375 Sc 0.375 Zr 0.625 Cl6, Li3YCl6, Li3YBr6, Li3YBr 5.7 F 0.3 、Li 2.75 Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl6、Li 2.6 In 0.8 Ta 0.2 Cl6、Li3InCl6、Li 3.25 InCl 5.75 O 0.25 and at least one of LiTaCl6.

[0024] The third aspect of the present invention is to provide a lithium ion battery, the scheme is as follows:

[0025] A lithium-ion battery comprises a housing and the battery positive electrode according to any of the above embodiments, or the battery positive electrode, battery negative electrode, electrolyte, and diaphragm prepared by the preparation method according to any of the above embodiments, arranged in the housing.

[0026] In one embodiment, the negative electrode of the battery is lithium metal foil.

[0027] In one embodiment, the electrolyte includes a solvent, an additive with a mass fraction of 0.5% to 10%, and a lithium salt LiPF6 with a concentration of 0.5-2 mol / L, wherein the solvent is TFPC (trifluoropropylene carbonate), MTFEC (methyl trifluoroethyl carbonate), tFEP (3,3,3-trifluoropropionate), and TFB (1,3,5-trifluorobenzene) in a volume ratio of 1-3:1-3:1-3:4-6; the additive is ethylene carbonate (FEC), difluorobenzene One or more of fluoroethylene carbonate (DFEC), suberonitrile (SUN), 1,4-dicyanobutane (ADN), ethoxypentafluorocyclotriphosphazene (PFPN), sulfolane (SL), trifluoropropanetrimethoxysilane (TTS), 1,3-propanesultone (PS), propenyl-1,3-sultone (PES), 2,2-difluoroethylmethanesulfonic acid (FS), lithium difluorophosphate (LiDFP) and 2,2,2-trifluoroethylmethanesulfonate (TFMS).

[0028] Compared with traditional technologies, the above-mentioned battery positive electrode and preparation method thereof, and lithium-ion battery have the following beneficial effects:

[0029] The preparation method of the above-mentioned battery positive electrode is to arrange a substrate material layer of a positive electrode material with an olivine structure on the current collector. The positive electrode material with an olivine structure has the characteristics of high-voltage resistance due to its stable crystal structure, and can maintain structural stability at a high voltage of 4.7V. The above-mentioned battery positive electrode utilizes the smaller lattice constant difference between the positive electrode material with an olivine structure and the lithium cobalt oxide positive electrode material, and can deposit the layered lithium cobalt oxide on the surface of the substrate material layer in an epitaxial growth manner to obtain an epitaxial growth material layer. The layered lithium cobalt oxide has excellent specific capacity performance under high voltage. At the same time, the positive electrode material with an olivine structure suppresses the transformation of the lithium cobalt oxide layered structure to the spinel structure through the pinning effect generated by lattice matching, which plays a role in improving the high-voltage stability of lithium cobalt oxide. Therefore, the above-mentioned battery positive electrode has a higher capacity performance and can improve the cycle performance of the battery.

[0030] The lithium-ion battery has the above-mentioned battery positive electrode, and thus has corresponding technical features and can obtain corresponding beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1Schematic diagram of the structure of a positive electrode of a battery according to an embodiment;

[0032] Figure 2 FIG. 1 is a schematic flow chart of a method for preparing a positive electrode of a battery according to an embodiment of the present invention.

[0033] Description of reference numerals:

[0034] 100. Battery positive electrode; 110. Current collector; 120. Substrate material layer; 130. Epitaxial growth material layer; 140. Surface protection layer. DETAILED DESCRIPTION

[0035] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0039] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0040] like Figure 1 As shown, a battery positive electrode 100 according to one embodiment includes a current collector 110, a substrate material layer 120, and an epitaxial growth material layer 130. The substrate material layer 120 is disposed on the current collector 110. The epitaxial growth material layer 130 is disposed on a side of the substrate material layer 120 away from the current collector 110. The substrate material layer 120 comprises a positive electrode material having an olivine structure, and the epitaxial growth material layer 130 comprises a layered structure of lithium cobalt oxide (LiCoO2).

[0041] The above-mentioned battery positive electrode 100 is provided with a substrate material layer 120 including a positive electrode material having an olivine structure on the current collector 110. The positive electrode material having an olivine structure has the characteristics of high-voltage resistance due to its stable crystal structure and can maintain structural stability at a high voltage of 4.7V. The above-mentioned battery positive electrode 100 utilizes the smaller lattice constant difference between the positive electrode material having an olivine structure and the lithium cobalt oxide positive electrode material to deposit the layered lithium cobalt oxide on the surface of the substrate material layer 120 in an epitaxial growth manner to obtain an epitaxial growth material layer 130. The layered lithium cobalt oxide has excellent capacity performance at high voltage. At the same time, the positive electrode material having an olivine structure suppresses the transformation of the lithium cobalt oxide layered structure to the spinel structure through the lattice matching effect, which plays a role in improving the high-voltage stability of the lithium cobalt oxide. Therefore, the above-mentioned battery positive electrode 100 has a higher capacity performance and can improve the cycle performance of the battery.

[0042] The material of the current collector 110 includes metal, which has high conductivity. In some examples, the material of the current collector 110 includes metal Al. In some examples, the current collector 110 is Al foil.

[0043] In some examples, the thickness of the current collector 110 is 8µm to 16µm. Further, in some examples, the thickness of the current collector 110 is 10µm to 14µm. In some specific examples, the thickness of the current collector 110 is, for example, 8µm, 8.5µm, 9µm, 9.5µm, 10µm, 10.5µm, 11µm, 11.5µm, 12µm, 12.5µm, 13µm, 14µm, 15µm, 16µm, etc.

[0044] In some of the examples, the in-plane lattice constant of the positive electrode material with an olivine structure is 9.5~14.5 Å. In some of the examples, the in-plane lattice constant of the layered structure LiCoO2 is 11.1~14.2 Å. In some of the examples, the lattice mismatch between the positive electrode material with an olivine structure and the layered structure LiCoO2 is less than 8%. The lattice constant of the above-mentioned positive electrode material with an olivine structure is close to that of lithium cobalt oxide, and the layered structure lithium cobalt oxide can be formed on the surface of the substrate material layer 120 by epitaxial growth. The transformation of the layered structure of the lithium cobalt oxide to the spinel structure is suppressed by the lattice matching effect, thereby effectively improving the high-voltage stability of the lithium cobalt oxide.

[0045] In some of these examples, the in-plane lattice constant of the cathode material with an olivine structure is consistent with the in-plane lattice constant of layered LiCoO2.

[0046] Olivine structured cathode materials generally have excellent high voltage stability. When the upper limit of the charge voltage is greater than 4.7V, the olivine structured cathode material plays a role in pinning and conforming the lithium cobalt oxide structure, thereby inhibiting the transformation of the lithium cobalt oxide layered structure to the spinel structure, and ensuring the stability of the material structure and performance. Optionally, the cathode material with an olivine structure is selected from LiMnPO4, LiCoPO4, LiMn 0.6 Fe 0.4 PO4、LiFe 0.5 Co 0.5 PO4、LiMn 0.6 Co 0.4 The lattice constant of the positive electrode material having an olivine structure is close to that of lithium cobalt oxide, and the layered lithium cobalt oxide can be formed on the surface of the substrate material layer 120 by epitaxial growth, thereby suppressing the transformation of the layered structure of the lithium cobalt oxide to the spinel structure through the lattice matching effect.

[0047] In some examples, the thickness of the substrate material layer 120 is 2µm to 8µm. Further, in some examples, the thickness of the substrate material layer 120 is 4µm to 6µm. In some specific examples, the thickness of the substrate material layer 120 is, for example, 2µm, 2.5µm, 3µm, 3.5µm, 4µm, 4.5µm, 5µm, 5.5µm, 6µm, 6.5µm, 7µm, 7.5µm, 8µm, etc.

[0048] In some examples, the thickness of the epitaxially grown material layer 130 is 1µm to 4µm. Further, in some examples, the thickness of the epitaxially grown material layer 130 is 2µm to 3µm. In some specific examples, the thickness of the epitaxially grown material layer 130 is, for example, 1µm, 1.3µm, 1.6µm, 2µm, 2.3µm, 2.6µm, 3µm, 3.3µm, 3.6µm, 4µm, etc.

[0049] like Figure 1 As shown, in some examples, the positive electrode of the battery further includes a surface protection layer 140. The surface protection layer 140 is disposed on a side of the epitaxial growth material layer 130 away from the substrate material layer 120. The material of the surface protection layer 140 includes LiF, LiBr, Li3N, Li2O, LiLaCl4, Li 0.7 Zr 0.3 La 0.7 Cl4、Li5CrZrCl 12 、Li2ZrCl6、Li 2.5 ZrCl5F 0.5 O 0.5 、Li 2.375 Sc 0.375 Zr 0.625 Cl6, Li3YCl6, Li3YBr6, Li3YBr 5.7 F 0.3 、Li 2.75 Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl6、Li 2.6 In 0.8 Ta 0.2 Cl6、Li3InCl6、Li 3.25 InCl 5.75 O 0.25 and at least one of LiTaCl6.

[0050] The surface protection layer 140 of the aforementioned material exhibits excellent ion conductivity and high-voltage resistance, ensuring efficient lithium ion transport at the interface under high-voltage conditions. Furthermore, the surface protection layer 140 further protects the inner layer of the positive electrode active material, preventing harmful side reactions between the positive electrode material and the electrolyte.

[0051] Furthermore, the material of the surface protection layer 140 is preferably LiLaCl4, Li 0.7 Zr 0.3 La 0.7 Cl4、Li5CrZrCl 12 、Li2ZrCl6、Li2.5 ZrCl5F 0.5 O 0.5 、Li 2.375 Sc 0.375 Zr 0.625 Cl6, Li3YCl6, Li3YBr6, Li3YBr 5.7 F 0.3 、Li 2.7 5Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl6、Li 2.6 In 0.8 Ta 0.2 Cl6、Li3InCl6、Li 3.25 InCl 5.75 O 0.25 and at least one of LiTaCl6.

[0052] The above materials have better lithium ion conductivity, which can not only isolate harmful side reactions between the positive electrode and the electrolyte, but also help improve the migration of lithium ions at the positive electrode interface, thereby improving the electrochemical performance of the battery.

[0053] In some examples, the thickness of the surface protection layer 140 is 5 nm to 20 nm. Further, in some examples, the thickness of the surface protection layer 140 is 10 nm to 15 nm. In some specific examples, the thickness of the surface protection layer 140 is, for example, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, etc.

[0054] Furthermore, the present invention also provides a method for preparing the battery positive electrode 100 according to any of the above examples.

[0055] like Figure 2 As shown, a method for preparing a positive electrode 100 of a battery according to an embodiment includes the following steps:

[0056] Step S110 , providing a current collector 110 .

[0057] Step S120 , preparing a substrate material layer 120 on the current collector 110 , wherein the material of the substrate material layer 120 includes a positive electrode material having an olivine structure.

[0058] In step S130 , epitaxial growth is performed on a side of the substrate material layer 120 away from the current collector 110 to obtain an epitaxial growth material layer 130 . The material of the epitaxial growth material layer 130 includes LiCoO 2 with a layered structure.

[0059] The method for preparing the above-mentioned battery positive electrode 100 arranges a substrate material layer 120 comprising a positive electrode material having an olivine structure on a current collector 110. The positive electrode material having an olivine structure, due to its stable crystal structure, has high-voltage resistance and can maintain structural stability at a high voltage of 4.7V. However, positive electrode materials having an olivine structure generally suffer from the disadvantage of low capacity utilization. The above-mentioned battery positive electrode 100 utilizes the smaller lattice constant difference between the positive electrode material having an olivine structure and the lithium cobalt oxide positive electrode material to form a layered lithium cobalt oxide structure on the surface of the substrate material layer 120 by epitaxial growth, thereby obtaining an epitaxial growth material layer 130. The layered lithium cobalt oxide structure has a higher capacity utilization, compensating for the lower capacity utilization of the positive electrode material having an olivine structure. At the same time, the positive electrode material having an olivine structure suppresses the transformation of the lithium cobalt oxide layered structure to a spinel structure through the lattice matching effect, thereby improving the high-voltage stability of the lithium cobalt oxide. As a result, the battery positive electrode 100 obtained by the above-mentioned preparation method has a higher capacity utilization and can improve battery cycle performance.

[0060] In some examples, in step S110 , the current collector 110 is cleaned.

[0061] In some examples, the cleaning process includes organic solvent cleaning and plasma cleaning. For example, anhydrous ethanol can be used for cleaning to remove organic matter on the surface of the current collector 110. Plasma cleaning is to transfer the current collector 110 cleaned with organic solvent to a magnetron sputtering chamber, and the chamber is vacuumed to 5×10 -5 Pa~8×10 -5 Pa, and then an inert gas, such as argon, is introduced. The flow rate of the inert gas is 10 sccm to 100 sccm, and specifically 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, 100 sccm, etc. The power is controlled to 20 W to 80 W, and plasma cleaning is performed. The cleaning time is, for example, 2 minutes to 40 minutes.

[0062] In some examples, in step S120 , the process for preparing the substrate material layer 120 is physical vapor deposition. Further, in some examples, in step S120 , the process for preparing the substrate material layer 120 is magnetron sputtering.

[0063] In some examples, a radio frequency mode is used when magnetron sputtering is used to prepare the substrate material layer 120. An inert gas, such as argon, is introduced at a flow rate of 10 sccm to 100 sccm, specifically 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, 100 sccm, etc. The controlled air pressure is 0.5Pa~4Pa, for example, 0.5Pa, 0.55Pa, 0.6Pa, 0.65Pa, 0.7Pa, 0.75Pa, 0.8Pa, 0.85Pa, 0.9Pa, 0.95Pa, 1Pa, 1.1Pa, 1.2 Pa, 1.3Pa, 1.4Pa, 1.5Pa, 1.6 Pa, 1.7Pa, 1.8Pa, 1.9Pa, 2.0Pa, 2.1Pa, 2.2Pa, 2.3Pa, 2.4Pa, 2.5Pa, 2.6Pa, 2.7Pa, 2.8Pa, 2.9Pa, 3.0Pa, 3.1Pa, 3.2Pa, 3.3Pa, 3.4Pa, 3.5Pa, 3.6 Pa, 3.7Pa, 3.8Pa, 3.9Pa, 4.0Pa, etc. The control power is 100W~200W, for example, 100W, 110W, 120W, 130W, 140W, 150W, 160W, 170W, 180W, 190W, 200W, etc.

[0064] In some examples, the step of preparing the epitaxial growth material layer 130 (step S130 ) includes:

[0065] A working gas with a flow rate of 10 sccm to 100 sccm is introduced, and an epitaxial growth material layer 130 is grown on the substrate material layer 120 using a radio frequency mode.

[0066] Specific examples of the working gas flow rate include 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, and 100 sccm. The working gas includes argon and oxygen in a volume ratio of 7-9:1-3. The gas pressure is controlled to be 0.2 Pa to 1 Pa, specifically 0.2 Pa, 0.3 Pa, 0.4 Pa, 0.5 Pa, 0.6 Pa, 0.7 Pa, 0.8 Pa, 0.9 Pa, and 1 Pa. The power is 100 W to 200 W, specifically 100 W, 110 W, 120 W, 130 W, 140 W, 150 W, 160 W, 170 W, 180 W, 190 W, and 200 W.

[0067] In some examples, the preparation method further includes the following steps:

[0068] Step S140 , preparing a surface protection layer 140 on a side of the epitaxial growth material layer away from the substrate material layer.

[0069] In some examples, in step S140 , the process for preparing the surface protection layer 140 is physical vapor deposition. Further, in some examples, in step S140 , the process for preparing the surface protection layer 140 is magnetron sputtering.

[0070] The gas pressure of magnetron sputtering is 0.1 Pa to 1 Pa, specifically 0.2 Pa, 0.3 Pa, 0.4 Pa, 0.5 Pa, 0.6 Pa, 0.7 Pa, 0.8 Pa, 0.9 Pa, 1 Pa, etc. The power is 20 W to 60 W, specifically 20 W, 30 W, 40 W, 50 W, 60 W, etc.

[0071] Furthermore, the present invention also provides a lithium-ion battery.

[0072] A lithium-ion battery in one embodiment includes a housing and the battery positive electrode 100 of any of the above examples, or the battery positive electrode 100 prepared by any of the above examples, a battery negative electrode, an electrolyte, and a separator.

[0073] In some of these examples, the lithium-ion battery is a high voltage battery.

[0074] As a high voltage battery, in some examples the battery's negative electrode is lithium metal foil.

[0075] In some examples of high-voltage batteries, the electrolyte includes a solvent, an additive, and a lithium salt, LiPF6. The mass fraction of the additive is 0.5% to 10%, and specifically, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc. The concentration of the lithium salt, LiPF6, is 0.5-2 mol / L.

[0076] The solvent is trifluoropropylene carbonate (TFPC), methyl trifluoroethyl carbonate (MTFEC), 3,3,3-trifluoropropionate (tFEP), and 1,3,5-trifluorobenzene (TFB) in a volume ratio of 1-3:1-3:1-3:4-6.

[0077] Among the above solvents, the fluorinated solvents composed of fluorinated cyclic carbonates, linear carbonates, and linear carboxylates have played an excellent multi-solvent synergistic role. They not only have a high lithium salt dissociation ability, but also maintain a low viscosity, ensuring a high ionic conductivity in the electrolyte. In addition, the fluorinated solvents themselves have a strong electron-withdrawing ability, so they have excellent high-voltage resistance and antioxidant properties. Among them, TFB, as a fluorinated diluent, also has good high-voltage stability. The introduction of TFB helps to form a local high-concentration environment, change the lithium ion solvation sheath structure, promote the formation of aggregated ion pairs, and then generate an interface layer rich in LiF and high-voltage resistant components, thereby improving the high-voltage cycle performance of lithium-ion batteries.

[0078] Among them, the additive is one or more of ethylene carbonate (FEC), difluoroethylene carbonate (DFEC), suberonitrile (SUN), 1,4-dicyanobutane (ADN), ethoxypentafluorocyclotriphosphazene (PFPN), sulfolane (SL), trifluoropropanetrimethoxysilane (TTS), 1,3-propane sultone (PS), propenyl-1,3-sultone (PES), 2,2-difluoroethylmethanesulfonic acid (FS), lithium difluorophosphate (LiDFP) and 2,2,2-trifluoroethylmethanesulfonate (TFMS).

[0079] When the above additives are added to the electrolyte, the additives will preferentially undergo redox reactions on the surface of the electrode material, for example, forming a cathode electrolyte interphase (CEI) with excellent oxidation stability on the surface of the positive electrode, thereby avoiding harmful side reactions between the electrode material and the electrolyte under high voltage conditions, and improving the electrochemical stability of lithium-ion batteries under high voltage conditions.

[0080] The material of the separator includes, for example, at least one of polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-methacrylate copolymer.

[0081] In some of these examples, after assembly, the lithium-ion battery has a charge and discharge cut-off voltage of 3V to 4.7V.

[0082] The high-voltage battery assembled by combining the battery positive electrode 100 with the high-voltage electrolyte can still exhibit excellent cycle performance after being charged to 4.7V.

[0083] The following specific examples are provided to further illustrate the present invention. The present invention provides the following specific examples for a better understanding of the present invention, but is not limited to the specific implementation methods described, and does not constitute a limitation on the scope of protection of the present invention.

[0084] Example 1

[0085] This embodiment provides a battery positive electrode and a lithium-ion battery.

[0086] The method for preparing the positive electrode of the battery of this embodiment comprises the following steps:

[0087] Step 1: Provide Al foil as a current collector and clean the current collector. Specifically, use anhydrous ethanol to clean the current collector to remove organic matter on the surface of the current collector. Transfer the current collector cleaned with organic solvent to the magnetron sputtering chamber, and evacuate the chamber to 6×10 -5 Pa, and then introduce argon with a flow rate of 20sccm and a control power of 40W for plasma cleaning, and the cleaning time is 5min.

[0088] Step 2: Argon gas was introduced into the magnetron sputtering chamber at a flow rate of 50 sccm, the working pressure was adjusted to 3 Pa, the power was set to 120 W, and LiFe was deposited on the current collector using the RF mode. 0.5 Co 0.5 PO4 positive electrode material, forming a substrate material layer with a thickness of 4µm.

[0089] In step 3, a working gas flow rate of 20 sccm (argon and oxygen in a volume ratio of 9:1) was introduced. The working gas pressure was adjusted to 0.8 Pa, and the power was set to 100 W. Radio frequency mode was used to grow a layered LiCoO2 cathode material on the substrate material layer, forming an epitaxial growth material layer with a thickness of 2 µm.

[0090] The preparation method of the lithium ion battery of this embodiment comprises the following steps:

[0091] Prepare the electrolyte: Mix trifluoropropylene carbonate (TFPC), methyl trifluoroethyl carbonate (MTFEC), ethyl 3,3,3-trifluoropropionate (tFEP), and 1,3,5-trifluorobenzene (TFB) in a volume ratio of 1.5:2:1.5:5 to create a mixed solvent. Add lithium salt LiPF6 to the mixed solvent at a concentration of 1 mol / L to create a basic high-voltage electrolyte. Add trifluoropropane trimethoxysilane (TTS) as an additive to the basic high-voltage electrolyte at a concentration of 2% by weight.

[0092] Lithium metal foil with a thickness of 100µm was selected as the battery negative electrode.

[0093] Assemble the battery positive electrode, PP separator, battery negative electrode and electrolyte together to form a button battery.

[0094] Example 2

[0095] This embodiment provides a battery positive electrode and a lithium-ion battery.

[0096] The steps of this embodiment are basically the same as those of embodiment 1, except that in step 2, the material of the substrate material layer is LiMn 0.6 Fe 0.4 PO4 positive electrode material.

[0097] Example 3

[0098] This embodiment provides a battery positive electrode and a lithium-ion battery.

[0099] The steps of this embodiment are basically the same as those of embodiment 1, except that in step 2, the material of the substrate material layer is LiMnPO4 positive electrode material.

[0100] Example 4

[0101] This embodiment provides a battery positive electrode and a lithium-ion battery.

[0102] Compared with Example 1, this embodiment further includes the following steps:

[0103] In step 4, a working gas with a flow rate of 20 sccm is introduced, the working gas pressure is adjusted to 0.4 Pa, the power is set to 30 W, and LiF is deposited on the surface of the epitaxial growth material layer using the RF mode to form a surface protection layer with a thickness of 10 nm.

[0104] Example 5

[0105] This embodiment provides a battery positive electrode and a lithium-ion battery.

[0106] Compared with Example 1, this embodiment further includes the following steps:

[0107] Step 4: introduce working gas with a flow rate of 20 sccm, adjust the working gas pressure to 0.6 Pa, set the power to 50 W, and use the RF mode to deposit Li on the surface of the epitaxial growth material layer. 2.5 ZrCl5F 0.5 O 0.5 , forming a surface protection layer with a thickness of 10 nm.

[0108] Example 6

[0109] This embodiment provides a battery positive electrode and a lithium-ion battery.

[0110] The steps of this embodiment are basically the same as those of embodiment 1, except that the additive added to the basic high-voltage electrolyte is 2,2-difluoroethylmethanesulfonic acid (FS).

[0111] Example 7

[0112] This embodiment provides a battery positive electrode and a lithium-ion battery.

[0113] The steps of this embodiment are basically the same as those of embodiment 1, except that the additive added to the basic high-voltage electrolyte is lithium difluorophosphate (LiDFP).

[0114] Comparative Example 1

[0115] The preparation method of the battery positive electrode of this comparative example comprises the following steps:

[0116] Step 1: Provide Al foil as the current collector and clean the current collector. Use anhydrous ethanol to clean the current collector to remove organic matter on the surface of the current collector. Transfer the current collector cleaned with organic solvent to the magnetron sputtering chamber, and evacuate the chamber to 6×10 -5 Pa, and then introduce argon with a flow rate of 20sccm and a control power of 40W for plasma cleaning, and the cleaning time is 5min.

[0117] In step 2, a working gas flow rate of 20 sccm (argon and oxygen in a volume ratio of 9:1) was introduced into the magnetron sputtering chamber. The working gas pressure was adjusted to 0.8 Pa, and the power was set to 160 W. A layered LiCoO2 cathode material was grown on the current collector using radio frequency mode, forming a 6 µm thick cathode material layer.

[0118] The preparation method of the lithium ion battery of this comparative example comprises the following steps:

[0119] Prepare the electrolyte: Mix EC, EMC, and DEC in a volume ratio of 4:3:3 to obtain a solvent. Add lithium salt LiPF6 to the mixed solvent to a concentration of 1 mol / L.

[0120] Lithium metal foil with a thickness of 100µm was selected as the battery negative electrode.

[0121] Assemble the battery positive electrode, PP separator, battery negative electrode and electrolyte together to form a button battery.

[0122] Comparative Example 2

[0123] The preparation method of the battery positive electrode of this comparative example comprises the following steps:

[0124] Step 1: Provide Al foil as the current collector and clean the current collector. Use anhydrous ethanol to clean the current collector to remove organic matter on the surface of the current collector. Transfer the current collector cleaned with organic solvent to the magnetron sputtering chamber, and evacuate the chamber to 6×10 -5 Pa, and then introduce argon with a flow rate of 20sccm and a control power of 40W for plasma cleaning, and the cleaning time is 5min.

[0125] In step 2, a working gas flow rate of 20 sccm (argon and oxygen in a volume ratio of 9:1) was introduced into the magnetron sputtering chamber. The working gas pressure was adjusted to 0.8 Pa, and the power was set to 160 W. A layered LiCoO2 cathode material was grown on the current collector using radio frequency mode, forming a 6 µm thick cathode material layer.

[0126] The preparation method of the lithium ion battery of this comparative example comprises the following steps:

[0127] Prepare the electrolyte: Mix trifluoropropylene carbonate (TFPC), methyl trifluoroethyl carbonate (MTFEC), ethyl 3,3,3-trifluoropropionate (tFEP), and 1,3,5-trifluorobenzene (TFB) in a volume ratio of 1.5:2:1.5:5 to create a solvent. Add lithium salt LiPF6 to the mixed solvent at a concentration of 1 mol / L to create a basic high-voltage electrolyte. Add trifluoropropane trimethoxysilane (TTS) as an additive to the basic electrolyte at an amount equal to 2% of the base electrolyte mass.

[0128] Lithium metal foil with a thickness of 100µm was selected as the battery negative electrode.

[0129] Assemble the battery positive electrode, PP separator, battery negative electrode and electrolyte together to form a button battery.

[0130] Comparative Example 3

[0131] The preparation method of the battery positive electrode of this comparative example comprises the following steps:

[0132] Step 1: Provide Al foil as the current collector and clean the current collector. Use anhydrous ethanol to clean the current collector to remove organic matter on the surface of the current collector. Transfer the current collector cleaned with organic solvent to the magnetron sputtering chamber, and evacuate the chamber to 6×10 -5 Pa, and then introduce argon with a flow rate of 20sccm and a control power of 40W for plasma cleaning, and the cleaning time is 5min.

[0133] Step 2: Argon gas was introduced into the magnetron sputtering chamber at a flow rate of 50 sccm, the working pressure was adjusted to 3 Pa, the power was set to 120 W, and LiFe was deposited on the current collector using the RF mode. 0.5 Co 0.5 PO4 positive electrode material, forming a positive electrode material layer with a thickness of 4µm.

[0134] The preparation method of the lithium ion battery of this comparative example comprises the following steps:

[0135] Prepare the electrolyte: Mix trifluoropropylene carbonate (TFPC), methyl trifluoroethyl carbonate (MTFEC), ethyl 3,3,3-trifluoropropionate (tFEP), and 1,3,5-trifluorobenzene (TFB) in a volume ratio of 1.5:2:1.5:5 to create a solvent. Add lithium salt LiPF6 to the mixed solvent at a concentration of 1 mol / L to create a basic high-voltage electrolyte. Add trifluoropropane trimethoxysilane (TTS) as an additive to the basic electrolyte at an amount equal to 2% of the base electrolyte mass.

[0136] Lithium metal foil with a thickness of 100µm was selected as the battery negative electrode.

[0137] Assemble the battery positive electrode, PP separator, battery negative electrode and electrolyte together to form a button battery.

[0138] The following performance tests were performed on the lithium-ion batteries prepared in the above examples and comparative examples.

[0139] 1. First discharge specific capacity

[0140] The lithium-ion battery was charged to 4.7V and then discharged to 3V with a current of 1C, and the capacity of the first discharge was recorded.

[0141] 2. Cycle performance

[0142] The lithium-ion battery was charged and discharged at 1C / 1C in the voltage range of 3-4.7V, and the number of cycles until the capacity decayed to 80% was recorded.

[0143] The test results are shown in Table 1.

[0144] Table 1 Initial discharge specific capacity and cycle performance of lithium-ion batteries of Examples and Comparative Examples

[0145]

[0146] As can be seen from the test results in Table 1, the cycle performance of the lithium-ion batteries prepared in Examples 1 to 7 is significantly improved compared to Comparative Examples 1 to 3, indicating that the lithium-ion batteries assembled with the battery positive electrode of the present invention and the high-voltage electrolyte can still exhibit excellent cycle performance after being charged to 4.7V.

[0147] Compared to Example 1, Examples 4 and 5 exhibit further improved cycle performance and initial discharge specific capacity. This is due to the surface protective layer's excellent ion conductivity and high-voltage resistance, which ensures efficient lithium ion transmission at the interface under high-voltage conditions. Furthermore, the surface protective layer further protects the inner cathode active material, preventing harmful side reactions between the cathode material and the electrolyte.

[0148] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The above-described embodiments merely represent several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be based on the appended claims, and the description may be used to interpret the content of the claims.

Claims

1. A battery positive electrode, characterized in that: The present invention comprises a current collector, a substrate material layer, and an epitaxial growth material layer, wherein the substrate material layer is arranged on the current collector, and the epitaxial growth material layer is arranged on a side of the substrate material layer away from the current collector. The material of the substrate material layer comprises a positive electrode material having an olivine structure, and the material of the epitaxial growth material layer comprises a layered LiCoO2 structure. The in-plane lattice constant of the positive electrode material having an olivine structure is 9.5 to 14.5 Å, and the in-plane lattice constant of the layered LiCoO2 structure is 11.1 to 14.2 Å. The lattice mismatch between the positive electrode material having an olivine structure and the layered LiCoO2 structure is less than 8%. The positive electrode of the battery further comprises a surface protection layer, which is arranged on a side of the epitaxial growth material layer away from the substrate material layer. The material of the surface protection layer comprises LiLaCl4, Li 0.7 Zr 0.3 La 0.7 Cl4、Li5CrZrCl 12 、Li2ZrCl6、Li 2.5 ZrCl5F 0.5 O 0.5 、Li 2.375 Sc 0.375 Zr 0.625 Cl6, Li3YCl6, Li3YBr6, Li3YBr 5.7 F 0.3 、Li 2.7 5Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl6、Li 2.6 In 0.8 Ta 0.2 Cl6、Li3InCl6、Li 3.25 InCl 5.75 O 0.25 and at least one of LiTaCl6; The thickness of the substrate material layer is 2µm~8µm, the thickness of the epitaxial growth material layer is 1µm~4µm, and the thickness of the surface protection layer is 5nm~20nm.

2. The positive electrode of the battery according to claim 1, characterized in that The positive electrode material having an olivine structure is selected from LiMnPO4, LiCoPO4, LiMn 0.6 Fe 0.4 PO4、LiFe 0.5 Co 0.5 PO4、LiMn 0.6 Co 0.4 One or more of PO4.

3. A method for preparing a positive electrode of a battery, characterized in that: The following steps are involved: providing a current collector; Preparing a substrate material layer on the current collector, wherein the material of the substrate material layer includes a positive electrode material having an olivine structure; An epitaxial growth material layer is obtained by epitaxially growing on a side of the substrate material layer away from the current collector, wherein the material of the epitaxial growth material layer includes layered LiCoO2; the in-plane lattice constant of the positive electrode material with an olivine structure is 9.5-14.5Å, the in-plane lattice constant of the layered LiCoO2 is 11.1-14.2Å, and the lattice mismatch between the positive electrode material with an olivine structure and the layered LiCoO2 is less than 8%; A surface protection layer is prepared on the side of the epitaxial growth material layer away from the substrate material layer, and the material of the surface protection layer includes LiLaCl4, Li 0.7 Zr 0.3 La 0.7 Cl4、Li5CrZrCl 12 、Li2ZrCl6、Li 2.5 ZrCl5F 0.5 O 0.5 、Li 2.375 Sc 0.375 Zr 0.625 Cl6, Li3YCl6, Li3YBr6, Li3YBr 5.7 F 0.3 、Li 2.75 Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl6、Li 2.6 In 0.8 Ta 0.2 Cl6、Li3InCl6、Li 3.25 InCl 5.75 O 0.25 and at least one of LiTaCl6; The thickness of the substrate material layer is 2µm~8µm, the thickness of the epitaxial growth material layer is 1µm~4µm, and the thickness of the surface protection layer is 5nm~20nm.

4. The method for preparing a positive electrode of a battery according to claim 3, wherein: The steps of preparing the epitaxial growth material layer include: A working gas with a flow rate of 10 sccm to 100 sccm is introduced, wherein the working gas includes argon and oxygen in a volume ratio of 7-9:1-3, the gas pressure is controlled to be 0.2 Pa to 1 Pa, the power is 100 W to 200 W, and the epitaxial growth material layer is grown on the substrate material layer using a radio frequency mode.

5. A lithium-ion battery, characterized in that: The invention comprises a shell and the battery positive electrode according to any one of claims 1 to 2 arranged in the shell, or the battery positive electrode, battery negative electrode, electrolyte and separator prepared by the preparation method according to any one of claims 3 to 4.

6. The lithium-ion battery according to claim 5, wherein The lithium-ion battery meets at least one of the following characteristics (1) to (2): (1) The negative electrode of the battery is a lithium metal foil; (2) The electrolyte comprises a solvent, an additive with a mass fraction of 0.5% to 10% and a lithium salt LiPF6 with a concentration of 0.5-2 mol / L, wherein the solvent is trifluoropropylene carbonate, methyl trifluoroethyl carbonate, 3,3,3-trifluoropropionate and 1,3,5-trifluorobenzene in a volume ratio of 1-3:1-3:1-3:4-6; the additive is selected from one or more of ethylene carbonate, difluoroethylene carbonate, suberonitrile, 1,4-dicyanobutane, ethoxypentafluorocyclotriphosphazene, cyclopentane sulfone, trifluoropropane trimethoxysilane, 1,3-propane sultone, propenyl-1,3-sultone, 2,2-difluoroethylmethanesulfonic acid, lithium difluorophosphate and 2,2,2-trifluoroethylmethanesulfonate.

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