Battery positive electrode, preparation method thereof and lithium ion battery

Abstract

The 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, the epitaxial growth material layer is arranged on one side, far away from the current collector, of the substrate material layer, the substrate material layer comprises a positive electrode material with an olivine structure, and the epitaxial growth material layer comprises lithium cobalt oxide with a layered structure. The positive electrode material with the olivine structure can keep stable structure under high voltage, and lithium cobalt oxide with a layered structure can be deposited on the surface of the substrate material layer in an epitaxial growth mode due to small lattice constant difference between the positive electrode material with the olivine structure and a lithium cobalt oxide positive electrode material; and the lithium cobalt oxide with the layered structure has excellent gram specific capacity under high voltage. The positive electrode material with the olivine structure inhibits the lattice change of the lithium cobalt oxide through a lattice matching effect, and improves the high-voltage stability of the lithium cobalt oxide. The battery positive electrode has relatively high capacity exertion, and the cycle performance of the battery can be improved.

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 getting higher and higher. By charging the positive electrode material to a higher voltage, more capacity can be released and a higher charging and discharging platform can be achieved, thereby improving the energy density of the battery. Generally speaking, batteries with voltages higher than the common standard voltage can be regarded as high-voltage batteries, which have advantages such as high energy output and long battery life.

[0003] Lithium-ion batteries are widely used due to their advantages such as high voltage, long life, no memory effect and high energy density. 2 ) is the earliest commercialized cathode material and has been widely used in the field of 3C batteries. However, under high voltage, lithium cobalt oxide will experience severe lattice distortion, accompanied by the release of lattice oxygen and the dissolution of transition metal elements, which will cause the material to fail and reduce the battery's 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 positive electrode for a battery, the scheme is as follows:

[0006] A positive electrode of a battery, comprising a current collector, a substrate material layer and an epitaxial growth material layer, wherein the substrate material layer is arranged on the current collector, 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 structure of lithium cobalt oxide (LiCoO 2 ).

[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 LiMnPO 4 、LiCoPO 4 、LiMn 0.6 Fe 0.4 PO 4 、LiFe 0.5 Co 0.5 PO 4 、LiMn 0.6 Co 0.4 PO 4One or more of .

[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 layered structure of LiCoO 2 The in-plane lattice constant is 11.1~14.2 Å.

[0010] In one embodiment, the positive electrode material having an olivine structure and the layered structure of LiCoO 2 The lattice mismatch is less than 8%.

[0011] In one embodiment, the positive electrode of the battery 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, Li 3 N.Li 2 O、LiLaCl 4 , Li 0.7 Zr 0.3 La 0.7 Cl 4 , Li 5 CrZrCl 12 , Li 2 ZrCl 6 , Li 2.5 ZrCl 5 F 0.5 O 0.5 , Li 2.375 Sc 0.375 Zr 0.625 Cl 6 , Li 3 YC 6 , Li 3 Yb 6 , Li 3 Yb 5.7 F 0.3 , Li 2.75 Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl 6 , Li 2.6 In 0.8 Ta 0.2 Cl 6 , Li 3 InCl 6 , Li 3.25 InCl 5.75 O 0.25 and LiTaCl 6At least one of .

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

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

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

[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 positive electrode of a battery 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, wherein the material of the epitaxial growth material layer includes a layered structure of LiCoO 2 .

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

[0021] A working gas with a flow rate of 10sccm~100sccm 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 0.2Pa~1Pa, the power is 100W~200W, 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, Li 3 N.Li 2 O、LiLaCl 4 , Li 0.7 Zr 0.3 La 0.7 Cl 4 , Li 5 CrZrCl 12 , Li 2 ZrCl 6 , Li 2.5 ZrCl 5 F0.5 O 0.5 , Li 2.375 Sc 0.375 Zr 0.625 Cl 6 , Li 3 YC 6 , Li 3 Yb 6 , Li 3 Yb 5.7 F 0.3 , Li 2.75 Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl 6 , Li 2.6 In 0.8 Ta 0.2 Cl 6 , Li 3 InCl 6 , Li 3.25 InCl 5.75 O 0.25 and LiTaCl 6 At least one of .

[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 shell and a battery positive electrode as described in any of the above embodiments arranged in the shell, or a battery positive electrode, a battery negative electrode, an electrolyte and a diaphragm prepared by the preparation method as described in any of the above embodiments.

[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 LiPF with a concentration of 0.5-2 mol / L. 6The solvent is TFPC (trifluoropropylene carbonate), MTFEC (methyl trifluoroethyl carbonate), tFEP (3,3,3-trifluoropropionate), TFB (1,3,5-trifluorobenzene) in a volume ratio of 1-3:1-3:1-3:4-6; the additive is one or more of ethylene carbonate (FEC), difluoroethylene carbonate (DFEC), suberonitrile (SUN), 1,4-dicyanobutane (ADN), ethoxypentafluorocyclotriphosphazene (PFPN), cyclopentane (SL), trifluoropropane trimethoxysilane (TTS), 1,3-propane sultone (PS), propenyl-1,3-sultone (PES), 2,2-difluoroethyl methanesulfonic acid (FS), lithium difluorophosphate (LiDFP) and 2,2,2-trifluoroethyl methanesulfonate (TFMS).

[0028] Compared with the conventional technology, 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 at high voltage. At the same time, the positive electrode material with an olivine structure suppresses the transformation of the layered structure of the lithium cobalt oxide to the spinel structure through the pinning effect generated by lattice matching, which plays a role in improving the high-voltage stability of the lithium cobalt oxide. Therefore, the above-mentioned battery positive electrode has a higher capacity and can improve the cycle performance of the battery.

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

[0031] Figure 1 A schematic structural diagram of a positive electrode of a battery according to an embodiment;

[0032] Figure 2 The figure is a schematic diagram of a process for preparing a positive electrode of a battery according to an embodiment.

[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] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related 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 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, and do not indicate or imply that the referred device or element 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] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] like Figure 1As shown, a positive electrode 100 of a battery in an 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 material of the substrate material layer 120 includes a positive electrode material having an olivine structure, and the material of the epitaxial growth material layer 130 includes a layered structure of lithium cobalt oxide (LiCoO 2 ).

[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 characteristic 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, and can 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 under 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 of the examples, the thickness of the current collector 110 is 8µm to 16µm. Further, in some of the 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 these examples, the in-plane lattice constant of the cathode material with an olivine structure is 9.5~14.5 Å. In some of these examples, the layered structure of LiCoO 2 The in-plane lattice constant of the LiCoO2 is 11.1~14.2 Å. In some of these examples, the positive electrode material with an olivine structure is similar to the layered structure of LiCoO2. 2The lattice mismatch is below 8%. The lattice constant of the positive electrode material with 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. The lattice matching effect inhibits the transformation of the layered structure of lithium cobalt oxide to the spinel structure, effectively improving the high-voltage stability of lithium cobalt oxide.

[0045] In some of these examples, the in-plane lattice constant of the cathode material with olivine structure is similar to that of the layered LiCoO 2 The in-plane lattice constant is consistent.

[0046] The positive electrode material with olivine structure usually has excellent high-voltage stability. When the upper limit of the charge cut-off voltage is greater than 4.7V, the positive electrode material with olivine structure 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 positive electrode material with olivine structure is selected from LiMnPO 4 、LiCoPO 4 、LiMn 0.6 Fe 0.4 PO 4 、LiFe 0.5 Co 0.5 PO 4 、LiMn 0.6 Co 0.4 PO 4 The lattice constant of the positive electrode material having an olivine structure is close to that of lithium cobalt oxide, and the lithium cobalt oxide with a layered structure can be formed on the surface of the substrate material layer 120 by epitaxial growth, and the transformation of the lithium cobalt oxide layered structure to the spinel structure is suppressed by 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 epitaxial growth material layer 130 is 1µm to 4µm. Further, in some examples, the thickness of the epitaxial growth material layer 130 is 2µm to 3µm. In some specific examples, the thickness of the epitaxial growth 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, Li 3 N.Li 2 O、LiLaCl 4 , Li 0.7 Zr 0.3 La 0.7 Cl 4 , Li 5 CrZrCl 12 , Li 2 ZrCl 6 , Li 2.5 ZrCl 5 F 0.5 O 0.5 , Li 2.375 Sc 0.375 Zr 0.625 Cl 6 , Li 3 YC 6 , Li 3 Yb 6 , Li 3 Yb 5.7 F 0.3 , Li 2.75 Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl 6 , Li 2.6 In 0.8 Ta 0.2 Cl 6 , Li 3 InCl 6 , Li 3.25 InCl 5.75 O 0.25 and LiTaCl 6 At least one of .

[0050] The surface protection layer 140 of the above material has excellent ion conductivity and high voltage resistance, ensuring the effective transmission of lithium ions at the interface under high voltage conditions. At the same time, the surface protection layer 140 can further protect the inner positive electrode active material and avoid 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 Cl 4 , Li 5 CrZrCl 12 , Li 2 ZrCl 6 , Li 2.5 ZrCl 5 F 0.5 O 0.5 , Li 2.375 Sc 0.375 Zr 0.625 Cl 6 , Li 3 YC 6 , Li 3 Yb 6 , Li 3 Yb 5.7 F 0.3 , Li 2.7 5 Y 0.16 Er 0.16 Yb 0.16 In 0.25 Zr 0.25 Cl 6 , Li 2.6 In 0.8 Ta 0.2 Cl 6 , Li 3 InCl 6 , Li 3.25 InCl 5.75 O 0.25 and LiTaCl 6 At least one of .

[0052] The above materials have more excellent 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 of the examples, the thickness of the surface protection layer 140 is 5 nm to 20 nm. Further, in some of the 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 of any of the above examples.

[0055] like Figure 2 As shown, a method for preparing a positive electrode 100 of a battery in one 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] Step S130, epitaxially growing an epitaxially grown material layer 130 on a side of the substrate material layer 120 away from the current collector 110, wherein the material of the epitaxially grown material layer 130 includes a layered structure of LiCoO 2 .

[0059] The preparation method of the above-mentioned battery positive electrode 100 is to set a substrate material layer 120 including a positive electrode material with an olivine structure on the current collector 110. 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. However, the positive electrode material with an olivine structure usually has the disadvantage of low capacity. The above-mentioned battery positive electrode 100 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 form 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 a higher capacity, which makes up for the disadvantage of low capacity of the positive electrode material with an olivine structure. At the same time, the positive electrode material with an olivine structure inhibits 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 battery positive electrode 100 obtained by the above-mentioned preparation method has a higher capacity and can improve the 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 substances on the surface of the current collector 110. Plasma cleaning is to transfer the current collector 110 cleaned with an organic solvent to a magnetron sputtering chamber, and the chamber is evacuated to 5×10 -5 Pa~8×10 -5Pa, and then an inert gas, such as argon, is introduced, the flow rate of the inert gas is 10 sccm-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 power is controlled to be 20 W-80 W, and plasma cleaning is performed, and the cleaning time is, for example, 2 min-40 min.

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

[0063] In some examples, when magnetron sputtering is used to prepare the substrate material layer 120, a radio frequency mode is used. An inert gas is introduced, such as argon gas, and the flow rate of the inert gas is 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] The flow rate of the working gas is specifically, for example, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, 100 sccm, etc. The working gas includes argon and oxygen in a volume ratio of 7-9:1-3. The control gas pressure is 0.2Pa~1Pa, specifically, 0.2Pa, 0.3Pa, 0.4Pa, 0.5Pa, 0.6Pa, 0.7Pa, 0.8Pa, 0.9Pa, 1Pa, etc. The power is 100W~200W, specifically, 100W, 110W, 120W, 130W, 140W, 150W, 160W, 170W, 180W, 190W, 200W, etc.

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

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

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

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

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

[0074] As a high voltage battery, in some examples, the battery cathode is lithium metal foil.

[0075] As a high voltage battery, in some examples, the electrolyte includes a solvent, an additive, and a lithium salt LiPF 6The mass fraction of the additive is 0.5% to 10%, for example, 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. Lithium salt LiPF 6 The concentration is 0.5-2mol / 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. And the fluorinated solvent itself has a strong electron-withdrawing ability, so it has 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, and promote the formation of aggregated ion pairs, thereby generating an interface layer rich in LiF and resistant to high voltage 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), cyclopentane sulfone (SL), trifluoropropane trimethoxysilane (TTS), 1,3-propane sultone (PS), propenyl-1,3-sultone (PES), 2,2-difluoroethyl methanesulfonic acid (FS), lithium difluorophosphate (LiDFP) and 2,2,2-trifluoroethyl methanesulfonate (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, such as forming a cathode electrolyte interphase (CEI) with excellent oxidation stability on the surface of the positive electrode, 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 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 a 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 and does not limit the protection scope 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 a magnetron sputtering chamber, and evacuate the chamber to 6×10 -5 Pa, 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 is introduced into the magnetron sputtering chamber at a flow rate of 50 sccm, the working pressure is adjusted to 3 Pa, the power is set to 120 W, and LiFe is deposited on the current collector using the RF mode. 0.5 Co 0.5 PO 4 The positive electrode material forms a substrate material layer with a thickness of 4µm.

[0089] Step 3: introduce working gas with a flow rate of 20 sccm, the working gas includes argon and oxygen with a volume ratio of 9:1. The working gas pressure is adjusted to 0.8 Pa, the power is set to 100 W, and the RF mode is used to grow the layered LiCoO on the substrate material layer. 2 Positive electrode material, forming an epitaxial growth material layer with a thickness of 2µm.

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

[0091] Preparation of electrolyte: Mix trifluoropropylene carbonate (TFPC), methyl trifluoroethyl carbonate (MTFEC), 3,3,3-trifluoropropionate (tFEP), and 1,3,5-trifluorobenzene (TFB) in a volume ratio of 1.5:2:1.5:5 to obtain a mixed solvent. Add lithium salt LiPF 6 , lithium salt LiPF 6 The concentration of trifluoropropane trimethoxysilane (TTS) was 1 mol / L to obtain a basic high-voltage electrolyte. The additive trifluoropropane trimethoxysilane (TTS) was added to the basic high-voltage electrolyte in an amount of 2% of the mass of the basic electrolyte.

[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 into 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 PO 4 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 LiMnPO 4 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] Step 4, introduce working gas with a flow rate of 20 sccm, adjust the working gas pressure to 0.4 Pa, set the power to 30 W, and use the RF mode to deposit LiF on the surface of the epitaxial growth material layer 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 ZrCl 5 F 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 positive electrode of the battery of this comparative example comprises the following steps:

[0116] Step 1: Provide Al foil as a 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, 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] Step 2: A working gas with a flow rate of 20 sccm is introduced into the magnetron sputtering chamber. The working gas includes argon and oxygen with a volume ratio of 9:1. The working gas pressure is adjusted to 0.8 Pa, the power is set to 160 W, and the RF mode is used to grow the layered LiCoO on the current collector. 2 The positive electrode material forms a positive electrode material layer with a thickness of 6µm.

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

[0119] Prepare electrolyte: Mix EC, EMC and DEC in a volume ratio of 4:3:3 to obtain a solvent. Add lithium salt LiPF 6 , lithium salt LiPF 6 The concentration is 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 into a button battery.

[0122] Comparative Example 2

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

[0124] Step 1: Provide Al foil as a 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, 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] Step 2: A working gas with a flow rate of 20 sccm is introduced into the magnetron sputtering chamber. The working gas includes argon and oxygen with a volume ratio of 9:1. The working gas pressure is adjusted to 0.8 Pa, the power is set to 160 W, and the RF mode is used to grow the layered LiCoO on the current collector. 2 The positive electrode material forms a positive electrode material layer with a thickness of 6µm.

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

[0127] Prepare electrolyte: Mix trifluoropropylene carbonate (TFPC), methyl trifluoroethyl carbonate (MTFEC), 3,3,3-trifluoropropionate (tFEP), and 1,3,5-trifluorobenzene (TFB) in a volume ratio of 1.5:2:1.5:5 to obtain a solvent. Add lithium salt LiPF 6 , lithium salt LiPF 6 The concentration of trifluoropropane trimethoxysilane (TTS) was 1 mol / L to obtain a basic high-voltage electrolyte. The additive trifluoropropane trimethoxysilane (TTS) was added to the basic electrolyte in an amount of 2% of the mass of the basic electrolyte.

[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 into a button battery.

[0130] Comparative Example 3

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

[0132] Step 1: Provide Al foil as a 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, 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 is introduced into the magnetron sputtering chamber at a flow rate of 50 sccm, the working pressure is adjusted to 3 Pa, the power is set to 120 W, and LiFe is deposited on the current collector using the RF mode. 0.5 Co 0.5 PO 4 The positive electrode material forms 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 electrolyte: Mix trifluoropropylene carbonate (TFPC), methyl trifluoroethyl carbonate (MTFEC), 3,3,3-trifluoropropionate (tFEP), and 1,3,5-trifluorobenzene (TFB) in a volume ratio of 1.5:2:1.5:5 to obtain a solvent. Add lithium salt LiPF 6 , lithium salt LiPF 6 The concentration of trifluoropropane trimethoxysilane (TTS) was 1 mol / L to obtain a basic high-voltage electrolyte. The additive trifluoropropane trimethoxysilane (TTS) was added to the basic electrolyte in an amount of 2% of the mass of the basic electrolyte.

[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 into 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 1C current, 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 at which the capacity decayed to 80% was recorded.

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

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

[0145]

[0146] It can be seen from the test results in Table 1 that the cycle performance of the lithium ion batteries prepared in Examples 1 to 7 is significantly improved compared with Comparative Examples 1 to 3, indicating that the lithium ion battery 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] Among them, compared with Example 1, the cycle performance of Example 4 and Example 5 is further improved, and the first discharge specific capacity is also improved, which is due to the excellent ion conductivity and high voltage resistance of the surface protection layer, which ensures the effective transmission of lithium ions at the interface under high voltage conditions. At the same time, the surface protection layer can further protect the inner layer positive electrode active material and avoid harmful side reactions between the positive electrode material and the electrolyte.

[0148] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A positive electrode of a battery, characterized in that: It includes a current collector, a substrate material layer and an epitaxial growth material layer, wherein the substrate material layer is arranged on the current collector, the epitaxial growth material layer is arranged on the 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 LiCoO2 with a layered structure.

2. The positive electrode of a battery as claimed in 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. The positive electrode of the battery according to claim 1, characterized in that The battery positive electrode meets at least one of the following characteristics (1) to (2): (1) The in-plane lattice constant of the positive electrode material with an olivine structure is 9.5-14.5Å, and the in-plane lattice constant of the layered LiCoO2 is 11.1-14.2Å; (2) The lattice mismatch between the positive electrode material having an olivine structure and the layered structure LiCoO2 is less than 8%.

4. The positive electrode of a battery according to any one of claims 1 to 3, characterized in that The positive electrode of the battery also includes 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 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.

5. The positive electrode of the battery as claimed in claim 4, characterized in that The battery positive electrode meets at least one of the following characteristics (1) to (3): (1) The thickness of the substrate material layer is 2µm~8µm; (2) The thickness of the epitaxial growth material layer is 1µm to 4µm; (3) The thickness of the surface protection layer is 5 nm to 20 nm.

6. 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 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.

7. The method for preparing a positive electrode of a battery according to claim 6, characterized in that: The steps of preparing the epitaxial growth material layer include: A working gas with a flow rate of 10sccm~100sccm 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 0.2Pa~1Pa, the power is 100W~200W, and the epitaxial growth material layer is grown on the substrate material layer using a radio frequency mode.

8. The method for preparing a positive electrode of a battery according to claim 6 or 7, characterized in that: The preparation method further comprises the following steps: 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.

9. A lithium ion battery, characterized in that: The invention comprises a shell and a positive battery electrode as claimed in any one of claims 1 to 5 arranged in the shell, or a positive battery electrode, a negative battery electrode, an electrolyte and a separator prepared by the preparation method as claimed in any one of claims 6 to 8.

10. The lithium ion battery according to claim 9, characterized in that 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-difluoroethyl methanesulfonic acid, lithium difluorophosphate and 2,2,2-trifluoroethyl methanesulfonate.

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