A three-dimensional porous LiAl alloy lithium metal anode based on an Al2O3-rich SEI protective film, and its preparation method and application

Abstract

The present invention relates to the field of battery technology, and more specifically to a three-dimensional porous LiAl alloy with an Al2O3-rich SEI protective film, as well as its preparation method and application. The present invention first constructs a three-dimensional porous LiAl alloy through an in-situ electrochemical dealloying method. Then, through an in-situ high-current pretreatment method, an Al2O3-rich SEI protective film is formed on the surface and in the pores of the three-dimensional porous LiAl alloy. Ultimately, a three-dimensional porous LiAl alloy with an Al2O3-rich SEI protective film is constructed. Using this as a lithium metal anode can improve the cycle life and safety of batteries.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a metal lithium negative electrode of a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film, and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] As the demand for battery capacity in electronic devices and electric vehicles continues to increase, the existing commercial lithium-ion batteries with mature technology and widespread application can no longer meet the capacity requirements. The main reason is that the theoretical specific capacity of the traditional graphite negative electrode used in lithium-ion batteries is only 372mA hg -1 , low energy density, which in turn limits the capacity of lithium-ion batteries. In order to meet the battery capacity requirements of various devices, lithium negative electrode materials with higher specific capacity are urgently needed. Metal lithium negative electrode has extremely high capacity density (theoretical specific capacity is 3860mA hg -1 ) and the lowest relative potential (-3.040V vs. standard hydrogen electrode), making it the best candidate for future lithium battery negative electrode materials.

[0004] However, due to the uneven distribution and transmission of charge and charged particles, uneven dendrites will grow on the surface, and problems such as unlimited volume changes, serious side reactions and instability of the solid electrolyte interface (SEI) have hindered the application of metallic lithium negative electrodes. The prior art discloses a variety of methods for solving lithium dendrites, including: electrolyte modification, direct surface modification of metallic lithium negative electrodes, and the use of three-dimensional structural materials as current collectors to form negative electrodes in combination with metallic lithium. However, electrolyte modification has the problems of narrow application scope and high cost; direct surface modification of metallic lithium negative electrodes also has the problems of narrow application scope and high cost, and the preparation process is complicated; the method of using three-dimensional nanomaterials as current collectors to form negative electrodes in combination with metallic lithium has the problems of poor lithium affinity, poor structural stability, and poor cycle stability. Moreover, these methods cannot obtain a stable SEI. Summary of the Invention

[0005] In order to overcome the above problems, the present invention provides a metal lithium negative electrode based on a three-dimensional porous LiAl alloy with an Al2O3-rich SEI protective film, and a preparation method and application thereof. The present invention is based on in-situ pretreatment technology, including in-situ electrochemical dealloying and in-situ high current pretreatment, and designs and synthesizes a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film. Using it as a metal lithium negative electrode can improve the electron / ion transfer rate, inhibit the growth of lithium dendrites, maintain the surface and volume stability of the electrode, and achieve highly stable, safe and long-cycle performance.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film, comprising:

[0008] (1) In an inert gas atmosphere, the LiAl alloy is delithiated by an in-situ electrochemical dealloying method to obtain a three-dimensional porous LiAl alloy;

[0009] (2) In a pure oxygen atmosphere, the three-dimensional porous LiAl alloy was subjected to an in-situ high current pretreatment method to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0010] The second aspect of the present invention provides a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film prepared by the above preparation method.

[0011] The third aspect of the present invention provides the use of the three-dimensional porous LiAl alloy based on the Al2O3-rich SEI protective film as a metallic lithium negative electrode.

[0012] A fourth aspect of the present invention provides a metallic lithium negative electrode, wherein the metallic lithium negative electrode is the three-dimensional porous LiAl alloy based on the above-mentioned Al2O3-rich SEI protective film.

[0013] A fifth aspect of the present invention provides a primary / secondary battery comprising the above-mentioned metallic lithium negative electrode.

[0014] The beneficial effects of the present invention are:

[0015] The present invention first constructs a three-dimensional porous LiAl alloy through an in-situ electrochemical dealloying method, and then forms an Al2O3-rich SEI protective film on the surface and in the pores of the three-dimensional porous LiAl alloy through an in-situ high-current pretreatment method. Finally, a three-dimensional porous LiAl alloy based on the Al2O3-rich SEI protective film is constructed. Using it as a metallic lithium negative electrode can improve the cycle life and safety of the battery. First, the three-dimensional porous LiAl alloy skeleton structure provides a stable framework for lithium deposition / stripping, buffers volume changes, and maintains the stability of the anode volume. Secondly, the LiAl alloy has excellent lithium affinity, and the lithium affinity sites are evenly distributed on the bicontinuous skeleton, uniform local current density, guides the orderly deposition of lithium, and inhibits the growth of lithium dendrites. In addition, the Al2O3-rich SEI protective film can effectively inhibit the side reactions between metallic lithium and the electrolyte, thereby reducing lithium loss and improving cycle reversibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 XRD patterns of commercially available LiAl alloys and the three-dimensional porous LiAl alloys prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3;

[0018] Figure 2 Scanning electron microscope images of three-dimensional porous LiAl alloys prepared at the same delithiation rate and different delithiation capacity in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3; wherein (a) and (b), (e) and (f), (i) and (j), and (m) and (n) are top views at different magnifications, respectively; (c) and (d), (g) and (h), (k) and (l), and (o) and (p) are cross-sectional views at different magnifications, respectively;

[0019] Figure 3 The scanning electron microscope images of the three-dimensional porous LiAl alloy prepared in Example 1, Comparative Example 4 and Comparative Example 5 at the same delithiation capacity and different delithiation rates are shown; (a) and (b) are 0.3 mA cm -2 SEM images at different magnifications, (c) and (d) at 0.5 mA cm -2 Scanning electron microscope images at different magnifications, (e) and (f) are 1 mA cm -2 Scanning electron microscope images at different magnifications.

[0020] Figure 4Scanning electron microscope images of three-dimensional porous LiAl alloys with Al2O3-rich SEI protective films prepared in Example 1 and Comparative Examples 6 and 7 at the same high current density and different cycle numbers;

[0021] Figure 5 Scanning electron microscope images of three-dimensional porous LiAl alloys with Al2O3-rich SEI protective films prepared in Example 1 and Comparative Example 8 at the same number of cycles and different high current densities;

[0022] Figure 6 The scanning electron microscope images of the three-dimensional porous LiAl alloy, pure lithium foil, and pure LiAl alloy after high current pretreatment in Example 1, Comparative Example 9, and Comparative Example 10, respectively, (a) and (b) are the three-dimensional porous LiAl alloy prepared in Example 1 at 1 mA cm- 2 SEM images of the plane and cross section after 40 cycles (40th); (c) and (d) are pure lithium foil at 1 mA cm -2 SEM images of the plane and cross section after 40 cycles; (e) and (f) are pure LiAl alloys at 1 mA cm -2 Scanning electron microscope images of the plane and cross section after 40 cycles;

[0023] Figure 7 In Experimental Example 1, the three-dimensional porous LiAl alloy with a SEI protective film rich in Al2O3, the three-dimensional porous LiAl alloy and pure lithium were used as negative electrode materials at 1 mA cm -2 and 10 mA cm -2 Cyclic stability test results at current density;

[0024] Figure 8 These are the full-cell electrochemical performance test results at 1C using three-dimensional porous LiAl alloy with an Al2O3-rich SEI protective film, three-dimensional porous LiAl alloy, and pure lithium as negative electrode materials in Experimental Example 1. DETAILED DESCRIPTION

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0026] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0027] A first typical embodiment of the present invention provides a method for preparing a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film, comprising:

[0028] (1) In an inert gas atmosphere, the LiAl alloy is delithiated by an in-situ electrochemical dealloying method to obtain a three-dimensional porous LiAl alloy;

[0029] (2) In a pure oxygen atmosphere, the three-dimensional porous LiAl alloy was subjected to an in-situ high current pretreatment method to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0030] In one or more embodiments, in step (1), the mass fraction of aluminum in the raw material LiAl alloy is less than 0.5%, preferably 0.2%.

[0031] In one or more embodiments, in step (1), the method for delithiation of LiAl alloy by in-situ electrochemical dealloying includes:

[0032] In the electrolyte, LiAl alloy is used as the positive electrode and copper foil as the negative electrode, and current is passed to remove lithium.

[0033] Preferably, the lithium removal rate is 0.4 to 0.6 mA cm -2 , the lithium removal capacity is 14-16 mAh cm -2 ; Preferably, the lithium removal rate is 0.5 mA cm -2 , the lithium removal capacity is 15 mAh cm -2 .

[0034] Preferably, the electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of dioxolane (DOL) and dimethyl ether (DME), and the volume ratio of the two is 1:0.9~1.1, preferably 1:1; the solute is LiNO3 and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the mass fraction of the solute LiNO3 is 1.5%~2.5%, preferably 2%; the concentration of the solute LiTFSI is 0.8~1.2 mol / L, preferably 1 mol / L.

[0035] In one or more embodiments, before performing the in-situ high current pretreatment method, the three-dimensional porous LiAl alloy is cleaned with dimethyl carbonate (DMC) to remove electrolyte and impurities on the electrode surface.

[0036] In one or more embodiments, in step (2), the method of performing an in-situ high current pretreatment on the three-dimensional porous LiAl alloy specifically includes:

[0037] In the electrolyte, three-dimensional porous LiAl alloy was used as the negative electrode and copper foil was used as the positive electrode for in-situ high current pretreatment.

[0038] Preferably, the electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of dioxolane (DOL) and dimethyl ether (DME), and the volume ratio of the two is 1:0.9~1.1, preferably 1:1; the solute is LiNO3 and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the mass fraction of the solute LiNO3 is 1.5%~2.5%, preferably 2%; the concentration of the solute LiTFSI is 0.8~1.2 mol / L, preferably 1 mol / L.

[0039] Preferably, the current density of the high current pretreatment is 0.8-1.2 mA cm -2 , the cycle is 38 to 42 times; preferably, the current density of the high current pretreatment is 1 mA cm -2 , the cycle is 40 times.

[0040] A second typical embodiment of the present invention provides a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film prepared by the above preparation method.

[0041] A third typical embodiment of the present invention provides the use of the three-dimensional porous LiAl alloy based on the Al2O3-rich SEI protective film as a metallic lithium negative electrode.

[0042] A fourth typical embodiment of the present invention provides a metallic lithium negative electrode, wherein the metallic lithium negative electrode is the three-dimensional porous LiAl alloy based on the above-mentioned Al2O3-rich SEI protective film.

[0043] A fifth typical embodiment of the present invention provides a primary / secondary battery including the above-mentioned metal lithium negative electrode.

[0044] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0045] In the following examples, the LiAl alloy was purchased from Tianjin Zhongneng Lithium Industry, with an Al content of 0.2% and a thickness of 0.5 mm.

[0046] Example 1

[0047] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 0.5 mA cm -2 , the lithium removal capacity is 15 mAh cm -2 , that is, the lithium removal time in this embodiment is 30h.

[0048] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0049] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 1 mA cm -2 After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0050] Comparative Example 1

[0051] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 0.5 mA cm -2 , the lithium removal capacity is 5 mAh cm -2 , that is, the lithium removal time in this embodiment is 10 h.

[0052] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0053] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 1 mA cm -2 After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0054] Comparative Example 2

[0055] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 0.5 mA cm-2 , the lithium removal capacity is 10 mAh cm -2 , that is, the lithium removal time in this embodiment is 20h.

[0056] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0057] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 1 mA cm -2 After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0058] Comparative Example 3

[0059] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 0.5 mA cm -2 , the lithium removal capacity is 20 mAh cm -2 , that is, the lithium removal time in this embodiment is 40h.

[0060] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0061] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 1 mA cm -2 After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0062] Comparative Example 4

[0063] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 0.3 mA cm -2 , the lithium removal capacity is 15 mAh cm -2 , that is, the lithium removal time in this embodiment is 50h.

[0064] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0065] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 1 mA cm -2After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0066] Comparative Example 5

[0067] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 1 mA cm -2 , the lithium removal capacity is 15 mAh cm -2 , that is, the lithium removal time in this embodiment is 15h.

[0068] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0069] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 1 mA cm -2 After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0070] Comparative Example 6

[0071] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 0.5 mA cm -2 , the lithium removal capacity is 15 mAh cm -2 , that is, the lithium removal time in this embodiment is 30h.

[0072] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0073] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 1 mA cm -2 After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0074] Comparative Example 7

[0075] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 0.5 mA cm-2 , the lithium removal capacity is 15 mAh cm -2 , that is, the lithium removal time in this embodiment is 30h.

[0076] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0077] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 1 mA cm -2 After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0078] Comparative Example 8

[0079] In a glove box filled with high-purity argon, the commercially available LiAl alloy was first cut into discs with a diameter of 15 mm, and then assembled into the first button battery in the order of positive electrode shell, LiAl alloy positive electrode, electrolyte, polypropylene diaphragm, electrolyte, copper foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1, the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled first button battery was then taken out and in-situ electrochemical delithiation was performed using a blue battery test system, with a delithiation rate of 0.5 mA cm -2 , the lithium removal capacity is 15 mAh cm -2 , that is, the lithium removal time in this embodiment is 30h.

[0080] The first button cell after delithiation was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy, which was then cleaned with DMC to remove the electrolyte and impurities on the electrode surface and placed in a glove box to dry for use.

[0081] The dried three-dimensional porous LiAl alloy is again assembled into a button battery in the glove box. Specifically, the second button battery is assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene diaphragm, electrolyte, three-dimensional porous LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solute is LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery is then taken out and subjected to in-situ high current pretreatment. The current density of the high current pretreatment is 0.5 mA cm -2 After in-situ high current pretreatment, the second button cell was transferred to a glove box for disassembly to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

[0082] Comparative Example 9

[0083] In order to verify the advantages of the three-dimensional porous structure in high-current pretreatment, the pure Li foil was subjected to high-current pretreatment. Specifically, a button battery was assembled in a glove box, and the second button battery was assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene separator, electrolyte, pure Li foil negative electrode and negative electrode shell. Among them, the electrolyte includes a solvent and a solute, and the solvent is a mixed solution of DOL and DME (volume ratio is) 1:1. The solutes are LiNO3 and LiTFSI, and the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button battery was then taken out and subjected to in-situ high-current pretreatment. The current density of the high-current pretreatment was 1 mA cm -2 , the cycle is 40 times.

[0084] Comparative Example 10

[0085] In order to verify the advantages of the three-dimensional porous structure in high-current pretreatment, pure LiAl alloy was subjected to high-current pretreatment. Specifically, a button cell was assembled in a glove box, and a second button cell was assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene separator, electrolyte, LiAl alloy negative electrode and negative electrode shell. The electrolyte includes a solvent and a solute. The solvent is a mixed solution of DOL and DME (volume ratio is 1:1), the solutes are LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 is 2%; the concentration of the solute LiTFSI is 1 mol / L. The assembled second button cell was then taken out and subjected to in-situ high-current pretreatment. The current density of the high-current pretreatment was 1 mA cm -2 , the cycle is 40 times.

[0086] Figure 1The XRD patterns of the commercially available LiAl alloy of the present invention and the three-dimensional porous LiAl alloy prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are shown in FIG. Figure 1 It can be seen that the composition of the three-dimensional porous LiAl alloys prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 has not changed, and the composition stability is high.

[0087] Figure 2 The scanning electron microscope images of the three-dimensional porous LiAl alloy prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 at the same delithiation rate and different delithiation capacity are shown. Figure 2 As can be seen from the figure, the LiAl alloy in Example 1 has an appropriate pore size and a uniformly distributed porous structure, with the cross-sectional view showing an ordered electron / ion channel structure. In contrast, the pores in Comparative Examples 1 and 2 are larger, the channel structure is disorganized, and no bicontinuous skeleton structure is formed. In Comparative Example 3, the pore size is smaller and the structure is more dense, which is not conducive to the rapid and efficient transmission of electrons and ions. Therefore, it can be seen that the structure of the pores in three-dimensional porous LiAl alloys can be controlled by regulating the delithiation capacity.

[0088] Figure 3 The scanning electron microscope images of the three-dimensional porous LiAl alloy prepared in Example 1, Comparative Example 4 and Comparative Example 5 at the same delithiation capacity and different delithiation rates are shown. Figure 3 As can be seen, in Comparative Example 4, at a low delithiation rate, almost no porous structure is formed, resulting in a relatively smooth surface. At a higher delithiation rate, the pores formed in Comparative Example 5 are larger and unevenly distributed. This demonstrates that the structure of the pores in a three-dimensional porous LiAl alloy can be controlled by regulating the delithiation rate.

[0089] Figure 4 The scanning electron microscope images of the three-dimensional porous LiAl alloy with Al2O3-rich SEI protective film prepared in Example 1 and Comparative Examples 6 and 7 at the same high current density and different cycle times are shown. Figure 4 As can be seen in the figure, after 20 high-current cycles in Comparative Example 6, the Al2O3 layer formed was thin due to the short cycle time, resulting in severe lithium dendrites and side reactions. After 60 high-current cycles, the Al2O3 insulating layer formed on the surface of the three-dimensional porous LiAl alloy became thicker, which was not conducive to the rapid migration of electrons and ions.

[0090] Figure 5 The scanning electron microscope images of the three-dimensional porous LiAl alloy with Al2O3-rich SEI protective film prepared in Example 1 and Comparative Example 8 at the same cycle number and different high current density are shown. Figure 5 It can be seen from the graph that due to the low current density, the anode surface is relatively rough and the lithium deposition is uneven.

[0091] Figure 6 The scanning electron microscope images of the three-dimensional porous LiAl alloy, pure lithium foil, and pure LiAl alloy after high current pretreatment in Example 1, Comparative Example 9, and Comparative Example 10 are shown. Figure 6 It can be seen that (a) and (b) are the three-dimensional porous LiAl alloy prepared in Example 1 at 1mAcm- 2 The scanning electron microscope images of the plane and cross section after 40 cycles (40th) show that the electrode surface is uniform and flat without dendrite formation. (c) and (d) are pure lithium foil at 1 mA cm -2 Scanning electron microscope images of the plane and cross section at 40th, it can be seen that a large number of lithium dendrites and dead lithium are observed on the surface of pure lithium foil, and the electrode structure is destroyed, resulting in severe voltage polarization and short circuit when the pure lithium foil is used as the negative electrode after high current pretreatment. (e) and (f) are pure LiAl alloy at 1mA cm -2 Scanning electron microscope images of the plane and cross section at 40th, broken electrode structure and dead lithium can be observed on the surface of pure LiAl alloy.

[0092] Experimental Example 1

[0093] The three-dimensional porous LiAl alloy with an Al2O3-rich SEI protective film prepared in Example 1, the three-dimensional porous LiAl alloy, and pure lithium were used as negative electrode materials to prepare a third button cell in an argon-filled glove box. Specifically, the third button cell was assembled in the order of positive electrode shell, copper foil positive electrode, electrolyte, polypropylene separator, electrolyte, negative electrode material, and negative electrode shell. The electrolyte included a solvent and a solute, wherein the solvent was a mixed solution of DOL and DME (volume ratio was 1:1), the solutes were LiNO3 and LiTFSI, the mass fraction of the solute LiNO3 was 2%, and the concentration of the solute LiTFSI was 1 mol / L.

[0094] At 1 mA cm -2 and 10 mA cm -2 The third button cell was tested for cycle stability at a current density of Figure 7 As shown, from Figure 7 As can be seen from the figure, the three-dimensional porous LiAl alloy with Al2O3-rich SEI protective film has a 1mA cm -2 The stable cycle was carried out for 900 h at a current density of 10 mA cm -2 The stable cycle time exceeds 400h at a higher current density.

[0095] Experimental Example 2

[0096] The three-dimensional porous LiAl alloy with an Al2O3-rich SEI protective film prepared in Example 1, the three-dimensional porous LiAl alloy, and pure lithium were used as negative electrode materials, and LFP was used as the positive electrode material. A fourth button cell was prepared in an argon-filled glove box. Specifically, the fourth button cell was assembled in the order of the positive electrode shell, LFP positive electrode, electrolyte, polypropylene separator, electrolyte, negative electrode material, and negative electrode shell. The electrolyte used was a 1M lithium hexafluorophosphate (LiPF6) solution dissolved in ethylene carbonate (EC) and dimethyl carbonate (DMC) (solvent volume ratio of 1:1).

[0097] The electrochemical performance test of the fourth button cell was carried out at 1C. Figure 8 As shown, from Figure 8 As can be seen from the figure, the full battery with a three-dimensional porous LiAl alloy with an Al2O3-rich SEI protective film as the negative electrode was cycled 200 times at 1C, with an initial specific capacity of 203.5 mAh g -1 After 200 cycles, the specific capacity is 186.5 mAh g -1 , the capacity retention rate is as high as 91.6%. At the same time, the average Coulombic efficiency is 99.98%. The initial specific capacity of the full battery with three-dimensional porous LiAl alloy as the negative electrode is 171.2 mAh g -1 The specific capacity after 200 cycles at 1C is 152.8 mAh g -1 , the capacity retention rate is 89.3%, and the Coulombic efficiency remains at a high level. In contrast, the initial specific capacity of the full battery with pure lithium as the negative electrode is only 130.5 mAh g -1 The specific capacity after 200 cycles at 1C is 75.8 mAh g -1 , the capacity decays rapidly, and the capacity retention rate is only 58.1%.

[0098] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film, characterized in that: include: (1) In an inert gas atmosphere, the LiAl alloy is delithiated by an in-situ electrochemical dealloying method to obtain a three-dimensional porous LiAl alloy; (2) In a pure oxygen atmosphere, the three-dimensional porous LiAl alloy was subjected to an in-situ high current pretreatment method to obtain a three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film.

2. The preparation method according to claim 1, wherein In step (1), the mass fraction of aluminum in the raw material LiAl alloy is less than 0.5%.

3. The preparation method according to claim 2, wherein In step (1), the mass fraction of aluminum in the raw material LiAl alloy is 0.2%.

4. The preparation method according to claim 1, wherein In step (1), the method for removing lithium from the LiAl alloy by an in-situ electrochemical dealloying method includes: In the electrolyte, LiAl alloy is used as the positive electrode and copper foil as the negative electrode, and current is passed to remove lithium.

5. The preparation method according to claim 4, wherein The lithium removal rate is 0.4~0.6 mA cm -2 , the lithium removal capacity is 14~16 mAh cm -2 .

6. The preparation method according to claim 5, wherein The delithiation rate was 0.5 mA cm -2 , the lithium removal capacity is 15 mAh cm -2 .

7. The preparation method according to claim 4, wherein The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of dioxolane (DOL) and dimethyl ether (DME), with a volume ratio of 1:0.9~1.1; the solute is LiNO3 and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the mass fraction of the solute LiNO3 is 1.5%~2.5%; the concentration of the solute LiTFSI is 0.8~1.2 mol / L.

8. The preparation method according to claim 7, wherein The volume ratio of dioxolane (DOL) and dimethyl ether (DME) is 1:1; the mass fraction of the solute LiNO3 is 2%; and the concentration of the solute LiTFSI is 1 mol / L.

9. The preparation method according to claim 1, wherein In step (2), the method of performing in-situ high current pretreatment on the three-dimensional porous LiAl alloy specifically includes: In the electrolyte, three-dimensional porous LiAl alloy was used as the negative electrode and copper foil was used as the positive electrode for in-situ high current pretreatment.

10. The preparation method according to claim 9, characterized in that The electrolyte includes a solvent and a solute, wherein the solvent is a mixed solution of dioxolane (DOL) and dimethyl ether (DME), with the volume ratio of the two being 1:0.9~1.1; the solute is LiNO3 and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), with the mass fraction of the solute LiNO3 being 1.5%~2.5%; and the concentration of the solute LiTFSI being 0.8~1.2 mol / L.

11. The preparation method according to claim 10, characterized in that The volume ratio of dioxolane (DOL) and dimethyl ether (DME) is 1:1; the mass fraction of the solute LiNO3 is 2%; and the concentration of the solute LiTFSI is 1 mol / L.

12. The preparation method according to claim 9, wherein The current density of high current pretreatment was 0.8~1.2 mA cm -2 , the cycle is 38~42 times.

13. The preparation method according to claim 12, wherein The current density of the high current pretreatment was 1 mA cm -2 , the cycle is 40 times.

14. A three-dimensional porous LiAl alloy based on an Al2O3-rich SEI protective film prepared by the preparation method according to any one of claims 1 to 13.

15. Use of the three-dimensional porous LiAl alloy based on the Al2O3-rich SEI protective film as claimed in claim 14 as a metallic lithium negative electrode.

16. A metallic lithium negative electrode, characterized in that: The metallic lithium negative electrode is the three-dimensional porous LiAl alloy based on the Al2O3-rich SEI protective film as claimed in claim 14.

17. A primary / secondary battery, characterized in that: Including the metallic lithium negative electrode as described in claim 16.

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