Negative electrode material with artificial SEI membrane, preparation method of negative electrode material and application of negative electrode material in lithium ion battery

Abstract

The invention discloses a negative electrode material with an artificial SEI film and a preparation method and application of the negative electrode material in a lithium ion battery, the negative electrode material with the artificial SEI film provided by the invention comprises a negative electrode material matrix and the artificial SEI film coated on at least one side surface of the negative electrode material matrix, the preparation raw materials of the artificial SEI membrane comprise a fluorine-containing organic compound. According to the invention, the fluorine-containing organic compound is used as rolling oil to roll the negative electrode material, fluorine atoms in the fluorine-containing organic compound are active for lithium metal in the negative electrode material, lithium fluoride can be formed on the surface of the negative electrode material while the negative electrode material is rolled and thinned, and a protective layer is artificially constructed on the thinned negative electrode material surface. And as an SEI film, a negative electrode material is protected in the charge-discharge process, and the electrochemical performance of the negative electrode material is improved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a negative electrode material with an artificial SEI film, its preparation method, and its application in lithium-ion batteries. Background Technology

[0002] Lithium metal anodes are one solution for high-energy-density lithium batteries. However, due to uneven charge density distribution, lithium metal anodes are prone to lithium dendrite growth, which can puncture the separator and cause short circuits. Furthermore, lithium metal has high reactivity, and upon contact with the electrolyte, it spontaneously forms a solid electrolyte interphase (SEI). During charge and discharge, lithium metal volume deformation and lithium dendrite formation can cause SEI rupture, allowing exposed lithium metal to continue reacting with the electrolyte to form another SEI, consuming electrolyte and leading to reduced coulombic efficiency, decreased capacity, and poor cycle stability. One approach to address these issues is to construct an artificial SEI film on the lithium metal surface. Artificial SEI films possess excellent electrochemical stability and electronic insulation, preventing continuous electrolyte decomposition. Their high mechanical modulus can suppress dendrite growth and volume changes in the lithium metal anode during cycling. Additionally, the high ionic conductivity of the artificial SEI film can further enhance the conductivity of lithium metal. + Uniform deposition is achieved, thereby suppressing the growth of lithium dendrites.

[0003] Currently, the mainstream methods for constructing artificial SEI films all involve secondary processing of the finished lithium anode and involve various raw material chemicals, resulting in complex production processes. Therefore, how to achieve efficient and large-scale industrial production of lithium anodes with artificial SEI films is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a negative electrode material with an artificial SEI film, its preparation method, and its application in lithium-ion batteries.

[0005] The technical problem solved by this invention is achieved by the following technical solution.

[0006] The present invention provides a negative electrode material with an artificial SEI film, comprising a negative electrode material substrate and an artificial SEI film covering at least one side surface of the negative electrode material substrate, wherein: the negative electrode material substrate contains lithium metal, and the raw materials for preparing the artificial SEI film include fluorine-containing organic compounds.

[0007] In some embodiments of the present invention, the fluorinated organic compound is a fluorine-substituted organic compound, wherein the general formula of the organic compound is C0. x H y O z S m P n, where: x=1-20, y=4-40, z=1-8, m=0-4, n=0-4.

[0008] In some embodiments of the present invention, the fluorinated organic compounds include fluorinated carbonate compounds, fluorinated phosphate compounds, and fluorinated sulfone compounds. Preferably, the carbonate compounds include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate, dihexyl carbonate, dioctyl carbonate, ethylene carbonate, propylene carbonate, and methyl ethyl carbonate; the sulfone compounds include dimethyl sulfoxide; and the phosphate compounds include one or more of trimethyl phosphate and triethyl phosphate.

[0009] In some embodiments of the present invention, the viscosity of the fluorinated organic compound at 25°C is 1.0-3.0 mPa·s.

[0010] In some embodiments of the present invention, the negative electrode material matrix is ​​made of lithium metal or a lithium alloy.

[0011] The present invention also provides a method for preparing the above-mentioned anode material with an artificial SEI film, comprising the following steps: providing an anode material, using a fluorinated organic compound as rolling oil, rolling the anode material on a roller press to obtain an ultrathin anode material with an artificial SEI film.

[0012] In some embodiments of the present invention, the negative electrode material is rolled on a roller press, the interval between intermittent replenishment of rolling oil in the roller press system is 15-30s, the duration of each replenishment of rolling oil is 2.0-4.0s, and the winding speed of the ultra-thin negative electrode material is 10-20m / min.

[0013] In some embodiments of the present invention, the negative electrode material is made of metallic lithium or lithium alloy, the thickness of the negative electrode material before rolling is ≥100μm, and the thickness of the ultra-thin negative electrode material after rolling is ≤50μm.

[0014] The present invention also provides a lithium-ion battery, comprising the above-described negative electrode material having an artificial SEI film or the negative electrode material having an artificial SEI film prepared by the above-described preparation method.

[0015] The present invention also provides an application of the above-mentioned lithium-ion battery in energy storage devices, electrical devices or electronic devices.

[0016] The present invention has the following beneficial effects: (1) The negative electrode material with an artificial SEI film provided by the present invention includes a negative electrode material substrate and an artificial SEI film covering at least one side surface of the negative electrode material substrate, wherein: the negative electrode material substrate contains lithium metal, and the raw materials for preparing the artificial SEI film include fluorinated organic compounds. The fluorinated organic compounds contain fluorine atoms, which are reactive with lithium metal and can react with the lithium metal in the negative electrode material to generate lithium fluoride (LiF), thereby forming an artificial SEI protective layer on the surface of the negative electrode material.

[0017] (2) The method for preparing a negative electrode material with an artificial SEI film provided by the present invention uses fluorine-containing organic compounds as rolling oil to roll the negative electrode material, which can not only avoid the introduction of impurity elements during rolling, but also simultaneously construct an artificial SEI film on the surface of the negative electrode material.

[0018] (3) The method for preparing a negative electrode material with an artificial SEI film provided by the present invention uses a fluorinated organic compound as rolling oil. During the production process, the rolling oil is continuously and uniformly covered on the surface of the negative electrode material and reacts with lithium in the negative electrode material to generate lithium fluoride, thereby obtaining a negative electrode material with an artificial SEI film. Moreover, the rolling oil, as a lubricant, can reduce the coefficient of friction, reduce roll wear, control the temperature of the rolled piece, and improve the surface quality of the product. A negative electrode material with an artificial SEI film on the surface can be directly obtained after rolling treatment. The above process can realize the large-scale production of ultra-thin negative electrode materials while constructing an artificial SEI film in situ, reducing process steps and saving production costs.

[0019] (4) The lithium-ion battery provided by the present invention includes the above-mentioned negative electrode material with an artificial SEI film or the negative electrode material with an artificial SEI film prepared by the above-mentioned preparation method. The ultrathin negative electrode material with an artificial SEI film has significantly reduced SEI film impedance and charge transfer impedance; the ultrathin negative electrode material with an artificial SEI film has significantly reduced nucleation overpotential and significantly increased cycle time.

[0020] (5) The application of the lithium-ion battery provided by the present invention in energy storage devices, electrical devices or electronic devices expands the application scope of lithium-ion batteries. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1A physical image of an ultrathin lithium strip with an artificial SEI film protective layer provided for this invention; Figure 2 The images show the thickness of the lithium strip before and after rolling. Figure 3 Dark field image of the surface morphology of the ultrathin lithium strip with an artificial SEI film protective layer prepared in Example 1; Figure 4 Bright-field image of the surface morphology of the ultrathin lithium strip with an artificial SEI film protective layer prepared in Example 1; Figure 5 Dark-field image of the surface morphology of the ultrathin lithium strip without an artificial SEI film protective layer prepared for Comparative Example 2; Figure 6 Bright-field image of the surface morphology of the ultrathin lithium strip without an artificial SEI film protective layer prepared for Comparative Example 2; Figure 7 EIS impedance spectra of symmetrical cells assembled using ultrathin lithium strips with and without artificial SEI film protective layers prepared using Examples 1, 1, and 2. Figure 8 The above figures show the nucleation overpotential curves of symmetrical cells assembled using ultrathin lithium strips with and without artificial SEI film protective layers prepared using Examples 1, 1, and 2. Figure 9 Cyclic curves of symmetrical batteries assembled using ultrathin lithium strips with and without artificial SEI film protective layers prepared using Examples 1, 1, and 2. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0024] The following is a detailed description of an anode material with an artificial SEI film, its preparation method, and its application in lithium-ion batteries, provided by embodiments of the present invention.

[0025] In a first aspect, the present invention provides a negative electrode material having an artificial SEI film, comprising a negative electrode material substrate and an artificial SEI film covering at least one side surface of the negative electrode material substrate, wherein: the negative electrode material substrate contains lithium metal, and the raw materials for preparing the artificial SEI film include fluorine-containing organic compounds.

[0026] Currently, in the large-scale rolling of anode materials such as lithium metal strips, organic liquids are used as rolling oils to lubricate and prevent sticking due to the softness and high viscosity of lithium metal. The rolling oil is uniformly distributed on the surface of the lithium strip. The rolling oils used mainly include polysiloxanes and mineral oils. Polysiloxane rolling oils introduce impurity atoms, affecting the electrochemical performance of lithium anodes, while mineral oil rolling oils, due to their high viscosity, are difficult to use for rolling ultra-thin lithium strips (≤50μm). Lithium-containing anode materials suffer from defects such as lithium dendrite growth, volume changes, and poor cycle stability. Constructing artificial SEI films is an effective way to solve these problems.

[0027] To overcome the aforementioned shortcomings, this invention proposes an anode material with an artificial SEI film. The artificial SEI film on the surface of the anode material is obtained by reacting a fluorinated organic compound with lithium in the anode material. Fluorine atoms in the fluorinated organic compound are reactive with lithium metal and can react with the anode material to generate lithium fluoride (LiF), forming the artificial SEI film. The LiF, uniformly distributed on the surface of the anode material, exhibits excellent electrochemical stability and electronic insulation, preventing the continuous decomposition of the electrolyte. Furthermore, its high mechanical modulus can suppress dendrite growth and volume changes in the lithium metal anode during cycling. The high ionic conductivity of LiF also allows for the formation of a more stable electrolyte. + Uniform deposition is achieved, thereby suppressing the growth of lithium dendrites.

[0028] In some alternative embodiments, the fluorinated organic compound is a fluorine-substituted organic compound, wherein the general formula of the organic compound is C0. x H y O z S m P n , where: x=1-20, y=4-40, z=1-8, m=0-4, n=0-4.

[0029] Fluorine-containing organic compounds are obtained by replacing some hydrogen atoms in organic compounds with fluorine atoms. The fluorine atoms in these compounds are reactive to lithium metal and can form lithium fluoride on the surface of the negative electrode material. This artificially constructs a protective layer on the surface of the negative electrode material as an SEI film, which protects the negative electrode material during charging and discharging and improves its electrochemical performance.

[0030] In some alternative embodiments, the fluorinated organic compounds include fluorinated carbonates, fluorinated phosphates, and fluorinated sulfones. Preferably, the carbonate compounds include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate, dihexyl carbonate, dioctyl carbonate, ethylene carbonate, propylene carbonate, and methyl ethyl carbonate; the sulfone compounds include dimethyl sulfoxide; and the phosphate compounds include one or more of trimethyl phosphate and triethyl phosphate.

[0031] The aforementioned fluorinated organic compounds are obtained by fluorinating organic compounds. Fluorination processes include any one or more of the following: direct fluorination, halogen exchange fluorination, liquid-phase fluorination, and electrolytic fluorination. For rolling oils with different molecular structures, the most suitable fluorination process can be selected accordingly.

[0032] In some alternative embodiments, the direct fluorination method includes the following steps: under stirring conditions, high-purity nitrogen gas is introduced into the rolling oil to purge air; then, an F2 / N2 mixture is continuously introduced into the rolling oil while the rolling oil is heated and stirred to obtain fluorinated rolling oil. Preferably, the continuous flow of high-purity nitrogen is 1.0-7.0 h; the continuous flow of a 10% F2 / N2 mixture is 0.5-8.0 h; and the heating temperature of the rolling oil is 25℃-45℃. The degree of fluorination of organic compounds can be achieved by adjusting the parameters in the fluorination process, which will not be elaborated here.

[0033] In some alternative embodiments, the viscosity of the fluorinated organic compound at 25°C is 1.0-3.0 mPa·s.

[0034] In some alternative embodiments, the negative electrode material matrix is ​​made of metallic lithium or a lithium alloy.

[0035] Secondly, the present invention provides a method for preparing the above-mentioned negative electrode material with an artificial SEI film, comprising the following steps: providing a negative electrode material, using a fluorinated organic compound as rolling oil, rolling the negative electrode material on a roller press to obtain an ultrathin negative electrode material with an artificial SEI film.

[0036] The present invention provides a method for preparing anode materials with an artificial SEI film. A fluorinated organic compound is used as the rolling oil, and the anode material is rolled using a rolling process. Because the fluorine atoms in the fluorinated organic compound of the rolling oil are reactive with lithium metal in the anode material, they can react with the lithium metal to generate lithium fluoride (LiF), forming an artificial SEI film. In the above preparation method, during the production of anode materials with an artificial SEI film, the fluorinated rolling oil is continuously and uniformly coated on the surface of the anode material and reacts with it to generate lithium fluoride. This process can simultaneously construct an artificial SEI film in situ while mass-producing ultra-thin anode materials, obtaining the finished product in a single process without the need for secondary processing. Compared with current mainstream technologies, this method improves lithium anode defects, reduces process steps, and lowers production costs.

[0037] In some embodiments of the present invention, the negative electrode material is rolled on a roller press, the interval between intermittent replenishment of rolling oil in the roller press system is 15-30s, the duration of each replenishment of rolling oil is 2.0-4.0s, and the winding speed of the super negative electrode material is 10-20m / min.

[0038] When rolling negative electrode materials on a roller press, the roller press system intermittently replenishes rolling oil. The length of the interval between each replenishment of rolling oil affects the amount of rolling oil used, thereby affecting the thickness of the artificial SEI film. The interval is 5-60 seconds, for example, it can be 5 seconds, 10 seconds, 15 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, or 60 seconds, preferably 15-30 seconds.

[0039] Each time the rolling mill replenishes the rolling oil, it takes a certain amount of time. The duration affects the amount of rolling oil used, which in turn affects the thickness of the artificial SEI film. The duration is 1-10s, for example, it can be 1.0s, 1.5s, 2.0s, 2.5s, 3.0s, 3.5s, 4.0s, 4.5s, 5.0s, 5.5s, 6.0s, 6.5s, 7.0s, 7.5s, 8.0s, 8.5s, 9.0s, 9.5s, or 10.0s, preferably 2.0-4.0s.

[0040] The winding speed of the ultra-thin anode material rolled on the roller press affects the distribution of the rolled oil, and thus affects the uniformity of the artificial SEI film. The winding speed is 1-30 m / min, for example, it can be 1 m / min, 2 m / min, 4 m / min, 6 m / min, 8 m / min, 10 m / min, 12 m / min, 14 m / min, 16 m / min, 18 m / min, 20 m / min, 22 m / min, 24 m / min, 26 m / min, 28 m / min, 30 m / min, preferably 10-20 m / min.

[0041] In some embodiments of the present invention, the negative electrode material is made of metallic lithium or a lithium alloy, the thickness of the negative electrode material before rolling is ≥100μm, and the thickness of the ultra-thin negative electrode material after rolling is ≤50μm. When the negative electrode material is made of a lithium alloy, the lithium alloy includes, but is not limited to, lithium-magnesium alloy, lithium-tin alloy, lithium-aluminum alloy, lithium-zinc alloy, lithium-indium alloy, lithium-boron alloy, lithium-calcium alloy, lithium-silicon alloy, lithium-silver alloy, lithium-antimony alloy, lithium-bismuth alloy, and lithium-carbon alloy.

[0042] Thirdly, the present invention also provides a lithium-ion battery, comprising the above-described negative electrode material having an artificial SEI film or the negative electrode material having an artificial SEI film prepared by the above-described preparation method.

[0043] Fourthly, the present invention also provides an application of the above-mentioned lithium-ion battery in an energy storage device, an electrical device, or an electronic device.

[0044] The following detailed description, in conjunction with embodiments, illustrates a negative electrode material with an artificial SEI film provided by the present invention, its preparation method, and its application in lithium-ion batteries. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into dibutyl carbonate molecules by halogen exchange fluorination to obtain fluorinated rolling oil.

[0046] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 20s, and the duration of each replenishment of rolling oil is 3.0s. The lithium strip winding speed is 15m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0047] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0048] Example 2 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into ethylene carbonate molecules by halogen exchange fluorination to obtain fluorinated rolling oil.

[0049] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 20s, and the duration of each replenishment of rolling oil is 3.0s. The lithium strip winding speed is 15m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0050] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0051] Example 3 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into dimethyl carbonate molecules by halogen exchange fluorination to obtain fluorinated rolling oil.

[0052] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 20s, and the duration of each replenishment of rolling oil is 3.0s. The lithium strip winding speed is 15m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0053] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0054] Example 4 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into diethyl carbonate molecules by halogen exchange fluorination to obtain fluorinated rolling oil.

[0055] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 20s, and the duration of each replenishment of rolling oil is 3.0s. The lithium strip winding speed is 15m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0056] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0057] Example 5 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into dibutyl carbonate molecules by halogen exchange fluorination to obtain fluorinated rolling oil.

[0058] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 20s, and the duration of each replenishment of rolling oil is 3.0s. The lithium strip winding speed is 15m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0059] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0060] Example 6 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into dipentyl carbonate molecules by direct fluorination to obtain fluorinated rolling oil.

[0061] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 15s, and the duration of each replenishment of rolling oil is 2.0s. The lithium strip winding speed is 10m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0062] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0063] Example 7 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into dioctyl carbonate molecules by direct fluorination to obtain fluorinated rolling oil.

[0064] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 25s, and the duration of each replenishment of rolling oil is 4.0s. The lithium strip winding speed is 12m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0065] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0066] Example 8 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into dihexyl carbonate molecules by liquid-phase fluorination to obtain fluorinated rolling oil.

[0067] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 25s, and the duration of each replenishment of rolling oil is 3.5s. The lithium strip winding speed is 16m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0068] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0069] Example 9 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine rolling oil is obtained by introducing fluorine atoms into dimethyl sulfoxide molecules using liquid-phase fluorination.

[0070] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 30s, and the duration of each replenishment of rolling oil is 4.0s. The lithium strip winding speed is 18m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0071] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0072] Example 10 A method for preparing an ultrathin lithium strip with an artificial SEI film includes the following steps: (1): Fluorine atoms are introduced into the trimethyl phosphate molecule by electrolytic fluorination to obtain fluorinated rolling oil.

[0073] (2): Using the above-mentioned fluorinated rolling oil as a lubricant, lithium strip is rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 30s, and the duration of each replenishment of rolling oil is 4.0s. The lithium strip winding speed is 20m / min, thus obtaining an ultra-thin lithium strip with an artificial SEI film.

[0074] (3): Using the ultrathin lithium strip with artificial SEI film as the electrode, assemble coin cells for testing.

[0075] Comparative Example 1 A method for preparing an ultrathin lithium strip with an artificial SEI film, differing from Example 1 in that a cyclopentasiloxane / polydimethylsiloxane mixture is used as a lubricant. This method introduces impurity elements onto the surface of the ultrathin lithium strip and includes the following steps: (1): Using a mixture of cyclopentylsiloxane / polydimethylsiloxane as a lubricant, ultra-thin lithium strips were rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system was 20s, and the duration of each replenishment of rolling oil was 3.0s. The lithium strip winding speed was 15m / min.

[0076] (2): Using the above-mentioned ultra-thin lithium strip as an electrode, assemble a button cell for testing.

[0077] Comparative Example 2 An ultrathin lithium strip without an artificial SEI film differs from Example 1 in that it uses unfluorinated dibutyl carbonate as a lubricant, and includes the following steps: (1): Dibutyl carbonate is used as a lubricant to roll ultra-thin lithium strip on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 20s, and the duration of each replenishment of rolling oil is 3.0s. The lithium strip winding speed is 15m / min.

[0078] (2): Using the above-mentioned ultra-thin lithium strip as an electrode, assemble a button cell for testing.

[0079] Comparative Example 3 An ultra-thin lithium strip that is difficult to roll into shape, differing from Example 1 in that it uses white oil (mineral oil) as a lubricant with a viscosity of 3.62 mPa·s (25°C), and includes the following specific steps: (1): Using white oil (mineral oil) as a lubricant, ultra-thin lithium strips are rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system is 20s, and the duration of each replenishment of rolling oil is 3.0s. The lithium strip winding speed is 15m / min.

[0080] Comparative Example 4 An ultra-thin lithium strip that is difficult to roll into shape, differing from Example 1 in that it uses cyclopentasiloxane as a lubricant with a viscosity of 0.6 mPa·s (25°C), and includes the following specific steps: (1): Using cyclopentadioxane as a lubricant, ultra-thin lithium strips were rolled on a roller press. The interval between intermittent replenishment of rolling oil in the roller press system was 20s, and the duration of each replenishment of rolling oil was 3.0s. The lithium strip winding speed was 15m / min.

[0081] Comparative Example 5 Similar to the steps in Example 1, except that the interval between intermittent replenishment of rolling oil in the roller press system is 3 seconds.

[0082] Comparative Example 6 Similar to the steps in Example 1, except that the interval between intermittent replenishment of rolling oil in the roller press system is 65 seconds.

[0083] Comparative Example 7 The steps are similar to those in Example 1, except that the duration of each replenishment of rolling oil is 0.5 seconds.

[0084] Comparative Example 8 The steps are similar to those in Example 1, except that the duration of each replenishment of rolling oil is 10 seconds.

[0085] Comparative Example 9 The steps are similar to those in Example 1, except that the lithium strip winding speed is 0.5 m / min.

[0086] Comparative Example 10 The steps are similar to those in Example 1, except that the lithium strip winding speed is 35m / min.

[0087] Battery assembly To verify the improvement of lithium-ion battery electrochemical performance by artificial SEI films, coin cell symmetric batteries were assembled using lithium-ion batteries with and without artificial SEI films as electrodes, and electrochemical tests were conducted, including the following steps: (1) Cut lithium strips with / without artificial SEI film into circular electrodes with a diameter of 14 mm; (2) The above-mentioned circular electrode is moved into an argon glove box and assembled into a button-type symmetrical battery in the order of positive electrode shell, electrode sheet, electrolyte, diaphragm, electrode sheet, gasket, spring sheet and negative electrode shell. (3) After the above coin cell was left to stand for 10 hours, the impedance was tested using an electrochemical workstation. (4) After the impedance test is completed, a cyclic test is performed on a constant current charge-discharge instrument.

[0088] Test Results Figure 1 The images show optical images of the rolling process of ultra-thin lithium strips in Examples 1, 1, 2 and 3. It can be seen that Examples 1, 1, and 2 can all successfully roll ultra-thin lithium strips, but Comparative Example 3 cannot successfully roll ultra-thin lithium strips due to the high viscosity of the white oil (mineral oil) and Comparative Example 4 cannot successfully roll ultra-thin lithium strips due to the low viscosity of the cyclopentadiene siloxane.

[0089] Figure 2 The images show the lithium strip before and after rolling. It can be observed that the thickness of the lithium strip before rolling is 107 μm, and the thickness of the ultra-thin lithium strip after rolling is 20 μm.

[0090] Figure 3 and Figure 4 The images shown are dark-field and bright-field images of the surface morphology of the ultrathin lithium strip with an artificial SEI film protective layer obtained by rolling in Example 1. Figure 5 and Figure 6 Dark-field and bright-field images of the surface morphology of the ultrathin lithium strip without an artificial SEI film protective layer prepared in Comparative Example 2 are shown respectively. It can be observed that the surface morphology of the lithium strip in Example 1 and the lithium strip in Comparative Example 2 are significantly different. The dark-field image of the lithium strip in Example 1 shows a "grayish-blue" substance, while the bright-field image shows a "black" substance, namely lithium fluoride.

[0091] Figure 7To obtain the EIS impedance spectra of symmetrical batteries assembled using ultrathin lithium strips with and without artificial SEI film protective layers prepared in Examples 1, 1, and 2, the impedance of the lithium strip in Comparative Example 1 was significantly greater than that in Examples 1 and 2 because the rolling oil used in Comparative Example 1 was a mixture of cyclopentadiene siloxane and polydimethylsiloxane, which contains silicon and has a significantly different organic molecular structure from that of lithium-ion electrolyte.

[0092] Figure 8 The diagram shows the nucleation overpotential curves of symmetrical cells assembled using ultrathin lithium strips with and without artificial SEI film protective layers prepared in Examples 1, 1, and 2. Note that residual siloxane on the surface of the lithium strip in Comparative Example 1 hinders Li... + The desolvation and deposition of lithium lead to a larger nucleation overpotential. However, since lithium fluoride is an excellent conductor of ions, the nucleation overpotential of the lithium band in Example 1 is significantly smaller than that in Comparative Example 2.

[0093] Figure 9 The cycling curves of symmetrical batteries assembled using ultrathin lithium strips with and without artificial SEI film protective layers prepared in Examples 1, 1, and 2 are shown. Compared to the lithium strips in Comparative Examples 1 and 2, the stable cycling time of the ultrathin lithium strip prepared in Example 1 is significantly increased because lithium fluoride helps to achieve uniform surface charge distribution and suppress lithium metal volume change, thus slowing down the growth of lithium dendrites.

[0094] The electrochemical performance of the ultrathin films prepared in Example 1 and Comparative Examples 5-10 is compared in the table below:

[0095] The results above demonstrate that rolling process parameters, such as the interval between intermittent oil replenishment in the roll press system, the duration of each oil replenishment, and the winding speed, significantly impact the formation of the artificial SEI film. If the oil replenishment interval is too short, the duration too long, or the winding speed too slow, excessive oil will remain on the lithium strip, hindering the reaction at the electrode / electrolyte interface. Conversely, if the oil replenishment interval is too long, the duration too short, or the winding speed too fast, insufficient oil will remain on the lithium strip, resulting in a smaller and less uniform artificial SEI film, which fails to improve the electrochemical performance of the lithium metal anode. By optimizing the rolling parameters, the formation of the artificial SEI film can be effectively controlled, leading to ultrathin lithium strips with optimal electrochemical performance.

[0096] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A negative electrode material having an artificial SEI film, characterized in that, The invention includes a negative electrode material substrate and an artificial SEI film covering at least one side of the negative electrode material substrate, wherein: the negative electrode material substrate contains lithium metal, and the raw materials for preparing the artificial SEI film include fluorine-containing organic compounds.

2. The negative electrode material with an artificial SEI film according to claim 1, characterized in that, The fluorine-containing organic compound is a fluorine-substituted organic compound, wherein: the general formula of the organic compound is CxHyOzSmPn, where: x=1-20, y=4-40, z=1-8, m=0-4, n=0-4.

3. The negative electrode material with an artificial SEI film according to claim 2, characterized in that, The fluorinated organic compounds include fluorinated carbonates, fluorinated phosphates, and fluorinated sulfones. Preferably, the carbonate compounds include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate, dihexyl carbonate, dioctyl carbonate, ethylene carbonate, propylene carbonate, and methyl ethyl carbonate; the sulfone compounds include dimethyl sulfoxide; and the phosphate compounds include one or more of trimethyl phosphate and triethyl phosphate.

4. The negative electrode material with an artificial SEI film according to claim 2, characterized in that, The viscosity of the fluorinated organic compound at 25°C is 1.0-3.0 mPa·s.

5. The negative electrode material with an artificial SEI film according to claim 1, characterized in that, The substrate of the negative electrode material is made of metallic lithium or a lithium alloy.

6. A method for preparing a negative electrode material with an artificial SEI film according to any one of claims 1-5, characterized in that, Includes the following steps: A negative electrode material is provided, and a fluorinated organic compound is used as the rolling oil to roll the negative electrode material on a roller press to obtain an ultrathin negative electrode material with an artificial SEI film.

7. The preparation method according to claim 6, characterized in that, The negative electrode material is rolled on a roller press. The roller press system intermittently replenishes the rolling oil at intervals of 15-30 seconds, and the duration of each oil replenishment is 2.0-4.0 seconds. The winding speed of the ultra-thin negative electrode material is 10-20 m / min.

8. The preparation method according to claim 6, characterized in that, The negative electrode material is made of lithium metal or lithium alloy. The thickness of the negative electrode material before rolling is ≥100μm, and the thickness of the ultra-thin negative electrode material after rolling is ≤50μm.

9. A lithium-ion battery, characterized in that, The negative electrode material having an artificial SEI film according to any one of claims 1-5 or the negative electrode material having an artificial SEI film prepared by the preparation method according to any one of claims 6-8.

10. The application of the lithium-ion battery according to claim 9 in an energy storage device, an electrical device, or an electronic device.

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