CN116314629A - Lithium metal negative electrode for solid lithium metal battery, preparation method and application - Google Patents

Lithium metal negative electrode for solid lithium metal battery, preparation method and application Download PDF

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CN116314629A
CN116314629A CN202310453927.XA CN202310453927A CN116314629A CN 116314629 A CN116314629 A CN 116314629A CN 202310453927 A CN202310453927 A CN 202310453927A CN 116314629 A CN116314629 A CN 116314629A
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lithium metal
solid
lpscl
negative electrode
powder
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张琳
刘涛
李建伟
赖康荣
赵国庆
慈立杰
闵光辉
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Shandong University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
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    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention belongs to the technical field of solid lithium metal batteries, relates to modification of a lithium metal negative electrode of a solid lithium metal battery, and particularly relates to a lithium metal negative electrode for a solid lithium metal battery, a preparation method and application thereof. The preparation method comprises the following steps: polishing the surface of the lithium metal sheet from bright light to matte light to convert P 2 S 5 The powder is scattered on the surface of the lithium metal sheet after being brushed, and then P is rubbed 2 S 5 Powder causes P 2 S 5 The powder is uniformly coatedThe surface of the polished lithium metal sheet is smeared with the paint to remove redundant P 2 S 5 Powder, the P on the surface of the lithium metal sheet after being brushed is carried out by adopting a force of 1.5 to 2.0N 2 S 5 Flattening the powder, and then standing for reaction for 10-24 hours to obtain the product; the whole preparation process is carried out in argon atmosphere. The invention not only effectively prevents the contact between the solid electrolyte and lithium metal and improves the interface stability, but also effectively inhibits the formation of lithium dendrite, ensures the circulation stability and can also improve the energy density of the solid lithium metal battery.

Description

Lithium metal negative electrode for solid lithium metal battery, preparation method and application
Technical Field
The invention belongs to the technical field of solid lithium metal batteries, relates to modification of a lithium metal negative electrode of a solid lithium metal battery, and particularly relates to a lithium metal negative electrode for a solid lithium metal battery, a preparation method and application thereof.
Background
The disclosure of this background section is only intended to increase the understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.
Solid state electrolytes are the core of all-solid state lithium battery technology and can be divided into two main categories, polymer solid state electrolytes and inorganic solid state electrolytes. Inorganic solid electrolytes can in turn be divided into oxide-based, sulfide-based and halide-based. In these solid electrolyte materials, li in sulfide electrolyte 6 PS 5 The Cl (LPSCl) electrolyte has the remarkable advantages of high ionic conductivity, good mechanical deformability, easiness in synthesis and the like. The LPSCl self-supporting film using polytetrafluoroethylene as a binder has extremely high ion conductivity, and provides possibility for improving the power density and the energy density of the all-solid-state lithium battery. In the contact process of the LPSCl film and Li metal, the electrolyte is easily reduced by the Li metal, and decomposition reaction occurs, so that the interface impedance is increased, and the battery cycle stability is reduced. Moreover, electrons tend to accumulate at grain boundaries, lithium dendrites generally grow at sulfide electrolyte grain boundaries, eventually breaking down the electricityElectrolyte, causing the battery to short. In addition, polytetrafluoroethylene is capable of reacting with lithium metal to form conductive carbon.
The introduction of a polymeric buffer layer between the solid electrolyte and the lithium metal can effectively alleviate the interface problem, but the introduction of this additional buffer layer will form two new interfaces, namely the interface where the buffer layer is in contact with the solid electrolyte and the interface where the buffer layer is in contact with the lithium metal negative electrode. Due to the introduction of the interface buffer layer, it is difficult to precisely control the thickness of the interface layer. Accordingly, corresponding interface resistance and space charge effect problems arise. The passivation surface formed by immersing lithium metal in an organic solvent improves the stability of the lithium anode. However, toxic organic solvents can pollute the environment.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a lithium metal negative electrode for a solid lithium metal battery, a preparation method and application thereof, which not only effectively prevent solid electrolyte from contacting lithium metal and improve interface stability, but also effectively inhibit lithium dendrite formation, ensure cycle stability and also improve energy density of the solid lithium metal battery. Meanwhile, the preparation method can avoid using toxic organic solvents, is simple, and can realize green and large-scale production.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
on one hand, the preparation method of the lithium metal negative electrode for the solid lithium metal battery comprises the steps of brushing the surface of a lithium metal sheet from bright light to matte light, and carrying out P 2 S 5 The powder is scattered on the surface of the lithium metal sheet after being brushed, and then P is rubbed 2 S 5 Powder causes P 2 S 5 The powder is uniformly smeared on the surface of the lithium metal sheet after being brushed to remove redundant P 2 S 5 Powder, the P on the surface of the lithium metal sheet after being brushed is carried out by adopting a force of 1.5 to 2.0N 2 S 5 Flattening the powder, and then standing for reaction for 10-24 hours to obtain the product; the whole preparation process is carried out in argon atmosphere.
The invention utilizes lithium metal and P 2 S 5 Reduction reaction is carried out, and solvent-free brush plating method is adopted to deposit lithiumA protective layer is synthesized on the surface of the metal, so that the contact between the solid electrolyte and lithium metal is effectively prevented, and the interface stability is improved. P because the solid electrolyte cannot be deformed 2 S 5 The lithium dendrites are easy to generate in pores after being granular and reacting with the surface of the lithium metal sheet, and the research shows that the lithium dendrites are easy to generate in the pores, thereby influencing the circulation stability; the invention adopts the rolling mode to roll P 2 S 5 The powder is flattened, so that the generation of pores can be avoided, and the powder can be better attached to the solid electrolyte. Further research shows that the flattening force should be appropriate; if the applied force is too small, the leveling effect is poor, and the circulation stability cannot be ensured; if the applied force is too large, the lithium metal sheet is deformed, and the electrochemical performance is affected. Therefore, the invention adopts the force of 1.5 to 2.0N to flatten P 2 S 5 The powder can ensure electrochemical performance and cycling stability.
In another aspect, a lithium metal negative electrode for a solid state lithium metal battery is obtained by the above-described method of preparation.
In a third aspect, a lithium metal negative electrode for a solid state lithium metal battery as described above is used in the preparation of a solid state lithium metal battery.
In a fourth aspect, a solid state lithium metal battery comprises the lithium metal negative electrode, the LPSCl solid state electrolyte and the positive electrode for the solid state lithium metal battery, wherein the modified surface of the lithium metal negative electrode for the solid state lithium metal battery is in contact with the LPSCl solid state electrolyte.
The beneficial effects of the invention are as follows:
the invention utilizes P 2 S 5 Forming a protective layer on the surface of the lithium metal by a solvent-free brush plating method, and applying a force of 1.5 to 2.0N to form P 2 S 5 Powder leveling, research shows that the lithium metal negative electrode prepared by the method not only effectively prevents the contact between the solid electrolyte and lithium metal and improves the interface stability, but also effectively inhibits the formation of lithium dendrites, ensures the circulation stability and can improve the energy density of the solid lithium metal battery.
Experiments show that the lithium metal cathode and the hot rolling for the solid lithium metal battery provided by the inventionThe LPSCl film prepared by the process is matched to form a symmetrical battery with the thickness of 0.1mA cm -2 The stable circulation can be carried out for more than 500 hours under the current density; the formed full cell can provide 155.7mA h g at 0.5C rate -1 The discharge specific capacity of (3) was 400 times, and the capacity retention was 75.5%.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 shows the preparation of P according to an embodiment of the present invention 2 S 5 Characterization of morphology structure of @ Li, (a) preparation of P for all-solid lithium battery by solvent-free method 2 S 5 Schematic program of @ Li, (b) cross-sectional morphology of Li metal, (c) cross-sectional morphology of Li metal by brush face treatment, (d) P 2 S 5 Cross-sectional morphology of @ Li, (e) P 2 S 5 Surface morphology of @ Li, (f) P 2 S 5 EDS energy spectrum results of @ Li;
FIG. 2 shows the preparation of P according to an embodiment of the present invention 2 S 5 Structural spectrum of @ Li, (a) Raman spectrum of lithium metal, (b) P 2 S 5 Raman spectrum of (c) P 2 S 5 Raman Spectroscopy of @ Li, (d) lithium metal and P 2 S 5 XRD pattern of @ Li;
FIG. 3 shows an embodiment of the invention P 2 S 5 Particles and P 2 S 5 XPS fine spectrum of @ Li, (a) P 2 S 5 Li 1s spectrum of particles, (b) P 2 S 5 Li 1s Spectrum of @ Li, (c) P 2 S 5 P2P spectrum of particles, (d) P 2 S 5 P2P spectrum of @ Li, (e) P 2 S 5 S2P spectrum of particles, (f) P 2 S 5 S2 p spectrum of @ Li;
FIG. 4 is a graph showing the electrochemical performance characteristics of a battery according to an embodiment of the present invention, (a) Li/LPSCl thin film/Li and P 2 S 5 @Li/LPSCl film/P 2 S 5 At 0.1mAcm @ Li -2 Voltage distribution at lower cycle time, (b) and (c) Nyquist plot of symmetric cell at different cycles, (d) P 2 S 5 Nyquist plot of @ Li/LPSCl film/p2s5@li symmetric cell at different temperatures, (e) activation energy of symmetric cell;
FIG. 5 is a Nyquist plot of Li/LPSCl film/Li versus battery of an embodiment of the present invention, (a) different cycles, (b) 11 cycles;
FIG. 6 is a graph of critical current density for a battery of an embodiment of the invention, (a) Li/LPSCl film/Li, (b) P 2 S 5 @Li/LPSCl film/P 2 S 5 @ Li, (c) is an enlarged region of (a), and (d) is an enlarged region of (b);
FIG. 7 shows an embodiment of the invention P 2 S 5 @Li/LPSCl film/P 2 S 5 Stability test results graph of @ Li on cell, (a) P 2 S 5 @Li/LPSCl film/P 2 S 5 At 0.2mAcm @ Li -2 Voltage distribution at lower cycle time, (b) schematic diagram of stripping/electroplating behavior of lithium metal anode, (c) P 2 S 5 Schematic of stripping/electroplating behavior of the @ Li negative electrode;
FIG. 8 is a graph showing the results of electrochemical performance test of an all-solid battery according to an embodiment of the present invention, (a) an assembly schematic of an all-solid battery, (b) a Li/LPSCl thin film/LNO@NCM811P 2 S 5 @Li/LPSCl film
Cycling performance of/LNO@NCM811 at 0.1C current density, (C) Li/LPSCl film
Charge-discharge curve of/LNO@NCM811 cell at 0.1C, (d) Li and P 2 S 5 ASSLbs at a rate of 0.1 to 5c, (e) charge-discharge curves, (f) and (g) P 2 S 5 At 0.05mV s for @ Li/LPSCl film/LNO @ NCM811 -1 And CV curves at different scan rates, (h) linear fitting of oxidation peaks, (i)
P 2 S 5 Cycling performance at 0.5C for @ Li/LPSCl film/LNO @ NCM 811;
FIG. 9 is a graph showing the results of electrochemical performance tests of all-solid-state batteries before and after modification in accordance with the examples of the present invention, (a) cycle performance of Li/LPSCl thin film/LNO@NCM811 at 0.1C, (b) charge and discharge curves of Li/LPSCl thin film/LNO@NCM811 at 0.1C, (C) charge and discharge curves of unmodified batteries in rate performance test, (d) Li/LPSCl thin film/LNO@NCM811 at 0.05mV s -1 CV Curve under, (e) Li
CV curves of LPSCl film/LNO@NCM811 at different scan rates;
FIG. 10 shows an embodiment P of the present invention 2 S 5 XPS spectrum of LSPCl film after cycling at Li/LPSCl film/LNO@NCM811, (a) fine spectrum of P2P, (b) fine spectrum of S2P, (c) fine spectrum of Cl 2P, and (d) fine spectrum of F1S.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
In view of the poor interface stability and cycle stability of the existing lithium metal negative electrode for the solid lithium metal battery, and the need of adopting a toxic organic solvent in the preparation method, the invention provides a lithium metal negative electrode for the solid lithium metal battery, and a preparation method and application thereof.
An exemplary embodiment of the invention provides a preparation method of a lithium metal cathode for a solid-state lithium metal battery, which comprises the steps of brushing the surface of a lithium metal sheet from bright light to matte light, and carrying out P 2 S 5 The powder is scattered on the surface of the lithium metal sheet after being brushed, and then P is rubbed 2 S 5 Powder causes P 2 S 5 The powder is uniformly smeared on the surface of the lithium metal sheet after being brushed to remove redundant P 2 S 5 Powder, the P on the surface of the lithium metal sheet after being brushed is carried out by adopting a force of 1.5 to 2.0N 2 S 5 Flattening the powder, standing for reaction for 10-24 hours,obtaining the product; the whole preparation process is carried out in argon atmosphere.
In some embodiments, the lithium metal sheet has a thickness of 150 to 250 μm.
In some embodiments, friction P 2 S 5 The powder proceeds continuously in one direction. For example in the circumferential direction.
In some embodiments, the moisture and oxygen content are maintained below 0.01ppm in an argon atmosphere during the preparation process.
In another embodiment of the present invention, a lithium metal negative electrode for a solid-state lithium metal battery is provided, which is obtained by the above-described preparation method.
The third embodiment of the invention provides an application of the lithium metal negative electrode for the solid-state lithium metal battery in preparing the solid-state lithium metal battery.
In a fourth embodiment of the present invention, a solid-state lithium metal battery is provided, including the lithium metal negative electrode, the LPSCl solid electrolyte and the positive electrode for a solid-state lithium metal battery, where the modified surface of the lithium metal negative electrode for a solid-state lithium metal battery is in contact with the LPSCl solid electrolyte.
In some embodiments, polytetrafluoroethylene is used as a binder in the LPSCl solid electrolyte. The binder is 3-7 per mill of the total mass of the LPSCl solid electrolyte.
In some embodiments, the LPSCl solid electrolyte is an LPSCl thin film having a thickness of 40-80 μm.
In one or more embodiments, the LPSCl film is prepared using a hot rolling process. Specifically, the temperature of the hot rolling process is 70-80 ℃.
In some embodiments, the active material of the positive electrode is LiNbO 3 @LiNi 0.8 Co 0.1 Mn 0.1 O 2 。
In order to enable those skilled in the art to more clearly understand the technical scheme of the present invention, the technical scheme of the present invention will be described in detail below with reference to specific examples and comparative examples.
Examples
P 2 S 5 Preparation of @ Li negative electrode
The lithium foil (200 μm) was first rubbed gently with a brush until the surface became matt. P (P) 2 S 5 Grinding and ball milling the powder, and refining 20mg of fine P 2 S 5 Powder-spreading on the treated lithium surface, pressing the metal surface with fingers with gloves, and continuously rubbing for 5 min in one direction to obtain P 2 S 5 The powder is uniformly smeared on the whole lithium surface, and then redundant P is removed 2 S 5 And (3) powder. Will P 2 S 5 The @ Li sample was placed between two polyimide films (Mylar, PPI Adhesive Products Ltd.,100 μm) and rolled (with a force of 2.0N applied) using a roller press (Hohsen Corp., HSAM-615H) until P 2 S 5 The thickness of the @ Li sample reaches 150 μm to ensure a uniform thickness of P 5 S 2 An @ Li layer. The modified lithium metal can be used after reacting for 12 hours in a glove box. In the comparative experiment, lithium metal was rubbed in the same manner without adding powder. All the above steps were carried out in an argon-filled glove box, in which the moisture and oxygen content was kept below 0.01 ppm.
The LPSCl solid electrolyte film is prepared by adopting a hot rolling process. Li6PS5Cl powder is used as a solid electrolyte, and Polytetrafluoroethylene (PTFE) is used as a binder. The LPSCl solid electrolyte powder was first sieved through a 200 mesh screen and then charged into a 50ml zirconia tank with a mass ratio of LPSCl to PTFE stoichiometry of 99.5:0.5. Then, 5g of ball-milling beads having a diameter of 3 mm were used at a rotational speed of 200r min -1 The mixture was ball-milled with a planetary ball mill for 1 hour. Then rolled with a stainless steel cylindrical rod at 75 ℃ until the desired thickness (50 μm) is reached. Punching the obtained material into a sheet with an area of 0.785cm by a sheet cutter 2 Is used for assembling button cells. All the above steps were carried out in an argon-filled glove box, in which the moisture and oxygen content was kept below 0.01 ppm.
P 2 S 5 Assembly of @ Li Battery
To assemble a symmetrical battery, the solid electrolyte film is sandwiched between two lithium sheets of 6mm diameter and 0.1mm thickness or modified P 2 S 5 @ Li. The sandwich was placed in a CR2025 coin cell and then pressed with a hydraulic press at a pressure of 5 MPa. The above procedure was carried out in an argon-filled glove box with water and oxygen contents kept below 0.01 ppm.
To assemble the full cell, a composite positive electrode with a diameter of 7mm is attached to one side of an electrolyte film, and metallic lithium or P with a diameter of 6mm 2 S 5 The @ Li was attached to the other side of the electrolyte membrane, the cell was placed in a CR2025 coin cell, the sandwich was placed in a CR2025 coin cell, and then pressed with a hydraulic press at a pressure of 5.5 MPa. All the above schemes were carried out in an argon filled glove box with water and oxygen levels kept below 0.01 ppm.
Results and discussion
As shown in fig. 1a, a schematic of a solvent-free lithium metal surface modification process for an all-solid state battery, the surface being modified by scrubbing and rubbing. In a typical process, the surface of lithium metal (200 μm) is scrubbed with a brush in one direction until it becomes matt. Then the pretreated P 2 S 5 The powder was sprayed onto the brush face lithium metal surface and the metal was rubbed in one direction with a gloved finger. Finally, unreacted powder was removed from the surface with polyethylene. By forcing P 2 S 5 The particles are contacted with lithium metal by using lithium metal and P 2 S 5 The spontaneous reduction reaction between the two makes the surface of lithium metal load even solid coating. P was studied using Scanning Electron Microscopy (SEM) and energy spectroscopy (EDS) 2 S 5 Morphology and elemental distribution of the @ Li anode. Fig. 1b is an optical photograph and SEM surface of the original lithium metal surface. As shown in fig. 1c, the surface of the lithium metal after the brushing surface treatment is in an irregular saw tooth shape, and the contact with the ultra-thin (50 μm) LPSCl film increases the risk of short circuit of the battery, the surface compactness is poor, and the risk that more lithium ions are attracted and deposited to form lithium dendrites in the circulation process is increased. As shown in FIG. 1d, P 2 S 5 The Li metal surface density after the coating modification is obviously improved, and the surface of the irregular serrated upper lithium metal is uniformly coated with a 7 mu m very flat and compact solid coating, which means that the contact between the lithium metal and the LPSCl film is improvedIs good. As shown in fig. 1e, P 2 S 5 The coating-modified lithium metal is coated with a solid coating over a large area and continuously. When P 2 S 5 When the particles rub against the surface of the lithium metal, the cavity on the surface of the lithium metal is filled with P 2 S 5 The particles fill and press against their surfaces, promoting spontaneous solid state reduction reactions. At the same time, the P and S elements are uniformly distributed in the P 2 S 5 The entire surface of the @ Li anode (fig. 1 f). This means P 2 S 5 The @ Li can inhibit the growth of lithium dendrites caused by non-uniform lithium deposition.
Detection of lithium Metal and P Using Raman Spectroscopy 2 S 5 In situ spontaneous reactions between particles. FIGS. 2a, b are Li metal and P 2 S 5 Raman spectrum of the particles. As shown in FIG. 2c, with P 2 S 5 Raman peak of particles, P 2 S 5 The absence of a representative raman peak at @ Li and at 388.3, 402.2 and 417.8cm -1 P of (2) 2 S 6 4- 、P 2 S 7 4- And PS (polystyrene) 4 3- The occurrence of a signal indicating the passage of lithium metal through P 2 S 5 The scrubbing/rubbing process, which occurs as a complete transition to lithiated species, forms various anions. As shown in fig. 2d, the peak centered at 20 degrees belongs to the diffraction peak of the sealing transparent polymer. There is no obvious diffraction peak of thiophosphate, reflecting its amorphous character, and it is highly expected to regulate Li+ flux and buffer interface region lattice mismatch compared with crystal structure.
Further confirmed by X-ray photoelectron spectroscopy (XPS) analysis 2 S 5 Spontaneous reactions between the particles can occur. FIGS. 3a, 3c and 3e show P 2 S 5 XPS fine spectrum of particles. As can be seen from the P2P and S2P spectra, P is caused by repeated rubbing and milling processes 2 S 5 Lithiation of powder, P 2 S 5 The binding energy of the particles shifts. These lithium compounds mainly include Li 3 PS 4 、Li 4 P 2 S 7 And Li (lithium) 4 P 2 S 6 Consistent with the results of raman spectroscopy. In FIG. 3b, 54.6eTwo gaussian component peaks at V and 55.4eV can be fitted to XPS spectra of Li 1S, where the peak at 54.6eV is related to Li-S bonds and the peak at 55.4eV is related to Li-O bonds in fig. 1 b. Furthermore, no characteristic peak of 53.1eV lithium metal was found, further confirming the presence of an in-situ LSP protection layer. As shown in FIG. 3d, 6 different bin states (P-S-P, P can be fitted δ+ -S δ-X And Li (lithium) 3 P). The peak located at 132.5eV in the fine spectrum of P2P is attributable to the P-S-P bond. In addition, a special pair of P2P peaks appear at 132.1eV and 131.3eV, which can be attributed to P δ+ -S δ-X (Li 3 PS 4 X＝3/4、Li 4 P 2 S 7 And Li (lithium) 4 P 2 S 6 X＝2/3、P 2 S 5 X=0), indicating the presence of PS 4 3- 、P 2 S 7 4- And P 2 S 6 4- . Li is present at 128.1eV 3 P, mainly composed of LPSs. Likewise, the S2P spectrum also confirms P δ+ -S δ-X And a response peak of P-S-P (FIG. 2 d).
As shown in FIG. 4a, the Li/LPSCl film/Li symmetric battery has a current density of 0.1mA cm -2 With a low overpotential of about 6mV, a short circuit occurs after 14 hours of cycling. During the circulation, PTFE and lithium metal surface can be defluorinated, and conductive carbon (sp 2 ) Thus, a poor mixed conductive interface is formed, generation of lithium dendrites is accelerated, and the lithium dendrites pierce through an electrolyte connecting a positive electrode and a negative electrode inside the battery, eventually causing an internal short circuit. Unstable adverse reactions easily occur in the continuous conductive interface growth and dendrite growth process between lithium metal and electrolyte, and considerable safety problems may be caused due to low dendrite growth efficiency of lithium. P (P) 2 S 5 @Li/LPSCl film/P 2 S 5 The @ Li symmetrical battery can be at 0.1mA cm at room temperature -2 The lower provides a long cycle life of 500 hours with no significant jitter in the voltage curve. Therefore, the in-situ protective LPSs layer has good engineering performance, can prevent side reaction between lithium metal and PTFE, inhibit growth of lithium dendrites, and is beneficial to improving electroplating/stripping efficiency of lithium ions.
Further toEIS of Li-symmetric cells were tested to reveal interfacial dynamics evolution during discharge/charge cycles. The original impedance of the Li/Li symmetric cell was 124 Ω, and after 10h of cycling the resistance of the original cell decreased, indicating that the reaction of the Li metal with PTFE reduced the impedance (fig. 5 a), and after 22h of cycling the impedance value indicated a short circuit of the cell (fig. 5 b). P in FIG. 4b and FIG. 4c 2 S 5 @Li/P 2 S 5 The @ Li symmetrical battery has little change in impedance after 90 hours of cycling. This further demonstrates that the in-situ LPS protective layer improves the stability of its interface, and the electrochemical performance of the symmetric cell is greatly improved. As shown in fig. 4d, P 2 S 5 @Li/LPSCl film/P 2 S 5 Nyquist curve for @ Li symmetric cells at 25 ℃ to 75 ℃. The activation energy (Ea) was calculated according to Arrhenius (1-1) law to give P 2 S 5 @Li/LPSCl film/P 2 S 5 The value of the @ Li interface is 0.13eV (FIG. 5 e).
δ＝Aexp(-Ea/kt)， (1-1)
Wherein δ represents ion conductivity, a is a factor before finger, ea is activation energy, k is a boltzmann constant, and t is temperature. The low interface Ea is attributable to P 2 S 5 An LPS protective layer formed by Li metal, and high ion conductivity and low energy barrier of the Li metal in LPS, which is beneficial to Li + Rapid transport through the interface.
Critical Current Density (CCD) is an important parameter characterizing the above-mentioned improvement of interface stability. To study Li/LPSCl film/Li and P 2 S 5 @Li/LPSCl film/P 2 S 5 Dendrite inhibition ability of @ Li symmetric cells were assembled to test the CCD before and after modification, and the results obtained are shown in fig. 6. The CCD of the Li/LPSCl film/Li symmetrical battery is only 0.2mAcm -2 (FIGS. 5a, 5 c) which are related to side reactions between the LPSCl film and lithium metal during cycling. In addition, the contact of PTFE with lithium metal increases the electron conductivity of the LPSCl film, accelerating dendrite formation, resulting in a short circuit of the cell. As shown in fig. 4b and 4d, P 2 S 5 @Li/LPSCl film/P 2 S 5 The CCD of the symmetric battery at room temperature is improved to 0.4mA cm -2 。
Further measurement ofTest P 2 S 5 @Li/LPSCl film/P 2 S 5 At 0.2mAcm for a @ Li symmetrical cell -2 Stability at current density, as shown in fig. 7a, can be cycled stably for over 100 hours. To intuitively highlight the advantages of the in-situ SEI layer, lithium metal and P 2 S 5 Schematic diagrams of the lithium deposition process of the @ Li anode are shown in fig. 7b, 7 c. When the LPSCl film is in contact with lithium metal, the non-uniformity of the lithium metal surface results in non-uniform lithium deposition. PTFE in the LPSCl film reacts with Li metal to generate conductive carbon, thereby accelerating the formation of lithium dendrites. Unlike unevenly deposited lithium metal, P 2 S 5 The @ Li anode can uniformly deposit lithium metal under high current density, and the stability of an interface is remarkably improved.
Further evaluation of P by assembling button cell 2 S 5 Electrochemical performance of Li negative electrode. As shown in FIG. 8a, LPSCl thin film was used as solid electrolyte, LPSCl electrolyte particles and LNO@NCM811 (LiNbO) 3 @LiNi 0.8 Co 0.1 Mn 0.1 O 2 Reference is made to Xuelei Li, liubeng Jin, dawei Song, hongzhou Zhang, xixi Shi, zhhenyu Wang, lianqi Zhang, lingyun Zhu, liNbO 3 -coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 The mixture of cathode with high discharge capacity and rate performance for all-solid-state lithium battery, journal of Energy Chemistry,40 (2020) 39-45) particles is a composite positive electrode (preparation process: liNbO 3 @LiNi 0.8 Co 0.1 Mn 0.1 O 2 Is a positive electrode material. LPSCl powder is electrolyte, VGCF is active material conductive agent, PTFE is binder. The stoichiometric mass ratio of the positive electrode material, electrolyte, active material conductive agent and binder was 100:100:6:1, and added to a 50ml zirconia can. Then, the mixture was ball milled for 1.5 hours at a rotational speed of 300r min -1 Then hot-pressed into a uniform mixture at 80 ℃ to form a composite positive electrode), lithium metal and P 2 S 5 Schematic configuration of @ Li as negative electrode, respectively. In the all-solid-state lithium battery, the area load of the composite positive electrode is about 3mg cm in the potential range of 2.7-4.3V in charge and discharge -2 . As shown in FIG. 8b, li/LPSCl film/LNO@NCM811 and P 2 S 5 Long-cycle first discharge specific capacities of 197 and 177mAh g at room temperature of 0.1C of @ Li/LPSCl film/LNO @ NCM811 all-solid-state battery -1 . After 150 cycles, the capacity was maintained at 81% of the initial capacity (P 2 S 5 @ Li anode). Notably, except for the first charge-discharge period, P 2 S 5 The average coulomb of @ Li as the negative electrode cell was over 99.5%, indicating that the electrode reaction was highly reversible. As shown in fig. 8i, the performance of the all-solid-state lithium battery was tested at a high current density of 0.5C, and the capacity retention rate reached 75.5% after 400 cycles, showing good cycle stability and rate performance. After 11 cycles of unmodified Li/LPSCl thin film/lno@ncm811 cell, the charging curve was overcharged and significantly fluctuated due to the tiny lithium dendrites and dissolution generated by the lithium metal as the negative electrode (fig. 9 d). The side effect is formed because the LPSCl film has poor inhibition capability to lithium dendrite, the electrolyte and lithium metal react seriously, PTFE reacts with lithium metal, and electrons are easily accepted and defluorinated to generate sp 2 . Thus, the coulombic efficiency of the original sample was very low (fig. 9 a). Furthermore, at 0.1, 1.0, 3.0 and 5.0C current densities, P 2 S 5 Reversible discharge capacities of 195, 128, 59 and 33mAh g for @ Li/LPSCl film/LNO @ NCM811 battery -1 When the current density is reduced from 5.0C to 0.1C, the corresponding capacity can be restored to 186mA hg -1 . In contrast, all-solid-state lithium batteries assembled from virgin Li metal show lower reversible capacity at different rates, and overcharging also occurs during cycling (fig. 9 c). As shown in fig. 8e, P 2 S 5 Constant current charge and discharge curve of @ Li/LPSCl film/LNO @ NCM811 battery rate capability. As shown in FIG. 8f, P 2 S 5 The @ Li/LPSCl film/@ NCM811 cell was scanned at a rate of 0.05 mVs -1 The CV curve of the first 4 cycles (2.7-4.4V) shows no significant change in the peak voltage difference of the sample, indicating good reversibility of lithium ion intercalation/extraction. The CV curve of the unmodified cell showed significant drift, indicating poor electrochemical performance (fig. 9 d). By measuring different scan rates (0.05-0.6 mV s -1 ) CV curve of the lower all-solid-state lithium battery, and Li in the drawing is deeply understood + Is shown (FIG. 8 g). As the scan rate increases, the current intensity of the redox peak increases significantly. The lithium ion diffusion coefficient was calculated according to Randes-Sevcik equation (1-2), for P 2 S 5 The redox process of the @ Li/LPSCl thin film/LNO @ NCM811 cell was subjected to a reaction kinetics study.
Ip ＝ (2.69 × 105) n 3/2 AD Li 1/2 C Li ν 1/2 (1-2)
P 2 S 5 The absolute value of the slope of the fitted line for the @ Li/LPSCl film/lno @ ncm811 cell indicates its excellent rate capability and cycling stability. Li/LPSCl film/@ NCM811 cell at 0.4mV s- 1 Significant polarization and shorting occurred at scan speed, and no li+ mobility coefficient could be calculated (fig. 9 e). The in situ LPS protective layer effectively blocks the reaction between LPSCl films, thus P 2 S 5 The @ Li/LPSCl membrane/LNO @ NCM811 cell has excellent electrochemical properties.
The composite positive electrode film, the electrolyte film and the negative electrode are pressed into an integrated sandwich structure in the battery sealing stage, and the viscosity of PTFE (polytetrafluoroethylene) is added, so that the morphology of the surface of lithium after circulation cannot be observed, the XPS is used for representing a sample after circulation, and the P is determined by comparing and analyzing the representation before and after circulation 2 S 5 Impact of the SEI layer formed in situ with lithium metal on the electrochemical performance of all-solid-state batteries.
As shown in fig. 10, P 2 S 5 The Raman spectrum of the @ Li/LPSCl film/LNO @ NCM811 after 100 cycles of circulation at 0.5C current density shows that P, S, cl, F and C elements in the LPSCl film are not chemically changed, and typical sulfur silver germanium ore type electrolyte is presented, which is consistent with the XPS spectrum result of the original LPSCl film, and further proves that the in-situ LPS protective layer has the capability of inhibiting side reactions.
By P 2 S 5 Spontaneous reaction with lithium metal, the SEI protective layer without solvent participation is prepared in situ. A LPS lithiation interface layer with high lithium dendrite inhibition capability is synthesized by adopting a solvent-free scrubbing/friction method. The SEI film is used as bridge between LPSCl film and Li metal, and can improve Li + In lithiumThe transport efficiency of the metal sulfide electrolyte interface and the surface energy can be effectively adjusted to reduce the cyclic polarization. Thanks to this lithiated interfacial layer, P 2 S 5 @Li/LPSCl film/P 2 S 5 The @ Li symmetrical battery can be at 0.1mA cm -2 The stable cycle can be performed for more than 500 hours at current density. Using high nickel positive electrode material LNO@NCM811 as positive electrode, LNO@NCM811/LPSCl film/P 2 S 5 The @ Li all-solid-state battery has high specific capacity and excellent cycle stability performance, and reaches 155mAh g at 0.5C -1 The capacity retention in 400 cycles was 75.5%. The embodiment provides a promising design method for improving the interface between the lithium metal anode and the SSE, and is beneficial to the practical application of the sulfide solid electrolyte with high energy density in the all-solid-state lithium battery.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A process for preparing the lithium metal negative electrode of solid-state lithium metal battery features that the surface of a lithium metal sheet is brushed to become matt from bright light, and P 2 S 5 The powder is scattered on the surface of the lithium metal sheet after being brushed, and then P is rubbed 2 S 5 Powder causes P 2 S 5 The powder is uniformly smeared on the surface of the lithium metal sheet after being brushed to remove redundant P 2 S 5 Powder, the P on the surface of the lithium metal sheet after being brushed is carried out by adopting a force of 1.5 to 2.0N 2 S 5 Flattening the powder, and then standing for reaction for 10-24 hours to obtain the product; the whole preparation process is carried out in argon atmosphere.
2. The method for preparing a lithium metal negative electrode for a solid lithium metal battery according to claim 1, wherein the thickness of the lithium metal sheet is 150 to 250 μm.
3. The method for producing a lithium metal negative electrode for a solid-state lithium metal battery according to claim 1, wherein the friction P 2 S 5 The powder proceeds continuously in one direction.
4. The method for producing a lithium metal negative electrode for a solid-state lithium metal battery according to claim 1, wherein the contents of moisture and oxygen in an argon atmosphere in the production process are each kept below 0.01 ppm.
5. A lithium metal negative electrode for a solid-state lithium metal battery, characterized by being obtained by the production method according to any one of claims 1 to 4.
6. Use of a lithium metal negative electrode for a solid state lithium metal battery according to claim 5 for the preparation of a solid state lithium metal battery.
7. A solid state lithium metal battery comprising the lithium metal negative electrode for a solid state lithium metal battery of claim 5, an LPSCl solid state electrolyte, and a positive electrode, the modified face of the lithium metal negative electrode for a solid state lithium metal battery being in contact with the LPSCl solid state electrolyte.
8. The solid state lithium metal battery of claim 7, wherein polytetrafluoroethylene is used as a binder in the LPSCl solid state electrolyte; preferably, the binder is 3 to 7 per mill of the total mass of the LPSCl solid electrolyte.
9. The solid lithium metal battery of claim 7, wherein the LPSCl solid electrolyte is an LPSCl thin film having a thickness of 40-80 μm;
preferably, the LPSCl film is prepared by a hot rolling process, and more preferably, the temperature of the hot rolling process is 70-80 ℃.
10. The solid state lithium metal battery of claim 7, wherein the active material of the positive electrode is LiNbO 3 @LiNi 0.8 Co 0.1 Mn 0.1 O 2 。
CN202310453927.XA 2023-04-20 2023-04-20 Lithium metal negative electrode for solid lithium metal battery, preparation method and application Pending CN116314629A (en)

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