A fluorinated doped solid electrolyte and its preparation method, a battery and its preparation method

Abstract

The present invention discloses a fluorinated doped solid electrolyte and its preparation method, a battery and its preparation method, which relates to the technical field of solid electrolyte materials for batteries. The chemical composition of the solid electrolyte is Na 5‑x YSi4O 12‑x F x , where x is the doping amount of the F element, and part of the F atoms replace the sites of the O atoms in the Na5YSi4O 12 structure; Preparation method: Mix Na2CO3, Y2O3, SiO2, and NaF evenly by wet grinding to obtain a mixed slurry. The doping ratio of NaF is controlled between 0% and 30%. A solid electrolyte sheet is obtained by firing and pressing. The present invention uses a two-step solid-phase reaction to prepare a fluorinated doped solid electrolyte, and its ionic conductivity is 1.65×10 ‑3 S cm ‑2 , which can reduce the sintering temperature, improve the density of the electrolyte sheet, and the fluorinated doping can improve the interface performance and cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolyte materials for batteries, and more specifically to the technical fields of fluorinated-doped solid electrolytes and their preparation methods, batteries and their preparation methods. Background Art

[0002] Lithium-ion batteries are considered to be the most promising next-generation new batteries due to their high energy density, good cycle life, low self-discharge, etc. Replacing traditional electrolytes with intrinsically safe solid electrolytes is of great significance for solving the safety and stability problems of lithium-ion batteries. Commonly used solid electrolytes can be divided into three categories: inorganic solid electrolytes, polymer solid electrolytes, and composite solid electrolytes. Inorganic solid electrolytes have the advantages of high ionic conductivity and wide voltage windows, but they have poor contact with electrodes, and there are side reactions between some electrolytes and lithium metal, thus limiting their applications. Although polymer solid electrolytes have good interfacial contact performance, they generally have low voltage windows and low ionic conductivities, and cannot well meet market demands. Organic-inorganic composite solid electrolytes can make up for each other's deficiencies and combine the advantages of the above electrolytes. While having good interfacial contact performance, their ionic conductivities have also been improved. The following technologies are disclosed in existing patents:

[0003] The patent with publication number CN117954681A and patent name "A fluoropolymer solid electrolyte for lithium metal batteries operating at room temperature" discloses the following content: The solid electrolyte consists of a polymer matrix, ceramic fillers, a lithium salt, a weakly solvating solvent, and a dispersant; its preparation method is: first, the polymer, ceramic fillers, lithium salt, weakly solvating solvent, and dispersant are fully mixed, and then stirred to obtain a mixed slurry; the mixed slurry is coated on a glass plate and then dried to obtain a solid electrolyte membrane. The advantage of the present invention is to construct a high-flux Li+ transport path by coupling a polymer electrolyte with a weakly solvating fluoroethylene carbonate (FEC) solvent to improve the room-temperature ionic conductivity; further, a stable anion-rich weakly solvating environment is constructed using trace amounts of residual FEC, and then a solid electrolyte interface (SEI) layer rich in inorganic matter is formed, which can reduce the interfacial impedance and effectively improve the interfacial stability, ensuring the electrochemical performance of the solid-state lithium battery operating at room temperature.

[0004] The patent with publication number CN113224379A and patent name "A fluorine-doped F-LLTO composite solid electrolyte, preparation method and application" discloses the following content: The chemical composition of the composite solid electrolyte of the present invention is Li 3x La 2 / 3-x TiO 3- y F y, x = 0.12 - 0.18, y = 0.005 - 0.5, where the F atoms partially replace the sites of O atoms in LLTO. The preparation method is to first prepare the LLTO precursor slurry, then incorporate fluoride, add a polymer spinning matrix and perform electrospinning, and then obtain the fluorine-doped lithium lanthanum titanium oxide composite solid electrolyte through high-temperature sintering and solution casting. By designing the chemical composition of F-LLTO, F-LLTO@PEO is prepared by electrospinning, high-temperature sintering, and casting methods. The conductivity and lithium dendrite inhibition ability are significantly improved compared with those before doping. Assembling into a all-solid-state lithium metal battery has excellent rate performance.

[0005] Patent No. CN111952673A, titled "A High-Performance All-Solid-State Lithium Battery and Its Preparation Method", discloses the following content: A high-performance all-solid-state lithium battery and its preparation method. The method includes the following steps: By weight, uniformly mix a carbon nitride precursor and a fluorine source and perform heat treatment to obtain fluorine-doped carbon nitride powder A; then mix powder A, a lithium salt, a polymer matrix, and an organic solvent and stir to obtain a mixed solution B. Perform film-forming treatment on the mixed solution B and dry to obtain a fluorine-doped carbon nitride-polymer composite solid electrolyte; Assemble the positive electrode sheet, the fluorine-doped carbon nitride-polymer composite solid electrolyte, and the negative electrode material together by hot pressing and encapsulate with a battery case to form an all-solid-state lithium battery. The battery preparation method of the present invention realizes the unity of ionic conductivity, thermal stability, electrochemical stability, and mechanical properties. The preparation process of the composite positive electrode material and the assembly process of the all-solid-state battery significantly improve the interfacial properties of the electrode / solid electrolyte.

[0006] Although the above-mentioned fluorine-doped solid electrolyte can improve the performance of the material, the interfacial properties, cycle stability, and the ability to reduce the sintering temperature are limited. Summary of the Invention

[0007] The purpose of the present invention is to provide a fluorine-doped solid electrolyte and its preparation method, a battery and its preparation method to solve the above technical problems.

[0008] The present invention specifically adopts the following technical solutions to achieve the above purpose:

[0009] The first aspect of the present invention provides a fluorine-doped solid electrolyte. The chemical composition of the solid electrolyte is Na 5-x YSi 4 O 12-x F x , where x is the doping amount of the F element, and the F atoms partially replace the sites of O atoms in the Na 5 YSi 4 O 12 structure.

[0010] In one embodiment, the ionic conductivity of the solid electrolyte Na 5-x YSi 4 O 12-x F x is 1.65×10 -3 Scm -2 。

[0011] The second aspect of the present invention provides a method for preparing a fluorinated-doped solid electrolyte for preparing the above-mentioned fluorinated-doped solid electrolyte, comprising the following steps:

[0012] S1. Mix Na 2 CO 3 , Y 2 O 3 , SiO 2 , and NaF uniformly by wet grinding to obtain a mixed slurry;

[0013] S2. Pre-sinter the mixed slurry at a temperature of 800°C - 900°C for 5h - 6h to obtain crushed materials;

[0014] S3. Press the crushed materials into an electrolyte sheet with a thickness of 600μm - 800μm using a tablet press, and keep it at a temperature of 900°C - 950°C for 8h to obtain Na 5-x YSi 4 O 12-x F x solid electrolyte sheets with different F doping amounts.

[0015] Specifically, due to the improvement of the preparation process and material properties by fluorination doping, after doping NaF as the F element, the sintering temperature of Na 5 YSi 4 O 12 can be reduced (from 1050 - 1100°C to 900 - 950°C). The reduction of the sintering temperature can greatly reduce the energy consumption in the production process. In addition to reducing the sintering temperature, fluorination doping can also improve the density of the Na 5 YSi 4 O 12 electrolyte sheet. The density increases from 85% to 94% under the ordinary sintering process. The increase in density leads to an increase in ionic conductivity.

[0016] Regarding the improvement of the interfacial properties and cycle stability by fluorination doping, after doping and sintering with the F element, it will diffuse and concentrate on the surface of the Na 5 YSi 4 O 12 electrolyte sheet. The presence of the F layer can inhibit electronic conduction and the formation of dendrites, which is beneficial to improving the cycle stability of the battery and increasing its service life.

[0017] In one embodiment, in step S1, the doping ratio of NaF is controlled between 0% and 30%.

[0018] In one embodiment, in step S1, the doping ratio of NaF is 10%, and preliminary experiments have found that the performance is optimal when the doping ratio of NaF is 10%.

[0019] The third aspect of the present invention provides a fluorinated doped battery, including the above-mentioned fluorinated doped solid electrolyte, and the solid electrolyte is prepared by using the preparation method of the above-mentioned fluorinated doped solid electrolyte.

[0020] The fourth aspect of the present invention provides a preparation method of a fluorinated doped battery for preparing the above-mentioned fluorinated doped battery, including the following steps:

[0021] A1. Prepare a sodium vanadium phosphate cathode material;

[0022] A2. Prepare a negative electrode sheet;

[0023] A3. Assemble in the order of positive electrode shell, positive electrode sheet, electrolyte sheet, negative electrode sheet, gasket, nickel foam, and negative electrode shell, and compact with a tablet press to obtain a fluorinated doped battery.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The fluorination doping of the present invention improves the preparation process and material properties. After doping NaF as the F element, it can reduce the sintering temperature of Na 5 YSi 4 O 12 (from 1050 - 1100 °C to 900 - 950 °C). The reduction of the sintering temperature can greatly reduce the energy consumption in the production and preparation process. In addition to reducing the sintering temperature, the fluorination doping can also improve the density of the Na 5 YSi 4 O 12 electrolyte sheet. The density increases from 85% to 94% under the ordinary sintering process. The increase in density leads to an increase in ionic conductivity.

[0026] 2. The fluorination doping of the present invention improves the interface performance and cycle stability. After the F element is doped and sintered, it will diffuse and concentrate on the surface of the Na 5 YSi 4 O 12 electrolyte sheet. The existence of the F layer can inhibit electronic conduction and the formation of dendrites, which is beneficial to improving the cycle stability of the battery and extending the service life. Description of the Drawings

[0027] Figure 1 (a) is Na5 YSi 4 O 12 SEM cross-sectional view of the undoped electrolyte sheet;

[0028] Figure 1 (b) is the SEM cross-sectional view of the F-doped Na 5 YSi 4 O 12 electrolyte sheet;

[0029] Figure 1 (c) is the SEM and EDS elemental distribution of the F-doped Na 5-x YSi 4 O 12-x F x electrolyte sheet surface;

[0030] Figure 1 (d) is the surface distribution map of Na element;

[0031] Figure 1 (e) is the surface distribution map of Y element;

[0032] Figure 1 (f) is the surface distribution map of Si element;

[0033] Figure 1 (g) is the surface distribution map of O element;

[0034] Figure 1 (h) is the surface map of F element.

[0035] Figure 2 (a) is Na 5 YSi 4 O 12 and F-doped Na 5 YSi 4 O 12 relative density comparison chart;

[0036] Figure 2 (b) is the XRD pattern of the F-doped Na 5 YSi 4 O 12 electrolyte sheet;

[0037] Figure 2 (c) is the EIS impedance analysis chart of the F-doped Na 5 YSi 4 O 12 electrolyte sheet;

[0038] Figure 2 (d) is the F-doped Na 5 YSi 4 O 12Test chart of the cycling performance of a symmetric cell assembled with an electrolyte. Detailed implementation mode

[0039] 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 with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0041] Example 1

[0042] This example provides a fluorine-doped solid electrolyte, and the chemical composition of the solid electrolyte is Na 5- x YSi 4 O 12-x F x , where x is the doping amount of the F element, and F atoms partially replace O atoms at the sites in the Na 5 YSi 4 O 12 structure.

[0043] The ionic conductivity of the solid electrolyte Na 5-x YSi 4 O 12-x F x is 1.65×10 -3 S cm -2 .

[0044] Example 2

[0045] This example provides a preparation method for a fluorine-doped solid electrolyte, which is used to prepare the above-mentioned fluorine-doped solid electrolyte, and includes the following steps:

[0046] S1. Mix Na 2 CO 3 , Y 2 O 3 , SiO 2 , and NaF evenly by wet grinding to obtain a mixed slurry, and control the doping ratio of NaF between 0% and 30%;

[0047] S2. Pre-sinter the mixed slurry at a temperature of 800°C - 900°C for 5h - 6h to obtain crushed materials;

[0048] S3. Press the crushed materials into an electrolyte sheet with a thickness of 600μm - 800μm using a tablet press, and keep it at a temperature of 900°C - 950°C for 8h to obtain Na 5-x YSi 4 O 12-x F x solid electrolyte sheets.

[0049] Specifically, for the improvement of the preparation process and material properties by fluorination doping, after doping NaF as the F element, it can reduce the sintering temperature of Na 5 YSi 4 O 12 (from 1050 - 1100°C to 900 - 950°C). The reduction of the sintering temperature can greatly reduce the energy consumption in the production and preparation process. In addition to reducing the sintering temperature, fluorination doping can also improve the density of the Na 5 YSi 4 O 12 electrolyte sheet. The density increases from 85% to 94% under the ordinary sintering process. The increase in density leads to an increase in ionic conductivity.

[0050] For the improvement of the interfacial properties and cycle stability by fluorination doping, after doping and sintering with the F element, it will diffuse and concentrate on the surface of the Na 5 YSi 4 O 12 electrolyte sheet. The existence of the F layer can inhibit electronic conduction and the formation of dendrites, which is beneficial to improving the cycle stability of the battery and extending its service life.

[0051] Example 3

[0052] This example provides a preparation method of a fluorinated-doped solid electrolyte for preparing the above-mentioned fluorinated-doped solid electrolyte, including the following steps:

[0053] S1. Mix Na 2 CO 3 , Y 2 O 3 , SiO 2 , and NaF evenly by wet grinding to obtain a mixed slurry. The doping ratio of NaF is 10%. Preliminary experiments found that the performance is the best when the doping ratio of NaF is 10%;

[0054] S2. Pre-sinter the mixed slurry at a temperature of 800°C - 900°C for 5h - 6h to obtain crushed materials;

[0055] S3. Crush the material and press it into an electrolyte sheet with a thickness of 600 μm - 800 μm using a tablet press. Keep it at a temperature of 900 °C - 950 °C for 8 hours to obtain Na 5-x YSi 4 O 12-x F x solid electrolyte sheets with different F doping amounts.

[0056] Na 5-x YSi 4 O 12-x F x The performance testing and characterization of the solid electrolyte sheets are as follows:

[0057] From Figure 1 it can be seen that Figure 1 (a) is the cross-sectional SEM image of the undoped electrolyte sheet of Na 5 YSi 4 O 12 ;

[0058] Figure 1 (b) is the cross-sectional SEM image of the electrolyte sheet of F-doped Na 5 YSi 4 O 12 ; Figure 1 (c) is the SEM and EDS elemental distribution on the surface of the electrolyte sheet of F-fluorinated doped Na 5-x YSi 4 O 12-x F x ; Figure 1 (d) is the surface distribution map of Na element; Figure 1 (e) is the surface distribution map of Y element; Figure 1 (f) is the surface distribution map of Si element; Figure 1 (g) is the surface distribution map of O element; Figure 1 (h) is the surface distribution map of F element). After fluorination doping, the Na 5 YSi 4 O 12 electrolyte sheet becomes dense, changing from the initial layered structure to a tight internal structure. Energy spectrum analysis is carried out on the cross-section and surface of the electrolyte sheet, and it is found that the F element is mainly concentrated on the surface of the electrolyte, and there is basically no fluorine element in the internal cross-section, which may be related to the volatilization of F to the surface during the sintering process, making it exactly that F is concentrated on the surface.

[0059] From Figure 2 the density test, it can be seen that Figure 2 (a) is for Na 5 YSi 4 O 12 and F-doped Na 5 YSi4 O 12 Apparent density comparison diagram; Figure 2 (b) is for F-doped Na 5 YSi 4 O 12 XRD pattern; Figure 2 (c) is for F-doped Na 5 YSi 4 O 12 EIS impedance analysis diagram; Figure 2 (d) is for F-doped Na 5 YSi 4 O 12 Symmetric battery cycle performance test diagram of electrolyte assembly. ), After F doping, the apparent density of Na 5 YSi 4 O 12 has an obvious increase. Combining with the prepared cross-sectional SEM, F doping can change the internal stratification of the electrolyte and improve the apparent density. Analyze the phase of F-doped Na 5 YSi 4 O 12 , doping does not change its phase structure. Test the conductivity of F-doped Na 5 YSi 4 O 12 , and it is found that its conductivity reaches 1.65×10 -3 S cm -2 exceeding the conductivity of Na 5 YSi 4 O 12 in the current literature (1.59×10 -3 S cm -2 ), and assembling it into a symmetric battery can stably cycle for 1100 h.

[0060] Example 4

[0061] This example provides a fluorinated doped battery, including the above-mentioned fluorinated doped solid electrolyte, and the solid electrolyte is prepared by using the preparation method of the above-mentioned fluorinated doped solid electrolyte.

[0062] The preparation method of the fluorinated doped battery includes the following steps:

[0063] A1. Prepare sodium vanadium phosphate cathode material;

[0064] A2. Prepare the negative electrode sheet;

[0065] A3. Assemble in the order of positive electrode shell, positive electrode sheet, electrolyte sheet, negative electrode sheet, gasket, nickel foam, negative electrode shell, and compact with a tablet press to obtain a fluorinated doped battery.

Claims

1. A fluorinated solid electrolyte, characterized in that: The chemical composition of the solid electrolyte is Na 5- x YSi4O 12-x F x , where x is the doping amount of F element, and F atoms partially replace Na5YSi4O 12 The sites of O atoms in the structure, fluorination doping improves the interface performance and cycle stability. After doping and sintering, the F element will diffuse and concentrate to Na5YSi4O 12 The surface of the electrolyte sheet; The preparation method of the electrolyte comprises the following steps: S1. Na2CO3, Y2O3, SiO2 and NaF are mixed evenly by wet grinding to obtain a mixed slurry, and the doping ratio of NaF is controlled between 10% and 30%; S2, pre-sintering the mixed slurry at a temperature of 800°C-900°C for 5h-6h to obtain material crushing; S3, crush the material and press it into electrolyte sheets with a thickness of 600μm-800μm using a tablet press, and keep it at a temperature of 900℃-950℃ for 8h to obtain Na2O3 electrolyte sheets with different F doping amounts. 5-x YSi4O 12-x F x Solid electrolyte sheet.

2. A fluorinated solid electrolyte according to claim 1, characterized in that: The solid electrolyte Na 5-x YSi4O 12-x F x The ionic conductivity is 1.65×10 -3 S cm -2 .

3. The fluorinated solid electrolyte according to claim 1, characterized in that: In step S1, the doping ratio of NaF is 10%.

4. A solid-state battery, characterized in that: The solid electrolyte is prepared by the preparation method of a fluorinated-doped solid electrolyte according to any one of claims 1 to 3, and the solid-state battery is a solid-state sodium ion battery.

5. A method for preparing a solid-state battery, characterized in that: Used to prepare the solid-state battery described in claim 4.

6. The method for preparing a solid-state battery according to claim 5, characterized in that: The steps include: A1. Preparation of sodium vanadium phosphate positive electrode material; A2. Prepare negative electrode sheet; A3. Assemble the positive electrode shell, positive electrode sheet, electrolyte sheet, negative electrode sheet, gasket, nickel foam, and negative electrode shell in order, and compact them with a tablet press to obtain a fluoride-doped battery.

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