Lithium ion solid electrolyte, preparation method thereof and lithium ion solid battery

Abstract

The invention discloses a lithium ion solid-state electrolyte, a preparation method thereof and a lithium ion solid-state battery, the chemical general formula of the lithium ion solid-state electrolyte is Na < 5-x > Li < x > Zn < 1.5 > X < 4 > O < 12 >, X is one or two of Si and Ge, and x is more than 0 and less than or equal to 5. According to the invention, a Na5Zn1. 5X4O12 type sodium ion solid electrolyte is taken as a precursor, a novel lithium ion solid electrolyte is synthesized through an ion exchange method, Na < + > has a larger radius than Li < + >, the selected sodium ion solid electrolyte has a three-dimensional ion transmission channel, and lithium ions have a smaller migration bottleneck in an open frame structure, so that the lithium ion solid electrolyte can be applied to lithium ion batteries. And rapid migration of Li < + > is facilitated, so that a relatively lower migration barrier and higher ionic conductivity are realized.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and more specifically, to a lithium ion solid electrolyte and a preparation method thereof, and a lithium ion solid state battery. Background Art

[0002] Lithium-ion batteries have become the most mature and widely used battery system due to their advantages such as high conversion efficiency, high energy density / power density, no memory effect, and long service life. However, lithium-ion battery systems based on organic liquid electrolytes also inevitably have problems such as flammability and leakage, which can easily lead to safety accidents. Replacing flammable organic liquid electrolytes with non-flammable lithium-ion solid electrolytes can fundamentally solve the above problems and greatly improve the safety of the battery system. At the same time, using metallic lithium as the negative electrode can achieve a significant increase in energy density.

[0003] As a key component of solid-state batteries, solid electrolyte materials have attracted more and more attention. For an ideal solid electrolyte, it is generally necessary to have high ionic conductivity, high chemical stability, a wide electrochemical stability window, suitable mechanical strength, environmental friendliness and low cost. Among various types of solid electrolytes, inorganic solid electrolytes have attracted much attention due to their many advantages such as high ionic conductivity and ion migration number, high mechanical properties and stability. So far, various types of inorganic solid electrolytes have been widely studied, including oxides, sulfides, halides and borohydrides. However, in the actual application of lithium-ion solid-state batteries, different types of inorganic solid electrolyte materials still face different difficulties such as low ionic conductivity and poor chemical and electrochemical stability. Therefore, the development of new high-performance lithium-ion solid electrolytes has always been one of the important research directions for realizing the application of solid-state lithium batteries.

[0004] In recent years, researchers have mostly expanded the lithium ion migration "bottleneck" and reduced the migration barrier by doping or replacing the existing framework structure solid electrolytes, thereby reducing the activation energy of ion migration and improving ion conductivity. Compared with lithium ion solid electrolytes, various sodium ion solid electrolytes can improve the conductivity of lithium ion by at least 10% at room temperature due to their three-dimensional ion transport pathways. -3 S cm -1 In addition, the abundant sodium resources and relatively lower preparation temperature also make it more cost-effective.

[0005] Therefore, there is an urgent need to provide a sodium-doped lithium-ion solid electrolyte to reduce the activation energy of ion migration and improve ionic conductivity. Summary of the invention

[0006] In view of this, the present invention provides a lithium ion solid electrolyte to achieve lower migration barrier and higher ion conductivity.

[0007] In one aspect, the present invention provides a lithium ion solid electrolyte having a general chemical formula of:

[0008] Na 5-x Li x Zn 1.5 X4O 12 ,

[0009] Wherein, X is one or both of Si and Ge, and the value range of x is 0<x≤5.

[0010] Optionally, the raw materials for preparing the lithium-ion solid electrolyte include: anhydrous sodium carbonate, XO2, and metal oxide ZnO.

[0011] On the other hand, the present invention also provides a method for preparing a lithium ion solid electrolyte, comprising the steps of:

[0012] Providing raw materials, the raw materials comprising: anhydrous sodium carbonate, XO2, and metal oxide ZnO, where X is one or both of Si and Ge;

[0013] The precursor is prepared, comprising: wet ball milling, drying and sintering the raw materials to obtain Na5Zn 1.5 X4O 12 Type sodium ion solid electrolyte precursor powder;

[0014] Ion exchange, comprising: adding the precursor powder to a lithium salt aqueous solution with gradient concentrations, heating and stirring, to obtain a Na / Li ion-exchanged mixture;

[0015] The mixture is washed, separated and dried to obtain the target lithium ion solid electrolyte Na 5- x Li x Zn 1.5 X4O 12 .

[0016] Optionally, in the step of preparing the precursor, the wet ball milling uses anhydrous ethanol as a dispersant, the ball milling speed is 500 rpm to 600 rpm, and the ball milling time is 10 h to 15 h;

[0017] And / or, the sintering temperature is 800° C. to 1000° C., and the sintering time is 8 h to 15 h.

[0018] Optionally, the cleaning process uses deionized water and anhydrous ethanol to centrifuge the mixture at a centrifugal speed of 6000 rpm to 8000 rpm.

[0019] Optionally, in the step of drying the mixture, the drying temperature is 75° C. to 80° C., and the drying time is 12 h to 14 h.

[0020] Optionally, the lithium salt includes any one of LiCl, LiOH, LiClO4, LiNO2, and LiNO3.

[0021] Optionally, in the ion exchange step, the concentration of the lithium salt aqueous solution is 1 mol L -1 ~3 mol L -1 The stirring temperature is 50℃~55℃, and the stirring time at different concentrations is 5h~6h.

[0022] Optionally, the method further comprises: adding the target lithium ion solid electrolyte Na 5-x Li x Zn 1.5 X4O 12 A lithium-ion solid electrolyte sheet is obtained by hot pressing or cold pressing with a plastic crystal electrolyte;

[0023] The hot pressing temperature is 500°C to 700°C, the pressure is 40MPa to 60MPa, and the hot pressing time is 1h to 2h.

[0024] And / or, the proportion of the plastic crystal electrolyte is 5wt.% to 10wt.%, the cold pressing temperature is 110°C to 130°C, the pressure is 80MPa to 100MPa, and the cold pressing time is 0.5h to 1h.

[0025] On the other hand, the present invention also provides a lithium-ion solid-state battery, comprising a positive electrode, a negative electrode, and a lithium-ion solid-state electrolyte between the positive electrode and the negative electrode, wherein the lithium-ion solid-state electrolyte is the above-mentioned lithium-ion solid-state electrolyte, prepared by the above-mentioned preparation method.

[0026] Compared with the prior art, the lithium ion solid electrolyte and preparation method thereof, and the lithium ion solid battery provided by the present invention achieve at least the following beneficial effects:

[0027] The present invention uses Na5Zn 1.5 X4O 12 A new type of lithium ion solid electrolyte was synthesized by ion exchange method using sodium ion solid electrolyte as precursor. + Compared with Li + With a larger radius, the selected sodium ion solid electrolyte has a three-dimensional ion transport channel. Lithium ions have a smaller migration bottleneck in this open framework structure, which is more conducive to Li + Rapid migration, resulting in relatively lower migration barriers and higher ionic conductivity.

[0028] The sodium ion solid electrolyte selected by the present invention can be obtained by one-step sintering, and the synthesis temperature is low; the electrolyte precursor is stable to water, ion exchange can be carried out in an aqueous solution, and the heating temperature is low, so it has good cost-effectiveness.

[0029] The lithium-ion solid-state battery assembled using the novel lithium-ion solid-state electrolyte of the present invention not only has high safety characteristics, but also exhibits higher energy density due to the use of metallic lithium as the negative electrode.

[0030] Of course, any product implementing the present invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0031] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0033] Figure 1 A flow chart of a method for preparing a lithium ion solid electrolyte provided by an embodiment of the present invention;

[0034] Figure 2 This is the AC impedance spectrum of the sodium ion solid electrolyte before ion exchange in Example 1;

[0035] Figure 3 The AC impedance spectrum of the lithium ion solid electrolyte prepared in Example 1;

[0036] Figure 4 This is the constant current charge and discharge curve of the lithium-ion solid-state battery in Example 1;

[0037] Figure 5 This is the cycle performance of the lithium-ion solid-state battery in Example 1. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0039] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0040] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0041] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0042] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0043] The embodiment of the present invention provides a lithium ion solid electrolyte, the general chemical formula of which is:

[0044] Na 5-x Li x Zn 1.5 X4O 12 ,

[0045] Wherein, X is one or both of Si and Ge, and the value range of x is 0<x≤5.

[0046] The lithium ion solid electrolyte provided by the embodiment of the present invention has a + Compared with Li + With a larger radius, the selected sodium ion solid electrolyte has a three-dimensional ion transport channel. Lithium ions have a smaller migration "bottleneck" in this open framework structure, which is more conducive to Li + Rapid migration, resulting in relatively lower migration barriers and higher ionic conductivity.

[0047] Optionally, raw materials for preparing lithium-ion solid electrolyte include: anhydrous sodium carbonate, XO2, and metal oxide ZnO.

[0048] Anhydrous sodium carbonate mainly provides sodium ions (Na + ), is formed by Na 5-x Li x Zn 1.5 X4O 12 An important source of sodium in the electrolyte. XO2 provides the X element (Si or Ge) in the electrolyte. Si or Ge, sodium, lithium, zinc and oxygen together form the skeleton structure of the electrolyte. ZnO provides zinc ions (Zn2+) and is an important source of zinc in the electrolyte. ZnO can improve the ionic conductivity of the electrolyte and improve the thermal stability of the electrolyte.

[0049] On the other hand, the present invention also provides a method for preparing a lithium ion solid electrolyte, referring to Figure 1 , including the steps of:

[0050] S1, providing raw materials, the raw materials comprising: anhydrous sodium carbonate, XO2, and metal oxide ZnO, X is one or two of Si and Ge;

[0051] S2, preparing a precursor, including: wet ball milling, drying and sintering the raw materials to obtain Na5Zn 1.5 X4O 12 Type sodium ion solid electrolyte precursor powder;

[0052] S3, ion exchange, comprising: adding the precursor powder to a lithium salt aqueous solution with gradient concentrations, heating and stirring, to obtain a Na / Li ion-exchanged mixture;

[0053] S4, washing, separating and drying the mixture to obtain the target lithium ion solid electrolyte Na 5- x Li x Zn 1.5 X4O 12 .

[0054] It should be noted that the purity of raw materials has an important impact on the performance of the final product, so high-purity raw materials should be used.

[0055] In step S2, the purpose of wet ball milling is to fully mix the raw materials and refine the particles to improve the reaction activity. The mixture after wet ball milling is dried to remove the solvent and water. The dried mixture is sintered at a high temperature to cause a chemical reaction to form Na5Zn 1.5 X4O 12 Type sodium ion solid electrolyte precursor powder.

[0056] In step S3, an appropriate lithium salt aqueous solution (such as LiCl, LiNO3, etc.) is selected and prepared into a gradient concentration. The gradient concentration of the lithium salt aqueous solution helps to achieve a gradual ion exchange process. The precursor powder is added to the gradient concentration of the lithium salt aqueous solution and heated and stirred. Heating and stirring can promote the ion exchange reaction, so that Na+ is gradually replaced by Li+.

[0057] In step S4, the mixture after ion exchange is washed to remove unreacted lithium salt and impurities. The washing can be performed using deionized water or a solvent such as an alcohol. The washed mixture is separated to obtain the target lithium ion solid electrolyte Na 5-x Li x Zn 1.5 X4O 12 The wet powder can be separated by filtration, centrifugation, etc. The separated wet powder is dried to remove water and solvent to obtain Na5Zn 1.5 X4O 12Type sodium ion solid electrolyte precursor powder.

[0058] The sodium ion solid electrolyte selected in the present invention can be sintered in one step to obtain Na5Zn 1.5 X4O 12 The sodium ion solid electrolyte precursor has a low synthesis temperature; the electrolyte precursor is stable to water, ion exchange can be carried out in an aqueous solution, and the heating temperature is low, so it has good cost-effectiveness.

[0059] Optionally, in the step of preparing the precursor, the wet ball milling uses anhydrous ethanol as a dispersant, the ball milling speed is 500rpm~600rpm, and the ball milling time is 10h~15h; and / or, the sintering temperature is 800℃~1000℃, and the sintering time is 8h~15h.

[0060] Specifically, the wet ball milling process selects anhydrous ethanol as a dispersant, which helps to uniformly disperse and refine the raw materials. The ball milling speed can be 500rpm, 510rpm, 520rpm, 530rpm, 540rpm, 550rpm, 560rpm, 570rpm, 580rpm, 590rpm, 600rpm, or any value between 500rpm and 600rpm. The ball milling speed of the embodiment of the present invention is controlled between 500rpm and 600rpm, which helps to fully mix and refine the raw materials, while avoiding excessive particle crushing or excessive heat generation due to excessive rotation speed. Optionally, the ball milling time is 10h, 11h, 12h, 13h, 14h, 15h, or any value between 10h and 15h. The ball milling time is 10h to 15h, which can ensure that the raw materials are fully refined and reach the required particle size distribution.

[0061] The wet-milled mixture is dried to remove anhydrous ethanol and water. The drying temperature and time need to be properly controlled to avoid decomposition or agglomeration of the raw materials. Optionally, the drying temperature can be set between 80°C and 120°C, and the time depends on the water content of the mixture and the efficiency of the drying equipment.

[0062] Optionally, the sintering temperature can be 800°C, 850°C, 900°C, 950°C, 1000°C, or any value between 800°C and 1000°C. The sintering temperature is controlled between 800°C and 1000°C, which is conducive to the chemical reaction between the raw materials and the formation of crystals. Optionally, the sintering time can be 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, or any value between 8h and 15h. The length of the sintering time will affect the growth of the crystal and the performance of the electrolyte. Too short a sintering time may result in incomplete crystal growth, while too long a sintering time may result in excessive crystal growth or other adverse phase changes. In the embodiment of the present invention, the sintering time is 8h to 15h, which can achieve complete crystal growth without causing excessive crystal growth.

[0063] Optionally, the cleaning process uses deionized water and anhydrous ethanol to centrifuge the mixture at a speed of 6000 rpm to 8000 rpm.

[0064] Specifically, deionized water is used to initially clean the mixture to remove soluble impurities and residual lithium salt aqueous solution. Anhydrous ethanol is used as a second cleaning solvent to further remove water and other residues. The volatility of anhydrous ethanol helps to quickly dry the mixture.

[0065] The centrifugal speed is controlled between 6000rpm and 8000rpm, which can generate sufficient centrifugal force to effectively separate the particles in the mixture after Na / Li ion exchange from the solution. It should be noted that the centrifugal time should be long enough to ensure that the particles of the mixture after Na / Li ion exchange are completely settled to the bottom of the centrifuge tube, while avoiding agglomeration or damage of the particles caused by too long a centrifugal time.

[0066] Optionally, in the step of drying the mixture, the drying temperature is 75° C. to 80° C., and the drying time is 12 h to 14 h.

[0067] The drying temperature is controlled between 75°C and 80°C, which helps to remove residual moisture and solvent (anhydrous ethanol) in the mixture, while avoiding decomposition or performance degradation of the electrolyte due to excessively high temperature.

[0068] The drying time is 12 h to 14 h, which can ensure that the water and solvent (anhydrous ethanol) in the mixture are fully removed, while avoiding excessive drying time that leads to waste of energy or over-drying of the electrolyte.

[0069] Optionally, the lithium salt includes any one of LiCl, LiOH, LiClO4, LiNO2, and LiNO3.

[0070] Lithium chloride (LiCl) has good ionic conductivity and stability. Lithium hydroxide (LiOH) has high reactivity and ionic conductivity. Lithium perchlorate (LiClO4) is a lithium salt with high ionic conductivity. The ionic conductivity of lithium nitrite (LiNO2) may be relatively low. Lithium nitrate (LiNO3) has good thermal stability and chemical stability.

[0071] Optionally, in the ion exchange step, the lithium salt aqueous solution has a concentration of 1 mol L -1 ~3 mol L -1 The stirring temperature is 50℃~55℃, and the stirring time at different concentrations is 5h~6h.

[0072] It should be noted that the ion exchange step is carried out by stirring at a set stirring temperature and time to allow lithium ions to be fully exchanged with sodium ions, which is the key to ensuring that lithium is successfully replaced into the crystal structure and adjusting the final Li content.

[0073] Optionally, the concentration of the lithium salt aqueous solution can be 1 mol L -1 , 1.5 mol L -1 , 2 mol L -1 , 2.5 mol L -1 、3molL -1 , or 1 mol L -1 ~3 mol L -1 Any value between 1mol L and 2mol L. A concentration that is too high may cause the solution to become viscous and affect the diffusion rate of lithium ions; a concentration that is too low may require a longer stirring time to achieve the desired ion exchange effect. -1 ~3 mol L -1 , which can ensure the effective diffusion and exchange of lithium ions, while avoiding excessive concentration that causes the solution to be too viscous or produces precipitation, affecting the diffusion rate of lithium ions.

[0074] Optionally, the stirring temperature can be 50°C, 51°C, 52°C, 53°C, 54°C, or 55°C. It should be noted that during the ion exchange process, a stirring temperature that is too high may cause the solution to evaporate too quickly or produce an adverse chemical reaction; a stirring temperature that is too low may reduce the efficiency of the ion exchange. Setting the stirring temperature between 50°C and 55°C helps to accelerate the diffusion rate of lithium ions and improve the efficiency of ion exchange. Of course, during the ion exchange process, it is necessary to ensure that the temperature is stable to avoid the impact of temperature fluctuations on the ion exchange process.

[0075] The stirring time at different concentrations can be 5h, 5.2h, 5.4h, 5.6h, 5.8h, or 6h. It should be noted that during the ion exchange process, the stirring time needs to be long enough to ensure that the lithium ions are fully diffused and exchanged with the sodium ions. At the same time, it is also necessary to avoid excessive stirring time that causes agglomeration or destruction of the particles. The stirring time at different concentrations is 5h to 6h, which can ensure that the lithium ions are fully diffused and exchanged with the sodium ions in the precursor.

[0076] The preparation method of the present invention obtains a sodium ion oxide solid electrolyte with low preparation temperature, high ion conductivity and high stability. Only at a relatively low temperature, through Na / Li ion exchange in an aqueous solution, a new type of lithium ion oxide solid electrolyte is obtained.

[0077] Optionally, the method further includes: adding the target lithium-ion solid electrolyte Na 5-x Li x Zn 1.5 X4O 12 A lithium-ion solid electrolyte sheet is obtained by hot pressing or cold pressing with a plastic crystal electrolyte;

[0078] The hot pressing temperature is 500°C to 700°C, the pressure is 40MPa to 60MPa, and the hot pressing time is 1h to 2h.

[0079] And / or, the proportion of the plastic crystal electrolyte is 5wt.% to 10wt.%, the cold pressing temperature is 110°C to 130°C, the pressure is 80MPa to 100MPa, and the cold pressing time is 0.5h to 1h.

[0080] Specifically, the target lithium-ion solid electrolyte Na 5-x Li x Zn 1.5 X4O 12 The lithium-ion solid electrolyte sheet is obtained by hot pressing. The hot pressing temperature is 500℃~700℃ and the hot pressing time is 1h~2h, which is conducive to the sintering and densification of the solid electrolyte powder and the formation of an electrolyte sheet with good ionic conductivity. The pressure is 40MPa~60MPa. Sufficient pressure can promote close contact and bonding between powder particles and help form a dense electrolyte structure. The hot pressing time is 1h~2h, which can ensure that the solid electrolyte powder is fully sintered and densified, while avoiding the decomposition or performance degradation of the electrolyte caused by too long hot pressing time.

[0081] The target lithium-ion solid electrolyte Na 5-x Li x Zn 1.5 X4O 12The lithium-ion solid electrolyte sheet is obtained by cold pressing with the plastic crystal electrolyte. The proportion of the plastic crystal electrolyte is controlled at 5wt.% to 10wt.%, which can ensure the uniform distribution of the plastic crystal electrolyte in the composite electrolyte sheet while maintaining sufficient ionic conductivity. The cold pressing temperature is 110℃ to 130℃, which helps the plastic crystal electrolyte soften and flow, making it compatible with Na 5-x Li x Zn 1.5 X4O 12 The solid electrolyte powder is better combined. The pressure is 80MPa~100MPa, which can promote the close contact and combination between the plastic crystal electrolyte and the solid electrolyte powder. The cold pressing time is 0.5h~1h, which can ensure that the plastic crystal electrolyte is fully softened and flowed, and forms a good composite structure with the solid electrolyte powder.

[0082] On the other hand, the present invention also provides a lithium ion solid state battery, comprising a positive electrode, a negative electrode, and a lithium ion solid state electrolyte between the positive electrode and the negative electrode, wherein the lithium ion solid state electrolyte is the above-mentioned lithium ion solid state electrolyte, which is prepared by the above-mentioned preparation method.

[0083] The positive electrode includes positive electrode active material particles, conductive additives and binders, and the negative electrode is metallic lithium. The positive electrode active material particles refer to lithium-intercalating compounds that can reversibly embed and deintercalate lithium ions, such as lithium iron phosphate, lithium iron manganese phosphate, layered transition metal oxides, etc.

[0084] Example 1

[0085] This example provides NCM811 / Na 5-x Li x Zn 1.5 SiO 12 / Li solid-state lithium battery preparation method, wherein steps (1) to (4) are Na 5-x Li x Zn 1.5 SiO 12 Preparation method of lithium ion solid electrolyte, step (5) is NCM811 / Na 5- x Li x Zn 1.5 SiO 12 / Li solid-state lithium battery assembly method, NCM811 specifically refers to LiNi 0.8 Co 0.1 Mn 0.1O2 is the basic ratio of nickel cobalt manganese oxide material, which is a type of NMC (nickel cobalt manganese) lithium battery, also known as ternary lithium battery. The ratios of nickel, cobalt and manganese are 80%, 10% and 10% respectively. NCM811 has a layered structure, in which nickel, cobalt and manganese elements are embedded in the lithium oxygen layered structure in a specific ratio. Due to the high nickel content, the energy density of NCM811 battery usually exceeds 270Wh / kg, which is much higher than other types of ternary batteries. The preparation method is as follows:

[0086] (1) Anhydrous sodium carbonate, silicon dioxide and zinc oxide were weighed and placed in a ball mill according to the stoichiometric ratio. The mass ratio of anhydrous sodium carbonate, silicon dioxide and zinc oxide was 424:240:121.5. Anhydrous ethanol was used as a dispersant for wet ball milling. The ball-to-material ratio was 20:1. The ratio of raw material powder to anhydrous ethanol was 1:2. The ball milling speed was 600 rpm s -1 The ball milling time was 15 h, and the ball-milled mixture was dried at 120 °C for 12 h to obtain precursor powder A;

[0087] (2) Precursor A was placed in a muffle furnace and sintered at a heating rate of 5 °C min -1 The sintering temperature is 950℃, the sintering time is 15h, and the Na5Zn is obtained by natural cooling to room temperature. 1.5 SiO 12 Sodium ion solid electrolyte;

[0088] (3) Take 1g of the above Na5Zn 1.5 SiO 12 Powder, successively in 50mL concentration of 1mol L -1 , 2 mol L -1 and 3 mol L -1 The LiCl aqueous solution was heated and stirred at 50°C and the stirring time at different concentrations was 6h;

[0089] (4) The mixture was washed and centrifuged with deionized water and anhydrous ethanol at 6000 rpm and dried at 80 °C for 12 h to obtain the target Na 5-x Li x Zn 1.5 SiO 12 Lithium-ion solid electrolyte.

[0090] (5) NCM811 / Na 5-x Li x Zn 1.5 SiO 12 / Li solid-state lithium battery preparation, including

[0091] (5.1) Take 0.2g electrolyte Na 5-x Lix Zn 1.5 SiO 12 The mixture was uniformly mixed with succinonitrile and LiTFSI (i.e., lithium bis(trifluoromethylsulfonyl)imide) in a mass ratio of 63:6:1, and the mixture was pressed at a temperature of 120°C and a pressure of 100 MPa for 0.5 h to obtain a lithium ion solid electrolyte sheet with a diameter of 1.5 cm;

[0092] (5.2) Li(Ni) was added in a mass ratio of 70:10:3.5:6:1. 0.8 Mn 0.1 Co 0.1 )O2 (i.e. NCM811), SuperP (i.e. conductive carbon black), PVDF (i.e. polyvinylidene fluoride, a lithium-ion battery binder that binds the positive and negative active materials, conductive agent and current collector together to form a complete electrode structure), succinonitrile and LiTFSI are uniformly mixed to obtain a positive electrode covered on one side of the above solid electrolyte sheet and hot pressed for 1 hour under the same conditions;

[0093] (5.3) In a glove box filled with argon, remove the oxide layer on the surface of the lithium metal strip and cut it into lithium metal discs with a diameter of 1.5 cm as the negative electrode;

[0094] (5.4) Cover the side of the lithium-ion solid electrolyte sheet without the positive electrode with a metallic lithium disc, and finally package it with a CR2032 button battery.

[0095] Example 2

[0096] This example provides NCM811 / Na 5-x Li x Zn 1.5 Ge4O 12 / Li lithium ion solid-state battery preparation method, wherein steps (1) to (4) are Na 5-x Li x Zn 1.5 Ge4O 12 A method for preparing a lithium ion solid electrolyte, wherein step (5) is Na 5- x Li x Zn 1.5 Ge4O 12 The assembly method of the lithium-ion solid-state battery is as follows:

[0097] (1) Anhydrous sodium carbonate, germanium dioxide and zinc oxide were weighed and placed in a ball mill according to the stoichiometric ratio. The mass ratio of anhydrous sodium carbonate, germanium dioxide and zinc oxide was 424:420:121.5. Anhydrous ethanol was used as a dispersant for wet ball milling. The ball-to-material ratio was 20:1. The ratio of raw material powder to anhydrous ethanol was 1:2. The ball milling speed was 600 rpm s-1 The ball milling time was 15 h, and the ball-milled mixture was dried at 120 °C for 12 h to obtain precursor powder A;

[0098] (2) Precursor A was placed in a muffle furnace and sintered at a heating rate of 5 °C min -1 The sintering temperature is 900℃, the sintering time is 15h, and the Na5Zn is obtained by natural cooling to room temperature. 1.5 Ge4O 12 Sodium ion solid electrolyte;

[0099] (3) Take 1g of the above Na5Zn 1.5 Ge4O 12 Powder, successively in 50mL concentration of 1mol L -1 , 2 mol L -1 and 3 mol L -1 The LiCl aqueous solution was heated and stirred at 50°C and the stirring time at different concentrations was 6h;

[0100] (4) The mixture was washed and centrifuged with deionized water and anhydrous ethanol at 6000 rpm and dried at 80 °C for 12 h to obtain the target Na 5-x Li x Zn 1.5 Ge4O 12 Lithium-ion solid electrolyte.

[0101] (5) NCM811 / Na 5-x Li x Zn 1.5 Ge4O 12 / Li solid-state lithium battery preparation, including

[0102] (5.1) Take 0.2g electrolyte Na 5-x Li x Zn 1.5 Ge4O 12 The mixture was uniformly mixed with succinonitrile and LiTFSI in a mass ratio of 63:6:1, and the mixture was pressed at a temperature of 110°C and a pressure of 100 MPa for 0.5 h to obtain a lithium ion solid electrolyte sheet with a diameter of 1.5 cm;

[0103] (5.2) Li(Ni) was added in a mass ratio of 70:10:3.5:6:1. 0.8 Mn 0.1 Co 0.1 )O2(NCM811), SuperP, PVDF, succinonitrile and LiTFSI were uniformly mixed to obtain a positive electrode covered on one side of the above solid electrolyte sheet and hot pressed under the same conditions for 1 h;

[0104] (5.3) In a glove box filled with argon, remove the oxide layer on the surface of the lithium metal strip and cut it into lithium metal discs with a diameter of 1.5 cm;

[0105] (5.4) Cover the side of the lithium-ion solid electrolyte sheet without the positive electrode with a metallic lithium disc, and finally package it with a CR2032 button battery.

[0106] Example 3

[0107] This example provides NCM811 / Na 5-x Li x Zn 1.5 Si 3.8 Ge 0.2 O 12 / Li solid-state lithium battery preparation method, wherein steps (1) to (4) are Na 5-x Li x Zn 1.5 Si 3.8 Ge 0.2 O 12 Preparation method of lithium ion solid electrolyte, step (5) is NCM811 / Na 5-x Li x Zn 1.5 Si 3.8 Ge 0.2 O 12 The assembly method of the / Li solid-state lithium battery is as follows:

[0108] (1) Anhydrous sodium carbonate, silicon dioxide, germanium dioxide and zinc oxide were weighed and placed in a ball mill according to the stoichiometric ratio. The mass ratio of sodium carbonate, silicon dioxide, germanium dioxide and zinc oxide was 265:228:21:122. Anhydrous ethanol was used as a dispersant for wet ball milling. The ball-to-material ratio was 20:1. The ratio of raw material powder to anhydrous ethanol was 1:2. The ball milling speed was 500 rpm s -1 The ball milling time was 10 h, and the ball-milled mixture was dried at 120 °C for 12 h to obtain precursor powder A;

[0109] (2) Precursor A was placed in a muffle furnace and sintered at a heating rate of 5 °C min -1 The sintering temperature is 900℃, the sintering time is 12h, and the Na5Zn is obtained by natural cooling to room temperature. 1.5 Si 3.8 Ge 0.2 O 12 Sodium ion solid electrolyte;

[0110] (3) Take 1g of the above Na5Zn 1.5 Si 3.8 Ge 0.2 O12 Powder, successively in 50mL concentration of 1mol L -1 , 2 mol L -1 and 3 mol L -1 The LiCl aqueous solution was heated and stirred at 50°C and the stirring time at different concentrations was 6h;

[0111] (4) The mixture was washed and centrifuged with deionized water and anhydrous ethanol at 6000 rpm and dried at 80 °C for 12 h to obtain the target Na 5-x Li x Zn 1.5 Si 3.8 Ge 0.2 O 12 Lithium-ion solid electrolyte;

[0112] (5) NCM811 / Na 5-x Li x Zn 1.5 Si 3.8 Ge 0.2 O 12 / Li solid-state lithium battery preparation, including

[0113] (5.1) Take 0.2g electrolyte Na 5-x Li x Zn 1.5 Si 3.8 Ge 0.2 O 12 The mixture was uniformly mixed with succinonitrile and LiTFSI in a mass ratio of 63:6:1, and the mixture was pressed at a temperature of 130°C and a pressure of 100 MPa for 0.5 h to obtain a lithium ion solid electrolyte sheet with a diameter of 1.5 cm;

[0114] (5.2) Li(Ni) was added in a mass ratio of 70:10:3.5:6:1. 0.8 Mn 0.1 Co 0.1 )O2(NCM811), SuperP, PVDF, succinonitrile and LiTFSI were uniformly mixed to obtain a positive electrode covered on one side of the above solid electrolyte sheet and hot pressed under the same conditions for 1 h;

[0115] (5.3) In a glove box filled with argon, remove the oxide layer on the surface of the lithium metal strip and cut it into lithium metal discs with a diameter of 1.5 cm to serve as the negative electrode;

[0116] (5.4) Cover the side of the lithium-ion solid electrolyte sheet without the positive electrode with a metallic lithium disc, and finally package it with a CR2032 button battery.

[0117] Comparative Example 1

[0118] This comparative example is NCM811 / Na 5-x Li x GdSi4O 12 / Li solid-state lithium battery preparation method, wherein steps (1) to (4) are Na 5-x Li x GdSi4O 12 Preparation method of lithium ion solid electrolyte, step (5) is NCM811 / Na 5-x Li x GdSi4O 12 / Li solid-state lithium battery assembly method.

[0119] (1) Anhydrous sodium carbonate, silicon dioxide, and gadolinium oxide were weighed and placed in a ball mill according to the stoichiometric ratio. The mass ratio of anhydrous sodium carbonate, silicon dioxide, and gadolinium oxide was 265:181:240. Anhydrous ethanol was used as a dispersant for wet ball milling. The ball-to-material ratio was 20:1. The ratio of raw material powder to anhydrous ethanol was 1:2. The ball milling speed was 500 rpm s -1 The ball milling time was 10 h, and the ball-milled mixture was dried at 120 °C for 12 h to obtain precursor powder A;

[0120] (2) Precursor A was placed in a muffle furnace and sintered at a heating rate of 5 °C min -1 The sintering temperature is 900℃, the sintering time is 12h, and the Na5GdSi4O is obtained by natural cooling to room temperature. 12 Sodium ion solid electrolyte;

[0121] (3) Take 1g of the above Na5GdSi4O 12 Powder, successively in 50mL concentration of 1mol L -1 , 2 mol L -1 and 3 mol L -1 The LiCl aqueous solution was heated and stirred at 50°C and the stirring time at different concentrations was 6h;

[0122] (4) The mixture was washed and centrifuged with deionized water and anhydrous ethanol at 6000 rpm and dried at 80 °C for 12 h to obtain the target Na 5-x Li x GdSi4O 12 Lithium-ion solid electrolyte;

[0123] (5) NCM811 / Na 5-x Li x GdSi4O 12 / Li solid-state lithium battery preparation, including

[0124] (5.1) Take 0.2g electrolyte Na 5-x Li x GdSi4O 12 The mixture was uniformly mixed with succinonitrile and LiTFSI in a mass ratio of 63:6:1, and the mixture was pressed at a temperature of 120°C and a pressure of 100 MPa for 0.5 h to obtain a lithium ion solid electrolyte sheet with a diameter of 1.5 cm;

[0125] (5.2) Li(Ni) was added in a mass ratio of 70:10:3.5:6:1. 0.8 Mn 0.1 Co 0.1 )O2(NCM811), SuperP, PVDF, succinonitrile and LiTFSI were uniformly mixed to obtain a positive electrode covered on one side of the above solid electrolyte sheet and hot pressed under the same conditions for 1 h;

[0126] (5.3) In a glove box filled with argon, remove the oxide layer on the surface of the lithium metal strip and cut it into lithium metal discs with a diameter of 1.5 cm to serve as the negative electrode;

[0127] (5.4) Cover the side of the lithium-ion solid electrolyte sheet without the positive electrode with a metallic lithium disc, and finally package it with a CR2032 button battery.

[0128] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0129] In order to conduct the ion conductivity test, the sodium ion solid electrolyte powder before ion exchange in the above-mentioned Example 1 and the lithium ion solid electrolyte powder obtained in Examples 1 to 3 and the comparative example were hot pressed at a temperature of 500°C to 700°C and a pressure of 50 MPa for 1h to 2h to obtain an electrolyte ceramic sheet with a density of about 70%.

[0130] By comparison Figure 2 and Figure 3 From the AC impedance spectrum, it can be found that the lithium-ion solid electrolyte obtained after ion exchange has a lower impedance, indicating that the "bottleneck" on the ion migration path of the solid electrolyte structure has less obstruction to lithium ions and is more conducive to the rapid migration of lithium ions, thus showing a higher room temperature ionic conductivity. Table 1 shows the room temperature ionic conductivity of the lithium-ion solid electrolytes prepared in Examples 1 to 3 and the comparative example, further proving the universality of the synthesis scheme for the preparation of this new lithium-ion solid electrolyte material.

[0131] Table 1 Room temperature ionic conductivity of lithium ion solid electrolytes prepared in Examples 1 to 3 and Comparative Examples

[0132] <![CDATA[Ionic conductivity (S cm -1 )]]> Example 1 <![CDATA[4.3×10 -4 ]]> Example 2 <![CDATA[5.4×10 -4 ]]> Example 3 <![CDATA[4.9×10 -4 ]]> Comparative Example 1 <![CDATA[3.2×10 -4 ]]>

[0133] The solid-state lithium battery of Example 1 was subjected to constant current charge and discharge test at a constant temperature of 40°C. The charge and discharge curves are shown in FIG. Figure 4 As shown, based on the new Na 5-x Li x Zn 1.5 SiO 12 Solid-state lithium battery with lithium-ion solid electrolyte can provide 178mA hg -1 reversible specific capacity. Figure 5 This indicates that the solid-state lithium battery has good cycle stability and can achieve more than 100 stable cycles. The above results indicate that the novel lithium-ion solid electrolyte provided by the present invention has good practicality and can provide the ionic conductivity required for battery operation.

[0134] In summary, the present invention uses Na5Zn 1.5 X4O 12 A new type of ionic solid electrolyte was synthesized by ion exchange method using a sodium ion solid electrolyte as a precursor. + Compared with Li + has a larger radius, so Na 5-x Li x Zn 1.5 X4O 12 The framework structure is more conducive to Li + Rapid migration, thus achieving relatively lower migration barriers and higher ion conductivity. The lithium-ion solid-state battery assembled using this new lithium-ion solid-state electrolyte not only has high safety characteristics, but also exhibits high energy density due to the use of metallic lithium as the negative electrode.

[0135] The sodium ion solid electrolyte selected by the present invention can be obtained by one-step sintering, and the synthesis temperature is low; the electrolyte precursor is stable to water, ion exchange can be carried out in an aqueous solution, and the heating temperature is low, so it has good cost-effectiveness.

[0136] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A lithium ion solid electrolyte, characterized in that: Its general chemical formula is: On 5-x Li x Zn 1.5 X4O 12 , Wherein, X is one or both of Si and Ge, and the value range of x is 0<x≤5.

2. The lithium ion solid electrolyte according to claim 1, characterized in that The raw materials for preparing the lithium ion solid electrolyte include: anhydrous sodium carbonate, XO2, and metal oxide ZnO.

3. A method for preparing a lithium ion solid electrolyte, characterized in that: Includes steps: Providing raw materials, the raw materials comprising: anhydrous sodium carbonate, XO2, and metal oxide ZnO, where X is one or both of Si and Ge; The precursor is prepared, comprising: wet ball milling, drying and sintering the raw materials to obtain Na5Zn 1.5 X4O 12 Type sodium ion solid electrolyte precursor powder; Ion exchange, comprising: adding the precursor powder to a lithium salt aqueous solution with gradient concentrations, heating and stirring, to obtain a Na / Li ion-exchanged mixture; The mixture is washed, separated and dried to obtain the target lithium ion solid electrolyte Na 5-x Li x Zn 1.5 X4O 12 .

4. The method for preparing a lithium ion solid electrolyte according to claim 3, characterized in that: In the step of preparing the precursor, the wet ball milling uses anhydrous ethanol as a dispersant, the ball milling speed is 500 rpm to 600 rpm, and the ball milling time is 10 h to 15 h; And / or, the sintering temperature is 800° C. to 1000° C., and the sintering time is 8 h to 15 h.

5. The method for preparing a lithium ion solid electrolyte according to claim 3, characterized in that: In the cleaning process, deionized water and anhydrous ethanol are used to centrifuge the mixture, and the centrifugal speed is 6000rpm to 8000rpm.

6. The method for preparing a lithium ion solid electrolyte according to claim 3, characterized in that: In the step of drying the mixture, the drying temperature is 75° C. to 80° C., and the drying time is 12 h to 14 h.

7. The method for preparing a lithium ion solid electrolyte according to claim 3, characterized in that: The lithium salt includes any one of LiCl, LiOH, LiClO4, LiNO2, and LiNO3.

8. The method for preparing a lithium ion solid electrolyte according to claim 7, characterized in that: In the ion exchange step, the concentration of the lithium salt aqueous solution is 1 mol L -1 ~3 mol L -1 The stirring temperature is 50℃~55℃, and the stirring time at different concentrations is 5h~6h.

9. The method for preparing a lithium ion solid electrolyte according to claim 3, characterized in that: Also includes: The target lithium ion solid electrolyte Na 5-x Li x Zn 1.5 X4O 12 A lithium-ion solid electrolyte sheet is obtained by hot pressing or cold pressing with a plastic crystal electrolyte; The hot pressing temperature is 500°C to 700°C, the pressure is 40MPa to 60MPa, and the hot pressing time is 1h to 2h. And / or, the proportion of the plastic crystal electrolyte is 5wt.% to 10wt.%, the cold pressing temperature is 110°C to 130°C, the pressure is 80MPa to 100MPa, and the cold pressing time is 0.5h to 1h.

10. A lithium-ion solid-state battery, characterized in that: It comprises a positive electrode, a negative electrode, and a lithium ion solid electrolyte between the positive electrode and the negative electrode, wherein the lithium ion solid electrolyte is the lithium ion solid electrolyte described in any one of claims 1 to 2, and is prepared by the preparation method described in any one of claims 3 to 8.

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