Sodium ion composite solid electrolyte material and preparation method and application thereof

Abstract

The application relates to the technical field of sodium ion solid-state batteries, and particularly discloses a sodium ion composite solid-state electrolyte material, a preparation method and application thereof. By adding a sintering aid into a sodium silicate solid-state electrolyte, the sintering temperature of the sodium silicate solid-state electrolyte is significantly reduced; in addition, the introduction of the sintering aid effectively promotes the grain growth of the electrolyte, thereby reducing the pores at the grain boundaries, improving the material density, reducing the grain boundary resistance, and significantly improving the ionic conductivity of the sodium silicate solid-state electrolyte. The composite electrolyte provided by the application has excellent performance, a simple preparation process and a good application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion solid-state batteries, in particular to a sodium ion composite solid-state electrolyte material and a preparation method and application thereof. BACKGROUND

[0002] Sodium ion batteries have good application prospects in the field of large-scale energy storage due to their advantages of abundant resource reserves and low preparation cost. However, the existing sodium ion batteries have safety problems such as liquid leakage and combustion due to the use of organic electrolyte, which is not conducive to practical application. Using solid-state electrolyte to replace organic electrolyte to develop all-solid-state sodium ion batteries is a fundamental measure to improve the safety performance of the battery and reduce the risk of thermal runaway. Therefore, solid-state batteries have gradually become a research hotspot and future development direction in the field of electrochemical energy storage.

[0003] Developing high-performance solid-state electrolytes is the key to realizing solid-state batteries. Among various solid-state electrolyte material systems, oxide electrolytes have attracted widespread attention from researchers due to their good mechanical properties and excellent chemical / electrochemical stability. However, its development still faces challenges such as high synthesis temperature, large grain boundary resistance and poor electrode-electrolyte interface contact: oxide electrolytes are usually prepared by high-temperature solid-phase reaction, and the high sintering temperature greatly increases the energy consumption cost of material synthesis (Energy Environ. Sci., 2018, 11, 1945-1976); in addition, the hard texture of oxide electrolytes leads to poor grain contact, so the grain boundary resistance dominates the total resistance (Adv. Energy Mater., 2019, 9, 1902373), and eliminating or reducing the grain boundary resistance is the key to improving the ionic conductivity of oxide solid-state electrolytes.

[0004] Among the reported oxide electrolyte systems, silicate electrolytes composed of RO6(R=Y, Gd, Sm, etc.) octahedra and SiO4tetrahedra exhibit extremely excellent ionic transport properties due to their open three-dimensional framework structure and rich sodium ion transport channels, thus showing high bulk ionic conductivity. However, their high sintering temperature (usually higher than 1150℃, Energy Technol., 2023, 11, 2201323) and large grain boundary resistance limit the total ionic conductivity. Therefore, exploring modification strategies to reduce the sintering temperature and improve the grain contact, effectively reducing the production energy consumption and electrolyte grain boundary resistance, has important significance for improving the application potential of silicate electrolytes and promoting the development of all-solid-state sodium ion batteries. SUMMARY

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a sodium-ion composite solid electrolyte material with simple preparation process, low grain boundary resistance and high ionic conductivity, as well as its preparation method and application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a sodium ion composite solid electrolyte material, which includes a solid electrolyte and a sintering aid;

[0008] The solid electrolyte includes Na. 5-x+3y R 1-y P x Si 4-x O 12 Where R is any one of Ho, In, Sc, Y, Yb, Er, Dy, Gd, and Sm;

[0009] Where x and y take values ​​in the ranges of 0 ≤ x ≤ 0.5 and 0 ≤ y ≤ 0.5, respectively;

[0010] The sintering aid is a sodium salt;

[0011] The sodium salt includes at least one of Na2O, NaF, Na2B4O7, Na3BO3, NaAlO2, and Na3AlF6.

[0012] To address the issues of high sintering temperature and high grain boundary resistance in silicate electrolytes, the inventors, through extensive research and experimentation, discovered that adding the aforementioned low-melting-point sintering aid to sodium silicate solid electrolytes can effectively promote grain growth, improve grain contact, thereby reducing porosity at grain boundaries, increasing material density, and lowering grain boundary resistance, thus significantly improving the ionic conductivity of oxide electrolytes. For example, by introducing the sintering aid, an ionic conductivity of 1.97 × 10⁻⁶ can be achieved at a relatively low sintering temperature (1000℃). -3 S cm -1 The composite electrolyte Na5YSi4O 12 • Prepared with 1.5% Na2B4O7.

[0013] As a preferred embodiment of the sodium ion composite solid electrolyte material of the present invention, the solid electrolyte is Na. 5-x+3y Y 1-y P x Si 4-x O 12 Na 5-x+3y Gd 1-y P x Si 4-x O 12 Or Na 5-x+3y Sm1-y P x Si 4-x O 12 (x=0,y=0);

[0014] Preferably, the solid-state electrolyte is Na5YSi4O 12 , Na5SmSi4O 12 or Na5GdSi4O 12 .

[0015] As a preferred embodiment of the sodium ion composite solid-state electrolyte material of the present application, the sintering aid is Na2B4O7 or NaAlO2.

[0016] As a preferred embodiment of the sodium ion composite solid-state electrolyte material of the present application, the content of the sintering aid is not more than 5wt%.

[0017] The use of the above content of sintering aid in the present application can effectively promote the close combination between the composite electrolyte grains, significantly reduce the grain boundary resistance, and improve the ionic conductivity.

[0018] As a preferred embodiment of the sodium ion composite solid-state electrolyte material of the present application, the content of the sintering aid is 0.5-2wt%.

[0019] Preferably, the content of the sintering aid is one of 0.5wt%, 1wt%, 1.5wt%, 2wt% or a range value of any two thereof.

[0020] When the content of the sintering aid is preferably in the above range, the close combination between the composite electrolyte grains can be more effectively promoted, the grain boundary resistance is significantly reduced, and the ionic conductivity is improved.

[0021] More preferably, the content of the sintering aid is 1.5wt%.

[0022] When the content of the sintering aid is 1.5wt%, the ionic conductivity of the prepared sodium ion composite solid-state electrolyte material is the highest. When the sintering aid is excessive, too many non-sodium ion conducting phases will be introduced, resulting in a significant decrease in the proportion of sodium ion conductors and destroying the continuous ion migration path. The accumulation of non-sodium ion conducting phases can further increase the grain boundary resistance, ultimately leading to a decrease in the ionic conductivity of the solid-state electrolyte ceramic sheet.

[0023] The present application also provides a preparation method of the above-mentioned sodium ion composite solid-state electrolyte material, comprising the following steps:

[0024] S1, mixing raw materials Na2CO3, R2O3 and SiO2, then performing wet ball milling, drying to obtain a precursor powder, and performing high-temperature heat treatment to obtain a solid-state electrolyte pre-sintered powder;

[0025] S2, adding a sintering aid to the solid-state electrolyte pre-sintered powder obtained in step S1, and then performing dry ball milling to obtain a composite solid-state electrolyte powder;

[0026] S3, cold-pressing the composite solid-state electrolyte to form a green body, and then performing high-temperature sintering to obtain a sodium-ion composite solid-state electrolyte ceramic sheet.

[0027] As a preferred embodiment of the preparation method of the sodium-ion composite solid-state electrolyte material, in step S1, the medium for wet ball milling is anhydrous ethanol or isopropanol, the rotation speed for ball milling is 200-1000 rpm, and the ball milling time is 0.5-30 h.

[0028] As a preferred embodiment of the preparation method of the sodium-ion composite solid-state electrolyte material, in step S1, the temperature for heat treatment is 600-900℃, and the time is 1-20 h.

[0029] In step S3, the temperature for high-temperature sintering is 900-1100℃, and the time is 1-20 h.

[0030] The application further provides an application of the above-mentioned sodium-ion composite solid-state electrolyte material in a sodium-ion solid-state battery.

[0031] The sodium-ion solid-state battery prepared by using the sodium-ion composite solid-state electrolyte material has the characteristics of good safety, high charge-discharge specific capacity, excellent cycle stability, etc.

[0032] The application further provides a sodium-ion solid-state battery comprising a positive electrode material, a negative electrode material, and the sodium-ion composite solid-state electrolyte material.

[0033] The sodium-ion solid-state battery of the application can be further used in large-scale energy storage equipment for solar power generation, wind power generation, intelligent power grid peak shaving, distributed power stations, backup power sources, or communication base stations.

[0034] Compared with the prior art, the application has the following beneficial effects:

[0035] The application provides a sodium-ion composite solid-state electrolyte material, a preparation method thereof, and an application thereof. By adding a sintering aid to a sodium silicate solid-state electrolyte, the sintering temperature can be significantly reduced. The sintering aid promotes the growth of crystal grains during the sintering process, thereby improving the density of the material and effectively reducing the grain boundary resistance. In addition, by further optimizing the type and addition amount of the sintering aid, the application can improve the ionic conductivity of the composite electrolyte Na5YSi4O 12·1.5wt% Na2B4O7 preparation conditions are reduced to below 1000℃, while the material's density is improved, realizing a significant improvement in its ionic conductivity. On this basis, the solid-state electrolyte material realizes excellent chemical / electrochemical performance, providing a more broad possibility for its application in all-solid-state sodium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 X-ray diffraction spectrum of the sodium ion composite solid-state electrolyte material of Example 1, Example 2 and the composite solid-state electrolyte of Comparative Example 1, Comparative Example 2;

[0037] Figure 2 X-ray diffraction spectrum of the sodium ion composite solid-state electrolyte material of Example 3, Example 4 and the composite solid-state electrolyte of Comparative Example 1, Comparative Example 2;

[0038] Figure 3 AC impedance spectrum of the sodium ion composite solid-state electrolyte material of Example 1 and the composite solid-state electrolyte of Comparative Example 1;

[0039] Figure 4 AC impedance spectrum of the sodium ion composite solid-state electrolyte material of Example 2 and the composite solid-state electrolyte of Comparative Example 2;

[0040] Figure 5 AC impedance spectrum of the sodium ion composite solid-state electrolyte material of Example 4 and the composite solid-state electrolyte of Comparative Example 1;

[0041] Figure 6 Scanning electron microscope image of the cross-section of the sodium ion composite solid-state electrolyte material of Example 3;

[0042] Figure 7 Scanning electron microscope image of the cross-section of the composite solid-state electrolyte of Comparative Example 1. DETAILED DESCRIPTION

[0043] For the purpose of better illustrating the object, technical scheme and advantages of the present application, the present application will be further described below in conjunction with the drawings and specific embodiments.

[0044] In the following examples and comparative examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified, and the components used in each parallel experiment are the same.

[0045] Example 1

[0046] The present embodiment provides a sodium ion composite solid-state electrolyte material (Na5YSi4O 12 ·Na2B4O7), comprising the following steps:

[0047] S1, according to Na5YSi4O 12 4g of Na₂CO₃, Y₂O₃, and SiO₂ raw materials were weighed according to the stoichiometric ratio, added to 10ml of isopropanol, and then placed in a high-energy ball mill jar for ball milling at 400rpm for 4h to obtain a mixed slurry. After ball milling, the mixed slurry was transferred to an 80℃ forced-air drying oven for drying, and then transferred to a muffle furnace for calcination at 800℃ for 8h to obtain sodium silicate solid electrolyte pre-calcined powder (Na₅YSi₄O₂). 12 );

[0048] S2. Weigh 1.5g of sodium silicate solid electrolyte pre-calcined powder Na5YSi4O 12 Add sintering aid Na2B4O7 at a ratio of 1wt%, place in a high-energy ball mill jar, and ball mill at 400rpm for 4h to obtain sodium ion composite solid electrolyte powder.

[0049] S3. Weigh 0.3g of sodium ion composite solid electrolyte precursor, place it in a mold, press it into a green blank under a pressure of 6MPa, and then place the green blank in a muffle furnace for solid-state sintering at 1000℃ for 9h to obtain sodium ion composite solid electrolyte ceramic sheet.

[0050] Example 2

[0051] Similar to Example 1, the difference is that in step S3 of Example 2, the solid-state sintering temperature is changed to 1050°C, that is, the green blank is placed in a muffle furnace and sintered at 1050°C for 9 hours. The rest of the preparation method is the same as that of Example 1.

[0052] Example 3

[0053] Similar to Example 1, the difference is that in step S2 of Example 3, sintering aid Na2B4O7 is added at a ratio of 1.5wt%, and the ball milling speed is 350rpm; the solid-state sintering temperature in step S3 is 1080℃, and the rest of the preparation method is the same as in Example 1.

[0054] Example 4

[0055] Similar to Example 1, the difference is that in step S2 of Example 4, sintering aid Na2B4O7 is added at a ratio of 1.5wt%, and the solid-state sintering temperature in step S3 is 1000℃. The rest of the preparation methods are the same as in Example 1.

[0056] Example 5

[0057] Similar to Example 1, the difference is that in step S2 of Example 5, sintering aid Na2B4O7 is added at a ratio of 2wt%, and the ball milling speed is 300 rpm; in step S3, the solid-state sintering temperature and time are 1050℃ and 2h, respectively, and the rest of the preparation method is the same as in Example 1.

[0058] Example 6

[0059] Similar to Example 1, the difference is that in step S1 of Example 6, the calcination temperature is adjusted to 650°C; in step S2, sintering aid Na2B4O7 is added at a ratio of 2wt%; in step S3, the solid-state sintering temperature is 1080°C, and the rest of the preparation methods are the same as in Example 1.

[0060] Example 7

[0061] This embodiment provides a sodium ion composite solid electrolyte material (Na5SmSi4O). 12 ·Na2B4O7), including the following steps:

[0062] S1, according to Na5SmSi4O 12 4g of Na₂CO₃, Sm₂O₃, and SiO₂ raw materials were weighed according to the stoichiometric ratio, and 10ml of isopropanol was added. The mixture was then placed in a high-energy ball mill jar for ball milling at 400rpm for 4 hours to obtain a mixed slurry. After ball milling, the slurry was transferred to an 80℃ forced-air drying oven for drying, and then calcined in a muffle furnace at 800℃ for 8 hours to obtain sodium silicate solid electrolyte pre-calcined powder (Na₅SmSi₄O₂). 12 );

[0063] S2, Weigh 1.5g of silicate electrolyte Na5SmSi4O 12 Add sintering aid Na2B4O7 at a ratio of 1wt%, place in a high-energy ball mill jar, and ball mill at 400 rpm for 4 hours to obtain sodium ion composite solid electrolyte powder.

[0064] S3. Weigh 0.3g of sodium ion composite solid electrolyte precursor, place it in a mold, press it into a green blank under a pressure of 6MPa, and then place the green blank in a muffle furnace for solid-state sintering at 900℃ for 20h to obtain sodium ion composite solid electrolyte ceramic sheet.

[0065] Example 8

[0066] Similar to Example 7, the difference is that the solid-state sintering temperature in step S3 of Example 8 is 950°C, and the rest of the preparation method is the same as that of Example 6.

[0067] Example 9

[0068] Similar to example 7, except that in step S2 of example 9, sintering aid Na2B4O7 was added in a proportion of 1.5wt%, the rotation speed of ball milling was 300rpm; the temperature of solid phase sintering in step S3 was 980℃, and the rest of the preparation method was the same as example 6.

[0069] Example 10

[0070] Similar to example 7, except that in step S2 of example 10, sintering aid Na2B4O7 was added in a proportion of 1.5wt%, the rotation speed of ball milling was 350rpm; the temperature of solid phase sintering in step S3 was 1000℃

[0071] Example 11

[0072] Similar to example 7, except that in step S1 of example 11, the temperature of calcination was adjusted to 700℃; in step S2, sintering aid Na2B4O7 was added in a proportion of 2wt%; the time of solid phase sintering in step S3 was 6h.

[0073] Example 12

[0074] Similar to example 7, except that in step S2 of example 12, sintering aid Na2B4O7 was added in a proportion of 2wt%, and the rest of the preparation method was the same as example 7.

[0075] Example 13

[0076] Similar to example 1, except that in step S2 of example 13, sintering aid NaAlO2 was added in a proportion of 1wt%, and the rest of the preparation method was the same as example 1.

[0077] Example 14

[0078] Similar to example 7, except that in step S2 of example 14, sintering aid NaAlO2 was added in a proportion of 1wt%, and the rest of the preparation method was the same as example 7.

[0079] Example 15

[0080] The embodiment provides a sodium ion composite solid-state electrolyte material (Na 5.3 Y 0.8 P 0.3 Si 3.7 O 12 ·Na2B4O7), comprising the following steps:

[0081] S1, adding Na5YSi4O12 S1, the total mass of 4g of Na2CO3, Y2O3, SiO2 and NH4H2PO4 raw materials were weighed according to the stoichiometric ratio, and then placed in a high-energy ball mill tank after adding 10ml of isopropyl alcohol for ball milling. The rotation speed of the ball mill was 400rpm, and the ball milling time was 4h. The mixed slurry was obtained. After the ball milling was completed, the mixed slurry was transferred to a 80℃ air drying oven for drying, and then transferred to a muffle furnace for calcination at 800℃ for 8h. A sodium silicate solid electrolyte pre-sintered powder (Na 5.3 Y 0.8 P 0.3 Si 3.7 O 12 );

[0082] S2, 1.5g of sodium silicate solid electrolyte pre-sintered powder Na 5.3 Y 0.8 P 0.3 Si 3.7 O 12 was weighed, and a sintering aid Na2B4O7 was added at a proportion of 1wt%, and then placed in a high-energy ball mill tank for ball milling at 400rpm for 4h. A sodium ion composite solid electrolyte powder was obtained.

[0083] S3, 0.3g of the sodium ion composite solid electrolyte precursor was weighed and placed in a mold, and then pressed into a green body under a pressure of 6MPa. The green body was then placed in a muffle furnace for solid phase sintering at 1050℃ for 9h. A sodium ion composite solid electrolyte ceramic sheet was obtained.

[0084] Example 16

[0085] Similar to Example 1, the difference is that in step S2 of Example 16, a sintering aid Na2B4O7 was added at a proportion of 5wt%, and the remaining preparation method was the same as that of Example 1.

[0086] Example 17

[0087] This example provides a kind of sodium ion composite solid electrolyte material (Na5GdSi4O 12 ·Na2B4O7), comprising the following steps:

[0088] S1, Na2CO3, Gd2O3 and SiO2 raw materials were weighed according to the stoichiometric ratio of Na5GdSi4O 12 , and then placed in a high-energy ball mill tank after adding 10ml of isopropyl alcohol for ball milling. The rotation speed of the ball mill was 400rpm, and the ball milling time was 4h. The mixed slurry was obtained. After the ball milling was completed, the mixed slurry was transferred to a 80℃ air drying oven for drying, and then transferred to a muffle furnace for calcination at 800℃ for 8h. A sodium silicate solid electrolyte pre-sintered powder (Na5GdSi4O 12);

[0089] S2, weigh 1.5 g of sodium silicate solid electrolyte pre-sintered powder Na5GdSi4O 12 , and add a sintering aid Na2B4O7 at a proportion of 1 wt%, put into a high-energy ball mill jar, ball mill at 400 rpm for 4 h to obtain a sodium ion composite solid electrolyte powder;

[0090] S3, weigh 0.3 g of sodium ion composite solid electrolyte precursor, put into a mold, press into a green body under a pressure of 6 MPa, and then place the green body in a muffle furnace for solid phase sintering at 1050℃ for 9 h to obtain a sodium ion composite solid electrolyte ceramic sheet.

[0091] Example 18

[0092] Similar to Example 17, except that in step S2 of Example 18, a sintering aid Na2B4O7 is added at a proportion of 1.5 wt%; and the solid phase sintering temperature in step S3 is 1080℃.

[0093] Comparative Example 1

[0094] Comparative Example 1 provides a preparation method of a solid electrolyte material Na5YSi4O 12 , comprising the following steps:

[0095] S1: weigh Na2CO3, Y2O3 and SiO2 raw materials with a total mass of 4 g according to the stoichiometric ratio of Na5YSi4O 12 , add 10 ml of isopropyl alcohol, and then place in a high-energy ball mill jar for ball milling, the ball milling speed is 400 rpm, and the ball milling time is 4 h to obtain a mixed slurry; after ball milling, the mixed slurry is transferred to a 80℃ air drying oven for drying, and then transferred into a muffle furnace for calcination at 800℃ for 8 h to obtain a sodium silicate solid electrolyte powder;

[0096] S2: weigh 0.3 g of sodium silicate solid electrolyte powder, put into a mold, and press into a green body under a pressure of 6 MPa. Then place the green body in a muffle furnace for solid phase sintering at 1000℃ for 9 h to obtain a composite solid electrolyte ceramic sheet.

[0097] Comparative Example 2

[0098] Similar to Comparative Example 1, except that in step S2 of Comparative Example 2, the solid phase sintering temperature is 1050℃, and the rest of the preparation method is the same as that of Comparative Example 1.

[0099] Comparative Example 3

[0100] Comparative Example 3 provides a solid electrolyte material Na5SmSi4O12 The preparation method includes the following steps:

[0101] S1: According to Na5SmSi4O 12 4g of Na2CO3, Sm2O3 and SiO2 raw materials were weighed according to the stoichiometric ratio, 10ml of isopropanol was added, and the mixture was placed in a high-energy ball mill jar for ball milling at 400rpm for 4h to obtain a mixed slurry. After ball milling, the mixed slurry was transferred to an 80℃ forced-air drying oven for drying, and then transferred to a muffle furnace for calcination at 800℃ for 8h to obtain sodium silicate solid electrolyte powder.

[0102] S2: Weigh 0.3g of sodium silicate solid electrolyte powder, place it in a mold, and press it into a green blank under a pressure of 6MPa. Then, place the green blank in a muffle furnace and sinter it at 900℃ for 9h to obtain the composite solid electrolyte ceramic sheet.

[0103] Comparative Example 4

[0104] Similar to Comparative Example 3, the difference is that in step S2 of Comparative Example 4, the solid-state sintering temperature is 950℃, while the rest of the preparation method is the same as that of Comparative Example 3.

[0105] Comparative Example 5

[0106] Comparative Example 5 provides a solid electrolyte material Na5GdSi4O 12 The preparation method includes the following steps:

[0107] S1: According to Na5GdSi4O 12 4g of Na2CO3, Gd2O3 and SiO2 raw materials were weighed according to the stoichiometric ratio, 10ml of isopropanol was added, and the mixture was placed in a high-energy ball mill jar for ball milling at 400rpm for 4h to obtain a mixed slurry. After ball milling, the mixed slurry was transferred to an 80℃ forced-air drying oven for drying, and then transferred to a muffle furnace for calcination at 800℃ for 8h to obtain sodium silicate solid electrolyte powder.

[0108] S2: Weigh 0.3g of sodium silicate solid electrolyte powder, place it in a mold, and press it into a green blank under a pressure of 6MPa. Then place the green blank in a muffle furnace and sinter it in the solid state at 1000℃ for 9h to obtain a composite solid electrolyte ceramic sheet.

[0109] Comparative Example 6

[0110] Similar to Example 1, except that in step S2 of Comparative Example 6, sintering aid Na2B4O7 was added at a ratio of 10 wt%, while the rest of the preparation method was the same as in Example 1.

[0111] Comparative Example 7

[0112] Similar to Example 7, except that in Step S2 of Comparative Example 7, a sintering aid Na2B4O7 was added in a proportion of 10wt%, and the rest of the preparation method was the same as that of Example 7.

[0113] Comparative Example 8

[0114] Similar to Example 1, except that in Step S2 of Comparative Example 8, a sintering aid MgB4O7 was added in a proportion of 1wt%, and the rest of the preparation method was the same as that of Example 1.

[0115] Test Example, Test for Ionic Conductivity and Densification of Composite Solid State Electrolyte Materials

[0116] The sodium ion composite solid-state electrolyte materials or composite solid-state electrolyte materials prepared in Examples 1-18 and Comparative Examples 1-8 were subjected to alternating current impedance testing, which was performed by an electrochemical workstation, and the ion conductivity was calculated according to the obtained alternating current impedance spectrum and the formula: σ = L / R·S; wherein σ is the ion conductivity (S / cm), L is the thickness of the electrolyte film (cm), R is the measured impedance (Ω), and S is the area of the electrolyte film (cm 2 ).

[0117] The ion conductivity test and the densification results of the sodium ion composite solid-state electrolyte materials or composite solid-state electrolyte materials prepared in Examples 1-18 and Comparative Examples 1-8 are shown in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] As can be seen from Table 1, compared with Comparative Examples 1-4, Examples 1-18 of the present application, by adding a sintering aid in a content of not more than 5wt% in the sodium silicate electrolyte, can help to densify the composite solid-state electrolyte sample, so that the sample has a higher ion conductivity. Among them, by adding 1.5wt% of Na2B4O7 sintering aid in the silicate electrolyte, the densification of the sodium ion composite solid-state electrolyte can be significantly improved, thereby reducing the grain boundary resistance, so that the sample has a higher ion conductivity.

[0122] Example 4 can achieve densification sintering at a lower temperature (1000℃), and the ion conductivity can be increased from 0.82mS·cm -1 to 1.86mS·cm -1, and the ion migration activation energy thereof is 0.27 eV. The results show that by optimizing the addition ratio of the sintering aid, the size of the grain boundary resistance can be effectively reduced, thereby effectively improving the ion transport performance of the sodium silicate solid electrolyte.

[0123] The addition of the appropriate amount of sodium salt sintering aid in the sodium silicate solid electrolyte described in the application can effectively promote the close combination between the composite electrolyte grains, significantly reduce the grain boundary resistance, and thereby improve the ion conductivity; however, the over-addition of the sintering aid in Comparative Examples 6-7, due to the low ion conductivity of the sintering aid itself, when the addition amount is too high, the ion conductivity of the composite electrolyte is actually reduced.

[0124] The sintering aid of magnesium salt MgB4O7 is used in Comparative Example 8, and the ion conductivity thereof is obviously lower than that of Comparative Example 3, which is not helpful for sintering.

[0125] wherein, Figure 1 The X-ray diffraction spectra of the sodium ion composite solid electrolyte materials of Example 1 and Example 2 and the composite solid electrolytes of Comparative Example 1 and Comparative Example 2 are shown in Figure 1; the obtained composite electrolyte has the same diffraction peaks as the silicate electrolyte, indicating that the addition of the sintering aid does not change the phase structure of the electrolyte.

[0126] Figure 2 The X-ray diffraction spectra of the composite solid electrolytes of Example 3, Example 4 and Comparative Example 1 and Comparative Example 2 are shown in Figure 2; the obtained composite electrolyte has the same diffraction peaks as the Na5YSi4O 12 silicate electrolyte, indicating that appropriate adjustment of the preparation conditions of the composite electrolyte does not change the phase of the composite electrolyte, and no impurity phase is generated.

[0127] Figure 3 The alternating current impedance spectrograms of the sodium ion composite solid electrolyte materials of Example 1 and the composite solid electrolyte of Comparative Example 1 are shown in Figure 3; according to the formula σ = L / R·S, the ion conductivities of the above-mentioned electrolytes are 1.38 mS·cm -1 , 0.82 mS·cm -1 , respectively.

[0128] Figure 4 The alternating current impedance spectrograms of the sodium ion composite solid electrolyte materials of Example 2 and the composite solid electrolyte of Comparative Example 2 are shown in Figure 4; according to the formula σ = L / R·S, the ion conductivities of the above-mentioned electrolytes are 1.69 mS·cm -1 , 0.87 mS·cm -1 , respectively.

[0129] Figure 5The AC impedance spectrograms of the sodium ion composite solid electrolyte material of Example 4 and the composite solid electrolyte of Comparative Example 1; according to the formula σ = L / R·S, the ion conductivities of the above electrolytes are 1.86 mS·cm -1 , 0.82 mS·cm -1 .

[0130] Figure 6 The scanning electron microscope image of the cross-section of the sodium ion composite solid electrolyte material of Example 3; compared with Comparative Example 1, the density of the composite solid electrolyte is significantly improved after adding the sintering aid, and the porosity is significantly reduced.

[0131] Figure 7 The scanning electron microscope image of the cross-section of the composite solid electrolyte of Comparative Example 1; there are a large number of pores between the silicate electrolyte grains without adding the sintering aid, and the density is low.

[0132] Finally, it should be explained that the above examples are only used to illustrate the technical solutions of the present application, but not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the present application.

Claims

1. A sodium-ion composite solid-state electrolyte material, characterized by, The sodium ion composite solid electrolyte material comprises a sodium solid electrolyte and a sintering aid; The solid-state electrolyte comprises Na 5-x+3y R 1-y P x Si 4-x O 12 wherein R is any one of Ho, In, Sc, Y, Yb, Er, Dy, Gd, Sm The value ranges of x and y are 0≤x≤0.5 and 0≤y≤0.5, respectively. The sintering aid is a sodium salt, and the content of the sintering aid is 0.5-2wt%. The sodium salt is NaAlO2.

2. The sodium-ion composite solid-state electrolyte material of claim 1, wherein, The solid-state electrolyte is Na 5-x+3y Y 1-y P x Si 4-x O 12 , Na 5-x+3y Gd 1-y P x Si 4-x O 12 or Na 5-x+3y Sm 1-y P x Si 4-x O 12 .

3. The method for producing a sodium-ion composite solid-state electrolyte material according to claim 1 or 2, characterized by, The preparation method comprises the following steps: S1, raw materials Na2CO3, R2O3, NH4H2PO4 and SiO2 are mixed and then wet ball-milled, and the precursor powder is obtained after drying, and the solid electrolyte pre-sintered powder is obtained after high-temperature heat treatment; S2, the sintering aid is added to the solid electrolyte pre-sintered powder obtained in step S1, and then secondary ball-milling is performed to obtain the composite solid electrolyte powder; S3, the composite solid electrolyte powder is cold-pressed to form a green body, and then high-temperature sintering is performed to obtain the sodium ion composite solid electrolyte material.

4. The method for preparing the sodium ion composite solid electrolyte material as described in claim 3, characterized in that, In step S1, the medium for wet ball-milling is anhydrous ethanol or isopropyl alcohol, the rotation speed of ball-milling is 200-1000 rpm, and the ball-milling time is 0.5-30 h.

5. The method of claim 3, wherein the sodium-ion composite solid-state electrolyte material is prepared by the steps of: preparing a sodium-ion composite solid-state electrolyte material by mixing a sodium-ion conducting material, a sodium-ion conducting polymer, and a sodium-ion conducting inorganic material; and drying the sodium-ion composite solid-state electrolyte material. In step S1, the temperature of heat treatment is 600-900℃, and the time is 1-20 h. In step S3, the temperature of high-temperature sintering is 900-1100℃, and the time is 1-20 h.

6. Application of the sodium ion composite solid electrolyte material according to claim 1 or 2 in a sodium ion solid-state battery.

7. A sodium-ion solid-state battery, characterized by, A sodium ion solid-state battery comprises a positive electrode material, a negative electrode material and the sodium ion composite solid electrolyte material according to claim 1 or 2.

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