Preparation method of lithium ion solid electrolyte

Abstract

The invention relates to the technical field of lithium ion solid-state batteries, and discloses a preparation method of a lithium ion solid-state electrolyte. According to the method, the solid-phase reaction is adopted for the first time to achieve conversion from the Na super-ion conductor to the Li super-ion conductor, only Na ions in the Na super-ion conductor are replaced with Li ions in the reaction process through the solid-phase reaction method, and the residual structure of the Na super-ion conductor does not change, so that the reaction process is more efficient, green, simple and convenient, and the method is suitable for industrial production. The purity of the obtained exchange product is also improved, and the preparation cost is also lower because the use of a solvent is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion solid-state batteries, and particularly to a preparation method of a lithium-ion solid electrolyte. Background Art

[0002] Na3Si2Zr2PO 12 is a sodium-ion solid electrolyte with high ionic conductivity and high stability. Lia3Si2Zr2PO 12 has also been proven to be a lithium-ion solid electrolyte with high ionic conductivity and high stability.

[0003] In the related art, Li3Si2Zr2PO can be prepared by using Na3Si2Zr2PO 12 to carry out a substitution reaction of Na and Li. 12 . However, currently, the conversion from Na3Si2Zr2PO 12 to Li3Si2Zr2PO 12 is usually carried out in a lithium-containing solution in the form of a liquid-phase reaction. This method has the problems of low reaction efficiency and high preparation cost. Summary of the Invention

[0004] In view of this, the present invention provides a preparation method of a lithium-ion solid electrolyte to solve the problems of low reaction efficiency and high preparation cost in the related art when using a Na superionic conductor to prepare a Li superionic conductor.

[0005] In a first aspect, the present invention provides a preparation method of a lithium-ion solid electrolyte, including the following steps:

[0006] Contact a Na superionic conductor powder with a lithium salt powder, and carry out a substitution reaction of Na and Li under stirring and heating conditions without adding a solvent to obtain a reaction product;

[0007] Wash and dry the reaction product;

[0008] wherein the heating temperature is lower than the melting point of the lithium salt.

[0009] In the above preparation method, for the first time, a solid-phase reaction is used to realize the conversion from a Na superionic conductor to a Li superionic conductor. By the method of solid-phase reaction, the reaction process only replaces the Na ions in the Na superionic conductor with Li ions, and the remaining structure of the Na superionic conductor does not change. Therefore, the reaction process is more efficient, green, and simple, the purity of the obtained exchange product is also improved, and the preparation cost is lower because the use of a solvent is avoided.

[0010] In an alternative embodiment, the heating conditions include: a heating temperature of 50 to 500 °C and a heating time of 2 to 100 h. It should be noted that the selection of the heating temperature needs to be determined according to the type of lithium salt used, ensuring that the heating temperature is lower than the melting point temperature of the lithium salt used.

[0011] In an alternative embodiment, the stirring conditions include: a stirring speed of 10 to 1000 rpm and a stirring time of 2 to 100 h.

[0012] In an alternative embodiment, when the Na superionic conductor powder is contacted with the lithium salt powder, the molar ratio of Li to Na is 1:(1 to 100).

[0013] In an alternative embodiment, the Na superionic conductor includes any compound having a Na ion conduction function or a sodium compound capable of performing Na / Li ion conversion;

[0014] Optionally, the Na superionic conductor includes Na3Si2Zr2PO 12 , Na4Zr2(SiO4)3, NaZr2(PO4)3, Na3Hf2Si2PO 12 , Na3La(PO4)2, Na 1.3 Ti 1.7 Al 0.3 (PO4)3, Na3V2(PO4)3 or Na 2.96 Nb 0.04 Zr 1.96 Si2PO 12 or at least one of them.

[0015] In an alternative embodiment, the lithium salt includes an inorganic lithium salt and / or an organic lithium salt;

[0016] Optionally, the lithium salt includes at least one of lithium sulfate, lithium nitrate, lithium chloride, lithium oxalate, and sulfonic acid group lithium.

[0017] In an alternative embodiment, the drying conditions include: a drying temperature of 100 to 900 °C and a drying time of 2 to 10 h. It should be noted that the selection of the drying temperature needs to be determined according to the type of Li superionic conductor prepared.

[0018] In an alternative embodiment, the washing of the reaction product includes:

[0019] Mixing the reaction product with a first solvent to remove soluble salts in the reaction product, then performing solid-liquid separation, and washing the obtained solid with a second solvent.

[0020] In an alternative embodiment, the first solvent comprises water and / or an organic solvent, and the organic solvent comprises at least one of ethanol, DMF, toluene or acetonitrile;

[0021] The second solvent comprises at least one of methanol, ethanol or deionized water. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 is the X-ray diffraction pattern of the exchange product prepared in Example 1 of the present invention;

[0024] Figure 2 is a comparison diagram of the X-ray diffraction patterns of the exchange products prepared in Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following embodiments are provided to better further understand the present invention. They are not limited to the best embodiments, and do not limit the content and protection scope of the present invention. Any product obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features that is the same or similar to the present invention falls within the protection scope of the present invention.

[0026] For those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in the art can be followed. For the reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0027] The following further describes the present invention in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present invention.

[0028] Example 1

[0029] Prepare a lithium-ion solid electrolyte (Li3Si2Zr2PO 12 ) according to the following method:

[0030] (1) Without adding a solvent, 5.3 g of Na3Si2Zr2PO 12 powder and 99 g of Li2SO4 powder are uniformly mixed in a mortar to obtain a raw material mixture, wherein the molar ratio of Li to Na is 1:30;

[0031] (2) Place the raw material mixture obtained in step (1) in a homogeneous reactor, and carry out the replacement reaction of Na and Li under stirring and heating conditions to obtain a reaction product, wherein the heating temperature is 350 °C, the stirring speed is 50 rpm, and the heating time is 24 hours;

[0032] (3) Dissolve the soluble salts in the reaction product obtained in step (2) in distilled water, filter out the remaining solid and wash it 3 times with deionized water, and dry the washed solid at 100 °C for 10 hours to obtain the lithium-ion solid electrolyte Li3Si2Zr2PO 12 .

[0033] Perform X-ray diffraction detection on the lithium-ion solid electrolyte Li3Si2Zr2PO prepared in this example 12 , and the obtained X-ray diffraction pattern is as Figure 1 shown. As can be seen from Figure 1 , this example can prepare a lithium-ion solid electrolyte Li3Si2Zr2PO with relatively high purity 12 .

[0034] Perform ionic conductivity testing on the lithium-ion solid electrolyte Li3Si2Zr2PO prepared in this example 12 , and the test result is 6.7×10 -3 S / cm.

[0035] Example 2

[0036] Prepare the lithium-ion solid electrolyte (Li3Si2Zr2PO 12 ) according to the method of Example 1, except that the heating temperature in step (2) of this example is 50 °C and the heating time is 24 hours.

[0037] Perform ionic conductivity testing on the lithium-ion solid electrolyte Li3Si2Zr2PO prepared in this example 12 , and the test result is 1.0×10 -3 S / cm.

[0038] Example 3

[0039] Prepare the lithium-ion solid electrolyte (Li3Si2Zr2PO 12 ) according to the method of Example 1, except that the heating temperature in step (2) of this example is 500 °C and the heating time is 12 hours.

[0040] Perform ionic conductivity testing on the lithium-ion solid electrolyte Li3Si2Zr2PO prepared in this example 12 , and the test result is 6.9×10 -3 S / cm.

[0041] Example 4

[0042] Prepare a lithium-ion solid electrolyte (Li3Si2Zr2PO 12 ) according to the method of Example 1, except that in step (1) of this example, an equimolar amount of LiNO3 powder is used to replace the Li2SO4 powder, and the heating temperature in step (2) is 200 °C and the heating time is 24 hours.

[0043] Perform an ionic conductivity test on the lithium-ion solid electrolyte Li3Si2Zr2PO prepared in this example 12 The test result is 5.6×10 -3 S / cm.

[0044] Example 5

[0045] Prepare a lithium-ion solid electrolyte (Li3Si2Zr2PO 12 ) according to the method of Example 1, except that in step (1) of this example, an equimolar amount of lithium oxalate powder is used to replace the Li2SO4 powder, and the heating temperature in step (2) is 350 °C and the heating time is 24 hours.

[0046] Perform an ionic conductivity test on the lithium-ion solid electrolyte Li3Si2Zr2PO prepared in this example 12 The test result is 5.0×10 -3 S / cm.

[0047] Example 6

[0048] Prepare a lithium-ion solid electrolyte (Li3Si2Zr2PO 12 ) according to the method of Example 1, except that in step (1) of this example, an equimolar amount of lithium sulfonate powder is used to replace the Li2SO4 powder, and the heating temperature in step (2) is 200 °C and the heating time is 24 hours.

[0049] Perform an ionic conductivity test on the lithium-ion solid electrolyte Li3Si2Zr2PO prepared in this example 12 The test result is 2.4×10 -3 S / cm.

[0050] Comparative Example 1

[0051] Prepare a lithium-ion solid electrolyte (Li3Si2Zr2PO 12 ) according to the following method:

[0052] (1) Without adding a solvent, 5.3 g of Na3Si2Zr2PO 12The powder is evenly mixed with 62.1 g of LiNO3 powder in a mortar to obtain a raw material mixture, where the molar ratio of Li to Na is 1:30;

[0053] (2) The raw material mixture obtained in step (1) is placed in a homogeneous reactor, and the replacement reaction of Na and Li is carried out under stirring and heating conditions to obtain a reaction product. The heating temperature is 350 °C, and the heating time is 24 hours (the melting point of lithium nitrate is 264 °C, and this reaction occurs in molten salt);

[0054] (3) The reaction product obtained in step (2) is placed in distilled water to dissolve soluble salts, the remaining solid is filtered out and washed 3 times with deionized water, and the washed solid is dried at 100 °C for 10 hours to obtain an ion exchange product.

[0055] The ion exchange product prepared in this comparative example was subjected to X-ray diffraction detection, and the obtained X-ray diffraction pattern is as Figure 2 shown. For comparison, the X-ray diffraction pattern of the exchange product prepared in Example 1 is listed in the same figure for comparison. It can be found that the product prepared in Comparative Example 1 contains diffraction peaks other than the product Li3Si2Zr2PO 12 obtained in Example 1, indicating that the purity of the exchange product prepared in Comparative Example 1 is lower than that in Example 1.

[0056] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a lithium-ion solid electrolyte, characterized in that, It includes the following steps: Contact the Na superionic conductor powder with the lithium salt powder, and carry out the replacement reaction of Na and Li under stirring and heating conditions without adding a solvent to obtain a reaction product; Wash and dry the reaction product; Wherein, the heating temperature of the heating is lower than the melting point of the lithium salt.

2. The preparation method according to claim 1, wherein The conditions of the heating include: the heating temperature is 50 - 500 °C, and the heating time is 2 - 100 h.

3. The preparation method according to claim 1 or 2, characterized in that, The conditions of the stirring include: the stirring speed is 10 - 1000 rpm, and the stirring time is 2 - 100 h.

4. The preparation method according to any one of claims 1 to 3, characterized in that, When contacting the Na superionic conductor powder with the lithium salt powder, the molar ratio of Li to Na is 1:(1 - 100).

5. The preparation method according to any one of claims 1 to 4, characterized in that, The Na superionic conductor includes any compound having a Na ion conduction function or a sodium compound capable of performing Na / Li ion conversion; Optionally, the Na superionic conductor includes Na3Si2Zr2PO 12 , Na4Zr2(SiO4)3, NaZr2(PO4)3, Na3Hf2Si2PO 12 , Na3La(PO4)2, Na 1.3 Ti 1.7 Al 0.3 (PO4)3, Na3V2(PO4)3, or Na 2.96 Nb 0.04 Zr 1.96 Si2PO 12 or at least one of the following.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The lithium salt includes an inorganic lithium salt and / or an organic lithium salt; Optionally, the lithium salt includes at least one of lithium sulfate, lithium nitrate, lithium chloride, lithium oxalate, and lithium sulfonate; 7. The preparation method according to any one of claims 1 to 6, characterized in that, The conditions of the drying include: the drying temperature is 100 - 900 °C, and the drying time is 2 - 10 h.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The washing of the reaction product includes: Mix the reaction product with a first solvent to remove the soluble salts in the reaction product, then perform solid-liquid separation, and wash the obtained solid with a second solvent.

9. The preparation method according to claim 8, wherein The first solvent includes water and / or an organic solvent, and the organic solvent includes at least one of ethanol, DMF, toluene, or acetonitrile; The second solvent includes at least one of methanol, ethanol, or deionized water.

Images