Surface-modified Li3In x Ga 1-x Cl6 material, its preparation and application in lithium metal solid-state batteries

Abstract

The present invention belongs to the field of solid-state batteries, and specifically relates to a surface-modified Li<subgt;3< / subgt;In<subgt;x< / subgt;Ga<subgt;1-x< / subgt>Cl<subgt;6< / subgt> material, its preparation, and its application in lithium metal solid-state batteries. Among them, the preparation method of the surface-modified Li<subgt;3< / subgt>In<subgt;x< / subgt>Ga<subgt;1-x< / subgt>Cl<subgt;6< / subgt> material is as follows: LiCl, InCl<subgt;3< / subgt>, and GaCl<subgt;3 are mixed for crystallization reaction to obtain the Li<subgt;3< / subgt>In<subgt;x< / subgt>Ga<subgt;1-x< / subgt>Cl<subgt;6 material; in Li<subgt;3< / subgt>In<subgt;x< / subgt>Ga<subgt;1-x< / subgt>Cl<subgt;6, x is 0.55 to 0.95; then the modifier of formula 1 () is used to perform surface modification treatment on the Li<subgt;3< / subgt>In<subgt;x< / subgt>Ga<subgt;1-x< / subgt>Cl<subgt;6 material, and then heat treatment is carried out to obtain the surface-modified Li<subgt;3< / subgt>In<subgt;x< / subgt>Ga<subgt;1-x< / subgt>Cl<subgt;6 material. The material prepared by the method of the present invention can improve the cycle, rate, and low-temperature performance of the lithium metal solid-state battery assembled therefrom.

Description

Technical Field

[0001] The present invention belongs to the field of solid-state batteries, and particularly relates to the field of solid electrolytes for lithium metal batteries. Background Art

[0002] Li3InCl6 has good room-temperature lithium-ion conductivity, excellent interfacial wettability, and relatively low interfacial impedance, showing great application potential. However, different from other halide solid electrolytes, Li3InCl6 has more prominent problems such as easy phase change and lattice misfit in an ambient atmosphere, and is more likely to generate secondary phases that are unfavorable for lithium-ion transport, such as LiCl and In(OH)3. This disadvantage of Li3InCl6 is more prominent in lithium metal solid-state batteries.

[0003] In view of the problems of easy phase change and lattice misfit of Li3InCl6 in an ambient atmosphere, the prior art provides some improvement ideas through coating means. For example, Chinese patent document with publication number CN117996164A discloses a composite solid electrolyte and its preparation method, which includes a halide solid electrolyte and a coating layer coated on the surface of the halide solid electrolyte. The coating layer includes a lithium salt, and the lithium salt includes a first lithium salt, and the decomposition voltage U of the first lithium salt ≥ 4V. Another example is that Chinese patent document with publication number CN118825456A discloses a scheme of carbon-coated solid electrolyte. Patent document with publication number WO2024222526A1 discloses a composite material, which includes a halide solid electrolyte and a coating layer coated outside the halide solid electrolyte, and the material of the coating layer includes a catecholamine self-polymer.

[0004] In summary, the prior art discloses some schemes for improving solid electrolytes through coating. However, the physical and chemical properties of Li3InCl6 are different from those of other solid electrolytes, and it faces more prominent phase change and lattice misfit problems in solid-state batteries, especially in metal lithium solid-state batteries, which will affect its performance. The prior art still lacks targeted improvement schemes. Summary of the Invention

[0005] In order to solve the problem that Li3InCl6 is more likely to undergo phase change, lattice and grain boundary changes under environmental conditions and is difficult to meet the application requirements of metal lithium solid-state batteries, the first object of the present invention is to provide a preparation method of a surface-modified Li3In x Ga 1-x Cl6 material, aiming to improve the lattice and grain boundary stability through the combined improvement of crystal nuclei and the surface, and further improve its performance in metal lithium solid-state batteries.

[0006] The second object of the present invention is to provide the surface-modified Li3In prepared by the above preparation method x Ga 1-xCl6 Material and Its Application in Lithium Metal Solid-State Batteries.

[0007] The third object of the present invention is to provide a lithium metal solid-state battery comprising the surface-modified Li3In x Ga 1-x Cl3 material.

[0008] A preparation method of a surface-modified Li3In x Ga 1-x Cl3 material, wherein LiCl, InCl3 and GaCl3 are mixed according to a stoichiometric ratio and subjected to a crystallization reaction to obtain Li3In x Ga 1-x Cl6 material; in Li3In x Ga 1-x Cl6, the x is 0.55 to 0.95;

[0009] Then, the modifier of formula 1 is used to perform surface modification on the Li3In x Ga 1-x Cl6 material, and then heat treatment is carried out to prepare the surface-modified Li3In x Ga 1-x Cl6 material;

[0010] Formula 1

[0011] R1 is an alkyl group with 1 to 4 carbon atoms; R2 is a substituted hydrocarbon group with at least one substituent of amino group and F.

[0012] In the present invention, Ga is used for lattice hybridization of Li3InCl6, and then surface modification is carried out in combination with the special functionalized modifier of formula 1. In this way, based on the combination of the core and the surface modification process, synergy can be achieved, the stability of the prepared material under environmental conditions can be optimized, problems such as crystal plane and grain boundary collapse can be reduced, and the activation energy of lithium transport can be reduced, and the ionic conductivity can be improved. In this way, the performance of cycling, rate and low temperature, etc. in the lithium metal solid-state battery assembled therefrom can be improved.

[0013] In the present invention, the x can be 0.8 to 0.92; further, it can be 0.85 to 0.91.

[0014] In the present invention, the solvent for the crystallization reaction is water.

[0015] The temperature of the crystallization reaction is 30 to 50 °C;

[0016] The time of the crystallization reaction is 2 to 8 h, and further it can be 3 to 5 h.

[0017] In the present invention, in the modifier of formula 1, the R1 is methyl or ethyl.

[0018] In the present invention, in R2, the substituted hydrocarbon group is a saturated carbon chain group or a partially unsaturated carbon chain group with 3 to 14 carbon atoms carrying the substituent; further, R2 is C m H 2m+1 C n F 2n+1 substituent, where m is 1 to 3; n is 5 to 9.

[0019] In the present invention, in the modifier of Formula 1, modifier a and modifier b are included in a weight ratio of 3 to 10:1 to 5;

[0020] wherein, modifier a is the modifier of Formula 1 with R2 being a fluoroalkyl group; further, R2 is C m H 2m+1 C n F 2n+1 substituent, where m is 1 to 3; n is 5 to 9.

[0021] The modifier b is the modifier of Formula 1 with R2 being an amino-substituted alkyl group; further, R2 is an amino-substituted alkyl group with 2 to 6 carbon atoms.

[0022] The research of this solution shows that innovatively using the combination of F-functionalized modifier a and amino-functionalized modifier b can unexpectedly achieve synergy, further strengthen the combined synergy of the core and surface modification processes, contribute to further strengthening the stability of the crystal phase, crystal plane, and crystal boundary of the material, and thus effectively improve its performance in lithium metal solid-state batteries.

[0023] Further, the weight ratio of modifier a to modifier b is 2 to 4:1.

[0024] In the present invention, the weight ratio of Li3In x Ga 1-x Cl6 material to the modifier of Formula 1 is 80 to 95:4 to 15; further it can be 88 to 94:6 to 12; still further it is 90 to 92:8 to 12.

[0025] The surface modification process is carried out under mechanical assistance, and the time for surface modification is 5 to 40 h; further it can be 20 to 30 h.

[0026] The mechanical assistance is, for example, ball milling.

[0027] In the present invention, the temperature of heat treatment is 100 to 200 °C.

[0028] Further, the heat treatment process includes a first heat treatment process at a temperature of 100 to 130 °C and a second heat treatment process at a temperature of 160 to 200 °C.

[0029] Among them, the heat treatment time is 0.1 - 5 h. Further, the time of the first-stage heat treatment process can be 1 - 3 h, and the time of the second-stage heat treatment is 0.1 - 0.3 h.

[0030] In the present invention, after heat treatment, the heat-treated product is cryogenically treated to obtain the surface-modified Li3In x Ga 1-x Cl6 material. The research of the present invention also shows that further cryogenically treating the heat-treated material helps to further improve the crystal phase, crystal plane and crystal boundary stability of the prepared material, helps to further enhance the environmental stability, and further enhances the performance of the material in the lithium metal solid-state battery.

[0031] The present invention also provides a surface-modified Li3In prepared by the above preparation method x Ga 1-x Cl6 material.

[0032] The present invention also provides an application of the surface-modified Li3In prepared by the above preparation method x Ga 1-x Cl6 material, which is used as a solid electrolyte for a lithium metal solid-state battery.

[0033] In the present invention, based on the conventional principles and ideas of solid-state batteries, the surface-modified Li3In x Ga 1-x Cl6 material can be used to prepare the required solid electrolyte sheets and metal lithium solid-state batteries.

[0034] For example, by a pressing method, the surface-modified Li3In of the present invention x Ga 1-x Cl6 material can be pressed into a solid electrolyte sheet. The pressing pressure can be adjusted as needed. For example, it can be 50 - 500 MPa.

[0035] In the present invention, the negative electrode of the lithium metal solid-state battery is a metal lithium negative electrode or a lithium-containing alloy. The lithium-containing alloy is, for example, a lithium-indium alloy. The positive electrode can be a positive electrode well-known in the industry. For example, the positive electrode material of the positive electrode includes a positive electrode active material, an electrolyte and a conductive agent. The positive electrode active material can be components such as NCM ternary material, lithium cobaltate, lithium nickelate, lithium iron phosphate, etc. The electrolyte is the surface-modified Li3In of the present invention x Ga 1-xCl6 material. The conductive agent described above can be conventional conductive agent components such as conductive carbon black, acetylene black, etc. The weights of the positive electrode active material, electrolyte, and conductive agent can be adjusted as needed, for example, they can be 50-80:10-50:1-10; further, they can be 60-70:25-35:5. In the present invention, the positive electrode can be obtained by pressing the positive electrode material. The pressing pressure can be, for example, 50-500 MPa.

[0036] The lithium metal solid-state battery described in the present invention includes a solid electrolyte sheet, a positive electrode layer provided on one surface of the solid electrolyte sheet, and a lithium metal-containing negative electrode layer provided on the other surface of the solid electrolyte sheet. In addition, in the present invention, a Li6PS5Cl layer is also allowed to exist between the solid electrolyte sheet and the negative electrode layer.

[0037] The present invention also provides a lithium metal solid-state battery, including an electrode core composite with a positive electrode, an electrolyte, and a negative electrode. The electrolyte is the surface-modified Li3In x Ga 1-x Cl6 material; the negative electrode is metallic lithium.

[0038] Beneficial effects

[0039] In the present invention, Ga is used for lattice hybridization of Li3InCl6, and then combined with the special functionalized modifier of formula 1 for surface modification. In this way, the stability of the prepared material under environmental conditions can be synergistically optimized, and problems such as crystal plane and grain boundary collapse can be reduced. In this way, its performance in the lithium metal solid-state battery can be improved.

[0040] The research of the present invention also shows that the combined modification scheme of the modifier a and the modifier b, or combined with cryogenic treatment, helps to further optimize the crystal phase, crystal plane, and lattice stability of the material, helps to further improve the environmental stability of the material, and helps to improve its performance in the lithium metal solid-state battery. Description of the drawings

[0041] Figure 1 It is the electrochemical impedance spectrogram of the electrolyte before and after the exposure treatment of the electrolyte sheet in Example 1;

[0042] Figure 2 It is the cycle curve diagram of the full battery assembled with the electrolyte sheet in Example 1 at 0.5C and 20°C.

[0043] Figure 3 It is the cycle curve diagram of the full battery assembled with the electrolyte sheet in Example 1 at 0.5C and -15°C. Specific embodiments

[0044] The present invention will be described in detail below in conjunction with examples, but the present invention is not limited thereto.

[0045] The surface-modified Li3In x Ga 1-x Cl6 material, one optional preparation step of which is as follows:

[0046] Step 1: Select high-purity LiCl (≥99.9%), InCl3 (purity ≥99.9%), and GaCl3 (purity ≥99.9%). Weigh LiCl:(InCl3 + GaCl3) at a molar ratio of 3:1, and the molar ratio of InCl3:GaCl3 is x:1 - x, where x is 0.55 - 0.95. Add the weighed LiCl, InCl3, and GaCl3 to an appropriate amount of deionized water (for example, about 5 - 15 mL of water corresponds to a total solid mass of about 1 g), and stir at room temperature on a magnetic stirrer until a clear and homogeneous solution is formed.

[0047] Step 2: Pour the completely dissolved solution into a heat-resistant glass baking tray or porcelain dish, and perform crystallization treatment at 30 - 50 °C for 2 - 5 h to obtain precipitated crystal powder.

[0048] Step 3: Transfer the crystal powder to a ball-milling tank, add a modifier (such as at least one of modifier a and modifier b). The mass ratio of the crystal powder to the modifier is 80 - 95:4 - 15. Use 1 - 5 mm zirconia grinding balls, and the mass ratio of the grinding balls to the above materials is 1 - 3:1. The ball-milling rate is 50 - 100 r / min, and the time is 10 - 30 h.

[0049] Step 4: Place the ball-milled material in a vacuum drying oven and treat it at 100 - 120 °C, and then perform heat treatment at 150 - 180 °C for 10 - 20 min.

[0050] In addition, according to needs, the heat-treated product can be cryogenically treated. The cryogenic treatment time can be 10 - 30 min. The cryogenic medium can be dry ice or liquid nitrogen.

[0051] In the present invention, the modifier can be, for example, at least one of modifier a and modifier b. As an optional scheme, the modifier a can specifically be Formula 1A;

[0052] Formula 1A

[0053] As an optional scheme, the modifier b is a compound of Formula 1B;

[0054] Formula 1B.

[0055] Example 1

[0056] Step 1: Select high-purity LiCl (≥99.9%), InCl3 (purity ≥99.9%), and GaCl3 (purity ≥99.9%). Weigh the three substances with a molar ratio of LiCl:(InCl3 + GaCl3) of 3:1, and a molar ratio of InCl3:GaCl3 of 100:10. Add the weighed LiCl, InCl3, and GaCl3 to an appropriate amount of deionized water (for example, about 15 - 20 mL of water corresponds to a total solid mass of about 1 g), and stir at room temperature on a magnetic stirrer until a clear and homogeneous solution is formed.

[0057] Step 2: Pour the completely dissolved solution into a heat-resistant glass baking tray or porcelain dish, and keep it crystallized in an oven at 30°C for 5 h to obtain the precipitated crystal powder.

[0058] Step 3: Transfer the crystal powder to a ball milling jar, add modifiers (including Formula 1A and Formula 1B in this case), and the mass ratio of the three is 92:6:2. Use 5 mm zirconia grinding balls, and the mass ratio of the grinding balls to the above materials is 3:1. The ball milling rate is 50 r / min, and the time is 30 h.

[0059] Step 4: Place the ball-milled material in a vacuum drying oven and treat it at 120°C for 1 h, and then heat-treat it at 180°C for 10 min to obtain the modified product.

[0060] Example 2

[0061] Compared with Example 1, the only difference is that the modifier in Step 3 is changed. The experimental groups are as follows:

[0062] Group A: Only use Formula 1A as the modifier, and the dosage of Formula 1A is the same as the total amount of Formula 1A and Formula 1B in Example 1. Other operations and parameters are the same as in Example 1;

[0063] Group B: Only use Formula 1B as the modifier, and the dosage of Formula 1B is the same as the total amount of Formula 1A and Formula 1B in Example 1. Other operations and parameters are the same as in Example 1;

[0064] Example 3

[0065] Compared with Example 1, the only difference is that after the heat treatment in Step 4, the product is placed in liquid nitrogen for cryogenic treatment (the treatment time is 25 - 35 min) to obtain the modified material.

[0066] Example 4

[0067] Compared with Example 1, the only differences are as follows: In Step 1, LiCl:(InCl3 + GaCl3) is weighed at a molar ratio of 3:1, and the molar ratio of InCl3:GaCl3 is 0.85:0.15. In Step 2, the reaction temperature is 40 °C and the reaction time is 4 h; in Step 3, the mass ratio of the crystal powder, Formula 1A, and Formula 1B is 90:7:3; the ball milling time is 25 h; in Step 4, the heat treatment temperature is 160 °C and the time is 20 min.

[0068] Comparative Example 1

[0069] Compared with Example 1, the only differences are as follows: In Step 1, GaCl3 is not added, and the missing molar amount is supplemented equally by InCl3, that is, the molar ratio of LiCl:InCl3 is 3:1, and other operations and parameters are the same as those in Example 1.

[0070] Comparative Example 2

[0071] Compared with Example 1, the only differences are as follows: In Step 1, GaCl3 is replaced by an equal molar amount of AlCl3, and other operations and parameters are the same as those in Example 1.

[0072] Comparative Example 3

[0073] Compared with Example 1, the only differences are as follows: In Step 3, the modifier is not added. Other operations and parameters are the same as those in Example 1.

[0074] Comparative Example 4

[0075] Compared with Example 2B, the only differences are as follows: In Step 3, Comparative Formula a( ) is used to replace Formula 1B, and other operations and parameters are the same as those in Example 2B.

[0076] Test:

[0077] The solid electrolyte powder prepared above is placed in a mold, and a pressure of 300 MPa is applied and kept for 2 min to form an electrolyte sheet, which is assembled into an ion-blocking symmetric cell (steel symmetric cell) of steel||electrolyte||steel structure. Then, the electrochemical impedance is tested under the conditions of a pressure of 75 Mpa and a temperature of 25 °C, and the ionic conductivity is calculated through the impedance value. The ionic conductivity σ of the solid electrolyte is calculated according to the following formula, where D is the thickness of the electrolyte, R is the impedance value, and S is the effective area of the measured electrolyte. This process uses a frequency range of 0.01 Hz - 1 MHz. The thickness D of the sample prepared in this experiment is 0.8 mm, and the area S is 78.5 mm 2 .

[0078] Subsequently, the obtained electrolyte sheet is exposed to an environment with 30% humidity for 24 h, and then its conductivity retention rate is tested.

[0079] The electrolytes of each case were pressed into tablets at a pressure of 300 MPa and placed in a polyether ether ketone sleeve as a separator. Then, lithium cobalt oxide, the electrolytes of each case, and carbon black were mixed at a mass ratio of 65:30:5 as the positive electrode composite material. 10 mg of the positive electrode composite material was taken and spread on one side of the electrolyte tablet and pressed under a pressure of 300 MPa. Then, Li6PS5Cl (particle size D50 = 4.5 microns) powder was placed on the other side of the electrolyte and pressed under a pressure of 200 MPa. Finally, a lithium-indium alloy sheet (molar ratio of lithium to indium is 35:65) was placed on this side of Li6PS5Cl as the negative electrode, and a stainless steel punch was used as the current collector. Cyclic tests were carried out on the all-solid-state battery, maintaining a test pressure of 80 Mpa, with a voltage range of 2.5 to 4.3 V, testing its retention rate under charge and discharge conditions of 0.5C and 20°C for 500 times, and evaluating its long-cycle stability at high rates. In addition, its retention rate under charge and discharge conditions of 0.1C and -15°C for 500 times was further tested to evaluate its low-temperature performance.

[0080] All the above battery assemblies were completed in a glove box filled with an argon atmosphere. Electrochemical impedance spectroscopy was analyzed on a PARSTAT MC (Princeton, USA) electrochemical workstation, and the battery cycling was carried out on a BlueTEC battery tester.

[0081] The results are shown in Table 1:

[0082]

[0083] It can be seen from Example 1 and Comparative Examples 1 to 4 in Table 1 that Ga is used for lattice hybridization of Li3InCl6, and then surface modification is carried out in combination with the special functionalized modifier of Formula 1. In this way, the stability of the prepared material under environmental conditions can be synergistically optimized, and its performance in the lithium metal solid-state battery can be improved.

[0084] In addition, it can be seen from Example 1 and Example 2 that surface modification treatment using the combined modifier helps to further improve the performance of the obtained lithium metal solid-state battery.

Claims

1. A surface-modified Li3In x Ga 1-x The preparation method of Cl6 material is characterized in that: LiCl, InCl3 and GaCl3 are mixed in a stoichiometric ratio and crystallized to obtain Li3In x Ga 1-x Cl6 materials; Li3In x Ga 1-x In Cl6, x is 0.55 to 0.95; the solvent for the crystallization reaction is water; and the temperature for the crystallization reaction is 30 to 50°C; Then add the modifier of formula 1 to Li3In x Ga 1-x The Cl6 material is subjected to surface modification treatment and then heat treated to obtain the surface modified Li3In x Ga 1-x Cl6 material; Formula 1 R1 is a C1-C4 alkyl group; R2 is a substituted hydrocarbon group having at least one substituent selected from amino and F.

2. The surface-modified Li3In according to claim 1 x Ga 1-x The preparation method of Cl6 material is characterized in that: The crystallization reaction time is 2~8h.

3. The surface-modified Li3In according to claim 1 x Ga 1-x The preparation method of Cl6 material is characterized in that: In the modifier of formula 1, R1 is methyl or ethyl; In the R2, the substituted hydrocarbon group is a saturated carbon chain group or a partially unsaturated carbon chain group having 3 to 14 carbon atoms and carrying the substituent.

4. The surface-modified Li3In according to claim 1 x Ga 1-x The preparation method of Cl6 material is characterized in that: The modifier of formula 1 comprises modifier a and modifier b in a weight ratio of 3-10:1-5; Wherein, modifier a is a modifier of formula 1 wherein R2 is a substituted alkyl group; The modifier b is a modifier of formula 1 wherein R2 is an amino-substituted alkyl group.

5. The surface-modified Li3In according to claim 1 x Ga 1-x The preparation method of Cl6 material is characterized in that: Li3In x Ga 1-x The weight ratio of Cl6 material to the modifier of Formula 1 is 80~95:4~15.

6. The surface-modified Li3In according to claim 1 x Ga 1-x The preparation method of Cl6 material is characterized in that: The surface modification process is carried out with mechanical assistance, and the surface modification time is 5 to 40 hours; The heat treatment temperature is 100~200℃; the heat treatment time is 0.1~5h.

7. The surface-modified Li3In according to any one of claims 1 to 6 x Ga 1-x The preparation method of Cl6 material is characterized in that: After the heat treatment, the heat-treated product is cryogenically treated to obtain the surface-modified Li3In x Ga 1-x Cl6 material.

8. A surface-modified Li3In prepared by the preparation method according to any one of claims 1 to 7 x Ga 1-x Cl6 material.

9. A surface-modified Li3In prepared by the preparation method according to any one of claims 1 to 7 x Ga 1-x The application of Cl6 material is characterized by: Use it as a solid electrolyte for lithium metal solid-state batteries.

10. A lithium metal solid-state battery comprising a battery cell comprising a positive electrode, an electrolyte and a negative electrode, characterized in that: The electrolyte is a surface-modified Li3In prepared by the preparation method according to any one of claims 1 to 7. x Ga 1-x Cl6 material; the negative electrode is metallic lithium.

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