Small-particle-size sulfide solid electrolyte material and preparation method and application thereof

Abstract

The application belongs to the technical field of solid-state lithium batteries, and particularly relates to a small-particle-size sulfide solid electrolyte material and a preparation method and application thereof. The method first prepares Li6PS5Cl and Li6PS5Br powders through ball milling and heat treatment, respectively, then the two kinds of powders are dry ball-mixed in proportion, and small-particle-size Li6PS5Cl x Br 1‑x The electrolyte (0.3<=x<=0.7) has small particle size, high ionic conductivity, can significantly improve the electrode / electrolyte interface contact, and can improve the charge-discharge performance and rate performance of the all-solid-state battery. The process is simple, controllable and low in cost, and is suitable for large-scale production. The process has strong universality, can be expanded to other multi-halogen-doped sulfide solid electrolyte systems, and has good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a small-particle-size sulfide solid electrolyte material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries have been widely researched and applied due to their advantages such as high energy density, long cycle life, no memory effect, and low self-discharge rate. Traditional lithium-ion batteries mostly use organic liquid electrolytes, which, although technically mature, pose safety hazards such as flammability and explosion, and their energy density is approaching its theoretical limit, making it difficult to meet the high safety and high energy density requirements of next-generation energy storage devices.

[0003] All-solid-state lithium batteries, which replace flammable liquid electrolytes with solid electrolytes, offer advantages such as high safety, high energy density, and long cycle life, and are widely recognized as the most promising next-generation energy storage technology. The solid electrolyte is the core component of all-solid-state batteries, serving both to isolate the positive and negative electrodes and prevent internal short circuits, while also providing a pathway for lithium-ion transport. Among various solid electrolyte systems, sulfide solid electrolytes, with their combination of high ionic conductivity and good machinability, have become a research hotspot.

[0004] To optimize the preparation process of sulfide solid electrolytes, improve electrode-electrolyte interface contact, and enhance overall battery performance, various methods have been employed to improve existing technologies. Chinese patent CN 120767395B discloses a sulfide solid electrolyte Li... 7-A PS 6-A X A The preparation method of (X is a halogen, 1≤A≤2) improves the fracture toughness, purity and ionic conductivity of the material by controlling the substrate particle size, reducing the amount of solvent and optimizing the sintering process, while reducing pollution, energy consumption and cost; Chinese patent CN120922895A discloses a sulfide solid electrolyte Li 7-A PS 6-A X A The preparation method of (X is a halogen, 1≤A≤2) involves first dry ball milling Li2S, P2S5 and LiX raw materials to amorphize them, then wet ball milling to obtain a precursor slurry with a particle size of 0.05-0.5μm. After drying, solid-state sintering is performed to obtain a submicron / nanoscale pure phase electrolyte, which improves interfacial contact, reduces impedance, and enhances battery performance. Chinese patent CN 120767396B discloses a sulfide solid electrolyte Li 7-A PS 6-A X A(X is a halogen, 1≤A≤2) It is composed of a mixture of large and small particles, with the large particles having a diameter of 3-20 μm and the small particles having a diameter of 0.2-0.8 μm. The small particles account for 90%-95%. This method optimizes the particle size distribution, improves ionic conductivity, improves solvent residue problems, simplifies the process and reduces costs.

[0005] Despite numerous optimizations to existing technologies, the resulting sulfide solid electrolyte powders still tend to exhibit problems such as excessively large particle size and uneven distribution. Therefore, developing a simple process for preparing small-particle-size sulfide solid electrolytes with high product purity, controllable particle size, and excellent ionic conductivity is of significant research value and application importance. Summary of the Invention

[0006] In view of this, the present invention aims to overcome the problems of large particle size, low ionic conductivity, and poor interfacial compatibility of existing sulfide solid electrolytes, and provides a small-particle-size sulfide solid electrolyte material, its preparation method, and its application. The sulfide solid electrolyte powder prepared by the method of the present invention has a significantly reduced particle size, significantly improved ionic conductivity, and excellent electrochemical stability. All-solid-state batteries assembled with this material exhibit stable cycle performance and excellent rate performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention first provides a method for preparing a small-particle-size sulfide solid electrolyte material. The method involves first preparing Li6PS5Cl powder and Li6PS5Br powder using ball milling and heat treatment, then mixing the two powders evenly by ball milling, followed by heat treatment to finally obtain small-particle-size Li6PS5Cl. x Br 1-x Solid electrolyte material, where 0.3≤x≤0.7.

[0008] Specifically, the preparation method of the small-particle-size sulfide solid electrolyte material includes the following steps: Step 1: Preparation of Li6PS5Cl and Li6PS5Br According to the molar ratio of Li:P:S:Cl=6:1:5:1, Li2S, P2S5 and LiCl raw materials were weighed and a small amount of elemental S was added. The mixture was dispersed in a polar organic solvent. The resulting dispersion was then placed in a ball mill jar, wet-milled, and the solvent was evaporated. Finally, the dried powder was placed in a ceramic boat for microwave heat treatment to obtain Li6PS5Cl powder.

[0009] According to the molar ratio of Li:P:S:Br=6:1:5:1, Li2S, P2S5 and LiBr raw materials were weighed and a small amount of elemental S was added. The mixture was dispersed in a polar organic solvent. The resulting dispersion was then placed in a ball mill jar, wet-milled, and the solvent was evaporated. Finally, the dried powder was placed in a ceramic boat for microwave heat treatment to obtain Li6PS5Br powder.

[0010] It should be noted that sulfur is easily lost during heat treatment, and Li₂S impurity phase is easily formed. Adding a small amount of elemental S can replenish sulfur, reduce impurity formation, and improve electrolyte purity. Microwave heat treatment can achieve rapid heating, effectively remove residual solvent, and inhibit the carbonization of solvent residues, which is beneficial for obtaining high-purity, small-particle-size products.

[0011] Step 2: Preparation of Li6PS5Cl x Br 1-x ; The Li6PS5Cl powder and Li6PS5Br powder obtained in step 1 were mixed and placed in a ball mill jar. Dry ball milling was then used to ensure uniform mixing of the two powders. Subsequently, the resulting mixed powder was transferred to a ceramic boat and subjected to microwave heat treatment to obtain Li6PS5Cl. x Br 1-x Solid electrolyte material powder.

[0012] It should be noted that dry ball milling, while achieving uniform mixing of the two electrolytes, can further reduce the powder particle size, promote the in-situ substitution of Cl by Br, and form uniformly halogen-doped Li6PS5Cl. x Br 1-x Phase structure.

[0013] Preferably, in step 1: the ball-to-material ratio of the wet ball mill is 1:10~20, the milling time is 1~12h, the ball milling beads are four sizes: 8mm, 5mm, 2mm and 0.5mm, and the ball milling is carried out by alternating forward and reverse rotation at speeds of 550r / min and 580r / min respectively; the microwave heat treatment power is 100~900W, the time is 1-5min; and the amount of elemental S added is 0.1%~5% of the total mass of the raw materials.

[0014] Preferably, in step 2: Li6PS5Cl and Li6PS5Br are weighed according to a molar ratio of x:(1-x), where 0.3≤x≤0.7; the ball-to-material ratio of the dry ball milling is 1:10~20, the ball milling time is 1~12h, the ball milling beads are four sizes of 8mm, 5mm, 2mm and 0.5mm, and the ball milling is carried out by alternating forward and reverse rotation at speeds of 550r / min and 580r / min respectively; the microwave heat treatment power is 100~900W, and the time is 1-5min.

[0015] Furthermore, the present invention provides a lithium-ion battery that uses the above-mentioned small-particle-size sulfide solid electrolyte material as the electrolyte; the positive electrode of the lithium-ion battery is composed of an active material, a conductive agent and the above-mentioned small-particle-size sulfide solid electrolyte material, wherein the active material accounts for 60% of the total mass of the composite positive electrode, and the conductive agent and solid electrolyte powder together account for 40% of the total mass of the composite positive electrode.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention prepares a sulfide solid electrolyte with fine particle size and uniform element distribution through stepwise synthesis and halogen doping control. By using Br to partially replace Cl to form lattice sites, the room temperature ionic conductivity of the material is significantly improved. When applied to an all-solid-state lithium-ion battery, the battery has stable cycle performance and excellent rate performance.

[0017] 2. The preparation method provided by this invention has strong versatility and can be extended to Li6PS5Cl x Br 1-x Li6PS5Cl x I 1-x Li6PS5Br x I 1-x Li6PS5Cl x Br y I 1-x-y Multi-halogen doped sulfide solid electrolyte systems can effectively improve ion transport capabilities while achieving small particle size control.

[0018] 3. The process route of this invention is simple, the reaction conditions are mild, the process is easy to control, the production cost is low, the equipment requirements are moderate, and it has good potential for industrial scale-up and mass production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 The Li6PS5Cl prepared in Examples 1-3 and the comparative example x Br 1-x XRD patterns.

[0021] Figure 2 The Li6PS5Cl prepared in Examples 1-3 and the comparative example x Br 1-x The EIS impedance spectrum.

[0022] Figure 3 The Li6PS5Cl prepared in Example 2 0.5 Br 0.5 The particle size distribution map.

[0023] Figure 4 Li6PS5Cl prepared for comparative example 0.5 Br 0.5 The particle size distribution map.

[0024] Figure 5 The Li6PS5Cl prepared for Example 2 and the comparative example 0.5 Br 0.5 The performance diagram of a symmetrical battery.

[0025] Figure 6 The Li6PS5Cl prepared in Example 2 0.5 Br 0.5 The full-cell rate performance diagram.

[0026] Figure 7 The Li6PS5Cl prepared in Example 2 0.5 Br 0.5 Full-cell long-cycle performance diagram Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 This embodiment provides a small-particle-size Li6PS5Cl 0.3 Br 0.7 The preparation method of sulfide solid electrolyte materials specifically includes the following steps: Step 1: Prepare Li6PS5Cl powder According to the molar ratio of Li:P:S:Cl=6:1:5:1, Li2S, LiCl, and P2S5 raw materials (total mass of raw materials is 2g) were weighed, and 0.025g of elemental S was added. The above raw materials were placed in a mortar and ground thoroughly. Then, they were dispersed in a polar organic solvent tetrahydrofuran (the volume ratio of polar organic solvent to mixed powder is 3:1). The resulting dispersion was transferred to a ball mill jar, and ball milling beads (ball-to-powder ratio 1:12, with ball diameters of 8mm, 5mm, 2mm, and 0.5mm) were added. The mixture was wet-milled for 6 hours using alternating forward rotation at 550r / min and reverse rotation at 580r / min. The solvent in the mixture after ball milling was evaporated at 130℃. The dried powder was placed in a porcelain boat and microwave-treated in an argon atmosphere (power 500W, time 1min) to obtain Li6PS5Cl powder.

[0029] Step 2: Preparation of Li6PS5Br powder According to the molar ratio of Li:P:S:Br=6:1:5:1, Li2S, LiBr, and P2S5 raw materials (total mass of raw materials is 2g) were weighed, and 0.025g of elemental S was added. The raw materials were then thoroughly ground and mixed in a mortar and dispersed in a polar organic solvent tetrahydrofuran (the volume ratio of polar organic solvent to mixed powder is 3:1). The resulting dispersion was transferred to a ball mill jar, and ball milling beads (ball-to-powder ratio 1:12, with ball diameters of 8mm, 5mm, 2mm, and 0.5mm) were added. The mixture was then wet-milled for 6 hours using alternating forward rotation at 550r / min and reverse rotation at 580r / min. The solvent in the mixture after ball milling was evaporated at 130℃, and the dried powder was placed in a ceramic boat and subjected to microwave heat treatment in an argon atmosphere (power of 500W, time of 1min) to obtain Li6PS5Br powder.

[0030] Step 3: Preparation of Li6PS5Cl 0.3 Br 0.7 Solid electrolyte powder The Li6PS5Cl and Li6PS5Br obtained in steps 1 and 2 were weighed and mixed at a molar ratio of 3:7 and placed in a ball mill jar. Milling beads (ball-to-powder ratio 1:12, with diameters of 8mm, 5mm, 2mm, and 0.5mm) were added, and the mixture was dry-milled at 550 rpm forward and 580 rpm reverse for 6 hours to ensure thorough mixing of the two powders. The uniformly mixed powder was then transferred to a ceramic boat and subjected to microwave heat treatment (500W power, 1 min) in an argon atmosphere to finally obtain small-particle-size Li6PS5Cl. 0.3 Br 0.7 Sulfide solid electrolyte powder.

[0031] Example 2 This embodiment provides a small-particle-size Li6PS5Cl0.5 Br 0.5 The preparation method of the sulfide solid electrolyte material is the same as that in Example 1, except that in step 3, Li6PS5Cl and Li6PS5Br are weighed and mixed in a molar ratio of 5:5.

[0032] Example 3 This embodiment provides a small-particle-size Li6PS5Cl 0.7 Br 0.3 The preparation method of the sulfide solid electrolyte material is the same as that in Example 1, except that in step 3, Li6PS5Cl and Li6PS5Br are weighed and mixed in a molar ratio of 7:3.

[0033] Comparative Example This comparative example uses a conventional one-step dry ball milling-muffle furnace sintering process to prepare Li6PS5Cl. 0.5 Br 0.5 Electrolyte powder, the specific steps are as follows: Step 1: Raw material mixing and dry ball milling According to Li6PS5Cl 0.5 Br 0.5 According to the stoichiometric ratio, accurately weigh Li₂S, LiCl, LiBr, and P₂S₅ raw materials (total mass of raw materials 2g), and add 0.025g of elemental S; place all the above raw materials in a mortar and grind them thoroughly, then transfer them to a ball mill jar and add grinding balls (ball-to-material ratio 1:12, ball diameters of 8mm, 5mm, 2mm, and 0.5mm respectively); use alternating dry ball milling at 550r / min forward and 580r / min reverse for 6 hours to mix all raw materials evenly and obtain a mixed powder.

[0034] Step 2: High-temperature sintering in a muffle furnace The mixed powder obtained in step 1 was transferred to a ceramic boat and placed in a muffle furnace for high-temperature sintering. The sintering heating rate was 3.5℃ / min, the sintering temperature was 450℃, and after holding at that temperature for 1 hour, it was naturally cooled to room temperature to finally obtain Li6PS5Cl. 0.5 Br 0.5 Sulfide solid electrolyte powder.

[0035] The technical solution provided by this invention effectively refines the particles of lithium-phosphorus-sulfur-chlorine solid electrolyte by adopting a stepwise synthesis process of "ball milling-heat treatment" and subsequent high-energy ball milling composite process, significantly improves the interfacial contact between the electrolyte and electrode materials, and synergistically enhances the ionic conductivity and structural stability of the solid electrolyte.

[0036] Combination Figure 1The XRD patterns shown indicate that the diffraction peaks of Examples 1-3 and the comparative example all match the standard card, indicating that the target phase structure was successfully synthesized in each example. Compared with the comparative example and Examples 1 and 3, the diffraction peak intensity of Example 2 is sharper and the impurity peaks are significantly suppressed, indicating that the process of the present invention (especially the halogen ratio of Example 2) can effectively suppress the formation of impurity phases and obtain a pure phase product with high crystallinity and high purity.

[0037] Further integration Figure 2 The EIS impedance spectra and room temperature ionic conductivity test results show that, at 25°C, the ionic conductivity of the comparative example is only 2.53 mS / cm, with a large impedance arc radius. However, the conductivity of all embodiments of this invention is significantly improved, with Example 2 showing the best performance at 4.9 mS / cm, while Examples 1 and 3 are 3.6 mS / cm and 3.9 mS / cm, respectively. This fully demonstrates that this invention suppresses excessive grain growth through microwave heat treatment and utilizes uniform Br / Cl doping to construct superior ion transport channels, significantly reducing the electrolyte's internal resistance.

[0038] Particle size distribution analysis Figure 3 and Figure 4 The refinement effect of the process of the present invention was further verified: the powder particle size prepared in Example 2 was mainly distributed in the range of 1~10μm, with fine and uniform particle size; in contrast, the powder particle size of the comparative example was significantly larger, mainly concentrated in the large particle size range. This result shows that the stepwise synthesis combined with the high-energy ball milling process of the present invention can effectively reduce the particle size of solid electrolyte powder, providing a structural basis for improving battery interface dynamics.

[0039] To verify the actual electrochemical performance, symmetric batteries and all-solid-state batteries were assembled using the electrolytes from Example 2 and the comparative example, respectively.

[0040] like Figure 5 As shown, a symmetrical battery was assembled with both electrodes made of lithium-indium alloy, formed under a pressure of 200 MPa, and subjected to charge-discharge tests. The results showed that the polarization voltage of the comparative example gradually increased significantly with time, and the cycle stability was poor. In contrast, the electrolyte symmetrical battery prepared in Example 2 exhibited a lower polarization voltage and a longer stable cycle time, proving that the material of the present invention not only has high bulk conductivity, but also excellent interfacial contact stability, which can effectively suppress side reactions.

[0041] The all-solid-state battery performance test used a mold battery assembly method, and the specific assembly conditions were as follows: the positive electrode was made of Li(Ni) 0.7 Co 0.2 Mn 0.1The active material O2 was mixed with 40 wt% solid electrolyte powder and pressed into a tablet. The electrolyte film was pressed from the electrolyte synthesized in Example 2. The negative electrode was a lithium indium alloy. The whole was formed under a pressure of 300 MPa and then subjected to charge and discharge tests.

[0042] like Figure 6 As shown, the rate performance test results of this all-solid-state battery demonstrate that at a low rate of 0.1C, the battery discharge specific capacity reaches as high as 175 mAh / g; as the rate increases to 3C, the specific capacity remains above 100 mAh / g, and the coulombic efficiency remains stable at around 100% throughout the process. This excellent rate performance confirms that the small-particle-size, high-conductivity electrolyte of this invention significantly improves charge transport capability under high current density.

[0043] Long-cycle stability ( Figure 7 The results show that after 500 cycles at 1C high rate, the discharge specific capacity of the battery assembled in Example 2 remained at 120 mAh / g, and the coulombic efficiency remained stable at nearly 100%. These results indicate that the small-particle-size sulfide solid electrolyte prepared in this invention possesses both high ionic conductivity and excellent interfacial mechanical stability, effectively maintaining the high-performance output of the all-solid-state battery during long-term cycling.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, or improvements made to the above embodiments within the spirit and principles of the present invention, such as extending the process of the present invention to other halogen-doped sulfide solid electrolyte systems, should be included within the scope of protection of the present invention.

[0045] Without departing from the technical concept of this invention, those skilled in the art can make several modifications and improvements based on the process route and technical principles disclosed in this invention, and these modifications and improvements should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a small-particle-size sulfide solid electrolyte material, characterized in that: First, Li6PS5Cl powder and Li6PS5Br powder were prepared separately using a ball milling-heat treatment method. Then, the two powders were ball-milled and mixed evenly, followed by heat treatment to finally obtain small-particle-size Li6PS5Cl. x Br 1-x Solid electrolyte material, 0.3≤x≤0.

7.

2. The method for preparing small-particle-size sulfide solid electrolyte material according to claim 1, characterized in that, Specifically, the steps include the following: Step 1: Preparation of Li6PS5Cl and Li6PS5Br According to the molar ratio of Li:P:S:Cl=6:1:5:1, Li2S, P2S5 and LiCl raw materials were weighed and a small amount of elemental S was added. The mixture was dispersed in a polar organic solvent. The resulting dispersion was then placed in a ball mill jar, wet-milled, and the solvent was evaporated. Finally, the dried powder was placed in a ceramic boat for microwave heat treatment to obtain Li6PS5Cl powder. According to the molar ratio of Li:P:S:Br=6:1:5:1, Li2S, P2S5 and LiBr raw materials were weighed and a small amount of elemental S was added. The mixture was dispersed in a polar organic solvent. The resulting dispersion was then placed in a ball mill jar, wet ball milled, and the solvent was evaporated. Finally, the dried powder was placed in a ceramic boat for microwave heat treatment to obtain Li6PS5Br powder. Step 2: Preparation of Li6PS5Cl x Br 1-x ; The Li6PS5Cl powder and Li6PS5Br powder obtained in step 1 were mixed and placed in a ball mill jar. Dry ball milling was then used to ensure uniform mixing of the two powders. Subsequently, the resulting mixed powder was transferred to a ceramic boat and subjected to microwave heat treatment to obtain Li6PS5Cl. x Br 1-x Solid electrolyte material powder.

3. The method for preparing small-particle-size sulfide solid electrolyte material according to claim 2, characterized in that, In step 1, the ball-to-material ratio of the wet ball mill is 1:10~20, and the ball milling time is 1~12h.

4. The method for preparing small-particle-size sulfide solid electrolyte material according to claim 2, characterized in that, In step 1, the power of the microwave heat treatment is 100~900W, and the time is 1-5min.

5. The method for preparing small-particle-size sulfide solid electrolyte material according to claim 2, characterized in that, In step 1, the amount of elemental S added is 0.1% to 5% of the total mass of the raw materials.

6. The method for preparing small-particle-size sulfide solid electrolyte material according to claim 2, characterized in that, In step 2, the ball-to-material ratio of the dry ball mill is 1:10~20, and the ball milling time is 1~12h.

7. The method for preparing small-particle-size sulfide solid electrolyte material according to claim 2, characterized in that, In step 2, the power of the microwave heat treatment is 100~900W, and the time is 1-5min.

8. A small-particle-size sulfide solid electrolyte material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 7.

9. The application of the small-particle-size sulfide solid electrolyte material of claim 8 in lithium-ion batteries.

10. A lithium-ion battery, characterized in that, The small-particle-size sulfide solid electrolyte described in claim 8 is used.

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