Solid electrolyte slurry and preparation method and application thereof

Abstract

The invention discloses solid electrolyte slurry as well as a preparation method and application thereof, and belongs to the technical field of energy storage materials. The solid electrolyte slurry provided by the invention comprises the following raw materials in parts by mass: 40-50 parts of a modified solid electrolyte, 0.5-1.5 parts of a binder and 50-55 parts of a solvent, the modified solid electrolyte comprises a solid electrolyte substrate and a coating layer coating the surface of the solid electrolyte substrate; the coating layer comprises at least one of aluminum oxide, titanium dioxide or silicon dioxide. The coating layer is prepared on the surface of the solid electrolyte substrate, so that side reaction is inhibited, the dispersity and storage stability of the slurry are improved, the pH adjusting step in the slurry preparation process can be reduced, performance fluctuation caused by local non-uniformity is avoided, the finally obtained solid electrolyte slurry has the characteristics of neutral pH and high viscosity, and the preparation method is suitable for industrial production. The preparation of a solid electrolyte layer and a solid battery with excellent electrochemical performance is facilitated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy storage materials, and particularly relates to a solid-state electrolyte slurry, a preparation method and application thereof. BACKGROUND

[0002] In the manufacturing of solid-state batteries, the viscosity and pH value of the electrolyte slurry have important influences on the production process, material performance and overall performance of the battery. High-viscosity slurry has better rheological properties in the coating process, can form a uniform and dense electrolyte layer, and avoid problems such as uneven thickness or edge overflow caused by excessive flowability of the slurry. In addition, high-viscosity slurry can accommodate a higher proportion of solid electrolyte particles, thereby improving the ion conduction performance of the coated layer and meeting the performance requirements of the electrolyte layer of high-energy-density batteries. The interface quality between the electrolyte layer and the electrode material of the solid-state battery determines the cycle life and rate performance of the battery, and a neutral pH value helps to maintain the stability of the interface chemistry, avoid damage or thickening of the interface layer, and improve the interface ion conduction efficiency. Moreover, the use of a neutral pH value slurry helps to reduce the dependence on waste liquid treatment systems in the production process, reduce the risk and cost of environmental pollution, and meet the requirements of green manufacturing.

[0003] In the prior art, the preparation methods of the pH-neutral high-viscosity electrolyte slurry mainly include the following: 1) stepwise mixing method: first, uniformly mix the binder with the solvent, then add the dispersant to promote mixing, and then add the electrolyte powder, pH adjuster and other ingredients to gradually adjust the viscosity and pH of the slurry to the target range; 2) solution method for slurry preparation: completely dissolve the electrolyte powder in a solution containing a pH adjuster, and then add other ingredients to generate the slurry; 3) high-shear dispersion method: use a high-speed shearing device to mix the electrolyte powder with the solvent to generate a high-viscosity slurry, and at the same time, adjust the shearing rate to achieve the uniformity and stability of the slurry; 4) multi-stage grinding method: gradually add the adjuster in the grinding stage to increase the viscosity and adjust the pH value of the slurry.

[0004] The above methods have the following disadvantages: 1) uneven pH adjustment: in the stepwise mixing method and the multi-stage grinding method, the pH adjuster is unevenly distributed in the slurry, which causes the local pH to deviate from the target range and affects the performance of the slurry; 2) poor stability: the slurry prepared by some methods is prone to stratification or sedimentation during storage, affecting the long-term use performance; 3) complex viscosity control: in the solution method, the viscosity adjustment process is affected by factors such as solvent evaporation and temperature change, making it difficult to achieve high-precision control; 4) low preparation efficiency: the high-shear dispersion method requires a long processing time to achieve the target performance, and the process is time-consuming and energy-consuming; 5) insufficient environmental protection: in some methods, strong acid or strong base is used to adjust the pH value, which may cause environmental pollution and increase the cost of waste liquid treatment. SUMMARY

[0005] To overcome at least one of the problems existing in the prior art, one of the purposes of the present application is to provide a solid-state electrolyte slurry, by modifying the setting of the coating layer in the solid-state electrolyte, reducing or avoiding the use of pH adjuster, significantly reducing the risk of local pH unevenness in the slurry, and ensuring the consistency of the electrolyte layer performance.

[0006] The second purpose of the present application is to provide a preparation method of the above-mentioned solid-state electrolyte slurry.

[0007] The third purpose of the present application is to provide a solid-state electrolyte layer.

[0008] The fourth purpose of the present application is to provide a solid-state battery.

[0009] To achieve the above-mentioned purposes, the technical solution adopted by the present application is:

[0010] The first aspect of the present application provides a solid-state electrolyte slurry, which comprises the following mass fractions of raw materials: 40-50 parts of modified solid-state electrolyte, 0.5-1.5 parts of binder, and 50-55 parts of solvent; the modified solid-state electrolyte comprises a solid-state electrolyte substrate and a coating layer coated on the surface of the solid-state electrolyte substrate; the composition of the coating layer comprises at least one of aluminum oxide, titanium dioxide or silicon dioxide.

[0011] In the modified solid-state electrolyte of the present application, the coating layer can isolate the direct contact of the solid-state electrolyte substrate with the raw materials such as solvent or binder, reduce its surface hydrolysis or ion exchange, and maintain pH neutrality; and the coating layer can reduce the surface energy of the particles, enhance the dispersibility, reduce the agglomeration, and improve the uniformity of the slurry; the coating layer can also act as a physical barrier, and can also slow down the particle sedimentation or phase separation during storage, and improve the storage stability of the slurry.

[0012] In addition, the present application optimizes the selection of the amount and ratio of each raw material to ensure the mutual cooperation between each raw material to obtain a slurry with suitable viscosity, dispersibility and flowability. Among them, based on the modified solid-state electrolyte, if the content of the binder is too low, the bonding force is insufficient, and the risk of stratification of the slurry is high; if the content of the binder is too high, it will lead to uncontrolled viscosity of the slurry, and then hinder ion migration, resulting in reduced conductivity of the finally prepared solid-state electrolyte layer; and based on the modified solid-state electrolyte, if the content of the solvent is too low, the flowability of the slurry is poor and it is difficult to uniformly coat; if the content of the solvent is too high, the solid content is insufficient, which will lead to a decrease in the density of the solid-state electrolyte layer. By selecting the amount and ratio of the modified solid-state electrolyte, the binder and the solvent, the slurry has good bonding strength and ion transmission channel continuity, while ensuring that the slurry has high viscosity and flowability, meeting the requirements of the coating process.

[0013] Preferably, the composition of the coating layer comprises titanium dioxide, silicon dioxide or a combination thereof; further preferably, the composition of the coating layer is selected from silicon dioxide.

[0014] Preferably, in the raw material of the solid-state electrolyte slurry, the mass content of the modified solid-state electrolyte is 40-50%; for example, it can be any value of 40%, 42%, 45%, 48% or 50% or a range value between any two of them.

[0015] With a suitable percentage of the amount of the modified solid-state electrolyte, the slurry has a suitable solid content, avoiding too low solid content and insufficient ion conduction capacity of the electrolyte layer, and the conductivity decreases; also avoiding too high solid content and too high viscosity of the slurry, uneven coating thickness and easy cracking.

[0016] Preferably, the solid-state electrolyte substrate comprises at least one of an oxide solid-state electrolyte, a sulfide solid-state electrolyte or a halide solid-state electrolyte; further preferably, the solid-state electrolyte substrate is selected from an oxide solid-state electrolyte.

[0017] Specifically, the chemical formula of the oxide solid-state electrolyte can be A x B y O z ; the chemical formula of the sulfide solid-state electrolyte can be (1-x)Li2S-xP2S5 or Li2S-P2S5-MX; the chemical formula of the halide solid-state electrolyte can be A x B y X z ; wherein 0

[0018] In some embodiments of the present application, the oxide solid-state electrolyte can be lithium lanthanum zirconium oxide (LLZO, Li7La3Zr2O 12 ), tantalum-doped lithium lanthanum zirconium oxide (LLZTO, Li 7-x La3Zr 2-x Ta x O 12 , x=0-2), niobium-doped lithium lanthanum zirconium oxide (LLZNO, Li 7-x La3Zr 2-x Nb x O 12 , x=0-0.6), gallium-doped lithium lanthanum zirconium oxide (LLGZO, Li 7-3x Ga x La3Zr2O 12, x = 0 ~ 0.6) and the like, or lithium titanium aluminum phosphate (LATP, Li 1+x Al x Ti 2-x (PO4)3, x = 0 ~ 0.6), lithium aluminum germanium phosphate (LAGP, Li 1+x Al x Ge 2-x (PO4)3, x = 0 ~ 0.5) and the like, or lithium tantalum phosphorus silicon oxide solid electrolyte (LTPSO, Li 1+x Ta2P 1-x Si x O8, x = 0 ~ 1) and the like.

[0019] Preferably, the binder is a self-thickening high molecular binder.

[0020] The use of a self-thickening high molecular binder can enhance the viscosity and stability of the slurry while maintaining a neutral environment.

[0021] Preferably, the self-thickening high molecular binder includes at least one of polyacrylate, polyvinyl alcohol, cellulose, polyacrylamide, polyurethane, polysiloxane, polyether, or polyvinylidene fluoride. In some embodiments of the present application, the polyacrylate can be carbomer, alkali-swellable emulsion polymer (ASE polymer), non-ionic hydrophobically modified polymer (HEUR polymer) and the like; the polyvinyl alcohol can be partially hydrolyzed polyvinyl alcohol, modified polyvinyl alcohol and the like; the cellulose can be hydroxypropyl methyl cellulose (HPMC), carboxymethyl cellulose (CMC), methyl cellulose (MC) or derivatives thereof and the like; the polyacrylamide can be partially hydrolyzed polyacrylamide (HPAM), cross-linked polyacrylamide or derivatives thereof and the like; the polyurethane (PU) can be hydrophobically modified polyurethane (HEUR type) and the like; the polysiloxane can be siloxane-modified polymer, silane coupling agent and the like; the polyether can be functionalized polyether and the like; the polyvinylidene fluoride can be polyvinylidene fluoride (PVDF), functionalized polyvinylidene fluoride (such as PVDF-HFP), fluorinated modified polyvinylidene fluoride and the like.

[0022] Preferably, the solid electrolyte slurry further includes a dispersant.

[0023] The addition of a dispersant in the slurry can better disperse the solid particles in the slurry, making the slurry have better dispersibility and storage stability.

[0024] Preferably, in the raw materials of the solid electrolyte slurry, the mass content of the dispersant is 0.3 ~ 0.8%; for example, it can be any one of 0.3, 0.4, 0.6 or 0.8 or a range value between any two of them.

[0025] The suitable amount of the dispersant can make the solid particles uniformly dispersed, with small local viscosity fluctuation, and avoid introducing too much impurities, reducing the influence on the electrochemical performance of the electrolyte layer, and further making the slurry be stored for a long time without stratification or sedimentation, and the electrolyte layer prepared from the slurry has good electrochemical performance.

[0026] Preferably, the dispersant comprises at least one of polyethylene glycol, polyethylene oxide or polyvinylpyrrolidone; and further preferably, the dispersant is selected from polyethylene glycol (PEG). The average molecular weight of the polyethylene glycol can be 200-1000, such as 200, 400, 600 or 1000; and in some embodiments of the present application, the polyethylene glycol is selected from PEG-400.

[0027] Preferably, the solid-state electrolyte slurry further comprises a pH adjuster.

[0028] Preferably, in the raw materials of the solid-state electrolyte slurry, the mass content of the pH adjuster is ≤1%; for example, it can be any value or a range value between any two values of 0%, 0.1%, 0.3%, 0.5%, 0.8% or 1%.

[0029] Since the present application adopts a coating layer to coat the solid-state electrolyte substrate, the modified solid-state electrolyte has stable surface performance, can maintain the pH neutrality of the slurry, and thus the amount of the pH adjuster to be added is less, which can effectively avoid local pH unevenness and ensure the consistency of the performance of the electrolyte layer.

[0030] Preferably, the pH adjuster comprises a citric acid-sodium citrate buffer system, an acetic acid-sodium acetate buffer system or a combination thereof; and further preferably, the pH adjuster is selected from the citric acid-sodium citrate buffer system or the acetic acid-sodium acetate buffer system.

[0031] The citric acid-sodium citrate buffer system and the acetic acid-sodium acetate buffer system are weak acid buffer systems, which can effectively reduce the COD value of the waste liquid, reduce the treatment cost of the waste liquid, meet the requirements of green manufacturing, and at the same time achieve good pH adjustment effect, compared with the traditional strong acid adjustment process.

[0032] Preferably, the pH value of the solid-state electrolyte slurry is in the range of 6.8-7.2; for example, it can be any value or a range value between any two values of 6.8, 6.9, 7, 7.1 or 7.2.

[0033] The pH value of the solid-state electrolyte slurry prepared by the present application is neutral, and the fluctuation range is small, which can effectively inhibit the occurrence of side reactions on the surface of the electrolyte powder, and improve the ionic conductivity and interface stability.

[0034] Preferably, the viscosity of the solid-state electrolyte slurry at 25℃ is ≥9000 mPa·s; further preferably 9000-20000 mPa·s; for example, it can be any one of 9000 mPa·s, 10000 mPa·s, 12000 mPa·s, 14000 mPa·s, 16000 mPa·s or 20000 mPa·s or a range value between any two of them.

[0035] The solid-state electrolyte slurry prepared by the method has high viscosity and small fluctuation range, can form a uniform and dense electrolyte layer, and has small thickness uniformity deviation.

[0036] The second aspect of the application provides a preparation method of the solid-state electrolyte slurry of the first aspect of the application, comprising the following steps: mixing raw materials of the solid-state electrolyte slurry to obtain the solid-state electrolyte slurry.

[0037] In some embodiments of the application, the mixing method comprises one-step mixing or dry mixing;

[0038] The one-step mixing is to mix the raw materials at one time, and sequentially perform low-speed mixing and high-speed mixing; the speed of the low-speed mixing is 50-300 r / min; the speed of the high-speed mixing is 700-900 r / min;

[0039] The dry mixing is to mix the solid raw materials, and then add the liquid raw materials for mixing.

[0040] In some specific embodiments of the application, in the one-step mixing, the raw materials can be mixed at one time by first pre-mixing the modified solid-state electrolyte and the solvent, and then adding other raw materials, and sequentially performing low-speed mixing and high-speed mixing; the pre-mixing speed can be 40-60 r / min, and the time can be 5-15 min; the low-speed mixing time can be 15-25 min; the high-speed mixing time can be 25-35 min, or the high-speed mixing is performed until the D90 of the slurry is ≤5 μm. Controlling specific low-speed and high-speed mixing speeds is conducive to uniform dispersion of particles in the slurry, reduces viscosity fluctuation, and improves the thickness uniformity of the electrolyte layer; and controlling specific mixing time can protect the structure of the binder and maintain high conductivity of the electrolyte layer.

[0041] Further, the particle size distribution of the slurry can be obtained while mixing, such as using dynamic light scattering technology to monitor the micro-distribution of the slurry, adjusting the ratio of dispersant and solid to improve the long-term storage stability of the slurry, and avoiding stratification.

[0042] A one-step mixing method is used to add modified solid electrolytes, solvents, and binders to the mixing equipment at once. Through a specific low-speed and high-speed stirring sequence, the raw materials can be quickly and uniformly mixed to gradually form a uniform, high-viscosity slurry. This process avoids complex step-by-step processing, simplifies the process flow, significantly improves preparation efficiency, and effectively reduces slurry preparation time.

[0043] In some specific embodiments of the present invention, in the one-step mixing method, the pH adjuster can be added at any stage of mixing; for example, it can be added during the premixing stage. Adding the pH adjuster during the premixing stage, so that it is added to the solvent in advance, can avoid local pH fluctuations during the slurry preparation process.

[0044] In some specific embodiments of the present invention, in the one-step mixing method, the dispersant is added together with the binder, or the dispersant is added after the binder is added.

[0045] In some specific embodiments of the present invention, in the dry mixing method, the solid raw material includes a modified solid electrolyte and a solid binder, and the liquid raw material includes a solvent and a liquid binder; further, the solid raw materials are mixed by dry mechanical mixing.

[0046] The dry mixing method utilizes dry mechanical mixing to uniformly mix modified solid electrolytes and binders, followed by the addition of solvents to generate a slurry. This method avoids the environmental impact of wet processes, but it requires sophisticated equipment and careful control of preparation uniformity and viscosity fluctuations.

[0047] Preferably, after mixing the raw materials of the solid electrolyte slurry, a degassing treatment is performed; more preferably, the degassing treatment is performed under vacuum conditions; the vacuum degree can be -0.1 to -0.09 MPa; and the degassing treatment time can be 10 to 20 minutes.

[0048] A third aspect of the present invention provides a solid electrolyte layer, which is obtained by curing a solid electrolyte slurry comprising the first aspect of the present invention.

[0049] A fourth aspect of the present invention provides a solid-state battery, the solid-state battery comprising a positive electrode, a negative electrode and a solid electrolyte layer of the third aspect of the present invention.

[0050] In some embodiments of the present invention, the solid-state battery is a lithium solid-state battery.

[0051] In some embodiments of the present invention, the positive electrode includes at least one of nickel-cobalt-manganese ternary materials, lithium iron phosphate, or lithium manganese phosphate; for example, it may be NCM811, NCM910, etc.

[0052] In some embodiments of the present application, the negative electrode comprises at least one of lithium metal, graphite or hard carbon.

[0053] The present application has the advantages that: the present application prepares a coating layer on the surface of a solid-state electrolyte substrate, which is beneficial to inhibit the occurrence of side reactions, improve the dispersibility and storage stability of the slurry, and also can reduce the pH adjustment step in the preparation process of the slurry, avoid performance fluctuations caused by local unevenness, and finally obtain a solid-state electrolyte slurry with the characteristics of pH neutrality and high viscosity, which is beneficial to prepare a solid-state electrolyte layer and a solid-state battery with excellent electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 The preparation flow chart of the solid-state electrolyte slurry in Example 1 of the present application is shown in the figure.

[0055] Figure 2 The long cycle performance comparison chart of the slurry prepared in Example 1 and Comparative Example 2 of the present application after being made into a solid-state battery is shown in the figure. DETAILED DESCRIPTION

[0056] The content of the present application will be further described in detail through specific examples. It should also be understood that the following examples are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the principles set forth in the present application are within the scope of protection of the present application. The following examples are only one example in the appropriate range, i.e. those skilled in the art can make appropriate choices within the scope of the present application, and are not limited to the specific data of the following examples. The raw materials, reagents or devices used in the following examples and comparative examples are commercially available or can be obtained by known methods unless otherwise specified.

[0057] Example 1

[0058] A solid-state electrolyte slurry, the raw material ratio is as follows:

[0059] 1) Preparing a pH neutral LATP powder: LATP (Li 1.3 Al 0.3 Ti 1.7 PO4)3) solid-state electrolyte powder with a particle size D50 = 2.5 μm, the amount is 45wt%; the pre-prepared pH neutral LATP powder is prepared by the following steps: LATP (Li 1.3 Al 0.3 Ti 1.7stoichiometric ratio of raw materials lithium carbonate, alumina, titanium dioxide and ammonium dihydrogen phosphate; ethanol as medium, ball milling of raw materials for 6 hours (speed 300 r / min, zirconium oxide ball); drying at 80°C, pre-sintering at 350°C for 5 hours in air atmosphere to decompose organic matter; tabletting of pre-sintered powder, high-temperature sintering at 900-1000°C for 12 hours (heating rate 5°C / min); crushing of sintered block, secondary ball milling until powder particle size 1-3 μm; dispersing 1 g of secondary ball-milled LATP powder in 100 mL of ethanol / water (volume ratio 9:1) solution, ultrasonic for 30 minutes; adding tetraethyl orthosilicate (TEOS, purity ≥98%, 2-5% of LATP mass, i.e. 0.02-0.05 g based on SiO2 mass), adding ammonia water to adjust pH to 9-10, hydrolyzing TEOS at 60°C constant temperature for 6 hours; centrifugal collection of powder, washing with ethanol for 3 times, vacuum drying at 80°C for 12 hours; annealing at 500°C in nitrogen atmosphere for 2 hours to enhance SiO2 layer stability, obtaining the pre-prepared pH neutral LATP powder;

[0060] 2) Self-thickening binder: neutral polyacrylate (Carbomer 934), amount ratio 0.8 wt%;

[0061] 3) Dispersant: polyethylene glycol (PEG 400), amount ratio 0.5 wt%;

[0062] 4) pH regulator: citric acid-sodium citrate buffer (pH = 7.0), amount adjusted as needed, amount ratio in this example 0.5 wt%;

[0063] 5) Solvent: deionized water, balance, i.e. amount ratio 53.2%.

[0064] The above solid-state electrolyte slurry is prepared by one-step mixing method, and the preparation flow chart is shown in Figure 1 , and the specific preparation steps are as follows:

[0065] 1) Raw material mixing: adding pre-prepared pH neutral LATP powder, Carbomer 934, PEG 400 and deionized water into a double planetary mixer (speed 50 r / min, temperature 25°C), pre-dispersing for 10 minutes; increasing the speed to 200 r / min, continuously stirring for 20 minutes;

[0066] 2) High-speed homogenization: adjusting the speed to 800 r / min, stirring for 30 minutes, and monitoring the particle size distribution of the slurry by dynamic light scattering instrument (DLS) during the process to ensure that D90≤5 μm;

[0067] 3) pH adjustment: adding citric acid-sodium citrate buffer dropwise to adjust the pH of the slurry to 7.0±0.1;

[0068] 4) Degassing treatment: transfer the slurry to a vacuum degassing machine (vacuum degree-0.095 MPa), degassing for 15 minutes to obtain the solid-state electrolyte slurry.

[0069] Example 2

[0070] A solid-state electrolyte slurry, the raw material ratio is as follows:

[0071] 1) Pre-prepared pH neutral LLZTO powder: LLZTO (Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ) powder with a SiO2 layer on the surface, pre-dried to a water content of <0.1wt%, particle size D50 = 2.5μm, and the amount of 45wt%;

[0072] 2) Binder: hydroxypropyl methylcellulose (HPMC), amount of 1.2wt%;

[0073] 3) Solvent: ethanol, the remaining amount, i.e. the amount of 48.8%.

[0074] The above slurry is prepared by one-step mixing method, and the specific preparation steps are as follows:

[0075] 1) Dry mixing of raw materials: add pre-prepared pH neutral LLZTO powder and HPMC into a ball mill (zirconia ball, ball to material ratio 5:1), ball mill at 300r / min for 2 hours; add the mixed mixture after ball milling and ethanol into a high-speed shearing machine (rotating speed 5000r / min), shear and disperse for 15 minutes;

[0076] 2) Viscosity adjustment: control the slurry viscosity to 10000±300mPa·s by adjusting the shearing time (10-20 minutes);

[0077] 3) Degassing treatment: transfer the slurry to a vacuum degassing machine (vacuum degree-0.095 MPa), degassing for 15 minutes to obtain the solid-state electrolyte slurry.

[0078] Example 3

[0079] A solid-state electrolyte slurry, the raw material ratio is as follows:

[0080] 1) Pre-prepared pH neutral LLZTO powder: same as example 1;

[0081] 2) Self-thickening binder: replaced by carboxymethyl cellulose (CMC);

[0082] 3) Dispersant: same as example 1;

[0083] 4) pH regulator: replaced with acetic acid-sodium acetate buffer system (pH = 7.0);

[0084] 5) solvent: same as example 1;

[0085] The amounts of the above raw materials are the same as in example 1.

[0086] The above solid-state electrolyte slurry is prepared by one-step mixing method, and the specific preparation steps are as follows:

[0087] 1) raw material mixing: acetic acid-sodium acetate buffer system, pre-prepared pH neutral LATP powder, Carbomer 934, PEG 400 and deionized water are added into a double planetary mixer (speed 50 r / min, temperature 25°C) for pre-dispersion for 10 minutes; the speed is increased to 200 r / min, and the stirring is continued for 20 minutes;

[0088] 2) high-speed homogenization: the speed is adjusted to 800 r / min, and the stirring is continued for 30 minutes, during which the particle size distribution of the slurry is monitored by dynamic light scattering instrument (DLS) to ensure that D90≤5 μm;

[0089] 3) defoaming treatment: the slurry is transferred to a vacuum defoaming machine (vacuum degree -0.095 MPa) for defoaming for 15 minutes to obtain the solid-state electrolyte slurry.

[0090] Comparative example 1

[0091] A solid-state electrolyte slurry, which is different from example 1 in that in this example, the pre-prepared pH neutral LATP powder is replaced by LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3) solid-state electrolyte powder; other raw materials and amounts, and preparation steps are the same as in example 1.

[0092] Comparative example 2

[0093] A solid-state electrolyte slurry, which is different from example 1 in that in this example, the pre-prepared pH neutral LATP powder is replaced by LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3) solid-state electrolyte powder; other raw materials and amounts are the same as in example 1; and, the preparation method of this example is also different from example 1, and the solid-state electrolyte slurry is prepared by step-by-step mixing method in this example, and the specific steps are as follows: first, Carbomer 934 is mixed with deionized water, then PEG 400 is added to promote mixing, then the electrolyte powder and citric acid-sodium citrate buffer are added, and the slurry viscosity and pH are gradually adjusted to the target range, and finally defoaming treatment is carried out.

[0094] Comparative Example 3

[0095] A solid-state electrolyte slurry, which is different from Example 1 in that the pre-prepared pH neutral LATP powder is replaced by LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3) solid-state electrolyte powder; and the amount of pH adjuster is adjusted to 2wt%; other raw materials and amounts, and preparation steps are the same as Example 1.

[0096] Performance test

[0097] 1) pH detection: detect the pH fluctuation range of the slurry within 12 months of storage at 25°C;

[0098] 2) Viscosity detection: use a rotary viscometer (Brookfield DV2T, rotor 62#, 25°C) to detect viscosity, repeat the test multiple times, record the first test viscosity of the slurry; and test the viscosity of the slurry at regular intervals during 12 months of storage at 25°C, compare with the first test viscosity, and calculate the viscosity fluctuation degree of the slurry with the largest viscosity change value.

[0099] 2) Storage stability: store the slurry at 25°C in a sealed environment, and observe the time when stratification occurs;

[0100] 3) Coating performance: use a doctor blade coater (gap 50μm) to test, record the thickness uniformity deviation of the coating layer; the thickness uniformity deviation of the coating layer should be ≤3%;

[0101] 4) Ionic conductivity: after the slurry is solidified, a solid-state electrolyte layer is formed, and the ionic conductivity (25°C) of the electrolyte layer is tested.

[0102] 5) Battery performance: after the slurry is solidified, a solid-state electrolyte layer is formed, the positive electrode is NCM811, and the negative electrode is lithium metal, a solid-state battery is assembled, and the energy density and capacity retention rate after 260 cycles are tested.

[0103] Table 1 Performance data of Examples 1-3 and Comparative Examples 1-3

[0104]

[0105] As can be seen from Table 1, the pre-prepared pH neutral solid electrolyte powder is used in Example 1 of the present application, combined with one-step mixing process, which significantly reduces the local pH value uneven phenomenon in the slurry, and the pH value of the slurry is maintained in the range of 6.8-7.2; the slurry viscosity fluctuation degree is also controlled to be less than ± 5%, which meets the high-performance coating process requirements; the slurry is stored for 12 months without stratification or sedimentation, and the stability is greatly improved compared with the comparative example; the slurry is placed at 25℃ for 24 hours, and the viscosity change rate is less than 1%, the viscosity stability is good; and compared with the step-by-step mixing method of Comparative Example 2, the one-step mixing process of Example 1 shortens the preparation time by 50%, and the waste liquid COD value is significantly reduced, which is more environmentally friendly and has higher production efficiency; the prepared solid electrolyte layer has good performance consistency, and the ion conductivity is significantly better than that of the comparative example.

[0106] Example 2 uses a dry mixing process, in which the modified solid electrolyte and the binder are uniformly mixed, and then the solvent is added to form a slurry. This method avoids the environmental impact of the wet process, and the obtained slurry has the characteristics of neutral pH value and high viscosity, and has small viscosity fluctuation degree, good storage stability, small thickness uniformity deviation of the coating layer, high ion conductivity of the solid electrolyte layer formed after the slurry is solidified, and low COD value of the waste liquid formed during the preparation process. Compared with the traditional step-by-step mixing method of Comparative Example 2, the processing difficulty and cost are lower, and the total slurry preparation time is shorter.

[0107] Example 3, compared with Example 1, uses a relatively weak weak acid-weak base buffer system, which can further reduce the COD value of the waste liquid and is more environmentally friendly; and by adding the buffer system to the solvent in advance, the local pH fluctuation can be reduced.

[0108] Comparative Example 1 uses uncoated solid electrolyte powder, which has unstable surface properties, large pH fluctuation range of the slurry, poor storage stability, and obvious stratification after 3 months, resulting in large thickness uniformity deviation of the coating layer and low ion conductivity of the solid electrolyte layer. Comparative Example 2 uses uncoated solid electrolyte powder and a traditional step-by-step mixing method, which not only has large slurry viscosity fluctuation degree, but also has long total time, high waste liquid COD value, and large thickness uniformity deviation of the coating layer. Comparative Example 3 uses uncoated solid electrolyte powder and adds more pH adjuster, which has poor slurry stability and low ion conductivity of the solid electrolyte layer formed.

[0109] Table 2 is a performance comparison of the slurry prepared in Example 1 and Comparative Example 2 after being made into a solid-state battery, Figure 2 is a long cycle performance comparison chart of the slurry prepared in Example 1 and Comparative Example 2 after being made into a solid-state battery. It can be seen that the solid-state battery prepared from the slurry of Example 1 has better long cycle performance.

[0110] Table 2 is a performance comparison of the slurry prepared in Example 1 and Comparative Example 2 after being made into a solid-state battery

[0111] Battery performance indicators Example 1 Comparative Example 2 Energy density (Wh / kg) 320 320 260-week capacity retention (%) 91 90

[0112] In summary, the application prepares a coating layer on the surface of the solid electrolyte substrate, which is conducive to inhibiting the occurrence of side reactions, improving the dispersion and storage stability of the slurry, and also can reduce the pH adjustment step in the preparation process of the slurry, avoid performance fluctuations caused by local unevenness, and ultimately obtain a solid electrolyte slurry with the characteristics of pH neutrality and high viscosity, which is conducive to the preparation of a solid electrolyte layer and a solid-state battery with excellent electrochemical performance.

Claims

1. A solid-state electrolyte slurry, characterized by, The solid-state electrolyte slurry comprises raw materials in the following mass fractions: 40-50 parts of modified solid-state electrolyte, 0.5-1.5 parts of binder, and 50-55 parts of solvent; the modified solid-state electrolyte comprises a solid-state electrolyte substrate and a coating layer coated on the surface of the solid-state electrolyte substrate; the composition of the coating layer comprises at least one of aluminum oxide, titanium dioxide, or silicon dioxide.

2. The solid-state electrolyte slurry of claim 1, wherein, In the raw materials of the solid-state electrolyte slurry, the mass content of the modified solid-state electrolyte is 40-50%.

3. The solid-state electrolyte slurry of claim 1, wherein, The solid-state electrolyte substrate comprises at least one of oxide solid-state electrolyte, sulfide solid-state electrolyte, or halide solid-state electrolyte; And / or, the binder is a self-thickening polymer binder; the self-thickening polymer binder comprises at least one of polyacrylate, polyvinyl alcohol, cellulose, polyacrylamide, polyurethane, polysiloxane, polyether, or polyvinylidene fluoride.

4. The solid-state electrolyte slurry of claim 1, wherein, The solid-state electrolyte slurry further comprises a dispersant; in the raw materials of the solid-state electrolyte slurry, the mass content of the dispersant is 0.3-0.8%; And / or, the solid-state electrolyte slurry further comprises a pH regulator; in the raw materials of the solid-state electrolyte slurry, the mass content of the pH regulator is ≤1%.

5. The solid-state electrolyte slurry of claim 4, wherein, The dispersant comprises at least one of polyethylene glycol, polyethylene oxide, or polyvinylpyrrolidone; And / or, the pH regulator comprises a citric acid-sodium citrate buffer system, an acetic acid-sodium acetate buffer system, or a combination thereof.

6. The solid-state electrolyte slurry of any one of claims 1-5, wherein, The pH value of the solid-state electrolyte slurry ranges from 6.8 to 7.2; And / or, the viscosity of the solid-state electrolyte slurry at 25°C is ≥9000 mPa·s.

7. A method for producing the solid-state electrolyte slurry according to any one of claims 1 to 6, characterized by, The method comprises the following steps: Mixing the raw materials of the solid-state electrolyte slurry to obtain the solid-state electrolyte slurry.

8. The preparation method according to claim 7, characterized in that, The mixing method comprises one-step mixing or dry mixing; The one-step mixing is mixing all the raw materials at one time, and sequentially performing low-speed mixing and high-speed mixing; the speed of the low-speed mixing is 50-300 r / min; the speed of the high-speed mixing is 700-900 r / min; The dry mixing is mixing the solid raw materials first, and then adding the liquid raw materials for mixing.

9. A solid-state electrolyte layer, characterized by, The solid-state electrolyte layer is prepared by curing the solid-state electrolyte slurry comprising any one of the solid-state electrolyte slurries in claims 1-6.

10. A solid state battery, characterized by, The solid-state battery comprises a positive electrode, a negative electrode, and the solid-state electrolyte layer in claim 9.

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