Phosphate solid electrolyte dispersion, and preparation method therefor and use thereof

Abstract

A phosphate solid electrolyte dispersion, and a preparation method therefor and the use thereof, which relate to the technical field of lithium-ion batteries. The dispersion contains a phosphate solid electrolyte, a dispersing agent and water. In the dispersion, the content of the phosphate solid electrolyte is greater than or equal to 40 wt%, wherein the particle size span A of the dispersion is smaller than or equal to 1.5, and A = (D90-D10) / D50, wherein D50, D90 and D10 are respectively the volume particle sizes of phosphate solid electrolyte particles in the dispersion, with the unit thereof being nm. The dispersion has good dispersity, stability and consistency; in addition, when the dispersion is used for a lithium-ion battery, the performance of the battery can be effectively improved.

Description

Phosphate solid electrolyte dispersion and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202310811571.2 filed on July 4, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of lithium-ion batteries, and in particular to a phosphate solid electrolyte dispersion, a preparation method of the phosphate solid electrolyte dispersion, and an application of the phosphate solid electrolyte dispersion. Background Art

[0004] Lithium-ion batteries are primarily composed of a positive electrode, a negative electrode, an electrolyte, and a separator. In addition, various additives such as solvents and binders are used as auxiliary materials to connect the various components in the battery to ultimately obtain a lithium-ion battery with excellent performance. Solvents primarily serve as solvents for the active materials in batteries. Even in the preparation of all-solid-state batteries, it is difficult to completely avoid the use of solvents. Commonly used lithium-ion battery positive electrode solvents include NMP, DMF, and DMSO, while commonly used negative electrode solvents are deionized water or aqueous solutions with the addition of other chemical reagents. Compared to organic solvents, deionized water has the unparalleled advantages of being safe, pollution-free, and inexpensive. Furthermore, with the advancement of technology, water can also be used as a solvent for positive electrode slurries. Therefore, the use of water-dispersed battery materials is an important development direction for lithium-ion batteries.

[0005] Oxide solid electrolytes have high ionic conductivity and good stability, making them key materials for solid-liquid hybrid batteries and all-solid-state batteries. Commonly used oxide solid electrolytes include Nasicon-type LATP, perovskite-type LLTO, garnet-type LLZO, and phosphate-type LAPF. Because LATP is unstable to negative electrode metal lithium and LLZO easily agglomerates in deionized water, it is generally not used in the negative electrode. Hydroxyl-containing phosphate solid electrolytes can participate in the formation of the negative electrode SEI. When added to the positive and negative electrode blends, separator coatings, and organic-inorganic composite solid electrolytes, they can improve battery safety performance. Therefore, the development of hybrid solid-liquid lithium-ion batteries with excellent overcharge performance requires the use of phosphate-type solid electrolytes.

[0006] Phosphate solid electrolytes synthesized by industrial solid-phase methods are all blocks or large micron-sized particles. When used, they need to be nano-processed to obtain small particles of hundreds of nanometers to improve the processing and storage performance of the solid electrolyte. The nano-processing process has very high requirements for the dispersibility of solid electrolytes. The solid electrolyte particles need to remain dispersed and not agglomerated during the grinding process, and the slurry must have a certain fluidity. Because most organic solvents have low surface tension, moderate polarity, and good compatibility with inorganic particles, it is easy to achieve uniform dispersion of solid electrolytes using organic solvents, but it is difficult to achieve stable dispersion using aqueous solvents.

[0007] There are three factors that affect the dispersion of oxide solid electrolytes in water: First, the properties of the material itself. Mechanically crushed particles have irregular morphologies. As grinding continues, the electrolyte particle size decreases and the specific surface area increases. This makes it difficult for the particles to maintain electrostatic repulsion greater than van der Waals forces and other attractive forces in the system, making them prone to agglomeration. Second, hydroxyl-containing phosphate electrolytes also have a certain number of hydroxyl groups on their surfaces, which can form hydrogen bonds between particles, causing the dispersion to be affected by the ratio of electrolyte material to solvent. At high solvent ratios, most electrolytes can be evenly dispersed: the free water molecule content is high, the average distance between small electrolyte particles is long, and nanoparticles are less likely to agglomerate. However, at low solvent ratios, small particles are more likely to agglomerate.

[0008] Prior art discloses nanoelectrolyte slurries, which are battery slurries obtained by mixing solid electrolyte nanoparticles, deionized water, a stabilizer, and a dispersant. The use of polycarboxylic acid dispersants and carboxymethyl cellulose stabilizers improves the dispersibility and storage stability of the solid electrolyte. However, the agglomeration of hydroxyl-containing phosphate solid electrolytes is due to the strong hydrogen bonding attraction between particles, which has a greater range than the van der Waals forces of conventional systems. This makes it impossible to eliminate agglomeration using polycarboxylic acid dispersants at low solvent content.

[0009] In summary, the high-solid content hydroxyl phosphate solid electrolyte aqueous dispersion will agglomerate after being ground, which will cause the slurry to settle, and then lead to a decrease in battery performance when making batteries.

[0010] Summary of the Invention

[0011] The purpose of the present invention is to overcome the above-mentioned technical problems and provide a new phosphate solid electrolyte dispersion and its preparation method and application. The dispersion adopts phosphate solid electrolyte, solvent water and dispersant. Even if the phosphate solid electrolyte content is high, the phosphate solid electrolyte particles in the dispersion are still easy to disperse and do not agglomerate, thereby improving the dispersibility, stability and consistency of the dispersion. At the same time, the above-mentioned dispersion is used in lithium-ion secondary batteries to improve the performance of lithium-ion secondary batteries.

[0012] In order to achieve the above object, the present invention provides a phosphate solid electrolyte dispersion in a first aspect, wherein the dispersion comprises a phosphate solid electrolyte, a dispersant and water;

[0013] In the dispersion, the content of the phosphate solid electrolyte is ≥40wt%;

[0014] Wherein, the particle size span of the dispersion is A≤1.5, A=(D 90 -D 10 ) / D 50 , D 50 、D 90 and D 10 are respectively the volume particle sizes of the phosphate solid electrolyte particles in the dispersion, both in nm.

[0015] In the present invention, unless otherwise specified, the phosphate solid electrolyte dispersion is referred to as dispersion for short.

[0016] In the present invention, unless otherwise specified, the dispersion having high consistency means that: the particle size span A is small, the phosphate solid electrolyte particles in the dispersion are uniform and have no obvious agglomeration; and the phosphate solid electrolyte particles in the dispersion have good dispersibility and are uniformly dispersed.

[0017] In the present invention, unless otherwise specified, the particle size span A refers to the particle size distribution result of the dispersion tested by a laser particle size analyzer, which reflects the uniformity of the particle size in the same system. The smaller A is, the more uniform the particles in the dispersion are and the better the consistency of the particle size. It is generally believed that when the particle size span A of the dispersion is ≤1.5, the formed dispersion agglomerated particles are relatively few and the dispersion is easier to disperse. During battery processing, the dispersion can be evenly distributed in the positive and negative electrode slurries, diaphragm slurries, or coated on the positive and negative electrode materials.

[0018] Preferably, the dispersion liquid consists of a phosphate solid electrolyte, a dispersion liquid and water.

[0019] Preferably, the dispersion is subjected to a shear rate of 100s -1 The viscosity is (1-15)×10 3 mPa·S.

[0020] Preferably, the solid content change rate S of the dispersion is ≤2%, where the solid content change rate refers to the solid content change value of the dispersion after standing for 30 days.

[0021] Preferably, the particle size change rate T of the dispersion is ≤15%, where the particle size change rate refers to the particle size D of the dispersion after standing for 30 days. 50 The change value of particle size, further the particle size change rate T≤10%.

[0022] Preferably, the redispersion rate R of the dispersion is ≤ 12%, and the redispersion rate refers to the particle size D after 40 mL of the dispersion is placed in a 50 mL centrifuge tube and then dispersed using a shaker for 30 days. 50 The change value of the oscillator is 20W in power, 240V in AC, 100rpm in speed, and 10min in vibration. The further redispersion rate R≤5%.

[0023] Preferably, the dispersant is selected from cellulose containing hydroxyl and carboxyl groups and salts thereof.

[0024] Preferably, the degree of substitution of the cellulose is 0.3-1.5, preferably 0.6-1, more preferably 0.8-1.

[0025] Preferably, the weight average molecular weight of the cellulose is 300-200,000 g / mol, preferably 1,000-50,000 g / mol, more preferably 2,000-20,000 g / mol.

[0026] A second aspect of the present invention provides a method for preparing a phosphate solid electrolyte dispersion, the method comprising: grinding a mixed slurry containing a phosphate solid electrolyte, a dispersant, and water to obtain a dispersion;

[0027] Wherein, in the mixed slurry, the content of the phosphate solid electrolyte is ≥40wt%.

[0028] The third aspect of the present invention provides an application of the dispersion provided in the first aspect, or the dispersion prepared by the preparation method provided in the second aspect, in a lithium-ion battery, specifically selected from the application in positive and negative electrode blending, diaphragm coating, and organic / inorganic solid electrolyte composite.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) Phosphate solid electrolytes are easily dispersed in aqueous dispersions with low solid content, but their dispersibility decreases significantly in aqueous dispersions with high solid content, with obvious micron-scale large particle agglomeration observed in the particle size test. This is mainly due to the reduction of free solvent in the dispersion system, the decrease in interparticle spacing, and the fact that some small particles break through the interparticle attraction-repulsion barrier to form agglomerations. In response to this, the present invention uses a specific cellulose dispersant, which is rich in hydroxyl groups and unsaturated cyclic structures to form a cross-linked network that wraps around the small electrolyte particles, preventing the phosphate electrolyte from agglomerating, thereby improving the dispersibility, stability, and consistency of the dispersion. Furthermore, hydrogen bonds can be formed between the hydroxyl-containing phosphate and the hydroxyl groups of cellulose, and the hydroxyl-containing phosphate can better cooperate with the cellulose to form a steric hindrance, forming a stable non-agglomerated system. In addition, by regulating the degree of substitution, molecular weight and type of the dispersant, the dispersant and the phosphate solid electrolyte form a hydrogen bond cross-linked network, and the viscosity, stability (solid content change rate S, particle size change rate T) and dispersibility (redispersion rate R) of the dispersion can be further regulated to obtain a phosphate solid electrolyte dispersion with uniform particle size distribution, stable solid content, stable particle size and easy redispersion.

[0031] In the dispersion provided by the present invention, after the surfactant is added, competitive adsorption occurs with the cellulose dispersant, resulting in the cellulose dispersant being unable to anchor the phosphate electrolyte particles, thereby reducing the anti-agglomeration effect; the addition of other thickeners will further increase the slurry viscosity and cross-link with the cellulose dispersant, reducing the dispersibility of the particles and resulting in a decrease in the slurry processing performance.

[0032] (2) The preparation method of the dispersion provided by the present invention directly grinds a mixed slurry containing a phosphate solid electrolyte, a dispersant, and water to obtain a highly dispersed, highly stable, and highly consistent dispersion; at the same time, the preparation method has the characteristics of simplified process, low cost, and environmental friendliness, and is convenient for industrial production;

[0033] (3) The dispersion provided by the present invention is used in lithium ion batteries, especially lithium ion secondary batteries, which can effectively improve the performance of the batteries. DETAILED DESCRIPTION

[0034] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0035] A first aspect of the present invention provides a phosphate solid electrolyte dispersion, the dispersion comprising a phosphate solid electrolyte, a dispersant and water;

[0036] In the dispersion, the content of the phosphate solid electrolyte is ≥40wt%;

[0037] Wherein, the particle size span of the dispersion is A≤1.5, A=(D 90 -D 10 ) / D 50 , D 50 、D 90 and D 10 are respectively the volume particle sizes of the phosphate solid electrolyte particles in the dispersion, both in nm.

[0038] In the present invention, unless otherwise specified, the volume particle size parameter (i.e., D 90 、D 10 、D 50 、D max ) were measured using the static light scattering method, and the testing instrument was a laser particle size analyzer.

[0039] The inventors of the present invention have discovered that, compared with the prior art, the present invention reduces the water content and improves the storage stability of the dispersion by increasing the phosphate solid electrolyte content in the phosphate solid electrolyte aqueous dispersion; in particular, in combination with a specific sterically hindered dispersant, a hydrogen bond cross-linked network can be formed to prevent the reduction in particle spacing due to the reduction in water, which in turn leads to a decrease in intermolecular forces and ultimately causes particle agglomeration.

[0040] Preferably, when the dispersant is selected from low molecular weight carboxymethyl cellulose or hydroxyethyl cellulose, it can absorb a large amount of water, causing its own volume to expand significantly, reducing the free activity space of the dispersed particles. At the same time, the carboxymethyl cellulose molecular chains are entangled with each other to form a three-dimensional network structure, and the phosphate solid electrolyte particles are surrounded in the grid, reducing the fluidity and increasing the viscosity of the dispersion.

[0041] In some embodiments of the present invention, preferably, the dispersion consists of a phosphate solid electrolyte, a dispersion and water; in the dispersion, the content of the phosphate solid electrolyte is ≥40 wt%; wherein the particle size span of the dispersion is A≤1.5, A=(D 90 -D 10 ) / D 50 , D 50 、D 90 and D 10 are respectively the volume particle sizes of the phosphate solid electrolyte particles in the dispersion, both in nm.

[0042] In some embodiments of the present invention, preferably, in the dispersion, the content of the phosphate solid electrolyte is 40-85wt%, for example, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, and any value in the range consisting of any two values.

[0043] In the present invention, the content of the phosphate solid electrolyte = (mass of the phosphate solid electrolyte) / (total mass of the dispersion). Preferably, the content of the phosphate solid electrolyte = (mass of the phosphate solid electrolyte) / (total mass of the phosphate solid electrolyte, dispersant and water).

[0044] In some embodiments of the present invention, preferably, the particle size span A of the dispersion is 0.8-1.5, for example, 0.8, 0.9, 0.95, 1, 1.05, 1.1, 1.12, 1.15, 1.18, 1.2, 1.3, 1.4, 1.5, and any value in the range of any two values, preferably 0.8-1.2, wherein A=(D 90 -D 10 ) / D 50 , and D 90 、D 10 and D 50 The preferred conditions are more conducive to improving the dispersion stability and consistency of the dispersion.

[0045] In some embodiments of the present invention, preferably, the particle size D of the phosphate solid electrolyte particles is max ≤1μm; Further preferably, the particle size D of the phosphate solid electrolyte particles 10 20-300nm, particle size D 50 50-500nm, particle size D 90 In the present invention, D max It refers to the maximum volume particle size of the phosphate solid electrolyte particles, μm.

[0046] In some embodiments of the present invention, preferably, in the dispersion, the mass ratio of the phosphate solid electrolyte to the dispersant is 1:0.001-0.08, for example, 1:0.001, 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.08, and any value in a range consisting of any two values, preferably 1:0.005-0.05, more preferably 1:0.01-0.03. The above mass ratio range is more conducive to improving the viscosity, solid content change rate, particle size change rate, and redispersion rate of the dispersion.

[0047] In the present invention, the dispersion is a non-Newtonian fluid, that is, the viscosity of the dispersion changes with the shear rate. Preferably, the dispersion is -1 The viscosity is (1-15)×10 3 mPa·s, for example, 1×10 3 mPa·s, 2×10 3 mPa·s, 3×10 3 mPa·s, 4×10 3 mPa·s, 5×10 3 mPa·s, 6×10 3 mPa·s, 8×10 3 mPa·s, 10×10 3 mPa·s, 11×10 3 mPa·s, 12×10 3 mPa·s, 13×10 3 mPa·s, 14×10 3 mPa·s, 15×10 3 mPa·s, and any value in the range consisting of any two values.

[0048] In the present invention, unless otherwise specified, the viscosity parameters of the dispersion are tested using a rotor viscometer, model NDJ-5S, with rotor No. 4, tested at 60 rpm, and the readings taken after the viscosity stabilizes.

[0049] In some embodiments of the present invention, preferably, the solid content change rate S of the dispersion is ≤2%, for example, 0.1%, 0.2%, 0.4%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, and any value in the range consisting of any two values. The solid content change rate refers to the solid content change value of the dispersion after standing for 30 days, that is, the upper or lower layer of the dispersion after standing for 30 days needs to meet the above range. Specifically, after standing for 30 days, the upper layer of the dispersion 5 mm from the liquid surface and the lower layer of the dispersion 5 mm from the bottom of the bottle both need to meet the above range.

[0050] In the present invention, unless otherwise specified, the solid content change rate S of the dispersion is measured using a drying method, and the specific testing steps are as follows:

[0051] (1) Take the prepared dispersion and test the solid content, which is recorded as the initial solid content w0;

[0052] (2) Take 100 mL of the dispersion in a 150 mL experimental bottle, seal the experimental bottle and let it stand for 30 days; after 30 days, take 1 mL of the dispersion at a point 5 mm from the liquid surface in the experimental bottle and measure the solid content, which is recorded as the solid content value w1 of the upper layer of the dispersion; take 1 mL of the dispersion at a point 5 mm from the bottom of the experimental bottle and measure the solid content, which is recorded as the solid content value w2 of the lower layer of the dispersion;

[0053] (3) The solid content change rate S of the dispersion is measured by the deviation of the solid content values ​​w1 and w2 of the upper and lower layers from the initial solid content value w0, where the solid content change value of the upper layer is S1 = |w1-w0| / w0×100%, and the solid content change value of the lower layer is S2 = |w2-w0| / w0×100%. The smaller the values ​​of S1 and S2, the more stable the solid content of the upper and lower layers of the dispersion.

[0054] In some embodiments of the present invention, preferably, the particle size change rate T of the dispersion is ≤ 15%, for example, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 5%, 6%, 8%, 10%, 11%, 12%, 13%, 14%, 15%, and any value in the range of any two values, more preferably T ≤ 10%. Wherein, the particle size change rate refers to the particle size D of the dispersion after standing for 30 days. 50 The change value of the upper and lower dispersions must meet the above range. Specifically, after standing for 30 days, the particle size D 50 All need to meet the above range.

[0055] In the present invention, unless otherwise specified, the particle size change rate T of the dispersion is measured by a laser particle size analyzer to determine the particle size D of the dispersion. 50The solvent in the test injector is deionized water. The dispersion sample is added dropwise to the test injector for testing. The test parameters are set as follows: the material refractive index is 2.42, the absorptivity is 1.0, and the shading degree is 1-4%. The specific test steps are as follows:

[0056] (1) Take the prepared dispersion and test the particle size, which is recorded as the initial average particle size D0;

[0057] (2) Take 100 mL of the dispersion in a 150 mL test bottle, seal the test bottle and let it stand for 30 days; after 30 days, take 1 mL of the dispersion at a point 5 mm from the liquid surface in the test bottle and measure the particle size, which is recorded as the particle size value of the upper layer of the dispersion D1; take 1 mL of the dispersion at a point 5 mm from the bottom of the test bottle and measure the particle size, which is recorded as the particle size value of the lower layer of the dispersion D2;

[0058] (3) The particle size change rate T of the dispersion is measured by the deviation between the particle size values ​​D1 and D2 of the upper and lower layers and the initial particle size value D0; wherein, the particle size change value of the upper layer of the dispersion is T1 = |D1-D0| / D0×100%, and the particle size change value of the lower layer is T2 = |D2-D0| / D0×100%; the smaller the values ​​of T1 and T2, the more stable the particle sizes of the upper and lower layers of the dispersion.

[0059] In some embodiments of the present invention, preferably, the redispersion rate R of the dispersion is ≤ 12%, for example, 0.1%, 0.2%, 0.4%, 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, and any value in the range of any two values, more preferably R ≤ 5%. The redispersion rate refers to the particle size D after 40 mL of the dispersion is taken from a 50 mL centrifuge tube and allowed to stand for 30 days and then dispersed using a shaker. 50 The change value of the oscillator is 20W, AC 240V, speed 100rpm, and oscillation for 10min. The upper and lower dispersions must meet the above range. Specifically, after standing for 30 days, the upper layer is 5mm from the liquid surface and the lower layer is 5mm from the bottom of the bottle. 50 All need to meet the above range.

[0060] In the present invention, unless otherwise specified, the redispersion rate R of the dispersion is measured by a laser particle size analyzer to determine the particle size D of the dispersion. 50 The solvent in the test injector is deionized water. The dispersion sample is added dropwise to the test injector for testing. The test parameters are set as follows: the material refractive index is 2.42, the absorptivity is 1.0, and the shading degree is 1-4%. The test steps are as follows:

[0061] (1) Take the prepared dispersion and test the particle size, which is recorded as the initial average particle size D0;

[0062] (2) 40 mL of the dispersion was placed in a 50 mL centrifuge tube, which was sealed and allowed to stand for 30 days. After 30 days, the dispersion was re-dispersed and the particle size was measured, which was recorded as the re-dispersed particle size D3. The dispersion method was to use a laboratory shaker with a power of 20 W, an AC voltage of 240 V, and a rotation speed of 100 rpm for 10 minutes.

[0063] (3) The redispersibility R of the dispersion is measured by the deviation between the redispersed particle size D3 and the initial particle size D0; R = |D3-D0| / D0×100%. The smaller the value of R, the less agglomerated the dispersion is and the easier it is to disperse.

[0064] In some embodiments of the present invention, the phosphate solid electrolyte is preferably selected from natural oxide materials or synthetic oxide materials containing Li, O, and P. Further preferably, the phosphate solid electrolyte further contains at least one element selected from H, halogen, and non-Li metal elements. In the present invention, the non-Li metal element is selected from at least one of Al, Zr, Fe, Sm, Pr, Nb, Ga, Zn, Y, Mg, Al, Cr, Ca, Ti, Cu, Sr, Ba, Ce, Sn, Sb, La, and Bi.

[0065] In a specific embodiment of the present invention, the phosphate solid electrolyte is selected from a group containing Li, O, P, H, halogen, and non-Li metal elements. Preferably, the phosphate solid electrolyte is selected from a lithium aluminum phosphate containing a hydroxyl group, and more preferably, the phosphate solid electrolyte is selected from a lithium aluminum phosphate containing a hydroxyl group and a halogen.

[0066] In some specific embodiments of the present invention, the phosphate solid electrolyte is selected from Li, O, P, H, halogen and non-Li metal elements (e.g., Al). Preferably, the phosphate solid electrolyte has a composition shown in Formula I, Li 1+x H 1-x Al(PO4)O 1-y X 2y (I), wherein 0≤x<1, 0<y<0.1, and X is selected from at least one of F, Cl, Br and I.

[0067] In other specific embodiments of the present invention, the phosphate solid electrolyte is selected from Li, O, P, H, halogen and non-Li metal elements (e.g., Al). Preferably, the phosphate solid electrolyte has a composition shown in Formula II, LiAl(PO4)(OH) 1-w X w (II), wherein 0≤w<1, and X is selected from at least one of F, Cl, Br and I.

[0068] In some embodiments of the present invention, further preferably, the phosphate solid electrolyte is selected from LAPF and / or LAPBr, more preferably LAPF. Using the preferred conditions is more conducive to improving the dispersibility of the dispersion.

[0069] In some embodiments of the present invention, preferably, the particle size D of the phosphate solid electrolyte is 50 0.5-1000 μm, for example, 0.5 μm, 1 μm, 3 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 500 μm, 1000 μm, and any value in a range consisting of any two values.

[0070] In some embodiments of the present invention, preferably, the dispersant is selected from cellulose containing hydroxyl and carboxyl groups and its salts. Compared with other types of dispersants (for example, fatty alcohol polyoxyethylene ether, polyacrylic acid, sodium dodecylbenzene sulfonate, sodium tetramethylbenzene sulfonate, etc.), the present invention adopts a specific dispersant, that is, cellulose containing hydroxyl and carboxyl groups as a dispersant, which can form a hydrogen bond cross-linked network on the one hand, preventing the reduction of the interparticle distance caused by the reduction of water, thereby causing the intermolecular force to decrease and ultimately causing the particles to agglomerate; on the other hand, it can also adjust the viscosity of the dispersion and improve the grinding efficiency of the dispersion; at the same time, it can reduce the surface tension of the solvent, prevent the surface solvent from seeping out during storage, and improve the stability of the solid content.

[0071] In some embodiments of the present invention, the degree of substitution of the cellulose is preferably 0.3-1.5, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 1, 1.05, 1.2, 1.5, and any value in a range consisting of any two values, preferably 0.6-1, and more preferably 0.8-1. When the degree of substitution is less than 0.3, the cellulose is not easily soluble in water; when the degree of substitution is greater than 1.5, the viscosity decreases, and it is difficult to improve the sedimentation stability of the slurry and prevent the agglomeration of electrolyte particles.

[0072] In some embodiments of the present invention, preferably, the weight average molecular weight of the cellulose is 300-200000 g / mol, for example, 300 g / mol, 1000 g / mol, 2000 g / mol, 5000 g / mol, 8000 g / mol, 10000 g / mol, 15000 g / mol, 20000 g / mol, 25000 g / mol, 30000 g / mol, 50000 g / mol, 80000 g / mol, 100000 g / mol, 150000 g / mol, 200000 g / mol, and any value in the range consisting of any two values, preferably 1000-50000 g / mol, more preferably 2000-20000 g / mol.

[0073] In the present invention, the greater the weight-average molecular weight of the cellulose, the greater the improvement in the viscosity of the final slurry. Using a low-weight-average molecular weight cellulose has little effect on the viscosity of the dispersion, resulting in a lower viscosity of the final dispersion and reduced solid content stability. Using a high-molecular-weight cellulose significantly increases the viscosity of the dispersion, reduces the fluidity of the dispersion, and reduces the grinding process capability, resulting in a large electrolyte particle size, and the inability to grind D10, D50, and D90 to the nanometer level.

[0074] In the present invention, unless otherwise specified, the cellulose tends to be monodisperse and uniformly high in molecular weight.

[0075] In some embodiments of the present invention, the cellulose is preferably selected from at least one of methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl hydroxyethyl cellulose, and is preferably selected from carboxymethyl cellulose. Using these preferred conditions is more conducive to improving the solid content change rate, particle size change rate, and redispersion rate of the dispersion, thereby effectively improving the stability and dispersibility of the dispersion.

[0076] In the present invention, unless otherwise specified, solvent water includes but is not limited to deionized water.

[0077] A second aspect of the present invention provides a method for preparing a phosphate solid electrolyte dispersion, the method comprising: grinding a mixed slurry containing a phosphate solid electrolyte, a dispersant, and water to obtain a dispersion;

[0078] Wherein, in the mixed slurry, the content of the phosphate solid electrolyte is ≥40wt%.

[0079] In the present invention, unless otherwise specified, the types and parameters of the phosphate solid electrolyte and dispersant are defined in accordance with the above-mentioned definitions, and the present invention will not elaborate on them here.

[0080] In the present invention, the preparation of the mixed slurry has a wide range of options, and the mixed slurry can be obtained by mixing the phosphate solid electrolyte, dispersant, and water. Preferably, the mixing conditions include: a temperature of 20-40°C, preferably 25-30°C; and a time of 0.1-10 hours, preferably 0.1-2 hours.

[0081] In some embodiments of the present invention, preferably, in the mixed slurry, the mass ratio of the phosphate solid electrolyte to the dispersant is 1:0.001-0.08, for example, 1:0.001, 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.08, and any value in the range consisting of any two numerical values, preferably 1:0.005-0.05, more preferably 1:0.01-0.03.

[0082] In some embodiments of the present invention, preferably, in the mixed slurry, the content of the phosphate solid electrolyte is 40-85wt%, for example, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, and any value in the range consisting of any two values.

[0083] In a preferred embodiment of the present invention, the mixed slurry is composed of the phosphate solid electrolyte, a dispersant and water, and the mass ratio of the phosphate solid electrolyte to the dispersant is 1:0.001-0.08, preferably 1:0.005-0.05, and more preferably 1:0.01-0.03; in the mixed slurry, the content of the phosphate solid electrolyte is ≥40wt%, preferably 40-85wt%.

[0084] In the present invention, the grinding method has a wide range of options, including but not limited to ball milling, sand milling, etc.

[0085] In some embodiments of the present invention, preferably, the grinding process includes: grinding the mixed slurry and grinding medium, wherein the mass ratio of the grinding medium to the phosphate solid electrolyte is 1-20:1, for example, 1:1, 3:1, 5:1, 8:1, 10:1, 20:1, and any value in the range consisting of any two numerical values, preferably 3-10:1.

[0086] In some embodiments of the present invention, the average particle size of the grinding medium is preferably 0.1-10 mm, for example, 0.1 mm, 0.5 mm, 1 mm, 2 mm, 5 mm, 10 mm, and any value within a range consisting of any two values. In the present invention, the material of the grinding medium includes but is not limited to zirconium balls.

[0087] In some embodiments of the present invention, preferably, the grinding conditions include: a linear speed of 1-30 m / s, preferably 10-20 m / s; and a grinding time of 1-200 h, preferably 3-30 h.

[0088] The third aspect of the present invention provides an application of the dispersion provided in the first aspect, or the dispersion prepared by the preparation method provided in the second aspect, in a lithium-ion battery, preferably in positive and negative electrode blending, diaphragm coating, and organic / inorganic solid electrolyte composite.

[0089] In the present invention, the lithium ion battery includes but is not limited to a lithium ion secondary battery and the like.

[0090] According to a particularly preferred embodiment of the present invention, a phosphate solid electrolyte dispersion is provided, wherein the dispersion comprises a phosphate solid electrolyte, a dispersant and water;

[0091] Wherein, the dispersant is selected from cellulose containing hydroxyl and carboxyl groups, the degree of substitution of the cellulose is 0.95-1.05, and the weight average molecular weight is 2000-20000 g / mol;

[0092] Wherein, in the dispersion, the mass ratio of the phosphate solid electrolyte to the dispersant is 1:0.01-0.03; in the dispersion, the content of the phosphate solid electrolyte is 40-85wt%;

[0093] Wherein, the particle size span A of the dispersion is 0.8-1.5, A=(D 90 -D 10 ) / D 50 , D 50 、D 90 and D 10 are respectively the volume particle size of the phosphate solid electrolyte particles in the dispersion, both in nm;

[0094] The solid content change rate S of the dispersion is ≤2%, which refers to the change in solid content of the dispersion after standing for 30 days; the particle size change rate T of the dispersion is ≤10%, which refers to the particle size D of the dispersion after standing for 30 days. 50The redispersion rate R≤5% of the dispersion, the redispersion rate refers to the particle size D after taking 40mL of the dispersion in a 50mL centrifuge tube and letting it stand for 30 days and then using a shaker to disperse it 50 The change value of the vibration machine is 20W in power, 240V AC, 100rpm in speed, and 10min in vibration.

[0095] The present invention will be described in detail below through examples.

[0096] The physical properties of the dispersions (S1-S8 and DS1-DS8) prepared in Examples 1-8 and Comparative Examples 1-8 are listed in Table 1.

[0097] Example 1

[0098] (1) 100 parts by weight of phosphate solid electrolyte (LiAl(PO4)(OH) 0.911 F 0.089 , D 50 3 μm), 3 parts by weight of a dispersant (carboxymethyl cellulose, with a degree of substitution of 1 and a weight-average molecular weight of 3000 g / mol), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 97 parts by weight of water are mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry is 50 wt%;

[0099] (2) The mixed slurry was ground in a sand mill (at a linear speed of 10 m / s for 24 h) to obtain a dispersion S1.

[0100] Example 2

[0101] (1) 100 parts by weight of phosphate solid electrolyte (LiAl(PO4)(OH) 0.911 F 0.089 , D 50 0.5 μm), 0.1 parts by weight of a dispersant (carboxymethyl cellulose, with a degree of substitution of 1 and a weight-average molecular weight of 300 g / mol), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 99.9 parts by weight of water are mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry is 50 wt%;

[0102] (2) The mixed slurry was ground in a sand mill (at a linear speed of 20 m / s for 8 h) to obtain a dispersion S2.

[0103] Example 3

[0104] (1) 100 parts by weight of phosphate solid electrolyte (LiAl(PO4)(OH) 0.911 F 0.089 , D50 1000 μm), 8 parts by weight of a dispersant (carboxymethyl cellulose, with a degree of substitution of 1 and a weight-average molecular weight of 50,000 g / mol), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 92 parts by weight of water are mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry is 50 wt%;

[0105] (2) The mixed slurry was ground in a ball mill (at a linear speed of 10 m / s for 24 h) to obtain a dispersion S3.

[0106] Example 4

[0107] (1) 100 parts by weight of phosphate solid electrolyte (LiAl(PO4)(OH) 0.911 F 0.089 , D 50 3 μm), 3 parts by weight of a dispersant (carboxymethyl cellulose, with a degree of substitution of 0.6 and a weight-average molecular weight of 3000 g / mol), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 97 parts by weight of water are mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry is 50 wt%;

[0108] (2) The mixed slurry was ground in a ball mill (at a linear speed of 10 m / s for 24 h) to obtain a dispersion S4.

[0109] Example 5

[0110] (1) 100 parts by weight of phosphate solid electrolyte (LiAl(PO4)(OH) 0.911 F 0.089 , D 50 3 μm), 3 parts by weight of a dispersant (carboxymethyl cellulose, with a degree of substitution of 1.2 and a weight-average molecular weight of 3000 g / mol), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 97 parts by weight of water are mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry is 50 wt%;

[0111] (2) The mixed slurry was milled in a ball mill (at a linear speed of 10 m / s for 24 h) to obtain a dispersion S5.

[0112] Example 6

[0113] (1) 100 parts by weight of phosphate solid electrolyte (LiAl(PO4)(OH) 0.911 F 0.089 , D 503 μm), 3 parts by weight of a dispersant (carboxymethyl cellulose, with a degree of substitution of 1 and a weight-average molecular weight of 3000 g / mol), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 147 parts by weight of water are mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry is 40 wt%;

[0114] (2) The mixed slurry was ground in a ball mill (at a linear speed of 10 m / s for 24 h) to obtain a dispersion S6.

[0115] Example 7

[0116] (1) 100 parts by weight of phosphate solid electrolyte (LiAl(PO4)(OH) 0.911 F 0.089 , D 50 3 μm), 3 parts by weight of a dispersant (carboxymethyl cellulose, with a degree of substitution of 1 and a weight-average molecular weight of 3000 g / mol), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 63.67 parts by weight of water are mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry is 60 wt%;

[0117] (2) The mixed slurry was milled in a ball mill (at a linear speed of 10 m / s for 24 h) to obtain a dispersion S7.

[0118] Example 8

[0119] (1) 100 parts by weight of phosphate solid electrolyte (Li 1.1 H 0.9 Al(PO4)O 0.95 F 0.1 , D 50 3 μm), 3 parts by weight of a dispersant (carboxymethyl cellulose, with a degree of substitution of 1 and a weight-average molecular weight of 3000 g / mol), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 14.65 parts by weight of water are mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry is 85 wt%;

[0120] (2) The mixed slurry was milled in a ball mill (at a linear speed of 10 m / s for 24 h) to obtain a dispersion S8.

[0121] Comparative Example 1

[0122] (1) 100 parts by weight of phosphate solid electrolyte (LiAl(PO4)(OH) 0.911 F 0.089 , D 503 μm), 300 parts by weight of a grinding medium (zirconium balls, with an average particle size of 2 mm) and 100 parts by weight of water were mixed to obtain a mixed slurry, wherein the content of the phosphate solid electrolyte in the mixed slurry was 50 wt%;

[0123] (2) The mixed slurry was ground in a sand mill (at a linear speed of 10 m / s for 24 h) to obtain a dispersion DS1.

[0124] Comparative Example 2

[0125] According to the method of Example 1, the difference is that

[0126] In step (1), the amount of dispersant is replaced with 10 parts by weight, and the amount of water is replaced with 90 parts by weight to obtain a mixed slurry with a phosphate solid electrolyte content of 50 wt%;

[0127] The remaining conditions were the same to obtain dispersion DS2.

[0128] Comparative Example 3

[0129] According to the method of Example 1, the difference is that

[0130] In step (1), the degree of substitution of the dispersant is replaced with 2.5,

[0131] The remaining conditions were the same to obtain dispersion DS3.

[0132] Comparative Example 4

[0133] According to the method of Example 1, the difference is that

[0134] In step (1), the weight average molecular weight of the dispersant is replaced with 100000 g / mol,

[0135] The other conditions were the same to obtain dispersion DS4.

[0136] Comparative Example 5

[0137] According to the method of Example 1, the difference is that

[0138] In step (1), the dispersant was replaced with polyacrylic acid (with a degree of substitution of 1 and a weight-average molecular weight of 3000 g / mol).

[0139] The remaining conditions were the same to obtain dispersion DS5.

[0140] Comparative Example 6

[0141] According to the method of Example 1, the difference is that

[0142] In step (1), the dispersant is replaced with sodium tripolyphosphate (with a degree of substitution of 1 and a weight-average molecular weight of 3000 g / mol).

[0143] The remaining conditions were the same to obtain dispersion DS6.

[0144] Comparative Example 7

[0145] According to the method of Example 1, the difference is that

[0146] Step (1), replacing 3 parts by weight of a dispersant (carboxymethyl cellulose, degree of substitution of 1, weight average molecular weight of 3000 g / mol) with 0.5 parts by weight of polyacrylic acid (degree of substitution of 1, weight average molecular weight of 3000 g / mol) and 2.5 parts by weight of carboxymethyl cellulose (degree of substitution of 1, weight average molecular weight of 3000 g / mol);

[0147] The remaining conditions were the same to obtain dispersion DS7.

[0148] Comparative Example 8

[0149] According to the method of Example 1, the difference is that

[0150] Step (1), replacing 3 parts by weight of a dispersant (carboxymethyl cellulose, degree of substitution is 1, and a weight-average molecular weight is 3000 g / mol) with 0.5 parts by weight of a fatty alcohol polyoxyethylene ether (degree of substitution is 1, and a weight-average molecular weight is 3000 g / mol) and 2.5 parts by weight of carboxymethyl cellulose (degree of substitution is 1, and a weight-average molecular weight is 3000 g / mol);

[0151] The remaining conditions were the same to obtain dispersion DS8.

[0152] Table 1

[0153] Note: 1- phosphate solid electrolyte content in the dispersion, wt%;

[0154] 2-Dispersion at a shear rate of 100s -1 Viscosity at 37°C, mPa·s; D 10 、D 50 、D 90 and D max Both refer to the volume particle size of phosphate solid electrolyte particles in the dispersion.

[0155] Table 1

[0156] Table 1

[0157] It can be seen from the results in Table 1 that, compared with Comparative Examples 1-8, the dispersions prepared in Examples 1-8, under the premise that the phosphate solid electrolyte content is ≥40 wt%, have a particle size span A ≤ 1.5 of the dispersions, thereby improving the dispersibility, stability and consistency of the dispersions.

[0158] Compared with Examples 2-3, Example 1 regulates the amount and weight-average molecular weight of the dispersant within a more preferred range, and further regulates the viscosity, solid content change rate, particle size change rate and redispersibility of the dispersion.

[0159] Compared with Examples 1 and 4-5, it can be seen that a too low degree of substitution will lead to an increase in the particle size span, because the solubility of the dispersant decreases when the degree of substitution is low, resulting in a decrease in performance. A too high degree of substitution will also lead to a decrease in performance, mainly because the water retention capacity of the dispersant decreases, the ability to form hydrogen bonds decreases, and it cannot play a dispersing role.

[0160] Compared with Examples 5 and 7, Example 1 regulates the content of phosphate solid electrolyte in the dispersion within a more preferred range, and further regulates the viscosity, solid content change rate, particle size change rate and redispersibility of the dispersion.

[0161] Compared with Example 1, Example 8 regulates the effects of the types of phosphate solid electrolyte and dispersant on the performance of the dispersion.

[0162] In Comparative Examples 7-8, the addition of polyelectrolyte dispersants and nonionic surfactants to high-solid phosphate water-based slurries will lead to an increase in the particle size span, a decrease in the particle size change rate and the redispersion performance, and exceed the index range. This is mainly because the surfactant will compete with the dispersant for adsorption, and the thickener will destroy the steric hindrance network formed by the cellulose dispersant.

[0163] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A phosphate solid electrolyte dispersion, characterized in that: The dispersion contains a phosphate solid electrolyte, a dispersant and water; In the dispersion, the content of the phosphate solid electrolyte is ≥40wt%; Wherein, the particle size span of the dispersion is A≤1.5, A=(D 90 -D 10 ) / D 50 , D 50 , D 90 and D 10 are respectively the volume particle sizes of the phosphate solid electrolyte particles in the dispersion, both in nm.

2. The dispersion according to claim 1, wherein The dispersion consists of a phosphate solid electrolyte, a dispersant and water.

3. The dispersion according to claim 1 or 2, wherein In the dispersion, the content of the phosphate solid electrolyte is 40-85wt%; and / or, the particle size span A of the dispersion is 0.8-1.5, preferably 0.8-1.2; And / or, the particle size D of the phosphate solid electrolyte particles max ≤1μm; And / or, the particle size D of the phosphate solid electrolyte particles 10 20-300nm, particle size D 50 50-500nm, particle size D 90 200-900nm.

4. The dispersion according to any one of claims 1 to 3, wherein In the dispersion, the mass ratio of the phosphate solid electrolyte to the dispersant is 1:0.001-0.08, preferably 1:0.005-0.05, more preferably 1:0.01-0.03; And / or, the dispersion is subjected to a shear rate of 100 s -1 The viscosity is (1-15)×10 3 mPa·s.

5. The dispersion according to any one of claims 1 to 4, wherein The solid content change rate S of the dispersion is ≤ 2%, where the solid content change rate refers to the solid content change value of the dispersion after standing for 30 days; And / or, the particle size change rate T of the dispersion is ≤15%, preferably T ≤10%, the particle size change rate refers to the particle size D of the dispersion after standing for 30 days. 50 The change value of And / or, the redispersion rate R of the dispersion is ≤12%, preferably R ≤5%, and the redispersion rate refers to the particle size D after 40 mL of the dispersion is dispersed in a 50 mL centrifuge tube and allowed to stand for 30 days using a shaker. 50 The change value, the power dispersed by the oscillator is 20W, the AC power is 240V, the speed is 100rpm, and the oscillation is 10min.

6. The dispersion according to any one of claims 1 to 5, wherein The phosphate solid electrolyte is selected from natural oxide materials and artificially synthesized oxide materials containing Li, O and P; And / or, the phosphate solid electrolyte further contains at least one element selected from H, halogen and non-Li metal elements, and the non-Li metal element is selected from at least one of Al, Zr, Fe, Sm, Pr, Nb, Ga, Zn, Y, Mg, Al, Cr, Ca, Ti, Cu, Sr, Ba, Ce, Sn, Sb, La and Bi; And / or, the phosphate solid electrolyte is selected from lithium aluminum phosphate containing hydroxyl groups; And / or, the phosphate solid electrolyte has a composition shown in Formula I, Li 1+x H 1-x Al(PO4)O 1-y X 2y (I), wherein 0≤x<1, 0<y<0.1, and X is selected from at least one of F, Cl, Br and I; And / or, the phosphate solid electrolyte has a composition shown in Formula II, LiAl(PO4)(OH) 1-w X w (II), wherein 0≤w<1, X is selected from at least one of F, Cl, Br and I; And / or, the particle size D of the phosphate solid electrolyte 50 0.5-1000μm.

7. The dispersion according to any one of claims 1 to 6, wherein The dispersant is selected from cellulose containing hydroxyl and carboxyl groups and salts thereof; and / or, the degree of substitution of the cellulose is 0.3-1.5, preferably 0.6-1, more preferably 0.8-1; and / or, the weight average molecular weight of the cellulose is 300-200000 g / mol, preferably 1000-50000 g / mol, more preferably 2000-20000 g / mol; And / or, the cellulose is at least one selected from methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose and carboxymethyl hydroxyethyl cellulose and salts thereof.

8. A method for preparing a phosphate solid electrolyte dispersion, characterized in that: The preparation method comprises: grinding a mixed slurry containing a phosphate solid electrolyte, a dispersant and water to obtain a dispersion; Wherein, in the mixed slurry, the content of the phosphate solid electrolyte is ≥40wt%.

9. The preparation method according to claim 8, wherein: In the mixed slurry, the mass ratio of the phosphate solid electrolyte to the dispersant is 1:0.001-0.08, preferably 1:0.005-0.05, more preferably 1:0.01-0.03; And / or, in the mixed slurry, the content of the phosphate solid electrolyte is 40-85wt%; And / or, the mixed slurry consists of the phosphate solid electrolyte, a dispersant and water; And / or, the grinding conditions include: a linear speed of 1-30 m / s, preferably 10-20 m / s; The time is 1-200h, preferably 3-30h.

10. Use of the dispersion according to any one of claims 1 to 7, or the dispersion prepared by the preparation method according to claim 8 or 9 in a lithium-ion battery, specifically selected from the use in positive and negative electrode blending, diaphragm coating, and organic / inorganic solid electrolyte composite.

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