Composite positive electrode material and preparation method thereof, composite positive electrode and preparation method thereof, solid-state battery

Abstract

The present invention provides a composite positive electrode material and a preparation method thereof, a composite positive electrode and a preparation method thereof, and a solid-state battery. The preparation method comprises: step S1, pre-treating the positive electrode material and the solid electrolyte respectively so that the two have different charges; step S2, mixing the raw materials including the positive electrode material and the solid electrolyte to obtain a composite positive electrode material, and controlling the water and oxygen contents in the environment to be independently less than 0.1 ppm during the pre-treatment and mixing process. The present application improves the ion conductivity of the composite positive electrode as a whole by making the positive electrode material and the solid electrolyte have different charges, thereby improving the electrical performance of the solid-state battery. Among them, controlling the water and oxygen contents in the environment to be independently less than 0.1 ppm is more conducive to minimizing the destructive effects of water and oxygen in the air on the solid electrolyte, thereby ensuring the modification effect of the solid electrolyte on the positive electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a composite positive electrode material and a preparation method thereof, a composite positive electrode and a preparation method thereof, and a solid-state battery. Background Art

[0002] The composite positive electrode in an all-solid-state battery usually requires the positive electrode material to be fully mixed with the solid electrolyte. Ideally, a layer of solid electrolyte particles is wrapped on the surface of the positive electrode particles to achieve better ion conduction and transmission.

[0003] But in fact, it may be due to the small particle size of the solid electrolyte powder particles, different amounts of positive and negative charges accumulated on the surface, or the short distance between the particles, the van der Waals force between them is much greater than their own gravity and attracts each other, or the surface hydrogen bonds and chemical bonds between the powder particles cause the solid electrolyte powder particles to easily agglomerate, thereby affecting the uniform dispersion of the solid electrolyte particles in the composite positive electrode, resulting in a decrease in the ion conductivity of the composite positive electrode and the inability to exert the positive electrode capacity.

[0004] Currently, most methods for mixing and dispersing solid-state electrolytes and cathode materials use solvents as dispersants. This process can easily introduce moisture or solvents that react with the materials themselves, significantly reducing the capacity of the cathode material. For example, Chinese patent application publication number CN111146425B proposes a method for coating an electrode material with a solid-state electrolyte, a coating material, and an electrode prepared using this coating method. The method involves dispersing the solid-state electrolyte in an alkane solvent to form a dispersion, and then adding the cathode material. However, this method requires selecting a solvent that is stable for the electrolyte and considering solvent recovery, resulting in a very high process flow and cost. Summary of the Invention

[0005] The main purpose of the present invention is to provide a composite positive electrode material and a preparation method thereof, a composite positive electrode and a preparation method thereof, and a solid-state battery, so as to solve the problem in the prior art that the dispersion process of solid electrolyte powder particles in the composite positive electrode is limited by the solvent and has high cost.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for preparing a composite positive electrode material is provided, which comprises: step S1, pretreating the positive electrode material and the solid electrolyte respectively so that the two have different charges; step S2, mixing the raw materials including the positive electrode material and the solid electrolyte to obtain a composite positive electrode material, and during the pretreatment and mixing process, controlling the water and oxygen content in the environment to be independently less than 0.1 ppm.

[0007] Furthermore, the mass ratio of the positive electrode material to the solid electrolyte is 50-95:5-50.

[0008] Furthermore, the above-mentioned pretreatment is carried out by a physical method or a chemical method, and the physical method is preferably selected from any one or more of friction charging, induction charging, contact charging, and corona discharge. Preferably, friction charging is to charge the positive electrode material or solid electrolyte by friction with the inner wall of the friction gun; preferably, induction charging and contact charging are each independently to charge the positive electrode material or solid electrolyte by an induction generator; preferably, corona discharge is to charge the positive electrode material or solid electrolyte after corona treatment with a plasma device; preferably, the chemical method is selected from any one or more of adding a surfactant, adjusting the pH value of the material, and bulk doping, and preferably the surfactant is a cationic surfactant and / or an anionic surfactant. The present invention relates to a surfactant, wherein the cationic surfactant is preferably selected from any one or more of cetyldimethylammonium chloride, dodecylammonium acetate, dodecylammonium chloride, dodecyltrimethylammonium bromide, dodecylbenzyltrimethylammonium chloride, dodecylpyridinium chloride, and 1-aminoethyl-2-undecylimidazoline hydrochloride; the anionic surfactant is preferably selected from any one or more of sodium alkylbenzenesulfonate, sodium dodecyl alcohol polyoxyethylene ether sulfate, dodecylammonium sulfate, triethanolamine lauryl sulfate, sodium fatty alcohol isethionate, dodecyl phosphate, and triethanolamine dodecyl phosphate; the pH value is preferably 2 to 11; the bulk doping is preferably cation doping and / or anion doping, and the doping cation in the cation doping is preferably selected from Mg 2+ , Ca 2+ 、Ba 2+ 、Ag + 、Sb 3+ 、Sr 2+ Cr + 、Ga + 、In 3+ Any one or more of the following, preferably the doping anion in the anion doping is selected from As 3- Br - 、Cl - 、F - 、P 3- 、S 2- , I - Any one or more of .

[0009] Furthermore, the particle size of the positive electrode material is 1 to 15 μm, and the positive electrode material is preferably selected from LiNi x Co y Mn z Any one or more of O2, lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate, wherein x+y+z=1, 0<x<1, 0≤y<1, 0<z<1.

[0010] Furthermore, the particle size of the solid electrolyte is 100 to 1000 nm, and the solid electrolyte is preferably selected from any one or more of an oxide electrolyte, a sulfide electrolyte and a halide electrolyte.

[0011] Furthermore, the above-mentioned preparation method also includes: performing a first mixing and a second mixing in sequence on the raw materials including the positive electrode material and the solid electrolyte to obtain a composite positive electrode material; wherein the rotation speed of the first mixing is less than the rotation speed of the second mixing; preferably, the rotation speed of the first mixing is 20 to 200 r / min, and the preferred time of the first mixing is 0.5 to 10 h; preferably, the rotation speed of the second mixing is 1000 to 10000 r / min, and the preferred time of the second mixing is 0.1 to 1 h; preferably, the raw materials also include a conductive agent and a binder, preferably the conductive agent is selected from any one or more of conductive graphite, acetylene black, carbon nanotubes, graphene, and carbon fiber, and the mass of the conductive agent is preferably 1 to 10 wt% of the total mass of the positive electrode material and the solid electrolyte; preferably, the binder is selected from any one or more of polyvinylidene fluoride, acrylic resin, polytetrafluoroethylene, and styrene-butadiene rubber, and the mass of the binder is preferably 0.1 to 10 wt% of the total mass of the positive electrode material and the solid electrolyte.

[0012] According to another aspect of the present invention, a composite positive electrode material is provided. The composite positive electrode material is the composite positive electrode material obtained by the above preparation method.

[0013] According to another aspect of the present invention, a method for preparing a composite positive electrode is provided, which comprises: rolling a composite positive electrode material into a composite positive electrode by horizontal rolling and vertical rolling; wherein the conditions for horizontal rolling and vertical rolling include that the water and oxygen contents are each independently less than 0.1 ppm; and the composite positive electrode material is the above-mentioned composite positive electrode material.

[0014] According to another aspect of the present invention, a composite positive electrode is provided. The composite positive electrode is a composite positive electrode obtained by the above-mentioned preparation method.

[0015] According to another aspect of the present invention, a solid-state battery is provided, comprising a composite positive electrode, a solid electrolyte membrane and a negative electrode, wherein the composite positive electrode is the aforementioned composite positive electrode.

[0016] By applying the technical solution of the present invention, the present application greatly suppresses the agglomeration problem of the solid electrolyte in the composite positive electrode by making the positive electrode material and the solid electrolyte carry heterogeneous charges. At the same time, the heterogeneous charge modification method does not affect the ionic conductivity of the solid electrolyte and the capacity of the positive electrode material, thereby improving the ion conductivity of the composite positive electrode as a whole, and thus improving the electrical performance of the solid-state battery. Among them, controlling the water and oxygen content in the environment to be independently less than 0.1ppm is more conducive to minimizing the destructive effect of water and oxygen in the air on the solid electrolyte, thereby ensuring the modification effect of the solid electrolyte on the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 shows a SEM image of a composite positive electrode provided according to Example 1 of the present invention;

[0019] Figure 2 A schematic diagram of a mixing process provided in accordance with Example 1 of the present invention is shown;

[0020] Figure 3 An optical photograph of a composite positive electrode provided according to Example 1 of the present invention is shown;

[0021] Figure 4 Shown is a SEM image of a composite positive electrode provided in Comparative Example 1 of the present invention;

[0022] Figure 5 A schematic diagram of a mixing device provided according to Example 1 of the present invention is shown;

[0023] Figure 6 shows a charge and discharge curve of a solid-state battery assembled with a composite positive electrode provided in Example 1 of the present invention; and

[0024] Figure 7 A charge and discharge curve diagram of a solid-state battery assembled with a composite positive electrode provided in Comparative Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] As analyzed in the background technology of this application, there is a problem in the prior art that the dispersion process of solid electrolyte powder particles in a composite positive electrode is limited by solvents and has high costs. In order to solve this problem, this application provides a composite positive electrode material and a preparation method thereof, a composite positive electrode and a preparation method thereof, and a solid-state battery.

[0027] In a typical embodiment of the present application, a method for preparing a composite positive electrode material is provided, which comprises: step S1, pretreating the positive electrode material and the solid electrolyte respectively so that the two have different charges; step S2, mixing the raw materials including the positive electrode material and the solid electrolyte to obtain a composite positive electrode material; and during the pretreatment and mixing process, the water and oxygen content in the environment are independently controlled to be less than 0.1 ppm.

[0028] The present application greatly suppresses the agglomeration problem of the solid electrolyte in the composite positive electrode by making the positive electrode material and the solid electrolyte carry different charges. At the same time, the modification method of carrying different charges does not affect the ionic conductivity of the solid electrolyte and the capacity of the positive electrode material, thereby improving the ion conductivity of the composite positive electrode as a whole, and thus improving the electrical performance of the solid-state battery. Among them, controlling the water and oxygen content in the environment to be less than 0.1ppm independently is more conducive to minimizing the destructive effect of water and oxygen in the air on the solid electrolyte, thereby ensuring the modification effect of the solid electrolyte on the positive electrode material. Preferably, the mass ratio of the above-mentioned positive electrode material and solid electrolyte is 50-95:5-50, which is conducive to giving full play to the advantages of the high ionic conductivity of the solid electrolyte, thereby achieving the purpose of better ion conduction and transmission, and thus making the capacity of the positive electrode material more fully utilized.

[0029] After experimental verification, the relationship between the charge and particle size of the positive electrode material and solid electrolyte is as follows:

[0030] q c ∝k c *r c ,q s ∝k s *r s ,

[0031] q c =Π(r c +r s )*q s / r s ,

[0032] Among them, q c is the charge of the positive electrode material, q s is the charge of the solid electrolyte, r c is the radius of the positive electrode material, r s is the radius of the solid electrolyte, kc is the charge constant of the positive electrode material, k s is the charge constant of the solid electrolyte. Therefore, the radius of the positive electrode material and the solid electrolyte can be set according to the size requirements of the battery, so that the positive electrode material and the solid electrolyte can reach the corresponding charge by physical or chemical methods.

[0033] In one embodiment of the present application, the above-mentioned pretreatment is carried out by a physical method or a chemical method. Preferably, the physical method is selected from any one or more of friction charging, induction charging, contact charging, and corona discharge. Preferably, friction charging is to charge the positive electrode material or solid electrolyte by friction with the inner wall of the friction gun; preferably, induction charging and contact charging are each independently to charge the positive electrode material or solid electrolyte by an induction generator; preferably, corona discharge is to charge the positive electrode material or solid electrolyte after corona treatment with a plasma device; preferably, the chemical method is selected from any one or more of adding a surfactant, adjusting the pH value of the material, and bulk doping. Preferably, the amount of surfactant added is 0.1 to 3 wt% of the positive electrode material or solid electrolyte, and preferably the surfactant is a cationic surfactant and / or an anionic surfactant. The present invention relates to a surfactant, preferably a cationic surfactant selected from any one or more of cetyldimethylammonium chloride, dodecylammonium acetate, dodecylammonium chloride, dodecyltrimethylammonium bromide, dodecylbenzyltrimethylammonium chloride, dodecylpyridinium chloride, and 1-aminoethyl-2-undecylimidazoline hydrochloride; preferably an anionic surfactant selected from any one or more of sodium alkylbenzenesulfonate, sodium dodecyl alcohol polyoxyethylene ether sulfate, dodecylammonium sulfate, triethanolamine lauryl sulfate, sodium fatty alcohol isethionate, dodecyl phosphate, and triethanolamine dodecyl phosphate; preferably, the pH value is 2 to 11; preferably, the bulk doping is cation doping and / or anion doping, preferably, the addition amount of the doped cation and / or the doped anion is 0.1 to 1 wt% of the positive electrode material or the solid electrolyte, and preferably, the doped cation in the cation doping is selected from Mg 2+ , Ca 2+ 、Ba 2+ 、Ag + 、Sb 3+ 、Sr 2+ Cr + 、Ga + 、In 3+ Any one or more of the following, preferably the doping anion in the anion doping is selected from As 3- Br - 、Cl - 、F - 、P 3- 、S 2- , I - Any one or more of .

[0034] The aforementioned physical or chemical methods can more quickly achieve the required charge level for the cathode material and solid electrolyte. Induction charging and contact charging generally refer to the process of passing the cathode material or solid electrolyte material through the inner wall of an induction generator cavity. The induction generator cavity is electrically connected and powered to generate an electric field. Contact charging occurs when the cathode material or solid electrolyte material is in contact with the inner wall of the induction generator cavity, while induction charging occurs when the cathode material or solid electrolyte material is not in contact with the inner wall of the induction generator cavity.

[0035] In one embodiment of the present application, the particle size of the positive electrode material is 1 to 15 μm, and the positive electrode material is preferably selected from LiNi x Co y Mn z Any one or more of O2, lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate, wherein x+y+z=1, 0<x<1, 0≤y<1, 0<z<1.

[0036] The particle size of the above-mentioned positive electrode material is more in line with the actual required positive electrode size, and the preferred positive electrode material itself has a higher capacity, which helps to improve the capacity and other comprehensive performance of the corresponding solid-state battery.

[0037] Preferably, the particle size of the above-mentioned solid electrolyte is 100 to 1000 nm, and the solid electrolyte is preferably selected from any one or more of an oxide electrolyte, a sulfide electrolyte and a halide electrolyte. The solid electrolyte of this particle size is conducive to better synergistic effect with the positive electrode material to obtain a composite positive electrode material with an overall charge of 0, thereby realizing the modification effect of the solid electrolyte on the positive electrode material.

[0038] In order to further improve the improvement effect of the solid electrolyte on the ion conductivity of the composite positive electrode, the above oxide electrolyte is preferably selected from any one or more of perovskite oxides, NASICON oxides, LISICON oxides or garnet oxides, and the sulfide electrolyte is preferably selected from thio-LISICON, Li 10 GeP2S 12 、Li6PS5Cl、Li 10 SnP2S 12 , any one or more of Li2S-P2S5, Li2S-SiS2 or Li2S-B2S3, preferably the halide electrolyte is selected from any one or more of Li3YCl6, Li3YBr6, Li3ErCl6, Li3YbCl6 or Li3InCl6.

[0039] In one embodiment of the present application, the preparation method further includes: performing a first mixing and a second mixing of raw materials including a positive electrode material and a solid electrolyte in sequence to obtain a composite positive electrode material; wherein the rotation speed of the first mixing is less than the rotation speed of the second mixing; preferably, the rotation speed of the first mixing is 20 to 200 r / min, and the preferred first mixing time is 0.5 to 10 h; preferably, the rotation speed of the second mixing is 1000 to 10000 r / min, and the preferred second mixing time is 0.1 to 1 h; preferably, the raw materials also include a conductive agent and a binder, preferably the conductive agent is selected from any one or more of conductive graphite, acetylene black, carbon nanotubes, graphene, and carbon fiber, and the mass of the conductive agent is preferably 1 to 10 wt% of the total mass of the positive electrode material and the solid electrolyte; preferably, the binder is selected from any one or more of polyvinylidene fluoride, acrylic resin, polytetrafluoroethylene, and styrene-butadiene rubber, and the mass of the binder is preferably 0.1 to 10 wt% of the total mass of the positive electrode material and the solid electrolyte.

[0040] Controlling the stirring speed and time of the aforementioned low-speed mixing followed by high-speed mixing facilitates uniform mixing of the positive electrode material, solid electrolyte, conductive agent, and binder, thereby improving the overall performance of the composite positive electrode material. The preferred conductive agent and its content contribute to improving the conductivity of the composite positive electrode material, while the preferred binder and its content contribute to enhancing the bonding between the components of the composite positive electrode material.

[0041] In another typical embodiment of the present application, a composite positive electrode material is provided. The composite positive electrode material is the composite positive electrode material obtained by the above preparation method.

[0042] The modification of the positive electrode material by the solid electrolyte enables the composite positive electrode material of the present application to have a higher capacity.

[0043] In another typical embodiment of the present application, a method for preparing a composite positive electrode is provided, which comprises: rolling the composite positive electrode material into a composite positive electrode by horizontal rolling and vertical rolling; wherein the conditions of horizontal rolling and vertical rolling include that the water and oxygen contents are each independently less than 0.1 ppm; and the above-mentioned composite positive electrode material is the aforementioned composite positive electrode material.

[0044] The above dry process is more conducive to obtaining a high-capacity composite positive electrode.

[0045] In another typical embodiment of the present application, a composite positive electrode is provided. The composite positive electrode is a composite positive electrode obtained by the above preparation method.

[0046] The composite positive electrode has a relatively high capacity.

[0047] In another typical embodiment of the present application, a solid-state battery is provided, comprising a composite positive electrode, a solid electrolyte membrane and a negative electrode, wherein the composite positive electrode is the composite positive electrode described above.

[0048] The solid-state battery including the above-mentioned composite positive electrode has higher electrical properties such as capacity.

[0049] The beneficial effects of the present application will be further illustrated below with reference to embodiments.

[0050] Example 1

[0051] Use Figure 2 The process flow shown is for preparing composite positive electrode materials and composite positive electrodes.

[0052] like Figure 5 As shown in the figure, the solid electrolyte LiSiPSCl in the powder bin 1 is negatively charged by corona discharge, and the positive electrode LiNi in the powder bin 2 is negatively charged. 0.8 Co 0.1 Mn 0.1 O2 (NCM811) carries a positive charge, wherein the solid electrolyte LiSiPSCl powder passes through a 300-mesh sieve, and the positive electrode NCM811 powder passes through a 150-mesh sieve.

[0053] 20 g of solid electrolyte LiSiPSCl (particle size of 300 nm) and 80 g of NCM811 were put into a stirring tank, mixed at a low speed of 100 r / min for 1 h, and then mixed at a high speed of 1000 r / min for 0.2 h.

[0054] 1 g of acetylene black was added from the powder bin 3, and 0.2 g of polytetrafluoroethylene was added from the powder bin 4 into the stirring tank. After low-speed mixing at 200 r / min for 1 hour, high-speed mixing at 2000 r / min for 0.1 hour was performed to obtain a composite positive electrode material.

[0055] The composite cathode material was transferred to a horizontal roller press and a vertical roller press for dry process film formation to obtain a composite cathode. The optical photograph is shown in FIG. Figure 3 As shown, its SEM picture is as Figure 1 As shown, the contents of water and oxygen during the above experiments were less than 0.1 ppm respectively.

[0056] Example 2

[0057] The difference from Example 1 is that 5 g of solid electrolyte LiSiPSCl and 95 g of NCM811 are put into the stirring tank to finally obtain a composite positive electrode.

[0058] Example 3

[0059] The difference from Example 1 is that 50 g of solid electrolyte LiSiPSCl and 50 g of NCM811 are put into a stirring tank to finally obtain a composite positive electrode.

[0060] Example 4

[0061] The difference from Example 1 is that 60 g of solid electrolyte LiSiPSCl and 40 g of NCM811 are put into a stirring tank to finally obtain a composite positive electrode.

[0062] Example 5

[0063] The difference from Example 1 is that 2 g of solid electrolyte LiSiPSCl and 98 g of NCM811 are put into the stirring tank to finally obtain a composite positive electrode.

[0064] Example 6

[0065] The difference from Example 1 is that sodium alkylbenzene sulfonate (1 wt% of the solid electrolyte LiSiPSCl) is added to the solid electrolyte LiSiPSCl to make the solid electrolyte negatively charged. 0.8 Co 0.1 Mn 0.1 0.5% hexadecyldimethylammonium chloride was added to O2 (NCM811) to make the positive electrode positively charged, and finally a composite positive electrode was obtained.

[0066] Example 7

[0067] The difference from Example 1 is that the pH value of the solid electrolyte LiSiPSCl is adjusted to 11 by adding ammonium bicarbonate (0.1wt% of the solid electrolyte LiSiPSCl) to make the solid electrolyte negatively charged, and the positive electrode LiNi is adjusted by adding 0.2% stearic acid. 0.8 Co 0.1 Mn 0.1 The pH value of O2 (NCM811) is 5, which makes the positive electrode positively charged, and finally obtains a composite positive electrode.

[0068] Example 8

[0069] The difference from Example 1 is that the particle size of NCM811 is 1 μm, and a composite positive electrode is finally obtained.

[0070] Example 9

[0071] The difference from Example 1 is that the particle size of NCM811 is 15 μm, and a composite positive electrode is finally obtained.

[0072] Example 10

[0073] The difference from Example 1 is that the particle size of NCM811 is 20 μm, and a composite positive electrode is finally obtained.

[0074] Example 11

[0075] The difference from Example 1 is that the particle size of the solid electrolyte LiSiPSCl is 200 nm, and a composite positive electrode is finally obtained.

[0076] Example 12

[0077] The difference from Example 1 is that the particle size of the solid electrolyte LiSiPSCl is 1000 nm, and a composite positive electrode is finally obtained.

[0078] Example 13

[0079] The difference from Example 1 is that the particle size of the solid electrolyte LiSiPSCl is 1200 nm, and a composite positive electrode is finally obtained.

[0080] Example 14

[0081] The difference from Example 1 is that the solid electrolyte is Li3YCl6, and a composite positive electrode is finally obtained.

[0082] Example 15

[0083] The difference from Example 1 is that the positive electrode material is lithium iron phosphate, and a composite positive electrode is finally obtained.

[0084] Example 16

[0085] The difference from Example 1 is that 20 g of solid electrolyte LiSiPSCl and 80 g of NCM811 were put into a stirring tank, mixed at a low speed of 20 r / min for 10 h, and then mixed at a high speed of 10000 r / min for 1 h.

[0086] 10 g of acetylene black was added from powder silo 3, and 10 g of polytetrafluoroethylene was added from powder silo 4 into the stirring tank. After low-speed mixing at 50 r / min for 5 h, high-speed mixing at 5000 r / min for 0.5 h was performed to finally obtain a composite positive electrode.

[0087] Example 17

[0088] The difference from Example 1 is that the solid electrolyte LiSiPSCl powder is introduced into the friction gun by air flow, and the powder rubs and collides with the polymer material PTFE on the inner wall of the gun body, so that the solid electrolyte LiSiPSCl powder is negatively charged, and the positive electrode LiNi is charged by air flow. 0.8 Co 0.1 Mn 0.1O2 (NCM811) powder is introduced into the friction gun, where the powder rubs and collides with the polymer material PTFE on the inner wall of the gun body, causing the positive electrode NCM811 powder to be positively charged, ultimately obtaining a composite positive electrode.

[0089] Example 18

[0090] The difference from Example 1 is that the solid electrolyte LiSiPSCl powder is passed through the inner wall of the induction motor cavity by air flow, and the cavity surface of the induction motor is connected to electricity to form a positive electric field, so that the solid electrolyte LiSiPSCl powder is negatively charged, and the positive electrode LiNi is passed through the air flow. 0.8 Co 0.1 Mn 0.1 The O2 (NCM811) powder passes through the inner wall of the induction motor cavity, and the surface of the induction motor cavity is electrified to create a negative electric field, which makes the positive electrode NCM811 powder positively charged, and finally obtains a composite positive electrode.

[0091] Example 19

[0092] The difference from Example 1 is that the solid electrolyte LiSiPSCl powder and sodium bromide NaBr powder are mixed in a certain stoichiometric ratio, and Br is sintered at a high temperature of 560°C. - Doping into the solid electrolyte LiSiPSCl makes it negatively charged, Br - The doping amount of the solid electrolyte is 0.2% by mass; the positive electrode LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) powder and MgO powder are mixed in a certain stoichiometric ratio, and MgO is sintered at 750℃. 2+ Doped into the positive electrode LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) makes the positive electrode positively charged, Mg 2+ The doping amount is 0.1% of the mass of the positive electrode material, and a composite positive electrode is finally obtained.

[0093] Comparative Example 1

[0094] The difference from Example 1 is that the solid electrolyte LiSiPSCl and NCM811 are not subjected to corona discharge treatment, and the composite positive electrode is finally obtained, and its SEM image is as follows Figure 4 shown.

[0095] from Figure 1 and Figure 4 It can be seen from the comparison that no corona discharge treatment was performed, that is, the uncharged solid electrolyte agglomerated more seriously in the composite positive electrode.

[0096] The composite positive electrodes obtained in Examples 1 to 19 and Comparative Example 1 were assembled into solid-state batteries with solid electrolyte membranes and In negative electrodes for electrochemical performance testing. The first three cycles were performed at a current density of 0.1 C. The charge and discharge curves corresponding to Example 1 are shown in FIG. Figure 6 As shown, the charge and discharge curve corresponding to Comparative Example 1 is as shown in FIG. Figure 7 By comparison, it can be seen that the gram capacity of the composite positive electrode NCM811 in Example 1 can be stabilized at 150 mAh g -1 , while the gram capacity of the composite positive electrode NCM811 in comparative example 1 is only 80 mAh g -1 At the same time, the polarization phenomenon is serious, indicating that the internal resistance of the composite positive electrode side of Comparative Example 1 is large and the ion transport is poor, which is mainly due to the serious agglomeration of the solid electrolyte on the composite positive electrode side.

[0097] The gram capacities of the composite positive electrodes of Examples 1 to 19 and Comparative Example 1 obtained from the above tests are listed in Table 1.

[0098] Table 1

[0099]

[0100]

[0101] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0102] This application greatly suppresses the agglomeration problem of the solid electrolyte in the composite positive electrode by making the positive electrode material and the solid electrolyte carry heterogeneous charges. At the same time, the heterogeneous charge modification method does not affect the ionic conductivity of the solid electrolyte and the capacity of the positive electrode material, thereby improving the ion conductivity of the composite positive electrode as a whole, and thus improving the electrical performance of the solid-state battery. Among them, controlling the water and oxygen content in the environment to be independently less than 0.1ppm is more conducive to minimizing the destructive effect of water and oxygen in the air on the solid electrolyte, thereby ensuring the modification effect of the solid electrolyte on the positive electrode material.

[0103] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite positive electrode material, characterized in that: The preparation method comprises: Step S1, pre-treating the positive electrode material and the solid electrolyte so that they have different charges; Step S2, mixing raw materials including the cathode material and the solid electrolyte to obtain a composite cathode material, and controlling the water and oxygen contents in the environment to be independently less than 0.1 ppm during the pretreatment and mixing processes; The particle size of the solid electrolyte is 100-1000 nm, and the solid electrolyte is selected from any one or more of an oxide electrolyte, a sulfide electrolyte and a halide electrolyte; The mass ratio of the positive electrode material to the solid electrolyte is 50-95:5-50.

2. The preparation method according to claim 1, characterized in that The pretreatment is performed by a physical method or a chemical method.

3. The preparation method according to claim 2, characterized in that The physical method is selected from any one or more of friction charging, induction charging, contact charging, and corona discharge.

4. The preparation method according to claim 3, characterized in that The triboelectric charging is to charge the positive electrode material or the solid electrolyte by causing friction with the inner wall of the triboelectric gun.

5. The preparation method according to claim 3, characterized in that The induction charging and the contact charging are each independently a process of causing the positive electrode material or the solid electrolyte to be charged by an induction generator.

6. The preparation method according to claim 3, characterized in that The corona discharge is performed by a plasma device to corona treat the positive electrode material or the solid electrolyte so that the positive electrode material or the solid electrolyte is charged.

7. The preparation method according to claim 2, characterized in that The chemical method is selected from any one or more of adding a surfactant, adjusting the pH value of the material, and bulk doping.

8. The preparation method according to claim 7, characterized in that The surfactant is a cationic surfactant and / or an anionic surfactant.

9. The preparation method according to claim 8, characterized in that The cationic surfactant is selected from any one or more of hexadecyldimethylammonium chloride, dodecylammonium acetate, dodecylammonium chloride, dodecyltrimethylammonium bromide, dodecylbenzyltrimethylammonium chloride, dodecylpyridinium chloride, and 1-aminoethyl-2-undecylimidazoline hydrochloride.

10. The preparation method according to claim 8, characterized in that The anionic surfactant is selected from any one or more of sodium alkylbenzene sulfonate, sodium lauryl alcohol polyoxyethylene ether sulfate, ammonium lauryl sulfate, triethanolamine lauryl sulfate, sodium fatty alcohol isethionate, dodecyl phosphate, and dodecyl phosphate triethanolamine.

11. The preparation method according to claim 7, characterized in that The pH value is 2~11.

12. The preparation method according to claim 7, characterized in that The bulk doping is cation doping and / or anion doping.

13. The preparation method according to claim 12, characterized in that The doping cation in the cation doping is selected from Mg 2+ , Ca 2+ 、Ba 2+ 、Ag + 、Sb 3+ 、Sr 2+ Cr + 、Ga + 、In 3+ Any one or more of .

14. The preparation method according to claim 12, characterized in that The doping anion in the anion doping is selected from As 3- Br - 、Cl - 、F - 、P 3- 、S 2- , I - Any one or more of .

15. The preparation method according to claim 1, characterized in that The particle size of the positive electrode material is 1-15 μm.

16. The preparation method according to claim 1, characterized in that The positive electrode material is selected from LiNi x Co y Mn z Any one or more of O2, lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate, wherein x+y+z=1, 0<x<1, 0≤y<1, and 0<z<1.

17. The preparation method according to claim 1, characterized in that The preparation method further comprises: performing a first mixing and a second mixing in sequence on raw materials including the positive electrode material and the solid electrolyte to obtain the composite positive electrode material; Wherein, the rotation speed of the first mixing is lower than the rotation speed of the second mixing.

18. The preparation method according to claim 17, characterized in that: The rotation speed of the first mixing is 20-200 r / min.

19. The preparation method according to claim 17, characterized in that The first mixing time is 0.5 to 10 hours.

20. The preparation method according to claim 17, characterized in that The rotation speed of the second mixing is 1000~10000 r / min.

21. The preparation method according to claim 17, characterized in that The second mixing time is 0.1-1 h.

22. The preparation method according to claim 17, characterized in that The raw materials also include a conductive agent and a binder.

23. The preparation method according to claim 22, characterized in that The conductive agent is selected from any one or more of conductive graphite, acetylene black, carbon nanotubes, graphene, and carbon fiber.

24. The preparation method according to claim 22, characterized in that The mass of the conductive agent is 1-10 wt % of the total mass of the positive electrode material and the solid electrolyte.

25. The preparation method according to claim 22, characterized in that The binder is selected from any one or more of polyvinylidene fluoride, acrylic resin, polytetrafluoroethylene, and styrene-butadiene rubber.

26. The preparation method according to claim 22, characterized in that The mass of the binder is 0.1-10 wt % of the total mass of the positive electrode material and the solid electrolyte.

27. A composite positive electrode material, characterized in that The composite positive electrode material is a composite positive electrode material obtained by the preparation method according to any one of claims 1 to 26.

28. A method for preparing a composite positive electrode, characterized in that: The preparation method comprises: The composite positive electrode material is rolled into a composite positive electrode by horizontal rolling and vertical rolling; The conditions of the horizontal rolling and the vertical rolling include that the contents of water and oxygen are each independently less than 0.1 ppm; The composite positive electrode material is the composite positive electrode material according to claim 27.

29. A composite positive electrode, characterized in that The composite positive electrode is a composite positive electrode obtained by the preparation method according to claim 28.

30. A solid-state battery comprising a composite positive electrode, a solid electrolyte membrane and a negative electrode, characterized in that: The composite positive electrode is the composite positive electrode according to claim 29.

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