Composite separator, and cerium oxide having oxygen vacancies, preparation method therefor and use thereof

Abstract

A composite separator, and cerium oxide having oxygen vacancies, a preparation method therefor and a use thereof. The composite separator comprises a separator substrate and a functional coating applied to the surface of the separator substrate. The functional coating comprises (111)-CeO2-x, wherein 0<X≤0.45; the surface of (111)-CeO2-x is provided with a (111) crystal plane; and the concentration of oxygen vacancies of (111)-CeO2-x is Rt, wherein 0<Rt≤90%. Regarding the cerium oxide (111)-CeO2-x having oxygen vacancies, since the surface of (111)-CeO2-x is provided with a high proportion of the (111) crystal plane, and Ce3+ ions are mainly present on the (111) crystal plane, the content of the Ce3+ ions is high, so that there are a large number of oxygen vacancies in (111)-CeO2-x. Since the oxygen vacancies have the functions of adsorbing anions and scavenging reactive oxygen species, when applied to lithium batteries, (111)-CeO2-x can effectively reduce the degree of thermal runaway and improve the migration capability of lithium ions on electrode-electrolyte interfaces.

Description

Composite separator, cerium oxide with oxygen vacancies and preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the field of lithium batteries, in particular to a composite separator, cerium oxide and a preparation method and application thereof. BACKGROUND

[0002] As one of the key components of lithium ion batteries, the separator not only determines the capacity and cycle performance of the lithium ion battery, but also plays a crucial role in safety performance. The performance of the separator directly affects the overall performance of the lithium ion battery.

[0003] Currently, a ceramic coating (such as alumina) is generally coated on the surface of the separator in the industry, which on the one hand improves the high-temperature dimensional stability of the separator, consumes impurities in the electrolyte to improve the cycle life, and on the other hand improves the wettability and liquid absorption capacity of the separator and the electrolyte, and improves the cycle rate performance of the battery. However, the conventional ceramic coating (such as alumina) can only improve the wettability of the separator, and the improvement of the ion transmission capacity of the separator and the negative electrode interface is limited, resulting in the problems of lower constant current charging ratio and negative electrode lithium precipitation at high rate of the battery.

[0004] In addition, the industry's conventional inert ceramic coating and the scheme of coating glue to improve the high-temperature dimensional stability of the ion membrane cannot avoid the accumulation of heat in the battery to cause thermal runaway. According to the thermal runaway time sequence, the ternary positive electrode material is prone to phase change to generate active oxygen (widely refers to oxygen source free radicals and non-free radicals, including superoxide anion (O2 - ), hydroxyl radical (·OH) and singlet oxygen ( 1 O2)) under high temperature conditions. The exothermic reaction between active oxygen and active electrolyte and lithium-embedded negative electrode is one of the main reasons for accelerating the thermal runaway of the battery.

[0005] Cerium oxide (CeO2) usually exists in the form of fluorite phase, which has a face-centered cubic (fcc) crystal structure. Each cerium ion is coordinated with 8 oxygen ions, and the electronic structure of cerium (i.e. [Xe]4f15d16s2) makes it easier to transfer reversible charge between Ce 4+ and Ce 3+ . The formation of Ce 3+ ions is usually accompanied by the presence of oxygen vacancies on the surface and in the bulk, which is generally indirectly characterized by the Ce 3+ / Ce atomic percentage ratio of the test sample to represent the oxygen vacancy concentration of the material. Oxygen vacancy CeO 2-x has the functions of adsorbing anions and scavenging active oxygen, and is widely used to improve the cycle and rate performance of lithium ion batteries.

[0006] Since the formation energy of oxygen vacancies of cerium oxide on the (111) crystal plane is low, the oxygen vacancies are mainly stably present on the (111) crystal plane of the particles, and the reactivity of cerium oxide is related to the concentration of oxygen vacancies, so the regulation of the structure and crystal plane of cerium oxide is particularly important. The common method for regulating the morphology and exposed crystal plane type of nano cerium oxide particles is hydrothermal / solvothermal method, which is assisted by surfactants or templates. However, the hydrothermal / solvothermal method for regulating the morphology of nano cerium oxide often uses toxic or expensive additives, surfactants, and needs high temperature and pressure and a long time of treatment, which cannot meet the environmental friendly requirements of preparing nano materials; on the other hand, the new functional groups introduced in the preparation process are not easy to be completely removed, which interferes with the performance of nano cerium oxide and limits the practical application field of nano cerium oxide. SUMMARY

[0007] To solve the above problems, the present application provides a cerium oxide (111)-CeO 2-x .

[0008] The present application provides a cerium oxide with oxygen vacancies, wherein the cerium oxide is (111)-CeO 2-x , wherein 0X≤0.45, the surface of the (111)-CeO 2-x has a (111) crystal plane.

[0009] The (111)-CeO 2-x has an oxygen vacancy concentration of Rt, wherein 0

[0010] Further, the proportion of the (111) crystal plane is Rc, and 10%≤Rc<100%, preferably, Rc is more than 30%, and more preferably, Rc is more than 50%.

[0011] Further, the (111)-CeO 2-x has an oxygen vacancy concentration retention rate of not less than 90% after 7 days of high-temperature storage at 55℃, and preferably, not less than 95%.

[0012] Further, the (111)-CeO 2-x has a D50 particle size of 50nm-2μm, and preferably, 100nm-1μm.

[0013] The present application also provides a preparation method of the cerium oxide with specific oxygen vacancies, comprising the following steps:

[0014] dispersing CeO2 in an acidic solution with a reducing agent, and stirring to disperse uniformly to obtain (111)-CeO2;

[0015] The (111)-CeO2 is subjected to deoxidation treatment to obtain (111)-CeO2 2-x wherein 0X≤0.45;

[0016] The (111)-CeO2 is subjected to deoxidation treatment to obtain (111)-CeO2 2-x The oxygen vacancy concentration ratio is Rt, wherein 0

[0017] Further, the (111)-CeO2 preparation process comprises the following steps:

[0018] The CeO2 is dispersed in an acidic solution one, and stirred uniformly to obtain a solution one;

[0019] The reducing agent is dispersed in an acidic solution two, and stirred uniformly to obtain a solution two;

[0020] The solution two is added to the solution one, and stirred uniformly to obtain (111)-CeO2.

[0021] Further, the molar ratio of the CeO2 to the reducing agent is 1:(0.01-10), preferably 1:(0.05-5).

[0022] Further, the concentration of the acidic solution one is 0.001-10 mol / L, preferably 1-6 mol / L; and / or

[0023] The concentration of the acidic solution two is 0.001-10 mol / L, preferably 1-6 mol / L; and / or

[0024] The concentration of the reducing agent in the solution two is 0.001-0.3 mol / L, preferably 0.01-0.05 mol / L.

[0025] Further, the reducing agent is selected from one of TiCl3, TiBr3, Ti2(SO4)3, TiPO4; or

[0026] The acidic solution one and the acidic solution two are one of a hydrohalic acid solution, a sulfuric acid solution, a phosphoric acid solution.

[0027] Further, the deoxidation treatment comprises vacuum deoxidation method, inert atmosphere deoxidation method or warm hydrogenation method.

[0028] Further, the (111)-CeO2 is prepared by the method 2-x The (111)-CeO2 is subjected to deoxidation treatment to obtain (111)-CeO2 2-x .

[0029] The application also provides a composite diaphragm, comprising a diaphragm substrate and a functional coating coated on the surface of the diaphragm substrate, wherein the functional coating comprises the (111)-CeO 2-x or (111)-CeO 2-x prepared by the aforementioned method.

[0030] The application provides a pole piece, comprising the (111)-CeO 2-x or (111)-CeO 2-x prepared by the aforementioned method.

[0031] The application provides the aforementioned (111)-CeO 2-x or (111)-CeO 2-x prepared by the aforementioned method.

[0032] The application provides cerium oxide (111)-CeO 2-x with oxygen vacancies, wherein the (111)-CeO 2-x has a higher proportion of (111) crystal surface on the surface, and the Ce 3+ ions mainly exist on the (111) crystal surface, and the content of Ce 3+ ions is higher, so that the (111)-CeO 2-x has more oxygen vacancies. Since the oxygen vacancies have the functions of adsorbing anions and scavenging active oxygen, when the (111)-CeO 2-x is applied in a lithium battery, it can effectively delay the degree of thermal runaway and improve the migration ability of lithium ions at the electrode electrolyte interface. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings are used to better understand the application and do not constitute undue limitations on the application. Among them:

[0034] FIG. 1 is a TEM image of cerium oxide (111)-CeO 2-x of Example 1 provided by the application.

[0035] FIG. 2 is a TEM image of cerium oxide (111)-CeO 2-x of Example 1 provided by the application.

[0036] FIG. 3 is a TEM image of cerium oxide (111)-CeO 2-x of Example 1 provided by the application.

[0037] FIG. 4 is a TEM image of cerium oxide of Comparative Example 5 provided by the application. DETAILED DESCRIPTION

[0038] The following description of exemplary embodiments of the application is provided as an enabling teaching of the application. Various changes and modifications to the embodiments described herein will be apparent to those of ordinary skill in the art. The scope of the application is not intended to be limited to the changes and modifications within the scope of the application and the equivalent thereof.

[0039] The first part of the present application provides a cerium oxide with oxygen vacancies, which is (111)-CeO 2-x wherein 0 < X < 0.45.

[0040] Further, the (111)-CeO 2-x has a (111) crystal plane on the surface, and the (111)-CeO 2-x has an oxygen vacancy concentration of Rt, wherein 0 < Rt < 90%, Rt is preferably 5% to 60%, and further preferably 10% to 40%. For example, Rt can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc.

[0041] The (111)-CeO 2-x The oxygen vacancy concentration Rt in the (111)-CeO 3+ The formation of Ce3+ions is usually accompanied by the presence of oxygen vacancies on the surface and in the bulk, and the oxygen vacancy concentration of the material is generally characterized by the XPS test of the sample Ce 3+ / Ce atomic percentage ratio. The material to be tested is placed in an X-ray photoelectron spectrometer, and after etching 10 nm, XPS test is performed. According to the Ce 3+ and Ce 4+ electron binding, the Ce element photoelectron peak is refined and peak processed, the area of each peak is measured to calculate the atomic concentration. The oxygen vacancy concentration Rt (%) = Ce 3+ peak area / (Ce 3+ peak area + Ce 4+ peak area) x 100%.

[0042] In this paper, according to Rt = 2x, the specific value of x can be calculated from the oxygen vacancy concentration Rt.

[0043] In this application, the proportion of the (111) crystal plane is Rc, where 10% ≤ Rc < 100%, and Rc is preferably 30% or more, more preferably 50% or more. For example, Rc can be 10%, 15%, 20%, 5%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, etc.

[0044] The (111)-CeO 2-x The (111) crystal plane ratio Rc is the ratio of the area of ​​the (111) crystal plane to all crystal planes on the material surface. The measurement method is as follows: the material to be tested is placed in a transmission electron microscope and photographed. The magnification of the electron microscope is set so that one particle enters the field of view. Eight points are selected for each particle and observed at 800k magnification as shown in Figure 1. The perimeter D1 of the 111 crystal plane and the perimeter D2 of other crystal planes are measured as shown in Figure 2. The (111) crystal plane ratio Rc (%) of the particle is calculated as D1 / (D2+D1)×100. The average value is calculated for 5 particles.

[0045] In this application, in the (111)-CeO 2-x The retention rate of oxygen vacancy concentration after 7 days of storage at 55°C is not less than 90%, preferably not less than 95%.

[0046] The oxygen vacancy concentration retention rate is the ratio of the oxygen vacancy concentration of the powder after standing for 7 days at 55℃ to that before standing. The oxygen vacancy concentration retention rate % = (oxygen vacancy concentration after 7 days of high-temperature storage at 55℃) / (initial oxygen vacancy concentration) * 100%.

[0047] In this application, the (111)-CeO 2-xD50 particle size of 50 nm to 2 pm, preferably 100 nm to 1 pm, for example, can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2000 nm.

[0048] In this paper, the D50 particle size is the particle size D50 of the dispersion liquid tested by a laser particle size analyzer. The solvent in the selected test sample injector is deionized water. The powder to be tested is dispersed in the solvent by ultrasonic or mechanical stirring, etc. The sample is added dropwise into the test sample injector for testing. The particle diameter of 50% of the sample volume is the D50 value. The test parameters are set as follows: the material refractive index is 2.42, the absorption rate is 1.0, and the shading degree is 1-4%.

[0049] In this application, the (111)-CeO 2-x The superoxide anion scavenging rate is greater than or equal to 50%. For example, it can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, etc.

[0050] The determination method of superoxide anion scavenging rate is as follows:

[0051] ①Prepare a DMSO solution of chlorinated nitro tetrazolium blue (NBT) with dry and pyrogallol aqueous solution, and store in the dark for standby;

[0052] ②Take pyrogallol solution, phosphate buffer and deionized water in a black cover bottle in the ratio of 1:3:6, mix uniformly, directly avoid light shock for 10 min as blank group, add the powder to be tested after avoiding light shock for 1 min as experimental group;

[0053] ③ The reaction suspension is filtered, the mass of the precipitate is measured, and the mass of the precipitate is divided by the mass of the precipitate of the blank group to evaluate the clearance rate.

[0054] The second part of the application provides a preparation method of cerium oxide of a specific special surface, comprising the following steps:

[0055] Step one: acid treatment

[0056] CeO2 is dispersed in an acid solution with a reducing agent, and stirred to be uniformly dispersed to obtain (111)-CeO2;

[0057] Step two: deoxygenation treatment

[0058] The (111)-CeO2 is subjected to deoxygenation treatment to obtain (111)-CeO2 2-x , wherein 0X≤0.45; the surface of the (111)-CeO2 2-x has a (111) crystal face, and the (111)-CeO2 2-x has an oxygen vacancy concentration of Rt, wherein 0

[0059] In step one, the preparation process of the (111)-CeO2 specifically comprises the following steps:

[0060] Step 1.1: CeO2 is dispersed in acid solution one, and stirred to be uniformly dispersed to obtain solution one;

[0061] Step 1.2: A reducing agent is dispersed in acid solution two, and stirred to be uniformly dispersed to obtain solution two;

[0062] Step 1.3: The solution two is slowly added to the solution one, and stirred to be uniformly dispersed to obtain (111)-CeO2.

[0063] The D50 particle size of the CeO2 is 50 nm-2 μm, preferably 100 nm-1 μm, for example, it can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2000 nm.

[0064] The molar ratio of the CeO2 to the reducing agent is 1:(0.01-10), preferably 1:(0.05-5), for example, it can be 1:0.01, 1:0.05, 1:0.08, 1:0.1, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, etc.

[0065] The concentration of the acidic solution one or the concentration of the acidic solution two is 0.001-10 mol / L, preferably 1-6 mol / L, for example, it can be 0.005 mol / L, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, 10 mol / L, etc.

[0066] Too high concentration of the acidic solution one and the acidic solution two will cause more corrosion of the CeO2, reduce the yield, in addition, it will also cause corrosion of the equipment, and even higher concentration of the acid will bring safety hazards, too low concentration will also cause low proportion of the (111) crystal surface of the CeO2, and then affect the oxygen vacancy concentration.

[0067] The molar ratio of CeO2 in the solution I to the acid in the acid solution I is 1:(0.1-20), preferably 1:(5-10), for example, it can be 1:0.1, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, etc.

[0068] The concentration of the reducing agent in the solution II is 0.001-0.3 mol / L, preferably 0.01-0.05 mol / L, for example, it can be 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, etc. Too high concentration of the reducing agent in the solution II will result in reduced chemical stability of the CeO2(111) crystal surface and waste of the reducing agent, and too low concentration will result in reduced reducing property and low proportion of the CeO2(111) crystal surface.

[0069] The reducing agent is selected from one of TiCl3, TiBr3, Ti2(SO4)3, and TiPO4.

[0070] The acid solution I and the acid solution II are one of a hydrohalic acid solution, a sulfuric acid solution, and a phosphoric acid solution.

[0071] The acid in the acid solution I and the acid solution II is preferably the same kind of acid.

[0072] The hydrohalic acid can be HCl, HBr, or HI.

[0073] In some embodiments, the acid solution II and the reducing agent have the same anion.

[0074] In some embodiments, the acid solution II is an HCl solution, and the reducing agent is TiCl3.

[0075] In some embodiments, the acid solution II is an HBr solution, and the reducing agent is TiBr3.

[0076] In some embodiments, the acid solution II is a sulfuric acid solution, and the reducing agent is Ti2(SO4)3.

[0077] In step two, the (111)-CeO2 is obtained by deoxidizing treatment of (111)-CeO2 by vacuum deoxidizing method, inert atmosphere deoxidizing method or warming hydrogenation method, etc. 2-x .

[0078] Specifically, when the vacuum deoxidizing method is adopted, the specific steps are as follows:

[0079] Step 2a: Place (111)-CeO2 in the reaction chamber, and vacuumize the reaction chamber by vacuum pump until the vacuum degree in the reaction chamber reaches -80 kPa to -99 kPa;

[0080] Step 2b: repeatedly introduce inert gas into the reaction chamber, and then vacuumize the reaction chamber by vacuum pump to clean the reaction chamber;

[0081] Step 2c: vacuumize the reaction chamber by vacuum pump until the pressure in the reaction chamber reaches -99 kPa to -100 kPa; turn on the heating device to heat and warm up to the preset temperature, and continue to react to prepare (111)-CeO2. 2-x .

[0082] The preset temperature is 400-1800°C, preferably 800-1200°C, for example, it can be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, etc.

[0083] The reaction time at the preset temperature is 0-48h, preferably 2-12h, for example, it can be 2h, 4h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h, 40h, 42h, 44h, 46h, 48h, etc.

[0084] Specifically, when the inert atmosphere deoxidizing method is adopted, the specific steps are as follows:

[0085] Step 2a: Place (111)-CeO2 in the reaction chamber, and vacuumize the reaction chamber by vacuum pump until the vacuum degree in the reaction chamber reaches -80 kPa to -99 kPa;

[0086] Step 2b: repeatedly introduce inert gas into the reaction chamber, and then vacuumize the reaction chamber by vacuum pump to clean the reaction chamber;

[0087] Step 2c: inert gas is introduced into the reaction chamber until the pressure in the reaction chamber reaches 101 kPa, the heating device is turned on for heating, the temperature is raised to the preset temperature, and the reaction continues, thereby preparing (111)-CeO 2-x .

[0088] The inert gas includes, but is not limited to, nitrogen, argon, and helium.

[0089] The preset temperature is 400-1800°C, preferably 800-1200°C, and for example, can be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, etc.

[0090] The reaction time at the preset temperature is 0-48 h, preferably 2-12 h, and for example, can be 1 h, 2 h, 4 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h, etc.

[0091] Specifically, when the warming hydrogenation method is used, the specific steps are as follows:

[0092] Step 2a: (111)-CeO2 is placed in the reaction chamber, and the reaction chamber is vacuumized by a vacuum pump until the vacuum degree in the reaction chamber reaches -80 kPa to -99 kPa;

[0093] Step 2b: inert gas is repeatedly introduced into the reaction chamber, and the reaction chamber is vacuumized by a vacuum pump for cleaning;

[0094] Step 2c: hydrogen-argon mixed gas is introduced into the reaction chamber until the pressure in the reaction chamber reaches 101 kPa, the heating device is turned on for heating, the temperature is raised to the preset temperature, and the reaction continues, thereby preparing (111)-CeO 2-x .

[0095] The hydrogen in the hydrogen-argon mixed gas accounts for 5%-95%.

[0096] The preset temperature is 400-1800°C, preferably 800-1200°C, and for example, can be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, etc.

[0097] The reaction time at the preset temperature is 0-48 h, preferably 2-12 h, for example, 1 h, 2 h, 4 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h, etc.

[0098] In the present application, the (111)-CeO2 is prepared by the preparation method described in the present application. 2-x The (111)-CeO2 is prepared by the preparation method described in the present application. 2-x The parameters thereof can refer to the foregoing description.

[0099] The present application also provides a composite separator, comprising a separator substrate and a functional coating layer coated on the surface of the separator substrate, wherein the functional coating layer comprises the (111)-CeO2 described above. 2-x The (111)-CeO2 is prepared by the preparation method described in the present application. 2-x .

[0100] In some embodiments, the functional coating layer is (111)-CeO2. 2-x The thickness of the functional coating layer is 0.1-10 μm, for example, 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm.

[0101] The separator substrate comprises, but is not limited to, a polyester polyolefin porous membrane, and a polyolefin porous membrane loaded with alumina and boehmite on one side or both sides.

[0102] The present application also provides a pole piece, wherein the pole piece comprises the (111)-CeO2 described above. 2-x The (111)-CeO2 is prepared by the preparation method described in the present application. 2-x .

[0103] In some embodiments, the pole piece comprises a pole piece body and a coating layer coated on the surface of the pole piece body, wherein the coating layer comprises the (111)-CeO2 described above. 2-x The (111)-CeO2 is prepared by the preparation method described in the present application. 2-x .

[0104] In some embodiments, the pole piece comprises a pole piece substrate, wherein the pole piece substrate is mixed with the (111)-CeO2 described above. 2-x The (111)-CeO2 is prepared by the preparation method described in the present application. 2-x .

[0105] The (111)-CeO2 described above is contained. 2-xThe coating material can be applied in the fields of coating the surface of the diaphragm, mixing the positive and negative electrodes, and coating the surface of the electrode sheet, without changing the current mainstream battery cell preparation process, and has the advantages of high stability and low cost, and is suitable for large-scale application. Compared with the positive electrode surface coating method, the coating material containing (111)-CeO 2-x has a larger loading amount and better functional surface continuity when coated on the surface of the diaphragm / electrode sheet, and the process is simpler and lower in cost, and the material is not easy to be oxidized at a high voltage of the positive electrode.

[0106] The (111)-CeO 2-x described in the present application can be applied in lithium batteries. Since the (111)-CeO 2-x has a large proportion of (111) crystal planes on the surface, the (111)-CeO 2-x has more trivalent cerium and oxygen vacancies, and when it is applied in a lithium battery, it can capture active oxygen in the battery cycle process through charge action, especially active oxygen generated by the positive electrode under extreme abnormal working conditions such as a hot box or overcharging, thereby preventing the exothermic oxidation-reduction reaction between the active oxygen and the negative active material, and avoiding the continuous heating of the battery cell, which can cause thermal runaway. Moreover, since the (111)-CeO 2-x lacks oxygen ions in the crystal lattice, the exposed metal ions with positive charges can adsorb anions in lithium salt, promoting the dissociation of lithium salt.

[0107] The preferred method for regulating the morphology and exposed crystal plane type of nano cerium oxide particles in the prior art is the hydrothermal / solvothermal method, which is assisted by surfactants or templates. Compared with the preparation method described in the present application, the process is simple, low in cost, and suitable for large-scale application.

[0108] Examples and test section

[0109] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0110] The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0111] The acid solution I and the acid solution II used in the following examples are the same acid and concentration unless otherwise specified, and are collectively referred to as the acid solution.

[0112] I. Examples

[0113] Example 1

[0114] Step 1: CeO2 particles with a D50 of 400 nm were dispersed in a 5 mol / L acidic HCl solution and stirred until uniformly dispersed. While continuously stirring, a 0.02 mol / L TiCl3 solution in 5 mol / L HCl was added dropwise. The reaction was allowed to proceed for 5 minutes. Finally, the treated dispersion was filtered, washed, and dried to obtain the treated (111)-CeO2. The molar ratio of CeO2 to HCl to TiCl3 in the acidic solution was 1:5:0.2, and the acid treatment reduction time was 5 minutes to obtain (111)-CeO2.

[0115] Step Two:

[0116] Step 2a: Place (111)-CeO2 in the reaction chamber and evacuate the reaction chamber using a vacuum pump until the vacuum level in the reaction chamber is -99kPa.

[0117] Step 2b: Repeatedly introduce inert gas into the reaction chamber, and then use a vacuum pump to evacuate the reaction chamber to clean it.

[0118] Step 2c: Introduce a 5% hydrogen-argon mixture into the reaction chamber. When the pressure reaches atmospheric pressure (101 kPa), turn on the heating device to heat the mixture to 500°C and continue the reaction for 2 minutes to prepare (111)-CeO. 2-x .

[0119] (111)-CeO prepared by the above method 2-x The test results of superoxide anion scavenging activity are shown in Table 1. (111)-CeO 2-x TEM images at different magnifications are shown in Figures 1-3.

[0120] Step 3: Add 1 part by weight of sodium polyacrylate dispersant to 2000 parts by weight of water and stir thoroughly. Then add 100 parts by weight of (111)-CeO 2-x The (111)-CeO was processed by a ball mill. 2-x The particles were uniformly dispersed to a particle size D50 of 400 nm. Then, 1 part by weight of thickener sodium carboxymethyl cellulose, 5 parts by weight of binder polyacrylate and 0.4 parts by weight of wetting agent sodium perfluorooctanoate were added and stirred thoroughly to obtain the coating slurry.

[0121] Step 4: Apply the coating slurry onto the diaphragm substrate using a micro-gravure coating machine, bake at 40°C for 2 minutes to form a functional layer, and then roll it up to obtain the composite diaphragm.

[0122] The diaphragm substrate is a polyethylene film with an alumina coating on both sides, wherein the alumina coating thickness is 2 μm and the polyethylene film thickness is 9 μm; (111)-CeO 2-xThe coating thickness is 2 pm;

[0123] The lithium battery composite separator prepared by the above method is used to assemble a lithium battery. The battery structure is NCM83||SiOC450 soft package battery. The (111)-CeO2-x coating faces the positive electrode side. Lithium hexafluorophosphate-LiFSI polyester electrolyte is used to assemble a soft package battery cell for testing. The specific performance test results are shown in Table 1.

[0124] Examples 2-3 differ from Example 1 only in that the (111)-CeO 2-x are uniformly dispersed into particles of different particle sizes D50. Other parameters are shown in Table 1.

[0125] Examples 4-5 differ from Example 1 only in that the concentration of TiCl3 in step one is different. Other parameters are shown in Table 2.

[0126] Examples 6-8 differ from Example 1 only in that the concentration of the HCl acid solution in step one is different. Other parameters are shown in Table 3.

[0127] Examples 9-10 differ from Example 1 only in that the type of acid solution in step one is different. Other parameters are shown in Table 4.

[0128] Examples 11-13 differ from Example 1 only in that the type of atmosphere in step 2c is different. Other parameters are shown in Table 5.

[0129] Comparative Examples 1-2 differ from Example 1 only in that the concentration of TiCl3 in step one is different. Other parameters are shown in Table 2.

[0130] Comparative Example 3 differs from Example 1 only in that the concentration of the HCl acid solution in step one is different. Other parameters are shown in Table 3.

[0131] Comparative Example 4 differs from Example 1 only in that the type of atmosphere in step 2c is different. Other parameters are shown in Table 5.

[0132] Comparative Example 5 differs from Example 1 only in that steps one and two are not performed, i.e., the CeO2 is not treated. Other parameters are shown in Table 6, and the TEM image of CeO2 is shown in FIG. 4. As can be seen from FIG. 4, the (200) crystal plane is the main crystal plane in the CeO2.

[0133] Comparative Example 6 differs from Example 1 only in that step two is not performed. Other parameters are shown in Table 6.

[0134] Comparative Example 7 differs from Example 1 only in that Step 1 is not performed. The other parameters are shown in Table 6.

[0135] Comparative Example 8 differs from Example 1 only in that the composite separator of the lithium battery is a polyethylene film coated with aluminum oxide on both sides, with the aluminum oxide coating having a thickness of 2 μm and the polyethylene film having a thickness of 9 μm. The other parameters are shown in Table 6.

[0136] II. Test Section

[0137] (I) Test Method:

[0138] 1. The determination method of overcharge pass rate is as follows:

[0139] The battery is discharged at a constant current to the discharge cut-off voltage, and then charged at a constant current to 160% SOC at the greater of 3C rate and 3 times the recommended charging current of the manufacturer, and then left for 1 h. If the battery does not catch fire or explode, it is considered to pass.

[0140] 2. The determination method of hot box pass rate is as follows:

[0141] The battery is first discharged at a constant current to the discharge cut-off voltage, and then charged to the full charge state. The battery is then placed in a test chamber. The test chamber is heated at a temperature increase rate of 5°C / min, and when the temperature in the chamber reaches 140°C±2°C, the temperature is kept constant. After 1 h, the temperature is increased at a rate of 5°C / min, and when the temperature in the chamber reaches 150°C±2°C, the temperature is kept constant. After 1 h, the temperature is increased at a rate of 5°C / min, and when the temperature in the chamber reaches 160°C±2°C, the temperature is kept constant. After 1 h, the entire process is considered to pass if the battery does not catch fire or explode.

[0142] 3. The determination method of room temperature cycle life is as follows:

[0143] a) The battery is first discharged at a current of 1C to the material discharge termination voltage at 23°C±2°C, and then left for 1 h;

[0144] b) The battery is charged to the material charge termination voltage at a current of 1C, and then converted to constant voltage charging when the current rate decreases to 0.05C, and then left for 1 h;

[0145] c) The battery is discharged at a current of 1C to the material discharge termination voltage, and the discharge specific capacity is recorded;

[0146] d) The steps a and b are repeated 3 times, and the average of the discharge specific capacity of the three tests is selected as the initial capacity. The battery is continuously charged and discharged at a current of 1C, and if the discharge capacity is lower than 80% of the initial capacity, the test is terminated, and the total number of cycles in which the capacity is higher than the initial capacity is recorded.

[0147] 4. The determination method of 3C constant current charge-in ratio is as follows:

[0148] a) first discharged at 0.33C current to the material discharge termination voltage at 23℃±2℃, and standing for 1h;

[0149] b) charged to the material charge termination voltage at 3C current, and then changed to constant voltage charging until the charge current ratio reduced to 0.05C, and standing for 1h;

[0150] c) discharged the battery at 0.33C current to the material discharge termination voltage, and recorded the discharge specific capacity;

[0151] d) 3C constant current charge ratio = 3C constant current charge capacity / (3C constant current charge capacity+ termination voltage constant voltage charge capacity)*100;

[0152] e) repeat the steps b and c for 3 times, and recorded the average value of 3C constant current charge ratio of three tests.

[0153] (II) Test results of each example

[0154] 1、Table 1 is (111)-CeO 2-x Effects of different particle sizes D50

[0155] 2、Table 2 is the effect of different TiCl3 concentrations in solution two

[0156] 3、Table 3 is the effect of different concentrations of acidic solution

[0157] 4、Table 4 is the effect of different types of acid when the same acidic solution is added twice in step one

[0158] 5、Table 5 is the effect of different types of gas in step two

[0159] 6、Table 6 is the comparison of each comparative example and example 1

[0160] From Tables 1-6, it can be seen that (111)-CeO 2-x When used in lithium batteries, the (111)-CeO When CeO2 is directly used or only subjected to acid treatment and then used in lithium batteries, the amount of trivalent cerium ions and oxygen vacancies in CeO2 is small, so the removal effect of superoxide ions is poor, resulting in poor battery performance of the lithium battery. When CeO2 is subjected to acid treatment and reduction or directly calcined, only a small part of tetravalent cerium is reduced to trivalent cerium, so the battery performance and safety of the lithium battery are still low.

[0161] Although the embodiments of the present application have been described above with reference to the accompanying drawings, the present application is not limited to the above-described specific embodiments and areas of application, and the above-described specific embodiments are merely illustrative and instructive, but are not restrictive. Many modifications can be made by those skilled in the art under the teachings of the present specification and without departing from the scope of the claims of the present application, and all such modifications are intended to be within the scope of the present application.

Claims

1. A composite separator, wherein, A separator substrate and a functional coating layer coated on a surface of the separator substrate, the functional coating layer comprising (111)-CeO 2-x wherein 0 < X < 0.45, the surface of the (111)-CeO 2-x has a (111) crystal plane.

2. The composite separator of claim 1, wherein, The (111)-CeO 2-x The oxygen vacancy concentration is Rt, where 0 < Rt≤ 90%.

3. The composite separator of claim 2, wherein, The Rt is 5% to 60% or 10% to 40%.

4. The composite separator according to any one of claims 1 to 3, wherein, The (111) crystal plane ratio is Rc, and 10%≤Rc<100%.

5. The composite separator of claim 4, wherein, The Rc is 30% or more or 50% or more.

6. The composite separator of claim 5, wherein, In the (111)-CeO 2-x The retention rate of the oxygen vacancy concentration after 7 days of high-temperature storage at 55°C is not less than 90% or 95%.

7. The composite separator of any one of claims 1-3, wherein, The (111)-CeO 2-x D50 particle size of 50 nm to 2 pm or 100 nm to 1 pm.

8. Cerium oxide having oxygen vacancies, wherein The cerium oxide is (111)-CeO 2-x wherein 0 < X < 0.45, the (111)-CeO 2-x has a (111) crystal plane on the surface.

9. The cerium oxide of claim 8, wherein, The (111)-CeO 2-x The oxygen vacancy concentration is Rt, where 0 < Rt≤ 90%.

10. The cerium oxide of claim 9, wherein, The Rt is 5% to 60% or 10% to 40%.

11. The cerium oxide according to any one of claims 8 to 10, wherein The (111) crystal plane ratio is Rc, and 10%≤Rc<100%.

12. The cerium oxide of claim 11, wherein, The Rc is 30% or more or 50% or more.

13. The cerium oxide of claim 12, wherein, In the (111)-CeO 2-x The retention rate of the oxygen vacancy concentration after 7 days of high-temperature storage at 55°C is not less than 90% or 95%.

14. The cerium oxide according to any one of claims 8 to 10, wherein, The (111)-CeO 2-x D50 particle size of 50 nm to 2 pm or 100 nm to 1 pm.

15. A method of preparing cerium oxide having oxygen vacancies as claimed in any one of claims 8 to 14, wherein, The method comprises the following steps: CeO2 is dispersed in an acidic solution with a reducing agent, and stirred to be uniformly dispersed to obtain (111)-CeO2; The (111)-CeO2is subjected to deoxidation treatment to obtain (111)-CeO2 2-x wherein 0 < X < 0.

45.

16. The method of manufacturing according to claim 15, wherein, The (111)-CeO2 preparation process comprises the following steps: CeO2 is dispersed in an acidic solution one, and stirred to be uniformly dispersed to obtain the solution one; A reducing agent is dispersed in an acidic solution two, and stirred to be uniformly dispersed to obtain the solution two; The solution two is added to the solution one, and stirred to be uniformly dispersed to obtain (111)-CeO2.

17. The method of making according to claim 16, wherein, The concentration of the acidic solution one is 0.001 to 10 mol / L; and / or The concentration of the acidic solution two is 0.001 to 10 mol / L; and / or The concentration of the reducing agent in the solution two is 0.001 to 0.3 mol / L.

18. The method of making according to claim 16, wherein, The concentration of the acidic solution one is 1 to 6 mol / L; and / or The concentration of the acidic solution two is 1 to 6 mol / L; and / or The concentration of the reducing agent in the solution two is 0.01 to 0.05 mol / L.

19. The method of making according to claim 16, wherein, The reducing agent is selected from one of TiCl3, TiBr3, Ti2(SO4)3 and TiPO4; and / or The acidic solution one and the acidic solution two are one of a hydrogen halide acid solution, a sulfuric acid solution and a phosphoric acid solution.

20. The method of making according to claim 15, wherein, The deoxidation treatment includes: vacuum deoxidation method, inert atmosphere deoxidation method or warm hydrogenation method to obtain (111)-CeO 2-x .

21. A pole piece, wherein, (111)-CeO2comprising the (111)-CeO2of any one of claims 8-14 2-x or the (111)-CeO2prepared by the method of any one of claims 15-20 2-x .

22. A (111)-CeO2 as claimed in any one of claims 8 to 14 2-x or prepared by the method as claimed in any one of claims 15 to 20 2-x for use in a lithium battery.

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