A method for preparing a lithium slurry battery electrode

Abstract

The application discloses a kind of lithium slurry battery electrode preparation methods.Belongs to large-scale electrochemical energy storage technical field.It includes the following includes:(I) the surface of current collector is grown graphene layer by CVD;(II) then its surface is treated with acid, and the treated current collector is soaked in ionic liquid, and then put into thermostat heat treatment;(III) remove the surface growth graphene's current collector and wash dry;(IV) active particles are dispersed in electrolyte with nanometer carbon coating, conductive agent and additive to prepare electrode slurry, and the slurry dispersion system and current collector jointly constitute slurry electrode.The application introduces graphite layer, and the non-integer contact between layers produces interface super-slip (friction coefficient <0.01), which greatly reduces the movement resistance between particles and reduces aggregation. Ionic liquid can form interface lubricating layer ability to synergistically construct interface lubricating layer. By combining the super-slip characteristics of non-integer contact between graphite layers and the lubricating properties of ionic liquid, a new type of slurry electrode particle and current collector rolling sliding interface is constructed, which improves the conductivity while greatly reducing the particle flow resistance, providing a new strategy for slurry system flow and performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a lithium slurry battery electrode preparation method, in particular to a method for preparing a slurry fluid electrode by using graphene and ionic liquid to jointly act on the current collector and construct a rolling sliding interface with active particles coated with nano-carbon, thereby constructing a new rolling sliding interface between the particles and the current collector in the slurry electrode by combining the non-integer contact between the graphite layers to produce super-slip characteristics and the lubricating properties of ionic liquid, thereby improving the electrical conductivity while reducing the flow resistance of the particles, and providing a new strategy for the flow and performance of the slurry system.

[0002] The present application belongs to the technical field of large-scale electrochemical energy storage, in particular to a lithium slurry battery fluid electrode preparation method. BACKGROUND

[0003] With the rapid development of renewable energy, large-scale energy storage technology has become a reliable solution to promote the effective use of renewable energy. Lithium slurry battery is a new type of electrochemical large-scale energy storage technology, which is composed of active particles, conductive agents and additives dispersed in electrolyte to form an electrochemical reaction system for cyclic energy storage. Compared with traditional homogeneous flow battery, lithium slurry battery has higher energy density, but also has problems such as non-homogeneous particle aggregation and reaction micro-channel blockage, which affects the performance and cycle life of the slurry battery.

[0004] During the operation of the slurry battery, the active particles, conductive agent particles and current collector in the slurry flow are prone to collision and friction, resulting in particle flow resistance and aggregation and blockage. The construction of a solid lubrication zone in the electrode helps to reduce the particle flow resistance and strengthen the slurry flow. In particular, the graphite layer is introduced to produce an interface super-slip (friction coefficient < 0.01) by using the non-integer contact between the layers, which greatly reduces the particle motion resistance and aggregation. In addition, ionic liquid is a commonly used green solvent or additive, which can form an interface lubrication layer by itself or with other solvents to greatly reduce the friction resistance. The present application combines the super-slip characteristics of the non-integer contact between the graphite layers and the lubricating properties of ionic liquid to construct a new rolling sliding interface between the particles and the current collector in the slurry electrode, which improves the electrical conductivity while greatly reducing the particle flow resistance, and provides a basis for the flow and performance of the slurry system.

[0005] Therefore, the present application proposes a slurry electrode preparation method suitable for lithium slurry battery, which provides a new strategy for long-term flow and high-performance large-scale application of lithium slurry battery. SUMMARY

[0006] The present application aims to provide a lithium slurry battery electrode preparation method, and the electrode is applied to lithium slurry energy storage battery as a lithium slurry battery electrode.

[0007] The technical scheme adopted by the present application is as follows:

[0008] A method for preparing a slurry fluid electrode by using graphene and ionic liquid to jointly act on the current collector and constructing a rolling sliding interface with active particles coated with nanocarbon, the preparation method comprising the following steps:

[0009] A lithium slurry battery electrode preparation method, characterized in that it comprises the following steps: (I) growing a graphene layer on the surface of the current collector by CVD; (II) then treating the surface of the current collector with acid, immersing the treated current collector in ionic liquid, and then placing it in a thermostat for heat treatment; (III) taking out the current collector with a graphene layer on the surface for cleaning and drying; (IV) dispersing active particles coated with nanocarbon, conductive agents and additives in an electrolyte to prepare an electrode slurry, and the slurry dispersion system and the current collector together constitute a slurry electrode. The current collector used in step (I) is aluminum foil, copper foil, carbon felt, carbon paper, conductive coated aluminum foil and conductive coated copper foil; the thickness of the graphene in step (I) is 0.3-20 nm; the temperature and time of the thermostat used in step (II) are 20-220°C and 0.1-12 hours; the cleaning liquid used in step (III) is one or a combination of deionized water, methanol, ethanol, ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, triethylene glycol, acetone, butanone, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, ammonia, propylene carbonate, γ-butyrolactone, ethylene carbonate and dimethyl carbonate; the conductive agent in step (IV) is one or a combination of conductive carbon black, Ketjen black, carbon nanotubes and graphene.

[0010] In step (II), the acid is one or a combination of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, carbonic acid, boric acid, phosphoric acid, hypochlorous acid, hypophosphorous acid, hydrofluoric acid, perchloric acid and sulfonic acid.

[0011] In step (II), the ionic liquid is an alcohol amine ionic liquid, or an ionic liquid composed of [XZ] + [Y] — wherein Z is imidazole, pyridine or pyrrolidine, X is 1-methyl-3-ethyl, 1-methyl-3-propyl, 1-allyl-3-methyl, 1-butyl-3-methyl, 1-hexadecyl-3-methyl or 1-ethyl-3-methyl; and Y is bisulfate, dihydrogen phosphate, chloride, bromide, iodide, tetrafluoroborate or bistrifluoromethylsulfonylimide; or an ionic liquid composed of [CAH] + [RCOO] — wherein CA is piperazine, imidazole, 5-pyrazolone, melamine, cyanuric chloride or 2-imidazolylethylamine; and R is H or C1-C2 alkyl.

[0012] In step (IV), the nanocarbon is graphene or graphenelike sheet material with a size of 0.3-100 nm.

[0013] In step (IV), the active particles are one or a combination of lithium manganate, lithium cobaltate, lithium nickelate, lithium nickel manganate, lithium cobalt manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminum, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt phosphate, titanium oxide, lithium titanate, titanium niobium oxide, barium titanate, niobium oxide, silicon powder, silicon oxide, silicon suboxide, graphite, mesocarbon microbeads, lithium metal particles, tin oxide, silicon carbon, and silicon oxygen carbon materials.

[0014] The lithium slurry battery electrode prepared by the preparation method has good flowability and electrochemical reactivity.

[0015] A lithium slurry battery is prepared by using the lithium slurry battery electrode prepared by the method.

[0016] Compared with the prior art, the method has the following advantages:

[0017] 1) The ionic liquid can form an interfacial lubricating layer by itself or in combination with other solvents to greatly reduce the frictional resistance of the friction pair (between the particles and the current collector), which has a technical advantage in the preparation of lithium slurry battery electrodes.

[0018] 2) The non-commensurate contact between graphene and graphite layers has super-slip phenomenon (friction coefficient < 0.01); the combination of ionic liquid and graphene can form an interfacial lubricating layer to improve the sliding properties of the friction pair, especially when the ionic liquid chain is oriented parallel to the graphite interface, the lubricating effect will be synergistically enhanced, greatly reducing the frictional resistance between the current collector and the particles; at the same time, the action of the ionic liquid can also form a compatible system with the ionic liquid-containing electrolyte, enhancing the compatibility.

[0019] 3) The interfacial lubricating layer formed can not only protect the particles and the current collector from being worn, but also ensure electron conduction and promote flow; the slurry electrode has good flowability and conductivity in the slurry battery, which can greatly improve the performance and long cycle life of the slurry battery.

[0020] 4) The method is simple, easy to operate, and the ionic liquid has the advantages of green and reusability. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Schematic diagram of the ionic liquid and graphene in the present application forming an interfacial lubricating layer between the current collector and the particles DETAILED DESCRIPTION

[0022] The application will be further described below in conjunction with examples, but it should not be understood as limiting the scope of protection of the present application.

[0023] The characterization and detection methods involved in the following examples are as follows:

[0024] 1. Friction coefficient test

[0025] Multi-functional friction and wear tester (UMT-3, Bruker)

[0026] 2. Battery performance test

[0027] Battery test system (CT-3008 5v 10A, Land CT 2001A)

[0028] Example 1:

[0029] (I) Take clean and dry aluminum foil current collector, put into tube furnace, pass CH4 gas, CVD growth of 3 layers of graphene (~1 nm) on the surface of aluminum foil; (II) then the graphene layer growth of the current collector is treated in phosphoric acid solution, so that the surface contains trace functional groups, then the treated current collector is immersed in 1-propyl-3-methylimidazolium chloride ionic liquid, and then put into an incubator at 60°C for 1 hour heat treatment; (III) take out the current collector with graphene grown on the surface and ionic liquid groups and wash in deionized water and dry; (IV) prepare positive electrode slurry by dispersing nickel cobalt lithium manganate (LiNi 0.8 Co 0.1 Mn 0.1 O2) active particles, conductive agent carbon nanotubes and additives in electrolyte (active particles: conductive agent: additives: electrolyte according to mass fraction ratio of 35:3:2:60), the slurry dispersion system and the current collector together constitute the slurry electrode. Then take metal lithium sheet as negative electrode, assemble half battery to test the electrochemical performance of the positive electrode slurry. The test voltage is 2.8-4.3V, and the capacity retention rate after 50 cycles is 80%. In addition, the active particles and the current collector are subjected to rotary sliding friction test, each test is repeated 3 times, the friction coefficient measurement accuracy is ±0.001, and the test friction coefficient is 0.032.

[0030] Example 2:

[0031] Repeat Example 1, but change the thickness of the graphene layer in step (I) to 2 layers (~0.67 nm). Assemble the prepared slurry electrode into a lithium half battery, and the electrochemical performance test obtains a capacity retention rate of 82% after 50 cycles of the battery; the friction coefficient between the active particles and the current collector is 0.031.

[0032] Example 3:

[0033] Repeat Example 2, but change the acid solution in step (II) to nitric acid. Assemble the prepared slurry electrode into a lithium half battery, and the electrochemical performance test obtains a capacity retention rate of 84% after 50 cycles of the battery; the friction coefficient between the active particles and the current collector is 0.029.

[0034] Example 4:

[0035] Example 3 was repeated, but the ionic liquid in step (II) was changed to 1-ethyl-3-methylimidazolium chloride ionic liquid. The prepared slurry electrode was assembled into a half battery against lithium, and the electrochemical performance test showed that the capacity retention rate of the battery after 50 cycles was 85%; the friction coefficient between the active particles and the current collector was 0.028.

[0036] Example 5:

[0037] Example 4 was repeated, but the temperature of the constant temperature oven in step (II) was changed to 120°C. The prepared slurry electrode was assembled into a half battery against lithium, and the electrochemical performance test showed that the capacity retention rate of the battery after 50 cycles was 87%; the friction coefficient between the active particles and the current collector was 0.027.

[0038] Example 6:

[0039] Example 5 was repeated, but the constant temperature heat treatment time in step (II) was changed to 2 hours. The prepared slurry electrode was assembled into a half battery against lithium, and the electrochemical performance test showed that the capacity retention rate of the battery after 50 cycles was 88%; the friction coefficient between the active particles and the current collector was 0.026.

[0040] Example 7:

[0041] Example 6 was repeated, but the cleaning solvent in step (III) was changed to ethanol. The prepared slurry electrode was assembled into a half battery against lithium, and the electrochemical performance test showed that the capacity retention rate of the battery after 50 cycles was 89%; the friction coefficient between the active particles and the current collector was 0.025.

[0042] Example 8:

[0043] Example 7 was repeated, but the thickness of the nanocarbon sheet layer in step (IV) was changed to 20 nanometers. The prepared slurry electrode was assembled into a half battery against lithium, and the electrochemical performance test showed that the capacity retention rate of the battery after 50 cycles was 90%; the friction coefficient between the active particles and the current collector was 0.024.

[0044] Example 9:

[0045] Example 8 was repeated, but the conductive agent in step (IV) was changed to Ketjen black. The prepared slurry electrode was assembled into a half battery against lithium, and the electrochemical performance test showed that the capacity retention rate of the battery after 50 cycles was 91%; the friction coefficient between the active particles and the current collector was 0.023.

[0046] Example 10:

[0047] Example 1 was repeated, but the current collector in step (I) was changed to copper foil, and the active particles in step (IV) were changed to lithium titanate. The prepared slurry electrode was assembled into a lithium half-cell, the test voltage was 1.4-2.5 V, and the capacity retention rate of the battery after 50 cycles was 83% according to electrochemical performance testing; the friction coefficient between the active particles and the current collector was 0.032.

Claims

1. A method of preparing a lithium slurry battery electrode, characterized by, The method comprises the following steps: (I) CVD growth of graphene layer on the surface of the current collector; (II) subsequent acid treatment of the surface, and immersion of the treated current collector in an ionic liquid and then heat treatment in an incubator; (III) removal of the current collector with the graphene layer on the surface for cleaning and drying; (IV) preparation of electrode slurry by dispersing the active particles coated with nanocarbon, conductive agent and additives in an electrolyte, and preparation of the slurry electrode by combining the slurry dispersion system and the current collector; the current collector used in step (I) is aluminum foil, copper foil, carbon felt, carbon paper, conductive-coated aluminum foil and conductive-coated copper foil; the thickness of the graphene in step (I) is 0.3-20 nm; the temperature of the incubator used in step (II) is 20-220 ℃, and the time is 0.1-12 hours; the cleaning liquid used in step (III) is one or a combination of deionized water, methanol, ethanol, ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, triethylene glycol, acetone, butanone, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, ammonia, propylene carbonate, γ-butyrolactone, ethylene carbonate and dimethyl carbonate; the conductive agent in step (IV) is one or a combination of conductive carbon black, Ketjen black, carbon nanotube and graphene.

2. The preparation method according to claim 1, characterized in that, The acid used in step (II) is one or a combination of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, carbonic acid, boric acid, phosphoric acid, hypochlorous acid, hypophosphorous acid, hydrofluoric acid, perchloric acid and sulfonic acid.

3. The preparation method according to claim 1, characterized in that, In step (II), the ionic liquid is an alcohol amine ionic liquid, or an ionic liquid having the composition [XZ] + [Y] — wherein Z is imidazole, pyridine or pyrrolidine, X is 1-methyl-3-ethyl, 1-methyl-3-propyl, 1-allyl-3-methyl, 1-butyl-3-methyl, 1-hexadecyl-3-methyl or 1-ethyl-3-methyl; and Y is hydrogen sulfate, dihydrogen phosphate, chloride, bromide, iodide, tetrafluoroborate or bis-trifluoromethylsulfonylimide; or an ionic liquid having the composition [CAH] + [RCOO] — wherein CA is piperazine, imidazole, 5-pyrazolone, melamine, cyanuric chloride or 2-imidazolylethylamine; and R is H or C1-C2 alkyl.

4. The preparation method according to claim 1, characterized in that, The nanocarbon in step (IV) is graphene or graphenelike sheet material with a size of 0.3-100 nm.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. In step (IV), the active particles are one or a combination of lithium manganate, lithium cobaltate, lithium nickelate, lithium nickel manganate, lithium nickel cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminumate, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt phosphate, titanium oxide, lithium titanate, titanium niobium oxide, barium titanate, niobium oxide, silicon powder, silicon oxide, silicon suboxide, graphite, mesocarbon microbeads, lithium metal particles, tin oxide, silicon carbon and silicon oxygen carbon material.

6. The lithium slurry battery electrode prepared by the method of any one of claims 1-5 has good flowability and electrochemical reactivity.

7. A lithium slurry battery characterized by comprising: The lithium slurry battery electrode of claim 6 is prepared as an electrode.

Images