CN110323489B - Solid lithium ion conductor and preparation method and application thereof - Google Patents

Solid lithium ion conductor and preparation method and application thereof Download PDF

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CN110323489B
CN110323489B CN201910570939.4A CN201910570939A CN110323489B CN 110323489 B CN110323489 B CN 110323489B CN 201910570939 A CN201910570939 A CN 201910570939A CN 110323489 B CN110323489 B CN 110323489B
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ion conductor
lithium ion
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lioh
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沈越
谢美兰
黄云辉
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Huazhong University of Science and Technology
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    • C—CHEMISTRY; METALLURGY
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
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Abstract

The invention relates to a solid lithium ion conductor and a preparation method and application thereof, belonging to the field of secondary batteries. The invention obtains the LiAlO-containing material by reacting LiOH with alkyl aluminum2And Li3AlO3The solid lithium ion conductor of the polycrystalline composite of (1). Preferably, the reaction is carried out in a liquid electrolyte, which is a solution of a lithium salt dissolved in an organic solvent. Preferably, the LiOH is LiOH obtained by in-situ reaction on a lithium sheet or LiOH in powder form. The electrode of the solid lithium ion conductor prepared by the invention has high room temperature ionic conductivity and low electronic conductivity, and the interface contact resistance can be greatly reduced by tightly combining the solid lithium ion conductor with lithium metal. The prepared solid lithium ion conductor is applied to the metal lithium battery, so that the problem of lithium dendrite can be effectively and remarkably improved, the metal lithium can be protected, and the cycle performance of the metal lithium battery can be comprehensively improved. The method for preparing the solid lithium ion conductor does not need heating, and has simple preparation process and low cost.

Description

Solid lithium ion conductor and preparation method and application thereof
Technical Field
The invention belongs to the field of secondary batteries, and particularly relates to a solid lithium ion conductor and a preparation method and application thereof.
Background
In recent years, new energy electric vehicles have been developed vigorously, but the current commercialized lithium ion battery technology cannot meet the requirement of long endurance mileage of electric vehicles. Therefore, the development of new battery technologies with high energy density and high output power has attracted much attention in the industry.
Lithium metal batteries, such as lithium sulfur batteries and lithium air batteries, have high energy density and are expected to be applied to electric vehicles and other energy storage systems in the future. Lithium metal has a high theoretical specific capacity (3860 mAhg)-1) And very low electrochemical potential batteries (-3.04V vs standard hydrogen electrodes), there are still some problems that are difficult to solve when using metallic lithium as the negative electrode. Non-cycling of lithium metalThe uniform deposition is easy to generate dendritic crystals, and the formation of lithium dendritic crystals can continuously react with the electrolyte on one hand, so that the active lithium and the electrolyte are continuously consumed; on the other hand, irreversible growth of lithium dendrites may pierce the separator to cause short circuit of the battery or even explosion, causing a safety problem.
At present, the protection method for lithium metal mainly has the following aspects: introducing an electrolyte additive; adopting high-salt electrolyte; coating a layer of artificial SEI film on the surface of the metal lithium; a solid electrolyte is used.
The use of a solid electrolyte is expected to fundamentally solve the above problems. Ideal solid state electrolysis requires high room temperature ionic conductivity, high mechanical strength, non-volatility, non-flammability, and electrochemical stability over the operating voltage range of the cell. Currently, solid electrolytes can be broadly classified into three categories: inorganic (ceramic/glassy) solid electrolytes, polymer electrolytes, and composite electrolytes. The inorganic solid electrolyte can maintain electrochemical stability over a wide temperature range relative to the polymer solid electrolyte, and thus the inorganic solid electrolyte-based battery has higher safety performance.
However, the existing inorganic solid electrolyte still has more problems: 1) the room temperature lithium ion conductivity of most solid electrolytes is low; 2) a large interface contact resistance exists between the solid electrolyte and the electrode; 3) some solid electrolytes have high electronic conductivity, which may allow lithium metal to be deposited directly inside the solid electrolyte. Therefore, the above problems need to be solved before commercialization of the solid electrolyte is possible.
The Atomic Layer Deposition (ALD) technique has the characteristics of conformal deposition, accurate and controllable film thickness and the like, and is widely used for modifying electrode materials. The present ALD technique can be used to grow oxides, nitrides, sulfides, etc., where Al is present2O3Is the most commonly used material for deposition. When mixing Al2O3When deposited on the surface of lithium metal, it can effectively prevent the corrosion of electrolyte, water vapor and oxygen to lithium metal, but Al2O3Has low lithium ion conductivity, and may reduce the lithium ion transmission coefficient at the electrode interface, thereby limitingAnd (3) the cycle performance of the battery. LiAlOxCompared with Al2O3Has higher lithium ion conductivity, and the literature reports that the ALD technology is utilized to deposit LiAlO at presentxThe film is used for coating the anode material and the graphite electrode, but the room temperature lithium ion conductivity of the deposited film is still low (10 to 10)-7S/cm). In addition, the ALD deposition technique requires high vacuum environment, expensive precursor source and slow film growth rate, which limits its wide application to some extent.
Therefore, the research on the solid electrolyte with high room temperature lithium ion conductivity and low electronic conductivity and the reduction of interface contact resistance have important significance for the development of all-solid-state metal lithium batteries.
Disclosure of Invention
The invention solves the technical problems that the room temperature lithium ion conductivity of the solid conductor is low, the interface contact resistance between the solid conductor and the electrode is large, and the high electronic conductivity can cause the metal lithium to be directly deposited in the solid electrolyte in the prior art. The invention obtains the LiAlO-containing material by reacting LiOH with alkyl aluminum2And Li3AlO3The solid lithium ion conductor of the polycrystalline composite of (1). The LiOH is obtained by in-situ reaction on the lithium sheet or is powdery LiOH. The electrode of the solid lithium ion conductor prepared by the invention has high room temperature ionic conductivity and low electronic conductivity, and the interface contact resistance can be greatly reduced by tightly combining the solid lithium ion conductor with lithium metal. The prepared solid lithium ion conductor is applied to the metal lithium battery, so that the problem of lithium dendrite can be effectively and remarkably improved, the metal lithium can be protected, and the cycle performance of the metal lithium battery can be comprehensively improved.
According to a first aspect of the present invention, a preparation method of a solid lithium ion conductor is provided, wherein the preparation method comprises a step of reacting LiOH with an aluminum alkyl solution to obtain the solid lithium ion conductor, and the solid lithium ion conductor is a polycrystalline composite.
Preferably, the reaction is carried out in a liquid electrolyte, which is a solution of a lithium salt dissolved in an organic solvent.
Preferably, the preparation process of the LiOH is as follows: and (3) placing the lithium sheet in a mixed solution of an organic solvent and water which can be mutually dissolved with water, so that the lithium sheet floats on the surface of the mixed solution, and LiOH is generated in situ by the lithium sheet contacting with the mixed solution.
Preferably, the LiOH is in powder form.
Preferably, the lithium salt is a lithium salt containing fluorine atoms, and the organic solvent is an ether organic solvent or an alkane organic solvent.
Preferably, the lithium salt containing fluorine atoms is at least one of lithium bistrifluoromethanesulfonimide, difluoride yellow imide and lithium hexafluorophosphate, the ether organic solvent is at least one of tetraethylene glycol dimethyl ether and diethylene glycol dimethyl ether, and the alkane organic solvent is at least one of n-hexane, n-pentane and n-octane.
Preferably, the polycrystalline composite contains LiAlO2、Li3AlO3、Al2O3、Li2CO3And LiF.
Preferably, the alkyl aluminum is trimethyl aluminum or triethyl aluminum.
According to another aspect of the present invention, there is provided a solid lithium ion conductor prepared by any one of the above-described preparation methods.
According to another aspect of the invention, there is provided the use of said solid state lithium ion conductor in a battery comprising a lithium metal negative electrode.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
(1) the method for preparing the solid lithium ion conductor is simple and easy to implement, has low cost, and can prepare the Li-Al-O oxide solid electrolyte through the chemical reaction of LiOH and a triethyl aluminum solution at normal temperature and normal pressure, wherein the solid electrolyte has high room-temperature ionic conductivity (C) ((C))>10-4S cm-1) And low electron conductivity: (<10-6S cm-1)。
(2) The solid lithium ion conductor is generated in situ on the surface of the metal lithium and is in close contact with the metal lithium, so that the interface contact resistance can be greatly reduced.
(3) The solid lithium ion conductor prepared by the method can effectively inhibit the growth of dendritic crystals, and can effectively prevent the corrosion of organic solvent, water molecules and oxygen to the metal lithium, and the solid lithium ion conductor can be applied to metal batteries, lithium-lithium iron phosphate batteries and lithium-oxygen batteries, so that the stability of the metal lithium and the cycle performance of the batteries can be greatly improved. The method for preparing the solid lithium ion conductor does not need heating, and has simple preparation process and low cost.
(4) When the solid lithium ion conductor is applied to a lithium-lithium symmetrical battery, the battery cycle can be as long as 1200 h. The main reasons for improving the stability of lithium metal in the battery system are the following two aspects: firstly, the solid electrolyte has high room temperature ionic conductivity, can reduce concentration polarization of lithium ions in the processes of lithium deposition and dissolution, and generates uniform lithium ion flow in the circulating process, so that lithium is uniformly nucleated; second, the solid lithium ion conductor has low electron conductivity, and can effectively inhibit nucleation and growth of lithium inside the solid electrolyte. Therefore, the stability of the lithium metal is significantly improved under the protection of the solid lithium ion conductor.
(5) When the solid lithium ion conductor is applied to a lithium ion battery (lithium iron phosphate), the solid electrolyte can effectively stabilize a lithium negative electrode and inhibit lithium dendrites, and the cycle performance of the lithium iron phosphate battery is obviously improved.
(6) When the solid electrolyte of the present invention is applied to a lithium-oxygen battery, it is used at 300mA g-1The lithium-oxygen cell was able to cycle for 179 cycles at the current density of (d). The main reasons for the improvement of the cycle performance of lithium-oxygen batteries are: the solid lithium ion conductor contains LiAlO2And Li3AlO3Containing Al in addition to the lithium ion compound2O3，Al2O3The thin film has extremely low permeability of oxygen and water vapor, so the solid lithium ion conductor can effectively inhibit the corrosion and damage of organic solvent, water molecules and oxygen molecules to the lithium negative electrode.
Drawings
Fig. 1 is an XPS spectrum of Al 2p measured using the solid lithium ion conductor of the present invention.
Fig. 2 is an XPS spectrum of Li 1s measured using the solid lithium ion conductor of the present invention.
Fig. 3 is a transmission diagram of a solid lithium ion conductor using the present invention.
Fig. 4 is a flow chart of the preparation of an electrode for in-situ growth of a solid lithium ion conductor in example 1.
Fig. 5 is a scanned plot of a lithium sheet after 70 cycles of a lithium-lithium symmetric battery using the solid-state lithium ion conductor of the present invention.
Fig. 6 is a graph comparing time-voltage curves of a lithium-lithium symmetric battery using the solid lithium ion conductor and a blank lithium sheet.
Fig. 7 is a scan of a lithium plate after 70 cycles using a blank lithium plate lithium-lithium symmetric cell.
Fig. 8 is a graph comparing the cycle-voltage-specific capacity curves of lithium-oxygen batteries using lithium sheets protected with solid lithium ion conductors according to the present invention and blank lithium sheets.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention relates to a preparation method of a solid lithium ion conductor, which comprises the following steps:
(1) dissolving organic lithium salt containing fluorine atoms in an ether organic solvent to obtain an electrolyte;
(2) adding an alkyl aluminum solution into the electrolyte in the step (1) to obtain a solution; adding LiOH powder into the solution under the inert gas atmosphere, and fully reacting to obtain a solid lithium ion conductor which contains LiAlO2And Li3AlO3The polycrystalline composite of (a).
The organic lithium salt containing fluorine atoms in the step (1) is lithium bistrifluoromethanesulfonimide, lithium bistrifluorosulfonimide or lithium hexafluorophosphate, the ether organic solvent is diethylene glycol dimethyl ether solution or tetraethylene glycol dimethyl ether, and the concentration of the electrolyte is 0.5-5 mol/L; the aluminum alkyl in the step (2) is triethyl aluminum or trimethyl aluminum, the concentration of the aluminum alkyl in the solution is 5mmol/L-200mmol/L, and the mass ratio of the LiOH powder to the volume of the solution is 0.36g/L-14.4 g/L.
The invention relates to a preparation method of an electrode of an in-situ growth solid lithium ion conductor, which comprises the following steps:
(1) dissolving organic lithium salt containing fluorine atoms in an ether organic solvent to obtain an electrolyte;
(2) under the condition of inert atmosphere, inserting one part of a lithium sheet into a mixed solution of an organic ether solvent and water which are mutually soluble with water, and generating LiOH in situ by the part of the lithium sheet inserted into the mixed solution;
(3) adding an alkyl aluminum solution into the electrolyte in the step (1) under the inert atmosphere condition to obtain a solution; dropwise adding the solution on the LiOH generated in the step (2), reacting the alkyl aluminum with the LiOH to obtain a solid lithium ion conductor, wherein the solid lithium ion conductor contains LiAlO2And Li3AlO3The polycrystalline composite of (a).
The organic lithium salt containing fluorine atoms in the step (1) is lithium bistrifluoromethanesulfonimide, lithium bistrifluorosulfonimide or lithium hexafluorophosphate, the ether organic solvent is diethylene glycol dimethyl ether solution or tetraethylene glycol dimethyl ether, and the concentration of the electrolyte is 0.5-5 mol/L; the organic ether solvent which can be mutually dissolved with water in the step (2) is diethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether; the aluminum alkyl in the step (3) is triethyl aluminum or trimethyl aluminum, and the concentration of the aluminum alkyl in the solution is 5mmol/L-200 mmol/L.
The solid lithium ion conductor prepared by any one of the methods of the invention.
The electrode of the in-situ growth solid lithium ion conductor prepared by any method of the invention.
The height of the solid lithium ion conductor is 40um-150 um.
The solid lithium ion conductor is applied to a metal lithium battery.
The solid lithium ion conductor is pressed into a ceramic sheet, the thickness of the ceramic sheet is 40-150 um, a metal lithium sheet is attached to one side of the ceramic sheet, the ceramic sheet is placed in a baking oven at the temperature of 200-300 ℃ for heating for 50-70 min, and the pressure of 0.5-5 MPa is applied in the heating process, so that an electrode containing the solid lithium ion conductor is obtained, and the electrode is applied to a metal lithium battery as an electrode;
preferably, the metal lithium battery is a lithium-lithium symmetric battery, a lithium-iron phosphate battery or a lithium-oxygen battery.
The electrode of the in-situ growth solid lithium ion conductor is applied as an electrode in a metal lithium battery;
preferably, the metal lithium battery is a lithium-lithium symmetric battery, a lithium-iron phosphate battery or a lithium-oxygen battery.
Example 1
The preparation method of the solid lithium ion conductor comprises the following steps: in this example, 2.87g of lithium bistrifluoromethanesulfonylimide was dissolved in 10mL of an electrolyte solution of diethylene glycol dimethyl ether with a glove box as an atmosphere, and the solution was stirred at room temperature for 12 hours to obtain 1.0mol L-1The electrolyte of (1). And then adding 0.05-2 mL of 1mol/L triethyl aluminum solution into the electrolyte, stirring for 6 hours to obtain a solution A, wherein the concentration of the alkyl aluminum in the solution A is 5-200 mmol/L, weighing 3.6-144 mg of LiOH powder, adding into the solution A, and stirring for 1 hour to obtain a complete reaction. And after the reaction is completed, obtaining white powder, washing the powder for three times by using diethylene glycol dimethyl ether, removing residual triethyl aluminum, and then placing the powder in a glove box for natural drying. 5-30 mg of the powder is pressed into a ceramic sheet with the thickness of 40-150 um by applying the pressure of 5-15 MPa. The main component of the solid lithium ion conductor is LiAlO according to X-ray photoelectron spectroscopy (XPS) analysis of Al 2p and Li 1s2，Li3AlO3，Al2O3，Li2CO3LiF and some organic compounds, as shown in fig. 1 and fig. 2. The solid lithium ion conductor has obvious lattice strips in a Transmission Electron Microscope (TEM)Lines, indicating that the composite is polycrystalline, as in fig. 3.
And sticking a metal lithium sheet on one side of the ceramic sheet, heating the ceramic sheet in an oven at 250 ℃ for 2 hours, and applying pressure of 0.5-5 MPa in the heating process to prepare the Li-Al-O electrode with low interface resistance.
The ion conductivity of the solid lithium ion conductor is tested by using an alternating current impedance method, and the specific process is as follows: uniformly pressing a fresh lithium sheet on the surface of the solid lithium ions, then pressing 3-5 layers of foamed nickel on the lithium sheet layer by layer to assemble the button cell, wherein the ionic conductivity of the solid electrolyte film is 1.67x10 at the temperature of 25 DEG C-4S cm-1(including grain boundaries and ion conductivity inside the crystal), bulk ion conductivity as high as 1.56x10-3S cm-1(including only the lithium ion conductivity within the crystal).
A flow chart of a process for preparing an electrode for in-situ growth of a solid lithium ion conductor is shown in fig. 4. In the embodiment, a glove box is used as an atmosphere environment, a fresh lithium sheet is placed in hydrous diethylene glycol dimethyl ether for reaction, a layer of LiOH is introduced to the surface of lithium metal, and after the reaction is completed, the lithium sheet is placed in the glove box for natural drying. The thickness of the LiOH layer can be adjusted differently by the reaction time and the concentration of water.
Dropping 30-200 uL of an electrolyte containing 5-200 mmol/L of triethylaluminum solution on the surface of the lithium sheet, wherein the electrolyte is 1.0mol L-1A solution of lithium bistrifluoromethanesulfonylimide in diethylene glycol dimethyl ether. After the reaction is completed, washing the reaction product for three times by using diethylene glycol dimethyl ether, removing residual triethyl aluminum, and then placing the reaction product in a glove box for natural drying, thus preparing a layer of solid lithium ion conductor on the surface of lithium metal, wherein the height of the ion conductor layer is 40-150 mu m, namely the depth of a lithium sheet inserted into the hydrous diethylene glycol dimethyl ether. The solid electrolyte prepared by the method is mainly prepared from LiAlO through XPS and TEM characterization2，Li3AlO3，Al2O3，Li2CO3Polycrystalline composites of LiF and some organic compounds.
Testing the ionic conductivity of the solid lithium ion conductor by using an alternating current impedance methodThe specific process is as follows: uniformly pressing a fresh lithium sheet on the surface of the solid lithium ions, then pressing 3-5 layers of foamed nickel on the lithium sheet layer by layer to assemble the button cell, wherein the ionic conductivity of the solid electrolyte film is 1.42x10 at the temperature of 25 DEG C-4S cm-1Bulk phase ionic conductivity up to 1.41x10-3S cm-1。
The method for preparing the solid lithium ion conductor in the embodiment of the invention is simple and easy to implement and has low cost. The solid lithium ion conductor contains LiAlO2And Li3AlO3The compounds have better lithium ion conducting capacity, so that the solid electrolyte has high room temperature lithium ion conductivity. In addition, due to Al3+Is a strong hard acid and O2-Is a strong weak base, and the electron cloud is strongly bound when the two form a compound, so that the solid electrolyte has low electron conductivity. The solid electrolyte is generated in situ on the surface of lithium metal and is tightly contacted with the lithium metal, so that the interface resistance can be greatly reduced.
Example 2
Preparing a layer of 40-150 um solid lithium ion conductor on the surface of lithium metal obtained in example 1, pressing two lithium sheets containing the solid lithium ion conductor together face to assemble a lithium-lithium symmetric battery, and tightly pressing 3-5 layers of nickel foam on one side of each lithium sheet to ensure tight contact between solid electrolytes.
Standing for 6h after the battery is mounted, and performing charge and discharge test on a LAND-CT2001A tester with current density of 0.2mAcm-2Capacity limit of 0.4mAh cm-2. After 70 cycles, the surface of the lithium metal is flat and has no cracks, and no lithium dendrites appear, as shown in figure 5. Even after 1200h of circulation, the battery can still keep stable basically, and the polarization voltage is below 0.04V, as shown in figure 6.
Comparative example 1
Dissolving 2.87g lithium bistrifluoromethanesulfonylimide in 10mL electrolyte of tetraethylene glycol dimethyl ether, stirring for 12h at room temperature to obtain 1.0mol L-1The electrolyte of (1). The obtained electrolyte was injected into a lithium-lithium symmetric battery to obtain the lithium-lithium symmetric battery of the present example, which employs glass fiber as a separator and a blankThe lithium sheet serves as an electrode.
Standing for 6h after the battery is mounted, and performing charge and discharge test on a LAND-CT2001A tester with current density of 0.2mAcm-2Capacity limited to 0.4mAh cm-2. After 70 cycles of cycling, the lithium pieces were severely pulverized as in fig. 7, and after 500h cycling, the polarization of the cell gradually increased as in fig. 6.
Comparative example 2
Dissolving 2.87g lithium bistrifluoromethanesulfonylimide in 10mL mixed solvent of diethylene glycol dimethyl ether and 1, 3-dioxolane (volume ratio 1:1), stirring at room temperature for 12h to obtain 1.0mol L-1The electrolyte of (1). The obtained electrolyte was injected into a lithium-lithium symmetric battery, which employs glass fiber as a separator and a blank lithium sheet as an electrode, to obtain the lithium-lithium symmetric battery of the present example.
Standing for 6h after the battery is mounted, and performing charge and discharge test on a LAND-CT2001A tester with current density of 0.2mAcm-2Capacity limited to 0.4mAh cm-2. After the cell was cycled for 550h, the polarization of the cell gradually increased.
Combining example 2, comparative example 1 and comparative example 2, it is shown that the solid lithium ion conductor prepared in example 1 can effectively suppress dendrites and can prevent corrosion of the lithium negative electrode by an organic solvent, so that the stability of the battery can be greatly improved. The main reasons why the solid electrolyte can effectively inhibit lithium dendrites are as follows: 1) the solid lithium ion conductor contains LiAlO2And Li3AlO3The compounds have better lithium ion conducting capacity, can reduce concentration polarization of lithium ions in the processes of lithium deposition and dissolution, and have uniform lithium ion flow on the surface of lithium metal in the deposition process, thereby being beneficial to uniform nucleation of lithium; 2) due to Al3+Is a strong hard acid and O2-Is a strong weak base, and the electron cloud is strongly bound when the two form a compound, so that the solid electrolyte has low electronic conductivity which inhibits lithium dendrites in the solid electrolyte.
Example 3
Preparing a layer of 40-150 um solid lithium ion conductor on the surface of lithium metal by the same method as in embodiment 1, using the solid lithium ion conductor as a negative electrode of a lithium-iron phosphate lithium battery, pressing aluminum coated with lithium iron phosphate on the solid lithium ion conductor to ensure that the lithium iron phosphate is tightly contacted with the solid lithium ion conductor, pressing 3-5 layers of nickel foam on one side of an aluminum foil current collector to assemble the battery.
After the battery is assembled, the battery is kept stand for 6 hours, and is subjected to charge and discharge tests on a LAND-CT2001A tester, and the charge and discharge are carried out at a multiplying power of 0.5C. After the battery is circulated for 200 circles, the specific capacity is still 135mAh g-1。
Comparative example 3
1.0mol of L was prepared in the same manner as in comparative example 1-1And lithium salt electrolyte, injecting the obtained electrolyte into the lithium-iron phosphate lithium battery, and taking the blank lithium piece as a negative electrode and PP as a diaphragm to obtain the lithium-iron phosphate lithium battery of the embodiment.
After the battery is assembled, the battery is kept stand for 6 hours, and is subjected to charge and discharge tests on a LAND-CT2001A tester, and the charge and discharge are carried out at a multiplying power of 0.5C. After the battery is stably circulated for 200 circles, the specific capacity of a blank sample is only 40mAh g-1。
Comparative example 4
1.0mol of L was prepared in the same manner as in comparative example 2-1And lithium salt electrolyte, injecting the obtained electrolyte into the lithium-iron phosphate lithium battery, and taking the blank lithium piece as a negative electrode and PP as a diaphragm to obtain the lithium-iron phosphate lithium battery of the embodiment.
After the battery is assembled, the battery is kept stand for 6 hours, and is subjected to charge and discharge tests on a LAND-CT2001A tester, and the charge and discharge are carried out at a multiplying power of 0.5C. After the battery is stably circulated for 200 circles, the specific capacity of a blank sample is only 55mAh g-1。
By combining example 3, comparative example 3 and comparative example 4, it is shown that the solid lithium ion conductor prepared in example 2 can effectively improve the stability of lithium metal, avoid corrosion of an organic solvent to a lithium negative electrode, inhibit lithium dendrite, and improve the cycling stability of lithium iron phosphate to a certain extent.
Example 4
1.0mol L of the composition was prepared in the same manner as in example 2-1A lithium salt electrolyte. The obtained electrolyte was injected into a lithium-oxygen battery, and the carbon nanotube film was used as a positive electrode, which was the same as that of example 1The solid lithium ion conductor prepared in the same manner was used as a negative electrode, and glass fiber was used as a separator, to obtain a lithium-oxygen battery of this example.
Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6h, and performing charge-discharge test on a LAND-CT2001A tester with the current density of 300mA g-1Capacity limit of 1000mAh g-1The lithium-oxygen cell was able to cycle for 179 cycles stably, as shown in fig. 8.
And when the blank lithium sheet is used as the negative electrode, under the same test condition, after the battery is cycled for 31 circles, the discharge voltage is lower than 2V, and the battery is stopped.
Example 5
Dissolving 2.87g lithium bistrifluoromethanesulfonylimide in 10mL diethylene glycol dimethyl ether solvent, stirring at room temperature for 12h to obtain 1.0mol L-1The electrolyte of (1). The obtained electrolyte was injected into a lithium-oxygen battery, and the lithium-oxygen battery of this example was obtained using a carbon nanotube film as a positive electrode, a solid lithium ion conductor prepared in the same manner as in example 1 as a negative electrode, and a glass fiber as a separator.
Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6h, and performing charge-discharge test on a LAND-CT2001A tester with the current density of 300mA g-1Capacity limit of 1000mAh g-1The cell can stably circulate for 156 circles.
When the blank lithium plate is used as the negative electrode, under the same test condition, after the battery is cycled for 27 circles, the discharge voltage is lower than 2V, and the battery is stopped.
Example 6
Dissolving 2.87g lithium bistrifluoromethanesulfonylimide in 10mL dimethyl sulfoxide solvent, stirring for 12h at room temperature to obtain 1.0mol L-1The electrolyte of (1). The obtained electrolyte was injected into a lithium-oxygen battery, and the lithium-oxygen battery of this example was obtained using a carbon nanotube film as a positive electrode, a solid lithium ion conductor prepared in the same manner as in example 1 as a negative electrode, and a glass fiber as a separator.
Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6h, and charging and discharging on a LAND-CT2001A testerElectric test with a current density of 300mA g-1Capacity limit of 1000mAh g-1The battery can stably circulate for 136 circles.
And when the blank lithium sheet is used as the negative electrode, under the same test condition, after the battery is cycled for 21 circles, the discharge voltage is lower than 2V, and the battery is stopped.
Combining example 4, example 5 and example 6, it is shown that the solid-state lithium ion conductor prepared in example 1 can effectively improve the cycle stability of the lithium-oxygen battery. This superior performance may result from the solid state lithium ion conductor containing in addition to LiAlO2,Li3AlO3Al in addition to the compound for directing lithium ions2O3，Al2O3The film has extremely low permeability of oxygen and water vapor and is often used as a packaging material of a thin film transistor and an electronic device, so that the solid lithium ion conductor can effectively inhibit the corrosion of organic solvent, water molecules and oxygen to the lithium metal cathode. Further, Al2O3The thin film has a high dielectric constant (9), and is commonly used as a dielectric layer of a thin film transistor, so that the solid lithium ion conductor has low electronic conductivity, and the low electronic conductivity can effectively inhibit the nucleation and growth of lithium dendrites in the solid electrolyte.
In summary, the present invention provides a method for preparing a solid-state lithium ion conductor. In the preparation process, the Li-Al-O solid electrolyte with high room temperature ionic conductivity and low electronic conductivity can be obtained only by introducing a LiOH layer on the surface of a metal lithium sheet and then carrying out chemical reaction with triethylaluminum. The main component of the solid lithium ion conductor is LiAlO2，Li3AlO3，Al2O3，Li2CO3Polycrystalline composites of LiF and some organic compounds. The solid lithium ion conductor can effectively inhibit the corrosion of organic solvent, water molecules and oxygen to metal lithium and inhibit lithium dendrite. When the solid lithium ion conductor is applied to a lithium-lithium symmetric battery, a lithium-iron phosphate battery and a lithium-oxygen battery, the cycling stability of the battery is better improved.
Compared with the preparation of the solid electrolyte, the preparation method of the solid lithium ion conductor is simple and easy to obtain, low in price and obvious in effect. The lithium-lithium symmetrical battery assembled by the solid electrolyte can stably cycle for 1200h, and the polarization voltage is basically kept within 0.04V. When the solid lithium ion conductor is used as a negative electrode of a lithium-oxygen battery, the battery can stably cycle for 179 cycles, which is more than 6 times that of a blank lithium plate as the negative electrode.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. The preparation method of the solid lithium ion conductor is characterized in that LiOH is reacted with an alkyl aluminum solution to obtain the solid lithium ion conductor, the LiOH is prepared by in-situ reaction on the surface of a lithium sheet, and the solid lithium ion conductor is a polycrystalline compound.
2. The method for producing a solid lithium ion conductor according to claim 1, wherein the reaction is carried out in a liquid electrolyte solution in which a lithium salt is dissolved in an organic solvent.
3. The method of preparing a solid lithium ion conductor according to claim 1 or 2, wherein the LiOH is prepared by: and (3) placing the lithium sheet in a mixed solution of an organic solvent and water which can be mutually dissolved with water, so that the lithium sheet floats on the surface of the mixed solution, and LiOH is generated in situ by the lithium sheet contacting with the mixed solution.
4. The method of preparing a solid lithium ion conductor according to claim 1 or 2, wherein the LiOH is in a powder form.
5. The method for producing a solid lithium ion conductor according to claim 2, wherein the lithium salt is a fluorine atom-containing lithium salt, and the organic solvent is an ether-type organic solvent or an alkane-type organic solvent.
6. The method for producing a solid lithium ion conductor according to claim 5, wherein the lithium salt containing a fluorine atom is at least one of lithium bistrifluoromethanesulfonimide, bisfluorosuccinimide, or lithium hexafluorophosphate, the ether-based organic solvent is at least one of tetraglyme and diglyme, and the alkane-based organic solvent is at least one of n-hexane, n-pentane, and n-octane.
7. The method of claim 5 or 6, wherein the polycrystalline composite comprises LiAlO2、Li3AlO3、Al2O3、Li2CO3And LiF.
8. The method of claim 1, wherein the aluminum alkyl is trimethylaluminum or triethylaluminum.
9. A solid lithium ion conductor prepared by the preparation process as claimed in any one of claims 1 to 8.
10. Use of the solid state lithium ion conductor of claim 9 in a battery comprising a lithium metal negative electrode.
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