CN112103502A - Lithium-sulfur secondary battery and preparation method and application thereof - Google Patents

Lithium-sulfur secondary battery and preparation method and application thereof Download PDF

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CN112103502A
CN112103502A CN202010958931.8A CN202010958931A CN112103502A CN 112103502 A CN112103502 A CN 112103502A CN 202010958931 A CN202010958931 A CN 202010958931A CN 112103502 A CN112103502 A CN 112103502A
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bentonite
sulfur
lithium
secondary battery
sulfur secondary
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CN112103502B (en
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吴炼
戴永强
余越
庞浩
麦裕良
廖兵
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Institute of Chemical Engineering of Guangdong Academy of Sciences
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
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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
    • H01M10/05—Accumulators with non-aqueous electrolyte
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
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    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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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
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    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
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Abstract

The invention discloses a lithium-sulfur secondary battery and a preparation method and application thereof. The bentonite/sulfur composite anode material with efficient ion channels and conductive network structures enables the sulfur carrying capacity of the lithium-sulfur secondary battery anode to be remarkably improved, promotes the transmission of ions/electrons in the battery anode, and strengthens the electrochemical reaction dynamics in the anode, thereby effectively improving the discharge specific capacity, the cycling stability and the rate capability of the lithium-sulfur secondary battery, being widely applied to various energy storage power systems and having high practical value.

Description

Lithium-sulfur secondary battery and preparation method and application thereof
Technical Field
The invention belongs to the technical field of chemical power sources, and particularly relates to a lithium-sulfur secondary battery and a preparation method and application thereof.
Background
As electronic and communication devices are gradually becoming smaller and lighter, the cruising performance requirements of electric vehicles are continuously increasing, and the necessity and demand for high energy density secondary batteries have been highly highlighted in consideration of environmental problems and exhaustion of petroleum resources. As a secondary battery system having an extremely high theoretical energy density, a lithium sulfur secondary battery using elemental sulfur as a positive electrode active material has received great attention.
The theoretical energy density of the lithium-sulfur battery is as high as 2600Wh/kg, and the sulfur resource is rich, low in price and environment-friendly, so that the lithium-sulfur battery is considered to be one of the most potential secondary battery systems. However, lithium sulfur batteries also have inherent problems of non-conductivity of elemental sulfur and end-discharge products, a "shuttle effect" of lithium polysulfide (LiPS), and a volume effect of a sulfur positive electrode, and practical application thereof faces great challenges. In recent years, many efforts have been made to solve these problems, and sulfur is mainly loaded into carriers such as carbon materials such as mesoporous/microporous carbon, carbon nanotubes, graphene, and the like, metal oxides/sulfides, MOFs, and MXene, so as to improve the conductivity of the sulfur positive electrode and/or suppress the "shuttle effect". Although the methods improve the performance of the lithium-sulfur battery to a certain extent, the materials adopted by the methods have the problems of high cost, difficulty in realizing large-scale industrial production and the like. In practical applications, the battery capacity is significantly reduced as the cycle progresses, and the battery life is rapidly reduced, so that stable service performance cannot be ensured. Therefore, new technologies and materials for improving the performance and life of lithium sulfur batteries to a practically applicable level are urgently proposed.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art.
Accordingly, an aspect of the present invention is to provide a lithium sulfur secondary battery that can overcome the problems of poor conductivity and narrow ion transport channel of a sulfur positive electrode material of a lithium sulfur battery.
Specifically, the positive electrode of the lithium-sulfur secondary battery comprises a bentonite/sulfur composite material, a conductive agent and a binder; the bentonite/sulfur composite material comprises bentonite, conductive carbon intercalation derived from an inorganic intercalation agent and an organic intercalation agent between layers of the bentonite, conductive carbon at least partially covering the surface of the modified bentonite, and loaded sulfur; the organic intercalation agent is selected from chitosan, acrylamide, organic quaternary ammonium salt cations or a combination thereof; the conductive carbon between the bentonite layers is obtained by carbonizing the organic intercalation agent; the conductive carbon covered on the surface of the modified bentonite is obtained by carbonizing nitrogen-containing carbon precursors such as polydopamine, chitosan and the like; the weight percentage of the sulfur in the composite material is more than or equal to 55 percent.
In a preferred embodiment, the sulfur is present in the composite in an amount of greater than or equal to 80 weight percent.
The bentonite/sulfur composite lithium-sulfur battery cathode material preferably has a high-efficiency ion channel and a conductive network structure.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein the inorganic intercalant in the bentonite/sulfur composite is selected from the group consisting of polymeric aluminum hydroxide ions, polymeric iron hydroxide ions, polymeric chromium hydroxide ions, polymeric cobalt hydroxide ions, polymeric nickel hydroxide ions, polymeric zirconium hydroxide ions, or a combination thereof.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein the organic quaternary ammonium salt cation in the bentonite/sulfur composite is selected from the group consisting of a tetramethylquaternary ammonium salt cation, a tetraethylquaternary ammonium salt cation, a tetrapropylquaternary ammonium salt cation, a tetrabutylquaternary ammonium salt cation, a hexadecyltrimethylquaternary ammonium salt cation, and an octadecyl trimethylquaternary ammonium salt cation.
The positive electrode of the lithium-sulfur battery takes sulfur elementary substance as active substance, theoretically, the higher the sulfur elementary substance content in the composite positive electrode is, the higher the capacity of the lithium-sulfur battery is, and the composite positive electrode material with low sulfur content is difficult to meet the requirements of lithium-sulfur battery industrial application. Efforts are currently being made to increase the capacity and energy density of lithium-sulfur batteries by increasing the sulfur content in the positive electrode. However, due to the problems of non-conductivity of elemental sulfur, a polysulfide shuttling effect and a sulfur volume effect existing in the charging and discharging processes of the lithium-sulfur battery, and the like, the performance of the lithium-sulfur battery is adversely affected by excessively high elemental sulfur content, and the performance of the lithium-sulfur battery, such as the capacity, is reduced.
In addition, the natural bentonite clay mineral material has good cation exchange performance, adsorption performance, thermal stability, chemical stability and mechanical stability, is cheap and easy to obtain, and is environment-friendly. Therefore, the bentonite can be used as a carrier material of the sulfur positive electrode of the lithium-sulfur battery, the preparation cost of the battery is reduced, and the large-scale industrial production is easy to realize.
In a preferred embodiment, the positive electrode of the lithium-sulfur secondary battery according to the present invention comprises 60 to 90 parts of the bentonite/sulfur composite, 0 to 20 parts of a conductive agent, and 10 to 20 parts of a binder.
In a preferred embodiment, the positive electrode of the lithium sulfur secondary battery according to the present invention comprises about 80 parts of the bentonite/sulfur composite, about 10 parts of the conductive agent, and about 10 parts of the binder.
In a preferred embodiment, the lithium sulfur secondary battery according to the present invention, wherein the conductive agent is selected from carbon black, acetylene black, ketjen black, or a combination thereof.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein the conductive agent is Super P conductive carbon black.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein the binder is selected from polyvinylidene fluoride (PVDF), LA132, polyvinylpyrrolidone, and sodium alginate.
In a preferred embodiment, the lithium sulfur secondary battery according to the present invention, wherein the bentonite/sulfur composite is prepared by:
modifying bentonite: preparing lithiated bentonite or sodium bentonite from natural bentonite by a cation exchange method;
intercalation modification: inorganic/organic co-intercalation modification is carried out on the lithiated bentonite or the sodium bentonite by using an inorganic intercalation agent and an organic intercalation agent;
coating a nitrogen-containing carbon precursor on the surface of the inorganic/organic co-intercalation bentonite;
high-temperature carbonization: carbonizing a nitrogen-containing carbon precursor coated on the surface of the bentonite and an organic intercalation agent between bentonite layers at the temperature of 500-900 ℃ to obtain a modified bentonite carrier material;
loading a sulfur simple substance on the modified bentonite carrier to obtain the modified bentonite;
wherein the nitrogen-containing carbon precursor comprises polydopamine and chitosan.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein lithium chloride, lithium nitrate, lithium hydroxide or sodium chloride, sodium carbonate may be used in the modification of bentonite to produce lithiated bentonite or sodiated bentonite.
In a preferred embodiment, the lithium sulfur secondary battery according to the present invention, wherein the temperature of the high temperature carbonization is preferably 650-; more preferably 700-; most preferably about 750 deg.c.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein the loading of elemental sulfur is preferably performed under protection of an inert gas; preferably, the inert gas comprises nitrogen and a noble gas; the rare gas comprises helium and argon.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein the sulfur used in the elemental sulfur-supporting material is preferably sublimed sulfur.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein the loading of elemental sulfur is preferably performed under heating; preferably, the heating temperature is 100-; preferably 140 ℃ and 160 ℃.
In a preferred embodiment, the lithium-sulfur secondary battery according to the present invention, wherein the reaction time of the elemental sulfur-supporting is 6 to 15 hours; preferably 8-13 h; most preferably about 10 hours.
According to the lithium-sulfur secondary battery, the bentonite/sulfur composite material is subjected to carbonization treatment after being modified by inorganic/organic intercalation and coated with a carbon precursor, and a three-dimensional continuous conductive carbon network structure is generated in situ between layers and on the surface of the bentonite while an ion channel between bentonite layers is constructed.
Another aspect of the present invention relates to a method for manufacturing the above lithium sulfur secondary battery, comprising the steps of:
(1) mixing the bentonite/sulfur composite material, a conductive agent and a binder into uniform slurry, coating the slurry on an aluminum foil current collector, and drying to obtain a positive plate; the drying is preferably vacuum drying;
(2) and (2) assembling the positive plate obtained in the step (1) with the negative plate, the battery diaphragm and the electrolyte to obtain the lithium-sulfur secondary battery.
In a preferred embodiment, the manufacturing method according to the present invention, wherein the negative electrode sheet is a metallic lithium sheet; the electrolyte solute is lithium bistrifluoromethylsulfonic acid imide and lithium nitrate, and the solvent is a mixed solution of 1,3 dioxolane and glycol dimethyl ether in a volume ratio of 1: 1.
Another aspect of the present invention relates to the use of the above-described lithium sulfur secondary battery in an energy storage power supply system.
The energy storage power supply system comprises an energy storage system for hydraulic power, firepower, wind power, solar energy and other energy sources and a power supply system in the fields of electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like.
The invention has the beneficial effects that:
the lithium-sulfur secondary battery adopts the composite positive electrode material with efficient ion channels and a conductive network structure, so that the sulfur carrying capacity of the positive electrode of the lithium-sulfur secondary battery is obviously improved, the transmission of ions/electrons in the positive electrode of the battery is promoted, and the electrochemical reaction kinetics in the positive electrode are enhanced, so that the discharge specific capacity, the cycling stability and the rate capability of the lithium-sulfur secondary battery are effectively improved (known from experimental results in examples and comparative examples).
Drawings
Fig. 1 is a graph showing a cycle charge and discharge test curve of a lithium sulfur secondary battery based on a bentonite/sulfur composite positive electrode material having a sulfur content of 80% and an activated carbon/sulfur composite positive electrode material;
fig. 2 is a graph showing rate performance of a lithium-sulfur secondary battery based on a bentonite/sulfur composite cathode material having a sulfur content of 80% and an activated carbon/sulfur composite cathode material.
Detailed Description
In order to make the objects, technical solutions and technical effects of the present invention more clear, the present invention will be described in further detail with reference to specific embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The experimental materials used, unless otherwise specified, are routinely commercially available.
Preparation of bentonite/sulfur composite anode material
5g of bentonite is added into 50mL of LiCl aqueous solution with the concentration of 1M, stirred for 2h at the temperature of 60 ℃, filtered, and the filter cake is repeatedly washed by deionized water until no chloride ions exist in the washing liquid.
Adding the washed filter cake into 500mL of deionized water, and stirring for 1h to obtain a suspension with the mass fraction of 1 wt%; the suspension is heated to 60 ℃ in the presence of 10mmol of Al3+Slowly adding a polymeric hydroxyl aluminum ion intercalating agent into the suspension while stirring, continuously adding a cetyl trimethyl ammonium bromide aqueous solution with the concentration of 1 wt% into the suspension according to the proportion of 1mmol of the cetyl trimethyl ammonium bromide to the bentonite while stirring, continuously stirring for 6 hours at 60 ℃ after the cetyl trimethyl ammonium bromide aqueous solution is added, standing and aging for 24 hours at room temperature, filtering, repeatedly washing the filter cake with deionized water until no chloride ions exist in the washing liquid, and drying at 105 ℃ to obtain the polymeric hydroxyl aluminum ion/cetyl trimethyl ammonium bromide intercalation modified bentonite.
The bentonite modified by the polyaluminum hydroxide ion/hexadecyl trimethyl ammonium bromide intercalation is added into 1.5L 10mM Tris-HCl buffer solution (pH 8.5) dissolved with 2g dopamine hydrochloride, the mixture is slowly stirred for 24 hours at room temperature, filtered, the filter cake is repeatedly washed by deionized water until the washing liquid is colorless and transparent, and the filter cake is dried in vacuum at 80 ℃.
And then heating to 750 ℃ at the heating rate of 5 ℃/min in nitrogen atmosphere, keeping for 2h, and naturally cooling to obtain the modified bentonite carrier material.
Uniformly mixing the modified bentonite carrier material and sublimed sulfur according to the mass ratio of 1.5:8.5, 2:8, 3:7, 4:6 and 4.5:5.5 respectively, heating to 155 ℃ in an argon atmosphere, and preserving the temperature for 12 hours to respectively obtain the bentonite/sulfur composite lithium-sulfur battery anode material with high-efficiency ion channels and conductive network structures, wherein the sulfur content of the bentonite/sulfur composite lithium-sulfur battery anode material is 85%, 80%, 70%, 60% and 55%.
Example 1
Taking the bentonite/sulfur composite cathode material with the sulfur content of 80%, preparing electrode slurry (80 parts of bentonite/sulfur composite material, 10 parts of conductive agent and 10 parts of binder) with the conductive agent (Super P conductive carbon black) and the binder (polyvinylidene fluoride (PVDF)) according to the mass ratio of 8:1:1, and then coating the electrode slurry on an aluminum foil current collector to prepare the bentonite/sulfur composite cathode material with the sulfur content of 2mg S/cm2The positive electrode sheet of (1).
The battery assembly and test conditions were: the positive plate is used as the positive electrode of the lithium-sulfur secondary battery, the lithium metal plate is used as the negative electrode, and the electrolyte is 1M LiTFSI/DOL DME (1:1) +2 percent LiNO3The electrolyte dosage is 15 muL/mg S, and the CR2025 button cell is assembled in a glove box filled with argon.
Performing constant-current charge and discharge test at room temperature (25 ℃) and at a current density of 0.1 ℃, wherein the charge and discharge are cut off until the voltage is 1.7-2.8V, the cyclic charge and discharge test curve is shown in figure 1, the first discharge specific capacity reaches 1285mAh/g, and the discharge specific capacity can reach 1002mAh/g after 20 cycles; the multiplying power performance test is carried out under the current densities of 0.1, 0.2, 0.5, 1 and 2C, the charging and discharging cut-off voltage is 1.7-2.8V, the multiplying power performance curve is shown in figure 2, when the current density is increased to 2C, the average specific discharge capacity can still reach 730mAh/g, and when the current density is recovered to 0.1C, the average specific discharge capacity can reach 1080 mAh/g. Therefore, the lithium-sulfur secondary battery has good cycle stability and rate capability.
Example 2
Compared with the embodiment 1, the difference lies in that the sulfur content of the bentonite/sulfur composite cathode material is 85%, the conductive agent is ketjen black, and the mixing mass ratio of the bentonite/sulfur composite cathode material, the conductive agent and the binder is different, specifically:
taking the bentonite/sulfur composite cathode material with the sulfur content of 85%, preparing electrode slurry (70 parts of bentonite/sulfur composite material, 20 parts of conductive agent and 10 parts of binder) with the conductive agent (Keqin black) and the binder (polyvinylidene fluoride (PVDF)) according to the mass ratio of 7:2:1, and then coating the electrode slurry on an aluminum foil current collector to prepare the bentonite/sulfur composite cathode material with the sulfur content of 2mg S/cm2The positive electrode sheet of (1).
The battery assembly and test conditions were: the positive plate is used as the positive electrode of the lithium-sulfur secondary battery, the lithium metal plate is used as the negative electrode, and the electrolyte is 1M LiTFSI/DOL DME (1:1) +2 percent LiNO3The electrolyte dosage is 15 muL/mg S, and the CR2025 button cell is assembled in a glove box filled with argon.
Performing constant-current charge and discharge test at room temperature (25 ℃) at a current density of 0.1 ℃, wherein the charge and discharge cut-off voltage is 1.7-2.8V, the first discharge specific capacity reaches 1306mAh/g, and the discharge specific capacity can reach 1104mAh/g after circulation for 20 times; the multiplying power performance test is carried out under the current densities of 0.1, 0.2, 0.5, 1 and 2C, the charging and discharging cut-off voltage is 1.7-2.8V, when the current density is increased to 2C, the average specific discharge capacity can still reach 795mAh/g, and when the current density is recovered to 0.1C, the average specific discharge capacity can reach 1188 mAh/g. Therefore, the lithium-sulfur secondary battery has good cycle stability and rate capability.
Example 3
Compared with the embodiment 1, the difference lies in that the sulfur content of the bentonite/sulfur composite cathode material is 70%, no conductive agent is added, the mixing mass ratio of the bentonite/sulfur composite cathode material and the binder is different, specifically:
taking the bentonite/sulfur composite cathode material with the sulfur content of 70 percent, preparing electrode slurry (80 parts of bentonite/sulfur composite material, 0 part of conductive agent and 20 parts of binder) with the binder (polyvinylidene fluoride (PVDF)) according to the mass ratio of 8:2 without adding the conductive agent, then coating the electrode slurry on an aluminum foil current collector to prepare the bentonite/sulfur composite cathode material with the sulfur content of 2mg S/cm2The positive electrode sheet of (1).
The battery assembly and test conditions were: the positive plate is used for twice of lithium and sulfurThe positive electrode of the battery, the lithium metal sheet as the negative electrode, and the electrolyte of the battery are 1M LiTFSI/DOL DME (1:1) + 2% LiNO3The electrolyte dosage is 15 muL/mg S, and the CR2025 button cell is assembled in a glove box filled with argon.
Performing constant-current charge and discharge test at room temperature (25 ℃) and at a current density of 0.1 ℃, wherein the charge and discharge cut-off voltage is 1.7-2.8V, the first discharge specific capacity reaches 1200mAh/g, and the discharge specific capacity can reach 952mAh/g after circulation for 20 times; the multiplying power performance test is carried out under the current densities of 0.1, 0.2, 0.5, 1 and 2C, the charging and discharging cut-off voltage is 1.7-2.8V, when the current density is increased to 2C, the average specific discharge capacity can still reach 683mAh/g, and when the current density is recovered to 0.1C, the average specific discharge capacity can reach 1025 mAh/g. Therefore, the lithium-sulfur secondary battery has good cycle stability and rate capability.
Example 4
Compared with the embodiment 1, the difference lies in that the sulfur content of the bentonite/sulfur composite cathode material is 70%, the conductive agent is acetylene black, and the specific steps are as follows:
taking the bentonite/sulfur composite cathode material with the sulfur content of 70%, preparing electrode slurry (80 parts of bentonite/sulfur composite material, 10 parts of conductive agent and 10 parts of binder) with the conductive agent (acetylene black) and the binder (polyvinylidene fluoride (PVDF)) according to the mass ratio of 8:1:1, and then coating the electrode slurry on an aluminum foil current collector to prepare the bentonite/sulfur composite cathode material with the sulfur content of 2mg S/cm2The positive electrode sheet of (1).
The battery assembly and test conditions were: the positive plate is used as the positive electrode of the lithium-sulfur secondary battery, the lithium metal plate is used as the negative electrode, and the electrolyte is 1M LiTFSI/DOL DME (1:1) +2 percent LiNO3The electrolyte dosage is 15 muL/mg S, and the CR2025 button cell is assembled in a glove box filled with argon.
Performing constant-current charge and discharge test at room temperature (25 ℃) at a current density of 0.1 ℃, wherein the charge and discharge are cut off until the voltage is 1.7-2.8V, the first discharge specific capacity reaches 1328mAh/g, and the discharge specific capacity can reach 1086mAh/g after 20 times of circulation; the multiplying power performance test is carried out under the current densities of 0.1, 0.2, 0.5, 1 and 2C, the charging and discharging cut-off voltage is 1.7-2.8V, when the current density is increased to 2C, the average specific discharge capacity can still reach 762mAh/g, and when the current density is recovered to 0.1C, the average specific discharge capacity can reach 1179 mAh/g. Therefore, the lithium-sulfur secondary battery has good cycle stability and rate capability.
Example 5
Compared with the embodiment 1, the difference lies in that the sulfur content of the bentonite/sulfur composite cathode material is 60%, the conductive agent is ketjen black, and the mixing mass ratio of the bentonite/sulfur composite cathode material, the conductive agent and the binder is different, specifically:
preparing the bentonite/sulfur composite cathode material with the sulfur content of 60%, preparing electrode slurry (60 parts of bentonite/sulfur composite material, 20 parts of conductive agent and 20 parts of binder) with the conductive agent (Keqin black) and the binder (polyvinylidene fluoride (PVDF)) according to the mass ratio of 6:2:2, and then coating the electrode slurry on an aluminum foil current collector to prepare the bentonite/sulfur composite cathode material with the sulfur content of 2mg S/cm2The positive electrode sheet of (1).
The battery assembly and test conditions were: the positive plate is used as the positive electrode of the lithium-sulfur secondary battery, the lithium metal plate is used as the negative electrode, and the electrolyte is 1M LiTFSI/DOL DME (1:1) +2 percent LiNO3The electrolyte dosage is 15 muL/mg S, and the CR2025 button cell is assembled in a glove box filled with argon.
Performing constant-current charge and discharge test at room temperature (25 ℃) at a current density of 0.1 ℃, wherein the charge and discharge are cut off until the voltage is 1.7-2.8V, the first discharge specific capacity reaches 1397mAh/g, and the discharge specific capacity can reach 1280mAh/g after 20 times of circulation; the multiplying power performance test is carried out under the current densities of 0.1, 0.2, 0.5, 1 and 2C, the charging and discharging cut-off voltage is 1.7-2.8V, when the current density is increased to 2C, the average specific discharge capacity can still reach 635mAh/g, and when the current density is recovered to 0.1C, the average specific discharge capacity can reach 1038 mAh/g. Therefore, the lithium-sulfur secondary battery has good cycle stability and rate capability.
Example 6
Compared with the embodiment 1, the difference lies in that the sulfur content of the bentonite/sulfur composite cathode material is 55%, no conductive agent is added, the mixing mass ratio of the bentonite/sulfur composite cathode material, the conductive agent and the binder is different, specifically:
taking the bentonite/sulfur composite cathode material with the sulfur content of 55% obtained by the preparation method, and adding no bentonite/sulfur composite cathode materialPreparing electrode slurry (90 parts of bentonite/sulfur composite material, 0 part of conductive agent and 10 parts of binder) by a conductive agent and a binder (polyvinylidene fluoride (PVDF)) according to a mass ratio of 9:1, and then coating the electrode slurry on an aluminum foil current collector to prepare a sulfur-carrying amount of 2mg S/cm2The positive electrode sheet of (1).
The battery assembly and test conditions were: the positive plate is used as the positive electrode of the lithium-sulfur secondary battery, the lithium metal plate is used as the negative electrode, and the electrolyte is 1M LiTFSI/DOL DME (1:1) +2 percent LiNO3The electrolyte dosage is 15 muL/mg S, and the CR2025 button cell is assembled in a glove box filled with argon.
Performing constant-current charge and discharge test at room temperature (25 ℃) at a current density of 0.1 ℃, wherein the charge and discharge are cut off until the voltage is 1.7-2.8V, the first discharge specific capacity reaches 1293mAh/g, and after 20 times of circulation, the discharge specific capacity can reach 1145 mAh/g; the multiplying power performance test is carried out under the current densities of 0.1, 0.2, 0.5, 1 and 2C, the charging and discharging cut-off voltage is 1.7-2.8V, when the current density is increased to 2C, the average specific discharge capacity can still reach 628mAh/g, and when the current density is recovered to 0.1C, the average specific discharge capacity can reach 990 mAh/g. Therefore, the lithium-sulfur secondary battery has good cycle stability and rate capability.
Comparative example 1
Compared with the embodiment 1, the difference is that the adopted cathode material is an activated carbon/sulfur composite material with the sulfur content of 80 percent, and specifically comprises the following components:
preparing an electrode slurry (80 parts of activated carbon/sulfur composite material, 10 parts of conductive agent and 10 parts of binder) from an activated carbon/sulfur composite positive electrode material with the sulfur content of 80%, a conductive agent (Super P conductive carbon black) and the binder (polyvinylidene fluoride (PVDF)) according to the mass ratio of 8:1:1, and then coating the electrode slurry on an aluminum foil current collector to prepare a composite positive electrode material with the sulfur loading of 2mg S/cm2The positive electrode sheet of (1).
The battery assembly and test conditions were: the positive plate is used as the positive electrode of the lithium-sulfur secondary battery, the lithium metal plate is used as the negative electrode, and the electrolyte is 1M LiTFSI/DOL DME (1:1) +2 percent LiNO3The electrolyte dosage is 15 muL/mg S, and the CR2025 button cell is assembled in a glove box filled with argon.
Performing constant-current charge and discharge test at room temperature (25 ℃) and at a current density of 0.1 ℃, wherein the charge and discharge are cut off until the voltage is 1.7-2.8V, the cyclic charge and discharge test curve is shown in figure 1, the first discharge specific capacity reaches 965mAh/g, and after 20 cycles, the discharge specific capacity is reduced to 511 mAh/g; the multiplying power performance test is carried out under the current densities of 0.1, 0.2, 0.5, 1 and 2C, the charging and discharging cut-off voltage is 1.7-2.8V, the multiplying power performance curve is shown in figure 2, when the current density is increased to 2C, the average specific discharge capacity is only 303mAh/g, and when the current density is recovered to 0.1C, the average specific discharge capacity reaches 626 mAh/g.
Comparing the specific discharge capacities of comparative example 1 and example 1, it can be found that the lithium sulfur secondary battery of example 1 has a higher specific discharge capacity and better cycle stability and rate performance.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (10)

1. A lithium-sulfur secondary battery is characterized in that the positive electrode of the lithium-sulfur secondary battery consists of a bentonite/sulfur composite material, a conductive agent and a binder; the bentonite/sulfur composite material comprises bentonite, conductive carbon intercalation derived from an inorganic intercalation agent and an organic intercalation agent between layers of the bentonite, conductive carbon at least partially covering the surface of the modified bentonite, and loaded sulfur;
the organic intercalation agent is selected from chitosan, acrylamide, organic quaternary ammonium salt cations or a combination thereof;
the conductive carbon between the bentonite layers is obtained by carbonizing the organic intercalation agent;
the conductive carbon covered on the surface of the modified bentonite is obtained by carbonizing a nitrogen-containing carbon precursor; the nitrogen-containing carbon precursor is preferably polydopamine or chitosan;
the weight percentage of the sulfur in the composite material is more than or equal to 55 percent.
2. The lithium sulfur secondary battery of claim 1 wherein the inorganic intercalant in the bentonite/sulfur composite is selected from the group consisting of polymeric aluminum hydroxy ions, polymeric iron hydroxy ions, polymeric chromium hydroxy ions, polymeric cobalt hydroxy ions, polymeric nickel hydroxy ions, polymeric zirconium hydroxy ions, or combinations thereof.
3. The lithium sulfur secondary battery according to claim 1, wherein the organic quaternary ammonium salt cation in the bentonite/sulfur composite is selected from the group consisting of a tetramethylquaternary ammonium salt cation, a tetraethylquaternary ammonium salt cation, a tetrapropylquaternary ammonium salt cation, a tetrabutylquaternary ammonium salt cation, a hexadecyltrimethylquaternary ammonium salt cation, and an octadecyltrimethylammonium quaternary ammonium salt cation.
4. The lithium sulfur secondary battery according to claim 1, wherein the positive electrode of the lithium sulfur secondary battery comprises 60 to 90 parts of the bentonite/sulfur composite, 0 to 20 parts of a conductive agent, and 10 to 20 parts of a binder.
5. The lithium sulfur secondary battery according to claim 4, wherein the conductive agent is selected from carbon black, acetylene black, Ketjen black, or a combination thereof.
6. The lithium sulfur secondary battery according to claim 4, wherein the binder is selected from polyvinylidene fluoride, LA132, polyvinylpyrrolidone, sodium alginate.
7. The lithium sulfur secondary battery according to claim 1, wherein the bentonite/sulfur composite is prepared by a method comprising:
modifying bentonite: preparing lithiated bentonite or sodium bentonite from natural bentonite by a cation exchange method;
intercalation modification: inorganic/organic co-intercalation modification is carried out on the lithiated bentonite or the sodium bentonite by using an inorganic intercalation agent and an organic intercalation agent;
coating a nitrogen-containing carbon precursor on the surface of the inorganic/organic co-intercalation bentonite;
high-temperature carbonization: carbonizing a nitrogen-containing carbon precursor coated on the surface of the bentonite and an organic intercalation agent between bentonite layers at the temperature of 500-900 ℃ to obtain a modified bentonite carrier material;
loading a sulfur simple substance on the modified bentonite carrier to obtain the modified bentonite;
wherein the nitrogen-containing carbon precursor comprises polydopamine and chitosan.
8. The method of manufacturing a lithium sulfur secondary battery according to any one of claims 1 to 7, comprising the steps of:
(1) mixing the bentonite/sulfur composite material, a conductive agent and a binder into uniform slurry, coating the slurry on an aluminum foil current collector, and drying to obtain a positive plate; the drying is preferably vacuum drying;
(2) and (2) assembling the positive plate obtained in the step (1) with the negative plate, the battery diaphragm and the electrolyte to obtain the lithium-sulfur secondary battery.
9. The production method according to claim 8, wherein the negative electrode sheet is a metallic lithium sheet; the electrolyte solute is lithium bistrifluoromethylsulfonic acid imide and lithium nitrate, and the solvent is a mixed solution of 1,3 dioxolane and glycol dimethyl ether in a volume ratio of 1: 1.
10. Use of the lithium sulfur secondary battery according to any one of claims 1 to 7 in an energy storage power system.
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