阅读说明：本技术 一种锂-硫半液流电池 (lithium-sulfur semi-flow battery ) 是由 张义永 张英杰 李雪 董鹏 孟奇 于 2019-09-18 设计创作，主要内容包括：本发明公开一种锂-硫半液流电池,包括液流硫正极区、锂金属负极区、隔膜；液流硫正极区包括工作电极、多硫化锂阴极电解液；工作电极包括活性材料、导电剂、粘结剂和集流体；活性材料为Ni/C复合材料、Pt/C复合材料或Pt<Sub>3</Sub>Ni/C复合材料；多硫化锂阴极电解液由多硫化锂溶于锂硫电解液中组成；锂金属负极区包括锂金属负极、锂硫电解液,锂金属负极为锂金属或锂金属合金；隔膜为单离子膜；本发明的锂-硫半液流电池,由于同时具有高能量密度、高功率密度和长寿命,不仅可作为电动汽车或混合电动车等各种机器的电源,还可以作为电网大规模储能装置而广泛利用。(the invention discloses a lithium-sulfur semi-flow battery, which comprises a sulfur flow positive electrode area, a lithium metal negative electrode area and a diaphragm; the liquid sulfur positive region comprises a working electrode and lithium polysulfide catholyte; the working electrode comprises an active material, a conductive agent, a binder and a current collector; the active material is Ni/C composite material, Pt/C composite material or Pt 3 a Ni/C composite material; the lithium polysulfide cathode electrolyte consists of lithium polysulfide dissolved in lithium sulfur electrolyte; the lithium metal negative electrode region comprises a lithium metal negative electrode and a lithium sulfur electrolyte, and the lithium metal negative electrode is lithium metal or lithium metal alloy; the diaphragm is a single ion film; the lithium-sulfur semi-flow battery has high energy density, high power density and long service life, and can be widely used as a power supply of various machines such as an electric vehicle or a hybrid electric vehicle and also as a large-scale energy storage device of a power grid.)

1. The lithium-sulfur semi-flow battery is characterized by comprising a liquid sulfur positive electrode area, a lithium metal negative electrode area and a diaphragm.

2. The lithium-sulfur semi-flow battery of claim 1, wherein the positive flow sulfur region comprises a working electrode, a lithium polysulfide catholyte.

3. The lithium-sulfur semi-flow battery of claim 2, wherein the working electrode comprises an active material, a conductive agent, a binder, a current collector; the mass ratio of the active material, the conductive agent and the binder is 8:1: 1.

4. The lithium-sulfur semi-flow battery of claim 3, wherein the active material is a Ni/C composite, a Pt/C composite, or Pt₃a Ni/C composite material; the conductive agent and the binder are common products of commercial batteries; the current collector is aluminum foil, stainless steel mesh or carbon paper.

5. The lithium-sulfur semi-flow battery according to claim 2, wherein the lithium polysulfide catholyte is obtained by dissolving lithium polysulfide in lithium sulfur electrolyte, and the concentration of the lithium polysulfide is 0.1 mol/L-2 mol/L; the solvent of the lithium-sulfur electrolyte is R (CH)₂CH₂O) n-R 'wherein n =1-6, R and R' are methyl or ethyl, the solute is lithium difluorooxalato borate, lithium bistrifluoromethylsulfonylimide, lithium difluorosulfonylimide, lithium difluorophosphate or lithium hexafluorophosphate, and the concentration of the lithium sulfur electrolyte is 1 mol/L.

6. the lithium-sulfur semi-flow battery according to claim 1, wherein the lithium metal negative electrode region comprises a lithium metal negative electrode, a lithium sulfur electrolyte, the lithium metal negative electrode is lithium metal or a lithium metal alloy, and the lithium metal alloy is a lithium tin alloy, a lithium silicon alloy or a lithium copper alloy; the solvent of the lithium-sulfur electrolyte is R (CH)₂CH₂O) n-R 'wherein n =1-6, R and R' are methyl or ethyl, the solute is lithium difluorooxalato borate, lithium bistrifluoromethylsulfonylimide, lithium difluorosulfonylimide, lithium difluorophosphate or lithium hexafluorophosphate, and the concentration of the lithium sulfur electrolyte is 1 mol/L.

7. The lithium-sulfur semi-flow battery according to claim 1, wherein the separator is PP, PE or PP/PE/PP.

8. the lithium-sulfur semi-flow battery according to claim 4, wherein the preparation method of the Ni/C composite material comprises the following specific steps:

(1) carrying out ultrasonic treatment on a C conductive carrier and deionized water for 1 ~ 5 hours to obtain a carbon ~ based carrier dispersion liquid with the concentration of 1 ~ 10mg/mL, wherein the C conductive carrier is one of graphene, Super p, carbon black, acetylene black and CNT;

(2) adding nickel acetate or nickel nitrate into the carbon ~ based carrier dispersion liquid obtained in the step (1) according to the mass ratio of C to Ni of 5 ~ 15:1, and performing ultrasonic treatment for 1 ~ 5 hours to obtain a mixed dispersion liquid;

(3) Freezing the mixed dispersion liquid obtained in the step (2) by using liquid nitrogen, and carrying out freeze drying to obtain mixed powder;

(4) and (3) under the protection of Ar gas, heating the mixed powder in the step (3) to 700 ~ 900 ℃ at a heating rate of 5 ℃/min, calcining for 1 ~ 3 hours, and naturally cooling to obtain the Ni/C composite material.

9. the lithium-sulfur semi-flow battery according to claim 8, wherein the preparation method of the Pt/C composite material is the same as the preparation method of the Ni/C composite material, and the nickel acetate or the nickel nitrate in the step (2) is replaced by platinum acetate or platinum nitrate.

10. the lithium-sulfur semi-flow battery of claim 4, wherein Pt₃the preparation method of the Ni/C composite material comprises the following specific steps:

(1) adding a C conductive carrier into DMF (dimethyl formamide), and carrying out ultrasonic treatment for 1 ~ 5 hours to obtain a carbon ~ based carrier dispersion liquid with the concentration of 1 ~ 10mg/mL, wherein the C conductive carrier is one of graphene, Super p, carbon black, acetylene black and CNT;

(2) adding platinum diacetylacetonate and nickel diacetylacetonate into the carbon ~ based carrier dispersion liquid obtained in the step (1) according to the mass ratio of the platinum diacetylacetonate to the nickel diacetylacetonate to C of 8:8:20 ~ 24:8:60, adding benzoic acid, adding the benzoic acid according to the mass ratio of the platinum diacetylacetonate to the benzoic acid of 8:50 ~ 70, and performing ultrasonic treatment for 1 ~ 5 hours to obtain a mixed dispersion liquid;

(3) heating the mixed dispersion liquid in the step (2) in a constant ~ temperature water bath at the temperature of 150 ~ 170 ℃, and reacting for 20 ~ 24 hours;

(4) centrifugally separating the product obtained in the step (3), and drying to obtain Pt₃a Ni/C composite material.

Technical Field

The invention relates to the field of electrochemical energy, in particular to a lithium-sulfur semi-flow battery with high energy density, high power density and long cycle life.

Background

In recent decades, the use of solar energy, tidal energy, and wind energy has increased, and electric vehicles with low carbon dioxide emissions have been spreading. Therefore, in order to effectively utilize renewable energy, the development of high-performance, safe, inexpensive, and environmentally friendly energy conversion and storage systems is imperative. Preferred among these energy storage systems are lithium ion batteries and supercapacitors. Lithium ion batteries are common electrochemical devices for storing electrical energy. However, despite their commercial success, lithium ion batteries have failed to meet the high power demands required for applications such as power tools, electric vehicles, and efficient storage of renewable energy. In contrast, supercapacitors, in addition to providing higher energy densities than conventional dielectric capacitors, also show promise for high power systems because they can instantaneously provide higher power densities than batteries. However, the energy density of supercapacitors is still insufficient for new applications requiring high energy and high power density.

to overcome these disadvantages, research on lithium ion batteries has focused on electrode material improvements, for example, the use of silicon negative electrodes and lithium rich positive electrodes. However, these materials themselves suffer from several drawbacks, including low first-pass coulombic efficiency, unsatisfactory rate performance, poor cycle life, poor thermal characteristics, and significant voltage decay. In fact, alternative battery systems, such as lithium air batteries, lithium sulfur batteries, and sodium/magnesium ion batteries, have proven to be superior to lithium ion batteries in terms of energy/power density, safety, and cost. However, these systems also have their own drawbacks. For example, in the process of charging and discharging the lithium-sulfur battery, the utilization rate of active substances of the battery is reduced and the cycle life of the battery is shortened due to the dissolution and shuttling of intermediates of the lithium-sulfur battery; meanwhile, the rate performance of the battery is poor due to poor conductivity of active substances, namely sulfur and lithium sulfide, and in order to improve the conductivity, a large amount of conductive additives are required to be added, so that the content of the active substances is reduced, the volume energy density of the battery is low, and the high energy density of the lithium-sulfur battery is difficult to exert. Therefore, in order to solve these problems, a new class of lithium-sulfur flow battery systems has recently been proposed. The system includes the use of a working electrode having electrocatalytic activity, a lithium polysulfide catholyte, a separator, and a negative region including a lithium metal negative electrode and a conventional lithium sulfur electrolyte. Although the lithium-sulfur semi-flow battery has high energy density and power density, the problems of catalytic activity and stability of the working electrode and selectivity of the separator must be solved to realize commercial application thereof.

disclosure of Invention

the invention provides a lithium-sulfur semi-flow battery with high energy density, high power density and long service life, which comprises a sulfur flow positive electrode area, a lithium metal negative electrode area and a diaphragm.

The liquid sulfur positive region includes a working electrode, a lithium polysulfide catholyte.

the working electrode comprises an active material capable of catalyzing the conversion of lithium polysulfide, a conductive agent, a binder and a current collector; the mass ratio of the active material capable of catalyzing the conversion of lithium polysulfide to the conductive agent to the binder is 8:1: 1; the conductive agent and the binder are common products of commercial batteries, preferably Super p is used as the conductive agent, and preferably polyvinylidene fluoride (PVDF) is used as the binder; the current collector is one of common current collectors such as aluminum foil, stainless steel mesh and carbon paper or is self-supporting, and the stainless steel mesh is preferred.

The active material capable of catalyzing the conversion of lithium polysulfide is Ni/C composite material, Pt/C composite material and Pt₃Ni, Pt-loaded Ni/C composite material or the like₃A conductive carrier of Ni.

The lithium polysulfide cathode electrolyte is formed by dissolving lithium polysulfide in lithium sulfur electrolyte, and the concentration of the lithium polysulfide is 0.1-2 mol/L, preferably 1 mol/L; the solvent of the lithium-sulfur electrolyte is R (CH)₂CH₂o) n-R 'wherein n =1-6, R and R' are methyl or ethyl, the solute is lithium difluorooxalato borate, lithium bistrifluoromethylsulfonylimide, lithium difluorosulfonylimide, lithium difluorophosphate or lithium hexafluorophosphate, and the concentration of the lithium sulfur electrolyte is 1 mol/L.

The lithium metal negative electrode region comprises a lithium metal negative electrode and lithium sulfur electrolyte, the lithium metal negative electrode is lithium metal or lithium metal alloy, and the lithium metal alloy is lithium tin alloy, lithium silicon alloy or lithium copper alloy; the solvent of the lithium-sulfur electrolyte is R (CH)₂CH₂O) n-R 'wherein n =1-6, R and R' are methyl or ethyl, the solute is lithium difluorooxalato borate, lithium bistrifluoromethylsulfonylimide, lithium difluorosulfonylimide, lithium difluorophosphate or lithium hexafluorophosphate, and the concentration of the lithium sulfur electrolyte is1mol/L。

the diaphragm comprises one of a single ion film such as PP or PE and three-layer films such as PP/PE/PP.

the preparation method of the Ni/C composite material comprises the following specific steps:

(1) carrying out ultrasonic treatment on a C conductive carrier and deionized water for 1 ~ 5 hours to obtain a carbon ~ based carrier dispersion liquid with the concentration of 1 ~ 10mg/mL, wherein the C conductive carrier is one of graphene, Super p, carbon black, acetylene black, CNT and the like;

(2) adding nickel acetate or nickel nitrate into the carbon ~ based carrier dispersion liquid obtained in the step (1) according to the mass ratio of C to Ni of 5 ~ 15:1, and performing ultrasonic treatment for 1 ~ 5 hours to obtain a mixed dispersion liquid;

(3) Rapidly freezing the mixed dispersion liquid in the step (2) by using liquid nitrogen, and freeze-drying by using a freeze dryer to obtain mixed powder;

(4) and (3) under the protection of Ar gas, placing the mixed powder in the step (3) in a tube furnace, heating to 700 ~ 900 ℃ at a heating rate of 5 ℃/min, calcining for 1 ~ 3 hours, and naturally cooling to obtain the Ni/C composite material.

The preparation method of the Pt/C composite material is the same as that of the Ni/C composite material, and nickel acetate or nickel nitrate in the step (2) is replaced by platinum acetate or platinum nitrate.

The Pt₃the preparation method of the Ni/C composite material comprises the following specific steps:

(1) adding a C conductive carrier into a round ~ bottom flask containing DMF, and carrying out ultrasonic treatment for 1 ~ 5 hours to obtain a carbon ~ based carrier dispersion liquid with the concentration of 1 ~ 10mg/mL, wherein the C conductive carrier is one of graphene, Super p, carbon black, acetylene black, CNT and the like;

(2) Mixing platinum diacetone (Pt (acac)₂) Nickel diacetone (Ni (acac)₂) Push button Pt (acac)₂:Ni(acac)₂adding C into the carbon ~ based carrier dispersion liquid obtained in the step (1) at a mass ratio of 8:8:20 ~ 24:8:60, adding benzoic acid, adding the benzoic acid according to a mass ratio of diacetone platinum to benzoic acid of 8:50 ~ 70, and performing ultrasonic treatment for 1 ~ 5 hours to obtain a mixed dispersion liquid;

(3) heating the mixed dispersion liquid in the step (2) in a constant ~ temperature water bath at the temperature of 150 ~ 170 ℃, and reacting for 20 ~ 24 hours;

(4) Centrifugally separating the product obtained in the step (3) to obtain Pt₃A Ni/C composite material.

the preparation method of the working electrode comprises the following specific steps:

(1) mixing 80 parts by weight of an active material capable of catalyzing the conversion of lithium polysulfide and 10 parts by weight of a conductive agent and grinding to obtain mixed powder;

(2) and (2) stirring and mixing the mixed powder obtained in the step (1) and 10 parts by weight of binder solution, coating the mixed slurry on a current collector until the thickness of the current collector is preferably 10 ~ 500 microns, and performing vacuum drying at 60 ℃ for 10 ~ 24 hours to remove the solvent to obtain the working electrode.

the lithium-sulfur semi-flow battery is assembled by taking a working electrode and a lithium polysulfide catholyte as a liquid sulfur positive electrode region, taking a lithium metal negative electrode and a lithium sulfur electrolyte as a lithium metal negative electrode region and a diaphragm together according to the assembly mode of a commercial liquid flow battery, so that the lithium-sulfur semi-flow battery is obtained; electrochemical redox of lithium polysulfide occurs in the liquid flow sulfur positive electrode area, lithium stripping/deposition occurs in the lithium metal negative electrode area, lithium polysulfide cathode electrolyte in the liquid flow sulfur positive electrode area also plays a role in providing active substance lithium polysulfide, electrolyte between the working electrode and the counter electrode mainly plays a role in transferring charges by conducting lithium ions, meanwhile, solute lithium salt has good solubility and ionic conductivity in the electrolyte, which has important influence on the working temperature, specific energy, cycle efficiency, safety performance and the like of the battery, the middle diaphragm separates the positive electrode active substance and the negative electrode active substance of the battery, only allows lithium ions to pass through, prevents any electron current between the positive electrode and the negative electrode from directly passing through, and avoids short circuit of the battery; the ion flow has as low a resistance as possible when passing through it, and it has a high energy density and power density.

The invention has the beneficial effects that:

1. The lithium-sulfur semiliquid flow battery has the performances of high energy density, high power density and long service life, can be used as a secondary battery for a driving power supply in mobile information instruments such as mobile phones and notebook computers, and can be widely used as a power supply of various machines such as electric vehicles or hybrid electric vehicles.

2. The lithium-sulfur semi-flow battery shows strong energy and power density and excellent cycle performance, the lithium-sulfur semi-flow battery utilizes the working electrode to catalyze the mutual conversion among lithium polysulfides, and meanwhile, the conversion among the lithium polysulfides is liquid-liquid reaction, so that the utilization rate and the reaction rate of active substances are improved, and the sulfur active substances have high theoretical specific capacity (such as sulfur: 1675 mAh/g), therefore, the lithium-sulfur semi-flow battery can overcome the challenges brought by the traditional lithium-sulfur battery, and finally realizes high capacity, good rate characteristic and excellent cycle performance, thereby being used as an advanced energy storage device.

3. The method has low implementation cost and large-scale application potential.

drawings

FIG. 1 is a schematic diagram of the structure of a lithium-sulfur semi-flow battery of example 1;

FIG. 2 shows Pt in example 9₃SEM image of Ni/C composite material;

FIG. 3 shows Pt in example 9₃A charge-discharge curve diagram of a lithium-sulfur semi-flow battery with a Ni/C composite material as a working electrode;

FIG. 4 shows Pt in example 9₃And (3) a cycle performance diagram of the lithium-sulfur semi-flow battery with the Ni/C composite material as the working electrode.

Detailed Description

The invention will be further illustrated by the following examples in conjunction with the drawings, but it will be understood that the examples are for the purpose of illustrating embodiments of the invention and that the scope of protection is not limited by the examples described without departing from the scope of the subject matter of the invention.

Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. In the following description, "%" is not particularly specified on a mass basis.