CN112993244B - Room-temperature full-liquid-state lithium-sulfur battery and preparation method thereof - Google Patents

Abstract

The invention provides a room-temperature full-liquid lithium-sulfur battery and a preparation method thereof, wherein the room-temperature full-liquid lithium-sulfur battery comprises a diaphragm, a room-temperature liquid alloy negative electrode and a liquid polysulfide positive electrode which are respectively arranged on two sides of the diaphragm, and a current collector connected with the liquid polysulfide positive electrode; the room-temperature liquid alloy cathode is formed by reacting lithium and mercury according to a preset proportion, and the diaphragm is a lithium ion battery diaphragm with a boron nitride coating; the liquid polysulfide anode is

(ii) a The current collector includes an aluminum foil coated with a conductive carbon material. According to the invention, the liquid alloy is used for replacing metal lithium, so that the generation of lithium dendrite is inhibited, and the cycle life and the safety performance of the battery are improved; the liquid polysulfide replaces the elemental sulfur anode, so that the conductivity of the anode is greatly improved, and the problem of volume expansion in the charging and discharging process is effectively solved; by carrying out surface modification and structure improvement on the diaphragm, shuttling of polysulfide is effectively inhibited, loss of active substances and self-discharge are reduced, and the coulomb efficiency of the lithium-sulfur battery is improved.

Description

A room temperature all-liquid lithium-sulfur battery and preparation method thereof

technical field

The invention relates to the technical field of lithium batteries, in particular to a room temperature full liquid lithium-sulfur battery and a preparation method thereof.

Background technique

In recent years, liquid batteries have broad prospects in the field of energy storage batteries, which have the following advantages: 1) liquid batteries have no volume change during charging and discharging; 2) liquid metal electrodes have no dendrite growth problems; 3) liquid electrode conductivity good, the electrode structure is simple, etc. The preparation of liquid lithium-sulfur batteries can solve many existing problems of lithium-sulfur batteries, such as the large volume expansion during charging and discharging, resulting in poor mechanical properties of the battery and serious loss of active materials; Shuttling leads to loss of active material and self-discharge; the growth of lithium dendrites at the negative electrode results in lower Coulombic efficiency and shorter cycle life with poor safety. Since alkali metals are solid at normal temperature and pressure, liquid batteries usually need to operate at higher temperatures (>300°C), while lithium-sulfur battery electrolytes cannot work normally at high temperatures; thus there is no room temperature Liquid lithium-sulfur batteries exist.

SUMMARY OF THE INVENTION

In order to solve the technical problem of inconvenient use of the existing solid-state lithium-sulfur battery, the present invention provides a room temperature all-liquid lithium-sulfur battery and a preparation method thereof.

；所述集流体包括涂覆有导电碳材料的铝箔。The invention provides a room temperature full liquid lithium-sulfur battery, comprising a diaphragm, a room temperature liquid alloy negative electrode and a liquid polysulfide positive electrode respectively installed on both sides of the diaphragm, and a current collector connected with the liquid polysulfide positive electrode; The alloy negative electrode is formed by the reaction of lithium and mercury according to a preset ratio, and the separator is a lithium ion battery separator with a negative boron nitride coating; the liquid polysulfide positive electrode is

; The current collector includes an aluminum foil coated with a conductive carbon material.

On the other hand, the present invention also provides a preparation method of a room temperature full liquid lithium-sulfur battery, comprising the following steps:

Step S1: making a room temperature liquid alloy negative electrode;

Step S2: making the diaphragm;

Step S3: making a liquid polysulfide positive electrode;

Step S4: making a current collector;

Step S5: injecting the room temperature liquid alloy negative electrode and the liquid polysulfide positive electrode into the replaceable membrane H-type electrolytic cell, inserting the foil electrode into the room temperature liquid alloy negative electrode, and inserting the current collector into the liquid polysulfide positive electrode on the lead clip, The separator is sandwiched between the positive electrode pool and the negative electrode pool, and the whole H-type electrolytic cell is sealed to form the room temperature full liquid lithium-sulfur battery.

Further, the step S1 specifically includes the following steps:

The room temperature liquid alloy negative electrode uses lithium and mercury after removing the oxide film. According to a preset ratio, the room temperature liquid lithium-based alloy negative electrode can be prepared by controlling the content of lithium in the liquid mercury.

Further, the mass ratio of lithium to mercury is (0.01-0.86): (99.14-99.99).

Further, the step S2 specifically includes the following steps:

In step S21, the boron nitride and guanidine carbonate or guanidine nitrate are ball-milled and dispersed into a solvent to obtain a uniform and stable dispersion;

In step S22, the dispersion liquid is suction-filtered onto the lithium ion battery separator, and after drying, a lithium ion battery separator with a boron nitride coating is obtained to form the separator.

Further, the step S3 specifically includes the following steps:

In step S31, an H-type electrolytic cell is used to assemble an ordinary lithium-sulfur battery, and the positive and negative electrodes are short-circuited and discharged, and the polysulfide will diffuse into the electrolyte, and the electrolyte will turn brown.

In step S32, the electrolyte is collected, elemental sulfur is added thereto, and the supernatant is taken after the reaction is sufficient to obtain a liquid polysulfide positive electrode.

Further, step S4 specifically includes the following steps:

The current collector is formed by coating a conductive carbon material on an aluminum foil.

Further, the conductive carbon material includes one or more of graphite, graphene, carbon nanotube, and carbon nanofiber.

Further, steps S1 to S5 are all performed under normal temperature and normal pressure conditions.

Further, steps S1 to S5 are all completed in a glove box filled with argon gas.

The beneficial effects of the present invention are: the present invention utilizes the advantages of the liquid battery to solve the existing problems of the lithium-sulfur battery, can work at room temperature, does not need high temperature heating, and saves energy. By replacing metal lithium with liquid alloy, the formation of lithium dendrites is inhibited, and the cycle life and safety performance of the battery are improved; by replacing the elemental sulfur cathode with liquid polysulfide, the conductivity of the cathode is greatly improved, and the volume during charge and discharge is effectively reduced. Expansion problem; surface modification and structural improvement of the separator can effectively inhibit the shuttle of polysulfides, reduce the loss of active materials and self-discharge, and improve the Coulombic efficiency of lithium-sulfur batteries.

Description of drawings

Figure 1 shows the cycle voltage curve of a symmetric battery with a room temperature liquid alloy anode, with a current density of 2.84 mA cm-2.

Figure 2 shows the cyclic voltammetry curves of the room temperature all-liquid lithium-sulfur battery.

Figure 3 is the electrochemical test curve of the room temperature all-liquid lithium-sulfur battery.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention and should not be construed as limiting the present invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", " Rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. The relationship is based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore It should not be construed as a limitation of the present invention.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the present invention, unless otherwise expressly specified and limited, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection , or integrally connected; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or the internal communication between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

In the present invention, unless otherwise expressly specified and limited, a first feature "on" or "under" a second feature may include the first and second features in direct contact, or may include the first and second features Not directly but through additional features between them. Also, the first feature being "above", "over" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is level higher than the second feature. The first feature is "below", "below" and "below" the second feature includes the first feature being directly below and diagonally below the second feature, or simply means that the first feature has a lower level than the second feature.

The present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings.

；所述集流体包括涂覆有导电碳材料的铝箔。As shown in Figures 1 to 3, the present invention provides a room temperature full liquid lithium-sulfur battery, comprising a diaphragm, a room temperature liquid alloy negative electrode and a liquid polysulfide positive electrode respectively installed on both sides of the diaphragm, and connected to the liquid polysulfide positive electrode The current collector; the room temperature liquid alloy negative electrode is formed by the reaction of lithium and mercury according to a preset ratio, and the diaphragm is a lithium ion battery diaphragm with a negative boron nitride coating; the liquid polysulfide positive electrode is

; The current collector includes an aluminum foil coated with a conductive carbon material.

The present invention solves the existing problems of the lithium-sulfur battery by utilizing the advantages of the liquid battery, and can work at room temperature without high-temperature heating, thereby saving energy. By replacing metal lithium with liquid alloy, the formation of lithium dendrites is inhibited, and the cycle life and safety performance of the battery are improved; by replacing the elemental sulfur cathode with liquid polysulfide, the conductivity of the cathode is greatly improved, and the volume during charge and discharge is effectively reduced. Expansion problem; surface modification and structural improvement of the separator can effectively inhibit the shuttle of polysulfides, reduce the loss of active materials and self-discharge, and improve the Coulombic efficiency of lithium-sulfur batteries.

On the other hand, the present invention also provides a preparation method of a room temperature full liquid lithium-sulfur battery, comprising the following steps:

Step S1: making a room temperature liquid alloy negative electrode;

Step S2: making the diaphragm;

Step S3: making a liquid polysulfide positive electrode;

Step S4: making a current collector;

Step S5: injecting the room temperature liquid alloy negative electrode and the liquid polysulfide positive electrode into the replaceable membrane H-type electrolytic cell, inserting the foil electrode into the room temperature liquid alloy negative electrode, and inserting the current collector into the liquid polysulfide positive electrode on the lead clip, The separator is sandwiched between the positive electrode pool and the negative electrode pool, and the whole H-type electrolytic cell is sealed to form the room temperature full liquid lithium-sulfur battery.

The present invention solves the existing problems of the lithium-sulfur battery by utilizing the advantages of the liquid battery, and can work at room temperature without high-temperature heating, thereby saving energy. By replacing metal lithium with liquid alloy, the formation of lithium dendrites is inhibited, and the cycle life and safety performance of the battery are improved; by replacing the elemental sulfur cathode with liquid polysulfide, the conductivity of the cathode is greatly improved, and the volume during charge and discharge is effectively reduced. Expansion problem; surface modification and structural improvement of the separator can effectively inhibit the shuttle of polysulfides, reduce the loss of active materials and self-discharge, and improve the Coulombic efficiency of lithium-sulfur batteries.

In an optional embodiment, the step S1 specifically includes the following steps:

The room temperature liquid alloy negative electrode uses lithium and mercury after removing the oxide film. According to a preset ratio, the room temperature liquid lithium-based alloy negative electrode can be prepared by controlling the content of lithium in the liquid mercury. The mass ratio of lithium to mercury is (0.01-0.86): (99.14-99.99).

Specifically, metal potassium and metal sodium can also be used instead of metal lithium to prepare different types of liquid alkali metal alloy negative electrodes.

In an optional embodiment, the step S2 specifically includes the following steps:

In step S21, the boron nitride and guanidine carbonate or guanidine nitrate are ball-milled and dispersed into a solvent to obtain a uniform and stable dispersion;

In step S22, the dispersion liquid is suction-filtered onto the lithium ion battery separator, and after drying, a lithium ion battery separator with a boron nitride coating is obtained to form the separator.

In an optional embodiment, the step S3 specifically includes the following steps:

In step S31, an H-type electrolytic cell is used to assemble an ordinary lithium-sulfur battery, and the positive and negative electrodes are short-circuited and discharged, and the polysulfide will diffuse into the electrolyte, and the electrolyte will turn brown.

In step S32, the electrolyte is collected, elemental sulfur is added thereto, and the supernatant is taken after the reaction is sufficient to obtain a liquid polysulfide positive electrode.

In an optional embodiment, step S4 specifically includes the following steps:

The current collector is formed by coating a conductive carbon material on an aluminum foil.

In an optional embodiment, the conductive carbon material includes one or more of graphite, graphene, carbon nanotubes, and carbon nanofibers.

In an optional embodiment, steps S1 to S5 are all performed under normal temperature and normal pressure conditions.

In an optional embodiment, steps S1 to S5 are all completed in a glove box filled with argon gas.

Specific examples are as follows:

Example 1

(1) Take 15 mg of metal lithium from which the oxide film has been removed, add it to 0.733 g of metal mercury, and let it stand for 24 h to obtain a room temperature liquid alloy negative electrode;

(2) 1 g of boron nitride and 1 g of guanidine carbonate were mixed and ball-milled for 48 h to obtain a uniform mixed powder, 20 mg of the mixed powder was added to 20 ml of NMP, and mechanically stirred for 12 h to obtain a stable and uniform dispersion A; The ion battery separator is used as filter paper, the dispersion A is suction filtered, the NMP on the separator is washed with deionized water, and the separator is dried to obtain a lithium ion battery separator with a boron nitride coating;

(3) Use an H-type electrolytic cell to assemble an ordinary lithium-sulfur battery, short-circuit the positive and negative electrodes to discharge, and the polysulfide will diffuse into the electrolyte, and the electrolyte will turn brown. Collect the electrolyte, add 10 mg of elemental sulfur to it, and take the supernatant after the reaction for 24 h to obtain a liquid polysulfide positive electrode.

(4) 90 mg of graphene and 10 mg of PVDF were added to 2 ml of NMP, and magnetically stirred for 12 h. The obtained slurry was coated on aluminum foil with a 200 μm spatula, dried and cut into circular pieces with a diameter of 15 mm to obtain a positive electrode collector.

(5) Inject the liquid alloy negative electrode and the liquid polysulfide positive electrode into the replaceable membrane H-type electrolytic cell, insert the foil electrode into the liquid alloy negative electrode, and immerse the current collector into the liquid polysulfide positive electrode on the lead clip. It is sandwiched between the positive electrode pool and the negative electrode pool, and the battery is sealed as a whole to test its electrochemical performance.

Embodiment 2

(1) Take 90 mg of metal lithium from which the oxide film was removed, add it to 4.398 g of metal mercury, and let it stand for 24 h to obtain a room temperature liquid alloy negative electrode;

(2) 2 g of boron nitride and 2 g of guanidine carbonate were mixed and ball-milled for 48 h to obtain a uniform mixed powder, 50 mg of mixed powder was added to 50 ml of NMP, and mechanically stirred for 12 h to obtain a stable and uniform dispersion A; The ion battery separator is used as filter paper, the dispersion A is suction filtered, NMP is washed off with deionized water, and the separator is dried to obtain a lithium ion battery separator with a boron nitride coating;

(3) Use an H-type electrolytic cell to assemble an ordinary lithium-sulfur battery, short-circuit the positive and negative electrodes to discharge, and the polysulfide will diffuse into the electrolyte, and the electrolyte will turn brown. Collect the electrolyte, add 20 mg of elemental sulfur to it, and take the supernatant after 24 hours of reaction to obtain a liquid polysulfide positive electrode.

The current collector is a conductive carbon material coated on an aluminum foil, and the conductive carbon material is one or more of graphite, graphene, carbon nanotube, carbon nanofiber, and the like.

(4) 180 mg of graphene and 20 mg of PVDF were added to 4 ml of NMP, and magnetically stirred for 12 h. The obtained slurry was coated on aluminum foil with a 200 μm scraper, dried and cut into a circular sheet with a diameter of 15 mm to obtain a positive electrode collector.

(5) The liquid alloy negative electrode and the liquid polysulfide positive electrode are injected into the replaceable membrane H-type electrolytic cell, the foil electrode is inserted into the liquid lithium amalgam negative electrode, and the current collector is clamped on the lead clip and immersed in the liquid polysulfide positive electrode. The separator was sandwiched between the positive electrode pool and the negative electrode pool, and the battery was sealed as a whole to test its electrochemical performance.

In the description of this specification, reference is made to the description of the terms "one embodiment", "some embodiments", "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. It is intended that a particular feature, structure, material or characteristic described in connection with this embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above content is a further detailed description of the present invention in conjunction with specific embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art to which the present invention pertains, some simple deductions or substitutions can be made without departing from the concept of the present invention.

Claims (10)

1. The room-temperature full-liquid lithium-sulfur battery is characterized by comprising a diaphragm, a room-temperature liquid alloy cathode and a liquid polysulfide anode which are respectively arranged on two sides of the diaphragm, and a current collector connected with the liquid polysulfide anode; the room-temperature liquid alloy cathode is formed by reacting lithium and mercury according to a preset proportion, and the diaphragm is a lithium ion battery diaphragm with a boron nitride coating; the liquid polysulfide positive electrode is

(ii) a The current collector includes an aluminum foil coated with a conductive carbon material.

2. The method for preparing the room-temperature all-liquid-state lithium-sulfur battery as claimed in claim 1, comprising the following steps:

step S1: manufacturing a room-temperature liquid alloy cathode;

step S2: manufacturing a diaphragm;

step S3: manufacturing a liquid polysulfide positive electrode;

step S4: manufacturing a current collector;

step S5: and injecting the room-temperature liquid alloy cathode and the liquid polysulfide anode into an H-shaped electrolytic cell with a replaceable film, inserting a foil electrode into the room-temperature liquid alloy cathode, clamping a current collector on a lead clamp, immersing the current collector into the liquid polysulfide anode, clamping a diaphragm between the anode cell and the cathode cell, and sealing the H-shaped electrolytic cell integrally to form the room-temperature full-liquid lithium-sulfur battery.

3. The method for preparing the room-temperature all-liquid-state lithium-sulfur battery according to claim 2, wherein the step S1 specifically comprises the following steps:

the room-temperature liquid-state alloy cathode adopts lithium and mercury with the oxide film removed, and the room-temperature liquid-state lithium-based alloy cathode can be prepared by controlling the content of the lithium in the liquid mercury according to a preset proportion.

4. The method for preparing the room-temperature all-liquid-state lithium-sulfur battery as claimed in claim 3, wherein the mass ratio of the lithium to the mercury is (0.01-0.86): (99.14-99.99).

5. The method for preparing the room-temperature all-liquid-state lithium-sulfur battery according to claim 2, wherein the step S2 specifically comprises the following steps:

step S21, ball-milling boron nitride and guanidine carbonate or guanidine nitrate, and dispersing into a solvent to obtain a uniform and stable dispersion liquid;

and step S22, carrying out suction filtration on the dispersion liquid to obtain the lithium ion battery diaphragm with the boron nitride coating after drying, and forming the diaphragm.

6. The method for preparing the room-temperature all-liquid-state lithium-sulfur battery according to claim 2, wherein the step S3 specifically comprises the following steps:

step S31, assembling a common lithium-sulfur battery by using an H-shaped electrolytic cell, and performing short-circuit discharge on the positive electrode and the negative electrode, wherein polysulfide can diffuse into electrolyte and the electrolyte becomes brown yellow;

and step S32, collecting the electrolyte, adding elemental sulfur into the electrolyte, taking supernate after full reaction, and obtaining the liquid polysulfide anode.

7. The method for preparing the room-temperature full-liquid lithium-sulfur battery as claimed in claim 2, wherein the step S4 comprises the following steps:

and coating a conductive carbon material on the aluminum foil to form the current collector.

8. The method of claim 7, wherein the conductive carbon material comprises one or more of graphite, graphene, carbon nanotubes, and carbon nanofibers.

9. The method of claim 2, wherein the steps S1 to S5 are performed under normal temperature and pressure conditions.

10. The method of claim 2, wherein steps S1 to S5 are performed in a glove box filled with argon gas.

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