CN109888178A

CN109888178A - A kind of flexible self-supporting lithium-sulfur battery composite cathode material and preparation method thereof

Info

Publication number: CN109888178A
Application number: CN201910177840.8A
Authority: CN
Inventors: 周永宁; 陈东; 岳昕阳; 李璕琭
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2019-03-10
Filing date: 2019-03-10
Publication date: 2019-06-14
Anticipated expiration: 2039-03-10
Also published as: CN109888178B

Abstract

The invention belongs to electrochemical technology field, specially a kind of flexible self-supporting lithium-sulfur battery composite cathode material and preparation method thereof.Lithium-sulfur battery composite cathode material of the invention is the flexible composite and flexible film being made of elemental sulfur, fibrous molybdenum trioxide and multi-walled carbon nanotube three, is denoted as MoO₃/ MCNT@S has the self supporting structure without additional collector, and included polysulfide barrier layer.The material is made using hydro-thermal method and suction method.Composite material of the present invention has excellent charge-discharge performance, in 0.1 ~ 2C of 1.5 ~ 2.8V of voltage range and current density, reversible capacity with higher and good cycle performance；Under the current density of 0.5C, specific capacity remains to be maintained at 600 ~ 800mAhg after 350 circles⁻¹.The electrode material has specific capacity high, and good rate capability has extended cycle life, and preparation method is simple and the comprehensive advantages such as low in raw material price.

Description

A kind of flexible self-supporting lithium-sulfur battery composite cathode material and preparation method thereof

Technical field

The invention belongs to electrochemical technology fields, and in particular to can be used as positive electrode and its preparation side of lithium-sulfur cell Method.

Background technique

In recent years, with the fast development of new energy science and technology, the performance requirement of secondary cell is continuously improved in people. However Current commercial is melted into its theoretical specific capacity of ripe lithium ion battery and specific energy is lower, has been no longer able to meet the life of people It is living to need.In addition, the cost of conventional lithium ion battery is also relatively high.Therefore, the cheap electricity of novel high-energy metric density, safety is developed Pond body system is the research hotspot of current energy storage field.Compared with conventional lithium ion battery, theoretical specific capacity has lithium-sulfur cell Obviously (theoretical specific capacity of sulphur anode is 1675 mAhg to advantage in lithium-sulfur cell⁻¹, energy density is 2600 Wh kg⁻¹, it is the decades of times of conventional lithium ion battery positive electrode).And elemental sulfur is with cheap, resourceful, environment is friendly The advantages that good, therefore lithium-sulfur cell is considered as most promising next-generation high-energy density secondary battery.But lithium-sulfur cell Some urgent problems to be solved: 1. sulphur simple substances poorly conductive itself are faced with, cause electrode that there is poor kinetics； 2. lithium-sulfur cell can generate a series of polysulfide reaction intermediates during discharge, very soluble in electrolyte, thus Cause " the shuttle effect " between positive and negative anodes, lead to the continuous loss of positive active material sulphur, battery capacity substantially decays；3. The discharging product lithium sulfide and over cure lithium formed under the action of " shuttle effect ", at battery cathode will will greatly affect electricity The reaction interface activity of pole.In addition, sulphur anode huge volume change in charge and discharge process will lead to the disengaging of active material sulphur To destroy battery structure, the irreversible decaying of battery capacity is caused.These problems are all related with the positive electrode of lithium-sulfur cell, The key solved these problems is the excellent composite positive pole of targeted design, can be effectively improved polysulfide in the electrolytic solution Dissolution, shuttle and the corrosion to cathode of lithium, and reduce the volume change in its charge and discharge process.

The present invention is prepared for novel lithium-sulfur cell composite sulfur positive electrode (MoO using hydro-thermal method combination suction method₃/MCNT@ S), it is a kind of flexible electrode material with self supporting structure, is the novel lithium with high specific capacity and good circulation performance Sulphur cell positive electrode material.

Summary of the invention

It is an object of the invention to propose that a kind of novel flexible self-supporting of good performance for lithium-sulfur cell is compound just Pole material and preparation method thereof.

Positive electrode proposed by the present invention for lithium-sulfur cell, be it is a kind of by elemental sulfur, fibrous molybdenum trioxide and The flexible composite and flexible film of multi-walled carbon nanotube three composition, is denoted as MoO₃/ MCNT@S has and is not necessarily to additional collector Self supporting structure, and included polysulfide barrier layer.Research has shown that the material has good chemical property, can make For the positive electrode of lithium-sulfur cell.Lithium sulphur electricity is not applied to it about the flexible self-supporting material containing molybdenum trioxide so far The report in pond.

Composite and flexible film MoO proposed by the present invention₃/ MCNT@S, with a thickness of 40 ~ 120 μm.

The preparation method of composite positive pole proposed by the present invention for lithium-sulfur cell, the specific steps are as follows:

(1) first by nanoscale MoO₃Particle, which is add to deionized water, to stir evenly, and is then added dropwise under magnetic stirring double Oxygen water, and mixed solution is heated in oil bath pan and obtains transparent MoO₃Solution recycles hydro-thermal method by MoO₃Solution is prepared into fibre Tie up shape MoO₃Lotion；

(2) the fibrous MoO for preparing step (1)₃Lotion, MCNT and SDS dispersing agent are add to deionized water and stir It is even, obtain solution A；The solution is filtered, is washed, and is dried, the MoO with self supporting structure is obtained₃Composite membrane；

(3) the fibrous MoO for preparing step (1)₃Lotion, MCNT, S powder and SDS dispersing agent are add to deionized water and stir It mixes uniformly, obtains solution B；MoO prepared by step (2)₃Composite membrane is placed in sand core funnel as filter membrane, and filters solution B, Washing, and dry, the flexible self-supporting sulphur composite positive pole with double membrane structure is obtained, MoO is denoted as₃/MCNT@S。

In step (1) of the present invention, threadiness MoO is prepared₃The condition of lotion are as follows: hydrogen peroxide concentration is 20 ~ 50%, oil bath pan Oil bath temperature be 70 ~ 100 DEG C, hydrothermal temperature be 100 ~ 300 DEG C, the reaction time be 0.5 ~ 1.5h.

In step (2) of the present invention, MoO is prepared₃The solution A condition of composite membrane are as follows: MoO₃The mass ratio of lotion and MCNT is The mass ratio of 2:1 ~ 3:1, MCNT and SDS dispersing agent is 1:8 ~ 1:10.

In step (3) of the present invention, MoO is prepared₃The solution B condition of/MCNT@S are as follows: MoO₃The mass ratio of lotion and MCNT@S Example is 2:1 ~ 3:1, and wherein the mass ratio of S and MCNT is 5:4 ~ 8:1, the mass ratio of MCNT@S and SDS dispersing agent be 1:8 ~ 1:10。

In the present invention, filtering filter membrane used is water system organic mixing nylon new Asia filter membrane (0.22 μm of aperture), sand used The barrel hole size of core funnel is 200 ~ 400 mesh.

In the present invention, drying material use vacuum drying mode, temperature be 30 ~ 70 DEG C, the time be 6 ~ for 24 hours.

In the present invention, MoO₃The pattern of/MCNT@S is obtained by scanning electron microscope, is staggered to form for fiber stick membranaceous Structure.

In the present invention, MoO₃/ MCNT@S composite material can be directly as the electrode of lithium-sulfur cell.Manufactured sample is dried It is cut into the circular electric pole piece that diameter is 12mm afterwards, is not necessarily to additional collector.

In the present invention, MoO₃The electrochemical property test of/MCNT@S composite material uses the lithium sulphur electricity being made of bipolar electrode Cell system.Wherein, MoO₃/ MCNT S composite material is used as working electrode, and high-purity lithium piece is used as to electrode and reference electrode simultaneously. Electrolyte is 1M LiTFSI/DOL-DME (DOL and DME volume ratio are 1:1)+2 ~ 4wt.%LiNO₃, diaphragm is Celgard2400,2320,2300.Battery is assembled in the glove box full of argon gas.The charge-discharge test of lithium-sulfur cell exists It is carried out on blue electricity (Land) battery test system.

In the present invention, the MoO of synthesis₃/ MCNT@S composite material have excellent charge-discharge performance, voltage range 1.5 ~ In 0.1 ~ 2C of 2.8V and current density, reversible capacity with higher and good cycle performance.Under the current density of 0.5C, Specific capacity remains to be maintained at 600 ~ 800 mAhg after 350 circles⁻¹.The electrode material has specific capacity height, good rate capability, circulation Service life is long, and preparation method is simple and the comprehensive advantages such as low in raw material price.

Above-mentioned performance shows the flexible self-supporting MoO prepared using hydro-thermal method and suction method₃/ MCNT@S anode composite material Material is a kind of novel anode material of function admirable, be can be applied in lithium-sulfur cell, especially flexible battery.

Detailed description of the invention

Fig. 1 is MoO₃The appearance picture of/MCNT S composite positive pole and flexible picture.

Fig. 2 is MoO₃The cyclic discharge capacity curve of/MCNT@S under 0.5C current density.

Specific embodiment

Embodiment 1

First by 0.5gMoO₃Particle, which is added in 50mL deionized water, stirs 30min, and it is 30% that 10mL concentration, which is then added dropwise, Hydrogen peroxide, then mixed solution is placed in 80 DEG C of oil bath pans and heats 1h, mixed solution is then moved into the water heating kettle of 100mL specification In, 30min is kept at 180 DEG C, product, that is, MoO after obtaining hydro-thermal reaction₃Lotion.By 2mL MoO₃Lotion, 10mgMCNT and 0.1gSDS dispersing agent is added in 50mL deionized water and is uniformly mixing to obtain solution A.The solution is filtered, is washed, and Drying, obtains the MoO with self supporting structure₃Composite membrane.By 3mL MoO₃Lotion, wherein S:MCNT=7 15mg MCNT@S(: 2, wt.%) it is dissolved in 50mL deionized water with 0.2g SDS dispersing agent and is uniformly mixing to obtain solution B.It will be prepared above MoO₃Composite membrane is placed in sand core funnel as filter membrane, and filters solution B, and washing after 60 DEG C of vacuum drying 12h, obtains thickness Degree is 62 μm of flexible self-supporting sulphur positive electrode (MoO with double membrane structure₃/MCNT@S)。

Scanning electron microscope characterization result shows that the flexible self-supporting sulphur positive electrode pattern with duplicature is fiber The membrane structure that stick is staggered to form.Using the material as working electrode, using high-purity lithium piece as to electrode assembling at simulated battery. Wherein electrolyte is 1M LiTFSI/DOL-DME (DOL and DME volume ratio are 1:1)+2wt.% LiNO₃, diaphragm is Celgard2400, battery are assemblied in the drying box of applying argon gas and carry out.Charge-discharge test the results show that the material 0.5C's Capacity is maintained at 666 mAhg after 350 circle of circulation under current density⁻¹。

Embodiment 2

First by 0.5gMoO₃Particle, which is added in 50mL deionized water, stirs 30min, and it is 30% that 10mL concentration, which is then added dropwise, Hydrogen peroxide, then mixed solution is placed in 80 DEG C of oil bath pans and heats 1h, mixed solution is then moved into the water heating kettle of 100mL specification In, 30min is kept at 180 DEG C, product, that is, MoO after obtaining hydro-thermal reaction₃Lotion.By 4mL MoO₃Lotion, 20mgMCNT and 0.2gSDS dispersing agent is added in 50mL deionized water and is uniformly mixing to obtain solution A.The solution is filtered, is washed, and Drying, obtains the MoO with self supporting structure₃Composite membrane.By 6mL MoO₃Lotion, wherein S:MCNT=7 30mg MCNT@S(: 2, wt.%) it is dissolved in 50mL deionized water with 0.4g SDS dispersing agent and is uniformly mixing to obtain solution B.It will be prepared above MoO₃Composite membrane is placed in sand core funnel as filter membrane, and filters solution B, and washing after 60 DEG C of vacuum drying 12h, obtains thickness Degree is 101 μm of flexible self-supporting sulphur positive electrode (MoO with double membrane structure₃/MCNT@S)。

Scanning electron microscope characterization result shows that the flexible self-supporting sulphur positive electrode pattern with duplicature is fiber The membrane structure that stick is staggered to form.Using the material as working electrode, using high-purity lithium piece as to electrode assembling at simulated battery. Wherein electrolyte is 1M LiTFSI/DOL-DME (DOL and DME volume ratio are 1:1)+2wt.% LiNO₃, diaphragm is Celgard2400, battery are assemblied in the drying box of applying argon gas and carry out.Charge-discharge test the results show that the material 0.2C's Capacity is about 880 mAhg after 200 circle of circulation under current density⁻¹。

Claims

1. a kind of flexible self-supporting lithium-sulfur battery composite cathode material, which is characterized in that for by elemental sulfur, fibrous molybdenum trioxide And the flexible composite and flexible film of multi-walled carbon nanotube three composition, it is denoted as MoO₃/ MCNT@S has without additional collection The self supporting structure of fluid, and included polysulfide barrier layer.

2. a kind of preparation method of flexible self-supporting lithium-sulfur battery composite cathode material as described in claim 1, feature exist In specific steps are as follows:

(1) first by nanoscale MoO₃Particle, which is add to deionized water, to stir evenly, and dioxygen is then added dropwise under magnetic stirring Water, and mixed solution is heated in oil bath pan and obtains transparent MoO₃Solution recycles hydro-thermal method by MoO₃Solution is prepared into fiber Shape MoO₃Lotion；

(2) the fibrous MoO for preparing step (1)₃Lotion, MCNT and SDS dispersing agent are add to deionized water and stir It is even, obtain solution A；The solution is filtered, is washed, and is dried, the MoO with self supporting structure is obtained₃Composite membrane；MCNT For multi-walled carbon nanotube, SDS is lauryl sodium sulfate；

(3) the fibrous MoO for preparing step (1)₃Lotion, MCNT, S powder and SDS dispersing agent are add to deionized water and stir Uniformly, solution B is obtained；MoO prepared by step (2)₃Composite membrane is placed in sand core funnel as filter membrane, and filters solution B, water It washes, and dries, obtain the flexible self-supporting sulphur composite positive pole with double membrane structure, be denoted as MoO₃/MCNT@S。

3. preparation method according to claim 2, which is characterized in that in step (1), the hydrogen peroxide concentration be 20 ~ 50%, oil bath temperature is 70 ~ 100 DEG C, and hydrothermal temperature is 100 ~ 300 DEG C, and the reaction time is 0.5 ~ 1.5h.

4. preparation method according to claim 2, which is characterized in that in step (2), MoO₃The mass ratio of lotion and MCNT Example is 2:1 ~ 3:1, and the mass ratio of MCNT and SDS dispersing agent is 1:8 ~ 1:10.

5. preparation method according to claim 2, which is characterized in that in step (3), MoO₃The quality of lotion and MCNT@S Ratio is 2:1 ~ 3:1, and wherein the mass ratio of S and MCNT is 5:4 ~ 8:1, and the mass ratio of MCNT@S and SDS dispersing agent is 1:8 ~1:10。

6. preparation method according to claim 2, which is characterized in that the filter membrane of the suction filtration is the organic mixing Buddhist nun of water system Imperial new Asia filter membrane, 0.22 μm of aperture, sand core funnel used are 200 ~ 400 mesh sand core funnels.

7. preparation method according to claim 2, which is characterized in that the drying uses vacuum drying mode, and temperature is 30 ~ 70 DEG C, the time be 6 ~ for 24 hours.