CN107768617B - Lithium-sulfur battery composite cathode material and preparation method thereof - Google Patents
Lithium-sulfur battery composite cathode material and preparation method thereof Download PDFInfo
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Abstract
Lithium-sulfur battery composite cathode material and preparation method thereof.The invention discloses the composite material and preparation method of core-shell structure polymeric layer cladding sulphur carbon, composite material is to be enclosed with the shell of conducting polymer film layer outside the core of sulphur carbon complex；Preparation method is to prepare sulphur carbon (SC) compound by molte-salt synthesis first, then reach desirable particle size (6 microns~10 microns) by low temperature ball mill grinding；Followed by using the tradition after process optimizationMethod prepares coated with silica sulphur carbon (SiO2@SC) compound；Then by low temperature chemical vapor deposition, the preparation of conducting polymer coated Si O2@SC compound is completed；The composite material with core-shell structure polymer overmold sulphur carbon is prepared finally by etching and activation method.Composite material specific discharge capacity of the invention is big, coulombic efficiency height and good cycle, and volume energy density with higher and mass energy density, it has broad application prospects in fields such as mobile communication, portable electronic device, energy storage device, unmanned plane, unmanned boat and electric cars.
Description
Technical field
There is nucleocapsid knot the present invention relates to a kind of high-energy density, height ratio capacity, high coulombic efficiency and long circulation life
The lithium-sulfur battery composite cathode material of structure conducting polymer cladding sulphur carbon.The invention further relates to the preparation sides of the positive electrode
Method.
Background technique
It is right with the rapid development of the related industries such as mobile communication, portable electronic device, electric car and energy storage device
The performance of battery, especially specific capacity, energy density, cycle life and high rate performance etc., propose increasingly higher demands.Cause
This, exploitation has very important strategic importance with high-performance, low cost and environmentally friendly new type lithium ion secondary cell.
Performance and price of positive electrode etc. are to restrict lithium ion battery further to high-energy density, long-life and low cost development
Bottleneck.Such as existing LiFePO4, LiMn2O4And the positive electrodes such as ternary material, due to being limited by its lower theoretical capacity,
Its specific capacity, the room for promotion of energy density are very limited.Therefore, high-energy density, long circulation life and low cost is novel
The research and development of anode material for lithium-ion batteries are the inexorable trends of lithium ion battery technology development.Elemental sulfur is with higher
It is theoretical specific capacity (1675mAh/g) and higher theoretical specific energy (2600Wh/kg), rich reserves, cheap, environmental-friendly
The advantages that, it is expected to become the excellent positive electrode of energy-density lithium ion battery.However, elemental sulfur itself poorly conductive (
Under 25 degrees Celsius of room temperature, conductivity is only 5 × 10-30S/cm the polysulfide), and in charge and discharge process formed with lithium ion
It is soluble in organic electrolyte, resulting in elemental sulfur is that anode lithium-sulfur cell poor circulation, the specific capacity constructed be low, multiplying power
The disadvantages of performance is poor, to constrain the further marketization of lithium-sulfur cell.Currently, there are many researchers both domestic and external
Improve the chemical property of sulfur electrode using various methods, it is compound to improve sulphur anode for example, by using carbon material and oxide material
The electric conductivity and cycle performance of material.Wherein, carbon material includes the active carbon of various pore structures, carbon pipe, carbon fiber, graphite
Alkene, graphene oxide etc.；Oxide material includes cobalt oxide, titanium oxide, silica, manganese oxide etc..These carbon materials and oxidation
The application of object material so that some aspects performance of sulphur anode composite material is improved, such as specific capacity, high rate performance,
Cycle performance etc., but the requirement for high coulombic efficiency is often ignored, and lithium sulphur electricity of the coulombic efficiency as industrialized production
Pond is particularly important, and reason is low coulombic efficiency for the lithium salts in quick consumption electrolyte and corrodes cathode of lithium, thus
Cause the rapid decay of battery capacity；Generally in nanometer and submicron-scale, although this sized materials mention the particle of sulphur anode
The high specific capacity and high rate performance of sulphur battery, but because its biggish specific surface area but increases the usage amount of electrolyte, drop
The low mass energy density of battery entirety；The too small compacted density for leading to material of particle size is low, also will affect the body of battery
Product energy density.In conclusion the market competitiveness that lithium-sulfur cell will be greatly reduced.Therefore, lithium-sulfur cell is being improved
Under the premise of specific capacity, high rate performance and cycle performance, the high coulombic efficiency and high-pressure solid of lithium-sulfur cell how are improved and kept
Density (particle size), which will develop its industrial applications, to have very important significance.
Summary of the invention
First technical problem to be solved by this invention, is just to provide a kind of lithium-sulfur battery composite cathode material.
Second technical problem to be solved by this invention, is just to provide the preparation method of above-mentioned positive electrode.
The lithium-sulfur cell with core-shell structural conductive polymer cladding sulphur carbon prepared using preparation method of the invention is multiple
Positive electrode is closed, there is high-energy density, height ratio capacity, high coulombic efficiency and long circulation life,
Above-mentioned first technical problem is solved, the technical solution adopted in the present invention is as follows:
A kind of lithium-sulfur battery composite cathode material, it is characterized in that: being enclosed with conducting polymer outside the core of sulphur carbon complex
The shell of film layer.
Above-mentioned second technical problem is solved, the technical solution adopted in the present invention is as follows:
A kind of preparation method of positive electrode as described above, it is characterised in that include the following steps:
S1, the preparation of sulphur carbon (SC) compound: preparing sulphur carbon complex by molte-salt synthesis, using the viscosity of excess sulphur come
Increase the reunion of sulphur carbon particle, then reaches ideal particle size (6 microns~10 microns) by low temperature ball mill grinding；
S2, silica (SiO2) cladding sulphur carbon complex preparation: using the tradition after process optimizationLegal system
Standby coated with silica sulphur carbon (SiO out2@SC) compound[1]；
The preparation of conducting polymer coated silica sulphur carbon complex: S3 is prepared by low temperature chemical vapor deposition method
Conducting polymer (polypyrrole (PPY) or polyaniline (PAN)) coated Si O out2@SC composite material；
The preparation of the conducting polymer cladding sulphur carbon composite of core-shell structure: S4 is prepared by etching and activation method
Composite material with core-shell structure (PPY or PDA)@SC.
The step S1 specifically: conductive carbon and sulphur simple substance are subjected to mechanical stirring by the mass ratio of 1:3~1:9 and mixed
It closes, stirring rate is 100 revs/min~500 revs/min, and mixing time is 30 minutes~120 minutes；By mixed sulphur carbon
Material, which is put into closed pressure vessel, to be reacted, and reaction temperature is 180 DEG C~250 DEG C, and the reaction time is 8~15 hours, instead
Answering pressure is 3MPa~5Mpa；
After reaction obtain sulphur carbon complex carry out low temperature ball mill grinding processing, finally obtain having a size of 6 microns~
The mass ratio of 12 microns of sulphur carbon composite, carbon and sulphur is 1:3~1:9；The rate of the low temperature ball mill grinding be 300 turns/
Minute~1000 revs/min, ball and quality of material ratio are 1:1~1:3, and the time is 0.5 hour~6 hours, ball mill grinding temperature
It is -20 DEG C~10 DEG C, the type of cooling is that air-cooled or liquid nitrogen is cooling.
The step S2 specifically: using traditional after optimizationMethod, by what is obtained after low temperature ball mill grinding
Sulphur carbon composite put into containing concentration be 0.1%~3% cetyl trimethylammonium bromide and concentration be 0.1~1%
In the alcohol of polyvinylpyrrolidone and the mixed solution of water, wherein the ratio of alcohol and water is 10:1~2:1；Add concentration
It is stirred mixing for 0.2%~2% ammonium hydroxide, mixing time is 1 hour~3 hours, and concentration is finally then added dropwise again again is
0.2%~5% teos solution quickly stirs 4~8 hours, obtains silica after conventional filtration, cleaning and drying
Coat sulphur carbon (SiO2@SC) compound[1]。
The step S3 specifically: gained silica sulphur carbon complex is put into low-temperature gaseous phase reactor, is passed through
Polymer monomer and oxidant carry out polymerization reaction；
The slewing rate of the low-temperature gaseous phase reactor is 500~1000 revs/min, temperature be 20 DEG C~40 DEG C, vacuum
Degree is 100Pa~800Pa, the reaction time is 30 minutes~120 minutes, and the ratio of polymer monomer and oxidant is 2:1~9:
1, finally obtain conducting polymer coated Si O2@SC compound.
The step S4 specifically: by gained conducting polymer coated Si O2@SC compound is put into concentration and rubs for 0.5
You/liter~hydrofluoric acid solutions of 2 mol/Ls in perform etching activation processing and (not only etch away silica, while also can be to leading
Electric polymer has activation effect, enhances the electric conductivity of polymer), the temperature of etching is 25 DEG C~60 DEG C, by conventional filtration,
The conducting polymer cladding sulphur carbon composite with core-shell structure is obtained after cleaning-drying.
High-ratio surface conductive carbon described in step S1 is the super P or Ketjen black after being activated, specific surface area
BET≥1000cm2/g。
Reaction chamber temperature in low temperature vapor deposition described in step S3 is 20 DEG C~40 DEG C, polymer monomer and oxidant
Ratio be 2:1~9:1, polymer unit be pyrroles or aniline, oxidant be vanadium oxide or iron oxide, the vacuum of reaction chamber
Degree is 100Pa~1000Pa.
The present invention prepares the compound of conductive carbon and sulphur by molte-salt synthesis, passes through bigger serface (BET >=1000cm2/
G) conductive porous carbon carries elemental sulfur, provides more electron propagation ducts for sulphur simple substance, is conducive to the electric discharge for improving battery
Specific capacity and high rate performance；The reunion that sulphur carbon is realized by excessive sulphur reaches desirable particle size using low temperature ball mill grinding
The sulphur carbon complex of size (6 microns~10 microns) reduces the specific surface area of material and the usage amount of electrolyte, improves electricity
The mass energy density of volume energy density and the battery entirety in pond.
Pass through the tradition after optimizationThe SiO2 SC compound of method preparation is presoma[1], using under cryogenic conditions
Chemical vapour deposition technique prepare conducting polymer coated Si O2@SC compound, low temperature is beneficial to keep the sulphur carbon of low melting point
The pattern and crystal structure of sulphur in compound, vapor deposition are conducive to prepare thickness controllably and the film layer of even compact, are conducive to
It reduces the specific surface area of composite material and improves captured sulfur result.
Conducting polymer by preparing core-shell structure after etching activation coats sulphur carbon composite, and core-shell structure is advantageous
In the volume expansion space for improving sulphur, electrode material cracks and falls off caused by efficiently reducing because of sulphur simple substance volume change,
Maintain the good cycle performance of battery and specific discharge capacity；Low temperature can keep the pattern and crystal structure of sulphur, stabilize multiple
The mass ratio of sulphur in condensation material is conducive to the battery constant volume in industrialization；Vapor deposition obtains that thickness is controllable and even compact
Film layer is conducive to physical barriers polysulfide and spreads to electrolyte and negative terminal surface, maintains the good cycle performance of electrode
With high coulombic efficiency.
Functional group and polysulfide on conducting polymer form chemical coordination energy, effectively prevent battery in charge and discharge
The dissolution divergence loss of generated polysulfide in the process improves the coulombic efficiency and cycle performance of battery.
The present invention is to prepare out to have the conducting polymer cladding sulphur carbon of core-shell structure compound by low temperature vapor deposition method
Material prepares sulphur carbon complex by the molte-salt synthesis of early period first, then by liquid and gas method prepare conducting polymer/
Coated with silica sulphur carbon composite obtains coating sulphur carbon with core-shell structural conductive polymer after activating eventually by etching
Composite material.
The present invention makes sulphur carbon complex particle agglomeration by the caking property of excess of sulfur, then is made by low temperature ball mill grinding
The sulphur carbon complex of desirable particle size (6 microns~10 microns), improves the compacted density of battery, reduces the specific surface of material
Product, reduces the use of electrolyte, and then improve the volume energy density and mass energy density of battery；The application passes through low
Warm Energy Deposition has effectively kept the pattern and crystal structure of sulphur simple substance, be conducive to improve composite material in sulfur content it is controllable
Property, be conducive to the lithium-sulfur cell constant volume in further industrial operation；It is controllable that vapour deposition process in the application prepares thickness
And the conducting polymer film layer of even compact, the expansion of the polysulfide effectively generated in physical barriers battery charge and discharge process
Loss is dissipated, the specific surface area of entire sulphur carbon material is also reduced, further reduces the usage amount of electrolyte；Polymer film
In functional group also can carry out chemical coordination with polysulfide and react, the further loss for preventing polysulfide improves battery
Coulombic efficiency and cycle performance；And the core-shell structure of the application is that volume of the sulphur simple substance of compound in charge and discharge process becomes
Change provides reasonable space, and the probability that electrode material surface cracking has been reduced to a great extent and has fallen off keeps battery good
Cycle performance and specific discharge capacity；The three-dimensional that conductive carbon and conductive polymer membrane have built a combination of inner and outside for sulphur simple substance is led
Electric network improves the specific discharge capacity and high rate performance of battery.Present invention has an advantage that excellent material performance, prepares energy
Consume low, operating procedure is simple, is suitble to industrial applications.The conductive polymer membrane of core-shell structure prepared by the present invention coats sulphur carbon
Composite material has specific discharge capacity big, and coulombic efficiency is high, and cycle performance is excellent, and energy density is high and is easy to produce in enormous quantities etc.
Feature has in related fieldss such as mobile communication, portable electronic device, energy storage device, unmanned plane, unmanned boat and electric cars
Wide application prospect.
Compared with the prior art, the advantages of the present invention are as follows: (1) composite particles big (6 micron~10 micron), the application
Sulphur carbon large scale is formed by the viscosity of excess of sulfur to reunite, then passes through low temperature ball mill grinding rate, object ball ratio and low temperature ball milling
Grinding time obtains the bulky grain sulphur carbon complex of ideal dimensions (6 microns~10 microns), with many nanoscales or sub-micro
The other sulphur carbon of meter level or other compounds are compared, and are had higher compacted density and lower specific surface area, will be reduced electrolyte
Usage amount, improve the total quality energy density and volume energy density of battery；(2) there is core-shell structure, core-shell structure is given
The volume change that sulphur in sulphur carbon complex generates in charge and discharge process provides space, avoids and makes because of volume expansion
Electrode material surface cracking and the generation from electrode surface obscission, maintain the good discharge capacity of battery and cyclicity
Energy；(3) preparation method is simple, is easy to produce in enormous quantities.
Detailed description of the invention
Fig. 1 is scanning electron microscope (SEM) photo of the bulky grain SC composite material in the embodiment of the present invention one；
Fig. 2 is the Scanning Electron microscope (SEM) of the PPY@SC composite material of the core-shell structure in the embodiment of the present invention one
Photo；
Fig. 3 is the SC composite electrode in the embodiment of the present invention one, PPY@SC composite electrode and with core-shell structure
The cycle performance curve graph under 0.5C multiplying power of PPY@SC composite electrode；
Fig. 4 is the PPY@SC composite electrode with core-shell structure in the embodiment of the present invention one under 0.5C multiplying power
Long circulating performance chart；
Fig. 5 is the composite positive pole structural schematic diagram with core-shell structural conductive polymer cladding sulphur carbon of the invention.
In figure: 1- polymer film, 2- elemental sulfur, 3- conductive carbon material.
Specific embodiment
Below by embodiment and attached drawing, present invention be described in more detail.
Embodiment one
S1: will treated Ketjen black (specific surface area 1400cm3/ g) and commercialization sulphur (purity 99.5%) according to
Heating in high-pressure closed vessel is put into after the weight ratio mixing of 1:9, container internal pressure is 3Mpa, and heating temperature is 200 degree, is added
The hot time is 10 hours；Obtained bulky grain product is put into progress low temperature ball mill grinding, ball and product in low temperature ball mill
Weight ratio be 1.5:1, ball milling revolution be 400 revs/min, Ball-milling Time be 2 hours, ball milling temperature be -10 degree, using liquid
Nitrogen is cooling, obtains the sulphur carbon complex (as shown in Figure 1) that partial size is about 8 microns；
S2: obtained sulphur carbon complex is utilized into optimizationMethod carries out SiO2Film layer cladding processing: by 1 gram
Sulphur carbon complex is put into 200 milliliters of alcohol and the mixed solution (alcohol: the volume ratio of water is 10:3) of water and is stirred,
In containing concentration be 0.1% cetyl trimethylammonium bromide, the polyvinylpyrrolidone containing 1% ammonium hydroxide and 2 grams, mixing
Solution stir 30 minutes after, then into alcohol and water mixed solution be added dropwise 0.8g ethyl orthosilicate, then stir 4 hours after,
Silicon dioxide layer (with a thickness of 40nm) cladding sulphur carbon complex is obtained after filtering, cleaning, drying；
S3: 1 gram of coated with silica sulphur carbon complex is put into low temperature vapor deposition reactor, vapor deposition temperature
Degree is 25 DEG C, and the gas pressure in reactor is 500Pa, and the speed of rotation of reactor is 1000 revs/min, the reaction time 40
Minute, polymer monomer is pyrroles, and oxidant is vanadium oxide, and the flow-rate ratio of polymer monomer and oxidant is 7:2, and reaction terminates
Afterwards, polypyrrole (thickness is about 20nm) coated silica@sulphur carbon complex is obtained；
S4: it is molten that 1 gram of polypyrrole coated silica@sulphur carbon complex is put into the hydrofluoric acid that concentration is 1 mol/L
Activation processing is performed etching in liquid, etching activation temperature is 30 degree, and etching activation time is 4 hours, after filtering, cleaning, drying
Obtain the polypyrrole cladding sulphur carbon composite with core-shell structure.
S5: the preparation of lithium-sulfur cell: the conducting polymer of core-shell structure is coated sulphur carbon composite, carbon black and gathers inclined fluorine
Ethylene (PVDF) is mixed according to the proportion that mass ratio is 8:1:1, then suitable N-Methyl pyrrolidone (NMP) is added dropwise, so
Low temperature ball mill grinding mixing is carried out afterwards, and wherein the revolution of low temperature ball mill pulverizer is 200 revs/min, the low temperature ball mill grinding time
It is 4 hours.The good slurry of low temperature ball mill grinding is uniformly applied to above aluminium foil, carrying out vacuum drying treatment, (drying temperature is
60 degrees Celsius, drying time is 4 hours), as positive electrode.Negative electrode material is metal lithium sheet, and polypropylene porous film is battery
Diaphragm, electrolyte are the DOL+DME+DMDS (volume ratio 1:1:1) of the LiCFOS containing 1 mol/L.In the hand of ar gas environment
After completing button cell assembly in casing, battery performance test is carried out on charge and discharge instrument.The voltage range of battery testing is
1.6V~2.8V.
Embodiment two
S1: will treated super P (specific surface area 1000cm3/ g) and commercialization sulphur (purity 99.5%) according to
Heating in high-pressure closed vessel is put into after the weight ratio mixing of 1:5, container internal pressure is 5Mpa, and heating temperature is 250 degree, is added
The hot time is 10 hours, and obtained bulky grain product is put into low temperature ball mill pulverizer progress low temperature ball mill grinding, ball and
The weight ratio of product is 1:1, and low temperature ball mill grinding revolution is 800 revs/min, and the low temperature ball mill grinding time is 2 hours, ball milling powder
Broken temperature is -10 degree, and the type of cooling is cooling for liquid nitrogen, obtains the sulphur carbon complex that partial size is about 6 microns；
S2: substantially the same manner as Example 1.The positive silicic acid second of 1.6g is only added dropwise into alcohol and water mixed solution
Ester after then stirring 6 hours, obtains silicon dioxide layer (with a thickness of 70nm) cladding sulphur carbon complex after filtering, cleaning, drying；
S3: 1 gram of coated with silica sulphur carbon complex is put into low temperature vapor deposition reactor, vapor deposition temperature
Degree is 25 DEG C, and the gas pressure in reactor is 500Pa, and the speed of rotation of reactor is 1000 revs/min, the reaction time 60
Minute, polymer monomer is aniline, and oxidant is vanadium oxide, and the flow-rate ratio of polymer monomer and oxidant is 4:1, and reaction terminates
Afterwards, polyaniline (thickness is about 25nm) coated silica@sulphur carbon complex is obtained；
S4: it is molten that 1 gram of polyaniline-coated silica@sulphur carbon complex is put into the hydrofluoric acid that concentration is 1 mol/L
Activation processing is performed etching in liquid, etching activation temperature is 40 degree, and etching activation time is 4 hours, after filtering, cleaning, drying
Obtain the polyaniline-coated sulphur carbon composite with core-shell structure.
S5: it is the same as example 1.
Embodiment three
S1: will treated super P (specific surface area 1000cm3/ g) and commercialization sulphur (purity 99.5%) according to
Heating in high-pressure closed vessel is put into after the weight ratio mixing of 1:3, container internal pressure is 3Mpa, and heating temperature is 200 degree, is added
The hot time is 10 hours, and obtained bulky grain product is put into low temperature ball mill pulverizer progress low temperature ball mill grinding, ball and
The weight ratio of product is 1:1, and low temperature ball mill grinding revolution is 400 revs/min, and the low temperature ball mill grinding time is 2 hours, ball milling powder
Broken temperature be 10 degree, the type of cooling be it is air-cooled, obtain the sulphur carbon complex that partial size is about 8 microns；
S2: substantially the same manner as Example 1.The ethyl orthosilicate of 2g is only added dropwise into alcohol and water mixed solution,
Then after stirring 4 hours, silicon dioxide layer (with a thickness of 80nm) cladding sulphur carbon complex is obtained after filtering, cleaning, drying；
S3: 1 gram of coated with silica sulphur carbon complex is put into low temperature vapor deposition reactor, vapor deposition temperature
Degree is 25 DEG C, and gas pressure in reactor is 1000Pa, and the speed of rotation of reactor is 1000 revs/min, and the reaction time is
60 minutes, polymer monomer was aniline, and oxidant is vanadium oxide, and the flow-rate ratio of polymer monomer and oxidant is 3:1, reaction knot
Shu Hou obtains polyaniline (thickness is about 30nm) coated silica sulphur carbon complex；
S4: it is molten that 1 gram of polyaniline-coated silica@sulphur carbon complex is put into the hydrofluoric acid that concentration is 1 mol/L
Activation processing is performed etching in liquid, etching activation temperature is 50 degree, and etching activation time is 4 hours, after filtering, cleaning, drying
Obtain the polyaniline-coated sulphur carbon composite with core-shell structure.
S5: it is the same as example 1.
Example IV:
Conductive carbon is carried out mechanical stirring by the mass ratio of 1:3 with sulphur simple substance and mixed by S1, and stirring rate is 100 revs/min
Clock, mixing time are 30 minutes；Mixed sulphur carbon material is put into closed pressure vessel and is reacted, reaction temperature is
180 DEG C, the reaction time is 8 hours, reaction pressure 3MPa；
Low temperature ball mill grinding processing is carried out sulphur carbon complex is obtained after reaction, finally obtaining size is about 10 microns
Sulphur carbon composite, the mass ratio of sulphur carbon is 5:1；The rate of the low temperature ball mill grinding is 300 revs/min, ball and material
Mass ratio is 1:1, and the time is 0.5 hour, and ball mill grinding temperature is -20 DEG C, and the type of cooling is cooling for liquid nitrogen.
S2 is put into the sulphur carbon composite obtained after low temperature ball mill grinding using traditional Stober method after optimization
Containing concentration be 0.1% cetyl trimethylammonium bromide and concentration be 0.1% polyvinylpyrrolidone alcohol and water
Mixed solution in, wherein the ratio of alcohol and water be 10:1；It adds the ammonium hydroxide that concentration is 0.2% and is stirred mixing, stir
Mixing the time is 1 hour, the teos solution that concentration is 0.2% is then finally added dropwise again again, quickly stirring 4 hours, conventional
Silica (thickness is about 20nm)@sulphur carbon complex is obtained after filtering, cleaning and drying[1]。
Gained silica@sulphur carbon complex is put into low-temperature gaseous phase reactor, passes through polymer monomer and oxidation by S3
Agent carries out polymerization reaction；
The slewing rate of the low-temperature gaseous phase reactor is 500 revs/min, temperature is 20 DEG C, vacuum degree 100Pa, anti-
It is 30 minutes between seasonable, the ratio of polymer monomer and oxidant is 2:1, finally obtains conducting polymer (thickness is about 15nm)
Coated silica@sulphur carbon complex.
Gained conducting polymer coated silica@sulphur carbon complex is put into the hydrogen fluorine that concentration is 0.5 mol/L by S4
Performed etching in acid solution activation processing (not only etch away silica, at the same also can to conducting polymer have activation effect,
Enhance the electric conductivity of polymer), the temperature of etching is 25 DEG C, is obtained after conventional filtration, cleaning-drying with core-shell structure
Conducting polymer coat sulphur carbon composite.
S5: it is the same as example 1.
High-ratio surface conductive carbon described in step S1 is the Ketjen black after being activated, and specific surface area BET is
1300cm2/g；Reaction chamber temperature in low temperature vapor deposition described in step S3 is 20 DEG C, the ratio of polymer monomer and oxidant
Example is 2:1, and polymer unit is pyrroles, and oxidant is vanadium oxide, and the vacuum degree of reaction chamber is 100Pa.
Embodiment five
Conductive carbon is carried out mechanical stirring by the mass ratio of 1:9 with sulphur simple substance and mixed by S1, and stirring rate is 500 revs/min
Clock, mixing time are 120 minutes；Mixed sulphur carbon material is put into closed pressure vessel and is reacted, reaction temperature is
250 DEG C, the reaction time is 15 hours, reaction pressure 5Mpa；
Low temperature ball mill grinding processing is carried out sulphur carbon complex is obtained after reaction, finally obtaining size is about 7 microns
Sulphur carbon composite, the mass ratio of sulphur carbon is 9:1；The rate of the low temperature ball mill grinding is 1000 revs/min, ball and material
Mass ratio is 1:3, and Ball-milling Time is 6 hours, and ball mill grinding temperature is 10 DEG C, and the type of cooling is air-cooled.
S2 is put into the sulphur carbon composite obtained after low temperature ball mill grinding using traditional Stober method after optimization
Containing concentration be 3% cetyl trimethylammonium bromide and concentration be 1% polyvinylpyrrolidone alcohol and water it is mixed
It closes in solution, wherein the ratio of alcohol and water is 12:1；It adds the ammonium hydroxide that concentration is 2% and is stirred mixing, mixing time
It is 3 hours, the teos solution that concentration is 5% is then finally added dropwise again again, quickly stirring 8 hours, conventional filtration, cleaning
With silica (thickness is about 100nm)@sulphur carbon complex is obtained after drying[1]。
Gained silica@sulphur carbon complex is put into low-temperature gaseous phase reactor, passes through polymer monomer and oxidation by S3
Agent carries out polymerization reaction；
The slewing rate of the low-temperature gaseous phase reactor is 1000 revs/min, temperature is 40 DEG C, vacuum degree 800Pa, anti-
It is 120 minutes between seasonable, the ratio of polymer monomer and oxidant is 9:1, finally obtains conducting polymer coated silica@
Sulphur carbon complex.
Gained conducting polymer coated silica@sulphur carbon complex is put into the hydrofluoric acid that concentration is 2 mol/Ls by S4
Activation processing is performed etching in solution (not only to etch away silica, while also there can be activation effect to conducting polymer, increase
The electric conductivity of strength polymer), the temperature of etching is 60 DEG C, obtains having core-shell structure after conventional filtration, cleaning-drying
Conducting polymer coats sulphur carbon composite.
S5: it is the same as example 1.
High-ratio surface conductive carbon described in step S1 is the Ketjen black after being activated, and specific surface area BET is
1400cm2/g；Reaction chamber temperature in low temperature vapor deposition described in step S3 is 40 DEG C, the ratio of polymer monomer and oxidant
Example is 9:1, and polymer unit is aniline, and oxidant is iron oxide, and the vacuum degree of reaction chamber is 1000Pa.
Testing result
The present embodiment to what above-described embodiment one was prepared through the invention there is core-shell structural conductive polymer to coat sulphur carbon
Lithium-sulfur battery composite cathode material carried out the characterization and electrochemical property test of SEM.It is from the testing result of Fig. 1 it is found that logical
It crosses fuse salt and the granular size of sulphur carbon complex that low temperature ball mill grinding method is prepared is about 8 microns, be by nanoscale
The secondary bulky grain of conductive carbon and sulfur particle composition.In addition, as shown in Figure 2, the composite positive pole of core-shell structure PPY@SC with
The surface flatness and pattern of sulphur carbon complex have apparent difference, it was demonstrated that polymer P PY is to sulphur carbon complex surface
Effective cladding has been carried out, apparent influence will have been generated on the chemical property of battery.Sulphur carbon complex electricity as can be seen from Figure 3
Pole is under the discharging condition of 0.5C (1C=1650mAh/g), initial capacity 1140mAh/g, but it is especially fast to decay, and 100
Capacity is only left 289mAh/g after circle, and capacity retention ratio is only 25%；And pass through the initial discharge of the SC composite material of PPY cladding
Specific capacity is 1218mAh/g, and the specific discharge capacity after the circulation of 100 circles is 792mAh/g, capacity retention ratio 65.5%；
And the initial discharge specific capacity of the composite material with core-shell structure PPY@SC is 1222mAh/g, the electric discharge ratio after 100 circle of circulation
Capacity is 910mAh/g, and capacity retention ratio 74.5% can be seen that by the performance comparison of three kinds of different composite materials and pass through
Coated with conductive polymer P PY effectively improves the specific discharge capacity and cycle performance of electrode material, but since sulphur simple substance exists
The convergent-divergent variation that volume can occur in charge and discharge process, so directly coating the compound of sulphur carbon using PPY in charge and discharge
It can to coat film layer rupture because volume increases in the process, allow polysulfide in later cyclic process more to electrolysis
It spreads and is lost in liquid, so that the specific capacity of electrode material constantly reduces and coulombic efficiency is gradually lowered.And there is nucleocapsid knot
Structure PPY@SC composite material is because its nucleocapsid space provides enough spaces when becoming sulfide to sulphur, to make conductive poly-
Compound film layer remains intact, and is conducive to keep polysulfide will not be to the point solution sad diffusion always outside electrode, to protect
Hold the higher specific discharge capacity of electrode material and coulombic efficiency.So from Fig. 4 it can also be seen that having core-shell structure PPY@SC
Combination electrode material under the conditions of the discharge-rate of 0.5C, by 400 circle circulation after specific discharge capacity be still up to
807mAh/g, coulombic efficiency are still maintained at 99.1%, this excellent cycle performance has benefited from the electric conductivity of polymer, complete equal
It is even wrapped and functional group and the more vulcanizations on the core-shell structure and conducting polymer in space are provided for sulphur volume expansion
The chemisorption of object.
Bibliography: [1] WernerArthur Fink,Ernst Bohn.Controlled growth of
Monodisperse silica spheres in the micron size range:Journal of Colloid and
Interface Science, 1968:P 62-69.
Claims (6)
1. a kind of preparation method of lithium-sulfur battery composite cathode material, the positive electrode be outside the core of sulphur carbon complex,
It is enclosed with the shell of conducting polymer film layer, the method characteristic is to include the following steps:
The preparation of sulphur carbon complex: S1 is prepared sulphur carbon complex by molte-salt synthesis, is increased sulphur carbon using the viscosity of excess sulphur
The reunion of particle, then 6 microns~10 micron grain size sizes are reached by low temperature ball mill grinding；
S2, the preparation of coated with silica sulphur carbon complex: using the tradition after process optimizationMethod prepares silica
Coat sulphur carbon complex；
S3, conducting polymer coated silica coat the preparation of sulphur carbon complex: being prepared by low temperature chemical vapor deposition method
Conductive polymer polypyrrole or polyaniline-coated coated with silica sulphur carbon complex composite material out；
Specifically: gained coated with silica sulphur carbon complex is put into low-temperature gaseous phase reactor, by polymer monomer and
Oxidant carries out polymerization reaction；The slewing rate of the low-temperature gaseous phase reactor is 500~1000 revs/min, temperature is 20 DEG C
~40 DEG C, vacuum degree be 100Pa~800Pa, the reaction time is 30 minutes~120 minutes, the ratio of polymer monomer and oxidant
Example is 2:1~9:1, finally obtains conducting polymer coated silica cladding sulphur carbon complex；
S4, the preparation of the composite material of core-shell structural conductive polymer cladding sulphur carbon: being prepared by etching and activation method has
The composite material of core-shell structure polypyrrole or polyaniline-coated sulphur carbon complex.
2. the preparation method of positive electrode according to claim 1, it is characterised in that: the step S1 are as follows: will be conductive
Carbon carries out mechanical stirring by the mass ratio of 1:3~1:9 with sulphur simple substance and mixes, and stirring rate is 100 revs/min~500 revs/min
Clock, mixing time are 30 minutes~120 minutes；Mixed sulphur carbon material is put into closed pressure vessel and is reacted, instead
Answering temperature is 180 DEG C~250 DEG C, and the reaction time is 8~15 hours, and reaction pressure is 3MPa~5Mpa；After reaction
The sulphur carbon complex arrived carries out low temperature ball mill grinding processing, finally obtains the sulphur carbon composite having a size of 6 microns~12 microns；
The rate of the low temperature ball mill grinding is 300 revs/min~1000 revs/min, and ball and quality of material ratio are 1:1~1:3, time
It is 0.5 hour~6 hours, ball mill grinding temperature is -20 DEG C~10 DEG C, and the type of cooling is that air-cooled or liquid nitrogen is cooling.
3. the preparation method of positive electrode according to claim 1, it is characterised in that: the step S2 are as follows: by low temperature
The sulphur carbon composite obtained after ball mill grinding put into containing concentration be 0.1%~3% cetyl trimethylammonium bromide and
In the alcohol of polyvinylpyrrolidone and the mixed solution of water that concentration is 0.1~1%, wherein the ratio of alcohol and water is 10:1
~2:1；It adds the ammonium hydroxide that concentration is 0.2%~2% and is stirred mixing, mixing time is 1 hour~3 hours, then again
The teos solution that concentration is 0.2%~5% is added dropwise, quickly stirs 4~8 hours, after conventional filtration, cleaning and drying
To coated with silica sulphur carbon complex.
4. the preparation method of positive electrode according to claim 1, it is characterised in that: the step S4 are as follows: by gained
It is that 0.5 mol/L~2 mol/Ls hydrofluoric acid is molten that conducting polymer coated silica cladding sulphur carbon complex, which is put into concentration,
Activation processing is performed etching in liquid, the temperature of etching is 25 DEG C~60 DEG C, is obtained after conventional filtration, cleaning-drying with core
The composite material of shell structure conducting polymer cladding sulphur carbon.
5. the preparation method of positive electrode according to claim 2, it is characterised in that: conductive carbon described in step S1 is warp
Overactivation treated super P or Ketjen black, specific surface area BET >=1000cm2/g。
6. the preparation method of positive electrode described in -5 any one according to claim 1, it is characterised in that: described in step S3
It is 20 DEG C~40 DEG C by the low-temperature gaseous phase temperature of reactor in low temperature chemical vapor deposition method, polymer monomer and oxidant
Ratio is 2:1~9:1, and polymer monomer is pyrroles or aniline, and oxidant is vanadium oxide or iron oxide, the vacuum degree of reaction chamber
For 100Pa~800Pa.
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| CN112573530B (en) * | 2020-12-18 | 2022-08-05 | 四川大学 | Sulfur species activated SiO 2 Preparation method of lithium battery negative electrode material |
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| CN114583144B (en) * | 2022-03-07 | 2023-07-14 | 西安理工大学 | Mechanical thermal synthesis method of sulfur-carbon positive electrode material with micro-network structure |
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