CN108321432B - Carbon-nitrogen polymer reference solid electrolyte for inhibiting growth of lithium dendrites and preparation method and application thereof - Google Patents
Carbon-nitrogen polymer reference solid electrolyte for inhibiting growth of lithium dendrites and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a carbon-nitrogen polymer reference solid electrolyte for inhibiting growth of lithium dendrites, a preparation method and application thereof. The invention takes light carbon nitrogen polymer as electrolyte filler to prepare the quasi-solid electrolyte which can effectively inhibit the growth of lithium dendrite in the lithium metal battery. The light carbon nitrogen polymer has a surprising layered structure, is beneficial to the absorption of electrolyte, thereby forming a muddy quasi-solid electrolyte which can be used for inhibiting the growth of dendritic crystals of a lithium cathode in a lithium metal battery.
Description
Technical Field
The invention belongs to the technical field of new energy, and particularly relates to a light carbon-nitrogen polymer reference solid electrolyte for inhibiting growth of lithium dendrites, and a preparation method and application thereof.
Background
With Li-S and Li-O2Typical lithium metal batteries are receiving much attention because of their higher energy density than lithium ion batteries. Lithium metal for the negative electrode is the best candidate for such high capacity conversion reaction battery systems due to the low voltage and high theoretical specific capacity (3860 mAh/g). However, during electrochemical cycling, lithium metal is unevenly deposited/stripped on the surface of the negative electrode, resulting in the growth of lithium dendrites, which may even penetrate the separator to cause short-circuiting of the battery, and the resulting deterioration of the electrochemical performance of the battery. In recent years, various strategies have been attempted to improve the lithium deposition process, inhibiting lithium dendrite growth. If the metallic lithium is melted and infiltrated into the conductive frame matrix with the lithium-philic surface, the flexible metallic lithium negative electrode with small volume change is constructed, and the lithium dendrite can be eliminated. The improvement of lithium metal by constructing a three-dimensional nanostructured current collector to replace a two-dimensional lithium-bearing planeDeposition behavior, thereby avoiding growth of lithium dendrites. Also important strategies are to alter the intrinsic properties, concentration of the electrolyte or to introduce electrolyte additives, such as based on ionic liquids or high concentrations of fluorosulfonylimide ions (FSI)-) Can effectively ensure the high-rate and stable lithium deposition process, FSI-The method can reduce on the surface of lithium metal (mainly generate LiF), and form a firm solid electrolyte interface layer (SEI) in situ, thereby ensuring that lithium dendrites cannot be generated in the lithium metal deposition process. For Li-S battery systems, the simultaneous addition of lithium polysulfide and lithium nitrate can produce a synergistic effect, strengthening the SEI, thereby protecting the lithium negative electrode from corrosion. The modification of the separator (such as introducing polar functional groups on the surface of the fibers of the separator) can also effectively ensure the uniform deposition of lithium metal on the negative electrode.
Solid or quasi-solid electrolytes have better mechanical strength than additive-reinforced electrolytes, and are expected to have better lithium dendrite suppression. However, all-solid electrolytes generally have insufficient conductivity, and the problem of poor interfacial contact is difficult to solve. Quasi-solid electrolytes, which have similar conductivity to electrolytes, and good interfacial wetting ability, are considered to be one of the best candidates for new lithium metal battery electrolytes. Quasi-solid electrolytes are often formed by curing nonaqueous electrolytes or lithium salts added to polymer backbones (e.g., polyethylene oxide) or inorganic nanoparticle (e.g., nanosilica) fillers. The quasi-solid state of the electrolyte does not cause a significant decrease in conductivity, and in some cases, may increase its conductivity due to space charge effects. However, the mechanical strength of conventional polyethylene oxide-based polymer films is weak and cannot effectively suppress lithium dendrites, and it is often necessary to add hard inorganic nanoparticles for improvement.
disclosure of Invention
In view of the above problems, the present invention aims to provide a novel polymer-based solid electrolyte with high mechanical strength, and a preparation method and applications thereof.
In one aspect, the present invention provides a light carbon nitrogen polymer-based solid electrolyte for suppressing growth of lithium dendrites (a carbon nitrogen polymer-based solid electrolyte for suppressing growth of lithium dendrites), including an electrolyte, and an electrolyte filler, the electrolyte filler being a light carbon nitrogen polymer.
The invention takes light carbon nitrogen polymer as electrolyte filler to prepare the quasi-solid electrolyte which can effectively inhibit the growth of lithium dendrite in the lithium metal battery. The light carbon nitrogen polymer has a surprising layered structure, is beneficial to the absorption of electrolyte, thereby forming a muddy quasi-solid electrolyte which can be used for inhibiting the growth of dendritic crystals of a lithium cathode in a lithium metal battery. Polymers g to C3N4Has high mechanical strength per se, and the close packing of the layered structure further enhances the mechanical strength, thereby being used as an electrolyte filler, g-C3N4Can effectively inhibit the growth of lithium dendrites. When the light carbon nitrogen polymer reference solid electrolyte is in contact with a lithium metal negative electrode, the quasi-solid electrolyte also has the same order of magnitude of interface impedance as a conventional electrolyte and good interface adhesion. In the long circulation process of the lithium metal symmetrical battery, the quasi-solid electrolyte can greatly slow down the increase of voltage polarization in the deposition/stripping process of the lithium metal, and the circulation stability of the battery is enhanced.
Preferably, the light carbon nitrogen polymer comprises self-assembled three-dimensional mesoporous spheres g-C3N4Two-dimensional nano thin layer g-C3N4Oxygen-doped stripping-less layer of O-g-C3N4S-doped S-g-C3N4At least one of (1).
The mass percentage of the light carbon nitrogen polymer in the light carbon nitrogen polymer-based solid electrolyte is 20-25 wt%.
Preferably, the electrolyte comprises a solute and a solvent, wherein the solute is lithium bis (trifluoromethanesulfonimide) LiTFSI and lithium hexafluorophosphate LiPF6Lithium perchlorate LiClO4And/or lithium bis (fluorosulfonyl) imide (LiFSI); the solvent is at least one of diglyme DGM, triglyme TEGDME, ionic liquid 1-ethyl-3 methyl bis (trifluoromethane) sulfimide EmimTFSI, ethylene carbonate EC and dimethyl carbonate DMC; concentration of solute in the electrolyteThe degree is 0.5 to 1.5 mol/L.
Preferably, the electrolyte is a diglyme DGM solution with a solute of lithium bistrifluoromethanesulfonimide LiTFSI, a triglyme solution with a solute of LiTFSI, or a lithium hexafluorophosphate LiPF6Ethylene carbonate EC and dimethyl carbonate DMC solution in a volume ratio of 1: 1; the concentration of solute in the electrolyte is 0.5-1.5 mol/L.
in another aspect, the invention provides a preparation method of the light carbon nitrogen polymer-based solid electrolyte, wherein the light carbon nitrogen polymer is fully mixed with an electrolyte to obtain the light carbon nitrogen polymer-based solid electrolyte.
Preferably, the particle size distribution of the light carbon nitrogen polymer is 3.5-8 μm. When the light carbon nitrogen polymer is in a nano structure, the light carbon nitrogen polymer is very easy to be mixed with electrolyte to form mud, and the simple forming process of the quasi-solid electrolyte is ensured.
In a third aspect, the invention also provides a lithium metal symmetric battery system based on the light carbon nitrogen polymer reference solid electrolyte, which comprises the light carbon nitrogen polymer reference solid electrolyte and metal lithium sheets positioned on two sides of the light carbon nitrogen polymer reference solid electrolyte.
When the light carbon nitrogen polymer reference solid electrolyte is used for a lithium metal symmetrical battery, the light carbon nitrogen polymer reference solid electrolyte has good interface stability and low interface impedance, the voltage polarization difference in the deposition/stripping process of the metal lithium is reduced, the cycle stability of the symmetrical battery is enhanced, and the surface of the metal lithium after the symmetrical battery is cycled for a long time is still smooth and compact.
In a fourth aspect, the invention also provides a lithium metal battery, which comprises a positive electrode, a negative electrode and a light carbon nitrogen polymer reference solid electrolyte, wherein the light carbon nitrogen polymer reference solid electrolyte is positioned between the positive electrode and the negative electrode, the negative electrode is a metal lithium sheet, and the positive electrode is FeS2Carbon-sulfur composite, LiFePO4、LiMn2O4、LiCoO2At least one of a nickel-rich ternary system and a lithium-rich manganese-based solid solution.
Preferably, the positive electrode is FeS2. When the light carbon nitrogen polymer reference solid electrolyte is used for Li-FeS2When the lithium metal battery is used, the appearance of a lithium negative electrode is improved, the shuttle effect of polysulfide is weakened, and the long service life of the battery with more than 400 cycles is ensured.
The present invention has the following positive effects.
(1) The invention takes the light carbon nitrogen polymer as the electrolyte filler of the quasi-solid electrolyte, and proves the superiority of the light carbon nitrogen polymer as the electrolyte filler. E.g. in the form of spheres g-C3N4In the synthesis process, a large number of thin-layer nanosheets are self-assembled and aggregated into uniform mesoporous spheres, the fine layered structure is favorable for absorption of electrolyte, and meanwhile, the powder with the nano structure is easily mixed with the electrolyte to form mud, so that the simple forming process of the quasi-solid electrolyte is ensured.
(2) Spherical g-C in the invention3N4The uniform mud-like substance mixed with the electrolyte can be effectively attached to the surface of the metal lithium or the electrode material, the interface impedance of the quasi-solid electrolyte and the metal lithium cathode is more stable than that of a pure electrolyte system, and the transmission impedance of the quasi-solid electrolyte and the metal lithium cathode at the interface can be as low as 115 omega cm2The diffusion activation energy at the interface in the temperature range of 30 to 70 ℃ was 0.45 eV.
(3) when the quasi-solid electrolyte is used for the lithium metal symmetrical battery, the polarization potential difference in the reversible deposition/stripping process of the metal lithium is obviously reduced, and the cycle stability of the symmetrical battery is enhanced. Stable deposition/exfoliation of lithium metal symmetric cells based on quasi-solid electrolytes benefits from the inhibition of lithium dendrite growth by the electrolyte.
(4) The light carbon nitrogen polymer reference solid electrolyte is used for Li-FeS2In the case of a lithium metal battery, the morphology of a lithium cathode is remarkably improved due to the inhibition of lithium dendrites, and the shuttle effect of polysulfide can be weakened by the quasi-solid electrolyte, so that the Li-FeS is ensured2The battery has a long life of more than 400 cycles.
The method has simple and convenient production process, is suitable for large-scale application, and has important significance for the development of lithium metal batteries.
Drawings
FIG. 1 shows g-C consisting of three-dimensional mesoporous spherical particles3N4XRD pattern of (a);
FIG. 2 shows g-C consisting of three-dimensional mesoporous spherical particles3N4SEM picture of (1);
FIG. 3 is a graph based on g-C3N4The interface alternating current impedance atlas of the quasi-solid electrolyte metal lithium symmetrical battery evolving along with time is inserted into the figure: the change of the interface impedance value with time;
FIG. 4 is a graph based on g-C3N4A temperature-varying alternating current impedance spectrum of a quasi-solid electrolyte lithium metal symmetric cell;
FIG. 5 is a graph based on g-C3N4An Arrhenius point diagram derived from impedance values of a quasi-solid electrolyte metal lithium symmetrical battery at different temperatures;
FIG. 6 is a graph based on g-C3N4The quasi-solid electrolyte or lithium metal symmetrical battery based on pure electrolyte is 0.5mA/cm2Potential profile of lithium metal deposition/stripping cycle at time, inset: comparing the potential curves amplified under specific cycle times;
FIG. 7 is a graph based on g-C3N4quasi-solid electrolyte or lithium metal symmetrical battery based on pure electrolyte at 2mA/cm2Potential profile of lithium metal deposition/stripping cycle at time, inset: comparing the potential curves amplified under specific cycle times;
FIG. 8 is a graph based on g-C3N4the lithium metal symmetrical battery of the quasi-solid electrolyte is at 2mA/cm2SEM surface topography after 120 cycles of lithium metal deposition/stripping;
FIG. 9 is a graph based on g-C3N4Li-FeS of quasi-solid electrolyte2A charge-discharge curve chart of the battery in the previous 200 cycles;
FIG. 10 is a diagram based on O-g-C3N4The interface alternating current impedance atlas of the quasi-solid electrolyte metal lithium symmetrical battery evolving along with time is inserted into the figure: the change of the interface impedance value with time;
FIG. 11 is a diagram based on O-g-C3N4Lithium metal of quasi-solid electrolyteSymmetrical cells at 0.5 and 2mA/cm2potential profile of lithium metal deposition/stripping cycle.
Detailed Description
The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.
According to the invention, a nano-structure polymer filler with high mechanical strength is added into the electrolyte to solidify the electrolyte to construct a quasi-solid electrolyte, so that the aim of inhibiting the growth of dendritic crystals of a lithium cathode in the lithium metal battery is achieved. Specifically, the light carbon-nitrogen polymer is used as an electrolyte filling agent and is uniformly mixed with an electrolyte to form a pasty quasi-solid electrolyte which can be used for inhibiting the growth of lithium negative pole dendrites in a lithium metal battery. The mass percentage of the light carbon nitrogen polymer in the light carbon nitrogen polymer-based solid electrolyte can be 20-25 wt%, and a good muddy electrolyte is difficult to form when the content is too high or too low.
The upper light carbon nitrogen polymer can be selected as self-assembled three-dimensional mesoporous spheres g-C3N4(brown yellow) two-dimensional nano thin layer g-C3N4(Bright yellow), oxygen-doped exfoliation layer O-g-C3N4(white), S-doped S-g-C3N4(grayish brown) or more.
The light carbon nitrogen polymer reference solid electrolyte is formed by uniformly mixing a carbon nitrogen polymer and an electrolyte, wherein the electrolyte comprises a solute and a solvent. The solute can be lithium bis (trifluoromethanesulfonylimide) LiTFSI and lithium hexafluorophosphate LiPF6lithium perchlorate LiClO4And lithium bis (fluorosulfonyl) imide (LiFSI). The solvent can be at least one of diglyme DGM, triglyme TEGDME, ionic liquid 1-ethyl-3 methyl bis (trifluoromethane) sulfimide EmimTFSI, ethylene carbonate EC and dimethyl carbonate DMC. The concentration of solute in the electrolyte can be 0.5-1.5 mol/L. The electrolyte may preferably be: diethylene glycol dimethyl ether (DGM) solution with solute of lithium bistrifluoromethanesulfonimide (LiTFSI), triethylene glycol dimethyl ether (TEGDME) solution with solute of LiTFSI, andis lithium hexafluorophosphate (LiPF)6) Is one of Ethylene Carbonate (EC) and dimethyl carbonate (DMC) solutions in a volume ratio of 1:1, the electrolyte concentration being 0.5-1.5 mol/L.
The following exemplarily illustrates a method for preparing the light carbon nitrogen polymer-based solid electrolyte provided by the present invention.
And fully mixing the light carbon nitrogen polymer with electrolyte to obtain the light carbon nitrogen polymer reference solid electrolyte. The particle size distribution of the light carbon nitrogen polymer can be 3.5-8 mu m. As an example, take 50-150mg of g-C3N4And putting the powder sample in an agate mortar, adding 250-350 mu l of electrolyte, and fully and uniformly grinding to obtain the light carbon-nitrogen polymer reference solid electrolyte. The thickness of the light carbon nitrogen polymer reference solid electrolyte can be adjusted according to needs, and the thickness of the light carbon nitrogen polymer reference solid electrolyte can be generally 80-120 micrometers.
The lithium metal symmetrical battery system provided by the invention is a battery with quasi-solid electrolyte and metal lithium sheets on both sides. Wherein the current density of the lithium deposition and stripping cycle test of the lithium metal symmetric battery system can be 0.5-2mA/cm2The deposition or stripping time in each cycle may be 1-3 hours.
The lithium metal battery provided by the invention has a metal lithium sheet for the cathode and a FeS anode2Carbon-sulfur composite, LiFePO4、LiMn2O4、LiCoO2A nickel-rich ternary system and a lithium-manganese-rich solid solution, without a diaphragm, and a quasi-solid electrolyte is arranged between the anode and the cathode. Li-FeS based on carbon-nitrogen polymers due to dendrite suppression2Quasi-solid state batteries have long lifetimes of greater than 400 cycles.
The invention takes the light carbon nitrogen polymer as the electrolyte filling agent to obtain the muddy quasi-solid electrolyte, and effectively inhibits the growth of lithium dendrite in the lithium metal battery. The quasi-solid electrolyte has an interfacial impedance similar to that of the electrolyte; when the lithium metal composite material is used for a lithium metal symmetric battery, the lithium metal composite material has good interface stability and low interface impedance, the voltage polarization difference in the lithium metal deposition/stripping process is greatly reduced, the cycle stability of the symmetric battery is enhanced, and the lithium metal composite material is improvedThe shape of the deposited lithium metal is improved, and the surface of the metal lithium after long-cycle of the symmetrical battery is still smooth and compact. For Li-FeS2When the battery is used, the shuttle effect of polysulfide is weakened, the attenuation of the battery capacity is remarkably slowed down, and the long service life of the battery with more than 400 cycles is ensured.
the present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.
Example 1
1) Mesoporous spherical g-C3N4Preparation of
Weighing 1.9977g of melamine, and dissolving in 80mL of dimethyl sulfoxide (DMSO); equal moles of cyanuric acid (2.0446g) were dissolved in 40mL of dimethyl sulfoxide. The two solutions were each stirred at 60 ℃ and after being dissolved homogeneously, mixed with each other, kept at 60 ℃ and stirred for 10 minutes, and then allowed to stand to room temperature. Centrifuging the mixture, washing with ethanol for 5 times, and drying in a vacuum drying oven at 50 deg.C to obtain white powder. And putting the white powder into a ceramic crucible, putting the ceramic crucible into a tubular furnace, heating to 550 ℃ at the heating rate of 2.3 ℃/min in the atmosphere of high-purity argon, and sintering for 4 hours to obtain brownish yellow sample powder. The XRD is shown in figure 1, and the diffraction peak corresponds to g-C of a nano structure3N4Pure phase. g-C3N4SEM is shown in FIG. 2, and g-C can be seen3N4The nano-particle is composed of spherical particles with the size of about 5 microns, and each particle is formed by self-assembling and aggregating a large number of thin-layer nano-sheets, so that the nano-particle shows a porous appearance.
2) Preparation of electrolyte
The electrolyte is prepared in an argon glove box with a water value and an oxygen value of less than 0.1 ppm. 1.4354g (5mmol) of lithium bistrifluoromethanesulfonimide (LiTFSI) was dissolved in 5mL of Diglyme (DGM), and the solution was placed on a magnetic stirrer and stirred for 24 hours to give 1mol/L of LiTFSI/DGM electrolyte.
3) Preparation of quasi-solid electrolyte
Mixing the g-C obtained in 1)3N4The powder samples were placed in a vacuum oven at 120 ℃ for 24 hours for vacuum drying and then transferred to an argon glove box. Taking 100mg of g-C3N4Putting the powder sample into an agate mortar, then adding 300 mu l of LiTFSI/DGM electrolyte, and fully and uniformly grinding to obtain mesoporous spherical g-C3N4A quasi-solid electrolyte as a polymer filler. The mass percentage of the light carbon nitrogen polymer in the light carbon nitrogen polymer-based solid electrolyte is 20 wt%.
4) Assembly and testing of lithium metal symmetric batteries
The 2032 coin cell assembly was carried out in an argon glove box with water and oxygen values less than 0.1 ppm. Specifically, a metal lithium sheet with a diameter of 12mm is taken, a layer of the quasi-solid electrolyte in 3) with a diameter of about 0.1mm is uniformly coated on the surface of the metal lithium sheet, and then a metal lithium sheet with a diameter of 10mm is paved on the surface of the quasi-solid electrolyte to assemble the button cell. For comparison, a symmetrical cell was similarly assembled with Celgard as separator and 70. mu.l of LiTFFSI/DGM electrolyte. The AC impedance test of the symmetrical cell was performed at room temperature, with a bias voltage of 100mV and a frequency range of 10-2-106Hz. To test the evolution of the interfacial impedance of metallic lithium with a quasi-solid electrolyte (or Celgard supported electrolyte) over time, the test was performed every 24 hours until the impedance value did not fluctuate significantly. FIG. 3 shows the change of the interfacial impedance between metallic lithium and a quasi-solid electrolyte with time, and it can be seen that the interfacial impedance value was stabilized at 115. omega. cm after 48 hours2Left and right. And then, carrying out a temperature-changing alternating-current impedance test on the symmetrical battery with the stable room temperature, wherein the temperature range is 30-70 ℃, the test is carried out once every 10 ℃, and the temperature is kept for 1 hour at each temperature node, so that the stability of a battery system is ensured. FIG. 4 shows the AC impedance spectrum of a symmetrical cell based on quasi-solid electrolyte at a temperature range of 30-70 deg.CAccording to the AC impedance values at different temperatures, the diffusion activation energy at the interface can be calculated to be 0.45eV according to the Arrhenius equation, and FIG. 5 is the corresponding Arrhenius point.
The assembled 2032 button-type symmetrical battery is subjected to charge-discharge test on a LAND electrochemical workstation at 0.5mA/cm2Under the current density of the lithium battery, constant current charging is carried out for 3 hours, then constant current discharging is carried out for 3 hours, the voltage polarization difference of the deposition/stripping process of the metal lithium is detected, and the circulation is developed according to the steps. FIGS. 6 and 7 are g-C based on mesoporous spheres3N4The quasi-solid electrolyte and pure electrolyte symmetric cell have cycle curves of lithium metal deposition/stripping process under different current densities, and as seen from the figure, the quasi-solid electrolyte significantly reduces the polarization potential difference in the lithium metal deposition/stripping process and enhances the cycle stability of the symmetric cell. At 0.5mA/cm2The polarization voltage difference is maintained at about 50mV after 50 cycles under the current density of (1), and the polarization voltage difference of a pure electrolyte system symmetrical battery reaches 400mV after 50 cycles. At a high level of 2mA/cm2The deposition/stripping time is kept constant (3 hours) at the current density of (2), and the polarization voltage difference of the quasi-solid system can be kept low by about 100 mV. After the symmetrical battery is circulated for a certain number of times, the battery is disassembled in a glove box filled with argon, a metal lithium sheet is taken out, the metal lithium sheet is placed in an electrolyte solvent DGM for cleaning for a plurality of times, the metal lithium sheet is naturally dried, and the metal lithium sheet is placed in a scanning electron microscope device under the protection of argon for appearance observation. FIG. 8 shows 2mA/cm2Under the current density, the appearance of the metal lithium surface of the quasi-solid electrolyte symmetrical battery after 120 cycles, as can be seen from the figure, the lithium metal surface after the large current density cycle is still smooth and compact, and the dendritic growth of the lithium of the negative electrode is effectively inhibited.
5) Quasi-solid electrolyte based Li-FeS2battery assembly and testing
a)FeS2Preparation of cathode material
Weighing commercial FeS235mg of powder sample and 10mg of Super P are put into a mortar and ground for 30min, and then 100 mul of NMP solution with 20 mg/mul of PVDF is added and ground for 10-15 min. Uniformly coating the black slurry onthe area is 50mm2On aluminum foil and dried in a vacuum oven at 80 c for 12 hours. Weighing the aluminum foil loaded with the active substances after vacuum drying again, bagging and putting into a glove box;
b) Battery assembly and testing
The 2032 coin cell assembly was carried out in an argon glove box with water and oxygen values less than 0.1 ppm. The specific process is that a layer of the quasi-solid electrolyte is uniformly coated on a lithium sheet with the diameter of 10mm, and then a positive electrode sheet carrying active substances is placed on the electrolyte to assemble Li-FeS2A lithium metal battery. Performing charge and discharge test on the assembled battery on LAND electrochemical workstation, wherein the voltage interval is 1-3V, and the current multiplying power is 0.1C (1C corresponds to FeS)24 electron conversion reaction or 892mAh/g theoretical specific capacity to achieve the desired current density at 1 hour). FIG. 9 is Li-FeS2According to a typical charge-discharge curve of the battery in the previous 200 cycles, as lithium dendrites are inhibited, the morphology of a lithium negative electrode is obviously improved, and the polarity of the quasi-solid electrolyte is also beneficial to weakening the shuttle effect of polysulfide, so that the long service life of the battery is ensured to be more than 400 cycles.
Example 2
1) Monolayer sheet-like O-g-C3N4preparation of
4g of melamine is placed in a muffle furnace, the muffle furnace is communicated with air, the temperature is raised to 550 ℃ at the speed of 2 ℃/min, and the temperature is kept for 4 hours at the temperature, so that a bright yellow massive loose solid sample is obtained. Fully grinding the sample into powder, placing the powder in a combustion boat, heating to 550 ℃ at the speed of 5 ℃/min, and preserving the temperature for 1 hour to obtain light yellow solid powder. The powder was then warmed to 550 ℃ at a rate of 2 ℃/min and held for 1 hour to give a white final sample. All the temperature raising processes are carried out in the air atmosphere;
2) Preparation of electrolyte
The electrolyte is prepared in an argon glove box with a water value and an oxygen value of less than 0.1 ppm. 1.4354g (5mmol) of lithium bistrifluoromethanesulfonimide (LiTFSI) is dissolved in 5mL of Diglyme (DGM), and then the solution is placed on a magnetic stirrer and stirred for 24 hours to obtain 1mol/L LiTFSI/DGM electrolyte;
3) Preparation of quasi-solid electrolyte
The lamellar O-g-C obtained in 1)3N4The powder samples were placed in a 120 ℃ vacuum oven for vacuum drying for 24 hours and then transferred to an argon glove box. 120mg of O-g-C was taken3N4Putting the powder sample into an agate mortar, adding 300 mu l of LiTFSI/DGM electrolyte, and fully and uniformly grinding to obtain oxygen-doped sheet layered O-g-C3N4A quasi-solid electrolyte as a polymer filler. The mass percentage of the light carbon nitrogen polymer in the light carbon nitrogen polymer-based solid electrolyte is 25 wt%;
4) Assembly and testing of lithium metal symmetric batteries
The 2032 coin cell assembly was carried out in an argon glove box with water and oxygen values less than 0.1 ppm. Specifically, a lithium metal sheet with a diameter of 12mm is taken, a layer of the quasi-solid electrolyte described in 3) with a diameter of about 0.1mm is uniformly coated on the surface of the lithium metal sheet, and then a lithium metal sheet with a diameter of 10mm is laid on the quasi-solid electrolyte to assemble the button cell. For comparison, a symmetric cell was also assembled with Celgard as the separator and 70. mu.l of LiTFSI/DGM electrolyte loaded. The above symmetrical cells were subjected to interfacial ac impedance testing (including stability of interfacial impedance over time and varying temperature ac impedance), as well as charging and discharging testing of lithium metal deposition/exfoliation at different current densities. FIG. 10 shows lithium metal with O-g-C3N4The change of the interface impedance between the reference solid electrolytes with time, it can be seen that the interface impedance value was stabilized at 550. omega. cm after 168 hours2Left and right. FIG. 11 shows a diagram based on O-g-C3N4The symmetrical battery of the quasi-solid electrolyte is 0.5mA/cm2And 2mA/cm2The cycling curve of the lithium metal deposition/stripping process at current density, as seen in the figure, the lower current density maintained better cycling stability, and the potential polarization after 80 cycles was still maintained at around 100 mV.
Finally, it must be said here that: the above embodiments are only used for further detailed description of the technical solutions of the present invention, and should not be understood as limiting the scope of the present invention, and the insubstantial modifications and adaptations made by those skilled in the art according to the above descriptions of the present invention are within the scope of the present invention.
Claims (7)
1. The light carbon nitrogen polymer-based solid electrolyte for inhibiting the growth of lithium dendrites is characterized by being a pasty quasi-solid electrolyte and comprising an electrolyte and an electrolyte filler, wherein the electrolyte filler is a light carbon nitrogen polymer, and the mass percent of the light carbon nitrogen polymer in the light carbon nitrogen polymer-based solid electrolyte is 20-25 wt%;
The electrolyte comprises a solute and a solvent, wherein the solute is bis (trifluoromethanesulfonimide) lithium LiTFSI and lithium hexafluorophosphate LiPF6Lithium perchlorate LiClO4And/or lithium bis (fluorosulfonyl) imide (LiFSI); the solvent is at least one of diglyme DGM, triglyme TEGDME, ionic liquid 1-ethyl-3 methyl bis (trifluoromethane) sulfimide EmimTFSI, ethylene carbonate EC and dimethyl carbonate DMC; the concentration of solute in the electrolyte is 0.5-1.5 mol/L.
2. The light carbon nitrogen polymer reference solid electrolyte as claimed in claim 1, wherein the light carbon nitrogen polymer comprises self-assembled three-dimensional mesoporous spheres g-C3N4Two-dimensional nano thin layer g-C3N4Oxygen-doped stripping-less layer of O-g-C3N4S-doped S-g-C3N4At least one of (1).
3. The light-weight carbon nitrogen polymer reference solid electrolyte as claimed in claim 1 or 2, wherein the electrolyte is a diglyme DGM solution with a solute of lithium bistrifluoromethanesulfonylimide LiTFSI, a triglyme solution with a solute of LiTFSI, or a lithium hexafluorophosphate LiPF solution6Ethylene carbonate EC and dimethyl carbonate DMC solution in a volume ratio of 1: 1; the concentration of solute in the electrolyte is 0.5-1.5 mol/L.
4. The method for preparing the light carbon nitrogen polymer-based solid electrolyte as claimed in any one of claims 1-3, wherein the light carbon nitrogen polymer is fully mixed with the electrolyte to obtain the light carbon nitrogen polymer-based solid electrolyte.
5. The method according to claim 4, wherein the light carbon nitrogen polymer has a particle size distribution of 3.5 to 8 μm.
6. A lithium metal symmetric battery system based on a light carbon nitrogen polymer based solid electrolyte, characterized in that the lithium metal symmetric battery system comprises a light carbon nitrogen polymer based solid electrolyte according to any one of claims 1-3 and metal lithium plates on both sides of the light carbon nitrogen polymer based solid electrolyte.
7. A lithium metal battery based on a light carbon nitrogen polymer based solid electrolyte, characterized in that the lithium metal battery comprises a positive electrode, a negative electrode and the light carbon nitrogen polymer based solid electrolyte as claimed in any one of claims 1 to 3, wherein the negative electrode is a metal lithium sheet, and the positive electrode is FeS2carbon-sulfur composite, LiFePO4、LiMn2O4、LiCoO2at least one of a nickel-rich ternary system and a lithium-rich manganese-based solid solution.
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| CN109494362B (en) * | 2018-10-31 | 2020-09-08 | 贵州梅岭电源有限公司 | Positive electrode material for thermal battery and preparation method thereof |
| CN109786870A (en) * | 2018-12-25 | 2019-05-21 | 上海力信能源科技有限责任公司 | A method of it reducing lithium battery and analyses lithium |
| CN109802173B (en) * | 2019-01-24 | 2021-03-26 | 北京化工大学 | Three-phase organic/inorganic composite gel-state polymer electrolyte and preparation method thereof |
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| CN114551793B (en) * | 2021-09-18 | 2023-10-03 | 万向一二三股份公司 | Lithium-based composite negative plate with long cycle life, preparation method thereof and solid lithium battery |
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