CN112072174A - Porous polymer electrolyte, preparation method thereof and lithium metal battery - Google Patents
Porous polymer electrolyte, preparation method thereof and lithium metal battery Download PDFInfo
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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Abstract
The invention provides a porous polymer electrolyte, a preparation method thereof and a lithium metal battery, wherein the preparation method of the porous polymer electrolyte comprises the following steps: preparing a lithium polymer electrolyte diaphragm of sulfonated polyether-ether-ketone; pentaerythritol tetraacrylate and an initiator are dissolved in electrolyte; immersing the lithium polymer electrolyte membrane of sulfonated polyether-ether-ketone into electrolyte, and carrying out in-situ polymerization to obtain a porous polymer electrolyte; according to the preparation method of the porous polymer electrolyte, after polymerization, C-C bonds in pentaerythritol tetraacrylate (PETEA) are converted into C-C bonds to construct a cross-linked network so as to form the porous polymer electrolyte with a semi-interpenetrating polymer network structure; the electrolyte has high ion conductivity and good cathode/electrolyte interface compatibility, and can inhibit the growth of lithium dendrites.
Description
Technical Field
The invention relates to the technical field of lithium metal batteries, in particular to a porous polymer electrolyte, a preparation method thereof and a lithium metal battery.
Background
Metal Batteries (LMBs) using lithium metal as the anode have been attracting much attention because of their promise as replacements for commercial lithium ion batteries with limited energy density, since metallic lithium has a minimum density (0.59 g/cm)3) Lowest anode potential-3.04 v (vs standard hydrogen electrode), and highest theoretical capacity 3860mAhg-1. However, commercial applications of lithium ion batteries to date still suffer from poor cycling performance and safety issues resulting from significant lithium dendrite growth. Metallic lithium is highly reactive with organic liquid electrolytes, resulting in the formation of a Solid Electrolyte Interphase (SEI) between the metallic lithium and the electrolyte. Unfortunately, the SEI formed is chemically non-uniform and structurally unstable, leading to non-uniform deposition of lithium ions during continuous charging, eventually leading to dendritic growth. On the one hand, dendrites growing from lithium foil cause severe anode pulverization, irreversible cell power density reduction and cell coulombic efficiency reduction; on the other hand, dendrites penetrate the separator, causing internal short circuits and thermal runaway, resulting in the occurrence of fire or even explosion. To date, a great deal of research has been conducted to solve the problem of dendrites in the practical application of LMB (lithium metal batteries), such as constructing porous current collectors, fabricating functional interface layers, and using novel solid electrolytes and additives. Among them, single ion conducting polymer electrolytes (SIPEs) having charge delocalized anions are anchored on the polymer backbone, and the counter-lithium ions are the main transport species. The transference number of lithium ions is close to 1. According to the following equation:
Δ c represents the steady state concentration gradient in the electrolyte; l, F and D are respectively the thickness of the electrolyte, the faraday constant and the effective charge carrier diffusion coefficient in the electrolyte, and a higher transport number of lithium ions will result in suppression of the concentration polarization of the electrolyte, thereby strongly suppressing the growth of lithium dendrites. Unfortunately, commercially available liquid electrolytes, such as LiPF6Is a diionic lithium salt (< 0.3) resulting in a more concentration polarized electrolyte to initiate lithium dendrite growth when the lithium ions are depleted. Therefore, the industrial use of lithium metal anodes is greatly limited in commercial liquid electrolyte-based batteries. Although SIPE can suppress lithium dendrite growth, low ionic conductivity (typically less than 10)-3×S cm-1) And poor electrode/electrolyte interface compatibility of SIPEs reported in most studies, thereby limiting their practical application in electric vehicles and large-scale energy storage systems. To our knowledge, the preparation has a large porosity and absorptionLiquid fraction SIPE typically has effective pore-forming methods such as templating, non-solvent induced phase separation, thermally induced phase separation and electrospinning. The ionic conductivity and the compatibility of the electrode/electrolyte interface can be improved.
In addition to the above parameters, it is desirable to have excellent thermal, chemical and electrochemical stability, thermal dimensional stability. However, the commercialized LiPF6Lithium salts are not thermally stable (>60 deg.C and moisture sensitivity: (>100ppm) while commercial Celgard separators are non-polar olefin-based polymers, such as Polyethylene (PE) and polypropylene (PP), exhibit poor electrolyte wettability and suffer severe thermal shrinkage at temperatures exceeding 130 ℃, limiting the use of commercial LMBs at higher temperatures.
Economic efficiency is one of the main concerns for the practical application of the novel SIPE. In previous studies (application No. CN201810525223.8), economically efficient and highly porous nanofiber SIPE membranes (es-lisppe) were prepared by electrospinning sulfonated polyetherketonelithium (Li-SPEEK) synthesized by simple sulfonation and lithiation of industrial Polyetherketone (PEEK). The es-lispece/1M LiPF6-EC/PC (v: v ═ 1:1) electrolyte exhibits enhanced ionic conductivity and lithium ion transport number, good mechanical strength, excellent thermal dimensional stability and fast electrolyte wetting speed. However, es-LiSPCE/1M LiPF6the-EC/PC (v: v ═ 1:1) electrolyte still suffers from insufficient ionic conductivity, poor compatibility with the electrodes and liquid electrolyte leakage due to excessive electrolyte uptake.
Based on the shortcomings of the existing electrolytes, there is a need for improvement.
Disclosure of Invention
In view of the above, the present invention provides a porous polymer electrolyte, a preparation method thereof and a lithium metal battery, so as to solve the technical problems in the prior art.
In a first aspect, the present invention provides a method for preparing a porous polymer electrolyte, comprising the steps of:
preparing a lithium polymer electrolyte diaphragm of sulfonated polyether-ether-ketone;
pentaerythritol tetraacrylate and an initiator are dissolved in electrolyte;
and (3) immersing the lithium polymer electrolyte membrane of the sulfonated polyether-ether-ketone into electrolyte, and carrying out in-situ polymerization to obtain the porous polymer electrolyte.
Optionally, in the preparation method of the porous polymer electrolyte, the initiator is azobisisobutyronitrile.
Optionally, the electrolyte comprises a lithium salt and a solvent, wherein the lithium salt is LiPF6The solvent comprises EC and DMC, and the volume ratio of EC to DMC is 1: 1.
Optionally, in the preparation method of the porous polymer electrolyte, the lithium polymer electrolyte membrane of sulfonated polyether ether ketone is immersed in an electrolyte, and in-situ polymerization is carried out at 55-65 ℃ for 4-8 h, so as to obtain the porous polymer electrolyte.
Optionally, the preparation method of the porous polymer electrolyte comprises the following steps:
adding polyether-ether-ketone into concentrated sulfuric acid, stirring for 2-12 hours at the temperature of 30-80 ℃ to obtain sulfonated polyether-ether-ketone, washing, and drying for later use;
dissolving sulfonated polyether ether ketone in a lithium-containing compound, stirring for lithium exchange, filtering after the lithium exchange is finished, and washing and drying filter residues to obtain sulfonated polyether ether ketone lithium;
adding sulfonated lithium polyetheretherketone into N, N-dimethylformamide, preparing a solution with the concentration of 28-30 wt%, heating, stirring and dissolving, and cooling to obtain a spinning solution;
and (3) placing the spinning solution in an instrument, and setting parameters for spinning to obtain the sulfonated polyether-ether-ketone lithium polymer electrolyte membrane.
Optionally, in the preparation method of the porous polymer electrolyte, the lithium-containing compound is lithium hydroxide or lithium hydride.
Optionally, in the preparation method of the porous polymer electrolyte, the lithium polymer electrolyte membrane of sulfonated polyetheretherketone is a porous membrane or a dense membrane.
Optionally, the porous membrane adopts nano SiO2Mixing the particles with sulfonated lithium polyetheretherketone, forming a film by solution casting, and washing off SiO with HF2Particles, and the obtained porous sulfonated polyether ether ketone lithium polymer electrolyte membrane.
In a second aspect, the invention also provides a porous polymer electrolyte prepared by the preparation method.
In a third aspect, the invention also provides a lithium metal battery comprising the porous polymer electrolyte.
Compared with the prior art, the preparation method of the porous polymer electrolyte has the following beneficial effects:
(1) the preparation method of the porous polymer electrolyte provided by the invention prepares a novel nano-fiber porous polymer electrolyte (es-FGPE) by thermally inducing pentaerythritol tetraacrylate (PETEA) precursor to polymerize in situ through pentaerythritol tetrafluoroethylene. Specifically, after polymerization, a C ═ C bond in pentaerythritol tetraacrylate (PETEA) is converted into C — C to construct a cross-linked network to form a porous polymer electrolyte (es-FGPE) of a semi-interpenetrating polymer network structure; the high dielectric constant of PETEA promotes compatibility with liquid electrolytes, maintaining high ionic conductivity even when electrolyte absorption levels are reduced due to the polymeric PETEA occupying the pores of the es-lispece nanofibers; the increased lithium ion transfer number can suppress Li+The formation of a depletion layer inhibits the growth of lithium dendrites; the PETEA-based three-dimensional polymer network built over the entire cell internal components can firmly bond the electrodes and es-FGPE nanofibers together, resulting in excellent cathode/electrolyte interfacial compatibility; the wholly aromatic polyether ether ketone can ensure the thermal dimensional stability of the polymer electrolyte in practical operation at high temperature. In addition, the greatly reduced electrolyte absorption can effectively overcome the problem of electrolyte leakage of the battery, thereby having higher safety, particularly, operation at high temperatures. The results show LiFePO assembled from es-FGPE4the/Li cell exhibits good cathode/electrolyte interface contact for ions, stable lithium anode surface and dendrite-free morphology, good rate performance and highly stable cycling capability over 1000 cycles. In thatThe cell also has a high degree of cycling stability at high temperatures up to 150 ℃.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a process flow diagram of a method for preparing a porous polymer electrolyte according to the present invention;
FIG. 2 is a surface topography of the es-LiSPCE film prepared in example 1 of the present invention at different magnifications;
FIG. 3 shows es-FGPE-LiPF prepared in example 1 of the present invention6-surface topography of EC/DMC electrolyte at different magnifications;
FIG. 4 shows the es-LiSPCE film, es-FGPE-LiPF prepared in example 1 of the present invention6-corresponding EDX element mapping images of S and O of the EC/DMC electrolyte;
FIG. 5 shows es-FGPE-LiPF prepared in example 1 of the present invention6EC/DMC electrolyte and es-LiSPCE-LiPF prepared in comparative example 16-temperature-ionic conductivity diagram of EC/DMC electrolyte;
FIG. 6 shows es-LiSPCE-LiPF prepared in example 1 of the present invention6-lithium ion mobility diagram of EC/DMC electrolyte;
FIG. 7 shows es-FGPE-LiPF prepared in example 1 of the present invention6-optical images of lithium foil after square wave constant current cycling test with EC/DMC electrolyte assembled into symmetric lithium cells;
FIG. 8 shows es-FGPE-LiPF prepared in example 1 of the present application6-SEM images of lithium foils after square wave constant current cycling tests with EC/DMC electrolytes assembled into symmetric lithium cells;
FIG. 9 shows es-FGPE-LiPF prepared in example 1 of the present application6EC/DMC electrolyte and prepared as in comparative example 1To es-LiSPCE-LiPF6Assembly of-EC/DMC electrolyte into Li/LiFePO4Performing an Electrochemical Impedance Spectroscopy (EIS) test chart after the lithium battery;
FIG. 10 is a graph showing es-LiSPCE/LiPF in comparative example 16Composition of-EC/DMC electrolyte Li/LiFePO4Post-lithium battery LiFePO4SEM images and EDS elemental maps of the cathode/electrolyte;
FIG. 11 shows es-FGPE-LiPF in example 1 of the present invention6Li/LiFePO of EC/DMC electrolyte composition4Post-lithium battery LiFePO4SEM images and EDS elemental maps of the cathode/electrolyte;
FIG. 12 shows the es-FGPE-LiPF prepared in example 2 of the present invention6EC/PC vs. es-LiSPCE-LiPF prepared in comparative example 26Li/LiFePO assembled from EC/PC4LiFePO of lithium battery at 150 DEG C4a/Li battery rate performance plot;
FIG. 13 shows Li/LiFePO assembled by es-FGPE-LiPF6-EC/DMC electrolyte prepared in example 2 of the present invention4A charge/discharge curve of a lithium battery;
FIG. 14 shows es-LiSPCE-LiPF prepared in comparative example 2 of the present invention6Li/LiFePO assembled from EC/DMC4A charge/discharge curve of a lithium battery;
FIG. 15 shows es-FGPE-LiPF prepared in example 2 of the present invention6Li/LiFePO of-EC/DMC electrolyte 41C cycle performance of the lithium battery at 50 ℃.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
The invention provides a preparation method of a porous polymer electrolyte, as shown in figure 1, comprising the following steps:
s1, preparing a lithium polymer electrolyte membrane (es-LiSPCE membrane) of sulfonated polyether ether ketone;
s2, dissolving pentaerythritol tetraacrylate (PETEA) and an initiator in electrolyte;
s3, immersing the lithium polymer electrolyte diaphragm of the sulfonated polyether ether ketone into electrolyte, and carrying out in-situ polymerization to obtain the porous polymer electrolyte (es-FGPE-LiPF)6-EC/DMC electrolyte).
It should be noted that the lithium polymer electrolyte membrane prepared by sulfonated polyetheretherketone in example S1 of the present application is prepared by the method of patent application No. CN201810525223.8, and specifically, the method for preparing the lithium polymer electrolyte membrane prepared by sulfonated polyetheretherketone in S1 includes:
adding polyether ether ketone (PEEK) into concentrated sulfuric acid, stirring at 30 deg.C for 6h to obtain sulfonated polyether ether ketone (SPEEK) with sulfonation degree of 80.9%, washing, and drying;
dissolving sulfonated polyether ether ketone (SPEEK) in an equimolar amount of lithium hydroxide aqueous solution to completely exchange hydrogen ions and lithium ions, filtering after the lithium exchange is finished, and washing and drying filter residues to obtain sulfonated polyether ether ketone lithium (Li-SPEEK);
adding sulfonated lithium polyetheretherketone into N, N-dimethylformamide, preparing a solution with the concentration of 9 wt%, heating, stirring, dissolving, and cooling to obtain a spinning solution;
and (3) placing the spinning solution in an instrument, and setting parameters for spinning to obtain the sulfonated polyether-ether-ketone lithium polymer electrolyte membrane (es-LiSPCE membrane).
Specifically, a spinning voltage of 27kv was set, a liquid flow rate of 3ul/min, and a receiving distance of 15cm, to obtain a sulfonated polyetheretherketone lithium polymer electrolyte membrane having a sulfonation degree of 80.9%.
In the embodiment S2, the initiator is azobisisobutyronitrile, the electrolyte includes a lithium salt and a solvent, and the lithium salt is 1MLiPF6The solvent comprises EC and DMC, the volume ratio of EC and DMC is 1:1, obviously, in practice, the solvent can also adopt the combination of two or more than two of PC, EMC, DEC, DME and MPC, and the lithium salt in the electrolyte can also adopt LiPF6、LiBF4Or LiBOB; the pentaerythritol tetraacrylate and the initiator are dissolved in the electrolyte and have the mass fractions of 5% and 1%, respectively.
In the embodiment S3, a lithium polymer electrolyte membrane of sulfonated polyether ether ketone is immersed in an electrolyte and polymerized in situ at 55-65 ℃ for 4-8 h to obtain a porous polymer electrolyte (es-FGPE-LiPF)6-EC/DMC electrolyte), in particular, a lithium polymer electrolyte separator of sulfonated polyetheretherketone (es-lispc film) is immersed in the prepared electrolyte for 24h to assemble LiFePO4Li battery, and finally carrying out in-situ polymerization in an oven at 60 ℃ for 6h to obtain the porous polymer electrolyte (es-FGPE-LiPF)6-EC/DMC electrolyte).
The preparation method of the porous polymer electrolyte provided by the application prepares a novel nano-fiber porous polymer electrolyte (es-FGPE-LiPF) by thermally inducing pentaerythritol tetraacrylate (PETEA) precursor to polymerize in situ through pentaerythritol tetrafluoroethylene6-EC/DMC). Specifically, the C ═ C bond in pentaerythritol tetraacrylate (PETEA) after polymerization is converted to C — C to build a cross-linked network to form a porous polymer electrolyte (es-FGPE) of a semi-interpenetrating polymer network structure. Pentaerythritol tetraacrylate (PETEA) has excellent properties such as high crosslink density, fast cure, good flexibility, low volatility, scratch resistance, fire resistance and chemical resistance. Have a wide range of applications in coatings, adhesives and batteries; the high dielectric constant of PETEA promotes compatibility with liquid electrolytes, maintaining high ionic conductivity even when electrolyte absorption levels are reduced due to the polymeric PETEA occupying the pores of the es-lispece nanofibers; the increased lithium ion transfer number can suppress Li+The formation of a depletion layer inhibits the growth of lithium dendrites; the PETEA-based three-dimensional polymer network built over the entire cell internal components can firmly bond the electrodes and es-FGPE nanofibers together, resulting in excellent cathode/electrolyte interfacial compatibility; the wholly aromatic polyether ether ketone can ensure the thermal dimensional stability of the polymer electrolyte in practical operation at high temperature. In addition, the greatly reduced electrolyte absorption can effectively overcome the problem of electrolyte leakage of the battery, thereby having higher safetyEspecially at high temperatures. The results show LiFePO assembled from es-FGPE4the/Li cell exhibits good cathode/electrolyte interface contact for ions, stable lithium anode surface and dendrite-free morphology, good rate performance and highly stable cycling capability over 1000 cycles. The battery also has high cycle stability at high temperatures up to 150 ℃, which demonstrates excellent safety and wide applicability of the battery device.
Based on the same inventive concept, the embodiment of the application also provides a porous polymer electrolyte prepared by the preparation method.
Based on the same inventive concept, the embodiment of the application also provides a lithium metal battery, which comprises the porous polymer electrolyte.
Example 2
The invention provides a preparation method of a porous polymer electrolyte, which has the same specific preparation process as example 1, and is different from the preparation method in that the electrolyte comprises lithium salt and solvent, and the lithium salt is 1MLiPF6The solvent comprises EC and PC, and the volume ratio of EC to PC is 1:1, thus obtaining the porous polymer electrolyte (es-FGPE-LiPF)6-EC/PC electrolyte)
Comparative example 1
A method for preparing a polymer electrolyte, comprising the steps of: the lithium polymer electrolyte membrane (es-LiSPCE membrane) of sulfonated polyether ether ketone prepared in example 1 is dissolved in electrolyte, wherein the electrolyte is 1M LiPF6EC/DMC (lithium salt 1MLiPF6The solvent comprises EC and DMC, and the volume ratio of EC to DMC is 1:1), namely the polymer electrolyte (es-LiSPCE-LiPF) is obtained6-EC/DMC)。
Comparative example 2
A preparation method of the polymer electrolyte is the same as that of comparative example 1, except that the solvent in the electrolyte comprises EC and PC, and the volume ratio of EC to PC is 1:1, so as to obtain the polymer electrolyte (es-LiSPCE-LiPF)6-EC/PC)。
Performance testing
The es-LiSPCE film and the es-FGPE-LiPF prepared in example 1 were tested separately6-EC/DMThe surface topography of the C electrolyte is shown in FIGS. 2 and 3. Wherein, fig. 2 is a surface topography of the es-lispece film under different magnifications, and fig. 3 is a surface topography of the es-FGPE (wherein j and k are surface topography of different magnifications, and l is a cross-sectional view).
As can be seen from fig. 2, the es-lispece membrane has a highly porous structure with nanofibers having an average diameter of 150 nm. es-FGPE-LiPF6The porosity and electrolyte absorption of the EC/DMC electrolyte were 81.6% and 461.9 wt.%, respectively. From FIG. 3, it can be seen that the Li-SPEEK-based nanofibers are covered by in-situ polymerization, PETEA forms a core-shell structure, and es-FGPE-LiPF is formed after a semi-interpenetrating network is constructed in the es-LiSPCE film6EC/DMC electrolyte, the mean diameter of the nanofibers increasing from 150nm to 400nm, the semi-interpenetrating network is well dispersed throughout the nanofiber membrane to strongly connect each nanofiber, and therefore, as shown in particular by l in fig. 3, the successful construction of lithium ion transport channels, benefiting from PETEA-based semi-interpenetrating networks with high ester-based dielectric constant, is successful.
Testing of es-LiSPCE membranes, es-FGPE-LiPF6Mapping images of corresponding EDX elements of S and O of EC/DMC electrolyte, the results are shown in fig. 4, and it can be seen from fig. 4 that these elements are uniformly distributed in the nanofiber membrane, indicating that continuous lithium ion transport channels are formed throughout the membrane to efficiently transport lithium ions.
Test the es-FGPE-LiPF prepared in example 16EC/DMC electrolyte and es-LiSPCE-LiPF prepared in comparative example 16Temperature-ionic conductivity graph of EC/DMC electrolyte, results are shown in figure 5. As can be seen from FIG. 5, the es-LiSPCE-LiPF is compared with pure es-LiSPCE-LiPF6EC/DMC electrolyte, es-FGPE-LiPF6The ionic conductivity of the EC/DMC electrolyte is greatly improved, and the high dielectric constant of PETEA is mainly benefited to effectively assist the rapid transfer of lithium ions.
The lithium ion transport number is one of the most important parameters of the polymer electrolyte, and is highly effective in suppressing the formation of a concentration gradient due to the reverse movement of anions during charge/discharge operations. The es-LiSPCE-LiPF prepared in example 1 was tested6The results of the migration number of lithium ions in the EC/DMC electrolyte are shown in FIG. 6, and the es-FGPE-LiPF is shown in FIG. 66The transference number of EC/DMC was 0.74.
The lithium ion transference number test method comprises the following steps: the polymer electrolyte membrane soaked with the electrolyte is clamped between two Li electrodes, a constant polarization voltage (5mV) is applied to a Li symmetrical battery, the resistance value of the system before and after the test and the change curve of the current along with the time are recorded, and the frequency range of the resistance test is 100kHz to 10 mHz. The lithium ion transport number can be calculated by:
where Δ V is the polarization voltage initially set, I0And ISIs the initial current and steady state current, R0And RSIs the initial resistance and the steady state resistance of the passivation layer on the Li electrode.
According to the following equation:
t++t-＝1
tsandtime of ion depletion layer, DappRepresents the apparent diffusion factor, Zc，C0And F and j are the cation charge number, electrolyte concentration, Faraday constant and current density, respectively. t is t-Is the anion transfer number. According to the formula, the anion migration number is reduced, namely the lithium ion migration number is increased, so that the depletion time of ions on the surface of the electrode can be effectively prolonged, the occurrence of uneven deposition of lithium ions is inhibited, and finally the growth of lithium dendrites is inhibited.
The es-FGPE-LiPF prepared in the application example 1 is used6Optical images of lithium foils after square wave constant current cycling tests with EC/DMC electrolytes assembled into symmetrical lithium cells, the results are shown in FIG. 7, and from FIG. 7, es-FGPE/LiPF6Pre-growth of lithium dendrites with EC/DMC electrolytesThe phase inhibition is confirmed by a rather uniform surface, which is similar to the surface of pure lithium foil, and the semi-interpenetrating polymer network constructed in the single-ion nanofiber membrane enables the es-FGPE membrane to be well adhered to the lithium foil, so that the Li/electrolyte interface is stabilized, and the effective inhibition of the growth of lithium dendrites is realized.
The es-FGPE-LiPF prepared in the application example 1 is used6The SEM images of the lithium foil after square-wave constant current cycle testing are shown in FIG. 8 (m and n are surface morphology graphs, and o and p are cross-sectional morphologies). The result shows that after the square wave constant current cycle test, the surface of the lithium metal still has a very smooth structure, the volume of the lithium metal electrode has no obvious change, and the growth of the lithium dendrite on the surface of the lithium metal electrode is effectively inhibited.
The es-FGPE-LiPF prepared in the application example 1 is used6EC/DMC electrolyte and es-LiSPCE/LiPF prepared in comparative example 16Assembly of-EC/DMC electrolyte into Li/LiFePO4The lithium battery was followed by Electrochemical Impedance Spectroscopy (EIS) tests, the results of which are shown in FIG. 9. As can be seen from FIG. 9, for the es-FGPE-LiPF-based6Cell of EC/DMC electrolyte this value is 118 Ω, ratio based on es-LiSPCE/LiPF6The values for the reduction in porosity and electrolyte absorption of EC/DMC electrolyte cells are more than two times lower.
Test of es-LiSPCE/LiPF in comparative example 16Composition of-EC/DMC electrolyte Li/LiFePO4Lithium cells, and the SEM images and EDS elemental maps of LiFePO4 cathode/electrolyte of the cells were tested, and the results are shown in fig. 10 (b in fig. 10 is the SEM image of the electrolyte-cathode interface, c is the EDS elemental map of P, d is the EDS elemental map of Fe, and e is the EDS elemental map of F); test of es-FGPE-LiPF in example 16Li/LiFePO of EC/DMC electrolyte composition4Lithium battery, and test battery LiFePO4SEM images and EDS elemental maps of the cathode/electrolyte, with the results shown in fig. 11 (in fig. 11, F is an SEM image of the electrolyte-cathode interface, g is an EDS elemental map of F, h is an EDS elemental map of p, and i is an EDS elemental map of Fe); wherein P is derived from LiFePO4Cathode, LiPF6Electrolyte and Li-SPEEK nano fiber, wherein F is from LiPF6Electrolyte(ii) a The results clearly show that es-LiSPCE/LiPF6The cell with-EC/DMC electrolyte has a large gap between the cathode and the es-lispece membrane, indicating loose interfacial contact, resulting in very high interfacial resistance. In contrast, LiFePO4Cathode and es-FGPE-LiPF6-the EC/DMC electrolyte is tightly connected by a three-dimensionally crosslinked semi-interpenetrating network formed. Successfully constructs the es-FGPE-LiPF-based6Enhanced interfacial compatibility in cells of EC/DMC electrolytes to achieve high performance of LMB.
The es-FGPE-LiPF prepared in example 2 was used6EC/PC electrolyte and es-LiSPCE-LiPF prepared in comparative example 26Li/LiFePO assembled separately from-EC/PC4Lithium battery, testing LiFePO at 150 ℃4the/Li battery rate performance results are shown in FIG. 12, and it can be seen from FIG. 12 that based on es-LiSPCE-LiPF6The EC/PC cell showed poor rate performance with low coulombic efficiency and a capacity of 20mAh g at 0.6C-1。
The es-FGPE-LiPF prepared in example 2 was used6EC/PC electrolyte and es-LiSPCE-LiPF prepared in comparative example 26Li/LiFePO assembled from EC/PC4Lithium batteries, and the charge/discharge curves of the batteries at 25 ℃ and 150 ℃ at 0.1C were tested, and the results are shown in fig. 13 and 14, respectively. The results show that the es-LiSPCE-LiPF is adopted under the high-temperature condition6The discharge capacity of the-EC/PC electrolyte lithium battery is obviously lower than that of the battery under the normal temperature condition, and conversely, the es-FGPE-LiPF6The high-temperature battery performance of the-EC/PC electrolyte lithium battery is obviously superior to the battery performance under the room temperature condition, which shows that the es-FGPE-EC/PC electrolyte can be applied to high temperature after crosslinking modification.
The es-FGPE-LiPF prepared in example 2 was used6Li/LiFePO assembled from EC/PC electrolyte4Lithium batteries were tested for 1C cycling performance at 150 ℃ and the results are shown in FIG. 15. As can be seen from the figure, es-FGPE-LiPF is performed at 150 ℃ and 1C6the-EC/PC electrolyte lithium battery showed 130mAh g-1The above high discharge capacity, after 100 charge/discharge cycles, has no significant decay, while having a high coulombic efficiency. Good high temperature high rateBattery formation performance benefits from enhanced electrode surface stability, excellent thermal dimensional stability and improved ionic conductivity.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A method for preparing a porous polymer electrolyte, comprising the steps of:
preparing a lithium polymer electrolyte diaphragm of sulfonated polyether-ether-ketone;
pentaerythritol tetraacrylate and an initiator are dissolved in electrolyte;
and (3) immersing the lithium polymer electrolyte membrane of the sulfonated polyether-ether-ketone into electrolyte, and carrying out in-situ polymerization to obtain the porous polymer electrolyte.
2. The method of claim 1, wherein the initiator is azobisisobutyronitrile.
3. The method of claim 1, wherein the electrolyte solution comprises a lithium salt and a solvent, and the lithium salt is LiPF6The solvent comprises EC and DMC, and the volume ratio of EC to DMC is 1: 1.
4. The preparation method of the porous polymer electrolyte as claimed in claim 1, wherein the lithium polymer electrolyte membrane of sulfonated polyether ether ketone is immersed in an electrolyte and polymerized in situ at 55-65 ℃ for 4-8 h to obtain the porous polymer electrolyte.
5. The method of preparing a porous polymer electrolyte according to claim 1, wherein the method of preparing the lithium polymer electrolyte separator of sulfonated polyetheretherketone comprises:
adding polyether-ether-ketone into concentrated sulfuric acid, stirring for 2-12 hours at the temperature of 30-80 ℃ to obtain sulfonated polyether-ether-ketone, washing, and drying for later use;
dissolving sulfonated polyether ether ketone in a lithium-containing compound, stirring for lithium exchange, filtering after the lithium exchange is finished, and washing and drying filter residues to obtain sulfonated polyether ether ketone lithium;
adding sulfonated lithium polyetheretherketone into N, N-dimethylformamide, preparing a solution with the concentration of 28-30 wt%, heating, stirring and dissolving, and cooling to obtain a spinning solution;
and (3) placing the spinning solution in an instrument, and setting parameters for spinning to obtain the sulfonated polyether-ether-ketone lithium polymer electrolyte membrane.
6. The method of claim 5, wherein the lithium-containing compound is lithium hydroxide or lithium hydride.
7. The method for preparing a porous polymer electrolyte according to claim 5, wherein the lithium polymer electrolyte separator of sulfonated polyetheretherketone is a porous membrane or a dense membrane.
8. The method for preparing a porous polymer electrolyte according to claim 5, wherein the porous membrane is prepared by applying nano SiO2Mixing the particles with sulfonated lithium polyetheretherketone, forming a film by solution casting, and washing off SiO with HF2Particles, and the obtained porous sulfonated polyether ether ketone lithium polymer electrolyte membrane.
9. A porous polymer electrolyte prepared by the method according to any one of claims 1 to 8.
10. A lithium metal battery comprising the porous polymer electrolyte of claim 9.
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