阅读说明：本技术 一种电化学储能聚合物电解质及制备方法 (Electrochemical energy storage polymer electrolyte and preparation method thereof ) 是由 张楚璠 付春 贾凤 孔京 黄伟 陈琛 于 2020-05-27 设计创作，主要内容包括：本发明公开了一种电化学储能聚合物电解质及制备方法。其组成包括聚合物、电解质锂盐、离子液体、固体氧化物、引发剂和螯合剂,聚合物均匀度好、机械强度佳、离子电导率高。该发明中的聚合物电解质含有FSI-、TFSI-、PFSI-阴离子的离子液体的加入提高了聚合物电解质的阻燃性、热稳定性及电化学稳定性,锂盐LiFSI、LiTFSI、LiPFSI的加入提高了离子电导率。螯合剂有助于离子液体和锂盐较为均匀地分散在聚合物立体骨架结构中,有利于提高聚合物电解质的离子传输效率,同时体系的均匀度和制备聚合物电解质的一致性也得到提高。(The invention discloses an electrochemical energy storage polymer electrolyte and a preparation method thereof. The lithium ion battery electrolyte comprises a polymer, electrolyte lithium salt, ionic liquid, solid oxide, an initiator and a chelating agent, and the polymer has good uniformity, good mechanical strength and high ionic conductivity. The polymer electrolyte in the invention contains ionic liquid of FSI-, TFSI-and PFSI-anions, so that the flame retardance, the thermal stability and the electrochemical stability of the polymer electrolyte are improved, and the ionic conductivity is improved by adding lithium salt LiFSI, LiTFSI and LiPFSI. The chelating agent helps the ionic liquid and the lithium salt to be uniformly dispersed in the polymer three-dimensional skeleton structure, is beneficial to improving the ion transmission efficiency of the polymer electrolyte, and simultaneously improves the uniformity of the system and the consistency of the prepared polymer electrolyte.)

1. An electrochemical energy storage polymer electrolyte, characterized in that: comprises ionic liquid, lithium salt, polymer, inorganic oxide, initiator and chelating agent; the anion of the ionic liquid is bis (trifluoromethyl) sulfonyl imide (TFSI-) or bis (fluoro) sulfonyl imide (FSI-) or bis (pentafluorophenyl) sulfonyl imide anion (PFSI)^-) The structure is as follows:

bis (trifluoromethyl) sulfonimide (TFSI)^-）

Bis (fluorosulfonyl) imide (FSI)^-）

Bis-pentafluorophenyl sulfonimide anion (PFSI)^-）

The cation in the structure is selected from imidazole, pyrrolidine and piperidine, and the structural general formula is as follows:

in the structure, R1 and R2 are alkyl groups having 1-5 carbon atoms.

2. An electrochemical energy storage polymer electrolyte according to claim 1, wherein: the anion of the lithium salt is the corresponding anion of the ionic liquid.

3. An electrochemical energy storage polymer electrolyte according to claim 1, wherein: the polymer is formed by polymerizing a monomer, wherein the monomer is one or more of vinylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl methacrylate, vinylidene fluoride, hexafluoropropylene, gamma-butyrolactone, epsilon-caprolactone, ethylene glycol diacrylate and glycerol triacrylate.

4. An electrochemical energy storage polymer electrolyte according to claim 1, wherein: the inorganic oxide is one or more of silicon dioxide, aluminum oxide and titanium dioxide.

5. An electrochemical energy storage polymer electrolyte according to claim 1, wherein: the initiator is one or more of dibenzoyl peroxide, azobisisobutyronitrile, dimethyl azobisisobutyrate and boron trifluoride; the chelating agent is one or more of citric acid, EDTA and tartaric acid.

6. A method of preparing an electrochemical energy storage polymer electrolyte as claimed in any one of claims 1 to 5, wherein: the preparation method comprises the following steps:

s1: firstly, dissolving a polymer monomer in a solvent, and mixing at 30-60 ℃ until the mixture is uniform;

s2: adding the ionic liquid, the lithium salt, the inorganic solid oxide, the initiator and the chelating agent into the system, stirring at the temperature of 60-120 ℃, and keeping the temperature for 6-12 hours;

s3: excess solvent was removed by rotary evaporation.

7. A method of preparing an electrochemical energy storage polymer electrolyte as claimed in claim 6, wherein: the concentration of the lithium salt is 0.5-2 mol/L.

8. A method of preparing an electrochemical energy storage polymer electrolyte as claimed in claim 6, wherein: the inorganic solid oxide accounts for 0.1-10% of the total mass of the electrolyte.

9. An electrochemical energy storage polymer electrolyte and method of making the same according to claim 6, wherein: the initiator accounts for 0.1-5% of the total mass of the electrolyte.

10. An electrochemical energy storage polymer electrolyte and method of making the same according to claim 6, wherein: the chelating agent accounts for 1-5% of the total mass of the electrolyte.

Technical Field

The invention relates to an electrochemical energy storage polymer electrolyte and a preparation method thereof, belonging to the technical field of lithium ion batteries.

Background

In the last two decades, with the development of technology and the further upgrading of demand, the market has given a higher expectation for high performance, in particular high safety, lithium ion batteries. Most of the current marketable power batteries are liquid flow lithium ion batteries, and the traditional batteries are limited in further improving energy density and ensuring safety. Since the redox flow battery is prone to performance attenuation defects such as capacity diving and failure, and even has the problems of safety accidents such as overheating and explosion, the novel electrode material is difficult to apply, and therefore research and development and industrialization of the novel battery need to be accelerated. Solid-state batteries are known as next-generation batteries, and are distinguished from conventional lithium ion batteries in that electrolytes are solid-state materials, which can be mainly classified into polymers, oxides, sulfides, and the like. Solid-state batteries are generally regarded as good due to the development of conventional lithium ion batteries that encounter bottlenecks such as safety, energy density limitations, and the like.

The development and application of a new system battery are rapid, and the energy density of the lithium air battery, the lithium sulfur battery and the solid-state battery respectively reaches 700 Wh/kg, 500 Wh/kg and nearly 300 Wh/kg at present. The energy density of the solid-state battery is high, the energy density is improved by more than one time compared with the best lithium battery at present, the endurance mileage of the electric vehicle can be improved from 256 miles to 480 miles, and the price is cheaper and is 100 dollars per kilowatt hour. Because the electrolyte does not contain liquid electrolyte, additional cooling devices, electronic controls and the like are not needed, and the weight can be effectively reduced. Among them, the polymer all-solid-state battery has advantages of light weight, good viscoelasticity, good film forming property, good electrochemical and chemical stability, high lithium ion migration number and the like, and is developed rapidly, so that the polymer all-solid-state battery is applied to electric vehicles by existing enterprises. There are problems such as interfacial resistance or stress of the electrode and the electrolyte, stability of the electrolyte, application temperature, electrochemical window, and conductivity limitation, which prevent the industrial application and further popularization of the solid polymer battery. Therefore, the development of solid electrolytes that can be used in a wide temperature range and have higher conductivity and electrochemical stability has been a hot research direction. Research has shown that adding trace amount of liquid electrolyte, such as solvent or ionic liquid, preparing gel electrolyte, etc. can help to take account of conductivity, interface and safety and obtain a feasible solution.

Researchers uniformly mix polymer monomers, an initiator, lithium salt and the like according to a certain proportion and then assemble a battery, polymerization is initiated under certain external conditions (such as thermal initiation, light initiation, gamma rays and the like), and the monomers are polymerized to obtain the electrolyte with a three-dimensional framework structure. However, due to the factors of non-uniform action of external conditions, thermal effect of polymerization process and the like in the in-situ polymerization process, the in-situ polymerized electrolyte has the challenges of consistency, safety and the like.

The ionic liquid electrolyte is conductive molten salt, has the advantages of no saturated vapor pressure, wide electrochemical window and good electrochemical stability, and has wide application prospect in the electrochemical fields of lithium batteries, super capacitors, electrochemical sensors, energy storage and the like. The ionic liquid is used as an additive or a main component of a solid electrolyte by utilizing the advantages of difficult combustion, weak volatility, good stability, wide liquid range, good conductivity, wide electrochemical window and the like of the ionic liquid, so that the working temperature range of the constructed battery can be widened, the problem of contact between an electrode and an electrolyte interface is solved, the electrochemical stability is better compared with other liquid electrolytes, the explosion-proof performance and the flame retardant performance are obviously improved, the safety performance is better, the development direction of the future lithium battery industry is met, and the ionic liquid has a wide application prospect.

In order to further balance the mechanical properties of the solid electrolyte and maintain the structure of the gel solid polymer, the mechanical properties can be enhanced by adding solid particles, and it has been reported in the literature that the solid particles may contribute to the reduction of crystallization of the solid electrolyte and the reduction of the inhibition of molecular chain motion due to crystallization.

In addition, the uniformity of the polymer electrolyte system may be poor during polymerization and post-treatment, and thus the use of a chelating or complexing agent as a "dispersant" would be beneficial to improve the uniformity of the system and the consistency of the polymer electrolyte preparation.

Disclosure of Invention

The invention aims to provide an electrochemical energy storage polymer electrolyte and a preparation method thereof, and the polymer electrolyte which takes a polymer, an ionic liquid and a lithium salt as main components and has good mechanical strength and high ionic conductivity is prepared.

An electrochemical energy storage polymer electrolyte and a preparation method thereof are characterized in that: comprises ionic liquid, lithium salt, polymer, inorganic oxide, initiator and chelating agent; the anion of the ionic liquid is bis (trifluoromethyl) sulfonyl imide (TFSI-) or bis (fluoro) sulfonyl imide (FSI-) or bis (pentafluorophenyl) sulfonylImine anion (PFSI)^-) The structure is as follows:

bis (trifluoromethyl) sulfonimide (TFSI)^-）

Bis (fluorosulfonyl) imide (FSI)^-）

Bis-pentafluorophenyl sulfonimide anion (PFSI)^-）

The cation in the structure is selected from imidazole, pyrrolidine and piperidine, and the structural general formula is as follows:

in the structure, R1 and R2 are alkyl groups having 1-5 carbon atoms.

And the anion of the lithium salt is the corresponding anion of the ionic liquid.

The polymer is formed by polymerizing the monomer, wherein the monomer is one or more of vinylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl methacrylate, vinylidene fluoride, hexafluoropropylene, gamma-butyrolactone, epsilon-caprolactone, ethylene glycol diacrylate and glycerol triacrylate.

The inorganic oxide is one or more of silicon dioxide, aluminum oxide and titanium dioxide.

The initiator is one or more of dibenzoyl peroxide, azobisisobutyronitrile, dimethyl azobisisobutyrate and boron trifluoride.

The chelating agent is one or more of citric acid, EDTA and tartaric acid.

Further, the preparation method of the polymer is as follows:

s1: firstly, dissolving a polymer monomer in a solvent, and mixing at 30-60 ℃ until the mixture is uniform;

s2: adding the ionic liquid, the lithium salt, the inorganic solid oxide, the initiator and the chelating agent into the system, stirring at the temperature of 60-120 ℃, and keeping the temperature for 6-12 hours;

s3: excess solvent was removed by rotary evaporation.

Further, the concentration of the lithium salt is 0.5-2 mol/L.

Further, the proportion of the inorganic solid oxide in the total mass of the electrolyte is 0.1-10%.

Further, the initiator accounts for 0.1-5% of the total mass of the electrolyte.

Further, the chelating agent accounts for 1-5% of the total mass of the electrolyte.

Has the advantages that:

the invention provides an electrochemical energy storage polymer electrolyte and a preparation method thereof, which contains FSI^-、TFSI^-、PFSI^-The addition of the anionic ionic liquid improves the flame retardance, the thermal stability and the electrochemical stability of the polymer electrolyte, and the addition of the lithium salt LiFSI, LiTFSI and LiPFSI can also improve the current efficiency. Meanwhile, the complex chelating agent is added in the polymerization stage, so that the ionic liquid and the lithium salt can be uniformly dispersed in the polymer three-dimensional skeleton structure, and the improvement of the ion transmission efficiency of the polymer electrolyte is facilitated. The chelating agent is also beneficial to improving the uniformity of the system and the consistency of the prepared polymer electrolyte.

Detailed Description

The present invention is described in detail by the following examples, which should not be construed as limiting the scope of the invention.

Example 1

An electrochemical energy storage polymer electrolyte and a preparation method thereof, wherein ethylene carbonate and propylene glycol dipropionate are selected as polymer monomers (the monomer ratio is 1: 1), and the monomers are dissolved in N-methyl pyrrolidone at 60 ℃; electrolyte lithium salt LiFSI (1 mol/L), ionic liquid EMImFSI (2 mol/L, structure shown below), silicon dioxide (content 3%), dibenzoyl peroxide (content 0.5%) and citric acid (content 5%) are added into the system, and the system is heated for 12 hours at 80 ℃; finally, the excess solvent was removed by rotary evaporation at 100 ℃.

EMimFSI

The conductivity test method adopts a traditional casting method, and then the lithium iron phosphate is loaded into a button cell, and a commercial lithium iron phosphate pole piece and a lithium piece are taken as electrodes for conductivity test. The ionic conductivity at 30 ℃ was found to be 3.4X 10^-3。

Example 2

An electrochemical energy-storage polymer electrolyte and a preparation method thereof, wherein methyl ethyl carbonate and methyl methacrylate are selected as polymer monomers (the monomer ratio is 1.5: 1), and the monomers are dissolved in N-methyl pyrrolidone at 60 ℃; adding electrolyte lithium salt LiPFSI (1 mol/L), ionic liquid MMimPFSI (1.5 mol/L, structure shown below), titanium dioxide (content 3%), azodiisobutyronitrile (content 2.5%) and EDTA (content 2%) into the system, and heating at 80 ℃ for 10 h; finally, the excess solvent was removed by rotary evaporation at 100 ℃.

The conductivity test method adopts a traditional casting method, and then the lithium iron phosphate is loaded into a button cell, and a commercial lithium iron phosphate pole piece and a lithium piece are taken as electrodes for conductivity test. The ionic conductivity at 30 ℃ was found to be 2.6X 10^-3。

Example 3

An electrochemical energy storage polymer electrolyte and a preparation method thereof, vinylidene fluoride and hexafluoropropylene are selected as polymer monomers (the monomer ratio is 1: 1), and the monomers are dissolved in N methyl pyrrolidone at the temperature of 80 ℃; electrolyte lithium salt LiPFSI (2 mol/L), ionic liquid PYR13TFSI (1.5 mol/L, structure shown below), aluminum oxide (content 5%), dimethyl azodiisobutyrate (content 1.5%), tartaric acid (content 5%) are added into the system, and the system is heated for 8 hours at 90 ℃; finally, the excess solvent was removed by rotary evaporation at 100 ℃.

The conductivity test method adopts a traditional casting method, and then the lithium iron phosphate is loaded into a button cell, and a commercial lithium iron phosphate pole piece and a lithium piece are taken as electrodes for conductivity test. The ionic conductivity at 30 ℃ was found to be 5.2X 10^-3。

Example 4

An electrochemical energy-storage polymer electrolyte and a preparation method thereof, wherein glycerol triacrylate, methyl methacrylate and epsilon-caprolactone are selected as polymer monomers (the monomer ratio is 2.2:1: 0.6), and the monomers are dissolved in N-methyl pyrrolidone at the temperature of 80 ℃; electrolyte lithium salt LiPFSI (1.5 mol/L), ionic liquid PYR22TFSI (1.5 mol/L, structure as follows), silicon dioxide (content 2.5%), dimethyl azodiisobutyrate (content 1.5%), and citric acid (content 5%) are added into the system and heated at 80 ℃ for 8 h; finally, the excess solvent was removed by rotary evaporation at 100 ℃.

The conductivity test method adopts a traditional casting method, and then the lithium iron phosphate is loaded into a button cell, and a commercial lithium iron phosphate pole piece and a lithium piece are taken as electrodes for conductivity test. The ionic conductivity at 30 ℃ was measured to be 4.6X 10^-3。

Example 5

An electrochemical energy-storage polymer electrolyte and a preparation method thereof, wherein ethylene glycol diacrylate, methyl methacrylate and gamma-butyrolactone are selected as polymer monomers (the monomer ratio is 2:1.8: 0.2), and the monomers are dissolved in N-methyl pyrrolidone at 100 ℃; electrolyte lithium salt LiPFSI (2 mol/L), ionic liquid PP13FSI (1.5 mol/L, structure as follows), silicon dioxide, aluminium oxide (content is 1%, 1.5% respectively), dibenzoyl peroxide (content is 1%), citric acid (content is 3%) are added into the system, and heating is carried out for 8h at 80 ℃; finally, the excess solvent was removed by rotary evaporation at 100 ℃.

The conductivity test method adopts a traditional casting method, and then the lithium iron phosphate is loaded into a button cell, and a commercial lithium iron phosphate pole piece and a lithium piece are taken as electrodes for conductivity test. The ionic conductivity at 30 ℃ was measured to be 4.1X 10^-3。

Example 6

An electrochemical energy-storage polymer electrolyte and a preparation method thereof, diethyl carbonate, methyl methacrylate and ethylene sulfite are selected as polymer monomers (the monomer ratio is 2:1: 1), and the monomers are dissolved in N-methyl pyrrolidone at 100 ℃; electrolyte lithium salt LiPFSI (2 mol/L), ionic liquid PP14PFSI (1.5 mol/L, structure as follows), silicon dioxide, titanium dioxide (content is 1 percent respectively), dibenzoyl peroxide (content is 1 percent), citric acid (content is 3 percent) are added into the system, and the system is heated for 8 hours at 80 ℃; finally, the excess solvent was removed by rotary evaporation at 100 ℃.

The conductivity test method adopts a traditional casting method, and then the lithium iron phosphate is loaded into a button cell, and a commercial lithium iron phosphate pole piece and a lithium piece are taken as electrodes for conductivity test. The ionic conductivity at 30 ℃ was measured to be 4.1X 10^-3。

Example 7

An electrochemical energy-storage polymer electrolyte and a preparation method thereof, dimethyl carbonate and methyl methacrylate are selected as polymer monomers (the monomer ratio is 1: 1), and the monomers are dissolved in N methyl pyrrolidone at 100 ℃; electrolyte lithium salt LiFSI (2 mol/L), ionic liquid PP14FSI (2 mol/L, structure shown below), titanium dioxide (content is 1.5 percent respectively), dibenzoyl peroxide (content is 1 percent), tartaric acid (content is 2.5 percent) are added into the system, and the system is heated for 8 hours at 80 ℃; finally, the excess solvent was removed by rotary evaporation at 100 ℃.

The conductivity test method adopts a traditional casting method, and then the lithium iron phosphate is loaded into a button cell, and a commercial lithium iron phosphate pole piece and a lithium piece are taken as electrodes for conductivity test. The ionic conductivity at 30 ℃ was measured to be 4.8X 10^-3。

Comparative example

The difference from example 1 is that:

the ionic liquid and the chelating agent were not used, and the others were the same. The ionic conductivity was measured to be 2.0X 10^-3。