CN101407625A

CN101407625A - Hyperbranched polyether type solid polymer elecrolytes and preparation thereof

Info

Publication number: CN101407625A
Application number: CNA2008101824130A
Authority: CN
Inventors: 吴锋; 冯婷; 吴川; 白莹
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2008-12-05
Filing date: 2008-12-05
Publication date: 2009-04-15
Anticipated expiration: 2028-12-05
Also published as: CN101407625B

Abstract

本发明涉及一种超支化聚醚型固体聚合物电解质及其制备方法。这种聚合物电解质材料包括聚合物基质材料(A)和聚合物基质材料(B)，锂盐(C)。聚合物基质材料A是含有醚氧基团的具有完全无定形结构的超支化聚醚，聚合物基质材料B是具有优良机械性能的聚合物基质材料。这种固体聚合物电解质膜通过挥发溶剂一步法制得，其制备工艺简便，具有较高的离子电导率和电化学稳定性，并具有良好的机械性能和热稳定性，可应用于二次锂离子电池制备。The invention relates to a hyperbranched polyether solid polymer electrolyte and a preparation method thereof. This polymer electrolyte material includes polymer matrix material (A) and polymer matrix material (B), lithium salt (C). The polymer matrix material A is a hyperbranched polyether with a completely amorphous structure containing ether oxygen groups, and the polymer matrix material B is a polymer matrix material with excellent mechanical properties. This solid polymer electrolyte membrane is prepared by a one-step method of volatile solvent. Its preparation process is simple, it has high ionic conductivity and electrochemical stability, and has good mechanical properties and thermal stability. It can be applied to secondary lithium ion Cell preparation.

Description

A kind of hyperbranched polyether type solid polymer elecrolytes and preparation method thereof

Technical field

The present invention relates to a kind ofly can be applied to solid polymer electrolyte of lithium ion battery and preparation method thereof, especially relate to a kind of hyperbranched polyether type solid polymer elecrolytes material and preparation method thereof.

Background technology

Copolymer solid electrolyte, promptly has the ionic conduction ability, high-molecular complex by superpolymer and inorganic salt generation, have good reliability, do not have characteristics such as leakage, easy-formation, and keeping high molecular essential characteristic, its application aspect lithium ion battery has caused people's extensive concern, and Chinese scholars has been launched in succession to the electrolytical research work of new polymers.The more polymer electrolyte system of research mainly contains several big classes such as PEO, PAN, PMMA, PVDF, PVC at present, and wherein, electrolyte system polyoxyethylene (PEO) receives much concern all the time owing to have the constitutional features of the ionic conduction of being easy to.Yet the polymer dielectric that traditional PEO system and an alkali metal salt form has higher crystallization phases when room temperature, the electrolytical room-temperature conductivity that forms low excessively, thereby limit its practical application.

In the solid polymer electrolyte system, two kinds of effective ways that are commonly used to improve specific conductivity are the second-order transition temperatures that suppress crystallization and reduce polymkeric substance.Thereby the polyethers that research has highly branched structure can effectively prevent the segmental crystallization, reduces second-order transition temperature.But when polyethers system degree of crystallinity reduced, its mechanical property also was damaged, can't the self-supporting film forming, be unfavorable for that the mechanics of dielectric film is stable.Comparing, have the good mechanical performance though PVDF, PAN, PMMA etc. have the polymer electrolyte of better mechanical property, is that the specific conductivity of solid polymer electrolyte of matrix is often too low with it, can't reach application requiring.

As mentioned above, a major issue that develops the solid polymer electrolyte system at present is to solve the contradiction between mechanical property and the ionic conductivity.

Summary of the invention

The objective of the invention is in order to solve the contradictory problems between the mechanical property and ionic conductivity in the solid polymer electrolyte system, and hyperbranched type polyethers solid polymer electrolyte of a kind of ionic conductivity height, good mechanical property, Heat stability is good, stable electrochemical property and preparation method thereof is provided.

Hyperbranched polyether type solid polymer elecrolytes of the present invention comprises a kind of hyperbranched polyether A, conduct with lower glass transition temperatures and high conductivity and supports mutually matrix material B and electric conducting lithium salt C.Wherein, A and B constitute the matrix system of polymer dielectric, and its quality proportioning is 1: 3～3: 1; Lithium salts C accounts for 5%～50% of hyperbranched polyether type solid polymer elecrolytes total mass.

In above-mentioned solid polymer electrolyte, described polymer electrolyte matrices material B is polyvinylidene difluoride (PVDF) (PVDF), polyvinylidene difluoride (PVDF)-R 1216 (brief note is PVDF-HFP), polyethylene terephthalate (PET) and derivative thereof, polyacrylonitrile (brief note is PAN), polymethylmethacrylate (brief note is PMMA), polyvinyl chloride (brief note is PVC), polyvinyl alcohol (PVA), polyvinyl butyral acetal (PVB), polyoxybutylene, polymeric amide, polyacrylamide, polyvinyl acetate, polyvinylpyrrolidone, poly-diacrylate Tetraglycol 99 ester, polysulfones, any or several in the polysiloxane series.Described lithium salts C comprises any or several in two (sulphonyl) imines lithiums of lithium perchlorate, lithium hexafluoro phosphate, LiBF4, trifluoromethyl sulfonic acid lithium, two (trifluoromethyl sulphonyl) imines lithium, two second dioxalic acid lithium tetraborate, fluoro Lithium bis (oxalate) borate, two (polyfluoro alkoxyl group sulphonyl) imines lithium, ring-type perfluoroalkyl, three (trifluoromethyl sulphonyl) lithium methide.

A kind of method for preparing hyperbranched polyether type solid polymer elecrolytes of the present invention, concrete steps are as follows:

(1) with 3-(2-hydroxyl triethoxy)-3 '-methyl trimethylene oxide as repeating unit, with BF ₃Ether is as initiator, and polymerization makes the hyperbranched polyether A that a class does not contain phenyl ring;

(2) hyperbranched polyether A, matrix material B and lithium salts are carried out drying;

(3) getting hyperbranched polyether A and matrix material B is 1: 3～3: 1 according to mass ratio, with the tetrahydrofuran (THF) dissolving, is stirred to evenly, makes the polymer electrolyte matrices system;

(4) in the described matrix system of step (3), add the lithium salts C that accounts for hyperbranched polyether type solid polymer elecrolytes total mass 5%～50%, be stirred well to evenly;

(5) above-mentioned solution is watered on the flat board, evaporating solvent, dry under 50～100 ℃ of conditions then, promptly make the solid polymer electrolyte that is used for lithium ion battery.

The present invention also is applied to prepared hyperbranched polyether type solid polymer elecrolytes in the lithium ion battery, the test proof, prepared solid polymer electrolyte has higher ionic conductivity, good mechanical property, Heat stability is good, stable electrochemical property.

Beneficial effect

The present invention is by carrying out blend to hyperbranched type polyethers with complete amorphous structure and the matrix material with good mechanical properties, and carries out compositely with lithium salts, makes solid polymer electrolyte.Because hyperbranched polyether A has complete unbodied structure, and has highly branched structure, can effectively prevent the segmental crystallization; And its molecular conformation almost spherical has effectively increased the free volume of polymkeric substance, helps sub-chain motion, effectively reduces second-order transition temperature, makes prepared solid polymer electrolyte have higher ionic conductivity, and room temperature can reach 1 * 10 ^-4More than the S/cm.Simultaneously,, make prepared solid polymer electrolyte also have the good mechanical performance, have excellent self-supporting effect because selected matrix material such as PVDF-HFP, PET have excellent mechanical property.Proof after tested, prepared solid polymer electrolyte has higher ionic conductivity, and its good mechanical property, Heat stability is good, stable electrochemical property.

Description of drawings

Fig. 1 prepares the XRD figure of sample for press embodiment 1: (a)-PVDF-HFP wherein; (b)-polyethers A/PVDF-HFP matrix system (mass ratio is 2: 1);

Fig. 2 is for pressing the specific conductivity curve of polyethers A/PVDF-HFP/LiTFSI polymer dielectric under differing temps of embodiment 1 preparation;

Fig. 3 presses the PVDF-HFP of embodiment 1 preparation and the TGA curve of polyethers A/PVDF-HFP/LiTFSI polymer dielectric;

Fig. 4 presses the polyethers A of embodiment 1 preparation and the DSC curve of polyethers A/PVDF-HFP/LiTFSI polymer dielectric;

Fig. 5 is temperature and the conductivity relation figure that presses the polyethers A/PET/LiTFSI polymer dielectric (Different L iTFSI content) of embodiment 2 preparations;

Fig. 6 is the multiplying power discharging curve that adopts the lithium ion battery of solid polymer electrolyte assembling among the embodiment 2;

Wherein, PVDF-HFP is the abbreviation of poly-(biasfluoroethylene-hexafluoropropylene); LiTFSI is the abbreviation of two (trifluoromethyl sulphonyl) imines lithium; PET is the abbreviation of polyethylene terephthalate; σ represents specific conductivity; T _gThe expression second-order transition temperature.

Embodiment

The present invention will be further described below in conjunction with drawings and Examples:

Embodiment 1

Present embodiment 1 used polymer electrolyte matrices materials A is to be repeating unit (having following structure) with ionic conduction group monomer structure 3-(2-hydroxyl triethoxy)-3 '-methyl trimethylene oxide:

With BF ₃Ether is as initiator, and polymerization makes the hyperbranched polyether A that a class does not contain phenyl ring, and its weight-average molecular weight is 10000; Used polymer electrolyte matrices material B is PVDF-HFP for poly-(biasfluoroethylene-hexafluoropropylene) brief note; Lithium salts C selects two (trifluoromethyl sulphonyl) imines lithium, notes by abridging to be LiTFSI.All raw materials are process vacuum-drying before using.With hyperbranched polyether (brief note for polyethers A) with to gather (biasfluoroethylene-hexafluoropropylene) be respectively to get a certain amount of at 2: 1 according to mass ratio (PVDF-HFP), dissolve with tetrahydrofuran (THF), be stirred to evenly, add mass percent then and be 20% LiTFSI (mass percent is calculated according to the total mass of solid polymer electrolyte), continue to be stirred to lithium salts and in solution, be evenly distributed.With this solution casting in polytetrafluoroethyldisk disk, evaporating solvent, 50 ℃ of dry 18h in vacuum drying oven then, prepared electrolytical thickness is about 1.5mm.Prepared sample is carried out: XRD (Fig. 1) test analysis, the XRD test is carried out on Rigaku Dmax-2400 type X-ray diffractometer to obtain the structural information of polymer dielectric film, the research parameter is: the Cu/K alpha-ray, λ=0.15406nm, voltage 40kV, electric current 100mA, 8 °/min of sweep velocity, 10 °-90 ° of sweep limits.Thermal performance test (Fig. 2, Fig. 3), the thermostability of solid polymer electrolyte is by DSC test and TGA test analysis, the NetzschPC-200 differential scanning calorimeter is adopted in the DSC test, use nitrogen protection, sudden colder to eliminate thermal history after heating up earlier, the proper testing temperature rise rate is 10 ℃/min; TGA2000 type thermogravimetric analyzer is adopted in the TGA test, and heat-up rate is 20 ℃/min, nitrogen protection.The test of ionic conductivity σ (Fig. 4) is measured as follows, adopt the obstructive type battery to form stainless steel/solid polymer electrolyte/stainless steel system, by electrochemical workstation (CHI660A, Shanghai occasion China instrument company) finishes, adopt ac impedance technology, in the ionic conductivity of 303～353K temperature range build-in test system, range of frequency 10～10 ⁵Hz.

Embodiment 2

To prepare polymer dielectric as embodiment 1 identical mode, difference is, matrix material B selects the PET material of better mechanical property for use, is respectively to get a certain amount of at 1: 3 with hyperbranched type polyethers (polyethers A) and polyethylene terephthalate (PET) according to mass ratio, dissolve with tetrahydrofuran (THF), be stirred to evenly, add the LiTFSI (mass percent is calculated according to the total mass of polymer dielectric film) of different mass per-cent then respectively, continue to be stirred to lithium salts and in solution, be evenly distributed.With this solution casting in the poly tetrafluoroethylene tool, evaporating solvent, 50 ℃ of dry 18h in vacuum drying oven then.

The solid polymer electrolyte (SPE) of preparation gained is clipped between two stainless steels (SS) electrode, forms the SS/SPE/SS battery, test its ionic conductivity prepared sample is carried out ionic conductivity (Fig. 5).Use prepared solid polymer electrolyte as dielectric film, the lithium sheet metal is as negative pole, iron lithium phosphate (LiFePO ₄) as anodal, (as glove box) assembling becomes lithium-ion secondary cell under the exsiccant environment, and it is carried out the charge and discharge cycles test, charging stopping potential 4.5V, discharge cut-off voltage 2.5V is under the room temperature, with 0.3,1 and the 2C current discharge, its multiplying power discharging curve is seen accompanying drawing 6 respectively.

Claims

1. a hyperbranched polyether type solid polymer electrolyte is characterized in that it comprises:

(1) a kind of hyperbranched polyether A with low glass transition temperature and high electrical conductivity;

(2) polymer matrix material B as a support phase; and

(3) conductive lithium salt C;

Among them, A and B constitute the matrix system of the polymer electrolyte, and their mass ratio is 1:3-3:1; the lithium salt C accounts for 5%-50% of the total mass of the hyperbranched polyether solid polymer electrolyte.

2. A kind of hyperbranched polyether type solid polymer electrolyte according to claim 1, it is characterized in that: solid polymer electrolyte matrix material B is selected from polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyparaffin Ethylene glycol phthalate and its derivatives, polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, polyoxybutylene, polyamide, polyacrylamide, Any one or more of polyvinyl acetate, polyvinylpyrrolidone, polytetraethylene glycol diacrylate, polysulfone, polysiloxane.

3. A kind of hyperbranched polyether type solid polymer electrolyte according to claim 1, is characterized in that: wherein lithium salt C comprises lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, Lithium bis(trifluoromethylsulfonyl)imide, lithium bisethylene dioxalate borate, lithium fluorooxalate borate, lithium bis(polyfluoroalkoxysulfonyl)imide, cyclic perfluoroalkylbis(sulfonyl ) any one or more of lithium imide and tris(trifluoromethylsulfonyl)methyllithium.

4. a preparation method of hyperbranched polyether type solid polymer electrolyte, is characterized in that comprising the following steps:

(1) With 3-(2-hydroxytriethoxy)-3'-methyloxetane as the repeating unit and BF ₃ ·ether as the initiator, a class of hyperbranched benzene ring-free Polyether A;

(2) drying hyperbranched polyether A, polymer matrix material B and lithium salt;

(3) Take the hyperbranched polyether A and the polymer matrix material B according to the mass ratio of 1:3 to 3:1, dissolve them in tetrahydrofuran, stir until uniform, and prepare the polymer electrolyte matrix system;

(4) In the matrix system described in step (3), add lithium salt C accounting for 5% to 50% of the total mass of the hyperbranched polyether solid polymer electrolyte, and fully stir until uniform;

(5) pour the above solution on a flat plate, evaporate the solvent, and then dry it at 50-100° C. to prepare a hyperbranched polyether solid polymer electrolyte.

5. the application of a kind of hyperbranched polyether type solid polymer electrolyte according to claim 1 is characterized in that: it is applied in the lithium ion battery.