WO2020107857A1

WO2020107857A1 - Method for preparing solid polymer electrolyte and solid secondary battery using same

Info

Publication number: WO2020107857A1
Application number: PCT/CN2019/090624
Authority: WO
Inventors: 韦伟峰; 马骋; 陈敏健
Original assignee: 中南大学
Priority date: 2018-11-26
Filing date: 2019-06-11
Publication date: 2020-06-04
Also published as: CN109546212B; CN109546212A

Abstract

Disclosed is a method for preparing a solid polymer electrolyte and the use thereof in a secondary battery. The solid polymer electrolyte is obtained by injecting a precursor solution containing a boron heterocyclic ring-containing alkene monomer, an alkene carbonic ester polymer monomer, a metal salt and an initiator into a porous support material, and subjecting same to an in situ polymerization reaction by means of heat, microwaves, etc. An ester group, an ether oxygen and a boron-containing functional group in the solid polymer electrolyte prepared in the present invention can produce a strong interaction with an alkali metal salt, so that microscopic movement of chain segments, the dissociation degree of the alkali metal salt, and non-uniform distribution of ions in the electrolyte are improved, and a higher ionic conductivity and ion migration number are obtained. Furthermore, by means of the in situ polymerization method, the compatibility and stability of an electrolyte/electrode heterogeneous interface are improved, thereby resulting in a better effect on the protection of the material of a negative electrode. Same can be applied to a multi-scale flexible energy storage device and can achieve a superior cycle stability and a high safety.

Description

Preparation method of solid polymer electrolyte and solid secondary battery

Technical field

The invention relates to a method for preparing a secondary battery electrolyte and a secondary battery, in particular to a method for preparing a solid polymer electrolyte and a solid secondary battery.

Background technique

As an important part of the new secondary battery, the electrolyte not only controls the internal ion transport dynamics of the battery, but also fundamentally determines the working mechanism of the battery, affecting the specific energy of the battery, rate charge and discharge performance, cycle life, safety performance and Production costs, etc. The traditional organic liquid electrolyte is volatile, flammable, and explosive, which is the root cause of poor safety performance of secondary batteries. The intrinsic brittleness of the inorganic solid electrolyte is large, and the heterogeneous interface with the electrode material is difficult to control, and it shows a high interface impedance, which cannot cope with the complex application environment of secondary batteries. The all-solid polymer electrolyte is light in weight, easy to form a film, and has good viscoelasticity. It is also very good in improving the energy density of the battery, widening the operating temperature range, extending the service life, improving safety performance, and versatile structure and shape design flexibility. It has great advantages, but its room temperature ionic conductivity is still low (<10 ^-4 S/cm), and the stability of the electrolyte/electrode heterogeneous interface is poor, resulting in a decrease in the recycling rate of electrode materials.

Summary of the invention

The present invention aims to provide a method for preparing a solid polymer electrolyte with greatly improved room temperature ion conductivity, and a solid secondary battery using the polymer electrolyte and a method for preparing the same. The present invention is achieved by the following scheme.

A method for preparing a solid polymer electrolyte includes the following steps:

(I) In an environment with a protective atmosphere and a water content and an oxygen content of less than 1 ppm, mix the ethylenic boron monomer, ethylenic carbonate monomer, metal salt and radical initiator compound to obtain a precursor solution; The metal salt is selected from one or more of alkali metal salt, calcium salt, magnesium salt, zinc salt or aluminum salt; the olefinic boron monomer has a structure of one of formula 1 to formula 6 and contains at least one ethylene Base, organic compounds with molecular weight below 2000g/mol,

Wherein R1～R9 are hydrogen atom, benzene ring, alkyl chain or benzene ring group, etheroxy group, ester group, cyano group, borooxy group or siloxy group or/and phosphorus One or more of the alkyl segments of the oxygen group;

(II) In an environment with a protective atmosphere and a water content and oxygen content of less than 1 ppm, coat the precursor solution prepared in step I on the surface of the porous support material or metal negative electrode used in the secondary battery. The solid-state polymer electrolyte is obtained by polymerization reaction for a certain period of time by light, heat or electricity. The porous support material can use materials used in existing polymer solid electrolytes, such as polyethylene, polypropylene, polyacrylonitrile, polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoroethylene), polymethyl methacrylate, The porous membrane composed of single or multiple components in polyimide, polyetherimide, aramid and cellulose and the porous composite membrane in which inorganic ceramic particles modify the surface of the above polymer matrix.

The vinyl carbonate monomer is vinylene carbonate, ethylene ethylene carbonate, ethyl propylene carbonate, allyl methyl carbonate, allyl phenyl carbonate, cis-3-hexenol methyl carbonate Ester, allyl succinimidyl carbonate, tert-butyl 4-vinylphenyl carbonate, allyl tert-butyl peroxycarbonate, diallyl pyrocarbonate, allyl diethylene glycol One or more of dicarbonate and bis(2-methylallyl) carbonate.

The ratio of the mass of the radical initiator compound to the sum of the mass of the ethylenic boron monomer and the mass of the vinylene carbonate monomer is 0.05 to 1 wt%.

A solid secondary battery includes a positive electrode, a solid electrolyte and a negative electrode, wherein the positive electrode and the negative electrode both use the positive electrode and the negative electrode of the existing secondary battery, for example, the positive electrode uses a lithium iron phosphate active material, the negative electrode uses a metal lithium sheet, and the solid electrolyte The solid polymer electrolyte prepared by the above method is used. When preparing a solid-state battery, there are the following three ways:

1. In an environment with a protective atmosphere and a water content and oxygen content of less than 1 ppm, after placing the positive electrode, porous support material, and negative electrode in the case accordingly, inject the above precursor solution into the inner cavity, and then encapsulate it with microwave , Light, heat or electricity way polymerization reaction for a certain time.

2. Prepare the solid electrolyte that is polymerized in situ on the porous support material by using the above solid-liquid dissolution method, and then directly use the positive electrode, the solid electrolyte, and the negative electrode in an environment with a protective atmosphere and water and oxygen contents of less than 1 ppm Assembled into a battery.

3. A solid electrolyte is prepared on the surface of the metal negative electrode that can be used for secondary batteries prepared by the above-mentioned solid-liquid decomposition method, and then the positive electrode is used directly in an environment with a protective atmosphere and the water content and oxygen content are both less than 1 ppm The metal negative electrode on which the solid electrolyte membrane is formed is directly assembled into a battery.

Compared with the existing solid polymer electrolyte, the solid polymer electrolyte prepared by the present invention contains a variety of organic groups that can complex with ions, which is beneficial to improve the dissociation rate of metal salts and the uniformity of ion distribution. Higher ion conductivity and high ion migration number can effectively reduce the concentration polarization in the secondary battery. Solid-state secondary batteries based on such solid electrolytes exhibit excellent cycle stability, thanks to the in-situ polymerization method used to ensure the close integration of the polymer electrolyte and electrode materials, and achieve a better electrolyte/electrode heterogeneous interface Stability and compatibility.

detailed description

Example 1

A preparation method of polymer solid electrolyte adopts the following steps:

(I) In a glove box protected by argon and having a water content and oxygen content of less than 1 ppm, 0.4 g of vinylene carbonate and 0.1 g of an ethylenic boron-containing monomer compound

After mixing with 0.1 g of lithium bistrifluoromethanesulfonimide, 0.0025 mg of azobisisobutyronitrile is added as an initiator to prepare a precursor solution;

(II) In a glove box protected by argon and having a water content and oxygen content of less than 1 ppm, inject the precursor solution prepared in step Ⅰ into the porous cellulose membrane, and select two stainless steel sheets to assemble the blocking electrode into a button type The battery was then placed at 60°C and heated for 24 hours to perform in-situ polymerization. An electrochemical workstation was used to perform impedance spectroscopy testing on the assembled stainless steel sheet symmetrical battery, and the measured lithium ion conductivity was 9.11×10 ^-4 S/cm. A battery assembled with an in situ polymer solid electrolyte containing no vinylene boron-containing monomer as a comparison has a conductivity of only 8.99×10 ^-4 S/cm.

Example 2

The metal lithium sheet is used as the electrode, and the precursor solution prepared in step I of Example 1 is injected into a porous cellulose membrane in a glove box protected by argon gas and the water content and oxygen content are both less than 1 ppm to seal and assemble the lithium metal symmetry The battery was placed at 60°C and heated for 24 hours to cause the precursor to polymerize in situ to form a solid electrolyte. Using an electrochemical workstation, the above-mentioned lithium metal symmetric battery cell was subjected to steady-state current polarization test and impedance spectrum test before and after polarization, and the measured lithium ion migration number was 0.68. As a comparison, a lithium metal symmetrical battery assembled using an in situ polymer solid electrolyte containing only vinylene carbonate and no olefinic boron-containing monomer was tested, and its lithium ion migration number was only 0.43.

Example 3

The positive electrode of lithium iron phosphate was selected, and the lithium metal sheet was used as the negative electrode. The precursor solution prepared in step I of Example 1 was injected into the porous cellulose membrane in a glove box protected by argon and having a water content and oxygen content of less than 1 ppm. Sealed, assembled into a lithium iron phosphate/lithium metal battery, and heated at 60 ℃ for 24h to in-situ polymerization of the precursor to obtain a solid lithium iron phosphate/lithium metal battery. As a comparison, a liquid lithium iron phosphate/lithium metal battery was assembled using an organic electrolyte, and the two assembled lithium iron phosphate/lithium metal batteries described above were subjected to constant current charging and discharging tests at a rate of 1C. The test voltage range was 2.5-4V. The solid lithium iron phosphate/lithium metal battery has an initial discharge specific capacity of 141.2mAh/g, which can be circulated stably for 600 cycles, while the initial discharge capacity of the assembled liquid lithium iron phosphate/lithium metal battery reaches 146mAh/g, but after 350 cycles There was a short circuit.

Example 4

A preparation method of polymer solid electrolyte adopts the following steps:

(Ⅰ) In a glove box protected by argon and having a water content and oxygen content of less than 1 ppm, 0.4 g of ethylene ethylene carbonate and 0.1 g of an ethylenic boron-containing monomer compound

And 0.049g sodium perchlorate and 0.0015mg initiator azobisisobutyronitrile are mixed to prepare a precursor solution;

(II) In a glove box protected by argon and having a water content and oxygen content of less than 1 ppm, inject the precursor solution prepared in step I into a polypropylene film modified on the surface of inorganic ceramic particles, and select two stainless steel sheets as The blocking electrode was assembled into a symmetrical button cell made of stainless steel, and then the cell was placed at 80°C and heated for 12 hours for in-situ polymerization. An electrochemical workstation was used to perform impedance spectroscopy testing on the assembled stainless steel symmetrical battery, and the measured sodium ion conductivity was 1.82×10 ^-4 S/cm.

Example 5

Using a metallic sodium sheet as the electrode, the precursor solution prepared in step I of Example 4 was injected into polypropylene modified on the surface of inorganic ceramic particles in a glove box protected by argon and having a water content and oxygen content of less than 1 ppm. And assembled into a metallic sodium symmetrical battery. After that, the battery was placed at 80°C and heated for 12 hours for in-situ polymerization. An electrochemical workstation was used to conduct the steady-state current polarization test and the impedance spectroscopy test before and after the polarization of the metal sodium symmetric battery, and the measured sodium ion migration number was 0.56.

Example 6

Using sodium vanadium phosphate as the positive electrode and sodium metal sheet as the negative electrode, the precursor solution prepared in step I of Example 4 was injected into the surface of the inorganic ceramic particles in a glove box protected by argon gas and the water content and oxygen content were both less than 1 ppm. In a polypropylene film, and sealed to form a sodium vanadium phosphate/sodium metal battery, and placed at 80 ℃ heating 12h to make the precursor in situ polymerization reaction to obtain a solid sodium vanadium phosphate/sodium metal battery. The assembled battery was subjected to constant current charging and discharging test at a rate of 1C. The test voltage range was 2.5-4V, and the initial discharge specific capacity was measured to be 98.6mAh/g.

Example 7

A preparation method of polymer solid electrolyte adopts the following steps:

(Ⅰ) In a glove box protected by argon and having a water content and oxygen content of less than 1 ppm, 0.4 g of ethyl propylene carbonate and 0.1 g of ethylenic boron-containing monomer compound

After mixing with 0.078g of magnesium perchlorate, 0.0025mg of azobisisobutyronitrile is added as an initiator to prepare a precursor solution;

(Ⅱ) In a glove box protected by argon and having a water content and oxygen content of less than 1 ppm, the precursor solution prepared in step Ⅰ is coated on a polyethylene film modified with inorganic ceramic particles and placed at 80°C Heating for 12 hours for in-situ polymerization can obtain solid polymer electrolyte.

Example 8

A preparation method of polymer solid electrolyte adopts the following steps:

(Ⅰ) In a glove box protected by argon and having a water content and oxygen content of less than 1 ppm, 0.4 g of allyl methyl carbonate and 0.1 g of ethylenic boron-containing monomer compound

And 0.22g of bis(trifluoromethanesulfonyl)imide zinc, after mixing, add 0.005g of azobisisobutyronitrile as an initiator to prepare a precursor solution; (Ⅱ) under argon protection and the water content and oxygen In a glove box with a content of less than 1 ppm, cover the precursor solution prepared in step I with polyvinylidene fluoride, select two stainless steel sheets as blocking electrodes and assemble a symmetrical button battery with stainless steel sheets, and then place the battery in 80 It was heated at ℃ for 12h to perform in-situ polymerization to prepare a solid polymer battery.

Claims

A method for preparing a solid polymer electrolyte, characterized in that it includes the following steps,

(I) Mix the olefinic boron monomer, olefinic carbonate monomer, metal salt and free radical initiator compound in an environment with a protective atmosphere and water content and oxygen content of less than 1 ppm to obtain a precursor solution; The metal salt is selected from one or more of alkali metal salt, calcium salt, magnesium salt, zinc salt or aluminum salt; the olefinic boron monomer has a structure of one of Formula 1 to Formula 6 and contains at least one Vinyl, organic compound with molecular weight below 2000g/mol,

Wherein R1～R9 are hydrogen atom, benzene ring, alkyl chain or benzene ring group, etheroxy group, ester group, cyano group, borooxy group or siloxy group or/and phosphorus One or more of the alkyl segments of the oxygen group;

(II) The precursor solution prepared in step I is coated on the surface of the porous support material or the metal anode material used in the secondary battery in an environment with a protective atmosphere and the water content and oxygen content are both less than 1 ppm. The solid-state polymer electrolyte is obtained by polymerization reaction for a certain period of time by light, heat or electricity.
The method for preparing a solid polymer electrolyte according to claim 1, wherein the ethylenic carbonate monomer is vinylene carbonate, ethylene ethylene carbonate, ethyl propylene carbonate, allyl methyl carbonate Ester, allylphenyl carbonate, cis-3-hexenol methyl carbonate, allyl succinimidyl carbonate, tert-butyl 4-vinylphenyl carbonate, allyl tert-butyl One or more of peroxycarbonate, diallyl pyrocarbonate, allyl diethylene glycol dicarbonate, and bis(2-methylallyl) carbonate.
The method for preparing a solid polymer electrolyte according to claim 1 or 2, wherein the ratio of the mass of the radical initiator compound to the sum of the mass of the olefinic boron monomer and the mass of the olefinic carbonate monomer is 0.05～1wt%.
A solid secondary battery includes a positive electrode, a solid electrolyte and a negative electrode, characterized in that the solid electrolyte is a solid polymer electrolyte prepared by the method according to any one of claims 1 to 3.