CN114551996B - A kind of cyclophosphazene modified flame retardant polymer electrolyte and preparation method thereof - Google Patents

Abstract

The invention discloses a cyclophosphazene modified flame-retardant polymer electrolyte and a preparation method thereof, wherein the flame-retardant polymer electrolyte comprises the following components: the flame retardant comprises a cyclophosphazene, a plasticizer, a polymer substrate, a glass fiber membrane framework and lithium salt, wherein the flame retardant and the polymer substrate are polymerized under illumination through a photoinitiator to form a crosslinked network structure. The beneficial effects of the invention are as follows: by utilizing ultraviolet polymerization and using cyclophosphazene modified solid polymer electrolyte, the electrochemical performance is ensured and the flame-retardant effect is increased under the condition of hardly influencing the ion transmission performance, so that the guarantee is provided for preparing the high-safety lithium ion battery.

Description

A kind of cyclophosphazene modified flame retardant polymer electrolyte and preparation method thereof

technical field

The invention relates to the field of polymer electrolytes, in particular to a cyclophosphazene-modified flame-retardant polymer electrolyte and a preparation method thereof.

Background technique

As people pay more and more attention to renewable energy, lithium-ion batteries have attracted much attention as a high-efficiency energy storage device with development potential in the market. It is an inevitable development trend in the future to realize high-energy density and fast-charging high-safety lithium-ion batteries. Among them, solid-state lithium-ion batteries are considered to be one of the most promising development directions, and solid-state electrolytes, as the core components of solid-state batteries, have received extensive research and attention. Solid-state electrolyte batteries are divided into inorganic solid-state electrolytes, organic polymer solid-state electrolytes and composite solid-state electrolytes. Among them, the organic polymer solid electrolyte has the advantages of high ionic conductivity, simple preparation process and good flexibility, so it is regarded as one of the research breakthroughs. However, polymers have the risk of being flammable, especially when they are used in the battery field. When there is thermal runaway, it may cause safety accidents.

Therefore, it is necessary to provide a polymer electrolyte with excellent flame-retardant effect to overcome the above-mentioned problems.

Contents of the invention

The object of the present invention is to provide a cyclophosphazene-modified flame-retardant polymer electrolyte and a preparation method thereof in order to overcome the shortcomings and deficiencies of the prior art. This scheme increases the effect of flame retardancy while ensuring the electrochemical performance without affecting the ion transport performance.

To achieve the above object, the first aspect of the present invention is to provide a cyclophosphazene modified flame retardant polymer electrolyte. Including the following components: flame retardant, plasticizer, polymer substrate, glass fiber membrane skeleton and lithium salt, the flame retardant is cyclophosphazene, and the flame retardant and polymer substrate pass through the photoinitiator under the light Polymerization forms a cross-linked network structure.

It is further provided that the polymer substrate is one or a combination of polymethylacrylate, polypropylene carbonate, polypropylene oxide, polymethacrylate, and polycarbonate acrylate.

It is further provided that the lithium salt is one or a mixture of LiPF ₆ , LiF ₄ , LiCLO ₄ , LiTf, LiFSI, LiTFSI, LiBOB, LiODFB.

It is further set that the mass ratio of the total amount of the plasticizer and lithium salt to the polymer base is 20:1˜1:1.

It is further provided that the photoinitiator accounts for 0.1-10% of the mass ratio of the polymer monomer.

It is further provided that the thickness of the glass fiber membrane is 10-1000 μm.

The further setting is: the plasticizer is succinonitrile.

A second aspect of the present invention provides a method for preparing the flame-retardant polymer electrolyte, comprising the following steps:

(1) Dissolving the plasticizer and the lithium salt, and adding the polymer substrate, the flame retardant and the photoinitiator and stirring together to obtain a mixed solution;

(2) Coat the mixed solution obtained in step (1) on the glass fiber membrane, and irradiate with ultraviolet light, so that the polymer substrate and the flame retardant are polymerized, and finally a cyclophosphazene-modified flame-retardant polymer is obtained. matter electrolyte.

It is further set that the stirring speed of the step (1) is 100-1000 rpm, the melting temperature of the plasticizer and lithium salt is 30-100° C., and the ultraviolet light irradiation time is 30s-1h.

In addition, the present invention also provides an application of the above-mentioned pentaphenoxycyclotriphosphazene-modified flame-retardant polymer electrolyte as an electrolyte in a lithium-ion battery.

The beneficial effects of the present invention are:

Utilizing ultraviolet photopolymerization and using cyclophosphazene to modify the solid polymer electrolyte, the electrochemical performance is guaranteed while increasing the flame retardant effect without affecting the ion transport performance, providing a high-safety lithium-ion battery. Guaranteed. The cyclophosphazene added in the invention has good thermal stability and flame retardancy. When it is heated, it will release free radicals with flame retardant properties, preventing the chain reaction of hydroxyl radicals, so as to achieve the effect of flame retardancy. Utilizing it in lithium-ion batteries can effectively improve battery safety performance.

For specific experimental data, please refer to the experimental data of the accompanying drawings.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, obtaining other drawings based on these drawings still belongs to the scope of the present invention without any creative effort.

Fig. 1 is to use the plane and section scanning electron microscope (SEM) picture of the solid polymer electrolyte prepared by the present invention;

Fig. 2 is the cyclic voltammetry (CV) diagram of the solid polymer electrolyte prepared by using Example 1 of the present invention;

Fig. 3 is the charging and discharging curve of the voltage range of 2.5V to 4.0V in the lithium iron phosphate half-cell using the solid polymer electrolyte prepared in Example 2 of the present invention;

Fig. 4 is a graph showing the ratio of 0.1C to 2C in the 2.5V-4.0V voltage range of the lithium iron phosphate half-cell using the solid polymer electrolyte prepared in Example 2 of the present invention;

Fig. 5 is a graph showing the combustion test results of the solid polymer electrolyte prepared in Example 4 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings.

Example 1

(a1) Add 8.5g of hexachlorocyclotriphosphazene and 40.0g of anhydrous K ₂ CO ₃ into an appropriate amount of acetone to dissolve. 3.5 g of 2-allylphenol solution was added dropwise therein, and the temperature was raised to reflux for 2.5 h. After cooling, 12.0 g of phenol dissolved in acetone was added, and the temperature was raised to reflux for 7 hours. After cooling and filtering, the filtrate was distilled to recover the solvent, then dissolved with an appropriate amount of toluene, washed with low-concentration NaOH, HCL and distilled water to neutrality, dried and filtered, and desolventized to obtain pentaphenoxycyclotriphosphazene APPCP.

(a2) Add 1M lithium bistrifluoromethanesulfonylimide LiTFSI into succinonitrile SN to dissolve at 70°C, and add ethoxylated trimethylolpropane triacrylate ETPTA, pentaphenoxycyclotriphosphine Nitrile APPCP and 2-hydroxy-2-methylpropiophenone HMPP were stirred together for 20 min. The mass ratio of the total mass of LiTFSI and SN to ETPTA is 8:1, the mass ratio APPCP:ETPTA=1:20, and HMPP accounts for 0.2% of the mass of ETPTA.

(a3) Coating the obtained mixed solution on a glass fiber membrane and irradiating with ultraviolet light for 5 minutes to obtain a flame-retardant polymer electrolyte modified by pentaphenoxycyclotriphosphazene.

Example 2

(a1) Add 8.5g of hexachlorocyclotriphosphazene and 40.0g of anhydrous K ₂ CO ₃ into an appropriate amount of acetone to dissolve. 3.5 g of 2-allylphenol solution was added dropwise therein, and the temperature was raised to reflux for 2.5 h. After cooling, 12.0 g of phenol dissolved in acetone was added, and the temperature was raised to reflux for 7 hours. After cooling and filtering, the filtrate was distilled to recover the solvent, then dissolved with an appropriate amount of toluene, washed with low-concentration NaOH, HCL and distilled water to neutrality, dried and filtered, and desolventized to obtain pentaphenoxycyclotriphosphazene APPCP.

(a2) Add 1M lithium bistrifluoromethanesulfonylimide LiTFSI into succinonitrile SN to dissolve at 70°C, and add ethoxylated trimethylolpropane triacrylate ETPTA, pentaphenoxycyclotriphosphine Nitrile APPCP and 2-hydroxy-2-methylpropiophenone HMPP were stirred together for 20 min. The mass ratio of the total mass of LiTFSI and SN to ETPTA is 8:1, the mass ratio APPCP:ETPTA=1:15, and HMPP accounts for 0.2% of the mass of ETPTA

(a3) Coating the obtained mixed solution on a glass fiber membrane and irradiating with ultraviolet light for 5 minutes to obtain a flame-retardant polymer electrolyte modified by pentaphenoxycyclotriphosphazene.

Example 3

(a1) Add 8.5g of hexachlorocyclotriphosphazene and 40.0g of anhydrous K ₂ CO ₃ into an appropriate amount of acetone to dissolve. 3.5 g of 2-allylphenol solution was added dropwise therein, and the temperature was raised to reflux for 2.5 h. After cooling, 12.0 g of phenol dissolved in acetone was added, and the temperature was raised to reflux for 7 hours. After cooling and filtering, the filtrate was distilled to recover the solvent, then dissolved with an appropriate amount of toluene, washed with low-concentration NaOH, HCL and distilled water to neutrality, dried and filtered, and desolventized to obtain pentaphenoxycyclotriphosphazene APPCP.

(a2) Add 1M lithium bistrifluoromethanesulfonylimide LiTFSI into succinonitrile SN to dissolve at 70°C, and add ethoxylated trimethylolpropane triacrylate ETPTA, pentaphenoxycyclotriphosphine Nitrile APPCP and 2-hydroxy-2-methylpropiophenone HMPP were stirred together for 20 min. The mass ratio of the total mass of LiTFSI and SN to ETPTA is 8:1, the mass ratio APPCP:ETPTA=1:10, and HMPP accounts for 0.2% of the mass of ETPTA.

(a3) Coating the obtained mixed solution on a glass fiber membrane and irradiating with ultraviolet light for 5 minutes to obtain a flame-retardant polymer electrolyte modified by pentaphenoxycyclotriphosphazene.

Example 4

(a1) Add 8.5g of hexachlorocyclotriphosphazene and 40.0g of anhydrous K ₂ CO ₃ into an appropriate amount of acetone to dissolve. 3.5 g of 2-allylphenol solution was added dropwise therein, and the temperature was raised to reflux for 2.5 h. After cooling, 12.0 g of phenol dissolved in acetone was added, and the temperature was raised to reflux for 7 hours. After cooling, filter, distill the filtrate to recover the solvent, dissolve it with an appropriate amount of toluene, wash it with low-concentration NaOH, HCL and distilled water to neutrality, dry and filter, and remove the solvent to obtain pentaphenoxycyclotriphosphazene APPCP

(a2) Add 1M lithium bistrifluoromethanesulfonylimide LiTFSI into succinonitrile SN to dissolve at 70°C, and add ethoxylated trimethylolpropane triacrylate ETPTA, pentaphenoxycyclotriphosphine Nitrile APPCP and 2-hydroxy-2-methylpropiophenone HMPP were stirred together for 20 min. The mass ratio of the total mass of LiTFSI and SN to ETPTA is 8:1, the mass ratio APPCP:ETPTA=1:5, and HMPP accounts for 0.2% of the mass of ETPTA.

(a3) Coating the obtained mixed solution on a glass fiber membrane and irradiating with ultraviolet light for 5 minutes to obtain a flame-retardant polymer electrolyte modified by pentaphenoxycyclotriphosphazene.

Example 5

The difference between Example 5 and Example 1 is that the lithium bistrifluoromethanesulfonimide LiTFSI is replaced by any one of LiPF ₆ , LiF ₄ , LiCLO ₄ , LiTf, LiFSI, LiBOB, and LiODFB, Other preparation conditions are the same.

Example 6

The difference between this embodiment 6 and embodiment 1 is that the ethoxylated trimethylolpropane triacrylate ETPTA is replaced by polymethylacrylate, polypropylene carbonate, polypropylene oxide, polymethacrylic acid Any one of ester, polycarbonate acrylate, other preparation conditions are the same.

Example 7

The difference between Example 7 and Example 1 is that the pentaphenoxycyclotriphosphazene APPCP is replaced by ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, hexaallylamine Any one of other cyclic phosphazenes such as cyclotriphosphazene, and other preparation conditions are the same.

Application example

The flame retardant polymer electrolyte prepared in the above embodiments of the present invention was used as the electrolyte of the lithium battery.

Experimental effect description:

The flame-retardant polymer electrolyte modified by cyclophosphazene in the present invention has excellent flame-retardant performance, and it can still maintain a period of non-combustion in the case of an open flame, which improves the safety of the electrolyte (Figure 5). From the CV curve of the electrolyte at a scan rate of 0.2mV/s, it can be seen that lithium ion transport is faster, and the addition of flame retardant does not affect its kinetic performance (Figure 2). At the same time, the electrolyte exhibits a wide electrochemical window and voltage range when matching the lithium iron phosphate cathode. And in the voltage range of 2.5V-4.0V, it can maintain stability in the charge-discharge cycle, the polarization is small, the specific capacity is high, and it can still maintain 140mAh/g after multiple cycles, indicating that the electrolyte is conducive to the transmission of lithium ions (Figure 3). At the same time, it can charge and discharge stably at a high rate, and the charge-discharge specific capacity can reach 140mAh/g at a 2C rate. The ion transmission is fast and there are few side reactions. In the future, it can be used as a fast-charge lithium-ion battery (Figure 4).

The above disclosures are only preferred embodiments of the present invention, and certainly cannot limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope of the present invention.

Claims (8)

1. a flame retardant polymer electrolyte modified by cyclophosphazene, characterized in that it comprises the following components: flame retardant, plasticizer, polymer substrate, glass fiber membrane skeleton and lithium salt, described flame retardant For cyclophosphazene, the flame retardant and the polymer substrate are polymerized by photoinitiators under light to form a crosslinked network structure; The mass ratio of the total amount of the plasticizer and lithium salt to the polymer base is 20:1 ~ 1:1, and the photoinitiator accounts for 0.1 ~ 10% of the mass ratio of the polymer monomer; The thickness of the glass fiber membrane is 10-1000 μm. 2. The flame retardant polymer electrolyte modified by cyclophosphazene according to claim 1, characterized in that: the polymer base is polymethylacrylate, polypropylene carbonate, polypropylene oxide, polymethyl One or more mixtures of acrylate, polycarbonate acrylate, and ethoxylated trimethylolpropane triacrylate. 3. The flame retardant polymer electrolyte modified by cyclophosphazene according to claim 1, characterized in that: the lithium salt is LiPF ₆ , LiF ₄ , LiCLO ₄ , LiTf, LiFSI, LiTFSI, LiBOB, LiODFB one or a mixture of several. 4. The cyclophosphazene-modified flame-retardant polymer electrolyte according to claim 1, characterized in that: the plasticizer is succinonitrile. 5. The flame retardant polymer electrolyte modified by cyclophosphazene according to claim 1, characterized in that: said cyclophosphazene is pentaphenoxycyclotriphosphazene, ethoxylated pentafluorocyclotriphosphazene , phenoxypentafluorocyclotriphosphazene or hexaallylaminocyclotriphosphazene. 6. The preparation method of the flame-retardant polymer electrolyte according to any one of claims 1-5, characterized in that it comprises the following steps: Dissolving the plasticizer and lithium salt, adding the polymer substrate, flame retardant and photoinitiator and stirring together to obtain a mixed solution; (2) Coat the mixed solution obtained in step (1) on the glass fiber membrane, and irradiate with ultraviolet light to polymerize the polymer substrate and the flame retardant, and finally obtain a cyclophosphazene-modified flame-retardant polymerization matter electrolyte. 7. The preparation method according to claim 6, characterized in that: the stirring speed of the step (1) is 100~1000rpm, the melting temperature of the plasticizer and the lithium salt is 30~100°C, the The time of ultraviolet light irradiation is 30 s ~ 1h. 8. an application of the flame retardant polymer electrolyte modified by cyclophosphazene as claimed in claim 1 as electrolyte in lithium ion battery.