Patent Application
20240380004
This application is based upon and claims priority to Chinese Patent Application No. 202310513066.X, filed on May 9, 2023, the entire contents of which are incorporated herein by reference.
The present invention relates to the technical field of lithium battery materials, and more particularly to a preparation method of a flame-retardant ultrathin PEO-based solid electrolyte.
The current lithium ion batteries have been unable to meet the increasing demand of people in terms of energy density, cycle life, and safety. It is one of the effective strategies to achieve lithium batteries with high specific energy and high safety by using a solid electrolyte and matching a lithium metal negative electrode to assemble solid lithium metal batteries.
Polyethylene oxide (PEO)-based solid electrolytes among multiple solid electrolytes have been widely studied because of easy processing, good lithium salt solubility, and stable lithium metal negative electrode.
However, PEO is a semi-crystalline polymer material, which leads to the limited migration of lithium ions in polymer and affects the capacity of the battery. At the same time, the mechanical strength of PEO is not enough to inhibit the growth of lithium dendrites, so as not to match a positive electrode with high surface capacity. Moreover, the thickness of PEO solid electrolytes used at present is large, which is not conducive to achieving high energy density.
In addition, PEO is a typical flammable polymer in a PEO-based solid polymer electrolyte system, which has a potential safety hazard similar to an organic electrolyte and is very fatal when applied to batteries. Aiming at the problem of flammability, the polymerization flame retardance is generally improved by adding a flame retardant (FR) in the prior art. An organophosphorus flame retardant has become the most commonly used flame retardant additive because of good thermal stability, high environmental safety, high flame retardant efficiency, and low cost. However, the incompatibility between phosphorus flame retardants and metal anodes will affect the performance of the battery.
In order to solve the above problem, the present invention provides a preparation method of a flame-retardant ultrathin PEO-based solid electrolyte. The electrochemical performance and flame retardance of a PEO-based solid polymer electrolyte are improved through a multifunctional flame-retardant filler (HNT@TMP), and the mechanical strength of the ultrathin PEO electrolyte is ensured through porous cellulose nanopaper (CN) with excellent mechanical flexibility and thermal stability, whereby the development of high energy density is facilitated.
In order to achieve the above object, the present invention provides a preparation method of a flame-retardant ultrathin PEO-based solid electrolyte, including the following steps:
Preferably, step S1 specifically includes the following sub-steps:
Preferably, the CN raw materials are dispersed in the aqueous solution by an ultrasonic wall breaker in step S11.
The power of the ultrasonic wall breaker is 650 W, the dispersion time is 10-30 min, the drying temperature is 100° C., and the drying time is 12 hours.
Preferably, TMP is adsorbed in the interior of HNT by vacuum impregnation to synthesize HNT@TMP in step S2.
Preferably, step S2 specifically includes the following sub-steps:
S25: drying the separated HNT@TMP in an oven at 60° C.
Preferably, the proportion of HNT@TMP is 40%, the ratio of PEO and LiTFSI is [EO/Li+]=16:1, and the stirring time is 12 hours, in step S3.
Preferably, both sides of the CN support layer are coated with the PEO-based solid electrolyte slurry using a coating machine in step S4.
The coating scale of the PEO-based solid electrolyte slurry is 15-35. The drying process includes: placing at room temperature for 12 hours and then placing in a vacuum oven at 60° C. for 12 hours.
Preferably, the hot pressing pressure is 40 MPa, the hot pressing temperature is 70° C., and the hot pressing time is 10-30 min, in step S5.
Preferably, the thickness of the CN support layer in step S1 is 5-50 μm.
The present invention has the following beneficial effects.
That is to say, a multifunctional HNT@TMP flame-retardant filler matches the ultrathin porous cellulose nanopaper (CN) with mechanical flexibility and thermal stability as a support layer, which can achieve the flame retardance, excellent mechanical performance and electrochemical performance of the PEO-based solid electrolyte, achieves ultrathin performance, and is conducive to achieving high energy density of a lithium battery.
The technical solution of the present invention will be described in further detail below through the drawings and the embodiments.
The present invention will be further described with reference to the drawings. It should be noted that this embodiment is based on this technical solution and gives a detailed implementation and a specific operation process. However, the protection scope of the present invention is not limited to this embodiment.
A preparation method of a flame-retardant ultrathin PEO-based solid electrolyte includes the following steps:
The thickness of the CN support layer in step S1 is 5-50 μm.
Preferably, step S1 specifically includes the following sub-steps:
Preferably, the CN raw materials are dispersed in the aqueous solution by an ultrasonic wall breaker in step S11.
The power of the ultrasonic wall breaker is 650 W, the dispersion time is 10-30 min, the drying temperature is 100° C., and the drying time is 12 hours.
Preferably, TMP is adsorbed in the interior of HNT by vacuum impregnation to synthesize HNT@TMP in step S2.
Preferably, step S2 specifically includes the following sub-steps:
Preferably, the proportion of HNT@TMP is 40%, the ratio of PEO and LiTFSI is [EO/Li+]=16:1, and the stirring time is 12 hours, in step S3.
Preferably, both sides of the CN support layer are coated with the PEO-based solid electrolyte slurry using a coating machine in step S4.
The coating scale of the PEO-based solid electrolyte slurry is 15-35. The drying process includes: placing at room temperature for 12 hours and then placing in a vacuum oven at 60° C. for 12 hours.
Preferably, the hot pressing pressure is 40 MPa, the hot pressing temperature is 70° C., and the hot pressing time is 10-30 min, in step S5.
In step 1, 20 mg of porous cellulose nanopaper raw materials are uniformly dispersed in an aqueous solution for 10-30 min by an ultrasonic wall breaker having a power of 650 W to obtain a precursor solution, and the obtained precursor solution is subjected to vacuum filtration at 100° C. for 12 hours to obtain ultrathin porous cellulose nanopaper.
In step 2, an HNT solution and a TMP solution are ultrasonically blended for 1 hour and then transferred into a vacuum bottle for vacuum impregnation for 1 hour. This process is repeated four times to obtain a mixed solution. After that, the mixed solution is stored under normal pressure for 5-7 days to obtain a mixed solution with HNT@TMP precipitated, which further increases the loading capacity of TMP. Finally, HNT@TMP is separated from the mixed solution by a centrifugal machine and dried in an oven at 60° C. to obtain a multifunctional flame-retardant filler HNT@TMP.
In step 3, PEO, LiTFSI, and HNT@TMP in a certain ratio are mixed and stirred in acetonitrile to obtain PEO-based solid electrolyte slurry. The specific ratio is as follows: the proportion of HNT@TMP is 40%, the ratio of PEO and LiTFSI is [EO/Li+]=16:1, and the stirring time is 12 hours.
In step 4, both sides of the porous cellulose nanopaper are coated with the PEO-based solid electrolyte slurry by a coating machine and dried. In this step, the coating scale of the PEO-based solid electrolyte slurry is 25. The drying process includes: placing at room temperature for 12 hours and then placing in a vacuum oven at 60° C. for 12 hours.
In step 5, the dried PEO-based solid electrolyte is hot-pressed. The hot pressing pressure is 40 MPa, the hot pressing temperature is 70° C., and the hot pressing time is 25 min.
In step 1, 20 mg of porous cellulose nanopaper raw materials are uniformly dispersed in an aqueous solution for 10-30 min by an ultrasonic wall breaker having a power of 650 W to obtain a precursor solution, and the obtained precursor solution is subjected to vacuum filtration at 100° C. for 12 hours to obtain ultrathin porous cellulose nanopaper.
In step 2, PEO, LiTFSI, and HNT in a certain ratio are mixed and stirred in acetonitrile to obtain PEO-based solid electrolyte slurry. The proportion of HNT is equal to that of HNT in Embodiment 1, the ratio of PEO and LiTFSI is [EO/Li+]=16:1, and the stirring time is 12 hours.
In step 3, both sides of the porous cellulose nanopaper are coated with the PEO-based solid electrolyte slurry by a coating machine and dried. The coating scale of the PEO-based solid electrolyte slurry is 25. The drying process includes: placing at room temperature for 12 hours and then placing in a vacuum oven at 60° C. for 12 hours.
In step 4, the dried PEO-based solid electrolyte is hot-pressed. The hot pressing pressure is 40 MPa, the hot pressing temperature is 70° C., and the hot pressing time is 25 min.
In step 5, the obtained PEO-based solid electrolyte is blended with TMP, and the proportion of TMP is equal to that of TMP in Embodiment 1.
In step 1, 20 mg of porous cellulose nanopaper raw materials are uniformly dispersed in an aqueous solution for 10-30 min by an ultrasonic wall breaker having a power of 650 W to obtain a precursor solution, and the obtained precursor solution is subjected to vacuum filtration at 100° C. for 12 hours to obtain ultrathin porous cellulose nanopaper.
In step 2, PEO and LiTFSI in a certain ratio are mixed and stirred in acetonitrile to obtain PEO-based solid electrolyte slurry. The ratio of PEO and LiTFSI is [EO/Li+]=16:1, and the stirring time is 12 hours.
In step 3, both sides of the porous cellulose nanopaper are coated with the PEO-based solid electrolyte slurry by a coating machine and dried. The coating scale of the PEO-based solid electrolyte slurry is 25. The drying process includes: placing at room temperature for 12 hours and then placing in a vacuum oven at 60° C. for 12 hours.
In step 4, the dried PEO-based solid electrolyte is hot-pressed. The hot pressing pressure is 40 MPa, the hot pressing temperature is 70° C., and the hot pressing time is 25 min.
In step 1, PEO and LiTFSI in a certain ratio are mixed and stirred in acetonitrile to obtain PEO-based solid electrolyte slurry. The ratio of PEO and LiTFSI is [EO/Li+]=16:1, and the stirring time is 12 hours.
In step 2, the obtained PEO-based solid electrolyte slurry is poured onto a polytetrafluoroethylene mold, dried at room temperature for 12 hours, and then dried under a vacuum environment of 60° C. for 12 hours.
To verify the PEO-based solid electrolytes prepared in Embodiment 1 and Comparative Examples 1-3, the following performance tests are performed:
The result of TEM characterization of the multifunctional flame-retardant filler HNT@TMP prepared in Embodiment 1 of the present invention is as shown in
A lithium ion migration number test is performed on the flame-retardant ultrathin PEO-based solid electrolyte with high ion migration number obtained in Embodiment 1 of the present invention and the PEO-based solid electrolyte obtained in Comparative Example 2 and Comparative Example 3. From the result as shown in
The flame-retardant ultrathin PEO-based solid electrolyte with high ion migration number obtained in Embodiment 1 of the present invention and the PEO-based solid electrolyte obtained in Comparative Example 2 and Comparative Example 3 match a LiFePO4 positive electrode and a lithium metal negative electrode to assemble a button battery for an electrochemical performance test. According to the result as shown in
From Embodiment 1 and Comparative Example 1, it can be seen that the multifunctional flame-retardant filler HNT@TMP prepared in the present invention effectively avoids the negative influence caused by the direct addition of a flame retardant in an electrolyte. From Embodiment 1 and Comparative Examples 2 and 3, it can be seen that in the thermal runaway process of a battery, due to the increase of temperature, the flame retardant in the HNT gasifies and captures free radicals in the combustion process of polymer, thus effectively inhibiting the combustion of the polymer electrolyte. At the same time, the unique charge distribution structure of “positive inside and negative outside” of the HNT can promote the dissociation of lithium salt and produce more freely conductible lithium ions, thereby accelerating the transmission of the lithium ions in the PEO-based electrolyte. Furthermore, the mechanical strength of the ultrathin PEO electrolyte is ensured through porous cellulose nanopaper (CN) with mechanical flexibility and thermal stability. Therefore, the flame-retardant ultrathin PEO-based solid electrolyte (having a thickness of 20-25 μm) with high ion migration number prepared in the present invention has better mechanical performance, ionic conductivity, lithium ion migration number, and flame retardance, and the assembled battery has better cycle performance and rate performance. Based on the above advantages, the electrolyte membrane is conducive to the realization of high energy density and high safety performance of all-solid-state lithium metal batteries.
Therefore, in the present invention, the preparation method of the flame-retardant ultrathin PEO-based solid electrolyte is adopted, a multifunctional flame-retardant filler (HNT@TMP) and an ultrathin porous cellulose nanopaper serve as a support layer, and a flame-retardant ultrathin PEO-based solid electrolyte with high ion migration number is prepared. The multifunctional flame-retardant filler (HNT@TMP) and the ultrathin porous cellulose nanopaper (CN) with mechanical flexibility and thermal stability serve as the support layer, which can achieve the flame retardance, excellent mechanical performance and electrochemical performance of the PEO-based solid electrolyte, achieves ultrathin performance, and is conducive to achieving high energy density of a lithium battery.
Finally, it should be noted that the above embodiments are intended only to illustrate and not to limit the technical solution of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those of ordinary skill in the art that modifications or equivalents may be made to the technical solution of the present invention and that such modifications or equivalents do not depart the modified technical solution from the spirit and scope of the technical solution of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202310513066.X | May 2023 | CN | national |
