High-voltage stable copolymer for constituting a polymer electrolyte for a lithium or sodium cell

Abstract

A copolymer for constituting a polymer electrolyte for a solid-electrolyte lithium or sodium cell. A polymer electrolyte that is usable in combination with high-voltage cathode active materials and makes it possible to provide solid-electrolyte lithium or sodium cells and/or batteries having a high energy density that is sufficient even for use in electricity-based vehicles, the copolymer encompasses at least two ion-conductive polymers, the copolymer encompassing at least one polymer polymerized by ring-opening polymerization of at least one lactone and/or of at least one lactide and/or of at least one cyclic carbonate and/or of at least one cyclic carbamate and/or of at least one lactam and/or of at least one epoxide, and/or at least one polymer polymerized by radical polymerization of acrylonitrile and/or of at least one acrylonitrile derivative; and encompasses at least one polyacrylate having at least one repeating unit.

Claims

1. A copolymer for constituting a polymer electrolyte for a lithium or sodium cell, the copolymer comprising at least two ion-conductive polymers, the copolymer comprising: at least one polymer polymerized by ring-opening polymerization of at least one lactone and/or of at least one lactide and/or of at least one cyclic carbonate and/or of at least one cyclic carbamate and/or of at least one lactam; at least one polymer polymerized by radical polymerization of acrylonitrile and/or of at least one acrylonitrile derivative; and at least one polyacrylate having at least one repeating unit of the general chemical formula: ##STR00021## wherein a denotes a number of repeating units; R denotes hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; X denotes a spacer; x denotes a quantity of the spacer X and being 1 or 0; Q denotes a carbonate group or a carboxylic acid ester group or an acetal group or a carbamate group or a lactam group or a nitrile group or an isonitrile group or a cyanate group or an isocyanate group or a thiol group or a thiocyanate group or an isothiocyanate group or a thiocarbonyl group or a silyl group.

2. The copolymer as recited in claim 1, the copolymer having a molecular weight a range from ≥20 kD to ≤200 kD.

3. The copolymer as recited in claim 1, wherein the copolymer comprises at least one polymer polymerized by ring-opening polymerization of at least one lactone and/or of at least one lactide and/or of at least one cyclic carbonate and/or of at least one cyclic carbamate and/or of at least one lactam.

4. The copolymer as recited in claim 3, wherein the at least one polymer polymerized by ring-opening polymerization being polymerized by ring-opening polymerization of at least one lactone and/or of at least one cyclic carbonate.

5. The copolymer as recited in claim 1, wherein the at least one polymer polymerized by ring-opening polymerization comprises at least one repeating unit of the general chemical formula ##STR00022## wherein b denotes the number of repeating units; R11 and R12 denote, mutually independently in each case, hydrogen or a halogen, or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; and m denotes a number of CR11R12 units, and wherein m is such that 1≤m≤14.

6. The copolymer as recited in claim 1, wherein the at least one polymer polymerized by ring-opening polymerization being polymerized by ring-opening polymerization of at least one caprolactone.

7. The copolymer as recited in claim 1, wherein the at least one polymer polymerized by ring-opening polymerization has a highest number of monomers of the polymers of the copolymer, based on a sum of a number of monomers of all polymers of the copolymer, of the monomers in the at least one polymer polymerized by ring-opening polymerization.

8. The copolymer as recited in claim 1, wherein Q denotes a carbonate group, or a cyclic carbonate group, or an acyclic carbonate group, or a carboxylic acid ester group, or a lactone group, or an acyclic carboxylic acid ester group, or an acetal group, or a cyclic acetal group, or an acyclic acetal group, or a carbamate group, or a cyclic carbamate group, or an acyclic carbamate group, or a nitrile group and/or a silyl group.

9. The copolymer as recited in claim 1, wherein Q denotes a cyclic carbonate group or a cyclic acetal group or a lactone group or an acyclic carboxylic acid ester group or an acyclic carbamate group or a nitrile group or a silyl group.

10. The copolymer as recited in claim 1, wherein Q denotes a dioxolane group, or a (2-oxo-1,3-dioxolan-4-yl)alkyl group, or a (2-oxo-1,3-dioxolan-4-yl) group, or a (1,3-dioxolan-4-yl)alkyl group or (1,3-dioxolan-4-yl) group, or an acetoxy group or an [(alkylamino)carbonyl]oxy group or a nitrile group or a silyl group.

11. The copolymer as recited in claim 1, wherein the at least one polyacrylate has at least one repeating unit of the general chemical formula ##STR00023## wherein a denotes a number of repeating units; R denotes hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; R1, R2, and R3 denote, mutually independently in each case, hydrogen or a halogen or fluorine, or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; and n denotes a number of CR1R2 units, and wherein n is such that 0≤n≤10.

12. The copolymer as recited in claim 1, wherein the at least one polyacrylate has at least one repeating unit of the general chemical formula ##STR00024## wherein a denotes a number of repeating units; R denotes hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; R1′ and R2′ denoting, mutually independently in each case, hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; n′ denotes a number of CR1′R2′ units, wherein n′ is such that 1≤n′≤10.

13. The copolymer as recited in claim 1, wherein the at least one polyacrylate has at least one repeating unit of the general chemical formula ##STR00025## wherein a denotes a number of repeating units; R denotes hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; R1″ and R2″ denote, mutually independently in each case, hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; n″ denotes a number of CR1″R2″ units, and wherein n″ is such that 0≤n″≤10; and R3′, R3″, and R3″ denote, mutually independently in each case, an alkyl group.

14. The copolymer as recited in claim 1, wherein R denotes hydrogen or an alkyl group or a methyl group or a nitrile group or a silyl group or hydrogen.

15. The copolymer as recited in claim 1, wherein the at least one polymer polymerized by radical polymerization of acrylonitrile and/or of at least one acrylonitrile derivative comprises at least one repeating unit of the general chemical formula ##STR00026## wherein b denotes a number of repeating units; R11′, R12′, and R13′ denotes, mutually independently in each case, hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group.

16. The copolymer as recited in claim 1, wherein the copolymer comprises the general chemical formula ##STR00027## wherein b denotes the number of repeating units; R11 and R12 denote, mutually independently in each case, hydrogen or a halogen, or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; and m denotes a number of CR11R12 units, wherein m is such that 1≤m≤14, wherein R1, R2, and R3 denote, mutually independently in each case, hydrogen or a halogen or fluorine, or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; and n denotes a number of CR1R2 units, wherein n is such that 0≤n≤10, wherein R1′ and R2′ denoting, mutually independently in each case, hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group; n′ denotes a number of CR1′R2′ units, wherein n′ is such that 1≤n′≤10, wherein R1″ and R2″ denote, mutually independently in each case, hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group, wherein n″ denotes a number of CR1″R2″ units, and wherein n″ is such that 0≤n″≤10; and R3′, R3″, and R3′″ denote, mutually independently in each case, an alkyl group, wherein R11′, R12′, and R13′ denotes, mutually independently in each case, hydrogen or a halogen or fluorine or an alkyl group or a nitrile group or an alkoxy group or an oligo- or polyalkylene oxide group or a silyl group.

17. The copolymer as recited in claim 1, wherein the copolymer further comprises at least one further ion-conductive polymer, the at least one further ion-conductive polymer comprising at least one nitrile group and/or at least one isonitrile group and/or at least one cyanate group and/or at least one isocyanate group and/or at least one thiol group and/or at least one thiocyanate group and/or at least one isothiocyanate group and/or at least one acetal group and/or at least one carbonyl group and/or at least one carboxylic acid ester group, and/or at least one carbonate group and/or at least one carbamate group and/or at least one thiocarbonyl group and/or at least one ether group and/or at least one silyl group.

18. The copolymer as recited in claim 1, wherein the copolymer comprises the at least one polymer polymerized by ring-opening polymerization; the at least one polymer polymerized by radical polymerization of acrylonitrile; and the at least one polyacrylate.

19. The copolymer as recited in claim 1, wherein the at least one polymer polymerized by ring-opening polymerization being polymerized by ring-opening polymerization of at least one lactone, wherein R denotes an alkyl group, X denotes no spacer, x denotes a quantity of the spacer X being 0, and Q denotes a carbonate group.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Further advantages and advantageous embodiments of the subject matter of the present invention are illustrated by the exemplifying embodiments and the FIGURE, and are explained in the description that follows. It is to be noted in this context that the exemplifying embodiments and the FIGURE are merely descriptive in nature and are not intended to limit the present invention in any form.

(2) FIG. 1 is a schematic graph to illustrate the ion conductivities of different exemplifying embodiments of polymer electrolytes according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(3) Preliminary Experiments

(4) Under comparable measurement conditions, homopolymers of ε-caprolactone (CL), (2-oxo-1,3-dioxolan-4-yl) acrylate (DOA), and (2-oxo-1,3-dioxolan-4-yl)butyl acrylate (DOBA) exhibited an electrochemical stability >4.5 V with respect to Li.sup.+/Li, whereas polyethylene oxide (PEO) exhibited an electrochemical stability with respect to Li.sup.+/Li of only less than <4.4 V.

(5) Exemplifying Embodiment Series 1: Poly(-caprolactone)-block-poly(2-oxo-1,3-dioxolan-4-yl)butyl acrylate block copolymers (PCL-block-POBA)

(6) Firstly, in a separate synthesis run, poly(ε-caprolactone) (PCL) was manufactured by ring-opening polymerization of (ε-caprolactone) (CL), and a poly(ε-caprolactone) macroinitiator was generated therefrom by way of a macroinitiator forming agent. In a further synthesis step, the poly(ε-caprolactone) macroinitiator was radically reacted with (2-oxo-1,3-dioxolan-4-yl)butyl acrylate (DOBA), by atom transfer radical polymerization (ATRP) in dimethyl formamide (DMF) at elevated temperature with the aid of copper bromide (CuBr) as catalyst, to yield a poly(ε-caprolactone)-block-poly(2-oxo-1,3-dioxolan-4-yl)butyl acrylate block copolymer. Several poly(ε-caprolactone)-block-poly(2-oxo-1,3-dioxolan-4-yl)butyl acrylate block copolymers, having a respective monomer ratio (CL:DOBA) of ε-caprolactone (CL) to (2-oxo-1,3-dioxolan-4-yl)butyl acrylate of 30:70, 50:50, and 70:30, were manufactured in this fashion.

(7) The poly(ε-caprolactone)-block-poly(2-oxo-1,3-dioxolan-4-yl)butyl acrylate (PCL-block-PDOBA) block copolymers thereby obtained were mixed with ≥10 wt % to ≤30 wt % lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Polymer electrolyte films were manufactured from the mixture using a solvent-based coating method.

(8) Ion conductivity as a function of temperature was determined for some of the polymer electrolyte films. The results of those measurements are shown in FIG. 1.

(9) The reference character 1a here characterizes the measurement results for a polymer electrolyte film made from a mixture of a poly(ε-caprolactone)-block-poly(2-oxo-1,3-dioxolan-4-yl)butyl acrylate (PCL-block-PDOBA) block copolymer having a monomer ratio (CL:DOBA) of 50:50 and 20 wt % lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

(10) The reference character 1b characterizes the measurement results for a polymer electrolyte film made from a mixture of a poly(ε-caprolactone)-block-poly(2-oxo-1,3-dioxolan-4-yl)butyl acrylate (PCL-block-PDOBA) block copolymer having a monomer ratio (CL:DOBA) of 50:50 and 30 wt % lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

(11) The reference character 2a characterizes the measurement results for a polymer electrolyte film made from a mixture of a poly(ε-caprolactone)-block-poly(2-oxo-1,3-dioxolan-4-yl)butyl acrylate (PCL-block-PDOBA) block copolymer having a monomer ratio (CL:DOBA) of 70:30 and 20 wt % lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

(12) The reference character 2b characterizes the measurement results for a polymer electrolyte film made from a mixture of a poly(ε-caprolactone)-block-poly(2-oxo-1,3-dioxolan-4-yl)butyl acrylate (PCL-block-PDOBA) block copolymer having a monomer ratio (CL:DOBA) of 70:30 and 30 wt % lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

(13) FIG. 1 shows that all the polymer electrolytes 1a, 1b, 2a, 2b that were investigated exhibit sufficient ion conductivity. In particular, all the polymer electrolytes 1a, 1b, 2a, 2b that were investigated exhibited an ion conductivity >10.sup.−5 S/cm at 80° C.

(14) FIG. 1 shows in particular that ion conductivity can be considerably increased by increasing the proportion of poly(ε-caprolactone) (PCL) and shifting the monomer ratio (CL:DOBA) from 50:50 (1a, 1b) to 70:30 (2a, 2b). The polymer electrolytes having a monomer ratio (CL:DOBA) of 70:30 in fact exhibited an ion conductivity of approximately 10.sup.−4 S/cm at 80°. Ion conductivity can thus advantageously be increased by increasing the stoichiometric ε-caprolactone proportion, in particular to more than 50%, in this example to 70%.

(15) FIG. 1 furthermore shows that a high ion conductivity can be achieved with even a small conducting-salt proportion of 20 wt %.

(16) Exemplifying Embodiment Series 2: Statistical poly(2-oxo-1,3-dioxolan-4-yl)acrylate-stat-polyacrylonitrile (PDOA-stat-PAN) copolymers

(17) In several synthesis runs separately from one another, different statistical poly(2-oxo-1,3-dioxolan-4-yl)acrylate-stat-polyacrylonitrile (PDOA-stat-PAN) copolymers were manufactured from (2-oxo-1,3-dioxolan-4-yl)acrylate (DOA) and acrylonitrile (AN), having respective monomer ratios (DOA:AN) of (2-oxo-1,3-dioxolan-4-yl)acrylate (DOA) to acrylonitrile (AN) of 20:80, 50:50, and 80:20, by radical polymerization in acetonitrile at approximately 70° C. using azobis(isobutyronitrile) as a radical starter. The copolymers had a molecular weight in a range from approximately 50 to 80 kDa, a PDI in a range from approximately 1.2 to 1.3, and a glass transition temperature in a range from approximately 60 to 80° C.