FLUORINATED GEL POLYMER ELECTROLYTE FOR A LITHIUM ELECTROCHEMICAL CELL
A gel polymer electrolyte for a lithium electrochemical cell, comprising: a) a three-dimensional cross-linked polymer network within a liquid electrolyte obtained by forming a reaction product of at least one fluorinated copolymer with at least one isocyanate compound comprising at least two isocyanate functional groups, and b) a liquid electrolyte solution included in the polymer network a), wherein the fluorinated copolymer comprises: i) at least one first recurring unit derived from at least one ethylenically unsaturated fluorinated monomer; and ii) at least one second recurring unit derived from at least one ethylenically unsaturated monomer having a hydroxyl group. A process for the manufacture of the gel polymer electrolyte for a lithium electrochemical cell; a lithium electrochemical cell comprising a cathode, an anode, and the present gel polymer electrolyte; and use of the gel electrolyte polymer in a lithium electrochemical cell as a separator and an electrolyte.
1 . A gel polymer electrolyte for a lithium electrochemical cell comprising:
a) a three-dimensional cross-linked polymer network within a liquid electrolyte obtained by forming a reaction product of at least one fluorinated copolymer with at least one isocyanate compound comprising at least two isocyanate functional groups, and b) a liquid electrolyte solution included in the polymer network a),
wherein the fluorinated copolymer comprises
i) at least one first recurring unit derived from at least one ethylenically unsaturated fluorinated monomer; and
ii) at least one second recurring unit derived from at least one ethylenically unsaturated monomer having a hydroxyl group.
2 . The gel polymer electrolyte according to claim 1 , wherein the polymer network a) comprises at least one urethane moiety bridging at least two fluorinated copolymers.
3 . The gel polymer electrolyte according to claim 1 , wherein the first recurring unit i) is derived from vinylidene fluoride (VDF), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene, or combinations thereof.
4 . The gel polymer electrolyte according to claim 1 , wherein the second recurring unit ii) is derived from an (meth)acrylic acid ester having a hydroxyl group.
5 . The gel polymer electrolyte according to claim 4 , wherein the (meth)acrylic acid ester having a hydroxyl group comprises an acrylate selected from the group consisting of 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate, 2-hydroxymethyl acrylate, 2-hydroxymethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl acrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl acrylate, 8-hydroxyoctyl methacrylate, 2-hydroxyethyleneglycol acrylate, 2-hydroxyethlyeneglycol methacrylate, 2-hydroxypropyleneglycol acrylate, 2-hydroxypropyleneglycol methacrylate, 2,2,2-trifluoroethyl acrylate, and 2,2,2-trifluoroethyl methacrylate.
6 . The gel polymer electrolyte according to claim 1 , wherein the at least one isocyanate compound comprising at least two isocyanate functional groups comprises a compound selected from the group consisting of 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, xylylenediisocyanate, isophoronediisocyanate, methylene bis(4-phenyl isocyanate), methyl cyclohexyldiisocyanate, trimethyl hexamethylene diisocyanate, hexamethylene diisocyanate, naphthalene-1,5-diisocyanate, and poly(ethylene adipate)-tolylene-2,4-diisocyanate.
7 . The gel polymer electrolyte according to claim 1 , wherein the liquid electrolyte solution b) comprises
at least one lithium salt; and
a liquid medium comprising at least one organic carbonate compound.
8 . The gel polymer electrolyte according to claim 7 , wherein the at least one lithium salt comprises a salt selected from the group consisting of lithium hexafluorophosphate (LiPF 6 ), lithium bis(fluorosulfonyl)imide Li(FSO 2 ) 2 N (LiFSI), lithium trifluoromethane sulfonate (LiCF 3 SO 3 ), LiN(SO 2 C m F 2m+1 )(SO 2 C n F 2n+1 ) and LiC(SO 2 C k F 2k+1 )(SO 2 C m F 2m+1 )(SO 2 C n F 2m+1 ) wherein k=1-10, m=1-10 and n=1-10, LiN(SO 2 C p F 2p SO 2 ) and LiC(SO 2 C p F 2p SO 2 )(SO 2 C q F 2q+1 ) wherein p=1-10 and q=1-10, and mixtures thereof.
9 . The gel polymer electrolyte according to claim 7 , wherein the at least one organic carbonate compound comprises a carbonate selected from the group consisting of ethylene carbonate (1,3-dioxalan-2-one), propylene carbonate, 4-methylene-1,3-dioxolan-2-one, 4,5-dimethylene-1,3-dioxolan-2-one, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, butylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, and mixtures thereof.
10 . The gel polymer electrolyte according to claim 1 , wherein the liquid electrolyte solution b) further comprises at least one additive.
11 . The gel polymer electrolyte according to claim 10 , wherein the additive is a film-forming additive.
12 . A process for the manufacture of the gel polymer electrolyte for a lithium electrochemical cell according to claim 1 , said process comprising the steps of:
a) dissolving at least one fluorinated copolymer in a volatile solvent;
b) mixing the dissolved polymer solution with a liquid electrolyte;
c) reacting the resulting solution from the step b) with at least one isocyanate compound comprising at least two isocyanate functional groups, so as to form a three-dimensional cross-linked polymer network;
d) casting the resulting solution from the step c) on a substrate; and
e) evaporating to produce a gel polymer electrolyte.
13 . The gel polymer electrolyte according to claim 1 , being a separator and an electrolyte in an electrochemical cell.
14 . A lithium electrochemical cell comprising
a cathode;
an anode; and
the gel polymer electrolyte according to claim 1 .
15 . A lithium electrochemical cell comprising
a cathode;
an anode; and
a gel polymer electrolyte,
wherein the gel polymer electrolyte is produced by the process according to claim 12 .