AQUEOUS BINDER COMPOSITION FOR LITHIUM ION ELECTRICAL STORAGE DEVICES
An electrode binder of a lithium ion secondary battery comprising: (a) a polyvinylidene binder dispersed in aqueous medium with (b) a (meth)acrylic polymer dispersant. The binder can be used in the assembly of electrodes of lithium ion secondary batteries.
1 . An electrode binder of a lithium ion secondary battery comprising:
(a) a polyvinylidene fluoride polymer dispersed in aqueous medium with
(b) a (meth)acrylic polymer dispersant.
2 . The electrode binder of claim 1 in which the (meth)acrylic polymer has a glass transition temperature of from −50 to +70° C.
3 . The electrode binder of claim 1 in which the (meth)acrylic polymer is prepared from a mixture of monomers comprising one or more carboxylic acid-containing (meth)acrylic monomers and in which the carboxylic acid groups are at least partially neutralized with a base.
4 . The electrode binder of claim 3 in which the mixture of monomers comprises a hydroxyl group-containing (meth)acrylic monomer.
5 . The electrode binder of claim 3 in which the base is an amine.
6 . The electrode binder of claim 5 in which the amine is a volatile tertiary amine.
7 . The electrode binder of claim 4 is self-crosslinking in that the mixture of monomers contains a monomer that contains reactive groups that are reactive with the carboxylic acid and/or the hydroxyl groups or are reactive with themselves.
8 . The electrode binder of claim 7 in which the reactive groups comprise N-alkoxymethyl (meth)acrylamide groups and/or blocked isocyanate groups.
9 . The electrode binder of claim 3 which additionally contains (c) a crosslinking agent reactive with carboxylic acid groups.
10 . The electrode binder of claim 9 in which the crosslinking agent comprises aminoplast, polycarbodiimides and/or polyepoxides.
11 . The electrode binder of claim 9 in which the polyvinylidene fluoride polymer is present in amounts of 50 to 98 percent by weight; the (meth)acrylic polymer is present in amounts of 2 to 50 percent by weight and the crosslinking agent is present in amounts of 2 to 50 percent by weight, the percentages by weight being based on resin solids.
12 . The electrode binder of claim 11 which has a resin solids content of 30 to 80 percent by weight.
13 . An electrode slurry for a lithium ion secondary battery comprising:
(a) an electrically active material capable of lithium intercalation/deintercalation,
(b) a binder comprising as separate components:
(i) a polyvinylidene fluoride polymer dispersed in aqueous medium with
(ii) a (meth)acrylic polymer dispersant,
(c) a conductive agent, and
(d) a thickener.
14 . The electrode slurry of claim 13 in which (a) comprises LiCoO 2 , LiNiO 2 , LiFePO 4 , LiCoPO 4 , LiMnO 2 , LiMn 2 O 4 , Li(NiMnCo)O 2 , Li(NiCoAl)O 2 , carbon-coated LiFePO 4 , and mixtures thereof.
15 . The electrode slurry of claim 13 in which (a) is LiFePO 4 .
16 . The electrode slurry of claim 13 in which (c) comprises graphite, activated carbon, acetylene black, furnace black and graphene.
17 . The electrode slurry of claim 13 further comprising an organic solvent.
18 . The electrode slurry of claim 13 in which
(a) is present in amounts of 45 to 95 percent by weight;
(b) is present in amounts of 2 to 20 percent by weight;
(c) is present in amounts of 2 to 20 percent by weight; and
(d) is present in amounts of 0.1 to 15 percent by weight;
the percentages by weight being based on total solids weight.
19 . The electrode slurry of claim 13 in which the (meth)acrylic polymer has a glass transition temperature of from −50 to +70° C.
20 . The electrode slurry of claim 13 in which the (meth)acrylic polymer is prepared from a mixture of monomers comprising one or more carboxylic acid-containing (meth)acrylic monomers and in which the carboxylic acid groups are at least partially neutralized with a base.
21 . The electrode slurry of claim 20 in which the mixture of monomers comprises a hydroxyl group-containing (meth)acrylic monomer.
22 . The electrode slurry of claim 20 in which the base is an amine.
23 . The electrode slurry of claim 22 in which the amine is a volatile tertiary amine.
24 . The electrode slurry of claim 21 in which the mixture of monomers is self-crosslinking in that the mixture contains a monomer that contains groups that are reactive with the carboxylic acid and/or the hydroxyl groups or with themselves.
25 . The electrode slurry of claim 24 in which the reactive groups comprise N-alkoxymethyl amide groups and/or blocked isocyanate groups.
26 . The electrode slurry of claim 20 which additionally contains (c) a crosslinking agent reactive with carboxylic acid groups.
27 . The electrode slurry of claim 26 in which the crosslinking agent comprises aminoplast, polycarbodiimides and/or polyepoxides.
28 . The electrode slurry of claim 26 in which the polyvinylidene fluoride polymer is present in amounts of 50 to 98 percent by weight; the (meth)acrylic polymer is present in amounts of 2 to 50 percent by weight and the crosslinking agent is present in amounts of 2 to 50 percent by weight, the percentages by weight being based on resin solids.
29 . The electrode slurry of claim 28 which has a resin solids content of 30 to 80 percent by weight.
30 . An electrode comprising:
(a) an electrical current collector;
(b) a cured film formed on the collector (a) comprising:
(i) a polyvinylidene fluoride polymer,
(ii) a crosslinked (meth)acrylic polymer,
(iii) a conductive material,
(iv) an electrode active material capable of lithium intercalation/deintercalation, and
(v) a thickener.
31 . The electrode of claim 30 in which (a) comprises copper or aluminum sheet or foil.
32 . The electrode of claim 30 in which the crosslinked (meth)acrylic polymer is formed from reacting active hydrogen groups associated with the (meth)acrylic polymer and a crosslinking agent containing reactive groups that are reactive with the active hydrogen groups.
33 . The electrode of claim 32 in which the active hydrogen groups comprise carboxylic acid groups.
34 . The electrode of claim 32 in which the crosslinking agent contains a reactive group in the (meth)acrylic polymer or in the separately added crosslinking material that are reactive with the active hydrogen groups.
35 . The electrode of claim 34 in which the reactive groups in the (meth)acrylic polymer comprise N-alkoxymethyl amide groups and/or blocked isocyanate groups.
36 . The electrode of claim 32 in which the separately added material comprises aminoplast, polycarbodiimides and/or polyepoxides.
37 . The electrode of claim 30 in which (iii) comprises graphite, activated carbon, acetylene black, furnace black and graphene.
38 . The electrode of claim 30 in which (iv) comprises LiCoO 2 , LiNiO 2 , LiFePO 4 , LiCoPO 4 , LiMnO 2 , LiMn 2 O 4 , Li(NiMnCo)O 2 , Li(NiCoAl)O 2 , carbon-coated LiFePO 4 , and mixtures thereof.
39 . The electrode of claim 30 in which
(i) is present in amounts of 1 to 20 percent by weight;
(ii) is present in amounts of 0.1 to 10 percent by weight;
(iii) is present in amounts of 2 to 20 percent by weight;
(iv) is present in amounts of 45 to 95 percent by weight; and
(v) is present in amounts of 0.1 to 15 percent by weight,
the percentages by weight being based on total weight of the mixture.
40 . An electrical storage device comprising:
(a) the electrode of claim 30 ,
(b) a counter electrode, and
(c) an electrolyte.
41 . The electrical storage device of claim 40 in which the electrolyte is a lithium salt dissolved in a solvent.
42 . The electrical storage device of claim 41 in which the lithium salt is dissolved in an organic carbonate.