Electrode-forming composition
The present invention pertains to an electrode-forming composition comprising: (a) at least one fluoropolymer [polymer (F)]; (b) particles of at least one active electrode material [particles (P)], said particles (P) comprising: —a core comprising at least one active electrode compound [compound (NMC)] of formula (I): Li[Li x (A p B Q C w ) 1-x ]O 2 (I) wherein A, B and C, different from each other, are selected from the group consisting of Fe, Ni, Mn and Co, x is comprised between 0 and 0.3, P is comprised between 0.2 and 0.8, preferably between 0.2 and 0.5, more preferably between 0.2 and 0.4, Q is comprised between 0.1 and 0.4, and W is comprised between 0.1 and 0.4, and —an outer layer consisting of a metal compound [compound (M)] different from Lithium, said outer layer at least partially surrounding said core; and (c) a liquid medium [medium (L)]. The present invention also pertains to a process for manufacturing said electrode-forming composition, to the use of said electrode-forming composition in a process for manufacturing a positive electrode and to the positive electrode obtainable therefrom.
1. An electrode-forming composition comprising:
(a) at least one fluoropolymer [polymer (F)];
(b) particles of at least one active electrode material [particles (P)], said particles (P) comprising:
a core comprising at least one active electrode compound (NMC) of formula (I-B):
Li[Li x″ (Ni P″ Mn Q″ Co W″ ) 1-x″ ]O 2 (I-B)
wherein x″ is equal to 0, P″ is comprised between 0.2 and 0.8, Q″ is comprised between 0.1 and 0.4, and W″ is comprised between 0.1 and 0.4, with the proviso that the sum (P″+Q″+W″) is equal to 1, and
an outer layer consisting of a metal compound (M), said compound (M) consisting of one or more metals selected from the group consisting of Ni, Cu, Al, Ag and alloys thereof, in their elemental oxidation state,
said outer layer at least partially surrounding said core; and
(c) a liquid medium (L).
2. The electrode-forming composition according to claim 1 , wherein polymer (F) is a vinylidene fluoride (VDF) polymer [polymer (VDF)] comprising:
(aa) at least 50% by moles of recurring units derived from vinylidene fluoride (VDF);
(bb) optionally, from 0.1% to 20% by moles of a fluorinated monomer different from VDF; and
(cc) optionally, from 0.1% to 10% by moles, based on the total amount of monomers (aa) and (bb), of at least one hydrogenated monomer.
3. The electrode-forming composition according to claim 2 , wherein polymer (F) is a polymer (VDF) comprising recurring units derived from vinylidene fluoride (VDF) and from at least one (meth)acrylic monomer (MA) of formula (II):
wherein:
R 1 , R 2 and R 3 , equal to or different from each other, are independently selected from a hydrogen atom and a C 1 -C 3 hydrocarbon group, and
R x is a hydrogen atom or a C 1 -C 5 hydrocarbon moiety comprising at least one hydroxyl group.
4. The electrode-forming composition according to claim 2 , wherein polymer (VDF) comprises:
(aa) at least 80% by moles of recurring units derived from vinylidene fluoride (VDF);
(bb) optionally, from 0.1% to 10% by moles of a fluorinated monomer different from VDF; and
(cc) optionally, from 0.1% to 3% by moles, based on the total amount of monomers (aa) and (bb), of at least one hydrogenated monomer.
5. The electrode-forming composition according to claim 2 , wherein the fluorinated monomer different from VDF is a fluorinated monomer selected from the group consisting of vinylfluoride (VF1), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), tetrafluoroethylene (TFE), perfluoromethylvinylether (MVE), trifluoroethylene (TrFE) and mixtures thereof.
6. The electrode-forming composition according to claim 1 , said composition further comprising at least one electroconductivity-imparting additive.
7. The electrode-forming composition according to claim 6 , wherein the at least one electroconductivity-imparting additive is selected from the group consisting of carbon black, graphene or carbon nanotubes, metal powders and metal fibers.
8. The electrode-forming composition according to claim 1 , wherein medium (L) comprises water.
9. The electrode-forming composition according to claim 1 , wherein medium (L) comprises at least one organic solvent (S).
10. A process for manufacturing the electrode-forming composition according to claim 1 , said process comprising mixing at least one polymer (F) and the particles (P) in a medium (L), wherein the particles (P) are manufactured by electroless plating.
11. The process according to claim 10 , wherein mixing of at least one polymer (F) and particles (P) in a medium (L) is carried out by means of a roll kneader, a mixer, a homo mixer, a ball mixer, or a bead mill.
12. A process for manufacturing a positive electrode, said process comprising:
(i) applying the electrode-forming composition according to claim 1 onto at least one surface of a current collector thereby providing a film; and
(ii) drying the film provided in step (i).
13. The process according to claim 12 , wherein the electrode-forming composition is applied by a conventional wet coating process selected from the group consisting of screen printing, coating using a roll coater, a blade coater, a slit coater, a curtain coater, a wire coater, a sprayer, a foam applicator and a brush coater.
14. A positive electrode obtainable by the process according to claim 12 .
15. An electrochemical device comprising the positive electrode according to claim 14 .
16. The electrode-forming composition according to claim 1 , wherein P is comprised between 0.2 and 0.4.
17. The electrode-forming composition according to claim 1 , wherein P″ is comprised between 0.2 and 0.4.