COMPOSITIONS WITH LITTLE OR NO SOLVENT COMPRISING CARBON NANOTUBES AND AT LEAST ONE POLYMER
The present invention relates to compositions of carbon nanotubes which can be used in solid form, that is to say in the absence of solvent. These compositions comprise at least one polymer and are readily dispersible in formulations for the manufacture of electrodes for batteries and in particular Li-ion batteries in liquid or solid processes. The invention also relates to the process for obtaining these powders, to their use in the manufacture of electrodes for batteries, and also to the batteries comprising them.
1 . A composition comprising carbon nanotubes and at least one polymer, in a carbon nanotubes/polymer mass ratio of less than 100/5, said composition being in the form of a powder of loose bulk density of between 0.11 and 0.5 g/cm 3 , having an apparent specific surface area of between 50 and 350 m 2 /g measured with the aid of a Micromeritics ASAP 2460 instrument and a content by mass of solvent of less than 10%, wherein the polymer is chosen from modified polysaccharides, polyvinylpyrrolidone homopolymers or copolymers, the loose bulk density (LBD) being defined by the ratio of the mass of powder and its volume after having been loosened, the measurement being performed by measuring the maximum volume occupied by the powder in a 100 cm 3 closed graduated cylinder of mass T turned over several times slowly with weighings performed using a balance accurate to 0.1 g and filling the cylinder to three-quarters and then weighed to give a mass m 1 , closed, and then slowly turned over several times until the maximum volume occupied by the powder, denoted v, in cm 3 , is obtained, resulting in an loose bulk density expressed in g/cm 3 and calculated by the following formula LBD=(m 1 −T)/v.
2 . The composition as claimed in claim 1 , wherein the polymer is chosen from polyvinylpyrrolidone homopolymers or copolymers having a molecular mass of between 20,000 and 60,000 g/mol.
3 . The composition as claimed in claim 1 , further comprising carbon black in carbon nanotubes/carbon black mass ratios ranging from 100/1 to 1/100.
4 . The composition as claimed in claim 1 , further comprising at least one organic carbonate such as ethyl carbonate, propyl carbonate, diethyl carbonate, dimethyl carbonate and fluoroethylene carbonate, alone or as a mixture.
5 . The compositions as claimed in claim 1 , further comprising at least one compound chosen from lithium bis(trifluoromethane)sulfonimide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium hexafluoroarsenate, and 4,5-dicyano-2-(trifluoromethyl)imidazole in acid or lithium salt form, alone or as a mixture, and in particular 4,5-dicyano-2-(trifluoromethyl)imidazole in acid or lithium salt form.
6 . The composition as claimed in claim 1 , further comprising PVDF, homopolymer or copolymer and/or a non-halogenated elastomer.
7 . A process for preparing a composition as claimed in claim 1 , using an atomizer and comprising the following steps:
preparing a composition as claimed in claim 1 , in the presence of a solvent in a deflocculator, at a temperature of between 5 and 80° C., in order to obtain a dispersion comprising carbon nanotubes,
atomizing the dispersion with a gas heated to a temperature of greater than 120° C. and recovering the powder.
8 . A process for preparing a composition as claimed in claim 1 , comprising the steps of extrusion of the composition with injection of supercritical CO 2 during the extrusion step with a proportion by mass of supercritical CO2 of between 25% and 1000% of the composition followed by degassing of the CO 2 and recovery of powder.
9 . The use of a composition as claimed in claim 1 , for the manufacture of electrodes with or without solvent.
10 . An electrode obtained according to the use of claim 9 .
11 . A battery comprising at least one electrode as claimed in claim 10 .