Process for the degradation of a poly(alkene carbonate), uses for preparing a lithium-ion battery electrode and the sintering of ceramics

Abstract

Provided is a process for the degradation of at least one polymer of an alkene carbonate, a polymeric composition for a lithium-ion battery electrode having a degradation residue obtained by this process, a process for the preparation thereof, an electrode and a battery incorporating it and a degradation process for the sintering of ceramics. The degradation process includes a reaction at 120° C. and 270° C., and under air of a primary amine with a poly(alkene carbonate) polyol, which depolymerizes it in order to obtain a non-polymeric degradation residue. This composition includes an active material, an electrically conductive filler, a polymeric binder and a residue from the degradation under air between 120° C. and 270° C. of a sacrificial phase which includes the polymer and which has been melt blended beforehand with the active material, with the filler and with the binder in order to obtain a precursor mixture of the composition.

Claims

1. A process for the degradation of at least one polymer of an alkene carbonate at a temperature of between 120° C. and 270° C., comprising a reaction under air of a primary amine with the at least one polymer which is a poly(alkene carbonate) polyol, the reaction depolymerizing the at least one polymer in order to obtain a non-polymeric degradation residue, wherein the reaction is carried out in an oven in communication with a stream of air exterior to the oven, the stream of air extracting the at least one poly(alkene carbonate) polyol as it is degraded.

2. The process according to claim 1, wherein the stream of air is formed of ambient air at atmospheric pressure of 1.013×10.sup.5 Pa.

3. The process according to claim 1, wherein the primary amine depolymerizes the at least one poly(alkene carbonate) polyol by the reaction without an organometallic catalyst in order to obtain the degradation residue which is vaporizable, the ratio by weight of the residue to the initial poly(alkene carbonate) polyol(s) being between 0.2% and 5%.

4. The process according to claim 3, wherein the degradation residue is a liquid/solid mixture comprising: between 10% and 90% by weight of a first residue comprising a carbonate of the alkene and/or oligomeric traces of the at least one poly(alkene carbonate) polyol, and between 90% and 10% by weight of a second residue comprising a degradation product of the primary amine.

5. The process according to claim 3, wherein, in order to obtain the degradation residue, the reaction is carried out between 130° C. and 260° C. for at most 2 hours.

6. The process according to claim 1, wherein the primary amine is chosen from aliphatic or aromatic monoamines and polyamines exhibiting: in the case where the primary amine is a monomer, a boiling point of greater than 180° C. and preferably equal to or greater than 200° C. at atmospheric pressure of 1.013×10.sup.5 Pa, and in the case where the primary amine is an oligomer or a polymer, a weight-average molecular weight of less than or equal to 2000 g/mol.

7. The process according to claim 6, wherein the primary amine is a monomeric aliphatic monoamine chosen from non-volatile alkylamines.

8. The process according to claim 6, wherein the primary amine is a monomeric aromatic monoamine chosen from anilines and aniline derivatives.

9. The process according to claim 6, wherein the primary amine is an oligomeric or polymeric aliphatic polyamine of polyetheramine type.

10. The process according to claim 1, wherein the at least one poly(alkene carbonate) polyol is a linear aliphatic diol, more than 50 mol % of the end groups of which are hydroxyl groups with which the primary amine interacts.

11. The process according to claim 10, wherein the at least one poly(alkene carbonate) polyol is chosen from poly(ethylene carbonate) diols and poly(propylene carbonate) diols with a weight-average molecular weight of between 700 g/mol and 2000 g/mol.

12. The process according to claim 1, wherein the primary amine/poly(alkene carbonate) polyol(s) ratio by weight for the reaction is less than or equal to 10% inclusive.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Other characteristics, advantages and details of the present invention will emerge on reading the following description of several exemplary embodiments of the invention, given by way of illustration and without limitation, in connection with the appended drawings, among which:

(2) FIG. 1 is a graph showing the change in the degree by weight of degradation of a poly(alkene carbonate) polyol (abbreviated to PAC) as a function of the amine/PAC ratio by weight for two reaction durations, by a degradation at 140° C. according to the invention using a primary amine according to the said second embodiment,

(3) FIG. 2 is a graph showing the change in the degree by weight of degradation of the same PAC as a function of the amine/PAC ratio by weight for these same durations, by a degradation at 170° C. according to the invention using the same primary amine,

(4) FIG. 3 is a graph showing the change in the degree by weight of degradation of the same PAC as a function of the amine/PAC ratio by weight for three reaction durations, by a degradation at 140° C. according to the invention using a primary amine according to the said first embodiment, and

(5) FIG. 4 is a graph showing the change in the degree by weight of degradation of the same PAC as a function of the amine/PAC ratio by weight for two reaction durations, by a degradation at 140° C. not in accordance with the invention using a secondary amine.

DETAILED DESCRIPTION

(6) Examples according to the invention and not in accordance with the invention of degradation of a poly(alkene carbonate) polyol respectively by two primary amines and by a secondary amine:

(7) Thermal degradation tests were carried out in an oven under air at a temperature in the oven of 140° C. (FIGS. 1, 3 and 4) or 170° C. (FIG. 2) on mixtures consisting: of approximately 5 g of a poly(propylene carbonate) polyol having the Converge® Polyol 212-10 name (sold by Novomer, abbreviated to PPC below) which is liquid at 25° C. and exhibits a weight-average molecular weight Mw of approximately 1000 g/mol, and of a variable weight of a primary amine (FIGS. 1-3) or secondary amine (FIG. 4) mixed with this polymer in a Haake Polylab OS internal mixer (capacity of 69 cm.sup.3) at a temperature between 60° C. and 75° C.

(8) The degradation of the PPC was quantified under isothermal conditions by measuring its loss in weight at different times.

(9) With reference to FIG. 1, a mixture according to the invention of PPC and of primary amine having the Jeffamine® T-403 name (Huntsman, oligomeric triamine according to the abovementioned formula II of polyetheramine type with three NH.sub.2 groups at the ends of aliphatic chains) was subjected to heating at 140° C. for 30 min and 1 h in the oven open to ambient air, on each occasion for different T-403/PPC ratios by weight ranging from 0% (control tests without T-403) to 10%. These tests show that T-403 used according to a ratio of only 2% virtually completely degraded the PPC (loss in weight of approximately 100%) after 1 h at 140° C., whereas the heat treatment alone (zero ratio) had shown virtually no degradation of the PPC.

(10) With reference to FIG. 2, this same PPC/Jeffamine® T-403 mixture was subjected to heating at 170° C. for 30 min and 1 h in the same oven open to ambient air, on each occasion for different T-403/PPC ratios by weight ranging from 0% (control tests without T-403) to 10%. These tests show that T-403 used according to a ratio of only 2% virtually completely degraded the PPC after only 30 min at 170° C., whereas the heat treatment alone had only slightly degraded the PPC.

(11) With reference to FIG. 3, another mixture according to the invention, PPC/TETA (Merck, triethylenetetramine), was subjected to heating at 140° C. for 30 min, 1 h and 1 h 45 min in the same oven open to ambient air, on each occasion for different TETA/PPC ratios by weight ranging from 0% (control tests without TETA) to 3%. These tests show that TETA used according to a ratio of only 1% virtually completely degraded the PPC (loss in weight of approximately 100%) after 1 h 45 min at 140° C., whereas the heat treatment alone had shown virtually no degradation of the PPC.

(12) With reference to FIG. 4, a mixture not in accordance with the invention, PPC/Dusantox 86 (Duslo, secondary amine, abbreviated to Du86), was subjected to heating at 140° C. for 1 h and 2 h in the same oven open to ambient air, on each occasion for different Du86/PPC ratios by weight ranging from 0% (control tests without Du86) to 0.06%. These tests show that Du86 has shown virtually no degradation of the PPC at 140° C., even after 2 h (loss in weight still less than or equal to 8%, whatever the ratio chosen), like the heat treatment alone (zero ratio).

(13) “Control” examples and examples according to the invention of the production of electrodes for a lithium-ion battery:

(14) A “control” anode composition C and an anode composition according to the invention I were prepared by means of the following ingredients: Active material: artificial graphite of lithium-ion battery grade. Binder: HNBR Zetpol® 0020 (Zeon Chemicals L.P, comprising 50% of acrylonitrile units by weight). Conductive filler: purified expanded graphite. sacrificial polymeric phase: blend of two propylene carbonate polymers (PPCs) having the names: Converge® Polyol 212-10 (Novomer): abovementioned liquid poly(propylene carbonate) polyol, and QPAC® 40 (Empower Materials): poly(propylene carbonate) which is solid at 25° C. (average molecular weight Mw greater than 50 000 g/mol).

(15) The composition I additionally comprised the primary amine having the Jeffamine® T-403 name, in contrast to the composition C, which was devoid of any amine.

(16) Each of the anode compositions C and I was prepared by the molten route using an internal mixer of Haake Polylab OS type with a capacity of 69 cm.sup.3 at a temperature between 60° C. and 75° C.

(17) The mixtures thus obtained were calendered at ambient temperature using a Scamex external roll mill until a thickness of 200 μm was achieved. They were subsequently again calendered at 50° C. in order to obtain films of mixtures with a thickness of 50 μm, which were deposited on a copper collector using a sheet calendar at 70° C.

(18) Each collector/film assembly thus obtained was then placed in an oven under ambient air in order to extract, from each film, the sacrificial polymeric phase (solid and liquid PPC). This sacrificial phase was degraded by subjecting each film to a temperature gradient from 50° C. to 250° C. and then to an isotherm for 30 min at 250° C., in order to obtain, after extraction of this phase, an anode composition film.

(19) The formulations of the precursor mixtures (before extraction) and of the compositions obtained (after extraction), in terms of fractions by weight in each mixture and in each composition respectively, are given in detail in Table 1 below.

(20) TABLE-US-00001 TABLE 1 Control anode film C Mixture C Composition C before extraction after extraction (m/m, %) (m/m, %) Binder: HNBR (Zetpol ® 0020) 1.8 3 Conductive filler: purified 1.8 3 expanded graphite Converge ® Polyol 212-10 25.6 ≅0 Polypropylene carbonate QPAC ® 13.8 ≅0 40 Active material: artificial graphite 57.0 94 Anode film according to the invention I Mixture I Composition I before extraction after extraction (m/m, %) (m/m, %) Binder: HNBR (Zetpol ® 0020) 1.8 3 Conductive filler: expanded 1.8 3 purified graphite Converge ® Polyol 212-10 25.6 ≅0 QPAC ® 40 13.8 ≅0 Primary amine: Jeffamine ® T-403 0.4 traces Active material: artificial graphite 57.0 94

(21) The composition I according to the invention exhibited, according to a fraction by weight of less than 1%, a degradation residue in the form of a liquid/solid mixture, the product of the depolymerization reaction of the sacrificial polymers by the primary amine, and comprised, in this example, after analysis: between 50% and 75% by weight of a propylene carbonate and of oligomeric traces of the sacrificial polymers, and between 25% and 50% by weight of an oxidized residue of the primary amine.

(22) Each C and I anode obtained was characterized by the following electrochemical protocol.

(23) The C and I anodes were cut out with a hollow punch (diameter 16 mm, surface area 2.01 cm.sup.2) and were weighed. The weight of active material was determined by subtracting the weight of the bare current collector prepared according to the same conditions (heat treatments). They were placed in an oven directly connected to a glovebox. They were dried at 100° C. under vacuum for 12 hours and then they were transferred into the glovebox (argon atmosphere: 0.1 ppm H.sub.2O and 0.1 ppm O.sub.2).

(24) The button cells (CR1620 format) were subsequently assembled using a lithium metal counterelectrode, a Cellgard 2500 separator and an LiPF.sub.6 EC/DMC (50/50 as ratio by weight) battery-grade electrolyte. The cells were characterized on a Biologic VMP3 potentiostat, by carrying out constant-current charge/discharge cycles between 1 V and 10 mV. The conditions were C/5, while considering the weight of active material and a theoretical capacity of 372 mAh/g. In order to compare the performances of the different systems, the capacities (expressed in mAh/g of anode) during the first discharge for the deinsertion of lithium (initial capacity after the first cycle) and at the tenth discharge (capacity at ten cycles) were evaluated. In addition, the degree of retention R (%) for the ratio of the capacity at ten cycles to the capacity at the first cycle was calculated.

(25) The results of this characterization are given below in Table 2.

(26) TABLE-US-00002 TABLE 2 Initial capacity Capacity at 10 cycles (mAh/g) - Anodes (mAh/g) % retention/1.sup.st cycle “Control” C 200 210 - 105% Invention I 260 260 - 100%

(27) These results show that the incorporation of the primary amine in the anode film mixture I makes it possible, after degradation according to the invention of the propylene carbonate polymers present in this mixture as sacrificial phase, to obtain, by this both thermal and chemical degradation, a composition which confers, on the anode: a markedly improved initial capacity, which is 30% greater than that of the anode C obtained without incorporation of primary amine in the mixture (i.e., by an exclusively thermal degradation of the sacrificial polymers), and a capacity at ten cycles which remains very high, which is 25% greater than that of the anode C and which testifies to complete maintenance of the capacity between the first and tenth cycles.