Additional files

List of names of molecules

Formula NameAr Argon

C2H2 AcetyleneC2H4 Ethylene

C2H5F FluoroethaneC2H5OC2H5 Diethyl ether

C2H5OH EthanolC2H6 EthaneC3H6 Propene

CD3CN TrideuteroacetonitrileCH2O Formaldehyde

CH3C(=O)H AcetaldehydeCH3OC(=O)H Methyl formate

CH3C(=O)OCH3 Methyl esterCH3F Fluoromethane

CH3OC2H5 Ethyl etherCH3OC2H5 Ethyl methyl etherCH3OCH3 Dimethyl etherCH3OH Methanol

CH4 MethaneCO Carbon monoxideCO2 Carbon dioxideDEC Diethyl carbonateDMC Dimethyl carbonateEA Ethyl acetateEC Ethylene carbonate

EMC Ethyl methyl carbonateH2 Dihydrogen

H2O WaterHF Hydrofluoric acid

LiPF6 Lithium saltN2 DinitrogenO2 Oxygen

OHCH2CH2F FluoroethanolOP(OC2H5)F2 1-difluorophosphoryloxyethane

PF5 Phosphorus pentafluoridePOF3 Fluorine phosphoryl

VC Vinylene carbonate

Influence of the reactor surface

In order to experimentally study the influence of the surface/volume ratio and of the assembly internal

walls on the nature and quantities of the degradation products, aluminium foil strips were inserted into

the assembly. As the internal surface of the pyrolysis device was perfectly flat, the insertion of these

aluminium strips made it possible to multiply its internal surface by a factor of 2. These bands were

assumed not to change its internal volume. Two DMC degradation manipulations were performed at

300°C for 1 hour with this assembly and no significant difference was found in the nature and

quantification of the gaseous species created with the manipulations carried out without these aluminium

foils. The pyrolysis performed in the 304L steel device (an alloy composed basically of iron, chrome and

nickel) thus does not appear to be sensitive to the modification of the surface/volume ratio.

Table A: Molar fraction of each solvent in the liquid phase relative to the totality of the electrolyte solvents

SolventQuantity of the initial substance

in the cell (mol)Molar fraction of the solvent in the

liquid phaseDMC 5.99 x 10 -2 4.57 x 10 -1

EMC 3.25 x 10 -2 2.48 x 10 -1

EC 3.12 x 10 -2 2, 38 x 10 -1

PC 7.44 x 10 -3 5.68 x 10 -2

Assuming that the liquid mixture of solvents, without lithium salt, is an ideal solution, it

is possible to calculate the saturating vapor pressures of each solvent as a function of the

temperature, taking into account their proportions in the electrolyte given in the table

by applying Raoult’s law:

Raoult's Law: Pi=x iLP i

sat

where:   Pi: partial pressure of the solvent i, Pa                                                                               

                 x iL: molar fraction of the solvent i in the liquid phase

                  Pisat : saturated vapor pressure of the pure solvent i at the mixture temperature, Pa

Figure A. Monitoring of the internal temperature increase (in °C) as a function of time (in s) of the assembly at the three study temperatures

(180, 240 and 300°C). * A cooling test (quenching) was performed after 1450 s for calibration at 300°C.

45 60 75 90 105 120 135 150 165 180 195 210 2250

200

400

600

800

1000

1200

DMC EMC EC PC

Pre

ssio

n de

vap

eur s

atur

ante

(kP

a)

Température (°C)Satu

ratin

gvap

ourp

ress

ure

(kPa

)

Temperature (°C)

Figure B. Molar fractions of the main products formed during the thermal degradation of the DMC under an inert atmosphere at the

three study temperatures: a) 180°C, b) 240°C, c) 300°C.

0 200 400 600 800 1000 1200 1400 16000

50

100

150

200

250

300

Temps initial t0

de l'expèrience

Tem

péra

ture

(°C

)

Temps (s)

180°C 240°C 300°C

*Trempe de l'assemblagedans le sable

Tem

pera

ture

(°C)

Time (s)

Quenching of theassembly in thesand.

Initial time ofthe experimentto

Figure C. Calibration curves of the reference species for each column: CH4 in the MS5A column under helium, CO2 in the PLOTQ column,

CH3OH in the OV1 column and H2 in the MS5A column under argon.

Method for estimating the amount of degraded solvent from the quantification of species created by

thermal degradation:

1) Calculation of the amount of substance of each species formed during the degradation of the

solvent according to the ideal gas law.

n(species formed)=P (assembly )×V (assembly )×C(species)

RT ×100

Where: P(assembly): Pressure of the assembly during its analysis in PaV(assembly): Volume of the assembly in m3

C(species) : Fraction of the species in the assembly (calculated from the concentration obtained with the calibration in%)R: Constant of perfect gases (8.314 J mol -1K -1)T: Bottle temperature during its analysis, in K  

2)       Calculation of the sum of the quantities of substance of each of the species formed, separated

into the quantities of substance of the elements carbon, oxygen and hydrogen, in order to verify

the conservation of the atomic mass. An empirical formula of a final product encompassing all of

the degradation products is thus obtained.

3)       Verification that the formula obtained from all of the products has a stoichiometric ratio of

carbon, oxygen and hydrogen atoms equivalent to that of the empirical formula of the solvent.

This step makes it possible to validate that the products formed indeed come from the pyrolysis

of the solvent.

 

4)   Division of the amount of substance of each element of the formula obtained previously by the

amount of substance of each element of the initial DMC. For example, for the carbon element, the

calculation is as follows:

%Carbon loss=n (carbon )∈the product ∑ ¿n ( carbon )∈the∈ jected DMC

×100 ¿

Three loss values for each element are thus obtained (carbon, hydrogen and oxygen). The average

of these three values makes it possible to obtain the estimate of the percentage of solvent loss

during handling. This calculation also makes it possible to estimate the concentration of solvent

remaining, and therefore not degraded, after handling. 

 

To validate the mass balance, it is first necessary to ensure that all of the species present in the assembly

have been analysed and quantified. To do this, the solvent concentration remaining after handling is

calculated from the experimentally established calibration curve. This gives a mass loss value of the

solvent. This value is then compared with the solvent loss value estimated from the quantification of the

minor species resulting from the solvent degradation carried out previously. The balance is validated if

the two values are identical, except in the case of manipulations where very little solvent was decomposed

because the solvent quantisation from its calibration curve lacks precision in this case.

Figure D. DMC Chromatograms

Figures D.1. to D.4 show the gaseous chromatograms obtained during degradation of the DMC carried out for 2 hours at 300°C. Some species can be analysed in two chromatographic columns. The species mentioned in parentheses are not quantified on the corresponding chromatogram, so they are quantified on the chromatogram of another column. Argon is not quantified. Peaks known as "composite peaks" contain species present in the mixture but not separated by the analysis column.

0 20 40 60 80 100 120

4,0x106

6,0x106

8,0x106

1,0x107

1,2x107

1,4x107

1,6x107

1,8x107

Sig

nal (

µV)

Temps (s)

(Composite)

(Blank)

(N2)

COCH4

Time (s)

Figure D.1. Chromatogram of the MS5A column (under a helium vector gas) obtained during the degradation of DMC for 2 hours at 300°C. The observed dinitrogen (N2) is due

to a microleak in the μGC injector because this peak is present in the same amount in the vector gas blank injections.

Time (s)

Time (s)

Figure D.2. Chromatogram of the OV1 column obtained during the degradation of DMC for 2 hours at 300°C.

0 20 40 60 80 100 120

-4,0x106

0,0

4,0x106

8,0x106

1,2x107

1,6x107

2,0x107

Sig

nal (

µV)

Temps (s)

Figure D.3. Chromatogram of the PLOTQ column obtained during the degradation of DMC for 2 hours at 300°C

(Composite)

CO2

(CH3OH + CH3OCH3)

Time (s)

0 20 40 60 80 100 120

1x106

2x106

3x106

4x106

5x106

6x106S

igna

l (µV

)

Temps (s)Figure D.4. Chromatogram of the MS5A column (under argon gas) obtained during the

degradation of DMC for 2 hours at 300°C

H2

(CH4) (CO)(N2)

Time (s)

Figure E. EMC Chromatograms

Figures E.1. to E.4. presented below show the gaseous chromatograms obtained during the EMC degradation carried out for 2 hours at 300°C.

0 20 40 60 80 100 1204,0x106

4,2x106

4,4x106

4,6x106

4,8x106

5,0x106

Sig

nal (

µV)

Temps (s)

Figure E.1. Chromatogram of the MS5A column (under a helium vector gas) obtained during EMC degradation for 2 hours at 300°C. The observed N2 is the result of a

microleak at the μGC injector because this peak is present in the same amount in the vector gas blank injections.

0 50 100 150 200 250 3005,0x105

1,0x106

1,5x106

2,0x106

2,5x106

3,0x106

3,5x106

Sig

nal (

µV)

Temps (s)

N2

CH4

CO

(Composite)

DMC

EMC

DEC

a)

Time (s)

Time (s)

0 5 10 15 20 25 305,0x105

1,0x106

1,5x106

2,0x106

2,5x106

3,0x106

3,5x106S

igna

l (µV

)

Temps (s)

Figure E.2. a): chromatogram of the OV1 column obtained during the degradation of EMC for 2 hours at 300°C. b) zoom on an area of interest of this chromatogram.

0 50 100 150 200 250 300

-5x106

-4x106

-3x106

-2x106

-1x106

0

1x106

Sig

nal (

µV)

Temps (s)Figure E.3. Chromatogram of the PLOTQ column obtained during the degradation of EMC

for 2 hours at 300°C.

(Composite)

CH3OCH3

CH3OH + CH3C(=O)H

CH3OC2H5

C2H5OH

C2H5OC2H5 CH3C(=O)OCH3

(Composite)CO2

C2H4

C2H6C3H6 CH3C(=O)H

CH3OH + CH3OCH3

(C2H5OH)

CH3OC2H5

b)

Time (s)

Time (s)

0 20 40 60 80 100 120 140-4,0x105

-2,0x105

0,0

2,0x105

4,0x105

6,0x105

8,0x105

1,0x106

1,2x106S

igna

l (µV

)

Temps (s)Figure E.4. Chromatogram of the MS5A column (under argon gas) obtained during the

degradation of EMC for 2 hours at 300°C. The observed N2 comes from a microleak at the μGC injector.

H2

(CH4) (CO)(

N2)

Time (s)