eEnvironm ntalILMIILIOA

nalysis of rganophosphates in ithium on
Battery Electrolytes by H C–ES - S

New separation techniques for the analysis of polar and ionic
analytes have aroused great interest in the field of metabolomics andenvironmental investigation in the past two decades. Hydrophilicinteraction liquid chromatography (HILIC) is a promising tool toaddress this challenge. HILIC separation is based on the polarityof analytes, which generally show stronger retention with increasingpolarity according to the HILIC separation mechanism. Furthermore,
the high content of organic solvent in the mobile phase leads togood ionization properties in the electrospray ionization (ESI), andconsequently enhances the detection sensitivity by hyphenatedmass spectrometry (MS) detector.
Analysis of organophosphates as the degradation productsof pesticides, flame retardants, plasticizers, or batteries is very
important for safety evaluation because their chemical structuresare similar to chemical warfare agents with high toxic potential(1). Lithium ion batteries possess electrolytes in cells that usuallyconsist of different formulations of linear and cyclic organiccarbonates and hexafluorophosphate (LiPF6) conducting salts.
One of the major issues is the degradation of LiPF6 as a resultof thermal and chemical instability of the P-F bond. Subsequent
reactions lead to battery performance loss. The presence oftraces of moisture and elevated temperatures in a battery cellpromote the decomposition of PF6 to the reactive intermediate
PF 5 after a reaction cascade culminating in fluorinated andTEP

TMP

DMFP

OOCMCRMMM

M

Jonas Henschel1, Martin Winter1,2, Sascha Nowak1, and Wen Jiang3, 1 EET Battery esearch enter, University ofünster, ünster, Germany, 2Forschungszentrum Jülich GmbH, IEK-12, Helmholtz Institute ünster (HI S), 3HILI ON AB

alkylated phosphates (3). Therefore, it is vital to monitor all theorganophosphates in batteries, which helps to better understandbattery performance loss and to avoid its potential threat to theenvironment during the disposal process.
Organophosphates cover a wide spectra of ionic and high polar
species as well as nonpolar analytes. Multiple separation techniquessuch as gas chromatography (GC), ion chromatography (IC), orreversed-phase liquid chromatography (LC) are often required forthe comprehensive determination of the organophosphates andtheir formed degradation products (1,2). However, we aimed todevelop an LC method using either HILIC or RP column that leads
to a simultaneous separation of all organophosphorus species
by one chromatography run for our study. In this application,
we demonstrate the separation potential of polar and ionicorganophosphate species with an iHILIC ® -Fusion(+) column
packed with charge modulated hydroxyethyl amide silica. A
mixed interaction, for example, hydrophilic partitioning and ionicinteractions, may be involved in the HILIC separation mechanism
depending on the chemical properties of the analytes.

Experimental
LC–MS system 1: Thermo Ultimate 3000 LC system and AB SCIEX
3200 QTrap® equipped with an ESI source, operated in ESI(+) andESI(-) mode for analysis of standards.

100TEP

O
O

P

PO

O

P

O

O

DBP

DEP

DMP

O

O

O

O

O

P
O

TMP

F

O–O

O

P–O

O

P–O

Rel. intensity (%)

O

50DBP
DFP

O

O

DMFP
0O–O

PDMPDEP

DFP04F

81216Time (min)FC

beTHE APPLICATIONS BOOK – D c meC

Figure 2: Extracted ion chromatograms of organophosphatestandards in HILI separation with iHILI ®-Fusion(+).

e2



C

Figure 1: hemical structures of organophosphatestandards used in the study.

r 2017eEnvironm ntal

Rel. intensity (%)

100

Table 1: Retention times (tR ) and suggested structures ofdegradation products from LiPF6 electrolyte

155.046
171.041183.077
199.072
213.089tR (min)m/z (M+H)+

1.3

213.0891.3

183.077

1.3

199.0728.8

199.072

9.1155.046

9.4

171.0419.7

171.04113.2

171.041

50TEP00481216Time (min)Figure 3: Extracted ion chromatograms of possible degradantorganophosphate products in lithium ion battery electrolyte.

---

The applicability of the iHILIC® Fusion(+) column for the studyof battery electrolyte degradation products was investigated and isillustrated in Figure 3 and Table 1. The hyphenation of HILIC with an
IT TOFTM MS system allowed us to separate and elucidate structural
information of several formed organophosphates in thermally treatedbattery electrolyte.
This work emphasizes the potential application of using
HILIC–ESI MS methods for the analysis of organophosphates in thebattery industry and for environmental investigation.
------

LC–MS system 2: Shimadzu Nexera X2 LC system and Shimadzu
LC‑MS IT TOF™ equipped with an ESI source, operated in ESI(+)
mode for analysis of thermally treated battery electrolyte.
Column: 150 × 2.1 mm, 3.5 μm iHILIC® Fusion(+) (P/N
100.152.0310, HILICON AB)
Gradient elution 1: A) acetonitrile; B) deionized water 1 M
ammonium formate, pH 2.9 (99.5:0.5); 0–3.5 min (90:10) A–B;
3.5 to 6.5 min, gradient elution from (90:10) A–B to (50:50) A–B;
6.5–14.5 min, (50:50) A–B.
Gradient elution 2: A) acetonitrile; B) deionized water 1 M
ammonium acetate, pH 6.1 (99:1); 0–3.5 min (95:5) A–B; 3.5 to
8 min, gradient elution from (95:5) A–B to (75:25) A–B; 8–16 min,(75:25) A–B.
Flow rate: 0.3 mL/min
Column temperature: 40 °C
Injection volume: 10 µL
Organophosphates: Trimethyl phosphate (TMP), triethyl phosphate(TEP), dimethyl phosphate (DMP), diethyl phosphate (DEP),
dibutyl phosphate (DBP), difluorophosphate (DFP), dimethyl
fluorophosphates (DMFP). Their detailed chemical structures areillustrated in Figure 1. A 50 µM measure of TMP, TEP, DMP, andDEP, 100 µM of DFP and DBP, and 350 µM of DMFP were preparedin 90:10 acetonitrile–water solution.
Battery electrolyte: 1 M LiPF6 in ethylene carbonate–ethyl methylcarbonate–vinylene carbonate (30:70:+2 w%, LP 572, BASF) with2v% water addition was stored at 80 °C for 14 days.
-Suggested Structure

References(1)V. Kraft et al., RSC Advances 6, 8–17 (2016).

(2)

I. Van der Veen and J. de Boer, Chemosphere 88, 1119–1153 (2012).

(3)

C. Campion et al., J. Electrochem. Soc. 152(12), A2327–A2334 (2005).

Results and Conclusion-As shown in Figure 2, seven standards of organophosphates
can be simultaneously separated and determined using aniHILIC®‑Fusion(+) column hyphenated to ESI MS detection. The
nonpolar organophosphates TEP, TMP, and DMFP were eluted first.
This is expected due to weaker interaction with the HILIC stationary
phase through the hydrophilic partioning. The other four ionic species,DFP, DBP, DEP, and DMP, show stronger retention and good peak
shapes by hydrophilic partitioning and ionic interaction.
r 2017

beee

THE APPLICATIONS BOOK – D c m3