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SYNTHESIS AND CHARACTERIZATION OF CHOLINE CHLORIDE–BASED DEEP EUTECTIC SOLVENT FOR POTENTIAL APPLICATION AS ELECTROLYTES IN LITHIUM-ION BATTERIES PREPARED BY: INTAN QHUZAIRIN BINTI ZAHARUDDIN (AS222) UNDER SUPERVISION OF: DR NABILAH AKEMAL MUHD ZAILANI DR RIZANA YUSOF

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Energy storage system Efficient & ecologically benign energy storage system   Batteries Fuel  cells Supercapacitors Advantage: Highest specific energy  ( Zhong   et al.,  2015)

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Batteries  ( Abruna  et al., 2008)   Lithium-ion batteries Nickel-metal-hydride batteries Nickel-cadmium batteries Advantages: *Higher energy densities  *Less expensive  *Safer

200
K-ion
Na-ion
Ni-MH
Ni-Cd
Smaller Siæ
100
Volumetric energy density / Wh

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Liquid electrolyte  in Lithium-ion batteries   Organic solvent-based LE Ionic liquid (IL)-based  LE Deep eutectic solvent (DES)-based  LE Disadvantages: *Flammable *Volatile *Low thermal stability Disadvantages: *High cost *Tedious preparation *Toxicity *Poor biodegradability

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DES-BASED LE DES: Mixture consists of  Hydrogen Bond Acceptor (HBA)  and  Hydrogen Bond Donor (HBD)  which are able to self-associate to form a new eutectic mixture at melting point lower than melting point of each constituent in the mixture  (Tome  et al.,  2018).

HBA  Choline Chloride ( ChCl ) Biodegradable Able to interrupt hydrogen bonding   HBD 1,4-butanediol Shorter alkyl chain  Fewer hydroxyl group  Salt  Lithium  triflate  ( LiTf ) Strong metal reducing agent Charging-discharging process  No significant specific interaction

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DES-BASED LE   Advantages over IL-based LE: *Lower cost *Easy to prepare *Non-toxic *High biodegradability Disadvantages: Viscous Reduce free mobility of ion Low ionic conductivity

This has been supported by study done by Al Omar  et al . (2015)

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PROBLEM STATEMENT IL-based LE presents toxicity, having poor biodegradability as well as involves expensive cost and tedious preparation.  OBJECTIVE OF STUDY To  synthesize DES  from  ChCl  and  different amount of 1,4-butanediol.

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PROBLEM STATEMENTS Amount of HBD influence the structure, viscosity and ionic conductivity of DES due to the excessive amount of hydrogen bonding between HBA and HBD. Thus, result in increasing of viscosity, reduce the free mobility of ion and hence decrease the ionic conductivity of DES.   OBJECTIVE OF STUDY To determine the effect of various amount of 1,4-butanediol on the structure, viscosity and ionic conductivity of DES using Fourier transform infrared spectroscopy (FTIR), tensiometer and ionic conductivity meter respectively.

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PROBLEM  STATEMENTS Addition of  LiTf  is to provide additional conducting species and is a requirement for fabrication of lithium ion batteries, however addition of excessive amount of lithium salt might increase the viscosity, restrict the free mobility of lithium ion and hence decrease the ionic conductivity of LE.  OBJECTIVE OF  STUDY To fabricate liquid electrolyte by adding various weight percent of  LiTf   salt into the highest ionic conductivity of DES.  To determine the effect of various weight percent of  LiTf  on the structural and ionic conductivity of liquid electrolyte using FTIR and ionic conductivity meter respectively.

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SIGNIFICANCE OF STUDY This study will explain the effect of various amount of HBD (1,4-butanediol) and  LiTf  salt towards the properties of DES and LE respectively (i.e.: structure, viscosity and ionic conductivity). Also, the research will contribute to the production of highly conducting and environmental-friendly liquid electrolyte for application in lithium ion batteries.

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Symbol Mole ratio (ChCl:1,4-butanediol) DES1:1 1:1 DES1:2 1:2 DES1:3 1:3

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Symbol Percentage  of  LiTf  ( wt %) LE2.5 2.5 LE5 5 LE10 10

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Physical characteristics  of synthesized DES Homogenous liquid Oily Unpleasant fishy odour

Mole ratio of DES Time taken to form homogenous liquid (min)  1:1 9.23 1:2 6.20 1:3 7.19

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STRUCTURAL STUDIES OF DES *ND = not detected

Wavenumber (cm -1 ) Peak ChCl   ( Shafie  et al., 2019) 1,4-butanediol  (Jesus  et al.,  2008)                    DES         1:1 1:2 1:3 OH stretching 3222        3292  3297 3298 3293 C-O stretching ND        1169 1170 1172 1172 CH 2  bending 1480       1428 1441 1442 1448 CH 3  bending 1349         ND ND ND ND C-N stretching 1083         ND 1049 1046 1046

OH stretching shift to higher  wavenumber along with reduced peak intensity

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D econvolution  and band-fitting of the broad O-H stretching peak (3700 – 3100 cm -1 ) Wang  et al.  (2019)

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DES System Amount 1,4-butanediol (ml) Surface tension ( mN /m)   DES1:1 88.35 28.445 DES1:2 176.71 27.916 DES1:3 265.06 28.093

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DES System   Amount 1,4-butanediol (ml) Ionic conductivity DES (10 -3  S cm -1 )   DES1:1 88.35 2.41 DES1:2 176.71 1.34 DES1:3 265.06 0.92

Hydrogen bond Van der Waals interaction As confirmed by FTIR analysis

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DES system  Conductivity (S cm -1 ) References ChCl / EG        1.79  x 10 -3   Zhong   et al .  (2020) TBABr /EG        0.5285  x 10 -3 Yusof   et  al .  ( 2014)

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Doped the DES1:1 (2.41 X 10 -3  S cm -1 ) with (2.5, 5 and 10  wt %) of  LiTf

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Wavenumber (cm -1 )   Peak DES1:1    LiTf   (Ramesh and Chai, 2007) LE2.5 LE5 LE10   OH 3297 ND 3303 3301 3335 C-O stretching 1170 ND 1169 1168 1169 CH 2  bending 1441 ND 1441 1441 1441 C-N stretching 1049 ND 1049 1048 1031 SO 3  (a) ND 1273 1266 1266 1253 CF 3  (a) ND 1143 ND ND ND

Appearance of salt peak in the mixture of LE

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OH stretching shift to higher  wavenumber along with reduce peak intensity

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LE  System             Ionic conductivity (10 -3  S cm -1 )          LE2.5                                         2.56           LE5                                            1.84           LE10                                          0.65

Hydrogen bond restrict the mobility of Li ion

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LE system  Conductivity (S cm -1 ) References EG/ChCl/ LiPF 6       7.95 x 10 -3   Millia   et al . (2018) TFA/ LiTFSI       1.86 x 10 -3 Dinh   et al . (2020)

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CONCLUSION 1. DES1:1, DES1:2 and DES1:3 were successfully synthesized 2.   3.   LE2.5, LE5 and LE10 were successfully synthesized 4.

Hydrogen bond & Van der Waals interaction

~28  mN /m due to limitation of instrument

Restrict free mobility of Li ion & reduce ionic conductivity

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Electrochemical impedance spectroscopy (EIS)

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