Ionic liquid doped PEO-based solid polymer electrolytes for lithium-ion polymer batteries

Polu, Anji Reddy,Rhee, Hee-Woo Elsevier 2017 International journal of hydrogen energy Vol.42 No.10

<P><B>Abstract</B></P> <P>The influence of adding the room-temperature ionic liquid 1-ethyl-3-methyllimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) to poly(ethylene oxide) (PEO)–lithium difluoro(oxalato)borate (LiDFOB) solid polymer electrolyte and the use of these electrolytes in solid-state Li/LiFePO<SUB>4</SUB> batteries has been investigated. Different structural, thermal, electrical and electrochemical studies exhibit promising characteristics of these polymer electrolyte membranes, suitable as electrolytes in rechargeable lithium-ion batteries. The crystallinity decreased significantly due to the incorporation of ionic liquid, investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The ion–polymer interaction, particularly the interaction of cations in LiDFOB and ionic liquid with ether oxygen atom of PEO chains, has been evidenced by FT-IR studies. The polymer electrolyte with ∼40 wt% of ionic liquid offers a maximum ionic conductivity of ∼1.85 × 10<SUP>−4</SUP> S/cm at 30 °C with improved electrochemical stabilities. The Li/PEO-LiDFOB-40 wt% EMImTFSI/LiFePO<SUB>4</SUB> coin-typed cell cycled at 0.1 C shows the 1st discharge capacity about 155 mAh g<SUP>−1</SUP>, and remains 134.2 mAh g<SUP>−1</SUP> on the 50th cycle. The addition of the ionic liquid to PEO<SUB>20</SUB>-LiDFOB polymer electrolyte has resulted in a very promising improvement in performance of the lithium polymer batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ionic liquid doped solid polymer electrolytes were synthesized for Li-ion batteries. </LI> <LI> Strong interaction among PEO, LiDFOB and EMImTFSI was confirmed by FTIR studies. </LI> <LI> High total ionic conductivity; 1.85 × 10<SUP>−4</SUP> S/cm at 30 °C. </LI> <LI> EMImTFSI ionic liquid gave significant enhancement in ionic conductivity and electrochemical performance. </LI> <LI> Good cycling capabilities for LiFePO<SUB>4</SUB> based Li metal polymer batteries. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nanocomposite solid polymer electrolytes based on poly(ethylene oxide)/POSS-PEG (n = 13.3) hybrid nanoparticles for lithium ion batteries

Anji Reddy Polu,이희우 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.31 No.-

We successfully prepared the nanocomposite solid polymer electrolytes based on poly(ethylene oxide)(PEO)/polyhedral oligomeric silsesquioxane-polyethylene glycol (POSS-PEG) complexed with LiN(-SO2CF3)2 (LiTFSI) salt and studied the effect of POSS-PEG (n = 13.3) hybrid nanoparticles on structural,thermal, mechanical and ionic conductivity properties. The crystallinity of the nanocomposite solidpolymer electrolytes has been characterized by X-ray diffraction (XRD). FTIR studies showed theevidence of the complexation between PEO, LiTFSI and POSS-PEG. Differential scanning calorimetry(DSC) was used to study their glass transition and melting behaviors and to measure their respectivedegrees of crystallinity. The degree of crystallinity reduced with POSS-PEG content, indicating restrictedsegmental motion of the polymer chains. The Young’s modulus increased from 0.076 to 0.19 MPa withthe addition of POSS-PEG. Ionic conductivity studies reveal that solid polymer electrolyte with 30 wt% ofPOSS-PEG has the highest ionic conductivity of 5.05 10 5 S/cm at room temperature (23 8C). Thetemperature dependence conductivity studies showed that the samples seemed to obey the Arrheniusbehavior.

Effect of POSS-PEG hybrid nanoparticles on cycling performance of polyether-LiDFOB based solid polymer electrolytes for all solid-state Li-ion battery applications

Anji Reddy Polu,이희우,Modigunta Jeevan Kumar Reddy,A.M. Shanmugharaj,류승훈,김동규 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.45 No.-

For the first time, the consequences of organic-inorganic hybrid nanoparticle polyhedral oligomericsilsesquioxane-polyethylene glycol (POSS-PEG(n = 4)) on the physicochemical and electrochemicalproperties of poly(ethylene oxide) (PEO)-lithium difluoro(oxalato)borate (LiDFOB) based nanocompositesolid polymer electrolyte (NSPE) membranes were systematically prepared and utilized as an activeseparator for battery applications. The thermal stability and structural properties of the prepared NSPEmembranes were analyzed by means of differential scanning calorimetry (DSC), thermogravimetry (TG)and X-ray diffraction (XRD) analyses. The morphological changes by POSS-PEG in polymer electrolytemembranes were investigated by field emission scanning electron microscopy (FE-SEM) andtransmission electron microscopy (TEM). The incorporation of POSS-PEG greatly enhanced the ionicconductivity, mechanical integrity and compatibility. The maximum ambient temperature ionicconductivity was found to be in the range of 7.28 10 5 S/cm for 40 wt% POSS-PEG. Finally, the solidstate lithiumcell was assembled as Li/NSPE/LiCoO2. The cell delivered a maximum discharge capacity of187 mAh g 1 at 0.1C-rate with very good capacity retention up to 50 cycles. The test results indicatedthat the electrolyte is found to be a better candidate than those reported earlier.

Effect of TiO2 nanoparticles on structural, thermal, mechanical and ionic conductivity studies of PEO12–LiTDI solid polymer electrolyte

Anji Reddy Polu,이희우 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.37 No.-

In the present study, poly(ethylene oxide) (PEO) complexed with lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI) nanocomposite solid polymer electrolyte membranes (NSPEMs) have beenprepared by solution cast technique using different weight percent of nano-sized TiO2 ceramic filler. Theeffect of filler incorporation on the structural, thermal, mechanical and ionic conductivity properties ofsolid polymer electrolytes have analyzed. X-ray diffraction (XRD) and polarized optical microscopy(POM) results indicated that the crystallinity has been reduced remarkably with the incorporation ofTiO2 nanofiller. The thermal stability and mechanical integrity of the nanocomposite polymer electrolytesystem increased significantly compared to filler free electrolytes. The maximum ionic conductivity isfound to be in the range of 2.11 10 5 S cm 1 for 8 wt% TiO2 nanofiller in PEO12–LiTDI electrolytesystem. These results indicated that the prepared TiO2 based nanocomposite membrane would be apromising alternative separator for rechargeable lithium-ion battery applications

Conductivity, XRD, and FTIR Studies of New Mg^(2+)-ion-conducting Solid Polymer Electrolytes: [PEG: Mg(CH_3COO)_2]

Anji Reddy Polu,Ranveer Kumar,Valerio Causin,Ramesh Neppalli 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.1

Solid polymer electrolytes based on poly (ethylene glycol) (PEG) doped with Mg(CH_3COO)_2 have been prepared by using the solution-casting method. The X-ray diffraction patterns of PEG with Mg(CH_3COO)_2 salt indicated a decrease in the degree of crystallinity with increasing concentration of the salt. The complexation of Mg(CH_3COO)_2 salt with the polymer was confirmed by using Fourier transform infrared spectroscopy (FTIR) studies. The ionic conductivity was measured for the [PEG: Mg(CH_3COO)_2] system in the frequency range 50 Hz - 1 MHz. The addition of Mg salt was found to improve the ionic conductivity significantly. The 15-wt-% Mg(CH_3COO)_2-doped system had a maximum conductivity of 1.07 ?10^(−6) S/cm at 303 K. The conductance spectrum shows two distinct regions: a dc plateau and a dispersive region. The temperature dependence of the ionic conductivity reveals the conduction mechanism to be an Arrhenius-type thermally activated process.

Structural, Thermal and Ionic conductivity studies of PEO: LiDFOB Solid Polymer Electrolytes

Anji Reddy Polu,이희우 한국고분자학회 2014 한국고분자학회 학술대회 연구논문 초록집 Vol.2014 No.10

Conductivity enhancement in K+-ion conducting solid polymer electrolyte [PEG : KNO3] and its application as an electrochemical cell

Polu Anji Reddy,Kareem Aseel Abdulameer,Kim Kwangmin,Kim Dongkyu,Venkanna Mekala,Rasheed Hussein Kh.,Kumar Kanapuram Uday 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.12

The solution-cast method was used to prepare new solid polymer electrolytes (SPEs) that conduct potassium ions and are based on polyethylene glycol (PEG) complexed with potassium nitrate (KNO3). This polymer electrolyte system was characterized using different experimental techniques, such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), composition vs. conductivity, temperature vs. conductivity, frequency-dependent conductivity, and dielectric measurements. The degree of crystallinity decreased with increasing salt concentration, according to the X-ray diffraction and DSC patterns of PEG with KNO3 salt. For PEG: KNO3 (80 : 20) composition, an optimum conductivity of 8.24× KT−6 S/cm was recorded at 30 °C. Compared with pure PEG, the optimum conducting composition (OCC) conductivity increased by two orders of magnitude. The temperature range of 303 to 333 K was used for the temperature-dependent conductivity experiments. The findings demonstrate that the conductivity obeys the Arrhenius rule and increases as the temperature rises. A dc plateau and a dispersive zone were observed in the conductance spectrum, which also follows Jonscher’s power law. It was investigated how temperature and frequency affect the dielectric permittivity. An electrochemical cell with the configuration K/(80PEG : 20KNO3)/(I2+C+electrolyte) was constructed using an 80 : 20 electrolyte system, and its discharge properties were investigated. The cell’s open circuit voltage was measured at 2.48 V.

Ionic liquid incorporated nanocomposite polymer electrolytes for rechargeable lithium ion battery: A way to achieve improved electrochemical and interfacial properties

카룹,이희우,P. Anil Reddy,Dipti Gupta,Liviu Mitu,Anji Reddy Polu,X. Sahaya Shajan 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.40 No.-

An ionic liquid incorporated nanocomposite electrolytes are prepared using solution cast technique byimmobilizing a solution of lithium N,N-bis(trifluoromethanesulfonyl)imide (LiTFSI) in N-ethyl-N-methylimidazolium - bis(trifluoromethanesulfonyl) imide (EMImTFSI) ionic liquid (IL) with addedmixtures of organic solvent and nanofiller such as acetonitrile and nanochitosan (32 nm) into apoly(ethylene oxide) (PEO) matrix. The achieved extreme ionic conductivity of ionic liquid basedelectrolyte is in the range of 10 2 S cm 1 which is one order higher than that of (PEO)8LiTFSI-10 wt% NCsystem. Cyclic voltammetry and linear sweep voltammetry (LSV) analyses indicates that the preparedelectrolytes possesses an excellent electrochemical stability of 3.9 V. These unique properties allow theeffective use of these membranes as active separators for the development of advanced lithium ionbatteries.

A comprehensive study of chalcogenide quantum dot sensitized solar cells with a new solar cell exceeding 1V output

Surana, Karan,Mehra, R.M.,Bhattacharya, B.,Rhee, Hee-Woo,Polu, Anji Reddy,Singh, Pramod K. Elsevier 2015 RENEWABLE & SUSTAINABLE ENERGY REVIEWS Vol.52 No.-

<P><B>Abstract</B></P> <P>In the last two decades quantum dots (QDs) have attracted research interest all across the globe owing to their unique size-dependent optical and electronic properties. Generally, smaller the size of the crystal, the larger is the energy gap and greater is the difference in energy between the highest valence band and the lowest conduction band. Therefore more energy is needed to excite the dot, and concurrently more energy is released when the crystal returns to its resting state. Chalcogenide QDs have gained worldwide acceptance for their application in quantum dot sensitized solar cells (QDSSC). This review article focuses chiefly on the progress made in chalcogenide QD based solar cells (SC) over the years along with a new type of QDSSC giving an output voltage of over 1V.</P>

A study of structural, electrical and electrochemical properties of PVdF-HFP gel polymer electrolyte films for magnesium ion battery applications

Xin Tang,Shenhua Song,Ravi Muchakayala,Zhongyi Zhang,Anji Reddy Polu 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.37 No.-

New magnesium ion conducting polymer electrolyte films are developed and their experimentalinvestigations are reported. The polymer electrolyte films are composed of various poly(vinylidenefluoride-co-hexafluoropropylene):magnesium trifluoromethanesulfonate compositions (PVdF-HFP:Mg(Tf)2 in weight ratio) with different quantities of 1-ethyl-3-methylimidazolium trifluoromethane-sulfonate ionic liquid (EMITf). X-ray diffraction reveals that the pristine PVdF-HFP polymer filmpossesses a semi-crystalline structure and its amorphicity increases with increasing Mg(Tf)2 and EMITfconcentrations. From thermal analysis, the melting temperature (Tm), relative crystallinity (xc) andthermal stability of the 90PVdF-HFP:10Mg(Tf)2 gel polymer electrolyte film doped with 40 wt.% EMITfare obtained as 112 8C, 21.8% and 355 8C, respectively. The room-temperature ionic conductivity of thegel polymer electrolyte film increases with increasing EMITf concentration and reaches a high value ofapproximately 4.63 10 3 S cm 1 at 40 wt.% EMITf due to its amorphicity increase and interconnectedpore structure. For the 40 wt.% EMITf electrolyte film, the temperature dependence of ionic conductivityfollows the Arrhenius relation with an activation energy of 0.35 eV. The electrochemical stabilitywindow of the 40 wt.% EMITf electrolyte film is determined as 4.8 V. The findings from this study arepromising and have great potential for practical ionic device applications, particularly in rechargeablemagnesium ion batteries.