Post-Mortem Investigations of Fluorinated Flame Retardants for Lithium Ion Battery Electrolytes by Gas Chromatography with Chemical Ionization

Abstract Using flame retardants (FRs) in lithium ion battery (LIB) electrolytes is usually a tradeoff between electrochemical performance and electrolyte flammability. Fluorinated FRs are a promising class of FRs which are currently under investigation. During this work, three FRs originating from triethyl phosphate with varying degree of fluorination were investigated regarding their electrochemical stability on cathode (LiNi 0.33 Co 0.33 Mn 0.33 O 2 , NCM) and anode (graphite) in half cells. During long-term cycling, changes in performance were observed. Especially on the anode side the FR addition showed a decrease in performance in comparison to the standard electrolyte (DEC/EC 1:1, 1M LiPF 6 ). The electrolytes containing the three FRs were extracted from the cells and analyzed regarding their changes in composition and structural degradation. The decomposition products were investigated by gas chromatography (GC) with electron impact (EI) ionization and mass selective (MS) detection. To obtain more information with regard to the identification of unknown decomposition products further GC‐MS experiments with positive chemical ionization (PCI) and negative chemical ionization (NCI) were performed. Twelve different volatile organic decomposition products were identified. These decomposition products can be subdivided regarding their basic structure. Ether based, carbonate based and phosphate based fluorinated and non-fluorinated decomposition products were identified. Furthermore, possible formation pathways for all groups of decomposition products were postulated taking existing literature into account.

[1]  K. Amine,et al.  Flame-retardant additives for lithium-ion batteries , 2003 .

[2]  E. Yasukawa,et al.  Nonflammable Trimethyl Phosphate Solvent-Containing Electrolytes for Lithium-Ion Batteries: II. The Use of an Amorphous Carbon Anode , 2001 .

[3]  Sylvie Grugeon,et al.  Deciphering the multi-step degradation mechanisms of carbonate-based electrolyte in Li batteries , 2008 .

[4]  Alexander Goldberg,et al.  On the difference in cycling behaviors of lithium-ion battery cell between the ethylene carbonate- and propylene carbonate-based electrolytes , 2011 .

[5]  M. Winter,et al.  Separation and Quantification of Organic Electrolyte Components in Lithium-Ion Batteries via a Developed HPLC Method , 2015 .

[6]  M. Winter,et al.  Structure determination of organic aging products in lithium-ion battery electrolytes with gas chromatography chemical ionization mass spectrometry (GC-CI-MS) , 2016 .

[7]  G. Nagasubramanian,et al.  Reducing Li-ion safety hazards through use of non-flammable solvents and recent work at Sandia National Laboratories , 2013 .

[8]  Kang Xu,et al.  Evaluation of Fluorinated Alkyl Phosphates as Flame Retardants in Electrolytes for Li-Ion Batteries: II. Performance in Cell , 2003 .

[9]  C. Timperley,et al.  Fluorinated phosphorus compounds: Part 3. The synthesis of symmetrical and unsymmetrical fluoroalkyl phosphates , 2000 .

[10]  Kang Xu,et al.  Evaluation of Fluorinated Alkyl Phosphates as Flame Retardants in Electrolytes for Li-Ion Batteries: I. Physical and Electrochemical Properties , 2003 .

[11]  R. Mcmillan,et al.  Fluoroethylene carbonate electrolyte and its use in lithium ion batteries with graphite anodes , 1999 .

[12]  Chusheng Chen,et al.  Comparative study of trimethyl phosphite and trimethyl phosphate as electrolyte additives in lithium ion batteries , 2005 .

[13]  Peter Bieker,et al.  Lithium‐Ionen‐Technologie und was danach kommen könnte , 2016 .

[14]  Kang Xu,et al.  An Attempt to Formulate Nonflammable Lithium Ion Electrolytes with Alkyl Phosphates and Phosphazenes , 2002 .

[15]  M. Winter,et al.  Methyl tetrafluoro-2-(methoxy) propionate as co-solvent for propylene carbonate-based electrolytes for lithium-ion batteries , 2012 .

[16]  M. Winter,et al.  Qualitative Investigation of the Decomposition of Organic Solvent Based Lithium Ion Battery Electrolytes with LC-IT-TOF-MS. , 2016, Analytical chemistry.

[17]  M. Winter,et al.  Ion chromatography electrospray ionization mass spectrometry method development and investigation of lithium hexafluorophosphate-based organic electrolytes and their thermal decomposition products. , 2014, Journal of chromatography. A.

[18]  M. Winter,et al.  Syntheses of novel delocalized cations and fluorinated anions, new fluorinated solvents and additives for lithium ion batteries , 2014 .

[19]  M. Winter,et al.  Supercritical carbon dioxide extraction of lithium-ion battery electrolytes , 2014 .

[20]  T. Abe,et al.  STM study on graphite/electrolyte interface in lithium-ion batteries: solid electrolyte interface formation in trifluoropropylene carbonate solution , 1999 .

[21]  Martin Winter,et al.  The Solid Electrolyte Interphase – The Most Important and the Least Understood Solid Electrolyte in Rechargeable Li Batteries , 2009 .

[22]  E. Yasukawa,et al.  Nonflammable Trimethyl Phosphate Solvent-Containing Electrolytes for Lithium-Ion Batteries: I. Fundamental Properties , 2001 .

[23]  Martin Winter,et al.  Ethylene Sulfite as Electrolyte Additive for Lithium‐Ion Cells with Graphitic Anodes , 1999 .

[24]  Sylvie Grugeon,et al.  Gas chromatography/mass spectrometry as a suitable tool for the Li-ion battery electrolyte degradation mechanisms study. , 2011, Analytical chemistry.

[25]  Martin Winter,et al.  Review—Chemical Analysis for a Better Understanding of Aging and Degradation Mechanisms of Non-Aqueous Electrolytes for Lithium Ion Batteries: Method Development, Application and Lessons Learned , 2015 .

[26]  B. Scrosati,et al.  Lithium batteries: Status, prospects and future , 2010 .

[27]  M. Winter,et al.  Investigations on novel electrolytes, solvents and SEI additives for use in lithium-ion batteries: Systematic electrochemical characterization and detailed analysis by spectroscopic methods , 2014 .

[28]  S. Moon,et al.  Electrochemical performance of lithium-ion batteries with triphenylphosphate as a flame-retardant additive , 2007 .

[29]  P. Novák,et al.  FTIR and DEMS investigations on the electroreduction of chloroethylene carbonate-based electrolyte solutions for lithium-ion cells , 1999 .

[30]  Martin Winter,et al.  Influence of the Fluorination Degree of Organophosphates on Flammability and Electrochemical Performance in Lithium Ion Batteries: Studies on Fluorinated Compounds Deriving from Triethyl Phosphate , 2016 .

[31]  M. Winter,et al.  1-Fluoropropane-2-one as SEI-forming additive for lithium-ion batteries , 2012 .

[32]  Kang Xu,et al.  Effects of Tris(2,2,2-trifluoroethyl) Phosphate as a Flame-Retarding Cosolvent on Physicochemical Properties of Electrolytes of LiPF6 in EC-PC-EMC of 3:3:4 Weight Ratios , 2002 .

[33]  Ganesan Nagasubramanian,et al.  Effects of additives on thermal stability of Li ion cells , 2005 .

[34]  Christopher M Wolverton,et al.  Electrical energy storage for transportation—approaching the limits of, and going beyond, lithium-ion batteries , 2012 .

[35]  M. Winter,et al.  Electrolytes for lithium and lithium ion batteries: From synthesis of novel lithium borates and ionic liquids to development of novel measurement methods , 2014 .

[36]  Sylvie Grugeon,et al.  Thermal behaviour of the lithiated-graphite/electrolyte interface through GC/MS analysis , 2012 .

[37]  M. Winter,et al.  Identification of alkylated phosphates by gas chromatography-mass spectrometric investigations with different ionization principles of a thermally aged commercial lithium ion battery electrolyte. , 2015, Journal of chromatography. A.

[38]  Jens Leker,et al.  Current research trends and prospects among the various materials and designs used in lithium-based batteries , 2013, Journal of Applied Electrochemistry.

[39]  Kang Xu,et al.  Nonflammable electrolytes for Li-ion batteries based on a fluorinated phosphate , 2002 .

[40]  M. Winter,et al.  What are batteries, fuel cells, and supercapacitors? , 2004, Chemical reviews.

[41]  Martin Winter,et al.  Fluorinated organic solvents in electrolytes for lithium ion cells , 2001 .

[42]  M. Winter,et al.  Extraction of lithium-ion battery electrolytes with liquid and supercritical carbon dioxide and additional solvents , 2015 .

[43]  M. Winter,et al.  Synergistic Effect of Blended Components in Nonaqueous Electrolytes for Lithium Ion Batteries , 2017, Topics in Current Chemistry.

[44]  M. Winter,et al.  Two-dimensional ion chromatography for the separation of ionic organophosphates generated in thermally decomposed lithium hexafluorophosphate-based lithium ion battery electrolytes. , 2015, Journal of chromatography. A.