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Henderson – NCSU V.D.6 Nonfluorinated (or Partially Fluorinated) Anions for Lithium Salts and Ionic Liquids (NCSU) Results Anion Synthesis. Several new anions have been synthesized. Examples of these are shown in Figure V 154. Synthesis procedures are now being optimized for scaled-up production of the salts. The DCP - and TCP 2 anions are initially prepared as potassium salts. Ionexchange and purification of the resulting lithium salts to electrochemical-grade materials is now underway. The anions containing nitrile groups are found to polymerize during thermal degradation (Figure V - 155)―a feature which may provide a shut-down mechanism for a battery during thermal abuse. Unfortunately, the TCP 2 salts have been found to have very poor solubility in aprotic solvents. Crystal structures for pure LiETAC (Figure V - 156) and a (THF) 1 :LiETAC solvate have been determined to gain insight into how this anion coordinates Li + cations. The electrochemical properties of the salts in aprotic solvent mixtures are currently being determined. F3C - DCP - - 2 TCP ETAC F3C - Figure V - 154: Examples of anions synthesized. Figure V - 155: TGA heating traces of the salts. Figure V - 156: Ion coordination in the crystal structure of LiETAC (Lipurple, O-red, N-blue, F-green). Characterization of Solvent-LiFSI Mixtures. Lithium bis(fluorosulfonyl)imide is a promising salt for electrolyte applications due to the very high conductivity of LiFSI mixtures with aprotic solvents (comparable to LiPF 6 ). Little is known about this salt at present. Some work has been conducted to gain insight into why the FSI - anion results in exceptional electrolyte properties. In addition, nitrile and dinitrile solvents may be of interest for electrolytes suitable for use with highvoltage (> 4.3 V) electrodes and/or low-temperature applications. A phase diagram for acetonitrile (AN) n - LiFSI mixtures has therefore been prepared (Figure V - 157). Both 6/1 and 4/1 crystalline solvate phases form which melt at low temperature, in common with (AN) n - LiTFSI mixtures. In contrast, (AN) n -LiPF 6 mixtures form a high melting 5/1 phase which consists of Li + cations tetrahedrally coordinated to four AN molecules, one uncoordinated AN molecule and uncoordinated PF 6 anions. Certain compositions of the (AN) n -LiFSI mixtures, in fact, form crystallinity gaps in which the samples cannot be crystallized. The data suggests that binary solvent-LiFSI electrolytes may be of practical utility due to the low T m of the solvates, whereas mixed solvents are generally required with LiPF 6 electrolytes due to the high T m of the corresponding solvates. Characterization of Solvent-BF 4 and LiDFOB (or BF 2 Ox) Mixtures. Phase diagrams for (AN) n - LiDFOB and adiponitrile (ADN) n -LiDCTA mixtures have been prepared (Figure V - 158). Crystal structures for (AN) 3 :LiDCTA, (AN) 1 :LiDCTA and (ADN) 1 :LiDCTA solvates have been determined (Figure V - 159 and Figure V - 160) to provide insight into the molecular interactions of these solvents with the Li + cations and DCTA - anions. Ionic Liquid (IL) Synthesis. ILs with N-alkyl-Nmethylpyrrolidinium cations and the difluoro(oxalato) borate anion (PY 1R DFOB where R is the alkyl chain length) have been synthesized and characterized. Despite utilizing various synthesis and purification procedures, the ILs always contain small amounts of BF - 4 and bis(oxalato)-borate (LiBOB) impurities. It is FY 2011 Annual Progress Report 613 Energy Storage R&D
V.D.6 Nonfluorinated (or Partially Fluorinated) Anions for Lithium Salts and Ionic Liquids (NCSU) Henderson – NCSU believed that this is due to an equilibrium which exists between these three anions. Electrolytes consisting of EC/DMC or EC/EMC with either LiTFSI or LiFSI are found to readily corrode Al, whereas those with LiPF 6 or LiDFOB do not. In contrast, neither PY 14 TFSI nor PY 14 DFOB mixtures with LiTFSI corrode Al at high potentials. Negligible current is observed for the ILbased electrolytes and no pitting corrosion of the electrode surfaces is noted. promising properties including low solvent volatility, low flammability, wide liquid temperature range, high conductivity, etc. These mixtures are now being tested as electrolytes with various electrode materials. Figure V - 158: Phase diagrams for (AN)n-LiDFOB and (ADN)n-LiDFOB mixtures. Figure V - 157: Phase diagrams for (AN)n-LiFSI and (AN)n-LiPF6 mixtures. Concentrated IL-Based Electrolytes. Recent work has demonstrated that highly concentrated IL LiTFSI-solvent mixtures in which 50 mol% of the salt is LiTFSI can be prepared with select amounts of solvent so that little or no bulk (uncoordinated) solvent is present in the electrolytes. These mixtures have very Conclusions and Future Directions Several new anions have been synthesized and are now being characterized. Phase diagrams and solvate crystal structures have been used to gain insight into the differences in solvation interactions of different salts including LiFSI and LiDFOB. This information is being correlated with electrolyte properties to aid in understanding the link between salt structure-property relationships and how this influence cell performance. Energy Storage R &D 614 FY 2011 Annual Progress Report
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V. FOCUSED FUNDAMENTAL RESEARCH Int
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V.A Introduction Duong - DOE, Srini
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V.B Cathode Development V.B.1 First
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V.B.1 First Principles Calculations
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V.B.1 First Principles Calculations
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V.B.2 Cell Analysis, High-energy De
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V.B.3 Olivines and Substituted Laye
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V.B.4 Stabilized Spinels and Nano O
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V.B.4 Stabilized Spinels and Nano O
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V.B.5 The Synthesis and Characteriz
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V.B.5 Synthesis & Characterization
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V.B.6 Cell Analysis-Interfacial Pro
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V.B.6 Cell Analysis-Interfacial Pro
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V.B.7 Role of Surface Chemistry on
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V.B.8 Characterization of New Catho
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V.B.8 Characterization of New Catho
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V.B.9 Layered Cathode Materials (AN
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V.B.10 Development of High Energy C
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V.B.10 Development of High Energy C
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V.B.11 Crystal Studies on High-ener
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V.B.12 Developing Materials for Lit
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V.B.13 Studies on the Local SOC and
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V.B.13 Studies on the Local SOC and
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V.B.14 New Cathode Projects (LBNL)
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V.C.1 Nanoscale Composite Hetero-st
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V.C.1 Nanoscale Composite Hetero-st
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V.C.2 Interfacial Processes - Diagn
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V.C.3 Search for New Anode Material
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V.C.4 Nano-structured Materials as
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V.C.4 Nano-structured Materials as
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V.C.5 Development of High Capacity
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V.C.5 Development of High Capacity
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V.C.6 Advanced Binder for Electrode
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V.C.6 Advanced Binder for Electrode
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V.C.7 Three-Dimensional Anode Archi
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Page 107 and 108: V.C.10 Atomic Layer Deposition for
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Page 117 and 118: V.C.12 Silicon Clathrates for Anode
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Page 121 and 122: V.C.13 Wiring Up Silicon Nanopartic
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Page 133 and 134: V.D.2 Interfacial Behavior of Elect
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Page 137 and 138: V.D.3 Molecular Dynamics Simulation
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Page 163 and 164: V.E Cell Analysis, Modeling, and Fa
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Page 183 and 184: V.E.6 Investigation of Critical Par
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V.F.1 Energy Frontier Research Cent
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V.F.2 Novel In Situ Diagnostics Too
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V.F.2 Novel In Situ Diagnostics Too
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V.G Integrated Lab-Industry Researc
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