Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors
Electrolyte stability can be improved by incorporating complexing agents that bind key decomposition intermediates and slow down decomposition. We show that hexamethyl-phosphoramide (HMPA) extends both the thermal stability threshold of sodium hexafluorophosphate (NaPF<sub>6</sub>) in di...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2021-07-01
|
| Series: | Energies |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1996-1073/14/15/4409 |
| _version_ | 1827686575558885376 |
|---|---|
| author | J. Landon Tyler Robert L. Sacci Jagjit Nanda |
| author_facet | J. Landon Tyler Robert L. Sacci Jagjit Nanda |
| author_sort | J. Landon Tyler |
| collection | DOAJ |
| description | Electrolyte stability can be improved by incorporating complexing agents that bind key decomposition intermediates and slow down decomposition. We show that hexamethyl-phosphoramide (HMPA) extends both the thermal stability threshold of sodium hexafluorophosphate (NaPF<sub>6</sub>) in dimethoxyethane (DME) electrolyte and the cycle life of double-layer capacitors. HMPA forms a stable complex with PF<sub>5</sub>, an intermediate in PF<sub>6</sub> anion thermal degradation. Unbound, this intermediate leads to autocatalytic degradation of the electrolyte solution. The results of electrochemical impedance spectroscopy (EIS) and galvanostatic cycling measurements show large changes in the cell without the presence of HMPA at higher temperatures (≥60 °C). Fourier transform infrared spectroscopy (FTIR) on the liquid and gas phase of the electrolyte shows without HMPA the formation of measurable amounts of PF<sub>5</sub> and HF. The complimentary results of these measurements proved the usefulness of using Lewis bases such as HMPA to inhibit the degradation of the electrolyte solution at elevated temperatures and potentially lead to improve cycle life of a nonaqueous capacitor. The results showed a large increase in capacitance retention during cycling (72% retention after 750,000 cycles). The results also provide evidence of major decomposition processes (0% capacitance retention after 100,000 cycles) that take place at higher temperatures without the additive of a thermal stability additive such as HMPA. |
| first_indexed | 2024-03-10T09:17:01Z |
| format | Article |
| id | doaj.art-670be4dc0d724b048401506aa3a12d9e |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-03-10T09:17:01Z |
| publishDate | 2021-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-670be4dc0d724b048401506aa3a12d9e2023-11-22T05:32:31ZengMDPI AGEnergies1996-10732021-07-011415440910.3390/en14154409Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for SupercapacitorsJ. Landon Tyler0Robert L. Sacci1Jagjit Nanda2Bredesen Center, University of Tennessee, Knoxville, TN 37996, USAChemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USAChemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USAElectrolyte stability can be improved by incorporating complexing agents that bind key decomposition intermediates and slow down decomposition. We show that hexamethyl-phosphoramide (HMPA) extends both the thermal stability threshold of sodium hexafluorophosphate (NaPF<sub>6</sub>) in dimethoxyethane (DME) electrolyte and the cycle life of double-layer capacitors. HMPA forms a stable complex with PF<sub>5</sub>, an intermediate in PF<sub>6</sub> anion thermal degradation. Unbound, this intermediate leads to autocatalytic degradation of the electrolyte solution. The results of electrochemical impedance spectroscopy (EIS) and galvanostatic cycling measurements show large changes in the cell without the presence of HMPA at higher temperatures (≥60 °C). Fourier transform infrared spectroscopy (FTIR) on the liquid and gas phase of the electrolyte shows without HMPA the formation of measurable amounts of PF<sub>5</sub> and HF. The complimentary results of these measurements proved the usefulness of using Lewis bases such as HMPA to inhibit the degradation of the electrolyte solution at elevated temperatures and potentially lead to improve cycle life of a nonaqueous capacitor. The results showed a large increase in capacitance retention during cycling (72% retention after 750,000 cycles). The results also provide evidence of major decomposition processes (0% capacitance retention after 100,000 cycles) that take place at higher temperatures without the additive of a thermal stability additive such as HMPA.https://www.mdpi.com/1996-1073/14/15/4409Na-ion electrolytessupercapacitorshigh-temperature electrolyte |
| spellingShingle | J. Landon Tyler Robert L. Sacci Jagjit Nanda Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors Energies Na-ion electrolytes supercapacitors high-temperature electrolyte |
| title | Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors |
| title_full | Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors |
| title_fullStr | Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors |
| title_full_unstemmed | Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors |
| title_short | Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors |
| title_sort | anion coordination improves high temperature performance and stability of napf6 based electrolytes for supercapacitors |
| topic | Na-ion electrolytes supercapacitors high-temperature electrolyte |
| url | https://www.mdpi.com/1996-1073/14/15/4409 |
| work_keys_str_mv | AT jlandontyler anioncoordinationimproveshightemperatureperformanceandstabilityofnapf6basedelectrolytesforsupercapacitors AT robertlsacci anioncoordinationimproveshightemperatureperformanceandstabilityofnapf6basedelectrolytesforsupercapacitors AT jagjitnanda anioncoordinationimproveshightemperatureperformanceandstabilityofnapf6basedelectrolytesforsupercapacitors |