2018 Fiscal Year Annual Research Report
Synthesis of Fire-Extinguishing High-Voltage Electrolytes for Safe Batteries
| Project/Area Number |
18F18332
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| Research Institution | The University of Tokyo |
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Principal Investigator |
山田 淳夫 東京大学, 大学院工学系研究科(工学部), 教授 (30359690)
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| Co-Investigator(Kenkyū-buntansha) |
ZHENG QIFENG 東京大学, 工学(系)研究科(研究院), 外国人特別研究員
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| Project Period (FY) |
2018-11-09 – 2021-03-31
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| Keywords | Lithium-ion battery / electrolyte / high-voltage / non-flammable / cyclic phosphate |
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| Outline of Annual Research Achievements |
Nonflammable electrolytes could intrinsically eliminate the battery safety concerns, but generally leads to compromised battery performance owing to ineffectively passivation on the carbonaceous anode. By introducing the ethylene carbonate-like structure, we have successfully designed and synthesized a nonflammable cyclic phosphate solvent that can not only effectively passivate carbonaceous anodes, but also passivate an Al cathode current collector even with corrosive lithium salt LiN(SO2F)2. Without using any SEI-forming additive or co-solvent, for the first time, a highly reversible and stable cycling of a graphite electrode in such a cyclic phosphate-based nonflammable electrolyte has been achieved.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
During the last 6 months, by mimicking the ethylene carbonate-like structure, we have successfully designed and synthesized a nonflammable cyclic phosphate solvent, namely 2-methoxy-1,3,2-dioxaphospholane 2-oxide (MDP). The MDP solvent has shown some promising results during the preliminary test, but the anode passivation was not very satisfactory. Thus, in order to improve the performance, the fluorinated group was introduced to synthesize 2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphospholane 2-oxide (TFEP), the resulting electrolyte can not only effectively passivate carbonaceous anodes, but also passivate an Al cathode current collector even with corrosive lithium salt LiN(SO2F)2. We are currently working on evaluation the full cell performance in this electrolyte.
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| Strategy for Future Research Activity |
In the future, the fluorinated groups are proposed to introduce to the cyclic phosphate at different position including and 2-methoxy-4-trifluoromethyl-1,3,2-dioxaphospholane¬-2-oxide (MTFP) and 2-methoxy-4-fluoro-1,3,2-dioxaphospholane¬-2-oxide (FMDP), with the hope to improve the SEI formation capability and high voltage stability. The viscosity, ionic conductivity, flammability of the resulting electrolytes will be investigated. The charge-discharge, rate capability and cycling performance will be fully evaluated for both half and full cells. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) will be used to study the surface composition and structure change after long-term cycling.
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