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UMD researchers develop highly reversible 5.3V Li-metal cell with 720 Wh/kg; 5.5V electrolyte

Over the last several years, increasing the energy density of batteries has been a top priority in battery technology development, congruent with increasing demands for faster mobile devices and longer-lasting electronic vehicles. The energy density of lithium-ion batteries can be enhanced by either increasing the capacity of electrodes, or by enhancing the cell voltage (V).

Extensive research has been devoted to exploring the pairing of various materials in the search for the most efficient cathode/anode mix, but until now, only limited advances have been achieved due to the narrow electrochemical stability window of traditional electrolyte.

Researchers at the University of Maryland (UMD) led by Chunsheng Wang—a professor with joint appointments in the Departments of Chemical & Biomolecular Engineering (ChBE), and Chemistry & Biochemistry—have developed a highly reversible 5.3 V battery offering a Mn3+-free LiCoMnO4 cathode, and graphite and Li-metal anodes.

A specially designed electrolyte was also created, which is stable to 5.5V for both the LiCoMnO4 cathode and (graphite and Li-metal) anodes. This resulted in a 5.3V Li-metal cell, delivering a high energy density of 720 Wh/kg for 1k cycles. This battery chemistry features a Coulombic efficiency of >99%, offering new development opportunity for high-voltage and energy Li-ion batteries. A paper on their work is published in the journal Chem.

The energy density of current Li-ion batteries is limited by the low capacity of intercalation cathode, which leaves relatively little room to further improve because the specific capacities of these cathodes approach the theoretical levels. Increasing the cell output voltage is a possible direction to largely increase the energy density of the batteries.

Extensive research has been devoted to exploring >5.0 V cells, but only limited advances have been achieved because of the narrow electrochemical stability window of the electrolytes (<5.0 V). Herein, we report a 5.5 V electrolyte (1 M LiPF 6 in fluoroethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, and hydrofluoroether [FEC/FDEC/HFE] with a Li difluoro(oxalate)borate [LiDFOB] additive) that enables 5.3 V LiCoMnO4 cathodes to provide an energy density of 720 Wh kg−1 for 1,000 cycles and 5.2 V graphite||LiCoMnO4 full cells to provide an energy density of 480 Wh kg−1 for 100 cycles. The 5.5 V electrolytes provide a large step toward developing high-energy Li batteries.

—Chen et al.

The key, said Long Chen—a ChBE post-doctoral research associate and one of the first authors on the paper, is the super electrolytes with an especially wide electrochemical window of 0 - 5.5V. This is due to the formation of a robust interfacial layer on the electrodes, he explained.

The high voltage electrolytes enable us to use high voltage cathode and high capacity Si- and potential Li-metal anodes, which will significantly increase the cell energy density. However, the Coulombic efficiency of >99% for 5.3V LiCoMnO4 still needs improvement to achieve a long cycle life.

—Chunsheng Wang

Resources

  • Chen, L., Fa, X., Hu, E., Ji, X., Chen, J., HouS., Deng, T., Li, J., Su, D., Yang, X., Wang, C. (2019) “Achieving High Energy Density through Increasing the Output Voltage: A Highly Reversible 5.3 V Battery.” Chem doi: XXX10.1016/j.chempr.2019.02.003XX

Comments

SJC

720 Wh/kg for 1k cycles...
WOW!

HarveyD

Will this be one of the technologies leading to future 5-5-5 batteries and much lighter more efficient future PHEVs/BEVs/FCEVs?

Will somebody mass produce such batteries at an affordable price by 2025 or so?

SJC

That is for half cell, less for full cell, but still a good indication of what can be done.

Lad

The increase to 5.3 volts is huge, especially when you consider the best production batteries run about 4.2 volts. And, with a energy density that is 3 x better than current batteries that is even more outstanding. However, there is still a long way to go before this chemistry is production ready. Still, it gives an idea of the potential high performance yet available using lithium as a base.

Centurion

Una quimica con un potencial enorme. Por lo leido deduzco que esos 720wh/kg són a celda completa con anodo, catodo y electrolito especifico.

Arnold

I am not making any claim here other that caution and full understanding of the effects of chemicals including when in combination is obviously important .
The flouro carbonates described are poorly described for the MSD information. Hydroflouroether is reported as low toxicity.
We know some lithium chemistry are toxic to microbes.
Flourinated 'anythings' are high on the list of common and often toxic chemicals.
Recycling incentives can help alleviate concerns.

Arnold

Anyone who has investigated especially the chlorinated hydro ''flouro carbons'' would have alarm bells ringing.

SJC

Having lithium in the anode can bring energy density up, Sion showed that years ago.

Juan Carlos Zuleta

Is this still a Li-ion battery? Seems like use of lithium metal in the anode could lead to an astonishing technological breakthough well apart from Li-air, Li-O, Li-S or even Solid State batteries.

Raymondbonnate1

But with two non-ferrous metal atoms for one Faraday or 26.8Ah x 5.5V = 147 Wh with 100% electrochemical efficiency.

SJC

They use a somewhat conventional cathode and electrolyte, but put lithium in the anode. Sion has done 400 Wh/kg with a lithium anode, the cycles are the problem with only 100 for a full cell.

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