Paving the Way Toward Highly Efficient High-Energy Potassium-Ion Batteries with Ionic-Liquid Electrolytes

<div><div><div><p>Potassium-ion batteries (KIB) are a promising complementary technology to lithium-ion batteries because of the comparative abundance and affordability of potassium. Currently, the most promising KIB chemistry consists of a potassium manganese hexacyanoferrate (KMF) cathode, a Prussian blue analog, and a graphite anode (723Whl−1 and 359Whkg−1 at 3.6V). No electrolyte has yet been formulated that is concurrently stable at the high operating potential of KMF (4.02V vs K+/K) and compatible with K+ intercalation into graphite, currently the most critical hurdle to adoption. Here we combine a KMF cathode and a graphite anode with a KFSI in Pyr1,3FSI ionic liquid electrolyte for the first time and show unprecedented performance. We use high-throughput techniques to optimize the KMF morphology for operation in this electrolyte system, achieving 119 mA h g−1 at 4 V vs K+/K and a coulombic efficiency >99.3%. In the same ionic liquid electrolyte graphite shows excellent electrochemical performance and we demonstrate reversible cycling by operando XRD. These results are a significant and essential step forward towards viable potassium-ion batteries.</p></div></div></div>

Download Full-text

Enhanced Ion Transport in an Ether Aided Super Concentrated Ionic Liquid Electrolyte for Long-Life Practical Lithium Metal Battery Applications

10.26434/chemrxiv.12588059.v1 ◽

2020 ◽

Author(s):

Urbi Pal ◽

Fangfang Chen ◽

Derick Gyabang ◽

Thushan Pathirana ◽

Binayak Roy ◽

...

Keyword(s):

Ionic Liquid ◽

Ion Transport ◽

Current Density ◽

Coulombic Efficiency ◽

High Energy ◽

Liquid Electrolyte ◽

High Mass ◽

Lithium Metal ◽

Ionic Liquid Electrolyte ◽

Lithium Metal Battery

We explore a novel ether aided superconcentrated ionic liquid electrolyte; a combination of ionic liquid, <i>N</i>-propyl-<i>N</i>-methylpyrrolidinium bis(fluorosulfonyl)imide (C<sub>3</sub>mpyrFSI) and ether solvent, <i>1,2</i> dimethoxy ethane (DME) with 3.2 mol/kg LiFSI salt, which offers an alternative ion-transport mechanism and improves the overall fluidity of the electrolyte. The molecular dynamics (MD) study reveals that the coordination environment of lithium in the ether aided ionic liquid system offers a coexistence of both the ether DME and FSI anion simultaneously and the absence of ‘free’, uncoordinated DME solvent. These structures lead to very fast kinetics and improved current density for lithium deposition-dissolution processes. Hence the electrolyte is used in a lithium metal battery against a high mass loading (~12 mg/cm<sup>2</sup>) LFP cathode which was cycled at a relatively high current rate of 1mA/cm<sup>2</sup> for 350 cycles without capacity fading and offered an overall coulombic efficiency of >99.8 %. Additionally, the rate performance demonstrated that this electrolyte is capable of passing current density as high as 7mA/cm<sup>2</sup> without any electrolytic decomposition and offers a superior capacity retention. We have also demonstrated an ‘anode free’ LFP-Cu cell which was cycled over 50 cycles and achieved an average coulombic efficiency of 98.74%. The coordination chemistry and (electro)chemical understanding as well as the excellent cycling stability collectively leads toward a breakthrough in realizing the practical applicability of this ether aided ionic liquid electrolytes in lithium metal battery applications, while delivering high energy density in a prototype cell.

Download Full-text

Improving Cycle Life Through Fast Formation Using a Super-Concentrated Phosphonium Based Ionic Liquid Electrolyte for Anode-Free and Lithium Metal Batteries

10.26434/chemrxiv.14702748 ◽

2021 ◽

Author(s):

Thushan Pathirana ◽

Dmitrii Rakov ◽

Fangfang Chen ◽

Maria Forsyth ◽

Robert Kerr ◽

...

Keyword(s):

Ionic Liquid ◽

Energy Density ◽

Electrochemical Impedance ◽

Cell Formation ◽

Lithium Ion ◽

High Energy ◽

Liquid Electrolyte ◽

High Energy Density ◽

Lithium Metal ◽

Ionic Liquid Electrolyte

<p>ABSTRACT </p><p>Cell formation of lithium-ion cells impacts the evolution of the solid electrolyte interphase (SEI) and the cell cycle stability. Lithium metal anodes are an important step in the development of high energy density batteries owing to the high theoretical specific capacity of lithium metal. However, most lithium metal battery research has used a conventional lithium-ion formation protocol; this is time consuming, costly and does not account for the different properties of the lithium metal electrode. Here, we have used a recently reported promising phosphonium bis(fluorosulfonyl)imide ionic liquid electrolyte coupled with an NMC622 high areal capacity cathode (>3.5 mAh/cm2) to investigate the effect of cell formation rates. A faster formation protocol comprised of a pulsed 1.25C current decreased the formation time by 56 % and gave a 38 % greater capacity retention after 50 cycles when compared to formation at C/20. Electrochemical impedance spectroscopy measurements showed that the fast formation gave rise to a lower-resistance SEI. Column-like lithium deposits with reduced porous lithium domains between the particles were observed using scanning electron microscope imaging. To underline the excellent performance of these high energy-density cells, a 56 % greater stack specific energy was achieved compared to the analogous graphite-based lithium-ion cell chemistries. </p>

Download Full-text

Ordered LiNi0.5Mn1.5O4 Cathode in Bis(fluorosulfonyl)imide-Based Ionic Liquid Electrolyte: Importance of the Cathode-Electrolyte Interphase

10.26434/chemrxiv.13005344.v1 ◽

2020 ◽

Author(s):

Hyeon Jeong Lee ◽

Zachary Brown ◽

Ying Zhao ◽

Jack Fawdon ◽

Weixin Song ◽

...

Keyword(s):

Ionic Liquid ◽

High Voltage ◽

Rate Capability ◽

Lithium Ion ◽

Cycling Performance ◽

High Energy ◽

Liquid Electrolyte ◽

High Energy Density ◽

X Ray ◽

Ionic Liquid Electrolyte

<div><div><div><p>The high voltage (4.7 V vs. Li+ /Li) spinel lithium nickel manganese oxide (LiNi0.5 Mn1.5 O4 , LNMO) is a promising candidate for the next-generation of lithium ion batteries due to its high energy density, low cost and environmental impact. However, poor cycling performance at high cutoff potentials limits its commercialization. Herein, hollow structured LNMO is synergistically paired with an ionic liquid electrolyte, 1M lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr1,3 FSI) to achieve stable cycling performance and improved rate capability. The optimized cathode-electrolyte system exhibits extended cycling performance (>85% capacity retention after 300 cycles) and high rate performance (106.2mAhg–1 at 5C) even at an elevated temperature of 65 ◦C. X-ray photoelectron spectroscopy and spatially resolved x-ray fluorescence analyses confirm the formation of a robust, LiF-rich cathode electrolyte interphase. This study presents a comprehensive design strategy to improve the electrochemical performance of high-voltage cathode materials.</p></div></div></div>

Download Full-text

SEI Pre-coated Graphite Anode in Lithium Ion Battery with EMITFSI Ionic Liquid Electrolyte

ECS Meeting Abstracts ◽

10.1149/ma2009-01/3/179 ◽

2009 ◽

Keyword(s):

Ionic Liquid ◽

Lithium Ion Battery ◽

Lithium Ion ◽

Liquid Electrolyte ◽

Graphite Anode ◽

Ionic Liquid Electrolyte

Download Full-text

Improving Cycle Life Through Fast Formation Using a Super-Concentrated Phosphonium Based Ionic Liquid Electrolyte for Anode-Free and Lithium Metal Batteries

10.26434/chemrxiv.14702748.v1 ◽

2021 ◽

Author(s):

Thushan Pathirana ◽

Dmitrii Rakov ◽

Fangfang Chen ◽

Maria Forsyth ◽

Robert Kerr ◽

...

Keyword(s):

Ionic Liquid ◽

Energy Density ◽

Electrochemical Impedance ◽

Cell Formation ◽

Lithium Ion ◽

High Energy ◽

Liquid Electrolyte ◽

High Energy Density ◽

Lithium Metal ◽

Ionic Liquid Electrolyte

<p>ABSTRACT </p><p>Cell formation of lithium-ion cells impacts the evolution of the solid electrolyte interphase (SEI) and the cell cycle stability. Lithium metal anodes are an important step in the development of high energy density batteries owing to the high theoretical specific capacity of lithium metal. However, most lithium metal battery research has used a conventional lithium-ion formation protocol; this is time consuming, costly and does not account for the different properties of the lithium metal electrode. Here, we have used a recently reported promising phosphonium bis(fluorosulfonyl)imide ionic liquid electrolyte coupled with an NMC622 high areal capacity cathode (>3.5 mAh/cm2) to investigate the effect of cell formation rates. A faster formation protocol comprised of a pulsed 1.25C current decreased the formation time by 56 % and gave a 38 % greater capacity retention after 50 cycles when compared to formation at C/20. Electrochemical impedance spectroscopy measurements showed that the fast formation gave rise to a lower-resistance SEI. Column-like lithium deposits with reduced porous lithium domains between the particles were observed using scanning electron microscope imaging. To underline the excellent performance of these high energy-density cells, a 56 % greater stack specific energy was achieved compared to the analogous graphite-based lithium-ion cell chemistries. </p>

Download Full-text

Enhanced Ion Transport in an Ether Aided Super Concentrated Ionic Liquid Electrolyte for Long-Life Practical Lithium Metal Battery Applications

10.26434/chemrxiv.12588059 ◽

2020 ◽

Author(s):

Urbi Pal ◽

Fangfang Chen ◽

Derick Gyabang ◽

Thushan Pathirana ◽

Binayak Roy ◽

...

Keyword(s):

Ionic Liquid ◽

Ion Transport ◽

Current Density ◽

Coulombic Efficiency ◽

High Energy ◽

Liquid Electrolyte ◽

High Mass ◽

Lithium Metal ◽

Ionic Liquid Electrolyte ◽

Lithium Metal Battery

We explore a novel ether aided superconcentrated ionic liquid electrolyte; a combination of ionic liquid, <i>N</i>-propyl-<i>N</i>-methylpyrrolidinium bis(fluorosulfonyl)imide (C<sub>3</sub>mpyrFSI) and ether solvent, <i>1,2</i> dimethoxy ethane (DME) with 3.2 mol/kg LiFSI salt, which offers an alternative ion-transport mechanism and improves the overall fluidity of the electrolyte. The molecular dynamics (MD) study reveals that the coordination environment of lithium in the ether aided ionic liquid system offers a coexistence of both the ether DME and FSI anion simultaneously and the absence of ‘free’, uncoordinated DME solvent. These structures lead to very fast kinetics and improved current density for lithium deposition-dissolution processes. Hence the electrolyte is used in a lithium metal battery against a high mass loading (~12 mg/cm<sup>2</sup>) LFP cathode which was cycled at a relatively high current rate of 1mA/cm<sup>2</sup> for 350 cycles without capacity fading and offered an overall coulombic efficiency of >99.8 %. Additionally, the rate performance demonstrated that this electrolyte is capable of passing current density as high as 7mA/cm<sup>2</sup> without any electrolytic decomposition and offers a superior capacity retention. We have also demonstrated an ‘anode free’ LFP-Cu cell which was cycled over 50 cycles and achieved an average coulombic efficiency of 98.74%. The coordination chemistry and (electro)chemical understanding as well as the excellent cycling stability collectively leads toward a breakthrough in realizing the practical applicability of this ether aided ionic liquid electrolytes in lithium metal battery applications, while delivering high energy density in a prototype cell.

Download Full-text

Ordered LiNi0.5Mn1.5O4 Cathode in Bis(fluorosulfonyl)imide-Based Ionic Liquid Electrolyte: Importance of the Cathode-Electrolyte Interphase

10.26434/chemrxiv.13005344 ◽

2020 ◽

Author(s):

Hyeon Jeong Lee ◽

Zachary Brown ◽

Ying Zhao ◽

Jack Fawdon ◽

Weixin Song ◽

...

Keyword(s):

Ionic Liquid ◽

High Voltage ◽

Rate Capability ◽

Lithium Ion ◽

Cycling Performance ◽

High Energy ◽

Liquid Electrolyte ◽

High Energy Density ◽

X Ray ◽

Ionic Liquid Electrolyte

<div><div><div><p>The high voltage (4.7 V vs. Li+ /Li) spinel lithium nickel manganese oxide (LiNi0.5 Mn1.5 O4 , LNMO) is a promising candidate for the next-generation of lithium ion batteries due to its high energy density, low cost and environmental impact. However, poor cycling performance at high cutoff potentials limits its commercialization. Herein, hollow structured LNMO is synergistically paired with an ionic liquid electrolyte, 1M lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr1,3 FSI) to achieve stable cycling performance and improved rate capability. The optimized cathode-electrolyte system exhibits extended cycling performance (>85% capacity retention after 300 cycles) and high rate performance (106.2mAhg–1 at 5C) even at an elevated temperature of 65 ◦C. X-ray photoelectron spectroscopy and spatially resolved x-ray fluorescence analyses confirm the formation of a robust, LiF-rich cathode electrolyte interphase. This study presents a comprehensive design strategy to improve the electrochemical performance of high-voltage cathode materials.</p></div></div></div>

Download Full-text