An official website of the United States government
Abstract Achieving increased energy density under extreme operating conditions remains a major challenge in rechargeable batteries. Herein, we demonstrate an all‐fluorinated ester‐based electrolyte comprising partially fluorinated carboxylate and carbonate esters. This electrolyte exhibits temperature‐resilient physicochemical properties and moderate ion‐paired solvation, leading to a half solvent‐separated and half contact‐ion pair in a sole electrolyte. As a result, facile desolvation and preferential reduction of anions/fluorinated co‐solvents for LiF‐dominated interphases are achieved without compromising ionic conductivity (>1 mS cm−1even at −40 °C). These advantageous features were found to apply to both lithium metal and sulfur‐based electrodes even under extreme operating conditions, allowing stable cycling of Li || sulfurized polyacrylonitrile (SPAN) full cells with high SPAN loading (>3.5 mAh cm−2) and thin Li anode (50 μm) at −40, 23 and 50 °C. This work offers a promising path for designing temperature‐resilient electrolytes to support high energy density Li metal batteries operating in extreme conditions.
more »
« less
Solvent selection criteria for temperature-resilient lithium–sulfur batteries
All-climate temperature operation capability and increased energy density have been recognized as two crucial targets, but they are rarely achieved together in rechargeable lithium (Li) batteries. Herein, we demonstrate an electrolyte system by using monodentate dibutyl ether with both low melting and high boiling points as the sole solvent. Its weak solvation endows an aggregate solvation structure and low solubility toward polysulfide species in a relatively low electrolyte concentration (2 mol L −1 ). These features were found to be vital in avoiding dendrite growth and enabling Li metal Coulombic efficiencies of 99.0%, 98.2%, and 98.7% at 23 °C, −40 °C, and 50 °C, respectively. Pouch cells employing thin Li metal (50 μm) and high-loading sulfurized polyacrylonitrile (3.3 mAh cm −2 ) cathodes (negative-to-positive capacity ratio = 2) output 87.5% and 115.9% of their room temperature capacity at −40 °C and 50 °C, respectively. This work provides solvent-based design criteria for a wide temperature range Li-sulfur pouch cells.
more »
« less
- Award ID(s):
- 2011924
- PAR ID:
- 10413500
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 119
- Issue:
- 28
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Achieving durable lithium (Li) metal anodes in liquid electrolytes remains challenging, primarily due to the instability of the formed solid‐electrolyte interphases (SEIs). Modulating the Li‐ion solvation structures is pivotal in forming a stable SEI for stabilizing Li metal anodes. Here a strategy is developed to fine‐tune the Li‐ion solvation structures through enhanced dipole–dipole interactions between the Li‐ion‐coordinated solvent and the non‐Li‐ion‐coordinating diluent, for creating a stable SEI in the developed binary salt electrolyte. The enhanced dipole–dipole interactions weaken the coordination between Li‐ions and the solvents while strengthening the interaction between Li‐ions and dual anions, thereby facilitating the Li‐ion transport and a robust anion‐derived SEI with a distinct bilayer structure. Consequently, the developed electrolyte exhibited exceptional electrochemical performance in high energy‐density Li||LiNi0.8Mn0.1Co0.1O2 (NMC811) cells, with long calendar life, stable cyclability at 1 C, and reliable operation between 25 and −20 °C, and it also demonstrat remarkable cycling stability for a Li||NMC811 pouch cell with projected energy density of 402 Wh kg−1, maintaining 80% capacity retention over 606 cycles under practical conditions.more » « less
-
Abstract A dual‐layer interphase that consists of an in‐situ‐formed lithium carboxylate organic layer and a thin BF3‐doped monolayer Ti3C2MXene on Li metal is reported. The honeycomb‐structured organic layer increases the wetting of electrolyte, leading to a thin solid electrolyte interface (SEI). While the BF3‐doped monolayer MXene provides abundant active sites for lithium homogeneous nucleation and growth, resulting in about 50% reduced thickness of inorganic‐rich components among the SEI layer. A low overpotential of less than 30 mV over 1000 h cycling in symmetric cells is received. The functional BF3 groups, along with the excellent electronic conductivity and smooth surface of the MXene, greatly reduce the lithium plating/stripping energy barrier, enabling a dendrite‐free lithium‐metal anode. The battery with this dual‐layer coated lithium metal as the anode displays greatly improved electrochemical performance. A high capacity‐retention of 175.4 mAh g−1at 1.0 C is achieved after 350 cycles. In a pouch cell with a capacity of 475 mAh, the battery still exhibits a high discharge capacity of 165.6 mAh g−1with a capacity retention of 90.2% after 200 cycles. In contrast to the fast capacity decay of pure Li metal, the battery using NCA as the cathode also displays excellent capacity retention in both coin and pouch cells. The dual‐layer modified surface provides an effective approach in stabilizing the Li‐metal anode.more » « less
-
Lithium metal batteries are capable of pushing cell energy densities beyond what is currently achievable with commercial Li-ion cells and are the ideal technology for supplying power to electronic devices at low temperatures (≤−20 °C). To minimize the thermal management requirements of these devices, batteries capable of both charging and discharging at these temperatures are highly desirable. Here, we report >4 V Li metal full cell batteries (N/P = 2) capable of hundreds of stable cycles down to −40 °C, unambiguously enabled by the introduction of cation/anion pairs in the electrolyte. Via controlled experimental and computational investigations in electrolytes employing 1,2-dimethoxyethane as the solvating solvent, we observed distinct performance transitions in low temperature electrochemical performance, coincident with a shift in the Li + binding environment. The performance advantages of heavily ion-paired electrolytes were found to apply to both the cathode and anode, providing Li metal Coulombic efficiencies of 98.9, 98.5, and 96.9% at −20, −40, and −60 °C, respectively, while improving the oxidative stability in support of >4 V cathodes. This work reveals a strong correlation between ion-pairing and low-temperature performance while providing a viable route to Li metal full batteries cycling under extreme conditions.more » « less
-
Several effective methods have been developed recently to demonstrate simultaneous high energy and high power density in Lithium - carbon fluoride (Li-CFx) batteries. These methods can achieve as high as a 1000 Wh/kg energy density at a 60–70 kW/kg power density (40–50 C rate) in coin cells and a 750 Wh/kg energy density at a 12.5 kW/kg power density (20 C rate) in pouch cells. This performance is made possible by an ingenious nano-architecture design, controlled porosity, boron doping, and electrolyte additives. In the present study, we show that a similarly great performance, a 931 Wh/kg energy density at a 59 kW/kg power density, can be achieved by using a polyacrylonitrile binder and a LiBF4 electrolyte in Li-graphite fluoride coin cells. We also demonstrate that the observed effect is the result of the right combination of the binder and the electrolyte. We propose that the mechanistic origin of the observed phenomena is an electro-catalytic effect of the polyacrylonitrile binder. While our proposed method has a competitive performance, it also offers a simple implementation and a scalable production of high-energy and high-power primary Li-CFx cells.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2200392119
