Reversible Sodium–Sulfur Batteries Enabled by a Synergistic Dual-Additive Design
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Chemistry↗
Engineering topics
Ren, Yuxun
Publications and source records attributed to Ren, Yuxun.
A Dual–Phase Electrolyte for High–Energy Lithium–Sulfur Batteries
Dissolution of lithium polysulfides (LiPSs) is essential for fast cathode kinetics, but detrimental for anode stability, especially under lean electrolyte conditions. Here in this work, the phase separation phenomenon between solvents with different polarities (tetramethyl sulfone [TMS] and dibutyl ether [DBE]) is utilized to enable the design of a dual-phase electrolyte. High-polarity, high-density TMS–lithium bis(trifluoromethanesulfonyl)imide–ammonium trifluoroacetate as the cathode electrolyte strongly solvates LiPSs, which propel the sulfur redox reaction. Moreover, the composite of DBE and a polymeric ion conductor serves as the anode electrolyte. The addition of DBE in the anode side effectively prevents the crossover of corrosive species (LiPSs and ammonia trifluoroacetate), enabling a significant improvement in Li-metal anode stability. The electrode-specific dual-phase electrolyte design provides electrochemical performance superior to conventional electrolytes. Without additional electrode engineering, pouch cells assemble with the dual-phase electrolyte cycle under a lean electrolyte (4 µL mg –1 ) and low-Li-excess condition (N/P = 3) for 120 cycles.
25 ENERGY STORAGE↗
Anode‐Free Lithium–Sulfur Cells Enabled by Rationally Tuning Lithium Polysulfide Molecules
Abstract The two major barriers of practical lithium–sulfur batteries are the poor reversibility of lithium‐metal anode and sluggish kinetics of sulfur cathode. Here, we report a simple yet cogent, molecular tailoring approach for lithium polysulfides, enabling a synergistic enhancement of anode reversibility and cathode kinetics. We show that SnI 4 coordinates with lithium polysulfides to form soluble complexes, resulting in a Li 2 SnS 3 ‐rich anode interphase layer. As Li 2 SnS 3 is stable against parasitic reactions and has a lower ionic resistance over cycling, the Li plating/stripping efficiency is greatly improved. In addition, the formation of soluble complexes between SnI 4 and lithium polysulfides play a non‐negligible role in suppressing the clustering behavior of lithium polysulfide molecules, resulting in a significant enhancement in sulfur conversion kinetics under lean electrolyte conditions. The synergistic improvement is validated in anode‐free, lean‐electrolyte pouch cells with a Li 2 S cathode that displays capacity retention of 78 % after 100 cycles.
Ren, Yuxun↗
Anode-Free Lithium–Sulfur Cells Enabled by Rationally Tuning Lithium Polysulfide Molecules
The two major barriers of practical lithium–sulfur batteries are the poor reversibility of lithium-metal anode and sluggish kinetics of sulfur cathode. Here, we report a simple yet cogent, molecular tailoring approach for lithium polysulfides, enabling a synergistic enhancement of anode reversibility and cathode kinetics. In this study, we show that SnI 4 coordinates with lithium polysulfides to form soluble complexes, resulting in a Li 2 SnS 3 -rich anode interphase layer. As Li 2 SnS 3 is stable against parasitic reactions and has a lower ionic resistance over cycling, the Li plating/stripping efficiency is greatly improved. In addition, the formation of soluble complexes between SnI 4 and lithium polysulfides play a non-negligible role in suppressing the clustering behavior of lithium polysulfide molecules, resulting in a significant enhancement in sulfur conversion kinetics under lean electrolyte conditions. The synergistic improvement is validated in anode-free, lean-electrolyte pouch cells with a Li 2 S cathode that displays capacity retention of 78 % after 100 cycles.
25 ENERGY STORAGE↗
Operating High-Energy Lithium-Metal Pouch Cells with Reduced Stack Pressure Through a Rational Lithium-Host Design
Transitioning from a liquid electrolyte to an inorganic solid electrolyte offers a potential pathway to enable highly reversible lithium-metal anodes. However, the solid-electrolyte-protected lithium-metal anode suffers from poor interfacial ionic contacts and requires an impractically high stack pressure (>1.0 MPa) to maintain the interfacial contacts. It is demonstrated here that combining a hollow silver/carbon fiber scaffold and an inorganic/organic composite electrolyte enables a highly reversible lithium-metal anode. Since the high surface area of the electrode provides intimate contact and the hollow structure of the electrode relieves the lithium plating-induced stress, the electrode/electrolyte interface remains stable during cycling even under mild stack pressure. This unconventional structural design is validated in practical pouch cells assembled with the 3D lithium host containing a onefold excess of lithium and a high-nickel cathode. At a mild stack pressure of 320 kPa, the pouch cell displays 83% capacity retention for 200 cycles. This work illustrates that combining a hollow electrode architecture and a robust solid electrolyte offers a practical pathway toward rechargeable lithium-metal anodes.
36 MATERIALS SCIENCE↗
A Self-Healable Sulfide/Polymer Composite Electrolyte for Long-Life, Low-Lithium-Excess Lithium-Metal Batteries
Solid electrolyte-protected lithium-metal anodes promise energy-dense, safe cells. While sulfide solid electrolytes enable facile processability and fast ion transport, they suffer from complex chemo-mechanical issues, including Li plating-induced fracture and Li stripping-induced contact loss. To address these issues, a grafting approach is implemented to functionalize the sulfide solid electrolyte (Li 3,85 Sn 0.85 Sb 0.15 S 4 ) with a self-healing unit. This leads to a dynamic bonding between the solid electrolyte network and a mechanically robust polymer scaffold, which reversibly accommodates the volume changes of the lithium-metal anode. Thus, the approach improves the interfacial contact between the lithium-metal anode and the composite electrolyte, enabling stable cycling at a mild stack pressure (160 kPa). With a negative to positive capacity ratio equals to 1, pouch full cells with a high-nickel cathode (nickel content > 90%) and lithium-metal anode display 92% capacity retention for 140 cycles. Engineering the interface between solid electrolyte and the polymeric binder offers a promising pathway to address the chemo-mechanical issues.
36 MATERIALS SCIENCE↗
A high-energy and long-cycling lithium–sulfur pouch cell via a macroporous catalytic cathode with double-end binding sites
Lithium-sulfur batteries are attractive alternatives to lithium-ion batteries because of their high theoretical specific energy and natural abundance of sulfur. However, the practical specific energy and cycle life of Li-S pouch cells are significantly limited by the use of thin sulfur electrodes/flooded electrolytes and polysulfides shuttle/Li metal degradation, respectively. In this work we propose a cathode design concept to achieve good Li-S pouch cell performances. The cathode is composed of uniformly embedded ZnS nanoparticles and Co-N-C single-atom catalyst to form double-end biding sites inside a highly oriented macroporous host, which can effectively immobilize and catalytically convert polysulfides intermediates during cycling, thus eliminating the shuttle effect and lithium metal corrosion. The ordered macropores enhance ionic transport under high sulfur loading by forming sufficient catalyst/conductive support/electrolyte triple-phase boundaries. This prevents the formation of inactive sulfur (dead sulfur). Our cathode structure shows improved performances in a pouch cell configuration under high sulfur loading and lean electrolyte operation. An Ah-level pouch cell with only 100% lithium excess can deliver a cell specific energy of > 300 Wh kg –1 with a Coulombic efficiency >95% for 80 cycles.
25 ENERGY STORAGE↗