Despite the high specific capacity and low redox potential of alkali metals, their practical application as anodes is still limited by the inherent dendrite‐growth problem. The fusible sodium–potassium (Na–K) liquid metal alloy is an alternative that detours this drawback, but the fundamental understanding of charge transport in this binary electroactive alloy anode remains elusive. Here, comprehensive characterization, accompanied with density function theory (DFT) calculations, jointly expound the Na–K anode‐based battery working mechanism. With the organic cathode sodium rhodizonate dibasic (SR) that has negligible selectivity toward cations, the charge carrier is screened by electrolytes due to the selective ionic pathways in the solid electrolyte interphase (SEI). Stable cycling for this Na–K/SR battery is achieved with capacity retention per cycle to be 99.88% as a sodium‐ion battery (SIB) and 99.70% as a potassium‐ion battery (PIB) for over 100 cycles. Benefitting from the flexibility of the liquid metal and the specially designed carbon nanofiber (CNF)/SR layer‐by‐layer cathode, a flexible dendrite‐free alkali‐ion battery is achieved with an ultrahigh areal capacity of 2.1 mAh cm−2. Computation‐guided materials selection, characterization‐supported mechanistic understanding, and self‐validating battery performance collectively promise the prospect of a high‐performance, dendrite‐free, and versatile organic‐based liquid metal battery.
Rechargeable alkali metal anodes hold the promise to significantly increase the energy density of current battery technologies. But they are plagued by dendritic growths and solid‐electrolyte interphase (SEI) layers that undermine the battery safety and cycle life. Here, a non‐porous ingot‐type sodium (Na) metal growth with self‐modulated shiny‐smooth interfaces is reported for the first time. The Na metal anode can be cycled reversibly, without forming whiskers, mosses, gas bubbles, or disconnected metal particles that are usually observed in other studies. The ideal interfacial stability confirmed in the microcapillary cells is the key to enable anode‐free Na metal full cells with a capacity retention rate of 99.93% per cycle, superior to available anode‐free Na and Li batteries using liquid electrolytes. Contradictory to the common beliefs established around alkali metal anodes, there is no repeated SEI formation on or within the sodium anode, supported by the X‐ray photoelectron spectroscopy elemental depth profile analyses, electrochemical impedance spectroscopy diagnosis, and microscopic imaging.
more » « less- Award ID(s):
- 1934122
- NSF-PAR ID:
- 10446341
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Science
- Volume:
- 8
- Issue:
- 12
- ISSN:
- 2198-3844
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Anodes for lithium metal batteries, sodium metal batteries, and potassium metal batteries are susceptible to failure due to dendrite growth. This review details the structure–chemistry–performance relations in membranes that stabilize the anodes’ solid electrolyte interphase (SEI), allowing for stable electrochemical plating/stripping. Case studies involving Li, Na, and K are presented to illustrate key concepts. “Classical” versus “modern” understandings of the SEI are described, with an emphasis on the new structural insights obtained through novel analytical techniques, including in situ liquid‐secondary ion mass spectroscopy, titration gas chromatography, and tip‐enhanced Raman spectroscopy. This Review highlights diverse approaches for increasing SEI stability, either by inserting a secondary layer between the native SEI and the separator, or by combining the membrane with a native SEI to form a hybrid composite. Exciting and nonintuitive findings are discussed, such as that the metal anode roughness profoundly affects the SEI structure and stability, or that organic artificial SEI‐layers may be more effective than the native inorganic–organic SEIs. Emerging multifunctional architectures are presented, which serve a dual role as metal hosts and metal surface protection layers. Throughout the Review, fruitful future research directions and the critical areas where there is incomplete understanding are discussed.
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Abstract Given the high energy density, alkali metals are preferred in rechargeable batteries as anodes, however, with significant limitations such as dendrite growth and volume expansion, leading to poor cycle life and safety concerns. Herein a room‐temperature liquid alloy system is proposed as a possible solution for its self‐recovery property. Full extraction of alkali metal ions from the ternary alloy brings it back to the binary liquid eutectic, and thus enables a self‐healing process of the cracked or pulverized structure during cycling. A half‐cell discharge specific capacity of up to 706.0 mAh g−1in lithium‐ion battery and 222.3 mAh g−1for sodium‐ion battery can be delivered at 0.1C; at a high rate of 5C, a sizable capacity of over 400 mAh g−1for Li and 60 mAh g−1for Na could be retained. Li and Na ion full cells with considerable stability are demonstrated when pairing liquid metal with typical cathode materials, LiFePO4, and P2‐Na2/3[Ni1/3Mn2/3]O2. Remarkable cyclic durability, considerable theoretical capacity utilization, and reasonable rate stability present in this work allow this novel anode system to be a potential candidate for rechargeable alkali‐ion batteries.
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null (Ed.)Sodium metal battery (SMB, NMB) anodes can become dendritic due to an electrochemically unstable native Na-based solid electrolyte interphase (SEI). Herein Li-ion activated tin sulfide graphene nanocomposite membrane (A-SnS–G) is employed as an artificial SEI layer, allowing cyclability of record-thin 100 μm Na metal foils. The thin Na metal is prepared by a self-designed metallurgical rolling protocol. A-SnS–G is initially placed onto the polypropylene (PP) separator but becomes in situ transferred onto the Na metal surface. Symmetric metal cells protected by A-SnS–G achieve low-overpotential extended high-rate cycling in a standard carbonate electrolyte (EC : DEC = 1 : 1, 5% FEC). Accumulated capacity of 1000 mA h cm −2 is obtained after 500 cycles at 4 mA cm −2 , with accumulated capacity-to-foil capacity (A/F) ratio of 90.9. This is among the most favorable cycle life, accumulated capacity, and anode utilization combinations reported. Protection by non-activated SnS–G membrane yields significantly worse cycling, albeit still superior to the baseline unprotected sodium. Post-mortem and dedicated light optical analysis indicate that metal swelling, dendrite growth and dead metal formation is extensive for the unprotected sample, but is suppressed with A-SnS–G. Per XPS, post-100 cycles near-surface structure of A-SnS–G is rich in metallic Sn alloys and inorganic carbonate salts. Even after 300 cycles, Li-based SEI components ROCO 2 -Li, Li 2 CO 3 and LiF are detected with A-SnS–G. As a proof of principle, an SMB with a high mass loading (6 mg cm −2 ) NVP cathode and a A-SnS–G protected anode delivered extended cyclability, achieving 74 mA h g −1 after 400 cycles at 0.4C.more » « less
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