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.
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.
more » « less- Award ID(s):
- 1911905
- NSF-PAR ID:
- 10455893
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Energy Materials
- Volume:
- 10
- Issue:
- 43
- ISSN:
- 1614-6832
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
The performance of Li metal batteries is tightly coupled to the composition and properties of the solid electrolyte interphase (SEI). Even though the role of the SEI in battery function is well understood (e.g., it must be electronically insulating and ionically conductive, it must enable uniform Li+ flux to the electrode to prevent filament growth, it must accommodate the large volume changes of Li electrodeposition), the challenges associated with probing this delicate composite layer have hindered the development of Li metal batteries for practical applications. In this review, we detail how nuclear magnetic resonance (NMR) spectroscopy can help bridge this gap in characterization due to its unique ability to describe local structure (e.g., changes in crystallite size and amorphous species in the SEI) in conjunction with ion dynamics while connecting these properties to electrochemical behavior. By leveraging NMR, we can gain molecular-level insight to aid in the design of Li surfaces and enable reactive anodes for next-generation, high-energy-density batteries.more » « less
-
The poor interfacial stability of Li metal leads to formation of unstable solid-electrolyte interphases (SEIs) and severely limits its practical applications. Protecting Li metal with an artificial SEI that has balanced stability, conductivity and mechanical strength is critical. Here we demonstrate a design strategy for stabilizing Li using Mo 6 S 8 /carbon artificial SEI films. These films are directly coated on Li foil and the Mo 6 S 8 particles provide ordered conduction channels for fast but regulated Li-ion flux, and provide hybrid anodes that have nearly four times higher exchange current densities. They also have seamless contact with Li metal and protect it from parasitic reactions, and hence significantly improve its stability. Consequently, Li metal batteries in which the hybrid anodes were paired with LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathodes (3.0 mA h per cell) exhibited significantly improved cycling stability (63% vs. 25% retention) and a stabilized Li interphase compared with pristine Li anodes.more » « less
-
more » « less
Abstract The interrelation is explored between external pressure (0.1, 1, and 10 MPa), solid electrolyte interphase (SEI) structure/morphology, and lithium metal plating/stripping behavior. To simulate anode‐free lithium metal batteries (AF‐LMBs) analysis is performed on “empty” Cu current collectors in standard carbonate electrolyte. Lower pressure promotes organic‐rich SEI and macroscopically heterogeneous, filament‐like Li electrodeposits interspersed with pores. Higher pressure promotes inorganic F‐rich SEI with more uniform and denser Li film. A “seeding layer” of lithiated pristine graphene (pG@Cu) favors an anion‐derived F‐rich SEI and promotes uniform metal electrodeposition, enabling extended electrochemical stability at a lower pressure. State‐of‐the‐art electrochemical performance is achieved at 1MPa: pG‐enabled half‐cell is stable after 300 h (50 cycles) at 1 mA cm−2rate −3 mAh cm−2capacity (17.5 µm plated/stripped), with cycling Coulombic efficiency (CE) of 99.8%. AF‐LMB cells with high mass loading NMC622 cathode (21 mg cm−2) undergo 200 cycles with a CE of 99.4% at C/5‐charge and C/2‐discharge (1C = 178 mAh g−1). Density functional theory (DFT) highlights the differences in the adsorption energy of solvated‐Li+onto various crystal planes of Cu (100), (110), and (111), versus lithiated/delithiated (0001) graphene, giving insight regarding the role of support surface energetics in promoting SEI heterogeneity.
-
more » « less
Abstract Since their commercialization by Sony in 1991, graphite anodes in combination with various cathodes have enabled the widespread success of lithium‐ion batteries (LIBs), providing over 10 billion rechargeable batteries to the global population. Next‐generation nonaqueous alkali metal‐ion batteries, namely sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs), are projected to utilize intercalation‐based carbon anodes as well, due to their favorable electrochemical properties. While traditionally graphite anodes have dominated the market share of LIBs, other carbon materials have been investigated, including graphene, carbon nanotubes, and disordered carbons. The relationship between carbon material properties, electrochemical performance, and charge storage mechanisms is clarified for these alkali metal‐ion batteries, elucidating possible strategies for obtaining enhanced cycling stability, specific capacity, rate capability, and safety aspects. As a key component in determining cell performance, the solid electrolyte interphase layer is described in detail, particularly for its dependence on the carbon anode. Finally, battery safety at extreme temperatures is discussed, where carbon anodes are susceptible to dendrite formation, accelerated aging, and eventual thermal runaway. As society pushes toward higher energy density LIBs, this review aims to provide guidance toward the development of sustainable next‐generation SIBs and PIBs.
