An official website of the United States government
Instabilities during metal electrodeposition create dendrites on the plating surfaces. In high energy density lithium metal batteries (LMBs) dendrite growth causes safety issues and accelerated aging. In this paper, analytical models predict that dendrite growth can be controlled and potentially eliminated by small advective flows normal to the surface of lithium metal electrode. Electrolyte flow towards the Li metal electrode lowers the dendrite growth rate, overpotential, and impedance. Flow in the opposite direction, however, enhances the dendrite growth. For every current density, there exists a critical velocity above which dendrite growth can be totally eliminated. The critical velocity increases almost linearly with increasing current density. For typical current densities and inter-electrode separation, the critical velocity is very small, indicating the potential for practical application.
more »
« less
In situ healing of dendrites in a potassium metal battery
The use of potassium (K) metal anodes could result in high-performance K-ion batteries that offer a sustainable and low-cost alternative to lithium (Li)-ion technology. However, formation of dendrites on such K-metal surfaces is inevitable, which prevents their utilization. Here, we report that K dendrites can be healed in situ in a K-metal battery. The healing is triggered by current-controlled, self-heating at the electrolyte/dendrite interface, which causes migration of surface atoms away from the dendrite tips, thereby smoothening the dendritic surface. We discover that this process is strikingly more efficient for K as compared to Li metal. We show that the reason for this is the far greater mobility of surface atoms in K relative to Li metal, which enables dendrite healing to take place at an order-of-magnitude lower current density. We demonstrate that the K-metal anode can be coupled with a potassium cobalt oxide cathode to achieve dendrite healing in a practical full-cell device.
more »
« less
- Award ID(s):
- 1922633
- PAR ID:
- 10144005
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 117
- Issue:
- 11
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- 5588 to 5594
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Lithium metal batteries (LMBs) are considered one of the most promising next-generation rechargeable batteries due to their high specific capacity. However, severe dendrite growth and subsequent formation of dead lithium (Li) during the battery cycling process impede its practical application. Although extensive experimental studies have been conducted to investigate the cycling process, and several theoretical models were developed to simulate the Li dendrite growth, there are limited theoretical studies on the dead Li formation, as well as the entire cycling process. Herein, we developed a phase-field model to simulate both electroplating and stripping process in a bare Li anode and Li anode covered with a protective layer. A step function is introduced in the stripping model to capture the dynamics of dead Li. Our simulation clearly shows the growth of dendrites from a bare Li anode during charging. These dendrites detach from the bulk anode during discharging, forming dead Li. Dendrite growth becomes more severe in subsequent cycles due to enhanced surface roughness of the Li anode, resulting in an increasing amount of dead Li. In addition, it is revealed that dendrites with smaller base diameters detach faster at the base and produce more dead lithium. Meanwhile, the Li anode covered with a protective layer cycles smoothly without forming Li dendrite and dead Li. However, if the protective layer is fractured, Li metal preferentially grows into the crack due to enhanced Li-ion (Li+) flux and forms a dendrite structure after penetration through the protective layer, which accelerates the dead Li formation in the subsequent stripping process. Our work thus provides a fundamental understanding of the mechanism of dead Li formation during the charging/discharging process and sheds light on the importance of the protective layer in the prevention of dead Li in LMBs.more » « less
-
Lithium (Li) metal anodes have regained intensive interest in recent years due to the ever-increasing demand for next-generation high energy battery technologies. Li metal, unfortunately, suffers from poor cycling stability and low efficiency as well as from the formation of dangerous Li dendrites, raising safety concerns. Utilizing solid-state electrolytes (SSEs) to prevent Li dendrite growth provides a promising approach to tackle the challenge. However, recent studies indicate that Li dendrites easily form at high current densities, which calls for full investigation of the fundamental mechanisms of Li dendrite formation within SSEs. Herein, the origin and evolution of Li dendrite growth through SSEs have been studied and compared by using Li 6.1 Ga 0.3 La 3 Zr 2 O 12 (LLZO) and NASICON-type Li 2 O–Al 2 O 3 –P 2 O 5 –TiO 2 –GeO 2 (LATP) pellets as the separators. We discover that a solid electrolyte interphase (SEI)-like interfacial layer between Li and SSE plays a critical role in alleviating the growth of dendritic Li, providing new insights into the interface between SSE and Li metal to enable future all solid-state batteries.more » « less
-
Lithium metal as an anode has been widely accepted due to its higher negative electrochemical potential and theoretical capacity. Nevertheless, the existing safety and cyclability issues limit lithium metal anodes from practical use in high-energy density batteries. Repeated Li deposition and dissolution processes upon cycling lead to the formation of dendrites at the interface which results in reduced Li availability for electrochemical reactions, disruption in Li transport through the interface and increased safety concerns due to short circuiting. Here, we demonstrate a novel strategy using Ionic Liquid Crystals (ILCs) as the electrolyte cum pseudo-separator to suppress dendrite growth with their anisotropic properties controlling Li-ion mass transport. A thermotropic ILC with two-dimensional Li-ion conducting pathways was synthesized and characterized. Microscopic and spectroscopic analyses elucidate that the ILC formed with a smectic A phase, which can be utilized for wide temperature window operation. The results of electrochemical studies corroborate the efficacy of ILC electrolytes in mitigating dendrite formation even after 850 hours and it is further substantiated by numerical simulation and the mechanism involved in dendritic suppression was deduced.more » « less
-
Li dendrite formed in Li metal batteries can be categorized into two different types. One is the detrimental Li dendrite that heads towards the separator with a potential to short cell. The other is the ill-defined fibrous Li formed within bulk Li metal. The detrimental Li dendrite may cause cell short, while the other dendrites, covered by SEI, mainly increase cell impedance and terminate the cell operation, most often, before any “short” really happens. Without decoupling these two different Li dendrites, it is hard to develop any effective approach to realize both stable and safe Li metal batteries. Herein, a straightforward approach is proposed to induce the growth of detrimental dendritic Li so the cells are “shorted” frequently and consistently. Based on this new protocol, various electrolytes are revisited and the SEI derived are compared and quantified, providing new insights for addressing the challenges in rechargeable Li metal battery technologies.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1073/pnas.1915470117
