Anode-electrolyte Interface Research Articles

Functionalized carbon nanofiber interlayer towards dendrite-free, Zn-ion batteries

Although the intrinsic safety, low cost, and high theoretical energy densities have made the Aqueous zinc-ion batteries (AZIBs) to be a promising candidate in the application of energy storage fields. However, battery failure caused by the dendrite formation has become the major issue that disrupt their practical application. To solve that, herein, we report a unique interface strategy for regulating the interfacial electrodeposition kinetics and inhibiting dendrite formation through covering a N,O co-doped Carbon nanofiber (CNF) interlayers on Zn metal anode surface. Such CNF interlayers with robust zincophilicity can effectively capture the Zn ions, and guiding the regular Zn electrodeposition in the anode-electrolyte interface, which have been demonstrated by both theoretical calculation and experimental results. Significantly, the electrochemical tests confirmed that the cell modified with CNF interlayers exhibits a high Zn plating/stripping reversibility with a low nucleation overpotential. Notably, the modified cell enables steadily operating for 1200 h with a low overpotential of 59.5 mV at a high current density of 5 mA cm−2 (1 mAh cm−2). Moreover, the rate capability and cyclic stability of Zn-MnO2 full battery can be greatly improved after covering the CNF interlayers on the Zn metal anode surface. This work is highly expected to provide a new route to enable dendrite-free Zn metal anodes and high-performance AZIBs.

Stabilizing Zinc Anodes by Regulating the Electrical Double Layer with Saccharin Anions

Zn anodes suffer from poor Coulombic efficiency (CE) and serious dendrite formation due to the unstable anode/electrolyte interface (AEI). The electrical double layer (EDL) structure formed before cycling is of great significance for building stable solid electrolyte interphase (SEI) on Zn surface but barely discussed in previous research about the stabilization of Zn anode. Herein, saccharin (Sac) is introduced as electrolyte additive for regulating the EDL structure on the AEI. It is found that Sac derived anions are preferentially adsorbed on the Zn metal surface instead of water dipole, creating a new H2 O-poor EDL structure. Moreover, the unique SEI is also detected on the Zn surface due to the decomposition of Sac anions. Both are proved to be capable of modulating Zn deposition behavior and preventing side reactions. Encouragingly, Zn|Zn symmetric cells using Sac additive deliver a high cumulative plated capacity of 2.75 Ah cm-2 and a high average CE of 99.6% under harsh test condition (10mA cm-2 , 10 mAh cm-2 ). The excellent stability is also achieved at a high rate of 40mA cm-2 . The effectiveness of this Sac additive is further demonstrated in the Zn-MnO2 full cells.

Operando Thermal Imaging Study of Internal Partial Methane Oxidation in Ni-YSZ Anodes of Commercial SOFCs

Thermal imaging is employed to study internal partial methane oxidation in a Ni-YSZ anode of a commercial, button-style solid oxide fuel cell at 800 °C in real time. When a stoichiometric 2:1 mixture of methane and oxygen is delivered to the anode, thermal imaging reveals formation of two distinct zones on the exposed surface of the anode: a smaller zone of increased temperature near the fuel delivery inlet and a larger zone of decreased temperature occupying the rest of the anode. We assign the former to exothermic complete oxidation of some methane to steam and carbon dioxide and the latter to endothermal reforming of the remaining methane with the steam and carbon dioxide generated in the hot zone. Simultaneous detection of catalytic products using mass spectrometry indicates that when combined the two sequential reactions convert almost 80% of the delivered methane, with the main products being carbon monoxide and hydrogen. Cell polarization during partial methane oxidation delivers an oxide ion flux to the anode-electrolyte interface. As the oxide flux is significantly lower than the oxygen gas flux delivered in the methane and oxygen mixture, the former is used to probe the catalytic products of partial methane oxidation. Our results reveal negligible amounts of unreacted methane and accumulated carbon on the anode surface during the partial oxidation process.

Intermetallic interphases in lithium metal and lithium ion batteries

AbstractA robust electrode–electrolyte interface is the cornerstone for every battery system, as demonstrated in the meandering history of the development of Li‐ion batteries (LIBs). In the thrust to replace the graphite anode with more energetic ones in LIBs, the effectual strategy for stabilizing the original graphite–electrolyte interface becomes obsolete and a new anode–electrolyte interface needs reconfiguration. Unfortunately, this interface has become the Achilles' heel for those anodes, such as Li‐metal anode (LMA) and Si‐based anode owing to their excessive reductivity, enormous volume change, and so forth. Encouragingly, in the last decade, impressive progress has been made on taming these extremely unstable interfaces and on the solid‐state batteries (SSBs) that are reported to be less susceptible to parasitic reactions. One of the distinguished strategies is the application of artificial Li‐alloying intermetallic interphases onto the surface of LMA, via the direct introduction of foreign metals to the Li anode or indirect hetero‐cations doping in the electrolyte, to regulate the Li deposition/stripping behavior, which has markedly improved the stability of the LMA–electrolyte interface. In parallel, the intermetallic interphases are also witnessed to profoundly enhance the anode–solid electrolyte contact and the corresponding charge transfer kinetics in various SSBs. This review will provide a panoramic overview of the application of the intermetallic interphases at the anode–electrolyte interfaces in the lithium metal batteries (LMBs), SSBs, and also derivative works in the conventional LIBs, which will focus on different concepts, methodologies, and understandings from the encircled studies.image

Establishing a Stable Anode-Electrolyte Interface in Mg Batteries by Electrolyte Additive.

Simple magnesium salts with high electrochemical and chemical stability and adequate ionic conductivity represent a new-generation electrolyte for magnesium (Mg) batteries. Similar to other Mg electrolytes, the simple-salt electrolyte also suffers from high charge-transfer resistance on the Mg surface due to the adsorbed species in the solution. In the current study, we built a model Mg cell system with the Mg[B(hfip)4]2/DME electrolyte and Chevrel phase Mo6S8 cathode, to demonstrate the effect of such anode-electrolyte interfacial properties on the full-cell performance. It was found that the cell required additional activation cycles to achieve its maximal capacity. The activation process is mainly attributed to the conditioning of the anode-electrolyte interface, which could be boosted by introducing an additive amount of Mg(BH4)2 to the Mg[B(hfip)4]2/DME electrolyte. Electrochemical and spectroscopic analyses revealed that the Mg(BH4)2 additive helps to remove the native oxide layer and promotes the formation of a solid electrolyte interphase layer on Mg. As a result, the full cell with the additive-containing electrolyte delivered a stable capacity from the second cycle onward. Further battery tests showed a reversible cycling for 600 cycles and an excellent rate capability, indicating good compatibility of the Mg(BH4)2 additive. The current study not only provides fundamental insights into the interfacial phenomena in Mg batteries but also highlights the facile tunability of the simple-salt Mg electrolytes.

Lithium-Metal Anodes Working at 60 mA cm-2 and 60 mAh cm-2 through Nanoscale Lithium-Ion Adsorbing.

Achieving high-current-density and high-area-capacity operation of Li metal anodes offers promising opportunities for high-performing next-generation batteries. However, high-rate Li deposition suffers from undesired Li-ion depletion especially at the electrolyte-anode interface, which compromises achievable capacity and lifetime. Here, electronegative graphene quantum dots are synthesized and assembled into an ultra-thin overlayer capable of efficient Li-ion adsorbing at the nanoscale on Li-metal to fully relieve Li-ion depletion. The protected Li anode achieves long-term reversible Li plating/stripping over 1000 h at both superior current density of 60 mA cm-2 and areal capacity of 60 mAh cm-2 . Implementation of the protected anode allows for the construction of Li-air full battery with both enhanced rate capability and cycling performance.

A simple strategy that may effectively tackle the anode-electrolyte interface issues in solid-state lithium metal batteries

Interface issues are the biggest challenges that hindering the commercialization of solid-state lithium metal batteries (SSLMBs). Here, we propose a novel strategy targeting for effectively resolving the tedious lithium-garnet solid electrolyte interface problem from the lithium side. We intentionally introduce α-MoO3 nanobelts into the molten metallic lithium, forming a Li-Mo composite. Compared to molten lithium, the composite improves wettability on the garnet electrolyte. As revealed by density functional theory calculations, such improvement could be ascribed to the reduced cohesive energy and the improved interface binding energy to the LLZTO. Intimate surface contact can be easily achieved without complicated surface treatment, which not only significantly reduces the interface resistance to ~ 1 Ω cm2, but could also effectively inhibits the generation of lithium dendrites. These features ensure a significant critical current density of 1700 µA cm−2 and a stable electrochemical Li plating/stripping process for more than 1200 h. A full cell with the Li-Mo composite anode and LiFePO4 cathode also presents a fairly stable cycling performance at room temperature. Different from most previous strategies that try to tackle the interface issues from the electrolyte side, our research results suggest that designing lithium composite anodes with low cohesive energy and high interface binding energy to the solid electrolyte is an attractive and feasible solution to overcome interface problems.

The tricky challenge holding back electric cars

Tiny metal deposits called dendrites threaten to curtail the development of rechargeable batteries. But engineers have solutions in sight . Gasoline-powered automobiles seem destined for the rearview mirror. In March 2021, the Swedish company Volvo declared that by 2030 it will sell only fully electric cars. Just weeks earlier, Ford had announced plans to go all-electric in Europe by the same year, while GM is aiming for its cars to be fully electric by 2035. Last year, electric vehicles made up less than 3% of all new car sales in the United States, but a recent analysis by BloombergNEF predicts that their global market share will soar to nearly 60% in just 20 years (1). The global market share of electric vehicles is set to soar in the coming years. Designing faster-charging batteries that mitigate dendrite deposits will be a key challenge. Image credit: Shutterstock/guteksk7. Electric vehicles that can travel long distances and recharge quickly require safe batteries that pack a lot of energy into a small volume. Building those batteries, however, means overcoming a number of challenges. Chief among them is the problem of dendrites—disruptive, spiky growths of metal inside a battery that raise the risk of dangerous discharges. Building a fast-charging battery that can suppress dendrites is a “holy grail problem,” says Yi Cui, an engineer at Stanford University in Palo Alto, CA. But recent findings suggest that the dendrite issue is not insurmountable. Experimental efforts to tame dendrites have produced promising, proof-of-concept demonstrations that capitalize on the strengths of lithium batteries while minimizing dendrite risk. These include strategies such as making nanoscale-level changes to the structure of the electrodes, studying the fundamental causes of dendrites, and exploring new materials for the anode-electrolyte interface and the electrolyte itself. If these findings scale up, they will pave the …

Inhibition of Lithium Dendrite Formation in Lithium Metal Batteries via Regulated Cation Transport through Ultrathin Sub‐Nanometer Porous Carbon Nanomembranes

AbstractSuppressing Li dendrite growth has gained research interest due to the high theoretical capacity of Li metal anodes. Traditional Celgard membranes which are currently used in Li metal batteries fall short in achieving uniform Li flux at the electrode/electrolyte interface due to their inherent irregular pore sizes. Here, the use of an ultrathin (≈1.2 nm) carbon nanomembrane (CNM) which contains sub‐nanometer sized pores as an interlayer to regulate the mass transport of Li‐ions is demonstrated. Symmetrical cell analysis reveals that the cell with CNM interlayer cycles over 2x longer than the control experiment without the formation of Li dendrites. Further investigation on the Li plating morphology on Cu foil reveals highly dense deposits of Li metal using a standard carbonate electrolyte. A smoothed‐particle hydrodynamics simulation of the mass transport at the anode–electrolyte interface elucidates the effect of the CNM in promoting the formation of highly dense Li deposits and inhibiting the formation of dendrites. A lithium metal battery fabricated using the LiFePO4 cathode exhibits a stable, flat voltage profile with low polarization for over 300 cycles indicating the effect of regulated mass transport.

Stability of Lithium Metal Electrodeposition across Viscoelastic Electrolytes

The key issue preventing the use of lithium metal anodes in high energy-density batteries is undesirable dendritic deposition at the lithium-electrolyte interface, which raises serious concerns over safety and battery life. Experimental and theoretical studies have been carried out to reveal the mechanism underlying this morphological instability and to suppress it via electrolyte engineering. We study this instability by perturbing a continuum electrodeposition model which couples ionic transport across the cell, mechanical response of the anode and separator, and Marcus reaction kinetics at the anode-electrolyte interface. The analysis is validated against known results for elastic separators, then generalized to include the viscoelastic response of polymer electrolytes and to examine the impact of relaxation time. The work bridges the regimes dominated by ionic transport and reaction kinetics and can guide experimental design of novel electrolytes and separators toward stable, safe lithium metal batteries.

Room‐Temperature Sodium–Sulfur Batteries and Beyond: Realizing Practical High Energy Systems through Anode, Cathode, and Electrolyte Engineering

AbstractThe increasing energy demands of society today have led to the pursuit of alternative energy storage systems that can fulfil rigorous requirements like cost‐effectiveness and high storage capacities. Based fundamentally on earth‐abundant sodium and sulfur, room‐temperature sodium–sulfur batteries are a promising solution in applications where existing lithium‐ion technology remains less economically viable, particularly in large‐scale stationary systems such as grid‐level storage. Here, the key challenges in the field are first highlighted, followed by comprehensive analyses of accessible strategies to overcome them, starting from engineering of the anode–electrolyte interface in both liquid and solid electrolytes. Recently reported polymer and solid‐state electrolytes are also surveyed. Thereafter, the core principles guiding use‐inspired design of cathode architectures, covering the spectrum of elemental sulfur and polysulfide cathodes, to emerging host structures, and covalent composites are focused upon. Future prospects are explored, with insights into other alkali‐metal systems beyond sodium–sulfur batteries, such as the potassium–sulfur battery. Finally a conclusion is provided by outlining the research directions necessary to attain high energy sodium–sulfur devices, and potential solutions to issues concerning large‐scale production, so as to ultimately realize widespread deployment of practical energy storage systems.

Driving the Interfacial Ion-Transfer Kinetics by Mesoporous TiO2 Spheres for High-Performance Aqueous Zn-Ion Batteries.

The aqueous zinc-ion batteries (ZIBs) have been considered as a promising energy storage device. However, the ion transfer at the Zn metal anode-electrolyte interface is limited by the sluggish kinetics resulting in high interface resistance. Herein, mesoporous TiO2 (m-TiO2) is coated on the Zn foil (Zn-TiO2) driving the ion's faster transfer to reduce interface resistance (70.1 Ω vs 799.3 Ω of bare Zn). The lower interface resistance is ascribed to shortening the ion transfer path provided by the mesoporous structure and the smaller Zn2+ absorption energy barrier of the surface of the Zn-TiO2 anode as well as the unobstructed ion transfer path at the crystal planes (100) of TiO2, which have been supported by the density functional theory (DFT) calculation and experiments. Therefore, the Zn-TiO2 anodes in the symmetrical cells display a low voltage hysteresis (36.5 mV) and long-term cycling stability (500 h at 4.4 mA cm-2). Especially, the Zn-TiO2/MnO2 full cells show superior cycling performance with a high capacity of 269.8 mAh g-1 after 50 cycles at 0.2 A g-1 and 210.9 mAh g-1 after 1000 cycles at 0.5 A g-1. The analysis of ion-transfer kinetics at the interface provides deep enlightenment and reference for the study of the metal anodes.

Operation Mechanism in Hybrid Mg-Li Batteries with TiNb2O7 Allowing Stable High-Rate Cycling.

We studied the structural evolution and cycling behavior of TiNb2O7 (TNO) as a cathode in a nonaqueous hybrid dual-salt Mg-Li battery. A very high fraction of pseudocapacitive contribution to the overall specific capacity makes the material suitable for ultrafast operation in a hybrid battery, composed of a Mg-metal anode, and a dual-salt APC-LiCl electrolyte with Li and Mg cations. Theoretical calculations show that Li intercalation is predominant over Mg intercalation into the TNO in a dual-salt electrolyte with Mg2+ and Li+, while experimentally up to 20% Mg cointercalation was observed after battery discharge. In hybrid Mg-Li batteries, TNO shows capacities which are about 40 mA h g-1 lower than in single-ion Li batteries at current densities of up to 1.2 A g-1. This is likely due to a partial Mg cointercalation or/and location of Li cations on alternative crystallographic sites in the TNO structure in comparison to the Li-intercalation process in Li batteries. Generally, hybrid Mg-Li cells show a markedly superior applicability for a very prolonged operation (above 1000 cycles) with 100% Coulombic efficiency and a capacity retention higher than 95% in comparison to conventional Li batteries with TNO after being cycled either under a low (7.75 mA g-1) or high (1.55 A g-1) current density. The better long-term behavior of the hybrid Mg-Li batteries with TNO is especially pronounced at 60 °C. The reasons for this are an appropriate cathode electrolyte interface containing MgCl2 species and a superior performance of the Mg anode in APC-LiCl electrolytes with a dendrite-free, fast Mg deposition/stripping. This stable interface stands in contrast to the anode electrolyte interface in Li batteries with a Li anode in conventional carbonate-containing electrolytes, which is prone to dendrite formation, thus leading to a battery shortcut.

Robust Anode-Supported Cells with Fast Oxygen Release Channels for Efficient and Stable CO2 Electrolysis at Ultrahigh Current Densities.

High-temperature electrolysis using solid oxide electrolysis cells (SOECs) provides a promising way for the storage of renewable energy into chemical fuels. During the past, nickel-based cathode-supported thin-film electrolyte configuration was widely adopted. However, such cells suffer from the serious challenge of anode delamination at high electrolysis currents due to enormous gaseous oxygen formation at the anode-electrolyte interface with insufficient adhesion caused by low sintering temperatures for ensuring high anode porosity and cathode pulverization because of potential nickel redox reaction. Here, the authors propose, fabricate, and test asymmetric thick anode-supported SOECs with firm anode-electrolyte interface and graded anode gas diffusion channel for realizing efficient and stable electrolysis at ultrahigh currents. Such a specially structured anode allows the co-sintering of anode support and electrolyte at high temperatures to form strong interface adhesion while suppressing anode sintering. The mixed oxygen-ion and electron conducting anode with graded channel structure provides a fast oxygen release pathway, large anode surface for oxygen evolution reaction, and excellent support for depositing nanocatalysts, to further improve oxygen evolution activity. As a result, the as-prepared cells demonstrate both high performance, comparable or even higher than state-of-the-art cathode-supported SOECs, and outstanding stability at a record current density of 2.5Acm-2 .

A Computational Comparison of Ether and Ester Electrolyte Stability on a Ca Metal Anode

Ca-ion batteries (CIBs) have the potential to provide inexpensive energy storage, but their realization is impeded by the lack of suitable electrolytes. Motivated by recent experimental progress, we perform ab initio molecular dynamics simulations to investigate early decomposition reactions at the anode-electrolyte interface. By examining different combinations of solvent—tetrahydrofuran (THF) or ethylene carbonate (EC)—and salt—Ca(BH 4 ) 2 , Ca(BF 4 ) 2 , Ca(BCl 4 ) 2 , and Ca(ClO 4 ) 2 —we identify a variety of behavioral trends between electrolyte solutions. Next, we perform a separate trajectory with pure THF and gradually increased negative charge; despite an addition of -32 e , no THF decomposition is detected. Charge analysis reveals that in a reductive environment, THF distributes excess charge evenly across its hydrocarbon backbone, while EC concentrates charge on its ester oxygens and carbonyl carbon, resulting in decomposition. Graphs of charge vs. time for both solvents reveal that EC decomposition products can be reduced by up to five electrons, while those of THF are limited to a single electron. Ultimately, we find Ca(BH 4 ) 2 and THF to be the most stable solution investigated herein, corroborating experimental evidence of its suitability as a CIB electrolyte.

(Invited) Computational Modeling of the Anode-Electrolyte Interface of Ca Ion Batteries

Rechargeable batteries are critical components of portable electronics, electric vehicles and grid storage. Li-ion is the dominant technology because of its low weight, large voltage and high capacity, but the demand for raw materials is putting strain on the supply chain, and there are several safety, ethical and environmental concerns. Therefore, developing adequate alternatives to Li-ion batteries is an active research area around the world. Multivalent ion batteries (MVIBs), utilizing Mg, Ca, Zn and Al, are promising due to being based on earth-abundant materials, and their higher weight can be compensated by their multivalent nature, which allows their ions to carry multiple charges. We are particularly interested in Ca ion batteries, which have received relatively little attention compared to Mg and Al, yet they are predicted to provide the largest voltage for a multivalent ion. However, their development has been limited by challenges in identifying adequate electrolytes to reversibly plate and strip metal Ca anodes. While there have been some encouraging recent developments, a systematic understanding of the interactions between electrolytes and Ca is needed. For example, it is not clear how the electrolyte (e.g., ethylene carbonate) decomposes at a Ca metal surface, nor are the structure and composition known of the solid-electrolyte interphase (SEI) that forms between the metal anode and the electrolyte. Furthermore, the diffusion of Ca2+ ions through the SEI is not well understood.We aim to address some of these points with computational modeling that combines density functional theory (DFT) with ab initio molecular dynamics (AIMD). We investigated the electrolyte decomposition of ethylene carbonate, with and without salt, at the Ca metal interface. We then compare this process to those occurring at Li and Al metal surfaces. The DFT calculations reveal the mechanism and energy barriers associated with the possible electrolyte decomposition pathways, while the AIMD trajectories show how quickly molecules decompose and their location. Next, we investigate the electron conductivity of the anode-electrolyte interface region at various stages of SEI layer formation. We accomplish this with the non-equilibrium Green’s function technique combined with DFT (NEGF-DFT), which not only tells us the conductivity but also the electron pathway through the interface. Finally, we investigate the possibility of protecting the electrolyte from reacting with the anode by separating them with an artificial SEI that still allows Ca2+ ions to diffuse through it. We propose that this strategy can aid in the development of rechargeable Ca ion batteries by bypassing the formation of an ionically insulating SEI as a result of electrolyte decomposition.

Effects of non‐planar interface and electrode parameters on the residual stress of solid oxide fuel cell

The thermomechanical response of solid oxide fuel cell will endanger its structural reliability. In this study, the effects of non-planar interface and electrode parameters are investigated by building a cosine anode-electrolyte interface with amplitude A and wavelength λ. Results show that the planar interface model cannot completely reflect the stress state of solid oxide fuel cells. Non-planar interface can stimulate high normal stress Sn and shear stress St at the interface, but these stresses are zero at the planar interface. Cosine interface causes approximately cosinoidal Sn and sinusoidal St. The bigger the ratio of amplitude to wavelength A/λ is, the more serious the Sn fluctuates. Electrode parameter analysis shows that increasing initial porosity of oxidized anode can reduce the maximum Sn but increases the maximum St and the cell deflection. Parameter study show that initial porosity between 0.15 and 0.25 is suitable. The effect of anode thickness on the maximum Sn and St is weak, while the electrolyte thickness has a relatively strong effect when the electrolyte thickness is less than 12 μm. A NiO volume fraction between 0.52 to 0.58 is recommended to avoid overlarge Sn, St, and deflection.

Efficient strategy to boost the electrochemical performance of yttrium stabilized zirconia electrolyte solid oxide fuel cell for low-temperature applications

Yttrium stabilized zirconia (YSZ) used as the state-of-the-art electrolyte for solid oxide fuel cells (SOFCs) requires high temperature (over 800 °C) to realize sufficient oxygen ion conductivity. Thus, the high operational temperature is the main restriction for the commercial process of YSZ-based SOFCs. To obtain decent ionic conductivity at intermediate-low temperatures, Sr-free cathode LaNiO3 is introduced into YSZ to construct a novel LaNiO3-YSZ composite electrolyte, which is sandwiched by two Ni0.8Co0.15Al0.05LiO2-δ (NCAL) electrodes to assemble systematical fuel cells. This device presents an excellent peak output of 1045 mW cm-2 at 600 °C and even 399 mW cm-2 at 450 °C. A series of characterizations indicates that the oxygen ion conductivity of the LaNiO3-YSZ composite is significantly promoted in comparison with that of pure YSZ, and the LaNiO3 component has certain proton conductivity after hydrogenation. Both of the two factors contributes to the superior performance of such devices at intermediate-low temperatures. Furthermore, the sharp decrease in electronic conductivity for LaNiO3 in hydrogen atmosphere combined with Schottky junction at the anode-electrolyte interface eliminates the short-circuiting problem. Our work demonstrates that incorporating Sr-free cathode LaNiO3 into the YSZ electrolyte is an efficient strategy to boost the performance and reduce the operational temperature of YSZ-based SOFCs.

Robustness-Heterogeneity-Induced Ultrathin 2D Structure in Li Plating for Highly Reversible Li-Metal Batteries.

Anode interface modification is crucial for the stabilization of Li-metal batteries (LMBs), which have been considered as the most promising system for the electric vehicle market owing to their high energy density (500 W h kg-1). However, the biggest challenge for LMBs lies in the preservation of anode reversibility, including plated Li morphology control and dendritic Li inhibition during cycling. Here, we propose a nanostructure modulation strategy of Li grains and plating to activate the anode kinetics of LMBs without the compromise of anode stability. This modulation is triggered by the rapid deposition of ultrathin polydopamine coating on the Cu foil (PDA@Cu), which results in an unusual interlaced growth of vertical or lie-down two-dimensional Li nanoflakes on PDA. The high binding energy (>3 eV) between Li atoms and rich imino/carbonyl groups enables a superior lithiophilicity of PDA to homogenize the Li-ion flowing and Li-mass electroplating with negligible nucleation overpotential. The high Coulombic efficiency (98%) and low voltage hysteresis (∼20 mV) are stabilized for at least 300 cycles in the Li-PDA@Cu cell architecture. This PDA@Cu electrode can even tolerate much higher current densities of 5 and 10 mA cm-2 for 170 and 100 cycles, respectively. The interlaced network of Li nanosheets reinforces the electric contact and therefore charge transfer at the anode-electrolyte interface characterized by small interfacial resistance (<3 Ω cm2) and activation energy (0.28 eV). A viewpoint of robustness loss or mechanical heterogeneity in Li plating is discussed to disclose the evolution from column-like Li grains to porous Li sponges and then to compactly stacked Li nanoflakes with porosity shrinkage.

NASICON Li1.2Mg0.1Zr1.9(PO4)3 Solid Electrolyte for an All‐Solid‐State Li‐Metal Battery

AbstractA thin solid electrolyte with a high Li+ conductivity is used to separate the metallic lithium anode and the cathode in an all‐solid‐state Li‐metal battery. However, most solid Li‐ion electrolytes have a small electrochemical stability window, large interfacial resistance, and cannot block lithium‐dendrite growth when lithium is plated on charging of the cell. Mg2+ stabilizes a rhombohedral NASICON‐structured solid electrolyte of the formula Li1.2Mg0.1Zr1.9(PO4)3 (LMZP). This solid electrolyte has Li‐ion conductivity two orders of magnitude higher at 25 °C than that of the triclinic LiZr2(PO4)3. 7Li and 6Li NMR confirm the Li‐ions in two different crystallographic sites of the NASICON framework with 85% of the Li‐ions having a relatively higher mobility than the other 15%. The anode–electrolyte interface is further investigated with symmetric Li/LMZP/Li cell testing, while the cathode–electrolyte interface is explored with an all‐solid‐state Li/LMZP/LiFePO4 cell. The enhanced performance of these cells enabled by the Li1.2Mg0.1Zr1.9(PO4)3 solid electrolyte is stable upon repeated charge/discharge cycling.