Interfacial solvation-structure regulation for stable Li metal anode by a desolvation coating technique.

Rechargeable lithium (Li) metal batteries face challenges in achieving stable cycling due to the instability of the solid electrolyte interphase (SEI). The Li-ion solvation structure and its desolvation process are crucial for the formation of a stable SEI on Li metal anodes and improving Li plating/stripping kinetics. This research introduces an interfacial desolvation coating technique to actively modulate the Li-ion solvation structure at the Li metal interface and regulate the participation of the electrolyte solvent in SEI formation. Through experimental investigations conducted using a carbonate electrolyte with limited compatibility to Li metal, the optimized desolvation coating layer, composed of 12-crown-4 ether-modified silica materials, selectively displaces strongly coordinating solvents while simultaneously enriching weakly coordinating fluorinated solvents at the Li metal/electrolyte interface. This selective desolvation and enrichment effect reduce solvent participation to SEI and thus facilitate the formation of a LiF-dominant SEI with greatly reduced organic species on the Li metal surface, as conclusively verified through various characterization techniques including XPS, quantitative NMR, operando NMR, cryo-TEM, EELS, and EDS. The interfacial desolvation coating technique enables excellent rate cycling stability (i.e., 1C) of the Li metal anode and prolonged cycling life of the Li||LiCoO2 pouch cell in the conventional carbonate electrolyte (E/C 2.6 g/Ah), with 80% capacity retention after 333 cycles.

Self-terminating, heterogeneous solid-electrolyte interphase enables reversible Li-ether cointercalation in graphite anodes.

Ether solvents are suitable for formulating solid-electrolyte interphase (SEI)-less ion-solvent cointercalation electrolytes in graphite for Na-ion and K-ion batteries. However, ether-based electrolytes have been historically perceived to cause exfoliation of graphite and cell failure in Li-ion batteries. In this study, we develop strategies to achieve reversible Li-solvent cointercalation in graphite through combining appropriate Li salts and ether solvents. Specifically, we design 1M LiBF4 1,2-dimethoxyethane (G1), which enables natural graphite to deliver ~91% initial Coulombic efficiency and >88% capacity retention after 400 cycles. We captured the spatial distribution of LiF at various length scales and quantified its heterogeneity. The electrolyte shows self-terminated reactivity on graphite edge planes and results in a grainy, fluorinated pseudo-SEI. The molecular origin of the pseudo-SEI is elucidated by ab initio molecular dynamics (AIMD) simulations. The operando synchrotron analyses further demonstrate the reversible and monotonous phase transformation of cointercalated graphite. Our findings demonstrate the feasibility of Li cointercalation chemistry in graphite for extreme-condition batteries. The work also paves the foundation for understanding and modulating the interphase generated by ether electrolytes in a broad range of electrodes and batteries.

Design principles of heterointerfacial redox chemistry for highly reversible lithium metal anode.

High electrochemical reversibility is required for the application of high-energy-density lithium (Li) metal batteries; however, inactive Li formation and SEI (solid electrolyte interface)-instability-induced electrolyte consumption cause low Coulombic efficiency (CE). The prior interfacial chemical designs in terms of alloying kinetics have been used to enhance the CE of Li metal anode; however, the role of its redox chemistry at heterointerfaces remains a mystery. Herein, the relationship between heterointerfacial redox chemistry and electrochemical transformation reversibility is investigated. It is demonstrated that the lower redox potential at heterointerface contributes to higher CE, and this enhancement in CE is primarily due to the regulation of redox chemistry to Li deposition behavior rather than the formation of SEI films. Low oxidation potential facilitates the formation of the surface with the highly electrochemical binding feature after Li stripping, and low reduction potential can maintain binding ability well during subsequent Li plating, both of which homogenize Li deposition and thus optimize CE. In particular, Mg hetero-metal with ultra-low redox potential enables Li metal anode with significantly improved CE (99.6%) and stable cycle life for 700 cycles at 3.0 mA cm-2. This work provides insight into the heterointerfacial design principle of next-generation negative electrodes for highly reversible metal batteries.

A crystalline carbon nitride-based separator for high-performance lithium metal batteries.

Lithium metal anodes with ultrahigh theoretical capacities are very attractive for assembling high-performance batteries. However, uncontrolled Li dendrite growth strongly retards their practical applications. Different from conventional separator modification strategies that are always focused on functional group tuning or mechanical barrier construction, herein, we propose a crystallinity engineering-related tactic by using the highly crystalline carbon nitride as the separator interlayer to suppress dendrite growth. Interestingly, the presence of Cl- intercalation and high-content pyrrolic-N from molten salt treatment along with highly crystalline structure enhanced the interactions of carbon nitride with Li+ and homogenized lithium flux for uniform deposition, as supported by both experimental and theoretical evidences. The Li-Li cell with the modified separator therefore delivered ultrahigh stability even after 3,000 h with dendrite-free cycled electrodes. Meanwhile, the assembled Li-LiFePO4 full-cell also presented high-capacity retention. This work opens up opportunities for design of functional separators through crystallinity engineering and broadens the use of C3N4 for advanced batteries.

Anode electrolysis of sulfides.

Traditional sulfide metallurgy produces harmful sulfur dioxide and is energy intensive. To this end, we develop an anode electrolysis approach in molten salt by which sulfide is electrochemically split into sulfur gas at a graphite inert anode while releasing metal ions that diffuse toward and are deposited at the cathode. The anodic splitting dictates the "sulfide-to-metal ion and sulfur gas" conversion that makes the reaction recur continuously. Using this approach, Cu2S is converted to sulfur gas and Cu in molten LiCl-KCl at 500 °C with a current efficiency of 99% and energy consumption of 0.420 kWh/kg-Cu (only considering the electricity for electrolysis). Besides Cu2S, the anode electrolysis can extract Cu from Cu matte that is an intermediate product from the traditional sulfide smelting process. More broadly, Fe, Ni, Pb, and Sb are extracted from FeS, CuFeS2, NiS, PbS, and Sb2S3, providing a general electrochemical method for sulfide metallurgy.

A completely precious metal-free alkaline fuel cell with enhanced performance using a carbon-coated nickel anode.

SignificanceWe present a groundbreaking advance in completely nonprecious hydrogen fuel cell technologies achieving a record power density of 200 mW/cm2 with Ni@CNx anode and Co-Mn cathode. The 2-nm CNx coating weakens the O-binding energy, which effectively mitigates the undesirable surface oxidation during hydrogen oxidation reaction (HOR) polarization, leading to a stable fuel cell operation for Ni@CNx over 100 h at 200 mA/cm2, superior to a Ni nanoparticle counterpart. Ni@CNx exhibited a dramatically enhanced tolerance to CO relative to Pt/C, enabling the use of hydrogen gas with trace amounts of CO, critical for practical applications. The complete removal of precious metals in fuel cells lowers the catalyst cost to virtually negligible levels and marks a milestone for practical alkaline fuel cells.

Compressible and Elastic Reduced Graphene Oxide Sponge for Stable and Dendrite-Free Lithium Metal Anodes.

Dendritic Li deposition, an unstable solid-electrolyte interphase (SEI), and a nearly infinite relative volume change during cycling are three major obstacles to the practical application of Li metal batteries. Herein, we introduce a compressible and elastic reduced graphene oxide sponge (rGO-S) to simultaneously eliminate Li dendrite growth, stabilize the SEI, and accommodate the volume change. The volume change is contained by compressing and expanding the rGO-S anode, which effectively releases the Li plating-induced stress during cycling. The smooth and dense Li metal is deposited on rGO-S without dendrites, which preserves the SEI, reduces consumption of the electrolyte, and prevents the formation of Li debris. The half-cells employing rGO-S show a steady and high Coulombic efficiency. The Li@rGO-S symmetric cells demonstrate excellent cycling stability over 1200 cycles with a low overpotential. When paired with LiFePO4 (LFP), the Li@rGO-S||LFP full cells exhibit a high specific capacity (150.3 mAh g-1 at 1C), superior rate performance, and good capacity retention.

Mediating Zn Ions Migration Behavior via ß-Cyclodextrin Modified Carbon Nanotube Film for High-Performance Zn Anodes.

Metallic Zn is considered as a promising anode material because of its abundance, eco-friendliness, and high theoretical capacity. However, the uncontrolled dendrite growth and side reactions restrict its further practical application. Herein, we proposed a ß-cyclodextrin-modified multiwalled carbon nanotube (CD-MWCNT) layer for Zn metal anodes. The obtained CD-MWCNT layer with high affinity to Zn can significantly reduce the transfer barrier of Zn2+ at the electrode/electrolyte interface, facilitating the uniform deposition of Zn2+ and suppressing water-caused side reactions. Consequently, the Zn||Zn symmetric cell assembled with CD-MWCNT shows a significantly enhanced cycling durability, maintaining a cycling life exceeding 1000 h even under a high current density of 5 mA cm-2. Furthermore, the full battery equipped with a V2O5 cathode displays an unparalleled long life. This work unveils a promising avenue toward the achievement of high-performance Zn metal anodes.

Lithiophilic Hydrogen-Substituted Graphdiyne Aerogels with Ionically Conductive Channels for High-Performance Lithium Metal Batteries.

Lithium (Li) metal stands as a promising anode in advancing high-energy-density batteries. However, intrinsic issues associated with metallic Li, especially the dendritic growth, have hindered its practical application. Herein, we focus on molecular combined structural design to develop dendrite-free anodes. Specifically, using hydrogen-substituted graphdiyne (HGDY) aerogel hosts, we successfully fabricated a promising Li composite anode (Li@HGDY). The HGDY aerogel's lithiophilic nature and hierarchical pores drive molten Li infusion and reduce local current density within the three-dimensional HGDY host. The unique molecular structure of HGDY provides favorable bulk pathways for lithium-ion transport. By simultaneous regulation of electron and ion transport within the HGDY host, uniform lithium stripping/platting is fulfilled. Li@HGDY symmetric cells exhibit a low overpotential and stable cycling. The Li@HGDY||lithium iron phosphate full cell retained 98.1% capacity after 170 cycles at 0.4 C. This study sheds new light on designing high-capacity and long-lasting lithium metal anodes.

Self-Healable, High-Stability Anode for Rechargeable Magnesium Batteries Realized by Graphene-Confined Gallium Metal.

In this work, a self-healable, high-stability anode material for rechargeable magnesium batteries (RMBs) has been developed by introducing a core-shell structure of Ga confined by reduced graphene oxide (Ga@rGO). Via this Ga@rGO anode, a specific capacity of 150 mAh g-1 at a current of 0.5 A g-1 stable up to 1200 cycles at room temperature and a specific capacity of 100 mAh g-1 under an ultrahigh current of 1 A g-1 stable up to 700 cycles at a slightly elevated temperature of 40 °C have been achieved. Additionally, the ultrahigh rate, high-cycling stability, and long-cycle life of the anode are attributed to the stabilized structure; such a low-cost, simple, and environmentally friendly direct drop coating (DDC) method is developed to maximize the original state of the active materials. Remarkably, the self-healing ability of anodes is still presented under the ultrahigh charging current. This anode is promising for the development of high rate and high stability RMBs.

Revealing Lithium Nitrate-Mediated Solid-Electrolyte Interphase of Lithium Metal Anode via Cryogenic Transmission Electron Microscopy.

The cycle stability of lithium metal anode (LMA) largely depends on solid-electrolyte interphase (SEI). Electrolyte engineering is a common strategy to adjust SEI properties, yet understanding its impact is challenging due to limited knowledge on ultrafine SEI structures. Herein, using cryogenic transmission electron microscopy, we reveal the atomic-level SEI structure of LMA in ether-based electrolytes, focusing on the role of LiNO3 additives in SEI modulation at different temperature (25 and 50 °C). Poor cycle stability of LMA in the baseline electrolyte without LiNO3 additives stems from the Li2CO3-rich mosaic-type SEI. Increased LiNO3 content and elevated operating temperature enhance cyclic performance by forming bilayer or multilayer SEI structures via preferential LiNO3 decomposition, but may thicken the SEI, leading to reduced initial Coulombic efficiency and increased overpotential. The optimal SEI features a multilayer structure with Li2O-rich inner layer and closely packed grains in the outer layer, minimizing electrolyte decomposition or corrosion.

Neural Network Inspired Binder Enables Fast Li-Ion Transport and High Stress Adaptation for Si Anode.

Extensive investigations have proven the effectiveness of elastic binders in settling the challenge of structural damage posed by volume expansion of high-capacity anode used in nanoscale silicon. However, the sluggish ionic conductivity of polymer binder severely restricts the electrode reactions, making it unsuitable for practical applications. Inspired by the biological tissues with rapid neurotransmission and robust muscles, we propose a biomimetic binder that contains ionic conductive polymer (by polymerization reaction of poly(ethylene glycol) diglycidyl ether and polyethylenimine) and rigid polymer backbone (polyacrylic acid), which can effectively mitigate both Li-ion transport resistance and lithiation stress to stabilize the silicon nanoparticles during cycles. Consequently, the silicon anode with biomimetic binder achieves a rate capability of 1897 mAh g-1 at 8.0 A g-1 and capacity retention of 87% after 150 cycles under areal capacity upon 3.0 mAh cm-2. These results demonstrate the possibility of decoupling ionic conductivity from mechanical properties toward practical high-capacity anodes for energy-dense batteries.

Separators Modified with Ultrathin Montmorillonite/Polymer Nanocoatings Achieve Dendrite-Free Lithium Deposition at High Current Densities.

Fatal dendritic growth in lithium metal batteries is closely related to the composition and thickness of the modified separator. Herein, an ultrathin nanocoating composed of monolayer montmorillonite (MMT), poly(vinyl alcohol) (PVA) on a polypropylene separator is prepared. The MMT was exfoliated into monolayers (only 0.96 nm) by intercalating PVA under ultrasound, followed by cross-linking with glutaraldehyde. The thickness of the nanocoating on the polypropylene separator, as determined using the pull-up method, is only 200-500 nm with excellent properties. As a result, the lithium-symmetric battery composed of it has a low overpotential (only 40 mV) and a long lifespan of more than 7900 h at high current density, because ion transport is unimpeded and Li+ flows uniformly through the ordered ion channels between the MMT layers. Additionally, the separator exhibited excellent cycling stability in Li-S batteries. This study offers a new idea for fabricating ultrathin clay/polymer modified separators for metal anode stable cycling at high current densities.

Adjusting Ion Diffusion Kinetics of Li Deposition Enabled by an Elastic Porous Melamine Sponge Host for Stable Lithium Metal Anodes.

Lithium (Li) dendritic growth and huge volume expansion seriously hamper Li-metal anode development. Herein, we design a lightweight 3D Li-ion-affinity host enabled by silver (Ag) nanoparticles fully decorating a porous melamine sponge (Ag@PMS) for dendrite-free and high-areal-capacity Li anodes. The compact Ag nanoparticles provide abundant preferred nucleation sites and give the host strong conductivity. Moreover, the high specific surface area and polar groups of the elastic, porous melamine sponge enhance the Li-ion diffusion kinetics, prompting homogeneity of Li deposition and stripping. As expected, the integrated 3D Ag@PMS-Li anode delivered a remarkable electrochemical performance, with a Coulombic efficiency (CE) of 97.14% after 450 cycles at 1 mA cm-2. The symmetric cell showed an ultralong lifespan of 3400 h at 1 mA cm-2 for 1 mAh cm-2. This study provides a facile and cost-effective strategy to design an advanced 3D framework for the preparation of a stable dendrite-free Li metal anode.

Stabilizing Zinc Anode through Ion Selection Sieving for Aqueous Zn-Ion Batteries.

Uncontrollable dendrite growth and corrosion induced by reactive water molecules and sulfate ions (SO42-) seriously hindered the practical application of aqueous zinc ion batteries (AZIBs). Here we construct artificial solid electrolyte interfaces (SEIs) realized by sodium and calcium bentonite with a layered structure anchored to anodes (NB@Zn and CB@Zn). This artificial SEI layer functioning as a protective coating to isolate activated water molecules, provides high-speed transport channels for Zn2+, and serves as an ionic sieve to repel negatively charged anions while attracting positively charged cations. The theoretical results show that the bentonite electrodes exhibit a higher binding energy for Zn2+. This demonstrates that the bentonite protective layer enhances the Zn-ion deposition kinetics. Consequently, the NB@Zn//MnO2 and CB@Zn//MnO2 full-battery capacities are 96.7 and 70.4 mAh g-1 at 2.0 A g-1 after 1000 cycles, respectively. This study aims to stabilize Zn anodes and improve the electrochemical performance of AZIBs by ion-selection sieving.

High-Performance Aqueous Calcium Ion Batteries Enabled by Zn Metal Anodes with Stable Ion-Conducting Interphases.

Aqueous calcium ion batteries, promising for energy storage, are still challenged by very limited anode choices. Although a Zn metal anode is popular in aqueous batteries, interface instability due to incessant corrosion and severe Zn dendrites hinders its development. Here, an interphase layer with densely packed nanocrystals of Ca3(CO3)2(OH)2·1.5H2O and ZnF2, and amorphous organic species, is demonstrated for a Zn metal anode with 1 M calcium trifluoromethyl sulfonate aqueous electrolyte. The hybrid interface fully avoids direct Zn-H2O contact, maintains fast ion conductivity, and effectively prevents corrosion and dendrite growth. Therefore, the symmetric cell stably lasts for 1600 h at 0.5 mA cm-2 and 2.5 mAh cm-2, far superior to 150 h for the control cell. Furthermore, the device maintains 80% capacity retention after 700 cycles at 1 A g-1, outperforming 13% retention after 200 cycles for the control device. This work indicates that interface and interphase engineering is also crucial for aqueous batteries.

Monitoring Hot Holes in Plasmonic Catalysis on Silver Nanoparticles by Using an Ion Label.

Energetic carriers generated by localized surface plasmon resonance (LSPR) provide an efficient way to drive chemical reactions. However, their dynamics and impact on surface reactions remain unknown due to the challenge in observing hot holes. This makes it difficult to correlate the reduction and oxidation half-reactions involving hot electrons and holes, respectively. Here we detect hot holes in their chemical form, Ag(I), on a Ag surface using surface-enhanced Raman scattering (SERS) of SO32- as a hole-specific label. It allows us to determine the dynamic correlations of hot electrons and holes. We find that the equilibrium of holes is the key factor of the surface chemistry, and the wavelength-dependent plasmonic chemical anode refilling (PCAR) effect plays an important role, in addition to the LSPR, in promoting the electron transfer. This method paves the way for visualizing hot holes with nanoscale spatial resolution toward the rational design of a plasmonic catalytic platform.

Phosphorized 3D Current Collector for High-Energy Anode-Free Lithium Metal Batteries.

The anode-free lithium metal battery (AF-LMB) demonstrates the emerging battery chemistry, exhibiting higher energy density than the existing lithium-ion battery and conventional LMB empirically. A systematic step-by-step while bottom-up calculation system is first developed to quantitatively depict the energy gap from theory to practice. The attainable high energy of AF-LMB necessitates a homogeneous Li+ flux on the anode side to achieve an improved Li reversibility against inventory loss. On such basis, a lithiophilic Cu3P-decorated 3D copper foil to promote dendrite-free lithium deposition is further reported. The phosphorized surface of high affinity toward Li+ incorporating the nanostructure of abundant nucleation sites synergistically regulates the Li nucleation/growth behavior, extending the cycling lifespan of high-loading AF-LMBs. The processed foil featuring lightweight and ultrathin merits further increases the energy density, both gravimetrically and volumetrically. This study provides a novel scheme for simultaneously realizing the uniform deposition of lithium and increasing the energy density of future AF-LMBs.

Rational Design of Quasi-1D Multicore-Shell MnSe@N-Doped Carbon Nanorods as High-Performance Anode Material for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are considered one of the promising candidates for energy storage devices due to the low cost and low redox potential of sodium. However, their implementation is hindered by sluggish kinetics and rapid capacity decay caused by inferior conductivity, lattice deterioration, and volume changes of conversion-type anode materials. Herein, we report the design of a multicore-shell anode material based on manganese selenide (MnSe) nanoparticle encapsulated N-doped carbon (MnSe@NC) nanorods. Benefiting from the conductive multicore-shell structure, the MnSe@NC anodes displayed prominent rate capability (152.7 mA h g-1 at 5 A g-1) and long lifespan (132.7 mA h g-1 after 2000 cycles at 5 A g-1), verifying the essence of reasonable anode construction for high-performance SIBs. Systematic in situ microscopic and spectroscopic methods revealed a highly reversible conversion reaction mechanism of MnSe@NC. Our study proposes a promising route toward developing advanced transition metal selenide anodes and comprehending electrochemical reaction mechanisms toward high-performance SIBs.

Dual-Parasitic Effect Enables Highly Reversible Zn Metal Anode for Ultralong 25,000 Cycles Aqueous Zinc-Ion Batteries.

The use of electrolyte additives is an efficient approach to mitigating undesirable side reactions and dendrites. However, the existing electrolyte additives do not effectively regulate both the chaotic diffusion of Zn2+ and the decomposition of H2O simultaneously. Herein, a dual-parasitic method is introduced to address the aforementioned issues by incorporating 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm]OTf) as cosolvent into the Zn(OTf)2 electrolyte. Specifically, the OTf- anion is parasitic in the solvent sheath of Zn2+ to decrease the number of active H2O. Additionally, the EMIm+ cation can construct an electrostatic shield layer and a hybrid organic/inorganic solid electrolyte interface layer to optimize the deposition behavior of Zn2+. This results in a Zn anode with a reversible cycle life of 3000 h, the longest cycle life of full cells (25,000 cycles), and an extremely high initial capacity (4.5 mA h cm-2), providing a promising electrolyte solution for practical applications of rechargeable aqueous zinc-ion batteries.