The early-stage growth and reversibility of Li electrodeposition in Br-rich electrolytes

In Situ Visual Observation of Surface Energy-Controlled Heterogeneous Nucleation of Metal Nanocrystals

Electrochemical growth of metal nanocrystals is pivotal for material synthesis, processing, and resource recovery. Understanding the heterogeneous interface between electrolyte and electrode is crucial for nanocrystal nucleation, but the influence of this interaction is still poorly understood. This study employs advanced in situ measurements to investigate the heterogeneous nucleation of metals on solid surfaces. By observing the copper nanocrystal electrodeposition, an interphase interaction-induced nucleation mechanism highly dependent on substrate surface energy is uncovered. It shows that a high-energy (HE) electrode tended to form a polycrystalline structure, while a low-energy (LE) electrode induced a monocrystalline structure. Raman and electrochemical characterizations confirmed that HE interface enhances the interphase interaction, reducing the nucleation barrier for the sturdy nanostructures. This leads to a 30.92-52.21% reduction in the crystal layer thickness and a 19.18-31.78% increase in the charge transfer capability, promoting the formation of a uniform and compact film. The structural compactness of the early nucleated crystals enhances the deposit stability for long-duration electrodeposition. This research not only inspires comprehension of physicochemical processes correlated with heterogeneous nucleation, but also paves a new avenue for high-quality synthesis and efficient recovery of metallic nanomaterials.

Directing Highly Ordered and Dense Li Deposition to Achieve Stable Li Metal Batteries

Li metal anode is promising to achieve high-energy-density battery. However, it has rapid capacity fading due to the generation of inactive Li (dead Li), especially at high current density. This study reveals that the random distribution of Li nuclei leads to large uncertainty for the further growth behavior on Cu foil. Here, periodical regulation of Li nucleation sites on Cu foil by ordered lithiophilic micro-grooves is proposed to precisely manipulate the Li deposition morphology. The management of Li deposits in the lithiophilic grooves can induce high pressure on the Li particles, leading to the formation of dense Li structure and smooth surface without dendrite growth. Li deposits comprising tightly packed large Li particles largely reduce the side reaction and the generation of isolated metallic Li at high current density. Less dead Li accumulating on the substrate significantly prolongs the cycling life of full cells with limited Li inventory. The precise manipulation of the Li deposition on Cu is promising for high-energy and stable Li metal batteries.

Investigating microstructure evolution of lithium metal during plating and stripping via operando X-ray tomographic microscopy

Efficient lithium metal stripping and plating operation capable of maintaining electronic and ionic conductivity is crucial to develop safe lithium metal batteries. However, monitoring lithium metal microstructure evolution during cell cycling is challenging. Here, we report the development of an operando synchrotron X-ray tomographic microscopy method capable of probing in real-time the formation, growth, and dissolution of Li microstructures during the cycling of a Li||Cu cell containing a standard non-aqueous liquid electrolyte solution. The analyses of the operando X-ray tomographic microscopy measurements enable tracking the evolution of deposited Li metal as a function of time and applied current density and distinguishing the formation of electrochemically inactive Li from the active bulk of Li microstructures. Furthermore, in-depth analyses of the Li microstructures shed some light on the structural connectivity of deposited Li at different current densities as well as the formation mechanism of fast-growing fractal Li microstructures, which are ultimately responsible for cell failure.

Electrolytes in Organic Batteries

Organic batteries using redox-active polymers and small organic compounds have become promising candidates for next-generation energy storage devices due to the abundance, environmental benignity, and diverse nature of organic resources. To date, tremendous research efforts have been devoted to developing advanced organic electrode materials and understanding the material structure-performance correlation in organic batteries. In contrast, less attention was paid to the correlation between electrolyte structure and battery performance, despite the critical roles of electrolytes for the dissolution of organic electrode materials, the formation of the electrode-electrolyte interphase, and the solvation/desolvation of charge carriers. In this review, we discuss the prospects and challenges of organic batteries with an emphasis on electrolytes. The differences between organic and inorganic batteries in terms of electrolyte property requirements and charge storage mechanisms are elucidated. To provide a comprehensive and thorough overview of the electrolyte development in organic batteries, the electrolytes are divided into four categories including organic liquid electrolytes, aqueous electrolytes, inorganic solid electrolytes, and polymer-based electrolytes, to introduce different components, concentrations, additives, and applications in various organic batteries with different charge carriers, interphases, and separators. The perspectives and outlook for the future development of advanced electrolytes are also discussed to provide a guidance for the electrolyte design and optimization in organic batteries. We believe that this review will stimulate an in-depth study of electrolytes and accelerate the commercialization of organic batteries.

In Situ Formed Magnesiophilic Sites Guiding Uniform Deposition for Stable Magnesium Metal Anodes

Owing to its high volumetric capacity and natural abundance, magnesium (Mg) metal has attracted tremendous attention as an ideal anode material for rechargeable Mg batteries. Despite Mg deposition playing an integral role in determining the cycling lifespan, its exact behavior is not clearly understood yet. Herein, for the first time, we introduce a facile approach to build magnesiophilic In/MgIn sites in situ on a Mg metal surface using InCl₃ electrolyte additive for rechargeable Mg batteries. These magnesiophilic sites can regulate Mg deposition behaviors by homogenizing the distributions of Mg-ion flux and electric field at the electrode-electrolyte interphase, allowing flat and compact Mg deposition to inhibit short-circuiting. The as-designed Mg metal batteries achieve a stable cycling lifespan of 340 h at 1.0 mA cm^-2 and 1.0 mAh cm^-2 using Celgard separators, while the full cell coupled with Mo₆S₈ cathode maintains a high capacity retention of 95.5% over 800 cycles at 1 C.

Novel Urea-Based Molecule Functioning as a Solid Electrolyte Interphase Enabler and LiPF6 Decomposition Inhibitor for Fast-Charging Lithium Metal Batteries

The practical application of lithium metal batteries is impeded by the growth of dendrites and decomposition of electrolytes especially at high temperature in normal carbonate-based electrolytes. Herein, a novel urea-based molecule, 1,3-dimethyl-2-imidazolidinone (DMI), with a high donor number is proposed, which exhibits an extraordinary solubility of LiNO₃ of over 5 M. As a result, a sufficient amount of LiNO₃ is readily introduced into the carbonate electrolytes with DMI as an additive, and an average coulombic efficiency of 99.1% for lithium plating/stripping is achieved due to a stable solid electrolyte interphase (SEI) rich in inorganic-rich lithium salts. The Li||Li symmetric cell achieves a stable operation for over 2500 h at 0.5 mA cm^-2 and 1 mAh cm^-2, and a granular shape of deposited Li metal is still preserved even at a high current density of 10 mA cm^-2. Besides, the decomposition of LiPF₆ is inhibited benefiting from its enhanced dissociation after the addition of DMI/LiNO₃ and DMI's function as a PF₅ scavenger. Consequently, the Li||LiFePO₄ cell succeeds to achieve an excellent capacity retention of 95.6% after 2200 cycles at a high rate of 5C, and a stable operation is realized at a high temperature of 60 °C even under harsh conditions (45 μm ultrathin Li and ∼1.5 mAh cm^-2 LiFePO₄). This work enriches the solvents and additives pool for stable and high-performance lithium metal batteries and will shed light on future developments of advanced battery electrolytes.

Crystallographically Textured Electrodes for Rechargeable Batteries: Symmetry, Fabrication, and Characterization

The vast of majority of battery electrode materials of contemporary interest are of a crystalline nature. Crystals are, by definition, anisotropic from an atomic-structure perspective. The inherent structural anisotropy may give rise to favored mesoscale orientations and anisotropic properties whether the material is in a rest state or subjected to an external stimulus. The overall perspective of this review is that intentional manipulation of crystallographic anisotropy of electrochemically active materials constitute an untapped parameter space in energy storage systems and thus provide new opportunities for materials innovations and design. To that end, we contend that crystallographically textured electrodes, as opposed to their textureless poly crystalline or single-crystalline analogs, are promising candidates for next-generation storage of electrical energy in rechargeable batteries relevant to commercial practice. This perspective is underpinned first by the fundamental─to a first approximation─uniaxial, rotation-invariant symmetry of electrochemical cells. On this basis, we show that a crystallographically textured electrode with the preferred orientation aligned out-of-plane toward the counter electrode represents an optimal strategy for utilization of the crystals' anisotropic properties. Detailed analyses of anisotropy of different types lead to a simple, but potentially useful general principle that "P_ec//P_c" textures are optimal for metal anodes, and "P_ec//S_c" textures are optimal for insertion-type electrodes.

Large-Scale Integration of a Zinc Metasilicate Interface Layer Guiding Well-Regulated Zn Deposition

Uneven distribution of electric fields at the electrolyte-anode interface and associated Zn dendrite growth is one of the most critical barriers that limit the life span of aqueous zinc-ion batteries. Herein, new-type Zn-A-O (A = Si, Ti) interface layers with thin and uniform thickness, porosity, and hydrophilicity properties are developed to realize homogeneous and smooth Zn plating. For ZnSiO₃ nanosheet arrays on Zn foil (Zn@ZSO), their formation follows an "etching-nucleation-growth" mechanism that is confirmed by a well-designed Zn-island-based identical-location microscopy method, the geometric area of which is up to 1000 cm² in one-pot synthesis based on a low-temperature wet-chemical method. Guided by the structural advantages of the ZSO layer, the Zn²⁺ flux gets equalized. Besides ultralow polarization, the life spans of symmetric cells and full cells coupled with a high-mass-loading K_0.27 MnO₂ ·0.54H₂ O (8 mg cm^-2 ) cathode, are increased by 3-7 times with the Zn@ZSO anode. Moreover, the large-scale preparation of Zn@ZSO foil contributes to a 0.5 Ah multilayer pouch cell with high performance, further confirming its prospects for practical application.

Lithium Bromide-Induced Organic-Rich Cathode/Electrolyte Interphase for High-Voltage and Flame-Retardant All-Solid-State Lithium Batteries

Poly(ethylene oxide) (PEO)-based solid electrolyte suffers from limited anodic stability and an intrinsic flammable issue, hindering the achievement of high energy density and safe all-solid-state lithium batteries. Herein, we surprisingly found out that a bromine-rich additive, decabromodiphenyl ethane (DBDPE), could be preferably oxidized at an elevated voltage and decompose to lithium bromide at an elevated potential followed by inducing an organic-rich cathode/electrolyte interphase (CEI) on NCM811 surface, enabling both high-voltage resistance (up to 4.5 V) and flame-retardancy for the PEO-based electrolyte. On the basis of this novel solid electrolyte, all-solid-state Li/NCM811 batteries deliver an average reversible capacity of 151.4 mAh g^-1 over the first 150 cycles with high capacity retention (83.0%) and high average Coulombic efficiency (99.7%) even at a 4.5 V cutoff voltage with a unprecedented flame-retardant properties. In view of these exploration, our studies revealed the critical role of LiBr in inducing an organic-rich thin and uniform CEI passivating layer with enhanced lithium ion surface diffusion and high-voltage resistant properties, which provides a new protocol for the further design of a high-voltage PEO-based all-solid-state electrolyte.

Remedies to Avoid Failure Mechanisms of Lithium-Metal Anode in Li-Ion Batteries

Rechargeable lithium-metal batteries (LMBs), which have high power and energy density, are very attractive to solve the intermittence problem of the energy supplied either by wind mills or solar plants or to power electric vehicles. However, two failure modes limit the commercial use of LMBs, i.e., dendrite growth at the surface of Li metal and side reactions with the electrolyte. Substantial research is being accomplished to mitigate these drawbacks. This article reviews the different strategies for fabricating safe LMBs, aiming to outperform lithium-ion batteries (LIBs). They include modification of the electrolyte (salt and solvents) to obtain a highly conductive solid–electrolyte interphase (SEI) layer, protection of the Li anode by in situ and ex situ coatings, use of three-dimensional porous skeletons, and anchoring Li on 3D current collectors.