In-situ growth flower-like binder-free 3D CuO/Cu2O-CTAB with tunable interlayer spacing for high performance lithium storage

Copper-based oxides are attractive anode materials for lithium-ion batteries (LIBs) due to their abundant resources, low cost, non-toxic and high capacity. However, copper-based oxides will produce a huge volume change during lithiation/delithiation, and the structural strain caused by periodic volume changes may cause the exfoliation of active materials. Herein, a flower-like binder-free three-dimensional (3D) CuO/Cu₂O-CTAB was prepared by introducing CTAB, which homogeneously grew in situ on a copper mesh framework. The binder-free 3D sample guarantees direct contact between the active material and the copper mesh, maintaining the structure stability. The flower-like CuO/Cu₂O-CTAB with a small size reveals larger active interfaces and provides more active sites. The introduction of CTAB enlarges the interlayer spacing of CuO/Cu₂O, increases the active sites for lithium storage, and adapts to the volume change of the material during lithiation/delithiation. In addition, the expanded interlayer structure helps decrease the ion diffusion energy barrier for accelerating electrochemical reaction kinetics. Therefore, CuO/Cu₂O-CTAB exhibits better lithium storage performance (2.9 mAh cm^?2 at 0.5 mA cm^?2) than bare CuO/Cu₂O (1.8 mAh cm^?2 at 0.5 mA cm^?2).     

Amino-Functionalized Interfacial Layer Enables an Ultra-Uniform Amorphous Solid Electrolyte Interphase for High-Performance Aqueous Zinc-Based Batteries

Aqueous rechargeable zinc-based batteries (ZBBs) are emerging as desirable energy storage systems because of their high capacity, low cost, and inherent safety. However, the further application of ZBBs still faces many challenges, such as the issues of uncontrolled dendrite growth and severe parasitic reactions occurring at the Zn anode. Herein, an amino-grafted bacterial cellulose (NBC) film is prepared as artificial solid electrolyte interphase (SEI) for the Zn metal anodes, which can significantly reduce zinc nucleation overpotential and lead to the dendrite-free deposition of Zn metal along the (002) crystal plane more easily without any external stimulus. More importantly, the chelation between the modified amino groups and zinc ions can promote the formation of an ultra-even amorphous SEI upon cycling, reducing the activity of hydrate ions, and inhibiting the water-induced side reactions. As a result, the Zn||Zn symmetric cell with NBC film exhibits lower overpotential and higher cyclic stability. When coupled with the V₂O₅ cathode, the practical pouch cell achieves superior electrochemical performance over 1000 cycles.     

In Situ Construction of High-Density Solid Electrolyte Interphase from MOFs for Advanced Zn Metal Anodes

Aqueous zinc anode has been re-evaluated due to the superiority in tackling safety and cost concerns. However, the limited lifespan originating from Zn dendritic and side reactions largely hamper commercial development. Currently, the coating prepared by simple slurry mixing is leaky and ineffectively isolate sulfate and water. Herein, inspired by the DFT calculations and the easy hydrolysis characteristic of MIL-125 (Ti), an in-situ grown high-dense TiO_2-x solid electrolyte interphase (HDSEI) with rich oxygen vacancies is successfully constructed in an aqueous electrolyte, in which the oxygen vacancies not only strengthen the hydrogen binding force thereby inhibiting the hydrogen precipitation by-reaction, but also reduce the migration energy barrier of zinc ions and enhance the mechanical properties. Profiting from the HDSEI, symmetric Zn cells survive up to remarkable 4200 h at 1 mA cm⁻², nearly 42-times than that of bare Zn anodes. In situ optical microscopy clearly reveals that the in situ grown HDSEI homogenizes the zinc deposition process, while bare zinc without HDSEI shows significant dendrites, confirming the protective nature of HDSEI. Furthermore, full Zn ion capacitors can deliver excellent electrochemical performance, providing a feasible in situ approach to construct HDSEI to implement dendrite-free metal anodes.     

An Inorganic-Rich SEI Layer by the Catalyzed Reduction of LiNO3 Enabled by Surface-Abundant Hydrogen Bonding for Stable Lithium Metal Batteries

Lithium (Li) metal anodes (LMAs) are promising anode candidates for realizing high-energy-density batteries. However, the formation of unstable solid electrolyte interphase (SEI) layers on Li metal is harmful for stable Li cycling; hence, enhancing the physical/chemical properties of SEI layers is important for stabilizing LMAs. Herein, thiourea (TU, CH₄N₂S) is introduced as a new catalyzing agent for LiNO₃ reduction to form robust inorganic-rich SEI layers containing abundant Li₃N. Due to the unique molecular structure of TU, the TU molecules adsorb on the Cu electrode by forming Cu S bond and simultaneously form hydrogen bonding with other hydrogen bonds accepting species such as NO₃⁻ and TFSI⁻ through its N H bonds, leading to their catalyzed reduction and hence the formation of inorganic-rich SEI layer with abundant Li₃N, LiF, and Li₂S/Li₂S₂. Particularly, this TU-modified SEI layer shows a lower film resistance and better uniformity compared to the electrochemically and naturally formed SEI layers, enabling planar Li growth without any other material treatments and hence improving the cyclic stability in Li/Cu half-cells and Li@Cu/LiFePO₄ full-cells.     

Revealing Structural Insights of Solid Electrolyte Interphase in High-Concentrated Non-Flammable Electrolyte for Li Metal Batteries by Cryo-TEM

High-concentrated non-flammable electrolytes (HCNFE) in lithium metal batteries prevent thermal runaway accidents, but the microstructure of their solid electrolyte interphase (SEI) remains largely unexplored, due to the lack of direct imaging tools. Herein, cryo-HRTEM is applied to directly visualize the native state of SEI at the atomic scale. In HCNFE, SEI has a uniform laminated crystalline-amorphous structure that can prevent further reaction between the electrolyte and lithium. The inorganic SEI component, Li₂S₂O₇, is precisely identified by cryo-HRTEM. Density functional theory (DFT) calculations demonstrate that the final Li₂S₂O₇ phase has suitable natural transmission channels for Li-ion diffusion and excellent ionic conductivity of 1.2 × 10^-5 S cm^-1.     

Perfluoro Macrocyclic Ether as an Ambifunctional Additive for High-Performance SiO and Nickel 88%-Based High-Energy Li-ion Battery

State-of-the-art lithium (Li)-ion batteries employ silicon anode active material at a limited fraction while strongly relying on fluoroethylene carbonate (FEC) electrolyte additive exceeding 10 wt.% to enable stable cycling. The swelling issue of silicon in the aspect of solid electrolyte interphase (SEI) instability and a risk of safety hazards and high manufacturing cost due to FEC has motivated the authors to design a well-working fluorinated additive substitute. High-capacity cells employing nickel-rich oxide cathode are pursued by operating at > 4.2 V versus Li/Li⁺, for which anodic stability of electrolyte is required. Herein, a highly effective new ambifunctional additive of icosafluoro-15-crown 5-ether is proposed at a little fraction of 0.4 wt.% for the stabilized interfaces and reduced swelling of high capacity (3.5 mAh cm⁻²) 5 wt.% SiO-graphite anode and LiNi_0.88Co_0.08Mn_0.04O₂ cathode. Utilizing together with a lowered fraction of FEC, reversible long 300 cycles at 4.35 V and 1 C (225 mA g⁻¹) are achieved. Material characterization results reveal that such stabilization is derived from the surface passivation of both anode and cathode with perfluoro ether, LiF, and Li_xPF_y species. The present study gives insight into electrolyte formulation design with lower cost and both-side stabilization strategies for silicon and nickel-rich active materials and their interfaces.     

Self-Adapting and Self-Healing Hydrogel Interface with Fast Zn2+ Transport Kinetics for Highly Reversible Zn Anodes

Construction of polymer-based artificial solid-electrolyte interphase films on Zn metal anode holds great potential in the suppression of both dendrite growth and side reaction in rechargeable aqueous Zn-ion batteries. However, the traditional polymer films suffer from the critical issues of sluggish Zn²⁺ transport kinetics and rigid interface. Herein, zinc alginate (ZA) hydrogel is designed and prepared as a dynamic interface and Zn²⁺ redistributor on Zn anode via in situ cross-linking reaction. The zincophilic and negatively charged carboxyl groups of ZA promote the transport of Zn²⁺ ions along a “Z-type” pathway, the repulsion of free SO₄^2- anions, and the desolvation of Zn²⁺ ions, consequently leading to the homogeneous deposition of Zn and the effective suppression of side reaction. Additionally, the dynamic flexibility of ZA hydrogel endows the Zn anode with self-adapting interface to accommodate the volume variation and repair the possible ruptures, thereby guaranteeing the long-term cycling stability. Assisted by the ZA layer, the Zn anode achieves a prolonged lifespan over 2200 h without the formation of Zn dendrites and by-products. Outstanding cycling stability is also demonstrated for the Zn anode when coupled with MnO₂ cathode, further demonstrating its prospects for practical application.     

Regulation of Interphase Layer by Flexible Quasi-Solid Block Polymer Electrolyte to Achieve Highly Stable Lithium Metal Batteries (Adv. Funct. Mater. 27/2023)

Low safety, unstable interfaces, and high reactivity of liquid electrolytes greatly hinder the development of lithium metal batteries (LMBs). Quasi-solid-state electrolytes (QGPEs) with superior mechanical properties and high compatibility can meet the demands of LMBs. Herein, a biodegradable polyacrylonitrile/polylactic acid-block-ethylene glycol polymer (PALE) as membrane skeleton for GPEs is designed and systematically investigated by regulating the length and structure of the cross-linked chain. Benefiting from the enriched affinitive sites of polar functional groups ( CO,  C O C,  CN, and  OH) in highly cross-linked polymer structure, the designed PALE membrane skeleton exhibits flame-retardant property and ultrahigh liquid electrolyte uptake property, and the derived quasi-solid-state PALE GPEs deliver enhanced stretchability and a higher electrochemical stable window of 5.11 V. Besides, the PALE GPEs effectively protect cathodes from corrosion while allowing uniform and fast transfer of Li⁺ ions. Therefore, the Li||Li symmetrical battery and LFP or NCM811||Li full-cell using PALE GPEs exhibit excellent cycling stability coupled with compact and flat inorganic/organic interface layers. And the excellent cycling stability of pouch cells under harsh operating conditions indicates the application possibilities of PALE GPEs in flexible devices with high-energy-density.