The effect of Ru substitution on the structure and electrochemical properties of P2‐type Na0.67CoO2 is investigated. The first‐discharge capacities of Na0.67CoO2 and Na0.6 Co0.78Ru0.22O2 materials ...are 128 and 163 mAh g−1 (23.5 mA g−1), respectively. Furthermore, the rate capability is improved due to the electro‐conducting nature of Ru doping. Operando X‐ray diffraction analysis reveals that the Na0.67CoO2 does not undergo a phase transition; however, multiple Na+/vacancy ordered superstructures within the P2 phase appear during Na+ extraction/insertion. In contrast, the Na0.6Co0.78Ru0.22O2 material undergoes a P2–OP4 phase transition during desodiation, with no formation of Na+/vacancy ordering within the P2 phase. The increased discharge capacity of Na0.6Co0.78Ru0.22O2 is most likely associated with additional cationic Ru4+/Ru5+ redox and increased anionic O2−/(O2n−) redox participation. Combined experimental (galvanostatic cycling, X‐ray absorption spectroscopy, differential electrochemical mass spectrometry) and theoretical (density functional theory calculations) studies confirm that Ru substitution provokes the oxygen‐redox reaction and that partial O2 release from the oxide lattice is the origin of the reaction. The findings provide new insight for improving the electrode performance of cathode materials via 4d Ru substitution and motivate the development of a new strategy for the design of high‐capacity cathode materials for sodium‐ion batteries.
The impact of Ru substitution on the electrochemical properties and structure of P2‐type Na0.67CoO2 layered cathode material is studied. Ru suppresses Na+/vacancy ordering and activates oxygen redox. Moreover, it increases capacity by utilizing both Co3+/Co4+, Ru4+/Ru5+ cationic redox, and O2−/(O2n−) anionic redox processes.
Oxygen‐redox‐based‐layered cathode materials are of great importance in realizing high‐energy‐density sodium‐ion batteries (SIBs) that can satisfy the demands of next‐generation energy storage ...technologies. However, Mn‐based‐layered materials (P2‐type Na‐poor NayAxMn1−xO2, where A = alkali ions) still suffer from poor reversibility during oxygen‐redox reactions and low conductivity. In this work, the dual Li and Co replacement is investigated in P2‐type‐layered NaxMnO2. Experimentally and theoretically, it is demonstrated that the efficacy of the dual Li and Co replacement in Na0.6Li0.15Co0.15Mn0.7O2 is that it improves the structural and cycling stability despite the reversible Li migration from the transition metal layer during de‐/sodiation. Operando X‐ray diffraction and ex situ neutron diffraction analysis prove that the material maintains a P2‐type structure during the entire range of Na+ extraction and insertion with a small volume change of ≈4.3%. In Na0.6Li0.15Co0.15Mn0.7O2, the reversible electrochemical activity of Co3+/Co4+, Mn3+/Mn4+, and O2‐/(O2)n‐ redox is identified as a reliable mechanism for the remarkable stable electrochemical performance. From a broader perspective, this study highlights a possible design roadmap for developing cathode materials with optimized cationic and anionic activities and excellent structural stabilities for SIBs.
The role of Li and Co dual substitution is investigated on the structure and electrochemical properties of P2‐type NaxMnO2 layered cathode material. Li provides possibility for oxygen redox activity due to partial migration from transition metal layer, and Co is crucial for improving conductivity.
SiOx is a promising next‐generation anode material for lithium‐ion batteries. However, its commercial adoption faces challenges such as low electrical conductivity, large volume expansion during ...cycling, and low initial Coulombic efficiency. Herein, to overcome these limitations, an eco‐friendly in situ methodology for synthesizing carbon‐containing mesoporous SiOx nanoparticles wrapped in another carbon layers is developed. The chemical reactions of vinyl‐terminated silanes are designed to be confined inside the cationic surfactant‐derived emulsion droplets. The polyvinylpyrrolidone‐based chemical functionalization of organically modified SiO2 nanoparticles leads to excellent dispersion stability and allows for intact hybridization with graphene oxide sheets. The formation of a chemically reinforced heterointerface enables the spontaneous generation of mesopores inside the thermally reduced SiOx nanoparticles. The resulting mesoporous SiOx‐based nanocomposite anodes exhibit superior cycling stability (≈100% after 500 cycles at 0.5 A g−1) and rate capability (554 mAh g−1 at 2 A g−1), elucidating characteristic synergetic effects in mesoporous SiOx‐based nanocomposite anodes. The practical commercialization potential with a significant enhancement in initial Coulombic efficiency through a chemical prelithiation reaction is also presented. The full cell employing the prelithiated anode demonstrated more than 2 times higher Coulombic efficiency and discharge capacity compared to the full cell with a pristine anode.
A novel synthesis method of SiOx composite for high‐performance anode for lithium‐ion batteries is proposed. Synthesized SiOx composite shows intact hybridization of graphene oxide sheets with mesoporous nanoparticles made spontaneously by the thermal reduction process. These structural features significantly improve the electrochemical properties of SiOx. In addition, the commercialization possibility of composite through prelithiation and full‐cell test is confirmed.
Herein, a new solvation strategy enabled by Mg(NO3)2 is introduced, which can be dissolved directly as Mg2+ and NO3− ions in the electrolyte to change the Li+ ion solvation structure and greatly ...increase interfacial stability in Li‐metal batteries (LMBs). This is the first report of introducing Mg(NO3)2 additives in an ester‐based electrolyte composed of ternary salts and binary ester solvents to stabilize LMBs. In particular, it is found that NO3− efficiently forms a stable solid electrolyte interphase through an electrochemical reduction reaction, along with the other multiple anion components in the electrolyte. The interaction between Li+ and NO3− and coordination between Mg2+ and the solvent molecules greatly decreases the number of solvent molecules surrounding the Li+, which leads to facile Li+ desolvation during plating. In addition, Mg2+ ions are reduced to Mg via a spontaneous chemical reaction on the Li metal surface and subsequently form a lithiophilic Li–Mg alloy, suppressing lithium dendritic growth. The unique solvation chemistry of Mg(NO3)2 enables long cycling stability and high efficiency of the Li‐metal anode and ensures an unprecedented lifespan for a practical pouch‐type LMB with high‐voltage Ni‐rich NCMA73 cathode even under constrained conditions.
Mg(NO3)2 is introduced as an additive to ester‐based electrolytes. It not only alters the solvation structures of Li‐ions but also forms lithiophilic Li–Mg alloys on lithium metal. This synergetic effect enables an unprecedented lifespan of over 1300 cycles for a practical pouch‐type Li‐metal battery with a high‐voltage Ni‐rich NCMA73 cathode even under constrained conditions.
Non-aqueous lithium-oxygen batteries cycle by forming lithium peroxide during discharge and oxidizing it during recharge. The significant problem of oxidizing the solid insulating lithium peroxide ...can greatly be facilitated by incorporating redox mediators that shuttle electron-holes between the porous substrate and lithium peroxide. Redox mediator stability is thus key for energy efficiency, reversibility, and cycle life. However, the gradual deactivation of redox mediators during repeated cycling has not conclusively been explained. Here, we show that organic redox mediators are predominantly decomposed by singlet oxygen that forms during cycling. Their reaction with superoxide, previously assumed to mainly trigger their degradation, peroxide, and dioxygen, is orders of magnitude slower in comparison. The reduced form of the mediator is markedly more reactive towards singlet oxygen than the oxidized form, from which we derive reaction mechanisms supported by density functional theory calculations. Redox mediators must thus be designed for stability against singlet oxygen.
The strengthening mechanism of the metallic material is related to the hindrance of the dislocation motion, and it is possible to achieve superior strength by maximizing these obstacles. In this ...study, the multiple strengthening mechanism-based nanostructured steel with high density of defects was fabricated using high-pressure torsion at room and elevated temperatures. By combining multiple strengthening mechanisms, we enhanced the strength of Fe-15 Mn-0.6C-1.5 Al steel to 2.6 GPa. We have found that solute segregation at grain boundaries achieves nanograined and nanotwinned structures with higher strength than the segregation-free counterparts. The importance of the use of multiple deformation mechanism suggests the development of a wide range of strong nanotwinned and nanostructured materials via severe plastic deformation process.
An Advanced Lithium-Sulfur Battery Kim, Junghoon; Lee, Dong-Ju; Jung, Hun-Gi ...
Advanced functional materials,
February 25, 2013, Letnik:
23, Številka:
8
Journal Article
Recenzirano
A lithium‐sulfur battery employing a high performances mesoporous hard carbon spherules‐sulfur cathode and a stable, highly conducting electrolyte is reported. The results demonstrate that the ...battery cycles with very high capacity, i.e., of the order of 750 mAh g−1 with excellent retention during cycling. In addition, by exploiting the high conductivity of our selected electrolyte, the battery performs very well also at low temperature, i.e., delivering a capacity of 500 mAh g−1(S) at 0 °C for over 170 charge‐discharge cycles. We believe that these results may substantially contribute to the progress of the lithium‐sulfur battery technology.
A porous hard carbon spherules‐sulfur (HCS‐S) composite cathode shows remarkable electrochemical behavior in a lithium cell using a solution of lithium triflate (LiCF3SO3) in tetraethylene glycol dimethyl ether (TEGDME) as the electrolyte. The new composite, characterized by high capacity, long cycle life, and remarkable sulfur content, is proposed as a new cathode material for high energy‐lithium batteries.
Sodium manganese oxides as promising cathode materials for sodium‐ion batteries (SIBs) have attracted interest owing to their abundant resources and potential low cost. However, their practical ...application is hindered due to the manganese disproportionation associated with Mn3+, resulting in rapid capacity decline and poor rate capability. Herein, a Li‐substituted, tunnel/spinel heterostructured cathode is successfully synthesized for addressing these limitations. The Li dopant acts as a pillar inhibiting unfavorable multiphase transformation, improving the structural reversibility, and sodium storage performance of the cathode. Meanwhile, the tunnel/spinel heterostructure provides 3D Na+ diffusion channels to effectively enhance the redox reaction kinetics. The optimized Na0.396Li0.044Mn0.97Li0.03O2 composite delivers an excellent rate performance with a reversible capacity of 97.0 mA h g–1 at 15 C, corresponding to 82.5% of the capacity at 0.1 C, and a promising cycling stability over 1200 cycles with remarkable capacity retention of 81.0% at 10 C. Moreover, by combining with hard carbon anodes, the full cell demonstrates a high specific capacity and favorable cyclability. After 200 cycles, the cell provides 105.0 mA h g–1 at 1 C, demonstrating the potential of the cathode for practical applications. This strategy might apply to other sodium‐deficient cathode materials and inform their strategic design.
A tunnel/spinel heterostructured cathode demonstrates superior rate capability and excellent cycling stability in Na‐ion half/full battery systems. Here, Li is a component of the transition metal layer and serves as a pillar to strengthen the crystal framework. Meanwhile, tunnel/spinel heterostructure provides 3D Na+ diffusion channels, effectively enhancing the redox reaction kinetics.
Oxygen‐redox‐based cathode materials for sodium‐ion batteries (SIBs) have attracted considerable attention in recent years owing to the possibility of delivering additional capacity in the ...high‐voltage region. However, they still suffer from not only fast capacity fading but also poor rate capability. Herein, P2‐Na0.75Li0.15Ni0.15Mn0.7O2 is introduced, an oxygen‐redox‐based layered oxide cathode material for SIBs. The effect of Ni doping on the electrochemical performance is investigated by comparison with Ni‐free P2‐Na0.67Li0.22Mn0.78O2. The Na0.75Li0.15Ni0.15Mn0.7O2 delivers a specific capacity of ≈160 mAh g−1 in the voltage region of 1.5–4.6 V at 0.1 C in Na cells. Combined experiments (galvanostatic cycling, neutron powder diffraction, X‐ray absorption spectroscopy, X‐ray photoelectron spectroscopy, and nuclear magnetic resonance (7Li NMR)) and theoretical studies (density functional theory calculations) confirm that Ni substitution not only increases the operating voltage and decreases voltage hysteresis but also improves the cycling stability by reducing Li migration from transition metal to Na layers. This research demonstrates the effect of Li and Ni co‐doping in P2‐type layered materials and suggests a new strategy of using Mn‐rich cathode materials via oxygen redox with optimization of doping elements for SIBs.
The role of Ni substitution on the structure and electrochemical properties of oxygen‐redox‐based P2‐type Na0.67Li0.22Mn0.78O2 layered cathode materials is investigated. Ni provides not only an increase of the operating voltage and decrease of voltage hysteresis, but also improves the cycling stability by reducing Li migration from transition metal to Na layers.
Although Li‐ion superconducting sulfides have been developed as solid electrolytes (SEs) in all‐solid‐state batteries, their high deformability, which is inherently beneficial for room‐temperature ...compaction, is overlooked and sacrificed. To solve this dilemmatic task, herein, highly deformable Li‐ion superconductors are reported using an annealing‐free process. The target thioantimonate, Li5.2Si0.2Sb0.8S4Br0.25I1.75, comprising bimetallic tetrahedra and bi‐halogen anions is synthesized by two‐step milling tuned for in situ crystallization, and exhibits excellent Li‐ion conductivity (σion) of 13.23 mS cm−1 (averaged) and a low elastic modulus (E) of 12.51 GPa (averaged). It has a cubic argyrodite phase of ≈57.39% crystallinity with a halogen occupancy of ≈90.67% at the 4c Wyckoff site. These increased halogen occupancy drives the Li‐ion redistribution and the formation of more Li vacancies, thus facilitating Li‐ion transport through inter‐cage pathway. Also, the facile annealing‐free process provides a unique glass‐ceramic structure advantageous for high deformability. These results represent a record‐breaking milestone from the combined viewpoint of σion and E among promising SEs. Electrochemical characterization, including galvanostatic cycling tests for 400 h, reveals that this material displays reasonable electrochemical stability and cell performance (150.82 mAh g−1 at 0.1C). These achievements shed light on the synthesis of practical SEs suffice both σion and E requirements.
Highly deformable argyrodite reaching a Li‐ion conductivty of 13.23 mS cm−1 and an elastic modulus of 12.51 GPa is achieved by applying an annealing‐free mechanochemical method. An increased halogen occupancy of ≈90.67% at the 4c Wyckoff site facilitates Li‐ion transport via the inter‐cage pathway. Simultaneously, the in situ crystallization process provides a unique glass‐ceramic structure with a 57.39% crystallinity beneficial for room‐temperature compaction.
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