A Promising Solid-State Synthesis of LiMn1- yFeyPO4 Cathode for Lithium-ion Batteries.

LiMn1-yFeyPO4 (LMFP) is a significant and cost-effective cathode material for Li-ion batteries, with a higher working voltage than LiFePO4 (LFP) and improved safety features compared to layered oxide cathodes. However, its commercial application faces challenges due to a need for a synthesis process to overcome the low Li-ion diffusion kinetics and complex phase transitions. Herein, a solid-state synthesis process using LFP and nano LiMn0.7Fe0.3PO4 (MF73) is proposed. The larger LFP acts as a structural framework fused with nano-MF73, preserving the morphology and high performance of LFP. These results demonstrate that the solid-state reaction occurs quickly, even at a low sintering temperature of 500 °C, and completes at 700 °C. However, contrary to the expectations, the larger LFP particles disappeared and fused into the nano-MF73 particles, revealing that Fe ions diffuse more easily than Mn ions in the olivine framework. This discovery provides valuable insights into understanding ion diffusion in LMFP. Notably, the obtained LMFP can still deliver an initial capacity of 142.3 mAh g-1, and the phase separation during the electrochemical process is significantly suppressed, resulting in good cycling stability (91.1% capacity retention after 300 cycles). These findings offer a promising approach for synthesizing LMFP with improved performance and stability.

Unraveling the Hydrolysis Mechanism of LiPF6 in Electrolyte of Lithium Ion Batteries.

Lithium hexafluorophosphate (LiPF6) has been the dominant conducting salt in lithium-ion battery (LIB) electrolytes for decades; however, it is extremely unstable in even trace water (ppm level). Interestingly, in pure water, PF6- does not undergo hydrolysis. Hereby, we present a fresh understanding of the mechanism involved in PF6- hydrolysis through theoretical and experimental explorations. In water, PF6- is found to be solvated by water, and this solvation greatly improved its hydrolytic stability; while in the electrolyte, it is forced to "float" due to the dissociation of its counterbalance ions. Its hydrolytic susceptibility arises from insufficient solvation-induced charge accumulation and high activity in electrophilic reactions with acidic species. Tuning the solvation environment, even by counterintuitively adding more water, could suppress PF6- hydrolysis. The undesired solvation of PF6- anions was attributed to the perennial LIB electrolyte system, and our findings are expected to inspire new thoughts regarding its design.

Understanding the Insight Mechanism of Chemical-Mechanical Degradation of Layered Co-Free Ni-Rich Cathode Materials: A Review.

Layered Cobalt (Co)-free Nickel (Ni)-rich cathode materials have attracted much attention due to their high energy density and low cost. Still, their further development is hampered by material instability caused by the chemical/mechanical degradation of the material. Although there are numerous doping and modification approaches to improve the stability of layered cathode materials, these approaches are still in the laboratory stage and require further research before commercial application. To fully exploit the potential of layered cathode materials, a more comprehensive theoretical understanding of the underlying issues is necessary, along with active exploration of previously unrevealed mechanisms. This paper presents the phase transition mechanism of Co-free Ni-rich cathode materials, the existing problems, and the state-of-the-art characterization tools employed to study the phase transition. The causes of crystal structure degradation, interfacial instability, and mechanical degradation are elaborated, from the material's crystal structure to its phase transition and atomic orbital splitting. By organizing and summarizing these mechanisms, this paper aims to establish connections among common research problems and to identify future research priorities, thereby facilitating the rapid development of Co-free Ni-rich materials.

Interfacial Model Deciphering High-Voltage Electrolytes for High Energy Density, High Safety, and Fast-Charging Lithium-Ion Batteries.

High-voltage lithium-ion batteries (LIBs) enabled by high-voltage electrolytes can effectively boost energy density and power density, which are critical requirements to achieve long travel distances, fast-charging, and reliable safety performance for electric vehicles. However, operating these batteries beyond the typical conditions of LIBs (4.3 V vs Li/Li+ ) leads to severe electrolyte decomposition, while interfacial side reactions remain elusive. These critical issues have become a bottleneck for developing electrolytes for applications in extreme conditions. Herein, an additive-free electrolyte is presented that affords high stability at high voltage (4.5 V vs Li/Li+ ), lithium-dendrite-free features upon fast-charging operations (e.g., 162 mAh g-1 at 3 C), and superior long-term battery performance at low temperature. More importantly, a new solvation structure-related interfacial model is presented, incorporating molecular-scale interactions between the lithium-ion, anion, and solvents at the electrolyte-electrode interfaces to help interpret battery performance. This report is a pioneering study that explores the dynamic mutual-interaction interfacial behaviors on the lithium layered oxide cathode and graphite anode simultaneously in the battery. This interfacial model enables new insights into electrode performances that differ from the known solid electrolyte interphase approach to be revealed, and sets new guidelines for the design of versatile electrolytes for metal-ion batteries.

Unraveling the New Role of Metal-Organic Frameworks in Designing Silicon Hollow Nanocages for High-Energy Lithium-Ion Batteries.

Metal-organic framework (MOF)-derived materials are attracting considerable attention because of the moldability in compositions and structures, enabling greater performances in diverse applications. However, the nanostructural control of multicomponent MOF-based complexes remains challenging due to the complexity of reaction mechanisms. Herein, we present a surface-induced self-nucleation-growth mechanism for the zeolitic imidazolate framework (ZIF) to prepare a new type of ZIF-8@SiO2 polyhedral nanoparticles. We discover that the Zn hydroxide moieties (Zn-OH) within ZIF-8 can trigger the hydrolysis of tetraethyl orthosilicate effectively on the ZIF-8 surface precisely, avoiding the formation of free orthosilicic acid (Si(OH)4) successfully. This is a pioneering work to elucidate the importance of MOF surface properties for preparing multicomponent materials. Then, a novel well-dispersed silicon hollow nanocage (H-Si@C) modified by the carbon was prepared after removal of the ZIF-8 and magnesiothermic reduction. The as-prepared H-Si@C demonstrates an overwhelmingly high lithium storage capability and extraordinary stability in lithium-ion batteries (LIBs), particularly the impressive performances when it was matched with the LiNi0.6Co0.2Mn0.2O2 cathode in a full cell. The MOF surface-induced self-nucleation-growth strategy is useful for preparing more multifunctional materials, while the study of lithium storage performances of the H-Si@C material is practical for LIB applications.

Electrolyte Chemistry in 3D Metal Oxide Nanorod Arrays Deciphers Lithium Dendrite-Free Plating/Stripping Behaviors for High-Performance Lithium Batteries.

Lithium dendrite-free deposition is crucial to stabilizing lithium batteries, where the three-dimensional (3D) metal oxide nanoarrays demonstrate an impressive capability to suppress dendrite due to the spatial effect. Herein, we introduce a new insight into the ameliorated lithium plating process on 3D nanoarrays. As a paradigm, novel 3D Cu2O and Cu nanorod arrays were in situ designed on copper foil. We find that the dendrite and electrolyte decomposition can be mitigated effectively by Cu2O nanoarrays, while the battery failed fast when the Cu nanoarrays were used. We show that Li2O (i.e., formed in the lithiation of Cu2O) is critical to stabilizing the electrolyte; otherwise, the electrolyte would be decomposed seriously. Our viewpoint is further proved when we revisit the metal (oxide) nanoarrays reported before. Thus, we discovered the importance of electrolyte stability as a precondition for nanoarrays to suppress dendrite and/or achieve a reversible lithium plating/stripping for high-performance lithium batteries.

Insight into the Coprecipitation-Controlled Crystallization Reaction for Preparing Lithium-Layered Oxide Cathodes.

The nucleation and growth of spherical Ni0.6Co0.2Mn0.2(OH)2 agglomerates using the hydroxide coprecipitation (HCP) method in the presence of ammonia is investigated through chemical equilibrium calculations and experiments. In the nucleation stage, the transition metal ions in the salt solution gradually complete the nucleation reaction in the diffusion process from pH 5.4 to 11 after dropping into the continuously stirred tank reactor, and then Me(NH3)n2+ and Me(OH)2(s) (Me: Ni, Co, and Mn) reach a dynamic precipitation dissolution equilibrium. In the growth stage, the concentration ratio of Me(NH3)n2+ and OH- (complexation and precipitation, Rc/p) in the solution has an important influence on obtaining high-quality materials, which is further confirmed using the first principles density functional theory calculations on surface energy and adsorption energy. Then, the HCP reaction could be divided into three parts through experiments: incomplete precipitation area (Rc/p > 10.1); time-dependent area (Rc/p = 0.1-10.1); and hard-to-control area (Rc/p <0.1). According to the optimal ratio (Rc/p = 3.4), a prediction formula for the optimal synthesis conditions of the materials is proposed (y = 0.7731 × ln(x + 0.0312) + 11.6708, the optimal pH value (y) corresponds to different ammonia concentrations (x)). The results obtained for the growth reaction mechanism and the prediction scheme would help the modification research of the materials and obtain the desired lithium-layered transition metal oxide cathode material with excellent performance in the shortest time.

Dimeric Tetrahydroanthracene Regioisomers and Their Monomeric Precursor Produced by Streptomyces fumigatiscleroticus HDN10255.

Four new tetrahydroanthracene derivatives (1, 3-5) and a known antibiotic, A-39183A (2), were discovered from the marine-sponge-derived actinomycete Streptomyces fumigatiscleroticus HDN10255. Their structures including absolute configurations were elucidated based upon MS and NMR spectroscopic data, ECD calculations, and biogenetic considerations. Compounds 2 and 4 showed considerable cytotoxicity with the best IC50 value of 1.8 µM against HeLa cells.

Engineering Sodium-Ion Solvation Structure to Stabilize Sodium Anodes: Universal Strategy for Fast-Charging and Safer Sodium-Ion Batteries.

Sodium-ion batteries are promising alternatives for lithium-ion batteries due to their lower cost caused by global sodium availability. However, the low Coulombic efficiency (CE) of the sodium metal plating/stripping process represents a serious issue for the Na anode, which hinders achieving a higher energy density. Herein, we report that the Na+ solvation structure, particularly the type and location of the anions, plays a critical role in determining the Na anode performance. We show that the low CE results from anion-mediated corrosion, which can be tackled readily through tuning the anion interaction at the electrolyte/anode interface. Our strategy thus enables fast-charging Na-ion and Na-S batteries with a remarkable cycle life. The presented insights differ from the prevailing interpretation that the failure mechanism mostly results from sodium dendrite growth and/or solid electrolyte interphase formation. Our anionic model introduces a new guideline for improving the electrolytes for metal-ion batteries with a greater energy density.

A Designed Durable Electrolyte for High-Voltage Lithium-Ion Batteries and Mechanism Analysis.

Rechargeable lithium-ion batteries (LIBs) dominate the energy market, from electronic devices to electric vehicles, but pursuing greater energy density remains challenging owing to the limited electrode capacity. Although increasing the cut-off voltage of LIBs (>4.4 V vs. Li/Li+ ) can enhance the energy density, the aggravated electrolyte decomposition always leads to a severe capacity fading and/or expiry of the battery. Herein, a new durable electrolyte is reported for high-voltage LIBs. The designed electrolyte is composed of mixed linear alkyl carbonate solvent with certain cyclic carbonate additives, in which use of the ethylene carbonate (EC) co-solvent was successfully avoided to suppress the electrolyte decomposition. As a result, an extremely high cycling stability, rate capability, and high-temperature storage performance were demonstrated in the case of a graphite|LiNi0.6 Co0.2 Mn0.2 O2 (NCM622) battery at 4.45 V when this electrolyte was used. The good compatibility of the electrolyte with the graphite anode and the mitigated structural degradation of the NCM622 cathode are responsible for the high performance at high potentials above 4.4 V. This work presents a promising application of high-voltage electrolytes for pursuing high energy LIBs and provides a straightforward guide to study the electrodes/electrolyte interface for higher stability.

Carbon Nanotubes Coupled with Metal Ion Diffusion Layers Stabilize Oxide Conversion Reactions in High-Voltage Lithium-Ion Batteries.

Creating new architectures combined with super diverse materials for achieving more excellent performances has attracted great attention recently. Herein, we introduce a novel dual metal (oxide) microsphere reinforced by vertically aligned carbon nanotubes (CNTs) and covered with a titanium oxide metal ion-transfer diffusion layer. The CNTs penetrate the oxide particles and buffer structural volume change while enhancing electrical conductivity. Meanwhile, the external TiO2-C shell serves as a transport pathway for mobile metal ions (e.g., Li+) and acts as a protective layer for the inner oxides by reducing the electrolyte/metal oxide interfacial area and minimizing side reactions. The proposed design is shown to significantly improve the stability and Coulombic efficiency (CE) of metal (oxide) anodes. For example, the as-prepared MnO-CNTs@TiO2-C microsphere demonstrates an extremely high capacity of 967 mA h g-1 after 200 cycles, where a CE as high as 99% is maintained. Even at a harsh rate of 5 A g-1 (ca. 5 C), a capacity of 389 mA h g-1 can be maintained for thousands of cycles. The proposed oxide anode design was combined with a nickel-rich cathode to make a full-cell battery that works at high voltage and exhibits impressive stability and life span.

Crystal reconstruction of binary oxide hexagonal nanoplates: monocrystalline formation mechanism and high rate lithium-ion battery applications.

Structural design and/or carbon modification are the most important strategies to improve the performance of materials in many applications, where metal (oxide)-based anode design attracts great attention in metal ion batteries due to their high capacities. However, achieving these two goals within one-step remains challenging due to the lower cost and higher efficiency needed to satisfy the demand in practical application. Herein, we report a new approach for the crystal reconstruction of metal oxides by acetylene treatment, in which a hierarchical binary oxide decorated with carbon (i.e., Mn2Mo3O8@C) is introduced. The mechanism of constructing unique monocrystalline hexagonal nanoplates and uniform carbon coating is discussed in detail. Benefiting from the uniqueness of structure and composition, the Mn2Mo3O8@C demonstrates an extremely high lithium storage capacity of 890 mA h g-1 and good rate capacities at 20 A g-1 over 1000 cycles. In addition, the high rate capabilities and long cycle lifespan are further confirmed when the Mn2Mo3O8@C anode is matched with the nickel-rich layered oxide cathode. This study not only introduces a new binary oxide anode with high performances in lithium (ion) batteries but also presents a convenient methodology to design more advanced functional materials.

Performance and Stability Improvement of Layered NCM Lithium-Ion Batteries at High Voltage by a Microporous Al2O3 Sol-Gel Coating.

A simple and low-cost polymer-aided sol-gel method was developed to prepare γ-Al2O3 protective layers for LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode materials. The selected polyvinyl alcohol polymer additive not only facilitates the formation of a uniform and thin γ-Al2O3 layer on the irregular and rough cathode particle surface to protect it from corrosion but also serves as a pore-forming agent to generate micropores in the film after sintering to allow fast transport of lithium ions, which guaranteed the excellent and stable battery performance at high working voltage. Detailed studies in the full battery mode showed that the leached corrosion species from the cathode had a more profound harmful effect to the graphite anode, which seemed to be the dominating factor that caused the battery performance decay.

Metal-Organic Coordination Strategy for Obtaining Metal-Decorated Mo-Based Complexes: Multi-dimensional Structural Evolution and High-Rate Lithium-Ion Battery Applications.

Multi-dimensional metal oxides have attracted great attention in diverse applications due to their intriguing performances. However, their structural design remains challenging, particularly that based on organic chelation chemistry. Although metal-organic complexes with different architectures have been reported, their structure formation mechanisms are not well understood because of the complex chelation processes. Herein, we introduce a new metal-organic coordination strategy to construct metal-decorated (Ni, Co, Mn) Mo-based complexes ranging from 2D nanopetals to 3D microflowers. The chelating process of the metal-organic complex can be tuned by a surfactant, giving rise to different structures, and then a further metal can be appended. Thus, different metal (oxide)-decorated MoO2 /C-N structures were designed, enabling an extremely high lithium storage capability of 1018 mA h g-1 and rate capacities of up to 10 A g-1 over 1000 cycles. Relationships between electrochemical behavior and structure have been analyzed kinetically. A high-rate lithium-ion battery has been assembled from Ni-MoO2 /C-N and an Ni-rich layered oxide as the anode and cathode, respectively. We believe that this general metal-organic coordination strategy should be applicable to other multi-functional materials with superior capabilities.

Lithium dendrite-free plating/stripping: a new synergistic lithium ion solvation structure effect for reliable lithium-sulfur full batteries.

A new synergistic lithium ion solvation structure effect tailored by mixed organic/inorganic lithium salts is introduced to mitigate the growth of lithium-dendrites. A uniform lithium plating, lower polarization and higher coulombic efficiency are confirmed by lithium plating/stripping. The effect of different solvation structures was analyzed by Raman spectroscopy and simulations. Then, a reliable lithium-sulfur full battery with high performance over hundreds of cycles was configured.

Bioinspired Architectures and Heteroatom Doping To Construct Metal-Oxide-Based Anode for High-Performance Lithium-Ion Batteries.

The pursuit of increased energy density and longer lifespan lithium-ion batteries (LIBs) is urgently needed to satisfy a dramatically increased demand in the energy market. Currently, metal-oxide-based anodes are being intensively studied due to their higher capacities over current graphite anodes. This work introduces a sustainable strategy to construct a metal-oxide-based anode with high capacity and an extremely long lifecycle, in which the features of bioinspired architectures and heteroatom doping can contribute greatly to increased performances. In detail, 1D tubelike metal oxide (e.g., MnO) coated on an N-doped carbon framework (i.e. MnO/N-C) has been designed by using the naturally abundant and renewable Metaplexis japonica fibers (MJFs) as the biotemplate and heteroatom source. Benefiting from the uniqueness of structure and compositions, as-prepared MnO/N-C demonstrates extremely high rate capacities of 951, 777, 497, and 435 mAh g-1 at the rates of 0.5, 2, 4, and 5 Ag-1 , respectively, with a good stability of more than 1000 cycles. It was found that the electrochemical performances are superior to most previous MnO-based anodes, in which the faster kinetics of conversion due to the advantage of the ion/electron transportation and morphological evolution has been verified. It is hoped that the concept of bioinspired architectures with heteroatom doping can be applied in wider applications for increased capability.

A new cold-adapted, alkali-stable and highly salt-tolerant esterase from Bacillus licheniformis.

Bacterial esterases and lipases, especially extremozymes attract increasing attention due to various advantages both in good properties and wide applications. In the present study, a cold-adapted, alkali-stable and highly salt-tolerant esterase (Est700) was cloned from Bacillus licheniformis, expressed and purified with a molecular mass of 25 kDa. The optimal temperature of Est700 was 30 °C, with 35% maximal activity retaining at 0 °C. Its optimal pH was 8.0 and showed high stability at pH 5.0-11.0. Noticeably, Est700 was highly activated by 3.5 M NaCl and the extent of this activation is much stronger than that of currently reported halophilic ones. It was also stable in 5 M NaCl with no activity loss. High salt concentrations changed the secondary structure and folding properties of Est700 with formation of more α-helix and less ß-sheet domains. With salt incubation, its melting temperature was estimated to be 57.2 °C, which is 12.8 °C higher than that of native one. Interestingly, Est700 lacks the acidic surface that is considered essential for enzyme stability at high salinity. However, it has a mainly positive surface electrostatic potential, which is probably different from most reported halotolerant esterases. These multiple properties make Est700 a valuable candidate in both basic research and industrial applications.

Assembling metal oxide nanocrystals into dense, hollow, porous nanoparticles for lithium-ion and lithium-oxygen battery application.

New dense hollow porous (DHP) metal oxide nanoparticles that are smaller than 100 nm and composed of Co3O4, FeOx, NiO and MnOx were prepared by densely assembling metal oxide nanocrystals based on the hard-template method using a carbon colloid as a sacrificial core. These nanoparticles are quite different from the traditional particles as their hollow interior originates from the stacking of nanocrystals rather than a spherical shell. The DHP nanoparticles preserve the intriguing properties of nanocrystals and possess desirable surface area and pore volume that enhance the active surface, which ultimately benefits applications such as lithium-ion batteries. The DHP Co3O4 nanoparticles demonstrated an enhanced capacity of 1168 mA h g(-1) at 100 mA g(-1)vs. 590 mA h g(-1) of powders and stable cycling performance greater than 250 cycles when used as an anode material. Most importantly, the electrochemical performance of DHP Co3O4 nanoparticles in a lithium-O2 battery was also investigated for the first time. A low charge potential of ∼4.0 V, a high discharge voltage near 2.74 V and a long cycle ability greater than 100 cycles at a delivered capacity of 2000 mA h g(-1) (current density, 200 mA g(-1)) were observed. The performances were considerably improved compared to recent results of mesoporous Co3O4, Co3O4 nanoparticles and a composite of Co3O4/RGO and Co3O4/Pd. Therefore, it would be promising to investigate such properties of DHP nanoparticles or other hollow metal (oxide) particles for the popular lithium-air battery.

Trace amounts of water-induced distinct growth behaviors of NiO nanostructures on graphene in CO2-expanded ethanol and their applications in lithium-ion batteries.

In this work, we have developed a new method to grow NiO nanomaterials on the surface of graphene nanosheets (GNSs). The morphologies of NiO nanomaterials grown on GNSs could be tailored by trace amounts of water introduced into the mixed solvents of CO2-expanded ethanol (CE). Small and uniform Ni-salt nanoparticles (Ni-salt-NPs) were grown on the surface of graphene oxide (GO) through the decomposition of nickel nitrate directly in CE. However, when trace amounts of water were introduced into the mixed solvents, Ni-salt nanoflakes arrays (Ni-salt-NFAs) were grown on the surface of GO with almost perpendicular direction. After thermal treatment in N2 atmosphere, these Ni-salt @GO composites were converted to NiO@GNSs composites. The forming mechanisms of the NiO-NPs@GNSs and NiO-NFAs@GNSs were discussed by series comparative experiments. The presence of the trace amounts of water affected the chemical composition and structure of the precursors formed in CE and the growth behaviors on the surface of GNSs. When used as anode materials for lithium-ion batteries, the NiO-NPs@GNSs composite exhibited better cycle and rate performance compared with the NiO-NFAs@GNSs.

Steaming multiwalled carbon nanotubes via acid vapour for controllable nanoengineering and the fabrication of carbon nanoflutes.

A new concept of steaming multiwalled carbon nanotubes (MWCNTs) via acid vapour was presented for controllable nanoengineering of the MWCNTs. This method is more simple, effective, precisely-controllable and environmentally-friendly compared to traditional ones. Moreover, novel porous carbon nanotubes, named carbon nanoflutes, were fabricated based on this strategy.