Concentration-Gradient Structural LiFe0.5Mn0.5PO4/C Prepared via Co-precipitation Reaction for Advanced Lithium-Ion Batteries.

The intrinsically low electronic conductivity and slow ion diffusion kinetics limit further development of olivine LiFexMn1-xPO4 cathode materials. In this paper, with the aim of improving the performance of such materials and alleviating the Jahn-Taller effect of Mn3+ ion, a bimetallic oxalate precursor with gradient distribution of elemental concentration followed with an efficient process is applied to synthesize LiFe0.5Mn0.5PO4 nanocomposite. The results shown that with certain structural modulation of the precursor, the discharge capacity of synthesized LiFe0.5Mn0.5PO4 increased from 149 mAh g-1 to 156 mAh g-1 at 0.1 C, the cycling capacity was also remarkably improved. the Fe0.5Mn0.5C2O4 ⋅ 2H2O-1 precursor with gradient distribution of elemental concentration effectively restricts the reaction between electrode material and electrolyte, thereby alleviates the dissolution of Mn3+ ion, reduces the decay of capacity and improves the stability of the material.

Reconstructing interfacial manganese deposition for durable aqueous zinc-manganese batteries.

Low-cost, high-safety, and broad-prospect aqueous zinc-manganese batteries (ZMBs) are limited by complex interfacial reactions. The solid-liquid interfacial state of the cathode dominates the Mn dissolution/deposition process of aqueous ZMBs, especially the important influence on the mass and charge transfer behavior of Zn2+ and Mn2+. We proposed a quasi-eutectic electrolyte (QEE) that would stabilize the reversible behavior of interfacial deposition and favorable interfacial reaction kinetic of manganese-based cathodes in a long cycle process by optimizing mass and charge transfer. We emphasize that the initial interfacial reaction energy barrier is not the main factor affecting cycling performance, and the good reaction kinetics induced by interfacial deposition during the cycling process is more conducive to the stable cycling of the battery, which has been confirmed by theoretical analysis, quartz crystal microbalance with dissipation monitoring, depth etching X-ray photon-electron spectroscopy, etc. As a result, the QEE electrolyte maintained a stable specific capacity of 250 mAh g-1 at 0.5 A g-1 after 350 cycles in zinc-manganese batteries. The energy density retention rate of the ZMB with QEE increased by 174% compared to that of conventional aqueous electrolyte. Furthermore, the multi-stacked soft-pack battery with a cathodic mass load of 54.4 mg maintained a stable specific capacity of 200 mAh g-1 for 100 cycles, demonstrating its commercial potential. This work proves the feasibility of adapting lean-water QEE to the stable aqueous ZMBs.

How does environmental punishment affect regional green technology innovation?-Evidence from Chinese Provinces.

As an important means of environmental regulation, environmental punishment lacks in empirical evidence on its impact on regional green technology innovation in China. Based on panel data of 30 provinces in China from 2010 to 2020, this paper systematically examines the relationship between environmental punishment and regional green technology innovation. It is found that environmental punishment has the quantity and quality enhancing effects on regional green technology innovation, and the quantity enhancing effect is greater than the quality enhancing effect. There is no significant effect difference between monetary punishment and non monetary punishment on green technology innovation effect, but the effect of punishment on institutions is obviously greater than that of punishment on individuals. And the performance of ecological provinces and provinces with better legal environment is also relatively better. Environmental punishment enhances the quantity and quality of green technology innovation through pressure, and improves the quality of green technology innovation through deterrence. Besides, in China, deterrence promotes regional green technology innovation together with the Central Government's environmental protection inspection, the national green manufacturing strategies and other policies concerned.

Rydberg state dynamics and fragmentation mechanism of N,N,N',N'-tetramethylmethylenediamine.

The non-adiabatic relaxation processes and the fragmentation dynamics of Rydberg-excited N,N,N',N'-tetramethylmethylenediamine (TMMDA) are investigated using femtosecond time-resolved photoelectron imaging and time-resolved mass spectroscopy. Excitation at 208 nm populates TMMDA in a charge-localized 3p state. Rapid internal conversion (IC) to 3s produces two charge-delocalized conformers with independent time constants and distinct population ratios. As the system explores the 3s potential surface, the structural evolution continues on a 1.55 ps timescale, followed by a slower (12.1 ps) relaxation to the ground state. A thorough comparison of the time-dependent mass and photoelectron spectra suggests that ionization out of the 3p state ends up with the parent ion, the vibrational energy of which is insufficient for the bond cleavage. On the contrary, by virtue of the additional energy acquired by IC from 3p, the internal energy deposited in 3s is available to break the C-N bond, leading to the fragment ion. The fragmentation is found to occur on the ion surface instead of the Rydberg surface.

Structural dynamics upon photoinduced charge transfer in N,N,N',N'-tetramethylmethylenediamine.

The ultrafast structural motion linked to the charge transfer process in Rydberg excited N,N,N',N'-tetramethylmethylenediamine (TMMDA) has been monitored in real time using femtosecond time-resolved photoelectron imaging coupled with quantum chemical calculations. Optical excitation to the 3 s Rydberg state initially populates the charge on one of the two amine groups, resulting in a charge-localized structure in the Franck-Condon (FC) region. As the wavepacket evolves on the 3 s potential surface, the molecular geometry changes with time, leading to the corresponding variation in the charge distribution. The ensuing structural evolution yields two distinct conformers GG+ and TT+ (see text for nomenclature), both with the charge delocalized between the two nitrogen atoms. By virtue of the sensitivity of the Rydberg electron binding energy (BE) on the nuclear geometry, the time-dependent BE spectrum offers an intuitive mapping of the charge transfer reaction that leads from the initially prepared charge-localized GG-FC structure to the fully charge-delocalized GG+ and TT+ structures. Complementary computations provide evidence that through-space interaction is responsible for the charge delocalization in the GG+ and TT+ structures.

Balanced Interfacial Ion Concentration and Migration Steric Hindrance Promoting High-Efficiency Deposition/Dissolution Battery Chemistry.

The solid-liquid transition reaction lays the foundation of electrochemical energy storage systems with high capacity, but realizing high efficiency remains a challenge. Herein, in terms of thermodynamics and dynamics, this work demonstrates the significant role of both interfacial H+ concentration and Mn2+ migration steric hindrance for the high-efficiency deposition/dissolution chemistry of zinc-manganese batteries. Specially, the introduction of formate anions can buffer the generated interfacial H+ to stabilize interfacial potential according to the Nernst equation, which stimulates high capacity. Compared with acetate and propionate anions, the formate anion also provides high adsorption density on the cathode surface to shield the electrostatic repulsion due to the small spatial hindrance. Particularly for the solvated Mn2+ , the formate-anion-induced lower energy barrier of the rate-determining step during the step-by-step desolvation process results in lower polarization and higher electrochemical reversibility. In situ tests and theoretical calculations verify that the electrolyte with formate anions achieve a good balance between ion concentration and ion-migration steric hindrance. It exhibits both the high energy density of 531.26 W h kg-1  and long cycle life of more than 300 cycles without obvious decay.

Efficient Mutual-Compensating Li-Loss Strategy toward Highly Conductive Garnet Ceramics for Li-Metal Solid-State Batteries.

Garnet-type Li7La3Zr2O12 (LLZO) is a promising solid-state electrolyte (SSE) due to its high Li+ conductivity and stability against lithium metal. However, wide research and application of LLZO are hampered by the difficulty in sintering highly conductive LLZO ceramics, which is mainly attributed to its poor sinterability and the hardship of controlling the Li2O atmosphere at a high sintering temperature (∼1200 °C). Herein, an efficient mutual-compensating Li-loss (MCLL) method is proposed to effectively control the Li2O atmosphere during the sintering process for highly conductive LLZO ceramics. The Li6.5La3Zr1.5Ta0.5O12 (LLZTO) ceramic SSEs sintered by the MCLL method own high relative density (96%), high Li content (5.54%), high conductivity (7.19 × 10-4 S cm-1), and large critical current density (0.85 mA cm-2), equating those sintered by a hot-pressing technique. The assembled Li-Li symmetric battery and a Li-metal solid-state battery (LMSSB) show that the as-prepared LLZTO can achieve a small interfacial resistance (17 Ω cm2) with Li metal, exhibits high electrochemical stability against Li metal, and has broad potential in the application of LMSSBs. In addition, this method can also improve the sintering efficiency, avoid the use of mother powder, and reduce raw-material cost, and thus it may promote the large-scale preparation and wide application of LLZO ceramic SSE.

Superior Na-Storage Properties of Nickel-Substituted Na2FeSiO4@C Microspheres Encapsulated with the In Situ-Synthesized Alveolation-like Carbon Matrix.

The poor electronic conductivity of Na2FeSiO4 always limits its electrochemical reactivities and no effective solution has been found to date. Herein, the novel Ni-substituted Na2Fe1-xNixSiO4@C nanospheres (50-100 nm) encapsulated with a 3D hierarchical porous skeleton (named as alveolation-like configuration) constructed using in situ carbon are first synthesized via a facile sol-gel method, and the effects of Ni substitution combined with the design of a unique carbon network on Na-storage properties are assessed systematically, focusing on alleviating the inherent defects of the Na2FeSiO4 cathode material. A series of characterization technologies such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and so forth, coupled with the electrochemical measurements and first-principles calculations, are used to explore the structure, morphology and electrochemical behaviors of the as-prepared materials. The results show that the synergism between Ni substitution and the special alveolation-like configuration enables fast Na ions mobility (from 10-14 to 10-12 cm2 s-1), reduces band gap energy (from 2.82 to 1.79 eV) and lowers Na-ion diffusion barriers, finally reciprocating the vigorous electrochemical kinetics of the electrode. Especially, the elaborately designed material-Na2Fe0.97Ni0.03SiO4@C-displays superior Na-storage properties of around 197.51 mA h g-1 (corresponding to 1.43 Na+ intercalation) at 0.1 C within 1.5-4.5 V along with desirable capacity retention (84.44% after 100 cycles), and the rate capability is also markedly enhanced (a capacity of 133.62 mA h g-1 at 2 C). Such the effective methodology employed in this work opens a potential pathway to synthesize the silicate cathode material with excellent electrochemical properties.

Carbon-Coated Yttria Hollow Spheres as Both Sulfur Immobilizer and Catalyst of Polysulfides Conversion in Lithium-Sulfur Batteries.

Li-S battery has tremendous application prospect on account of the high theoretical specific capacity and large energy density, while its large-scale application is impeded by the severe shuttle effect and the slow electrochemical kinetics of polysulfides conversion. Herein, the Lewis acidic yttria hollow spheres (YHS) are rationally designed as both sulfur immobilizer and catalyst of polysulfides conversion for the advanced Li-S batteries. It can be known that the Lewis acidic yttria can effectively capture the Lewis basic polysulfides and thus mitigate the shuttle effect of Li-S battery; besides, yttria shows the enhanced catalytic effect for the kinetics of interconversion reaction from polysulfides to Li2S. As a result, either as a sulfur host or as the separator coating, yttria plays a vital part in realizing the high specific discharge capacity and good cycle stability for Li-S battery. In particular, Li-S battery with YHS@C/S cathode and YHS/CNT-0.6- modified separator (2.1 mg cm-2 active material loading) shows a good specific discharge capacity of 912.5 mAh g-1 at 0.5C. Even after 200 steady cycles, the discharge specific capacity can keep as 842.3 mAh g-1, and the capacity decay rate is only 0.038% per cycle. When active material areal loading is increased to 4.24 mg cm-2, it still maintains a considerable areal capacity of 3.79 mAh cm-2. In consequence, the synergy of polysulfides confinement and catalytic conversion reaction provides a meaningful exploration for achieving the high performance of Li-S batteries.

Tellurium Surface Doping to Enhance the Structural Stability and Electrochemical Performance of Layered Ni-Rich Cathodes.

The Ni-rich layered oxides are considered as a candidate of next-generation cathode materials for high energy density lithium-ion batteries; however, the finite cyclic life and poor thermostability impede their practical applications. There is often a tradeoff between structure stability and high capacity because the intrinsical instability of oxygen framework will lead to the structural transformation of Ni-rich materials. Because of the strong binding energy between the Te atom and O atom, herein a new technology of surface tellurium (Te) doping in the Ni-rich layered oxide (LiNi0.88Co0.09Al0.03O2) is proposed to settle the above predicament. Based on density function theory calculations and experiment analysis, it has been confirmed that the doped Te6+ ions are positioned in the TM layer near the oxide surface, which can constrain the TM-O slabs by strong Te-O bonds and prevent oxygen release from the surface, thus enhancing the stability of the lattice framework in deep delithium (>4.3 V). Especially, 1 wt % Te doping (Te 1%-NCA) shows the superiority in performance improvement. Furthermore, the reversibility of H2-H3 phase transition is also improved to relieve effectively the capacity decline and the structural transformations at extended cycling, which can facilitate the fast Li+ diffusion kinetic. Consequently, Te 1%-NCA cathode exhibits the improved cycling stability even at high voltages (4.5 and 4.7 V), good rate capability (159.2 mA h g-1 at 10 C), and high thermal stability (the peak temperature of 258 °C). Therefore, the appropriate Te surface doping provides a significant exploration for industrial development of the high-performance Ni-rich cathode materials with high capacity and structural stability.

Preparation and Performance of the Heterostructured Material with a Ni-Rich Layered Oxide Core and a LiNi0.5Mn1.5O4-like Spinel Shell.

The LiNi1- x- yCo xAl yO2 (NCA)-layered materials are regarded as a research focus of power lithium-ion batteries (LIBs) because of their high capacity. However, NCA materials are still up against the defects of cation mixing and surface erosion of electrolytes. Herein, a novel design strategy is proposed to obtain a heterostructured cathode material with a high-capacity LiNi0.88Co0.09Al0.03O2 layer ( R3̅ m) core and a stable LiNi0.5Mn1.5O4-like spinel ( Fd3̅ m) shell, which is prepared through spontaneous redox reaction of the precursor with KMnO4 in an alkaline solution and subsequent calcination procedure. The structure, morphology, element distribution, and electrochemical performances of the as-prepared NCA are studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. The results show that the LiNi0.5Mn1.5O4-like spinel ( Fd3̅ m) shell layer with a robust cubic close-packed crystal structure is uniformly adhered to the surface of the NCA and can availably suppress the side reactions with the electrolyte and surface-phase transformation, which will facilitate insertion/extraction of Li+ ions during cycling. Benefiting from the enhanced structural stability and improved kinetics, the heterostructured NCA delivers a better cycling performance. The discharge specific capacity is as high as 153.7 mA h g-1 at 10 C, and even at high charge voltage of 4.5 V, the capacity retention can still increase 11% at 1 C (200 mA g-1) after 100 cycles. Besides, the material exhibits a prominent thermal stability of 248 °C at 4.3 V. Therefore, this novel structure design strategy can contribute to the development and commercialization of high-performance cathode materials for power LIBs.

N-Heterocyclic carbene copper catalyzed quinoline synthesis from 2-aminobenzyl alcohols and ketones using DMSO as an oxidant at room temperature.

A facile and practical process for the synthesis of quinolines through an N-heterocyclic carbene copper catalyzed indirect Friedländer reaction from 2-aminobenzyl alcohol and aryl ketones using DMSO as an oxidant at room temperature is reported. A series of quinolines were synthesized in acceptable yields.

Caging Na3V2(PO4)2F3 Microcubes in Cross-Linked Graphene Enabling Ultrafast Sodium Storage and Long-Term Cycling.

Sodium-ion batteries are widely regarded as a promising supplement for lithium-ion battery technology. However, it still suffers from some challenges, including low energy/power density and unsatisfactory cycling stability. Here, a cross-linked graphene-caged Na3V2(PO4)2F3 microcubes (NVPF@rGO) composite via a one-pot hydrothermal strategy followed by freeze drying and heat treatment is reported. As a cathode for a sodium-ion half-cell, the NVPF@rGO delivers excellent cycling stability and rate capability, as well as good low temperature adaptability. The structural evolution during the repeated Na+ extraction/insertion and Na ions diffusion kinetics in the NVPF@rGO electrode are investigated. Importantly, a practicable sodium-ion full-cell is constructed using a NVPF@rGO cathode and a N-doped carbon anode, which delivers outstanding cycling stability (95.1% capacity retention over 400 cycles at 10 C), as well as an exceptionally high energy density (291 Wh kg-1 at power density of 192 W kg-1). Such micro-/nanoscale design and engineering strategies, as well as deeper understanding of the ion diffusion kinetics, may also be used to explore other micro-/nanostructure materials to boost the performance of energy storage devices.

Encapsulation of CoS x Nanocrystals into N/S Co-Doped Honeycomb-Like 3D Porous Carbon for High-Performance Lithium Storage.

A honeycomb-like 3D N/S co-doped porous carbon-coated cobalt sulfide (CoS, Co9S8, and Co1-x S) composite (CS@PC) is successfully prepared using polyacrylonitrile (PAN) as the nitrogen-containing carbon source through a facile solvothermal method and subsequent in situ conversion. As an anode for lithium-ion batteries (LIBs), the CS@PC composite exhibits excellent electrochemical performance, including high reversible capacity, good rate capability, and cyclic stability. The composite electrode delivers specific capacities of 781.2 and 466.0 mAh g-1 at 0.1 and 5 A g-1, respectively. When cycled at a current density of 1 A g-1, it displays a high reversible capacity of 717.0 mAh g-1 after 500 cycles. The ability to provide this level of performance is attributed to the unique 3D multi-level porous architecture with large electrode-electrolyte contact area, bicontinuous electron/ion transport pathways, and attractive structure stability. Such micro-/nanoscale design and engineering strategies may also be used to explore other nanocomposites to boost their energy storage performance.

Nitrogen/sulfur co-doped hollow carbon nanofiber anode obtained from polypyrrole with enhanced electrochemical performance for Na-ion batteries.

Polypyrrole and sulfur derived hollow carbon nanofibers co-doped with nitrogen/sulfur are synthesized and applied as the anode for Na-ion batteries (NIBs). Successful doping of hollow carbon nanofiber with nitrogen and sulfur is confirmed by X-ray photoelectron spectroscopy, scanning and tunneling electron microscopy. Further analysis certifies that sulfur doping has a significant impact in improving the elecctrochemical performance of the carbon-based anodes for NIBs. The obtained N-doped hollow carbon nanofiber and N/S co-doped hollow carbon nanofiber exhibit similar morphologies but different electrochemical behavior. As expected, the N/S co-doped hollow carbon nanofiber anode exhibits enhanced electrochemical performance, including high specific capacity, outstanding long-term stability, and good rate stability.

Nanorod-Nanoflake Interconnected LiMnPO4·Li3V2(PO4)3/C Composite for High-Rate and Long-Life Lithium-Ion Batteries.

Olivine-type structured LiMnPO4 has been extensively studied as a high-energy density cathode material for lithium-ion batteries. However, preparation of high-performance LiMnPO4 is still a large obstacle due to its intrinsically sluggish electrochemical kinetics. Recently, making the composites from both active components has been proven to be a good proposal to improve the electrochemical properties of cathode materials. The composite materials can combine the advantages of each phase and improve the comprehensive properties. Herein, a LiMnPO4·Li3V2(PO4)3/C composite with interconnected nanorods and nanoflakes has been synthesized via a one-pot, solid-state reaction in molten hydrocarbon, where the oleic acid functions as a surfactant. With a highly uniform hybrid architecture, conductive carbon coating, and mutual cross-doping, the LiMnPO4·Li3V2(PO4)3/C composite manifests high capacity, good rate capability, and excellent cyclic stability in lithium-ion batteries. The composite electrodes deliver a high reversible capacity of 101.3 mAh g-1 at the rate up to 16 C. After 4000 long-term cycles, the electrodes can still retain 79.39% and 72.74% of its maximum specific discharge capacities at the rates of 4C and 8C, respectively. The results demonstrate that the nanorod-nanoflake interconnected LiMnPO4·Li3V2(PO4)3/C composite is a promising cathode material for high-performance lithium ion batteries.