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Developing large capacity electrode with fast charging capability has always been our goal for high-energy Li-ion batteries. To design a superior electrode, large enough capacity, suitable voltage plateau and good ionic/electronic conductivity need to be taken into account at the same time. Herein, by fusing the semiconductor Ge into nonmetal P, a novel metallic GexP60-x solid solution with wide range tuneable region is proposed, which is proved a kind of Ge-P binary alloy instead of typical ionic/covalent compound. The synthesized GexP60-x is not a metal phophide, which is in contradictory to our conventional view. Attributed from its unique phosphorus-like layered structure, those GexP60-x alloys possess a high conductivity (∼2.4 × 106 S/m). More specially, the Ge-P interaction is not a strong covalent bond like metal phosphides and thereby, the conversion reaction process based on chemical bond breaking in metal phosphides would not take place in those GexP60-x alloys, being replaced by alloying-type mechanism only. Therefore, such GexP60-x alloys are the first ones which can simultaneously exhibit both large capacity (>1800 mAh/g), unexpected high reversibility (ICE>90%) and suitable voltage plateau (∼0.5 V), delivering 770 mAh/g within 15 min with low yet safe voltage for fast-charging battery. This discovery that nonmetallic and semiconductor elements can form conductive alloys based on solid solution chemistry injects fresh blood into high-performanced anode families and offers a new strategy for material design toward advanced fast charging electrodes for energy storage.

Due to climate variation and global warming, utilization of renewable energy becomes increasingly imperative. Rechargeable potassium-ion batteries (PIBs) have lately attracted much attention due to their earth-abundance and cost-effectiveness. Because soft carbon materials are cheap, abundant, and safe, extensive feasible research studies have indicated that they could become promising anode materials for PIBs. In spite of gaining achievements, fundamental questions regarding effects of the basic structure unit inside soft carbon on potassium storage potential have not been sufficiently addressed yet. Here, a series of soft carbon pyrolyzed from 900 to 2900 °C were systematically and quantitatively characterized by combining Raman spectroscopy, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, X-ray pair distribution function analysis, and advanced evaluation of wide-angle X-ray scattering data. All these characterizations reveal structural details of soft carbon with increasing pyrolysis temperature. Our results show that the potassium storage behavior, especially the potential plateau is closely correlated to non-uniformity in interlayer distance and defect concentration in soft carbon, which is further confirmed by reverse Monte Carlo (RMC) modeling and density functional theory calculation. On the basis of these results, optimizing strategies are discussed to design an advanced soft carbon anode. This work provides significant insights into the structure engineering of soft carbon for high-performance rechargeable PIBs.

The small energy density and chemomechanical degradation of layered manganese oxide limit practical application to sodium-ion batteries (SIBs). Typically, Na

For reaching high-performance of electrode materials, it is generally believed that understanding the structure evolution and heterogeneous alignment effect is the key. Presently, a very simple and universally applicable self-healing method is investigated to prepare defect-free Prussian blue analogs (PBAs) that reach their theoretical capacity as cathode materials for sodium-ion batteries (SIBs). For direct imaging of the local structure and the dynamic process at the atomic scale, we deliver a fast ion-conductive nickel-based PBA that enables rapid Na+ extraction/insertion within 3 minutes and a capacity retention of nearly 100% over 4000 cycles. This guest-ion disordered and quasi-zero-strain nonequilibrium solid–solution reaction mechanism provides an effective guarantee for realizing long-cycle life and high-rate capability electrode materials that operate via reversible two-phase transition reaction. Unconventional materials and mechanisms that enable reversible insertion/extraction of ions in low-cost metal–organic frameworks (MOFs) within minutes have implications for fast-charging devices, grid-scale energy storage applications, material discovery, and tailored modification.

Prussian Blue Analogs (PBAs) such as copper hexacyanoferrate (CuHCF) are traditional intercalation cathodes for rechargeable Na-ion batteries. However, the electrochemical performance of these PBAs suffers from insufficient activation and sharp performance deterioration. Here, the insufficient electrochemical activity and frame deformation issues in the CuHCF cathodes were investigated to enhance their specific capacity and improve their cycling stability. The high-crystallinity CuHCF nanosheets (CuHCF-P) with low-water-content were synthesized by a pyrophosphate-assistant co-precipitation method. It has a highly reversible 1.5-Na insertion/desertion capability with a specific capacity of ~120 mAh g−1 at 0.1 C, which is the highest among all the CuHCF cathodes reported. First-principle study and XPS detection demonstrate that both Cu and Fe are redox-active centers in CuHCF-P cathode, which facilitates a high Na+ storage capability. And the decrease of water content in CuHCF framework increases Fe/Cu 3d-orbital occupy-sites, which activates both of the transition-metals. Furthermore, the full cells fabricated with as-prepared CuHCF-P cathode and commercial hard carbon anode exhibit excellent performances with a reversible capacity of 109 mAh g−1 at 0.1 C over 200 cycles.

Solid-state electrolytes (SSEs) with high ionic conductivities are the key components in solid-state batteries, and the ionic conductivities of SSEs are strongly related to their underlying crystal...

P2-type Na2/3Ni1/3Mn2/3O2 (P2-NaNM) is a promising cathode material for practical applications in Na-ion batteries due to its high capacity. However, the rearrangement of Na+/vacancy order and cathodic charge order across the Na extraction/intercalation and structural rearrangements of P2-NaNM at high voltages result in rapid capacity fading and insufficient rate capability. Here, a combined structural modulation strategy was presented to solve these challenges via reducing the Na layers spacing through substituting Na sites by Mg ions while simultaneously stabilizing the transition metal (TM) layers through Mg/Ti co-doping. Benefited from the symbiotic effect, P2-NaNM exhibits a significantly enhanced cycling stability and rate capability in the voltage range of 3.0–4.4 ​V. We further revealed that Mn remains Mn4+ while Ni2+ becomes Ni3+ at the surface of Mg/Ti co-substituted P2-NaNM upon charge/discharge process.

Taking into the consideration safety, environmental impact, and economic issue, the construction of aqueous batteries based on aqueous electrolyte has become an indispensable technical option for large-scale electrical energy storage. The narrow electrochemical window is the main problem of conventional aqueous electrolyte. Here, an economical room-temperature inorganic hydrated molten salt (RTMS) electrolyte with a large electrochemical stability window of 3.1 V is proposed. Compared with organic fluorinated molten salts, RTMS is composed of lithium nitrate hydrate and sodium nitrate with much lower cost. Based on the RTMS electrolyte, a hybrid Li/Na-ion full battery is fabricated from cobalt hexacyanoferrate cathode (NaCoHCF) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) anode. The full cell with the RTMS electrolyte exhibits a fantastic performance with high capacity of 139 mAh g-1 at 1 C, 90 mAh g-1 at 20 C, and capacity retention of 94.7% over 500 cycles at 3 C. The excellent performances are contributed to the unique properties of RTMS with a large electrochemical window, solvated H2 O free and high mobility of Li+ , which exhibits excellent Li-ions insertion and extraction capacity of NaCoHCF. This RTMS cell provides a new economic choice for large-scale energy storage.

Aqueous sodium-ion batteries (ASIBs) show superior characteristics with high safety and low cost for large scale energy storage systems. However, easily occurring hydrogen evolution at a negative potential is a huge barrier to the application of anode materials in ASIBs. Even the most promising insert-type anode material, NaTi2(PO4)3 (NTP), cannot be commercialized due to its inadequate operating potential (−0.807 V vs. Ag/AgCl) that is close to the hydrogen evolution potential (−0.817 V vs. Ag/AgCl). Here, we report a redox potential regulation strategy to overcome this technical problem by integrating the redox couples of Ti4+/Ti3+ and Fe3+/Fe2+ to yield Na1.5Ti1.5Fe0.5(PO4)3 (NTFP) and increasing its operating potential up to −0.721 V vs. Ag/AgCl, which effectively prevents the potential overlap with the reductive decomposition of H2O. Importantly, the excellent electrochemical properties and low energy consuming synthetic route to NTFP open a new perspective to energetically develop low cost and highly stable ASIBs as a large-scale energy storage tool.

Regulating material properties by accurately designing its structure has always been a research hotspot. In this study, by a simple and eco-friendly mechanical ball milling, we could successfully engineer the defect degree of the graphite. Moreover, according to the accurate deconstruction of the structure by atomic pair distribution function analysis (PDF) and X-ray absorption near-edge structure analysis (XANES), those structural defects of the ball-milled graphite (BMG) mainly exist as carbon atom vacancies within the graphene structure, which are beneficial to enhance the lithium and sodium storage performance of BMG. Therefore, BMG-30 h exhibits superior lithium and sodium storage performance.

The Stober method is a highly efficient synthesis strategy for homogeneous monodisperse polymer colloidal spheres and carbon spheres. This work delivers an extended Stober method and investigates the synthesis process. By calcining the precursor under appropriate conditions, solid secondary particles of amorphous carbon (SSAC) and hollow secondary particles of graphitized carbon (HSGC) can be directly synthesized. The two materials have a nano-primary particle structure and a closely-packed sub-micron secondary particle structure, which can be used in energy storage. We find that SSAC and HSGC have high potassium-ion storage capacity with reversible capacities of 274 mA h g−1 and 283 mA h g−1 at 20 mA g−1 respectively. Significantly, SSAC has better rate performance with a specific capacity of 107 mA h g−1 at 1 A g−1.

LiCoO

Herein, the coordination-induced increase in the electron density of fused C6 rings in MOFs as high performance anode materials for Li+ ion batteries is described. Zn-PTCA is able to deliver a high specific capacity of 700 mA h g−1 at 50 mA g−1 and exhibits excellent cycle performance over 1100 cycles and good rate capability.

Hard carbon (HC) is one of the most promising anode materials for sodium-ion batteries (SIBs) due to its suitable potential and high reversible capacity. At the same time, the correlation between carbon local structure and sodium-ion storage behavior is not clearly understood. In this paper, the two series of HC materials with perfect spherical morphology and tailored microstructures were designed and successfully produced using resorcinol formaldehyde (RF) resin as precursor. Via hydrothermal self-assembly and controlled pyrolysis, RF is a flexible precursor for high-purity carbon with a wide range of local-structure variation. Using these processes, one series of five representative RF-based HC nanospheres with varying degrees of graphitization were obtained from an RF precursor at different carbonization temperatures. The other series of HC materials with various microscopic carbon layer lengths and shapes was achieved by carbonizing five RF precursors with different cross-linking degrees at a single c...

The detrimental effects on the electrochemical performances of high-capacity nickel-rich layered oxide cathode LiNi0.8Co0.1Mn0.1O2 (Ni-rich NCM) are continuous irreversible phase transition, particle disintegration, and unstable cathode-electrolyte interface, which are usually induced by deleterious cathode-electrolyte reactions. Here, we report those side reactions are limited by a uniform inorganic/polymer cathode-electrolyte-interface (CEI) formed by in-situ electrochemical oxidation of a trace amount of dual additives in the traditional carbonate-based electrolytes. This CEI film not only eliminates the adverse cathode-electrolyte interface reaction and prevents the electrolyte penetration into the grain boundary but also hinders the formation of inactive rock-salt phase on the material surface. More significantly, it is demonstrated that this N, B, O-rich interface layer offers a fast Li+ diffusion kinetic process to ensure a high-rate performance of the cathode, which is still a technical difficulty for the large application of Ni-rich NCM. Here, under the synergistic effect of dual additives containing lithium bis(oxalate)borate (LiBOB) and dopamine, the cell exhibits high-capacity retention over 92% after 200 cycles at 1 C, and also obtain a high specific capacity of 118 mA h g−1 at the high rate of 20 C. Building a stable and effect Li+-ion conductive interface film by optimizing the electrolyte formula is a facial and effective approach to develop aggressive high-capacity cathodes for high-energy storage applications.

Prussian blue analogs (PBAs) with stable framework structures are ideal cathodes for rechargeable sodium-ion batteries. The chelating agent-assisted coprecipitate method is an effective way to obtain low-defect PBAs that can limit the appearance of too many vacancies and water molecules and achieve an optimized Na-storage performance. However, for this method, the mechanism of chelating agent-assisted synthesis is still unclear. Herein, the synthesis process of nickel hexacyanoferrate (NiHCF) has been investigated by in situ infrared spectroscopy detection. The results show that the chelating agent oxalate slows down the nucleation process and effectively inhibits the formation of the Fe-C≡N-Ni frame in the aging process, producing highly crystallized and low-defect NiHCF samples. High-quality NiHCF presents a high specific capacity of 86.3 mAh g

Insufficient durability of proton exchange membrane fuel cells (PEMFCs) remains one of the important factors hindering their large-scale commercial applications. To investigate the degradation mechanism, we describe the durability test of 10-kW metal plate fuel cell stack containing 30 cells under dynamic driving cycles. After 600 h of testing, the mean voltage decay percentage of the stack under the rated current densities of 1000 mA cm−2 is 2.67%. A semi-empirical model is introduced to predict the remaining useful life of the stack, and the result satisfies the 5000 h target set by the department of energy (DOE). Three cells with the highest, moderate, and lowest rate of decay are disassembled and characterized by electrochemical and physical methods. Scanning electron microscopy (SEM) shows that the cross-section of the cathode catalyst layer (CL) of the 30# MEA has the lowest thickness of 8.45 μm compared with the fresh sample and other samples. Transmission electron microscopy (TEM) shows serious agglomeration of the 30# catalyst. These observations led to serious performance degradation in the 30# cell. The defects in the design of the stack structure leads to the attenuation of the consistency of the stack and further explains stack performance degradation.

This work proposes a semi-empirical model-based prognostics method which can achieve degradation prediction and estimate the remaining useful life of proton exchange membrane fuel cells (PEMFCs) under automotive profiles. Based on the polarization behavior of PEMFCs, a voltage prediction model is proposed to predict the degradation trend of PEMFCs by introducing degradation models of electrochemical surface area and equivalent resistance, respectively. In addition, a recovery factor is introduced to characterize the performance recovery of PEMFCs after shutdown and restart. When analyzing the aging parameters that affect the performance of PEMFCs, system identification is introduced to achieve the one-to-one correspondence between the aging parameters and the experimental conditions. Two experimental cases with different PEMFCs, which are loaded with different profiles, have been performed to validate the proposed voltage prediction model's accuracy. The results show that the proposed voltage prediction model can achieve accurate degradation trend prediction of PEMFCs, whether predicting the complete profile or the degradation corresponding to the maximum current.

Prussian blue analogues (PBAs) have attracted great interests due to their stable and open framework structures as novel electrode materials in rechargeable sodium-ion batteries (SIBs). However, Na+ diffusion within electrode materials not only relates to many confined spaces formed by lattice frameworks for Na-ion storage but also highly involves with Na+ migration channel generated by lattice periodic arrangement. In this work, the correlation between PBAs crystallinity and Na+ insertion/extraction properties were systematically investigated. High-crystallized nickel hexacyanoferrate (NiHCF-h) exhibits a fast Na-ion migration process with a high diffusion coefficient of 8.1 × 10−10 cm−2 s−2, and a high capacity retention of 73.7% at 4.25 A g−1. Even crystal size is six times larger than low-crystallized nickel hexacyanoferrate (NiHCF-l), the high-crystallized NiHCF-h shows a faster Na+ insertion/extraction process. The basic structural characterization and pair distribution function (PDF) analysis show that NiHCF-h has a long-range lattice periodicity, enabling Na ions transfer more easily through migration channels. This demonstrates that the crystallinity of PBAs is an extremely important factor in ionic migration process, even with proved vacancies and H2O molecules in PBAs framework structure.

Rechargeable and affordable aqueous zinc-ion batteries (ZIBs) with high energy density are needed for large-scale energy storage systems. However, the development of ZIBs has stagnated due to the lack of stable high-capacity cathode materials. Here, a typical spinel ZnV2O4 has been investigated as a ZIB cathode, and a significant electroactivation reaction was observed during the initial electrochemical cycles. After electroactivation, ZnV2O4 exhibits a high reversible capacity of 312 mAh g−1 and retains a capacity of 206 mAh g−1 over 1000 cycles at a high rate of 10 C. The electroactivation process was then analyzed via in-situ XRD, ex-situ PDF, ex-situ HADDF-STEM, ex-situ XPS, and various electrochemical measurements. The electroactivation enhances the surface electrochemical reaction with self-adaptive adjustment of the lattice structure. This guarantees outstanding electrochemical performance. The encouraging results deepen our understanding of rechargeable aqueous batteries and offer insight into the design of high-performance electrode materials for rechargeable aqueous ZIBs.

Structural isomerism of colloidal semiconductor nanocrystals has been largely unexplored. Here, we report one pair of structural isomers identified for colloidal nanocrystals which exhibit thermally-induced reversible transformations behaving like molecular isomerization. The two isomers are CdS magic-size clusters with sharp absorption peaks at 311 and 322 nm. They have identical cluster masses, but slightly different structures. Furthermore, their interconversions follow first-order unimolecular reaction kinetics. We anticipate that such isomeric kinetics are applicable to a variety of small-size functional nanomaterials, and that the methodology developed for our kinetic study will be helpful to investigate and exploit solid–solid transformations in other semiconductor nanocrystals. The findings on structural isomerism should stimulate attention toward advanced design and synthesis of functional nanomaterials enabled by structural transformations., Few structural isomers of colloids, with identical masses but different structures, have been identified. Here, the authors observe an interesting example of structural isomerism in a pair of semiconductor magic-size clusters, which reversibly transform between one another with first-order unimolecular reaction kinetics.