For future applications in portable electronics, electric vehicles and grid storage, batteries with higher energy storage density than existing lithium ion batteries need to be developed. Recent ...efforts in this direction have focused on high-capacity electrode materials such as lithium metal, silicon and tin as anodes, and sulphur and oxygen as cathodes. Lithium metal would be the optimal choice as an anode material, because it has the highest specific capacity (3,860 mAh g(-1)) and the lowest anode potential of all. However, the lithium anode forms dendritic and mossy metal deposits, leading to serious safety concerns and low Coulombic efficiency during charge/discharge cycles. Although advanced characterization techniques have helped shed light on the lithium growth process, effective strategies to improve lithium metal anode cycling remain elusive. Here, we show that coating the lithium metal anode with a monolayer of interconnected amorphous hollow carbon nanospheres helps isolate the lithium metal depositions and facilitates the formation of a stable solid electrolyte interphase. We show that lithium dendrites do not form up to a practical current density of 1 mA cm(-2). The Coulombic efficiency improves to ∼ 99% for more than 150 cycles. This is significantly better than the bare unmodified samples, which usually show rapid Coulombic efficiency decay in fewer than 100 cycles. Our results indicate that nanoscale interfacial engineering could be a promising strategy to tackle the intrinsic problems of lithium metal anodes.
Understanding the local cation order in the crystal structure and its correlation with electrochemical performances has advanced the development of high‐energy Mn‐rich cathode materials for Li‐ion ...batteries, notably Li‐ and Mn‐rich layered cathodes (LMR, e.g., Li1.2Ni0.13Mn0.54Co0.13O2) that are considered as nanocomposite layered materials with C2/m Li2MnO3‐type medium‐range order (MRO). Moreover, the Li‐transport rate in high‐capacity Mn‐based disordered rock‐salt (DRX) cathodes (e.g., Li1.2Mn0.4Ti0.4O2) is found to be influenced by the short‐range order of cations, underlining the importance of engineering the local cation order in designing high‐energy materials. Herein, the nanocomposite is revealed, with a heterogeneous nature (like MRO found in LMR) of ultrahigh‐capacity partially ordered cathodes (e.g., Li1.68Mn1.6O3.7F0.3) made of distinct domains of spinel‐, DRX‐ and layered‐like phases, contrary to conventional single‐phase DRX cathodes. This multi‐scale understanding of ordering informs engineering the nanocomposite material via Ti doping, altering the intra‐particle characteristics to increase the content of the rock‐salt phase and heterogeneity within a particle. This strategy markedly improves the reversibility of both Mn‐ and O‐redox processes to enhance the cycling stability of the partially ordered DRX cathodes (nearly ≈30% improvement of capacity retention). This work sheds light on the importance of nanocomposite engineering to develop ultrahigh‐performance, low‐cost Li‐ion cathode materials.
The multi‐phase heterogeneous nature of ultrahigh‐energy Mn‐based partially disordered cathodes is revealed by combined experimental and computational studies. This fundamental understanding enables the novel nanocomposite design, which controls a phase fraction within a single particle. Consequently, T30 cathode via a nanocomposite engineering shows more reversible redox properties and a superior cycle retention, showing new insights into developing advanced Mn‐based cathodes.
Developing earth-abundant, active and stable electrocatalysts which operate in the same electrolyte for water splitting, including oxygen evolution reaction and hydrogen evolution reaction, is ...important for many renewable energy conversion processes. Here we demonstrate the improvement of catalytic activity when transition metal oxide (iron, cobalt, nickel oxides and their mixed oxides) nanoparticles (∼20 nm) are electrochemically transformed into ultra-small diameter (2-5 nm) nanoparticles through lithium-induced conversion reactions. Different from most traditional chemical syntheses, this method maintains excellent electrical interconnection among nanoparticles and results in large surface areas and many catalytically active sites. We demonstrate that lithium-induced ultra-small NiFeOx nanoparticles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base. We achieve 10 mA cm(-2) water-splitting current at only 1.51 V for over 200 h without degradation in a two-electrode configuration and 1 M KOH, better than the combination of iridium and platinum as benchmark catalysts.
The reversible electrochemical insertion of multivalent ions into materials has promising applications in many fields, including batteries, seawater desalination, element purification, and wastewater ...treatment. However, finding materials that allow for the insertion of multivalent ions with fast kinetics and stable cycling has proven difficult because of strong electrostatic interactions between the highly charged insertion ions and atoms in the host framework. Here, an open framework nanomaterial, copper hexacyanoferrate, in the Prussian Blue family is presented that allows for the reversible insertion of a wide variety of monovalent, divalent, and trivalent ions (such as Rb+, Pb2+, Al3+, and Y3+) in aqueous solution beyond that achieved in previous studies. Electrochemical measurements demonstrate the unprecedented kinetics of multivalent ion insertion associated with this material. Synchrotron X‐ray diffraction experiments point toward a novel vacancy‐mediated ion insertion mechanism that reduces electrostatic repulsion and helps to facilitate the observed rapid ion insertion. The results suggest a new approach to multivalent ion insertion that may help to advance the understanding of this complex phenomenon.
Copper hexacyanoferrate exhibits rapid and reversible insertion of a wide variety of multivalent ions. Synchrotron X‐ray diffraction experiments demonstrate the presence of a novel ion insertion mechanism that is facilitated by vacancies within the open framework crystal structure. This may allow the insertion of partially hydrated ions, which reduces electrostatic interactions between the ions and the host framework.
A challenge for tissue engineering is producing three-dimensional (3D), vascularized cellular constructs of clinically relevant size, shape and structural integrity. We present an integrated ...tissue-organ printer (ITOP) that can fabricate stable, human-scale tissue constructs of any shape. Mechanical stability is achieved by printing cell-laden hydrogels together with biodegradable polymers in integrated patterns and anchored on sacrificial hydrogels. The correct shape of the tissue construct is achieved by representing clinical imaging data as a computer model of the anatomical defect and translating the model into a program that controls the motions of the printer nozzles, which dispense cells to discrete locations. The incorporation of microchannels into the tissue constructs facilitates diffusion of nutrients to printed cells, thereby overcoming the diffusion limit of 100-200 μm for cell survival in engineered tissues. We demonstrate capabilities of the ITOP by fabricating mandible and calvarial bone, cartilage and skeletal muscle. Future development of the ITOP is being directed to the production of tissues for human applications and to the building of more complex tissues and solid organs.
Abundant availability of seawater grants economic and resource‐rich benefits to water electrolysis technology requiring high‐purity water if undesired reactions such as chlorine evolution reaction ...(CER) competitive to oxygen evolution reaction (OER) are suppressed. Inspired by a conceptual computational work suggesting that OER is kinetically improved via a double activation within 7 Å‐gap nanochannels, RuO2 catalysts are realized to have nanoscopic channels at 7, 11, and 14 Å gap in average (dgap), and preferential activity improvement of OER over CER in seawater by using nanochanneled RuO2 is demonstrated. When the channels are developed to have 7 Å gap, the OER current is maximized with the overpotential required for triggering OER minimized. The gap value guaranteeing the highest OER activity is identical to the value expected from the computational work. The improved OER activity significantly increases the selectivity of OER over CER in seawater since the double activation by the 7 Å‐nanoconfined environments to allow an OER intermediate (*OOH) to be doubly anchored to Ru and O active sites does not work on the CER intermediate (*Cl). Successful operation of direct seawater electrolysis with improved hydrogen production is demonstrated by employing the 7 Å‐nanochanneled RuO2 as the OER electrocatalyst.
In this work, a nanochanneled‐RuO2 catalyst is experimentally demonstrated using lithiation and de‐lithiation of RuO2 nanoparticles. An associative activation that works on a single specific peroxide intermediate (OOH) enables the selectively enhanced electrochemical oxygen evolution reaction to compare with the chlorine evolution reaction by breaking linear scaling relationships.
Sodium-ion batteries have recently attracted significant attention as an alternative to lithium-ion batteries because sodium sources do not present the geopolitical issues that lithium sources might. ...Although recent reports on cathode materials for sodium-ion batteries have demonstrated performances comparable to their lithium-ion counterparts, the major scientific challenge for a competitive sodium-ion battery technology is to develop viable anode materials. Here we show that a hybrid material made out of a few phosphorene layers sandwiched between graphene layers shows a specific capacity of 2,440 mA h g(-1) (calculated using the mass of phosphorus only) at a current density of 0.05 A g(-1) and an 83% capacity retention after 100 cycles while operating between 0 and 1.5 V. Using in situ transmission electron microscopy and ex situ X-ray diffraction techniques, we explain the large capacity of our anode through a dual mechanism of intercalation of sodium ions along the x axis of the phosphorene layers followed by the formation of a Na3P alloy. The presence of graphene layers in the hybrid material works as a mechanical backbone and an electrical highway, ensuring that a suitable elastic buffer space accommodates the anisotropic expansion of phosphorene layers along the y and z axial directions for stable cycling operation.
Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant ...attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Here, we demonstrate physical and mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of lithiated Si by lessening the tensile stress concentrations in Si structures. This study will contribute to improved design of Si structures at the electrode level for high-performance Li-ion batteries.
The wet‐chemical processability of sulfide solid electrolytes (SEs) provides intriguing opportunities for all‐solid‐state batteries. Thus far, sulfide SEs are wet‐prepared either from solid ...precursors suspended in solvents (suspension synthesis) or from homogeneous solutions using SEs (solution process) with restricted composition spaces. Here, a universal solution synthesis method for preparing sulfide SEs from precursors, not only Li2S, P2S5, LiCl, and Na2S, but also metal sulfides (e.g., GeS2 and SnS2), fully dissolved in an alkahest: a mixture solvent of 1,2‐ethylenediamine (EDA) and 1,2‐ethanedithiol (EDT) (or ethanethiol). Raman spectroscopy and theoretical calculations reveal that the exceptional dissolving power of EDA–EDT toward GeS2 is due to the nucleophilicity of the thiolate anions that is strong enough to dissociate the GeS bonds. Solution‐synthesized Li10GeP2S12, Li6PS5Cl, and Na11Sn2PS12 exhibit high ionic conductivities (0.74, 1.3, and 0.10 mS cm−1 at 30 °C, respectively), and their application for all‐solid‐state batteries is successfully demonstrated.
The universal solution synthesis of sulfide solid electrolytes is first demonstrated. The alkahest solvent, 1,2‐ethylenediamine–1,2‐ethanedithiol, fully dissolves not only Li2S (or Na2S), P2S5, and LiCl, but also metal sulfides (e.g., GeS2 and SnS2), forming homogeneous solid electrolyte solutions. Solution‐synthesized Li10GeP2S12, Li6PS5Cl, and Na11Sn2PS12 exhibit high ionic conductivities, and their applicability to all‐solid‐state batteries is successfully demonstrated.
Stable cycling of lithium metal anode is challenging due to the dendritic lithium formation and high chemical reactivity of lithium with electrolyte and nearly all the materials. Here, we demonstrate ...a promising novel electrode design by growing two-dimensional (2D) atomic crystal layers including hexagonal boron nitride (h-BN) and graphene directly on Cu metal current collectors. Lithium ions were able to penetrate through the point and line defects of the 2D layers during the electrochemical deposition, leading to sandwiched lithium metal between ultrathin 2D layers and Cu. The 2D layers afford an excellent interfacial protection of Li metal due to their remarkable chemical stability as well as mechanical strength and flexibility, resulting from the strong intralayer bonds and ultrathin thickness. Smooth Li metal deposition without dendritic and mossy Li formation was realized. We showed stable cycling over 50 cycles with Coulombic efficiency ∼97% in organic carbonate electrolyte with current density and areal capacity up to the practical value of 2.0 mA/cm2and 5.0 mAh/cm2, respectively, which is a significant improvement over the unprotected electrodes in the same electrolyte.
PDF
