Constructing Na‐Ion Cathodes via Alkali‐Site Substitution

Na‐ion batteries have experienced rapid development over the past decade and received significant attention from the academic and industrial communities. Although a large amount of effort has been made on material innovations, accessible design strategies on peculiar structural chemistry remain elusive. An approach to in situ construction of new Na‐based cathode materials by substitution in alkali sites is proposed to realize long‐term cycling stability and high‐energy density in low‐cost Na‐ion cathodes. A new compound, [K_0.444(1)Na_1.414(1)][Mn_3/4Fe_5/4](CN)₆, is obtained through a rational control of K⁺ content from electrochemical reaction. Results demonstrate that the remaining K⁺ (≈0.444 mol per unit) in the host matrix can stabilize the intrinsic K‐based structure during reversible Na⁺ extraction/insertion process without the structural evolution to the Na‐based structure after cycles. Thereby, the as‐prepared cathode shows the remarkably enhanced structural stability with the capacity retention of >78% after 1800 cycles, and a higher average operation voltage of ≈3.65 V versus Na⁺/Na, directly contrasting the non‐alkali‐site‐substitution cathode materials. This provides new insights into alkali‐site‐substitution constructing advanced Na‐ion cathode materials.     

Sodium Storage Behavior in Natural Graphite using Ether‐based Electrolyte Systems

This work reports that natural graphite is capable of Na insertion and extraction with a remarkable reversibility using ether‐based electrolytes. Natural graphite (the most well‐known anode material for Li–ion batteries) has been barely studied as a suitable anode for Na rechargeable batteries due to the lack of Na intercalation capability. Herein, graphite is not only capable of Na intercalation but also exhibits outstanding performance as an anode for Na ion batteries. The graphite anode delivers a reversible capacity of ≈150 mAh g^?1 with a cycle stability for 2500 cycles, and more than 75 mAh g^?1 at 10 A g^?1 despite its micrometer‐size (≈100 μm). An Na storage mechanism in graphite, where Na⁺‐solvent co‐intercalation occurs combined with partial pseudocapacitive behaviors, is revealed in detail. It is demonstrated that the electrolyte solvent species significantly affect the electrochemical properties, not only rate capability but also redox potential. The feasibility of graphite in a Na full cell is also confirmed in conjunction with the Na_1.5VPO_4.8F_0.7 cathode, delivering an energy of ≈120 Wh kg^?1 while maintaining ≈70% of the initial capacity after 250 cycles. This exceptional behavior of natural graphite promises new avenues for the development of cost‐effective and reliable Na ion batteries.     

A Family of High‐Performance Cathode Materials for Na‐ion Batteries,Na3(VO1−xPO4)2 F1+2x (0 ≤ x ≤ 1): Combined First‐Principles and Experimental Study

Room‐temperature Na‐ion batteries (NIBs) have recently attracted attention as potential alternatives to current Li‐ion batteries (LIBs). The natural abundance of sodium and the similarity between the electrochemical properties of NIBs and LIBs make NIBs well suited for applications requiring low cost and long‐term reliability. Here, the first successful synthesis of a series of Na₃(VO_1?x PO₄)₂F_1+2x (0 ≤ x ≤ 1) compounds as a new family of high‐performance cathode materials for NIBs is reported. The Na₃(VO_1?x PO₄)₂F_1+2x series can function as high‐performance cathodes for NIBs with high energy density and good cycle life, although the redox mechanism varies depending on the composition. The combined first‐principles calculations and experimental analysis reveal the detailed structural and electrochemical mechanisms of the various compositions in solid solutions of Na₃(VOPO₄)₂F and Na₃V₂(PO₄)₂F₃. The comparative data for the Na _y (VO_1?x PO₄)₂F_1+2x electrodes show a clear relationship among V³⁺/V⁴⁺/V⁵⁺ redox reactions, Na⁺?Na⁺ interactions, and Na⁺ intercalation mechanisms in NIBs. The new family of high‐energy cathode materials reported here is expected to spur the development of low‐cost, high‐performance NIBs.     

Fluorinated Polyimide as a Novel High‐Voltage Binder for High‐Capacity Cathode of Lithium‐Ion Batteries

An increase in the energy density of lithium‐ion batteries has long been a competitive advantage for advanced wireless devices and long‐driving electric vehicles. Li‐rich layered oxide, xLi₂MnO₃?(1?x)LiMn_1?y?zNi_yCo_zO₂, is a promising high‐capacity cathode material for high‐energy batteries, whose capacity increases by increasing charge voltage to above 4.6 V versus Li. Li‐rich layered oxide cathode however suffers from a rapid capacity fade during the high‐voltage cycling because of instable cathode–electrolyte interface, and the occurrence of metal dissolution, particle cracking, and structural degradation, particularly, at elevated temperatures. Herein, this study reports the development of fluorinated polyimide as a novel high‐voltage binder, which mitigates the cathode degradation problems through superior binding ability to conventional polyvinylidenefluoride binder and the formation of robust surface structure at the cathode. A full‐cell consisting of fluorinated polyimide binder‐assisted Li‐rich layered oxide cathode and conventional electrolyte without any electrolyte additive exhibits significantly improved capacity retention to 89% at the 100th cycle and discharge capacity to 223–198 mA h g^?1 even under the harsh condition of 55 °C and high charge voltage of 4.7 V, in contrast to a rapid performance fade of the cathode coated with polyvinylidenefluoride binder.     

High‐Performance Manganese Hexacyanoferrate with Cubic Structure as Superior Cathode Material for Sodium‐Ion Batteries

Sodium manganese hexacyanoferrate (Na_xMnFe(CN)₆) is one of the most promising cathode materials for sodium‐ion batteries (SIBs) due to the high voltage and low cost. However, its cycling performance is limited by the multiple phase transitions during Na⁺ insertion/extraction. In this work, a facile strategy is developed to synthesize cubic and monoclinic structured Na_xMnFe(CN)₆, and their structure evolutions are investigated through in situ X‐ray diffraction (XRD), ex situ Raman, and X‐ray photoelectron spectroscopy (XPS) characterizations. It is revealed that the monoclinic phase undergoes undesirable multiple two‐phase reactions (monoclinic ? cubic ? tetragonal) due to the large lattice distortions caused by the Jahn–Teller effects of Mn³⁺, resulting in poor cycling performances with 38% capacity retention. The cubic Na_xMnFe(CN)₆ with high structural symmetry maintains the structural stability during the repeated Na⁺ insertion/extraction process, demonstrating impressive electrochemical performances with specific capacity of ≈120 mAh g^?1 at 3.5 V (vs Na/Na⁺), capacity retention of ≈70% over 500 cycles at 200 mA g^?1. In addition, the TiO₂//C‐MnHCF full battery is fabricated with an energy density of 111 Wh kg^?1, suggesting the great potential of cubic Na_xMnFe(CN)₆ for practical energy storage applications.     

Engineering Transition Metal Layers for Long Lasting Anionic Redox in Layered Sodium Manganese Oxide

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 Na_y[A_xMn_1−x]O₂, 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 Na_xMnO₂. Experimentally and theoretically, it is demonstrated that the efficacy of the dual Li and Co replacement in Na_0.6[Li_0.15Co_0.15Mn_0.7]O₂ 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 Na_0.6[Li_0.15Co_0.15Mn_0.7]O₂, the reversible electrochemical activity of Co³⁺/Co⁴⁺, Mn³⁺/Mn⁴⁺, and O^2-/(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.     

Combined First‐Principle Calculations and Experimental Study on Multi‐Component Olivine Cathode for Lithium Rechargeable Batteries

The electrochemical properties and phase stability of the multi‐component olivine compound LiMn_1/3Fe_1/3Co_1/3PO₄ are studied experimentally and with first‐principles calculation. The formation of a solid solution between LiMnPO₄, LiFePO₄, and LiCoPO₄ at this composition is confirmed by XRD patterns and the calculated energy. The experimental and first‐principle results indicate that there are three distinct regions in the electrochemical profile at quasi‐open‐circuit potentials of ～3.5 V, ～4.1 V, and ～4.7 V, which are attributed to Fe³⁺/Fe²⁺, Mn³⁺/Mn²⁺, and Co³⁺/Co²⁺ redox couples, respectively. However, exceptionally large polarization is observed only for the region near 4.1 V of Mn³⁺/Mn²⁺ redox couples, implying an intrinsic charge transfer problem. An ex situ XRD study reveals that the reversible one‐phase reaction of Li extraction/insertion mechanism prevails, unexpectedly, for all lithium compositions of Li_xMn_1/3Fe_1/3Co_1/3PO₄ (0 ≤ x ≤ 1) at room temperature. This is the first demonstration that the well‐ordered, non‐nanocrystalline (less than 1% Li–M disorder and a few hundred nanometer size particle) olivine electrode can be operated solely in a one‐phase mode.     

Synthesis and Characterization of 2D Molybdenum Carbide (MXene)

Large scale synthesis and delamination of 2D Mo₂CT _x (where T is a surface termination group) has been achieved by selectively etching gallium from the recently discovered nanolaminated, ternary transition metal carbide Mo₂Ga₂C. Different synthesis and delamination routes result in different flake morphologies. The resistivity of free‐standing Mo₂CT _x films increases by an order of magnitude as the temperature is reduced from 300 to 10 K, suggesting semiconductor‐like behavior of this MXene, in contrast to Ti₃C₂T _x which exhibits metallic behavior. At 10 K, the magnetoresistance is positive. Additionally, changes in electronic transport are observed upon annealing of the films. When 2 μm thick films are tested as electrodes in supercapacitors, capacitances as high as 700 F cm^?3 in a 1 m sulfuric acid electrolyte and high capacity retention for at least 10,000 cycles at 10 A g^?1 are obtained. Free‐standing Mo₂CT _x films, with ≈8 wt% carbon nanotubes, perform well when tested as an electrode material for Li‐ions, especially at high rates. At 20 and 131 C cycling rates, stable reversible capacities of 250 and 76 mAh g^?1, respectively, are achieved for over 1000 cycles.     

High Thermoelectric Performance in Sulfide‐Type Argyrodites Compound Ag8Sn(S1−xSex)6 Enabled by Ultralow Lattice Thermal Conductivity and Extended Cubic Phase Regime

Argyrodites with a general chemical formula of A₈BC₆ are known for complex phase transitions, ultralow lattice thermal conductivity, and mixed electronic and ionic conduction. The coexistence of ionic conduction and promising thermoelectric performance have recently been reported in selenide and telluride argyrodites, but scarcely in sulfide argyrodites. Here, the thermoelectric properties of Ag₈Sn(S_1?xSe_x)₆ are reported. Specifically, Ag₈SnS₆ exhibits intrinsically ultralow lattice thermal conductivities of 0.61–0.31 W m^?1 K^?1 over the whole temperature range from 32 to 773 K due to distorted local crystal structure, relatively weak chemical bonding, rattler‐like Ag atoms, low‐lying optical modes, and dynamic disorder of Ag ions at high temperatures. Se doping shifts the orthorhombic–cubic phase transition from 457 K at x = 0 to 430 K at x = 0.10, thereby expanding the temperature range of the thermoelectrically favored cubic phase. A figure of merit zT value ≈ 0.80 is achieved at 773 K in Ag₈Sn(S_1?xSe_x)₆ (x = 0.03), the highest zT value reported in sulfide argyrodites. These results fill a knowledge gap of the thermoelectric study of argyrodites and contribute to a comprehensive understanding of the chemical bonding, lattice dynamics, and thermal transport of argyrodites.     

A Composite of Carbon‐Wrapped Mo2C Nanoparticle and Carbon Nanotube Formed Directly on Ni Foam as a High‐Performance Binder‐Free Cathode for Li‐O2 Batteries

Cathode design is indispensable for building Li‐O₂ batteries with long cycle life. A composite of carbon‐wrapped Mo₂C nanoparticles and carbon nanotubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo₂C nanoparticles with well‐controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/OER) catalyst. The carbon coating can prevent the aggregation of the Mo₂C nanoparticles. The even distribution of Mo₂C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li‐O₂ batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g^?1 and a low average charge voltage of ≈4.0 V at 200 mA g^?1. With a cutoff capacity of 1000 mAh g^?1, the Li‐O₂ batteries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo₂C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li‐O₂ batteries.     

Kinetic Monte Carlo Simulations of Anisotropic Lithium Intercalation into LixFePO4 Electrode Nanocrystals

The kinetic anisotropy of lithium ion adsorption and lithium absorption for Li_xFePO₄ olivine nanocrystals is simulated and reported. The kinetics depend on the orientation of the electrolyte/Li_xFePO₄ interface with respect to the far‐field ionic flux. As a consequence of these kinetics and a Li miscibility gap in Li_xFePO₄, the particle geometry and orientation also have an effect on the morphology of the two‐phase evolution. These processes accompany the charge and discharge behavior in battery microstructures and a direct influence on battery behavior is suggested. A kinetic Monte Carlo (KMC) algorithm based on a cathode particle rigid lattice is used to simulate the kinetics in this system. In these simulations the adsorption kinetics of the electrolyte/electrode interface are treated by coupling the normal flux outside the particle from a continuum numerical simulation of Li‐ion diffusion in the electrolyte to the atomistic KMC model within the particle. The interfacial reaction depends on local concentration and the potential drop at the interface via the Butler–Volmer (B–V) relation. The atomic potentials for the KMC simulation are derived from empirical solubility limits (as determined by OCV measurements). The main results show that the galvanostatic lithium‐uptake/cell‐voltage has three regimes: 1) a decreasing cell potential for Li‐insertion into a Li‐poor phase; 2) a nearly constant potential after the nucleation of a Li‐rich phase Li_(1‐β)FePO₄; 3) a decreasing cell potential after the Li‐poor phase has been evolved into a Li‐rich phase. The behavior in the second regime is sensitive to crystallographic orientation.     

Controlled Nitrogen Doping in Crumpled Graphene for Improved Alkali Metal-Ion Storage under Low-Temperature Conditions

The significant performance decay in conventional graphite anodes under low-temperature conditions is attributed to the slow diffusion of alkali metal ions, requiring new strategies to enhance the charge storage kinetics at low temperatures. Here, nitrogen (N)-doped defective crumpled graphene (NCG) is employed as a promising anode to enable stable low-temperature operation of alkali metal-ion storage by exploiting the surface-controlled charge storage mechanisms. At a low temperature of −40 °C, the NCG anodes maintain high capacities of ≈172 mAh g⁻¹ for lithium (Li)-ion, ≈107 mAh g⁻¹ for sodium (Na)-ion, and ≈118 mAh g⁻¹ for potassium (K)-ion at 0.01 A g⁻¹ with outstanding rate-capability and cycling stability. A combination of density functional theory (DFT) and electrochemical analysis further reveals the role of the N-functional groups and defect sites in improving the utilization of the surface-controlled charge storage mechanisms. In addition, the full cell with the NCG anode and a LiFePO₄ cathode shows a high capacity of ≈73 mAh g⁻¹ at 0.5 °C even at −40 °C. The results highlight the importance of utilizing the surface-controlled charge storage mechanisms with controlled defect structures and functional groups on the carbon surface to improve the charge storage performance of alkali metal-ion under low-temperature conditions.     

Reversible Sodium and Lithium Insertion in Iron Fluoride Perovskites

Li‐ion batteries are omnipresent in consumer electronics and are seen as the most promising technology for electric vehicles. Na‐ion batteries have emerged as viable and cheaper alternatives for stationary applications where Li‐ion batteries are too expensive. However, the larger size of sodium ion compared to lithium makes traditional positive materials for Li‐ion batteries not always suitable for the reversible insertion of sodium ions. Herein, a microwave‐assisted solution synthesis of NaFeF₃ perovskite nanoparticles from presynthesized rutile FeF₂ colloidal particles, sodium ethoxide, and ammonium fluoride is presented. This NaFeF₃ material shows a reversible electrochemical activity of 1Na or 1Li per iron with low polarization and excellent capacity retention after 100 cycles. The unexpected reversible insertion of both sodium and lithium ions, herein studied through ex situ and operando X‐ray diffraction measurements, is attributed to a kinetic stabilization of corner‐shared cubic A_xFeF₃ (A = Li, Na) frameworks along the cycles involving low volume change without high thermodynamic cost as supported by a polymorphism theoretical analysis.     

Adiponitrile (C6H8N2): A New Bi‐Functional Additive for High‐Performance Li‐Metal Batteries

Rechargeable batteries with a Li metal anode and Ni‐rich Li[Ni_xCo_yMn_1?x?y]O₂ cathode (Li/Ni‐rich NCM battery) have been emerging as promising energy storage devices because of their high‐energy density. However, Li/Ni‐rich NCM batteries have been plagued by the issue of the thermodynamic instability of the Li metal anode and aggressive surface chemistry of the Ni‐rich cathode against electrolyte solution. In this study, a bi‐functional additive, adiponitrile (C₆H₈N₂), is proposed which can effectively stabilize both the Li metal anode and Ni‐rich NCM cathode interfaces. In the Li/Ni‐rich NCM battery, the addition of 1 wt% adiponitrile in 0.8 m LiTFSI + 0.2 M LiDFOB + 0.05 M LiPF₆ dissolved in EMC/FEC = 3:1 electrolyte helps to produce a conductive and robust Li anode/electrolyte interface, while strong coordination between Ni⁴⁺ on the delithiated Ni‐rich cathode and nitrile group in adiponitrile reduces parasitic reactions between the electrolyte and Ni‐rich cathode surface. Therefore, upon using 1 wt% adiponitrile, the Li/full concentration gradient Li[Ni_0.73Co_0.10Mn_0.15Al_0.02]O₂ battery achieves an unprecedented cycle retention of 75% over 830 cycles under high‐capacity loading of 1.8 mAh cm^?2 and fast charge–discharge time of 2 h. This work marks an important step in the development of high‐performance Li/Ni‐rich NCM batteries with efficient electrolyte additives.     

Ultralow-Salt-Concentration Electrolyte for High-Voltage Aqueous Zn Metal Batteries

Aqueous Zn metal batteries are regarded as a promising pathway for large-scale energy storage systems due to their green, low-cost, and intrinsically safe characteristics. However, they have long been suffered from narrow voltage windows and severe parasitic reactions (e.g., hydrogen evolution, corrosion, etc.), which hinder their further development. The above challenges are essentially related to the existence of hydrated ions (i.e., Zn(H₂O)_x²⁺ and SO₄²⁻·(H₂O)_x), which are highly reactive species. Herein, a counterintuitive ultralow-salt-concentration electrolyte strategy to solve the aforementioned problems by decreasing Zn salt concentration to reduce active hydrated ions is presented, so as to minimize water-induced side reactions and thus anomalously enlarge the electrolyte splitting voltage window. Additionally, the gap between the charge and discharge medium voltages of full cells is also narrowed due to the reduced polarization in the ultralow-salt-concentration electrolyte. By adopting this strategy, the Zn-Fe₄[Fe(CN)₆]₃ full cell stably works at a high-voltage of 1.40–2.30 V with a high cathode loading of ≈7 mg cm⁻² and the Zn-polyaniline full cell can stably work at 0.50–1.50 V with a high cathode loading of ≈11 mg cm⁻².     

Enhancing the Thermoelectric Properties via Modulation of Defects in P-Type MNiSn-Based (M = Hf,Zr, Ti) Half-Heusler Materials

The thermoelectric figure-of-merit (zT) of p-type MNiSn (M = Ti, Zr, or Hf) half-Heusler compounds is lower than their n-type counterparts due to the presence of a donor in-gap state caused by Ni occupying tetrahedral interstitials. While ZrNiSn and TiNiSn, have been extensively studied, HfNiSn remains unexplored. Herein, this study reports an improved thermoelectric property in p-type HfNi_1−xCo_xSn. By doping 5 at% Co at the Ni sites, the Seebeck coefficient becomes reaching a peak value exceeding 200 µV K⁻¹ that breaks the record of previous reports. A maximum power factor of ≈2.2 mW m⁻¹ K⁻² at 973 K is achieved by optimizing the carrier concentration. The enhanced p-type transport is ascribed to the reduced content of Ni defects, supported by first principle calculations and diffraction pattern refinement. Concomitantly, Co doping also softens the lattice and scatters phonons, resulting in a minimum lattice thermal conductivity of ≈1.8 W m⁻¹ K⁻¹. This leads to a peak zT of 0.55 at 973 K is realized, surpassing the best performing p-type MNiSn by 100%. This approach offers a new method to manipulate the intrinsic atomic disorder in half-Heusler materials, facilitating further optimization of their electronic and thermal properties.     

Achieving Superior Thermoelectric Performance in Ge4Se3Te via Symmetry Manipulation with I–V–VI2 Alloying

Although orthorhombic GeSe is predicted to have an ultrahigh figure of merit, ZT ≈ 2.5, up to now, the highest experimental value is ≈0.2 due to the low carrier concentration (n_H ≈ 10¹⁸ cm⁻³). Improving symmetry is an effective approach for enhancing the ZT of GeSe-based materials. With Te-alloying, Ge₄Se₃Te displays the two-dimensional hexagonal structure and high n_H ≈ 1.23 × 10²¹ cm⁻³. Interestingly, Ge₄Se₃Te transformed from the hexagonal into the rhombohedral phase with only ≈2% I–V–VI₂-alloying (I = Li, Na, K, Cu, Ag; V = Sb, Bi; VI = Se, Te). According to the calculated results of Ge_0.82Ag_0.09Bi_0.09Se_0.614Te_0.386 single-crystal grown via AgBiTe₂-alloying, it exhibits a higher valley degeneracy than the hexagonal Ge₄Se₃Te. For instance, AgBiTe₂-alloying induces a strong band convergence and band inversion effect, resulting in a significantly enhanced Seebeck coefficient and power factor with a similar n_H from 17 µV K⁻¹ and 0.63 µW cm⁻¹ K⁻² for pristine Ge₄Se₃Te to 124 µV K⁻¹ and 5.97 µW cm⁻¹ K⁻² for 12%AgBiTe₂-alloyed sample, respectively. Moreover, the sharply reduced phonon velocity, nano-domain wall structure, and strong anharmonicity lead to low lattice thermal conductivity. As a result, a record-high average ZT ≈0.95 over 323–773 K with an excellent ZT ≈ 1.30 is achieved at 723 K.     

A High‐Performance Li–B–H Electrolyte for All‐Solid‐State Li Batteries

Highly Li‐ion conductive Li₄(BH₄)₃I@SBA‐15 is synthesized by confining the LiI doped LiBH₄ into mesoporous silica SBA‐15. Uniform nanoconfinement of P6₃ mc phase Li₄(BH₄)₃I in SBA‐15 mesopores leads to a significantly enhanced conductivity of 2.5 × 10^?4 S cm^?1 with a Li‐ion transference number of 0.97 at 35 °C. The super Li‐ion mobility in the interface layer with a thickness of 1.2 nm between Li₄(BH₄)₃I and SBA‐15 is believed to be responsible for the fast Li‐ion conduction in Li₄(BH₄)₃I@SBA‐15. Additionally, Li₄(BH₄)₃I@SBA‐15 also exhibits a wide apparent electrochemical stability window (0 to 5 V vs Li/Li⁺) and a superior Li dendrite suppression capability (critical current density 2.6 mA cm^?2 at 55 °C) due to the formation of stable interphases. More importantly, Li₄(BH₄)₃I@SBA‐15‐based Li batteries using either high‐capacity sulfur cathode or high‐voltage oxide cathode show excellent electrochemical performances, making Li₄(BH₄)₃I@SBA‐15 a very attractive electrolyte for next‐generation all‐solid‐state Li batteries.     

Dual‐Salt Mg‐Based Batteries with Conversion Cathodes

Mg batteries as the most typical multivalent batteries are attracting increasing attention because of resource abundance, high volumetric energy density, and smooth plating/stripping of Mg anodes. However, current limitations for the progress of Mg batteries come from the lack of high voltage electrolytes and fast Mg‐insertable structure prototypes. In order to improve their energy or power density, hybrid systems combining Li‐driven cathode reaction with Mg anode process appear to be a potential solution by bypassing the aforementioned limitations. Here, FeS _x (x = 1 or 2) is employed as conversion cathode with 2–4 electron transfers to achieve a maximum energy density close to 400 Wh kg^?1, which is comparable with that of Li‐ion batteries but without serious dendrite growth and polysulphide dissolution. In situ formation of solid electrolyte interfaces on both sulfide and Mg electrodes is likely responsible for long‐life cycling and suppression of S‐species passivation at Mg anodes. Without any decoration on the cathode, electrolyte additive, or anode protection, a reversible capacity of more than 200 mAh g^?1 is still preserved for Mg/FeS₂ after 200 cycles.     

Br‐Doped Li4Ti5O12 and Composite TiO2 Anodes for Li‐ion Batteries: Synchrotron X‐Ray and in situ Neutron Diffraction Studies

Synchrotron X‐ray diffraction data were used to determine the phase purity and re‐evaluate the crystal‐structure of Li₄Ti₅O_12‐xBr_x electrode materials (where the synthetic chemical inputs are x = 0.05, 0.10 0.20, 0.30). A maximum of x′ = 0.12 Br, where x′ is the Rietveld‐refined value, can be substituted into the crystal structure with at least 2% rutile TiO₂ forming as a second phase. Higher Br concentrations induced the formation of a third, presumably Br‐rich, phase. These materials function as composite anodes that contain mixtures of TiO₂, Li₄Ti₅O_12‐xBr_x, and a Br‐rich third, unknown, phase. The minor quantities of the secondary phases in combination with Li₄Ti₅O_12‐xBr_x where x′ ～ 0.1 were found to correspond to the optimum in electrochemical properties, while larger quantities of the secondary phases contributed to the degradation of the performance. In situ neutron diffraction of a composite anatase TiO₂/Li₄Ti₅O₁₂ anode within a custom‐built battery was used to determine the electrochemical function of the TiO₂ component. The Li₄Ti₅O₁₂ component was found to be electrochemically active at lower voltages (1.5 V) relative to TiO₂ (1.7 V). This enabled Li insertion/extraction to be tuned through the choice of voltage range in both components of this composite or in the anatase TiO₂ phase only. The use of composite materials may facilitate the development of multi‐component electrodes where different active materials can be cycled in order to tune power output.