Mg-Doped Na4Fe3(PO4)2(P2O7)/C Composite with Enhanced Intercalation Pseudocapacitance for Ultra-Stable and High-Rate Sodium-Ion Storage

Na₄Fe₃(PO₄)₂(P₂O₇) (NFPP) is considered as a promising cathode material for sodium-ion batteries (SIBs) due to its low cost, non-toxicity, and high structural stability, but its electrochemical performance is limited by the poor electronic conductivity. In this study, Mg-doped NFPP/C composites are presented as cathode materials for SIBs. Benefiting from the enhanced electrochemical kinetics and intercalation pseudocapacitance resulted from the Mg doping, the optimal Mg-doped NFPP/C composite (NFPP-Mg5%) delivers high rate performance (capacity of ≈40 mAh g⁻¹ at 20 A g⁻¹) and ultra-long cycling life (14 000 cycles at 5 A g⁻¹ with capacity retention of 80.8%). Moreover, the in situ X-ray diffraction and other characterizations reveal that the sodium storage process of NFPP-Mg5% is dominated by the intercalation pseudocapacitive mechanism. In addition, the full SIB based on NFPP-Mg5% cathode and hard carbon anode exhibits the discharge capacity of ≈50 mAh g⁻¹ after 200 cycles at 500 mA g⁻¹. This study demonstrates the feasibility of improving the electrochemical performance of NFPP by doping strategy and presents a low-cost, ultra-stable, and high-rate cathode material for SIBs.     

Organic-Carbon Core–Shell Structure Promotes Cathode Performance for Na-Ion Batteries

The organic-carbon core-shell structure is constructed for the cathode material of [N,N'-bis(2-anthraquinone)]-perylene-3,4,9,10-tetracarboxydiimide (PTCDI-DAQ, 200 mAh g⁻¹) through an interesting strategy called the surface self-carbonization. As expected, the organic-carbon core–shell structure (PTCDI-DAQ@C) can endow PTCDI-DAQ the outstanding cathode performance in Na-ion batteries. In half cells using 1 m NaPF₆/DME, PTCDI-DAQ@C can maintain 173 mAh g⁻¹ for nearly one year, while PTCDI-DAQ quickly decreases from 203 to 121 mAh g⁻¹ only after 100 cycles. Meanwhile, the constructed Na-ion full cells with the Na-intercalated hard carbon anode can deliver the peak discharge capacity of 195 mAh g⁻¹_cathode and the high median voltage of 1.7 V in 0.9–3.2 V, corresponding to the peak energy densities of 332 Wh kg⁻¹_cathode and 184 Wh kg⁻¹_{total mass}, respectively. Notably, the electrode materials only include the very cheap elements of C, H, O, N, and Na. Furthermore, the Na-ion full cells can also show the very impressive high-temperature (197 mAh g⁻¹_cathode at 50 °C) and subzero (185/90 mAh g⁻¹_cathode at −10/−40 °C) performances, respectively. To the best of the authors’ knowledge, the comprehensive properties of the Na-ion full cells are the best results based on organic cathodes.     

Manipulating the Local Electronic Structure in Li-Rich Layered Cathode Towards Superior Electrochemical Performance

Manipulating the local electronic structure is employed to address the capacity/voltage decay and poor rate capability of Li-rich layered cathodes (LLOs) via the dual-doping of Na⁺ and F⁻ ions, as well as the regulation of Li⁺/Ni²⁺ intermixing and the content of “Li O Li” configuration. The designed cathode exhibits a high initial Coulombic efficiency of about 90%, large specific capacity of 296 mAh g⁻¹ and energy density of 1047 Wh kg⁻¹ at 0.2 C, and a superior rate capability of 222 mAh g⁻¹ at 5 C with a good capacity retention of 85.7% even after 500 cycles. And the operating voltage is increased without compromising the high-capacity advantage. Such improved electrochemical performances primarily result from the band shift of the TM 3d-O 2p and non-bonding O-2p to lower energy, which would decrease Li⁺ diffusion activation energy and increase oxygen vacancy forming energy, finally improving the Li⁺ diffusion kinetics and stabilizing lattice oxygen. Moreover, the increased “Li O Li” configuration in the Li₂MnO₃ phase via increasing the Mn concentration can increase the reversible capacity to offset the negative effect of inactive doping and Li⁺/Ni²⁺ intermixing. This strategy of modulating the local electronic structure of LLOs provides great potential to design high-energy-density Li-ion batteries.     

Enabling High-Performance NASICON-Based Solid-State Lithium Metal Batteries Towards Practical Conditions

Solid-state lithium metal batteries (SSLMBs) are promising next-generation high-energy rechargeable batteries. However, the practical energy densities of the reported SSLMBs have been significantly overstated due to the use of thick solid-state electrolytes, thick lithium (Li) anodes, and thin cathodes. Here, a high-performance NASICON-based SSLMB using a thin (60 µm) Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) electrolyte, ultrathin (36 µm) Li metal, and high-loading (8 mg cm⁻²) LiFePO₄ (LFP) cathode is reported. The thin and dense LAGP electrolyte prepared by hot-pressing exhibits a high Li ionic conductivity of 1 × 10⁻³ S cm⁻¹ at 80 °C. The assembled SSLMB can thus deliver an increased areal capacity of ≈1 mAh cm⁻² at C/5 with a high capacity retention of ≈96% after 50 cycles under 80 °C. Furthermore, it is revealed by synchrotron X-ray absorption spectroscopy and in situ high-energy X-ray diffraction that the side reactions between LAGP electrolyte and LFP cathode are significantly suppressed, while rational surface protection is required for Ni-rich layered cathodes. This study provides valuable insights and guidelines for the development of high-energy SSLMBs towards practical conditions.     

Covalently Interlinked Graphene Sheets with Sulfur-Chains Enable Superior Lithium–Sulfur Battery Cathodes at Full-Mass Level

Sulfur represents a low‑cost, sustainable, and high theoretical capacity cathode material for lithium–sulfur batteries, which can meet the growing demand in portable power sources, such as in electric vehicles and mobile information technologies. However, the shuttling effect of the formed lithium polysulfides, as well as their low conductivity, compromise the electrochemical performance of lithium–sulfur cells. To tackle this challenge, a so far unexplored cathode, composed of sulfur covalently bonded directly on graphene is developed. This is achieved by leveraging the nucleophilicity of polysulfide chains, which react readily with the electrophilic centers in fluorographene, as experimental and theoretical data unveil. The reaction leads to the formation of carbon–sulfur covalent bonds and a particularly high sulfur content of 80 mass%. Owing to these features, the developed cathode exhibits excellent performance with only 5 mass% of conductive carbon additive, delivering very high full‑cathode‑mass capacities and rate capability, combined with superior cycling stability. In combination with a fluorinated ether as electrolyte additive, the capacity persists at ≈700 mAh g⁻¹ after 100 cycles at 0.1 C, and at ≈644 mAh g⁻¹ after 250 cycles at 0.2 C, keeping ≈470 mAh g⁻¹ even after 500 cycles.     

A General Route for Encapsulating Monodispersed Transition Metal Phosphides into Carbon Multi-Chambers toward High-Efficient Lithium-Ion Storage with Underlying Mechanism Exploration

Transition metal phosphides (MP_x) with high theoretical capacities and low cost are regarded as the most promising anodes for lithium-ion batteries (LIBs), but the large volume variations and sluggish kinetics largely restrict their development. To solve the above challenges, herein a generic but effective method is proposed to encapsulate various monodispersed MP_x into flexible carbon multi-chambers (MP_x@NC, MNi, Fe, Co, and Cu, etc.) with pre-reserved voids, working as anodes for LIBs and markedly boosting the Li⁺ storage performance. Ni₂P@NC, one representative example of MP_x@NC anode, shows high reversible capacity (613 mAh g⁻¹, 200 cycles at 0.2 A g⁻¹), and superior cycle stability (475 mAh g⁻¹, 800 cycles at 2 A g⁻¹). Full cell coupled with LiFePO₄ displays a high reversible capacity (150.1 mAh g⁻¹ at 0.1 A g⁻¹) with stable cycling performance. In situ X-ray diffraction and transmission electron microscope techniques confirm the reversible conversion reaction mechanism and robust structural integrity, accounting for enhanced rate and cycling performance. Theoretical calculations reveal the synergistic effect between MP_x and carbon shells, which can significantly promote electron transfer and reduce diffusion energy barriers, paving ways to design high-energy-density materials for energy storage systems.     

Systematic Modification of MoO3-Based Cathode by the Intercalation Engineering for High-Performance Aqueous Zinc-Ion Batteries

Aqueous Zn-ion batteries are attracting extensive attention, but their large-scale application is prevented by the poor electrochemical kinetics and terrible lifespan. Herein, a strategy of introducing the conductive poly(3,4-ethylenedioxythiophene) (PEDOT) into the interlayers of α-MoO₃ is reported to systematically overcome the above shortcomings. Through data analyses of the cyclic coltammetry, electrochemical impedance spectroscopy, and galvanostatic intermittent titration technique, the electrochemical kinetics of the PEDOT-intercalated MoO₃ (PEDOT-MoO₃) is proved to be significantly improved. The first-principles calculations microscopically disclose that the changed energy band and the lowered binding energy between Zn²⁺ and host O²⁻ boost electrochemical kinetics of PEDOT-MoO₃. Meanwhile, its decreased hydrophilicity and the suppressed dissolution of molybdenum stabilizes the repeated cycling processes. Interestingly, it is found that excellent electrochemical kinetics of cathode electrode can restrain the growth of zinc dendrite on the Zn anode, prolonging the lifespan of aqueous Zn-ion batteries. As a result, the PEDOT-MoO₃ exhibits the enhanced specific capacity (341.5 vs 146.7 mAh g⁻¹ at 0.1 A g⁻¹), high rate capacity (178.2 vs 19.4 mAh g⁻¹ at 30 A g⁻¹) and prolonged cycling stability (77.6% capacity retention over 500 cycles vs 2.3% capacity retention over 100 cycles at 30 A g⁻¹) compared with pristine MoO₃. Moreover, the PEDOT-MoO₃ as cathode of quasi-solid-state ZIBs also delivers an impressive electrochemical performance.     

Tailoring the Redox Reactions for High-Capacity Cycling of Cation-Disordered Rocksalt Cathodes

Cation-disordered rocksalts (DRXs) have emerged as a new class of high-capacity Li-ion cathode materials. One unique advantage of the DRX chemistry is the structural flexibility that substantially lessens the elemental constraints in the crystal lattice, such as Li content, choice of transition metal redox center paired with appropriate d⁰ metal, and incorporation of F anion, which allows optimization of the key redox reactions. Herein, a series of the DRX oxyfluorides based on the Mn redox have been designed and synthesized. By tailoring the stoichiometry of the DRX compositions, high-capacity cycling by promoting the cationic Mn²⁺/Mn⁴⁺ redox reactions while suppressing those from anionic O is successfully demonstrated. A highly fluorinated DRX compound, Li_1.2Mn_0.625Nb_0.175O_1.325F_0.675 (M_0.625F_0.675), delivers a capacity of ≈170 mAh g⁻¹ at C/3 for 100 cycles. This work showcases the concept of balancing the cationic and anionic redox reactions in the DRX cathodes for improved electrochemical performance through the rational composition design.     

Bilayered VOPO4⋅2H2O Nanosheets with High-Concentration Oxygen Vacancies for High-Performance Aqueous Zinc-Ion Batteries

2D materials with atomically precise thickness and tunable chemical composition hold promise for potential applications in nanoenergy. Herein, a bilayer-structured VOPO₄⋅2H₂O (bilayer-VOP) nanosheet is developed with high-concentration oxygen vacancies ([Vo˙˙]) via a facile liquid-exfoliation strategy. Galvanostatic intermittent titration technique study indicates a 6 orders of magnitude higher zinc-ion coefficient in bilayer-VOP nanosheets (4.6 × 10⁻⁷ cm⁻² s⁻¹) compared to the bulk counterpart. Assistant density functional theory (DFT) simulation indicates a remarkably enhanced electron conductivity with a reduced bandgap of ≈ 0.2 eV (bulk sample: 1.5 eV) along with an ultralow diffusion barrier of ≈ 0.08 eV (bulk sample: 0.13 eV) in bilayer-VOP nanosheets, thus leading to superior diffusion kinetics and electrochemical performance. Mott–Schottky (impedance potential) measurement also demonstrates a great increase in electronic conductivity with ≈ 57-fold increased carrier concentration owing to its high concentration [Vo˙˙]. Benefited by these unique features, the rechargeable zinc-ion battery composed of bilayer-VOP nanosheets cathode exhibits a remarkable capacity of 313.6 mAh g⁻¹ (0.1 A g⁻¹), an energy density of 301.4 Wh kg⁻¹, and a prominent rate capability (168.7 mAh g⁻¹ at 10 A g⁻¹).     

A Structure Self-Healing Li-Rich Cathode Achieved by Lithium Supplement of Li-Rich LLZO Coating

Lithium-rich manganese-based cathode materials (LLMO) are considered as the promising candidates for realizing high energy density lithium-ion batteries. However, the severe structure deterioration and capacity fading hinder their large-scale application. Herein, an innovative electrochemical lithium supplement strategy is put forward to inhibit the structure collapse and enhance the cycling stability of Lithium-rich manganese-based cathodes. Besides, combining with the superior Li-ion conductor Li_6.25La₃Zr₂Al_0.25O₁₂ (LLZAO), remarkable rate capability is achieved. As a result, a capacity retention of 95.7% after 300 cycles at 1.0 C (1.0 C = 200 mA g⁻¹), as well as a stable cycling at 5.0 C with discharge capacity of 136.9 mAh g⁻¹, are harvested. Moreover, the excess lithium ions in LLZAO mitigate the spinel-like phase transformation via inserting into the lithium layer and stabilizing the cathode structure. In addition, the lithium ions migration behavior in the elaborated cathode is thoroughly expounded and the correlation between diffusion kinetics and LLZAO is revealed. These findings boost the updating of LLMO and pave a new pathway for stabilizing LLMO structures.     

High-Energy-Density Quinone-Based Electrodes with [Al(OTF)]2+ Storage Mechanism for Rechargeable Aqueous Aluminum Batteries

Rechargeable aqueous aluminum batteries (AABs) are potential candidates for future large-scale energy storage due to their large capacity and the high abundance of aluminum. However, AABs face the challenges of inferior rate capability and cycling life due to the high charge density of Al³⁺, which induces the sluggish intercalation/extraction dynamics and structure collapse of inorganic cathode materials during discharge–charge cycles. Here, the optimization of macrocyclic calix[4]quinone (C4Q) with a large cavity and multi-adjacent carbonyls structure from quinone compounds to become excellent cathode materials for high-energy-density AABs is reported. It exhibits a high capacity of 400 mAh g⁻¹, a high rate capability (300 mAh g⁻¹ at 800 mA g⁻¹), and an excellent low-temperature performance (224 mAh g⁻¹ at − 20  ° C). The combination of experiments and theoretical calculations proves that Al(OTF)²⁺ cations coordinate with the carbonyl groups of C4Q during the discharge process, which can reduce desolvation penalty. Moreover, the fabricated pouch-type Al-C4Q battery delivers an energy density of 93 Wh kg⁻¹_cell, showing great potential for large-scale applications. This work is expected to facilitate the application of organic cathode for AABs.     

In Situ Synthesis of Graphene-Coated Silicon Monoxide Anodes from Coal-Derived Humic Acid for High-Performance Lithium-Ion Batteries

Silicon monoxide (SiO) is attaining extensive interest amongst silicon-based materials due to its high capacity and long cycle life; however, its low intrinsic electrical conductivity and poor coulombic efficiency strictly limit its commercial applications. Here low-cost coal-derived humic acid is used as a feedstock to synthesize in situ graphene-coated disproportionated SiO (D-SiO@G) anode with a facile method. HR-TEM and XRD confirm the well-coated graphene layers on a SiO surface. Scanning transmission X-ray microscopy and X-ray absorption near-edge structure spectra analysis indicate that the graphene coating effectively hinders the side-reactions between the electrolyte and SiO particles. As a result, the D-SiO@G anode presents an initial discharge capacity of 1937.6 mAh g⁻¹ at 0.1 A g⁻¹ and an initial coulombic efficiency of 78.2%. High reversible capacity (1023 mAh g⁻¹ at 2.0 A g⁻¹), excellent cycling performance (72.4% capacity retention after 500 cycles at 2.0 A g⁻¹), and rate capability (774 mAh g⁻¹ at 5 A g⁻¹) results are substantial. Full coin cells assembled with LiFePO₄ electrodes and D-SiO@G electrodes display impressive rate performance. These results indicate promising potential for practical use in high-performance lithium-ion batteries.     

Single-Atom Cadmium-N4 Sites for Rechargeable Li–CO2 Batteries with High Capacity and Ultra-Long Lifetime

The rechargeable Li–CO₂ battery shows great potential in civil, military, and aerospace fields due to its high theoretical energy density and CO₂ capture capability. To facilitate the practical application of Li–CO₂ battery, the design of efficient, low-cost, and robust non-noble metal cathodes to boost CO₂ reduction/evolution kinetics is highly desirable yet remains a challenge. Herein, single-atom cadmium is reported with a Cd-N₄ coordination structure enable rapid kinetics of both the discharge and recharge process when employed as a cathode catalyst, and thus facilitates exceptional rate performance in a Li–CO₂ battery, even up to 10 A g⁻¹, and remains stable at a high current density (100 A g⁻¹). An unprecedented discharge capacity of 160045 mAh g⁻¹ is attained at 500 mA g⁻¹. Excellent cycling stability is maintained for 1685 and 669 cycles at 1 A g⁻¹ and capacities of 0.5 and 1 Ah g⁻¹, respectively. Density functional theory calculations reveal low energy barriers for both Li₂CO₃ formation and decomposition reactions during the respective discharge and recharge process, evidencing the high catalytic activity of single Cd sites. This study provides a simple and effective avenue for developing highly active and stable single-atom non-precious metal cathode catalysts for advanced Li–CO₂ batteries.     

Fe2VO4 Nanoparticles Anchored on Ordered Mesoporous Carbon with Pseudocapacitive Behaviors for Efficient Sodium Storage

Iron vanadates are attractive anode materials for sodium-ion batteries (SIBs) because of their abundant resource reserves and high capacities. However, their practical application is restricted by the aggregation of materials, sluggish reaction kinetics, and inferior reversibility. Herein, Fe₂VO₄ nanoparticles are anchored on the ordered mesoporous carbon (CMK-3) nanorods to assemble 3D Fe₂VO₄@CMK-3 composites, by solvothermal treatment and subsequent calcination. The resulting composites provide abundant active sites, high electrical conductivity, and excellent structural integrity. The pseudocapacitive-controlled behavior is the dominating sodium storage mechanism, which facilitates a fast charge/discharge process. The Fe₂VO₄@CMK-3 composites exhibit stable sodium-ion storage (219 mAh g⁻¹ under 100 mA g⁻¹ after 300 cycles), good rate performance (144 mAh g⁻¹ at 3.2 A g⁻¹), and excellent cycling performance (132 mAh g⁻¹ at 1 A g⁻¹ with capacity retention of 96.4% after 800 cycles). When coupled with a NaNi_1/3Fe_1/3Mn_1/3O₂ cathode, the sodium-ion full cell displays excellent cycling stability (94 mAh g⁻¹ after 500 cycles at 500 mA g⁻¹). These findings point to the potential of Fe₂VO₄@CMK-3 for application as anodes in SIBs.     

I3–/I– Redox Enhanced Sodium Metal Batteries by Using Graphene Oxide Encapsulated Mesoporous Carbon Sphere Cathode

Sodium-metal batteries (SMBs) employing transition-metal-free cathodes are of great importance for energy storage applications that require low cost and high energy density. A strategy to enhance the energy density of transition-metal-free-cathode SMBs by transforming the electrolyte from a dead mass to an energy-storage contributor is reported. NaI is used for the partial substitution of NaClO₄ in the electrolyte and thus provides the additional electrochemistry of I₃⁻/I⁻ redox couple to enhance battery performance. Graphene oxide (GO) encapsulated mesoporous (10 nm) carbon spheres (N-MCS@GO) that are nitrogen-doped (15.71 at%) are fabricated as the cathode for the I₃⁻/I⁻ redox enhanced SMBs. It is experimentally demonstrated that: the mesoporous structure increases the capacitive energy storage by providing a substantial interface that enhances the electrochemistry of I₃⁻/I⁻ redox couples; and encapsulation of the mesoporous carbon spheres with GO suppresses self-discharge and increases Coulombic efficiencies from 70.4% to 91.9%. In full-cell configuration, N-MCS@GO working with the NaI-activated electrolyte can deliver a capacity of 279.6 mAh g⁻¹ with an energy density of 459.2 Wh kg⁻¹ in 0.5–3 V at 200 mA g⁻¹. I₃⁻/I⁻ redox in the full cell maintains its activity without obvious decay after 1000 cycles at 1 A g⁻¹, highlighting the practical application of the I₃⁻/I⁻ redox enhanced SMBs.     

Si/SiO2@Graphene Superstructures for High-Performance Lithium-Ion Batteries

The superstructure composed of various functional building units is promising nanostructure for lithium-ion batteries (LIBs) anodes with extreme volume change and structure instability, such as silicon-based materials. Here, a top-down route to fabricate Si/SiO₂@graphene superstructure is demonstrated through reducing silicalite-1 with magnesium reduction and depositing carbon layers. The successful formation of superstructure lies on the strong 3D network formed by the bridged-SiO₂ matrix coated around silicon nanoparticles. Furthermore, the mesoporous Si/SiO₂ with amorphous bridged SiO₂ facilitates the deposition of graphene layers, resulting in excellent structural stability and high ion/electron transport rate. The optimized Si/SiO₂@graphene superstructure anode delivers an outstanding cycling life for ≈1180 mAh g⁻¹ at 2 A g⁻¹ over 500 cycles, excellent rate capability for ≈908 mAh g⁻¹ at 12 A g⁻¹, great areal capacity for ≈7 mAh cm⁻² at 0.5 mA cm⁻², and extraordinary mechanical stability. A full cell test using LiFePO₄ as the cathode manifests a high capacity of 134 mAh g⁻¹ after 290 loops. More notably, a series of technologies disclose that the Si/SiO₂@graphene superstructure electrode can effectively maintain the film between electrode and electrolyte in LIBs. This design of Si/SiO₂@graphene superstructure elucidates a promising potential for commercial application in high-performance LIBs.     

Rational Design of Multifunctional Integrated Host Configuration with Lithiophilicity-Sulfiphilicity toward High-Performance Li–S Full Batteries

High-energy-density Li–S batteries are considered one of the next-generation energy storage systems, but the uncontrolled Li-dendrite growth in Li metal anodes and the shuttling of polysulfides in S cathode severely impede the commercial development of Li–S batteries. Herein, a conductive composite architecture that is made up of bio-derived N-doped porous carbon fiber bundles (N-PCFs) with co-imbedded cobalt and niobium carbide nanoparticles is employed as a multifunctional integrated host for simultaneously addressing the challenges in both Li anodes and S cathodes. The implantation of Co and NbC nanoparticles bestows the N-PCFs matrix with synergistically enhanced degree of graphitization, electrical conductivity, hierarchical porosity, and surface polarization. Theoretical calculations and experimental results show that NbC with specific lithiophilic and sulfiphilic features can synchronously regulate the Li and S electrochemistry by realizing homogeneous lithium deposition with suppressed Li-dendrite growth and exerting catalytic effects for promoting the polysulfide conversion together with fast Li₂S nucleation. Hence, the assembled Li–S full batteries exhibit a superb rate capability (704 mAh g⁻¹ at 5 C) and cycling life (≈82.3% capacity retention after 500 cycles) at a sulfur loading over 3.0 mg cm⁻², as well as high reversible areal capacity (>6.0 mAh cm⁻²) even at a higher sulfur loading of 6.7 mg cm⁻².     

Combining Janus Separator and Organic Cathode for Dendrite-Free and High-Performance Na-Organic Batteries

The growth of Na-dendrites and the dissolution of organic cathodes are two major challenges that hinder the development of sodium-organic batteries (SOBs). Herein, a multifunctional Janus separator (h-BN@PP@C) by using an interfacial engineering strategy, is proposed to tackle the issues of SOBs. The carbon layer facing the organic cathode serves as a barrier to capture dissolved organic materials and enhance their utilization. Meanwhile, the h-BN layer facing the Na anode possesses high thermal conductivity and mechanical strength, which mitigates the occurrence of localized-temperature “hot spots” and promotes the formation of a NaF-enriched SEI, thereby suppressing dendrite growth. Consequently, the Janus separator enables a stable Na plating/stripping cycling for 1000 h at 3 mA cm⁻². Equipped with the Janus separator, organic cathodes including dibenzo[b,i]thianthrene-5,7,12,14-tetraone (DTT), pentacene-5,7,12,14-tetrone and Calix[4]quinone cathodes demonstrate high capacity and remarkable cycling performance. In particular, the DTT exhibits a bipolar co-reaction storage mechanism and achieves an ultrahigh capacity (≈342.6 mAh g⁻¹), long-term cycling stability (capacity decay rate of 0.15% per cycle over 550 cycles at 500 mA g⁻¹) and fast kinetics (1000 mA g⁻¹≈2.8 C). This study offers a straightforward, effective, and promising solution to address the challenges in SOBs.     

Optimized Ti?O Subcompounds and Elastic Expanded MXene Interlayers Boost Quick Sodium Storage Performance

To develop quick-charge sodium-ion battery, it is significant to optimize insertion-type anode to afford fast Na⁺ diffusion rate and excellent electron conductivity. First-principles calculations reveal the Ti O subcompound superiority for Na⁺ diffusion following Ti(II) O > Ti(III) O > Ti(IV) O. Hence, in situ growth of amorphous Ti O subcompounds with rich oxygen defects based on Ti₃C₂T_x-MXene is developed. Meanwhile, the composite presents expanded MXene interlayer spacing and much enhanced conductivity. The synergistic effect of enhanced electron/ion conduction gives a high capacity of 107 mAh g⁻¹ at 50 A g⁻¹, which gives 50% and 150% increasements compared with one counterpart without valence adjustment and another one without MXene expansion. It only needs 20 s (at 30 A g⁻¹) to complete the discharge/charge process and obtains a capacity of 144.5 mAh g⁻¹, which also shows a long-term cycling stability at quick-charge mode (121 mAh g⁻¹ after 10000 cycles at 10 A g⁻¹). The enhanced performance comes from fast electron transfer among Ti O subcompounds contributed by rich-defect amorphous TiO_2–x, and a reversible change of elastic MXene with interlayer spacing between 1.4 and 1.9 nm during Na⁺ insertion/extraction process. This study provides a feasible route to boost the kinetics and develop quick-charge sodium-ion battery.     

Towards All-Solid-State Polymer Batteries: Going Beyond PEO with Hybrid Concepts

To go beyond polyethylene oxide in lithium metal batteries, a hybrid polymer/oligomer cell design is presented, where an ester oligomer provides high ionic conductivity of 0.2 mS cm⁻¹ at 40 °C within thicker composite cathodes with active mass loadings of up to 11 mg cm⁻² (LiNbO₃-coated) LiNi_0.6Mn_0.2Co_0.2 (NMC622), while a 30 µm thin scaffold-supported polymer electrolyte affords mechanical stability. Corresponding discharge capacities of the hybrid cells exceed 170 mAh g⁻¹ (11 mg cm⁻²) or 160 mAh g⁻¹ (6 mg cm⁻²) at rates of either 0.1 or 0.25 C. Multilayer pouch cells are projected to enable energy densities of 235 Wh L⁻¹ (6 mg cm⁻²) and even up to 356 Wh L⁻¹ (11 mg cm⁻²), clearly superior to other reported polymer-based cell designs. Polyester electrolytes are environmentally benign and safer compared to common liquid electrolytes, while the straightforward synthesis and affordability of precursors render hybrid polyester electrolytes suitable candidates for future application in solid-state lithium metal batteries.