Electrochemically Induced Crystalline-to-Amorphous Transition of Dinuclear Polyoxovanadate for High-Rate Lithium-Ion Batteries

Polyoxometalates are intriguing high-capacity anode materials for alkali-metal-ion storage due to their multi-electron redox capabilities and flexible structure. However, their poor electrical conductivity and high working voltage severely restrict their practical application. Herein, the dinuclear polyoxovanadate Sr₂V₂O₇·H₂O with unusually high electrical conductivity is reported as a promising anode material for lithium-ion batteries. During the initial lithiation process, the Sr₂V₂O₇·H₂O anode experiences an electrochemically induced crystalline-to-amorphous transition. The resulting amorphous structure provides high redox activity and fast reaction kinetics via reversible V^4.9+/V^2.8+ redox couple through the intercalation mechanism. Furthermore, when coupled with the LiFePO₄ cathode, the strong V O bonds of the amorphous anode provide excellent structural stability, with the full-cell capable of performing >12 000 cycles with a capacity retention of 72%. Another advantage of Sr_2xV₂O_7-δ·yH₂O (0.5 ≤ x ≤ 1.0) is its composition adjustability, which enables delicately regulating the Sr vacancy content without destroying the structure. The defect Sr_2xV₂O_7-δ·yH₂O (x = 0.5) electrodes show significantly improved specific capacity and rate capability without sacrificing other key properties, delivering a high specific capacity of 479 mAh g^-1 at 0.1 mA cm^-2 and 41.9% of its capacity in 2 min. Overall, the preliminary study points the way forward for the facile preparation of high-quality polyoxometalates for advanced energy storage applications and beyond.     

Stabilizing Redox-Active Hexaazatriphenylene in a 2D Conductive Metal–Organic Framework for Improved Lithium Storage Performance

Organic redox-active materials are promising electrode candidates for lithium-ion batteries by virtue of their designable structure and cost-effectiveness. However, their poor electrical conductivity and high solubility in organic electrolytes limit the device's performance and practical applications. Herein, the π-conjugated nitrogen-containing heteroaromatic molecule hexaazatriphenylene (HATN) is strategically embedded with redox-active centers in the skeleton of a Cu-based 2D conductive metal–organic framework (2D c-MOF) to optimize the lithium (Li) storage performance of organic electrodes, which delivers improved specific capacity (763 mAh g⁻¹ at 300 mA g⁻¹), long-term cycling stability (≈90% capacity retention after 600 cycles at 300 mA g⁻¹), and excellent rate performance. The correlation of experimental and computational results confirms that this high Li storage performance derives from the maximum number of active sites (CN sites in the HATN unit and CO sites in the CuO₄ unit), favorable electrical conductivity, and efficient mass transfer channels. This strategy of integrating multiple redox-active moieties into the 2D c-MOF opens up a new avenue for the design of high-performance electrode materials.     

Critical Review of Fluorinated Electrolytes for High-Performance Lithium Metal Batteries

Lithium metal batteries (LMBs), due to their ultra-high energy density, are attracting tremendous attentions. However, their commercial application is severely impeded by poor safety and unsatisfactory cycling stability, which are induced by lithium dendrites, side reactions, and inferior anodic stability. Electrolytes, as the indispensable and necessary components in lithium metal batteries, play a crucial role in regulating the electrochemical performance of LMBs. Recently, the fluorinated electrolytes are widely investigated in high-performance LMBs. Thus, the design strategies of fluorinated electrolytes are thoroughly summarized, including fluorinated salts, fluorinated solvents, and fluorinated additives in LMBs, and insights of the fluorinated components in suppressing lithium dendrites, improving anodic stability and cycling stability. Finally, an outlook with several design strategies and challenges will be proposed for novel fluorinated electrolytes.     

Incombustible Polymer Electrolyte Boosting Safety of Solid-State Lithium Batteries: A Review

Lithium-ion batteries with their portability, high energy density, and reusability are frequently used in today's world. Under extreme conditions, lithium-ion batteries leak, burn, and even explode. Therefore, improving the safety of lithium-ion batteries has become a focus of attention. Researchers believe using a solid electrolyte instead of a liquid one can solve the lithium battery safety issue. Due to the low price, good processability and high safety of the solid polymer electrolytes, increasing attention have been paid to them. However, polymer electrolytes can also decompose and burn under extreme conditions. Moreover, lithium dendrites are formed continuously due to the uneven charge distribution on the surface of the lithium metal anode. A short circuit caused by a lithium dendrite can cause the battery to thermal runaway. As a result, the safety of polymer solid-state batteries remains a challenge. In this review, the thermal runaway mechanism of the batteries is summarized, and the batteries abuse test standard is introduced. In addition, the recent works on the high-safety polymer electrolytes and the solution strategies of lithium anode problems in polymer batteries are reviewed. Finally, the development direction of safe polymer solid lithium batteries is prospected.     

Nanocellulose-Carboxymethylcellulose Electrolyte for Stable,High-Rate Zinc-Ion Batteries

Aqueous Zn ion batteries (ZIBs) are one of the most promising battery chemistries for grid-scale renewable energy storage. However, their application is limited by issues such as Zn dendrite formation and undesirable side reactions that can occur in the presence of excess free water molecules and ions. In this study, a nanocellulose-carboxymethylcellulose (CMC) hydrogel electrolyte is demonstrated that features stable cycling performance and high Zn²⁺ conductivity (26 mS cm⁻¹), which is attributed to the material's strong mechanical strength (≈70 MPa) and water-bonding ability. With this electrolyte, the Zn-metal anode shows exceptional cycling stability at an ultra-high rate, with the ability to sustain a current density as high as 80 mA cm⁻² for more than 3500 cycles and a cumulative capacity of 17.6 Ah cm⁻² (40 mA cm⁻²). Additionally, side reactions, such as hydrogen evolution and surface passivation, are substantially reduced due to the strong water-bonding capacity of the CMC. Full Zn||MnO₂ batteries fabricated with this electrolyte demonstrate excellent high-rate performance and long-term cycling stability (>500 cycles at 8C). These results suggest the cellulose-CMC electrolyte as a promising low-cost, easy-to-fabricate, and sustainable aqueous-based electrolyte for ZIBs with excellent electrochemical performance that can help pave the way toward grid-scale energy storage for renewable energy sources.     

Sufficient Utilization of Mn2+/Mn3+/Mn4+ Redox in NASICON Phosphate Cathodes towards High-Energy Na-Ions Batteries

Na superionic conductor of Na₃MnTi(PO₄)₃ only containing high earth-abundance elements is regarded as one of the most promising cathodes for the applicable Na-ion batteries due to its desirable cycling stability and high safety. However, the voltage hysteresis caused by Mn²⁺ ions resided in Na⁺ vacancies has led to significant capacity loss associated with Mn reaction centers between 2.5–4.2 V. Herein, the sodium excess strategy based on charge compensation is applied to suppress the undesirable voltage hysteresis, thereby achieving sufficient utilization of the Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ redox couples. These findings indicate that the sodium excess Na_3.5MnTi_0.5Ti_0.5(PO₄)₃ cathode with Ti⁴⁺ reduction has a lowest Mn²⁺ occupation on the Na⁺ vacancies in its initial composition, which can improve the kinetics properties, finally contributing to a suppressed voltage hysteresis. Based on these findings, it is further applied the sodium excess route on a Mn-richer phosphate cathode, which enables the suppressed voltage hysteresis and more reversible capacity. Consequently, this developed Na_3.6Mn_1.15Ti_0.85(PO₄)₃ cathode achieved a high energy density over 380 Wh kg⁻¹ (based on active substance mass of cathode) in full-cell configurations, which is not only superior to most of the phosphate cathodes, but also delivers more application potential than the typical oxides cathodes for Na-ion batteries.     

Toward Flexible Embodied Energy: Scale-Inspired Overlapping Lithium-Ion Batteries with High-Energy-Density and Variable Stiffness

High performance flexible batteries are essential ingredients for flexible devices. However, general isolated flexible batteries face critical challenges in developing multifunctional embodied energy systems, owing to the lack of integrative design. Herein, inspired by scales in creatures, overlapping flexible lithium-ion batteries (FLIBs) consisting of energy storage scales and connections using LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) and graphite electrodes are presented. The scale-dermis structure ensures a high energy density of 374.4 Wh L⁻¹ as well as a high capacity retention of 93.2% after 200 charge/discharge cycles and 40 000 bending times. A variable stiffness property is revealed that can be controlled by battery configurations and deformation modes. Furthermore, the overlapping FLIBs can be housed directly into the architecture of several flexible devices, such as robots and grippers, allowing to create multifunctionalities that go far beyond energy storage and include load-bearing and variable flexibility. This study broadens the versatility of FLIBs toward energy storage structure engineering of flexible devices.     

Polyether-b-Amide Based Solid Electrolytes with Well-Adhered Interface and Fast Kinetics for Ultralow Temperature Solid-State Lithium Metal Batteries

Solid-state lithium metal batteries (SSLMBs) are highly desirable for energy storage because of the urgent need for higher energy density and safer batteries. However, it remains a critical challenge for stable cycling of SSLMBs at low temperature. Here, a highly viscoelastic polyether-b-amide (PEO-b-PA) based composite solid-state electrolyte is proposed through a one-pot melt processing without solvent to address this key process. By adjusting the molar ratio of PEO-b-PA to lithium bis(trifluoromethanesulphonyl)imide (ethylene oxide:Li = 6:1) and adding 20 wt.% succinonitrile, fast Li⁺ transport channel is conducted within the homogeneous polymer electrolyte, which enables its application at ultra-low temperature (−20 to 25 °C). The composite solid-state electrolyte utilizes dynamic hydrogen-bonding domains and ion-conducting domains to achieve a low interfacial charge transfer resistance (<600 Ω) at −20 °C and high ionic conductivity (25 °C, 3.7 × 10⁻⁴ S cm⁻¹). As a result, the LiFePO₄|Li battery based on composite electrolyte exhibits outstanding electrochemical performance with 81.5% capacity retention after 1200 cycles at −20 °C and high discharge specific capacities of 141.1 mAh g⁻¹ with high loading (16.1 mg cm⁻²) at 25 °C. Moreover, the solid-state SNCM811|Li cell achieves excellent safety performance under nail penetration test, showing great promise for practical application.     

Amorphization Boost Multi-Ions Storage for High-Performance Aqueous Batteries

Regarding the complex properties of various cations, the design of aqueous batteries that can simultaneously store multi-ions with high capacity and satisfactory rate performance is a great challenge. Here an amorphization strategy to boost cation-ion storage capacities of anode materials is reported. In monovalent (H⁺, Li⁺, K⁺), divalent (Mg²⁺, Ca²⁺, Zn²⁺) and even trivalent (Al³⁺) aqueous electrolytes, the capacity of the resulting amorphous MoO_x is more than quadruple than that of crystalline MoO_x and exceeds those of other reported multiple-ion storage materials. Both experimental and theoretical calculations reveal the generation of ample active sites and isotropic ions in the amorphous phase, which accelerates cation migration within the electrode bulk. Amorphous MoO_x can be coupled with multi-ion storage cathodes to realize electrochemical energy storage devices with different carriers, promising high energy and power densities. The power density exceeded 15000 W kg⁻¹, demonstrating the great potential of amorphous MoO_x in advanced aqueous batteries.     

In Situ Artificial Hybrid SEI Layer Enabled High-Performance Prelithiated SiOx Anode for Lithium-Ion Batteries

Considered the promising anode material for next-generation high-energy lithium-ion batteries, SiO_x has been slow to commercialize due to its low initial Coulombic efficiency (ICE) and unstable solid electrolyte interface (SEI) layer, which leads to reduced full-cell energy density, short cycling lives, and poor rate performance. Herein, a novel strategy is proposed to in situ construct an artificial hybrid SEI layer consisting of LiF and Li₃Sb on a prelithiated SiO_x anode via spontaneous chemical reaction with SbF₃. In addition to the increasing ICE (94.5%), the preformed artificial SEI layer with long-term cycle stability and enhanced Li⁺ transport capability enables a remarkable improvement in capacity retention and rate capability for modified SiO_x. Furthermore, the full cell using Li(Ni_0.8Co_0.1Mn_0.1)O₂ and a pre-treated anode exhibits high ICE (86.0%) and capacity retention (86.6%) after 100 cycles at 0.5 C. This study provides a fresh insight into how to obtain stable interface on a prelithiated SiO_x anode for high energy and long lifespan lithium-ion batteries.