A Fully Amorphous, Dynamic Cross-Linked Polymer Electrolyte for Lithium-Sulfur Batteries Operating at Subzero-Temperatures.

Solid-state lithium-sulfur batteries have shown prospects as safe, high-energy electrochemical storage technology for powering regional electrified transportation. Owing to limited ion mobility in crystalline polymer electrolytes, the battery is incapable of operating at subzero temperature. Addition of liquid plasticizer into the polymer electrolyte improves the Li-ion conductivity yet sacrifices the mechanical strength and interfacial stability with both electrodes. In this work, we showed that by introducing a spherical hyperbranched solid polymer plasticizer into a Li+ -conductive linear polymer matrix, an integrated dynamic cross-linked polymer network was built to maintain fully amorphous in a wide temperature range down to subzero. A quasi-solid polymer electrolyte with a solid mass content >90 % was prepared from the cross-linked polymer network, and demonstrated fast Li+ conduction at a low temperature, high mechanical strength, and stable interfacial chemistry. As a result, solid-state lithium-sulfur batteries employing the new electrolyte delivered high reversible capacity and long cycle life at 25 °C, 0 °C and -10 °C to serve energy storage at complex environmental conditions.

"Pore-Hopping" Ion Transport in Cellulose-Based Separator Towards High-Performance Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have great potential for large-scale energy storage. Cellulose is an attractive material for sustainable separators, but some key issues still exist affecting its application. Herein, a cellulose-based composite separator (CP@PPC) was prepared by immersion curing of cellulose-based separators (CP) with poly(propylene carbonate) (PPC). With the assistance of PPC, the CP@PPC separator is able to operate the cell stably at high voltages (up to 4.95 V). The "pore-hopping" ion transport mechanism in CP@PPC opens up extra Na+ migration paths, resulting in a high Na+ transference number (0.613). The separator can also tolerate folding, bending and extreme temperature under certain circumstances. Full cells with CP@PPC reveal one-up capacity retention (96.97 %) at 2C after 500 cycles compared to cells with CP. The mechanism highlights the merits of electrolyte analogs in separator modification, making a rational design for durable devices in advanced energy storage systems.

Advanced Covalent Organic Frameworks for Multi-Valent Metal Ion Batteries.

Covalent organic frameworks (COFs) have received increased interest in recent years as an advanced class of materials. By virtue of the available monomers, multiple conformations and various linkages, COFs offer a wide range of opportunities for complex structural design and specific functional development of materials, which has facilitated the widespread application in many fields, including multi-valent metal ion batteries (MVMIBs), described as the attractive candidate replacing lithium-ion batteries (LIBs). With their robust skeletons, diverse pores, flexible structures and abundant functional groups, COFs are expected to help realize a high performance MVMIBs. In this review, we present an overview of COFs, describe advances in topology design and synthetic reactions, and study the application of COFs in MVMIBs, as well as discuss challenges and solutions in the preparation of COFs electrodes, in the hope of providing constructive insights into the future direction of COFs.

Multifunctional Carbon Modification Enhancement for Vanadium-Based Phosphates as an Advanced Cathode of Zinc-Ion Batteries.

In recent years, rechargeable aqueous zinc-ion batteries (ZIBs) have shown extraordinary potential due to their safety, nontoxicity, sustainable zinc resources, and low price. However, the lack of suitable cathode materials hinders the development of ZIBs. Recently, layered phosphates have been widely used as cathode materials. As one typical phosphate cathode, vanadium oxyphosphate (VOPO4) has inherently low electronic conductivity and structural dissolution in electrochemical reactions, limiting its development. To solve these problems, VOPO4/C is prepared by combining multifunctional carbon material with a VOPO4 interlayer and an external surface, which not only improves the electronic conductivity of the composite material but also effectively inhibits the dissolution of VOPO4 in the electrolyte. As a result, the prepared VOPO4/C could deliver a reversible capacity of 140 mA h g-1 at a current density of 100 mA g-1. Furthermore, the rate performance of the VOPO4/C composite has also been improved significantly. In the process of charging and discharging, zinc ions in the composite show perfect intercalate and deintercalate performance.

Regulating the Li Nucleation/Growth Behavior via Cu2O Nanowire Array and Artificial Solid Electrolyte Interphase toward Highly Stable Li Metal Anode.

Lithium (Li) metal has been considered to be the most promising anode material for next-generation rechargeable batteries. Unfortunately, the hazards induced by dendrite growth and volume fluctuation hinder its commercialized application. Here, a three-dimensional (3D) current collector composed of a vertically aligned Cu2O nanowire that is tightly coated with a polydopamine protective layer is developed to solve the encountered issues of lithium metal batteries (LMBs). The Cu2O nanowire arrays (Cu2O NWAs) provide abundant lithiophilic sites for inducing Li nucleation selectively to form a thin Li layer around the nanowires and direct subsequent Li deposition. The well-defined nanochannel works well in confining the Li growth spatially and buffering the volume change during the repeated cycling. The PDA coatings adhered onto the outline of the Cu2O NWAs serve as the artificial solid electrolyte interface to isolate the electrode and electrolyte and retain the interfacial stability. Moreover, the increased specific area of copper foam (CF) can dissipate the local current density and further suppress the growth of Li dendrites. As a result, CF@Cu2O NWAs@PDA realizes a dendrite-free morphology and the assembled symmetrical batteries can work stably for over 1000 h at 3 mA cm-2. When CF@Cu2O NWAs@PDA is coupled with a LiFePO4 cathode, the full cells exhibit improved cycle stability and rate performance.

Covalent Organic Framework with Highly Accessible Carbonyls and π-Cation Effect for Advanced Potassium-Ion Batteries.

Covalent organic frameworks (COF) possess a robust and porous crystalline structure, making them an appealing candidate for energy storage. Herein, we report an exfoliated polyimide COF composite (P-COF@SWCNT) prepared by an in situ condensation of anhydride and amine on the single-walled carbon nanotubes as advanced anode for potassium-ion batteries (PIBs). Numerous active sites exposed on the exfoliated frameworks and the various open pathways promote the highly efficient ion diffusion in the P-COF@SWCNT while preventing irreversible dissolution in the electrolyte. During the charging/discharging process, K+ is engaged in the carbonyls of imide group and naphthalene rings through the enolization and π-K+ effect, which is demonstrated by the DFT calculation and XPS, ex-situ FTIR, Raman. As a result, the prepared P-COF@SWCNT anode enables an incredibly high reversible specific capacity of 438 mA h g-1 at 0.05 A g-1 and extended stability. The structural advantage of P-COF@SWCNT enables more insights into the design and versatility of COF as an electrode.

[Co3(µ3-O)]-Based Metal-Organic Frameworks as Advanced Anode Materials in K- and Na-Ion Batteries.

A new metal-organic framework {(Me2NH2)2[Co3(µ3-O)(btb)2(py)(H2O)]·(DMF)2(H2O)2}n (Cobtbpy) was solvothermal synthesized (H3btb = 1,3,5-tri(4-carboxylphenyl)benzene, py = pyridine, DMF = N,N-dimethylformamide). Cobtbpy shows a (3,6)-connected rtl 3D network with a point symbol of (4·62)2(42·610·83) based on the [Co3(µ3-O)] clusters. The obtained Cobtbpy has stable, accessible, dense active sites and can be applied in the potassium- and sodium-ion batteries. Through mixing with single-walled carbon nanotubes, the prepared composite anode material Cobtbpy-0.9 achieved a high reversible capability, delivering 416 mAh/g in the potassium-ion batteries and 379 mAh/g in the sodium-ion batteries at 0.05 A/g. The outstanding properties of Cobtbpy-0.9 in the batteries demonstrated that this MOFs-based carbon composite is a highly desirable electrode material candidate for high-performance potassium- and sodium-ion batteries.

Regulation of Cathode-Electrolyte Interphase via Electrolyte Additives in Lithium Ion Batteries.

As the power supply of the prosperous new energy products, advanced lithium ion batteries (LIBs) are widely applied to portable energy equipment and large-scale energy storage systems. To broaden the applicable range, considerable endeavours have been devoted towards improving the energy and power density of LIBs. However, the side reaction caused by the close contact between the electrode (particularly the cathode) and the electrolyte leads to capacity decay and structural degradation, which is a tricky problem to be solved. In order to overcome this obstacle, the researchers focused their attention on electrolyte additives. By adding additives to the electrolyte, the construction of a stable cathode-electrolyte interphase (CEI) between the cathode and the electrolyte has been proven to competently elevate the overall electrochemical performance of LIBs. However, how to choose electrolyte additives that match different cathode systems ideally to achieve stable CEI layer construction and high-performance LIBs is still in the stage of repeated experiments and exploration. This article specifically introduces the working mechanism of diverse electrolyte additives for forming a stable CEI layer and summarizes the latest research progress in the application of electrolyte additives for LIBs with diverse cathode materials. Finally, we tentatively set forth recommendations on the screening and customization of ideal additives required for the construction of robust CEI layer in LIBs. We believe this minireview will have a certain reference value for the design and construction of stable CEI layer to realize desirable performance of LIBs.