A crystalline carbon nitride-based separator for high-performance lithium metal batteries.

Lithium metal anodes with ultrahigh theoretical capacities are very attractive for assembling high-performance batteries. However, uncontrolled Li dendrite growth strongly retards their practical applications. Different from conventional separator modification strategies that are always focused on functional group tuning or mechanical barrier construction, herein, we propose a crystallinity engineering-related tactic by using the highly crystalline carbon nitride as the separator interlayer to suppress dendrite growth. Interestingly, the presence of Cl- intercalation and high-content pyrrolic-N from molten salt treatment along with highly crystalline structure enhanced the interactions of carbon nitride with Li+ and homogenized lithium flux for uniform deposition, as supported by both experimental and theoretical evidences. The Li-Li cell with the modified separator therefore delivered ultrahigh stability even after 3,000 h with dendrite-free cycled electrodes. Meanwhile, the assembled Li-LiFePO4 full-cell also presented high-capacity retention. This work opens up opportunities for design of functional separators through crystallinity engineering and broadens the use of C3N4 for advanced batteries.

Superstructure-Assisted Single-Atom Catalysis on Tungsten Carbides for Bifunctional Oxygen Reactions.

Single-atom catalysis (SAC) attracts wide interest for zinc-air batteries that require high-performance bifunctional electrocatalysts for oxygen reactions. However, catalyst design is still highly challenging because of the insufficient driving force for promoting multiple-electron transfer kinetics. Herein, we report a superstructure-assisted SAC on tungsten carbides for oxygen evolution and reduction reactions. In addition to the usual single atomic sites, strikingly, we reveal the presence of highly ordered Co superstructures in the interfacial region with tungsten carbides that induce internal strain and promote bifunctional catalysis. Theoretical calculations show that the combined effects from superstructures and single atoms strongly reduce the adsorption energy of intermediates and overpotential of both oxygen reactions. The catalyst therefore presented impressive bifunctional activity with an ultralow potential gap of 0.623 V and delivered a high power density of 188.5 mW cm-2 for assembled zinc-air batteries. This work opens up new opportunities for atomic catalysis.

Realization of Long-Life Proton Battery by Layer Intercalatable Electrolyte.

Proton batteries have attracted increasing interests because of their potential for grid-scale energy storage with high safety and great low-temperature performances. However, their development is significantly retarded by electrolyte design due to free water corrosion. Herein, we report a layer intercalatable electrolyte (LIE) by introducing trimethyl phosphate (TMP) into traditional acidic electrolyte. Different from conventional role in batteries, the presence of TMP intriguingly achieves co-intercalation of solvent molecules into the interlayer of anode materials, enabling a new working mechanism for proton reactions. The electrode corrosion was also strongly retarded with expanded electrochemical stability window. The half-cell therefore showed an outstanding long-term cycling stability with 91.0 % capacity retention at 5 A g-1 after 5000 cycles. Furthermore, the assembled full batteries can even deliver an ultra-long lifetime with a capacity retention of 74.9 % for 2 months running at -20 °C. This work provides new opportunities for electrolyte design of aqueous batteries.

An Amorphous Anode for Proton Battery.

Developing advanced electrode materials is crucial for improving the electrochemical performances of proton batteries. Currently, the anodes are primarily crystalline materials which suffer from inferior cyclic stability and high electrode potential. Herein, we propose amorphous electrode materials for proton batteries by using a general ion-exchange protocol to introduce multivalent metal cations for activating the host material. Taking Al3+ as an example, theoretical and experimental analysis demonstrates electrostatic interaction between metal cations and lattice oxygen, which is the primary barrier for direct introduction of the multivalent cations, is effectively weakened through ion exchange between Al3+ and pre-intercalated K+. The as-prepared Al-MoOx anode therefore delivered a remarkable capacity and outstanding cycling stability that outperforms most of the state-of-the-art counterparts. The assembled full cell also achieved a high voltage of 1.37 V. This work opens up new opportunities for developing high-performance electrodes of proton batteries by introducing amorphous materials.

An ultralong-life SnS-based anode through phosphate-induced structural regulation for high-performance sodium ion batteries.

As a star representative of transition metal sulfides, SnS is viewed as a promising anode-material candidate for sodium ion batteries due to its high theoretical capacity and unique layered structure. However, the extremely poor electrical conductivity and severe volume expansion strongly hinder its practical application while achieving a high reversible capacity with long-cyclic stability still remains a grand challenge. Herein, different from the conventional enhancement method of elemental doping, we report a rational strategy to introduce PO43- into the SnS layers using phytic acid as the special phosphorus source. Intriguingly, the presence of PO43- in the form of Sn-O-P covalent bonds can act as a conductive pillar to buffer the volume expansion of SnS while expanding its interlay spacing to allow more Na+ storage, supported by both experimental and theoretical evidences. Profiting from this effect combined with microstructural metrics by loading on high pyridine N-doped reduced graphene oxide, the as-prepared material presented an unprecedented ultra-long cyclic stability even after 10,000 cycles along with high reversible capacity and excellent full-cell performances. The findings herein open up new opportunities for elevating electrochemical performances of metal sulfides and provide inspirations for the fabrication of advanced electrode materials for broad energy use.

Mixed Lithium Oxynitride/Oxysulfide as an Interphase Protective Layer To Stabilize Lithium Anodes for High-Performance Lithium-Sulfur Batteries.

Lithium metal is strongly recognized as a promising anode material for next-generation high-energy-density systems. However, unstable solid electrolyte interphase and uncontrolled lithium dendrites growth induce severe capacity decay and short cycle life accompanied by high security risks. Here, we propose a simple method for constructing an artificial solid electrolyte interphase layer on the surface of lithium metal through spontaneous reaction, where ammonium persulfate and lithium nitrate are exploited as oxidants. The satisfactory artificial protective layer with uniform and dense morphology is composed of mixed lithium compounds, mainly including Li xSO y and Li xNO y species, which could effectively stabilize the interphase between electrolyte and lithium metal anode and restrain the "shuttle effect" of polysulfides. By employing the premodified lithium metal as anodes for lithium-sulfur batteries, the resulting cells exhibit excellent cycle stability (capacity decay of 0.09% per cycle over 300 cycles at 1 C and Coulombic efficiency of over 98%) and outstanding rate capability (850.8 mAh g-1 even at 4 C). Hence, introducing a stable artificial protective layer to protect lithium anode delivers a new strategy for solving the issues related to lithium-metal batteries.