In Situ Construction of an Ultra‐Stable Conductive Composite Interface for High‐Voltage All‐Solid‐State Lithium Metal Batteries

The garnet electrolyte presents poor wettability with Li metal, resulting in an extremely large interfacial impedance and drastic growth of Li dendrites. Herein, a novel ultra‐stable conductive composite interface (CCI) consisting of Li_ySn alloy and Li₃N is constructed in situ between Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) pellet and Li metal by a conversion reaction of SnN_x with Li metal at 300 °C. The Li_ySn alloy as a continuous and robust bridge between LLZTO and Li metal can effectively reduce the LLZTO/Li interfacial resistance from 4468.0 Ω to 164.8 Ω. Meanwhile, the Li₃N as a fast Li‐ion channel can efficiently transfer Li ions and give their uniform distribution at the LLZTO/Li interface. Therefore, the Li/LLZTO@CCI/Li symmetric battery stably cycles for 1200 h without short circuit, and the all‐solid‐state high‐voltage Li/LLZTO@CCI/LiNi_0.5Co_0.2Mn_0.3O₂ battery achieves a specific capacity of 161.4 mAh g^?1 at 0.25 C with a capacity retention rate of 92.6 % and coulombic efficiency of 100.0 % after 200 cycles at 25 °C.     

Graphitic Carbon Nitride (g-C3N4): An Interface Enabler for Solid-State Lithium Metal Batteries

Solid-state Li metal batteries (SSLMBs) have attracted considerable interests due to their promising energy density as well as high safety. However, the realization of a well-matched Li metal/solid-state electrolyte (SSE) interface remains challenging. Herein, we report g-C₃N₄ as a new interface enabler. We discover that introducing g-C₃N₄ into Li metal can not only convert the Li metal/garnet-type SSE interface from point contact to intimate contact but also greatly enhance the capability to suppress the dendritic Li formation because of the greatly enhanced viscosity, decreased surface tension of molten Li, and the in situ formation of Li₃N at the interface. Thus, the resulting Li-C₃N₄|SSE|Li-C₃N₄ symmetric cell gives a significantly low interfacial resistance of 11 Ω cm² and a high critical current density (CCD) of 1500 μA cm⁻². In contrast, the same symmetric cell configuration with pristine Li metal electrodes has a much larger interfacial resistance (428 Ω cm²) and a much lower CCD (50 μA cm⁻²).     

Interfacial Evolution of Lithium Dendrites and Their Solid Electrolyte Interphase Shells of Quasi‐Solid‐State Lithium‐Metal Batteries

Unstable electrode/solid‐state electrolyte interfaces and internal lithium dendrite penetration hamper the applications of solid‐state lithium‐metal batteries (SSLMBs), and the underlying mechanisms are not well understood. Herein, in situ optical microscopy provides insights into the lithium plating/stripping processes in a gel polymer electrolyte and reveals its dynamic evolution. Spherical lithium deposits evolve into moss‐like and branch‐shaped lithium dendrites with increasing current densities. Remarkably, the on‐site‐formed solid electrolyte interphase (SEI) shell on the lithium dendrite is distinctly captured after lithium stripping. Inducing an on‐site‐formed SEI shell with an enhanced modulus to wrap the lithium precipitation densely and uniformly can regulate dendrite‐free behaviors. An in‐depth understanding of lithium dendrite evolution and its functional SEI shell will aid in the optimization of SSLMBs.     

石墨相碳化氮(g-C3N4)纳米材料在分析化学中的应用进展

石墨相碳化氮(g-C_3N_4)具有类似于石墨烯的片层结构,其独特的电子能带结构、热稳定性以及高化学稳定性,优异的光学、电学性质,使之在生物成像、光、电传感器方面具有广阔的应用前景。该文综述了g-C_3N_4纳米材料在电化学、光学分析等分离分析方面的应用进展,并展望了其发展前景。     

A Highly Efficient All‐Solid‐State Lithium/Electrolyte Interface Induced by an Energetic Reaction

The energetic chemical reaction between Zn(NO₃)₂ and Li is used to create a solid‐state interface between Li metal and Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) electrolyte. This interlayer, composed of Zn, ZnLi_x alloy, Li₃N, Li₂O, and other species, possesses strong affinities with both Li metal and LLZTO and affords highly efficient conductive pathways for Li⁺ transport through the interface. The unique structure and properties of the interlayer lead to Li metal anodes with longer cycle life, higher efficiency, and better safety compared to the current best Li metal electrodes operating in liquid electrolytes while retaining comparable capacity, rate, and overpotential. All‐solid‐state Li||Li cells can operate at very demanding current–capacity conditions of 4 mA cm^?2–8 mAh cm^?2. Thousands of hours of continuous cycling are achieved at Coulombic efficiency >99.5 % without dendrite formation or side reactions with the electrolyte.     

A Plastic–Crystal Electrolyte Interphase for All‐Solid‐State Sodium Batteries

The development of all‐solid‐state rechargeable batteries is plagued by a large interfacial resistance between a solid cathode and a solid electrolyte that increases with each charge–discharge cycle. The introduction of a plastic–crystal electrolyte interphase between a solid electrolyte and solid cathode particles reduces the interfacial resistance, increases the cycle life, and allows a high rate performance. Comparison of solid‐state sodium cells with 1) solid electrolyte Na₃Zr₂(Si₂PO₄) particles versus 2) plastic–crystal electrolyte in the cathode composites shows that the former suffers from a huge irreversible capacity loss on cycling whereas the latter exhibits a dramatically improved electrochemical performance with retention of capacity for over 100 cycles and cycling at 5 C rate. The application of a plastic–crystal electrolyte interphase between a solid electrolyte and a solid cathode may be extended to other all‐solid‐state battery cells.     

Solid‐State Electrolyte Anchored with a Carboxylated Azo Compound for All‐Solid‐State Lithium Batteries

Organic electrode materials are promising for green and sustainable lithium‐ion batteries. However, the high solubility of organic materials in the liquid electrolyte results in the shuttle reaction and fast capacity decay. Herein, azo compounds are firstly applied in all‐solid‐state lithium batteries (ASSLB) to suppress the dissolution challenge. Due to the high compatibility of azobenzene (AB) based compounds to Li₃PS₄ (LPS) solid electrolyte, the LPS solid electrolyte is used to prevent the dissolution and shuttle reaction of AB. To maintain the low interface resistance during the large volume change upon cycling, a carboxylate group is added into AB to provide 4‐(phenylazo) benzoic acid lithium salt (PBALS), which could bond with LPS solid electrolyte via the ionic bonding between oxygen in PBALS and lithium ion in LPS. The ionic bonding between the active material and solid electrolyte stabilizes the contact interface and enables the stable cycle life of PBALS in ASSLB.     

Ionic‐Liquid–Nanoparticle Hybrid Electrolytes: Applications in Lithium Metal Batteries

Development of rechargeable lithium metal battery (LMB) remains a challenge because of uneven lithium deposition during repeated cycles of charge and discharge. Ionic liquids have received intensive scientific interest as electrolytes because of their exceptional thermal and electrochemical stabilities. Ionic liquid and ionic‐liquid–nanoparticle hybrid electrolytes based on 1‐methy‐3‐propylimidazolium (IM) and 1‐methy‐3‐propylpiperidinium (PP) have been synthesized and their ionic conductivity, electrochemical stability, mechanical properties, and ability to promote stable Li electrodeposition investigated. PP‐based electrolytes were found to be more conductive and substantially more efficient in suppressing dendrite formation on cycled lithium anodes; as little as 11 wt % PP‐IL in a PC‐LiTFSI host produces more than a ten‐fold increase in cell lifetime. Both PP‐ and IM‐based nanoparticle hybrid electrolytes provide up to 10 000‐fold improvements in cell lifetime than anticipated based on their mechanical modulus alone. Galvanostatic cycling measurements in Li/Li₄Ti₅O₁₂ half cells using IL–nanoparticle hybrid electrolytes reveal more than 500 cycles of trouble‐free operation and enhanced rate capability.     

聚环氧乙烷聚合物电解质基高电压固态锂金属电池的研究进展

采用液态碳酸酯电解质的锂离子电池在遭遇极端工况时, 极易发生泄露、燃烧、甚至爆炸等重大安全事故. 相对比, 聚环氧乙烷(PEO)固态聚合物电解质可以显著提升锂电池的安全性, 并且其优异的可塑性使其可以被制成特定形状进而满足特殊领域的差异化需求; 更为重要的是: PEO固态聚合物电解质与锂金属负极兼容性好. 然而, PEO固态聚合物电解质电化学氧化窗口低, 难以匹配高电压正极材料(≥4 V), 极大限制了其在高电压、高能量密度固态聚合物锂金属电池中的进一步应用. 近期经过国内外科研工作者在PEO固态聚合物电解质结构设计、PEO端羟基改性、含硼锂盐引入、功能型粘结剂设计开发以及正极界面层构筑等方面所做出的不懈努力, PEO固态聚合物电解质基高电压固态锂金属电池取得了系列化重大科研进展. 基于此, 本综述主要从以下八个方面: (1)高电压正极片表面修饰超薄聚合物层、(2)高电压正极颗粒包覆、(3)对碳黑颗粒进行包覆、(4)使用富含羧基的粘结剂、(5)不对称固态聚合物电解质结构设计、(6)正极界面原位形成耐高电压界面层、(7)醚氧官能团(-OCH₃)封端PEO, 提升其本征耐高电压性能、(8)含硼锂盐做添加剂, 详细综述了采用PEO固态聚合物电解质构建的高电压固态锂金属电池所取得的最新研究进展以及相应的高电压固态锂金属电池界面稳定作用机制. 最后还对未来PEO固态聚合物电解质在高电压固态锂金属电池方面所存在的巨大挑战和发展趋势进行了详细展望和总结阐述.     

Fluorinated Aromatic Diluent for High‐Performance Lithium Metal Batteries

In lithium metal batteries, electrolytes containing a high concentration of salts have demonstrated promising cyclability, but their practicality with respect to the cost of materials is yet to be proved. Here we report a fluorinated aromatic compound, namely 1,2‐difluorobenzene, for use as a diluent solvent in the electrolyte to realize the “high‐concentration effect”. The low energy level of the lowest unoccupied molecular orbital (LUMO), weak binding affinity for lithium ions, and high fluorine‐donating power of 1,2‐difluorobenzene jointly give rise to the high‐concentration effect at a bulk salt concentration near 2 m , while modifying the composition of the solid‐electrolyte‐interphase (SEI) layer to be rich in lithium fluoride (LiF). The employment of triple salts to prevent corrosion of the aluminum current collector further improves cycling performance. This study offers a design principle for achieving a local high‐concentration effect with reasonably low bulk concentrations of salts.     

Ultrathin 2D Graphitic Carbon Nitride on Metal Films: Underpotential Sodium Deposition in Adlayers for Sodium‐Ion Batteries

Efficient and low‐cost anode materials for the sodium‐ion battery are highly desired to enable more economic energy storage. Effects on an ultrathin carbon nitride film deposited on a copper metal electrode are presented. The combination of effects show an unusually high capacity to store sodium metal. The g‐C₃N₄ film is as thin as 10 nm and can be fabricated by an efficient, facile, and general chemical‐vapor deposition method. A high reversible capacity of formally up to 51 Ah g^?1 indicates that the Na is not only stored in the carbon nitride as such, but that carbon nitride activates also the metal for reversible Na‐deposition, while forming at the same time an solid electrolyte interface layer avoiding direct contact of the metallic phase with the liquid electrolyte.     

MoB/g‐C3N4 Interface Materials as a Schottky Catalyst to Boost Hydrogen Evolution

Proton adsorption on metallic catalysts is a prerequisite for efficient hydrogen evolution reaction (HER). However, tuning proton adsorption without perturbing metallicity remains a challenge. A Schottky catalyst based on metal–semiconductor junction principles is presented. With metallic MoB, the introduction of n‐type semiconductive g‐C₃N₄ induces a vigorous charge transfer across the MoB/g‐C₃N₄ Schottky junction, and increases the local electron density in MoB surface, confirmed by multiple spectroscopic techniques. This Schottky catalyst exhibits a superior HER activity with a low Tafel slope of 46 mV dec^?1 and a high exchange current density of 17 μA cm^?2, which is far better than that of pristine MoB. First‐principle calculations reveal that the Schottky contact dramatically lowers the kinetic barriers of both proton adsorption and reduction coordinates, therefore benefiting surface hydrogen generation.     

A Diffusion‐‐Reaction Competition Mechanism to Tailor Lithium Deposition for Lithium‐Metal Batteries

Lithium metal is recognized as one of the most promising anode materials owing to its ultrahigh theoretical specific capacity and low electrochemical potential. Nonetheless, dendritic Li growth has dramatically hindered the practical applications of Li metal anodes. Realizing spherical Li deposition is an effective approach to avoid Li dendrite growth, but the mechanism of spherical deposition is unknown. Herein, a diffusion‐reaction competition mechanism is proposed to reveal the rationale of different Li deposition morphologies. By controlling the rate‐determining step (diffusion or reaction) of Li deposition, various Li deposition scenarios are realized, in which the diffusion‐controlled process tends to lead to dendritic Li deposition while the reaction‐controlled process leads to spherical Li deposition. This study sheds fresh light on the dendrite‐free Li metal anode and guides to achieve safe batteries to benefit future wireless and fossil‐fuel‐free world.     

Graphitic Carbon Nitride/Nitrogen‐Rich Carbon Nanofibers: Highly Efficient Photocatalytic Hydrogen Evolution without Cocatalysts

An interconnected framework of mesoporous graphitic‐C₃N₄ nanofibers merged with in situ incorporated nitrogen‐rich carbon has been prepared. The unique composition and structure of the nanofibers as well as strong coupling between the components endow them with efficient light‐harvesting properties, improved charged separation, and a multidimensional electron transport path that enhance the performance of hydrogen production. The as‐obtained catalyst exhibits an extremely high hydrogen‐evolution rate of 16885 μmol h^?1 g^?1, and a remarkable apparent quantum efficiency of 14.3 % at 420 nm without any cocatalysts, which is much higher than most reported g‐C₃N₄‐based photocatalysts even in the presence of Pt‐based cocatalysts.     

Ultrathin 2D Graphitic Carbon Nitride on Metal Films: Underpotential Sodium Deposition in Adlayers for Sodium-Ion Batteries

Efficient and low-cost anode materials for the sodium-ion battery are highly desired to enable more economic energy storage. Effects on an ultrathin carbon nitride film deposited on a copper metal electrode are presented. The combination of effects show an unusually high capacity to store sodium metal. The g-C₃N₄ film is as thin as 10 nm and can be fabricated by an efficient, facile, and general chemical-vapor deposition method. A high reversible capacity of formally up to 51 Ah g⁻¹ indicates that the Na is not only stored in the carbon nitride as such, but that carbon nitride activates also the metal for reversible Na-deposition, while forming at the same time an solid electrolyte interface layer avoiding direct contact of the metallic phase with the liquid electrolyte.     

C=C π Bond Modified Graphitic Carbon Nitride Films for Enhanced Photoelectrochemical Cell Performance

Applications of graphitic carbon nitride (g‐CN) in photoelectrochemical and optoelectronic devices are still hindered due to the difficulties in synthesis of g‐CN films with tunable chemical, physical and catalytic properties. Herein we present a general method to alter the electronic and photoelectrochemical properties of g‐CN films by annealing. We found that N atoms can be removed from the g‐CN networks after annealing treatment. Assisted by theoretical calculations, we confirm that upon appropriate N removal, the adjacent C atoms will form new C=C π bonds. Detailed calculations demonstrate that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are located at the structure unit with C=C π bonds and the electrons are more delocalized. Valence band X‐ray photoelectron spectroscopy spectra together with optical absorption spectra unveil that the structure changes result in the alteration of the g‐CN energy levels and position of band edges. Our results show that the photocurrent density of the annealed g‐CN film is doubled compared with the pristine one, thanks to the better charge separation and transport within the film induced by the new C=C π bonds. An ultrathin TiO₂ film (2.2 nm) is further deposited on the g‐CN film as stabilizer and the photocurrent density is kept at 0.05 mA cm⁻² at 1.23 V versus reversible hydrogen electrode after two‐cycle stability assessment. This work enables the applications of g‐CN films in many electronic and optoelectronic devices.     

锂金属负极界面修饰及其在硫化物全固态电池中的应用

随着我国新能源产业的快速发展,全固态电池由于其理论上的高能量密度和高安全性受到广泛关注,而硫化物全固态电池具有离子电导率高的优势成为目前的研发热点,但是金属锂负极的锂枝晶生长和与硫化物电解质之间的不稳定性严重阻碍了硫化物全固态电池的研发.本工作在高温150℃下制备了均匀的LiF界面层来抑制金属锂负极/硫化物电解质之间的界面反应和锂枝晶.LiF/Li之间具有较高的界面能,所以可以有效抑制锂枝晶的生长.LiNbO₂@LiCoO₂//Li₆PS₅Cl//LiF@Li (LNO@LCO//LPSCl//LiF@Li)全电池0.05 C, 0.1 C, 0.2 C和0.5 C倍率的正极放电克容量分别为138.4 mAh/g, 105.0 mAh/g, 80.3 mAh/g和60.4 mAh/g, 0.05 C循环50周后,正极容量保持率为80.2%.该方法为后续金属锂负极在全固态电池中的应用提供了新的方案.     

Palladium Nanoparticles Supported on Titanium‐Doped Graphitic Carbon Nitride for Formic Acid Dehydrogenation

Pd nanoparticles (NPs) supported on Ti‐doped graphitic carbon nitride (g‐C₃N₄) were synthesized by a deposition–precipitation route and a subsequent reduction with NaBH₄. The features of the NPs were studied by XRD, TEM, FTIR, XPS, EXAFS and N₂‐physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti‐doped g‐C₃N₄. Compared to Pd loaded on pristine g‐C₃N₄, the Pd NPs supported on Ti‐doped g‐C₃N₄ exhibited a high catalytic activity in formic acid dehydrogenation in water at room temperature. The enhanced activity could be attributed to the small Pd NPs size, as well as the strong interaction between Pd NPs and Ti‐doped g‐C₃N₄.     

A Liquid/Liquid Electrolyte Interface that Inhibits Corrosion and Dendrite Growth of Lithium in Lithium‐Metal Batteries

A proof‐of‐concept study on a liquid/liquid (L/L) two‐phase electrolyte interface is reported by using the polarity difference of solvent for the protection of Li‐metal anode with long‐term operation over 2000 h. The L/L electrolyte interface constructed by non‐polar fluorosilicane (PFTOS) and conventionally polar dimethyl sulfoxide solvents can block direct contact between conventional electrolyte and Li anode, and consequently their side reactions can be significantly eliminated. Moreover, the homogeneous Li‐ion flow and Li‐mass deposition can be realized by the formation of a thin and uniform solid‐electrolyte interphase (SEI) composed of LiF, Li_xC, Li_xSiO_y between PFTOS and Li anode, as well as the super‐wettability state of PFTOS to Li anode, resulting in the suppression of Li dendrite formation. The cycling stability in a lithium–oxygen battery as a model is improved 4 times with the L/L electrolyte interface.