Rechargeable Dual‐Ion Batteries with Graphite as a Cathode: Key Challenges and Opportunities

Rechargeable graphite dual‐ion batteries (GDIBs) have attracted the attention of electrochemists and material scientists in recent years due to their low cost and high‐performance metrics, such as high power density (≈3–175 kW kg^?1), energy efficiency (≈80–90%), long cycling life, and high energy density (up to 200 Wh kg^?1), suited for grid‐level stationary storage of electricity. The key feature of GDIBs is the exploitation of the reversible oxidation of the graphite network with concomitant and highly efficient intercalation/deintercalation of bulky anionic species between graphene layers. In this review, historical and current research aspects of GDIBs are discussed, along with key challenges in their development and practical deployment. Specific emphasis is given to the operational mechanism of GDIBs and to unbiased and correct reporting of theoretical cell‐level energy densities.     

Graphitic‐Shell Encapsulation of Metal Electrocatalysts for Oxygen Evolution,Oxygen Reduction,and Hydrogen Evolution in Alkaline Solution

Developing highly efficient, cost effective, and environmentally friendly electrocatalysts for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) is of interest for sustainable and clean energy technologies, including metal–air batteries and fuel cells. In this work, the screening of electrocatalytic activities of a series of single metallic iron, cobalt, and nickel nanoparticles and their binary and ternary alloys encapsulated in a graphitic carbon shell toward the OER, ORR, and HER in alkaline media is reported. Synthesis of these compounds proceeds by a two‐step sol–gel and carbothermal reduction procedure. Various ex situ characterizations show that with harsh electrochemical activation, the graphitic shell undergoes an electrochemical exfoliation. The modified electronic properties of the remaining graphene layers prevent their exfoliation, protect the bulk of the metallic cores, and participate in the electrocatalysis. The amount of near‐surface, higher‐oxidation‐state metals in the as‐prepared samples increases with electrochemical cycling, indicating that some metallic nanoparticles are not adequately encased within the graphite shell. Such surface oxide species provide secondary active sites for the electrocatalytic activities. The Ni–Fe binary system gives the most promising results for the OER, and the Co–Fe binary system shows the most promise for the ORR and HER.     

Molecular dynamics simulations of submonolayer hexane and pentane films on graphite

We present results of molecular dynamics computer simulations of hexane (C₆H₁₄ or C6) and pentane (C₅H₁₂ or C5) adlayers physisorbed onto a graphite substrate, for various submonolayer coverages. The hexane and pentane molecules incorporate explicit hydrogens and the graphite is modelled as a six-layer all-atom structure. Even though C6 and C5 have different structures at monolayer completion, both systems generally behave similarly in the submonolayer regime and results are in reasonable agreement with experiment for both systems. Specifically, there are four distinct topological regimes involving empty space: at densities closest to full coverage, there are large domains with individual vacancies, then with decreasing density, large vacancy patches appear first, followed by the formation of connected networks of smaller domains with multiple orientations that ultimately separate into individual patches. The energetics and melting behaviour of all systems are readily understood within the framework of the topology presented at various densities.     

Computer Simulation Study of the Chemical Potential of Argon Adsorbed on Graphite

Abstract

A multilayer film of argon adsorbed on the basal plane of graphite at 103 K was simulated using isokinetic molecular dynamics. The local chemical potentials in the film were evaluated using three algorithms suggested in the literature: test particle insertion, real particle calculation and the ratio method, which relies on calculations of the local energy distribution functions for test and real particles. Although none of these was suitable for calculations involving the partially solidified first adsorbed layer, the test particle and the ratio method produced useful results for regions in the film corresponding to second and higher layers. The ratio method is shown to be the most realistic, giving constant local chemical potentials of reasonably high precision for all points other than in the first layer.     

An amperometric lactate biosensor based on lactate dehydrogenase immobilized onto graphene oxide nanoparticles‐modified pencil graphite electrode

A novel amperometric lactate biosensor was developed based on immobilization of lactate dehydrogenase onto graphene oxide nanoparticles‐decorated pencil graphite electrode. The enzyme electrode was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and cyclic voltammetry at different stages of its construction. The biosensor showed optimum response within 5 s at pH 7.3 (0.1 M sodium phosphate buffer) and 35°C, when operated at 0.7 V. The biosensor exhibited excellent sensitivity (detection limit as low as 0.1 μM), fast response time (5 s), and wider linear range (5–50 mM). Analytical recovery of added lactic acid in serum was between 95.81–97.87% and within‐batch and between‐batch coefficients of variation were 5.04 and 5.40%, respectively. There was a good correlation between serum lactate values obtained by standard colorimetric method and the present biosensor (r = 0.99). The biosensor measured lactate levels in sera of apparently healthy subjects and persons suffering from lactate acidosis and other biological materials (milk, curd, yogurt, beer, white wine, and red wine). The enzyme electrode lost 25% of its initial activity after 60 days of its regular uses, when stored dry at 4°C.     

抗癌药物奥沙利铂与DNA分子相互作用的研究

奥沙利铂被称为第三代铂类药物,特别对胃肠道肿瘤具有较好的疗效.目前大多数的研究表明奥沙利铂的主要作用靶点是DNA分子,但它与DNA分子形成的关键结构和作用机制仍处在探索阶段.本研究运用紫外可见吸收光谱和原子力显微镜观察探索奥沙利铂与DNA在活体外的相互作用过程,从而揭示奥沙利铂产生抗癌作用的主要分子结构基础.首先使用紫外光谱研究了较高浓度奥沙利铂与DNA的作用过程.在此基础上,进一步采用原子力显微镜在高定向热解石墨表面观察了不同浓度奥沙利铂与质粒DNA在37℃条件下作用不同时间后的结构形貌变化,分析了奥沙利铂与DNA相互作用的过程.高分辨原子力显微观察结果表明奥沙利铂与DNA作用后可导致质粒DNA的结构发生显著的变化.随着作用时间的增加,DNA分子逐渐由伸展的链状变化为相互缠绕并带有许多结点的紧密结构,最终变化为更紧密的球状结构.本研究结果表明奥沙利铂可通过化学键合作用和静电作用使质粒DNA逐渐凝集为紧密的球状结构,这种结构可能对奥沙利铂的抗癌活性和毒性产生重要影响.     

Localized High‐Concentration Electrolytes Boost Potassium Storage in High‐Loading Graphite

Reversible intercalation of potassium‐ion (K⁺) into graphite makes it a promising anode material for rechargeable potassium‐ion batteries (PIBs). However, the current graphite anodes in PIBs often suffer from poor cyclic stability with low coulombic efficiency. A stable solid electrolyte interphase (SEI) is necessary for stabilizing the large interlayer expansion during K⁺ insertion. Herein, a localized high‐concentration electrolyte (LHCE) is designed by adding a highly fluorinated ether into the concentrated potassium bis(fluorosulfonyl)imide/dimethoxyethane, which forms a durable SEI on the graphite surface and enables highly reversible K⁺ intercalation/deintercalation without solvent cointercalation. Furthermore, this LHCE shows a high ionic conductivity (13.6 mS cm^?1) and excellent oxidation stability up to 5.3 V (vs K⁺/K), which enables compatibility with high‐voltage cathodes. The kinetics study reveals that K⁺ intercalation/deintercalation does not follow the same pathway. The potassiated graphite exhibits excellent depotassiation rate capability, while the formation of a low stage intercalation compound is the rate‐limiting step during potassiation.     

Low‐Temperature Growth of Hard Carbon with Graphite Crystal for Sodium‐Ion Storage with High Initial Coulombic Efficiency: A General Method

Practical application of hard carbon materials in sodium‐ion batteries (SIBs) is largely limited by their low initial coulombic efficiency (ICE), which may be improved by increasing the graphitization degree. However, biomass‐derived hard carbon is usually nongraphitizable and extremely difficult to graphitize by direct heating even at 3000 °C. Herein, a general strategy is reported for fabricating hard carbon materials with graphite crystals at 1300 °C promoted by external graphite that serves as a crystal template for the growth of graphite crystals. The graphite crystals enable the contacted pseudographitic domains with a high‐level ordered structure, large domain size, and low defects, leading to an enhanced ICE. The obtained hard carbon materials with graphite crystals, using the carbonized eggshell membranes, and sucrose‐derived microsphere as precursors, achieve very high ICE of 89% and 91% with reversible capacity of 310 and 301 mA h g^?1, respectively. Therefore, using external graphite to promote high‐level ordering pseudographitic domains at low temperature is quite useful to improve ICE for SIB applications.     

An In Situ Interface Reinforcement Strategy Achieving Long Cycle Performance of Dual‐Ion Batteries

Dual‐ion batteries (DIBs) with high operation voltage offer promising candidates for low‐cost clean energy chemistries. However, there still exist tough issues, including structural collapse of the graphite cathode due to solvent co‐intercalation and electrolyte decomposition on the electrode/electrolyte interface, which results in unsatisfactory cyclability and fast battery failure. Herein, Li₄Ti₅O₁₂ (LTO) modified mesocarbon microbeads (MCMBs) are proposed as a cathode material. The LTO layer functions as a skeleton and offers electrocatalytic active sites for in situ generation of a favorable and compatible cathode electrolyte interface (CEI) layer. The synergetic LTO‐CEI network can change the thermodynamic behavior of the PF₆^? intercalation process and maintain the structural integrity of the graphite cathode, as a “Great Wall” to protect the cathode from structural collapse and electrolyte decomposition. Such LTO‐CEI reinforced cathode exhibits a prolonged cyclability with 85.1% capacity retention after 2000 cycles even at cut‐off potential of 5.4 V versus Li⁺/Li. Moreover, the LTO‐modified MCMB (+)//prelithiated MCMB (?) full cell exhibits a high energy density of ≈200 Wh kg^?1, remarkably enhanced cyclability with 93.5% capacity retention after 1000 cycles. Undoubtedly, this work offers in‐depth insight into interface chemistry, which can arouse new originality to boost the development of DIBs.