Decreasing Irreversible Capacity of Graphite Electrodes in Lithium-Ion Batteries by Direct Contact of Graphite with Metallic Lithium

The feasibility of reducing the irreversible capacity of negative graphite electrodes in lithium-ion batteries by a direct contact of such electrodes with lithium in the electrolyte is studied. It is shown that the dynamics of the formation of the passive film on graphite and the degree of the decrease in the irreversible capacity depend on the ratio between weights of graphite and lithium in contact. This method of reducing the irreversible capacity does not diminish the reversible capacity of graphite during the cycling. The irreversible capacity of the initial graphite cycled in 1 M LiPF₆ in a mixture of propylene carbonate and diethyl carbonate at a current density of 20 mA g^–1 is 550–1150 mA h g^–1. The reversible capacity of electrodes cycled in the same conditions reaches 290 mA h g^–1.     

A highly cross-linked polymeric binder for high-performance silicon negative electrodes in lithium ion batteries

A support bandage for electrodes: A cross-linked polymeric binder inhibits mechanical fracture of silicon negative electrodes during cycling. Nanosized silicon powder with a 3D interconnected network of poly(acrylic acid) and sodium carboxymethylcellulose as binder exhibits high reversible capacity of over 2000?mAh?g(-1) after 100 cycles at 30?°C while maintaining a high capacity and high current density.     

Cyclability enhancement and decreasing the irreversible capacity of anodes based on germanium nanowires for lithium-ion batteries

The electrochemical behavior of electrodes based on germanium nanowires in an electrolyte containing 1 m LiClO₄ in a propylene carbonate–dimethoxyethane mixture (7 : 3) with 2 wt% vinylene carbonate (VC) was studied. The additive of VC in this electrolyte decreased the irreversible capacity, increased the reversible capacity, and decreased the degradation rate of germanium electrodes in the course of cycling.     

Reversible Anionic Redox Activities in Conventional LiNi1/3Co1/3Mn1/3O2 Cathodes

Redox reactions of oxygen have been considered critical in controlling the electrochemical properties of lithium‐excessive layered‐oxide electrodes. However, conventional electrode materials without overlithiation remain the most practical. Typically, cationic redox reactions are believed to dominate the electrochemical processes in conventional electrodes. Herein, we show unambiguous evidence of reversible anionic redox reactions in LiNi_1/3Co_1/3Mn_1/3O₂. The typical involvement of oxygen through hybridization with transition metals is discussed, as well as the intrinsic oxygen redox process at high potentials, which is 75 % reversible during initial cycling and 63 % retained after 10 cycles. Our results clarify the reaction mechanism at high potentials in conventional layered electrodes involving both cationic and anionic reactions and indicate the potential of utilizing reversible oxygen redox reactions in conventional layered oxides for high‐capacity lithium‐ion batteries.     

Effect of surface structure on the charge storage capacity of carbon black electrodes

In this work we study the effect of surface structure on the charge storage capacity of carbon black electrodes with various changes in surface chemistry, morphology, and doping species. Cyclic voltammetry and chronopotentiometry studies, performed under alkaline conditions with carbon paste electrodes, indicate the importance of surface structure and grain size on the faradic and capacitive charge contributions of these materials. Among the various carbon blacks studied, the lithiated material shows superior charge storage capacity, suggesting the importance of alkaline metals and oxygenated groups on the carbon surface. For the graphitic carbon, the appearance of a reversible redox process with cycling resembles the electrochemical behavior reported for hydrogen storage in carbon nanotubes. Electronic Publication     

石墨烯包覆天然球形石墨作为锂离子电池的负极材料，是否需要乙炔黑导电剂？

我们通过包覆炭化的方法制备得到了石墨烯包覆的天然球形石墨(G/SG)材料,并使用扫描电子显微镜、X射线衍射仪以及多种电化学测试手段考察了不同石墨烯含量的复合材料的形貌结构及电化学性能。我们发现,在不添加乙炔黑(AB)的情况下,G/SG复合材料表现出较高的首次库伦效率,很好的循环稳定性和高倍率性能。当石墨烯包覆量为1%时,材料50次循环后的可逆容量可与添加10%AB的天然石墨电极(SG)等同;当石墨烯包覆量为2.5%时,材料的比容量完全高于添加10%AB的石墨电极。材料电化学性能的改善归因于石墨烯的包覆。一方面,石墨烯的柔软可变性可以保证天然石墨颗粒在充放电过程中的结构完整性,从而有效改善材料的循环稳定性;另一方面,石墨烯的存在提高了电极的导电性,促进更好导电网络的形成。因此,石墨烯包覆天然球形石墨材料中,石墨烯不仅是活性物质,也发挥导电剂的作用。当添加5%的乙炔黑时,在50 mA·g^-1电流循环50次后,5%G/SG电极的可逆容量从381.1 mAh·g^-1提高到404.5 mAh·g^-1,在1 A·g^-1电流时可逆容量从82.5 mAh·g^-1提高到101.9 mAh·g^-1,这表明G/SG电极仍然需要乙炔黑导电剂。乙炔黑颗粒填充在复合材料的空隙中,通过点接触的形式连接到G/SG颗粒,与石墨烯协同作用形成了更加有效的导电网络。尽管石墨烯包覆和乙炔黑添加对天然石墨电极具有积极的影响,例如增加了天然石墨电极的导电性和储锂性能(包括可逆容量,倍率性能和循环性能),但随着石墨烯或乙炔黑的增加,电极密度通常会降低。因此,在实际应用中应考虑石墨负极材料的质量和体积容量的平衡。这些结果对天然石墨的进一步商业应用具有重要意义。我们的工作为天然石墨电极在锂电池中的电化学行为提供了一种新的认识,并且有助于制备更高性能的负极材料。     

电化学转换反应及其在二次电池中的应用

电化学转换反应作为一种新的电极反应机制,近年来受到相当多的关注. 转换反应不仅能够利用金属化合物的多价态氧化还原,大幅度提高电化学容量利用率,而且对于主体晶格的结构、嵌脱阳离子的尺寸并无特殊要求,可以应用于众多不同种类的金属化合物,针对不同的金属离子设计高容量正负极活性材料. 因此,基于转换反应构建高容量电极材料正成为二次电池发展的一个新方向. 本文简要分析了电化学转换反应的基本原理和实现条件,并结合作者课题组近年来的研究工作探讨了这类反应在锂离子及钠离子电池中的潜在应用.     

Electrostatic Interactions Leading to Hierarchical Interpenetrating Electroconductive Networks in Silicon Anodes for Fast Lithium Storage

Recently, the frequency of combining MXene, which has unique properties such as metal-level conductivity and large specific surface area, with silicon to achieve excellent electrochemical performance has increased considerably. There is no doubt that the introduction of MXene can improve the conductivity of silicon and the cycling stability of electrodes after elaborate structure design. However, most exhaustive contacts can only improve the electrode conductivity on the plane. Herein, a MXene@Si/CNTs (HIEN-MSC) composite with hierarchical interpenetrating electroconductive networks has been synthesized by electrostatic self-assembly. In this process, the CNTs are first combined with silicon nanoparticles and then assembled with MXene nanosheets. Inserting CNTs into silicon nanoparticles can not only reduce the latter‘s agglomeration, but also immobilizes them on the three-dimensional conductive framework composed of CNTs and MXene nanosheets. Therefore, the HIEN-MSC electrode shows superior rate performance (high reversible capacity of 280 mA h⁻¹ even tested at 10 A g⁻¹), cycling stability (stable reversible capacity of 547 mA h g⁻¹ after 200 cycles at 1 A g⁻¹) and applicability (a high reversible capacity of 101 mA h g⁻¹ after 50 cycles when assembled with NCM622 into a full cell). These results may provide new insights for other electrodes with excellent rate performance and long-cycle stability.     

Highly disordered silicon-containing carbon from polymethylphenylsiloxane as anode material for lithium-ion batteries: Anomalous behavior in thin layer

Carbon-enriched glass-like material was produced by pyrolysis of polymethylphenylsiloxane. The physicochemical (examined by X-ray powder diffraction analysis, photoelectron spectroscopy, Raman scattering method, and energy-dispersive X-ray analysis) and electrochemical (examined by galvanostatic/potentiostatic cycling of electrodes in an organic electrolyte) properties of this material make it possible to regard it as a silicon-doped hard carbon. A thin-film electrode made of this material is cardinally different from pasted powder electrodes in the small hysteresis of charge-discharge curves and high reversible and low irreversible capacity with respect to lithium ions.     

Self-discharge behavior of LaNi5-based hydrogen storage electrodes in different electrolytes

Nickel–metal hydride (Ni–MH) batteries using hydrogen storage alloys as negative electrode materials have been developed and commercialized because of their high energy density, high rate capability and long cycle life, without causing environmental pollution (Song et al. J Alloys Comp 298:254, 2000; Jang et al. J Alloys Comp 268:290, 1998). However, the self-discharge rate is relatively higher than that of the Ni–Cd batteries, which would certainly be disadvantageous in practical applications. The capacity loss of a battery during storage is often related to self-discharge in the cells. Self-discharge takes place from a highly charged state of a cell to a lower state of charge (SOC) and is typically caused by the highly oxidizing or reducing characteristic of one or both of the electrodes in the cell. This self-discharge behavior may be affected by various factors such as gases, impurities, temperature, type of alloy electrode, electrolytes, or charge/discharge methods. The loss of capacity can be permanent or recoverable, depending on the nature of the mechanism (chemical or electrochemical) and aging condition. In this paper, the effects of electrolyte composition and temperature on self-discharge behavior of LaNi₅-based hydrogen storage alloy electrodes for Ni–MH batteries have been investigated. It was found that both reversible and irreversible capacity loss of MH electrode tested at 333 K were higher than that at 298 K. When tested at 298 K and 333 K, reversible capacity loss was mainly affected by the electrolyte, while the irreversible capacity loss was not affected. The dissolution of Al from the electrode can be reduced more effectively in an electrolyte with Al addition, compared with that in normal electrolyte. This resulted in a lower reversible capacity loss for the electrode exposed in the Al³⁺-rich electrolyte. SEM analysis has shown that some needle shape and hexagonal corrosion products were formed on the surface of the alloy electrodes, especially after storage at high temperature.     

A Robust Solid Electrolyte Interphase Layer Augments the Ion Storage Capacity of Bimetallic‐Sulfide‐Containing Potassium‐Ion Batteries

Metal–organic framework‐derived NiCo_2.5S₄ microrods wrapped in reduced graphene oxide (NCS@RGO) were synthesized for potassium‐ion storage. Upon coordination with organic potassium salts, NCS@RGO exhibits an ultrahigh initial reversible specific capacity (602 mAh g^?1 at 50 mA g^?1) and ultralong cycle life (a reversible specific capacity of 495 mAh g^?1 at 200 mA g^?1 after 1 900 cycles over 314 days). Furthermore, the battery demonstrates a high initial Coulombic efficiency of 78 %, outperforming most sulfides reported previously. Advanced ex situ characterization techniques, including atomic force microscopy, were used for evaluation and the results indicate that the organic potassium salt‐containing electrolyte helps to form thin and robust solid electrolyte interphase layers, which reduce the formation of byproducts during the potassiation–depotassiation process and enhance the mechanical stability of electrodes. The excellent conductivity of the RGO in the composites, and the robust interface between the electrodes and electrolytes, imbue the electrode with useful properties; including, ultrafast potassium‐ion storage with a reversible specific capacity of 402 mAh g^?1 even at 2 A g^?1.     

An investigation on electrochemical behavior of nanosize zinc sulfide electrode in lithium-ion cells

Nanosize zinc sulfides were synthesized through the chemical reaction method. The as-prepared zinc sulfide nanopowders were characterized by X-ray diffraction, transmission electron microscopy and electrochemical testing. The results revealed that zinc sulfide electrodes exhibited a reversible lithium storage capacity of about 400 mAh/g with stable cyclability. Zinc sulfide nanopowders show promise as anode materials for lithium-ion batteries.     

Organic Thiocarboxylate Electrodes for a Room‐Temperature Sodium‐Ion Battery Delivering an Ultrahigh Capacity

Organic room‐temperature sodium‐ion battery electrodes with carboxylate and carbonyl groups have been widely studied. Herein, for the first time, we report a family of sodium‐ion battery electrodes obtained by replacing stepwise the oxygen atoms with sulfur atoms in the carboxylate groups of sodium terephthalate which improves electron delocalization, electrical conductivity and sodium uptake capacity. The versatile strategy based on molecular engineering greatly enhances the specific capacity of organic electrodes with the same carbon scaffold. By introducing two sulfur atoms to a single carboxylate scaffold, the molecular solid reaches a reversible capacity of 466 mAh g⁻¹ at a current density of 50 mA g⁻¹. When four sulfur atoms are introduced, the capacity increases to 567 mAh g⁻¹ at a current density of 50 mA g⁻¹, which is the highest capacity value reported for organic sodium‐ion battery anodes until now.     

A Dual Plating Battery with the Iodine/[ZnIx(OH2)4−x]2−x Cathode

Plating battery electrodes typically deliver higher specific capacity values than insertion or conversion electrodes because the ion charge carriers represent the sole electrode active mass, and a host electrode is unnecessary. However, reversible plating electrodes are rare for electronically insulating nonmetals. Now, a highly reversible iodine plating cathode is presented that operates on the redox couples of I₂/[ZnI_x(OH₂)_4?x]^2?x in a water‐in‐salt electrolyte. The iodine plating cathode with the theoretical capacity of 211 mAh g^?1 plates on carbon fiber paper as the current collector, delivering a large areal capacity of 4 mAh cm^?2. Tunable femtosecond stimulated Raman spectroscopy coupled with DFT calculations elucidate a series of [ZnI_x(OH₂)_4?x]^2?x superhalide ions serving as iodide vehicles in the electrolyte, which eliminates most free iodide ions, thus preventing the consequent dissolution of the cathode‐plated iodine as triiodides.     

Engineering Active Sites of Polyaniline for AlCl2+ Storage in an Aluminum-Ion Battery

The reversible capacity of AlCl₄⁻ intercalation/de-intercalation in conventional cathodes of aluminum-ion batteries (AIBs) is difficult to improve due to the large size of AlCl₄⁻ anions. Therefore, it is highly desirable to realize the intercalation/de-intercalation of smaller Al-based ions. Here, we fabricated polyaniline/single-walled carbon nanotubes (PANI/SWCNTs) composite films and protonated the PANI nanorods. The protonation endows PANI with more active sites and enhanced conductivity. Hyper self-protonated PANI (PANI(H⁺)) exhibits reversible AlCl₂⁺ intercalation/de-intercalation during the discharge/charge process. As a result, the discharge capacity of the Al/PANI(H⁺) battery is twice as high as that of the initial composite films. PANI(H⁺)@SWCNT electrodes also have a stable cycling life with only 0.003 % capacity decay per cycle over 8000 cycles. Owing to the excellent mechanical properties, PANI(H⁺)@SWCNT composite films can act as the electrodes of flexible AIBs.     

聚吡咯改性电沉积Sn负极材料的电化学性能

本工作采用直接在铜箔表面恒电流电沉积的方法制备Sn负极,以NiCl₂为沉积电解液的添加剂得到了Sn空心管,提高了单纯Sn负极的可逆比容量,60次循环后仍剩余184.3 mAh·g^-1。进一步引入聚吡咯进行表面修饰改性,有效地提高了沉积电极的电化学循环性能,60次循环后仍剩余440.6 mAh·g^-1可逆比容量,同时具备良好的循环稳定性。沉积电极可直接用作锂离子电池负极,无需任何粘结剂,电极装配操作简单。     

聚吡咯改性电沉积Sn负极材料的电化学性能

本工作采用直接在铜箔表面恒电流电沉积的方法制备Sn负极,以NiCl2为沉积电解液的添加剂得到了Sn空心管,提高了单纯Sn负极的可逆比容量,60次循环后仍剩余184.3 mAh·g-1。进一步引入聚吡咯进行表面修饰改性,有效地提高了沉积电极的电化学循环性能,60次循环后仍剩余440.6 mAh·g-1可逆比容量,同时具备良好的循环稳定性。沉积电极可直接用作锂离子电池负极,无需任何粘结剂,电极装配操作简单。     

All-solid-state rechargeable lithium batteries using SnX-P2X5 (X = S and O) amorphous negative electrodes

SnS-P₂S₅ and SnO-P₂O₅ amorphous materials were prepared by a mechanical milling technique. The SnO-P₂O₅ milled materials worked as a reversible electrode with higher capacity than SnO crystal in rechargeable lithium cells with conventional liquid electrolytes. All-solid-state cells with a SnX-P₂X₅ (X = S and O) amorphous electrode and the Li₂S-P₂S₅ glass-ceramic electrolyte were charged and discharged at room temperature. The sulfide electrodes exhibited better charge-discharge performance than the oxide electrodes, suggesting that SnS-P₂S₅ electrodes are more compatible with Li₂S-P₂S₅ sulfide solid electrolytes. All-solid state batteries 80SnS·20P₂S₅/LiCoO₂ showed a charge-discharge plateau of about 3.4 V and high reversible capacity of over 400 mAh/g, even after 50 cycles. The SnX (X = S and O)-based amorphous materials are promising negative electrode materials with high capacity for rechargeable lithium batteries using not only liquid electrolytes but solid electrolytes.     

Rechargeable lithiated silicon-sulfur (SLS) battery prototypes

Amorphous columnar structured silicon film electrodes were prepared and electrochemically tested in dioxolane based electrolyte solution, containing LiNO₃. The electrochemical performance of prelithiated amorphous silicon anodes coupled with sulfur composite cathodes was evaluated in full Si-Li-Sulfur (SLS) cells. The reversible capacity at the first 10 cycles was 600 mAh/g sulfur with gradual fading to ~ 380 mAh/g sulfur after 60 cycles which is the highest obtained capacity reported for SLS full cells. Possible reasons for this capacity fading are discussed.     

VOCl as a Cathode for Rechargeable Chloride Ion Batteries

A novel room temperature rechargeable battery with VOCl cathode, lithium anode, and chloride ion transporting liquid electrolyte is described. The cell is based on the reversible transfer of chloride ions between the two electrodes. The VOCl cathode delivered an initial discharge capacity of 189 mAh g^?1. A reversible capacity of 113 mAh g^?1 was retained even after 100 cycles when cycled at a high current density of 522 mA g^?1. Such high cycling stability was achieved in chloride ion batteries for the first time, demonstrating the practicality of the system beyond a proof of concept model. The electrochemical reaction mechanism of the VOCl electrode in the chloride ion cell was investigated in detail by ex situ X‐ray diffraction (XRD), infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS). The results confirm reversible deintercalation–intercalation of chloride ions in the VOCl electrode.