Research progress on carbon materials as negative electrodes in sodium-and potassium-ion batteries

Carbon materials,including graphite,hard carbon,soft carbon,graphene,and carbon nanotubes,are widely used as high-performance negative electrodes for sodium-ion and potassium-ion batteries(SIBs and PIBs).Compared with other materials,carbon materials are abundant,low-cost,and environmentally friendly,and have excellent electrochemical properties,which make them especially suitable for negative electrode materials of SIBs and PIBs.Compared with traditional carbon materials,modifications of the morphology and size of nanomaterials represent effective strategies to improve the quality of electrode materials.Different nanostructures make different contributions toward improving the electrochemical performance of electrode materials,so the synthesis of nanomaterials is promising for controlling the morphology and size of electrode materials.This paper reviews the progress made and challenges in the use of carbon materials as negative electrode materials for SIBs and PIBs in recent years.The differences in Na+and K+storage mechanisms among different types of carbon materials are emphasized.

Enhanced electrochemical performance of Li-ion batteries with nanoporous titania as negative electrodes

Nanoporous anatase TiO_2 （np-TiO_2） electrodes have been developed via the anodization of titanium foils in fluoride containing electrolytes, and its application in rechargeable lithium-ion batteries （LIBs） was investigated. Four different types of np-TiO_2 electrodes with different pore diameters of 14.7±8.2 nm, 12.85±6.8 nm, 11.0±5.5, and 26.7±13.6 nm were fabricated for evaluating the effect of nanoporous characteristics on the LIB performance. The discharge capacity of the four battery types 1, 2, 3, and 4 were 132.7 mAh·g^-1, 316.7 mAh·g^-1, 154.3 mAh·g^-1, and 228.4 mAh·g^-1, respectively. In addition, these electrodes 1, 2, 3, and 4 exhibited reversible capacity of 106.9 mAh·g^-1 after 295th, 180.9 mAh·g^-1 after 220th, 126.1 mAh·g^-1 after 150th, and 206.7 mAh·g^-1 after 85th cycle at a rate of 1 C, respectively. It was noted that the cyclic life of the batteries had an inverse relationship, and the capacity had a proportional relationship to the pore diameter. The enhanced electrochemical performance of the nanoporous electrodes can be attributed to the improved conductivity and the enhanced kinetics of lithium insertion/extraction at electrode/electrolyte interfaces because of the large specific surface area of np-TiO_2 electrodes.

Boosting Pseudocapacitive Behavior of Supercapattery Electrodes by Incorporating a Schottky Junction for Ultrahigh Energy Density

Pseudo-capacitive negative electrodes remain a major bottleneck in the development of supercapacitor devices with high energy density because the electric double-layer capacitance of the negative electrodes does not match the pseudocapacitance of the corresponding positive electrodes.In the present study,a strategically improved Ni-Co-Mo sulfide is demonstrated to be a promising candidate for high energy density supercapattery devices due to its sustained pseudocapacitive charge storage mechanism.The pseudocapacitive behavior is enhanced when operating under a high current through the addition of a classical Schottky junction next to the electrode-electrolyte interface using atomic layer deposition.The Schottky junction accelerates and decelerates the diffusion of OH-/K+ions during the charging and discharging processes,respectively,to improve the pseudocapacitive behavior.The resulting pseudocapacitive negative electrodes exhibits a specific capacity of 2,114 C g^(-1)at 2 A g^(-1)matches almost that of the positive electrode’s 2,795 C g^(-1)at 3 A g^(-1).As a result,with the equivalent contribution from the positive and negative electrodes,an energy density of 236.1 Wh kg^(-1)is achieved at a power density of 921.9 W kg^(-1)with a total active mass of 15 mg cm-2.This strategy demonstrates the possibility of producing supercapacitors that adapt well to the supercapattery zone of a Ragone plot and that are equal to batteries in terms of energy density,thus,offering a route for further advances in electrochemical energy storage and conversion processes.

Superior electrocatalytic negative electrode with tailored nitrogen functional group for vanadium redox flow battery

Development of electrodes with high electrocatalytic activity and stability is essential for solving problems that still restrict the extensive application of vanadium redox flow batteries(VRFBs).Here,we designed a novel negative electrode with superior electrocatalytic activity by tailoring nitrogen functional groups,such as newly formed nitro and pyridinic-N transformed to pyridonic-N,from the prenitrogen-doped electrode.It was experimentally confirmed that an electrode with pyridonic-N and nitro fuctional groups(tailored nitrogen-doped graphite felt,TNGF) has superior electrocatalytic acivity with enhanced electron and mass transfer.Density functional theory calulations demonstrated the pyridonic-N and nitro functional groups promoted the adsorption,charge transfer,and bond formation with the vanadium species,which is consistent with expermental results.In addition,the V2+/V3+redox reaction mechanism on pyridonic-N and nitro functional groups was estabilised based on density functional theory(DFT) results.When TNGF was applied to a VRFB,it enabled enhanced-electrolyte utilization and energy efficiencies(EE) of 57.9% and 64.6%,respectively,at a current density of 250 mA cm^(-2).These results are 18.6% and 8.9% higher than those of VRFB with electrode containing graphitic-N and pyridinicN groups.Interestingly,TNGF-based VRFB still operated with an EE of 59% at a high current density of300 mA cm^(-2).The TNGF-based VRFB exhibited stable cycling performance without noticeable decay of EE over 450 charge-discharge cycles at a current density of 250 mA cm^(-2).The results of this study suggest that introducing pyridonic-N and nitro groups on the electrode is effective for improving the electrochemical performance of VRFBs.

Electrochemical reactivity of In-Pb solid solution as a negative electrode for rechargeable Mg-ion batteries

A composite In-Pb:carbon was successfully synthetized by a two-step mechanochemical synthesis in order to obtain an adequate particles size and structure to investigate the electrochemical reactivity of the In-Pb solid solution towards Mg.A potential synergetic coupling of electroactive elements In and Pb was examined using electrochemical and ex situ X-ray diffraction analyses.The potential profile of the solid solution indicates the formation of Mg_(2)Pb and Mg In.However,the diffraction study suggests a peculiar electrochemically-driven amorphization of Mg In during the magnesiation,in strong contrast to Mg In crystallization in In-based and In Bi-based electrodes reported in the literature.Combining In and Pb favors the amorphization of Mg In and a high first magnesiation capacity of about 550 m Ah g^(-1),but is thereafter detrimental to the material’s reversibility.These results emphasize the possible influence of electrochemically-driven amorphization and crystallization processes on electrochemical performance of battery materials.

Effect of the lead deposition on the performance of the negative electrode in an aqueous lead-carbon hybrid capacitor

Lead-carbon hybrid capacitors are the electrochemical devices between supercapacitors and lead-acid batteries,with low prices,stability in high and low temperature,good security and broad application prospects.This paper introduces an electrodeposition behavior of Pb^(2+)on the negative electrode,which can improve the cycle life of the lead-carbon hybrid capacitor.During the charging process,lead ions in the electrolyte can diffuse from the positive electrode of the lead-carbon hybrid capacitor into the negative electrode.When charging at a low current density,the lead ions around the negative electrode can be reduced to lead,and it is then quickly converted to lead sulfate crystals.With the increase of the number of cycles,the final result is sulfation.Sulfation can reduce the specific surface area of the electric double layer,thereby reducing the capacitance performance of the carbon material.As a result,it reduces the charge-discharge efficiency of the lead-carbon hybrid capacitor.The service life of lead-carbon hybrid capacitor is significantly improved by the inhibition of lead deposition by anion exchange membrane.The capacity retention rate at 5 A/g is improved from 84%after 1000 cycles to 95%after 10,000 cycles.The discovery of lead deposition in the negative electrode is conducive to improving the performance of long-life lead-carbon hybrid capacitors.

Modified Al negative electrode for stable high-capacity Al-Te batteries

Metal aluminum batteries(MABs)are considered potential large-scale energy storage devices because of their high energy density,resource abundance,low cost,safety,and environmental friendliness.Given their high electrical conductivity,high theoretical specific capacity,and high discharge potential,Te is considered a potential positive electrode material for MABs.Nonetheless,the critical issues induced by the chemical and electrochemical dissolution of tellurium and subsequent chemical precipitation on bare Al negative electrodes result in poor cycle stability and low discharge capacity of Al-Te batteries.Here an efficient TiB_(2)-based modified layer has been proposed to address bare Al electrodes(Al/TB).Consequently,the low-voltage hysteresis and long cycle life of the Al/TB negative electrode have been achieved.In addition,the electrochemical performance of the Al-Te battery based on the Al/TB negative electrode is dramatically improved.Furthermore,the modified separator technology is introduced to match with the as-designed Al/TB negative electrode.Therefore,the record-setting long-term cycle stability of up to 500 cycles has been achieved in the Al-Te battery.The facile strategy also opens a potential route for other high-energy density battery systems,such as Al-S and Al-Se batteries.

Improving electrochemical properties of carbon paper as negative electrode for vanadium redox battery by anodic oxidation

Anodic oxidation with different electrolyte was employed to improve the electrochemical properties of carbon paper as negative electrode for vanadium redox battery(VRB).The treated carbon paper exhibits enhanced electrochemical activity for V^2+/V^3+redox reaction.The sample(CP-NH3)treated in NH3 solution demonstrates superior performance in comparison with the sample(CP-NaOH)treated in NaOH solution.X-ray photoelectron spectroscopy results show that oxygen-and nitrogen-containing functional groups have been introduced on CP-NH3 surface by the treatment,and Raman spectra confirm the increased surface defect of CP-NH3.Energy storage performance of cell was evaluated by charge/discharge measurement by using CP-NH3.Usage of CP-NH3 can greatly improve the cell performance with energy efficiency increase of 4.8%at 60 mA/cm^2.The excellent performance of CP-NH3 mainly results from introduction of functional groups as active sites and improved wetting properties.This work reveals that anodic oxidation is a clean,simple,and efficient method for boosting the performance of carbon paper as negative electrode for VRB.

Si/C Composites as Negative Electrode for High Energy Lithium Ion Batteries

Silicon is very promising negative electrode materials for improving the energy density of lithium-ion batteries （LIBs） because of its high specific capacity, moderate potential, environmental friendliness, and low cost. However, the volume variation of Si negative electrodes is huge during lithiation/delithiation processes which results in pulverization, low cycling efficiency, and permanent capacity loss. In order to overcome this problem, tremendous efforts have been attempted. Among them the most successful strategy is to incorporate other components into silicon to form composite, especially the carbon medium. In this mini review, the recent progress on Si/C materials used as negative electrode of LIBs is summarized such as Si/amorphous carbon composite, Si/graphene composites, Si/carbon nanotubes or fibers composites. The fabrication, structure, electrochemical performances of different Si/C composites are discussed. In addition, some future directions are pointed out.

Electrolytic silicon/graphite composite from SiO_(2)/graphite porous electrode in molten salts as a negative electrode material for lithium-ion batteries

Nano-silicon(nano-Si)and its composites have been regarded as the most promising negative electrode materials for producing the next-generation Li-ion batteries(LIBs),due to their ultrahigh theoretical capacity.However,the commercial applications of nano Si-based negative electrode materials are constrained by the low cycling stability and high costs.The molten salt electrolysis of SiO_(2)is proven to be suitable to produce nano-Si with the advantages of in-situ microstructure control possibilities,cheap affordability and scale-up process capability.Therefore,an economical approach for electrolysis,with a SiO_(2)/graphite porous electrode as cathode,is adopted to produce nano-Si/graphite composite negative electrode materials(SGNM)in this study.The electrolytic product of the optimized porous electrode is taken as the negative electrode materials for LIBs,and it offers a capacity of 733.2 mAh·g^(-1)and an initial coulombic efficiency of 86.8%in a coin-type cell.Moreover,the capacity of the SGNM retained 74.1%of the initial discharging capacity after 50 cycles at 0.2C,which is significantly higher than that of the simple mixture of silicon and graphite obtained from the formation of silicon carbide(SiC)between nano-Si and graphite particles.Notably,this new approach can be applied to a large-scale production.

Al homogeneous deposition induced by N-containing functional groups for enhanced cycling stability of Al-ion battery negative electrode

Rechargeable Al-ion batteries(AIBs)are considered as one of the most fascinating energy storage systems due to abundant Al resource and low cost.However,the cycling stability is subjected to critical problems for using Al foil as negative electrode,including Al dendrites,corrosion and pulverization.For addressing these problems,here a lightweight self-supporting N-doped carbon rod array(NCRA)is demonstrated for a long-life negative electrode in AIBs.Experimental analysis and first-principle calculations reveal the storage mechanism involving the induced deposition of N-containing function groups to Al as well as the ideal skeleton of the NCRA matrix for Al plating/stripping,which is favorable for regulating Al nucleation and suppressing dendrites growth.Compared with the Al foil,the NCRA exhibits lower areal mass density(∼72%of Al foil),smaller thickness(40%of Al foil),but much longer cycle life(>4 times of Al foil).Benefiting from the remarkable stability of the array structure,symmetric cells show excellent cycling stability with small voltage hysteresis(∼80 mV)and meanwhile there are no corrosion and pulverization problems even after cycled for 120 hours.Besides,full cells also manifest long lifespan(1,500 cycles)and increased Coulombic efficiency(100±1%).

MnO2-directed synthesis of NiFe-LDH@FeOOH nanosheeet arrays for supercapacitor negative electrode

The complex-architectured NiFe-LDH@FeOOH negative material was first prepared by simple two-step hydrothermal method.In this study,the porous nanostructure of FeOOH nanosheets features a large number of accessible channels to electroactive sites and the two-dimensional layered structure of NiFe-LDH nanosheets have an open spatial structure with high specific surface area,which enhance the diffusion of ions in the active material.Benefited from above advantages,the excellent electrochemical properties were demonstrated.NiFe-LDH@FeOOH nanocomposites present high specific capacitance(1195 F/g at a current density of 1 A/g),lower resistance and well cycling performance(90.36% retention after 1000 cycles).Furthermore,the NiFe-LDH@MnO2//NiFe-LDH@FeOOH supercapacitor exhibits22.68 Wh/kg energy density at 750 W/kg power density,demonstrating potential application in energy storage devices.

Effects of Annealing Temperature on Microstructure and Electrochemical Properties of Perovskite-type Oxide LaFeO3 as Negative Electrode for Metal Hydride/Nickel（MH/Ni） Batteries

We reported the effects of annealing temperatures on microstructure and electrochemical properties of perovskite-type oxide LaFeO3 prepared by stearic acid combustion method. X-Ray diffraction（XRD） patterns show that the annealed LaFeO3 powder has orthorhombic structure. Scanning electron microscopy（SEM） and transmission electron microscopy（TEM） images show the presence of homogeneously dispersed, less aggregated, and small crystals（30--40 nm） at annealing temperatures of 500 and 600 ℃. However, as the annealing temperature was increased to 700 and 800 ℃, the crystals began to combine with each other and grew into further larger crystals（90--100 nm）. The electrochemical performance of the annealed oxides was measured at 60 ℃ using chronopotentiometry, potentiodynamic polarization, and cyclic voltammetry. As the annealing temperature increased, the discharge capacity and anti-corrosion ability of the oxide electrode first increased and then decreased, reaching the optimum values at 600 ℃, with a maximum discharge capacity of 563 mA-h/g. The better electrochemical performance of LaFeO3 annealed at 600℃ could be ascribed to their smaller and more homogeneous crysals.

Surface-oxidation-mediated construction of Ppy@VNO/NG core-shell host targeting highly capacitive and durable negative electrode for supercapacitors

Vanadium nitride(VN)-based materials have been investigated as negative electrode materials for supercapacitors(SCs)owing to their high theoretical capacitances and suitable negative potential windows.However,viable VNbased negative electrode materials suffer from irreversible electrochemical oxidation of the soluble vanadium species,leading to rapid capacitance fading when operated in aqueous electrolytes.Developing a versatile approach to enhance the stability of VN in aqueous electrolytes is still a challenge.Here,an interface engineering strategy is developed to intentionally introduce surface nanolayers of vanadium oxides(VO_(x))as a reactive template on the VN surface to formulate welldesigned polypyrrole@VNO(Ppy@VNO)core-shell nanowires(NWs)incorporated into a 3D porous N-doped graphene(NG)hybrid aerogel as a durable negative electrode for SCs.Experimental and theoretical investigations reveal that the in-situ constructed Ppy@VNO core-shell host can offer more efficient pathways for rapid electron/ion transport and accessible electroactive sites.Most importantly,a reversible surface redox reaction is realized through the transformation of the valence state of V,and a long cyclic stability is achieved.The Ppy@VNO/NG hybrid aerogel can deliver a high specific capacitance of 650 F g^(-1) at 1 A g^(-1) with approximately 70.7%capacitance retention(up to the twenty-fold current density),and an excellent cycling stability without any capacitance decay after 10,000 cycles at both low and high current densities(1 and 10 A g^(-1),respectively).This work paves the way for the development of advanced electrode materials for SCs.

Novel Biomass-derived Hollow Carbons as Anode Materials for Lithium-ion Batteries

A novel hollow carbon derived from biomass lotus-root has been prepared by a one-step carbonization method.The carbon anode obtained at 900℃ showed the best electrochemical performance,corresponding to a high specific capacity of 445 mA·h/g at 0.1 C,as well as excellent cycling stability after 500 cycles.Further investigation exhibits that the lithium storage of hollow carbon involves Li^(+) adsorption in the defect sites and Li^(+) insertion.The results showed that the intrinsic structure of lotus root can inspire us to prepare biomass carbon with a hollow structure as an excellent anode for lithium-ion batteries.

Nano-channel-based physical and chemical synergic regulation for dendrite-free lithium plating

Uncontrollable dendrite growth resulting from the non-uniform lithium ion(Li^(+))flux and volume expansion in lithium metal(Li)negative electrode leads to rapid performance degradation and serious safety problems of lithium metal batteries.Although N-containing functional groups in carbon materials are reported to be effective to homogenize the Li^(+)flux,the effective interaction distance between lithium ions and N-containing groups should be relatively small(down to nanometer scale)according to the Debye length law.Thus,it is necessary to carefully design the microstructure of N-containing carbon materials to make the most of their roles in regulating the Li^(+)flux.In this work,porous carbon nitride microspheres(PCNMs)with abundant nanopores have been synthesized and utilized to fabricate a uniform lithiophilic coating layer having hybrid pores of both the nano-and micrometer scales on the Cu/Li foil.Physically,the three-dimensional(3D)porous framework is favorable for absorbing volume changes and guiding Li growth.Chemically,this coating layer can render a suitable interaction distance to effectively homogenize the Li^(+)flux and contribute to establishing a robust and stable solid electrolyte interphase(SEI)layer with Li-F,Li-N,and Li-O-rich contents based on the Debye length law.Such a physical-chemical synergic regulation strategy using PCNMs can lead to dendrite-free Li plating,resulting in a low nucleation overpotential and stable Li plating/stripping cycling performance in both the Li||Cu and the Li||Li symmetric cells.Meanwhile,a full cell using the PCNM coated Li foil negative electrode and a LiFePO4 positive electrode has delivered a high capacity retention of~80%after more than 200 cycles at 1 C and achieved a remarkable rate capability.The pouch cell fabricated by pairing the PCNM coated Li foil negative electrode with a NCM 811 positive electrode has retained~73%of the initial capacity after 150 cycles at 0.2 C.

Carbon-emcoating architecture boosts lithium storage of Nb_(2)O_(5)

Intercalation transition metal oxides (ITMO)have attracted great attention as lithium-ion battery negative electrodes due to high operation safety,high capacity and rapid ion intercalation.However,the intrinsic low electron conductivity plagues the lifetime and cell performance of the ITMO negative electrode.Here we design a new carbon-emcoating architecture through single CO_(2)activation treatment as demonstrated by the Nb_(2)O_(5)/C nanohybrid.Triple structure engineering of the carbon-emcoating Nb_(2)O_(5)/C nanohybrid is achieved in terms of porosity,composition,and crystallographic phase.The carbon-embedding Nb_(2)O_(5)/C nanohybrids show superior cycling and rate performance compared with the conventional carbon coating,with reversible capacity of 387 m A h g(-1)at 0.2 C and 92%of capacity retained after 500cycles at 1 C.Differential electrochemical mass spectrometry(DEMS) indicates that the carbon emcoated Nb_(2)O_(5)nanohybrids present less gas evolution than commercial lithium titanate oxide during cycling.The unique carbon-emcoating technique can be universally applied to other ITMO negative electrodes to achieve high electrochemical performance.

Electrochemical performances of four lanthanum transition-metal complex oxides

As novel negative electrode materials for alkaline batteries, the electrochemical properties of four lanthanum transition-metal (La-TM) complex oxides LaTiO(3), LaVO(4), LaCrO(3) and LaMnO(3) were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) were employed to characterize their microstructures. All the La-TM oxides were made up of single phases. Electrochemical measurements showed that the maximum discharge capacities of LaTiO(3), LaVO(4), LaCrO(3), and LaMnO(3) electrodes at 303 K were 367, 187, 318, and 278 mAh/g, respectively. X-ray photoelectron spectroscopy (XPS) and XRD Rietveld analysis were carried out to discuss the electrochemical reaction mechanism. Electrode kinetics was studied by electrochemical impedance spectrum (EIS). The results showed that the maximum discharge capacity was directly related to the charge-transfer resistance (R(ct)) of La-TM oxide electrode. The cyclic properties of the four oxides should be further improved and the discharge capacity of LaMnO(3) (about 96 mAh/g) was the highest after 10(th) charge/discharge cycles.