As the demand for energy storage escalates, sodium?ion batteries （SIBs） are increasingly in the spotlight due to their low cost and the plentiful availability of sodium resources. Particularly, hard carbon anode materials have emerged as a focal point of research, attributed to their superior cyclic stability and elevated energy density. This review delves into the advancements in hard carbon anode materials for SIBs, encompassing the screening and design of HCs precursors, surface modifications, pore structure adjustments, carbonization induction, heteroatom doping strategies, and additional tactics to augment the performance of HCs. By thoroughly examining the influence of HCs's pore structure, surface functional groups, and microstructure on the sodium storage mechanism, the review explores the potential for optimizing HCs performance through various fabrication processes. Furthermore, the article addresses the interfacial reaction mechanisms between HCs and electrolytes, along with possible avenues for enhancing HCs's cycling and rate capabilities through interface engineering. Ultimately, the review anticipates the future trajectory of HCs technology, including the design of nanostructures, surface modifications, and green manufacturing processes, underscoring the pressing need for the development of high?performance, cost?effective, and environmentally benign SIBs.
Sodium?ion batteries are considered a promising alternative to lithium?ion and lead?acid batteries, offering a balance between performance and cost?effectiveness for applications requiring moderate energy density and low cost. Hard carbon stands out as the most promising anode material for sodium?ion batteries, with the majority of scholars attributing its sodium storage capacity primarily to its porous structure. However, characterization techniques for this porous structure are currently very limited. This hinders in?depth analysis of the hard carbon pore structure and makes it more difficult to design performance enhancement strategies. This review provides an overview of current methods for characterizing the pore structure of hard carbon, including transmission electron microscopy, gas adsorption, X?ray small angle scattering, and helium true density testing. The combined use of these methods helps accurately characterize the pore structure of hard carbon and provides research ideas and technical support for the design of high?performance hard carbon anodes.
The high nickel cathode material LiNi x Co y Mn1-x-y O2(x≥0.6,NCM) is considered to be one of the most valuable cathode materials for lithium?ion batteries due to its low cost,high energy density and long service life.Although the high nickel content leads to a significant increase in the specific capacity and energy density of NCM,the increase in nickel content leads to poor cycling and thermal stability,which severely limits its practical application.Doping modification is an effective strategy to improve the structural stability and electrochemical performance of NCM.In this review,the common doping preparation methods of NCM are first described in detail.Subsequently,the effects of various doped elements on the lithium storage,rate performance and cycling performance of NCM were systematically analyzed.Finally,the development and future challenges of NCM are prospected,which is expected to provide an important reference for the application of NCM.
Sodium?ion batteries are gradually becoming a powerful alternative to lithium?ion batteries in the low?speed two?wheeled electric vehicle market and large?scale energy storage applications due to their excellent low?temperature performance, significant cost?effectiveness,and high safety features.The potential of hard carbon with improved performance to substitute graphite in the sodium ion battery anode has attracted widespread attention.However,the high energy consumption and expensive cost still need to be overcome for commercialization of hard carbon anode.The key to developing anode materials for sodium?ion batteries that combine low cost,high sodium ion storage capacity,and excellent cycling stability will help to extend the application of hard carbon anodes in sodium?ion batteries.Biomass has become an attractive raw material for the preparation of hard carbon due to its renewable,low?cost,and environmentally friendly characteristics.It has been shown that the sodium storage properties of biomass?derived hard carbon are affected by multiple factors such as carbonization temperature,precursor variety,and microstructure.Hence,this review summarizes the relevant models proposed for the sodium storage mechanism in terms of the sodium storage behavior of hard carbon.The preparation of hard carbon anode materials,including the effect of electrochemical optimization procedures such as pyrolysis,activation, and doping is discussed.A further analysis of the sodium storage mechanism offers guidance for addressing the current issues such as the selection of precursors,the low initial Coulombic efficiency,and the limited means of closed pore regulation.
Nickel?iron (NiFe)?based transition metal catalysts have garnered significant attention in recent years for their excellent electrocatalytic performance,particularly in the oxygen evolution reaction (OER).However, the catalytic efficiency of NiFe?based transition metal catalysts still has a certain gap compared with precious metal Ru or Ir, so it is necessary to modify it.Research has shown that defect engineering can effectively enhance the OER catalytic activity of NiFe?based transition metal catalysts.The types of defects in NiFe?based transition metal catalysts, the characterization methods, and the methods for constructing defect materials are summarized, and an overview the research progress of the OER study of defect?type NiFe?based transition metal catalysts is given; the challenges of defect engineering to improve the OER performance are discussed and prospects for future development are proposed.
Sodium vanadium phosphate (Na3V2(PO4)3, abbreviated as NVP）, exhibits unique advantages in sodium?ion batteries due to its excellent thermal stability and broad sodium?ion transport channels. However, the expensive vanadium raw materials have diminished the attention on the commercial development of NVP. In this work, NVP was successfully synthesized using solid?state methods from NaVO3, a byproduct from the upstream of the vanadium extraction industry, and compared with NVP synthesized from V2O5 and NH4VO3 at different calcination temperatures. The results indicate that the vanadium source has a significant impact on the structure and morphology of NVP, which further influences the battery capacity and rate performance. NVP prepared using NaVO3 at 750 ℃ exhibits excellent electrochemical performance, achieving an initial high capacity of 105.6 mA·h/g at 0.1 C, and still obtaining high capacities of 101.5, 99.9, and 92.9 mA·h/g at subsequent rates of 1.0, 2.0, and 5.0 C, respectively. Moreover, it achieves a reversible capacity of 97.1 mA·h/g and a high capacity retention rate of 94.6% after 300 cycles at 1.0 C, and retains 94.0% capacity after 500 cycles at 5.0 C. This simple, efficient, and cost?effective synthesis strategy provides a reference for the scaled?up production of NVP.
The efficient production of hydrogen as a clean energy carrier relies on the performance optimization of electrocatalysts for the hydrogen evolution reaction (HER).Although platinum (Pt)?based catalysts exhibit exceptional HER activity,their high cost and stability issues can be mitigated through rational design of the support material.Nickel hydroxide (Ni(OH)?) has emerged as a promising support due to its unique proton conductivity,interfacial modulation properties,and stabilizing effects on Pt. However,a systematic understanding of the structure–activity relationship between Ni(OH)? supports and Pt nanoparticles,as well as the impact of synthesis parameters on catalytic performance,remains lacking.This study focuses on the regulation of Ni(OH)? support phase evolution and Pt interfacial growth behavior by hydrothermal synthesis temperature.By analyzing the structure–performance relationship through the synthesis parameter–microstructure–catalytic performance correlation mechanism),the synergistic effects of temperature on the crystallinity of the support,Pt particle size distribution,and interfacial electronic structure were elucidated.Experimental results indicate that the Pt@Ni(OH)? catalyst synthesized at 100 ℃ exhibits outstanding HER activity in 1 mol/L KOH electrolyte,with overpotentials of only 5 mV at 10 mA/cm2 and 62 mV at 100 mA/cm2,along with a Tafel slope of 70.0 mV/dec.After 50 hours of continuous operation,the electrode maintains nearly unchanged HER performance,demonstrating remarkable stability.
During the process of water electrolysis,the "bubble effect" will significantly reduce the overall performance of the system.The classical nucleation theory (CNT model） fails to reveal the regulatory mechanism of the electrical double layer (EDL),surface microstructure,and mass transfer synergy on nucleation kinetics in actual electrochemical systems.This study develops an electrode interface bubble nucleation model with the synergistic effect of electrical double layer?mass transfer?surface microstructure,considering the synergistic regulation mechanism of ion migration diffusion behavior,electrode surface nano microstructure,and concentration boundary layer on the nucleation process.The research results show that the synergistic effect of EDL and microporous structurel generates significant potential gradients at the surface micropores,leading to an increase in local supersaturation and prioritizing bubble nucleation.At high overpotentials,the effect of the concentration boundary layer on nucleation energy barrier exhibits a nonlinear relationship.The thinner the concentration boundary layer is,the more significant the decreasing trend of the nucleation rate at high potential will be.The growth of bubbles is dominated by the net concentration flux near the three?phase contact line (TPCL),exhibiting a two?stage growth characteristic.The study provides a theoretical basis for optimizing the surface design of gas evolution electrodes.
