Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders thei...Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders their practical capacity. Herein, the anion-site regulation is proposed to elevate the electrode kinetics and properties of polyanionic cathode. Multivalent anion P_(2)O_(7)^(4-) is selected to substitute the PO_(4)^(3-) in Na_(3)V_(2)(PO_(4))_(3) (NVP) lattice and regulate the ratio of polyanion groups to prepare Na_(3+x)V_(2)(PO_(4))_(3-x)(P_(2)O_(7))_(x)(NVPP_(x), 0 ≤ x ≤ 0.15) materials.The optimal Na_(3.1)V_(2)(PO_(4))_(2.9)(P_(2)O_(7))_(0.1) (NVPP_(0.1)) material can deliver remarkably elevated specific capacity(104 mAh g^(-1) at 0.1 C, 60 mAh g^(-1) at 20 C, respectively), which is higher than those of NVP. Moreover, NVPP_(0.1) exhibits outstanding cyclic stability(91% capacity retention after 300 cycles at 1 C). Experimental analyses reveal that the regulation of anions improves the structure stability, increases the active Na occupancy in the lattice and accelerates the Na+migration kinetics. The strategy of anion-site regulation provides the researchers a reference for the design of new high-performance polyanionic materials.展开更多
In recent years,rechargeable lithium-ion batteries(LIBs)have become widely used in everyday applications such as portable electronic devices,electric vehicles and energy storage systems.Despite this,the electrochemica...In recent years,rechargeable lithium-ion batteries(LIBs)have become widely used in everyday applications such as portable electronic devices,electric vehicles and energy storage systems.Despite this,the electrochemical performance of LIBs cannot meet the energy demands of rapidly growing technological evolutions.And although significant progress has been made in the development of corresponding anodes based primarily on carbon,oxide and silicon materials,these materials still possess shortcomings in current LIB applications.For example,graphite exhibits safety concerns due to an operating potential close to that of lithium(Li)metal plating whereas Li4Ti5O12 possesses low energy density for high operation potential and silicon experiences limited cyclability for large volume expansion during charging/discharging.Alternatively,polyanionic compounds such as(PO_(4))^(3–),(SiO_(4))^(4–),(SO_(4))^(2–)and(BO_(3))^(3−)as electrode materials have gained increasing attention in recent years due to their ability to stabilize structures,adjust redox couples and provide migration channels for"vip"ions,resulting in corresponding electrode materials with long-term cycling,high energy density and outstanding rate capability.Based on these advantages and combined with recent findings in terms of silicate anodes,this review will summarize the recent progress in the development of polyanion-based anode materials for LIBs and sodium-ion batteries.Furthermore,this review will present our latest research based on polyanion groups such as(GeO_(4))^(4–)to compensate for the lack of available studies and to provide our perspective on these materials.展开更多
High safety and high energy-density sodium-ion batteries require the promising polyanionic insertion-type cathode possessing fast dis-/charging capability,yet persistent challenges remain in the kinetic optimization t...High safety and high energy-density sodium-ion batteries require the promising polyanionic insertion-type cathode possessing fast dis-/charging capability,yet persistent challenges remain in the kinetic optimization to accelerate their intrinsically low Na^(+)diffusivity.Exampled by the representative Na_(3)V_(2)(PO_(4))O_(2)F(NVPOF)with considerable theoretical energy density,structural distortion results in a one-dimensional sluggish Nat diffusion out of the two-dimensional Na pathway provided structurally.Previous endeavors with Na site or transition-metal site regulation successfully optimize the Na^(+)diffusion energy barrier of the available one-dimensional path.However,these substituted elements with non-equivalent valances or sizes further elevate the energy barrier of the other unavailable Na^(+)diffusion path.Herein,by defining the independently accessible Na^(+)diffusion pathways in the crystallographic structure as Na^(+) diffusion degree of freedom(df_([Na^(+)])),we demonstrate broadening df_([Na^(+)])to two in NVPOF by a mild perturb at the dangling site can fundamentally revise the Na diffusion behaviour.As demonstrated by in-situ synchrotron,various spectroscopic techniques,and density functional theory(DFT)modeling,this mild perturb equalizes the Na^(+) diffusion energy barriers along a and b directions and enables two-dimensional Nat transportation.The as-prepared NvPOF depicts an altered solid-solution phase transition,higher disorder in the framework and dramatically enhanced Na diffusivity,which leads to unprecedentedly high sodium storage properties in half cell(68.6 mAh g^(-1) at 100 C;103.3 mAh g^(-1) after 1300 cycles at 20 C;1 C=130 mA g^(-1))and full cell(313.8 Wh kg^(-1)@4063.5 W kg^(-1);113.9 Wh kg^(-1)@16,397.2 W kg^(-1)).This study enlightens the valuable role of broadening df_([Na^(+)])in fundamentally maximizing the polyanionic insertion-type performance.展开更多
Iron-based mixed polyanion-type sodium-ion cathode materials like Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_(7)(NFPP)typically suffer from poor electronic conductivity,resulting in capacity retention under high-rate cycling and ...Iron-based mixed polyanion-type sodium-ion cathode materials like Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_(7)(NFPP)typically suffer from poor electronic conductivity,resulting in capacity retention under high-rate cycling and rapid capacity degradation.In this study,we introduce an innovative dual-carbon enhancement strategy that integrates carbon nanotubes(CNTs)into the precursor mixing stage,combined with citric acid as both an organic carbon source and a dispersant.Unlike conventional methods where CNTs are added post-synthesis or during slurry preparation-often leading to uneven dispersion-we incorporate CNTs during the initial mixing process.Citric acid not only provides carbon for pyrolysis but also forms a gel-like precursor that ensures homogeneous dispersion of CNTs and raw materials.This one-step sintering approach produces NFPP particles uniformly coated with carbon layers intimately connected to well-dispersed CNTs,potentially forming chemical bonds between them.The resulting pyrolytic carbon and CNT-coated NFPP(NFPP-CNT)exhibits a dense and interconnected electron-conductive network,significantly enhancing its electronic conductivity and electrochemical performance.The precisely designed NFPP-CNT delivers a reversible capacity of 111 mAh/g at 0.1 C and maintains a reversible capacity of 78.8 mAh/g even at an ultra-high rate of 100 C.NFPP-CNT also demonstrates outstanding high-rate capacity retention,with 85.7% capacity remaining after 27,000 cycles at 100 C.This novel synthesis method and the multifaceted role of citric acid endow NFPP with superior high-rate,long-cycle,and low-temperature performance,making it a highly competitive material for large-scale electric energy storage systems(EESs).展开更多
基金financially supported by the National Natural Science Foundation of China (No. 91963118)Science Technology Program of Jilin Province (No. 20200201066JC)+1 种基金“13th Five-Year” Science and Technology Research from the Education Department of Jilin Province (No.JJKH20201179KJ)the 111 Project (No. B13013)。
文摘Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders their practical capacity. Herein, the anion-site regulation is proposed to elevate the electrode kinetics and properties of polyanionic cathode. Multivalent anion P_(2)O_(7)^(4-) is selected to substitute the PO_(4)^(3-) in Na_(3)V_(2)(PO_(4))_(3) (NVP) lattice and regulate the ratio of polyanion groups to prepare Na_(3+x)V_(2)(PO_(4))_(3-x)(P_(2)O_(7))_(x)(NVPP_(x), 0 ≤ x ≤ 0.15) materials.The optimal Na_(3.1)V_(2)(PO_(4))_(2.9)(P_(2)O_(7))_(0.1) (NVPP_(0.1)) material can deliver remarkably elevated specific capacity(104 mAh g^(-1) at 0.1 C, 60 mAh g^(-1) at 20 C, respectively), which is higher than those of NVP. Moreover, NVPP_(0.1) exhibits outstanding cyclic stability(91% capacity retention after 300 cycles at 1 C). Experimental analyses reveal that the regulation of anions improves the structure stability, increases the active Na occupancy in the lattice and accelerates the Na+migration kinetics. The strategy of anion-site regulation provides the researchers a reference for the design of new high-performance polyanionic materials.
基金supported by the National Natural Science Foundation of China with Grant No.21875045 and 22005059the China Postdoctoral Science Foundation with Grant No.2019M661339.
文摘In recent years,rechargeable lithium-ion batteries(LIBs)have become widely used in everyday applications such as portable electronic devices,electric vehicles and energy storage systems.Despite this,the electrochemical performance of LIBs cannot meet the energy demands of rapidly growing technological evolutions.And although significant progress has been made in the development of corresponding anodes based primarily on carbon,oxide and silicon materials,these materials still possess shortcomings in current LIB applications.For example,graphite exhibits safety concerns due to an operating potential close to that of lithium(Li)metal plating whereas Li4Ti5O12 possesses low energy density for high operation potential and silicon experiences limited cyclability for large volume expansion during charging/discharging.Alternatively,polyanionic compounds such as(PO_(4))^(3–),(SiO_(4))^(4–),(SO_(4))^(2–)and(BO_(3))^(3−)as electrode materials have gained increasing attention in recent years due to their ability to stabilize structures,adjust redox couples and provide migration channels for"vip"ions,resulting in corresponding electrode materials with long-term cycling,high energy density and outstanding rate capability.Based on these advantages and combined with recent findings in terms of silicate anodes,this review will summarize the recent progress in the development of polyanion-based anode materials for LIBs and sodium-ion batteries.Furthermore,this review will present our latest research based on polyanion groups such as(GeO_(4))^(4–)to compensate for the lack of available studies and to provide our perspective on these materials.
基金supported by the National Natural Science Foundation of China(52272091)Agency for Science,Technology and Research(A*STAR)through Low Carbon Energy Research Finding Initiative(LCERFI01-0033|U2102d2006)+3 种基金A*STAR MTC programmatic project(M23L9b0052)Indonesia-NTU Singapore Institute of Research for Sustainability and Innovation(INSPIRASI)(6635/E3/KL.02.02/2023)Singapore NRF Singapore-China flagship program(023740-00001)Natural Science Foundation of Jiangxi Province(20232ACB214001).
文摘High safety and high energy-density sodium-ion batteries require the promising polyanionic insertion-type cathode possessing fast dis-/charging capability,yet persistent challenges remain in the kinetic optimization to accelerate their intrinsically low Na^(+)diffusivity.Exampled by the representative Na_(3)V_(2)(PO_(4))O_(2)F(NVPOF)with considerable theoretical energy density,structural distortion results in a one-dimensional sluggish Nat diffusion out of the two-dimensional Na pathway provided structurally.Previous endeavors with Na site or transition-metal site regulation successfully optimize the Na^(+)diffusion energy barrier of the available one-dimensional path.However,these substituted elements with non-equivalent valances or sizes further elevate the energy barrier of the other unavailable Na^(+)diffusion path.Herein,by defining the independently accessible Na^(+)diffusion pathways in the crystallographic structure as Na^(+) diffusion degree of freedom(df_([Na^(+)])),we demonstrate broadening df_([Na^(+)])to two in NVPOF by a mild perturb at the dangling site can fundamentally revise the Na diffusion behaviour.As demonstrated by in-situ synchrotron,various spectroscopic techniques,and density functional theory(DFT)modeling,this mild perturb equalizes the Na^(+) diffusion energy barriers along a and b directions and enables two-dimensional Nat transportation.The as-prepared NvPOF depicts an altered solid-solution phase transition,higher disorder in the framework and dramatically enhanced Na diffusivity,which leads to unprecedentedly high sodium storage properties in half cell(68.6 mAh g^(-1) at 100 C;103.3 mAh g^(-1) after 1300 cycles at 20 C;1 C=130 mA g^(-1))and full cell(313.8 Wh kg^(-1)@4063.5 W kg^(-1);113.9 Wh kg^(-1)@16,397.2 W kg^(-1)).This study enlightens the valuable role of broadening df_([Na^(+)])in fundamentally maximizing the polyanionic insertion-type performance.
基金granted by the National Natural Science Foundation of China(Nos.52172210 and 51772163).
文摘Iron-based mixed polyanion-type sodium-ion cathode materials like Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_(7)(NFPP)typically suffer from poor electronic conductivity,resulting in capacity retention under high-rate cycling and rapid capacity degradation.In this study,we introduce an innovative dual-carbon enhancement strategy that integrates carbon nanotubes(CNTs)into the precursor mixing stage,combined with citric acid as both an organic carbon source and a dispersant.Unlike conventional methods where CNTs are added post-synthesis or during slurry preparation-often leading to uneven dispersion-we incorporate CNTs during the initial mixing process.Citric acid not only provides carbon for pyrolysis but also forms a gel-like precursor that ensures homogeneous dispersion of CNTs and raw materials.This one-step sintering approach produces NFPP particles uniformly coated with carbon layers intimately connected to well-dispersed CNTs,potentially forming chemical bonds between them.The resulting pyrolytic carbon and CNT-coated NFPP(NFPP-CNT)exhibits a dense and interconnected electron-conductive network,significantly enhancing its electronic conductivity and electrochemical performance.The precisely designed NFPP-CNT delivers a reversible capacity of 111 mAh/g at 0.1 C and maintains a reversible capacity of 78.8 mAh/g even at an ultra-high rate of 100 C.NFPP-CNT also demonstrates outstanding high-rate capacity retention,with 85.7% capacity remaining after 27,000 cycles at 100 C.This novel synthesis method and the multifaceted role of citric acid endow NFPP with superior high-rate,long-cycle,and low-temperature performance,making it a highly competitive material for large-scale electric energy storage systems(EESs).
