One main challenge for phosphate cathodes in sodium-ion batteries(SIBs)is to increase the working voltage and energy density to promote its practicability.Herein,an advanced Na3V2(PO4)2F3@C cathode is prepared success...One main challenge for phosphate cathodes in sodium-ion batteries(SIBs)is to increase the working voltage and energy density to promote its practicability.Herein,an advanced Na3V2(PO4)2F3@C cathode is prepared successfully for sodium-ion full cells.It is revealed that,carbon coating can not only enhance the electronic conductivity and electrode kinetics of Na3V2(PO4)2F3@C and inhibit the growth of particles(i.e.,shorten the Na^+-migration path),but also unexpectedly for the first time adjust the dis-/charging plateaux at different voltage ranges to increase the mean voltage(from 3.59 to 3.71 V)and energy density from 336.0 to 428.5 Wh kg^-1 of phosphate cathode material.As a result,when used as cathode for SIBs,the prepared Na3V2(PO4)2F3@C delivers much improved electrochemical properties in terms of larger specifc capacity(115.9 vs.93.5 mAh g^-1),more outstanding high-rate capability(e.g.,87.3 vs.60.5 mAh g^-1 at 10 C),higher energy density,and better cycling performance,compared to pristine Na3V2(PO4)2F3.Reasons for the enhanced electrochemical properties include ionicity enhancement of lattice induced by carbon coating,improved electrode kinetics and electronic conductivity,and high stability of lattice,which is elucidated clearly through the contrastive characterization and electrochemical studies.Moreover,excellent energy-storage performance in sodium-ion full cells further demonstrate the extremely high possibility of Na3V2(PO4)2F3@C cathode for practical applications.展开更多
As a cathode for sodium-ion batteries(SIBs),Na3V2(PO4)2F3(NVPF)with 3D open framework is a promising candidate due to its high working voltage and large theoretical capacity.However,the severe capacity degradation and...As a cathode for sodium-ion batteries(SIBs),Na3V2(PO4)2F3(NVPF)with 3D open framework is a promising candidate due to its high working voltage and large theoretical capacity.However,the severe capacity degradation and poor rate capability hinder its practical applications.The present study demonstrated the optimization of Na-storage performance of NVPF via delicate lattice modulation.Aliovalent substitution of V^(3^(+))at Na^(+)in NVPF induces the generation of electronic defects and expansion of Na^(+)-migration channels,resulting in the enhancement in electronic conductivity and acceleration of Na^(+)-migration kinetics.It is disclosed that the formed stronger Na O bonds with high ionicity than V O bonds lead to the significant increase in structural stability and ionicity in the Na^(+)-substituted NVPF(NVPF-Nax).The aforementioned effects of Na^(+)substitution achieve the unprecedented electrochemical performance in the optimized Na_(3.14)V1.93Na0.07(PO_(4))_(2)F_(3)(NVPF-Na_(0.07)).As a result,NVPF-Na0.07 delivers a high-rate capability(77.5 mAh g^(−1)at 20 C)and ultralong cycle life(only 0.027%capacity decay per cycle over 1000 cycles at 10 C).Sodium-ion full cells are designed using NVPF-Na0.07 as cathode and Se@reduced graphene oxide as anode.The full cells exhibit excellent wide-temperature electrochemical performance from−25 to 25C with an outstanding rate capability(96.3 mAh g^(−1)at 20 C).Furthermore,it delivered an excellent cycling performance over 300 cycles with a capacity retention exceeding 90%at 0.5 C under different temperatures.This study demonstrates a feasible strategy for the development of advanced cathode materials with excellent electrochemical properties to achieve high-efficiency energy storage.展开更多
In this study,a pseudo-layered Na super-ionic conductor of Na3V2(PO4)2F3 (NVPF)/C cathode for sodium-ion batteries is prepared successfully using a facile polyol refluxing process without any impurity phases.The X-ray...In this study,a pseudo-layered Na super-ionic conductor of Na3V2(PO4)2F3 (NVPF)/C cathode for sodium-ion batteries is prepared successfully using a facile polyol refluxing process without any impurity phases.The X-ray diffraction and Rietveld refinement results confirm that NVPF possesses tetragonal NASICON-type lattice with a space group of P42/mnm.In this preparative method,polyol is utilized as a solvent as well as a carbon source.The presence of nanosized NVPF particles in the carbon network is confirmed by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM).The existence of carbon is analyzed by Raman scattering and elemental analysis.When applied as a Na-storage material in a potential window of 2.0-4.3 V,the electrode exhibits two flat voltage plateaus at 3.7 and 4.2 V with an electrochemically active V^3+/V^4+ redox couple.In addition,Na3V2(PO4)2F3/C composite achieved a retention capacity of ~ 88% even after 1,500 cycles at 15 C.Moreover,at high current densities of 30 and 50 C,Na3V2(PO4)2F3/C cathode retains the specific discharge capacities of 108.4 and 105.9 mAh·g-1,respectively,revealing the structural stability of the material prepared through a facile polyol refluxing method.展开更多
基金supported by the National Natural Science Foundation of China(91963118)the Fundamental Research Funds for the Central Universities(2412019ZD010).
文摘One main challenge for phosphate cathodes in sodium-ion batteries(SIBs)is to increase the working voltage and energy density to promote its practicability.Herein,an advanced Na3V2(PO4)2F3@C cathode is prepared successfully for sodium-ion full cells.It is revealed that,carbon coating can not only enhance the electronic conductivity and electrode kinetics of Na3V2(PO4)2F3@C and inhibit the growth of particles(i.e.,shorten the Na^+-migration path),but also unexpectedly for the first time adjust the dis-/charging plateaux at different voltage ranges to increase the mean voltage(from 3.59 to 3.71 V)and energy density from 336.0 to 428.5 Wh kg^-1 of phosphate cathode material.As a result,when used as cathode for SIBs,the prepared Na3V2(PO4)2F3@C delivers much improved electrochemical properties in terms of larger specifc capacity(115.9 vs.93.5 mAh g^-1),more outstanding high-rate capability(e.g.,87.3 vs.60.5 mAh g^-1 at 10 C),higher energy density,and better cycling performance,compared to pristine Na3V2(PO4)2F3.Reasons for the enhanced electrochemical properties include ionicity enhancement of lattice induced by carbon coating,improved electrode kinetics and electronic conductivity,and high stability of lattice,which is elucidated clearly through the contrastive characterization and electrochemical studies.Moreover,excellent energy-storage performance in sodium-ion full cells further demonstrate the extremely high possibility of Na3V2(PO4)2F3@C cathode for practical applications.
基金111 Project,Grant/Award Number:B13013Education Department of Jilin Province,Grant/Award Number:.JJKH20201179KJ+1 种基金Science Technology Program of Jilin Province,Grant/Award Number:20200201066JCNational Natural Science Foundation of China,Grant/Award Number:91963118。
文摘As a cathode for sodium-ion batteries(SIBs),Na3V2(PO4)2F3(NVPF)with 3D open framework is a promising candidate due to its high working voltage and large theoretical capacity.However,the severe capacity degradation and poor rate capability hinder its practical applications.The present study demonstrated the optimization of Na-storage performance of NVPF via delicate lattice modulation.Aliovalent substitution of V^(3^(+))at Na^(+)in NVPF induces the generation of electronic defects and expansion of Na^(+)-migration channels,resulting in the enhancement in electronic conductivity and acceleration of Na^(+)-migration kinetics.It is disclosed that the formed stronger Na O bonds with high ionicity than V O bonds lead to the significant increase in structural stability and ionicity in the Na^(+)-substituted NVPF(NVPF-Nax).The aforementioned effects of Na^(+)substitution achieve the unprecedented electrochemical performance in the optimized Na_(3.14)V1.93Na0.07(PO_(4))_(2)F_(3)(NVPF-Na_(0.07)).As a result,NVPF-Na0.07 delivers a high-rate capability(77.5 mAh g^(−1)at 20 C)and ultralong cycle life(only 0.027%capacity decay per cycle over 1000 cycles at 10 C).Sodium-ion full cells are designed using NVPF-Na0.07 as cathode and Se@reduced graphene oxide as anode.The full cells exhibit excellent wide-temperature electrochemical performance from−25 to 25C with an outstanding rate capability(96.3 mAh g^(−1)at 20 C).Furthermore,it delivered an excellent cycling performance over 300 cycles with a capacity retention exceeding 90%at 0.5 C under different temperatures.This study demonstrates a feasible strategy for the development of advanced cathode materials with excellent electrochemical properties to achieve high-efficiency energy storage.
文摘In this study,a pseudo-layered Na super-ionic conductor of Na3V2(PO4)2F3 (NVPF)/C cathode for sodium-ion batteries is prepared successfully using a facile polyol refluxing process without any impurity phases.The X-ray diffraction and Rietveld refinement results confirm that NVPF possesses tetragonal NASICON-type lattice with a space group of P42/mnm.In this preparative method,polyol is utilized as a solvent as well as a carbon source.The presence of nanosized NVPF particles in the carbon network is confirmed by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM).The existence of carbon is analyzed by Raman scattering and elemental analysis.When applied as a Na-storage material in a potential window of 2.0-4.3 V,the electrode exhibits two flat voltage plateaus at 3.7 and 4.2 V with an electrochemically active V^3+/V^4+ redox couple.In addition,Na3V2(PO4)2F3/C composite achieved a retention capacity of ~ 88% even after 1,500 cycles at 15 C.Moreover,at high current densities of 30 and 50 C,Na3V2(PO4)2F3/C cathode retains the specific discharge capacities of 108.4 and 105.9 mAh·g-1,respectively,revealing the structural stability of the material prepared through a facile polyol refluxing method.
