Electrolyte additives are pivotal for stable cycling of rechargeable sodium-ion batteries(SIBs),which dictate the creation of the protective interface film on electrodes.Cyclic sulfur-containing additives,such as1,3,2...Electrolyte additives are pivotal for stable cycling of rechargeable sodium-ion batteries(SIBs),which dictate the creation of the protective interface film on electrodes.Cyclic sulfur-containing additives,such as1,3,2-dioxathiolane-2,2-dioxide(DTD),with the structure of sulfur surrounded by four oxygen atoms,have been proposed but less knowledge is available on the relationship between their molecular structures and interfacial stability.This work compares two similar molecule structure of cyclic sulfurcontaining additives,DTD and ethylene sulfite(ES),to investigate their effects on the electrochemical performance of NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)(NFM)||hard carbon(HC)pouch cells.Therein,ES with the structure of sulfur surrounded by three oxygen atoms,as electrolyte additive,is investigated in the SIBs for the first time.It is shown that adding 3.0%ES or 2.0%DTD(the optimal proportion)in the Control electrolyte(1 M NaPF_(6)in EC:EMC=3:7 with 5.0%FEC in weight)can improve cyclic stability and rate performance,respectively.Even under the high-temperature conditions,both ES and DTD exhibit good performance,but DTD is superior.Combinations of electrochemical methods,multi-spectroscopy,and theoretical calculations have been employed to evaluate and compare the effects of ES and DTD on sodium-ion battery.They reveal that ES and DTD can generate different content and composition by redox reaction on cathode and anode surface.The more and effective high-valence sulfur-containing components for DTD are the main reason to explain the better effect on DTD.This work shares new insights into the relationship between cyclic sulfur-containing additive molecule structure and electrolyte-electrode interface films effect,which fills the blanks of previous research.展开更多
The rational assembly of quantum dots on two-dimensional(2 D) carbonaceous materials is very promising to produce materials, but remains a challenge. Here, we develop an assembly strategy of growing Na3 V2(PO4)3 quant...The rational assembly of quantum dots on two-dimensional(2 D) carbonaceous materials is very promising to produce materials, but remains a challenge. Here, we develop an assembly strategy of growing Na3 V2(PO4)3 quantum dots with superlattice structure(NVP-QDs-SL) for obtaining precise control of the size, distribution and crystallinity. The multifunctional lignocelluloses(LCs) used as a hard carbon source induce heterogeneous nucleation and confined growth of NVP-QDs-SL, leading to the uniform distribution of NVP-QDs-SL in H/S-doped hard carbon ultra-thin nanosheets(HCS). Detailed electrochemical analysis results from sodium-ion batteries of NVP-QDs-SL show that NVP-QDs-SL could trap the electrons inside HCS, significantly enhancing Na ion storage and transfer kinetics. Compared to the common Na3 V2(PO4)3 nanoparticle cathode, the NVP-QDs-SL/HCS cathode exhibits a high reversible capacity of 149.2 m A h g^-1 at a 0.1 C rate, which is far beyond the theoretical capacity of Na3 V2(PO4)3(117.6 m A h g^-1).At the ultrahigh current rate of 100 C, this cathode still remains a high discharge capacity of 40 m A h g-1.Even after cycling at 20 C over 3000 cycles, an ultrahigh coulombic efficiency close to 100% is still obtained,highlighting its excellent long cycling life, remarkable rate performance and energy density.展开更多
Microstructure evolution and hardening effect of pure tungsten and W-1.5%ZrO_(2) alloy under carbon ion irradiation are investigated by using transmission electron microscopy and nano-indentation.Carbon ion irradiatio...Microstructure evolution and hardening effect of pure tungsten and W-1.5%ZrO_(2) alloy under carbon ion irradiation are investigated by using transmission electron microscopy and nano-indentation.Carbon ion irradiation is performed at 700℃ with irradiation damages ranging from 0.25 dpa to 2.0 dpa.The results show that the irradiation defect clusters are mainly in the form of dislocation loop.The size and density of dislocation loops increase with irradiation damages intensifying.The W-1.5%ZrO_(2) alloy has a smaller dislocation loop size than that of pure tungsten.It is proposed that the phase boundaries have the ability to absorb and annihilate defects and the addition of ZrO_(2) phase improves the sink strength for irradiation defects.It is confirmed that the W-1.5% ZrO_(2) alloy shows a smaller change in hardness than the pure tungsten after being irradiated.From the above results,we conclude that the addition of ZrO_(2) into tungsten can significantly reduce the accumulation of irradiated defects and improve the irradiation resistance behaviors of the tungsten materials.展开更多
Porous carbon sheets have wide application prospects in many fields,especially in energy storage of supercapacitor due to the features combining both 2D structure and porous architectures.Herein,a self-deposition appr...Porous carbon sheets have wide application prospects in many fields,especially in energy storage of supercapacitor due to the features combining both 2D structure and porous architectures.Herein,a self-deposition approach is proposed to obtain N-doped mesoporous carbon nanosheets (N-MCNs),using 3-aminophenol (3-AF) as precursor and Mg(OH)_(2) sheet as hard template.This process realizes the direct carbon formation using 3-AF monomer as carbon precursor under the catalysis of hard template avoiding the polymerization and utilization of solvent.The mass ratio of 3-AF to Mg(OH)_(2) plays an important role in determining the pore structures and the resulting capacitance behavior.The results show that N-MCNs with a mass ratio of 3-AF and Mg(OH)_(2) of 1:1 have good electrochemical behavior for supercapacitors.This N-MCNs based electrode exhibits a high capacitance of 240 F·g^(-1)at 1 A·g^(-1),good rate performance(75.4%retention ratio at 20 A·g^(-1)),and high cycling stability with 98.3% initial capacitance retained after 10000 cycles.Symmetric supercapacitors on N-MCNs achieve energy density of 18.2 W·h·kg^(-1) and power density of 0.4 kW·kg^(-1) operated within a wide potential range of 0–1.6 V in 1.0 mol·L^(-1) Na_(2)SO_(4) solution,exhibiting its potential for electrode materials with high performance.展开更多
As the size of semiconductor devices shrinks,there is an escalating demand for carbon hard mask films with high etching selectivity for effective pattern transfer and excellent optical transparency,especially at the 6...As the size of semiconductor devices shrinks,there is an escalating demand for carbon hard mask films with high etching selectivity for effective pattern transfer and excellent optical transparency,especially at the 633 nm alignment wavelength used in photolithography.However,simultaneously achieving high etch selectivity and high optical transparency in carbon films deposited by plasma-enhanced chemical vapor deposition(PECVD)is challenging,due to the conflicting effects of deposition temperature and ion bombardment energy.This study describes the design and implementation of a deposition-etching(dep-etch)process that addresses the challenge of inherent trade-off between low extinction coefficient(k,at 633 nm)and high etch selectivity by an integrated inductively coupled plasma and capacitive coupled plasma generator plasma-enhanced chemical vapor deposition(ICP-CCP PECVD)platform,creating a hybrid dep-etch system that decouples film transparency from etch selectivity by enhancing plasma density and coupling ion bombardment for low-temperature deposition.This process prevents the formation of large sp^(2) clusters,reducing film defects,facilitating the escape of hydrogen atoms,and promoting the formation of sp^(3)C-C bonds.Consequently,the films meet the stringent criteria for advanced carbon hard mask applications,achieving an ultra-low extinction coefficient below 0.01 at 633 nm,and etching selectivity of 18.3:1 against thermal oxide SiO_(2).展开更多
Porous carbon nitride(CN)spheres with partially crystalline frameworks have been successfully synthesized via a nanocasting approach by using spherical mesoporous cellular silica foams(MCFs)as a hard template,and ethy...Porous carbon nitride(CN)spheres with partially crystalline frameworks have been successfully synthesized via a nanocasting approach by using spherical mesoporous cellular silica foams(MCFs)as a hard template,and ethylenediamine and carbon tetrachloride as precursors.The resulting spherical CN materials have uniform diameters of ca.4μm,hierarchical three-dimensional(3-D)mesostructures with small and large mesopores with pore diameters centered at ca.4.0 and 43 nm,respectively,a relatively high BET surface area of~550 m^(2)/g,and a pore volume of 0.90 cm^(3)/g.High-resolution transmission electron microscope(HRTEM)images,wide-angle X-ray diffraction(XRD)patterns,and Raman spectra demonstrate that the porous CN material has a partly graphitized structure.In addition,elemental analyses,X-ray photoelectron spectra(XPS),Fourier transform infrared spectra(FT-IR),and CO_(2) temperature-programmed desorption(CO_(2)-TPD)show that the material has a high nitrogen content(17.8 wt%)with nitrogen-containing groups and abundant basic sites.The hierarchical porous CN spheres have excellent CO_(2) capture properties with a capacity of 2.90 mmol/g at 25℃and 0.97 mmol/g at 75℃,superior to those of the pure carbon materials with analogous mesostructures.This can be mainly attributed to the abundant nitrogen-containing basic groups,hierarchical mesostructure,relatively high BET surface area and stable framework.Furthermore,the presence of a large number of micropores and small mesopores also enhance the CO_(2) capture performance,owing to the capillary condensation effect.展开更多
Glassy carbon(GC)is a type of non-graphitizing disordered carbon material at ambient pressure and high temperatures,which has been widely used due to its excellent mechanical properties.Here we report the changes in t...Glassy carbon(GC)is a type of non-graphitizing disordered carbon material at ambient pressure and high temperatures,which has been widely used due to its excellent mechanical properties.Here we report the changes in the microstructure and mechanical properties of GC treated at high pressures(up to 5 GPa)and high temperatures.The formation of intermediate sp2-sp3 phases is identified at moderate treatment temperatures before the complete graphitization of GC,by analyzing synchrotron X-ray diffraction,Raman spectra,and transmission electron microscopy images.The intermediate metastable carbon materials exhibit superior mechanical properties with hardness reaching up to 10 GPa and compressive strength reaching as high as 2.5 GPa,nearly doubling those of raw GC,and improving elasticity and thermal stability.The synthesis pressure used in this study can be achieved in the industry on a commercial scale,enabling the scalable synthesis of this type of strong,hard,and elastic carbon materials.展开更多
Li_(2)C_(2)O_(4),with a high theoretical capacity of 525 mAh·g^(−1)and good air stability,is regarded as a more attractive cathode prelithiation additive in contrast to the reported typical inorganic pre-lithiati...Li_(2)C_(2)O_(4),with a high theoretical capacity of 525 mAh·g^(−1)and good air stability,is regarded as a more attractive cathode prelithiation additive in contrast to the reported typical inorganic pre-lithiation compounds which are quite air sensitive.However,its obtained capacity is much lower than the theoretical value and its delithiation potential(>4.7 V)is too high to match with the most commercial cathode materials,which greatly impedes its practical application.Herein,we greatly improve the pre-lithiation performance of Li_(2)C_(2)O_(4)as cathode additive with fulfilled capacity at a much-reduced delithiation voltage,enabling its wide applicability for typical commercial cathodes.We increase the capacity of Li_(2)C_(2)O_(4)from 436 to 525 mAh·g^(−1)by reducing its particle size.Through optimizing the types of conductive additives,introducing nano-morphological NiO,MnO2,etc.as catalysts,and innovatively designing a bilayer electrode,the delithiation potential of Li_(2)C_(2)O_(4)is successfully reduced from 4.778 to 4.288 V.We systematically study different particle size,conductive additives,and catalysts on the delithiation behavior of Li_(2)C_(2)O_(4).Finally,it is applied to pre-lithiate the hard carbon anode,and it is found that Li_(2)C_(2)O_(4)could effectively increase the capacity of the full cell from 79.0 to 140.0 mAh·g^(−1)in the first cycle.In conclusion,our study proves that improving the reactivity is an effective strategy to boost the pre-lithiation of Li_(2)C_(2)O_(4).展开更多
Hard carbon is widely regarded as one of the most promising anode materials for sodium-ion batteries(SIBs),yet achieving high energy density requires a significant enhancement of the low-voltage plateau capacity near~...Hard carbon is widely regarded as one of the most promising anode materials for sodium-ion batteries(SIBs),yet achieving high energy density requires a significant enhancement of the low-voltage plateau capacity near~0.1 V(vs.Na^(+)/Na).Although closed-pore structures dominate plateau storage,their formation mechanisms remain elusive.We present a synergistic strategy combining CO_(2) etching with high-temperature carbonization to systematically elucidate the evolution of closed pores and their influence on sodium storage behavior.CO_(2) etching generates open pores that reorganize into closed pores during secondary treatment.Crucially,precursor selection dictates closed-pore density,with N-rich chitosan-derived hard carbon developing denser closed-pore architecture than exclusively O-doped precursors.The optimized hard carbon anode delivers a high reversible capacity of 388.8 mAh·g^(−1) at 0.05 A·g^(−1),with excellent cycling stability(83.8%capacity retention after 800 cycles at 0.5 A·g^(−1)).In-situ and ex-situ analyses demonstrate that Na+ions reversibly fill the engineered closed pores,accounting for over 200 mAh·g^(−1)(approximately 57%of the total reversible capacity)via a plateau-dominated storage.Consequently,full cells assembled with this optimized hard carbon anode achieve an energy density of 165.2 Wh·kg^(−1).This work offers new mechanistic insights into pore evolution and provides a practical route for tailoring high-performance hard carbon anodes for next-generation SIBs.展开更多
基金supported by the National Natural Science Foundation of China(21875076)the Guangdong Provincial International Joint Research Center for Energy Storage Materials(2023A0505090009)the Science and Technology Planning Project of Guangzhou City(2023B03J1278)。
文摘Electrolyte additives are pivotal for stable cycling of rechargeable sodium-ion batteries(SIBs),which dictate the creation of the protective interface film on electrodes.Cyclic sulfur-containing additives,such as1,3,2-dioxathiolane-2,2-dioxide(DTD),with the structure of sulfur surrounded by four oxygen atoms,have been proposed but less knowledge is available on the relationship between their molecular structures and interfacial stability.This work compares two similar molecule structure of cyclic sulfurcontaining additives,DTD and ethylene sulfite(ES),to investigate their effects on the electrochemical performance of NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)(NFM)||hard carbon(HC)pouch cells.Therein,ES with the structure of sulfur surrounded by three oxygen atoms,as electrolyte additive,is investigated in the SIBs for the first time.It is shown that adding 3.0%ES or 2.0%DTD(the optimal proportion)in the Control electrolyte(1 M NaPF_(6)in EC:EMC=3:7 with 5.0%FEC in weight)can improve cyclic stability and rate performance,respectively.Even under the high-temperature conditions,both ES and DTD exhibit good performance,but DTD is superior.Combinations of electrochemical methods,multi-spectroscopy,and theoretical calculations have been employed to evaluate and compare the effects of ES and DTD on sodium-ion battery.They reveal that ES and DTD can generate different content and composition by redox reaction on cathode and anode surface.The more and effective high-valence sulfur-containing components for DTD are the main reason to explain the better effect on DTD.This work shares new insights into the relationship between cyclic sulfur-containing additive molecule structure and electrolyte-electrode interface films effect,which fills the blanks of previous research.
基金supported financially by the National Natural Science Foundation of China (Nos. 51672139, 51472127 and 51272144)the Projects Supported by the Key Laboratory of Pulp and Paper Science and Technology of Ministry of Education (No. KF2016-01)
文摘The rational assembly of quantum dots on two-dimensional(2 D) carbonaceous materials is very promising to produce materials, but remains a challenge. Here, we develop an assembly strategy of growing Na3 V2(PO4)3 quantum dots with superlattice structure(NVP-QDs-SL) for obtaining precise control of the size, distribution and crystallinity. The multifunctional lignocelluloses(LCs) used as a hard carbon source induce heterogeneous nucleation and confined growth of NVP-QDs-SL, leading to the uniform distribution of NVP-QDs-SL in H/S-doped hard carbon ultra-thin nanosheets(HCS). Detailed electrochemical analysis results from sodium-ion batteries of NVP-QDs-SL show that NVP-QDs-SL could trap the electrons inside HCS, significantly enhancing Na ion storage and transfer kinetics. Compared to the common Na3 V2(PO4)3 nanoparticle cathode, the NVP-QDs-SL/HCS cathode exhibits a high reversible capacity of 149.2 m A h g^-1 at a 0.1 C rate, which is far beyond the theoretical capacity of Na3 V2(PO4)3(117.6 m A h g^-1).At the ultrahigh current rate of 100 C, this cathode still remains a high discharge capacity of 40 m A h g-1.Even after cycling at 20 C over 3000 cycles, an ultrahigh coulombic efficiency close to 100% is still obtained,highlighting its excellent long cycling life, remarkable rate performance and energy density.
基金Project supported by the President's Foundation of the ChinaAcademy of Engineering Physics(Grant No.YZJJLX2018003)the National Natural Science Foundation of China(Grant Nos.U2004180 and 12105261)the Program for Changjiang Scholars and Innovative Research Team in Universities,China(Grant No.IRT1234).
文摘Microstructure evolution and hardening effect of pure tungsten and W-1.5%ZrO_(2) alloy under carbon ion irradiation are investigated by using transmission electron microscopy and nano-indentation.Carbon ion irradiation is performed at 700℃ with irradiation damages ranging from 0.25 dpa to 2.0 dpa.The results show that the irradiation defect clusters are mainly in the form of dislocation loop.The size and density of dislocation loops increase with irradiation damages intensifying.The W-1.5%ZrO_(2) alloy has a smaller dislocation loop size than that of pure tungsten.It is proposed that the phase boundaries have the ability to absorb and annihilate defects and the addition of ZrO_(2) phase improves the sink strength for irradiation defects.It is confirmed that the W-1.5% ZrO_(2) alloy shows a smaller change in hardness than the pure tungsten after being irradiated.From the above results,we conclude that the addition of ZrO_(2) into tungsten can significantly reduce the accumulation of irradiated defects and improve the irradiation resistance behaviors of the tungsten materials.
基金the Natural Science Foundation of Hebei (B02020208088)S&T Program of Hebei (20544401D, 20314401D, 206Z4406G, 21314402D, B2021208074, 21344601D)Tianjin Science and Technology Project (19YFSLQY00070)。
文摘Porous carbon sheets have wide application prospects in many fields,especially in energy storage of supercapacitor due to the features combining both 2D structure and porous architectures.Herein,a self-deposition approach is proposed to obtain N-doped mesoporous carbon nanosheets (N-MCNs),using 3-aminophenol (3-AF) as precursor and Mg(OH)_(2) sheet as hard template.This process realizes the direct carbon formation using 3-AF monomer as carbon precursor under the catalysis of hard template avoiding the polymerization and utilization of solvent.The mass ratio of 3-AF to Mg(OH)_(2) plays an important role in determining the pore structures and the resulting capacitance behavior.The results show that N-MCNs with a mass ratio of 3-AF and Mg(OH)_(2) of 1:1 have good electrochemical behavior for supercapacitors.This N-MCNs based electrode exhibits a high capacitance of 240 F·g^(-1)at 1 A·g^(-1),good rate performance(75.4%retention ratio at 20 A·g^(-1)),and high cycling stability with 98.3% initial capacitance retained after 10000 cycles.Symmetric supercapacitors on N-MCNs achieve energy density of 18.2 W·h·kg^(-1) and power density of 0.4 kW·kg^(-1) operated within a wide potential range of 0–1.6 V in 1.0 mol·L^(-1) Na_(2)SO_(4) solution,exhibiting its potential for electrode materials with high performance.
基金supported by the National Key R&D Program of China(2021YFA1500804)the National Natural Science Foundation of China(22121004,22038009,22250008)the Haihe Laboratory of Sustainable Chemical Transformations,the Program of Introducing Talents of Discipline to Universities(BP0618007)。
文摘As the size of semiconductor devices shrinks,there is an escalating demand for carbon hard mask films with high etching selectivity for effective pattern transfer and excellent optical transparency,especially at the 633 nm alignment wavelength used in photolithography.However,simultaneously achieving high etch selectivity and high optical transparency in carbon films deposited by plasma-enhanced chemical vapor deposition(PECVD)is challenging,due to the conflicting effects of deposition temperature and ion bombardment energy.This study describes the design and implementation of a deposition-etching(dep-etch)process that addresses the challenge of inherent trade-off between low extinction coefficient(k,at 633 nm)and high etch selectivity by an integrated inductively coupled plasma and capacitive coupled plasma generator plasma-enhanced chemical vapor deposition(ICP-CCP PECVD)platform,creating a hybrid dep-etch system that decouples film transparency from etch selectivity by enhancing plasma density and coupling ion bombardment for low-temperature deposition.This process prevents the formation of large sp^(2) clusters,reducing film defects,facilitating the escape of hydrogen atoms,and promoting the formation of sp^(3)C-C bonds.Consequently,the films meet the stringent criteria for advanced carbon hard mask applications,achieving an ultra-low extinction coefficient below 0.01 at 633 nm,and etching selectivity of 18.3:1 against thermal oxide SiO_(2).
基金This work was supported by the National Natural Science Foundation of China(NSFC)(Nos.2089012,20721063,20821140537,20871030)State Key Basic Research Program of PRC(Nos.2006CB932302 and 2009AA033701)+3 种基金Shanghai Leading Academic Discipline Project(No.B108)Science&Technology Com-mission of Shanghai Municipality(No.08DZ2270500)C.S.Ha also thanks the National Research Foundation(NRF)of Korea for support through the Korea-China Joint Research Center Program on Mesoporous Thin Films(No.K20803001459-10B1200-00310)the Acceleration Research Program(No.2010-0000790).
文摘Porous carbon nitride(CN)spheres with partially crystalline frameworks have been successfully synthesized via a nanocasting approach by using spherical mesoporous cellular silica foams(MCFs)as a hard template,and ethylenediamine and carbon tetrachloride as precursors.The resulting spherical CN materials have uniform diameters of ca.4μm,hierarchical three-dimensional(3-D)mesostructures with small and large mesopores with pore diameters centered at ca.4.0 and 43 nm,respectively,a relatively high BET surface area of~550 m^(2)/g,and a pore volume of 0.90 cm^(3)/g.High-resolution transmission electron microscope(HRTEM)images,wide-angle X-ray diffraction(XRD)patterns,and Raman spectra demonstrate that the porous CN material has a partly graphitized structure.In addition,elemental analyses,X-ray photoelectron spectra(XPS),Fourier transform infrared spectra(FT-IR),and CO_(2) temperature-programmed desorption(CO_(2)-TPD)show that the material has a high nitrogen content(17.8 wt%)with nitrogen-containing groups and abundant basic sites.The hierarchical porous CN spheres have excellent CO_(2) capture properties with a capacity of 2.90 mmol/g at 25℃and 0.97 mmol/g at 75℃,superior to those of the pure carbon materials with analogous mesostructures.This can be mainly attributed to the abundant nitrogen-containing basic groups,hierarchical mesostructure,relatively high BET surface area and stable framework.Furthermore,the presence of a large number of micropores and small mesopores also enhance the CO_(2) capture performance,owing to the capillary condensation effect.
基金supported by the National Key R&D Program of China(Grants No.2018YFA0703400)the National Natural Science Foundation of China(Grants Nos.51672238,91963203,51722209,and 51525205)+2 种基金M.Hu acknowledges fellowship support by the Alexander von Humboldt Foundation.Z.Zhao acknowledges 100 talents plan of Hebei Province(Grants No.E2016100013)NSF for Distinguished Young Scholars of Hebei Province of China(Grants No.E2018203349)K.Luo acknowledges the China Postdoctoral Science Foundation(Grants No.2017M620097).
文摘Glassy carbon(GC)is a type of non-graphitizing disordered carbon material at ambient pressure and high temperatures,which has been widely used due to its excellent mechanical properties.Here we report the changes in the microstructure and mechanical properties of GC treated at high pressures(up to 5 GPa)and high temperatures.The formation of intermediate sp2-sp3 phases is identified at moderate treatment temperatures before the complete graphitization of GC,by analyzing synchrotron X-ray diffraction,Raman spectra,and transmission electron microscopy images.The intermediate metastable carbon materials exhibit superior mechanical properties with hardness reaching up to 10 GPa and compressive strength reaching as high as 2.5 GPa,nearly doubling those of raw GC,and improving elasticity and thermal stability.The synthesis pressure used in this study can be achieved in the industry on a commercial scale,enabling the scalable synthesis of this type of strong,hard,and elastic carbon materials.
基金the financial support provided by the National Natural Science Foundation of China(No.52072138)the National Key Research and Development Program of China(No.2018YFE0206900)+1 种基金the Shenzhen Science and Technology Program(No.JCYJ20220530160816038)the Australian Research Council(ARC)through the Discovery Project(No.DP180102297).
文摘Li_(2)C_(2)O_(4),with a high theoretical capacity of 525 mAh·g^(−1)and good air stability,is regarded as a more attractive cathode prelithiation additive in contrast to the reported typical inorganic pre-lithiation compounds which are quite air sensitive.However,its obtained capacity is much lower than the theoretical value and its delithiation potential(>4.7 V)is too high to match with the most commercial cathode materials,which greatly impedes its practical application.Herein,we greatly improve the pre-lithiation performance of Li_(2)C_(2)O_(4)as cathode additive with fulfilled capacity at a much-reduced delithiation voltage,enabling its wide applicability for typical commercial cathodes.We increase the capacity of Li_(2)C_(2)O_(4)from 436 to 525 mAh·g^(−1)by reducing its particle size.Through optimizing the types of conductive additives,introducing nano-morphological NiO,MnO2,etc.as catalysts,and innovatively designing a bilayer electrode,the delithiation potential of Li_(2)C_(2)O_(4)is successfully reduced from 4.778 to 4.288 V.We systematically study different particle size,conductive additives,and catalysts on the delithiation behavior of Li_(2)C_(2)O_(4).Finally,it is applied to pre-lithiate the hard carbon anode,and it is found that Li_(2)C_(2)O_(4)could effectively increase the capacity of the full cell from 79.0 to 140.0 mAh·g^(−1)in the first cycle.In conclusion,our study proves that improving the reactivity is an effective strategy to boost the pre-lithiation of Li_(2)C_(2)O_(4).
基金the financial supports from the National Natural Science Foundation of China(No.22179123)the Taishan Scholar Program of Shandong Province,China(No.tsqn202211048)the Major Basic Research Projects of Shandong Natural Science Foundation(No.ZR2024ZD37).
文摘Hard carbon is widely regarded as one of the most promising anode materials for sodium-ion batteries(SIBs),yet achieving high energy density requires a significant enhancement of the low-voltage plateau capacity near~0.1 V(vs.Na^(+)/Na).Although closed-pore structures dominate plateau storage,their formation mechanisms remain elusive.We present a synergistic strategy combining CO_(2) etching with high-temperature carbonization to systematically elucidate the evolution of closed pores and their influence on sodium storage behavior.CO_(2) etching generates open pores that reorganize into closed pores during secondary treatment.Crucially,precursor selection dictates closed-pore density,with N-rich chitosan-derived hard carbon developing denser closed-pore architecture than exclusively O-doped precursors.The optimized hard carbon anode delivers a high reversible capacity of 388.8 mAh·g^(−1) at 0.05 A·g^(−1),with excellent cycling stability(83.8%capacity retention after 800 cycles at 0.5 A·g^(−1)).In-situ and ex-situ analyses demonstrate that Na+ions reversibly fill the engineered closed pores,accounting for over 200 mAh·g^(−1)(approximately 57%of the total reversible capacity)via a plateau-dominated storage.Consequently,full cells assembled with this optimized hard carbon anode achieve an energy density of 165.2 Wh·kg^(−1).This work offers new mechanistic insights into pore evolution and provides a practical route for tailoring high-performance hard carbon anodes for next-generation SIBs.
