Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) has been recognized as a candidate solid electrolyte for high-safety Lianode based solid-state batteries because of its electro-chemical stability against Li-metal and high i...Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) has been recognized as a candidate solid electrolyte for high-safety Lianode based solid-state batteries because of its electro-chemical stability against Li-metal and high ionic conductivity. Solvent(e.g., isopropanol(IPA)) has been commonly applied for preparing LLZO powders and ceramics. However, the deterioration of the proton-exchange between LLZO and IPA/absorbed moisture during the mixing and tailoring route has aroused less attention. In this study, a solvent-free dry milling route was developed for preparing the LLZO powders and ceramics. For orthogonal four categories of samples prepared using solvent-free and IPA-assisted routes in the mixing and tailoring processes, the critical evaluation was conducted on the crystallinity, surficial morphology, and contamination of ascalcinated and as-tailored particles, the cross-sectional microstructure of green and sintered pellets,the morphology and electro-chemical properties of grain boundaries in ceramics, as well as the interfacial resistance and performance of Li anode based symmetric batteries. The wet route introduced Li-rich contaminations(e.g., Li OH·H)_(2)O and Li)_(2)CO)_(3)) onto the surfaces of LLZO particles and Li-Ta-O segregations at the adjacent and triangular grain boundaries. The LLZO solid electrolytes prepared through dry mixing in combination with the dry tailoring route without the use of any solvent were found to the optimal performance. The fundamental material properties in the whole LLZO preparation process were found, which are of guiding significance to the development of LLZO powder and ceramic production craft.展开更多
In recent years,the composite materials based on polyanionic frameworks as secondary sodium ion battery electrode material have been developed in large-scale energy storage applications due to its safety and stability...In recent years,the composite materials based on polyanionic frameworks as secondary sodium ion battery electrode material have been developed in large-scale energy storage applications due to its safety and stability.The Na_(2)FeP_(2)O_(7)/C(theoretical capacity 97 mA·h·g^(-1))is recognized as optimum Na-storage cathode materials with a trade-off between electrode performance and cost.In the present work,The Na_(2)FeP_(2)O_(7)/C and boron-doped Na_(2)FeP_(2-x)BxO_(7)/C composites were synthesized via a novel method of liquid phase combined with high temperature solid phase.The non-metallic element B doping not only had positive influence on the crystal structure stability,Na+diffusion and electrical conductivity of Na_(2)FeP_(2)O_(7)/C,but also contributed to the high-value recycling of B element in waste borax.The structure and electrochemical properties of the cathode material were investigated via X-ray diffraction(XRD),scanning electron microscopy(SEM),The X-ray photoelectron spectroscopy(XPS),electrochemical impedance spectroscopy(EIS),cyclic voltammetry(CV),and charge/discharge cycling.The results showed that different amounts of boron doping had positive effects on the structure and electrochemical properties of the material.The initial charge/discharge performances of born doped materials were improved in comparison to the bare Na_(2)FeP_(2)O_(7)/C.The cycle performance of the Na_(2)FeP_(1.95)B_(0.05)O_(7)/C showed an initial reversible capacity of 74.8 mA·h·g^(-1) and the high capacity retention of 91.8%after 100 cycles at 1.0 C,while the initial reversible capacity of the bare Na_(2)FeP_(2)O_(7)/C was only 66.2 mA·h·g^(-1).The improvement of apparent Na+diffusion and electrical conductivity due to B doping were verified by the EIS test and CVs at various scan rate.The experimental results from present work is useful for opening new insight into the contrivance and creation of applicable sodium polyanionic cathode materials for high-performance.展开更多
Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite's formation greatly limits the applications.In this paper,we systematically investigate the st...Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite's formation greatly limits the applications.In this paper,we systematically investigate the stability,electronic properties,and Li-ion mobility of the LLZO surface by the ifrst-principles calculations.We consider the(110) and(001) slab structures with different terminations in the t-and c-LLZO.Our results indicate that both(110) and(001) surfaces prefer to form Li-rich termination due to their low surface energies for either t-or c-LLZO.Moreover,with the decrease of Li contents the stability of Li-rich surfaces is improved initially and degrades later.Unfortunately,the localized surface states at the Fermi level can induce the formation of metallic Li on the Li-rich surfaces.In comparison,Li/La-termination has a relatively low metallic Li formation tendency due to its rather low diffusion barrier.In fact,Li-ion can spontaneously migrate along path II(Li3→Li2) on the Li/La-T(001) surface.In contrast,it is more difficult for Li-ion diffusion on the Li-T(001) surface,which has a minimum diffusion barrier of 0.50 eV.Interestingly,the minimum diffusion barrier decreases to 0.34 eV when removing four Li-ions from the Li-T(001) surface.Thus,our study suggests that by varying Li contents,the stability and Li-ion diffusion barrier of LLZO surfaces can be altered favorably.These advantages can inhibit the formation of metallic Li on the LLZO surfaces.展开更多
基金the financial support from the National Key R&D Project (2018YFE0181300)the National Natural Science Foundation of China (Grant No. 52102284)+2 种基金the China Postdoctoral Science Foundation (2020M682871)the Guangdong Natural Science Funds (2019A1515010675)the Science and Technology Project of Shenzhen (JCYJ20190808142209376 and JCYJ20210324094206019)。
文摘Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) has been recognized as a candidate solid electrolyte for high-safety Lianode based solid-state batteries because of its electro-chemical stability against Li-metal and high ionic conductivity. Solvent(e.g., isopropanol(IPA)) has been commonly applied for preparing LLZO powders and ceramics. However, the deterioration of the proton-exchange between LLZO and IPA/absorbed moisture during the mixing and tailoring route has aroused less attention. In this study, a solvent-free dry milling route was developed for preparing the LLZO powders and ceramics. For orthogonal four categories of samples prepared using solvent-free and IPA-assisted routes in the mixing and tailoring processes, the critical evaluation was conducted on the crystallinity, surficial morphology, and contamination of ascalcinated and as-tailored particles, the cross-sectional microstructure of green and sintered pellets,the morphology and electro-chemical properties of grain boundaries in ceramics, as well as the interfacial resistance and performance of Li anode based symmetric batteries. The wet route introduced Li-rich contaminations(e.g., Li OH·H)_(2)O and Li)_(2)CO)_(3)) onto the surfaces of LLZO particles and Li-Ta-O segregations at the adjacent and triangular grain boundaries. The LLZO solid electrolytes prepared through dry mixing in combination with the dry tailoring route without the use of any solvent were found to the optimal performance. The fundamental material properties in the whole LLZO preparation process were found, which are of guiding significance to the development of LLZO powder and ceramic production craft.
基金the National Key Research and Development Program of China(2019YFE0123900)the National Natural Science Foundation of China(51974069)。
文摘In recent years,the composite materials based on polyanionic frameworks as secondary sodium ion battery electrode material have been developed in large-scale energy storage applications due to its safety and stability.The Na_(2)FeP_(2)O_(7)/C(theoretical capacity 97 mA·h·g^(-1))is recognized as optimum Na-storage cathode materials with a trade-off between electrode performance and cost.In the present work,The Na_(2)FeP_(2)O_(7)/C and boron-doped Na_(2)FeP_(2-x)BxO_(7)/C composites were synthesized via a novel method of liquid phase combined with high temperature solid phase.The non-metallic element B doping not only had positive influence on the crystal structure stability,Na+diffusion and electrical conductivity of Na_(2)FeP_(2)O_(7)/C,but also contributed to the high-value recycling of B element in waste borax.The structure and electrochemical properties of the cathode material were investigated via X-ray diffraction(XRD),scanning electron microscopy(SEM),The X-ray photoelectron spectroscopy(XPS),electrochemical impedance spectroscopy(EIS),cyclic voltammetry(CV),and charge/discharge cycling.The results showed that different amounts of boron doping had positive effects on the structure and electrochemical properties of the material.The initial charge/discharge performances of born doped materials were improved in comparison to the bare Na_(2)FeP_(2)O_(7)/C.The cycle performance of the Na_(2)FeP_(1.95)B_(0.05)O_(7)/C showed an initial reversible capacity of 74.8 mA·h·g^(-1) and the high capacity retention of 91.8%after 100 cycles at 1.0 C,while the initial reversible capacity of the bare Na_(2)FeP_(2)O_(7)/C was only 66.2 mA·h·g^(-1).The improvement of apparent Na+diffusion and electrical conductivity due to B doping were verified by the EIS test and CVs at various scan rate.The experimental results from present work is useful for opening new insight into the contrivance and creation of applicable sodium polyanionic cathode materials for high-performance.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12064015 and 12064014)。
文摘Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite's formation greatly limits the applications.In this paper,we systematically investigate the stability,electronic properties,and Li-ion mobility of the LLZO surface by the ifrst-principles calculations.We consider the(110) and(001) slab structures with different terminations in the t-and c-LLZO.Our results indicate that both(110) and(001) surfaces prefer to form Li-rich termination due to their low surface energies for either t-or c-LLZO.Moreover,with the decrease of Li contents the stability of Li-rich surfaces is improved initially and degrades later.Unfortunately,the localized surface states at the Fermi level can induce the formation of metallic Li on the Li-rich surfaces.In comparison,Li/La-termination has a relatively low metallic Li formation tendency due to its rather low diffusion barrier.In fact,Li-ion can spontaneously migrate along path II(Li3→Li2) on the Li/La-T(001) surface.In contrast,it is more difficult for Li-ion diffusion on the Li-T(001) surface,which has a minimum diffusion barrier of 0.50 eV.Interestingly,the minimum diffusion barrier decreases to 0.34 eV when removing four Li-ions from the Li-T(001) surface.Thus,our study suggests that by varying Li contents,the stability and Li-ion diffusion barrier of LLZO surfaces can be altered favorably.These advantages can inhibit the formation of metallic Li on the LLZO surfaces.
