Yongfu Tang - Academia.edu (original) (raw)

Papers by Yongfu Tang

Research paper thumbnail of Reviving the rock-salt phases in Ni-rich layered cathodes by mechano-electrochemistry in all-solid-state batteries

Research paper thumbnail of Interlayer Doping of Pseudocapacitive Hydrated Vanadium Oxide Via Mn2+ for High-Performance Aqueous Zinc-Ion Battery

Research paper thumbnail of In situ Observation of Li Deposition‐Induced Cracking in Garnet Solid Electrolytes

ENERGY & ENVIRONMENTAL MATERIALS, 2021

Research paper thumbnail of In-situ imaging Co3O4 catalyzed oxygen reduction and evolution reactions in a solid state Na-O2 battery

Nano Energy, 2020

Abstract Co3O4 nano materials have attracted tremendous attention as effective catalysts for sodi... more Abstract Co3O4 nano materials have attracted tremendous attention as effective catalysts for sodium oxygen batteries (SOBs). However, their electrochemical processes and fundamental catalytic mechanism remain unclear till now. Herein, in-situ environmental transmission electron microscopy technique was used to study the catalysis mechanism of the Co3O4 nanocubes in SOBs during discharge and charge processes. It is found that during the 1st discharge and charge processes, Na2O2 formed and decomposed, respectively, around the Co3O4 nanocubes, but the following discharge and charge processes were very difficult. In order to promote the charge kinetics, we increased the charging temperature up to 500 °C, when the decomposition of Na2O2 became facile. Aberration corrected high-angle annular dark field imaging indicated that a thin layer of CoO grew epitaxially on the surface of Co3O4 nanocubes after the first discharge. Density functional theory calculations indicate that the CoO surface is energetically more favorable than Co3O4 for the nucleation of Na2O2. This study provides not only new fundamental understandings to the electrochemical reaction mechanisms of SOBs, but also strategies to improve the cycling performance of solid state SOBs.

Research paper thumbnail of Carbon-Encapsulated Co 3 O 4 @CoO@Co Nanocomposites for Multifunctional Applications in Enhanced Long-life Lithium Storage, Supercapacitor and Oxygen Evolution Reaction

Electrochimica Acta, 2016

Abstract Porous nanostructure composites materials had attracted widely attention due to their po... more Abstract Porous nanostructure composites materials had attracted widely attention due to their potential application in energy storage (Lithium ion batteries (LIBs) and supercapacitor) and electrocatalyst of oxygen evolution reaction (OER). Co 3 O 4 @CoO@Co@C nanocomposites had been successfully synthesized using glucose as carbon source and cobalt nitrate as metalprecurs or of Co 3 O 4 @CoO@Co@C, which has excellent electrochemical performance for LIBs, supercapacitor and OER. Three kinds of morphology samples marked by Co 3 O 4 @CoO@Co@C-2/1, Co 3 O 4 @CoO@Co@C-1/1 and Co 3 O 4 @CoO@Co@C-1/2 are synthesized due to different atomic ratio of cobalt/carbon in precursors. Electrochemical and catalytic performance of Co 3 O 4 @CoO@Co@C-2/1 nanocomposites is more excellent than Co 3 O 4 @CoO@Co@C-1/1 and Co 3 O 4 @CoO@Co@C-1/2. Co 3 O 4 @CoO@Co@C-2/1 shows that discharge capacity can maintain 450 mA h g −1 and coulombic efficiency is nearly 100% during 500 cycles for LIBs. It indicates the excellent cycling stability of Co 3 O 4 @CoO@Co@C-2/1 as electrode for supercapacitor that about 78.3% of initial specific capacitance can be retained after 10000 cycles at current density of 2 A g −1 . Co 3 O 4 @CoO@Co@C-2/1 as catalyst of OER shows excellent electrochemical durability over 15 hours continuous experiment.

Research paper thumbnail of Sodium–Sulfur Batteries: In Situ TEM Studies of Sodium Polysulfides Electrochemistry in High Temperature Na–S Nanobatteries (Small 23/2021)

Research paper thumbnail of Co3ZnC@NC Material Derived from ZIF-8 for Lithium-Ion Capacitors

Research paper thumbnail of Degradation by Kinking in Layered Cathode Materials

Research paper thumbnail of In situ observation of electrochemical Ostwald ripening during sodium deposition

Nano Research

Sodium (Na) metal batteries (SMBs) using Na anode are potential “beyond lithium” electrochemical ... more Sodium (Na) metal batteries (SMBs) using Na anode are potential “beyond lithium” electrochemical technology for future energy storage applications. However, uncontrollable Na dendrite growth has plagued the application of SMBs. Understanding Na deposition mechanisms, particularly the early stage of Na deposition kinetics, is critical to enable the SMBs. In this context, we conducted in situ observations of the early stage of electrochemical Na deposition. We revealed an important electrochemical Ostwald ripening (EOR) phenomenon which dictated the early stage of Na deposition. Namely, small Na nanocrystals were nucleated randomly, which then grew. During growth, smaller Na nanocrystals were contained by bigger ones via EOR. We observed two types of EOR with one involving only electrochemical reaction driven by electrochemical potential difference between bigger and smaller nanocrystals; while the other being dominated by mass transport governed by surface energy minimization. The results provide new understanding to the Na deposition mechanism, which may be useful for the development of SMB for energy storage applications.

Research paper thumbnail of A Coral‐Like FeP@NC Anode with Increasing Cycle Capacity for Sodium‐Ion and Lithium‐Ion Batteries Induced by Particle‐Refinement

Angewandte Chemie International Edition

Electrodes with higher Na + storage capability and cycling stability are vital to improve the ene... more Electrodes with higher Na + storage capability and cycling stability are vital to improve the energy density and rate capability of sodium ion batteries (SIBs). Herein, we present a coral-like FeP composite with FeP nanoparticles anchored and dispersed on a nitrogen-doped three-dimensional carbon framework ( FeP@NC ). Due to the highly continuous N-doped carbon framework and a spring-buffering graphitized carbon layer around the FeP nanoparticle, the sodium ion battery with FeP@NC composite can exhibit an ultra-stable cycling performance at 10 A g -1 with a capacity retention of 82.0% in 10000 cycles. More importantly, an interesting particle refinement achieving capacity increasing mechanism during cycling has been well confirmed. Particularly, the FeP nanoparticles go through a refining-recombination process during the first cycle and present a global refining trend after dozens of cycles, which results in a gradually increase in graphitization degree and interface magnetization, and further provides more extra active sites for Na + storage and contributes to a rising capacity with cycling . The capacity ascending phenomenon can also extend to lithium-ion batteries (LIBs). This paper holds a new feasibility insight mechanism of the enhanced capacity during cycling and also offers a feasible solution to design high performance anode material for SIBs/LIBs.

Research paper thumbnail of Ultrastable Anode/Electrolyte Interface in Solid-State Lithium-Metal Batteries Using LiCux Nanowire Network Host

High interfacial resistance and uncontrollable lithium (Li) dendrite are major challenges in soli... more High interfacial resistance and uncontrollable lithium (Li) dendrite are major challenges in solid-state Li-metal batteries (SSLMBs), as they lead to premature short-circuiting and failure of SSLMBs. Here, we report the synthesis of a composite anode comprising a three-dimensional LiCux nanowire network host infiltrated with Li (Li* anode) with low interfacial impedance and superior electrochemical performance. The Li* anode is fabricated by dissolving Cu foil into molten Li followed by solidification. The Li* anode exhibits good wettability with Li6.4La3Zr1.4Ta0.6O12 (LLZTO) and high mechanical strength, rendering low Li*/LLZTO interfacial impedance, homogeneous deposition of Li, and suppression of Li dendrites. Consequently, the Li* anode-based symmetric cells and full cells with LiNi0.88Co0.1Al0.02O2 (NCA), LiFePO4 (LFP), and FeF2 cathodes deliver remarkable electrochemical performance. Specifically, the Li*/LLZTO/Li* symmetrical cell achieves a remarkably long cycle lifetime of 10 000 h with 0.1 mA·cm-2; the Li*/LLZTO/NCA full cell maintains capacity retention of 73.4% after 500 cycles at 0.5C; and all-solid-state Li*/LLZTO/FeF2 full cell achieves a reversible capacity of 147 mAh·g-1 after 500 cycles at 100 mA·g-1. This work demonstrates potential design tactics for an ultrastable Li*/garnet interface to enable high-performance SSLMBs.

Research paper thumbnail of Layered LiCoO2–LiFeO2 Heterostructure Composite for Semiconductor-Based Fuel Cells

Nanomaterials

Enabling fast ionic transport at a low-temperature range (400–600 °C) is of great importance to p... more Enabling fast ionic transport at a low-temperature range (400–600 °C) is of great importance to promoting the development of solid oxide fuel cells (SOFCs). In this study, a layer-structured LiCoO2–LiFeO2 heterostructure composite is explored for the low-temperature (LT) SOFCs. Fuel cell devices with different configurations are fabricated to investigate the multifunction property of LiCoO2–LiFeO2 heterostructure composites. The LiCoO2–LiFeO2 composite is employed as a cathode in conventional SOFCs and as a semiconductor membrane layer in semiconductor-based fuel cells (SBFCs). Enhanced ionic conductivity is realized by a composite of LiCoO2–LiFeO2 and Sm3+ doped ceria (SDC) electrolyte in SBFC. All these designed fuel cell devices display high open-circuit voltages (OCVs), along with promising cell performance. An improved power density of 714 mW cm−2 is achieved from the new SBFC device, compared to the conventional fuel cell configuration with LiCoO2–LiFeO2 as the cathode (162 mW...

Research paper thumbnail of In situ imaging electrocatalytic CO2 reduction and evolution reactions in all-solid-state Li–CO2 nanobatteries

Nanoscale

We herein present a real time study of a Li–CO2 battery with a Ni–Ru/MnO2 cathode by using the in... more We herein present a real time study of a Li–CO2 battery with a Ni–Ru/MnO2 cathode by using the in situ environmental transmission electron microscopy (ETEM) technique.

Research paper thumbnail of Novel K2Ti8O17 Anode via Na+/Al3+ Co-Intercalation Mechanism for Rechargeable Aqueous Al-Ion Battery with Superior Rate Capability

Nanomaterials

A promising aqueous aluminum ion battery (AIB) was assembled using a novel layered K2Ti8O17 anode... more A promising aqueous aluminum ion battery (AIB) was assembled using a novel layered K2Ti8O17 anode against an activated carbon coated on a Ti mesh cathode in an AlCl3-based aqueous electrolyte. The intercalation/deintercalation mechanism endowed the layered K2Ti8O17 as a promising anode for rechargeable aqueous AIBs. NaAc was introduced into the AlCl3 aqueous electrolyte to enhance the cycling stability of the assembled aqueous AIB. The as-designed AIB displayed a high discharge voltage near 1.6 V, and a discharge capacity of up to 189.6 mAh g−1. The assembled AIB lit up a commercial light-emitting diode (LED) lasting more than one hour. Inductively coupled plasma–optical emission spectroscopy (ICP-OES), high-resolution transmission electron microscopy (HRTEM), and X-ray absorption near-edge spectroscopy (XANES) were employed to investigate the intercalation/deintercalation mechanism of Na+/Al3+ ions in the aqueous AIB. The results indicated that the layered structure facilitated the...

Research paper thumbnail of In Situ TEM Observations of Discharging/Charging of Solid‐State Lithium‐Sulfur Batteries at High Temperatures

Small

Understanding the structural evolution of Li2 S upon operation of lithium-sulfur (Li-S) batteries... more Understanding the structural evolution of Li2 S upon operation of lithium-sulfur (Li-S) batteries is inadequate and a complete decomposition of Li2 S during charge is difficult. Whether it is the low electronic conductivity or the low ionic conductivity of Li2 S that inhibits its decomposition is under debate. Furthermore, the decomposition pathway of Li2 S is also unclear. Herein, an in situ transmission electron microscopy (TEM) technique implemented with a microelectromechanical systems (MEMS) heating device is used to study the precipitation and decomposition of Li2 S at high temperatures. It is revealed that Li2 S transformed from an amorphous/nanocrystalline to polycrystalline state with proceeding of the electrochemical lithiation at room temperature (RT), and the precipitation of Li2 S is more complete at elevated temperatures than at RT. Moreover, the decomposition of Li2 S that is difficult to achieve at RT becomes facile with increased Li+ ion conduction at high temperatures. These results indicate that Li+ ion diffusion in Li2 S dominates its reversibility in the solid-state Li-S batteries. This work not only demonstrates the powerful capabilities of combining in situ TEM with a MEMS heating device to explore the basic science in energy storage materials at high temperatures but also introduces the factor of temperature to boost battery performance.

Research paper thumbnail of A novel strategy to construct supported silver nanocomposite as an ultra-high efficient catalyst

Applied Catalysis B: Environmental

Research paper thumbnail of In-situ imaging the electrochemical reactions of Li-CO2 nanobatteries at high temperatures in an aberration corrected environmental transmission electron microscope

Nano Research

Rechargeable lithium-carbon dioxide (Li-CO2) batteries have attracted much attention due to their... more Rechargeable lithium-carbon dioxide (Li-CO2) batteries have attracted much attention due to their high theoretical energy densities and capture of CO2. However, the electrochemical reaction mechanisms of rechargeable Li-CO2 batteries, particularly the decomposition mechanisms of the discharge product Li2CO3 are still unclear, impeding their practical applications. Exploring electrochemistry of Li2CO3 is critical for improving the performance of Li-CO2 batteries. Herein, in-situ environmental transmission electron microscopy (ETEM) technique was used to study electrochemistry of Li2CO3 in Li-CO2 batteries during discharge and charge processes. During discharge, Li2CO3 was nucleated and accumulated on the surface of the cathode media such as carbon nanotubes (CNTs) and Ag nanowires (Ag NWs), but it was hard to decompose during charging at room temperature. To promote the decomposition of Li2CO3, the charge reactions were conducted at high temperatures, during which Li2CO3 was decomposed to lithium with release of gases. Density functional theory (DFT) calculations revealed that the synergistic effect of temperature and biasing facilitates the decomposition of Li2CO3. This study not only provides a fundamental understanding to the high temperature Li-CO2 nanobatteries, but also offers a valid technique, i.e., discharging/charging at high temperatures, to improve the cyclability of Li-CO2 batteries for energy storage applications.

Research paper thumbnail of In Situ Electrochemical Study of NaO2/CO2 Batteries in an Environmental Transmission Electron Microscope

Metal-air batteries are potential candidates for post-lithium energy storage devices due to their... more Metal-air batteries are potential candidates for post-lithium energy storage devices due to their high theoretical energy densities. However, our understanding to the electrochemistry of metal-air batteries is still in its infancy. Herein we report in-situ studies in the Na-O2/CO2 (O2 and CO2 mixture) and Na-O2 batteries with either carbon nanotubes (CNTs) or Ag nanowires as the air cathode medium in an advanced aberration corrected environmental transmission electron microscope. In the Na-O2/CO2/CNT nanobattery, the discharge reactions occurred in two steps: (1) 2Na+ + 2e- + O2  Na2O2; (2) Na2O2+ CO2  Na2CO3 + O2; concurrently a parasitic Na plating reaction took place. The charge reaction proceeded via: (3) 2Na2CO3 + C → 4Na+ + 3CO2 + 4e-. In the Na-O2/CO2/Ag nanobattery, the discharge reactions were essentially the same as the Na-O2/CO2/CNT nanobattery, however, the charge reaction in the former was very sluggish, suggesting that direct decomposition of Na2CO3 is difficult. In the Na-O2 battery, the discharge reaction occurred via reaction (1), but the reverse reaction was very difficult, indicating the sluggish decomposition of Na2O2. Overall the Na-O2/CO2/CNT nanobattery exhibited much better cyclability and performance than the Na-O2/CO2/Ag and the Na-O2/CNT nanobatteries, underscoring the importance of carbon and CO2 in facilitating the Na-O2 nanobatteries. Our study provides important understanding to the electrochemistry of the Na-O2/CO2 and Na-O2 nanobatteries, which may help the development of high performance Na-O2/CO2 and Na-O2 batteries for energy storage applications.

Research paper thumbnail of In Situ Imaging Polysulfides Electrochemistry of LiS Batteries in a Hollow Carbon Nanotubule Wet Electrochemical Cell

Understanding polysulfide electrochemistry is critical for mitigation of the polysulfide shuttle ... more Understanding polysulfide electrochemistry is critical for mitigation of the polysulfide shuttle effect in Li-S batteries. However, in situ imaging polysulfides evolution in Li-S batteries has not been possible. Herein, we constructed a hollow carbon nanotubule (CNT) wet electrochemical cell that permits real-time imaging of polysulfide evolutions in Li-S batteries in a Cs-corrected environmental transmission electron microscope. Upon discharge, sulfur was electrochemically reduced to long-chain polysulfides, which dissolved into the electrolyte instantly and were stabilized by Py14+ cations solvation. Metastable polysulfides prove to be problematic for Li-S batteries, therefore, destabilizing the Py14+-solvated polysulfides by adding low polarized solvents into the electrolyte to weaken the interaction between Py14+ cation and long-chain polysulfides renders a rapid polysulfides-to-Li2S transition, thus efficiently mitigating polysulfide formation and improving the performance of Li-S batteries dramatically. Moreover, the CNT wet electrochemical cell proves to be a universal platform for in situ probing electrochemistry of various batteries.

Research paper thumbnail of Understanding all solid-state lithium batteries through in situ transmission electron microscopy

Materials Today

Abstract Owing to the use of solid electrolytes instead of flammable and potentially toxic organi... more Abstract Owing to the use of solid electrolytes instead of flammable and potentially toxic organic liquid electrolytes, all solid-state lithium batteries (ASSLBs) are considered to have substantial advantages over conventional liquid electrolyte based lithium ion batteries(LIBs) in terms of safety, energy density, battery packaging, and operable temperature range. However, the electrochemistry and the operation mechanism of ASSLBs differ considerably from conventional LIBs. Consequently, the failure mechanisms of ASSLBs, which are not well understood, require particular attention. To improve the performance and realize practical applications of ASSLBs, it is crucial to unravel the dynamic evolution of electrodes, solid electrolytes, and their interfaces and interphases during cycling of ASSLBs. In situ transmission electron microscopy (TEM) provides a powerful approach for the fundamental investigation of structural and chemical changes during operation of ASSLBs with high spatio-temporal resolution. Herein, recent progress in in situ TEM studies of ASSLBs are reviewed with a specific focus on real-time observations of reaction and degradation occurring in electrodes, solid electrolytes, and their interfaces. Novel electro-chemo-mechanical coupling phenomena are revealed and mechanistic insights are highlighted. This review covers a broad range of electrode and electrolyte materials applied in ASSLBs, demonstrates the general applicability of in situ TEM for elucidating the fundamental mechanisms and providing the design guidance for the development of high-performance ASSLBs. Finally, challenges and opportunities for in situ TEM studies of ASSLBs are discussed.

Research paper thumbnail of Reviving the rock-salt phases in Ni-rich layered cathodes by mechano-electrochemistry in all-solid-state batteries

Research paper thumbnail of Interlayer Doping of Pseudocapacitive Hydrated Vanadium Oxide Via Mn2+ for High-Performance Aqueous Zinc-Ion Battery

Research paper thumbnail of In situ Observation of Li Deposition‐Induced Cracking in Garnet Solid Electrolytes

ENERGY & ENVIRONMENTAL MATERIALS, 2021

Research paper thumbnail of In-situ imaging Co3O4 catalyzed oxygen reduction and evolution reactions in a solid state Na-O2 battery

Nano Energy, 2020

Abstract Co3O4 nano materials have attracted tremendous attention as effective catalysts for sodi... more Abstract Co3O4 nano materials have attracted tremendous attention as effective catalysts for sodium oxygen batteries (SOBs). However, their electrochemical processes and fundamental catalytic mechanism remain unclear till now. Herein, in-situ environmental transmission electron microscopy technique was used to study the catalysis mechanism of the Co3O4 nanocubes in SOBs during discharge and charge processes. It is found that during the 1st discharge and charge processes, Na2O2 formed and decomposed, respectively, around the Co3O4 nanocubes, but the following discharge and charge processes were very difficult. In order to promote the charge kinetics, we increased the charging temperature up to 500 °C, when the decomposition of Na2O2 became facile. Aberration corrected high-angle annular dark field imaging indicated that a thin layer of CoO grew epitaxially on the surface of Co3O4 nanocubes after the first discharge. Density functional theory calculations indicate that the CoO surface is energetically more favorable than Co3O4 for the nucleation of Na2O2. This study provides not only new fundamental understandings to the electrochemical reaction mechanisms of SOBs, but also strategies to improve the cycling performance of solid state SOBs.

Research paper thumbnail of Carbon-Encapsulated Co 3 O 4 @CoO@Co Nanocomposites for Multifunctional Applications in Enhanced Long-life Lithium Storage, Supercapacitor and Oxygen Evolution Reaction

Electrochimica Acta, 2016

Abstract Porous nanostructure composites materials had attracted widely attention due to their po... more Abstract Porous nanostructure composites materials had attracted widely attention due to their potential application in energy storage (Lithium ion batteries (LIBs) and supercapacitor) and electrocatalyst of oxygen evolution reaction (OER). Co 3 O 4 @CoO@Co@C nanocomposites had been successfully synthesized using glucose as carbon source and cobalt nitrate as metalprecurs or of Co 3 O 4 @CoO@Co@C, which has excellent electrochemical performance for LIBs, supercapacitor and OER. Three kinds of morphology samples marked by Co 3 O 4 @CoO@Co@C-2/1, Co 3 O 4 @CoO@Co@C-1/1 and Co 3 O 4 @CoO@Co@C-1/2 are synthesized due to different atomic ratio of cobalt/carbon in precursors. Electrochemical and catalytic performance of Co 3 O 4 @CoO@Co@C-2/1 nanocomposites is more excellent than Co 3 O 4 @CoO@Co@C-1/1 and Co 3 O 4 @CoO@Co@C-1/2. Co 3 O 4 @CoO@Co@C-2/1 shows that discharge capacity can maintain 450 mA h g −1 and coulombic efficiency is nearly 100% during 500 cycles for LIBs. It indicates the excellent cycling stability of Co 3 O 4 @CoO@Co@C-2/1 as electrode for supercapacitor that about 78.3% of initial specific capacitance can be retained after 10000 cycles at current density of 2 A g −1 . Co 3 O 4 @CoO@Co@C-2/1 as catalyst of OER shows excellent electrochemical durability over 15 hours continuous experiment.

Research paper thumbnail of Sodium–Sulfur Batteries: In Situ TEM Studies of Sodium Polysulfides Electrochemistry in High Temperature Na–S Nanobatteries (Small 23/2021)

Research paper thumbnail of Co3ZnC@NC Material Derived from ZIF-8 for Lithium-Ion Capacitors

Research paper thumbnail of Degradation by Kinking in Layered Cathode Materials

Research paper thumbnail of In situ observation of electrochemical Ostwald ripening during sodium deposition

Nano Research

Sodium (Na) metal batteries (SMBs) using Na anode are potential “beyond lithium” electrochemical ... more Sodium (Na) metal batteries (SMBs) using Na anode are potential “beyond lithium” electrochemical technology for future energy storage applications. However, uncontrollable Na dendrite growth has plagued the application of SMBs. Understanding Na deposition mechanisms, particularly the early stage of Na deposition kinetics, is critical to enable the SMBs. In this context, we conducted in situ observations of the early stage of electrochemical Na deposition. We revealed an important electrochemical Ostwald ripening (EOR) phenomenon which dictated the early stage of Na deposition. Namely, small Na nanocrystals were nucleated randomly, which then grew. During growth, smaller Na nanocrystals were contained by bigger ones via EOR. We observed two types of EOR with one involving only electrochemical reaction driven by electrochemical potential difference between bigger and smaller nanocrystals; while the other being dominated by mass transport governed by surface energy minimization. The results provide new understanding to the Na deposition mechanism, which may be useful for the development of SMB for energy storage applications.

Research paper thumbnail of A Coral‐Like FeP@NC Anode with Increasing Cycle Capacity for Sodium‐Ion and Lithium‐Ion Batteries Induced by Particle‐Refinement

Angewandte Chemie International Edition

Electrodes with higher Na + storage capability and cycling stability are vital to improve the ene... more Electrodes with higher Na + storage capability and cycling stability are vital to improve the energy density and rate capability of sodium ion batteries (SIBs). Herein, we present a coral-like FeP composite with FeP nanoparticles anchored and dispersed on a nitrogen-doped three-dimensional carbon framework ( FeP@NC ). Due to the highly continuous N-doped carbon framework and a spring-buffering graphitized carbon layer around the FeP nanoparticle, the sodium ion battery with FeP@NC composite can exhibit an ultra-stable cycling performance at 10 A g -1 with a capacity retention of 82.0% in 10000 cycles. More importantly, an interesting particle refinement achieving capacity increasing mechanism during cycling has been well confirmed. Particularly, the FeP nanoparticles go through a refining-recombination process during the first cycle and present a global refining trend after dozens of cycles, which results in a gradually increase in graphitization degree and interface magnetization, and further provides more extra active sites for Na + storage and contributes to a rising capacity with cycling . The capacity ascending phenomenon can also extend to lithium-ion batteries (LIBs). This paper holds a new feasibility insight mechanism of the enhanced capacity during cycling and also offers a feasible solution to design high performance anode material for SIBs/LIBs.

Research paper thumbnail of Ultrastable Anode/Electrolyte Interface in Solid-State Lithium-Metal Batteries Using LiCux Nanowire Network Host

High interfacial resistance and uncontrollable lithium (Li) dendrite are major challenges in soli... more High interfacial resistance and uncontrollable lithium (Li) dendrite are major challenges in solid-state Li-metal batteries (SSLMBs), as they lead to premature short-circuiting and failure of SSLMBs. Here, we report the synthesis of a composite anode comprising a three-dimensional LiCux nanowire network host infiltrated with Li (Li* anode) with low interfacial impedance and superior electrochemical performance. The Li* anode is fabricated by dissolving Cu foil into molten Li followed by solidification. The Li* anode exhibits good wettability with Li6.4La3Zr1.4Ta0.6O12 (LLZTO) and high mechanical strength, rendering low Li*/LLZTO interfacial impedance, homogeneous deposition of Li, and suppression of Li dendrites. Consequently, the Li* anode-based symmetric cells and full cells with LiNi0.88Co0.1Al0.02O2 (NCA), LiFePO4 (LFP), and FeF2 cathodes deliver remarkable electrochemical performance. Specifically, the Li*/LLZTO/Li* symmetrical cell achieves a remarkably long cycle lifetime of 10 000 h with 0.1 mA·cm-2; the Li*/LLZTO/NCA full cell maintains capacity retention of 73.4% after 500 cycles at 0.5C; and all-solid-state Li*/LLZTO/FeF2 full cell achieves a reversible capacity of 147 mAh·g-1 after 500 cycles at 100 mA·g-1. This work demonstrates potential design tactics for an ultrastable Li*/garnet interface to enable high-performance SSLMBs.

Research paper thumbnail of Layered LiCoO2–LiFeO2 Heterostructure Composite for Semiconductor-Based Fuel Cells

Nanomaterials

Enabling fast ionic transport at a low-temperature range (400–600 °C) is of great importance to p... more Enabling fast ionic transport at a low-temperature range (400–600 °C) is of great importance to promoting the development of solid oxide fuel cells (SOFCs). In this study, a layer-structured LiCoO2–LiFeO2 heterostructure composite is explored for the low-temperature (LT) SOFCs. Fuel cell devices with different configurations are fabricated to investigate the multifunction property of LiCoO2–LiFeO2 heterostructure composites. The LiCoO2–LiFeO2 composite is employed as a cathode in conventional SOFCs and as a semiconductor membrane layer in semiconductor-based fuel cells (SBFCs). Enhanced ionic conductivity is realized by a composite of LiCoO2–LiFeO2 and Sm3+ doped ceria (SDC) electrolyte in SBFC. All these designed fuel cell devices display high open-circuit voltages (OCVs), along with promising cell performance. An improved power density of 714 mW cm−2 is achieved from the new SBFC device, compared to the conventional fuel cell configuration with LiCoO2–LiFeO2 as the cathode (162 mW...

Research paper thumbnail of In situ imaging electrocatalytic CO2 reduction and evolution reactions in all-solid-state Li–CO2 nanobatteries

Nanoscale

We herein present a real time study of a Li–CO2 battery with a Ni–Ru/MnO2 cathode by using the in... more We herein present a real time study of a Li–CO2 battery with a Ni–Ru/MnO2 cathode by using the in situ environmental transmission electron microscopy (ETEM) technique.

Research paper thumbnail of Novel K2Ti8O17 Anode via Na+/Al3+ Co-Intercalation Mechanism for Rechargeable Aqueous Al-Ion Battery with Superior Rate Capability

Nanomaterials

A promising aqueous aluminum ion battery (AIB) was assembled using a novel layered K2Ti8O17 anode... more A promising aqueous aluminum ion battery (AIB) was assembled using a novel layered K2Ti8O17 anode against an activated carbon coated on a Ti mesh cathode in an AlCl3-based aqueous electrolyte. The intercalation/deintercalation mechanism endowed the layered K2Ti8O17 as a promising anode for rechargeable aqueous AIBs. NaAc was introduced into the AlCl3 aqueous electrolyte to enhance the cycling stability of the assembled aqueous AIB. The as-designed AIB displayed a high discharge voltage near 1.6 V, and a discharge capacity of up to 189.6 mAh g−1. The assembled AIB lit up a commercial light-emitting diode (LED) lasting more than one hour. Inductively coupled plasma–optical emission spectroscopy (ICP-OES), high-resolution transmission electron microscopy (HRTEM), and X-ray absorption near-edge spectroscopy (XANES) were employed to investigate the intercalation/deintercalation mechanism of Na+/Al3+ ions in the aqueous AIB. The results indicated that the layered structure facilitated the...

Research paper thumbnail of In Situ TEM Observations of Discharging/Charging of Solid‐State Lithium‐Sulfur Batteries at High Temperatures

Small

Understanding the structural evolution of Li2 S upon operation of lithium-sulfur (Li-S) batteries... more Understanding the structural evolution of Li2 S upon operation of lithium-sulfur (Li-S) batteries is inadequate and a complete decomposition of Li2 S during charge is difficult. Whether it is the low electronic conductivity or the low ionic conductivity of Li2 S that inhibits its decomposition is under debate. Furthermore, the decomposition pathway of Li2 S is also unclear. Herein, an in situ transmission electron microscopy (TEM) technique implemented with a microelectromechanical systems (MEMS) heating device is used to study the precipitation and decomposition of Li2 S at high temperatures. It is revealed that Li2 S transformed from an amorphous/nanocrystalline to polycrystalline state with proceeding of the electrochemical lithiation at room temperature (RT), and the precipitation of Li2 S is more complete at elevated temperatures than at RT. Moreover, the decomposition of Li2 S that is difficult to achieve at RT becomes facile with increased Li+ ion conduction at high temperatures. These results indicate that Li+ ion diffusion in Li2 S dominates its reversibility in the solid-state Li-S batteries. This work not only demonstrates the powerful capabilities of combining in situ TEM with a MEMS heating device to explore the basic science in energy storage materials at high temperatures but also introduces the factor of temperature to boost battery performance.

Research paper thumbnail of A novel strategy to construct supported silver nanocomposite as an ultra-high efficient catalyst

Applied Catalysis B: Environmental

Research paper thumbnail of In-situ imaging the electrochemical reactions of Li-CO2 nanobatteries at high temperatures in an aberration corrected environmental transmission electron microscope

Nano Research

Rechargeable lithium-carbon dioxide (Li-CO2) batteries have attracted much attention due to their... more Rechargeable lithium-carbon dioxide (Li-CO2) batteries have attracted much attention due to their high theoretical energy densities and capture of CO2. However, the electrochemical reaction mechanisms of rechargeable Li-CO2 batteries, particularly the decomposition mechanisms of the discharge product Li2CO3 are still unclear, impeding their practical applications. Exploring electrochemistry of Li2CO3 is critical for improving the performance of Li-CO2 batteries. Herein, in-situ environmental transmission electron microscopy (ETEM) technique was used to study electrochemistry of Li2CO3 in Li-CO2 batteries during discharge and charge processes. During discharge, Li2CO3 was nucleated and accumulated on the surface of the cathode media such as carbon nanotubes (CNTs) and Ag nanowires (Ag NWs), but it was hard to decompose during charging at room temperature. To promote the decomposition of Li2CO3, the charge reactions were conducted at high temperatures, during which Li2CO3 was decomposed to lithium with release of gases. Density functional theory (DFT) calculations revealed that the synergistic effect of temperature and biasing facilitates the decomposition of Li2CO3. This study not only provides a fundamental understanding to the high temperature Li-CO2 nanobatteries, but also offers a valid technique, i.e., discharging/charging at high temperatures, to improve the cyclability of Li-CO2 batteries for energy storage applications.

Research paper thumbnail of In Situ Electrochemical Study of NaO2/CO2 Batteries in an Environmental Transmission Electron Microscope

Metal-air batteries are potential candidates for post-lithium energy storage devices due to their... more Metal-air batteries are potential candidates for post-lithium energy storage devices due to their high theoretical energy densities. However, our understanding to the electrochemistry of metal-air batteries is still in its infancy. Herein we report in-situ studies in the Na-O2/CO2 (O2 and CO2 mixture) and Na-O2 batteries with either carbon nanotubes (CNTs) or Ag nanowires as the air cathode medium in an advanced aberration corrected environmental transmission electron microscope. In the Na-O2/CO2/CNT nanobattery, the discharge reactions occurred in two steps: (1) 2Na+ + 2e- + O2  Na2O2; (2) Na2O2+ CO2  Na2CO3 + O2; concurrently a parasitic Na plating reaction took place. The charge reaction proceeded via: (3) 2Na2CO3 + C → 4Na+ + 3CO2 + 4e-. In the Na-O2/CO2/Ag nanobattery, the discharge reactions were essentially the same as the Na-O2/CO2/CNT nanobattery, however, the charge reaction in the former was very sluggish, suggesting that direct decomposition of Na2CO3 is difficult. In the Na-O2 battery, the discharge reaction occurred via reaction (1), but the reverse reaction was very difficult, indicating the sluggish decomposition of Na2O2. Overall the Na-O2/CO2/CNT nanobattery exhibited much better cyclability and performance than the Na-O2/CO2/Ag and the Na-O2/CNT nanobatteries, underscoring the importance of carbon and CO2 in facilitating the Na-O2 nanobatteries. Our study provides important understanding to the electrochemistry of the Na-O2/CO2 and Na-O2 nanobatteries, which may help the development of high performance Na-O2/CO2 and Na-O2 batteries for energy storage applications.

Research paper thumbnail of In Situ Imaging Polysulfides Electrochemistry of LiS Batteries in a Hollow Carbon Nanotubule Wet Electrochemical Cell

Understanding polysulfide electrochemistry is critical for mitigation of the polysulfide shuttle ... more Understanding polysulfide electrochemistry is critical for mitigation of the polysulfide shuttle effect in Li-S batteries. However, in situ imaging polysulfides evolution in Li-S batteries has not been possible. Herein, we constructed a hollow carbon nanotubule (CNT) wet electrochemical cell that permits real-time imaging of polysulfide evolutions in Li-S batteries in a Cs-corrected environmental transmission electron microscope. Upon discharge, sulfur was electrochemically reduced to long-chain polysulfides, which dissolved into the electrolyte instantly and were stabilized by Py14+ cations solvation. Metastable polysulfides prove to be problematic for Li-S batteries, therefore, destabilizing the Py14+-solvated polysulfides by adding low polarized solvents into the electrolyte to weaken the interaction between Py14+ cation and long-chain polysulfides renders a rapid polysulfides-to-Li2S transition, thus efficiently mitigating polysulfide formation and improving the performance of Li-S batteries dramatically. Moreover, the CNT wet electrochemical cell proves to be a universal platform for in situ probing electrochemistry of various batteries.

Research paper thumbnail of Understanding all solid-state lithium batteries through in situ transmission electron microscopy

Materials Today

Abstract Owing to the use of solid electrolytes instead of flammable and potentially toxic organi... more Abstract Owing to the use of solid electrolytes instead of flammable and potentially toxic organic liquid electrolytes, all solid-state lithium batteries (ASSLBs) are considered to have substantial advantages over conventional liquid electrolyte based lithium ion batteries(LIBs) in terms of safety, energy density, battery packaging, and operable temperature range. However, the electrochemistry and the operation mechanism of ASSLBs differ considerably from conventional LIBs. Consequently, the failure mechanisms of ASSLBs, which are not well understood, require particular attention. To improve the performance and realize practical applications of ASSLBs, it is crucial to unravel the dynamic evolution of electrodes, solid electrolytes, and their interfaces and interphases during cycling of ASSLBs. In situ transmission electron microscopy (TEM) provides a powerful approach for the fundamental investigation of structural and chemical changes during operation of ASSLBs with high spatio-temporal resolution. Herein, recent progress in in situ TEM studies of ASSLBs are reviewed with a specific focus on real-time observations of reaction and degradation occurring in electrodes, solid electrolytes, and their interfaces. Novel electro-chemo-mechanical coupling phenomena are revealed and mechanistic insights are highlighted. This review covers a broad range of electrode and electrolyte materials applied in ASSLBs, demonstrates the general applicability of in situ TEM for elucidating the fundamental mechanisms and providing the design guidance for the development of high-performance ASSLBs. Finally, challenges and opportunities for in situ TEM studies of ASSLBs are discussed.