Combining the first-principles calculations and structural enumeration with recognition,the delithiation process of LiNiO_(2)is investigated,where various supercell shapes are considered in order to obtain the formati...Combining the first-principles calculations and structural enumeration with recognition,the delithiation process of LiNiO_(2)is investigated,where various supercell shapes are considered in order to obtain the formation energy of Li_(x)NiO_(2).Meanwhile,the voltage profile is simulated and the ordered phases of lithium vacancies corresponding to concentrations of 1/4,2/5,3/7,1/2,2/3,3/4,5/6,and 6/7 are predicted.To understand the capacity decay in the experiment during the charge/discharge cycles,deoxygenation and Li/Ni antisite defects are calculated,revealing that the chains of oxygen vacancies will be energetically preferrable.It can be inferred that in the absence of oxygen atom in high delithiate state,the diffusion of Ni atoms is facilitated and the formation of Li/Ni antisite is induced.展开更多
First-principles calculations have been performed to study the lithium intercalations in MoS2. The formation energies, changes of volumes, electronic structures and charge densities of the lithium intercalations in Mo...First-principles calculations have been performed to study the lithium intercalations in MoS2. The formation energies, changes of volumes, electronic structures and charge densities of the lithium intercalations in MoS2 are presented. Our calculations show that during lithium intercalations in MoS2, the lithium intercalation formation energies per lithium atom are between 2.5 eV to 3.0 eV. The volume expansions of MoS2 due to lithium intercalations are relatively small展开更多
In this letter the study of Li-doped zinc oxide by electron paramagnetic resonance method is described.A signal observed at g_=2.013,g_=1.955 on the degassed sample at 923K was designated to F_s^+ centers(surface oxyg...In this letter the study of Li-doped zinc oxide by electron paramagnetic resonance method is described.A signal observed at g_=2.013,g_=1.955 on the degassed sample at 923K was designated to F_s^+ centers(surface oxygen ion vacancies with a single trapped electron).When the sample was quenched from 1003K into liquid oxygen at 77K under 24 KPa O_2,[Li^+O^-] ion pairs valued at g_=2.026 and g=2.003 with superhyperfine constant a=2.0G,which resulted from ~7Li nucleus,formed at Li^+-substitutional site in ZnO lattice.A probable mechanism of [Li^+O^-]ion pair formation was proposed.展开更多
Anode-free all-solid-state batteries(AFASSBs), composed of a fully lithiated cathode and a bare current collector(CC) that eliminates excess lithium, can maximize the energy density(because of a compact cell configura...Anode-free all-solid-state batteries(AFASSBs), composed of a fully lithiated cathode and a bare current collector(CC) that eliminates excess lithium, can maximize the energy density(because of a compact cell configuration) and improve the safety of solid-state systems. Although significant progress has been made by modifying CCs in liquid-based anode-free batteries, the role of CCs and the mechanism of Li formation on CCs in AFASSBs are still unexplored. Here, we systematically investigate the effect of the surface roughness of the CCs on the Li plating/stripping behavior in AFASSBs. The results show that the moderately roughened CC substantially improves the Coulombic efficiency and cycle stability of AFASSBs owing to the increased contact points between the solid electrolyte and the roughened CC. In contrast, the excessively roughened CC deteriorates the performance owing to the contact loss.Moreover, an ex situ interface analysis reveals that the roughened surface of the CC could suppress the interfacial degradation during the Li ion extraction from a sulfide solid electrolyte to a CC. This provides an indication to the origin that hinders the electrochemical performance of AFASSBs. These findings show the potential for the application of surface-engineered CCs in AFASSBs and provide guidelines for designing advanced CCs.展开更多
The transformation mechanism of （γ ＋γ′） was studied by analyzing the microstructure and elemental distri- bution of the U720Li samples heated at 1250℃ and cooled at the rates in the range of 1-100℃/s. Although...The transformation mechanism of （γ ＋γ′） was studied by analyzing the microstructure and elemental distri- bution of the U720Li samples heated at 1250℃ and cooled at the rates in the range of 1-100℃/s. Although the （γ ＋γ′） is deemed to be formed by a eutectic reaction and has been called eutectic （γ ＋γ′）, it was found in the present study that the （γ ＋γ′） precipitation begins with a peritectic reaction of （L ＋ γ）γ′, and develops by the eutectic reaction of L （γ ＋γ′）. The energy for the γ′ nucleation is low because the interfacial energy for the γ /γ′ interface is about one-tenth of the solid/liquid interface, and hence, the nucleation rate is high and the fine structure of （γ ＋ γ′） is formed at the initial precipitation stage. The γ and γ′ in （γ ＋ γ′） tend to grow into a lamellar structure because it is difficult for them to nucleate directly from the residual liquids, and hence, the γ′ precipitates naturally tend to grow divergently direction of the regions rich in AI and Ti, forming a fan-like structure of the （γ ＋γ′）. As a result, the γ′ precipitates will coarsen finally because the space between them is enlarged. The solidification of the final residual liquids is a diffusion dependent process. When cooled at a higher rate, a higher degree of super cooling is reached and finally the solidification is finished by the pseudo- eutectic reaction of L → （γ ＋ boride） and L→ （γ ＋γ′）, which can absorb Zr and B. When cooled at a rate low enough, most of the residual liquids are consumed by the （γ ＋γ′） growth due to the sufficient diffusion, and the boride and Zr- bearing phase are precipitated at a quasi-equilibrium state. Under this condition, Ti is depleted at the （γ ＋γ′） growth front. However, the η-Ni3Ti phase is formed there occasionally due to the boride precipitation, because the compositions of the two phases are complementary.展开更多
基金Project supported by the Science Fund of the Guangdong Major Project of Basic and Applied Basic Research,China(Grant No.2019B030302011)the Fund of the Science and Technology Program of Guangzhou,China(Grant No.202201010090)。
文摘Combining the first-principles calculations and structural enumeration with recognition,the delithiation process of LiNiO_(2)is investigated,where various supercell shapes are considered in order to obtain the formation energy of Li_(x)NiO_(2).Meanwhile,the voltage profile is simulated and the ordered phases of lithium vacancies corresponding to concentrations of 1/4,2/5,3/7,1/2,2/3,3/4,5/6,and 6/7 are predicted.To understand the capacity decay in the experiment during the charge/discharge cycles,deoxygenation and Li/Ni antisite defects are calculated,revealing that the chains of oxygen vacancies will be energetically preferrable.It can be inferred that in the absence of oxygen atom in high delithiate state,the diffusion of Ni atoms is facilitated and the formation of Li/Ni antisite is induced.
基金This work was supported by the National Natural Science Foundation of China under Grant No.10374076by the Natural Science Foundation of Fujian Province under Grant Nos.E0410025 and E032001.
文摘First-principles calculations have been performed to study the lithium intercalations in MoS2. The formation energies, changes of volumes, electronic structures and charge densities of the lithium intercalations in MoS2 are presented. Our calculations show that during lithium intercalations in MoS2, the lithium intercalation formation energies per lithium atom are between 2.5 eV to 3.0 eV. The volume expansions of MoS2 due to lithium intercalations are relatively small
基金Supported by Chinese National Scientific Foundation
文摘In this letter the study of Li-doped zinc oxide by electron paramagnetic resonance method is described.A signal observed at g_=2.013,g_=1.955 on the degassed sample at 923K was designated to F_s^+ centers(surface oxygen ion vacancies with a single trapped electron).When the sample was quenched from 1003K into liquid oxygen at 77K under 24 KPa O_2,[Li^+O^-] ion pairs valued at g_=2.026 and g=2.003 with superhyperfine constant a=2.0G,which resulted from ~7Li nucleus,formed at Li^+-substitutional site in ZnO lattice.A probable mechanism of [Li^+O^-]ion pair formation was proposed.
基金supported by the Institutional Program(2E31852)of Korea Institute of Science and Technology(KIST)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT,2022R1C1C1006019)。
文摘Anode-free all-solid-state batteries(AFASSBs), composed of a fully lithiated cathode and a bare current collector(CC) that eliminates excess lithium, can maximize the energy density(because of a compact cell configuration) and improve the safety of solid-state systems. Although significant progress has been made by modifying CCs in liquid-based anode-free batteries, the role of CCs and the mechanism of Li formation on CCs in AFASSBs are still unexplored. Here, we systematically investigate the effect of the surface roughness of the CCs on the Li plating/stripping behavior in AFASSBs. The results show that the moderately roughened CC substantially improves the Coulombic efficiency and cycle stability of AFASSBs owing to the increased contact points between the solid electrolyte and the roughened CC. In contrast, the excessively roughened CC deteriorates the performance owing to the contact loss.Moreover, an ex situ interface analysis reveals that the roughened surface of the CC could suppress the interfacial degradation during the Li ion extraction from a sulfide solid electrolyte to a CC. This provides an indication to the origin that hinders the electrochemical performance of AFASSBs. These findings show the potential for the application of surface-engineered CCs in AFASSBs and provide guidelines for designing advanced CCs.
文摘The transformation mechanism of （γ ＋γ′） was studied by analyzing the microstructure and elemental distri- bution of the U720Li samples heated at 1250℃ and cooled at the rates in the range of 1-100℃/s. Although the （γ ＋γ′） is deemed to be formed by a eutectic reaction and has been called eutectic （γ ＋γ′）, it was found in the present study that the （γ ＋γ′） precipitation begins with a peritectic reaction of （L ＋ γ）γ′, and develops by the eutectic reaction of L （γ ＋γ′）. The energy for the γ′ nucleation is low because the interfacial energy for the γ /γ′ interface is about one-tenth of the solid/liquid interface, and hence, the nucleation rate is high and the fine structure of （γ ＋ γ′） is formed at the initial precipitation stage. The γ and γ′ in （γ ＋ γ′） tend to grow into a lamellar structure because it is difficult for them to nucleate directly from the residual liquids, and hence, the γ′ precipitates naturally tend to grow divergently direction of the regions rich in AI and Ti, forming a fan-like structure of the （γ ＋γ′）. As a result, the γ′ precipitates will coarsen finally because the space between them is enlarged. The solidification of the final residual liquids is a diffusion dependent process. When cooled at a higher rate, a higher degree of super cooling is reached and finally the solidification is finished by the pseudo- eutectic reaction of L → （γ ＋ boride） and L→ （γ ＋γ′）, which can absorb Zr and B. When cooled at a rate low enough, most of the residual liquids are consumed by the （γ ＋γ′） growth due to the sufficient diffusion, and the boride and Zr- bearing phase are precipitated at a quasi-equilibrium state. Under this condition, Ti is depleted at the （γ ＋γ′） growth front. However, the η-Ni3Ti phase is formed there occasionally due to the boride precipitation, because the compositions of the two phases are complementary.
