Monocrystal LiMn_(0. 6)Fe_(0. 4)PO_4 cathode material was obtained via hydrothermal method at 180℃ for 10 h without any surfactant. The effects of hydrothermal time on the phase and morphology of the material were di...Monocrystal LiMn_(0. 6)Fe_(0. 4)PO_4 cathode material was obtained via hydrothermal method at 180℃ for 10 h without any surfactant. The effects of hydrothermal time on the phase and morphology of the material were discussed.By controlling the reaction solutions, the rodlike, flowerlike,and strawlike LiMn_(0.6)Fe_(0.4)PO_4 cathode materials were synthesized. Electrochemical performances show that the rodlike LiMn_(0. 6)Fe_(0. 4)PO_4 has the best electrochemical properties. The initial discharge capacity of the rodlike structure is 106.4 mAh·g^(-1), which is higher than those of flowerlike and strawlike materials.展开更多
Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibri...Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.展开更多
LiMn_(y)Fe_(1-y)PO_(4) is considered a promising cathode material for next-generation lithium-ion batteries(LIBs) due to its high energy density and low cost. Its energy density degradation is often ascribed to the ca...LiMn_(y)Fe_(1-y)PO_(4) is considered a promising cathode material for next-generation lithium-ion batteries(LIBs) due to its high energy density and low cost. Its energy density degradation is often ascribed to the capacity loss during cycling. However, in this study, we find that the energy density degradation mainly roots in voltage decay. We have synthesized a series of LiMn_(y)Fe_(1-y)PO_(4) /C(0.5 ≤ y ≤ 0.8) and find this voltage decay is correlated with the Mn content. A high amount Mn leads to a heavier voltage decay.In-situ X-ray diffraction(XRD) and high-resolution transmission electron microscopy(HRTEM) reveal the nature of this effect, which show a mismatch along the b-axis of-2.68%(charge) and +3.4%(discharge), a volume misfit of-4.41%(charge) and +4.54%(discharge) between Li_(x)Mn_(y)Fe_(1-y)PO_(4) and Mn_(y)Fe_(1-y)PO_(4) during phase transitions. The resultant misfit strains during Li+insertion compared to extraction result in structural degradations, such as amorphization and impurity(Mn F3) accumulation after cycling. The voltage decay can be alleviated by kinetic relaxations and recovered by a wild reannealing. This work demonstrates effective strategies to improve the energy density and cycling performance of LiMn_(y)Fe_(1-y)PO_(4) /C,providing good references for other LIB cathodes, such as the Li-rich cathodes.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 21231005 and 51071087)the Major State Basic Research Development Program of China(Nos. 2011CB935900 and 2010CB631303)+2 种基金the Discipline Innovative Engineering Plan (B12015)the Research Fund for the Doctoral Program of Higher Education of China (No.20120031110001)the Tianjin Science & Technology Project (No. 10SYSYJC27600)
文摘Monocrystal LiMn_(0. 6)Fe_(0. 4)PO_4 cathode material was obtained via hydrothermal method at 180℃ for 10 h without any surfactant. The effects of hydrothermal time on the phase and morphology of the material were discussed.By controlling the reaction solutions, the rodlike, flowerlike,and strawlike LiMn_(0.6)Fe_(0.4)PO_4 cathode materials were synthesized. Electrochemical performances show that the rodlike LiMn_(0. 6)Fe_(0. 4)PO_4 has the best electrochemical properties. The initial discharge capacity of the rodlike structure is 106.4 mAh·g^(-1), which is higher than those of flowerlike and strawlike materials.
基金financially supported by the National Natural Science Foundation of China(No.51904250)the China Postdoctoral Science Foundation(No.2021M692254)+2 种基金the Sichuan Science and Technology Program(No.2022YFG0098)the Fundamental Research Funds for the Central Universities(Nos.2021CDSN-02,2022SCU12002,2022CDZG-17,2022CDSN-08,2022CDZG-9)the Hohhot Science and Technology Program(No.2023-Jie Bang Gua Shuai-Gao-3)。
文摘Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.
基金supported by the 21C Innovation Laboratory,Contemporary Amperex Technology Ltd. by project No. 21C-OP-202103the National Natural Science Foundation of China(52072061)。
文摘LiMn_(y)Fe_(1-y)PO_(4) is considered a promising cathode material for next-generation lithium-ion batteries(LIBs) due to its high energy density and low cost. Its energy density degradation is often ascribed to the capacity loss during cycling. However, in this study, we find that the energy density degradation mainly roots in voltage decay. We have synthesized a series of LiMn_(y)Fe_(1-y)PO_(4) /C(0.5 ≤ y ≤ 0.8) and find this voltage decay is correlated with the Mn content. A high amount Mn leads to a heavier voltage decay.In-situ X-ray diffraction(XRD) and high-resolution transmission electron microscopy(HRTEM) reveal the nature of this effect, which show a mismatch along the b-axis of-2.68%(charge) and +3.4%(discharge), a volume misfit of-4.41%(charge) and +4.54%(discharge) between Li_(x)Mn_(y)Fe_(1-y)PO_(4) and Mn_(y)Fe_(1-y)PO_(4) during phase transitions. The resultant misfit strains during Li+insertion compared to extraction result in structural degradations, such as amorphization and impurity(Mn F3) accumulation after cycling. The voltage decay can be alleviated by kinetic relaxations and recovered by a wild reannealing. This work demonstrates effective strategies to improve the energy density and cycling performance of LiMn_(y)Fe_(1-y)PO_(4) /C,providing good references for other LIB cathodes, such as the Li-rich cathodes.
