Electrochemical insertion/extraction of Li on cathode materials of spinel type LiMn2O4 and ordered rock-salt type LiCo0.5 Ni0.5O2 was measured on samples of which structures were well characterized. On the basis of ex...Electrochemical insertion/extraction of Li on cathode materials of spinel type LiMn2O4 and ordered rock-salt type LiCo0.5 Ni0.5O2 was measured on samples of which structures were well characterized. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materiaIs on electrochemical Li insertion/extraction performance was discussed. These two transition metal oxides belong to onegroup that the crystallinity of these oxides affects to the performance.展开更多
LiNi0. 45 Co0. 10 Mn0. 4sO2 was synthesized from Li2CO3 and a triple oxide of nickel, cobalt and manganese at 950 ℃ in air. The structures and characteristics of LiNi0. 45 Co0.10 Mn0. 45 O2, LiCoO2 and LiMn2 O4 were ...LiNi0. 45 Co0. 10 Mn0. 4sO2 was synthesized from Li2CO3 and a triple oxide of nickel, cobalt and manganese at 950 ℃ in air. The structures and characteristics of LiNi0. 45 Co0.10 Mn0. 45 O2, LiCoO2 and LiMn2 O4 were investigated by XRD, SEM and electrochemical measurements. The results show that LiNi0.4s Co0.10 Mn0. 45 O2 has a layered structure with hexagonal lattice. The commercial LicoO2 has sphere-like appearance and smooth surfaces, while the LiMn2 O4 and LiNi0.45 Co0. 10 Mn0. 45 O2 consist of cornered and uneven particles. LiNi0. 45 Co0.10 Mn0. 45 O2 has a large disLiMn2 O4 and LiCoO2, respectively. LiCoO2 and LiMn2 O4 have higher discharge voltage and better rate-capability than LiNi0. 45Co0.10 Mn0. 45 O2. All the three cathodes have excellent cycling performance with capacity retention of above 89.3 % at the 250th cycle. Batteries with LiMn2 O4 or LiNi0.45 Co0.10 Mn0. 45 O2 cathodes show better safety performance under abusive conditions than those with LiCoO2 cathodes.展开更多
Modified lithium manganese oxides were prepared by using LiMn 2 O 4 and LiCoO 2 as precursors by solid state reaction.A study has been carried out by TG - DSC,XRD and FTIR to analyze the reaction process and structura...Modified lithium manganese oxides were prepared by using LiMn 2 O 4 and LiCoO 2 as precursors by solid state reaction.A study has been carried out by TG - DSC,XRD and FTIR to analyze the reaction process and structural characterization of products.The results showed that the LiMn 2 O 4 reacted chemically with LiCoO 2 at high temper - ature.Li and Co atom could insert into the LiMn 2 O 4 crystal lattice and obtained the Cobalt - Doped spinel com - pound.The results of constant - current cyclic test showed that the cyclic stability of the products are increased with the amount of doped LiCoO 2 ,while their initial capacity is decreased.展开更多
Cobalt was used to modify the surface of spinel LiMn2O4 by a solution technique to produce Co3+-modified surface material (COMSM). Cobalt was only doped into the surface of LiMn2O4 spinel. XPS(X-ray photoelectron spec...Cobalt was used to modify the surface of spinel LiMn2O4 by a solution technique to produce Co3+-modified surface material (COMSM). Cobalt was only doped into the surface of LiMn2O4 spinel. XPS(X-ray photoelectron spectroscopy) analysis confirms the valence state of Co3+. COMSM has stable spinel structure and can prevent active materials from the corrosion of electrolyte. The ICP(inductively coupled plasma) determination of the spinel dissolution in electrolyte showed the content of Mn dissolved from COMSM was smaller than that from the pure spinel. AC impedance patterns show that the charge-transfer resistance (Ret) for COMSM is smaller than that for pure spinel. The particles of COMSM are bigger in size than those of pure spinel according to the micrographs of SEM(scanning electron microscopy). The determinations of the electrochemical characterization show that COMSM has both good cycling performance and high initial capacity of 124.1 mA/h at an average capacity loss of 0.19 mAh/g per cycle.展开更多
Spinel LiCo0.09Mn1.91O3.92F0.08 as cathode material was modified with LiCoO2 by the sol-gel method, and the crystal structure, morphology and electrochemical performance were characterized with XRD, SEM, EDS, AAS and ...Spinel LiCo0.09Mn1.91O3.92F0.08 as cathode material was modified with LiCoO2 by the sol-gel method, and the crystal structure, morphology and electrochemical performance were characterized with XRD, SEM, EDS, AAS and charge-discharge test in this paper. The results show that a good clad coated on parent material can be synthesized by the sol-gel method, and the materials with modification have perfect spinel structure. LiCo0.09Mn1.91O3.92F0.08 materials coated by LiCoO2 improve the stability of crystal structure and decrease the dissolution of Mn into electrolyte. With the LiCoO2 content increasing, the specific capacity and cycle performance of samples are improved. The capacity loss is also suppressed distinctly even at 55 ℃.展开更多
LiMn2O4/Li4Ti5O12 composite was synthesized by in-situ composite technique using LiMn2O4,lithium acetate,tetrabutyl titanate as starting materials and characterized by various electrochemical methods in combination wi...LiMn2O4/Li4Ti5O12 composite was synthesized by in-situ composite technique using LiMn2O4,lithium acetate,tetrabutyl titanate as starting materials and characterized by various electrochemical methods in combination with X-ray diffractometry(XRD), infrared(IR)spectroscopy and scanning electron microscopy(SEM).The results show that Li4Ti5O12 is coated on the surface of crystalline LiMn2O4 to form LiMn2O4/Li4Ti5O12 composite.The structure of LiMn2O4 does not change due to the introduction of Li4Ti5O12.By being coated with Li4Ti5O12,the rate capability and high temperature cyclability of LiMn2O4 is improved greatly.At room temperature,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 108.4 mA·h/g and the capacity loss per cycle is only 0.053%after 20 cycles at 2.0C.While at 55℃,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 109.9 mA·h/g and the capacity loss per cycle is only 0.036%after 60 cycles at 1.0C.展开更多
In order to improve the cycle performance of LiMn2O4, the modified LiMn,O4 was prepared by solid-state reactions using LiMn2O4 and LiCoO2 as precursors. XRD and EDS were used to study the structure properties of the m...In order to improve the cycle performance of LiMn2O4, the modified LiMn,O4 was prepared by solid-state reactions using LiMn2O4 and LiCoO2 as precursors. XRD and EDS were used to study the structure properties of the modified LiMn2O4. The electrochemical properties of the modified LiMn2O4 were also investigated. The results show that Li and Co atoms could insert into the LiMn2O4crystal lattice and a newly formed spinel phase, modified LiMn2O4 was obtained. The modified LiMn2O4 exhibits excellent cycle ability at room and elevated temperatures compared to pure LiMn2O4. The improved electrochemical stability of the modified LiMn2O4 attributes to the entrance of Li and Co ions inserted into the spinel crystal structure.展开更多
LiCoxMn2.04 cathode materials for lithium ion batteries were synthesized by mechanical activation-solid state reaction at 750 ℃ for 24 h in air atmosphere, and their crystal structure, morphology, element composition...LiCoxMn2.04 cathode materials for lithium ion batteries were synthesized by mechanical activation-solid state reaction at 750 ℃ for 24 h in air atmosphere, and their crystal structure, morphology, element composition and electrochemical performance were characterized with XRD, SEM, ICP-AES and charge-discharge test. The experimental results show that all samples have a single spinel structure, well formed crystal shape and uniformly particle size distribution. The lattice parameters of LiCo Mn2-xO4 decrease and the average oxidation states of manganese ions increase with an increase in Co content. Compared with pure LiMn2O4, the LiCo Mn2xO4 （x=0.03-0.12） samples show a lower special capacity, but their cycling life are improved. The capacity loss of LiCo009Mn191O4 and LiCo0.1Mn1.88O4 is only 1.85% and 0.95%, respectively, after the 20th cycle. The improvement of the cycle performance is attributed to the substitution of Co at the Mn sites in the spinel structure, which suppresses the Jahn-Teller distortion and improves the structural stability.展开更多
LiMn2O4 nanoparticles are facilely synthesized using a sol-gel processing method. Graphene is added to LiMn2O4 electrode aiming at increasing specific capacity and improving rate capability. In order to further improv...LiMn2O4 nanoparticles are facilely synthesized using a sol-gel processing method. Graphene is added to LiMn2O4 electrode aiming at increasing specific capacity and improving rate capability. In order to further improve cycling stability of LiMn2O4/graphene electrode, atomic layer deposition （ALD） is used to deposit ultrathin ZnO coating composed of six ZnO ALD layers and modify the surface of either LiMn2O4/graphene electrode or individual LiMn2O4 particles to form nanoarchitectured LiMn2O4/graphene/ZnO electrodes. Both ZnO-ALD-modified LiMn2O4/graphene electrodes demonstrate enhanced cycling performance at 1C, retaining the final discharge capacity above 122 mA h g 1 after 100 electrochemical cycles, which is higher than 115 mA h g-1 of pristine LiMn2O4/graphene electrode and 109 mA h g-1 of bare LiMn2O4 electrode. The improved electrochemical performance of nanoarchitectured LiMn2O4/graphene/ZnO electrodes can be attributed to the cooperative effects from high electronic conductivity of graphene sheets to facilitate electron transportation and effective protection of ZnO ALD coating to restrict Mn dissolution and electrolyte decomposition.展开更多
A series of LiMn2O4/LiFePO4 blend cathodes was prepared by hand milling and ball milling in order to compensate the disadvantage of spinel LiMnaO4 and olivine LiFePO4. The morphologies of the blends were studied by sc...A series of LiMn2O4/LiFePO4 blend cathodes was prepared by hand milling and ball milling in order to compensate the disadvantage of spinel LiMnaO4 and olivine LiFePO4. The morphologies of the blends were studied by scanning electron microscopy, and their electrochemical properties were studied by charge-discharge cycling, cyclic voltarnmetry and electrochemical impedance spectroscopy. It is easy to obtain uniform LiMn2Oa/LiFePO4 blends by the hand milling technique, while significant particle agglomeration is caused by the ball milling technique. When the LiMn2O4：LiFePO4 mass ratio is 1：1, the nano-sized LiFePO4 powders not only uniformly cover the micron-sized LiMn2O4 particles but also effectively fill in the cavities of the LiMn2O4 space. Such morphology offers a good electrical contact and a high tap density, which leads to a high discharge capacity and good cycle stability.展开更多
LiMn2O4 nano-wires with ideal size distribution were readily synthesized by flux method. Samples prepared conventionally were used as the comparison references to investigate the effect of flux. The structural, morpho...LiMn2O4 nano-wires with ideal size distribution were readily synthesized by flux method. Samples prepared conventionally were used as the comparison references to investigate the effect of flux. The structural, morphological and electrochemical properties of nano-sized materials were examined by powder X-ray diffraction（XRD） analysis, scanning electron microscopy（SEM） and charge-discharge cycling analysis. Results from galvanostatic charge-discharge analysis show that the samples prepared at 700 ℃ via flux method（FM-700） afford the highest initial discharge capacity of 125.5 mA·h/g between 3.0 to 4.3 V at a rate of 0.2 C. After 50 cycles, a cycling retention of 89.6% is evident. Overall, the LiMn2O4 nano-wires developed in this work seem to be promising cathode materials for lithium ion batteries suitable to different energy-saving settings.展开更多
The cathode materials LiMn2O4 and rare earth elements La-doped or La and F dual-doped spinel lithium manganese oxides.were synthesized by the citric acid-assisted sol-gel method. The synthesized samples were investiga...The cathode materials LiMn2O4 and rare earth elements La-doped or La and F dual-doped spinel lithium manganese oxides.were synthesized by the citric acid-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis （DTA） and thermogravimetry （TG） measurements, X-ray diffraction （XRD）, scanning electronic microscope （SEM）, cyclic voltammetry （CV）, and charge-discharge test. XRD data shows that all the samples exhibit the same pure spinel phase, and the LiLa0.01Mn1.99O3.99F0.01 and LiLao.olMnl.9904 samples have smaller lattice parameters and unit cell volume than LiMn2O4. SEM indicates that LiLa0.01Mn1.99O3.99F0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn2O4, LiLa0.01Mn1.99O4, and LiLa0.01Mn1.99O3.99F0.01 are 129.9, 122.8, and 126.4 mAh·g^-1, and the capacity losses of the initial values after 50 cycles are 14.5%, 7.6%, and 8.0%, respectively The CVs show that the La and F dual-doped spinel displays a better reversibility than LiMn2O4.展开更多
Abstract Lithium λ-MnO2 ion-sieves were prepared from spinel LiMn2O4 via treatment with nitric acid. The LiMn2O4 was synthesized by a solid state reaction between LiOH· H2O and MnO2. The effects of the calcinati...Abstract Lithium λ-MnO2 ion-sieves were prepared from spinel LiMn2O4 via treatment with nitric acid. The LiMn2O4 was synthesized by a solid state reaction between LiOH· H2O and MnO2. The effects of the calcination time and temperature on the preparation of the LiMn2O4 precursor and the lithium ion-sieve were investigated. In addition, the Li^＋ extraction ratio, the Mn^2＋ dissolving ratio and the adsorption properties of the lithium ion-sieve were all measured. The lithium ion-sieve had a high exchange capacity and was selective for Li^＋. Specifically, at pH = 13, the ion exchange capacity of Li^＋ was 30.9mg/g in 10 mmol/L LiCl solution and the lithium extraction ratio and manganese dissolving ratio were 95% and 25%, respec- tively.展开更多
文摘Electrochemical insertion/extraction of Li on cathode materials of spinel type LiMn2O4 and ordered rock-salt type LiCo0.5 Ni0.5O2 was measured on samples of which structures were well characterized. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materiaIs on electrochemical Li insertion/extraction performance was discussed. These two transition metal oxides belong to onegroup that the crystallinity of these oxides affects to the performance.
基金Project(50302016) supported by the National Natural Science Foundation of China Project(2005037698) supported by the Postdoctoral Science Foundation of China
文摘LiNi0. 45 Co0. 10 Mn0. 4sO2 was synthesized from Li2CO3 and a triple oxide of nickel, cobalt and manganese at 950 ℃ in air. The structures and characteristics of LiNi0. 45 Co0.10 Mn0. 45 O2, LiCoO2 and LiMn2 O4 were investigated by XRD, SEM and electrochemical measurements. The results show that LiNi0.4s Co0.10 Mn0. 45 O2 has a layered structure with hexagonal lattice. The commercial LicoO2 has sphere-like appearance and smooth surfaces, while the LiMn2 O4 and LiNi0.45 Co0. 10 Mn0. 45 O2 consist of cornered and uneven particles. LiNi0. 45 Co0.10 Mn0. 45 O2 has a large disLiMn2 O4 and LiCoO2, respectively. LiCoO2 and LiMn2 O4 have higher discharge voltage and better rate-capability than LiNi0. 45Co0.10 Mn0. 45 O2. All the three cathodes have excellent cycling performance with capacity retention of above 89.3 % at the 250th cycle. Batteries with LiMn2 O4 or LiNi0.45 Co0.10 Mn0. 45 O2 cathodes show better safety performance under abusive conditions than those with LiCoO2 cathodes.
文摘Modified lithium manganese oxides were prepared by using LiMn 2 O 4 and LiCoO 2 as precursors by solid state reaction.A study has been carried out by TG - DSC,XRD and FTIR to analyze the reaction process and structural characterization of products.The results showed that the LiMn 2 O 4 reacted chemically with LiCoO 2 at high temper - ature.Li and Co atom could insert into the LiMn 2 O 4 crystal lattice and obtained the Cobalt - Doped spinel com - pound.The results of constant - current cyclic test showed that the cyclic stability of the products are increased with the amount of doped LiCoO 2 ,while their initial capacity is decreased.
基金supported by the Basic Research Fund of Tsinghua University under grant No.JC1999054‘985’Project of School of Materials Science and Engineering of Tsinghua Universitythe Scientific Fund of the Education Committee of Fujian Province.
文摘Cobalt was used to modify the surface of spinel LiMn2O4 by a solution technique to produce Co3+-modified surface material (COMSM). Cobalt was only doped into the surface of LiMn2O4 spinel. XPS(X-ray photoelectron spectroscopy) analysis confirms the valence state of Co3+. COMSM has stable spinel structure and can prevent active materials from the corrosion of electrolyte. The ICP(inductively coupled plasma) determination of the spinel dissolution in electrolyte showed the content of Mn dissolved from COMSM was smaller than that from the pure spinel. AC impedance patterns show that the charge-transfer resistance (Ret) for COMSM is smaller than that for pure spinel. The particles of COMSM are bigger in size than those of pure spinel according to the micrographs of SEM(scanning electron microscopy). The determinations of the electrochemical characterization show that COMSM has both good cycling performance and high initial capacity of 124.1 mA/h at an average capacity loss of 0.19 mAh/g per cycle.
文摘Spinel LiCo0.09Mn1.91O3.92F0.08 as cathode material was modified with LiCoO2 by the sol-gel method, and the crystal structure, morphology and electrochemical performance were characterized with XRD, SEM, EDS, AAS and charge-discharge test in this paper. The results show that a good clad coated on parent material can be synthesized by the sol-gel method, and the materials with modification have perfect spinel structure. LiCo0.09Mn1.91O3.92F0.08 materials coated by LiCoO2 improve the stability of crystal structure and decrease the dissolution of Mn into electrolyte. With the LiCoO2 content increasing, the specific capacity and cycle performance of samples are improved. The capacity loss is also suppressed distinctly even at 55 ℃.
基金Project(20376086)supported by the National Natural Science Foundation of ChinaProject(2005037700)supported by Postdoctoral Science Foundation of China+2 种基金Project(07JJ3014)supported by Hunan Provincial Natural Science Foundation of ChinaProject(07A058)supported by Scientific Research Fund of Hunan Provincial Education DepartmentProject(2004107)supported by Postdoctoral Science Foundation of Central South University
文摘LiMn2O4/Li4Ti5O12 composite was synthesized by in-situ composite technique using LiMn2O4,lithium acetate,tetrabutyl titanate as starting materials and characterized by various electrochemical methods in combination with X-ray diffractometry(XRD), infrared(IR)spectroscopy and scanning electron microscopy(SEM).The results show that Li4Ti5O12 is coated on the surface of crystalline LiMn2O4 to form LiMn2O4/Li4Ti5O12 composite.The structure of LiMn2O4 does not change due to the introduction of Li4Ti5O12.By being coated with Li4Ti5O12,the rate capability and high temperature cyclability of LiMn2O4 is improved greatly.At room temperature,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 108.4 mA·h/g and the capacity loss per cycle is only 0.053%after 20 cycles at 2.0C.While at 55℃,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 109.9 mA·h/g and the capacity loss per cycle is only 0.036%after 60 cycles at 1.0C.
文摘In order to improve the cycle performance of LiMn2O4, the modified LiMn,O4 was prepared by solid-state reactions using LiMn2O4 and LiCoO2 as precursors. XRD and EDS were used to study the structure properties of the modified LiMn2O4. The electrochemical properties of the modified LiMn2O4 were also investigated. The results show that Li and Co atoms could insert into the LiMn2O4crystal lattice and a newly formed spinel phase, modified LiMn2O4 was obtained. The modified LiMn2O4 exhibits excellent cycle ability at room and elevated temperatures compared to pure LiMn2O4. The improved electrochemical stability of the modified LiMn2O4 attributes to the entrance of Li and Co ions inserted into the spinel crystal structure.
基金the Foundation of Key Laboratory of Yunnan Province(No.14051038)
文摘LiCoxMn2.04 cathode materials for lithium ion batteries were synthesized by mechanical activation-solid state reaction at 750 ℃ for 24 h in air atmosphere, and their crystal structure, morphology, element composition and electrochemical performance were characterized with XRD, SEM, ICP-AES and charge-discharge test. The experimental results show that all samples have a single spinel structure, well formed crystal shape and uniformly particle size distribution. The lattice parameters of LiCo Mn2-xO4 decrease and the average oxidation states of manganese ions increase with an increase in Co content. Compared with pure LiMn2O4, the LiCo Mn2xO4 （x=0.03-0.12） samples show a lower special capacity, but their cycling life are improved. The capacity loss of LiCo009Mn191O4 and LiCo0.1Mn1.88O4 is only 1.85% and 0.95%, respectively, after the 20th cycle. The improvement of the cycle performance is attributed to the substitution of Co at the Mn sites in the spinel structure, which suppresses the Jahn-Teller distortion and improves the structural stability.
基金supported by the LABOR-RCS grant (LEQSF(2011-14)-RD-A-13)
文摘LiMn2O4 nanoparticles are facilely synthesized using a sol-gel processing method. Graphene is added to LiMn2O4 electrode aiming at increasing specific capacity and improving rate capability. In order to further improve cycling stability of LiMn2O4/graphene electrode, atomic layer deposition （ALD） is used to deposit ultrathin ZnO coating composed of six ZnO ALD layers and modify the surface of either LiMn2O4/graphene electrode or individual LiMn2O4 particles to form nanoarchitectured LiMn2O4/graphene/ZnO electrodes. Both ZnO-ALD-modified LiMn2O4/graphene electrodes demonstrate enhanced cycling performance at 1C, retaining the final discharge capacity above 122 mA h g 1 after 100 electrochemical cycles, which is higher than 115 mA h g-1 of pristine LiMn2O4/graphene electrode and 109 mA h g-1 of bare LiMn2O4 electrode. The improved electrochemical performance of nanoarchitectured LiMn2O4/graphene/ZnO electrodes can be attributed to the cooperative effects from high electronic conductivity of graphene sheets to facilitate electron transportation and effective protection of ZnO ALD coating to restrict Mn dissolution and electrolyte decomposition.
基金Supported by the State Key Development Program for Basic Research of China（No.2015CB251103）, the National Natural Science Foundation of China（Nos.51272088, 20473075） and the Research Fund for High Technology Development of Jilin Province, China（No.20120310）.
文摘A series of LiMn2O4/LiFePO4 blend cathodes was prepared by hand milling and ball milling in order to compensate the disadvantage of spinel LiMnaO4 and olivine LiFePO4. The morphologies of the blends were studied by scanning electron microscopy, and their electrochemical properties were studied by charge-discharge cycling, cyclic voltarnmetry and electrochemical impedance spectroscopy. It is easy to obtain uniform LiMn2Oa/LiFePO4 blends by the hand milling technique, while significant particle agglomeration is caused by the ball milling technique. When the LiMn2O4：LiFePO4 mass ratio is 1：1, the nano-sized LiFePO4 powders not only uniformly cover the micron-sized LiMn2O4 particles but also effectively fill in the cavities of the LiMn2O4 space. Such morphology offers a good electrical contact and a high tap density, which leads to a high discharge capacity and good cycle stability.
基金Supported by the National Natural Science Foundation of China（Nos.21301066, 21271082）.
文摘LiMn2O4 nano-wires with ideal size distribution were readily synthesized by flux method. Samples prepared conventionally were used as the comparison references to investigate the effect of flux. The structural, morphological and electrochemical properties of nano-sized materials were examined by powder X-ray diffraction（XRD） analysis, scanning electron microscopy（SEM） and charge-discharge cycling analysis. Results from galvanostatic charge-discharge analysis show that the samples prepared at 700 ℃ via flux method（FM-700） afford the highest initial discharge capacity of 125.5 mA·h/g between 3.0 to 4.3 V at a rate of 0.2 C. After 50 cycles, a cycling retention of 89.6% is evident. Overall, the LiMn2O4 nano-wires developed in this work seem to be promising cathode materials for lithium ion batteries suitable to different energy-saving settings.
文摘The cathode materials LiMn2O4 and rare earth elements La-doped or La and F dual-doped spinel lithium manganese oxides.were synthesized by the citric acid-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis （DTA） and thermogravimetry （TG） measurements, X-ray diffraction （XRD）, scanning electronic microscope （SEM）, cyclic voltammetry （CV）, and charge-discharge test. XRD data shows that all the samples exhibit the same pure spinel phase, and the LiLa0.01Mn1.99O3.99F0.01 and LiLao.olMnl.9904 samples have smaller lattice parameters and unit cell volume than LiMn2O4. SEM indicates that LiLa0.01Mn1.99O3.99F0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn2O4, LiLa0.01Mn1.99O4, and LiLa0.01Mn1.99O3.99F0.01 are 129.9, 122.8, and 126.4 mAh·g^-1, and the capacity losses of the initial values after 50 cycles are 14.5%, 7.6%, and 8.0%, respectively The CVs show that the La and F dual-doped spinel displays a better reversibility than LiMn2O4.
文摘Abstract Lithium λ-MnO2 ion-sieves were prepared from spinel LiMn2O4 via treatment with nitric acid. The LiMn2O4 was synthesized by a solid state reaction between LiOH· H2O and MnO2. The effects of the calcination time and temperature on the preparation of the LiMn2O4 precursor and the lithium ion-sieve were investigated. In addition, the Li^＋ extraction ratio, the Mn^2＋ dissolving ratio and the adsorption properties of the lithium ion-sieve were all measured. The lithium ion-sieve had a high exchange capacity and was selective for Li^＋. Specifically, at pH = 13, the ion exchange capacity of Li^＋ was 30.9mg/g in 10 mmol/L LiCl solution and the lithium extraction ratio and manganese dissolving ratio were 95% and 25%, respec- tively.
