首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 437 毫秒
1.
The nonaqueous rechargeable lithium-O(2) battery containing an alkyl carbonate electrolyte discharges by formation of C(3)H(6)(OCO(2)Li)(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, CO(2), and H(2)O at the cathode, due to electrolyte decomposition. Charging involves oxidation of C(3)H(6)(OCO(2)Li)(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li accompanied by CO(2) and H(2)O evolution. Mechanisms are proposed for the reactions on discharge and charge. The different pathways for discharge and charge are consistent with the widely observed voltage gap in Li-O(2) cells. Oxidation of C(3)H(6)(OCO(2)Li)(2) involves terminal carbonate groups leaving behind the OC(3)H(6)O moiety that reacts to form a thick gel on the Li anode. Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, and C(3)H(6)(OCO(2)Li)(2) accumulate in the cathode on cycling correlating with capacity fading and cell failure. The latter is compounded by continuous consumption of the electrolyte on each discharge.  相似文献   

2.
The oxidation kinetics of Li(2)O(2) was studied in a carbonate-free electrolyte using electrodes consisting of non-catalyzed and catalyzed Vulcan carbon (VC) and chemically synthesized Li(2)O(2) particles. VC and Au nanoparticles supported on VC (Au/C) were fairly inactive for catalyzing the oxidation of Li(2)O(2), where oxidation currents greater than 10 mA g(carbon)(-1) were found only at voltages equal to and greater than 4.0 V vs. Li (V(Li)). Pt and Ru nanoparticles supported on VC (Pt/C and Ru/C) could significantly increase the kinetics of Li(2)O(2) oxidation, where Li(2)O(2) could be removed largely at voltages below 4 V(Li). In addition, Pt/C and Ru/C showed quick initiation of Li(2)O(2) oxidation in contrast to VC and Au/C.  相似文献   

3.
Vinylgallium compounds [C(6)H(6-n){(H)C=C(SiR(2) R')-GaR'(2)}(n ] (3, R=Ph, Me; R'=Ph, Me; R'=tBu, Et; n=1, 2) are easily accessible by hydrogallation of the corresponding alkynylbenzene derivatives with H-GaCl(2) and subsequent reaction with alkyllithium derivatives. Treatment of 3 with an excess amount of tert-butyl- or ethyllithium yielded by transmetalation and ortho-deprotonation of the aromatic rings the unprecedented solvent-free oligolithium cluster compounds [{(C(6)H(4)Li)HC=C(SiPh(3))Li}(2)(tBuLi)(2)] (4), [{(C(6)H(4)Li)HC=C(SiPh(2)Me)Li}(4)] (5) and [{(C(6)H(3)Li){HC=C(SiMe(3))Li}(2)}(3)] (6) in moderate yields. Their solid-state structures revealed the presence of unique molecular lithium clusters with 6, 8, or 9 lithium atoms that may be derived from two edge-sharing Li(4) tetrahedra (4), three Li(4) tetrahedra in a chain joined by two common edges (5) or a tricapped trigonal prism of lithium atoms (6).  相似文献   

4.
Shirai A  Ikeda Y 《Inorganic chemistry》2011,50(5):1619-1627
(7)Li NMR spectra of DEME-TFSA [DEME=N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium; TFSA=bis(trifluoromethanesulfonyl)amide], EMI-TFSA (EMI=1-ethyl-3-methylimidazolium), MPP-TFSA (MPP = N-methyl-N-propylpyridinium), DEME-PFSA [PFSA=bis(pentafluoroethanesulfonyl)amide], and DEME-HFSA [HFSA=bis(heptafluoropropanesulfonyl)amide] ionic liquid (IL) solutions containing LiX (X=TFSA, PFSA, or HFSA) and C211 (4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane) were measured at various temperatures. As a result, it was found that the uncomplexed Li(I) species existing as [Li(X)(2)](-) in the present ILs exchange with the complexed Li(I) ([Li·C211](+)) and that the exchange reactions proceed through the bimolecular mechanism, [Li·C211](+) + [*Li(X)(2)](-)=[*Li·C211](+) + [Li(X)(2)](-). Kinetic parameters [k(s)/(kg m(-1) s(-1)) at 25 °C, ΔH(++)/(kJ mol(-1)), ΔS(++)/(J K(-1) mol(-1))] are as follows: 5.57×10(-2), 69.8 ± 0.4, and -34.9 ± 1.0 for the DEME-TFSA system; 5.77×10(-2), 70.6 ± 0.2, and -31.9 ± 0.6 for the EMI-TFSA system, 6.13×10(-2), 69.0 ± 0.3, and -36.7 ± 0.7 for the MPP-TFSA system; 1.35 × 10(-1), 65.2 ± 0.5, and -43.1 ± 1.4 for the DEME-PFSA system; 1.14×10(-1), 64.4 ± 0.3, and -47.1 ± 0.6 for the DEME-HFSA system. To compare these kinetic data with those in conventional nonaqueous solvents, the exchange reactions of Li(I) between [Li·C211](+) and solvated Li(I) in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) were also examined. These Li(I) exchange reactions were found to be independent of the concentrations of the solvated Li(I) and hence proposed to proceed through the dissociative mechanism. Kinetic parameters [k(s)/s(-1) at 25 °C, ΔH(++)/(kJ mol(-1)), ΔS(++)/(J K(-1) mol(-1))] are as follows: 1.10 × 10(-2), 68.9 ± 0.2, and -51.3 ± 0.4 for the DMF system; 1.13×10(-2), 76.3 ± 0.3, and -26.3 ± 0.8 for the DMSO system. The differences in reactivities between ILs and nonaqueous solvents were proposed to be attributed to those in the chemical forms of the uncomplexed Li(I) species, i.e., the negatively charged species ([Li(X)(2)](-)) in ILs, and the positively charged ones ([Li(solvent)(n)](+)) in nonaqueous solvents.  相似文献   

5.
To make a practical molecular dynamics (MD) simulation of the large-scale reactive chemical systems of Li-H and Li-C, we have optimized parameters of the reactive force field (ReaxFF) for these systems. The parameters for this force field were obtained from fitting to the results of density functional theory (DFT) calculations on the structures and energy barriers for a number of Li-H and Li-C molecules, including Li(2), LiH, Li(2)H(2), H(3)C-Li, H(3)C-H(2)C-Li, H(2)C=C-LiH, HCCLi, H(6)C(5)-Li, and Li(2)C(2), and to the equations of state and lattice parameters for condensed phases of Li. The accuracy of the developed ReaxFF was also tested by comparison to the dissociation energies of lithium-benzene sandwich compounds and the collision behavior of lithium atoms with a C(60) buckyball.  相似文献   

6.
A recently proposed system with a central planar tetracoordinate carbon linking two three-membered rings, C(5)(2-), lends itself to extension in one, two, and three dimensions. Our construction of potential realizations begins with an analysis of the electronic structure of C(5)(2-). Dimers such as C(10)Li(3-), C(10)Li(4), and a trimer C(15)Li(6) are then examined, and their geometries are optimized to find clues for ways the C(5)(2-) unit may polymerize in the presence of countercations. Coordination through the terminal carbons is favored in the oligomers and polymers; several electronically and structurally reasonable systems of the stoichiometry C(5)M(x) (M = Li, x = 2; M = Be, Pt, Zn, x = 1) emerge from band structure calculations and energetic considerations.  相似文献   

7.
The following crystalline oligonuclear metal alkyls have been synthesised under mild conditions and structurally characterised: [(THF)Li(mu-A)(mu-Cl)(mu3-OMe)Zn]2, [Li(mu-A)2Tl]2(4 and 4'), [Li4(mu-A)3(micro3-OMe)]5, [(mu-A)Li2(mu-A)2(mu3-OMe)Ce(A)](6) and [Ce(A)(mu2-OMe){mu2-OS(O)(CF3)O}]2(11)[= CH(SiMe3){SiMe(OMe)2}]. Compounds 2-6 were obtained from [Li(mu-A)]infinity(1) and ZnCl2(3), TlCl (4 and 4' and 5) and CeCl3(6), and 11 was isolated from K(A)(prepared from 1 + KOBu(t)) and cerium(III) triflate Ce(OTf)3. The principal novel features are (i) and (ii) as follows. As for (i), the diversity of ligand-to-metal bonding is noteworthy, the ligand being (a)C,O-bridging in 3{as in the known compounds 1 and in [Li2Mg5(mu3-OMe)6(mu2-OMe)2(mu2-A)4](2)}; (b)C,O,O'-bridging and O,O'-chelating in 4 and 4'; (c)C,O,O'-bridging in 5; (d)C,O,O'-bridging and C,O-chelating in 6; and (e)C,O-chelating in 11. Regarding (ii), it is interesting that the ligand [A]- is surprisingly ready to undergo fragmentation by Si-OMe cleavage and thereby present bridging methoxy ligands (mu2-OMe)2 to a pair of Ce3+ ions in 11, or mu3-OMe acting as a cap for triangular arrays of three hard metal ions (Mg3 in 2, LiZn2 in 3, Li3 in 5, and Li2Ce in 6).  相似文献   

8.
The combination of equimolar amounts of LiOAr and Mg(OAr)2 (OAr=aryloxide) in polar media afforded several lithium aryloxomagnesiates. Factors influencing the structural chemistry of the compounds, such as the degree of ligand bulk, type of Lewis base donors, and crystallization solvent, are examined. Structural characterization reveals a discrete, solvent-separated species, [Li(thf)4][Mg(BHT)3].THF (1) (BHT=2,6-tBu2-4-MeC6H2O) and a family of molecular compounds with various Li/Mg stoichimetries, including a 1:1 Li/Mg ratio in [LiMg(Odpp)3(thf)2].0.5PhMe (2) (Odpp=2,6-Ph2C6H3O) and [Li(Et2O)Mg(Odpp)3].0.5PhMe (3), a 2:1 Li/Mg ratio as in [{Li(thf)2}2Mg(OMes)4].2THF (4) (OMes=2,4,6-Me3C6H2O) and [{Li(tmeda)}2Mg(m-Odtp)4].0.5Et2O (5) (m-Odtp=3,5-tBu2C6H3O), and a novel 2:3 Li/Mg ratio in [{Li(thf)2}2Mg3(m-Odtp)8(thf)2].3THF (6). Two new homometallic magnesium bis(aryloxides), Mg(Odpp)2(thf)2 (7) and Mg(Odpp)2(Et2O)2 (8), are also included for the sake of comparison. The solution behavior of the heterobimetallic compounds in arene and polar solvent is analyzed by 1H NMR spectroscopy.  相似文献   

9.
Reaction of {Li(THF)Ar'MnI(2)}(2) (Ar' = C(6)H(3)-2,6-(C(6)H(2)-2,6-(i)Pr(3))(2)) with LiAr', LiC≡CR (R = (t)Bu or Ph), or (C(6)H(2)-2,4,6-(i)Pr(3))MgBr(THF)(2) afforded the diaryl MnAr'(2) (1), the alkynyl salts Ar'Mn(C≡C(t)Bu)(4){Li(THF)}(3) (2) and Ar'Mn(C≡CPh)(3)Li(3)(THF)(Et(2)O)(2)(μ(3)-I) (3), and the manganate salt {Li(THF)}Ar'Mn(μ-I)(C(6)H(2)-2,4,6-(i)Pr(3)) (4), respectively. Complex 4 reacted with one equivalent of (C(6)H(2)-2,4,6-(i)Pr(3))MgBr(THF)(2) to afford the homoleptic dimer {Mn(C(6)H(2)-2,4,6-(i)Pr(3))(μ-C(6)H(2)-2,4,6-(i)Pr(3))}(2) (5), which resulted from the displacement of the bulkier Ar' ligand in preference to the halogen. The reaction of the more crowded {Li(THF)Ar*MnI(2)}(2) (Ar* = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-(i)Pr(3))(2)) with Li(t)Bu gave complex Ar*Mn(t)Bu (6). Complex 1 is a rare monomeric homoleptic two-coordinate diaryl Mn(II) complex; while 6 displays no tendency to eliminate β-hydrogens from the (t)Bu group because of the stabilization supplied by Ar*. Compounds 2 and 3 have cubane frameworks, which are constructed from a manganese, three carbons from three acetylide ligands, three lithiums, each coordinated by a donor, plus either a carbon from a further acetylide ligand (2) or an iodide (3). The Mn(II) atom in 4 has an unusual distorted T-shaped geometry while the dimeric 5 features trigonal planar manganese coordination. The chloride substituted complex Li(2)(THF)(3){Ar'MnCl(2)}(2) (7), which has a structure very similar to that of {Li(THF)Ar'MnI(2)}(2), was also prepared for use as a possible starting material. However, its generally lower solubility rendered it less useful than the iodo salt. Complexes 1-7 were characterized by X-ray crystallography and UV-vis spectroscopy. Magnetic studies of 2-4 and 6 showed that they have 3d(5) high-spin configurations.  相似文献   

10.
采用CO加氢反应、X射线衍射、程序升温还原和CO程序升温脱附等技术研究了Li助剂对活性炭负载的Co催化剂(Co/AC)上CO加氢反应性能的影响.结果表明,Li的添加抑制了气态烃的生成,提高了C5+和直链混合伯醇的选择性,但催化剂活性下降.这可能源于Li的加入抑制了Co2+物种的还原,降低了反应速控步骤—强吸附CO的解离...  相似文献   

11.
Reaction of UCl(4) with 5 equiv of Li(N═C(t)BuPh) generates the homoleptic U(IV) ketimide complex [Li(THF)(2)][U(N═C(t)BuPh)(5)] (1) in 71% yield. Similarly, reaction of UCl(4) with 5 equiv of Li(N═C(t)Bu(2)) affords [Li(THF)][U(N═C(t)Bu(2))(5)] (2) in 67% yield. Oxidation of 2 with 0.5 equiv of I(2) results in the formation of the neutral U(V) complex U(N═C(t)Bu(2))(5) (3). In contrast, oxidation of 1 with 0.5 equiv of I(2), followed by addition of 1 equiv of Li(N═C(t)BuPh), generates the octahedral U(V) ketimide complex [Li][U(N═C(t)BuPh)(6)] (4) in 68% yield. Complex 4 can be further oxidized to the U(VI) ketimide complex U(N═C(t)BuPh)(6) (5). Complexes 1-5 were characterized by X-ray crystallography, while SQUID magnetometry, EPR spectroscopy, and UV-vis-NIR spectroscopy measurements were also preformed on complex 4. Using this data, the crystal field splitting parameters of the f orbitals were determined, allowing us to estimate the amount of f orbital participation in the bonding of 4.  相似文献   

12.
Lithium-7 NMR measurements were used to investigate the stoichiometry and stability of Li+ complexes with 15-crown-5 (15C5), benzo-15-crown-5 (B15C5), dibenzo-15-crown-5 (DB15C5) and 12-crown-4 (12C4) in a number of nitromethane (NM)-acetonitrile (AN) binary mixtures. In all cases, the exchange between the free and complexed lithium ion was fast on the NMR time scale and a single population average resonance was observed. While all crown ethers form 1:1 complexes with Li+ ion in the binary mixtures used, both 1:1 and 2:1 (sandwich) complexes were observed between lithium ion and 12C4 in pure nitromethane solution. Stepwise formation constants of the 1:1 and 2:1 (ligand/metal) complexes were evaluated from computer fitting of the NMR-mole ratio data to equations which relate the observed metal ion chemical shifts to formation constants. There is an inverse linear relationship between the logarithms of the stability constants and the mole fraction of acetonitrile in the solvent mixtures. The stability order of the 1:1 complexes was found to be 15C5·Li+>B15C5·Li+>DB15C5·Li+>12C4·Li+. The optimized structures of the free ligands and their 1:1 and 2:1 complexes with Li+ ion were predicted by ab initio theoretical calculations using the Gaussian 98 software, and the results are discussed.  相似文献   

13.
Di(tert-butyl)sulfur diimide and bis(trimethylsilyl)sulfur diimide were reacted with different metalated amines to form versatile novel multidentate ligand systems with side-arm donation. Their complexation properties in terms of ligand design, denticity and the cation size are discussed. We report herein the synthesis and structure elucidation of [(tBuN)(2)S{LiMe(2)N(C(6)H(4))S(NtBu)(2)}(2)] (1), [(Li{Me(2)N(C(6)H(4))S(NSiMe(3))(2)})(2)] (2), [(Li(thf){Me(2)N(C(6)H(4))S(NSiMe(3))(2)})(2)] (3), [(Li{2-PicS(NSiMe(3))(2)})(2)] (4), [(Li{Me(2)N(CH(2))(2)N(Me)S(NSiMe(3))(2)})(2)] (5), [(Na{Me(2)N(CH(2))(2)N(Me)S(NSiMe(3))(2)})(2)] (6) and [(K{Me(2)N(C(6)H(4))S(NSiMe(3))(2)})(2)] (7).  相似文献   

14.
通过冻干干燥法辅助制备了分布均匀的纳米Li2FeSiO4材料.通过X射线衍射(XRD)、拉曼光谱(Raman)、扫描电子显微镜(SEM)、N2吸附-脱附、循环伏安(CV)和充放电测试等手段对材料的结构及电化学性能进行了表征.结果表明,冻干法处理后得到的Li2FeSiO4材料颗粒尺寸更小,能够缩短锂离子的扩散距离;同时较大的比表面积可以使材料与电解液接触更加充分.在1.5~4.8 V电压范围内,与采用传统烘干干燥法制备的材料相比,采用冻干法制备的材料表现出更高的可逆比容量,并具有良好的倍率性能和循环稳定性.  相似文献   

15.
用Li+部分替代MTiO3(M=Ca、Sr)催化剂中的Ti4+,明显地提高了乙烷氧化脱氢(ODHE)反应中乙烯的选择性。在CaTi0.9Li0.1O3-δ催化剂上,反应温度为850℃时,乙烯选择性为77.4%,乙烷转化率为81.7%。Li掺杂的作用是增加了催化剂的P型半导性和未充分还原的氧物种数目。  相似文献   

16.
以LiOH·H2O, NH4VO3, NH4H2PO4 和麦芽糖等为原料, 采用水热法合成了碳包覆的磷酸钒锂化合物, 考察了碳含量对材料电化学性能的影响. 利用XRD, TEM, SEM和恒流充放电测试等手段对产物的结构、 形貌和电化学性能进行表征. 结果表明, 在650℃煅烧的样品为单一纯相的单斜晶体结构. 晶体颗粒分布为100~300 nm, 粒度分散均匀, 分散性良好, 无团聚现象, 且在颗粒表面包覆了一层无定形碳, 这有利于改善材料的导电率. 含碳量为10.23%的样品, 在倍率1.0C的电流密度下, 在3.0~4.3 V电压范围内, 样品的首次放电比容量高达118.8 mA·h/g, 循环15圈后放电比容量为115.1 mA·h/g, 容量保持率为96.88%.  相似文献   

17.
Quinuclidine-stabilized amido- and azidogallanes, HGa[N(TMS)2]2(quin) (1), H2Ga[N(TMS)2](quin) (2), HGa-[N(H)(2,6-iPr2C6H3)]2(quin) (3), and H2GaN3(quin) (4), were synthesized from the quinuclidine adducts of mono- and dichlorogallane. Structural determinations revealed that all compounds were monomeric with four-coordinate gallium centers. Reactions of the five-coordinate compound, HGaCl2(quin)2, with 2 equiv of Li[N(TMS)2] or Li[N(H)(2,6-iPr2C6H3)] resulted in the isolation of compound 1 or 3. A ligand redistribution during the reaction of H2GaCl(quin) with Li[N(H)(2,6-iPr2C6H3)] produced compound 3 and H3Ga(quin) in a 1:1 molar ratio.  相似文献   

18.
The reduction of the digermene Ar'(H)GeGe(H)Ar' (Ar' = C6H3-2,6(C6H3-2,6-Pri2)2) with Li, Na, or K afforded [Li(THF)3Et2O][LiAr'(H)GeGe(H)Ar'] (1), Na2Ar'Ge(mu-H)2GeAr' (2), or K2{Ar'(H)GeGe(H)Ar'} (3), which have three different structures. 1 features a planar C(ipso)H)GeGe(H)C(ipso) dianion core with an associated Li+ cation. In contrast, 2 features a unique bridged hydride structure in which two Na+ ions also bridge the germaniums. In 3, the C(ipso)(H)GeGe(H)C(ipso) array has a nonplanar trans bent core with associated K+ ions. There is single Ge-Ge bonding in 1 and 3, but the Ge-Ge bonding in 2 may involve biradical character.  相似文献   

19.
采用草酸盐共沉淀法制备了钠掺杂改性的Li0.98Na0.02Ni0.6Co0.2Mn0.2O2正极材料,借助X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、能量分散谱(EDS)、感应耦合等离子体原子发射光谱(ICP-AES)、电化学阻抗谱(EIS)和恒电流充放电测试等手段对材料的颗粒形貌、晶体结构和电化学性能进行了研究.结果表明,掺钠后的材料具有更完善的α-NaFeO2结构(空间群为+/Ni2+阳离子混排和更大的Li层间距,易于Li+在晶格中的快速脱嵌迁移.电化学性能测试结果证实掺钠样品具有优异的循环稳定性和高倍率性能,在2.7~4.3 V,1C下循环100次后,放电比容量仍为146 mA·h/g(容量保持率为95.4%),在0.1C,0.2C,0.5C,1C,3C,5C,10C和20C时的放电比容量分别为181,168,162,155,143,136,126和113 mA·h/g.  相似文献   

20.
The tetracyclic dilithio-Si,Si'-oxo-bridged bis(N,N'-methylsilyl-beta-diketiminates) 2 and 3, having an outer LiNCCCNLiNCCCN macrocycle, were prepared from [Li{CH(SiMe(3))SiMe(OMe)(2)}](infinity) and 2 PhCN. They differ in that the substituent at the beta-C atom of each diketiminato ligand is either SiMe(3) (2) or H (3). Each of and has (i) a central Si-O-Si unit, (ii) an Si(Me) fragment N,N'-intramolecularly bridging each beta-diketiminate, and (iii) an Li(thf)(2) moiety N,N'-intermolecularly bridging the two beta-diketiminates (thf = tetrahydrofuran). Treatment of [Li{CH(SiMe(3))(SiMe(2)OMe)}](8) with 2Me(2)C(CN)(2) yielded the amorphous [Li{Si(Me)(2)((NCR)(2)CH)}](n) [R = C(Me)(2)CN] (4). From [Li{N(SiMe(3))C(Bu(t))C(H)SiMe(3)}](2) (A) and 1,3- or 1,4-C(6)H(4)(CN)(2), with no apparent synergy between the two CN groups, the product was the appropriate (mu-C(6)H(4))-bis(lithium beta-diketiminate) 6 or 7. Reaction of [Li{N(SiMe(3))C(Ph)=C(H)SiMe(3)}(tmeda)] and 1,3-C(6)H(4)(CN)(2) afforded 1,3-C(6)H(4)(X)X' (X =CC(Ph)N(SiMe3)Li(tmeda)N(SiMe3)CH; X' = CN(SiMe3)Li(tmeda)NC(Ph)=C(H)SiMe3)(9). Interaction of A and 2[1,2-C(6)H(4)(CN)(2)] gave the bis(lithio-isoindoline) derivative [C6H4C(=NH)N{Li(OEt2)}C=C(SiMe3)C(Bu(t))=N(SiMe3)]2 (5). The X-ray structures of 2, 3, 5 and 9 are presented, and reaction pathways for each reaction are suggested.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号