Thermodynamic equilibrium theory-guided design and synthesis of Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4)/C cathode for lithium-ion batteries

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.

Effect of Mo^(6+)doping on the structure and electrochemical properties of spinel-type LiMn_(2)O_(4)cathode materials

The Jahn-Teller effect and the dissolution of Mn are significant factors contributing to the capacity degradation of spinel LiMn_(2)O_(4) cathode materials during charging and discharging.In this study,Mo^(6+)-doped polycrystalline octahedral Li_(1.05)Mn_(2-x)Mo_(x)O_(4)(x=0,0.005,0.01,0.015)cathode materials were prepared by simple solid-phase sintering,and their crystal structures,microscopic morphologies,and elemental compositions were characterized and analyzed.The results showed that the doping of Mo^(6+)promoted the growth of(111)crystalline facets and increased the ratio of Mn^(3+)/Mn^(4+).The electrochemical performance of the materials was also tested,revealing that the doping of Mo^(6+)significantly improved the initial charge/discharge specific capacity and cycling stability.The modified sample(LMO-0.01Mo)retained a reversible capacity of 114.83 mA h/g with a capacity retention of 97.29%after 300 cycles.Additionally,the doping of Mo^(6+)formed a thinner,smoother SEI film and effectively inhibited the dissolution of Mn.Using density-functional theory(DFT)calculations to analyze the doping mechanism,it was found that doping shortens the Mn-O bond length inside the lattice and increases the Li-O bond length.This implies that the Li^(+)diffusion channel is widened,thereby increasing the Li^(+)diffusion rate.Additionally,the modification reduces the energy band gap,resulting in higher electronic conductivity.

有机物及钴含量对锌电解的影响

湿法炼锌过程出现烧板情况,分析原因主要是因有机物、钴含量异常引起。对铟萃余液中P_(2)0_(4)和煤油进行化验定量分析,在电解实验中找出萃取液中适合锌电解的P_(2)0_(4)和煤油最高允许值,采用活性碳吸附铟萃余液中的有机物P_(2)0_(4),并验证含钴量对析出锌质量的影响,通过试验等研究了锌电解系统中的有机物、钴含量和采取处理的措施,解决锌电解烧板问题,取得了较好的效果。

聚离子液体的制备及其对La^(3+)的吸附试验研究

研究制备了聚1-丁基-3-乙烯基咪唑溴盐(P[BVIM]Br-MNPs)、聚1-己基-3-乙烯基咪唑溴盐(P[HVIM]Br-MNPs)、聚1-辛基-3-乙烯基咪唑溴盐(P[OVIM]Br-MNPs)3种聚离子液体固相吸附剂,考察了P_(2)0_(4)掺杂比、固相吸附剂用量、吸附时间、吸附温度、水相初始pH和La^(3+)浓度对3种聚离子液体吸附La^(3+)的影响,用Langmuir与Freundlich等温吸附模型对试验数据进行拟合。结果表明:在吸附温度70℃、1 g P[OVIM]Br-MNPs掺杂1 mL P_(2)0_(4)条件下,P[OVIM]Br-MNPs对La^(3+)的饱和吸附量为57.80 mg/g,吸附效果较好,吸附过程以单层吸附为主。

Synthesis,Structures of 2D Coordination Layers Metal-Organic Frameworks with Highly Selective CO_(2)Uptake

Main observation and conclusion By a strategy of fine-tuning of packing mode between the adjacent layers in a 2D net metal-organic frameworks(MOFs)through ligand changing,two 2D sql-type MOFs with highly selective CO_(2)uptake,CuHIN and CuHPB,were successfully synthesized.Compared with the precursor MOF-2,the fine-tuning structure of CuHIN shows selective adsorption of CO_(2)over N_(2)and CH_(4)with the CO_(2)uptake amounts as high as 4.7 wt%at 0.15 bar and at 298 K,and CO_(2)selectivity towards N_(2)and CH_(4)is 165.8 and 10.22 at 1 bar and at 298 K,respectively.In addition,for the 2D MOFs,the dynamic porous structure depends on the interaction of the adjacent layers.The suitable interaction is good for gliding smoothly and gas adsorption.

Mg^(2+)和Cu^(2+)分步沉淀pH曲线的测定与分析

运用手持技术pH传感器,研究用NaOH溶液分别滴定MgCl_(2)溶液、CuS0_(4)溶液以及两者混合溶液的p H曲线,结合理论计算和实验图像分析Mg^(2+)、Cu^(2+)开始沉淀的pH及沉淀完全的pH,通过“宏观-微观-符号-曲线”四重表征分析pH曲线变化,探讨离子分步沉淀的最佳pH范围。