Microstructure and energy storage properties of Li1.2[Mn0.52-0.5xNi0.20-0.5xCo0.08+x]O2 cathode materials

以碳酸钠为沉淀剂,乳酸钠为络合剂合成碳酸盐前驱体,950℃烧结制备了Li_1.2[Mn_0.52-0.5xNi_0.20-0.5xCo_0.08+x]O₂（x=0, 0.02, 0.04, 0.06）系列材料,探讨元素含量变化对材料的结构、形貌、充放电性能的影响。研究结果表明：随着x的增大,材料的晶格常数c/a比值增加,层状结构更加完整。当x=0.02时,该材料的充放电性能最优,其首次放电容量为261.0 mA·h/g,0.5C下循环100次后的放电容量仍有189.9 mA·h/g,容量保持率高达98.85%,2C倍率下放电容量最高达到157.6 mA·h/g。进一步增大x值时,由于Co含量的上升,使得更多的Co^3+/4+ 2g轨道与O^2- 2p轨道发生带隙重叠,从而使得材料的比容量和循环性能下降。     

Preparation of LiNi0.80Co0.15Al0.05O2 cathode material via Li-rich method

本文采用共沉淀法制备球形Ni_0.80Co_0.15Al_0.05(OH)_2.05前驱体,经预氧化后,采用富锂配比在氧气和空气气氛下烧结合成LiNi_0.80Co_0.15Al_0.05O₂正极材料.用X射线衍射,扫描电镜和恒电流充放电测试等方法对该材料的结构,形貌及电化学性能进行表征.结果表明:当锂配比为1.15时,氧气和空气中烧结合成的LiNi_0.80Co_0.15Al_0.05O₂正极材料的形貌,结构和电化学性能相当.富锂配比方法可在空气气氛下制备出电化学性能优异的LiNi_0.80Co_0.15Al_0.05O₂正极材料.0.1 C放电克比容量在200 mA·h/g以上,首次效率在87%左右;1 C放电克比容量在168 mA·h/g以上;800周循环容量保持率在80%以上.     

Synthesis of LiNi0.8Co0.2O2 cathode material through sintering in an air environment and electrochemical properties characterization

制备锂离子电池正极材料LiNi_0.8Co_0.2O₂通常需要在纯氧气气氛下进行烧结.本工作以硫酸镍,硫酸钴和氢氧化钠为原料,采用并流共沉淀法制备了高密度Ni_0.8Co_0.2(OH)₂前驱体,再采用高温固相反应法在空气中烧结制备了锂离子电池LiNi_0.8Co_0.2O₂正极材料.采用X射线衍射(XRD),扫描电镜(SEM),恒流充放电测试(ECT),循环伏安(CV)与比表面积(BET)测试等方法对目标样品进行了表征,详细考察了烧结条件对材料结构,微观形貌及电化学性能的影响.结果表明,锂/(钴+镍)摩尔比为1.13∶1时,在管式炉中和空气气氛下于第一段烧结温度700 ℃保温9 h,于第二段烧结温度750 ℃保温12 h,合成的材料比表面积适中(0.78 m²/g),具有规则的六边形α-NaFeO₂层状结构,晶粒分布均匀,电化学性能最优.在0.5 C充放电倍率下和2.7~4.3 V电压范围内,其首次放电比容量达到153.0 mA·h/g,循环20次后放电比容量仍为150.7 mA·h/g,容量保持率达到98.5%,显示了优异的循环稳定性能,可用做高能量密度动力电池正极材料.     

铁酸铜尖晶石催化甲醛氧化的性能研究

通过溶胶-凝胶-自蔓延燃烧法制备了系列Cu_xFe_3-xO₄尖晶石催化剂。采用XRD和XPS表征方法对催化剂晶相结构及表面元素价态进行了分析,考察了Cu_xFe_3-xO₄催化甲醛的氧化效率。采用密度泛函理论探究了甲醛吸附在CuFe₂O₄表面的最稳定构型和吸附机理。结果表明,Cu_xFe_3-xO₄催化剂主要由Cu-Fe尖晶石相和部分CuO、Fe₂O₃相组成。Cu_0.5Fe_2.5O₄催化甲醛氧化效率最佳,在温度高于250℃时氧化效率达到90%以上。甲醛在CuFe₂O₄(100)表面的吸附属于化学吸附,吸附能为 -107.15 kJ/mol。     

加热和水处理共同调控PbI2薄膜形貌及其在钙钛矿太阳电池中的应用研究

该文研究加热和水处理共同作用对PbI₂薄膜形貌的调控和对钙钛矿太阳电池性能的影响。使用的钙钛矿体系为（FAPbI₃）_1-x（MAPbBr₃）_x,并在两步法工艺基础上对PbI₂薄膜进行不同时间加热和短时间水处理可将PbI₂薄膜制备成多孔结构。将双重处理后的PbI₂薄膜制备成钙钛矿薄膜后,可发现钙钛矿薄膜质量明显提升,表现在：钙钛矿的晶粒尺寸明显增大、结晶性增强、吸光能力提升、载流子传输更快。且此种方式能有效调控钙钛矿薄膜中的PbI₂残留量。在器件效率方面,只对PbI₂薄膜进行加热处理制备的电池的开路电压、短路电流、填充因子和效率分别为1.05 V、23.12 mA/cm²、73.81%和17.92%,而在最优双重处理工艺下制备的电池的这4个相应的参数分别为1.09 V、24.75 mA/cm²、77.85%和21.10%。     

Rb掺杂Li4Ti5O12作为锂离子电池负极材料的合成及电化学性能

合成了不同Rb掺杂量的钛酸锂（Li_4-xRb_xTi₅O₁₂; x = 0.010, 0.015, 0.020）作为锂离子电池的负极材料。测试结果显示,Rb离子掺杂有效增强了钛酸锂的电子电导率。相同的测试条件下,相比于未掺杂样品和高Rb含量掺杂样品（x = 0.015, 0.020）,适量的Rb掺杂钛酸锂（Li_3.99Rb_0.01Ti₅O₁₂; x = 0.010）表现出最优的电化学性能。Li_3.99Rb_0.01Ti₅O₁₂材料表现出161.2 mA∙h/g的初始容量,且在1 C下经过1000次循环后容量保持率可达90.9%。此外,全电池Li_3.99Rb_0.01Ti₅O₁₂ // LiFePO₄在0.5 C条件下首次放电容量为144 mA∙h/g,经过150次循环后,容量保持率为78.8%。     

ZnxCd1-xS的共沉淀法制备及其光催化活性研究

利用共沉淀一步法在常温下合成具有高光催化活性的Zn_xCd_1-xS固溶体光催化剂,用XRD、SEM、XPS、BET、UV-VIS DRS和PL对制备出的Zn_xCd_1-xS样品进行结构和光学性能的表征,并在模拟太阳光照射下对罗丹明B（RhB）溶液进行降解,评价其光催化活性。结果表明,Zn_xCd_1-xS对可见光的吸收阀值随Zn含量增加而减少,禁带宽度随之增大;颗粒状Zn_xCd_1-xS固溶体对罗丹明B具有较高的光催化活性,其中Zn_0.8Cd_0.2S的光催化性能最优,在90 min内对RhB的降解率达到98.5%,远高于CdS和ZnS光催化剂;经过4次重复使用后,Zn_0.8Cd_0.2S对RhB的降解率维持在75%以上。Zn_0.8Cd_0.2S的比表面积和孔隙体积相对于CdS分别增至154.6 m²/g和0.40 cm³/g,其光催化活性显著增强的主要原因是由于其较高的光生电子空穴对的分离效率及较低的复合率。     

镍钴锰酸锂电极材料改性研究进展

镍钴锰酸锂（LiNi_xCo_yMn_1-x-yO₂,NCM）是一种具有高使用容量的三元正极材料,但存在元素混排、相变、热稳定性差、微裂纹等缺陷,导致电池出现容量衰减和安全问题,影响其广泛应用。针对目前三元材料存在的问题,归纳总结了特殊结构与形貌、掺杂、替代、包覆、修饰、复合等改性方法的最新研究进展,探讨了不同方法对材料电化学性能、循环稳定性和安全性的影响,分析比较了不同方法的优缺点。结合材料、电化学、热和力等多学科知识及本课题组利用负热膨胀材料对能源材料改性的研究成果,提出了原位利用电极循环过程中的热调控形变和界面行为改善材料性能的新思路,为解决电池的热失控和应力等安全问题提供参考。     

AC Impedance of Li(Ni1/3Co1/3Mn1/3)O2/graphite cell as UPS

以Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池为研究对象,在模拟备用电源工况下对动力电池进行交流阻抗测试。通过建立等效电路来研究欧姆阻抗R_s、电荷传递阻抗R_ct和扩散阻抗CPE_W随不同搁置时间、荷电状态（state of charge,SOC）的变化规律,研究Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池在备用电源工况下,容量和阻抗的变化趋势。结果表明：随着搁置时间的增加,电池容量衰减1.7%左右。随着搁置时间的增加,不同SOC下的欧姆阻抗R_s具有相同的变化趋势,电荷传递阻抗明显增加。随着SOC的降低,由双电层产生的电荷传递阻抗在逐渐增加。在SOC=0%时,扩散阻抗随搁置时间的增加而增加,在SOC=100%、50%的扩散阻抗有细微的增加。容量衰退和阻抗结果显示出Li（Ni_1/3Co_1/3Mn_1/3）O₂/graphite动力电池可以很好地在备用电源工况上使用。     

Al2O3/SiOxNy/SiNx叠层钝化膜对PERC太阳电池性能及LID效应的研究

由于等离子体增强化学的气相沉积（PECVD）法制备的SiO_xN_y薄膜中含有大量H原子,因而具有优异的表面钝化性能。通过在PERC太阳电池的Al₂O₃/SiN_x背钝化叠层中间插入一层SiO_xN_y薄膜,形成Al₂O₃/SiO_xN_y/SiN_x结构,可避免SiN_x所带的固定正电荷对Al₂O₃负电荷场钝化效应的负面影响。试验结果表明,硅片少子寿命从原来的130 μs提高至162 μs,电池转换效率增加0.09%。同时,基于Al₂O₃/SiO_xN_y/SiN_x背钝化的PERC太阳电池的LID也得到了改善,由对照组的1.83%下降到实验组的1.09%。     

铁基载氧体的污泥化学链气化过程中氮迁移热力学模拟与实验研究

基于吉布斯自由能最小化原理,采用HSC Chemistry 6.0软件,对污泥化学链气化过程中NO_x前驱物（NH₃和HCN）与Fe₂O₃载氧体的氧化还原行为进行了热力学模拟。基于污泥热解实验中NO_x前驱物的含量,计算载氧体与污泥的摩尔比（OC/SS）对NH₃、HCN以及NH₃和HCN混合气氧化过程的影响。热力学模拟结果表明：Fe₂O₃能显著促进NO_x前驱物的氧化和裂解,主要生成N₂,几乎无NO_x生成;当NH₃、HCN以及混合气（NH₃和HCN）分别作为还原剂时,其最优OC/SS分别为0.02、0.04和0.05;由于HCN还原性强于NH₃,其氧化速率较快。基于Fe₂O₃/Al₂O₃混合物（FeAl）载氧体,实验对比了污泥化学链气化与污泥热解过程中NO_x前驱物的释放特性,发现Fe₂O₃能显著降低烟气中NO_x前驱物的产率,NH₃和HCN产率分别下降32%和62%。实验结果与热力学模拟结果一致。     

Improvement of the catalytic properties of Ti-doted Raney-Nickel for H2-Anodes of alkalione fuel cells by Ni(OH)2-surface coating

This paper belongs to a series of three dealing with the latest improvements in the alkaline H₂---O₂ fuel cells operating under mild conditions thanks to their Raney-Ni-catalysts. The first of these papers describes the benefication of a Ni(OH)₂ surface coating on the catalytic activity of Ti-doted Raney-Ni in supported electrodes. This Ni(OH)₂ surface coating is produced by carefully optimized oxidation. A Ni(OH)₂-content of 5 up to 6wt% increases the attainable current density by the factor 3–4. In addition, the exchange current density is markedly enlarged up to a Ni(OH)₂-fraction by 5%, but remains unchanged when further increasing the Ni(OH)₂ percentage. Thus, one may conclude that the Ni(OH)₂ surface coating improves markedly the charge exchange reaction. On the other side, the surface diffusion of H-atoms on the pore walls to the location of charge exchange reaction is hindered by too much Ni(OH)₂.     

Electrochromic properties of lithiated Co-oxide (LixCoO2) and Ni-oxide (LixNiO2) thin films prepared by the sol–gel route

Layered Li_xCoO₂ and Li_xNiO₂ thin films (x1) were prepared by a peroxo wet chemistry route from Li(I), Co(II) and Ni(II) acetate precursors and the addition of H₂O₂. Structural changes during the processing of xerogel to final oxide were followed by X-ray diffraction and infrared spectroscopy. Electrochromic properties were determined with in-situ potentiodynamic, potentiostatic and galvanostatic spectroelectrochemical measurements. Single dipped films with composition Li_0.99Co_1.01O₂ or Li_0.94Ni_1.06O₂ exhibited stable voltammetric response in 1 M LiClO₄/propylene carbonate electrolyte after about 60 cycles. The total charge exchanged in a reversible charging/discharging cycle was about ±30 mC cm⁻² for Li_0.99Co_1.01O₂ and ±20 mC cm⁻² for Li_0.94Ni_1.06O₂ oxide films. Galvanostatic measurements showed that about 1/2 (x0.5) and 2/3 (x0.3) of Li⁺ ions could be reversibly removed from the structure of Li_0.99Co_1.01O₂ and Li_0.94Ni_1.06O₂ films, respectively. Practical applicability of Li_0.99Co_1.01O₂ and Li_0.94Ni_1.06O₂ oxide films was studied in electrochromic devices with WO₃(H⁺)Li⁺ormolyteLi_0.99Co_1.01O₂ and WO₃(H⁺)Li⁺ormolyteLi_0.94Ni_1.06O₂ configuration. The monochromatic transmittance T_s (λ=633 nm) of dark blue coloured devices was extremely low (T_s3%), whereas in bleached state the value reached around T_s70%.     

Boosting discharge capability of α-Ni(OH)2 by cobalt doping based on robust spherical structure

α-Ni(OH)₂ is a promising candidate of the currently commercialized β-Ni(OH)₂ due to its higher theoretical discharge capacity in alkaline solution; however, its instability and poor conductivity plague the practical application. Herein, we propose α-Ni(OH)₂ with Co doping and spherical structure to strengthen the stability and enhance the conductivity and use it as the cathode for nickel-metal hydride batteries. Studies show that proper Co doping promotes the electrochemical reaction between the active materials and the electrolyte due to the spherical α-Ni(OH)₂ with enlarged interlayer distance and abundant hole channels, as well as high conductivity of Co, therefore, the obtained spherical α-Ni(OH)₂ with 7 mol% Co doping delivers significantly improved discharge capability, which is 384.6 mAh g^?1 at 70 mA g^?1 (0.2 C), increased by 54.3 mAh g^?1 compared with pure α-Ni(OH)₂, and at a high current of 5 C, it still gives 269.4 mAh g^?1, in contrast 218.5 mA g^?1 for the pure α-Ni(OH)₂. Besides, the cycling stability of the α-Ni(OH)₂ with 7 mol% Co doping maintains 340 cycles at a capacity retention of 80% (1C), which is extended 110 cycles in contrast to the pure α-Ni(OH)₂. These results provide the underpinning platform of α-Ni(OH)₂ for battery applications with high discharge ability and cycle life.     

Hydrogen production by biomass gasification in supercritical or subcritical water with Raney-Ni and other catalysts

Gasification of peanut shell, sawdust and straw in supercritical or subcritical water has been studied in a batch reactor with the presence of a series of Raney-Ni and its mixture with ZnCl₂ or Ca(OH)₂. The main gas products were hydrogen, methane, carbon dioxide, and a small amount of carbon monoxide. Different types of Raney-Ni, containing different metal components such as Fe, Mo or Cr, have different influences on the gasification yield and hydrogen selectivity. The catalysis effect can be improved obviously by adding ZnCl₂ or Ca(OH)₂. Increasing the reaction temperature or adding ZnCl₂ and Ca(OH)₂ could improve the mass of H₂ in gas products and reduce the mass of CH₄ and CO₂ at the same time. The possible mechanism is that ZnCl₂ can decompose the biomass particle by accelerating cellulose hydrolyzation in high-temperature water, increasing more specific surface to admit catalysts, while Ca(OH)₂ can absorb CO₂ to produce CaCO₃ deposit, which can drop out from the reactant system, and which will drive the reaction to get more hydrogen. With respect to the biomass conversion to gas product and selectivity of H₂ at low temperature, the series of Raney-Ni has shown many advantages over other catalysts; thus, this kind of catalyst has great potential to be utilized in the hydrogen industry for the gasification of biomass.     

Selective removal of CO from hydrogen-rich stream over CuO/CexSn1−xO2–Al2O3 catalysts

The solid solutions of Ce_xSn_1−xO₂ incorporated with alumina to form Ce_xSn_1−xO₂–Al₂O₃ mixed oxides, by the suspension/co-precipitation method, were used to prepare CuO/Ce_xSn_1−xO₂–Al₂O₃ catalysts for the selective oxidation of CO in excess hydrogen. Incorporating Al₂O₃ increased the dispersion of Ce_xSn_1−xO₂, but did not change their main structures and did not weaken their redox properties. Doping Sn⁴⁺ into CeO₂ increased the mobility of lattice oxygen and enhanced the activity of the 7%CuO/Ce_xSn_1−xO₂–Al₂O₃ catalyst in the selective oxidation of CO. The selective oxidation of CO was weakened as the doped fraction of Sn⁴⁺ exceeded 0.5. Incorporating appropriate amounts of Sn⁴⁺ and Al₂O₃ could obtain good candidates 7%CuO/Ce_xSn_1−xO₂–Al₂O₃(20%), 1–x=0.1–0.5, for a preferential oxidation (PROX) unit in a polymer electrolyte membrane fuel cell system for removing CO. Its activity was comparable with, and its selectivity was much larger than, that of the noble catalyst 5%Pt/Al₂O₃.     

Characterization of Cu(InxGa1−x)2Se3.5 thin films prepared by rf sputtering

Cu(In_xGa_1−x)₂Se_3.5 thin films were fabricated by rf sputtering from CuIn_xGa_1−xSe₂ and Na mixture target by controlling the mixture ratio. X-ray diffraction analyses show that the structure of Cu(In_xGa_1−x)₂Se_3.5, thin films is different from chalcopyrite structure: especially, CuIn₂Se_3.5 thin films have a defect chalcopyrite structure. The lattice parameters for Cu(In_xGa_1−x)₂Se_3.5 thin film are slightly smaller than those for CuIn_xGa_1−xSe₂ thin film and linearly decreased with increasing Ga content. The optical absorption coefficients for Cu(In_xGa_1−x)₂Se_3.5, thin films exceed 2 × 10⁴ cm⁻¹ in energy region above the fundamental band edge. The band gap for Cu(In_xGa_1−x)₂Se_3.5 thin films is larger than that for CuIn.Ga_1−x2Se₂ with the same Ga content and increased with increasing Ga content.     

On the computer simulation of the P–C isotherms of ZrFe2 type hydrogen storage materials

This paper deals with computer simulation of the P–C isotherms of some ZrFe₂ type (Zr(Fe_1−xCr_x)₂, Zr_1−xTi_xFe_1.4Cr_0.6, Zr_1−2xMm_xTi_xFe_1.4Cr_0.6 : x00.4) of hydrogen storage materials. A feasible mathematical model has been developed to simulate the P–C isotherms. The randomized variables in the model applied for simulating the P–C isotherms of the above-mentioned ZrFe₂ type hydrogen storage materials correspond to change in enthalpy (ΔH) and entropy (ΔS) of hydride formation. Several ZrFe₂ type materials as in above have been synthesized and their P–C isotherms, enthalpy and entropy change has been evaluated experimentally in order to have input data for simulation. A special software was developed to simulate the P–C isotherms using the said model. A close match between the experimentally observed and simulated P–C isotherms for the above said ZrFe₂ type alloys has been obtained.     

Electrochemical characteristics of iron carbide as an active material in alkaline batteries

Electrochemical properties of iron carbide (Fe₃C) for use as an alkaline battery anode were investigated during charge–discharge cycles. Results of electrochemical measurements and Mössbauer spectroscopy suggested that Fe₃C is oxidized irreversibly to Fe₃O₄ during discharge processes and that the produced Fe₃O₄ is subsequently changed to Fe(OH)₂ and Fe during the charging process, raising the discharge/charge capacity in further galvanostatic cycles. In addition, the electrode particles were observed to be less than 100 nm in diameter and to be highly dispersed on the surface of carbon black. These phenomena seems to be caused by dissolution and deposition of Fe(OH)₂ and Fe via intermediate iron species, leading to exposure of a fresh Fe₃C surface to the electrolyte after the second discharge.     

Electrochemical thermal stability of the LiFePO4/LiNi0.8Co0.15Al0.05O2 blend cathode material for lithium ion batteries

为了改善LiNi_0.8Co_0.15Al_0.05O₂正极材料的电化学热稳定性能,加入LiFePO₄共混制成了LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂锂离子电池用混合正极材料。使用X射线衍射（XRD）和扫描电子显微镜（SEM）表征了结构和形貌,测试了电化学性能。结果显示,简单球磨的混合LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂正极材料中,纳米LiFePO₄粒子包覆在LiNi_0.8Co_0.15Al_0.05O₂粒子表面提高了混合正极材料在充放电过程中的电化学稳定性和结构稳定性。LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂混合正极材料在50 ℃下循环100周容量保持率为82.0%,明显地优于单一LiNi_0.8Co_0.15Al_0.05O₂材料的72.9%。