Al_2O_3包覆对Na_(0.44)MnO_2正极材料高温储钠性能的改善

Na_(0.44)MnO_2具有特殊的三维隧道结构和良好的化学稳定性,是一种理想的钠离子电池正极材料。本文研究了Na_(0.44)MnO_2正极材料的高温电化学性能,采用液相法对Na_(0.44)MnO_2正极材料进行Al_2O_3包覆改性,并通过电化学、形貌分析、结构分析、化学成分表征等方法研究Al_2O_3包覆的改性机制。结果表明:Al_2O_3包覆层有效地隔离了Na_(0.44)MnO_2与电解液的直接接触,缓解了高温下锰的溶解,从而维持了稳定的电极/溶液界面结构。Na_(0.44)MnO_2@Al_2O_3在55°C下的电化学性能相比未包覆Na_(0.44)MnO_2有显著提升:循环100次后容量保持率达79.2%,远高于未包覆的66.5%;在10C (1C=120 mAh·g~(-1))的大电流密度下放电比容量达到63.6 mAh·g~(-1),而未包覆的仅有12.3 mAh·g~(-1)。     

NaOH浓度对Na0.44MnO2储钠性能的影响

我们通过球磨法及后续的高温焙烧合成出了短棒状的Na_0.44MnO₂,并研究了其作为碱性水溶液钠离子电池正极时,电解液NaOH浓度对其电化学性能的影响。结果表明,提高NaOH浓度有利于抑制嵌氢反应的发生并改善电极的循环性能和倍率性能,但同时也会造成析氧反应的提前触发,浓度过高时则又会降低其倍率性能。Na_0.44MnO₂在8 mol·L^?1 NaOH中表现出了最佳的电化学性能,0.5C(1C=121 mA·g^?1)的电流密度下,比容量达到79.2 mAh·g^?1,50C时,仍能释放出35.3 mAh·g^?1的比容量,在0.2–1.2 V(vs.NHE)的电压窗口内,500周后容量保持率64.3%。此外,我们也发现缩小电压窗口可以减少副反应、改善循环性能。Na_0.44MnO₂在浓碱电解液中也表现出了优异的耐过充能力。上述结果不仅表明通过优化电解液体系和测试条件可大大改善Na_0.44MnO₂的储钠性能,同时也证实了Na_0.44MnO₂作为一种水溶液钠离子电池正极材料,在大规模储能领域具有良好的应用前景。     

磷酸钒钠Na_3V_2(PO_4)_3电化学储能研究进展

锂离子电池在全球范围内的广泛应用加剧了对锂资源的消耗,其成本和原料将限制其未来发展。钠与锂具有相似物理化学性质,并且储量丰富。根据锂离子"摇椅式"电池原理,富钠离子化合物可类似富锂离子正极材料,提供可脱嵌的钠离子及结构。钠离子较锂离子大,其可逆脱嵌反应要求材料结构具有较大的容钠位与离子迁移通道。聚阴离子体磷酸钒钠Na_3V_2(PO_4)_3属于钠离子超导体(NASICON)材料,其NASICON结构骨架形成了稳定的容钠位,并且开放的三维离子迁移通道利于提高钠离子的扩散。Na_3V_2(PO_4)_3作为电池正极材料,具有理想的比容量、电压平台与循环稳定性,从而受到了广泛关注。本文首先介绍了Na_3V_2(PO_4)_3结构特点,其次结合团队已有的工作基础对Na_3V_2(PO_4)_3在钠离子电池、混合离子电池、水系电池,混合超级电容器等体系中的应用与反应机理进行了阐述;总结了基于Na_3V_2(PO_4)_3设计的复合材料与结构并探讨了Na_3V_2(PO_4)_3可能存在的问题与未来发展趋势。     

不同组分下富锂正极材料xLi_2MnO_3·(1-x)LiNi_(0.5)Mn_(0.5)O_2(x=0.1-0.8)的晶体结构与电化学性能

采用溶胶-凝胶法制备了一系列富锂锰基正极材料xLi2MnO3?(1-x)LiNi0.5Mn0.5O2(x=0.1-0.8),通过X射线衍射(XRD)仪,扫描电子显微镜(SEM)和电化学测试等检测手段表征了所得样品的晶体结构与电化学性能,研究了不同组分下富锂材料的结构与电化学性能.结果表明:Li2MnO3组分含量较高时,材料的首次放电容量较高,但循环稳定性较差;该组分含量较少时,所得样品中出现尖晶石杂相,且放电容量较低,但循环稳定性较好;综合来看,x=0.5时材料的电化学性能最优.x=0.4,0.6时材料也表现出了较好的电化学性能,值得关注.     

锌电极电化学行为Ⅵ.锌粉在碱性电解液中的电化学腐蚀

锌电极是广泛使用于一次和二次电池中的阳极材料. 在二次电池中主要是以锌粉作为电极材料. 长期以来,由于锌粉电极在充放电过程中发生形变和枝晶生长等^[1],致使它组成的二 次电池循环寿命差. 为了研究锌粉在碱性电解液中的腐蚀行为,人们通常是使用锌盘电极来模拟锌粉的情况^[2]. 但是锌盘与锌粉不同. 为此,我们采用电解沉积锌粉于锌盘电极上,制成 粉状电极研究锌粉在碱性溶液中的腐蚀行为及一些非离子型有机缓蚀剂对锌粉的缓蚀作用     

Na3V2(PO4)2O2F的合成及其在钠离子电池中的应用

目前,合成Na3V2(PO4)2O2F(NVPF)材料的方法包括高温固相法、水热法、溶剂热法等,这些方法均不利于该材料的大规模工业化生产.本文开发了温和的低温共沉淀法合成NVPF材料,该材料首次放电容量为105.6 mAh·g-1,首次效率为90.16％.经过简单的热处理过程,可以有效去除由于液相合成带来的结晶水以及吸...     

超级电容器电极材料MnO_2纳米棒的制备及其电化学性能(英文)

以洋葱碳为还原剂,KMnO4为氧化剂,稀硫酸溶液为溶剂,采用水热法一步制备MnO2纳米棒.利用X射线衍射仪和透射电子显微镜分析了MnO2纳米棒的物相、结构、形貌;将MnO2纳米棒作为电极材料组装了超级电容器,采用电池测试系统测定了超级电容器的电化学性能.结果表明,所得到的产物为α-MnO2,其直径为5~10nm,长度为50~100nm;以MnO2纳米棒作为电极材料组装的超级电容器具有较高的比容量和稳定性,有望在超级电容器的研究和应用中得到推广.     

纳米Bi-Ni氧化物改性碱性MnO2电极

电化学行为;纳米Bi-Ni氧化物改性碱性MnO2电极     

钠离子电池Na2MnSiO4正极材料的合成、结构及其电化学性能研究

首次采用溶胶-凝胶法制备Na₂MnSiO₄/C纳米复合正极材料. X射线衍射（XRD）和Rietveld结构精修结果表明,合成的Na₂MnSiO₄材料为单斜晶系、Pn空间群. 红外光谱（FTIR）结果证实材料中不含有Na₂SiO₃和SiO₂等杂质. 电化学测试结果表明,该材料在1 mol·L^-1 NaClO₄/PC电解液中,电流密度为14 mA·g^-1、电压范围为1.5 ~4.2 V（vs. Na⁺/Na）测试条件下,其首次可逆放电比容量高达113 mAh·g^-1.     

Improved Initial Charging Capacity of Na-poor Na0.44MnO2 via Chemical Presodiation Strategy for Low-cost Sodium-ion Batteries

Sodium-ion batteries(SIBs)are promising for grid-scale energy storage applications due to the natural abundance and low cost of sodium.Among various Na insertion cathode materials,Na0.44MnO2 has attracted the most attention because of its cost effectiveness and structural stability.However,the low initial charge capacity for Na-poor Na0.44MnO2 hinders its practical applications.Herein,we developed a facile chemical presodiated method using sodiated biphenly to transform Na-poor Na0.44MnO2 into Na-rich Na0.66MnO2.After presodiation,the initial charge capacity of Na0.44MnO2 is greatly enhanced from 56.5 mA·h/g to 115.7 mA·h/g at 0.1 C(1 C=121 mA/g)and the excellent cycling stability(the capacity retention of 94.1%over 200 cycles at 2 C)is achieved.This presodiation strategy would open a new avenue for promoting the practical applications of Na-poor cathode materials in sodium-ion batteries.     

掺杂λ-MnO2的制备及其在KOH水溶液中的电化学性质

电化学性能;碱性溶液;掺杂λ-MnO2的制备及其在KOH水溶液中的电化学性质     

PVA碱性凝胶聚合物电解质薄膜电化学稳定性研究

应用溶解—铸膜法制备聚乙烯醇(polyvinylalcohol,PVA)碱性凝胶聚合物电解质(gelpolymerelectrolyte,GPE)薄膜.交流阻抗(EIS)测试表明,随着KOH含量的增加,该薄膜的离子电导率表现为先增大而后减小的变化趋势,当KOH含量为42%(bymass,下同)时,电导率达到最大值,为2.01×10-3S/cm.X射线衍射(XRD)结果表明,当膜中KOH含量大于20%时,晶态的PVA就逐渐转变为非晶态结构.又当KOH含量增加到一定值后,由于体系中未电离的非晶态KOH量的增多而导致离子电导率下降.循环伏安(CV)和拉曼光谱(Raman)结果表明,该薄膜具有很好的电化学稳定性,可应用于碱性二次电池.     

Synthesis and electrode performance of carbon coated Na2FePO4F for rechargeable Na batteries

Carbon-coated Na₂FePO₄F is synthesized by a simple solid-state method with ascorbic acid as carbon source. Structural characterization of Na₂FePO₄F by synchrotron X-ray diffraction, scanning/transmission electron microscopy, and Raman spectroscopy reveals that ascorbic acid effectively suppresses the particle growth of Na₂FePO₄F, forming the nano-sized carbon coated materials. Electrode performance of Na₂FePO₄F for rechargeable sodium batteries is also examined. The carbon-coated Na₂FePO₄F sample (1.3 wt% carbon) delivers initial discharge capacity of 110 mAh g^-1 at a rate of 1/20 C (6.2 mA g^-1) with well-defined voltage plateaus at 3.06 and 2.91 V vs. Na metal. The sample also shows acceptable capacity retention and rate capability as the positive electrode materials for rechargeable Na batteries, which is operable at room temperature.     

LiV3O8在Li2SO4水溶液中的电化学性能

采用低温固相法合成了具有纳米结构的LiV₃O₈材料.扫描电子显微镜（SEM）及透射电子显微镜（TEM）测试显示该材料具有纳米结构.X射线衍射（XRD）表明该材料属于单斜晶系,P2₁Im空间群.并采用循环伏安法（CV）及电化学阻抗谱图测试对该材料在1、2 mol·L^-1Li₂SO₄水溶液及饱和Li₂SO₄水溶液中的电化学行为进行了研究.结果表明,LiV₃O₈在饱和Li₂SO₄水溶液中具有最好的电化学性能.以LiV₃O₈作为负极材料,LiNi_1/3Co_1/3Mn_1/3O₂作为正极材料,饱和Li₂SO₄水溶液作为电解液组成了水性锂离子电池,进行恒流充放电测试,结果表明,在0.5C(1C=300 mA·g^-1)的充放电倍率下,该水性锂离子电池的首次放电比容量为95.2 mAh·g^-1,循环100次后仍具有37.0 mAh·g^-1的放电比容量.     

Enhanced Electrochemical Performance of Na0.67Fe0.5Mn0.5O2Cathode with SnO2 Modification

P2-type layered oxide Na_0.67Fe_0.5Mn_0.5O₂ is recognized as a very promising cathode material for sodium-ion batteries due to the merits of high capacity, high voltage, low cost, and easy preparation. However, its unsatisfactory cycle and rate performances remain huge obstacles for practical applications. Here, we report a strategy of SnO₂ modification on P2-type Na_0.67Fe_0.5Mn_0.5O₂ to improve the cycle and rate performance. Scanning electron microscope(SEM) and transmission electron microscope(TEM) images indicate that an insular thin layer SnO₂ is coated on the surface of Na_0.67Fe_0.5Mn_0.5O₂ after medication. The coating layer of SnO₂ can protect Na_0.67Fe_0.5Mn_0.5O₂ from corrosion by electrolyte and the cycle performance is well enhanced. After 100 cycles at 1 C rate(1 C=200 mA/g), the capacity of SnO₂ modified Na_0.67Fe_0.5Mn_0.5O₂ retains 83 mA·h/g(64% to the initial capacity), while the capacity for the pristine Na_0.67Fe_0.5Mn_0.5O₂ is only 38 mA·h/g(33.5% to the initial capacity). X-Ray photoelectron spectroscopy reveals that the ratio of Mn⁴⁺ increases after SnO₂ modification, leading to less oxygen vacancy and expanded lattice. As a result, the capacity of Na_0.67Fe_0.5Mn_0.5O₂ increases from 178 mA·h/g to 197 mA·h/g after SnO₂ modification. Furthermore, the rate performance of Na_0.67Fe_0.5Mn_0.5O₂ is enhanced with SnO₂ coating, due to high electronic conductivity of SnO₂ and expanded lattice after SnO₂ coating. The capacity of SnO₂ modified Na_0.67Fe_0.5Mn_0.5O₂ at 5 C increases from 21 mA·h/g(pristine Na_0.67Fe_0.5Mn_0.5O₂) to 35 mA·h/g.     

MnO2 Nanowires as an Electrode Material for Gel Polymer Electrolyte-Based Zn-Air Battery

Zn-air batteries (ZABs) have drawn an attention due to their high energy density, less complicated chemistry, and relatively low cost. Electrocatalyst plays a significant role in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) that occurs during the operation. Various valance states of manganese make MnO₂ as an attractive electrocatalyst. In the present work, MnO₂ nanowires with diameter of 80–90 nm are synthesized via hydrothermal route and tested for electrocatalytic performance in a comparative study of ZABs fabricated using liquid and gel polymer electrolytes (GPEs). The open circuit voltage (OCV) of device lies in the range of 1.35–1.4 V. GPEs based devices show higher stability and exhibited 45 cycles (20 min per cycle) having discharge plateau above 1.06 V at a discharge current density of 1.59 mA cm⁻² while liquid electrolyte-based devices show 20 cycles (4 min per cycle at discharge current rate of 3 mA cm⁻²).