Interface-modulated fabrication of hierarchical yolk–shell Co<Subscript>3</Subscript>O<Subscript>4</Subscript>/C dodecahedrons as stable anodes for lithium and sodium storage

Transition-metal oxides (TMOs) have gradually attracted attention from researchers as anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of their high theoretical capacity.However,their poor cycling stability and inferior rate capability resulting from the large volume variation during the lithiation/sodiation process and their low intrinsic electronic conductivity limit their applications.To solve the problems of TMOs,carbon-based metal-oxide composites with complex structures derived from metal-organic frameworks (MOFs) have emerged as promising electrode materials for LIBs and SIBs.In this study,we adopted a facile interface-modulated method to synthesize yolk-shell carbon-based Co3O4 dodecahedrons derived from ZIF-67 zeolitic imidazolate frameworks.This strategy is based on the interface separation between the ZIF-67 core and the carbon-based shell during the pyrolysis process.The unique yolk-shell structure effectively accommodates the volume expansion during lithiation or sodiation,and the carbon matrix improves the electrical conductivity of the electrode.As an anode for LIBs,the yolk-shell Co3O4/C dodecahedrons exhibit a high specific capacity and excellent cycling stability (1,100 mAh·g-1 after 120 cycles at 200 mA·g-1).As an anode for SIBs,the composites exhibit an outstanding rate capability (307 mAh·g-1 at 1,000 mA·g-1 and 269 mAh·g-1 at 2,000 mA·g-1).Detailed electrochemical kinetic analysis indicates that the energy storage for Li+ and Na+ in yolk-shell Co3O4/C dodecahedrons shows a dominant capacitive behavior.This work introduces an effective approach for fabricating carbonbased metal-oxide composites by using MOFs as ideal precursors and as electrode materials to enhance the electrochemical performance of LIBs and SIBs.     

In-situ encapsulation of α-Fe2O3 nanoparticles into ZnFe2O4 micro-sized capsules as high-performance lithium-ion battery anodes

Transition metal oxides as anode materials for high-performance lithium-ion batteries suffer from severe capacity decay,originating primarily from particle pulverization upon volume expansion/shrinkage and the intrinsically sluggish electron/ion transport.Herein,in-situ encapsulation of α-Fe2O3 nanoparticles into micro-sized ZnFe2O4 capsules is facilely fulfilled through a co-precipitation process and followed by heat-treatment at optimal calcination temperature.The porous ZnFe2C4 scaffold affords a synergistic confinement effect to suppress the grain growth of α-Fe2O3 nanocrystals during the calcination process and to accommodate the stress generated by volume expansion during the charge/discharge process,leading to an enhanced interfacial conductivity and inhibit electrode pulverization and mechanical failure in the active material.With these merits,the prepared α-Fe2O3/ZnFe2O4 composite delivers prolonged cycling stability and improved rate capability with a higher specific capacity than sole α-Fe2O3 and ZnFe2O4.The discharge capacity is retained at 700 mAh g-1 after 500 cycles at 200 mA g-1 and 940 mAh g-1 after 50 cycles at 100 mA g-1.This work provides a new perspective in designing transition metal oxides for advanced lithium-ion batteries with superior electrochemical properties.     

Crystalline and amorphous MnO2 cathodes with open framework enable high-performance aqueous zinc-ion batteries

Currently, δ-MnO₂ is one of the popularly studied cathode materials for aqueous zinc-ion batteries (ZIBs) but impeded by the sluggish kinetics of Zn²⁺ and the Mn cathode dissolution. Here, we report our discovery in the study of crystalline/amorphous MnO₂ (disordered MnO₂), prepared by a simple redox reaction in the order/disorder engineering. This disordered MnO₂ cathode material, having open framework with more active sites and more stable structure, shows improved electrochemical performance in 2 mol·L⁻¹ ZnSO₄/0.1 mol·L⁻¹ MnSO₄ aqueous electrolyte. It delivers an ultrahigh discharge specific capacity of 636 mA·h·g⁻¹ at 0.1 A·g⁻¹ and remains a large discharge capacity of 216 mA·h·g⁻¹ even at a high current density of 1 A·g⁻¹ after 400 cycles. Hence disordered MnO₂ could be a promising cathode material for aqueous ZIBs. The storage mechanism of the disordered MnO₂ electrode is also systematically investigated by structural and morphological examinations of ex situ, ultimately proving that the mechanism is the same as that of the δ-MnO₂ electrode. This work may pave the way for the possibility of using the order/disorder engineering to introduce novel properties in electrode materials for high-performance aqueous ZIBs.     

高致密球形LiNi0.8Co0.1Mn0.1O2颗粒的合成及性能研究

以氨水为络合剂,NaOH为沉淀剂,通过共沉淀制备了高致密、粒度均匀的球形前驱体Ni0.8Co0.1Mn0.1(OH)2.通过焙烧该前驱体和LiOH.H2O的混合物制备出球形锂离子电池正极材料LiNi0.8Co0.1Mn0.1O2.采用XRD、SEM、TEM、TGA/DSC以及恒流充放电测试对材料的结构、形貌和电化学性能进行表征.结果表明,球形前驱体是由纳米级一次颗粒团聚形成,而不是晶粒的长大,且反应时间对前驱体的形貌、粒径分布及振实密度有显著影响.750℃焙烧16 h后的正极材料,保持了完好的球形形貌,具有最佳的层状结构和电化学性能,振实密度最大(2.98 g/cm3),首次放电容量为202.4 mAh/g,倍率性能佳,在3C的放电电流下容量为174.1 mAh/g,且循环性能优良,在40次循环以后,放电容量保持率为92.3%.     

以Fe2O3为原料通过水热–高温煅烧法合成LiFePO4/C纳米复合材料及其电化学性能研究（英文）

采用三氧化二铁(Fe2O3)为铁源,抗坏血酸作碳源,通过在200℃下水热反应并经煅烧后合成出LiFePO4/C纳米复合材料.抗坏血酸在水热反应体系中不但作为最终反应产物的碳源,而且还起到了限制LiFePO4颗粒生长的作用.抗坏血酸的用量对产物的形貌、结构、碳含量有重要影响,进而影响产物的电化学性能.当抗坏血酸用量为1 g时,制得的LiFePO4/C纳米复合材料的粒径在220～280 nm.该材料用作锂离子电池的正极材料时,在0.1C的电流密度下循环500次后其放电容量仍保持159 mAh/g,并且具有较好的倍率性能.     

Interfacial Engineering Coupled Valence Tuning of MoO3 Cathode for High‐Capacity and High‐Rate Fiber‐Shaped Zinc‐Ion Batteries

Aqueous Zn‐ion batteries (ZIBs) have garnered the researchers' spotlight owing to its high safety, cost effectiveness, and high theoretical capacity of Zn anode. However, the availability of cathode materials for Zn ions storage is limited. With unique layered structure along the [010] direction, α‐MoO₃ holds great promise as a cathode material for ZIBs, but its intrinsically poor conductivity severely restricts the capacity and rate capability. To circumvent this issue, an efficient surface engineering strategy is proposed to significantly improve the electric conductivity, Zn ion diffusion rate, and cycling stability of the MoO₃ cathode for ZIBs, thus drastically promoting its electrochemical properties. With the synergetic effect of Al₂O₃ coating and phosphating process, the constructed Zn//P‐MoO_3?x@Al₂O₃ battery delivers impressive capacity of 257.7 mAh g^?1 at 1 A g^?1 and superior rate capability (57% capacity retention at 20 A g^?1), dramatically surpassing the pristine Zn//MoO₃ battery (115.8 mAh g^?1; 19.7%). More importantly, capitalized on polyvinyl alcohol gel electrolyte, an admirable capacity (19.2 mAh cm^?3) as well as favorable energy density (14.4 mWh cm^?3; 240 Wh kg^?1) are both achieved by the fiber‐shaped quasi‐solid‐state ZIB. This work may be a great motivation for further research on molybdenum or other layered structure materials for high‐performance ZIBs.     

LiNi₁/₃Co₁/₃Mn₁/₃O₂-graphene composite as a promising cathode for lithium-ion batteries

The use of graphene as a conductive additive to enhance the discharge capacity and rate capability of LiNi(1/3)Co(1/3)Mn(1/3)O(2) electrode material has been demonstrated. LiNi(1/3)Co(1/3)Mn(1/3)O(2) and its composite with graphene (90:10 wt %) were prepared by microemulsion and ball-milling techniques, respectively. The structural and morphological features of the prepared materials were investigated with powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Characterization techniques depict single-phase LiNi(1/3)Co(1/3)Mn(1/3)O(2) with particle sizes in the range of 220-280 nm. Electrochemical studies on LiNi(1/3)Co(1/3)Mn(1/3)O(2) and LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene were conducted using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy methods by constructing a lithium half-cell. Cyclic voltammograms show the well-defined redox peaks corresponding to Ni(2+)/Ni(4+). Charge-discharge tests were performed at different C rates: 0.05, 1, and 5 between 2.5 and 4.4 V. The results indicate the better electrochemical performance of the LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene composite in terms of high discharge capacity (188 mAh/g), good rate capability, and good cycling performance compared to LiNi(1/3)Mn(1/3)Co(1/3)O(2). The improved electrochemical performance of the LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene composite is attributed to a decrease in the charge-transfer resistance.     

Hollow Bio-derived Polymer Nanospheres with Ordered Mesopores for Sodium-Ion Battery

Bio-inspired hierarchical self-assembly provides elegant and powerful bottom-up strategies for the creation of complex materials.However,the current self-assembly approaches for natural bio-compounds often result in materials with limited diversity and complexity in architecture as well as microstructure.Here,we develop a novel coordination polymerization-driven hierarchical assembly of micelle strategy,using phytic acid-based natural compounds as an example,for the spatially controlled fabrication of metal coordination bio-derived polymers.The resultant ferric phytate polymer nanospheres feature hollow architecture,ordered meso-channels of^12 nm,high surface area of 401 m2 g−1,and large pore volume of 0.53 cm3 g−1.As an advanced anode material,this bio-derivative polymer delivers a remarkable reversible capacity of 540 mAh g−1 at 50 mA g−1,good rate capability,and cycling stability for sodium-ion batteries.This study holds great potential of the design of new complex bio-materials with supramolecular chemistry.     

不同锰源对尖晶石型锰酸锂性能影响的研究

分别以自制锰源和工业用电解二氧化锰为原料,采用固相合成法,将锰源和碳酸锂的混合物合成尖晶石型锰酸锂.通过扫描电子显微镜、X射线衍射的方法研究了不同锰源合成的尖晶石型锰酸锂之间形貌和结构的区别,通过电性能测试研究了不同锰酸锂对锂离子电池电性能的影响.结果表明：合成的锰酸锂都有良好的尖晶石型立方结构,以碳酸锰为原料的自制三...     

丰富氧缺陷MnO_(x)掺杂的碳纳米纤维基锌离子电池阴极材料的制备及性能EI北大核心CSCD

可充电水系锌离子电池(ZIBs)由于性能优良、价格低廉、环境友好等优点而被广泛研究,而针对高容量、长循环寿命的ZIBs阴极结构设计成为该领域研究的热点。采用同轴静电纺丝法,以PAN溶液为皮层,含有Mn(NO_(3))_(2)·xH_(2)O的PAN溶液为芯层制备纳米纤维膜,并对其炭化后得到了一种表面具有类皮脂腺凸起结构的碳纳米纤维(MCNFs),在其表面电化学沉积MnO_(2),制得了与电解液具有优良亲和性的MnO_(2)@MCNFs阴极材料。研究表明:设计得到的类皮脂腺结构不仅增大了阴极比表面积,而且在MCNFs基底与电化学沉积的α-MnO_(2)活性物质之间形成铆接效应,加固了界面结合,减少活性物质脱落,降低界面电阻,缩短了电子传导和离子扩散路径。对其电化学性能进行测试,芯层Mn(NO_(3))_(2)·xH_(2)O含量为3%的阴极在100 mA/g的电流密度下,首周次比容量达581.16 mAh/g;在1 A/g电流密度下循环1000周次后比容量仍大于120 mAh/g,库仑效率保持在99%左右。     

Simple synthesis of a porous Sb/Sb2O3 nanocomposite for a high-capacity anode material in Na-ion batteries

High-capacity anode materials are highly desirable for sodium ion batteries.Here,a porous Sb/Sb2O3 nanocomposite is successfully synthesized by the mild oxidization of Sb nanocrystals in air.In the composite,Sb contributes good conductivity and Sb2O3 improves cycling stability,particularly within the voltage window of 0.02-1.5 V.It remains at a reversible capacity of 540 mAh·g-1 after 180 cycles at 0.66 A·g-L Even at 10 A·g-1,the reversible capacity is still preserved at 412 mAh.g-1,equivalent to 71.6％ of that at 0.066 A.g-1.These results are much better than Sb nanocrystals with a similar size and structure.Expanding the voltage window to 0.02-2.5 V includes the conversion reaction between Sb2O3 and Sb into the discharge/charge profiles.This would induce a large volume change and high structure strain/stress,deteriorating the cycling stability.The identification of a proper voltage window for Sb/Sb2O3 paves the way for its development in sodium ion batteries.     

掺杂Fe3+对高电压正极材料LiNi0.5Mn1.5O4结构和性能的影响

以Li2CO3、MnO2、NiO、FeC2O4·2H2O为原料,用高温固相法合成了尖晶石结构的LiNi0.5Mn1.5O4/LiNi0.5Mn1.45Fe0.05O4锂离子电池正极材料;并对合成的样品进行XRD、SEM及电化学性能测试。结果表明:引入Fe3+可以提高材料的结构稳定性,并且改善了材料的导电性,一定程度上减缓材料的容量衰减,LiNi0.5Mn1.45Fe0.05O4表现出较好的电化学性能,0.2C倍率下经20次充放电循环,未掺杂样品与掺杂样品的放电比容量分别为115.4mAh/g和120.1mAh/g,容量保持率由92.1%提高到96.5%。     

Synthesis and electrochemical properties of modification LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion battery

The layered LiNi1/3CO1/3Mn1/3-xMg(x)O2 (x = 0, 0.01, 0.03, 0.05) cathode materials were prepared by solid state reaction, then copper oxide was coated on the product. The structures, morphologies and electrochemical properties of the LiNi1/3Co1/3Mn1/3-xMg(x)O2 and CuO-coated LiNi1/3Co1/3Mn1/3-xMg(x)O2 were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and electrochemical tests. The results showed that the electrochemistry properties and cycle performance of magnesium doped LiNi1/3Co1/3Mn1/3O2 and CuO-coated LiNi1/3Co1/3Mn1/3-xMg(x)O2 materials were improved. The optimal doping content of Mg was x = 0.03 in the LiNi1/3Co1/3Mn1/3-xMg(x)O2 samples to achieve high discharge capacity and good cyclic stability, and the first discharge special capacity was 158.5 mAh/g at 0.2 C in the voltage of 2.5-4.3 V, then CuO-coated LiNi1/3Co1/3Mn1/3-0.03Mg0.03O2 was investigated. The electrode reaction reversibility and electronic conductivity were enhanced through Mg-doped and CuO-coated.     

基于Fe/Co-MOF制备的高性能镍铁电池铁电极及其电化学性能

铁电极是构筑高性能镍铁电池的关键。本文报道了一种基于Fe/Co-MOF制备镍铁电池铁电极的新思路,并系统研究了该材料的电化学性能。XRD、SEM和HRTEM等结果表明,Fe/Co-MOF烧结产物以八面体颗粒为主,主要由Fe_3O_4相及少量Fe-Co合金构成。作为镍铁电池的阳极时,相比于未加入Co的材料,目标材料的电化学性能得到了明显改善。Fe/Co-MOF烧结产物的放电平台稳定在1.18V,比Fe-MOF烧结产物的放电平台(1.10V)高约0.08V。尽管Fe/Co-MOF烧结产物在前10次循环出现了明显的容量衰减,但之后保持了较好的循环稳定性能,在1.0A·g-1电流密度下循环90次后比容量稳定在233.1mAh·g-1,而Fe-MOF烧结后产物的比容量仅为181.2mAh·g-1。交流阻抗结果显示Fe/Co-MOF烧结产物表现出更低的电荷传递阻抗。     

Layered Birnessite Cathode with a Displacement/Intercalation Mechanism for High-Performance Aqueous Zinc-Ion Batteries

Mn-based rechargeable aqueous zinc-ion batteries(ZIBs)are highly promising because of their high operating voltages,attractive energy densities,and eco-friendliness.However,the electrochemical performances of Mn-based cathodes usually suffer from their serious structure transformation upon charge/discharge cycling.Herein,we report a layered sodium-ion/crystal water co-intercalated Birnessite cathode with the formula of Na0.55Mn2O4·0.57H2O(NMOH)for high-performance aqueous ZIBs.A displacement/intercalation electrochemical mechanism was confirmed in the Mn-based cathode for the first time.Na+and crystal water enlarge the interlayer distance to enhance the insertion of Zn^2+,and some sodium ions are replaced with Zn^2+ in the first cycle to further stabilize the layered structure for subsequent reversible Zn^2+/H^+ insertion/extraction,resulting in exceptional specific capacities and satisfactory structural stabilities.Additionally,a pseudo-capacitance derived from the surface-adsorbed Na^+ also contributes to the electrochemical performances.The NMOH cathode not only delivers high reversible capacities of 389.8 and 87.1 mA h g^−1 at current densities of 200 and 1500 mA g^−1,respectively,but also maintains a good long-cycling performance of 201.6 mA h g^−1 at a high current density of 500 mA g^−1 after 400 cycles,which makes the NMOH cathode competitive for practical applications.     

Stabilising Cobalt Sulphide Nanocapsules with Nitrogen-Doped Carbon for High-Performance Sodium-Ion Storage

Conversion-type anode materials with a high charge storage capability generally su er from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material described in this paper, namely cobalt sulphide nanoparticles encapsulated in carbon cages(Co9S8@NC), can circumvent these problems. This electrode material exhibited a reversible sodium-ion storage capacity of 705 mAh g^-1 at 100 mA g^-1 with an extraordinary rate capability and good cycling stability. Mechanistic study using the in situ transmission electron microscope technique revealed that the volumetric expansion of the Co9S8 nanoparticles is bu ered by the carbon cages, enabling a stable electrode–electrolyte interface. In addition, the carbon shell with high-content doped nitrogen significantly enhances the electron conductivity of the Co9S8@NC electrode material and provides doping-induced active sites to accommodate sodium ions. By integrating the Co9S8@NC as negative electrode with a cellulose-derived porous hard carbon/graphene oxide composite as positive electrode and 1 M NaPF6 in diglyme as the electrolyte, the sodium-ion capacitor full cell can achieve energy densities of 101.4 and 45.8 Wh kg^-1 at power densities of 200 and 10,000 W kg^-1, respectively.     

PVDF-HFP基凝胶电解质用于LiNi0.5Co0.2Mn0.3O2三元正极锂离子电池

以聚偏氟乙烯-六氟丙烯(Poly(vinylidene fluoride-hexafluoropropylene),PVDF-HFP)为聚合物基体,新戊二醇二丙烯酸酯(Neopentyl glycol diacrylate,NPGDA)为交联剂,在引发剂偶氮二异丁腈(2,2′-Azobis(2-methylpropionitrile),AIBN)的作用下通过室温现场聚合法制备凝胶电解质用于锂离子电池。探索不同质量比PVDF-HFP/NPGDA对凝胶电解质性能和LiNi_(0.5)-Co_(0.2)Mn_(0.3)O_2三元正极锂离子电池性能的影响。结果表明,当质量比为1∶1时,凝胶电解质具有较高的离子电导率,为8.45mS·cm~(-1),锂离子迁移数为0.78,电化学窗口为4.5V。在电流密度30mA·g~(-1)恒流充放电,首次放电比容量为143mAh·g~(-1),循环50次后仍高达135.3mAh·g~(-1)。电流密度为300mA·g~(-1)时,放电比容量为100.2mAh·g~(-1)。     

Li2ZrO3包覆锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2的制备及其电化学性能

富锂锰基材料因其具有较高的充放电比容量而备受关注。针对其首次库仑效率低、循环和倍率性能差的问题,将具有三维Li^+通道的锂离子导体Li2ZrO3引入至富锂锰基正极材料Li[Li0.2Ni0.2Mn0.6]O2的表面对其进行包覆改性研究。通过XRD,TEM,SEM,EDS综合分析可知:Li2ZrO3成功包覆到样品表面。包覆层厚度为3 nm(包覆量1%,质量分数)时复合材料的电化学性能得到显著提升。0.1 C(1 C=200 mAh·g^-1)倍率下首次放电比容量可达271.5 mAh·g^-1,库仑效率为72.4%,降低了首次不可逆容量损失;0.5 C下循环100周次后放电比容量为191.5 mAh·g^-1,容量保持率为89.5%,5 C倍率放电比容量为75 mAh·g^-1,倍率性能提升。适当厚度的均匀Li2ZrO3包覆层可在样品表面形成核壳结构使样品更稳定,减少表面副反应,阻止生成较厚SEI膜,这得益于Li2ZrO3本身的高电导率、高电化学稳定性和较好的锂离子传导性。     

Al2O3膜表面包覆LiNi1/3Co1/3Mn1/3O2的微观结构和电化学特性

采用液相浸渍法在球形颗粒LiNi1／3Co1／2Mn1／3O2的表面包覆上了一层Al2O3膜．结构分析表明，表面A1203膜的厚度约100nm，具有一定的无定形结构，核体材料具有纯六方相结构．实验结果证明，表面Al2O3膜能够有效提高正极材料的耐过充能力和循环稳定性．在截止电压为3．0—4．5V，充放电倍率为1C的条件下，Al2O3表面包覆膜后正极活性物质50次循环的容量保持率提高了11．5％．     

二次水热法制备鸟巢状TiO2/Co3O4纳米结构及其锂电性能

以TiO_2粉末和NaOH为原料,在机械外力场作用下,采用水热法制备TiO_2纳米线。随后将得到的TiO_2纳米线与六水合硝酸钴(Co(NO_3)_2·6H_2O)和尿素(Urea)共同水热反应制备TiO_2/Co_3O_4纳米结构材料。分别利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、电池充放电测试仪和电化学工作站等,对材料的相组成、微观形貌、锂电性能和阻抗性能进行测试。结果表明,TiO_2/Co_3O_4纳米复合材料为鸟巢状结构,其在33.5mA/g电流密度下恒电流充放电的首次放电容量为777mAh/g,充电容量为759mAh/g,100次循环后的可逆容量仍保持在663mAh/g,具有良好的循环稳定性和电化学特性。