高容量有机正极材料杯[4]醌在离子液体中的储锂性能

选用理论容量高达446 mAh·g~(-1)的杯[4]醌(calix[4]quinone,C4Q)作为正极材料,研究其储锂性能。由于C4Q在常规有机电解液中的溶解问题会在一定的程度上限制其性能最大化,我们选用Li[TFSI]/[PY13][TFSI]([PY13][TFSI]:1-丙基-1-甲基吡咯烷鎓双三氟甲基磺酰亚胺)离子液体电解液与C4Q进行匹配组装锂离子电池,较大程度地提升了其循环稳定性和倍率性能。在0.1C的电流密度下,循环100圈后的放电比容量为280 mAh·g~(-1),1 000圈后的容量保持率高达72%。当电流密度增加至1C时,放电容量仍有154 mAh·g~(-1)。     

Niobium oxyphosphate nanosheet assembled two-dimensional anode material for enhanced lithium storage

The development of high-capacity and high-rate anodes has become an attractive endeavor for achieving high energy and power densities in lithium-ion batteries(LIBs).Herein,a new-type anode material of reduced graphene oxide(rGO) supported niobium oxyphosphate(NbOPO_4) nanosheet assembled twodimensional composite material(NbOPO_4/rGO) is firstly fabricated and presented as a promising highperformance LIB anode material.In-depth electrochemical analyses and in/ex situ characterizations reveal that the intercalation-conversion reaction takes place during the first discharge process,followed by the reversible redox process between amorphous NbPO_4 and Nb which contributes to the reversible capacity in the subsequent cycles.Meanwhile,the lithiation-generated Li3 PO_4,behaving as a good lithium ion conductor,facilitates ion transport.The rGO support further regulates the structural and electron/ion transfer properties of NbOPO_4/rGO composite compared to neat NbOPO_4, resulting in greatly enhanced electrochemical performances.As a result,NbOPO_4/rGO as a new-type LIB anode material achieves a high capacity of 502.5 mAh g^-1 after 800 cycles and outstanding rate capability of 308.4 mAh g^-1 at 8 A g^-1.This work paves the way for the deep understanding and exploration of phosphate-ba sed high-efficiency anode materials for LIBs.     

Nd3+掺杂对LiFePO4结构及电化学性能的改善

采用两步加热高温固相法合成了掺杂Nd3+的LiFe1-xNdxPO4/C复合材料(x=0,0.01,0.02,0.04,0.06,0.08).用TG-DSC对前驱体进行分析和SQUID(超导量子干涉仪)对样品中Fe3+的磁性测定,优化了合成工艺条件;采用XRD、FE-SEM、EDS等方法分析了样品的结构并对其电化学性能进行了测试.结果表明:LiFe1-xNdxPO4/C复合材料具有橄榄石型结构;当Nd3+的掺杂量6%(物质的量分数)、煅烧温度700℃、煅烧时间16h时,样品在0.2C(1C=170.0mA·g-1)电流密度下的最大放电比容量可达165.2mAh·g-1,循环100次后的容量保持率仍为92.8%,在1C、2C、5C下的最大放电比容量分别为146.8、125.7和114.8 mAh·g-1.通过测定样品在不同较低倍率下的放电比容量,采用外推法得出制备样品的实测理论比容量为168.7 mAh·g-1.     

Porous bowl-shaped VS_2 nanosheets/graphene composite for high-rate lithium-ion storage

Two-dimensional (2D) layered vanadium disulfide (VS_2) is a promising anode material for lithium ion batteries (LIBs) due to the high theoretical capacity.However,it remains a challenge to synthesize monodispersed ultrathin VS_2 nanosheets to realize the full potential.Herein,a novel solvothermal method has been developed to prepare the monodispersed bowl-shaped NH_3-inserted VS_2 nanosheets (VS_2).The formation of such a unique structure is caused by the blocked growth of (001) or (002) crystal planes in combination with a ripening process driven by the thermodynamics.The annealing treatment in Ar/H_2creates porous monodispersed VS_2(H-VS_2),which is subsequently integrated with graphene oxide to form porous monodispersed H-VS_2/rGO composite coupled with a reduction process.As an anode material for LIBs,H-VS_2/rGO delivers superior rate performance and longer cycle stability:a high average capacity of 868/525 mAh g~(-1) at a current density of 1/10 A g~(-1);a reversible capacity of 1177/889 mAh g~(-1) after 150/500 cycles at 0.2/1 A g~(-1).Such excellent electrochemical performance may be attributed to the increased active sites available for lithium storage,the alleviated volume variations and the shortened Li-ion diffusion induced from the porous structure with large specific surface area,as well as the protective effect from graphene nanosheets.     

Electrospun Sb2Se3@C nanofibers with excellent lithium storage properties

Antimony-based materials have become promising anodes within lithium-ion batteries(LIBs)due to their low cost and the high theoretical capacity.However,there is a potential to further enhance the electrochemical performance of such antimony-based materials.Herein,Sb2Se3@C nanofibers(Sb2Se3@CNFs)are designed and obtained via a novel electrospinning method.Upon electrochemically testing as an anode within LIBs,the Sb2Se3@CNFs(annealed at 600℃)delivers a remarkably good cycling performance of 625 mAh/g at 100 mA/g after 100 cycles.Moreover,it still remains at 490 mAh/g after 500 cycles with an applied current density of 1.0 A/g.The excellent performance of the Sb2 Se3@CNFs can be attributed to the fact that the N-doped C matrices not only remit the volume expansion of materials,but also enhance the electrical and ionic conductivity thusly increasing the lithium-ion diffusion.The obtained Sb2Se3@CNFs are promising anode for LIBs in the future.     

Amorphous Zr(OH)_4 coated LiNi_(0.915)Co_(0.075)Al_(0.01)O_2 cathode material with enhanced electrochemical performance for lithium ion batteries

LiNi_(0.915)Co_(0.075)Al_(0.01)O_2(NCA) with Zr(OH)_4 coating is demonstrated as high performance cathode material for lithium ion batteries(LIBs). The coated materials are synthesized via a simple dry coating method of NCA with Zr(OH)_4 powders, and then characterized with scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). Experimental results show that amorphous Zr(OH)_4 powders have been successfully coated on the surface of spherical NCA particles, exhibiting improved electrochemical performance. 0.50 wt% Zr(OH)_4 coated NCA delivers a capacity of 197.6 mAh/g at the first cycle and 154.3 mAh/g after 100 cycles with a capacity retention of 78.1% at 1 C rate. In comparison, the pure NCA shows a capacity of 194.6 mAh/g at the first cycle and 142.5 mAh/g after 100 cycles with a capacity retention of 73.2% at 1 C rate. Electrochemical impedance spectroscopy(EIS) results show that the coated material exhibits a lower resistance, indicating that the coating layer can efficiently suppress transition metals dissolution and decrease the side reactions at the surface between the electrode and electrolyte. Therefore, surface coating with amorphous Zr(OH)_4 is a simple and useful method to enhance the electrochemical performance of NCA-based materials for the cathode of LIBs.     

Electrochemical Properties of PP13TFSI-LiTFSI-P(VdF-HFP) Ionic Liquid Gel Polymer Electrolytes (cited: 1)

N-Methyl-N-propylpiperidiniumbis(trifluoromethanesulfonyl)imide (PP13TFSI), bis(triflu-oromethanesulfonyl)imide lithium salt (LiTFSI), and poly(vinylidene difluoride-co-hexafluoropropylene) (P(VdF-HFP)) were mixed and made into ionic liquid gel polymerelectrolytes (ILGPEs) by solution casting. The morphology of ILGPEs was observed by scanning electron microscopy. It was found that the ILGPE had a loosened structure with liquid phase uniformly distributed. The ionic conductivity, lithium ion transference num-ber and electrochemical window were measured by electrochemical impedance spectroscopy, chronoamperometric and linear sweep voltammetry. The ionic conductivity and lithium ion transference number of this ILGPE reached 0.79 mS/cm and 0.71 at room temperature, and the electrochemical window was 0 to 5.1 V vs. Li⁺/Li. Battery tests indicated that the ILGPE is stable when being operated in Li/LiFePO₄ batteries. The discharge capacity maintained at about 135, 117, and 100 mAh/g at 30, 75, and 150 mA/g rates, respectively. The capacity retentions were almost 100% after 100 cycles without little capacity fading.     

Yolk-shell Si/C composites with multiple Si nanoparticles encapsulated into double carbon shells as lithium-ion battery anodes

The conceptual design of yolk-shell structured Si/C composites is considered to be an effective way to improve the recyclability and conductivity of Si-based anode materials. Herein, a new type of yolk-shell structured Si/C composite(denoted as TSC-PDA-B) has been intelligently designed by rational engineering and precise control. In the novel structure, the multiple Si nanoparticles with small size are successfully encapsulated into the porous carbon shells with double layers benefiting from the strong etching effect of HF. The TSC-PDA-B product prepared is evaluated as anode materials for lithium-ion batteries(LIBs).The TSC-PDA-B product exhibits an excellent lithium storage performance with a high initial capacity of 2108 mAh g~(-1) at a current density of 100 mA g~(-1) and superior cycling performance of 1113 mAh g~(-1) over 200 cycles. The enhancement of lithium storage performance may be attributed to the construction of hybrid structure including small Si nanoparticles, high surface area, and double carbon shells, which can not only increase electrical conductivity and intimate electrical contact with Si nanoparticles, but also provide built-in buffer voids for Si nanoparticles to expand freely without damaging the carbon layer.The present findings can provide some scientific insights into the design and the application of advanced Si-based anode materials in energy storage fields.     

Pushing Up Lithium Storage through Nanostructured Polyazaacene Analogues as Anode

According to the evidence from both theoretical calculations and experimental findings, conjugated ladder polymers containing large π‐conjugated structure, a high number of nitrogen heteroatoms, and a multiring aromatic system, could be an ideal organic anode candidate for lithium‐ion batteries (LIBs). In this report, we demonstrated that the nanostructured polyazaacene analogue poly(1,6‐dihydropyrazino[2,3g]quinoxaline‐2,3,8‐triyl‐7‐(2H)‐ylidene‐7,8‐dimethylidene) (PQL) shows high performance as anode materials in LIBs: high capacity (1750 mAh g^?1, 0.05C), good rate performance (303 mAh g^?1, 5C), and excellent cycle life (1000 cycles), especially at high temperature of 50 °C. Our results suggest nanostructured conjugated ladder polymers could be alternative electrode materials for the practical application of LIBs.     

Enhanced Anode Performances of Polyaniline-TiO(2)-Reduced Graphene Oxide Nanocomposites for Lithium Ion Batteries

Here, we report a three-layer-structured hybrid nanostructure consisting of transition metal oxide TiO(2) nanoparticles sandwiched between carbonaceous polymer polyaniline (PANI) and graphene nanosheets (termed as PTG), which, by simultaneously hindering the agglomeration of TiO(2) nanoparticles and enhancing the conductivity of PTG electrode, enables fast discharge and charge. It was demonstrated that the PTG exhibited improved electrochemical performance compared to pure TiO(2). As a result, PTG nanocomposite is a promising anode material for highly efficient lithium ion batteries (LIBs) with fast charge/discharge rate and high enhanced cycling performance [discharge capacity of 149.8 mAh/g accompanying Coulombic efficiency of 99.19% at a current density of 5C (1000 mA/g) after 100 cycles] compared to pure TiO(2). We can conclude that the concept of applying three-layer-structured graphene-based nanocomposite to electrode in LIBs may open a new area of research for the development of practical transition-metal oxide graphene-based electrodes which will be important to the progress of the LIBs science and technology.     

Cyclotetrabenzil Derivatives for Electrochemical Lithium-Ion Storage

Organic electrode materials could revolutionize batteries because of their high energy densities, the use of Earth-abundant elements, and structural diversity which allows fine-tuning of electrochemical properties. However, small organic molecules and intermediates formed during their redox cycling in lithium-ion batteries (LIBs) have high solubility in organic electrolytes, leading to rapid decay of cycling performance. We report the use of three cyclotetrabenzil octaketone macrocycles as cathode materials for LIBs. The rigid and insoluble naphthalene-based cyclotetrabenzil reversibly accepts eight electrons in a two-step process with a specific capacity of 279 mAh g⁻¹ and a stable cycling performance with ≈65 % capacity retention after 135 cycles. DFT calculations indicate that its reduction increases both ring strain and ring rigidity, as demonstrated by computed high distortion energies, repulsive regions in NCI plots, and close [C⋅⋅⋅C] contacts between the naphthalenes. This work highlights the importance of shape-persistency and ring strain in the design of redox-active macrocycles that maintain very low solubility in various redox states.     

哌啶型离子液体混合电解液在Li/LiCoO2电池中的性能研究

合成并考察了N-甲基-N-乙（丙,丁）基哌啶-二( 三氟甲基磺酰) 亚胺三种离子液体( PP12（3,4）TFSI )作为电解液添加剂的影响. 使用热分析和电化学技术研究了离子液体混合电解液的热稳定性和电化学性能.实验表明,哌啶型离子液体可以提高有机电解液的热稳定性,并且侧链的长短对 LiCoO₂ 电极的电化学性能有重要的影响.当以PP13TFSI配成的混合电解液,在3.0~4.35 V之间、电流密度为150 mA•g^-1时, LiCoO₂ 电极的首次放电容量为156.6 mAh•g^-1,200周循环后容量为133.9mAh•g^-1,容量保持率为85.5%,远远优于在传统有机电解液中的循环性能.     

Cost‐Effective Biomass Carbon/Calix[4]Quinone Composites for Lithium Ion Batteries

Searching for new cheap encapsulating materials to decrease the solubility of organic small molecules as the cathode materials in electrolytes and improve the performance of organic lithium‐ion batteries (LIBs) is very important and highly desirable. In this research, we found that a novel cheap biomass carbon (named as PPL), prepared by pyrolyzing calyxes of Physalis Peruviana L, can efficiently encapsulate calix[4]quinone to form composites, which can be used as cathodes in LIBs. The initial discharge capacity of the as‐fabricated battery was 437 mAh g^?1 and could maintain 228 mAh g^?1 after 100 cycles. Even at 1 C, the discharge capacity was still 217 mAh g^?1.     

A1掺杂量对正极材料LiNi_(1/3)Co_(2/3-x)A1_xO_2结构和电化学性能的影响

以共沉淀法合成的前驱体Ni_(1/3)Co_(2/3-x)Al_x(OH)_2与低共熔锂盐0.38LiOH·H_2O-0.62LiNO_3制备了锂离子电池正极材料LiNi_(1/3)Co_(2/3-x)Al_xO_2(x=1/12,1/3,1/2,7/12).采用X射线衍射(XRD)、扫描电镜(SEM)和电化学性能测试对其结构、形貌和电化学性质进行表征.结果表明,LiNi_(1/3)Co_(2/3-x)Al_xO_2在1/12≤x≤1/3范围内可以保持单一的六方层状a-NaFeO_2结构,当A1掺杂量(x)高于1/3时,会出现杂相.其中,LiNi_(1/3)Co_(1/3)Al_(1/3)O_2结晶程度最高,阳离子混排效应最小,并且颗粒小而均匀,振实密度可以达到2.88 g·cm~(-3),首次放电容量为151.5 mAh·g~(-1),循环50次后放电容量保持在91.4%,在1C和2C倍率下放电容量仍可达到133.7和120.9 mAh·g~(-1)     

A Biodegradable Polydopamine‐Derived Electrode Material for High‐Capacity and Long‐Life Lithium‐Ion and Sodium‐Ion Batteries

Polydopamine (PDA), which is biodegradable and is derived from naturally occurring products, can be employed as an electrode material, wherein controllable partial oxidization plays a key role in balancing the proportion of redox‐active carbonyl groups and the structural stability and conductivity. Unexpectedly, the optimized PDA derivative endows lithium‐ion batteries (LIBs) or sodium‐ion batteries (SIBs) with superior electrochemical performances, including high capacities (1818 mAh g^?1 for LIBs and 500 mAh g^?1 for SIBs) and good stable cyclabilities (93 % capacity retention after 580 cycles for LIBs; 100 % capacity retention after 1024 cycles for SIBs), which are much better than those of their counterparts with conventional binders.     

原位聚合法制备凝胶型离子液体／PMMA聚合物电解质

采用原位聚合法制备了含有N-甲基、丙基哌啶双三氟甲磺酰亚胺离子液体的凝胶型聚合物电解质．利用SEM和XPS测试了电解质膜与LiFePO4电极的界面状态,充放电循环后,在电解质膜与LiFePO4之间有一层薄膜,这层薄膜中含有N和S元素．结果表明,随着充放电的不断进行,凝胶型电解质中未聚合的甲基丙烯酸甲酯与电极表面的锂离子之间发生电子转移,形成SEI膜,至少要三个循环后才能形成稳定的SEI膜．随着SEI膜的增厚,放电容量增加,阻碍了电子转移,使系统更加的稳定．在不同倍率下测试了凝胶型离子液体／PMMA聚合物电解质电池性能,当充放电达到30个循环时,0．2、0．5和1C下电池比容量分别为132、128和120mAh／g．     

热处理对富氮碳纳米纤维结构及储锂性能的影响

以聚丙烯腈(PAN)为原料,经静电纺丝、稳定化和碳化,制备了碳纳米纤维(CNFs)。系统地研究了氮的种类及含量对锂离子电池(LIBs)中Li+的储存性能和负极容量的影响。碳化过程中纤维从无定形碳向石墨化碳结构转变,含氮官能团减少,结构的变化对Li+在CNFs电极中的存储位置有很大的影响。结果表明,Li+不仅可以存储在石墨化碳层之间,还可以存储在氮功能化引起的缺陷部位,后者主要是由于碳材料的氮掺杂而使LIBs的电化学性能改善。碳化温度为600℃时,可以产生足够高的氮含量,从而提高电极的容量。在电流密度为0.1 A·g^-1时,循环200次之后比容量高达560 mAh·g^-1,即使在1 A·g^-1的高电流密度下,循环1000次比电容量仍然保持在200 mAh·g^-1。     

Design of hierarchical and mesoporous FeF3/rGO hybrids as cathodes for superior lithium-ion batteries

Iron fluoride (FeF₃) is considered as a promising cathode material for Li-ion batteries (LIBs) due to its high theoretical capacity (712 mAh/g) with a 3e^? transfer. Herein, we have designed a strategy of hierarchical and mesoporous FeF₃/rGO hybrids for LIBs, where the hollow FeF₃ nanospheres are the main contributor to the specific capacity and the 2D rGO nanosheets are the matrix elevating the electronic conductivity and buffering the volume expansion. The unique FeF₃/rGO hybrid can be rationally synthesized by a non-aqueous in-situ precipitation method, offering the merits of large specific surface area with rich active sites, fast transport channels for lithium ions, effective alleviation of volume expansion during cycles, and accelerating the electrochemical reaction kinetics. The FeF₃/rGO hybrid electrode possesses a high initial discharge capacity of 553.9 mAh/g at a rate of 0.5 C with 378 mAh/g after 100 cycles, acceptable rate capability with 168 mAh/g at 2 C, and feasible high-temperature operation (320 mAh/g at 70 °C). The superior electrochemical behaviors presented here demonstrates that the FeF₃/rGO hybrid is a potential electrode for LIBs, which may open up a new vision to design high-efficiency energy-storage devices such as LIBs based on transition metal fluorides.     

Zr~(4+)离子掺杂对LiFePO_4结构及电化学性能的影响

应用固相反应法于惰性气氛下合成掺Zr的L iFePO4正极材料.考察Zr4+掺杂浓度对于目标化合物结构及其电化学性能的影响.XRD,交流阻抗和恒流充放电测试等实验表明,少量的Zr4+掺杂并未影响目标材料产物的结构,反而有利于降低L iFePO4电荷转移反应的阻抗,从而有利于克服该电极过程中的动力学限制.该正极材料表现出优良的倍率放电性能,在0.1C倍率下,L i0.99Zr0.01FePO4的首次放电比容量达135.6mAh.g-1.30次循环后,容量衰减仅3.8%.     

Two π-Conjugated Covalent Organic Frameworks with Long-Term Cyclability at High Current Density for Lithium Ion Battery

Organic lithium ion batteries (LIBs) are considered as one of the next-generation green electrochemical energy storage (EES) devices. However, obtaining both high capacity and long-term cyclability is still the bottleneck of organic electrode materials for LIBs because of weak structural and chemical stability and low conductivity. Covalent organic frameworks (COFs) show potential to overcome these problems owing to its good stability and high capacity. Herein, the synthesis and characterization of two π-conjugated COFs, derived from the Schiff-base reaction of 2,4,6-triaminopyrimidne (TM) respectively with 1,4-phthalaldehyde (PA) and 1,3,5-triformylbenzene (TB) by a mechanochemical process are presented. As anode materials for LIBs, the COFs exhibit favorable electrochemical performance with the highest reversible discharge capacities of up to 401.3 and 379.1 mAh g⁻¹ at a high current density (1 A g⁻¹), respectively, and excellent long-term cyclability with 74.8 and 72.7 % capacity retention after 2000 cycles compared to the initial discharge capacities.