Porous Si-Cu3Si-Cu Microsphere@C Core–Shell Composites with Enhanced Electrochemical Lithium Storage

Low-cost Si-based anode materials with excellent electrochemical lithium storage present attractive prospects for lithium-ion batteries (LIBs). Herein, porous Si-Cu₃Si-Cu microsphere@C composites are designed and prepared by means of an etching/electroless deposition and subsequent carbon coating. The composites show a core–shell structure, with a porous Si/Cu microsphere core surrounded by the N-doped carbon shell. The Cu and Cu₃Si nanoparticles are embedded inside porous silicon microspheres, forming the porous Si/Cu microsphere core. The microstructure and lithium storage performance of porous Si-Cu₃Si-Cu microsphere@C composites can be effectively tuned by changing electroless deposition time. The Si-Cu₃Si-Cu microsphere@C composite prepared with 12 min electroless deposition delivers a reversible capacity of 627 mAh g⁻¹ after 200 cycles at 2 A g⁻¹, showing an enhanced lithium storage ability. The superior lithium storage performance of the Si-Cu₃Si-Cu microsphere@C composite can be ascribed to the improved electronic conductivity, enhanced mechanical stability, and better buffering against the large volume change in the repeated lithiation/delithiation processes.     

FeP nanoparticles derived from metal-organic frameworks/GO as high-performance anode material for lithium ion batteries

Double carbon coated Fe P composite(Fe P@NC@r GO)was in situ fabricated via the phosphorization process of the as-prepared Prussian blue@graphene oxide(PB@GO)precursor.The Fe P nanocrystals were successfully embedded in the nitrogen-doped porous carbon matrix.When used as the anode for lithium ion batteries(LIBs),the Fe P@NC@r GO anode shows superior lithium storage properties,delivering a high specific capacity of 830 m A h g~(-1)after 100 cycles at 100 m A g~(-1)and excellent rate capability of 359 m A h g~(-1)at 5 A g~(-1).The outstanding performance mainly ascribes to the synergistic effect of the double carbon coating and porous structure design.The introduction of porous carbon and graphene coating on Fe P nanoparticles greatly enhance the electronic conductivity of the active material and well accommodates the large volume variation of Fe P during the cycling process.     

Construction of CoS_2 nanoparticles embedded in well-structured carbon nanocubes for high-performance potassium-ion half/full batteries

Metal sulfides have been widely investigated as promising electrode materials for potassium-ion batteries(PIBs) due to their high theoretical capacities.However,the practical application of metal sulfides in PIBs is still hindered by their intrinsic shortcomings of low conductivity and severe volume changes during the potassiation/depotassiation process.Herein,a simple template-based two-step annealing strategy is proposed to impregnate CoS_2 nanoparticles in the well-structured carbon nanocubes(denoted CoS_2/CNCs) as an advanced anode material for PIBs.The ex-situ XRD measurements reveal the K storage mechanism in CoS_2/CNCs.Benefiting from the unique structures,including abundant active interfacial sites,high electronic conductivity,and significantly alleviated volume variation,CoS_2/CNCs present a high specific capacity(537.3 mAh g~(-1) at0.1 A g~(-1)),good cycling stability(322.4 mAh g~(-1) at 0.5 A g~(-1) after 300 cycles),and excellent rate capability(153.1 mAh g~(-1) at5 A g~(-1)).Moreover,the obtained nanocomposite shows superior potassium storage properties in K-ion full cells when it is coupled with a KVP04 F cathode.     

Polydopamine-mediated synthesis of Si@carbon@graphene aerogels for enhanced lithium storage with long cycle life

The application of Si as the anode materials for lithium-ion batteries (LIBs) is still severely hindered by the rapid capacity decay due to the structural damage caused by large volume change (> 300%) during cycling. Herein, a three-dimensional (3D) aerogel anode of Si@carbon@graphene (SCG) is rationally constructed via a polydopamine-assisted strategy. Polydopamine is coated on Si nanoparticles to serve as an interface linker to initiate the assembly of Si and graphene oxide, which plays a crucial role in the successful fabrication of SCG aerogels. After annealing the polydopamine is converted into N-doped carbon (N-carbon) coatings to protect Si materials. The dual protection from N-carbon and graphene aerogels synergistically improves the structural stability and electronic conductivity of Si, thereby leading to the significantly improved lithium storage properties. Electrochemical tests show that the SCG with optimized graphene content delivers a high capacity (712 mAh/g at 100 mA/g) and robust cycling stability (402 mAh/g at 1 A/g after 1500 cycles). Furthermore, the full cell using SCG aerogels as anode exhibits a reversible capacity of 187.6 mAh/g after 80 cycles at 0.1 A/g. This work provides a plausible strategy for developing Si anode in LIBs.     

Preparation and electrochemical properties of core-shell Si/SiO nanocomposite as anode material for lithium ion batteries

The Si/SiO nanocomposite was synthesized by a sol–gel method in combination with a following heat-treatment process. It was analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV) and capacity measurement as anode material for lithium ion battery. Si nanoparticles were coated with SiO and a core-shell structured nanocomposite was formed. The core-shell Si/SiO nanocomposite displays better reversibility of lithium insertion/extraction and higher coulomb efficiency than virginal Si nanoparticles. The SiO shell envelops the Si nanoparticles to suppress the aggregation of the nanoparticles during cycling. As a result, the core-shell Si/SiO nanocomposite exhibits better capacity retention than virginal Si nanoparticles, indicating that this is a promising approach to improve the electrochemical performance of nano anode materials for lithium ion battery.     

Designing N-doped graphene/ReSe_2/Ti_3C_2 MXene heterostructure frameworks as promising anodes for high-rate potassium-ion batteries

Developing high-performance anodes for potassium ion batteries(KIBs) is of paramount significance but remains challenging.In the normal sense,electrode materials are prepared by ubiquitous wet chemical routes,which otherwise might not be versatile enough to create desired heterostructures and/or form clean interfacial areas for fast transport of K-ions and electrons.Along this line,rate capability/cycling stability of resulting KIBs are greatly handicapped.Herein we present an all-chemical vapor deposition approach to harness the direct synthesis of nitrogen-doped graphene(NG)/rhenium diselenide(ReSe_2)hybrids over three-dimensional MXene supports as superior heterostructure anode material for KIBs.In such an innovative design,1 T'-ReSe2 nanoparticles are sandwiched in between the NG coatings and MXene frameworks via strong interfacial interactions,thereby affording facile K~+ diffusion,enhancing overall conductivity,boosting high-power performance and reinforcing structural stability of electrodes.Thus-constructed anode delivers an excellent rate performance of 138 mAh g^-1 at 10.0 A g^-1 and a high reversible capacity of 90 mAh g^-1 at 5 A g^-1 after 300 cycles.Furthermore,the potassium storage mechanism has been systematically probed by advanced in situlex situ characterization techniques in combination with first principles computations.     

Metal–Organic Frameworks-Derived Mesoporous Si/SiOx@NC Nanospheres as a Long-Lifespan Anode Material for Lithium-Ion Batteries

Silicon (Si)-based anode materials with suitable engineered nanostructures generally have improved lithium storage capabilities, which provide great promise for the electrochemical performance in lithium-ion batteries (LIBs). Herein, a metal–organic framework (MOF)-derived unique core–shell Si/SiO_x@NC structure has been synthesized by a facile magnesio-thermic reduction, in which the Si and SiO_x matrix were encapsulated by nitrogen (N)-doped carbon. Importantly, the well-designed nanostructure has enough space to accommodate the volume change during the lithiation/delithiation process. The conductive porous N-doped carbon was optimized through direct carbonization and reduction of SiO₂ into Si/SiO_x simultaneously. Benefiting from the core–shell structure, the synthesized product exhibited enhanced electrochemical performance as an anode material in LIBs. Particularly, the Si/SiO_x@NC-650 anode showed the best reversible capacities up to 724 and 702 mAh g⁻¹ even after 100 cycles. The excellent cycling stability of Si/SiO_x@NC-650 may be attributed to the core–shell structure as well as the synergistic effect between the Si/SiO_x and MOF-derived N-doped carbon.     

Improving the electrode performance of Ge through Ge@C core-shell nanoparticles and graphene networks

Germanium is a promising high-capacity anode material for lithium ion batteries, but it usually exhibits poor cycling stability because of its huge volume variation during the lithium uptake and release process. A double protection strategy to improve the electrode performance of Ge through the use of Ge@C core-shell nanostructures and reduced graphene oxide (RGO) networks has been developed. The as-synthesized Ge@C/RGO nanocomposite showed excellent cycling performance and rate capability in comparison with Ge@C nanoparticles when used as an anode material for Li ion batteries, which can be attributed to the electronically conductive and elastic RGO networks in addition to the carbon shells and small particle sizes of Ge. The strategy is simple yet very effective, and because of its versatility, it may be extended to other high-capacity electrode materials with large volume variations and low electrical conductivities.     

Development of a high-performance anode for lithium ion batteries using novel ordered mesoporous tungsten oxide materials with high electrical conductivity

An ordered mesoporous WO(3-X) with high electrical conductivity (m-WO(3-X)) was prepared and evaluated as an anode material for lithium ion batteries (LIBs). Ordered mesoporous tungsten trioxide (m-WO(3)) with an identical pore structure to that of m-WO(3-X) and bulk WO(3-X) (b-WO(3-X)) was prepared for the comparison purpose. An m-WO(3-X) electrode exhibited a high reversible capacity (748 mAh g(-1), 6.5 Li/W) and a high volumetric capacity (～1500 mAh cm(-3)), which is comparable to the Li metal itself (ca. 2000 mAh cm(-3)). Also, an improved rate capability and a good cyclability were observed in the m-WO(3-X) electrode when compared with m-WO(3) and b-WO(3-X) electrodes. From electrochemical impedance spectroscopy (EIS) analysis, the advanced anode performance of the m-WO(3-X) electrode was probably attributed to large ordered mesopores and a high electrical conductivity. Differential scanning calorimetry (DSC) result displayed that the safety of m-WO(3-X) was more improved than those of graphite and Si anode materials.     

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。     

二次包覆法制备煤沥青基硅/碳复合物及其锂离子电池性能

本文采用市售纳米硅为硅源,以软化点低、得碳率高、价格便宜的煤沥青作为碳源,通过两步包覆法制备了煤沥青基硅/碳(Si/C/C)复合物,并研究其作为锂离子电池负极材料的电化学性能。 结果表明,所得复合物的粒径在300~350 nm间,Si纳米粒子被C包覆并相互连结成C-Si-C网络结构,其中Si含量为27%的硅/碳复合物(Si/C/C-27%)作为锂电池电极材料表现了良好的储锂性能。 在0.1 A/g的小电流密度下,Si/C/C-27%的放电比容量为1281 mA·h/g;在3 A/g的大电流密度下,其放电比容量仍能保持在582 mA·h/g,表现了良好的倍率性能。Si/C/C-27%在2 A/g的电流密度下经过100次的循环后其比容量保持率为76.61%,表现了良好的循环稳定性。 相比于煤沥青基碳的一次包覆所得的硅/碳复合材料(Si/C),Si/C/C有效提高了Si纳米粒子的导电性并抑制了其在嵌锂和脱锂过程中的体积膨胀。 本文提出的二次包覆的新方法为制备具有优异电化学性能的锂离子电池负极材料提供了新的研究思路。     

Enhanced anode performances of the Fe3O4-carbon-rGO three dimensional composite in lithium ion batteries

A three dimensional composite was constructed by anchoring Fe(3)O(4) nanoparticles encapsulated within carbon shells onto reduced graphene oxide sheets, which exhibited enhanced anode performances in lithium ion batteries with a specific capacity of 842.7 mAh g(-1) and superior recycle stability after 100 cycles.     

基于不同前驱体制备的硬碳负极材料的储锂性能

以聚丙烯腈、石油沥青和花生壳为前驱体,在1200℃下碳化制备三种不同的硬碳材料。通过扫描电子显微、X射线衍射、氮气吸附/脱附测试和拉曼光谱等方法探究不同前驱体所制备的硬碳材料的表面形貌和物相结构。通过恒流充放电测试考察了这三种硬碳负极材料的电化学性能。结果表明,花生壳基硬碳的初始放电比容量最高,但首圈库仑效率最低,石油沥青基硬碳的首圈库仑效率最高但是比容量最低,聚丙烯腈基硬碳具有较高的循环比容量和稳定性。     

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.     

氮掺杂碳层包覆金属钴颗粒与氮掺杂石墨烯纳米复合材料作为高容量锂离子电池负极材料

合成了一种石墨烯基纳米复合材料即：由氮掺杂碳层包覆的金属钴纳米颗粒,充分分散于氮掺杂的石墨烯表面。这种纳米复合材料进一步提高了石墨烯的导电性,增加了石墨烯的储锂容量。该材料被用作锂离子电池负极材料,在性能测试中展现了良好的循环性能,在以100 mA·g^-1的电流密度循环200圈后,放电容量高达950.1 mAh·g^-1,库伦效率约为98%。     

氮掺杂碳层包覆金属钴颗粒与氮掺杂石墨烯纳米复合材料作为高容量锂离子电池负极材料

合成了一种石墨烯基纳米复合材料即：由氮掺杂碳层包覆的金属钴纳米颗粒,充分分散于氮掺杂的石墨烯表面。这种纳米复合材料进一步提高了石墨烯的导电性,增加了石墨烯的储锂容量。该材料被用作锂离子电池负极材料,在性能测试中展现了良好的循环性能,在以100 mA·g^-1的电流密度循环200圈后,放电容量高达950.1 mAh·g^-1,库伦效率约为98%。     

Investigation of PZT-5H and PZT-8 type piezoelectric effect on cycling stability on Si-MWCNT containing anode materials

Silicon (Si) containing materials cannot be used in commercial lithium ion batteries due to the mechanical stress problem triggered by volume expansion during cycling. The high-volume change causes mechanical instability of Si anode materials during charging/discharging, resulting fast capacity fading. It is thought that piezoelectric materials can be a solution for the volume expansion problem because of their ability to generate electric field when pressure is applied on them. For this purpose, PZT-8 and PZT-5H type piezoelectric materials were mixed with silicon and multiwalled carbon nanotube (MWCNT) to obtain anode composites and tested electrochemically versus lithium metal. The piezoelectiric effect on the electrochemical activity of these anodes is investigated by preparing the anode composite without any piezoelectric material additive (Sample #3). At the end of the 50 charge/discharge cycles, the capacities reached 420 mAh/g, 300 mAh/g and 100 mAh/g for PZT-8-added, PZT-5H-added and no-PZT samples, respectively. These results showed that PZT addition improves capacity performance of Si-MWCNT anodes. Additionally, the obtained anode composites were characterized with X-ray diffraction and scanning electron microscopy.     

Interconnected sandwich structure carbon/Si-SiO_2/carbon nanospheres composite as high performance anode material for lithium-ion batteries

In the present work,an interconnected sandwich carbon/Si-SiO_2/carbon nanospheres composite was prepared by template method and carbon thermal vapor deposition(TVD).The carbon conductive layer can not only efficiently improve the electronic conductivity of Si-based anode,but also play a key role in alleviating the negative effect from huge volume expansion over discharge/charge of Si-based anode.The resulting material delivered a reversible capacity of 1094 mAh/g,and exhibited excellent cycling stability.It kept a reversible capacity of 1050 mAh/g over 200 cycles with a capacity retention of 96%.     

优化碳包覆对正极材料LiFePO4/C高倍率性能的影响

碳包覆层的结构和形态对LiFePO4正极材料的电子电导率影响很大. 本文以聚丙烯和葡萄糖为碳源, 二茂铁为催化剂前驱体, 采用原位固相法合成LiFePO4/C复合材料, 并对其微观结构和形貌, 碳的结构与含量, 电化学性能进行分析. 结果表明, 聚丙烯热解形成的碳包覆层石墨化程度高, 可提高材料的高倍率放电性能. 二茂铁的加入有助于优化包覆层的碳结构. 制备的LiFePO4/C复合材料具有优异的高倍率电化学性能, 10C (1C=170 mA·g-1)放电比容量达到145 mAh·g-1.     

NiSe2 nanoparticles encapsulated in CNTs covered and N-doped TiN/carbon nanofibers as a binder-free anode for advanced sodium-ion batteries

Metal selenides are promising anodes for sodium-ion batteries (SIBs) due to the high theoretical capacity through conversion reaction mechanism. However, developing metal selenides with superior electrochemical sodium-ion storage performance is still a great challenge. In this work, a novel composite material of free-standing NiSe₂ nanoparticles encapsulated in N-doped TiN/carbon composite nanofibers with carbon nanotubes (CNTs) in-situ grown on the surface (NiSe₂@N-TCF/CNTs) is prepared by electrospinning and pyrolysis technique. In this composite materials, NiSe₂ nanoparticles on the surface of carbon nanofibers were encapsulated into CNTs, thus avoiding aggregation. The in-situ grown CNTs not only improve the conductivity but also act as a buffer to accommodate the volume expansion. TiN inside the nanofibers further enhances the conductivity and structural stability of carbon-based nanofibers. When directly used as anode for SIBs, the NiSe₂@N-TCF/CNT electrode delivered a reversible capacity of 392.1 mAh/g after 1000 cycles and still maintained 334.4 mAh/g even at a high rate of 2 A/g. The excellent sodium-ion storage performance can be attributed to the fast Na⁺ diffusion and transfer rate and the pseudocapacitance dominated charge storage mechanism, as is evidenced by kinetic analysis. The work provides a novel approach to the fabrication of high-performance anode materials for other batteries.