Rolling up MXene sheets into scrolls to promote their anode performance in lithium-ion batteries

Although Ti3 C2 MXene sheets have attracted extensive attention in lithium-ion storage techniques,their restacking makes against and even hinders the Li ions diffusion within them,thereby decreasing the capacity as well as rate performance of conventional MXene anode.Here,for the first time,we roll up the Ti3 C2 Tx sheets into scrolls with unclosed topological structure and the interlayer galleries to alleviate the restacking problem.Thus,Ti3 C2 Tx scrolls as anode materials in lithium-ion batteries(LIBs)have higher capacity and better rate performance than Ti3 C2 Tx sheets.On the bases of these,high-capacity silicon nanoparticles are added during the rolling process to in-situ produce Ti3 C2 Tx/Si composite scrolls.The addition of 10%silicon nanoparticles shows the best overall improvement among capacity,rate capability and cyclic stability for Ti3 C2 Tx scrolls.

Nano-sized carboxylates as anode materials for rechargeable lithium-ion batteries

Nano-sized caiboxylales Na2C7H3NO4 and Na2C6H2N2O4 were prepared and investigated as anode materials for lithium-ion batteries.Both carboxylates exhibit high reversible capacities around 190 mAh/g above a cut-off voltage of 0.8 V vs.Li＋/Li.potentially improving the safety of the batteries.In addition,good rate performance and long cycle life of these carboxylates make them promising candidates as anode materials for lithium-ion batteries.

LiOH-mediated crystallization regulating strategy enhancing electrochemical performance and structural stability of SiO anodes for lithium-ion batteries

Silicon monoxide(SiO)is widely recognized as a promising anode material for next-generation lithium-ion batteries.Owing to its metastable amorphous structure,SiO exhibits a highly complex degree of crystallization at the microscopic level,which significantly influences its electrochemical behavior.As a consequence,accurately regulating the crystallization of SiO,and further establishing the relationship between crystallinity and electrochemical performance are very critical for SiO anodes.In this article,carbon-coated SiO materials with different crystallinity degrees were synthesized using lithium hydroxide monohydrate(LiOH·H_(2)O)as a structural modifier to reveal this rule.Additionally,moderate amount of LiOH·H_(2)O addition results in the forming of an oxygen-rich shell,which effectively inhibits the inward migration of oxygen atoms on the SiO surface and suppresses volume expansion.However,the crystallinity of SiO will gradually enhance and the crystalline phase appears with increasing the amount of LiOH·H_(2)O,which will generate a deteriorative Li+diffusion kinetic.After balancing the above two contradictions,a mass fraction of 1%LiOH·H_(2)O for the additive yielded SiO@C-1,characterized by optimal crystallinity.SiO@C-1 demonstrates exceptional long-cycle stability with 74.8%capacity retention after 500 cycles at 1 A·g^(-1).Furthermore,it achieves a capacity retention of 52.2%even at a high density of 5 A·g^(-1).This study first reveals the relationship between SiO crystallinity and electrochemical performance,which efficiently guides the design of high-performance SiO anodes.

Amorphous Sb/C composite with isotropic expansion property as an ultra-stable and high-rate anode for lithium-ion batteries

Antimony(Sb)is an intriguing anode material for Li-ion batteries(LIBs)owing to its high theoretical capacity of 660 m Ah·g^(-1)and appropriate working potential of~0.8 V(vs.Li^(+)/Li).However,just like all alloying materials,the Sb anode suffers from huge volume expansion(230%)during repeated insertion/extraction of Li+ions,resulting in structural deterioration and rapid capacity decay.In this work,a novel amorphous Sb/C composite with atomically dispersed Sb particles in carbon matrix is prepared via a straightforward high-energy ball milling approach.The intimate intermixing of amorphous Sb with C provides homogeneous element distribution and isotropic volume expansion during cycling,resulting in persistent structural stability.Meanwhile,the disordered structure of amorphous material shortens the diffusion distance of lithium ions/electrons,promoting fast reaction kinetics and rate capability.Benefiting from the aforementioned effects,the amorphous Sb/C exhibits a high reversible capacity of537.4 m Ah·g^(-1)at 0.1 A·g^(-1)and retains 201.0 m Ah·g^(-1)at an ultrahigh current rate of 10.0 A·g^(-1).Even after 1500deep cycles at 2.0 A·g^(-1),the amorphous Sb/C electrode still maintains 86.3%of its initial capacity,which outperforms all existing Sb-based anodes reported so far.Postmortem analysis further reveals a greatly reduced volume variation of merely 34.6%for the amorphous Sb/C electrode,much lower than that of 223.1%for crystalline Sb materials.This study presents a new approach to stabilizing Sb-based alloy anodes and contributes to the construction of high-performance amorphous anode materials for LIBs,enabling advanced energy storage.

SiO-Sn_(2)Fe@C composites with uniformly distributed Sn_(2)Fe nanoparticles as fast-charging anodes for lithium-ion batteries

SiO-based materials represent a promising class of anodes for lithium-ion batteries(LIBs),with a high theoretical capacity and appropriate and safe Li-insertion potential.However,SiO experiences a large volume change during the electrochemical reaction,low Li diffusivity,and low electron conductivity,resulting in degradation and low rate capability for LIBs.Here,we report on the rapid crafting of SiO–Sn_(2)Fe@C composites via a one-step plasma milling process,leading to an alloy of Sn and Fe and in turn refining SiO and Sn_(2)Fe into nanoparticles that are well dispersed in a nanosized,few-layer graphene matrix.The Sn and Fe nanoparticles generated during the first Li-insertion process form a stable network to improve Li diffusivity and electron conductivity.As an anode mate-rial,the SiO–Sn_(2)Fe@C composite manifests high reversible capacities,superior cycling stability,and excellent rate capability.The capacity retention is found to be as high as 95%and 84%at the 100th and 300th cycles under 0.3 C.During rate capability testing at 3,6,and 11 C,the capacity retentions are 71%,60%,and 50%,respectively.This study highlights that this simple,one-step plasma milling strategy can further improve SiO-based anode materials for high-performance LIBs.

Recent advances of SiO_(x)-based anodes for sustainable lithium-ion batteries

The world is facing an ever-growing global energy crisis with unprecedented depth and complexity.The sustainable development of high energy density lithium-ion batteries for electric vehicles and portable electric devices has become a feasible way to deal with this problem.Silicon suboxides(SiO_(x))have been deemed as one of the most promising anode materials because of their ultrahigh theoretical lithium storage capacity,proper working potential,natural abundance,and environmental friendliness.However,the mass utilization of SiO_(x)-based anodes is severely obstructed by their low electrical conductivity and inevitable volume expansion.While lithium silicate and lithium oxide formed in the first lithiation process act as buffer layers to some extent,it is urgent to address the accompanying low initial Coulombic efficiency and unsatisfactory cycling stability.In this review,we summarized recent advances in the synthesis methods of SiO_(x)-based materials.Besides,the benefits and shortcomings of the various methods are briefly concluded.Then,we discussed the effective combination of SiO_(x) with carbon materials and designs of porous structure,which could considerably enhance the electrochemical performance in detail.Furthermore,progresses on the modified strategies,advanced characteristics and industrial applications for SiO_(x)-based anodes are also mentioned.Finally,the remaining challenges encountered and future perspectives on SiO_(x)-based anodes are highlighted.

高性能锂离子电池SiO/C/G复合负极材料研究

以一氧化硅、蔗糖及天然石墨为原料,通过高能球磨和热解工艺制备了电化学性能优异的SiO/C/G复合负极材料。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对复合材料的物相和形貌进行了表征。所制备的复合材料中,纳米SiO颗粒(<50 nm=被无定形碳粘结并均匀分散在石墨鳞片上。电化学性能测试表明,该复合材料100次循环后,可逆容量高达1108.9 mAh/g,容量保持率为103.8%。优异的电化学性能主要归因于纳米SiO颗粒在无定形碳基体中的均匀分布、无定形碳基体的缓冲作用和石墨相对复合材料导电性能的改善。

SiO/C复合材料在锂离子电池中的应用

硅基负极材料因其较高的比容量而受到研究者广泛的关注。本文选取高比容量SiO_x与NG复合材料作为锂离子电池负极材料,研究了不同SiO/C复合比例对全电池的能量密度和循环性能的影响。不同比例SiO_x/C复合材料的首次容量和首次效率有明显差别。与石墨材料相比,SiO_x/C复合材料的膨胀程度略有增加。随着SiO_x比例的增加,全电池的能量密度先是上升然后下降,但其循环稳定性却有所降低。当SiO_x比例在4%时,全电池能量密度提升4.2%,500周循环后容量保持率在80%以上,可以满足商业化锂离子电池的使用要求。

预歧化处理的高性能锂离子电池SiO/C负极材料

以SiO和蔗糖为原料,SiO经高温歧化反应处理后,通过机械球磨、喷雾干燥、高温热解工艺制备出具有优异电化学性能的锂离子电池SiO/C负极材料。经XRD、FTIR、XPS、SEM、TEM结构分析表明,歧化反应处理的片状SiO包含非晶态SiO和纳米晶相Si、SiO_2,蔗糖热解形成的无定形碳包覆在细片状SiO的表面,组成球形SiO/C颗粒。电化学测试结果表明,预歧化处理的SiO/C复合材料的首次放电容量为1 314.6mAh/g,首次库伦效率达到71%;100周循环后的放电容量为851.2mAh/g,容量保持率达到78.5%,循环稳定性远高于未经歧化处理的SiO/C复合材料。电化学性能的提高归因于SiO预歧化反应及热解碳包覆。

锂离子电池用SiO/C负极材料的制备及性能研究

选择沥青、柠檬酸和蔗糖为碳源,通过机械球磨、喷雾干燥、高温热解工艺制备了不同的SiO/C复合材料。利用XRD、TG、SEM来研究用不同碳源制备的SiO/C复合材料的微观结构与形貌,结果表明,以沥青为碳源制备的SiO/C复合材料含有最高的碳含量。电化学测试结果表明,以沥青、柠檬酸和蔗糖为碳源制备的SiO/C复合材料首次库仑效率分别为62.7%、54.6%和53.6%,100次循环后比容量分别为661.7、565.1和322.8 mAh/g。由此说明,以沥青为碳源制备的SiO/C复合材料具备最好的电化学性能,原因主要是由于其含有最高的无定形碳含量。

Scalable construction of SiO/wrinkled MXene composite by a simple electrostatic self-assembly strategy as anode for high-energy lithium-ion batteries

Available onlineSilicon monoxide(SiO)is a promising anode material fo r lithium-ion batteries(LIBs)due to its high theoretical specific capacity(~2400 mAh/g),low working potential(<0.5 V vs.Li^+/Li),low cost,easy synthesis,nontoxicity,abundant natural source and smaller volume expansion than Si.However,low intrinsic electrical conductivity,low initial Coulombic efficiency(ICE)and inevitable volume expansion(~200%)impede its practical application.Here we fabricate SiO/wrinkled MXene composite(SiO-WM)by an electrostatic self-assembly method.Importantly,this method is simple,scalable and taking into account all the issues of SiO.As a result,the SiO-WM exhibits imp roved rate capability,cycling performance and ICE than bare SiO.

High-performance SiO/C as anode materials for lithium-ion batteries using commercial SiO and glucose as raw materials

Silicon monoxide(SiO)is considered as a promising anode material for lithium-ion batteries(LIBs)due to its higher capacity and longer cycle life than those of graphite and silicon,respectively.In this study,glucose was developed as a suitable and inexpensive carbon source to synthesize SiO/C composite with a high performance.In addition,the effects of the calcination temperature and the amount of c arbon source on the electrochemical performance of the SiO/C composite were investigated.The addition of 5 wt%glucose and a calcination temperature of 800℃ demonstrated the optimum conditions for SiO/C synthesis.The resultant SiO/C showed an initial charge capacity of 1259 mAh·g^(-1) and a high initial coulombic efficiency of 71.9%.A charge capacity of 850 mAh·g^(-1) after 100 cycles at 200 mA·g^(-1) was achieved,demonstrating the best value of the SiO/C-based materials.The composition changes of SiO under the calcination temperature played a significant role in the electrochemical performance.Overall,the obtained SiO/C material with a high capacity and good stability is suitable for LIB applications as an anode material.

锂离子电池负极材料Si-SiO_x-Sn/C的制备及电化学性质

采用碳热还原法在氮气保护下于管式炉中焙烧SiO、SnO2和碳的混合物,制备复合负极材料Si-SiOx-Sn/C。通过X射线衍射(XRD)、扫描电镜(SEM)对材料的结构进行表征,通过电化学阻抗谱(EIS)和充放电测试对材料的电化学性能进行测试和分析。结果表明:900℃焙烧2 h的样品由晶体锡、无定形硅及其氧化物和碳组成,首次放电比容量高达1 144 mAh.g-1。10次循环后容量保持稳定,充放电效率保持较高状态。

不同导电添加剂对SiO/C锂离子电池性能的影响（英文）

以SiO/C复合材料为负极的锂离子电池相比传统石墨为负极的锂离子电池具有更高能量密度,因而越来越受到开发人员的重视。而SiO/C材料由于Si的存在导致材料本体导电性差,在实体锂离子电池的制作过程中会出现内阻大和倍率性能差等问题,因此导电添加剂组成对电池性能的影响成为研究关键。本文用商业化的LiCoO_2、SiO/复合材料和电解液为主要原料,以VGCF和Super P为导电添加剂,制作了2.5 Ah容量的锂离子软包电池。SEM分析测试表明导电碳黑Super P和VGCF分散均匀,可与SiO/C颗粒形成点和线的接触,进而增强负极极片的导电性能。应用两种导电添加剂所制作的SiO/C锂离子电池的能量密度超过了600 Wh/L。相对于采用Super P导电添加剂,VGCF导电添加剂制备的锂离子电池充放电过程的膨胀更小,且倍率性能更加优异,同时低温和循环寿命均表现出更好的性能。

Sub-nanometer structured silicon-carbon composite nanolayers armoring on graphite for fast-charging and high-energy-density lithium-ion batteries

Silicon/carbon composites are promising alternatives to current graphite anodes in commercial lithiumion batteries(LIBs)because of their high capacity and excellent safety.Nevertheless,the unsatisfactory fastcharging capability and cycle stability of Si/C composites caused by slow charge transport capability and huge volume change under industrial electrode conditions severely hamper their development.Here,a novel Si/C anode was fabricated by homogeneously depositing amorphous C-Si nanolayers on graphite(C-Si@graphite).C-Si nanolayers with uniformly dispersed sub-nanometer Si particles in 3D carbon skeleton significantly boost electron and Li-ion transport and efficiently relieve Si's agglomeration and volume change.As a result,the tailored C-Si@graphite electrodes show an excellent rate capacity(760.3 mAh·g^(-1)at 5.0C)and long cycle life of over 1000 cycles at 1.0C and800 cycles at 2.0C under industrial electrode conditions.In addition,the assembled full cells(C-Si@graphite,anode;Li[Ni_(0.8)Co_(0.1)Mn_(0.1)]O_(2),cathode)present superior fastcharging capability(240.4 Wh·kg^(-1),charging for16.2 min,3.0C)and long cycle life(80.7%capacity retention after 500 cycles at 1.0C),demonstrating the massive potential of C-Si@graphite for practical application.

Bimetallic CoNiSe_(2)/C nanosphere anodes derived from Ni-Co-metal-organic framework precursor towards higher lithium storage capacity

Through uncomplicated carbonation process,a carbon-embedded CoNiSe_(2)/C nanosphere was synthesized from Ni-Co-MOF (metal-organic framework) precursor whose controllable structure and synergistic effect of bimetallic Ni/Co brought CoNiSe_(2)/C anodes with high specific surface area (172.79 m^(2)/g) and outstanding electrochemical performance.CoNiSe_(2)/C anodes obtained reversible discharge capacities of850.9 mAh/g at 0.1 A/g after cycling for 100 cycles.In addition,CoNiSe_(2)/C exhibits excellent cycle stability and reversibility in the rate test at a current density of 0.1–2.0 A/g.When the current density returns to 0.5 A/g for 150 cycles,its discharge ratio the capacity is 330.8 m Ah/g.Electrochemical impedance spectroscopy (EIS) tests suggested that CoNiSe_(2)/C anodes had a lower charge transfer impedance of 130.02Ωafter 30 cycles.In-situ X-ray diffraction (XRD) tests confirmed the alloying mechanism of CoNiSe_(2)/C which realized higher lithium storage capacity.This work affords substantial evidence for the extension of bimetallic selenides in secondary batteries,promoting the development of bimetallic selenides in anode materials for LIBs.

SiO_x-based(0

Silicon(Si) materials as anode materials for applications in lithium-ion batteries(LIBs) have received increasing attention.Among the Si materials,the electrochemical properties of SiOx-based(0<x≤2)composites are the most prominent.However,due to the cycling stability of SiOx being far from practical,there are some problems,such as Iow initial coulombic efficiency(ICE),obvious volume expansion and poor conductivity.Researchers in various countries have optimized the electrochemical properties of SiOx-based composites by means of pore formation,surface modification,and the choice of constituents.In this review,SiOx-based composites are classified into three categories based on the valency of Si(SiO2 composites,SiO composites and SiOx(0<x<2) composites).The synthesis,morphologies and electrochemical properties of the SiOx-based composites that are applied in LIB are discussed.Finally,the prope rties of several common SiOx-based composites are briefly compared and the challenges faced by SiOx-based composites are highlight.

Preparation and electrochemical characterization of ultrathin WO3-x/C nanosheets as anode materials in lithium ion batteries

Ultrathin two-dimensional （2D） nanomaterials offer unique advantages compared to their counterparts in other dimensionalities. O-vacancies in such materials allow rapid electron diffusion. Carbon doping often improves the electric conductivity. Considering these merits, the WO3-x/C ultrathin 2D nanomaterial is expected to exhibit excellent electrochemical performance in Li-ion batteries. Here, ultrathin WO3-xC nanosheets were prepared via an acid-assisted one-pot process. The as-prepared WO3-x/C ultrathin nanosheets showed good electrochemical performance, with an initial discharge capacity of 1,866 mA·h·g^-1 at a current density of 200 mA·g^-1 After 100 cycles, the discharge and charge capacities were 662 and 661 mA·h·g^-1, respectively. The reversible capacity of the WO3-x/C ultrathin nanosheets exceeded those of WO3 and WOg-x nanosheets. The electrochemical testing results demonstrated that WO3-x/C ultrathin nanosheets are promising alternative anode materials for Li-ion batteries.

A facile self-catalyzed CVD method to synthesize Fe3C/N-doped carbon nanofibers as lithium storage anode with improved rate capability and cyclability

Uniform Fe3 C/N-doped carbon nanofibers were successfully synthesized through a facile self-catalyzed CVD method by using acetylene as carbon source and Fe3O4 as iron source and autocatalytic template for the reaction under moderate preparation conditions. The experimental and theoretical calculation results demonstrate that Fe3 C can improve the lithium storage performance of carbon nanofibers. Besides, the addition of PPy can not only control the growth rate of carbon fibers but also help to form uniform carbon fibers. As a result, the obtained Fe3 C/N-doped carbon nanofiber composites display favorable electrochemical performance as an anode for lithium-ion batteries, which including satisfactory rate performance of 402 m A h g-1 under 1.2 Ag-1, and good cycling stability of 502.3 m A h g-1 under 200 m Ag-1 over 400 cycles. The introduction of Fe3 C species and the uniform carbon fiber morphology are responsible for the long-cycling and high rate performance of materials.

Si O/C浆料稳定性及半干法匀浆工艺研究

硅负极因其极高的比容量成为高能量密度锂电池的研究热点,目前硅氧已实现批量生产和应用。锂离子电池的性能、寿命和一致性与其电极性能直接相关,匀浆是电极生产中的关键工序。本工作研究了硅氧碳负极(SiO/C)浆料的稳定性并考察了半干法匀浆工艺,对比了碳含量分别为1.6wt%和3.1wt%的SiO/C-1和SiO-2在水系浆料中的稳定性。SiO/C-1在水中产气明显,原因为Si在碱性条件下与H2O反应生成H2,而SiO/C-2浆料无产气,浆料和极片状态较好。SEM, EDS, TEM等表征结果表明SiO/C-2表面存在厚度20~30 nm均匀的碳包覆层,可阻隔水分并提高稳定性。为提高硅负极浆料稳定性并提高匀浆效率,研发了半干法匀浆工艺,对浆料固含率、黏度、细度、流变、产气等参数进行了测试,对极片剥离力、电阻、电镜下的微观形貌以及电池循环性能进行了考察,结果表明优化后的半干法匀浆工艺制得的浆料固含量为51.8wt%,黏度为4900 mPa·s,细度为20μm,浆料静置24 h后黏度为10000 mPa·s,浆料48 h基本无产气,制作负极片剥离力为15 N/m,电阻率为0.106Ω/cm,搭配高镍NCM(Ni9)制作的330 Wh/kg软包电池高温循环寿命可达800周,明显优于普通湿法工艺。