Improved Li-storage Performance Research Articles

Element Screening of High-Entropy Silicon Anodes for Superior Li-Storage Performance of Li-Ion Batteries.

The high-entropy silicon anodes are attractive for enhancing electronic and Li-ionic conductivity while mitigating volume effects for advanced Li-ion batteries (LIBs), but are plagued by the complicated elements screening process. Inspired by the resemblances in the structure between sphalerite and diamond, we have selected sphalerite-structured SiP with metallic conductivity as the parent phase for exploring the element screening of high-entropy silicon-based anodes. The inclusion of the Zn in the sphalerite structure is crucial for improving the structural stability and Li-storage capacity. Within the same group, Li-storage performance is significantly improved with increasing atomic number in the order of BZnSiP3 < AlZnSiP3 < GaZnSiP3 < InZnSiP3. Thus, InZnSiP3-based electrodes achieved a high capacity of 719 mA h g-1 even after 1,500 cycles at 2,000 mA g-1, and a high-rate capacity of 725 mA h g-1 at 10,000 mA g-1, owing to its superior lithium-ion affinity, faster electronic conduction and lithium-ion diffusion, higher Li-storage capacity and reversibility, and mechanical integrity than others. Additionally, the incorporation of elements with larger atomic sizes leads to greater lattice distortion and more defects, further facilitating mass and charge transport. Following these screening rules, high-entropy disordered-cation silicon-based compounds such as GaCuSnInZnSiP6, GaCu(or Sn)InZnSiP5, and CuSnInZnSiP5, as well as high-entropy compounds with mixed-cation and -anion compositions, such as InZnSiPSeTe and InZnSiP2Se(or Te), are synthesized, demonstrating improved Li-storage performance with metallic conductivity. The phase formation mechanism of these compounds is attributed to the negative formation energies arising from elevated entropy.

Versatile multi-lithiophilic metal oxide nano seeds embedded in hollow carbon nanospheres via electrostatically functional template for dendrite-free lithium metal anodes

Lithium metal anodes, which are promising candidates for anode materials in Li-ion batteries, are highly regarded for their combination of high energy density and low electrochemical potential, making them a compelling option for next-generation anodes. However, the growth of dendritic Li during the charging and discharging processes, along with the resulting decrease in stability and efficiency, poses a significant obstacle to the commercialization of Li metal anodes. To address the challenges associated with Li metal anodes, we propose the use of hollow carbon incorporating zinc oxide (ZnO) and magnesium oxide (MgO) as anode materials. ZnO has high lithiophilicity, enabling selective reactions with Li ions, and MgO exhibits a low nucleation overpotential. By placing these two substances inside the hollow carbon structure, stable Li growth can occur within the hollow carbon, enabling the formation of a reliable Li metal anode. Furthermore, to simplify and precisely synthesize the proposed structure, polystyrene-b-polyacrylic acid was introduced. Metals such as Zn and Mg can be uniformly attached to the hollow carbon through the carboxylic group of acrylic acid. The synthesized structure exhibited significantly improved Li storage performance compared to that of hollow carbon. It demonstrated superior metrics, achieving a Coulombic efficiency of 99.8% over 350 cycles. The introduction of Zn and Mg with distinct properties effectively enhanced the internal storage performance of Li in hollow carbon.

Reduced Volume Expansion of Micron-Sized SiOx via Closed-Nanopore Structure Constructed by Mg-Induced Elemental Segregation.

The inherently huge volume expansion during Li uptake has hindered the use of Si-based anodes in high-energy lithium-ion batteries. While some pore-forming and nano-architecting strategies show promises to effectively buffer the volume change, other parameters essential for practical electrode fabrication, such as compaction density, are often compromised. Here we propose a new in situ Mg doping strategy to form closed-nanopore structure into a micron-sized SiOx particle at a high bulk density. The doped Mg atoms promote the segregation of O, so that high-density magnesium silicates form to generate closed nanopores. By altering the mass content of Mg dopant, the average radii (ranged from 5.4 to 9.7 nm) and porosities (ranged from 1.4 % to 15.9 %) of the closed pores are precisely adjustable, which accounts for volume expansion of SiOx from 77.8 % to 22.2 % at the minimum. Benefited from the small volume variation, the Mg-doped micron-SiOx anode demonstrates improved Li storage performance towards realization of a 700-(dis)charge-cycle, 11-Ah-pouch-type cell at a capacity retention of >80 %. This work offers insights into reasonable design of the internal structure of micron-sized SiOx and other materials that undergo conversion or alloying reactions with drastic volume change, to enable high-energy batteries with stable electrochemistry.

Reduced Volume Expansion of Micron‐Sized SiOx via Closed‐Nanopore Structure Constructed by Mg‐Induced Elemental Segregation

AbstractThe inherently huge volume expansion during Li uptake has hindered the use of Si‐based anodes in high‐energy lithium‐ion batteries. While some pore‐forming and nano‐architecting strategies show promises to effectively buffer the volume change, other parameters essential for practical electrode fabrication, such as compaction density, are often compromised. Here we propose a new in situ Mg doping strategy to form closed‐nanopore structure into a micron‐sized SiOx particle at a high bulk density. The doped Mg atoms promote the segregation of O, so that high‐density magnesium silicates form to generate closed nanopores. By altering the mass content of Mg dopant, the average radii (ranged from 5.4 to 9.7 nm) and porosities (ranged from 1.4 % to 15.9 %) of the closed pores are precisely adjustable, which accounts for volume expansion of SiOx from 77.8 % to 22.2 % at the minimum. Benefited from the small volume variation, the Mg‐doped micron‐SiOx anode demonstrates improved Li storage performance towards realization of a 700‐(dis)charge‐cycle, 11‐Ah‐pouch‐type cell at a capacity retention of &gt;80 %. This work offers insights into reasonable design of the internal structure of micron‐sized SiOx and other materials that undergo conversion or alloying reactions with drastic volume change, to enable high‐energy batteries with stable electrochemistry.

Hierarchical structure promoted lithiation/delithiation behavior of a double-carbon microsphere supported nano-Co3O4 anode.

Due to limited mass loading, high-capacity electrode materials such as transition metal oxides (TMOs) are essential for microscale Li-ion batteries (LIBs) integrated in nano-/micro-electromechanical systems (N/MEMS). Unfortunately, their electrochemical performances are largely plagued by severe mechanical degradation and slow electron transport. Therefore, it is crucial to develop strategies that can improve the structural stability and electronic conductivity of TMO electrodes. In this work, double-carbon (carbon nanotubes and ketjen black) microsphere (DCMS) supported Co3O4 electrodes are fabricated simply through a spray drying and solvothermal method, which are designed to have a mesoporous three-dimensional (3D) hierarchical heterostructure containing well-dispersed Co3O4 nanoparticles within the DCMS framework. An in situ transmission electron microscopy (TEM) study reveals that the DCMS framework can not only provide facile strain accommodation, but also good electronic conductivity, leading to a much improved Li-storage performance compared to other Co3O4-based anodes. The hierarchical electrode exhibits maximum charge capacities of 1205.2 and 678.1 mA h g-1 at current densities of 0.1 and 2 A g-1, respectively, as well as a capacity retention of 92.2% at 0.3 A g-1 after 100 cycles. This study provides a low-cost, simple and general method for developing advanced high-capacity electrodes.

Facile coupling MnS nanoparticles with nitrogen, sulfur-doped carbon microsheet with improved Li-storage performance

Facile coupling MnS nanoparticles with nitrogen, sulfur-doped carbon microsheet with improved Li-storage performance

Preparation of Hollow Nanostructured Si Spheres by Zincothermic Reduction of SiO2 to Si for Lithium-Ion Batteries

The choice of SiO2 precursor plays an important role in designing and synthesizing specific nanostructured Si materials with improved Li-storage performance. Herein, various SiO2 precursors are used to prepare nanostructured Si spheres via zincothermic reduction and their effects on the reduction process are systematically investigated. It is found that the size and structure of SiO2 precursors have a significant effect on the zincothermic reduction process. Among various precursors, nano-SiO2 and bio-SiO2 (e.g., SiO2 derived from rice husk (RH-SiO2) and bamboo leaves (BL-SiO2)) are successfully reduced to Si spheres, while crystalline bulk SiO2 (i.e., micro-SiO2) cannot be reduced. The ease of zincothermic reduction of nano- and bio-SiO2 is due to the high surface area of SiO2 that allows sufficient and facile chlorination–reduction reactions. In addition, the hollow Si spheres prepared from nano-SiO2, RH-SiO2, and BL-SiO2 are used as anode materials for lithium-ion batteries, all of which exhibit good electrochemical performances, delivering the specific discharge capacities of 947.6, 1130.7, and 1050 mAh g–1 over 300 cycles at 1 A g–1, respectively. Overall, this work offers a deeper understanding of zincothermic reduction and demonstrates the broad applicability of zincothermic reduction for the preparation of nanostructured Si from a variety of Si sources.

Improved Li storage performance of SnO nanodisc on SnO2 quantum dots embedded carbon matrix

Li-ion batteries with conversion type anode are attractive choice, for electric vehicles and portable electronic devices, because of their high theoretical capacity and cycle stability. On the contrary, enormous volume change during lithiation/delithiation and irreversible conversion reaction limits use of such anodes. To overcome these challenges, incorporating nano-sized SnO x on flexible carbonaceous matrix is an efficient approach. A facile and scalable fabrication of SnO nanodisc decorated on SnO2 quantum dots embedded carbon (SnO x @C) is reported in the present study. Detailed structural and morphological investigation confirms the successful synthesis of SnO x @C composite with 72.3 wt% SnO x loading. The CV profiles of the nanocomposite reveal a partial reversibility of conversion reaction for the active materials SnO x . Such partial reversible conversion enhances the overall capacity of the nanocomposite. It delivers a very high discharge capacity of 993 mAh g−1 at current density of 0.05 A g−1 after 200 cycles; which is 2.6 times higher than that of commercial graphitic anode (372 mAh g−1) and very close to the calculated capacity of the SnO x @C composite. This unique nanocomposite remarkably improves Li storage performance in terms of reversible capacity, rate capability and cycling performance. It is established that such engineered anode can efficiently reduce the electrode pulverization and in turn make conversion reaction of tin partially reversible.

Improved Li-storage performance of Mg2+-doped LiVPO4F@C cathode material synthesized by a fast carbothermal reduction reaction

LiVPO4F is a promising cathode material for lithium-ion batteries due to its advantages in safety, discharge potential and energy density. In this work, we report a fast carbothermal reduction reaction to synthesize the Mg2+-doped LiVPO4F@C cathode materials with superior electrochemical performances. It indicates that Mg substitution of V can increase the pyrolytic temperature by 40 °C and improve the Li+diffusivity by two times at the discharge plateau. In particular, the LiV0.97Mg0.03PO4F@C cathode material exhibits a high discharge capacity of 140.3 mA h/g at 1 C with a high discharge potential of 4.2 V and a prominent capacity retention of 88.2% after 500 cycles. The fast carbothermal reduction reaction and Mg doping strategies developed in this work may be promising to promote the practical application of LiVPO4F for energy storage.

In-situ synthesis of freestanding porous SnOx-decorated Ni3Sn2 composites with enhanced Li storage properties

In this paper, novel freestanding 3D hierarchical porous SnOx-decorated Ni3Sn2 (3D-HP SnOx@Ni3Sn2) composites are synthesized facilely by two-step chemical dealloying of designed as-cast Sn-45 at.% Ni alloy in different corrosive solutions. The results show that the 3D-HP SnOx@Ni3Sn2 composites have a typical bimodal pore size distribution composed of a micron-sized ligament-channel structure with highly nanoporous channel walls built by ultrafine SnOx (x = 1, 2) nanoparticles (3–6 nm). The unique 3D-HP composites as a binder-free integrated anode for lithium ion batteries (LIBs) display a significantly improved Li storage performance with first reversible capacity of 2.68 mAh cm−2 and good cycling stability with 85.1% capacity retention and over 98.4% coulombic efficiency after 100 cycles (just 0.004 mAh cm2 per cycle for capacity fading). This can be mainly ascribed to the synergistic effect between chemically inert 3D microporous Ni3Sn2 substrate with robust mechanical stress buffer and good transfer mass channels and in-situ growth of nanoporous SnOx with large specific surface areas and high electrochemical active sites. We believe that the present work can offer a promising anode candidate toward advanced LIBs.

A self-driven alloying/dealloying approach to nanostructuring micro-silicon for high-performance lithium-ion battery anodes

The nanostructuring of low-cost micro-sized silicon (mSi) is paramount to achieve the practical viability of deploying high-capacity Si anodes for lithium-ion batteries (LIBs). Conventional methods for converting mSi to nanoporous Si (nSi) involve low product yield, toxic chemical reagents, high energy consumption, etc. Herein, we report a self-driven alloying/dealloying approach to converting mSi to nSi in molten salts, where mSi alloys with Mg powders to generate Mg2Si and, subsequently, the Mg2Si dealloys in a Mg2Si||Sn primary battery with the production of nSi at the negative electrode and the liquid Mg-Sn alloy at the positive electrode. Finally, the Mg-Sn decomposes to Mg gas and liquid Sn through a vacuum-distillation process. Taking the micro-sized Si kerf waste as an example, the pyrolytic carbon-coated (PCC) nSi delivers a capacity of 1080.2 mAh g−1 at 1 A g−1 after 1000 cycles with a capacity retention rate of 83.7%. Furthermore, a fabricated PCC-nSi-2||LiNi0.6Co0.2Mn0.2O2 (NCM622) full cell demonstrates a high energy density of 466 Wh kg−1 as well as good cycling stability for 200 cycles. The improved Li-storage performance is attributed to the synergetic effects of the nanoporous Si and carbon coating. Overall, the self-driven nanostructuring approach along with the vacuum-distillation process maintains a high utilization of mSi, eliminates the use of toxic reagents, and keeps a closed-loop material circle, and thus offers an efficient and green pathway to valorize various mSi for making enhanced lithium-storage anodes.

Cerium vanadate/carbon nanotube hybrid composite nanostructures as a high-performance anode material for lithium-ion batteries

Li + insertion/de-insertion process into/out for the pristine CeVO 4 and CeVO 4 /CNT HCNS electrodes. • Pristine CeVO 4 and CeVO 4 /CNT HCNS were successfully prepared via a silicone oil-bath method. • The Li insertion/de-insertion electrochemical reaction with the CeVO 4 was analyzed. • The discharge performance of CeVO 4 /CNT HCNS electrode was improved compared to the pristine CeVO 4 . • The electrode delivered a reversible capacity of 586.82 mA h g −1 after 1200 cycles at 500 mA g −1 . The pristine CeVO 4 and CeVO 4 /CNT hybrid composite nanostructured samples were facilely synthesized using a simple silicone oil-bath method. From the X-ray diffraction results, the formation of tetragonal CeVO 4 with an additional minor phase of V 2 O 5 was identified. When investigated as an anode material for lithium (Li)-ion batteries, the CeVO 4 /CNT hybrid composite nanostructure (HCNS) electrode demonstrated improved Li storage performance over the pristine CeVO 4 . The Li insertion/de-insertion electrochemical reaction with the CeVO 4 was analyzed on the basis of cyclic voltammetry study. The cyclic voltammetry analysis revealed that the three-step reduction of V 5+ to V 3+ , V 3+ to V 2+ , and V 2+ to V + processes is involved and among them, only V 5+ to V 3+ is reversible during the Li-ion insertion into CeVO 4 . The CeVO 4 /CNT HCNS electrode exhibited a discharge capacity as high as 443 mA h g −1 (capacity retention of 96.3%) over 200 cycles at 100 mA g −1 , whereas the pristine CeVO 4 is limited to 138 mA h g −1 (capacity retention of 48%). Even at a high current density of 500 mA g −1 , the CeVO 4 /CNT HCNS electrode delivered an excellent reversible capacity of 586.82 mA h g −1 after 1200 cycles.

Revealing the Effect of Oxygen Defects and Morphology on Li-Storage Performance of Calcium Iron Oxide

Nanostructure design and modulation of ion/electron paths are effective strategies for achieving high-performance iron-based anode materials for next-generation Li-ion batteries (LIBs). In the present work, we attempt to explore the correlation among morphologies, defect concentration, transport phenomenon, and Li-storage performance of CaFe2O4 (CFO). Herein, two different morphologies (nanoparticles/nanofibers) of CFO are prepared by facile and cost-effective techniques and characterized by field emission scanning electron microscope (FE-SEM), thermogravimetric (TG), high-resolution transmission electron microscope (HR-TEM), and X-ray diffractometer (XRD). X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analysis revealed the presence of a higher concentration of oxygen defects in nanofibers of CFO, which further improves their conductivity and ionic transference number. As an anode for LIBs, the nanofibers of CFO exhibit excellent lithium storage performance with a reversible and stable capacity of 610 (±10) mAh g−1 (almost two times of their nanoparticles) and good rate capability. The improved Li-storage performance is attributed to morphological featured of nanofibric network as well as the presence of oxygen defects. Furthermore, The CFO nanofibers//self-prepared LiCoO2 full cell delivers a high energy density of 150 Wh Kg−1 (as per the total active mass of anode and cathode). Based on the cyclic voltammogram, galvanostatic charge/discharge cycling, ex situ - HR-TEM, XPS, and magnetic (M-H) studies, a possible Li-storage mechanism is also proposed.

A New Strategy for Maximizing the Storage Capacity of Lithium in Carbon Materials.

A novel strategy for maximizing the lithium storage capacity of carbon materials is reported. To redesign the interior structure, a large amount of Li, 4 wt%, is doped into the carbon during its synthesis. The Li-doped carbon is subsequently annealed, during which the diffusion of Li induces a disordered structure, thereby generating many nanocavities. The diffused Li atoms aggregate into a superdense state within the carbon structure; when the Li agglomerates escape from the carbon during the delithiation process, new void spaces are created at their location. Thus, the interior of carbon is evacuated to form a new structure capable of storing a large amount of Li, realizing a high reversible capacity during charging. At a rate of 1 C, the average reversible capacity of the material is three times higher than that of commercial graphite, with a stable cycling performance over 300 cycles. This is a remarkably improved Li storage performance for pure carbon, without the need for the silicon, tin, or transition metal oxide, that are becoming popular as next-generation materials. Therefore, this novel strategy can potentially aid in the design of high-performance materials via better carbon material design and combinations with other types of materials.

Outstanding Li-storage performance of LiFePO4@MWCNTs cathode material with 3D network structure for lithium-ion batteries

In this work, the MWCNTs-decorated LiFePO4 microspheres (LiFePO4@MWCNTs) with a 3D network structure have been synthesized by a facile and efficient spray-drying approach followed by solid-state reaction in a reduction atmosphere. In the as-prepared composite, the MWCNTs around LiFePO4 nanoparticles can provide 3D conductive networks which greatly facilitate the transport of Li+-ion and electron during the electrochemical reaction. Compared to the pure LiFePO4 material, the LiFePO4@MWCNTs composite as cathode for lithium-ion batteries exhibits significantly improved Li-storage performance in terms of rate capability and cyclic stability. Therefore, we can speculate that the spray-drying approach is a promising route to prepare the high-performance electrode materials with 3D network structure for electrochemical energy storage.

Improved Li-storage performance of CNTs-decorated LiVPO4F/C cathode material for electrochemical energy storage

Lithium vanadium fluorophosphate (LiVPO4F) has been attracted increasing attention as an advanced cathode for Li-ion batteries because of its excellent thermal stability and high operating voltage. Nevertheless, the pure LiVPO4F possesses a low electrical conductivity which prevents its usage for practical application in energy storage. In this work, the CNTs-decorated LiVPO4F/C (CNTs@LiVPO4F/C) nanocomposite has been prepared via a conventional sol-gel approach. The XRD results reveal that all the diffraction peaks obtained for CNTs@LiVPO4F/C are indexed to the triclinic structure. TEM images show that the conductive CNTs are distributed homogeneously over the LiVPO4F/C particles. Benefiting from the enhanced conductivity, the as-prepared CNTs@LiVPO4F/C electrode exhibits outstanding electrochemical performance with high reversible capacity of 121.1 mAh g−1 at a high current rate of 10C. Therefore, the novel CNTs@LiVPO4F/C cathode material developed from this investigation with superior Li-storage performance has promising practical applications in electrochemical energy storage systems.

Tailored synthesis of monodispersed nano/submicron porous silicon oxycarbide (SiOC) spheres with improved Li-storage performance as an anode material for Li-ion batteries

A spherical silicon oxycarbide (SiOC) material (monodispersed nano/submicron porous SiOC spheres) is successfully synthesized via a specially designed synthetic strategy involving pyrolysis of phenyltriethoxysilane derived pre-ceramic polymer spheres at 900 °C. In order to prevent sintering of the pre-ceramic polymer spheres upon heating, a given amount of hollow porous SiO2 nanobelts which are separately prepared from tetraethyl orthosilicate with CuO nanobelts as templates are introduced into the pre-ceramic polymer spheres before pyrolysis. This material is investigated as an anode for lithium-ion batteries in comparison with the large-size bulk SiOC material synthesized under the similar conditions but without hollow SiO2 nanobelts. The maximum reversible specific capacity of ca. 900 mAh g−1 is delivered at the current density of 100 mA g−1 and ca. 98% of the initial capacity is remained after 100 cycles at 100 mA g−1 for the SiOC spheres material, which are much superior to the bulk SiOC material. The improved lithium storage performance in terms of specific capacity and cyclability is attributed to its particular morphology of monodisperse nano/submicron porous spheres as well as its modified composition and microstructure. This SiOC material has higher Li-storage activity and better stability against volume expansion during repeated lithiation and delithiation cycling.

Improved Li-storage performance with PEDOT-decorated MnO2 nanoboxes.

In this paper, MnO2 nanoboxes coated with poly(3,4-ethylenedioxythiophene) film (denoted as MnO2@PEDOT) are investigated as an anode material in lithium-ion batteries. The MnO2 nanoboxes are developed through the surface chemical oxidation decomposition of MnCO3 cubes and the subsequent removal of their remaining cores. PEDOT is coated on the surface of MnO2 nanoboxes via in situ polymerization of 3,4-ethylenedioxythiophene. The charge-discharge tests demonstrate that this special configuration endows the resulting MnO2@PEDOT with remarkable electrochemical performances, that is a reversible capacity of 628 mA h g-1 after 850 cycles at a current density of 1000 mA g-1 and a rate capacity of 367 mA h g-1 at 3000 mA g-1. The results indicate that the nanoboxes provide the paths for Li-ion diffusion, the reaction sites for Li-ion intercalation/deintercalation and the space to buffer the volume change during the charge-discharge process, while the conductive polymer ensures the structural stability and improves the electronic conductive property of MnO2.

Highly uniform Co9S8 nanoparticles grown on graphene nanosheets as advanced anode materials for improved Li-storage performance

A Co9S8/GNS (graphene nanosheets) nanocomposites has been synthesized via a facile solvothermal approach followed by thermal treatment in nitrogen at 500°C using graphite oxide sheets, CoCl2·6H2O and thiourea as the starting materials. Highly uniform Co9S8 nanoparticles with a size of about 80–90nm are evenly grafted on the surface of GNS, forming a unique Co9S8/GNS hybrid nanostructure. When evaluated as anode materials for lithium ion batteries, impressive electrochemical performances of the as-prepared nanocomposites are achieved compared to that of pure bulk Co9S8, with an high reversible capacity of 1480mAhg−1. Moreover, the as-synthesized nanocomposites present excellent cycling durability and high-rate capability. The improvement in the electrochemical properties could be attributed to the well-designed structure of the Co9S8/GNS nanocomposite which possesses large number of accessible active sites for lithium-ion insertion, fast ion diffusion rate and good electronic conductivity.

In situ fabrication of three-dimensional nitrogen and boron co-doped porous carbon nanofibers for high performance lithium-ion batteries

This paper reports the fabrication of three-dimensional porous carbon nanofibers network with high doping level of nitrogen (N, 5.17 at.%) and boron (B, 6.87 at.%) through a general electrospinning strategy followed by a calcination process. The employed ammonia borane (NH3BH3, denote as AB) not only functions as a porogen reagent to generate porous structures but also as the heteroatoms source to induce N and B co-doping. Such highly unique nanoarchitectures offer remarkably improved Li storage performance including high reversible capacity (∼910 mAh g−1 at a current density of 100 mA g−1) with good cycling and rate performances.