Lithium Storage Capability Research Articles

One‐pot hydrothermal synthesis of porous anatase TiO2 nanotube formed bundles for lithium ion battery anodes

AbstractAnatase phase of TiO2 nanomaterial has been deemed a potential anode material for lithium ion battery (LIB) applications because of its remarkable electrochemical properties. However, TiO2 anodes always suffer from intrinsic poor electrical conductivity and slow ion kinetics, which would restrict their practical usage. To address this issue, efficient control and design of the anatase crystal structure of TiO2 material with desirable morphology is one of the critical approaches. In this work, a good lithium storage capability of 181 mA hr g−1 at rate of 0.2C, high rate performance of 70 mA hr g−1 at 20C, and excellent cyclability of 117 mA hr g−1 with a capacity retention of 93% at 1C after 100 cycles and 84 mA hr g−1 at 10C after 1,000 cycles are observed in an optimized porous anatase TiO2 one‐dimensional nanotube bundle nanomaterial fabricated through a simple hydrothermal process with post calcination treatment. These excellent electrochemical properties of the product can be ascribed to its anatase crystal phase, 1D nanostructure, and porous framework with a large surface area, which provide it with an efficient electrode/electrolyte contact area and a faster ion/electron diffusion pathway.

New Chemical Synthesis Strategy To Construct a Silicon/Carbon Nanotubes/Carbon-Integrated Composite with Outstanding Lithium Storage Capability

The Si/C anode is one of the most promising candidate materials for the next-generation lithium-ion batteries (LIBs). Herein, a silicon/carbon nanotubes/carbon (Si/CNTs/C) composite is in situ synthesized by a one-step reaction of magnesium silicide, calcium carbonate, and ferrocene. Transmission electron microscopy reveals that the growth of CNTs is attributed to the catalysis of iron atoms derived from the decomposition of ferrocene. In comparison to a Si/C composite, the cycle stability of the Si/CNTs/C composite can obviously be improved as an anode for LIBs. The enhanced performance is mainly attributed to the following factors: (i) the perfect combination of Si nanoparticles and in situ grown CNTs achieves high mechanical integrity and good electrical contact; (ii) Si nanoparticles are entangled in the CNT cage, effectively reducing the volume expansion upon cycling; and (iii) in situ grown CNTs can improve the conductivity of composites and provide lithium ion transport channels. Moreover, the full cell constructed by a LiFePO4 cathode and Si/CNTs/C anode exhibits excellent cycling stability (137 mAh g-1 after 300 cycles at 0.5 C with a capacity retention rate of 91.2%). This work provides a new way for the synthesis of a Si/C anode for high-performance LIBs.

Cyclically formed dual mechanical/functional interface stabilizing silicon with enhanced lithium complementary effect

Silicon has been focused as a potential candidate in practical lithium-ion batteries due to its amiable feature of high theoretical specific capacity and environmental friendliness. However, its long-term stability requires further improvements for the significant volumetric expansion during lithium insertion. A novel strategy of a complementary effect created by the special extra lithium-storage capability of transition metal oxides is proposed and explored for the modification of silicon in the study. Si@MnO/C composite with highly compact structure is thus prepared by a facile electrostatic process combined with heat treatment. The results demonstrate that the strategical introduction of ultrafine MnO plays a crucial role in the generation of the complementary effect, which outstandingly enhances the durability as well as the kinetics of silicon anode. A reversible capacity of 1085.7 mAh g−1 with a Coulombic efficiency over than 99% has been obtained after 500 cycles at the current density of 200 mA g−1. Even at a high current density of 2000 mA g−1, a retention capacity of 946.3 mAh g−1 could be maintained after 920 cycles.

The Vital Role of Electrolyte Reduction Potential in Forming a Stable SEI in Phosphorus-Based Anodes.

In view of their high lithium storage capability, phosphorus-based anodes are promising for lithium-ion batteries. However, the low reduction potential (0.74V versus Li+ /Li) of the commonly used ethylene carbonate-based electrolyte does not allow the early formation of a solid electrolyte interphase (SEI) prior to the initial phosphorus alloying reaction (1.5V versus Li+ /Li). In the absence of a protective SEI, the phosphorus anode develops cracks, creating additional P/electrolyte interfaces. This results in the loss of P and the formation of a discontinuous SEI, all of which greatly reduce the electrochemical performance of the anode. Here, the effect of solvent reduction potential on the structure of the SEI is investigated. It is found that solvents with a high reduction potential, such as fluoroethylene carbonate, decompose to form an SEI concomitantly with the P alloying reaction. This results in a continuous, mechanically robust, and Li3 PO4 -rich SEI with improved Li-ion conductivity. These attributes significantly improve the cyclic stability and rate performance of the phosphorus-based anode.

Nano‐single‐crystal‐constructed submicron MnCO3 hollow spindles enabled by solid precursor transition combined Ostwald ripening in situ on graphene toward exceptional interfacial and capacitive lithium storage

AbstractHollow structuring has been identified as an effective strategy to enhance the cycling stability of electrodes for rechargeable batteries due to the outstanding volume expansion buffering efficiency, which motivates ardent pursuing on the synthetic approaches of hollow materials. Herein, an intriguing route, combining solid precursor transition and Ostwald ripening (SPTOR), is developed to craft nano single‐crystal (SC)‐constructed MnCO3 submicron hollow spindles homogeneously encapsulated in a reduced graphene oxide matrix (MnCO3 SMHSs/rGO). It is noteworthy that the H‐bonding interaction between Mn3O4 nanoparticles (NPs) and oxygen‐containing groups on GO promotes uniform anchoring of Mn3O4 NPs on GO, mild reductant ascorbic acid triggers the progressive solid‐to‐solid transition from Mn3O4 NPs to MnCO3 submicron solid spindles (SMSSs) in situ on GO, and the Ostwald ripening process induces the gradual dissolution of interior polycrystals of MnCO3 SMSSs and subsequent recrystallization on surface SCs of MnCO3 SMHSs. Remarkably, MnCO3 SMHSs/rGO delivers a 500th lithium storage capacity of 2023 mAh g−1 at 1000 mA g−1, which is 10 times higher than that of MnCO3 microspheres/rGO fabricated from a conventional Mn2+ salt precursor (202 mAh g−1). The ultrahigh capacity and ultralong lifespan of MnCO3 SMHSs/rGO can be primarily attributed to the superior reaction kinetics and reversibility combined with exceptional interfacial and capacitive lithium storage capability, enabled by the fast ion/electron transfer, large specific surface area, and robust electrode pulverization inhibition efficacy. Moreover, fascinating in‐depth lithium storage reactions of MnCO3 are observed such as the oxidation of Mn2+ in MnCO3 to Mn3+ in charge process after long‐term cycles and the further lithiation of Li2CO3 in discharge process. As such, the SPTOR approach may represent a viable strategy for crafting various hollow functional materials with metastable nanomaterials as precursors.

Synthesis of TiO2 Nanobelt Bundles Decorated with TiO2 Nanoparticles and Aggregates and Their Use as Anode Materials for Lithium-Ion Batteries.

TiO2 nanobelt bundles decorated with TiO2 aggregates were prepared using an easy and scalable hydrothermal method at various temperatures (170, 190, 210, and 230 °C). It was demonstrated that the synthesis temperature is a key parameter to tune the number of aggregates on the nanobelt surface. Prepared TiO2 aggregates and nanobelt bundles were used to design anode materials in which the aggregates regulated the pore size and connectivity of the interconnected nanobelt bundle structure. A galvanostatic technique was employed for the electrochemical characterization of TiO2 samples. Using TiO2 as a model material due to its small volume change during the cycling of lithium-ion batteries (LIBs), the relationship between the morphology of the anode materials and the capacity retention of the LIBs on cycling is discussed. It was clearly found that the size and connectivity of the pores and the specific surface area had a striking impact on the Li insertion behavior, lithium storage capability, and cycling performance of the batteries. The initial irreversible capacity was shown to increase as the specific surface area increased. As the pore size increased, the ability of the mesoporous anatase to release strain was stronger, resulting in better cycling stability. The TiO2 powder prepared at a temperature of 230 °C displayed the highest discharge and charge capacities (203.3 mAh/g and 140.8 mAh/g) and good cycling stability.

Explosion Strategy Engineering Oxygen-Functionalized Groups and Enlarged Interlayer Spacing of the Carbon Anode for Enhanced Lithium Storage

Amorphous carbon monoliths with tunable microstructures are candidate anodes for future lithium-based energy storage. Enhancing lithium storage capability and solid-state diffusion kinetics are the precondition for practical applications. Transforming intrinsic oxygen-rich defects into active sites and engineering enlarged interlayer spacing are of great importance. Herein, a novel explosion strategy is designed based on oxalate pyrolysis producing CO and CO2 to successfully prepare lignin-derived carbon monolith (LSCM) with active carbonyl (C═O) groups and enlarged interlayer spacing. Explosion promotes the demethylation of methoxyl groups and cleavage of carboxyl groups to form C═O groups. CO2 etches carbon atoms in a short time to improve the heteroatom level, expanding the interlayer spacing. ZnC2O4 is decomposed at 400 °C, simultaneously producing CO and CO2, which constructs less C═O groups and large interlayer spacing. MgC2O4 is decomposed at 450 and 480 °C, staged-weakly producing CO and CO2, which constructs more C═O groups and larger interlayer spacing. CaC2O4 is decomposed at 480 and 700 °C, staged-uniformly producing CO and CO2, which constructs abundant C═O groups and largest interlayer spacing. The LSCM prepared by staged-uniform explosion exhibits high lithium storage capacity, superior rate capability, and cycling performance. The assembled lithium ion capacitor device achieves excellent energy/power densities of 78 Wh kg-1/100 W kg-1 and superior durability (capacitance retention of 8 4.6% after 20,000 cycles). This work gives a novel insight to engineer advanced oxygen-functionalized carbons for enhanced lithium storage.

Integrated structure design and synthesis of a pitaya-like SnO2/N-doped carbon composite for high-rate lithium storage capability.

Tin dioxide (SnO2) with a high theoretical capacity of 1494 mA h g-1 has great potential to break through the capacity limitation of the conventional graphite anode (372 mA h g-1) in lithium-ion batteries. However, its practical application still faces several obstacles such as high volumetric expansion and poor electrical conductivity. To solve these problems, innovative design and synthesis of SnO2-based nanocomposite structures are necessary. Herein, we demonstrate an integrated design of a hierarchical pitaya-like P-SnO2/C@NC core-shell nanostructure which includes the core of SnO2 nanoparticles (∼4-12 nm) uniformly embedded in the porous carbon sphere and the shell of a continuous nitrogen-doped carbon (NC) layer. Specifically, during repetitive lithiation and delithiation processes, the ultrasmall SnO2 nanoparticles reduce the internal stress greatly, the porous carbon matrix provides buffer space for a large volume change, and the N-doped carbon shell further guarantees the whole structure unit sufficient electrical conductivity and structural stability. Consequently, the resultant battery exhibits a reversible capacity of 936.8 mA h g-1 after 100 cycles at 100 mA g-1 and even an average capacity of 460.0 mA h g-1 at a high current density of 3.2 A g-1. The excellent electrochemical performance of pitaya-like SnO2/C@NC proves the efficacy of this structure design and thus provides significant reference for the construction of other electrode materials in rechargeable alkali metal ion batteries.

An ultrahigh mass-loading integrated high coulombic efficiency Si–graphite electrode for high-energy-density lithium ion batteries

A tailored silicon electrode with a tough graphite framework, optimized heteroatom penetration and rational binder engineering shows impressive lithium storage capability.

Ball-Milling-Triggered Synthesis of Si/C/SiC@MCMB Composites from Carbon Dioxide for Improved Lithium Storage Capability

The excessive emission of carbon dioxide (CO2) poses a serious threat to the sustainable development of human beings. The efficient conversion of CO2 into high-value-added chemicals is of great significance for solving the greenhouse effect and energy crisis. Herein, a new strategy is proposed to turn CO2 into Si/C/SiC composites through a one-step ball-milling reaction with Mg2Si at room temperature. Moreover, mesophase carbon microspheres (MCMB) are introduced into reactants to prepare Si/C/SiC@MCMB composites for possible commercial application. This method realizes the synchronous formation of Si, C, and SiC with a tight interfacial contact at room temperature, which enhances the electronic conductivity and structural stability of Si/C. It is found that the addition of MCMB greatly restricts the formation of SiC inactive phase and leads to a thin lamellar structure for lithium storage. When evaluated as a lithium-ion battery anode, the Si/C/SiC@MCMB composites exhibit superior cycling stability and rating performance. This room temperature synthesis strategy has the advantages of low cost, simple operation process, and easy scalable production, which not only provide a new route to turn CO2 into a benefit but also provide a new way for the design and synthesis of high-capacity Si/C anodes.

Bi3Se4 nanodots in porous carbon: A new anode candidate for fast lithium/sodium storage

• A new Bi 3 Se 4 -based anode material is successfully developed and firstly applied in lithium and sodium ion batteries. • For the first time, in-situ XRD is employed to disclose the lithium storage mechanism of Bi 3 Se 4 /C-800 anode. • C-Se bonds are proved to strengthen the heterointerface and improve reaction knietics via experiments and theoretical calculations. • Bi 3 Se 4 /C-800 electrode exhibits ultra-long cycling life and fast-charging capability. Bismuth selenide has attracted considerable attention as anode materials due to its high theoretical capacity. However, its development has been limited to Bi 2 Se 3 -based composites up to now. Herein, a facile strategy to regulate the atomic ratio of Bi x Se y is propsed and a new Bi 3 Se 4 -based anode material is successfully developed. Firstly, in-situ XRD technique is employed to disclose the combined conversion and alloying reactions mechanism. Besides, a uniform structure with Bi 3 Se 4 nanodots embedded within a sheet-like carbon framework is verified, ensuring fast kinetics and efficient alleviation of stress derived from dramatic volume expansion. Furthermore, experimental results combined with theoretical calculations prove the formation of robust interfacial C-Se bonds, which could simultaneously enhance the inherent bulk electronic conductivity and accelerate ionic transportation. As expected, Bi 3 Se 4 -based electrode achieves an ultralong cycle life of 1500 cycles at a high current density of 2 A g −1 and fast lithium storage capability of 211 mAh g −1 at an ultrahigh rate of 20 A g −1 . Such exceptional performance fully proves the huge potential of Bi 3 Se 4 -based electrode and also provides guidance for the exploration of other high-performance Bi x Se y -based anodes. A new Bi 3 Se 4 -based anode material is proposed via facilely optimizing the selenization temperature. Advanced in-situ technique combined with computational simulations are employed to evaluate phase evolution, lithium storage mechanism and electrolchemical performance. Consequently, Bi 3 Se 4 /C hybrid exhibits fast-charging capability and durable cycling life benefiteed from robust structure and stable C-Se bonds.

Porous silicon covalently-grafted with chloro-styrenic carbons for fast Li+ diffusion and durable lithium-storage capability

Silicon-based anode materials have critical issues such as drastic volume changes, huge stress generation, and the thickening of solid‒electrolyte interphase layer. Thus, a new strategy for improving silicon interface is necessary for significantly enhanced Li+ ion transportation and structural stability during prolonged cycling, while simultaneously reducing severe side reactions. Herein, we prepared porous silicon particles covalently linked with styrene-based polymers (polystyrene (PS) and poly(4-chlorostyrene) (PCS)) via a facile non-atmospheric thermolytic process at a low-temperature (≤400 °C), in which the decomposed styrenic carbon fragments are covalently grafted on the silicon surface via Si–O–C and Si–C species. Notably, PCS-grafted porous silicon exhibited the significantly enhanced electrochemical performance (i.e., a high rate capability of 1270 mAh g−1 at 20 A g−1, 90.7% of initial capacity at 4 A g−1, and a reversible capacity of 1725 mAh g−1 after 200 cycles), because of the dual covalent linkages of Si–C and Si–O–C species in chloro-styrenic carbons that provide durable lithium storage capability and fast Li+ transportation. Specifically, the Si–C linkage enforced the formation of a durable interlayer that protects the Si active material from reactive electrolytes, and the polarized Si–O–C linkage facilitates the rapid transport of Li+ ions.

Space-confined synthesis of a novel Ge@HCS-rGO yolk-shell nanostructure as anode materials for enhanced lithium storage

Germanium (Ge) is considered as a promising anode material due to its high lithium storage capability. However, the huge volume change during cycling cause serious structural degradation and poor cycling stability. Yolk-shell nanostructure design is an effective way to solve such problems for electrode materials such as Ge and Si. Herein, we proposed the design and synthesis of a novel Ge@hollow carbon sphere-reduced graphene oxide (Ge@HCS-rGO) yolk-shell nanostructure as anode via a space-confined strategy for the first time. Rational void space is engineered in the yolk-shell structure, offering a buffer zone for adapting the volume expansion of Ge core particles with protective carbon shells upon lithiation, while the 3D conductive network with hierarchical pores provides fast electron and Li-ion transport channels. Benefiting from the unique structural dual-protection of 3D conductive network and yolk-shell nanostructure, the as-synthesized Ge@HCS-rGO anode exhibits high discharge capacity (2117.3 mA h g−1 at 0.2 C), enhanced cycling stability (958.6 mA h g−1 up to 200 cycles at 0.2 C) and excellent rate capability (1010.0 mA h g−1 at 4 C). The electrochemical performance of Ge@HCS-rGO yolk-shell anode is greatly improved compared with bare Ge and Ge@HCS anode, suggesting its great potential to develop high performance electrode materials with large volume expansion.

Fe 3 O 4 Nanoparticles Enhanced Amorphous Ferric Silicate/Reduced Graphene Oxide for High‐Performance Lithium‐Ion Storage

Ferric silicate (FS) has been explored as a potential lithium ion batteries candidate for its environment benign, low cost, rich reserves, and high capacity. Despite these advantages, poor electronic conductivity and large volume variation obstruct its practical utilization. To improve its electrochemical performance, a unique hybrid structure with Fe3O4@ferric silicate nanosheets anchored on the reduced graphene oxide ([email protected]/RGO) is fabricated. The disordered amorphous nanosheet structure of FS not only shortens the transferred length for lithium ions but also facilities the Li+ diffusion and can effectively keep the structure integrity. RGO substrate ameliorates the electronic conductivity and slackens the strain upon cycling. Fe3O4 (FO) nanoparticles embedded in FS further boost the electronic conductivity and the lithium storage capability. The synergistic effects bestow the composite superior electrochemical properties. [email protected]/RGO shows high reversible capacity of 1113 mA h g−1 at 0.2 A g−1, an excellent rate performance of 681 mA h g−1 at 2 A g−1, and a splendid cycling stability with a capacity of 859 mA h g−1 at 1 A g−1 after 800 cycles.

A novel strategy to accelerate electrochemical kinetics in polymorphic Nb2O5 nanosheets for highly stable and rate-capable lithium storage

Nb2O5-based nanomaterials are emerged as a promising electrode material for lithium-ion batteries. However, the rapid capacity loss during cycling and poor rate capability limits their usage in practical applications. In this work, a novel strategy is employed to address these issues. Polymorphic Nb2O5 nanosheets with surface carbon modification were synthesized. The developed nanosheets were coexist in orthorhombic (T), tetragonal (M) and monoclinic (H) phases with abundant interfaces and tunable amount of carbon contents. The combined effect of surface carbon coating along with coexistence of multiphases on the electrochemical performance of Nb2O5 nanosheets were investigated. It is found that the Nb2O5 nanosheets (Nb2O5 @C-2) with carbon coating thickness of 6 nm delivers enhanced reversible capacity (~187.7 mAh·g−1 at 5C with a capacity retention rate of 97.1 %.), outstanding rate capability (116.8 mAh·g−1 at 35C as compare to many states of art Nb2O5-based anode materials) and good cycling stability even after 700 cycles. The excellent performance of the Nb2O5@C-2 electrode owed to the synergy between Nb2O5 and ultrathin amorphous carbon layer with multiphases, creation of abundant interfaces, increase in ionic conductivity and stable structure. It is suggested that the lithium storage capabilities of Nb2O5 can be tuned by optimizing the thickness of carbon layer.

An Effective Way to Prepare Submicron MoO2 Anodes for High-Stable Lithium-Ion Batteries

Herein, MoO2-based submicrons (named MoO2@C) are synthesized through an effective one-step hydrothermal process. The prepared MoO2 submicrons wrapped in carbonouse layer are uniformly produced and can be applied to the anodes in lithium-ion batteries (LIBs). The novel MoO2@C electrodes demonstrate attractive lithium storage ability. Moreover, compared with the commercial pure MoO2, the MoO2@C delivers a superior electrochemical capacity (e.g, 760.83 mAh g-1 capacity in long-life test at high rate of 1 A g-1) with outstanding capacity retention ratio and stability as well as rate capability. The superior lithium storage capabilities result from plenty of the Li+ sites and adequate electrolyte infiltration effect, which allows the fast transport of electrons and ions, and well-dispersed MoO2 submicrons in carbon-based layers that effectively prevents aggregation of nano size particles.

Carbon Nanofiber Decorated Ternary Transition Metal Oxide Anodes for Fast Charging Lithium‐Ion Batteries

Fast charging rate capability of electrochemically active ternary transition metal Ni–Co–Mn oxides (NCMO) anode incorporated with the carbon nanofibers (CNF‐NCMO) is prepared by a simple thermal decomposition of acetylene gas on spherical Ni–Co–Mn oxide particles, and the tap density of the particles is around 1.3 g cm−3. The CNF‐NCMO showed the reversible capacity of 447 mAh g−1 at 10C rate (10 A g−1) in lithium metal half‐cells at room temperature (loading level was 1.4 mg cm−2). However, pristine NCMO only shows a reversible capacity of 124 mAh g−1 at 10C rate. The improved lithium storage and rate capability are mainly ascribed to the conductive CNF networks, reducing the contact and charge transfer resistance between the NCMO samples. Also, these results suggest that the carbon nanofibers act as a buffer layer for preventing the volume expansion during the lithium conversion reactions with the improved structural integrity.

Ball-Milled Silicon with Amorphous Al2O3/C Hybrid Coating Embedded in Graphene/Graphite Nanosheets with a Boosted Lithium Storage Capability.

Electrochemical active silicon has attracted great attention as anodes for lithium-ion batteries owing to a high theoretical capacity of 4200 mA h g-1. In this work, ball-milled silicon particles with submicron size were strategically modified with a hybrid coating of amorphous alumina and carbon, which simultaneously embedded in a porous framework of in situ exfoliated graphene/graphite nanosheets (GGN). The composite exhibits an enhanced electrochemical performance, including high cycling stability and superior rate capability. An initial discharge capacity of 1294 mA h g-1 and a reversible charge capacity of 1044 mA h g-1 at 0.2 A g-1 can be achieved with a high initial Coulombic efficiency of up to ca. 81%. Additionally, the composite can remain 902 mA h g-1 after 100 discharge/charge cycles, accounting for a high retention of about 86%. This silicon composite is a promising anode material for high performance lithium-ion batteries with a high energy density, and the facile one-pot fabrication route is low cost and scalable, with a great prospect for practical application.

Improved Lithium Storage Capability of Si Anode by Ball-Milling Produced Graphitic Carbon Sheet and Fe3O4 Nanoparticles

Improved Lithium Storage Capability of Si Anode by Ball-Milling Produced Graphitic Carbon Sheet and Fe3O4 Nanoparticles

Unshackling the reversible capacity of SiOx/graphite-based full cells via selective LiF-induced lithiation

Composite Si@SiOxC anodes with high specific capacity are considered the most promising alternatives to graphite in industrial lithium-ion batteries. However, their cycling stability remains a limiting factor, which originates from the severe volume deformation of silicon-derived species. In this work, the cyclabilities of composite anodes are improved by unshackling the highly reversible lithium storage capabilities from the redundancy capacity of the anode materials. A selective LiF-induced lithiation strategy is proposed based on exploiting interface separation energy differences between LiF and the active materials. An interesting preferential redeposition of LiF is observed at the Si@SiOx particles, which differentiates the otherwise similar lithiation potentials of LiCx and Li15Si4, thereby enabling lithium storage in graphite that was previously underused. The resulting full cell exhibits better rate and cycling performances without sacrificing specific capacity. In an ultra-high area capacity full cell (4.9 mA h cm−2), the capacity retention increases markedly from 66.1% to 94.2% after 300 cycles. The selective lithiation strategy developed herein is feasible for practical industrial applications, and importantly, it requires no changes to the existing mature lithium-ion battery manufacturing process. This study offers a new approach for the development of silicon/graphite composite anodes with long cycling lifetimes.