Fast Lithium Ion Transport Research Articles

Low-Temperature Synthesis of a Porous High-Entropy Transition-Metal Oxide as an Anode for High-Performance Lithium-Ion Batteries.

Transition-metal oxides (TMOs) are promising anode materials for high-performance lithium-ion batteries (LIBs) because of their abundant reserves and high theoretical capacity. However, the poor conductivity, unstable solid electrolyte interface (SEI) film, and poor cycling stability still limit their practical applications. As a novel kind of anode material, a high-entropy oxide (HEO) is a single-phase crystal structure composed of multiple metal elements, demonstrating a huge potential for energy storage applications due to the synergistic effect of various metal species. Herein, we have designed the porous spinel-phase HEO (Cr0.2Fe0.2Co0.2Ni0.2Zn0.2)3O4 synthesized at low temperature by a sol-gel method. On the one hand, the unique porous nanostructure not only promotes transport of the electrolyte but also alleviates the volume change of active materials upon cycling. On the other hand, the stabilization effect of entropy can suppress the formation of cation short-range order within the crystalline structure of HEO by a lattice distortion effect, thus guaranteeing a fast lithium-ion transport and achieving an excellent electrochemical performance. As a result, the as-prepared HEO-450 electrode delivers 1022 mAh/g after 1000 cycles at 1 A/g and 220 mAh/g at an ultrahigh current density of 30 A/g, respectively.

Li+ transportation mechanisms in the halide solid-state electrolytes Li3YCl6 and Li3InCl6

Developing outstanding halide solid-state electrolytes (SSEs) has attracted a lot of attention in the area of all-solid-state batteries, owing to their excellent compatibility with high-voltage active materials. In halide compounds, lithium (Li+) ions are usually confined in the center of octahedral units, which seriously impedes the fast transportation of lithium ions. However, the representative SSEs, Li3YCl6 and Li3InCl6, present ultrafast ionic conductivities below 0.1 mS/cm at room temperature, which may be closely connected with their particular configurations. Through assessments of the transportation mechanisms in Li3YCl6 and Li3InCl6 by careful density functional theory simulations, two kinds of lithium-ion diffusion channels can be identified. Furthermore, the overall performances of Li3YCl6 and Li3InCl6, including energetic stability, electronic chemical window and electronic structures, are systematically studied. This will bring deep insights into and reliable criteria for exploring next-generation halide SSEs.

Effect of zinc-based active sites on porous carbon and electrochemical properties in lithium-sulfur batteries

Hierarchically porous carbon (HPC) is considered as one of the promising cathodes of lithium-sulfur batteries (LSBs) owing to its appealing merits. However, it is still preventing the shuttle effect poorly due to the weak interaction between nonpolar carbon and polar polysulfide (LiPS). Herein, we report a facile method to prepare polar hierarchically porous carbon by in-situ loading the different amounts of zinc-based active sites (p-HPC-X) onto the HPC materials. The close combination of a carbon interconnected skeleton and ZnS nanoparticles derived zinc-based active sites forms the strong interaction that suppresses the soluble polysulfide shuttle effect and catalyzes the kinetics redox reactions of lithium polysulfide/sulfide. Moreover, the effect of polar sites introduced in situ on the morphology/porosity of carbon materials is also focused on. Crystallization of zinc-based active sites during the freeze-drying process and self-assembly during carbonization allow the pore size distribution of porous carbon to be customized, which offers fast lithium-ion and electron transport channels. Due to the synergistic effect of the hierarchical pore structure and suitable polarity sites, the p-HPC-X exhibits high capacity and good cycling performance. Especially p-HPC-1, it yields a high reversible capacity of 683.7 mAh g−1 and a low fading rate of 0.041% per cycle over 900 cycles at a current density of 1 C. This work offers novel insights into realizing the effect of in-situ loaded active sites on pore structure and electrochemical performance in LSBs.

A new metallic composite cathode originated from hyperbranched polymer coated MOF for High-performance Lithium-Sulfur batteries

To improve the polysulfides redox conversion and mitigate the shuttle effect for lithium-sulfur (Li-S) batteries, a hyperbranched polymer coated MOF-derived zirconium nitrogen oxides and N-doping carbon composites (Zr2N2O/NC-6) are designed and prepared by pyrolytic method. Thanks to some advantages of this type of new composites including fast lithium-ion transport, lithium polysulfides (LiPSs) anchoring and multiple functional sites, the cells with S/Zr2N2O/NC-6 cathode exhibit good cycle stability (the capacity retention is 81.8% at 1C after 300 cycles) and rate capability (566.8 mAh g−1 at 5C). More importantly, even if the sulfur loading is up to 8.16 mg cm−2 and low electrolyte/sulfur (E/S) ratio (7.79 µL mg−1), the cells with S/Zr2N2O/NC-6 cathode deliver an initial area capacity of 7.2 mAh cm−2 and the capacity also can maintain at 5.34 mAh cm−2 after 80 cycles at 0.2C, which are much better than the commercial lithium-ion batteries. This work exhibits a MOF-derived novel material Zr2N2O/NC used as the sulfur host for the first time, which can have a guiding role in designing multifunctional materials with adsorption, ion transport and catalytic features for the high-performance lithium sulfur batteries with application potential.

Functionalized Graphene Quantum Dots Modified Dioxin-Linked Covalent Organic Frameworks for Superior Lithium Storage.

Covalent organic framework, as an emerging porous nano-frame structure with pre-designed structure and custom properties, has been demonstrated as a prospective electrode for rechargeable Li-ion batteries. For improving the reversible capacity and long-term cycle stability of COF materials, we propose a GQDs modified COF material (COF-GQDs) and apply it as the anode for LIBs for the first time. This COF-GQDs electrode delivers enhanced long-term cycling performance with a large capacity of ∼820 mAh g-1 after 300 cycles at 100 mA g-1 and an improved rate performance. The enhanced lithium-storage performance, in terms of obvious-shortened activation process and high reversible capacities, can be attributed to the modification of carboxyl GQDs, which would activate more active sites (activated C=C groups from benzene rings) for lithium-storage, and provide fast lithium-ion transportation kinetic. Besides, the decreased interphase resistance, enhanced electronic conductivity, and prevented aggregation of needle-flake COF structure, originated from the addition of GQDs, which lead to the enhanced improved cycling stability of the COF-GQDs electrode. This manuscript can promote the further exploration on the design of COF-related materials with modification of functionalized carbonaceous materials to achieve enhanced lithium-storage properties for next-generation energy storage.

High-specific-capacity molybdate anode materials for lithium-ion batteries with good low-temperature performance

Molybdate materials have proved to be potential anode because of their superior specific capacity, stable three-dimensional framework structure and fast lithium-ion transport ability. However, the low-temperature properties and electrochemical reaction mechanism still lack in-depth research. Here, two molybdate materials, LiCr(MoO4)2/C and Li3Cr(MoO4)3/C, are synthesized by a sample ball-milling assisted high-temperature solid state method and studied as anode materials for lithium-ion batteries (LIBs) at room temperature and low temperature. Between 0.01 V and 3.00 V, LiCr(MoO4)2/C and Li3Cr(MoO4)3/C exhibit high specific capacities of 1158 and 1077 mA h·g−1 at 50 mA·g−1 at 25 °C, respectively. LiCr(MoO4)2/C delivers a high specific capacity of 352 mA h·g−1 at a high current density of 5000 mA·g−1. After 500 cycles, LiCr(MoO4)2/C and Li3Cr(MoO4)3/C both retain reversible capacities over 600 mA h·g−1 at 250 mA·g−1. Even at low temperature of 0 °C, − 10 °C, − 20 °C, Li3Cr(MoO4)3/C still delivers high capacities of 1061, 891 and 742 mA h·g−1, respectively. Ex-situ X-ray diffraction (XRD) is conducted to study the electrochemical reaction mechanism. Moreover, low-temperature cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests are used to explore the limitations of low-temperature performance. This work provides low-temperature anode material for LIBs and deepens the understanding of low-temperature performance.

Enhanced homogeneity of electrochemical reaction via low tortuosity enabling high-voltage nickel-rich layered oxide thick-electrode

Inhomogeneous electrochemical reactions during the charging-discharging process of high-voltage nickel-rich layered oxide cathodes play a major role in cracks formation and deteriorating cyclability. Especially in thick electrodes, the severe concentration polarization aggravates the inhomogeneity and further diminishes the cycle life. In this work, a low-tortuous thick electrode of LiNi0.7Co0.1Mn0.2O2 (NCM712) is constructed by the ice-templating strategy and the effect of low tortuosity on electrochemical performance is investigated. Low-tortuous NCM712 electrode exhibits reduced concentration polarization and fast lithium-ion transport kinetics, consequently enabling superior rate capability. Furthermore, benefiting from the effective electronic and ionic transport network in low-tortuous thick electrode, NCM712 particles present homogeneous electrochemical reaction and alleviated intragranular stress, which suppresses cation mixing and cracking formation at high voltage condition. The homogeneity of electrochemical reaction in the low-tortuous thick electrode is favorable to attain the structural integrity, the robust electrolyte interface and superior cyclability. This strategy provides a new concept to homogenize the electrochemical reaction of thick nickel-rich layered oxide electrodes by low tortuosity electrode architecture design, leading to superb electrochemical performance with high energy density.

Enhanced Dynamic Phase Stability and Suppressed Mn Dissolution in Low-Tortuosity Spinel LMO Electrode

Microspinel LiMn 2 O 4 (LMO) is a widely used cathode material in power lithium-ion batteries. However, inevitable Mn dissolution and dynamic phase instability will cause the degradation of microspinel LMO during cycling. Here, a low-tortuosity LMO (LMO-LT) electrode is fabricated by an ice-templating method, which exhibits enhanced dynamic phase stability, alleviated Mn dissolution, and rare particle microcracks during cycling. It is shown that the low-tortuosity electrode enables fast lithium-ion diffusion and thus small concentration polarization, leading to uniform electrochemical reaction within microregions of the LMO-LT electrode. Furthermore, the fast lithium-ion transport kinetics and even mesoscopic scale reactions of the LMO-LT electrode effectively alleviate irreversible phase transition and Mn dissolution as well as suppress crack generation in LMO particles. As a result, the full cell [negative-to-positive capacity ratio (N/P) = 1.1] with thick LMO-LT cathode (13 mg cm −2 ) and Li 4 Ti 5 O 12 anode sustains 80.0% capacity over 200 cycles. The LMO-LT electrode further delivers 78.9% capacity of that at 0.1 C at the high rate of 5 C. This work provides an important strategy to enhance dynamic phase stability and suppress Mn dissolution at the mesoscopic scale, promoting the development of high-performance LMO electrodes.

PVDF-HFP based polymer electrolytes with high Li+ transference number enhancing the cycling performance and rate capability of lithium metal batteries

Lithium metal batteries are confronted with safety issues in liquid electrolyte systems owing to rapid growth of lithium dendrite and uneven lithium deposition. Exploration of gel polymer electrolytes (GPEs) with excellent ionic conductivity and high Li+ migration number is a possible strategy to replace liquid electrolyte. Herein, a high-powered GPEs relied on poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) modified by polymer polyethylene glycol (PEG) and lithium montmorillonite (LiMNT) via bond interactions is reported. The prepared porous polymer electrolyte presents a captivating ionic conductivity of 1.82 × 10−3 S·cm−1 and lithium ions transference number up to 0.513 at 25 °C. In view of the eminent ionic conductivity and efficient migration number of Li+, the three-dimensional porous polymer electrolyte is very conducive to the fast transport and stable deposition of lithium ions, restraining the occurrence and growth rate of lithium dendrites, which improves the cycle performance and rate capability of lithium battery. LiFePO4| PPL122 electrolyte |Li battery delivers a desired cycling performance with a capacity retention of 92% after 1000 cycles at 1 C.

MnO₂ Nanoparticles Anchored Multi Walled Carbon Nanotubes as Potential Anode Materials for Lithium Ion Batteries.

Herein, we report a facile hydrothermal synthesis of MnO₂ nanoparticles anchored multi walled carbon nanotubes (MnO₂@MWCNTs) as potential anode materials for lithium-ion (Li-ion) batteries. The prepared MnO₂@MWCNTs were characterized by several techniques which confirmed the formation of MnO₂ nanoparticles anchored MWCNTs. The X-ray diffraction and Raman-scattering analyses of the prepared material further revealed the effective synthesis of MnO₂@MWCNTs. The fabricated Li-ion battery based on MnO₂@MWCNTs exhibited a reversible capacity of ~823 mAhg-1 at a current density of 100 mAg-1 for the first cycle, and delivered a capacity of ~421 mAhg-1 for the 60 cycles. The coulombic efficiency was found to be ~100% which showed excellent reversible charge-discharge behavior. The outstanding performance of the MnO₂@MWCNTs anode for the Li-ion battery can be attributed to the distinctive morphology of the MnO₂ nanoparticles anchored MWCNTs that facilitated the fast transport of lithium ions and electrons and accommodated a broad volume change during the cycles of charge/discharge.

Porosity Engineering of MXene Membrane towards Polysulfide Inhibition and Fast Lithium Ion Transportation for Lithium-Sulfur Batteries.

Detrimental lithium polysulfide (LiPS) shuttle effects and sluggish electrochemical conversion kinetics in lithium-sulfur (Li-S) batteries severely hinder their practical application. Separator modification has been extensively investigated as an effective strategy to address above issues. Nevertheless, in the case of functional separators, how to effectively block the LiPSs from diffusion while enabling the rapid Li ion transport remains a challenge. Herein, by using an "oxidation-etching" method, MXene membranes are presented with controllable in-plane pores as interlayer to regulate Li ion transportation and LiPS immobilization. Porous MXene membranes with optimized pore density and size can simultaneously anchor LiPS and ensure fast Li ion diffusion. Consequently, even with pure sulfur cathode, the improved Li-S batteries deliver excellent rate performance up to 2 C with a reversible capacity of 677.6mAhg-1 and long-term cyclability over 500 cycles at 1 C with a low capacity decay of 0.07% per cycle. This work sheds new insights into the design of high-performance interlayers with manipulated nanochannels and tailored surface chemistry to regulate LiPSs trapping and Li ion diffusion in Li-S batteries.

One-pot hydrothermal synthesis of N-rGO supported Fe2O3 nanoparticles as a superior anode material for lithium-ion batteries

Fe2O3 nanoparticles with a diameter of 60–70 nm are uniformly grown on the surface of N-rGO sheets via a facile hydrothermal method to form two-dimensional hybrid nanostructures. When evaluated as an anode material for lithium-ion batteries, this Fe2O3/N-rGO composite exhibits outstanding lithium storage performance, with a high reversible capacity of 1398 mAh g−1 at 0.5 A g−1 after 200 cycles and 652 mAh g−1 at 15 A g−1. The excellent performance of the Fe2O3/N-rGO hybrid can be attributed to the N-rGO sheets that benefit the fast transport of both lithium ions and electrons during electrochemical reactions; besides, the well-dispersed Fe2O3 nanoparticles and the flexible N-rGO substrate could effectively release the volume effect of the Fe2O3 during discharge/charge processes. Due to the unique two-dimensional hybrid nanostructure, Fe2O3/N-rGO composite shows significant pseudocapacitive behavior during discharge/charge processes, which partially accounts for the excellent lithium ion storage performance.

Low crystalline 1T-MoS2@S-doped carbon hollow spheres as an anode material for Lithium-ion battery

A low crystalline 1T-MoS2@S-doped carbon (MoS2@SC) composite was successfully synthesized via a facile hydrothermal process. The composite is comprised by few-layer 1T-MoS2 nanosheets covered by an amorphous carbon layer with an expanded interlayer d-spacing of 1.01 nm. This structure is conducive to the fast transport of lithium-ions and volume accommodation during the charge–discharge process when the composite is applied as an anode material for LIBs. Additionally, the high conductivity and layered structure of 1T-MoS2 also facilitate fast of ion/electron transport, contributing to the improvement of the electrochemical properties. Therefore, this material demonstrated a high rate performance and excellent cycling stability, with the capacities of 847 and 622 mA h g−1 achieved at the current densities of 0.2 A g−1 and 2 A g−1, respectively. Even at a larger current density of 2 A g−1, MoS2@SC delivered a high reversible capacity of 659 mA h g−1 with an average capacity loss of 0.006% per cycle after 500 cycles.

Anchoring perovskite-Type FeMnO3 microspheres on CNT conductive networks via electrostatic self-assembly for high-performance lithium-ion capacitors

Lithium-ion capacitors (LICs) are emerging energy storage devices that integrate the high energy density of lithium-ion batteries with the high-power density of supercapacitors. However, their practical performance is severely limited by the sluggish reaction kinetic for battery-type anodes. To address this issue, we propose an electrostatic self-assembly strategy for fabricating perovskite-type FeMnO3 microspheres anchored within the carbon nanotube conductive network (FeMnO3-CNTCN) as the anode materials for LICs. In the well-interconnected 3D construction, FeMnO3 microspheres with multi-step redox reaction can provide abundant active sites for the lithium storage, while highly conductive and flexible CNT substrate ensures fast lithium-ion transport and electron transfer. Benefiting from the synergistic interplay between two components, the FeMnO3-CNTCN anode exhibits the splendid cyclability and rate performance. Furthermore, the entire LIC with FeMnO3-CNTCN anode delivers a superior energy density of 163 Wh kg−1 at a power density of 245 W kg−1, along with a capacity retention of 83% after 10,000 cycles. These results demonstrate the promising prospect of FeMnO3-CNTCN in high-performance LICs, and the proposed electrostatic self-assembly strategy opens up a chance for the facile synthesis of the composite materials in advanced energy storage.

Enhanced Cycling and Rate Capability by Epitaxially Matched Conductive Cubic TiO Coating on LiCoO2 Cathode Films.

Layered lithium transition-metal oxides, such as LiCoO2 and its doped and lithium-rich analogues, have become the most attractive cathode material for current lithium-ion batteries due to their excellent power and energy densities. However, parasitic reactions at the cathode–electrolyte interface, such as metal-ion dissolution and electrolyte degradation, instigate major safety and performance issues. Although metal oxide coatings can enhance the chemical and structural stability, their insulating nature and lattice mismatch with the adjacent cathode material can act as a physical barrier for ion transport, which increases the charge-transfer resistance across the interface and impedes cell performance at high rates. Here, epitaxial engineering is applied to stabilize a cubic (100)-oriented TiO layer on top of single (104)-oriented LiCoO2 thin films to study the effect of a conductive coating on the electrochemical performance. Lattice matching between the (104) LiCoO2 surface facets and the (100) TiO plane enables the formation of the titanium mono-oxide phase, which dramatically enhances the cycling stability as well as the rate capability of LiCoO2. This cubic TiO coating enhances the preservation of the phase and structural stability across the (104) LiCoO2 surface. The results suggest a more stable Co3+ oxidation state, which not only limits the cobalt-ion dissolution into the electrolyte but also suppresses the catalytic degradation of the liquid electrolyte. Furthermore, the high c-rate performance combined with high Columbic efficiency indicates that interstitial sites in the cubic TiO lattice offer facile pathways for fast lithium-ion transport.

Mechanistic Origin of Superionic Lithium Diffusion in Anion-Disordered Li6PS5 X Argyrodites.

The rational development of fast-ion-conducting solid electrolytes for all-solid-state lithium-ion batteries requires understanding the key structural and chemical principles that give some materials their exceptional ionic conductivities. For the lithium argyrodites Li6PS5X (X = Cl, Br, or I), the choice of the halide, X, strongly affects the ionic conductivity, giving room-temperature ionic conductivities for X = {Cl,Br} that are ×103 higher than for X = I. This variation has been attributed to differing degrees of S/X anion disorder. For X = {Cl,Br}, the S/X anions are substitutionally disordered, while for X = I, the anion substructure is fully ordered. To better understand the role of substitutional anion disorder in enabling fast lithium-ion transport, we have performed a first-principles molecular dynamics study of Li6PS5I and Li6PS5Cl with varying amounts of S/X anion-site disorder. By considering the S/X anions as a tetrahedrally close-packed substructure, we identify three partially occupied lithium sites that define a contiguous three-dimensional network of face-sharing tetrahedra. The active lithium-ion diffusion pathways within this network are found to depend on the S/X anion configuration. For anion-disordered systems, the active site–site pathways give a percolating three-dimensional diffusion network; whereas for anion-ordered systems, critical site–site pathways are inactive, giving a disconnected diffusion network with lithium motion restricted to local orbits around S positions. Analysis of the lithium substructure and dynamics in terms of the lithium coordination around each sulfur site highlights a mechanistic link between substitutional anion disorder and lithium disorder. In anion-ordered systems, the lithium ions are pseudo-ordered, with preferential 6-fold coordination of sulfur sites. Long-ranged lithium diffusion would disrupt this SLi6 pseudo-ordering, and is, therefore, disfavored. In anion-disordered systems, the pseudo-ordered 6-fold S–Li coordination is frustrated because of Li–Li Coulombic repulsion. Lithium positions become disordered, giving a range of S–Li coordination environments. Long-ranged lithium diffusion is now possible with no net change in S–Li coordination numbers. This gives rise to superionic lithium transport in the anion-disordered systems, effected by a concerted string-like diffusion mechanism.

An advanced solid polymer electrolyte composed of poly(propylene carbonate) and mesoporous silica nanoparticles for use in all-solid-state lithium-ion batteries

Composite solid polymer electrolytes (CSPEs) are promising candidates for replacing potentially hazardous organic liquid electrolytes used in Li ion batteries (LIBs). CSPEs are easy to process, have the ability to form films, and make better interfacial contact. However, their poor mechanical strength, low ionic conductivity, and long cycling stability limit their practical applications. Here, we demonstrate the fabrication of a cost-effective, flexible, self-standing, and highly stable CSPE using poly(propylene carbonate) (PPC) as the host matrix and highly mesoporous silica nanoparticles (MSNs) as the filler. The fabricated CSPE had a high ionic conductivity of approximately 8.5 × 10−4 S cm−1 at 60°C, electrochemical potential stability up to approximately 4.8 V vs. Li/Li+, an ultra-high lithium transference number of approximately 0.86, impressive stability over 1000 h of Li stripping/plating, and an excellent electrode compatibility. With cyclability over 200 cycles and a negligible overpotential, the Li/CSPE/LFP cell delivered a reversible capacity of 171 and 103 mAh g−1 at 0.1 C and 1 C, respectively, with a good rate capability up to 5 C. The interaction of Li+ with PPC and the MSNs is demonstrated by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) and X-ray photoelectron spectroscopy (XPS) studies. The enhanced physico-electrochemical properties of the CSPE were attributed to the large MSNs-related surface area, which enables firm interaction with the PPC matrix and provides a less-tortuous polymer-ceramic phase for fast lithium ion transportation. The proposed MSNs-reinforced CSPE thus opens new possibilities for the fabrication and engineering of solid-state batteries.

Tortuosity Modulation toward High‐Energy and High‐Power Lithium Metal Batteries

AbstractLithium metal batteries (LMBs) are well recognized as potentially high‐energy systems to power portable electronics and electric vehicles. However, LMBs always undergo uncontrollable lithium deposition in metallic lithium anodes due to inhomogeneous lithium ion flux, which causes limited power output and impedes their practical applications. Low‐tortuous arrays in metallic lithium anodes have been intensively investigated to guide the fast transport of lithium ions and homogeneous growth of metallic lithium, thereby achieving high‐power LMBs. In this review, the correlation between the electrochemical kinetics and tortuosity of LMBs is first disclosed, especially in the metallic lithium anodes. Subsequently, the material design strategies for the low‐tortuous anodes are systematically summarized, including regulating lithium‐ion flux, electric field, and lithium nucleation by low‐tortuous insulating, conductive, and lithiophilic arrays, respectively. At the same time, low‐tortuous arrays are also efficient in guiding ion transport in the cathodes and solid composite electrolytes of LMBs. Finally, the currently existing challenges of modulating low‐tortuous structures to achieve high‐energy and high‐power LMBs are discussed.

Lithium Metal Batteries: A Solid‐State Battery Cathode with a Polymer Composite Electrolyte and Low Tortuosity Microstructure by Directional Freezing and Polymerization (Adv. Energy Mater. 1/2021)

The image representing article number 2002387 by Chun Huang, Patrick S. Grant and co-workers shows a solid-state lithium metal battery opening like opening a book. The team report a novel structured cathode comprising aligned active material particles (magenta) embedded in a new polymer composite electrolyte (green). Unlike conventional random microstructures in cathodes, the low tortuosity channels between the aligned columns of active material particles facilitate fast lithium ion transport through the cathode, resulting in near theoretical energy storage performance.

Silicon-Based Anode of Lithium Ion Battery Made of Nano Silicon Flakes Partially Encapsulated by Silicon Dioxide.

Ubiquitous mobile electronic devices and rapidly increasing electric vehicles demand a better lithium ion battery (LIB) with a more durable and higher specific charge storage capacity than traditional graphite-based ones. Silicon is among the most promising active media since it exhibits ten times of a specific capacity. However, alloying with lithium by silicon and dissociation of the silicon-lithium alloys induce high volume changes and result in pulverization. The loss of electrical contacts by silicon with the current collector of the anode causes rapid capacity decay. We report improved anode cycling performance made of silicon flakes partially encapsulated by silicon dioxide and coated with conductive nanocarbon films and CNTs. The silicon dioxide surface layer on a silicon flake improves the physical integrity for a silicon-based anode. The exposed silicon surface provides a fast transport of lithium ions and electrons. CNTs and nanocarbon films provide electrical connections between silicon flakes and the current collector. We report a novel way of manufacturing silicon flakes partially covered by silicon dioxide through breaking oxidized silicon flakes into smaller pieces. Additionally, we demonstrate an improved cycling life and capacity retention compared to pristine silicon flakes and silicon flakes fully encapsulated by silicon dioxide. Nanocarbon coatings provide conduction channels and further improve the anode performance.