Porous structured silicon has been regarded as a promising candidate to overcome pulverization of silicon-based anodes. However, poor mechanical strength of these porous particles has limited their ...volumetric energy density towards practical applications. Here we design and synthesize hierarchical carbon-nanotube@silicon@carbon microspheres with both high porosity and extraordinary mechanical strength (>200 MPa) and a low apparent particle expansion of ~40% upon full lithiation. The composite electrodes of carbon-nanotube@silicon@carbon-graphite with a practical loading (3 mAh cm
) deliver ~750 mAh g
specific capacity, <20% initial swelling at 100% state-of-charge, and ~92% capacity retention over 500 cycles. Calendered electrodes achieve ~980 mAh cm
volumetric capacity density and <50% end-of-life swell after 120 cycles. Full cells with LiNi
Mn
Co
O
cathodes demonstrate >92% capacity retention over 500 cycles. This work is a leap in silicon anode development and provides insights into the design of electrode materials for other batteries.
Since the first report of using micromechanical cleavage method to produce graphene sheets in 2004, graphene/graphene‐based nanocomposites have attracted wide attention both for fundamental aspects ...as well as applications in advanced energy storage and conversion systems. In comparison to other materials, graphene‐based nanostructured materials have unique 2D structure, high electronic mobility, exceptional electronic and thermal conductivities, excellent optical transmittance, good mechanical strength, and ultrahigh surface area. Therefore, they are considered as attractive materials for hydrogen (H2) storage and high‐performance electrochemical energy storage devices, such as supercapacitors, rechargeable lithium (Li)‐ion batteries, Li–sulfur batteries, Li–air batteries, sodium (Na)‐ion batteries, Na–air batteries, zinc (Zn)–air batteries, and vanadium redox flow batteries (VRFB), etc., as they can improve the efficiency, capacity, gravimetric energy/power densities, and cycle life of these energy storage devices. In this article, recent progress reported on the synthesis and fabrication of graphene nanocomposite materials for applications in these aforementioned various energy storage systems is reviewed. Importantly, the prospects and future challenges in both scalable manufacturing and more energy storage‐related applications are discussed.
The recent overall status and progress of graphene and graphene‐based nanocomposites for energy storage devices, such as H2 storage, supercapacitors, Li‐ion batteries, Li‐S batteries, Li‐air batteries, Na‐ion batteries, Na‐air batteries, Zn‐air batteries, and vanadium redox flow batteries are summarized and discussed. The challenges, prospects, and potential development directions of these promising materials for advanced energy storage systems are also investigated.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Silicon has been intensively studied as an anode material for lithium‐ion batteries (LIB) because of its exceptionally high specific capacity. However, silicon‐based anode materials usually suffer ...from large volume change during the charge and discharge process, leading to subsequent pulverization of silicon, loss of electric contact, and continuous side reactions. These transformations cause poor cycle life and hinder the wide commercialization of silicon for LIBs. The lithiation and delithiation behaviors, and the interphase reaction mechanisms, are progressively studied and understood. Various nanostructured silicon anodes are reported to exhibit both superior specific capacity and cycle life compared to commercial carbon‐based anodes. However, some practical issues with nanostructured silicon cannot be ignored, and must be addressed if it is to be widely used in commercial LIBs. This Review outlines major impactful work on silicon‐based anodes, and the most recent research directions in this field, specifically, the engineering of silicon architectures, the construction of silicon‐based composites, and other performance‐enhancement studies including electrolytes and binders. The burgeoning research efforts in the development of practical silicon electrodes, and full‐cell silicon‐based LIBs are specially stressed, which are key to the successful commercialization of silicon anodes, and large‐scale deployment of next‐generation high energy density LIBs.
Research on various silicon anode materials for lithium‐ion batteries has thrived over the past decade. Meanwhile, electrolyte and binder research, and engineering on the electrode scale bear the same importance to boost battery performance. A proper combination of the strategies reviewed here can be the key to bringing silicon anodes closer to wide practical applications.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This paper gives a comprehensive review about the most recent progress in synthesis, characterization, fundamental understanding, and the performance of graphene and graphene oxide sponges. Practical ...applications are considered including use in composite materials, as the electrode materials for electrochemical sensors, as absorbers for both gases and liquids, and as electrode materials for devices involved in electrochemical energy storage and conversion. Several advantages of both graphene and graphene oxide sponges such as three dimensional graphene networks, high surface area, high electro/thermo conductivities, high chemical/electrochemical stability, high flexibility and elasticity, and extremely high surface hydrophobicity are emphasized. To facilitate further research and development, the technical challenges are discussed, and several future research directions are also suggested in this paper.
Graphene sponges prepared by template and free-standing assembly share an ultra-light, conductive, elastic pore network with long-range pore order. Few layer pore walls preserve high surface area and with continued improvements these sponges are being harnessed for enhancement in a rapidly expanding range of applications.
Ultrathin oxide coatings are demonstrated to offer multiple functions for improving the cycling performance of lithium ion batteries. The coatings can serve as an artificial solid electrolyte ...interphase layer, which significantly suppresses electrolyte decomposition as well as mitigates mechanical degradation. Structure modification is critical for increasing the ion conductivity, and therefore leads to improved current efficiency.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
There are growing concerns over the environmental, climate, and health impacts caused by using non‐renewable fossil fuels. The utilization of green energy, including solar and wind power, is believed ...to be one of the most promising alternatives to support more sustainable economic growth. In this regard, lithium‐ion batteries (LIBs) can play a critically important role. To further increase the energy and power densities of LIBs, silicon anodes have been intensively explored due to their high capacity, low operation potential, environmental friendliness, and high abundance. The main challenges for the practical implementation of silicon anodes, however, are the huge volume variation during lithiation and delithiation processes and the unstable solid‐electrolyte interphase (SEI) films. Recently, significant breakthroughs have been achieved utilizing advanced nanotechnologies in terms of increasing cycle life and enhancing charging rate performance due partially to the excellent mechanical properties of nanomaterials, high surface area, and fast lithium and electron transportation. Here, the most recent advance in the applications of 0D (nanoparticles), 1D (nanowires and nanotubes), and 2D (thin film) silicon nanomaterials in LIBs are summarized. The synthetic routes and electrochemical performance of these Si nanomaterials, and the underlying reaction mechanisms are systematically described.
The most recent advance in the applications of 0D (nanoparticles), 1D (nanowires and nanotubes), and 2D (thin film) silicon nanomaterials in lithium ion batteries (LIBs) are summarized. The synthetic routes, electrochemical performance, and underlying reaction mechanisms of these nanomaterials are described and the advantages and limitations using nanostructured silicon in LIBs are also discussed.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Lithium titanate (Li
4Ti
5O
12, or LTO) is a promising anode for lithium-ion batteries due to its rate capability and cycling stability. However, its structural instability and solid electrolyte ...interphase formation at low potential limits its application within a high cut-off voltage above 1
V, which significantly sacrifices the cell voltage and energy density. This work demonstrates how a few atomic layers of Al
2O
3 deposited on LTO electrode improved its cycling performance (no capacity degradation after 100
cycles) and provided a higher Coulombic efficiency compared with the standard uncoated LTO electrode when they are cycled at low potential down to 1
mV. It has been found that the ultrathin oxide layers served as a passivation film not only stabilized the LTO structure but also surprisingly suppressed some undesirable chemical reactions.
► Ultrathin oxide coating was conformally deposited on Lithium Titanate electrode, as proved by HRTEM images combined with EDX analysis. ► A few nanometer Al
2O
3 enabled the lithium titanate to be cycled at deep potential down to 1
mV vs. Li/Li
+ with significantly improved cycling stability and Columbic efficiency with almost no capacity degradation after 100
cycles. ► It has been found oxide coating stabilized SEI and suppressed side reaction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The unique TiO2–C/MnO2 core–double-shell nanowires are synthesized for the first time using as anode materials for lithium ion batteries (LIBs). They combine both advantages from TiO2 such as ...excellent cycle stability and MnO2 with high capacity (1230 mA h g–1). The additional C interlayer intends to improve the electrical conductivity. The self-supported nanowire arrays grown directly on current-collecting substrates greatly simplify the fabrication processing of electrodes without applying binder and conductive additives. Each nanowire is anchored to the current collector, leading to fast charge transfer. The unique one-dimensional core–double-shell nanowires exhibit enhanced electrochemical performance with a higher discharge/charge capacity, superior rate capability, and longer cycling lifetime.
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IJS, KILJ, NUK, PNG, UL, UM
The solid electrolyte interphase (SEI), a passivation layer formed on electrodes, is critical to battery performance and durability. The inorganic components in SEI, including lithium carbonate ...(Li2CO3) and lithium fluoride (LiF), provide both mechanical and chemical protection, meanwhile control lithium ion transport. Although both Li2CO3 and LiF have relatively low ionic conductivity, we found, surprisingly, that the contact between Li2CO3 and LiF can promote space charge accumulation along their interfaces, which generates a higher ionic carrier concentration and significantly improves lithium ion transport and reduces electron leakage. The synergetic effect of the two inorganic components leads to high current efficiency and long cycle stability.
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IJS, KILJ, NUK, PNG, UL, UM
Reduced graphene oxides loaded with tin–antimony alloy (RGO-SnSb) nanocomposites were synthesized through a hydrothermal reaction and the subsequent thermal reduction treatments. Transmission ...electron microscope images confirm that SnSb nanoparticles with an average size of about 20–30 nm are uniformly dispersed on the RGO surfaces. When they were used as anodes for rechargeable sodium (Na)-ion batteries, these as-synthesized RGO-SnSb nanocomposite anodes delivered a high initial reversible capacity of 407 mAh g–1, stable cyclic retention for more than 80 cycles and excellent cycle stability at ultra high charge/discharge rates up to 30C. The significantly improved performance of the synthesized RGO-SnSb nanocomposites as Na-ion battery anodes can be attributed to the synergetic effects of RGO–based flexible framework and the nanoscale dimension of the SnSb alloy particles (<30 nm). Nanosized intermetallic SnSb compounds can exhibit improved structural stability and conductivity during charge and discharge reactions compared to the corresponding individuals (Sn and Sb particles). In the meantime, RGO sheets can tightly anchor SnSb alloy particles on the surfaces, which can not only effectively suppress the agglomeration of SnSb particles but also maintain excellent electronic conduction. Furthermore, the mechanical flexibility of the RGO phase can accommodate the volume expansion and contraction of SnSb particles during the prolonged cycling, therefore, improve the electrode integrity mechanically and electronically. All of these contribute to the electrochemical performance improvements of the RGO-SnSb nanocomposite-based electrodes in rechargeable Na-ion batteries.
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IJS, KILJ, NUK, PNG, UL, UM
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