Etched graphite with internally grown Si nanowires from pores as an anode for high density Li-ion batteries

Ag nanoparticle modified porous Si microspheres as high-performance anodes for Li-ion batteries

This study aimed to address the challenges associated with silicon (Si) anode materials in Li-ion batteries, such as their large volume effect and poor electrical conductivity. To overcome these limitations, a novel composite microsphere called pSi/Ag was developed using quartz waste through a combination of high-energy ball-milling, spray drying, and magnesiothermic reduction techniques. The morphology and structure of the pSi/Ag composite were thoroughly characterized using various methods, including X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. The results revealed that the Ag nanoparticles were uniformly dispersed within the porous micron-sized Si sphere particles, leading to enhanced electrochemical performance compared to pure porous silicon that did not undergo the spray drying process. The use of micron-sized Si prevented the excessive formation of the solid electrolyte interphase film, and the pSi/Ag-5 anode, prepared with 5 wt% AgNO3 as a precursor, demonstrated an impressive initial Coulombic efficiency of 92.8%. Moreover, a high specific capacity of 1251.4 mA h g-1 over 300 cycles at a current density of 4000 mA g-1 was attributed to the improved conductivity provided by the Ag nanoparticles in the Si matrix. The straightforward synthesis method employed in this study to produce pSi/Ag presents a promising approach for the future development of high-performance silicon anodes in Li-ion batteries.

Nanoscale Borate Coating Network Stabilized Iron Oxide Anode for High-Energy-Density Bipolar Lithium-Ion Batteries

High-capacity metal oxides based on non-toxic earth-abundant elements offer unique opportunities as advanced anodes for lithium-ion batteries (LIBs). But they often suffer from large volumetric expansion, particle pulverization, extensive side reactions, and fast degradations during cycling. Here, an easy synthesis method is reported to construct amorphous borate coating network, which stabilizes conversion-type iron oxide anode for the high-energy-density semi-solid-state bipolar LIBs. The nano-borate coated iron oxide anode has high tap density (1.6 g cm^-3 ), high capacity (710 mAh g^-1 between 0.5 - 3.0 V, vs Li/Li⁺ ), good rate performance (200 mAh g^-1 at 50 C), and excellent cycling stability (≈100% capacity resention over 1,000 cycles at 5 A g^-1 ). When paired with high-voltage cathode LiCoO₂ , it enables Cu current collector-free pouch-type classic and bipolar full cells with high voltage (7.6 V with two stack layers), achieving high energy density (≈350 Wh kg^-1 ), outstanding power density (≈6,700 W kg^-1 ), and extended cycle life (75% capacity retention after 2,000 cycles at 2 C), superior to the state-of-the-art high-power LIBs using Li₄ Ti₅ O₁₂ anode. The design and methodology of the nanoscale polyanion-like coating can be applied to other metal oxides electrode materials, as well as other electrochemical materials and devices.

Strategy for enhanced performance of silicon nanoparticle anodes for lithium-ion batteries

The modification of silicon nanoparticles for lithium-ion battery anode materials has been a hot exploration subject in light of their excellent volume buffering performance. However, huge volume expansion leads to an unstable solid electrolyte interface (SEI) layer on the surface of the silicon anode material, resulting in short cell cycle life, which is an important factor limiting the application of silicon nanoparticles. Herein, a dual protection strategy to improve the cycling stability of commercial silicon nanoparticles is demonstrated. Specifically, the Si/s-C@TiO2 composite was produced by the hydrothermal method to achieve the embedding of commercial silicon nanoparticles in spherical carbon and the coating of the amorphous TiO2 shell on the outer surface. Buffering of silicon nanoparticle volume expansion by spherical carbon and also the stabilization of the TiO2 shell with high mechanical strength on the surface constructed a stable outer surface SEI layer of the new Si/s-C@TiO2 electrode during longer cycling. In addition, the spherical carbon and lithiated TiO2 further enhanced the electronic and ionic conductivity of the composite. Electrochemical measurements showed that the Si/s-C@TiO2 composite exhibited excellent lithium storage performance (780 mA h g-1 after 100 cycles at a current density of 0.2 A g-1 with a coulombic efficiency of 99%). Our strategy offers new ideas for the production of high stability and high-performance anode materials for lithium-ion batteries.

Reinforced concrete inspired Si/rGO/cPAN hybrid electrode: highly improved lithium storage via Si electrode nanoarchitecture engineering

Electrode nanoarchitecture engineering is a transformative way to improve the structural stability and build robust transport charge pathways for high-capacity silicon in lithium ion batteries (LIBs). However, the violent expansion of silicon during the lithiation/delithiation process is the chief reason for its limited industrialization. Here, we fabricated an integrated electrode structure using polyacrylonitrile (PAN) and graphene oxide (GO) inspired by reinforced concrete. Based on low-temperature annealing, cyclized PAN was assembled on the surface of silicon nanoparticles and tightly combined with reduced graphene oxide (rGO), which could construct stable and efficient transport channels for electrons and lithium ions and address the issues of electrode structure and interface stability. The resultant Si/rGO/cPAN (RC-Si) as the LIB anode exhibits exceptional combined performances including extraordinary mechanical properties, excellent cycling stability (∼1150 mA h g^-1 at 2 A g^-1 over 500 cycles), superior rate capability (∼600 mA h g^-1 at 12 A g^-1), and high areal capacity (∼5.6 mA h cm^-2 at 0.5 mA cm^-2). The novel electrode design concept is promising to promote the practical application of silicon anodes and open a new avenue to develop other high-capacity anodes for high-performance batteries.

Large areal capacity all-in-one lithium-ion battery based on boron-doped silicon/carbon hybrid anode material and cellulose framework

Si, featuring ultra-large theoretical specific capacity, is a very promising alternative to graphite for Li-ion batteries (LIBs). However, Si suffers from intrinsic low electrical conductivity and structural instability upon lithiation, thereby severely deteriorating its electrochemical performance. To address these issues, B-doping into Si, N-doped carbon coating layer, and carbon nanotube conductive network are combined in this work. The obtained Si/C hybrid anode material can be "grown" onto the Cu foil without using any binder and delivers large specific capacity (2328 mAh g^-1 at 0.2 A g^-1), great rate capability (1296.8 mAh g^-1 at 4 A g^-1), and good cyclability (76.7% capacity retention over 500 cycles). Besides, a cellulose separator derived from cotton is found to be superior to traditional polypropylene separator. By using cellulose as both the separator host and the mechanical skeleton of two electrodes, a flexible all-in-one paper-like LIB is assembled via a facile layer-by-layer filtration method. In this all-in-one LIB, all the components are integrated together with robust interfaces. This LIB is able to offer commercial-level areal capacity of 3.47 mAh cm^-2 (corresponding to 12.73 mWh cm^-2 and 318.3 mWh cm^-3) and good cycling stability even under bending. This study offers a new route for optimizing Si-based anode materials and constructing flexible energy storage devices with a large areal capacity.

Introducing a Pseudocapacitive Lithium Storage Mechanism into Graphite by Defect Engineering for Fast-Charging Lithium-Ion Batteries

The extreme fast-charging capability of lithium-ion batteries (LIBs) is very essential for electric vehicles (EVs). However, currently used graphite anode materials cannot satisfy the requirements of fast charging. Herein, we demonstrate that intrinsic lattice defect engineering based on a thermal treatment of graphite in CO₂ is an effective method to improve the fast-charging capability of the graphite anode. The activated graphite (AG) exhibits a superior rate capability of 209 mAh g^-1 at 10 C (in comparison to 15 mAh g^-1 for the pristine graphite), which is attributed to a pseudocapacitive lithium storage behavior. Furthermore, the full cell LiFePO₄||AG can achieve SOCs of 82% and 96% within 6 and 15 min, respectively. The intrinsic carbon defect introduced by the CO₂ treatment succeeds in improving the kinetics of lithium ion intercalation at the rate-determining step during lithiation, which is identified by the distribution of relaxation times (DRT) and density functional theory (DFT) calculations. Therefore, this study provides a novel strategy for fast-charging LIBs. Moreover, this facile method is also suitable for activating other carbon-based materials.

Glancing angle deposition of large-scale helical Si@Cu3Si nanorod arrays for high-performance anodes in rechargeable Li-ion batteries

Silicon (Si) anode materials have attracted substantial interest due to their high theoretical capacity. Here, the growth of helical Si@Cu₃Si nanorod arrays via glancing angle deposition (GLAD) followed by an annealing process is reported. Pre-deposited Cu atoms were driven into Si-nanorods and successfully reacted with Si to form a Si-Cu alloy at a high temperature. By varying the rotation rate and annealing temperature, the resultant Si@Cu₃Si nanorod arrays showed a reasonably accessible surface area with precise control spacing behavior in favor of accommodating Si volume expansion. Meanwhile, the Si@Cu₃Si anode materials showed higher electrical conductivity, facilitating Li⁺ ion diffusion and electron transfer. The Si@Cu₃Si nanorod arrays in half cells exhibited a volumetric capacity as high as 3350.1 mA h cm^-3 at a rate of 0.25 C and could maintain 1706.7 mA h cm^-3 after 100 cycles, which are superior to those of pristine Si materials. This facile and innovative technology provided new insights into the development of Si-based electrode materials.

Constructing a Reinforced and Gradient Solid Electrolyte Interphase on Si Nanoparticles by In-Situ Thiol-Ene Click Reaction for Long Cycling Lithium-Ion Batteries

Constructing a stable solid electrolyte interphase (SEI) on high-specific-capacity silicon (Si) anode is one of the most effective methods to reduce the crack of SEI and improve the cycling performance of Si anode. Herein, the authors construct a reinforced and gradient SEI on Si nanoparticles by an in-situ thiol-ene click reaction. Mercaptopropyl trimethoxysilane (MPTMS) with thiol functional groups (SH) is first grafted on the Si nanoparticles through condensation reaction, which then in-situ covalently bonds with vinylene carbonate (VC) to form a reinforced and uniform SEI on Si nanoparticles. The modified SEI with sufficient elastic Li_x SiO_y can homogenize the stress and strain during the lithiation of Si nanoparticles to reduce their expansion and prevent the SEI from cracking. The Si nanoparticles-graphite blending anode with the reinforced SEI exhibits excellent performance with an initial coulombic efficiency of ≈90%, a capacity of 1053.3 mA h g^-1 after 500 cycles and a high capacity of 852.8 mA h g^-1 even at a high current density of 3 A g^-1 . Moreover, the obtained anode shows superior cycling stability under both high loadings and lean electrolyte. The in-situ thiol-ene click reaction is a practical method to construct reinforced SEI on Si nanoparticles for next-generation high-energy-density lithium-ion batteries.

Interface Engineering of Silicon and Carbon by Forming a Graded Protective Sheath for High-Capacity and Long-Durable Lithium-Ion Batteries

Silicon is one of the most promising anode materials for lithium-ion batteries, whereas its low electronic conductivity and huge volumetric expansion upon lithiation strongly influence its prospective applications. Herein, we develop a facile method to introduce a graded protective sheath onto the surface of Si nanoparticles by utilizing lignin as the carbon source and Ni(NO₃)₂ as the auxiliary agent. Interestingly, the protective sheath is composed of NiSi₂, SiC, and C from the interior to the exterior, thereby guaranteeing excellent compatibility between the neighboring components. Thanks to this unique coating layer, the obtained nanocomposite delivers a large reversible specific capacity (1586.3 mAh g^-1 at 0.2 A g^-1), excellent rate capability (879.4 mAh g^-1 at 5 A g^-1), and superior cyclability (88.2% capacity retention after 500 cycles at 1 A g^-1). Such great performances are found to derive from a slight volumetric expansion, high Li⁺ ion diffusion coefficients, good interface stability, and fast electrochemical kinetics. These properties are obviously superior to those of their counterparts, benefiting from the interface engineering. This study offers new insights into constructing high-capacity and long-durable electrode materials for energy storage.

Fabrication of Carbon Nanofibers Decorated with Various Kinds of Metal Oxides for Battery Applications

Carbon nanofibers decorated with various metal oxide nanoparticles were fabricated by combining an electrospinning technique of bicomponent polymer mixture and a sol-gel reaction and subsequent carbonization process. Electrospun polymer nanofibers consisting of polyacrylonitrile (PAN) and poly(vinyl pyrrolidone) (PVP) with controllable diameters were fabricated with PAN/PVP core/shell types via phase-separation due to the immiscibility between two polymers. The electrospun nanofibers served as supporting materials with binding sites of PVP to incorporate titanium oxide precursor. Subsequently, the carbonization of the fibers led to the formation of carbon nanofibers@TiO2 for energy application, in which rutile TiO2 nanoparticles were decorated on the surface of carbon nanofiber. Especially, this TiO2 decorated carbon nanofiber electrode exhibited excellent electrochemical property in lithium-ion batteries (≈600 mA h g−1 at C/5 rate for 100 cycles). Furthermore, the carbon nanofibers were also successfully modified with other metal oxides, including NiO, SnO2, and ZrO2 nanoparticles, in a similar manner.

Porous Si/Cu Anode with High Initial Coulombic Efficiency and Volumetric Capacity by Comprehensive Utilization of Laser Additive Manufacturing-Chemical Dealloying

Si has been extensively investigated as an anode material for lithium-ion batteries because of its superior theoretical capacity. However, a scalable fabrication method for a Si-based anode with high initial coulombic efficiency (ICE) and large volumetric capacity remains a critical challenge. Herein, we proposed a novel porous Si/Cu anode in which planar Si islands were embedded in the porous Cu matrix through combined laser additive manufacturing and chemical dealloying. The compositions and dimensions of the structure were controlled by metallurgical and chemical reactions during comprehensive interaction. Such a structure has the advantages of micro-sized Si and porous architecture. The planar Si islands decreased the surface area and thus increased ICE. The porous Cu matrix, which acted as both an adhesive-free binder and a conductive network, provided enough access for electrolyte and accommodated volume expansion. The anode structure was well maintained without observable mechanical damage after cycling, demonstrating the high structure stability and integrity. The porous Si/Cu anode showed a high ICE of 93.4% and an initial volumetric capacity of 2131 mAh cm^-3, which retained 1697 mAh cm^-3 after 100 cycles at 0.20 mA cm^-2. Furthermore, the full-cell configuration (porous Si/Cu //LiFePO₄) exhibited a high energy density of 464.9 Wh kg^-1 and a capacity retention of 84.2% after 100 cycles.

A Scalable Silicon Nanowires-Grown-On-Graphite Composite for High-Energy Lithium Batteries

Silicon (Si) is the most promising anode candidate for the next generation of lithium-ion batteries but difficult to cycle due to its poor electronic conductivity and large volume change during cycling. Nanostructured Si-based materials allow high loading and cycling stability but remain a challenge for process and engineering. We prepare a Si nanowires-grown-on-graphite one-pot composite (Gt-SiNW) via a simple and scalable route. The uniform distribution of SiNW and the graphite flakes alignment prevent electrode pulverization and accommodate volume expansion during cycling, resulting in very low electrode swelling. Our designed nanoarchitecture delivers outstanding electrochemical performance with a capacity retention of 87% after 250 cycles at 2C rate with an industrial electrode density of 1.6 g cm^-3. Full cells with NMC-622 cathode display a capacity retention of 70% over 300 cycles. This work provides insights into the fruitful engineering of active composites at the nano- and microscales to design efficient Si-rich anodes.

Stable high-capacity and high-rate silicon-based lithium battery anodes upon two-dimensional covalent encapsulation

Silicon is a promising anode material for lithium-ion and post lithium-ion batteries but suffers from a large volume change upon lithiation and delithiation. The resulting instabilities of bulk and interfacial structures severely hamper performance and obstruct practical use. Stability improvements have been achieved, although at the expense of rate capability. Herein, a protocol is developed which we describe as two-dimensional covalent encapsulation. Two-dimensional, covalently bound silicon-carbon hybrids serve as proof-of-concept of a new material design. Their high reversibility, capacity and rate capability furnish a remarkable level of integrated performances when referred to weight, volume and area. Different from existing strategies, the two-dimensional covalent binding creates a robust and efficient contact between the silicon and electrically conductive media, enabling stable and fast electron, as well as ion, transport from and to silicon. As evidenced by interfacial morphology and chemical composition, this design profoundly changes the interface between silicon and the electrolyte, securing the as-created contact to persist upon cycling. Combined with a simple, facile and scalable manufacturing process, this study opens a new avenue to stabilize silicon without sacrificing other device parameters. The results hold great promise for both further rational improvement and mass production of advanced energy storage materials.

Stabilizing silicon without sacrificing other device parameters is essential for practical use in lithium and post lithium battery anodes. Here, the authors show the skin-like two-dimensional covalent encapsulation furnishing a remarkable level of integrated lithium storage performances of silicon.

Interconnected Vertically Stacked 2D-MoS2 for Ultrastable Cycling of Rechargeable Li-Ion Battery

A two-dimensional (2D) layer-structured material is often a high-capacity ionic storage material with fast ionic transport within the layers. This appears to be the case for nonconversion layer structure, such as graphite. However, this is not the case for conversion-type layered structure such as transition-metal sulfide, in which localized congestion of ionic species adjacent to the surface will induce localized conversion, leading to the blocking of the fast diffusion channels and fast capacity fading, which therefore constitutes one of the critical barriers for the application of transition-metal sulfide layered structure. In this work, we report the tackling of this critical barrier through nanoscale engineering. We discover that interconnected vertically stacked two-dimensional-molybdenum disulfide can dramatically enhance the cycling stability. Atomic-level in situ transmission electron microscopy observation reveals that the molybdenum disulfide (MoS₂) nanocakes assembled with tangling {100}-terminated nanosheets offer abundant open channels for Li⁺ insertion through the {100} surface, featuring an exceptional cyclability performance for over 200 cycles with a capacity retention of 90%. In contrast, (002)-terminated MoS₂ nanoflowers only retain 10% of original capacity after 50 cycles. The present work demonstrates a general principle and opens a new route of crystallographic design to enhance electrochemical performance for assembling 2D materials for energy storage.

Scalable synthesis of ant-nest-like bulk porous silicon for high-performance lithium-ion battery anodes

Although silicon is a promising anode material for lithium-ion batteries, scalable synthesis of silicon anodes with good cyclability and low electrode swelling remains a significant challenge. Herein, we report a scalable top-down technique to produce ant-nest-like porous silicon from magnesium-silicon alloy. The ant-nest-like porous silicon comprising three-dimensional interconnected silicon nanoligaments and bicontinuous nanopores can prevent pulverization and accommodate volume expansion during cycling resulting in negligible particle-level outward expansion. The carbon-coated porous silicon anode delivers a high capacity of 1,271 mAh g⁻¹ at 2,100 mA g⁻¹ with 90% capacity retention after 1,000 cycles and has a low electrode swelling of 17.8% at a high areal capacity of 5.1 mAh cm⁻². The full cell with the prelithiated silicon anode and Li(Ni_1/3Co_1/3Mn_1/3)O₂ cathode boasts a high energy density of 502 Wh Kg⁻¹ and 84% capacity retention after 400 cycles. This work provides insights into the rational design of alloy anodes for high-energy batteries.

Silicon is a promising anode material for lithium-ion batteries but experiences large volume changes during cycling. Here the authors report a scalable method to synthesize porous ant-nest-like silicons. The unique structure of this anode solves the swelling problem and enables impressive performance.

Double-Holey-Heterostructure Frameworks Enable Fast, Stable, and Simultaneous Ultrahigh Gravimetric, Areal, and Volumetric Lithium Storage

Deliberate design of advantageous nanostructures holds great promise for developing high-performance electrode materials for electrochemical energy storage. However, it remains a tremendous challenge to simultaneously gain high gravimetric, areal, and volumetric capacities as well as high rate performance and cyclability to meet practical requirements mainly due to the intractable insufficient ion diffusion and limited active sites for dense electrodes with high areal mass loadings. Herein we report a double-holey-heterostructure framework, in which holey Fe₂O₃ nanosheets (H-Fe₂O₃) are tightly and conformably grown on the holey reduced graphene oxide (H-RGO). This hierarchical nanostructure allows for rapid ion and electron transport and sufficient utilization of active sites throughout a highly compact and thick electrode. Therefore, the free-standing flexible H-Fe₂O₃/H-RGO heterostructure anode can simultaneously deliver ultrahigh gravimetric, areal, and volumetric capacities of 1524 mAh g^-1, 4.72 mAh cm^-2, and 2621 mAh cm^-3, respectively, at 0.2 A g^-1 after 120 cycles, and extraordinary rate performance with a capacity of 487 mAh g^-1 (1.51 mAh cm^-2) at a high current density of 30 A g^-1 (93 mA cm^-2) as well as excellent cycling stability with a capacity retention of 96.3% after 1600 cycles, which has rarely been achieved before.

Shell-Protective Secondary Silicon Nanostructures as Pressure-Resistant High-Volumetric-Capacity Anodes for Lithium-Ion Batteries

The nanostructure design of a prereserved hollow space to accommodate 300% volume change of silicon anodes has created exciting promises for high-energy batteries. However, challenges with weak mechanical stability during the calendering process of electrode fabrication and poor volumetric energy density remain to be solved. Here we fabricated a pressure-resistant silicon structure by designing a dense silicon shell coating on secondary micrometer particles, each consisting of many silicon nanoparticles. The silicon skin layer significantly improves mechanical stability, while the inner porous structure efficiently accommodates the volume expansion. Such a structure can resist a high pressure of over 100 MPa and is well-maintained after the calendering process, demonstrating a high volumetric capacity of 2041 mAh cm^-3. In addition, the dense silicon shell decreases the surface area and thus increases the initial Coulombic efficiency. With further encapsulation with a graphene cage, which allows the silicon core to expand within the cage while retaining electrical contact, the silicon hollow structure exhibits a high initial Coulombic efficiency and fast rise of later Coulombic efficiencies to >99.5% and superior stability in a full-cell battery.

Boron Embedded in Metal Iron Matrix as a Novel Anode Material of Excellent Performance

Boron, the most ideal lithium-ion battery anode material, demonstrates highest theoretical capacity up to 12 395 mA h g^-1 when forming Li₅ B. Furthermore, it also exhibits promising features such as light weight, considerable reserves, low cost, and nontoxicity. However, boron-based materials are not in the hotspot list because Li₅ B may only exist when B is in atomically isolated/dispersed form, while the aggregate material can barely be activated to store/release Li. At this time, an ingenious design is demonstrated to activate the inert B to a high specific capacity anode material by dispersing it in a Fe matrix. The above material can be obtained after an electrochemical activation of the precursors Fe₂ B/Fe and B₂ O₃ /Fe. The latter harvests the admirable capacity, ultrahigh tap density of 2.12 g cm^-3 , excellent cycling stability of 3180 mA h cm^-3 at 0.1 A g^-1 (1500 mA h g^-1 ) after 250 cycles, and superlative rate capability of 2650 mA h cm^-3 at 0.5 A g^-1 , 2544 mA h cm^-3 at 1.0 A g^-1 , and 1696 mA h cm^-3 at 2.0 A g^-1 . Highly conductive matrix promoted reversible Li storage of boron-based materials might open a new gate for advanced anode materials.

Scallop-Inspired Shell Engineering of Microparticles for Stable and High Volumetric Capacity Battery Anodes

Building stable and efficient electron and ion transport pathways are critically important for energy storage electrode materials and systems. Herein, a scallop-inspired shell engineering strategy is proposed and demonstrated to confine high volume change silicon microparticles toward the construction of stable and high volumetric capacity binder-free lithium battery anodes. As for each silicon microparticle, the methodology involves an inner sealed but adaptable overlapped graphene shell, and an outer open hollow shell consisting of interconnected reduced graphene oxide, mimicking the scallop structure. The inner closed shell enables simultaneous stabilization of the interfaces of silicon with both carbon and electrolyte, substantially facilitates efficient and rapid transport of both electrons and lithium ions from/to silicon, the outer open hollow shell creates stable and robust transport paths of both electrons and lithium ions throughout the electrode without any sophisticated additives. The resultant self-supported electrode has achieved stable cycling with rapidly increased coulombic efficiency in the early stage, superior rate capability, and remarkably high volumetric capacity upon a facile pressing process. The rational design and engineering of graphene shells of the silicon microparticles developed can provide guidance for the development of a wide range of other high capacity but large volume change electrochemically active materials.

Stabilizing Si/graphite composites with Cu and in situ synthesized carbon nanotubes for high-performance Li-ion battery anodes

A Si/graphite/Cu–CNT composite was prepared using a mechanical ball-milling method followed by a Cu-catalyzed chemical vapor deposition process.

Electrochemical performance enhancement of graphite negative electrode by nano-metallic-oxides

Severe mechanical strain and rapid capacity decay during Li⁺ insertion/extraction processes restrict the potential applications of copper oxides as lithium-ion battery anode materials and modified electrode materials.

Fast-charging high-energy lithium-ion batteries via implantation of amorphous silicon nanolayer in edge-plane activated graphite anodes

As fast-charging lithium-ion batteries turn into increasingly important components in forthcoming applications, various strategies have been devoted to the development of high-rate anodes. However, despite vigorous efforts, the low initial Coulombic efficiency and poor volumetric energy density with insufficient electrode conditions remain critical challenges that have to be addressed. Herein, we demonstrate a hybrid anode via incorporation of a uniformly implanted amorphous silicon nanolayer and edge-site-activated graphite. This architecture succeeds in improving lithium ion transport and minimizing initial capacity losses even with increase in energy density. As a result, the hybrid anode exhibits an exceptional initial Coulombic efficiency (93.8%) and predominant fast-charging behavior with industrial electrode conditions. As a result, a full-cell demonstrates a higher energy density (≥1060 Wh l-1) without any trace of lithium plating at a harsh charging current density (10.2 mA cm-2) and 1.5 times faster charging than that of conventional graphite.It is desirable to develop fast-charging batteries retaining high energy density. Here, the authors report a hybrid anode via incorporation of an implanted amorphous silicon nanolayer and edge-plane-activated graphite, which meets both criteria.

Silicene Flowers: A Dual Stabilized Silicon Building Block for High-Performance Lithium Battery Anodes

Nanostructuring is a transformative way to improve the structure stability of high capacity silicon for lithium batteries. Yet, the interface instability issue remains and even propagates in the existing nanostructured silicon building blocks. Here we demonstrate an intrinsically dual stabilized silicon building block, namely silicene flowers, to simultaneously address the structure and interface stability issues. These original Si building blocks as lithium battery anodes exhibit extraordinary combined performance including high gravimetric capacity (2000 mAh g^-1 at 800 mA g^-1), high volumetric capacity (1799 mAh cm^-3), remarkable rate capability (950 mAh g^-1 at 8 A g^-1), and excellent cycling stability (1100 mA h g^-1 at 2000 mA g^-1 over 600 cycles). Paired with a conventional cathode, the fabricated full cells deliver extraordinarily high specific energy and energy density (543 Wh kg_ca^-1 and 1257 Wh L_ca^-1, respectively) based on the cathode and anode, which are 152% and 239% of their commercial counterparts using graphite anodes. Coupled with a simple, cost-effective, scalable synthesis approach, this silicon building block offers a horizon for the development of high-performance batteries.

Hot-Chemistry Structural Phase Transformation in Single-Crystal Chalcogenides for Long-Life Lithium Ion Batteries

Tuned chalcogenide single crystals rooted in sulfur-doped graphene were prepared by high-temperature solution chemistry. We present a facile route to synthesize a rod-on-sheet-like nanohybrid as an active anode material and demonstrate its superior performance in lithium ion batteries (LIBs). This nanohybrid contains a nanoassembly of one-dimensional (1D) single-crystalline, orthorhombic SnS onto two-dimensional (2D) sulfur-doped graphene. The 1D nanoscaled SnS with the rodlike single-crystalline structure possesses improved transport properties compared to its 2D hexagonal platelike SnS₂. Furthermore, we blend this hybrid chalcogenide with biodegradable polymer composite using water as a solvent. Upon drying, the electrodes were subjected to heating in vacuum at 150 °C to induce polymer condensation via formation of carboxylate groups to produce a mechanically robust anode. The LIB using the as-developed anode material can deliver a high volumetric capacity of ∼2350 mA h cm^-3 and exhibit superior cycle stability over 1500 cycles as well as a high capacity retention of 85% at a 1 C rate. The excellent battery performance combined with the simplistic, scalable, and green chemistry approach renders this anode material as a very promising candidate for LIB applications.

Silicon Diphosphide: A Si-Based Three-Dimensional Crystalline Framework as a High-Performance Li-Ion Battery Anode

The development of an electrode material for rechargeable Li-ion batteries (LIBs) and the understanding of its reaction mechanism play key roles in enhancing the electrochemical characteristics of LIBs for use in various portable electronics and electric vehicles. Here, we report a three-dimensional (3D) crystalline-framework-structured silicon diphosphide (SiP2) and its interesting electrochemical behaviors for superior LIBs. During Li insertion in the SiP2, a three-step electrochemical reaction mechanism, sequentially comprised of a topotactic transition (0.55-2 V), an amorphization (0.25-2 V), and a conversion (0-2 V), was thoroughly analyzed. On the basis of the three-step electrochemical reaction mechanism, excellent electrochemical properties, such as high initial capacities, high initial Coulombic efficiencies, stable cycle behaviors, and fast-rate capabilities, were attained from the preparation of a nanostructured SiP2/C composite. This 3D crystalline-framework-structured SiP2 compound will be a promising alternative anode material in the realization and mass production of excellent, rechargeable LIBs.

Metallurgically lithiated SiOx anode with high capacity and ambient air compatibility

A common issue plaguing battery anodes is the large consumption of lithium in the initial cycle as a result of the formation of a solid electrolyte interphase followed by gradual loss in subsequent cycles. It presents a need for prelithiation to compensate for the loss. However, anode prelithiation faces the challenge of high chemical reactivity because of the low anode potential. Previous efforts have produced prelithiated Si nanoparticles with dry air stability, which cannot be stabilized under ambient air. Here, we developed a one-pot metallurgical process to synthesize LixSi/Li2O composites by using low-cost SiO or SiO2 as the starting material. The resulting composites consist of homogeneously dispersed LixSi nanodomains embedded in a highly crystalline Li2O matrix, providing the composite excellent stability even in ambient air with 40% relative humidity. The composites are readily mixed with various anode materials to achieve high first cycle Coulombic efficiency (CE) of >100% or serve as an excellent anode material by itself with stable cyclability and consistently high CEs (99.81% at the seventh cycle and ∼99.87% for subsequent cycles). Therefore, LixSi/Li2O composites achieved balanced reactivity and stability, promising a significant boost to lithium ion batteries.

Well-constructed silicon-based materials as high-performance lithium-ion battery anodes

Silicon has been considered as one of the most promising anode material alternates for next-generation lithium-ion batteries, because of its high theoretical capacity, environmental friendliness, high safety, low cost, etc. Nevertheless, silicon-based anode materials (especially bulk silicon) suffer from severe capacity fading resulting from their low intrinsic electrical conductivity and great volume variation during lithiation/delithiation processes. To address this challenge, a few special constructions from nanostructures to anchored, flexible, sandwich, core-shell, porous and even integrated structures, have been well designed and fabricated to effectively improve the cycling performance of silicon-based anodes. In view of the fast development of silicon-based anode materials, we summarize their recent progress in structural design principles, preparation methods, morphological characteristics and electrochemical performance by highlighting the material structure. We also point out the associated problems and challenges faced by these anodes and introduce some feasible strategies to further boost their electrochemical performance. Furthermore, we give a few suggestions relating to the developing trends to better mature their practical applications in next-generation lithium-ion batteries.

Fe@N-Graphene Nanoplatelet-Embedded Carbon Nanofibers as Efficient Electrocatalysts for Oxygen Reduction Reaction

An activated carbon nanofiber (CNF) is prepared with incorporated Fe-N-doped graphene nanoplatelets (Fe@NGnPs), via a novel and simple synthesis approach. The activated CNF-Fe@NGnP catalysts exhibit substantially improved activity for the oxygen reduction reaction compared to those of commercial carbon blacks and Pt/carbon catalysts.

A direct synthesis of Si-nanowires on 3D porous graphene as a high performance anode material for Li-ion batteries

A facile direct fabrication route to the synthesis of Si-nanowires on a highly conductive porous 3D graphene network of graphene foam utilizing a conductive flexible support and facilitating improved Si-mass loadings is demonstrated.

Solution-grown GeO2 nanoparticles with a nearly 100% yield as lithium-ion battery anodes

Germanium oxide (GeO₂) nanoparticles were synthesized with a nearly 100% production yield in a nonionic reverse micelle system at ambient temperature as high performance lithium-ion battery anodes.

All-Aqueous Directed Assembly Strategy for Forming High-Capacity, Stable Silicon/Carbon Anodes for Lithium-Ion Batteries

Silicon (Si) particles have emerged as a promising active material for next-generation lithium-ion battery anodes. However, the large volume changes during lithiation/delithiation cycles result in fracture and pulverization of Si, leading to rapid fading of performance. Here, we report a simple, all-aqueous, directed assembly-based strategy to fabricate Si-based anodes that show capacity and capacity retention that are comparable or better than other more complex methods for forming anodes. We use a cationic surfactant, cetyltrimethylammonium bromide (CTAB), to stabilize Si nanoparticles (SiNPs) in water. This suspension is added to an aqueous suspension of para-amino benzoic acid-terminated carbon black (CB), pH 7. Charge interactions cause the well-dispersed SiNP to bind to the CB, allowing most of the SiNP to be available for lithiation and charge transfer. The CB forms a conducting network when the suspension pH is lowered. The dried SiNP/CTAB/CB anode exhibits a capacity of 1580 mAh g(-1) and efficiency of 97.3% after 50 cycles at a rate of 0.1C, and stable performance at cycling rates up to 5C. The directed spatial organization of the SiNP and CB using straightforward colloidal principles allows good contact between the well-dispersed active material and the electrically conducting network. The pore space in the CB network accommodates volume changes in the SiNPs. When CTAB is not used, the SiNPs form aggregates in the suspension, and do not contact the CB effectively. Therefore, the electrochemical performance of the SiNP/CB anode is inferior to that of the SiNP/CTAB/CB anode. This aqueous-based, room temperature, directed assembly technique is a new, but simple, low-cost scalable method to fabricate stable Si-based anodes for lithium-ion batteries with performance characteristics that match those made by other more sophisticated techniques.

High-Performance Silicon Battery Anodes Enabled by Engineering Graphene Assemblies

We propose a novel material/electrode design formula and develop an engineered self-supporting electrode configuration, namely, silicon nanoparticle impregnated assemblies of templated carbon-bridged oriented graphene. We have demonstrated their use as binder-free lithium-ion battery anodes with exceptional lithium storage performances, simultaneously attaining high gravimetric capacity (1390 mAh g(-1) at 2 A g(-1) with respect to the total electrode weight), high volumetric capacity (1807 mAh cm(-3) that is more than three times that of graphite anodes), remarkable rate capability (900 mAh g(-1) at 8 A g(-1)), excellent cyclic stability (0.025% decay per cycle over 200 cycles), and competing areal capacity (as high as 4 and 6 mAh cm(-2) at 15 and 3 mA cm(-2), respectively). Such combined level of performance is attributed to the templated carbon bridged oriented graphene assemblies involved. This engineered graphene bulk assemblies not only create a robust bicontinuous network for rapid transport of both electrons and lithium ions throughout the electrode even at high material mass loading but also allow achieving a substantially high material tap density (1.3 g cm(-3)). Coupled with a simple and flexible fabrication protocol as well as practically scalable raw materials (e.g., silicon nanoparticles and graphene oxide), the material/electrode design developed would propagate new and viable battery material/electrode design principles and opportunities for energy storage systems with high-energy and high-power characteristics.

A facile route for growth of CNTs on Si@hard carbon for conductive agent incorporating anodes for lithium-ion batteries

Conductive agent incorporating Si anodes consisting of directly grown carbon nanotubes on hard carbon encapsulating Si nanoparticles were prepared by a one-pot chemical vapour deposition process. Owing to this fabulous structure, Si-based anodes exhibit excellent cycle retention and rate capability with a high-mass-loading of 3.5 mg cm(-2).

Hollow carbon nanospheres/silicon/alumina core-shell film as an anode for lithium-ion batteries

Hollow carbon nanospheres/silicon/alumina (CNS/Si/Al₂O₃) core-shell films obtained by the deposition of Si and Al₂O₃ on hollow CNS interconnected films are used as the anode materials for lithium-ion batteries. The hollow CNS film acts as a three dimensional conductive substrate and provides void space for silicon volume expansion during electrochemical cycling. The Al₂O₃ thin layer is beneficial to the reduction of solid-electrolyte interphase (SEI) formation. Moreover, as-designed structure holds the robust surface-to-surface contact between Si and CNSs, which facilitates the fast electron transport. As a consequence, the electrode exhibits high specific capacity and remarkable capacity retention simultaneously: 1560 mA h g⁻¹ after 100 cycles at a current density of 1 A g⁻¹ with the capacity retention of 85% and an average decay rate of 0.16% per cycle. The superior battery properties are further confirmed by cyclic voltammetry (CV) and impedance measurement.

One-minute deposition of micrometre-thick porous Si anodes for lithium ion batteries

3–14 μm-thick porous Si anodes were vapor-deposited on Cu current collectors in 10–60 s and discharge capacities of 1000 mA h g_Si⁻¹ and 0.66 mA h cm_anode⁻² were achieved for the 50th cycle.

A silicon nanowire-reduced graphene oxide composite as a high-performance lithium ion battery anode material

Toward the increasing demands of portable energy storage and electric vehicle applications, silicon has been emerging as a promising anode material for lithium-ion batteries (LIBs) owing to its high specific capacity. However, serious pulverization of bulk silicon during cycling limits its cycle life. Herein, we report a novel hierarchical Si nanowire (Si NW)-reduced graphene oxide (rGO) composite fabricated using a solvothermal method followed by a chemical vapor deposition process. In the composite, the uniform-sized [111]-oriented Si NWs are well dispersed on the rGO surface and in between rGO sheets. The flexible rGO enables us to maintain the structural integrity and to provide a continuous conductive network of the electrode, which results in over 100 cycles serving as an anode in half cells at a high lithium storage capacity of 2300 mA h g(-1). Due to its [111] growth direction and the large contact area with rGO, the Si NWs in the composite show substantially enhanced reaction kinetics compared with other Si NWs or Si particles.

One-Dimensional Silicon Nanostructures for Li Ion Batteries

One dimensional (1D) silicon nanostructures have attracted significant interest as an anode material for lithium ion batteries (LIBs) as its 1D geometry accommodates the large volume change of the Si during cycling and enables facile electron transport during all stages of operation. Furthermore, the high aspect ratio of 1D Si nanostructures enables us to investigate atomic-scale mechanisms of the lithiation process and corresponding volume change behavior. Various 1D nanostructures with different morphologies and compositions have been explored to achieve a robust cycle performance, reversible morphological changes, and high rate capabilities. In this Perspective, we summarize the recent significant advances of 1D Si nanostructures and discuss electrode design strategies based on the recent geometry and composition engineering.