Advanced Energy‐Storage Architectures Composed of Spinel Lithium Metal Oxide Nanocrystal on Carbon Textiles

Current battery technologies are known to suffer from kinetic problems associated with the solid‐state diffusion of Li⁺ in intercalation electrodes materials. Not only the use of nanostructure materials but also the design of electrode architectures can lead to more advanced properties. Here, advanced electrode architectures consisting of carbon textiles conformally covered by Li₄Ti₅O₁₂ nanocrystal are rationally designed and synthesized for lithium ion batteries. The efficient two‐step synthesis involves the growth of ultrathin TiO₂ nanosheets on carbon textiles, and subsequent conversion into spinel Li₄Ti₅O₁₂ through chemical lithiation. Importantly, this novel approach is simple and general, and it is used to successfully produce LiMn₂O₄/carbon composites textiles, one of the leading cathode materials for lithium ion batteries. The resulting 3D textile electrode, with various advantages including the direct electronic pathway to current collector, the easy access of electrolyte ions, the reduced Li⁺/e^? diffusion length, delivers excellent rate capability and good cyclic stability over the Li‐ion batteries of conventional configurations.     

Amorphous Carbon Coated High Grain Boundary Density Dual Phase Li4Ti5O12‐TiO2: A Nanocomposite Anode Material for Li‐Ion Batteries

This work introduces an effective, inexpensive, and large‐scale production approach to the synthesis of a carbon coated, high grain boundary density, dual phase Li₄Ti₅O₁₂‐TiO₂ nanocomposite anode material for use in rechargeable lithium‐ion batteries. The microstructure and morphology of the Li₄Ti₅O₁₂‐TiO₂‐C product were characterized systematically. The Li₄Ti₅O₁₂‐TiO₂‐C nanocomposite electrode yielded good electrochemical performance in terms of high capacity (166 mAh g^?1 at a current density of 0.5 C), good cycling stability, and excellent rate capability (110 mAh g^?1 at a current density of 10 C up to 100 cycles). The likely contributing factors to the excellent electrochemical performance of the Li₄Ti₅O₁₂‐TiO₂‐C nanocomposite could be related to the improved morphology, including the presence of high grain boundary density among the nanoparticles, carbon layering on each nanocrystal, and grain boundary interface areas embedded in a carbon matrix, where electronic transport properties were tuned by interfacial design and by varying the spacing of interfaces down to the nanoscale regime, in which the grain boundary interface embedded carbon matrix can store electrolyte and allows more channels for the Li+ ion insertion/extraction reaction. This research suggests that carbon‐coated dual phase Li₄Ti₅O₁₂‐TiO₂ nanocomposites could be suitable for use as a high rate performance anode material for lithium‐ion batteries.     

Li4Ti5O12 Nanoparticles Embedded in a Mesoporous Carbon Matrix as a Superior Anode Material for High Rate Lithium Ion Batteries

A mesoporous Li₄Ti₅O₁₂/C nanocomposite is synthesized by a nanocasting technique using the porous carbon material CMK‐3 as a hard template. Modified CMK‐3 template is impregnated with Li₄Ti₅O₁₂ precursor, followed by heat treatment at 750 °C for 6 h under N₂. Li₄Ti₅O₁₂ nanocrystals of up to several tens of nanometers are successfully synthesized in micrometer‐sized porous carbon foam to form a highly conductive network, as confirmed by field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, and nitrogen sorption isotherms. The composite is then evaluated as an anode material for lithium ion batteries. It exhibits greatly improved electrochemical performance compared with bulk Li₄Ti₅O₁₂, and shows an excellent rate capability (73.4 mA h g^?1 at 80 C) with significantly enhanced cycling performance (only 5.6% capacity loss after 1000 cycles at a high rate of 20 C). The greatly enhanced lithium storage properties of the mesoporous Li₄Ti₅O₁₂/C nanocomposite may be attributed to the interpenetrating conductive carbon network, ordered mesoporous structure, and the small Li₄Ti₅O₁₂ nanocrystallites that increase the ionic and electronic conduction throughout the electrode.     

Stable Lithium Electrodeposition at Ultra‐High Current Densities Enabled by 3D PMF/Li Composite Anode

Lithium metal batteries (LMBs) are promising candidates for next‐generation energy storage due to their high energy densities on both weight and volume bases. However, LMBs usually undergo uncontrollable lithium deposition, unstable solid electrolyte interphase, and volume expansion, which easily lead to low Coulombic efficiency, poor cycling performance, and even safety hazards, hindering their practical applications for more than forty years. These issues can be further exacerbated if operated at high current densities. Here a stable lithium metal battery enabled by 3D porous poly‐melamine‐formaldehyde (PMF)/Li composite anode is reported. PMF with a large number of polar groups (amine and triazine) can effectively homogenize Li‐ion concentration when these ions approach to the anode surface and thus achieve uniform Li deposition. Moreover, the 3D structured anode can serve as a Li host to mitigate the volume change during Li stripping and plating process. Galvanostatic measurements demonstrate that the 3D composite electrode can achieve high‐lithium Coulombic efficiency of 94.7% at an ultrahigh current density of 10 mA cm^?2 after 50 cycles with low hysteresis and smooth voltage plateaus. When coupled with Li₄Ti₅O₁₂, half‐cells show enhanced rate capabilities and Coulombic efficiencies, opening great opportunities for high‐energy batteries.     

Hierarchically Porous Li4Ti5O12 Anode Materials for Li‐ and Na‐Ion Batteries: Effects of Nanoarchitectural Design and Temperature Dependence of the Rate Capability

Integrated design of both porous structure and crystalline morphology is expected to open up the way to a new class of materials. This report demonstrates new nanostructured Li₄Ti₅O₁₂ materials with hierarchically porous structures and flower‐like morphologies. Electrochemical studies of the electrodes of Li‐ion and Na‐ion batteries clearly reveal the advantage of nanoarchitectural design of active materials. In addition, the temperature dependence of Na⁺‐insertion/extraction capacity in relation to Li₄Ti₅O₁₂ electrodes is for the first time evaluated and it is found that elevation of the cell operating temperature effectively improves the rate capability of the Na‐ion batteries. Based on the new findings, it is suggested that specially designed Li₄Ti₅O₁₂ materials allow for high‐performance Na‐ion batteries that are available as large‐scale storage devices for applications such as automotive and stationary energy storage.     

In Situ Generation of Artificial Solid‐Electrolyte Interphases on 3D Conducting Scaffolds for High‐Performance Lithium‐Metal Anodes

Rational structure design of the current collector along with further engineering of the solid‐electrolyte interphases (SEI) layer is one of the most promising strategies to achieve uniform Li deposition and inhibit uncontrolled growth of Li dendrites. Here, a Li₂S layer as an artificial SEI with high compositional uniformity and high lithium ion conductivity is in situ generated on the surface of the 3D porous Cu current collector to regulate homogeneous Li plating/stripping. Both simulations and experiments demonstrate that the Li₂S protective layer can passivate the porous Cu skeleton and balance the transport rate of lithium ions and electrons, thereby alleviating the agglomerated Li deposition at the top of the electrode or at the defect area of the SEI layer. As a result, the modified current collector exhibits long‐term cycling of 500 cycles at 1 mA cm^?2 and stable electrodeposition capabilities of 4 mAh cm^?2 at an ultrahigh current density of 4 mA cm^?2. Furthermore, full batteries (LiFePO₄ as cathode) paired with this designed 3D anode with only ≈200% extra lithium show superior stability and rate performance than the batteries paired with lithium foil (≈3000% extra lithium). These explorations provide new strategies for developing high‐performance Li metal anodes.     

3D Hierarchical Porous α‐Fe2O3 Nanosheets for High‐Performance Lithium‐Ion Batteries

To develop a long cycle life and good rate capability electrode, 3D hierarchical porous α‐Fe₂O₃ nanosheets are fabricated on copper foil and directly used as binder‐free anode for lithium‐ion batteries. This electrode exhibits a high reversible capacity and excellent rate capability. A reversible capacity up to 877.7 mAh g^?1 is maintained at 2 C (2.01 A g^?1) after 1000 cycles, and even when the current is increased to 20 C (20.1 A g^?1), a capacity of 433 mA h g^?1 is retained. The unique porous 3D hierarchical nanostructure improves electronic–ionic transport, mitigates the internal mechanical stress induced by the volume variations of the electrode upon cycling, and forms a 3D conductive network during cycling. No addition of any electrochemically inactive conductive agents or polymer binders is required. Therefore, binder‐free electrodes further avoid the uneven distribution of conductive carbon on the current collector due to physical mixing and the addition of an insulator (binder), which has benefits leading to outstanding electrochemical performance.     

Highly‐Safe and Ultra‐Stable All‐Flexible Gel Polymer Lithium Ion Batteries Aiming for Scalable Applications

With the development of flexible electronics, flexible lithium ion batteries (LIBs) have received great attention. Previously, almost all reported flexible components had shortcomings related to poor mechanical flexibility, low energy density, and poor safety, which led to the failure of scalable applications. This study demonstrates a fully flexible lithium ion battery using LiCoO₂ as the cathode, Li₄Ti₅O₁₂ as the anode, and graphene film as the flexible current collector. The graphene oxide modified gel polymer electrolyte exhibits higher ionic conductivity than a conventional liquid electrolyte and improves the safety of the flexible battery. The optimum design of the flexible graphene battery exhibits super electrochemical performance, with a 2.3 V output voltage plateau and a satisfactory capacity of 143.0 mAh g^?1 at 1 C. The mass energy density and power density are both ≈1.4 times higher than a standard electrode using metal foils as current collectors. No capacity loss is observed after 100 thousand cycles of mechanical bending. More importantly, even in the clipping state, this flexible gel polymer battery can still demonstrate a stable and safe electrochemical performance. This work may lead to a promising strategy of high‐performance scalable LIBs for the next‐generation flexible electronics.     

Challenges of Spinel Li4Ti5O12 for Lithium‐Ion Battery Industrial Applications

Rechargeable lithium‐ion batteries (LIBs) offer the advantages of having great electrical energy storage and increased continuous and pulsed power output capabilities, which enable their applications in grid energy storage and electric vehicles (EVs). For safety, high power and durability considerations, spinel Li₄Ti₅O₁₂ is one of the most appealing potential candidate as an anode material for power LIBs due to its excellent cycling stability and thermal stability. However, there are still a number of challenges remaining for Li₄Ti₅O₁₂ battery applications. Herein, an updated overview of the latest advances in Li₄Ti₅O₁₂ research is provided and key challenges for its future development (i.e., fast‐charging, specific capacity, swelling, interface chemistry, matching cathode and electrolyte as well as batteries design and manufacturing) are highlighted.     

Nanoparticles Encapsulated in Porous Carbon Matrix Coated on Carbon Fibers: An Ultrastable Cathode for Li‐Ion Batteries

Nanostructured V₂O₅ is emerging as a new cathode material for lithium ion batteries for its distinctly high theoretic capacity over the current commercial cathodes. The main challenges associated with nanostructured V₂O₅ cathodes are structural degradation, instability of the solid‐electrolyte interface layer, and poor electron conductance, which lead to low capacity and rapid decay of cyclic stability. Here, a novel composite structure of V₂O₅ nanoparticles encapsulated in 3D networked porous carbon matrix coated on carbon fibers (V₂O₅/3DC‐CFs) is reported that effectively addresses the mentioned problems. Remarkably, the V₂O₅/3DC‐CF electrode exhibits excellent overall lithium‐storage performance, including high Coulombic efficiency, excellent specific capacity, outstanding cycling stability and rate property. A reversible capacity of ≈183 mA h g^?1 is obtained at a high current density of 10 C, and the battery retains 185 mA h g^?1 after 5000 cycles, which shows the best cycling stability reported to date among all reported cathodes of lithium ion batteries as per the knowledge. The outstanding overall properties of the V₂O₅/3DC‐CF composite make it a promising cathode material of lithium ion batteries for the power‐intensive energy storage applications.     

A High Areal Capacity Flexible Lithium‐Ion Battery with a Strain‐Compliant Design

Early demonstrations of wearable devices have driven interest in flexible lithium‐ion batteries. Previous demonstrations of flexible lithium‐ion batteries trade off between low areal capacity, poor mechanical flexibility and/or high thickness of inactive components. Here, a reinforced electrode design is used to support the active layers of the battery and a freestanding carbon nanotube (CNT) layer is used as the current collector. The supported architecture helps to increase the areal capacity (mAh cm^‐2) of the battery and improve the tensile strength and mechanical flexibility of the electrodes. Batteries based on lithium cobalt oxide and lithium titanate oxide shows excellent electrochemical and mechanical performance. The battery has an areal capacity of ≈1 mAh cm^‐2 and a capacity retention of around 94% after cycling the battery for 450 cycles at a C/2 rate. The reinforced electrode has a tensile strength of ≈5.5–7.0 MPa and shows excellent capacity retention after repeatedly flexing to a bending radius ranging from 45 to 10 mm. The relationships between mechanical flexing, electrochemical performance, and mechanical integrity of the battery are studied using electrochemical cycling, electron microscopy, and electrochemical impedance spectroscopy (EIS).     

A Lithium Amide‐Borohydride Solid‐State Electrolyte with Lithium‐Ion Conductivities Comparable to Liquid Electrolytes

High ionic conductivity of up to 6.4 × 10^?3 S cm^?1 near room temperature (40 °C) in lithium amide‐borohydrides is reported, comparable to values of liquid organic electrolytes commonly employed in lithium‐ion batteries. Density functional theory is applied coupled with X‐ray diffraction, calorimetry, and nuclear magnetic resonance experiments to shed light on the conduction mechanism. A Li₄Ti₅O₁₂ half‐cell battery incorporating the lithium amide‐borohydride electrolyte exhibits good rate performance up to 3.5 mA cm^?2 (5 C) and stable cycling over 400 cycles at 1 C at 40 °C, indicating high bulk and interfacial stability. The results demonstrate the potential of lithium amide‐borohydrides as solid‐state electrolytes for high‐power lithium‐ion batteries.     

N‐Doped Graphene Modified 3D Porous Cu Current Collector toward Microscale Homogeneous Li Deposition for Li Metal Anodes

Lithium metal is the most promising anode material for high‐energy‐density batteries due to its high specific capacity of 3860 mAh g^?1 and low reduction potential of ?3.04 V versus standard hydrogen electrode. However, huge volume change, safety concerns, and low efficiency impede the practical applications of Li metal anodes. Herein, it is shown that the nitrogen‐doped graphene modified 3D porous Cu (3DCu@NG) current collector can mitigate the above problems. The N‐doped graphene, coating on the surface of 3D current collector, not only contributes to a uniform Li⁺ flux, but also leads to a scattered distribution of electrons throughout the surface, finally contributing to a uniform Li deposition and the improved electrochemical performance. In addition, the continuously porous structure of 3DCu@NG provides a space for the metallic Li deposition and could effectually accommodate the volume expansion during cycling. As a result, the Li‐3DCu@NG anode exhibits a high areal capacity of 4 mAh cm^?2, a high Li utilization of ≈98%, and an ultralow voltage hysteresis of ≈19 mV. The multifunctional N‐doped graphene modified 3D porous current collector promisingly provides a strategy for safe and high‐energy lithium metal anodes.     

Porosity‐Controlled TiNb2O7 Microspheres with Partial Nitridation as A Practical Negative Electrode for High‐Power Lithium‐Ion Batteries

Titanium niobium oxide (TiNb₂O₇) has been recognized as a promising anode material for lithium‐ion batteries (LIBs) in view of its potential to operate at high rates with improved safety and high theoretical capacity of 387 mAh g^?1. However, it suffers from poor Li⁺ ion diffusivity and low electronic conductivity originated from its wide band gap energy (E_g > 2 eV). Here, porous TiNb₂O₇ microspheres (PTNO MSs) are prepared via a facile solvothermal reaction. PTNO MSs have a particle size of ≈1.2 μm and controllable pore sizes in the range of 5–35 nm. Ammonia gas nitridation treatment is conducted on PTNO MSs to introduce conducting Ti_1?xNb_xN layer on the surface and form nitridated PTNO (NPTNO) MSs. The porous structure and conducting Ti_1?xNb_xN layer enhance the transport kinetics associated with Li⁺ ions and electrons, which leads to significant improvement in electrochemical performance. As a result, the NPTNO electrode shows a high discharge capacity of ≈265 mAh g^?1, remarkable rate capability (≈143 mAh g^?1 at 100 C) and durable long‐term cyclability (≈91% capacity retention over 1000 cycles at 5 C). These results demonstrate the great potential of TiNb₂O₇ as a practical high‐rate anode material for LIBs.     

A Hollow‐Shell Structured V2O5 Electrode‐Based Symmetric Full Li‐Ion Battery with Highest Capacity

The symmetric batteries with an electrode material possessing dual cathodic and anodic properties are regarded as an ideal battery configuration because of their distinctive advantages over the asymmetric batteries in terms of fabrication process, cost, and safety concerns. However, the development of high‐performance symmetric batteries is highly challenging due to the limited availability of suitable symmetric electrode materials with such properties of highly reversible capacity. Herein, a triple‐hollow‐shell structured V₂O₅ (THS‐V₂O₅) symmetric electrode material with a reversible capacity of >400 mAh g^?1 between 1.5 and 4.0 V and >600 mAh g^?1 between 0.1 and 3.0 V, respectively, when used as the cathode and anode, is reported. The THS‐V₂O₅ electrodes assembled symmetric full lithium‐ion battery (LIB) exhibits a reversible capacity of ≈290 mAh g^?1 between 2 and 4.0 V, the best performed symmetric energy storage systems reported to date. The unique triple‐shell structured electrode makes the symmetric LIB possessing very high initial coulombic efficiency (94.2%), outstanding cycling stability (with 94% capacity retained after 1000 cycles), and excellent rate performance (over 140 mAh g^?1 at 1000 mA g^?1). The demonstrated approach in this work leaps forward the symmetric LIB performance and paves a way to develop high‐performance symmetric battery electrode materials.     

3D Si/C Fiber Paper Electrodes Fabricated Using a Combined Electrospray/Electrospinning Technique for Li‐Ion Batteries

Although the theoretical capacity of silicon is ten times higher than that of graphite, the overall electrode capacity of Si anodes is still low due to the low Si loading and heavy metal current collector. Here, a novel flexible 3D Si/C fiber paper electrode synthesized by simultaneously electrospraying nano‐Si‐PAN (polyacrylonitrile) clusters and electrospinning PAN fibers followed by carbonization is reported. The combined technology allows uniform incorporation of Si nanoparticles into a carbon textile matrix to form a nano‐Si/carbon composite fiber paper. The flexible 3D Si/C fiber paper electrode demonstrate a very high overall capacity of ≈1600 mAh g^‐1 with capacity loss less than 0.079% per cycle for 600 cycles and excellent rate capability. The exceptional performance is attributed to the unique architecture of the flexible 3D Si/C fiber paper, i.e., the resilient and conductive carbon fiber network matrix, carbon‐coated Si nanoparticle clusters, strong adhesion between carbon fibers and Si nanoparticle clusters, and uniform distribution of Si/C clusters in the carbon fiber frame. The scalable and facile synthesis method, good mechanical properties, and excellent electrochemical performance at a high Si loading make the flexible 3D Si/C fiber paper batteries extremely attractive for plug‐in electric vehicles, flexible electronics, space exploration, and military applications.     

Elucidating the Effect of Iron Doping on the Electrochemical Performance of Cobalt‐Free Lithium‐Rich Layered Cathode Materials

The eco‐friendly and low‐cost Co‐free Li_1.2Mn_0.585Ni_0.185Fe_0.03O₂ is investigated as a positive material for Li‐ion batteries. The electrochemical performance of the 3 at% Fe‐doped material exhibits an optimal performance with a capacity and voltage retention of 70 and 95%, respectively, after 200 cycles at 1C. The effect of iron doping on the electrochemical properties of lithium‐rich layered materials is investigated by means of in situ X‐ray diffraction spectroscopy and galvanostatic intermittent titration technique during the first charge–discharge cycle while high‐resolution transmission electron microscopy is used to follow the structural and chemical change of the electrode material upon long‐term cycling. By means of these characterizations it is concluded that iron doping is a suitable approach for replacing cobalt while mitigating the voltage and capacity degradation of lithium‐rich layered materials. Finally, complete lithium‐ion cells employing Li_1.2Mn_0.585Ni_0.185Fe_0.03O₂ and graphite show a specific energy of 361 Wh kg^?1 at 0.1C rate and very stable performance upon cycling, retaining more than 80% of their initial capacity after 200 cycles at 1C rate. These results highlight the bright prospects of this material to meet the high energy density requirements for electric vehicles.     

Hierarchically Porous,Ultrathick, “Breathable” Wood‐Derived Cathode for Lithium‐Oxygen Batteries

In this work, a hierarchically porous and ultrathick “breathable” wood‐based cathode for high‐performance Li‐O₂ batteries is developed. The 3D carbon matrix obtained from the carbonized and activated wood (denoted as CA‐wood) serves as a superconductive current collector and an ideal porous host for accommodating catalysts. The ruthenium (Ru) nanoparticles are uniformly anchored on the porous wall of the aligned microchannels (denoted as CA‐wood/Ru). The aligned open microchannels inside the carbon matrix contribute to unimpeded oxygen gas diffusion. Moreover, the hierarchical pores on the microchannel walls can be facilely impregnated by electrolyte, forming a continuous supply of electrolyte. As a result, numerous ideal triphase active sites are formed where electrolyte, oxygen, and catalyst accumulate on the porous walls of microchannels. Benefiting from the numerous well‐balanced triple‐phase active sites, the assembled Li‐O₂ battery with the CA‐wood/Ru cathode (thickness: ≈700 µm) shows a high specific area capacity of 8.58 mA h cm^?2 at 0.1 mA cm^?2. Moreover, the areal capacity can be further increased to 56.0 mA h cm^?2 by using an ultrathick CA‐wood/Ru cathode with a thickness of ≈3.4 mm. The facile ultrathick wood‐based cathodes can be applied to other cathodes to achieve a super high areal capacity without sacrificing the electrochemical performance.     

A Novel Strategy to Suppress Capacity and Voltage Fading of Li‐ and Mn‐Rich Layered Oxide Cathode Material for Lithium‐Ion Batteries

Poor cycling stability is one of the key scientific issues needing to be solved for Li‐ and Mn‐rich layered oxide cathode. In this paper, sodium carboxymethyl cellulose (CMC) is first used as a novel binder in Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode to enhance its cycling stability. Electrochemical performance is conducted by galvanostatic charge and discharge. Structure and morphology are characterized by X‐ray diffraction, scanning electronic microscopy, high‐resolution transmission electron microscopy, and X‐ray photoelectron spectroscopy. Results reveal that the CMC as binder can not only stabilize the electrode structure by preventing the electrode materials to detach from the current collector but also suppress the voltage fading of the Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode due to Na⁺ ions doping. Most importantly, the dissolution of metal elements from the cathode materials into the electrolyte is also inhibited.     

Conductive Copper Niobate: Superior Li+‐Storage Capability and Novel Li+‐Transport Mechanism

Niobates with shear ReO₃ crystal structures are remarkably promising anode materials for Li⁺ batteries due to their large capacities, inherent safety, and high cycling stability. However, they generally suffer from limited rate capabilities rooted in their insufficient electronic and Li⁺ conductivities. Here, micrometer‐sized copper niobate (Cu₂Nb₃₄O₈₇) bulk as a new anode material having a high electronic conductivity of 2.1 × 10^?5 S cm^?1 and an impressive average Li⁺ diffusion coefficient of ≈3.5 × 10^?13 cm² s^?1 is exploited, which synergistically leads to an excellent rate capability (184 mAh g^?1 at 10 C) while remaining a large reversible capacity and superior cycling stability. Moreover, the fast Li⁺ transport pathways of grain boundary (micrometer scale) → lattice deformation area (nanometer scale) → (010) crystallographic plane (angstrom scale) are demonstrated in Cu₂Nb₃₄O₈₇. Therefore, these results could pave the way for practical application of Cu₂Nb₃₄O₈₇ in high‐performance Li⁺ batteries.