Strategies for Building Robust Traffic Networks in Advanced Energy Storage Devices: A Focus on Composite Electrodes

The charge transport system in an energy storage device (ESD) fundamentally controls the electrochemical performance and device safety. As the skeleton of the charge transport system, the "traffic" networks connecting the active materials are primary structural factors controlling the transport of ions/electrons. However, with the development of ESDs, it becomes very critical but challenging to build traffic networks with rational structures and mechanical robustness, which can support high energy density, fast charging and discharging capability, cycle stability, safety, and even device flexibility. This is especially true for ESDs with high-capacity active materials (e.g., sulfur and silicon), which show notable volume change during cycling. Therefore, there is an urgent need for cost-effective strategies to realize robust transport networks, and an in-depth understanding of the roles of their structures and properties in device performance. To address this urgent need, the primary strategies reported recently are summarized here into three categories according to their controllability over ion-transport networks, electron-transport networks, or both of them. More specifically, the significant studies on active materials, binders, electrode designs based on various templates, pore additives, etc., are introduced accordingly. Finally, significant challenges and opportunities for building robust charge transport system in next-generation energy storage devices are discussed.

Synthesis of nano-sized urchin-shaped LiFePO4 for lithium ion batteries

In this article, the facile synthesis of sea urchin-shaped LiFePO₄ nanoparticles by thermal decomposition of metal-surfactant complexes and application of these nanoparticles as a cathode in lithium ion secondary batteries is demonstrated. The advantages of this work are a facile method to synthesize interesting LiFePO₄ nanostructures and its synthetic mechanism. Accordingly, the morphology of LiFePO₄ particles could be regulated by the injection of oleylamine, with other surfactants and phosphoric acid. This injection step was critical to tailor the morphology of LiFePO₄ particles, converting them from nanosphere shapes to diverse types of urchin-shaped nanoparticles. Electron microscopy analysis showed that the overall dimension of the urchin-shaped LiFePO₄ particles varied from 300 nm to 2 μm. A closer observation revealed that numerous thin nanorods ranging from 5 to 20 nm in diameter were attached to the nanoparticles. The hierarchical nanostructure of these urchin-shaped LiFePO₄ particles mitigated the low tap density problem. In addition, the nanorods less than 20 nm attached to the edge of urchin-shaped nanoparticles significantly increased the pathways for electronic transport.

In this article, the facile synthesis of sea urchin-shaped LiFePO₄ nanoparticles by thermal decomposition of metal-surfactant complexes and application of these nanoparticles as a cathode in lithium ion secondary batteries is demonstrated.

Tuning polaronic redox behavior in olivine phosphate

In order to understand and improve the conductivity of LiFePO₄, lots of attempts have been made both experimentally and theoretically.

Preparation of Reduction-Responsive Camptothecin Nanocapsules by Combining Nanoprecipitation and In Situ Polymerization for Anticancer Therapy

Stimuli-responsive systems for controlled drug release have been extensively explored in recent years. In this work, we developed a reduction-responsive camptothecin (CPT) nanocapsule (CPT-NC) by combining nanoprecipitation and in situ polymerization using a polymerized surface ligand and a disulfide bond-containing crosslinker. Dissolution rate studies proved that the CPT-NCs have robust drug-release profiles in the presence of glutathione (GSH) owing to the division of the disulfide bond crosslinker which triggers the collapse of the polymer layer. Furthermore, the in vitro investigations demonstrated that the CPT-NCs exhibited a high-cellular uptake efficiency and cytotoxicity for cancer cells of squamous cell carcinoma (SCC-15). Our approach thus presents an effective intracellular drug delivery strategy for anticancer therapy.

Self-Assembly of Antisite Defectless nano-LiFePO4 @C/Reduced Graphene Oxide Microspheres for High-Performance Lithium-Ion Batteries

LiFePO₄ @C/reduced graphene oxide (rGO) hierarchical microspheres with superior electrochemical activity and a high tap density were first synthesized by using a Fe³⁺ -based single inorganic precursor (LiFePO₄ OH@RF/GO; RF=resorcinol-formaldehyde, GO=graphene oxide) obtained from a template-free self-assembly synthesis followed by direct calcination. The synthetic process requires no physical mixing step. The phase transformation pathway from tavorite LiFePO₄ OH to olivine LiFePO₄ upon calcination was determined by means of the in situ high-temperature XRD technique. Benefitting from the unique structure of the material, these microspheres can be densely packed together, giving a high tap density of 1.3 g cm^-3 , and simultaneously, defectless LiFePO₄ primary nanocrystals modified with a highly conductive surface carbon layer and ultrathin rGO provide good electronic and ionic kinetics for fast electron/Li⁺ ion transport.

Lithium Dendrite Suppression and Enhanced Interfacial Compatibility Enabled by an Ex Situ SEI on Li Anode for LAGP-Based All-Solid-State Batteries

The electrode-electrolyte interface stability is a critical factor influencing cycle performance of All-solid-state lithium batteries (ASSLBs). Here, we propose a LiF- and Li₃N-enriched artificial solid state electrolyte interphase (SEI) protective layer on metallic lithium (Li). The SEI layer can stabilize metallic Li anode and improve the interface compatibility at the Li anode side in ASSLBs. We also developed a Li_1.5Al_0.5Ge_1.5(PO₄)₃-poly(ethylene oxide) (LAGP-PEO) concrete structured composite solid electrolyte. The symmetric Li/LAGP-PEO/Li cells with SEI-protected Li anodes have been stably cycled with small polarization at a current density of 0.05 mA cm^-2 at 50 °C for nearly 400 h. ASSLB-based on SEI-protected Li anode, LAGP-PEO electrolyte, and LiFePO₄ (LFP) cathode exhibits excellent cyclic stability with an initial discharge capacity of 147.2 mA h g^-1 and a retention of 96% after 200 cycles.

Mechanistic insights of Li+ diffusion within doped LiFePO4 from Muon Spectroscopy

The Li⁺ ion diffusion characteristics of V- and Nb-doped LiFePO₄ were examined with respect to undoped LiFePO₄ using muon spectroscopy (µSR) as a local probe. As little difference in diffusion coefficient between the pure and doped samples was observed, offering D_Li values in the range 1.8–2.3 × 10⁻¹⁰ cm² s⁻¹, this implied the improvement in electrochemical performance observed within doped LiFePO₄ was not a result of increased local Li⁺ diffusion. This unexpected observation was made possible with the µSR technique, which can measure Li⁺ self-diffusion within LiFePO₄, and therefore negated the effect of the LiFePO₄ two-phase delithiation mechanism, which has previously prevented accurate Li⁺ diffusion comparison between the doped and undoped materials. Therefore, the authors suggest that µSR is an excellent technique for analysing materials on a local scale to elucidate the effects of dopants on solid-state diffusion behaviour.

Design Nitrogen (N) and Sulfur (S) Co-Doped 3D Graphene Network Architectures for High-Performance Sodium Storage

To develop high-performance sodium-ion batteries (NIBs), electrodes should possess well-defined pathways for efficient electronic/ionic transport. In this work, high-performance NIBs are demonstrated by designing a 3D interconnected porous structure that consists of N, S co-doped 3D porous graphene frameworks (3DPGFs-NS). The most typical electrode materials (i.e., Na₃ V₂ (PO₄ )₃ (NVP), MoS₂ , and TiO₂ ) are anchored onto the 3DPGFs-NS matrix (denoted as NVP@C@3DPGFs-NS; MoS₂ @C@3DPGFs-NS and TiO₂ @C@3DPGFs-NS) to demonstrate its general process to boost the energy density of NIBs. The N, S co-doped porous graphene structure with a large surface area offers fast ionic transport within the electrode and facilitates efficient electron transport, and thus endows the 3DPGFs-NS-based composite electrodes with excellent sodium storage performance. The resulting NVP@C@3DPGFs-NS displays excellent electrochemical performance as both cathode and anode for NIBs. The MoS₂ @C@3DPGFs-NS and TiO₂ @C@3DPGFs-NS deliver capacities of 317 mAhg^-1 at 5 Ag^-1 after 1000 cycles and 185 mAhg^-1 at 1 Ag^-1 after 2000 cycles, respectively. The excellent long cycle life is attributed to the 3D porous structure that could greatly release mechanical stress from repeated Na⁺ extraction/insertion. The novel structure 3D PGFs-NS provides a general approach to modify electrodes of NIBs and holds great potential applications in other energy storage fields.

Scalable Synthesis of Triple-Core-Shell Nanostructures of TiO2 @MnO2 @C for High Performance Supercapacitors Using Structure-Guided Combustion Waves

Core-shell nanostructures of metal oxides and carbon-based materials have emerged as outstanding electrode materials for supercapacitors and batteries. However, their synthesis requires complex procedures that incur high costs and long processing times. Herein, a new route is proposed for synthesizing triple-core-shell nanoparticles of TiO₂ @MnO₂ @C using structure-guided combustion waves (SGCWs), which originate from incomplete combustion inside chemical-fuel-wrapped nanostructures, and their application in supercapacitor electrodes. SGCWs transform TiO₂ to TiO₂ @C and TiO₂ @MnO₂ to TiO₂ @MnO₂ @C via the incompletely combusted carbonaceous fuels under an open-air atmosphere, in seconds. The synthesized carbon layers act as templates for MnO₂ shells in TiO₂ @C and organic shells of TiO₂ @MnO₂ @C. The TiO₂ @MnO₂ @C-based electrodes exhibit a greater specific capacitance (488 F g^-1 at 5 mV s^-1 ) and capacitance retention (97.4% after 10 000 cycles at 1.0 V s^-1 ), while the absence of MnO₂ and carbon shells reveals a severe degradation in the specific capacitance and capacitance retention. Because the core-TiO₂ nanoparticles and carbon shell prevent the deformation of the inner and outer sides of the MnO₂ shell, the nanostructures of the TiO₂ @MnO₂ @C are preserved despite the long-term cycling, giving the superior performance. This SGCW-driven fabrication enables the scalable synthesis of multiple-core-shell structures applicable to diverse electrochemical applications.

Synchrotron radiation in situ X-ray absorption fine structure and in situ X-ray diffraction analysis of a high-performance cobalt catalyst towards the oxygen reduction reaction

Transition metal-based composites are one of the most important electrocatalysts because of their rich redox chemistry. The reaction kinetics of a redox couple is dependent on the chemical valence and is a key issue in electrocatalytic performance. In this study, a metallic Co catalyst was synthesized by pyrolyzing Co(OH)₂. The effect of the chemical valence of Co on the oxygen reduction reaction (ORR) was investigated by comparing the electrocatalytic properties of three Co-based catalysts containing Co⁰, Co²⁺, and Co³⁺. The electrocatalytic properties were evaluated mainly by linear scan voltammetry (LSV) and a direct borohydride fuel cell (DBFC) where the Co-based catalysts were used as cathodes. The LSV results show that the ORR peak current density increases with a decrease in chemical valence. The DBFC with the Co⁰ cathode exhibits highest power density and good durability. In situ X-ray diffraction combined with in situ X-ray absorption fine structure tests was carried out to reveal the dynamic microstructure evolution of the Co⁰ cathode during ORR. The in situ results clearly demonstrate the evolution of metallic Co to Co(OH)₂ and then to CoOOH during the ORR.

Insights into the Electrochemical Reaction Mechanism of a Novel Cathode Material CuNi2(PO4)2/C for Li-Ion Batteries

In this work, we first report the composite of CuNi₂(PO₄)₂/C (CNP/C) can be employed as the high-capacity conversion-type cathode material for rechargeable Li-ion batteries (LIBs), delivering a reversible capacity as high as 306 mA h g^-1 at a current density of 20 mA g^-1. Furthermore, CNP/C also presents good rate performance and reasonable cycling stability based on a nontraditional conversion reaction mode. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) characterizations show that CNP is reduced to form Cu/Ni and Li₃PO₄ during the discharging process, which is reversed in the following charging process, demonstrating that a reversible conversion reaction mechanism occurs. X-ray absorption spectroscopy (XAS) discloses that Ni²⁺/Ni⁰ exhibits a better reversibility compared to Cu²⁺/Cu during the conversion reaction process, while Cu⁰ is more difficult to be reoxidized during the recharge process, leading to capacity loss as a consequence. The fundamental understanding obtained in this work provides some important clues to explore the high-capacity conversion-type cathode materials for rechargeable LIBs.

An open holey structure enhanced rate capability in a NaTi2(PO4)3/C nanocomposite and provided ultralong-life sodium-ion storage

Sodium-ion battery (SIB) technology is competitive in the fields of transportation and grid storage, which require electrode materials showing rapid energy conversion (high rate capability) and long cycle life. In this work, a NaTi₂(PO₄)₃/C (NTP/C) nanocomposite with an open holey-structured framework was successfully prepared for the first time using a solvothermal reaction followed by pyrolysis. The nanocomposite realized fast sodium-ion transport and thus preferable battery performances. Within the wide rate range of 0.5-50C, only a very small decrease in capacity from 124 to 120 mA h g^-1 was observed. A high discharge capacity of 103 mA h g^-1 (88.3% retention of the 1st cycle) was delivered even after 10 000 cycles at an ultrahigh rate of 50C without any obvious morphological change and without structural pulverization. Forming open channels for ion transport proved to contribute to such performance enhancement and therefore has the potential to become a universal model for the development of sustainable electrode materials in SIBs and other battery systems.

Polymer-Templated LiFePO4/C Nanonetworks as High-Performance Cathode Materials for Lithium-Ion Batteries

Lithium iron phosphate (LFP) is currently one of the main cathode materials used in lithium-ion batteries due to its safety, relatively low cost, and exceptional cycle life. To overcome its poor ionic and electrical conductivities, LFP is often nanostructured, and its surface is coated with conductive carbon (LFP/C). Here, we demonstrate a sol-gel based synthesis procedure that utilizes a block copolymer (BCP) as a templating agent and a homopolymer as an additional carbon source. The high-molecular-weight BCP produces self-assembled aggregates with the precursor-sol on the 10 nm scale, stabilizing the LFP structure during crystallization at high temperatures. This results in a LFP nanonetwork consisting of interconnected ∼10 nm-sized particles covered by a uniform carbon coating that displays a high rate performance and an excellent cycle life. Our "one-pot" method is facile and scalable for use in established battery production methodologies.

High performance composites of spinel LiMn2O4/3DG for lithium ion batteries

A highly crystalline nanosized spinel LiMn₂O₄/3DG composite cathode material for high rate lithium ion batteries was successfully prepared by mixing spinel LiMn₂O₄ particles with reduced graphene oxide (3DG). Spinel LiMn₂O₄ and reduced three-dimensional graphene oxide were synthesized using a hydrothermal method and freeze-drying technology, respectively. The structure, morphology and electrochemical performance of the synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge techniques. The results showed that the LiMn₂O₄/3DG composites exhibited excellent rate capability and stable cycling performance. The discharge capacity was 131 mA h g⁻¹ and the capacity remains at 89.3% after 100 cycles at a 0.5 C rate, while the discharge capacity was 90 mA h g⁻¹ at 10 C. Compared with spinel LiMn₂O₄ materials, the LiMn₂O₄/3DG composites showed obvious improvement in electrochemical performance.

3DG/LiMn₂O₄ composites exhibit a high specific capacity and excellent rate performance.

V2O5-Based nanomaterials: synthesis and their applications

Comprehensive depiction the phase-pure V₂O₅ with unique 1D, 2D, and 3D nanostructures. Illustrate the development of carbonaceous materials into the V₂O₅ electrodes. Introduce the cation doped V₂O₅ samples as the cathode material.

Photochromic thermoplastics doped with nanostructured tungsten trioxide

Photochromic materials were successfully fabricated by blending WO₃ nanocrystals with different morphologies (nanosheet, nanorod, and amorphous) into a polymer matrix.

Preparation of Layered-Spinel Microsphere/Reduced Graphene Oxide Cathode Materials for Ultrafast Charge-Discharge Lithium-Ion Batteries

Although Li-rich layered oxides (LLOs) have the highest capacity of any cathodes used, the rate capability of LLOs falls short of meeting the requirements of electric vehicles and smart grids. Herein, a layered-spinel microsphere/reduced graphene oxide heterostructured cathode (LS@rGO) is prepared in situ. This cathode is composed of a spinel phase, two layered structures, and a small amount of reduced graphene oxide (1.08 wt % of carbon). The assembly delivers a considerable charge capacity (145 mA h g^-1 ) at an ultrahigh charge- discharge rate of 60 C (12 A g^-1 ). The rate capability of LS@rGO is influenced by the introduced spinel phase and rGO. X-ray absorption and X-ray photoelectron spectroscopy data indicate that Cr ions move from octahedral lattice sites to tetrahedral lattice sites, and that Mn ions do not participate in the oxidation reaction during the initial charge process.

Insights into Solid-Electrolyte Interphase Induced Li-Ion Degradation from in Situ Auger Electron Spectroscopy

Surface reactions occurring on LiMn₂O₄, LiCoO₂, LiNiO₂, Li[Ni_1/3Mn_1/3Co_1/3]O₂, and LiFePO₄ during charging and overcharging are studied by in situ and ex situ Auger electron spectroscopy. Carbon surface stability at the cathode solid-electrolyte interphase (SEI), associated with carbonate formation, decomposition, and CO/CO₂ evolution, on different electrodes during cycling correlates with their cycle life. To understand how associated CO and CO₂ evolution affects cycle stability, LiMn₂O₄ is cycled in flowing gas. Flowing Ar enhances cycle life by a factor of 2, while flowing Ar with 1% CO₂ reduces cycle life by a factor of 2. CO₂ is proposed to degrade cycle life by trapping Li and metal ions as carbonate in the anode SEI.

Solvothermal Synthesis of a Hollow Micro-Sphere LiFePO₄/C Composite with a Porous Interior Structure as a Cathode Material for Lithium Ion Batteries

To overcome the low lithium ion diffusion and slow electron transfer, a hollow micro sphere LiFePO₄/C cathode material with a porous interior structure was synthesized via a solvothermal method by using ethylene glycol (EG) as the solvent medium and cetyltrimethylammonium bromide (CTAB) as the surfactant. In this strategy, the EG solvent inhibits the growth of the crystals and the CTAB surfactant boots the self-assembly of the primary nanoparticles to form hollow spheres. The resultant carbon-coat LiFePO₄/C hollow micro-spheres have a ~300 nm thick shell/wall consisting of aggregated nanoparticles and a porous interior. When used as materials for lithium-ion batteries, the hollow micro spherical LiFePO₄/C composite exhibits superior discharge capacity (163 mAh g⁻¹ at 0.1 C), good high-rate discharge capacity (118 mAh g⁻¹ at 10 C), and fine cycling stability (99.2% after 200 cycles at 0.1 C). The good electrochemical performances are attributed to a high rate of ionic/electronic conduction and the high structural stability arising from the nanosized primary particles and the micro-sized hollow spherical structure.

Topological Transformations of Core-Shell Precursors to Hierarchically Hollow Assemblages of Copper Silicate Nanotubes

Functional hollow materials have attracted extensive research attention due to their promising prospects for catalysis. Herein, we report an alternative synthesis of hierarchically hollow structured materials directly from core-shell structured templates, based on confined chemical reactions between the solid matter of a core and shell under hydrothermal conditions. More specifically, we have developed a novel and facile strategy to transform core-shell structured Cu₂O@mSiO₂ (m = mesoporous) to tubular copper silicate assemblages (TCSA). Depending on the original shapes of Cu₂O, TCSA can be tailored as spherical or cubic assemblages with stacking copper silicate nanotubes (inner diameter: 4.5 nm, thickness: 0.8 nm, length: ca. 96 nm) in the shell. Moreover, by utilizing the residual reductive Cu(I) (ca. 10 at% of total surface copper) on TCSA support, in situ generations of Pd nanoparticles (∼4.5 nm) and Au nanoparticles (∼5.8 nm) were successfully achieved based on the spontaneous galvanic replacement reactions. Two integrated nanocatalysts (viz., Pd/TCSA and Au/TCSA) have been prepared with this approach. As an example, Pd/TCSA exhibits excellent activity and recyclability for Suzuki-Miyaura cross-coupling reactions.

Excess Li-Ion Storage on Reconstructed Surfaces of Nanocrystals To Boost Battery Performance

Because of their enhanced kinetic properties, nanocrystallites have received much attention as potential electrode materials for energy storage. However, because of the large specific surface areas of nanocrystallites, they usually suffer from decreased energy density, cycling stability, and effective electrode capacity. In this work, we report a size-dependent excess capacity beyond theoretical value (170 mA h g^-1) by introducing extra lithium storage at the reconstructed surface in nanosized LiFePO₄ (LFP) cathode materials (186 and 207 mA h g^-1 in samples with mean particle sizes of 83 and 42 nm, respectively). Moreover, this LFP composite also shows excellent cycling stability and high rate performance. Our multimodal experimental characterizations and ab initio calculations reveal that the surface extra lithium storage is mainly attributed to the charge passivation of Fe by the surface C-O-Fe bonds, which can enhance binding energy for surface lithium by compensating surface Fe truncated symmetry to create two types of extra positions for Li-ion storage at the reconstructed surfaces. Such surface reconstruction nanotechnology for excess Li-ion storage makes full use of the large specific surface area of the nanocrystallites, which can maintain the fast Li-ion transport and greatly enhance the capacity. This discovery and nanotechnology can be used for the design of high-capacity and efficient lithium ion batteries.

Carbon Nanofibers Heavy Laden with Li3V2(PO4)3 Particles Featuring Superb Kinetics for High-Power Lithium Ion Battery

Fast lithium ion and electron transport inside electrode materials are essential to realize its superb electrochemical performances for lithium rechargeable batteries. Herein, a distinctive structure of cathode material is proposed, which can simultaneously satisfy these requirements. Nanosized Li3V2(PO4)3 (LVP) particles can be successfully grown up on the carbon nanofiber via electrospinning method followed by a controlled heat-treatment. Herein, LVP particles are anchored onto the surface of carbon nanofiber, and with this growing process, the size of LVP particles as well as the thickness of carbon nanofiber can be regulated together. The morphological features of this composite structure enable not only direct contact between electrolytes and LVP particles that can enhance lithium ion diffusivity, but also fast electron transport through 1D carbon network along nanofibers simultaneously. Finally, it is demonstrated that this unique structure is an ideal one to realize high electron transport and ion diffusivity together, which are essential for enhancing the electrochemical performances of electrode materials.

Core-shell ZnCo2O4@TiO2 nanowall arrays as anodes for lithium ion batteries

In this paper ZnCo₂O₄ nanowall arrays (NWAs) were first obtained through self-assembly followed by calcination. Then atomic layer deposition was used to fabricate core-shell ZnCo₂O₄@TiO₂ NWAs as anode materials for lithium ion batteries (LIBs). The hierarchical NWA nanostructure has fast ion diffusion and electron transport at the electrode/electrolyte interface, while the excellent chemical stability of the TiO₂ shell can protect the ZnCo₂O₄ NWAs from volume expansion during the charge and discharge processes. The core-shell ZnCo₂O₄@TiO₂ core-shell NWAs composite is versatile as an anode material and exhibits enhanced electrochemical performance for LIBs. The initial capacity was 1598 mA h g^-1 (Coulombic efficiency reached 84.0%), and the reversible capacity after 90 cycles was 827 mA h g^-1 at a current density of 100 mA g^-1, showing high capacity and good cycling stability (much better than ZnCo₂O₄ NWAs). The ZnCo₂O₄@TiO₂ nanocomposite also showed excellent rate capability with a reversible capacity of 532 mA h g^-1 even at a current rate of 4500 mA g^-1. The encouraging experimental results suggest that the novel core-shell structure NWAs have great potential for practical applications in LIBs.

Surface Modification of the LiFePO4 Cathode for the Aqueous Rechargeable Lithium Ion Battery

The LiFePO₄ surface is coated with AlF₃ via a simple chemical precipitation for aqueous rechargeable lithium ion batteries (ARLBs). During electrochemical cycling, the unfavorable side reactions between LiFePO₄ and the aqueous electrolyte (1 M Li₂SO₄ in water) leave a highly resistant passivation film, which causes a deterioration in the electrochemical performance. The coated LiFePO₄ by 1 wt % AlF₃ has a high discharge capacity of 132 mAh g^-1 and a highly improved cycle life, which shows 93% capacity retention even after 100 cycles, whereas the pristine LiFePO₄ has a specific capacity of 123 mAh g^-1 and a poor capacity retention of 82%. The surface analysis results, which include X-ray photoelectron spectroscopy and transmission electron microscopy results, show that the AlF₃ coating material is highly effective for reducing the detrimental surface passivation by relieving the electrochemical side reactions of the fragile aqueous electrolyte. The AlF₃ coating material has good compatibility with the LiFePO₄ cathode material, which mitigates the surface diffusion obstacles, reduces the charge-transfer resistances and improves the electrochemical performance and surface stability of the LiFePO₄ material in aqueous electrolyte solutions.

Preparation and Rate Capability of Carbon Coated LiNi1/3Co1/3Mn1/3O2 as Cathode Material in Lithium Ion Batteries

LiNi_1/3Co_1/3Mn_1/3O₂ (NCM) is regarded as a promising material for next-generation lithium ion batteries due to the high capacity, but its practical applications are limited by the poor electronic conductivity. Here, a one-step method is used to prepare carbon coated LiNi_1/3Co_1/3Mn_1/3O₂ (NCM/C) by applying active carbon as reaction matrix. TEM shows LiNi_1/3Co_1/3Mn_1/3O₂ particles are homogeneously coated by carbon with a thickness about 10 nm. NCM/C delivers the discharge capacity of 191.2 mAh g^-1 at 0.5 C (85 mA g^-1) with a columbic efficiency of 91.1%. At 40 C (6800 mA g^-1), the discharge capacity of NCM/C is 54.6 mAh g^-1, whereas NCM prepared through sol-gel route only delivers 13.2 mAh g^-1. After 100 charge and discharge cycles at 1 C (170 mA g^-1) the capacity retention is 90.3% for NCM/C, whereas it is only 72.4% for NCM. The superior charge/discharge performance of NCM/C owes much to the carbon coating layer, which is not only helpful to increase the electronic conductivity but also contributive to inhibit the side reactions between LiNi_1/3Co_1/3Mn_1/3O₂ and the liquid electrolyte.

Core–shell-structured Li3V2(PO4)3–LiVOPO4 nanocomposites cathode for high-rate and long-life lithium-ion batteries

A facile strategy has been developed to construct unique core–shell-structured Li_2.7V_2.1(PO₄)₃ nanocomposites with a Li₃V₂(PO₄)₃ core and LiVOPO₄ shell by using nonstoichiometric design and high-energy ball milling (HEBM) treatment.

Uniform core–shell Cu6Sn5@C nanospheres with controllable synthesis and excellent lithium storage performances

Well-proportioned PANI-derived carbon shells effectively limit the agglomeration of Cu₆Sn₅ nanocores and hence present extraordinary lithium storage performances.

Variation of carbon coatings on the electrochemical performance of LiFePO4 cathodes for lithium ionic batteries

Asphalt-derived and glucose-derived carbon proved to be soft carbon-coating (SCC) and hard carbon-coating (HCC), and it was found that LFP/SCC showed a superior performance in capacity and rate capability than that of LFP/HCC.

Development of a novel carbon-coating strategy for producing core–shell structured carbon coated LiFePO4 for an improved Li-ion battery performance

A unique process for producing core–shell structured carbon coated LiFePO₄ has successfully developed.

Advanced cathode materials for lithium-ion batteries using nanoarchitectonics

In recent years, the global climate has further deteriorated because of the excessive consumption of traditional energy sources. The replacement of traditional fossil fuels with limited reserves by alternative energy sources has become one of the main strategies to alleviate the increasingly serious environmental issues. As a sustainable and promising store of renewable energy, lithium-ion batteries have replaced other types of batteries for many small-scale consumer devices. Notwithstanding their worldwide applications, it has become abundantly clear that the design and fabrication of electrode materials is urgently required to adapt to meet the growing global demand for energy and the power densities needed to make electric vehicles fully commercially viable. To dramatically enhance battery performance, further advances in materials chemistry are essential, especially in novel nanomaterials chemistry. The construction of nanostructured cathode materials by reducing particle size can boost electrochemical performance. The present review is intended to provide readers with a better understanding of the unique contribution of various nanoarchitectures to lithium-ion batteries over the last decade. Nanostructured cathode materials with different dimensions (0D, 1D, 2D, and 3D), morphologies (hollow, core-shell, etc.), and composites (mainly graphene-based composites) are highlighted, aiming to unravel the opportunities for the development of future-generation lithium-ion batteries. The advantages and challenges of nanomaterials are also addressed in this review. We hope to simulate many more extensive and insightful studies on nanoarchitectonic cathode materials for advanced lithium-ion batteries with desirable performance.

Improved Electrochemical Performance of LiFePO4@N-Doped Carbon Nanocomposites Using Polybenzoxazine as Nitrogen and Carbon Sources

Polybenzoxazine is used as a novel carbon and nitrogen source for coating LiFePO₄ to obtain LiFePO₄@nitrogen-doped carbon (LFP@NC) nanocomposites. The nitrogen-doped graphene-like carbon that is in situ coated on nanometer-sized LiFePO₄ particles can effectively enhance the electrical conductivity and provide fast Li⁺ transport paths. When used as a cathode material for lithium-ion batteries, the LFP@NC nanocomposite (88.4 wt % of LiFePO₄) exhibits a favorable rate performance and stable cycling performance.

3D graphene-based hybrid materials: synthesis and applications in energy storage and conversion

Porous 3D graphene-based hybrid materials (3D GBHMs) are currently attractive nanomaterials employed in the field of energy. Heteroatom-doped 3D graphene and metal, metal oxide, and polymer-decorated 3D graphene with modified electronic and atomic structures provide promising performance as electrode materials in energy storage and conversion. Numerous synthesis methods such as self-assembly, templating, electrochemical deposition, and supercritical CO2, pave the way to mass production of 3D GBHMs in the commercialization of energy devices. This review summarizes recent advances in the fabrication of 3D GBHMs with well-defined architectures such as finely controlled pore sizes, heteroatom doping types and levels. Moreover, current progress toward applications in fuel cells, supercapacitors and batteries employing 3D GBHMs is also highlighted, along with the detailed mechanisms of the enhanced electrochemical performance. Furthermore, current critical issues, challenges and future prospects with respect to applications of 3D GBHMs in practical devices are discussed at the end of this review.