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Battery performance is highly related to the intrinsic properties of battery materials. To develop commercial anode electrode materials for advanced sodium‐based batteries, it is crucial to understand whose fundamental issues including compositions and structure of the bulk and interface, dynamics and electrochemical reactions during cycling. The key for present and ongoing success of carbon‐based and sodium metal anode is to overcome an intrinsic challenge associated with transport and storage of ions and complicated interface activities, especially for the sodiation process with associated risk of dendrite. Advanced Nuclear Magnetic Resonance (NMR) technique has unique advantages in characterizing the local or microstructure of anode electrode materials and their interfacial evolutions down to the atomic level by a noninvasive and nondestructive manner. In this review, an overview is provided of the recent advances in understanding the fundamental issues of carbon based and sodium metal anode materials using advanced NMR approaches. Here, latest advancements of NMR are presented for applications in characterizing structures and dynamics of anode electrode material as well as their interfacial evolutions. Finally, the prospect and limitation of NMR techniques in batteries research will be highlighted, thereby paving the way for accelerating the development of next generation sodium batteries. [ABSTRACT FROM AUTHOR]

The coupling of high-capacity cathodes and lithium metal anodes promises to be the next generation of high-energy-density batteries. However, the fast-structural degradations of the cathode and anode challenge their practical application. Herein, we synthesize an electrolyte additive, tris(2,2,3,3,3-pentafluoropropyl) borane (TPFPB), for ultra-stable lithium (Li) metal||Ni-rich layered oxide batteries. It can be preferentially adsorbed on the cathode surface to form a stable (B and F)-rich cathode electrolyte interface film, which greatly suppresses the electrolyte-cathode side reactions and improves the stability of the cathode. In addition, the electrophilicity of B atoms in TPFPB enhances the solubility of LiNO3 by 30 times in ester electrolyte to significantly improve the stability of the Li metal anode. Thus, the Li||Ni-rich layered oxide full batteries using TPFPB show high stability and an ultralong cycle life (up to 1500 cycles), which also present excellent performance even under high voltage (4.8 V), high areal mass loading (30 mg cm−2) and wide temperature range (−30∼60°C). The Li||LiNi0.9Co0.05Mn0.05O2 (NCM90) pouch cell using TPFPB with a capacity of 3.1 Ah reaches a high energy density of 420 Wh kg−1 at 0.1 C and presents outstanding cycling performance. [ABSTRACT FROM AUTHOR]

Constructing stable surface modification layer is an effective strategy to suppress dendrite growth and side reactions of Zinc (Zn) metal anode in aqueous Zn‐ion battery. Herein, a multicomponent Cu−Zn alloy interlayer with superior Zn affinity, high toughness and effective inhibition effect on lattice distortion is constructed on Zn foil (Cu−Zn@Zn) to fabricate ultra‐stable Zn metal anode. Owning to the advantages of high binding energy of Cu−Zn alloy layer with Zn atoms and less contact area between metallic Zn and electrolyte, the as‐prepared Cu−Zn@Zn electrode not only restricts the aggregation of Zn atoms, but also suppresses the pernicious hydrogen evolution and corrosion, leading to homogeneous Zn deposition and outstanding electrochemical performances. Accordingly, the symmetric battery with Cu−Zn@Zn electrode exhibits an ultra‐long cycle life of 5496 h at 1 mA cm−2 for 1 mAh cm−2, and the Cu−Zn@Zn//V2O5 pouch cell demonstrates excellent cycling stability with a capacity retention of 88 % after 600 cycles. [ABSTRACT FROM AUTHOR]

Multi‐heteroatoms co‐doped carbon coating can significantly enhance the electronic conductivity and mass transfer rate of the electrode materials due to the synergistic effect. In this study N, S co‐doped carbon coating is introduced on the surface of niobium oxides (GNO@NSC) by using a convenient thiourea evaporation method. Theory calculations and experimental results confirm the synergistic effect of N, S co‐doping in GNO@NSC composite. N, S co‐doping not only enlarges the layer distance of the carbon materials but also leads to more activation sites for lithium storage; meanwhile, the introduction of the co‐doping carbon layer on GNO significantly enhances the bonding interaction with GNO, leading to excellent structural stability and conductivity of the composite. As a result, the GNO@NSC composite possesses excellent structural reversibility, a large specific capacity, and high‐rate performance. GNO@NSC nanowires deliver a highly reversible capacity of 288 mAh g–1 and display excellent cycling stability, and its capacity retention is 78.9% after 6000 cycles at a high current density of 1 A g–1. This study reveals the functional mechanism of N, S co‐doped carbon coating and the origin of performance improvement of niobium oxides, which can be used for reference to design and develop relevant materials. [ABSTRACT FROM AUTHOR]

Li metal has been widely regarded as a promising anode for next‐generation batteries due to its high theoretical capacity and low electrochemical potential. The unstable solid‐electrolyte interphase (SEI) and uncontrollable dendrite growth, however, incur severe safety hazards and hamper the practical application of Li metal anodes. Herein, an advanced artificial SEI layer constructed by [LiNBH]n chains, which are crosslinked and self‐reinforced by their intermolecular LiN ionic bonds, is designed to comprehensively stabilize Li metal anodes on a molecular level. Benefiting from its polymer‐like structure, the [LiNBH]n layer is flexible and effectively tolerates the volume change of Li metal anodes. In addition, this layer with high polarity in its structure, helps to regulate the homogeneous distribution of the Li+ flux on Li electrodes via the further formation of LiN bonds. The designed [LiNBH]n layer is electrically nonconductive but highly ionically conductive, thus facilitating Li+ diffusion and confining Li deposition beneath the layer. Therefore, under the protection of the [LiNBH]n layer, the Li metal anodes exhibit stable cycling at a 3 mA cm−2 for more than 700 h, and the full cells with high lithium iron phosphate and sulfur cathodes mass loading also present excellent cycling stability. [ABSTRACT FROM AUTHOR]

Abstract: The development of lithium (Li) metal anodes Li metal batteries faces huge challenges such as uncontrolled Li dendrite growth and large volume change during Li plating/stripping, resulting in severe capacity decay and high safety hazards. A 3D porous copper (Cu) current collector as a host for Li deposition can effectively settle these problems. However, constructing a uniform and compact 3D porous Cu structure is still an enormous challenge. Herein, an electrochemical etching method for Cu–Zinc (Zn) alloy is reported to precisely engrave a 3D Cu structure with uniform, smooth, and compact porous network. Such a continuous structure endows 3D Cu excellent mechanical properties and high electrical conductivity. The uniform and smooth pores with a large internal surface area ensures well dispersed current density for homogeneous Li metal deposition and accommodation. A smooth and stable solid electrolyte interphase is formed and meanwhile Li dendrites and dead Li are effectively suppressed. The Li metal anode conceived 3D Cu current collector can stably cycle for 400 h under an Li plating/stripping capacity of 1 mA h cm−2 and a current density of 1 mA cm−2. The Li@3D Cu||LiFePO4 full cells present excellent cycling and rate performances. The electrochemical dealloying is a robust method to construct 3D Cu current collectors for dendrite‐free Li metal anodes. [ABSTRACT FROM AUTHOR]

Well-controlled nanostructures and a high fraction of Sn/Li2O interface are critical to enhance the coulombic efficiency and cyclic performance of SnO2-based electrodes for lithium-ion batteries (LIBs). Polydopamine (PDA)-coated SnO2 nanocrystals, composed of hundreds of PDA-coated 'corn-like' SnO2 nanoparticles (diameter ca. 5 nm) decorated along a 'cob', addressed the irreversibility issue of SnO2-based electrodes. The PDA-coated SnO2 were crafted by capitalizing on rationally designed bottlebrush-like hydroxypropyl cellulose-graft-poly (acrylic acid) (HPC- g-PAA) as a template and was coated with PDA to construct a passivating solid-electrolyte interphase (SEI) layer. In combination, the corn-like nanostructure and the protective PDA coating contributed to a PDA-coated SnO2 electrode with excellent rate capability, superior long-term stability over 300 cycles, and high Sn→SnO2 reversibility. [ABSTRACT FROM AUTHOR]

A systematic study is made of the effect of the nitrogen species on the performance of Li-ion storage and the capacities of carbon-based anodes in Li-ion batteries (LIBs). Electrospun carbon nanofiber (CNF) films are fabricated for use as binder-free electrodes using a polyacrylonitrile precursor. When the CNF films are subjected to carbonization, transformation occurs from an amorphous to a graphitic structure with associated reduction of nitrogen-containing functional groups. The structural change strongly affects where the Li ions are stored in the CNF electrodes. It is revealed that Li ions can be stored not only between the graphene layers, but also at the defect sites created by nitrogen functionalization. The latter is mainly responsible for the widely reported improved electrochemical performance of LIBs due to N-doping of carbon materials. An optimized carbonization temperature of 550 °C is identified, which gives rise to a sufficiently high nitrogen content and thus a high capacity of the electrode. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the formation of SEI films on Li4Ti5O12 (LTO) anodes offers a major benefit to large-scale applications of lithium ion batteries made therefrom. This paper reveals that an SEI film is formed above 1 V due to the interfacial reaction between the electrode and electrolyte: LTO anodes are previously considered free from SEI films when cycled between 1 and 3 V. The reactivity and the formation of SEI films are much affected by the morphology and surface area of the electrode. To study the above, LTO powders with different morphologies are synthesized using lithium acetate (LA) and lithium hydroxide (LH) as the lithium sources. LTO–LH consisting of agglomerates of primary small particles with a large surface area has higher reactivity than LTO–LA with a cubic structure and small surface area. As a result, the LTO–LH anode with a smooth SEI film offers better cyclic performance than the LTO–LA anode with a porous SEI film. The addition of vinylene carbonate to the electrolyte facilitates rapid formation of a protective SEI film on LTO–LA, greatly improving the rate and cyclic performance: stable specific capacity of 155.6 mAh g−1 and remarkable 135.2 mAh g−1 after 500 cycles at 10 C are recorded. [Copyright &y& Elsevier]

Abstract: The lithium ion batteries using Li4Ti5O12 as the anode material are easily being inflated during charge and discharge, which, however, does not occur in the batteries using graphite as the anode material. The high reduction reactivity of electrolyte on the Li4Ti5O12 material may be the main reason. In this work, the reduction reactivities of electrolyte on the uncoated and carbon-coated Li4Ti5O12 electrodes are compared for the first time. The results show that the reduction decomposition of electrolyte does occur on the uncoated Li4Ti5O12 electrode at around 0.7V, while it only takes place at the first cycle on the carbon-coated Li4Ti5O12 electrode. The carbon coating layers cover the catalytic active sites of Li4Ti5O12 particles and separate the Li4Ti5O12 particles from the electrolyte. A successive solid electrolyte interface (SEI) film is formed on the carbon layer during the formation process, which can prevent the further reduction decomposition of electrolyte at around 0.7V. The impurity phases of rutile and anatase TiO2 do not influence the reduction reactivity of electrolyte. This work is not only important to understand the reduction decomposition mechanism of electrolyte on the Li4Ti5O12 electrode, but also provides an effective solution to suppress the reduction decomposition of electrolyte in the batteries. [Copyright &y& Elsevier]

Abstract: Li4Ti5O12 anode material is synthesized using TiO2 with different crystal structure as titanium source by solid-state method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical test methods are applied to characterize the effects of TiO2 crystal structure on the structure, morphology and electrochemical performance of Li4Ti5O12. Results show that the reaction of TiO2 with Li2CO3 is an exothermic behavior. The reactivity of TiO2 with Li2CO3 gradually decreases and the particles size of Li4Ti5O12 increases with the TiO2 crystal structure changing from amorphous to rutile. The TiO2 crystal structure has a slight influence on the reversibility of Li4Ti5O12, while the specific capacities of Li4Ti5O12 at different current densities decreases obviously with the TiO2 crystal structure changing from amorphous to rutile and the sample using amorphous TiO2 as titanium sources shows highest specific capacity. The capacity retentions of all Li4Ti5O12 samples are above 97% after 50 cycles and these materials show good cycle performance. The TiO2 crystal structure has not large effects on the cycling performance of Li4Ti5O12 material. [Copyright &y& Elsevier]

Liquid state soft packed LiFePO cathode lithium ion cells with capacity of 2 Ah were fabricated using graphite or LiTiO as negative electrodes to investigate the 3 C/10 V overcharge characteristics at room temperature. The LiFePO/LiTiO cell remained safe after the 3 C/10 V overcharge test while the LiFePO/graphite cell went to thermal runaway. Temperature and voltage variations during overcharge were recorded and analyzed. The cells after overcharge were disassembled to check the changes of the separated cell components. The results showed that the LiTiO as anode active material for LiFePO cell showed obvious safety advantage compared with the graphite anode. The lithium ionic diffusion models of LiTiO anode and graphite anode were built respectively with the help of morphology characterizations performed by scanning electron microscopy. It was found that the different particle shapes and lithium ionic diffusion modes caused different lithium ionic conductivities during overcharge process. [ABSTRACT FROM AUTHOR]

Abstract: The thermogravimetric (TG) and differential thermal analysis (DTA) were used to investigate the thermal stability of fully charged and discharged LiCoO2 cathode and graphite anode in nitrogen and air atmospheres. The results showed that the weight of charged and discharged LiCoO2 cathode samples exhibited an obvious decrease between 100 and 120°C in two atmospheres. The exothermic decomposition reaction of fully charged LiCoO2 cathode occurred at 250°C in two atmospheres. A small decomposition reaction of the discharged LiCoO2 cathode occurred at 300°C. When the temperature of samples was elevated to 600°C, the weight of fully charged and discharged LiCoO2 cathode in air atmosphere did not change; while the weight of samples in nitrogen atmosphere decreased. This was because the Co3O4 as the decomposition product of the cathodes could be reduced to CoO by the carbon black above 600°C in N2 atmosphere. The solid electrolyte interphase (SEI) film of fully charged and discharged graphite anode was decomposed at 100–120°C in two atmospheres, and the weight loss of fully charged graphite anode at 100–120°C was obviously less than that of the fully discharged graphite anode. When the samples were heated to 300°C, there was no fierce exothermic reaction for the lithiated graphite anode in N2 atmosphere, whereas an exothermic reaction in air atmosphere occurred rapidly. [Copyright &y& Elsevier]

To boost the commercialization of high energy density lithium ion batteries (LIBs) used for electric vehicles, the development of electrode materials with high volumetric capacity is of great significance. In this work, a novel Si/slightly exfoliated graphite (SEG)/carbon composite used as anode for LIBs with high volumetric capacity is fabricated. The Si nanoparticles are uniformly intercalated in the squashed interlayers of SEG which are then further filled by amorphous carbon. The SEG acts as a conductivity skeleton, while the spaces between squashed interlayers(folds) in SEG function as buffer spaces for the expansion of Si nanoparticles during lithiation reactions. The amorphous carbon connects the Si nanoparticles with SEG to form a 3D conductive network. Owing to the high packing density (0.7 g cm −3 ) and unique structure, this material possesses a high volumetric capacity of 1050 mAh cm −3 . Meanwhile, the Si/SEG/C composite also exhibits excellent rate and cyclic performance, presenting a reversible capacities of 1456 and 1056 mAh g −1 at 100 and 500 mA g −1 with capacity retention of 84.7% after 50 cycles at 500 mA g −1 . This work opens up an avenue to craft the Si/C composite with high volumetric energy densities and rate performance. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been regarded as one of the most attractive anode materials for the next generation lithium-ion batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, the architecture of Si-based anode material still needs to be well designed to overcome the structure degradation and instability of the solid-electrolyte interphase caused by a large volume change during cycling. Here we report the electrochemical performances of a novel binder-free Si/carbon composite film consisting of alternatively stacked Si-porous carbon layers and graphene layers, which is synthesized by electrostatic spray deposition followed by heat treatment. For this composite film, Si nanoparticles are embedded in the porous carbon layer composed of nitrogen-doped carbon framework, carbon black and carbon nanotubes. And the combined Si-porous carbon layer is further sandwiched by flexible and conductive graphene sheets. The multilayered Si-porous carbon/graphene electrode shows a maximum reversible capacity of 1020 mAh g −1 with 75% capacity retention after 100 cycles and a good rate capability on the basis of the total electrode weight. The excellent electrochemical performances are attributed to the fact that the layer-by-layer porous carbon matrix can accommodate the volume change of Si particles and maintain the structural and electrical integrities. [ABSTRACT FROM AUTHOR]