N-Doped Carbon Nanonecklaces with Encapsulated BiOCl Nanoparticles as High-Rate Anodes for Lithium-Ion Batteries.

The unique two-dimensional layered structure of BiOCl makes it highly promising for energy storage applications. In this study, we successfully synthesized BiOCl nanoparticles encapsulated in N-doped carbon nanonecklaces (BiOCl NPs/N-CNNs) using well-established electrospinning and solvothermal substitution. As an anode material for lithium-ion batteries, BiOCl NPs/N-CNNs exhibited enhanced rate performance, delivering a capacity of 220.2 mA h g-1 at 8 A g-1. Furthermore, it demonstrated remarkable long cycle stability, retaining a capacity of 200.5 mA h g-1 after 9000 cycles with a discharge rate of 8.0 A g-1. The superior electrochemical performance can be attributed to the stacked layered structure of BiOCl, facilitated by van der Waals force, as well as the ingenious nanonecklace structures. These structures not only provide fast ion diffusion pathways but also enhance electrolyte penetration and offer more active sites for Li+ insertion and extraction. Additionally, the nanonecklace structure prevents the aggregation of nanopolyhedra, promoting the complete reaction of BiOCl with Li+. Moreover, the unique nanopolyhedron structure alleviates the stress caused by the volume expansion of Bi nanoparticles during cycling and reduces the internal resistance of the electrode.

Insights into the multi-functional lithium difluoro(oxalate)borate additive in boosting the Li-ion reaction kinetics for Li3VO4 anodes.

The rational design of a solid electrolyte interphase (SEI) with high ionic conductivity and high electrochemical stability is significantly important in improving the electrochemical performance of anode materials. Herein, lithium difluoro(oxalate)borate (LiDFOB) is used as an electrolyte additive to generate protective SEI films on Li3VO4 (LVO) anodes. The addition of LiDFOB is beneficial to form a dense, uniform, stable and LiF-richer SEI, which is helpful to boost the Li-ion storage kinetics. In addition, the generated SEI can inhibit the further decomposition of electrolytes and maintain the morphology of LVO anodes during charge/discharge processes. As a result, LVO-based anodes exhibit a much higher capacity (769.5 mA h g-1 at 0.5 A g-1), enhanced rate performance (243.3 mA h g-1 at 5.0 A g-1) and excellent long-term cycling stability (209.9 mA h g-1 after 5000 cycles) when cycled in 1 wt% LiDFOB addition electrolyte. This work confirms that LiDFOB is a promising multi-functional additive for LiPF6 electrolytes and provides new insights into SEI construction towards high-performance LVO anodes.

Heterostructured Li3VO4-Ga2O3-embedded porous carbon nanofibers as advanced anode materials for lithium-ion batteries.

The development of lithium-ion batteries (LIBs) is still facing challenges due to the design and optimization of anode materials and their Li-ion storage mechanisms. In this study, we aimed to address this issue by constructing three-dimensional hierarchical heterojunction structures using a double needle electrospinning strategy. The heterostructure was composed of insertion-type Li3VO4 and conversion/alloying-type Ga2O3 embedded porous carbon nanofibers (Li3VO4-Ga2O3@PCNF). The designed heterostructured Ga2O3 and Li3VO4 materials were found to effectively enhance charge transfer dynamics, thereby improving capacity and rate capability. Additionally, the facilitated efficient contact between the electrode and electrolyte, enabling the diffusion of ions and electrons. When applied as an anode material in LIBs, the Li3VO4-Ga2O3@PCNF composite achieved a high capacity of 630.0 mA h g-1 at 0.5 A g-1, and full capacity recovery after 6 periods of rate testing over 480 cycles. When simulating the practical application under a high discharge current of 6.0 A g-1, the Li3VO4-Ga2O3@PCNF could still deliver a high discharge capacity of 322.0 mA h g-1 after 2000 cycles. Furthermore, the composite exhibited a remarkable capacity retention of 77.2% after 2000 cycles at 6.0 A g-1. This research provides valuable guidance for the design of high-performance Li3VO4-based anodes, particularly in addressing the issue of inferior electronic conductivity.

Lithium Polyacrylate as Lithium and Carbon Source in the Synthesis of Li3 VO4 for High-Rate and Long-Life Li-Ion Batteries.

Li3 VO4 is a promising anode material for use in lithium-ion batteries, however, the conventional synthesis methods for Li3 VO4 anodes involve the separate use of lithium and carbon sources, resulting in inefficient contact and low crystalline quality. Herein, lithium polyacrylate (LiPAA) was utilized as a dual-functional source and an in-situ polymerization followed by a spray-drying method was employed to synthesize Li3 VO4 . LiPAA serves a dual purpose, acting as both a lithium source to improve the crystal process and a carbon source to confine the particle size within a desired volume during high-temperature treatment. Additionally, the in-situ synthesis of a porous carbon decorating skeleton prevents the growth and agglomeration of Li3 VO4 particles and provides abundant ion/electron diffusion channels and contact areas. Based on the synthesis route and the constructed primary-secondary structure, the Li3 VO4 anodes obtained in this study exhibit an impressive capacity of 596.2 mAh g-1 . Moreover, they demonstrate enhanced rate performance over 600 cycles during 10 periods of rate testing, as well as a remarkably long lifespan of 5000 cycles at high currents. The utilization of LiPAA as a dual-functional source represents a broad approach that holds great potential for future research on high-performance electrodes requiring both lithium and carbon sources.

Recent Advances and Perspectives on the Promising High-Voltage Cathode Material of Na3 (VO)2 (PO4 )2 F.

Na3 (VO)2 (PO4 )2 F (NVOPF) has emerged as one of the most promising cathode materials for sodium-ion batteries (SIBs) attributed to its high specific capacity (130 mAh g-1 ), high operation voltage (>3.9 V vs Na+ /Na), and excellent structural stability (<2% volume change). However, the comparatively low intrinsic electronic conductivity (≈10-7 S cm-1 ) of NVOPF leads to unsatisfactory electrochemical performance, especially at high rates, limiting its practical applications. To improve the conductivity and enhance Na storage performance, many efforts have been devoted to designing NVOPF, including morphology optimization, hybridization with conductive materials, metal-ion doping, Na-site regulation, and F/O ratio adjustment. These attempts have shown some encouraging achievements and shed light on the practical application of NVOPF cathodes. This work aims to provide a general introduction, synthetic methods, and rational design of NVOPF to give a deeper understanding of the recent progress. Additionally, the unique microstructure of NVOPF and its relationship with Na storage properties are also described in detail. The current status, as well as the advances and limitations of such SIB cathode material, are reported. Finally, future perspectives and guidance for advancing high-performance NVOPF cathodes toward practical applications are presented.

Hierarchical Self-Assembly Strategy for Scalable Synthesis of Li3VO4/N Doped C Nanosheets for High-Rate Li-Ion Storage.

While the comprehensive merits of high safety and high capacity make Li3VO4 (LVO) a potential anode material for lithium-ion batteries, the practical application of LVO was severely impeded by the unfavorable high-rate capability and unscalable preparation. Here, LVO/N doped C nanosheets (LVO@NC NSs) assembled from primary LVO@NC nanoparticles are prepared via a scalable and concise spray drying approach. The 2D morphology and the interconnected LVO@NC constituents endow the LVO@NC NSs with continuously excellent reaction activity, leading to prominent rate performance. When cycling at 0.2 A g-1, the obtained LVO@NC NSs exhibit a high charge capacity of 628.4 mAh g-1 after 300 cycles, showing little improvement compared with the initial charge capacity. After 9 periods of rate testing ranging from 0.1 to 6.0 A g-1 for 460 cycles, a high charge capacity of 610.3 mAh g-1 remains. It also exhibits an outstanding long lifespan at the charge/discharge currents of 3.0/6.0 A g-1, delivering a high charge capacity of 277.0 mAh g-1 in the 5000th cycle. The scalable and concise preparation as well as the enhanced high-rate capability of the LVO@NC NSs make them hold great promise as an anode candidate for high-power lithium-ion storage devices.

Revealing the Multi-Electron Reaction Mechanism of Na3 V2 O2 (PO4 )2 F Towards Improved Lithium Storage.

Na3 V2 O2 (PO4 )2 F (NVOPF) as an attractive electrode material has received much attention based on the one-electron reaction of V4+ /V5+ . However, the electrochemical reactions involving lower vanadium valences were not investigated till now. Herein, a composite of graphene decorated nanosheet-assembled NVOPF microflowers (NVOPF/G) was synthesized and the multi-electron reaction of NVOPF/G was conducted by controlling the operation voltage windows. The reaction mechanism, structural changes, and vanadium valences during the insertion/extraction of Li ions (from 2 to 6) were elucidated clearly by in-situ X-ray diffraction and ex-situ X-ray photoelectron spectroscopy. Theoretical computations also revealed the Li-ion locations in the structure of NaV2 O2 (PO4 )2 F. Due to the additional redox couple of V3+ /V4+ , NVOPF/G displayed a much higher initial capacity of 183.3 mAh g-1 in the wider voltage window of 1.0-4.8 V than that of 2.5-4.8 V (129.3 mAh g-1 ). Moreover, excellent Li-storage performance of NVOPF/G at a lower voltage (≤2.5 V) with the active reaction of V2+ /V3+ /V4+ was obtained for the first time, demonstrating the high potential of NVOPF/G as an anode material for Li ion storage.

CNTs/LiV3O8/Y2O3 Composites with Enhanced Electrochemical Performances as Cathode Materials for Rechargeable Solid-State Lithium Metal Batteries.

Solid-state lithium metal battery (SSLMB) is regarded as a safer energy storage system compared to the liquid one. The performance of the SSLMB depends on the cathode performance and the side reactions derived from the interface of the cathode and the electrolyte, which becomes much severe at high temperatures. Herein, we carried out a facile spray-drying route to prepare a CNTs/LiV3O8/Y2O3 (M-LVO-Y) composite. The synthesized cathode material exhibits an outstanding Li+ storage performance with a high reversible capacity of 279.9 mA h g-1 at 0.05 A g-1, excellent power capability (182.5 mA h g-1 at 2 A g-1), and a long cycle lifespan of 500 cycles with a capacity retention of 66.5% at a current density of 1 A g-1. The fabricated rechargeable solid-state Li/M-LVO-Y-2 lithium metal battery (LMB) with a poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE) achieves a high discharge capacity of 302.1 mA h g-1 at 0.05 A g-1 and a stable cycling performance with the highest capacity of 72.1% after 100 cycles at 0.2 A g-1 and 80 °C. The above battery performance demonstrates that SSLMBs with the CNTs/LiV3O8/Y2O3 cathode and the PEO-based SPE film can provide high energy density and are suitable for applying in a high-temperature environment.

Recent Progress and Challenges in the Optimization of Electrode Materials for Rechargeable Magnesium Batteries.

Rechargeable magnesium batteries (RMBs) have been regarded as one of the promising electrochemical energy storage systems to complement Li-ion batteries owing to the low-cost and high safety characteristics. However, the various challenges including the sluggish solid-state diffusion of highly polarizing Mg2+ ions in hosts, and the formation of blocking layers on Mg metal surface have seriously impeded the development of high-performance RMBs. In order to solve these problems toward practical applications of RMBs, a tremendous amount of work on electrodes and electrolytes has been conducted in the last few decades. Creative optimization strategies including the modification of cathodes and anodes such as shielding the charges of divalent Mg2+ , expanding the layers of host materials, and optimizing the interface of electrode-electrolyte are raised to promote the technology. In this review, the detailed description of innovative approaches, representative examples, and facing challenges for developing high-performance electrodes are presented. Based on the review of these strategies, guidelines are provided for future research directions on improving the overall battery performance, especially on the electrodes.

Methanol-derived high-performance Na3V2(PO4)3/C: from kilogram-scale synthesis to pouch cell safety detection.

Na3V2(PO4)3 (NVP) is regarded as a potential cathode material that can be applied in sodium ion batteries (SIBs) owing to its NASICON structure. However, most of the reported works have focused on the synthesis of materials and the improvement of their electrochemical properties, with little research on the design and safety of pouch cells. Herein, we implemented a cost-saving route to realize the industrial-scale synthesis of NVP cathode materials. The obtained NVP samples possess an impressive Na-ion storage capability with high reversible capacity (116.3 mA h g-1 at 0.2 C), superior power capability (97.9 mA h g-1 at 30 C), and long lifespan (71.6% capacity retention after 2500 cycles at 20 C). It was remarkable that industrial-scale NVP/hard carbon (HC) sodium-ion pouch cells could be designed with an 823 mA h discharge capacity at a current of 200 mA (about 0.25 C), and which possess a long life and high rate performance (1000 cycles with a little decay at a current of 4000 mA). Besides, the pouch cells also exhibit excellent thermal stability when demonstrated for application in unmanned aerial vehicles (UAVs), and puncturing experiment results can further prove the excellent safety performance of NVP-hard carbon pouch cells.

Interchain-Expanded Vanadium Tetrasulfide with Fast Kinetics for Rechargeable Magnesium Batteries.

Magnesium batteries are promising energy storage systems because of the advantages of low raw material cost, high theoretical capacity, and high operational safety properties. However, the divalent Mg2+ has a sluggish kinetic in the cathode materials which resulted in poor electrochemical performance. Many strategies were adopted to improve the mobility of Mg2+ in the host structures. In this paper, we report on the optimization of chain-like structure VS4@reduced graphene oxide (VS4@rGO) through expanding interchain distance to increase the ion diffusivity. By combining theoretical calculations and experimental investigations, the expansion of interchain distance and reversible intercalation of MgCl+ are revealed. With the fast kinetics of MgCl+ (instead of Mg2+) intercalation into expanded VS4@rGO, higher capacity of 268.3 mA h g-1 at 50 mA g-1 and better rate capability of 85.9 mA h g-1 at 2000 mA g-1 have been obtained. In addition, the expanded VS4@rGO framework shows a high specific capacity of 147.2 mA h g-1 after 100 cycles and a very wide operating temperature range (-35 to 55 °C). The high discharge capacity, excellent rate capability, and broad temperature adaptability demonstrate promising application of VS4@rGO in magnesium batteries.

A rechargeable aluminum-ion battery based on a VS2 nanosheet cathode.

As a typical member of transition-metal dichalcogenides (TMDs), VS2 has been evaluated as the aluminum-ion battery cathode for the first time. To further improve their stability and conductivity, the as-prepared VS2 nanosheets are modified with graphene (denoted as G-VS2). And the G-VS2 electrode delivers a high initial discharge capacity of 186 mA h g-1 at 100 mA g-1 with almost 100% coulombic efficiency after 50 cycles. Furthermore, an explicit intercalation mechanism of Al into G-VS2 has been investigated by in/ex situ XRD, ex situ Raman and TEM spectroscopy. And the G-VS2 composite proves to be an impressive cathode material for aluminum-ion batteries (AIBs). This work might put forward the application of TMDs in AIBs.

H2V3O8 Nanowires as High-Capacity Cathode Materials for Magnesium-Based Battery.

Magnesium-based batteries have received much attention as promising candidates to next-generation batteries because of high volumetric capacity, low price, and dendrite-free property of Mg metal. Herein, we reported H2V3O8 nanowire cathode with excellent electrochemical property in magnesium-based batteries. First, it shows a satisfactory magnesium storage ability with 304.2 mA h g-1 capacity at 50 mA g-1. Second, it possesses a high-voltage platform of ∼2.0 V vs Mg/Mg2+. Furthermore, when evaluated as a cathode material for magnesium-based hybrid Mg2+/Li+ battery, it exhibits a high specific capacity of 305.4 mA h g-1 at 25 mA g-1 and can be performed in a wide working temperature range (-20 to 55 °C). Notably, the insertion-type ion storage mechanism of H2V3O8 nanowires in hybrid Mg2+/Li+ batteries are investigated by ex situ X-ray diffraction and Fourier transform infrared. This research demonstrates that the H2V3O8 nanowire cathode is a potential candidate for high-performance magnesium-based batteries.

VO2 Nanoflakes as the Cathode Material of Hybrid Magnesium-Lithium-Ion Batteries with High Energy Density.

The hybrid magnesium-lithium-ion batteries (MLIBs) combining the dendrite-free deposition of the Mg anode and the fast Li intercalation cathode are better alternatives to Li-ion batteries (LIBs) in large-scale power storage systems. In this article, we reported hybrid MLIBs assembled with the VO2 cathode, dendrite-free Mg anode, and the Mg-Li dual-salt electrolyte. Satisfactorily, the VO2 cathode delivered a stable plateau at about 1.75 V, and a high specific discharge capacity of 244.4 mA h g-1. To the best of our knowledge, the VO2 cathode displays the highest energy density of 427 Wh kg-1 among reported MLIBs in coin-type batteries. In addition, an excellent rate performance and a wide operating temperature window from 0 to 55 °C have been obtained. The combination of VO2 cathode, dual-salt electrolyte, and Mg anode would pave the way for the development of high energy density, safe, and low-cost batteries.