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To meet the growing demand for electric vehicles and consumer electronics, sustainable energy storage systems are undergoing rapid development. As one of the most promising anode materials for next-generation high-energy batteries, lithium metal has the lowest redox potential (-3.04 V compared to standard hydrogen electrodes) and high theoretical capacity (3860 mAh g-1). Three issues related to electrochemical stability and performance have received the most attention: 1) heterogeneous deposition of lithium, 2) high reactivity of lithium metal, and 3) “hostless” properties of lithium metal. The above issues are entangled with each other, leading to efficiency degradation and even serious safety failures.
Nowadays, many efforts have been devoted to solving these thorny problems, among which two strategies have been widely used: i) constructing a 3D skeleton can provide a mechanically stable host for lithium metal, mitigating its volume change and lowering the local current density distribution, thus realizing the uniform deposition of lithium metal; ii) fabricating artificial SEI membranes with reasonable compositions can help to block the direct contact between lithium metal and the electrolyte, thus inhibit the corrosion of lithium metal by the electrolyte. Among these strategies, the utilization of three-dimensional conductive substrates, especially carbon scaffolds such as carbon cloth, has attracted much attention due to its stable physicochemical properties, tunable surface structure and high flexibility. However, carbon-based materials are usually lithium-phobic and have poor affinity for lithium, which is unfavorable for initial lithium nucleation and subsequent growth of lithium metal. Therefore, there is an urgent need to improve the lithophilicity of carbon-based substrates. The introduction of heterogeneous seeds as lithophilic sites on carbon-based materials can realize the selective deposition and physicochemical encapsulation of lithium metal, thus easing the growth of dendrites. Lithophilic sites can be categorized into several groups: i) impurity elements such as F, N, and O, which bind to lithium via intermolecular/interatomic forces; and ii) metallic substances such as Ag, Sn, and Zn and their corresponding compounds, e.g., ZnO and CuO, which react with lithium via chemical forces. However, conventional synthesis methods with slow heating rates (e.g., sol-gel, calcination, and solvothermal) are difficult to prepare uniform ultrafine nanoparticles. Therefore, it is crucial to advance new technologies for fabricating lithophilic nanoseeds.
The main point of this paper
Applications of the Ultrafast Joule Heating (UJH) method:
Exploration of the UJH method in the field of energy storage, especially in rapid high temperature processing.
Challenges of the UJH method:
The need to design layered structures with sufficient lithium storage space and low Li+ diffusion resistance.
Application scope of UJH technology:
Fabrication of a wide range of materials such as monometallics, metal oxides, ceramics, mixed entropy alloys, etc.
Importance of metal sulfides (MxSy):
Attracted for their electrical conductivity, variable valence and catalytic properties.
The two-dimensional layered structure provides channels for Li+ insertion and extraction.
Synthesis of MxSy by UJH method:
Systematic synthesis of MxSy, especially Ni3S2, as a lithophilic site.
Application of Ni3S2:
Inhibition of dendrite growth as a lithophilic site on vertical graphene-modified carbon cloth (CC/VG).
Performance of CC/VG@Ni3S2/Li composite anode:
Cycled 800 times in a symmetric battery, showing excellent long-term cycling capability.
Performance of CC/VG@Ni3S2-Li||LFP full cell:
Provides 155.6 mAh g-1 discharge capacity and 92.44% capacity retention after 500 cycles at 0.5 C.
Synergistic approach to UJH method:
A low-cost, generalized method is proposed for constructing a stable, high-performance flexible lithium metal anode (LMA) layered skeleton that avoids dendrites and volume expansion.
Importance of lithophilic skeletons:
The design and fabrication of lithophilic backbones is critical to the construction of advanced lithium metal anodes.
Application of ultrafast joule heating (UJH) method:
Fast loading of nickel sulfide (Ni3S2) on vertical graphene (VG) by UJH method is used to enhance the performance of lithium metal batteries.
Advantages of CC/VG@Ni3S2 structure:
Ni3S2 nanoparticles are uniformly anchored on the optimized backbone to form CC/VG@Ni3S2, which ensures high conductivity and uniform deposition of lithium metal without dendrites.
Electrochemical performance:
The CC/VG@Ni3S2-coupled symmetric cell can be stably long-term cycled for 1800 h (900 cycles) at 14 mV overpotential under 1 mA cm-2 and 1 mAh cm-2 conditions.
The full cell coupled with lithium iron phosphate (LFP) cathode achieved 92.44% capacity retention after 500 cycles at 0.5 C with excellent rate performance.
Significance of the new strategy:
The new strategy of synthesizing metal sulfides on layered carbon-based materials provides new ideas for the development of high-performance lithium metal batteries (LMBs).
Efficiency and low cost of the UJH method:
The UJH method provides a low-cost and high-efficiency method for the preparation of lithophilic skeletons, which helps to construct stable and high-performance lithium metal anodes.
Fast loading capability of UJH method:
The UJH method is able to realize ultra-fast loading of metal sulfides on carbon-based materials, which is of great significance for improving battery performance and accelerating battery charging speed.
Uniform distribution effect of UJH method:
The Ni3S2 nanoparticles prepared by the UJH method were uniformly distributed on the CC/VG substrate, which helped to regulate lithium deposition and alleviate the growth of dendrites.
We successfully synthesized metal sulfides (MxSy) on carbon-based materials by UJH. The ultrafine MxSy nanoparticles were uniformly distributed on the CC/VG substrate and retained the highly conductive graphene structure.COMSOL multiphysics field simulations verified that the uniformly distributed Ni3S2 seeds could regulate the lithium deposition and alleviate the growth of dendrites. Benefiting from the synergistic effect of Ni3S2 lithium-friendly sites and the layered CC/VG framework, the three-dimensional flexible host stabilizes the interface between the lithium anode and the electrolyte. The prepared composite anode shows higher Coulombic efficiency, longer cycle life and enhanced rate capability. In addition, the complete battery paired with the LFP cathode exhibited a high discharge capacity (155.6 mAh g-1) and good capacity retention (92.44%). Our work provides a valuable strategy for synthesizing metal sulfides on carbon-based materials and holds promise for high-performance lithium anodes for high-energy batteries.
