3D Hierarchical Porous Cu-Based Composite Current Collector with Enhanced Ligaments for Notably Improved Cycle Stability of Sn Anode in Li-Ion Batteries

3D Co-Doping α-Ni(OH)2 Nanosheets for Ultrastable, High-Rate Ni-Zn Battery

The α-Ni(OH)₂ is regarded as one promising cathode for aqueous nickel-zinc batteries due to its high theoretical capacity of ≈480 mAh g^-1 , its practical deployment however suffers from the poor stability in strong alkaline solution, intrinsic low electrical conductivity as well as the retarded ionic diffusion. Herein, a 3D (three dimensional) macroporous α-Ni(OH)₂ nanosheets with Co doping is designed through a facile and easily scalable electroless plating combined with electrodeposition strategy. The unique micrometer-sized 3D pores come from Ni substrate and rich voids between Co-doping α-Ni(OH)₂ nanosheets can synergistically afford facile, interconnected ionic diffusion channels, sufficient free space for accommodating its volume changes during cycling; meanwhile, the Co-doping can stabilize the structural robustness of the α-Ni(OH)₂ in the alkaline electrolyte during cycling. Thus, the 3D α-Ni(OH)₂ shows a high capacity of 284 mAh g^-1 at 0.5 mA cm^-2 with an excellent retention of 78% even at 15 mA cm^-2 , and more than 2000 stable cycles at 6 mA cm^-2 , as well as the robust cycling upon various flexible batteries. This work provides a simple and efficient pathway to enhance the electrochemical performance of Ni-Zn batteries through improving ionic transport kinetics and stabilizing crystal structure of cathodes.

Mechanics-based design of lithium-ion batteries: a perspective

From the overall framework of battery development, the battery structures have not received enough attention compared to the chemical components in batteries. The mechanical-electrochemical coupling behavior is a starting point for investigation on battery structures and the subsequent battery design. This perspective systematically reviews the efforts on the mechanics-based design for lithium-ion batteries (LIBs). Two typical types of mechanics-based LIB designs, namely the design at the preparation stage and that at the cycling stage, have been discussed, respectively. The former systemizes the structure design of multiscale battery components from the particle level to the cell level. The latter focuses on the external mechanics-related control, including external pressures and charge-discharge protocols, of in-service LIBs. Moreover, the general problems currently being faced in the mechanics-based LIB design are summarized, followed by the outlook of possible solutions.

Controllable 3D Porous Ni Current Collector Coupled with Surface Phosphorization Enhances Na Storage of Ni3 S2 Nanosheet Arrays

3D porous Ni is fabricated via an easily scalable electroless plating method using a dynamic template formed through in-situ hydrogen bubbles. The pore size in the range of several micrometers is controllable through adjusting the Ni²⁺ depositing rate and hydrogen bubbles releasing rate. The Ni₃ S₂ nanosheet arrays anode is then grown on the unique 3D porous Ni current collector followed by subsequent surface phosphorization. The tremendous interconnected pores and rich voids between the Ni₃ S₂ nanosheet arrays cannot only provide rapid transferring channels for Na⁺ , but also accommodate volumetric changes of the Ni₃ S₂ electrode during cycling, guaranteeing the integrity of the active material. In addition, the surface phosphorized layer enhances the electronic conductivity through providing an electron transport highway along the 3D Ni₃ S₂ , NiP₂ layer, and 3D porous Ni current collector, and simultaneously stabilizes the electrode/electrolyte interphase as a protecting layer. Because of these merits, the phosphorized 3D porous Ni₃ S₂ (3D P-Ni₃ S₂ ) electrode is capable of delivering an ultra-stable capacity of 387.5 mAh g^-1 at 0.1 A g^-1 , and a high capacity retention of 85.3% even at a high current density of 1.6 A g^-1 .

Lightweight Through-Hole Copper Foil as a Current Collector for Lithium-Ion Batteries

In the past few decades, much effort has been dedicated to improve electrochemical performance of lithium-ion batteries (LIBs) through material design. Less attention, however, has been paid to structure engineering of battery components, which is an effective way for improving the electrochemical performance of LIBs. In this work, a lightweight Cu current collector with a through-hole array and columnar crystal on the surface (CC/THCu) was designed and fabricated using a nanosecond ultraviolet laser and electrodeposition processing to enhance specific capacity and cycle stability of LIBs. The synergistic effect of the columnar crystal and through-hole structure for improving electrochemical performances of LIBs assembled with the CC/THCu current collector was investigated. The results show that the complex structure provides spaces for volume expansion and reduces volume variation. When the hole fraction reaches 20%, the weight loss of CC/THCu is 28.41%. The corresponding LIB with the 20% hole fraction CC/THCu shows a high residual capacity rate of 81.2% and enhanced specific capacity (55.9% compared to the LIB with a bare Cu current collector). At a high rate of 1 C, the remaining specific capacity of the LIB with the CC/THCu current collector is better than that with the bare Cu current collector after 200 cycles. The CC/THCu current collector effectively improves the specific capacity and cycle stability of LIBs in contrast to the bare Cu current collector.

A SnOx Quantum Dots Embedded Carbon Nanocage Network with Ultrahigh Li Storage Capacity

Tin-based materials with high specific capacity have been studied as high-performance anodes for energy storage devices. Herein, a SnO_x (x = 0, 1, 2) quantum dots@carbon hybrid is designed and prepared by a binary oxide-induced surface-targeted coating of ZIF-8 followed by pyrolysis approach, in which SnO_x quantum dots (under 5 nm) are dispersed uniformly throughout the nitrogen-containing carbon nanocage. Each nanocage is cross-linked to form a highly conductive framework. The resulting SnO_x@C hybrid exhibits a large BET surface area of 598 m² g^-1, high electrical conductivity, and excellent ion diffusion rate. When applied to LIBs, the SnO_x@C reveals an ultrahigh reversible capacity of 1824 mAh g^-1 at a current density of 0.2 A g^-1, and superior capacities of 1408 and 850 mAh g^-1 even at high rates of 2 and 5 A g^-1, respectively. The full cell assembled using LiFePO₄ as cathode exhibits the high energy density and power density of 335 Wh kg^-1 and 575 W kg^-1 at 1 C based on the total active mass of cathode and anode. Combined with in situ XRD analysis, the superior electrochemical performance can be attributed to the SnO_x-ZnO-C asynchronous and united lithium storage mechanism, which is formed by the well-designed multifeatured construction composed of SnO_x quantum dots, interconnected carbon network, and uniformly dispersed ZnO nanoparticles. Importantly, this designed synthesis can be extended for the fabrication of other electrode materials by simply changing the binary oxide precursor to obtain the desired active component or modulating the type of MOFs coating to achieve high-performance LIBs.

High Areal Capacity Porous Sn-Au Alloys with Long Cycle Life for Li-ion Microbatteries

Long-term stability is one of the most desired functionalities of energy storage microdevices for wearable electronics, wireless sensor networks and the upcoming Internet of Things. Although Li-ion microbatteries have become the dominant energy-storage technology for on-chip electronics, the extension of lifetime of these components remains a fundamental hurdle to overcome. Here, we develop an ultra-stable porous anode based on SnAu alloys able to withstand a high specific capacity exceeding 100 µAh cm^-2 at 3 C rate for more than 6000 cycles of charge/discharge. Also, this new anode material exhibits low potential (0.2 V versus lithium) and one of the highest specific capacity ever reported at low C-rates (7.3 mAh cm^-2 at 0.1 C). We show that the outstanding cyclability is the result of a combination of many factors, including limited volume expansion, as supported by density functional theory calculations. This finding opens new opportunities in design of long-lasting integrated energy storage for self-powered microsystems.

Designing Multiscale Porous Metal by Simple Dealloying with 3D Morphological Evolution Mechanism Revealed via X-ray Nano-tomography

Designing materials with multiscale, hierarchical structure is critical to drive the advancement of new technology. Specifically, porous metals with multiscale porosity from nanometer to micrometer sizes would lead to enhanced physical and chemical properties-the micron-sized pores can increase the effective diffusivity of ion transport within the porous media, and the nano-sized pores provide high specific surface area, enabling functionalities that are unique to nanoporous metals. A new ternary precursor alloy selection concept utilizing the different mixing enthalpies is demonstrated in this work for the design of multiscale, bimodal porous copper from a simple, one-step dealloying of Cu-Fe-Al ternary alloy. The nanoporosity in the bimodal porous structure is formed from dealloying of the Cu-rich phase, whereas the microporosity is controlled by dissolving the Fe-rich phase, determined by both the initial Fe particle size and sintering profile. In addition to advancing the materials design method, the multiscale pore formation during dealloying was directly visualized and quantified via an interrupted in situ synchrotron X-ray nano-tomography. The 3D morphological analysis on tortuosity showed that the presence of the microporosity can compensate the increase of the diffusion path length due to nanoporosity, which facilitates diffusion within the porous structure. Overall the focus of the work is to introduce a new strategy to design multiscale porous metals with enhanced transport properties, and sheds light on the fundamental mechanisms on the 3D morphological evolution of the system using advanced synchrotron X-ray nano-tomography for future materials development and applications.

Chemically monodisperse tin nanoparticles on monolithic 3D nanoporous copper for lithium ion battery anodes with ultralong cycle life and stable lithium storage properties

In this report, a simple and effective low-temperature synthesis route has been proposed to smoothly achieve monodisperse tin nanoparticles upon monolithic 3D nanoporous copper (3D-NPC@MTNPs) from chemical dealloying of as-cast Al-45 at% Cu alloy sheets in HCl solution; they exhibit superior Li storage properties and ultralong cycle life as the anode for lithium ion batteries (LIBs). The results show that the 3D-NPC@MTNPs composite can be fabricated on a large scale by electroless plating of Sn on a uniform NPC matrix with a pore size of ca. 200 nm in an acidic plating bath below room temperature. Compared to two dimensional copper foil supported tin thin films (2D-CF@TTFs), the 3D-NPC@MTNPs electrode displays a markedly higher first reversible capacity of 0.485 mA h cm-2 as well as superior cycling stability with 52.4% capacity retention and over 96.7% coulombic efficiency after 500 cycles. This can be largely ascribed to the synergistic effect between the favorable monodispersity of Sn nanoparticles with ultrafine particle size and single crystal nature and the unique 3D nanoporous electrode architecture with a large specific surface area and a good mass transfer channel, which facilitates the accommodation of mechanical strain, improvement of structural stability, enhancement of bonding force, and acceleration of mass transfer, which are indicative of a quite promising candidate as a high-performance anode for LIBs.

Integrated Anode Electrode Composited Cu⁻Sn Alloy and Separator for Microscale Lithium Ion Batteries

A novel integrated electrode structure was designed and synthesized by direct electrodepositing of Cu⁻Sn alloy anode materials on the Celgard 2400 separator (Cel-CS electrode). The integrated structure of the Cel-CS electrode not only greatly simplifies the battery fabrication process and increases the energy density of the whole electrode, but also buffers the mechanical stress caused by volume expansion of Cu⁻Sn alloy active material; thus, effectively preventing active material falling off from the substrate and improving the cycle stability of the electrode. The Cel-CS electrode exhibits excellent cycle performance and superior rate performance. A capacity of 728 mA·h·g-1 can be achieved after 250 cycles at the current density of 100 mA·g-1. Even cycled at a current density of 5 A·g-1 for 650 cycles, the Cel-CS electrode maintained a specific capacity of 938 mA·h·g-1, which illustrates the potential application prospects of the Cel-CS electrode in microelectronic devices and systems.

A long-cycling anode based on a coral-like Sn nanostructure with a binary binder

We report a facile one-pot displacement reaction for the synthesis of a 3D coral-like Sn nanostructure towards a long-cycling Li-ion battery anode.