Three-Dimensional Ordered Macro/Mesoporous Cu/Zn as a Lithiophilic Current Collector for Dendrite-Free Lithium Metal Anode

Coregulation of Li/Li+ Spatial Distribution by Electric Field Gradient with Homogenized Li-Ion Flux for Dendrite-Free Li Metal Anodes

Lithium (Li) metal batteries are highly sought after for their exceptional energy density. However, their practical implementation is impeded by the formation of dendrites and significant volume fluctuations in Li, which stem from the uneven distribution of Li-ions and uncontrolled deposition of Li on the current collector. Here, an amino-functionalized reduced graphene oxide covered with polyacrylonitrile (PrGN) film with an electric field gradient structure is prepared to deal with such difficulties. This novel current collector serves to stabilize Li-metal anodes by regulating Li-ion flux through vertically aligned channels formed by porous polyacrylonitrile (PAN). Moreover, the amino-functionalized reduced graphene oxide (rGN) acts as a three-dimensional (3D) host, reducing nucleation overpotential and accommodating volume expansion during cycling. The combination of the insulating PAN and conducting rGN creates an electric field gradient that promotes a bottom-up mode of Li electrodeposition and safeguards the anode from interfacial parasitic reactions. Consequently, the electrodes exhibit exceptional cycle life with stable voltage profiles and minimal hysteresis under high current densities and large areal capacities.

Ultrathin Lithiophilic 3D Arrayed Skeleton Enabling Spatial-Selection Deposition for Dendrite-Free Lithium Anodes

Lithium metal batteries are promising to become a new generation of energy storage batteries. However, the growth of Li dendrites and the volume expansion of the anode are serious constraints to their commercial implementation. Herein, a controllable strategy is proposed to construct an ultrathin 3D hierarchical host of honeycomb copper micromesh loaded with lithiophilic copper oxide nanowires (CMMC). The uniquely designed 3D hierarchical arrayed skeletons demonstrate a surface-preferred and spatial-selective effect to homogenize local current density and relieve the volume expansion, effectively suppressing the dendrite growth. Employing the constructed CMMC current collector in a half-cell, >400 cycles with 99% coulombic efficiency at 0.5 mA cm^-2 is performed. The symmetric battery cycles stably for >2000 h, and the full battery delivers a capacity of 166.6 mAh g^-1 . This facile and controllable approach provides an effective strategy for constructing high-performance lithium metal batteries.

A BF3 -Doped MXene Dual-Layer Interphase for a Reliable Lithium-Metal Anode

A dual-layer interphase that consists of an in-situ-formed lithium carboxylate organic layer and a thin BF₃ -doped monolayer Ti₃ C₂ MXene on Li metal is reported. The honeycomb-structured organic layer increases the wetting of electrolyte, leading to a thin solid electrolyte interface (SEI). While the BF₃ -doped monolayer MXene provides abundant active sites for lithium homogeneous nucleation and growth, resulting in about 50% reduced thickness of inorganic-rich components among the SEI layer. A low overpotential of less than 30 mV over 1000 h cycling in symmetric cells is received. The functional BF₃  groups, along with the excellent electronic conductivity and smooth surface of the MXene, greatly reduce the lithium plating/stripping energy barrier, enabling a dendrite-free lithium-metal anode. The battery with this dual-layer coated lithium metal as the anode displays greatly improved electrochemical performance. A high capacity-retention of 175.4 mAh g^-1 at 1.0 C is achieved after 350 cycles. In a pouch cell with a capacity of 475 mAh, the battery still exhibits a high discharge capacity of 165.6 mAh g^-1 with a capacity retention of 90.2% after 200 cycles. In contrast to the fast capacity decay of pure Li metal, the battery using NCA as the cathode also displays excellent capacity retention in both coin and pouch cells. The dual-layer modified surface provides an effective approach in stabilizing the Li-metal anode.

A Highly Reversible Lithium Metal Anode by Constructing Lithiophilic Bi-Nanosheets

As a favorable candidate for the next-generation anode materials, metallic lithium is faced with two crucial problems: uncontrollable lithium plating/stripping process and huge volume expansion during cycling. Herein, a 3D lithiophilic skeleton modified with nanoscale Bi sheets (Ni@Bi Foam, i.e., NBF) through one-step facile substitution reaction is constructed. Benefiting from the nanoscale modification, smooth and dense lithiophilic Li₃ Bi layer is in situ formed, which improves the uniform deposition of Li subsequently. Meanwhile, the 3D structure inhibits the growth of Li dendrites effectively by reducing local areal current density. Consequently, the NBF exhibits outstanding cycling stability with a high average Coulombic efficiency of 98.46% at 1 mA cm^-2 with 1 mAh cm^-2 (>500 cycles). Symmetrical cell with NBF exhibits a high reversibility at 1 mA cm^-2 with 1 mAh cm^-2 (>2000 h). Moreover, superior long-term cycling and rate performance of NBF@Li anode are also acquired when assembled with high areal loading of LiFePO₄ (10.1 mg cm^-2 ) cathode (Negative/Positive ratio: 2.91). Even in anode-free metal lithium batteries, NBF has higher capacity during cycling compared with NF. To conclude, NBF shows excellent electrochemical performance and provides an idea of facile preparation method which can be extend to other metal batteries.

Uniform Deposition of Li-Metal Anodes Guided by 3D Current Collectors with In Situ Modification of the Lithiophilic Matrix

The lithium (Li)-metal anode is deemed as the "holy gray" of the next-generation Li-metal system because of its high theoretical specific capacity, minimal energy density, and lowest standard electrode potential. Nevertheless, its commercial application has been limited by the large volume variation during charge and discharge, the unstable interface between the Li metal and electrolyte, and uneven deposition of Li. Herein, we present a 3D host (Cu) with lithiophilic matrix (CuO and SnO₂) in situ modification via a facile ammonia oxidation method to serve as a current collector for the Li-metal anode. The 3D Cu host embellished by CuO and SnO₂ is abbreviated as 3D CSCC. By increasing interfacial activity, lowering the nucleation barrier, and accommodating changes in volume of the Li metal, the 3D CSCC electrode effectively demonstrates a homogeneous and dendrite-free deposition morphology with an excellent cycling performance up to 3000 h at a 1.0 mA cm^-2 current density. Additionally, the full cells paired with Li@3D CSCC anodes and LiCoO₂ cathodes show good capacity retention performance at 0.2 C.

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.

3D Printed Lithium-Metal Full Batteries Based on a High-Performance Three-Dimensional Anode Current Collector

A three-dimensional (3D) printing method has been developed for preparing a lithium anode base on 3D-structured copper mesh current collectors. Through in situ observations and computer simulations, the deposition behavior and mechanism of lithium ions in the 3D copper mesh current collector are clarified. Benefiting from the characteristics that the large pores can transport electrolyte and provide space for dendrite growth, and the small holes guide the deposition of dendrites, the 3D Cu mesh anode exhibits excellent deposition and stripping capability (50 mAh cm^-2), high-rate capability (50 mA cm^-2), and a long-term stable cycle (1000 h). A full lithium battery with a LiFePO₄ cathode based on this anode exhibits a good cycle life. Moreover, a 3D fully printed lithium-sulfur battery with a 3D printed high-load sulfur cathode can easily charge mobile phones and light up 51 LED indicators, which indicates the great potential for the practicability of lithium-metal batteries with the characteristic of high energy densities. Most importantly, this unique and simple strategy is also able to solve the dendrite problem of other secondary metal batteries. Furthermore, this method has great potential in the continuous mass production of electrodes.

Regulating Lithium Electrodeposition with Laser-Structured Current Collectors for Stable Lithium Metal Batteries

Lithium-metal batteries (LMBs) are promising electrochemical energy storage devices with high energy densities. However, the extreme reactivity of metallic lithium, the large volumetric change of the electrode during cycling, and the notorious dendrite formation issues lead to low cyclic stability and safety concerns, hindering the practical application of LMBs. In particular, the intrinsic tendency of uneven lithium deposition and the large internal electrode stress lead to the piecing of solid electrolyte interphases (SEIs), thereby resulting in fast decay of the anode. We develop a facile laser processing technique to fabricate laser-structured copper foils (LSCFs) that are able to regulate the lithium deposition kinetics and increase the cycle life of LMBs. By simply scribing commercial foils using a 355 nm laser, microstructural features with fish-scale patterns are obtained. The lithium deposition follows a drastically different mode on the LSCF compared with commercial planar copper foils which relieves the internal stress of lithium and prohibits the piecing of SEI. A high Coulombic efficiency of >96% of the lithium metal anode is maintained for over 100 cycles on the LSCF at a current density of 1 mA cm^-2 and an areal capacity of 1 mAh cm^-2 while the benchmark decayed to below 80% after 50 cycles. Full cells based on LiFePO₄ cathodes display a reasonable specific capacity of 125 mAh g^-1 over 300 cycles at a rate of 1 C. This work provides a fast yet effective laser-based approach to construct highly stable lithium metal anodes.

Insights into the deposition chemistry of Li ions in nonaqueous electrolyte for stable Li anodes

Comprehensive understanding of the Li deposition chemistry from Li⁺ to Li atom is crucial for suppressing dendrite formation and growth.