Three-dimensional Current Collector Research Articles

“Mechanical–electrochemical” coupling structure and the application as a three-dimensional current collector for lithium metal anode

To construct a lithiophilic-lithiophobic gradient collector has been regarded as an effective strategy to address the challenge of lithium dendrite growth in Li metal anode. However, it was also found that the uneven stress accumulation, induced by the directional deposition, would cause fatigue-like failure in the gradient structure. In this work, a hybrid carbon nano fiber (CNF) structure, consisting of a gradient nitrogen doping CNF layer and a Cu doped CNF layer, was fabricated. The Cu-decorated carbon nanofibers not only provide a deposits-free (lithiophilic) surface, but also act as “reinforcing rib” to resist the fatigue stress. The unique hybrid structure delivered a high Coulomb efficiency and resistance to repeat stress application.

High-energy-density Li–S battery with positive electrode of lithium polysulfides held by carbon nanotube sponge

Lithium-sulfur battery suffers from the low utilization of sulfur and the high electrolyte/sulfur (E/S) ratio that decrease the cell-based performance. Lithium polysulfides (Li2Sx)-dissolved electrolyte, so called catholyte, enables high utilization of sulfur, but the cell inherently has high E/S ratio due to the limited solubility of Li2Sx. Herein, a composite electrode of Li2Sx (x = 4, 6, 8) and sub-millimeter-long few-wall carbon nanotube (CNT) is proposed. The CNT forms self-supporting sponge-like paper and works as a three-dimensional current collector, in which the Li2Sx is deposited by solution casting and drying. The Li2S6-CNT electrode realizes high specific capacity (1249 mAh gsulfur−1) under a lean electrolyte condition of E/S = 4 μL mgsulfur−1, which is much better than the S8-CNT electrode (233 mAh gsulfur−1). After full charge and conversion of Li2Sx to S, the Li2Sx-CNT electrode maintains its high capacity of 1100 mAh gsulfur−1. The full cell with the Li2S6-CNT and the Li thin foil electrodes realizes 400–500 Wh kgcell−1 for E/S = 4.0 at the 2nd and 3rd discharge and 300 Wh kgcell−1 for E/S = 5.8 at the 97th discharge, based on the total mass of the interior of a cell (electrodes, separator, and electrolyte). Holding solvated Li2Sx by the CNT sponge is the key for the high energy density.

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.

Recent Progress and Perspectives of Sodium Metal Anodes for Rechargeable Batteries

Sodium metal anodes have attracted significant attention due to their high specific capacity, low redox potential and abundant resources. However, the dendrites and unstable solid electrolyte interphase(SEI) of sodium anodes restrict the development of sodium metal batteries. This review includes the recent progress on the Na anode protection in sodium metal batteries. The strategies are summarized as modified three-dimensional current collectors, artificial solid electrolyte interphases, and electrolyte modifications. Conclusions and perspectives are envisaged for the further understanding and development of Na metal anodes.

Study on the Cycling Performance of Li-Metal Anodes Impregnated into 3D Current Collectors for Li-Metal Batteries

Lithium (Li) metal is the most attractive anode material for batteries because of its high specific capacity (3861 mAh/g) and low negative potential (- 3.04 V vs. NHE). However, the Li dendrite growth during Li deposition leads to serious safety problems and poor cycling performance. With durative forming and growing of the Li dendrite during cycling, the accompanying large surface area of SEI layers induces a constant loss of both working Li metal and electrolyte, leading to a low Coulombic efficiency and a rapid capacity decay. Thus, there has been much research effort to achieve the suppression of the Li dendrite formation.According to the previous reports, employing three-dimensional (3D) current collectors is one approach to reduce the effective current density and delay dendrite growth. In this study, we developed a strategy by impregnating Li metal into the 3D current collectors of nickel (Ni) foam and carbon (C) foam backbone to improve the cycling performance of Li-metal anodes for Li-metal batteries. As a result, Li @ Ni foam and Li @ C foam cells showed better capacity retention for 500 cycles than pure Li metal anodes.

Dendrite-free lithium electrodeposition enabled by 3D porous lithiophilic host toward stable lithium metal anodes

Abstract Lithium metal is a promising anode utilized in cutting-edge high-energy batteries owing to the low density, low electrochemical potential, and super high theoretical capacity. Unfortunately, continuous uncontrollable lithium dendrite growth and ‘dead’ lithium result in capacity decay, low coulombic efficiency and short circuit, severely hindering the practical utilization of lithium anode. Herein, we propose a three-dimensional porous lithiophilic current collector for lithium storage. The conductive 3D structure constructed by carbon fiber (CF) can well accommodate the deposited lithium, eliminating volume change between the lithium depositing/stripping process. Moreover, the polydopamine (PDA) coating on the CF surface possesses a large number of polar groups, which can homogenize Li+ ions distribution and apply as the sites for lithium deposition, decreasing nucleation overpotential. As a result, under the 1 mA cm−2 current density, the PDA coated CF (PDA@CF) electrode exhibits high CE (∼98%) for 1000 cycles. Galvanostatic measurements demonstrate that the Li anode using PDA@CF achieves 1000 h cycling life under 1 mA cm−2 with a low overpotential (<15 mV). The LiFePO4 full cell shows enhanced rate performance and stable long-term cycling.

Graphene/TiO2 decorated N-doped carbon foam as 3D porous current collector for high loading sulfur cathode

The intrinsic contradiction between high loading and high capacity in sulfur cathode severely limits the commercial viability of Li-S batteries. Herein, Graphene/TiO2 decorated N-doped carbon foam (G/T-NF@CNT) is proposed as three-dimensional (3D) current collector for high loading sulfur cathode. This rationally designed current collector can not only provide enough space to accommodate active sulfur, but also endow sulfur cathode with strong polysulfide confining ability. More interestingly, 3D porous conductive structure has sufficient channels to realize rapid mass mobilization; meanwhile the high conductivity networks boost transfer kinetics of electrons. The electrochemical measurements demonstrate that G/T-NF@CNT/S cathode has a remarkable capacity of 788 mA h g−1 (5.83 mA h cm-2) at 0.1 A g−1 after 100 cycles with a high sulfur loading of 7.4 mg cm-2. This work provides new insights on multifunctional current collectors for thick sulfur cathodes in Li-S batteries.

High Mass-Loading Sulfur-Composite Cathode for Lithium-Sulfur Batteries

This research is aimed to increase mass loading of sulfur in the composite electrode in order to increase the energy density of lithium-sulfur cell. This requires designing the electrode with the use of conductive agents to maintain the conductivity of the sulfur composite. Therefore, the composite of sulfur with polyacrylonitrile (PAN) and carbon nanotubes (CNT) was synthesized by heating. Following that, mass loading of sulfur was increased by using several layers of carbon fiber paper with a large free space as a three-dimensional current collector. As a result of the heat treatment and formation of covalent bonding between pyrolyzed PAN and sulfur, uniform distribution and enhanced conductivity were achieved, while CNT maintained structural integrity, acting as interwoven network. Due to these advantages, the mass loading of sulfur was increased up to 5 mg cm-2 while maintaining high initial specific capacity of 1400 mAh g-1 and stable cyclability.

A lightweight 3D Zn@Cu nanosheets@activated carbon cloth as long-life anode with large capacity for flexible zinc ion batteries

Zinc metal is actively developed as the most potential next generation anode material for aqueous rechargeable batteries. However, Zn deposition and uncontrollable dendrite growth of metallic Zn anodes during cycles lead to poor cycle performance and coulombic efficiency, hindering their practical application. Constructing a three-dimensional (3D) current collector has been demonstrated to significantly inhibit the formation of zinc dendrites. Herein, a lightweight 3D flexible Zn plating/stripping scaffold, Cu nanosheets grown on activated carbon cloth (Cu nanosheets@ACC), is prepared by an electrochemical deposition technology. Compared with activated carbon cloth (ACC), Cu nanosheets@ACC current collector delivers higher special surface area and conductivity. Besides, Cu nanosheets layer not only can provide numerous, uniformly distributed Zn deposition sites but also can significantly decrease Zn nucleation overpotential. As a consequence, Zn@Cu nanosheets@ACC (Zn grown on Cu nanosheets@ACC) anode delivers a highly reversible Zn plating/stripping behavior with satisfactory cyclic stability rather than uncontrollable Zn dendrites growth. Moreover, a zinc ion battery based on the Zn@Cu nanosheets@ACC anode and MnO2@ACC (MnO2 grown on ACC) cathode presents high average coulombic efficiency (97.9%) and excellent cycling stability (94.8%) over 1000 cycles at 1 A/g as well as satisfactory mechanical properties, displaying great potential for long-life flexible zinc ion batteries.

Guiding Smooth Li Plating and Stripping by a Spherical Island Model for Lithium Metal Anodes.

Lithium metal anodes are considered as promising candidates for next-generation high-energy-density batteries. However, the dendrite formation of Li metal anodes during charge-discharge results in some serious issues. Herein, we show a simple way to flatten the Li metal deposition surface on Ag-modified Cu foil using a spherical island model. In this model, Ag nuclei induce the deposition of Li atoms with low nucleation potentials at the initial heterogeneous nucleation stage. Then, Li homogeneously grows around the spherical islands and these regular islands overlap each other and form a flat Li surface. On the bare Cu foil surface, the Li growth behavior is random, and the deposition surface is porous and covered with dendrites. Stable long-term plating/stripping of a symmetric battery over 800 h at 1 mA cm-2 was achieved. Moreover, the super flat Li structure can be achieved by constructing islands into a three-dimensional (3D) current collector using the spherical island model. Benefiting from the spherical island model, Li||LiFePO4 and Li||O2 batteries with this 3D anode structure can obtain a stable performance.

A facile strategy to reconcile 3D anodes and ceramic electrolytes for stable solid-state Li metal batteries

Lithium metal batteries (LMBs) are regarded as the promising candidate for next-generation energy storage devices. Three-dimensional (3D) current collector is one of the effective anode materials for suppressing lithium (Li) dendrite and accommodating the variation of Li volume during the cycling. However, since the protruding 3D skeleton will also pierce the separator and cause catastrophic battery failure, the safety risk of short circuit still exists. The use of ceramic solid-state electrolyte (SSE) with high mechanical stability on the 3D anode can eliminate the danger of short circuit caused by Li dendrites or 3D skeleton. Nevertheless, in solid-state batteries, 3D anodes with highly electroactive areas suffer from considerable interface reactions and high interface impedance. Herein, we demonstrate a facile in-situ polymerized sealing (IPS) strategy to reconcile the 3D anode with ceramic SSE. The optimized battery configuration consists of 3D anode, in-situ polymerized interlayer and NASICON-type ceramic electrolyte of Li1.3Ti1.7Al0.3(PO4)3 (LATP). The in-situ polymerized interlayer not only significantly reduces the interfacial resistance between the 3D anode and LATP, but also encapsulates liquid electrolyte within the electrode for indispensable interface reactions and rapid Li+ transport. Resultingly, the symmetric cell of 3D Li | LATP | 3D Li delivered a long cycle life of 500 ​h. Moreover, this unique configuration can be paired with a LiNi0.6Co0.2Mn0.2O2 cathode and operate at room temperature, which exhibits excellent performances. This work provides a practical strategy for building safe and durable high-energy solid-state LMBs suitable for next-generation energy storage devices.

3D uniform nitrogen-doped carbon skeleton for ultra-stable sodium metal anode

Sodium metal batteries are arousing extensive interest owing to their high energy density, low cost and wide resource. However, the practical development of sodium metal batteries is inherently plagued by the severe volume expansion and the dendrite growth of sodium metal anode during long cycles under high current density. Herein, a simple electrospinning method is applied to construct the uniformly nitrogen-doped porous carbon fiber skeleton and used as three-dimensional (3D) current collector for sodium metal anode, which has high specific surface area (1,098 m2/g) and strong binding to sodium metal. As a result, nitrogen-doped carbon fiber current collector shows a low sodium deposition overpotential and a highly stable cyclability for 3,500 h with a high coulombic effciency of 99.9% at 2 mA/cm2 and 2 mAh/cm2. Moreover, the full cells using carbon coated sodium vanadium phosphate as cathode and sodium pre-plated nitrogen-doped carbon fiber skeleton as hybrid anode can stably cycle for 300 times. These results illustrate an effective strategy to construct a 3D uniformly nitrogen-doped carbon skeleton based sodium metal hybrid anode without the formation of dendrites, which provide a prospect for further development and research of high performance sodium metal batteries.

Cu3Pt alloy-functionalized Cu mesh as current collector for dendritic-free anodes of potassium metal batteries

Abstract Potassium metal batteries are considered a promising type of batteries for next generation of energy storage systems due to the natural abundance and relatively low redox potential of potassium. However, similar to lithium metal anode, the practical application of potassium metal anode also suffers from issues induced by uncontrollable dendrite growth. To overcome this challenge, using three-dimensional (3D) porous current collectors to construct potassium metal anodes is an effective way to inhibit dendrite growth during the repeated charge/discharge processes. In this paper, the 3D Cu meshes with a layer of Cu3Pt are successfully functionalized in through a fast Galvanic replacement reaction. Compared to the bare Cu mesh, the obtained Cu3Pt-funtionalized Cu mesh (Cu3Pt–Cu mesh) has ultra-rough surface and quite-large surface area, which can provide uniform electrical field and ion flux distributions and reduce the localized current density. Moreover, density function theory calculations and experimental results both show that Cu3Pt has high affinity for potassium, which lowers the nucleation overpotential and induces uniform potassium deposition. Therefore, this Cu3Pt–Cu mesh can achieve long cycle life and high Coulombic efficiency in both half-cells and symmetric cells. A full potassium battery is developed by using prussian blue (KPB) as the cathode material. The full battery can deliver an ultra-long cycle life more than 250 cycles, revealing the great potential of the Cu3Pt–Cu mesh in practical application for potassium metal batteries.

Supercooled liquid sulfur maintained in three-dimensional current collector for high-performance Li-S batteries.

In lithium-sulfur (Li-S) chemistry, the electrically/ionically insulating nature of sulfur and Li2S leads to sluggish electron/ion transfer kinetics for sulfur species conversion. Sulfur and Li2S are recognized as solid at room temperature, and solid-liquid phase transitions are the limiting steps in Li-S batteries. Here, we visualize the distinct sulfur growth behaviors on Al, carbon, Ni current collectors and demonstrate that (i) liquid sulfur generated on Ni provides higher reversible capacity, faster kinetics, and better cycling life compared to solid sulfur; and (ii) Ni facilitates the phase transition (e.g., Li2S decomposition). Accordingly, light-weight, 3D Ni-based current collector is designed to control the deposition and catalytic conversion of sulfur species toward high-performance Li-S batteries. This work provides insights on the critical role of the current collector in determining the physical state of sulfur and elucidates the correlation between sulfur state and battery performance, which will advance electrode designs in high-energy Li-S batteries.

Dynamic Intelligent Cu Current Collectors for Ultrastable Lithium Metal Anodes.

Three-dimensional (3D) current collectors have shown great potential in realizing dendrite-free lithium (Li) metal anodes. However, the rigid 3D current collectors could not simultaneously suppress Li dendrite growth and allow Li plating/stripping under high capacities and large current densities. Here, we report a dynamic intelligent Cu (DICu) current collector that dynamically accommodates the volume change by changing the packing density of the assembled particles. The Li/DICu electrode achieves a high Coulombic efficiency of 99.6% after 800 cycles. The symmetrical cell shows exceptional cycling stability under the high current density of 10 mA cm-2. Notably, when assembled in full-cell batteries, the Li/DICu|LiFePO4 battery maintains a specific capacity of 139.5 mAh g-1 at 1 C for 500 cycles, and the Li/DICu|S battery delivers a specific capacity of 804 mAh g-1 after 500 cycles at 0.5 C, corresponding to the best performance among Li metal batteries with Cu-based current collectors to date.

Water-based slurries for high-energy LiFePO4 batteries using embroidered current collectors

Greater specific energy densities in lithium-ion batteries can be achieved by using three-dimensional (3D) porous current collectors, which allow for greater areal mass loadings of the electroactive material. In this paper, we present the use of embroidered current collectors for the preparation of thick, pouch-type Li-ion batteries. Experiments were performed on LiFePO4 (LFP) water-based slurries using styrene-butadiene rubber (SBR) as binder and sodium carboxymethyl cellulose (CMC) as thickener, and formulations of different rheological characteristics were investigated. The electrochemical performance (cyclic voltammetry, rate capability) and morphological characteristics of the LFP half-pouch cells (X-ray micro computed tomography and scanning electron microscopy) were compared between the formulations. An optimum electrode formulation was identified, and a mechanism is proposed to explain differences between the formulations. With the optimum electrode formulation, 350 µm casted electrodes with high mechanical stability were achieved. Electrodes exhibited 4–6 times greater areal mass loadings (4–6 mAh cm−2) and 50% greater electroactive material weight than with foils. In tests of half- and full-pouch embroidered cells, a 50% capacity utilization at 1C-rate and 11% at 2C-rate were observed, with a full recovery at C/5-rate. The cycling stability was also maintained over 55 cycles.

Realizing both high gravimetric and volumetric capacities in Li/3D carbon composite anode

Three-dimensional (3D) current collectors are verified to be highly effective to suppress the dendrite growth and alleviate the volume effect of the secondary Li anode. But this strategy has an intrinsic disadvantage: low practical volumetric capacity density. The main reasons are the limited Li storage space and the low space utilization. Here, a multichannel carbon fiber paper with Au modification on one side (MCNF-Au) is developed as the collector. In this architecture, multichannel structure provides abundant space for Li depositing; the special multichannel geometry generates structural stress which pushes Li-ions to deposit into the inner channels; Au modified on the back side of the matrix enables Li to fill the deep voids between the fibers via heterogeneous nucleation. The latter two guarantee the maximum utilization of the possible spaces. Consequently, the gravimetric and volumetric capacities of Li/MCNF-Au reach 3000 mAh g−1 and 1546 mAh cm−3, respectively. When the anode matches with sulfur cathode (20 mgsulfur cm−2), the full cell delivers a high capacity of 1091 mAh g−1 along with good cycle stability at low Li excess (30%). This unique structure provides new inspiration for the volumetric capacity improvement of Li anode.

In Situ Growth of Hierarchical Ni-Mn-O Solid Solution on a Flexible and Porous Ni Electrode for High-Performance All-Solid-State Asymmetric Supercapacitors.

To endow all-solid-state asymmetric supercapacitors with high energy density, cycling stability, and flexibility, we design a binder-free supercapacitor electrode by in situ growth of well-distributed broccoli-like Ni0.75 Mn0.25 O/C solid solution arrays on a flexible and three-dimensional Ni current collector (3D-Ni). The electrode consists of a bottom layer of compressed but still porous Ni foam with excellent flexibility and high electrical conductivity, an intermediate layer of interconnected Ni nanoparticles providing a large specific surface area for loading of active substances, and a top layer of vertically aligned mesoporous nanosheets of a Ni0.75 Mn0.25 O/C solid solution. The resultant 3D-Ni/Ni0.75 Mn0.25 O/C cathode exhibits a specific capacitance of 1657.6 mF cm-2 at 1 mA cm-2 and shows no degradation of the capacitance after 10 000 cycles at 3 mA cm-2 . The assembled 3D-Ni/Ni0.75 Mn0.25 O/C//activated carbon asymmetric supercapacitor has a high specific capacitance of 797.7 mF cm-2 at 2 mA cm-2 and an excellent cycling stability with 85.3 % of capacitance retention after 10 000 cycles at a current density of 3 mA cm-2 . The energy density and power density of the asymmetric supercapacitor are up to 6.6 mW h cm-3 and 40.8 mW cm-3 , respectively, indicating a fairly promising future of the flexible 3D-Ni/Ni0.75 Mn0.25 O/C electrode for efficient energy storage applications.

Understanding the effect of p-, n-type dopants and vinyl carbonate electrolyte additive on electrochemical performance of Si thin film anodes for lithium-ion battery

Amorphous silicon (Si) is one of the most prospective high performance anode material for lithium-ion batteries and thin films of this material are promising for microbattery applications. Undoped, p- and n-type doped Si thin films were deposited by madgnetron sputtering on a three-dimensional current collector designed to accommodate the volume expansion of anode upon charge-discharge cycling, improve the active material adhesion, and to enhance the rate capability of the anode. The designed Si thin film anodes with and without doping were first investigated in lithium cell using various electrochemical techniques confirming the positive effect of doping on their performance. Raman spectroscopy was performed before and after cycling the electrodes to further elucidate such effects. The trends in change of an electrolyte during first lithiation/delithiation were observed by in situ Raman technique. Along with this, the morphology features of a solid electrolyte interphase (SEI) layer formed on the surface of the electrode and its modifications upon addition of 5% vinyl carbonate (VC) to the electrolyte were studied. The n-type doping and unique SEI layer formed with poly(VC) polymeric species suppressed the electrode crack formation preventing the capacity loss due to the material disintegration upon cycling, which resulted in an outstanding cycling performance of Si thin film with the capacity of 1305 mAh g−1 retained over 400 cycles.

A stable artificial protective layer for high capacity dendrite-free lithium metal anode

The metallic lithium (Li) is considered as the most promising anode material for high-energy batteries. Nevertheless, the uncontrollable growth of Li dendrite and unstable electrolyte/electrode interface still hinder the development of Li-based battery. In this work, a novel strategy has been proposed to stabilize Li anode by in-situ polymerizing polypyrrole (PPy) layer on Ni foam (PPy@Ni foam) as an artificial protective layer. The PPy protective layer can effectively decrease the contact between Li metal and electrolyte during cycling. In addition, the morphology characterization shows that the PPy layer can help the even Li deposition underneath the layer, leading to a dendrite-free Li anode. As a result, when deposited 2 mAh•cm−2 Li metal, the PPy@Ni foam can keep stable Coulombic efficiency (99%) during nearly 250 cycles, much better than the pure Ni foam (100 cycles). Even in the case of the Li capacity of 10 mAh•cm−2, the stable cycling performance for 60 cycles can still be achieved. Furthermore, when assembled with LiFePO4 material as the cathode for a full cell, the PPy@Ni foam can keep high capacity retention of 85.5% at 500 cycles. In our work, we provide a simple and effective method to enhance the electrochemical performances of Li metal-based batteries, and reveal a new avenue to design three-dimensional (3D) metallic current collector for protecting the Li metal anode.