Recent Advances in High-Performance Microbatteries: Construction, Application, and Perspective

Gallium-Carbon: A Universal Composite for Sustainable 3D Printing of Integrated Sensor-Heater-Battery Systems in Wearable and Recyclable Electronics

This study presents a novel three-dimensional (3D) printable gallium-carbon black-styrene isoprene styrene block copolymer (Ga-CB-SIS), offering a versatile solution for the rapid fabrication of stretchable and integrated sensor-heater-battery systems in wearable and recyclable electronics. The composite exhibits sinter-free characteristics, allowing for printing on various substrates, including heat-sensitive materials. Unlike traditional conductive inks, the Ga-CB-SIS composite, composed of gallium, carbon black, and styrene isoprene block copolymers, combines electrical conductivity, stretchability, and digital printability. By introducing carbon black as a filler material, the composite achieves promising electromechanical behavior, making it suitable for low-resistance heaters, batteries, and electrical interconnects. The fabrication process involves a simultaneous mixing and ball-milling technique, resulting in a homogeneous composition with a CB/Ga ratio of 4.3%. The Ga-CB-SIS composite showcases remarkable adaptability for digital printing on various substrates. Its self-healing property and efficient recycling technique using a deep eutectic solvent contribute to an environmentally conscious approach to electronic waste, with a high gallium recovery efficiency of ∼98%. The study's innovation extends to applications, presenting a fully digitally printed stretchable Ga-CB-SIS battery integrated with strain sensors and heaters, representing a significant leap in LM-based composites. This multifunctional and sustainable Ga-CB-SIS composite emerges as a key player in the future of wearable electronics, offering integrated circuits with sensing, heating, and energy storage elements.

Recent progress of high-performance in-plane zinc ion hybrid micro-supercapacitors: design, achievements, and challenges

With the increasing demand for wearable and miniature electronics, in-plane zinc (Zn) ion hybrid micro-supercapacitors (ZIHMSCs), as a promising and compatible energy power source, have attracted tremendous attention due to their unique merits. Despite enormous development and breakthroughs in this field, there is still a lack of a systematic and comprehensive review to update the recent progress of in-plane ZIHMSCs in the design and fabrication of both micro-anodes and micro-cathodes, the exploration and optimization of new electrolytes, and the investigation of related-energy storage mechanisms. This minireview summarizes the key breakthroughs and recent advances in the construction of high-performance in-plane ZIHMSCs. First, the background and fundamentals of in-plane ZIHMSCs are briefly introduced. Then, new concepts, strategies, and latest exciting developments in the preparation and interfacial engineering of Zn metal micro-anodes, the fabrication of advanced micro-cathodes, and the exploration of new electrolyte systems are discussed, respectively. Finally, the key challenges and future directions for the development of high-performance in-plane ZIHMSCs are presented as well. This review not only accounts for the recent research progress in the field of the in-plane ZIHMSCs, but also provides important new insights into the design of next-generation miniaturized energy storage devices.

Flexible Energy Storage Devices to Power the Future

The field of flexible electronics is a crucial driver of technological advancement, with a strong connection to human life and a unique role in various areas such as wearable devices and healthcare. Consequently, there is an urgent demand for flexible energy storage devices (FESDs) to cater to the energy storage needs of various forms of flexible products. FESDs can be classified into three categories based on spatial dimension, all of which share the features of excellent electrochemical performance, reliable safety, and superb flexibility. In this review, the application scenarios of FESDs are introduced and the main representative devices applied in disparate fields are summarized first. More specifically, it focuses on three types of FESDs in matched application scenarios from both structural and material aspects. Finally, the challenges that hinder the practical application of FESDs and the views on current barriers are presented.

Fabrication of Fe-Fe1-xO based 3D coplanar microsupercapacitors by electric discharge rusting of pure iron substrates

Iron oxides with advanced functional properties show great potential for applications in the fields of water splitting, drug delivery, sensors, batteries and supercapacitors. However, it is challenging to develop a simple and efficient strategy for fabricating patterned iron oxide based electrodes for supercapacitor applications. Herein, a facile, simple, scalable, binder-free, surfactant-free and conductive additive-free electric discharge rusting (EDR) technique is proposed to directly synthesize Fe1-xO oxide layer on a pure iron substrate. This new EDR strategy is successfully adopted to fabricate Fe-Fe1-xO integrative patterned electrodes and coplanar microsupercapacitors (CMSC) in one step. The CMSC devices with different geometries could be directly patterned by EDR, which is automatically controlled by a computer numerical control system. The fabricated Fe-Fe1-xO based 3D 2F-CMSC exhibits a maximum areal specific capacitance of 112.4 mF cm-2. Another important finding is the fabrication of 3D 2F-CMSC devices, which show good capacitive behavior at an ultra high scanning rate of 20 000 mV s-1. The results prove that EDR is a low-cost and versatile strategy for the scalable fabrication of high-performance patterned supercapacitor integrative electrodes and devices. Furthermore, it is a versatile technique which shows a great potential for development of next generation microelectronic devices, such as microbatteries and microsensors.

Identification of phosphorus sites in amorphous LiPON thin film by observing internuclear proximities

Amorphous lithium phosphorus oxynitrides (LiPON), prepared by reactive magnetron sputtering, have become the electrolytes of choice for all-solid-state thin film microbatteries since its discovery in early 1990s. Nevertheless, there is still a lack of understanding of their atomic-level structure and its influence on ionic conductivity. Solid-state NMR spectroscopy represents a promising technique to determine the atomic-level structure of LiPON glasses but is challenging owing to its low sensitivity in the case of thin film materials. Recently, 31P solid-state NMR spectra of LiPON thin films were acquired under magic-angle spinning (MAS) conditions and assigned with the help of density functional theory (DFT) calculations of NMR parameters. However, the identification of the different P local environments in these materials is still a challenge owing to their amorphous structure and the lack of resolution of the 31P MAS NMR spectra. We show herein how the NMR observation of internuclear proximities helps to establish the nature of P sites in LiPON thin films. The 31P-14N proximities are probed by a transfer of population in double resonance (TRAPDOR) experiment, whereas 31P-31P proximities are observed using one-dimensional (1D) 31P double-quantum (DQ)-filtered and two-dimensional (2D) 31P homonuclear correlation spectra as well as dipolar dephasing experiments using DQ-DRENAR (DQ-based dipolar-recoupling effects nuclear alignment reduction) technique. The obtained NMR data further support the recently proposed assignment of 31P NMR signals of LiPON thin films. With the help of this assignment, the simulation of the quantitative 1D 31P NMR spectrum indicates that PO43- orthophosphate anions prevail in LiPON thin films and N atoms are mainly incorporated in [O3PNPO3]5- dimeric anions. PO3N4- isolated tetrahedra and [O3POPO3]4- anions are also present but in smaller amounts.

Deeply Reconstructed Hierarchical Ni-Co Microwire for Flexible Ni-Zn Microbattery with Excellent Comprehensive Performance

The rise of flexible electronics calls for efficient microbatteries (MBs) with requirements in energy/power density, stability, and flexibility simultaneously. However, the ever-reported flexible MBs only display progress around certain aspects of energy loading, reaction rate, and electrochemical stability, and it remains challenging to develop a micro-power source with excellent comprehensive performance. Herein, a reconstructed hierarchical Ni-Co alloy microwire is designed to construct flexible Ni-Zn MB. Notably, the interwoven microwires network is directly formed during the synthesis process, and can be utilized as a potential microelectrode which well avoids the toxic additives and the tedious traditional powder process, thus greatly simplifying the manufacture of MB. Meanwhile, the hierarchical alloy microwire is composed of spiny nanostructures and highly active alloy sites, which contributes to deep reconstruction (≈100 nm). Benefiting from the dense self-assembled structure, the fabricated Ni-Zn MB obtained high volumetric/areal energy density (419.7 mWh cm-3 , 1.3 mWh cm-2 ), and ultrahigh rate performance extending the power density to 109.4 W cm-3 (328.3 mW cm-2 ). More surprisingly, the MB assembled by this inherently flexible microwire network is extremely resistant to bending/twisting. Therefore, this novel concept of excellent comprehensive micro-power source will greatly hold great implications for next-generation flexible electronics.

Alkaline Ni-Zn Microbattery Based on 3D Hierarchical Porous Ni Microcathode with High-Rate Performance

Miniaturized energy storage devices with superior performance and compatibility with facile fabrication are highly desired in smart microelectronics. Typical fabrication techniques are generally based on powder printing or active material deposition, which restrict the reaction rate due to the limited optimization of electron transport. Herein, we proposed a new strategy for the construction of high-rate Ni-Zn microbatteries based on a 3D hierarchical porous nickel (Ni) microcathode. With sufficient reaction sites from the hierarchical porous structure as well as excellent electrical conductivity from the superficial Ni-based activated layer, this Ni-based microcathode is featured with fast-reaction capability. By virtue of facile electrochemical treatment, the fabricated microcathode realized an excellent rate performance (over 90% capacity retention when the current density increased from 1 to 20 mA cm^-2). Furthermore, the assembled Ni-Zn microbattery achieved a rate current of up to 40 mA cm^-2 with a capacity retention of 76.9%. Additionally, the high reactivity of the Ni-Zn microbattery is also durable in 2000 cycles. This 3D hierarchical porous Ni microcathode, as well as the activation strategy, provides a facile route for the construction of microcathodes and enriches high-performance output units for integrated microelectronics.

All-Solid-State Thin-Film Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) system coupled with thin-film solid electrolyte as a novel high-energy micro-battery has enormous potential for complementing embedded energy harvesters to enable the autonomy of the Internet of Things microdevice. However, the volatility in high vacuum and intrinsic sluggish kinetics of S hinder researchers from empirically integrating it into all-solid-state thin-film batteries, leading to inexperience in fabricating all-solid-state thin-film Li-S batteries (TFLSBs). Herein, for the first time, TFLSBs have been successfully constructed by stacking vertical graphene nanosheets-Li2S (VGs-Li2S) composite thin-film cathode, lithium-phosphorous-oxynitride (LiPON) thin-film solid electrolyte, and Li metal anode. Fundamentally eliminating Li-polysulfide shuttle effect and maintaining a stable VGs-Li2S/LiPON interface upon prolonged cycles have been well identified by employing the solid-state Li-S system with an "unlimited Li" reservoir, which exhibits excellent long-term cycling stability with a capacity retention of 81% for 3,000 cycles, and an exceptional high temperature tolerance up to 60 °C. More impressively, VGs-Li2S-based TFLSBs with evaporated-Li thin-film anode also demonstrate outstanding cycling performance over 500 cycles with a high Coulombic efficiency of 99.71%. Collectively, this study presents a new development strategy for secure and high-performance rechargeable all-solid-state thin-film batteries.

High-Energy-Density Zinc-Air Microbatteries with Lean PVA-KOH-K2CO3 Gel Electrolytes

Small-scale, primary electrochemical energy storage devices ("microbatteries") are critical power sources for microelectromechanical system (MEMS)-based sensors and actuators. However, the achievable volumetric and gravimetric energy densities of microbatteries are typically insufficient for intermediate-term applications of MEMS-enabled distributed internet-connected devices. Further, in the increasing subset of Internet of Things (IoT) nodes, where actuation is desired, the peak power density of the microbattery must be simultaneously considered. Metal-air approaches to achieving microbatteries are attractive, as the anode and cathode are amenable to miniaturization; however, further improvements in energy density can be obtained by minimizing the electrolyte volume. To investigate these potential improvements, this work studied very lean hydrogel electrolytes based on poly(vinyl alcohol) (PVA). Integration of high potassium hydroxide (KOH) loading into the PVA hydrogel improved electrolyte performance. The addition of potassium carbonate (K₂CO₃) to the KOH-PVA gel decreased the carbonation consumption rate of KOH in the gel electrolyte by 23.8% compared to PVA-KOH gel alone. To assess gel performance, a microbattery was formed from a zinc (Zn) anode layer, a gel electrolyte layer, and a carbon-platinum (C-Pt) air cathode layer. Volumetric energy densities of approximately 1400 Wh L^-1 and areal peak power densities of 139 mW cm^-2 were achieved with a PVA-KOH-K₂CO₃ electrolyte. Further structural optimization, including using multilayer gel electrolytes and thinning the air cathode, resulted in volumetric and gravimetric energy densities of 1576 Wh L^-1 and 420 Wh kg^-1, respectively. The batteries described in this work are manufactured in an open environment and fabricated using a straightforward layer-by-layer method, enabling the potential for high fabrication throughput in a MEMS-compatible fashion.

Integration of Li4Ti5O12 Crystalline Films on Silicon Toward High-Rate Performance Lithionic Devices

The growth of crystalline Li-based oxide thin films on silicon substrates is essential for the integration of next-generation solid-state lithionic and electronic devices including on-chip microbatteries, memristors, and sensors. However, growing crystalline oxides directly on silicon typically requires high temperatures and oxygen partial pressures, which leads to the formation of undesired chemical species at the interface compromising the crystal quality of the films. In this work, we employ a 2 nm gamma-alumina (γ-Al₂O₃) buffer layer on Si substrates in order to grow crystalline thin films of Li₄Ti₅O₁₂ (LTO), a well-known active material for lithium-ion batteries. The ultrathin γ-Al₂O₃ layer enables the formation of a stable heterostructure with sharp interfaces and drastically improves the LTO crystallographic and electrochemical properties. Long-term galvanostatic cycling of 50 nm LTO films in liquid-based half-cells demonstrates a high capacity retention of 91% after 5000 cycles at 100 C. Rate capability tests showcase a specific charge of 56 mA h g^-1 at an exceptional C-rate of 5000 C (15 mA cm^-2). Moreover, with sub-millisecond current pulse tests, the reported thin-film heterostructure exhibits rapid Li-ion (de)intercalation, which could lead to fast switching timescales in resistive memory devices and electrochemical transistors.

Advanced Three-Dimensional Microelectrode Architecture Design for High-Performance On-Chip Micro-Supercapacitors

The rapid development of miniaturized electronic devices has greatly stimulated the endless pursuit of high-performance on-chip micro-supercapacitors (MSCs) delivering both high energy and power densities. To this end, an advanced three-dimensional (3D) microelectrode architecture design offers enormous opportunities due to high mass loading of active materials, large specific surface areas, fast ion diffusion kinetics, and short electron transport pathways. In this review, we summarize the recent advances in the rational design of 3D architectured microelectrodes including 3D dense microelectrodes, 3D nanoporous microelectrodes, and 3D macroporous microelectrodes. Furthermore, the emergent microfabrication strategies are discussed in detail in terms of charge storage mechanisms and structure-performance correlation for on-chip MSCs. Finally, we conclude with a perspective on future opportunities and challenges in this thriving field.

Self-Assembled Epitaxial Cathode-Electrolyte Nanocomposites for 3D Microbatteries

The downscaling of electronic devices requires rechargeable microbatteries with enhanced energy and power densities. Here, we evaluate self-assembled vertically aligned nanocomposite (VAN) thin films as a platform to create high-performance three-dimensional (3D) microelectrodes. This study focuses on controlling the VAN formation to enable interface engineering between the LiMn₂O₄ cathode and the (Li,La)TiO₃ solid electrolyte. Electrochemical analysis in a half cell against lithium metal showed the absence of sharp redox peaks due to the confinement in the electrode pillars at the nanoscale. The (100)-oriented VAN thin films showed better rate capability and stability during extensive cycling due to the better alignment to the Li-diffusion channels. However, an enhanced pseudocapacitive contribution was observed for the increased total surface area within the (110)-oriented VAN thin films. These results demonstrate for the first time the electrochemical behavior of cathode-electrolyte VANs for lithium-ion 3D microbatteries while pointing out the importance of control over the vertical interfaces.

Multifunctional Mesoporous Polyaniline/Graphene Nanosheets for Flexible Planar Integrated Microsystem of Zinc Ion Microbattery and Gas Sensor

The prosperity of smart portable microdevices urgently requires an advanced integrated microsystem equipped with cost-effective safe microbatteries and ultra-stable sensitive sensors. However, the practical application of smart microdevices is limited by complex active materials with single function. Here, the two-dimensional (2D) mesoporous nanosheets of polyaniline decorated on graphene with large specific surface area of 141 m²  g^-1 , ample active sites, comparable conductivity, and ordered mesopores of 18 nm for a new-type co-planar integrated microsystem of zinc ion microbattery and gas sensor are developed. These unique triple-function mesoporous nanosheets are well proved for dendrite-free zinc anode with long cyclability (>500 h) and small overpotential (48 mV), a high performance cathode of zinc ion microbattery with outstanding volumetric capacity of 78 mAh cm^-3 outperforming their counterparts reported, and a highly sensitive gas sensor with a resistance response (ΔR/R₀ %) of 118% for 20 ppm NH₃ . Moreover, the co-planar battery-sensor integrated microsystem exhibits superior mechanical stability and smart integration. Therefore, this work will open many opportunities to develop multifunctional 2D mesoporous materials for high performance smart integrated microsystems.

On-chip integration of bulk micromachined three-dimensional Si/C/CNT@TiC micro-supercapacitors for alternating current line filtering

Three-dimensional (3D) micro-supercapacitors (MSCs) with superior performances are desirable for miniaturized electronic devices. 3D interdigitated MSCs fabricated by bulk micromachining technologies have been demonstrated for silicon wafers. However, rational design and fabrication technologies of 3D architectures still need to be optimized within a limited footprint area to improve the electrochemical performances of MSCs. Herein, we report a 3D interdigitated MSC based on Si/C/CNT@TiC electrodes with high capacitive properties attributed to the excellent electronic/ionic conductivity of CNT@TiC core–shells with a high aspect ratio morphology. The symmetric MSC presents a maximum specific capacitance of 7.42 mF cm⁻² (3.71 F g⁻¹) at 5 mV s⁻¹, and shows an 8 times areal capacitance increment after material coating at each step, fully exploiting the advantage of 3D interdigits with a high aspect ratio. The all-solid-state MSC delivers a high energy density of 0.45 μW h cm⁻² (0.22 W h kg⁻¹) at a power density of 10.03 μW h cm⁻², and retains ∼98% capacity after 10 000 cycles. The MSC is further integrated on-chip in a low-pass filtering circuit, exhibiting a stable output voltage with a low ripple coefficient of 1.5%. It is believed that this work holds a great promise for metal-carbide-based 3D interdigitated MSCs for energy storage applications.

A novel fabrication strategy for the realization of a bulk micromachined 3D Si/C/CNT@TiC micro-supercapacitor is experimentally demonstrated.

Advances in wearable textile-based micro energy storage devices: structuring, application and perspective

The continuous expansion of smart microelectronics has put forward higher requirements for energy conversion, mechanical performance, and biocompatibility of micro-energy storage devices (MESDs). Unique porosity, superior flexibility and comfortable breathability make the textile-based structure a great potential in wearable MESDs. Herein, a timely and comprehensive review of this field is provided according to recent research advances. The following aspects, device construction of textile-based MESDs (TMESDs), fabric processing of textile components and smart functionalization (e.g., mechanical reliability, energy harvesting, sensing, self-charging and self-healing, etc.) are discussed and summarized thoroughly. Also, the perspectives on the microfabrication processes and multiple applications of TMESDs are elaborated.

Updated Insights into 3D Architecture Electrodes for Micropower Sources

Microbatteries (MBs) and microsupercapacitors (MSCs) are primary on-chip micropower sources that drive autonomous and stand-alone microelectronic devices for implementation of the Internet of Things (IoT). However, the performance of conventional MBs and MSCs is restricted by their 2D thin-film electrode design, and these devices struggle to satisfy the increasing IoT energy demands for high energy density, high power density, and long lifespan. The energy densities of MBs and MSCs can be improved significantly through adoption of a 2D thick-film electrode design; however, their power densities and lifespans deteriorate with increased electrode thickness. In contrast, 3D architecture electrodes offer remarkable opportunities to simultaneously improve MB and MSC energy density, power density, and lifespan. To date, various 3D architecture electrodes have been designed, fabricated, and investigated for MBs and MSCs. This review provides an update on the principal superiorities of 3D architecture electrodes over 2D thick-film electrodes in the context of improved MB and MSC energy density, power density, and lifespan. In addition, the most recent and representative progress in 3D architecture electrode development for MBs and MSCs is highlighted. Finally, present challenges are discussed and key perspectives for future research in this field are outlined.

Nickel Sulfide Microrockets as Self-Propelled Energy Storage Devices to Power Electronic Circuits "On-Demand"

Miniaturized energy storage devices are essential to power the growing number and variety of microelectronic technologies. Here, a concept of self-propelled microscale energy storage elements that can move, reach, and power electronic circuits is reported. Microrockets consisting of a nickel sulfide (NiS) outer layer and a Pt inner layer are prepared by template-assisted electrodeposition, and designed to store energy through NiS-mediated redox reactions and propel via the Pt-catalyzed decomposition of H₂ O₂ fuel. Scanning electrochemical microscopy allows visualizing and studying the energy storage ability of a single microrocket, revealing its pseudocapacitive nature. This proves the great potential of such technique in the field of micro/nanomotors. On-demand delivery of energy storage units to electronic circuits has been demonstrated by releasing microrockets on an interdigitated array electrode as an example of electronic circuit. Owing to their self-propulsion ability, they reach the active area of the electrode and, in principle, power its functions. These autonomously moving energy storage devices will be employed for next-generation electronics to store and deliver energy in previously inaccessible locations.

A Durable Ni-Zn Microbattery with Ultrahigh-Rate Capability Enabled by In Situ Reconstructed Nanoporous Nickel with Epitaxial Phase

Powering device for miniaturized electronics is highly desired with well-maintained capacity and high-rate performance. Though Ni-Zn microbattery can meet the demand to some extent with intrinsic fast kinetic, it still suffers irreversible structure degradation due to the repeated lattice strain. Herein, a stable Ni-Zn microbattery with ultrahigh-rate performance is rationally constructed through in situ electrochemical approaches, including the reconstruction of nanoporous nickel and the introduction of epitaxial Zn(OH)₂ nanophase. With the enhanced ionic adsorption effect, the superior reactivity of the superficial nickel-based nanostructure is well stabilized. Based on facile miniaturization and electrochemical techniques, the fabricated nickel microelectrode exhibits 63.8% capacity retention when the current density is 500 times folded, and the modified hydroxides contribute to the great stability of the porous structure (92% capacity retention after 10 000 cycles). Furthermore, when the constructed Ni-Zn microbattery is measured in a practical metric, excellent power density (320.17 mW cm^-2 ) and stable fast-charging performance (over 90% capacity retention in 3500 cycles) are obtained. This surface reconstruction strategy for nanostructure provides a new direction for the optimization of electrode structure and enriches high-performance output units for integrated microelectronics.

Recent Advances and Perspectives on the Polymer Electrolytes for Sodium/Potassium-Ion Batteries

Owing to the low cost of sodium/potassium resources and similar electrochemical properties of Na⁺ /K⁺ to Li⁺ , sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) are regarded as promising alternatives to lithium-ion batteries (LIBs) in large-scale energy storage field. However, traditional organic liquid electrolytes bestow SIBs/KIBs with serious safety concerns. In contrast, quasi-/solid-phase electrolytes including polymer electrolytes (PEs) and inorganic solid electrolytes (ISEs) show great superiority of high safety. However, the poor processibility and relatively low ionic conductivity of Na⁺ and K⁺ ions limit the further practical applications of ISEs. PEs combine some merits of both liquid-phase electrolytes and ISEs, and present great potentials in next-generation energy storage systems. Considerable efforts have been devoted to improving their overall properties. Nevertheless, there is still a lack of an in-depth and comprehensive review to get insights into mechanisms and corresponding design strategies of PEs. Herein, the advantages of different electrolytes, particularly PEs are first minutely reviewed, and the mechanism of PEs for Na⁺ /K⁺ ion transfer is summarized. Then, representative researches and recent progresses of SIBs/KIBs based on PEs are presented. Finally, some suggestions and perspectives are put forward to provide some possible directions for the follow-up researches.

Effect of Nanopores on Mechanical Properties of the Shape Memory Alloy

Nanoporous Shape Memory Alloys (SMA) are widely used in aerospace, military industry, medical and health and other fields. More and more attention has been paid to its mechanical properties. In particular, when the size of the pores is reduced to the nanometer level, the effect of the surface effect of the nanoporous material on the mechanical properties of the SMA will increase sharply, and the residual strain of the SMA material will change with the nanoporosity. In this work, the expression of Young’s modulus of nanopore SMA considering surface effects is first derived, which is a function of nanoporosity and nanopore size. Based on the obtained Young’s modulus, a constitutive model of nanoporous SMA considering residual strain is established. Then, the stress–strain curve of dense SMA based on the new constitutive model is drawn by numerical method. The results are in good agreement with the simulation results in the published literature. Finally, the stress-strain curves of SMA with different nanoporosities are drawn, and it is concluded that the Young’s modulus and strength limit decrease with the increase of nanoporosity.

Open-Structured Nanotubes with Three-Dimensional Ion-Accessible Pathways for Enhanced Li+ Conductivity in Composite Solid Electrolytes

Composite solid electrolytes (CSEs) hold great promise toward safe lithium metal batteries with high energy density, due to integration of the merits of polymer matrixes and fillers. Rational design of filler nanostructures has attracted increasing attention for improving the ionic transport of CSEs in solid batteries. In this work, we fabricated open-structured Li_0.33La_0.557TiO₃ (LLTO) nanotubes (NTs) as ion-conductive fillers in CSEs by a gradient electrospinning method for the first time. Different from nanoparticles (NPs) and nanowires (NWs), our nanotubes are composed of connected small NPs, which offer three-dimensional (3D) Li⁺-accessible pathways, large polymer/filler interfacial ionic conduction regions, and enhanced wettability against the polymer matrix. As a result, the solid electrolytes based on LLTO NTs and polyacrylonitrile (PAN) can display a high ionic conductivity of up to 3.6 × 10^-4 S cm^-1 and a wide electrochemical window of 5 V at room temperature (RT). Furthermore, Li-Li symmetric cells using the LLTO NTs/PAN CSE can work stably over 1000 h with a polarization of 20 mV. LiFePO₄-Li full cells exhibit a high capacity of 142.5 mAh g^-1 with a capacity retention of 90% at 0.5 C after 100 cycles. All of these results demonstrate that the design of open-structured nanotubes as fillers is a promising strategy for high-performance solid electrolytes.

Electron cloud migration effect-induced lithiophobicity/lithiophilicity transformation for dendrite-free lithium metal anodes

Enabling stable lithium metal anodes is significant for developing electrochemical energy storage systems with higher energy density. However, safety hazards, infinite volume expansion, and low coulombic efficiency (CE) of lithium metal anodes always hinder their practical application. Herein, a nano-thickness lithiophilic Cu-Ni bimetallic coating was synthesized to prepare dendrite-free lithium metal anodes. The electron cloud migration effect caused by the different electronegativities of Cu and Ni can achieve lithiophobicity/lithiophilicity transformation and thus promote uniform Li deposition/dissolution. By changing the ratio of Cu to Ni, the electron cloud migration can be reasonably adjusted for obtaining dendrite-free lithium anodes. As a result, the as-obtained Cu-Ni bimetallic coating is able to guarantee dendrite-free lithium metal anodes with a stable long cycling time (>1500 hours) and a small voltage hysteresis (∼26 mV). In addition, full cells with LiFePO₄ as a cathode present excellent cycling stability and high coulombic efficiency. This work can open a new avenue for optimizing the lithiophilicity of materials and realizing dendrite-free anodes.