Reinforcing Germanium Electrode with Polymer Matrix Decoration for Long Cycle Life Rechargeable Lithium Ion Batteries

Facile Fabrication of Large-Area CuO Flakes for Sodium-Ion Energy Storage Applications

CuO is recognized as a promising anode material for sodium-ion batteries because of its impressive theoretical capacity of 674 mAh g-1, derived from its multiple electron transfer capabilities. However, its practical application is hindered by slow reaction kinetics and rapid capacity loss caused by side reactions during discharge/charge cycles. In this work, we introduce an innovative approach to fabricating large-area CuO and CuO@Al2O3 flakes through a combination of magnetron sputtering, thermal oxidation, and atomic layer deposition techniques. The resultant 2D CuO flakes demonstrate excellent electrochemical properties with a high initial reversible specific capacity of 487 mAh g-1 and good cycling stability, which are attributable to their unique architectures and superior structural durability. Furthermore, when these CuO flakes are coated with an ultrathin Al2O3 layer, the integration of the 2D structures with outer nanocoating leads to significantly enhanced electrochemical properties. Notably, even after 70 rate testing cycles, the CuO@Al2O3 materials maintain a high capacity of 525 mAh g-1 at a current density of 50 mA g-1. Remarkably, at a higher current density of 2000 mA g-1, these materials still achieve a capacity of 220 mAh g-1. Moreover, after 200 cycles at a current density of 200 mA g-1, a high charge capacity of 319 mAh g-1 is sustained. In addition, a full cell consisting of a CuO@Al2O3 anode and a NaNi1/3Fe1/3Mn1/3O2 cathode is investigated, showcasing remarkable cycling performance. Our findings underscore the potential of these innovative flake-like architectures as electrode materials in high-performance sodium-ion batteries, paving the way for advancements in energy storage technologies.

Biomass Alginate Derived Oxygen-Enriched Carbonaceous Materials with Partially Graphitic Nanolayers for High Performance Anodes in Lithium-Ion Batteries

Lithium-ion batteries with high reversible capacity, high-rate capability, and extended cycle life are vital for future consumer electronics and renewable energy storage. There is a great deal of interest in developing novel types of carbonaceous materials to boost lithium storage properties due to the inadequate properties of conventional graphite anodes. In this study, we describe a facile and low-cost approach for the synthesis of oxygen-doped hierarchically porous carbons with partially graphitic nanolayers (Alg-C) from pyrolyzed Na-alginate biopolymers without resorting to any kind of activation step. The obtained Alg-C samples were analyzed using various techniques, such as X-ray diffraction, Raman, X-ray photoelectron spectroscopy, scanning electron microscope, and transmission electron microscope, to determine their structure and morphology. When serving as lithium storage anodes, the as-prepared Alg-C electrodes have outstanding electrochemical features, such as a high-rate capability (120 mAh g^-1 at 3000 mA g^-1) and extended cycling lifetimes over 5000 cycles. The post-cycle morphologies ultimately provide evidence of the distinct structural characteristics of the Alg-C electrodes. These preliminary findings suggest that alginate-derived carbonaceous materials may have intensive potential for next-generation energy storage and other related applications.

Functionalized germanane/SWCNT hybrid films as flexible anodes for lithium-ion batteries

Germanium, with a high theoretical capacity based on alloyed lithium and germanium (1384 mA h g-1 Li15Ge4), has stimulated tremendous research as a promising candidate anode material for lithium-ion batteries (LIBs). However, due to the alloying reaction of Li/Ge, the problems of inferior cycle life and massive volume expansion of germanium are equally obvious. Among all Ge-based materials, the unique layered 2D germanane (GeH and GeCH3) with a graphene-like structure, obtained by a chemical etching process from the Zintl phase CaGe2, could enable storage of large quantities of lithium between their interlayers. Besides, the layered structure has the merit of buffering the volume expansion due to the tunable interlayer spacing. In this work, the beyond theoretical capacities of 1637 mA h g-1 for GeH and 2048 mA h g-1 for GeCH3 were achieved in the initial lithiation reaction. Unfortunately, the dreadful capacity fading and electrode fracture happened during the subsequent electrochemical process. A solution, i.e. introducing single-wall carbon nanotubes (SWCNTs) into the structure of the electrodes, was found and further confirmed to improve their electrochemical performance. More noteworthy is the GeH/SWCNT flexible electrode, which exhibits a capacity of 1032.0 mA h g-1 at a high current density of 2000 mA g-1 and a remaining capacity of 653.6 mA h g-1 after 100 cycles at 500 mA g-1. After 100 cycles, the hybrid germanane/SWCNT electrodes maintained good integrity without visible fractures. These results indicate that introducing SWCNTs into germanane effectively improves the electrochemical performance and maintains the integrity of the electrodes for LIBs.

Nitrogen and boron doped carbon layer coated multiwall carbon nanotubes as high performance anode materials for lithium ion batteries

Lithium ion batteries (LIBs) are at present widely used as energy storage and conversion device in our daily life. However, due to the limited power density, the application of LIBs is still restricted in some areas such as commercial vehicles or heavy-duty trucks. An effective strategy to solve this problem is to increase energy density through the development of battery materials. At the same time, a stable long cycling battery is a great demand of environmental protection and industry. Herein we present our new materials, nitrogen and boron doped carbon layer coated multiwall carbon nanotubes (NBC@MWCNTs), which can be used as anodes for LIBs. The electrochemical results demonstrate that the designed NBC@MWCNTs electrode possesses high stable capacity over an ultra-long cycling lifespan (5000 cycles) and superior rate capability even at very high current density (67.5 A g⁻¹). Such impressive lithium storage properties could be ascribed to the synergistic coupling effect of the distinctive structural features, the reduced diffusion length of lithium ions, more active sites generated by doped atoms for lithium storage, as well as the enhancement of the electrode structural integrity. Taken together, these results indicate that the N, B-doped carbon@MWCNTs materials may have great potential for applications in next-generation high performance rechargeable batteries.

A Fast Charge/Discharge and Wide-Temperature Battery with a Germanium Oxide Layer on a Ti3C2 MXene Matrix as Anode

A rapid charge/discharge secondary battery is critical in portable electronic devices and electric vehicles. Germanium, due to the metallic property and facile alloying reaction with lithium, displays great potential in fast charge/discharge batteries in contrast to other intercalation batteries. In order to accommodate the over 300% volume change, a 2D hybrid composite electrode consisting of a homogeneous, amorphous GeO_x(x=1.57) layer bonded on Ti₃C₂ MXenes was successfully developed via an industry available method. The expanded interlayer space inside the MXene matrix accommodates the restricted isotropic expansion from the stress-released, ultrathin GeO_x layer. Owing to the improved e^-/Li⁺ conductivity from both metallic reduced Ge and MXene, the battery showed an excellent charge/discharge performance as fast as 3 min (20.0 C). A high-capacity retention of ∼1048.1 mAh/g along with a Coulombic efficiency (CE) of 99.8% at 0.5 C after 500 cycles was achieved. Under 1.0 C, the capacity was still up to 929.6 mAh/g with a CE of 99.6% (<0.02% capacity decay per cycle) after ultralong (1000) cycling. An almost doubled capacity of 671.6 mAh/g compared to graphite (372 mAh/g at 0.1 C) under 5.0 C and a capacity of 300.5 mAh/g under 10.0 C after 1000 cycles were respectively received. Under cold conditions, due to the low interface energy barrier, an efficient alloying reaction happens which prevents the Li plating on the electrode surface. High capacities of 631.6, 333.9, and 841.7 mAh/g under -20, -40, and 60 °C after 100 cycles demonstrate a wide temperature tolerance of the battery. In addition, a full-cell battery paired with LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) displayed a high capacity of 536.8 mAh/g after 200 cycles. A high capacity retention of a full pouch cell after 50 cycles was also obtained. The superhigh rate capability along with long cycling, wide temperature range, scalable production, and relatively low cost of this hybrid composite display promising potential in specific energy storage applications.

Ionic Liquid Based Polymer Gel Electrolytes for Use with Germanium Thin Film Anodes in Lithium Ion Batteries

Thermally stable, flexible polymer gel electrolytes with high ionic conductivity are prepared by mixing the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (C4mpyrTFSI), LiTFSI and poly(vinylidene difluoride-co-hexafluoropropylene (PVDF-HFP). FT-IR and Raman spectroscopy show that an amorphous film is obtained for high (60 %) C4mpyrTFSI contents. Thermogravimetric analysis (TGA) confirms that the polymer gels are stable below ∼300 °C in both nitrogen and air environments. Ionic conductivity of 1.9×10-3 S cm-2 at room temperature is achieved for the 60 % ionic liquid loaded gel. Germanium (Ge) anodes maintain a coulombic efficiency above 95 % after 90 cycles in potential cycling tests with the 60 % C4mpyrTFSI polymer gel.

Applications of 2D MXenes in energy conversion and storage systems

This article provides a comprehensive review of MXene materials and their energy-related applications.

A Dual Carbon-Based Potassium Dual Ion Battery with Robust Comprehensive Performance

Dual carbon-based potassium dual ion batteries (K-DCBs) have recently attracted ever-increasing attention owing to the potential advantages of high performance-to-cost ratio, good safety, and environmental friendliness. However, the reported K-DCBs still cannot simultaneously meet the requirements of high capacity, long cycling stability, and low cost, which are necessary for practical applications. In this study, a K-DCB with good comprehensive performance including capacity, cycling stability, medium discharge voltage, and energy density is developed by introducing the optimal cathode and anode materials, i.e., KS6 and natural graphite, respectively. An initial capacity of ≈54.6 mAh g-1 and 92.5% capacity retention after 400 cycles can be delivered in a wide voltage window of 2.4-5.4 V at the current density of 100 mA g-1 . A high medium discharge voltage around 4.2 V and an energy density up to 158.3 Wh kg-1 are meanwhile delivered by the K-DCB. In addition, the working mechanism of the devices is understood in detail. It is believed that valuable contributions to the electrochemical performance improvement of the related devices toward practical applications can be provided by this study.