Various architectures with nanostructured silicon have demonstrated promising battery performance while posing a challenge in industrial production. The current ratio of silicon in graphite as anode is less than 5 wt %, which greatly limits the battery energy density. In this article, we report a scalable synthesis of a large silicon cage composite (micrometers) that is composed of a silicon skeleton and an ultrathin (<5 nm) mesoporous polypyrrole (PPy) skin via a facile wet-chemical method. The industry available, microsized AlSi alloy was used as precursor. The hollow skeleton configuration provides sufficient space to accommodate the drastic volume expansion/shrinkage upon charging/discharging, while the conductive polymer serves as a protective layer and fast channel for Li + /e − transport. The battery with the microsilicon (μ-Si) cage as anode displays an excellent capacity retention upon long cycling at high charge/discharge rates and high material loadings. At 0.2 C, a specific capacity of ∼1660 mAh/g with a Coulombic efficiency (CE) of ∼99.8% and 99.4% was achieved after 500 cycles at 3 mg/cm 2 loading and 400 cycles at 4.4 mg/cm 2 loading, respectively. At 1.0 C, a capacity as high as 1149 mAh/g was retained after 500 cycles with such high silicon loading. The areal capacity of as high as 6.4 mAh/cm 2 with 4.4 mg/ cm 2 loading was obtained, which ensures a high battery energy density in powering large devices such as electric vehicles.

Developing solid polymer electrolytes (SPEs) is a promising approach to realize practical dendrite-free lithium metal batteries (LMBs). Tuning the nanoscale polymer network chemsitry is of critical importance for SPE design. In this work, we took lessons from the rubber chemistry and developed a series of comb-chain crosslinker-based SPEs (ConSPEs) using a preformed polymer as the multifunctional crosslinker. The high-functionality crosslinker increased the connectivity of nanosized cross-linked domains, which led to a robust network with dramatically improved toughness and superior lithium dendrite resistance even at a current density of 2 mA cm–2. The uniform and flexile network also dramatically improved the anodic stability to over 5.3 V versus Li/Li+. Additive-free, all-solid-state LMBs with the ConSPE showed high discharge capacity and stable cycling up to 10 C rate, and could be stably cycled at 25 °C. Our results demonstrated that ConSPEs are promising for high-performance and dendrite-free LMBs.

An inter-layer-calated thin Li metal (ILC-Li) electrode using nondelaminated 2D Ti 3 C 2 T x MXene stacks (15 μm) coated on a thin Li host (30 μm) was developed. The excellent electrical conductivity and expanded interlayer space of the MXene provide a fast e − /Li + transport while the layer limits the Li growth along the perpendicular direction, thus largely mitigating the dendrite growth. The highly reversible Li deposition/extraction greatly reduces the dead lithium and electrolyte consumption by forming a thin solid-electrolyte-interphase (SEI) layer. A small overpotential of less than 135 mV in symmetric cells was achieved after >1050 cycles at 10 mA cm −2 and 10 mAh cm −2 . In a full cell, the battery exhibited an improved capacity retention when compared with Li foil, particularly with lean electrolyte of 2.5 μL mAh −1 , thus leading to a high energy density up to 366.6 Wh/kg. The current approach is manufacture scalable, which displays promising potentials in lithium ion batteries.

No abstract

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 LiNi0.8Mn0.1Co0.1O2 (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.

The influence of the amount of hydrogen fluoride (HF) on product formation from the hydrothermal reaction of titanium butoxide and concentrated HF is investigated. Low HF contents lead to a preference for the formation of small TiO2 nanoparticles, medium HF contents lead to a preference for TiO2 nanosheets, and high HF contents lead to a preference for large TiOF2 particles. Meanwhile, TiO2 nanosheets display higher activity in photocatalytic hydrogen generation than that of smaller TiO2 nanoparticles; this demonstrates the higher photocatalytic activity of (001) facets over others. The synergistic effect between TiO2 nanosheets and TiOF2 particles could improve the performance of TiO2 nanosheets owing to possible charge separation over their interface, although TiOF2 particles themselves barely show any activity.

Ultrasonic bubbles on the solid surface of various sonochemical devices largely affect signal resolution due to the serious reflection/scattering of sound waves. The Laplace pressure of the cavitation bubble can be tuned by constructing an ultrathin hydrophilic layer, which leads to the solvation or pinching off of the bubbles from the surface. In this article, we successfully coated a polydopamine polymer layer on the high-density polyethylene (HDPE) surface. The formed hydrophilic layer with a contact angle of less than 45° almost completely eliminates the bubbles in both water and 32.5 vol % diesel exhaust fluid solutions upon sonication, which results in the operation of the piezoelectric sensor over 500 h, while the sensor with pure HDPE only ran for less than 2 h. Further, the coated sensors showed high stability under the temperatures of 60–80 °C. An improved mechanical property was confirmed via abrasion test, enabling long-term stability in harsh environments, including acidic urine and ultrasonic agitation. The acoustic bubble suppression via the hydrophilic polymer coating on HDPE surface displays broad applications, particularly with acoustic sensors, sonobuoys, and nondestructive surface detection in sonochemistry.

No abstract