Dendrite growth of metal anodes is one of the key hindrances for both secondary aqueous metal batteries and nonaqueous metal batteries. In this work, a freestanding Ti3C2T x MXene@Zn paper is designed as both zinc metal anode and lithium metal anode host to address the issue. The binder-free Ti3C2T x MXene@Zn paper exhibits merits of good mechanical flexibility, high electronic conductivity, hydrophilicity, and lithiophilicity. The crystal growth mechanism of Zn metal on common Zn foil and Ti3C2T x MXene@Zn composite is also studied. It is found that the Ti3C2T x MXene@Zn paper can effectively suppress the dendrite growth of Zn, enabling reversible and fast Zn plating/stripping kinetics in an aqueous electrolyte. Moreover, the Ti3C2T x MXene@Zn paper can be used as a 3D host for a lithium metal anode. In this host, Zn is utilized as a nucleation agent to suppress the Li dendrite growth. The freestanding Ti3C2T x MXene@Zn@Li anode exhibits superior reversibility with high Coulombic efficiency (97.69% over 600 cycles at 1.0 mA cm–2) and low polarization compared with the Cu@Li anode. These findings may be useful for the design of dendrite-free metal-based energy storage systems.

Owing to its distinctive structure and properties, 2D silicon (2DSi) has been widely applied in hydrogen storage, sensors, electronic device, catalysis, electrochemical energy storage, etc. However, scalable and low-cost fabrication of high-quality 2DSi remains a great challenge. In this work, a physical vacuum distillation method is designed to obtain high-quality 2DSi from a bulk layered calcium–silicon alloy. With this method, the lower boiling point calcium metal is evaporated to construct 2DSi and can be further recycled. The effect of vacuum conditions on morphology, components, and electrochemical properties is further explored. As an anode for lithium-ion batteries, the 2DSi delivers a stable cyclability of 835 mAh g–1 after 3000 cycles at 5000 mA g–1 (0.003025% capacity decay per cycle). The electrochemical performance enhancing mechanism is also probed. In addition, a 2D/2D flexible and binder-free paper by combining 2DSi with 2D MXene is constructed. As a lithiophilic nuclear agent for lithium metal anodes, the 2DSi can efficiently suppress the Li dendrite growth and reduce nucleation barriers, achieving a high Coulombic efficiency (98% at 1 mA cm–2, 97% at 2 mA cm–2) around 600 cycles and a long lifespan of 1000 h. The crystal growth difference of lithium metal on Cu foil and 2DSi is studied. This work may provide a pathway for green, low-cost, and scalable synthesis of 2D materials.

Background and Purpose— Malignant brain edema after ischemic stroke has high mortality but limited treatment. Therefore, early prediction is important, and we systematically reviewed predictors and predictive models to identify reliable markers for the development of malignant edema. Methods— We searched Medline and Embase from inception to March 2018 and included studies assessing predictors or predictive models for malignant brain edema after ischemic stroke. Study quality was assessed by a 17-item tool. Odds ratios, mean differences, or standardized mean differences were pooled in random-effects modeling. Predictive models were descriptively analyzed. Results— We included 38 studies (3278 patients) with 24 clinical factors, 7 domains of imaging markers, 13 serum biomarkers, and 4 models. Generally, the included studies were small and showed potential publication bias. Malignant edema was associated with younger age (n=2075; mean difference, −4.42; 95% CI, −6.63 to −2.22), higher admission National Institutes of Health Stroke Scale scores (n=807, median 17–20 versus 5.5–15), and parenchymal hypoattenuation >50% of the middle cerebral artery territory on initial computed tomography (n=420; odds ratio, 5.33; 95% CI, 2.93–9.68). Revascularization (n=1600, odds ratio, 0.37; 95% CI, 0.24–0.57) were associated with a lower risk for malignant edema. Four predictive models all showed an overall C statistic >0.70, with a risk of overfitting. Conclusions— Younger age, higher National Institutes of Health Stroke Scale, and larger parenchymal hypoattenuation on computed tomography are reliable early predictors for malignant edema. Revascularization reduces the risk of malignant edema. Future studies with robust design are needed to explore optimal cutoff age and National Institutes of Health Stroke Scale scores and to validate and improve existing models.

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In the past decades, the world has witnessed the successful commercialization of “rocking‐chair”‐type lithium‐ion batteries with lithium metal free anodes. Owing to their safe, green, easy manufacturing, and cost‐efficiency characteristics, rechargeable zinc batteries have recently received more and more attention. However, the practical application of Zn metal batteries is hampered mainly by the dendritic growth of Zn metal anode, which leads to poor Coulombic efficiency, hazards, and various side reactions. Herein, the emerging “rocking‐chair”‐type Zn‐ion batteries are systemically reviewed with Zn host anodes instead of Zn metal anodes. As an introduction, the fundamental principles, advantages, and challenges of “rocking‐chair”‐type Zn‐ion batteries are discussed. Subsequently, the design principles and recent advances of cathode, anode, and electrolyte for “rocking‐chair” Zn‐ion batteries are summarized. To conclude, perspectives on the future of “rocking‐chair” Zn‐ion batteries are presented. It is hoped that this review may provide alternative directions for the design of Zn‐ion batteries.

Silicon has been considered as the most promising anode candidate for next-generation lithium-ion batteries. However, the fast capacity decay caused by huge volume expansion and low electronic conductivity limit the electrochemical performance. Herein, atomic distributed, airstable, layer-by-layer-assembled Si/C (L-Si/C) is designed and in situ constructed from commercial micron-sized layered CaSi 2 alloy with the greenhouse gas CO 2 . The inner structure of Si as well as the content and graphitization of C can be regulated by simply adjusting the reaction conditions. The rationally designed layered structure can enhance electronic conductivity and mitigate volume change without disrupting the carbon layer or destroying the solid electrolyte interface. Moreover, the single-layer Si and C can enhance lithium-ion transport in active materials. With these advantages, L-Si/C anode delivers an 82.85% capacity retention even after 3200 cycles and superior rate performance. The battery-capacitance dual-model mechanism is certified via quantitative kinetics measurement. Besides, the self-standing architecture is designed via assembling L-Si/C and MXene. Lithiophilic L-Si/C can guide homogeneous Li deposition with alleviated volume change. With the MXene/L-Si/C host for lithium−metal batteries, an ultralong life span up to 500 h in a carbonate-based electrolyte is achieved. A full cell with a high-energy 5 V LiNi 0.5 Mn 1.5 O 4 cathode is constructed to verify the practicality of L-Si/C and MXene/L-Si/C. The rational design of a special layer structure may propose a strategy for other materials and energy storage systems.

Metal anodes based on a plating/stripping electrochemistry such as metallic Li, Na, K, Zn, Mg, Ca, Al, and Fe have attracted widespread attention over the past several years because of their high theoretical specific capacity, low electrochemical potential, and superior electronic conductivity. Metal anodes can be paired with cathodes to construct high-energy-density rechargeable metal batteries. However, inherent issues including large volume changes, uncontrollable growth of dangerous dendrites, and an unstable solid electrolyte interphase (SEI) hinder their further development. MXene as an emerging 2D material has shown great potential to address the inherent issues of metal anodes due to its 2D structure, abundant surface functional groups, and the ability to construct macroscopic architectures. To date, under the assistance of MXene, various strategies have been proposed to achieve stable and dendrite-free metal anodes, such as MXene-based host design, designing metalphilic MXene-based substrates, modifying the metal surface with MXene, constructing MXene arrays, and decorating separators or electrolytes with MXene. Herein the applications and advances of MXene in stable and dendrite-free metal anodes are carefully summarized and analyzed. Some perspectives and outlooks for future research are also proposed.

High-performance cathodes are essential for all kinds of rechargeable batteries, and vanadium pentoxide (V2O5) has wide applications as a cathode in various batteries because of its high theoretical capacity, abundant reserves, and high safety performances. However, the irreversible phase transitions and sluggish ion diffusion limit its advancements. Herein, morphology-tunable micron-sized nanoporous V2O5 arrays are synthesized from V2CT x MXene by a one-step annealing process. The component and structure of the V2CT x MXene are simply controlled by regulating the reaction time. The effects of annealing conditions on crystallinity, microstructure, and electrochemical performance of V2O5 are further probed. The rationally designed V2O5 possesses special porous architecture, 2D structure, and pseudocapacitive effect, which ensures high ion accessibility, excellent structure stability, and fast charge transport. As a consequence, the optimal V2O5 cathode for gel zinc-ion batteries exhibits high capacity (358.7 mA h g–1 at 200 mA g–1 after 400 cycles), superior rate performance (250.4 mA h g–1 at 8000 mA g–1), and stable long-term cyclability (279 mA h g–1 at 2000 mA g–1 over 3500 cycles). The zinc storage enhancing mechanism is assessed by quantitative kinetics analysis. Furthermore, the V2O5 cathode also delivers an improved potassium storage performance. This work may provide a universal avenue to fabricate high-performance electrodes from MXene-based materials for next generation battery systems.