Synchronously Consolidating Li, Se, S, and C for Robust Li-SeS Batteries.

S-redox involving solvated polysulfides is accompanied by volumetric change and structural decay of the S-based cathodes. Here, we propose a synchronous construction strategy for consolidating Li, Se, S, and C elements within a composite cathode via a paradigm reaction of 8Li+2Se+CS2 = 2Li4SeS+C. The obtained composite features crystalline Li4SeS encapsulated in a carbon nanocage (Li4SeS@C), exhibiting ultrahigh electrical conductivity, ultralow activation barrier, and excellent structural integrity, accordingly enabling large specific capacity (615 mAh g-1) and high capacity retention (87.3% after 350 cycles) at 10 A g-1. TOF-SIMS demonstrates its superior volumetric efficiency to a similar derivative SeS@C (2Se+CS2 = 2SeS+C), and DFT reveals its lower activation barrier than Li2S@C and Li2Se@C. This consolidation design significantly improves the electrochemical performance of S-based cathodes, and the paradigm reaction guarantees structural diversity and flexibility. Moreover, employing a synchronous construction mechanism to maximize the synergistic effect between element consolidation and carbon encapsulation opens up a new approach for developing robust S or chalcogenide cathodes.

Optimized Phase and Crystallinity of Cr2(NCN)3 Dominating Electrochemical Lithium Storage Performance.

Cr2(NCN)3 is a potentially high-capacity and fast-charge Li-ion anode owing to its abundant and broad tunnels. However, high intrinsic chemical instability severely restricts its capacity output and electrochemical reversibility. Herein we report an effective crystalline engineering method for optimizing its phase and crystallinity. Systematic studies reveal the relevancy between electrochemical performance and crystalline structure; an optimal Cr2(NCN)3 with high phase purity and uniform crystallinity exhibits a high reversible capacity of 590 mAh g-1 and a stable cycling performance of 478 mAh g-1 after 500 cycles. In-operando heating XRD reveals its high thermodynamical stability over 600 °C, and in-operando electrochemical XRD proves its electrochemical Li storage mechanism, consisting of the primary Li-ion intercalation and subsequent conversion reactions. This study introduces a facile and low-cost method for fabricating high-purity Cr2(NCN)3, and it also confirms that the Li storage of Cr2(NCN)3 can be further improved by tuning its phase and crystallinity.

Healable and Conductive Two-Dimensional Sulfur Iodide for High-Rate Sodium Batteries.

Self-healing functional materials can repair cracks and damage inside the battery, ensuring the stability of the battery material structure. This feature minimizes performance degradation during the charging and discharging processes, improving the efficiency and stability of the battery. Here, we have developed a novel healing conductive two-dimensional sulfur iodide (SI4) composite cathode. This process integrates both sulfur and iodine compounds into carbon nanocages, forming a SI4@C core-shell structure. This cathode design improves electrical conductivity and repairability, facilitates rapid activation, and ensures structural integrity, resulting in a typical Na-SI4 battery with high capacity and an exceptionally long cycle life. At 10.0 A g-1, the capacity of the Na-SI4 battery can still reach 217.4 mAh g-1 after more than 500 cycles, and the capacity decay rate per cycle is only 0.06%. In addition, the cathode exhibits a cascade redox reaction involving S and I, contributing to its high capacity. The in situ growth of a carbon shell further enhances the conductivity and structural robustness of the entire cathode. The flexibility and bendability of SI4@C-carbon cloth make it applicable for flexible electronic devices, providing more possibilities for battery design. The strategy of engineering a two-dimensional self-healing structure to construct a superior cathode is expected to be widely applied to other electrode materials. This study provides a new pathway for designing novel binary-conversion-type sodium-ion batteries with excellent long-term cycling performance.

Thermochemical Cyclization Constructs Bridged Dual-Coating of Ni-Rich Layered Oxide Cathodes for High-Energy Li-Ion Batteries.

Enhancing microstructural and electrochemical stabilities of Ni-rich layered oxides is critical for improving the safety and cycle-life of high-energy Li-ion batteries. Here we propose a thermochemical cyclization strategy where heating polyacrylonitrile with LiNi0.8Co0.1Mn0.1O2 can simultaneously construct a cyclized polyacrylonitrile outer layer and a rock-salt bridge-like inner layer, forming a compact dual-coating of LiNi0.8Co0.1Mn0.1O2. Systematic studies demonstrate that the mild cyclization reaction between polyacrylonitrile and LiNi0.8Co0.1Mn0.1O2 induces a desirable "layered to rock-salt" structural transformation to create a nano-intermedium that acts as the bridge for binding cyclized polyacrylonitrile to layered LiNi0.8Co0.1Mn0.1O2. Because of the improvement of the structural and electrochemical stability and electrical properties, this cathode design remarkably enhances the cycling performance and rate capability of LiNi0.8Co0.1Mn0.1O2, showing a high reversible capacity of 183 mAh g-1 and a high capacity retention of 83% after 300 cycles at 1 C rate. Notably, this facile and scalable surface engineering makes Ni-rich cathodes potentially viable for commercialization in high-energy Li-ion batteries.

Liquid-Phase Exfoliated Few-Layer Iodine Nanosheets for High-Rate Lithium-Iodine Batteries.

Rechargeable lithium-iodine (Li-iodine) batteries attract significant attention owning to their high energy density, wide abundance and low cost of iodine resources. However, iodine suffers from low electrical conductivity and high solubility in aprotic electrolyte, leading to fast capacity degradation, low columbic efficiency, as well as poor rate capability. Herein, we propose a simple method for the large-scale production of two-dimensional (2D) few-layer iodine nanosheets (FLINs) via liquid-phase exfoliation of iodine in deionized water. 2D FLINs could effectively improve rate capability by providing sufficient active sites and shortening the Li ion diffusion path. Meanwhile, graphene oxide (GO)@carbon nanotubes (CNT) hosts are designed to suppress the dissolution of iodine and enhance the electrical conductivity. GO@CNT@FLINs film exhibits excellent rate capability (220 mAh g-1 at 0.2 A g-1 and 96 mAh g-1 at 8 A g-1 ) and outstanding cycle stability (93.2 mAh g-1 at 2 A g-1 after 1000 cycles) for lithium storage due to the synergistic effects of GO@CNT hosts and 2D structure of FLINs. The controllable synthesis of FLINs provides a bright prospect for achieving high rate capability of Li-iodine batteries and is of utmost importance to potential large-scale applications.

Realizing Few-Layer Iodinene for High-Rate Sodium-Ion Batteries.

Elemental 2D materials with fascinating characteristics are regarded as an influential portion of the 2D family. Iodine is as a typical monoelemental molecular crystal and exhibits great prospects of applications. To realize 2D iodine, not only is it required to separate the weak interlayer van der Waals interactions, but also to reserve the weak intramolecular halogen bonds; thus, 2D iodine is still unexploited until now. Herein, atomically thin iodine nanosheets (termed "iodinene") with the thickness around 1.0 nm and lateral sizes up to hundreds of nanometers are successfully fabricated by a liquid-phase exfoliation strategy. When used for the cathode of rechargeable sodium-ion batteries, the ultrathin iodinene exhibits superb rate properties with a high specific capacity of 109.5 mA h g-1 at the high rate of 10 A g-1 owing to its unique 2D ultrathin architecture with remarkably enhanced pseudocapacitive behavior. First-principles calculations reveal that the diffusion of sodium ions in few-layered iodinene changes from the original horizontal direction in bulk to the vertical with a small energy barrier of 0.07 eV because of the size effect. The successful preparation and intensive structural investigation of iodinene paves the way for the development of novel iodine-based science and technologies.

Nanopile Interlocking Separator Coating toward Uniform Li Deposition of the Li Metal Anodes.

Uncontrollable growth of lithium (Li) dendrite has severely hindered the development of Li metal anodes, while separator modification is regarded as a simple and effective way to mitigate the growth of Li dendrite. However, the "drop-dregs" phenomenon of coating layer desquamated from polyolefin separator due to their different Young's modulus would induce a nonuniform Li ionic flux, finally resulting in deteriorative electrochemical performance and even thermal runaway of the battery. Herein, we introduce a novel nanopile mechanical interlocking strategy to create delamination-free separator modification, which could stably generate a homogeneous Li ionic flux to guide long-term uniform Li deposition. Both experimental and simulation results demonstrate a strong bonding strength between the coating layer and membrane matrix based on this physical interlocking mechanism. Consequently, with a nearly dendrite-free Li deposition and a largely reduced interface impedance, 1000 h stable cycling of Li/Li half cells enrolled this modified separator is successfully achieved. Also, a significant improvement in Li/LiFePO4 full cells in long-term cycling stability to 500 cycles further indicates its promising practical potential. Moreover, this presented approach without any binding agents or surface activation procedures could be facilely scaled up, providing an applicable and durable separator modification solution toward stable Li metal anodes.

Germanium-based high-performance dual-ion batteries.

Recently, dual-ion batteries (DIBs) have received immense attention owing to their high operating voltage and low cost, and further studies on the enhancement of their energy densities and cyclabilities are being intensively pursued. Herein, a novel Ge-based DIB has been developed for the first time by using a rationally designed nanocomposite of Ge particles embedded in one-dimensional carbon nanofibers (Ge/CNFs) as an anode. The resulting battery shows a high discharge capacity of 281 mA h g-1 at a discharge current of 0.25 A g-1 and a superb rate capability of 94 mA h g-1 at a discharge current of 2.5 A g-1, which greatly surpasses those of most of the reported DIBs. These remarkable properties can be ascribed to the fact that the uniform one-dimensional nanostructure facilitates the improvement of lithium-ion diffusion within the hybrids, and the carbon matrix effectively alleviates the volume expansion of Ge during the cycling process and simultaneously enhances the electrical conductivity of the hybrids. The charge storage mechanism of Ge/CNFs is found to be Ge alloying with Li, accompanied by a phase transformation process from crystalline Ge to amorphous LixGe alloys. This work paves the way for the rational utilization of Ge-based materials in new-generation high-performance DIBs.

Iodine encapsulated in mesoporous carbon enabling high-efficiency capacitive potassium-Ion storage.

The development of potassium-ion batteries (KIBs) are hampered by the lack of appropriate electrode materials allowing for the reversible insertion/de-insertion of the large K-ion. Iodine, as a conversion-type cathode for rechargeable batteries, has high theoretical capacity and excellent electrochemical reversibility, making it a potential cathode material for KIBs. However, due to the defects of iodine with the poor electronic conductivity and easy dissolution in the electrolyte, an intensive quest for iodine-based KIBs enabling high-performance potassium-ion storage is still underway. In this work, a high-efficiency capacitive K-I2 battery has been successfully achieved by constructing a nanocomposite of iodine encapsulated in mesoporous carbon (CMK-3). The as-prepared CMK-3/iodine nanocomposite exhibites excellent rate performance (89.3 mA h g-1 at 0.5 A g-1) and superior cycling stability, which remarkably exceeds most of reported KIBs cathode materials. Such a excellent electrochemical performance can be ascribed to the engineered structure of CMK-3/iodine hybridized electrode which can alleviate the impact of the shuttle phenomenon, improve electronic conductivity and facilitate ion diffusion. As a consequence, iodine within the conductive protecting CMK-3 can afford an extraordinary pseudo-capacitive potassium-ion storage, which sheds light on the development prospect of conversion-type electrode materials to meet urgent demand for advanced KIBs.

Self-Assembled Biomolecular 1D Nanostructures for Aqueous Sodium-Ion Battery.

Aqueous sodium-ion battery of low cost, inherent safety, and environmental benignity holds substantial promise for new-generation energy storage applications. However, the narrow potential window of water and the enlarged ionic radius because of hydration restrict the selection of electrode materials used in the aqueous electrolyte. Here, inspired by the efficient redox reaction of biomolecules during cellular energy metabolism, a proof of concept is proposed that the redox-active biomolecule alizarin can act as a novel electrode material for the aqueous sodium-ion battery. It is demonstrated that the specific capacity of the self-assembled alizarin nanowires can reach as high as 233.1 mA h g-1, surpassing the majority of anodes ever utilized in the aqueous sodium-ion batteries. Paired with biocompatible and biodegradable polypyrrole, this full battery system shows excellent sodium storage ability and flexibility, indicating its potential applications in wearable electronics and biointegrated devices. It is also shown that the electrochemical properties of electrodes can be tailored by manipulating naturally occurring 9,10-anthroquinones with various substituent groups, which broadens application prospect of biomolecules in aqueous sodium-ion batteries.