Retarding anion migration for alleviating concentration polarization towards stable polymer lithium-metal batteries.

Traditional dual-ion lithium salts have been widely used in solid polymer lithium-metal batteries (LMBs). Nevertheless, concentration polarization caused by uncontrolled migration of free anions has severely caused the growth of lithium dendrites. Although single-ion conductor polymers (SICP) have been developed to reduce concentration polarization, the poor ionic conductivity caused by low carrier concentration limits their application. Herein, a dual-salt quasi-solid polymer electrolyte (QSPE), containing the SICP network as a salt and traditional dual-ion lithium salt, is designed for retarding the movement of free anions and simultaneously providing sufficient effective carriers to alleviate concentration polarization. The dual salt network of this designed QSPE is prepared through in-situ crosslinking copolymerization of SICP monomer, regular ionic conductor, crosslinker with the presence of the dual-ion lithium salt, delivering a high lithium-ion transference number (0.75) and satisfactory ionic conductivity (1.16 × 10-3 S cm-1 at 30 °C). Comprehensive characterizations combined with theoretical calculation demonstrate that polyanions from SICP exerts a potential repulsive effect on the transport of free anions to reduce concentration polarization inhibiting lithium dendrites. As a consequence, the Li||LiFePO4 cell achieves a long-cycle stability for 2000 cycles and a 90% capacity retention at 30 °C. This work provides a new perspective for reducing concentration polarization and simultaneously enabling enough lithium-ions migration for high-performance polymer LMBs.

Degradation Mechanisms of Electrodes Promotes Direct Regeneration of Spent Li-Ion Batteries: A Review.

The rapid growth of electric vehicle use is expected to cause a significant environmental problem in the next few years due to the large number of spent lithium-ion batteries (LIBs). Recycling spent LIBs will not only alleviate the environmental problems but also address the challenge of limited natural resources shortages. While several hydro- and pyrometallurgical processes are developed for recycling different components of spent batteries, direct regeneration presents clear environmental, and economic advantages. The principle of the direct regeneration approach is restoring the electrochemical performance by healing the defective structure of the spent materials. Thus, the development of direct regeneration technology largely depends on the formation mechanism of defects in spent LIBs. This review systematically details the degradation mechanisms and types of defects found in diverse cathode materials, graphite anodes, and current collectors during the battery's lifecycle. Building on this understanding, principles and methodologies for directly rejuvenating materials within spent LIBs are outlined. Also the main challenges and solutions for the large-scale direct regeneration of spent LIBs are proposed. Furthermore, this review aims to pave the way for the direct regeneration of materials in discarded lithium-ion batteries by offering a theoretical foundation and practical guidance.

High-Entropy Laminates with High Ion Conductivities for High-Power All-Solid-State Lithium Metal Batteries.

Solid-state electrolytes (SSEs) are crucial to high-energy-density lithium metal batteries, but they commonly suffer from slow Li+ transfer kinetics and low mechanical strength, severely hampering the application for all-solid-state batteries. Here, we develop a two-dimensional (2D) high-entropy lithium-ion conductor, lithium-containing transition-metal phosphorus sulfide, HE-LixMPS3 (Lix(Fe1/5Co1/5Ni1/5Mn1/5Zn1/5)PS3) with five transition-metal atoms and lithium ions (Li+) dispersed into [P2S6]2- framework layers, exhibiting high lattice distortions and a large amount of cation vacancies. Such unique features enable to efficiently accelerate the migration of Li+ in 2D [P2S6]2- interlamination, delivering a high ionic conductivity of 5 × 10-4 S cm-1 at room temperature. Moreover, the HE-LixMPS3 laminate can be employed as a building block to construct an ultrathin SSE film (∼10 µm) based on strong C-S bonding between HE-LixMPS3 and nitrile-butadiene rubber. The SSE film delivers a strong mechanical robustness (6.0 MPa, 310% elongation) and a high ionic conductivity of 4 × 10-4 S cm-1, showing a long cycle stability of 800 h in lithium symmetric cells. Coupled with LiFePO4 cathode and lithium anode, the all-solid-state battery presents a high Coulombic efficiency of 99.8% within 2000 cycles at 5.0 C.

Ultralow-Dielectric-Constant Atomic Layers of Amorphous Carbon Nitride Topologically Derived from MXene.

Low-dielectric-constant materials such as silicon dioxide serving as interconnect insulators in current integrated circuit face a great challenge due to their relatively high dielectric constant of ≈4, twice that of the recommended value by the International Roadmap for Devices and Systems, causing severe parasitic capacitance and associated response delay. Here, novel atomic layers of amorphous carbon nitride (a-CN) are prepared via a topological conversion of MXene-Ti3 CNTx under bromine vapor. Remarkably, the assembled a-CN film exhibits an ultralow dielectric constant of 1.69 at 100 kHz, much lower than the previously reported dielectric materials such as amorphous carbon (2.2) and fluorinated-doped SiO2 (3.6), ascribed to the low density of 0.55 g cm-3 and high sp3 C level of 35.7%. Moreover, the a-CN film has a breakdown strength of 5.6 MV cm-1 , showing great potential in integrated circuit application.

MXene Derivatives for Energy Storage and Conversions.

Associated with the rapid development of 2D transition metal carbides, nitrides, and carbonitrides (MXenes), MXene derivatives have been recently exploited and exhibited unique physical/chemical properties, holding promising applications in the areas of energy storage and conversions. This review provides a comprehensive summarization of the latest research and progress on MXene derivatives, including termination-tailored MXenes, single-atom implanted MXenes, intercalated MXenes, van der Waals atomic layers, and non-van der Waals heterostructures. The intrinsic relationship between structure, properties, and corresponding applications for MXene derivatives are then emphasized. Finally, the essential challenges are addressed and perspectives for the MXene derivatives are also discussed.

N,S-Doped Porous Carbon Nanobelts Embedded with MoS2 Nanosheets as a Self-Standing Host for Dendrite-Free Li Metal Anodes.

Metallic Li is one of the most promising anodes for high-energy secondary batteries. However, the enormous volume changes and severe dendrite formation during the Li plating/stripping process hinder the practical application of Li metal anodes (LMAs). We have developed a sulfate-assisted strategy to synthesize a self-standing host composed of N,S-doped porous carbon nanobelts embedded with MoS2 nanosheets (MoS2 @NSPCB) for use in LMAs. In situ measurements and theoretical calculations reveal that the uniformly distributed MoS2 derivatives within the carbon nanobelts serve as stable lithiophilic sites which effectively homogenize Li nucleation and suppress dendrite formation. In addition, the hierarchical porosity and 3D nanobelt networks ensure fast Li-ion diffusion and accommodate the volume change of Li deposits during the plating/stripping process. As a result, a Li-Li symmetric cell using the MoS2 @NSPCB host operates steadily over 1500 h with an ultralow voltage hysteresis (≈24.2 mV) at 3 mA cm-2 /3 mAh cm-2 . When paired with a LiFePO4 cathode, the current collector-free LMA endows the full cell with a high energy density of 460 Wh kg-1 and good cycling performance (with a capacity retention of ≈70% even after 1600 cycles at 10 C).

Formation of Super-Assembled TiOx /Zn/N-Doped Carbon Inverse Opal Towards Dendrite-Free Zn Anodes.

Uncontrolled growth of Zn dendrites and side reactions are the major restrictions for the commercialization of Zn metal anodes. Herein, we develop a TiOx /Zn/N-doped carbon inverse opal (denoted as TZNC IO) host to regulate the Zn deposition. Amorphous TiOx and Zn/N-doped carbon can serve as the zincophilic nucleation sites to prevent the parasitic reactions. More importantly, the highly ordered IO host homogenizes the local current density and electric field to stabilize Zn deposition. Furthermore, the three-dimensional open networks could regulate Zn ion flux to enable stable cycling performance at large current densities. Owing to the abundant zincophilic sites and the open structure, granular Zn deposits could be realized. As expected, the TZNC IO host guarantees the steady Zn plating/stripping with a long-term stability over 450 h at the current density of 1 mA cm-2 . As a proof-of-concept demonstration, a TZNC@Zn||V2 O5 full cell shows long lifespan over 2000 cycles at 5.0 A g-1 .

High-Entropy Atomic Layers of Transition-Metal Carbides (MXenes).

High-entropy materials (HEMs) have great potential for energy storage and conversion due to their diverse compositions, and unexpected physical and chemical features. However, high-entropy atomic layers with fully exposed active sites are difficult to synthesize since their phases are easily segregated. Here, it is demonstrated that high-entropy atomic layers of transition-metal carbide (HE-MXene) can be produced via the selective etching of novel high-entropy MAX (also termed Mn +1 AXn (n = 1, 2, 3), where M represents an early transition-metal element, A is an element mainly from groups 13-16, and X stands for C and/or N) phase (HE-MAX) (Ti1/5 V1/5 Zr1/5 Nb1/5 Ta1/5 )2 AlC, in which the five transition-metal species are homogeneously dispersed into one MX slab due to their solid-solution feature, giving rise to a stable transition-metal carbide in the atomic layers owing to the high molar configurational entropy and correspondingly low Gibbs free energy. Additionally, the resultant high-entropy MXene with distinct lattice distortions leads to high mechanical strain into the atomic layers. Moreover, the mechanical strain can efficiently guide the nucleation and uniform growth of dendrite-free lithium on HE-MXene, achieving a long cycling stability of up to 1200 h and good deep stripping-plating levels of up to 20 mAh cm-2 .

Dendrite-Free Lithium Anodes with Ultra-Deep Stripping and Plating Properties Based on Vertically Oriented Lithium-Copper-Lithium Arrays.

Although lithium metal is the best anode for lithium-based batteries, the uncontrollable lithium dendrites especially under deep stripping and plating states hamper its practical applications. Here, a dendrite-free lithium anode is developed based on vertically oriented lithium-copper-lithium arrays, which can be facilely produced via traditional rolling or repeated stacking approaches. Such vertically oriented arrays not only enable both the lithium-ion flux and the electric field to be regulated, but also can act as a "dam" to guide the regular plating of lithium, thus efficiently buffering the volume change of the lithium anode upon cycling. As a consequence, the vertically oriented anode exhibits an excellent deep stripping and plating capability upto 50 mAh cm-2 , high rate capabilities (20 mA cm-2 ), and long cycle life (2000 h). Based on this anode, a full lithium battery with a LiCoO2 cathode delivers a good cycle life, holding great potential for practical lithium-metal batteries with high energy densities.

Room-temperature sodium thermal reaction towards electrochemically active metals for lithium storage.

Due to the superior capacity for lithium storage, metallic tin and germanium are considered as one of the candidate anodes for the next generation of lithium ion batteries. Herein, metallic tin and germanium particles are successfully prepared by using a mild replacement reaction between metallic sodium and the corresponding tetrachloride under room temperature. The as-obtained metals exhibit nanocrystals of several nanometers. Used as anode of lithium-ion batteries, the as-obtained metallic nanocrystals display improved cycling stability, superior rate performance and high reversible capacity as well. Furthermore, it provides a facile approach to fabricate other electrochemically active metallic nanocrystals by using this mild and environmental benignity replacement reaction.