Stabilization of the Li metal anode through constructing a LiZn alloy/polymer hybrid protective layer towards uniform Li deposition.

Constructing an artificial solid electrolyte interphase (SEI) layer is an effective strategy for solving uncontrolled Li dendrite growth resulting from an unstable and heterogeneous Li/electrolyte interface. Herein, we develop a hybrid layer of a LiZn alloy and a polyethylene oxide (PEO) polymer to protect the Li metal anode for achieving a Li dendrite-free Li metal anode surface. The LiZn alloy is advantageous for fast Li+ transport, and is uniformly dispersed in the PEO matrix to regulate electronic and Li+ ion flux distributions homogeneously. Furthermore, the flexible PEO network can alleviate the volume change during cycling. The synergistic effect enables Li deposition underneath the hybrid film. Hence, the hybrid protection film results in significantly improved cycling stability with respect to the pristine Li metal anode. A symmetric Li/Li cell with a composite protective layer can be cycled for over 1000 h at a current density of 1 mA cm-2 with a fixed capacity of 1 mA h cm-2, and a full cell with a high areal capacity of the LiFePO4 (2.45 mA h cm-2) cathode exhibits an outstanding cycling performance.

Revisiting porous foam Cu host based Li metal anode: The roles of lithiophilicity and hierarchical structure of three-dimensional framework.

Lithium (Li) metal anode (LMA) is one of the most promising anodes for high energy density batteries. However, its practical application is impeded by notorious dendrite growth and huge volume expansion. Although the three-dimensional (3D) host can enhance the cycling stability of LMA, further improvements are still necessary to address the key factors limiting Li plating/stripping behavior. Herein, porous copper (Cu) foam (CF) is thermally infiltrated with molten Li-rich Li-zinc (Li-Zn) binary alloy (CFLZ) with variable Li/Zn atomic ratio. In this process, the LiZn intermetallic compound phase self-assembles into a network of mixed electron/ion conductors that are distributed within the metallic Li phase matrix and this network acts as a sublevel skeleton architecture in the pores of CF, providing a more efficient and structured framework for the material. The as-prepared CFLZ composite anodes are systematically investigated to emphasize the roles of the tunable lithiophilicity and hierarchical structure of the frameworks. Meanwhile, a thin layer of Cu-Zn alloy with strong lithiophilicity covers the CF scaffold itself. The CFLZ with high Zn content facilitates uniform Li nucleation and deposition, thereby effectively suppressing Li dendrite growth and volume fluctuation. Consequently, the hierarchical and lithiophilic framework shows low Li nucleation overpotential and highly stable Coulombic efficiency (CE) for 200 cycles in conventional carbonate based electrolyte. The full cell coupled with LiFePO4 (LFP) cathode demonstrates high cycle stability and rate performance. This work provides valuable insights into the design of advanced dendrite-free 3D LMA toward practical application.

Highly lithiophilic and structurally stable Cu-Zn alloy skeleton for high-performance Li-rich ternary anodes.

Lithium (Li)-rich ternary alloy, comprising a multi-alloy phase as the built-in three-dimensional (3D) framework and a Li metal phase as a reversible Li reservoir, is a promising high-energy-density anode for rechargeable Li metal batteries. The introduction of metal/metalloid components to the alloy can effectively regulate Li deposition and maintain the dimensional integrity of the Li anode. Herein, the lithium-copper-zinc (Li-Cu-Zn) ternary alloy, as a new type of alloy anode, is synthesized via a facile thermal melting method. The fully delithiated 3D scaffold comprised two Cu-Zn alloy phases named CuZn and CuZn5. These alloy phases exhibit higher lithiophilicity and structural stability than Li-Zn and Li-Cu alloys. Moreover, the CuZn phase is electrochemically inert, ensuring the geometric stability of the anode, while the CuZn5 phase can readily undergo alloying reaction with Li to form the LiZn phase, thereby facilitating uniform Li nucleation and deposition. The hybridized multiphase alloy structure and specific energy storage mechanism of the Cu-Zn based alloy scaffold in the ternary alloy anode facilitate dendrite-free Li deposition and prolonged cycle lifetime. The Li metal full battery based on lithium iron phosphate (LiFePO4) cathode exhibits high cycling stability with high-capacity retention of 95.4% after 1000 cycles at 1C.

Ultrathin Li-rich Li-Cu alloy anode capped with lithiophilic LiC6 headspace enabling stable cyclic performance.

Li-rich dual-phase Li-Cu alloy is a promising candidate toward practical application of Li metal anode due to its in situ formed unique three-dimensional (3D) skeleton of electrochemical inert LiCux solid-solution phase. Since a thin layer of metallic Li phase appears on the surface of as-prepared Li-Cu alloy, the LiCux framework cannot regulate Li deposition efficiently in the first Li plating process. Herein, a lithiophilic LiC6 headspace is capped on the upper surface of the Li-Cu alloy, which can not only offer free space to accommodate Li deposition and maintain dimensional stability of the anode, but also provide abundant lithiophilic sites and guide Li deposition effectively. This unique bilayer architecture is fabricated via a facile thermal infiltration method, where the Li-Cu alloy layer with an ultrathin thickness around 40 µm occupies the bottom of a carbon paper (CP) sheet, and the upper part of this 3D porous framework is reserved as the headspace for Li storage. Notably, the molten Li can quickly convert these carbon fibers of the CP into lithiophilic LiC6 fibers while the CP is touched with the liquid Li. The synergetic effect between the LiC6 fibers framework and LiCux nanowires scaffold can ensure a uniform local electric field and stable Li metal deposition during cycling. As a consequence, the CP capped ultrathin Li-Cu alloy anode demonstrates excellent cycling stability and rate capability.

A hybrid polymer protective layer with uniform Li+ flux and self-adaption enabling dendrite-free Li metal anodes.

Lithium (Li) metal is considered as an ideal negative electrode material for next-generation secondary batteries; however, the hideous dendrite growth and parasitic reactions hinder the practical applications of Li metal batteries. Herein, a hybrid polymer film composed of polyvinyl alcohol (PVA) and polyacrylic acid (PAA) is adopted as an artificial protective layer to inhibit the dendritic formation and side reactions in Li metal anodes. PVA with large quantities of polar functional groups can induce even distribution of Li ions (Li+). Alternatively, PAA can in situ react with Li metal to form highly elastic and ionic conducting lithium polyacrylic acid (LiPAA), thereby enabling tight contact and flexible self-adaption with Li metal anodes. Therefore, such a rationally designed functional composite layer, with good binding ability and relatively high Li+ conductivity, as well as excellent capability of homogenizing Li+ flow, accordingly enables Li metal anodes to reveal dendrite-free plating/stripping behaviours and minimum volume variation. As a result, the PVA-PAA modified Li metal anode delivered stable cycling for 700 and 250 h, respectively, at current densities of 1 and 3 mA cm-2 under an areal capacity of 1 mA h cm-2, in a carbonate ester-based electrolyte without any additive, exhibiting boosted cycling and rate performances. The Li anode with a functional PVA-PAA hybrid interlayer can maintain the dense and smooth texture without dendrite formation after long cycles. The full cell of Li|LiFeO4 with our modified Li anode and a cathode with a high areal capacity of 2.45 mA h cm-2 delivers, change to achieved a long-term lifespan of 180 cycles at 1.0 C, with a capacity retention of 96.7%. This work demonstrates a simple and effective strategy of designing multi-functional artificial protective layers, targeting dendrite-free Li anodes.

Li-Ca Alloy Composite Anode with Ant-Nest-Like Lithiophilic Channels in Carbon Cloth Enabling High-Performance Li Metal Batteries.

Constructing a three-dimensional (3D) multifunctional hosting architecture and subsequent thermal infusion of molten Li to produce advanced Li composite is an effective strategy for stable Li metal anode. However, the pure liquid Li is difficult to spread across the surface of various substrates due to its large surface tension and poor wettability, hindering the production and application of Li composite anode. Herein, heteroatomic Ca is doped into molten Li to generate Li-Ca alloy, which greatly regulates the surface tension of the molten alloy and improves the wettability against carbon cloth (CC). Moreover, a secondary network composed of CaLi 2 intermetallic compound with interconnected ant-nest-like lithiophilic channels is in situ formed and across the primary scaffold of CC matrix by infiltrating molten Li-Ca alloy into CC and then cooling treatment (LCAC), which has a larger and lithiophilic surface to enable uniform Li deposition into interior space of the hybrid scaffold without Li dendrites. Therefore, LCAC exhibits a long-term lifespan for 1100 h under a current density of 5 mA cm -2 with fixed areal capacity of 5 mAh cm -2. Remarkably, full cells paired with practical-level LiFePO 4 cathode of 2.45 mAh cm -2 deliver superior performance.

Construction of reduced graphene oxide wrapped yolk-shell vanadium dioxide sphere hybrid host for high-performance lithium-sulfur batteries.

Owing to the considerable theoretical energy density, lithium-sulfur batteries have been deemed as a competitive candidate for the next-generation energy storage devices. However, its commercialization still depends on the moderation of the shuttle effect and the conductivity improvement of the sulfur cathode. Herein, a novel reduced graphene oxide (rGO) wrapped yolk-shell vanadium dioxide (VO2) sphere hybrid host (rGO/VO2) is reported to simultaneously tackle these barriers. In particular, the polar VO2 sphere can chemically anchor and catalyze the conversion of polysulfides effectively both on the yolk and the shell surfaces. Meanwhile, the highly conductive 3D porous rGO network not only allows sufficient penetration of electrolyte and provides efficient transport pathways for lithium ions and electrons, but also buffers the volume variation during the lithiation process. Besides, the dissolution of the polysulfides can also be alleviated by physical confinement via the interconnected carbon network. Benefiting from these synergistic features, such designed rGO/VO2/S cathode delivers outstanding cycle stability (718.6 mA h g-1 initially, and 516.1 mA h g-1 over 400 cycles at 1C) with a fading rate of 0.07% per cycle. Even at 3C, a capacity of 639.7 mA h g-1 is reached. This proposed unique structure could provide novel insights into high-energy batteries.

Tailored multifunctional hybrid cathode substrate configured with carbon nanotube-modified polar Co(PO3)2/CoP nanoparticles embedded nitrogen-doped porous-shell carbon polyhedron for high-performance lithium-sulfur batteries.

Despite the overwhelming advantages of high theoretical specific energy and low-cost, the realistic application of lithium-sulfur batteries is still restricted by the shuttle effect of intermediate polysulfides, low conductivity of sulfur and volume variation during charging and discharging. Tailored sulfur cathode is of significant importance for realizing high-performances. This study reports a carbon nanotube (CNT)-modified polar Co(PO3)2/CoP nanoparticles embedded nitrogen-doped porous-shell carbon polyhedron (CNT/CPO/CPNC-1) as a sulfur host to simultaneously overcome the barriers of lithium-sulfur batteries. The shuttle effect can be significantly restrained by the physical confinement of unique porous structure and the chemical adsorption/catalysis conversion of polar Co(PO3)2/CoP and the heteroatom doping of nitrogen. Meanwhile, the porous-shell carbon with interconnected carbon nanotubes can simultaneously provide a conductive framework, facilitate rapid electrical transport, and enable a large inner space to buffer volume expansion. As a result, CNT/CPO/CPNC-1/S cathode demonstrates an excellent reversible capacity of 1371.3 mAh g-1 at 0.1 C with stable Coulombic efficiency of 98% and an outstanding cycling stability with an ultralow capacity decay rate of 0.048% per cycle (500 cycles at 1.0 C). This work pioneers the employment of Co(PO3)2/CoP/carbon hybrid materials as sulfur host and sheds a new light to explore the high-performance lithium-sulfur batteries.

One-Step Synthesis of a Coral-Like Cobalt Iron Oxyhydroxide Porous Nanoarray: An Efficient Catalyst for Oxygen Evolution Reactions.

The design of high-efficiency and cost-effective electrocatalysts is one of the most crucial factors for facilitating the oxygen evolution reaction (OER). Therefore, we prepared Cox Fe1-x OOH with coral-like nanonet arrays on carbon cloth (CC) as high-performance OER catalysts by a facile hydrothermal method. The resulting Cox Fe1-x OOH was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectrometry. When serving as a catalyst electrode in the OER, Co0.875 Fe0.125 OOH/CC exhibits excellent catalytic activity. Co0.875 Fe0.125 OOH/CC has a low overpotential of 300 mV at a current density of 20 mA cm-2 (150 mV less than that of FeOOH/CC) and a small Tafel slope of 83 mV dec-1 in 1.0 M KOH in OER. Moreover, it also has a superior electrochemical durability for more than 50 h.

Excellent rate capability and cycling stability in Li+-conductive Li2SnO3-coated LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries.

High-voltage LiNi0.5Mn1.5O4 is a promising cathode candidate for lithium-ion batteries (LIBs) due to its considerable energy density and power density, but the material generally undergoes serious capacity fading caused by side reactions between the active material and organic electrolyte. In this work, Li+-conductive Li2SnO3 was coated on the surface of LiNi0.5Mn1.5O4 to protect the cathode against the attack of HF, mitigate the dissolution of Mn ions during cycling and improve the Li+ diffusion coefficient of the materials. Remarkable improvement in cycling stability and rate performance has been achieved in Li2SnO3-coated LiNi0.5Mn1.5O4. The 1.0 wt% Li2SnO3-coated LiNi0.5Mn1.5O4 cathode exhibits excellent cycling stability with a capacity retention of 88.2% after 150 cycles at 0.1 C and rate capability at high discharge rates of 5 C and 10 C, presenting discharge capacities of 119.5 and 112.2 mAh g-1, respectively. In particular, a significant improvement in cycling stability at 55 °C is obtained after the coating of 1.0 wt% Li2SnO3, giving a capacity retention of 86.8% after 150 cycles at 1 C and 55 °C. The present study provides a significant insight into the effective protection of Li-conductive coating materials for a high-voltage LiNi0.5Mn1.5O4 cathode material.