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.

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.

Exploration of bifunctional Vanadium-based Metal-Organic framework with double active centers for Potassium-ion batteries.

Exploration of suitable electrode hosts with large open channels that can reversibly accommodate K+ with large radius have been extensively investigated. Nevertheless, the reported inorganic counterparts were inevitably restricted by the difficulty of large K+ diffusion capability in crystal structure and the huge volume change. Herein, we report a bifunctional vanadium-based metal-organic framework (MIL-47) with double active centers and larger lamellar spacing that could serve as both cathode and anode material, respectively by controlling the redox potential range in potassium-ion batteries. The results suggest that the stable K-storage mechanism is the reversible rearrangement of the conjugated carboxyl groups of organic terephthalic acid into enolate and the reversible redox activity of V ions, with the specific capacity of 272 mAh g-1 (0.01-1.5 V) and 50 mAh g-1 (1.5-3.8 V) at the current density of 10 mA g-1 for MIL-47 anode and MIL-47 cathode, respectively. The unsaturated functional group of MIL-47 and the intermediate bridged V atom not only provide multi-dimensional channels for electron and ion transport but also stabilize its crystal structure. Additionally, a symmetric full-cell in potassium-ion batteries based on MIL-47 was constructed successfully by avoiding the utilization of K metal with safety concerns. Our results provide new insight into structure design for next-generation large-scale energy storage applications.

A Stabilized Polyacrylonitrile-Encapsulated Matrix on a Nanolayered Vanadium-Based Cathode Material Facilitating the K-Storage Performance.

Layered vanadium-based metal oxides were regarded as promising cathode materials accounting for suitable K+ transport channels as well as high work potential in K-ion batteries. Nevertheless, because of the large radius of K+ and the rigid structure of inorganic materials, the typical K0.486V2O5 suffers from volume expansion seriously in the repeated charging and discharging processes along with poor ionic and electronic conductivity, consequently determining inevitably poor electrochemical properties. Herein, we proposed a stabilized polymer (PAN) matrix on K0.486V2O5 nanobelts by a liquid-assisted methodology and further electrospinning technology. As a result, a nanocomposite containing a 3D conductive and interconnected mesh structure was thus constructed. By avoiding the full carbonization of polyacrylonitrile (PAN) with appropriate thermal treatment, the elastic properties of the PAN precursor can be retained, effectively inhibiting the volume effect, and the stabilized PAN-encapsulated matrix can also greatly accelerate transport rates of K+ and electrons at a high rate as well as restrict the decomposition of organic electrolytes and side reactions. This work can supply significant basic scientific value of the polymer surface coating methodology for the far-reaching development of inorganic cathode materials in K-ion batteries.

Organic 2,5-dihydroxy-1,4-benzoquinone potassium salt with ultrahigh initial coulombic efficiency for potassium-ion batteries.

Here, we propose a new organic 2,5-dihydroxy-1,4-benzoquinone potassium salt (K2C6H2O4) endowing an ultrahigh initial coulombic efficiency of 96% as an advanced anode for potassium-ion batteries. Theoretical calculations and experimental results suggest that K+ can reversibly insert into this organic compound due to the flexible and stable structure of the K2C6H2O4 molecule as well as fast K+ kinetics in the selected dimethyl ether-based electrolyte.

Assessing electrochemical properties and diffusion dynamics of metal ions (Na, K, Ca, Mg, Al and Zn) on a C2N monolayer as an anode material for non-lithium ion batteries.

We perform first-principles molecular dynamics (FPMD) simulations together with a CI-NEB method to explore the structure, electrochemical properties and diffusion dynamics of a C2N monolayer saturated with various univalent, bivalent and trivalent metal ions. A characteristic irregular adsorption structure consisting of an inner coplanar layer at the large atomic pore and loosely bound outer layer is discovered for all six types of ions. The predicted specific capacities and mean open circuit voltages (OCVs) for them are: 600 mA h g-1, and 0.26 V (Na); 385 mA h g-1, and 1.56 V (K); 600 mA h g-1, and 0.96 V (Mg); 713 mA h g-1, and 1.31 V (Ca); 411 mA h g-1, and 1.40 V (Zn); 1175 mA h g-1, and 0.78 V (Al). For the energy favorable migration pathway, the diffusion energy barrier height for each ionic species is found to be 0.24 eV (Na+), 0.10 eV (K+), 0.25 eV (Mg2+) and 0.10 eV (Ca2+). The values are larger than 1.0 eV for both Zn2+ and Al3+. FPMD simulation at 400 K further predicted that the diffusion coefficients of Na and K atoms absorbed on the C2N monolayer are 5.33 × 10-9 m2 s-1 and 8.52 × 10-9 m2 s-1, respectively, which are one order of magnitude higher than those of other remaining ions discussed in our work. The C2N monolayer shows promising electrochemical properties and ion diffusion dynamics for use as the anode material in alkali metal ion batteries.

Para-Conjugated Dicarboxylates with Extended Aromatic Skeletons as the Highly Advanced Organic Anodes for K-Ion Battery.

A new family of the para-conjugated dicarboxylates embedding in biphenyl skeletons was exploited as the highly advanced organic anodes for K-ion battery. Two members of this family, namely potassium 1,1'-biphenyl-4,4'-dicarboxylate (K2BPDC) and potassium 4,4'-E-stilbenedicarboxylate (K2SBDC), were selectively studied and their detailed redox behaviors in K-ion battery were also clearly unveiled. Both K2BPDC and K2SBDC could exhibit very clear and highly reversible two-electron redox mechanism in K-ion battery, as well as higher potassiation potentials (above 0.3 V vs K+/K) when compared to the inorganic anodes of carbon materials recently reported. Meanwhile, the satisfactory specific and rate capacities could be realized for K2BPDC and K2SBDC. For example, the K2BPDC anode could realize the stable rate capacities of 165/143/135/99 mAh g-1 under the high current densities of 100/200/500/1000 mA g-1, respectively, after its electronic conductivity was improved by mixing a very small amount of graphene. More impressively, the average specific capacities of ∼75 mAh g-1 could be maintained for the K2BPDC anode for 3000 cycles under the high current density of 1 A g-1.