Gradient Electrolyte Strategy Achieving Long-Life Zinc Anodes.

Aqueous Zn-ion batteries are plagued by a short lifespan caused by localized dendrites. High-concentration electrolytes are favorable for dense Zn deposition but have poor performance in batteries with glass-fiber separators. In contrast, low-concentration electrolytes can wet the separators well, ensuring the migration of zinc ions, but the dendrites grow rapidly. In this work, we propose an electrolyte gradient strategy wherein a zinc-ion concentration gradient is established from the anode to the separator, ensuring that the separator keeps a good wettability in low-concentration areas and the zinc anode achieves dendrite-free deposition in a high-concentration area. By using this strategy in a common electrolyte, zinc sulfate, a Zn||Zn symmetric cell achieves 14 000 ultralong cycles (exceeding 8 months) at 5 mA cm-2 and 1 mAh cm-2 . When the current is further increased to 20 mA cm-2 , the symmetric cell could still run for over 10 000 cycles. Assembled Zn||NVO full cells also demonstrate prominent performance. At a high current of 16 mA cm-2 , the NVO cathode with high loading (8 mg cm-2 ) still has a capacity of 58% after 1200 cycles. Overall, the gradient electrolyte strategy provides a promising approach for practical long-life Zn anodes with the advantages of simple operation and low cost.

A green and sustainable strategy toward lithium resources recycling from spent batteries.

Recycling lithium from spent batteries is challenging because of problems with poor purity and contamination. Here, we propose a green and sustainable lithium recovery strategy for spent batteries containing LiFePO4, LiCoO2, and LiNi0.5Co0.2Mn0.3O2 electrodes. Our proposed configuration of "lithium-rich electrode || LLZTO@LiTFSI+P3HT || LiOH" system achieves double-side and roll-to-roll recycling of lithium-containing electrode without destroying its integrity. The LiTFSI+P3HT-modified LLZTO membrane also solves the H+/Li+ exchange problem and realizes a waterproof protection of bare LLZTO in the aqueous working environment. On the basis of these advantages, our system shows high Li selectivity (97%) and excellent Faradaic efficiency (≥97%), achieving high-purity (99%) LiOH along with the production of H2. The Li extraction processes for spent LiFePO4, LiNi0.5Co0.2Mn0.3O2, and LiCoO2 batteries is shown to be economically feasible. Therefore, this study provides a previously unexplored technology with low energy consumption as well as high economic and environmental benefits to realize sustainable lithium recycling from spent batteries.

In Situ Construction of Protective Films on Zn Metal Anodes via Natural Protein Additives Enabling High-Performance Zinc Ion Batteries.

The strong activity of water molecules causes a series of parasitic side reactions on Zn anodes in the aqueous electrolytes. Herein, we introduce silk fibroin (SF) as a multifunctional electrolyte additive for aqueous zinc-ion (Zn-ion) batteries. The secondary structure transformation of SF molecules from α-helices to random coils in the aqueous electrolytes allows them to break the hydrogen bond network among free water molecules and participate in Zn2+ ion solvation structure. The SF molecules released from the [Zn(H2O)4(SF)]2+ solvation sheath appear to be gradually adsorbed on the surface of Zn anodes and in situ form a hydrostable and self-healable protective film. This SF-based protective film not only shows strong Zn2+ ion affinity to promote homogeneous Zn deposition but also has good insulating behavior to suppress parasitic reactions. Benefiting from these multifunctional advantages, the cycle life of the Zn||Zn symmetric cells reaches over 1600 h in SF-containing ZnSO4 electrolytes. In addition, by adopting a potassium vanadate cathode, the full cell shows excellent cycling stability for 1000 cycles at 3 A g-1. The in situ construction of a protective film on the Zn anode from natural protein molecules provides an effective strategy to achieve high-performance Zn metal anodes for Zn-ion batteries.

Copper Particle-Enhanced Lithium-Mediated Synthesis of Green Ammonia from Water and Nitrogen.

Ammonia (NH3) is one of the most frequently produced chemical products in the world, and it plays an indispensable role in life on Earth. However, its synthesis by the Haber-Bosch (H-B) process is highly energy intensive, resulting in extensive carbon emissions that are unsustainable due to their ability to harm the environment. Herein, we propose a facile and mass-producible strategy for increasing the rate and efficiency of nitrogen fixation through the use of copper particle-catalyzed Li nitridation and a solid electrolyte as a medium to reduce Li salt; the above strategy results in the conversion of water and nitrogen into NH3 through the use of renewable electrical energy at room temperature and atmospheric pressure. Copper particles are uniformly pressed into Li metal by a simple rolling method, and their critical role in accelerating the nitrogen fixation process is revealed by both electrochemical tests and simulations. The nitridation of the Li in the composite is reduced to a few minutes instead of the more than 40 h that are needed for bare Li and N2 at room temperature and atmospheric pressure. Our new method provides three important advantages over the H-B method: (1) the new method can be operated at atmospheric pressure, thereby lowering equipment requirements and increasing security; (2) the use of water instead of fossil fuels as a hydrogen source decreases the consumption of these fuels and the emission of CO2; and (3) the low equipment requirements lead to the ready miniaturization and decentralization of the NH3 synthesizing process, thus promoting the possible use of renewable sources of electricity (e.g., wind or solar energy).

Vertical Crystal Plane Matching between AgZn3 (002) and Zn (002) Achieving a Dendrite-Free Zinc Anode.

Metallic zinc anodes in zinc-ion batteries suffer from problematic Zn dendrite chemistry. Previous works have shown that preferred-orientation crystal planes can help dendrite-free metal anodes. This work reports a nanothickness (≈570 nm) AgZn3  coating to regulate the Zn growth. First, AgZn3 @Zn anode avoids the problem, in Ag@Zn anode, that the rate of electrochemical Ag-Zn alloying is slower than that of Zn dendrites growth. Batteries life increased from 112 h (pure Zn) and 932 h (Ag@Zn) to 1360 h (AgZn3 @Zn) at 2 mA cm-2  and 1 mAh cm-2 . Then, plasma sputtering can remove nonconductive ZnO and improve Zn-ion affinity, which brings a longer life for AuZn3 @Zn (423 h), CuZn3 @Zn (385 h), and AgZn3 @Zn (1150 h) than pure Zn (93 h) at 1 mAh cm-2 . More importantly, AgZn3 (002) has a high matching with the Zn (002), which can guide ordered Zn epitaxial deposition, thereby achieving dense and dendrite-free Zn growth. This work clearly captures the fascinating structure of the densely stacked Zn layers on the AgZn3  layer. This strategy not only improves the performance of zinc-ion batteries greatly but will also help one understand the matching mechanism of the (002) vertical crystal plane.

Synergistic Manipulation of Na+ Flux and Surface-Preferred Effect Enabling High-Areal-Capacity and Dendrite-Free Sodium Metal Battery.

The propensity of sodium anode to form uniform electrodeposit is bound up with the nature of electrode surface and regulation of Na-ion flux, as well as distribution of electronic field, which is quite crucial for high-areal-capacity sodium metal batteries (SMBs). Herein, a novel metallic sodium/sodium-tin alloy foil anode (Na/NaSn) with 3D interpenetrated network and porous structure is prepared through facile alloy reaction. The strong sodiophilic properties of sodium-tin alloy can lower the nucleation energy, resulting in smaller depositing potential and strong adsorption of Na+ , while synergistic effect of porous skeleton and additional potential difference (≈0.1 V) between Na and Na-Sn alloy (Na15 Sn4 ) can alleviate volume expansion, redistribute the Na-ion flux and regulate electronic field, which favors and improves homogeneous Na deposition. The as-fabricated Na/NaSn electrode can endow excellent plating/stripping reversibility at high areal capacity (over 1600 h for 4 mAh cm-2 at 1 mA cm-2 and 2 mAh cm-2 at 2 mA cm-2 ), fast electrochemical kinetics (500 h under 4 mAh cm-2 at 4 mA cm-2 ) and superior rate performances. A novel strategy in the design of high-performance Na anodes for large-scale energy storage is provided.

Effect of deashing on activation process and lead adsorption capacities of sludge-based biochar.

To explore the effect of inorganic minerals on activation process and lead adsorption of sludge-based biochar, sludge-based biochar was pre-deashed using hydrochloric acid or hydrofluoric acid followed by potassium acetate activation. The results indicate that hydrochloric or hydrofluoric acid deashing can improve the pore parameters of sludge-based biochars and promote subsequent activation effect of potassium acetate. The specific surface area of biochar activated by potassium acetate after hydrochloric acid and hydrofluoric acid pretreatment increased from 583.36 m2/g to 718.70 m2/g and 991.55 m2/g, respectively. The enhancement of pore structure is conducive to enhancing the physical adsorption of lead on sludge-based biochar, while the chemical adsorption is not significantly affected at the same time. Thereby, the biochar and activated biochar pretreated with hydrofluoric acid showed better lead adsorption capacities (16.70 and 49.47 mg/g) than untreated biochar (7.56 and 38.49 mg/g).