Dilute Hybrid Electrolyte for Low-Temperature Aqueous Sodium-Ion Batteries

Electrolyte Design Strategies for Aqueous Sodium-Ion Batteries: Progress and Prospects

Sodium-ion batteries (SIBs) have emerged as one of today's most attractive battery technologies due to the scarcity of lithium resources. Aqueous sodium-ion batteries (ASIBs) have been extensively researched for their security, cost-effectiveness, and eco-friendly properties. However, aqueous electrolytes are extremely limited in practical applications because of the narrow electrochemical stability window (ESW) with extremely poor low-temperature performance. The first part of this review is an in-depth discussion of the reasons for the inferior performance of aqueous electrolytes. Next, research progress in extending the electrochemical stabilization window and improving low-temperature performance using various methods such as "water-in-salt", eutectic, and additive-modified electrolytes is highlighted. Considering the shortcomings of existing solid electrolyte interphase (SEI) theory, recent research progress on the solvation behavior of electrolytes is summarized based on the solvation theory, which elucidates the correlation between the solvation structure and the electrochemical performance, and three methods to upgrade the electrochemical performance by modulating the solvation behavior are introduced in detail. Finally, common design ideas for high-temperature resistant aqueous electrolytes that are hoped to help future aqueous batteries with wide temperature ranges are summarized.

Challenges and Breakthroughs in Enhancing Temperature Tolerance of Sodium-Ion Batteries

Lithium-based batteries (LBBs) have been highly researched and recognized as a mature electrochemical energy storage (EES) system in recent years. However, their stability and effectiveness are primarily confined to room temperature conditions. At temperatures significantly below 0 °C or above 60 °C, LBBs experience substantial performance degradation. Under such challenging extreme contexts, sodium-ion batteries (SIBs) emerge as a promising complementary technology, distinguished by their fast dynamics at low-temperature regions and superior safety under elevated temperatures. Notably, developing SIBs suitable for wide-temperature usage still presents significant challenges, particularly for specific applications such as electric vehicles, renewable energy storage, and deep-space/polar explorations, which requires a thorough understanding of how SIBs perform under different temperature conditions. By reviewing the development of wide-temperature SIBs, the influence of temperature on the parameters related to battery performance, such as reaction constant, charge transfer resistance, etc., is systematically and comprehensively analyzed. The review emphasizes challenges encountered by SIBs in both low and high temperatures while exploring recent advancements in SIB materials, specifically focusing on strategies to enhance battery performance across diverse temperature ranges. Overall, insights gained from these studies will drive the development of SIBs that can handle the challenges posed by diverse and harsh climates.

Ionic Competition between Na+ and H+ in Aqueous Sodium-Ion Battery Electrolytes

Aqueous electrolytes have become a research hotspot because of their high safety and low cost, while the inevitable ionization phenomenon of water in aqueous solution leads to the existence of competitive ions (H+) except the active ions. In this article, we take aqueous Na base electrolyte as an example to clear the ion competition behavior by modeling, simulating together with experimental verification. First, the reaction tendency of the two ions (Na+ and H+) is obtained by calculating the Gibbs energy change of the reaction. Furthermore, the properties of electrolytes with different concentrations including transportation are obtained by modeling. After that, relevant experiments are also proceeded to verify the simulation results. Then, the ion competition behavior is analyzed by in situ observation by controlling the constant concentration of Na+: the high concentration of Na+ can reduce the proportion of H+ and reduce the competitiveness of H+; a high concentration of Na+ causes the increased viscosity and reduces the ion diffusion. Based on this, the correlation between ion competitiveness and ion ratio is also confirmed by keeping the concentration of Na+ unchanged and adjusting the concentration of H+ (adjusting pH). The influence of the ion competition phenomenon (Na+ and H+) is the reaction characteristics of the substance itself and the ratio of ion concentration. Finally, the electrochemical performance is further verified in 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDI) symmetric cells and in full-cells with vanadium phosphate sodium (NVP) as the cathode and PTCDI as the anode.

A Comprehensive Evaluation of Battery Technologies for High-Energy Aqueous Batteries

Aqueous batteries have garnered significant attention in recent years as a viable alternative to lithium-ion batteries for energy storage, owing to their inherent safety, cost-effectiveness, and environmental sustainability. This study offers a comprehensive review of recent advancements, persistent challenges, and the prospects of aqueous batteries, with a primary focus on energy density compensation of various battery engineering technologies. Additionally, cutting-edge high-energy aqueous battery designs are emphasized as a reference for future endeavors in the pursuit of high-energy storage solutions. Finally, a dual-compatibility battery configuration perspective aimed at concurrently optimizing cycle stability, redox potential, capacity utilization for both anode and cathode materials, as well as the selection of potential electrode candidates, is proposed with the ultimate goal of achieving cell-level energy densities exceeding 400 Wh kg-1 .