A Durable and High-Voltage Mn-Graphite Dual-Ion Battery Using Mn-Based Hybrid Electrolytes

Rechargeable Mn-metal batteries (MMBs) can attract considerable attention because Mn has the intrinsic merits including high energy density (976 mAh g-1 ), high air stability, and low toxicity. However, the application of Mn in rechargeable batteries is limited by the lack of proper cathodes for reversible Mn2+ intercalation/de-intercalation, thus leading to low working voltage (<1.8 V) and poor cycling stability (≤200 cycles). Herein, a high-voltage and durable MMB with graphite as the cathode is successfully constructed using a LiPF6 -Mn(TFSI)2 hybrid electrolyte, which shows a high discharge voltage of 2.34 V and long-term stability of up to 1000 cycles. Mn(TFSI)2 can reduce the plating/stripping overpotential of Mn ions, while LiPF6 can efficiently improve the conductivity of the electrolyte. Electrochemical in-situ characterization implies the dual-anions intercalation/de-intercalation at the cathode and Mn2+ plating/stripping reaction at the anode. Theoretical calculations unveil the top site of graphite is the energetically favorable for anions intercalation and TFSI- shows the low migration barrier. This work paves an avenue for designing high-performance rechargeable MMBs towards electricity storage.

Fluoxetine removal by anodic oxidation using different anode materials and graphite cathode

Fluoxetine (FLX) is a selective serotonin reuptake inhibitor (SSRI) medication commonly used to treat mental health disorders, but it can be harmful to the environment if not properly disposed of due to incomplete metabolism. In this study, electrochemical anodic oxidation with mixed metal oxide anodes was studied as a method to remove FLX from water and wastewater. Iridium dioxide-coated titanium (Ti/IrO2) and ruthenium dioxide-coated Ti (Ti/RuO2) electrodes were found to be more effective than platinum-coated Ti (Ti/Pt) electrodes, with removal efficiencies of 91.5% and 93.9%, respectively. Optimal conditions for FLX removal were determined to be an applied current of 150 mA, initial pH of 5, and oxidation time of 120 min. The rate of FLX degradation (kFLX) for the Ti/Pt, Ti/IrO2, and Ti/RuO2 electrodes were determined to be 0.0081 min-1 (R2:0,8161), 0.0163 min-1 (R2:0,9823), and 0.0168 (R2:0,9901) min-1 for 25 mg/L initial FLX concentration, respectively. The kFLX values varied based on the initial FLX concentration and decreased as the initial FLX concentration increased. The specific energy consumption (SEC) after 120 min of operation was 51.0 kWh/m3 for the Ti/Pt electrode, 39.6 kWh/m3 for the Ti/IrO2 electrode, and 48.6 kWh/m3 for the Ti/RuO2 electrode under optimised conditions. Overall, electrochemical anodic oxidation is an effective method for removing FLX from water and wastewater, with Ti/IrO2 and Ti/RuO2 electrodes providing superior performance compared to Ti/Pt electrodes.

Azacyclic Anchor-Enabled Cohesive Graphite Electrodes for Sustainable Anion Storage

Advanced energy-storage devices are indispensable for expanding electric mobility applications. While anion intercalation-type redox chemistry in graphite cathodes has opened the path to high-energy-density batteries, surpassing the limited energy density of conventional lithium-ion batteries , a significant challenge remains: the large volume expansion of graphite upon anion intercalation. In this study, a novel polymeric binder and cohesive graphite cathode design for dual-ion batteries (DIBs) is presented, which exhibits remarkable stability even under high voltage conditions (>5 V). The innovative binder incorporates an acrylate moiety ensuring superior oxidative stability and self-healing features, along with an azide moiety, which allows for azacyclic covalent bonding with graphite and interchain crosslinking. A simple 1-h ultraviolet treatment is sufficient for binder fixation within the electrode, leading to the covalent bond formation with graphite and the creation of a robust three-dimensional network. This modification facilitates deeper and more reversible anion intercalation, leading to improved capacity, extended lifespan, and sustainable anion storage. The binder design, exhibiting exceptional adhesive properties and effective stress mitigation, enables the construction of ultrathick graphite cathodes. These findings provide valuable insights for the development of advanced binders, paving the way for high-performance DIBs.

Sodium Dual-Ion Batteries with Concentrated Electrolytes

Na-based dual-ion batteries (DIBs) are a class of post-lithium technology with advantages including extremely fast charging, cost-effectiveness, and high natural abundance of raw materials. Operating up to high voltages (≈5.0 V), the decomposition of classic carbonate-based electrolyte formulations and the subsequent fade of capacity continues to be a major drawback in the development of these systems. Here, the performance of a Na-DIB was investigated in different commonly employed electrolyte system, and a highly concentrated (3 m NaPF6 ) and fluorine-rich carbonate-based formulation was optimized to achieve a good performance when compared with literature (based on energy and power density, calculated at coin cell and only using the active mass of active materials).

Ca2+-Based Dual-Carbon Batteries in Ternary Ionic Liquid Electrolytes

Herein, we propose Ca²⁺-based dual-carbon batteries (DCBs) that undergo a simultaneous occurrence of reversible accommodations of Ca²⁺ in a graphite anode (mesocarbon microbeads) and of bis(trifluoromethanesulfonyl)imide (TFSI^-) in a graphite cathode (KS6L). For this purpose, we precisely tune electrolytes composed of Ca²⁺ complexed with a single tetraglyme molecule ([Ca:G₄]) in N-butyl-N-methylpyrrolidinium TFSI (Pyr₁₄TFSI) ionic liquid (IL). This ternary electrolyte is required for the enhancement of anodic stability that is needed to accomplish maximal TFSI^- intercalation into KS6L at a high potential. A solution of 0.5 M [Ca:G₄] in IL ([Ca:G₄]/IL) is found to be optimal for DCBs. First, the electrochemical properties and the structural evolution of each graphite in a half-cell configuration are described to demonstrate excellent electrochemical performance. Second, the negligible intercalation of Pyr₁₄⁺ into an MCMB anode is ascertained in 0.5 M [Ca:G₄]/IL. Finally, DCBs are constructed by coupling two electrodes to show high capacity (54.0 mA h g^-1 at 200 mA g^-1) and reasonable cyclability (capacity fading of 0.022 mA h g^-1 cycle^-1 at 200 mA g^-1 during 300 charge/discharge cycles). This work is the first to examine DCBs based on Ca²⁺ intercalation and helps pave the way for the development of a new type of next-generation batteries.

Ultrafast Rechargeable Zinc Battery Based on High-Voltage Graphite Cathode and Stable Nonaqueous Electrolyte

Zinc-based battery chemistries have lately drawn great attention for grid-scale energy storage due to their material abundance and high safety. However, the low Coulombic efficiency (CE) and dendrite growth of zinc (Zn) anodes and the limited working voltage of current oxide cathodes are the major barriers hindering the development of rechargeable Zn-based batteries (RZBs). Here, we report an ultrafast and high-voltage Zn battery in a new cell configuration employing a graphite cathode, a Zn anode, and nonaqueous 1 M zinc bis(trifluoromethylsulfonyl)imide (Zn(TFSI)₂) in acetonitrile (AN) electrolyte. This RZB operates through the (de)intercalation of TFSI^- anions into the graphite and the electrochemical Zn²⁺ plating/stripping at the anode. The optimized Zn(TFSI)₂/AN electrolyte features high reductive/oxidative stability, good ionic conductivity (∼28 mS cm^-1), and low viscosity (∼0.4 mPa·s), enabling the unprecedented cycling stability (over 1000 h) of the Zn anode with a dendrite-free morphology, the ultrafast Zn plating/stripping with a high CE (>99%), and the good compatibility with the graphite cathode. Consequently, this RZB exhibits a high average output voltage (2.2 V), a high energy/power density (86.5 Wh kg^-1 at 4400 W kg^-1), and a long cycle life (97.3% capacity retention after 1000 cycles). The present work offers new insights and opportunities to the Zn-based electrochemistry.

Beyond Activated Carbon: Graphite-Cathode-Derived Li-Ion Pseudocapacitors with High Energy and High Power Densities

Supercapacitors have aroused considerable attention due to their high power capability, which enables charge storage/output in minutes or even seconds. However, to achieve a high energy density in a supercapacitor has been a long-standing challenge. Here, graphite is reported as a high-energy alternative to the frequently used activated carbon (AC) cathode for supercapacitor application due to its unique Faradaic pseudocapacitive anion intercalation behavior. The graphite cathode manifests both higher gravimetric and volumetric energy density (498 Wh kg^-1 and 431.2 Wh l^-1 ) than an AC cathode (234 Wh kg^-1 and 83.5 Wh l^-1 ) with peak power densities of 43.6 kW kg^-1 and 37.75 kW l^-1 . A new type of Li-ion pseudocapacitor (LIpC) is thus proposed and demonstrated with graphite as cathode and prelithiated graphite or Li₄ Ti₅ O₁₂ (LTO) as anode. The resultant graphite-graphite LIpCs deliver high energy densities of 167-233 Wh kg^-1 at power densities of 0.22-21.0 kW kg^-1 (based on active mass in both electrodes), much higher than 20-146 Wh kg^-1 of AC-derived Li-ion capacitors and 23-67 Wh kg^-1 of state-of-the-art metal oxide pseudocapacitors. Excellent rate capability and cycling stability are further demonstrated for LTO-graphite LIpCs.

Potassium Dual-Ion Hybrid Batteries with Ultrahigh Rate Performance and Excellent Cycling Stability

Potassium-ion batteries (KIBs) are regarded as a potential alternative battery technology to conventional lithium-ion batteries owing to their low potential, natural abundance, and the low cost of potassium. However, sluggish reaction kinetic of the much larger K⁺ ions leads to low rate capability and poor cycling performance of KIBs, restricting KIB's practical applications. Herein, we propose a novel full battery called a potassium dual-ion hybrid battery (KDHB) by employing an absorption-type hierarchical porous carbon as the anode material and an anion intercalation-type expanded graphite (EG) as the cathode material. Owing to the hybrid mechanism of the battery and capacitive reaction, the KDHB exhibits superior rate performance with a high capacity of 82 mA h g^-1 even at a high current density of 3 A g^-1 with negligible capacity decay. Moreover, the KDHB exhibits excellent cycling performance with 74.2% capacity retention after 2000 cycles at 1 A g^-1, which is so far the best performance of the reported KDIBs.

A Novel Calcium-Ion Battery Based on Dual-Carbon Configuration with High Working Voltage and Long Cycling Life

Rechargeable batteries based on multivalent cations (e.g., Mg2+ and Al3+) have attracted increased interest in recent years because of the merits of natural abundance, low cost, good chemical safety, and larger capacity. Among these batteries, the Ca-ion battery (CIB) shows attractive priority because Ca2+ has the closest reduction potential (-2.87 V vs standard hydrogen electrode (SHE)), to that of Li (-3.04 V vs SHE), enabling a wide voltage window for the full battery. However, most Ca-ion batteries have low working voltage (below 2 V), as well as poor cycling stability (less than 50 cycles). Here, a high-performance Ca-ion full battery with a novel dual-carbon configuration design with low-cost and environmentally friendly mesocarbon microbeads and expanded graphite as the anode and cathode, respectively, is reported. This Ca-ion-based dual-carbon battery (Ca-DCB) can work successfully in conventional carbonate electrolyte dissolving Ca(PF6)2, with a reversible discharge capacity of 66 mAh g-1 at a current rate of 2 C and a high working voltage of 4.6 V. Moreover, the Ca-DCB exhibits good cycling stability with a discharge capacity of 62 mAh g-1 after 300 cycles with a high capacity retention of 94%, which is the best performance of the reported CIBs, suggesting it is a promising candidate for next-generation energy storage devices.