Cooperative Cationic and Anionic Redox Reactions in Ultrathin Polyvalent Metal Selenide Nanoribbons for High-Performance Electrochemical Magnesium-Ion Storage

Abstract

Rechargeable magnesium batteries (RMBs) are considered as potential energy storage devices due to their high volumetric specific capacity, good safety, as well as source abundance. Despite extensive efforts devoted to constructing an efficient magnesium battery system, the sluggish Mg2+ diffusion in conventional cathode materials often leads to slow rate kinetics, low capacity, and poor cycling lifespan. Although transition metal selenides with soft anion frameworks have attracted extensive attention, their Mg2+ storage mechanism still needs to be clarified. Herein, we demonstrate that the ultrathin CoSe2 nanoribbons can be used as a robust cathode material for RMBs and reveal a novel Mg2+ storage mechanism based on cooperative cationic (Co) and anionic (Se) redox processes via systematic ex-situ characterizations. Compared to other metal selenide cathodes based on conversion reactions of solely metal cations, the cooperative cationic–anionic redox reactions of the CoSe2 cathode contribute to obtaining an enhanced specific capacity and boosted electrochemical kinetics. Moreover, on one hand, the ultrathin nanoribbon structure enables effective contact between the electrode material and electrolyte and on the other hand significantly reduces the length and time consumption of Mg2+ diffusion, leading to dominated surface-driven capacitance-controlled Mg2+ storage behavior and rapid Mg2+ storage kinetics. As a result, the ultrathin CoSe2 nanoribbon cathode exhibits a reversible discharge capacity of ∼130 mAh g–1 at 100 mA g–1, good rate capability (116 mAh g–1 at 300 mA g–1), and long cyclability over 600 cycles. This finding confirms the development potentiality of polyvalent metal selenide cathode materials based on a cooperative cationic–anionic redox mechanism for the construction of next-generation multivalent secondary batteries.

Copper Tetraselenophosphate Cathode for Rechargeable Magnesium Batteries: A Redox-Active Polyatomic Anion Strategy to Design the Cathode Material

“…The CV curves with a scanning rate of 0.2–1.0 mV s –1 are shown in Figure a. The correlation between the redox peak current ( i ) and the scanning rate ( v ) is described as i = av b , in which the a and b values are determined by three of the most significant peaks. ,, As shown in Figure b, the peaks of A 1 , A 2 , and C have b values of 0.673, 0.676, and 0.949, respectively, suggesting a high contribution of pseudo-capacitive behavior. Moreover, the diffusive and pseudo-capacitive contributions were analyzed for Cu 3 PSe 4 via the equation i ( v ) = k 1 v + k 2 v 1/2 , and the results are shown in Figure c,d, , wherein the capacitive contribution of Cu 3 PSe 4 is 73% at 0.8 mV s –1 .…”

Copper Doping of CoSe2 Nanoparticles Encapsulated into Carbon Nanotubes with Enhanced Electron Conductance as Cathode for Rechargeable Magnesium Batteries

“…The magnesium ions can easily intercalate into these gaps during the charge process, leading to efficient ion transfer. For instance, the Jin's research group prepared CoSe 2 nanoribbon for RMBs with a capacity of 130 mAh g −1 at 100 mA g −1 , and investigated its cooperative reaction mechanism of magnesium ion storage [16] . Nevertheless, CoSe 2 owns relatively low electrical conductivity, which can lead to sluggish charge transfer kinetics and reduced energy efficiency [17] .…”

“…For instance, the Jin's research group prepared CoSe 2 nanoribbon for RMBs with a capacity of 130 mAh g À 1 at 100 mA g À 1 , and investigated its cooperative reaction mechanism of magnesium ion storage. [16] Nevertheless, CoSe 2 owns relatively low electrical conductivity, which can lead to sluggish charge transfer kinetics and reduced energy efficiency. [17] In addition, CoSe 2 can undergo significant structural changes during the charge-discharge process, leading to degradation of the material and reduced battery performance.…”

Introducing high-valence molybdenum to stimulate lattice oxygen in a NiCo LDH cathode for chloride ion batteries

“…Li + , Na + , Mg 2+ , etc. ), 1–3 other alternative new concept batteries, the anion-based batteries that are based on the reversible shuttling of halide ions ( e.g. F − , Cl − , Br − , etc.…”