Advances and Challenges in Metal Sulfides/Selenides for Next‐Generation Rechargeable Sodium‐Ion Batteries

205

142

Thanks to low costs and the abundance of the resources, sodium‐ion (SIBs) and potassium‐ion batteries (PIBs) have emerged as leading candidates for next‐generation energy storage devices. So far, only few materials can serve as the host for both Na+ and K+ ions. Herein, a cubic phase CuSe with crystal‐pillar‐like morphology (CPL‐CuSe) assembled by the nanosheets are synthesized and its dual functionality in SIBs and PIBs is comprehensively studied. The electrochemical measurements demonstrate that CPL‐CuSe enables fast Na+ and K+ storage as well as the sufficiently long duration. Specifically, the anode delivers a specific capacity of 295 mA h g−1 at current density of 10 A g−1 in SIBs, while 280 mA h g−1 at 5 A g−1 in PIBs, as well as the high capacity retention of nearly 100% over 1200 cycles and 340 cycles, respectively. Remarkably, CPL‐CuSe exhibits a high initial coulombic efficiency of 91.0% (SIBs) and 92.4% (PIBs), superior to most existing selenide anodes. A combination of in situ X‐ray diffraction and ex situ transmission electron microscopy tests fundamentally reveal the structural transition and phase evolution of CuSe, which shows a reversible conversion reaction for both cells, while the intermediate products are different due to the sluggish K+ insertion reaction.

Section: Sodium Storage Performance Of Cusementioning

confidence: 99%

Nanosheets‐Assembled CuSe Crystal Pillar as a Stable and High‐Power Anode for Sodium‐Ion and Potassium‐Ion Batteries

Lin

Yang

et al. 2019

205

142

“…[1][2][3] However, because of its narrow interlayer spacing ≈0.34 nm, the larger size of Na + compared to Li + makes it difficult if not unsuitable for intercalation in graphite, which is commercially employed for LIB. [7,8] The ionization potential of Na + is also lower than Li + which results in a lower operating voltage and consequently, a lower energy density. [7,8] The ionization potential of Na + is also lower than Li + which results in a lower operating voltage and consequently, a lower energy density.…”

mentioning

confidence: 99%

A 3D Trilayered CNT/MoSe₂/C Heterostructure with an Expanded MoSe₂ Interlayer Spacing for an Efficient Sodium Storage

Yousaf

Wang

Chen

et al. 2019

238

157

attention because of its low cost and abundant supply of sodium. [1][2][3] However, because of its narrow interlayer spacing ≈0.34 nm, the larger size of Na + compared to Li + makes it difficult if not unsuitable for intercalation in graphite, which is commercially employed for LIB. [4][5][6] Further, the large radius of Na + in SIB electrodes produces sluggish electrochemical kinetics, provides higher diffusion barriers, and causes large volume expansion which leads to low rate capability and poor cyclic stability. [7,8] The ionization potential of Na + is also lower than Li + which results in a lower operating voltage and consequently, a lower energy density. [9] A lot of efforts in the development of advanced anode materials for SIBs have been proposed to address these issues.Recently, 2D transition metal dichalcogenides (TMDCs) have received considerable attention in electrochemical energy storage and conversion devices due to their layered structure, and the favorable electronic, chemical, and mechanical properties and stability. [10][11][12] TMDCs such as MoS 2 are often considered a promising anode candidate for LIBs. [13] However, when MoS 2 is employed in SIBs, it displays a lower capacity and a poor cyclic stability as a result of the low intrinsic conductivity and the small interlayer distance (≈0.62 nm). [14] In contrast, MoSe 2 possesses a slightly larger interlayer distance (≈0.64 nm) and better electrical conductivity due to small bandgap (≈1.1 eV). Moreover, it possesses higher theoretical capacity (≈422 mAh g −1 ) [10,15] than graphite (≈35 mAh g −1 ) [6] which makes it one of the most promising TMDC candidates for SIBs. However, the practical applications of MoSe 2 as an anode is limited by capacity fading due to the large volume expansion during long charging/discharging processes and the poor rate capability due to the low intrinsic electrical conductivity. [10] Modifying the nanostructure of the SIB electrodes can often solve some of these problems. For example, expanding the interlayer distance of MoSe 2 can lead to an improvement of the Na + storage and reducing the Na + diffusion barrier energy can enhance the reaction kinetics for the Na + intercalation/deintercalation. [16] Due to the high surface energy and weak van der Waal interactions between layers, Freestanding composite structures with embedded transition metal dichalcogenides (TMDCs) as the active material are highly attractive in the development of advanced electrodes for energy storage devices. Most 3D electrodes consist of a bilayer design involving a core-shell combination. To further enhance the gravimetric and areal capacities, a 3D trilayer design is proposed that has MoSe 2 as the TMDC sandwiched in-between an inner carbon nanotube (CNT) core and an outer carbon layer to form a CNT/ MoSe 2 /C framework. The CNT core creates interconnected pathways for the e − /Na + conduction, while the conductive inert carbon layer not only protects the corrosive environment between the electrolyte and MoSe 2 but also is fully tunable fo...

“…[29][30][31][32] Transition metal dichalcogenides (TMDs) have gained comprehensive attention in the field of energy storage due to their unique electrochemical properties, high electrical conductivity, and high capacity. [41] To achieve high performance rechargeable batteries, it is important to understand the physical and chemical changes in electrode materials during the charge/discharge process. [41] To achieve high performance rechargeable batteries, it is important to understand the physical and chemical changes in electrode materials during the charge/discharge process.…”

mentioning

confidence: 99%

Nature of FeSe₂/N‐C Anode for High Performance Potassium Ion Hybrid Capacitor

Wang

et al. 2019

242

137

In addition, in-depth understanding of the nature of electrode material is an essential step in the development of electrode materials. [21][22][23][24] The electrode materials play a vital role in the battery. [25,26] During the deintercalation and conversion reactions, the electrode material is subjected to various physical and chemical changes, such as phase transitions and electrochemical reorganization. [27] These series of physical and chemical changes will affect the electrochemical performance. [28] Therefore, it is necessary to optimize and improve the electrochemical performance of the battery by studying the reaction mechanism. [29][30][31][32] Transition metal dichalcogenides (TMDs) have gained comprehensive attention in the field of energy storage due to their unique electrochemical properties, high electrical conductivity, and high capacity. [33][34][35][36][37][38][39][40] The inadequacies are also obvious, including volume expansion, agglomeration, low ion-diffusion coefficient, and side reaction during discharge/charge, resulting in the rapid decay of capacity. [41] To achieve high performance rechargeable batteries, it is important to understand the physical and chemical changes in electrode materials during the charge/discharge process. Researchers have made remarkable progress. [42] Usually TMDs involve a multi-step reaction mechanism as anode material for lithium ion batteries and sodium ion batteries (intercalation and conversion). [43][44][45] However, the physical and chemical changes in these TMDs in the potassium ion batteries are still not clear, which hinders the design and development of electrode materials. Therefore, exploring the reaction mechanism of metal selenide not only allows us to understand the relationship between TMDs and K + , but also achieve a long life cycle that would be a breakthrough for large-scale energy storage equipment.Herein, we successfully synthesized carbon-coated FeSe 2 clusters via a solvothermal method. The FeSe 2 clusters are well wrapped by the carbon layer, which improves electron conductivity and alleviates volume expansion. Benefiting from the unique structure, FeSe 2 /N-C exhibit ultra-stable cycle performance with a reversible capacity of up to 170 mAh g −1 at a high current of 2000 mA g −1 , which remains ≈158 mAh g −1 after 2000 cycles. The capacity retention is close to 100%. The electrodes also show remarkable rate performance. Furthermore, first-principles calculations, in situ X-ray diffraction, and ex situ transmission electron microscopy (in situ XRD and ex-TEM) Potassium ion hybrid capacitors have great potential for large-scale energy devices, because of the high power density and low cost. However, their practical applications are hindered by their low energy density, as well as electrolyte decomposition and collector corrosion at high potential in potassium bis(fluoro-sulfonyl)imide-based electrolyte. Therefore, anode materials with high capacity, a suitable voltage platform, and stability become a key factor. Here, N-doping carbon-co...