MoSe 2 /N‐Doped Carbon as Anodes for Potassium‐Ion Batteries

128

In this work, an ether‐based electrolyte is adopted instead of conventional ester‐based electrolyte for an Sb2O3‐based anode and its enhancement mechanism is unveiled for K‐ion storage. The anode is fabricated by anchoring Sb2O3 onto reduced graphene oxide (Sb2O3‐RGO) and it exhibits better electrochemical performance using an ether‐based electrolyte than that using a conventional ester‐based electrolyte. By optimizing the concentration of the electrolyte, the Sb2O3‐RGO composite delivers a reversible specific capacity of 309 mAh g−1 after 100 cycles at 100 mA g−1. A high specific capacity of 201 mAh g−1 still remains after 3300 cycles (111 days) at 500 mA g−1 with almost no decay, exhibiting a longer cycle life compared with other metallic oxides. In order to further reveal the intrinsic mechanism, the energy changes for K atom migrating from surface into the sublayer of Sb2O3 are explored by density functional theory calculations. According to the result, the battery using the ether‐based electrolyte exhibits a lower energy change and migration barrier than those using other electrolytes for K‐ion, which is helpful to improve the K‐ion storage performance. It is believed that the work can provide deep understanding and new insight to enhance electrochemical performance using ether‐based electrolytes for KIBs.

Section: Resultsmentioning

confidence: 99%

K‐Ion Storage Enhancement in Sb₂O₃/Reduced Graphene Oxide Using Ether‐Based Electrolyte

Zhuang

Xie

et al. 2019

128

“…At the beginning of insertion reaction, the electrode maintains its cubic symmetry. [35] Besides Cu and Se as the final products, additional reflections at 29.7° and 31.0° can be observed at the low discharge potential of 0.01 V. After careful indexing, these peaks can be attributed to the formation of intermediate phases K 0.5 CuSe with space group of Fmmm. According to the conversion reaction, CuSe is expected to transform into Cu and K 2 Se phases.…”

Section: Structural Transition Of Cuse In Sibs and Pibsmentioning

confidence: 95%

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

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.

“…[50] The content of N is 2.5% in overall material (atomic %). [53,54] After the first cycle, CV profiles showed little change, implying the high reversible electrochemical reaction of FeSe 2 . [51] Previous literature reports that N-doping can improve the conductivity and increase active sites of materials, which is beneficial to the electrochemical properties.…”

Section: Doi: 101002/aenm201903277mentioning

confidence: 99%

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

Wang

et al. 2019

Self Cite

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...