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Sodium‐Ion Batteries: Building Effective Layered Cathode Materials with Long‐Term Cycling by Modifying the Surface via Sodium Phosphate 下载免费PDF全文
Jae Hyeon Jo Ji Ung Choi Aishuak Konarov Hitoshi Yashiro Shuai Yuan Liyi Shi Yang‐Kook Sun Seung‐Taek Myung 《Advanced functional materials》2018,28(14)
Surface stabilization of cathode materials is urgent for guaranteeing long‐term cyclability, and is important in Na cells where a corrosive Na‐based electrolyte is used. The surface of P2‐type layered Na2/3[Ni1/3Mn2/3]O2 is modified with ionic, conducting sodium phosphate (NaPO3) nanolayers, ≈10 nm in thickness, via melt‐impregnation at 300 °C; the nanolayers are autogenously formed from the reaction of NH4H2PO4 with surface sodium residues. Although the material suffers from a large anisotropic change in the c‐axis due to transformation from the P2 to O2 phase above 4 V versus Na+/Na, the NaPO3‐coated Na2/3[Ni1/3Mn2/3]O2/hard carbon full cell exhibits excellent capacity retention for 300 cycles, with 73% retention. The surface NaPO3 nanolayers positively impact the cell performance by scavenging HF and H2O in the electrolyte, leading to less formation of byproducts on the surface of the cathodes, which lowers the cell resistance, as evidenced by X‐ray photoelectron spectroscopy and time‐of‐flight secondary‐ion mass spectroscopy. Time‐resolved in situ high‐temperature X‐ray diffraction study reveals that the NaPO3 coating layer is delayed for decomposition to Mn3O4, thereby suppressing oxygen release in the highly desodiated state, enabling delay of exothermic decomposition. The findings presented herein are applicable to the development of high‐voltage cathode materials for sodium batteries. 相似文献
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Natalia Voronina Jae Hyeon Jo Aishuak Konarov Jongsoon Kim Seung‐Taek Myung 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(20)
In this work, rhombohedral KTi2(PO4)3 is introduced to investigate the related theoretical, structural, and electrochemical properties in K cells. The suggested KTi2(PO4)3 modified by electro‐conducting carbon brings about a flat voltage profile at ≈1.6 V, providing a large capacity of 126 mAh (g‐phosphate)?1, corresponding to 98.5% of the theoretical capacity, with 89% capacity retention for 500 cycles. Structural analyses using electrochemical performance measurements, first‐principles calculations, ex situ X‐ray absorption spectroscopy, and operando X‐ray diffraction provide new insights into the reaction mechanism controlling the (de)intercalation of potassium ions into the host KTi2(PO4)3 structure. It is observed that a biphasic redox process by Ti4+/3+ occurs upon discharge, whereas a single‐phase reaction followed by a biphasic process occurs upon charge. Along with the structural refinement of the electrochemically reduced K3Ti2(PO4)3 phase, these new findings provide insight into the reaction mechanism in Na superionic conductor (NASICON)‐type KTi2(PO4)3. The present approach can also be extended to the investigation of other NASICON‐type materials for potassium‐ion batteries. 相似文献
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Orynbay Zhanadilov Hee Jae Kim Hou-Jen Lai Jyh-Chiang Jiang Aishuak Konarov Almagul Mentbayeva Zhumabay Bakenov Kee-Sun Sohn Payam Kaghazchi Seung-Taek Myung 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(44):2302973
Rechargeable zinc aqueous batteries are key alternatives for replacing toxic, flammable, and expensive lithium-ion batteries in grid energy storage systems. However, these systems possess critical weaknesses, including the short electrochemical stability window of water and intrinsic fast zinc dendrite growth. Hydrogel electrolytes provide a possible solution, especially cross-linked zwitterionic polymers that possess strong water retention ability and high ionic conductivity. Herein, an in situ prepared fiberglass-incorporated dual-ion zwitterionic hydrogel electrolyte with an ionic conductivity of 24.32 mS cm−1, electrochemical stability window up to 2.56 V, and high thermal stability is presented. By incorporating this hydrogel electrolyte of zinc and lithium triflate salts, a zinc//LiMn0.6Fe0.4PO4 pouch cell delivers a reversible capacity of 130 mAh g−1 in the range of 1.0–2.2 V at 0.1C, and the test at 2C provides an initial capacity of 82.4 mAh g−1 with 71.8% capacity retention after 1000 cycles with a coulombic efficiency of 97%. Additionally, the pouch cell is fire resistant and remains safe after cutting and piercing. 相似文献
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