Tunable pseudocapacitive contribution by dimension control in nanocrystalline-constructed (Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)O solid solutions to achieve superior lithium-storage properties

Abstract

Ultrafine crystalline materials have been extensively investigated as high-rate lithium-storage materials due to their shortened charge-transport length and high surface area. The pseudocapacitive effect plays a considerable role in electrochemical lithium storage when the electrochemically active materials approach nanoscale dimensions, but this has received limited attention. Herein, a series of (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O electrodes with different particle sizes were prepared and tested. The ultrafine (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O nanofilm (3-5 nm) anodes show a remarkable rate capability, delivering high specific charge and discharge capacities of 829, 698, 602, 498 and 408 mA h g À1 at 100, 200, 500, 1000 and 2000 mA g À1 , respectively, and a dominant pseudocapacitive contribution as high as 90.2% toward lithium storage was revealed by electrochemical analysis at a high scanning rate of 1.0 mV s À1 . This work offers an approach to tune the lithium-storage properties of (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O by size control and gives insights into the enhancement of pseudocapacitance-assisted lithium-storage capacity.

High-entropy energy materials: challenges and new opportunities

“…Early research on the rock-salt structure in the energy field focused on (Co 0.2 Mg 0.2 Cu 0.2 Ni 0.2 Zn 0.2 )O, especially its application as a conversion anode material in lithium-ion batteries (LIBs). 12,53,54 By introducing different metal cations and anions, recent studies have shown the possibility of synthesizing Li-containing rock-salt cathode materials. 18,67 The perovskite structure comprises at least two cation sublattices, both of which can be substituted and shared by multiple metals to form a variety of HECs.…”

“…A unique entropy-stabilized conversion mechanism was proposed for rock-salt high-entropy oxides (HEOs) as lithium storage anodes, leading to improved cycling stability and Coulombic efficiency. 12,17,18,53,54 Also, layered O3-type HEOs were investigated as intercalation-type cathodes Yanjiao Ma towards sodium/lithium storage, showing good long-term cyclability and rate performance owing to entropy stabilization of the host matrix. 13,55 In this article, we provide a comprehensive overview by focusing on the applications of HEMs, which can be mainly classified in HEAs, high-entropy ceramics (HECs), as well as some other high-entropy composites, in fields of hydrogen evolution and storage, carbon dioxide conversion, oxygen catalysis, rechargeable batteries and supercapacitors (Fig.…”

A new spinel high-entropy oxide (Mg0.2Ti0.2Zn0.2Cu0.2Fe0.2)3O4 with fast reaction kinetics and excellent stability as an anode material for lithium ion batteries

“…It's well-known that the specic surface area, pore diameter, and pore volume all inuence the electrochemical performance of the active electrode materials. [58][59][60] The specic surface area and pore size distribution of the synthesized (Mg 0.2 Ti 0.2 Zn 0.2 Cu 0.2 Fe 0.2 ) 3 O 4 particles were measured via nitrogen adsorption-desorption isotherm analysis ( Fig. S2(a) †).…”

“…High-entropy oxides (HEOs), as a new kind of multicomponent and single-phase solid solution TMOs, have greater electronic conductivity and multiple electrochemically active components as compared with single metal oxides. [53][54][55][56][57][58] They display stepwise lithium storage behaviors, thus efficiently alleviating the volume change and then solving induced electrode pulverization problem to some extent. Herein, we have successfully synthesized a new spinel-structured (Mg 0.2 Ti 0.2 -Zn 0.2 Cu 0.2 Fe 0.2 ) 3 O 4 materials via a facile one-step solid state reaction method and subsequently high-energy ball-milling.…”

Preparation and Electrical Properties of High Entropy La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 Perovskite Ceramics Powder

“…金更好的机械强度、延展性、硬度和耐磨耐腐蚀性 而受到广泛关注 [1][2][3] 。随着高熵合金的发展，以控制 结构熵来影响固溶体相稳定性的设计理念也随之发 展起来。结构熵 ΔS config =-R ∑ x i N i=1 ln x i (式中 R 表示通用气体常数， xi 表示相应元素的摩 尔分数)。如果一个系统的结构熵(ΔSconfig)大于 1.5 R，则该系统为高熵材料; 当 1 R≤ΔSconfig<1.5 R 为 "中熵"; ΔSconfig<1 R 为"低熵" [4] 。目前，高熵材 料已经扩大到非金属化合物领域， 如氧化物 [5] 、 碳化 物 [6] 、硼化物 [7] 、氮化物 [8] 以及硫化物 [9] 。 Rost 等 [5] 首次将高熵材料的研究延伸到氧化物 体系，成功制备出具有单一岩盐型结构 (FCC)的 (Mg0.2Ni0.2Co0.2Cu0.2Zn0.2O)高熵氧化物，并证明高 结构熵是使含有五种不同阳离子的岩盐型氧化物以 单相形式稳定存在的关键。 Berardan 等 [10] 研究发现， 与传统二元或掺杂氧化物相比，这些新型氧化物具 有独特的性能优势，这为高熵氧化物陶瓷领域的发 展提供了极大的动力。目前，已经研发的多种结构 高熵氧化物陶瓷中最早研究的是岩盐型高熵氧化物 体系，具有优秀的储锂性能 [11] 、高介电常数 [12] 、锂 离子超导 [13] 和反铁磁性 [14] 等特点，在催化剂载体上 也有很好的应用 [15][16] ; 萤石结构的高熵氧化物具有 高电导率和低热导率等特点 [17][18] ; 尖晶石型和反尖 晶石型高熵陶瓷拥有良好的铁磁性、储锂性能和电 催化性能 [19][20] ; 烧绿石结构 [21] 和石榴石结构 [22] 的 高熵陶瓷大都具有较低的热导率，可用作热绝缘材 料。 钙钛矿(ABO3)氧化物包含一个配位数 12 的 A 位阳离子、一个配位数 6 的 B 位阳离子和一个氧阴 离子。对于钙钛矿氧化物，可以通过掺杂不同阳离 子来调控物理性质，以满足不同的实际应用要求。 近几年，钙钛矿型高熵氧化物也得到了快速发展， 但研究主要集中在成分组成和制备方法的探索上 [23] (1) 对于五组元的高熵体系，1000 ℃下煅烧，TΔSmix 足 够大使得 ΔGmix＜0，体系最终形成单相结构。四组 元钙钛矿氧化物的结构熵变小，在相同温度下无法 补偿作为相位分离驱动力的高焓，体系的稳定性遭 到破坏，从而形成第二相 [24,27] 为了分析 La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 的电学 性能，对其制成的工作电极进行 CV 和 GCD 测试。 从图 5 的 CV 曲线可以看出，每一条 CV 曲线都具 有明显且对称的电流峰值，这表明电极材料中的金 属离子之间发生了可逆的氧化还原反应 [28][29] 。随着 扫描速率的增大，氧化/还原峰面积都不断增加，且 两者面积几乎相同，说明电极在反应过程中电子离 子传递速率较快，准可逆性良好，拥有典型的法拉 第赝电容特性 [30] 。同时由于发生极化，氧化峰和还 原峰分别向高电位和低电位处移动 [31] ，即使在 100 mV/s 的扫描速率下，CV 曲线的氧化峰和还原峰依 然很明显，说明该材料具有良好的倍率性能 [32][33] [34] [6] ELINOR C, CSANADI TAMAS, SALVATORE G, et al Processing…”