Ag/MnO<sub>2</sub>复合电极材料的制备及其电化学性能

夏傲; 曾啸雄; 宜珏; 韩曰鹏; 谈国强

doi:10.13801/j.cnki.fhclxb.20210916.004

Ag/MnO₂复合电极材料的制备及其电化学性能

doi: 10.13801/j.cnki.fhclxb.20210916.004

陕西科技大学材料科学与工程学院，西安 710021

基金项目: 中国博士后科学基金(2016M592746)；陕西科技大学博士科研启动基金项目(BJ15-04)

详细信息

通讯作者:
夏傲，博士，副教授，硕士生导师，研究方向为能源材料和纳米材料　E-mail：xiaao@sust.edu.cn

中图分类号: TM912.9；TB331
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出版历程
- 收稿日期: 2021-05-21
- 修回日期: 2021-08-25
- 录用日期: 2021-08-27
- 网络出版日期: 2021-09-16
- 刊出日期: 2022-03-23

Preparation and electrochemical properties of Ag/MnO₂ composite electrode materials

School of Materials Science and Engineering, Shaanxi University of Science & Technology, Xi′an 710021, China

摘要

摘要: 过渡金属氧化物MnO₂因其制备工艺简单、储量丰富、环保且具有较高的理论比容量，在电池储能方面有较大潜力。本论文借助溶胀法对水热合成的δ-MnO₂进行剥离制得MnO₂纳米片。再利用紫外光照以及NaBH₄的还原作用在MnO₂纳米片表面负载Ag纳米颗粒，从而得到Ag/MnO₂复合材料。对Ag/MnO₂复合材料进行了结构和形貌表征以及电化学性能测试。结果表明，作为锂离子电池负极材料，Ag/MnO₂的电化学性能明显优于纯相δ-MnO₂。Ag/MnO₂在100 mA/g电流密度下的首次可逆比容量达到1001.1 mA·h/g，库伦效率为79.9%；在0.1、0.2、0.5、1.0、2.0 A/g电流密度下的平均可逆比容量分别为936.3、607.5、429.5、351.1和278 mA·h/g，当电流密度重新回到0.1 A/g时，其平均可逆比容量仍可达到658.7 mA·h/g。MnO₂电化学性能的改善归因于均匀负载的导电Ag颗粒，使得电极材料的导电性显著提升，利于带电粒子的传输。此外，Ag/MnO₂复合材料的纳米结构使得锂离子在固相中的传输路径缩短，进而提高了锂离子扩散速率。
- MnO₂ /
- Ag /
- 负极材料 /
- 锂离子电池 /
- 电化学性能
Abstract: Transition metal oxide MnO₂ has great potential in battery storage because of its simple preparation process, abundant reserves, environmental protection and high theoretical specific capacity. In this paper, MnO₂ nanosheets were prepared by exfoliating the hydrothermally synthesized δ-MnO₂ by the swelling method. The Ag/MnO₂ composites were obtained by loading Ag nanoparticles on the surface of MnO₂ nanosheets under UV irradiation and NaBH₄ reduction. The structure and morphology of Ag/MnO₂ composites were characterized and their electrochemical properties were tested. The results show that the electrochemical performance of Ag/MnO₂ as anode material for lithium ion batteries is obviously better than that of the pure phase δ-MnO₂. The first reversible specific capacity of Ag/MnO₂ at the current density of 100 mA/g reaches 1001.1 mA·h/g, and the coulombic efficiency is 79.9%. At the current density of 0.1, 0.2, 0.5, 1.0 and 2.0 A/g, the average reversible specific capacity is 936.3, 607.5, 429.5, 351.1 and 278 mA·h/g, respectively. When the current density returns to 0.1 A/g, the average reversible specific capacity can still reach 658.7 mA·h/g. The improvement of the electrochemical performance of Ag/MnO₂ is attributed to the fact that the uniformly loaded conductive Ag particles significantly enhance the electrical conductivity of the electrode material, which is conducive to the transport of charged particles. In addition, the nano-structure of Ag/MnO₂ composites shortens the transport path of lithium ions in the solid phase, thus increasing the diffusion rate of lithium ions.
- MnO₂ /
- Ag /
- anode material /
- lithium ion battery /
- electrochemical properties

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图 1 δ-MnO₂和Ag/MnO₂样品的XRD图谱对比

Figure 1. Comparison of XRD patterns of δ-MnO₂ and Ag/MnO₂ samples

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图 2 样品Ag/MnO₂的XPS图谱：(a) 全谱；(b) Mn2p；(c) Ag3d；(d) O1s

Figure 2. XPS spectrum of the Ag/MnO₂ sample: (a) Survey spectra; (b) Mn2p; (c) Ag3d; (d) O1s

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图 3 Ag/MnO₂样品的EDS (a) 和元素分布图 (b)

Figure 3. EDS (a) and element mapping images (b) of Ag/MnO₂ sample

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图 4 δ-MnO₂ (a) 以及Ag/MnO₂ (b) 微观形貌SEM图像

Figure 4. SEM images of δ-MnO₂ (a) and Ag/MnO₂ (b)

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图 5 Ag/MnO₂的低分辨率 (a) 及高分辨率 (b) TEM图像

Figure 5. Low resolution (a) and high resolution (b) TEM images of Ag/MnO₂

d—Indices of crystal face

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图 6 Ag/MnO₂形成过程示意图

Figure 6. Diagram of Ag/MnO₂ formation process

TMAOH—Tetramethylammonium hydroxide

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图 7 (a) δ-MnO₂和Ag/MnO₂的BET图谱；(b) Ag/MnO₂的N₂吸附-脱附等温线 (插图为孔径分布图)

Figure 7. (a) BET of δ-MnO₂ and Ag/MnO₂; (b) BET isotherm plots and corresponding pore size distributions (inset) of Ag/MnO₂

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图 8 δ-MnO₂和Ag/MnO₂在0.1 A/g下首次充放电曲线

Figure 8. First charge/discharge curves of δ-MnO₂ and Ag/MnO₂ at current densitiy of 0.1 A/g

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图 9 δ-MnO₂和Ag/MnO₂复合材料的倍率性能曲线

Figure 9. Ratio performance curves of δ-MnO₂ and Ag/MnO₂composite material

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图 10 δ-MnO₂和Ag/MnO₂在1 A/g的循环性能图

Figure 10. Cycling performance of δ-MnO₂ and Ag/MnO₂ at 1 A/g

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图 11 δ-MnO₂和Ag/MnO₂的首次循环伏安曲线

Figure 11. First cyclic voltammetry curves of δ-MnO₂ and Ag/MnO₂

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图 12 (a) Ag/MnO₂电极在不同扫速下的CV曲线；(b) Ag/MnO₂电极b值计算；(c) Ag/MnO₂电极在0.1 mV/s扫速下赝电容贡献面积比例；(d) Ag/MnO₂电极在不同扫速下赝电容比例

Figure 12. (a) Cyclic voltammetry curves of Ag/MnO₂ electrode at various scan rates; (b) Calculation of b value of Ag/MnO₂ electrode; (c) Contribution area ratio of pseudocapacitance at 0.1 mV/s scanning speed of Ag/MnO₂ electrode; (d) Normalized contribution ratios of capacitive and diffusion-controlled capacities at different scan rates

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图 13 δ-MnO₂(a) 和Ag/MnO₂(b) 的电化学阻抗图谱(内插图为模拟等效电路图)

Figure 13. Electrochemical impedance spectra of δ-MnO₂ (a) and Ag/MnO₂(b) (Fitting circuit diagram are in inset)

R_s—Ohmic resistance; R_ct—Charge transfer resistance; CPE—Equivalent circuit defines the double-layer capacitance; W—Warburg resistance

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图 14 δ-MnO₂和Ag/MnO₂复合材料的Z′与ω^−1/2在低频区的拟合曲线

Figure 14. Relationship between Z′ and ω^−1/2 at the low frequency range of δ-MnO₂ and Ag/MnO₂ composites

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表 1 δ-MnO₂和Ag/MnO₂合成样品的电化学阻抗谱(EIS)模型参数

Table 1. Electrochemical impedance spectroscopy (EIS) model parameters for the synthesized of δ-MnO₂ and Ag/MnO₂ samples

Sample	R_s/Ω	R_ct/Ω	CPE /F	W/Ω
δ-MnO₂	77.33	283.40	3.45×10⁻³	8.95×10⁻⁵
Ag/MnO₂	5.83	34.50	4.68×10⁻³	7.89×10⁻⁴
Notes: R_s—Ohmic resistance; R_ct—Charge transfer resistance; CPE—Equivalent circuit defines the double-layer capacitance; W—Warburg resistance.

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表 2 δ-MnO₂和Ag/MnO₂复合材料的阻抗因子(σ)和扩散系数(D_Li⁺)

Table 2. Impedance factor (σ) and diffusion rate (D_Li⁺) of δ-MnO₂ and Ag/MnO₂ composites

Sample	σ/(Ω·cm²·S^−1/2)	D_Li⁺/(cm²·S⁻¹)
δ-MnO₂	334.55	2.95×10⁻²²
Ag/MnO₂	39.00	2.17×10⁻²⁰

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