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面向鋅離子電池的二氧化錳柔性電極制備及電化學性能

Preparation and electrochemical properties of manganese dioxide flexible electrodes for zinc-ion batteries

  • 摘要: 二氧化錳(MnO2)作為鋅離子電池常用的正極材料,在自然界中儲量豐富、安全性好、理論容量高,受到研究學者的廣泛關注. 制備高性能鋅離子電池的關鍵問題之一是構造具有穩定微觀結構的陰極. 本文選用具有優良導電性的柔性碳布(CC)作為基底,分別使用還原沉積法和電化學沉積法制備了碳布@二氧化錳(CC@MnO2)陰極,使用SEM、TEM、XRD、XPS等測試手段對兩種工藝條件下得到的電極結構和形貌進行表征分析,探明了電極的微觀結構組成. 進一步將其組裝成扣式鋅離子電池,對比研究了不同工藝參數下電池的電化學性能. 結果表明,還原沉積法中,使用0.40 mol·L–1 KMnO4 + 0.50 mol·L–1 H2SO4的混合溶液制備的電極具備最優的儲鋅性能(電流密度在0.1 A·g–1時能提供最大為291 mA·h·g–1的放電比容量)、能量密度(293.3 W·h·kg–1)和循環穩定性(1 A·g–1電流密度下進行1000次循環后,容量保持率為90.48%,庫倫效率為99.87%). 此外,通過對電極進行不同充放電狀態下的非原位XRD和SEM檢測,進一步探索了充放電過程的儲能機制. 本文深入探討了基于還原沉積法的CC@MnO2電極優化制備工藝,為高性能鋅離子電池的開發提供了重要的參考依據.

     

    Abstract: Manganese dioxide (MnO2), a commonly used cathode material for zinc-ion batteries (ZIBs), has attracted considerable attention owing to its abundant reserves in nature, safety, and high theoretical capacity. One of the key challenges in the preparation of high-performance zinc-ion batteries is the construction of a cathode with a stable microstructure. In this study, a flexible and conductive carbon cloth (CC) was chosen as the substrate onto which manganese dioxide (MnO2) was deposited through either reductive deposition or electrochemical deposition methods to form a carbon cloth@ manganese dioxide (CC@MnO2) cathode. For the reductive deposition method, a precursor solution of KMnO4 and H2SO4 was used, and various concentrations were adopted to synthesize the CC@MnO2 cathode. The synthesized electrode is referred to as the CC@MnO2-reductive deposition cathode. Specifically, KMnO4 solutions with concentrations of 0.25, 0.40, and 0.55 mol·L?1 were mixed with H2SO4 at concentrations of 0.20 mol·L?1 and 0.50 mol·L?1. For the electrochemical deposition method, MnO2 nanoparticles were decorated on CC using a three-electrode system under the potentiostatic mode at a potential of 1.1 V for 1500 s. A depositing electrolyte consisting of 0.1 mol·L?1 MnSO4 + 0.1 mol·L?1 Na2SO4 was used. The synthesized electrode is referred to as the CC@MnO2-electrochemical deposition cathode. The cathodes synthesized under different parameters were comparatively analyzed via scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron microscopy to explore their morphology and microstructure. Furthermore, the prepared CC@MnO2 cathodes were assembled into button-type zinc-ion batteries, and their electrochemical properties, charging/discharging performance, and cycling stability were evaluated. The test results showed that the Zn//CC@MnO2 cells based on the reductive deposition method with a 0.40 mol·L?1 KMnO4 + 0.50 mol·L?1 H2SO4 mixed solution delivered optimal zinc storage performance (providing a discharge-specific capacity of up to 291 mA·h·g?1 at a current density of 0.1 A·g?1), energy density of 293.3 W·h·kg–1), and cycling stability with a capacity retention of 90.48% after 1000 cycles at a current density of 1 A·g?1 and Coulomb efficiency of 99.87%. The superior electrochemical performance of the CC@MnO2-RD cathode compared with that of the CC@MnO2-ED cathode is attributable to the improved structural stability and uniformity of the former. In addition, a reversible two-step insertion storage mechanism involving H+ and Zn2+ in the CC@MnO2 cathode for ZIBs was verified through ex-situ X-ray diffraction and scanning electron microscopy measurements at different charging/discharging states. This paper highlights the optimized preparation process of CC@MnO2 electrodes based on the reductive deposition method, demonstrating advantages such as low cost and ease of fabrication. These findings can serve as a reference for developing high-performance zinc-ion batteries.

     

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