鎳基超級電容器電極材料之製備

Preparation of Nickel-based materials for supercapacitor electrodes

周金德(Chin-Te Chou)

指導教授 ： 林炯棟

義守大學/理工學院/材料科學與工程學系/碩士(2014年)

https://doi.org/10.6343/ISU.2014.00082

摘要

本研究嘗試使用無電鍍鎳法(Electroless nickel)來製備超級電容電極材料，此方法是無需電源的供應以及不用在高壓高溫環境下就可以進行。為了進一步提高無電鍍鎳磷膜之比電容值，本研究利用酸蝕刻使得鎳磷膜層形成黑鎳膜且在膜層表面會產生多孔洞性結構，進一步提高比表面積。另外，我們也發現三維的立體基板(如泡沫鎳)有助於比電容值的提昇，因而本研究也嘗試以水熱法製備三維的石墨烯水凝膠(Graphene hydrogel)來製作成電極，並且將無電鍍鎳鍍覆其上，探討比電容性質。
實驗結果顯示，當鎳磷膜層經過酸腐蝕後，會產生火山口狀以及珊瑚礁狀等多孔結構。以濃硝酸6.5 M、7 M以及7.5 M分別進行蝕刻，都可以得到不錯的比電容值，在蝕刻時間為15秒時，掃描速率為10 mV/s的情況下，可分別獲得507 Fg-1、638 Fg-1以及865 Fg-1。若以混合酸(硝酸:硫酸=1:1)進行蝕刻，在時間為10秒時，掃描速率10 mV/s，比電容值約441 Fg-1，其蝕刻速率比濃硝酸要來的快，這可以縮短蝕刻所需時間；但是快速的蝕刻，亦會對膜層造成嚴重破壞，則比電容值會因此下降。此外，也發現磷含量的增加，會造成其蝕刻的難度提高。在酸性鍍液中，將亞磷酸鈉量增加，使得磷含量提高至約7.8%，經由濃硝酸蝕刻後，當蝕刻時間達25秒時鈦基板表面還有殘存的鎳磷膜，並在掃描速率10 mV/s獲得510 Fg-1比電容值。而使用鹼性鍍液時，將亞磷酸鈉含量降低，使得磷含量下降至約4.4%，由於磷含量下降，蝕刻相對較為容易，也對其膜層破壞得較為嚴重，而產生大量的火山口形貌，在腐蝕時間10秒時，掃描速率10 mV/s，其比電容值約446.8 Fg-1。經由EDS分析可知，隨著蝕刻時間的增加，膜層的磷含量隨之增加，這說明在蝕刻過程中，主要是Ni原子先被溶解於酸中。另外，我們發現經500次循環後，其比電容值(500~800Fg-1)下降幅度僅為3~10%左右，擁有良好的循環壽命。另外，我們也成功的製備出石墨烯水凝膠，並在石墨烯水凝膠上鍍覆無電鍍鎳。

關鍵字

超級電容器 ； 無電鍍鎳 ； 黑鎳膜 ； 石墨烯

並列摘要

In this study, the Ni-P films were deposited on the titanium substrate by using electroless nickel and were applied as electrode materials for supercapacitors. This method need not have a power supply and does not prepare under the conditions of high pressure and high temperature. To improve the specific capacitance of Ni-P electrodes, an acid-etching method was used to form a black nickel coating and these electroless nickel films can exhibit a porous structure resulting in the increasing of surface area. In addition, we also found three dimensional open substrates ( such as nickel foam ) could enhance specific capacitance, so the Ni-P coated three dimensional graphene hydrogels were prepared by hydrothermal synthesis and electroless nickel plating. Their specific capacitances and microstructures were further explored in details.
The results showed that when Ni-P coating was etched by acid, a crater-shaped and porous structures such as coral-like can be formed. With concentrated nitric acid (6.5M, and 7M and 7.5M), the specific capacitances can reach 507Fg-1, 638Fg-1, and 865Fg-1, respectively, at the etching time of 15 sec and scanning rate of 10 mV/s. If the mixed acid was used, specific capacitance was about 441Fg-1 after 10 sec etching, the etching rate was faster than that with concentrated nitric acid, which could shorten the time needed for etching, but a rapid etching would also cause a serious damage to the films, then the specific capacitance was diminished. In addition, it was also found that the increase of P content can increase its etching resistance. For acid bath, as the content of sodium hypophosphite increased, the P content raised to about 7.8%, the specific capacitance was 510 Fg-1 after 25 sec etching. Content of sodium hypophosphite in alkaline bath was also adjusted to decrease the P content to around 4.4%, the films tended to etch easily, but also the more serious damages of films occurred, which incurred a large crater morphology, its specific capacitance was 446.8Fg-1 after 10 sec etching. The EDS analysis showed that phosphorus content of films increased with the increasing of etching time, this suggested that Ni atoms were firstly dissolved in acid during the process of etching. In terms of life cycle, we found that the drop of samples with high specific capacitance (500~800Fg-1) was only 3~10% after 500 cycling. In addition, we have successfully prepared the electroless nickel coated graphene hydrogels.

並列關鍵字

electroless nickel ； black film ； Super capacitors ； Graphene

參考文獻

[1].W. Martin and J.B. Ralph,” What Are batteries, fuel cells, and supercapacitors?”, Chem. Rev., vol.104, 2004, pp. 4245-4269.

[2].G. Wang, L. Zhang and J. Zhang” A review of electrode materials for electrochemical supercapacitors”, Chem. Soc. Rev., vol.41, 2012, pp.797-828.

[3].H.I. Becker, “Low voltage electrolytic capacitor”, US Patent 2,800,616, 1957.

[4].R.A. Rightmire, “Electrical energy storage apparatus”, US Patent 3,288,641, 1966.

[6].W. Xing, A.M. Wilson, K. Eguehi, G. Zank, and J.R. Dahn, “Pyrolyzed Polysiloxanes for use as anode materials in lithium-ion batteries”, J. Electrochem.Soc,1997,144,2410-2414.