Journal of The Electrochemical Society, 165 (16) A3723-A3731 (2018)
A3723
0013-4651/2018/165(16)/A3723/9/$37.00 © The Electrochemical Society
An Investigation of the Electrochemical Behaviors of M0.85Se
(M=Ni, Co) Materials for Alkaline Aqueous Battery
Yirong Zhu, z Xiaoru Yun, Jingying Li, Kaixiong Xiang, Li Xiao, Han Chen,z
College of Metallurgy and Material Engineering, Hunan University of Technology, Zhuzhou 412007,
People’s Republic of China
Metal selenides, as a new class of alkaline aqueous battery materials, have attracted more researchers’ attention in recent years. In
this work, the M0.85Se (M=Ni, Co) materials with different morphologies are successfully synthesized via a two-step hydrothermal
method by using different solvents. The effects of solvents and transition metals on structure, morphology, specific surface area
and pore structure and electrochemical properties of the products are systematically explored. The electrochemical measurements
reveal that the Ni0.85Se products prepared by H2O and ethanol exhibit higher specific capacity (83.8 and 65.3 mAh g−1 at 1 A g−1),
whereas the Co0.85Se products prepared by H2O and ethanol display better rate capability (75.1 and 69.0% of capacity retention rate
at 50 A g−1) and cycling stability (97.6 and 94.5% of capacity retention at 5 A g−1 after 2000 cycles), respectively. The different
electrochemical properties can be ascribed to the fact that the Ni0.85Se electrodes show diffusion-controlled faradaic chracteristic while
the Co0.85Se electrodes present mixed behavior of diffusion-controlled faradaic and capacitive feature. Such work is of fundamental
importance and it providesa valuable reference for the tailoring of these different properties by the use of varioussolventsand transition
metals.
Manuscript submitted October 19, 2018; revised manuscript received November 24, 2018. Published December 4, 2018.
The fast development of society and economy, together with the
worsening of environment and the depletion of fossil fuels, prompt
people to seek and develop advanced electrode materials for en-
ergy storage.1–4 Secondary batteries, as one of the most effective
and practical energy storage devices, have recently raised widespread
attention.5–8 Among these researched secondary batteries, alkaline
aqueous batteries possess a higher specific power and better cycling
life despite a lower specific capacity compared with lithium ion bat-
teries, and their unique advantages of alkaline aqueous batteries ren-
der them attract more researchers’ attention.9–11 However, researchers
continue to improve the properties of alkaline aqueous batteries in
order to meet the increasingly growing social demand. It is generally
accepted that the performances of the energy storage devices largely
depend on the properties of electroactive materials. Thus, the study
on electrode materials has become the research hotspots. Currently,
the researches of active electrode materials mainly focus on improv-
ing the electrochemical properties of existing electrode materials and
developing novel electrode materials with desirable electrochemical
performances.
metal oxides and sulfides. Although the M0.85Se (M=Ni, Co) mate-
rials have been reported by some researchers as advanced electrode
materials for application in energy storage, the effects of morphology
on the electrochemical properties of the M0.85Se (M=Ni, Co) materi-
als as alkaline aqueous battery have not been systematically explored.
Moreover, there is no report about the comparison of the electro-
chemical performances (including specific capacity, rate capability
and cycling stability) between the Ni0.85Se and Co0.85Se materials.
In this work, we reported the two-step hydrothermal synthesis
of the M0.85Se (M=Ni, Co) materials and investigated their electro-
chemical properties. Different morphologies of the M0.85Se (M=Ni,
Co) materials were obtained via hydrothermal synthesis route by us-
ing different solvents. Electrochemical measurements such as cyclic
voltammetry (CV), galvanostatic charge-discharge (GCD) and elec-
trochemical impedance spectroscopy (EIS) were conducted to study
and compare the electrochemical performances of the M0.85Se (M=Ni,
Co) materials.
Experimental
Metal selenides, as a new type of battery cathode materials, have
attracted researchers’ much attention very recently in view of their
intriguing advantages such as abundant redox chemistry, low energy
band and high electrical conductivity,12,13 which show tremendous
prospect in the fields of energy storage and conversion, including
solar cells,14–17 fuel cell,18–21 lithium ion batteries,22–28 sodium ion
batteries29–34 and supercapacitors.35–40 However, metal selenide-based
materials for application in energy storage and conversion are still far
less studied than the extensively reported metal oxide-based and metal
sulfide-based materials. Wang et al.35 synthesized novel 3D hierarchi-
cal GeSe2 nanostructures by a simple thermal evaporation method
and employed them as supercapacitor electrode materials for the first
time, which showed a superior electrochemical performance with a
high specific capacity. Yuan et al.41 prepared pure single-crystalline
SnSe nanosheet clusters by a facile surfactant-free aqueous solution
strategy and utilized them as anode materials for sodium ion batteries,
which exhibited high reversible capacity, outstanding rate capability
and superior cycling stability. Since this pioneer work, some other
metal selenides have been reported, including Co0.85Se,24,39 ZnSe,25
SnSe2,27,36 FeSe2,30,34 NixCo1-xSe38 and Ni0.85Se,40 which appear to be
prospective electrode materials for energy storage. The superior elec-
trochemical behaviors of metal selenides originate from the narrower
bandgap and the higher electrical conductivity than the corresponding
Materials and chemicals.—All the chemicals in the experiments
were analytical grade and were used without further purification.
NiCl6 · 6H2O, CoCl2 · 6H2O, Na2SeO3, N2H4 · H2O (80%), KOH
and urea were supplied from Sinopharm Chemical Reagent Beijing
Co., Ltd. Super P, polyvinylidene fluoride (PVDF) and N-methyl-2-
pyrrolidone (NMP) were purchased from Sigma-Aldrich.
Materials preparation.—The Ni0.85Se products with two different
morphologies were prepared by the two-step hydrothermal method.
The two precursors were first prepared according to the following
steps. Firstly, 1.1885 g of NiCl2 · 6H2O was dissolved in 60 mL of
distilled water (H2O) and ethanol (EA), respectively. After intense
stirring for 20 min, 0.3003 g of urea was further added to the above-
mixed solution. After continual stirring for another 20 min, the as-
obtained mixed solution was poured into a 100 mL of Teflon-lined
stainless steel autoclave and maintained at 130◦C in an oven for 10 h.
After natural cooling to room temperature, the resulting two precursors
were respectively centrifuged by utilizing distilled water and absolute
ethanol for three times, and dried under vacuum at 60◦C for 12 h.
For the preparation of the two Ni0.85Se products, 0.1 g of two pre-
cursors and 0.3 g of Na2SeO3 were respectively dissolved in 50 mL of
distilled water and vigorously stirred for 20 min, and then 10 mL of
N2H4 · H2O (80%) was further added into the above-mixed solution.
After continual stirring for another 20 min, the as-obtained mixed
solution was transferred into a 100 mL of Teflon-lined stainless steel
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