Hierarchical Ni(OH)2/Cu(OH)2 interwoven nanosheets in situ grown on Ni–Cu–P alloy plated cotton fabric for flexible high-performance energy storage

Flexible energy storage electrodes with high conductivity and capacity are crucial for wearable electronic clothes. Herein, a flexible hierarchical Ni(OH)2/Cu(OH)2 interwoven nanosheets in situ coated on Ni–Cu–P alloy plated cotton fabric textile (NCO/CF), which displays perfect conductive and electrochemical performance, is prepared by electroless deposition and electrochemical oxidation method. While the Ni–Cu–P alloy layer coated on the fabric effectively contributes to excellent mechanical performance and electro-conductivity of the as-prepared NCO/CF electrode, the hierarchical Ni(OH)2/Cu(OH)2 interwoven nanosheets in the oxidation layer effectively lead to a high energy storage performance with a specific areal capacity of 4.7 C cm−2 at a current density of 2 mA cm−2. When the power density of the two-electrode system based on NCO/CF and the carbon cloth (CC) is 2.4 mW cm−2, the energy density is 1.38 mW h cm−2. Furthermore, the flexible solid-state energy storage f-NCO/CF//CC is assembled in a self-powered system and supplies continuous power for electronic devices, demonstrating that NCO/CF is promising to be applied in various energy storage devices to power portable and wearable devices in the future.

it was taken out, washed by distilled water and dried at 60 o C overnight.After these treatments, the clean CF was gotten.Then, a 5 cm*5 cm of clean CF was immersed in the mixture of 2 g/L NaBH 4 and 0.04 g/L NaOH solution.And the solution was sonicated for 30 min, and then dried at room temperature.After that, the dried sample was placed in an electroless nickel plating bath with a pH of 10 and a temperature of

Synthesis of NCO/CFs
The electrochemical oxidation was conducted in a three-electrode configuration with a platinum counter electrode, a Hg/HgO electrode as the reference electrode, and 2 M KOH as the electrolyte.The oxidation of the Ni/Cu/CFs (1 cm*1.5 cm) was carried out in a potential window of -0.9~1V at a scan rate of 10 mV s -1 for 100 cycles of the cyclic voltammetry.

Characterizations
The corresponding EDS mapping images were obtained under a field emission scanning electron microscope (FESEM, S-4800, HITACHI, Japan).The morphologies were observed using a field emission scanning electron microscope (FESEM, S-4800, HITACHI, Japan).The X-ray diffraction (XRD) patterns of film electrodes were recorded using a Rigaku D/Max 2550 X-ray diffractometer with Cu Ka radiation at 40kV and 300mA.The X-ray photoelectron spectroscopy (XPS) analysis of film electrodes was performed by a PHI 5000C X-ray physical electronics photoelectron spectrometer with Mg Ka radiation at 15kV and 500W.A Micromeritics TriStarII 3020 surface area and porosity analyzer was utilized to study the pore structure of the samples.

Electrochemical Measurements
Electrochemical measurements of the electrode materials were carried out at room temperature in a standard three-electrode configuration on a CHI 760D (Chenhua, Shanghai) workstation with 2M KOH aqueous solution as the electrolyte.NCO/CF electrode (1cm*2cm) was used as the working electrode.A platinum electrode and a a Hg/HgO electrode were used as counter and the reference electrode, respectively.The specific capacity (C, C cm -2 ) of NCO/CF was calculated by the Equation (1) as follows: Where I (A) is the discharge current.Δt (s) is the discharge time.S (cm 2 ) is the geometric area of the working electrode.
Electrochemical measurements of the battery-supercapacitor hybrid system, NCO/CF-3//CC, were carried out in the two-electrode configuration, also on a CHI 760D (Chenhua, Shanghai) workstation with 2M KOH aqueous solution as the electrolyte.NCO/CF electrode (1cm*2cm) and the carbon cloth (CC) (1cm*2cm) were two electrodes.Energy density (E, mWh cm -2 ) and power density (P, mW cm -2 ) from the charge/discharge curves can be calculated by the Equation ( 2) and (3) as follows: Where ΔV is the potential window (V).
Further, the flexible solid-state energy storage f-NCO/CF//CC was assembled based on NCO/CF as the positive electrode (1 cm *1 cm) and the CC (1 cm *1 cm) as the negative electrode with KOH/PVA gel electrolyte.The KOH/PVA gel electrolyte was prepared by mixing 2.5 g PVA and 1.6 g KOH into 30.0mL distilled water and stirring at 85 ℃, until the solution became transparent.The cellulose separator was sandwiched in between two electrodes, subsequently sealed by the clip for further use.
80 o C for 2h.The composition of the electroless plating solution included 40 g/L NaH 2 PO 2 •H 2 O, 50 g/L Na 3 C 6 H 5 O 7 •2H 2 O, 30 g/L NiSO 4 •6H 2 O and 2.5, 3.3, or 5 g/L CuSO 4 •6H 2 O. Finally, the plated samples were rinsed thoroughly with distilled water and dried at 60 o C overnight, named Ni/Cu/CF-1, Ni/Cu/CF-2 and Ni/Cu/CF-3 respectively, after different concentrations of CuSO 4 •6H 2 O.After electroless plating process, a uniform Ni-Cu-P layer with the thickness was coated on the CF.For the purpose of comparison, Ni/CF was prepared without CuSO 4 •6H 2 O in the electroless plating bath.

Figure S5 .
Figure S5.GCD curves of NCO/CFs at a scan rate of 2 mA cm -2 .