Celgard

CR2032-type coin cells were assembled to deposit Li on the current collectors to evaluate the Coulombic efficiency, electrochemical impedance spectra and other properties. The cells were assembled in an argon-filled glove box. The coin cell was composed of a Li foil as the counter/reference electrode, a Celgard separator, and a current collector as the working electrode. The electrolyte was 1 M LiTFSI in DOL/DME (1:1 by volume, 30 μl, BASF) without any additives unless noted otherwise. The Coulombic efficiency was tested at 0.5 mA cm⁻² on a LAND electrochemical testing system at room temperature. The batteries were first cycled at 0–1 V (versus Li⁺/Li) at 50 μA for five cycles to stabilize the SEI and remove surface contaminations. After that, 1 mA h cm⁻² of Li was deposited onto the current collector and then charged to 0.5 V (versus Li⁺/Li) to strip the Li at 0.5 mA cm⁻² for each cycle. The Coulombic efficiency was calculated based on the ratio of Li stripping and plating. Electrochemical impedance spectra measurement was performed using an Autolab workstation (Metrohm) in the frequency range of 100 kHz to 100 mHz after specific cycles.
Symmetric cells were employed to evaluate the cycling stability and cycle life (short-circuit time T_sc) of the Li anodes on different current collectors. The symmetric cell was assembled using a hollow spacer substituting for the Celgard separator in a CR2032-type coin cell, as illustrated in Supplementary Fig. 11. The electrolyte (1 M LiTFSI in DOL/DME, 200 μl) was carefully charged into the spacer without entrainment of bubbles. For the long-term galvanostatic discharge/charge test, 2 mA h cm⁻² of Li was first deposited on the current collectors at 0.5 mA cm⁻² and the cells were then charged and discharged at 0.2 mA cm⁻² for 2.5 h in each half cycle. For the unidirectional galvanostatic polarization (accelerated test for T_sc), Li was continuously plated onto the current collectors from the counter electrode at 0.5 mA cm⁻² until short circuit. The average T_sc was obtained from at least three cells for each current collector.
For full cells with 3D Cu-based Li-metal anodes, LiFePO₄ (Sanxin Industrial) was employed as cathode material. LiFePO₄ was casted on an Al foil with an areal capacity density of ∼0.5 mA h cm⁻². The 3D Cu was first assembled into a half cell using a Li foil as counter electrode. After plating 1 mA h cm⁻² of Li metal into the 3D current collector, Li anode was extracted from the half cell and reassembled into a full cell against LiFePO₄ cathode. The electrolyte was the same as that in the half cells (1 M LiTFSI in DOL/DME, 30 μl). Assembly of pouch cells was similar to that of the coin cells. The electrodes (∼42 cm² in area) were stacked and assembled in a pouch cell. Li anodes plated in the 3D current collector were assembled into a pouch cell against LiFePO₄ cathodes with 4 ml of the electrolyte to gain the pouch full cell with a capacity of ∼40 mA h.

Monocrystalline silicon substrates (surface orientation (100), 40 × 40 mm, Telecom-STV Co., Ltd., Zelenograd, Russia) and stainless-steel plates (316SS, 16 mm diameter, Tob New Energy Technology Co., Ltd., Xiamen, China) were used as substrates for ALD. Prior to deposition, the silicon and stainless-steel substrates were cleaned in an ultrasonic bath in acetone and deionized water for 10 and 5 min, respectively. To remove the native silicon oxide layer, the silicon substrates were immersed for 5 min in 10% hydrofluoric acid solution(HF). Then, silicon substrates were cleaned using piranha solution (H₂SO₄/H₂O₂, volume ratio 7:3) for 20 min to remove organic contaminants and produce a hydroxylic surface. Finally, the silicon substrates were rinsed in deionized (DI) water and dried under an argon atmosphere [29 (link)].
ALD of nickel–cobalt oxide (NCO), nickel oxide (NO), and cobalt oxide (CO) were performed with a commercial R-150 setup (Picosun Oy, Espoo, Finland) at a temperature of 300 °C and a reactor base pressure of 8–12 hPa. Bis(cyclopentadienyl) nickel(II) and Bis(cyclopentadienyl) cobalt(II) (Ni(Cp)₂, Co(Cp)₂; 99%, Dalchem, Nizhny Novgorod, Russia) were used as the nickel and cobalt-containing precursors. Co(Cp)₂ and Ni(Cp)₂ were kept in stainless-steel bottles (Picohot™ 200, Picosun Oy) and heated during deposition to 160 and 110 °C, respectively. The pulse times and purge times were 1 s and 10 s for both Co(Cp)₂ and Ni(Cp)₂. Remote oxygen plasma was used as a counter-reagent. The plasma power was 3 kW, with a frequency range of 1.9–3.2 MHz. The total plasma pulse time was 19.5 s (Ar purge during 0.5 s with flow rate 40 sccm; Ar and O₂ plasma purge during 14 s with flow rate 90 sccm; Ar purge during 5 s with flow rate 40 sccm). Deposition conditions were based on our previous studies devoted to obtaining cobalt and nickel oxide [55 (link),56 (link)].
The spectroscopic ellipsometry parameters (Ψ and Δ) for films deposited on a silicon substrate were measured out with an Ellips-1891 SAG ellipsometer (CNT, Novosibirsk, Russia) in a wavelength range from 370 to 1000 nm and an incidence angle of 70°. The Spectr software package (1.10, CNT, Novosibirsk, Russia) was used to construct and fit a structural-optical model function. After fitting the parameters of the optical model and experimental spectra, the thicknesses of the films were calculated. The errors of the film thickness calculation were no more than 0.3 nm. The gradient of the thickness (GT) was calculated using Equation (1): $GT=\frac{{\mathrm{T}}_{\max }-{\mathrm{T}}_{\min }}{{\mathrm{T}}_{\max }+{\mathrm{T}}_{\min }}\times 100\%,$
where T_max and T_min are the maximum and minimum film thicknesses, respectively [29 (link)].
X-ray reflectometry (XRR) and X-ray diffraction (XRD) studies were performed with a Bruker D8 DISCOVER (Cu-Kα = 1.5406 Å) diffractometer. Surface-sensitive grazing incidence XRD (GIXRD) modes were used for XRD measurements using a 2θ range of 30–65° with a step of 0.1° and an exposure of 1 s at each step. The incidence angle of the primary X-ray beam was 0.7°. XRR measurements were performed in an angle range of 0.3–5° (increment 0.01°) using symmetric scattering geometry. The obtained results were processed by the Rietveld method using the TOPAS software package (ver. 5, Bruker, Billerica, MA, USA) and by the simplex method using the LEPTOS (ver. 7.7, Bruker, Billerica, MA, USA) for XRD and XRR, respectively.
X-ray photoelectron spectra (XPS) were acquired with an Escalab 250Xi spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). The samples were sputtered by Ar⁺ ions with an energy of 500 eV for 30 and 45 or 90 s. The samples were excited by Al-Kα (1486.7 eV) X-rays at a pressure of 7 × 10⁻⁸ Pa.
Scanning electron micrographs of planar and cross-sectional views were obtained by a Supra 55 VP scanning electron microscope (SEM, Zeiss, Oberkochen, Germany) with a Gemini-I column and a field emission cathode. Spatial resolution was about 1.3 nm at an accelerating voltage of 15 kV. A total of 3–4 randomly selected positions on the surface of the sample were investigated. Everhart–Thornley and InLens secondary electron detectors were used for SEM studies. Energy-dispersive X-ray (EDX) analysis was performed using the INCA X-Max system (Oxford Instruments, High Wycombe, UK) installed on the SEM Supra 55 VP.
Stainless-steel plates with deposited films were used for electrochemical studies. Lithium foil, polyolefin porous film 2325 (Celgard, Charlotte, NC, USA), and TC-E918 (Tinci, Guangzhou, China) solutions were used as the counter, separator, and electrolyte, respectively. The composition of TC-E918 was a 1M solution of LiPF₆ in a mixture of organic carbonates (ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate). The coin cells (CR2032) were assembled in an argon atmosphere using an OMNI-LAB glove box (VAC). Cyclic voltammetry (CV) was performed using a PGSTAT302N+ potentiostat (Autolab, Utrecht, The Netherlands) in a range of 0.01–3.00 V with a scan rate of 0.5 mV/s. Discharge tests at different current densities were run with a CT3008W-5V10mA charge/discharge stand (Neware, Shenzhen, China), calibrated to work with low currents in a voltage range from 3.00 V–0.01 V, and current densities of 10, 20, 40, 80, 160, 320, 480, 640, 800 µA/cm². Deconvolution of the CV patterns was performed using the Origin (ver. 9.0.0) software package.

Two types of microporous polymer separators were studied: Celgard^® H2010 (trilayer) and Celgard^® Q20S1HX (Ceramic-Coated Trilayer); both membranes encompass a PP/PE/PP composition with a thickness of 20 and 16 μm, respectively. The latter possesses an additional 4 μm ceramic coating on one side. The materials were supplied by Celgard (Celgard, LLC, Charlotte, NC, USA). Table 1 presents further information provided by the manufacturer.

Hydrochloric
acid, sodium hydroxide, potassium hydroxide, sodium citrate (tribasic),
salicylic acid, potassium phosphate (dibasic), potassium phosphate
(monobasic), sodium hypochlorite solution (10–15%), and sodium
nitroferricyanide(III) dihydrate were purchased from Millipore Sigma
(Burlington, Massachusetts). Sustainion X37–50 grade RT, PiperION-A80,
Fumasep FAA 3–50, and isomolded graphite plates were purchased
from The Fuel Cell Store (College Station, Texas). Nafion 211 and
Nafion 212 were purchased from Fuel Cell Earth (Woburn, Massachusetts).
Celgard 3401 and Celgard 2400 were purchased from Celgard (Charlotte,
North Carolina). All solutions were made using deionized (DI) water
(>18.0 MΩ·cm, Milli-Q Gradient System, Millipore Sigma).
Custom glass H-cells were purchased from Adams & Chittenden Scientific
Glass (Berkeley, California).

The electrochemical properties of the elastic solid-state polymer electrolyte are investigated using CR2032 coin cells assembled in an Ar-filled glovebox. For the assembly process, the LFP cathodes are used as working electrodes lithium metal is used as the anode, and Celgard 3500 (Celgard LLC, Concord, NC, USA) is used as the separator. The precursor is injected into the separator and the cells are packaged immediately. After that, the assembled cells are heated at 70 °C for 2 h to generate the in situ polymerized LZT/SN-SPE (or SN-SPE). Due to the liquid nature of the precursor, Celgard 3500 separators are applied to all cells to prevent a short circuit in the assembled cells before polymerization. The charge/discharge experiments are carried out on a Neware Battery system with the potential ranges of 2.5–4 V at a current density of 1 C. Li||Li symmetric cells are prepared with an identical method except that LFP is replaced by Li foils (diameter of 12 mm). The Li plating/stripping experiments are measured on a Neware Battery system.