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Page 4 of 14 Chen et al. Energy Mater. 2025, 5, 500064 https://dx.doi.org/10.20517/energymater.2024.163

Subsequently, the coated cathode was sectioned into 12 mm diameter discs for alucone coating using ALD
methods. The cathode alucone coating layer using the ALD method was deposited at 100 °C by introducing
trimethylaluminum (TMA) and ethylene glycol into an ALD reactor (PALD-150D, China). The thickness of
the alucone coating layer on the cathode NCM811 surface was about 2 nm.

Lithium metal anode coating using alucone by ALD
The alucone coating through ALD methods for LMA (diameter 15.6 mm) followed the same procedure as
the cathode coating. The thickness of the alucone coating layer on the LMA surface was about 2 nm. The
entire process was conducted inside a glovebox in an argon environment.

Characterizations
Powder X-ray diffraction (XRD) measurements were performed on all materials using Cu-Kα radiation
(Bruker, D8 Advance, Germany). The morphology of uncoated and ALD-coated NCM811 powder was
analyzed using a field emission scanning electron microscope (SEM) (LEO Zeiss 1550, Switzerland), while
elemental distribution was assessed through energy-dispersive X-ray spectroscopy (EDS). Elemental
contents and valence states of the samples were analyzed using Thermo Fisher Scientific's K-Alpha X-ray
photoelectron spectroscopy (XPS) equipment, and the XPS system was equipped with dual turbo molecular
pumps, a monochromatic micro-focused low-power Al K-Alpha X-ray source, and a 128-channel detector,
to achieve efficient data acquisition.

A depth profile analysis was performed utilizing the time-of-flight secondary ion mass spectrometry (TOF-
SIMS) technique, employing the TOF-SIMS 5-100 instrument from ION-TOF GmbH, Germany. X-ray
adsorption spectroscopy (XAS) experiments were conducted at the BL14W1 beamline of the Shanghai
Synchrotron Radiation Facility (SSRF), utilizing Co K-edge X-rays. Ni L-edge experiment was conducted on
the BL12B beamline at the State Key Laboratory of Synchrotron Radiation at the University of Science and
Technology of China, Hefei 230029, China. The pair distribution function analysis (PDF) was performed
using an EMPYREAN X-ray diffractometer with Ag target (Netherlands, Malvern Panalytical).

Cell assembly
Both working and counter electrodes were Li plates for a Li-Li symmetrical cell, which was assembled into a
CR2032-type coin cell using the as-prepared CSSE in a glove box filled with argon, maintaining both water
and oxygen levels below 0.5 ppm. Similarly, the full cell was assembled with pristine or alucone-coated
LMA, CSSE, and alucone-coated or alucone-free NCM811 cathode in an Ar-filled glove box to form full
cells (LMA-Alucone|LLZO/PEO/LiTFSI|Alucone-NCM811, or LMA|LLZO/PEO/LiTFSI|NCM 811). The
external pressure is typical of the spring force applied (~100 kPa). It should be noted that no liquid
electrolyte was added into the assembled cells.

Electrochemical measurements
The electrochemical impedance spectroscopy (EIS) test was conducted by using the Biologic multi-channel
electrochemical workstation with a frequency range of 100 mHz to 100 kHz and an AC amplitude of 10 mV.
The method for calculating ionic conductivity was included in the Supplementary Material.

The electrochemical performance test was performed for the assembled coin cell after resting for 12 h. A
VMP3 (Bio-Logic) battery cycler was used to measure the electrochemical performance of the symmetrical
and full cells. The performance of lithium metal batteries with NCM811 as the cathode was tested with a
voltage range from 2.8 to 4.3 V.