Facile Lithium Densification Kinetics by Hyperporous/Hybrid Conductor for High-Energy-Density Lithium Metal Batteries

Abstract

Lithium metal anode (LMA) emerges as a promising candidate for lithium (Li)-based battery chemistries with high-energy-density. However, inhomogeneous charge distribution from the unbalanced ion/electron transport causes dendritic Li deposition, leading to "dead Li" and parasitic reactions, particularly at high Li utilization ratios (low negative/positive ratios in full cells). Herein, an innovative LMA structural model deploying a hyperporous/hybrid conductive architecture is proposed on single-walled carbon nanotube film (HCA/C), fabricated through a nonsolvent induced phase separation process. This design integrates ionic polymers with conductive carbon, offering a substantial improvement over traditional metal current collectors by reducing the weight of LMA and enabling high-energy-density batteries. The HCA/C promotes uniform lithium deposition even under rapid charging (up to 5 mA cm^-2) owing to its efficient mixed ion/electron conduction pathways. Thus, the HCA/C demonstrates stable cycling for 200 cycles with a low negative/positive ratio of 1.0 when paired with a LiNi_0.8Co_0.1Mn_0.1O₂ cathode (areal capacity of 5.0 mAh cm^-2). Furthermore, a stacked pouch-type full cell using HCA/C realizes a high energy density of 344 Wh kg^-1 _cell/951 Wh L^-1 _cell based on the total mass of the cell, exceeding previously reported pouch-type full cells. This work paves the way for LMA development in high-energy-density Li metal batteries.

Keywords: fast‐charging; lithium metal densification; lithium‐filling host; mixed conductor; nonsolvent‐induced phase separation.

Scheme 1

Fabrication process of hyperporous/hybrid conductive architecture on CNT film (HCA/C).

Figure 1

Structure‐forming design factors of HCA. a) Composition paths of a complex after immersion (t < 1s): yellow and red lines induce sponge‐like and finger‐like structures, respectively. b) Solubility parameters of solvent, nonsolvent, and R _HPS between solvent and nonsolvent. c, e, g) Cross‐sectional and d, f, h) top‐view SEM images of HCA/C fabricated by ethanol, 1‐propanol, and 1‐butanol nonsolvent (left‐to‐right) The insets of top‐view SEM images indicate magnified ones to confirm the formation structure of three components in architectures. i) Changes in porosity of HCA/C with different nonsolvent. j) Comparisons of electronic conductivity and electrolyte‐impregnated ionic conductivity for various electrodes.

Figure 2

Fast‐charging feasibility of HCA/C. Schematic illustration of structural growth of lithium metal during electrochemical deposition on a) Cu foil and b) HCA/C. SEM images after lithium deposition of 5 mAh cm⁻² on Cu foil (left) and in HCA/C (right) under current densities of c, d) 1 mA cm⁻² and e, f) 5 mA cm⁻².

Figure 3

Cycle persistence of thin Li deposited electrodes. a) Cycling performance of asymmetric cells at a current density of 1 mA cm⁻² with an areal capacity of 1 mAh cm⁻². b) Rate durability of Cu‐Li5 and HCA/C‐Li5. Cycle efficiency under harsh electrochemical environments of Cu‐Li5||Li and HCA/C‐Li5||Li at c) the current density of 5 mA cm⁻² with the areal capacity of 1 mAh cm⁻² and d) the current density of 1.5 mA cm⁻² with the areal capacity of 3 mAh cm⁻².

Figure 4

Post‐mortem analyses of thin Li deposited electrodes in cycled asymmetric cells. Top‐view SEM images of a) Cu from Cu‐Li5||Li and b) HCA from HCA/C‐Li5||Li5 after 30 cycles. Nyquist plots of c) Cu‐Li5||Li cell and d) HCA/C‐Li5||Li cell after different cycles. e) ¹⁹F NMR spectra of the electrolyte extracted from cells after selected cycles. f) The comparison ratio of salt consumption calculated from ¹⁹F NMR spectra after cycles.

Figure 5

Electrochemical evaluation of full cells. a) Rate performance and b) Long‐term cycle persistence of Cu‐Li5||LFP and HCA/C‐Li5||LFP, assembled using coin cells, with N/P ratio of 2.0 (1 C = 2.5 mA cm⁻²). c) Cycle retention of Cu‐Li5||NCM811 and HCA/C‐Li5||NCM811 coin cell with high‐loaded cathode and N/P ratio of 1.0 (1 C = 5.0 mA cm⁻²). d) Schematic illustration to elucidate the configuration inside the designed stack pouch full cell. This practical pouch cell was prepared with an N/P ratio of 1.0 and limited amounts of liquid electrolyte (3.0 g Ah⁻¹). e) Cycle performance of the pouch cell (1 C = 20 mA cm⁻²).