Inter-layer-calated Thin Li Metal Anode with Improved Battery

Capacity Retention and Dendrite Suppression Xi Chen, Mingwei Shang, and Junjie Niu*

Department of Materials Science and Engineering, CEAS, University of Wisconsin-Milwaukee, Milwaukee,

Wisconsin 53211, United States

Motivation and Challenges in Li Metal Anode • Rapidly growing demand on portable electronics and electrical vehicles pushed

expectation of energy densities in Li ion batteries to 500Wh/kg even higher.

• Among all anode candidates, Li metal has highest theoretical specific capacity of

3860 mAh/g.

• Lowest electrochemical potentials of -3.04V versus the standard hydrogen

electrode.

• Dendritic/mossy Li growth

• Uncontrollable solid electrolyte interphase (SEI)

• Low columbic efficiency (CE)

Manufacturing Process and Morphology

Figure 1. Manufacturing process and morphology of the ILC-Li electrode. (a) Atomic structure of Ti3C2Tx MXene. (b) SEM morphology

of a layered MXene stack. TEM (c) and high-resolution TEM (d) images of MXene. (e) two-side press of MXene stacks onto a thin Li host. (f)

Top and side views of the electrode with 30 and 300 μm Li hosts, respectively. SEM cross-section morphologies of the ILC-Li electrode with

~300 μm (g) and 30 μm (h) Li hosts. (i) Enlarged SEM image of the cross-section of ILC-Li electrode.

Figure 2. Morphology evolution of the Li foil and ILC-Li electrodes upon Li plating/stripping at different current densities after 10

cycles. SEM images of the Li foil electrode upon plating (a) and stripping (e) at a current density of 1 mA/cm2 and a capacity of 1mAh/cm2.

SEM images of the ILC-Li electrode upon plating (b,c,d) and stripping (f,g,h) at 1-3 mA/cm2 and 1-3 mAh/cm2, respectively. 3D confocal

surface roughness images (600 x 600 μm) of the pristine Li foil (i), the 10th cycled Li foil upon plating (j), the pristine ILC-Li (k) and the 10th

cycled ILC-Li upon plating (l) electrodes, respectively.

In-situ Observation of the Mossy/Dendritic Li

Growth/Depletion

Morphology Evolution

Illustrations of the Component Distribution of SEI

Figure 3. In-situ observation of the mossy/dendritic Li growth/depletion upon Li plating and stripping inside a capillary cell.

(a) First 2 cycles mossy/dendritic Li growth process upon Li plating (1st cycle: 0-40 minutes. 2nd cycle: 80-120 minutes) and Li

depletion process upon Li stripping (1st cycle: 40-80 minutes. 2nd cycle: 120-160 minutes) of ILC-Li electrode. (b) Schematic of the

capillary cell setup. (c) First cycle mossy/dendritic Li growth process upon Li plating (0-40minutes) and Li depletion process upon Li

stripping (40-80 minutes) of Li granule electrode. Current density: ~4.77 mA cm-2. Scale bar: 1 mm.

Electrochemical Stability and Full-cell Battery

Performance

Battery Performance at Lean Electrolyte Conditions

Figure 6. Battery performance of full cells at lean electrolyte conditions. (a) Scheme of ILC-Li│NCA full cell setup. Cycling capability of the

battery with ILC-Li/NCA (blue) and Li foil/NCA (black) at 0.2 C by using electrolyte of 2.5 ul (a), 5.0 ul (b), 7.5 ul (c), and 10.0 ul (d), respectively.

The thickness of Li host is 30 μm. The capacity was based on the specific discharge capacity. NCA loading: 20.5 mg/cm2. (e) Coulombic

efficiency evolution of the MXene-Cu/Li and Cu/Li cells at 0.5 mA/cm2 and 1.0 mAh/cm2, respectively.

Figure 5. Electrochemical stability and full-cell battery performance of the ILC-Li/Li foil electrodes paired with NMC cathode. (a)

Galvanostatic cycling of symmetric cells with ILC-Li (red, cyan, blue) and Li foil (black) electrodes at various current densities and capacities. (b)

Nyquist plots from EIS measurements of pristine ILC-Li (blue) and Li foil (black) electrodes in symmetric cells. (c) Nyquist plots of cycled ILC-Li

and Li foil electrodes in symmetric cells. (d) Rate performance of the battery vs NMC532 from 0.1 to 10.0 C. (e) Cycling performance of the

battery at 0.2 C charge/0.5C discharge. The specific capacity was calculated based on the discharge capacity of each cycle. Voltage profiles of

the ILC-Li/NMC532 (f) and Li foil/NMC532 (g) at different cycles. (h) Nyquist plots of pristine (h) and cycled (i) ILC-Li/NMC532 and Li foil/NMC532

full cells from EIS measurements. NMC532 loading: 10 mg/cm2.

Figure 4. XPS depth profiles of the electrode and illustrations of the component distribution of SEI. (a) XPS depth profiling of

the ILC-Li electrode upon stripping after 3 cycles at 1.0 mA/cm2 and 1.0 mAh/cm2. Overall (b) and component anatomy (c) of the

organic-rich and inorganic-rich SEI layers with Li foil and ILC-Li electrodes on the basis of XPS data.

References (1) Chen, X.; Shang, M.; Niu, J. Inter-Layer-Calated Thin Li Metal Electrode with Improved Battery Capacity Retention and Dendrite Suppression.

Nano Lett. 2020, 20 (4), 2639–2646. https://doi.org/10.1021/acs.nanolett.0c00201.

(2) Chen, X.; Lv, Y.; Shang, M.; Niu, J. Ironing Controllable Lithium into Lithiotropic Carbon Fiber Fabric: A Novel Li-Metal Anode with Improved

Cyclability and Dendrite Suppression. ACS Applied Materials & Interfaces 2019, 11 (24), 21584–21592. https://doi.org/10.1021/acsami.9b05364.