Build Zero Volume Swelling of Lithium Composite Anode to Achieve High Energy Density

Literature Appreciation: Build Zero Volume Swelling of Lithium Composite Anode to Achieve High Energy Density Stable Flexible Lithium Metal Battery

Author Information and Article Summary

In 2022, the Deng Yonghong research group of Southern University of Science and Technology cooperated with Professor Zheng Zijian of Hong Kong Polytechnic University (First Author: Luo Chao, doctoral student of Southern University of Science and Technology) and developed a roller to roller method to prepare zero-volume expanded lithium composite negative electrode, which can significantly improve the energy density and flexible mechanical properties of lithium metal batteries. The negative electrode has a sandwich structure: Including the upper electronic insulation layer, the lithium affinity layer at the bottom and the porous layer in the middle. The author further verified the excellent flexibility, energy density and cycle retention rate of the lithium metal battery by matching NCM and LCO positive electrodes.

Figure 1.Schematic diagram of the zero-volume expansion anode with lithium embedding

Testing Program

1.Build lithium composite anode and lithium metal full battery.

2.Structural Characterization: The morphological characterization of the FE-SEM, the surface chemical structure, the XPS, and the swelling behavior, the SWE2100 (IEST).

3.Electrochemical Performance Characterization: The cycle performance of electric buckle and soft package.

4.Mechanical Performance Characterization: Bending performance of electrode and pouch battery.

Interpretation of Result

Figure 2. Design principle and volume swelling behavior of lithium metal anode with zero volume swelling

Using an electronic insulating porous film (EIfilm), combining a Cu-coated carbon fiber matrix (Cu CM) and an ultra-thin Li Mg alloy sheet, the author prepared a hollow composite lithium metal anode. The successful preparation of the sandwich structure lithium composite anode was confirmed by using the SEM and the element mapping diagram. To demonstrate the zero-volume swelling properties of this composite, the authors assembled Li against the NCM₈₁₁The single-layer cell, using the test method of in-situ swelling thickness and swelling force, can obviously compare the little thickness or stress swelling of zero VE-Li anode in the process of charge and discharge cycle, which proves the excellent swelling suppression performance of the composite material.

Figure 3. SEI and cycle stability analysis diagram of the lithium metal anode with zero volume swelling

By XPS characterizing the lithium metal interface changes brought by the upper layer insulation functional layer of the new lithium metal anode, it is proved that SEI contains the inorganic layer Li with the best inhibitory effect on lithium dendrite₃N, and the Li F. And the positive pole are NCM₈₁₁Compared with the two kinds of LCO batteries, the battery cell has the highest cycle capacity retention rate with zero VE-Li as the negative electrode.

Figure 4. Electrochemical and mechanical stability of a single layer of lithium metal whole battery

Through dynamic bending and resistance testing, the authors found that zero VE-Li showed no significant changes in resistance and morphology after 4,000 bending experiments, showing excellent flexibility. The zero VE-Li electrode was matched with the high surface load flexible positive electrode to assemble the flexible batteries. From the evaluation of electrochemical cycle stability and mechanical stability, the zero volume swelling negative electrode showed high Cullomb efficiency, high cycle capacity retention rate and good flexible characteristics.

Figure 5. Electrochemical and mechanical stability of a multi-layer lithium metal whole battery

The authors went on to prepare double-sided zero-volume expansion anode and found them to have higher mass specific capacity than commercial anode materials. The assembled multi-layer flexible lithium-metal batteries have a high weight energy density and volume energy density, and can still maintain a 75% capacity retention rate after 3,000 laps of bending experiments. By comparing the energy density values of flexible lithium-based batteries in other related literature, the flexible lithium-metal whole battery based on the zero-volume swelling lithium composite anode developed in this work has an extremely high surface energy density (22.7 mWh cm)^-2), Practical volume energy density (375 W h L^-1, Based on the volume of the positive and negative electrode, diaphragm, and packaging material) and a record-setting flexible quality factor (FOM, 45.6).

Sum Up

This paper develops a zero-volume-expanded lithium composite anode, which has excellent electrochemical properties and mechanical flexibility, and can significantly improve the energy density of lithium metal batteries. The negative electrode has a sandwich structure: Including the upper electronic insulation layer in the bottom, the lithium affinity layer at the bottom and the porous layer in the middle. The author further verified the excellent flexibility, energy density and cycle retention rate of the corresponding flexible lithium metal battery by matching NCM and LCO positive electrodes. The zero-volume expansion design provides new ideas for the practical application of lithium metal batteries. The volume-to-volume manufacturing process also shows its potential for large-scale production. In principle, the zero-volume swelling design is also suitable to build other negative metal batteries (such as sodium, potassium, and zinc metal batteries) to improve energy density, cycling, and structural stability.

The Original Literature

Chao Luo, Hong Hu, Tian Zhang, Shujing Wen, Ruo Wang, Yanan An, Shang-Sen Chi, Jun  Wang, Chaoyang Wang, Jian Chang*, Zijian Zheng*, and Yonghong Deng*.Roll-to-roll Fabrication of Zero-Volume-Expansion Lithium Composite Anodes to Realize High-Energy-Density Flexible and Stable Lithium Metal Batteries.Advanced Materials, doi.org/10.1002/adma.202205677.

IEST Related Test Equipment Recommended

SWE series in-situ swelling analysis system (IEST): Using a highly stable and reliable automation platform, equipped with high precision thickness measurement sensor, to measure the thickness change amount and change rate of the whole charge and discharge process of the cell, which can realize the following functions:

1.Constant pressure condition to test the battery swelling thickness curve.

2.Test the battery swelling force curve under the constant gap condition.

3.Battery compression performance test: stress and strain curve-compression modulus.

4.Battery swelling force step by step test.

5. Different temperature control: -20~80℃.