Build zero volume expansion of lithium composite anode to achieve high energy density stable flexible lithium metal battery
Author：INITIAL ENERGY SCIENCE&TECHNOLOGY Co.,Ltd（IEST）
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Time：2022-08-29 10:52:38
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 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 lithium metal battery by matching NCM and LCO positive electrodes.
Figure 1. Schematic diagram of the zero-volume expansion anode with lithium embedding
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 X PS, and the expansion 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 soft-pack battery。
Figure 2. Design principle and volume expansion behavior of lithium metal anode with zero volume expansion
Using an electronic insulating porous film (EI film), combining a Cu-coated carbon fiber matrix (CuCM) 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 expansion properties of this composite, the authors assembled Li against the NCM₈₁₁ The single-layer cell, using the test method of in-situ expansion thickness and expansion force, can obviously compare the little thickness or stress expansion of zero VE-Li anode in the process of charge and discharge cycle, which proves the excellent expansion suppression performance of the composite material.
Figure 3. SEI and cycle stability analysis diagram of the lithium metal anode with zero volume expansion
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 dendrite Li₃N and the LiF. And the positive pole are NCM₈₁₁ Compared 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 expansion 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 expansion lithium composite anode developed in this work has an extremely high surface energy density (22.7 mWh cm⁻²), Practical volume energy density (375 Wh 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).
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 expansion 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.
I EST related test equipment recommended
SWE series in-situ expansion analysis system (I EST ）:
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 expansion thickness curve;
2.Test the battery expansion force curve under the constant gap condition;
3.Battery compression performance test: stress and strain curve-compression modulus；
4.Battery expansion force step by step test;
5.Different temperature control: -20~80℃.
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.
