The accelerated adoption of electric vehicles supports the transition to a more sustainable transportation sector. However, many EVs will be retired in the next decade, posing a sustainability challenge, especially due to the lack of recycling of end-of-life batteries.
In view of this, Academician Chen Zhongwei and researcher Zhang Yongguang of Dalian Institute of Chemical Physics demonstrated a regeneration route that can give a second life to the waste cathode in lithium-ion batteries (LIB) and post-LIB. The regeneration in this paper begins with a leaching process involving acetic acid, which selectively dissolves high-value elements in the cathode, including lithium, cobalt, nickel, and manganese. Depending on the chelating agent added, further co-precipitation reactions in the leachate form precursors for different cathode materials. The regenerated lithium layered oxide cathode provides a reversible area capacity of up to 2.73 mAh cm−2 and has excellent structural stability for LIB, while the obtained Prussian blue analogue shows a retention rate of 83.7% after 2000 cycles of sodium-ion battery (SIB). Life cycle and techno-economic assessments show that current regeneration can reduce the manufacturing costs of LIBs and SIBs by $21.65 kWh−1 and $41.67 kWh−1, respectively, with less impact on human health, the environment, and natural resources. This work paves the way for the transition to more sustainable storage technologies. The research results were published in the latest issue of Nature Sustainability under the title "Sustainable regeneration of spent cathodes for lithium-ion and post-lithium-ion batteries".
It is worth mentioning that Professor Chen Zhongwei is a Fellow of the Royal Society of Canada, a Fellow of the Canadian Academy of Engineering, a recipient of Canada's highest National Science and Technology Award, a National Chief Scientist of Canada, and previously served as the Director of the Clean Energy Advanced Materials Laboratory at the University of Waterloo and the Director of the Center for Electrochemical Energy at the University of Waterloo. At the age of 44, Professor Chen Zhongwei became the youngest member of the Chinese Academy of Sciences and the Chinese Academy of Sciences in Canada. Associate Editor-in-Chief of ACS Applied Materials & Interface, Co-Founder and Vice President of the International Electrochemical Energy Science Society (IAOEES).
On July 28, 2023, the inaugural meeting of the first academic committee of the National Key Laboratory of Energy Catalytic Conversion was successfully held in Dalian Institute of Chemical Physics. After the deliberation and approval of the Party Group of the Chinese Academy of Sciences, Dalian Institute of Chemical Physics hired Chen Zhongwei, academician of the Royal Society of Canada and academician of the Canadian Academy of Engineering, as the director of the laboratory.
【Extraction of high-value elements】
The extraction of high-value elements is an initial and critical step in the cathodic regeneration process. This step involves the use of acetic acid and hydrogen peroxide as leaching agents to dissolve the valuable metals in the spent cathode material into solution, thus facilitating the separation of undissolved impurities. The efficiency of the process is highly dependent on the reaction temperature and the composition of the cathode material being processed. Leaching efficiency: The leaching of cobalt (Co) and lithium (Li) from LiCoO2 (LCO) and nickel (Ni), Co, manganese (Mn) and Li from LiNi1/3Co1/3Mn1/3O2 (NCM) is highly temperature dependent. For example, the extraction capacity of LCO and NCM is significantly higher at 90 °C than at 25 °C. Slurry density effect: The metal leaching efficiency decreases with the increase of slurry density. For LCO, more than 95.6% of Co and 97.4% of Li are leached at a slurry density of 10 g/L, while for NCM, the leaching efficiency is higher at lower slurry density but lower at higher density. Figure 1 illustrates the effect of slurry density on the leaching efficiency of different metals in LCO and NCM, highlighting the optimal conditions for maximum metal recovery.
Figure 1. Extraction of high-value elements
【Regenerative cathode materials for lithium-ion batteries】
The regeneration of cathode materials is to synthesize new cathode materials by co-precipitation with leaching solution. The focus of this study is on two recycled cathode materials: Li1.04 (Ni0.34Co0.32Mn0.34), 0.96O2 (R-NCM) or Li1.04 (Ni0.80Co0.10Mn0.10) 0.96O2 (R-NCM811). Synthesis process: The molar ratios of nickel, cobalt, and manganese in the leachate are adjusted to obtain the desired composition, followed by co-precipitation and high-temperature lithiation to form a regenerated cathode powder. Analytical characterization showed that the regenerated powder retained the spherical structure of the precursor and exhibited equivalent or better electrochemical performance than commercial NCM powder, and the regenerated cathode exhibited high reversible capacity, good cycling stability (capacity retention rate of 81.2% after 500 cycles) and high coulombic efficiency (>99.7%). Figure 2 illustrates the morphological and structural characteristics of recycled NCM powder. Structural stability: FIB-SEM and in-situ XRD analysis showed that the microcracks were minimal and the phase stability was strong during cycling.
Figure 2. Recycled cathode material for LIB
[Recycled cathode material for post-LIB]
Prussian blue analogues (PBAs) for post-LIB applications were developed to utilize transition metal ions in leachate to form various PBAs by co-precipitation. These materials exhibit excellent electrochemical properties, including high specific capacity and long-term cycling stability. From the synthesis and morphology point of view, PBA exhibits a homogeneous cubic structure with precise control of metal composition, which is essential for optimizing electrochemical performance. Electrochemical performance: The NCM-PBA electrode exhibits impressive cycling stability (83.7% capacity retention after 2000 cycles) and high coulombic efficiency, highlighting its potential for SIB applications. In addition, SEM, XRD, and TOF-SIMS analyses confirmed structural integrity and uniform Na ion distribution in circulating PBAs, highlighting their applicability to SIB applications.
Figure 3. Regenerated cathode material for post-LIB
Life Cycle and Techno-Economic Assessment
The Life Cycle Assessment (LCA) assesses the environmental impact of the regeneration process, showing a significant reduction in global warming potential (GWP100) and fossil resource scarcity compared to commercial cathode production. Cost analysis shows significant savings in manufacturing costs for LIB and SIB battery packs using recycled materials (Figure 4). For example, a 1 kWh LIB battery pack using regenerative NCM costs around $34.94/kWh, while transitioning to a SIB using NCM-PBA further reduces the cost to $21.08/kWh.
Figure 4. Evaluation of cathodic regeneration technology
【Summary】
In this paper, two different cathodic regeneration methods are designed to recover all high-value elements from black matter and reuse them into novel cathode materials for lithium-ion and post-lithium-ion batteries, enabling the transition to next-generation sustainable battery systems. In order to extract the high-value elements without any impurities and control the crystallization process, they opted for a milder leaching agent. The obtained LIB cathode material and the PBA cathode material for post-LIB have an optimized microstructure and matched capacities, which are comparable to or better than commercial materials. As batteries continue to evolve and diversify, this approach allows for comprehensive sustainability while reducing costs and environmental impact. In particular, the transition to post-lithium-ion batteries has dramatically reduced the impact on human health, the environment, and natural resources, while manufacturing costs have also been greatly reduced. These attempts to transition to lithium-ion alternatives through recycling processes will provide a promising avenue to address the sustainability and affordability of batteries, further accelerating the world's progress towards sustainable development.
Source: Frontiers of Polymer Science
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