Lithium-ion batteries with LiCoO2 (LCO) cathodes are widely used in various electronic devices, resulting in a large amount of spent LCO (SLCO). Therefore, there is an urgent need for an efficient technique for recycling SLCO. However, due to the presence of cobalt oxide with a spinel phase on the surface of highly-degraded LCO, the strong electrostatic repulsion from the transition metal octahedron poses a high Li replenishment barrier, making the regeneration of highly-degraded LCO a challenge. Herein, we propose a structural transformation strategy for reconstructing Li replenishment channels to aid the direct regeneration of highly-degraded LCO. In this approach, ball milling is employed to disrupt the inherent structure of highly-degraded LCO, thereby releasing the internal stress and converting the surface spinel phase into a homogeneous amorphous structure, which promotes Li insertion and regeneration. The regenerated LCO (RLCO) exhibits an outstanding discharge capacity of 179.10 mAh·g−1 in the voltage range of 3.0–4.5 V at 0.5 C. The proposed strategy is an effective regeneration approach for highly-degraded LCO, thereby facilitating the efficient recycling of spent lithium-ion battery cathode materials.
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The rapid increase in demand for lithium-ion batteries (LIBs), driven by their widespread use in electric vehicles, consumer electronics, and energy storage systems, has led to a significant rise in the generation of waste LIBs. These batteries contain valuable metals such as lithium, cobalt, nickel, and manganese, which are essential for the production of new batteries. However, the disposal of these batteries, especially after their life cycle ends, poses substantial environmental and economic challenges. Traditional recycling methods, such as hydrometallurgy and pyrometallurgy, are effective in recovering metals from spent batteries, but they are hindered by high energy consumption, environmental pollution, and complex processing techniques. Consequently, more sustainable and efficient recycling technologies have become the focus of research, with direct regeneration techniques emerging as a promising solution to overcome the limitations of conventional methods.
This review discusses the recent advancements in direct regeneration technologies for recycling the cathode materials of waste LIBs. Direct regeneration refers to methods that restore the electrochemical properties and structural integrity of degraded cathode materials, making them suitable for reuse in new batteries. These techniques are designed to enhance the resource recovery process by efficiently restoring the performance of the cathode materials while reducing environmental impact. Key methods under direct regeneration include electrochemical recovery, solid-state sintering, and hydrothermal regeneration. These methods have shown significant promise in improving material recovery rates and enhancing the economic feasibility of the recycling process.
Electrochemical recovery methods involve using electrochemical reactions to selectively recover valuable metals from spent cathode materials while restoring their electrochemical performance. This process can be performed under relatively mild conditions, which significantly reduces the environmental impact compared to traditional methods. Solid-state sintering techniques, on the other hand, involve high-temperature processes that repair the crystal structure of the cathode materials, restoring their electrochemical stability and performance. Hydrothermal regeneration, a more environmentally friendly approach, uses aqueous solutions under high temperature and pressure to regenerate the cathode materials, making it a promising method for green recycling. All these techniques offer substantial advantages, such as reducing material loss, minimizing harmful byproducts, and enhancing the overall efficiency of the recycling process.
While these methods have demonstrated considerable potential in laboratory settings, there are several challenges that must be overcome to scale these technologies for industrial applications. One of the primary barriers to the widespread adoption of direct regeneration methods is the high cost of reagents and the energy requirements of some techniques, which make them less economically competitive with traditional recycling methods. In addition, the complexity of controlling reaction conditions and maintaining consistent material quality during large-scale regeneration processes poses significant challenges. Furthermore, ensuring that the regenerated materials meet the stringent performance standards required for new, high-performance batteries is a critical issue that needs to be addressed.
Despite these challenges, direct regeneration technologies offer a viable alternative to conventional recycling methods, with the potential to significantly reduce reliance on raw material extraction and minimize the environmental footprint of LIBs. The main advantage of these technologies lies in their ability to restore cathode materials to their original or near-original performance levels, thus extending the lifecycle of valuable materials. This ability not only helps conserve resources but also reduces the environmental damage associated with the mining and processing of raw materials.
Direct regeneration technologies for LIB cathode materials have shown significant promise in recent years, offering an environmentally friendly and resource-efficient alternative to traditional recycling methods. However, for these technologies to be successfully implemented on a large scale, several challenges need to be addressed. High processing costs and energy consumption, the need for better control over reaction parameters, and the integration of regeneration techniques into existing recycling infrastructures are the key hurdles that need to be overcome. Additionally, ensuring that regenerated cathode materials maintain their long-term stability and performance is crucial for their commercial viability.
The future of LIB recycling will likely focus on optimizing these direct regeneration methods to improve their scalability, reduce costs, and enhance their overall efficiency. Research should prioritize the development of more cost-effective reagents, energy-efficient processes, and technologies that can be easily integrated into current recycling systems. Additionally, innovations in material science, particularly in the design of more durable and stable cathode materials, will play an important role in enhancing the regeneration process. As these technologies continue to mature, they will contribute to a more sustainable and circular economy for LIBs, reducing the need for new mining activities and minimizing the environmental impact of battery disposal.
Ultimately, the successful development of direct regeneration technologies will help bridge the gap between the growing demand for LIBs and the need for sustainable resource management. By improving the efficiency and reducing the environmental impact of recycling, these technologies have the potential to make a significant contribution to the sustainable development of the battery industry, supporting the long-term goals of reducing carbon emissions and conserving valuable resources.
Transition metal dichalcogenides (TMDs) have been regarded as promising cathodes for aqueous zinc-ion batteries (AZIBs) but suffer from sluggish reaction kinetics due to their poor conductivity and the strong electrostatic interaction between Zn-ion and cathode materials. Herein, a well-defined structure with MoSSe nanosheets vertically anchored on graphene is used as the cathode for AZIBs. The dissolution of Se into MoS2 lattice together with heterointerface design via developing C–O–Mo bonds improves the inherent conductivity, enlarges interlayer spacing, and generates abundant anionic vacancies. As a result, the Zn2+ intercalation/deintercalation process is greatly improved, which is confirmed by theoretical modeling and ex-situ experimental results. Remarkably, the assembled AZIBs exhibit high-rate capability (124.2 mAh·g−1 at 5 A·g−1) and long cycling life (83% capacity retention after 1,200 cycles at 2 A·g−1). Moreover, the assembled quasi-solid-state Zn-ion batteries demonstrate a stable cycling performance over 100 cycles and high capacity retention over 94% after 2,500 bending cycles. This study provides a new strategy to unlock the electrochemical activity of TMDs via interface design and atomic engineering, which can also be applied to other TMDs for multivalent batteries.
It remains challenging to effectively estimate the remaining capacity of the secondary lithium-ion batteries that have been widely adopted for consumer electronics, energy storage, and electric vehicles. Herein, by integrating regular real-time current short pulse tests with data-driven Gaussian process regression algorithm, an efficient battery estimation has been successfully developed and validated for batteries with capacity ranging from 100% of the state of health (SOH) to below 50%, reaching an average accuracy as high as 95%. Interestingly, the proposed pulse test strategy for battery capacity measurement could reduce test time by more than 80% compared with regular long charge/discharge tests. The short-term features of the current pulse test were selected for an optimal training process. Data at different voltage stages and state of charge (SOC) are collected and explored to find the most suitable estimation model. In particular, we explore the validity of five different machine-learning methods for estimating capacity driven by pulse features, whereas Gaussian process regression with Matern kernel performs the best, providing guidance for future exploration. The new strategy of combining short pulse tests with machine-learning algorithms could further open window for efficiently forecasting lithium-ion battery remaining capacity.
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