Capacity Fading Mechanism of the Commercial 18650 LiFePO4-Based Lithium-Ion Batteries: An in Situ Time-Resolved High-Energy Synchrotron XRD Study

From Present Innovations to Future Potential: The Promising Journey of Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have become integral to modern technology, powering portable electronics, electric vehicles, and renewable energy storage systems. This document explores the complexities and advancements in LIB technology, highlighting the fundamental components such as anodes, cathodes, electrolytes, and separators. It delves into the critical interplay of these components in determining battery performance, including energy density, cycling stability, and safety. Moreover, the document addresses the significant sustainability challenges posed by the widespread adoption of LIBs, focusing on resource depletion and environmental impact. Various recycling practices, including hydrometallurgy, pyrometallurgy, and direct recycling, are evaluated for their efficiency in metal recovery and ecological footprint. The advancements in recycling technologies aim to mitigate the adverse effects of LIB waste, emphasizing the need for sustainable and scalable solutions. The research underscores the importance of ongoing innovation in electrode materials and recycling methodologies, reminding us of our responsibility and commitment to finding and implementing these solutions, as this continuous improvement is crucial to enhance the performance, safety, and sustainability of LIBs, ensuring their continued relevance in the evolving energy storage landscape.

Recent advances in battery characterization using in situ XAFS, SAXS, XRD, and their combining techniques: From single scale to multiscale structure detection

Revealing and clarifying the chemical reaction processes and mechanisms inside the batteries will bring a great help to the controllable preparation and performance modulation of batteries. Advanced characterization techniques based on synchrotron radiation (SR) have accelerated the development of various batteries over the past decade. In situ SR techniques have been widely used in the study of electrochemical reactions and mechanisms due to their excellent characteristics. Herein, the three most wide and important synchrotron radiation techniques used in battery research were systematically reviewed, namely X-ray absorption fine structure (XAFS) spectroscopy, small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD). Special attention is paid to how these characterization techniques are used to understand the reaction mechanism of batteries and improve the practical characteristics of batteries. Moreover, the in situ combining techniques advance the acquisition of single scale structure information to the simultaneous characterization of multiscale structures, which will bring a new perspective to the research of batteries. Finally, the challenges and future opportunities of SR techniques for battery research are featured based on their current development.

Evolution fate of battery chemistry during efficient discharging processing of spent lithium-ion batteries

Residual electricity in spent lithium-ion batteries (LIBs) may cause safety issues during their dismantling and shredding in pretreatment processes. However, the migration and transformation of pollutants generated from spent LIBs during discharging were rarely reported, which is critical for prevention of pollution risk and facilitation of discharging efficiency. Herein, this work is focused on the evolution fate of battery chemistry during discharging processing. Here, migration of metal ions inside battery, galvanic corrosion on surface of battery and chemical evolution outside battery were investigated to attain the comprehensive understanding of discharging process. Firstly, efficient and complete discharging can be achieved using 5 wt% CuSO4 as discharging medium, which mainly drive the migration of Li, instead of transition metals, from anode to cathode, resulting in enrichment of Li in cathode material. Besides, different degrees of galvanic corrosion phenomena on surface of spent LIBs can be discovered in different electrolyte solutions, involving with the corrosion of Al or Fe shells and resulting in the leakage of organic electrolytes inside battery into electrolyte solution. The detailed characterization results of the composition of solute indicate that hydroxide precipitates liberated from corroded shell and organic pollutants are their main existence states.

Electrochemical Restoration of Battery Materials Guided by Synchrotron Radiation Technology for Sustainable Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have been ubiquitous in modern society, especially in the fields of electronic devices, electric vehicles and grid storage, while raising concerns about a tremendous number of spent batteries in the next five to ten years. As environmental awareness and resource security is gaining increasingly extensive attention, how to effectively deal with spent LIBs has become a challenging issue academically and industrially. Accordingly, the development of battery recycling has surfaced as a highly researched topic in the battery community. Recently, the structural and electrochemical restoration of recycled electrode materials have been proposed as a non-destructive method to save more energy and chemical agents compared with mature metallurgical methods. Such a refurbishment process of electrode materials is also regarded as a reverse process of their degradation in the working condition. Notably, synchrotron radiation technology, which is previously applied to diagnose battery degrade, has started to play major roles in gaining more insight into the structural restoration of electrode materials. Here, the contribution of synchrotron radiation technology to reveal the underlying degradation and regeneration mechanisms of LIBs cathodes is highlighted, providing a theoretical basis and guidance for the direct recycling and reuse of degraded cathodes.

From Li to Na: Exploratory Analysis of Fe-Based Phosphates Polyanion-Type Cathode Materials by Mn Substitution

Both LiFePO4 (LFP) and NaFePO4 (NFP) are phosphate polyanion-type cathode materials, which have received much attention due to their low cost and high theoretical capacity. Substitution of manganese (Mn) elements for LFP/NFP materials can improve the electrochemical properties, but the connection between local structural changes and electrochemical behaviors after Mn substitution is still not clear. This study not only achieves improvements in energy density of LFP and cyclic stability of NFP through Mn substitution, but also provides an in-depth analysis of the structural evolutions induced by the substitution. Among them, the substitution of Mn enables LiFe0.5 Mn0.5 PO4 to achieve a high energy density of 535.3 Wh kg-1 , while NaFe0.7 Mn0.3 PO4 exhibits outstanding cyclability with 89.6% capacity retention after 250 cycles. Specifically, Mn substitution broadens the ion-transport channels, improving the ion diffusion coefficient. Moreover, LiFe0.5 Mn0.5 PO4 maintains a more stable single-phase transition during the charge/discharge process. The transition of NaFe0.7 Mn0.3 PO4 to the amorphous phase is avoided, which can maintain structural stability and achieve better electrochemical performance. With systematic analysis, this research provides valuable guidance for the subsequent design of high-performance polyanion-type cathodes.

Boron-Catalyzed Graphitization Carbon Layer Enabling LiMn0.8 Fe0.2 PO4 Cathode Superior Kinetics and Li-Storage Properties

The poor electrode kinetics and low conductivity of the LiMn_0.8 Fe_0.2 PO₄ cathode seriously impede its practical application. Here, an effective strategy of boron-catalyzed graphitization carbon coating layer is proposed to stabilize the nanostructure and improve the kinetic properties and Li-storage capability of LiMn_0.8 Fe_0.2 PO₄ nanocrystals for rechargeable lithium-ion batteries. The graphite-like BC₃ is derived from B-catalyzed graphitization coating layers, which can not only effectively maintain the dynamic stability of the LiMn_0.8 Fe_0.2 PO₄ nanostructure during cycling, but also plays an important role in enhancing the conductivity and Li⁺ migration kinetics of LiMn_0.8 Fe_0.2 PO₄ @B-C. The optimized LiMn_0.8 Fe_0.2 PO₄ @B-C exhibits the fastest intercalation/deintercalation kinetics, highest electrical conductivity (8.41 × 10^-2 S cm^-1 ), Li⁺ diffusion coefficient (6.17 × 10^-12 cm² s^-1 ), and Li-storage performance among three comparison samples (B-C0, B-C6, and B-C9). The highly reversible properties and structural stability of LiMn_0.8 Fe_0.2 PO₄ @B-C are further proved by operando XRD analysis. The B-catalyzed graphitization carbon coating strategy is expected to be an effective pathway to overcome the inherent drawbacks of the high-energy density LiMn_0.8 Fe_0.2 PO₄ cathode and to improve other cathode materials with low-conductivity and poor electrode kinetics for rechargeable second batteries.

Mechanical Failure Mechanism of Silicon-Based Composite Anodes under Overdischarging Conditions Based on Finite Element Analysis

Overdischarge is a severe safety issue that can induce severe mechanical failure of electrode materials in lithium-ion batteries. A considerable volume change of silicon-based composite anodes undoubtedly further aggravates the mechanical failure. However, the mechanical failure mechanism of silicon-based composite anodes under overdischarging conditions still lacks in-depth understanding despite many efforts paid under normal charging conditions. Herein, we have modeled and tracked the mechanical failure evolution of silicon/carbon nanofibers, a typical silicon-based anode, under overdischarging conditions based on the finite element simulation, with derived optimization strategies of optimal Young's modulus and stable microstructure. The severe contact damage between silicon nanoparticles and carbon nanofibers, which causes larger shedding and breakage risks, has been found to contribute to mechanical failure. To improve the electrode stability, an optimal Young's modulus interval ranging from ∼75 to ∼150 GPa is found. Furthermore, increasing the embedding depth of silicon nanoparticles in carbon nanofibers has proven to be an effective strategy for improving electrochemical stability due to the faster lithium salt diffusion and more uniform current density distribution, which was further verified by the experimental capacity retention ratio of carbon-coated silicon and silicon/carbon nanofibers (84 vs 75% after 100 cycles). Our results provide meaningful insights into the mechanical failure of silicon-based composite anodes during overdischarging, giving reasonable guidance for electrode safety designs and performance optimization.

Double Donors Tuning Conductivity of LiVPO4F for Advanced Lithium-Ion Batteries

To fulfill the increasing demand of lithium-ion batteries for realizing high energy density and great cycling stability under high rate, the cathode material capable of efficient electron and Li⁺-ion transportation is necessarily demanded. Herein, we propose a double-donor doping strategy by taking the carbon-coated LiVPO₄F as a model system. The Hall effect confirms that either or both Mg²⁺ substitution of Li⁺ and Nb⁵⁺ substitution of V³⁺ cause the carrier-type transformation from p-type to n-type. The great enhancements of electronic conductivity and ionic conductivity are realized in Li_0.995Mg_0.005V_0.98Nb_0.02PO₄F, which also exhibits a markedly improved Li⁺ diffusion coefficient and reduced electrochemical polarization. The carbon-coating layer can effectively prevent the decomposition reaction of electrolyte, allowing for good structural stability of Li_0.995Mg_0.005V_0.98Nb_0.02PO₄F when suffering fast Li⁺ insertion/extraction. As expected, the Li_0.995Mg_0.005V_0.98Nb_0.02PO₄F cathode exhibited superior electrochemical properties with an initial discharge capacity of 124.5 mA h g^-1 and capacity retention of 97.3% after 600 cycles at 1.6C. Even under a high rate of 8C, the discharge energy density was 392 Wh kg^-1 at the beginning and showed a retention rate of 84.4% after 2000 cycles.

Application of Operando X-ray Diffractometry in Various Aspects of the Investigations of Lithium/Sodium-Ion Batteries

The main challenges facing rechargeable batteries today are: (1) increasing the electrode capacity; (2) prolonging the cycle life; (3) enhancing the rate performance and (4) insuring their safety. Significant efforts have been devoted to improve the present electrode materials as well as to develop and design new high performance electrodes. All of the efforts are based on the understanding of the materials, their working mechanisms, the impact of the structure and reaction mechanism on electrochemical performance. Various operando/in-situ methods are applied in studying rechargeable batteries to gain a better understanding of the crystal structure of the electrode materials and their behaviors during charge-discharge under various conditions. In the present review, we focus on applying operando X-ray techniques to investigate electrode materials, including the working mechanisms of different structured materials, the effect of size, cycling rate and temperature on the reaction mechanisms, the thermal stability of the electrodes, the degradation mechanism and the optimization of material synthesis. We demonstrate the importance of using operando/in-situ XRD and its combination with other techniques in examining the microstructural changes of the electrodes under various operating conditions, in both macro and atomic-scales. These results reveal the working and the degradation mechanisms of the electrodes and the possible side reactions involved, which are essential for improving the present materials and developing new materials for high performance and long cycle life batteries.

Olivine Positive Electrodes for Li-Ion Batteries: Status and Perspectives

Among the compounds of the olivine family, LiMPO4 with M = Fe, Mn, Ni, or Co, only LiFePO4 is currently used as the active element of positive electrodes in lithium-ion batteries. However, intensive research devoted to other elements of the family has recently been successful in significantly improving their electrochemical performance, so that some of them are now promising for application in the battery industry and outperform LiFePO4 in terms of energy density, a key parameter for use in electric vehicles in particular. The purpose of this review is to acknowledge the current state of the art and the progress that has been made recently on all the elements of the family and their solid solutions. We also discuss the results from the perspective of their potential application in the industry of Li-ion batteries.