LiMn2O4 Cathode Research Articles

Spent-graphite anode from failed batteries: Regeneration and chemical prelithiation for sustainable fresh Li-ion batteries

Recycling of spent lithium-ion batteries require substantial attention for a sustainable future. Increasing deployment of batteries leads to large volume of failed batteries few years later depending on life time of the batteries. Recycling of graphite from the failed batteries has been mostly ignored. Graphite requirement of 1800 kt by 2030 is projected, which is approximately 260 % increase compared to present consumption. Present work unveils a solution to the increasing demand of battery-grade graphite anodes by a sustainable process. The combined practice of regeneration and prelithiation of spent-graphite (SG) is a viable solution for industrial scale processing. Regeneration process includes two steps, washing with N-Methyl-2-pyrrolidone and thermal processing. Regenerated SG has been tested for half-cell that delivered a poor initial Coulombic efficiency (ICE) of about 65 % only, which could affect the full-cell performance. To improve ICE, a chemical prelithiation strategy leading to higher ICE with a mean value of 103.5 % has been achieved. Also, reversible capacity of about 410 mAh/g at a specific current of 100 mA/g, good cycling stability and rate capability has been demonstrated. Further, the prelithiated SG anode coupled with LiMn2O4 cathode delivered an initial energy density of 370 Wh/kg in a lab-scale cell demonstrating its potential.

Streamlined two-step synthesis of spinel LiMn2O4 cathode for enhanced battery applications

Spinel LiMn2O4 is a promising cathode material for Li-ion batteries, but suffers from capacity fading, which can be mitigated. To this end, we developed a straightforward and cost-effective two-step synthesis strategy for high-phase-purity and crystalline spinel LiMn2O4 nanopowder; the precursor Mn2O3 was fabricated via a thermal decomposition reaction, followed by a solid-state reaction with lithium acetate dihydrate. Morphological investigation revealed the presence of nanosized octahedral particles of LiMn2O4, consistent with outcomes obtained via the established sol-gel method. The subsequent annealing process was elucidated; it led to the formation of pure crystalline spinel LiMn2O4 with a crystallite size of only 62.08 nm. The nanopowder synthesized via the two-step process exhibited exceptional cycling performance, with a substantial initial charge/discharge capacity of 136.6/133.3 mAh/g and an 81 % capacity retention after 100 charge–discharge cycles. Notably, the attained morphology closely mirrored those observed in particles prepared using the conventional sol-gel method and electrochemical results is remarkably improved. Therefore, the developed method is expected to have great potential for practical application in the development of Li-ion batteries as well as other energy storage technologies.

Synthesis and Electrochemical Study of Calcium-Doped Spinel LiMn2O4 Cathode

Synthesis and Electrochemical Study of Calcium-Doped Spinel LiMn2O4 Cathode

Thermal‐Induced Structure Evolution at the Interface between Cathode and Solid‐State Electrolyte

The interfaces between the electrode and solid‐state electrolyte play a decisive role in the performance of all‐solid‐state batteries. For example, the formation of the interphase between cathode and solid‐state electrolyte can affect interfacial impedance and thus the rate capability. Herein, the thermal stability at the solid–solid interface between LiMn2O4 cathode and garnet electrolyte LLZTO via combined in situ techniques is studied, including in situ X‐Ray diffraction, in situ transmission electron microscopy, and in situ Raman. The dynamic process of interfacial reaction at different scales is elucidated. Starting from 300 °C, Mn ions from LiMn2O4 would migrate into the solid‐state electrolyte, accompanied with the formation of LiMn3O4 interphase. As the temperature increases to 500 °C, the LiMn3O4 interphase transforms to MnO structure which hinders Li‐ion transportation and therefore increases the interfacial impedance. Although both LiMn2O4 and LLZTO could withstand continuous heating, their interface is inherently thermally unstable at relatively low temperature, which requires special attention during thermal treatment for practical fabrication. Findings provide mechanistic insights into the interfacial reaction which serves as a guidance for the design and manufacturing of all‐solid‐state batteries.

Effect of atomic substitution on the LiMn2O4 cathode, as well as the suggestion to improve cycling stability and high capacity retention by creating a new route using MWCNTs

It is crucial to develop a doped cathode material for high capacity and long cycle lithium ion batteries in order to realize low cost and high-performance energy storage. LiMn1.977(Ce, Cu, Ti, CeCuTi)0.023O4 nanoparticles are a promising cathode material because of their unmatched high structural stability, high capacity, and safety during charge/discharge cycles. Among doped LiMn2O4 samples, the Ti-doped LiMn2O4 cathode calcined at 700 °C shows the highest capacity of 144.701 mAh g−1 after 20 cycles with a high current density of 0.1C which reaches 186.413 mAh g−1 when multi-walled carbon nanotubes (MWCNTs) are added (capacity retention = 98.924 %). Furthermore, when the T700 sample was subjected to an external force of 1000 N, it showed high capacity retention (=92.284 %). This is due to the larger surface area of the Ti700 sample, resulting in high porosity for reversible storage of lithium, and also the presence of titanium in the lattice increases the dielectric constant. This study provides a reliable and easy way to fabricate and analyze LiMn1.977(Ce, Cu, Ti, CeCuTi)0.023O4 nanoparticle-based cathodes with excellent performance.

Upcycling electrode materials from spent single-use zinc‑carbon/alkaline batteries into rechargeable lithium-ion battery application

Battery recycling/upcycling is a key component of modern e-waste reduction by transforming discarded electrode powder to value-added materials and chemical feedstocks for the proposed applications. In this study, electrode powder from spent zinc‑carbon/alkaline batteries was upcycled into LiMn2O4 cathode and carbon anode for rechargeable lithium-ion battery. The main metallic contents (zinc and manganese) in electrode powder were quantitatively leached using diluted H2SO4 with the presence of H2O2 as a reducing agent. By applying sequential precipitation, ZnS nanospheres and MnCO3 nanocubes were obtained as determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The recovered MnCO3 was heated with a stoichiometric amount of Li2CO3 to produce high crystalline and pure LiMn2O4. For the electrochemical performance, the results show that upcycled LiMn2O4 exhibits initial discharge capacity of 99.0 mAh g−1 for zc-LiMn2O4 and 111.0 mAh g−1 for al-LiMn2O4, compared to 90.4 mAh g−1 for pristine LiMn2O4. Moreover, recovered carbon materials obtained as an insoluble powder after acid leaching possess unique morphology and crystallinity. The zc‑carbon shows superior cycling performance with reversible charge capacity of 552 mAh g−1 at 1C rate after 100 cycles. This study provides the great potential for upcycling waste battery electrodes to high-value LiMn2O4 cathode and carbon anode for lithium-ion battery application.

Spinel Ni-doped LiMn2O4 cathode material with high oxygen reduction catalytic performance for low temperature solid ceramic fuel cells

In this work, Ni-doped LiMn2O4 spinel oxides were studied as the cathode materials of low temperature proton ceramic fuel cell. Increasing the content of doping Ni to 0.5, the calculated active energy of the polarization process of the cell decreased from 0.62 to 0.49 eV. The cell performance increased with the Ni doping of LiMn2O4 cathode, and the optimal power density reached to 547 mW cm−2 at 550 °C with a low polar resistance of 0.42 Ω cm2 for LiNi0.5Mn1.5O4. Ni partially replacing Mn at the B site could increase the content of Mn4+, resulting in the increase of oxygen vacancy content to maintain the charge balance, which is beneficial to the oxygen reduction reaction. These results demonstrate that spinel oxide could be a promising cathode material with highly oxygen reduction activity for advanced low temperature solid ceramic fuel cells.

Ce and Cu co-doped LiMn2O4 cathode material: Synthesis, characterization and electrochemical performances

In this study, a rare earth (Ce) and a conventional transition metal (Cu) are doped to investigate the improvement in the electrochemical nature of LiMn2O4 (LiMn2-x-yCexCuyO4 (0.01 ≤ x ≤ 0.05 and y = x)) using the sol-gel method assisted by citric acid as the chelating element. The physiochemical properties of co-doped cathode material are evaluated and analyzed using XRD, TG/DTA, SEM, TEM with EDS, FT-IR and Raman spectra. By increasing the concentration of the dopants, the Mn oxidation states increased, which indicated the embedding of the dopants into the structure of the cathode compound and also restricted the Jahn-Teller effect. The cubic spinel structure with space group Fd3‾m was revealed by the structural investigation, and the average grain size ranged from 0.36 to 0.59 μm. The TEM patterns confirm that there is no aggregation in the compound's structure. The high conductivity and stability of Cu contribute effectively to its benefits in decreasing capacity fade. LiMn2-x-yCexCuyO4 was enriched with dual doping in order to enhance the stability of structure of the cathode material. Finally, the charge/discharge curves of the electrochemical cells of LiMn1.94Ce0.03Cu0.03O4 were performed and the discharge and retension capacity of the synthesized LiMn1.94Ce0.03Cu0.03O4 samples are 89.70 mAh.g−1 (1st cycle), 77.4 mAh.g−1 (2nd cycle) and 86.28 %, which are better than the LMO.

Performance enhancement of lithium-ion battery using modified LiMn2O4 cathode followed by ultrasonic-assisted electrochemically synthesized graphene

Herein, the LiMn2O4 (LMO) cathode was modified using ultrasonic-assisted electrochemically synthesized graphene to enhance lithium-ion batteries' charging and discharging performance. Graphene was synthesized from graphite using an electrochemical exfoliation process in which 0.1 M molar (NH4)2SO4 was utilized as the electrolyte with +10 to +12V DC power, followed by ultrasonication in acetone for 2 h. The FESEM, EDX, XRD, Raman, FTIR, UV–vis, and TGA results suggested that ultrasonically treated graphene (EG1) is superior to electrochemically exfoliated graphene (EG2). Thus, EG1 was used to modify the LMO cathode to fabricate lithium-ion batteries. Afterward, the electrochemical performances of the LMO and LMO/EG1 cathode batteries were investigated. Surface morphological analysis revealed that EG1 is composed of two-dimensional, planar, brighter, and less oxidized graphene nanosheets with an average particle size of 18.02 nm. XRD results exhibited that EG1 has a smaller crystalline size and a thinner average stacking thickness of its layered structure than EG2. According to Raman analysis, the intensity ratio I2D/IG of EG2 and EG1 were 0.70 and 0.81, respectively, deduced that both are multi-layered graphene structures; however, EG1 contains a lesser number of graphene layers than EG2. The electrochemical analysis showed that LMO/EG1 cathode batteries have 89 % coulombic efficiency at 0.1C, while LMO batteries have only 81 %. The discharge capacity retention rate of the LMO batteries was 71.4 %, while it was 94.8 % for LMO/EG1 after observing 100 cycles at 0.1 C. Therefore, LMO/EG1 has excellent cycle stability and electrochemical performance and could potentially enhance the performance in hybrid automotive and electronic devices.

Improved Elevated Temperature Performance of LiFePO4/Graphite Cell by Blending NMC640 in Cathode

Physical mixtures of LiMn2O4 (LMO) and NMC active cathode materials is a well-known strategy in commercial batteries to achieve better cycling and storage performance than cells with a pure LMO cathode. In this work, we demonstrated a similar synergic effect in LiFePO4(LFP)/NMC640 cathode material blends. Blending LFP with NMC640 in the weight ratio of 90% to 10% lead to improvements in cycling and storage compared to cells with LFP alone. A clear linear coordination between capacity loss and iron deposition on the graphite anode was observed in these blended cells. This work shows that blending NMC in LFP cathode is a promising strategy to improve the high-temperature stability of LFP/graphite cells for long-term operation.

Efficient separation of Li and Mn from spent LiMn2O4 cathode materials by NH4HSO4 reduction roasting-selective ammonia leaching

With the imminent peak in the retirement of rechargeable lithium-ion batteries worldwide, the development of efficient methods for recycling valuable elements from LIBs has attracted considerable attention. In this work, a novel method of NH4HSO4 reduction roasting-selective ammonia leaching was proposed to thoroughly separate Li and Mn from the spent LiMn2O4 cathode materials. Using the TG-DSC-FTIR, XRD, SEM-EDS and ICP methods, the detailed mechanism of reduction roasting process was revealed, showing that the Mn4+ and Mn3+ in the spinel structure of LiMn2O4 were reduced by the NH4+ from the molten ammonium salt, and transformed into water-soluble MnSO4 and Li2Mn2(SO4)3. According to the water-leaching performance of the roasting products, the sulfation conversion rate of Mn reaches 98.1 %, while Li is almost completely transformed under the optimal roasting conditions (475 ℃, 60 min). Using the NH3·H2O-air leaching-system, complete separation of Li and Mn can be achieved. It was shown that the introduction of air into the ammonia solution at a rate of 0.2 L/min under the optimal leaching condition leads to Mn precipitation in the form of nanoscale Mn3O4 particles with a precipitation rate of over 99.99 %, while Li still remains completely leached. Based on the in situ detection of the oxidation reduction potential and pH during the selective leaching, the key mechanism of efficient Mn precipitation was revealed. that is, the increasing potential accelerates the oxidation of Mn(OH)2, and the rapid consumption of Mn(OH)2 promotes the hydrolysis of Mn2+, thereby achieving a significant improvement in the separation efficiency of Li and Mn.

Cobalt doped spinel LiMn2O4 cathode toward high-rate performance lithium-ion batteries

Great efforts have been devoted to improving the cycling stability and the high-rate performance of spinel LiMn2O4 cathode. Herein, we demonstrate that Co doping can improve the electrochemical performance of spinel LiMn2O4. We elucidate the atomic position of Co in spinel LiMn2O4 configuration and the stability improvement mechanism of the Co-doped LiMn2O4 cathode by using the state-of-art spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM). The results show that the Co3+ ions occupy the Mn octahedral 16d sites to reconstruct a more robust LiCoxMn2−xO4 framework, which is beneficial for stabilizing the LiMn2O4 crystal structure by ameliorating Mn dissolution and inhibiting Jahn-Teller distortion. Concomitantly, the doped Co atoms can offer short path lengths for Li+ ions intercalation and deintercalation that leads to accelerated Li+ diffusion kinetics. The as-designed optimal LiCo0.05Mn1.95O4 presents a respectable capacity retention of 83.81 % after 1000 cycles at 10C (1C = 148 mAh g−1), with an initial discharge capacity of 86.31 mAh g−1. Especially, excellent capacity retention of 78.52 % is obtained after 1000 cycles even at a high current rate of 15C. Our research shed light on the microscopic mechanism of Co doping on the cycling stability enhancement of spinel LiMn2O4 toward high-rate performance LIBs.

In Situ Electrochemically‐Bonded Self‐Adapting Polymeric Interface for Durable Aqueous Zinc Ion Batteries

AbstractThe implementation of aqueous zinc ion batteries (AZBs) is hindered by the notorious Zn dendrite growth and side reactions on Zn anodes. Herein, a novel strategy is introduced to overcome these hurdles by designing a self‐adapting soft polymeric composite interface (SAP). Unlike conventional methods relying on passive coating process, the approach leverages dynamic in situ electrochemical bonding via Zn─O interactions formed during cycling, ensuring intimate contact between the SAP interface and Zn electrode. The SAP interface boasts a robust network of hydrogen bonding and electrostatic interactions, which not only promotes the desolvation of Zn2+ and the repulsion of SO42−, facilitating uniform and rapid Zn2+ migration while effectively suppressing parasitic reactions; but also exhibits remarkable self‐adapting and self‐healing capabilities, enabling the interface to accommodate volume changes and repair mechanical failures over prolonged cycling. Consequently, highly reversible Zn electrodes are achieved with SAP, showcasing 3300 h at 1 mA cm−2/0.5 mAh cm−2 and 350 h at 20 mA cm−2/10 mAh cm−2 in the symmetric cells. The advantages of the SAP interface are further verified when paired with high mass loading LiMn2O4 cathodes in AZBs. The versatile SAP interface offers insights into advanced interface design for efficient and durable AZBs.

Upcycling of spent LiMn2O4 cathode towards sodium-ion battery cathode through molten salt electrolysis approach

Recycling and valorizing spent lithium-ion batteries (LIBs) are requisite to achieve resource sustainability and environment safety. Herein, we reported a molten salt electrolysis method to recycle degraded LiMn2O4, synergistically achieving the selective leaching of lithium (Li) and high-valued reutilization of manganese (Mn). In molten Na2CO3-K2CO3, 94.3 % of Li from LiMn2O4 was released into molten salt by the electrolysis at 1.2 V for 7 h, while in-situ forming Na0.55Mn2O4⋅1.5H2O. During the electrolysis, LiMn2O4 at the cathode was electrochemically decomposed to Li2O and manganese oxide, accompanied by the reaction of resultant Mn oxide with Na2CO3 salt to generate Na0.55Mn2O4⋅1.5H2O. Finally, Li2CO3 in molten salt can be selectively extracted by water leaching. The obtained Na0.55Mn2O4⋅1.5H2O material as a sodium-ion battery (SIB) cathode delivers a discharge specific capacity of 58.9 mAh g−1 at 100 mA g−1, showing good cycle performance with a capacity retention of 93.9 % after 100 cycles. Hence, molten salt electrolysis achieves both extraction of Li and high-value reutilization of Mn, offering an electricity-driven materials separation, recovery, and reutilization with reduced environmental impact.

The role of atomic layer deposited coatings on lithium-ion transport: A comprehensive study

The use of ultrathin film coatings prepared through Atomic Layer Deposition (ALD) has become widespread for improving lithium-ion diffusivity of active particles, which plays a crucial role in determining the rate capability of Lithium-ion Batteries (LIBs). In this study, the impact of ALD coating thickness on ionic diffusivity in CeO2-coated LiMn2O4 (LMO) cathode particles is comprehensively investigated through first-principles calculations by focusing on the trade-offs between the physical properties of the film and its impact on the diffusivity of ions. Our findings indicate that several physical factors affect the diffusivity of the coating, including the crystal-amorphous structure that depends on thickness, as well as surface and bulk diffusion, and the influence of neighboring atoms. These factors contribute to the observed trade-offs in diffusivity. In addition, we observe a previously unknown phenomenon: variation in diffusivity along the thickness of the coating, which can be explained by the aforementioned physical factors. This study is the first to provide a fundamental atomic-level understanding of how the thickness of the coating affects the diffusivity of coated particles. Our findings provide valuable insights into the control of ALD coating thickness and the design of cathodes to improve the performance of LIBs.

Effect of Oxidative Synthesis Conditions on the Performance of Single-Crystalline LiMn2- x Mx O4 (M = Al, Fe, and Ni) Spinel Cathodes in Lithium-Ion Batteries.

LiMn2 O4 (LMO) spinel cathode materials attract much interest due to the low price of manganese and high power density for lithium-ion batteries. However, the LMO cathodes suffer from the Mn dissolution problem at particle surfaces, which accelerates capacity fade. Herein, the authors report that the oxidative synthesis condition is a key factor in the cell performance of single-crystalline LiMn2- x Mx O4 (0.03 ≤ x ≤ 0.1, M = Al, Fe, and Ni) cathode materials prepared at 1000 °C. The use of oxygen flow during the spinel-phase formation minimizes the presence of oxygen vacancies generated at 1000 °C, thereby yielding a stoichiometrically doped LMO product; otherwise, the spinel cathode prepared in atmospheric air readily loses capacity due to the oxygen vacancies in the structure. As a way of circumventing the use of oxygen flow, a one-pot, two-step heating in air at 1000 °C and subsequently at 600 °C is used to yield the stoichiometric LMO product. The lithiation heating at 1000-600 ⁰C resulted in a significant improvement in the cycling stability of the prepared LMO cathode in graphite-based full cells. This study on oxidative synthesis conditions also confirms the advantage of minimizing the surface area of the cathode particles.

Enhancing the Electrochemical Performance of Li2-xMnO3 via Dual Strategies: Using MOF-Derived Manganese Oxide Precursor and Tuning Li Content

Cathode materials play a crucial role in determining the electrochemical properties and fabrication cost of Lithium-ion batteries (LIBs). Li2MnO3 has garnered increasing attentions due to its high theoretical capacity, but it suffers from severe issues, such as structural deterioration and irreversible capacity loss. In this paper, we propose a novel strategy to synthesize Li2-xMnO3 cathodes using MOF-derived manganese oxide via a simple solid-state reaction. When used as cathodes for LIBs, the MOF-Li2MnO3 exhibits a high reversible capacity of 92.5 mAh g−1 after 120 cycles at 25 mA g−1, as compared to pristine Li2MnO3 (31.7 mAh g−1). Additionally, hybrid phases including orthorhombic-LiMnO2 and cubic LiMn2O4 are introduced into Li-deficient materials, which exhibit different electrochemical behaviors from MOF-Li2MnO3. The MOF-Li1.75MnO3 delivers an unprecedented capacity of 151.9 mAh g−1 after 120 cycles at 25 mA g−1. Overall, the synergistic effect of adopting MOF-derived precursor and inducing multiphase by tuning Li content is conducive to enhancing the electrochemical performance of Li2MnO3 cathode.

Proof of Concept: The GREENcell—A Lithium Cell with a F-, Ni- and Co-Free Cathode and Stabilized In-Situ LiAl Alloy Anode

Given the rising upscaling trend in lithium-ion battery (LiB) production, there is a growing emphasis on the environmental and economic impacts alongside the high energy density demands. The cost and environmental impact of battery production primarily arise from the critical elements Ni, Co, and F. This drives the exploration of Ni-free and Co-free cathode alternatives such as LiMn2O4 (LMO) and LiFePO4 (LFP). However, the absence of Ni and Co results in reduced capacity and insufficient cyclic stability, particularly in the case of LMO due to Mn dissolution. To compensate for both low cathode capacitance and low cycle stability, we propose the GREENcell, a lithium cell combining a F-free polyisobutene (PIB) binder-based LMO cathode with a stabilized in -situ LiAL alloy anode. A LiAl alloy anode with the chemical composition of LiAl already shows a theoretical capacity of 993 Ah·kg−1. Therefore, it promises extraordinarily higher energy densities compared to a commercial graphite anode with a capacity of 372 Ah·kg−1. Following an iterative development process, different optimization strategies, especially those targeting the stability of the Al-based anode, were evaluated. During Al foil selection, foil purity and thickness could be identified as two of the dominant influencing parameters. A pressed-in stainless steel mesh provides both mechanical stability to the anode and facilitates alloy formation by breaking up the Al oxide layer beforehand. Additionally, a binder-stabilized Al oxide or silicate layer is pre-coated on the Al surface, posing as a SEI-precursor and ensuring a uniform liquid electrolyte distribution at the phase boundary. Employing a commercially available Si-containing Al alloy mitigated the mechanical degradation of the anode, yielding a favorable impact on long-term stability. The applicability of the novel optimized GREENcell is demonstrated using laboratory coin cells with LMO and LFP as the cathode. As a result, the functionality of the GREENcell was demonstrated for the first time, and thanks to the anode stabilization strategies, a capacity retention of >70% after 200 was achieved, representing an increase of 32.6% compared to the initial Al foil.

Study of Alternative Binders for Battery Electrode in Aqueous System

Materials used to prepare energy storage devices need to be affordable, durable, and safe for environment. PVDF, which is the most popular polymer used as a binder in battery electrodes, requires the use of and toxic solvents for processing, such as N-methyl-pyrrolidone (NMP).1 Water insoluble organic polymers could replace PVDF as the binder in aqueous batteries or redox flow batteries with solid boosters.2 For example, ethyl cellulose is a biodegradable and water-insoluble polymer. Ethyl cellulose-based slurry can be prepared using ethanol as solvent, which makes the process cheaper and more sustainable. Also cross-linked gluten could be used as a binder. In that case water-based slurry could be used to prepare the electrode. Replacing PVDF with more environmentally friendly binder would be beneficial in many ways. It would shorten the assembly procedure due to high speed of solvent evaporation, there are no strict requirements for humidity control and the recycling procedure is easier as there are no fluorinated compounds.3 Therefore, this replacement would enable to produce safer and cheaper energy storage devices.In this work positive electrodes with different composition have been described using galvanostatic charging-discharging and cyclic voltammetry. Various cell setups have been tested. LiMn2O4 (LMO) has been used as active material for cathode and carbon black Super P as conductive additive. PDVF has been compared with various organic biodegradable polymers as the binder. Using ethyl cellulose as a binder, discharge capacity 100 mAhg−1 was achieved at 0.2C rate for LMO cathode which is comparable to the results obtained with PVDF as a binder. 500 cycles at the rate of 1C showed somewhat better capacity retention for electrodes prepared using PVDF. Also rotating disk electrode experiments were conducted to study the effect of binder to the kinetics of the reaction. The results show that some biodegradable and cheaper binders could be promising option to replace PVDF as binder in aqueous systems. This is highly important in aqueous redox flow battery with solid boosters, where large amount of solid charge storage material is used in tanks to increase the capacity of the system.2 Acknowledgements: The research was supported by the Estonian Research Council grant MOBTP1023, Archimedes Foundation project SLTKT16432T and by the EU through the European Regional Development Fund under project TK141 (2014–2020.4.01.15–0011).

A Green Recycling Method for LiMn2O4 Cathode Materials by Simple Heat Treatment

Herein, a facile method with high efficiency is proposed for the separation and regeneration of LiMn2O4 (LMO) cathode material for spent lithium‐ion batteries through a simple heat treatment method. At first, the aluminum foil is separated at 450 °C in air, with a separation efficiency as high as 97.95%. Then, separation LMO is regenerated with high crystallinity at 650 °C with an optimum calcination time of 6 h. Importantly, this method allows D‐LMO to exhibit high reversible capacity (133 mAh g−1 at 0.1C), high rate performance (101 mAh g−1 at 5C), and long lifespan (0.5C, 92.1% capacity retention ratio after 100 cycles). A positive effect of the pyrolysis of polyvinylidene fluoride on D‐LMO is also suggested by the results. Moreover, a detailed investigation of the kinetics of the separation and regeneration is done, and the electrochemical mechanism is explored. Furthermore, this method requires much less energy input and chemical consumption, which would be helpful for environmental protection and green recycling.