LiMn2O4 Research Articles

Investigation on prospective thermoelectrics — cubic Nd-doped LMO and rhombohedral Cu4Mn2Te4 materials — first principles approach

Structural, electronic, magnetic and optical properties of Cu4Mn2Te4 have been reported earlier by the authors, and here, the transport properties of the same are discussed along with the band structure investigation of the neodymium-doped cubic material LMO (LiMn2O4), namely LiMn[Formula: see text]Nd[Formula: see text]O4 compound, under spin polarized schemes through the First Principles calculations. The Full Potential-Linearized Augumented Plane Wave Method (FP-LAPW) method is adopted to investigate the electronic structures based on the framework of Density Functional Theory (DFT). Exchange potentials are treated using the Generalized Gradient Approximations (GGA). Cohesive energy calculations reveal that the ferromagnetic phase of LiMn[Formula: see text]Nd[Formula: see text]O4 and the antiferromagnetic phase of Cu4Mn2Te4 exhibits a stable phase. Of these, FM-LiMn[Formula: see text]Nd[Formula: see text]O4 shows a semi-metallic-like behavior in spin-up channel and metallic behavior in spin-down channel whereas antiferromagnetic Cu4Mn2Te4 exhibits a band gap in both spin-up and spin-down channels. Dirac points are identified at −0.0625[Formula: see text]eV in the band structure plot of FM-LiMn[Formula: see text]Nd[Formula: see text]O4 at its high symmetry points [Formula: see text] and W which is an indication of high electron mobility at ambient condition. The presence of flat and dispersive bands around the Fermi energy level is an indication of high thermopower, and it is present in both the compounds FM-LiMn[Formula: see text]Nd[Formula: see text]O4 and AFM-Cu4Mn2Te4. From the present computations, at 300[Formula: see text]K, a power factor range of ([Formula: see text] scaled by relaxation time in [Formula: see text]W/msK2) [Formula: see text] and [Formula: see text] is obtained for ferromagnetic LiMn[Formula: see text]Nd[Formula: see text]O4 compounds at up and down spins, respectively. A typical power factor ([Formula: see text]Wm[Formula: see text]s[Formula: see text]K[Formula: see text]) of [Formula: see text] and [Formula: see text] is obtained for antiferromagnetic Cu4Mn2Te4 at 325[Formula: see text]K required for good thermoelectric performance.

Li2 MnO3 : A Catalyst for a Liquid Cl2 Electrode in Low-Temperature Aqueous Batteries.

Li2 MnO3 has been contemplated as a high-capacity cathode candidate for Li-ion batteries; however, it evolves oxygen during battery charging under ambient conditions, which hinders a reversible reaction. However, it is unclear if this irreversible process still holds under subambient conditions. Here, the low-temperature electrochemical properties of Li2 MnO3 in an aqueous LiCl electrolyte are evaluated and a reversible discharge capacity of 302 mAh g-1 at a potential of 1.0V versus Ag/AgCl at -78 °C with good rate capability and stable cycling performance, in sharp contrast to the findings in a typical Li2 MnO3 cell cycled at room temperature, is observed. However, the results reveal that the capacity does not originate from the reversible oxygen oxidation in Li2 MnO3 but the reversible Cl2 (l)/Cl- (aq.) redox from the electrolyte. The results demonstrate the good catalytic properties of Li2 MnO3 to promote the Cl2 /Cl- redox at low temperatures.

Multifunctional AlPO4 reconstructed LiMn2O4 surface for electrochemical lithium extraction from brine

LiMn2O4 (LMO) electrochemical lithium-ion pump has gained widespread attention due to its green, high efficiency, and low energy consumption in selectively extracting lithium from brine. However, collapse of crystal structure and loss of lithium extraction capacity caused by Mn dissolution loss limits its industrialized application. Hence, a multifunctional coating was developed by depositing amorphous AlPO4 on the surface of LMO using sol-gel method. The characterization and electrochemical performance test provided insights into the mechanism of Li+ embedment and de-embedment and revealed that multifunctional AlPO4 can reconstruct the physical and chemical state of LMO surface to improve the interface hydrophilicity, promote the transport of Li+, strengthen cycle stability. Remarkably, after 20 cycles, the capacity retention rate of 0.5AP-LMO reached 93.6% with only 0.147% Mn dissolution loss. The average Li+ release capacity of 0.5AP-LMO//Ag system in simulated brine is 28.77 mg/(g h), which is 90.4% higher than LMO. Encouragingly, even in the more complex Zabuye real brine, 0.5AP-LMO//Ag can still maintain excellent lithium extraction performance. These results indicate that the 0.5AP-LMO//Ag lithium-ion pump shows promising potential as a Li+ selective extraction system.

Structural stabilization of Cr-doped spinel LiMn2O4 for long-term cyclability towards electrochemical lithium recovery in original brine

Current explosive demand in raw lithium greatly boosts lithium mining, and electrochemical Li-extraction using spinel LiMn2O4 (LMO) from original brine has gained much attentions. In this study, Cr-doped LMO is prepared via a facile precipitation-calcination to elucidate the structural alterations and suppress Jahn-Teller distortion, and a novel hybrid capacitive deionization (HCDI) system of “Li-poor LiMn1.8Cr0.2O4||brine (recovery liquid)||activated carbon” is constructed for electrochemical Li-extraction. The results prove that Cr-doping effectively suppresses Mn3+ disproportionation induced by Jahn–Teller distortion, leading to a stabilized spinel framework for long lifespan. Importantly, the Cr-doping LMO realizes a stable (de)lithiation over 500 cycles with low manganese dissolution rate of 0.027 % per cycle. Meanwhile, the Li-extraction capacity can reach 22 mg g−1 in 1.0 M LiCl electrolyte with retention rate of 86.05 % after 500 cycles. In the assembled HCDI system, average Li-extraction capacity in brine reaches ∼15 mg g−1 after 15 cycles. Therefore, the HCDI system using Cr-doping LMO could introduce a new perspective for the industrial Li-extraction facing original brine.

Binder-Free LiMn2 O4 Nanosheets on Carbon Cloth for Selective Lithium Extraction from Brine via Capacitive Deionization.

In this study, a three-step strategy including electrochemical cathode deposition, self-oxidation, and hydrothermal reaction is applied to prepare the LiMn2 O4 nanosheets on carbon cloth (LMOns@CC) as a binder-free cathode in a hybrid capacitive deionization (CDI) cell for selectively extracting lithium from salt-lake brine. The binder-free LMOns@CC electrodes are constructed from dozens of 2D LiMn2 O4 nanosheets on carbon cloth substrates, resulting in a uniform 2D array of highly ordered nanosheets with hierarchical nanostructure. The charge/discharge process of the LMOns@CC electrode demonstrates that visible redox peaks and high pseudocapacitive contribution rates endow the LMOns@CC cathode with a maximum Li+ ion electrosorption capacity of 4.71mmol g-1 at 1.2V. Moreover, the LMOns@CC electrode performs outstanding cycling stability with a high-capacity retention rate of 97.4% and a manganese mass dissolution rate of 0.35% over ten absorption-desorption cycles. The density functional theory (DFT) theoretical calculations verify that the Li+ selectivity of the LMOns@CC electrode is attributed to the greater adsorption energy of Li+ ions than other ions. Finally, the selective extraction performance of Li+ ions in natural Tibet salt lake brine reveals that the LMOns@CC has selectivity ( = 7.48) and excellent cycling stability (100 cycles), which would make it a candidate electrode for lithium extraction from salt lakes.

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.

In Situ Forming Gel Polymer Electrolyte for High Energy-Density Lithium Metal Batteries.

In situ forming gel polymer electrolyte (GPE) is one of the most feasible ways to improve the safety and cycle performances of lithium metal batteries with high energy density. However, most of the in situ formed GPEs are not compatible with high-voltage cathode materials. Here, this work provides a novel strategy to in situ form GPE based on the mechanism of Ritter reaction. The Ritter reaction in liquid electrolyte has the advantage of appropriate reaction temperature and no additional additives. The polymer chains are cross-linked by amide groups with the formation of GPE with superior electrochemical properties. The GPE has high ionic conductivity (1.84 mS cm-1 ), wide electrochemical stability window (>5.25V) and high lithium ion transference number (≈0.78), compatible with high-voltage cathode materials. The Li|LiNi0.6 Co0.2 Mn0.2 O2 batteries with in situ formed GPE show excellent long-term cycle stability (93.4%, 300 cycles). The density functional theory calculation and X-ray photoelectron spectroscopyresults verify that the amide and nitrile groups are beneficial for stabilizing cathode structure and promoting uniform Li deposition on Li anode. Furthermore, the in situ formed GPE exhibits excellent electrochemical performance in Graphite|LiMn2 O4 and Graphite|LiNi0.5 Co0.2 Mn0.3 O2 pouch batteries. This approach is adaptable to current battery technologies, which will be sure to promote the development of high energy-density lithium-ion batteries.

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.

Real-Time Detection and Speciation of Mn Dissolution in a Li-Ion Battery Cathode

Rechargeable lithium-ion batteries (LIB) are widely used in portable electronic devices, electric vehicles, medical devices, etc. thanks to their improved performance in recent decades. The properties of the cathode still largely limit the overall performance, as the cathode usually has lower theoretical capacity and suffers from more serious degradation effects.1 Among these, dissolution of transition metals is an important but poorly understood side reaction. On the one hand, it dominates the cathode capacity fading by causing irreversible loss of active redox sites, phase transformation, cation mixing, grain fracture, etc. On the other hand, the dissolved transition metal ions can exacerbate the formation of the solid electrolyte interphase (SEI) on the anode through a dissolution-migration-deposition (DMD) process.2 Here, we focus on the dissolution of manganese from LiMn2O4 (LMO), a benchmark cathode material, through real-time analysis of the electrolyte by combining online inductively coupled plasma–optical emission spectroscopy (online ICP-OES) and rotating ring-disc electrode (RRDE) collection, Figure 1. Both methods offer real-time dissolution information as functions of time and potential/state of charge, while the former shows superior detection limits and the latter provides oxidation state information of the dissolving species.According to online ICP-OES, we find that Mn dissolves readily from fully lithiated LMO when brought in contact with aqueous 0.2 M Li2SO4, but that a dissolution-passivation process stops further detectable dissolution until well past fully delithiated λ-MnO2. The dissolution becomes detectable again on the returning scan to the potential of pristine LMO, and grows exponentially in the overlithiated region.3 Our RRDE results indicate that Mn2+ is the dominating dissolved Mn species only in overlithiation region, whereas it only accounts for a minor proportion in the dissolved species from delithiation region. The data from both techniques suggest that the dissolution of Mn is related to the surface state of the electrode, rather than its degree of lithiation, as widely believed in the past.4 Our results provide a better understanding of the mechanism of transition metal dissolution in cathode materials, as well as an entry point for screening next-generation cathodes and metal ion batteries with superior degradation characteristics.5

LT-LiMn0.5Ni0.5O2: A Unique Co-Free Cathode for High Energy Li-Ion Cells

Over the past decade, designing advanced, high energy density lithium-ion batteries has become necessary because of the increasing demand for electric vehicles and energy storage devices. Research efforts have focused largely on developing layered, Ni-rich cathode materials due to their high specific capacity. However, their structural and thermal instability and the relatively high cost of nickel raises a concern about their long-term viability.1 Developing next generation cathode materials, based on earth abundant elements such as manganese and iron, has therefore attracted much research interest.2 In the late 1990s, the Mn-based spinel cathode, LiMn2O4 (LMO), dominated the early development of Li-ion batteries for the electric vehicle market. The 3-D network of channels provided by the Mn2O4 spinel framework for Li+-ion diffusion channels enables a good rate performance. However, the operational capacity of Li1-xMn2O4 spinel cathodes in a lithium cell at ~4 V over the range 0<x£1 is limited by its low electrochemical capacity relative to layered cathodes. Although deep-discharging the cell at ~3 V allows the insertion of extra Li ions into the spinel framework (i.e., Li1+xMn2O4, 0£x£1), a rapid fade of capacity occurs as a result of a severe crystallographic (Jahn Teller) distortion, which prevents the use of the lower voltage reaction in commercial cells.In this presentation, a novel LT-LiMn0.5Ni0.5O2 (LT-LMNO) cathode material with unique electrochemical properties will be reported, where LT refers to its low synthesis temperature (400 °C). In striking contrast to a layered electrode with the same composition, HT-LiMn0.5Ni0.5O2 (where HT = high temperature synthesis, ~850 °C), LT-LMNO has a composite configuration with structurally-integrated lithiated spinel- and layered-like components.3, 4 It provides an electrochemical capacity almost twice that of LMO. This discovery provides a new strategy for developing next-generation. Mn-rich spinel-based cathodes.References Bianchini, M.; Roca-Ayats, M.; Hartmann, P.; Brezesinski, T.; Janek, J., There and Back Again - The Journey of LiNiO2 as a Cathode Active Material. Chem. Int. Ed. Engl. 2019, 58 (31), 10434-10458.Croy, J. R.; Gutierrez, A.; He, M.; Yonemoto, B. T.; Lee, E.; Thackeray, M. M., Development of Manganese-rich Cathodes as Alternatives to Nickel-rich Chemistries. Power Sources 2019, 434, 226706.Thackeray, M. M.; Lee, E.; Shi, B.; Croy, J. R., Review: From LiMn2O4 to Partially-Disordered Li2MnNiO4: The Evolution of Lithiated-Spinel Cathodes for Li-Ion Batteries. Electrochem. Soc. 2022, 169 (2), 020535.Shi, B.; Gim, J.; Li, L.; Wang, C.; Vu, A.; Croy, J. R.; Thackeray, M. M.; Lee, E., LT-LiMn5Ni0.5O2: A Unique Co-free Cathode for High Energy Li-ion Cells. Chem. Comm. 2021, 57 (84), 11009-11012.

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).

Rational Design of Zincophilic Ag/Permselective PEDOT:PSS Heterogeneous Interfaces for High-Rate Zinc Electrodeposition.

Designing artificial interface is a promising strategy to protect Zn metal anode but achieving long Zn plating/stripping lifespans and efficient nucleation/deposition kinetics, particularly at high current densities, remains a challenge. In this study, a permselective zincophilic heterogeneous interface consisting of metallic Ag layer and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is designed via a simple chemical displacement and drop casting process. The artificial interface plays a multifunctional role in inhibiting dendrite growth/side reactions by reducing the nucleation barrier through a large number of Zn nucleation sites offered by the bottom Ag layer, homogenizing electrical field/Zn2+ flux and shielding SO4 2- migration via the compact, conducting, and Zn2+ -permselective PEDOT:PSS supporting layer. Moreover, the heterogeneous interface demonstrates enhanced structural integrity owing to the binder effect of PEDOT:PSS. As a result, the modified Zn anode demonstrates a cyclic lifespan of 200h and a reduced voltage hysteresis of ≈150mV at 20mA cm-2 /5 mAh cm-2 , far surpassing its counterparts. Moreover, the protected Zn anode allows the LiMn2 O4 -based full cells with remarkable rate and cycling performance. These findings provide new insight into the design of an efficient artificial interface for highly reversible and high-rate Zn electrodeposition.

3D Nanocomposite Thin Film Cathodes for Micro‐Batteries with Enhanced High‐Rate Electrochemical Performance over Planar Films

AbstractHigh energy and high power density rechargeable micro‐batteries are a necessity for powering the next generation of flexible electronics, internet of things, and medical technology devices. In theory, significant improvements in the capacity, current and power densities of micro‐batteries would result if 3D architectures with enhanced interdigitated component interface areas and shortened ion diffusion path‐lengths were used. Further gains are achievable if the materials utilized have high crystalline quality and are preferentially oriented for fast lithium intercalation. In this work, this is achieved by creating epitaxial thin film cathodes comprised of nanopillars of LiMn2O4 (LMO) embedded in a supporting matrix of electronically conducting SrRuO3 (SRO). The first electrochemical study of such a 3D vertically aligned nanocomposite (VAN) that displays clear cathode redox signatures is provided, and demonstrates remarkable capacity retention under high‐rate regimes. The electrochemical performance is shown to be dependent on the nanopillar topography, namely the crystallographic orientation, nanopillar dimensions, and electrode/electrolyte interfacial surface area. This work offers a pathway to realizing 3D architectured micro‐batteries with high‐capacity retention under high‐rate conditions enabling fast charge capabilities.

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.

General Synthesis of Single-Crystal Spinel Cathodes with the Tailored Orientation of Exposed Crystal Planes for Advanced Lithium-Ion Batteries.

The spinel Mn-based cathodes with 3D Li+ diffusion channels, high voltage, and low-cost show promise for developing high-power lithium-ion batteries (LIBs). But the disproportionation and Jahn-Teller distortion lead to structural degeneration and capacity decay, especially at high working temperatures. Herein, considering the merits of single crystals and orientation of exposed crystal planes, single-crystal truncated octahedral LiMn2 O4 (TO-LMO) with exposed {111}, {100} and {110} facets is rationally designed, in which the mainly exposed {111} facets are truncated by a small portion of {100} and {110} facets. The Li-deficient intermediate phase is innovatively proposed to prepare the single-crystal TO-LMO. The synergistic effects of single crystals and the orientation of exposed crystal planes significantly reduce the disproportionation of Mn3+ ions and thereby improve their structural stability. Consequently, the cycling stability of the single-crystal TO-LMO is remarkably enhanced, obtaining outstanding capacity retention of 84.3% after 2000 cycles, much better than that of 61.2% for octahedral LiMn2 O4 . The feasibility of preparing single-crystal truncated octahedral LiNi0.5 Mn1.5 O4 with exposed {111}, {100}, and {110} facets via the Li-deficient intermediate phase is further demonstrated. These findings offer new insight into regulating the orientation of exposed crystal planes and improving the reversibility of Mn-based redox couples in LIBs.

An investigation of the lattice parameter and micro-strain behaviour of LiMn2O4 coated with LiMn1.5Ni0.5O4 to attain high-rate capability and cycling stability

This research provides new insights on the lattice parameters, development of micro strain, and electrochemical properties of uniquely-designed core-shell structure of the LiMn2O4@LiMn1.5Ni0.5O4 composite. The investigation of lattice expansion and contraction during cycling, and evolution of micro strain, provided a better mechanistic understanding of Li+ diffusion. The LiMn2O4 (LMO) was successfully interfaced with LiMn1.5Ni0.5O4 (LMNO) to modify the surface of spinel LiMn2O4 particles through solution combustion and Pluronic polymer assisted composite synthesis. The unique synthesis approach significantly enhanced the rate capability. The LMO@LMNO composite was characterized using XRD, XPS, TEM, CV and charge/discharge characterization. The material characterization results confirmed that the LMO@LMNO composite had slightly larger lattice parameter (8.24027 Å) compared to the pristine LMO (8.2402 Å) and LMNO (8.18511 Å). The micro-strain of the composite is 2.1 × 10−3 μm/m (LMO@LMNO); this is higher than the individual components 1.28 × 10−3 μm/m (LMO), and 1.22 × 10−3 μm/m (LMNO). As expected, the micro-strain of the composite increased during composite formation which induces defects and microscopic stresses. The LMO@LMNO sample exhibited superior electrochemical properties at all current rates as compared LMO. The LMNO delivered a low capacity for high current rates compared to LMO and LMO@LMNO samples; this was attributed to the unique synthesis approach. The first cycle capacities of LMO, LMNO, and LMO@LMNO, were 101 mAh g−1, 125 mAh g−1, 123 mAh g−1 (0.2C). As expected, the discharge capacities for LMO, LMNO, and LMO@LMNO reduced after 120 cycles to 95 mAh g−1 (94 %), 122 mAh g−1 (97.3 %) and 119 mAh g−1 (96.2 %), respectively. In brief, composite LMO@LMNO core-shell structure exhibited superior electrochemical properties due to the higher Ni ratios coupled with the formation a surface layer.

Semi-Metallic Superionic Layers Suppressing Voltage Fading of Li-Rich Layered Oxide Towards Superior-Stable Li-Ion Batteries.

Li-rich layered oxides (LRLOs) with greater specific capacity density are constrained by voltage attenuation and inferior rate performance because of irreversible oxygen release, metal dissolving and poor lithium-ion transport capacity. Herein, a simple surface modification is designed to solve the performance degradation and structural collapse of LRLOs. Combining experiments with density functional theory (DFT) calculations, a semi-metallic LiMn2 O4 -like structure (LMO) with spin-polarized conducting electrons, is introduced to the surface of the cathode restrains the activated surficial lattice oxygen ions by its stable oxygen vacancies. Additionally, Ni doping results in a fast-ion conductor Li0.8 Nb0.96 Ni0.2 O3 structure (LNO) with lowered lithium ions diffusion barrier, which is tightly conjugating to substrate and synergistically reinforces the Li diffusion path through the cathode-electrolyte interphase. Moreover, Mn dissolution is successfully relieved due to the decrease in Mn concentration in the coating layers. As a result, the modified material (LRLO@LMO@LNO) exhibits an ultra-high discharge capacity of 120.4 mAh g-1 even at 10 C with a very small discharge voltage attenuation of 313 mV after 600 cycles (0.52 mV per cycle) at 1 C. Undoubtedly, this method discloses a simple and effective approach to promote the practical utilization of high-energy-density.

Four-step constant voltage operation of hybrid capacitive deionization with composite electrodes for bifunctional deionization and lithium recovery

Efficient recovery of valuable resources from wastewater has emerged as a critical challenge in the era of carbon neutral society. Capacitive deionization (CDI) has been employed in electrochemical lithium recovery (ELR) processes based on selective Li+ intercalation to LiMn2O4 (LMO). We herein propose a four-step constant voltage operation (forward/zero/reverse/zero) of bifunctional hybrid CDI to produce deionized water as well as Li+-rich concentrate within a cycle. Especially, selective Li+ enrichment was possible without influent replacement since adsorption of competing ions and liberation of Li+ could occur simultaneously. This unique performance was enabled by composite electrodes on capacitive activated carbon cloth (ACC) impregnated with redox-active materials; LMO@ACC and Ag@ACC. Together with material characterization and electroanalysis on the composite electrodes, deionization (step 1; forward voltage) and Li+ enrichment (step 3; reverse voltage) by assembled LMO@ACC//Ag@ACC cell were evaluated by single pass experiments with binary NaCl and LiCl solution (10 mM each). Besides, a multi-stage operation with internal recycle confirmed long-term stability and continuous increase of Li purity for practical implementation. The advanced bifunctional CDI (ELR coupled with water treatment) paved a way to advance the resource recycle from wastewater.

Selective recovery of lithium from spent lithium-ion battery by an emission-free sulfation roasting strategy

As the economy recovered from the COVID-19 epidemic, the price of Li2CO3 skyrocketed to the highest. Recovery of lithium from spent lithium-ion batteries (LIBs) is significant for addressing lithium shortage and environmental issues. Sulfation roasting is often accused of being unsustainable and not environmentally friendly due to the consumption of expensive sulfation reagents and emission of SO2. Herein, a novel and green recycling process for selective separation of lithium from spent LiMn2O4 (LMO) batteries was proposed based on a SO2 emission free sulfation roasting with waste copperas. Lithium in the cathode power were selectively sulfated into soluble Li2SO4 with a conversion of 99.50%, while manganese was riched as insoluble oxides. At low temperature (e.g. 400 °C), LMO were difficult to be sulfated due to the limited sulfation ability of SO42- and mass transfer. When the roasting temperature reached 700 °C, SO2 was produced and the generated SO2 reacted in situ with the LMO to form Li2SO4 and MnSO4, preventing SO2 emissions into the atmosphere. As temperature continued to increase, the MnSO4 acted as a sulfation reagent and sulfated the unreacted LMO. All the sulfur was immigrated in Li2SO4, rather than being emitted as SO2.