Dissolution Of Mn Ions Research Articles

Surface iron concentration gradient: A strategy to suppress Mn3+ Jahn-Teller effect in lithium manganese iron phosphate

To address the low energy density of LiFePO4 (LFP) for electric vehicles and high-voltage energy storage, LiMn0.5Fe0.5PO4 (LMFP) provides a potential solution but faces performance degradation due to Mn3+-induced Jahn-Teller distortion and Mn ion dissolution during cycling. This study proposes a surface engineering strategy to enhance LMFP’s electrochemical performance by increasing surface iron concentration and reducing manganese content, based on the electronic differences between Mn3+ and Fe3+ in MO6 octahedra. Density Functional Theory (DFT) calculations confirmed the viability of this approach by analyzing volume changes and binding energies with HF during charging. Guided by DFT, an LMFP@LFP/C material was synthesized with a high-iron-concentration surface layer (∼2 nm), as observed through AC-STEM. Post-cycling TEM analysis and corrosion simulations demonstrated that LMFP@LFP/C suppresses Mn ion dissolution and stabilizes the crystal lattice compared to unmodified LMFP/C. Electrochemical tests showed that LMFP@LFP/C has superior electronic conductivity and faster lithium-ion diffusion. It delivered an initial discharge capacity of 150.82 mAh g−1 at 0.1C, surpassing LMFP/C (147.65 mAh g−1). At 1C, LMFP@LFP/C retained 95.85 % of its capacity after 500 cycles, significantly outperforming LMFP/C (74.18 %). This surface modification strategy advances phosphate-based cathode materials for electric vehicles and renewable energy applications.

Interfacial deterioration in highly fluorinated cation-disordered rock-salt cathode: Carbonate-based electrolyte vs. ether-based electrolyte

Cation-disordered rock-salts (DRX) emerge as an intriguing class of high-capacity cathode materials, garnering significant attention in the development of advanced energy-storage systems. Fluorination strategies have been raised to regulate redox and structure for better DRX electrochemical performance. However, research on the interfacial processes during fluorinated DRX cycling remains limited. Here, we evaluate a highly fluorinated DRX, Li2Mn2/3Nb1/3O2F (LMNOF), in different electrolytes to correlate its cycling performance with distinct interfacial evolutions. During cycling in the carbonate-based electrolyte, a thick Mn-containing CEI forms on the LMNOF surface, leading to gradual capacity decay. Intriguingly, the addition of fluoroethylene carbonate (FEC) would bring about surface oxygen loss, Mn-ion dissolution and formation of a fluorinated surface layer by reacting with the LMNOF surface, which critically deteriorate the cycling performance. In comparison, the ether-based electrolyte is compatible with the LMNOF surface, resulting in a more favorable cycling stability. This work sheds light on the interfacial deterioration mechanism of LMNOF cathode in traditional carbonate-based electrolyte, emphasizing the importance of using advanced non-reactive electrolytes to enhance DRX performance.

Electrode interface modulation using 1,3-propane sultone functionalized additives for high-performance Zn-MnO2 aqueous batteries

Rechargeable aqueous zinc-manganese dioxide (Zn-MnO2) batteries have gained significant attention in the field of energy storage systems owing to their cost-effectiveness, environmental friendliness, power, and ability to mitigate thermal propagation. However, Zn- MnO2 batteries encounter challenges and limitations, including capacity degradation and voltage hysteresis by the dissolution of Mn ions in the bulk electrolyte. In this study, interfacial stabilization is improved by promoting the decomposition of the 1,3-propane sultone (PS) electrolyte additive, which occurs close to the oxidation decomposition at 1.5 V. This facilitates the formation of a stable cathode–electrolyte interphase (CEI) and effectively suppresses Mn-ion dissolution. Density functional theory (DFT) simulations provide insights into the formation of a CEI layer product structure during cell operation, resulting in the thermodynamically reduced dissolution of Mn (Mn2+) into the electrolyte when a sulfur-based decomposed layer covers MnO2. Consequently, the cathode protection layer ensures high cycle retention, Coulombic efficiency, and high C-rate cell operating conditions for the Zn-MnO2 battery cell. This work presents a promising strategy for designing electrolytes to develop high-performance aqueous zinc-ion batteries.

Boosting interface compatibility of high-voltage LiNi0.5Mn1.5O4 cathode materials with an ionic-conductive Li0.33La0.56TiO3 coating

High voltage LiNi0.5Mn1.5O4 (LNMO) is a crucial cathode material for lithium-ion batteries (LIBs) aiming at high energy densities. However, its performance is hindered by the dissolution of transition metal ions and the instability of the cathode electrolyte interface (CEI) film at elevated voltages. To address these issues, we report a solvothermal method to prepare LNMO coated with Li+-conductor Li0.33La0.56TiO3 (LNMO@LLTO). Our study reveals that the LLTO coating not only enhances ion diffusion at the interface, minimizing the Li+ concentration gradient, and acts as a barrier against Mn-ion dissolution. This coating minimizes side reactions, mitigates structural degradation, and promotes the formation of a stable and balanced CEI film that incorporates LLTO, thus ensuring the long-term cycle stability. When compared to bulk LNMO, the LNMO@LLTO cathode demonstrates superior performance, maintaining reversible capacities of 111.4 and 102.2 mAh·g−1 after 500 cycles at 2 and 5C at 25 °C, respectively. Even at 60 °C, the LNMO@LLTO maintains a high capacity of 94.3 mAh·g−1 with minimal electrochemical polarization after 200 cycles at 2C. This simple preparation technique, together with its performance promotion, offers new insights into the development of high voltage cathode materials for high energy density LIBs.

Mn-HCF@Fe-HCF Core–Shell Architecture: Enhancing Structural Stability and Electrochemical Performance of Sodium-Ion Batteries

To overcome the structural failure of Manganese-based Prussian blue analogue (Mn-HCF) as a cathode material of sodium ion batteries caused by Mn ion dissolution induced by Jahn–Teller effect, we coated Mn-HCF with iron-based Prussian blue (Fe-HCF) to prepare the core–shell Mn-HCF@Fe-HCF cathode material for sodium ion batteries through co-precipitation method. The research results indicate that this structure effectively blocks the direct contact between Mn-HCF and electrolyte, thereby minimizing the dissolution of [Formula: see text] in the electrolyte and significantly improving the cycling stability and rate performance. The discharge capacity of this material at a current density of 0.1[Formula: see text]C (14[Formula: see text]mA[Formula: see text][Formula: see text] is 129.7[Formula: see text]mAh[Formula: see text][Formula: see text]. It still has a capacity of 87.4[Formula: see text]mAh[Formula: see text][Formula: see text] at a current density of 2[Formula: see text]C (280[Formula: see text]mA[Formula: see text][Formula: see text], and still has a capacity retention rate of 84.3% (91[Formula: see text]mAh[Formula: see text][Formula: see text] after 100 cycles at a current density of 0.5[Formula: see text]C (70[Formula: see text]mA[Formula: see text][Formula: see text]. Compared with the capacity retention rate of 51.5% of Mn-HCF 100 cycles before coating, the cycle stability of Mn-HCF@Fe-HCF is greatly improved.

High-performance lithium batteries achieved by electrospun MXene-Enhanced cation-selective membranes

Conventional separators applied in lithium batteries face limitations like low porosity, poor electrolyte wettability, lower cation selectivity, and thermal instability, which impact battery performance and safety characteristics. Besides the challenge in separator design, transition metal ion migration from positive electrodes during cycling greatly accelerates capacity fading because of unrestricted diffusion of transition metal cation across the separator. This study explores an innovative strategy for the separator design by incorporating MXene (spraying MXene solution on both sides of the separator), a two-dimensional material, into electrospun Polyacrylonitrile/Polyetherimide membranes with the function of cation selection. Li+ can be accelerated, and its transference number increases along with the anion limitation in the MXene layer. Ni, Co, and Mn ion dissolution from the positive electrode is inhibited due to the cation selectivity of the MXene layer. Leveraging electrospinning advantages, the resultant membranes exhibit high porosity, excellent liquid absorption, mechanical strength, and superior thermal properties. Benefiting from MXene's layered structure and excellent adsorption ability, the membrane significantly inhibits the dissolution of transition metal ions while enabling smooth lithium deposition due to its cation selectivity. Eventually, the Li||NMC811 batteries deliver outstanding cyclic performance (91.3 % capacity retention after 200 cycles) and robust lithium dendrite suppression (800 h of stable cycling). Moreover, the MXene-modified membrane demonstrates exceptional electrolyte wettability, significantly improving ionic transference number (0.67) and conductivity (1.6 mS/cm). Modification of membrane surfaces with MXene offers insights into addressing transition metal ion migration from the positive electrode material perspective, providing a promising avenue for high-performance LIBs.

A Feasible Dual Modification Strategy of Internal Anion Redox Chemistry and Surface Engineering on P2 Layer-Structured Cathodes in Sodium-Ion Batteries.

Boosting the anion redox reaction opens up a possibility of further capacity enhancement on transition-metal-ion redox-only layer-structured cathodes for sodium-ion batteries. To mitigate the deteriorating impact on the internal and surface structure of the cathode caused by the inevitable increase in the operation voltage, probing a solution to promote the bulk-phase crystal structure stability and surface chemistry environment to further facilitate the electrochemical performance enhancement is a key issue. A dual modification strategy of establishing an anion redox hybrid activation trigger agent inside the crystal structure in combination with surface oxide coating is successfully developed. P2-type layer structure cathode materials with Zn/Li (Na-O-Zn@Na-O-Li) anion redox hybrid triggers and a ZnO coating layer possess superior capacity and cycle performance, along with outstanding structural stability, decreased Mn-ion dissolution effect, and less crystal particle cracking during the cycling process. This study represents a facile modification solution to perform structure optimization and property enhancement toward high-performance layered structure cathode materials with anion redox features in sodium-ion batteries.

Reinforcing the stability of cobalt-free lithium-rich layered oxides via Li-poor Ni-rich surface transformation

We report a lithium-rich layered oxide Li1.2Mn0.6Ni0.2O2 (LMNO) with an electrochemically stable Li-poor nickel-rich surface by simple excessive calcination treatment, greatly suppressing the surface side reactions and Mn-ion dissolution.

High-cycling Stability of Zn/MnHCF Batteries Boosted by Non-aqueous Ethanol Electrolyte

Potassium manganese hexacyanoferrate (MnHCF) is a promising cathode material in aqueous zinc-ion batteries (ZIBs) due to its high capacity and operating potential. This study improves its electrochemical performance by using ethanol (EA) as the electrolyte solvent, which can effectively inhibit the dissolution of Mn ions and crystalline phase transformation of MnHCF. This study is of great significance for improving the cycling stability of ZIBs.

Promoting the electrochemical performance of commercial LiMn2O4 by hydrothermal modification with poly (vinylidene fluoride)

The fast capacity decay and poor rate performance hinder the application of commercial LiMn2O4 (LMO) cathode in Li-ion batteries despite the low cost and environmental friendliness. Herein, commercial LMO was hydrothermally modified with poly (vinylidene fluoride) (PVDF). The PVDF-modified LMO with 1.0 wt% PVDF exhibits excellent rate performance (delivering discharge capacities of 128.2, 121.7, 112.4, 99.9, 85.5, 62.4 mAh g−1 at current densities of 20, 50, 100, 200, 400, 800 mA g−1, respectively) and superior cyclability (attaining capacity retention above 90% after 150 cycles at 100 mA g−1). The enhanced performance associates with the uniform PVDF coating on the surface of LMO particles (which suppresses the dissolution of Mn-ions in electrolyte to maintain the structural stability of LMO) and F-doing in LMO (which improves Li+ conductivity and reversible capacity). The PVDF-modification may push the application of the commercial LMO cathode forward.

Understanding the Effect of Al Doping on the Electrochemical Performance Improvement of the LiMn2O4 Cathode Material.

It is well known that the electrochemical performance of spinel LiMn2O4 can be improved by Al doping. Herein, combining X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) with in situ electron-beam (E-beam) irradiation techniques, the influence of Al doping on the structural evolution and stability improvement of the LiMn2O4 cathode material is revealed. It is revealed that an appropriate concentration of Al3+ ions could dope into the spinel structure to form a more stable LiAlxMn2-xO4 phase framework, which can effectively stabilize the surface and bulk structure by inhibiting the dissolution of Mn ions during cycling. The optimized LiAl0.05Mn1.95O4 sample exhibits a superior capacity retention ratio of 80% after 1000 cycles at 10 C (1 C = 148 mA h g-1) in the voltage range of 3.0-4.5 V, which possesses an initial discharge capacity of 90.3 mA h g-1. Compared with the undoped LiMn2O4 sample, the Al-doped sample also shows superior rate performance, especially the capacity recovery performance.

Polypyrrole/Al2O3/LiMn2O4 cathode for enhanced storage of Li ions

LiMn2O4 (LMO) is a promising cathode material for the assembly of lithium ion batteries in that it satisfies the requirement for a high specific capacity, but it lacks structural stability during long-term cycling. To overcome this challenge, Al2O3 and PPy are coated onto LiMn2O4 (PPy/Al2O3/LMO) using a sol–gel method followed by oxidative chemical polymerization. The discharge capacity of PPy/Al2O3/LMO reaches 121.73 mAh g−1 at a rate of 1C. The retention is as high as 95.81% even after 100 charge/discharge cycles. The enhanced performance of PPy/Al2O3/LMO for Li ion storage results from improved electron conductivity, a more rapid ion migration rate, and reduced Mn ion dissolution. This strategy could be further utilized for the synthesis of other cathode materials for use in lithium ion batteries.

Efficient Stabilization of Na Storage Reversibility by Ti Integration into O′3-Type NaMnO 2

The development of an energy storage system with abundant elements is a key challenge for a sustainable society, and the interest of Na intercalation chemistry is extending throughout the research community. Herein, the impact of Ti integration into NaMnO 2 in a binary system of x NaMnO 2 –( 1 – x ) TiO 2 ( 0.5 ≤ x ≤ 1 ) is systematically examined for rechargeable Na battery applications. Stoichiometric NaMnO 2 , which is classified as an in-plane distorted O ′ 3-type layered structure, delivers a large initial discharge capacity of approximately 200 mAh g -1 , but insufficient capacity retention is observed, most probably associated with dissolution of Mn ions on electrochemical cycles. Ti-substituted samples show highly improved electrode performance as electrode materials. However, the appearance of a sodium-deficient phase, Na 4 Mn 4 Ti 5 O 18 with a tunnel-type structure, is observed for Ti-rich phases. Among the samples in this binary system, Na 0.8 Mn 0.8 Ti 0.2 O 2 ( x = 0.8 ), which is a mixture of a partially Ti-substituted O ′ 3-type layered oxide (Na 0.88 Mn 0.88 Ti 0.12 O 2 ) and tunnel-type Na 4 Mn 4 Ti 5 O 18 as a minor phase elucidated by Rietveld analysis on both neutron and X-ray diffraction patterns, shows good electrode performance on the basis of energy density and cyclability. Both phases are electrochemically active as evidenced by in situ X-ray diffraction study, and the improvement of reversibility originates from the suppression of Mn dissolution on electrochemical cycles. From these results, the feasibility of Mn-based electrode materials for high-energy rechargeable Na batteries made from only abundant elements is discussed in detail.

Unravelling high-temperature stability of lithium-ion battery with lithium-rich oxide cathode in localized high-concentration electrolyte

Abstract Lithium (Li)-rich manganese (Mn)-rich oxide (LMR) cathode materials, despite of the high specific capacity up to 250 mAh g−1 suffer from instability of cathode/electrolyte interfacial layer at high working voltages, causing continuous voltage decay and capacity fading, especially at elevated temperatures. In various battery systems, localized high-concentration electrolytes (LHCEs) have been widely reported as a promising candidate to form effective electrode/electrolyte interphases. Here, an optimized LHCE is studied in graphite (Gr)-based full cells containing LMR cathode, being cycled at 25, 45 and 60 °C with the reference of a conventional LiPF6-based electrolyte. It is revealed that the LHCE can effectively suppress continuous electrolyte decompositions and mitigate the dissolution of Mn ions due to the formation of more protective electrode/electrolyte interphases on both anode and cathode, which, in turn, lead to significantly improved cycling stability and enhanced rate capability under the selected temperatures. The mechanistic understanding on the failure of the conventional LiPF6-containing electrolyte and the function of the LHCE in Gr||LMR cells under high temperatures provides valuable perspectives of electrolyte development for practical applications of LMR cathodes in high energy density batteries over a wide temperature range.

Self-templated hollow LiMn2O4 nanofibers as extremely long lifespan lithium ion battery cathode

The poor cyclability and inferior capacity retention caused by severe Jahn–Teller effect and dissolution of Mn ions into electrolyte during cycling hinder the commercial application of spinel LiMn2O4 with low cost and non-toxic. Herein, hollow LiMn2O4 nanofibers composed of LiMn2O4 nanograins are proposed, forming 3D network framework with uniform distribution. The slender and firm nanofibers can effectively buffer the irreversible phase transitions triggered by Mn3+ disproportionation and Jahn–Teller distortion and lead to the extremely long cycle life of LiMn2O4 cathode. Meanwhile, the huge specific surface area provided by hollow structure ensures the full contact between the materials and electrolyte, being beneficial to the diffusion of Li ions and transfer of electron to maintain its capacity. It can be observed that the capacity retention is 97.5% after 1000 cycles at 1C. The structure design of the hollow nanofibers modified the LiMn2O4 cathode material at the micro-level, which greatly improves the long-term cycling stability of the material and provides reference for the modification in lithium ion batteries.

Understanding the role of water-soluble guar gum binder in reducing capacity fading and voltage decay of Li-rich cathode for Li-ion batteries

The practical application of high-capacity Li-rich cathode materials is hindered by capacity fading and voltage decay. The capacity fading and voltage decay could be effectively overcome by using water-soluble guar gum (GG) binder instead of traditional polyvinylidene fluoride (PVDF). However, the specific role of the GG binder is not clear yet, though the GG binder can significantly improve the electrochemical performance of Li-rich cathode. To understand the effect of GG binder on the morphology, microstructure of electrode and electrode/electrolyte interfaces, ex-situ scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray adsorption near edge spectroscopy (XANES), in-situ electrochemical impedance spectroscopy (EIS) were applied to comparatively study the charge-discharge processes of Li-rich Li1.2Ni0.2Mn0.6O2 cathode when using GG and PVDF as binders. The results indicate that the GG binder can prevent electrode crack and active material loss, ascribing to the strong mechanical adhesion of GG binder with active material particles and current collector. It has found that the GG binder can also induce the formation of a uniform layer on Li1.2Ni0.2Mn0.6O2 particles’ surface. As a consequence, both the electrolyte decomposition and the electrode corrosion were significantly inhibited. The strong chelation between Mn2+ and polar OH group restrain Mn ion dissolution, which contributes to surface structural transformation mitigation. The present study reveals the role of water-soluble GG binder in reducing capacity fading and voltage decay of Li-rich material and is of great importance in design functional binders for high-performance Li-rich electrodes.

Mn Ion Dissolution Mechanism for Lithium-Ion Battery with LiMn2O4 Cathode: In Situ Ultraviolet-Visible Spectroscopy and Ab Initio Molecular Dynamics Simulations.

The dissolution of transition-metal (TM) cations into a liquid electrolyte from cathode material, such as Mn ion dissolution from LiMn2O4 (LMO), is detrimental to the cycling performance of Li-ion batteries (LIBs). Though much attention has been paid to this issue, the behavior of Mn dissolution has not been clearly revealed. In this work, by using a refined in situ ultraviolet-visible (UV-vis) spectroscopy technique, we monitored the concentration changes of dissolved Mn ions in liquid electrolyte from LMO at different state of charge (SOC), confirming the maximum dissolution concentration and rate at 4.3 V charged state and Mn2+ as the main species in the electrolyte. Through ab initio molecular dynamics (AIMD) simulations, we revealed that the Mn dissolution process is highly related to surface structure evolution, solvent decomposition, and lithium salt. These results will contribute to understanding TM dissolution mechanisms at working conditions as well as the design of stable cathodes.

Descriptor-Based Analysis of Atomic Layer Deposition Mechanisms on Spinel LiMn2O4 Lithium-Ion Battery Cathodes

Protective coatings have been shown to effectively suppress Mn ion dissolution from the spinel LiMn2O4 lithium-ion battery cathode by stabilizing the surface against undesired side reactions with t...

Chemical valence electron-engineered LiNi0.4Mn1.5MtO4 (Mt = Co and Fe) cathode materials with high-performance electrochemical properties

LiNi0.5Mn1.5O4 (LNMO) with a spinel crystalline structure exhibits excellent properties such as a high voltage of ~4.7 V and a fairly high theoretical capacity of ~147 mAh g−1 as well as low cost. However, LNMO cathode materials exhibit a deteriorated high-rate performance and capacity fading because of their low structural stability caused by dissolution of Mn ions into the electrolyte via the Jahn–Teller effect during the Li+ ion insertion/desertion process. Herein, to obtain electrochemical/structural stabilities and to prevent dissolution of Mn ions from pristine LNMO, we designed Mt-doped LNMO cathode materials (LiNi0.4Mn1.5MtO4) with different transition metal elements (Mt = Co and Fe) having a chemical valence electron of Mt3+ using a hydrothermal method. All samples exhibited that the Mt-doped LNMO structures were homogeneously doped with Co and Fe elements. Furthermore, compared with the undoped LNMO materials, the Mt-doped LNMO cathode materials showed superior electrochemical properties in terms of high discharge capacities (121.1 mAh g−1) at 120 mA g−1 and good cycle retentions (over 99.7%) after 200 cycles as well as improved high-rate performance, because of the well-engineered valance and disordered structure for the doping of Mt3+, preventing the dissolution of Mn ions via the Jahn–Teller distortion.

Improved High Temperature Performance By a Modified Phosphate-Coating on 5 V LiNi0.5Mn1.5O4 Cathode Materials for Li Ion Battery

In this work, the FePO4-coated spinel LiNi0.5Mn1.5O4 cathode materials are successfully prepared by the solid-state reaction and wet precipitation method. The effect of FePO4 coating on the physical and electrochemical properties were examined by X-ray diffraction (XRD), micro-Raman spectroscopy (micro-Raman), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), C-rate and cycling tests (at 25 oC and 55 oC). The results show that FePO4 coating can greatly mitigate the dissolution of Mn ions into electrolyte from LiNi0.5Mn1.5O4, resulting in excellent cycling stability and rate capability. In all samples tested, it was found that the sample containing 1 wt.% of FePO4 coating presents the best electrochemical performance. It delivers discharge capacities of 112.05 mAh g-1 (at 25 oC) and 101.71 mAh g-1 (at 55 oC) at 1 C rate, with the corresponding capacity retention of 99.3% and 88.4% after 100 cycles. In addition, the cathode material presents a superior high discharge capacity of 104.92 mAh g-1 and 91.70 mAh g-1 at 5 C and 10 C rates, respectively. More importantly, the enhancement of electrochemical performance is related to the fact that the phosphate coating layer effectively diminishes the side reactions, which occurred at interface of the 5 V LiNi0.5Mn1.5O4 cathode and the electrolyte. Keywords: lithium-ion batteries, spinel LiNi0.5Mn1.5O4, 5V cathode materials, FePO4-coated, high-temperature.