The sustainable electrochemical behavior of Li-metal/ion batteries heavily relies on the modulation of solid-electrolyte interphases (SEI) formed on their electrodes. In this study, we introduced trimesic acid (TMA) and terephthalic acid (TPA) into a conventional liquid electrolyte solution (LP57) comprised of 1.0 M LiPF6 in EC/EMC (3:7) to create suspension electrolyte systems. These solutions were tested in high-voltage Li and Li-ion cells comprising Li metal or graphite anodes (respectively) and LiNi0.5Mn1.5O4 (LNMO spinel) cathodes. The electrolyte solutions' modifications tested herein resulted in forming a LiF-rich interphase on the negative electrodes, which improved the Li-plating and stripping process, lowered voltage hysteresis, and reduced electrolyte solutions decomposition during prolonged electrochemical processes. We tested the suspension electrolyte systems in comparison to LP57 in Li & boxv;LNMO and Gr & boxv;LNMO cells at 30 degrees C and established significant improvements in the electrochemical performance, including long-term cycling, rate capability and capacity retention, average voltage, hysteresis, and evolution of the direct current internal resistance (DCIR) of cells containing the modified suspension solutions compared to the reference cells. The LNMO cathodes in Li-cells comprising the suspension electrolyte systems displayed remarkable structural, morphological, and thermal stability during prolonged cycling, delivering 98 % and 92 % capacity retention after 400 cycles in LP57 + TMA and LP57 + TPA, respectively, compared to only 38 % in the cells containing the conventional LP57 solution.

The design of cathode/electrolyte interfaces in high-energy density Li-ion batteries is critical to protect the surface against undesirable oxygen release from the cathodes when batteries are charged to high voltage. However, the involvement of the engineered interface in the cationic and anionic redox reactions associated with (de-)lithiation is often ignored, mostly due to the difficulty to separate these processes from chemical/catalytic reactions at the cathode/electrolyte interface. Here, a new electron energy band diagrams concept is developed that includes the examination of the electrochemical- and ionization- potentials evolution upon batteries cycling. The approach enables to forecast the intrinsic stability of the cathodes and discriminate the reaction pathways associated with interfacial electronic charge-transfer mechanisms. Specifically, light is shed on the evolution of cationic and anionic redox in high-energy density lithium-rich 0.33Li2MnO3·0.67LiNi0.4Co0.2Mn0.4O2 (HE-NCM) cathodes, particularly those that undergo surface modification through SO2 and NH3 double-gas treatment to suppress the structural degradation. The chemical composition and energy distribution of the occupied and unoccupied electronic states at the different charging/discharging states are quantitatively estimated by using advanced spectroscopy techniques, including operando Raman spectroscopy. The concept is successfully demonstrated in designing artificial interfaces for high-voltage olivine structure cathodes enabling stable battery operation up to 5.1 V versus Li+/Li.

Li-ion batteries based on high specific capacity LixSiO-Graphite anodes and LiNi0.89Co0.05 Mn0.05Al0.01O2 (NCMA) cathodes may have numerous practical applications owing to high energy density without a necessary compromise on safety. SiO, which is an attractive Li insertion anode material, offers more cycling stability than Si and a higher capacity than graphite. Therefore, a new trend has emerged for developing composite C-Si anodes, possessing the excellent cyclability of graphite coupled with high capacity SiO. The composite structure described herein prevents the volume expansion of SiO and maintains the structural integrity during prolonged cycling. However, graphite electrodes suffer from exfoliation in propylene carbonate (PC) based electrolyte solutions, which avoids well known safety benefits related to a possible use of PC based electrolyte solutions in all kinds of Li batteries. Herein, it is reported that trifluoro propylene carbonate (TFPC) is compatible with graphite anodes. New electrolyte formulations are developed and tested containing fluorinated co-solvents and compared the performance of several electrolyte solutions, including conventional alkyl carbonates-based solutions in full Li-ion cells, which included LixSiO-Graphite anodes and LiNi0.89Co0.05Mn0.05Al0.01O2 (NCMA) cathodes. Cells with new electrolyte solutions developed herein demonstrated nearly twice capacity retention in prolonged cycling experiments compared to similar reference cells containing conventional electrolyte solutions.

Lithiated transition metal oxides are the most important cathode materials for lithium-ion batteries. Many efforts have been devoted in recent years to improving their energy density, stability, and safety, as demonstrated by thousands of publications. However, the commercialization of several promising materials is limited due to obstacles like stability limitations. To overcome the limitations of energetically high-voltage or high-capacity cathode materials, unconventional solutions for their surface engineering were suggested; among them, metal-organic frameworks (MOFs) and zeolites have been employed. MOFs possess favorable characteristics for stabilization goals, including manageable structures, topological control, high porosity, large surface area, and low density. This review article explores promising strategies for improving the electrochemical behavior of favorable cathode materials through surface modifications by using MOFs and zeolites. Investigating the potential of this frameworks-based surface engineering for high energy density batteries' electrodes is essential for optimal control of their surface chemistry. It may be highly effective to upgrade the performance of high-energy cathode materials, thus extending the practical use of very high energy density rechargeable batteries. Metal-organic frameworks (MOFs) and zeolites are unconventional solutions for the surface engineering of high-voltage or high-capacity cathode materials. Framework materials have favorable characteristics like manageable structures, topological control, high porosity, large surface area, and low density. These frameworks-based surface modifications can improve the electrochemical behavior of Li-ion battery cathode materials, upgrading the performance of rechargeable batteries.image

The work reported herein discusses the improved electrochemical and thermal behavior of LiNi0.5Mn1.5O4 (LNMO) spinel cathodes via surface engineering using a series of zeolites. The limiting issues of these high voltage electrodes are phase transition during Li-ions intercalation/de-intercalation processes, weakening the active material's structure. Besides, it initiates harmful interfacial side reactions, including solution species oxidation and Ni & Mn dissolution, affecting their long-term cycling stability severely and detrimentally. Therefore, we propose a zeolite-based surface modification of LNMO involving a simple surface coating strategy that includes liquid-phase (ethanol) mixing followed by heat treatment at 200 degrees C under nitrogen gas flow. The cathodes comprising LNMO coated with 2 wt% zeolites exhibited significantly improved cycling stability than the reference cathodes with the uncoated material. Furthermore, we discovered that the zeolite species adsorbed to the LNMO surface act as buffer interphase that enhance the electrodes' redox kinetics, trapping dissolved-TMs ions and serving as local Li+-ions reservoirs. Pouch cells containing graphite anodes and zeolite-coated LNMO cathodes demonstrated impressively improved electrochemical behavior in capacity retention during prolonged cycling, enhanced rate capability, lower voltage hysteresis, and direct current internal resistance (DCIR) evo-lution. The zeolite-based surface coating participates in (i) lowering HF formation in battery solutions by absorbing trace water, (ii) HF scavenging, and (iii) lowering TMs cations dissolution. Furthermore, Si and Al constituents of the zeolites can deposit on Li-anodes and possibly increase their stability, later established by additional electrochemical studies of full-pouch cells comprising uncoated LNMO cathodes vs. zeolite-coated graphite anodes. Other pivotal findings of this work are the coherent structural, morphological, and thermal stabilization of zeolite-coated LNMO cathodes during prolonged cycling experiments.

Correction for ‘Impact of thermal gas treatment on the surface modification of Li-rich Mn-based cathode materials for Li-ion batteries’ by Maximilian Mellin et al. , Mater. Adv. , 2023, 4 , 3746–3758, https://doi.org/10.1039/D3MA00236E.

Lithiated oxides like Li[Ni x Co y Mn z ]O 2 ( x + y + z = 1) with high nickel content ( x ≥ 0.8) can possess high specific capacity ≥200 mA h g −1 and have attracted extensive attention as perspective cathode materials for advanced lithium-ion batteries.

Here, three types of surface coatings based on adsorption of organic aromatic acids or their Li salts are applied as functional coating substrates to engineer the surface properties of high voltage LiNi0.5 Mn1.5 O4 (LNMO) spinel cathodes. The materials used as coating include 1,3,5-benzene-tricarboxylic acid (trimesic acid [TMA]), its Li-salt, and 1,4-benzene-dicarboxylic acid (terephthalic acid). The surface coating involves simple ethanol liquid-phase mixing and low-temperature heat treatment under nitrogen flow. In typical comparative studies, TMA-coated (3-5%) LNMO cathodes deliver >90% capacity retention after 400 cycles with significantly improved rate performance in Li-coin cells at 30 °C compared to uncoated material with capacity retention of ≈40%. The cathode coating also prevents the rapid drop in the electrochemical activity of high voltage Li cells at 55 °C. Studies of high voltage full cells containing TMA coated cathodes versus graphite anodes also demonstrate improved electrochemical behavior, including improved cycling performance and capacity retention, increased rate capabilities, lower voltage hysteresis, and very minor direct current internal resistance evolution. In line with the highly positive effects on the electrochemical performance, it is found that these coatings reduce detrimental transition metal cations dissolution and ensure structural stability during prolonged cycling and thermal stability at elevated temperatures.

Herein, a systematic surface modification approach via double gas (SO2 and NH3) treatment at elevated temperatures is described, aimed to achieve a stable electrochemical performance of Li and Mn-rich NCM cathode materials of a typical composition 0.33Li2MnO3·0.67LiNi0.4Co0.2Mn0.4O2 (HE-NCM). Partial surface reduction of Mn4+ and the formation of a modified interface comprising Li-ions conductive nano-sized Li2SO4/Li2SO3 phases are established. Li-coin cells' prolonged cycling performance demonstrated significantly improved capacity retention (∼2.2 times higher than untreated cathode materials) for the double-gas-treated cathodes after 400 cycles at a 1.0 C rate. Stable discharge potential and lower voltage hysteresis during cycling were also achieved through the double gas treatment. Comparative electrochemical studies in full-pouch cells [vs. Graphite anodes] also demonstrated considerably stabilized electrochemical behavior for the double-gas-treated HE-NCM cathode materials. Lower gasses (O2, CO2, and H2) evolution in the first charge-discharge cycle and improved thermal stability are indeed crucial achievements of this treatment. Electrodes' post-cycling investigation revealed morphological integrity of the gas-treated cathode materials and lower transition metals (TMs) dissolution from the active cathodes. The positive effects of the double gas treatment are clearly related to the modified surfaces and lessening undesirable side reactions at the electrode-electrolyte solution interface.

High-energy cathode materials that are Li- and Mn-rich lithiated oxides—for instance, 0.35Li2MnO3.0.65LiNi0.35Mn0.45Co0.20O2 (HE-NCM)—are promising for advanced lithium-ion batteries. However, HE-NCM cathodes suffer from severe degradation during cycling, causing gradual capacity loss, voltage fading, and low-rate capability performance. In this work, we applied an effective approach to creating a nano-sized surface layer of Li2SO4 on the above material, providing mitigation of the interfacial side reactions while retaining the structural integrity of the cathodes upon extended cycling. The Li2SO4 coating was formed on the surface of the material by mixing it with nanocrystalline Li2SO4 and annealing at 600 °C. We established enhanced electrochemical behavior with ~20% higher discharge capacity, improved charge-transfer kinetics, and higher rate capability of HE-NCM cathodes due to the presence of the Li2SO4 coating. Online electrochemical mass spectrometry studies revealed lower CO2 and H2 evolution in the treated samples, implying that the Li2SO4 layer partially suppresses the electrolyte degradation during the initial cycle. In addition, a ~28% improvement in the thermal stability of the Li2SO4-treated samples in reactions with battery solution was also shown by DSC studies. The post-cycling analysis allowed us to conclude that the Li2SO4 phase remained on the surface and retained its structure after 100 cycles.

AbstractAmong extensively studied Li‐ion cathode materials, LiCoO2 (LCO) remains dominant for portable electronic applications. Although its theoretical capacity (274 mAh g−1) cannot be achieved in Li cells, high capacity (≤240 mAh g−1) can be obtained by raising the charging voltage up to 4.6 V. Unfortunately, charging Li‐LCO cells to high potentials induces surface and structural instabilities that result in rapid degradation of cells containing LCO cathodes. Yet, significant stabilization is achieved by surface coatings that promote formation of robust passivation films and prevent parasitic interactions between the electrolyte solutions and the cathodes particles. In the search for effective coatings, the authors propose RbAlF4 modified LCO particles. The coated LCO cathodes demonstrate enhanced capacity (>220 mAh g−1) and impressive retention of >80/77% after 500/300 cycles at 30/45 °C. A plausible mechanism that leads to the superior stability is proposed. Finally the authors demonstrate that the main reason for the degradation of 4.6 V cells is the instability of the anode side rather than the failure of the coated cathodes.

Functional surface coatings were applied on high voltagespinel (LiNi0.5Mn1.5O4; LNMO) and Ni-rich (LiNi0.85Co0.1Mn0.05O2;NCM851005) NCM cathode materials using few-layered 2H tungstendiselenide (WSe2). Simple liquid-phase mixing with WSe2in 2-propanoland low-temperature (130 degrees C) heat treatment in nitrogenflow dramaticallyimproved electrochemical performance, including stable cycling, high-rateperformance, and lower voltage hysteresis in Li coin cells at 30 and 55 degrees C.Significantly improved capacity retention at 30 degrees C[Q401/Q9of 99% vs 38%for LNMO andQ322/Q23of 64% vs 46% for NCM851005] indicated efficientfunctionality. TEM and XPS clarified the coating distribution andcoordination with the cathode surface, while postcycling studies revealedits sustainability, enabling lower transition metal dissolution and minormorphological deformation/microcrack formation. A modified and stableSEI was apparently formed owing to W and Se deposition on the Li anodeduring cycling. The synergistic functionalization provided a significant dual benefit of cathodic and anodic stability.

In this work, we continued our systematic investigations on synthesis, structural studies, and electrochemical behavior of Ni-rich materials Li[NixCoyMnz]O2 (x + y + z = 1; x ≥ 0.8) for advanced lithium-ion batteries (LIBs). We focused, herein, on LiNi0.85Co0.10Mn0.05O2 (NCM85) and demonstrated that doping this material with high-charge cation Mo6+ (1 at. %, by a minor nickel substitution) results in substantially stable cycling performance, increased rate capability, lowering of the voltage hysteresis, and impedance in Li-cells with EC-EMC/LiPF6 solutions. Incorporation of Mo-dopant into the NCM85 structure was carried out by in-situ approach, upon the synthesis using ammonium molybdate as the precursor. From X-ray diffraction studies and based on our previous investigation of Mo-doped NCM523 and Ni-rich NCM811 materials, it was revealed that Mo6+ preferably substitutes Ni residing either in 3a or 3b sites. We correlated the improved behavior of the doped NCM85 electrode materials in Li-cells with a partial Mo segregation at the surface and at the grain boundaries, a tendency established previously in our lab for the other members of the Li[NixCoyMnz]O2 family.

This work is part of ongoing and systematic investigations by our groups on the synthesis, electrochemical behavior, structural investigations, and computational modeling of the Ni-rich materials Li[NixCoyMnz]O2 (x+y+z=1; x≥0.8) for advanced lithium-ion batteries. This study focuses on the LiNi0.85Co0.10Mn0.05O2 (NCM85) material and its improvement upon doping with B3+ cations. The data demonstrate the substantial improvement of the doped electrodes in terms of cycling performance, lower voltage hysteresis and reduced self-discharge upon high temperature storage. The electronic structure of the undoped and B-doped material was modelled using density functional theory (DFT), which identified interstitial positions as the preferential location of the dopant. DFT models were also used to shed light on the influence of boron on surface segregation, surface stability, and oxygen binding energy in NCM85 material. Experimental evidence supports the suggestion that the boron segregates at the surface, effectively reducing the surface energy and increasing the oxygen binding energy, and possibly, as a result, inhibiting oxygen release. Additionally, the presence of borate species near the surface can reduce the nucleophilicity of surface oxygens. Cycling of the Li-cells did not cause noticeable changes in the microstructure of the B-doped materials, whereas significant microstructural changes, like a propagating network of cracks, was observed across all grains in the cycled undoped NCM85 cathodes. Analysis by high-resolution microscopy and 6Li and 11B solid-state nuclear magnetic resonance (ss NMR) allowed for the correlation of capacity fade and degradation of the different NCM85 materials with their structural characteristics.

In continuation of the work on the stabilization of the electrochemical performance of Li and Mn‐rich LixNiyCozMnwO2 (HE‐NCM, x > 1, w > 0.5, x + y + z + w = 2) cathode materials via atomic layer deposition (ALD) surface coatings, herein, the active role of aluminum oxides‐based coatings, during prolonged cycling in battery prototypes with graphite anodes, is discussed. Notable progress in electrochemical cycling and rate performance of Na‐aluminate‐coated Li1.142Mn0.513Ni0.230Co0.115O2 cathode material is established. These coated electrodes delivered a stable discharge capacity of 145 mAh g−1 (66% retention), compared to only 118 mAh g−1 (55% retention) for the uncoated sample at a 1.0 C rate after 400 cycles. Steady average discharge potential, lower voltage hysteresis, and stable energy density profiles are the noteworthy achievements for the coated material during cycling. Significant improvement in the coated material's thermal stability compared with the uncoated one has also been confirmed. The present study also enlightens about the Na‐aluminate coating's orientation and distribution on HE‐NCM material's surface. 23Na and 27Al solid‐state nuclear magnetic resonance (NMR) studies reveal the Na‐aluminate coating's crystalline constituent's disappearance upon cycling. The partial dissolution of Na5AlO4 coating, followed by forming a secondary disordered edge‐site phase that remains even after long‐term cycling, is disclosed.

Among the cathode materials for advanced Li-ion batteries, nickel-rich Ni-Co-Mn (NCM) LiNixCoyMnyO2 (x > 0.5, x + 2y = 1) attracts great interest as promising materials owing to their high capacity, low cost, good cycling stability, safety and the fact that their stable capacity can be extracted by charging up to 4.3 V vs. Li. In this work, the effect of the synthesis route—freeze-drying, self-combustion, solid state and co-precipitation on the performance of NCM622 (LiNixCoyMnyO2, x = 0.6, y = 0.2) cathodes—in Li cells was thoroughly studied. The material prepared by freeze-drying exhibited superior electrochemical properties. The effect of in situ and ex situ Zr4+ cations doping on the electrodes’ capacity, stability and average voltage was also studied. Doping via a top–down, ex situ mode improved the performance in terms of capacity stabilization, whereas electrodes comprising materials that were doped via a bottom–up in situ approach showed stable average voltage upon prolonged cycling. These effects are discussed and explained herein.

The active role of alumina, pentalithium aluminate (Li 5 AlO 4 , Li‐aluminate), and pentasodium aluminate (Na 5 AlO 4 , Na‐aluminate) as the surface protection coatings produced via atomic layer deposition on Li and Mn‐rich NCM cathode materials 0.33Li 2 MnO 3 ·0.67LiNi 0.4 Co 0.2 Mn 0.4 O 2 is discussed. A notable improvement in the electrochemical behavior of the coated cathodes has been found while tested in Li‐coin cells at 30 °C. Though all the coated cathodes demonstrate enhanced electrochemical cycling and rate performances, Na‐aluminate coated cathodes exhibit exemplary behavior. Prolonged cycling and rate capability testing demonstrate that after more than 400 cycles at 1 C rate, the uncoated cathode delivers only 63 mAh g −1 , while those with alumina, Li‐aluminate, and Na‐aluminate coatings exhibit approximately two times higher specific capacities. The coated cathodes display steady average discharge potential and lower evolution of the voltage hysteresis during prolonged cycling compared to the uncoated cathode. Importantly, Na‐aluminate coated cathode shows a lowering in gases (O 2 , CO 2 , H 2 , etc.) evolution. Post‐cycling analysis of the electrodes demonstrates higher morphological integrity of the coated cathode materials and lower transition metals dissolution from them. The coatings mitigate undesirable side reactions between the electrodes and the electrolyte solution in the cells.

We present in this paper a modification and stabilization approach for the surface of a high specific capacity Ni-rich cathode material LiNi0.85Co0.10Mn0.05O2 (NCM85) via SO2 gas treatment at 250-400 degrees C, in order to enhance its electrochemical performance in advanced lithium-ion batteries. It was established that SO2 interactions with NCM85 result in the formation of a nanometer-sized Li2SO4 surface layer on the oxide particles with no impact on the bulk structure of the material and its morphology. We consider the above interactions as oxidation-reduction processes resulting in direct oxidation of sulfur and partial reduction of Ni3+ as revealed by high-resolution XPS and electron paramagnetic resonance studies. The important impacts of the SO2 treatment are a remarkably stable cycling performance of cathodes comprising this material with similar to 10% increase in capacity retention and lesser voltage hysteresis upon cycling compared to untreated NCM85 cathodes. The SO2-treated NCM85 material is also significantly thermally stable, demonstrating lower heat evolution upon thermal reactions with standard EC-EMC/LiPF6 solutions by 12-20%, compared to untreated material. The proposed approach to modify the surface of Ni-rich NCM cathode materials by SO2 treatment is demonstrated to be a promising method to enhance their electrochemical performance. This work demonstrates a leap in performance of Ni-rich NCM cathode materials by increasing the content of nickel compared to any benchmark cathodes and is a promising approach for stabilization by surface modification.

In this study, we present a novel surface modification approach via SO(2)gas treatment at 200 degrees C-400 degrees C to enhance the electrochemical performance of Li and Mn-rich cathode materials 0.35Li(2)MnO(3)0.65LiNi(0.35)Mn(0.45)Co(0.20)O(2)(HE-NCM) for advanced lithium-ion batteries. It was established by X-ray photoelectron spectroscopy that the SO(2)treatment leads to the formation of surface sulfates and sulfites on the material, while the bulk remains unaffected, as confirmed by X-ray and electron diffraction studies. Based on the results obtained, we proposed possible mechanisms of the SO(2)thermal treatment that include partial reduction of manganese (however, we could not find any substantial evidence for it in the XPS data) and oxidation of sulfur. The electrochemical performance was evaluated by testing the materials as cathodes in coin-type half-cells with metallic lithium anodes at 25 degrees C and 30 degrees C. The main findings are as follows: the SO2-treated materials demonstrate similar to 10% higher capacity at all C-rates and lower the voltage hysteresis during prolonged cycling compared to the untreated samples. The proposed approach to modify the surface of HE-NCM materials by SO(2)treatment is demonstrated to be a promising method to enhance the electrochemical performance of these cathodes.

We demonstrate a novel surface modification of Li- and Mn-rich cathode materials 0.33Li2MnO3·0.67LiNi0.4Co0.2Mn0.4O2 for lithium-ion batteries (high-energy Ni-Co-Mn oxides, HE-NCM) via their heat treatment with trimesic acid (TA) or terephthalic acid at 600 °C under argon. We established the optimal regimes of the treatment-the amounts of HE-NCM, acid, temperature, and time-resulting in a significant improvement of the electrochemical behavior of cathodes in Li cells. It was shown that upon treatment, some lithium is leached out from the surface, leading to the formation of a surface layer comprising rock-salt-like phase Li0.4Ni1.6O2. The analysis of the structural and surface studies by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy confirmed the formation of the above surface layer. We discuss the possible reactions of HE-NCM with the acids and the mechanism of the formation of the new phases, Li0.4Ni1.6O2 and spinel. The electrochemical characterizations were performed by testing the materials versus Li anodes at 30 °C. Importantly, the electrochemical results disclose significantly improved cycling stability (much lower capacity fading) and high-rate performance for the treated materials compared to the untreated ones. We established a lower evolution of the voltage hysteresis with cycling for the treated cathodes compared to that for the untreated ones. Thermal studies by differential scanning calorimetry also demonstrated lower (by ∼32%) total heat released in the reactions of the materials treated with fluoroethylene carbonate (FEC)-dimethyl carbonate (DEC)/LiPF6 electrolyte solutions, thus implying their significant surface stabilization because of the surface treatment. It was established by a postmortem analysis after 400 cycles that a lower amount of transition-metal cations dissolved (especially Ni) and a reduced number of surface cracks were formed for the 2 wt % TA-treated HE-NCMs compared to the untreated ones. We consider the proposed method of surface modification as a simple, cheap, and scalable approach to achieve a steady and superior electrochemical performance of HE-NCM cathodes.