High Voltage Stability Research Articles

Multifunctional Na2TiO3 Coating-Enabled High-Voltage and Capacitive-like Sodium-Ion Storage of Na0.44MnO2.

Sodium-ion batteries, as an attractive option for large-scale energy storage, still face the problems of low energy density and unsatisfactory rate performance. Among various cathodes, the tunnel-type Na0.44MnO2 with large S-shaped Na+ transport tunnels is one of the promising cathode materials for fast and robust sodium-ion storage, yet suffering from Mn dissolution and structural collapse. Herein, a Na-rich layered oxide Na2TiO3 is first constructed as a multifunctional coating layer on the surface of the Na0.44MnO2 nanorod. Na2TiO3 not only acts as an Na+ reservoir, but also serves as a protective layer to prevent Na0.44MnO2 from electrolyte etching. Besides, the derived Ti-doped Na0.44MnO2 transition layer supplies additional Na+ diffusion pathways along the radial direction of the nanorod with a short migration distance. The optimized 3 wt % Na2TiO3-coated Na0.44MnO2 exhibits enhanced an initial capacity of 127 mAh g-1 at 2-4.5 V. In addition, it shows an ultra-high capacitive-like capacity ratio of 96.7%, hence delivering an excellent rate performance of 80.2 mAh g-1 at 20C. Long-term cycling tests indicate splendid stability against high voltage, achieving 97.7% capacity retention at 20C after 900 cycles. This work provides an effective strategy to improve the rate performance and high-voltage stability of Na0.44MnO2 for high energy and power density batteries.

Phosphonic acid-imidazolium containing polymer ionomeric membranes derived from poly (phenylene oxide) towards boosting the performance of HT-PEM fuel cells

Phosphoric acid (PA)-dependent proton conductivity and polymer-offered mechanical properties are contradictory in high-temperature proton exchange membranes (HT-PEMs). Microphase separation strategy contributes to achieve a tradeoff between proton conductivity and mechanical properties. Herein, a kind of phosphonic acid-imidazolium containing polymer (PICP) ionomeric membranes, in which acidophilic (imidazolium) and acidophobic groups (-PO3H2) can be induced to form a microphase separation structure by PA, are firstly prepared. The acidophilic phase with adsorbed PA plays the role of proton conduction and the acidophobic phase can not only provides -PO3H2 group synergistically conduct protons but also largely maintains the intrinsic mechanical properties. As a result, the PICP ionomeric membranes with microphase separation structure possess high proton conductivity (48 mS cm−1, 160 °C) and satisfying mechanical strength (16.5 MPa) simultaneously at a moderate PA doping level (130 wt%). The fuel cell based on such HT-PEMs demonstrates a peak power density of 493 mW cm−2 and high voltage stability. This is the first report of phosphonic acid-imidazolium containing ionomeric membranes with satisfactory fuel cell performance and durability, representing a meaningful step towards practical HT-PEM fuel cells.

Plasma preparation of highly reactive Ag-Cu NPs anchored in N-PC as catalysts for Aluminum-air battery

Efficient, stable and economical catalysts play a crucial role in enhancing the kinetics of slow oxygen reduction reactions (ORR) in Aluminum-air batteries. Among the potential next-generation candidates, Ag catalysts are promising due to their high activity and low cost, but weaker oxygen adsorption has hindered industrialization. To address this bottleneck, Ag-alloying has emerged as a principal strategy. In this work, we successfully prepared Ag-Cu nanoparticles (NPs) with a rich eutectic phase and uniform dispersion structure using plasma evaporation. The increased solid solution of Ag and Cu led to changes in the electronic structure, resulting in an upward shift of the d-band center, which significantly improved oxygen adsorption. The combination of Ag and Cu in the NPs synergistically enhanced the adsorption of Ag and the desorption of Cu. Density functional theory (DFT) calculations revealed that Ag-Cu25 NPs exhibited the smallest limiting reaction barrier, leading to increased ORR activity. To further optimize the catalyst's performance, we utilized N-doped porous nanocarbon (N-PC) with high electrical conductivity and abundant mesoporous channels as the support for the Ag-Cu NPs. The N-PC support provided optimal mass transfer carriers for the highly active Ag-Cu25 NPs. As a result, the Ag-Cu25/NPC catalyst displayed excellent ORR activity in alkaline media, with a half-wave potential (E1/2) of 0.82 V. Furthermore, the Al-air battery incorporating the Ag-Cu25/NPC catalyst exhibited outstanding electrochemical performance. It demonstrated high open-circuit voltages of 1.89 V and remarkable power densities of 193 mW cm−2. The battery also sustained a high current output and maintained a stable high voltage for 120 hours under mechanical charging, showcasing its significant potential for practical applications.

High-voltage stability of O3-type sodium layered cathode enabled by preferred occupation of Na in the OP2 phase

Cobalt-free O3-type layered sodium nickel manganese oxide, Na[Ni0.5Mn0.5]O2, is one of the most attractive candidates as a cathode material for low-cost and practical sodium-ion batteries (SIBs). However, stable cycling with high reversible capacity in SIBs using Na[Ni0.5Mn0.5]O2 as a cathode is still hampered by an irreversible phase transition at voltages above 4.0 V (vs. Na/Na+). In this study, to suppress the detrimental phase transition, Mg substitution into Ni sites is proposed, and a series of Na[Ni0.5-xMgxMn0.5]O2 (x = 0, 0.05, 0.1 and 0.15) materials are synthesized and characterized. The substitution of Mg over 10 mol% into Ni site regulates sodium occupancy into P-type stacking, resulting in the OP2 phase upon high-voltage operation. This enables the material to tolerate strains in the crystal structure by alleviating the irreversible O3′−O3″ phase transition, which was evidenced by the results of operando X-ray diffraction and density functional theory calculation. Compared to its corresponding members, the optimized Na[Ni0.4Mg0.1Mn0.5]O2 cathode delivers a high reversible capacity of 177 mAh g−1 as well as improved cycling stability and rate capability in the wide voltage range of 2.0 − 4.3 V. Moreover, the Mg substitution strategy enhances the thermal and chemical stability against moisture, indicating its excellent practical applicability.

Hexacyclic Chelated Lithium Stable Solvates for Highly Reversible Cycling of High-Voltage Lithium Metal Battery.

Ether-based electrolytes that are endowed with decent compatibility towards lithium anode have been regarded as promising candidates for constructing energy-dense lithium metal batteries (LMBs), but their applications are hindered by low oxidation stability in conventional salt concentration. Here, we reported that regulating the chelating power and coordination structure can remarkably increase the high-voltage stability of ether-based electrolytes and lifespan of LMBs. Two ether molecules of 1,3-dimethoxypropane (DMP) and 1,3-diethoxypropane (DEP) are designed and synthesized as solvents of electrolytes to replace the traditional ether solvent (1,2-dimethoxyethane, DME). Both computational and spectra reveal that the transition from five- to six-membered chelate solvation structure by adding one methylene on DME results in the formation of weak Li solvates, which increase the reversibility and high-voltage stability in LMBs. Even under lean electrolyte (5 mL Ah-1 ) and low anode to cathode ratio (2.6), the fabricated high-voltage Li||LiNi0.8 Co0.1 Mn0.1 O2 LMBs using electrolyte of 2.30 M Lithiumbisfluorosulfonimide (LiFSI)/DMP still show capacity retention over 90 % after 184 cycles. This work highlights the importance of designing the coordination structures in non-fluorine ether electrolytes for rechargeable batteries.

Reinterpreting the correlation between cycling stability of Ni-rich layered oxide cathode and the charging cut-off voltage in Li-ion batteries

Conventional view is that increasing the charging cut-off voltage will reduce the cycle life of LiNi0.8Co0.1Mn0.1O2 (NCM811) due to the intensification of electrode-electrolyte interface reaction, which strongly depends on the interface chemistry. However, we found the different trend when NCM811 is cycled in TLE electrolyte (ternary fluorinated lithium salts electrolyte). Specifically, the higher charging cut-off voltage applied, the better cycling stability obtained with 1000 cycles at 4.5 V/4.7 V, while 500 cycles at 4.3 V (capacity retention > 80 %). Herein, we revisit the correlation between cycling stability and charging cut-off voltage and have found that the cycling stability of NCM811 is more strongly related to interface chemistry. Charging at 4.5/4.7 V in TLE electrolyte, the content of inorganic components in cathode-electrolyte-interphase (CEI) and anode-electrolyte-interphase (AEI) are much higher than that obtained at 4.3 V due to the energy levels of the frontier molecular orbital of lithium salts, which is more resistant to oxidation and has higher mechanical strength to suppress the particle cracks. More importantly, the inorganic rich interface can prevent the crossover reaction between cathode and anode. This work clarifies the significance of interface chemistry to achieve high-voltage stability, and provides a valuable electrolyte formula for commercial application of high-performance Ni-rich layered oxide cathode at high-voltage.

Integration of Superconducting Magnetic Energy Storage for Fast-Response Storage in a Hybrid Solar PV-Biogas with Pumped-Hydro Energy Storage Power Plant

Electric distribution systems face many issues, such as power outages, high power losses, voltage sags, and low voltage stability, which are caused by the intermittent nature of renewable power generation and the large changes in load demand. To deal with these issues, a distribution system has been designed using both short- and long-term energy storage systems such as superconducting magnetic energy storage (SMES) and pumped-hydro energy storage (PHES). The aim of this paper is to propose a metaheuristic-based optimization method to find the optimal size of a hybrid solar PV-biogas generator with SMES-PHES in the distribution system and conduct a financial analysis. This method is based on an efficient algorithm called the “enhanced whale optimization” algorithm (EWOA), along with the proposed objective functions and constraints of the system. The EWOA is employed to reduce the hybrid system’s life cycle cost (LCC) and improve its reliability, both of which serve as performance indicators for the distribution system. The proposed method for sizing a grid-connected hybrid solar PV-biogas generator with SMES-PHES is compared with other metaheuristic optimization techniques, including the African vulture optimization algorithm (AVOA), grey wolf optimization algorithm (GWO), and water cycle algorithm (WCA). The numerical results of the EWOA show that the combination of a hybrid solar PV-biogas generator with SMES-PHES can successfully reduce the LCC and increase reliability, making the distribution system work better.

A solid-state electrolyte incorporating Li6.25Al0.25La3Zr2O12 into an ethylene oxide-based network for use in lithium metal batteries

In this study, solid-state hybrid electrolytes (ENLSEs) appropriate for use in a lithium metal battery (LMB) are produced with an ethylene oxide-basis network and garnet Li7La3Zr2O12 (LLZO) via solvent-free UV polymerization. The optimum composition of ENLSE is determined by varying the weight ratio of the ethylene oxide network, LLZO, and lithium salt. The ENLSEs show high lithium-ion conductivity (1.03 × 10−4 S cm−1) at 50 °C, a result of the concurrent Li+ transport of ethylene-oxide chain and LLZO. The electrolytes exhibit a high voltage stability of 5.75 V (vs Li/Li+) and a considerable lithium-ion transfer number (tLi+∼0.68), suppress dendrite growth, and promote electrochemical stability. A LMB full cell delivers 99.4 mA h g−1 of capacity at a current of 5 mA g−1 with 55 % capacity retention over at least 70 charge-discharge cycles, suggesting that ENLSEs have potential as solid-state electrolytes for LMBs.

Exploiting High-Voltage Stability of Dual-Ion Aqueous Electrolyte Reinforced by Incorporation of Fiberglass into Zwitterionic Hydrogel Electrolyte.

Rechargeable zinc aqueous batteries are key alternatives for replacing toxic, flammable, and expensive lithium-ion batteries in grid energy storage systems. However, these systems possess critical weaknesses, including the short electrochemical stability window of water and intrinsic fast zinc dendrite growth. Hydrogel electrolytes provide a possible solution, especially cross-linked zwitterionic polymers that possess strong water retention ability and high ionic conductivity. Herein, an in situ prepared fiberglass-incorporated dual-ion zwitterionic hydrogel electrolyte with an ionic conductivity of 24.32 mS cm-1 , electrochemical stability window up to 2.56V, and high thermal stability is presented. By incorporating this hydrogel electrolyte of zinc and lithium triflate salts, a zinc//LiMn0.6 Fe0.4 PO4 pouch cell delivers a reversible capacity of 130 mAh g-1 in the range of 1.0-2.2V at 0.1C, and the test at 2C provides an initial capacity of 82.4 mAh g-1 with 71.8% capacity retention after 1000 cycles with a coulombic efficiency of 97%. Additionally, the pouch cell is fire resistant and remains safe after cutting and piercing.

Modification of NMC811 with titanium for enhanced cycling and high-voltage stability

LiNi1-x-yMnxCoyO2 (NMC) with a nickel content of ≥80% is currently considered one of the most promising lithium-ion battery cathode materials for applications that require both a high energy density and reasonable costs. However, its widespread use has so far been limited by its inherently lower structural stability and higher surface reactivity compared to NMC materials with a lower nickel content. Here, we explore wet-chemical titanium-based bulk and surface modifications to improve the cycling and high-voltage stability of NMC811. We find that both doping and coating with titanium improve cycling stability. For example, the capacity retention of graphite/NMC811 full cells cycled for 200 cycles between 2.8 and 4.4 V at C/3 improves from 86.1% for the pristine NMC811 to 89.4% and 91.5% for the doped and coated samples, respectively. Combining doping and coating in a two-step process results in a material with the most balanced properties in terms of capacity, cycling stability, rate performance, and high-voltage stability.

1,3,5-Trifluorobenzene endorsed EC-free electrolyte for high-voltage and wide-temperature lithium-ion batteries

Ethylene carbonate (EC) is susceptible to the aggressive chemistry of nickel-rich cathodes, making it undesirable for high-voltage lithium-ion batteries (LIBs). The arbitrary elimination of EC leads to better oxidative tolerance but always incurs interfacial degradation and electrolyte decomposition. Herein, an EC-free electrolyte is deliberately developed based on gradient solvation by pairing solvation-protection agent (1,3,5-trifluorobenzene, F3B) with propylene carbonate (PC)/methyl ethyl carbonate (EMC) formulation. F3B keeps out of inner coordination shell but decomposes preferentially to construct robust interphase, inhibiting solvent decomposition and electrode corrosion. Thereby, the optimized electrolyte (1.1 M) with wide liquid range (−70–77 °C) conveys decent interfacial compatibility and high-voltage stability (4.6 V for LiNi0.6Mn0.2Co0.2O2, NCM622), qualifying reliable operation of practical NCM/graphite pouch cell (81.1% capacity retention over 600 cycles at 0.5 C). The solvation preservation and interface protection from F3B blaze a new avenue for developing high-voltage electrolytes in next-generation LIBs.

Single Crystal Li1+x[Ni0.6Mn0.4]1−xO2 Made by All-Dry Synthesis

Cobalt-free, single crystal layered-oxide positive electrode materials like Li1+x[Ni0.6Mn0.4]1−xO2 (NM64) have received recent interest because of their low cost, high-voltage stability, and good cycle life. In this work, single crystal NM64 is successfully produced with a simple all-dry synthesis process that requires no water, no intermediate chemicals, and produces little waste. The all-dry synthesized NM64 has ≤ 4% nickel in the lithium layer based on Rietveld refinement of powder XRD patterns, has a median particle size of 2–5 μm based on SEM and particle size analysis, and has excellent high-voltage stability at C/5 up to 4.4 V vs Li+/Li compared to a commercial material. Additionally, tungsten coating is shown to decrease the median particle size and improve the cycling stability in half cells from 91% retained capacity after 100 cycles to 93% retained capacity when 0.3% tungsten is added. It is believed that this incredibly simple process could be adopted relatively easily into current commercial positive electrode manufacturing facilities to reduce the complexity, cost, and time of manufacture.

LiMgPO4 -Coating-Induced Phosphate Shell and Bulk Mg-Doping Enables Stable Ultra-High-Voltage Cycling of LiCoO2 Cathode.

Stable cycling of LiCoO2 (LCO) cathode at high voltage is extremely challenging due to the notable structural instability in deeply delithiated states. Here, using the sol-gel coating method, LCO materials (LMP-LCO) are obtained with bulk Mg-doping and surface LiMgPO4 /Li3 PO4 (LMP/LPO) coating. The experimental results suggest that the simultaneous modification in the bulk and at the surface is demonstrated to be highly effective in improving the high-voltage performance of LCO. LMP-LCO cathodes deliver 149.8mAhg-1 @4.60 V and 146.1mAhg-1 @4.65 V after 200 cycles at 1C. For higher cut-off voltages, 4.70 and 4.80V, LMP-LCO cathodes still achieve 144.9mAhg-1 after 150 cycles and 136.8mAhg-1 after 100 cycles at 1C, respectively. Bulk Mg-dopants enhance the ionicity of CoO bond by tailoring the band centers of Co 3d and O 2p, promoting stable redox on O2- , and thus enhancing stable cycling at high cut-off voltages. Meanwhile, LMP/LPO surface coating suppresses detrimental surface side reactions while allowing facile Li-ion diffusion. The mechanism of high-voltage cycling stability is investigated by combining experimental characterizations and theoretical calculations. This study proposes a strategy of surface-to-bulk simultaneous modification to achieve superior structural stability at high voltages.

Synthesis of co-doped high voltage lithium cobalt oxide with high rate electrochemical performance

LiCoO2 can further develops its capacity potential by increasing cut-off voltage, but the irreversible phase transition and structural damage at high voltage will lead to severe capacity fading. Here, we propose a method of multi-doping of four elements Ti, Mg, Al, and Y, which realizes the stable cycling of LiCoO2 at a cut-off voltage of 4.5 V through the synergistic effect among the four elements. The cell delivers the increased initial discharge capacity of 173.5 mAh/g, with the capacity retention rate as high as 91.1% after 100 charging-discharging cycles at the rate of 1 C in the voltage ranging from 3.0 to 4.5 V. Moreover, the capacity retention is still as high as 74.2% after 300 cycles. At the same time, the capacity can still be maintained close to 70% after 100 cycles at the temperature of 50 ℃. The specific discharge capacity of the cathode is 130.0 mAh/g, even if at high rate of 5 C. More than 5 times that of unmodified LiCoO2. We verified the effect of four-element co-doping on phase and surface stability by characterizing the materials before and after the cycle. At the same time, the positive effects of four doping elements on structural stability and electronic conductivity were clarified by DFT method. This work provides a promising idea of multi-element synergistic doping and contributes to solving problem of stable high voltage LiCoO2.

Intermolecular Acid–Base‐Pairs Containing Poly (p‐Terphenyl‐co‐Isatin Piperidinium) for High Temperature Proton Exchange Membrane Fuel Cells

How to optimize and regulate the distribution of phosphoric acid in matrix, and pursuing the improved electrochemical performance and service lifetime of high temperature proton exchange membrane (HT‐PEMs) fuel cell are significant challenges. Herein, bifunctional poly (p‐terphenyl‐co‐isatin piperidinium) copolymer with tethered phosphonic acid (t‐PA) and intrinsic tertiary amine base groups are firstly prepared and investigated as HT‐PEMs. The distinctive architecture of the copolymer provides a well‐designed platform for rapid proton transport. Protons not only transports through the hydrogen bond network formed by the adsorbed free phosphoric acid (f‐PA) anchored by the tertiary amine base groups, but also rely upon the proton channel constructed by the ionic cluster formed by the t‐PA aggregation. Thorough the design of the structure, the bifunctional copolymers with lower PA uptake level (<100%) display prominent proton conductivities and peak power densities (99 mS cm−1, 812 mW cm−2 at 160 °C), along with lower PA leaching and higher voltage stability, which is a top leading result in disclosed literature. The results demonstrate that the design of intermolecular acid–base‐pairs can improve the proton conductivity without sacrificing the intrinsic chemical stability or mechanical property of the thin membrane, realizing win‐win demands between the mechanical robustness and electrochemical properties of HT‐PEMs.

Transformed Solvation Structure of Noncoordinating Flame‐Retardant Assisted Propylene Carbonate Enabling High Voltage Li‐Ion Batteries with High Safety and Long Cyclability

AbstractThe evolution of high‐energy‐density lithium‐ion batteries (LIBs) urgently requires the development of high‐safety electrolytes with high voltage resistance. Here, noncoordinating flame retardant pentafluoro‐(phenoxy)‐cyclotriphosphazene (FPPN) endows propylene carbonate (PC, 70 vol%)‐based electrolytes with high graphite anode compatibility, non‐flammability, high voltage stability, and excellent separator/electrode wettability. Theoretical calculations reveal that FPPN significantly affects Li+‐PC‐anion interactions and favors Li+ desolvation. Based on in situ optical microscopy and in situ differential electrochemical mass spectrometry, it is innovatively proposed that large amounts of H2 and C3H6 from PC decomposition play a dominant role in destroying the graphitic structure. The evolution of H2 and C3H6 is dramatically alleviated and totally suppressed, respectively, when FPPN prevents PC‐induced graphite exfoliation. More encouragingly, an optimized PC/FPPN‐based electrolyte (70 vol% PC) enables a high voltage LiCoO2/graphite pouch cell (4.35 V, ≈2.6 Ah, ≈242 Wh kg−1) with excellent cycle life and high safety. This work deepens the understanding of PC‐graphite compatibility and opens a new avenue of realizing practical application of PC‐based electrolytes (PC content over 50 vol%) in high capacity (over 2 Ah) LIBs.

O3-Type Na0.95Ni0.40Fe0.15Mn0.3Ti0.15O2 Cathode Materials with Enhanced Storage Stability for High-Energy Na-Ion Batteries.

O3-type layered oxides with high initial sodium content are promising cathode candidates for Na-ion batteries. However, affected by the undesired transition metal slab sliding and reaction with H2O/CO2, their further application is typically hindered by unsatisfactory cycling stability upon charging to high voltage and poor storage stability under humid air. Herein, we demonstrate a Fe/Ti cosubstitution strategy to simultaneously enhance the electrochemical performance and storage stability of pristine O3-NaNi0.5Mn0.5O2 cathode material, via employing high redox potential and inactive stabilized dopants. The resultant Fe/Ti cosubstituted Na0.95Ni0.40Fe0.15Mn0.3Ti0.15O2 undergoes highly reversible O3-P3-OP2 phase transitions with a small cell volume change of 2.8%, instead of complex O3-O'3-P3-P'3-P3'-O1 phase transitions in NaNi0.5Mn0.5O2. Consequently, the cathode displays a high specific capacity of 161.6 mAh g-1 with an average working voltage of 3.28 V and 81.8% capacity retention after 200 cycles at 5C. Furthermore, the cathode material remains very stable after exposure to air for 7 days and even after soaking in water for 1 h, owing to the prohibition of sodium losing by elevating redox potential and contracting sodium layer spacing. This work proposes an effective method to enhance the electrochemical performance and storage stability of O3-type layered oxide cathodes and promises advancing Na-ion batteries toward large-scale industrialization.

Boosting the interfacial superionic conduction of halide solid electrolytes for all-solid-state batteries

Designing highly conductive and (electro)chemical stable inorganic solid electrolytes using cost-effective materials is crucial for developing all-solid-state batteries. Here, we report halide nanocomposite solid electrolytes (HNSEs) ZrO2(-ACl)-A2ZrCl6 (A = Li or Na) that demonstrate improved ionic conductivities at 30 °C, from 0.40 to 1.3 mS cm−1 and from 0.011 to 0.11 mS cm−1 for Li+ and Na+, respectively, compared to A2ZrCl6, and improved compatibility with sulfide solid electrolytes. The mechanochemical method employing Li2O for the HNSEs synthesis enables the formation of nanostructured networks that promote interfacial superionic conduction. Via density functional theory calculations combined with synchrotron X-ray and 6Li nuclear magnetic resonance measurements and analyses, we demonstrate that interfacial oxygen-substituted compounds are responsible for the boosted interfacial conduction mechanism. Compared to state-of-the-art Li2ZrCl6, the fluorinated ZrO2−2Li2ZrCl5F HNSE shows improved high-voltage stability and interfacial compatibility with Li6PS5Cl and layered lithium transition metal oxide-based positive electrodes without detrimentally affecting Li+ conductivity. We also report the assembly and testing of a Li-In||LiNi0.88Co0.11Mn0.01O2 all-solid-state lab-scale cell operating at 30 °C and 70 MPa and capable of delivering a specific discharge of 115 mAh g−1 after almost 2000 cycles at 400 mA g−1.

A New Class of High-Capacity Fe-Based Cation-Disordered Oxide for Li-Ion Batteries: Li-Fe-Ti-Mo Oxide.

Low-cost Fe can be used for forming cation-disordered rocksalt Li-excess (DRX) materials instead of high-cost d0 -species and then the Fe-based DRX can be promising electrode materials because they can theoretically achieve high capacity, resulting from additional oxygen redox reaction and stable cation-disordered structure. However, Fe-based DRX materials suffer from large voltage hysteresis, low electrochemical activity, and poor cyclability, so it is highly challenging to utilize them as practical electrode materials for a cell. Here, novel high-capacity Li-Fe-Ti-Mo electrode materials (LFTMO) with high average discharge voltage and reasonable stability are reported. The effect of Ti/Mo on electrochemical reactions in Fe-based DRX materials (LFTMO) is studied by controlling its composition ratio and using techniques for analyzing the local environment to find the key factors that improve its activity. It is found out that the introduction of appropriate quantity of redox-active Mo4+/5+ to Fe-based DRX materials can help stabilize the oxygen redox reaction via changing a local structure and can suppress a Fe redox reaction, which can cause poor performance. The understandings will help develop high capacity and long cyclability Fe-based DRX electrode materials.

Highly Oxidation‐Resistant Ether Gel Electrolytes for 4.7 V High‐Safety Lithium Metal Batteries

AbstractEther electrolytes are considered to be one of the most promising candidates for lithium metal batteries (LMBs) since they help to form a stable solid electrolyte interface (SEI) on lithium anodes. However, conventional liquid ether electrolytes are not suitable for the high‐voltage LMBs over 4.5 V due to their narrow potential windows. Herein, a gel electrolyte strategy is demonstrated to improve the high voltage stability of ether electrolytes in LMBs with Li‐rich layered oxide (LLO) cathodes that usually operate at 4.6 V and above. Compared with a liquid electrolyte, the electrochemical window of the gel electrolyte with cross‐linked amide framework is increased by 1 V. The strong cross‐linked framework not only regulates the uniform growth of cathode electrolyte interface (CEI)/SEI on the cathode/anode sides, but also greatly increases the Li+ transference number and inhibits the generation of harmful substances by anchoring PF6− anions, thus providing a long cycle for LMBs at a high voltage up to 4.7 V. Simultaneously, the flame retardancy and flexibility of the gel electrolyte ensures the safe operation of high‐voltage LMBs. Therefore, the LLO||Li pouch cell using gel electrolyte realizes stable cycling at a high voltage 4.6 V, and can pass the acupuncture test.