High Open Voltage Research Articles

Simultaneous structure and surface engineering of metal-organic framework derived LiNi0.5-xFe2xMn1.5-xO4 cathode material for improving high voltage performance of lithium-ion batteries

This study presents a novel material synthesis approach utilizing a terephthalic acid-based metal-organic framework as a precursor and employing an ethanol-assisted hydrothermal treatment to produce high-performance Fe-doped LiNi0.5Mn1.5O4 (LNMO) cathode material. This strategy yields a well-crystallized spinel structure with uniformly distributed transition metal ions. Additionally, the appropriate quantity of Fe dopant can achieve the desired Mn3+/Mn4+ ratio, level of structural disordering, and crystal phase purity for Fe-doped LNMO. The synthesis process also aids in forming an amorphous Li2CO3 surface layer, approximately 1 nm thick, which protects the active material from excessive reaction with electrolyte. The typical Fe-doped LNMO cathode (S-05) exhibits superior performance compared to a commercialized LNMO counterpart. It delivers an initial discharge capacity of 135 mAh g-1 at 1 C with exceptional cycling stability over 500 cycles (capacity retention of 90%) under high voltage (5.0 V vs. Li+/Li). Furthermore, its rate capability significantly improves, with a capacity retention of 85% (5 C/0.2 C). This enhanced performance aligns with evidence of activated Ni2+/Ni3+/Ni4+ redox reactions and suppressed cathode electrolyte interphase resistance, leading to promoted Li+ diffusion. Moreover, it is found the cathode helps alleviate electrolyte degradation at high voltages by inhibiting the formation of singlet oxygen in the electrolyte.

Integrated hierarchical lanthanum niobium oxide surface coating to stabilize high-voltage performance and suppress Ni2+/Li+ cationic disorder in nickel-rich layered cathodes

Integrated hierarchical lanthanum niobium oxide surface coating to stabilize high-voltage performance and suppress Ni2+/Li+ cationic disorder in nickel-rich layered cathodes

Alleviating Voltage Hysteresis by Interconnecting Truncated Octahedral LiNi0.5Mn1.5O4 Cathode Particles Using Exfoliated Graphene

AbstractHigh‐voltage spinel LiNi0.5Mn1.5O4 (LNMO) has been highlighted as one of the most promising cathode materials for next‐generation Li‐ion batteries. However, its performance is known to have shortcomings, i. e., voltage hysteresis induced by the increasing impedance of LNMO during electrochemical cycling at high voltage operation. This paper demonstrates an innovative design of LNMO cathode materials to alleviate voltage hysteresis by combining unique characteristics of truncated octahedral LNMO with 2D exfoliated graphene (EG). The exposed (100) plane of truncated LNMO particles is known to have superior Li+ ion conduction. Meanwhile, the (111) plane is known to have excellent resistance to metal dissolution. Moreover, it was revealed that the presence of the EG framework as an interconnection aide could significantly improve the charge transfer process, helping to alleviate the voltage polarization. The sample with optimum LNMO‐EG composition shows a stable electrochemical performance with a capacity retention of 86.56 % after 300 cycles of charge‐discharge measurement at 1 C while exhibiting almost 3 times lower voltage hysteresis (0.233 mV/cycle) compared to the pristine LNMO (0.678 mV/cycle). This result demonstrates that combining the uniqueness of truncated LNMO and 2D EG can be a promising strategy to improve the electrochemical performance of LNMO cathode materials for next‐generation batteries.

Waxberry-like TiO2 with Synergistic Surface Modification of Pyrolytic Carbon Coating and Carbon Nanotubes as an Anode for Li-Ion Battery.

Titanium dioxide (TiO2) as an anode material for lithium-ion batteries (LIBs) has the advantages of tiny volume expansion, high operating voltage, and outstanding safety performance. However, due to the low conductivity of TiO2 and the slow diffusion rate of lithium ions (Li+), it is limited in the application of LIBs. Therefore, waxberry-like TiO2 comodified by pyrolytic carbon coating and carbon nanotubes was prepared in this work. The waxberry-like TiO2 with nanorods on its surface shortens the diffusion distance of Li+. Carbon nanotubes and waxberry-like TiO2 are tightly combined through electrostatic assembly and form a cross-linked conductive network to provide more electron transmission paths. A thin layer of pyrolytic carbon wraps carbon nanotubes and waxberry-like TiO2, which enhance the conductivity of the composites and ensure the structural integrity of the materials throughout the cycling process. The experimental data revealed that the discharge-specific capacity of TiO2@CNT@C is 170.5 mAh g-1 after 3000 cycles at a large current density of 5 A g-1, and the discharge-specific capacity is still 143 mAh g-1 at the superhigh rate of 10 A g-1, which provides excellent rate performance and cyclic stability. The efficient dual-carbon modification strategy could potentially be extended to other materials.

Challenges and Modification Strategies on High-Voltage Layered Oxide Cathode for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have attracted great attention due to their advantages on resource abundance, cost and safety. Layered oxide cathodes (LOCs) of SIBs possess high theoretical capacity, facile synthesis and low cost, and are promising candidates for large scale energy storage application. Increasing operating voltage is an effective strategy to achieve higher specific capacity and also high energy density of SIBs. However, at high operating voltages, LOCs will undergo a series of phase transitions in bulk phase, leading to huge change of volume and layer spacings accompanied by severe lattice stress and cracking formation. Degeneration of surface also occurs between LOCs and electrolytes, resulting in sustained growth of cathode electrolyte interphase (CEI) and release of O2 and CO2. These induce structural destruction and electrochemical performance degradation in high voltage regions. Recently, many strategies have been proposed to improve electrochemical performance of LOCs under high voltages, including bulk element doping, structural design, surface coating and gradient doping. This review describes pivotal challenges and occurrence mechanisms at high voltages, and summarizes strategies to improve stability of bulk and surface. Viewpoints will be provided to promote development of high energy density SIBs.

Synthesis of Trisiloxane with the Dioxaborolane Group as a Cathode Film-Forming Electrolyte Additive for High-Temperature LiMn2O4/Li4Ti5O12 Batteries.

LiMn2O4 batteries have been widely applied as various portable electronic devices and electric vehicles owing to the merits of low cost, high operating voltage, excellent rate capability, and environmental friendliness. However, the poor performance at elevated temperatures remains a serious technical challenge in terms of commercial application purposes. A borate-containing trisiloxane compound of TSMBO is designed and synthesized as a cathode film-forming electrolyte additive to improve the electrochemical performances of LiMn2O4/Li4Ti5O12 batteries, especially at high temperatures of 55 °C. Atomic force microscopy measurement confirms that the trisiloxane moiety in TSMBO can construct a cathode electrolyte interface (CEI) with higher mechanical strength and better flatness compared to the disiloxane moiety in the TSMBO analogue with a similar chemical structure. The robust CEI film on the surface of the LiMn2O4 cathode and the inhibited hydrolysis of LiPF6 in the electrolyte significantly suppress the dissolution of Mn from the LiMn2O4 cathode and maintain the structural integrity of the LiMn2O4 lattice over cycling. Thus, the LiMn2O4/Li4Ti5O12 coin cell using the TSMBO-containing electrolyte with an optimized addition level of 0.5 wt % exhibits a higher capacity retention of 49.3% compared with 34.3% for the baseline electrolyte after 300 cycles under 1C rate at 55 °C. The LiMn2O4/Li4Ti5O12 pouch cell tests show excellent high-temperature and cycling performance at 55 °C and a higher capacity retention of 90.4% after 500 cycles at 2C compared to 79.7% for that with the baseline electrolyte after 430 cycles at 2C. This work demonstrates that TSMBO is a promising electrolyte additive for practical use to improve the cycling stability of LiMn2O4/Li4Ti5O12 batteries at elevated temperatures.

Kinetics Enhancement of High‐Voltage LCO via In‐Situ Formed Cyanide‐Rich Polymer Interfaces

AbstractLithium cobalt oxide (LiCoO2) is widely used as cathode material for lithium‐ion batteries due to its high operation voltage and high specific capacity. However, conventional LiCoO2 (LCO) undergoes severe structural phase transitions and compositional changes at high voltage (>4.4 V) leading to failure. Herein, a multifunctional crosslinked polymer interface is insitu formed on LCO particles, which can build a nanoscale conformal coating layer on the interface of LCO, preventing the side reaction with the electrolyte. Moreover, thanks to its high‐voltage talerances and high Li+ conductivity, the in‐situ polymerized interface has excellent high‐voltage stability and Li+ transport kinetics, which significantly improves the electrochemical performances of LCO at 4.55 or 4.6 V. This study confirms the feasibility of in situ polymer modification of LCO, providing new ideas and methods for the structural stabilization and performance enhancement of high‐voltage lithium cobalt oxides.

One-pot synthesis of hydroxypropyl methylcellulose-based gel polymer electrolytes for high-performance supercapacitors

The electrolyte is a crucial component that significantly affects the electrochemical performance of supercapacitors. The hydroxypropyl methylcellulose (HPMC)-based gel polymer electrolyte (GPE) with high operating voltage was synthesized via an innovative “one-pot” method in this study, and the impacts of organic solvent/water ratio and LiNO3 concentration on gelation and conductivity of the GPE were investigated systematically. Under the optimal condition with a DMF/water ratio of 10:0 and the incorporation of 7 % LiNO3, the ionic conductivity reached 1.06 S m−1. Integrated into symmetric supercapacitors, the HPMC-based GPE demonstrated an expanded electrochemical window of 2.7 V. It also possessed a specific capacitance of 115.8 F g−1 at 1.0 A g−1, an energy density of 29.31 Wh kg−1, and outstanding cyclic stability, retaining 86 % of its initial capacitance after 2000 cycles. Through cyclic stability tests under pressure conditions, the assembled flexible supercapacitors were able to maintain capacitance retention of 60 % and coulombic efficiency of 97 %. This work offers a streamlined synthesis for HPMC-based GPE with superior electrochemical properties, which exhibits its potential in advancing supercapacitor technology for flexible electronics.

Insights into Tiny High‐Entropy Doping Promising Efficient Sodium Storage of Na3V2(PO4)2O2F toward Sodium‐Ion Batteries

AbstractBoth high operation voltage and theoretical capacity promise polyanion‐type fluorophosphate Na3V2(PO4)2O2F as a competitive cathode toward high‐energy‐density sodium‐ion batteries (SIBs). However, the intrinsic low kinetic characteristics seriously influence its high‐power property and service life. To well address this, a creative tiny high‐entropy (HE) doping methodology is purposefully developed to fabricate nanoscale Na3V1.94(Cr, Mn, Co, Ni, Cu)0.06(PO4)3O2F (NVPOF‐HE) as the advanced cathode materials for SIBs. The grain refinement effect induced by collaborative regulations from polyvinyl pyrrolidone and tiny HE heteroatomic doping is reasonably proposed for nanosizing particle dimension of NVPOF‐HE. Systematic experiments and theoretical calculations authenticate that the HE doping efficiently promotes the electronic/ionic transport and high‐voltage capacity contribution, and weakens the lattice expansion over Na+‐(de)intercalation processes. Thanks to the appealing virtues mentioned here, the nano NVPOF‐HE, compared to single‐ion/dual‐ion/triple‐ion doped cases, achieves even better Na+‐storage performance in terms of both high‐rate capacities and long‐term cycling stability. Furthermore, the NVPOF‐HE assembled full SIBs deliver a high materials‐level energy density of 463 Wh kg−1 and electrochemical stability of ≈93.8% capacity retention after 1000 cycles at 5 C rate. More essentially, the fundamental insights gained here provide a significant scientific and technological advancement in high‐performance and durable polyanionic cathodes toward next‐generation SIBs.

The novel methods of insulation detection based on Adaptive Levenberg–Marquardt algorithm and Third-Order Variable Forgetting Factor Recursive Least Squares-Decouple algorithm

Electric vehicles (EVs) are central to the future of automotive development, with high-voltage insulation performance critical for operational safety. Existing insulation detection methods face challenges such as limited scope, low accuracy, poor interference resistance, and slow response. This study introduces two insulation detection models based on the unbalanced bridge method and low-frequency signal injection, analyzing their theoretical effectiveness and confirming superior detection capability in the unbalanced bridge method. Furthermore, to address feedback voltage waveform issues in this method, an adaptive Levenberg–Marquardt (ALM) algorithm is proposed to prevent the divergence typically seen in traditional approaches. Additionally, a decoupling algorithm utilizing a Third-order Variable Forgetting Factor Recursive Least Squares (TVFF-Decouple) simplifies algorithm complexity significantly while enabling anomaly detection. Finally, AEKF and SRCKF algorithms were used for observation, identifying an optimal combination that reduces noise interference effectively. Simulations and bench tests demonstrate that the proposed methods swiftly and accurately detect positive and negative insulation resistances and equivalent Y capacitance under various conditions.

The analysis of the overall failure of practical Zn−Ni battery

Zn−Ni batteries are viewed as promising power sources for electric tools and electric vehicles (EVs) due to their benefits of high safety, high working voltage and attractive rate performance. However, the practical applications of the Zn−Ni batteries are hampered by poor cycling performance, posing significant challenges for their widespread utilization. To effectively address this pressing concern, a profound investigation of the intrinsic failure mechanisms underlying Zn−Ni batteries holds paramount importance. This paper carries out a thorough analysis of battery behavior to simulate industrial application scenarios using two different assembly methods of Zn−Ni batteries. One type is a battery composed of one Ni(OH)2 cathode and one Zn anode (abbreviated as OO). The other type is the battery assembled with one Ni(OH)2 cathode and two Zn anodes (abbreviated as OT). Ultimately, it is revealed that the principal factors of Zn anode failure in OO battery are the growth of zinc dendrites, passivation and uneven current distribution. In contrast, for OT battery, the cathode emerges as the failed electrode. Specifically, the rupture of spheres on the positive electrode surface and the detached powder from the substrate result in the decline in capacity and finally the failure of the battery. Two classical battery assembly methodologies were employed to investigate in-depth the failure mechanisms of Zn−Ni batteries, ultimately revealing that the reasons for battery failure mechanism differed, thus providing valuable and practical guidance for future research aimed at enhancing battery lifespan.

Unveiling the Role of Filler Characteristics in Enhancing the High-Voltage Performance of Succinonitrile-Based Solid-State Lithium-Metal Batteries.

For exploiting high-energy lithium-metal batteries, it is of utmost importance to develop electrolytes that possess exceptional ionic conductivity and an extensive electrochemical stability range. In this study, 3D PAN nanofibers and polymer electrolytes incorporating various inorganic fillers with different Lewis acid-base properties were fabricated. PAN@Al-SSE exhibits exceptional ionic conductivity (0.48 mS·cm-2 at room temperature), a high Li+ transference number (0.41), and a wide electrochemical window (5.26 V). The device is able to operate stably in Li symmetric cells for more than 1000 h under a potential of 0.03 V under a current density of 0.2 mA·cm-2. Besides, the groundbreaking technology equips high-voltage Li-LiCoO2 solid-state batteries with exceptional cycling performance (91.3% and 82.1% retention after 100 cycles at 0.2 and 1 C, respectively) at room temperature. Mechanistic studies indicate that the Lewis acid-base properties of surface fillers are instrumental and crucial to form a stable solid-electrolyte interphase layer. γ-Al2O3, in particular, with more Lewis acid sites, ensures the dissociation of LiTFSI and induces the excessive decomposition and polymerization of succinonitrile. There exists an equilibrium effect between dissociation and polymerization in a succinonitrile-based solid electrolyte, which plays a critical role in improving the manifestation of succinonitrile-based solid-state lithium cells, especially under high-voltage conditions.

The Development and Prospect of Stable Polyanion Compound Cathodes in LIBs and Promising Complementers.

Cathode materials are usually the key to determining battery capacity, suitable cathode materials are an important prerequisite to meet the needs of large-scale energy storage systems in the future. Polyanionic compounds have significant advantages in metal ion storage, such as high operating voltage, excellent structural stability, safety, low cost, and environmental friendliness, and can be excellent cathode options for rechargeable metal-ion batteries. Although some polyanionic compounds have been commercialized, there are still some shortcomings in electronic conductivity, reversible specific capacity, and rate performance, which obviously limits the development of polyanionic compound cathodes in large-scale energy storage systems. Up to now, many strategies including structural design, ion doping, surface coating, and electrolyte optimization have been explored to improve the above defects. Based on the above contents, this paper briefly reviews the research progress and optimization strategies of typical polyanionic compound cathodes in the fields of lithium-ion batteries (LIBs) and other promising metal ion batteries (sodium ion batteries (SIBs), potassium ion batteries (PIBs), magnesium ion batteries (MIBs), calcium ion batteries (CIBs), zinc ion batteries (ZIBs), aluminum ion batteries (AIBs), etc.), aiming to provide a valuable reference for accelerating the commercial application of polyanionic compound cathodes in rechargeable battery systems.

Charge-Selective 2D Heterointerface-Driven Multifunctional Floating Gate Memory for In Situ Sensing-Memory-Computing.

Flash memory, dominating data storage due to its substantial storage density and cost efficiency, faces limitations such as slow response, high operating voltages, absence of optoelectronic response, etc., hindering the development of sensing-memory-computing capability. Here, we present an ultrathin platinum disulfide (PtS2)/hexagonal boron nitride (hBN)/multilayer graphene (MLG) van der Waals heterojunction with atomically sharp interfaces, achieving selective charge tunneling behavior and demonstrating ultrafast operations, a high on/off ratio (108), extremely low operating voltage, robust endurance (105 cycles), and retention exceeding 10 years. Additionally, we achieve highly linear synaptic potentiation and depression, and observe the reversibly gate-tunable transitions between positive and negative photoconductivity. Furthermore, we employed the VGG11 neural network for in situ trained in-sensor-memory-computing to classify the CIFAR-10 data set, pushing accuracy levels comparable to pure digital systems. This work could pave the way for seamlessly integrated sensing, memory, and computing capabilities for diverse edge computing.

Enhanced electrochemical performance of K0.67[Ni0.3Mn0.6Co0.1] O2 as a cathode material for secondary K-Ion batteries: Improved K-Ion insertion and reduced charge transfer barrier

Potassium-ion batteries, with their high operating voltage and cost-efficiency, emerged as promising contenders for large-scale energy storage system. Nevertheless, the practical application is hindered by the significant challenges of achieving high capacity and good rate capability in cathodes. Herein, a novel layered oxide cathode, K0.67[Ni0.3Mn0.6Co0.1] O2 (KNMCO), has been synthesized via solid-state (S-KNMCO) and co-precipitation (C-KNMCO) routes. The X-Ray diffraction (XRD) peaks of KNMCO are identified in R3 m space group and well-indexed to hexagonal unit cell. The FE-SEM shows non-spherical morphologies for both samples. Additionally, high-resolution transmission electron microscopy (HR-TEM) images of the synthesized cathode materials shows the interlayer spacing of S-KNMCO is higher than that of C-KNMCO. Furthermore, the electrochemical performance of S-KNMCO and C-KNMCO is characterized using K-metal as anode and electrolyte KPF6 in EC/DEC (1:1, v/v). The S-KNMCO and C-KNMCO exhibit the maximum specific discharge capacity of ∼101 mAhg-1 and ∼66 mAhg-1 at the current rate of C/20 respectively. Additionally, these cells show the good rate capability and coulombic efficiency (∼94%). This research offers novel perspectives on the development of cathode substances for KIBs.

Conformational isomerism breaks the electrolyte solubility limit and stabilizes 4.9 V Ni-rich layered cathodes

By simply increasing the concentration of electrolytes, both aqueous and non-aqueous batteries deliver technical superiority in various properties such as high-voltage operation, electrode stability and safety performance. However, the development of this strategy has encountered a bottleneck due to the limitation of the intrinsic solubility, and its comprehensive performance has reached its limit. Here we demonstrate that the conformational isomerism of the solvent would significantly affect the solubility of electrolytes. By transforming the configuration of solvent from cis-cis to cis-trans upon thermal triggering, we successfully break the solubility limit, and a beyond concentrated electrolyte with the lowest solvent-to-salt molar ratio of 0.70 is constructed. Transitions between cis-cis and cis-trans conformers are observed through Nuclear Magnetic Resonance (NMR) testing. The electrolyte consists entirely of anion-mediated solvation structures and promotes the formation of robust inorganic-dominated cathode electrolyte interphase. As a result, it enables stable cycling of 4.9 V-class LiNi0.8Co0.1Mn0.1O2 positive electrodes. Moreover, a high capacity of 151.2 mAh g−1 can be maintained after 1000 cycles at cut-off voltage of 4.8 V. This work provides a chemical pathway to build new concept electrolytes working under harsh conditions.

Li2FeCl4 as a Cost-Effective and Durable Cathode for Solid-State Li-Ion Batteries.

Low-cost cathode materials with high energy density and good rate performance are critical for the development of next-generation solid-state Li-ion batteries (SSLIBs). Here, we report Li2FeCl4 as a cathode material for SSLIBs with highly reversible Li intercalation and deintercalation, a high operation voltage of 3.7 V vs Li+/Li, good rate capability, and good cycling stability with an 86% capacity retention after 6000 cycles. Operando synchrotron XRD reveals that the phase evolution of Li2FeCl4 during charge-discharge cycling involves both solid-solution and two-phase reactions, which maintains a very stable framework during Li insertion and extraction.

Graphene wrapped porous polyaniline/manganese oxide nanocomposites with enhanced structural stability and conductivity for high‐performance symmetric supercapacitor

AbstractManganese oxides have emerged as promising electrode materials for supercapacitors. Despite extensive efforts to improve their conductivity and structural stability through various manganese oxide/conductor nanocomposites, achieving efficient and reliable energy storage electrode materials has remained challenging. In this study, we propose a meticulous “dual enhancement” strategy, where three‐dimensional (3D) nanostructured polyaniline/manganese oxide composites (PM) are synthesized via an in situ method and further integrated with graphene wrapping to form polyaniline/manganese oxide/graphene nanocomposites (PMG). Electrochemical characterization reveals that PMG exhibits a remarkable specific capacitance of up to 403 F g−1 (at 1 A g−1), with a favorable capacitance retention of 80.2% after 5000 cycles, along with a wide potential window. This enhancement is attributed to the synergistic effects of polyaniline, which provides a supportive framework and electron transport pathways, and graphene, which offers external protection and enhances conductivity pathways. Assembled symmetrical supercapacitors demonstrate outstanding energy density (32.7–23.3 Wh kg−1) and power density (720–4500 W kg−1) at a high operating voltage of 1.8 V, surpassing the performance of many reported high‐performance supercapacitors. This study provides valuable insights for advancing manganese oxide electrode materials and is expected to catalyze their widespread adoption in energy storage applications.Highlights “Dual enhancement” is implemented by PANI supporting and rGO wrapping. The conductivity and structural stability of composite electrode is greatly enhanced. Improved capacitance (403 F g−1, 1 A g−1) and cycling stability (80.2%) is achieved. The symmetrical supercapacitor has high voltage and energy density (32.7 Wh kg−1).

High drain field impact ionization transistors as ideal switches

Impact ionization effect has been demonstrated in transistors to enable sub-60 mV dec−1 subthreshold swing. However, traditionally, impact ionization in silicon devices requires a high operation voltage due to limited electrical field near the device drain, contradicting the low energy operation purpose. Here, we report a vertical subthreshold swing device composed of a graphene/silicon heterojunction drain and a silicon channel. This structure creates a low voltage avalanche impact ionization phenomenon and leads to steep switching of the silicon-based device. Experimental measurements reveal a small average subthreshold swing of 16 µV dec−1 over 6 decades of drain current and nearly hysteresis-free, and the operating voltage at which a vertical subthreshold swing occurs can be as low as 0.4 V at room temperature. Furthermore, a complementary silicon-based logic inverter is experimentally demonstrated to reach a voltage gain of 311 at a supply voltage of 2 V.

Permeable void-free interface for all-solid-state alkali-ion polymer batteries.

All-solid-state batteries suffer from a loss of contact between the electrode and electrolyte particles, leading to poor cyclability. Here, a void-free ion-permeable interface between the solid-state polymer electrolyte and electrode is constructed in situ during cycling using charge/discharge voltage as the stimulus. During the charge-discharge, the permeation phase fills the voids at the interface and penetrates the electrode, forming strong bonds with the cathode and effectively mitigating the contact problem. Our all-solid-state potassium ion polymer batteries maintain high Coulombic efficiency more than 2000 cycles at a high operating voltage of 4.5 volt and stably cycle more than 500 cycles even at 4.6 volt. Our rational design for mitigating the contact problem is versatile, as demonstrated by the scalability of all-solid-state graphite-based polymer potassium-ion pouch cells and all-solid-state lithium-ion polymer batteries.