Energy Density Lithium-ion Batteries Research Articles

Mitigating PTFE decomposition in ultra thick dry-processed anodes for high energy density lithium-ion batteries

Dry electrode technology is a next-generation method for manufacturing lithium-ion batteries because it is useful for fabricating thick electrodes without solvents, facilitating high energy densities and cutting down on the battery manufacturing costs. However, the commonly used polytetrafluoroethylene (PTFE) binder in dry electrode technology undergoes severe decomposition in dry-processed anodes during the first lithiation process due to its low lowest unoccupied molecular orbital level. This phenomenon seriously aggravates battery performance, such as in terms of the initial coulombic efficiency and cycle life. Thus, a strategy to suppress this irreversible reaction of PTFE should be established for dry-processed anodes to increase the energy density of LIBs without adverse effects on battery performance. To address this challenge, in this work, fluoroethylene carbonate (FEC) as an electrolyte additive has been introduced to form a preemptive and stable FEC-derived solid electrolyte interface (SEI) to protect a graphite and the PTFE binder. This SEI considerably alleviates the irreversible reaction of PTFE, thereby securing the reversible capacity and maintaining the structure of the electrode through the great binding properties. These results provide guidance for increasing the electrochemical stability in dry-processed anode systems, which gets closer the innovative dry anode technology for cost-effectiveness and high energy density.

Enhancing the Cathode/Electrolyte interface in Ni-Rich Lithium-Ion batteries through homogeneous oxynitridation enabled by NO3− dominated clusters

To meet the demand for higher energy density in lithium-ion batteries, extensive research has focused on advanced cathodes and metallic lithium anodes. However, Ni-rich cathodes suffer from the inactive phase-transition and side reactions at the cathode-electrolyte interfaces (CEI). In this study, we propose a novel approach to enhance the solubility of LiNO3 in carbonate electrolyte systems using a local high-concentrated addition strategy with triethyl phosphate as a co-solvent. Rather than the traditional solvent-dominated solvation clusters, the NO3− dominated electrolyte is examined to elucidate unique complexation phenomena. Two distinct clusters in NO3− dominated electrolyte arising from as a consequence of intramolecular interactions intrinsic to the constituents. This promotes the formation of a homogeneous oxynitride interphase and facilitates more expeditious lithium ion diffusion kinetics. Hence, the less stress fragmentation and irreversible phase transformation occur on the cathode surface with the homogeneous oxynitridation interface. This innovative design enables efficient cycling of the Li || NCM811 cell, offering a promising strategy to improve lithium-ion batteries performance.

Optimisation of powder extrusion moulding process for thick ceramic electrodes of LiCoO2 for enhanced energy-density lithium-ion batteries

Lithium-ion batteries are widely used in portable electronic devices because of their high energy and power density. To enhance the energy density of these batteries, one strategy involves increasing the active material loading by increasing the thickness of the electrodes. In previous studies, we demonstrated that powder extrusion moulding (PEM) is a scalable and efficient method for producing additive-free LTO and LFP ceramic electrodes, which exhibit remarkable electrochemical performance with thicknesses up to 500 μm. This study focuses on the preparation and optimisation of the entire manufacturing process for thick ceramic electrodes of LiCoO2 (LCO) with a high mass loading of 180 mg cm−2 using the PEM process. Different powder loadings of mixtures of LCO and a thermoplastic multi-component binder were explored to obtain a formulation suitable for rheology. The optimal formulation comprises 60 vol% of powder. After binder removal via a combination of solvent and thermal treatment, followed by air sintering, parts with varying porosities were obtained. Striking a balance between porosity and thermal degradation is crucial for achieving optimal electrochemical behaviour. Electrochemical evaluations of the electrodes sintered at 900 °C and 1000 °C revealed areal capacity values as high as 17 mAh cm−2 at C/25 and 7 mAh cm−2 at C/6.25, respectively. These values far exceed the 1−2 mAh cm−2 obtained from commercial LCO electrodes. These results indicate a strategy for the production of electrodes to fabricate lithium-ion batteries with a low ratio of inactive materials and, therefore, with higher energy densities.

Stable operation of SiO anodes enabled by a multifunctional molecular crosslinker

SiO anodes are promising for energy-dense lithium-ion batteries, however, they suffer from short cycle life caused by large volume change (∼200%) and low initial Coulomb efficiency (ICE). Herein, we report a conceptual strategy to boost the electrochemical performance of SiO by enhancing the interaction between binders and conductive additives via a molecular crosslinker with both pyrene ring and adamantyl group (AdPy). Benefiting from the inclusion interaction between beta-cyclodextrin polymers (βCDp) and AdPy as well as the π-π interaction between single-walled carbon nanotube (SWCNT) and AdPy, a robustly conductive and adhesive network is constructed for maintaining integral electrode structure and robust conductive network during charge/discharge cycles. The resultant SiO electrode with SWCNT/AdPy-βCDp networks achieves larger initial capacity, higher ICE and better cycle stability than those of SiO electrode with SWCNT/βCDp complex, indicating the key role of AdPy crosslinker in enhancing electrochemical performance. Experimental results suggest that the interaction between binders and conductive additives can effectively alleviate stress generated from SiO volume changes during cycling. This work provides a promising platform to construct dynamic cross-linking conductive and adhesive network for boosting the lithium storage performance of high-capacity electrode materials.

Electrolyte-Enabled High-Voltage Operation of a Low-Nickel, Low-Cobalt Layered Oxide Cathode for High Energy Density Lithium-Ion Batteries.

The lithium-ion battery industry acknowledges the need to reduce expensive metals, such as cobalt and nickel, due to supply chain challenges. However, doing so can drastically reduce the overall battery energy density, attenuating the driving range for electric vehicles. Cycling to higher voltages can increase the capacity and energy density but will consequently exacerbate cell degradation due to the instability at high voltages. Herein, an advanced localized high-concentration electrolyte (LHCE) is utilized to enable long-term cycling of a low-Ni, low-Co layered oxide cathode LiNi0.60Mn0.31Co0.07Al0.02O2 (NMCA) in full cells with graphite or graphite-silicon anodes at 4.5V (≈4.6 vs Li+/Li). NMCA cells with the LHCE deliver a high initial capacity of 194mAhg-1 at C/10 rate along with 73% capacity retention after 400 cycles compared to 49% retention in a baseline carbonate electrolyte. This is facilitated by reduced impedance growth, active material loss, and gas evolution with the NMCA cathode. These improvements are attributed to the formation of robust, inorganic-rich interphase layers on both the cathode and anode throughout cycling, which are induced by a favorable salt decomposition in the LHCE. This study demonstrates the efficacy of electrolytes toward facilitating the operation of high-energy-density, long-life, and cost-effective cathodes.

Preparation of the Porous Copper Foil Current Collector for High-Performance Lithium-Ion Batteries by Electro-Codeposition: Effect of Stirring Speed

As an indispensable component of lithium-ion batteries (LIBs), the application of porous copper (Cu) foil current collector is an effective method to improve the performance and energy density of LIBs. In this work, a porous Cu (PCu) foil was fabricated by acid washing the Cu-Fe3O4 foil prepared by the electro-codeposition in a stirred CuSO4 solution containing the magnetic Fe3O4 nanoparticles. The effect of the stirring speed on the properties of PCu foils and the battery performance of PCu foil as current collectors were investigated. The surface roughness of the PCu foil increases, while its volume density decreases as the stirring speed rises. The volume density of PCu foil (6.63 g cm−3) prepared at 400 rpm (PCu400) is reduced by 22.4% than that of the commercial Cu foil (8.55 g cm−3). The specific capacity (241.2 mAh g−1) of the cell with PCu400 current collector is 31.3% higher than that of the cell with commercial Cu current collector (183.7 mAh g−1) after 300 charge-discharge cycles at 2 C. The electro-codeposition of porous Cu foil current collectors offers a promising method for high-performance lightweight LIBs.

A Slightly Expanded Graphite Anode with High Capacity Enabled By Stable Lithium-Ion/Metal Hybrid Storage.

Integrating lithium-ion and metal storage mechanisms to improve the capacity of graphite anode holds the potential to boost the energy density of lithium-ion batteries. However, this approach, typically plating lithium metal onto traditional graphite anodes, faces challenges of safety risks of severe lithium dendrite growth and short circuits due to restricted lithium metal accommodation space and unstable lithium plating in commercial carbonate electrolytes. Herein, a slightly expanded spherical graphite anode is developed with a precisely adjustable expanded structure to accommodate metallic lithium, achieving a well-balanced state of high capacity and stable lithium-ion/metal storage in commercial carbonate electrolytes. This structure also enables fast kinetics of both Li intercalation/de-intercalation and plating/stripping. With a total anode capacity of 1.5 times higher (558mAhg-1) than graphite, the full cell coupled with a high-loading LiNi0.8Co0.1Mn0.1O2 cathode (13mgcm-2) under a low N/P ratio (≈1.15) achieves long-term cycling stability (75% of capacity after 200 cycles, in contrast to the fast battery failure after 50 cycles with spherical graphite anode). Furthermore, the capacity of the full cell also reaches a low capacity decay rate of 0.05% per cycle at 0.2C under the low temperature of -20°C.

Assembled MXene-Liquid Metal Cages on Silicon Microparticles as Self-Healing Battery Anodes.

In pursuit of higher energy density in lithium-ion batteries, silicon (Si) has been recognized as a promising candidate to replace commercial graphite due to its high theoretical capacity. However, the pulverization issue of Si microparticles during lithiation/delithiation results in electrical contact loss and increased side reactions, significantly limiting its practical applications. Herein, we propose to utilize liquid metal (LM) particles as the bridging agent, which assemble conductive MXene (Ti3C2Tx) sheets via coordination chemistry, forming cage-like structures encapsulating mSi particles as self-healing high-energy anodes. Due to the integration of robust Ti3C2Tx sheets and deformable LM particles as conductive buffering cages, simultaneously high-rate capability and cyclability can be realized. Post-mortem analysis revealed the cage structural integrity and the maintained electrical percolating network after cycling. This work introduces an effective approach to accommodate structural change via a resilient encapsulating cage and offers useful interface design considerations for versatile battery electrodes.

Improving electrochemical performances of LiNi0.5Mn1.5O4 by the strategy of oxygen vacancy doping

Despite the dazzling potential to be utilized as a high energy density lithium-ion battery cathode, the practical application of LiNi0.5Mn1.5O4 (LNMO) is hampered by the structural distortion related to Jahn-Teller effect of Mn3+ and the capacity degradation related to Mn2+ dissolution at high voltage. Herein, LNMO cathode materials doped with different contents of oxygen vacancies are synthesized by directly adjusting the oxygen ratio in the calcination atmosphere. Experimental and theoretical calculation results show that doping an appropriate amount of oxygen vacancies can regulate the electronic structure of Mn and Ni around oxygen vacancy, adjust the relative amount of Mn3+/Mn4+, increase the degree of disorder, and improve the electronic and ionic conductivity of LNMO, thereby enhancing its electrochemical performance. Especially, the modified LNMO exhibits a high capacity of 121.2 mAh g−1 at 0.5 C, a good capacity retention of 87.6 % after 100 cycles, and an excellent rate performance when the content of oxygen vacancies is about 20.60 %, corresponding to the oxygen ratio of 50 % in the calcination atmosphere. This study emphasizes the influence of doping oxygen vacancies on LNMO performance, enhancing its electrochemical properties without the introduction of additional elements. Moreover, these findings offer a fresh approach to enhancing the electrochemical performance of advanced batteries.

High-efficiency and low-consumption preparation of ultra-thin and high-performance nanotwinned copper foils by high-gravity intensified direct current electrodeposition

In study, a novel strategy was adopted by the integration of microstructure control and electrodeposition process intensification for high-efficiency, low-consumption and convenient electrodeposition of high performance and ≤4.5 μm ultra-thin copper foils for lithium-ion battery (LIB) collectors. The microstructure and the electrodeposition process of copper foils were effectively controlled and enhanced by the synergy of optimized electrolyte and Multi-Concentric Cylindrical Electrodes-Rotating Bed (MCCE-RB) which was used to generate high-gravity fields. Equiaxed nanotwinned copper (nt-Cu) foils possessed ultra-thin thicknesses ranging from 3.70 to 4.08 μm. They exhibited tensile strength and elongation of 787 MPa and 21.2 %, respectively. In contrast to the conventional direct current electrodeposition, electrodeposition and current efficiency were increased by 15.1 % and 27.2 %, respectively, while the energy consumption was decreased by 23.7 % in the high-gravity field. This is beneficial to improve the weight and energy density of LIBs by applying the strategy and technique of high-gravity intensifying.

Enhanced Low-Temperature Resistance of Lithium-Metal Rechargeable Batteries Based on Electrolyte Including Ethyl Acetate and LiDFOB Additives.

To meet the demand for higher energy density in lithium-ion batteries and expand their application range, coupling lithium metal anodes with high-voltage cathodes is an ideal solution. However, the compatibility between lithium metal batteries and electrolytes affects their applicability. In this study, proposes a locally concentrated electrolyte based on ethyl acetate (EA) as the solvent, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the lithium salt, and lithium difluorooxoborate (LiDFOB) as a sacrificial agent to enhance the low-temperature and high-voltage endurance of Li//Lithium cobalt oxide (LCO) batteries. The Li//LCO battery can operate within the voltage range of 3 to 4.5 V, with an initial discharge specific capacity of 174.5 mAh g-1 at 20 °C. At -40 °C, after 200 cycles, the capacity retention rate is 87.7 %. It can operate under extreme conditions of -70 °C, with a discharge specific capacity of 112.6 mAh g-1. Additionally, LCO//HC batteries using this electrolyte demonstrate excellent performance. Present work provides a new perspective for the optimization of electrolytes for low-temperature lithium-ion batteries.

In Situ Construction of a Multifunctional Interphase Enabling Continuous Capture of Unstable Lattice Oxygen Under Ultrahigh Voltages.

The use of nickel-rich layered materials as cathodes can boost the energy density of lithium batteries. However, developing a safe and long-term stable nickel-rich layered cathode is challenging primarily due to the release of lattice oxygen from the cathode during cycling, especially at high voltages, which will cause a series of adverse effects, leading to battery failure and thermal runaway. Surface coating is often considered effective in capturing active oxygen species; however, its process is rather complicated, and it is difficult to maintain intact on the cathode with large volume changes during cycling. Here, we propose an in situ construction of a multifunctional cathode/electrolyte interphase (CEI), which is easy to prepare, repairable, and, most importantly, capable of continuously capturing active oxygen species during the entire life span. This unique protective mechanism notably improves the cycling stability of Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) cells at rigorous working conditions, including ultrahigh voltage (4.8 V), high temperature (60 °C), and fast charging (10 C). An industrial 1 A h graphite||NCM811 pouch cell achieved stable operation of 600 cycles with a capacity retention of 79.6% at 4.4 V, exhibiting great potential for practical use. This work provides insightful guidance for constructing a multifunctional CEI to bypass limitations associated with high-voltage operations of nickel-rich layered cathodes.

Enhanced cycling stability in 4.6 V LiCoO2 for high energy density lithium-ion batteries through Al and Y co-doping

For the first time, this work investigates the synergetic impact of yttrium (Y) and aluminium (Al) co-doping on the electrochemical properties of 4.6 V LiCoO2 (LCO) cathode for high energy density lithium-ion batteries. The optimized LCO demonstrates an impressive initial discharge capacity of 208.6 mAh g−1 in the voltage range of 3–4.6 V, along with superior structural stability, retaining over 86 % of its initial capacity even after 125 cycles at the current of 100 mA g−1 that is far higher than the capacity retention of 40 % for the pristine LCO under the same condition. Thanks to the synergistic effect, Al in Co layers enhances the bonds of Al/Co-O to stabilize oxygen in the LCO crystal structure while Y serves “pillar” in Li layers, migrated from the initial Co layers during cycling process, effectively curtail the formation and expansion of interlayer cracking, which contributes to the long-term cycle stability of LCO under high voltage. Most importantly, Al/Y co-doping is a facile process compatible with the existing industrial infrastructure for LCO mass production, and thus it can be scaled up readily for commercial applications. Al/Y co-doped LCO is assembled into commercial-level pouch cells with graphite anode, achieves an extremely high energy density of 750 Wh/L, and exhibits a superior cycling stability and obtains a capacity retention of 88.2 % at 25 °C after 800 cycles with the high cutoff voltage of 4.55 V.

Noncombustible gel polymer electrolyte inspired by bio-radical chemistry for high voltage and high safety Ni-rich lithium batteries

For high energy density lithium-ion batteries (LIBs) with nickel-rich ternary cathodes, the chemical degradation of electrolytes caused by free radical reactions and the hazards of thermal runaway have always been significant challenges. Inspired by the free radical scavenging of living organisms and multiphase synergistic flame retardant mechanism, we innovatively designed and prepared a multifunctional flame retardant HCCP-TMP that combines flame retardancy and free radical scavenging by combining hindered amine and cyclophosphazene. Only 1 wt% HCCP-TMP can make the polyacrylate-based gel polymer electrolyte (GPE) incombustible. Moreover, the equipped NCM811//Graphite pouch cells don't exhibit combustion behavior after thermal runaway and can resist mechanical abuse. Based on the above noncombustible GPE, the NCM811//Li battery exhibits capacity retention rate of 82.2 % after 100 cycles at a current density of 2 C and in the voltage range of 3.0–4.7 V, exhibiting excellent cyclability under high voltage. This simple molecular design simultaneously improves the fire safety and high voltage stability, demonstrating enormous application potential in the field of advanced LIBs with high safety and high energy density.

Dynamically constructing robust cathode-electrolyte-interphase on nickel-rich cathode by organic boron additive for high-performance lithium-ion batteries

Nickel-rich ternary cathode materials LiNi0.8Co0.1Mn0.1O2 (NCM811) have attracted broad attention due to their high voltage and high energy density for lithium-ion batteries. However, rapid capacity decay due to unstable particle surface inhibit the application. Artificial cathode electrolyte interface (CEI) is undoubtedly a more effective and simpler way to solve this issue. Here, stable and highly conductive in situ CEI is designed using a low-cost organic boron additive isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (ITD). Higher occupied molecular orbital energy endows ITD ability to participate in forming CEI. ITD-contained CEI can reduce nickel dissolving, resulting in a lower self-discharge rate, which is benefit from the uniform and stable CEI on the NCM811 surface. As expected, ITD-based CEI can restrain NCM811crystal cracking in Li||NCM811 half batteries, improving capacity retention from 29.4 % to 93.0 % after 200 cycles at 1C (1C = 200 mA g−1). It is worth mentioning that ITD–derived CEI is conducive to ion migration, which improve the rate capacity retention from 91.5 % to 95.5 %.

Composition and state prediction of lithium-ion cathode via convolutional neural network trained on scanning electron microscopy images

High-throughput materials research is strongly required to accelerate the development of safe and high energy-density lithium-ion battery (LIB) applicable to electric vehicle and energy storage system. The artificial intelligence, including machine learning with neural networks such as Boltzmann neural networks and convolutional neural networks (CNN), is a powerful tool to explore next-generation electrode materials and functional additives. In this paper, we develop a prediction model that classifies the major composition (e.g., 333, 523, 622, and 811) and different states (e.g., pristine, pre-cycled, and 100 times cycled) of various Li(Ni, Co, Mn)O2 (NCM) cathodes via CNN trained on scanning electron microscopy (SEM) images. Based on those results, our trained CNN model shows a high accuracy of 99.6% where the number of test set is 3840. In addition, the model can be applied to the case of untrained SEM data of NCM cathodes with functional electrolyte additives.

Boosting the initial coulombic efficiency for SiO anodes through component controlling and microcrystalline size limiting regulated by carbon layer

Silicon-based anode materials are attracting considerable attention due to their high specific capacity for further improving the energy density of lithium-ion batteries (LIBs). Among them, silicon monoxide (SiO) has a good balance between high specific capacity and cycling lifespan, which is increasingly valuable in the market of lithium-ion batteries. However, its poor initial coulombic efficiency (ICE) severely impedes the commercialization of SiO. Although prelithiation and surface carbon coating are considered effective methods to reduce irreversible consumption during the initial lithiation process, the synergistic relationship between prelithiation and carbon coating has not yet been confirmed. Herein, we used LiH as solid-phase prelithiation reagent and acetylene as carbon source for carbon coating to improve the ICE as well as cyclic stability of SiO anode. Results show that the process sequence of pre-lithiation and carbon coating has a significant impact on regulating the internal lithium silicate components and the microcrystalline size of silicon and lithium silicates. A prioritizing carbon layer coating subsequent to prelithiation can achieve physical barrier effect, effectively regulating the prelithiation reaction process to refine the internal silicon and lithium silicate crystal material, and avoiding the formation of lithium-poor Li2Si2O5 phase. The obtained SOC-P sample exhibits a superior ICE of 88.1 % and a stable irreversible capacity of 842.9 mAh/g after 200 cycles. This work provides practical reference idea for solving the low initial efficiency issue of SiO anode material.

Layer by Layer: Improved Tortuosity in High Loading Aqueous NMC811 Electrodes

Thick electrode production is a key enabler for realizing high energy density Lithium-ion batteries. Therefore, the investigation of tortuosity as a crucial limiting parameter was conducted in this work. A thickness threshold (>150 μm) for a drastic increase in tortuosity for aqueous processed LiNi0.8Mn0.1Co0.1O2 (NMC811) electrodes was determined. Symmetrical cells, under blocking conditions, were analyzed via electrochemical impedance spectroscopy. To counteract this phenomenon, multi-layer coated electrodes with varying binder concentrations were investigated. This novel coating method, combined with the reduction of binder material, leads to a tortuosity decrease of more than 80%, when compared to high-loading electrodes (>8.5 mAhcm−2) coated with the conventional doctor-blade technique. Additionally, a simplified transmission line model is opposed to a linear fitting method for analyzing the impedance data.

Investigating advanced strategies for enhancing energy density in lithium-ion batteries

Lithium-ion batteries have become a versatile energy storage solution for various applications, such as portable electronics and electric vehicles, due to their numerous advantages. The increasing demand for higher energy density has prompted researchers to explore innovative strategies to improve the performance of these batteries. This study systematically investigates cutting-edge techniques aimed at enhancing the energy density of lithium-ion batteries. By conducting a detailed analysis of different battery components, this study evaluates the feasibility, efficiency, and potential impact of these approaches on future battery technologies. By giving some concrete examples, such as NMA(LiNi1-x-yMnxAlyO2), LFP(LiFePO4) batteries in cathode, popular silicon-based materials in anode, novel dual conductive binder and solid electrolyte (solid electrolyte interface), some of the working principles are described and the electrochemical properties of the batteries are comparatively analysed. This research aims to provide readers with a comprehensive understanding and research direction for advancing the energy density capabilities of lithium-ion batteries.

Unveiling the vacancy-mediated charge kinetics and capacity fading mechanism in Mn-based cathode for lithium-ion battery

In the recent past, Li2MnSiO4 (LMS) has been considered a promising cathode material for high energy density lithium-ion batteries (LIBs). Extraction of the maximum amount of Li from the host LMS and reversibility of Li insertion and extraction is still challenging, probably because of poor conductivity and, thereby, poor Li-kinetics. To improve the Li-diffusion and ionic conductivity, oxygen vacancies (OVs) in pristine LMS (LMS180) have been created, and then their impact on the Li-reactivity of LMS is studied. The quantity of OVs is determined by X-ray photoelectron spectroscopy (XPS) and calculated to be 6.8% in LMS180 heated at 300 ºC in Ar (LMSA300) and ∼ 8.2% in LMS180 heated at 500° C in Ar (LMSA500), subsequently it is supported and validate by the electron paramagnetic response (EPR) and high-resolution transmission electron microscopy (HR-TEM). The best sample, i.e., LMSA500, exhibits a total conductivity of 8.06×10−6 S/cm, resulting in an initial charge capacity of 292 (±5) mAh/g at 10 mA/g. The OVs are found to facilitate the facile lithium-ion movement by providing the lowest migration energy. Furthermore, knowing the impacts of OVs presence in LMS and their effect on Li-diffusion enables us to address traditional capacity fading processes in LMS.