Lithium Transport Research Articles

Crystalline Electrolyte Boosts High Performance of All-Solid-State Lithium-Ion Batteries.

The rigid solid-solid contact at the interface between the solid electrolyte and electrodes in full-solid-state lithium-ion batteries (ASSBs) presents a considerable challenge to lithium ion transport. To address this, we propose using Li-concentrated succinonitrile (Li-SN45) as an efficient bilateral interface modifier in ASSBs. This material boasts exceptional ionic conductivity of 3.38 mS cm-1 and excellent corrosion resistance to the Li metal anode. The assembled ASSBs using layered cathodes and Li metal demonstrate outstanding discharge capacity (170 mAh g-1 @ 20 mA g-1) and superior long-term cycling performance (97% capacity retention after 100 cycles). MALDI-TOF results suggest the formation of a crystalline structure in Li-SN45, which facilitates smooth "anion-free" Li+ hopping paths assisted by the oxygen atoms, as revealed by the solved crystal structure. Our findings enriched the understanding of Li transport dynamics in electrolytes of ASSBs, paving the way to designing superior next-generation ASSBs with fast Li transport.

Poly(ionic) Liquid-Enhanced Ion Dynamics in Cellulose-Derived Gel Polymer Electrolytes.

Gel polymer electrolytes (GPEs) are regarded as a promising alternative to conventional electrolytes, combining the advantages of solid and liquid electrolytes. Leveraging the abundance and eco-friendliness of cellulose-based materials, GPEs were produced using methyl cellulose and incorporating various doping agents, either an ionic liquid (1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [Pyr14][TFSI]), its polymeric ionic liquid analogue (Poly(diallyldimethylammonium bis(trifluoromethylsulfonyl)imide) [PDADMA][TFSI]), or an anionically charged backbone polymeric ionic liquid (lithium poly[(4-styrenesulfonyl)(trifluoromethyl(S-trifluoromethylsulfonylimino) sulfonyl) imide] LiP[STFSI]). The ion dynamics and molecular interactions within the GPEs were thoroughly analyzed using Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy (ATR-FTIR), Heteronuclear Overhauser Enhancement Spectroscopy (HOESY), and Pulsed-Field Gradient Nuclear Magnetic Resonance Diffusion (PFG-NMR). Li+ transference numbers (tLi+) were successfully calculated. Our study found that by combining slow-diffusing polymeric ionic liquids (PILs) with fast-diffusing lithium salt, we were able to achieve transference numbers comparable to those of liquid electrolytes, especially with the anionic PIL, LiP[STFSI]. This research highlights the influence of the polymer's nature on lithium-ion transport within GPEs. Additionally, micro supercapacitor (MSC) devices assembled with these GPEs exhibited capacitive behavior. These findings suggest that further optimization of GPE composition could significantly improve their performance, thereby positioning them for application in sustainable and efficient energy storage systems.

Robust polymer electrolytes with fast ion-transport nanochannels constructed by carbon dots for long lifespan Li metal batteries

As an anode material in energy storage systems, Li metal has exceptional merits, including high specific capacity, low density, and low redox potential. However, challenges such as lithium dendrites and unstable solid electrolyte interphase (SEI) hinder the practical application of lithium metal batteries (LMBs). Solid polymer electrolytes (SPEs), notably PVDF-HFP, are expected to overcome the above problems because of their mechanical merits and safe features, but their limited ion transportation behaviors result in insufficient ionic conductivity at room temperature. Herein, we invent an approach to prepare high performance electrolytes composed by porous PVDF-HFP and functionalized carbon dots (CDs). Such porous PVDF-HFP polymer membranes are created by a subtle phase inversion process, possessing a sponge-like structure, vertical lithium-ion transport channels and CDs decorated surfaces, thus able to uptake the liquid electrolyte (LE) to form gel polymer electrolytes (GPEs). The CDs fillers are produced in large scale with adjustable surface states, which can enhance Li salts disassociation to release free Li ions. As a result, the optimal conductivity of the as-prepared GPEs at room temperature is up to 8.7 mS cm−1 and the lithium transference number reaches 0.64. Our GPEs endow Li symmetric batteries with very stable SEI and long cycling life over 2200 h, and help realize high capacities and retention rates of the LMBs using LiFePO4(LFP) or LiCoO2(LCO) cathodes.

Isotopic Labeling: A Powerful Tool to Investigate Lithium Transport in a Polymer-Ceramic Composite Electrolyte Designed for Solid-State Batteries

Isotopic Labeling: A Powerful Tool to Investigate Lithium Transport in a Polymer-Ceramic Composite Electrolyte Designed for Solid-State Batteries

Improving Bulk and Interfacial Lithium Transport in Garnet-Type Solid Electrolytes through Microstructure Optimization for High-Performance All-Solid-State Batteries.

Garnet-type Li6.4La3Zr1.4Ta0.6O7 (LLZTO) is regarded as a highly competitive next-generation solid-state electrolyte for all-solid-state lithium batteries owing to reliable safety, a wide electrochemical operation window of 0-6 V versus Li+/Li, and a superior stability against Li metal. Nevertheless, insufficient interface contacts caused by pores, along with Li dendrite growth at these voids and grain boundary regions, have hindered their commercial application. Herein, we suggest a method to produce high-quality LLZTO using LiAlO2 (LAO) as a chemical additive that leads to an improved microstructure with larger grain size (∼25 μm), a high relative density (∼96%), lower porosity (∼3.7%), and continuous secondary phases in grain boundary regions. This improved structure results in (i) improved Li-ion conductivity and enhanced interfacial resistance between Li metal and LLZTO by a denser structure with fewer pores and (ii) suppression of Li dendrite penetration in the electrolyte by secondary phases in grain boundary regions.

Improving the Cycle Stability of LiNiO2 through Al3+ Doping and LiAlO2 Coating.

In this study, we addressed the poor cycling and rate performance of LiNiO2, a material with ultrahigh nickel content considered a strong contender for high-energy-density lithium-ion battery cathodes. We introduced nano-Al2O3 during the lithiation process to achieve dual modified material through bulk phase element doping and in situ LiAlO2 coating. Comparison revealed notable improvements in the modified materials. In particular, LiNi0.99Al0.01O2 maintained a capacity retention rate of 73.1% after 300 cycles in a long-cycle test at 0.5C current density, outperforming the undoped material. In rate performance tests, the doped samples consistently exhibited higher discharge-specific capacities than that of the undoped counterpart. Notably, at a high current density of 5C, LiNi0.99Al0.01O2 exhibited a discharge-specific capacity of 101.75 mAh g-1. The results indicate that an appropriate amount of Al doping can effectively stabilize the layered structure of the cathode material and delay the irreversible phase transition from H2 to H3. Further, Al doping facilitates the formation of a LiAlO2 coating on the surface of the particles. This coating acts as a fast-ion conductor, enhancing the transport of lithium ions and reducing the erosion of the active material by the electrolyte.

Synergistic Anion and Solvent-Derived Interphases Enable Lithium-Ion Batteries under Extreme Conditions.

Lithium-ion batteries (LIBs) face increasingly stringent demands as their application expands into new areas, including extreme temperatures and fast charging. To meet these demands, the electrolyte should enable fast lithium-ion transport and form stable interphases on electrodes simultaneously. In practice, however, improving one aspect often compromises another. For instance, the trend toward electrolytes forming anion-derived interphases typically reduces transport efficiency due to weak-solvating solvents. We propose that instead of relying on anions to form the interphase, leveraging both solvents and anions to form interphases can potentially lead to a balancing point between robust interphase formation and effective ion transport. Guided by this design principle, 2,2-difluoroethyl ethyl carbonate (DFDEC) was identified as the promising solvent. With the new electrolyte using DFDEC as the major solvent and lithium bis(fluorosulfonyl) imide (LiFSI) as the salt, graphite||LiNi0.8Mn0.1Co0.1O2 (NMC811) full cells are capable of fast charging and demonstrate long-term cycling stability with a cutoff voltage of 4.5 V. Notably, the battery shows a capacity retention of 84.3% after 500 cycles with an average Coulombic efficiency (CE) as high as 99.93%. This new electrolyte also enables stable battery cycling across a wide temperature range (-20 to 60 °C), with excellent capacity retention.

Recent research progress on Li29Zr9Nb3O40-based solid electrolytes for lithium batteries

All-solid-state batteries have become a research hotspot because of their high specific capacity and safety. Solid-state electrolytes are the key material of all-solid-state lithium-ion batteries, and their properties directly affect the overall performance of lithium-ion batteries. So far, many inorganic solid electrolytes have been reported, such as NASICON, LISICON, perovskite, and garnet-type solid electrolyte. However, some lithium-rich rock salt-structured electrolytes, such as Li2ZrO3, LiNbO4, and Li6Zr2O7, have been underappreciated in the field of solid-state electrolytes due to their lower ionic conductivity at room temperature. While investigating solid solution formation, Li6Zr[Formula: see text][Formula: see text]Nb[Formula: see text]O[Formula: see text][Formula: see text][Formula: see text], a new phase known as Li[Formula: see text]Zr9Nb3O[Formula: see text] with a rock-salt structure was discovered. After decades, it was not until a team prepared Li[Formula: see text]Zr9Nb3O[Formula: see text] ceramics by sol-gel method, which exhibited high ionic conductivity (10[Formula: see text]–10[Formula: see text]S cm[Formula: see text]) at room temperature, that the substance showed great potential as a solid electrolyte in all-solid-state lithium-ion batteries. In this paper, the crystal structure, lithium-ion transport mechanism, preparation method, and element doping of Li[Formula: see text]Zr9Nb3O[Formula: see text] are described comprehensively based on research progress in recent years. Then, development prospects and challenges of the concrete application of Li[Formula: see text]Zr9Nb3O[Formula: see text]in all-solid-state lithium-ion batteries are also discussed.

Metal‐Organic Framework Hosted Silicon for Long‐Cycling, Low‐Cost, and Flexible Batteries

AbstractDeveloping biodegradable electrodes is a significant step toward environmental sustainability and cost reduction in battery technology. This paper presents a new approach that utilizes metal‐organic framework (MOF)‐encapsulated silicon nanoparticles (SiNPs) as the active anode material within a cellulose‐based electrode. The electrode is free‐standing, flexible, biodegradable, and significantly reduces the strain experienced by SiNPs during volume expansion, resulting in improved capacity and cycle life stability of SiNPs. The high porosity of the electrode creates efficient lithium (Li+) ion transport channels and enhances electrolyte absorption, thus promoting effective contact between the electrolyte and active material. The outcome is rapid electrode kinetics and a highly reversible discharge capacity of 1744.6 mAh g−1 at 0.5 A g−1 versus Li/Li+ over 1000 cycles. Further, full cell tests are conducted that demonstrate a stable cycle performance exceeding 3400 cycles, with an initial discharge capacity retention of 80.5% at 0.5 A g−1. By employing cellulose and avoiding toxic organic solvents and binders, the proposed approach is promising for a substantial reduction of the production costs of Li‐ion batteries. The scalability of the proposed method further enhances its practical viability, offering intriguing economic implications for the future of battery technology.

Preparation of interconnected tin oxide nanoparticles on multi-layered MXene for lithium storage anodes

MXenes, a novel class of two-dimensional (2D) materials known for their excellent electronic conductivity and hydrophilicity, have emerged as promising candidates for lithium-ion battery anodes. This study presents a simple wet-chemical method for depositing interconnected SnO2 nanoparticles (NPs) onto MXene sheets. The SnO2 NPs act as both a high-capacity energy source and a spacer to prevent MXene sheets from restacking. The highly conductive MXene facilitates rapid electron and lithium-ion transport and mitigates the volume changes of SnO₂ during the lithiation/delithiation process by confining the SnO₂ NPs between the MXene layers. This composite anode, SnO2@MXene, leverages the high capacity of SnO2 and the structural and mechanical stability MXene provides. The SnO2@MXene anode exhibits superior electrochemical performance, with a high specific capacity of 678 mAh g− 1 at a current rate of 2.0 A g− 1 over 500 cycles, outperforming pristine MXenes and SnO2 nanoparticles.

Quantifying Lithium-Ion Battery Rate Capacity, Electrode Structuring, and Transport Phenomena Using E-I Measurements

The specific energy of lithium-ion batteries (LIBs) can be enhanced through various approaches, one of which is increasing the proportion of active materials by thickening the electrodes. However, this typically leads to the battery having lower performance at a high cycling rate, a phenomenon commonly known as rate capacity retention. One solution to this is perforating the electrode, by creating channels or corrugations in the active electrode material, either as holes or as channels. This is known to reduce the rate capacity retention effect, but in order to engineer this better, a simplified transport process analysis needs to be established. In this paper, we propose a classic electrochemical analysis based on voltage–charge cycling measurements in order to obtain a classical mass transport coefficient, hm, that is further used as a main indicator for electrode design quality assessment. We also demonstrate theoretically and experimentally how the mass transfer coefficient, hm, can be determined and how it changes as the electrode layer thickness increases, with and without electrode corrugations.

Defect-Mediated Formation of Oriented Phase Domains in a Lithium-Ion Insertion Electrode.

The performance and robustness of electrodes are closely related to transformation-induced nanoscale structural heterogeneity during (de)lithiation. As a result, it is critical to understand at atomic scale the origin of such structural heterogeneity and ultimately control the transformation microstructure, which remains a formidable task. Here, by performing in situ studies on a model intercalation electrode material, anatase TiO2, we reveal that defects─both preexisting and as-formed during lithiation─can mediate the local anisotropic volume expansion direction, resulting in the formation of multiple differently oriented phase domains and eventually a network structure within the lithiated matrix. Our results indicate that such a mechanism operated by defects, if properly harnessed, could not only improve lithium transport kinetics but also facilitate strain accommodation and mitigate chemomechanical degradation. These findings provide insights into the connection of defects to the robustness and rate performance of electrodes, which help guide the development of advanced lithium-ion batteries via defect engineering.

Lithium Transport in Crystalline and Amorphous Cathode Coatings for Li-Ion Batteries

Lithium Transport in Crystalline and Amorphous Cathode Coatings for Li-Ion Batteries

Cationic Covalent Organic Framework-Modified Polypropylene Separator for High-Performance Lithium Metal Batteries.

As an important component of lithium batteries, the wettability and thermal stability of the separator play a significant role in cell performance. Despite the availability of numerous commercial separators, issues such as low ion selectivity and poor thermal stability continue to limit the efficiency and reliability of the batteries. Herein, two cationic covalent organic frameworks (Br-COF and TFSI-COF) with abundant imidazole cationic groups were designed to modify commercial polypropylene (PP) separators. The strong lithium-ion affinity of the cationic COF enables the effective dissociation of lithium salt ion clusters, simplifying the solvent structure of lithium ions to promote lithium ions transport. Additionally, solvent anions can be anchored to the cationic COF by electrostatic interactions, reducing side reactions on the lithium metal anode surface to form a favorable SEI layer, which can effectively inhibit the growth of lithium dendrites. The rapid dissociation of anions in lithium salts with some organic solvents and cationic COFs was revealed by a molecular dynamics simulation. A LiF-rich SEI layer on the lithium metal anode surface was formed, which can speed up Li+ transport at interfaces, leading to consistent lithium deposition and outstanding battery performance. The ordered porous structure of the cationic COF provides interconnected and continuous channels, improving the wettability between the liquid electrolyte and separators, which is conducive to ion transport. When paired with a LiFePO4 cathode and electrolyte (1.0 M LiTFSI in DEC: EC: DMC = 1:1:1), the LiFePO4/TFSI-COF@PP/Li cell demonstrates a prominent cycling capacity of 148.0 mAh g-1 at 0.5 C with a Coulombic efficiency of 98.0% in the first cycle, and the capacity retention is 82.0% after 100 cycles, showing good cycling stability. Thus, this investigation provides inspiration for the expansion of cationic COF-modified separators for next-generation lithium metal batteries.

SEI Formation and Lithium-Ion Electrodeposition Dynamics in Lithium Metal Batteries via First-Principles Kinetic Monte Carlo Modeling.

The stabilization and enhanced performance of lithium metal batteries (LMBs) depend on the formation and evolution of the Solid Electrolyte Interphase (SEI) layer as a critical component for regulating the Li metal electrodeposition processes. This study employs a first-principles kinetic Monte Carlo (kMC) model to simulate the SEI formation and Li+ electrodeposition processes on a lithium metal anode, integrating both the electrochemical electrolyte reduction reactions and the diffusion events giving place to the SEI aggregation processes during battery charge and discharge processes. The model replicates the competitive interactions between organic and inorganic SEI components, emphasizing the influence of the cycling regime. Results indicate that grain boundaries within the SEI facilitate faster lithium-ion transport compared to crystalline regions, crucial for improving the performance and stability of LMBs. The findings underscore the importance of dynamic SEI modeling for further development of next-generation high-energy-density batteries.

Synergistic implementation of efficient adsorption-diffusion-conversion in lithium-sulfur batteries via built-in electric field constructed by transition metal selenides

The adsorption of lithium polysulfides (LiPSs), the transport of lithium ions, and the redox kinetics collectively play pivotal roles in determining the application of lithium-sulfur (Li-S) batteries. Herein, a defect-rich p-Co3Se4/n-ZnSe p-n junction (ZCSNC) is engineered by chemical vapor deposition (CVD)-selenation. The n-type semiconductor ZnSe and the p-type semiconductor Co3Se4 contained in ZCSNC effectively anchor LiPSs and promote the catalytic reaction kinetics through synergistic effects, respectively. Meanwhile, the presence of heterogeneous interfaces in the p-n junction and the difference in work functions spontaneously form a built-in electric field, which promotes the transport and transfer of lithium ions and LiPSs. Therefore, the ZCSNC functional material contributes to improving the electrochemical performance of Li-S batteries through the process of adsorption-diffusion-conversion. The Li-S cells with ZCSNC-modified separators show excellent rate performance (741.1 mAh/g at 5C) and long-lasting cycling performance (only 0.04 % capacity decay per cycle over 1000 cycles). Notably, the ZCSNC still has excellent rate discharge capacities (683.9 and 649.7 mAh/g at 2C, respectively) at high sulfur loading and low temperature of 0 °C. This study illustrates that a p-n junction containing a built-in electric field can effectively modulate the kinetics of redox reactions of LiPSs through synergistic interactions.

Biomass-based three-dimensional network porous carbon anodes derived from discontinuous activation for high performance Li-ion batteries

An approach of discontinuous activation and frozon-dry pretreatment toward a three-dimensional network porous carbon was proposed by using apple as the carbon source. The porous carbon, characterized by its high surface area and abundant porosity, was optimized through the manipulation of temperature and activator quantities during the activation process. The sample obtained by first calcining at 500 °C and then at 800 °C shows ultra-high rate electrochemical performance of over 900 mA h g−1 after 100 cycles and over 500 mA h g−1 after 500 cycles under the condition of charging and discharging current density of 0.2 A g−1 due to the high porosity. It is ascribed to the unique porous structure that can make the electrolyte and lithium ion transport and path short on the surface and inside the electrode material, further enhance its fast transport ability. The described approach represents an innovative and potentially impactful method for producing porous carbon electrodes with excellent electrochemical performance, particularly in the context of high-rate capability lithium-ion batteries.

Influence of Conductive Additives and Binder on the Impedance of Lithium-Ion Battery Electrodes: Effect of an Inhomogeneous Distribution

The conductive additive and binder domain (CBD) is an essential component of lithium-ion battery electrodes. It enhances the electrical connectivity and mechanical stability within the solid electrode matrix. Migration of the binder during electrode drying can lead to an inhomogeneous distribution of the CBD, impeding transport of lithium ions into the electrodes, and diminishing the electronic pathways between solid particles and the current collector. This is especially prominent in thick electrodes at high drying rates. Therefore, we investigate the effect of a non-uniform CBD distribution on the electrochemical performance of NMC622 electrodes via microstructure-resolved three-dimensional (3D) simulations on virtual electrodes, based on tomographic image data, and compare them with experimental results. The valuable information derived by combining microstructure-resolved models with electrochemical impedance spectroscopy measurements on symmetric cells under blocking electrolyte conditions is used to characterize the lithium-ion transport in the electrode pore space, including the contributions of the CBD. The effect of this inhomogeneity on electrode performance is then gauged via galvanostatic discharge simulations under changing discharge currents and for varying electrode densities. Through our work, we demonstrate the significance of the CBD distribution and enable predictive simulations for future battery design.

On the Volume Expansion of Lithium Ion Battery Electrodes (I) after Wetting, and (II) Selection of the Right Amount of Electrolyte

The electrolyte is necessary for transport of lithium ions between the negative and positive electrode within the battery cell. The lower the amount of electrolyte, the higher the energy density and specific energy. Hence, it is important to understand which cell parameters are relevant to determine the right amount of electrolyte. Here, three different cell designs in 1 to 5 Ah pouch cells where investigated for cell impedance after filling, cell capacity after formation, C-rate performance, and capacity retention for up to 3,000 full cycles. Wetting the cell with electrolyte, the cell pore volume changed between 25%–35% due to changes of 6%–16% in the thickness of the anode and cathode. Although electrolyte volumes >0.85 times the wet cell pore volume showed minimal resistance before formation, only electrolyte volumes of 1.08 times the wet cell pore volume were sufficient for a successful formation process. For long-term cycling, a minimum electrolyte volume of 1.19 times the wet cell pore volume was required to improve long-term cycling performance. Future experiments will investigate the correlation of capacity fade with electrolyte consumption for different electrolytes.

In situ anchoring of FeNi nanoparticles into three-dimensional nitrogen-doped carbon framework as a self-supporting electrode for high-performance lithium storage

Constructing free-standing electrodes with superior lithium storage capacity and good mechanical performance are fascinating for next-generation lithium-ion batteries (LIBs). Nevertheless, their practical application is hindered by complicated synthesis procedures and high cost. Herein, a highly stable, self-supporting and flexible electrode material for LIBs was constructed by encapsulating spherical FeNi nanoparticles into one-dimensional N-doped carbon fiber film (FeNi/N- CFM) using the electrospinning technique and subsequent heat treatment. The FeNi/N-CFM can be directly used as anode materials for LIBs without conductive additive, current collector and binder. The synergistic effect of uniformly dispersed small FeNi nanoparticles and three-dimensional (3D) conductive network constructed by CF framework effectively improves the utilization rate of active materials, enhances the transport of both electrons and lithium ions, facilitates the electrolyte penetration, and promotes the lithium-ion storage kinetics and stability, thus leading to a greatly enhanced electrochemical performance. Benefiting from the unique architectural feature and flexibility, the FeNi/N-CFM composites employed as binder-free electrodes for LIBs exhibit good lithium storage performance (an initial discharge capacity of 1031.5 mA h g−1 and a reversible capacity of 481.3 mA h g−1 at 100 mA g−1 after 100 cycles), rate capacity (305.1 mA h g−1 at 1000 mA g−1) and outstanding reversibility (coulombic efficiency of around 100 % after 100 cycles). Furthermore, this work also provides a facile and effective pathway to design and fabricate free-standing electrodes.