Next-generation Li-ion Batteries Research Articles

Plasma-Enhanced Atomic Layer Deposition of Lithium Nickel Oxide Thin Film Model Systems

The main bottleneck in the development of the next generation of Li-ion batteries with higher energy densities, as demanded for long-range electrical mobility, is the lack of understanding and control of the reactions at the electrode-electrolyte interfaces. Reactions at the cathode side cause rapid capacity loss during cycling and represent a major issue for batteries with high-voltage cathodes, which are crucial in reaching the required energy densities. Promising candidates for use in next generation of batteries are Ni-rich Li(Ni1-x-yMnxCoy)O2 (NMC) cathodes, which show high capacity, high potential, and contribute to address the geopolitical issue of decreasing the Co content in the cathode. Ni-rich NMCs exhibit similar electrochemical properties as pure LiNiO2 and therefore LiNiO2 thin films can be used as model systems to gain fundamental understanding of the interfacial processes that hinder the large-scale implementation of Ni-rich NMCs. Atomic layer deposition (ALD) is a suitable technique to fabricate these model systems, as it gives precise control over film thickness, uniformity, chemical composition, and crystal orientation.Previous work on LiNiO2 by ALD is not extensively reported in literature. Moreover, films grown by a supercycle process, in which two ALD subcycles are alternated, suffered from a low Ni at.% and a large C content because of precursor ligand residues, and films fabricated using a complex multilayered approach showed severe Si contamination from the Li precursor [1]. In this contribution we report on ALD lithium nickel oxide (LNO) thin films with stoichiometries close to LiNiO2 and low levels of contaminants.The ALD process is based on lithium hexamethyldisilazide (LiHMDS) and nickel bis(N,N’-di-tert-butylacetamidinate) (Ni(tBu-MeAMD)2) as precursors and O2 plasma as co-reactant. 1 ALD cycle of Li2O is combined with x cycles of NiO using a supercycle approach. In this contribution we explore the relation between the Ni/Li cycle ratio x and material properties of the LNO films.The growth of the LNO films is monitored by means of in-situ spectroscopic ellipsometry. The ellipsometric data of films with a high Ni/Li cycle ratio are fitted with a general oscillator model used for NiO films, while a Cauchy model was adopted in case of a low Ni/Li cycle ratio and Li2O films. The growth per supercycle (GPSC) of LNO shows an intermixing effect, as it does not follow the linear trend calculated from the growth per cycle (GPC) values of the individual Li2O and NiO ALD processes, which are 1.0 Å/cycle and 0.34 Å/cycle respectively.XPS surface measurements show that the Ni/Li atomic ratio is tuned from 0 to 10 as function of the Ni/Li cycle ratio x. Low levels of Si and N contamination, below 4% and 2% respectively, are observed. A shift of the main peak in the Ni 2p3/2 spectrum to higher binding energies indicates a shift in oxidation state from Ni2+ to Ni3+ as decreases [2]. According to surface measurements, the LNO film with x=5 shows a stoichiometry close to LiNiO2, but depth profile measurements indicate that the Ni at.% is significantly higher in the bulk than on the surface of the films, most certainly attributed to the formation of a Li2CO3 surface layer upon air exposure. Li2CO3 is also present in the bulk of the LNO films, but the bulk C at.% stays below 4%.These results show that we can use ALD to fabricate a high-voltage cathode model system, which we plan to characterize in-situ and post-mortem in combination with both liquid and solid electrolytes to study the cathode-electrolyte interface.[1] Maximov et al., Energies, 13 (2020) 2345[2] Fu et al., Applied Surface Science 441 (2018) 1048 This work is part of the ‘BatteryNL – Next Generation Batteries based on Understanding Materials Interfaces’ project (with project number NWA.1389.20.089) of the NWA research programme ‘Research on Routes by Consortia (ORC)’ funded by the Dutch Research Council (NWO). Figure:(a) The GPSC of LNO ALD process shows an intermixing effect when comparing the experimental results with the expected GPSC based on the two processes (b) Ni 2p3/2 XPS spectrum for different Ni/Li cycle ratios x. A shift to higher binding energies is observed with decreasing x, indicating a shift from Ni2+ to Ni3+. (c) XPS surface measurements of LNO films show low levels of contaminants and a Ni/Li atomic ratio varying with the Ni/Li cycle ratio. (d) Depth profile of LNO with x=5 shows an increased Ni at.% and a low C at.% in the bulk of the film. Figure 1

Stabilized Positive Electrode Material to Enable High Energy/Power Density Lithium-Ion Batteries

Recently, the large-scale deployment of electric vehicles (EVs) and stationary battery systems has putforward urgent requests for rechargeable batteries with higher energy/power density and longerlifespans. As such, next-generation Li-ion batteries (LiBs) are expected to meet these requirements. Thepossibility of using Ni-rich high-capacity cathode materials (NMC) can help to achieve that goal, however,they still suffer from significant capacity fade via several chemical and mechanical degradation modes.One is crack formation within secondary particles which leads to parasitic reactions that evolve oxygenand potentially initiate the formation of inactive crystal structures. LiBs mechanical and chemicaldegradation mechanisms can be extended by applying protective coatings to the cathode’s surface. Manystudies explore atomic layer deposition (ALD) for this purpose. However, the complementary molecularlayer deposition (MLD) technique might offer the benefit of depositing flexible hybrid coatings that canaccommodate potential volume changes of the electrode during the battery cycling. This study reportsthe deposition of novel organic-inorganic films via the ALD-MLD method. Characterization analysis suchas FTIR, XPS, SEM-EDS, and TEM confirmed the film deposition on the surface of the NMC electrode.Besides, the electrochemical results showed the enhancement of the coated electrode, as evidenced byproviding a longer life with a 93% capacity retention after 150 cycles (3.0-4.4 V vs. Li/Li+), while theuncoated one retained only 83% of its initial capacity. Moreover, in situ dilatometry showed irreversiblevolume change for uncoated NMC while it was mostly reversible for coated ones during the cycling. Itrevealed the dilation behavior of the electrode, resulting in crack formation, which is significantlysuppressed for the coated samples. Stable cycling of Ni-rich cathode materials in crucial conditions suchas high voltage windows and elevated temperatures is still extremely challenging. To evaluate this, in situdilatometry was performed at elevated temperatures (40 °C and 55 °C) and higher voltage ranges (3.0-4.6V). The results confirmed that in both conditions, the dilation behavior of the coated sample is still undercontrol while the capacity is comparable to the uncoated sample. This revealed that the coatings presentgood lithium-ion kinetics and reduce electrolyte decomposition. Overall, this work showed the liability ofthe ALD-MLD films deposited on NMC electrodes to mitigate the degradation mechanisms and providesinsight into a method that seems promising as a protective and elastic coating for future high-energylithium-ion battery cathodes. Figure 1

The potentials of LiMnPO4 cathode material for aqueous Li-ion batteries: An investigation into solid state and green chemistry approaches

The phospho-olivine LiMnPO4 nanocrystal holds promise as a cathode material for next-generation Li-ion batteries (LIBs). In this study, we employed solid-state and green chemistry approaches to prepare LiMnPO4 powders, with aloe vera extract serving as a capping agent for the latter approach. Selective synthesis of nanoparticles with more active sites for efficient Li+ intercalation-deintercalation was achieved. The phase purity, morphology, and composition of the nanoparticles were characterized using XRD, SEM/TEM, and EDS, respectively. Electrochemical performance was evaluated through cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) in an aqueous environment. The solid-state synthesized LiMnPO4 nanoparticles (LiMnPO4-SS) exhibited electrolyte-dependent performance but demonstrated good reversibility of Li+ extraction and insertion. Specific capacity, retention of discharge capacity, and Coulombic efficiency were found to be 92.3 ± 0.5 mAhg−1, 98 %, and 93 %, respectively, after 50 cycles at 0.2 C. Additionally, energy density was measured as 15.8 ± 1.4 Whkg−1 at 189.2 ± 1.9 Wkg−1 power density. The green-synthesized LiMnPO4 nanoparticles (LiMnPO4-GS) showed a specific capacity of 106.4 ± 0.9 mAhg−1 (corresponding to ∼62 % of theoretical capacity) after 50 cycles, with capacity retention of ∼97 % and ∼80 % Coulombic efficiency. The energy density was 18.2 ± 1.7 Whkg−1 at 218.1 ± 2.1 Wkg−1 power density. EIS measurements indicated reduced charge transfer resistance for LiMnPO4-GS, optimizing interfacial electrochemical reaction activity. The observed regular micromorphology and (200) plane of nanosized LiMnPO4 contributed to the excellent electrochemical performance. Overall, this investigation highlights the correlation among synthesis method, calcination temperature, electrolyte, crystal structure, and morphology, providing insights for the design of next-generation LIBs.

Constructing a stable interface on Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode via lactic acid-assisted engineering strategy

Ni-rich layered oxides are potential cathode materials for next-generation high energy density Li-ion batteries due to their high capacity and low cost. However, the inherently unstable surface properties, including high levels of residual Li compounds, dissolution of transition metal cations, and parasitic side reactions, have not been effectively addressed, leading to significant degradation in their electrochemical performance. In this study, we propose a simple and effective lactic acid-assisted interface engineering strategy to regulate the surface chemistry and properties of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode. This novel surface treatment method successfully eliminates surface residual Li compounds, inhibits structural collapse, and mitigates cathode-electrolyte interface film growth. As a result, the lactic acid-treated LiNi0.8Co0.1Mn0.1O2 achieved a remarkable capacity retention of 91.7% after 100 cycles at 0.5 C (25 °C) and outstanding rate capability of 149.5 mA h g−1 at 10 C, significantly outperforming the pristine material. Furthermore, a pouch-type full cell incorporating the modified LiNi0.8Co0.1Mn0.1O2 cathode demonstrates impressive long-term cycle life, retaining 81.5% of its capacity after 500 cycles at 1 C. More importantly, the thermal stability of the modified cathode is also dramatically improved. This study offers a valuable surface modification strategy for enhancing the overall performance of Ni-rich cathode materials.

A Brief Overview of Silicon Nanoparticles as Anode Material: A Transition from Lithium-Ion to Sodium-Ion Batteries.

The successful utilization of silicon nanoparticles (Si-NPs) to enhance the performance of Li-ion batteries (LIBs) has demonstrated their potential as high-capacity anode materials for next-generation LIBs. Additionally, the availability and relatively low cost of sodium resources have a significant influence on developing Na-ion batteries (SIBs). Despite the unique properties of Si-NPs as SIBs anode material, limited study has been conducted on their application in these batteries. However, the knowledge gained from using Si-NPs in LIBs can be applied to develop Si-based anodes in SIBs by employing similar strategies to overcome their drawbacks. In this review, a brief history of Si-NPs' usage in LIBs is provided and discuss the strategies employed to overcome the challenges, aiming to inspire and offer valuable insights to guide future research endeavors.

Revealing the key role of MnSiO3 in boosting the lithium storage performance of bamboo-derived anode materials

Carbon/manganese oxide hybrid materials, as potential candidates for lithium-ion battery anode materials, have attracted extensive attention due to their abundant resources and simple preparation. However, poor rate performance, weak cycle stability, and relatively high cost still limit their further development as commercial materials for next-generation Li-ion batteries. Herein, a novel carbon/manganese oxide hybrid material was fabricated from low-cost carbonized bamboo leaves and manganese nitrate for the lithium-ion battery anode. Interestingly, an additional MnSiO3 component found in this hybrid material is able to increase the material's intrinsic conductivity for improving the charge transfer as well as to enhance the Li+ diffusion ability for accelerating the reaction kinetics. Thus, the rate capability and cycle performance of the prepared hybrid material with additional MnSiO3 have been significantly improved by 18.4 and 52.6 %, respectively, compared to hybrid material without the MnSiO3 component. Moreover, the cycle performance of this hybrid material is also superior to that of many similar carbon/silicate and carbon/manganese oxide hybrid materials. Thanks to the excellent electrochemical performance, our hybrid material has also been successfully fabricated into a lithium-ion full battery, which displays considerable energy storage performance and good practical application ability.

Unlocking the potential of silicon anodes in lithium-ion batteries: A claw-inspired binder with synergistic interface bonding

Binders play a crucial role in enhancing the cycling stability of silicon anodes in next-generation Li-ion batteries. However, traditional linear polymer binders have difficulty withstanding the volume expansion of silicon during cycling. Herein, inspired by the fact that animals’ claws can grasp objects firmly, a claw-like taurine-grafted-poly (acrylic acid) binder (Tau-g-PAA) is designed to improve the electrochemical performance of silicon anodes. The synergistic effects of different polar groups (sulfo and carboxyl) in Tau-g-PAA facilitate the formation of multidimensional interactions with silicon nanoparticles and the diffusion of Li ions, thereby greatly improving the stability and rate performance of silicon anodes, which aligns with results from density functional theory (DFT) simulations. As expected, a Tau-g-PAA/Si electrode exhibits excellent cycling performance with a high specific capacity of 1003 ​mA ​h ​g−1 ​at 1 ​C (1 ​C ​= ​4200 ​mA ​h ​g−1) after 300 cycles, and a high rate performance. The design strategy of using polar small molecule-grafted polymers to create claw-like structures could inspire the development of better binders for silicon-based anodes.

Investigating the Structural and Lithium Storage Properties of High-Entropy Oxides in the Mg-Co-Ni-Cu-Zn-O System

Recently, a new class of materials known as high-entropy oxides (HEOs) has emerged as an alternative electrode material for the next-generation Li-ion batteries. However, the discovery of these materials brings forth a broad range of compositions remained unexplored. This study aimed to investigate the structural and electrochemical characteristics of the non-equiatomic HEOs. Accordingly, ten different samples were synthesized in the Mg-Co-Ni-Cu-Zn-O system at very high (35 mol. %) and very low (5 mol. %) constituent proportions. Our experimental and theoretical results indicated that the thermodynamic stability of the HEOs was affected significantly by the enthalpic contributions arising from the lattice strain. These findings may provide a more consistent design approach in selection of a suitable component for the synthesis of the single-phase HEOs. Furthermore, the specific capacity, cycling stability and lithiation voltage of the electrodes have also been shown to be influenced by each individual constituent of the electrode.

Superb Li-Ion Storage of Sn-Based Anode Assisted by Conductive Hybrid Buffering Matrix.

Although Sn has been intensively studied as one of the most promising anode materials to replace commercialized graphite, its cycling and rate performances are still unsatisfactory owing to the insufficient control of its large volume change during cycling and poor electrochemical kinetics. Herein, we propose a Sn-TiO2-C ternary composite as a promising anode material to overcome these limitations. The hybrid TiO2-C matrix synthesized via two-step high-energy ball milling effectively regulated the irreversible lithiation/delithiation of the active Sn electrode and facilitated Li-ion diffusion. At the appropriate C concentration, Sn-TiO2-C exhibited significantly enhanced cycling performance and rate capability compared with its counterparts (Sn-TiO2 and Sn-C). Sn-TiO2-C delivers good reversible specific capacities (669 mAh g-1 after 100 cycles at 200 mA g-1 and 651 mAh g-1 after 500 cycles at 500 mA g-1) and rate performance (446 mAh g-1 at 3000 mA g-1). The superiority of Sn-TiO2-C over Sn-TiO2 and Sn-C was corroborated with electrochemical impedance spectroscopy, which revealed faster Li-ion diffusion kinetics in the presence of the hybrid TiO2-C matrix than in the presence of TiO2 or C alone. Therefore, Sn-TiO2-C is a potential anode for next-generation Li-ion batteries.

Theoretical insight into oxygen vacancy formation in Li1.25Ni0.5Mn0.25O2 cathode material

Here, we have studied the thermodynamic stability of lattice oxygen in Li-rich Co-free cathode material Li1.25Ni0.5Mn0.25O2 using first-principles calculations. It is found that the oxygen at O2 coordination is more likely to be released in Li-rich cathode Li1.25Ni0.5Mn0.25O2, and the stability of oxygen is closely related to temperature and oxygen partial pressure. The Li1.25Ni0.5Mn0.25O2 cathode will spontaneously form O-vacancies above 842 K. When the oxygen partial pressure increases to 22 atm, the lattice oxygen is stable even at 1000 K. The presence of O-vacancy will cause more localized charges, and Ni-ions will also undergo a reduction reaction in the electrode. This theoretical study gives new insight about the thermodynamic stability of lattice oxygen and will help to suppress the formation of O-vacancy in Li-rich cathode materials, paving the way for developing Li-rich cathode materials for next-generation Li-ion batteries.

Tracking Decomposition Layer Formation in Thin-Film Si Electrodes via Thermogalvanic Profiles.

Si anodes are of great interest for next-generation Li-ion batteries due to their exceptional energy density. One of the problems hindering the adoption of this material is the presence of electrolyte decomposition reactions that result in capacity fade and Coulombic inefficiency. This work studies the influence of the decomposition layer in Si on its electrochemical performance using thermogalvanic profiling, a non-destructive in operando technique. This is accomplished by comparing thermogalvanic profiles of uncoated thin-film Si to those of lithium phosphorus oxynitride (LiPON)-coated Si, in which decomposition reactions are inhibited. Through a combination with physico-chemical methods including scanning electron microscopy and time-of-flight secondary ion mass spectrometry, the thermogalvanic profiles are found to contain signatures that reflect the nature of the decomposition layer. More specifically, this decomposition layer appears to gradually develop a passivating function during the first electrochemical cycles. Thermogalvanic profiles collected at later cycles indicate that this passivating behavior is eventually lost, causing the observed capacity degradation. The identification of a passivating regime in Si is highly relevant for the development of high-capacity Li-ion batteries. In addition, the use of thermogalvanic profiles to track the properties of decomposition layers could be of interest for monitoring the formation or degradation of battery cells.

Ab initio study of Li-shrouded Si-doped [formula omitted]-Graphyne nanosheet as propitious anode in Li-ion batteries

Li-ion batteries (LIBs) have become a house-hold name in the energy-storage research community in the wake of their noteworthy attributes. With increasing energy demands, the urgency to develop high performance LIBs is also rising rapidly which has compelled the researchers to design and fabricate new high capacity materials. Bearing that in mind, we have investigated a carbon–silicon based anode, i.e. Si-doped γ-Graphyne (SiG) nanolayer for its applicability as LIB electrode. Carbon and Silicon are two complementary choices for anode material due to the reason that the weakness of one is complemented by the other i.e. the extensive volume changes of Si anodes is compensated by the stable carbon matrix and the lower Li affinity of carbon is complemented by large capacities of Si anode. The Density Functional Theory (DFT) based studies reveal that SiG nanolayer has a dynamically and thermally stable structure with reliable mechanical properties. Density of states (DOS) calculation substantiates the good conductivity of the nanolayer. The binding energy of the Li atom (adatom) is −1.33 eV resulting from a charge transfer of 0.88e from Li to the nanolayer. The SiG anode achieved a specific capacity of 1005.05 mAhg−1 (almost 2.7 times the Graphite anode used in commercial LIBs). Climbing Image-Nudged Elastic Band (CI-NEB) calculations depict an easy migration of the adatoms through the anode with an energy barrier of 0.67 eV having diffusion coefficient (D) as 8.91 × 10−14 cm2/s. A low working voltage of 0.44 V is obtained advocating a safe operation and good cyclability. So, the theoretical investigation presents favorable outcomes for Si-doped γ-Graphyne to be applicable as a progressive anode in next-generation LIBs.

NbO2 a Highly Stable, Ultrafast Anode Material for Li- and Na-Ion Batteries.

Anode materials with fast charging capabilities and stability are critical for realizing next-generation Li-ion batteries (LIBs) and Na-ion batteries (SIBs). The present work employs a simple synthetic strategy to obtain NbO2 and studies its applications as an anode for LIB and SIB. In the case of the LIB, it exhibited a specific capacity of 344 mAh g-1 at 100 mA g-1. It also demonstrated remarkable stability over 1000 cycles, with 92% capacity retention. Additionally, it showed a unique fast charging capability, which takes 30 s to reach a specific capacity of 83 mAh g-1. For the SIB, NbO2 exhibited a specific capacity of 244 mAh g-1 at 50 mA g-1 and showed 70% capacity retention after 500 cycles. Furthermore, detailed density functional theory reveals that various factors like bulk and surface charging processes, lower ion diffusion energy barriers, and superior electronic conductivity of NbO2 are responsible for the observed battery performances.

Atomic pins bridging integrated surface to assist high-rate stability for Co-free Li-rich cathode

Li- and Mn-rich oxides (LMR) have emerged as promising cathode materials for next-generation Li-ion batteries due to their cost effectiveness, impressive capacity, and high energy density. However, the poor electrochemical kinetics and structural instability in hostile interface environments have result in continuous voltage/capacity decay and undesirable rate performance, impeding the large-scale commercial application of LMR materials. In this study, we introduce an atomic pins-assisted integrated surface reconstruction (AISR) strategy to address the interfacial degradation and instability issues. Utilizing the bidirectional diffusion effect of the aluminum-containing intermediate layer during the heat treatment process, we employ aluminum atoms as bridging centers to in situ construct a composite interface structure. This approach capitalizes on the element diffusion reaction and anchoring effect to achieve multifunctional modification through the Al-based ionic conductor network constructing and near-surface Al doping for LMR material. Intriguingly multiple kinetic investigations and calculations reveal that the epitaxial ionic conductor layer suppresses interfacial side reactions, enhances ionic conductivity, and improves electronic conductivity by regulating cationic/anionic redox activity through Al surface doping.Impressively, the modified electrodes exhibited an increased reversible capacity at both 0.1C/5C rates (0.1C, 2 ∼ 4.8 V, from 264.2 mAh∙g−1 to 274 mAh∙g−1; 5C, 2 ∼ 4.6 V, from 145.5 mAh∙g−1 to 197.9 mAh∙g−1) and improved capacity retention after 250 cycles at 1C/5C rates (2 ∼ 4.6 V: 1C, from 69.46% to 81.92%; 5C from 57.73% to 81.35%). We systematically summarized the rate-dependent failure mechanism and the corresponding integrated interface reconstruction principle. These key findings offer valuable insights for the development of high-energy–density and long-life lithium-ion batteries in commercial applications.

Single-step fabrication of fibrous Si/Sn composite nanowire anodes by high-pressure He plasma sputtering for high-capacity Li-ion batteries

To realize high-capacity Si anodes for next-generation Li-ion batteries, Si/Sn nanowires were fabricated in a single-step procedure using He plasma sputtering at a high pressure of 100–500 mTorr without substrate heating. The Si/Sn nanowires consisted of an amorphous Si core and a crystalline Sn shell. Si/Sn composite nanowire films formed a spider-web-like network structure, a rod-like structure, or an aggregated structure of nanowires and nanoparticles depending on the conditions used in the plasma process. Anodes prepared with Si/Sn nanowire films with the spider-web-like network structure and the aggregated structure of nanowires and nanoparticles showed a high Li-storage capacity of 1219 and 977 mAh/g, respectively, for the initial 54 cycles at a C-rate of 0.01, and a capacity of 644 and 580 mAh/g, respectively, after 135 cycles at a C-rate of 0.1. The developed plasma sputtering process enabled us to form a binder-free high-capacity Si/Sn-nanowire anode via a simple single-step procedure.

Continuum-level modeling of Li-ion battery SEI by upscaling atomistically informed reaction mechanisms

Understanding and controlling solid-electrolyte interphase (SEI) formation to stabilize cell performance is a significant challenge for next-generation Li-ion battery technologies. In recent years, computational modeling has become an essential tool in providing fundamental insights into SEI properties and dynamics. However, neither atomistic nor continuum-level approaches alone can capture the complexities of SEI chemistry across all relevant length and time scales. In this work, a continuum-level model is developed that is informed by reaction mechanisms obtained from first-principle calculations. The atomistically informed continuum-level model is used to understand electrolyte degradation, including the decomposition of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC). The model presented here is the most chemically complex continuum-level SEI model in the literature to date. The SEI model is calibrated against experimental irreversible leakage currents and shows qualitative agreement with expected SEI growth trends. The model framework is expected to accelerate fundamental understanding of SEI formation, facilitate mechanism development feedback, and dynamically interact with experimental insights.

Syringeless electrospun non-woven separator membrane for high-energy and high-power Li-ion battery application

Developing separators to meet the various requirements of next-generation Li-ion batteries (LIBs) is quite challenging because safety issues (good mechanical and thermal properties) and high power and energy density (small thickness and large porosity) exhibit a negative correlation, resulting in a technical contradiction. In general, an electrospun nonwoven membrane is a potential candidate for use in next-generation LIBs, but sufficiently thin electrospun-based nonwoven webs cannot be used as separators owing to their poor mechanical properties and exceedingly large porosity, which fail to prevent dendrite growth. To overcome these shortcomings, we fabricated a composite nonwoven separator using polyvinylidene fluoride (PVDF) and lithium lanthanum zirconium oxide (Li6.4La3Zr2Al0.2O12, LLZO) particles via a syringeless colloidal electrospinning method. To demonstrate the feasibility of our separator membrane for use in high-power and high-energy LIBs, we evaluated the electrochemical performance of an assembled LiNi0.6Co0.2Mn0.2O2 (NCM622)/graphite cell at a high C-rate. The assembled cell containing our separator membrane delivered an outstanding capacity of 115 mAh∙g-1 with a capacity retention of 97% after 100 cycles, even at 3 C. In addition, a Li-metal cell with our PVDF/LLZO separator achieved capacity retention of 86% after 250 cycles at 0.5 C.

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes Enabled by a Graphite Conductive Additive.

Cobalt-free cation-disordered rocksalt (DRX) cathodes are a promising class of materials for next-generation Li-ion batteries. Although they have high theoretical specific capacities (>300 mA h/g) and moderate operating voltages (∼3.5 V vs Li/Li+), DRX cathodes typically require a high carbon content (up to 30 wt %) to fully utilize the active material which has a detrimental impact on cell-level energy density. To assess pathways to reduce the electrode's carbon content, the present study investigates how the carbon's microstructure and loading (10-20 wt %) influence the performance of DRX cathodes with the nominal composition Li1.2Mn0.5Ti0.3O1.9F0.1. While electrodes prepared with conventional disordered carbon additives (C65 and ketjenblack) exhibit rapid capacity fade due to an unstable cathode/electrolyte interface, DRX cathodes containing 10 wt % graphite show superior cycling performance (e.g., reversible capacities ∼260 mA h/g with 85% capacity retention after 50 cycles) and rate capability (∼135 mA h/g at 1000 mA/g). A suite of characterization tools was employed to evaluate the performance differences among these composite electrodes. Overall, these results indicate that the superior performance of the graphite-based cathodes is largely attributed to the: (i) formation of a uniform graphitic coating on DRX particles which protects the surface from parasitic reactions at high states of charge and (ii) homogeneous dispersion of the active material and carbon throughout the composite cathode which provides a robust electronically conductive network that can withstand repeated charge-discharge cycles. Overall, this study provides key scientific insights on how the carbon microstructure and electrode processing influence the performance of DRX cathodes. Based on these results, exploration of alternative routes to apply graphitic coatings is recommended to further optimize the material performance.

In situ cathode-electrolyte interphase enables high cycling stability of Co-free Li-rich layered cathodes

Despite the extensive research in Li-rich layered oxides (LLOs), which are promising candidates for high-energy density cathodes, their cycle life still cannot meet the real-world application requirements. The poor cycle performance arises from the electrolyte decomposition at high voltage, resulting in damage and subsequent surface-initiated conversion of the cathode from layered to spinel phase. This problem is even more challenging for Co-free LLO cathodes. Here, we report a one-pot synthesis of in situ carbonate-coated nanostructured Co-free LLO (Li2CO3@LLO) through a polyol-assisted method. This inorganic coating suppresses oxygen release, provides good Li–ion transport, and protects the cathode from adverse reactions with the electrolyte. The obtained material exhibits excellent long-term stability, with 76% capacity retention after 1000 cycles at a 0.2 C rate without any Co addition, demonstrating a path forward for using LLOs as a next-generation Li–ion battery cathode.

Enhancing the Electrode Gravimetric Capacity of Li1.2Mn0.4Ti0.4O2 Cathode Using Interfacial Carbon Deposition and Carbon Nanotube-Mediated Electrical Percolation.

Mn-based cation-disordered rocksalt oxides (Mn-DRX) are emerging as promising cathode materials for next-generation Li-ion batteries due to their high specific capacities and cobalt- and nickel-free characteristic. However, to reach the usable capacity, solid-state synthesized Mn-DRX materials require activation via postsynthetic ball milling, typically incorporating more than 20 wt % conductive carbon that adversely reduces the electrode-level gravimetric capacity. To address this issue, we first deposit amorphous carbon on the surface of the Li1.2Mn0.4Ti0.4O2 (LMTO) particles to increase the electrical conductivity by 5 orders of magnitude. Although the cathode material gravimetric first charge capacity reaches 180 mAh/g, its highly irreversible behavior leads to a first discharge capacity of 70 mAh/g. Subsequently, to ensure a good electrical percolation network, the LMTO material is ball-milled with a multiwall carbon nanotube (CNT) to obtain a 78.7 wt % LMTO active material loading in the cathode electrode (LMTO-CNT). As a result, a 210 mAh/g cathode electrode gravimetric first charge and 165 mAh/g first discharge capacity values are obtained, compared to the respective capacity values of 222 and 155 mAh/g for the LMTO material ball-milled with 20 wt % SuperP C65 electrode (LMTO-SP). After 50 cycles, LMTO-CNT delivers a 121 mAh/g electrode gravimetric discharge capacity, largely outperforming the value of 44 mAh/g of LMTO-SP. Our study demonstrates that while ball milling is necessary to achieve a significant amount of capacity of LMTO, a careful selection of additives, such as CNT, effectively reduces the required carbon quantity to achieve a higher electrode gravimetric discharge capacity.