Improved Capacity Retention Research Articles

CF3-Substituted Ethylene Carbonates for High-Voltage/High-Energy Rechargeable Lithium Metal-LiNi0.8Co0.1Mn0.1O2 Batteries.

The development of advanced liquid electrolytes for high-voltage/high-energy rechargeable Li metal batteries is an important strategy to attain an effective protective surface film on both the Li metal anode and the high-voltage composite cathode. Herein, we report a study of two CF3-substituted ethylene carbonates as components of the electrolyte solutions for Li metal|NCM811 cells. We evaluated trifluoromethyl ethylene carbonate (CF3-EC) and trans-ditrifluoromethylethylene carbonate Di-(CF3)-EC as cosolvents and additives to the electrolyte solutions. Using CF3-substituted ethylene carbonates as additives to a fluoroethylene carbonate (FEC)-based electrolyte solution enables improved capacity retention of high-power Li metal|NCM811 cells. The composition of the products from the transformations of CF3-EC and Di-(CF3)-EC in Li|NCM811 cells was studied by FTIR, XPS, and 19F NMR spectroscopy. We concluded that fluorinated Li alkyl carbonates are the main reaction products formed from these cyclic carbonates during the cycling of Li|NCM 811 cells, and fragmentation of the ring with the formation of CO2, CO, or olefins is not characteristic of CF3-substituted ethylene carbonates. The NCM 811 cathodes and Li metal anodes were characterized by X-ray diffraction, SEM, XPS, and FTIR spectroscopy. The role of CF3-substituted ethylene carbonate additives in stabilizing high energy density secondary batteries based on Li metal anodes was discussed. A bright horizon for developing sustainable rechargeable batteries with the highest possible energy density is demonstrated.

Isovalent Co-Substitution of Iron and Titanium into Single-Crystal NMC622

Substitutional Li[Ni0.6Mn0.2Co0.2]O2 oxides (known as NMC622) were made by all-dry synthesis with Fe and Ti substituting Co and Mn, respectively. The substitutions were performed in three series, Fe substitution for Co, Ti substitution for Mn, and Fe and Ti co-substitution for Co and Mn, according to the formula Li(Ni0.6Mn0.2−y Co0.2−x Fe x Ti y )O2. The resulting oxides were evaluated as cathode materials for Li-ion batteries. Fe-substitution for Co resulted in increased intersite mixing, resulting in increased polarization and capacity fade. Ti-substitution for Mn also resulted in increased intersite mixing, but the mixing was due to Ti3+ in the Li-layer. As a result, Ti-substituted NMCs had improved capacity retention and reduced polarization. These effects were independent of each other, so that Ti could partially offset the negative aspects of Fe-substitution. Additionally, layered Mn-free Li(Ni0.6Ti0.2Co0.2)O2 (NTC622) was produced as an endmember of this series for the first time with low intersite mixing and superior electrochemical performance in comparison to previous reports. These results demonstrate benefits of all-dry Ti-substitution in NMC and the all-dry synthesis method as an avenue towards new cathode composition discovery.

Enhancing lithium titanate anode performance through surface modification with fluorine and nitrogen co-doped carbon nanotubes

In this study, we explore the efficacy of fluorine and nitrogen co-doped carbon nanotubes (F@N-CNT) as a novel surface modifier for lithium titanate (LTO) anodes in lithium-ion batteries (LIBs). The integration of F@N-CNT enhances the electrochemical properties of LTO anodes by improving electrical conductivity and facilitating lithium-ion diffusion., Electrodes modified with F@N-CNT exhibited significant improvements in capacity retention, achieving 71 % capacity retention over 200 cycles at 2 C and delivering energy capacities up to 162.9 mAh g−1 at 0.2 C, with an impressive high-rate performance of 74.8 mAh g−1 at 30 C. This study demonstrates that F@N-CNT effectively forms a conductive network within the LTO matrix, resulting in superior high-rate performance and stability. It presents a comprehensive analysis of the microstructural changes induced by co-doping and elucidates their impact on the electrochemical performance, providing valuable insights into the design of high-performance anodes for future energy storage applications. This approach not only addresses the current limitations of LTO anodes but also introduces a scalable strategy for enhancing the overall functionality of LIBs.

Advancing Lithium-Ion Batteries' Electrochemical Performance: Ultrathin Alumina Coating on Li(Ni0.8Co0.1Mn0.1)O2 Cathode Materials.

Ni-rich Li(NixCoyMnz)O2 (x ≥ 0.8)-layered oxide materials are highly promising as cathode materials for high-energy-density lithium-ion batteries in electric and hybrid vehicles. However, their tendency to undergo side reactions with electrolytes and their structural instability during cyclic lithiation/delithiation impairs their electrochemical cycling performance, posing challenges for large-scale applications. This paper explores the application of an Al2O3 coating using an atomic layer deposition (ALD) system on Ni-enriched Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathode material. Characterization techniques, including X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, were used to assess the impact of alumina coating on the morphology and crystal structure of NCM811. The results confirmed that an ultrathin Al2O3 coating was achieved without altering the microstructure and lattice structure of NCM811. The alumina-coated NCM811 exhibited improved cycling stability and capacity retention in the voltage range of 2.8-4.5 V at a 1 C rate. Specifically, the capacity retention of the modified NCM811 was 5%, 9.11%, and 11.28% higher than the pristine material at operating voltages of 4.3, 4.4, and 4.5 V, respectively. This enhanced performance is attributed to reduced electrode-electrolyte interaction, leading to fewer side reactions and improved structural stability. Thus, NCM811@Al2O3 with this coating process emerges as a highly attractive candidate for high-capacity lithium-ion battery cathode materials.

Ultralight, dual-conductive, all-fiber based 3D anode current collector for anode-free lithium metal battery

The anode-free Li metal batteries (AFLMBs), by pairing Li-containing cathode with bare anode current collector (CC), have the potential to enable the maximum improvement (>70 %) in energy density of lithium batteries. Here, we report an ultralight, dual-conductive all-fiber based Cu–CNF-CNT as anode CC, which takes advantage of the high electronic conductivity of carbon nanotube (CNT), good ionic conductivity of copper-coordinated cellulose nanofiber (Cu–CNF), and the three-dimensional porous structure by nanofibers. The interactions between CNTs and Cu-CNFs enables good mechanical strength (4.71 MPa), high electrical conductivity (31.7 S/cm), low density (1.1 g/cm3) and good wettability with electrolyte. The 3D microstructure effectively homogenizes the Li+ flux and buffers the volume changes during cycling, leading to stable Li plating/stripping. As a result, AFLMB using Cu–CNF-CNT exhibits improved capacity retention by 33 % compared to that using Cu CC. The significantly elevated energy-density shows great application potential of the Cu–CNF-CNT in AFLMBs.

Introducing Ionic Transport Islands in Graphite Anode towards Fast-Charging Lithium-Ion Batteries

The development of lithium-ion batteries (LIBs) possessing excellent fast charging performance is particularly important for expanding the worldwide application market of LIBs. However, the grievous growth of lithium dendrites during high rate charging and discharging process occurring on the surface of the anode material still restricts the development of commercial fast charging LIBs, which raises capacity deterioration and even enormous safety risks. Herein, we developed simple physical mixing of active carbon (AC) powder into graphite negative slurry to generate the hybrid fast charging anode (called AS anode), which can realize unprecedented fast charging capability whether at room temperature or low temperature, along with greatly improved capacity retention cycling at high 2 C rate. Importantly, the density functional theory calculation and combined characterizations including in situ electrochemical confocal system spectroscopy and lithium ion (Li+) diffusion coefficient analysis can decipher that AC particles with rapid Li+ diffusion and adsorption can act as ion transport islands in graphite electrode to accelerate the transport process of lithium ion inside the whole negative electrode, leading to the faster charging performance. This work not only promotes the development of anode construction with fast charging capability for LIBs, but also deciphers the ion transport mechanism inside the electrode.

Exploring optimal cathode composite design for high-performance all-solid-state batteries

All-solid-state batteries (ASSBs) have attracted considerable attention due to their high stability, offering a safer alternative to currently used batteries. Extensive research has been conducted to improve cathode part performance. However, the conventional hand mixing (HM) process results in inhomogeneous particle distribution, causing poor interparticle contact due to uneven stress distribution, and the solution process causes unwanted solid electrolyte (SE) deterioration when using a polar solvent although it ensures uniform SE distribution. To overcome these limitations, based on the design rule considering SE surface coverage of less than 100 %, we propose a cathode/SE composite, showing decent ionic/electronic conductivities, uniform SE distribution, and intimate interparticle contact, achievable through a mass-producible mechanical mixing (MM) process. Unlike the HM cell, the MM cell forms well-defined ionic percolating pathways and shows excellent structural stability. Consequently, the MM cell exhibits improved capacity retention during 1000 cycles and stable cyclability even under the harsh condition of 7 wt% SE. Finite element analysis theoretically demonstrates that uniform electrode and electrolyte currents are responsible for the improved performances including increased cathode utilization efficiency and reduced overpotentials. This study reveals the importance of composite design and uniform SE distribution in developing high-performance ASSBs at a practical cell level.

Boosting Aluminum Adsorption and Deposition on Single‐Atom Catalysts in Aqueous Aluminum‐Ion Battery

AbstractIn the quest for sustainable energy storage technologies, lithium‐based batteries, despite their prominence, face limitations such as high costs, safety risks, and supply chain issues. This has propelled the exploration of alternative materials, with aqueous aluminum‐ion batteries (AAIBs) emerging as a promising candidate due to their high energy density, abundance, and cost‐effectiveness. However, the low equilibrium reduction potential of aluminum ions presents significant challenges, including hydrogen evolution and poor cyclability. Addressing these, the study pioneers the application of single‐atom catalysts (SACs) in AAIBs, leveraging their high atom utilization and stability to enhance aluminum deposition and suppress hydrogen evolution. Sn, In, Cu, and Ni SACs are evaluated through density functional theory analysis and experimental validation, with Sn SAC identified as the most effective. Subsequently, the Sn SAC based anode demonstrates enhanced performance, achieving stable cycling over 500 h at 0.5 mA cm−2, significantly improved capacity retention (60 mAh g−1@300 cycles), and rate performance (50 mAh g−1@1 A g−1) in full cell tests. This work underscores the potential of SACs in advancing AAIB technology and opens new pathways for energy storage solutions.

Enhancement of La–Ti modification on the conductivity and stability of Co-free Li- and Mn-rich layered cathode

Lithium (Li) - and manganese (Mn)-rich oxides (xLi2MnO3·(1−x) LiTMO2, TM = Ni, Co, Mn, etc.) are one of the most promising cathode materials because of their high theorical capacity, which is contributed by the redox of both transition metal cations and oxygen anion. However, anionic redox leads to transition-metal migration and release of lattice oxygen, which further triggers voltage decay and capacity fade. Here, we report a dual-doping and multiphase co-existence strategy to tackle the structure degradation of Li- and Mn-rich materials and enhance electrochemical kinetics. La–Ti dual cations doping strength the TM-O bonds and improve cycling stability, and the inducement of LaMnO3+δ (LaMO) phase provides higher conductivity. As a result, the unique architecture presents a favourable rate performance, improved capacity retention, and suppressed voltage decay. After 200 cycles at 1C (250 mA g−1), the La–Ti dual cations doped Li-and Mn-rich material shows 24 % higher capacity retention and 52 % lower voltage decay compared to the non-doped material. This study demonstrates the potential of dual transition-metal ion doping combined with doping-induced perovskite phase to enhance the performance of Li- and Mn-rich materials.

Investigating Capacity Fade Mechanisms in Dual-Ion Mg-MCl x Batteries

Mg batteries are a promising alternative to Li-based chemistries due to the high abundance, low cost, and high volumetric capacity of Mg relative to Li. Mg is also less prone to dendritic plating morphologies, promising safer operation. Mg plating and stripping is highly efficient in chloride-containing electrolytes; however, chloride is incompatible with many candidate cathode materials. In this work, we capitalize on the positive effect of chloride by using transition metal chloride cathodes with a focus on low cost, Earth-abundant metals. Both soluble and sparingly soluble chlorides show capacity fade upon cycling. Active material dissolution and subsequent crossover to the Mg anode are the primary drivers of capacity fade in highly soluble metal chloride cathodes. We hypothesize that incomplete conversion and chemical reduction by the Grignard-based electrolyte are major promoters of capacity fade in sparingly soluble metal chlorides. Modifications to the electrolyte can improve capacity retention, suggesting that future work in this system may yield low cost, high retention Mg-MClx batteries.

Functionalized polypropylene separator coated with polyether/polyester blend for high-performance lithium metal batteries

Commercial polyolefin separators used in lithium metal batteries (LMBs) have the disadvantages of insufficient thermal stability and poor wettability with electrolytes, which causes bad safety and battery performance. Poly(ε-caprolactone) (PCL)-based electrolytes have drawn widespread attention in the field of polymer electrolytes owing to their electrochemical stability and high lithium-ion transference number. This work proposes a strategy of functionalizing commercial polypropylene (PP) separator coated by blending PCL (M w ~ 50,000) and poly(ethylene oxide) (PEO, M V ~ 600,000). Compared to commercial PP separators, PP-blended PEO60w/PCL5w separators possess better wettability with electrolytes and electrochemical performances. The initial discharge specific capacity of LiFePO4-based LMBs assembled with PP-blended PEO60w/PCL5w separators reaches 144 mAh g-1 (1C) and 103 mAh g-1 (5C) at room temperature, respectively. Notably, Li/PP-blended PEO60w/PCL5w/LiFePO4 shows an improved capacity retention rate of 77% after 800 cycles, confirming that the functionalized separator with coated PEO/PCL blend has great potential for application in the field of LMBs.

Revealing the origin of enhanced structural stability for nickel-rich LiNi0.83Co0.11Mn0.06O2 cathodes in situ modified with multifunctional polysiloxane

Multifunctional polysiloxane (MPS) layer is elaborately constructed on the surface of LiNi0.83Co0.11Mn0.06O2 (NCM83) particles via in situ hydrolysis-polycondensation of tetraethyl orthosilicate. Impressively, optimal NCM83 (NCM83-2) electrode covered with average 7 nm-thickness of fresh MPS layer delivers improved capacity retention ratio of 81.8 % after 150 cycles at 25 °C and retains the value of 78.7 % after 200 cycles at 60 °C and 1.0 C. Moreover, NCM83-2 electrode presents lower polarization degree with sluggish growth of the capacity platform. The significant advantages of NCM83-2 can be interpreted by the fact that the MPS layer effectively mitigates microcracks generation by inhibiting phase transition and lattice oxygen loss. Moreover, the MPS protective layer suppresses the thickening of cathode electrolyte interphase film and boosts the structural stability of NCM83 electrode to optimize electrochemical properties. Therefore, this strategy may provide promising enlightenments for preserving structural integrity and improving interfacial stability of nickel-rich cathodes for lithium-ion batteries.

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 %.

Overcoming low initial coulombic efficiencies of Si anodes through prelithiation in all-solid-state batteries

All-solid-state batteries using Si as the anode have shown promising performance without continual solid-electrolyte interface (SEI) growth. However, the first cycle irreversible capacity loss yields low initial Coulombic efficiency (ICE) of Si, limiting the energy density. To address this, we adopt a prelithiation strategy to increase ICE and conductivity of all-solid-state Si cells. A significant increase in ICE is observed for Li1Si anode paired with a lithium cobalt oxide (LCO) cathode. Additionally, a comparison with lithium nickel manganese cobalt oxide (NCM) reveals that performance improvements with Si prelithiation is only applicable for full cells dominated by high anode irreversibility. With this prelithiation strategy, 15% improvement in capacity retention is achieved after 1000 cycles compared to a pure Si. With Li1Si, a high areal capacity of up to 10 mAh cm–2 is attained using a dry-processed LCO cathode film, suggesting that the prelithiation method may be suitable for high-loading next-generation all-solid-state batteries.

The role of PrPO4 in improving the electrochemical performance of cobalt-free Lithium-rich oxide cathode

The utilization of lithium-rich layered oxides (LLOs) materials shows promising possibilities for the innovation of high-capacity Li-ion batteries with enhanced energy density. However, their practical applications are limited by continuous voltage decay, inferior cycling stability, and poor rate capability. In this work, a novel doping strategy is proposed, where PrPO4 is introduced during the high-temperature solid-state reaction to prepare Co-free Li-rich layered oxides. It is found that other than as a dopant, PrPO4 can activate Li2MnO3 to form well-distributed Pr0.96Mn0.982O3 and Li3PO4 in LLOs particles, which availably suppresses the phase transition. The obtained material increases the initial coulombic efficiency (ICE) from 75.8% to 84.1%, and improves capacity retention from 74.6% to 90.9% compared with the pristine material. Meanwhile, the average voltage decay decreases from 2.33 mV/cycle to 1.25 mV/cycle over 200 cycles. This work provides valuable insights into the development of LLOs using rare-earth phosphate, offering valuable knowledge for further advancements in this field.

Influence of Phosphate Surface Coating on Performance of Aqueous‐Processed NMC811 Cathodes in 3 Ah Lithium‐Ion Cells

AbstractAqueous processing of state‐of‐the‐art cathode materials for lithium‐ion batteries like LiNi0.8Mn0.1Co0.1O2 (NMC811) has evolved as a more sustainable and cost‐effective alternative to the conventional 1‐methyl‐2‐pyrrolidone‐based process. However, the implementation of aqueous processing is challenging due to the water sensitivity of nickel‐rich layered oxides. This study investigates the influence of a phosphate‐based NMC811 surface coating on the performance of aqueous‐processed NMC811 cathodes in 3 Ah cells. The results show that the cells with phosphate‐coated NMC811 outperform those with uncoated NMC811, i. e., they exhibited higher initial capacity and improved capacity retention during cycling. Post‐mortem characterization techniques reveal that the phosphate coating limits the lithium loss during aqueous cathode manufacturing and further reduces side reactions during cycling, resulting in a smaller increase of cell impedance.

Addressing Irreversibility and Structural Distortion in WS2 Inorganic Fullerene-Like Nanoparticles: Effects of Voltage Cutoff Experiments in Beyond Li+-Ion Storage Applications.

Large interlayer spacing beneficially allows Na+- and K+-ion storage in transition-metal dichalcogenide (TMD)-based electrodes, but side reactions and volume change, which pulverize the TMD crystalline structure, are persistent challenges for the utilization of these materials in next-generation devices. This study first determines whether irreversibility due to structural distortion, which results in poor cycling stability, is also apparent in the case of inorganic fullerene-like (IF) tungsten disulfide (WS2) nanocages (WS2IF). To address these problems, this study proposes upper and lower voltage cutoff experiments to limit specific reactions in Na+/WS2IF and K+/WS2IF half-cells. Three-dimensional (3D) differential capacity curves and derived surface plots highlight the continuation of reversible reactions when a high upper cutoff technique is applied, thereby indirectly suggesting restricted structural dissolution. This resulted in improved capacity retention with stable performance and a higher Coulombic efficiency, laying the ground for the use of TMD-based materials beyond Li+-ion storage devices.

A Two-Step Surface Modification Optimization for Performance Recovery of NaNi0.33Fe0.33Mn0.33O2

Due to its excellent electrochemical performance, O3-type NaNi0.33Fe0.33Mn0.33O2 (NFM) is one of the most promising cathode materials for sodium ion. However, its poor air stability has limited the industrialization process. In this work, a low-temperature two-step method which included carbon doping and acid treatment was used to improve the electrochemical property of the air-aged NaNi0.33Fe0.33Mn0.33O2. X-ray diffraction results indicated that the structure of modified NFM (NFM-M) has good crystal structure stability. NFM-M, NFM-48H (NFM after air ageing of 48 h) and fresh NFM possessed a discharge capacity of 95.25, 74.92, and 100.79 mAh·g−1 in the first cycle, respectively. The modified sample exhibits outstanding cycling stability, with a capacity retention of 90.15% after 100 cycles at 0.1 C rate. Moreover, the NFM-M sample delivers excellent rate capability with improved capacity retention of 66.9% at 2.0 C rate.

A Timescale characterization of (NMC811)/SiOx-graphite 1Ah pouch cell: Improving cycling stability with carbonate-based electrolytes and triallyl phosphate (TAP) co-additive

The role of 2 wt% triallyl phosphate as an electrolyte additive in (NMC811)/SiOx-graphite 1Ah pouch cells is studied using electrochemical impedance spectroscopy, long-term cycling, rate, timescale characterisation and X-ray photoelectron spectroscopy. Six kinetic processes are identified within the 100 kHz to 0.01 Hz frequency range. Anode processes consistently occur faster than the cathode and at higher frequencies. The triallyl phosphate (TAP) additive improves capacity retention from 70% to 85% after 500 cycles at 45 °C, exhibiting a higher and more stable coulombic efficiency, with ∼100% reduction in DCIR growth. TAP cells produce less gas during cycling. Timescale characterization suggests that the high impedance in the base formulation originates from cathodic charge transfer and cathode electrolyte interface (CEI) films in non-TAP-containing samples. The XPS data confirm the DRT findings, indicating the presence of high-impedance species associated with solvent oxidation and transition metal oxides (TMO) in the CEI of the TAP-free sample. The initial higher impedance of 14%–0.06 Ω observed in TAP cells is due to the formation of a thicker CEI in the TAP samples. Consequently, TAP samples show a ∼10 mAhg−1 lower rate capacity, at higher C-rates of 3C and 5C, while both samples exhibit consistent rate-capacity retention.

Ultrafast laser one-step construction of 3D micro-/nanostructures achieving high-performance zinc metal anodes

Aqueous zinc-ion batteries provide a most promising alternative to the existing lithium-ion batteries due to their high theoretical capacity, intrinsic safety, and low cost. However, commercializing aqueous zinc-ion batteries suffer from dendritic growth and side reactions on the surface of metallic zinc, resulting in poor reversibility. To overcome this critical challenge, here, we report a one-step ultrafast laser processing method for fabricating three-dimensional micro-/nanostructures on zinc anodes to optimize zinc nucleation and deposition processes. It is demonstrated that the three-dimensional micro-/nanostructure with increased specific surface area significantly reduces nucleation overpotential, as well as preferentially absorbs zinc ions to prevent dendritic protuberances and corrosion. As a result, the presence of three-dimensional micro-/nanostructures on the zinc metal delivers stable zinc plating/stripping beyond 2500 h (2 mA cm-2/1 mAh cm-2) in symmetric cells, a high Coulombic efficiency (99.71%) in half cells, and moreover an improved capacity retention (71.8%) is also observed in full cells. Equally intriguingly, the pouch cell with three-dimensional micro-/nanostructures can operate across various bending states without severely compromising performance. This work provides an effective strategy to construct ultrafine and high-precision three-dimensional micro-/nanostructures achieving high-performance zinc metal anodes and is expected to be of immediate benefit to other metal-based electrodes.