Current Rate Of 1C Research Articles

Balancing high graphitization and porous structure in N-doped carbon lamella for effective sulfur host of Li[sbnd]S battery

Porous carbon synchronously with high conductivity and abundant porous structure is considered to be an effective sulfur host material for boosting the lithium-storage property in battery fields. Herein, a natural silk cocoon derived in-situ N-doping porous carbon lamella with ultrahigh graphitization degree is prepared by a facile synchronous carbonization and catalysis using the bimetallic mixed salts of FeCl3 and ZnCl2. The pore structure and graphitization degree are easily regulated by changing carbonization temperature to balance the synergistic adsorption and conversion actions toward the polysulfides adhered to porous carbon lamellar. When the carbon lamellar is used to design sulfur cathode, the abundant porous structure not only encapsulates active sulfur, but also facilitates electrolyte infiltration. The shuttle effect of polysulfides can be restrained by the synergistic adsorption of porous structure and N-doping. Especially, the ultrahigh graphitized carbon lamellas provide an excellent conductive network for the favorable redox conversion of polysulfide species during charge/discharge. Owing to the structure merits of the porous carbon lamella prepared at 1000 °C, the corresponding carbon/sulfur composite cathode delivers a first discharge capacity of 807.7 mAh g−1 at 0.2C. Even at a current rate of 1C, the stable long cycling performance of 1000 cycles is still maintained. This high graphitized porous carbon materials will provide potential application in other energy-storage fields.

Boosting the rate performance of all-solid-state batteries with a novel double layer solid electrolyte

When compared to traditional liquid electrolytes, solid electrolytes face significant challenges due to insufficient ionic conductivity and poor interfacial contact. To overcome these challenges, a cathode-supported double layer gradient structured solid polymer electrolyte membrane is developed. This innovative design enhances the wetting ability of the solid electrolyte on the cathode, leading to improved rate performance. Furthermore, the double layer solid electrolyte enhances mechanical strength, ensuring excellent cycling performance. As a result, the LiFePO4/Li solid state battery demonstrates superior battery performances, for instance, it can achieve a discharge capacity of 121 mAh g−1 at a current rate of 5C, with a capacity retention of 99 % after 380 cycles. This work offers a promising strategy for further enhancing the performance of all solid-state batteries.

Effect of strontium phosphate coating on NCM811 powders for high-performance Li-ion battery cathode

The NCM811 cathode material, characterized by a high nickel content, is known for its substantial energy capacity but is afflicted by challenges, including electrolyte degradation and inadequate cyclic stability. In this study, a chemical bath deposition technique is utilized to apply a layer of Sr3(PO4)2 material onto the surface of NCM811 particles to address these problems. This procedure yields a continuous protective coating that shields the NCM811 particles from detrimental interactions with the electrolyte, such as HF attack and the formation of surface cracks, while also promoting the diffusion of lithium ions during charge/discharge cycles. XRD analysis indicated that the application of Sr3(PO4)2 coating did not cause any changes in the structure of the NCM811 cathode material. SEM images of all coated samples demonstrated that all coated samples have spherical morphology. Additionally, both Raman and FTIR examinations provide evidences supporting the existence of strontium phosphate material on the surface of the NCM811 cathode material. The distinctive 5.9 nm-thick Sr3(PO4)2 coating enables the NCM811 material to maintain 96 % of its capacity after 100 charge/discharge cycles in a voltage range of 2.8–4.4 V vs. Li/Li+ at a current rate of 1C.

Crystal water-capturing and film-forming bifunctional electrolyte additive for stabilizing sodium iron hexacyanoferrate cathode for Na-ion batteries

Due to its affordability, strong structural stability, and high rate capability, rhombohedral sodium ferrous hexacyanoferrate (FeHCF) has been identified as a potential cathode material for sodium ion batteries. Nevertheless, the presence of inherent crystal water and the susceptibility of its interface stability significantly hinder its capacity and cycling performance. In this study, we propose a novel modification approach involving the addition of ZnCl2 to effectively capture crystal water and facilitate the in-situ formation of a ZnO coating on the FeHCF surface. Due to the decreased crystal water content and the presence of stable ZnO interphases, the occurrence of side reactions between the electrode and electrolyte, as well as crystal particle cracks in FeHCF during repeated sodiation/desodiation processes, is effectively reduced. Consequently, the modified FeHCF demonstrates an extended operational lifespan of 1000 cycles, with an initial discharge capacity of 112.0 mAh/g and a capacity retention rate of 77.8 % at a current rate of 1C within the voltage range of 2.0–4.2 V. Our research offers valuable insights into the removal of crystal water and the engineering of incident interfaces to enhance the cycle life of FeHCF cathodes in sodium-ion batteries.

Stabilization of LiCoO2 Cathodes in High Voltage Lithium Metal Batteries Through 2-(Trifluoromethyl)Benzamide (2-TFMBA) Electrolyte Additives.

Increasing the charging cutoff voltage of LiCoO2 to 4.6V is significant for enhancing battery density. However, the practical application of Li‖LiCoO2 batteries with a 4.6V cutoff voltage faces significant impediments due to the detrimental changes under high voltage. This study presents a novel bifunctional electrolyte additive, 2-(trifluoromethyl)benzamide (2-TFMBA), which is employed to establish a stable and dense cathode-electrolyte interface (CEI). Characterization results reveal that an optimized CEI is achieved through the synergistic effects of the amide groups and trifluoromethyl groups within 2-TFMBA. The resulting CEI not only enhances the structural stability of LiCoO2 but also serves as a high-speed lithium-ion conduction channel, which expedites the insertion and extraction of lithium ions. The Li‖LiCoO2 batteries with 0.5wt% 2-TFMBA achieves an 84.7% capacity retention rate after enduring 300 cycles at a current rate of 1C, under a cut-off voltage of 4.6V. This study provides valuable strategic insights into the stabilization of cathode materials in high-voltage batteries.

Microstructured pebble stone like Ni-NiO composite as anode of high-performance lithium-ion batteries

Ni-NiO electrodes were synthesized via thermal oxidation of pure nickel powder and evaluated as anode of lithium-ion batteries (LIBs). The composite synthesized at 600˚C, 800˚C, and 1000˚C exhibited nanochips, crushed gravel stone, and pebble stone-like morphology, respectively. The nanochips- and crushed gravel stone featured-like electrodes exhibited erratic behavior, and specific capacity faded rapidly from 754.49 mAh g-1 and 101.12 mAh g-1 to 464.04 mAh g-1 and 9.55 mAh g-1, respectively over 10th cycle at a current rate of 1C as the electrode experiences internal short circuit. The pebble stone-like Ni-NiO electrode exhibited improved and stable cyclic performance with 1st discharge capacity of 365.17 mAh g-1 and reduced to 67.42 mAh g-1 even after 40th cycle at 1C current rate. The improved electrochemical performance of composite Ni-NiO with a pebble stone-like feature can be attributed to the mechanical stability of the electrode, which can buffer volume expansion, and the presence of more nanoparticles on the electrode surface allows more interaction with Li+.

Zn dendrite suppression and solid electrolyte interface control using N-allylthiourea as an electrolyte additive for aqueous Zn-ion batteries

Despite being promising candidates for Li-ion batteries, the development of aqueous Zn-ion batteries is still impeded by inherent unresolved problems such as dendrite growth and side reactions on the anode side. In this study, a stabilized Zn-electrolyte interface is established using N-allylthiourea (ATU) as an additive in mildly acidic electrolytes because of its strong affinity towards Zn2+ ions and the Zn metal. Through this favorable electrostatic adsorption, side reactions owing to water molecules are inhibited, and uniform Zn deposition is achieved, leading to highly reversible stripping/plating performance. Consequently, a stable cycling performance of up to 500 h at a current density of 1 mA cm–2 and an areal capacity of 1 mAh cm–2 is demonstrated for Zn symmetric cells. Furthermore, a Zn|VO2 full cell validates the possible practical use of ATU where it delivers a promising cycling performance of up to 300 cycles at a current rate of 1C (200 mA g–1). This study contributes insights into the role of additives in optimizing battery performance and creates opportunities for further exploration of similar compounds in pursuit of sustainable energy storage systems.

Rational design of dual catalysts towards efficient polysulfides conversion for high performance Li–S batteries

Lithium-sulfur batteries are promising alternatives to lithium-ion batteries due to their high theoretical capacity and high energy density. However, severe active materials losing and capacity decay caused by shuttle effect restrict its practical application. Inspired by bipolar magnet, here we proposed dual catalysts embedded in nitrogen-doped carbon with different polar sites towards efficient lithium polysulfides conversion. The dual catalysts are composed of interlacing metal Co and Eu2O3 particles, in which the electronegative O2− in Eu2O3 and Co metal sites synergistically accelerate intermediates conversion. With this rational design, the cathode delivered an areal capacity of about 2.6 mAh cm−2 at the current rate of 1C during 100 cycles with the sulfur areal loading of 4.2 mg cm−2. Furthermore, the cathode could deliver a reversible capacity over 1000 mAh g−1 at 0.5C, and performed an excellent rate and cycling stability.

A Classical Newman-Type Model for Pure-Silicon Anodes

Due to its high gravimetric and volumetric capacity, silicon is a promising candidate as a new anode material for lithium-ion batteries. In studies over the last two decades, silicon has been investigated in various designs such as silicon nanowires, silicon thin films, silicon wafers, or silicon nanoparticles. Silicon is also found in commercially available cells, both as a pure-silicon anode as well as a silicon-graphite composite anode.In addition to experiments, lithium-ion batteries containing conventional anode materials like graphite as well as novel anode materials like silicon are also studied simulatively. Various modeling approaches for lithium-ion batteries can be found in the literature. Focusing only on physicochemical approaches, the Newman model and its variations are the most widely used for conventional material combinations. However, the literature does not provide any physicochemical modeling approach tailored specifically to alloying reactions that provides the same insight into the battery as the Newman model does. Thus, the question arises whether classical models such as the Newman model can also be applied to lithium-ion batteries with pure-silicon anodes.To examine whether the Newman model can provide accurate results even for pure-silicon anodes, we parameterized a classical Newman model for a lithium-ion battery with a pure-silicon anode and a nickel cobalt aluminum oxide (NCA) cathode. The silicon anode consists of 70 wt% silicon, 20 wt% graphite, and 10 wt% binders and additives. However, the graphite is considered electrochemically inactive. The parameterization is based on values from a) the electrode manufacturing process (e.g., initial porosity, coating thickness), b) measured values (e.g., open-circuit potentials), and c) literature data (e.g., exchange current density, solid-phase diffusivity). For parameterization, we used laboratory cells in CR2023 coin cell format with a capacity of about 5 mAh. The model was validated using 3 mAh Swagelok T-cells with an three-electrode setup using a lithium-metal reference as well as custom-built large-format 5 Ah multilayer pouch cells.The simulation results of CC-CV charge and discharge processes at different current rates show good agreement with measurements with a root-mean-squared error of about 22 mV at a current rate of C/10 (see Figure a), and less than 5% deviation in discharge capacity at a current rate of 2C (see Figure b). Overall, the Newman model appears to be a viable choice for pure-silicon anodes as well. However, care must be taken in parameterization. A literature review revealed that material parameters such as the exchange current density can vary by up to 13 orders of magnitude. In addition, reconstruction of the full-cell potential via half-cell potentials is of paramount importance when using partially lithiated materials, since the degree of lithiation does not necessarily approach the 0 and 1 limits. For the deliberately partially lithiated silicon used in our study, we found the utilization to be between 0.04 and 0.31, thus, a comparison between measurements and simulations during the crystallization process in the fully lithiated state is not possible. Discharge tests with multilayer pouch cells showed that the temperature rise cannot be neglected and might become rate-limiting at even higher current rates, while the discharge capacity shows that the electrode kinetics is most likely not rate-limiting.Since simulation studies are a cost-effective method for designing new cells, our results are of practical importance. Demonstrating that the Newman model is applicable not only to conventional intercalation materials such as graphite but also to cells containing a pure-silicon alloy material with micrometer-sized particles may encourage more researchers to simulatively explore novel electrode materials. However, in general, any model and parameterization should be validated by experiments. Figure 1

Embedded real-time state observer implementation for lithium-ion cells using an electrochemical model and extended Kalman filter

Accurate knowledge of the current state of lithium-ion battery cells is crucial for enhanced operational management of battery electric vehicles. Electrochemistry-based models provide the unique ability to predict cell internal states for advanced state monitoring, such as the anode potential, being of great interest for preventing lithium plating during fast charging. Furthermore, they are extendable by electrochemistry-based descriptions of cell degradation mechanisms. However, unlike the widely used equivalent circuit models, they are more computationally expensive and therefore have been scarcely used in embedded systems for online applications. This work addresses an efficient implementation of the popular pseudo-two-dimensional (p2D) electrochemical model in combination with a nonlinear filtering algorithm on a state-of-the-art microcontroller for automotive applications. For the first time, it is shown that with a suitable discretization scheme for the finite-difference approximation, a state observer convergence duration below 40 ms can be achieved for constant current, constant voltage charging at a current rate of 2C, with fast recovery of even local states. The mean relative error of the model internal states is less than 2% compared to an about 15 times slower implementation. This works therefore contributes valuably to demonstrating fast and robust performance of online state estimation using electrochemical models.

The preparation, electrochemical properties, Na+ migration mechanism and kinetics of a new anode material Na4TiO(PO4)2 with open framework for Na ion batteries

A new anode material for NIB Na4TiO(PO4)2 and the carbon coating counterpart Na4TiO(PO4)2/C, which were never reported elsewhere, were synthesized by a traditional high-temperature solid-phase method and explored both experimentally and theoretically. The morphology and the composition of Na4TiO(PO4)2 and Na4TiO(PO4)2/C were examined by XRD, SEM, TEM, ICP, EDS and XPS. Na4TiO(PO4)2/C material shows better rate capability and cycle stability than Na4TiO(PO4)2. It provided an initial charge and discharge capacity of 117/234.5 mAh g−1 at a current rate of 1C, and retained a capacity of 103/107.4 mAh g−1 after 240 cycles. Except the initial several cycles, the Coulomb efficiencies of Na4TiO(PO4)2/C were higher than 95%. When the current density experienced 0.1 C, 0.2 C, 0.5 C, 1 C and 2 C and returned to 0.1 C, the discharge capacity of 149.29 mAh g−1 can be obtained by the Na4TiO(PO4)2/C electrode, closed to the initial 171.12 mAh g−1. The chemical diffusion coefficient in discharge process varies from 1.3 × 10−9 to 2.6 × 10−9 cm2 s−1 and from 9.2 × 10−10 to 4.9 × 10−9 cm2 s−1 for charge process, showing features of fast ion conducting materials. Both nudged elastic bands (NEB) method and molecular MD show a relatively low diffusion barrier of ca. 0.4 eV on a-c plane and a 0.1 eV higher energy barrier along b-axis. The theoretical calculations show that the high mobility of Na+ originates from the ample cavities and the complicated three dimensional conducting framework in the lattice. Ex-situ experiments reveal an ultra-stable framework of Na4TiO(PO4)2 material in the intercalation/deintercalation process and also a less than 0.92% contraction in this process.

Reuse, Recycle, and Regeneration of LiFePO4 Cathode from Spent Lithium-Ion Batteries for Rechargeable Lithium- and Sodium-Ion Batteries

Rechargeable lithium-ion batteries are dominating the energy storage market with a current market value of $50 billion. However, the exponential production of lithium-ion batteries is accompanied by an increased backflow as environmentally hazardous spent/end-of-life batteries, which need to be recycled efficiently. Herein, we demonstrate the possibility of reuse, recycle, and regeneration of a spent LiFePO₄ (LFP) cathode for rechargeable lithium- and sodium-ion batteries. An approach of reusing the spent-LFP electrode in developing a new lithium-ion battery was initially explored. The refabricated LFP lithium-ion half-cells delivered excellent capacity and rate capability. Further, an unprecedented approach of using a spent-LFP electrode for sodium ion storage was investigated. The adopted low-temperature, rapid (15 min) microwave delithiation process could completely delithiate the LFP electrode, forming FePO₄. This recycled FePO₄ was tested for its sodium ion storage capability. Finally, an aspect of commercially viable, nearly zero-energy chemical lithiation/sodiation of microwave-derived FePO₄ was also explored. Thus, regenerated LiFePO₄ as lithium-ion half-cells exhibited a reversible capacity of 145 mAh/g at a current rate of 1C and 107 mAh/g at 10C and 96% capacity retention at 5C for 300 cycles. Similarly, the chemically sodiated FePO₄ sodium-ion cell demonstrated a capacity close to 138 mAh/g at C/15, which is comparable to freshly prepared NaFePO₄ (NFP) electrode’s performances. Our electrochemical results confirm the potential of these rapid, sustainable, and energy-efficient methods for reutilization, recycling, and regeneration of failed LFP cathodes recovered from 32 650 cells for their proficient usage in both lithium- and sodium-ion storage.

A nano-silica/polyacrylonitrile/polyimide composite separator for advanced fast charging lithium-ion batteries

In this work, composite separators were fabricated based on silica particles embedded in polyacrylonitrile and polyimide. The efficient and cost-effective electrospinning technique was used, followed by thermal pressing. The results demonstrate that the electrospun composite separator membranes have high thermal stability and high tensile strength, which can effectively improve battery safety. Furthermore, compared with a commercial Celgard separator, the composite separator membranes have better affinity towards liquid electrolyte, higher porosity and lower internal resistance in the transportation of ions between electrodes, leading to stable cyclability and superior C-rate capacity. The highest discharge capacity of 147 mAh.g−1 was obtained at a current rate of 1C with coin cells assembled with separator CS-3 (10 wt% silica (SiO2), 5 wt% 4,4′-oxydianiline (ODA), 5 wt% pyromellitic dianhydride (PMDA), and 10 wt% polyacrylonitrile (PAN) in dimethylformamide (DMF)). Furthermore, the capacity retention was 93% after 200 cycles of charging and discharging.

Electrochemically active layer on the surface of poly(anthraquinonyl sulfide) anode in dual-ion batteries

The dissolution characteristics of organic electrode materials, which are widely used in metal-ion, solid-state, and dual-ion batteries, affect the cycle performance of batteries. In this study, poly(anthraquinonyl sulfide), natural graphite, and N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid are used as the anode, cathode, and electrolyte, respectively, to construct a dual-ion battery. Experiments reveal that when two glass fiber layers are used as separator in this battery, they significantly affect its performance, and the discharge capacity and retention rate of the cell are 47.4 mAh g−1 and 91.4%, respectively, after 100 cycles at the current rate of 2C. In addition, the self-discharge effect is greatly reduced. The glass fiber layer next to the poly(anthraquinonyl sulfide) anode is analyzed using scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry. The results indicate that the poly(anthraquinonyl sulfide) particles form an electrochemically active layer, which was attached to the glass fiber and can participate in electrochemical reactions. The formation of the electrochemically active layer improves the electrochemical performance of the dual-ion battery.

Crack-free single-crystalline Ni-rich layered NCM cathode enable superior cycling performance of lithium-ion batteries

Ni-rich layered oxides are extensively employed as a promising cathode material in lithium ion batteries (LIBs) due to their high energy density and reasonable cost. However, the hierarchical structure of secondary particles with grain boundaries inevitably induces the structural collapse and severe electrode/electrolyte interface parasitic reactions as the intergranular crack arises from the anisotropic shrink and expansion. Herein, the single-crystalline LiNi0.83Co0.11Mn0.06O2 (SC-NCM) with primary particles of 3–6 μm diameter is developed and comprehensively investigated, which exhibits superior cycling performance at both room temperature and elevated temperature (55 °C) as well as significantly improved structural integrity after long-term cycling. Remarkably, the SiO-C||SC-NCM pouch-type full cell with a practical loading (8.7 mAh cm−2) delivers a capacity retention of 84.8 % at 45 °C after 600 cycles at a current rate of 1C (1C = 200 mA g−1), retaining a high specific energy density of 225 Wh/kg. Using a combination of X-ray photoelectron spectroscopy, time-of-flight secondary-ion mass spectrometry and scanning transmission electron microscopy, we reveal that SC-NCM particles with micron-sizes effectively mitigate the undesired electrode/electrolyte side interactions and prevent the generation of intergranular cracks, thereby alleviating irreversible structural degradation. The strategy of developing single-crystalline micron-sized particles may offer a new path for maintaining the structural stability and improving cycling life of Ni-rich layered NCM cathodes even under high temperature.

Self-Ordered TiO2 Nanotubes Prepared By Anodization in Fluorine-Free Electrolyte As Additive-Free Anode for Lithium-Ion Microbatteries

TiO2-based material is widely studied as a promising anode for rechargeable lithium ion batteries due to its unique properties such as high safety, easy handling and low production cost. On top of that, the high structural stability of TiO2 arises from the low volume expansion of less than 4% upon cycling, without Li dendrite formation or electrolyte decomposition that turns them into stable and safe anode materials. Nevertheless, the low ionic conductivity represents the main obstacle behind the low practical capacity of TiO2 electrode. Manufacturing of TiO2 nanostructures is one of the effective solutions to create short diffusion pathways for Li, to enhance the ionic conductivity by lattice defects and, finally, the electrochemical performance of titania. TiO2 nanotubes represent the ideal one-dimensional nanostructure, especially when they are aligned and perfectly arranged in close packed arrays with high surface area. Ordered TiO2 nanotubes are commonly synthesized by the anodic oxidation of titanium in fluoride ion-containing electrolytes [1]. However, the use of such an anodization bath requires complicated safety measures, due to its harmful impact on both health and the environment, which in turn is translated into a higher production cost. Despite several attempts have been reported to grow self-ordered TiO2-NTs in fluoride-free electrolytes, only bundles of interwoven and disordered tubular morphologies were formed [2,3]. Herein, we report the successful fabrication of vertically aligned and highly ordered TiO2-NTs by means of anodization in a fluoride-free aqueous electrolyte. The typical formation bath is composed of diluted sulfuric acid as electrolyte basis and chloride ions. Various synthesis parameters such as chloride concentration, pH, voltage, growth time, and temperature were explored to optimize the ideal fabrication conditions of the nanotubes. Structure, composition and morphology of the grown oxide tubes were investigated. The vertical alignment in an ordered porous nanostructure revealed from our results push the grown nanotubes into very promising position as candidates for lithium ion storage. The electrochemical performance of the NTs was evaluated vs. Li/Li+ without binder or conductive additives. The effect of the annealing temperature on the crystallinity and the lithium ion storage properties was investigated. The TiO2-NT electrodes demonstrated a reversible capacity of 150 µAh cm-2 after 50 charging/discharging cycles with a Coulombic efficiency close to 100% and without decomposition of the tubular structure at a current rate of 1C. The noticed cycling stability of the NT electrodes is attributed to the high structural stability of TiO2 and the perfect contact between the oxide films and the substrate which is utilized as a current collector.

Hierarchical micro-mesoporous carbon prepared from waste cotton textile for lithium-sulfur batteries

As the next generation battery, the lithium-sulfur battery with high theoretical specific capacity and energy density needs to overcome the low practical discharge capacity and the poor cycle performance for the poor conductivity of sulfur and the shuttle effect of polysulfide. In this study, a hierarchical micro-mesoporous carbon (HPC) is designed and synthesized as a sulfur host from the cotton textile with KOH activation at 700 °C to combine the advantages of these two structures, where mesoporous structure can improve the infiltration of electrolyte to act as fast ionic channel and micropores have an excellent ability of binding sulfur. The HPC showed an excellent high specific surface area (2835.47 m2 g−1) and a high pore volume (2.82 cm3 g−1), and the ratio of the mesoporous reaches 57.85%. The sulfur in HPC/S was uniformly distributed in the host structure and no surface crystallization was observed by TEM characterization. Assembled in the lithium-sulfur battery, the cathode mixed with HPC/S and conductive agent delivers an initial discharge capacity of 1577 mAh g−1 at 0.1C, and a reversible capacity of 434.5 mAh g−1 after 300 cycles at the current rate of 1C.

Investigation of the influence of temperature on the degradation mechanism of commercial nickel manganese cobalt oxide-type lithium-ion cells during long-term cycle tests

Abstract The effect of temperature in long-term cycle tests was investigated using commercial nickel manganese cobalt oxide 18650-type lithium-ion cells, which were cycled at a current rate of 1C at 25 °C and 50 °C. The cell capacity decreased more rapidly at 50 °C than at 25 °C. Conversely, the internal resistance increased more rapidly at 25 °C than at 50 °C before increasing dramatically after ca. 700 cycles at 50 °C. Electrochemical impedance spectroscopy performed after the cycle tests revealed that the increase in ohmic resistance was larger at 50 °C, while the increase in charge-transfer resistance was larger at 25 °C. To elucidate the reasons for the differences in the degradation tendencies at different test temperatures, the electrochemical electrode properties, electrolyte compositions, and electrode materials were analyzed. The half-cell analyses showed that capacity fading was mainly caused by cell imbalances and cathode degradation at both test temperatures. 1H and 19F nuclear magnetic resonance spectroscopy revealed that the ohmic resistance increase at 50 °C was mainly due to decomposition of the electrolytes. X-ray photoelectron spectroscopy spectra indicated that the increase in charge-transfer resistance at 25 °C arose from the generation of high-valence Ni species on the cathode surface. Detailed analyses using hard X-ray photoelectron spectroscopy and transmission electron microscopy confirmed the existence of such Ni species only at the outermost layer as an amorphous phase. These results indicates that the degradation mechanism depends on temperature, and the appropriate control of temperature is important for prolonging the life of lithium-ion cells with nickel manganese cobalt oxide cathode.

Enhanced Electrochemical Properties of LiNi0.8Co0.1Mn0.1O2 at Elevated Temperature by Simultaneous Structure and Interface Regulating

Inferior cycling stability at elevated temperature is a big challenge for the commercial application of nickel-rich cathode materials because more serious phase transition, transition metal ion dissolution and side reaction of interface happen at elevated temperature than at room temperature. In the present work, strategies of element doping and surface coating are utilized together to stabilize the structure and interface electrochemistry. We successfully synthesized a Zr-doped and LiAlO2-Al2O3 coated LiNi0.8Co0.1Mn0.1O2 material by a simple ball milling and wet chemical method. Owing to the synergistic effect of Zr doping and dual LiAlO2-Al2O3 coating, when cycled at 50°C, the modified LiNi0.8Co0.1Mn0.1O2 sample exhibited significantly improved cycling stability with a capacity retention of over 96.8% after 60 cycles at a current rate of 1C, while the pristine sample could only retain a capacity of 73.3%. This improved electrochemical performance can be attributed to the effective doping and coating technique employed to the LiNi0.8Co0.1Mn0.1O2 sample. The Zr doping is beneficial to reduce cation mixing and suppress the phase transition, while the LiAlO2-Al2O3 coating helps to enhance the protection of the electrode/electrolyte interface and reduce the transition metal ion dissolution.

Synthesis of Si anode with a microsized-branched structure from recovered Al scrap for use in Li-Ion batteries

Silicon (Si), with a theoretical capacity of 3579 mAh g−1, is an attractive anode material for Lithium-ion batteries. Currently, nano-sized Si, with a diameter less than 150 nm, is the focus of research efforts. However, the difficulty of obtaining a uniform dispersion and increasing the loading ratio of nano-sized Si remains challenging. In this work, a Lithium-ion battery anode was constructed using micro-sized Si from acid-etching of cast Al-Si alloy scraps. The acquired Si has a unique branched structure, with a diameter of 0.5–1 μm in branches and 5–10 μm in length. Compared to the typical, low-loading ratio of much less than 1 mg cm−2 in nano-sized Si, this micro-sized Si anode has a typical loading ratio of 2 mg cm−2. The branched Si with conventional carbon coating demonstrated an initial discharge (lithiation) capacity of 3153 mAh g−1 at the current rate of 1/16C. Moreover, it maintained a discharge capacity of 1133 mAh g−1 at the 100th cycle, under a current rate of 1/4C. The capacity decay was less than 0.2% per cycle from the 20th to the 100th cycle. The rate performance was also promising, with a discharge capacity of 488 mAh g−1 at the current rate of 1C.