LiCoO2 Batteries Research Articles

Electrolyte additive strategy to eliminate hydrofluoric acid and construct robust cathode electrolyte interphase for 4.6 V Li||LiCoO2 batteries

The high voltage of Li||LiCoO2 battery can increase the energy density. However, the cycling performance associated with cathode structural stability remains challenging. To address this question, we proposed an electrolyte strategy for improving the performance of 4.6 V Li||LiCoO2 battery by using trimethylsilyl isocyanate (TMIS) as electrolyte additive. The trimethylsilyl group of trimethylsilyl isocyanate can trap HF while the isocyanate group brings polyamide components to the CEI and the SEI. By the synergistic action, the Co3+ dissolution problem of the LiCoO2 cathode was effectively curbed. Furthermore, TMIS regulates the construction of anion-dominated LiF-rich SEI by influencing the solvation structure of Li+. As expected, the 4.6 V Li||LiCoO2 battery with trimethylsilyl isocyanate retains 77.9% initial capacity after 200 cycles at 0.5 C.

Low‐Solvent‐Coordination Solvation Structure for Lithium‐Metal Batteries via Electric Dipole‐Dipole Interaction

AbstractUnveiling inherent interactions among solvents, Li+ ions, and anions are crucial in dictating solvation‐desolvation kinetics at the electrode/electrolyte interface. Developing an electrolyte with a low ion‐transport barrier and minimal solvent coordination in its interfacial solvation structure is essential for forming an anion‐derived solid‐electrolyte interface, a key component for high‐performance Li‐metal batteries. In this study, we harness electric dipole‐dipole synergistic interactions to formulate an electrolyte with significantly reduced interfacial solvent coordination. Operando characterization and theoretical analysis reveal that 2‐fluoropyridine (FPy) with high dipole preferentially adsorbs onto the Li metal surface. The adsorbed FPy molecule squeezes succinonitrile in the primary solvation sheath through steric hindrance, leading to the formation of an inorganic‐rich interphase. Consequently, the introduction of FPy enhances the reversible capacity of the LiCoO2||Li cell, which maintains a capacity of 143 mAh g−1 after 500 cycles at a 1 C rate. Moreover, the cycle life of LiCoO2 batteries with a limited supply of lithium extends from 120 cycles to over 200 cycles. These findings offer a strategy that can be applied broadly to design interfacial solvation structures for various metal‐ion/metal‐based batteries.

Imaging in-operando LiCoO2 nanocrystallites with Bragg coherent X-ray diffraction

Although the LiCoO2 (LCO) cathode material has been widely used in commercial lithium ion batteries (LIB) and shows high stability, LIB’s improvements have several challenges that still need to be overcome. In this paper, we have studied the in-operando structural properties of LCO within battery cells using Bragg Coherent X-ray Diffraction Imaging to identify ways to optimise the LCO batteries’ cycling. We have successfully reconstructed the X-ray scattering phase variation (a fingerprint of atomic displacement) within a ≈ (1.6 × 1.4 × 1.3) μm3 LCO nanocrystal across a charge/discharge cycle. Reconstructions indicate strained domains forming, expanding, and fragmenting near the surface of the nanocrystal during charging, with a determined maximum relative lattice displacements of 0.467 Å. While discharging, all domains replicate in reverse the effects observed from the charging states, but with a lower maximum relative lattice displacements of 0.226 Å. These findings show the inefficiency-increasing domain dynamics within LCO lattices during cycling.

Inverse Open Circuit Voltage Curve Model for LiCoO2 Battery at Different Temperatures

Lithium-ion batteries are widely used in a variety of applications. For effective battery management, accurate estimation of the state of charge (SOC) is essential. One of the most commonly employed methods for SOC estimation relies on the open circuit voltage (OCV) curve with respect to SOC. However, inverting the OCV-SOC function is not always straightforward. This paper proposes a novel analytical function that directly models the inverse OCV-SOC function, providing a more efficient and reliable method for SOC estimation. Moreover, the dependency of the proposed function on battery temperature is also being investigated, allowing for a wider application of the method under different OCV measuring conditions.

Fluorinated functional groups enhanced composite in-situ gel electrolytes for high voltage cathode of quasi solid-state lithium battery

Gel electrolyte is an ideal system for improving the cycling stability and safety of lithium metal battery. However, traditional gel system with acrylic ester system is still not suitable for high-voltage battery system limited by its intrinsic structure and unstable interface. The polymer structures with -CF3 modified acrylic ester are proposed to improve the stability of both structure and interface in high-voltage battery systems. The LiF-rich anode-electrolyte interface assisted by fluorine contained in-situ gel electrolyte ensures stable cycling of lithium anode. The quasi-solid state lithium battery assembled with the LiFePO4 can still achieve a capacity retention rate of 81.2 % after 900 cycles at a rate of 1 C. Furthermore, the uniform organic cathode-electrolyte interface constructed by crosslinked -CF3 modified polymer effectively inhibits the corrosion of HF on the cathode material. The interaction between the anion and solvent molecules prevents the continuous decomposition reaction of the electrolyte on the surface of the LiCoO2 cathode at high voltage, which guarantees LiCoO2 battery can still achieve a capacity retention rate of 82.1 % after 500 cycles at a voltage of 4.45V. Design of fluorine contained in-situ polymer gel electrolyte could promote the development of quasi solid-state battery in practical industrial application.

Improved Stability of Single‐Crystal LiCoO2 Cathodes at 4.8 V through Solvation Structure Regulation

AbstractIncreasing the charging cut‐off voltage can significantly improve the capacity of LiCoO2 cathode. However, when the cut‐off voltage exceeds 4.5 V (vs Li/Li+), LiCoO2 undergoes irreversible phase transitions, leading to particle cracking and structural failure. Additionally, the decomposition of the electrolyte compromises the stability of the cathode/electrolyte interface, resulting in diminished battery capacity. Herein, the elements Al, Mg, and Zr are doped into single‐crystal LiCoO2 to enhance the structural stability of LiCoO2. Moreover, a 3 Å zeolite film is used to regulate the solvation structure to enhance the oxidation resistance of the electrolyte. This design enables a more stable cathode/electrolyte interface during high‐voltage cycling. At a cut‐off voltage of 4.8 V, the Li||LiCoO2 battery exhibits an initial discharge capacity of 236.2 mAh g−1 at 0.1 C and maintains 86.6% capacity retention after 100 cycles at 1 C. The pouch full cell, which utilizes a graphite anode and LiCoO2 cathode, operating within a charge–discharge range of 2.8–4.65 V, achieves a specific energy of 276 Wh kg−1 with 81% capacity retention after 200 cycles. This work introduces a desolvated electrolyte into the LiCoO2 battery system, providing a professional approach to addressing the challenges of high‐voltage LiCoO2.

Low-Solvent-Coordination Solvation Structure for Lithium-Metal Batteries via Electric Dipole-Dipole Interaction.

Unveiling inherent interactions among solvents, Li+ ions, and anions are crucial in dictating solvation-desolvation kinetics at the electrode/electrolyte interface. Developing an electrolyte with a low ion-transport barrier and minimal solvent coordination in its interfacial solvation structure is essential for forming an anion-derived solid-electrolyte interface, a key component for high-performance Li-metal batteries. In this study, we harness electric dipole-dipole synergistic interactions to formulate an electrolyte with significantly reduced interfacial solvent coordination. Operando characterization and theoretical analysis reveal that 2-fluoropyridine (FPy) with high dipole preferentially adsorbs onto the Li metal surface. The adsorbed FPy molecule squeezes succinonitrile in the primary solvation sheath through steric hindrance, leading to the formation of an inorganic-rich interphase. Consequently, the introduction of FPy enhances the reversible capacity of the LiCoO2||Li cell, which maintains a capacity of 143 mAh g-1 after 500 cycles at a 1C rate. Moreover, the cycle life of LiCoO2 batteries with a limited supply of lithium extends from 120 cycles to over 200 cycles. These findings offer a strategy that can be applied broadly to design interfacial solvation structures for various metal-ion/metal-based batteries.

Modification of Li3PO4 layer effectively boosting lithium storage and thermal safety performance for LiCoO2 batteries

To meet the demand for high-performance LiCoO2 batteries, it is necessary to overcome challenges such as interface degradation and rapid capacity degradation caused by changes in bulk structure, especially under deep delithiation and high temperature conditions. The ion conductive coating layer of Li3PO4 has been directly modified on the surface of LiCoO2 particles using magnetron sputtering method, significantly improving the lithium storage performance of LiCoO2@Li3PO4 composites. Compared to pure LiCoO2, the modified LiCoO2 sample exhibits obviously better cycle life and high-temperature performance. Especially, under the conditions of 2 and 1 C, the LiCoO2@Li3PO4 electrode delivers excellent cycling performance at high voltage of 4.5 V, with capacity retention rates of 89.7% and 75.7% at room temperature and high temperature of 45 °C, being far greater than those of 12.3% and 29.1% for bare LiCoO2 electrodes. It is discovered that the Li3PO4 coating layer not only effectively enhances interface compatibility and suppresses the irreversible phase transition of LiCoO2, but also further improves the Li+ transport kinetics and significantly reduces battery polarization, ultimately enabling the modified LiCoO2 electrode to exhibit excellent lithium storage performance and thermal safety characteristics under high voltage conditions. Thus, such effective modified strategy can undoubtedly provide an important academic inspiration for LiCoO2 implication.

Al Impurity Upcycled High-Voltage Cathodes from Spent LiCoO2 Batteries.

Al impurity is among the most likely components to enter the spent lithium-ion battery (LIB) cathode powder due to the strong adhesion between the cathode material and the Al current collector. However, high-value metal elements tend to be lost during the deep removal of Al impurities to obtain high-purity metal salt products in the conventional hydrometallurgical process. In this work, the harmful Al impurity is designed as a beneficial ingredient to upcycle high-voltage LiCoO2 by incorporating robust Al-O covalent bonds into the bulk of the cathode assisted with Ti modification. Benefiting from the strong Al-O and Ti-O bonds in the bulk, the irreversible phase transitions of the upcycled R-LCO-AT have been significantly suppressed at high voltages, as revealed by in situ XRD. Moreover, a Li+-conductive Li2TiO3 protective layer is constructed on the surface of R-LCO-AT by pinning slow-diffusion Ti on the grain boundaries, resulting in improved Li+ diffusion kinetics and restrained interface side reactions. Consequently, the cycle stability and rate performance of R-LCO-AT were significantly enhanced at a high cutoff voltage of 4.6 V, with a discharge capacity of 189.5 mAhg-1 at 1 C and capacity retention of 92.9% over 100 cycles at 4.6 V. This study utilizes the detrimental impurity element to upcycle high-voltage LCO cathodes through an elaborate bulk/surface structural design, offering a strategy for the high-value utilization of spent LIBs.

Comprehensive recovery of valuable metals from spent LiCoO2 cathode material by a method of NH4HSO4 roasting- (NH₄)₂S leaching

With the retirement of rechargeable lithium-ion batteries (LIBs) entering peak period, the recycling of LiCoO2 has become a hot topic. The spent LiCoO2 batteries are rich in carcinogenic metal Co and high-value metal Li, so they are needed to be recovered in time before causing serious environmental pollution and resource waste. Thus, a clean and efficient process is proposed for the comprehensive recovery of Li, Co, and Mn from the spent LiCoO2 cathode material. It is an integrated pyro-hydrometallurgical process, mainly consisting of sulfation roasting with NH4HSO4 and selective sulfurizing leaching with (NH4)2S solution. Using low melting point ammonium salt as roasting auxiliary, 99.7 %, 99.1 %, and 99.8 % of Li, Co, and Mn in the spent LiCoO2 powder can be converted into sulfate when roasting under 400 ℃ for 75 min. Then 99.5 % of Li in the sulfation roasting product can be selectively leached with an aqueous (NH4)2S solution, which is also a precipitator for Co, Mn, and impurity Al. In addition, 96.4 % of Co and 96.0 % of Mn in the sulfurized precipitate can be separated with impurity elements Al and C via oxidation roasting–water leaching process. Compared to traditional recycling, this method can achieve a higher Li leaching rate at a low roasting temperature, and the recovery of Co and Mn can be realized without adding any acid/base reagents or impurity cations. More importantly, the circulation of NH3/NH4+ and S element in the recycling system has been taken into account, making it an environmental-friendly and economical process. In this study, the sulfation reduction roasting and selective sulfurizing leaching mechanisms were both revealed in details, and the behavior of the valuable elements was also elucidated.

A comparative study of overcharge thermal runaway force-electrical-thermal characteristics and safety assessment of lithium batteries with different cathode materials

This work compares the differences in thermal runaway (TR) behavior and force-electrical-thermal characteristics of three predominant types of lithium-ion batteries (LiNixCoyMn1-x-yO2 (NCM), LiFePO4 (LFP), LiCoO2 (LCO)) with the highest market share under various overcharge rates. The voltage and temperature of cells during the experiment are monitored. Early warning based on expansion force is currently a hot research topic. This study analyzes the evolution of expansion force from overcharging to TR, and lays the foundation for expansion force early warning. The results show that LFP batteries exhibit the lowest overcharging tolerance. However, LFP batteries exhibit the lowest TR hazard and only exhibit smoke release, no explosion or fire. NCM and LCO batteries exhibit more serious TR hazards. A novel safety assessment method based on seven experimental characteristics is proposed to evaluate the TR risks and hazards of three types of batteries qualitatively and quantitatively. Overall, this study compares the TR behaviors of three common lithium-ion batteries, introduces the expansion force parameter for comparative analysis, and reveals the mechanisms of multidimensional parameter evolution offering valuable insights for battery selection. The findings guide the safe use and risk management of lithium-ion batteries in electric vehicles.

Advanced State of Charge Estimation Using Deep Neural Network, Gated Recurrent Unit, and Long Short-Term Memory Models for Lithium-Ion Batteries under Aging and Temperature Conditions

Accurate estimation of the state of charge (SoC) of lithium-ion batteries is crucial for battery management systems, particularly in electric vehicle (EV) applications where real-time monitoring ensures safe and robust operation. This study introduces three advanced algorithms to estimate the SoC: deep neural network (DNN), gated recurrent unit (GRU), and long short-term memory (LSTM). The DNN, GRU, and LSTM models are trained and validated using laboratory data from a lithium-ion 18650 battery and simulation data from Matlab/Simulink for a LiCoO2 battery cell. These models are designed to account for varying temperatures during charge/discharge cycles and the effects of battery aging due to cycling. This paper is the first to estimate the SoC by a deep neural network using a variable current profile that provides the SoC curve during both the charge and discharge phases. The DNN model is implemented in Matlab/Simulink, featuring customizable activation functions, multiple hidden layers, and a variable number of neurons per layer, thus providing flexibility and robustness in the SoC estimation. This approach uniquely integrates temperature and aging effects into the input features, setting it apart from existing methodologies that typically focus only on voltage, current, and temperature. The performance of the DNN model is benchmarked against the GRU and LSTM models, demonstrating superior accuracy with a maximum error of less than 2.5%. This study highlights the effectiveness of the DNN algorithm in providing a reliable SoC estimation under diverse operating conditions, showcasing its potential for enhancing battery management in EV applications.

–C≡N functionalizing polycarbonate-based solid-state polymer electrolyte compatible to high-voltage cathodes

Solid-state polymer electrolytes (SPEs) capable of withstanding high voltage are considered to be key for next-generation energy storage devices with inherent safety as well as high energy density. This study involves the rational design of solid-state –C≡N functionalized P(VEC1-CEA0.3)/LiTFSI@CE SPEs and its synthesis by in-situ free radical polymerization of vinyl ethylene carbonate (VEC) and 2-cyanoethyl acrylate (CEA). In situ polymerization yields electrode/electrolyte interfaces with low interfacial resistance, forming a stable SEI layer enriched with LiF, Li3N, and RCOOLi, ensuring stable Li plating/stripping for over 1400 h. The –C≡N moiety renders the αH on the adjacent αC positively charged, thereby endowing it with the capability to anchor TFSI−. Simultaneously, the incorporation of –C≡N moiety diminishes the electron-donating ability of the C = O, C–O–C, and –C≡N functional groups, facilitating not only the ion conductivity enhancement but also a more rapid Li+ migration proved by DFT theoretical calculations and Raman spectroscopy. At room temperature, tLi+ of 0.60 for P(VEC1-CEA0.3)/LiTFSI@CE SPEs is achieved when the ionic conductivity σLi+ is 2.63 × 10−4 S cm−1 and the electrochemical window is expanded to 5.0 V. Both coin cells with high-areal-loading cathodes and the 6.5-mAh pouch cell, exhibit stable charge/discharge cycling. At 25 °C, the 4.45-V Li|P(VEC1-CEA0.3)/LiTFSI@CE|LiCoO2 battery performs stable cycling over 200 cycles at 0.2 C, with a capacity retention of 82.1%.

Constructing stable electrode–electrolyte interfaces by sulfone-based additive to improve the high-voltage performance of LiCoO2

LiCoO2 battery can provide high reversible capacity at a high voltage of 4.6 V, however, maintaining its stability at high voltages remains a major challenge. To address this issue, ethyl methyl sulfone (EMS) is employed as an electrolyte additive to construct stable interfaces between the electrode and electrolyte under high-voltage condition. The characterization results indicate that the addition of EMS can inhibit the decomposition of the standard electrolyte (STD) and the dissolution of Co2+ from cathode, as well as the formation of lithium dendrites on the Li anode, thereby enhancing the stability of both cathode/electrolyte and anode/electrolyte interfaces. Consequently, the cycling performance of LiCoO2 battery using STD+3 %EMS is augmented by 16.9 % at 1 C under a cut-off voltage of 4.6 V over 100 cycles, delivering a specific capacity of 137 mA h g−1. This research provides novel insights into the design of electrolyte additives for high-voltage LiCoO2 batteries and contributes to the further development of high-voltage lithium-ion batteries.

Open-Circuit Voltage Variation in LiCoO2 Battery Cycled in Different States of Charge Regions

Open-Circuit Voltage Variation in LiCoO2 Battery Cycled in Different States of Charge Regions

Deep understanding of LiCoO2 electrode degradation for optimized recycling strategies

Empowered by a synergistic combination approach of Scanning Transmission X-ray Microscopy (STXM) imaging and X-ray Absorption Near Edge Structure (XANES) spectroscopy, a quantitative analysis on the composition and spatial distribution of the cathode in a failed 18650 LiCoO2 (LCO) battery was conducted. Distinct compositional differences between the central and peripheral cathode regions in the failed LCO battery were discerned by utilizing bulk XANES in Total Electron Yield (TEY) and Fluorescence Yield (FY) modes. The central region shows more severe degradation in terms of LCO reduction and excess cathode-electrolyte interface (CEI) buildup. Meanwhile, the STXM technique precisely imaged a specific region of interest in the center of the cathode, covering C, O, and F K-edges, and Co L2,3-edge, to deeply investigate the degradation. Quantitative chemical mapping with spatially resolved XANES spectroscopy, facilitate an in-depth understating of the interfacial reactions on battery electrodes and battery failure fundamentals.

Ethyl fluoroacetate with weak Li+ interaction and high oxidation resistant induced low-temperature and high-voltage graphite//LiCoO2 batteries

Lithium-ion batteries (LIBs) operating at low temperature has always been a significant challenge. In this work, Ethyl fluoroacetate (EFA) was utilized as a single solvent to design a low-temperature electrolyte (LTE). The weak Li+-solvent interaction facilitates fast de-solvation process and improved low-temperature performance, while the high oxidation resistance and fluorine-rich electrolyte/electrolyte interface induced by the fluorinated groups enables wide operating voltage and stable cycling of the LIBs. The EFA-based electrolyte endows the high-voltage (4.45 V) Graphite//LiCoO2 pouch cell with prominent low-temperature adaptability (89.7 % capacity retention retains at −40 °C, and capable of charging at −20 °C) and outstanding cycling performance (87.7 % capacity retention after 400 cycles). This work sheds light on the design of high-voltage and low-temperature electrolytes for lithium-ion batteries.

Preferentially selective recovery of lithium from spent LiCoO2 by sulfation roasting of MnSO4

The selective recovery of valuable metals from spent lithium-ion batteries (LIBs) has engrossed significant scientific attention due to prompting environmental potential and addressing resource scarcity. Hereby, we propose an innovative and economically more environment friendly manganese sulfate roasting water leaching process to selectively recuperate lithium preferentially from spent LiCoO2 batteries. Notably, it is found that manganese sulfate roasting agents can be recirculated thoroughly without SOx emission during the sulfation roasting process. To better understand the conversion mechanism of LiCoO2, the effects of numerous parameters including, roasting time, roasting temperature, and a molar ratio of MnSO4/LiCoO2 during the recovering process were investigated. An exceptional recovery rate of 98.62% with a remarkable lithium selectivity of 99.35% by manganese sulfate leaching was achieved. This work proposes an environmentally friendly and promising strategy to extract lithium selectively from spent lithium cathodes without introducing SOx emission.

Enhanced capacity of LiCoO2 and graphite battery by using methylene methanedisulfonate as electrolyte additive

Enhanced capacity of LiCoO2 and graphite battery by using methylene methanedisulfonate as electrolyte additive

A low-temperature solid-to-solid reaction for lithium-ion battery recycling and the utilization of defect-enriched Co3O4 from spent LiCoO2 batteries for efficient oxygen evolution reaction

An efficient, eco-friendly and cost-effective strategy for the recovery of precious metals from spent lithium-ion batteries (LIBs) is of great significance for the sustainable natural resource utilization and environmental protection. Herein, a low-temperature solid-to-solid reaction combined water leaching technology is proposed for the preferential extraction of Li from spent LiCoO2 batteries. In the solid-to-solid reaction, crystal water released from the oxalic acid dihydrate acts as a lubricant and initiates the reduction reaction to convert the spent LiCoO2 into water-soluble Li salts (LiHC2O4 or Li2C2O4) and water-insoluble CoC2O4. After water leaching, the collected Li-rich solution and the Co-rich residue are separately transformed into Li2CO3 and Co3O4. Additionally, a defect-enriched Co3O4 is prepared by water quenching process, exhibiting excellent performances towards oxygen evolution reaction. This work not only achieves a facile, low-cost and energy-saving strategy for recycling spent LIBs, but also proposes a vacancy-defected engineering route for electrocatalyst design in energy-related applications.