Improvement of superior cycle performance of LiNi0.8Co0.15Al0.05O2 cathode for lithium-ion batteries by multiple compound modifications

Surface Stabilization of O3-type Layered Oxide Cathode to Protect the Anode of Sodium Ion Batteries for Superior Lifespan.

Fast development of portable electronic devices (such as a smart phone, iPad, and Galaxy Note) and electrified vehicles (such as EVs and HEVs) require better and smaller lithium ion batteries as their energy storages. What is needed for the cathode of the lithium ion battery is a material capable of a higher volumetric energy density as well as gravimetric energy density. However, not only the development of cathode material but also the commercialization of high energy density anode material has been limited due to cathode material’s much lower energy density compared to anode material. In this regard, Li-rich material (Li2MnO3-LiMO2, M=Ni, Mn and Co) that has 150 % higher energy density than commercialized LiCoO2 is the unique next generation cathode material to solve the problem of cathode material’s low energy density. In the past decade, many researches have focused on the surface stabilization method of this material to improve its intrinsic problems of poor cycle/ rate capability and such surface treatment methods have been demonstrated in a few examples, including AlF3 coating and spinel heterostructures, yielding noticeable improvements in rate and cycle ability. Although such surface treatments showed improved rate and cycle performances, achieving the high volumetric energy density and long-term cycle life which are more critical factors for the commercialization of Li-rich material still remained unsatisfied. In general, Li-rich material’s reversible capacity is related with its particle size since the Li2MnO3 phase in large Li-rich material, which is a major component to realize high energy density, is not fully activated in low voltage range below 4.6 V. For this reason, many previous papers reported their results with only small primary particle size below 100nm. The high surface area induced by the small particle size increases side reactions with electrolyte resulting poor long-term cycle life as well as lowers the volumetric energy density. Note that Li-rich material’s deteriorations are generated from its surface and continue to affect its cycling capability and the deteriorations can be divided into two mechanisms: one is side reactions with electrolyte, and another is the phase collapse. The side reactions with electrolyte at its high working voltage yield active material attack speiceses such as HF and electrolyte exhaustion causing Li-rich material’s fast discharge capacity decay during cycles. Furthurmore, it is hardly show long-term cycle life with over 200 cycles since the phase transition from layered structure to spinel-like and NiO rock salt is generated on the surface of active material, and followed by expention of this transition into the bulk. For instance, AlF3 coated Li-rich LNCMO has abrupt capacity fade after 100 cycles, although it showed good rate and cycle capability within 100 cycles. Hence, new active material design, rather than simple surface modification methods such as coating or doping, is required to solve above previous limits.The new material design needs to start with a simple question: how to minimize the damages of surface deteriorations such as side reasction with electrolyte and phase trasnsition on bulk material and maximize volumetric energy density. The most effective solution for the question is increasing the primary particle size with the stable activation method, since the volumetric energy density of cathode material is maximized from synthesis of micron secondary particles consisted of primary particles by using co-precipitation method in industry. Here we demonstrate a novel approach for lithium storage, which is a material design of a secondary structure which consists of large flake shaped primary particle (hundred nanometers x mictrometers) with a novel activation method using simple chemical treatment to achieve superior long-term cycle life with high volumetric energy density. In this design, the large primary particle effectively reduced its surface area producing markedly decreased surface instability reaction as well as high tap density. Interstingly, the chemical approach activated only surface Li2MnO3 phase of large primary particle and the very surface activation effectively overcame the activation problem, which is limit of large primary particle have. This novel concept is very meaningful in that it is the first and unique method to achieve cathode material’s high volumetric energy density with long-term cycle life. As a result, this novel designed material affords remarkable battery performance with extremely high cycle retention during 400 cycles and high volumetric energy density ever reported before.

The Li- and Mn-rich layered oxide cathode material class is a promising cathode material type for high energy density lithium-ion batteries. However, this cathode material type suffers from layer to spinel structural transition during electrochemical cycling, resulting in energy density losses during repeated cycling. Thus, improving structural stability is an essential key for developing this cathode material family. Elemental doping is a useful strategy to improve the structural properties of cathode materials. This work examines the influences of Mg doping on the structural characteristics and degradation mechanisms of a Li1.2Mn0.4Co0.4O2 cathode material. The results reveal that the prepared cathode materials are a composite, exhibiting phase separation of the Li2MnO3 and LiCoO2 components. Li2MnO3 and LiCoO2 domain sizes decreased as Mg content increased, altering the electrochemical mechanisms of the cathode materials. Moreover, Mg doping can retard phase transition, resulting in reduced structural degradation. Li1.2Mn0.36Mg0.04Co0.4O2 with optimal Mg doping demonstrated improved electrochemical performance. The current work provides deeper understanding about the roles of Mg doping on the structural characteristics and degradation mechanisms of Li-and Mn-rich layered oxide cathode materials, which is an insightful guideline for the future development of high energy density cathode materials for lithium-ion batteries.

Facile migration of potassium ions in a ternary P3-type K0.5[Mn0.8Fe0.1Ni0.1]O2 cathode in rechargeable potassium batteries

Recently, lithium ion batteries (LIBs) have received great attention as a suitable power source for electric vehicles (EVs) because of its highest energy and power densities among currently available energy storage systems. For successful implementation the achievable energy density of current LIBs should be further improved to meet the industrial requirements. In this respect, the development of advanced materials is crucial for improving the energy density of LIBs. During the last decade, layered lithium transition metal oxides (e.g., LiMO2, M = transition metal) have been used as the most popular cathode materials in commercial LIBs [1]. From a structural point of view, Li+ can be reversibly inserted and extracted in the given structure based on the redox reactions of transition metals. Therefore, the choice of transition metals is crucial for determining the electrochemical properties of these cathode materials. By increasing the Ni concentration, the reversible capacity of the cathode materials can be effectively increased due to the double redox reaction of Ni2+/Ni4+. In practice, high-Ni layered cathode materials (Ni > 80%) can offer a high reversible capacity over 200 mAh g-1 [2]. As a result of increasing the Ni concentration, however, the cathode materials suffer from poor cycle performance and thermal stability mainly induced by side reactions with electrolyte and residual Li at the surface. To overcome these limitations, effective surface coatings are required to make the surface more stable and suppress undesirable side reactions [3]. Herein, we propose a surface coating with LiNbO3 onto NCM811 cathode material to minimize undesirable side reactions as well as improve the thermal stability [4]. Thanks to the high ionic conductivity and thermal resistance of LiNbO3, LiNbO3 coated NCM811 exhibit much improved cycle performance and rate capabilities even at high operating temperature of 60 oC. Moreover, we also investigate the effect of LiNbO3 crystallinity on the electrochemical properties of LiNbO3 coated NCM811. It would provide a practical guideline for the development of a highly reliable high-capacity cathode material for EV applications.

Lithium-ion batteries (LIBs) using organic liquid electrolytes have been applied in portable devices such as laptops and cellular phones owing to its wide electrochemical stability, high voltages, and excellent energy density. LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode have attracted significant interest as the cathode materials for LIBs owing to their high capacity, excellent rate capability and low cost. NCM523 cathode materials have a disadvantage of structural instability, which caused by the reduction of Ni ions releases oxygen from the crystal structure at the high temeprature or high charged state, which can lead thermal runaway by reacting with the flammable electrolyte. The use of organic liquid electrolytes in LIBs raises safety issues due to its flammable character and the impact on the explosion is greater in particular for relatively large systems such as electrical vehicles and grid storage. To overcome the safety issues, solid state batteries (SSBs) using a non-combustible solid state Li-ion conductor are regarded as the realistic alternative to prohibit the leakage of liquid electrolytes and the resultant fire hazards. However, due to the large resistance in the electrode-electrolyte interface, the capacity retention and cycle effieciency of the SSBs become worse. Previous studies on SSBs have been mainly focused on developing solid state electrolytes with high ion conductivity. Despite growing interest in stability, the systematic studies of safety of SSBs depending on the type of electrolyte has never been evaluated so far. It is necessary for understanding structural deformations on the cathode material in the effects of the reactions beween the electrode and various types of electrolytes, which is essential for ensuring the safety of the batteries. In this study, we investigate the structural degradation and thermal stability on NCM523 cathode materials by taking an advantage of in situ transmission electron microscopy (TEM) in various electrolyte conditions, including conventional liquid electrolyte, poly(ethylene oxide) (PEO) complexes with LiClO4 (PEO-based solid electrolyte), and PEO/LiClO4/Li1.3Al0.3Ti1.7(PO4)3 (LATP) composite electrolyte (PEO-inorganic composite electrolyte). Since the LATP oxide electrolyte has brittleness and the PEO has flexibility, it adopts a composite electrolyte having inorganic and organic phases with good interface contact with the cell electrode. A cell composed of each electrolyte was prepared and charged with cut-off voltages of 3.9 V and 4.3 V at a rate of 0.05 C after the second formation process for stabilzing the cell. The capacity at the same cut-off voltage decreases in the order of conventional liquid electrolyte, PEO-based solid electrolyte, and PEO-inorganic composite electrolytes. To understand the thermal stability and the degradation mechanism, modifications in selected-area electron diffraction (SAED) and electron energy-loss (EEL) spectra of oxygen K-edge and transition metal (Ni, Co, Mn) L-edges of each of charged NCM523 cathode materials are monitored in real time at the range from room temperature to 300°C. Our work demonstrated that contact resistance at the interface between the electrode and electrolyte is important factor. This work provides important information on the relationship with structural deformation and thermal stability of the cathode materials, which is an essential part of the rational design to develope for high engergy densities and safe SSBs. All the details will be available at the meeting. Acknowledgement This work was supported by the Korea Institute of Science and Technology (KIST) Institutional Program (Project 2E28142). This work was also supported by the National Research Foundation of Korea (NRF) grant (No. 2018R1A2B2005205).

Na+-doped layered LiNi1/3Co1/3Mn1/3O2 cathode derived from low nickel matte with high structural stability and fast diffusion kinetics

The development of advanced cathode materials is crucial for improving the energy density, stability, and rate performance of Na-ion batteries (NIBs). Two promising strategies—lithium doping stabilization and high-entropy engineering—have been explored to address key challenges such as phase instability, sluggish sodium diffusion, and capacity degradation. In this study, we compare and highlight the design principles and performance enhancements achieved through these approaches.In the first strategy, lithium doping was employed to stabilize the P2-structured layered oxide cathode, Na0.66(Li0.18Fe0.12Mn0.7)O2 [1]. A major limitation in P2-type cathodes is the irreversible and detrimental P2–O2 phase transition at high voltage, which leads to structural degradation and poor cyclability. By partially substituting manganese with lithium in the transition metal layer, the P2-O2 phase transition was effectively eliminated. This structural stabilization enabled high capacity retention of ~87% after 80 cycles with an initial capacity of 190 mAh g⁻¹ within a wide voltage range of 1.5–4.5 V. Operando synchrotron X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy confirmed the reversibility of lithium migration and the structural integrity of the cathode material over prolonged cycling.The second strategy involves high-entropy engineering in the Na0.6(Ti0.2Mn0.2Co0.2Ni0.2Ru0.2)O2 cathode, where equiatomic mixing of multiple transition metals (TMs) was leveraged to enhance entropy stabilization and Na-ion diffusion kinetics[2]. The uniform distribution of TMs disrupted Na/vacancy ordering, reducing phase transitions and promoting a solid solution-type sodium extraction mechanism. This multi-principal component (MPC) cathode exhibited remarkable rate capability, delivering a high discharge capacity of 164 mAh g⁻¹ at 0.1 C and retaining 68 mAh g⁻¹ at an ultra-high rate of 86 C. Computational modeling using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations demonstrated the existence of a percolating network of low-barrier diffusion pathways, facilitating rapid sodium transport.The two works underscore the importance of tailored cation substitution strategies in optimizing layered oxide cathodes for next-generation NIBs. By fine-tuning compositional design and leveraging advanced computational and in situ characterization techniques, it is possible to engineer materials that overcome current performance limitations. Most recent research focusing on integrating these approaches to develop cathodes that simultaneously offer high capacity, robust cyclability, and superior rate performance will also be discussed.[1] L.F. Yang, X. Li, J. Liu, S. Xiong, X.T. Ma, P. Liu, J.M. Bai, W.Q. Xu, Y.Z. Tang, Y.Y. Hu, M.L. Liu, H. Chen, Lithium-Doping Stabilized High-Performance P2-Na0.66Li0.18Fe0.12Mn0.7O2 Cathode for Sodium Ion Batteries, Journal of the American Chemical Society, 141 (2019) 6680-6689.[2] L.F. Yang, C. Chen, S. Xiong, C. Zheng, P. Liu, Y.F. Ma, W.Q. Xu, Y.Z. Tang, S.P. Ong, H.L. Chen, Multiprincipal Component P2-Na-0.6(Ti0.2Mn0.2Co0.2Ni0.2Ru0.2)O-2 as a High-Rate Cathode for Sodium-Ion Batteries, JACS Au, 1 (2021) 98-107.

Li-rich Mn-based cathodes have been regarded as promising cathodes for lithium-ion batteries because of their low cost of raw materials (compared with Ni-rich layer structure and LiCoO2 cathodes) and high energy density. However, for practical application, it needs to solve the great drawbacks of Li-rich Mn-based cathodes like capacity degradation and operating voltage decline. Herein, an effective method of surface modification by benzene diazonium salts to build a stable interface between the cathode materials and the electrolyte is proposed. The cathodes after modification exhibit excellent cycling performance (the retention of specific capacity is 84.2% after 350 cycles at the current density of 1 C), which is mainly attributed to the better stability of the structure and interface. This work provides a novel way to design the coating layer with benzene diazonium salts for enhancing the structural stability under high voltage condition during cycling.

Electrochemical behaviours of SiO2-coated LiNi0.8Co0.1Mn0.1O2 cathode materials by a novel modification method

High-performance Li1.2Mn0.6Ni0.2O2 cathode materials prepared through a facile one-pot co-precipitation process for lithium ion batteries

Introduction The lithium batteries are being developed as power sources for plug-in hybrid electric and electric vehicles, and for these applications, high energy cathodes are necessary to reduce battery size because the mounting space is significantly limited.[1] Hence, layered lithium nickel-cobalt-manganese oxide, Li[NixCoyMnz]O2 (x + y + z = 1), which delivers a high discharge capacity of over 170 mAh g− 1, has been intensively studied for high energy density lithium-ion batteries.[2] However, these cathodes exhibit some serious problems, such as capacity fade and poor thermal stability, which hinder their use in vehicle applications. In particular, oxygen evolution from the delithiated cathode can cause serious safety concerns. These limitations necessitate the development of new materials to resolve the above-mentioned difficulties.Recently, we introduced unique materials, which have a core−shell (core with gradient shell) or full concentration gradient (FCG) structure in a particle level.[3] The structure is basically composed of a Ni-rich core that delivers high capacity and a Mn-rich shell that provides outstanding thermal stability. Our latest report included a new type of FCG material composed of long rod-shaped primary particles approximately 2.5 μm in length,[4] which demonstrated good electrochemical performance and excellent thermal properties due to lower grain boundary resistance ascribed to lower specific surface area contacting with the electrolyte during cycling. However, the Mn concentration could not be varied because of the difficulty of the rod-shaped particle synthesis.Here, we report the design of FCG Li[NixCo0.16Mn0.84−x]O2 (x = 0.64, 0.59, and 0.51) cathode materials with fixed Mn contents of 20, 25, and 33% in the transition-metal layer. We also report the effects of Mn concentration in terms of structural, electrochemical, and thermal characteristics of the FCG materials. Experimental Spherical FCG [NixCo0.16Mn0.84-x](OH)2 (x = 0.51, 0.59, and 0.64) precursors were synthesized by a coprecipitation method. A Ni-poor aqueous solution (molar ratio of Ni:Co:Mn = 0.47:0.20:0.33, 0.55:0.20:0.25, 0.60:0.20:0.20,), consisting of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O as starting materials, was slowly pumped from tank 2 into a Ni-rich (molar ratio of Ni:Mn = 0.67:0.33, 0.75:0.25, 0.80:0.20) stock solution in tank 1. The homogeneously mixed solution was then fed into a continuously stirred tank reactor (CSTR, 4 L) in a replenished N2 atmosphere. Simultaneously, a 3.0 mol L- 1 NaOH solution (aq.) and the desired amount of a NH4OH chelating agent solution (aq.) were pumped separately into the reactor. The concentration of the solution, pH, temperature, and stirring speed of the mixture in the reactor were carefully controlled. During the early stage of the coprecipitation process, Ni-rich hydroxide (center composition) first precipitated. Nickel-cobalt-manganese hydroxide of different compositions then gradually layered onto the initially formed [NixCo0.16Mn0.84 − x](OH)2 (x = 0.51, 0.59, and 0.64) particles, resulting in a linear composition change of Ni and Co toward the outer surface of the particles. Precursor powders were obtained through filtering, washing, and drying at 100 °C overnight. The obtained FCG [NixCo0.16Mn0.84 − x](OH)2 (x = 0.51, 0.59, and 0.64) was mixed with LiOH·H2O, and the mixture was calcined at various temperatures for 10 h in air: 780 °C for Li[Ni0.64Co0.16Mn0.20]O2, 845 °C for Li[Ni0.59Co0.16Mn0.25]O2, and 920 °C for Li[Ni0.51Co0.16Mn0.33]O2.The chemical compositions of the resulting powders were determined by atomic absorption spectroscopy (AAS, Vario 6, Analyticjena). Line scans for the full-gradient materials were obtained with an electron probe X-ray microanalyzer (EPMA, JXA-8100, JEOL). Results and discussion To judge the relative merits of the FCG Li[NixCo0.16Mn0.84 − x]O2 cathodes, coin-type half-cells were tested at 55 °C and C-rates of 0.1 and 0.5 (20.6 and 102.8 mA g− 1) with a cutoff voltage of 4.3 V, and the results are presented in Figure 1. The trend observed at 25 °C was similarly found for cycling at the elevated temperature. The Li[Ni0.64Co0.16Mn0.20]O2 cell againdelivered the highest initial capacity of 201.7 mAh g− 1 and exhibited the worst capacity retention, whereas the Li[Ni0.51Co0.16Mn0.33]O2 cathode with the lowest discharge capacity of 184.8 mAh g− 1 best retained its initial capacity after 100 cycles. It is generally known that a high Mn content in Li[NixCoyMn1 − x − y]O2 is detrimental to the rate capability of the Li-ion battery.Figure 1. Initial charge-discharge curves of the FCG Li[NixCo0.16Mn0.84-x]O2 (x = 0.51, 0.59, and 0.64) (a) between 2.7 and 4.3 V at 55 °C (current density of 0.1 C-rate corresponds to 20.6 mA g- 1). Corresponding cycling performance of half-cells (b) between 2.7 and 4.3 V at 55 °C by applying a constant current of 0.5-C rate (102.8 mA g- 1).

A stable dual LiAlO2/Li2SiO3 coating LiNi0.8Co0.1Mn0.1O2 cathode towards ultra-long-life and wide-temperature lithium-ion battery

Simultaneous Li2MoO4 coating and Mo6+ doping improves the structural stability and electrochemical properties of nickel-rich LiNi0.83Co0.11Mn0.06O2

To simultaneously address the inherent limitations of the capacity and cycling instability of Na[Ni0.5Mn0.5]O2 cathodes, it is necessary to concurrently stabilize particle surfaces and crystal structure. Encouraged by previously conducted research activities in this field, we have adopted an effective strategy for simultaneous MgO coating and Mg doping to produce substantially improved high voltage stability compared to the previously reported results in the literature on Na[Ni0.5Mn0.5]O2 cathodes. The MgO coating layer effectively suppressed the unfavorable side reactions during cycling while the partial Mg doping into the bulk Ni sites improved the structural stability by moderating the extent of the irreversible multiphase transformation. As a result, the combination of a MgO coating with Mg doping provides enhanced electrochemical performance and structural stability of Na[Ni0.5Mn0.5]O2 within the voltage range of 2.0–4.2 V. The practical acceptability of the simultaneous MgO coating and Mg doping of the Na[Ni0.5Mn0.5]O2 cathode was obviously verified using scaled-up pouch-type full cells with hard carbon anodes. Compared with previously reported similar cathode materials, the proposed MgO-NM55 cathode showed great competitiveness for high-voltage stability in SIBs. Moreover, the use of earth's abundant and inexpensive Mg and Na elements, and a simple practical strategy are highly desirable for developing high-energy and low-cost SIBs. Although the practical use of the MgO-NM55 cathode in SIBs will require further work, the methodology used in this study will be helpful in developing an efficient design of high performance cathode materials for SIBs. References J.-Y. Hwang, S.-T. Myung and Y.-K. Sun, Soc. Rev., 2017, 46, 3529–3614. J.-Y. Hwang, C. S. Yoon, I. Belharouak and Y.-K. Sun, J. Mater. Chem. A, 2016, 4, 17952.P.-F. Wang, H.-R. Yao, X.-Y. Liu, J.-N. Zhang, L. Gu, X.-Q. Yu, Y.-X. Yin and Y.-G. Guo, Adv. Mater., 2017, 29, 1700210.S. Komaba, N. Yabuuchi, T. Nakayama, A. Ogata, T. Ishikawa and I. Nakai, Inorg. Chem., 2012, 51, 6211.