Sphere-shaped hierarchical cathode with enhanced growth of nanocrystal planes for high-rate and cycling-stable li-ion batteries

Correlating concerted cations with oxygen redox in rechargeable batteries

Rechargeable batteries currently power much of our world, but with the increased demand for electric vehicles (EVs) capable of traveling hundreds of miles on a single charge, new paradigms are necessary for overcoming the limits of energy density, particularly in rechargeable batteries. The emergence of reversible anionic redox reactions presents a promising direction toward achieving this goal; however this process has both positive and negative effects on battery performance. While it often leads to higher capacity, anionic redox also causes several unfavorable effects such as voltage fade, voltage hysteresis, sluggish kinetics, and oxygen loss. However, the introduction of cations with topological chemistry tendencies has created an efficient pathway for achieving long-term oxygen redox with improved kinetics. The cations serve as pillars in the crystal structure and meanwhile can interact with oxygen in ways that affect the oxygen redox process through their impact on the electronic structure. This review delves into a detailed examination of the fundamental physical and chemical characteristics of oxygen redox and elucidates the crucial role that cations play in this process at the atomic and electronic scales. Furthermore, we present a systematic summary of polycationic systems, with an emphasis on their electrochemical performance, in order to provide perspectives on the development of next-generation cathode materials.

Directional and Orderly Arranged Ni0.9Mn0.1(OH)2 Enables the Synthesis of Single-Crystal Ni-Rich Co-Free LiNi0.9Mn0.1O2 with Enhanced Internal Structural Stability

In this paper, the effect of the structure characteristics of the precursor on the electrochemical properties of a single-crystal cobalt-free high-nickel LiNi0.9Mn0.1O2 cathode is systematically studied. Precursors with different morphologies are synthesized by adjusting the coprecipitation reaction conditions. The results of SEM and XRD show that with the increase in the orderly stacking arrangement of internal primary nanosheets of Ni0.9Mn0.1(OH)2, the exposed active {010} planes at the surface increase. The prepared cathode materials finally inherit the structural features of the precursor, and the single-crystal Co-free Ni-rich LiNi0.9Mn0.1O2 cathode with highly exposed active {010} planes shows a well-ordered crystal structure and low Li+/Ni2+ cation mixing. The characterization results reveal that the high percentage of {010} planes will improve the Li+ transportation kinetics, decrease electrochemical impedance, and significantly alleviate the accumulation of rock-salt phases. Therefore, the material with this structure shows good electrochemical performance.

Co-doping studies to enhance the life and electro-chemo-mechanical properties of the LiMn2O4 cathode using multi-scale modeling and neuro-computing techniques

A number of engineered cathode materials with longer life cycles and better electro-chemo-mechanical properties can be obtained by partially replacing some of the elements with other relevant ones without compromising much with the structure. To design such superior cathode materials, in this work, we replace a small number (5% or 10%) of Mn³⁺, with one of the following elements: aluminium, nickel, magnesium, gallium, chromium, and yttrium. Additionally, S^2- and F^- were used to replace some (∼1%) of the O^2- ions (anion) in the crystal. In this work, we have used a combination of Quantum Mechanics (QM), Classical Molecular Dynamics (CMD), Neural Network (NN) and Computational Fluid Dynamics (CFD) modeling. QM has been used to validate the Classical Molecular Dynamics (CMD) simulation results for engineered structures where experimental data are not available. CMD simulations are used to obtain material properties such as lattice expansion, Young's modulus, and diffusion coefficients for un-doped, doped and co-doped structures. NN modeling was used to reduce the computational time to evaluate millions of possible crystal configurations. Finally, the impact of co-doping strategies at the macroscale has been studied using CFD simulations. As a first step, we employed neuro-computing techniques to identify the optimum ionic configuration for all crystal structures, saving ∼88% of the computational time. Next, molecular scale simulations were performed to study the material properties. Molecular dynamics (MD) modeling findings suggest that the relative volume expansion between the fully charged and discharged states of the battery can be reduced by ∼1.9% to ∼2.25%, indicating an improvement in the life of the cathode material by several hundreds of cycles. Findings from both QM and CMD simulations suggest that for these novel engineered materials, electro-chemo-mechanical properties, such as ionic mobility, chemical diffusion coefficient and elasticity, improved. Furthermore, CMD simulations showed that the inter-ionic space between doped metal ions and oxygen is smaller compared to the spacing between Mn³⁺-O^2- in the original LMO spinel, indicating an improvement in the material's structural strength along with the total number of the discharge cycle. Finally, macro scale computational modelling results show that chances of thermal runaway can be reduced significantly for some of the co-doped structures since the intercalation induced maximum stress is lower.

Preparation of single-crystal ternary cathode materials via recycling spent cathodes for high performance lithium-ion batteries

With the rapid consumption of lithium-ion batteries (LIBs), the recycling of spent LIBs is becoming imperative. However, the development of effective and environmentally friendly methods towards the recycling of spent LIBs, especially waste electrode materials, still remains a great challenge. Herein, on the basis of a Li-based molten salt, we have developed a facile and effective strategy to recycle spent polycrystalline ternary cathode materials into single-crystal cathodes. The regenerated plate-like single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ material with exposed {010} planes achieves an excellent rate performance and outstanding cycling stability. In particular, a high capacity of 155.1 mA h g^-1 and a superior capacity retention of 94.3% can be achieved by the recycled cathode material even after 240 cycles at 1 C. Meanwhile the single-crystal structure can be well reserved without any cracks or pulverization being observed. Moreover, this recycling method can be expanded to recycle other waste Ni-Co-Mn ternary cathode materials (NCM) or their mixtures for producing high-performance single-crystal cathode materials, demonstrating its versatility and flexibility in practical applications. Therefore, the strategy of converting spent NCM cathodes into single-crystal ones with satisfactory electrochemical performance may open up a cost-effective pathway for resolving the issues caused by the large amounts of spent LIBs, thus facilitating the sustainable development of LIBs.

Engineering Crystal Orientation of Cathode for Advanced Lithium-ion Batteries: A Minireview

Engineering crystal orientation has attracted widespread attention since it is related to the cyclability and rate performance of cathode materials for lithium-ion batteries (LIBs). Regulating the crystal directional growth with optimal exposed crystal facets is an effective strategy to improve the performance of cathode materials, but still lacks sufficient attention in research field. Herein, we briefly introduce the characterization techniques and identification methods for crystal facets, then summarize and illuminate the major methods for regulating crystal orientation and their internal mechanism. Furthermore, the optimization strategies for layered-, spinel-, and olivine-structure cathodes are discussed based on the characteristic of crystal structure, and the relationship between exposure of special crystal facets and lithium storage performance is deeply analyzed, which could guide the rational design of cathodes for LIBs.

Heteroatom-Substituted P2-Na2/3Ni1/4Mg1/12Mn2/3O2 Cathode with {010} Exposing Facets Boost Anionic Activity and High-Rate Performance for Na-Ion Batteries

As an attractive cathode candidate for sodium-ion batteries, P2-type Na_2/3Ni_1/3Mn_2/3O₂ is famous for its high stability in humid air, attractive capacity, and high operating voltage. However, the low Na⁺ transport kinetics, oxygen-redox reactions, and irreversible structural evolution at high-voltage areas hinder its practical application. Herein, a comprehensive study of a microbar P2-type Ni_2/3Ni_1/4Mg_1/12Mn_2/3O₂ material with {010} facets is presented, which exhibits high reversibility of structural evolution and anionic redox activity, leading to outstanding rate capability and cyclability. The notable rate performance (53 mA h g^-1 at 20 C, 2.0-4.3 V) contributed to the high exposure of {010} facets via controlling the growth orientation of the precursor, which is certified by density functional theory calculation and lattice structural analysis. Mg substitution strengthens the reversibility of anionic oxygen redox and structural evolution in high-voltage areas that was confirmed by the in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy tests, leading to outstanding cyclic reversibility (68.9% after 1000 cycles at 5 C) and slowing down the voltage fading. This work provides new insights into constructing electrochemically active planes combined with heteroatom substitution to improve the Na⁺ transport kinetics and structural stability of layered oxide cathodes for sodium storage.

Highly Oriented {010} Crystal Plane Induced by Boron in Cobalt-Free Li- and Mn-Rich Layered Oxide

Li- and Mn-rich layered oxide (LMR) materials are a promising candidates for next-generation Li-ion battery (LIB) anode materials because of their high specific capacity. However, their low initial Coulombic efficiency, voltage decay, and irreversible phase transition during cycling are the fatal drawbacks of LMR materials. This work reports on a cobalt-free LMR material composed of primary particles with a boron-induced exposed long- strip-like {010} plane. Because of this unique structure, the long strip-like cathode exhibits excellent electrochemical performance with a discharge capacity of 202 mAh g^-1 at 1 C and a retention rate of 95.2% after 200 cycles. In addition, it is found that this long strip-like structure can modulate the redox of oxygen and enhance the reversibility. The irreversible phase transition process from the layered to a spinel and then to a rock-salt phase during cycling is also significantly suppressed. This work provides a feasible method for regulating the exposed {010} plane and a new idea for the structural design of LMR materials.

Controllable preparation of one-dimensional Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials for high-performance lithium-ion batteries

Lithium-rich layered oxides are attractive candidates of high-energy-density cathode materials for high-performance lithium ion batteries because of their high specific capacity and low cost. Nevertheless, their unsatisfactory rate capability and poor cycling stability have strongly hindered commercial applications in lithium ion batteries, mainly due to the ineffectiveness of the complicated synthesis techniques to control their morphologies and sizes. In this work, the Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode materials with a one-dimensional rod-like morphology were synthesized via a facile co-precipitation route followed by a post-calcination treatment. By reasonably adding NH₃·H₂O in the co-precipitation reaction, the sizes of the metal oxalate precursors could be rationally varied. The electrochemical measurements displayed that the Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ short rods delivered a high capacity of 286 mA h g^-1 at 0.1C and excellent capacity retention of 85% after 100 cycles, which could be contributed to the improvement of the electrolyte contact, Li⁺ diffusion, and structural stability of the one-dimension porous structure.

Simple Glycerol-Assisted and Morphology-Controllable Solvothermal Synthesis of Lithium-Ion Battery-Layered Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Materials

High-performance lithium-rich-layered oxide is regarded as a promising candidate for lithium-ion battery (LIB) cathode materials because of its outstanding high specific capacity. Despite in-depth research over the past decade, there are still a number of serious problems limiting its commercialization. Here, we report a simple morphological design and size-controllable material preparation strategy to enhance the electrochemical performance of LIB cathode materials. We use a simple solvothermal method to obtain a carbonate precursor material with different morphologies by adjusting the solvent ratio of the system, which will be conveniently formed into Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ by calcination. Moreover, further relation between the morphology and electrochemical performance of cathode materials is systematically investigated. The microsphere cathode material with suitable size exhibits superior electrochemical performances among all samples in terms of initial reversible capacity (280.4 mA h g^-1 at 0.1 C) and cycle performance (87.67% retention after 200 cycles at 1 C). Even at 5 C, a high discharge capacity of 150.8 mA h g^-1 can be obtained. In addition, this work provides a feasible and effective approach to controllable synthesis of stable structures and high-performance oxide electrode materials for LIBs.

Ni-Rich Layered Oxide with Preferred Orientation (110) Plane as a Stable Cathode Material for High-Energy Lithium-Ion Batteries

The cathode, a crucial constituent part of Li-ion batteries, determines the output voltage and integral energy density of batteries to a great extent. Among them, Ni-rich LiNi_xCo_yMn_zO₂ (x + y + z = 1, x ≥ 0.6) layered transition metal oxides possess a higher capacity and lower cost as compared to LiCoO₂, which have stimulated widespread interests. However, the wide application of Ni-rich cathodes is seriously hampered by their poor diffusion dynamics and severe voltage drops. To moderate these problems, a nanobrick Ni-rich layered LiNi_0.6Co_0.2Mn_0.2O₂ cathode with a preferred orientation (110) facet was designed and successfully synthesized via a modified co-precipitation route. The galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) analysis of LiNi_0.6Co_0.2Mn_0.2O₂ reveal its superior kinetic performance endowing outstanding rate performance and long-term cycle stability, especially the voltage drop being as small as 67.7 mV at a current density of 0.5 C for 200 cycles. Due to its unique architecture, dramatically shortened ion/electron diffusion distance, and more unimpeded Li-ion transmission pathways, the current nanostructured LiNi_0.6Co_0.2Mn_0.2O₂ cathode enhances the Li-ion diffusion dynamics and suppresses the voltage drop, thus resulting in superior electrochemical performance.

Rod-shaped Cu1.81Te as a novel cathode material for aluminum-ion batteries

Aluminum-ion batteries (AIBs) are supposed to be one of the energy storage systems with great potentialities on account of their high safety, low cost and high theoretical volumetric capacity. Herein, we report a novel rod-shaped Cu1.81Te cathode material for AIBs. At 40 mA g-1, the initial discharge capacity can reach 144 mA h g-1. The diffusion coefficient of Al3+ calculated by the galvanostatic intermittent titration technique (GITT) and cyclic voltammetry (CV) tests at different scan rates is larger than that in sulfides, indicating that telluride has faster kinetics. The results of ex situ X-ray photoelectron spectroscopy (XPS), ex situ X-ray diffraction (XRD) and 27Al nuclear magnetic resonance (NMR) prove that the mechanism of the charging and discharging processes is the reversible intercalation and deintercalation of Al3+, which is very important for the subsequent researchers to understand and investigate the mechanism of the Al/Cu1.81Te battery. This work also proves that telluride can also be used as a cathode material for aluminum storage.

The Effects of Trace Yb Doping on the Electrochemical Performance of Li-Rich Layered Oxides

Layered lithium-rich cathode materials are one of the most promising cathode materials owing to their higher mass energy density than the commercial counterparts. A series of trace Yb-doped lithium-rich cathode materials Li_1.2 Mn_0.54 Ni_0.13 Co_0.13-x Yb_x O₂ (0≤x≤0.050) were synthesized and the effects were investigated by XRD, X-ray photoelectron spectroscopy, and high-resolution TEM. The participation of Yb ions in electrochemical reactions and the larger binding energy of Yb-O than M-O (M=Mn, Ni, Co), which expands the lithium layer spacing and stabilizes the oxygen stacking, resulted in excellent performance of materials doped with a limited Yb content (x≤0.005). However, higher doping amounts (x>0.005) significantly increased the charge-transfer impedance and led to a sharp deterioration in electrochemical performance. The reason lies in the large difference in ionic radius between the transition metals (Mn, Co, and Ni) and Yb. There is an upper limit to the amount of Yb ions in the lattice. If the amount of Yb is higher than the limit, excess Yb ions enter the Li layers instead of staying in the transition-metal layers or even segregate on the surface and form electrochemically inert oxides.

Crystal structural design of exposed planes: express channels, high-rate capability cathodes for lithium-ion batteries

Developing high-performance lithium ion batteries (LIBs) requires optimization of every battery component. Currently, the main problems lie in the mismatch of electrode capacities, especially the excessively low capacity of cathodes compared with that of anodes. Due to the anisotropy of the crystal structure, different crystal planes play different roles in the transmission of lithium ions. Among these, the {010} facets of layered-structure materials, the (110) planes of spinel cathodes and the (010) planes of olivine cathodes can provide open surface structures, which furnish express channels for the rapid and efficient transmission of lithium ions, leading to enhanced rate performance. However, due to the high-energy surfaces of these crystal planes, they tend to disappear in the synthetic process, forming thermodynamic equilibrium products dominated by low-energy and electrochemically-inactive planes. From the structure design of the material itself, preparing functional materials with specific morphologies and crystal structures is considered to be the most effective way to improve the cyclability and rate performance of LIB cathodes. In this review, we highlight the latest developments in selectively exposing the crystal planes of LIB cathode materials. The synthetic method, the corresponding electrochemical performance, especially the rate capability, and the growth mechanism have been systematically summarized for layered-structure cathodes of LiCoO2, LiNixCoyMn1-x-yO2 and Li2MnO3·LiMO2, spinel cathodes of LiMn2O4 and LiNi0.5Mn1.5O4, and olivine cathodes of LiFePO4. This in-depth discussion and understanding is beneficial for the rational design of well-performing LIB cathodes and can provide direction and perspectives for future work.

Exposing the {010} Planes by Oriented Self-Assembly with Nanosheets To Improve the Electrochemical Performances of Ni-Rich Li[Ni0.8Co0.1Mn0.1]O2 Microspheres

A modified Ni-rich Li[Ni_0.8Co_0.1Mn_0.1]O₂ cathode material with exposed {010} planes is successfully synthesized for lithium-ion batteries. The scanning electron microscopy images have demonstrated that by tuning the ammonia concentration during the synthesis of precursors, the primary nanosheets could be successfully stacked along the [001] crystal axis predominantly, self-assembling like multilayers. According to the high-resolution transmission electron microscopy results, such a morphology benefits the growth of the {010} active planes of final layered cathodes during calcination treatment, resulting in the increased area of the exposed {010} active planes, a well-ordered layer structure, and a lower cation mixing disorder. The Li-ion diffusion coefficient has also been improved after the modification based on the results of potentiostatic intermittent titration technique. As a consequence, the modified Li[Ni_0.8Co_0.1Mn_0.1]O₂ material exhibits superior initial discharges of 201.6 mA h g^-1 at 0.2 C and 185.7 mA h g^-1 at 1 C within 2.8-4.3 V (vs Li⁺/Li), and their capacity retentions after 100 cycles reach 90 and 90.6%, respectively. The capacity at 10 C also increases from 98.3 to 146.5 mA h g^-1 after the modification. Our work proposes a novel approach for exposing high-energy {010} active planes of the layered cathode material and again confirms its validity in improving electrochemical properties.

Enhanced Electrochemical Performance of Layered Lithium-Rich Cathode Materials by Constructing Spinel-Structure Skin and Ferric Oxide Islands

Layered lithium-rich cathode materials have been considered as competitive candidates for advanced lithium-ion batteries because they are environmentally benign, high capacity (more than 250 mAh·g^-1), and low cost. However, they still suffer from poor rate capability and modest cycling performance. To address these issues, we have proposed and constructed a spinel-structure skin and ferric oxide islands on the surface of layered lithium-rich cathode materials through a facile wet chemical method. During the surface modification, Li ions in the surface area of pristine particles could be partially extracted by H⁺, along with the depositing process of ferric hydrogen. After calcination, the surface structure transformed to spinel structure, and ferric hydrogen was oxidized to ferric oxide. The as-designed surface structure was verified by EDX, HRTEM, XPS, and CV. The experimental results demonstrated that the rate performance and capacity retentions were significantly enhanced after such surface modification. The modified sample displayed a high discharge capacity of 166 mAh·g^-1 at a current density of 1250 mA·g^-1 and much more stable capacity retention of 84.0% after 50 cycles at 0.1C rate in contrast to 60.6% for pristine material. Our surface modification strategy, which combines the advantages of spinel structure and chemically inert ferric oxide nanoparticles, has been shown to be effective for realizing the layered lithium-rich cathodes with surface construction of fast ion diffusing capability as well as robust electrolyte corroding durability.

Tailoring Anisotropic Li-Ion Transport Tunnels on Orthogonally Arranged Li-Rich Layered Oxide Nanoplates Toward High-Performance Li-Ion Batteries

High-performance Li-rich layered oxide (LRLO) cathode material is appealing for next-generation Li-ion batteries owing to its high specific capacity (>300 mAh g^-1). Despite intense studies in the past decade, the low initial Coulombic efficiency and unsatisfactory cycling stability of LRLO still remain as great challenges for its practical applications. Here, we report a rational design of the orthogonally arranged {010}-oriented LRLO nanoplates with built-in anisotropic Li⁺ ion transport tunnels. Such a novel structure enables fast Li⁺ ion intercalation and deintercalation kinetics and enhances structural stability of LRLO. Theoretical calculations and experimental characterizations demonstrate the successful synthesis of target cathode material that delivers an initial discharge capacity as high as 303 mAh g^-1 with an initial Coulombic efficiency of 93%. After 200 cycles at 1.0 C rate, an excellent capacity retention of 92% can be attained. Our method reported here opens a door to the development of high-performance Ni-Co-Mn-based cathode materials for high-energy density Li-ion batteries.

Li1.17Mn0.50Ni0.16Co0.17O2 assembled microspheres as a high-rate and long-life cathode of Li-ion batteries

Li_1.17Mn_0.50Ni_0.16Co_0.17O₂ assembled microspheres deliver excellent electrochemical performances due to the fast Li-ion movement during the sintering process.

Advanced cathode materials for lithium-ion batteries using nanoarchitectonics

In recent years, the global climate has further deteriorated because of the excessive consumption of traditional energy sources. The replacement of traditional fossil fuels with limited reserves by alternative energy sources has become one of the main strategies to alleviate the increasingly serious environmental issues. As a sustainable and promising store of renewable energy, lithium-ion batteries have replaced other types of batteries for many small-scale consumer devices. Notwithstanding their worldwide applications, it has become abundantly clear that the design and fabrication of electrode materials is urgently required to adapt to meet the growing global demand for energy and the power densities needed to make electric vehicles fully commercially viable. To dramatically enhance battery performance, further advances in materials chemistry are essential, especially in novel nanomaterials chemistry. The construction of nanostructured cathode materials by reducing particle size can boost electrochemical performance. The present review is intended to provide readers with a better understanding of the unique contribution of various nanoarchitectures to lithium-ion batteries over the last decade. Nanostructured cathode materials with different dimensions (0D, 1D, 2D, and 3D), morphologies (hollow, core-shell, etc.), and composites (mainly graphene-based composites) are highlighted, aiming to unravel the opportunities for the development of future-generation lithium-ion batteries. The advantages and challenges of nanomaterials are also addressed in this review. We hope to simulate many more extensive and insightful studies on nanoarchitectonic cathode materials for advanced lithium-ion batteries with desirable performance.

Aligned Li+ Tunnels in Core-Shell Li(NixMnyCoz)O2@LiFePO4 Enhances Its High Voltage Cycling Stability as Li-ion Battery Cathode

Layered transition-metal oxides (Li[Ni_xMn_yCo_z]O₂, NMC, or NMCxyz) due to their poor stability when cycled at a high operating voltage (>4.5 V) have limited their practical applications in industry. Earlier researches have identified Mn(II)-dissolution and some parasitic reactions between NMC surface and electrolyte, especially when NMC is charged to a high potential, as primarily factors responsible for the fading. In our previous work, we have achieved a capacity of NMC active material close to theoretical value and optimized its cycling performance by a depolarized carbon nanotubes (CNTs) network and an unique "pre-lithiation process" that generates an in situ organic coating (∼40 nm) to prevent Mn(II) dissolution and minimize the parasitic reactions. Unfortunately, this organic coating is not durable enough during a long-term cycling when the cathode operates at a high potential (>4.5 V). This work attempts to improve the surface protection of the NMC532 particles by applying an active inorganic coating consisting of nanosized- and crystal-orientated LiFePO₄ (LFP) (about 50 nm, exposed (010) face) to generate a core-shell nanostructure of Li(Ni_xMn_yCo_z)O₂@LiFePO₄. Transmission electron microscopy (TEM) and etching X-ray photoelectron spectroscopy have confirmed an intimate contact coating (about 50 nm) between the original structure of NMC and LFP single-particle with atomic interdiffusion at the core-shell interface, and an array of interconnected aligned Li⁺ tunnels are observed at the interface by cross-sectional high-resolution TEM, which were formed by ball-milling and then strictly controlling the temperature below 100 °C. Batteries based on this modified NMC cathode material show a high reversible capacity when cycled between 3.0 and 4.6 V during a long-term cycling.

Hollow Porous Hierarchical-Structured 0.5Li2MnO3·0.5LiMn0.4Co0.3Ni0.3O2 as a High-Performance Cathode Material for Lithium-Ion Batteries

We report a novel hollow porous hierarchical-architectured 0.5Li₂MnO₃·0.5LiMn_0.4Co_0.3Ni_0.3O₂ (LLO) for lithium-ion batteries (LIBs). The obtained lithium-rich layered oxides possess a large inner cavity, a permeable porous shell, and excellent structural robustness. In LIBs, such unique features are favorable for fast Li⁺ transportation and can provide sufficient contact between active materials and electrolytes, accommodate more Li⁺, and improve the kinetics of the electrochemical reaction. The as-prepared LLO displays an extremely high initial discharge capacity (296.5 mAh g^-1 at 0.2 C), high rate capability (162.6 mAh g^-1 at 10 C), and excellent cycling stability (237.6 mAh g^-1 after 100 cycles at 0.5 C and 153.8 mAh g^-1 after 200 cycles at 10 C). These values are superior to most literature data.

Facile Synthesis of Platelike Hierarchical Li1.2Mn0.54Ni0.13Co0.13O2 with Exposed {010} Planes for High-Rate and Long Cycling-Stable Lithium Ion Batteries

Lithium-rich layered oxides are promising cathode candidates for the production of high-energy and high-power electronic devices with high specific capacity and high discharge voltage. However, unstable cycling performance, especially at high charge-recharge rate, is the most challenge issue which needs to be solved to foster the diffusion of these materials. In this paper, hierarchical platelike Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode materials were synthesized by a facile solvothermal method followed by calcination. Calcination time was found to be a key parameter to obtain pure layered oxide phase and tailor its hierarchical morphology. The Li-rich material consists of primary nanoparticles with exposed {010} planes assembled to form platelike layers which exhibit low resistance to Li⁺ diffusion. In detail, the product by calcination at 900 °C for 12 h exhibits specific capacity of 228, 218, and 204 mA h g^-1 at 200, 400, and 1000 mA g^-1, respectively, whereas after 100 cycles at 1000 mA g^-1 rate of charge and recharge the specific capacity was retained by about 91%.

Carbon wrapped hierarchical Li3V2(PO4)3 microspheres for high performance lithium ion batteries

Nanomaterials are extensively studied in electrochemical energy storage and conversion systems because of their structural advantages. However, their volumetric energy density still needs improvement due to the high surface area, especially the carbon based nanocomposites. Constructing hierarchical micro-scaled materials from closely stacked subunits is proposed as an effective way to solve the problem. In this work, Li₃V₂(PO₄)₃@carbon hierarchical microspheres are prepared by a solvothermal reaction and subsequent annealing. Hierarchical Li₃V₂(PO₄)₃ structures with different subunits are obtained with the aid of polyvinyl pyrrolidone (PVP). Moreover, excessive PVP interconnect and form PVP-based hydrogels, which later convert into conductive carbon layer on the surface of Li₃V₂(PO₄)₃ microspheres during the annealing process. As a cathode material for lithium ion batteries, the 3D carbon wrapped Li₃V₂(PO₄)₃ hierarchical microspheres exhibit high rate capability and excellent cycling stability. The electrode has the capacity retention of 80% after 5000 cycles even at 50C.

Pre-Lithiation of Li(Ni1-x-yMnxCoy)O2 Materials Enabling Enhancement of Performance for Li-Ion Battery

Transition metal oxide materials Li(NixMnyCoz)O2 (NMCxyz) based on layered structure are potential cathode candidates for automotive Li-ion batteries because of their high specific capacities and operating potentials. However, the actual usable capacity, cycling stability, and first-cycle Coulombic efficiency remain far from practical. Previously, we reported a combined strategy consisting of depolarization with embedded carbon nanotube (CNT) and activation through pre-lithiation of the NMC host, which significantly improved the reversible capacity and cycling stability of NMC532-based material. In the present work we attempt to understand how pre-lithiation leads to these improvements on an atomic level with experimental investigation and ab initio calculations. By lithiating a series of NMC materials with varying chemical compositions prepared via a conventional approach, we identified the Ni in the NMC lattice as the component responsible for accommodating a double-layered Li structure. Specifically, much better improvements in the cycling stability and capacity can be achieved with the NMC lattices populated with Ni(3+) than those populated with only Ni(2+). Using the XRD we also found that the emergence of a double-layer Li structure is not only reversible during the pre-lithiation and the following delithiation, but also stable against elevated temperatures up to 320 °C. These new findings regarding the mechanism of pre-lithiation as well as how it affects the reversibility and stability of NMC-based cathode materials prepared by the conventional slurry approach will promote the possibility of their application in the future battery industry.

High-Rate and Cycling-Stable Nickel-Rich Cathode Materials with Enhanced Li(+) Diffusion Pathway

The nickel-rich LiNi0.7Co0.15Mn0.15O2 material was sintered by Li source with the Ni0.7Co0.15Mn0.15(OH)2 precursor, which was prepared via hydrothermal treatment after coprecipitation. The intensity ratio of I(110)/I(108) obtained from X-ray diffraction patterns and high-resolution transmission electronmicroscopy confirm that the particles have enhanced growth of (110), (100), and (010) surface planes, which supply superior inherent Li(+) deintercalation/intercalation. The electrochemical measurement shows that the LiNi0.7Co0.15Mn0.15O2 material has high cycling stability and rate capability, along with fast charge and discharge ability. Li(+) diffusion coefficient at the oxidation peaks obtained by cyclic voltammogram measurement is as large as 10(-11) (cm(2) s(-1)) orders of magnitude, implying that the nickel-rich material has high Li(+) diffusion capability.

Hybrid LiV3O8/carbon encapsulated Li1.2Mn0.54Co0.13Ni0.13O2 with improved electrochemical properties for lithium ion batteries

Core–shell Li_1.2Mn_0.54Co_0.13Ni_0.13O₂@LiV₃O₈/C composite material was prepared by sol–gel method. It possessed an initial coulombic efficiency of 94% at 0.1C rate over 2.0–4.8 V potential range, and good rate capability and stable operation voltage.

Improving the electrochemical performance of Li1.2Ni0.13Co0.13Mn0.54O2 by Li-ion conductor

Electrochemical performances of Li-rich layered Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode are improved by modification of Li-ion conductor Li_1.3Al_0.3Ti_1.7(PO₄)₃.

Promoting the cyclic and rate performance of lithium-rich ternary materials via surface modification and lattice expansion

Nickel-rich layered lithium transition-metal oxides have been studied intensively as high-energy positive-electrode materials for lithium batteries because of their high specific capacity and relatively low-cost.