Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high-capacity electrode materials. According to the concept of energy quality, a high-voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high-capacity Li-rich cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after-treatment, and the specific energy is improved from 912 to 1033 Wh kg-1 . The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.

High-Capacity Cathode Material with High Voltage for Li-Ion Batteries

A cation/anion co-doped Li1.12Na0.08Ni0.2Mn0.6O1.95F0.05 cathode for lithium ion batteries

Li-rich layered materials have been considered as the most promising cathode materials for future high-energy-density lithium-ion batteries. However, they suffer from severe voltage decay upon cycling, which hinders their further commercialization. Here, we report a Li-rich layered material 0.5Li2MnO3·0.5LiNi0.8Co0.1Mn0.1O2 with high nickel content, which exhibits much slower voltage decay during long-term cycling compared to conventional Li-rich materials. The voltage decay after 200 cycles is 201 mV. Combining in situ X-ray diffraction (XRD), ex situ XRD, ex situ X-ray photoelectron spectroscopy, and scanning transmission electron microscopy, we demonstrate that nickel ions act as stabilizing ions to inhibit the Jahn–Teller effect of active Mn3+ ions, improving d–p hybridization and supporting the layered structure as a pillar. In addition, nickel ions can migrate between the transition-metal layer and the interlayer, thus avoiding the formation of spinel-like structures and consequently mitigating the ...

Mitigating Voltage Decay of Li-Rich Cathode Material via Increasing Ni Content for Lithium-Ion Batteries

Li-rich cathode materials have attracted increasing attention because of their high reversible discharge capacity (>250 mA h g-1 ), which originates from transition metal (TM) ion redox reactions and unconventional oxygen anion redox reactions. However, many issues need to be addressed before their practical applications, such as their low kinetic properties and inefficient voltage fading. The development of cutting-edge technologies has led to cognitive advances in theory and offer potential solutions to these problems. Herein, a recent in-depth understanding of the mechanisms and the frontier electrochemical research progress of Li-rich cathodes are reviewed. In addition, recent advances associated with various strategies to promote the performance and the development of modification methods are discussed. In particular, excluding Li-rich Mn-based (LRM) cathodes, other branches of the Li-rich cathode materials are also summarized. The consistent pursuit is to obtain energy storage devices with high capacity, reliable practicability, and absolute safety. The recent literature and ongoing efforts in this area are also described, which will create more opportunities and new ideas for the future development of Li-rich cathode materials.

Challenges and Recent Advances in High Capacity Li-Rich Cathode Materials for High Energy Density Lithium-Ion Batteries.

Due to their high specific capacities beyond 250 mA h g−1, lithium-rich oxides have been considered as promising cathodes for the next generation power batteries, bridging the capacity gap between traditional layered-oxide based lithium-ion batteries and future lithium metal batteries such as lithium sulfur and lithium air batteries. However, the practical application of Li-rich oxides has been hindered by formidable challenges. To address these challenges, the understanding of their electrochemical behaviors becomes critical and is expected to offer effective guidance for both materials and cell development. This review aims to provide fundamental insights into the reaction mechanisms, electrochemical challenges and modification strategies of lithium-rich oxides. We first summarize the research history, the pristine structures, and the classification of lithium-rich oxides. Then we review the critical reaction mechanisms that are closely related to their electrochemical features and performances, such as lattice oxygen oxidation, oxygen vacancy formation, transition-metal migration, layered to spinel transitions, ‘two-phase mechanism’, and lattice evolution. These discussions are coupled with state-of-the-art characterization techniques. As a comparison, the anionic redox reactions of layered sodium transition metal oxides are also discussed. Finally, after a brief overview of the correlation among the aforementioned mechanisms, we provide perspectives on the rational design of lithium-rich oxides with high energy densities and long-term cycling stability.

Li-rich cathodes for rechargeable Li-based batteries: reaction mechanisms and advanced characterization techniques

Enhancing the Kinetics of Li-Rich Cathode Materials through the Pinning Effects of Gradient Surface Na+ Doping

Cathode Materials: Enhancing the Kinetics of Li-Rich Cathode Materials through the Pinning Effects of Gradient Surface Na+ Doping (Adv. Energy Mater. 6/2016)

Synthesis and Electrochemical Properties of a High Capacity Li-rich Cathode Material in molten KCl-Na2CO3 flux

The invention discloses a preparation method of a high-capacity lithium-rich anode material. According to the method, a material precursor, lithium salt and alkali metal or alkaline-earth metal molten salt are calcined at certain temperature according to a certain sequence and ratio, and then the high-capacity lithium-rich anode material is obtained. The obtained lithium-rich anode material is smooth and dense in particle surface and excellent in electrochemical performance, and has the advantages of being high in discharge capacity, low in irreversible capacity, stable in circulation and the like. The method is simple in technological condition, raw materials are cheap, growth of crystal particles of the lithium-rich anode material is controlled through the molten salt, and meanwhile the problem of non-uniform sintering in the sintering process and especially the large-scale sintering process of the material is solved. High practicality is achieved, and the preparation method is suitable for mass production.

Preparation method of high-capacity lithium-rich anode material

The invention discloses a preparation method of a high-capacity positive electrode material. The preparation method comprises the following steps: 1, preparing a transition metal salt solution, an alkaline solution and a base solution with certain ion strength; 2, adding the solutions to a reaction still and aging under the condition of controlled stirring rate, pH valve and reaction temperature; and 3, dissolving a lithium salt in ultrapure water to prepare a solution, adding a spherical precursor in the lithium salt solution, stirring and mixing, heating to evaporate water, drying and calcining to obtain the high-capacity positive electrode material 0.5Li2MnO3.0.5LiNi1/3Co1/3Mn1/3O2. By virtue of a mode of controlling the ion strength of the base solution, the precipitation reaction rate is controlled, and crystal nucleation and growth rate is controlled so that the uniform and controllable spherical precursor can be formed. The aim of uniformly mixing the precursor and the lithium salt is fulfilled through wet-process mixing, thus being beneficial to generation of the high-capacity positive electrode material with remarkable performance via calcining.

Ren-Peng Qing

Papers

Enhancing the Kinetics of Li-Rich Cathode Materials through the Pinning Effects of Gradient Surface Na+ Doping

Cathode Materials: Enhancing the Kinetics of Li-Rich Cathode Materials through the Pinning Effects of Gradient Surface Na+ Doping (Adv. Energy Mater. 6/2016)

Synthesis and Electrochemical Properties of a High Capacity Li-rich Cathode Material in molten KCl-Na2CO3 flux

Preparation method of high-capacity lithium-rich anode material

High-capacity positive electrode material for lithium ion battery