![]() Oxygen vacancies (OVs), as one of the most common and important defects in transition metal oxide materials, can effectively regulate the electronic structure, electrical conductivity and surface structure of transition metal oxides. Rational and controlled used of defects can enable tuning of key physical properties of materials such as, for instance, doping in semiconductors to enhance the electronic conductivity. Among these cathode materials, Li-rich layered oxide materials have attracted great attention due to their specific discharge capacity, which can reach 270 mA h g −1, holding great promise for the development of next generation cathodes for commercial Li-ion technologies.īy altering the physical and chemical properties of the hosting material, structural defects in battery electrodes can greatly affect the electro-chemical performance and lifetime of (Li-ion) batteries. Since then, LiMn 2O 4, LiFePO 4, LiNi xCo yMn zO 2/LiNi xCo yAl zO 2, 11 LiNi xMn 2− xO 4, 12 and Li-rich layered oxides such as LiO 2 13 and Li 2Ru 1− xM xO 3 (M = Mn, Sn, Ti) 14,15 have also been used as cathode materials in commercial LiBs. ![]() The good intercalation behaviour of the conventional cathode, layered LiCoO 2, was first reported in the early 1980s, 7,8 leading to successful commercialization of LiBs in 1991. Thus, the specific capacity of commercially available LiBs is ultimately limited by the performance of available (stable) cathode materials. 10 Whereas the capacity of a graphite anode is close to 400 mA h g −1, that of LiCoO 2, a commercially used cathode material, is only about 140 mA h g −1, and that of LiFePO 4 is about 160 mA h g −1. The capacity of available cathode materials in LiBs is generally lower than that of commercial anode materials. In the 1980s, the development of transition metal oxides anode materials proposed by Goodenough for Li-ion battery, 7,8 together with the emergence of practical graphite anodes, 9 opened up the commercial era for LiBs. In 1958, Harris proposed to use organic electrolyte as the electrolyte in LiBs, opening for an era of intense study and rapid developments. ![]() ![]() Lewis was the first to propose and study the lithium metal battery. 5,6 Research in lithium batteries can be traced back to 1912. Their functioning depends on the movement of Li-ions between cathode and anode. 4 In the past 20 years, the Li-ion battery has firmly established itself in the market of mobile terminal equipment, computer, mobile phones, electric vehicle, etc., thanks to its relatively high energy density, excellent charging and discharging performance and commercially suitable operational lifetimes.īeing rechargeable, Li-ion batteries (LiBs) are a secondary battery technology. Among various energy storage technologies, electrochemical energy storage, that is, the use of batteries, has attracted growing attention as this technology is in principle capable to fulfil several of the requirements demanded by modern society for both mobile and stationary applications. 1–3 In order to solve the mismatch between generation of renewable energy and its demand and use further in time and space, the development of scalable and efficient energy storage technologies is essential. For practical applications to be widely accessible, renewable sources such as solar, wind and hydraulic energy need to be converted into secondary forms such as electricity. Introduction The growing concerns on energy availability, distribution and the environmental costs of energy production have turned development of clean and renewable solutions into a modern international priority. Recent successes and residual unsolved challenges are presented and discussed to stimulate further interest and research in harnessing OVs towards next generation oxide-based cathode materials. This review summarises some of the most recent and exciting progress made on the understanding and control of OVs in cathode materials for Li-ion battery, focusing primarily on Li-rich layered oxides. Understanding the role of OVs for the performance of layered lithium transition metal oxides holds great promise and potential for the development of next generation cathode materials. However, OVs can also lead to accelerated degradation of the cathode material structure, and from there, of the battery performance. Oxygen vacancies (OVs) can promote Li-ion diffusion, reduce the charge transfer resistance, and improve the capacity and rate performance of LiBs. The substantial capacity gap between available anode and cathode materials for commercial Li-ion batteries (LiBs) remains, as of today, an unsolved problem.
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