Lithium battery has become an indispensable product in daily life. Especially in the field of electric vehicles, lithium batteries are playing a growing role. Today, Science magazine launched two articles in a row, introducing the latest development of lithium batteries.
One paper is research progress. It comes from FengWang of bruckhawn national laboratory and Gerbrand Ceder team of the University of California, Berkeley. It reports the abnormal principle of lithium titanate negative charge in the field of lithium battery. Another paper, outlook, by Jun Lu of Argonne national laboratory and Matthew Li of the University of Waterloo in Canada, describes the unique role and reduction of Co in lithium-ion batteries.
The evolution of lithium batteries
1. Science: to reveal the dynamic mechanism of lithium titanate rapid charging
In lithium batteries capable of fast charging, lithium and negative electrode generally form a solid solution. In this case, there is almost no dynamic barrier. Lithium can be continuously contained through solid solution transformation, and ion diffusion is the only limiting factor.
However, the negative electrode of lithium titanate (Li4Ti5O12) is an exception.
In the lithium titanate negative electrode, the lithium-ion interacts with both phases and diffuses slowly, but still has a high rate capacity. The bizarre behavior, which has caught the attention of scientists, could open the way for the development of entirely new, fast-rechargeable batteries.
With this in mind, Feng Wang of the Brookhaven national laboratories and Gerbrand Ceder of the University of California, Berkeley, used electron energy loss spectroscopy and density functional theory to investigate this abnormal Li + migration behavior.
They found that between the initial Li4Ti5O12 and the final Li7Ti5O12 materials, a diffusion interface was formed, along the metastable intermediate Li polyhedron dynamics path of the two-phase interface, to ensure the rapid migration of Li4+xTi5O12, which is a key factor for the rapid propagation of lithium ions.
This study provides a new direction for finding high - speed electrode materials.
2. Science: cobalt in lithium-ion batteries
LCO has been used in photovoltaic applications in lithium-ion batteries, giving them high conductivity and stable structure. Given that Co is mined in Africa in a less abundant way, at a higher price, and because of political and ethical issues, it is now being replaced with nickel and manganese to develop cheaper cathode materials.
Currently, most lithium-ion batteries use two kinds of positive electrode materials, NCA and NMC. In this way, Co can ensure high speed and flexible energy, and to some extent enhance cycle stability. How to further reduce or even not use Co on the premise of ensuring battery performance, in order to further reduce the cost, is a practical problem in today's lithium-ion battery field.
In view of this, Jun Lu of Argonne national laboratory in the United States and Matthew Li of the University of Waterloo in Canada introduced the unique role and reduction of Co in lithium-ion batteries.
This paper first summarizes the unique role and important advantage of Co in NCA and NMC: adding Co improves the stability of LNO. The content of Co can be reduced reasonably, but it is impossible to eliminate it completely.
Secondly, the culture introduces the use of other metals such as Ti in place of Co to achieve important progress in acceptable performance. However, other metals tend to limit the mixing of lithium and nickel, resulting in a decrease in kinetic performance and capacity.
The authors point out that determining the best composition of the new anode material will require a lot of rigorous experimental comparison, and machine learning may lead to new ideas. Whether to avoid Co altogether depends on the future market in cobalt mining and cobalt recycling.
