It will be concluded in this blog about the previous development of advanced materials for Lithium Batteries(LIBs). Among which most of the points are from a latest review paper "Function materials for rechargeable batteries, Adv. Mater, 2011, 23, 1695-1715". The schematic of previous study concerning electrode materials is showed below: From the side of Cathode materials, Lithium metal oxides are commonly used to act as the provider of Li-ion in the charging procedure. The potential capacity of this cathode materials is competitive but a poor ability of capacity retention remains a big problem. The polyanionic based materials are regarded as the next generation materials for Cathode due to its safety and reversibility of Lithium storage. This category could be represented by LiFePO4. Latest research indicates that the nanosize effect plays a great role in the contribution ofextremelyhigh performance, which would be a hot point in the future research. There are also organic materials which has also attracted a lot attentions, but will not described in details here. When comes to the materials for anode, lithium alloys (mainly with main-group elements)show great potential capacity due to its reaction with Lithium. However, the great volume expansion during the reactions could never be neglected. Hollow nanostructures could reduce the inner strain due to the volume variation. For instance, Ag coated 3D porous silicon has been developed to reduce the effect of volume expansion, which could be illustrated by the figure below: What's more, carbon coating of the tin based materials will decrease the volume expansion in a large extend.Another kind of anode materials—Transition metal oxides also attract similar considerations in a similar way. Such combination of two kinds of materials will take advantage of the characteristics of two or more kinds of materials, which represent the trend of developing novel anode materials.
The induced stress in Li-ion batteries electrode(LIBs) will be discussed in this article, which focus mainly on the modeling and simulating. Two papers from JPS: "Zhang et.al, JPS, 2012, 220-227" and "Haftbaradaran et.al, JPS, 2011, 361-370" are analysed to demonstrate the latest development of this problem. The internal stress will increase the density of defects in batteries, which as a result will affect the capacity and life span of them. The poor cyclic performance of battery could be modeled by strongly coupled diffusion-stress model.Haftbaradaran et.al has developed it to deal with the highly nonlinear behavior of diffusion process in high solute concentration.The validity ofcontinuumhas been proved by comparing with simulation results by Molecular dynamics, one of thecomparisonis demonstrated below, the discrete point are results obtained by MD method while the line represent calculation of thecontinuummodel. Four points concerning the nonlinear behavior of diffusion behavior has been discussed in the work by Haftbaradaran et.al byeliminating their effects one by one in new comparisons between the theoretical and simulating results. In the work of Zhang et.al, more attentions has been paid to the layered structure of electrode in LIBs. Their model has been adapted to discuss the symmetry of of electrode plate, conditions bilayer electrode plate and the effects of charging conditions. The role of current collector in relation with the electrode has been discussed and it has been concluded that the materials of current collector should be as thin as possible and the elastic modulus should be smaller to enhance a much lower stress in the electrode. That is to say, the diffusion induced stress could be well modeled nowadays to predict the performance of new materials in battery electrode. From my perspective, the applicable of models in different kind of materials should be evaluated because the structure and and chemical properties vary between different kind of electrode materials.
标签: ELECTRODE
