Lithium Ion Battery Materials Characterization
20Pages

Advanced Energy Storage Technologies Lithium-Ion Battery Series

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The Lithium-ion battery is an energy storage device capable of almost continuous charging and discharging. In comparison to traditional battery technologies, lithium-ion batteries provide a significantly higher performance and efficiency In terms of application. The lithium-ion battery market can be segmented into consumer electronics, automotive, storage grid energy, and industrial use. Improving global economic conditions, rising disposable income, the need for clean energy and surging demand for quality & uninterrupted power are a few of the major factors anticipated to boost demand...

Electrode Analysis Cathode/Anode The development of cathode and anode materials for lithium-ion batteries is based on improvement to power and energy density as well as the thermal/chemical stability for enhancements in battery life and charge cycling. The theoretical capacity of a lithium-ion battery is determined by the materials used. In electrode processing, knowledge of particle morphology—including particle size, shape, powder density, porosity and surface area—have critical affect to manufacturability and the desired performance characteristics of the electrode. (positive plate)...

Particle Size/Particle Shape Particle size influences capacity, cycling, and coulomb efficiency. Particle size will impact the amount of solid-state diffusion of lithium-ions that intercalate at the electrode. Smaller particles, especially nanoparticles, will lead to smaller volume changes upon cycling. This contributes to less mechanical stress, increased hardness, and greater resistance to fracture. It has been reported that a broad particle size distribution may increase the energy density more than a mono-dispersed distribution. Controlling and customizing particle size distribution can...

Density/T.A.P. Density The density of the graphite anode has an effect on its ability to withstand degradation under challenging load and discharge operations. A higher anode electrode particle density decreases the porosity resulting in a lower active surface area of the electrode. This reduces the electrode/electrolyte contact area. True/absolute density and envelope density can help by determining electrochemical performance attributed to the electrodes available porosity for intercalation. A clear correlation has been found between irreversible capacity and internal pore volume. T.A.P....

Separator/Binder Evaluation The separator permits ion flow from one electrode to the other while preventing any electron flow, essentially separating the anode from the cathode. The typical separator is made up of polyolefins, usually polypropylene and/ or polyethylene, along with other polymers, ceramics, and ceramic/polymer blends. to prevent thermal runaway of the cell. Separators are highly porous, typically >40% porosity, approximately 25 µm thick and exhibit low ionic resistivity. Layered or composite separators are used as safety devices Binder materials are used to hold the active...

Pore Size, Shape , Distribution, and Tortuosity The separator pore size must be smaller than the particle size of the electrode components, i.e. the electrode active materials and any conducting additives. Most separator membranes contain submicron pore sizes that block the penetration of particles. Uniform distribution and a tortuous structure of the pores are also a requirement. Uniform distribution prevents uneven current distribution throughout the separator and tortuosity suppresses the growth of dendritic lithium. See pages 14 and 15 Zeta Potential To further understand the transport...

Electrolyte Analysis Liquid electrolyte plays a key role in commercial lithium-ion batteries to allow conduction of the lithium-ions between cathode and anode. The most commonly used electrolyte is comprised of lithium salt, such as LiPF6 in an organic solution. solution to prevent lithium dendritic formation and degradation of the solution. High purity is required to prevent oxidation at the electrode and to promote good cycle life. In addition to lithium salt, various additives are also included in the final electrolyte solution. These additives are mixed with the LiPF6 Zeta Potential...

Manufacturing and Failure Analysis Materials characterization during and prior to manufacturing is a critical control parameter to ensure the optimal operation of cell components and the final assembled battery. From raw materials to component manufacture and the assembled battery itself, material characterization plays a vital role in determining the desired electrochemical Particle Size/Particle Shape-Raw Materials Particle size and shape influences packing density which in turn affects electrode thickness and therefore energy density. It has been shown that the particle size distribution...

Performance Degradation Over the life of a cell, physical and electrochemical occurrences contribute to degradation in performance. This drop in performance is most notably recognized through capacity fade during charge and discharge cycling or by reduced shelf life. Expansion and contraction may cause interfacial stress that adversely effects the electrode performance, to the point that delamination may occur causing a reduction in contact between the electrode material and the current collector. Pore size changes can occur from this mechanical failure resulting in reduction in electrolyte...