The magnification increases: what happens to improve lithium-ion battery multiplier performance

Forfatter: Iflowpower – Leverandør av bærbar kraftstasjon

For power lithium-ion batteries, we pay more attention to the most energy density and power density, energy density is related to the vehicle's battery life, and the power density is related to electric vehicles. Dynamic performance. How to improve the lithium-ion battery multiplier performance, the designers have their own unique insights, and the small boldness is here to talk about some ideas that I enhance lithium ion battery multiplier performance, hoping to be able to throw brick.

1. Material selection is usually the improvement of the power lithium-ion battery multiplier performance is from the choice of materials. For example, we have previously in the article "ionic conductive, electronically conductive stupid is unclear? You want to know all!" The ionic and electron conductivity of the current high-nickel-based three-membered material and the traditional cobalt-free material [1], at normal temperature 20 ° C, the electron conductivity of the LCO material is only 5x10-8s / cm, while NCM111 The electron conductivity of the material can reach 2.

2x10-6s / cm. As the nickel content is further improved, the electronic conductivity of the ternary material is also clear, and the electronic conductivity of the NCM8111 material is more than 4.10-3s / cm, ion conductance.

In terms of the same trend, the LCO material is only 2.3 x 10-7 s / cm at 20 ° C, while the NCM111 material ion conductivity is 3.2X10-6S / cm, NCM532 bits 1.

7x10-3s / CM, NCM622 bits 3.4x10-3s / cm, NCM811 materials achieve 6.3x10-3S / cm, so that the ternary material is seen from electronic conductivity or ion conductivity, especially high-nickel termination or NCA The material is more suitable for the magnification of lithium-ion batteries.

Of course, in addition to these intrinsic characteristics of the material, the magnification performance is also affected by multiple factors such as morphology. For example, the material surface area of ​​small particles is larger, and the diffusion distance between Li + internal in the particles. Short, therefore theoretically have better magnification performance.

The choice of negative electrode materials is relatively large, such as the intermediate phase of small particles, a good performance in the magnification performance, Australian Federal Science and Industrial Organization (CSIRO) Energy Technology SrsiVakkumar, Jynerkar, Ag Pandolfo [5] Assessing the graphite material of different types and particle sizes, the smaller the particle size of the graphite material, the higher the magnification performance, and the thickness of the graphite surface coating can also improve the magnification performance of the graphite negative electrode. However, the reduction in particle size also brings a series of problems, such as the decrease in reversible capacity and decrease in compaction density, and also declares that although the above measures can improve the discharge magnification performance of the graphite negative electrode, it is difficult to effectively improve graphite negative electrode. Charging magnification performance.

The Li4Ti5o12 material itself has a higher Li + diffusion coefficient (10-16-10-15m2 / s) [2], while the lithium titanate ion battery material often produces nanoscale particles because of the low electrical conductivity. Further, the active area is further increased, and the diffusion distance of Li +, the lithium titanate ion battery thus has very excellent magnification performance, which can achieve rapid charging, which is also the original source of Dong Mingzhu to see Yinlong, but there is a lithium titanate material The voltage platform is 1.55V, theoretically reversible capacity is 170mAh / g, resulting in a low energy than energy, seriously affects the battery life of electric cars, which also leads to the root cause of Yinlong to fall into the crisis.

Xiao He. In order to solve these problems in terms of lithium titanate, it retains the advantages of high-magnification performance, and scientific research workers have done a lot of effort. Japan Toshiba [3] developed niobium titanium oxygen NTO new negative electrode material, reversible capacity of the material But up to 341mAh / g is much higher than the LTO material, close to graphite materials, but with high pressure real density, the volume energy density is twice as the graphite negative electrode, and the material also retains fast charging characteristics, from 0% SOC charging to 90% SOC is just 6 minutes, almost perfectly satisfied with electric car demand, current Toshiba has announced that the SOJITZ, and Brazilian mining company CBMM has reached a cooperation agreement, jointly developed the material.

As the World Excellent School, the University of Cambridge is also committed to developing high-capacity, high-performance high-performance lithium-ion battery negative electrode materials. In an article published in Nature, Kentj.griffTh [4] analyzes the latest research of Cambridge University.

Results: NB16W5O55 and NB18W16O93 materials, these two materials can be reversible in C / 5 times over 200mAh / g, and the diffusion coefficient of Li + in both materials reaches 10-13-10-12m2 / s, which is much higher than LTO. 10-16-10-15m2 / s) material, can achieve excellent magnification performance on the size of the micron particle particle, but larger particles not only reduce the area of ​​the active material / electrolyte, which reduces the occurrence of side reactions, but also It has greatly added the compaction density of the material, so the two materials are exceptionally excellent in unit volume capacity, rolling all negative electrode materials. 2.

Formulation optimization determines another key to the magnification of lithium-ion battery in the battery formulation, existed "ionic conductive" and "electron conductive" in the lithium ion battery, in which ion conductivity includes Li + in electrolyte, The diffusion of the internal pore and the active substance inside the active material, the electron conductive is electrically conductive between the active material particles, and the electron conductive electron conductive can also be divided into "short-range conductive" and "long-range conductive", such as a conductive agent represented by carbon black. It is responsible for the short-range conductivity, the conductive agent represented by carbon fiber and carbon nanotubes is responsible for long-range conductivity. The magnification performance of lithium-ion batteries is a comprehensive embodiment of a conductive form.

The key to Samanthal.morelly, Drazer University, USA, the key to affecting lithium-ion battery is not what we usually think "Ion diffusion "The process, more is to rely on electron conductivity, such as the magnification of the electrodes added to 3% carbon black, is divided into 2.5% electrodes, but according to the" ion transmission "limit theory, more charcoal black means More 蜿蜒 通, in turn reduces the magnification performance of the lithium ion battery, and the research statement is compared to the long-range electrical conductive, the short-range conductive of the carbon black supplied to the surface of the NCM particles and the magnification performance of the battery of lifting lithium ions.

Used. It is not difficult to achieve high-band performance and difficult, difficult, difficult to compare each other, generally compaptible, and a balance between the two is very difficult, and it is very difficult to find a balance between the two is very difficult. Kazuakikisu, Japan, Tokyo University of Ranges, etc.

When the compact density is too high, the electrode porosity will drop sharply, resulting in new ion diffusion impedance, while the compact density will result in the new increase of contact impedance, therefore only suitable compaction density can guarantee lithium Excellent interval performance of ion batteries also take into account the characteristics of high energy density. 3. Selection of battery structure Related to multiplier batteries The temperature during the discharge process is also a very important problem.

The lithium-ion battery will have a lot of heat during large current discharge, and the accumulation of heat inside the lithium-ion battery. Resulting in elevation of temperature, there is a large temperature gradient, so the internal decay of the lithium ion battery is inconsistent, affecting the life of the lithium-ion battery. How to choose a suitable structure is especially important, Germany's STEPHANKOSCH et al.

[8] through the two-dimensional electric-thermolatized model to the shape and position of the lithium ion battery ears to large-size lithium ion batteries The impact of thermal characteristics has found that the width of the ears and the thickness of the current collector will affect the temperature distribution of the lithium ion battery during the discharge process. The narrower the ear, the less the collector, the temperature distribution in the battery is not average Big, and also find that it is possible to effectively reduce the unevenness of the internal temperature of the battery during the discharge during both ends of the battery on both ends of the battery. By selecting a suitable material, formula, and structures can reduce the impedance and polarization of the battery interior when the lithium ion battery is discharged at a large rate, reduce the unevenness of the temperature, and effectively enhance the multiplier performance of the battery.

The improvement of the magnification performance is a comprehensive engineering. From the comprehensive consideration of multiple factors, Xiaobian is based on the nine bull and a hair, and the knowledge is limited to some obvious, I hope that all the friends criticize and correct it.