Automotive Li-ion battery hidden danger hidden
China's new energy vehicles brought a wave of enthusiasm, is to have in terms of mobile communications and mobile audio-visual lithium batteries bring great convenience to be the most popular and concerns of the competition.
However, when more people in the mileage, battery life and even how to deal with other aspects of waste batteries brains, a very important fundamental problem seems to be ignored, that is - it is enough security?
March 1978, served in the U.S. oil company Exxon chemist (Engineer) Stanley - Weitinghanmu invention of lithium, probably did not think the next 30 years, the invention of technology to human life brought a huge change, and lithium, the lightest metal known in nature from human to become more intimate with them.
At that time, Weitinghanmu sulfur compounds to make titanium anode, lithium metal as anode, made of the world's first prototype of a lithium battery.
It works by lithium-ion battery positive and negative movement between the current cycle, in order to achieve charge and discharge process. Therefore, lithium battery, also known as lithium-ion batteries.
Decades, through continuous improvement of the anode and cathode materials, smaller, more and cheaper energy density of lithium batteries to be manufactured, the advent of mobile phones, to further promote its miniaturization and lightweight, and later common in the micro-electronic products, such as music players, even today be seen as being more efforts into a wave of choice for electric vehicles.
However, in recent years, cell phones and music players frequent the explosion seems to sound the alarm again - this brought convenience to people living things do not seem quite that safe. Is the manufacturer of the relaxed quality management? R & D are some elements of the battery changed? Storage capacity or the attention of people and neglects the security?
A cell phone lithium battery contains lithium metal less than 5g, an electric mini-cars the most original, if the rechargeable electrical 30kwh above, the lithium metal battery pack contains about 50kg or so, mobile phone battery will be very scared of the explosion is still a group of mini-cars In case the battery case, the consequences would be inconceivable.
China's lithium batteries have occurred after the installation of electric vehicles, parked in the garage at night suddenly caught fire, together with the vehicle with the ashes of the situation, a few months ago there have been spontaneous combustion phenomenon of hybrid buses, only to find and dispose of early, before major damage is not stuffed. Obviously, contingency planning, is the battery, electric vehicle industry responsibility.
In fact, the lithium battery explosion safety hazard exists, for many reasons, need to be cracked, but apparently all the elements of their own can not get away.
Usually a lithium battery cathode, anode, separator, electrolyte, monomer packing five major elements. At that time, Sony developed the first commercial lithium batteries, the cathode of lithium cobalt oxide lithium-made compounds, but the cobalt are rare, then use more of manganese, iron, vanadium, nickel, and polymer composite materials, Even the air as the medium of the electrode, different cathode materials, energy, security, operating voltage varies.
Negative from graphite and various mixed, synthetic, composite materials to play. Graphite elements space, storage space for lithium-ion lattice.
Charging, the cathode to the anode of lithium ion transfer most of the boxes, when the negative electrode of lithium ion on the excessive accumulation to a certain limit, the lithium ions will overflow and generate dendritic crystal growth and spread of these crystals, pierce the membrane, so that positive and negative exposure, so the short circuit occurred, and this time the short circuit will instantly release a lot of heat, so easy to heat and combustion of the electrolyte boiling up, the final explosion, known as "thermal failure." Besides high temperature, piercing, breakdown, metal shavings connectivity and vehicle collisions have become the squeeze on the battery positive and negative short-circuit thermal failure occurred reasons.
Thus, although now some use of solid polymer electrolyte in lithium batteries, no leakage due to the possibility of reducing the explosion, but the lithium battery is the outside world through an internal chemical reaction into electrical charge into the chemical energy stored to the battery, The same chemical energy by chemical reaction into electrical energy output, this process will produce temperature, once the temperature is too high, the danger will follow.
Moreover, lithium battery itself has a self-discharge characteristics, that is not charging the battery outside world, letting go of the conditions, it being within the extent of varying the speed of chemical reactions, the battery self-discharge rate performance, and vice versa, "the self-discharge rate "is high. The chemical reaction inside on the table would make a music player since the explosion occurred in the off state.
Heat charge and discharge characteristics of endothermic is a lithium battery, but sometimes too fast charging phenomenon also fever, it is too late because the chemical reaction energy into chemical energy, discharge the battery temperature is too late to chemical energy conversion into electrical energy caused, so charging management system generally unharmed, but the discharge, but will go wrong.
Based on this principle, lithium batteries should not be too large discharge current, if the current is too, too long duration, intense and may cause chemical reaction temperature, fever, and even caught fire and exploded.
In fact, publicity about the lithium battery can be quickly charged and fast discharge of the concept is relatively lead-acid batteries, just a little faster, but if the lithium battery charge and discharge exceeds the limit, risk may be lurking not far away.
As for how much current discharge lithium batteries in the end the right should be practical to set, but for automotive driving conditions, the instantaneous large current discharge are common, this is a test for lithium batteries.
Now, the charge-discharge process is controlled, through manufacturing process, metal powder, dust, wages, and so reduce the risk, but their chemical reactions within the battery currently difficult to control.
From this, in the course of lithium batteries is a miniature "volcano", scrapped after the lithium battery seems to be a "extinct." Understand the body as long as the dismantling scrapped, the "five elements" are complete, the chemical reaction will not be interrupted, but lower level, so a single lithium battery recycling will seal them as dangerous goods.
The principle of the analysis of the lithium battery, resulting in failure factors, developers, manufacturers need to recognize the dual lithium face of an angel and the devil, and the need to find a way to minimize security risks.
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