The safety comparison of lithium cobaltate, lithium manganese ate, lithium iron phosphate and polymer lithium battery is introduced

From the current use of lithium ion battery mainstream technology, there are mainly lithium cobalt acid, lithium manganese acid, lithium iron phosphate battery and polymer lithium battery types, their different materials and structural characteristics will affect the battery preparation technology and use, thus bringing different safety.

First, lithium cobalt acid battery: lithium cobalt acid battery safety is poor, the cost is very high, mainly used in small and medium-sized models of batteries, widely used in notebook computers, mobile phones, Mp3/4 and other small electronic equipment, nominal voltage 3.7V.The most important characteristic of the preparation is that a large number of lithium ions remain in the positive electrode after being fully charged. That is to say, the cathode on hold more adhesive on the anode of lithium ion, but in the condition of overcharge, the positive excess lithium ion will still be on the swim to the cathode, because can't hold on the cathode will form a metal lithium, because this kind of metallic lithium is dendritic crystal, thus known as dendrite, the dendrite once formed, will provide the opportunity to Pierce the diaphragm, diaphragm Pierce will form the internal short circuit.
Since the electrolyte is mainly composed of carbonates, lightning and boiling points are low, so they can burn or even explode at higher temperatures. It is easy to control the formation of lithium dendrites in small capacity lithium batteries. Therefore, lithium cobalt oxide batteries are limited to small capacity batteries such as portable electronic devices, but can not be used in power batteries.

Two, polymer lithium battery: in the actual available theory than the energy has been greatly improved, relative to lithium cobalt acid battery, can better play the role of high capacity, but from the material, polymer lithium battery also uses lithium cobalt acid and organic electrolyte, so it does not fundamentally solve the safety problem. From the point of view of use, if the battery short circuit will produce too much current. Polymer lithium battery electrolyte for colloid, not easy to leak, also ruled out the possibility of leakage, but will therefore occur more violent combustion, therefore, spontaneous combustion is polymer

Three, lithium manganese acid battery: lithium manganese acid battery material has certain advantages, it can ensure that under full charge state, the positive lithium ion can be completely embedded in the negative carbon hole, rather than like lithium cobalt acid will have a certain residual in the positive electrode, which fundamentally avoid the generation of dendrite. Because the stable structure of lithium manganese oxide makes its oxidation performance much lower than lithium cobalt oxide, even if the external short circuit (rather than internal short circuit), it can basically avoid the precipitation of lithium metal caused by combustion and explosion.
Lithium manganate battery not only has a huge market space, but also has a huge technical development space. Compared with ternary materials, lithium iron phosphate and other cathode materials, lithium manganate has the advantages of abundant resources, low cost, no pollution, good safety, good rate performance and so on. It is an ideal cathode material for power battery.

Four, lithium iron phosphate battery: this is an ideal power battery, can be used for power tools and power cars, the theoretical capacity of lithium iron phosphate battery is 170mAh/g, the actual capacity of materials can reach 160mAh/g. In terms of safety, the P-O bond in lithium iron phosphate crystal is stable and difficult to decompose. Even at high temperature or overcharging, it will not collapse and give off heat or form strong oxidizing substances like lithium cobalt oxide, so it has good safety. The thermal peak of lithium iron phosphate battery can reach 350℃-500℃, while lithium manganese acid and lithium cobalt acid battery is only about 200℃.
Lithium iron phosphate battery safety performance is very good, not prone to combustion and explosion and other dangers. With reasonable structural design, the safety of the battery is further improved, so the battery does not burn or explode in the case of impact, needling, short circuit and so on.

Methods for safety assessment of lithium batteries

Safety assessment instrument for lithium batteries
In the safety research of lithium battery, calorimeter is the most important instrument. The most commonly used calorimeter is the accelerated calorimeter. ARC is a new thermal analysis instrument recommended by the United Nations for the assessment of dangerous goods. It can provide time-temperature-pressure data of chemical reactions under adiabatic conditions.
Methods for ARC safety assessment
By accurate temperature tracking, ARC avoids heat exchange between the sample under test and the environment, thus providing a near-adiabatic environment for testing and analyzing the exothermic behavior of the sample under test. In addition to testing thermal runaway, Arc can provide an adiabatic environment, using Arc with DC constant current source, charging and discharging equipment, can test the specific heat capacity of the battery and the adiabatic temperature rise in the process of charging and discharging.
The safety of lithium battery is one of the most important problems in power battery. The safety of the battery has a lot to do with the design of the battery pack and the conditions of abuse. For a single battery, safety is not only related to the cathode material, but also to the anode, diaphragm and electrolyte.
The above is the safety comparison of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate and polymer lithium battery. In my opinion, the safety of lithium battery needs to be studied from the four aspects of cell, PACK, system and functional safety. If the safety of lithium-ion batteries is not fundamentally addressed, sales in the market will certainly go stumbling.
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