Damage mechanism and failure warning of lithium battery

　　Author ：Iflowpower – Portable Power Station Supplier

0 Introduction Battery burst failure is a major safety hazard in the backup power supply system, how to prevent battery pack bursts is challenging in battery maintenance technology. At present, the unpredictability of the battery burst failure has become the driving force of the research battery fault warning technology. The key to achieving battery failure is to find the best warning parameters.

Obviously, the best warning parameters must have the following three features, that is, highly correlated with the battery failure, repeatable measurement, comparable. Battery aging theory is to guide battery design, manufacturing and improvement the theoretical basis, but the research object of aging theory is important for battery overall performance, and battery failure is important based on battery differences. Therefore, battery aging theory does not apply to battery styles Analysis and research of failure, this disclosure of highlighting the idea of ​​various battery fault warning methods.

Existing engineering practical methods, whether it is a monomer voltage method or a circuit current + monomer voltage method, or a large current discharge method or a fast capacity test method, there is no implies with battery capacity as an early warning parameters, but actually The battery capacity is neither directly repeated measurement (such as a regular capacity discharge test), nor has indirect repetitive measurement (such as by measuring the end voltage or internal resistance calculation capacity). In order to get rid of battery aging theory, the battery warning ideas is urgently needed to re-examine battery safety countermeasures from a new perspective, in order to establish the theoretical basis for finding the best warning parameters, this is the problem to be solved by battery injury theory. 1 Battery injury mechanism 1.

1 Battery damage Meaning Interpretation of common warnings to be harmful to batteries, can be further scientific as: overcharged or overprints will cause irreversible electrochemical reactions outside the energy storage reaction, this design The irreversible reaction will damage the original structure and energy storage capacity of the battery. This can be imposed on battery damage: over-filled damage to damage to the battery structure and energy storage capacity. On the surface, this meaning is not significantly different from battery aging theory and battery application common sense.

However, this meaning will naturally lead to two truly meaningful issues: 1) A well-established existing standard system in engineering practical will prevent Battery damage? 2) After the battery damage occurs, what kind of repeatable measurement has been left in the battery, can it compare the physical quantity change? 1.2 Good existing standard system Meaning battery failure may originate from artificial mistakes, or it may originate from equipment failure, these reasons are not research objects in battery injury, and battery damage theory is more concerned about the non-prevention of battery self failure. In order to exclude all kinds of non-payment factors, you must first mean a good existing standard system.

A intact existing standard system should include: a real power device that is fully qualified, a set of real battery packs that are completely qualified by the monomer and connected according to the procedures, and have a qualified management and maintenance personnel executing one Strict maintenance procedures, in short, this should be an impeccable, but it is a standard system in reality. So, is there a battery damage to such a good existing standard system? 1.3 Local monomer overrunction (monomeric microjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj) 1) Battery group parameter 100 segment 2V, nominal capacity 100A·H, where 1 actual capacity is 97A·H, the rest of the 99th actual capacity is 100A·H; 2) Power supply device parameters conventional voltage closed loop control mode, all of which are fully charged conversion set voltage = 240.

00V (execution error = 0, monomer = 2.400V), the tetan of discharge termination = 170.00V (execution error) = 0, monomer = 1.

700V). When the system is run between all charge and discharge, it will inevitably appear two special time periods, ie (1) will appear in the first special period of time, and the starting point time is 97A.·H battery cell voltage> 2.

400V, and total voltage 240.00V (at this time, the power supply will continue to charge), the end point time is a total voltage = 240.00V (at this time, the power supply device exactly performs a full-fire switching).

Depending on the meanings of battery damage, 97A·H batteries run in the special time period, while other 99th 100A·The H battery is running within the security range. (2) The second special time period will appear under the discharge operation, and the starting point time is 97A·The H battery monomer voltage is 1.700V, and the total voltage is> 170.

00V (at this time, the power supply will continue to discharge), the end point time is the total voltage = 170.00V (this time the battery pack is terminated). At this special time section 97A·H 's battery is running over the excess state, the remains 99 sections 100A·The H battery is still running within the security range.

The objective existence of these two special time periods, that is, (1) The difference between the real system and this example is nothing more than the size of the capacity, and the size of the capacity only changes the length of the special time period, does not affect The existence of the special time period; this example shows that the battery pack does have an inner security hazard, indicating that there is an inevitably inner connection between battery damage and battery bursts. (2) Good equipment, accurate control does not prevent the occurrence of battery damage, but this individual battery over-filled is covered under holistic safe operation, quantitatively, the ratio of damage only 1%, injury time Less than 3%. (3) Of course, a 1% damage ratio, or 3% damage time is not enough to threaten the safety of the entire backup power supply system, in order to count the micro-damage injury, but as long as it is repeated in the operation of the backup power supply system This kind of fine damage process will be repeated.

In other words, the process of microsurizing is actually flooded to the full process of the backup power supply system. (4) Differential damage from the battery parameters, the consequences of primary microwas injury is the damage and energy storage capacity of the battery, which will further increase the monomer difference between the battery. This consequence has become the next time.

The cause of the micro-injury, it is clear that there is a vicious circle of mutual causal relationships, thereby impossible to inquire: the consequences of battery damage continue to deepen during a secondary micro-loss, until the battery is completely invalid, the continuation of the failure process may run Conditions, but must be accelerated after multiple injuries to deteriorate until the inevitable result of failure. 1.4 Mechanical Fracture Model Case Comparison for the image understanding of the battery packs that belong to the electrical field, the mechanism of the sudden failure is caused by the mechanism of sudden failure, and the fracture model of the mechanical field can be used to make a simple class ratio: a battery pack, a spring steel sheet with a mechanics.

(Leaf spring); the difference in the parameters of each battery group, the same, the unevenness of the leaf section;.