Can GAC's latest battery test really solve the lithium battery problem?

Recently, the battery acupuncture test of Guangzhou Automobile Magazine has pushed the safety of new energy batteries to the forefront. The reason is not that there is a rollover phenomenon in the test, but that people generally express different views on this acupuncture test.

This "acupuncture" is not another "acupuncture"

First of all, it should be admitted that acupuncture test is the most important means in battery safety test. So far, among more than 300 safety tests of lithium batteries, acupuncture is recognized as the most stringent test. If a manufacturer can pass this test, it is absolutely commendable.

However, the 20 15 edition of National Safety Requirements for Power Batteries for Electric Vehicles (the old national standard) and the 2020 edition (the new national standard) have completely different purposes, standards and test methods for acupuncture test. What I said earlier is the old version of acupuncture test, which is aimed at the requirements of acupuncture test for single cells.

But because this test is too strict, only a few enterprises in the industry can pass, and most enterprises can't. Therefore, on October 24th, 2065438+2008/kloc-0, the Ministry of Industry and Information Technology issued a new draft of national standards, which cancelled the requirement of single cell acupuncture test.

The new edition, the 2020 edition (the new national standard), was officially implemented from this year 1. It is no longer required to test the single battery, but to protect and control the thermal diffusion of ternary lithium battery after thermal runaway, so as to pass the new national standard. The whole package test is used for card battery test. Single batteries are separated by "magazines" to form a safety cabin for thermal management and rapid cooling of batteries with heat loss.

This is why the magazine battery still emits heat and smoke during the test. Most brands in the market can actually block heat conduction through physical partitions. As long as electric vehicles pass the new national standard, most of them use this idea, and GAC is not the only one.

This is the problem. Since it is feasible to separate batteries, should safety be guaranteed? In my opinion, obviously, as a single battery, the problem of thermal runaway has not been solved (the temperature of magazine battery reaches 686 degrees after acupuncture), and it is still a ammunition with the risk of thermal runaway at any time. Moreover, the protection of the battery system has the risk of aging failure, which has not been solved at all, and the risk is still great.

Previously, BYD's blade battery also passed the battery needle test, which was indeed tested according to the old national standard method. In Ai 'an, GAC adopted bare needle test of battery cells instead of full package test. Obviously BYD's blade battery is more convincing. Can the battery needle test of Guangzhou Automobile Magazine really solve the safety problem of lithium batteries?

In short, the new national standard actually admits that the thermal runaway of the battery will occur, and it is difficult for everyone to solve the thermal runaway of the ternary lithium battery. Now the real test index of the new national standard is changed to "escape time", that is, after the battery is out of control, passengers should be allowed to escape for not less than 5 minutes. At the 202 1+ 1 committee of electric vehicles 100 people, BYD called for extending the national standard escape time to 30 minutes.

In addition, GAC's magazine battery puncture test did not announce whether the battery was 523, 622 or 8 1 1. Popularize it first. At present, ternary lithium batteries are divided into three types: 523, 622, 8 1 1, which respectively represent the proportions of nickel, cobalt and manganese in the cathode materials of ternary lithium batteries. The higher the proportion of nickel, the greater the energy density of the power battery pack. But the higher the nickel content, the worse the thermal stability of the battery, that is, the easier it is to get out of control. This is also the cause of frequent battery spontaneous combustion accidents in recent years, with 8 1 1 power batteries being the majority. The market gradually began to avoid the high-nickel 8 1 1 ternary lithium battery, and even began to regress, using the low-nickel 523 ternary lithium battery many years ago.