9v alkaline battery.Analysis on BYD e6 battery technology

Today, the editor analyzes the core technology of the new e6 to see what technical highlights this car has? What technologies does it rely on to achieve an ultra-long cruising range of 450km?

Today, the editor analyzes the core technology of the new e6 to see what technical highlights this car has? And what technology does it rely on to achieve an ultra-long cruising range of 450km?

First of all, the e6’s battery pack takes into account both safety and performance.

In terms of performance, the new e6 follows the old lithium iron phosphate battery technology route, and the battery capacity is increased from 82kWh to 91kWh, thus effectively ensuring that the e6's pure electric cruising range reaches 450km. For most consumers, this is definitely a very satisfying number, and it basically eliminates the embarrassing situation of having to charge it after a day or two.

However, from the perspective of unit power consumption, the e6 clearly reflects the essence of relying on stacked batteries to increase mileage. The average driving range of 4.9 kilometers per kilowatt hour is far behind other competitors, even if it is not compared with the small pure electric Zhidou D2 , it is also at a disadvantage compared with the similarly compact Emgrand, BAIC EU260, and even Tesla, which has a more obvious accumulation of batteries.

The core reason for this phenomenon is that other competitors use ternary lithium-ion batteries, while BYD uses lithium iron phosphate batteries. Generally speaking, ternary lithium-ion batteries have higher energy density, while iron phosphate batteries The energy density of lithium is generally low.

Why does lithium iron phosphate have a low energy density? This starts with the battery structure. Usually the battery system (including the battery pack and BMS control system) is integrated into the vehicle, and the battery system can be decomposed into pACK, cells, and battery materials. A battery cell is mainly composed of positive electrode, negative electrode, electrolyte, separator and other materials.

These four materials each perform their own duties. During discharge, lithium ions and electrons escape from the negative electrode, and the electrons reach the positive electrode through the external circuit, while the lithium ions enter the positive electrode through the electrolyte. In the positive electrode, the lithium ions, positive electrode material, and electrons are reconnected. combined to complete current conduction. The purpose of the separator is to separate the positive and negative electrodes and prevent short circuits.

Therefore, the amount of battery discharge is determined by the positive and negative electrodes, which accommodate more active materials including lithium ions. Since graphite carbon materials are currently commonly used as negative electrodes, the specific capacity exceeds 350mAh/g, while the positive electrode materials are usually composed of lithium cobalt oxide, lithium iron phosphate, and nickel cobalt manganese (i.e. ternary lithium), and the specific capacity is usually lower than 200mAh/g. g. That is, negative electrode activity and positive electrode activity.

Therefore, the energy density of the battery is determined by the cathode material. The specific capacity of lithium iron phosphate is lower than that of nickel-cobalt-manganese ternary materials, so the unit power consumption of BYD e6 lags behind other competitors.

So the question comes again: Why does BYD use lithium iron phosphate? In fact, although the specific capacity of lithium iron phosphate is lower than ternary, it has the advantages of high safety, long life, and low cost.

Safety: The thermal stability of ternary materials is relatively poor. It will decompose at an external temperature of about 200 degrees and release oxygen, thereby fueling high-temperature fires in the battery. However, lithium iron phosphate only decomposes at 700°C, and even if it decomposes, it will not release oxygen.

Long life: At present, the 1C cycle life of ternary batteries is about 2,500 times, while the lithium iron phosphate battery is about 3,500-5,500 times, so the life span is longer and more stable.

Low cost: From the perspective of raw materials, the cost of lithium iron phosphate is about 40-50% of that of ternary materials, so it can significantly control costs. Calculated based on 91kWh, the battery system cost of e6 is about 100,000 yuan. If ternary materials are used, the cost price will soar to 160,000-180,000 yuan.

Therefore, after comprehensive consideration of various factors such as energy density, safety, and cost, BYD e6 chose lithium iron phosphate batteries instead of ternary materials. This is a compromise and consideration that does not completely succumb to performance.

Secondly, BYD’s battery intelligent temperature control system is a conscientious configuration

Since the charging and discharging characteristics of lithium-ion batteries are closely related to temperature, too high or too low temperatures can cause additional power loss, especially in winter, when battery power will shrink significantly under extremely low temperatures. To this end, BYD e6 has added a constant temperature control system to the old model, which can keep the battery at normal temperature and work at the optimal temperature, thus effectively preventing unexpected situations such as battery failure in low-temperature environments. This is commendable.

The above are the core technologies that enable BYD e6 to achieve a pure electric cruising range of 450km. However, the editor must tell readers the following two things to pay special attention to.

First, the charging time of BYD e6 will be relatively long. Because it has a battery pack of up to 91kWh, the use time will be more than 2 hours when the input voltage is 380V three-phase AC and the charging cabinet power is 40KW. If a household 220V power supply is used, the charging time will be as long as 8-10 hours to fully charge.

Second, the battery pack of this car is installed on the chassis and is relatively protruding, so the ground clearance is only 138mm. This height is equivalent to a small bottle of mineral water. Therefore, be sure not to drive on uneven roads when driving. Not to mention rural roads, you need to understand that your battery pack can be worth 100,000 yuan!