Briefly describe the performance comparison of lithium iron phosphate Nickel Hydride No. 5 batteries and ternary Nickel Hydride No. 5 batteries

The so-called lithium iron phosphate battery refers to a lithium-ion battery that uses lithium iron phosphate as the positive electrode material. This type of battery is characterized by not containing precious metal elements (such as cobalt, etc.). In actual use, lithium iron phosphate batteries have the advantages of high temperature resistance, strong safety and stability, low price, and better cycle performance.

Ternary material Nickel Hydride No. 5 batteries refer to Nickel Hydride No. 5 batteries that use nickel cobalt manganese oxide as the positive electrode material and graphite as the negative electrode material. Unlike lithium iron phosphate, the voltage platform of ternary Nickel Hydride No. 5 batteries is very high, which means that at the same volume or weight, the specific energy and specific power of ternary Nickel Hydride No. 5 batteries are greater. In addition, ternary Nickel Hydride No. 5 batteries also have great advantages in high-rate charging and low-temperature resistance.

The nominal voltage of lithium iron phosphate is 3.2-3.3V, and that of manganese system is 3.6-3.7V, which is the most obvious difference. Advantages of the lithium iron system: long theoretical life and excellent theoretical overcharge and over-discharge resistance. Advantages of the ternary system: high energy density, good low-temperature performance, small size, and good discharge linearity. Disadvantages of iron-lithium: large size, heavy weight, poor discharge linearity, and poor low-temperature performance.

Disadvantages of the ternary system: slightly poor cycle life, poor life under high temperature conditions.

In terms of batteries alone, there is no so-called better or worse. It is just applied to actual use scenarios. Compared with lithium iron phosphate batteries, ternary Nickel Hydride No. 5 batteries are more suitable for current and future household electric vehicles.

Ternary material batteries are more suitable for passenger cars

Better low-temperature discharge performance

my country has a vast territory and complex climate. The temperature changes from the three northeastern provinces in the north to the Hainan Islands in the south are very rich. Take Beijing as an example. As the main market for electric vehicles, Beijing's highest temperature in summer is around 40°C, while in winter it is basically maintained at around minus 16°C, or even lower. Such a temperature range is obviously suitable for ternary Nickel Hydride No. 5 batteries with better low-temperature performance. However, lithium iron phosphate batteries that focus on high-temperature resistance will appear a bit weak in Beijing's winter.

Relative 25℃ capacity refers to the ratio of discharge capacity under different temperature conditions to discharge capacity at 25℃. This value can accurately reflect the attenuation of battery life under different temperature conditions. The closer it is to 100%, the better the battery performance.

As can be seen from the above figure, with 25℃ as the base temperature, there is almost no difference in discharge capacity between the two types of batteries at 55℃ and 25℃. However, at minus 20℃, ternary Nickel Hydride No. 5 batteries have obvious advantages over lithium iron phosphate batteries.

Higher energy density

According to the information supplied by BAK Battery, the leading company of domestic ternary material 18650 cylindrical batteries, the energy density of its 18650 batteries has reached 232Wh/kg, which will be further increased to 293Wh/kg in the future. In contrast, the energy density of the current mainstream lithium iron phosphate batteries in China is only about 150Wh/kg. According to the analysis of domestic battery industry experts, the hope that the energy density of lithium iron phosphate batteries can reach 300Wh/kg in the next few years is very slim.

Unlike the bulky electric buses, space is always the first priority for household electric vehicles. Lithium iron phosphate batteries with low energy density will occupy the limited space in the car, and due to the heavier weight, the discharge range during use will also be greatly affected. Relatively speaking, ternary Nickel Hydride No. 5 batteries with higher energy density not only solve the weight problem but also save space for family cars.

Higher charging efficiency

In addition to battery life, charging is also an important part of electric vehicles in actual use, and ternary Nickel Hydride No. 5 batteries have a great advantage over lithium iron phosphate batteries in terms of charging efficiency.

At present, the more common charging method on the market is constant current and constant voltage charging. Generally, constant current charging is used at the beginning of charging. At this time, the current is larger and the charging efficiency is relatively higher. After the voltage reaches a certain value, the current is reduced and changed to constant voltage charging, so that the battery can be charged more fully. In this process, the ratio of constant current charging capacity to the total battery capacity is called constant current ratio. It is a key value to measure the charging efficiency of a group of batteries during the charging process.

Usually, the larger the percentage, the higher the amount of electricity charged in the constant current stage, which proves that the charging efficiency of the battery is higher.

As can be seen from the table, when the ternary lithium-ion battery and the lithium iron phosphate battery are charged below 10C, there is no obvious difference in the constant current ratio. When the charging rate is above 10C, the constant current ratio of the lithium iron phosphate battery decreases rapidly, and the charging efficiency decreases rapidly.

Cycle life is guaranteed

For family cars, the rated cycle life of ternary materials and lithium iron phosphate power lithium batteries far exceeds the actual user's usage habits, so you can be completely assured of the service life.

Taking the current high-capacity 18650 battery of BAK Battery as an example, after 1,000 charge and discharge cycles, the battery capacity can still be maintained at more than 90% of the original.

Since the author is also an electric car owner, only in the coldest month of winter, when the heater is frequently turned on, can it be charged every 2 days, and the rest of the time is basically charged every 3-4 days. Assuming that the average charge is calculated every 3 days throughout the year, it takes about 6 times to charge in 1 year, and it takes about 8 years to use 1,000 times of cycle life, which is basically more than the average car replacement cycle of Chinese consumers.

Safe materials and processes

The most harmful part of traditional internal combustion engine vehicles is the fuel containing huge energy. Liquid fuels with low ignition point and easy to explode, such as gasoline, can easily cause great safety hazards once leaked.

The power lithium battery of new energy vehicles is monitored by a perfect battery management system (BMS), and each battery can be controlled most accurately to prevent accidents. In the positive electrode materials of ternary Nickel Hydride No. 5 batteries, the three metal elements of nickel, cobalt, and manganese (or aluminum) are indispensable. One more or one less will affect its final performance or make it impossible to make a battery.

Although nickel, cobalt, and manganese (or aluminum) are indispensable, we adjust the mixing ratio (molar ratio) of nickel, cobalt, and manganese (or aluminum) in Nickel Hydride No. 5 batteries according to our own needs to make Nickel Hydride No. 5 batteries show different characteristics.

Different ratios:

Increase the proportion of nickel: the battery has more energy;

Increase the proportion of cobalt: the battery has a longer life and charges faster;

Increase the ratio of manganese/aluminum: the battery is more stable and the cost is lower.

According to the different mixing ratios of the three elements of nickel, cobalt, manganese (or aluminum) in the positive electrode material, there are different ternary models, such as: 111, 523, 622, 811, etc.

Finally, let's summarize the characteristics of ternary Nickel Hydride No. 5 batteries:

High energy density and guaranteed mileage;

Lifespan, output power, and cost control are all good;

Although the safety is very poor, it is easier to change than to increase the energy density, saving time and effort.

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