Which is better, lithium-ion battery or nickel-metal hydride battery? The difference between lithium-ion battery and nickel-metal hydride battery

NiMH batteries and lithium-ion batteries are widely used in the market. They are both pollution-free and environmentally friendly batteries, and are an important area for the development of new energy. So which one is better, NiMH batteries or lithium-ion batteries?

The difference between lithium-ion batteries and nickel-metal hydride batteries

Structurally, the positive electrode of a nickel-hydrogen battery is Ni (OH), the negative electrode is a metal hydride, and the electrolyte is a 6 mol/L potassium hydroxide solution. Lithium-ion batteries embed lithium ions into petroleum coke and graphite to form a negative electrode. The positive electrode materials are commonly LixCoO2, LixNiO2 or LixMnO4. The electrolyte composition is relatively complex, and LiPF6 + diethylene carbonate + dimethyl carbonate are mixed in proportion.

Nickel-metal hydride batteries are an important choice for hybrid electric vehicle (HEV) batteries due to their mature technology and good safety, but they are difficult to meet the needs of a higher degree of electrification; nickel- metal hydride lithium batteries currently dominate, mainly because the battery energy of existing hybrid vehicles is only 1-2kWh, which cannot be driven purely by electricity or the pure electric range is less than 3km.

In the longer term, NiMH cannot be used in PHEV and EV. This is mainly because the specific energy and energy density of NiMH cannot meet the requirements of PHEV and EV; the raw material Ni(OH) is expensive, and the cost of manufacturing high-energy batteries will be even higher; the development of NiMH battery technology is basically mature, and there is very limited room for improving battery performance and reducing costs.

NiMH batteries have the same memory effect as NiCd batteries, but the memory effect is much smaller than that of NiCd batteries. Therefore, it is not necessary to discharge the battery every time it is charged (because improper operation will damage the battery). It is only necessary to fully charge and discharge the battery once every three months to alleviate the memory effect.

The self-discharge rate of NiMH batteries is 25-35% (month), and that of lithium-ion batteries is 2-5% (month). NiMH batteries have a high self-discharge rate, while lithium-ion batteries have a very low discharge rate compared to them.

At present, the capacity of general NiMH batteries can reach 2900mAh (milliampere-hours, commonly referred to as mAh in mainland my country as r milliampere-hours). If not used for a long time, they will leak slightly corrosive and harmful liquids (which can be harmful to the human body or damage the device using the battery). Lithium-ion batteries have the potential to burn or explode if not used properly. Relatively speaking, NiMH batteries are the safest batteries.

The voltage of NiMH battery is 1.2V, and the voltage of Li-ion battery is 3.7V. Li-ion battery has better discharge and discharge performance.

Nickel-hydrogen batteries have low environmental pollution, the main ones being some acid and alkali waste gases, the harmful ones being HCI. If environmental protection measures are in place, there should be no problem.

Compared with nickel-metal hydride batteries, the advantages of lithium-ion batteries are mainly reflected in:

1. High specific energy and energy density, about twice that of nickel-hydrogen batteries, can greatly improve the endurance of electric vehicles . Higher power, low self-discharge, no memory effect, these characteristics can improve the convenience of using electric vehicles;

2. Low cost of raw materials;

3. There is a lot of room for technological improvement and cost reduction.

4. Volume: Rechargeable lithium-ion batteries are widely used in many new mobile devices because they are smaller (relatively), lighter, have lower self-discharge rate, and have no memory effect than ordinary nickel-cadmium/nickel-metal hydride batteries. The batteries of mobile devices such as mobile phones, laptops, PDAs, etc. that we usually use have been gradually replaced by lithium-ion batteries.

The memory effect of NiMH batteries is not very obvious, but it is a little bit. When you need to use it urgently, you don't have to discharge it before charging it. When you use it normally, it is best to discharge it before charging it.

5. Capacity: Lithium-ion batteries have high energy and are compact; the voltage of a single lithium-ion battery is three times that of a nickel-metal hydride battery; there is no memory effect and it can be charged whenever you use it. However, you cannot charge it after using it once, as too many charge and discharge times will affect the battery life. Lithium-ion batteries are not suitable for long-term storage, as they will permanently lose some of their capacity over time. It is best to charge 40% and store them in the refrigerator.

6. Charging method: The charging requirements of lithium-ion batteries are different from those of nickel-cadmium/nickel-metal hydride batteries. The voltage of a rechargeable lithium-ion battery cell is 3.6V (some battery blocks may be marked as lithium-ion batteries). The charging of lithium-ion batteries generally adopts the voltage and current limiting method. If you want to charge lithium-ion batteries independently, you should pay attention to the fact that its charging method is different from the constant current charging method used by nickel-cadmium/nickel-metal hydride batteries, and you cannot use ordinary nickel-cadmium/nickel-metal hydride battery chargers.

Although NiMH batteries and Li-ion batteries are different, they are both new-age energy batteries that have played an irreplaceable role in the advancement of human life! Objectively speaking, when weight becomes a key factor affecting product performance and battery maintenance can be done in a timely manner, using Li-ion batteries is a natural method, while when high power, good safety, high reliability and economical practicality are required, NiMH batteries will have more advantages.