Nickel-metal hydride batteries and lithium-ion batteries are widely used in the market. They are non-polluting and environmentally friendly batteries and are important areas for new energy development. So which is better, Ni-MH battery or Li-ion battery?
The difference between lithium-ion batteries and nickel-metal hydride batteries
Structurally, the positive electrode of the nickel-hydrogen battery is Ni(OH), the negative electrode is metal hydride, and the electrolyte is 6mol/L potassium hydroxide solution. The lithium ion battery is a negative electrode by inserting lithium ions into petroleum coke and graphite. The positive electrode material is usually LixCoO2, LixNiO2 or LixMnO4. The electrolyte composition is relatively complex, and LiPF6 + diethylene carbonate + dimethyl carbonate is mixed in proportion.
Due to its mature technology and good safety, nickel-metal hydride batteries are an important choice for hybrid electric vehicle (HEV) batteries, but it is difficult to meet the demand for higher electrification; nickel-metal hydride lithium batteries currently dominate the existing hybrid vehicles. The energy of the battery is only 1-2kWh, and it cannot be driven by pure electric power or with a battery life of less than 3km.
In the longer term, NiMH cannot be applied to PHEVs and EVs. Mainly because the specific energy and energy density of nickel-hydrogen 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 higher; the development of nickel-hydrogen battery technology is basically mature, and battery performance is improved. And the room for cost reduction is very limited.
Nickel-metal hydride batteries and nickel-cadmium batteries have the same memory effect, but they are much smaller than nickel-cadmium batteries. So there is no need to perform a discharge operation every time it is charged (because improper operation will damage the battery), it only needs to be fully charged and discharged once every three months to alleviate the memory effect.
Nickel-metal hydride batteries are 25-35% (months), and lithium-ion batteries are 2-5% (months). Nickel-metal hydride batteries have a high self-discharge rate, while lithium-ion batteries have a very low discharge rate.
At present, the capacity of general nickel-hydrogen battery can reach 2900mAh (mah-hour, which is commonly called mAh in mainland my country as r milliamp-hour). device), and lithium-ion batteries have a chance of burning or exploding if they are not in use. Relatively speaking, nickel-metal hydride batteries are the safest batteries.
The voltage of nickel-hydrogen battery is 1.2V, and the voltage of lithium-ion battery is 3.7V. The lithium-ion battery has better discharge and discharge performance.
Nickel-metal hydride batteries have low environmental pollution, mainly some acid and alkali waste gas, and the most harmful one is HCI. There should be no problem if environmental protection measures are in place.
Comparing lithium-ion batteries with nickel-metal hydride batteries, the advantages are mainly reflected in:
1. High specific energy and energy density, about twice that of nickel-metal hydride batteries, which can greatly improve the battery life of electric vehicles. Higher power, small self-discharge, and no memory effect can improve the convenience of electric vehicles. ;
2. Low cost of raw materials;
3. There is a lot of room for technological improvement and a lot of room for cost reduction.
4. Volume: Rechargeable lithium-ion batteries are widely used in many new mobile devices because they have the advantages of small size (relatively), light weight, low self-discharge rate and no memory effect compared with ordinary nickel-cadmium/nickel-metal hydride batteries. . The batteries of mobile phones, notebook computers, PDAs and other mobile devices we usually use have been gradually replaced by lithium-ion batteries.
The memory effect of NiMH batteries is not very obvious, a little bit. When it is urgent to use, it is not necessary to discharge the light and then recharge it. It is best to discharge the light and then fill it in normal use.
5. Power: Lithium-ion battery has large energy and small battery; the voltage of a single lithium-ion battery is 3 times that of nickel-hydrogen battery; there is no memory effect, and it can be charged at any time. But it can't be charged at a time, so too many times of charging and discharging will affect the life of the battery. Lithium-ion batteries are not suitable for long-term storage, as they will permanently lose part of their capacity over time. It is best to store it in the freezer of the refrigerator after charging 40%.
6. Charging method: The charging requirements of lithium-ion batteries are different from those of nickel-cadmium/nickel-metal hydride batteries. The single-unit voltage of rechargeable lithium-ion batteries is 3.6V (some battery blocks may be called as lithium-ion batteries). Lithium-ion batteries are generally charged by the voltage-limiting and current-limiting method. If a friend wants to charge the lithium-ion battery independently, it should be noted that its charging method is different from the constant current charging method used by nickel-cadmium/nickel-hydrogen batteries and cannot be used. Charger for ordinary NiCd/NiMH batteries.
Although nickel-metal hydride batteries and lithium-ion batteries are different, they are all energy batteries in the new era, and they have played an irreplaceable role in the progress of human life! Objective evaluation, when the weight becomes a key factor affecting the performance of the product and the battery can be maintained in time, the use of lithium-ion batteries is a matter of course, and when high power, good safety, high reliability and economical practicability are required , NiMH batteries will be more advantageous.
