What is a nickel-metal hydride battery?
Nickel-metal hydride (NiMH) batteries are high-performance rechargeable batteries. They are classified into high-voltage and low-voltage types. The positive electrode active material is Ni(OH)₂ (called the NiO electrode), the negative electrode active material is a metal hydride, also known as a hydrogen storage alloy (the electrode is called the hydrogen storage electrode), and the electrolyte is a 6 mol/L potassium hydroxide solution.
What is a lithium battery?
Lithium-ion batteries are a type of battery that uses lithium metal or lithium alloys as the positive/negative electrode materials and a non-aqueous electrolyte solution. Lithium-ion batteries can be broadly classified into two categories: lithium metal batteries and lithium-ion batteries. Lithium-ion batteries do not contain metallic lithium and are rechargeable.
Which is better, nickel-metal hydride batteries or lithium batteries?
Both nickel-metal hydride (NiMH) and lithium-ion (LiMH) battery chargers are designed based on voltage, but their charging solutions differ depending on whether the battery has a memory effect. The advantages and disadvantages of the two products are as follows:
1. Advantages and disadvantages of nickel-metal hydride batteries
Advantages: Low price, highly versatile, high current output, environmentally friendly and stable.
Disadvantages: Heavy weight, short battery life.
For the same volume, nickel-metal hydride (NiMH) batteries have a higher capacity. For example, the nominal capacity of a common AA battery can reach 2900 mAh, while that of a nickel-cadmium (NiCd) battery is only 1100 mAh. NiMH batteries have a larger output current than carbon-zinc or alkaline batteries, making them more suitable for high-power-consuming products. Some special power-type models even have a larger output current than ordinary NiCd batteries.
It has a long cycle life, capable of over 500 cycles under proper usage conditions. However, it has poor high-temperature resistance; avoid allowing the battery temperature to exceed 45 degrees Celsius. Otherwise, its lifespan will decrease rapidly, and its internal resistance will increase. Overcharging significantly impacts battery life and poses a certain degree of danger; therefore, charging should be stopped once the battery is fully charged.
Both nickel-metal hydride (NiMH) and nickel-cadmium (NiCd) batteries operate at 1.2V, but NiMH batteries have a higher volumetric energy density. Due to the superior high-rate discharge performance of NiCd batteries, NiMH batteries cannot yet replace NiCd batteries in many power tool applications. Therefore, the RoHS standard temporarily permits the use of NiCd batteries in the power tool field.
2. Advantages and disadvantages of lithium batteries
Advantages: No memory effect, lightweight.
Disadvantages: High cost, lower current draw, and not resistant to overcharging (compared to nickel-metal hydride).
Lithium batteries are classified into primary lithium batteries (non-rechargeable) and secondary lithium batteries (rechargeable). Secondary lithium batteries are further divided into Li-ion lithium batteries and Li-Polymer lithium polymer batteries.
Compared to nickel-metal hydride batteries, lithium-ion batteries are lighter while having a 48% higher volumetric energy density. As a result, the production and sales volume of lithium-ion rechargeable batteries is gradually surpassing that of nickel-metal hydride batteries. These batteries have low self-discharge, no memory effect, and can be charged and discharged more than 600 times.
Lithium-ion batteries are susceptible to explosion if overcharged due to their susceptibility to overcharging, necessitating the inclusion of a built-in control IC to prevent overcharging. This significantly increases the cost. Because lithium-ion battery specifications are not standardized, situations sometimes arise where batteries are unavailable after a particular model is discontinued; however, this situation has improved considerably.
Lithium-ion batteries are more suitable for mobile phones than nickel-metal hydride batteries. However, in the use of digital cameras, since digital cameras have a much higher current requirement and consume much more power than mobile phones, nickel-metal hydride batteries are slightly better at high current output.
