Advantages and disadvantages of nickel-metal hydride batteries:
Advantages of nickel-metal hydride batteries
1. High energy density, 1.5 times that of nickel-cadmium batteries;
2. The battery voltage is 1.2V-1.3V, comparable to that of a nickel-cadmium battery;
3. No memory effect, long cycle life;
4. It can discharge at high current and has strong resistance to overcharging and over-discharging;
5. Pollution-free, green and environmentally friendly battery.
Disadvantages of nickel-metal hydride batteries:
1. The price is higher than that of nickel-cadmium batteries, and the negative electrode material is a rare earth alloy.
2. High self-discharge rate.
Advantages and disadvantages of lithium-ion batteries:
Advantages of lithium-ion batteries
a. High voltage: The working voltage of a single cell is as high as 3.7-3.8V (the cell voltage can be charged up to 4.2V), which is 3 times that of Ni-Cd and Ni-H batteries.
b. High specific energy: The actual specific energy that can be achieved at present is about 555Wh/kg, that is, the material can achieve a specific capacity of more than 150mAh/g (3-4 times that of Ni-Cd, 2-3 times that of Ni-MH), which is close to about 88% of its theoretical value.
c. Long cycle life: Generally, they can reach over 500 cycles, even over 1000 cycles, while lithium iron phosphate batteries can reach over 2000 cycles. For appliances with low-current discharge, the longer the battery life, the greater the appliance's competitiveness.
d. Good safety performance: pollution-free and without memory effect. As the predecessor of Li-ion, lithium-ion batteries have limited application areas because metallic lithium is prone to dendrite formation and short circuits. Li-ion does not contain elements such as cadmium, lead, and mercury that pollute the environment. A major drawback of Ni-Cd batteries produced by some processes (such as sintering) is the memory effect, which severely restricts the use of the battery. However, Li-ion does not have this problem at all.
e. Low self-discharge: The self-discharge rate of fully charged Li-ion after one month of storage at room temperature is about 2%, which is much lower than that of Ni-Cd (25-30%) and Ni and MH (30-35%).
f. Fast charging and discharging: The capacity can reach more than 80% of the nominal capacity in 30 minutes of charging. Now, phosphorus iron batteries can reach 90% of the nominal capacity in 10 minutes.
g. High operating temperature range: The operating temperature is -25~55C, and with the improvement of electrolyte and positive electrode, it is expected to be widened to -40~70C.
Disadvantages of lithium-ion batteries:
a. Aging: Unlike other rechargeable batteries, the capacity of lithium-ion batteries degrades slowly, regardless of the number of uses, but related to temperature. A possible mechanism is a gradual increase in internal resistance, which is more noticeable in electronic products operating at high currents. Replacing graphite with lithium titanate appears to extend lifespan.
The relationship between storage temperature and the rate of permanent capacity loss:
Storage temperature for charging capacity: 0℃, 25℃, 40℃, 60℃
40%~60% 2% 2%/year 4%/year 15%/year 25%/year
100% 6%/year 20%/year 35%/year 80%/June
b. Intolerant to overcharging: When overcharged, excessive lithium ions will be permanently fixed in the crystal lattice and cannot be released, which can lead to short battery life and gas production causing bulging.
c. Intolerant to over-discharge: During over-discharge, too many lithium ions are de-intercalated or de-intercalated in the electrode, which can lead to lattice collapse, thereby shortening the lifespan and causing gas swell.
d. Multiple protection mechanisms are required: Since improper use can reduce lifespan and may even lead to explosion, lithium-ion batteries are designed with multiple protection mechanisms.
Protection circuit: prevents overcharging, over-discharging, overload, and overheating.
Vent: to prevent excessive internal pressure in the battery.
