System to introduce two of the most common high-energy green battery

4This is currently on the market will be the most common two kinds of high-energy green rechargeable batteries, lithium-ion batteries and nickel-metal hydride batteries do a system of knowledge, for all of the two kinds of cells have a comprehensive understanding of, and the choose and buy contrast Angle and the battery using a reference note.
A definition,
Lithium-ion battery (Li – ion Batteries) is a lithium compounds as a positive, negative electrode of alkaline battery for carbon materials.
Nickel Metal Hydride batteries (Nickel Metal Hydride ‘) the positive active material mainly made of Nickel cathode active material is mainly composed of hydrogen storage alloy made from a kind of alkaline battery.
Second, the principle of
Lithium ion batteries is mainly rely on lithium ion moves between the positive and negative to work. In the process of charging and discharging, Li + embedded (Intercalation) back and forth between the two electrodes and embedded off: when the rechargeable battery, Li + embedded from the anode, after anode, electrolyte embedded lithium anode in a rich state; Discharge is the opposite.
The positive reaction: 1, discharging lithium ions embedded, charging lithium ion embedded.
Charging: LiFePO4 – Li1 – xFePO4 + xLi + + xe -
When discharge: Li1 – xFePO4 + xLi + + xe – > LiFePO4
2, the cathode reaction: discharge lithium ion to take off the plug, rechargeable lithium ion insertion.
Charging: xLi + + xe – + 6 c – > LixC6
Discharge: LixC6 – xLi + + xe – + 6 c
Nickel metal hydride batteries in the battery, the potassium hydroxide (KOH) hydrogen ions (H +) in the electrolyte can be released, by these compounds absorb it, avoid the formation of hydrogen (H2), to maintain the battery internal pressure and volume. When the battery is discharging, the hydrogen ion will be back to the original place by the reverse process.
1, the charging
The positive reaction: Ni (OH) 2 + OH – - > NiOOH + H2O + e -
The cathode reaction: M + H2O + e – - MH + OH -
Overall reaction: M + Ni (OH) 2 – MH + NiOOH
2, when the discharge
The positive: NiOOH + H2O + e – - > Ni (OH) 2 + OH -
Negative: MH + OH – - M + H2O + e -
The overall reaction: MH + NiOOH – M + Ni (OH) 2
Three, features,
1, voltage, the voltage of lithium-ion batteries is 3 times of nimh battery voltage.
= 3.6 V lithium ion battery voltage
= 1.2 V nimh battery voltage
2, according to quality, lithium ion battery has a higher energy density.
Lithium ion battery power/weight = 150 ~ 200 wh/kg (540 ~ 720 kj/kg)
Nickel metal hydride battery power/weight = 60-120 Wh/kg (watt hour/kg)
3, by volume, lithium ion battery has a higher energy density.
Lithium ion battery power/volume = 250 ~ 530 wh/L (0.9 ~ 1.9 kJ/cm3)
Nickel metal hydride battery power/volume = 140-300 Wh/L (watt hour per litre) or 504-1188 kj/kg (kilojoules/kg)
4, output power: the lithium ion battery has a larger output power.
Lithium ion battery power/weight = 300 ~ 1500 w/kg 20 seconds (@)
Nickel metal hydride battery power/weight = 250-1000 – W/kg
5, self-discharge rate: lithium ion battery has a low self-discharge rate
Lithium ion battery self-discharge rate < 5% ~ 10% / month, generally below 2% per month (recoverable) Nickel metal hydride battery self-discharge ratio = generally 2-30% a month, see temperature, low self-discharge model for 10 to 30% a year 6, charge and discharge efficiency: lithium-ion battery charging and discharging rate is higher. Lithium ion battery charge and discharge efficiency = 100% Nickel metal hydride battery charge and discharge efficiency = 66% 7, recycling times: two kinds of cell cycles were close, circulation service life is long. Lithium ion battery charge and discharge cycles = 500-2000 (lithium iron phosphate batteries can reach more than 2000 times) Nickel metal hydride battery charge and discharge cycles = 500-1800 8, the operating temperature range: two kinds of high performance battery temperature range is very wide, compared in low temperature environment, nickel metal hydride battery discharge characteristics better. Lithium ion batteries work temperature range – 20 ℃ ~ 60 ℃ Nickel metal hydride battery working temperature range – 30 ℃ to 50 ℃ (low temperature ni-mh battery can be normal use in the low temperature to 40 ℃) Four advantages, 1, high specific energy, a charge may exercise the distance is long, the specific energy is very high, relative to character, the lithium ion battery (current over the highest energy accumulator) > nimh battery;
2, than high power: when work in large current discharge smoothly, accelerate good gradeability, both is very high than power, lithium ion obvious advantages;
3, small self-discharge, has both the advantages and lithium

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