The Toyota hybrid uses relatively inexpensive traditional nickel-metal hydride batteries, while Honda's Accord hybrid uses more expensive lithium batteries. Therefore, many friends think that Toyota is simple and Honda is kind, but in fact it doesn't work. simple judgment, the reason why Toyota and Honda choose different types of batteries for hybrid models is mainly based on the characteristics of nickel-metal hydride batteries and lithium batteries and the principles of their own hybrid models. Let me share with you:
There is a structural difference between lithium-ion batteries and nickel-hydrogen batteries.
Structurally speaking, the cathode of nickel-hydrogen batteries is Ni(OH). The negative electrode is a metal hydride and the electrolyte is a 6 mol/L potassium hydroxide solution.
Lithium batteriesion integrate lithium ions into petroleum coke and graphite to form a negative electrode. Commonly used cathode materials are LixCoO2, LixNiO2 or LixMnO4. The composition of the electrolyte is relatively complex, LiPF6 + diethylene. carbonate+dimethyl The base carbonate is mixed according to the proportion.
Advantages and disadvantages of nickel-hydrogen batteries
Advantages:
From the previous description of the structure, we can understand that liquid hydrogen battery has a simple structure and rich materials, so the price is relatively cheap. In addition, the number of charge and discharge cycles of nickel-metal hydride batteries is relatively long, generally up to 1,000 to 2,000 times.
NiMH batteries do not have overly strict charging requirements. They can be overloaded, are durable and have relatively stable quality.
Nickel-metal hydride batteriesallique have a relatively large discharge current, so they are widely used in various fields.
The safety of nickel-metal hydride batteries is very high. The flash point of nickel-metal hydride batteries can reach 400°C, and the specific heat capacity and evaporation heat of the electrolyte are relatively high. if extreme abnormalities such as short circuit and puncture occur, even if the battery is damaged, the ascent is too likely to cause violent burns.
Disadvantages:
Nickel-metal hydride batteries self-discharge, which means that the power of the nickel-metal hydride battery will decrease if it is not used for a certain period of time. time. after it is fully charged.
Ni-MH batteries have a relatively low memory effect if they are charged directly without being completely discharged, they do note will not be fully charged, thus shortening battery life. This is why this phenomenon is also called battery memory effect.
In addition, compared with lithium-ion batteries, the energy density ratio of nickel-metal hydride batteries is very low, and the volume is relatively large for the same amount of electricity.
Advantages and disadvantages of Li-ion batteries
Relatively speaking, lithium-ion batteries were developed to solve the shortcomings of nickel-chromium and nickel-metal hydride batteries.
Advantages:
Lighter and higher energy density ratio.
The self-discharge phenomenon is weak. In other words, although lithium-ion batteries have self-discharge, they are much lighter than nickel-metal hydride batteries.
An important advantage of lithium-ion batteries is that they do not have a memory effect, i.e.No matter how much energy is left in the battery, it can be charged directly by plugging it into the charger. and it will be fully charged.
Disadvantages:
Lithium-ion batteries are more expensive, the discharge current is relatively small, and the number of complete charge and discharge cycles is relatively small. After repeated charging and discharging, the charging and discharging capacity of the battery is reduced. The lithium-ion battery will be certain. The degree is reduced. According to the latest ternary lithium battery standards, after 1000 full charge and discharge times, the power of the lithium battery is about 80%.
The price is higher. Since the structure of lithium-ion batteries is more complex and the cost of anode materials is higher, the overall cost of lithium-ion batteries is higher.
Lithium-ion batteries can catch fire in a collision. ApAfter the collision, the battery core may discharge with a large current and burn the diaphragm, resulting in a short circuit in a larger area, resulting in high current. Electrolyte temperature vaporization, when the pressure on the battery shell is exceeded, it will cause violent combustion and explosion.
Accord's I-MMD hybrid principle determines that it can only use lithium-ion batteries.
In most working conditions, the hybrid model's engine Accord i-MMD is not directly pushed. the car moves forward, the engine in hybrid mode only drives the generator to produce electricity. Most of the power drives the electric motor to drive the car. The remaining power charges the lithium battery. The engine is only used to drive the car directly while cruising. high speed and when the lithium battery is insufficient. This priceHybrid ncipe requires its battery to have higher charge and discharge efficiency and larger discharge capacity. Therefore, only lithium-ion batteries with a high energy density ratio and high charging and discharging efficiency can be used.
Polymer batteryStrictly speaking, it is called “lithium polymer battery” (Li-polymer, also called lithium polymer battery): it is also a battery lithium-ion. battery A kind of battery, but compared with liquid lithium (Li-ion) battery, it has many obvious advantages such as high energy density, smaller size, ultra-thin, light weight and safety high. In terms of shape, lithium polymer batteries are ultra-thin and can be made into batteries of any shape and capacity to meet the needs of various products. The minimum thickness that this type ofbattery can reach can reach 0.5mm. Its rated voltage is the same as Li-ion 3.7V, and there is no memory effect.
“Lithium battery” is a type of battery that uses lithium metal or lithium alloy as the negative electrode material and uses a non-aqueous electrolyte solution. Lithium metal batteries were first proposed and studied by Gilbert N. Lewis in 1912. In the 1970s, M. S. Whittingham proposed and began studying lithium-ion batteries. Since the chemical properties of lithium metal are very active, the processing, storage and use of lithium metal are subject to very high environmental requirements. Therefore, lithium batteries have not been used for a long time. With the development of science and technology, lithium batteries have now become mainstream.
The main differencesthese in between are:
1. Polymer batteries do not have battery leakage problems. There is no liquid electrolyte inside the battery. uses solid state glue. Lithium batteries haveLiquid exists
2. Polymer batteries can be made into thin batteries: with a capacity of 3.6V 400mAh, its thickness can reach 0.5mm. Lithium batteries cannot be very thin
3. Polymer batteries can be bent and deformed: Polymer batteries can bend up to about 900 degrees. Lithium batteries cannot be bent or overbent
4. Polymer batteries can be made into single high-voltage batteries: Liquid electrolyte batteries can only obtain high voltage by connecting multiple batteries in series and polymer batteries.
5. Since the polymer battery itself does not contain liquidide, it can be transformed into a multilayer combination within a single cell to achieve high voltage.
6. The capacity of polymer batteries will be twice that of lithium-ion batteries of the same size.