Lithium battery works, mainly by lithium-ion moving back and forth between the positive and negative, such asLiFePo4 battery pack, charge of work is to move lithium-ion cathode from the anode to a process, lithium-ion from the material inside out is a fast process, into the material inside is a slow process. For graphite materials, the lithium-ion out of the time than going in a hundred times worse than the speed difference of two orders of magnitude, easier to discharge, charging more difficult to slow. So some companies said, "to improve the cathode, you can let the battery charge 5 minutes into the number of how much power," This is totally untrustworthy, because the charge is not the final say by positive, but the negative final say.
Today's battery material system, the anode material graphite, there are other carbon materials, recently want to add silicon oxide, as well as fast-charging lithium carbonate, in fact, have different characteristics. Lithium-ion charge a lot of time, the first through the electrolyte, in which diffusion, which makes the low temperature when charging there is a problem, because the low temperature, the electrolyte horsepower is not enough, the ion diffusion rate is not enough, Of the time in order to fast charge, this matter will become more difficult.
Li-ion in the electrolyte transport is a problem, but the lithium-ion electrolyte from the inside after the transport to the electrode interface, the door is too small to enter, lithium-ion into the non-lithium-ion into the electrolyte is not a problem, Go, go after the house which is too crowded, and are crowded at the door more dangerous, will result in short-circuit at the door, the more low temperature, the greater the problem.
Consumers have a need for fast charging, a normal car, if the charging power is increased, the time will be shortened accordingly. Especially when people go outside, they expect more fast speed to charge, for example solar powered portable generator. Can reach a few minutes full of electricity is not a great thing, but to an hour, or even half an hour or less, whether this fast charge also depends on the battery, charging infrastructure is not able to meet the requirements, This involves security issues.
In addition to security issues, fast charging, including charging mode will affect the battery life, the battery voltage set a little higher, the cost is to reduce life expectancy. Fast charge, the higher the temperature can reach the effect, but also at the expense of the cost of battery life. This may not be apparent when you start using the vehicle, but the more the impact on the back of the battery will be more obvious.
Battery life is related to the depth of charge and discharge. For example, a cell phone battery to charge to 90% of the time to stop, when more than 20% of the time to start charging, than every other people have to fill every time, every time to use the shutdown when charging case, the service life Much longer. Therefore, the lithium battery is concerned, in the middle is better.
To give an example of fast charge, the US National Laboratory Leaf Nissan had done a different charge of the experiment, but also do experiments at different temperature conditions, the main experiment is a fast charge of 50 kW DC charge, 33 kW of communication The difference between charging. Through experiments found that if the temperature can keep the battery temperature is better, the voltage can be controlled better, the impact is not too great. Reasonable fast charge there are two conditions, one is able to control the temperature, the second is not step-up, to do inside the voltage range.
In summary, the fast charge in addition to care about speed, but also concerned about safety and battery life, battery life with the battery charge and discharge depth is closely related to a reasonable charge, reasonable fast charge can be done on the battery has no effect, but high magnification Fast battery charging will have an impact on the battery.
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