Interpretation of the development of power battery technology

Last year, the global ban on fuel trucks was released, letting people realize that the era of new energy vehicles is coming, and pure electric vehicles, plug-in hybrids, fuel-cell vehicles, etc., why is it a future in just a few years? The main theme is on the one hand, global strategy, policy and other aspects of support, on the other hand, the continuous improvement of power battery technology, longer battery life, shorter charging time, directly related to the user's commuting needs, so that new energy vehicles come Come to us and replace the traditional fuel car in the future, which is inseparable from everyone's daily travel. So there is what people say: "The development of new energy vehicles is the development of battery technology."

Lead-acid batteries

Pure electric vehicles were first used in lead-acid batteries, lead and its oxides were used as electrode materials, and sulfuric acid solutions were used as electrolytes. This is the power source for most electric bicycles today, and low cost is its biggest advantage, but because The energy density of lead-acid batteries is low, which brings about problems such as large volume and small capacity. It cannot meet the control of one car for its own weight, the consumption of driving force, and the service life of more than 10,000 kilometers per year. Used in production cars, and eventually eliminated by car manufacturers.

Sealed packaging lead-acid battery pack

NiMH batteries

Nickel-metal hydride batteries are very close to our daily life. It is very common to hear small electric appliances such as rechargeable toothbrushes from the early days. The positive electrode is a compound of nickel-hydrogen and the negative electrode is a metal hydride. The energy density and the number of charge and discharge times are compared. The lead-acid battery has a small improvement, and the electrolyte is non-flammable, safety is guaranteed, and the manufacturing process is mature. BYD is the world's second largest nickel-hydrogen battery manufacturer before the car is built.

NiMH battery pack

However, because of the general charging efficiency of nickel-metal hydride batteries, there are memory effects of charging, low operating voltage (can not use high-voltage fast charging), and it is not suitable for a single power source of automobiles, and is suitable for auxiliary engine work. The best thing to do in this area is Toyota. The hybrid system uses Atkinson engine + NiMH battery pack. The Atkinson engine itself has the advantage of high efficiency in the intermediate speed range, but it also has the problem of low speed and high speed. Ni-MH batteries are just a big help to solve the problem of lack of start-up and high-speed power.

Since the widespread use of lithium batteries, nickel-metal hydride batteries have also been completely replaced in the car, such as Toyota's new hybrid system has adopted a more efficient engine + lithium battery combination. Compared with lithium batteries, the capacity of nickel-metal hydride batteries, the life of cycle charging and environmental protection are not dominant, and the cost advantage is also weakened by the development of lithium batteries. This is why nickel-metal hydride batteries have gradually withdrawn from the automotive field. Where.

lithium battery

Lithium battery is the mainstream choice of new energy vehicles at this stage. Lithium compounds (lithium manganate, lithium iron phosphate, etc.) are used as electrode materials. Graphite is used as anode material. Its advantages are high energy density, small volume, light weight and charging efficiency. high. The main factor determining the type or performance of lithium battery lies in the material of the two poles of the battery. The material of the positive electrode is the key at the present stage, such as the mainstream lithium iron phosphate, lithium cobaltate in the ternary material, nickel cobalt manganese, etc. There are differences in many dimensions such as cost, low temperature charge and discharge, and safety.

GM Group lithium battery pack

But regardless of any type, all lithium battery packs will face the "natural enemy" of low temperature. Although the optimal operating temperature of different lithium battery types is different, the activity of lithium ions accompanying the lower than the optimal range is reduced, and the impact on the cruising range is relatively large, which is also reflected in our previous tests: Electric vehicles equipped with lithium battery packs, the actual life in the northern winter, can only achieve more than 60% of the theoretical life, up to 70%.

Tengshi EV400 limit mileage test results

The negative impact of low temperature is not well solved by the battery itself. Therefore, many auto manufacturers have tried to warm the battery pack and increase the temperature control system for the power battery alone. Most of the brand models adopting this approach have a certain mitigation effect, but The actual effect is still an excellent solution, because some electric vehicle temperature control systems consume more power than low temperature.

Emgrand EV450 equipped with 2.0 version of isothiocyanate battery intelligent temperature control management system

What can be expected in this regard is that GM has already intentionally cooperated with LG Group of South Korea to purchase products that are equipped with multiple temperature-controlled components directly inside the battery pack, not only to dissipate the battery as it is now, but also to be cold. The weather increases the temperature of the battery. The landing of this technology is worth looking forward to. It is reported that GM's next round of pure electric and plug-in hybrid new cars will be used to replace the battery packs currently supplied by the Hitachi brand.

Hydrogen fuel cell

Everyone knows that H2 + O2 burns the final water, so hydrogen is an ideal clean energy source. In the case of hydrogen itself, combustion can release a lot of energy, the low temperature performance is good, the most important hydrogenation efficiency is high, the hydrogenation can travel more than 600 kilometers in just 5 minutes, and this data has room for improvement, above These are far superior to existing lithium batteries.

Regarding the investment in hydrogen fuel cell vehicles, the car companies in Japan and South Korea have already started research, and now they have invested in the markets of their respective countries in a small scale. For example, the modern NEXO hydrogen fuel cell vehicles that I tested before the Spring Festival have been extensive. Used in the PyeongChang Winter Olympics and went on sale.

Hyundai NEXO hydrogen fuel cell vehicle

And why is hydrogen so good, why not promote it? Because it is too difficult to get hydrogen with current technology. Everyone has learned that electrolyzed water can get hydrogen, but it consumes electric energy to electrolyze water, and then burns hydrogen to finally become water. The power consumption and loss of this process is not as good as charging lithium batteries directly, and the cost is too high. The cost and process are more suitable for extraction from oil and natural gas, but the amount is not large, so the fuel cell vehicle "only smells its name and is difficult to promote."

Graphene battery

For the discussion of the power battery of new energy vehicles in the future, the most reliable and most discussed is the graphene battery. The translation of some professional perspectives is: there are two ways to use this material in combination with lithium batteries. The composite material of graphene is used as the conductive agent of the lithium battery, and the second is directly used as the negative electrode. The effect is to increase the activity of the lithium battery, thereby improving the cruising range and charging speed of the electric vehicle.

Graphene-carbonized sponge lithium-oxygen battery

Graphene batteries can effectively solve the short board of lithium batteries, and the product characteristics are directly linked to the users of new energy vehicles. The benefits of this material are indeed large, and South Korea's Samsung has already announced the technology, but the cost is a big bottleneck. The acquisition of graphene is not easy. In the early days, it was a material used in thespecial field. When, The way to reduce costs will be a big problem for this high-quality product to "fly into the homes of ordinary people", and various auto manufacturers have not announced plans to make efforts in this regard.

To put it simply, the working principle of a pure electric vehicle is "charging direct electricity", and the hydrogen fuel cell vehicle is H2 + O2 "burning" (chemical reaction) electric energy and water, which is equivalent to "burning hydrogen" to generate electricity. The two kinds of "batteries" are also zero-emission, the lithium-ion battery capacity density of electric vehicles is smaller, the low-temperature activity is poor, the battery life is slow, the charging speed is slow, the hydrogen fuel cell is completely absent, and the work efficiency is much higher. Hydrogen is called the cause of quality energy.

Solid state lithium battery

As the name suggests, solid-state lithium batteries are no longer using liquid electrolytes. Solid-state electrolytes are more capable than current mainstream lithium batteries, which means that pure electric vehicles are even higher, even reaching the cruising range of energy-saving gasoline vehicles, and charging. Compared with the current stage, the efficiency has a qualitative leap. It is reported that the most ideal charging speed of an electric vehicle equipped with a solid-state battery can increase 800 kilometers in one minute. This can be said to be the best core component of a new energy vehicle.

At this stage, some overseas energy, technology companies, and battery manufacturers such as Panasonic have started research and development of solid-state batteries. The only automakers involved in this area are Toyota, Honda and Nissan. This is due to the assistance of Japan’s national level. Push. From the plans of all parties that have begun to study solid-state batteries, it is expected that there will be breakthroughs in cost, energy density and manufacturing in 2020, and this research and development will be carried out by 2030, and it will be widely used in new energy vehicles. That is, it is still a little far away from us. This is also the reason why major auto companies have not mentioned the solid-state battery when they released the 2025 global ban on fuel vehicles.

Many car companies and even new car forces have released new energy plans for the future. Stay tuned for more...

To sum up

Environmental protection seems to be a big direction in the world, and electric energy is an essential energy for ordinary people's lives. Therefore, new energy vehicles that use electricity as fuel are the easiest to achieve, and the transition is the smoothest. From a realistic point of view, after the fuel car is banned in 2025, only new energy vehicles can be bought. How is the battery of a car important? As the battery development mentioned in this article, the old battery type has gradually become History, some of the new battery technologies are still in the concept stage, and some of them will come to you as long as they overcome the problems of technology and cost.

The page contains the contents of the machine translation.