Nickel Hydride No. 5 battery technology is improving but lacks revolutionary changes

Recently, the Ministry of Science and Technology announced the "Implementation Methods for Key Special Projects of New Energy Vehicles in the National Key R&D Plan (Draft for Comments)", which clearly proposed that the single-cell specific energy of power lithium batteries will reach 200 watt-hours/kilogram by the end of 2015 and 300 watt-hours/kilogram by 2020.

As we all know, the current single-cell specific energy of lithium batteries of various materials is only 200 watt-hours/kilogram, which is already the limit of some lithium batteries, and the single-cell specific energy of 300 watt-hours/kilogram has exceeded the theoretical value of some lithium batteries. Where will lithium batteries go in the future?

Technology is improving but lacks revolutionary changes

Looking back on the past ten years, Nickel Hydride No. 5 battery technology has been continuously improving, and the most obvious feeling is that the battery capacity has been significantly increased. Anyone who has used a laptop knows that in 2005, the battery life of laptops was generally around 2 hours, and almost only 1 hour, while now the battery life of laptops is generally more than 5 hours, and some can even reach 10 hours.

Another obvious benefit of technological progress is that prices are constantly falling. The price drop has led to the continuous expansion of the application field of lithium batteries, squeezing out the market of secondary batteries such as nickel-metal hydride, nickel-cadmium, and lead-acid batteries.

Other progress includes: the variety of batteries continues to increase, polymer lithium batteries begin to dominate the industry, and square, cylindrical, and soft-pack lithium batteries gradually form a three-legged tripod; the charging time is significantly shortened. Ten years ago, it took 5-6 hours to fully charge a mobile phone battery, but now it generally only takes 2-3 hours, and this is when the capacity doubles.

Objectively speaking, the technological progress of lithium batteries in the past decade is indeed great, but there is a lack of revolutionary changes. Lithium batteries are no different from 10 years ago: the structure has not changed, and the important supporting materials have basically not changed. In particular, the positive electrode materials are still the same as 10 years ago, still lithium cobalt oxide, lithium manganese oxide, ternary materials and lithium iron phosphate. The only change is the market share of different materials. Ten years ago, it was lithium cobalt oxide, but now it is lithium cobalt oxide, lithium manganese oxide, ternary materials and lithium iron phosphate.

There are frequent reports on high-voltage and high-specific-energy cathode materials such as LiCoPO4 and Li3V2(PO4)3. New cathode materials that can solve all problems, such as silicon cathode and metal cathode, are frequently reported in the newspapers. New materials such as graphene and carbon nanotubes are often used in lithium batteries, and new electrolytes such as glass ceramics and ionic liquids are emerging in an endless stream. There are many papers with higher energy density, lower unit cost, more cycles, and faster charging speed, and the investment is also huge, but there are no actual products yet.

However, the downstream application market is undergoing fundamental changes. Mobile phones have completed the transformation from feature phones to smartphones. Although tablets cannot replace laptops, they have occupied part of the market. The rise of electric vehicles is leading the automotive revolution, and wearable devices are rapidly emerging, all of which put higher demands on lithium batteries.

The fact is that lithium batteries currently cannot meet the requirements of smartphones and electric vehicles. In 2005, the battery capacity of mobile phones was only about 1000mAh, and its standby time could easily reach 1 week, and it was no problem to use it normally for 2 days. Now, the standby time of mobile phones with a capacity of 3000mAh is good for 2 days, and it can't even last a day in actual use.

As a consumer electronic product, mobile phones are very convenient to charge, and it is easy to solve whether at home or at work. The emergence of mobile power further solves the problem of not being able to charge when going out, so the problem of mobile phone batteries is not very prominent.

But electric cars are completely different. Most electric cars have a range of only about 200 kilometers, which is far from the range of 500-600 kilometers of internal combustion engine cars. Even TSLA can only reach 400 kilometers, which is the result of adding a large number of lithium batteries.

This is not the biggest problem. What really affects the use of electric vehicles is the long charging time and the serious lack of charging facilities. At normal speed, it takes 4-8 hours for the power Nickel Hydride No. 5 battery of an electric car to be fully charged. If the speed is increased, it can be fully charged in 1-2 hours, but it will affect the performance and life of the power Nickel Hydride No. 5 battery.

Experiments have proven that if fast charging is always used, the life of power lithium batteries will drop to one-third of the original, and the battery performance will drop significantly, and the probability of safety accidents will increase greatly. Internal combustion engine vehicles do not have such problems. The time for refueling or gas filling does not exceed 5 minutes, and safety and stability can be guaranteed. In addition, gas stations are very common now, and they are very fast and convenient to use. More importantly, the cost of lithium batteries as car power is too high, accounting for about half of the total cost of electric vehicles.

A strict system affects the whole body

The structure of lithium batteries looks very simple, with positive electrode materials, negative electrode materials, diaphragms and electrolytes, plus electrodes. In fact, although it is inconspicuous, the Nickel Hydride No. 5 battery material system is very strict, and it is really a matter of one hair. If you want to change it even a little bit, assuming that only one electrode is replaced with a new material, no one dares to guarantee it without years of testing.

Lithium batteries came out in the 1970s, and were mass-produced by Sony in the 1990s. Today, lithium batteries have been born for nearly half a century, and the material system has undergone major changes. The development of positive electrode materials from the initial lithium cobalt oxide to the current lithium cobalt oxide, lithium manganese oxide, ternary materials and lithium iron phosphate in parallel can be said to be a great progress.

But in fact, it took at least ten years for each positive electrode material to go from invention to practical application to mass production of lithium batteries. For each change in positive electrode material, even if the negative electrode material is not changed, the composition of its electrolyte and the diaphragm must be changed accordingly to achieve the best matching effect. At the same time, it must undergo a long period of safety testing to verify its safety, and finally go through the industrialization process before it can enter the market. Not only that, it also needs market testing and customer recognition, which also takes time. This is also the fundamental reason why Nickel Hydride No. 5 battery material research is very hot now, various new materials and new technologies are reported in an endless stream, while lithium batteries themselves are progressing slowly and the material system has basically not changed.

In comparison, it is much easier to improve the manufacturing process and battery management technology without changing the Nickel Hydride No. 5 battery material system. The emergence of soft-pack lithium batteries and the continuous improvement of Nickel Hydride No. 5 battery capacity are the result of continuous progress in manufacturing process technology.

At the same time, in order to meet the needs of new products such as wearable devices, Panasonic has developed a pin-type Nickel Hydride No. 5 battery with a diameter of 3.5mm and a length of 1cm, while Samsung has launched an ultra-small Pin battery with a diameter of 3.6mm and a length of about 20mm. As the trend of smartphone flexibility becomes more prominent, various flexible and bendable Nickel Hydride No. 5 battery products have been launched one after another. In terms of battery management technology, TSLA is a model. Its advanced battery management technology creatively groups more than 6,000 cylindrical Nickel Hydride No. 5 battery cells in series and parallel, successfully reducing battery costs and improving energy storage efficiency, laying the foundation for TSLA to lead the transformation of electric vehicles.

Where is the future

Although TSLA has provided a new development idea for the development of electric vehicles, it is only a temporary solution. In the absence of a significant improvement in the performance of lithium batteries, it is very difficult for electric vehicles to be promoted on a large scale. So the question is, how can the performance of lithium batteries be further improved? In what direction will it develop in the future?

The author believes that the demand of the application market is the biggest force driving the progress of lithium batteries. The development history of secondary batteries fully proves this point. The rise of nickel-cadmium, nickel-metal hydride and other batteries is driven by the small consumer battery product market, and the decline is also due to the erosion of this market by lithium batteries.

Lead-acid batteries can occupy the largest market share of secondary batteries because they occupy the automotive starter battery market, which is also the root of their longevity. However, due to the lack of new application markets, the technological progress of lead-acid batteries is very limited, and they are also facing strong competition from lithium batteries.

At present, lithium batteries have completely occupied the consumer electronics market. As consumer electronics products continue to change, lithium batteries are also constantly improving. Since there are no secondary batteries that can compete with lithium batteries in the consumer electronics market, lithium batteries will occupy the consumer electronics market for a long time.

At the same time, lithium batteries are gradually opening up the power Nickel Hydride No. 5 battery market such as power tools, electric bicycles, and electric vehicles, providing good power for their future technological progress. In addition, its competitors, fuel power batteries, flow batteries and other new batteries are still in their infancy and are still some distance away from industrialization. This provides a rare historical opportunity for Nickel Hydride No. 5 battery technology change.

Therefore, the author believes that the future development direction of lithium batteries should be aimed at power lithium batteries and energy storage batteries. In the opportunity period when competitors have not yet developed, by increasing battery specific energy, reducing production costs, and increasing the number of cycles, actively occupy the automotive power market, expand the energy storage market, and squeeze the lead-acid battery market space, and use the advantages of industrialization to influence the industrialization process of new batteries such as fuel power batteries and liquid flow batteries, and then seize a favorable competitive position.

To achieve the above goals, the most fundamental thing is to achieve revolutionary changes in lithium batteries. From the current material structure of lithium batteries, positive electrode materials have become the most critical factor restricting their performance improvement.

Whether it is the industrialized lithium cobalt oxide, lithium manganese oxide, ternary materials and lithium iron phosphate, or the various new positive electrode materials under research, there are limitations: first, the theoretical specific energy is limited, relative to the negative electrode material; second, there is a large gap between the actual specific energy and the theoretical value; third, if the Nickel Hydride No. 5 battery is charged too quickly, it is easy to cause changes in the structure of the positive electrode material. Therefore, the author believes that to achieve revolutionary changes in lithium batteries, it is necessary to first break through the limitations of positive electrode materials.

On the one hand, we should continue to develop new positive electrode materials with high working voltage, high theoretical and actual specific energy, good temperature characteristics, rich material sources, long cycle life, safety and reliability, and low cost. Judging from the material characteristics and the history of positive electrode material research in the past, it is very difficult to achieve this, and the possibility of completion within 10 or 20 years is extremely low.

Second, we should give full play to the potential of existing positive electrode materials, creatively use new material preparation technologies represented by nanotechnology and new materials such as carbon nanotubes and graphene, and improve the existing positive electrode material preparation process by modifying and coating existing positive electrode materials, solve the problems of low actual specific energy, long charging time, and high production cost of current positive electrode materials, and accelerate the application of lithium batteries in the power market and energy storage market.

The author believes that the second method is more likely to be realized. First, it does not require major changes to the existing Nickel Hydride No. 5 battery material system, but only minor adjustments, which is low in difficulty and short in time; second, new technologies such as nanotechnology and new materials such as carbon nanotubes and graphene are constantly maturing, laying a good foundation for their application in lithium batteries.

Once a breakthrough is achieved in positive electrode materials, the entire material system of lithium batteries will inevitably change. Only in this way can the performance of lithium batteries be fundamentally improved. Of course, it is also difficult to achieve breakthroughs in diaphragms and electrolytes. In comparison, the difficulty of breakthroughs in negative electrode materials is much smaller. In addition, progress in battery preparation technology and battery assembly technology is also necessary, which is also an important factor in improving the specific energy of lithium batteries and reducing costs.

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