The technical bottleneck of electric vehicle development is in battery performance, so what is the bottleneck of power battery? Why do power batteries need to be divided into soft and hard packs? What is the practical significance? The following is explained from the level of science.
Power battery is the bottleneck of the development of new energy vehicles
At present, the performance index of power battery can not meet the requirements of car dynamics, specifically, mainly the specific energy index is too different compared with gasoline and diesel. In order to narrow the gap, car manufacturers are trying a variety of solutions, such as hybrid power, is a relatively successful example.
Because of the power battery specific energy and fuel specific energy difference is large, a car running at the same speed 260 km, the weight of on-board power is more than five times the weight of fuel on board. The current pure electric bus measures are to adopt multi-frequency charging measures to make up for it; city cabs and pure electric buses are also taking the same measures. The current pure electric passenger cars are basically the models below the A0 level, that is, a relatively short driving range a day; B-class passenger car manufacturers adhere to the hybrid power program.
How to crack the bottleneck of power battery?
In summary, are three measures.
① vehicle manufacturers, borrowing lightweight materials (high-strength steel, aluminum alloy, etc.), the entire body structure to lightweight, so that it can be loaded with a heavier battery.
②Charging facilities, some manufacturers research fast charging technology, some manufacturers try to "change" power technology.
③Power battery manufacturers, from the battery materials (positive electrode, negative electrode, etc.) to research and improve its specific energy.
At present, the light weight, fast charging, "change" power technology has its effect, but the room for improvement is very limited, and can not continue to promote, the most promising or power battery manufacturers from the battery materials (cathode, cathode, etc.) for research, the effect of the more objective, and sustainable. Battery manufacturers from the battery package form (soft package, hard package) and battery pack linkage way to improve step by step.
The bottleneck of power battery is not completely broken, but the progress is promising. In 2008, the specific energy of Chinese lithium-ion power was 80wh/kg, but by the end of 2017, its specific energy has exceeded 300wh/kg, which is nearly 4 times in 10 years.
Power battery package structure is also a specific measure to break the bottleneck
Power battery is divided into two kinds of soft and hard package, hard package subdivided into: cylindrical, square. Package structure has its own advantages and disadvantages, the basic intention is to meet the different requirements of the market. Market trends, the proportion of soft pack batteries is increasingly high, estimated at more than 50%.
(1) cylindrical battery features: ① cylindrical battery production process is mature, the high degree of automated production, PACK cost is lower; ② more models. 18650, 21700, 26500, etc.; ③ cylindrical battery form variety, suitable for the full layout of the electric vehicle space design; ④ cylindrical battery pack heat dissipation area is large, generally using steel or aluminum shell package than energy is relatively low.
(2) square battery cell characteristics: aluminum-cased square and cylindrical type is also generally aluminum-cased, the protection of the cell is better than aluminum-plastic film batteries (i.e., soft pack batteries), cell safety relative to cylindrical batteries has also improved; however, the consistency of the guarantee is more difficult, too many models, the process is difficult to unify, suitable for customized production, not convenient for automated production of battery packs.
(3) soft pack battery pool characteristics: soft pack battery is another name for polymer batteries, compared with cylindrical batteries, has a small size, light weight, high specific energy, high safety, design flexibility and many other advantages. ① soft pack battery weight is 40% lighter than the same capacity of steel-cased lithium batteries, 20% lighter than aluminum-cased batteries; ② large capacity. The capacity of soft pack battery is 10-15% higher than that of steel case battery of the same size, and 5-10% higher than that of aluminum case battery. ③Small internal resistance. The internal resistance of soft pack battery is smaller than that of lithium battery, and the minimum internal resistance of domestic soft pack battery cells can be less than 35mΩ, which greatly reduces the self-consumption of the battery. ④Flexible design. The shape of the soft pack battery can be customized according to the customer's needs, and new cell models can be developed.
Soft pack battery is in line with the basic direction of improving the specific energy, is an effective measure to crack the bottleneck. Auto manufacturers want power packs, do not know about the battery cells, it is best to communicate with the power battery manufacturers, the general direction is to promote soft pack batteries.
