Power cells are a bottleneck in the development of new energy vehicles

The technical bottleneck of electric vehicle development is battery performance, what is the bottleneck of power battery? Why should power battery divide soft, hard pack? What is its practical significance? The following is explained from the level of popular science.

Power cells are a bottleneck in the development of new energy vehicles

At present, the performance index of the power battery can not meet the requirements of the power of the car. Specifically, it is mainly too different from the energy index compared with gasoline and diesel fuel. To narrow the gap, automakers are experimenting with a variety of solutions, such as hybrid power, which is a more successful example.

Because the power battery has a larger difference between energy and fuel than energy, a car runs 260 kilometers at the same speed, and the vehicle's power weight is more than 5 times the weight of the car's fuel. At present, pure electric buses take measures to use multi-frequency charging measures to make up for; Urban taxis take the same measures as pure electric buses. The current pure electric passenger car is basically a model below A0, that is, the daily mileage is relatively short; Class B and above passenger car manufacturers adhere to the hybrid power scheme.

How to break the bottleneck of power cell?

To sum up, it is a three-aspect flying measure: 1. The vehicle factory borrows light materials(high-strength steel, aluminum alloy, etc.) to lighten the entire body structure so that it can carry more heavy batteries. 2 Charging facilities, some manufacturers research fast charging technology, some manufacturers try to "replace" electricity technology. 3 Power battery manufacturers, from the battery materials(positive, negative, etc.) to attack, improve their specific energy.

At present, lightweight, fast-charging, and "switching" electric technologies have their effects, but the room for improvement is very limited and can not be sustained. The most promising is that power battery manufacturers will attack from battery materials(positive and negative poles, etc.). Its effect is more objective and sustainable. Battery manufacturers from the battery outsourcing form(soft package, hard pack) and battery package links to improve step by step.

The power cell bottleneck has not completely broken through, but the progress is gratifying. China's lithium ion power has exceeded 80 WH / kg in 2008 and has exceeded 300 WH / kg in energy by the end of 2017, which has nearly quadrupled in 10 years.

Power cell packaging structure is also a concrete measure to solve the bottleneck

The power battery is divided into two types: soft and hard, and the hard pack is subdivided into: cylindrical and square. The packaging structure has its own advantages and disadvantages. The basic intention is to meet the different requirements of the market. Market trends suggest that the share of soft-pack batteries is increasing, with estimates exceeding 50 per cent.

1) Features of cylindrical lithium batteries: 1 The production process of cylindrical lithium batteries is mature, the degree of automation is high, and the cost of PACK is low; 2 Model more. 18650, 21700, 26500, etc.; There are many forms of cylindrical batteries, which are suitable for the adequate layout of the space design of electric vehicles; 4 The heat dissipation area of cylindrical batteries is large, and steel shells or aluminum shells are generally used to encapsulate relatively low energy.

2) Square lithium battery pool characteristics: aluminum shell square and cylindrical type are generally aluminum shells, the protection of the core is better than aluminum plastic membrane batteries(ie, soft pack batteries), the core safety has also been compared with cylindrical batteries have greatly improved; However, the consistency guarantee is more difficult, the model is too many, the process is difficult to unify, suitable for customization production, not convenient for battery package automation production.

3) Soft-pack lithium battery pool characteristics: Soft-pack battery is another name for polymer batteries. Compared with cylindrical batteries, it has many advantages such as small size, light weight, high energy, high safety, and flexible design. 1 The weight of the flexible battery is 40 % lighter than that of the same capacity lithium steel shell and 20 % lighter than the aluminum shell battery; 2 Large capacity. Soft pack batteries have a capacity of 10 to 15 % higher than steel shell batteries of the same size and 5 to 10 % higher than aluminum shell batteries. 3 Small resistance. The internal resistance of the soft-pack battery is smaller than that of the lithium battery. At present, the internal resistance of the domestic soft-pack battery core can be below 35mΩ, which greatly reduces the battery's self-consumption. The design is flexible. The shape of the soft pack battery can be customized according to the customer's needs and a new type of core can be developed.

Lithium battery is in line with the basic direction of improving specific energy and is an effective measure to solve bottleneck. The automobile manufacturer wants the power battery pack, does not understand to the power core, best communicates with the power battery factory, the general direction is to advocate the soft pack battery.

The page contains the contents of the machine translation.