The development momentum of laminated batteries, represented by blade batteries, has started to show signs in the last two years.
The general trend in energy storage cells is to upgrade to large capacity and low cost.
COMPARED TO SMALL AND MEDIUM CAPACITY CELLS SUCH AS 50-100 AH, LARGE CELLS HAVE OBVIOUS ADVANTAGES FOR CENTRALISED ENERGY STORAGE
1) The use of large battery components at the pack end is reduced, with greater cost reduction space and higher volumetric energy density;
2) It is easier to achieve high capacity with large cells at the same system voltage;
3) The number of series and parallel cells is reduced, BMS data acquisition and monitoring accuracy is improved, and safety is better ensured;
4) The use of large cells in back-end integration has a high degree of simplification of the assembly process, which can significantly save land infrastructure and container costs.
Based on the above advantages, large cells (over 200 Ah) have become the mainstream cell choice for centralised domestic, industrial and commercial user-side energy storage systems. Taking 280 Ah as an example, the penetration rate of 280 Ah in the domestic industrial and commercial side has reached more than 60% as of 2022 H1.
With the pursuit of system cost reduction and efficiency improvement by the country and downstream owners, energy storage cells will be further upgraded to larger capacity in the next 2-3 years, and the cell capacity is expected to increase to more than 300 Ah. Battery technology, production and materials are proposed higher requirements.
Globally, there are three major product lines for energy storage batteries: Softpack, large cylinders and square.
For reasons such as space utilisation, production efficiency and industry chain preference, it is difficult for large cylindrical and soft pack batteries to become the mainstream battery solution for centralised energy storage in the short and medium term.
SQUARE BATTERIES CAN BE DIVIDED INTO TWO CATEGORIES: LAMINATED BATTERIES AND WRAPPED BATTERIES, ACCORDING TO THE DIFFERENCES IN THE CELL ASSEMBLY PROCESS.
On the one hand, the wound process has a long development time, low cost, high efficiency and yield, and mature industrial equipment are its main advantages. On the other hand, with the continuous improvement of cell capacity and size, the disadvantages of conventional wound batteries are coming to the fore:
1) The winding at the corner has an arc, which not only causes its space utilisation rate to be lower than that of the lamination (the larger the battery capacity, the more obvious the waste of space), but also causes undulating deformation of the battery , resulting in deterioration of the battery interface and uneven current distribution accelerating battery degradation;
2) After the wound battery terminal is bent, the coating material undergoes large bending deformation, which easily leads to problems such as powder drops and burrs, and increases the risk of internal short circuit and thermal runaway of the battery. With the continuous expansion of cell capacity, the demands on wound batteries for extreme production by battery suppliers will increase rapidly and the compatibility of large capacity batteries and winding processes will increase abruptly.
COMPARED TO WOUND BATTERIES, COMPOSITE BATTERIES HAVE A NATURAL COMPATIBILITY WITH LARGE-CAPACITY BATTERIES, WHICH ARE DESIGNED AS FOLLOWS
1) The number of tabs of the laminated battery is twice that of the wound battery. Increasing the number of tabs makes the electron transfer distance shorter, the resistance is 10% -15% lower than that of the winding battery, the heat generation is smaller and the theoretical life is longer.It can meet the requirements of large-scale energy storage for high safety and ultra-long life;
2) There is no problem with the C-angle when packing the pole pieces of the laminated battery, which can make full use of the corner space of the shell, improve the volume and mass energy density, and help reduce the floor area and civil consumption construction cost of the energy storage system;
3) The lamination does not have the problem of unbalanced internal voltage in the C-angle.In the long-term battery cycle, each layer of the pole piece can keep the interface relatively flat, avoiding problems such as uneven current distribution, and has excellent performance capacity retention in the middle and late stages.
In terms of drawbacks, the development time of the large cell lamination process is short, the maturity of industrial support is insufficient, and there are shortcomings such as low device efficiency, high investment per GWh, and low automated production yield.
In summary, the laminated battery has the advantages of higher upper limit of volume energy density, more stable internal structure and longer cycle life in theory.High, low yield, insufficient efficiency, difficult process and so on.
Now that cell capacity has been increased to more than 300 Ah, the energy storage sector is becoming a new growth pole for laminated battery supplies after soft-pack batteries. In fact, the development momentum of laminated batteries represented by leaf batteries has started to show signs in the last two years.
According to GGII research, the square laminated battery has delivered more than 3 GWh to the energy storage market in 2022H1, and the overall penetration rate is about 7%.
As the laminating process matures and the efficiency of household laminating machines improves, the problems of low efficiency and high cost of laminated battery technology are expected to be completely solved, and a competitive situation of “complementing and competing” is created. is formed with the wound battery technology.