CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Chinese patent application No. CN201810442762.5, filed on May 10, 2018, which is incorporated herein by reference in its entirety.

FIELD OF THE PRESENT DISCLOSURE

The present disclosure relates to the field of battery, and particularly relates to a secondary battery.

BACKGROUND OF THE PRESENT DISCLOSURE

Rechargeable batteries are widely used in new energy automotives due to significant characteristics of light weight, high energy density, no pollution, none memory effect, long service life and the like. A charging/discharging process of the rechargeable battery is realized by the intercalation and the deintercalation of the active ions (such as lithium ions and the like) between the positive active material and the negative active material, therefore the design of the positive active material, the design of the negative active material, the design of the positive electrode plate and the design of the negative electrode plate will directly affect the performance of the battery. Specifically, whether the positive active material, the negative active material, the positive electrode plate and the negative electrode plate are reasonably designed will affect the charging speed, the energy density, the cycle performance and the storage performance of the battery.

At present, the common problem existed in the design field of the electrode plate is that only one certain parameter of the electrode plate (i.e. the positive electrode plate or the negative electrode plate) is concerned, such as the per unit area coating weight, the pressing density and the like, however, the improvement on the performance of the battery is not obvious when only one certain parameter of the electrode plate is improved.

SUMMARY OF THE PRESENT DISCLOSURE

In view of the problem existing in the background, an object of the present disclosure is to provide a secondary battery, the battery has the characteristics of excellent dynamics performance and long cycle life at the same time.

In order to achieve the above object, the present disclosure provides a secondary battery, which comprises a positive electrode plate, a negative electrode plate, a separator and an electrolyte, the positive electrode plate comprises a positive current collector and a positive film, the positive film is provided on at least one surface of the positive current collector and comprises a positive active material, the negative electrode plate comprises a negative current collector and a negative film, the negative film is provided on at least one surface of the negative current collector and comprises a negative active material. The negative active material comprises graphite, and an average particle diameter of the positive active material represented by D50 and a thickness of the negative film represented by Hnsatisfy a relationship: 6≤0.06Hn×(4−1/D50)≤31. A unit of the average particle diameter of the positive active material represented by D50 is μm and a unit of the thickness of the negative film represented by Hnis μm.

Compared with the existing technologies, the present disclosure at least includes the following beneficial effects: in the present disclosure, by reasonably matching the relationship among the parameters of the positive active material, the parameters of the negative active material, the parameters of the positive negative electrode plate and the parameters of the negative electrode, the speed of the active ions deintercalating from the positive active material and the speed of the active ions intercalating into the negative active material are reasonably matched, therefore the battery having the characteristics of excellent dynamics performance and long cycle life at the same time can be obtained.

