Lithium battery usage increases as the largest capacity drops what reason be?

Source: 2020 - 03 - 29 14:58 hits: time is know for lithium battery, here only talk about lithium battery internal and external causes: 1. Internal reason ( 1) The electrode side, repeated charge and discharge can reduce the activity of the electrode surface area, to improve the current density, increasing polarization; The structure of the active material change; Active particles electric contact, or even fall off. Electrode data ( Including the collector fluid) The corrosion; ( 2) In terms of electrolyte solution, electrolyte or differentiation resulting in a decline in the conductivity of conductive salt, this divergence form interface passivation; Lithium ion battery liquid electrolyte by solute (commonly Such as LiPF6, LiBF4, LiClO4 lithium) , solvent, and special additives. The electrolyte has good ionic conductivity and electrical insulation, between positive and negative electrode ionic conduction current role. ( 3) Barrier, jam or damage to the battery internal short circuit barrier to separate the positive and negative of the battery, such as to prevent short circuit directly between the north and south poles. In the process of lithium ion battery cycle, gap gradually drying failure is the important reason for the battery performance in early fall. This is mainly due to the electrolyte in a gap in the dry solution resistance increases, the gap of the electrochemical stability and mechanical properties, and in the process of charging the electrolyte wettability deterioration. Because of the existence of dry gap battery ohm resistance increases, incomplete discharge in the battery many times by the large capacity of overcharge, the battery capacity can't return to the initial state, greatly reducing the discharge capacity and service life of the battery. 2. The external reason ( 1) Fast charge and discharge fast charging, the current density is too large, the cathode is serious, the accumulation of lithium will be more obvious, copper foil and the carbon clearance between active material embrittlement on copper foil, easy to crack. Battery natural winding is limited by a fixed space, copper foil can not freely extended against pressure. Under the action of stress, the crack propagation and the expansion of the original. Due to the expansion of space, copper foil fracture. ( 2) The temperature when the temperature is significantly higher than room temperature, the thermal stability of the organic electrolyte become a key consideration. It is generally believed that the positive/organic electrolyte reaction is the influence of main factors on the safety of kk ion battery. Due to the positive electrode and the electrolyte reaction kinetics is very fast, so that the whole controlled heat resistance of the battery. If the battery of the ambient temperature is high enough to cause the reaction of the electrolyte, will lead to the thermal runaway of the battery, even fire and explosion. The size of the discharge current directly affect the discharge capacity of lithium ion batteries. In the case of large current discharge, not only there are serious electrolyte interfacial polarization, and also has the active body, namely the electromagnet. , embedded diffusion of ions and the electrode polarization. ( 3) Depth charge discharge for a long time to remove them from the internal structure, one is the formation of electrolyte excessive volatility, 2 it is lithium battery cathode excessive response, make its dielectric film against change from the contact component drop, constitute a permanent capacity loss; Mainly from the middle of the night charges for voltage stability and power grid voltage increases, the charger has stopped charging, voltage rise, will continue to collect fees, overcharging change capacity loss results in the formation of the battery anode data structure, the differentiation of oxygen and the electrolyte severe oxidation reaction, then burning blast; Organic solvent/electrolyte electrolyte of lithium salt; Lithium ion precipitation may lead to the cathode copper trap and the dissolution of the anode copper dendrite. ( 4) Impact and the impact is usually process, such as welding is firm or not, the internal circuit design is reasonable, etc.