In soft package lithium-ion battery bulge of the three major reasons

Source: 2020 - 03 - 23 14:04 hits: a soft membrane of lithium ion battery bulging there are three main reasons, and put forward the measure to restrain the soft membrane lithium ion battery bulging soft package the cause of the expansion of lithium ion battery has a lot of. Based on experimental research and development experience, the author will be the cause of the lithium battery bulging is divided into three categories. 2 it is caused by differentiation of liquid oxygen in electrolyte gas production bulge. Third, battery packaging not strictly introduced technical defects such as moisture, point of damage caused by the bulge. In different cell system, the battery is the dominant factor of different thickness changes. In the graphite anode system, the thickness of the electrode and gas production role to play in promoting to the expansion of the battery. 1. The expansion of the graphite negative electrode plates thickness change affecting factors and mechanism of the thickness of the lithium ion battery cells during the process of adding an extension mainly attributed to the cathode and anode swelling rate is only 2-4%, generally speaking, graphite cathode, glue, conductive carbon and graphite materials own inflation rate of 10%, graphite anode inflation changes the main influence factors include: SEI film composition, charged state ( Charge state, SOC) Process parameters, such as influencing factors. ( 1) SEI constitutes the initial charge and discharge process of lithium ion battery, the electrolyte of solid-liquid interface response from the recycling of graphite particles, forming covered electrode passivation layer on the surface of the data ( The SEI film) 。 Due to the attack of SEI, anode thickness increased significantly, battery thickness increased about 4%. From the point of long cycle, according to the physical structure and the specific appearance of different graphite, cycle will be affected by the dissolution of the SEI and the dynamic process of impact of the new SEI. For example, the inflation rate is greater than spheroidal graphite flake graphite. ( 2) Battery charged state in the process of circulation, graphite anode volume expansion contact battery SOC periodic function, and lithium ion insertion graphite ( The progress of the battery SOC) Bulk expands gradually, from graphite anode of lithium ion battery SOC to reduce gradually, and the corresponding volume of graphite anode. ( 3) The process parameters in terms of process parameters, the compaction density has a great influence on the graphite anode. In the polar plate of cold pressing process, the graphite anode membrane compressive stress is larger, in the subsequent polar plate of high temperature baking process is difficult to fully release. In the cycle of the battery charge and discharge process, the membrane stress release in the circulation process, due to the lithium ion insertion and release, the expansion of the electrolyte on the bonding agent and other factors, membrane swelling rate increased. Compaction density range resolution, on the other hand, the anodic film space capacity range, great capacity of pore in the membrane layer, can absorb useful expansion volume, area capacity is small, when single puffy, do not accord with the volume of the space to absorb expansion, at this point, the swelling can only to external expansion membrane layer, as the anode volume expansion performance. ( 4) Adhesive bonding strength of other factors, Adhesive, graphite particles, conductive carbon and liquid interface bonding strength between) , charging and discharging rate, adhesive and swelling of electrolyte and the shape of the graphite particles and its volume density, as well as the binder in the process of circulation failure caused by the pole piece add quantity, etc. , have a certain influence on the anode. Inflation rate calculation: the second element method was used to measure the size of the anode in the X and Y direction, the thickness of anode plate is measured with a micrometer in Z direction. The compaction density and coating quality of the expansion of the negative influence to the compaction density and coating quality as the influencing factors, all factors orthogonal test scheme for three different levels ( See table 1) Other conditions, the same.