What design and scheme can improve the safety of lithium ion battery?

Lithium ion battery potential security problems greatly affect the consumer confidence. Although people have been looking forward that BMS can accurately monitor the security situation (SOS) and can predict and prevent some failure. However, due to complicated thermal runaway situation, it is difficult to ensure the safety of facing the life cycle of all conditions by a technical system. Therefore, the root cause analysis and research of lithium ion of a safe and reliable battery is still necessary.

BMS battery management system

Battery management system (BMS)Power battery is expected to solve the key problems in the use of high hopes. Need to manage the battery management system and its consistency, make its under different conditions (temperature, altitude, maximum ratio, charge state, cycle life...) to obtain the maximum energy storage efficiency and safety, round-trip. BMS includes some common modules: data acquisition unit, communication unit and battery status (SOC, SOC, SOP...) evaluation model. With the development of the power battery, the management of the BMS ability requirements are more stringent. Increases the heat management module, for example, high pressure monitoring module...By the increase of these security module, is expected to improve the safety and reliability in the process of power battery is in use.

Pile of integration design

Battery after thermal runaway could cause destructive activities such as smoke, fire, explosion, endangering the personal safety of the user. Even if is the safest way to configure selection theory, is not enough to make people relax. If choose LiFePO4 and Li4Ti5O12 make it safe and suitable for fast charge and discharge the battery of the positive and negative materials, their electromotive force are all located in the electrolyte electrochemical window, also no longer need the SEI film. However, this is also because the oxidation reduction electric to appear at the top of anion P or 4 s orbital overlap and cation to cope with the electrode under some conditions of work. Reasonable batteries again working condition of design and manufacture of also is unable to avoid the accident happens, only reasonable battery pack integrated design can make electric piles under the condition of the batteries out problems timely stop loss.

As mentioned earlier, the safety of the battery and battery life at the material level is the result of a pair of contradictory. In order to solve the problem of security and life balance, Tesla Motors Co. Ltd takes the lead to make the model gives us a good lesson. Tesla's ModelS using the Panasonic (Panasonic Co. Ltd) NCR18650A type of high energy density battery, in a pile of used batteries, more than 7000 day. This is a chance to thermal runaway in the combination of high way, but through the electric pile of integration and design of BMS, USES a lot of innovative patent, make ModelS the probability of safety accidents occurred in the process of actual use is greatly reduced. Tesla's patents in public, for example, the safety performance of monomer, module, the module safety performance and safety performance of the battery pack assembly can strengthen more or less represents the advanced way to solve the integration.

Tesla through electrode on the batteries, shell to add fireproofing materials and casing, the minimum safety distance between monomer, the gasket keep single spacing remain unchanged after the fire, using efficient relief valve rupture location prediction monomer, monomer on the safety valve is cut off and the electrical connections, so as to prevent heat diffusion between monomer batteries and after thermal runaway caused a chain reaction. At the same time, through on the inner surface of the battery electrode and the battery shell arrangement between thermal barrier, decorate insulation layer between the modules, will Pack partition, thereby blocking between modules in the event of a thermal runaway of heat conduction and spread out of control. These measures from batteries to the module level, layers of security, in order to the internal thermal runaway after maximum stop in time.

Thermal runaway plan design

After the way of plan design for thermal runaway variety, multi-level, in addition to the various integration when considering the safety of the design, have been supervised and active cooling pipe to battery cooling and thermal runaway alleviation system startup jet cooling liquid in order to reduce the impact of thermal runaway; Electrical safety valve to open, making the thermal runaway of high temperature gas discharge system in time, again by the discharge valve; Other systems using the built-in high temperature energy absorption thermal runaway, reduce the harm...Finally, in the event of antecedent means can't control the situation, through installing ball proof board at the bottom of the location of the pack, the crew capsule and pack plus heat resistance between layers with maximum likelihood decreased after the occurrence of thermal runaway of personal injury. These design can not only make the internal thermal runaway of energy reduction in time, can also see the battery level after completely out of control, the catastrophic consequences are still within the scope of control so as to fundamentally safeguard the personal safety of users.

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