What important progress has the graduate school made in the research of all-solid-state lithium-ion batteries and key materials?

by:CTECHi     2021-07-27

The next generation of lithium-ion batteries for electric vehicles and mobile phones will choose all-solid-state lithium-ion batteries with higher energy density and better safety. In order to accelerate the research and development of new materials and all-solid-state lithium-ion batteries, the country set up a national key research and development plan for material genome technology for the first time during the 13th Five-Year Plan period. The new concept and technology of intelligent analysis) accelerate the research and development of all-solid-state lithium-ion batteries, and establish a national key special project for all-solid-state battery research and development based on material genome technology. The key special project is led by Professor Pan Feng, School of New Materials, Peking University Shenzhen Graduate School, as the chief scientist Take the lead in organizing the joint responsibility of 11 units. An important part of the project's research and development includes the research and development of high-performance all-solid-state lithium-ion batteries and key materials (for example: new solid electrolytes, etc.) and mechanisms (for example: adjustment of the interfaces of solid-state battery materials, etc.). Traditional inorganic ceramic electrolytes have the disadvantages of large interface impedance and poor matching with electrode materials. At present, it is difficult to obtain large-scale application in the field of solid-state batteries. Therefore, the development of new solid-state electrolytes with smaller interface impedance has an impact on the energy density and electrochemical performance of solid-state batteries. Promotion is of great significance.

The long-cycle stability of solid-state batteries and the cycle capacity at different temperatures

Professor Pan Feng’s research group recently Significant progress has been made in the research on solid electrolytes and high-energy-density solid-state batteries. Lithium-containing ionic liquids ([EMI0.8Li0.2][TFSI]) are loaded as guest molecules into porous metal-organic framework material (MOF) nanoparticles In the carrier, a new composite solid electrolyte material was prepared. Among them, lithium-containing ionic liquids are responsible for lithium ion conduction, while porous metal-organic framework materials provide solid carriers and ion transmission channels to prevent the risk of leakage of traditional liquid lithium-ion batteries, and at the same time have certain effects on lithium dendrites. Inhibition of use, so that metal lithium can be directly used as the negative electrode of solid-state batteries. The new solid electrolyte material not only has a high bulk ionic conductivity (0.3mScm-1), but also has the best interface lithium ion transport performance due to its unique micro-interface wetting effect (nano-wettedeffect). There is a good match between the particles. Due to the above characteristics, the solid-state battery assembled with the new solid electrolyte, lithium iron phosphate positive electrode and lithium metal negative electrode can achieve extremely high electrode material loading (25mgcm-2), and perform well in the temperature range of -20-100°C The electrochemical performance. We see that the battery management system and the power lithium battery pack together form the battery pack as a whole. The two components that have a communication relationship with the battery management system, the vehicle controller and the charger. The battery management system, upwards, communicates with the electric vehicle controller via CANbus, reports the battery pack status parameters, receives instructions from the complete vehicle controller, and determines the power output according to the requirements of the entire vehicle; downwards, monitors the operating status of the entire battery pack, Protect the battery pack from over-discharge, overheating and other abnormal operating conditions; during the charging process, interact with the charger, manage the charging parameters, and monitor the normal completion of the charging process.

2BMS composition

Large power lithium battery pack

Battery The management system, in general, is composed of a master control module and an acquisition module or called a slave control module. Individual voltage acquisition, temperature acquisition and equalization functions are generally allocated to the slave control module; the collection of total voltage, total current, internal and external communication, fault recording, and fault decision-making are all functions of the master control module.

BMS functional structure

According to the physical distribution and arrangement of the acquisition module and the main control module, BMS is divided into centralized There are two types: distributed and distributed.

Centralized, formally, the entire management system is housed in a box. All voltage, temperature, and current acquisition signal lines are directly connected to the controller. The information interaction between the acquisition module and the main control module is directly realized on the circuit board. This form is generally used in small cars with a relatively low overall voltage and a small number of battery strings.

The desirability is that the slave board is omitted, thereby eliminating the communication wiring harness and interface between the main board and the slave board, the cost is low, and the signal transmission reliability is high.

The shortcomings are also obvious. All the wiring harnesses are routed directly to the control box. No matter where the controller is arranged, some of the wiring harnesses will always run for a long time. The probability of signal interference is increased, and the quality and production level of the wiring harness and the fixing method are also tested.

Distributed, a master control box and several slave control boxes are combined together. The main control box is only connected to the communication line, and the main control is responsible for the signal lines collected, the power line supplied to the slave board and other necessary wiring harnesses. The slave control box is arranged in the battery module accessories responsible for collecting temperature and voltage, and the collected signals are reported to the main control module through the CAN line. In some battery modules, the voltage and temperature collection lines are directly built inside the module and lead out with a wire-to-wire connector. When assembling the battery pack, just plug the connector directly.

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