Analysis of key technology development trend of power battery and battery management system in 2018


It is now the end of 2017,and everyone is analyzing the development trend of China's new energy vehicle technology in 2018.The Ministry of Science and Technology's 2018 Key Special Application Guide for New Energy Vehicles has been released,which is very instructive for enterprises.The following is an analysis of the development trend of key technologies of power battery and battery management system in 2018 after the author studied the Application Guide.

1.Key Technologies of China's New Energy Vehicles

The Application Guide lists the main direction of China's new energy vehicle technology in 2018:power battery and battery management system;Motor drive and power;Intelligent electronic and electric vehicles;Fuel cell power system;Plug in/add in hybrid power system;Pure electric power system.

A total of 24 research tasks were subdivided in 6 directions.The 2018 Key Special Application Guide for New Energy Vehicles is a concrete embodiment of the top-level design.

① The planning of enterprises and the government should be consistent,and the business activities of enterprises(including technological breakthrough)should be carried out under the top-level design of the government;

② The specific new energy vehicle research(development)project of the enterprise in 2018 must be in 6 directions and 24 research tasks;

③ The specific technology research and development projects of enterprises should be corresponding to the annual plan of the central government to tackle key technical problems.

The research tasks of power battery and battery management system in 2018 are divided into five

1.High safety and high specific energy passenger vehicle power battery system technology(major common key technologies)

① Research content:

In view of the high integration requirements of passenger vehicles,carry out mechanical electrical thermal design of battery system based on vehicle integration;Develop advanced and reliable battery management system and compact and efficient thermal management system;Design and verify the electrical configuration and parameter matching,durability and reliability of modules and systems;Based on the thermal simulation model,the disaster caused by thermal runaway and thermal diffusion,and the analysis model,study the fire spread and fire safety measures of the battery system,and develop and verify the safety design and protection system of the battery system;Carry out research on lightweight and compact technology,manufacturing process and assembly technology of battery system,and develop high safety and high specific energy passenger vehicle power battery system;Carry out research on battery system performance test and evaluation technology.

② Assessment indicators:

The specific energy of the battery system is≥210Wh/kg,the cycle life is≥1200 times(80%of the discharge depth(DOD),simulating the annual temperature distribution),the absolute value of the estimated error of the state of charge(SOC),power state(SOP)and state of health(SOH)within the full life cycle and wide operating temperature range is≤3%,the maximum temperature difference between individual batteries is≤2℃,and the time required for rapid charging to more than 80%of the SOC state is≤1 hour,Meet the requirements of national standards such as safety and wide temperature application range,as well as the requirements of ISO 26262 ASIL-C functional safety requirements and industrial standards.The cost is≤1.2 yuan/Wh,the annual production capacity is≥10000 sets,and the products are at least supported by two complete vehicle enterprises,and the loading application is not less than 3000 sets;Submit the disaster analysis and hazard evaluation report of thermal runaway and thermal diffusion accidents;Establish the design,manufacture and test specifications of battery system based on vehicle integration.

③ My interpretation:

The main technical direction of passenger vehicle power battery system is:

i) It is an integrated battery system for the whole vehicle,rather than the power change mode technology actively advocated by some manufacturers at present;

Ii) The specific energy of the battery system is≥210Wh/kg,and the cycle life is≥1200 times(80%of the discharge depth(DOD).The specific energy is≥210Wh/kg,indicating that the battery must refer to the ternary battery.It is almost impossible to promote lithium iron phosphate battery in passenger vehicles.

Iii)The cost of the battery system is≤1.2 yuan/Wh,indicating that the current cost of the battery system is basically higher than it,which is the threshold for subsequent subsidies.

2.High safety and long life bus power battery system technology

① Research content:

According to the actual application requirements of ultra-high safety level and ultra-long warranty mileage of passenger cars,the overall configuration,function and mechanical electrical thermal integration design technology of power battery system based on modular and decentralized layout were studied;Develop advanced and reliable battery management system and efficient thermal management system;Carry out electrical configuration and parameter matching of power battery system,as well as design and verification of durability and reliability;Based on the thermal simulation model,thermal runaway and thermal diffusion disaster analysis model,study the fire spread and fire safety measures of the battery system,carry out the safety design of the battery system,and develop and verify the protection system and monitoring system;Break through the lightweight and compact technology of the battery system,establish the intelligent manufacturing process of the battery system,and develop the high safety and long life bus power battery system;Carry out research on battery system performance test and evaluation technology.

② Assessment indicators:

The specific energy of the battery system is≥170Wh/kg,the cycle life is≥3000 times(80%DOD,simulating the annual temperature distribution),the absolute value of the estimation error of SOC,SOP and SOH within the full life cycle and wide operating temperature range is≤3%,the maximum temperature difference between individual batteries is≤2℃,and the time required for rapid charging to above 80%SOC state is≤15 minutes,meeting the requirements of national standards such as safety and the requirements of wide temperature use range,It also complies with the functional safety requirements of ISO 26262 ASIL-C and the requirements of industrial standards,to ensure that the system is free of fire and explosion within 30 minutes after the thermal runaway of the monomer,the cost is≤1.2 yuan/Wh,the annual production capacity is≥3000 sets,the products are at least supported by 3 complete vehicle enterprises,and the loading application is not less than 1000 sets;Submit the disaster analysis and hazard evaluation report of thermal runaway and thermal diffusion accidents;Establish technical specifications for battery system design,manufacturing and testing.

③ My interpretation:

The main technical direction of bus power battery system is:

i) Based on the research of the power battery system with modular and decentralized layout,this shows that the passenger car power battery system is different from the requirements of passenger cars,one is integrated,the other is modular and decentralized.

Ii) The specific energy of the battery system is≥170Wh/kg,and the cycle life is≥3000 times(80%DOD,which means that lithium iron phosphate is still the main target for passenger cars,and the life is the main indicator;

iii) There is no fire or explosion in the system within 30 minutes after the thermal runaway of the monomer.This indicator indicates that the safety time is not less than 30 minutes,which is the subjective direction of the follow-up.

Iv) The cost of the bus power battery system is≤1.2 yuan/Wh,which indicates that the whole vehicle enterprise is concerned about the system cost,not the single battery price.

3.High specific energy lithium/sulfur battery technology

① Research content:

Explore new reaction mechanism of sulfur electrode,develop sulfur electrode materials with high specific capacity and long life and suitable electrolyte system;Study the growth mechanism and inhibition measures of lithium dendrite,and develop lithium anode with high cycle coulomb efficiency and good cycle stability;Carry out research on functional diaphragm with high strength and safety;Master the design and preparation technology of high load sulfur electrode and lithium/sulfur battery;Carry out research on safety improvement technology of lithium/sulfur battery,develop lithium/sulfur power battery with high safety and long life,and realize loading assessment.

② Assessment indicators:

The specific energy of single battery is≥400Wh/kg,the cycle life is≥500 times(100%DOD),and the safety meets the national standard requirements.

③My interpretation:

i) Lithium/sulfur battery is a new type of battery,which is prepared to meet the loading requirements.At present,the conditions for getting on the vehicle are not mature.

Ii) Specific energy of single battery≥400Wh/kg,cycle life≥500 times(100%DOD),which does not meet the life requirements for passenger cars and buses.

4.High specific energy solid state lithium battery technology

① Research content:

Research on the design and preparation technology of solid polymer electrolyte and inorganic solid electrolyte,and develop solid electrolyte system with wide electrochemical window and high room temperature ionic conductivity;Study the solid/solid interface construction technology and stabilization technology between active particles and electrolyte,electrode and electrolyte layer,and develop the preparation technology of solid electrode and solid battery;Carry out research on production process and special equipment of solid state battery,develop solid state lithium battery with high safety and long life,and realize loading demonstration.

② Assessment indicators:

At room temperature,the specific energy of the single battery is≥300Wh/kg,and the cycle life is≥2000 times(more than 0.3C rate charge and discharge,100%DOD).The safety meets the national standard requirements,and the loading assessment is achieved.

③ My interpretation:

i) Lithium/sulfur battery technology and solid-state lithium battery technology are the next generation of batteries to meet the loading requirements.

Ii) The new battery,which is currently popular in the market,will be further away from the realization of loading requirements.

Iii) It is impossible to recommend other old batteries that have been installed on the vehicle for any improvement.

5.Testing and evaluation technology of power battery

① Research content:

Study the performance evaluation methods of key materials and monomers of power battery,and build a closed-loop linkage evaluation mechanism of"material battery performance";Study the evolution law of electrical performance and safety performance of battery in the whole life cycle,and establish simulation analysis technology;Carry out research on functional evaluation and performance characterization methods of management systems,and develop software and hardware testing equipment or devices;Study the performance evaluation methods of battery system and the reliability,thermal safety and functional safety evaluation methods facing the actual working conditions,carry out the disaster analysis of battery thermal runaway and thermal diffusion,and study the safety classification standard of power battery;Carry out benchmarking analysis of power battery systems at home and abroad,and establish an authoritative test and evaluation platform and database for power batteries.

② Assessment indicators:

Establish a comprehensive evaluation system for power battery,including electrical performance testing methods from materials to systems,safety characterization methods of single battery in the whole life cycle,function and performance evaluation methods of management system,reliability,thermal safety and functional safety evaluation methods of power battery system facing actual working conditions;Establish an internationally advanced power battery test and evaluation platform;More than 10 standard proposals have been formed in terms of test evaluation and power battery safety classification;Establish a product database,in which the number of battery system samples shall not be less than 200.

③ My interpretation:

i) It is of great significance to study the performance evaluation methods of key materials and monomers of power batteries,which battery manufacturers must solve;

Ii) Vehicle manufacturers mainly understand the performance evaluation methods of these key materials and monomers of power batteries.

3 Summary of development trend of key technologies of battery system technology

① The main research direction of key technologies of passenger vehicle power battery system technology refers to high safety and high specific energy with integrated design as the focus.The key indicators are:specific energy of battery system≥210Wh/kg,cycle life≥1200 times(80%discharge depth(DOD).

② The main direction of the key technologies of the bus power battery system technology refers to the high safety and long life with the focus on distributed design.The key indicators are:the specific energy of the battery system≥170Wh/kg,and the cycle life≥3000 times(80%DOD).

③ The cost index of passenger car power battery system and passenger car power battery system is≤1.2 yuan/Wh.This conclusion is an important basis for the further decline of the subsidy policy.

④ Three element batteries for passenger cars and lithium iron batteries for passenger cars are the basic trend.Fast charging is required for passenger cars.The fast charging time is less than 15 minutes.

⑤ High specific energy lithium/sulfur battery and high specific energy solid state lithium battery are the next generation batteries.At present,the requirements for their service life have not been emphasized.It is unlikely that they will be installed on a large scale in 2018.

⑥ The safety of electric bus is the key indicator:no fire or explosion occurs in the system within 30 minutes after the single thermal runaway.

4 Summary

① The development trend of key technologies is reflected by indicators with time nodes.Some adjectives can be used many times,but the indicator value is the core of understanding and mastering key technologies.

② The 2018 Key Special Application Guide for New Energy Vehicles issued by the Ministry of Science and Technology is at the national level,and its indicator value is the most authoritative.Information from other experts(scholars)does not represent top-level design.

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