1.2V NiMH batteries

Brief Analysis of the Key Technologies of Fuel-Power 1.2V NiMH batteries Vehicles

Some technical indicators of my country's fuel-power battery have reached or exceeded the level of similar products in the world. You who keep up with the times must want to know the key materials and technologies.

Technical Chain of Fuel-Power Battery for Vehicles

The power generation principle of fuel-power battery is similar to that of primary battery or secondary battery. Hydrogen oxidation reaction and oxygen reduction reaction occur on both sides of the electrolyte diaphragm, and electrons work through the external circuit. The reaction product is water. A single cell of a fuel-power battery includes a membrane electrode assembly (MEA), a bipolar plate and a sealing element.

Unlike primary batteries and secondary batteries, fuel-power battery power generation requires a relatively complex system.

The mainstream technology of the power chain of fuel-power battery vehicles is the electric-electric hybrid mode. When running smoothly, it relies on fuel-power batteries to supply power. When high power output is required, the fuel-power battery and the secondary battery are jointly powered. Under low load or idling conditions, the fuel-power battery charges the secondary battery.

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►Pt-M catalyst

Pt-Co/C, Pt-Fe/C, Pt-Ni/C and other binary alloy catalysts improve stability, improve mass specific activity, and reduce the amount of precious metals used. For example, Chen et al. prepared electrocatalysts with high activity and high stability.

►Pt core-shell catalyst

Using non-Pt materials as supporting cores and surface precious metals as shells, the amount of Pt can be reduced and the mass specific activity can be improved. For example, the [email protected]/C core-shell catalyst prepared by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, has better oxygen reduction activity and stability than commercial Pt/C catalysts.

►Pt single atomic layer catalyst

Preparing a core-shell structure catalyst with a single atomic layer of Pt is an effective way to reduce the amount of Pt, improve the utilization rate of Pt, and improve the ORR performance of the catalyst. The research group of Adzic of the US National Laboratory and Zhang Junliang of Shanghai Jiaotong University are relatively active in this regard.

►Non-precious metal catalysts

The research on non-precious metal catalysts mainly includes transition metal atom clusters, transition metal chelates, transition metal nitrides and carbides. In this regard, various heteroatom-doped nanocarbon materials have become research hotspots, such as N-doped non-precious metal catalysts, which show good application prospects.

►Solid electrolyte membrane

The proton exchange membrane (PEM) in automotive fuel cells is a solid electrolyte membrane, which is used to isolate fuel and oxidant and transfer protons (H+). The currently commonly used commercial proton exchange membrane is perfluorosulfonic acid membrane.

In addition, in order to improve performance, the durability of increasingly thin proton exchange membranes is tested, so a series of enhanced composite membranes modified from plasma membranes are constantly being developed.

►Gas diffusion layer (GDL)

The GDL is located between the flow field and the catalyst layer. Its purpose is to support the catalyst layer, stabilize the electrode structure, and have mass/heat/electricity transfer functions. Usually, the GDL consists of a support layer (hydrophobic porous carbon paper or carbon cloth) and a microporous layer (composed of electrocarbon black and hydrophobic agent). Table 1 compares domestically produced carbon paper with imported commercial carbon paper. The next step is to establish mass production equipment.

In addition to improving the conductive function of the gas diffusion layer, the research on the mass transfer function of the gas diffusion layer has gradually attracted people's attention in recent years.

►Membrane electrode assembly (MEA)

MEA is a combination of membrane, catalyst layer and diffusion layer, and is one of the core components of fuel cells.

Dalian Institute of Chemical Physics, Chinese Academy of Sciences has developed a new type of MEA that reaches international standards.

►Bipolar plate (BP)

The purpose of BP is to conduct electrons, distribute reaction gases and take away generated water.

Dalian Institute of Chemical Physics, Chinese Academy of Sciences has studied the surface modification technology of metal bipolar plates to improve the conductivity and corrosion resistance of bipolar plates.

►Fuel cell stack

Fuel cell stack is the core of the fuel cell power generation system.

At present, Dalian Institute of Chemical Physics, Chinese Academy of Sciences has established a complete technical system from the preparation of materials, MEA, bipolar plate components to stack assembly and testing, and developed a fuel cell stack.

Fuel cell stack developed by Dalian Institute of Chemical Physics, Chinese Academy of Sciences

Japan Toyota's fuel cell stack adopts 3D flow field design, which makes the fluid appear perpendicular to the catalyst layer, strengthens mass transfer and reduces mass transfer polarization.

Fuel cell system components

Fuel cells include fuel supply subsystem, oxidant supply subsystem, water heat management subsystem and monitoring subsystem, etc. Important system components include air compressor, humidifier, hydrogen circulation pump, high-pressure hydrogen bottle, etc.

► Air compressor

The task of the on-board air compressor is to supply the oxidant (oxygen in the air) required for fuel cell power generation. Common types of air compressors include centrifugal, screw, Roots, etc.

► Humidifier

The reaction gas brings the water required for the fuel cell reaction into the fuel cell through the humidifier. Common humidifier forms include membrane humidifier, enthalpy wheel humidifier, etc. At present, the development trend is to use hydrogen reflux pump to bring in water from the reaction tail gas, and the system does not need humidifier components.

In addition to the above-mentioned system components, the control strategy of the system is also very important. The durability can be improved by optimizing the control strategy based on the existing materials.

Conclusion

Fuel cell electric vehicles have high power performance, fast charging, long driving range, and near zero emissions. They are strong competitors for future new energy vehicles.

The 2018 my country Hydrogen Resources and Hydrogen Energy Industry Development Forum will be held in Dalian, Liaoning from September 18 to 19, 2018. The conference will discuss the development prospects and investment opportunities of the global and Chinese hydrogen energy industry chain, hydrogen production technology and cost analysis, the potential of industrial by-product hydrogen resources in my country, hydrogen purification and impurity removal technology, hydrogen storage and transportation mode, hydrogen fuel cell vehicle (FCV) industry infrastructure construction, hydrogen energy storage system and large-scale renewable energy integration, hydrogen and CO2 production of high-value chemicals methanol, olefins and aromatics, etc.

The 2018 my country Fuel Cell, Bipolar Plate and Membrane Electrode Key Materials Forum will be held in Dalian, Liaoning from September 19 to 20. The conference will discuss the development status and market outlook of fuel cell batteries in the world and my country, design ideas for fuel cell batteries in different application scenarios, fuel cell standards and testing technologies, quality control and intelligent manufacturing for large-scale production of battery stacks, performance optimization and cost control of bipolar plates, membrane electrodes, proton exchange membranes, catalysts and gas diffusion layers, and analysis of key factors for long-term stable operation of automotive fuel cell batteries.

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