1. 1 cathode material
Lithium-ion battery cathode materials are mainly divided into lithium-rich manganese-based materials, ternary composite materials, spinel-type LiMn 2 O 4 , lithium iron phosphate and lithium nickel manganese oxide. Li-rich manganese-based solid solution cathode material Li 1 + x M 1 – x O 2 (M is a transition metal such as Ni, Co and Mn) with high specific capacity (> 200 mAh/g), high energy density, low cost and environmental protection Friendly, etc., but there are shortcomings such as low initial discharge efficiency, low coulombic efficiency, poor cycle life, unsatisfactory high temperature performance, and low rate performance. Researcher Wang Zhaoxiang from the Institute of Physics, Chinese Academy of Sciences combines experimental research with theoretical calculations. From the exploration of the driving force of Mn migration, this paper studies a series of problems caused by Mn migration and proposes a method to inhibit Mn migration. Professor Wang Xianyou of Xiangtan University started from the relationship between material structure and performance, and improved and improved by optimizing material structure, design material composition (O excess), controlling material phase composition (Co-doped) and surface modification (coated with polyaniline). The way of lithium material performance. In the coating modification, Professor Chen Zhaoyong of Changsha University of Science and Technology conducted an in-depth study: a microporous Al 2 O 3 /PAS double-layer cladding structure was constructed on the surface of the lithium-rich manganese-based cathode material, and the cathode material was at a rate of 0.1 C. The specific capacity is up to 280 mAh/g, and after 100 cycles at 0. 2 C, there is still 98% capacity retention and no structural transformation of the material. The research of Ni-Co-Mn ternary cathode material mainly focuses on optimizing the composition and preparation conditions, coating or doping modification, etc., in order to further improve the capacity, cycle characteristics and rate performance. The first discharge specific capacity of the first discharge specific capacity is 209. 4 mAh/g, 1. 0 C. The first discharge specific capacity of the material is 0. 1 C mAh/g, 1. 0 C. 7%。 Capacity retention rate of 95. 5%, the capacity retention rate at high temperatures is still 87.7%. The coating material may also be LiTiO 2 , Li 2 ZrO 3 or the like, which can improve the stability of the ternary positive electrode material. Preparation of spinel LiMn 2 O 4 by solid phase combustion synthesis can reduce the reaction temperature, accelerate the reaction rate and improve the crystal structure of the product. The main methods for modifying the spinel LiMn 2 O 4 are coating and doping, such as coating ZnO, Al 2 O 3 , doping Cu, Mg and Al. The modification of lithium iron phosphate is mentioned. The methods used are element co-doping (such as vanadium ion and titanium ion), addition of ferrocene and other catalytic graphitization additives, and compounding with graphene, carbon nanotubes and the like. For lithium nickel manganate cathode materials, high temperature stability can also be improved by doping modification and coating, and improving synthesis methods and processes. Other researchers have proposed some other types of cathode materials, such as carbonyl conjugated phthalocyanine compounds, with an initial discharge specific capacity of 850 mAh/g; graphene-mesoporous carbon/selenium (G-MCN/Se) ternary For the composite film positive electrode, when the selenium content was 62%, the first discharge specific capacity of 1 C was 432 mAh/g, and remained at 385 mAh/g after 1 300 cycles, showing good cycle stability.
1.2 Anode material
Graphite materials are currently the main anode materials, but researchers have been exploring other anode materials. Compared with the cathode material, the anode material has no obvious research hotspot. The electrolyte will reductively decompose on the surface of the graphite anode during the first cycle of the battery to form a solid electrolyte phase interface (SEI) membrane, resulting in the first irreversible capacity loss, but the SEI membrane can prevent the electrolyte from continuing to decompose on the graphite surface, thus protecting the electrode. The role. Zhang Ting of South China Normal University added dimethyl sulfite as a SEI film-forming additive to improve the compatibility between the graphite anode and the electrolyte and improve the electrochemical performance of the battery. Some researchers have used nano-titanate-carbon composites as anode materials, and coated with ZnO, Al 2 O 3 and other materials by magnetron sputtering to improve rate performance and cycle stability; spray drying pyrolysis The silicon-carbon composite anode material prepared by the method has a first discharge specific capacity of 1 033. 2 mAh/g at a current of 100 mA/g, and a first charge and discharge efficiency of 77.3%; self-supporting flexible silicon/graphene The composite film anode material was cycled 50 times at a current of 100 mA/g, the specific capacity was still 1 500 mAh/g, and the coulombic efficiency was stabilized at 99% or more. The reason is that the graphene sheets have high electrical conductivity and flexibility.
1.3 lithium ion battery
Electrolyte The traditional carbonate electrolyte system has problems such as flammability and poor thermal stability. It develops an electrolyte system with high flash point, non-flammability, wide electrochemical stability window and wide temperature adaptability. It is a key material for lithium ion batteries.
2 NiMH battery
A research hotspot in nickel-metal hydride batteries is hydrogen storage alloy materials. Professor Guo Jin of Guangxi University believes that the rapid cooling at liquid nitrogen temperature and the non-equilibrium treatment of mechanical ball milling regulate the hydrogen storage performance of Mg 17 Al 12 alloy. Associate Professor Lan Zhiqiang of Guangxi University used the heat treatment process combined with mechanical alloying to prepare Mg 90 Li 1 – x Si x (x =0, 2, 4 and 6) composite hydrogen storage materials, and studied the addition of Si to the solid solution storage of Mg-Li system. The effect of hydrogen performance. The introduction of rare earth elements can inhibit the amorphization phenomenon and the disproportionation process of the alloy composition during the hydrogen absorption and desorption cycle, and increase the reversible hydrogen absorption and desorption of the alloy. The conventional hydrogen storage alloy materials on the market are mostly doped with rare earth elements (La). , Ce, Pr, Nd, etc.), but the price of Pr and Nd is higher. Zhu Xilin reported on the application of an AB 5 hydrogen storage alloy not doped with Pr and Nd in a nickel-hydrogen battery. The square battery applied to the electric bus has been safely operated for 100 000 km. Another research hotspot for hydrogen storage materials is metal nitrogen hydrides such as Mg(BH 2 ) 2 -2LiH, 4MgH 2 – Li 3 AlH 6 , Al-Li 3 AiH 6 and NaBH 4 -CO(NH 2 ) 2 . Reducing the particle size and adding an alkali metal additive can improve the hydrogen storage performance of the metal coordination hydrogen storage material, wherein the particle size is reduced, which is mainly achieved by high energy mechanical ball milling. The Amine-Decorated12-Connected MOF CAU-1 material reported by Professor Sun Lixian of Guilin University of Electronic Technology has excellent H 2 , CO 2 and methanol adsorption properties, which are of great significance and application value for CO 2 emission reduction and hydrogen storage. They also developed A variety of aluminum-based alloy hydrogen-generating materials, such as 4MgH 2 -Li 3 AlH 6 , Al-Li 3 AiH 6 and NaBH 4 -CO(NH 2 ) 2 , are used in combination with fuel cells.
The search for electrode materials with high rate performance and long cycle life is the focus of research on supercapacitors, among which carbon materials are the most common supercapacitor electrode materials, such as porous carbon materials, biomass carbon materials and carbon composite materials. Some researchers have prepared nanoporous carbon aerogel materials and proved that good electrochemical capacitance characteristics come from the three-dimensional network skeleton structure and ultra-high specific surface area. Nie Pengru, Huazhong University of Science and Technology, obtained a three-dimensional porous carbon material and used it as an electrode material for supercapacitors in the process of recovering waste lead-acid batteries by citric acid wet leaching. This method can promote the close integration of the energy storage industry and the environmental protection industry, and produce good ecological and environmental benefits. The researchers also explored the use of different biomass carbon materials (sucrose, pollen, algae, etc.) as electrode materials for supercapacitors. In the aspect of composite materials, researchers have designed a sandwich-shaped MoO 3 /C composite material, the α-MoO 3 layer and the graphene layer are horizontally interleaved and stacked, which has excellent electrochemical properties; graphene/carbon quantum dot composite The material can also be used as an electrode material with a specific capacitance of 256 F/g at a current of 0.5 A/g. Professor Liu Zonghuai of Shaanxi Normal University prepared a mesoporous manganese oxide nanoelectrode material assembled from manganese oxide nanoparticles with a specific surface area of 456 m 2 /g and a specific capacitance of 281 F/g at a current of 0.25 A/g. Liu Peipei of South China University of Technology prepared a three-dimensional nano-flowered NiO-Co 3 O 4 composite material with a specific capacitance of 1 988. 6 F/g at a current of 11 A/g, and a capacitance retention rate of 1,500 cycles. 94. 0%; Wang Yijing of Nankai University studied the growth mechanism, microstructure and performance of NiCo 2 O 4 materials with different morphologies. Tang Ke, from Chongqing University of Arts and Sciences, analyzed the relationship between equivalent resistance and charging current. The equivalent circuit model was used to study the variation of capacitance, storage capacity and charging efficiency of supercapacitor with current. The temperature storage performance of supercapacitor was discussed. Impact.
4 fuel cell
The commercialization of proton exchange membrane fuel cells (PEMFC) is primarily constrained by cost and longevity. Since the catalyst used in PEMFC is mainly a noble metal such as Pt, it is costly and easily degraded in the working environment, resulting in a decrease in catalytic activity. Researcher Shao Zhigang from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences reported a Pd-Pt core-shell catalyst that introduces Pd to reduce the amount of Pt used and increase the activity of the catalyst. In addition, researchers have improved the interaction between metal and carrier by using polymer stabilization, surface grouping and metal surface carbon cluster modification to obtain PEMFC metal oxygen reduction catalyst with high activity and high stability. Cao Tai of Beijing Institute of Technology introduced a lightweight, low-cost and large-scale synthesis method for the synthesis of uniform, nitrogen-doped, bamboo-shaped carbon nanotubes with cobalt nanoparticles at the top. The products have excellent properties. Redox catalytic activity. Carbon-based catalysts and other non-platinum catalysts for fuel cells, which may replace conventional platinum-based catalysts, are obtained by hydrothermal carbonization, high-temperature thermal cracking, etc., and have comparable performance to commercial platinum carbon catalysts.
5 other batteries
5. 1 sodium ion battery
The charge and discharge process of Na 0. 44 MnO 2 material was studied in Dai Kehua of Northeastern University. It was found that Mn 2 + was formed on the surface of the material at low potential. The conductive resin phenolic resin PFM could improve the reversible specific capacity of pure Sn powder. To achieve stable charging and discharging. The Zhongnan University Xiao Zhongxing et al. sintered by the hydrothermal method and the high-temperature solid-phase method to synthesize the higher purity Na 0. 44 MnO 2 , and the metal sodium was used as the negative electrode to assemble a button-type battery, with a capacity of 0. 5 C cycle 20 times. The retention rate was 98.9%; Zhang Junxi of Shanghai Electric Power College synthesized NaFePO 4 crystallites of olivine structure, which was used as a cathode material for sodium ion batteries and had good electrochemical performance. Associate Professor Deng Jianqiu of Guilin University of Electronic Technology prepared a nano-linear strontium sulfide by hydrothermal method and used it as a negative electrode material for sodium ion batteries. The material has a first discharge specific capacity of 552 mAh/g at 100 mA/g. After 55 cycles, the capacity retention is 85.5%. It is cycled 40 times at 2 A/g and returns to 100 mA/ The current of g and the specific capacity of the discharge are restored to 580 mAh/g, indicating that the cycle performance of the negative electrode material is good, and the structure can be kept stable after a large current cycle.
5. 2 lithium-sulfur battery
Research on lithium-sulfur batteries is currently focused on electrode materials, such as porous carbon materials, composite materials, etc., aimed at improving battery safety, cycle life and energy density. The carbon material developed by Zhang Hongzhang of the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences has a large pore volume (> 4. 0 cm 3 /g), a high specific surface area (>1 500 m 2 g), and a high sulfur content (>70%). Under the condition of high sulfur content (3 mg/cm 2 ), the specific specific capacity of 0.1 C discharge is 1 200 mAh/g; Professor Chen Yong of Hainan University uses Ti 3 C 2 of two-dimensional accordion structure as the positive electrode material. Combined with sulfur to obtain S/Ti 2 C 3 composite, the initial discharge specific capacity reached 1 291 mAh/g at a current of 200 mAh/g, and the reversible specific capacity of the cycle was still 970 mAh/g.
5. 3 flow battery
Researcher Zhang Huamin from the Dalian Institute of Chemistry and Physics, Chinese Academy of Sciences gave a report on the research progress and application of liquid battery energy storage technology, and introduced the development progress of liquid battery electrolyte, non-fluoride ion conductive membrane and high specific power reactor. And research results in the flow battery system. They developed a 32 kW class high-power density flow battery stack that was charged and discharged at a current density of 120 mA/cm 2 with an energy efficiency of 81.2%, enabling large-scale production, of which 5 MW/10 MWh flow battery The energy storage system has been implemented on the grid.
Lithium-ion batteries, supercapacitors and fuel cells are still the focus of research on batteries; other batteries, such as sodium-ion batteries, flow batteries and lithium-sulfur batteries, are also evolving. The current research focus of various types of batteries is still to develop electrode materials in order to achieve higher capacity, efficiency, cycle performance and safety performance.
Introduction to all solid electrolyte materials