LiFePO4/CNT Composite Cathode Materials and Performance (part 2)

2.3 Installation experimental tests and electrochemical cell

75% piece extremely positive active material, 17% acetylene black, 8% of polyvinylidene fluoride (PVDF) composition. Dell Vostro A860n battery hp Pavilion dv4 battery

N-methyl pyrrolidone prepared by adding some liquidity in the slurry stripper law evenly coated on aluminum foil, dried at 80 ℃, then roll in the roller press, film, very smooth and film formation dense. Training placed on the ~ 80 100 ℃ in a vacuum furnace, and a negative pressure, the heat treatment under vacuum for several hours. Focus on a very good film washed in 1cm2 pieces the size of the wafer, as stand-electrode, electrolyte with 1M LiPF6 of EC: DMC (1:1) (Merck) mixture, using the divide Celgard 2400 film lithium as a negative, in the argon glove box in the cell CR2032-type packed. With terrestrial 2001A tester on the battery and test the discharge cycle, charge current and discharge mode, the voltage range of 2.5V to 4.2V, constant current mode charge-discharge rate and variable load discharge test at ambient temperature. 367759-001 PB992A

3 Results and discussion

3.1 LiFePO4/CNT composite cathode material powders of the crystal structure analysis

For the X-ray diffraction to determine phase LiFePO4/CNT composite cathode. carbon composite cathode material doped LiFePO4/CNT three samples CNT-1, 2,3 by the XRD analysis are represented by phase pure LiFePO 4, and a good crystallinity.

3.2 LiFePO4/CNT burn the morphology of the sample

700 ℃ after heat treatment of samples LiFePO4/CNT SEM images shown in Figure 2. Samples of uniform particle size, were several hundred nanometers to 1 micron, the size is smaller. At the same time you can see samples of carbon nanotubes LiFePO4/CNT particles distributed in the activity. Particles had a carbon coating can increase the conductivity of the sample, the carbon nanotubes in the particles and the particles of cathode material is connected to the particles to provide additional driver path. Because the density of carbon nanotubes smaller, therefore, by adding a small amount can produce more abundant conductive path. toshiba satellite m115 battery toshiba satellite m40 battery

3.3 Structural parameters of carbon and iron phosphate lithium / carbon composite capacity characteristics of the cathode

The composite LiFePO4/CNT as cathode in lithium-ion batteries to turn C / 5 C / 2, C, 2C and 3C under the constant rate of electric charge and discharge performance test cycle. Figure 3, three curves represent three samples of the reversible capacity at a low flow rate (C / 5) Next, CNT-2 sample to 135 mAh / g, NCL-1 samples of 120mAh / g. The carbon content of the reversible capacity than the sample CNT-3 significantly higher than the CNT-1, 2 small, low rate is only 105mAh / g. However, three samples of the load capacity at a time and discharge rate increases with the decline inevitable happens. This is mainly due to carbon nanotubes dispersed in the precursor is still limited in the context of precursor evaporation of the solvent can not guarantee a high consistency, some places have taken place in carbon nanotubes of liquidation is not conducive to electrical conductivity of the cathode composite materials increase. toshiba satellite m105 battery toshiba satellite m110 battery

4 Conclusions

1) as a carbon source and citric acid chelating agent by a sol - gel method LiFePO4/CNT powder composite cathode.

2) the method of carbon nanotubes by adding conductive paths to improve the cathode material. In the low capacity to 135mAh / g at 1C rate charge-discharge capacity retention 110mAh / g, 2C, when the capacity remained at 80mAh / g. And with the carbon content increases, the capacity of lithium-ion batteries has also increased.

3) carbon particles in the distribution business is also less uniform, thus the high rate discharge capacity is still being improved. toshiba satellite a80 battery toshiba satellite m100 battery

LiFePO4/CNT Composite Cathode Materials and Performance (part 1)

1 Introduction

LiFePO4 its raw materials cheaper, better environmental compatibility, higher capacity, the advantages of good stability has become a potential candidate cathode material for lithium-ion battery. Dell Inspiron Mini 12 battery Dell Inspiron mini 9 battery

Pure LiFePO 4 at a very low drop rate (<C/80), only 0.6 molar amount of reversible Li insertion and extraction, now more than low conductivity of pure iron phosphate lithium, the rate of diffusion of lithium-ion battery is very low due. To improve the performance of LiFePO4, the study has been modified method are: high metal ion doped lithium-bit, ultra-thin, conductive composite materials (including modification of the surface point of surface coating ). A technology with carbon composite materials is to study more, the most effective and inexpensive, and easier to mass production method. The role of the carbon composite has three main points: grain refinement, in close contact to improve conductivity, the secondary reaction of the reduction of the Atmosphere. Reported a variety of carbon materials as a carbon source, such as freezing carbon, carbon black, sugar, cellulose acetate, sugar, glycolic acid, citric acid, polypropylene. Dell Vostro A840 battery Dell Vostro A860 battery

Carbon nanotubes (CNT) have a higher conductivity and a high-dimensional structure of cathode materials can be used to improve conductivity. Li and others added to the amount of cathode material LiNi0.7Co0.3O2 carbon nanotubes as a conductive agent, has greatly improved the capacity of the battery. In this paper, sol-gel precursor and the addition of carbon nanotubes LiFePO4 powder, made from a material lithium ion LiFePO4/CNT cathode carbon sol-gel-coated particles to provide activity based on carbon nanotubes to improve through contacts between the particles and particles, carbon reinforced the network driver, thereby improving the electrical properties of lithium-ion batteries.

2, experience

2.1 Purification of carbon nanotubes

carbon impurities are mainly amorphous carbon and iron. Therefore, the need to be purified before use of carbon nanotubes: Carbon nanotubes 4M nitric acid heated to 80 ℃ at about 6am, after the ultrasound, filtration, repeatedly until the washing Laundry liquid pH value of about 5.8. toshiba satellite m55 battery toshiba tecra a3 battery

2.2 LiFePO4/CNT composite cathode material powders synthesis and characterization

Citric acid, lithium nitrate, ferric nitrate and ammonium dihydrogen phosphate as reagent preparation 0.03mol precursors. The amount of citric acid dissolved in deionized water, heating and stirring, then adding lithium nitrate, iron nitrate and ammonium phosphate aqueous solution of diamine, the solution is transparent brown. Three same precursor prepared by adding carbon nanotubes, followed by the quantity 0.25 g, 0.1 g, 0.05 g, which represents LiFePO4 of 5wt%, 2wt%, 1wt%, respectively, CNT-1 2.3 name. Heat precursor 1h stirring, cooled to room temperature, 30min ultrasound, moved into a vacuum oven set at 12, so that carbon nanotubes are mixed with the precursor. In the 80 ℃ constant temperature bath of water until complete evaporation of the solvent. Precursors after drying in a nitrogen atmosphere, 300 ℃ calcined 8am, then at 700 ℃ for 8h. For the X-ray diffraction (Rigaku D / Max B Ⅲ) to determine the phase of final product, scanning electron microscopy (field emission scanning electron microscope LEO-1530) to observe the microstructure. toshiba satellite m45 battery toshiba satellite m50 battery

Battery-powered devices low-power design

Manufacturing process from the beginning until all the applications, low-power technology has become indispensable for all design needs. Energy-sensitive applications, especially single cell must provide the product for several hours operating time, more needs to join the ultra-low power design concepts. To meet these requirements, must be integrated micro-controller, it not only to understand the battery characteristics, Huan must understand in order to achieve continuous use for 10,15 or even 20 years no need to replace the battery, how to design the device. Dell inspiron 1425 battery Dell inspiron 1427 battery

To operate at very low power conditions, it must look to new ways of looking at these very low power applications. Traditionally, these complex applications are in a more convenient point of view to analyze the electricity consumption, for example of the use of the application and power to ask a hypothetical, in order to generate “typical” power consumption.

However, for example, to achieve continuous operation of a 20-year single-battery-powered applications, applications must learn self-discharge rate than the lower battery power, which makes each nA of power in the overall power budget even more critical.

Industry standard CR2032 button cell battery self-discharge current is less than 250nA. Is a common CR2032 lithium / manganese dioxide battery, nominal (no load) voltage of 3.0V. In practice, to achieve the longest battery life, you must use a highly integrated microcontroller (MCU). In sleep mode, the MCU must be able to below 1μA range in good working order, while providing the right mix of processing power and integrated on-chip peripherals and memory. Dell Inspiron 1440 battery Dell Inspiron Mini 10 battery

When each nA of power are critical, the only assumption on the performance or power to do the method is no longer absolutely feasible. To assess the optimal design of choice, the need to examine more parameters, although in some less sensitive to energy applications, these parameters did not seem critical. For instance, for advanced ultra-low-power sleep mode the microcontroller is already very common, however, micro-controller for the whole family will sleep mode power consumption the same approach may be not quite correct. Well-known microcontroller product line can show more than 1,700% change. Therefore, for ultra-low power design, focus on the chosen microcontroller family to performance without sacrificing low power conditions to upgrade the memory, and the pin must be compatible.

Another focus is to assess, over time, equipment, battery changes. All the engineers are aware, a battery voltage over time is largely determined by the structure of the battery and load. To CR2032, for example, a pair of AA / AAA alkaline batteries will have different firing patterns, therefore, a well-designed application, the battery must be in different conditions, can operate the same performance. Dell Inspiron Mini 1011 battery Dell Inspiron Mini 10v battery

To not consider the battery characteristics, in terms of pairs of an engineering team to Zai one pair of power-sensitive of Ying Yong in the same series of micro-Kongzhi Qi Cai Yong Chan Pin but also to pledge a single battery product to the normal operation of power supply to maintain for many years, is Xiangdang not easy. Consider the design team focus on low-voltage power characteristics, and operational performance. At this point, the microcontroller can operate at 2V or lower applied voltage, in order to gain more battery power. In addition, low voltage conditions, the micro-controller high-frequency operation must be maintained to ensure maximum application performance.

With low-power design needs of stable growth, the effective instruction set architecture (ISA) growing importance. Energy-sensitive applications are likely to have 99% of the time in sleep mode, inevitably, these devices must be on a regular basis, or a predefined time interval, or be awakened by external stimuli. In this regard, in order to achieve the task, designed to consider the key lies in the total energy usage. Design team must select ISA allows the microcontroller, these components have a higher percentage of single-cycle instructions to perform specific tasks, which can short implementation time and lower power consumption to complete the task. toshiba tecra a6 battery toshiba tecra a7 battery

For example, the use of a generic C function memcpy from a memory address of 32 bytes of data copied to another location, and for the PIC24F and MSP430 compiler, then the resulting code requires more than a 790 MSP430 % duty cycle (316 vs. 40). 4MHz at 3V and conditions, this example MSP430 consumes more energy than a 230% higher. This shows the importance of ISA.

In the construction of future applications, the embedded electronics industry has reached a watershed, the current design of integrated components, assessment and practice methods will be undergoing changes. Special significance of this shift, the next few years, more applications will integrate in its low-power design techniques. toshiba tecra a4 battery toshiba tecra a5 battery