From various aspects that are conducive to battery low temperature discharge performance, while other performance indicators of battery capacity, weight, try to improve battery -40 ° C low temperature discharge properties, extend battery life. The products studied in this paper are mainly used in the valve-controlled lead-acid battery in the fields of military vehicles, extreme low temperature environments. The battery is technically, and the battery has a low temperature of 5 hours in -40 ° C to 50% or more. More than 30% industry index requirements.Valve-type sealed lead-acid battery is widely used in submarines, tanks, computers, communications, solar batteries, etc. in some special use areas, or in use areas. For example, low temperature capacity requirements, -40 ° C low temperature 5 hours (termination voltage 10.2V) capacity is not less than 30% of normal temperature capacity. The normal lead paste formulation is used, and the low temperature capacity of -40 ° C will drop to about 30% of normal temperature, so that the product is very low. The temperature is reduced, and the viscosity of the electrolyte is increased, the permeability is weakened; the internal resistance of the battery increases, the internal voltage drop is increased. Under these factors, the battery discharge capacity is reduced. In addition, in low temperature environmental conditions, the general valve-controlled lead-acid battery negative electrode active material decreases with temperature, and the charging acceptance capacity is rapidly lowered, and the discharge performance of the battery will further reduce the battery's performance.
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This paper starts from various aspects of the low temperature discharge performance of the battery, while the battery capacity, weight, etc. satisfies the requirements, minimizing battery -40 ° C low temperature discharge performance, extend battery life.
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1 temperature on lead-acid battery
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(1) The actual capacity of the battery
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The temperature on the lead-acid battery is large, and the capacity is reduced as the temperature is reduced.
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The rated capacity of the battery is usually specified at ambient temperature at 25 ° C and in the predetermined discharge rate. The battery's best operating temperature is 25 ° C, when the battery discharge operating temperature is not 25 ° C, due to the effect of electrochemical, the actual capacity should be converted into a 25 ° C reference temperature in the formula (1).
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Where: CT is the measured capacity (AH);
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CE is a nominal capacity (AH) at ambient temperature at 25 ° C;
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T is the actual ambient temperature (° C);
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K is a temperature coefficient of capacity, 10 hours-rate capacity experiment
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K = 0.006 / ° C, 3 hour capacity of K = 0.008 / ° C, 1 hour rate capacity experiment k = 0.01 / ° C. As can be seen from the formula (1), when the ambient temperature is higher than 25 ° C, the actual release capacity CT of the battery is greater than the design rated capacity Ce; and the actual release capacity CT is lower than the design when the ambient temperature is below 25 ° C. Rated capacity CE. It can also be seen from the value of temperature coefficient k, the larger the discharge rate, the larger the temperature on the capacity [1].
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(2) Relationship between temperature and battery electrolyte performance
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The battery capacity decreases with temperature, which is closely related to the temperature of the electrolyte viscosity and internal resistance. When the electrolyte temperature is high, the diffusion speed increases, and the internal resistance is lowered, and its electromotive force is slightly increased. Therefore, the capacity and active material utilization rate of the lead-acid battery increases with temperature. When the electrolyte temperature is lowered, its viscosity is increased, and the ionic movement is larger resistance, and the diffusion ability is lowered. The resistance of the electrolyte at low temperature increases, and the resistance of electrochemical reaction increases, resulting in a decrease in battery capacity.
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(3) Effect of low temperature on lead-acid battery polar plate
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Under low temperature working conditions, the sponge lead is easily smaller than small size, which is easily designed to be frozen and clogged, thereby greatly reducing the utilization of active substances. If the large current discharge is used in a low temperature harsh case, the small holes in the negative electrode active substance will be blocked more severe, and the sponge-shaped lead may become dense PBSO4 such that the battery can be greatly reduced. For the positive electrode plate, its temperature coefficient is negative, and thus has a high electrode potential at low temperatures. Thereby, the positive electrode discharge rate is much larger than the negative electrode discharge rate at low temperatures. Thus, the procedure of the positive electrode PBO2 is converted to PBSO4 before the negative electrode generates the PBSO 4 layer, so the positive electrode plate does not generate a dense PBSO4 crystal grain at low temperatures. Therefore, the temperature is too low will result in a decrease in the capacity of the valve-controlled sealed lead-acid battery [2].
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2 development of low temperature cells
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(1) Development plan for low temperature battery
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From various aspects that facilitate low temperature discharge performance, while other performance indicators such as battery capacity, weight, the battery life is allowed to increase the battery life at -40 ° C low temperature, and extend the battery life. The specific scheme is as follows:
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1 From the positive plate, adjust the PB-CA-Sn-Al alloy ingredient, increase the SN content to 1.2% to 1.5% to increase the grid mechanical strength and corrosion resistance. Add 0.1% AG to the alloy, increase the grid resistance resistance, which is conducive to improving the deep cycle discharge cycle performance of the battery. With the radioactive plate gate structure, the middle portion of the polar ear is moved, the thickness of the polar plate is thinned, and the number of plates is increased, and the battery large current discharge capacity is improved.
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2 In order to extend the battery life, improve the low temperature high current discharge capacity, use a high-density lead paste formulation to add a conductive agent in the amount of the lead paste. Adopt larger assembly pressure, internalization, further improve the battery life. The addition of the conductive additive in the positive electrode plate can reduce the electrical resistance of the plate, the battery low temperature discharge performance is significantly improved; the conversion efficiency of the positive electrode active material can be improved, and the positive electrode plate is more likely to pass; to ensure the high pore rate of the positive electrode plate, more acid Diffusion inside the liquid toward the plate and improves the utilization of active material;
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3 Adding a peripheral, the addition ratio of the ochee, the addition ratio of the humic acid, and more effectively avoid the formation of the lead passivation layer of the sulfate, and improves the battery low temperature discharge capacity;
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4 The addition of the activated carbon in the negative electrode lead, ensures the high porosity of the negative electrode plate, more beneficial to spread the acid to the polar plate, improve the active material utilization;
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5 The number of positive and negative electrode sheets is added to the pole group, and the real surface area of the plate is improved, ensuring high discharge capacity of the battery;
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6 Select high-porosity, low internal resistance AGM high-quality partition, improve the ionic passability of the electrolyte, thereby ensuring good low temperature performance of the battery;
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7 use high purity, high-solid nano silica sol and mixed rubber electrolyte of the Na2SO4 additive dilute H2SO4, so that the electrolyte rubber is uniform, no moisture, improves the charging capacity of the battery over discharge, ensuring the battery life.
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(2) The main technical indicators of the main technical indicators of low temperature batteries are shown in Table 1.
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(3) The performance of the low temperature battery and the ordinary battery compared to the low temperature formulation and the normal formulation of 12V100AH battery performance, such as shown in Figure 1.
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This figure is a comparison of the discharge curve of the ultra-low temperature and negative electrode active material formulation of the present invention to the conventional battery under -40 ° C.
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By detecting, a battery made of ultra-low temperature and negative electrode active material formulations, ultra-low temperature conditions (-40 ° C), and the discharge capacity reaches 50% or more of the rated capacity [3].
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(4) Comparing the performance of other manufacturers of products Comparison of the battery test results of the battery and different manufacturers of the present invention, see Table 2.
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3 conclude
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By using a change design and low temperature formula, the low temperature valve controlled lead-acid battery can be achieved under ultra-low temperature conditions (-40 ° C), and the discharge capacity reaches 50% or more of the rated capacity.
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