Industry Observation | Old Trees and New Flowers——Introduction to Lead-Carbon Battery Technology and Analysis of Energy Storage Applications
January 11, 2023
The charging and discharging reaction mechanism is as follows:
The negative electrode active material of ordinary lead-acid batteries is lead (Pb), while in lead-carbon batteries, the negative electrode is changed from pure Pb to carbon material (C) with electric double layer capacitance characteristics + battery characteristic sponge lead (Pb) mixed composition The dual-functional composite negative electrode, that is, the lead-carbon (Lead-carbon) negative electrode, is then matched with the PbO2 positive electrode to form a lead-carbon battery. Generally speaking, the changes of lead-carbon batteries mainly appear on the negative electrode, and the changes in the electrode solution and positive electrode are not large. It can be said that lead-carbon batteries can be said to be new flowers blooming on the old tree of lead-acid batteries, and many good application results have been produced in recent years. In this regard, the added carbon is naturally to be credited.
At present, many battery companies at home and abroad are producing lead-carbon batteries. Representative companies include Japan's Furukawa, Ecoult, East Penn, and Axion, and domestic Sacred Sun, Shuangdeng, Nandu, and C&D.
Analysis of working principle of lead-carbon battery
One of the core problems in traditional lead-acid batteries is the sulfation of the negative electrode, that is, in the high-rate discharge mode, the spongy lead on the negative electrode reacts with HSO4- quickly to form PbSO4. At this time, because the pair of reactants HSO4- and Pb The supply mismatch of PbSO4 causes the nucleation rate of PbSO4 to be too fast, which makes the generated PbSO4 (which is insulating in nature) "paste" on the surface of the negative electrode, or generates extremely large particles; Uniformly generated inside the negative plate, or only fine, uniform and easy-to-reduce velvet PbSO4 is generated on the surface.
The PbSO4 accumulation layer or large particle PbSO4 formed on the surface significantly reduces the effective surface area and materials required for electron transfer and reaction, making subsequent reactions more difficult, thus making the interior of the negative plate a "dead" area. When charging, because the surface PbSO4 layer hinders the body reaction of the lead-acid battery, the potential of the negative electrode at this time has to electrolyze the water in the battery into hydrogen, resulting in the depletion of the electrolyte, which will further lead to the deterioration of battery performance.
1.Provide reaction centers: new reactive centers are formed on the surface of these carbon particles;
2.Form a conductive network to reduce polarization;
3.Form a finer and uniform mass transfer network to promote the uniform progress of electrochemical reactions on the surface and inside of the electrode, thereby reducing the concentrated precipitation effect of PbSO4 on the surface;
4.As a heterogeneous material, it hinders the growth of PbSO4 particles and makes them evenly distributed;
5.Through the capacitive effect of carbon, the capacity and power characteristics of the battery are improved.
Working and Performance Features
The negative electrode of the lead-carbon battery forms a relatively uniform and fine network of lead metal-carbon particles. This structure is conducive to shortening the diffusion distance and improving the uniformity of the reaction, and the carbon itself has good conductivity and capacitance characteristics. Compared with traditional lead-acid batteries, it has better low-temperature start-up ability, charge acceptance ability and high-current charge-discharge performance.
When working with high current: the capacitor carbon material acts as a "buffer". When the lead-carbon battery is working under frequent instantaneous high-current charging and discharging, the carbon material with capacitive characteristics mainly releases or receives the current. Like acid batteries, "negative electrode sulfation" occurs sharply under high current, which effectively prolongs the service life of the battery;
When working with low current: the sponge lead negative electrode is mainly used to continuously provide energy, and the energy stored in the carbon as capacitive energy due to high current impact will also react with the lead nearby, and the reaction will gradually become uniform.
Energy & power density can be increased to 40~60Wh/kg, about 300~400W/kg, the performance is already close to the capacity of some lithium batteries, and more importantly, its cost is still 0.6~0.8rmb/Wh, low Compared with other batteries such as lithium batteries, it has the most advantages in occasions where cost control is strict.
Long life, long cycle life under shallow charge and discharge conditions (such as 4500 times (70%DOD))
Market Positioning and Technical Analysis: Lead Carbon Vs Lithium Batteries Vs Others?
In recent years, the development of lithium-ion batteries has been very fast, giving many people the impression that "lead-acid batteries should be eliminated if they are backward". However, in fact, with the introduction and improvement of lead-carbon battery technology, its core competitiveness: low cost (0.6~0.8rmb/Wh) and good life make it widely used in stationary energy storage, low-speed electric vehicles, electric bicycles And other fields have made great achievements, becoming a strong opponent of lithium battery and other technologies.
1. In terms of stationary energy storage, energy storage fields such as photovoltaic power station energy storage, wind power energy storage, and grid peak regulation often require batteries to have the characteristics of high power density, long cycle life, and low price. Lead-carbon batteries have a greater competitive advantage in occasions with ample space and high cost requirements, and relatively speaking, the initial investment cost is relatively low. Lithium batteries are more suitable for occasions that require space and are less cost-sensitive due to their high energy density and high cost, and will be more developed in distributed energy storage occasions. Compared with other energy storage technologies, such as capacitors (very low energy storage density, which can only be used for power buffering) and flow batteries (medium technology maturity, significantly larger volume), lead-carbon technology still has good competitiveness at this stage .
2. In terms of transportation energy storage, the main competitive advantages of lead-carbon batteries are low cost, stable performance, and good safety. A. The low cost makes it have an advantage in the low-end market such as low-speed electric vehicles. Although the country has the idea of promoting lithium batteries, after all, market rules need to be respected. B. Stable performance enables lead-carbon batteries to provide reliable protection under extreme conditions such as high and low temperatures. For example, the start-stop power supply of a car must be able to output a large current at -20°C, while the low-temperature performance of lithium batteries has always been a universality. long-standing problem. C. Good safety: The safety of transportation tools cannot be overemphasized. Lithium batteries have shortcomings in this regard objectively, and lead-acid-lead-carbon batteries have inherent obvious advantages in this regard.
Therefore, the author believes that lead-carbon batteries will maintain their dominant position in some subdivided fields in recent years. Although technologies such as lithium batteries are growing rapidly, each of these battery technologies has its own advantages and disadvantages, and no energy storage technology can be used in various scales and scenarios. According to the needs of the field, choosing the appropriate energy storage technology application is the kingly way.
Lead-acid battery is an ancient and practical battery technology. The new generation of lead-carbon battery produced by introducing the optimization of capacitor carbon has become an important booster for this amazing battery technology to continue its legend in the new era. Cost, performance stability, and safety are the core advantages of this type of battery, so it will still have good competitiveness in the fields of stationary energy storage and low-end electric vehicles in recent years. Of course, various technologies are constantly improving, and we are also eagerly expecting that more, newer and better energy storage technologies will continue to emerge and mature, bringing convenience to our lives.