Battery application is wide, they play a very important role in electrical energy storage in traction power supply systems (such as automobiles, motorcycles, etc.) and renewable energy power generation systems (solar energy, wind energy, etc.).
In the above-mentioned two typical battery application, mobile and stationary, there are different criteria for battery selection. In addition to cost, life (including cycle time and replaceability), energy density, power density (per unit mass or unit volume) and temperature performance, there are several factors that are becoming more and more important in the selection basis of batteries. Including the environmental friendliness of the battery application system, the degree of recyclability of components and the independent production capacity of products.
1.Battery application: the overall structure of energy storage management power system and transportation system
With the liberalization of the European electricity market and the creation of next-generation energy markets, fluctuations in electricity prices are now becoming more frequent, especially during peak electricity consumption periods. One solution to this problem is energy storage, including both centralized energy storage (such as pumped hydro) and distributed energy storage (such as battery energy storage applied to photovoltaic power generation systems). Furthermore, the exponential growth of distributed energy sources (eg wind, solar, mostly intermittent) will also have a significant impact on the volatility of electricity prices, boosting the need for energy storage and other complementary generation to achieve Balance of supply and demand of electrical energy. Electric energy storage can manage the grid well in terms of power supply and demand balance and power quality, and is a good technical choice.
In the battery application, whether it is the current successful battery application of hybrid electric vehicles, the new generation of plug-in hybrid electric vehicles under development, or the future full electric vehicles, and the industry is thinking about how to meet the energy needs of buildings and transportation. (such as Honda), etc. have shown that battery application have a bright future in the field of transportation to achieve carbon-free emissions. Therefore, finding a high-efficiency (high specific power and high specific energy) energy storage technology solution to overcome the current energy storage bottleneck of electric vehicles has become a top priority in the development of the automotive field.
How to improve battery performance in terms of energy density, safety, cost, and rechargeability to meet the special requirements in fixed stations and transportation applications is a major scientific issue in battery application research.
Hybrid electric vehicles (HEVs) can be divided into different degrees of power mixing according to the degree to which the generator is used in a driving cycle while driving. The earliest batteries were used in micro-hybrid vehicles (such as Citroen's C3 Stop&Go, which uses lead-acid batteries), with a lower degree of hybridization; later, hybrid electric vehicles with a higher degree of hybridization appeared, such as the Toyota Prius (using nickel-metal hydride power batteries) ), charging the battery through the engine can save 25% of fuel; up to the latest plug-in hybrid vehicles, with the highest degree of hybridization, the battery can be charged directly from the mains terminal. Therefore, batteries with high specific energy (meaning endurance) and high specific power (meaning acceleration and starting ability) are in increasing demand. Experts in this field generally believe that it is necessary to implement lithium-ion battery technology to meet the battery application of the above-mentioned in vehicles.
2.Development history of battery energy storage technology
Since Gaston Plante invented the lead-acid battery in 1859, battery technology has continued to improve. Until the end of the 1980s, there were mainly two types of battery products occupying the energy storage market: lead-acid batteries (mainly used for batteries to start cars, provide reliable power supply for communication networks, etc.) and Jin-cadmium batteries (mainly for batteries used in mobile tools, toys, emergency lighting, etc.). Thanks to the efforts of Japanese battery companies, lithium-ion batteries entered the market in the early 1990s. At that time, lithium batteries already had a high specific energy (100W·h/kg), which was twice that of nickel-cadmium batteries and more than three times that of lead-acid batteries. Since then, the performance of lithium batteries has been greatly improved, and by 2008, it had reached 200W·h/kg.
At present, lithium-ion batteries are used in mobile products, with a global market share of more than 70%. In terms of its performance indicators and possible future improvement potential, lithium-ion batteries are the most promising technical solution to overcome the energy storage problems encountered in battery application such as hybrid vehicles and photovoltaic power generation systems. The performance advantages of lithium-ion technology stand out at the conclusion of the ASTOR project, which was implemented by European car manufacturers (EUCAR) from 2001 to 2004. A total of 25 commercial battery systems and technology prototypes were tested in the project. In the framework of the SUBAT European program from 2004 to 2005, the impact of different battery technologies on the environment was assessed, and the results also showed that lithium-ion battery technology is very suitable for HEV battery application. In addition, the European network INVESTIRE, which has been working on evaluating the battery application of energy storage to new energy power generation systems, has also concluded that lithium-ion batteries are suitable for photovoltaic power generation systems.
3.Battery application: Lithium-ion battery is the core of hybrid vehicle
Thanks to the policy support of various countries for energy conservation and emission reduction, as well as the rising oil prices, the market for batteries used in hybrid vehicles is expanding. Worldwide sales of hybrid vehicles were 84,000 in 2004 and 205,000 in 2005. According to the research results of the SUBAT project, by 2012, in the Chinese market alone, sales of hybrid vehicles will reach 8,000,000 units. Currently, except for the Toyota Viitz, which is only sold in Japan (the Viitz uses a Stop&Go operating system equipped with a 12V lithium-ion battery), the rest of the commercialized hybrid electric vehicles use nickel-metal hydride batteries. Such as Toyota's Prius (Prius) and Lexus (Lexus) are used, high-voltage nickel-metal hydride batteries. Currently, Toyota has an 83 percent market share in hybrid electric vehicles, leaving Honda and General Motors far behind. From a battery application technology and commercial perspective, Toyota's Prius II was a real success, needing only one flaw to break through before it was available for sale. However, we will have to stress that in a Zero Emission Vehicle (ZEV), the battery (NiMH) has a very short cruising range, only 2km in pure electric driving mode. This shows that hybrid vehicles still have a lot of room for improvement in this area. Due to environmental constraints, rising fossil fuel prices, and advances in battery technology, the success of the Prius II has drawn the interest of all EV makers.
The Citroen C3 sold by PSA uses a start-stop system, in which the engine is shut down when the vehicle is stopped to reduce fuel consumption and reduce pollutant emissions. However, the car uses a lead-acid battery, and due to its performance constraints, the battery unit cannot recover braking energy, nor can it boost the engine during acceleration. It is expected that in the near future, hybrid vehicles will use lithium battery technology, and by 2015, lithium batteries will occupy 40% to 50% of the market. According to the study of the SUBAT project, the cost of lithium batteries will decrease in 2012 due to the continuous growth of China's hybrid vehicle market (China will have both the role of a car manufacturer and a consumer), and the cost of electrode materials due to technological progress. year began to decline.
At present, the battery application to plug-in hybrid electric vehicles is only in the stage of prototype development. However, we would also like to mention here two French companies that have done well in plug-in hybrid vehicles - Batscap/Bathium (for lithium metal polymer) and Dassault/SVE (for lithium ion polymer) thing). They are expected to start promoting electric vehicles and ships in 2009.
Regarding the battery application in hybrid vehicles, the acceptable depth of charge and discharge without reducing their service life is a key indicator. To date, several battery technologies are competitive in hybrid vehicle battery application, including:
1) Graphite/NCA electrode pair, originally developed by SAFT and sold by JCS for Mercedes-Benz's S-Class and BMW7 series hybrid vehicles. Meanwhile, JCS also supplies batteries for Ford's first rechargeable hybrid vehicle.
2) Graphite/LFP electrode pair [A123, Chinese battery manufacturer, French Atomic Energy Agency (CEA)].
3) LiMn2O4/graphite electrode pair (especially Nissan-NEC).
Note: NCA = NCA = LiNi0.8Co0.15Al0.05O2，LFP = LiFePO4
In the automotive battery market, automakers such as Nissan and Toyota develop their own batteries. In the field of hybrid vehicles, major companies include Toyota, Panasonic, Nissan-NEC, BYD, LEJ (Mitsubishi), while the major suppliers of battery cells are A123, SDI, JCS, Continental, Bosch and Delphi. Major suppliers of battery modules include Sanyo, LGC, JCS, Enerdel, Toshiba and Murata.
4.Battery application: Lithium-ion battery technology is the core of photovoltaic power generation applications
Over the years, thedevelopment of battery application in the photovoltaic field has been continuously improved and accelerated, thanks to the economic incentives provided by various countries through some projects, such as government electricity price subsidies for photovoltaic grid-connected power generation, especially in Germany, Japan, Spain, the United States, Australia, France and a few others (though each country has its own unique conditions that apply).
As far as the battery application in photovoltaic power generation is concerned, the need for energy storage in off-grid systems (islands) is obvious, mainly to compensate for the intermittency of photovoltaic power generation. The current situation is that the new role of energy storage in grid-connected photovoltaic power generation systems is being seriously studied: energy storage systems can smooth the peaks and valleys of electricity generation and consumption in the grid by storing and releasing electricity within a reasonable time. .period. Poor (when PV production is reduced, the energy storage system will delay the electricity consumption support according to the grid power purchase agreement and/or the PV feed agreement).
Lead-acid batteries are widely used in off-grid photovoltaic power generation systems due to their low price and good applicability. However, technical problems in the lead-acid battery application will restrict the development of off-grid photovoltaic power generation systems. In particular, lead-acid batteries have a short lifespan, resulting in high system maintenance costs (close to 50% of system costs).
Grid-connected photovoltaic power generation will develop rapidly in the next 20 years. In order to meet the demand of photovoltaic grid-connected energy storage, the traditional energy storage system should be reviewed and summarized, and corresponding improvements should be made. Like battery application for hybrid vehicles, lithium-ion battery technology currently has the best chance of overcoming many of the problems in photovoltaic cell battery application. This has been confirmed by INVE-STIRE, a European network dedicated to evaluating battery storage systems for renewable energy battery application. The goal of energy storage in this field is to enter the photovoltaic power generation market and give the system a comprehensive competitive advantage (energy storage can provide ancillary services such as power quality or frequency regulation; it can enter the photovoltaic market by integrating with photovoltaic modules); it can store electricity for consumers to use . or sell/feed into the grid when needed).
In 2010, Japan's Sharp Corporation started production of a factory that mainly produces lithium batteries for household photovoltaic systems. By configuring lithium-ion batteries, these homes will have the ability to power independently, and the price of lithium-ion batteries will play an important role in the energy storage economy of battery application.
Read more: Basic knowledge of battery