Current status of lithium titanate battery technology
Lithium titanate has three-dimensional lithium ion diffusion channels unique to the spinel structure, and has the advantages of excellent power characteristics and good high and low temperature performance. Compared with carbon anode materials, the potential of lithium titanate is high (1.55V higher than that of metal lithium), which leads to the fact that the solid-liquid layer usually grown on the surface of the electrolyte and carbon anode is basically not formed on the surface of lithium titanate. .
More importantly, it is difficult for lithium dendrites to form on the surface of lithium titanate within the voltage range used by normal batteries. This largely eliminates the possibility of short circuits being formed inside the cell by lithium dendrites. Therefore, the safety of lithium-ion batteries with lithium titanate as the negative electrode is the highest among the various types of lithium-ion batteries that the author has seen.
Most people in the industry have heard that the lithium battery cycle life of replacing graphite with lithium titanate as the negative electrode material of lithium battery can reach tens of thousands of times, which is much higher than the common traditional lithium ion battery, and it will die after only a few thousand cycles.
Because most professional lithium battery people have never really made lithium titanate battery products, or they have only done it a few times and encountered difficulties. So they couldn’t calm down and think about it carefully. Why do most of the traditional lithium-ion batteries that are perfectly made can usually only complete 1000 to 2000 charge-discharge cycles?
Is the root cause of the short cycle life of traditional lithium-ion batteries due to one of the basic components – the graphite negative electrode being overwhelmed? Once the graphite negative electrode is replaced with a spinel-type lithium titanate negative electrode, the basically the same lithium-ion battery chemical system can be cycled for tens of thousands or even hundreds of thousands of times.
Lithium titanate battery has long cycle life, extraordinary safety, excellent power characteristics and good economy. These characteristics will be an important cornerstone for the achievement of the large-scale lithium battery energy storage industry that is currently emerging.
In the past 10 years, research on lithium titanate battery technology at home and abroad has been surging. Its industrial chain can be divided into lithium titanate material preparation, lithium titanate battery production and lithium titanate battery system integration and its application in the electric vehicle and energy storage market.
Lithium titanate material
The international leaders in the research and industrialization of lithium titanate materials include Aoti Nanotechnology Company of the United States, Ishihara Sangyo Co., Ltd. of Japan, and Johnson Matthey of the United Kingdom. Among them, the lithium titanate material produced by Austrian Titanium has excellent performance in terms of magnification, safety, long life and high and low temperature. However, because the production method is too long and delicate, the production cost is high, which makes it difficult to commercialize.
Ishihara Sangyo is one of the largest titanium dioxide manufacturers in Asia. The company has production bases in Japan, Singapore and Taiwan. Ishihara Industry made full use of its abundant raw material resources and successfully developed a variety of low-cost, high-rate, and different particle size lithium titanate products by wet process.
There are many domestic mass production of lithium titanate materials, such as Sichuan Xingneng New Materials Co., Ltd., Zhuhai Yinlong New Energy Co., Ltd., Huzhou Weihong Power Co., Ltd., Shenzhen Betterray New Energy Materials Co., Ltd., Hunan Shanshan New Materials Co., Ltd. and a number of smaller lithium titanate manufacturers around Anhui and Shenzhen.
Sichuan Xingneng is a professional manufacturer of lithium titanate materials with an annual production capacity of 3000t. The lithium titanate production process has customer adaptability and stability, and can be flexibly adjusted without changing the existing production lines and equipment to produce suitable products. Lithium titanate required by different customers, and maintain the stability of product technical indicators. Relying on the upstream lithium ore and titanium ore resources, Xingneng can realize the co-production from raw ore to final materials, which can improve the performance of lithium titanate products and reduce the cost, and avoid the impact of fluctuations in the raw material market.
In 2011, Zhuhai Yinlong completed the acquisition of 53.6% of the equity of Ao Ti Nano Technology Co., Ltd. in the United States, thus becoming one of the few companies in China that also owns lithium titanate material preparation, battery production, lithium titanate electric vehicles, energy storage systems, frequency modulation A company with a number of core technologies and more than 30 patents for applications such as peak shaving.
At present, Beibei Aotai Nanotechnology Co., Ltd. (abbreviated as “Beijing Aotai”) has an annual production capacity of 100t of lithium titanate materials and provides high-quality nano-scale lithium titanate for Beibei Aotai and Zhuhai Yinlong. Zhuhai Yinlong New Energy has also carried out strategic cooperation with Ishihara Industry on the research and development of new lithium titanate materials. The cost of the material will decrease with the increase of its output, and it is expected to be close to the current cost price of graphite anode materials in the next few years.
Huzhou Weihong is currently one of the most successful companies in promoting lithium titanate battery technology and other fast-charging batteries in the domestic industry.
The lithium titanate material produced by Huzhou Weihong is mainly used for its own lithium titanate battery products. The continuous expansion of Huzhou Weihong’s lithium titanate battery products in domestic and foreign markets has also played a good demonstration role in the application of lithium titanate technology in electric vehicles and energy storage markets.
Lithium titanate batteries and their applications in electric vehicles and energy storage
There are not many manufacturers that can mass-produce lithium titanate batteries in the world, mainly represented by Austrian Titanium from the United States and Toshiba Group from Japan. The application markets of lithium titanate batteries mainly include electric vehicles, energy storage markets and industrial applications.
American Austrian Titanium has its unique core technology in the manufacture of lithium titanate batteries. It is still in a leading position in the manufacture of large-scale lithium titanate batteries in the world, and has solved the so-called “flatulence” problem. At present, its fourth-generation 65Ah single-cell lithium titanate battery has been used in energy storage systems, and there is no obvious capacity decay even after tens of thousands of cycles at 65°C.
In the application of lithium titanate battery system, the hybrid electric bus provided by Austrian Titanium for California has been put into operation since 2008. Its fuel economy index is 106.4kg/L, which is much higher than the 23.8kg/L of ordinary diesel generators. The company provided a 1MW storage system for the 10.5MW wind farm of the Hawaii Natural Energy Institute and was connected to the local grid, and provided technical support services for a period of 3 years. This lithium titanate battery energy storage system is mainly used to regulate the voltage fluctuation of renewable energy and control the load change rate of the unit within 1MW/min.
Austrian Titanium’s 1MW large-capacity high-power energy storage unit is currently the only large-capacity lithium titanate battery product in the US power grid that has passed the field commercial operation and performance quality inspection for more than two years. The number of cycles of the energy storage system exceeds 500,000 times, the total charge and discharge capacity exceeds 3,300MWh, the system capacity loss is less than 2%, and the power has no obvious attenuation.
Toshiba of Japan mass-produces lithium titanate batteries under the brand name “SCiB”. Among them, 3.2Ah, 10Ah and 20Ah aluminum shell square batteries are mainly used for electric motorcycles, electric vehicles and car start-stop batteries. SCiB battery has the advantages of fast charging and long life. It can be charged by more than 90% in 10 minutes, and the capacity decay of 3000 times of repeated charging and discharging is less than 10%. It has been applied to “EV-neo” electric motorcycles in batches.
In terms of energy storage, Toshiba is applying lithium titanate batteries to large-scale energy storage power stations and home energy storage systems with the help of Japan’s New Sunshine Project. Another Japanese company, Murata, has developed a new lithium titanate battery using 5V lithium nickel manganese oxide as the positive electrode. The voltage difference is 3.2V, and the energy density can reach 130Wh/K song, which exceeds the current level of lithium iron phosphate batteries.
China has already produced many lithium titanate batteries, such as Huzhou Weihong, Zhuhai Yinlong, Shenzhen Boleida, Tianjin Jiewei Power Industry Co., Ltd., Sichuan Xingneng, CITIC Guoan Mengguli Power Technology Co., Ltd., Hunan Shanshan and a number of smaller lithium titanate battery manufacturers around Anhui and Shenzhen.
Zhuhai Yinlong’s current mass-produced lithium titanate battery products include 20Ah and 65Ah soft pack batteries and 25Ah, 30Ah and 55Ah cylindrical batteries, and the performance indicators have reached the lithium titanate batteries produced by Austrian Titanium in the United States. The 100% DOD cycle of the battery exceeds 16,000 cycles, and the 10% DOD cycle reaches 1.6 million cycles. These batteries have all passed the third-party testing of the North Automobile Quality Supervision, Inspection and Identification Laboratory (201 Institute).
In terms of application, Yinlong’s new pure electric bus uses a cylindrical lithium titanate battery with long life and fast charging and discharging. Slow charge for 30 to 60 minutes. This series of models has been successfully put into public transport systems in Zhanjiang, Guangdong, Handan, Shijiazhuang and other places in Hebei.
The antique Dangdang bus specially designed and developed by Yinlong for Beijing Public Transport was put into commercial operation in September 2014. The car was also designated as the official designated car for the Beijing APEC meeting. In the energy storage market, Yinlong has cooperated with State Grid and China Southern Power Grid to undertake the 863 national projects in energy storage, and provided two 2MWh and one for Zhangbei wind and solar energy storage and transmission demonstration station and Shenzhen Baoqing battery energy storage station respectively. Part of the module, battery box design and system solution of the 600kWh lithium titanate system.
Shenzhen Bo Leida can prepare Li4Ti5O12 materials with good performance through a unique material processing method, and through technical research projects, starting from the improvement of the production process of lithium titanate batteries, the design and preparation of high-performance Li4Ti5O12 has made significant progress. The mass-produced products include 17Ah, 20Ah and 25Ah cylindrical batteries, which solved the problem of lithium titanate batteries being prone to flatulence, obtained high-performance lithium titanate battery products, and obtained authoritative third-party test reports.
Starting from the design of high-power Li4Ti5O12 electrode materials, Bo Leida Company studied the interfacial side reactions of Li4Ti5O12 materials to reveal the gas production mechanism and solution mechanism, and made a major breakthrough in the large-scale application of Li4Ti5O12 electrode materials in power batteries.
Tianjin Gateway has obtained the transfer of lithium titanate battery production technology from Austrian Titanium, and combines its own technology accumulation in polymer soft pack power battery production for many years to live alone. The company has successfully broken through the problem of flatulence, and has the technology and capability to mass-produce large-scale single-cell lithium titanate batteries with a battery capacity of 60Ah and a cumulative shipment of 20 million Ah.
The battery can withstand continuous charge and discharge above 10C, with a lifespan of more than 20,000 times and a temperature range of -40 to 60 °C. It is mainly used in fast-charging buses and frequency-modulated energy storage power stations.
Difficulties and development directions of lithium titanate battery technology development
Reasons for developing lithium titanate battery technology in China
The competition of lithium titanate battery technology in various energy storage batteries in our country should have the advantages of timing, location, and people. In terms of service life, the ultra-long cycle life of lithium titanate battery is far better than that of various lead-acid batteries; its efficiency, cost and electrochemical performance are even better than those of sodium-sulfur and flow vanadium battery systems.
Over the years, the main market for lithium battery products has been portable appliances such as mobile phones and laptop computers. Although the consumption of mobile phones and laptops in China is large, most of them are not domestic brands. Therefore, the domestic lithium battery manufacturers’ lithium battery sales ability in portable electrical appliances is inferior to that of Japanese and Korean products.
However, the applicable market for lithium titanate technology is hybrid electric vehicles, special industrial applications and energy storage applications such as frequency regulation and grid voltage support. These markets are still in their infancy around the world, and it’s unclear who will dominate. Lithium titanate technology is expected to be the leader in these markets.
China’s population base accounts for about 1/5 of the world’s population. Due to its large population, China’s market for electric vehicles, energy storage and industrial applications is a huge market coveted by multinational companies in many countries. In recent years, the Chinese government has attached great importance to the development of electric vehicles and energy storage industries, and various national incentive policies have been introduced. Lithium titanate battery systems made in China have accumulated commercial application data for several years in hybrid electric buses in Chongqing and Europe, wind and solar storage demonstration stations in Zhangbei and Shenzhen Baoqing energy storage power station.
In addition, the upstream and downstream of China’s lithium battery industry chain has already become a climate. In addition to complete battery material supply and equipment manufacturing capabilities, the production capacity of lithium battery products is also three-thirds of Japan and South Korea. This makes my country’s lithium battery manufacturers have innate conditions to transform from traditional lithium battery production to lithium titanate battery product production.
China already has companies with both strength and experience in the production of lithium titanate materials, such as Sichuan Xingneng, Zhuhai Yinlong, and Huzhou Weihong. Representative companies that stand out in the production of lithium titanate batteries include Huzhou Weihong, Zhuhai Yinlong, Shenzhen Boleida, and Tianjin Jiewei.
These companies have initially established their own sales channels in the electric vehicle and energy storage markets at home and abroad. It is particularly worth pointing out that Shenzhen Bo Leida has a series of proprietary technologies and intellectual property rights from material production to battery production and system integration. At present, it is still a rare manufacturer with independent intellectual property rights in China’s lithium battery industry.
Bottleneck of lithium titanate material, battery and battery pack production
Since lithium titanate battery technology has many advantages that other lithium batteries can’t match, why is it so far used in China’s energy industry and even the world’s energy field? There are three reasons for this:
1. The production of lithium titanate materials The production of lithium titanate materials is not complicated in principle. However, in order to be used as a negative electrode material for lithium-ion batteries, it is necessary not only to pay attention to the material with suitable specific surface area, particle size, density and electrochemical performance, etc., but also to be able to adapt to the production process of large-scale lithium batteries. One of the reasons why lithium titanate materials cannot be produced normally on many traditional lithium battery production lines is that the pH of the materials is 11 or 12, which is extremely hygroscopic.
2. Lithium titanate battery production In fact, directly using conventional lithium ion battery production lines to produce lithium titanate battery products is not as simple as just replacing graphite with lithium titanate materials. Because lithium titanate materials have much higher humidity requirements than conventional lithium-ion battery production. In order to control humidity, some preparation processes need to be adjusted accordingly to meet the special requirements of lithium titanate battery production. In addition, some production equipment also needs to be improved accordingly. If conditions permit, it is best to redesign a compact, compact and fully enclosed automated production line for lithium titanate battery products.
3. Lithium titanate battery packs are different from conventional lithium-ion batteries. At present, lithium titanate batteries produced at home and abroad will often see a small amount of gas generated in the single cells of the soft pack after being put into use in groups for a period of time. These gases are different from those produced when fresh batteries are formed. The former can be removed by the battery production process. But the latter is generated during the use of the battery, or it is difficult to avoid it under the current process conditions.
The author believes that it should be a good research topic to study the chemical reaction mechanism of gas production during circulation. In addition, one of the advantages of lithium titanate battery technology is its high power performance. Although the battery itself can withstand high current charge and discharge, thick single cells are still not suitable for high power applications because the heat generated by the high current is difficult to dissipate because the battery is too thick. Therefore, for high-power lithium titanate batteries, the large and thin pouch battery structure is still a reasonable choice.
The future development direction of lithium titanate technology
The advantages of lithium titanate material as a lithium battery anode are: ultra-high safety, ultra-long life, wide working range at high and low temperature, high power, low cost and green environmental protection.
Disadvantages: Lithium titanate materials have low energy density and strong water absorption, high environmental requirements for battery production, corresponding updating of production processes, investment in necessary equipment and higher requirements for humidity control in new processes, and lithium titanate batteries. The app market is not fully open yet.
In the current environment where the Chinese government vigorously advocates the development of new energy and related industries, how to promote lithium titanate battery technology and its application in the electric vehicle and energy storage market is an indispensable opportunity for China’s lithium titanate battery industry. , the time will not come. It should be a unique opportunity for domestic Zhuhai Yinlong, Huzhou Weihong, Shenzhen Boleida, Sichuan Xingneng, Shenzhen Beterui and other enterprises that have some advantages and sales channels of independent intellectual property rights. Many people do not realize that China’s intellectual property advantage in lithium titanate technology is not available in the so-called “mainstream chemistry” currently dominated by lithium iron phosphate batteries.
The development of high-capacity and high-potential cathode materials to improve the energy density of lithium titanate batteries is a good move to catch up with Japan and South Korea. Of course, at the same time, the entire lithium-ion battery chemical system must be studied, such as high-potential electrolytes and anti-oxidative separators. The efforts of China’s lithium battery industry to develop lithium titanate battery technology will be rewarded handsomely by the emerging markets for electric vehicles, energy storage and industrial applications.