【New Energy Applications】Which are safer: lithium iron phosphate batteries or ternary lithium batteries?

Currently, the battery technology pathways for pure electric vehicles in China can be broadly divided into two types: one is ternary batteries, and the other is lithium iron phosphate batteries. The thermal runaway temperature of lithium iron phosphate is higher than that of ternary systems, giving its cathode material an advantage in terms of safety. Regarding the battery packs used in vehicles, ternary batteries are more than 15% smaller in size and more than 20% lighter in weight compared to lithium iron phosphate batteries, allowing vehicles equipped with them to make better use of their interior space. Globally, ternary batteries currently account for over 80% of the global lithium-ion battery market. According to data from the global management consulting firm ATKearney, 93% of the materials used in lithium-ion secondary batteries account for ternary battery materials, and this share exceeds 81% in the market for batteries used in electric vehicles, where high output and safety performance are required. In the Chinese market, power battery manufacturers started developing in the lithium iron phosphate sector earlier and thus hold a larger overall market share. Moreover, unlike foreign markets, there are relatively few new energy buses there, while private cars are more common. Public data shows that in 2015, the output of power batteries reached 15.7 Gwh, with lithium iron phosphate batteries remaining dominant, accounting for nearly 69% of the market share ； Lithium-nickel-manganese batteries accounted for 27% of shipments. In the field of passenger vehicles, ternary materials are the predominant type of battery, with battery shipments reaching 1.93 Gwh ； In the bus sector, lithium iron phosphate batteries are predominantly used, accounting for 84% of the batteries in pure electric buses, while ternary material batteries account for only 12.9%. However, as new energy passenger vehicles place greater demands on things such as range, many power battery manufacturers are accelerating research and development of ternary lithium batteries, and their use in the market is continuing to expand.

Guo Shengchang, Director of AVIC Lithium Battery Research Institute: The policy delaying the inclusion of ternary batteries in the commercial vehicle catalog will have a significant impact on companies that work with ternary materials in the short term. In the long term, it still depends on the development of lithium-iron phosphate and ternary material technologies; as these two materials address their weaknesses, their prospects for development remain promising. 　　At the same time, Guo Shengchang pointed out that currently, investment and attention in the lithium battery industry are focused on raw materials and battery production. However, to achieve sustainable circular development, it is necessary to emphasize hierarchical utilization and recycling in order to maximize the value of these materials. 　　Regarding the recycling of lithium-ion batteries, the recycling system for ternary materials is currently being established. At this stage of industrial development, the recovery of nickel and cobalt is becoming increasingly mature; in particular, some manufacturers are already actively making arrangements for the recycling of power batteries. However, the lithium-iron battery industry has not yet developed a complete industrial cycle. 　　Guo Shengchang believes that to truly establish a recycling system for lithium iron phosphate batteries, four key issues must be resolved. The first is the disassembly of modules – in what form of automation, or at what low cost, should this disassembly take place ； The second part is the sorting and evaluation of batteries, as the cost of battery sorting is currently relatively high; the question is how to carry out sorting at a low cost while ensuring safety ； The third is hierarchical utilization – finding ways to extend the lifespan of old batteries, thereby reducing costs across the entire industry ； Finally, there is recycling: when it can no longer be used, the value contained within it is recycled.

The Ins and Outs of the Suspension of Tri-metal Lithium Batteries: On January 24, 2016, Zhang Xiangmu, Director of the Equipment Industry Department of the Ministry of Industry and Information Technology, stated at the 2016 China Electric Vehicle 100 Forum’s summit on \"The Development and Breakthroughs in Power Batteries\" that a risk assessment of tri-metal lithium batteries would be conducted; until such an assessment was completed, the inclusion of buses equipped with these batteries in the list of recommended models for the promotion and use of new energy vehicles would be suspended. The Ministry of Industry and Information Technology argues that ternary lithium batteries have a high specific energy and good cycle performance, making them an important direction for the development of lithium batteries in the future. However, China started late in this field, and the safety development and testing for use in buses are not yet sufficient. The ministry is considering raising the technical standards for safety in new energy vehicles, and is carrying out risk assessments of vehicles equipped with ternary lithium batteries under the current safety standard framework. Previously, Xu Yanhua, deputy secretary-general of the China Association of Automobile Manufacturers, said that since ternary lithium batteries are still in their infancy in China, there is insufficient research on their safety for use in electric buses, and the relevant testing standards are not well-established. She suggested that the Ministry of Industry and Information Technology suspend the acceptance of applications for pure-electric buses using ternary lithium-ion batteries to be included in the list of vehicles exempt from vehicle purchase tax.

As early as August 6, 2015, the Ministry of Industry and Information Technology issued a notice titled \"On Carrying Out Inspections and Rectifications for Safety Hazards Related to the Promotion and Use of Energy-saving and New Energy Vehicles.\" This notice was issued in the context of several cases of spontaneous combustion involving pure-electric and hybrid buses in certain areas. According to preliminary investigations by relevant authorities, the accident vehicle had safety defects and potential risks in its design and during normal use. To draw lessons from these incidents and prevent similar accidents from occurring again, the Ministry of Industry and Information Technology issued a directive requiring manufacturers of energy-saving and new energy vehicles to carry out inspections and rectifications of potential safety hazards. In aspects such as product design, manufacturing, operation, and recycling, companies must prioritize safety to ensure the safe operation of energy-saving and new energy vehicles. According to statistics, there have indeed been many incidents of electric bus fires in our country in recent years. Data shows that from 2011 to the present, there have been at least 22 fire incidents involving new energy vehicles in China. Among them, several fires involving electric buses occurred in 2015; one of the reasons was the large number of batteries in such vehicles, which increased the likelihood of accidents.

Comparison between ternary lithium batteries and lithium iron phosphate batteries: Lithium-ion batteries come in various types, including lithium iron phosphate, ternary materials such as lithium nickel cobalt manganese oxide, lithium carbonate, and lithium nickel oxide. Among these, the ones that are most commonly used in vehicles at present are ternary lithium batteries and lithium iron phosphate batteries. NCM lithium-ion batteries and LFP lithium-ion batteries have different characteristics; the main trade-offs lie between “energy density” and “safety”. NCM lithium batteries have a higher energy density, smaller size, and lighter weight; however, their safety is often questioned. Although lithium iron phosphate batteries have a low energy density, they are considered safer. Both of these materials decompose when they reach a certain temperature; the lithium ternary material decomposes at around 200 degrees. Furthermore, the chemical reactions of ternary lithium materials are more intense; they release oxygen molecules, and under high temperatures the electrolyte burns rapidly, triggering a chain reaction. Lithium iron phosphate, on the other hand, decomposes at 700–800 degrees; it does not release oxygen molecules like ternary lithium materials, so its combustion is less intense. Simply put, ternary lithium materials are more prone to catching fire than lithium iron phosphate materials.

Looking at the development trend, domestic passenger vehicle manufacturers are increasingly turning to the use of ternary lithium batteries. Currently, electric vehicles produced by companies such as BAIC, BYD, and Jianghuai all come equipped with ternary lithium batteries. The corresponding suppliers are also accelerating the production of ternary lithium batteries; for example, the second factory of EVE Energy is planned to mainly produce ternary lithium batteries. Lithium iron phosphate batteries are increasingly being used in the electric bus market. According to data from last November, lithium iron phosphate batteries accounted for 64.9% of the installations in electric buses, while lithium ternary batteries accounted for only 27.6%. In contrast, in the market for pure-electric passenger vehicles, ternary lithium batteries accounted for over 76% of installations as of last November.

In-depth analysis: What exactly are ternary materials, and why do they cause safety issues? February 26, 2016, First Electric Network: The debate over different battery technology approaches has a long history; the decision to temporarily suspend the use of ternary-material batteries in new energy buses sparked widespread controversy within the industry. On February 26, DiDi Chuxing Network held a salon titled “The Debate on the Safety of Lithium Nickel Manganese Oxide Battery Materials” in Beijing. Elite representatives from the fields of power batteries, complete vehicles, and research gathered together to discuss the development of power battery technology and the market trends in this sector. The guests who participated in the salon discussion included: Liu Yanlong, Secretary-General of the China Chemical and Physical Power Sources Industry Association; Nie Liang, founder of Borten Technology; Ma Junfeng, Senior Director at Beijing Boston Battery Technology Co., Ltd.; Tong Ziqian, senior consultant at Beijing Zosy Information Consulting Co., Ltd.; Wang Qingsheng from the Institute of Functional Materials and New Energy Technologies at St. Petersburg State Technical University in Russia; Tan Haohai, Sales Director at Far East Foster New Energy Co., Ltd.; and Song Huajie, Associate Senior Engineer at BYD Battery R&D Center. Qiu Kaijun, CEO of FirstEV.com, served as the host of the salon. What is a ternary material battery? What is the current usage status? Why does it cause concerns about safety? During the discussion in the first half, the guests expressed their opinions, but all denied the conclusion that the safety of ternary materials could be questioned in isolation. Overall, the transition of vehicles from fuel-powered to electric is underway at a very rapid pace, and all electric vehicles face the challenge of ensuring battery safety.

Wang Qingsheng: The claim that \"ternary materials are unsafe\" is based on a conceptual error. Ternary materials, like other cathode materials such as lithium iron phosphate, each have their own advantages and disadvantages; there is no such thing as safe or unsafe materials. Focusing solely on the materials to assess safety is too one-sided; other cathode materials such as ternary materials and lithium iron phosphate each have their own advantages and disadvantages. Judging safety based only on the materials is inadequate, as these materials yield different results when used under varying conditions such as environment, structure, size, and manufacturing processes. This is a complex systematic engineering issue. What we need to do is leverage the advantages of battery materials and mitigate their disadvantages. The safety or insecurity of a material is not determined by its physical properties; what’s most important is how it can be properly controlled and used during operation. The temperature at which oxidation and exothermic reduction occur in ternary materials differs to some extent from that of lithium iron phosphate. However, this does not mean that a higher oxidation exothermic temperature in lithium iron phosphate makes the material safer. The safety of batteries is assessed based on thermal considerations; if a battery is designed to generate very little heat and has excellent heat dissipation capabilities, then it remains safe regardless of its size or the materials used. Conceptual errors have led to the belief that ternary materials are unsafe, and lithium iron phosphate also poses potential risks. Therefore, studying the safety of materials involves examining their physicochemical properties, as well as the mechanisms related to material compatibility, heat generation, and heat dissipation; the notion of whether a material is safe or not is irrelevant in this context.

Liu Yanlong: Lithium-ion batteries of the ternary type represent the future direction of development. The progress of power batteries is closely related to the strategies established in China for their development in earlier stages. During the 11th Five-Year Plan period, more support was given to lithium iron phosphate-based batteries; from 2013 to 2015, the industrialization of power batteries accelerated. Based on the trends in policy development, it can be inferred that future policies will provide more support for ternary batteries, which is why many companies have chosen to focus on developing such batteries. In September 2015, a preliminary estimate was made of the production capacity of domestic power battery manufacturers; by that month, more than 30 companies had a combined production capacity of over 30 billion watt-hours. With a few exceptions where ternary batteries were used, over 250 billion watt-hours of this capacity was generated using lithium iron phosphate batteries, and this figure includes capacities that are set to be expanded in the future as well. Looking at the application of power batteries in 2015, the market size exceeded 20 billion yuan; over 70% of these batteries were lithium iron phosphate types. Buses accounted for a large proportion of such batteries, while passenger cars tended to use ternary lithium batteries more often. However, the new energy bus subsidy policy for 2016–2020 imposed requirements regarding Ekg, prompting bus manufacturers to shift to ternary lithium. Overall, ternary lithium batteries represent the future direction of development. Regarding the materials themselves, when lithium nickel manganese oxide materials and lithium iron phosphate materials experience uncontrolled heating, their temperatures at which thermal decomposition occurs differ; the temperature for lithium nickel manganese oxide materials is lower, while that for lithium iron phosphate materials is higher. Furthermore, when conducting tests, the results of compression testing show that ternary materials exhibit more severe reactions in a short period of time; for example, they may catch fire and explode quickly, while lithium iron phosphate tends to produce more smoke. In terms of process control, it is necessary to interrupt the process as early as possible before the thermal decomposition temperature is reached; this way, certain measures can be taken to prevent accidents. The material itself has certain properties, and various protective measures need to be taken during subsequent manufacturing and use processes in order to make ternary material batteries safer.

Ma Junfeng: The entire vehicle lacks a proper thermal management solution. Boston Battery chose the ternary lithium technology route because electric vehicles are moving toward lighter designs, and the Ekg criteria have led to the need for a technology with high energy density. At present, ternary materials are relatively suitable for mass production; they have a high energy density and satisfactory performance at low temperatures. The energy density of battery packs made from Boston’s ternary lithium cells can reach around 125 Wh/kg. Safety has little to do with battery materials; the more important factor is the application scenario. The number of new energy vehicles in use is rising rapidly, and the likelihood of accidents is increasing; therefore, it is necessary to reconsider the issue of battery safety. From what perspectives can we ensure that our industry develops better in the future? How can we prevent serious accidents from occurring in vehicles, or at least ensure that in the event of a fire or explosion, our passengers can safely evacuate from the vehicle? Looking back at the development in China over the past two years, new energy vehicles are brought to the market in about five to six months. Most of these vehicles are modified versions, and at least half of them do not take thermal management into account, which is a weakness that affects the batteries. Boston Battery’s current market strategy is to work with vehicle models that have relatively lenient requirements regarding batteries. Since the entire vehicle cannot provide an optimal environment, the batteries are used in a state where their activity level is not too high, thereby reducing safety risks. This safety issue is considered more from the perspective of the entire vehicle and its parking capabilities; considering it from the perspective of materials is somewhat off-topic.