This is a very interesting question. According to statistics from the Energy Storage Application Branch of the my country Chemical and Physical Power Sources Industry Association, my country ranked second in cumulative installed capacity of chemical energy storage in 2017, reaching 385.0 MW, of which lithium battery installed capacity was the largest, reaching 60%.
Don't rush to answer the questions raised at the beginning; let's hear what the professionals have to say first.
Not long ago, Peng Minghong, general manager of Shanghai Guoxuan New Energy (Hefei) Energy Storage Technology Co., Ltd., said in an exclusive interview with my country Energy Storage Network that there are basically no real energy storage cells on the market, and major power lithium battery manufacturers have not invested in dedicated energy storage cell production lines.
If Peng Minghong's statement is correct, then it means that the 231MW lithium-ion energy storage projects in my country, as reported by the association, did not use lithium-ion batteries specifically designed for energy storage. So what kind of lithium-ion batteries did these projects use?
After consulting with several industry professionals, the answer was always power lithium batteries. So the question arises: are power lithium batteries the naturally best choice for energy storage projects, or a less-than-ideal option born of necessity? What are the differences between power lithium batteries and energy storage lithium batteries?
In terms of application scenarios, power lithium batteries are mainly used in electric vehicles, electric bicycles and other power tools, while energy storage lithium batteries are mainly used in peak shaving and frequency regulation power auxiliary services, renewable energy grid connection and microgrids.
Due to different application scenarios, the performance requirements of batteries also vary. First, as a mobile power source, power lithium batteries require the highest possible volumetric (and gravimetric) energy density while ensuring safety, in order to achieve longer driving range. At the same time, users also want electric vehicles to be able to charge safely and quickly, so power lithium batteries have high requirements for energy density and power density. However, for safety reasons, energy-type batteries with a charge/discharge capacity of around 1C are currently commonly used.
Most energy storage devices do not need to be moved, so there are no direct requirements regarding the energy density of lithium batteries used for energy storage. As for power density, different energy storage scenarios have different requirements.
Chen Yongchong, head of the Energy Storage Technology Research Group at the Institute of Electrical Engineering, Chinese Academy of Sciences, once pointed out that for scenarios involving power peak shaving, off-grid photovoltaic energy storage, or peak-valley price difference energy storage on the user side, the energy storage battery generally needs to be continuously charged or discharged for more than two hours. Therefore, capacity-type batteries with a charge/discharge rate of ≤0.5C are suitable. For energy storage scenarios involving power frequency regulation or smoothing of renewable energy fluctuations, the energy storage battery needs to be rapidly charged and discharged in time intervals of seconds to minutes. Therefore, power-type batteries with a charge/discharge rate of ≥2C are suitable. In some application scenarios that simultaneously undertake frequency regulation and peak shaving, energy-type batteries are more suitable. Of course, in such scenarios, power-type and capacity-type batteries can also be used together.
Secondly, compared to power lithium batteries, energy storage lithium batteries have higher requirements for calendar lifespan. The lifespan of new energy vehicles is generally 5-8 years, while the lifespan of energy storage projects is generally expected to be greater than 10 years. Power lithium batteries have a cycle life of 1000-2000 cycles, while energy storage lithium batteries generally require a cycle life of more than 3500 cycles, and there is a desire to achieve ultra-long calendar lifespans through the development of new operation and maintenance regeneration technologies.
Third, in terms of cost, power lithium batteries face competition from traditional fuel-powered sources, while energy storage lithium batteries face cost competition from traditional peak-shaving and frequency regulation technologies. Furthermore, energy storage power stations are typically at the megawatt level or even hundreds of megawatts, therefore, energy storage lithium batteries require lower costs and higher safety standards than power lithium batteries.
This demonstrates the significant differences between power lithium batteries and energy storage lithium batteries. Despite the gradual release of the energy storage market, dedicated energy storage lithium battery production lines in China have not yet officially commenced operations. The fundamental reason for this is likely insufficient demand in the energy storage market, leading battery manufacturers to concentrate their resources on power lithium batteries. Furthermore, research and development efforts for energy storage battery technologies tailored to different energy storage application scenarios are still inadequate, and industrialization remains a considerable distance away.
Of course, the market demand and supply of energy storage may in many cases be a "chicken or egg" problem. Is it because the supply of high-performance, cost-effective energy storage lithium batteries is insufficient, leading to weak demand, or is it because weak demand cannot drive the supply of high-performance, cost-effective energy storage lithium batteries?
This is perhaps a matter of opinion. However, CATL Vice Chairman Huang Shih-lin has publicly opposed using the production capacity of power lithium batteries, especially outdated ones, for energy storage projects.
He publicly stated, "Many people have asked whether the surplus production of power lithium batteries can be used for energy storage, but there is a big misunderstanding here." He added, "Energy storage batteries have higher requirements than power lithium batteries, and the outdated production of power lithium batteries may be gradually phased out."
Therefore, we believe that on the eve of the energy storage market boom, facing the differences between energy storage batteries and power lithium batteries and making early arrangements for the research and development and production of energy storage batteries should be a wise choice.
