Looking at the development of China's lithium battery industry from the perspective of national lithium battery standards

Before 2013, although many standards in the industry put forward requirements for the safety of lithium batteries, including lithium battery transportation requirements (UN38.3), portable sealed battery safety requirements (IEC 62133-2012), mobile phone battery specifications (GB/ T18287-2013), etc., but these standards are either not mandatory or not comprehensive enough.

With the frequent occurrence of accidents, the industry has begun to call: it is time to regulate the industry. In December 2014, "Safety Requirements for Lithium-Ion Batteries and Battery Packs for Portable Electronic Products" (GB31241-2014) appeared in a long-awaited appearance, and the mixed lithium battery industry finally ushered in a reshuffle.

National standards for lithium batteries force technical reforms in the industry

The test of the new standard GB31241 for lithium batteries has achieved no dead angle coverage. In addition to the general safety requirements (safety working parameters, labeling requirements, warning instructions, durability), it also specially proposes tests on the battery pack environment and battery pack safety. More than 30 tests, such as tests, battery pack protection circuit safety test requirements, and system protection circuit safety requirements, were the most stringent national mandatory standards at that time. Subsequent lithium battery standards have also been added, subtracted, and modified based on this template.

For large lithium battery production enterprises, the release of the national standard for lithium batteries has little impact on the production of enterprises, because the production equipment of large lithium battery enterprises is relatively superior, and the production process is relatively strict, even exceeding the national standards. However, for small battery factories without standardized production equipment, the national standards for lithium batteries put forward almost harsh requirements for their products and processes. It can be said that the national standard for lithium batteries is the most basic guarantee for the safety of lithium battery products. It forces the industry to upgrade equipment and make technological breakthroughs.

In order to ensure the safe use of lithium-ion batteries, manufacturers have carried out strict and careful battery safety performance design to meet national safety standards:

1. Pass various environmental abuse tests. Carry out various abuse experiments on the battery, such as external short circuit, overcharge, acupuncture, impact, incineration, etc., to investigate the safety performance of the battery; conduct temperature shock experiments and mechanical performance experiments such as vibration, drop, and impact to investigate the actual use environment of the battery. performance below.

Second, the research and development adopts advanced SEI film. As the "protective umbrella" of the electrode material, on the one hand, the SEI film can consume part of the lithium ions and reduce the charge-discharge efficiency of the electrode material; The material causes damage and greatly improves the cycle performance and service life of the electrode.

3. Research and development of new electrolytes. At present, most commercial lithium-ion batteries use LiPF6 EC/DMC as the electrolyte because of its high ionic conductivity and good electrochemical stability. Due to the safety problems of liquid electrolyte lithium-ion batteries such as leakage and explosion, the research on solid electrolytes has been put on the agenda.

Fourth, mining new lithium battery cathode materials. As the core of the lithium battery, the cathode material accounts for more than 40% of the total cost of the lithium battery, and its performance directly affects the performance indicators of the lithium electronic battery. Based on the differentiated requirements for the performance of lithium batteries, various mainstream lithium battery cathode materials are suitable for use in various fields. Experts predict that the market size of lithium battery cathode materials is expected to reach 59.5 billion yuan by 2020.

Power lithium batteries dominated by ternary materials are on the rise

In the context of the rapid expansion of the lithium battery industry, cathode materials that determine important indicators such as energy density, cycle life and safety of lithium batteries have attracted much attention from the industry. At present, the anode materials of lithium-ion batteries are still mainly made of graphite, while a hundred schools of thought contend in the field of cathode materials. Materials such as lithium cobalt oxide, lithium manganate, lithium nickel cobalt oxide, lithium iron phosphate, etc. field.

As far as the current stage is concerned, lithium iron phosphate batteries still occupy a dominant position in the market. An important reason is that lithium iron phosphate materials have a stable olivine structure, which theoretically allows all lithium in the structure to be released, and has good charge-discharge reversibility, the cycle performance is excellent. Another material, lithium manganate, has high redox exothermic stability, and the capacity retention rate still reaches more than 90% after more than 300 charge-discharge cycles. Its industrial maturity, cost, and consistency are better than those of lithium iron phosphate, but its security is poor.

In addition, most manufacturers in the industry believe that ternary materials will become the mainstream of the future market. On the one hand, the ternary material has better performance at low temperature, and the discharge efficiency at minus degrees Celsius is much higher than other materials. As we all know, high temperature management is more convenient than low temperature, and it is difficult to realize thermal management design from low temperature to high temperature; on the other hand, the energy density and voltage platform of ternary materials are high, which is of great help to improve the cruising range of electric vehicles. On the contrary, lithium iron phosphate batteries have entered a bottleneck in the research and development of energy density.

In the future, lithium-ion batteries must develop in the direction of high safety, high energy density, long life, high reliability and low cost. Among them, safety is the first priority. The new subsidy policy is linked to the energy density of batteries, resulting in many manufacturers who blindly pursue high energy density. The Great Leap Forward" is untenable in the face of security.

On the premise of ensuring security, reducing costs and improving performance is the only way out. Some battery manufacturers increase the energy density by increasing the size of the battery. Under the existing conditions, the energy density of the 21700 ternary lithium battery system can reach about 300Wh/kg, which is 20% higher than the 250Wh/kg of the 18650 lithium battery system. The increase in the capacity of the battery cell means that the same energy The number of required cells is reduced, so that although the weight and cost of a single cell increases, the weight and cost of the battery system PACK is reduced.

However, blindly increasing the size of the battery is not a long-term solution. At the current state of the art, high energy density and high cycle life cannot be achieved at the same time. It is estimated that for every 10% increase in capacity, the battery cycle life will be reduced by about 20%; the charge-discharge rate will be reduced by 30~40%; at the same time, the battery will have a temperature rise of about 20%. If you continue to increase the size, you will face the risk of sacrificing safety. Therefore, it is the top priority to guide the industry to have a correct understanding of ternary lithium batteries, avoid blindly pursuing high energy density, and improve safety.

The development of electric vehicles lags behind expectations, and lithium batteries become the ideal choice for energy storage technology

According to the "Energy Saving and New Energy Vehicle Industry Development Plan (2012-2020)", it is planned that by 2020, the production capacity of pure electric vehicles and plug-in hybrid vehicles will reach 2 million, and the cumulative production and sales will exceed 5 million. In the context of the new energy double-point policy and the transformation of the automobile industry, domestic new energy vehicle products emerge in an endless stream and are updated rapidly, but their cost performance still cannot fully meet the actual needs, and the cost of electric vehicles, especially the cost of battery packs, still exceeds the burden of ordinary consumers. ability. With the decline in subsidies for new energy vehicles, and affected by factors such as slowing economic growth, Sino-US trade frictions, and weak domestic demand, the embarrassing situation of "new cars sell well, but not profitable" continued to be staged in the third quarter.

In general, the product backlog caused by market weakness has plagued most new energy vehicle companies. In addition, there are many new domestic car companies still in the "ppt" stage of car manufacturing. Facing the tightening of subsidy policies, the increase in the threshold of cruising range and battery energy density, the inability to achieve mass production and delivery has led to financing difficulties. A big trouble. It can be seen that the development of domestic electric vehicles still lags behind the expectations of the Chinese people. With the "big invasion" of foreign brands, the competition in the domestic new energy vehicle market will be more severe in the future.

In the field of energy storage, the dominance of lithium-ion batteries has been firmly established. In June 2018, the national standard "Lithium-ion batteries for power energy storage" (GB/T 36280-2018) was released and will be implemented in January 2019. The energy storage industry is expected to usher in rapid development as battery technology brings about a reduction in the cost of lithium batteries and an increase in energy density.