By Liang Tao, PetroChina Petrochemical Research Institute

Over the past dozen years, China has made great progress in lithium battery materials, but currently still lags behind some countries in lithium battery technologies, a key to both vehicle electrification and industrialization of electric vehicles. Lithium battery enterprises will prioritize improving materials like cathode materials, anode materials, electrolytes, adhesives, etc.

Rapid development of China’s lithium battery materials and technologies

China set up special projects in 2001 to greatly develop electric vehicles, mainly relying on energy control system, drive motor control system and power battery management system. Further, China also made plans to research lithium battery technologies. A series of policies were issued to support lithium battery and electric vehicle industries. At present China is a main producer of electric vehicles in the world.

Domestic lithium battery firms will invest more in researching high energy density materials, low-cost materials, safer materials and lightweight materials, in an attempt to make technical breakthrough in key materials, realize scale production and meet demand from China’s burgeoning electric vehicle market. Table 1 shows global lithium battery patent applications of different regions.

Development of main lithium battery materials

High nickel ternary cathode materials

High nickel ternary cathode materials have higher requirements on raw materials, and are harder to be produced given more complicated technologies. Hence higher costs compared with ordinary ternary materials. Global shipment of ternary cathode materials reached 404 000 tons (47.6% of cathode materials’ total) in 2019. Despite progress in recent two years, high nickel ternary cathode material companies currently hold limited market shares. However, capacity of high nickel ternary materials is increasing due to rising demand, and related technologies are improving.

Solid electrolytes

Utilizing solid electrolytes – including types of perovskite, NASICON, LISICON, thio-LISICON, etc. – to replace liquid electrolytes is regarded as an effective way to solve security issues facing electric vehicles powered by lithium batteries. Solid electrolytes have many advantages, e.g. incombustibility, good security, good machining property, good chemical stability, etc. Disadvantages mainly include generally low Li+ conduction efficiency, relative large electrochemical impedance, etc. With new progress of research, solid electrolytes will be improved continually.

Silicon anode materials

To increase specific capacity of lithium batteries, many enterprises are researching silicon anode materials, considered as a kind of most promising anode material. At present a major way to increase gram volume, cyclic stability and pole piece liquid absorption capacity of anode materials is to use additives, in the future mainly composite additives, ideally made by silicon, lithium and carbon. Silicon-carbon composite anode materials can effectively solve silicon pulverization during charge and discharge process. Hence, they may replace graphite to become ideal anode materials of new-generation high energy density lithium batteries.

Lithium battery adhesives

Lithium battery adhesives – divided into oil soluble adhesives and water-based adhesives – are closely related to battery performance (e.g. cycle performance, rapid charge and discharge capability, etc.). Therefore, lithium battery adhesives should have low resistance and perform stably in electrolytes.

Four development trends

Lithium battery materials are closely tied to electric vehicles (in aspects of vehicle range, safety performance, etc.). Four development trends include: 1) high nickel ternary cathode materials; 2) solid electrolytes; 3) silicon-carbon composite anode materials; 4) water-based adhesives.