Zhao Zhuqing

人民网北京4月18日电(记者赵竹青)在电动汽车续航焦虑日益凸显的今天，中国科学院宁波材料技术与工程研究所动力锂电池工程实验室传来振奋人心的消息：科研团队在国际上首次揭示了富锂锰基正极材料的“负热膨胀”特性，开创性地提出让老化电池“返老还童”的创新方法。成果于北京时间4月16日发表于国际顶级学术期刊《自然》。

As the most potential cathode material for lithium batteries, lithium-rich manganese-based cathode materials can increase the energy density of existing lithium batteries by more than 30% with an ultra-high discharge ratio capacity of 0 mA hours per gram, and at the same time have significant cost advantages, and are regarded as the "stars of tomorrow" to break through the bottleneck of electric vehicle range. However, the structural disorder caused by this material in the process of charging and discharging leads to the stubborn disease of "aging" of continuous attenuation of battery voltage, which restricts its industrialization process for a long time.

In the face of this dilemma, the team of Ningbo Institute of Materials unexpectedly found in the experiment that the lithium-rich manganese-based cathode material will "shrink" when heated, showing the "negative thermal expansion" characteristics that are completely opposite to the "thermal expansion and cold contraction" of conventional substances. Amazingly, by adjusting the oxygen activity of this cathode material, its coefficient of thermal expansion can be flexibly controlled, allowing it to switch between positive, zero, and negative.

Based on this property, the research team designed a cathode material with "zero thermal expansion". This new cathode material has almost no volume change when the temperature changes, and is expected to solve the problem of shortening the life of lithium batteries due to temperature fluctuations, and provide new possibilities for the development of next-generation high-energy lithium battery technology.

The research team has also developed a new method to "rejuvenate" aging lithium-rich manganese-based batteries by electrochemical means: by allowing the battery to be continuously cycled several times without a full charge (e.g., 100% charge), the average discharge voltage of the battery can be restored to close to 0%, and the structural damage of the lithium-rich manganese-based cathode material can be repaired. This finding provides a new idea for prolonging the life of lithium-rich manganese-based batteries: by intelligently adjusting the charging strategy, the structural problems of lithium-rich manganese-based cathode materials can be repaired regularly, thereby significantly extending the service life of the battery.

The reviewers of the journal Nature commented: "These research results not only promote the basic scientific progress in the field of batteries, but also provide new guiding principles for the design of functional materials, which is of important interdisciplinary significance." ”