新一代锂离子电池无钴正极材料——CIC energiGUNE。

新一代锂离子电池无钴正极材料——CIC energiGUNE。
美国Northstar蓄电池

锂离子电池领域的研究目标之一是开发不含钴的新型高能量密度正极材料。避免使用钴的原因是其供应风险，因为研究表明，到 2030 年之前，钴的供应量将不足以满足市场需求。因此，目前正在研究新的无钴替代品，例如高压尖晶石 LNMO。 

在 CIC energiGUNE 的高级阴极研究线中，我们参与了几个欧洲资助的研发项目，即 CoFBAT、  3believe、  HighSpin、Nextcell，其中使用了这种阴极材料。所有这些项目的全球目标是将这种无钴阴极材料从实验室规模带到可用于汽车应用或固定储能的首个原型。

钴在电池中的应用

钴是生产锂离子电池的关键元素。已经超过 60% 的开采钴用于电池阴极。此外，全球 50-60% 的钴资源位于政治不稳定的刚果 (DRC)，并且是在有问题的工作条件下开采的。

事实上，它已于 2017 年被欧盟委员会确定为 关键原材料。因此，无钴锂离子正极材料是未来电动汽车锂离子电池的关键。

NCM（镍钴锰氧化物）是最常用的 阴极材料之一，特别是在汽车应用中，因为它具有高能量密度。这种材料的化学计量可以根据三种金属中每一种的含量而变化。

事实上，在过去几年中，钴含量已从高钴含量 NCM-111 降低到低钴含量化学计量，如 NCM-622 和 NCM-811。这些材料还具有非常高的比容量，但反过来会降低循环寿命（钴为结构提供稳定性）。美国Northstar蓄电池

Moreover, their synthesis process becomes more complex due to the formation of lithium off-stoichiometric phases. Despite of the mentioned disadvantages, the low amount of cobalt (and subsequently lower cost) have led to the fast commercialization of these cobalt-poor materials.

However, new cobalt-free chemistries are even more attractive, as the cost of the cathode material can be reduced by up to 60% (compared to NCM). One of the most mature technologies among the cobalt-free family is the LNMO, as it has several advantages.

It presents a long high voltage plateau and very fast lithium insertion and extraction. This means that the battery can be charged/discharged in very short time and can operate at elevate voltage (around 4.7 V), which yields to high energy densities of 650 Wh/kg at cell level (vs the cathode mass).

Electrolytes for high voltage operation

The most challenging aspect for this technology is to find an electrolyte that is stable in the voltage window of this material (3.5 to 4.9 V). In this sense, the research followed by CIC energiGUNE in the last years includes the use of gel polymer electrolytes with the aim of improving the battery safety at these high voltages.  

However, one of the major bottlenecks towards commercialization of this battery system is its reduced life cycle compared to commercial lithium-ion batteries. For this reason, thanks to the large variety of characterization facilities available within the CIC energiGUNE platforms, new protocols for diagnosing the degradation of gel-based lithium batteries have been developed.

这种精确的诊断使我们能够改进处理方法并制定延长电池寿命的缓解策略。如今，超过 250 个循环已达到 80% SoH（在汽车应用中被认为是寿命终止 (EoL)。

在最新的 HighSpin 项目中，我们将在可持续性和更环保的工艺上更进一步，使用水基溶剂作为阴极。还设想了用于回收关键材料的回收路线。美国Northstar蓄电池

In addition to this, the research activities of the Advanced cathode research line also include the understanding of the structural properties and redox activity of the synthetized LNMO material and its relation to the electrochemical properties. Operando x-ray absorption spectroscopy has been employed to elucidate the influence of the transition metal order on the reaction mechanism of the LNMO spinel.

Other techniques like solid-state nuclear magnetic resonance (ssNMR) and neutron powder diffraction (NPD) were also used ex-situ to provide insights on the changes of the lattice parameters and the metal dispositions around the Li site.

This fundamental study has revealed an important insight about the dynamics of LNMO’s cycling mechanisms. This will help to develop new strategies for the future LNMO material development.

由于钴等一些电池材料的需求增长速度空前，开发可替代欧盟确定的关键材料的替代品是电池研究目前面临的主要挑战之一。 美国Northstar蓄电池

LNMO 是一种很有前途的无钴正极替代品，因此主要的研究工作都集中在它的开发上。CIC energiGUNE 正走在加速商业化的道路上，将更环保的电池从实验室带入实际应用。