使用高频脉冲电流充电可减少老化效应，一个国际团队证实

An improved charging protocol might help lithium-ion batteries to last much longer. Charging with a high-frequency pulsed current reduces ageing effects, an international team demonstrated. The study was led by Philipp Adelhelm (HZB and Humboldt University) in collaboration with teams from the Technical University of Berlin and Aalborg University in Denmark. Experiments at the X-ray source BESSY II were particularly revealing.
改进充电方案或可大幅延长锂离子电池寿命。国际研究团队证实，采用高频脉冲电流充电能减缓电池老化效应。该研究由菲利普·阿德尔赫姆（HZB与柏林洪堡大学）主导，柏林工业大学与丹麦奥尔堡大学团队共同参与。在BESSY II同步辐射光源开展的实验尤其具有启发性。

Lithium-ion batteries are powerful, and they are used everywhere, from electric vehicles to electronic devices. However, their capacity gradually decreases over the course of hundreds of charging cycles. The best commercial lithium-ion batteries with electrodes made of so-called NMC532 (molecular formula: LiNi_0.5Mn_0.3Co_0.2O₂) and graphite have a service life of up to eight years. Batteries are usually charged with a constant current flow. But is this really the most favourable method? A new study by Prof Philipp Adelhelm's group at HZB and Humboldt-University Berlin answers this question clearly with no. The study in the journal Advanced Energy Materials analyses the effect of the charging protocol on the service time of the battery.
锂离子电池功能强大，从电动汽车到电子设备，它们无处不在。然而，经过数百次充电循环后，其容量会逐渐下降。由所谓NMC532（分子式：LiNi Mn Co O）和石墨制成电极的最佳商用锂离子电池，使用寿命长达八年。电池通常以恒定电流充电。但这真的是最有利的方法吗？HZB和柏林洪堡大学Philipp Adelhelm教授团队的新研究给出了明确否定答案。发表于《Advanced Energy Materials》期刊的该研究分析了充电协议对电池使用寿命的影响。

Ageing effects analysed
衰老效应分析

Part of the battery tests were carried out at Aalborg University. The batteries were either charged conventionally with constant current (CC) or with a new charging protocol with pulsed current (PC). Post-mortem analyses revealed clear differences after several charging cycles: In the CC samples, the solid electrolyte interface (SEI) at the anode was significantly thicker, which impaired the capacity. The team also found more cracks in the structure of the NMC532 and graphite electrodes, which also contributed to the loss of capacity. In contrast, PC-charging led to a thinner SEI interface and fewer structural changes in the electrode materials.
部分电池测试在奥尔堡大学进行。这些电池要么采用恒流（CC）常规充电，要么采用脉冲电流（PC）新充电协议。事后分析显示多次充放电循环后存在明显差异：CC样本中阳极的固体电解质界面（SEI）明显更厚，从而损害了电池容量。研究团队还发现NMC532和石墨电极的结构中出现更多裂纹，这也导致了容量损失。相比之下，PC充电导致SEI界面更薄，电极材料的结构变化更少。

Synchrotron experiments at BESSY II and PETRA III
BESSY II和PETRA III的无性向同步加速器实验

HZB researcher Dr Yaolin Xu then led the investigation into the lithium-ion cells at Humboldt University and BESSY II with operando Raman spectroscopy and dilatometry as well as X-ray absorption spectroscopy to analyse what happens during charging with different protocols. Supplementary experiments were carried out at the PETRA III synchrotron. "The pulsed current charging promotes the homogeneous distribution of the lithium ions in the graphite and thus reduces the mechanical stress and cracking of the graphite particles. This improves the structural stability of the graphite anode," he concludes. The pulsed charging also suppresses the structural changes of NMC532 cathode materials with less Ni-O bond length variation.
HZB研究员徐耀林博士随后在洪堡大学和BESSY II利用原位拉曼光谱、膨胀测量法以及X射线吸收光谱对锂离子电池进行了研究，以分析在不同充电协议下发生的情况。补充实验在PETRA III同步加速器上进行。"脉冲电流充电促进了锂离子在石墨中的均匀分布，从而减少了石墨颗粒的机械应力和开裂。他总结道："这提高了石墨阳极的结构稳定性。"脉冲充电还抑制了NMC532阴极材料的结构变化，使Ni-O键长度变化更小。

The pulse current frequency is crucial
脉冲电流频率至关重要

However, the frequency of the pulsed current counts: High-frequency PC charging protocols with square-wave current extend the service life of commercial LIBs the most, with a doubled cycle life (with 80% capacity retention) achieved in this study. Co-author Prof. Dr Julia Kowal, an expert in electrical energy storage technology at TU Berlin, emphasises: "Pulsed charging could bring many advantages in terms of the stability of the electrode materials and the interfaces and significantly extend the service life of batteries."
然而，脉冲电流的频率至关重要：采用方波电流的高频PC充电协议最能延长商用LIB的寿命，本研究中实现了循环寿命翻倍（保持80%容量）。合著者、TU Berlin电能存储技术专家Julia Kowal教授强调："脉冲充电在电极材料及界面稳定性方面可带来诸多优势，并显著延长电池寿命。"