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让“死”锂复活,恢复电池活力 精选

已有 6840 次阅读 2022-1-4 21:16 |个人分类:新科技|系统分类:海外观察

让“死”锂复活,恢复电池活力

诸平

revitalizing-batteries.gif 


Fig. 1 An animation shows how charging and discharging a lithium battery test cell causes an island of “dead” (or detached) lithium metal to creep back and forth between the electrodes. The movement of lithium ions back and forth through the electrolyte creates areas of negative (blue) and positive (red) charge at the ends of the island, which swap places as the battery charges and discharges. Lithium metal accumulates at the negative end of the island and dissolves at the positive end; this continual growth and dissolution causes the back-and-forth movement seen here. SLAC and Stanford researchers discovered that adding a brief, high-current discharging step right after charging the battery nudges the island to grow in the direction of the anode, or negative electrode. Reconnecting with the anode brings the island’s dead lithium back to life and increases the battery’s lifetime by nearly 30%. Credit: Greg Stewart / SLAC National Accelerator Laboratory

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Fig. 2 When an island of inactivated lithium metal travels to a battery's anode, or negative electrode, and reconnects, it comes back to life, contributing electrons to the battery's current flow and lithium ions for storing charge until it's needed. The island moves by adding lithium metal at one end (blue) and dissolving it at the other end (red). Researchers from SLAC and Stanford discovered that they could drive the island's growth in the direction of the anode by adding a brief, high-current discharging step right after the battery charges. Reconnecting the island to the anode increased the lifetime of their lithium-ion test cell by nearly 30%. Credit: Greg Stewart / SLAC National Accelerator Laboratory 

据美国斯坦福直线加速器中心(Stanford Linear Accelerator Center简称SLAC国家加速器实验室SLAC National Accelerator Laboratory202213日提供的消息,美国能源部 SLAC国家加速器实验室和斯坦福大学(Stanford University)的研究人员可能已经找到了一种方法来复活可充电锂电池,有可能提高电动汽车的续航里程和下一代电子设备的电池寿命( Revitalizing batteries by bringing 'dead' lithium back to life)。上述动画展示了锂电池测试电池的充电和放电如何导致(或分离)锂金属岛在电极之间来回蠕动。锂离子在电解质中来回移动,在岛的末端产生负(蓝色)和正(红色)电荷区域,随着电池充电和放电而交换位置。锂金属在岛的负端积聚,在正端溶解;这种持续的增长和分解导致了这里看到的来回运动。SLAC 和斯坦福大学的研究人员发现,在给电池充电后立即添加一个简短的高电流放电步骤会推动小岛朝着阳极或负极的方向生长。重新连接阳极使岛上的死锂恢复生机,并将电池的寿命延长近 30%

随着锂电池(lithium batteries)的循环,它们会积聚与电极断开的小岛状惰性锂,从而降低电池存储电荷的能力。但研究小组发现,他们可以让这种的锂像蠕虫一样向其中一个电极蠕动,直到它重新连接,部分逆转了不需要的过程。添加这个额外的步骤减缓了他们测试电池的退化(degradation),并将其寿命延长了近 30%。相关研究结果于20211222日已经在《自然》(Nature)杂志网站发表——Fang LiuRong XuYecun WuDavid Thomas BoyleAnkun YangJinwei XuYangying ZhuYusheng YeZhiao YuZewen ZhangXin XiaoWenxiao HuangHansen WangHao ChenYi Cui. Dynamic spatial progression of isolated lithium during battery operations. Nature,  Published: 22 December 2021, 600: 659–663. DOI10.1038/s41586-021-04168-w. https://www.nature.com/articles/s41586-021-04168-w.此论文的第一作者、斯坦福大学博士后研究员刘芳(Fang Liu音译)说:我们现在正在探索使用极快的放电步骤恢复锂离子电池容量损失的可能性。

失去连接(Lost connection

大量研究都集中在寻找方法来制造比目前用于手机、笔记本电脑和电动汽车的锂离子技术更轻、寿命更长、安全性更高、充电速度更快的可充电电池。一个特别的重点是开发锂金属电池,它可以按单位体积或重量存储更多的能量。例如,在电动汽车中,这些下一代电池可以增加每次充电的里程数,并可能占用更少的行李箱空间。

两种电池类型都使用带正电的锂离子,在电极之间来回穿梭。随着时间的推移,一些金属锂变得电化学惰性,形成孤立的锂岛,不再与电极连接。这会导致容量损失,并且是锂金属技术和锂离子电池快速充电的一个特殊问题。然而,在这项新的研究中,研究人员证明他们可以调动和回收孤立的锂以延长电池寿命extend battery life)。

领导这项研究的斯坦福大学和SLAC教授、斯坦福材料与能源研究所 (Stanford Institute for Materials and Energy Research简称SIMES) 的研究员崔屹(Yi Cui音译)说:我一直认为孤立的锂是不好的,因为它会导致电池衰减甚至着火。但我们已经发现了如何将这种锂与负极重新电连接以重新激活它(参看图所示)

在蠕动,没有死(Creeping, not dead

当崔屹教授推测向电池的阴极和阳极施加电压可以使孤立的锂岛在电极之间物理移动时,这项研究的想法就已经诞生了——他的团队现在已经通过他们的实验证实了这一过程。

科学家们制造了一个带有锂镍锰钴氧化物 (lithium-nickel-manganese-cobalt-oxide简称NMC) 阴极、一个锂阳极和一个介于两者之间的孤立锂岛的光学电池(optical cell)。该测试设备使他们能够实时跟踪使用时电池内部发生的情况。他们发现孤立的锂岛根本没有,而是对电池操作做出了反应。给电池充电时,锂岛慢慢向阴极移动;放电时,它向相反的方向转移。

崔屹说:它就像一只非常缓慢的蠕虫,它的头部向前一英寸,尾巴向内拉动,以纳米级为单位移动。在这种情况下,它通过在一端溶解锂并在另一端将锂又沉积出来传输。如果我们能让锂蠕虫保持移动,它最终将接触阳极并重新建立电连接。

延长寿命(Boosting lifetime

科学家们用其他测试电池,并通过计算机模拟验证的结果也证明了,如何通过修改充电协议(charging protocol)在真正的电池中回收孤立的锂。

刘芳说:我们发现我们可以在放电过程中将分离的锂向阳极移动,并且这些运动在更高的电流下更快。因此,我们在电池充电后立即添加了一个快速、高电流的放电步骤,将孤立的锂移动到足够远的位置,使其与阳极重新连接。这会重新激活锂,使其能够参与电池的寿命。

她补充说:我们的研究结果对设计和开发更强大的锂金属电池也具有广泛的意义。

上述介绍,仅供参考。欲了解更多信息,敬请注意浏览原文或者相关报道

Abstract

The increasing demand for next-generation energy storage systems necessitates the development of high-performance lithium batteries1,2,3. Unfortunately, current Li anodes exhibit rapid capacity decay and a short cycle life4,5,6, owing to the continuous generation of solid electrolyte interface7,8 and isolated Li (i-Li)9,10,11. The formation of i-Li during the nonuniform dissolution of Li dendrites12 leads to a substantial capacity loss in lithium batteries under most testing conditions13. Because i-Li loses electrical connection with the current collector, it has been considered electrochemically inactive or ‘dead’ in batteries14,15. Contradicting this commonly accepted presumption, here we show that i-Li is highly responsive to battery operations, owing to its dynamic polarization to the electric field in the electrolyte. Simultaneous Li deposition and dissolution occurs on two ends of the i-Li, leading to its spatial progression toward the cathode (anode) during charge (discharge). Revealed by our simulation results, the progression rate of i-Li is mainly affected by its length, orientation and the applied current density. Moreover, we successfully demonstrate the recovery of i-Li in Cu–Li cells with >100% Coulombic efficiency and realize LiNi0.5Mn0.3Co0.2O2 (NMC)–Li full cells with extended cycle life.




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