锂离子电池是当今’电动汽车和电池储能系统行业,的主要选择，但它们含有许多关键矿物—，包括锂,钴,镍,和石墨—，这些矿物被认为对经济和国家安全原因至关重要,，因此容易受到供应链中断的影响。随着可再生能源,电气化基础设施,和大功率数字技术的不断发展,，对低成本,资源丰富,且能够快速充放电的储能系统的需求日益增长。
Lithium-ion batteries are the leading choice in today的 electric vehicle and battery energy storage system industries, but they contain a number of critical minerals — including lithium, cobalt, nickel, and graphite — that are considered essential for economic and national security reasons, and therefore vulnerable to supply chain disruptions. As renewable energy, electrified infrastructure, and high-power digital technologies continue to grow, there is an increasing need for energy storage systems that are low-cost, resource-abundant, and capable of fast charging and discharging.
这种需求,以及其他原因,激励了麻省理工学院的一组研究人员—，由核科学与工程系卡尔·理查德·索德伯格动力工程系教授Ju Li,领导(NSE)和材料科学与工程系—领导，开发互补的储能解决方案。
That need, among other reasons, has motivated a group of researchers — based at MIT and led by Ju Li, the Carl Richard Soderberg Professor of Power Engineering in the departments of Nuclear Science and Engineering (NSE) and Materials Science and Engineering — to develop complementary energy storage solutions.
该团队正在寻找,，特别是, 钠金属电池,，它提供了一些有吸引力的功能。钠的含量比锂丰富约 1,000 倍，而 , 磅的重量比 , 的成本约为锂的百分之一。然而，, 的一个关键挑战是钠金属具有高反应性,，这使得这些电池难以同时实现长期稳定性和快速循环。
The team is looking, in particular, at sodium-metal batteries, which offer several attractive features. Sodium is about 1,000 times more abundant than lithium and, pound for pound, about one-hundredth the cost. A key challenge, however, is that sodium metal is highly reactive, making it difficult for these batteries to achieve both long-term stability and fast cycling.
《Joule—》杂志上的一篇新论文由麻省理工学院团队的 15 名成员撰写并于本周在线发表— 展示了如何通过为该电池系统找到合适的电解质来解决这一困境。
A new paper in the journal Joule — written by 15 members of the MIT team and published online this week — shows how this dilemma can be addressed by finding the right electrolyte for this battery system.
电解质是电池, 的三个主要成分之一，另外还有负极(、阳极) 和正极(、阴极)。电解质的作用类似于电池, 的“blood”，允许带电离子在两个电极之间移动。 “电解质应该只是传输这些离子,” Li 解释道。 “It的 应该是离子导体。” 但不幸的是, 大多数电解质会与电极, 发生不必要的化学反应，这会极大地破坏电池稳定性。
An electrolyte is one of three main components of a battery, along with the negative electrode (the anode) and the positive electrode (the cathode). The electrolyte acts like the “blood” of the battery, allowing electrically charged ions to move between the two electrodes. “The electrolyte is supposed to just transmit those ions,” explains Li. “It的 supposed to be an ion conductor.” But unfortunately, most electrolytes get involved in unwanted chemical reactions with the electrodes, which can greatly undermine battery stability.
这些 “ 副反应” 的后果可能很严重, NSE 博士后、焦耳论文的四位主要作者之一 Weiyin Chen, 说。反应过程中产生的不溶性化合物会在电极上积聚,，形成阻碍离子传输的屏障，最终导致电池失效。
The consequences of these “side reactions” can be severe, says Weiyin Chen, a postdoc in NSE and one of four lead authors of the Joule paper. Insoluble compounds produced during the reactions can build up on the electrodes, creating a barrier that blocks ion transport and can eventually cause the battery to fail.
直到最近, Chen 表示, 钠金属电池中使用的电解质还没有完全稳定地抵抗阳极和阴极, 上的这些不需要的反应，尽管这种稳定性对于可充电电池实现长循环寿命至关重要。最初的突破发生在 2021,，当时 Li 小组及其合作者发现了一种 “ 磺酰胺” 分子 —，由硫,、氧, 和氮原子 — 组成，, 当用作溶剂, “ 时，在锂的两个电极上都神奇地稳定据李说，电池,”。这种分子被称为 DMTMSA。
Until recently, Chen says, no electrolyte used in sodium-metal batteries was fully stable against these unwanted reactions at both the anode and cathode, even though such stability is essential for rechargeable batteries to achieve a long cycle life. An initial breakthrough occurred in 2021, when the Li group and their collaborators identified a “sulfonamide” molecule — consisting of sulfur, oxygen, and nitrogen atoms — that, when used as a solvent, “is magically stable at both electrodes in lithium batteries,” according to Li. This molecule is known as DMTMSA.
基于这一发现, Li 和他的同事开始研究相关分子是否可以改进钠电池。目标不仅是保持稳定性,，而且还能够实现快速充电和放电。如果充电太慢,，则可能需要整夜才能充电,，如果放电太慢,，则电池在需要时无法提供太多电力。
Building on that discovery, Li and his colleagues set out to see if related molecules could improve sodium batteries. The goal was not only to maintain stability, but also to enable fast charging and discharging. If charging is too slow, it could take all night to recharge, and if discharging is too slow, the battery cannot deliver much power when needed.
溶剂是怎么过马路的?
How did the solvent cross the road?
Chen 用类比解释了这个想法: 假设您需要穿过一条挤满行人的街道,，就像离子从一个电极传播到另一个电极一样。 “您可以携带紧贴身体的小背包更快地穿过人群,，而不是拖着带轮子的笨重手提箱,” Chen 说。
Chen explains the idea with an analogy: Suppose you need to cross a street jam-packed with pedestrians, much like ions traveling from one electrode to another. “You can move more quickly through the crowd with a small backpack that is snug against your body, rather than dragging a bulky suitcase on wheels,” Chen says.
类似的情况也发生在电池: 中。当钠离子被较小的溶剂, 包围时，它们比被较大的, 较大的溶剂包围时移动得更快。更快的离子传输可以实现更快速的充电和放电。团队’的目标,因此,是识别足够小的溶剂分子，以改善离子传输，同时仍保持电解质稳定性。
A similar situation occurs in batteries: When sodium ions are surrounded by smaller solvents, they can move faster than when they are surrounded by larger, bulkier solvents. Faster ion transport enables more-rapid charging and discharging. The team的 goal, accordingly, was to identify solvent molecules that are small enough to improve ion transport while still maintaining electrolyte stability.
, 然而, 是一个复杂的因素— 需要权衡: 更快的离子传输通常以牺牲电解质稳定性为代价。许多高导电性电解质更容易与电极发生反应,，从而缩短电池寿命。幸运的是，他们的计划, Li 说, �%9减少溶剂的用量提供了克服这种权衡的新途径。”
There is, however, a complicating factor — a trade-off to be addressed: Faster ion transport often comes at the expense of electrolyte stability. Many highly conductive electrolytes react more easily with the electrodes, shortening battery life. Fortunately for their plan, Li says, “reducing the size of solvents provides a new pathway to overcome this trade-off.”
接下来的问题就变成了如何找到一种具有其他所需特性的较小溶剂。他们采用的想法是寻找 “ 同属,” 的分子，Li, “ 表示它们属于相似的家族，并且分子相似。” 特别是,，他们搜索与 DMTMSA, 相关的分子，希望找到更小的候选分子，但可以保留使 DMTMSA 如此有前途的稳定性。
The question then becomes how to find a smaller solvent that has other desirable properties. The idea they adopted is to look for molecules that are “congeneric,” says Li, “meaning that they belong to a similar family and are molecularly similar.” In particular, they searched for molecules related to DMTMSA, hoping to find candidates that were smaller but could retain the stability that made DMTMSA so promising.
Chia-Wei Hsu, 麻省理工学院材料科学与工程专业的博士生, 创建了一种 AI 引导算法,，该算法在 24 小时内在计算机上设计了 100,000 个候选分子。然后，Hsu 通过应用一组技术标准 —（包括形状与 DMTMSA 的相似性和可比的电子特性）将候选者范围缩小到 200 名。涵盖所有可能性的 27 名代表性候选人被选中进行实验测试。
Chia-Wei Hsu, an MIT PhD student in materials science and engineering, created an AI-guided algorithm, which designed 100,000 candidate molecules on his computer within 24 hours. Hsu then narrowed down the pool to 200 candidates by applying a set of technical criteria — including similarity in shape to DMTMSA and comparable electronic properties. Twenty-seven representative candidates covering the full range of possibilities were selected for experimental tests.
“我们在相同的条件下对它们进行了测试，以使其成为公平的, 面对面的竞争,” Chen 说。明显的赢家出现了,，一种名为 DMFSA, 的溶剂，它是最小且最好的。
“We tested them all under the same conditions to make it a fair, head-to-head competition,” Chen says. A clear winner emerged, a solvent called DMFSA, which was both the smallest and the best.
这项工作, 声称 Jinhyuk Lee, 是麦吉尔大学材料工程副教授，他没有参与该研究, “ 解决了电池研究中最持久的挑战之一: 在不牺牲长期稳定性的情况下提高高充电和放电速率下的电池性能。通过仔细调整溶剂分子的大小,，作者展示了一种新的设计策略，可以实现更低成本, 更高性能的电池。”
This work, claims Jinhyuk Lee, an associate professor of materials engineering at McGill University who is not part of the study, “addresses one of the most persistent challenges in battery research: improving battery performance at high charging and discharging rates without sacrificing long-term stability. By carefully tailoring the size of solvent molecules, the authors demonstrate a new design strategy that could enable lower-cost, higher performance batteries.”
组还没做完。一项新的研究正在进行中，以寻找更好的溶剂。这次, 的方法与, 类似，但以DMFSA ( 而不是较大的DMTMSA 分子) 作为起点。 Chen 认为，他们发现的新溶剂最终可能会导致可充电钠金属电池的出现，该电池将低成本, 丰富的材料与快速充电和高功率性能, 结合起来，为更广泛的能源存储应用打开了大门。
The group is not done. A new search is underway to find an even better solvent. This time, the approach is similar, but DMFSA (rather than the larger DMTMSA molecule) serves as the starting point. Chen believes the new solvents they are uncovering could eventually lead to rechargeable sodium-metal batteries that combine low-cost, abundant materials with fast charging and high-power performance, opening the door to broader energy storage applications.
作者强调,这项工作的首要目标不仅仅是推进钠电池。它还引入了一种新的电解质设计方法，该方法使用溶剂尺寸和分子相似性作为关键指南。将这种 light, 钠金属电池的研究作为一个模型系统来展示更通用的设计原理。
The overriding goal of this work, the authors emphasize, is not only to advance sodium batteries. It的 also to introduce a new approach to electrolyte design that uses solvent size and molecular similarity as the key guideposts. Viewing the research in this light, sodium-metal batteries serve as a model system for demonstrating a more general design principle.
“因为这个概念广泛适用,” Lee评论, �%9它的影响可能远远超出钠电池范围，并影响广泛的未来储能技术的设计。”
“Because the concept is broadly applicable,” Lee comments, “its impact could extend well beyond sodium batteries and influence the design of a wide range of future energy storage technologies.”
这项工作的, 部分, 得到了韩国政府, 资助的韩国国家研究基金会拨款以及美国国家科学基金会研究生研究奖学金的支持。该项目中使用的表征设备部分来自 MIT.nano 表征设施。
This work was supported, in part, by a National Research Foundation of Korea grant funded by the government of Korea government, as well as U.S. National Science Foundation graduate research fellowship. The characterization equipment used in this project is partly from the MIT.nano Characterization Facilities.