Square-Scheme Electrochemistry in Battery Electrodes
Square-Scheme Electrochemistry in Battery Electrodes
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DOI：
10.1021/accountsmr.1c00155
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发表时间：
2021-11
影响因子：
14.6
通讯作者：
M. Okubo;Kosuke Kawai;Zihan Ma;A. Yamada
中科院分区：
文献类型：
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作者：
M. Okubo;Kosuke Kawai;Zihan Ma;A. Yamada
10.因此，如果没有重大的技术进步，就不可能实现可持续发展。例如，灵活的电力管理需要采用先进的储能/转换技术的智能电源。在太阳能和风能等可再生能源中观察到的突然功率峰值/下降的补救措施需要在将高功率储能系统集成到微电网中时使用高功率储能系统进行快速负载均衡。电化学能量存储装置有效地转换电能和化学能，其可以潜在地用作分布式电源。其中，锂离子电池是目前的事实标准，其相对高的能量密度和能量效率是基于局部化学嵌入化学，由此客体锂离子可逆地嵌入（脱嵌），同时发生氧化还原反应和最小的结构变化。然而，它们的能量密度、功率密度、寿命周期成本、日历寿命和安全性对于广泛使用来说仍然不令人满意。当存储容量被最大化时，作为其结果，产生不稳定的深度充电/放电状态，以开发具有高能量密度的电池，在许多情况下发生随后的不可逆相变或化学反应。可逆电极反应和随后的不可逆相变的组合有时会导致以100%库仑效率的大电压滞后为特征的充电/放电曲线。由于大的电压滞后会显著降低能量效率，揭示反应机理对于减少能量损失至关重要。在本帐户中，我们全面讨论了独特的可逆充电/放电反应，概括为“平方方案”，其中包括热力学和动力学过程。在分析平方方案中遇到的困难是，能源效率和效率低下的过程共存，并相互竞争，后者涉及的时间依赖现象。在这里，我们提供的理论模型和解析表达式动力学正方形计划电极在几种电化学条件下，包括恒电流充电/放电，恒电流间歇滴定技术（GITT），恒电位间歇滴定技术（PITT），和恒流/恒压（CC-CV）充电/放电。对于两种典型的方形电极：Na 1-xTi0.5Co0.5O2和Na 2-xMn 3 O 7，证实了分析模型的有效性。钠离子电池正极材料Na 1-xTi0.5Co0.5O2在过渡金属氧化/还原后发生高自旋态和低自旋态之间的相变，而大容量氧氧化还原正极材料Na 2-xMn 3 O 7在氧化物离子氧化后出现O-O键形成，在过氧化氢还原后出现O-O键断裂，两者都会引发较大的电压滞后。该帐户强调的重要性，定量分析的平方计划，其中大量的电压滞后可以发生在任何电极材料与大容量或高电压，经历不可逆的化学反应时，深充电或放电。这种寄生的能量消耗转换在数小时或数天内缓慢进行，应小心避免，以实现节能和稳定的电池系统。
ConspectusSustainable development cannot be achieved without substantial technological advancements. For instance, flexible electricity management requires smart power sourcing with advanced energy storage/conversion technologies. Remedies for abrupt power spikes/drops observed in renewable energy sources such as solar and wind require rapid load-leveling using high-power energy storage systems when they are integrated into a microgrid. Electrochemical energy storage devices efficiently convert electrical and chemical energy, which can potentially function as distributed power sources. Among these, lithium-ion batteries are a presentde factostandard with their relatively high energy density and energy efficiencies that are based on topochemical intercalation chemistry, whereby guest lithium ions are (de)intercalated reversibly with simultaneous redox reactions and minimal structural changes. However, their energy density, power density, life-cycle cost, calendar life, and safety remain unsatisfactory for widespread use. When the storage capacity is maximized, as a result of which a labile deep charge/discharge state is generated, to develop batteries with high energy density, subsequent irreversible phase transformations or chemical reactions occur in many cases. The combination of the reversible electrode reactions and the subsequent irreversible phase transformations sometimes causes a charge/discharge curve characterized by a large voltage hysteresis with 100% Coulombic efficiency. Because a large voltage hysteresis significantly degrades the energy efficiency, unveiling the reaction mechanism is of primary importance in mitigating energy loss.In this Account, we comprehensively discuss the distinct and reversible charge/discharge reactions, generalized by the term “square scheme”, which includes both thermodynamic and kinetic processes. The difficulties encountered in analyzing the square scheme are that both energy efficient and inefficient processes coexist and compete with each other, where the latter involves the time-dependent phenomenon. Here, we provide the theoretical models and analytical expressions for kinetic square-scheme electrodes under several electrochemical conditions, including galvanostatic charge/discharge, the galvanostatic intermittent titration technique (GITT), the potentiostatic intermittent titration technique (PITT), and constant-current/constant-voltage (CC–CV) charge/discharge. The validity of the analytical models was confirmed for two typical square-scheme electrodes: Na1–xTi0.5Co0.5O2and Na2–xMn3O7. Na1–xTi0.5Co0.5O2, which is a sodium-ion battery cathode material, undergoes phase transitions between high-spin and low-spin states after transition-metal oxidation/reduction, while Na2–xMn3O7, which is a large-capacity oxygen-redox cathode material, exhibits O–O bond formation after oxide-ion oxidation and O–O bond cleavage after peroxide reduction, both of which trigger large voltage hysteresis. This Account emphasizes the importance of the quantitative analyses of the square scheme in which a large amount of voltage hysteresis can occur within any electrode material with a large capacity or high voltage that undergoes irreversible chemical reactions upon deep charging or discharging. Such parasitic energy-consuming transformations slowly proceed over a number of hours or days and should be carefully avoided to realize energy-efficient and stable battery systems.