Lithium storage schemes based on conversion chemistry have been used in a large variety of negative electrodes achieving capacities 2–3 times higher than graphite. However, to date, relatively few positive electrode examples have been reported. Here, we report a new conversion positive electrode, Ni(PO₃)₂, and systematic studies on its working and degradation mechanisms. Crystalline Ni(PO₃)₂ undergoes an electrochemistry‐driven amorphization process in the first discharge to form a fine microstructure, consisting of Ni domains ∼2 nm wide that form a percolating electron‐conducting network, embedded in a glassy LiPO₃ matrix. P does not participate electrochemically, remaining as P⁵⁺ in [PO₃]⁻ throughout. The electrode does not recrystallise in the following first charge process, remaining amorphous over all subsequent cycles. The low ionicity of the Ni−[PO₃] bond and the high Li⁺ conductivity of the LiPO₃ glass lead to high intrinsic electrochemical activity, allowing the micro‐sized Ni(PO₃)₂ to achieve its theoretical capacity of 247 mAh/g. The performance of the Ni(PO₃)₂ electrode ultimately degrades due to the growth of larger and more isolated Ni grains. While the theoretical capacity of Ni(PO₃)₂ is itself limited, this study sheds new light on the underlying chemical mechanisms of conversion positive electrodes, an important new class of electrode for solid‐state batteries.

中文翻译：

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偏磷酸镍作为锂离子电池的转换正极

基于转换化学的锂存储方案已用于各种负极，其容量是石墨的2-3倍。然而，迄今为止，已经报道了相对较少的正极示例。在这里，我们报告一个新的转换正极Ni（PO ₃）₂，并对其工作和降解机理进行系统研究。Ni（PO ₃）₂晶体在第一次放电中经历了电化学驱动的非晶化过程，形成了一个精细的微结构，该微结构由约2 nm宽的Ni域组成，形成渗透的电子传导网络，嵌入到玻璃状LiPO ₃基质中。P不参与电化学作用，保留为P ⁵⁺在[PO ₃ ] ^-中。电极在随后的第一个充电过程中不会重结晶，在所有后续循环中保持非晶态。Ni- [PO ₃ ]键的低离子性和LiPO ₃玻璃的高Li ⁺电导率导致高固有的电化学活性，使微型Ni（PO ₃）₂达到其理论容量247 mAh / G。Ni（PO ₃）₂电极的性能最终由于较大且更孤立的Ni晶粒的生长而降低。Ni（PO ₃）₂的理论容量 由于它本身是有限的，这项研究为转化型正极的潜在化学机理提供了新的思路，这是固态电池的重要一类新的电极。