羧甲基纤维素（CMC）是一种广泛应用于石墨负极的水系粘结剂。然而，CMC反离子（Li⁺/Na⁺/K⁺）的种类与组成如何在分子尺度上调控界面离子传输并影响电极性能仍缺乏清晰认识。本文采用分子动力学模拟构建电解液/CMC/石墨三相界面模型，以CMC-Li、CMC-Na、CMC-K及混合反离子CMC作为粘结剂，系统探究充电过程中Li⁺穿越粘结剂相并进入石墨的微观迁移路径。结果表明，在CMC-Li体系中，Li⁺能够持续由电解液穿过粘结剂相并嵌入石墨层间，在模拟时间尺度内形成稳定的传输通路。相比之下，在CMC-Na与CMC-K体系中，Na⁺/K⁺难以进入石墨内部而倾向于在石墨表面富集，形成阳离子富集界面屏障，从而抑制Li⁺向石墨迁移。进一步地，随着在CMC中逐步以Li⁺替代Na⁺/K⁺，该界面阻塞效应减弱，Li⁺对石墨的可及性随之提高。本研究为CMC-Li相较CMC-Na/K在实验中性能表现更优提供了微观机制解释，并为粘结剂离子传输性能的优化提供了理论依据与设计思路。

Carboxymethyl cellulose (CMC) is a water-processable binder widely used for graphite anodes. However, a microscopic understanding of why the identity of CMC counterions (Li⁺/Na⁺/K⁺) strongly affects electrode performance remains limited. Here, molecular dynamics (MD) simulations are used to track Li⁺ transport accessibility across electrolyte/CMC/graphite three-phase interfaces, comparing pure CMC-Li, CMC-Na, CMC-K, and mixed-counterion CMC binders. We find that CMC-Li sustains a continuous Li⁺ transport pathway from the electrolyte through the binder phase toward graphite. In contrast, in CMC-Na and CMC-K, Na⁺/K⁺ ions preferentially enrich at the graphite/binder interface, forming a cation-enriched interfacial layer which reduces Li⁺ accessibility to graphite. Partial replacement of Na⁺/K⁺ in CMC-Na and CMC-K with Li⁺ weakens this interfacial blocking effect and increases Li⁺ accessibility. Furthermore, a stage-resolved kinetic analysis visualizes the progressive suppression of Li⁺ crossing the binder phase upon the barrier layer formation. These results provide a microscopic rationale for the experimentally observed performance advantage of CMC-Li over CMC-Na and CMC-K binders.