The quest for more powerful and safer energy storage solutions has driven intense research into lithium metal batteries (LMBs). Central to this advancement is the development of a stable and efficient lithium metal anode. However, the intrinsic high reactivity of lithium metal poses significant challenges, primarily the uncontrolled growth of dendrites during electrochemical cycling. This phenomenon compromises battery performance and poses safety concerns. Heptafluorobutyric acid (HFA) has emerged as a critical chemical agent capable of addressing these limitations through strategic surface modification of the lithium anode.

The core of HFA's effectiveness lies in its ability to react with the lithium metal surface. This reaction serves a dual purpose: first, it cleans the lithium surface by removing the naturally formed, often detrimental, passivation layer (primarily composed of Li2CO3 and LiOH). This native layer impedes uniform ion transport and can promote uneven lithium plating. Second, the reaction forms a new protective layer, primarily lithium heptafluorobutyrate, which has proven to be highly beneficial for battery operation. This newly formed interface is characterized by its lithiophilic nature, meaning it has a strong affinity for lithium ions.

The lithiophilic property imparted by the heptafluorobutyrate layer is instrumental in achieving uniform lithium deposition. Unlike bare lithium surfaces, which exhibit preferential nucleation sites and thus uneven plating, the modified surface acts as a more uniform scaffold for lithium deposition. This uniformity is crucial for preventing the initiation and propagation of lithium dendrites. By ensuring that lithium ions are distributed evenly across the anode surface, the risk of localized current densities, which drive dendrite growth, is significantly reduced. This leads to a much more stable and predictable electrochemical process.

Furthermore, the HFA treatment directly contributes to improved Coulombic efficiency (CE). CE is a key metric for battery longevity and efficiency, representing the ratio of lithium ions reversibly plated and stripped. High CE values (close to 100%) indicate minimal loss of active lithium during cycling. The stabilized interface created by HFA treatment minimizes side reactions and parasitic processes that consume lithium and electrolyte, thereby substantially boosting the CE. For instance, CE values of nearly 99.3% have been reported for HFA-modified lithium anodes, a substantial improvement over unmodified anodes.

The practical implications of this stabilization are profound. In Li/Li symmetric cells, a common testbed for anode stability, the HFA-treated lithium anodes demonstrate exceptional longevity, maintaining stable voltage profiles for extended periods, often exceeding 1000 hours. This stability is a direct result of the suppressed dendrite growth and the robust nature of the lithium heptafluorobutyrate interface. When incorporated into full battery cells (e.g., Li||NMC811), these modified anodes exhibit significantly better capacity retention and cycle life, even under demanding operating conditions such as high cathode loading or limited lithium excess.

The efficacy of heptafluorobutyric acid in enhancing lithium metal anode performance underscores the importance of tailored chemical solutions in advancing battery technology. Its ability to create a stable, lithiophilic interface not only resolves critical challenges related to dendrite formation but also unlocks the full potential of lithium metal as a superior anode material for next-generation energy storage. NINGBO INNO PHARMCHEM CO.,LTD provides high-purity HFA and its derivatives to support cutting-edge battery research and development.

For companies operating in the battery manufacturing sector, understanding and utilizing chemicals like heptafluorobutyric acid is essential for developing competitive and high-performance products. These advanced materials are key to achieving the breakthroughs needed for electric vehicles, portable electronics, and grid storage solutions.