The Study On Preparation And Application In Silicon Anode Of Tannic Acid Enhanced Alginate Based Composite Binder

Lithium ion batteries are widely used as energy storage solution due to their safety,durability,and high energy density.Silicon-based negative electrodes have emerged as a promising avenue for enhancing the performance of these batteries.However,the main obstacle in their development is the poor cycling stability resulting from the volume effect of silicon.To tackle this challenge,tannic acid composite alginate double network structure has been designed and constructed,which could restrain the volume expansion effect of silicon negative electrode with an improved electrochemical performance.The details are as follows:（1）An ionic bond network/polar group network/small molecule composite structure was constructed using alginate,polyvinylpyrrolidone,tannic acid,and nickel ions as crosslinking agents for the alginate network.And a composite binder of alginate-polyvinylpyrrolidone-tannic acid small molecules was obtained using a"one-pot method".From a material perspective,the alginate network provided good mechanical properties for the binder,the polyvinylpyrrolidone network provided good adhesion properties for the binder,and the tannic acid formed a large number of concentrated hydrogen bonds in the network,providing the binder with self-healing ability and good toughness.From a structural point of view,the dual network structure composed of alginate and polyvinylpyrrolidone can enhance the overall mechanical properties through intermolecular interactions and physical entanglement.Tannic acid small molecules can serve as hydrogen bond cross-linking points between the two networks and can also wrap silicon particles more closely in collaboration with the dual network.The experimental findings indicate that this particular binder boasts impressive cycling stability,with a remarkable discharge specific capacity of 1675.9 mAh·g^-1 that persists even after 200 cycles at a current density of 0.2 C.Furthermore,it exhibits superior rate performance,delivering an outstanding discharge specific capacity of1173.1 mAh·g^-1 when subjected to a current density of 1 C.Thus,it is postulated that the dual-network binder composed of tannic acid small molecules and composite alginate has the potential to enhance the cycling stability and other electrochemical properties of silicon anodes to a considerable degree.（2）Firstly,a covalently crosslinked polyacrylamide network was obtained by using acrylamide as a raw material and N’N’-methylenebisacrylamide as a crosslinking agent through a thermally initiated polymerization method.Then,the polyvinylpyrrolidone network was replaced with the polyacrylamide network to obtain an alginate-polyacrylamide-tannic acid small molecule composite binder with an ionic bond network/covalent bond network/small molecule composite structure.Compared with the alginate-polyvinylpyrrolidone-tannic acid binder,this binder introduces covalent bond crosslinking and has stronger mechanical properties.The silicon negative electrode prepared with this binder has a residual discharge specific capacity of 1889.4mAh·g^-1 after 200 cycles at a current density of 0.2 C,and a discharge specific capacity of 1086.6 mAh·g^-1 at a current density of 1 C,demonstrating excellent electrochemical performance.