| With the promising development of new energy and 3C digital products,people urgently need lithium-ion batteries with higher safety.Although liquid lithium-ion batteries have excellent electrochemical performance,due to the flammable electrolyte and polyolefin separator’s potential safety hazards.Although solid-state lithium batteries have improved safety performance to a certain extent,the application of solid-state electrolytes based on polymers is still limited due to their flammability.In this paper,the intrinsic flame retardant polymer chlorinated polyvinyl chloride（CPVC）was used as the research object,and two systems of lithium-ion battery separator and polymer electrolyte were designed respectively.The specific research results were as follows:Firstly,a series of CPVC separators with porous structure were obtained.The pore structure of the separators was highly designable.By changing the concentration of CPVC and pore-forming agent in the casting solution,membranes with different pore structures can be obtained.When polypropylene glycol was used as the pore-forming agent,the CPVC porous membrane has high porosity and a uniform and dense large-small composite pore structure,which gives the CPVC membrane five times higher electrolyte absorption efficiency than the PP membrane.At the same time,the characterization of the electrochemical performance of the battery shows that the prepared CPVC separator can achieve a high ionic conductivity of 1.95×10-3 S/cm,and has an oxidation voltage of 4.2V.The assembled LFP|CPVC|Li battery can reach 0.5 C-rate cycling for 100cycles still has 82%capacity retention and 99.3%coulombic efficiency.In terms of thermal properties,the CPVC separator has excellent thermal shrinkage performance compared with the PP separator,and when the separator was ignited by an open flame,Cl can be released in advance,so that it can achieve self-extinguishing after 1 s of ignition.Then,based on the above research,the SPE of PEO-CPVC/PE and PEO/CPVC systems was prepared by compounding CPVC and PEO by means of blending and filling.The effect of CPVC blending ratio on the performance of SPE was studied,and the results showed that the introduction of CPVC below 60°C could reduce the PEO crystallization ratio and improve the ionic conductivity of SPE.PEO-CPVC/PE（C10/PE）ionic conductivity can reach 2.3×10-5 S/cm at 60°C,and it can improve the ionic conductivity of PEO-based SPE at low temperature,and shows an oxidation voltage of 4.6 V.The ionic conductivity of the PEO/CPVC system is high,reaching 0.1×10-3 S/cm at 60°C,and the electrochemical stability voltage is increased to 4.8V.And after CPVC blending,the conductive phase tends to agglomerate to form a granular structure,which further reduces the crystallinity of the PEO phase;compared with the PEO-CPVC/PE system,the conductive phase-supporting phase structure of the PEO/CPVC system is more uniform,so it has higher ionic conductivity and electrochemical stability.However,the C10/PE solid-state battery possesses better cycling stability,with a capacity retention of 91%for 100cycles at 60°C and 0.5 C rate.In addition,CPVC can increase the thermal stability of the SPE system,which reduces the maximum thermal weight loss rate of SPE and slows down the thermal decomposition of SPE.Not only that,CPVC improves the flame retardant performance of the composite SPE,making the SPE have self-extinguishing performance.Compared with PEO/PE,the flame during combustion can be extinguished faster.At the same time,the generated char layer hinders the continuous combustion of the flame,which improves the battery’s performance and safety performance. |
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