固态电池有望解决动力电池在高能量密度和高安全性之间的矛盾，是下一代动力电池技术竞争的制高点。然而，研究表明，现有商业固态电池仍然会发生热失效，固态电池的安全特性及其失效机理尚未清晰，缺乏有效的固态电池安全设计方案。因此，本课题采用材料-单体闭环联动的研究方法，针对固液混合电池和全固态电池的热失效特性及其机理开展了深入研究。首先，在固液混合电池单体层级，分析了四种氧化物固液混合电池热失效特性，阐明了自由电解液与嵌锂负极释热反应限制氧化物固液混合电池安全性提升的机制。提出了安全电解液与原位聚合相结合的聚合物固液混合电池设计方法，揭示了聚合网络抑制锂盐侵蚀负极、延缓正极相变释氧和阻隔正负极接触的安全作用机理，大幅提升了固液混合电池的安全性，同时兼顾良好的电化学性能。在此基础上，总结了电解液与聚合单体协同优化的聚合物固液混合电池安全设计准则。其次，在全固态电池关键材料层级，探究了典型的氧化物/硫化物固态电解质与正负极材料高温失效产热-产气特性，发现了硫化物固态电解质与正极材料剧烈反应放热现象，并通过解析各升温阶段中硫化物固态电解质与高镍正极的主要反应产物，揭示了正极释氧及其固体分解产物与硫化物固态电解质反应诱发的全固态电池两种失效路径，即气-固反应和固-固反应失效路径。提出了固态电解质与正负极材料加压成型的热分析制样方法，明确了压力大小、加压时间、样品总质量和组分比例对硫化物固态电解质与正极材料失效行为的影响规律，建立了硫化物全固态电池关键材料热稳定性评价方法。最后，在硫化物全固态电池单体层级，分析了其在机械滥用和热滥用下的产热-产气特性，发现了硫化物全固态电池在极端热滥用下的热失效现象，并明确了正极材料与硫化物固态电解质的产热反应是电池热失效的关键触发反应。进一步，对比分析了相同正负极体系/容量的液态电池和固液混合电池在机械滥用和热滥用下的产热-产气特性，建立了包括热箱热失效温度、失效产气总量、产气爆炸上限和针刺安全性指数在内的四维指标，量化了硫化物全固态电池和聚合物固液混合电池相较于液态电池的安全性提升程度，总结梳理了硫化物全固态电池在针刺内短路、环境热冲击和热失效产气三方面的安全性提升机理。

Solid-state batteries are expected to resolve the contradiction between high energy density and high safety that troubles current power batteries, positioning themselves as a critical area in the competition for next-generation power battery technology. However, research indicates that existing commercial solid-state batteries still experience thermal failure process. The safety characteristics and failure mechanisms of solid-state batteries are not yet fully understood, and there is a lack of effective safety design for these batteries. Therefore, this study employs a material-cell closed-loop interactive research method to conduct an in-depth investigation into the thermal failure characteristics and mechanisms of both hybrid solid-liquid batteries (HSLBs) and all-solid-state batteries (ASSBs). Firstly, at the single-cell level of HSLBs, the thermal failure characteristics of four types of oxide-based HSLBs are analyzed. The study specifies that the safety improvement of oxide-based HSLBs is hindered by the exothermal reactions between free liquid electrolyte and lithiated anode. A design method for polymer-based HSLBs is introduced, which involves combining a high-safety liquid electrolyte with in-situ polymerization. This method improves battery safety by inhibiting lithium salt erosion of the anode, delaying oxygen release from cathode phase transformation, and preventing direct contact between the cathode and anode. Consequently, the safety of HSLBs is significantly improved without sacrificing electrochemical performance. Based on these findings, safety design guidelines for polymer-based HSLBs are summarized, emphasizing the synergistic optimization of liquid electrolyte and polymer monomers.Secondly, at the key material level of ASSBs, the study explores the heat and gas generation characteristics of thermal failure for typical oxide/sulfide solid-state electrolytes (SEs) and electrode materials. It is found that sulfide SEs exhibit intense exothermic reactions with cathode materials. By analyzing the main reaction products of sulfide SEs and cathode at various heating stages, two failure pathways induced by the interaction of oxygen released from the cathode and its solid decomposition products with the sulfide SEs for ASSBs are identified: gas-solid reactions and solid-solid reactions. Furthermore, a thermal analysis sample preparation method involving the pressing of SEs and electrode materials is proposed. The influence of pressure magnitude, pressing duration, total sample mass, and component ratio on the failure behavior of sulfide SEs and cathode materials is investigated. Consequently, a thermal stability evaluation method for the key materials in sulfide-based ASSBs is established.Finally, at the single-cell level of sulfide-based ASSBs, the heat and gas generation characteristics under mechanical and thermal abuse are analyzed. The study identifies the thermal failure phenomena of sulfide-based ASSBs under extreme thermal abuse, pinpointing the exothermic reactions between cathode materials and sulfide SEs as the key triggers of battery thermal failure. A comparative analysis is conducted on the heat and gas generation characteristics under mechanical and thermal abuse for liquid batteries and HSLBs with the same electrode systems and capacity. Four-dimensional metrics are established, including thermal failure temperature in hot-box tests, total gas generation, gas upper explosive limit, and nail penetration safety index, to quantify the safety improvement levels of sulfide-based ASSBs and polymer-based HSLBs. The study summarizes the safety improvement mechanisms of sulfide-based ASSBs under internal short-circuits due to nail penetration, environmental thermal shocks, and gas generation during thermal failure circumstances.