We present SplitChain, a protocol intended to support the creation of scalable proof-of-stake and account-based blockchains without undermining decentralization and security. This is achieved by using sharding, i.e. by splitting the blockchain into several lighter chains managed by their own disjoint sets of validators called shards. These shards balance the load by processing disjoint sets of transactions in parallel. SplitChain distinguishes itself from other sharded blockchains by reducing the synchronization constraints among shards while maintaining security guarantees in an asynchronous setting. A dedicated routing protocol enables transactions to be redirected between shards with a low number of hops and messages. Finally, the protocol is designed to dynamically adapt the number of shards to the system load to avoid over-dimensioning issues encountered in static sharding-based solutions.